# Woodsmaneh! Cool Growing Info



## woodsmaneh! (Jul 9, 2011)

Over the years I have collected some interesting info on growing and thought this is a good spot to share it, so I will post it all here, something different every week. If you have some good info feel free to post. Peace and good growing to you all. 

Here is the first one on Bud Rot

* Here is some info on Botrytis, I use an Ozone generator and follow the steps below and have not had any issues in a few years. I will also run a dehumidifier on a timer at night. Hope this helps.

Bud Rot 
Bud rot (Botrytis) is a very common worldwide fungus that attacks both indoor and outdoor crops under certain conditions. Bud rot is also known as brown rot, grey mould and other names. Airborne Botrytis spores can be found everywhere, all times of the year, and will attack many different species of plants. Botrytis will attack flowers, and eventually leaves and stems. 

Growers running sea of green, perpetual harvest, remote grows, outdoor, or multiple strains (each with different flowering periods) should keep an eye out for Botrytis near harvest time. 

Outdoor growers need to be hypersensitive to weather conditions near harvest time. Rain, morning dew, frost and cool fall nights may increase the risk of bud rot and powdery mildew. 

Fully developed marijuana buds provide ideal conditions for spore germination: warm and moist plant tissues. Botrytis will initially attack the largest and densest buds in the garden, because they provide the ideal conditions for germination. Weak plants will also be attacked rapidly. 

[FONT=&quot]Identifying and preventing budrot[/FONT] 

Budrot will infect and turn colas to mush in a matter of days and may destroy a crop in a week if left unchecked. Botrytis loves warm, and humid (50% or over humidity) conditions. Lowering humidity will slow and stop spore germination. Good ventilation and decent air circulation help prevent infection. 
A grow room may smell noticeably moldy if Botrytis has attacked one or more colas. Once a cola has been infected, Botrytis will spread incredibly fast. Entire colas will turn to brown mush and spores will be produced, attacking other nearby colas. Ventilation may spread viable spores throughout the room. 

[FONT=&quot]Measures to prevent bud rot in the final stages of flowering:[/FONT] 

Early veg and flower pruning of undergrowth to promote air circulation 
Hepa filter room and intake air sources. 
Introduce low levels of ozone into room air . Ozone is effective against pollen, powdery mildew and other airborne spores. 
Lowering room humidity (warming nighttime air and venting frequently or using a dehumidifier) 
Decreasing watering cycles and amounts to reduce room humidity 
Large, dense colas should be periodically inspected. Brown tissues deep within the bud will smell mouldy and may become liquid. 
Removing fan leaves during the last few days before harvest to promote air circulation 

Serenade 
"Serenade controls the following: ....Botrytis, Powdery mildew, Downey mildew..." 

"Certified organic by OMRI  and EPA/USDA National Organic Program, Serenade offers growers the luxury of application without weather or timing restrictions and there are no phyto-toxicity issues" 
"To apply, simply spray on leaves and shoots to provide complete coverage. Best results will be had be pre-treating plants before signs of disease set it and then every week to protect newly formed foliage" 

[FONT=&quot]What if bud rot is found?[/FONT] 
Once bud rot has been detected, the grower should isolate infected buds by removing them from the grow room immediately and harvesting the infected colas, followed by a rapid dry of the harvested colas. Take immediate steps to reduce room humidity. Afterwards, the entire crop should be carefully inspected for infection and damage. The grower may want to harvest early if more than one rotting cola has been found. Spores may have spread and are germinating deep within other colas. 

[FONT=&quot]Can I salvage budrot-infected colas?[/FONT] 

Yes. Remove the infected colas from the main room, Trim out the infection (Trim more than you can see  Botrytis often infects adjacent tissues) and quick-dry them. Re-inspect buds  they should [FONT=&quot]not[/FONT] smell mouldy.​ 
*


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## woodsmaneh! (Jul 9, 2011)

*Hi Guys I noticed some of the humidity comments and the fact that some run at 40%, your short changing yourself and your plant. The stomata open wide at higher humidity levels 60 to 70% and can gobble up all that co2, lover levels and they start to close.

Here is everything you need to know in a nut shell well maybe a small book.

[FONT=&quot]Plantworks: Part 1  Humidity and Vapor Pressure Deficit[/FONT]
[FONT=&quot]By [/FONT][FONT=&quot]Urban Garden Magazine[/FONT][FONT=&quot]&#8901;[/FONT][FONT=&quot] July 12, 2010 [/FONT][FONT=&quot]&#8901;[/FONT][FONT=&quot]Email This Post[/FONT][FONT=&quot]&#8901;[/FONT][FONT=&quot]Print This Post[/FONT][FONT=&quot]&#8901;[/FONT][FONT=&quot]Post a comment[/FONT]
[FONT=&quot]Filed Under[/FONT] [FONT=&quot] humid, [/FONT][FONT=&quot]humidity[/FONT][FONT=&quot], [/FONT][FONT=&quot]Issue 11[/FONT][FONT=&quot], [/FONT][FONT=&quot]vapor pressure deficit[/FONT]
[FONT=&quot]Think like a plant.[/FONT]
[FONT=&quot]Have you ever been given this odd-sounding advice? Even when we are encouraged to try and understand how plants work, our inherent tendency to personify the natural world is inescapable. Growers often like to draw parallels between humans and plants, after all, theres no doubt that plants are marvellous, highly specialized and well-adapted organisms. You might even go as far to say they are intelligent. But lets be honest here. Plants are totally different from us, especially in the way they react and respond to their environment. However, if we can get our heads around the world from a plants perspective, we become what is commonly referred to as green-fingered. We become  better growers.[/FONT]
[FONT=&quot]Have you ever wondered how plants feel humidity? An understanding of what humidity is, what it means to plants, and how you can manage it in your indoor garden will help you and your plants stay happy all year round.
The humidity of the air is basically the amount of water in the air. Water can only truly stay in the air when it is the invisible gas  water vapour. Small droplets of water in air, such as fog or mist, are not water vapor; they are simply larger particles of water temporarily suspended in the air that are ready to be turned into water vapour by evaporation.[/FONT]
[FONT=&quot]Temperature plays an important role when it comes to humidity. The warmer the air, the more water vapour it can hold. This means the maximum amount of water that air can hold is directly related to the temperature of the air. As the amount of water air can hold constantly changes with temperature it is difficult to pin an absolute or fixed amount of water that can be held by air. So whats the best way to quantify humidity if the goal posts are changing all the time? The answer is something called Relative Humidity (RH)  this is a measure in terms of percentage, of the water vapor in the air compared to the total amount of water vapor that the air could potentially hold at a given temperature.[/FONT]
[FONT=&quot]Why is RH so important?[/FONT] 
[FONT=&quot]As growers we measure the RH of our gardens using digital or analogue hygrometers. These readings are very important because RH has a direct effect on the plants ability to transpire and therefore grow. Generally, plants do not like to lose lots of water through transpiration. Plants have some degree of control of their rate of transpiration through management of their stomata but the general rule is the drier the air, the more plants will transpire.
Now lets move on to the idea of pressure  this is an important concept to grasp when it comes to understanding a plants response to humidity. All gasses in the air exert a pressure. The more water vapor in the air the greater the vapor pressure. This means that in high RH conditions there is a greater vapor pressure being exerted on plants than in low RH conditions. High vapor pressure can be thought of as a force in the air pushing on the plants from all directions. This pressure is exerted onto the leaves by the high concentration of water vapor in the air making it harder for the plant to push back by losing water into the air by transpiration. This is why with high RH plants transpire less. Conversely, in environments with low RH, only a small amount of pressure is exerted on the plants leaves, making it easy for them to lose water into the air.[/FONT]
[FONT=&quot]What is Vapor Pressure Deficit (VPD)?[/FONT] 
[FONT=&quot]VPD can be defined as the difference (or deficit) between the pressure exerted by water vapor that could be held in saturated air (100% RH) and the pressure exerted by the water vapor that is actually held in the air being measured.
The VPD is currently regarded of how plants really feel and react to the humidity in the growing environment. From a plants perspective the VPD is the difference between the vapor pressure inside the leaf compared to the vapor pressure of the air. If we look at it with an RH hat on; the water in the leaf and the water and air mixture leaving the stomata is (more often than not) completely saturated -100% RH. If the air outside the leaf is less than 100% RH there is potential for water vapor to enter the air because gasses and liquids like to move from areas of high concentration (in this example the leaf) into areas of lower concentration (the air). So, in terms of growing plants, the VPD can be thought of as the shortage of vapor pressure in the air compared to within the leaf itself.[/FONT]
[FONT=&quot]Another way of thinking about VPD is the atmospheric demand for water or the drying power of the air. VPD is usually measured in pressure units, most commonly millibars or kilopascals, and is essentially a combination of temperature and relative humidity in a single value. VPD values run in the opposite way to RH vales, so when RH is high VPD is low. The higher the VPD value, the greater the potential the air has for sucking moisture out of the plant.
As mentioned above, VPD provides a more accurate picture of how plants feel their environment in relation to temperature and humidity which gives us growers a better platform for environmental control. The only problem with VPD is its difficult to determine accurately because you need to know the leaf temperature. This is quite a complex issue as leaf temperature can vary from leaf to leaf depending on many factors such as if a leaf is in direct light, partial shade or full shade. The most practical approach that most environmental control companies use to assess VPD is to take measurements of air temperature within the crop canopy. For humidity control purposes its not necessary to measure the actual leaf VPD to within strict guidelines, what we want is to gain insight into is how the current temperature and humidity surrounding the crop is affecting the plants. A well-positioned sensor measuring the air temperature and humidity close to, or just below, the crop canopy is adequate for providing a good indication of actual leaf conditions.[/FONT]
[FONT=&quot]Managing Humidity[/FONT] 
[FONT=&quot]




[/FONT]
[FONT=&quot]Managing the humidity in your indoor garden is essential to keep plants happy and transpiring at a healthy rate. Transpiration is very important for healthy plant growth because the evaporation of water vapor from the leaf into the air actively cools the leaf tissue. The temperature of a healthy transpiring leaf can be up to 2-6°C lower than a non-transpiring leaf, this may seem like a big temperature difference but to put it into perspective around 90% of a healthy plants water uptake is transpired while only around 10% is used for growth. This shows just how important it is to try and control your plants environment to encourage healthy transpiration and therefore healthy growth.
So what should you aim to keep your humidity at? Many growers say a RH of 70% is good for vegetative growth and 50% is good for generative (fruiting /flowering) growth. This advice can be followed with some degree of success but its not the whole story as it fails to take into account the air temperature.[/FONT]
[FONT=&quot]Humidification systems to increase RH.[/FONT] 
[FONT=&quot]Table 1 shows the VPD in millibars at various air temperatures and relative humidity. Most cultivated plants grow well at VPDs between 8 and 10, so this is the green shaded area. Please note that the ideal VPD range varies for different types of plants and the stage of growth. The blue shaded are on the right indicates humidification is needed where the red shaded area on the left indicates dehumidification is needed.[/FONT]
[FONT=&quot]




[/FONT]
[FONT=&quot]By looking at this example we can see that at 70% RH the temperate should be between 72-79°F (22-26°C) to maintain healthy VPDs. If your growing environment runs on the warm side during summer, like many indoor growers, a RH of 75% should be maintained for temperatures between 79-84°F (26-29°C.)[/FONT]
[FONT=&quot]The problem with running a high relative humidity when growing indoors it that fungal diseases can become an issue and carbon filters become less effective. It is commonly stated that above 60% RH the absorption efficiency drops and above 85% most carbon filters will stop working altogether. For this reason it is good practice to run your RH between 60-70% with the upper temperature limit depending on your crops ideal VPD range, in the example it would be 64-79°F (18-26°C.)[/FONT]
[FONT=&quot]The table also shows that if your temperature is above 72°F (22°C), 50% RH becomes critically low and should generally be avoided to minimize plant stress.
Please understand that by presenting this information we do not want you to go to your indoor gardens and run your growing environment to within strict VPD values. Whats important to take from this is that VPD can help you provide a better indication of how much moisture the air wants to pull from your plants than RH can. If you want to work out for yourself the VPD of your plants leaves you can follow the steps below:[/FONT]


[FONT=&quot]Measure the leaf temperature and look up the vapor pressure at 100% RH on table 2 below.[/FONT]
[FONT=&quot]Measure the air temperature and relative humidity and look up the nearest vapor pressure figure on table 2.[/FONT]
[FONT=&quot]Subtract the air vapor pressure from the leaf vapor pressure[/FONT]
 [FONT=&quot]Example:
Leaf Temperature = 24°C (100% RH) Leaf VP: 29.8
Air Temperature = 25°C @ 60% RH Air VP: 19.0
VPD= 10.8[/FONT]
[FONT=&quot]




[/FONT]
[FONT=&quot]Humiditys Effect on Plants[/FONT] 
[FONT=&quot]Plants cope with changing humidity by adjusting the stomata on the leaves. Stomata open wider as VPD decreases (high RH) and they begin to close as VPD increases (low RH). Stomata begin to close in response to low RH to prevent excessive water loss and eventually wilting but this closure also affects the rate of photosynthesis because CO2 is absorbed through the stomata openings. Consistently low RH will often cause very slow growth or even stunting. Humidity therefore indirectly affects the rate of photosynthesis so at higher humidity levels the stomata are open allowing co2 to be absorbed.[/FONT]
[FONT=&quot]




[/FONT]
[FONT=&quot]Leaf roll on Thai basil- Localized humidity stress causes by the lights being too close.[/FONT]
[FONT=&quot]When humidity gets too low plants will really struggle to grow. In response to high VPD plants will try to stop the excessive water loss from their leaves by trying to avoid light hitting the surface of the leaf. They do this by rolling the leaf inwards from the margins to form tube like structures in an attempt to expose less of the leaf surface to the light, as shown in the photo.[/FONT]
[FONT=&quot]For most plants, growth tends to be improved at high RH but excessive humidity can also encourage some unfavourable growth attributes. Low VPD causes low transpiration which limits the transport of minerals, particularly calcium as it moves in the transpiration stream of the plant  the xylem. If VPD is very low (95-100% RH) and the plants are unable to transpire any water into the air, pressure within the plant starts to build up. When this is coupled with a wet root zone, which creates high root pressure, it combines to create excessive pressure within the plant which can lead to water being forced out of leaves at their edges in a process called guttation. Some plants have modified stomata at their leaf edges called hydathodes which are specially adapted to allow guttation to occur. Guttation can be spotted when the edges of leaves have small water droplets on, most evident in early morning or just after the lights have come on. If you see leaves that appear burnt at the edges or have white crystalline circular deposits at the edges it could be evidence that guttation has occurred.[/FONT]
[FONT=&quot]




[/FONT]
[FONT=&quot]Guttation on tomato plants caused by high RH and wet coco coir.[/FONT]
[FONT=&quot]




[/FONT]
[FONT=&quot]Powdery Mildew from poor humidity control.[/FONT]
[FONT=&quot]Most growers are well aware that with high humidity comes and increased risk of fungal diseases. Water droplets can form on leaves when water vapor condenses out of the air as temperature drops, providing the perfect breeding ground for diseases like botrytis and powdery mildew. If humidity remains high it further promotes the growth of fungal diseases. The water droplet exuded through guttation also creates the perfect environment for fungal spores to germinate inviting disease to take hold.[/FONT]
[FONT=&quot]Quick reference chart:[/FONT]
[FONT=&quot]Low VPD / High RH[/FONT]
[FONT=&quot]High VPD / Low RH[/FONT]
[FONT=&quot]Mineral deficiencies[/FONT]
[FONT=&quot]Wilting[/FONT]
[FONT=&quot]Guttation[/FONT]
[FONT=&quot]Leaf roll[/FONT]
[FONT=&quot]Disease[/FONT]
[FONT=&quot]Stunted plants[/FONT]
[FONT=&quot]Soft growth[/FONT]
[FONT=&quot]Leathery/crispy leaves[/FONT]
[FONT=&quot]So hopefully now you are not just thinking like a plant  youre feeling it too![/FONT]
[FONT=&quot]Next time, part two of Plantworks will be looking at foliar spraying and how plants absorb nutrients into their leaves.[/FONT]
[FONT=&quot][/FONT] 
[FONT=&quot]references are:[/FONT] 
[FONT=&quot]BCMAFF Floriculture Factsheet No.400-5 (June 1994) [/FONT]
[FONT=&quot]Autogrow Systems Ltd  [/FONT][FONT=&quot]Humidity and VPD[/FONT]
[FONT=&quot]If you are interested in calculating VPD, an on-line calculator can be found here: [/FONT][FONT=&quot]Autogrow VPD Calculator[/FONT]

[FONT=&quot]In situations where CO2 is used there is little point in injecting the CO2 when the stomata are closed  so avoid having an environment where the VPD is high (above 11 millibars (approx.)) during this period. A lowish VPD (between 6-




will encourage the stomata to open wide and gobble up all that lovely CO2. If you cant get the VPD down when the lights are on then maybe switch off CO2 injection and save the planet.[/FONT][FONT=&quot]During the night period, VPD is not as important because stomata are closed. However, problems can occur when indoor gardens run with a drastically higher VPD during the night in comparison to the day, which could come from using excessive dehumidification during the night. You should aim to have slightly lower VPD in the night than during the day, which is usual for most indoor growers. [/FONT][FONT=&quot]If fungal growth is your main concern, running the RH between 55-65% at 70F during the night should be fine. Even running as low as 45% at 70F in the last few weeks should be ok if you want peace of mind when growing varieties that are particularly susceptible to botrytis or mildew. Note that RH can vary from place to place inside the grow area so you may be getting 65% at your RH sensor but without any air stirring going on it could be getting much higher in cooler areas (a cold corner or inside a crowded crop canopy facing a cold wall) where there is not much air movement.[/FONT]*


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## woodsmaneh! (Jul 9, 2011)

*Here are a few more tips on mildew

CULTURAL CONTROL
Heat

Powdery mildew is sensitive to heat. Neither species will grow at 90 °F (32 °C). and will quickly perish when above 100 ° F (38 °C).
To get a complete kill maintain the temperature for an hour. This may not be a feasible option in most indoor gardens for several reasons. The first is that it may be difficult to heat the space to such a high temperature. The second is that even a single peak of 100 ° F (38 °C) affects the growth of plants. Vegetative plants with flowers or fruits in mid stage growth (weeks 3-7) may stretch a little from the experience. The heat treatment has relatively little effect on first and second week flowers or flowers nearing maturity.
You can minimize heats impact on plants in several ways. Heat the garden at the end of the day, as the lights are turned off. Since the plants are not photosynthesizing, they have lower water needs.
If the plants are being grown hydroponically, lower the temperature of the water to 60 degrees. Keeping the roots cool will help the upper plant parts beat the heat. Its not difficult to do this, even if you dont have a water chiller. Just add ice to the reservoir or flow through system. Roots of plants growing in soil can also be cooled using thermal ice packs at the base of the stem.
The heat treatment should kill off most of the fungus and its spores. The chances are there will still be some fungal re-growth. These can be eliminated using spot treatments.
Pruning

If one particular plant seems to be infected with a few tiny white spots on a few of its leaves, get a bag large enough to drop the leaves into and then cut them off into the bag. Remove the bag from the room. This prevents spores, the white powder on top of the leaves, from becoming airborne while being removed. Remember to wash your hands and clean the scissors or knife with soap and water, hydrogen peroxide, alcohol or bleach. Spray the plant with one of the sprays listed below after pruning to prevent re-infection and encourage healing.
If, you notice a re-infection a few days later, there is a good chance that this plant is very susceptible to powdery mildew and presents a good location for the infection to start and spread from. The plant should be removed immediately by placing a bag over it and removing it from the space. Then the space should be sprayed with one of the sprays listed below.
ORGANIC and IPM CONTROL


Here are some sprays that you can use to control the powdery mildew in your crop. All of these are safe to use for herb or for edible crops. Sprays are washed away by water, including rain.
Cinnamon Oil and Tea
Cinnamon is an effective destroyer of powdery mildew, with an effectiveness rate of 50-70%. It wont kill it completely but it will keep it in check somewhat. It also potentiates other suppressive sprays so it is good to use in combination. To make your own, boil water, turn off the heat and add one ounce of ground cinnamon to one and a half pints water. Let the tea cool to room temperature. Add half a pint of 100 proof grain alcohol or rubbing alcohol and let sit. Strain the cinnamon. The spray is ready to use. A faster method is to add 2 teaspoons cinnamon oil to one pint of water and a dash of castile soap. Other herbs are also fungicidal. Clove, rosemary, and wintergreen oils are used in some botanical fungicides. The solution should consist of no more than 2% oil.
Garlic

Garlic is antifungal and anti-bacterial and has several pathways for destroying fungi including its high sulfur content. It can also be added to other anti-fungal sprays. Several garlic sprays are available commercially.
A homemade formula: Soak three ounces of crushed garlic in one ounce of neem or sesame oil and 100 proof or higher drinking alcohol or 70% or higher rubbing alcohol for a day or two. Strain. Then soak the garlic in a cup of water for a day. Strain. Mix the oil/alcohol, soaked water and 1 tablespoon liquid castile soap in a gallon container. Then fill with water and shake. The formula is ready to use.
A simpler brew consists of a teaspoon of garlic oil in a pint of water. To keep the oil and water mixed add a 1/8teaspoon of soap. Use garlic as a vaccination. Spray on new growth before there is a sign of infection.
Garlic is a general purpose insecticide as well as fungicide, so it should be used with caution on outdoor plants. It kills beneficial insects as well as plant pests.
Hydrogen Peroxide
Hydrogen peroxide (hp) is a contact fungicide that leaves no residue. It is an oxidized product of water and has an extra oxygen atom that is slightly negatively charged. When it comes in contact with the fungi the oxygen atoms attach to molecules on the cell walls, oxidizing or burning them.
Household hp sold in drug stores has a concentration of 3%. Garden shops sell 10% hp. Zerotol® contains 27% hydrogen peroxide and an unstated amount of peroxyacetic acid. Together they have a more potent chemistry than hp, with an activity of about 40% hp. It is considered hazardous because it can cause skin burn similar to that caused by concentrated acids.
To treat plants with drug store grade 3% hp use 4 1/2 tablespoons and fill to make a pint of solution, or a quart of hp to 3 quarts of water. With horticultural grade 10% hp use about 4 teaspoons per pint, 5 ounces per gallon. With Zerotol® use about 1 teaspoon per pint, 2 1/2 tablespoons per gallon.
Limonene
Limonene is refined from the oil of citrus rinds. It has a pleasant citrus odor and is the active ingredient in many of the new cleaning products. It also has fungicidal qualities. Ive used pure diluted limonene and it controlled powdery mildew, but did not eradicate it. Perhaps a higher concentration would have been more successful. Start using 0.5-1% limonene in water 1/2-1 teaspoon per pint.
Milk
Milk kills powdery mildew so well that both home and commercial rose growers all over the world have adopted it for their fungicidal sprays. Use one part milk to nine parts water. Ive only used 1% milk, but other recipes call for either whole or skim milk and use up to 1 part in 5 milk. Some recipes add garlic or cinnamon to the mix. When using more than 30% milk, a benign mold is reported to grow on top of the leaves. Use a milk spray at the first sign of infection then protect the new growth weekly.
Messenger®
Messengers active ingredient is a naturally occurring protein called harpin that stimulates the plants own natural defense system. It has been proven to promote more vigorous hardier plants that are more resistant to disease and have increased yields. It is used to prevent infection and decrease its virulence
Neem Oil
Neem oil is pressed from the seed of the neem tree (Azadirachta indica), native to Southeast Asia, but now cultivated worldwide. Neem oil has low mammalian toxicity. It degrades rapidly once it is applied so it is safe for the environment including non-target species and beneficial insects.
Neem oil protects plants with its fungicidal properties: it disrupts the organisms metabolism on contact, forms a barrier between the plant and the invading fungus, and it inhibits spore germination. It has translinear action, that is, it is absorbed by the leaf and moves around using the leafs circulatory system  it can also be used as a systemic. When it is applied to the irrigation water it is absorbed by the roots and delivered throughout the plant. Adding a 0.5% solution, about 1 teaspoon per quart, to the irrigation water will protect the plant from infection.
Neem oil is best used before the plant or the garden exhibits a major infection. By using it before powdery mildew appears, it prevents the spores from germinating. It should not be used on buds or flowers.
Oil Spray
Growers have used different oil sprays to prevent and cure fungal infections. Until recently most horticultural oil sprays were made from petroleum distillates. However, most organic growers have switched to using botanical oils. Aside from the safety factor botanicals such as cottonseed, jojoba, neem and sesame oils have fungicidal properties. They can be used in combination with other spray ingredients listed here. The oils are mixed at about 1-2% concentrations. A 1% solution is about a teaspoon per pint or 3 tablespoons per gallon. Add castile soap to help the ingredients mix. Oil sprays should only be used on the leaves, not the buds or flowers. Use weekly on new growth.
pH Up
pH-Up is a generic term for alkaline pH adjustors, used to increase water pH in indoor gardens. They come as either a powder or liquid. Its active ingredient is usually lye (KOH) or potash (K2CO3).
Fungi require an acidic environment to grow and die in alkaline environments. Changing the leaf surface environment from acidic to alkaline clears up the infection. An alkaline solution with a pH of 8 will make the environment inhospitable for the fungus and will stop its growth. This is one of the simplest means of controlling the fungus. It can be used on critically infected plants.
Potassium/Sodium Bicarbonate
Potassium bicarbonate (KHCO3) and Sodium bicarbonate (NaHCO3) are wettable powders that change the pH of the leaf surface toward alkaline. Another reaction takes place; the fungus cell wall actually bursts in the presence of bicarbonate. Potassium is one of the macro-nutrients used by plants and therefore is preferred over sodium, as sodium can build up in the soil. Sodium bicarbonate can be found in your kitchen (baking soda), so some prefer it for ease of obtaining. Both are more effective when used with an oil and spreader such as castile soap. They can be used to cure bad infections and prevents new ones.
Use one teaspoon of bicarbonate powder, a teaspoon of oil and a few drops of castile soap in a pint of water, or 3 tablespoons each potassium bicarbonate and oil and a half teaspoon soap in a gallon of water. Spray on new growth.
Serenade® and Sonata®
Serenade® and Sonata® are composed of different bacteria. They use different pathways to stop mycellial growth. They are considered totally safe to humans and animals since the bacteria attack only fungi. Watch out if you are a mushroom, otherwise you are safe. The two bacteria work well together.
They are easy to use, quite safe and effective.
Sulfur
Sulfur has been used to control powdery mildew for centuries. Sulfur sprays can be used indoors but they are not popular because of residue that remains on the plant. In greenhouses gardeners use sulfur vaporizers that heat elemental sulfur to the point of vaporization. The sulfur condenses on all surfaces including the leaves. A fine deposit of very low pH sulfur granules covers the leaf surfaces. The low pH environment inhibits fungal growth. The heaters use a 60 watt light bulb to heat sulfur which is held in a container above the light. The bulb supplies enough heat to evaporate the sulfur, but not enough for it to ignite. The problem with vaporizers is that they also leave a fine sulfur film on the leaves and flowers.
Active mildew: 7 to 8 hours per night 1 to 2 times a week.
Preventative maintenance: 4 to 5 hours once a week
Vinegar
Apple cider vinegar is toxic to powdery mildew because of its high acidity (low pH). Use it at the rate of 1 tablespoon per quart of water several times a week . Some gardeners recommend alternating using vinegar with potassium bicarbonate and milk.
PREVENTION


Isolate all new plants in a separate area where they cant infect other plants.
Filter incoming air to prevent spores from entering the room in the airstream.
Install a germicidal UVC light, like the ones used in food handling areas. The light is fatal to all airborne organisms passing through the appliance. This will kill powdery mildew spores that are airborne.
Spray the leaves with neem oil weekly. Neem oil presents both a physical barrier and a chemical deterrent.
Cinnamon oil and cinnamon tea can also be sprayed as a powdery mildew preventative. If you are using cinnamon oil use 1 part oil to 200 parts water. (1 teaspoon oil in a liter of water.)
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## ClamDigger (Jul 9, 2011)

soo much good info*, "you must spread some Reputation around before giving it to woodsmaneh! again"
*neem oil is very important, in preventing pests, and as a physical barrier, i have also heard that Sesame oil prevents PM spores from growing.


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## woodsmaneh! (Jul 9, 2011)

Yup Neem is the dope for sure here is info on Neem and a artical writen by a buddy of mine.

Keep in mind Neem will control bugs but it is not a knock down killer it takes time that's why you use it right from the start.

*[FONT=&quot]There is some really good information here on what you can do with neem and how and why you should use it often.[/FONT]* 
*[FONT=&quot]What is it? Neem Oil[/FONT]* 
 [FONT=&quot]Neem oil comes from the pressed seed of the neem tree  Azadiracta indica Juss  to be exact. Its native to eastern India and Burma and has been used for medicinal purposes and pest control in India for thousands of years.[/FONT]
 [FONT=&quot]Claims are that the bark and leaves have quite a few antis covered.[/FONT]
 

[FONT=&quot]antiseptic[/FONT]
[FONT=&quot]antiviral[/FONT]
[FONT=&quot]anti-inflammatory[/FONT]
[FONT=&quot]antiulcer[/FONT]
[FONT=&quot]antifungal[/FONT]
 [FONT=&quot]to name a few.[/FONT]
*[FONT=&quot]Is It Safe?[/FONT]* 
 [FONT=&quot]Well neem products are used in medication and consumed by humans. So any exposure to neem while treating your plants does not pose a threat. There are no restrictions put in place by the EPA.[/FONT]
 [FONT=&quot]I spoke to a few growers that have been using neem oil in their pest control program and they are delighted with it. Not just from the safety aspect but the control. They have found the neem oil to be effective as a *repellant  insecticide  miticide* and *fungicide.* It also functions as an *antifeedant* which discourages insects feeding patterns.[/FONT]
*[FONT=&quot]Insects would rather die than eat plants treated with neem oil.[/FONT]* 
_[FONT=&quot]Extracts from neem have shown incredible success with not only battling fungus problems but also many forms of root rot.[/FONT]_ 
*[FONT=&quot]Why it Works[/FONT]* 
 [FONT=&quot]Extracts from the tree contain *azadirachtin, a relatively safe and effective naturally occurring insecticide*. Let me preface the following comments by reminding you that the terms *"naturally occurring and/ or organic" do not universally mean safe.* _Pyrethrums, rotenone, and even the very dangerous nicotine are all organics that should be handled with great caution._ 

[/FONT]
*[FONT=&quot]Where is it Used?[/FONT]* 
*[FONT=&quot]Neem[/FONT]* [FONT=&quot] extracts, on the other hand *are used in a wide variety of cosmetics*, as a *topical treatment for minor wounds*_, to treat stomach ailments, as an insecticide in grain storage containers,_ and a whole host of other applications. [/FONT]
*[FONT=&quot]How Does it Work?[/FONT]* 
 [FONT=&quot]Neem works in many ways. *It is effective both as a topical and a systemic*. It is *an antifeedant, an oviposition deterrent (anti-egg laying), a growth inhibitor, a mating disrupter, and a chemosterilizer*. Azadirachtin closely mimics the hormone ecdysone which is necessary for reproduction in insects. When present, it takes the place of the real hormone and thus disrupts not only the feeding process, but the metamorphic transition as well. *It interferes with the formation of chitin (insect "skin")* and *stops pupation* in larvae, thus short-circuiting the insect life cycle. Tests have shown that azadirachtin is effective in some cases at concentrations as low as 1 ppm.[/FONT]
*[FONT=&quot]How to Use?[/FONT]* 
 [FONT=&quot]Neem oil or extract is most often used in an aqueous (water) suspension as a foliar spray or soil drench. Commonly, it is diluted to about a .05% solution. A drop or two of dish soap (not detergent) helps keep the oil emulsified. The mixture is then applied as a mist to all leaf surfaces and as a soil drench to the root system. It should not be applied as a foliar spray on hot days or in bright sun as leaf burn may occur. *Remember to agitate the container frequently as you apply* and do not mix any more than you will use in one day. Neem breaks down rapidly in water and/ or sunlight. [/FONT]
*[FONT=&quot]What to Expect[/FONT]* 
 [FONT=&quot]Some users of insecticide need to be able to observe the instant results of their efforts in order to be convinced of the effectiveness of their choice. The application of neem derivatives does not provide this immediate gratification. There is virtually no knockdown (instant death) factor associated with its use. Insects ingesting neem usually take about 3 - 14 days to die. [/FONT]
*[FONT=&quot]Why Keep Using It?[/FONT]* 
 [FONT=&quot]Its greatest benefit; however, is in preventing the occurrence of future generations. It is also interesting to note that in studies it was found that when doses were given, purposefully insufficient to cause death or complete disruption of the metamorphic cycle, up to 30 surviving generations showed virtually no resistance/immunity to normal lethal doses. [/FONT]
 [FONT=&quot]I have been using neem oil as both a preventative and fixative and have had no insect problems. *It is said to be effective for mites, whitefly, aphids, thrips, fungus gnats, caterpillars, beetles, mealy bugs, leaf miners, g-moth, and others.* It seems to be fairly specific in attacking insects with piercing or rasping mouth parts. Since these are the pests that feed on plant tissues, they are our main target species. Unless beneficials like lady bugs, certain wasps, spiders etc. come in direct contact with spray; it does little to diminish their numbers.[/FONT]
 *[FONT=&quot]What about beneficial insects?[/FONT]*​ [FONT=&quot]Not all bugs are bad. Some are beneficial to plants because they eat the insects that feast on your plants.[/FONT]
 [FONT=&quot]One of the many benefits of using neem oil insecticide is that it doesn't harm beneficial insects, such as lady bugs because they don't eat your plants. They'd rather make lunch out of aphids and other plant destroyers.[/FONT]
 [FONT=&quot]Of course, you don't want insects in your home. But if you move your plants outside for any length of time, you may expose your neem-treated plant to the good bugs. Don't worry -- they won't be harmed.[/FONT]
*[FONT=&quot]SOURCES OF RELEVANT INFORMATION[/FONT]* 

_[FONT=&quot]Helson, B.V. 1992. Naturally derived insecticides: Prospects for forestry use. Forestry Chronicle 68: 349-354.[/FONT]_ 

_[FONT=&quot]Helson, B.V.; Lyons, D.B. 1999 Chemical and biorational control of the pine false webworm. pp. 17-22 in D.B. Lyons, G.C. Jones and T.A. Scarr, eds. Proceedings of a Workshop on the Pine False Webworm.[/FONT]_ 
_[FONT=&quot]CFS, Great Lakes Forestry Centre, Ontario Ministry of Natural Resources. Sault Ste. Marie, Ont. 49p.[/FONT]_ 

_[FONT=&quot]Helson, B.V.; de Groot, P.; McFarlane, J.W.; Zylstra, B.; Scarr, T. 1998. Leader and systemic applications of neem EC formulations for control of white pine weevil (Coleoptera: Curcolionidae) on jack pine and white pine. Proc. Entomol. Soc. Ont. 129: 107-113[/FONT]_ 

_[FONT=&quot]Helson, B.; Lyons, B.; de Groot, P. 1999. Evaluation of neem EC formulations containing azadirachtin for forest insect pest management in Canada. pp. 79-89 in RP [/FONT]_ 

_[FONT=&quot]Singh, RC Saxena (Eds.), Azadirachta indica A. Juss. International. Neem Conference, Gatton, Australia, Feb. 1996. Oxford & IBH Publishing Co. PVT. Ltd. New Delhi.[/FONT]_ 

_[FONT=&quot]Lyons, D.B.; Helson, B.V.; Jones, G.C.; McFarlane, J.W. 1998. Effectiveness of neem- and iflubenzuron-based insecticides for control of the pine false webworm, Acantholyda erythrocephala (Hymenoptera: Pamphiliidae). Proc. Entomol. Soc. Ont. 129: 115-126[/FONT]_ 

_[FONT=&quot]Lyons, D.B.; Helson, B.V.; Jones, G.C.; McFarlane, J.W.; Scarr, T. 1996. [/FONT]_ 
_[FONT=&quot]Systemic activity of neem seed extracts containing azadirachtin in pine foliage for control of the pine false webworm, Acantholyda[/FONT]_ 
_[FONT=&quot]erythrocephala (Hymenoptera: Pamphiliidae). Proc. Entomol. Soc. Ont. 127: 45-55.[/FONT]_ 

_[FONT=&quot]Wanner, K.W.; Helson, B.V.; Kostyk, B.C. 1997. Foliar and systemic applications of neem seed extract for control of spruce budworm, Choristoneura fumiferana (Clem.) (Lepidoptera:Tortricidae), infesting black and white spruce seed orchards. Can. Ent. 129: 645-655.[/FONT]_ 

[FONT=&quot]http://urbangardenmagazine.com/2010/11/neem-oil/[/FONT]

*[FONT=&quot]Natures Plant Protector[/FONT]*
*[FONT=&quot]Bill Sutherland from [/FONT]**[FONT=&quot]Growing Edge Technologies[/FONT]**[FONT=&quot] discusses neem oil and how it can form an important part of your indoor garden pest control program.[/FONT]*
*[FONT=&quot]
WHAT IS NEEM OIL?[/FONT]*


[FONT=&quot]Neem oil is a natural product derived from the seeds of the neem tree (_Azadirachta indica). _The neem tree is native to tropical and semi-tropical regions of South Asia but also grows in the Middle East and some parts of Africa. Most of the widespread cultivation and use of neem is in India, where it has been used for over two thousand years as a medicinal treatment for a plethora of ailments and disorders. The neem tree is an evergreen, which grows to around 60 ft (18 m) and produces white aromatic flowers followed by a small fruit that looks much like a large olive. Inside the fruit lies the payload; one large seed from which the oil is extracted by either cold pressing or solvent extraction. A by-product of neem oil extraction is a solid dried product called neem cake, which can be used as an organic fertilizer as well as a good method of controlling soil-dwelling pests. Here we will focus on the properties, uses and advantages of neem oil when used as a natural pest control agent for your homegrown fruits and flowers.[/FONT]
[FONT=&quot]Please note: Neem oil products are not currently registered for use as a pesticide in Canada.[/FONT]
*[FONT=&quot]What does neem oil do?[/FONT]*
[FONT=&quot]This may sound disappointing, but it needs to be said: neem is not an insecticide that kills on contact, and it has a low instant knock down effect. However, it is still very effective! Unlike other chemical insecticides, neem oil gets into an insects body after the ingestion of neem coated plant material and gets to work within a few hours. The predominant active component in neem oil is called azadirachtin, and once in a pests body it directly affects the hormonal system, more so than the digestive or nervous system. The way in which azadirachtin targets the hormonal system means that insects are far less likely to develop resistance in future generations. As well as azadirachtin, other liminoid compounds present in natural neem oil (nimbin, salanin, gedunin, azadirone, melandriol and more) play a significant collaborative role in deterring feeding and reducing pest populations.[/FONT]
*[FONT=&quot]Biological Effects of Neem Oil on Insects[/FONT]*
[FONT=&quot]Historical use and recent research studies show that a broad range of phytophagous (plant eating) pest insects are affected and can be controlled by neem oil, these include:[/FONT]


[FONT=&quot]Orthoptera: grasshoppers, katydids, crickets etc.[/FONT]
[FONT=&quot]Coleoptera: wide range of beetles/weevils[/FONT]
[FONT=&quot]Hemiptera: leafhoppers, aphids, psyllids & some scale insects[/FONT]
[FONT=&quot]Lepidoptera: cutworms, borers & caterpillars[/FONT]
[FONT=&quot]Thysanoptera: thrips[/FONT]
[FONT=&quot]Diptera: Sciarid fly, fruit fly, buffalo/blow & march fly[/FONT]
[FONT=&quot]Heteroptera: sucking bugs  Green veggie bug, spotted fruit bug etc.[/FONT]
[FONT=&quot]Others: nematodes, snails, and also some fungi and pathogenic viruses[/FONT]
*[FONT=&quot]1. Insect Growth Regulation[/FONT]*
[FONT=&quot]Neem oil is unique in nature since it works on juvenile hormones. The insect larva feeds and when it grows, it sheds its old skin and continues growing. This molting phenomenon, also know as _ecdysis,_ is predominantly governed by the enzyme _ecdysone. _When the ingested neem, or more specifically azadirachtin, enters into the body of larva, the activity of ecdysone is suppressed. This causes molting failure and results in the larva not developing to the next life stage, and ultimately dying. If only a small amount of neem-coated foliage is ingested, and the concentration of azadirachtin is insufficient to cause molting failure, the larva will manage to enter a short-lived prepupal stage where it will die. In some instances, where the concentration of azadirachtin is still less, the adult emerging from the pupa will be malformed and sterile, without any capacity for reproduction.[/FONT]
*[FONT=&quot]2. Feeding Deterrent[/FONT]*
[FONT=&quot]One of most important properties of neem oil is feeding deterrence. Most insects are permanently hungry during their larval stages, particularly when they are mobile on the leaf surface. An insects maxillary gland is responsible for initiating feeding. When these glands give a signal, peristalsis in the alimentary canal is increased, which makes the larva feel hungry, and makes it start eating. When a leaf is treated with neem oil, the presence of the liminoids azadirachtin, salanin and melandriol produces an anti-peristaltic wave in an insects alimentary canal, producing something similar to a vomiting sensation combined with a reduced ability to swallow. Because of this sensation, an insect will avoid feeding on neem-treated leaf surfaces.[/FONT]
*[FONT=&quot]3. Oviposition Deterrent[/FONT]*
[FONT=&quot]Another way in which neem oil reduces pests is by not allowing the females to deposit eggs. This property is known as oviposition deterrence, and quickly thwarts the pest population growth. Interestingly, studies by Knapp & Kashenge (Insect Sci. Applic.2003) on spider mites, and Singh & Singh (Phytoparasitica, 199 on fruit flies have shown that natural neem oil formulations are more effective as oviposition deterrents and insect mortality than azadirachtin concentrates alone. Results from Knapps & Kashenges study showed that azadirachtin does not seem to play a major role in the control of spider mites. Although, azadirachtin is an important component of neem oil, the other less studied ingredients seem to have a positive synergistic effect when it comes to effecting the behavior, effectiveness and mortality of plant pests.[/FONT]
*[FONT=&quot]Neem Oils Effect on Non-Target Species and Beneficial Insects[/FONT]*
[FONT=&quot]One of the problems with the use of chemical pesticides has been their impact on non-target species, particularly when used outdoors. Often they have proved harmful to other beneficial species present in the ecosystem. Neem oil products have proved to be remarkably benign to insects such as adult bees and butterflies that pollinate crops and trees, ladybugs that consume aphids, and wasps that act as parasites on various crop pests. As mentioned above, neem oil has to be ingested to be effective. Those insects that feed on plant tissues, therefore, easily succumb. However natural enemies that feed only on other insects, and bees and butterflies that feed on nectar rarely come in contact with significant concentrations of neem oil to cause themselves harm.[/FONT]
*[FONT=&quot]Neem Oils Other Benefits as a Foliar Spray[/FONT]*
[FONT=&quot]Beside its insecticidal and nematicidal properties, neem oil is also a promising agent for the control of viral and fungal plant diseases. Neem oil in combination with paraffin oil has been shown to greatly reduce disease incidences of the yellow vein mosaic virus of okra and legumes, and leaf curl of chili, all of which can cause enormous losses. Neem oil has also been shown to reduce transmission of the tobacco mosaic virus in greenhouse vegetable crops of pepper, cucumber and tomato.[/FONT]
[FONT=&quot]Neem oil has been demonstrated to suppress fungal activity. Fungi are constantly evolving enemies of growers and some can reach epidemic proportions. Neem oil has been shown to protect seeds against fungal diseases while in storage, and be beneficial as a preventative spray for fungal leaf diseases such as powdery and downy mildew.[/FONT]
[FONT=&quot]Neem oil also contains some key nutrients that make it a good foliar fertilizer. A typical good quality neem oil product found in your local grow store will contain the following plant nutrients:[/FONT]


[FONT=&quot]Total Nitrogen 1.20% by mass[/FONT]
[FONT=&quot]Phosphorus as P 0.07% by mass[/FONT]
[FONT=&quot]Potassium as K 0.01% by mass[/FONT]
[FONT=&quot]Magnesium as Mg 0.03% by mass[/FONT]
[FONT=&quot]Copper as Cu 10 ppm[/FONT]
[FONT=&quot]Magnesium, as Mn 0.40 ppm[/FONT]
[FONT=&quot]Zinc as Zn 20.00 ppm[/FONT]
[FONT=&quot]Iron content 14.00 ppm[/FONT]
[FONT=&quot]So, not only will regular spraying of neem oil onto your plant foliage control pests, it will also help prevent diseases and act as a foliage fertilizer! Amazing stuff.[/FONT]
*[FONT=&quot]How to Use Natural Cold-Pressed Neem Oil:[/FONT]*
*[FONT=&quot]Foliar Spraying[/FONT]*
[FONT=&quot]Like most of the vegetable oils, natural cold-pressed Neem oil is non-soluble in water and has to be made soluble with suitable emulsifiers before spraying. Some commonly available emulsifiers that can be used are liquid soaps, eco-friendly detergents, surfactants, wetting agents, soap nut powder, and many other organic emulsifiers.[/FONT]


[FONT=&quot]Collect together your equipment.[/FONT]
[FONT=&quot]To make 10 liters of spray-able neem, pour 1 liter of water into a container, add 1015 ml of liquid soap, or a suitable emulsifier, and agitate well until the soap/emulsifiers completely dissolve.[/FONT]
[FONT=&quot]To this solution add 50 ml of neem oil and agitate well until a pale yellowish white emulsion is formed.[/FONT]
[FONT=&quot]Add this prepared emulsion to 9 liters of water in a bucket and stir thoroughly. The neem solution is now ready for spraying.[/FONT]
[FONT=&quot]Spraying should be done within 8 hours of mixing, using a suitable sprayer. This solution can be used as a foliar spray on crops, and also can be sprayed on the surface of growing media for effective action against root pests.[/FONT]
[FONT=&quot]It is recommended to repeat the spraying 5 times at intervals of 7 to 10 days. Spraying should be undertaken during periods of low light intensity; outdoors or in greenhouses this should be in the early morning or late in the evening. If you grow under lights, raise them high and consider turning a few off to reduce light intensity before spraying.[/FONT]
*[FONT=&quot]Soil Drench[/FONT]*


[FONT=&quot]To make 10 liters of drench-able neem. Add 1 liter of water to a container. Add 2030 ml of liquid soap, or suitable emulsifier, and agitate well until the soap/emulsifiers completely dissolve.[/FONT]
[FONT=&quot]To this solution add 250350 ml of neem oil and agitate well until a pale yellowish white emulsion is formed.[/FONT]
[FONT=&quot]Add this prepared emulsion to 9 liters of water in a bucket and stir thoroughly. The neem solution is now ready to pour onto the growing medium. Apply enough for a small amount of run-off to occur.[/FONT]
[FONT=&quot]Please Note: Drenching potting soil with neem will adversely affect the beneficial biology of the rhizosphere. If you need to drench the root zone with neem, a follow up application with a good quality actively aerated compost tea will help to re-inoculate the beneficial bacteria, fungi and protozoa.[/FONT]
*[FONT=&quot]Neem Oils Effect on Plants[/FONT]*
[FONT=&quot]Neem oil not only coats the plant foliage after spraying, it is actually absorbed into the leaf material and can be transported around the plant systemically. Neems liminoid compounds (mainly azadirachtin) can be taken up by the roots after root zone applications, thereby reaching leaf and stem material throughout the whole plant. This reinforces the anti-feeding deterrent properties or neem oil, which makes the whole plant rather unappealing to invading pests.[/FONT]
[FONT=&quot]Due to this persistence in the plant, neem oil products should not be used on plants that are approaching maturity. As a general rule, avoid spraying or soil drenching neem oil on plants that have five weeks left before harvest. As mentioned above, neem products have been used topically and ingested for medicinal use by humans for thousands of years and are completely non-toxic. However, neem has a very bitter taste that can, if used too late in a plants life cycle, be passed into the developing consumable produce.[/FONT]
*[FONT=&quot]Summary of the Advantages of Neem Oil[/FONT]*


[FONT=&quot]Broad spectrum of activity[/FONT]
[FONT=&quot]No known insecticide resistance mechanisms[/FONT]
[FONT=&quot]Compatible with many other insecticides and fungicides[/FONT]
[FONT=&quot]New mode of action with possible multiple sites of attack[/FONT]
[FONT=&quot]Low use rates[/FONT]
[FONT=&quot]Compatible with other biological control agents for Integrated Pest Management programs.[/FONT]
[FONT=&quot]Not persistent in the environment[/FONT]
[FONT=&quot]Minimal impact on non-target organisms[/FONT]
[FONT=&quot]Formulation flexibility[/FONT]
[FONT=&quot]Application flexibility  can be sprayed or drenched[/FONT]


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## mellokitty (Jul 9, 2011)

*resounding applause*

subbed up....


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## woodsmaneh! (Jul 9, 2011)

[FONT=&quot]Occasionally, using dolomite lime is warranted, but the truth is, it often makes things worse, sometimes just a little, and sometimes a lot. Lets look at why...[/FONT]
*[FONT=&quot]What Is Dolomite Lime?[/FONT]*
[FONT=&quot]Dolomite lime is a rock. It can be quite pretty. It is calcium magnesium carbonate, CaMg(CO3)2. It has about 50% calcium carbonate and 40% magnesium carbonate, giving approximately 22% calcium and at least 11% magnesium.[/FONT]
[FONT=&quot]When you buy it for your garden, it has been ground into granules that can be course or very fine, or it could be turned into a prill.[/FONT]
[FONT=&quot]Now, dolomite lime is even allowed in organic gardening. It is not inherently bad, but how it is used in the garden is usually mildly to severely detrimental.[/FONT]
*[FONT=&quot]Why Are We Told To Use Dolomite Lime?[/FONT]*
[FONT=&quot]I have touched on this before when I talked about pH. The idea is that minerals in your soil are continuously being leached by watering and consequently your soil is always moving towards more acidic.[/FONT]
[FONT=&quot]Dolomite lime is used to counteract this, to sweeten the soil. It can do that, but that doesnt mean its good.
[/FONT]
*[FONT=&quot]Why Are Minerals Leaching From Your Soil?[/FONT]*
[FONT=&quot]Minerals may or may not be leaching from your soil. If they are, it could be partially because of watering, but there are other reasons, too.[/FONT]
[FONT=&quot]If your soil is low in organic matter, which is generally the case, it probably cant hold onto minerals very well, especially if it is low in clay and high in sand and silt. If you have lots of clay, you probably dont have much to worry about.[/FONT]
[FONT=&quot]Chemical fertilizers cause acidity, so if you use them, that is part of the problem, too. Dolomite lime is not the answer. Organic gardening is. Lets look at why dolomite is probably not what you want.[/FONT]
*[FONT=&quot]Heres The Important Part[/FONT]*
[FONT=&quot]The main point I want to make is that even if minerals are leaching from your soil, it doesnt make sense to blindly go back adding just two of them (the calcium and magnesium in dolomite lime) without knowing you need them. You might already have enough or too much of one or both of them. We need to think a little more than that when organic gardening.[/FONT]
[FONT=&quot]Your soil needs a calcium:magnesium of somewhere between 7:1 (sandier soils) and 10:1 (clayier soils). Outside of this range, your soil will have water problems, your plants will have health problems and insect and disease problems, and you will have weed problems.[/FONT]
[FONT=&quot]One of your most important goals in the garden is to add specific mineral fertilizers to move the calcium to magnesium ratio towards this range. As a side note, I understand it may seem strange to some that we should have to do this, but our soils are way out of balance and were trying to grow things that wouldnt naturally grow there, so we have to do this.[/FONT]
[FONT=&quot]The problem with dolomite lime? It has a calcium:magnesium ratio of 2:1. Thats way too much magnesium for most soils. Magnesium is certainly an essential mineral. Too much of it, however, causes many problems, compaction being one of the most common, but also pest and weed problems.[/FONT]
[FONT=&quot]So if you add this to your lawn every year, chances are youre just causing more compaction and weed problems.[/FONT]
*[FONT=&quot]When Should You Use Dolomite Lime?[/FONT]*
[FONT=&quot]You should only use dolomite lime when you have a soil test showing a huge deficiency of magnesium in your soil.[/FONT]
[FONT=&quot]Even then, calcitic lime (calcium carbonate) is generally the way to go because it has a small amount of magnesium and often a calcium:magnesium ratio of about 10:1, with a calcium content 34% to 40% or more.[/FONT]
[FONT=&quot]I use calcitic lime regularly in my organic gardening, but even then, only when I need it. A soil test is the main way to find out if you need it.[/FONT]


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## woodsmaneh! (Jul 9, 2011)

*[FONT=&quot]Managing Soluble Salts[/FONT]*​*[FONT=&quot][/FONT]**[FONT=&quot]Texas Greenhouse Management Handbook[/FONT]*​ [FONT=&quot]The presence of excessive soluble salts is perhaps the most limiting factor in the production of greenhouse crops. Generally speaking salt accumulations result from the use of poor quality irrigation water, over fertilization or growing media with an inherently high salt content. Although soluble salts can inhibit plant growth, when managed properly their effects may be reduced.[/FONT]
*[FONT=&quot][/FONT]*​ *[FONT=&quot]Salt Injury to Plants[/FONT]*[FONT=&quot][/FONT]
[FONT=&quot]Plant injury resulting from excessive soluble salts may first occur as a mild chlorosis of the foliage, later progressing to a necrosis of leaf tips and margins. This type of injury is largely attributed to the mobility of soluble salts within the plant. As these salts are rapidly translocated throughout the plant, they accumulate at the leaf tips and margins. Once the salts reach a toxic level they cause the characteristic "burn" associated with excessive salts.[/FONT]
[FONT=&quot]Roots may also be injured by the presence of soluble salts. This often predisposes the plant to a wide range of root diseases (i.e., phythium, fusarium, etc.). Extreme injury may also interfere with water uptake and result in excessive wilting of the plant. It is extremely important to inspect the root systems of plants on a regular basis in order to monitor the effects of soluble salts.[/FONT]
*[FONT=&quot]Irrigation Water[/FONT]*[FONT=&quot][/FONT]
[FONT=&quot]Irrigation water is a major contributor of soluble salts to the growing medium. These occur primarily as salts of Na, Ca and Mg, although others may be present.[/FONT]
[FONT=&quot]Soluble salts in irrigation water are measured in terms of electrical conductivity (EC). The higher the salt content the greater the EC. In general EC values exceeding 2.0 millimhos/ cc are considered detrimental to plant growth. Water quality should be monitored on a frequent basis in order to avoid potential problems from soluble salts.[/FONT]
*[FONT=&quot]Fertilizers[/FONT]*[FONT=&quot][/FONT]
[FONT=&quot]Fertilizers are forms of salts and therefore contribute to the total soluble salt content of the growing medium. Depending on the inherent salt content of the irrigation water used, fertility levels must be adjusted to avoid salt accumulations.[/FONT]
[FONT=&quot]Fertilizers are often classified by the amount of total salts they contain. This "salt index" can be used to determine the amount of salts contributed to the growing medium. Table 1 presents the salt index of a number of commonly used fertilizers.[/FONT]
[FONT=&quot]Table 1. Relative salt index for several fertilizers.[/FONT]
*[FONT=&quot]Fertilizer[/FONT]*[FONT=&quot][/FONT]
*[FONT=&quot]Salt index[/FONT]*[FONT=&quot][/FONT]
[FONT=&quot]Sodium nitrate[/FONT]
[FONT=&quot]100[/FONT]
[FONT=&quot]Potassium chloride[/FONT]
[FONT=&quot]116[/FONT]
[FONT=&quot]Ammonium nitrate[/FONT]
[FONT=&quot]105[/FONT]
[FONT=&quot]Urea[/FONT]
[FONT=&quot]75[/FONT]
[FONT=&quot]Potassium nitrate[/FONT]
[FONT=&quot]74[/FONT]
[FONT=&quot]Ammonium sulfate[/FONT]
[FONT=&quot]69[/FONT]
[FONT=&quot]Calcium nitrate[/FONT]
[FONT=&quot]53[/FONT]
[FONT=&quot]Magnesium sulfate[/FONT]
[FONT=&quot]44[/FONT]
[FONT=&quot]Diammonium phosphate[/FONT]
[FONT=&quot]34[/FONT]
[FONT=&quot]Concentrated superphosphate[/FONT]
[FONT=&quot]10[/FONT]
[FONT=&quot]Gypsum[/FONT]
[FONT=&quot]5[/FONT]​ [FONT=&quot]Sodium nitrate was arbitrarily set at 100. The lower the index value the smaller the contribution the fertilizer makes to the level of soluble salts.[/FONT]
*[FONT=&quot]Growing Media[/FONT]*[FONT=&quot][/FONT]
[FONT=&quot]Growing media can be formulated from a variety of components. These include peat, perlite, vermiculite, pine bark and others. Generally speaking these materials do not contain excessive quantities of soluble salts. However it is important to monitor the quality of media components carefully.[/FONT]
[FONT=&quot]In some cases it is necessary to thoroughly leach a medium before using it. This is particularly important for seed germination and other forms of propagation. Leaching may be accomplished by running water through individual pots or trays prior to planting or by leaching the entire volume of bulk medium.[/FONT]
[FONT=&quot]For a quantitative evaluation of this process the electrical conductivity of the leachate may be evaluated. When the EC is less than 2.0 millimhos the medium is free of excessive salts.[/FONT]
*[FONT=&quot]Managing Soluble Salts[/FONT]*[FONT=&quot][/FONT]
[FONT=&quot]Managing soluble salts involves an integrated approach to production. This includes the type of growing medium used, irrigation frequency, water quality, fertility regime and plant tolerance.[/FONT]
[FONT=&quot]Growing media should contain a substantial quantity of large pores to facilitate good drainage. Media with these characteristics are easily leached and reduce the potential for the accumulation of soluble salts. When irrigating this medium it is important to apply enough water to allow sufficient quantities to leach through the container. Approximately 15-20% more water than the container can hold should be applied at each irrigation if the salt hazard is high. Water pressure must be adjusted to avoid overflow.[/FONT]
[FONT=&quot]Since the concentration of soluble salts in plant tissues increases as moisture levels decrease, it is important to monitor the water content of the growing medium. In the presence of excessive soluble salts, growing media should not be allowed to dry out. Maintaining adequate moisture levels can be difficult in porous growing media and requires careful attention.[/FONT]
[FONT=&quot]Providing adequate fertility is important in maintaining optimum plant growth. However if fertility levels are too high injury from soluble salts may occur. Determining the amount of nutrients to use must be based on the quality of irrigation water as well as the fertilizer's salt index. Generally most fertility regimes used for the production of potted greenhouse crops are between 150 and 350 ppm (N). Higher levels of fertility create a much greater potential for injury from soluble salts.[/FONT]
[FONT=&quot]Perhaps the most effective means of managing soluble salts is to avoid producing salt sensitive plants. Each plant species has a distinct response to salt accumulations and growers often can select those with tolerance. Among the plants with a known susceptibility to soluble salts are chlorophytum, African violets, calceolaria, chrysanthemums, geraniums and petunias.[/FONT]


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## woodsmaneh! (Jul 9, 2011)

*[FONT=&quot]Most Common Problems[/FONT]*[FONT=&quot]
The *most common problems are over watering and over fertilizing*, followed closely by an incorrect pH and root bound. Before any corrective steps are taken these factors must be ruled out. 


*Nutrient Deficiencies* - Nutrient deficiencies in modern gardens are really rare. What most people see as a Nutrient Deficiency is, 9 times out of 10, a pH problem. A pH that is too high or too low locks out your plants ability to uptake nutrients. Since the plant can not uptake those nutrients they appear to be deficient. When in fact, there are plenty of nutrients in the solution/soil but, due to pH Lock-out, they are unavailable to the plant. Adding supplements or more nutrients (which is what most do) will only compound this problem by throwing the pH off even more and further raising the nutrient PPM. The best thing to do if you suspect ANY form of nutrient deficiency is to check and adjust the pH as necessary. The proper pH ranges for both hydroponics & soil is shown in the chart below. Pay particular attention to the ranges that certain nutrients are available and when they are locked out.

[/FONT]
[FONT=&quot] 

[/FONT]*[FONT=&quot]Over Watering[/FONT]*[FONT=&quot] - Signs of over watering include: Leaf wilting/drooping and Chlorosis (Leaf Yellowing). Also, smelly soggy soil is another indication in soil gardens.

*Solution* - Increase the temperature and airflow to evaporate some of the excess water. Also, you can add some h2o2 when watering to help the roots still receive O2. And just dont water as much. You should only water when your soil/medium is dry. If you have smelly soggy soil the best thing to do is transplant it into fresh dry soil.


*Over Fertilizing* - Signs of over fertilization include: dead/burnt leaf tips/margins and leaves curling under.

*Solution* - Check and adjust the pH level as necessary. Flush and decrease the fertilizer/nutrient level.

*pH Problems* - pH problems can manifest it self in many different ways. Anywhere from: nutrient deficiencies to over fertilization and leaf burn. The key to telling which you have is, knowing your pH.

*Solution* - Check and adjust the pH level as necessary.


*Root Bound* - _See root bound below in the *Root Problems* section._


*Heat Stress* - Signs of heat stress can look a lot like nutrient burn, except it occurs only on the top of the plant closest to the lamps. A yellowing of the upper leaves is usually a bleaching from being too close to HID lights.

*Solution* - A good test to see if your lights are too close is to put your hand between the light and the plant. If your hand gets too hot for comfort, the light is too close and needs to be moved up higher.



*Leaf Problems*

*Yellowing (Chlorosis)* - Chlorosis is a yellowing of leaf tissue due to a lack of chlorophyll. Possible causes of chlorosis include poor drainage, damaged roots, compacted roots (see Root Bound below), high alkalinity, and nutrient deficiencies. Nutrient deficiencies may occur because there is an insufficient amount in the soil or because the nutrients are unavailable due to a high pH. ***Note*- Always check the pH before increasing nutrient level. In the last few weeks of flowering a yellowing of the leaves is completely normal as the plant uses up all stored nutrients.


*Yellowing - Lower/Middle Leaves* - Yellowing of the lower leaves/older growth is a sign of a possible Nitrogen (N) deficiency. Nitrogen is a transferable element (this means the plant can move it around as needed). If a plant is not receiving enough Nitrogen from the roots then it will rob Nitrogen from the older growth. Plants that are Nitrogen deficient will exhibit a lack of vigor and grow slowly resulting in a weak and stunted plant that is significantly reduced in quality and yield. In a Hydroponic system, usually the pH is too high and has locked out the available Nitrogen. In soil a yellowing of the lower leaves could also be an indication of a root bound plant (see Root Bound below).

*Solution* - First, check the pH, and adjust if necessary. The correct pH for marijuana is 6.3 - 6.8 in soil and 5.5 - 6.1 in a hydroponic system. Second, make sure you are giving the correct amount/type of fertilizer/nutrients. For the vegetative stage of growth marijuana needs a fertilizer/nutrient with a high Nitrogen (N) content like 2-1-1 (or 20-10-10).


*Yellowing - Upper (New Growth)* - Yellowing of the upper (new growth) of the plants could be a sign of a Sulphur (S) deficiency. Sulphur deficiency is pretty rare but usually start off as a yellowing of the entire younger leaf including the veins. Other signs of sulfur deficiency are: Elongated roots, woody stems, and Leaf tips curling downward. ***Note- Most yellowing of the upper leaves is a bleaching from being too close to the lights.*

*Solution* - Check and adjust the pH level as necessary. Check your fertilizer/nutrient levels and make sure you are giving the correct amount/type for you particular stage of growth. Also a good test to see if your lights are too close is to put your hand between the light and the plant. If your hand gets too hot for comfort, the light is too close and needs to be moved up higher.


*Leaf Curling Up* - Leaf curling up can be a sign of a Magnesium (Mg) deficiency caused by too low of a pH level. Magnesium deficiency will show as a yellowing (which may turn brown and crispy) and interveinal (in between the veins) yellowing beginning in the older leaves. Interveinal chlorosis (yellowing) will start at the leaf tip and progressing inward between the veins. It could also be a sign of excess heat and humidity in the grow room.

*Solution* - Check and adjust the pH level as necessary. When the pH is not at the proper level marijuana will lose its ability to absorb some of the essential elements required for healthy growth. If youre growing in soil Magnesium will begin to be locked out at a pH of 6.5 and lower, in hydro it starts at 5.8 and below. If the pH is correct, then add 1 teaspoon of Epsom salts per each gallon to your water. Or, to foliar feed them, add a ½ teaspoon per quart to a spray bottle. ***Note*- If your tap water is over 200 ppm Magnesium will be locked out due to the calcium in the water. Magnesium can get locked out by too much Calcium (Ca), Chlorine (Cl) or Ammonium Nitrogen (NH4+). If this is your problem we suggest using bottled or RO (reverse osmosis) water. 


*Leaf Curling Down* - When the leaves curl under and burn at the tips and margins its usually a sign that the nutrient level is too high.

*Solution* - Check and adjust the pH level as necessary. Flush and decrease the nutrient level. 


*Droopy Leaves* - Leaves that are drooping are most likely caused by over watering/under watering or lack of light.

*Solution* - First off, for soil, Place you finger into your soil a few inches and see if it's dry or wet. If over watering is your problem, increase the temperature and airflow to evaporate some of the excess water also you can add some h2o2 when watering to help the roots still receive O2. ***Warning!*- Chronic over watering can lead to soggy roots and stagnant, icky soil. if you slide the plant out of the pot to check the soil and it stinks or is soggy then transplant into fresh dry soil. For a hydroponic system, check to see if your medium is dry or wet before you water (or your pump comes on). If your medium is still pretty wet, then you are over watering and need to water less often. If your medium is very dry before watering, under watering is your problem, just water more frequently. And lastly, If lack of light is the problem, Add more light.









*Root Problems*

*Root Bound* - Root bound is where the roots of your plant outgrow the container they are potted in. Plants that are root bound exhibit stunted growth, stretching, smaller and slower bud production, easier to burn with nutrient solution, needs watering too often, and wilting. A root bound plant will always start yellowing with the bottom leaves and work its way up the plant until all the fan leaves are gone.

*Solution* - To fix this problem you need to transplant your plant into a bigger pot. The 'rule of thumb' with soil is 1 gallon of soil for every foot of growth except for clones which can use a smaller size. So a 2' tall plant is going to need AT LEAST a 2 gallon container. First thing you need to do is gently remove your plant from its smaller container. While its out, inspect its roots, if the roots run in a tight circle around the outside of the root ball, you caught it just in time. Very carefully use your fingers to dig into the outside 1/2" of these circular roots, loosen them up and pull them gently (yes, I said gently




) outward. If the roots are extremely tight, you can VERY carefully slice a thin layer (less then a ½") off the outside of the entire root-ball. Once you have tended to the roots Its time to replant it. Set the now un-bound root-ball into its new larger pot.***Note*- Do not pack down this new soil, you want the soil to be settled (with no air pockets) but loose enough to allow the roots to easily penetrate it.


*Stunted Roots* - Stunted roots (slow or no new root growth) is could be caused by a calcium deficiency, aluminum toxicity, copper toxicity, pH acidity, or soil toxicity.

*Solution* - As always check and adjust the pH level as necessary. If soil toxicity, of any kind, is your problem then you need to flush it real good.



*Stem Problems*

*Stem Breakage* - Everyone from time to time has had this problem or will. This is when your stem is broken. Stem breaks can come from a number of things: training, dropping something on it, animals, weather. No matter how it happened the most important thing is to not panic.






*Solution* - Fixing this is not really a problem. Splint it with something and tape it in place. Marijuana has a great ability to come back even after a stem break. Give her a week or so to recover before she will start to grow again. And be more careful next time![/FONT]


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## woodsmaneh! (Jul 18, 2011)

*Only IBL and F4 seeds are uniform.

[FONT=&quot]What is an F1, F2, and IBL

[/FONT] [FONT=&quot]An IBL (inbred line) is a genetically homogeneous strain that grows uniformly from seed.[/FONT]
 [FONT=&quot]A hybrid is a strain made up of two genetically unlike parents, IBL or hybrid.[/FONT]
 [FONT=&quot]When you cross two different IBL strains for the FIRST time, it is called the F1 generation. When you cross two of the same F1 hybrid (inbreed), it is called the F2 generation.[/FONT]
 [FONT=&quot]The process of selective inbreeding must continue at least until the F4 to stabilize the recurrently selected traits. When you cross two specimens of an IBL variety, you get more of the same, because an IBL is homozygous, or true breeding for particular traits.
[/FONT]*


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## woodsmaneh! (Jul 18, 2011)

*[FONT=&quot]You can use up to 25% in you soil mix, I think Sub-cool is now using it in his supersoil mix.


What are Worm Castings? [/FONT]*[FONT=&quot]Worm Castings are Mother Natures soil enrichment of choice. This rich humus-like digested output of the worm includes a wide range of nutrients and microbial life that all types of vegetation require to grow. Worm Castings are one of the most natural soil enrichments available and more importantly are environmentally friendly, all natural, easy to use, and safe to handle, with a pleasant earthy aroma.[/FONT]

*[FONT=&quot]What do Worm Castings do? [/FONT]* [FONT=&quot]Worm Castings restore soil health in many ways.[/FONT]
 · [FONT=&quot]A source of organic matter with lots of nutrients a nd moisture-holding capacity. Worm[/FONT]
 [FONT=&quot]Castings hold 9 times their weight in moisture, which is beneficial in drought[/FONT]
 [FONT=&quot]conditions .[/FONT]
 · [FONT=&quot]Adds active microbial life to the soil, allowing it to slowly release and make the[/FONT]
 [FONT=&quot]valuable nutrient and trace minerals more available to tender plant roots.[/FONT]
 · [FONT=&quot]Rich in growth hormones and vitamins, and acts as a powerful biocide against[/FONT]
 [FONT=&quot]diseases and nematodes.[/FONT]
 · [FONT=&quot]A natural aerator, allowing oxygen to permeate the root zone to improve drainage and[/FONT]
 [FONT=&quot]encourage root growth.[/FONT]
 · [FONT=&quot]Restores soil without fear of burning or harming tender plant life.[/FONT]
 [FONT=&quot]Restoring the soil makes nutrients more available to crops, turf applications and desired[/FONT]
 [FONT=&quot]vegetation. This means there is less need for synthetic fertilizers and pesticides. Best of all, Worm Castings contain no toxins and are therefore safe to use without fear of ground water contamination.[/FONT]

*[FONT=&quot]How are Worm Castings different from Compost?[/FONT]* 
 [FONT=&quot]Worm Castings are significantly better than compost. They are the result of carefully selected compost that is fully digested by worm. This makes Worm Castings an entirely mature product. It contains no pathogenic agents, and is considered a biological product which is convenient to handle. Worm Castings contain a far more diverse microbial population than other composts. These micro-organisms play an important part in soil fertility. Not only do they mineralize complex substances into plant-available nutrients, but bacteria in the worms digestive system also synthesize a whole series of biologically active substances including plant growth hormones.[/FONT]

*[FONT=&quot]How do Worm Castings work?[/FONT]* 
 [FONT=&quot]Worm Castings are an all-purpose natural soil enrichment that is pure earthworm castings. It is 100% non-toxic and odourless. It is the product of aerobically composted vegetable scraps fed to earthworms, and free from weed seeds, toxins and pathogens.[/FONT]

*[FONT=&quot]WORM CASTINGS[/FONT]* 

*[FONT=&quot]Worm Castings improve Soil Structure in all Soil Types[/FONT]* 
 [FONT=&quot]Worm Castings restore soil structure. The term soil structure is used to describe the way soil particles are grouped into aggregates. Soil structure is affected by biological activity, organic matter, and cultivation and tillage practices. Soil fertility and structure are closely related. An ideal soil structure is often described as granular or crumb-like. It provides for good movement of air and water through a variety of different pore sizes. Plant roots extend down, and soil animals  including small earthworms  travel through the spaces between the aggregates. An ideal soil structure is also stable and resistant to erosion. The clay-humus complex, in combination with adequate calcium which helps to bind the aggregates together, forms the basis of this structure. The glutinous by-products of soil bacteria and the hair-like threads of actinomycetes and fungi mycelium add to soil stability. All tillage operations change soil structure. Excessive cultivation, especially for seedbed preparation, can harm soil structure. Working clay soil when wet leads to compaction and subsequent soil puddling. The soil is easily puddled by rain, easily eroded, and will have poor aeration. Tillage, when too dry, shatters the aggregates. Soil structure can be enhanced by careful cultivation, growing sod crops and returning crop residues. Worm Castings (organic matter) and the humification process improve structural stability, and can rebuild degraded soil structures. Therefore it is vital to return organic material to the soil and to maintain its biological activity, which helps to improve the soil structure.[/FONT]

*[FONT=&quot]How Worm Castings work with Soil pH[/FONT]* 
 [FONT=&quot]Worm Castings act like a buffer for plants. Where soil pH levels are too high or low, Worm Castings make soil nutrients available again to the plant. Compared to the soil itself, Worm Castings are much higher in bacteria, organic material and available nitrogen, calcium, magnesium, phosphorus and potassium.[/FONT]

*[FONT=&quot]WORM CASTINGS [/FONT]* 

*[FONT=&quot]Soil Biology[/FONT]* 
 [FONT=&quot]Soil organisms play an important role in forming and stabilizing soil structure. In a healthy soil ecosystem, fungal filaments and exudes from microbes and earthworms help bind soil particles together into stable aggregates that improve water infiltration and protect soil from erosion, crusting and compaction. Macrospores formed by earthworms and other burrowing creatures facilitate the movement of water into and through soil. Good soil structure enhances root development, which further improves the soil.[/FONT]
 [FONT=&quot]Restoring soil structure helps reduce runoff and improve the infiltration and filtering capacity of soil. In a healthy soil ecosystem, soil organisms reduce the impacts of pollution by buffering, detoxifying- and decomposing potential pollutants. Bacteria and other microbes are increasingly used for remediation of contaminated water and soil.[/FONT]
 [FONT=&quot]In a healthy soil ecosystem, soil biota regulates the flow and storage of nutrients in many ways. For example, they decompose plant and animal residue, fix atmospheric nitrogen, transform nitrogen and other nutrients among various organic and inorganic forms, release plant available forms of nutrients, mobilize phosphorus, and form mycorrhizal (fungus -root) associations for nutrient exchange. Even applied fertilizers may pass through soil organisms before being utilized by crops. A relatively small number of soil organisms cause plant disease. A healthy soil ecosystem has a diverse soil food web that keeps pest organisms in check through competition and predation. Some soil organisms release compounds that enhance plant growth or reduce disease susceptibility. Plants may exude specific substances that attract beneficial organisms[/FONT]
 [FONT=&quot]or repel harmful ones, especially when they are under stress from activities such as grazing.[/FONT]

*[FONT=&quot]Microbial Activity[/FONT]* 

 [FONT=&quot]Worm Castings stimulate microbial activity. Although earthworms derive their nutrition from microorganisms, many more microorganisms (such as bacteria, fungi and actinomycetes) are present in their feces or casts than in the organic matter that they consume. As organic matter passes through their intestines, it is fragmented and inoculated with microorganisms. Increased microbial activity facilitates the cycling of nutrients from organic matter and their conversion into forms readily taken up by plants.[/FONT]
 [FONT=&quot]Compared to synthetic fertilize r formulations, Worm Castings contain relatively low[/FONT]
 [FONT=&quot]concentrations of actual nutrients, but they perform important functions, which the synthetic formulations do not. They increase the organic content and consequently the water-holding capacity of the soil. They improve the physical structure of the soil, which allows more air to get to plant roots. Where organic sources are used for fertilizer, bacterial and fungal activity increases in the soil. Mycorrhizal fungi, which make other nutrients more available to plants, thrive in soil where the organic matter content is high.[/FONT]

*[FONT=&quot]Water Availability[/FONT]* 
 [FONT=&quot]Worm Castings contain a high percentage of humus. Humus helps soil particles form into clusters, which create channels for the passage of air and improve its capacity to hold water. The castings are in the form of tiny pellets which are coated with a gel. This crumb-like structure helps improve drainage and aeration.[/FONT]

*[FONT=&quot]Balancing Soil Nutrient[/FONT]* 
 [FONT=&quot]The ability of the micro biologically active Worm Castings to regenerate the nutrients from the atmosphere, organic matter and water allows them to replace those lost from chemical fertilizers by leaching, plant uptake and chemical reactions. In relation to moisture holding capacity and improvement of soil structure, chemical fertilizers have negligible effect, as they primarily consist of water-soluble salts. On the other hand, the aggregate nature of the Worm Castings has appreciable water holding capacity, and its use leads to restored soil structure and increases nutrient reserves in soil. The presence of nitrogen fixing bacteria in Worm Castings means that nitrogen can be fixed[/FONT]
 [FONT=&quot]from the atmosphere and converted to plant soluble nitrates. Worm Castings are rich in humus, which contains essential plant nutrients and micronutrients. Moreover, these castings are also rich in vitamins, beneficial microorganisms, antibiotics and enzymes.[/FONT]
 [FONT=&quot]Worm Castings restore soil, will not wash out with watering, and will not burn even delicate plants. Worm castings have a very soil-like texture and all the necessary nutrients that plants, crops and all types of vegetation require. The castings slowly release nutrients when required by the plants. Castings are high in soluble nitrogen, potash, potassium, calcium, magnesium and many other trace elements. Worm Castings allow plants to quickly and easily absorb all essential nutrients and trace elements. Because the earthworm grinds and uniformly mixes the nutrients and trace elements into simple forms (1 to 2 microns), plants need only minimal effort to absorb these nutrients.[/FONT]
*[FONT=&quot]SUGGESTED APPLICATION RATES[/FONT]* 
*[FONT=&quot]Potted Plants, Seeds, Seed Flats [/FONT]* · [FONT=&quot]Use 1 part Worm Castings to 3 parts potting soil mix[/FONT]
*[FONT=&quot]Potted Plans, Window Boxes, Hanging Baskets ([/FONT]* [FONT=&quot]established)[/FONT]
 · [FONT=&quot]Add 1 to 2 inches of Worm Castings to top of soil[/FONT]
 · [FONT=&quot]Mix in, taking care not to damage shallow roots[/FONT]
 · [FONT=&quot]Water well[/FONT]
 · [FONT=&quot]Repeat every 2 to 3 months[/FONT]
*[FONT=&quot]Lawns[/FONT]* 
 [FONT=&quot](established)[/FONT]
 · [FONT=&quot]Use Worm Castings as a top dress at 10 lbs. per 1000 sq. ft.[/FONT]
 · [FONT=&quot]Apply twice a year  in spring and once again in late fall[/FONT]
*[FONT=&quot]Lawns[/FONT]* 
 [FONT=&quot](new)[/FONT]
 · [FONT=&quot]Apply 10 lbs. of Worm Castings to 1000 sq. ft.[/FONT]
 · [FONT=&quot]Work lightly into topsoil[/FONT]
 · [FONT=&quot]Mix in grass seed[/FONT]
 · [FONT=&quot]Cover with shredded straw and keep watered[/FONT]
*[FONT=&quot]Roses, Trees, Bushes, Berries[/FONT]* 
 [FONT=&quot](new or freshly transplanted)[/FONT]
 · [FONT=&quot]Mix 1 part Worm Castings to 3 parts soil[/FONT]
 · [FONT=&quot]Surround newly dug hole with mixture[/FONT]
 · [FONT=&quot]In the hole, spread root over a mound of the mix, and cover[/FONT]
*[FONT=&quot]Bushes [/FONT]* · [FONT=&quot]Use 5 lbs. of Worm Castings per 10 Bushes[/FONT]
*[FONT=&quot]Perennials [/FONT]* · [FONT=&quot]Work ½ cup of Worm Castings into the soil above root zone,[/FONT]
 [FONT=&quot]taking care not to damage the shallow roots[/FONT]
 · [FONT=&quot]Apply in spring, early summer, and fall[/FONT]
*[FONT=&quot]Tables and Annual Flowers [/FONT]* · [FONT=&quot]Line bottom and sides of plant holes/seed furrows with[/FONT]
 [FONT=&quot]1 to 2 inches of Worm Castings[/FONT]
 · [FONT=&quot]Set plants/seeds in place and cover with soil[/FONT]
 [FONT=&quot]During the growing season, side dress once every 2 months at a[/FONT]
 [FONT=&quot]rate of ½ cup per plant or 1 cup per linear foot of row[/FONT]
*[FONT=&quot]Gardens [/FONT]* · [FONT=&quot]Apply 5 lbs. of Worm Castings per square foot[/FONT]
*[FONT=&quot]Note: [/FONT]* [FONT=&quot]The release time for nutrients is around 4 months for continual release of nutrients.[/FONT]
 [FONT=&quot]Repeat application is recommended at 4 month intervals.[/FONT]
 [FONT=&quot]Application rates may vary depending on soil test results.[/FONT]

*[FONT=&quot]Worm castings vs. Chemical fertilizers in Soil1[/FONT]* 
*[FONT=&quot]Criteria for Comparison Chemical Fertilizers Worm Castings[/FONT]* 
*[FONT=&quot]Macro Nutrient Contents[/FONT]* 
 [FONT=&quot]Mostly contains only one (N in urea) or at the most two (N & P in DAP)[/FONT]
 [FONT=&quot]nutrients in any one type of chemical fertilizer[/FONT]
 [FONT=&quot]Contains all nutrients in sufficient[/FONT]
 [FONT=&quot]quantities, i.e., nitrogen (N),[/FONT]
 [FONT=&quot]phosphorus (P) and potassium (K)[/FONT]
*[FONT=&quot]Secondary Nutrient Contents[/FONT]* 
 [FONT=&quot]Not Available[/FONT]
 [FONT=&quot]Calcium (Ca), manganese (Mn) and sulphur (S) are available in required quantities[/FONT]
*[FONT=&quot]Micro Nutrients Contents[/FONT]* 
 [FONT=&quot]Not Available[/FONT]
 [FONT=&quot]Zinc (Zn), boron (B), manganese, (Mn), iron (Fe), copper (Cu), molybdenum (Mo) and chorine (Cl)[/FONT]
 [FONT=&quot]are also present[/FONT]
*[FONT=&quot]pH balancing[/FONT]* 
 [FONT=&quot]Distorts soil pH, which creates saline and alkaline conditions[/FONT]
 [FONT=&quot]Helps control soil pH and corrects the salinity and alkalinity in soil[/FONT]
*[FONT=&quot]EC Correction[/FONT]* 
 [FONT=&quot]Creates imbalance in soil EC, affecting nutrients assimilation[/FONT]
 [FONT=&quot]Helps balance the EC to improve plant nutrient adsorption[/FONT]
*[FONT=&quot]Organic Carbon[/FONT]* 
 [FONT=&quot]Not Available[/FONT]
 [FONT=&quot]Very high organic carbon and humus contents improve soil characteristics[/FONT]
*[FONT=&quot]Moisture Retention Capacity[/FONT]* 
 [FONT=&quot]Reduces moisture retention capacity of the soil[/FONT]
 [FONT=&quot]Increases moisture retention capacity of the soil[/FONT]
*[FONT=&quot]Soil Texture[/FONT]* 
 [FONT=&quot]Damages soil texture to reduce aeration[/FONT]
 [FONT=&quot]Improves soil texture for better aeration[/FONT]
*[FONT=&quot]Beneficial Bacteria and Fungi[/FONT]* 
 [FONT=&quot]Reduces biological activities and thus the fertility is impaired[/FONT]
 [FONT=&quot]Very high biological life improves the soil fertility and productivity on sustainable basis[/FONT]
*[FONT=&quot]Plant Growth Hormones[/FONT]* 
 [FONT=&quot]Not Available[/FONT]
 [FONT=&quot]Sufficient quantity helps in better growth and production[/FONT]


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## woodsmaneh! (Jul 18, 2011)

*I have well water and it is 380ppm so I use a RO system with double DI filters to bring it down to under 8ppm and it PH is 7.0

Municipal water supplies* 

Many indoor gardeners are reliant on municipal water supplies and have few other options for a better quality water source. Its likely that some plant losses have and do occur as a result of some municipal water supplies, particularly in sensitive species and in water culture systems where there is no media to act as a buffer. On the other hand, many municipal water supplies are quite suitable and given that they have had organic matter and pathogens removed already, are a good deal as far as hydroponic systems go. Interestingly plants have rather different responses and requirements from a water supply than humans and this is where problems can occur. Municipal water treatment ensures that drinking water meets the World Health Organization (WHO) and EPA standards for mineral, chemical and biological contamination levels, making it generally very safe to drink and use. However, what is safe for us to drink may not be so good for plant growth, particularly when we consider many hydroponic systems are recirculating which allows build-up of unwanted contaminants in the plant root zone. 


Recirculating solution culture systems such as NFT have less buffering capacity to water treatment chemical residues than organic media-based systems.

Water treatment options used by municipal suppliers change over time and hydroponic growers should be aware of the implications of these. Many years ago the main concern was the use of chlorine as a disinfection agent to destroy bacteria and human pathogens. Chlorine had the advantage in that it disinfected water effectively; however, residual chlorine in water sources, which could often be detected by smell, could be toxic to sensitive plants and where it built up in certain hydroponics systems. Also when chlorine reacts with organic matter it forms substances (trihalomethanes) which are linked to increased risk of cancer and other health problems. Chlorine was, however, quite easy to remove from water with the use of aeration or even just aging the water a few days before irrigating plants. In the 1990s it was found that some organisms such as Cryptosporidium were resistant to chlorine and the resulting health issues from this meant that drinking water regulations were changed and alternative disinfection methods began to be used. These included use of ozone and UV light, chloramines (chlorine plus ammonia) and chlorine dioxide. 

Filtration, flocculation, settling, UV and ozone used for water supply treatment are non-problematic as far as hydroponic systems go, as they leave no residue and are effective. However, use of chloramines and some of the other chemicals by municipal water treatment plants may still pose problems where high levels are regularly dosed into water supplies. Chloramines are much more persistent than chlorine and take a lot longer to dissipate from treated water, so gardeners who are concerned can use a couple of different treatment methods just as those with aquarium fish often choose to do. There are specifically designed activated carbon filters which can remove most of the chloramines in a domestic water supply and also dechloraminating chemical or water conditioners available in pet shops. Carbon filters must be of the correct type that have a high quality granular activated carbon and allow a longer contact time which is required for chloramines removal. Even then not every trace may be removed, but levels are lowered enough to prevent problems. Use of ascorbic acid (vitamin C) is also used in the industry, and by laboratories to remove chloramines from water after they have done their disinfection job.
Chemicals are also added to drinking water to adjust its hardness or softness, pH and alkalinity. Water that is naturally acidic is corrosive to pipes and sodium hydroxide may be added to reduce this. Sodium is a contaminate we dont need in hydroponic systems, but may be present at surprisingly high levels in certain water supplies. Domestic water softeners may also contaminate the water with sodium which is not seen as a problem for drinking, but can run amuck with a well balanced hydroponic system and sodium sensitive crop.

*What water problems may look like* 

Its extremely difficult to determine if something in the water supply is causing plant growth problems. Root rot pathogens may originate in water, but they can come from a number of sources, including fungal spores, blown in dust or brought in by insects. Mineral problems can be a little easier to trace if the water supply analysis is available to check levels of elements. Plant problems which may be caused by water treatment chemicals are difficult to diagnose as some plants are much more sensitive than others and the type of system also plays a role.* Research studies have reported that chloramines in hydroponic nutrient solutions can cause growth inhibition and root browning in susceptible plants.* One study reported that the critical chloramines amount at which lettuce plant growth was significantly inhibited was 0.18 mg Cl/g root fresh weight, however, the levels at which some other species would be damaged is as yet undetermined. Similar problems exist with the use of other water treatment chemicals; chlorine and hydrogen peroxide are good disinfection agents, but too much in the hydroponic nutrient will cause root damage and just what is a safe level is dependant on a number factors such as the level of organic loading in the system. 

*Hard water* 

Hard water is water that has a high mineral content, usually calcium and magnesium, with calcium present as calcium carbonate or calcium sulfate. Hard water can occur in wells and municipal sources and has a tendency to form hard lime scale on surfaces and equipment. A hard water supply is generally not a major problem for hydroponic gardens; calcium and magnesium are useful elements for plant uptake, however, high levels in the water can upset the balance of a nutrient solution making other ions less available. Commercial growers routinely use hard water supplies and adjust their nutrient formulation to take into account the Ca and Mg naturally occurring in the water and also adjust for any alkalinity problems with water acidification. Smaller growers can use one of the many excellent hard water nutrient products on the market to get a similar effect. 

*Ground water  wells* 

Many commercial hydroponics growers use well water for hydroponic systems and adjust their nutrient formulations to suit the natural mineral content of their water supply. Smaller growers would be advised to find out what is in their well water source just to check for potential problems as water which has percolated through soils tends to pick up some minerals and in some areas, high levels of unwanted elements such as sodium or trace elements. Well water can also contain pathogens and may need treatment before use, although often it is just the mineral levels that need adjustment. Water from dams, lakes and springs is usually similar to well water, but can contain much higher levels of sediment, organic matter and fungal pathogen spores. 

*Rain water* 

Rain water collection can be a good way to bypass problems with municipal or well water in some areas; however, there are still some risks. Acid rain from industrial areas, sodium in coastal sites and high pathogen spore loads in agricultural areas can still occur. Generally rain water is low in minerals, but in the process of collection from roofs and other surfaces, can collect wind blown dust and fungal spores. While this is generally not a problem for healthy plants, rain water should be treated before use with young seedlings and clones where pathogens could infect sensitive tissue and open wounds. 

*Solutions to water quality problems* 

Organic material such as coconut fiber gives a greater buffering capacity for some water problems, including residues from chemical water treatments, than solution culture systems. Drain to waste media systems are also useful where the water supply contains unwanted elements such as sodium as these arent as susceptible to the accumulation that can occur where the solution is recirculated over a long period of time. Where problems with unwanted minerals and very hard water exist, frequent changing and replacement of the nutrient in the system can also be useful to keep things in balance. Water with a high alkalinity will need considerably more acid to keep the pH down to acceptable levels than water with low alkalinity; however, by acidifying the water first before making up a nutrient solution or adding to the reservoir, much less acid will need to be added to the system to adjust pH over time. 
There are a range of other treatment options that indoor gardeners can use to improve the quality of their water supply. If pathogen contamination is an issue, slow sand filtration is one of the most effective methods, although perhaps not that practical for those with limited space. Chemical disinfection methods for pathogen control include hydrogen peroxide, chlorine and other compounds, although care should be taken that most of the active chemical has dissipated before the water is used to make up the nutrient solution. Heat, distillation, reverse osmosis and UV treatment can all be used for pathogen control, with many small RO and UV treatment systems now on the market. UV filters for aquariums can be used for small hydroponic growers to treat water with good success, provided sufficient contact time is allowed. If excess minerals or unwanted elements such as sodium are present in a water supply, reverse osmosis (RO) or distillation can be used to remove these. Organic matter in ground water sources can be removed with settling and filtration and treatment with H2O2, while chemical contamination problems and removal of water treatment compounds are more easily treated with the correct type of activated carbon filter with a sufficient contact time.

*Super-charged water for hydroponics* 

While it seems logical that pure, clean and demineralized water is the best place to start when making up a hydroponic nutrition solution, the possibility of creating a water source that has certain benefits for plants is a relatively new concept. Water is not just a carrier for essential nutrient ions, the nutrient solution becomes a whole biological system in its own right with organic matter, root exudates, various species of microbes including fungi, bacteria and their by-products (both good and bad), beneficial and unwanted mineral elements and a range of additives growers may be using. Some studies have found that inexplicable growth increases could be obtained using certain ground water sources compared to rain or RO (essentially pure) water to make up a hydroponic nutrient solution indicating there may be natural factors in such waters which have benefits. Not all ground water sources have this effect; in fact, some can have negative influences on plant growth. Furthermore, another essential plant nutrient  oxygen in dissolved form - is usually present in water supplies; however, some water treatment processes can drive much of the dissolved oxygen (DO) out of a water source. In theory it would be possible to not only remove those things in the water we dont want  pathogen spores, unwanted minerals, chemical residues from water treatment - but to also boost the water with useful properties such as a high DO content, a population of useful and disease suppressant microbes and some natural and potentially beneficial minerals and compounds. One way of achieving this would be with the use of slow sand filters or mineral filters for water supplies which are inoculated with beneficial microbes and with oxygenation of the water for a few days before making up nutrient solutions or topping up reservoirs. Further down the track we may see quicker and easier methods of supercharging water for hydroponic systems, taking water quality to a whole new level of science.


*Chlorine Gas:*
This highly reactive halogen gas is volatile enough that can be easily detected by its odor, especially in the shower or when aerating faucets are used. This is one of chlorines short-comings as a disinfectant: It off-gases (volatilizes) from exposed water. Hobbyists have made good use of this effect for many years. Chlorinated tap water, especially drawn through an aerating faucet, will off-gas and effectively lose all its chlorine to the atmosphere within days. Some growers may not fully understand the off-gassing process and may not use the most effective setup for off-gassing. The best process is an open-top container with a power head or pump to circulate the water, or even just an air stone. This obviously calls for a relatively large container, but it also means that fewer containers are needed, as the circulation greatly enlarges the effective surface area for off-gassing. Exposed surface area is critical. The best situation without circulation in theory could be shallow trays with large surface exposed to room air, but that is impractical in application  it would be very messy and require large amounts of space. Buckets are acceptable, but not overfilled, please. If bottles must be used, do not fill past the shoulder (where the bottle starts narrowing)  this will allow the largest possible surface exposure. I used 45gal tanks or food-safe plastic tubs (trash can scale), both with pumps and heaters, open-topped. I have never detected residual chlorine after 24 hours operation in these, but allowed 48 hours for safety and to remove the requirement for routine testing. Static containers may or may not be safe to use after just 24 hours. Most, with good surface area exposed, will be after 48 hours, but this is best confirmed by test. If after you have found the required time for off-gassing, then you can add a bit more to ensure removal and no longer routinely test so long as the utility does not change the concentration. We no longer have hobby liquid tests for chlorine or chloramine, but must rely on swimming pool tests.
If you do not have the space and time to off-gas chlorinated water, there are many products available which will neutralize the dissolved chlorine. The active ingredient historically was sodium thiosulfate, and it is still highly effective for this use. This material captures any free dissolved chlorine gas and coverts the elemental chlorine (Cl2 dissolved gas) to the chloride ion (Cl-) which is harmless at those concentrations. The reaction is rapid. Just add the recommended amount, stir very briefly and add to the reservoir.
With dissolved chlorine gas disinfectant, there is only one job to be done, and it can be accomplished in two ways: Remove the chlorine gas (off-gassing), or inactivate it (chemical conversion to the chloride ion by thiosulfate). These are simple and straightforward.
*Chloramines:*
The growing situation with chloramines is more complex and demanding. We cannot efficiently off-gas chloramines, so the simplest solution with chlorine does not apply at all. We equally cannot use just thiosulfate  it does not do enough. There are 3 separate and distinct jobs, all of which must be done to ensure the safety of chloraminated water for use in our reservoir:

1. Break the chloramine-ammonia bond. Thiosulfate alone can do this at about the same dosage used for chlorine-only disinfectant.

2. Convert the freed dissolved gas chlorine (Cl2) to chloride ion (Cl-). Thiosulfate again can do this as well; at about the same dosage as before, so double the chlorine-only dose can do both of these two jobs well.

3. Lock the freed ammonia dissolved gas (NH3) into the ammonium ion (NH4+) form (which is usable by the nitrification bacteria). The former is toxic; the concentration may only be high enough to damage the plants, or can be high enough to kill them. Thiosulfate alone is useless for this job, regardless of the dosage. Thiosulfate has no effect whatsoever on dissolved ammonia gas. Bummer! We must use newer and specialized agents which specify on the bottle that they do each and all of the three jobs required.
There are a number of commercial products which specify in print that they destroy (or other terms to that effect) chloramines. That is valid even if the only active agent is thiosulfate  it does break the chlorine-ammonia bond which defines chloramine, so technically the chloramine is no longer there. Does that mean the water so treated is safe to use? No, it definitely does not. The freed chlorine gas must be converted to chloride ion, but as with the bond breaking, thiosulfate can do that as well, and is cheap and safe - so double the chlorine-only dose and cover the freed chlorine as well. Is the water now safe to use in the reservoir tank? No, unfortunately not. It still has all the ammonia released floating around at hazardous levels. If the product does not specify that it locks the ammonia into the harmless ammonium ion form, or at least notes that it neutralizes both the chlorine and the ammonia released, we have to assume it does not do this  commercial products never claim less that they do. Destroying chloramine is required, but is not sufficient. This is a key point, do not be misled. Both of the freed dissolved gases must be neutralized to make the water safe. This is where the marketing wizards take advantage of the chemically and biologically naïve. You do have to both read and understand the fine print, or you could kill your fish. Strictly as an FYI, yes, I have killed fish that way. I will not do that again. Specialized agents are available which do the whole job  break the chloramine bond and convert both freed toxic gases to harmless ions. Unfortunately, this is another situation where you cannot trust your local fish store, nor the chains, or mail-order houses. They quite likely do not understand the chemistry themselves. You need to ask on-line for suggestions of brands which do all the necessary jobs reliably, or search the manufacturers site for detailed information  if they do not clearly state that all three tasks are done, that product is not suitable.
There is another complication with post-chloraminated water. It still reads positive for ammonia on most hobby test kits. Read the information on your test kit for ammonia. If it specifies that it reads total ammonia nitrogen (or TAN), you will see positives with your test after using a good anti-chloramines agent. These are not false positives. They are real and valid, but do not necessarily indicate a hazard to your fish  which the kit instructions historically have listed as hazardous. Remember that ammonium ion (NH4+) is harmless, only ammonia dissolved gas (NH3) is dangerous, just as was the case for chlorine gas versus the ion form. The effective anti-chloramine agents lock all free ammonia gas into the ammonium ion form  which is harmless. The problem is that our 20th century tests are no longer adequate in this century. There are tests available which read only free ammonia (NH3), but to me they are not yet user-friendly. Technology changes rapidly these days, hopefully more user-friendly but adequate test kits will available soon. Until then, we must use the proper dose of an effective agent and rely on it working, or prescreen with difficult-to-use tests.
For what it is worth, I use Seachems Prime for chloramines, and Genesis for chlorine-only.
References:
1. http://en.wikipedia.org/wiki/Chlorination
2. http://en.wikipedia.org/wiki/Chloramine
3. http://www.epa.gov/ogwdw000/disinfectio  index.html
4. http://www.lenntech.com/processes/disin  lorine.htm
5. http://www.lenntech.com/processes/disin  amines.htm


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## april (Jul 18, 2011)

Wow buddy, WOW!!! awesome shit!!


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## woodsmaneh! (Jul 18, 2011)

[FONT=&quot]Occasionally, using dolomite lime is warranted, but the truth is, it often makes things worse, sometimes just a little, and sometimes a lot. Lets look at why...[/FONT]
*[FONT=&quot]What Is Dolomite Lime?[/FONT]*
[FONT=&quot]Dolomite lime is a rock. It can be quite pretty. It is calcium magnesium carbonate, CaMg(CO3)2. It has about 50% calcium carbonate and 40% magnesium carbonate, giving approximately 22% calcium and at least 11% magnesium.[/FONT]
[FONT=&quot]When you buy it for your garden, it has been ground into granules that can be course or very fine, or it could be turned into a prill.[/FONT]
[FONT=&quot]Now, dolomite lime is even allowed in organic gardening. It is not inherently bad, but how it is used in the garden is usually mildly to severely detrimental.[/FONT]
*[FONT=&quot]Why Are We Told To Use Dolomite Lime?[/FONT]*
[FONT=&quot]I have touched on this before when I talked about pH. The idea is that minerals in your soil are continuously being leached by rain and consequently your soil is always moving towards more acidic.[/FONT]
[FONT=&quot]Dolomite lime is used to counteract this, to sweeten the soil. It can do that, but that doesnt mean its good.[/FONT]
*[FONT=&quot]Why Are Minerals Leaching From Your Soil?[/FONT]*
[FONT=&quot]Minerals may or may not be leaching from your soil. If they are, it could be partially because of rain, but there are other reasons, too.[/FONT]
[FONT=&quot]If your soil is low in organic matter, which is generally the case, it probably cant hold onto minerals very well, especially if it is low in clay and high in sand and silt. If you have lots of clay, you probably dont have much to worry about.[/FONT]
[FONT=&quot]Chemical fertilizers cause acidity, so if you use them, that is part of the problem, too. Dolomite lime is not the answer. Organic gardening is. Lets look at why dolomite is probably not what you want.[/FONT]
*[FONT=&quot]Heres The Important Part[/FONT]*
[FONT=&quot]The main point I want to make is that even if minerals are leaching from your soil, it doesnt make sense to blindly go back adding just two of them (the calcium and magnesium in dolomite lime) without knowing you need them. You might already have enough or too much of one or both of them. We need to think a little more than that when organic gardening.[/FONT]
[FONT=&quot]Your soil needs a calcium:magnesium of somewhere between 7:1 (sandier soils) and 10:1 (clayier soils). Outside of this range, your soil will have water problems, your plants will have health problems and insect and disease problems, and you will have weed problems.[/FONT]
[FONT=&quot]One of your most important goals in the garden is to add specific mineral fertilizers to move the calcium to magnesium ratio towards this range. As a side note, I understand it may seem strange to some that we should have to do this, but our soils are way out of balance and were trying to grow things that wouldnt naturally grow there, so we have to do this.[/FONT]
[FONT=&quot]The problem with dolomite lime? It has a calcium:magnesium ratio of 2:1. Thats way too much magnesium for most soils. Magnesium is certainly an essential mineral. Too much of it, however, causes many problems, compaction being one of the most common, but also pest and weed problems.[/FONT]
[FONT=&quot]So if you add this to your lawn every year, chances are youre just causing more compaction and weed problems.[/FONT]
*[FONT=&quot][/FONT]*
[FONT=&quot]You should only use dolomite lime when you have a soil test showing a huge deficiency of magnesium in your soil.[/FONT]
[FONT=&quot]Even then, calcitic lime (calcium carbonate) is generally the way to go because it has a small amount of magnesium and often a calcium:magnesium ratio of about 10:1, with a calcium content 34% to 40% or more.[/FONT]
[FONT=&quot]A soil test is the main way to find out if you need it.[/FONT]


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## woodsmaneh! (Jul 18, 2011)

*[FONT=&quot]NPK Basic Components of Fertilisers [/FONT]*
Most compound fertilisers will contain three elements essential for growth, NPK which stands for Nitrogen (N) Phosphorus (P) and Potassium (K). These elements help plants grow in different ways and an understanding of this will help you when choosing the correct fertiliser for a plant or for a stage in the development of a plant.
When you buy a packaged commercial fertiliser you will see an analysis of the NPK content. An equally balanced fertiliser may be described as 5:5:5 - 5% Nitrogen, 5% Phosphorus and 5% Potassium. You may also see Potassium described as Potash.
*Nitrogen the N in NPK* 

Nitrogen is used by the plant to produce leafy growth and formation of stems and branches. Plants most in need of nitrogen include grasses and leafy vegetables such as cabbage and spinach. Basically, the more leaf a plant produces, the higher its nitrogen requirement. See  nitrogen requirements of vegetables.
Although 78% of the atmosphere is nitrogen, most plants cannot utilise this. Plants in the bean family, legumes, have nodules on their roots where bacteria live that fix nitrogen from the air for use by the plant. They provide their own nitrogen fertiliser this way.
*Shortage of Nitrogen in Plants - Symptoms* 

You can tell if your plants need nitrogen when their growth is stunted with weak stems and they will have yellowed or discoloured leaves 
*Application of Nitrogen* 

Nitrogenous fertilisers are quickly washed out of the soil by rain and need to be renewed annually. With crops that require a lot of nitrogen over a period of time, like cabbages, adding nitrogen incrementally through the growth period is the most efficient application method.  
*Phosphorus the P in NPK* 

Phosphorus is essential for seed germination and root development. It is needed particularly by young plants forming their root systems and by fruit and seed crops. Root vegetables such as carrots, swedes and turnips obviously need plentiful phosphorus to develop well. 
*Shortage of Phosphorus in Plants - Symptoms* 

Without ample phosphorus you will see stunted growth, probably a purple tinge to leaves and low fruit yields. 
*Application of Phosphorus* 

Phosphates remain in the soil for two or three years after application so the amount in a general fertilizer is probably enough. Add just before planting or top dress during growth periods. 
*Potassium the K in NPK* 

Potassium has the chemical symbol  *K* from its Latin name kalium. It promotes flower and fruit production and is vital for maintaining growth and helping plants resist disease. It's used in the process of building starches and sugars so is needed in vegetables and fruits. Carrots, parsnips, potatoes, tomatoes and apples all need plenty of potassium to crop well.
Potassium is naturally found in wood ash which is where it its name potash is derived from To recap poatsh is potassium and vice versa when discussing fertilisers. 
*Shortage of Potassium in Plants - Symptoms* 

Plants that are short of potash will have low resistance to disease, scorching of leaves and poor fruit yield. Tomatoes will really show the effects of a shortage of potassium  
*Application of Potassium* 

Potash usually last for two or three years in the soil but for vegetable production (tomatoes, potatoes especially) additional will be required. This can be applied as a liquid feed, either commercial or made from comfrey, for tomatoes or a specially prepared fertiliser, high in potassium for potatoes. 
*[FONT=&quot]Additional Elements in Plant Nutrition[/FONT]* 

Although NPK is always mentioned when discussing plant nutrition and fertilisers, calcium, magnesium and sulphur are technically considered major elements or macro nutrients as well. Deficiencies of these will cause a crop to fail as certainly as a lack of one of the 'big three', NPK 
More information on NPK - nitrogen, phosphorus and potassium or potash 
Apart from these additional elements, plants also require trace elements in minute quantities. These are known as micro-nutrients. More information on trace elements or micro-nutrients 
*Calcium (Ca)* 

Calcium is required for the plant to utilise and transport other nutrients internally, particularly phosphorus. Without calcium the plants growth will be stunted In soils where the pH is correct for vegetable growing (usually between 5.5 and 7.5) it is usually available. Shortages are easily corrected by liming (agricultural lime is primarily calcium carbonate) or the addition of gypsum. There is a fascinating article on gypsum by Dr Sarvesh Kumar Shah on the site. 
*Sulphur (S)* 

Sulphur is vital for protein production and management in the plant. Symptoms of sulphur deficiency are similar to those of lack of nitrogen, low growth rates, yellowing of the leaves etc. and brassicas, which are sensitive to lack of nitrogen, are sensitive to lack of sulphur. 
Sulphur deficiency is not usually a problem It is a component of artificial fertilisers, sulphate of ammonia, superphosphates etc. It used to literally fall from the skies when coal fires and coal fired power stations pumped it into the air in the smoke. Clean air means this no longer happens to the same extent.
The main loss of sulphur from the soil is caused by leaching and in the removed crops. Composting kitchen wastes and foliage will return the sulphur to the soil. Green manures will prevent leaching and return sulphur as well.
Lack of sulphur can be corrected by adding sulphur or artificial fertilisers containing sulphur. It is very unlikely you will need to correct sulphur levels and differentiating sulphur deficiency from nitrogen deficiency will require laboratory analysis
*Magnesium (Mg)* 

Magnesium is essential for the formation of chlorophyll (it is the central atom in the chlorophyll molecule C 55H 72O 5N 4 *Mg* ) and deficiency is quite common. The visible symptom of magnesium deficiency is yellowing between the veins of leaves, eventually growing to cover the whole leaf. Because chlorophyll, which is what causes leaves to be green, is the power house of the plant, absorbing the energy from sunlight to process nutrients, lack of chlorophyll results in:
 

Reduced yield and stunted growth.
Increased susceptibility to disease.
Eventually death of the plant.
 Magnesium deficiency is most often seen in tomatoes followed by potatoes and fruits like apples, currants and gooseberries. The reason for this is that all these crops like high levels of potassium to produce high yields and potassium can lock up magnesium, making it unavailable to the plants. This is why better commercial tomato feeds include magnesium as part of their formulation.
Often incurable viral disease in tomatoes is confused with magnesium deficiency but attempting to cure by adding magnesium can do no harm and is worth trying anyway.
Curing a magnesium deficiency is reasonably easy. Plants can quickly absorb magnesium through the leaves, a process known as foliar feeding, so spraying with Epsom salts (magnesium sulphate) is effective. Mix 20g/litre and using a fine spray, cover the plant. Excess solution can be watered into the soil.
To ensure there is enough magnesium available in the soil, instead of using ordinary lime in the rotation you can use dolomite lime which contains around 8% magnesium. You can also obtain magnesium sulphate in bulk as the mineral kieserite. Do not over use dolomite limestone or kieserite as too much will induce potassium deficiency. Like many things in growing, correct balance is the objective.
*Trace Elements in Plant Nutrition * 

These are elements that are vital to plant growth but are only required in minute amounts, very much like vitamins in human diets. They are known as micro-nutrients because of the tiny amounts found in normal soils.  
For the average home vegetable grower micro nutrients are an acedemic rather than a practical subject. Identifying micro nutrient deficiencies is difficult even for experts and usually requires laboratory analysis. With iron deficiency, even laboratory analysis is difficult.
Luckily for us, most of these deficiencies are very rare and rotation, use of compost and manures will cure them. 
*Boron (B)* 

Boron is necessary for calcium to perform its functions in the plant but too much boron is also harmful to the plant. Excess use of magnesium sulphate will also cause a boron imbalance. The symptoms of boron deficiency are poor development of the growing tip of the plant. It is more likely in soils with pH above 6.5. 
Confirming boron deficiency is a job for laboratory analysis. Adding borax to the soil will correct the deficiency but borax is also a herbicide. For garden growers who are unlikely to want to pay for professional testing and recommendations the best advice is to avoid over use of magnesium sulphate, rotate and use plenty of home made compost.
*Copper (Cu)* 

Copper deficiency is rare but can occur on sandy, peaty and chalky soils with their high pH levels. It is required for root formation. Once again it requires professional analysis to confirm and to determine a proper course of action to rectify. Usually the single use of a copper sulphate based fungicide (Bordeaux mixture) will re-stock the soil for as long as you are likely to grow on it. 
Excess copper is very toxic to plants and to people. In plants it causes reduced growth, yellowing of the foliage, and stunted root development
*Iron (Fe)* 

Iron deficiency causes yellowing of the leaves and a general lack of vigour. It is fortunately rare but unfortunately hard to both diagnose or determine by laboratory analysis.  
Generally not something the home grower needs to concern himself with but should you suspect you have it then use sulphate of iron fertilizer 
*Manganese (Mn)* 

Manganese deficiency is often caused by over liming and is most often found on peaty and sandy soils with a high pH. Symptoms are similar to iron deficiency and can be confirmed by laboratory analysis of the leaf. Susceptible crops include peas and beets. 
Adding sulphur to the soil, which will increase the acidity (decreasing pH) will solve the problem.
The following micro-nutrients are rarely lacking and analysis and remedy are professional jobs. Normal additions of composts and manures will resolve deficiency problems. Excess in the soil will probably be due to industrial contamination.
*Molybdenum (Mo)* 

Molybdenum is only required in minute amounts, excess is as harmful as molybdenum deficiency.  
*Zinc (Zn)* 

Zinc deficiency is more likely in soils with high pH than low. Crops most sensitive are tomatoes, onions and beans.  

n the 19 th century the primary power source of transport was the horse and instead of carbon monoxide the waste productive was fertiliser. This waste product in turn powered market gardens and farms in crop production. 

*Farmyard & Animal Manures to Improve Soil Fertility * 


Nowadays obtaining these waste products is not as easy, but it is still possible and animal manures have the major benefit of adding humus to the soil. Humus improves the soil by acting as a sponge to retain and release water for plants as well as opening the structure, allowing roots to more easily grow and obtain nutrients from the mineral content of the soil. Finally, humus provides a base of the micro-fauna of the soil. Everything from bacteria and nematodes to earthworms rely on humus and our plants rely on them.  
*Horse Manure.* 

Considered by many gardeners to be the finest sort of animal manure you can use. Riding schools and stables often have large quantities of horse manure that they will be happy to give away or at least sell cheaply. Often they are prepared to deliver and even in a city you may well find sources. In London the army and police both have stables that have been know to give away their waste problem to grateful gardeners.  
Check your local paper for an advert or just call local stables and ask.
The best horse manure comes from stables that bed their horses on straw. Manure from horses bedded on wood shavings takes much longer to rot down but is still well worth having.
Check the manure and if it contains a large proportion of wood shavings in relation to dung and urine, then pile it for a year before using it in the garden
*Cow Manure* 

Often dairy farmers will deliver rotted cow manure for garden use, but usually in large quantities. Although not quite as good as horse manure, it is well worth using and will add humus as well as fertilise the soil. Some gardeners consider it a little wet for clay soils but by the same token better for light sandy soils. 
With both cow and horse manure they can be applied fresh in the autumn on to dug ground and forked or rotovated in to the top soil in the spring. The action of rain will wash out some nitrogen though and straw and wood shavings may only be partially decomposed. 
With large amounts of manure, the best way is to pile it up and cover with a tarpaulin, turning after a month or so. This will decompose any straw or wood shavings and also kill off any weed seeds that have survived the animal's gut. 
Small amounts are probably best handled by mixing into the compost heap as an activator. 
*Poultry and Pigeon Manure* 

If you keep a few chickens then you will have a constant supply of chicken droppings as well as a daily delivery of fresh eggs. You can always approach local free-range egg suppliers who may well have poultry droppings to dispose of. 
Pigeon fanciers are often in the same position of having a waste disposal problem you can help them with. Remember the pigeon fancier may well be in the centre of a city.
With all poultry manure it is generally too strong to use directly on the garden but it does make an excellent activator for a compost heap. There is little bulk in poultry manure so using it as an activator makes most sense. The only plant that you can apply it to directly is comfrey. 
*Pig Manure* 

Pig manure is only really useful if it is mixed with straw. If it is neat it will not have much organic matter and it should just be added to a compost heap. The main problem with pig manure is that it is unpleasant to smell and this can result in complaints from those around even if you are not bothered.  
*Goat Manure* 

Goat manure has a similar proportion of minerals and trace elements as horse manure so is well worth seeking out and using if you can find a goat keeper willing to part with it. 
*Sheep Manure* 

To obtain sheep manure you will probably have to collect it yourself with the permission of the landowner. It is unlikely that you would be asked to pay for it. Although it is a fair bit of work to collect it, sheep manure is excellent for making a liquid manure feed. 
Just place the droppings in a hessian sack or any porous container that you can place in a barrel of water. After a couple of weeks remove the sack and use the contents on the compost heap. The liquid feed can be applied to boost ailing plants in need of extra nitrogen.
*Rabbit & Rodent Pet Manure* 

These are actually quite high in nutrients but the quantities are going to be quite small. The best use of them is in the compost heap as an activator. 
*Cat and Dog Manure* 

Both cat and dog droppings can carry organisms harmful to human beings. Dog droppings can contain the eggs of the parasitic worm, toxocara, which can also infect humans. Cats can carry toxiplasma, another disease that can be passed on to humans. Accordingly it is safer to dispose of these elsewhere rather than use them  

When you look at a farmer's field full of cauliflowers, all fat and looking wonderful and then look around the average allotment site's offering you have to wonder what the farmer knows that we don't. 
The fact is that the farmer makes his living from his crops and invests in getting the best possible yield. First of all the farmer needs to know what the optimum nutrient supply for the crop should be, so he has the soil analysed to find out what is already there in his ground. From this starting point he calculates what he is going to need to add and decides how to add it.
The average gardener or vegetable grower isn't going to spend out for a laboratory soil analysis and there is an argument that providing the optimum nutrition for growth doesn't provide necessarily produce the best flavour either. High nitrogen supplies also tend to produce lush growth, beloved by aphids, so our pest problems can be made worse by too much fertiliser use.
Over-use of fertilisers is, from the farmer's point of view, a waste of money as there is no benefit to it. It can also cause environmental problems, causing algal blooms in streams and rivers.
Having said all of that, starving our plants is not going to produce good results and it's worth looking at what the nutritional requirements of our plants are and how we can supply them. Before we do that, it's important to understand what the components of fertilisers are and what they do - see What the NPK Means in Plant Fertiliser
Different fertilisers will provide different percentages of various nutrients so the quantity added will depend on the content. For example, if you want to add 10g of nitrogen per square metre you would need to add 83g of dried blood (12% nitrogen) or 50g of sulphate of ammonia (20% nitrogen) but if you wanted to supply that nitrogen from cow manure you would need 1,660g at its average 0.6% supply. 
Of course, your cow manure will supply valuable humus that the fertilisers will not. There's more information on the NPK Values of Common Manures and Composts 
Unlike artificial fertilisers, the 'natural' fertilisers tend to dissolve slowly and thereby release their nutrients more slowly. More information on natural fertilisers.
*Artificial Fertilisers* 

These are manufactured chemicals or sometimes mined and processed minerals. They are not usually approved for use in organic systems but they do not have any potential risks like pesticides to humans. More information on  artificial fertilisers.
Straight fertilisers are those that purely supply one element, like bloodmeal or hoof & horn. 
*Straight Artificial Fertilisers:* 

 NPK Levels in Straight Artificial Fertilisers​ 
 *N Nitrogen %*​ *P Phosphorus %*​ *K Potassium
(Potash) %*​ *Sulphate of Ammonia*
 20​ 

*Prilled Urea* 
 46​ 

*Nitro Chalk* 
 27​ 

*Nitrate of Soda* 
 16​ 

*Sulphate of Potash* 


 50​ *Superphosphate*

 18.5​ 
*Rock Phosphate* 

 26​ 
*Triple Superphosphate* 

 45​ 
*Basic Slag* 

 10​ 
​ *Compound Artificial Fertilisers*

Compound artificial fertilisers are produced by combining straight fertilisers in various proportions to form balances suitable for general growing or for specific crop requirements. 
 NPK Levels in Compound Artificial Fertilisers​ 
 *N Nitrogen %*​ *P Phosphorus %*​ *K Potassium
(Potash) %*​ *Growmore*
 7​ 7​ 7​ *Vitax Q4*
 5.3​ 7.5​ 10​ *J I Base*
 5.2​ 7.7​ 10​ *Chempack BTD*
 6​ 8​ 10​ *Hydro Complex*
 12​ 11​ 18​ *A potato fertiliser*
 7​ 5​ 12​ Many more compound fertilisers are available, often balanced to provide the NPK ratios favoured by specific crops such as tomato foods and incorporating various trace elements.
*Trace Elements & Micro-Nutrients * 

Just as people need vitamins and minerals in their diet for long term health, plants require other elements in their diet to thrive. Many of the compound fertilisers add these trace elements just as vitamins are added to some of our foods. These other elements are covered in  Additional Elements of Plant Nutrition and in Trace Elements or Micro-Nutrients of Plant Nutrition 
Having covered the range and types of fertilisers available let's take a look at some specific plant requirements and how we can meet them The main element for growth is nitrogen. Nitrogen is vital to the production of the leaves, which in turn power the plant's growth and the more leafy growth a plant produces the more nitrogen it will require.
Because nitrogen has the shortest life in the soil, being easily washed out by heavy rain for example, it is the one element to concentrate on and with crops that are in the ground for a long time worth applying in stages rather than one go. 
*Nitrogen Requirements of Various Crops * 

 *Very High Nitrogen Requirement*​ *High Nitrogen*​ *Medium Nitrogen*​ 

Brussels Sprouts
Cabbages
Rhubarb
 

Beetroot
Celery
Leeks
Spinach
 

Broccoli
Calabrese
Cauliflower
Lettuce
 
 *Low Nitrogen*​ *Very Low Nitrogen*​ *No Nitrogen*​ 

Asparagus
Runner Beans
Parsnip
Swede
Onion
 

Carrots
Radish
 

Peas
Broad Beans
 Remember that legumes produce their own nitrogen due to a symbiotic relationship with bacteria that fix nitrogen from the air for the plant, which is why peas and broad beans generally need no nitrogen supplement and runner beans with all their foliage need just low levels to supplement their own produced nitrogen.
Specific fertiliser requirements and feeding plans for various vegetables are listed below under resources along with other articles in this section.

*Fertiliser Tips * 

*Apply More Fertiliser for Light Soils* 

Light and free-draining soils, usually sandy in composition, lose nutrients more quickly than other types, especially in rainy spells. Apply fertiliser more frequently on these soils, especially nitrogen fertilisers to maintain levels. 
*Apply Less Fertiliser for Clay Soils* 

Heavy clay soils and soils containing a lot of organic matter require less frequent application. This is because both substances act as reservoirs holding the nutrients and releasing them slowly over time to the plants 
*Very Acid or Very Chalky Soils* 

Phosphates and potash become more soluble in an acid soil, making them easier for rain to wash away. In chalky (alkaline) soils, phosphate becomes insoluble when mixed with the calcium present in chalky soils. In both cases, divide the application into two or three and apply over the growing season. 
*Lime and Fertiliser* 

Never apply or store fertiliser and lime together. There will be a chemical reaction between the lime and the nitrogen in the fertiliser, making neither effective. Especially when growing vegetables, check and adjust if necessary the pH (acidity) of the soil. Acid soils may contain nutrients but they are less available to the plants. 
*Feed at the Right Time* 

Only add fertilisers to plants before and during the growing season. Applications made after the season will just be washed out of the soil and not do any good unless you use an over-winter green manure crop to hold them for the next season. 
*Boosting Failing Plants* 

If plants are showing signs of nutrient deficiency then you can give a boost using liquid fertilisers that are absorbed more quickly by the plant. Sometimes the problem isn't the amount of nutrient available but a lack of micro-nutrients preventing take-up by the plants. Try a spray of seaweed extract or a foliar feed with Epsom salts to release the nutrients. (see  Additional Elements in Plant Nutrition)
*Make Your Own Liquid Feeds* 

If you have comfrey or nettles available you can make your own liquid fertiliser by adding the leaves into a barrel of water and allowing them to ferment for three of four weeks. This will make a fertiliser high in potash, great for tomatoes and hanging baskets. 
A high nitrogen liquid feed can be made by suspending a hessian sack of horse or sheep droppings into a barrel of water until the water turns the colour of tea. 
*Controlled Release Fertilisers* 

When growing in containers or baskets you can use controlled release fertilisers. These gradually dissolve over the growing season ensuring a constant supply of nutrient is available to the plants over the season. 
Specific fertiliser requirements and feeding plans for various vegetables are listed below under resources along with other articles in this section.
_I am constantly surprised how many gardeners ignore liming. The acidity of the soil has a huge effect on fertility because the acidity of soil controls how available nutrients are to your crops._ 
_Clay soils are also harder to work the more acid they are for some complicated chemical reason._ 
Different soil types will behave differently so one vital tool for the serious gardener is a tester for acidity levels. You can also judge the acidity of the soil by the types of weeds that grow and their behaviour.
Sorrel, creeping buttercup, nettle, dock and mares tail are all signs your soil is becoming or is too acid. Reducing soil acidity will help deter some weeds  they are evolved for acid soils unlike our beloved crops.
*Soil PH Explained* 

The letters pH stand for Power of Hydrogen and is a measure of the molar concentration of hydrogen ions in the solution and as such is a measure of acidity. Wow! For us non-chemists and for gardeners the scale generally runs from 4.00, which is highly acid in soil terms, through 7.00 which is neutral to 8.00 which is alkaline.  
*To LOWER soil acidity we need to RAISE the pH value and vice versa * 
Keeping it simple, if your soil is too acid then nutrients will not be available to the plants even if they are present. To LOWER soil acidity we need to RAISE the pH value (that one always confused me) and vice versa.





Different plants require different levels of acidity  hence we have ericaceous composts for acid loving plants. Most vegetables thrive when the soil is slightly acid i.e. a pH level between 6.5 and 7, Potatoes tend to prefer a lower pH, more acid, soil and Brassicas prefer a slightly alkaline soil, pH of 7.0 or even slightly higher. That's why it is suggested to lime in the autumn after potatoes and to follow with Brassicas who like the high ph.
*Changing the acidity level of the soil* 

To raise the pH and lower acidity or sweeten the soil, we add lime. To lower pH and increase acidity you can add sulphate of ammonia or urea which are high nitrogen fertilizers.  
*From this you can see that adding manure will also lower pH and make the soil more acid.* 
Its counter to what you expect, but adding loads of manure year after year will actually reduce soil fertility by making it too acid so the plants cannot access the nutrients. They become locked up.
*Never Mix Lime and Fertilizer* 

If you have ever had a pee (slightly acid) into a toilet with bleach (very alkaline) in it, you will have noticed there is an unpleasant reaction, Just the same if you mix your lime and fertilizer. They will at best cancel each other out in an unpleasant, to the soil, reaction. 
*So never lime in the same year you fertilize if you can avoid it and certainly not in the same couple of months.* 

*Different Soils * 

Clay soils tend to become acid more quickly than sandy soils and the amount of organic matter has an effect as well. Clay soils can also be slow to react to the addition of lime as well. 
*Do you need to lime and how much to lime  measuring pH* 

*Measuring Soil Acidity (pH level)* 

You can buy various types of test kit, often you mix a soil sample with water then compare a colour change to a chart, but this is a bit of a pain for taking more than a couple of samples. I use an electronic meter, which is much easier just requiring polishing and inserting into wet soil. 
Whichever kit you use, it will come with instructions and will give you a reading. Never make a judgement on the basis of just one test. You may have hit a spot particularly high or low pH. Take samples or test from a number of spots and this will give you a much better general view of your soils acidity level.
*Types of Garden Lime* 

*Agricultural Lime or Garden Lime* 

Agricultural Lime or Garden Lime is made from pulverized limestone or chalk. As well as raising the pH it will provide calcium for the crops and trace nutrients. Some recent experiments are indicating our soils may well benefit from the addition of rock dust, adding trace nutrients to the soil.  
*Dolomite Lime* 

Dolomite lime is similar to garden lime but contains a higher percentage of magnesium. 
*Quicklime and Slaked Lime* 

Quicklime is produced by burning rock limestone in kilns. It is highly caustic and cannot be applied directly to the soil. Quicklime reacts with water to produce slaked, or hydrated, lime, thus quicklime is spread around the land in heaps to absorb rain and form slaked lime, which is then spread on the soil. Their use is prohibited by the organic standards and while fast acting, the effect is short lived in comparison to garden lime. 
*How Much Lime to Use* 

How much lime to use will depend on your soil type and how far you have to raise your pH by. The chart below will give you a rough guide for how much ground limestone to use. For hydrated lime you only need between half and three quarters the amount. 
Do be careful, too much lime can raise your pH too far and an alkaline soil is as bad as an acid soil for yield.
*When to Lime* 

Its usually best to lime your soil in the autumn and allow it to work its way into the soil over the winter. You do not want to lime when you have crops in the ground as the lime may well damage the crops Since brassicas like both high amounts of nitrogen & humus as well as a high pH, manure in the autumn for them and lime in the early spring,  
*Conclusion* 

Testing the soil takes little time and is very cheap. The benefit of liming is huge so do it as part of your rotation and you will see better crops for your efforts. 
 Amount of Lime to Raise Soil pH from 5.5 to 6.5 ​ *Soil Type *​ *KG / M2 *​ *lb / yd2 *​ *Clay*​ 0.9​ 1.66​ *Sand*​ 0.7​ 1.29​ *Light*​ 0.8​ 1.47​ *Organic*​ 1.1​ 2.03​ *Peat*​ 1.7​ 3.13​


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## mRIZO (Nov 11, 2011)

this is the kind of thread I've been JONESING for!! thank you!!


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## woodsmaneh! (Nov 12, 2011)

*[FONT=&quot]Molasses and Plant Carbohydrates - b.com]Texas Plant & Soil Lab Report [/FONT]*
 [FONT=&quot]The following is an article I found on molasses and its use with plants. Thought others might find it useful, I did.

[/FONT][FONT=&quot]&#8220;Molasses and Plant Carbohydrates&#8221;[/FONT][FONT=&quot] 
Sugars relating to plant functions for maximum economic production. 
Texas Plant & Soil Lab, Inc., [/FONT][FONT=&quot]Texas Plant & Soil Lab (Home)[/FONT][FONT=&quot] 

Environmental factors that affect when and how much sugar to use: 
a. How much nitrate is in the soil, and plant sap (petiole test). 
b. Soil moisture conditions. 
c. Sunlight intensity. 
d. Temperature. 
e. Wind 
f. Fruiting stage / load 
g. Growth / vigor [shade lower leaves] 

The right amount at the right time can improve fruiting and produce normal 
plant growth with less attraction for disease and insects. 

Needed for healthy plants - fruit production - plant development & 
maturity. 
Roots take nutrients from the soil and transport them up the stalk thru the 
petiole (stem) to the leaves where the sunlight aids the production of
photosynthates (sugars are not the ONLY product of photosynthesis)
carbohydrates (C, H & O), principally glucose (C6H12O6) and then other sugars and photosynthates are formed. 

Plant Sugars and other photosynthates are first translocated (boron is essential to the translocation) to a fruiting site. If fruit is not available, the sugars, along with excess nitrates, spur the rapid vegetative growth of the plant at the expense of creating fruiting bodies (first sink) for the storage of the sugars.

Once the proper balance of environmental factors (heat units, light intensity, soil moisture, nutrient balance, etc) are met, the fruiting buds form and then fruit formation gets the first crack at the sugar supply. 

Any excess sugars are then translocated to the number two sink, (growing terminals,) to speed their growth. The left-over sugars, etc. then go to the number 3 sink, (the roots,) to aid their growth. Here the new root hairs take up nutrients to help continue the cycle of sugar and other photosynthate production, fruiting, growth of terminals and roots. 

ADDED SUGARS CAN AID THE PLANT IN SEVERAL WAYS: 
- MOLASSES is probably the best outside source of many sugars, such as table sugar, corn syrup and several more complex sugars such as polysaccharides found in humus products. 
- Sugar can be added to the soil in irrigation water, drip & pivot being the most effective. 

In the soil it can: 

- Feed microbes to stimulate the conversion of nitrates to the more efficient NH2 form of N to synthesize protein more directly by the plants. 

- The roots can directly absorb some of the sugars into the sap stream to supplement the leaf supply to fruit where it is most needed, and ALSO directly feed the roots for continued productive growth.

- This ADDED sugar can also help initiate fruiting buds in a steady-slow 
fashion while maintaining normal growth. 

-EXCESSIVE amounts of ADDED SUGARS applied foliarly can shock the 
plant resulting in shortened growth internodes, increased leaf maturity & initiation of excess fruiting sites. This can be a short term effect lasting only a few days.

Pollination, soil moisture, nutrient balance and sufficiency as well as adequate light for photosynthate production decide how much of the induced fruit can mature. [/FONT]


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## woodsmaneh! (Nov 12, 2011)

*[FONT=&quot]ESSENTIAL ELEMENTS, MOBILITY AND pH EFFECT[/FONT]*[FONT=&quot][/FONT]​ *[FONT=&quot]essential element[/FONT]*[FONT=&quot] - an element required by plants for normal growth, development and completion[/FONT][FONT=&quot] 
[/FONT][FONT=&quot] of its life cycle, and which cannot be substituted for by other chemical[/FONT][FONT=&quot] 
[/FONT][FONT=&quot] compounds.[/FONT][FONT=&quot] [/FONT][FONT=&quot] [/FONT]
*[FONT=&quot]17 ELEMENTS ARE REQUIRED BY PLANTS[/FONT]*[FONT=&quot] [/FONT][FONT=&quot] [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] *3 supplied naturally by air and water *- comprise the bulk of the plant [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] *C, H, 0 * [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot] 6 macronutrients[/FONT]*[FONT=&quot] - required at 0.1 to 6% of the dry weight of plants [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] *N, P, K, S, Ca, Mg * [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot] 8 micronutrients[/FONT]**[FONT=&quot] [/FONT]*[FONT=&quot]- required at 1 to 300 ppm of the dry weight of plants [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] *Fe, Zn, Cu, Mo, B, Mn, Cl, Ni * [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] Cl and Ni are ubiquitous - hence, will not be addressed in detail [/FONT][FONT=&quot] [/FONT]
[FONT=&quot]The essential elements can be easily remembered by a catch phrase such as [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot]C[/FONT]**[FONT=&quot]. HOPKiNS CaFe, CuB, Mn, C.l. MoNiZnsky, Mgr[/FONT]*[FONT=&quot] [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] [/FONT][FONT=&quot] [/FONT]
*[FONT=&quot]NUTRIENT MOBILITY[/FONT]*[FONT=&quot] [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot]Two directions of movement in plants[/FONT]*[FONT=&quot] [/FONT][FONT=&quot] [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot]1)[/FONT]**[FONT=&quot] acropetal[/FONT]*[FONT=&quot] - means towards the apex; transport up the in xylem [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot]2)[/FONT]**[FONT=&quot] basipetal [/FONT]*[FONT=&quot]- means towards the base; transport down in the phloem [/FONT][FONT=&quot] [/FONT]
*[FONT=&quot]Two classifications of nutrient mobility [/FONT]*[FONT=&quot] [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot]1)[/FONT]**[FONT=&quot] mobile [/FONT]*[FONT=&quot]- moves both up and down the plant by both acropetal and basipetal  transport (in both [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] the xylem and the phloem). [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] Deficiency appears on older leaves first. [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot] N, P, K, Mg, S [/FONT]*[FONT=&quot] [/FONT][FONT=&quot] [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot]2)[/FONT]**[FONT=&quot] immobile[/FONT]**[FONT=&quot] [/FONT]*[FONT=&quot]- moves up the plant by only acropetal (in the xylem) transport [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] Deficiency appears on new leaves first. [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot] Ca, Fe, Zn, Mo, B, Cu, Mn[/FONT]*[FONT=&quot] [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] [/FONT][FONT=&quot] [/FONT]
*[FONT=&quot]EFFECT OF pH[/FONT]*[FONT=&quot] [/FONT][FONT=&quot] [/FONT][FONT=&quot] 
[/FONT][FONT=&quot]The pH determines solubility in the soil[/FONT][FONT=&quot] [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot]1)[/FONT]*[FONT=&quot] *more available at low pH (below 5.5), and less available at high pH. * [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] *Fe, Zn, Cu, Mn, B* [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot]2) more available at high pH (above 6.5), and less available at low pH.[/FONT]*[FONT=&quot] [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] *N, K, Mg, Ca, S, Mo * [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot]3)[/FONT]*[FONT=&quot] *more available at intermediate pH (6-7) * [/FONT][FONT=&quot] 
[/FONT][FONT=&quot] *P * [/FONT][FONT=&quot] [/FONT]
*[FONT=&quot]Ideal pH[/FONT]*[FONT=&quot] [/FONT][FONT=&quot]  
[/FONT]*[FONT=&quot]slightly acid:[/FONT]*[FONT=&quot] [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot]a)[/FONT]*[FONT=&quot] around 6.5 for field soil [/FONT][FONT=&quot] 
[/FONT]*[FONT=&quot]b)[/FONT]*[FONT=&quot] around 5.5-6.0 for artificial growing media made with peat moss or composted bark[/FONT][FONT=&quot][/FONT]


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## woodsmaneh! (Nov 12, 2011)

*[FONT=&quot]Guano Guide by 3LB [/FONT]*
[FONT=&quot]This is the original Guano Guide posted by The 3LB's.

Well here goes ... First up the Guano Guide. These were always meant to remain works in progress, so keep that in mind as you read through. The article appears with some editing.

Guano Guide-The Scoop on Poop by the 3LB~CW 

The three_little_birds manual on manure - it's the shit!

"Birds love the oil rich seeds of this fruitful plant and in their ecstasies of eating have swallowed many seeds whole. Throughout the ages Cannabis has flown here and there in the bellies of birds and then found itself plopped down on the earth in a pile of poop, ready to go." 
Bill Drake 
[/FONT][FONT=&quot]marijuana[/FONT][FONT=&quot] - The Cultivator's Handbook - 1979

Some ancient Italian in a proverb-making mood observed, "Hemp will grow anywhere, but without manure, though it were planted in heaven itself, it will be of no use at all." How lucky it is for Hemp to find Heaven in a pile of birdshit. How fortunate for the birds to find themselves high. How fortunate for the first men and women to notice how the little singing creatures became euphoric after eating the seeds of the tall, strong smelling plant. The planet is tight."
Bill Drake 
[/FONT][FONT=&quot]marijuana[/FONT][FONT=&quot] - The Cultivator's Handbook - 1979


Growing up on a small family farm, one of the three little birds childhood memories include complaining to her father about being surrounded by the terrible smell of wastes from the livestock they were raising. 

"Sweetheart, that's not stink . . . That's the smell of money," was Dad's reply.

She certainly understood the value of the livestock her family was raising for profit, which was where Daddy's money came from. Early on, she also made the connection between the farm animals and the tasty meat on their own table. 

She understood another ironic meaning for her Dad's statement when one of her first paying jobs came shoveling stock barns at a State Fair. And finally, one day as she appreciated the fine aroma of some beautiful blooming wildflowers growing in a recently grazed pasture, she also began to understand the role manure plays as a fertilizer in making our soils rich and productive. Her Fathers saying about manure smelling like money was a few simple words, but, as was often the case with his wisdom, it held many meanings.

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 

The use of manure in agriculture is an age-old and time-honoured tradition. Manure has been used as a soil amendment and fertilizer since before mankind first began recording words and symbols in writing. Scientists as prominent as Carl Sagan have suggested that the very first cultivated agricultural crop was likely cannabis. Its possible that the mingling of manure and [/FONT][FONT=&quot]marijuana[/FONT][FONT=&quot] goes all the way back to the very beginning of mankind's attempts to grow crops for a purpose, rather than surviving by simple hunting and gathering. 

Under the influence of some fine herb, it becomes simple to imagine going back in time. Looking back, in the minds eye we can see a tribe of nomadic people looking similar to modern man, but leading a primitive hunter-gatherer existence. We can imagine the clan following available game while taking advantage of locally available fruits and nuts. These men (and women) were not necessarily bigger or stronger than the wild animals they competed against for survival, but they were smarter. And during those seasonal migrations, one of those very distant ancestors likely noticed that their favorite herb plants were thriving especially well in areas where their nomadic tribe disposed of wastes near their seasonal camps.

They may have realized that the very herds of animals their clan had been following helped to distribute and nourish the plants they favored. Perhaps, as Bill Drake suggests, it was a discovery from a pile of birdshit where it all began. Regardless of where it started, with a little more thought, our ancestors realized that crops could be fertilized, and even grown with a purpose. Some speculate that this is how agriculture was born; that it all began with a fortuitously placed pile of shit.
In the end folks can call it what they like. Whether it's a fancier name like castings or guano, or one of the more common names like crap, poop, manure, or dung. In the end it's all just shit! The three_little_birds want you to know, however, that it can be very good shit. We want you to know that manures are one of the keys to unlocking the awesome potential of organic gardening.

In the immeasurable time prior to the invention of agriculture, before man began to till the soil, dead and rotting vegetation naturally returned to the earth as rich and fertile humus. In traditional forms of farming, our ancestors learned to use the components of animal dung and bedding wastes in a sustainable fashion. Before the discovery of chemical fertilizers and pesticides, manure was used as a resource, not a waste product. Natural humus, built up during the ages before agriculture, was replaced by manure, rich in nitrogen and other elements that plants depend upon. Today, that is no longer true.

From an environmental perspective, manure is a resource that is being wasted at a terrible rate. In some agricultural areas where a large number of livestock are concentrated and raised, manure is not a resource, but rather, it has become an environmental hazard. Consider, for instance, that a single hog will produce 3000 pounds of manure in under a year. Its easy to see then how the large concentration of wastes found in corporate factory farms can rival a good-sized city for the total volume of organic waste produced. 

According to one estimate, the USA alone has something in the range of 175 million farms animals. That multitude of animals excretes over two billion tons of waste per year. Due to mismanagement, misuse, and ignorance, very few of the potential nutrients from these wastes are returned to the land, less than 20% according to some estimates. Instead, this incredible mass of manure threatens to pollute river, streams, lakes, and even the subterranean groundwater that supplies many folk with their drinking water. 

Therefore, finding proper solutions for the treatment and disposal of all that manure, in an economically feasible fashion, is an absolute necessity of modern agriculture. In the end, good stewardship requires sustainable farming practices that concentrate on finding a balance on the farm. So, as long as humans raise and consume animal livestock, as long as we keep animals such as horses for purpose or pleasure, it is wise to properly use manure to build and sustain our soil. 

As a side note, one advanced form of gardening, vegan organics, does offer hope for budding organic gardeners who will have nothing to do with the use of manures and guanos. We mention this since some folk might be dismissive of the very thought of handling animal dung, and some indoor gardeners might be repelled by the thought of bringing it into their homes or grow areas. Perhaps for some folk this will be enough reason to decide this particular form of organic gardening is not for them. 

We hope not because working with manures in your garden does not have to include large messes or smells . . . it's just a question of knowing your shit!

For a simple definition, manure is the dung and urine of animals. It is made up of undigested and partially digested food particles, as well as a cocktail of digestive juices and bacteria. As much as 30% of the total mass of manure may be bacteria, so it should be no surprise that dung can serve as excellent inoculants for a compost pile. Mixing manure in your compost can provide all the necessary bacterial populations to quickly and efficiently break down all the other materials common to the heap. 

Manures can contain the full range of major, minor, and micronutrients that our plants need for strong health and vigour. Most manure will contain these nutrients in forms that are readily available to plants. The organic components of manure will continue to break down slowly over time, providing food for plants in the longer term as well. When composted with even longer-lived rock fertilizers such as Rock Phosphate or Greensand, manures can be used for true long-term soil building. 

In addition to providing excellent service to gardeners as a potential fertilizer and soil builder, guanos and manures can also both be effectively applied as teas. Manure and guano teas act as fertilizers, providing available nutrients in forms easily assimilated by plants. They also serve as very effective inoculants of many beneficial bacteria

The nutrient value of manures can vary significantly from species to species, due to different digestive systems and feeding patterns. Even within a species, the fertilizer content of dung will vary depending on factors such as diet, the animals general health, as well as their age. Young animals devote much of their energy to growth, so their manure will be poorer in nutrients than that of mature animals. A lot full of baby pigs on starter feed will deposit wastes with a different nutrient value than the wastes produced by a lot full of swine ready to go to market.

An animals diet certainly plays a factor as well. The Rodale Book on Composting (an excellent resource) uses the example of an animal fed only straw and hay. The waste from that animal will be significantly different in nutrient content when compared to a sibling fed a diet including more nutritious feed such as wheat bran, cottonseed meal, or gluten meal. 

The purpose an animal is used and bred for can even cause the nutrient value of a manure to vary. Dairy cows serve here as an excellent example. Milk production is somewhat taxing, even to a dairy cow. In addition to large amounts of calcium, milk also contains high levels of nitrogen, phosphorus and potassium, the three primary plant nutrients. Since so many nutrients are being used to produce milk, less actual plant fertilizer will be available in those animal wastes for soil building.

Another factor that will change the fertilizer value of manure is relative age and the way it has been handled. Manures left exposed to the elements will quickly lose their nutrient value. Rain can quickly leach soluble nutrients from manure. A thin pile of crap can lose as much as one half of its fertilizer value in under a week. To fully capture the nutrient potential of manure, its necessary to compost the shit quickly while its still fresh. 

With the exception of guanos (which are mined fossilized waste deposits) and castings (which are mild and well digested), it is generally advisable to compost wastes and manures before direct use in your garden. When added directly to soil, fresh manures can act in a similar fashion to chemical fertilizers. The Nitrogen in fresh manures (ammonia and highly soluble nitrates) can burn delicate plant root systems and even interfere with seed germination. 

Another good reason to compost manures before use is the fact that some animal manure can be full of weed seeds. Proper high temperature composting techniques can kill those unwanted guests as well as many potential soil pathogens. Used alone, animal manures may not be completely balanced fertilizers. However, once the manures have been properly amended and composted, any imbalances can be easily corrected and the manure itself can be broken down and digested into nutrients that are both balanced and available for our favorite plants and herbs.

Proper composting will actually increase nutrient value in manure. Some types of bacteria in a compost pile will fix nitrogen. This preserves this essential nutrient by preventing escape as gaseous ammonia. If the conscientious composter prevents leaching, all of the original phosphorus and potassium can be preserved. As an added benefit, the composting process will increase the solubility of these nutrients.

We want to continue our discourse with a simple listing of manures that can be used to good effect by budding gardeners. But, we would be remiss if we did not begin by first discussing the few manures we believe are NOT suitable for use in gardening. 

Human wastes, as well as the wastes of domestic cats and dogs, are considered totally unsuitable for use as fertilizer. DO NOT GARDEN WITH THESE WASTES! With these sources, too large a potential exists for the spread of deadly parasites and disease. Just say no to any suggestion for the use of those few manure sources. 

That said, there are a great variety of guanos, manures, and castings that are safe and available for use by the enterprising horticulturalist. The list includes but is not limited to:

 The Manures
1. Chicken Manure
2. Poultry Manures (including Duck, Pigeon & Turkey Manure)
3. Cattle Manure
4. Goat Manure
5. Horse Manure
6. Pig Manure
7. Rabbit Manure
8. Sheep Manure

 The Guanos
1. Bat Guano - (including Mexican, Jamaican, & Indonesian bat guanos)
2. Seabird Guano - (including Peruvian seabird guano) 

[/FONT]
[FONT=&quot] Miscellaneous Wastes / Manures
1. Earthworm Castings
2. Cricket Castings
3. Aquarium & Aquatic Turtle Wastewater
5. Green Manures

The Manures 
Now it's time to describe the various manures and their unique attributes.

Bird Manures - are treated separately from animal manures since fowls don't excrete urine separately like mammals do. Because of this, bird manures tend to be "hotter". Overall they are much richer in many nutrients than animal manures, especially nitrogen. Because of their higher nutrient content, some growers prefer birdshit to the other animal manures.

Chicken Manure (1.1-1.4-0.6) - is the most common bird shit available for farmers. It's high in nitrogen and can easily burn plants unless composted first. 
Feathers (often included with chicken manure) tend to further increase available nitrogen - an added bonus. A small amount of dried chicken manure can be used as a top-dressing or mixed in small concentrations directly into soil. Chicken manures are probably best used after complete composting. Chicken droppings are often composted with other manures as well as green matter, leaves, straw, shredded corncobs, or other convenient source of organic carbons. Chicken manure is also a common ingredient in some mushroom compost recipes. One potential concern for the budding organic farmer, is the large amount of antibiotics fed to domestic fowl in large production facilities. It is also suggested that some caution should be used when handling chicken droppings, whether fresh or dried. Dried chicken shit is very fine and is a lung irritant. Caution is also counseled since bird (and bat guanos) can carry spores that cause human respiratory disease, so please wear a mask when handling bird and bat guanos and fresh foul waste.

Poultry Manures (1.1-1.4-0.6) - are often simply chicken shit mixed also with the droppings of other domesticated birds including duck droppings, pigeon poop, and turkey turds. They are "hotter" than most animal droppings, and in general they can be treated like chicken shit.

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 

Animal Manures vary by species, and also depending of how the animals are kept and manures are collected. Urine contains a large percentage of nitrogen and potassium. This means that animals boarded in a fashion where urine is absorbed with their feces (by straw or other similar bedding), can produce organic compost that is richer in nutrients.

Cattle Manure (0.6-0.2-0.5) - is considered "cold" manure since it is moister and less concentrated than most other animal shit. It breaks down and gives off nutrients fairly slowly. Cow shit is an especially good source of beneficial bacteria, because of the complex bovine digestive system. Cow digestion includes regurgitation (cows chew their "cud") and a series of stomachs, all evolved to help cows more fully digest grasses. Since cow manure is more fully digested, it also is less likely to become a source of weed seeds than some other manure. Depending on your location, many sources of cattle manure can be from dairy cows. Recent expansion in the use of bovine growth hormones to increase milk production certainly could become a concern for organic farmers trying to source safe cattle manures. The healthier the cow, and the healthier the cow's diet, the more nutrients its manure will carry.

Goat Manure (0.7-0.3-0.9) - can be treated in a similar fashion to sheep dung or horse shit. It is usually fairly dry and rich and is a "hot" manure (therefore best composted before use).

Horse Manure (0.7-0.3-0.6) - is richer in nitrogen than cattle or swine manure, so it is a "hot" manure. A common source of horse manure is rural stables, where owners usually bed the beasts very well. Horse manures sourced from stables, therefore, may also contain large amounts of other organic matter such as wood shavings or straw with manure mixed in. Some sources of mushroom compost contain large quantities of horse manure and bedding in their mix. So from one standpoint, horseshit's use in herb growing is already fairly well documented. Horseshit, because it is hot, should be composted along with other manures and higher carbon materials, and in some cases wet down, to prevent it from cooking too hot and fast which destroys potential plant nutrients. As is true with all the different manures, healthier, well maintained animals will produce more nutritious and better balanced fertilizer. Since horses are usually well tended, this means horse manure from stables is usually a pretty good source for those in search of shit. Unfortunately, horse crap also contains a higher number of weed seeds than other comparable manure fertilizers.

Pig Manure (0.5-0.3-0.5) - is highly concentrated or "hot" manure. It is less rich in nitrogen than horse or bird crap, but stronger than many of the other animal manures. Swine crap is wetter overall than other mammal manures, and is often stored by farmers in the form of liquid slurry, that is mostly water. When allowed to dry, hog shit becomes a very fine dust, which can be a lung irritant. Pig shit is less likely to have nutrients "burn off" in the compost pile than horse manure, but is best used when mixed and composted with other manures and/or large quantities of vegetable matter.

Rabbit Manure (2.4-1.4-0.6) - is the hottest of the animal manures. It may even be higher in nitrogen than some poultry manures. As an added bonus it also contains fairly high percentages of phosphates. Because of it's high nitrogen content, rabbit crap is best used in small quantities (as a light top dressing or lightly mixed into soil) or composted before use. An excellent fertilizer by itself, some folks combine rabbit hutches with worm farms to create what is a potentially very rich source of nutritious worm castings. As with other animal manures, healthier animals fed a nutritious diet will produce a superior manure fertilizer.

Sheep Manure (0.7-0.3-0.9) - is another hot manure similar to horse or goat manure. It is generally high in nutrients and heats up quickly in a compost pile because it contains little water. Sheep and goat pellets, because they are lighter, are easier to handle than some other manures. Sheep shit contains relatively few weed seeds but more organic matter than other animal manures. As a side note, sheep farming is generally more destructive to the environment than cattle farming (or many other grazers). Sheep have a "split lip" allowing them to graze closer to the ground, so they tend to strip grass bare to the root. This heavy grazing kills many grasses, leaving earth more prone to destructive erosion. While its hardly considered environmentally friendly, cattle grazing is less heavy on the land than sheep farming.
The Guanos 
Bat Guano 
"There are, in Cuba, a great number of caves providing a considerable supply of the richest fertilizer. In these caves, where bats shelter, a fertilizer has accumulated, a true guano, the result of a mixture of solid and liquid excrement, the remains of the fruit that fed the animals, and their own carcasses. All these materials, sheltered from the sun, air and rain, form a rich mix of nitrogenous, carbonaceous and saline elements. They contain uric acid, ammonium urate, nitrates, phosphates and calcium carbonate, alkaline salts, etc. The huge quantity of guano amassed in some caves can be explained by the number of beasts that have sheltered there for so many years". 

Alvaro Reinoso - "Ensayos sobre el cultivo de la caña de azúcar", ("Essays on sugar-cane cultivation"), Havana - 1862

Bat and seabird guanos are some of the most wonderful, extraordinary, versatile, naturally occurring organic fertilizers known to man. They are not considered to be a renewable resource, and they are sometimes mined in an environmentally destructive fashion, so environmentally conscious growers sometimes avoid guanos. 

Bat Guano - Bat guano is found as deposits in some caves that have been inhabited by these little flying mammals. Bat crap can sometimes also be found in smaller quantities in other places bats inhabit (old or abandoned buildings, trees, etc.). Bat guano has many horticultural uses. Its presence can help to guarantee efficient soil regeneration. When used as a fertilizer or tea, bat crap fosters abundant harvests of a high quality, making it an invaluable agricultural fertilizer for producing outstanding organic herbs, fruits, and vegetables. Many dedicated organic farmers insist that bat guano brings out the best flavors in their organic herbs. The bottom line is bat guano has many excellent properties that give it great value for growing an organic product of the highest quality. It may very well be possible to justify the boast that bat guano is "superior to all other natural fertilizers".

Bat Guano consists primarily of excrement of bats (no surprises there - eh?) It also contains the remains of bats that lived and died in that location over many long years. Bat guano is usually found in caves, and bats are not the only residents. Therefore, bat guano almost certainly contains the remains and excrement of other critters such as insects, mice, snakes and (gasp!) even birds. And, guano is by no means just collected excrement and animal remains, as guano ages it can undergo a array of complex decomposition and leaching processes. 

The fertilizer quality of any particular bat guano depends on variety of factors. These can include: the type of rock in which the guano cave formed, the feeding habits of the bat species producing the guano, the guanos age, and the progress of mineralization in the guano (which undergoes an endless transformation through chemical and biological processes). Guano can appear in a wide range of colors including white, yellow, brown, hazel, gray, black, or red, but color does not indicate or influence its quality. 

One of the factors that can determine the fertilizer quality of bat guano is the dietary habits of the different bat species who inhabit a cave. Some bats are vegetarian, eating primarily fruits. Other bats are carnivorous; their diet usually consists of insects and similar small critters. As an example, the specific form of nitrogen in guano will depend on the feeding habits of the bats living in the caves. Bats that feed on insects eject fragments of chitin, the main component of insects' exoskeletons. Chitin resists decomposition, and contributes a long lasting form of nitrogen that appears in many older guano deposits. Obviously, chitin from digested insect remains is not likely to be found in any quantity in the guano of fruit eating bats.

Even a caves location will effect the composition of guano deposits found within. Different chemical reactions during the actual cave making process result in different nutrient characteristics in the various guanos. Over time, guano combines in various ways with the actual rock and minerals from the bedrock of their region. Ultimately, minerals may be deposited throughout layers of guano by a variety of means. Minerals that have been dissolved in water filtering through porous rock from above can fortify guano deposits as they drip from cave ceilings. In caves where water filters through the guano, soluble elements will likely be washed out, so the composition of the guano changes in other ways as well. 

In addition to minerals deposited by leaching water, another factor in guano composition is the huge amount of particulates that fall from the cave ceilings and walls where the bats sleep and hibernate. The release of their liquid excrement at high-pressure pounds cave walls, and the physical presence of the bats as they constantly flit about, both combine to cause erosion. Chemical reactions caused by the bat crap (as well as many natural cave making processes), also work to break down cave ceilings and walls. All of these factors result in an invisible rain of minute solid mineral particulates. All of these mineral particulates are mixed into the copious quantities of bat crap (and other matter) deposited on the floor. As a result, bat guanos have a wide range natural / organic source mineral nutrients that are immediately available for plants, called chelates. 

Another large component of bat guano deposits is the fauna within, the great collection of microorganisms that work as decomposers. Their main function is to accelerate the process of breaking down organic matter in the guano. These beneficial bacteria populations work to increase the guanos wealth of essential nutrients, and can provide their own benefit to gardeners as a soil innoculant. 

Once bat guano is deposited, it begins and endless process of transformation. From fresh deposits, nitrogen is the essential element that is usually released first. This is partially as ammonia, with its characteristic strong smell, which is omnipresent in fresh guano. The rest of the nitrogen oxidizes and forms nitrates that are often dissolved and leached by water. The phosphorus contained in guano comes partly from bat excrement, but is generally from skeletal remains (it may also come from mineral elements in the cave.) Many of the decomposition processes work to concentrate phosphorous levels in bat guano deposits as they age, and this provides some of guanos greatest value to gardeners. Potassium is often the least represented of the three essential macro-elements, due to the solubility of its compounds, which are usually washed out of guano deposits by natural cave conditions. 

During decomposition the actual proportion of the different fertilizer components of the guano change. As the guano breaks down, the levels of organic matter, nitrogen, and potassium will fall. At the same time, the relative levels of calcium, phosphates, sand, and clay levels will rise. The actual excrement and remains of bats are the main source of the elements nitrogen, phosphorus and potassium in guano. The organic compounds in the excrement contain sulphur, phosphorus, and nitrogen. After decomposition and oxidation, these combine to form sulphuric, phosphoric, and nitric acids.

Over time, those acids react with mineral elements from cave rock to form a variety of mineral salts - including sulphates, phosphates, and nitrates. Leaching washes out most of the soluble compounds including the nitrates, sodium, and potassium compounds. At the same time, the insoluble phosphates and sulphates build up in larger proportions. These include calcium phosphate, iron phosphate, aluminium phosphate and calcium sulphate. . 

As we have already said, bat guano is an ecological fertilizer, obtained naturally from the excrement and physical remains of bats living in caves. This product is rich in nutrients, outclassing all other existing organic fertilizers, with a better balance of essential nutrients (N-P-K), a wealth of micro-organisms and much higher levels of organic matter. Its chemical and biological composition vary according to the bats' feeding habits, type of cave, age of guano, etc.

A great variety of different agrochemical analyses have been carried out on bat guanos through the years. All the different analysis show that the nutrient and micro-organism content of bat guanos are high, but it varies according to the type of guano. Because the chemical, physical and biological composition of bat guano (and other organic fertilizers) will naturally vary, it is impossible to set a specific single value for any nutrient. The table below is copied from internet research and is a summary of the variety of results obtained from bat guano analyses. 
Source: Omar Páez Malagón, January 2004

Total Nitrogen(N) 1.00-6.00% 
Phosphorus Oxide (P2O5) 1.50-9.00% 
Potassium Oxide (K2O) 0.70-1.20% 
Calcium Oxide (CaO) 3.60-12.0% 
Magnesium Oxide (MgO) 0.70-2.00% 
Iron (Fe) 0.70-1.50% 
Copper (Cu) 0.20-0.50% 
Manganese Oxide (MnO) 0.40-0.70% 
Zinc (Zn) 0.40-0.65% 
Sodium (Na+) 0.45-0.50% 
Organic matter (OM) 30-65% pH (in H2O) 4.3-5.5 
Ratio C/N 8-15/1 
Humidity (Hy) 40-30% 
Total humic extract 25-15.00% 
Microbial flora 30 - 45x107 u.f.c./ gr 
Note:

These values are not always uniform, but provide useful data for calculating doses of nutrients or micro-organisms and analyzing the product's physical properties for agricultural or industrial use. These indicators are for intermediate guano, in the natural state of transition between fresh guano and old or fossil guano. Source: Omar Páez Malagón, January 200
seabird guano-contains an equivalent percentage of plant nutrients,helps bind soil particles,aids in nitrogen fixation and greatly enhances beneficial bacteria. A great all around nutrient with quite a history.The most famous of all seabird guano's was that used by the inca's,the word guano actually originated from Quichua, language of the Inca civilization and means "the droppings of sea birds".The guano was collected on the rainless islands and coast of Peru.Where the atmospheric conditions insured a minimal loss of nutrients,leaving the Legendary fertilizer of the Incas.Seabird guano can be used as an soil amendment or as a tea at 1-2tbsp per gal.Bcause of its balanced npk ratio,an average of 10-10-2.5,seabird guano can be used as a base when making tea's (throught out the grow)

Green Manure 
Green Manure is a crop grown for the purpose of supplying the soil with nutrients and organic matter. It is called a cover crop when the green manure is grown for the added purpose of reducing soil erosion. Green manures are usually legumes or grasses, and they are grown with the simple intent that they will be turned back under the soil. Cover crops and green manures are certainly cost effective for large-scale farmers, but many backyard gardeners have no idea how simple and effective they are to use. And, as we mentioned earlier, they do offer a manure option for growers who choose vegan organics.

Green manures improve soil in a variety of ways. Green manures add significant amount of organic matter into the soil. Like animal manures, the decomposing of green manures works to enhance biological activity in the soil. Green manures can also diminish the frequency of common weeds, and when used in a crop rotation, they can help to reduce disease and pests. When turned under, the rotting vegetation supports beneficial bacterial populations. As those decomposers do their work, nutrients stored by the cover crop are returned to the soil. 

Alfalfa roots regularly grow to depths of five feet or more, soybeans and clover can reach almost as deep. Since their roots go deeper than folk would commonly cultivate with a rototiller or plow, a green manure crop can bring subsoil minerals up to where even shallow rooted plants can reach them. Green manures also help to improve overall soil structure, because those deep reaching roots leave behind minute channels deep into the soil. When these deep roots decay, they provide organic matter that promotes long-term soil building.

Except for buckwheat (a member of the rhubarb family) and rapeseed (related to the cabbages), all commonly used green manures are either legumes or grasses. Rye and oats are two good examples of grass family members that are commonly used as green manures. When we think of legumes, beans and peas are the classics which come to mind, but the legume family also includes relatives such as clover and alfalfa. Members of the legume family can be particularly valuable as green manures, due to their ability to fix nitrogen from the atmosphere. 

In the legume family, a very specific type of bacteria works in league with plant roots. These microorganisms, called nitrogen fixing bacteria, form nodules on the plant roots where they work in a form of partnership with their host. Functioning in concert with the plant roots, nitrogen fixing bacteria transform atmospheric nitrogen (which plants otherwise cant use), into ammonia, which plant roots can easily absorb. 

If one of these plants is uprooted, the small nodules become visible as white or pinkish bumps the size of a large pinhead. The more nodules visible the better, since more nodules equals more nitrogen fixed. To assure that enough of these bacteria are present, commercially sold legume seeds are often treated with a bacterial innoculant. Make sure to get the appropriate innoculant for your specific legume crop if its necessary to inoculate your own soil or legume seed stock. 

Each kind of legume requires a specific species of bacteria for effective nitrogen fixation, and each innoculant works for only a few species. Its usually possible to buy an innoculant mix designed for all peas, snap or dry beans, as well as lima beans. Soybeans will require their own specific innoculant. A totally different innoculant will be needed to serve the needs of the vetches (as well as fava beans.) Still another nitrogen fixing bacteria will work with all the true clovers, but sweet clovers will require yet another innoculant. 

With careful stewardship, a legume cover crop can enrich the soil with enough nitrogen to supply most of the following years crop nitrogen needs. Commonly used legumes for cover crops include: alfalfa; fava, mung and soy beans; a whole variety of clovers; cowpeas and field peas; common or hairy vetch; the lupines; and finally our favorite name among the legume cover crops - Birdsfoot trefoil. 

Although the grasses and other non-legumes do not have the ability to fix nitrogen from the atmosphere, they still provide all the other benefits of green manures. Other non-legume crops grown for green manure include; barley, bromegrass, buckwheat, millet, oats, rapeseed, winter rye, ryegrass, grain sorghum, and wheat. 

Seed for cover crop and green manures doesnt need to come from fancy little packets at the garden center. Purchase grass and legume seeds by the pound, if you can, to save money. Farm and agricultural supply centers, what we call feed & seed stores, usually offer the most economical source. If your garden area is small, a single pound of seed may go a long way. With the smaller seeds, a pound could be expected to last through a couple of plantings. The larger seeds of legumes, like beans and peas, dont store as well, so its advised to purchase them fresh annually. 

The use of green manures and cover crops is relatively simple, the primary necessity being the time to grow the plants. Some preplanning is always helpful to make sure the correct crop is selected to best meet the growers needs. So, for example, if enriching soil nitrogen levels is a goal, then its best to choose a cover crop from the legume family due to their ability to fix nitrogen. 

Some green manure plantings tolerate poor soil quality better than others, so some cover crops may be chosen because they tolerate particularly acidic (or alkaline) conditions. If a grower needs to break up hardpan soil and improve drainage, some cover crops grow very strong and deep roots. Such conditions call for green manures like alfalfa and birdsfoot trefoil that can thrust their roots through anything but the most dreadfully compressed soils.

As stated earlier, deep-rooted plants can also bring up essential nutrients from the subsoil. And, some do even more; they actually accumulate nutrients, concentrating them. Growing these green manures can produce a measurable (although not huge) increase in soil nutrients. Some legumes, especially red clover, can help to increase phosphorus levels. Buckwheat also increases phosphorus, as well as helping to supplement calcium. Vetches are also accumulator plants, working to increase levels of both calcium and sulfur. 

Buckwheat and Rye are examples of crops often grown as green manures that also function to control weeds. Winter Rye is actually a natural herbicide; it produces chemicals that are toxic to many weed seedlings. Buckwheat works by outgrowing its weedy competitors. The large leaves of buckwheat effectively shade out many common annual weeds. 

Its also necessary to consider the seasonal needs of your garden when planning a green manure planting. Some green manures are early season crops, while others do better when planted during the heat of summer. Winter rye and winter wheat are usually planted in the late summer or fall and then turned under in the following spring.

Another key to getting the most from a green manure planting is to turn them under at the proper time. Winter cover crops of rye and wheat, for instance, should be turned under as soon as the spring soil is dry enough to work. Its best when turning under a winter wheat to allow at least two weeks for the green manure to work in the soil before beginning any spring planting. 

In order to assure good germination rates, its necessary to wait even longer for winter rye manures to be ready for replanting. A three to four week wait is suggested after turning under a winter rye crop before sowing seeds of another crop. This is due to the same herbicidal quality that makes winter rye effective in the control of weeds. In general with most grass cover crops, the best timing is to turn them under before they form mature seed.

Turning under legumes at any time will enhance the organic matter in soil and promote an active population of beneficial soil bacteria. But, to get the full benefit of a legume plantings ability to fix nitrogen, they should be allowed to grow a full season. Perennials like alfalfa, red clover, and birdsfoot trefoil can produce additional soil enriching nitrogen if allowed to grow for a second season. If allowed those two years of growth, they can be mowed multiple times, providing a high quality source of compost or material for mulching. An alfalfa cover planting can serve as a gardeners own sure source of fresh materials for the manufacture of alfalfa teas.

[/FONT]
[FONT=&quot]Miscellaneous Wastes / Manures 

1. Earthworm Castings
2. Cricket Castings
3. Aquarium Wastewater

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*[FONT=&quot]Finding Manure[/FONT]*[FONT=&quot] 
As weve stated, one of the best reasons to use manures in growing is the fact that society (as a whole) has a surplus of animal shit. The disposal or dispersal of animal wastes is a real problem for areas where large agricultural operations produce copious excesses of waste. Even Vegans who might avoid pure animal products like bone meal or blood meal, might do well to consider using manures in growing, because the use of manures is beneficial to our planet's environment. 

The best advice we can give for finding good sources of shit is to look around! We suggest you simply contact people who raise the various cows, horses, pigs or chickens that make this fertilizer. If you are lucky, they'll probably let you take a load home for free. Stables are usually listed in the phone book, and state fairs and traveling circuses can also serve as great sources for free manure. For the hopelessly urban farmer, the local zoo may also offer free crap. As an added benefit, zoos can offer some pretty exotic shit, like crap from critters like lions and tigers and bears, (oh my!) Some folk claim that manure from predator species like these can help to deter garden pests, such as rabbits and deer. 

If none of these manure sources are available, or if you just prefer your shit pre-packaged, just head off to the local nursery or home-and-garden center. Wal-Mart, Lowes, and Home Depot are all examples of large outlets which will carry packaged manure products, usually cow and steer crap. Often these are at least partially composted and come labeled as "humus and manure". Nowadays, even many grocery stores carries manure products like humus and manure or mushroom compost. The budget conscious shopper can often wait until late in the season when stores are "closing out" such products before winter, to grab these items at increased discounts.

Garden centers or hydro shops are usually better sources for the more exotic ingredients like worm castings and the various bat and bird guanos. Ingredients for green manures can often be found in rural animal feed stores, or other similar agricultural supply center. [/FONT]


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## ClamDigger (Nov 12, 2011)

nice job, thats some good reading.
gotta love those worm castings!


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## woodsmaneh! (Nov 14, 2011)

*[FONT=&quot]Etiology and epidemiology of Pythium root rot in hydroponic crops: current knowledge and perspectives[/FONT]*


*[FONT=&quot]John Clifford SuttonI, [/FONT]**[FONT=&quot]*[/FONT]**[FONT=&quot]; Coralie Rachelle SopherI; Tony Nathaniel Owen-GoingI; Weizhong LiuI; Bernard GrodzinskiI; John Christopher HallI; Ruth Linda BenchimolII[/FONT]*
[FONT=&quot]I[/FONT][FONT=&quot]Department of Environmental Biology, University of Guelph, Guelph, ON, Canada, N1G 2W1 
IIEmbrapa Amazônia Oriental, Caixa Postal 48, 66017-970, Belém, PA, Brasil[/FONT]


*[FONT=&quot]ABSTRACT[/FONT]*
[FONT=&quot]The etiology and epidemiology of Pythium root rot in hydroponically-grown crops are reviewed with emphasis on knowledge and concepts considered important for managing the disease in commercial greenhouses. Pythium root rot continually threatens the productivity of numerous kinds of crops in hydroponic systems around the world including cucumber, tomato, sweet pepper, spinach, lettuce, nasturtium, arugula, rose, and chrysanthemum. Principal causal agents include _Pythium aphanidermatum, Pythium dissotocum_, members of _Pythium_ group F, and _Pythium ultimum_ var. _ultimum_. Perspectives are given of sources of initial inoculum of Pythium spp. in hydroponic systems, of infection and colonization of roots by the pathogens, symptom development and inoculum production in host roots, and inoculum dispersal in nutrient solutions. Recent findings that a specific elicitor produced by _P. aphanidermatum_ may trigger necrosis (browning) of the roots and the transition from biotrophic to necrotrophic infection are considered. Effects on root rot epidemics of host factors (disease susceptibility, phenological growth stage, root exudates and phenolic substances), the root environment (rooting media, concentrations of dissolved oxygen and phenolic substances in the nutrient solution, microbial communities and temperature) and human interferences (cropping practices and control measures) are reviewed. Recent findings on predisposition of roots to _Pythium_ attack by environmental stress factors are highlighted. The commonly minor impact on epidemics of measures to disinfest nutrient solution as it recirculates outside the crop is contrasted with the impact of treatments that suppress _Pythium_ in the roots and root zone of the crop. New discoveries that infection of roots by _P. aphanidermatum_ markedly slows the increase in leaf area and whole-plant carbon gain without significant effect on the efficiency of photosynthesis per unit area of leaf are noted. The platform of knowledge and understanding of the etiology and epidemiology of root rot, and its effects on the physiology of the whole plant, are discussed in relation to new research directions and development of better practices to manage the disease in hydroponic crops. Focus is on methods and technologies for tracking _Pythium_ and root rot, and on developing, integrating, and optimizing treatments to suppress the pathogen in the root zone and progress of root rot.[/FONT]


[FONT=&quot]Pythium root rot is ubiquitous and frequently destructive in almost all kinds of plants produced in hydroponic systems, including cucumber, tomato, sweet pepper, spinach, lettuce, arugula, and roses. In Canada, root rot epidemics continually threaten the productivity of greenhouse vegetables and flowers such as chrysanthemums in hydroponic troughs on mobile benches which, compared to ground beds, would have allowed substantial increases in production efficiencies. Pythium root rot is also considered a potential threat to plant biomass production in manned space vehicles and at extraterrestrial installations in projected space missions (41, 70, 92). Indeed _Pythium_ has already been encountered on plant materials in space vehicles operated in earth orbit. In greenhouse and growth room studies, Pythium root rot became severe in hydroponic tobacco, _Arabidopsis_ and antirrhinum, which are key plants employed for genetic, molecular and physiological studies (N. Ortiz, W. Liu, & J.C. Sutton, 2003 unpublished observations). Thus, the problem of Pythium root rot needs to be resolved in diverse commercial and research situations. [/FONT]
[FONT=&quot]Management of Pythium root rot in the production of hydroponic crops is generally a difficult challenge. Extraordinary sanitation measures do not necessarily exclude or destroy the causal pathogens, and once initiated, epidemics are difficult to contain. Recent advances in knowledge and understanding of the etiology and epidemiology of root rot, and in methods and approaches to control the disease, are providing a framework for major improvements in root rot management and in the overall health and productivity of hydroponic crops. This review considers recent findings in small-scale and commercial hydroponic systems in relation to methods and technologies to optimize root rot management.[/FONT]

*[FONT=&quot]Hydroponic systems and the root environment[/FONT]*
[FONT=&quot]In cool temperate climates such as in southern Canada, hydroponic crops normally are grown in greenhouses with sophisticated systems for controlling conditions of the microclimate (temperature, humidity, carbon dioxide, light) and nutrient solution composition (pH, and dissolved oxygen concentration). On the other hand, in warm or tropical climates such as in São Paulo and Belém, Brazil, hydroponic crops are grown without sophisticated climate control, but with at least partial protection against harsh weather conditions, and with standardized nutrient solution. In such climates, hydroponic crops generally are produced in greenhouses constructed with wooden or concrete frames and covered on top with clear plastic film to exclude rain, and, in some instances, with screening against intense sunlight. Wooden lattice or plastic film may be used on one or more sides for protection against wind and rain. [/FONT][FONT=&quot]Roots of hydroponic plants either grow in the nutrient solution only, or in rockwool (stone wool), coconut fiber, sawdust, sand or other medium that is irrigated with nutrient solution. No soil is employed. Some crops, especially flowers and other ornamentals, are grown in single- or multi-plant containers with a rooting medium that is irrigated via tubing from above or by means of a trough below the container. Hydroponic vegetables often are grown in slabs or blocks of rockwool, coconut fiber or other medium enclosed in plastic film and fed with nutrient solution via plastic capillary tubes ([/FONT][FONT=&quot]Fig. 1[/FONT][FONT=&quot]). Others are grown in troughs formed from black-on-white plastic on the greenhouse floor, or in troughs of rigid plastic positioned at ground level or on benches. Nutrient solution is circulated through the troughs, which may or may not contain a rooting medium. Troughs usually are arranged in parallel and interconnected into large systems that accommodate thousands or tens of thousands of plants ([/FONT][FONT=&quot]Fig. 2[/FONT][FONT=&quot]). Lettuce, arugula (_Eruca sativa_ Mill. or _Eruca versicaria_ subsp. _sativa_ Shallot), _Nasturtium officinalis_ R.BR., and other small-sized plants are sometimes grown on gently sloping sheets of corrugated plastic or other material, and nutrient solution is allowed to flow down channels in the sheets and through the root zone of the plants. Nutrient solution in the various systems is either circulated once or is continuously recirculated. In Canada, the hydroponics crops industry is in transition from continuous or frequent discharge of used nutrient solutions into the environment to continuous recirculation through root zones of crops. Hydroponic systems are being adapted for continuous recirculation over concerns about pollution of water resources with greenhouse effluents and to conform with new environmental legislation. [/FONT]

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[/FONT]​ 
*[FONT=&quot]Causal agents of pythium root rot[/FONT]*
[FONT=&quot]The main species of _Pythium_ reported to cause root rot in hydroponic crops are _P. aphanidermatum_ (Edson) Fitzp., _P. dissotocum_ Drechsler, _P. ultimum_ Trow var. _ultimum_, and members of _Pythium_ group F (4, 14, 23, 28, 39, 61, 68, 73, 82, 86, 106). _Pythium aphanidermatum, P. dissotocum_, and _Pythium_ F produce abundant zoospores, while _P. ultimum_ var. _ultimum_ produces zoospores only rarely. Zoospores are produced asexually in sporangia and associated vesicles. The sporangia of _P. aphanidermatum_ are filamentous and lobed (or inflated), while those of _P. dissotocum_ are filamentous, dendroidly branched and not inflated or slightly inflated (112). _Pythium_ group F is characterized by filamentous non-inflated sporangia (82, 100). Each of the species is able to produce oospores (thick-walled sexual spores) in infected roots and in the rhizosphere. These _Pythium_ spp. each attack a wide range of host plants. A few other species, such as _P. intermedium_ and _P. irregulare_ (82, 101), have also been reported in hydroponically-grown plants. The genus _Pythium_ belongs in the family Pythiaceae of the class Oomycetes, members of which were regarded as fungi for over a century and a half. However, Oomycetes are now commonly described as fungal-like and assigned to the Kingdom Straminipila (16).[/FONT]

*[FONT=&quot]Sources of pythium inoculum in hydroponic crops[/FONT]*
[FONT=&quot]The principal species of _Pythium_ that attack hydroponic crops frequently occur in soils and plant residues in greenhouses and outdoors (61, 73, 86). Inoculum of _Pythium_ spp. can be introduced into greenhouses and hydroponic systems in many ways including airborne dust, in soil and plant fragments on greenhouse tools and equipment, on people's footwear, and in water used to prepare nutrient solution (39, 59, 75, 78, 95, 99). _Pythium_ spp. were reported also in peat brought into greenhouses for use in rooting media (23, 87). [/FONT]
[FONT=&quot]In Canada, transplants are a common source of _Pythium_ in hydroponic vegetable crops. Some hydroponic vegetable growers produce their own transplants, but a majority obtain them from specialist producers who supply the plants in rockwool cubes. Growers who produce their own transplants often do so on benches in greenhouses that are not otherwise used for crop production. In several instances _P. aphanidermatum_ and _P. dissotocum_ were easily recovered from soil trapped in benches used for growing transplants, and the pathogens were frequent in roots of cucumber, pepper, and tomato transplants (W. Liu & J.C. Sutton, 2000-2003, unpublished). Specialists generally begin production of transplants in rockwool plugs (about 2.5 x 2.5 x 4.0 cm) contained in plastic trays, and subsequently transfer them to rockwool cubes (about 10.0 x 10.0 x 6.5 cm) positioned in rows on laser-levelled concrete floors. Every few hours the floors are flooded with nutrient solution and allowed to drain so as to keep the cubes moistened. In this type of ebb and flood system, the nutrient solution is pumped from tanks below ground level, through pipes beneath the floors, and out onto the floors before draining back into the tanks. Despite extraordinary sanitation measures, some plants produced in these systems were found to be infected with _P. aphanidermatum_ and _P. dissotocum_ (Sutton, J.C. & W. Liu, 2002, unpublished). The presumed inoculum source was the underground plumbing, which possibly harbored oospores and mycelium. In many instances, infected transplants from various production systems were symptomless when ready for shipping to growers. [/FONT][FONT=&quot]It is possible that transplants of hydroponic salad crops such as lettuce, arugula, and _Nasturtium officinalis_ also become infected by _Pythium_ prior to being set out in hydroponic systems. In Pará State, Brazil, transplants are often produced in cells of seedling flats containing various rooting media, and positioned on benches sheltered from rain, wind, and direct sunlight. Some growers utilize styrofoam trays floating on water in tanks. Infection of transplants by _Pythium_ seems possible in these systems, however we are not aware of any reports to confirm or refute this. [/FONT]
[FONT=&quot]Hydroponic materials used previously for crop production may frequently harbor _Pythium_. Some growers re-use rooting media such as slabs of rockwool or coconut fiber, without sterilization or other measures to destroy pathogens in the media. This practice allows carry-over of inoculum of various pathogens, including _Pythium_ spp., to the subsequent crop. Pipes, tubing, tanks and other plumbing components of hydroponic systems are often potential sources of _Pythium_ in successive crops, even when the systems are treated with disinfectants. In studies in small-scale hydroponic systems, the chemical sterilants Virkon (potassium monopersulfate; Pace Chemicals, Burnaby, Canada) and Chemprocide (didecyldimethyl ammonium chloride; Dispar Inc., Joliette, Canada) were only partially effective in destroying _P. aphanidermatum_ (C.R. Sopher and J.C. Sutton, 2003, unpublished). Sodium hypochlorite was completely effective, but can corrode some components of hydroponic systems. Oospores of _Pythium _spp. can frequently be found in biofilms, mucilaginous materials and root tissue fragments in hydroponic plumbing (C.R. Sopher and J.C. Sutton, 2003, unpublished) and are undoubtedly a principal form of inoculum. Oospores are also resistant to chemical sterilants. Oospore populations are also known to survive for months or years in field soils (2, 61, 10. [/FONT]
[FONT=&quot]Insect vectors are considered important means by which _Pythium_ and other pathogens are introduced and dispersed in hydroponic crops. In North America, fungus gnats (_Bradysia_ spp.) and shore flies (_Scatella stagnalis_ Fallen.) were reported to acquire _Pythium_ by external contamination or ingestion (27, 29, 40). _Pythium_ oospores were found in the digestive tracts of larvae and adults of each of these insects. In fungus gnats, oospores acquired during the larval stage remain in the digestive tract during pupation, and can be aerially transmitted generally in a viable state by the adults and eventually excreted in the frass (40). In Canada, fungus gnats are found wherever greenhouse crops are grown, and readily enter greenhouses through doors and ventilators (37). Their larvae feed on fungal mycelia and organic residues in soils, soilless mixes, hydroponic media, and nutrient solutions. The larvae are also known to feed on roots and root hairs of cucumbers and other plants, thereby making wounds through which pathogens may invade. It is likely that similar or different insects are factors in epidemics of root rot in hydroponic crops produced in warm temperate and tropical climates, but we have not encountered any reports on this possibility. [/FONT]

*[FONT=&quot]Infection of roots by Pythium[/FONT]*
_[FONT=&quot]Pythium aphanidermatum, P. dissotocum[/FONT]_[FONT=&quot], and _Pythium_ group F infect roots of hydroponic plants by means of zoospores and mycelia (21, 73, 82, 86, 99, 122). The initial (primary) inoculum in root rot epidemics (that is, the inoculum which initiates the epidemics) is chiefly zoospores produced from sporangia formed by germinating oospores, or perhaps by mycelium (31), in plant residues, soil, hydroponic pipes and tubing, and other inoculum sources in the crop environment. Generations of zoospores arising from sporangia formed on infected roots of the hydroponic crop are a principal form of subsequent (or secondary) inoculum in root rot epidemics. Mycelia are the principal units of inoculum of _P. ultimum_ var. _ultimum_, which produces few or no zoospores and is better adapted to conditions of greenhouse soils and soilless mixes than to systems with circulating nutrient solution (43). The reader is referred to Martin & Loper (61) for details of _P. ultimum_ var. _ultimum_. [/FONT]
[FONT=&quot]Consistent with general acceptance by plant disease epidemiologists, the term infection is used here to refer to the process of establishment of a parasitic relationship of the pathogen in the host (9). In _Pythium_ zoospores this process includes zoospore encystment at the root surface, synthesis of a thick cell wall, adhesion to the root surface, germination and germ tube growth, penetration of the root surface, and sufficient post-penetration development to allow the newly-formed colony to function independently of the germinated spore (33). Zoospores of _P. aphanidermatum_ and other _Pythium_ spp. were reported to penetrate non-wounded surfaces of all portions of young roots, including root cap cells, root hairs, and regions of meristematic activity, cell elongation, and cell maturation (21, 48, 56, 11. In general, however, root tips, elongation zones, and young root hairs are frequently penetrated. _Pythium aphanidermatum_ and other _Pythium_ spp. have been reported to penetrate roots directly by means of penetration pegs, fine hyphae, and enzymatic action (21, 2. Formal descriptions of _P. aphanidermatum_ and _P. dissotocum_ include appressoria (112), and indeed some authors observed appressoria or appressoria-like structures on roots by means of transmission or scanning electron microscopy (15, 21, 86). In other studies, however, scanning electron microscopy did not reveal appressoria (2 or appressoria were not mentioned (21). Production of appressoria is known to vary with temperature and pH (21), and it is possible that incidence and density of appressoria during epidemics of _Pythium_ root rot in hydroponic crops is highly variable. Besides direct penetration of roots, _P. aphanidermatum_ and other _Pythium_ spp. are able to infect wounded tissues, such as sites of emergence of lateral roots and sites of attack by larvae of fungus gnats. [/FONT]
[FONT=&quot]Findings in several studies indicate that root mucilage on surfaces of roots and in surrounding nutrient solution is an important factor influencing infection of roots by _Pythium_ hyphae, and in promoting _Pythium_ populations in the root zone. _Pythium_ group F, _P. ultimum_ var. _ultimum_, and other _Pythium_ spp. penetrate roots in zones of increased mucilage production such as junctions of cortical cells, zones of elongation, and at the base of lateral roots and root hairs (43, 67, 86, 11. Cucumber plants often produce abundant root mucilage that accumulates in the nutrient solution. Zheng _et al._ (122) reported on the role of this mucilage in epidemics of root rot caused by _P. aphanidermatum_. They found that the pathogen was more frequent in roots with associated mucilage than in those lacking mucilage, and that the amounts of mucilage correlated positively with root browning. These findings, combined with microscopic observations of _Pythium_ hyphae in mucilage and roots, indicated that the mucilage supported prolific growth of _P. aphanidermatum_ and served as a food base from which hyphae of the pathogen were able to invade the roots, including old roots which zoospores normally do not infect. [/FONT]

*[FONT=&quot]Colonization and symptom development[/FONT]*
[FONT=&quot]Colonization of plants by _P. aphanidermatum_ and _P. dissotocum_ in hydroponic plants is normally biotrophic in initial stages and subsequently necrotrophic (73). In the biotrophic phase the roots are colonized without development of overt symptoms, a condition sometimes referred to as subclinical (9. In the necrotrophic phase, the roots become discolored, generally as a hue of brown, grey-brown, reddish-brown, yellow-brown, or yellow, depending on the type of host and species or isolate of the pathogen. _Pythium_ group F was found to colonize roots of hydroponic tomato plants without inducing visible symptoms under optimal conditions for plant growth, but some strains caused severe necrosis especially in stressed plants (14, 85, 86). [/FONT]
[FONT=&quot]Root colonization by _P. aphanidermatum, P. dissotocum_, and _Pythium_ group F is both intercellular and intracellular (21, 71, 85, 9. Haustoria-like structures were reported in cells of spinach and pepper roots infected by _P. dissotocum_ (71, 9. _P. aphanidermatum_ normally colonizes the cortex of pepper roots (73), while _P. dissotocum_ has been found in the stele of immature root tips of strawberry (69) and tends to colonize epidermal cells of roots (21). Each of these pathogens increased cytoplasmic granulation in cortical tissues of pepper (73). _Pythium_ group F was found to colonize the epidermis and outer cortex of tomato roots, inducing marked disorganization of the host cells in a phase of pathogenesis interpreted as necrotrophy, and to subsequently ingress to the inner cortex and stele, where it induced various kinds of host defense reactions (85). [/FONT]
[FONT=&quot]The necrotrophic phase of _Pythium_ root rot in hydroponic pepper plants is marked by root tip browning and expansive browning (_P. aphanidermatum_) or yellowing (_P. dissotocum_) of the roots (71, 73). All isolates of _P. aphanidermatum_ and _P. dissotocum_ also produced architectural changes in the root systems, chiefly stunting, stubbiness, and root proliferation (73). Some isolates of _P. dissotocum_ produced swelling of roots and proliferation of callus cells. Similar kinds of symptoms were found in hydroponically-grown chrysanthemums (5, lettuce, antirrhinums, (J.C. Sutton, W. Liu, M. Johnstone, and N. Ortiz-Uribe, 2002-2003, unpublished observations). In all hosts, roots were colonized by the _Pythium_ isolates well in advance of expansive root browning or yellowing, such that much more root was colonized than exhibited overt symptoms as illustrated for chrysanthemum ([/FONT][FONT=&quot]Fig. 3[/FONT][FONT=&quot]). Thus, in agreement with comments of Kamoun _et al._ (52), root necrosis did not represent a hypersensitive reaction or incompatible response in which the host cells are quickly killed and advance of the pathogen is blocked.[/FONT]

[FONT=&quot]




[/FONT]​ 
[FONT=&quot]Root browning is a susceptible necrosis reaction that develops in root tissues after they are infected and colonized by _P. aphanidermatum_ and other _Pythium_ spp. Browning is associated with accumulation of phenolic polymers, which in part may become bound to cell walls of root tissues (20, 72). In recent studies, concentrations of bound phenolics, which include simple as well as polymerized forms, greatly increased in pepper roots inoculated with _P. aphanidermatum_, but remained low in noninoculated controls (72, 103). Concentrations of free phenolics, however, increased only slightly in inoculated roots and were similar to those in noninoculated roots. While it is possible that synthesis of free phenolics did not increase in inoculated roots, it is more likely that synthesis did increase but that concentrations in the roots remained low because of systemic transport to other parts of the host or release into the nutrient solution, as was found in hydroponic lettuce (11). Most phenolics in higher plants are derived at least in part from phenylalanine, a product of the shikimic acid pathway. Deamination (release of ammonia) from phenylalanine by phenylalanine ammonia lyase (PAL) yields _trans_-cinnamic acid, derivatives of which are simple phenolic compounds called phenylpropanoids, important building blocks of more complex phenolic compounds (105). Elicitors of _P. aphanidermatum_ and other pathogens are known to increase PAL in cultured plant cells and protoplasts (91). Collectively, the available evidence indicates that _P. aphanidermatum_ and other _Pythium_ spp. markedly activate the shikimic acid and phenylpropanoid pathways, and promote biosynthesis of phenolic compounds in infected roots. [/FONT][FONT=&quot]Recent findings point to the exciting possibility that _Pythium aphanidermatum_ triggers necrosis in host roots by means of a specific elicitor. Veit _et al._ (113) sequenced a secondary metabolite of the pathogen, and determined its ability to induce cell death in carrot, _Arabidopsis_, and tobacco. The metabolite, called the _P. aphanidermatum_ necrosis-inducing elicitor or PaNie, has a high degree of sequence similarity with necrosis-inducing elicitors of _Phytophthora_ spp. and _Fusarium oxysporum_ (3, 24, 81). Evidence indicates that PaNie induces the phenylpropanoid pathway in the host (91). [/FONT]
[FONT=&quot]Symptoms on aerial portions of crops affected by _Pythium_ root rot often include stunted shoots, wilted leaves, and smaller, fewer fruits (71, 122). The leaf canopy of sweet pepper, cucumber, and several other hosts normally remains green until root rot is extremely severe such that many roots are brown, decayed and fragmenting. Moreover, in our experience, leaves of pepper plants inoculated with _P. aphanidermatum_ or _P. dissotocum_ within a few days often appear darker green than those of noninoculated control plants. Foliage of commercial crops with severe root rot often appears in good health except that it is typically stunted. Canopy stunting may go unnoticed for a considerable time because all plants in the cohort are similarly affected (71, 9. _Pythium_ root rot stunts shoot growth and reduces flowering and fruiting long before the foliage wilts or becomes chlorotic. Wilting is initially temporary, often in association with high daytime temperatures, but in many instances becomes permanent. Under some conditions, severely-affected peppers and certain other kinds of hydroponic crops are able to regenerate roots sufficiently to sustain green foliage for long periods, but growth and productivity normally are reduced or poor. [/FONT]

*[FONT=&quot]Inoculum production[/FONT]*
_[FONT=&quot]Pythium aphanidermatum, P. dissotocum[/FONT]_[FONT=&quot] and _Pythium_ group F produce abundant sporangia, zoospores, and oospores in association with roots of hydroponic crops. Sporangia are generally formed on mycelium at or near the root surface (86). Sporangia of _P. aphanidermatum_ have been encountered also in association with mycelia in cucumber root exudates floating in the plant nutrient solution (122). In field soils, lobate sporangia such as those of _P. aphanidermatum_ may survive only a day or two, and are exogenously dormant on account of microbiostasis (61, 96, 97). The survival of sporangia and their ability to produce zoospores in root zones of hydroponic crops is not well-understood. However, zoospores can be found in nutrient solutions during most phases of root rot epidemics, though are sometimes difficult to detect (53, 66, 71, 100). The majority of zoospores probably arise from sporangia on mycelium while some may form from sporangia formed from germinated oospores (97). As in all _Pythium_ spp., the zoospores are not formed in the sporangium itself but in a vesicle outside it (112). [/FONT]
[FONT=&quot]Oospores of _P. aphanidermatum, P. dissotocum_, and _Pythium_ group F form in infected roots, especially in cortical tissues, and can be found on mycelia in nutrient solution surrounding the roots and rooting media, such as among slivers of rockwool. In investigations of hydroponic peppers inoculated with _P. aphanidermatum_ or _P. dissotocum_, oospores were less numerous in discoloured (brown) portions of roots than in portions that were not discoloured (73). Density of oospores in the roots varied markedly with pathogen isolate. Oospores are the principal survival structures of _Pythium_ spp. (61), but quantitative aspects of oospore survival in hydroponic systems remain to be explored. Based on observations of _P. aphanidermatum_ and other _Pythium_ species in soils and host residues (61), oospores may survive for at least several months in fragments of dead roots or in a free state in troughs, used rooting media, and plumbing components of hydroponic systems. Oospores exhibit constitutive dormancy, so that some of them do not germinate even under conditions conducive to the germination of mature oospores (61). Temperature, pH, age, and other variables influence the conversion of dormant to germinable oospores (1). Germination frequency of _P. aphanidermatum_ oospores from culture was found to be initially low (27%) and progressively increased after 1 to 2 weeks (2), whereas only 10% of those produced in soil were capable of germination (10. [/FONT]
[FONT=&quot]Hyphae are a further form of _Pythium_ inoculum of potential importance in root rot epidemics. Hyphal fragments of _P. aphanidermatum_ and _P. dissotocum_ recovered from nutrient solution in root zones of peppers grown in small-scale trough systems were, in most instances, associated with fragments of rotted roots (A. Khan, N. Owen-Going & J.C. Sutton, unpublished). However, dissociated hyphae are easily overlooked. Growth of hyphae of _P. aphanidermatum_ from slimy masses of root exudates in the nutrient solution to roots of cucumbers was reported in trough systems (122). The role of hyphae in plant to plant spread of _P. aphanidermatum_ was demonstrated in cucumbers grown in rockwool slabs with recirculating nutrient solution amended with a nonionic surfactant to inactivate zoospores (100).[/FONT]

*[FONT=&quot]Inoculum dispersal[/FONT]*
[FONT=&quot]Circulating nutrient solution is a principal means by which propagules of _Pythium_ are dispersed in hydroponic crops. Patterns and rates of dispersal of _Pythium_ propagules can be expected to vary in relation to the type of propagule, pattern and dynamics of flow of the nutrient solution, and impediments in flow paths such as roots, rooting media, and physical components and structure of the hydroponic system. Motion of nutrient solution through root zones in hydroponic troughs with no rooting medium (the so-called nutrient-film technique or NFT) include zones of rapid streaming between root masses and zones of slow movement or stagnation in areas occupied by roots (36). The latter increase proportionately as root systems grow. Roots, rooting media, and plumbing components in various kinds of hydroponic systems provide large surface areas on which propagules are potentially deposited or trapped. Movement of nutrient solution through collecting pipes and in mixing tanks is generally rapid and turbulent. The physical structure of the hydroponic system may markedly influence propagule dispersal. For example, when nutrient solution is fed to individual slabs of rockwool compartmentalized in plastic film and recirculated from the slabs through pipes and mixing tanks, propagules have the immediate possibility of dispersal only among the few plants, often two to six, growing in any particular slab ([/FONT][FONT=&quot]Fig. 1[/FONT][FONT=&quot]). This contrasts with troughs that each accommodate numerous, often hundreds, of plants, and which thus favor immediate downstream dispersal of propagules to many plants within the trough ([/FONT][FONT=&quot]Fig. 2[/FONT][FONT=&quot]). [/FONT]
[FONT=&quot]Zoospores of _Pythium_ and other Pythiaceous microbes are dispersed by transport in nutrient solution (36, 77, 99, 100) and are also motile by means of two flagella (17, 33). Zoospores of _Phytophthora_ spp. were found to be dispersed only short distances (<10 cm) in stagnant or standing water, but comparatively long distances in flowing water (36). In hydroponic troughs in which root systems are well-developed, zoospore populations tend to be high and aggregated in zones of slow movement of nutrient solution, and zoospore dispersal is largely localized among nearby roots (36, 84). These findings, and perhaps intuition, suggest that localized dispersal of _Pythium_ and _Phytophthora_ zoospores may predominate in roots grown in rockwool and other media where movement of nutrient solution is slow. However, there is abundant evidence, though largely circumstantial, that portions of zoospore populations are dispersed rapidly throughout major portions of small- and commercial-scale hydroponic systems (53, 65, 66, 71, 9. When flow of the nutrient solution is turbulent, zoospores abruptly shed their flagella and encyst, thereby losing the necessary ability for chemotaxis towards potential infection sites on roots. Even minor movement and vibration of zoospore suspensions, such as in glassware on a moving laboratory cart, can trigger shedding of flagella. Observations in commercial crops of sweet pepper grown in troughs without a rooting medium indicated that few zoospores or other _Pythium_ propagules returned to the crop in nutrient solution that was recirculated through pipes and mixing tanks (71). About 10 to 55 zoospores mL-1 nutrient solution were found at outflows of the troughs, but d&quot;0.1 zoospores mL-1 solution were recovered, all encysted, before the nutrient solution flowed into the mixing tank, and none usually was found after the mixing tank. Zoospores probably were not recovered on account of deflagellation, lysis, encystment, sedimentation, adhesion to various surfaces, inactivation, and death. [/FONT]
[FONT=&quot]Dispersal of oospores and hyphal fragments of _Pythium_ in hydroponic nutrient solutions has been reported only incidentally (39, 71, 100). It can be anticipated that these propagules are dispersed as free entities or in association with root fragments, especially during stages of epidemics when roots are rotting. Fragments of sloughed root cortices with oospores and hyphae of _P. aphanidermatum_ were frequently observed in epidemics of root rot in small-scale trough systems (J.C. Sutton, A. Khan & N. Owen-Going, 2002; unpublished). In contrast to oospores, hyphal fragments of _Pythium_ spp. are short-lived in many environments (61), yet there remains the possibility that they may survive long enough to make contact and possibly infect other roots. Based on apparent circumstantial evidence from cucumbers in small-scale hydroponic systems, Stanghellini _et al._ (100) concluded that hyphal fragments either do not occur or do not function as effective inoculum for dissemination in recirculating nutrient solution. [/FONT]
_[FONT=&quot]Pythium[/FONT]_[FONT=&quot] propagules may be dispersed between troughs, or among slabs of rockwool or other rooting media by fungus gnats and shore flies (discussed above), splashing water, greenhouse equipment, and workers (29, 39, 40, 59). Water dripping from the greenhouse roof can often splash onto exposed rooting media, nutrient solutions, plants, and the greenhouse floor, thus affording the possibility of splash dispersal of _Pythium_ propagules. Transmission of only a few propagules from trough to trough or slab to slab may allow _Pythium_ to establish effectively in previously uncontaminated root zones (66). Several investigators have reported trough to trough transmission (66, 98, 100, 116), though the mode of transmission was usually not known. While dispersed zoospores may encyst and so become immobilized, the cysts are more resistant to extremes of temperature, desiccation, or ionic environment than are zoospores (33). However, their ability to adhere to roots and other surfaces decreases over time. [/FONT]

*[FONT=&quot]Epidemiology of root rot[/FONT]*
[FONT=&quot]An understanding of root rot epidemics is fundamental to the development and refinement of methods and practices to manage the disease in hydroponic crops, but remains fragmentary. While root rot is almost universal in commercial hydroponic systems, and in many instances becomes sufficiently severe to cause serious crop losses, it is also true that in many other instances progress and spread of the disease is comparatively slow and losses are perceived as minor. From the literature, and an abundance of anecdotal evidence from greenhouse growers and crop advisory personnel, it is clear that a myriad of variables significantly influence _Pythium_ species and root rot development in hydroponic systems. Important variables range from subtleties such as calcium in the root zone, which at millimolar levels strongly influence adhesion of zoospores to roots (33), to elevated temperature, which can bring about abrupt and explosive increases in root necrosis in large portions of crops (4, 28, 39, 54, 61, 83, 107). This portion of the present article will now focus on effects of factors associated with the host, the pathogen, the environment of the nutrient solution and plant canopy, and human interferences on disease severity and pathogen ecology. Excellent perspectives of the general principles of epidemiology are given in Zadoks & Schein (119) and Bergamin Filho & Amorim (7). For a critical review of the epidemiology of diseases caused by _Pythium_ spp. in plants grown in soil, attention is drawn to Martin & Loper (61). [/FONT]

*[FONT=&quot]Host Factors[/FONT]*
[FONT=&quot]To our knowledge, all cultivars of all vegetables and flowers produced in greenhouse hydroponic systems in Canada, the USA, Brazil, France, and other countries are susceptible to moderate or severe epidemics of Pythium root rot. These crops include cucumbers, tomatoes, sweet peppers, lettuce, spinach, arugula, nasturtium, and roses. Other crops such as chrysanthemum and antirrhinum have not yet been widely successful in hydroponic systems in part on account of severe root rot. In Canada, casual observations and anecdotal reports indicate that tomatoes generally are less severely affected than are cucumbers and sweet peppers. We are not aware of any published reports of quantitative differences in cultivar susceptibility to root rot in various hydroponic crops, but in some instances growers consider that some cultivars of hydroponic vegetable crops are less susceptible than others. Kamoun _et al._ (52) reported differences in host susceptibility to _Pythium_ root rot based on plant age and tissue development. [/FONT]
[FONT=&quot]Susceptibility to _Pythium_ root rot is normally reported in terms of the severity of browning (or other discoloration) and fragmentation of the roots, or as root growth parameters such as volume, length, fresh mass and dry mass. Estimation of symptoms, however, focuses only on the necrotrophic phase of disease and neglects susceptibility to the biotrophic phase including the infection process and colonization. In our experience, root systems of peppers and chrysanthemums inoculated with _P. aphanidermatum_ or _P. dissotocum_ in small-scale hydroponic units under some conditions were symptomless yet heavily colonized by the pathogen. Other investigators reported similar findings with _P. dissotocum_ and _Pythium_ group F (86, 9. Further, we have frequently noted that a large proportion of colonized but symptomless roots (e.g. 30-70%) turn brown during a short interval (e.g. 12 to 24 h) between observations. Critical assessment of susceptibility requires estimation of infection frequency and colonization in inoculum dose-response studies, as well as estimation of symptoms. Environmental conditions need to be critically controlled in view of the sensitivity of colonized roots to the transition from biotrophy to necrotrophy. [/FONT]
 [FONT=&quot]Phenological growth stage and age of roots influence root rot severity in hydroponic crops but quantitative relationships of these variables and rates of disease increase are not well-understood. Root browning and rotting often progress for almost the entire life of the crop, which in Canada is about 4 months for cucumbers, 10 to 11 months for tomatoes, and 10 to 18 months for sweet peppers. Each of these hosts has an extraordinary ability to continually produce new roots, which frequently become attacked by _Pythium_. In general, zoospores of _P. aphanidermatum, P. dissotocum_, and _Pythium_ group F, as well as other _Pythium_ species, infect young roots regardless of the phenological growth stage of the host, but do not infect older roots (33, 61, 89). However, Zheng _et al._ (122) found that hyphae of _P. aphanidermatum_ growing from root mucilage in the nutrient solution invaded young and old cucumber roots. In this study, root growth, quantities of root mucilage, and percent discolored roots oscillated in patterns that were similar and synchronous, which suggested that the dynamics of root growth and mucilage accumulation are fundamental factors contributing to patterns of root browning and rot associated with _P. aphanidermatum_. Root mucilage is readily utilized by rhizosphere bacteria (55), including microbial agents that, by destroying the mucilage, may restrict saprophytic development of _P. aphanidermatum_ and its ability to attack roots via hyphae (122). In general, qualitative and quantitative shifts in mucilage and other exudates from roots at various stages of crop development appear to markedly affect root zone microbes including _Pythium_ spp., which depend on exogenous nutrients for germination and infection (61).[/FONT]
[FONT=&quot]Recent studies in our laboratory have demonstrated for the first time that environmental stress factors can increase the susceptibility of hydroponically-grown plants to _Pythium_ root rot. The studies were conducted using pepper plants in single-plant hydroponic units with aerated nutrient solution. When temperature of the nutrient solution was raised to 28ºC or 34ºC for a few hours or days and subsequently lowered to 22-24ºC _prior to_ inoculation of the root systems with _P. aphanidermatum_, root browning progressed earlier and more rapidly than in control plants maintained at 22-24ºC before inoculation (C.R. Sopher & J.C. Sutton, unpublished). Similarly, when plants were kept in nutrient solution (pH 5. amended with certain simple phenolic compounds for 48 h and then placed in unamended solution for 24 h before inoculation with _P. aphanidermatum_, disease severity increased more rapidly than in untreated controls (103). This finding suggested that phenolics escaping from diseased roots might predispose downstream healthy plants to attack by _Pythium_. Collectively, the studies demonstrated that high temperature and phenolic compounds predisposed the plants to root rot. By definition, predisposition refers to increased susceptibility of plants to disease brought about by environmental factors acting _prior to_ infection by the pathogen (39). It is likely that other environmental stressors or stress conditions, such as low intensity light and low concentration of dissolved oxygen in the nutrient solution also predispose plants to _Pythium_ root rot. Chérif _et al._ (14) found that _Pythium_ F colonized roots of hydroponically-grown tomatoes more extensively when concentration of dissolved oxygen was moderate (5.8-7.0%) or low (0.8-1.5%), than at high levels (11-14%), however, it was not determined whether the influence of reduced oxygen was through increasing susceptibility of the host, or through effects on the pathogen or the host-pathogen interaction.[/FONT]

*[FONT=&quot]Pathogen Factors[/FONT]*
[FONT=&quot]Substantial intraspecific variation in pathogenicity and virulence exists in species of _Pythium_ that attack hydroponic crops. Symptoms produced by isolates of _P. dissotocum_ in pepper varied widely but generally overlapped with those caused by other isolates, and included zones of root-tip browning of different sizes and hues, different severity of expansive root yellowing, architectural changes, root swelling, and callus cell proliferation (73). Isolates of _P. aphanidermatum_ usually are highly virulent in hydroponic crops, but variation in virulence was reported in tomato (32) and among twelve plant species grown in soil (63). Rafin & Tirilly (82) reported that isolates of _Pythium_ group F variously caused localized necrosis at root apices and more severe and progressive root rot. In view of the intraspecific variation in _P. aphanidermatum_ and _P. dissotocum_, the variation in _Pythium_ spp. grouped as _Pythium_ F, and the environmental sensitivity of symptom expression by various _Pythium_ strains, it is probable that the composition of _Pythium_ species and strains in a given crop can markedly influence patterns of root rot epidemics (71, 73). [/FONT]

*[FONT=&quot]Environmental and Microbial Factors[/FONT]*
[FONT=&quot]Development of severe root browning and root rot in hydroponic crops produced in greenhouses in Canada often coincides with hot weather when temperature of the nutrient solutions and of the greenhouse in general is high. Some growers have replenished the nutrient solution with fresh solution prepared with cool water from wells to help alleviate the problem. _Pythium aphanidermatum_ is widely known to cause severe symptoms of root rot in various crops when root zone temperature is moderate or high (e&quot;23-27ºC) (4, 28, 61, 73, 107). In chrysanthemums grown in single-plant containers with controlled root-zone temperature, the pathogen caused progressively more severe root rot symptoms with increase in temperature from 20ºC to 32ºC ([/FONT][FONT=&quot]Fig. 3[/FONT][FONT=&quot]). In a parallel study, progress curves for root discoloration caused by _P. dissotocum_ were similar at 24-32ºC, but lower at 20ºC. Root disease caused by _P. dissotocum_ in spinach was reported to be severe at 21-27ºC but even more severe in winter months when nutrient solution temperatures were low (2. Fortnum _et al._ (26) found that root necrosis caused by _P. myriotylum_ in tobacco seedlings in a greenhouse float system was lowest when the nutrient solution temperature was 15ºC and highest at 30ºC. It is important to recognize that effects of temperature on symptom development can differ markedly from those when the pathogen colonizes the tissues symptomlessly during the biotrophic phase. In our experience, roots of hydroponic peppers and chrysanthemums can be extensively colonized by _P. aphanidermatum_ or _P. dissotocum_ but remain almost symptomless at 16 to 18ºC, yet develop severe symptoms within minutes or hours when the temperature is raised to 24-28ºC (N. Owen-Going, W. Liu & J.C. Sutton, unpublished). Temperature also differentially affects other stages of _Pythium_ infection cycles such as the production, dispersal and germination of zoospores, oospore germination, and infection processes (61). The progress curves of root browning represent integrated effects, both direct and indirect, of temperature on the pathogens and their interactions with the roots. [/FONT]
[FONT=&quot]Concentration of dissolved oxygen in the nutrient solution is a critical factor influencing root rot and crop productivity (14, 38, 88, 120). In general, root rot increases when oxygen levels are low (14). Gases move to and from roots of plants in many types of hydroponic systems chiefly by mass flow of gas dissolved in moving solution, which contrasts with diffusion through gas-filled pores as occurs in soils. Oxygen concentration in the root zone of hydroponic crops is commonly 6 to 8% (123) and growers have been encouraged to maintain a minimum of 5 mg oxygen L-1 nutrient solution (36). Concentration of dissolved oxygen can quickly decline, however, especially when temperature of the nutrient solution is high. In the absence of biological factors, the level of dissolved oxygen in water declines, for example, from about 9 to 7 mgL-1 as temperature increases from 20 to 35ºC at 101.3 kPa and 100% relative humidity. Of greater importance, however, is greatly increased demand for oxygen by roots and root-zone microbes as temperature increases, factors that become particularly important when crops have produced dense masses of roots and when microbial populations are high. It has been further estimated that a crop that is environmentally stressed requires about ten times more oxygen than one not under stress (39, 94). While allowing the nutrient solution to free fall back into the nutrient recharge tank helps to maintain adequate oxygen levels, injection of oxygen directly into the solution may be needed, especially in continuously recirculating systems. Oxygenation is one of the few practical measures available to growers when root rot is well advanced, and helps to avoid further necrosis, disintegration, and sliminess of the roots (39). The observations of Chérif _et al._ (14) suggest that elevated levels (e.g. 11-14%) of oxygen would be advantageous in protecting roots and promoting crop productivity.[/FONT]
[FONT=&quot]Recirculation of nutrient solution in greenhouse hydroponic systems increases the risk of accumulation of phenolic and other organic acids to phytotoxic levels in the root zone (49, 50, 51, 114). These organic compounds are excreted as root exudates and by rhizosphere microbes, and are also released by constituent devices in the growing system (114, 117). Concentrations of total phenolic compounds of 23-30 µg gallic acid equivalents per litre of nutrient solution were found in root zones of 6-month-old hydroponic pepper crops in Ontario (T.N. Owen-Going and J.C. Sutton, 2004, unpublished observations). Phenolic compounds commonly associated with roots and nutrient solution of tomatoes and peppers, for example, include benzoic, caffeic, chlorogenic, ferulic, _p_-hydroxybenzoic, salicylic, and vanillic acids, most of which produce phytotoxic effects at 200 to 400 µM in the nutrient solution (10, 49, 72). Rhizosphere microbes can utilize phenolic acids (8, 115), and the rate of utilization is substantially affected by oxygen concentration (74). Thus, microbes can potentially ameliorate the toxicity of phenolic compounds to hydroponic crops (11). Recent studies of hydroponic peppers in our laboratory demonstrated that several phenolic acids applied in the nutrient solution at a final concentration of 200 µM exhibited allelopathic effects, but concentrations of 2 to 200 µM also predisposed the plants to root rot caused by _P. aphanidermatum_ (72, 103). In this system allelopathic phenolics rapidly increased in roots infected by _P. aphanidermatum_, promoted sporangia production by the pathogen, leaked into the nutrient solution, exhibited toxicity to pepper, and predisposed pepper to attack by the pathogen. Based on these findings, it was hypothesized that _P. aphanidermatum_, by increasing phenolics in roots, initiates autocatalytic cycles of events that accelerate root rot epidemics and health decline in peppers (103). [/FONT]
[FONT=&quot]Hydroponic systems are often extraordinarily conducive to root rot epidemics in part because the root zones lack communities of microbes that can effectively antagonize pathogenic species of _Pythium_ associated with the roots, rooting media, and nutrient solution. In contrast to microbial communities in natural soils, microbial diversity and density in hydroponic systems are frequently low. A majority of hydroponic crops are germinated (or otherwise propagated), and subsequently transplanted, in hydroponic units with rooting media, nutrient solution, and components such as plastic containers, troughs, and tubes that contain comparatively few microbial propagules. It can be anticipated that, during crop development, further incidental microbes enter the root zone, and that the density and diversity of microbial communities increases as availability and diversity of food sources from rhizodeposition increase, but published data to support this are sparse. In cucumbers transplanted into small-scale hydroponic trough units with recirculating nutrient solution, estimated density of fungal propagules was initially about 102 colony forming units (cfu)/mL, increased to near 104 cfu/mL by day 53, and remained near this value until the study ended on day 102 (122). Bacterial density increased from slightly below 105 cfu/mL to peaks of 108 - 109 cfu/mL at 74 and 95 days. Propagule density of _Pythium, Penicillium, Fusarium_, other fungi, and bacteria was, in most cases, one hundred to one thousand times greater in the root mucilage than in adjacent nutrient solution. Patterns of increase in density of bacterial and fungal propagules in the nutrient solution were also reported for rockwool-grown tomatoes at about 4 to 6 months after transplanting (109). [/FONT]
[FONT=&quot]While buildup of root-zone microflora during the life of a hydroponic crop can be substantial, sanitation practices and use of new plastic materials and rooting media preclude all but minor carry-over of microflora into the subsequent crop. Thus, the very practices that aim to eliminate pathogens also remove microbes that potentially antagonize pathogens, which again contrast with crops grown in natural soils. However, some hydroponic cucumber growers in Ontario, Canada, boldly reused rockwool slabs for up to four successive crops and found that root rot was always less severe in the used slabs than in crops where new slabs were used. These anecdotal reports were consistent with recent scientific findings that the microflora of used rockwool plays an important role in suppressing root and crown rot symptoms caused by _P. aphanidermatum_ in cucumber (79). These investigators also found that suppressiveness was easily transferable between water-saturated rockwool slabs, and was associated with differences in structure of bacterial populations as visualized by using polymerase chain reaction (PCR) followed by denaturing gradient gel electrophoresis (DGGE). Despite the suppressiveness of used rockwool, it would be inappropriate to advise growers to reuse rockwool slabs on account of the potential presence of other pathogens and pests. Subsequent investigations of the rhizosphere microflora in cucumbers grown in used rockwool revealed that fast-growing bacteria predominated at the root tips, whereas slow growing bacteria were most abundant at root bases (25). Further, the proportion of fast-growing bacteria decreased as plants developed through vegetative and reproductive stages, even on root tips, which are young tissues regardless of plant phenological growth stage. DNA microarray technology, combined with PCR-DGGE and conventional colony counts on agar media, should allow critical characterization, profiling, and tracking of root zone microflora and their relationships to pathogen suppression. [/FONT]
[FONT=&quot]General experience in the greenhouse industry indicates that the type and structure of hydroponic systems greatly influence severity of root rot epidemics in hydroponic crops. In Canada, reports of severe epidemics are more frequent for crops grown in trough systems, in which the nutrient solution circulates among roots of scores, hundreds, or thousands of plants before returning to the mixing tank, than in highly compartmentalized systems such as rockwool slabs in which only a few plants share a common root zone. The industry findings are consistent with expected patterns of pathogen dispersal, especially zoospores, in relation to compartmentalization of root zones. Risk of severe root rot is also considered higher in systems with continuously recirculating nutrient solution (&quot;closed systems&quot compared to those where the solutions are allowed to run to waste (&quot;open systems&quot (42, 64). However, in a study of tomatoes grown in rockwool, incidence of colonization of roots by _Pythium_ was higher in an open system than in a closed system (109). In container-grown crops, which generally are ornamentals such as gerberas and roses, root rot is normally more severe when the containers are positioned on the bottom of wide-based troughs through which nutrient solution is allowed to flow, as opposed to when the containers are elevated well above the troughs and the plants are fed entirely through capillary tubes positioned in the rooting medium. Effects of the presence and type of rooting medium on root rot epidemics in commercial hydroponic systems are not well-understood. In Ontario, Canada, root rot epidemics in pepper and tomato have tended to be severe when crops were grown in trough systems with rockwool or with no rooting medium. Some growers reported fewer root rot problems when they used coconut fiber or certain grades of peat as opposed to rockwool. When containers are used in hydroponic systems it would probably be advantageous to use pathogen-suppressive rooting media (34, 35). [/FONT]

*[FONT=&quot]Human Interferences[/FONT]*
[FONT=&quot]Numerous practices used to produce and protect hydroponic crops influence the incidence and patterns of increase and spread of root rot epidemics. It is outside the scope of this article to review what is known of these practices in relation to root rot, however principal measures that are used, or that have potential use against root rot in various kinds of hydroponic systems are summarized in [/FONT][FONT=&quot]Table 1[/FONT][FONT=&quot]. Further details are available in the following publications: Bélanger & Menzies (5); Bélanger _et al_. (6); Chatterton _et al._ (12); Chérif & Bélanger (13); Ehret _et al._ (1; Evans (22); Folman _et al. _(25); Jarvis (39); Jensen & Collins (42); Jung (49); Khan _et al._ (53); Lopes (59); Lopes _et al._ (60); Menzies & Bélanger (65); Paulitz (75); Paulitz & Bélanger (76); Punja & Yip (80); Runia (90); Schuerger (93); Sutton _et al._ (104); Utkhede _et al._ (110); Zheng _et al._ (122) [/FONT]
[FONT=&quot]From the epidemiologic perspective, disease management practices can achieve two principal effects (7, 119). First, they can reduce the level of initial (or primary) inoculum of the pathogen in the crop environment. This is the inoculum that can initiate the epidemic, analogous to a match lighting a fire. Secondly, they can reduce the rate of increase in severity of the epidemic, analogous to the rate at which the fire burns and spreads. In [/FONT][FONT=&quot]Table 1[/FONT][FONT=&quot], practices that are thought to influence chiefly the initial inoculum of _Pythium_ are distinguished from those that help to keep down the rate of increase of root rot after epidemics have begun (eg 19, 30). In Ontario, infected transplants, though often symptomless, frequently contribute to the initiation of root rot epidemics in crops. Thus root rot control should begin with the seed, cutting, and other propagative material. [/FONT]
[FONT=&quot]Among the practices that aim to reduce rates of increase of root rot, it is important to distinguish the epidemic impact made by disinfesting the nutrient solution as it recirculates outside of the crop from that made by treatments that suppress _Pythium_ in the roots and root zone of the crop ([/FONT][FONT=&quot]Table 1[/FONT][FONT=&quot]). In tomatoes (121) and in our investigations with lettuce and chrysanthemums in small-scale trough systems (18-20 plants per trough) with recirculating nutrient solution (44, 71) treatment of the solution with ultraviolet radiation (UV-C) at doses sufficient to kill _Pythium_ propagules gave little or no suppression of root rot. Similar treatment in a commercial-scale pepper crop in hydroponic troughs (NFT) did not significantly suppress root rot increase (102). These findings are not surprising given that most _Pythium_ zoospores are dispersed locally among roots in the crop, and of those in effluent from troughs few survive the turbulent ride in nutrient solution through pipes and mixing tanks to the UV apparatus. Emphasis is needed on treating the root zone, such as with microbial agents, to protect the roots.[/FONT]
[FONT=&quot]Several strains of specific microbes have been identified that have strong potential for controlling root rot in various kinds of hydroponic crops. They include _Pseudomonas chlororaphis_ Tx-1 (= _Pseudomonas aureofaciens_ Tx-1) (12, 53)._ Pseudomonas fluorescens_ 63-28 (58, 76) _Comamonas acidovorans_ C-4-7-28 (5, _Bacillus cereus_ HYU06 (5, _Bacillus subtilis_ BACT-O (111), _Gliocladium catenulatum_ J1446 (80), _Lysobacter enzymogenes_ 3.1T8 (25), and _Clonostachys rosea_ (J.C. Sutton, 2003, unpublished observations). In our experience in commercial systems, biological control treatments should begin when plants are at the seedling or rooted-cutting stage, though good control is often possible in older plants in which disease has already begun to increase. Certain agents, such as _P. chlororaphis_, in some instances protect crops for several weeks or months without need for reapplication. Several of the microbes also appear to induce systemic resistance to powdery mildew and other foliage diseases (example: 122).[/FONT]

*[FONT=&quot]Symptom development, growth of the shoots and crop productivity[/FONT]*
[FONT=&quot]A surprising aspect of hydroponic crops with _Pythium_ root rot is that the foliage often appears green and healthy even when root rot has become severe. Foliar discoloration normally develops only when the root systems have become almost entirely rotted. Under controlled conditions, the leaf canopy of pepper plants inoculated with _P. aphanidermatum_ or _P. dissotocum_ often becomes darker green than that of the noninoculated controls, which may indicate an important role of growth regulators in development of foliage symptoms. [/FONT]
[FONT=&quot]The relationship of root disease caused by the various _Pythium_ species and plant growth is currently understood chiefly from investigations in small-scale hydroponic systems. Reduced mass of roots and shoots, and reduced yield and quality of fruits or flowers were noted for several crops (12, 45, 53, 54, 65, 66, 71, 110). In pepper, _P. aphanidermatum_ reduced the volume, fresh and dry mass, total length, and surface area of the roots, as well as total leaf area, and height, fresh mass and dry mass of the shoots over two to three weeks following inoculation (53, 72). In other experiments, concentrations of chlorophyll a, chlorophyll b, and total carotenoids expressed based on leaf area or fresh mass, were significantly higher in inoculated plants than in noninoculated controls (C.R. Sopher, 2003, unpublished). [/FONT]
[FONT=&quot]The first characterization of alterations in whole-plant photosynthetic rate and carbon assimilation associated with _Pythium_ infection of the roots was recently described in hydroponic peppers (45, 46, 47). Inoculation of plants with _P. aphanidermatum_ resulted in reduced whole-plant net carbon exchange rates (NCER), and a loss of 28% in cumulative carbon gain within 7 days. Leaf area, and dry weight of the shoots and roots, were significantly decreased, and the shoot:root ratio was higher in inoculated than in noninoculated plants. However, no differences were observed in NCER and evapotranspiration in inoculated compared to control plants when data were expressed based on leaf area and root dry mass, respectively. Thus _Pythium_ infection did not appear to affect the photosynthetic apparatus directly, and the reductions in photosynthesis and growth were not caused by inefficient water transport by diseased roots. The main effect of root rot was to suppress the rate of increase in leaf area of the plants, as opposed to influencing the efficiency of photosynthesis per unit leaf area.[/FONT]

*[FONT=&quot]Implications and possibilities for root rot management[/FONT]*
[FONT=&quot]The knowledge and understanding of the etiology and epidemiology of _Pythium_ root rot provides a valuable platform for rationalizing new research directions and developing better technologies and practices for managing root rot in hydroponic crops. Epidemiological information suggests that focus is needed in direct protection of roots against _Pythium_ through treatments applied in the root zone, and that protection is needed beginning at the seedling stage and throughout a major portion of the crop cycle. Collectively, available data suggest that treatments that kill or inactivate _Pythium_ in nutrient solution as it recirculates outside the crop are at best marginally effective in reducing the progress of root rot in large- and small-scale hydroponic systems. Such treatments may be important, however, for reducing the introduction of _Pythium_ into hydroponic crops, and for destroying other pathogens, including viruses and bacteria. [/FONT]
[FONT=&quot]Technologies to facilitate tracking of _Pythium_ spp. and root disease are an obvious step in optimizing effectiveness of root-zone treatments such as use of microbial agents and oxygenation of the nutrient solution, as well as other measures to control root rot. Roots of hydroponic crops are generally out of sight and not easy to examine with any thoroughness, so that severity of root browning is difficult to determine. Further, visual examination does not detect infected roots that happen to be symptomless. Antibody-based dipsticks, other immunoassay-based diagnostic kits, and DNA microarrays that allow tracking of _Pythium_ have already been developed (57, 62, 77). Such assays have potential applications in standardizing the health of propagative materials, and to minimize the risk of introducing _Pythium_ into hydroponic systems in, for example, the roots of transplants growing in rockwool cubes. They can also be used to detect or roughly quantify _Pythium_ throughout later stages of crop development. Detection of _Pythium_ does not necessarily imply that there is, or will be, a destructive epidemic of root rot. As summarized in previous sections of this article, development of severe root rot depends on numerous environmental and host factors, particularly high temperature and reduced levels of dissolved oxygen in the nutrient solution. A much better quantitative understanding of environmental variables in relation to root rot, and especially environmental stressors that predispose roots to _Pythium_ attack, would open the doors for root rot prediction, and alerts for remedial action, driven by sensors in the canopy and nutrient solution. After decades of speculation, it is time to put some numbers on environmental stress conditions in relation to root rot. The recent findings that phenolic compounds accumulate in the nutrient solution, especially during root rot epidemics, and can threaten crop health directly and by predisposing plants to _Pythium_ attack, signify a need for further investigations of phenolics, including any necessity for remediation of the solutions against phenolics. The new understanding of physiological responses of the plant canopy to root infection by _Pythium_ (46) has paved the way for determining root disease severity by remote sensing in the canopy, and thereby avoiding the frustrations of examining roots directly. [/FONT]
[FONT=&quot]Introduction of microbial agents, manipulation of the root zone microflora, oxygenation of the nutrient solution, and regulation of nutrient solution temperature are among the best available approaches to suppressing _Pythium_ in the root zone, but each requires considerable investigation to provide practical and dependable know-how for growers. Much headway has been made in assessing effectiveness of microbes against _Pythium_ in short-term experiments, but critical knowledge needed for long-term root protection throughout crop cycles, and in the face of shifts in the general microflora, chemical environment, and physical conditions in the root zone, is relatively sparse. Better understanding of the root-zone microflora in relation to _Pythium_, root rot, plant growth and disease resistance, root mucilages, allelopathic compounds of plant or microbial origin, and other key variables, should be possible with the aid of DNA microarray and other recent technologies to detect major microbial species and genes in the hydroponic system. Data banks of dissolved oxygen levels and temperature of the nutrient solution in relation to important variables such as _Pythium_, microbial agents, other microflora, root rot, and crop growth and productivity are needed to develop protocols for their rational use and to adequately understand the value of such use. Given the inadequate levels of host resistance to _Pythium_, new approaches to improve resistance such as through antibody-based mechanisms justify vigorous exploration. Fundamentally, new levels of integration of management practices against _Pythium_ root rot and other diseases are needed that are appropriate to the kind of hydroponic system, whether sophisticated as in many greenhouses in Canada, the USA and some European countries, or simple yet functional like many of those in Brazil and other countries with warm climates.[/FONT]

*[FONT=&quot]LITERATURE CITED[/FONT]*
[FONT=&quot]1. Adams, P.B. _Pythium aphanidermatum_ oospore germination is affected by time, temperature, and pH. *Phytopathology,* Worcester, v.61, n.9, p.1149-1150, 1971. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]2. Ayers, W.A.; Lumsden, R.D. Factors affecting production and germination of oospores of three _Pythium_ species. *Phytopathology,* St. Paul, v.65, n.10, p.1094-1100, 1975. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]3. Bailey, B.A. Purification of a protein from _Fusarium oxysporum_ that induces ethylene and necrosis in leaves of _Erythroxylum coca_. *Phytopathology,* St. Paul, v.85, n.10, p.1250-1255, 1995. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]4. Bates, M.; Stanghellini, M. Root rot of hydroponically-grown spinach caused by _Pythium aphanidermatum_ and _P. dissotocum_. *Plant Disease,* St. Paul, v.68, n.11, p.989-991, 1984. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]5. Bélanger, R.R.; Menzies, J.G. Use of silicon to control diseases in vegetable crops. *Fitopatologia Brasileira,* Brasilia, v.28 (Suplemento):S42-S45, 2003. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]6. Bélanger, R.R.; Bowen, P.A.; Ehret, D.L.; Menzies, J.G. Soluble silicon: its role in crop and disease management of greenhouse crops. *Plant Disease,* St. Paul v.79, n.4, p.329-336, 1995. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]7. Bergamin Filho, A.; Amorim, L.* Doenças de Plantas Tropicais: Epidemiologia e Controle Econômico,* São Paulo Editora Agronômica Ceres Lda, 1996. 289p. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]8. Brune, A. Microbial degradation of aromatic compounds: aerobic versus anaerobic processes. *Mitteilungen der Deutschen Bodenkundlichen Gesellschaft,* Oldenburg, v.87, n.1, p.65-78, 1998. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]9. Butt, D.J.; Royle, D.J. The importance of terms and definitions for a conceptually unified epidemiology. _In_: J. Palti; J. Kranz (Eds) *Comparative Epidemiology. A Tool for Better Disease Management,* Wageningen, Centre for Agricultural Publishing and Documentation, The Netherlands, p.29-45, 1980. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]10. Candela, M.E.; Alcazar, M.D.; Espin, A.; Egea, C.; Almela, L. Soluble phenolic acids in _Capsicum annuum_ stems infected with _Phytophthora capsici_. *Plant Pathology,* St. Paul, v.44, n.1, p.116-123, 1995. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]11. Caspersen, S.; Waechter, A.; Sundin, P.; Jensén, P. Bacterial amelioration of ferulic acid toxicity to hydroponically-grown lettuce (_Lactuca sativa_ L.). *Soil Biology Biochemistry,* Oxford, v.32, n.8, p.1063-1070, 2000. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]12. Chatterton, S.; Sutton, J.C.; Boland, G.J. Timing _Pseudomonas chlororaphis_ applications to control _Pythium aphanidermatum, Pythium dissotocum_, and root rot in hydroponic peppers. *Biological Control*, San Diego, v.30, n.2 p.360- St. Louis, 3, 2004. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
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[FONT=&quot]88. Rong, G.S.; Tachibana, S. Effect of dissolved oxygen levels in a nutrient solution on the growth and mineral nutrition of tomato and cucumber seedlings. *Journal of the Japanese Society for Horticultural Science,* Tokyo, v.66, n.2, p.331-337, 1997. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]89. Royle, D.J.; Hickman, C.J. Analysis of factors governing in vitro accumulation of zoospores of _Pythium aphanidermatum_ on roots. I. Behaviour of zoospores. *Canadian Journal of Microbiology,* Ottawa, v.10, n.1, pp.151-162, 1964. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]90. Runia, W.T. A review of possibilities for disinfection of recirculation water from soilless cultures. *Acta Horticulturae,* (The Hague), v.382, p.221-229, 1995. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]91. Schnitzler, J.P.; Seitz, H.U. Rapid responses of cultured carrot cells and protoplasts to an elicitor from the cell wall of _Pythium aphanidermatum_ (Edson) Fitzp. *Zeitschrift für Naturforschung, *Tübingen, v.44c, p.1020-1028, 1989. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]92. Schuerger, A.C. Microbial contamination of advanced life support (ALS) systems poses a moderate threat to the long-term stability of space-based bioregenerative systems. *Life Support Biosphere Science,* New York, v.5, n.4, p.325-337, 1998. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]93. Schuerger, A. Alternative methods for controlling root diseases in hydroponic systems. *Proceedings of the 13th Annual Conference on Hydroponics,* Hydroponic Society of America, Orlando, FL, pp. 8-17, 1992. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]94. Schwartz, M. Oxygenating of nutrient solution in normal and stress conditions. *Soilless Culture,* Wageningen, v.5, n.1, p.5-53, 1989. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]95. Shokes; McCarter. Occurrence, dissemination and survival of plant pathogens in surface irrigation ponds in southern Georgia. *Phytopathology,* St. Paul, v.69, n.5, p.510-516, 1979 [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]96. Stanghellini, M. Spore germination, growth, and survival of _Pythium_ in soil. *Proceedings of The American Phytopathological Society,* St. Paul, v.1, p.211-214, 1974. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]97. Stanghellini, M.; Burr, T.J. Germination in vivo of _Pythium aphanidermatum_ oospores and sporangia. *Phytopathology,* St. Paul, v.63, n.12, p.1493-1496, 1973. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]98. Stanghellini, M.; Kronland, W.C. Yield loss in hydroponically grown lettuce attributed to subclinical infection of feeder roots by _Pythium dissotocum_. *Plant Disease*, St. Louis, v.70, n.11, p.1053-1056, 1986. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]99. Stanghellini, M.; Rasmussen, S.L. Hydroponics: a solution for zoosporic pathogens. *Plant Disease,* St. Louis, v.78, n.12, p.1129-1138, 1994. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]100. Stanghellini, M.; Rasmussen, S.L.; Kim, D.H.; Rorabaugh, P.A. Efficacy of nonionic surfactants in the control of zoospore spread of _Pythium aphanidermatum_ in a recirculating hydroponic system. *Plant Disease,* St. Louis, v.80, n.4, p.422-428, 1996. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]101. Stanghellini, M.E.; White, J.G.; Tomlinson, J.A.; Clay, C. Root rot of hydroponically grown cucumbers caused by zoospore-producing isolates of _Pythium intermedium_. *Plant Disease,* St. Louis, v.72, n.4, p.358-359, 1988. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]102. Sutton, J.C.; Evans, R. Water treatment technologies for managing root diseases in hydroponic peppers. Phase II. Final Report* ,* Industrial Research Assistance Program, National Research Council, Ottawa., 1999. 58p. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]103. Sutton, J.C.; Owen-Going, N.; Sopher, C.R.; Hall, J.C. Interactive effects of _Pythium aphanidermatum_ and allelopathic phenolics accelerate root rot epidemics in hydroponic peppers (_Capsicum annuum_ L.). *Fitopatologia Brasileira,* Brasilia, v.28, (Suplemento), S363, 2003. (Abstract 747). [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]104. Sutton, J.C.; Yu, H.; Grodzinski, B.; Johnstone, B. Relationships of ultraviolet radiation dose and inactivation of pathogen propagules in water and hydroponic nutrient solutions. *Canadian Journal of Plant Pathology,* Ottawa, v.22, n.3, p.300-309, 2000. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]105. Taiz, L.; Zeiger, E. Plant physiology. 3rd edition. Sinauer Associates Inc., Sunderland, MA, 2002. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]106. Thinggard, K.; Middleboe, A.L. _Phytophthora_ and _Pythium_ in pot plant cultures on an ebb and flow bench with recirculating nutrient solution. *Journal of Phytopathology,* Berlin, v. 125, p.343-352, 1989. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]107. Thomson, T.B.; Athow, K.L.; Laviolette, F.A. The effect of temperature on the pathogenicity of _Pythium aphanidermatum, P. debaryanum_, and _P. ultimum_. *Phytopathology,* Worcester, v.61,n.8, p.933-935, 1971. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]108. Trujillo, E.E.; Hine, R. The role of papaya residues in papaya root rot caused by _Pythium aphanidermatum_ and _Phytophthora parasitica_. *Phytopathology,* Worcester, v.55, n.12, p.1293-1298, 1965.[/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]109. Tu, J.C.; Papadopoulos, A.P.; Hao, X.; Zheng, J. The relationship of Pythium root rot and rhizosphere microorganisms in a closed circulating and an open system in rockwool culture of tomato. *Acta Horticulturae,* The Hague, v.481, p.577-583, 1999. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]110. Utkhede, R.S.; Koch, C.A.; Menzies J.G. Rhizobacterial growth and yield promotion of cucumber plants inoculated with _Pythium aphanidermatum_. *Canadian Journal of Plant Pathology,* Ottawa, v.21, n.3, p.265-271, 1999. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]111. Utkhede, R.S.; Lévesque, C.A.; Dinh, D. _Pythium aphanidermatum_ root rot in hydroponically-grown lettuce and the effect of chemical and biological agents on its control. *Canadian Journal of Plant Pathology,* Ottawa, v.22, n.2, p.138-144, 2000. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]112. Van der Plaats-Niterink, A.J. Monograph of the genus _Pythium_. Studies in Mycology, No. 21. *Centraalbureau Voor Schimmelcultures,* Baarn, The Netherlands, 1981. 242p.[/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]113. Veit, S.; Worle, J.M.; Nurnberger, T.; Koch, W.; Seitz, H.U. *A Novel Protein Elicitor (PaNie) from Pythium aphanidermatum induces multiple defense responses in carrot, Arabidopsis, and tobacco. Plant Physiology, *Bethesda,* v.127, n.3, p. 832-841, 2001.* [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]114. Waechter-Kristensen, B.; Caspersen, S.; Adalsteinsson, S.; Sundin, P.; Jensén, P. Organic compounds and microorganisms in closed hydroponic culture: occurrence and effects on plant growth and mineral nutrition. *Acta Horticulturae,* The Hague, v.481, p.197-204, 1999. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]115. Waechter-Kristensen, B.; Gertsson, U.E.; Sundin, P. Prospects for microbial stabilization in the hydroponic culture of tomato using circulating nutrient solution. *Acta Horticulturae,* v.361, p.382-387, 1994. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]116. Wakeham, A.J.; Pettitt, T.R.; White, J.G. A novel method for detection of viable zoospores of _Pythium_ in irrigation water. *Annals of Applied Biology,* Cambridge, v.131, n.3, p.427-435, 1997.[/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]117. Walker, T.S.; Bais, H.P.; Grotewold, E.; Vivanco, J.M. Root exudation and rhizosphere biology. *Plant Physiology,* Bethesda, v.132, n.1, p.44-51, 2003. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]118. Wulff, E.G.; Pham, A.T.F.; Chérif, M.; Rey, P.; Tirilly, Y.; Hocke nhull, J. Inoculation of cucumber roots with zoospores of mycoparasitic and plant pathogenic _Pythium_ species: Differential zoospore accumulation, colonization ability, and plant growth response. *European Journal of Plant Pathology,* The Netherlands, v.104, n.1, p.69-76, 1998. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]119. Zadoks, J.C.; Schein, R.D. *Epidemiology and Plant Disease Management*. Oxford University Press, New York, 427p, 1979.[/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]120. Zeroni, M.; Gale, J.; Ben-Asher, J. Root aeration in a deep hydroponic system and its effect on growth and yield of tomato. *Scientia Horticulturae,* Amsterdam, v.19, n.3, p.213-220, 1983. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]121. Zhang, W.; Tu, J.C. Effect of ultraviolet disinfection of hydroponic solutions on _Pythium_ root rot and non-target bacteria. *European Journal of Plant Pathology,* The Netherlands, v.106, n.5, p.415-421, 2000. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]122. Zheng, J.; Sutton, J.C.; Yu, H. Interactions among _Pythium aphanidermatum_, roots, root mucilage, and microbial agents in hydroponic cucumbers. *Canadian Journal of Plant Pathology,* Ottawa, v.22, n.4, p.368-379, 2000. [/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]
[FONT=&quot]123. Zinnen, T.M. Assessment of plant diseases in hydroponic culture. *Plant Disease,* St. Louis, v. 72, n.2, p.96-99, 1988.[/FONT][FONT=&quot] [ [/FONT][FONT=&quot]Links[/FONT][FONT=&quot] ][/FONT]


[FONT=&quot]Data de chegada: 10/05/2005. Aceito para publicação em: 23/11/2005. [/FONT]


[FONT=&quot]* Autor para correspondência: [/FONT][FONT=&quot]jcs[email protected][/FONT]

[FONT=&quot][/FONT][FONT=&quot]All the content of the journal, except where otherwise noted, is licensed under a [/FONT][FONT=&quot]Creative Commons License[/FONT]
_[FONT=&quot] Grupo Paulista de Fitopatologia[/FONT]_
[FONT=&quot]FCA/UNESP - Depto. De Produção Vegetal
Caixa Postal 237
18603-970 - Botucatu, SP Brasil
Tel.: (55 14) 3811 7262
Fax: (55 14) 3811 7206





[/FONT][FONT=&quot][email protected][/FONT]


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## CR500ROOST (Nov 16, 2011)

When I come into the advanced marijuana section these are The threads I wanna see not how much will I yield and is it male or female.


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## woodsmaneh! (Nov 16, 2011)

*[FONT=&quot]http://www.uoguelph.ca/research/apps/news/pub/article.cfm?id=90[/FONT]*

*[FONT=&quot]Higher dissolved oxygen great for productivity, health and vigor[/FONT]*
 [FONT=&quot] Higher dissolved oxygen great for productivity, health and vigor [/FONT]
*[FONT=&quot]By Robert Fieldhouse 
(Guelph, October 13, 2005)[/FONT]* 

 [FONT=&quot]Dissolving more oxygen into hydroponic solutions could boost greenhouse productivity and provide a whole host of other benefits too, say University of Guelph researchers.[/FONT] [FONT=&quot]Prof. Mike Dixon and Dr. Youbin Zheng, Department of Environmental Biology, are investigating the positive aspects of using an oxygen diffuser to increase oxygen levels in greenhouse hydroponic solutions used to grow roses, tomatoes, cucumbers and peppers. [/FONT]

 
*[FONT=&quot]Dr. Youbin Zheng, Department of Environmental Biology, is studying if oxygen levels can be boosted in hydroponic solutions to help growers ward off harmful microbes and boost productivity. [/FONT]* 
 
 [FONT=&quot]Preliminary results suggest a higher dissolved oxygen level increase productivity, health and root vigor in greenhouse plants, and helps keep harmful microbes in check.[/FONT] [FONT=&quot]These findings are really beneficial to the industry, says Zheng. If we can use oxygen to boost plant health, making them stronger and more resistant to disease, we've discovered a very helpful tool.[/FONT] [FONT=&quot]Oxygen isn't as prevalent in warm water as in cool water, so oxygen levels tend to be low -- about two to four parts per million (ppm) -- at high greenhouse temperatures, compared to eight to nine ppm in cool water. Under hot weather in the greenhouse, the root zone is especially short on oxygen, says Zheng, because root respiration depletes oxygen in hydroponic solutions. Excessive watering can further depress oxygen levels because it makes growth media, such as rockwool or coconut fibre, less porous, blocking air. These factors all weaken plant disease defense systems, making them more susceptible to disease-causing microbes such as _Fusarium _and _Pythium _which cause root decay.[/FONT] [FONT=&quot]To prevent this problem, greenhouse growers typically bubble air into hydroponic solutions to bring oxygen levels up to about nine ppm. But sometimes this still isn't enough.[/FONT] [FONT=&quot]Two years ago, the BC Greenhouse Growers' Association asked Dixon to investigate using even higher oxygen levels in hydroponic solutions. His literature review revealed that very little work had been done in this area suggesting the problem was largely ignored  until now.[/FONT] [FONT=&quot]Dixon and Zheng are using an oxygen diffuser recently developed and manufactured by Seair Diffusion Systems Inc., an Edmonton-based company with an interest in the greenhouse sector. The diffuser concentrates atmospheric oxygen, and dissolves it into hydroponic solutions. With this technology, oxygen levels can reach as high as 60 ppm in hydroponic solutions.[/FONT] [FONT=&quot]The research team is currently studying the effects of different oxygen levels, ranging from about nine ppm to 40 ppm.[/FONT] [FONT=&quot]So far, preliminary results are promising. But creating optimal supersaturated oxygen solutions requires extreme precision. Oxygen can be damaging at very high levels, says Dixon , so it's important to establish application methods for using this technology for different crops.[/FONT]
 [FONT=&quot]But if the methods can be worked out, Dixon says the oxygen diffusers are inexpensive and stand to emerge as an economical, environmentally friendly solution for growers looking to enhance their crops.[/FONT] [FONT=&quot]Greenhouse growers are voracious technical consumers  they'll try anything, says Dixon . But by the same token, they're also very shrewd business people, and they won't waste money unnecessarily.[/FONT] [FONT=&quot]Dixon and Zheng will continue their research and will further investigate oxygen's effect on plant growth, physiology and disease. For example, they will inoculate greenhouse plants with specific microbes to see how the plants cope with this challenge under different oxygen levels.[/FONT]

 [FONT=&quot]Other researchers involved in this project include technician Linping Wang, graduate student Johanna Valentine and undergraduate student Mark Mallany, Department of Environmental Biology.[/FONT] [FONT=&quot]This research is being conducted at greenhouses in Guelph and Leamington , Ontario . It is sponsored by Seair Diffusion Systems Inc., Flowers Canada Ontario and the Fred Miller Rose Research Fund. [/FONT]


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## woodsmaneh! (Nov 16, 2011)

*[FONT=&quot]The cation exchange capacity of the soil[/FONT]**[FONT=&quot][/FONT]*​ [FONT=&quot] [/FONT]
[FONT=&quot] When small quantities of inorganic salts, such as the soluble mineral matter of soil and commercial fertilizers, are added to water they dissociate into electrically charged units called ions. The positively charged ions (cations) such as hydrogen (H+), potassium (K+), calcium (Ca++) magnesium (Mg++), ammonium (NH4+), iron (Fe++), manganese (Mn++), and zinc (Zn++) are absorbed mostly on the negatively charged surfaces of the soil colloids (microscopic clay and humus particles) and exist only in small quantities in the soil solution. Thus, the humus-clay colloids serve as a storehouse for certain essential ions (cations). The negatively charged ions (anions), such as nitrates (N03-) phosphates (HPO4--), sulfates (SO4--), and chlorides (Cl-), are found almost exclusively in the soil solution and can therefore be leached away easily with overwatering. The roots and root hairs are in intimate contact with the soil colloidal surfaces, which are bathed in the soil solution, and therefore nutrient uptake can take place either from the soil solution or directly from the colloidal surfaces (cation exchange). The soil solution is the most important source of nutrients, but since it is very dilute its nutrients are easily depleted and must be replenished from soil particles. The solid phase of the soil, acting as a reservoir of nutrients, slowly releases them into the soil solution by the solubilization of soil minerals and organics, by the solution of soluble salts, and by cation exchange. A more dramatic increase in the nutrient content of the soil solution takes place with the addition of commercial fertilizers. As plants absorb nutrients (ions) they exchange them for other ions. For example, for the uptake of one potassium (K+) ion or one ammonium (NH4+) ion, one hydrogen (H+) ion is released into the soil solution or directly into the soil colloids by the process of cation exchange. Similarly, for the uptake of one calcium (Ca++) or one magnesium (Mg++) ion, two hydrogen (H+) ions are released by the root. Thus, as the plant absorbs these essential cations, the soil solution and the colloidal particles contain more and more hydrogen (H+) ions, which explains why the removal of cations (ammonium (NH4+) nitrogen is a good example) by crops tends to make soils acidic, i.e., having a low pH. Also, as the plant (absorbs essential anions such as nitrates (NO3-) and phosphates (HPO4-), the soil solution is enriched with more and more hydroxyl groups (OH-) and bicarbonates (HCO3-), which explains why the removal of anions (nitrate (NO3-) nitrogen is a good example) by crops tends to make soils alkaline, i.e., having a high pH.[/FONT][FONT=&quot][/FONT]


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## woodsmaneh! (Nov 16, 2011)

*marijuana**
[FONT=&quot]Cannabinoids (THC, CBD, CBN...)[/FONT]

[FONT=&quot]The Active Ingredients Of Cannabis[/FONT]

[FONT=&quot]Cannabis products include [/FONT]**marijuana**[FONT=&quot], hashish, and hashish oil.[/FONT]**

[FONT=&quot]THC (Tetrahydrocannabinol) gets a user high, a larger THC content will produce a stronger high. Without THC you don't get high.[/FONT]

[FONT=&quot]CBD (Cannabidiol) increases some of the effects of THC and decreases other effects of THC. High levels of THC and low levels of CBD contribute to a strong, clear headed, more energetic high.[/FONT]

[FONT=&quot]Cannabis that has a high level of both THC and CBD will produce a strong head-stone that feels almost dreamlike. Cannabis that has low levels of THC and high levels of CBD produces more of a stoned feeling. The mind feels dull and the body feels tired.[/FONT]

[FONT=&quot]CBN (Cannabinol) is produced as THC ages and breaks down, this process is known as oxidization. High levels of CBN tend to make the user feel messed up rather than high.[/FONT]

[FONT=&quot]CBN levels can be kept to a minimum by storing cannabis products in a dark, cool, airtight environment. [/FONT]**marijuana**[FONT=&quot] should be dry prior to storage, and may have to be dried again after being stored somewhere that is humid.[/FONT]**

[FONT=&quot]THCV (Tetrahydrocannabivarin) is found primarily in strains of African and Asian cannabis. THCV increases the speed and intensity of THC effects, but also causes the high to end sooner. Weed that smells strong (prior to smoking) might indicate a high level of THCV.[/FONT]

[FONT=&quot]CBC (Cannabichromene) is probably not psychoactive in pure form but is thought to interact with THC to enhance the high.[/FONT]

[FONT=&quot]CBL (Cannabicyclol) is a degradative product like CBN. Light converts CBC to CBL.[/FONT]

[FONT=&quot]If you are a grower, you can experiment with different strains of cannabis to produce the various qualities you seek. A medical user looking for something with sleep inducing properties might want to produce a crop that has high levels of CBD.[/FONT]

[FONT=&quot]Another user looking for a more energetic high will want to grow a strain that has high levels of THC and low levels of CBD. In general, Cannabis sativa has lower levels of CBD and higher levels of THC. Cannabis indica has higher amounts of CBD and lower amounts of THC than sativa. See [/FONT]**marijuana**[FONT=&quot] strains.[/FONT]**

[FONT=&quot]For a more scientific description, see below for an excerpt from [/FONT]**marijuana**[FONT=&quot] growers guide by Mel Frank.[/FONT]**

[FONT=&quot]Cannabis is unique in many ways. Of all plants, it is the only genus known to produce chemical substances known as herbal cannabinoids. These cannabinoids are the psychoactive ingredients of [/FONT]**marijuana**[FONT=&quot]; they are what get you high, buzzed, or stoned. By 1974, there were 37 naturally occurring cannabinoids that had been discovered.[/FONT]**

[FONT=&quot]There are 3 types of cannabinoids:[/FONT]
[FONT=&quot]--- Herbal: occur naturally only in the cannabis plant[/FONT]
[FONT=&quot]--- Endogenous: occur naturally in humans and other animals[/FONT]
[FONT=&quot]--- Synthetic: cannabinoids produced in a lab[/FONT]

[FONT=&quot]Most of the cannabinoids appear in very small amounts (less than .01 percent of total cannabinoids) and are not considered psychoactive, or else not important to the high. Many are simply homologues or analogues (similar structure or function) to the few major cannabinoids which are listed.[/FONT]

[FONT=&quot]There are several numbering systems used for cannabinoids. The system used here is based on formal chemical rules for numbering pyran compounds (any of a class of organic compounds of the heterocyclic series in which five carbon atoms and one oxygen atom are present in a ring structure). Another common system is used more by Europeans and is based on a monoterpenoid system which is more useful considering the biogenesis of the compound.[/FONT]

[FONT=&quot]Tetrahydrocannabinol - THC[/FONT]

[FONT=&quot]Delta 9-trans-tetrahydrocannabinol - delta-9 THC is the main psychotomimetic (mindbending) ingredient of [/FONT]**marijuana**[FONT=&quot]. Estimates state that 70 to 100 percent of the [/FONT]**marijuana**[FONT=&quot] high results from the delta-9 THC present. It occurs in almost all cannabis in concentrations that vary from traces to about 95 percent of all the cannabinoids in the sample.[/FONT]**

[FONT=&quot]In very potent strains, carefully prepared [/FONT]**marijuana**[FONT=&quot] can be 30 percent delta-9 THC by dry weight (seeds and stems removed from flowering buds). Buds are the popular name given to masses of female flowers that form distinct clusters.[/FONT]**

[FONT=&quot]Delta 8-trans-tetrahydrocannabinol - delta-8 THC is reported in low concentration, less than one percent of the delta-9 THC present. Its activity is slightly less than that of delta-9 THC. It may be an artefact of the extraction/analysis process. Almost everyone who uses the term THC, refers to delta-9 THC and delta-8 THC combined, as THC.[/FONT]

[FONT=&quot]Cannabidiol - CBD[/FONT]

[FONT=&quot]Cannabidiol - CBD also occurs in almost all strains. Concentration range from none, to about 95 percent of the total cannabinoids present. THC and CBD are the two most abundant naturally occurring cannabinoids. CBD is not psychotomimetic in the pure form, although it does have sedative, analgesic, and antibiotic properties.[/FONT]

[FONT=&quot]In order for CBD to affect the high, THC must be present in quantities ordinarily psychoactive. CBD can contribute to the high by interacting with THC to potentiate (enhance) or antagonize (interfere or lessen) certain qualities of the high.[/FONT]

[FONT=&quot]CBD appears to potentiate the depressant effects of THC and antagonize is excitatory effects. CBD also delays the onset of the high but can make it last considerably longer (as much as twice as long). The kind of grass that takes a while to come on but keeps coming on.[/FONT]

[FONT=&quot]Opinions are conflicting as to whether it increases or decreases the intensity of the high, intensity and high being difficult to define. Terms such as knock-out or sleepy, dreamlike, or melancholic are often used to describe the high from grass with sizeable proportions of CBD and THC.[/FONT]

[FONT=&quot]When only small amounts of THC are present with high proportions of CBD, the high is more of a buzz, and the mind feels dull and the body de-energized.[/FONT]

[FONT=&quot]Cannabinol - CBN[/FONT]

[FONT=&quot]Cannabinol - CBN is not produced by the plant per se. It is the degradation (oxidative) product of THC. Fresh samples of [/FONT]**marijuana**[FONT=&quot] contain very little CBN but curing, poor storage, or processing such as when making hashish, can cause much of the THC to be oxidized to CBN. Pure forms of CBN have at most 10 percent of the psychoactivity of THC.[/FONT]**

[FONT=&quot]Like CBD, it is suspected of potentiating certain aspects of the high, although so far these effects appear to be slight. CBN seems to potentiate THC's disorienting qualities. One may feel more dizzy or drugged or generally messed up but not necessarily higher.[/FONT]

[FONT=&quot]In fact, with a high proportion of CBN, the high may start well but feels as if it never quite reaches its peak, and when coming down one feels tired or sleepy. High CBN in homegrown grass is not desirable since it represents a loss of 90 percent of the psychoactivity of its precursor THC.[/FONT]

[FONT=&quot]Tetrahydrocannabivarin - THCV[/FONT]

[FONT=&quot]Tetrahydrocannabivarin - THCV or THV is the propyl homologue of THC. In the aromatic ring the usual five-carbon pentyl is replaced by a short three-carbon propyl chain. The propyl cannabinoids have so far been found in some strains originating from Southeast and Central Asia and parts of Africa.[/FONT]

[FONT=&quot]In one study, THCV made up to 48.23 percent (Afghanistan strain) and 53.69 percent (South Africa) of the cannabinoids found. We've seen no reports on its activity in humans. From animal studies it appears to be much faster in onset and quicker to dissipate than THC. It may be the constituent of one or two toke grass, but its activity appears to be somewhat less than that of THC. Some people use the term THC to refer collectively to delta-9 THC, delta-8 THC, and THCV.[/FONT]

[FONT=&quot]An interesting note is that people who have a prescription for Marinol (synthetic medical THC) may be tested for THCV. Marinol contains no THCV, if a person tests positive it means they have been using [/FONT]**marijuana**[FONT=&quot], or another cannabis product. This is usually sufficient grounds to terminate the prescription of a person who has signed a contract not to ingest any cannabis while taking Marinol.[/FONT]**

[FONT=&quot]Cannabichromene - CBC[/FONT]

[FONT=&quot]Cannabichromene - CBC is another major cannabinoid, although it is found in smaller concentrations than CBD and THC. It was previously believed that is was a minor constituent, but more exacting analysis showed that the compound often reported as CBD may actually be CBC.[/FONT]

[FONT=&quot]Relative to THC and CBD, its concentration in the plants is low, probably not exceeding 20 percent of total cannabinoids. CBC is believed not to be psychotomimetic in humans; however, its presence in plants is purportedly very potent has led to the suspicion that it may be interacting with THC to enhance the high.[/FONT]

[FONT=&quot]Cannabicyclol - CBL[/FONT]

[FONT=&quot]Cannabicyclol (CBL) is a degradative product like CBN. During extraction, light converts CBC to CBL. There are no reports on its activity in humans, and it is found in small amounts, if at all, in fresh plant material.[/FONT]

[FONT=&quot]Cannabinoids And The High[/FONT]

[FONT=&quot]The [/FONT]**marijuana**[FONT=&quot] high is a complex experience. It involves a wide range of psychical, physical, and emotional responses. The high is a subjective experience based in the individual and one's personality, mood, disposition, and experience with the drug.[/FONT]**

[FONT=&quot]Given the person, the intensity of the high depends primarily on the amount of THC present in the [/FONT]**marijuana**[FONT=&quot]. Delta-9 THC is the main ingredient of [/FONT]**marijuana**[FONT=&quot] and must be present in sufficient quantities for a good [/FONT]**marijuana**[FONT=&quot] high.[/FONT]**

[FONT=&quot]People who smoke grass that has very little cannabinoids other than delta-9 THC usually report that the high is very intense. Most people that don't smoke daily will feel something from a joint having delta-9 THC of 3 percent concentration to material.[/FONT]

[FONT=&quot]Cannabis products having a THC concentration of 5-10 percent would be considered good, 10-25 percent would be considered very good, and over 25 percent would be excellent quality by daily users standards. In general, we use potency to mean the sum effects of the cannabinoids and the overall high induced.[/FONT]

**marijuana**[FONT=&quot] is sometimes rated more potent than the content of delta-9 THC alone would suggest. It also elicits qualitatively different highs. The reasons for this have not been sorted out. Few clinical studies with known combinations of several cannabinoids have been undertaken with human subjects.[/FONT]**

[FONT=&quot]So far, different highs and possibly higher potency seem to be due to the interaction of delta-9 THC and other cannabinoids (THCV,CBD,CBN, and possibly CBC). Except for THCV, in the pure form, these other cannabinoids do not have much psychoactivity.[/FONT]

[FONT=&quot]Another possibility for higher potency is that homologues of delta-9 THC with longer side chains at C-3 (and higher activity) might be found in certain [/FONT]**marijuana**[FONT=&quot] strains.[/FONT]**

[FONT=&quot]Compounds with longer side chains have been made in laboratories and their activity is sometimes much higher, with estimates over 500 times that of natural delta-9 THC.[/FONT]

[FONT=&quot]The possibility that there are non-cannabinoids that are psychoactive or interacting with the cannabinoids has not been investigated in detail. Non-cannabinoids with biological activity have been isolated from the plants, but only in very small quantities.[/FONT]

[FONT=&quot]None are known to be psychotomimetic. However, they may contribute to the overall experience in non-mental ways, such as the stimulation of the appetite.[/FONT]

[FONT=&quot]Different blends of cannabinoids account for the different qualities of intoxication produced by different strains of cannabis. The intensity of the high depends primarily on the amount of delta-9 THC present and on the method of ingestion.[/FONT]

[FONT=&quot]A complex drug such as [/FONT]**marijuana**[FONT=&quot] affects the mind and body in many ways. Sorting out what accounts for what response can become quite complex.[/FONT]*


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## woodsmaneh! (Nov 16, 2011)

I put the summery first, It is also backed up by science links attached.


*Summary:* 
*
Pre-harvest flushing puts the plant(s) under serious stress.*  The plant has to deal with nutrient deficiencies in a very important part of its cycle. Strong changes in the amount of dissolved substances in the root-zone stress the roots, possibly to the point of direct physical damage to them. Many immobile elements are no more available for further metabolic processes. We are losing the fan leaves and damage will show likely on new growth as well. 

The grower should react in an educated way to the plant needs. Excessive, deficient or unbalanced levels should be avoided regardless the nutrient source. Nutrient levels should be gradually adjusted to the lesser needs in later flowering. Stress factors should be limited as far as possible. If that is accomplished throughout the entire life cycle, there shouldnt be any excessive nutrient compounds in the plants tissue. It doesnt sound likely to the author that you can correct growing errors (significant lower mobile nutrient compound levels) with pre-harvest flushing.  

*For one thing, the most common way that growers flush their crops is by giving their crops water that has no nutrients in it. But this doesn't fully cleanse your crops. It only starves your plants so they lose vigorous floral growth and resin percentages just before harvest. Other growers use flushing formulas that generally consist of a few chemicals that sometimes have the ability to pull a limited amount of residues out of your plants.* 


*Nutrient fundamentals and uptake:* 

Until recently it was common thought that all nutrients are absorbed by plant roots as ions of mineral elements. However in newer studies more and more evidence emerged that additionally plant roots are capable of taking up complex organic molecules like amino acids directly thus bypassing the mineralization process.  

The major nutrient uptake processes are: 

1) Active transport mechanism into root hairs (the plant has to put energy in it, ATP driven) which is selective to some degree. This is one way the plant (being immobile) can adjust to the environment.  

2) Passive transport (diffusion) through symplast to endodermis.  

http://www.biol.sc.edu/courses/bio102/f99-3637.html 

The claim only chemical ferted plants need to be flushed should be taken with a grain of salt. Organic and synthetic   ferted plants take up mineral ions alike, probably to a different degree though. Many influences play key roles in the taste and flavour of the final bud, like the nutrition balance and strength throughout the entire life cycle of the plant, the drying and curing process and other environmental conditions. 

3) Active transport mechanism of organic molecules into root hairs via endocytosis.  

*Here is a simplified overview of nutrient functions:* 

Nitrogen is needed to build chlorophyll, amino acids, and proteins. Phosphorus is necessary for photosynthesis and other growth processes. Potassium is utilized to form sugar and starch and to activate enzymes. Magnesium also plays a role in activating enzymes and is part of chlorophyll. Calcium is used during cell growth and division and is part of the cell wall. Sulphur is part of amino acids and proteins.  

Plants also require trace elements, which include boron, chlorine, copper, iron, manganese, sodium, zinc, molybdenum, nickel, cobalt, and silicon.  

Copper, iron, and manganese are used in photosynthesis. Molybdenum, nickel, and cobalt are necessary for the movement of nitrogen in the plant. Boron is important for reproduction, while chlorine stimulates root growth and development. Sodium benefits the movement of water within the plant and zinc is needed for enzymes and used in auxins (organic plant hormones). Finally, silicon helps to build tough cell walls for better heat and drought tolerance.  

http://www.sidwell.edu 

You can get an idea from this how closely all the essential elements are involved in the many metabolic processes within the plant, often relying on each other.  

*Nutrient movement and mobility inside the plant:* 

Besides endocytosis, there are two major pathways inside the plant, the xylem and the phloem. When water and minerals are absorbed by plant roots, these substances must be transported up to the plant's stems and leaves for photosynthesis and further metabolic processes. This upward transport happens in the xylem. While the xylem is able to transport organic compounds, the phloem is much more adapted to do so.  

The organic compounds thus originating in the leaves have to be moved throughout the plant, upwards and downwards, to where they are needed. This transport happens in the phloem. Compounds that are moving through the phloem are mostly:  
Sugars as sugary saps, organic nitrogen compounds (amino acids and amides, ureides and legumes), hormones and proteins. 

http://www.sirinet.net 

Not all nutrient compounds are movable within the plant.  

1) N, P, K, Mg and S are considered mobile: they can move up and down the plant in both xylem and phloem.  
Deficiency appears on old leaves first. 

2) Ca, Fe, Zn, Mo, B, Cu, Mn are considered immobile: they only move up the plant in the xylem.  
Deficiency appears on new leaves first. 

http://generalhorticulture.tamu.edu 

*Storage organelles:* 

Salts and organic metabolites can be stored in storage organelles. The most important storage organelle is the vacuole, which can contribute up to 90% of the cell volume. The majority of compounds found in the vacuole are sugars, polysaccharides, organic acids and proteins though.  

http://jeb.biologists.org.pdf 

*Trans-location:* 

Now that the basics are explained, we can take a look at the trans-location process. It should be already clear that only mobile elements can be trans located through the phloem. Immobile elements cant be trans located and are not more available to the plant for further metabolic processes and new plant growth.  

Since flushing (in theory) induces a nutrient deficiency in the root-zone, the translocation process aids in the plants survival. Trans-location is transportation of assimilates through the phloem from source (a net exporter of assimilate) to sink (a net importer of assimilate). Sources are mostly mature fan leaves and sinks are mostly apical meristems, lateral meristem, fruit, seed and developing leaves etc.  

You can see this by the yellowing and later dying of the mature fan leaves from the second day on after flushing started. Developing leaves, bud leaves and calyxes dont serve as sources, they are sinks. Changes in those plant parts are due to the deficient immobile elements which start to indicate on new growth first.  

Unfortunately, several metabolic processes are unable to take place anymore since other elements needed are no longer available (the immobile ones). This includes processes where nitrogen and phosphorus, which have likely the most impact on taste, are involved.  

For example nitrogen: usually plants use nitrogen to form plant proteins. Enzyme systems rapidly reduce nitrate-N (NO3-) to compounds that are used to build amino-nitrogen which is the basis for amino acids. Amino acids are building blocks for proteins; most of them are plant enzymes responsible for all the chemical changes important for plant growth.  

Sulphur and calcium among others have major roles in production and activating of proteins, thereby decreasing nitrate within the plant. Excess nitrate within the plant may result from unbalanced nutrition rather than an excess of nitrogen.  

http://muextension.missouri.edu 

*Summary:* 

Pre-harvest flushing puts the plant(s) under serious stress. The plant has to deal with nutrient deficiencies in a very important part of its cycle. Strong changes in the amount of dissolved substances in the root-zone stress the roots, possibly to the point of direct physical damage to them. Many immobile elements are no more available for further metabolic processes. We are losing the fan leaves and damage will show likely on new growth as well.  

The grower should react in an educated way to the plant needs. Excessive, deficient or unbalanced levels should be avoided regardless the nutrient source. Nutrient levels should be gradually adjusted to the lesser needs in later flowering. Stress factors should be limited as far as possible. If that is accomplished throughout the entire life cycle, there shouldnt be any excessive nutrient compounds in the plants tissue. It doesnt sound likely to the author that you can correct growing errors (significant lower mobile nutrient compound levels) with pre-harvest flushing.  

Drying and curing (when done right) on the other hand have proved (In many studies) to have a major impact on taste and flavour, by breaking down chlorophylls and converting starches into sugars. Most attributes blamed on un-flushed buds may be the result of unbalanced nutrition and/or over fertilization and improper drying/curing.


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## randomseed (Nov 16, 2011)

Really good info up in here.

The only beef I have with this is the Lime post.
In an organic soil recycling program I cannot overstate how important I think the liming of the soil really is.
Over the cource of two years on the same dirt Ive tested reduced amounts of lime following advice like this and it always led to serious issue which have always been solved by getting more lime into the soil.

I would agree however if the comments where based on using store bought dirt, there is almost always plenty.

I don't disagree with you're basic facts its just in usages like mine it becomes absolutly critical to the long term health of the soil.




Keep the info flowing.


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## woodsmaneh! (Nov 17, 2011)

randomseed said:


> Really good info up in here.
> 
> The only beef I have with this is the Lime post.
> In an organic soil recycling program I cannot overstate how important I think the liming of the soil really is.
> ...


Lime is fine to use in gardening if used right. Most people use it and then plant. Wrong you need to age the soil if you put lime in it. Most bags of lime have instructions on them and they say to use in the fall so it can age.

Peace


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## randomseed (Nov 17, 2011)

woodsmaneh! said:


> Lime is fine to use in gardening if used right. Most people use it and then plant. Wrong you need to age the soil if you put lime in it. Most bags of lime have instructions on them and they say to use in the fall so it can age.
> 
> Peace


There has been a decent amount of work of late into lime actually be far more active then people have thought, esspecially in high acid enviroments (the acidity speeding up the breakdown proccess). I have actually ran some PH tests taking a nutrient solution and just tossing some lime in and the PH did in fact move quite a bit in response.
Im not putting any of this out there as facts to follow but I do feel that the subject is still wide open for debate.


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## LT1RX7 Drifter (Nov 17, 2011)

all good info but god damn thats got to be the most copy and paste amount of info i have ever seem


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## woodsmaneh! (Nov 17, 2011)

LT1RX7 Drifter said:


> all good info but god damn thats got to be the most copy and paste amount of info i have ever seem


you should see how much time it takes to take out all the crap and page returns. I don't take credit for the words in most cases but good info is good info, I don't get paid to do it. Well if rep is getting paid I get a little.The like button has made getting rep much harder and besides like is so boring, u know kind of like when u think your going to get lucky and than she says " I like u" full stop u be going home alone with Mrs Thumb and her 4 daughters....


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## woodsmaneh! (Nov 17, 2011)

*Just Fishing Officer why do you ask?*


Below are so shots of my Jumbo RDWC system I built and my smaller 13 gal x nine Undercurrent. Couple shots from last crop.




randomseed said:


> There has been a decent amount of work of late into lime actually be far more active then people have thought, esspecially in high acid enviroments (the acidity speeding up the breakdown proccess). I have actually ran some PH tests taking a nutrient solution and just tossing some lime in and the PH did in fact move quite a bit in response.
> Im not putting any of this out there as facts to follow but I do feel that the subject is still wide open for debate.


This is a learning place so if you have some good solid info post her up and we all learn from each other. All my info comes from many sources and people far smarter than I will ever be, but that's the beauty of the web. 

Peace and thanks for stopping in.


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## woodsmaneh! (Dec 23, 2011)

*Easy cloning
*
This is what I do, why I do it, and how.

What you need
Sharp small scissors I use Friskers and get them from Hommer depot. They last me for years but all I use them for is clowning. I clean them with an alcohol swab before using. They stay sharp and have great control. I always put the cover back on and clean them before putting them away.
16 oz. translucent beer cups, I use the translucent ones because they allow me to see if they are watered enough and the development of the root system. I use a small pocket knife to poke 2 holes one on each side. Stick the knife in a ¼ inch and give it a small twist. Holes plug slots almost never. This is for drainage.

Rooting gel, get some good stuff, if in a jam get powder. This provides the boost to get them going.
Seed starter soil; make sure its *SEED STARTER SOIL*. Buy the best you can afford. I use MG and it works great for starting them.
Get your stuff together, fill cups to the top with *SEED STARTER SOIL *set them in the trays and water with 6.5 ph water. If using chlorinated water put some in a pail for 2 hours. It will off gas by then. Water the cups, here is when you will see the magic of the cups being translucent. So there all wet now you cut.

You best bet is to make sure you have a node to stick in the dirt. So cut below the 3 node just above the 4 one. Clip leaves off the 3erd node and pull the clone through your thumb and finger (make a O with them) as you pull it through gently squeeze your thumb over the finger to close the O and trap the clone tips just above your finger. Now cut the tips off, stick in gel/powder and stick it in the cups as far as you can but leave the leaves above the top of the cup.

Water when you see the colour of the dirt change, the magic of the cups. Hope this helps.
I get 98% success this way. No dome just under the lights.


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## woodsmaneh! (Dec 23, 2011)

http://cannabisseedsnow.com/cannabis-sativa-info/life-cycle-of-cannabis/

_by _ADMIN
Cannabis is normally grown as an annual plant, completing its life cycle within one year. A seed that is planted in the spring will grow strong and tall through the summer and flower in the fall, producing more seeds. The annual cycle starts all over again when the new seeds sprout the following year. In nature, cannabis goes through distinct growth stages. The chart below delineates each stage of growth.

*Life Cycle of Cannabis*
After 3-7 days of germination, plants enter the seedling growth stage which lasts about a month. During the first growth stage the seed germinates or sprouts, establishes a root system, and grows a stem and a few leaves.

*Germination*
During germination moisture, heat, and air activate hormones (cytokinins, gibberellins, and auxins) within the durable outer coating of the seed.
Cytokinins signal more cells to form and giberellins to increase cell size. The embryo expands, nourished by a supply of stored food within the seed. Soon, the seeds coating splits, a rootle! grows downward, and a sprout with seed leaves pushes upwards in search of light

*Seedling Growth*
The single root from the seed grows down and branches out, similar to the way the stem branches up and out above ground. Tiny rootlets draw in water and nutrients (chemical substances needed for life). Roots also serve to anchor a plant in the growing medium. Seedling should receive 16-18 hours of light to maintain strong healthy growth.

*Vegetative Growth*
Vegetative growth is maintained by giving plants 16-24 hours of light every day. As the plant matures, the roots take on specialized functions. The center and old, mature portions contain a water transport system and may also store food. The tips of the roots produce elongating cells that continue to push farther and farther into the soil in search of more water and food. The single-celled root hairs are the parts of the root that actually absorb water and nutrients. Without water, frail root hairs will dry up and die. They are very delicate and are easily damaged by light, air, and klutzy hands if moved or exposed. Extreme care must be exercised during transplanting.
Like the roots, the stem grows through elongation, also producing new buds along the stem. The central or terminal bud carries growth upward; side or lateral buds turn into branches or leaves. The stem functions by transmitting water and nutrients from the delicate root hairs to the growing buds, leaves, and flowers. Sugars and starches manufactured in the leaves are distributed through the plant via the stem. This fluid flow takes place near the surface of the stem. If the stem is bound too tightly by string or other tie downs, it will cut the flow of life-giving fluids, thereby strangling and killing the plant.
The stem also supports the plant with stiff cellulose, located within the inner walls. Outdoors, rain and wind push a plant around, causing much stiff cellulose production to keep the plant supported upright. Indoors, with no natural wind or rain present, stiff cellulose production is minimal, so plants develop weak stems and may need to be staked up, especially during flowering.Once the leaves expand, they start to manufacture food (carbohydrates). Chlorophyll (the substance that gives plants their green color) converts carbon dioxide (CO.,) from the air, water, and light energy into carbohydrates and oxygen. This process is called photosynthesis. It requires water drawn up from the roots, through the stem, into the leaves where it encounters carbon dioxide. Tiny breathing pores called stomata are located on the underside of the leaf and funnel CO^ into contact with the water. In order for photosynthesis to occur, the leafs interior tissue must be kept moist. The stomata open and close to regulate the flow of moisture, preventing dehydration. Marijuana leaves are also protected from drying out by an outer skin. The stomata also permit the outflow of water vapor and waste oxygen. The stomata are very important to the plants well being and must be kept clean to promote vigorous growth. Dirty, clogged stomata would breathe about as well as you would with a sack over your head!

*Pre-Flowering
*
Cannabis grown from seed dawns pre-flowers after the fourth week of vegetative growth. They generally appear between the fourth and sixth node from the bottom of the plant. Cannabis plants are normally either all male or all female. Each sex has its own distinct flowers. Pre-flowers will be either male or female. Growers remove and destroy the males (or use them for breeding stock) because they have low levels of cannabinoids (THC, CBD, CBN, etc.). Female plants are cultivated for their high cannabinoid content.

*Mother Plants
*
Growers select strong, healthy, potent mother plants they know are female. Mothers are given 18-24 hours of light daily so they stay in the vegetative growth stage. Growers cut branch tips from the mother plants and root them. The rooted cuttings are called clones. Cultivating several strong, healthy mother plants is the key to having a consistent supply of all-female clones.

*Cloning
*
Branch tips are cut and rooted to form clones. Clones take 10-20 days to grow a strong healthy root system. Clones are given 18-24 hours of light so they stay in the vegetative growth stage. Once the root system is established, clones are transplanted into larger containers. Now they are ready to grow for 1-4 weeks in the vegetative growth stage before being induced to flower.
Cannabis flowers outdoors in the fall when days become shorter and plants are signaled that the annual life cycle is coming to an end. At flowering, plant functions change. Leafy growth slows, and flowers start to form. Flowering is triggered in most commercial varieties of cannabis by 12 hours of darkness and 12 hours of light every 24 hours. Plants that developed in tropical regions often start flowering under more light and less darkness. Flowers form during the last stage of growth. Left unpollinated, female flowers develop without seeds, sinsemilla. When fertilized with male pollen, female flower buds develop seeds.
Unpollinated, female cannabis flowers continue to swell and produce more resin while waiting for male pollen to successfully complete their life cycle. After weeks of heavy flower and cannabinoid-laden resin production, THC production peaks out in the unfertilized, frustrated sinsemilla!
Cannabis has both male and female plants. When both male and female flowers are in bloom, pollen from the male flower lands on the female flower, thereby fertilizing it. The male dies after producing and shedding all his pollen. Seeds form and grow within the female flowers. As the seeds are maturing, the female plant slowly dies. The mature seeds then fall to the ground and germinate naturally or are collected for planting next spring.


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## woodsmaneh! (Dec 24, 2011)

*Spider Mites*
by W.S. Cranshaw and D.C. Sclar [SUP]1[/SUP] (11/06)

*Quick Facts...*
· Spider mites are common plant pests. Symptoms of injury include flecking, discoloration (bronzing) and scorching of leaves. Injury can lead to leaf loss and even plant death.
· Natural enemies include small lady beetles, predatory mites, minute pirate bugs, big-eyed bugs and predatory thrips.
· One reason that spider mites become a problem is insecticides that kill their natural predators.
· Irrigation and moisture management can be important cultural controls for spider mites.

Spider mites are common pest problems on many plants around yards and gardens in Colorado. Injury is caused as they feed, bruising the cells with their small, whiplike mouthparts and ingesting the sap. Damaged areas typically appear marked with many small, light flecks, giving the plant a somewhat speckled appearance.
Following severe infestations, leaves become discolored, producing an unthrifty gray or bronze look to the plant. Leaves and needles may ultimately become scorched and drop prematurely. Spider mites frequently kill plants or cause serious stress to them.

Spider mites (Family: Tetranychidae) are classed as a type of arachnid, relatives of insects that also includes spiders, ticks, daddy-longlegs and scorpions. Spider mites are small and often difficult to see with the unaided eye. Their colors range from red and brown to yellow and green, depending on the species of spider mite and seasonal changes in their appearance.
Many spider mites produce webbing, particularly when they occur in high populations. This webbing gives the mites and their eggs some protection from natural enemies and environmental fluctuations. Webbing produced by spiders, as well as fluff produced by cottonwoods, often is confused with the webbing of spider mites.
The most important spider mite is the *twospotted spider mite* (_Tetranychus urticae_). This mite attacks a wide range of garden plants, including many vegetables (e.g., beans, eggplant), fruits (e.g., raspberries, currants, pear) and flowers. The twospotted spider mite is also the most important species on house plants. It is a prolific producer of webbing.
Evergreens tend to host other mites, notably the spruce spider mite (_Oligonychus ununguis_) on spruce and juniper,_Oligonychus subnudus_ on pines, and _Platytetranychus libocedri _on arborvitae and juniper. Honeylocust, particularly those in drier sites, are almost invariably infested with the honeylocust spider mite (_Platytetranychus multidigituli_). Other mites may affect shade trees such as elm, mountain ash and oak.
Another complex of mites is associated with turfgrass, including the clover mite and Banks grass mite. These are discussed separately in fact sheet 5.505, _Clover and Other Mites of Turfgrass_. Clover mites also are the common mite that enters homes in fall and spring, sometimes creating significant nuisance problems in the process.

*Life History and Habits*
Spider mites develop from eggs, which usually are laid near the veins of leaves during the growing season. Most spider mite eggs are round and extremely large in proportion to the size of the mother. After egg hatch, the old egg shells remain and can be useful in diagnosing spider mite problems.
There is some variation in the habits of the different mites that attack garden plants, trees and shrubs. Outdoors, the twospotted spider mite and honeylocust spider mite survive winter as adults hidden in protected areas such as bark cracks, bud scales or under debris around the garden. Other mites survive the cool season in the egg stage. As winter approaches, most mites change color, often turning more red or orange. This habit may be why they are sometimes called "red spiders."
Most spider mite activity peaks during the warmer months. They can develop rapidly during this time, becoming full-grown in as little as a week after eggs hatch. After mating, mature females may produce a dozen eggs daily for a couple of weeks. The fast development rate and high egg production can lead to extremely rapid increases in mite populations.
Other species of spider mites are most active during the cooler periods of the growing season, in spring and fall. This includes the spruce spider mite and most of the mites that can damage turfgrass. These cool-season spider mites may cease development and produce dormant eggs to survive hot summer weather.
Dry conditions greatly favor all spider mites, an important reason why they are so important in the more arid areas of the country. They feed more under dry conditions, as the lower humidity allows them to evaporate excess water they excrete. At the same time, most of their natural enemies require more humid conditions and are stressed by arid conditions. Furthermore, plants stressed by drought can produce changes in their chemistry that make them more nutritious to spider mites.

*Control
*
*Biological Controls*
Various insects and predatory mites feed on spider mites and provide a high level of natural control. One group of small, dark-colored lady beetles known as the "spider mite destroyers" (_Stethorus_ species) are specialized predators of spider mites. Minute pirate bugs, big-eyed bugs (_Geocoris_ species) and predatory thrips can be important natural enemies.
A great many mites in the family Phytoseiidae are predators of spider mites. In addition to those that occur naturally, some of these are produced in commercial insectaries for release as biological controls. Among those most commonly sold via mail order are _Galendromus occidentalis_, _Phytoseiulus persimilis_, _Mesoseiulus longipes_ and _Neoseiulus californicus_. Although these have been successful in control of spider mites on interior plants, effective use outdoors has not been demonstrated in Colorado. Predatory mites often have fairly high requirements for humidity, which can be limiting. Most suppliers provide information regarding use of the predator mites that they carry.
One reason that spider mites become problems in yards and gardens is the use of insecticides that destroy their natural enemies. For example, carbaryl (Sevin) devastates most spider mite natural enemies and can greatly contribute to spider mite outbreaks. Malathion can aggravate some spider mite problems, despite being advertised frequently as effective for mite control. Soil applications of the systemic insecticide imidacloprid (Merit, Marathon) have also contributed to some spider mite outbreaks.



*Water Management*
Adequate watering of plants during dry conditions can limit the importance of drought stress on spider mite outbreaks. Periodic hosing of plants with a forceful jet of water can physically remove and kill many mites, as well as remove the dust that collects on foliage and interferes with mite predators. Disruption of the webbing also may delay egg laying until new webbing is produced. Sometimes, small changes where mite-susceptible plants are located or how they are watered can greatly influence their susceptibility to spider mite damage.

*Chemical Controls*
Chemical control of spider mites generally involves pesticides that are specifically developed for spider mite control (_miticides_ or _acaricides_). Few insecticides are effective for spider mites and many even aggravate problems. Furthermore, strains of spider mites resistant to pesticides frequently develop, making control difficult. Because most miticides do not affect eggs, a repeat application at an approximately 10- to 14-day interval is usually needed for control. Table 1 includes a summary of pesticides that may be useful for managing spider mites.

*Control of Spider Mites on House Plants*
Control on house plants can be particularly frustrating. There generally are no biological controls and few effective chemical controls (primarily soaps and horticultural oils). When attempting control, treat all susceptible house plants at the same time. Trim, bag and remove heavily infested leaves and discard severely infested plants. Periodically hose small plants in the sink or shower. Wipe leaves of larger plants with a soft, damp cloth. Reapply these treatments at one- to two-week intervals as long as populations persist.



*Table 1: Pesticides useful to control spider mites in yards and gardens.* *Active Ingredient**Trade Name(s)**Comments*acephateOrthene, certain Isotox formulationsInsecticide with some effectiveness against spider mites. Systemic.abamectin*Avid**For commercial use only on ornamental plants. Primarily effective against twospotted spider mite; less effective against mites on conifers. Limited systemic movement.*bifenthrinTalstar, othersInsecticide with good miticide activity.hexythiazoxHexygonFor commercial use only on ornamental plants. Selective miticide that affects developing stages and eggs only. One application per season label restriction.horticultural oilsSunspray, othersUsed at the "summer oil" rate (2 percent), oils are perhaps the most effective miticide available for home use.insecticidal soapseveralMarginally effective against twospotted spider mite and where webbing prevents penetration. Broadly labeled.spiromesifanForbidFor commercial use only on ornamental plants. Selective against mites and conserves natural enemies.sulfurvariousGenerally sold in dust formulation for control of various fungal diseases and some mites on some ornamental and vegetable crops.




[SUP]1[/SUP]W.S. Cranshaw, Colorado State University Extension entomologist and professor, and D.C. Sclar, research assistant; bioagricultural sciences and pest management. Revised 11/06.
Colorado State University, U.S. Department of Agriculture, and Colorado counties cooperating. Extension programs are available to all without discrimination. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned.
http://www.ext.colostate.edu/pubs/insect/05507.html


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## woodsmaneh! (Jan 29, 2012)

*Introduction *
In preparation for writing this paper, I read the related papers from previous HSA proceedings. I am impressed by the amount of useful information. The annual meeting and proceedings of HSA have become an important source of technical information on the hydroponic culture of plants. This information is not necessarily available at the annual meetings of related professional societies such as The American Society for Horticultural Science, or The American Society of Agronomy.

It was necessary for me to read other papers because many of them discuss nutrient management in recirculating hydroponic systems. Authors at every meeting in the past 5 years have stressed the need to recirculate and reuse nutrient solutions to reduce environmental and economic costs. Dr. Pieter Schippers (1991 HSA proceedings) reviewed nutrient management and clearly indicated the need for data when he said; "One of the weakest points in hydroponics...is the lack of information on managing the nutrient solution." I was moderately surprised to find that previous authors recommended measuring the concentrations of individual nutrients in solution as a key to nutrient control and maintenance. Monitoring ions in solution is unnecessary. Even worse, the rapid depletion of some nutrients often causes people to add toxic amounts of nutrients to the solution. Monitoring solutions is interesting, but it is not the key to effective maintenance.


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*Managing nutrients by mass balance*

During the past 12 years, we have managed nutrients in closed hydroponic systems according to the principle of "mass balance," which means that the mass of nutrients is either in solution or in the plants. We add nutrients to the solution depending on what we want the plant to take up.

Plants quickly remove their daily supply of some nutrients while other nutrients accumulate. This means that the concentrations of nitrogen, phosphorous, and potassium can be at low levels in the solution (0.1 mM or a few ppm) because these nutrients are in the plant, where we want them. Maintaining a high concentration of nutrients in the solution can results in excessive uptake that can lead to nutrient imbalances.

For example, the water removed from solution through transpiration must be replaced and it is necessary to have about 0.5 mM phosphorous in the refill solution. If the refill solution was added once each day, the phosphorous would be absorbed by the plant in a few hours and the solution phosphorous concentration would be close to zero. This does not indicate a deficiency; rather it indicates a healthy plant with rapid nutrient uptake. If the phosphorous level is maintained at 0.5 mM in the recirculating solution, the phosphorous concentration in the plant can increase to 1% of the dry mass, which is 3 times higher than the optimum in most plants. This high phosphorous level can induce iron and zinc deficiency (Chaney and Coulombe, 1982).

Feeding plants in this way is like the daily feeding of a pet dog, some dogs would be far overweight if their food bowls were kept continuously full.


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*Differential nutrient removal from solution*

The essential nutrients can be put into 3 categories based on how quickly they are removed from solution. Group 1 elements are actively absorbed by roots and can be removed from solution in a few hours. Group 2 elements have intermediate uptake rates and are usually removed from solution slightly faster than water is removed. Group 3 elements are passively absorbed from solution and often accumulate in solution

Table 1. Approximate uptake rates of the essential plant nutrients.
Group 1. Active uptake, fast removal - NO3, NH4, P, K, Mn
Group 2. Intermediate uptake - Mg, S, Fe, Zn, Cu, Mo, C
Group 3. Passive uptake, slow removal - Ca, B

One of the problems with individual ion monitoring and control is that the concentration of the group 1 elements (N, P, K, Mn) must be kept low to prevent their toxic accumulation in plant tissue. Low concentrations are difficult to monitor and control. Table 2 shows typical measurement errors associated with the use of ICP emission spectrophotometry for analysis of hydroponic solutions. Nitrogen cannot be measured by ICP-ES. Accuracy for the macronutrients is good, but solution levels of B, Cu, and Mo cannot be accurately measured by ICP-ES. The calculations in this table are for a typical refill solution, not for the low concentrations that should be maintained in the circulating solution. The measurement errors for K, P, and Mn can be 10 times higher because the solution levels are lower.

Table 2. Typical measurement error associated with the use of Inductively Coupled Plasma Emission Spectrophotometry for analysis of nutrient concentrations in hydroponic solution.
The total amount of nutrients in solution can easily and accurately be determined by measuring the electrical conductivity of the solution. However, because of the differential rate of nutrient uptake, conductivity measurements mostly measure the calcium, magnesium and sulfate remaining in solution. The micronutrients contribute less than 0.1% to electrical conductivity.
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*Developing an appropriate refill solution*

The objective is to develop a recipe for a refill solution that replenishes both nutrients and the water. Plants have evolved to tolerate large nutrient imbalances in the root-zone, but in recirculating hydroponic systems, imbalances in nutrient replenishment are cumulative. It is thus important to understand the principles for nutrient replacement, especially when the solution is continuously recycled over the life cycle of a crop.

Traditional nutrient solution recipes, such as Hoagland solution, can be used as refill solution if they are diluted to about 1/3 strength so that the electrical conductivity is kept constant. Hoagland solution, however, was originally developed for tomatoes and is not always appropriate as refill solution for other types of plants.

Two factors must be considered in developing a refill solution:


Solution Composition.
Solution Concentration.

*Solution Composition*
The composition of the solution (the ratio of nutrients) should be determined by the desired concentrations of each element in the plant. A starting point for refill solution composition is the ratio of the elements in the plant leaves, which can be determined from a reference book on Plant Analysis Interpretation. I am familiar with four books that list the optimum concentrations of nutrients in plant tissue (and there are probably other books):

*Plant Analysis: An interpretation Manual.* 1986. D. Reuter & J. Robinson, (eds). Inkata Press, Melbourne.
*Plant Analysis Handbook.* 1991. J. Benton Jones, B. Wolf, H. Mills. Micro-Macro Publishing, Inc. Athens, GA.
*Plant Analysis.* 1987. P. Martin-Prevel and J. Gagnard. Lavoisier Publishing Inc. New York.
*Diagnostic Criteria for Plants and Soils.* 1966. Homer Chapman. Univ. of Calif., Riverside, CA.

Each of these books is organized differently and each has strengths and weaknesses. I recommend collecting the information from all of them for a particular crop and comparing the recommendations for the optimum range of nutrient concentrations.

Foliar analysis is based on the nutrient concentration in leaf tissue because leaves conduct the most photosynthesis and thus have the highest enzyme levels in plants. Average nutrient concentrations of whole plants are usually less than the concentrations in leaves, so a refill solution based solely on leaf tissue concentration will over supply nutrients for stems, seeds, and fruits. We have made many measurements of nutrient concentrations in different parts of wheat plants.

Young plants easily develop nutrient deficiencies but rarely develop nutrient toxicities so we use a relatively concentrated initial starter solution. A refill solution with adequate nutrients for early vegetative leaf growth is usually too concentrated when plants are developing stems and leaves so we alter the composition of the refill solution with the growth stage of the plant to prevent nutrient accumulation in the solution. The life cycle can be divided into 3 stages:

Early vegetative growth, which is primarily composed of leaf tissue (starter solution).
Late vegetative growth, during which growth is composed of about equal amounts of stem and leaf tissue (vegetative refill solution).
Reproductive growth, during which leaf growth is minimal and nutrients are mobilized into seeds or fruits (seed refill solution).
Root growth primarily occurs during early vegetative growth and is much less significant during late vegetative growth. Root growth decreases and even stops during reproductive growth.
[/LIST]​*Nitrogen*: When nitric acid is used for pH control, about half of the nitrogen is supplied in the pH control solution. Nitrogen in the refill solution can thus be less than in Hoagland's solution. Ammonium nitrate (NH4NO3) can be added to the pH control solution if necessary to obtain even higher levels of N in the plants, but ammonium reduces the uptake of other cations so it should only be used if necessary.

*Potassium*: The supply of K is more constant with a low level in the starter solution and a more concentrated refill solution.

*Calcium*: Grasses have a lower requirement for calcium than dicots.

*Magnesium and Sulfur* (MgSO4): We have not found that 1 mM is necessary.

*Iron* (Fe): The use of modern chelating agents means that iron can be maintained in solution and much lower levels can be maintained.

*Boron*: Grasses have much a lower requirement for boron than dicots.

*Zinc and Copper*: These elements are ubiquitous contaminants. Hoagland and Arnon in the 1940's and 50's probably got most of these elements from contamination of the solution. Modern plastics, especially PVC pipe, greatly reduce copper and zinc contamination.

*Silicon*: A beneficial element. See section on silicon in this paper.

*Solution Concentration*
The concentration of ions in the refill solution is determined by the ratio of transpiration to growth. Transpiration determines the rate of water removal; growth determines the rate of nutrient removal. A good estimate of the transpiration to growth ratio for hydroponically grown crops is 300 to 400 kg (Liters) of water transpired per kg of dry mass of plant growth. The exact ratio depends on the humidity of the air; low humidity increases transpiration but does not increase growth. Elevated CO2 closes stomates and increases photosynthesis so the transpiration to growth ratio can decrease to about 200 to 1.

Knowledge of these ratios is useful in determining the approximate concentration of the refill solution. For example, 1/4 strength Hoagland's solution is about right for plants grown in ambient CO2, but 1/3 strength Hoagland's solution may be required for plants grown in elevated CO2. Total ion concentration can be maintained by controlling solution electrical conductivity. If the conductivity increases, the refill solution should be made more dilute, but the composition should be kept the same. The electrical conductivity does not change rapidly so it is usually necessary to monitor it only a few times each week. We have successfully used this approach in long-term studies (months) without discarding any solution. This procedure can eliminate the need to monitor nutrient solution concentrations in the solution.


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*Examples of refill solution concentration calculations*

An analysis of the mass balance of potassium (K) is useful to demonstrate recovery in plant tissue.

*Case # 1*: Assume a transpiration to dry-mass growth ratio of 300:1 and a desired K concentration in the plant of 4% (40 g kg-1). For every kg of plant growth, 300 Liters of solution went through the plant, so there must be 40 g of K in 300 Liters of refill solution, or 0.133 g L-1. The molar mass (atomic weight) of K is 39 g mol-1. The refill solution must have 0.133 / 39 = 0.0034 moles L-1 of K in it, or 3.4 mM K.
*Case # 2*: Low humidity. If the transpiration to growth ratio was 400:1 the refill solution should be more dilute by 300/400 or 3/4. 40g in 400 L = 0.1 g L-1 divided by 39 = 2.6 mM K.
*Case # 3*: If the plant was in a fruit or seed fill stage of growth, potassium requirements might only be about 2% K (20 mg kg-1) in the new growth. If the transpiration to growth ratio was 300:1, the refill solution would be: 20 g K in 300 L = 0.067 g L-1 / 39 = 1.7 mM K.

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*Nutrient recovery in plant tissue*

As mentioned earlier, the mass balance approach to nutrient management assumes that all of the nutrients are either in the solution or in the plant. Surprisingly few detailed mass balance studies to test this assumption have been conducted, however, studies in our laboratory and studies by Dr. Wade Berry at UCLA clearly indicate that the recovery of several elements is less than 100%, while recovery of some micronutrients is much greater than 100%. Table 5 indicates the average recoveries of elements from solution in six replicate 23-day studies. These recoveries are typical of recirculating hydroponic systems. Because recovery of macronutrients is 50 to 85%, additional macronutrients should be added to the refill solution. Reduced amounts of some micronutrients may be warranted when the contamination is reproducible.

Table 5. Average recoveries of the essential nutrients in plant tissue at the end of six replicate 22 day studies with wheat. The recovery of all of the macronutrients, and iron and boron was 50 to 85% of that added to the nutrient solution (minus what was left in solution at the end of the trial). The recovery of Mn, Zn, Cu, and Mo was greater than 100% because of contamination of the hydroponic solution from elements in the plastics or the magnetic drive pumps. Many different types of plastics were used to build this system and many plastics use zinc and copper as emulsifiers in manufacturing. These recoveries are typical in recirculating hydroponic systems.

Element.........% Recovery
N............................70
P............................75
K............................85
Ca..........................50
Mg..........................70
S.............................50
Fe...........................50
Mn.........................280
B.............................60
Zn.........................400
Cu.........................600
Mo.......................1000

*Frequency of addition of refill solution*

Because nutrients with active uptake are depleted in hours, it might seem that automatic addition of refill solution is required to avoid depletion. Frequent addition of refill is not necessary. The nutrients that are rapidly absorbed from solution are all mobile in plants, which means that plants can store the nutrients in roots, stems, or leaves and remobilize them as needed. We have done studies with nitrogen in which we spiked the solution once every 2 days and let the solution deplete to near zero (which occurred after about 12 hours). Plant growth was identical to the controls, which were maintained at a constant ample N level. However, we also did another study in which an excessive level of N was added to the starter solution, but the N was not replenished. The plants rapidly absorbed the N until it was depleted to about 20 µM nitrate at 16 days after seedling emergence. These plants had ample nitrate in the leaves at harvest on day 23, but assimilated N and dry mass gain were slightly lower than the controls (at a constant ample N). The results of this study suggest that remobilized nutrients may not be as useful as freshly absorbed nutrients.

It is relatively easy to use a float valve to obtain frequent small additions of nutrients, but this may not result in improved plant growth compared to daily additions of refill solution. In practice, the frequency of addition of refill solution is determined by the ratio of solution volume to plant growth rate. Small volumes with big plants need frequent refilling of both nutrients and water.


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*Examples of nutrient concentrations in hydroponic solution over the life cycle*

Figure 1 shows the concentrations of nutrients over a 70 day life cycle of wheat. Note that the concentrations of K, Ca, S, and Mg increased after anthesis on day 35 because less of these nutrients are required in the seeds. The spikes in the concentration of Mn were caused when the solution was analyzed immediately after the addition of refill solution. These measurements were made before we installed a float valve to provide automatic, frequent additions of refill solution. Frequent additions of refill solution would smooth out the concentrations of all of the elements. The plant tissue concentrations of all elements were ample in this study, and, in fact, K and P concentrations were excessive. After this study, we reduced the concentration of K and P in the refill solution to the level indicated in Table 4. The starting K concentration was 4 mM in this study, but our current starting K concentration is 1.5 mM, which is maintained at about 0.5 mM K in the circulating solution by adding 4.5 mM K in the refill solution.


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*Commercial plant analysis laboratories*

Analysis of hydroponic solution is unnecessary, inaccurate, and difficult to interpret, but analysis of plant tissue is useful, accurate, and relatively easy to interpret. All four of the plant analysis books referenced previously provide guidelines for optimum concentrations of nutrients in plant tissue (usually in the youngest, fully expanded leaf blades). I highly recommend sampling plant tissue at intervals during the life cycle to help refine the composition of the refill solution. Tissue sampling becomes less important over time as procedures are refined and optimal nutrient levels in plant leaves are obtained. 
The analytical methodology of choice for plant analysis is emission spectrophotometry. Many laboratories around the country analyze plant tissue on a daily basis. Almost all of these are listed in the publication entitled "Soil and Plant Analysis Laboratory Registry for the United States and Canada" (Council on Soil Testing and Plant Analysis, Georgia Univ. Station, Athens, GA 30612-0007; about $15/copy). This provides analytical services offered, contact person, phone and fax numbers. Be sure to check with the laboratory before sending them a sample. Each lab has different recommendations for plant sampling, drying, and shipment. The lab should be able to provide you with an analysis of nutrient toxicities and deficiencies. J. Benton Jones article in the 1993 HSA Proceedings more thoroughly explains details associated with plant sampling and analysis.

As an example of the typical cost of analysis, the 1995 analytical charges at the Soil and Plant Analysis Laboratory at Utah State University are as follows:

ICP-emission spectrophotometry for 22 elements: $15
Kjeldahl or LECO Total Nitrogen analysis: $8
nitrate-N analysis: $6
Total nitrogen plus ICP-ES elements (package discount): $20

*pH monitoring and control*

Is pH control important?

Most people assume pH control is essential, but there is considerable misunderstanding about the effect of pH on plant growth. Plants grow equally well between pH 4 and 7, if nutrients do not become limiting. This is because the direct effects of pH on root growth are small; the problem is reduced nutrient availability at high and low pH. The recommended pH for hydroponic culture is between 5.5 to 5.8 because overall availability of nutrients is optimized at a slightly acid pH. The availabilities of Mn, Cu, Zn and especially Fe are reduced at higher pH, and there is a small decrease in availability of P, K, Ca, Mg at lower pH. Reduced availability means reduced nutrient uptake, but not necessarily nutrient deficiency.

Unfortunately, hydroponic systems are so poorly buffered that it is difficult to keep the pH between 4 and 7 without automatic pH control. Phosphorous (H2PO4 to HPO4) in solution buffers pH, but if phosphorous is maintained at levels that are adequate to stabilize pH (1 to 10 mM), it becomes toxic to plants. Plants actively absorb phosphorous from solution so a circulating solution, with about 0.05 mM P has much less buffering capacity than the fresh refill solution that is added to replace transpiration losses. Figure 2a is a titration curve of fresh refill solution compared to the recirculating solution. Six mmoles of base were required to raise the pH of fresh solution from 5.8 to 8, but only 1 mmole of base raised the pH of the circulating solution to 8. Figure 2b shows the slopes (derivatives) of the lines in Figure 2a. Figure 2b clearly shows poor buffering of the circulating solution between pH 5 to 9; small amounts of acid or base rapidly change the solution pH. The fresh refill solution is buffered by phosphorous, which has its maximum buffering capacity at pH 7.2. This point is called the pKa of the buffer and it is the point at which half of the phosphorous is in the H2PO4 form and half is in the HPO4 form. In other words, the phosphate ion absorbs and desorbs hydrogen ions to stabilize the pH. Unfortunately, phosphorous is quickly removed from the solution.

We were surprised to find that the circulating solution was better buffered below pH 5 than the fresh solution. The reasons for this are unclear; we cannot identify compounds in the refill solution that provide buffering capacity at pH 4. We are preparing to repeat these measurements and are investigating this finding.

*How important is maintaining pH 5.8?*

We control the pH at 4 to study root respiration (to eliminate bicarbonate in solution). We compared growth at pH 4 and pH 5.8 with wheat and were not able to find a significant difference in root growth rate or root metabolism. We now routinely grow wheat crops at pH 4 during the entire life cycle. However, although there is usually a broad optimum pH, it is still best to maintain pH at about 5.8 to optimize nutrient availability. pH levels below 4 may start to reduce root growth, in one study our pH control solenoid failed just after seed germination and the pH went to 2.5 for 48 hours. The roots turned brown and died, but new roots quickly grew back and the plants appeared to make a complete recovery.

*An automated pH Control System.*

Although organic pH buffers can be used to stabilize pH (Bugbee and Salisbury, 1985), in the long run it is better and less expensive to use an automated pH control system that adds acid or base to the solution. These systems require 3 components: a pH electrode, a pH controller, and a solenoid. We have had 7 pH control systems in continuous operation at the Utah State University Crop Physiology Laboratory during the past 8 years. It is useful to pass on our experience with the system components.

*pH electrodes*. We have not found that expensive electrodes last any longer than cheap electrodes (about 2 years per electrode) so we use cheap electrodes. We currently use a general purpose pH electrode from Omega (model PHE-4201; $49). It appears to be important to avoid rapid flow of solution across the tip of the electrode. Rapid response time is not important and the high flow appears to greatly decrease electrode life and also causes significant calibration drift. We check the calibration of the electrode every 2 to 3 months and adjust it if necessary.

*pH controller.* In about 1987 a new, digital-display pH controller became available (model 3671, $225., Whatman Lab Sales, Hillsboro, OR, 1-800-942-8626). This controller has been excellent in our laboratory - we have yet to have a controller fail. Automatic temperature control is completely available with the controller for another $65. but it is unnecessary.

When the pH increases to 5.8, the controller opens a solenoid that allows nitric acid (HNO3) to flow into the bulk solution. When nitrate nitrogen is used the solution pH increases as the nitrate is absorbed so only one solenoid is necessary. The acid inlet should be in close proximity to the tip of the pH electrode so that frequent small additions of acid occur and the bulk solution pH is stable.

*Acid/base solenoid*. A peristaltic pump can be used to add acid or base, but a solenoid is less expensive. Proper solenoid selection is important because common solenoids quickly deteriorate from acid corrosion. We use a shielded core acid solenoid from The Automatic Switch Company (ASCO, model D8260G56V or G53V; about $76.). These solenoids do not corrode, but in our experience, about 50% of the diaphragms in the valves failed in less than 2 years in continuous use. The valves are rated for a million cycles so they should last at least 10 years. We are currently working with ASCO to determine the cause of the premature failure. We previously used ASCO valve number D8260G54V, but this valve is not shielded core and corrodes in less than a year, even with 0.1 molar acid. Most plumbing suppliers sell ASCO solenoids, it pays to shop around for good price and quick delivery. Many other companies sell acid resistant valves that may be suitable, but some require a transformer for 24 volt operation.

The total cost (1995) of a pH control system as described above is $350. to $400. depending on availability of system components.


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*Why add silicon to nutrient solution?*

Although silicon has not been recognized as an essential element for higher plants, its beneficial effects have been shown in many plants. Silicon is abundant in all field grown plants, but it is not present in most hydroponic solutions. Silicon has long been recognized as particularly important to rice growth, but a recent study indicated that it may only be important during pollination in rice (Ma et al. 1989). The beneficial effects of silicon (Si) are twofold: 1) it protects against insect and disease attack (Cherif et al. 1994; Winslow, 1992; Samuels, 1991), and 2) it protects against toxicity of metals (Vlamis and Williams, 1967; Baylis et al. 1994). For these reasons, I recommend adding silicon (about 0.1 mM) to nutrient solutions for all plants unless the added cost outweighs its advantages.


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*Experiences with phythium control in hydroponic solution*

The phythium fungus has been the only serious disease we have encountered in our systems, and disease problems have been relatively rare, particularly when all parts of the system are kept covered to keep dust and dirt particles away from the solution. Every plant pathologist on the planet recommends sanitation as the best control procedure for phythium, yet many hydroponic systems are not as well sealed as they should be. 
Last year, we discovered that Mn deficiency predisposed the plants to phythium infection. A student worker accidently used MgCl2 in place of MnCl2 for a micronutrient stock solution and we didn't discover the mistake for several months because we were doing short (25 day) studies and there was enough Mn contamination so that no visual symptoms were apparent (growth rate was reduced only about 15% and there was about 10 mg kg-1 Mn in the leaf tissue). During this time several of the systems became infected with phythium. The same systems have never been infected when Mn was adequate. Copper is well known to suppress microbial growth, but increased copper levels are toxic to plants. Manganese and zinc (divalent cations) may have a similar disease suppressive potential, but are less toxic to plants. In the interest of minimizing phythium growth, we have increased solution Mn to a level higher than that required for optimum growth. Careful studies will be required to confirm the beneficial effects of Mn on disease suppression; meanwhile, there is little disadvantage to maintaining manganese, zinc, and copper levels slightly above the minimum required for plant growth.


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*Designing hydroponic systems: The importance of flow rate*

Most hydroponic systems have inadequate flow rates, which results in reduced oxygen levels at root surfaces. This stresses roots and can increase the incidence of disease. Oxygen is soluble only as a micronutrient, yet its uptake rate is much faster than any other nutrient element.

The nutrient film technique was designed to improve aeration of the nutrient solution because of the thin film of solution, but the slow flow rates in NFT cause channeling of the solution and reduced flow to areas with dense roots. The root surfaces in these areas become anaerobic, which diminishes root respiration, reduces nutrient uptake, increases N losses via denitrification, and makes roots susceptible to infection. The problems with the nutrient film technique have been discussed by several authors. Bugbee and Salisbury (1989) discuss the importance of flow rate and adequate root-zone oxygen levels.


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*Isolite: A new substrate for hydroponics*

Many different substrates are used for plant support in hydroponic culture, but one of the unique requirements for research is that the media be easily separated from the roots. Peat, perlite, and vermiculite are good substrates but roots and root hairs grow into these substrates, so they are unsuitable for studies of root size and morphology. Sand can easily be removed from roots, but roots grown in sand are shorter and thicker than hydroponic roots because the sand particles are so dense. We have also found that plant growth in sand is less than in other substrates, presumably because of reduced root growth. Calcined clay (brand names: Turface, Profile, Arcillite) was the medium of choice for research hydroponics for many years because it can easily be removed from roots. Calcined clay, however, has two disadvantages: 1) It is not chemically inert. Different batches supply different amounts of available nutrients and this causes variable results. It can be repeatedly rinsed in nutrient solution to desorb undesirable nutrients, but this adds to its cost. 2) Calcined clay is not a uniform particle size, and the water holding capacity depends on particle size. Not all batches are the same.

We recently tested and began using an extruded, diatomaceous-earth product called Isolite. Isolite is mined off the coast of Japan where there is a unique diatomaceous-earth deposit mixed with 5% clay. The clay acts as a binder in the extrusion and baking of the diatomaceous-earth. Diatomaceous-earth materials were originally organisms composed primarily of silicon dioxide (SiO2). Silicon dioxide is physically and chemically inert and these characteristics make it useful for horticultural applications like putting greens and urban trees where the soil is subject to severe compaction. Isolite is available in particle sizes from 1 to 10-mm diameter. Our tests indicate that Isolite is chemically inert and has good water holding characteristics. Its disadvantage is cost at $1.22 per Liter ($.79 per pound) for small quantities, although it can be reused. We have reused it after rinsing and drying at 80 C. Isolite is made by Sumitomo Corp. and is available in the USA from Sundine Enterprises, Arvada, CO; 303-423-8669.


*Microorganisms and organic compounds in the solution: Is filtering useful?*

Many people think that filtering the recirculating solution is useful, but we have never filtered our solutions. Our measurements indicate that total organic carbon in the recirculating solution does not exceed 15 mg per liter, even near the end of a 2 month life cycle. About 30% of the organic carbon in the solution is in the chelating agent. Total organic carbon includes the carbon that is in microbial biomass, so it is clear that neither organic compounds nor microorganisms are at high levels in the solution. The solution also appears as clear prior to harvest at 80 days as fresh solution.

Roots leak organic compounds, but there is an equilibrium between microorganisms on root surfaces and the exudates so that compounds are degraded to CO2 at the root surface. Estimates of the quantity of root exudates vary widely, but there is considerable evidence that carbon efflux increases when plants are stressed (Barber and Gunn, 1974; Smucker, 1984; Haller and Stolp, 1985). Bowen and Rovira (1976) found that roots in solution culture produce smaller quantities of exudate than in soil. Trollenier and Hect-Buchholz (1984) found that reduced root growth due to inadequate aeration in hydroponic culture was accompanied by a dramatic increase in root microbe population, which they attributed to increased exudation from roots. The bottom line is that healthy roots in a well aerated hydroponic system should not increase the microorganisms or organics in the solution and filtering is thus unnecessary.


*Summary comments on specific elements*

*Nitrogen*: Plant requirements for nitrogen are sometimes larger than all of the other elements combined. It can thus be difficult to supply nitrogen in the refill solution without adding excess amounts of other cations. The best solution is to use nitric acid (HNO3) for pH control. This can supply 50% of the nitrogen needs of the crop without adding excess cations. If extra nitrogen is required, ammonium nitrate can be added to the pH control solution. However, because ammonium decreases the uptake of other cations (K, Ca, Mg, and micronutrients) I do not recommend its use in hydroponic solutions unless extra nitrogen is required by the crop for maximum yields.

*Phosphorous and Potassium*: are rapidly drawn down to µM levels is solution. These low levels do not mean that the plant is starving for these elements, it means that the plant is healthy and actively absorbed these elements from solution.

*Calcium*: requirements are almost 3 times higher for dicots than for monocots (grasses). Calcium is nontoxic, even at high tissue concentrations, but it accumulates in solution if too much is added to the refill solution.

*Magnesium*: is highly mobile and can accumulate to toxic levels in upper leaves if the solution concentration is too high.


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## woodsmaneh! (Jan 29, 2012)

*RESEARCH: HYDROPONICS*[HR][/HR] 

*Nutrient Management in Recirculating Hydroponic Culture*
*Bruce Bugbee
Presented at the **South Pacific Soil-less Culture Conference*
*Feb 11, 2003 in Palmerston North, New Zealand *
[HR][/HR]
*PAGE TOPICS: (CLICK ON TOPIC BELOW TO JUMP TO DISCUSSION)* 

*INTRODUCTION*
*MANAGING NUTRIENTS BY MASS BALANCE*
*DIFFERENTIAL NUTRIENT REMOVAL FROM SOLUTION*
*DEVELOPING AN APPROPRIATE REFILL SOLUTION*
*- **SOLUTION COMPOSITION*
*- **SOLUTION CONCENTRATION*
*EXAMPLE OF REFILL SOLUTION CONCENTRATION CALCULATIONS*
*NUTRIENT RECOVERY IN PLANT TISSUE*
*FREQUENCY OF ADDITION OF REFILL SOLUTION*
*EXAMPLES OF NUTRIENT CONCENTRATIONS IN HYDROPONIC SOLUTION OVER THE LIFE CYCLE*
*COMMERCIAL PLANT ANALYSIS LABORATORIES*
*pH MONITORING AND CONTROL*
*WHY ADD SILICON TO NUTRIENT SOLUTION?*
*EXPERIENCES WITH PHYTHIUM CONTROL IN HYDROPONICS SOLUTION*
*DESIGNING HYDROPONIC SYSTEMS: THE IMPORTANCE OF FLOW RATE*
*ISOLITE: A NEW SUBSTRATE FOR HYDROPONICS*
*MICROORGANISMS AND ORGANIC COMPOUNDS IN THE SOLUTION: IS FILTERING USEFUL?*
*SUMMARY COMMENTS ON SPECIFIC ELEMENTS*
*LITERATURE CITED*
[HR][/HR] *INTRODUCTION** In preparation for writing this paper, I read the related papers from previous HSA proceedings. I am impressed by the amount of useful information. The annual meeting and proceedings of HSA have become an important source of technical information on the hydroponic culture of plants. This information is not necessarily available at the annual meetings of related professional societies such as The American Society for Horticultural Science, or The American Society of Agronomy.

It was necessary for me to read other papers because many of them discuss nutrient management in recirculating hydroponic systems. Authors at every meeting in the past 5 years have stressed the need to recirculate and reuse nutrient solutions to reduce environmental and economic costs. Dr. Pieter Schippers (1991 HSA proceedings) reviewed nutrient management and clearly indicated the need for data when he said; "One of the weakest points in hydroponics...is the lack of information on managing the nutrient solution." I was moderately surprised to find that previous authors recommended measuring the concentrations of individual nutrients in solution as a key to nutrient control and maintenance. Monitoring ions in solution is unnecessary. Even worse, the rapid depletion of some nutrients often causes people to add toxic amounts of nutrients to the solution. Monitoring solutions is interesting, but it is not the key to effective maintenance.*  [HR][/HR] *MANAGING** NUTRIENTS BY MASS BALANCE** During the past 12 years, we have managed nutrients in closed hydroponic systems according to the principle of "mass balance," which means that the mass of nutrients is either in solution or in the plants. We add nutrients to the solution depending on what we want the plant to take up.

Plants quickly remove their daily supply of some nutrients while other nutrients accumulate. This means that the concentrations of nitrogen, phosphorous, and potassium can be at low levels in the solution (0.1 mM or a few ppm) because these nutrients are in the plant, where we want them. Maintaining a high concentration of nutrients in the solution can result in excessive uptake that can lead to nutrient imbalances.

For example, the water removed from solution through transpiration must be replaced and it is necessary to have about 0.5 mM phosphorous in the refill solution. If the refill solution was added once each day, the phosphorous would be absorbed by the plant in a few hours and the solution phosphorous concentration would be close to zero. This does not indicate a deficiency; rather it indicates a healthy plant with rapid nutrient uptake. If the phosphorous level is maintained at 0.5 mM in the recirculating solution, the phosphorous concentration in the plant can increase to 1% of the dry mass, which is 3 times higher than the optimum in most plants. This high phosphorous level can induce iron and zinc deficiency (Chaney and Coulombe, 1982).

Feeding plants in this way is like the daily feeding of a pet dog, some dogs would be far overweight if their food bowls were kept continuously full.*  [HR][/HR] *DIFFERENTIAL** NUTRIENT REMOVAL FROM SOLUTION** The essential nutrients can be put into 3 categories based on how quickly they are removed from solution. Group 1 elements are actively absorbed by roots and can be removed from solution in a few hours. Group 2 elements have intermediate uptake rates and are usually removed from solution slightly faster than water is removed. Group 3 elements are passively absorbed from solution and often accumulate in solution.

TABLE 1. Approximate uptake rates of the essential plant nutrients.*

*GROUP 1**Active uptake, fast removal**NO[SUB]3[/SUB], NH[SUB]4[/SUB], P, K, Mn**GROUP 2**Intermediate uptake**Mg, S, Fe, Zn, Cu, Mo, C**GROUP 3**Passive uptake, slow removal**Ca, B*

*One of the problems with individual ion monitoring and control is that the concentration of the group 1 elements (N, P, K, Mn) must be kept low to prevent their toxic accumulation in plant tissue. Low concentrations are difficult to monitor and control. Table 2 shows typical measurement errors associated with the use of ICP emission spectrophotometry for analysis of hydroponic solutions. Nitrogen cannot be measured by ICP-ES. Accuracy for the macronutrients is good, but solution levels of B, Cu, and Mo cannot be accurately measured by ICP-ES. The calculations in this table are for a typical refill solution, not for the low concentrations that should be maintained in the circulating solution. The measurement errors for K, P, and Mn can be 10 times higher because the solution levels are lower.

TABLE 2. Typical measurement error associated with the use of Inductively Coupled Plasma Emission Spectrophotometry for analysis of nutrient concentrations in hydroponic solution. *

*Element**Nutrient Solution
Concentration (mM)**ICP Accuracy (mM)**Typical Measurement
Error (%)**K **3.5**0.1**3**Ca **1.0**0.002**0.2**S **0.75**0.01**1**P**0.5**0.01**2**Mg**0.25**0.002**1**Micro-Nutrients**(µM)**(µM)**(%)**Fe**5.0**0.15**3**Mn**3.0**0.3**10**Zn**1.0**0.15**15**B**1.0**3.0**300**Cu**0.1**0.2**200**Mo**0.03**1.0**3300*

*The total amount of nutrients in solution can easily and accurately be determined by measuring the electrical conductivity of the solution. However, because of the differential rate of nutrient uptake, conductivity measurements mostly measure the calcium, magnesium and sulfate remaining in solution. The micronutrients contribute less than 0.1% to electrical conductivity.*  [HR][/HR] *DEVELOPING** AN APPROPRIATE REFILL SOLUTION** The objective is to develop a recipe for a refill solution that replenishes both nutrients and the water. Plants have evolved to tolerate large nutrient imbalances in the root-zone, but in recirculating hydroponic systems, imbalances in nutrient replenishment are cumulative. It is thus important to understand the principles for nutrient replacement, especially when the solution is continuously recycled over the life cycle of a crop.

Traditional nutrient solution recipes, such as Hoagland solution, can be used as refill solution if they are diluted to about 1/3 strength so that the electrical conductivity is kept constant. Hoagland solution, however, was originally developed for tomatoes and is not always appropriate as refill solution for other types of plants.

Two factors must be considered in developing a refill solution:
1. **Solution Composition*
*2. **Solution Concentration*  [HR][/HR] *SOLUTION** COMPOSITION** The composition of the solution (the ratio of nutrients) should be determined by the desired concentrations of each element in the plant. A starting point for refill solution composition is the ratio of the elements in the plant leaves, which can be determined from a reference book on Plant Analysis Interpretation. I am familiar with four books that list the optimum concentrations of nutrients in plant tissue (and there are probably other books):*

*Plant Analysis: An interpretation Manual. 1986. D. Reuter & J. Robinson, (eds). Inkata Press, Melbourne. *
*Plant Analysis Handbook. 1991. J. Benton Jones, B. Wolf, H. Mills. Micro-Macro Publishing, Inc. Athens, GA. *
*Plant Analysis. 1987. P. Martin-Prevel and J. Gagnard. Lavoisier Publishing Inc. New York. *
*Diagnostic Criteria for Plants and Soils. 1966. Homer Chapman. Univ. of Calif., Riverside, CA.*
*Each of these books is organized differently and each has strengths and weaknesses. I recommend collecting the information from all of them for a particular crop and comparing the recommendations for the optimum range of nutrient concentrations.

Foliar analysis is based on the nutrient concentration in leaf tissue because leaves conduct the most photosynthesis and thus have the highest enzyme levels in plants. Average nutrient concentrations of whole plants are usually less than the concentrations in leaves, so a refill solution based solely on leaf tissue concentration will over supply nutrients for stems, seeds, and fruits. We have made many measurements of nutrient concentrations in different parts of wheat plants. Table 3 shows that the concentrations of most elements are much higher in leaves than in other plant parts.

TABLE 3. Approximate optimum nutrient concentrations in different parts of a wheat plant. *

*%**Leaves**Stem**Seeds**Roots**N**5**2**3**3**P**0.3**0.2**0.5**0.2**K**2.5**2.3**0.7**2.0**Ca**1.2**0.3**0.1**0.2**Mg**0.5**0.05**0.2**0.05**S**0.5**0.3**0.2**0.2**mg/kg**Leaves**Stem**Seeds**Roots**Fe**100**40**100**800***Mn**75**20**50**25**B**5**3**0.5**5**Zn**50**20**50**30**Cu**10**1**5**10**Mo**2**1**1**1**Cl**1**1**1**1*

**Iron precipitates on the root surface.

Young plants easily develop nutrient deficiencies but rarely develop nutrient toxicities so we use a relatively concentrated initial starter solution. A refill solution with adequate nutrients for early vegetative leaf growth is usually too concentrated when plants are developing stems and leaves so we alter the composition of the refill solution with the growth stage of the plant to prevent nutrient accumulation in the solution. The life cycle can be divided into 3 stages: *

*Early vegetative growth, which is primarily composed of leaf tissue (starter solution). *
*Late vegetative growth, during which growth is composed of about equal amounts of stem and leaf tissue (vegetative refill solution). *
*Reproductive growth, during which leaf growth is minimal and nutrients are mobilized into seeds or fruits (seed refill solution). *
*Root growth primarily occurs during early vegetative growth and is much less significant during late vegetative growth. Root growth decreases and even stops during reproductive growth.

Table 4 shows the nutrient solution that we use for hydroponic culture of wheat. Although wheat is not a commercial hydroponic crop, the same principles apply to all crops. The refill solutions are more dilute at the later stages of the life cycle because the nutrient requirements of stems and seeds are less than for leaves.

TABLE 4. A comparison of half-strength Hoagland Solution with Utah Wheat Solutions. The system is initially filled with the starter solution. Vegetative refill solution is used during leaf and stem growth. The seed fill solution is used after the leaves stop growing and the grain is filling. *

*UTAH WHEAT SOLUTION* *mM**Hoagland
Solution**Starter
Solution**Vegetative
Refill**Seed Fill
Refill**N**7.5**3**6**3**P**0.5**0.5**0.5**0.5**K**3**1.5**4.5**2.5**Ca**2**1**1**0.5**Mg**1**0.5**0.3**0.3**S**1**0.5**0.3**0.3**µM**Hoagland
Solution**Starter
Solution**Vegetative
Refill**Seed Fill
Refill**Fe**44.6**10**2.5**2.5**Fe-HEDTA**0**25**5**5**Mn**4.5**3**6**3**B**23**2**1**0.2**Zn**0.4**3**1**1**Cu**0.15**0.3**0.3**0.2**Mo**0.05**0.09**0.03**0.03**Cl**9**6**12**6**Si**0**100**100**0*

*The rationale underlying the differences between Hoagland's solution and Utah Wheat solution are not obvious so a discussion of differences is useful.

NITROGEN: When nitric acid is used for pH control, about half of the nitrogen is supplied in the pH control solution. Nitrogen in the refill solution can thus be less than in Hoagland's solution. Ammonium nitrate (NH4NO3) can be added to the pH control solution if necessary to obtain even higher levels of N in the plants, but ammonium reduces the uptake of other cations so it should only be used if necessary.

POTASSIUM: The supply of K is more constant with a low level in the starter solution and a more concentrated refill solution.

CALCIUM: Grasses have a lower requirement for calcium than dicots.

MAGNESIUM and SULFUR (MgSO4): We have not found that 1 mM is necessary.

IRON (Fe): The use of modern chelating agents means that iron can be maintained in solution and much lower levels can be maintained.

BORON: Grasses have much a lower requirement for boron than dicots.

ZINC and COPPER: These elements are ubiquitous contaminants. Hoagland and Arnon in the 1940's and 50's probably got most of these elements from contamination of the solution. Modern plastics, especially PVC pipe, greatly reduce copper and zinc contamination.

SILICON: A beneficial element. **See section on silicon in this paper.*  [HR][/HR] *SOLUTION** CONCENTRATION **The concentration of ions in the refill solution is determined by the ratio of transpiration to growth. Transpiration determines the rate of water removal; growth determines the rate of nutrient removal. A good estimate of the transpiration to growth ratio for hydroponically grown crops is 300 to 400 kg (Liters) of water transpired per kg of dry mass of plant growth. The exact ratio depends on the humidity of the air; low humidity increases transpiration but does not increase growth. Elevated CO2 closes stomates and increases photosynthesis so the transpiration to growth ratio can decrease to about 200 to 1.

A knowledge of these ratios is useful in determining the approximate concentration of the refill solution. For example, 1/4 strength Hoagland's solution is about right for plants grown in ambient CO[SUB]2[/SUB], but 1/3 strength Hoagland's solution may be required for plants grown in elevated CO[SUB]2[/SUB]. Total ion concentration can be maintained by controlling solution electrical conductivity. If the conductivity increases, the refill solution should be made more dilute, but the composition should be kept the same. The electrical conductivity does not change rapidly so it is usually necessary to monitor it only a few times each week. We have successfully used this approach in long-term studies (months) without discarding any solution. This procedure can eliminate the need to monitor nutrient solution concentrations in the solution.*  [HR][/HR] *EXAMPLES** OF REFILL SOLUTION CONCENTRATION CALCULATIONS **An analysis of the mass balance of potassium (K) is useful to demonstrate recovery in plant tissue. *

*CASE #1: Assume a transpiration to dry-mass growth ratio of 300:1 and a desired K concentration in the plant of 4% (40 g kg[SUP]-1[/SUP]). For every kg of plant growth, 300 Liters of solution went through the plant, so there must be 40 g of K in 300 Liters of refill solution, or 0.133 g L[SUP]-1[/SUP]. The molar mass (atomic weight) of K is 39 g mol[SUP]-1[/SUP]. The refill solution must have 0.133 / 39 = 0.0034 moles L[SUP]-1[/SUP] of K in it, or 3.4 mM K. *
*CASE #2: Low humidity. If the transpiration to growth ratio was 400:1 the refill solution should be more dilute by 300/400 or 3/4. 40g in 400 L = 0.1 g L[SUP]-1[/SUP] divided by 39 = 2.6 mM K. *
*CASE #3: If the plant was in a fruit or seed fill stage of growth, potassium requirements might only be about 2% K (20 mg kg[SUP]-1[/SUP]) in the new growth. If the transpiration to growth ratio was 300:1, the refill solution would be: 20 g K in 300 L = 0.067 g L[SUP]-1[/SUP] / 39 = 1.7 mM K. *
  [HR][/HR] *NUTRIENT** RECOVERY IN PLANT TISSUE** As mentioned earlier, the mass balance approach to nutrient management assumes that all of the nutrients are either in the solution or in the plant. Surprisingly few detailed mass balance studies to test this assumption have been conducted, however, studies in our laboratory and studies by Dr. Wade Berry at UCLA clearly indicate that the recovery of several elements is less than 100%, while recovery of some micronutrients is much greater than 100%. Table 5 indicates the average recoveries of elements from solution in six replicate 23-day studies. These recoveries are typical of recirculating hydroponic systems. Because recovery of macronutrients is 50 to 85%, additional macronutrients should be added to the refill solution. Reduced amounts of some micronutrients may be warranted when the contamination is reproducible.

TABLE 5. Average recoveries of the essential nutrients in plant tissue at the end of six replicate 22 day studies with wheat. The recovery of all of the macronutrients, and iron and boron was 50 to 85% of that added to the nutrient solution (minus what was left in solution at the end of the trial). The recovery of Mn, Zn, Cu, and Mo was greater than 100% because of contamination of the hydroponic solution from elements in the plastics or the magnetic drive pumps. Many different types of plastics were used to build this system and many plastics use zinc and copper as emulsifiers in manufacturing. These recoveries are typical in recirculating hydroponic systems.*

*ELEMENT**% RECOVERY**N **70**P **75**K **85**Ca **50**Mg **70**S **50**Fe **50**Mn **280**B **60**Zn **400**Cu **600**Mo **1000*
  [HR][/HR] *FREQUENCY** OF ADDITION OF REFILL SOLUTION **Because nutrients with active uptake are depleted in hours, it might seem that automatic addition of refill solution is required to avoid depletion. Frequent addition of refill is not necessary. The nutrients that are rapidly absorbed from solution are all mobile in plants, which means that plants can store the nutrients in roots, stems, or leaves and remobilize them as needed. We have done studies with nitrogen in which we spiked the solution once every 2 days and let the solution deplete to near zero (which occurred after about 12 hours). Plant growth was identical to the controls, which were maintained at a constant ample N level. However, we also did another study in which an excessive level of N was added to the starter solution, but the N was not replenished. The plants rapidly absorbed the N until it was depleted to about 20 µM nitrate at 16 days after seedling emergence. These plants had ample nitrate in the leaves at harvest on day 23, but assimilated N and dry mass gain were slightly lower than the controls (at a constant ample N). The results of this study suggest that remobilized nutrients may not be as useful as freshly absorbed nutrients.

It is relatively easy to use a float valve to obtain frequent small additions of nutrients, but this may not result in improved plant growth compared to daily additions of refill solution. In practice, the frequency of addition of refill solution is determined by the ratio of solution volume to plant growth rate. Small volumes with big plants need frequent refilling of both nutrients and water.*  [HR][/HR] *EXAMPLES** OF NUTRIENT CONCENTRATIONS IN HYDROPONIC SOLUTION OVER THE LIFE CYCLE **Figure 1 shows the concentrations of nutrients over a 70 day life cycle of wheat. Note that the concentrations of K, Ca, S, and Mg increased after anthesis on day 35 because less of these nutrients are required in the seeds. The spikes in the concentration of Mn were caused when the solution was analyzed immediately after the addition of refill solution. These measurements were made before we installed a float valve to provide automatic, frequent additions of refill solution. Frequent additions of refill solution would smooth out the concentrations of all of the elements. The plant tissue concentrations of all elements were ample in this study, and, in fact, K and P concentrations were excessive. After this study, we reduced the concentration of K and P in the refill solution to the level indicated in Table 4. The starting K concentration was 4 mM in this study, but our current starting K concentration is 1.5 mM, which is maintained at about 0.5 mM K in the circulating solution by adding 4.5 mM K in the refill solution.*  *COMMERCIAL** PLANT ANALYSIS LABORATORIES** Analysis of hydroponic solution is unnecessary, inaccurate, and difficult to interpret, but analysis of plant tissue is useful, accurate, and relatively easy to interpret. All four of the plant analysis books referenced previously provide guidelines for optimum concentrations of nutrients in plant tissue (usually in the youngest, fully expanded leaf blades). I highly recommend sampling plant tissue at intervals during the life cycle to help refine the composition of the refill solution. Tissue sampling becomes less important over time as procedures are refined and optimal nutrient levels in plant leaves are obtained.

The analytical methodology of choice for plant analysis is emission spectrophotometry. Many laboratories around the country analyze plant tissue on a daily basis. Almost all of these are listed in the publication entitled "Soil and Plant Analysis Laboratory Registry for the United States and Canada" (Council on Soil Testing and Plant Analysis, Georgia Univ. Station, Athens, GA 30612-0007; about $15/copy). This provides analytical services offered, contact person, phone and fax numbers. Be sure to check with the laboratory before sending them a sample. Each lab has different recommendations for plant sampling, drying, and shipment. The lab should be able to provide you with an analysis of nutrient toxicities and deficiencies. J. Benton Jones article in the 1993 HSA Proceedings more thoroughly explains details associated with plant sampling and analysis.

As an example of the typical cost of analysis, the 1995 analytical charges at the Soil and Plant Analysis Laboratory at Utah State University are as follows: * *ICP-emission spectrophotometry for 22 elements:**$15**Kjeldahl or LECO Total Nitrogen analysis:**$8**nitrate-N analysis:**$6**Total nitrogen plus ICP-ES elements (package discount):**$20* [HR][/HR] *pH** MONITORING AND CONTROL
Is pH control important? **Most people assume pH control is essential, but there is considerable misunderstanding about the effect of pH on plant growth. Plants grow equally well between pH 4 and 7, if nutrients do not become limiting. This is because the direct effects of pH on root growth are small, the problem is reduced nutrient availability at high and low pH. The recommended pH for hydroponic culture is between 5.5 to 5.8 because overall availability of nutrients is optimized at a slightly acid pH. The availabilities of Mn, Cu, Zn and especially Fe are reduced at higher pH, and there is a small decrease in availability of P, K, Ca, Mg at lower pH. Reduced availability means reduced nutrient uptake, but not necessarily nutrient deficiency.

Unfortunately, hydroponic systems are so poorly buffered that it is difficult to keep the pH between 4 and 7 without automatic pH control. Phosphorous (H2PO4 to HPO4) in solution buffers pH, but if phosphorous is maintained at levels that are adequate to stabilize pH (1 to 10 mM), it becomes toxic to plants. Plants actively absorb phosphorous from solution so a circulating solution, with about 0.05 mM P has much less buffering capacity than the fresh refill solution that is added to replace transpiration losses. Figure 2a is a titration curve of fresh refill solution compared to the recirculating solution. Six mmoles of base were required to raise the pH of fresh solution from 5.8 to 8, but only 1 mmole of base raised the pH of the circulating solution to 8. Figure 2b shows the slopes (derivatives) of the lines in Figure 2a. Figure 2b clearly shows poor buffering of the circulating solution between pH 5 to 9; small amounts of acid or base rapidly change the solution pH. The fresh refill solution is buffered by phosphorous, which has its maximum buffering capacity at pH 7.2. This point is called the pKa of the buffer and it is the point at which half of the phosphorous is in the H2PO4 form and half is in the HPO4 form. In other words, the phosphate ion absorbs and desorbs hydrogen ions to stabilize the pH. Unfortunately, phosphorous is quickly removed from the solution.

We were surprised to find that the circulating solution was better buffered below pH 5 than the fresh solution. The reasons for this are unclear, we cannot identify compounds in the refill solution that provide buffering capacity at pH 4. We are preparing to repeat these measurements and are investigating this finding.

How important is maintaining pH 5.8? We control the pH at 4 to study root respiration (to eliminate bicarbonate in solution). We compared growth at pH 4 and pH 5.8 with wheat and were not able to find a significant difference in root growth rate or root metabolism. We now routinely grow wheat crops at pH 4 during the entire life cycle. However, although there is usually a broad optimum pH, it is still best to maintain pH at about 5.8 to optimize nutrient availability. pH levels below 4 may start to reduce root growth, in one study our pH control solenoid failed just after seed germination and the pH went to 2.5 for 48 hours. The roots turned brown and died, but new roots quickly grew back and the plants appeared to make a complete recovery.

An automated pH control system. Although organic pH buffers can be used to stabilize pH (Bugbee and Salisbury, 1985), in the long run it is better and less expensive to use an automated pH control system that adds acid or base to the solution. These systems require 3 components: a pH electrode, a pH controller, and a solenoid. We have had 7 pH control systems in continuous operation at the Utah State University Crop Physiology Laboratory during the past 8 years. It is useful to pass on our experience with the system components.

pH electrodes. We have not found that expensive electrodes last any longer than cheap electrodes (about 2 years per electrode) so we use cheap electrodes. We currently use a general purpose pH electrode from Omega (model PHE-4201; $49). It appears to be important to avoid rapid flow of solution across the tip of the electrode. Rapid response time is not important and the high flow appears to greatly decrease electrode life and also causes significant calibration drift. We check the calibration of the electrode every 2 to 3 months and adjust it if necessary.

pH controller. In about 1987 a new, digital-display pH controller became available (model 3671, $225., Whatman Lab Sales, Hillsboro, OR, 1-800-942-8626). This controller has been excellent in our laboratory - we have yet to have a controller fail. Automatic temperature control is completely available with the controller for another $65. but it is unnecessary.

When the pH increases to 5.8, the controller opens a solenoid that allows nitric acid (HNO3) to flow into the bulk solution. When nitrate nitrogen is used the solution pH increases as the nitrate is absorbed so only one solenoid is necessary. The acid inlet should be in close proximity to the tip of the pH electrode so that frequent small additions of acid occur and the bulk solution pH is stable.

Acid/base solenoid. A peristaltic pump can be used to add acid or base, but a solenoid is less expensive. Proper solenoid selection is important because common solenoids quickly deteriorate from acid corrosion. We use a shielded core acid solenoid from The Automatic Switch Company (ASCO, model D8260G56V or G53V; about $76). These solenoids do not corrode, but in our experience, about 50% of the diaphragms in the valves failed in less than 2 years in continuous use. The valves are rated for a million cycles so they should last at least 10 years. We are currently working with ASCO to determine the cause of the premature failure. We previously used ASCO valve number D8260G54V, but this valve is not shielded core and corrodes in less than a year, even with 0.1 molar acid. Most plumbing suppliers sell ASCO solenoids, it pays to shop around for good price and quick delivery. Many other companies sell acid resistant valves that may be suitable, but some require a transformer for 24 volt operation.

The total cost (1995) of a pH control system as described above is $350. to $400. depending on availability of system components.*  [HR][/HR] *WHY** ADD SILICON TO NUTRIENT SOLUTION?** Although silicon has not been recognized as an essential element for higher plants, its beneficial effects have been shown in many plants. Silicon is abundant in all field grown plants, but it is not present in most hydroponic solutions. Silicon has long been recognized as particularly important to rice growth, but a recent study indicated that it may only be important during pollination in rice (Ma et al. 1989). The beneficial effects of silicon (Si) are twofold: 1) it protects against insect and disease attack (Cherif et al. 1994; Winslow, 1992; Samuels, 1991), and 2) it protects against toxicity of metals (Vlamis and Williams, 1967; Baylis et al. 1994). For these reasons, I recommend adding silicon (about 0.1 mM) to nutrient solutions for all plants unless the added cost outweighs its advantages. *  [HR][/HR] *EXPERIENCES** WITH PHYTHIUM CONTROL IN HYDROPONIC SOLUTION** The phythium fungus has been the only serious disease we have encountered in our systems, and disease problems have been relatively rare, particularly when all parts of the system are kept covered to keep dust and dirt particles away from the solution. Every plant pathologist on the planet recommends sanitation as the best control procedure for phythium, yet many hydroponic systems are not as well sealed as they should be.

Last year, we discovered that Mn deficiency predisposed the plants to phythium infection. A student worker accidently used MgCl2 in place of MnCl2 for a micronutrient stock solution and we didn't discover the mistake for several months because we were doing short (25 day) studies and there was enough Mn contamination so that no visual symptoms were apparent (growth rate was reduced only about 15% and there was about 10 mg kg-1 Mn in the leaf tissue). During this time several of the systems became infected with phythium. The same systems have never been infected when Mn was adequate. Copper is well known to suppress microbial growth, but increased copper levels are toxic to plants. Manganese and zinc (divalent cations) may have a similar disease suppressive potential, but are less toxic to plants. In the interest of minimizing phythium growth, we have increased solution Mn to a level higher than that required for optimum growth. Careful studies will be required to confirm the beneficial effects of Mn on disease suppression; meanwhile, there is little disadvantage to maintaining manganese, zinc, and copper levels slightly above the minimum required for plant growth.*  [HR][/HR] *DESIGNING** HYDROPONIC SYSTEMS: THE IMPORTANCE OF FLOW RATE** Most hydroponic systems have inadequate flow rates, which results in reduced oxygen levels at root surfaces. This stresses roots and can increase the incidence of disease. Oxygen is soluble only as a micronutrient, yet its uptake rate is much faster than any other nutrient element.

The nutrient film technique was designed to improve aeration of the nutrient solution because of the thin film of solution, but the slow flow rates in NFT cause channeling of the solution and reduced flow to areas with dense roots. The root surfaces in these areas become anaerobic, which diminishes root respiration, reduces nutrient uptake, increases N losses via denitrification, and makes roots susceptible to infection. The problems with the nutrient film technique have been discussed by several authors. Bugbee and Salisbury (1989) discuss the importance of flow rate and adequate root-zone oxygen levels.*  [HR][/HR] *ISOLITE:** A NEW SUBSTRATE FOR HYDROPONICS** Many different substrates are used for plant support in hydroponic culture, but one of the unique requirements for research is that the media be easily separated from the roots. Peat, perlite, and vermiculite are good substrates but roots and root hairs grow into these substrates, so they are unsuitable for studies of root size and morphology. Sand can easily be removed from roots, but roots grown in sand are shorter and thicker than hydroponic roots because the sand particles are so dense. We have also found that plant growth in sand is less than in other substrates, presumably because of reduced root growth. Calcined clay (brand names: Turface, Profile, Arcillite) was the medium of choice for research hydroponics for many years because it can easily be removed from roots. Calcined clay, however, has two disadvantages: 1) It is not chemically inert. Different batches supply different amounts of available nutrients and this causes variable results. It can be repeatedly rinsed in nutrient solution to desorb undesirable nutrients, but this adds to its cost. 2) Calcined clay is not a uniform particle size, and the water holding capacity depends on particle size. Not all batches are the same.

We recently tested and began using an extruded, diatomaceous-earth product called Isolite. Isolite is mined off the coast of Japan where there is a unique diatomaceous-earth deposit mixed with 5% clay. The clay acts as a binder in the extrusion and baking of the diatomaceous-earth. Diatomaceous-earth materials were originally organisms composed primarily of silicon dioxide (SiO2). Silicon dioxide is physically and chemically inert and these characteristics make it useful for horticultural applications like putting greens and urban trees where the soil is subject to severe compaction. Isolite is available in particle sizes from 1 to 10-mm diameter. Our tests indicate that Isolite is chemically inert and has good water holding characteristics. Its disadvantage is cost at $1.22 per Liter ($.79 per pound) for small quantities, although it can be reused. We have reused it after rinsing and drying at 80 C. Isolite is made by Sumitomo Corp. and is available in the USA from Sundine Enterprises, Arvada, CO; 303-423-8669.*  [HR][/HR] *MICROORGANISMS** AND ORGANIC COMPOUNDS IN THE SOLUTION: IS FILTERING USEFUL?** Many people think that filtering the recirculating solution is useful, but we have never filtered our solutions. Our measurements indicate that total organic carbon in the recirculating solution does not exceed 15 mg per liter, even near the end of a 2 month life cycle. About 30% of the organic carbon in the solution is in the chelating agent. Total organic carbon includes the carbon that is in microbial biomass, so it is clear that neither organic compounds nor microorganisms are at high levels in the solution. The solution also appears as clear prior to harvest at 80 days as fresh solution.

Roots leak organic compounds, but there is an equilibrium between microorganisms on root surfaces and the exudates so that compounds are degraded to CO2 at the root surface. Estimates of the quantity of root exudates vary widely, but there is considerable evidence that carbon efflux increases when plants are stressed (Barber and Gunn, 1974; Smucker, 1984; Haller and Stolp, 1985). Bowen and Rovira (1976) found that roots in solution culture produce smaller quantities of exudate than in soil. Trollenier and Hect-Buchholz (1984) found that reduced root growth due to inadequate aeration in hydroponic culture was accompanied by a dramatic increase in root microbe population, which they attributed to increased exudation from roots. The bottom line is that healthy roots in a well aerated hydroponic system should not increase the microorganisms or organics in the solution and filtering is thus unnecessary.*  [HR][/HR] *SUMMARY** COMMENTS ON SPECIFIC ELEMENTS*
*NITROGEN: Plant requirements for nitrogen are sometimes larger than all of the other elements combined. It can thus be difficult to supply nitrogen in the refill solution without adding excess amounts of other cations. The best solution is to use nitric acid (HNO3) for pH control. This can supply 50% of the nitrogen needs of the crop without adding excess cations. If extra nitrogen is required, ammonium nitrate can be added to the pH control solution. However, because ammonium decreases the uptake of other cations (K, Ca, Mg, and micronutrients) I do not recommend its use in hydroponic solutions unless extra nitrogen is required by the crop for maximum yields.

PHOSPHOROUS and POTASSIUM are rapidly drawn down to µM levels is solution. These low levels do not mean that the plant is starving for these elements, it means that the plant is healthy and actively absorbed these elements from solution.

CALCIUM requirements are almost 3 times higher for dicots than for monocots (grasses). Calcium is nontoxic, even at high tissue concentrations, but it accumulates in solution if too much is added to the refill solution.

MAGNESIUM is highly mobile and can accumulate to toxic levels in upper leaves if the solution concentration is too high.*  [HR][/HR] *LITERATURE** CITED*

*Barber, D. and K. Gunn. 1974. The effect of mechanical forces on the exudation of organic substrates by the roots of cereal plants grown under sterile conditions. New Phytol. 73:39-45. *
*Baylis, A., C. Gragopoulou, and K. Davidson. 1994. Effects of Silicon on the Toxicity of Aluminum to Soybean. Comm. Soil Sci. Plant Anal. 25:537-546. *
*Bugbee, B. and F. Salisbury. 1985. An evaluation of MES and Amberlite IRC-50 as pH buffers for Nutrient Solution Studies. J. Plant Nutr. 8:567-583. *
*Bugbee, B. and F. Salisbury. 1989. Controlled Environment Crop Production: Hydroponic vs. Lunar Regolith. In: D. Ming and D. Henninger. (eds) Lunar Base Arriculture. Amer. Soc. Agron. Madison, WI. *
*Bowen, G. and A. Roveria. 1976. Microbial colonization of plant roots. Ann. Rev. Plant Phytopathology 14:121-144. *
*Chaney, R. and B. Coulombe. 1982. Effect of phosphate on regulation of Fe-stress in soybean and peanut. J. Plant Nutr. 5:469-487. *
*Cherif, M., J. Menzies, D. Ehret, C. Boganoff, and R.Belanger. 1994. Yield of Cucumber Infected with Phythium aphanidermatum when Grown with Soluble Silicon. HortScience 29:896-97. *
*Haller, T. and H. Stolp. 1985. Quantitative estimation of root exudation of the maize plant. Plant and Soil 86:207-216. *
*Ma, J., K. Nishimura, and E. Takahashi. 1989. Effect of Silicon on the growth of the Rice Plant at Different Growth Stages. Soil Sci. Plant Nutr. 35:347-356. *
*Samuels, A. A.D.M. Glass, D. Ehret, and J. Menzies. 1991. Mobility and Deposition of Silicon in Cucumber Plants. Plant, Cell, and Environment 14:485-492. *
*Smucker, A. 1984. Carbon utilization and losses by plant root systems. p. 27-46. IN: Roots, nutrient and water influx, and plant growth. Am. Soc. Agron. Special publ. 49, Madison, WI. *
*Trollenier, G. and C. Hect-Bucholz. 1984. Effect of aeration status of nutrient solution on microorganisms, mucilage and ultrastructure of wheat roots. Plant and Soil 80:381-390. *
*Valamis, J. and D. Williams. 1967. Manganese and Silicon Interaction in the Gramineae. Plant and Soil. 28:131-140. *
*Winslow, M. 1992. Silicon, Disease Resistance, and Yield of Rice Genotypes under Upland Cultural Conditions. Crop Sci. 32:1208-1213. *
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## woodsmaneh! (Jan 29, 2012)

*Municipal water supplies* 

Many indoor gardeners are reliant on municipal water supplies and have fewother options for a better quality water source. Its likely that some plantlosses have and do occur as a result of some municipal water supplies,particularly in sensitive species and in water culture systems where there isno media to act as a buffer. On the other hand, many municipal water suppliesare quite suitable and given that they have had organic matter and pathogensremoved already, are a good deal as far as hydroponic systems go. Interestinglyplants have rather different responses and requirements from a water supplythan humans and this is where problems can occur. Municipal water treatmentensures that drinking water meets the World Health Organization (WHO) and EPAstandards for mineral, chemical and biological contamination levels, making itgenerally very safe to drink and use. However, what is safe for us to drink maynot be so good for plant growth, particularly when we consider many hydroponicsystems are recirculating which allows build-up of unwanted contaminants in theplant root zone. 


Recirculating solution culture systems suchas NFT have less buffering capacity to water treatment chemical residues thanorganic media-based systems.

Water treatment options used by municipal suppliers change over time andhydroponic growers should be aware of the implications of these. Many years agothe main concern was the use of chlorine as a disinfection agent to destroybacteria and human pathogens. Chlorine had the advantage in that it disinfectedwater effectively; however, residual chlorine in water sources, which couldoften be detected by smell, could be toxic to sensitive plants and where itbuilt up in certain hydroponics systems. Also when chlorine reacts with organicmatter it forms substances (trihalomethanes) which are linked to increased riskof cancer and other health problems. Chlorine was, however, quite easy toremove from water with the use of aeration or even just aging the water a fewdays before irrigating plants. In the 1990s it was found that some organismssuch as Cryptosporidium were resistant to chlorine and the resulting healthissues from this meant that drinking water regulations were changed andalternative disinfection methods began to be used. These included use of ozoneand UV light, chloramines (chlorine plus ammonia) and chlorine dioxide. 

Filtration, flocculation, settling, UV and ozone used for water supplytreatment are non-problematic as far as hydroponic systems go, as they leave noresidue and are effective. However, use of chloramines and some of the otherchemicals by municipal water treatment plants may still pose problems wherehigh levels are regularly dosed into water supplies. Chloramines are much morepersistent than chlorine and take a lot longer to dissipate from treated water,so gardeners who are concerned can use a couple of different treatment methodsjust as those with aquarium fish often choose to do. There are specificallydesigned activated carbon filters which can remove most of the chloramines in adomestic water supply and also dechloraminating chemical or water conditionersavailable in pet shops. Carbon filters must be of the correct type that have ahigh quality granular activated carbon and allow a longer contact time which isrequired for chloramines removal. Even then not every trace may be removed, butlevels are lowered enough to prevent problems. Use of ascorbic acid (vitamin C)is also used in the industry, and by laboratories to remove chloramines fromwater after they have done their disinfection job.
Chemicals are also added to drinking water to adjust its hardness or softness,pH and alkalinity. Water that is naturally acidic is corrosive to pipes andsodium hydroxide may be added to reduce this. Sodium is a contaminate we dontneed in hydroponic systems, but may be present at surprisingly high levels incertain water supplies. Domestic water softeners may also contaminate the waterwith sodium which is not seen as a problem for drinking, but can run amuck witha well balanced hydroponic system and sodium sensitive crop.

*What water problems may look like* 

Its extremely difficult to determine if something in the water supply iscausing plant growth problems. Root rot pathogens may originate in water, butthey can come from a number of sources, including fungal spores, blown in dustor brought in by insects. Mineral problems can be a little easier to trace ifthe water supply analysis is available to check levels of elements. Plantproblems which may be caused by water treatment chemicals are difficult todiagnose as some plants are much more sensitive than others and the type ofsystem also plays a role.* Research studies havereported that chloramines in hydroponic nutrient solutions can cause growthinhibition and root browning in susceptible plants.* One studyreported that the critical chloramines amount at which lettuce plant growth wassignificantly inhibited was 0.18 mg Cl/g root fresh weight, however, the levelsat which some other species would be damaged is as yet undetermined. Similarproblems exist with the use of other water treatment chemicals; chlorine andhydrogen peroxide are good disinfection agents, but too much in the hydroponicnutrient will cause root damage and just what is a safe level is dependant on anumber factors such as the level of organic loading in the system. 

*Hard water* 

Hard water is water that has a high mineral content, usually calcium andmagnesium, with calcium present as calcium carbonate or calcium sulfate. Hardwater can occur in wells and municipal sources and has a tendency to form hardlime scale on surfaces and equipment. A hard water supply is generally not amajor problem for hydroponic gardens; calcium and magnesium are useful elementsfor plant uptake, however, high levels in the water can upset the balance of anutrient solution making other ions less available. Commercial growersroutinely use hard water supplies and adjust their nutrient formulation to takeinto account the Ca and Mg naturally occurring in the water and also adjust forany alkalinity problems with water acidification. Smaller growers can use oneof the many excellent hard water nutrient products on the market to get asimilar effect. 

*Ground water  wells* 

Many commercial hydroponics growers use well water for hydroponic systems andadjust their nutrient formulations to suit the natural mineral content of theirwater supply. Smaller growers would be advised to find out what is in theirwell water source just to check for potential problems as water which haspercolated through soils tends to pick up some minerals and in some areas, highlevels of unwanted elements such as sodium or trace elements. Well water canalso contain pathogens and may need treatment before use, although often it isjust the mineral levels that need adjustment. Water from dams, lakes andsprings is usually similar to well water, but can contain much higher levels ofsediment, organic matter and fungal pathogen spores. 

*Rain water* 

Rain water collection can be a good way to bypass problems with municipal orwell water in some areas; however, there are still some risks. Acid rain fromindustrial areas, sodium in coastal sites and high pathogen spore loads inagricultural areas can still occur. Generally rain water is low in minerals,but in the process of collection from roofs and other surfaces, can collectwind blown dust and fungal spores. While this is generally not a problem forhealthy plants, rain water should be treated before use with young seedlingsand clones where pathogens could infect sensitive tissue and open wounds.

*Solutions to water quality problems* 

Organic material such as coconut fiber gives a greater buffering capacity forsome water problems, including residues from chemical water treatments, than solutionculture systems. Drain to waste media systems are also useful where the watersupply contains unwanted elements such as sodium as these arent as susceptibleto the accumulation that can occur where the solution is recirculated over along period of time. Where problems with unwanted minerals and very hard waterexist, frequent changing and replacement of the nutrient in the system can alsobe useful to keep things in balance. Water with a high alkalinity will needconsiderably more acid to keep the pH down to acceptable levels than water withlow alkalinity; however, by acidifying the water first before making up anutrient solution or adding to the reservoir, much less acid will need to beadded to the system to adjust pH over time. 
There are a range of other treatment options that indoor gardeners can use toimprove the quality of their water supply. If pathogen contamination is anissue, slow sand filtration is one of the most effective methods, althoughperhaps not that practical for those with limited space. Chemical disinfectionmethods for pathogen control include hydrogen peroxide, chlorine and othercompounds, although care should be taken that most of the active chemical hasdissipated before the water is used to make up the nutrient solution. Heat,distillation, reverse osmosis and UV treatment can all be used for pathogencontrol, with many small RO and UV treatment systems now on the market. UVfilters for aquariums can be used for small hydroponic growers to treat waterwith good success, provided sufficient contact time is allowed. If excessminerals or unwanted elements such as sodium are present in a water supply,reverse osmosis (RO) or distillation can be used to remove these. Organicmatter in ground water sources can be removed with settling and filtration andtreatment with H2O2, while chemical contamination problems and removal of watertreatment compounds are more easily treated with the correct type of activatedcarbon filter with a sufficient contact time.

*Super-charged water for hydroponics* 

While it seems logical that pure, clean and demineralized water is the bestplace to start when making up a hydroponic nutrition solution, the possibilityof creating a water source that has certain benefits for plants is a relativelynew concept. Water is not just a carrier for essential nutrient ions, thenutrient solution becomes a whole biological system in its own right withorganic matter, root exudates, various species of microbes including fungi,bacteria and their by-products (both good and bad), beneficial and unwantedmineral elements and a range of additives growers may be using. Some studieshave found that inexplicable growth increases could be obtained using certainground water sources compared to rain or RO (essentially pure) water to make upa hydroponic nutrient solution indicating there may be natural factors in suchwaters which have benefits. Not all ground water sources have this effect; infact, some can have negative influences on plant growth. Furthermore, anotheressential plant nutrient  oxygen in dissolved form - is usually present inwater supplies; however, some water treatment processes can drive much of thedissolved oxygen (DO) out of a water source. In theory it would be possible tonot only remove those things in the water we dont want  pathogen spores,unwanted minerals, chemical residues from water treatment - but to also boostthe water with useful properties such as a high DO content, a population ofuseful and disease suppressant microbes and some natural and potentiallybeneficial minerals and compounds. One way of achieving this would be with theuse of slow sand filters or mineral filters for water supplies which areinoculated with beneficial microbes and with oxygenation of the water for a fewdays before making up nutrient solutions or topping up reservoirs. Further downthe track we may see quicker and easier methods of supercharging water forhydroponic systems, taking water quality to a whole new level of science.


*Chlorine Gas:*
This highly reactive halogen gas is volatile enough that can be easilydetected by its odor, especially in the shower or when aerating faucets areused. This is one of chlorines short-comings as a disinfectant: It off-gases(volatilizes) from exposed water. Hobbyists have made good use of this effectfor many years. Chlorinated tap water, especially drawn through an aeratingfaucet, will off-gas and effectively lose all its chlorine to the atmospherewithin days. Some growers may not fully understand the off-gassing process andmay not use the most effective setup for off-gassing. The best process is anopen-top container with a power head or pump to circulate the water, or evenjust an air stone. This obviously calls for a relatively large container, butit also means that fewer containers are needed, as the circulation greatlyenlarges the effective surface area for off-gassing. Exposed surface area iscritical. The best situation without circulation in theory could be shallowtrays with large surface exposed to room air, but that is impractical inapplication  it would be very messy and require large amounts of space.Buckets are acceptable, but not overfilled, please. If bottles must be used, donot fill past the shoulder (where the bottle starts narrowing)  this willallow the largest possible surface exposure. I used 45gal tanks or food-safeplastic tubs (trash can scale), both with pumps and heaters, open-topped. Ihave never detected residual chlorine after 24 hours operation in these, butallowed 48 hours for safety and to remove the requirement for routine testing.Static containers may or may not be safe to use after just 24 hours. Most, withgood surface area exposed, will be after 48 hours, but this is best confirmedby test. If after you have found the required time for off-gassing, then youcan add a bit more to ensure removal and no longer routinely test so long asthe utility does not change the concentration. We no longer have hobby liquidtests for chlorine or chloramine, but must rely on swimming pool tests.
If you do not have the space and time to off-gas chlorinated water, thereare many products available which will neutralize the dissolved chlorine. Theactive ingredient historically was sodium thiosulfate, and it is still highlyeffective for this use. This material captures any free dissolved chlorine gasand coverts the elemental chlorine (Cl2 dissolved gas) to the chloride ion(Cl-) which is harmless at those concentrations. The reaction is rapid. Justadd the recommended amount, stir very briefly and add to the reservoir.
With dissolved chlorine gas disinfectant, there is only one job to be done,and it can be accomplished in two ways: Remove the chlorine gas (off-gassing),or inactivate it (chemical conversion to the chloride ion by thiosulfate).These are simple and straightforward.
*Chloramines:*
The growing situation with chloramines is more complex and demanding. Wecannot efficiently off-gas chloramines, so the simplest solution with chlorinedoes not apply at all. We equally cannot use just thiosulfate  it does not doenough. There are 3 separate and distinct jobs, all of which must be done toensure the safety of chloraminated water for use in our reservoir:

1. Break the chloramine-ammonia bond. Thiosulfate alone can do this at aboutthe same dosage used for chlorine-only disinfectant.

2. Convert the freed dissolved gas chlorine (Cl2) to chloride ion (Cl-).Thiosulfate again can do this as well; at about the same dosage as before, sodouble the chlorine-only dose can do both of these two jobs well.

3. Lock the freed ammonia dissolved gas (NH3) into the ammonium ion (NH4+) form(which is usable by the nitrification bacteria). The former is toxic; theconcentration may only be high enough to damage the plants, or can be highenough to kill them. Thiosulfate alone is useless for this job, regardless ofthe dosage. Thiosulfate has no effect whatsoever on dissolved ammonia gas.Bummer! We must use newer and specialized agents which specify on the bottlethat they do each and all of the three jobs required.
There are a number of commercial products which specify in print that theydestroy (or other terms to that effect) chloramines. That is valid even ifthe only active agent is thiosulfate  it does break the chlorine-ammonia bondwhich defines chloramine, so technically the chloramine is no longer there.Does that mean the water so treated is safe to use? No, it definitely does not.The freed chlorine gas must be converted to chloride ion, but as with the bondbreaking, thiosulfate can do that as well, and is cheap and safe - so doublethe chlorine-only dose and cover the freed chlorine as well. Is the water nowsafe to use in the reservoir tank? No, unfortunately not. It still has all theammonia released floating around at hazardous levels. If the product does notspecify that it locks the ammonia into the harmless ammonium ion form, or atleast notes that it neutralizes both the chlorine and the ammonia released,we have to assume it does not do this  commercial products never claim lessthat they do. Destroying chloramine is required, but is not sufficient. Thisis a key point, do not be misled. Both of the freed dissolved gases must beneutralized to make the water safe. This is where the marketing wizards takeadvantage of the chemically and biologically naïve. You do have to both readand understand the fine print, or you could kill your fish. Strictly as an FYI,yes, I have killed fish that way. I will not do that again. Specialized agentsare available which do the whole job  break the chloramine bond and convertboth freed toxic gases to harmless ions. Unfortunately, this is anothersituation where you cannot trust your local fish store, nor the chains, ormail-order houses. They quite likely do not understand the chemistry themselves.You need to ask on-line for suggestions of brands which do all the necessaryjobs reliably, or search the manufacturers site for detailed information  ifthey do not clearly state that all three tasks are done, that product is notsuitable.
There is another complication with post-chloraminated water. It still readspositive for ammonia on most hobby test kits. Read the information on your testkit for ammonia. If it specifies that it reads total ammonia nitrogen (orTAN), you will see positives with your test after using a good anti-chloraminesagent. These are not false positives. They are real and valid, but do notnecessarily indicate a hazard to your fish  which the kit instructionshistorically have listed as hazardous. Remember that ammonium ion (NH4+) isharmless, only ammonia dissolved gas (NH3) is dangerous, just as was the casefor chlorine gas versus the ion form. The effective anti-chloramine agents lockall free ammonia gas into the ammonium ion form  which is harmless. The problemis that our 20th century tests are no longer adequate in this century. Thereare tests available which read only free ammonia (NH3), but to me they are notyet user-friendly. Technology changes rapidly these days, hopefully moreuser-friendly but adequate test kits will available soon. Until then, we mustuse the proper dose of an effective agent and rely on it working, or prescreenwith difficult-to-use tests.
For what it is worth, I use Seachems Prime for chloramines, and Genesisfor chlorine-only.
References:
1. http://en.wikipedia.org/wiki/Chlorination
2. http://en.wikipedia.org/wiki/Chloramine
3. http://www.epa.gov/ogwdw000/disinfectio index.html
4. http://www.lenntech.com/processes/disin lorine.htm
5. http://www.lenntech.com/processes/disin amines.htm


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## woodsmaneh! (Jan 29, 2012)

Organic growers use soil amend*ments to improve soil fertility and create a healthy habitat for soil life. Many of the nutrients and minerals in the amendments are insoluble and are slowly released. The gradual release is similar to natural nutrient cycles and leads to healthy crops with little or no nutrient leaching. Before apply*ing amendments, have your soil tested to find out about nutrient deficiencies or excesses. Observ*ing weeds and crops can also provide information about nutri*ent levels.
Calcium improves tilth, reduces compaction and increases the CEC. The CEC (cation exchange capacity) is the capacity of the soil to hold nutrients.
The pH of agricultural soils is ideally 6.0-7.0. Soils with a pH below 6.0 are acidic; a pH >7.0 indicates an alkaline soil.
Phosphorous is used to produce sturdy plants with strong root sys*tems and stalks. Adequate levels are needed for the over winter survival of perennials, and high yields of seed crops (e.g. pulses and oilseeds).
Sulphur is needed by all crops, especially oilseeds, brassicas and legumes.
Calphos, Greensand, Sul-Po-Mag and Carbonatite are rock products with insoluble nutrients and minerals. To increase the availability of phosphorous and other nutrients, add these to ma*nure piles, compost or green ma*nures. Microbial activity releases the nutrients and makes them available to crops.

Boron is an essential trace mineral which is needed for high yields and strong plants. It is usually absent in other soil amendments, and deficien*cies occur after decades of mining the soil. It is a dry granular product which also contains a wide range of trace minerals.
Calphos (colloidal phosphate) is untreated soft phosphate clay from Flor*ida. It contains 20% phosphate including 3% available P. The phosphate is more immediately available than that from rock phosphate and is re*leased over 5 years. Calphos also contains 20% calcium (which helps to raise the soil pH) and a range of trace minerals. With a dry granular tex*ture, Calphos flows well and will not rust machinery. Add at a rate of 20*50 lb. of Calphos to one ton of manure, or 500-2000 lb/acre in late sum*mer or early fall. It also acts as a moisture absorbent in livestock bedding and a manure conditioner to reduce odour and nitrogen loss.
Earthworm Casting are from earthworms that are fed a diet of all non-manure based products, non post-consumer waste products except some shredded cardboard or paper in the bedding. Castings are a very rich source of biology including large amounts of beneficial fungi, protozoa, and nematodes. The castings are a finely screened product. The earth*worms make nutrients much more available to plants.
Humate Concentrate, 12% is a liquid form of the naturally occurring oxidized lignite known as humic acid. It is applied as a seed soak, foliar spray and direct soil spray. Plants are able to take up micro-nutrients eas*ier and become stronger and healthier, able to handle stress better. The soil structure is restored and beneficial micro-organisms increase. The use of fertilizers is reduced as humate increases the carrying ability of the wa*ter.

Hydrolyzed Fish (Fermented Salmon) (NPK : 1.4-0.2*0.2) is a liquid organic fertilizer, containing the 3 stan*dard macronutrients (NPK), 30 micronutrients, 14 amino acids, 10 fatty acids and a multitude of other beneficial compounds. It is used as both a drench and foliar applied fertilizer resulting in the dual benefit of growth en*hancement and disease suppression. This liquid requires dilution and mixing. It is stable and will not gas, is not temperature sensitive, and has a long shelf life.
Garlic water serves as an effective natural insect repel*lent in gardens and greenhouses. It may also be effective against deer and small animals.
Greensand (iron-potassium silicate or glauconite) is an ocean deposit developed from seashells and organic mat*ter. It contains 7% potash (which is slowly released), and micronutrients including sulphur, boron, iron, manganese and zinc. Greensand improves the tilth of heavy soils, and increases the water-holding capacity of sandy soils. Apply at any time at 300-500 lb./acre or 2-5 pounds per 100 square feet.
Gypsum (calcium sulphate) provides calcium (22%) and sulphur (17%), without changing the soil pH.
Hot pepper wax is sprayed on foliage; the thin layer of wax acts as a moisture guard and the hot pepper serves as an insect repellent.
Kelp fertilizer mix is a 3-way mix of kelp meal, lignite, and organic cane sugar. It provides trace minerals, humic acids, and sugar to stimulate microbial activity. This starter fertilizer helps plants emerge quickly, have greater resistance to pests and diseases, extended shelf life, and better nutrition. 
Kelp meal is granular dehydrated seaweed harvested from abundant beds on the North Atlantic shores of Can*ada. 

Limestone provides calcium and 'sweetens' acidic soils by increasing the pH. Dolomitic lime provides both cal*cium and magnesium. Calcitic lime provides only cal*cium and is suitable for soils with adequate levels of magnesium. Adding lime to acidic soils helps to reduce weed pressure from both grasses and broadleaf weeds (dandelions and creeping Charlie). 
Liquid Seaweed Concentrate is a seaweed solution containing readily available nutrients (NPK: 0-0-1) and over 80 trace minerals. Mixed with irrigation water, seaweed emulsion provides readily available nutrients and micronutrients to seedlings, transplants and field crops. Spray in early morning or evening, and not under full sun.
Spanish River Carbonatite is mined from a volcanic deposit in northern Ontario. It improves the CEC of the soil, and provides calcium, phosphorous, potassium, vermiculite and many trace minerals. 
Organic sugar is the essential food of micro-organisms. Plants produce sugar from photosynthesis and the roots exude sugar to feed the microbes (in exchange for nutri*ents). Stimulate microbial activity and nutrient release with sugar in the soil.
Sul-Po-Mag (langbeinite or K-Mag) contains 22% po*tassium (which is readily available for plants), 11% mag*nesium, and 22% sulphur.


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## woodsmaneh! (Feb 9, 2012)

*Cleaning & Sterilizing Reusable Growing Media*
Aggregate media such as grow rocks, Geolite, Hydroton, etc. should be cleaned between crops to remove debris and roots that accumulated in the media. As well, any system parts that come in contact with nutrient solution, such as growing trays, feed/drain lines, water pump, etc., should be sterilized before putting the system back into use. Cleaned media can be sterilized at the same time simply by placing it in the system beforehand, or it can be sterilized separately. 
It's important to note that, in spite of sterilization, any remaining root fragments will begin to disintegrate and turn brown after approximately 2-3 weeks into the next growing cycle. This will leave a brown sediment on the reservoir floor and may tint the nutrient solution with a brown color as well. Thus the cleaning procedure outlined below is intended to minimize the number of root fragments remaining in the cleaned media. 

*Preparation*

During harvest, leave appx 2-3 inches of the plant's mainstem sticking out of the media to serve as a handle for subsequent processing of the root ball.
Perform the cleaning on the same day the system is put out of service, while the media is still wet and roots are still fresh. This will insure that the media sinks during the cleaning process.
*Cleaning*

While grasping the root ball by the mainstem, hold it inside a suitable sized empty container and shake vigorously to dislodge the media particles. Large root balls can be very tight and easily hold more than a gallon of media, so you may need to first tear the roots on the outside of the ball so those on the inside are exposed and can be dislodged more easily. From the dislodged media, remove any obvious large clumps of roots.
Place a 5 gallon bucket in a bathtub or any suitable location with a drain. Then hook up a garden hose to your water supply and place the other end of the hose inside the bucket on the bottom. Turn on the water and allow it to constantly run so that it overflows the bucket top.
Slowly add the loose media to the bucket (with the water still running). The media will sink to the bottom while the remaining thousands of small root fragments will rise to the top where the current of flowing water will carry them over the edge of the bucket to the drain. Stir the media occasionally to release any fragments that may have become trapped under the media. When no more roots float to the top, the media is clean and can be returned to its container .
*Sterilizing*
Hydrogen peroxide (H2O2) is by far the most practical product to use for sterilizing aggregate media. Unlike system parts with smooth surfaces, media such as hydroton are designed with irregular surfaces and small pores meant to capture & store nutrient solution. As a result, bleach can be flushed from smooth system parts with one fresh-water rinse, but media requires several flushes before chlorine levels in the remaining solution become safe enough for plants. This is not a concern with H2O2 as one flush is enough to return media to a safe condition. And unlike bleach, because the weak H2O2 solution will naturally breakdown to a harmless condition when exposed to air for several hours, no rinsing is required if you don't need to replant right away. 
Because it is the least expensive, bleach may be more practical to use for the rest of your system. However, many find that the small savings doesn't outweigh the convenience of sterilizing both the system & media together at the same time and flushing only once, or not at all depending on the urgency to replant. 
To sterilize with H2O2, you can use the same 5 gallon bucket that was used to clean the media. Fill it with 4 gallons of water, then add 2 cups (16 oz) of the common drug store variety hydrogen peroxide, this is typically a 3% solution (check the label). For other strengths use a scaled down quantity. For example, if using a 30% strength use only 1/10 or 1.6 oz. See the H2O2 page for more. 
Place the container (with the media inside) into the H2O2 solution. After standing in the solution for 1 hour, remove it and let it drain back into the bucket. Rinse if needed, then repeat with the next container of media.


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## woodsmaneh! (Feb 9, 2012)

*The 40/60 Phenomena*


The 40/60 Phenomena are events observed during the indoor cultivation of flowering cannabis, and when using a strict 12 hour inductive photoperiod (aka 12/12). The events start with the first day of the inductive stage (12/12), and end on the day a mature crop is ready for harvest, collectively this period of time is called the Days Spent Flowering.
*Stretch Phase (early flowering)*
The stretch phase is a period of time during early flowering where rapid extraordinary outward growth takes place. Some growers have reported seeing 5 inches of growth in a single day during the stretch. This phase is characterized first by the extraordinary growth accompanied by longer than usual internodes, then the explosive outward growth slowly tapers off as internodes shorten. The end of the phase is signaled when growth tapers down to approximately 1/2 inch or less per day. This coincides with a time span equaling 40% of the total Days Spent Flowering. At this point growth shifts from outward to building bulk on existing growth, otherwise known as late flowering or the fattening phase.
*Fatten Phase (late flowering) *
The last 60% of the inductive phase is a period where outward growth is less significant. In fact, it can appear as if growth has stopped completely due to the very short internodes. During this phase a more complex set of growth activities occur. It's not much different from an apple tree that stopped producing new apples and is now devoting its remaining time to maturing or ripening the apples it already has. With female cannabis, flower production accelerates, floral clusters begin to grow wider or _fatten_, resin production increases and peaks, sinsemilla calyxes plump, pistils start to wither and change color, and not long after that the plant is ready for harvest.

*How To Use The Phenomena*

The time-table of the stretch and fatten phases are important events for cultivators growing an unknown variety for the first time. The two most common anxieties for indoor growers during flowering of an untested variety are....

Running out of headroom or grow space due to unanticipated growth.
Being unable to predict the harvest date in advance.
An indoor grower with limited space, especially limited headroom, can find his plants pressing against hot lights if he doesn't take measures to plan for the explosive growth that takes place during the stretch phase. Knowing how long the stretch will last can give him that advantage. Similarly, a grower with limited time doesn't want to wait until the show is over to know when it will end. There are many things he may want to do with his time now that it's freed up from the high maintenance demands of extraordinarily fast growing plants during the stretch. Having an idea whether this period of lower maintenance will extend another 40, 60, 80, or ??? days will also help in the timely scheduling of his next crop.
*The 40/60 phenomena relate to two milestones.*

The Duration of the Stretch
Days Spent Flowering
*When one of those two flowering events are known, the other two can be predicted.*
You can find the calculator here
http://www.angelfire.com/cantina/fourtwenty/articles/4060.htm


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## Bonkleesha (Feb 9, 2012)

halfway thru page 2. bookmarked. cool stuff here, this has potential to be a sticky, for sure. did u kknow earthworm castings are pH neutral because of a gland they go thru at the end of earthworm? i just learned that.

+reps, too.


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## woodsmaneh! (Mar 25, 2012)

*AzaMax*

*Botanical Insecticide, Miticide, and Nematicide*

AzaMax is a natural product with a broad spectrum of pest control and broad plant applications. AzaMax is made from special Azadirachtin Technical extracted using patented extraction technology from Neem, a tree known for its innumerable benefits. AzaMax contains Azadirachtin A&B as active ingredients and more than 100 limonoids from its special technology. The special feature of AzaMax is that it does not use hard chemical solvents and uses food grade formulation ingredients. *AzaMax is licensed in all 50 states.*
AzaMax is an antifeedant and insect growth regulator and controls pests through starvation and growth disruption. AzaMax effectively controls spider mites, thrips, fungus gnats, aphids, whiteflies, leaf miners, worms, beetles, leafhoppers, scales, mealy bugs, nematodes and other soil borne pests. Best of all, AzaMax can be applied up to the time or day of harvest. The product is exempted from residue tolerance, thus there is no harmful residue on veggies, fruits, herbs and flowers etc. Truly, AzaMax is a product of Nature in tune with Technology.
Lable and directions

http://www.google.ca/search?hl=&q=azamax+mixing&sourceid=navclient-ff&rlz=1B3GGLL_en-GBCA380CA380&ie=UTF-8&aq=4&oq=Azamax


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## woodsmaneh! (Mar 25, 2012)

*Solving Marijuana Plan Leaf Curl/Cupping Problems*

*OK rule number #1 when you see this happening is flush with 25% nutrients*; use 2 to 3 times the pot size to do this. Flushing means lots of run-off. You use 25% because some elements are not mobile without other elements, so if you have a mag lock up flushing with water won't get the mag out, as it needs nitrogen to be mobile. Your killing your plants with kindness remember they are weeds. Here are more answers for you, you might want to save it for reference later The only time you don't use rule #1 is in the last 2 weeks of flower when bottom leaves stop being used for photosynthesis.
Unless another marijuana grower inspects the damage a true assessment might not be possible. It's hard to tell "exactly" what the culprit is. Unfortunately the solution the marijuana grower chooses many times is not the right one. A misdiagnosis only serves to make matters worse by promoting further decline. The ultimate and correct solution is in the hands of the marijuana grower.

Here are some common problems when marijuana leaves are curling.



*Too much marijuana fertilizer*
The most common cause of marijuana leaf cupping aka leaf margin rolling, leaf margin burn, and leaf tip curl/burn is overzealous use of marijuana plant food. In relationship to factors such as marijuana plant vigour and rate of growth. Leaf burn is often the very first sign of too much marijuana fertilizer.
A hard, crispy feel to the marijuana leaf frequently occurs as well, as opposed to a soft and cool feel of a happy pot leaf. Back off on the amount and/or frequency of using marijuana fertilizer. Too much marijuana fertilizer can also burn the roots, especially the sensitive root tips, which then creates another set of problems. Note - as soil dries, the concentration of the remaining salts rises further exacerbating the problem.
*High Heat*
The marijuana plant is losing water via its leaves faster than what can be replaced by the root system. The marijuana leaf responds by leaf margin cupping or rolling up or down (most times up) in order to conserve moisture. A good example is reflected by the appearance of broad-bladed turf grass on a hot summer day, high noon, with low soil moisture levels - the leaf blade will roll upward/inward with the grass taking on a dull, greyish-green appearance. Upon sunrise when moisture levels have returned to normal, the leaf blade will be flat. Lower the heat in the marijuana grow-op and concentrate on developing a large robust root system. An efficient and effective root system will go a long way to prevent heat induced pot leaf desiccation or marijuana leaf margin curling. One short episode of high heat is enough to permanently disable or destroy leaf tissue and cause a general decline in the leaves affected, which often occurs to leaves found at the top of the cannabis plant. The damaged pot leaf (usually) does not fully recover, no matter what you do. Bummer in the summer. One can only look to new growth for indications that the problem has been corrected.
*Too much light*
Yes, its true, you can give your marijuana plant too much light. Cannabis does not receive full sun from sunrise to sunset in its natural state. It is shaded or given reduced light levels because of adjacent plant material, cloudy conditions, rain, dust, twilight periods in the morning and late afternoon, and light intensity changes caused by a change in the seasons. Too much light mainly serves to bleach out and destroy chlorophyll as opposed to causing marijuana leaf cupping, but it often goes hand-in-hand with high heat for indoor marijuana growers. Turn down the time when the lights on in your marijuana grow room. If you're using a 24 hr cycle, turn it down to 20 hrs. Those on 18 - 6 marijuana growth cycle can turn their lights down two or three hours. Too much light can have many adverse effects on marijuana plants. Concentrate on developing/maintaining an efficient and robust root system.
*Over Watering*
For marijuana growers using soil, this practice only serves to weaken the root system by depriving the roots of proper gas exchange. The marijuana plants roots are not getting enough oxygen which creates an anerobic condition inducing root rot and root decline with the end result showing up as leaf stress, stunted growth, and in severe cases, death. Over watering creates a perfect environment for damp-off disease, at, or below the soil line. Many times marijuana growers believe their cannabis plant is not getting enough marijuana fertilizers (which it can't under such adverse conditions), so they add more marijuana fertilizers. Making the problem worst. Not better. Often problem 1 and 4 go together. Too much marijuana fertilizer combined with too much water. Creating plenty of marijuana plant problems.
*Not Enough Water*
Not only is the marijuana plant now stressed due to a low supply of adequate moisture, but carbohydrate production has been greatly compromised (screwed up). Step up the watering frequency, and if need be, organic marijuana growers may need to water from the bottom up until moisture levels reach a norm throughout the medium. One of the best methods in determining whether a marijuana plant requires watering is lifting the pots. The pots should be light to lift before a water session. After watering the marijuana plants lift the pots to get an understanding how heavy they've become fully watered. If the pot feels light to the lift - its time to water. Dont wait until the soil pulls away from the side of the pot before watering. And of course, leach, once in a while to get rid of excess salts. These are the five most common problems marijuana growers encounter when growing cannabis. Correcting the problems early will save the marijuana plants, but may reduce overall yield. With practice and experience these problems are easily overcome which will then enable the marijuana grower to produce fantastic marijuana plants. With heavy yields.


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## woodsmaneh! (Mar 25, 2012)

*Magnesium (Mg) *- Micronutrient and Mobile Element


Magnesium helps supports healthy veins while keeping a healthy leaf production and its structure. Magnesium is significant for chlorophyll-production and enzyme break downs. Magnesium which must be present in relatively large quantities for the plant to survive, but yet not to much to where it will cause the plant to show a toxicity.


Magnesium is one of the easiest deficiencies to tell the green veins along with the yellowness of the entire surrounding leave is a dead giveaway, but sometimes thats not always the case here. In case you have one of those where it doesnt show the green veins, sometimes leaf tips and edges may discolor and curl upward. The growing tips can turn lime green when the deficiency progresses to the top of the plant. The edges will feel like dry and crispy and usually affects the lower leaves in younger plants, then will affect the middle to upper half when it gets older, but It can also happen on older leaves as well. The deficiency will start at the tip then will take over the entire outer left and right sides of the leaves. The inner part will be yellow and or brownish in color, followed by leaves falling without withering. The tips can also twist and turn as well as curving upwards as if you curl your tongues.


Excessive levels of magnesium in your plants will exhibit a buildup of toxic salts that will kill the leaves and lock out other nutrients like Calcium (Ca). Mg can get locked out by having too much Calcium, Chlorine or ammonium in your soil/water.
One of the worst problems a person can have is a magnesium def caused by a ph lockout. By giving it more magnesium to cure the problem when you are thinking you are doing good, but actually you are doing more harm then good. When the plants cant take in a nutrient because of the ph being off for that element, the plant will not absorb it but it will be in the soil therefore causing a buildup. A buildup will be noticed by the outer parts of the plant becoming whitish and or a yellowish color. The tips and part way in on the inner leaves will die and feel like glass. Parts affected by Magnesium deficiency are: space between the veins (Interveinal) of older leaves; may begin around interior perimeter of leaf.




Watering with 1 tablespoon Epsom salts/gallon of water. Until you can correct nutrient lockout, try foliar feeding. That way the plants get all the nitrogen and Mg they need. The plants can be foliar feed at ½ teaspoon/quart of Epsom salts (first powdered and dissolved in some hot water). When mixing up soil, use 2 teaspoon dolomite lime per gallon of soil.
If the starting water is above 200 ppm, that is pretty hard water, that will lock out mg with all of the calcium in the water. Either add a 1/4 teaspoon per gallon of epsom salts or lime (both will effectively reduce the lockout or invest into a reverse osmosis water filter.
Mg can get locked-up by too much Ca, Cl or ammonium nitrogen. Don't overdo Mg or you'll lock up other nutrients


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## woodsmaneh! (Mar 25, 2012)

*Bud Rot
*
Bud rot (Botrytis) is a very common worldwide fungus that attacks both indoor and outdoor crops under certain conditions. Bud rot is also known as brown rot, grey mould and other names. Airborne Botrytis spores can be found everywhere, all times of the year, and will attack many different species of plants. Botrytis will attack flowers, and eventually leaves and stems.

Growers running sea of green, perpetual harvest, remote grows, outdoor, or multiple strains (each with different flowering periods) should keep an eye out for Botrytis near harvest time.

Outdoor growers need to be hypersensitive to weather conditions near harvest time. Rain, morning dew, frost and cool fall nights may increase the risk of bud rot and powdery mildew.

Fully developed marijuana buds provide ideal conditions for spore germination: warm and moist plant tissues. Botrytis will initially attack the largest and densest buds in the garden, because they provide the ideal conditions for germination. Weak plants will also be attacked rapidly.

*Identifying and preventing budrot*

Budrot will infect and turn colas to mush in a matter of days and may destroy a crop in a week if left unchecked. Botrytis loves warm, and humid (50% or over humidity) conditions. Lowering humidity will slow and stop spore germination. Good ventilation and decent air circulation help prevent infection.
A grow room may smell noticeably moldy if Botrytis has attacked one or more colas. Once a cola has been infected, Botrytis will spread incredibly fast. Entire colas will turn to brown mush and spores will be produced, attacking other nearby colas. Ventilation may spread viable spores throughout the room.

*Measures to prevent bud rot in the final stages of flowering:*

Early veg and flower pruning of undergrowth to promote air circulation
Hepa filter room and intake air sources.
*Introduce low levels of ozone into room air*. Ozone is effective against pollen, powdery mildew and other airborne spores.
*Lowering room humidity* (warming nighttime air and venting frequently or using a dehumidifier)
*Decreasing watering* cycles and amounts to reduce room humidity
Large, dense colas should be periodically inspected. Brown tissues deep within the bud will smell mouldy and may become liquid.
Removing fan leaves during the last few days before harvest to promote air circulation

*Serenade*
"Serenade controls the following: ....Botrytis, Powdery mildew, Downey mildew..."

*"Certified organic by OMRI *and EPA/USDA National Organic Program, Serenade offers growers the luxury of application without weather or timing restrictions and there are no phyto-toxicity issues"
"To apply, simply spray on leaves and shoots to provide complete coverage. Best results will be had be pre-treating plants before signs of disease set it and then every week to protect newly formed foliage"

*What if bud rot is found?*
Once bud rot has been detected, the grower should isolate infected buds by removing them from the grow room immediately and harvesting the infected colas, followed by a rapid dry of the harvested colas. Take immediate steps to reduce room humidity. Afterwards, the entire crop should be carefully inspected for infection and damage. The grower may want to harvest early if more than one rotting cola has been found. Spores may have spread and are germinating deep within other colas.

*Can I salvage budrot-infected colas?*

Yes. Remove the infected colas from the main room, Trim out the infection (Trim more than you can see  Botrytis often infects adjacent tissues) and quick-dry them. Re-inspect buds  they should _not_ smell mouldy.


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## woodsmaneh! (Mar 25, 2012)

Occasionally, using dolomite lime is warranted, but the truth is, it often makes things worse, sometimes just a little, and sometimes a lot. Lets look at why...

*What Is Dolomite Lime?*
Dolomite lime is a rock. It can be quite pretty. It is calcium magnesium carbonate, CaMg(CO3)2. It has about 50% calcium carbonate and 40% magnesium carbonate, giving approximately 22% calcium and at least 11% magnesium. When you buy it for your garden, it has been ground into granules that can be course or very fine, or it could be turned into a prill. Now, dolomite lime is even allowed in organic gardening. It is not inherently bad, but how it is used in the garden is usually mildly to severely detrimental.

*Why Are We Told To Use Dolomite Lime?*
I have touched on this before when I talked about pH. The idea is that minerals in your soil are continuously being leached by rain and consequently your soil is always moving towards more acidic. Dolomite lime is used to counteract this, to sweeten the soil. It can do that, but that doesnt mean its good.

*Why Are Minerals Leaching From Your Soil?*
Minerals may or may not be leaching from your soil. If they are, it could be partially because of rain, but there are other reasons, too. If your soil is low in organic matter, which is generally the case, it probably cant hold onto minerals very well, especially if it is low in clay and high in sand and silt. If you have lots of clay, you probably dont have much to worry about.
Chemical fertilizers cause acidity, so if you use them, that is part of the problem, too. Dolomite lime is not the answer. Organic gardening is. Lets look at why dolomite is probably not what you want. 
*
Heres The Important Part*
The main point I want to make is that even if minerals are leaching from your soil, it doesnt make sense to blindly go back adding just two of them (the calcium and magnesium in dolomite lime) without knowing you need them. You might already have enough or too much of one or both of them. We need to think a little more than that when organic gardening.
Your soil needs a calcium:magnesium of somewhere between 7:1 (sandier soils) and 10:1 (clayier soils). Outside of this range, your soil will have water problems, your plants will have health problems and insect and disease problems, and you will have weed problems. One of your most important goals in the garden is to add specific mineral fertilizers to move the calcium to magnesium ratio towards this range. As a side note, I understand it may seem strange to some that we should have to do this, but our soils are way out of balance and were trying to grow things that wouldnt naturally grow there, so we have to do this. The problem with dolomite lime? It has a calcium:magnesium ratio of 2:1. Thats way too much magnesium for most soils. Magnesium is certainly an essential mineral. Too much of it, however, causes many problems, compaction being one of the most common, but also pest and weed problems. So if you add this to your lawn every year, chances are youre just causing more compaction and weed problems.

*When Should You Use Dolomite Lime?*
You should only use dolomite lime when you have a soil test showing a huge deficiency of magnesium in your soil.
Even then, calcitic lime (calcium carbonate) is generally the way to go because it has a small amount of magnesium and often a calcium:magnesium ratio of about 10:1, with a calcium content 34% to 40% or more. I use calcitic lime regularly in my organic gardening, but even then, only when I need it. A soil test is the main way to find out if you need it.


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## woodsmaneh! (Mar 25, 2012)

*Diagnosing Nutritional Deficiencies
*

*Texas Greenhouse Management Handbook*
The correct diagnosis of nutritional deficiencies is important in maintaining optimum plant growth. The recognition of these symptoms allows growers to "fine tune" their nutritional regime as well as minimize stress conditions. However, the symptoms expressed are often dependent on the species of plant grown, stage of growth or other controlling factors. Therefore, growers should become familiar with nutritional deficiencies on a crop-by-crop basis.
Record keeping and photographs are excellent tools for assisting in the diagnosis of nutrient deficiencies. Photographs allow growers to compare symptoms to previous situations in a step-by-step approach to problem solving. Accurate records help in establishing trends as well as responses to corrective treatments.
Because plant symptoms can be very subjective it is important to approach diagnosis carefully. The following is a general guideline to follow in recognizing the response to nutrient deficiencies:
*Nitrogen (N)* - Restricted growth of tops and roots and especially lateral shoots. Plants become spindly with general chlorosis of entire plant to a light green and then a yellowing of older leaves which proceeds toward younger leaves. Older leaves defoliate early.
*Phosphorus (P)* - Restricted and spindly growth similar to that of nitrogen deficiency. Leaf color is usually dull dark green to bluish green with purpling of petioles and the veins on underside of younger leaves. Younger leaves may be yellowish green with purple veins with N deficiency and darker green with P deficiency. Otherwise, N and P deficiencies are very much alike.
*Potassium (K)* - Older leaves show interveinal chlorosis and marginal necrotic spots or scorching which progresses inward and also upward toward younger leaves as deficiency becomes more sever.
*Calcium (Ca)* - From slight chlorosis to brown or black scorching of new leaf tips and die-back of growing points. The scorched and die-back portion of tissue is very slow to dry so that it does not crumble easily. Boron deficiency also causes scorching of new leaf tips and die-back of growing points, but calcium deficiency does not promote the growth of lateral shoots and short internodes as does boron deficiency.
*Magnesium (Mg)* - Interveinal chlorotic mottling or marbling of the older leaves which proceeds toward the younger leaves as the deficiency becomes more severe. The chlorotic interveinal yellow patches usually occur toward the center of the leaf with the margins being the last to turn yellow. In some crops, the interveinal yellow patches are followed by necrotic spots or patches and marginal scorching of the leaves.
*Sulfur (S)* - Resembles nitrogen deficiency in that older leaves become yellowish green and the stems become thin, hard, and woody. Some plants show colorful orange and red tints rather than yellowing. The stems, although hard and woody, increase in length but not in diameter.
*Iron (Fe)* - Starts with interveinal chlorotic mottling of immature leaves and in severe cases the new leaves become completely lacking in chlorophyll but with little or no necrotic spots. The chlorotic mottling on immature leaves may start first near the bases of the leaflets so that in effect the middle of the leaf appears to have a yellow streak.
*Manganese (Mn)* - Starts with interveinal chlorotic mottling of immature leaves and, in many plants, it is indistinguishable from that of iron. On fruiting plants, the blossom buds often do not fully develop and turn yellow or abort. As the deficiency becomes more severe, the new growth becomes completely yellow but, in contrast to iron necrotic spots, usually appear in the interveinal tissue.
*Zinc (Zn)* - In some plants, the interveinal chloratic mottling first appears on the older leaves and in others, it appears on the immature leaves. It eventually affects the growing points of all plants. The interveinal chlorotic mottling may be the same as that for iron and manganese execpt for the development of exceptionally small leaves. When zinc deficiency onset is sudden, such as the zinc left out of the nutrient solution, the chlorosis can appear identical to that of iron and manganese without the little leaf.
*Boron (B)* - From slight chlorosis to brown or black scorching of new leaf tips and die-back of the growing points similar to calcium deficiency. Also the brown and black die-back tissue is very slow to dry so that it can not be crumbled easily. Both the pith and epidermis of stems may be affected as exhibited by hollow stems to roughened and cracked stems.
*Copper (Cu)* - Leaves at top of the plant wilt easily followed by chlorotic and necrotic areas in the leaves. Leaves on top half of plant may show unusual puckering with veinal chlorosis. Absences of a knot on the leaf where the petiole joins the main stem of the plant beginning about 10 or more leaves below the growing point.
*Molybdenum (Mo)* - Older leaves show interveinal chlorotic blotches, become cupped and thickened. chlorosis continues upward to younger leaves as deficiency progresses.
*Summary*
The diagnosis of nutrient deficiencies can be a key to optimizing plant growth. However, this technique is very subjective and requires careful observation. Plants respond to nutrient deficient conditions in several different ways. Growers must become familiar with these on a crop-by-crop basis. Photographs and record keeping can be very useful tools in the diagnosis of nutrient deficiencies.


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## woodsmaneh! (Mar 25, 2012)

First a little Plant Science 101 - For a successful, productive garden, hydroponic, indoor and greenhouse growers must control six "essential elements" - air, light, nutrients, water, humidity and temperature. Remove or alter the ratio of only one of these elements, growth will slow, and plants could eventually die. In this article, we will review the air element, specifically carbon dioxide (CO2), it's role in the most vital plant process - photosynthesis - and how to effectively implement CO2 systems.

Photosynthesis begins when stomata, pore-like openings on the undersides of leaves, are activated by light and begin breathing in carbon dioxide (CO2) from the air. This CO2 is broken down into carbon (C) and oxygen (O). Some of the O is used for other plants processes, but most is expelled back into the air. The C is combined with water to form sugar molecules, which are then converted into carbohydrates. These carbohydrates (starches) combine with nutrients, such as nitrogen, to produce new plant tissues. CO2 is vital to plant growth and development, and yet is often the most overlooked element in indoor gardening.

Successful indoor growers implement methods to increase CO2 concentrations in their enclosure. The typical outdoor air we breathe contains 0.03 - 0.045% (300 - 450 ppm) CO2. Research demonstrates that optimum growth and production for most plants occur between 1200 - 1500 ppm CO2. These optimum CO2 levels can boost plant metabolism, growth and yield by 25 - 60%.

Plants under effective CO2 enrichment and management display thicker, lush green leaves, an abundance of fragrant fruit and flowers, and stronger, more vigorous roots. CO2 enriched plants grow rapidly and must also be supplied with the other five "essential elements" to ensure proper development and a plentiful harvest.

Commercially available CO2 generators offer the most economical, practical and consistent method of enriching indoor gardens. Using atmospheric control systems in conjunction with CO2 generators, ensure the most effective production and use of CO2.

Atmospheric control systems with automatic override or defeat, and CO2 monitoring logic, enrich and maintain optimum levels in the environment during the photo (light) periods, when most plants can absorb CO2; and they defeat CO2 production during dark periods. Automating your CO2 enrichment system pays for itself quickly with shorter crop cycles, improved quality and higher yields.

When enriching an indoor garden with CO2, proper light is essential for effective assimilation. For plants to use CO2 efficiently, light spectrum and intensity should be appropriate for the plant species in your garden. Remember - CO2 enriched plants under intensified lighting demand higher levels of nutrients, water, space and room temperatures of 80-85 F. (27 - 29 C.).

As CO2 is a critical component of growth, plants in environments with inadequate CO2 levels - below 200 ppm - will cease to grow or produce. And, growers should be cautious when experimenting with CO2 levels above 2000 ppm. CO2 is heavier than oxygen and will displace the O2 required by both plants and human to function and live. (FYI: OSHA max allowable for human exposure is 5000 PPM). So, air circulation and ventilation is critical to profitable CO2 enrichment.

Plants use all of the CO2 around their leaves within a few minutes leaving the air around them CO2 deficient. Without air circulation and ventilation, the plants' stomata are stifled and plant growth is stunted.

Proper air circulation with oscillating fans and in-line blowers, will eliminate potential stagnation problems and ensure efficient CO2 enrichment.

If you have never enriched your garden with CO2, start with 700 - 900 ppm (double the normal atmospheric levels). If yields improve, increase CO2 enrichment to 1200 - 1500 ppm. If there is no response to the CO2 enrichment, double-check your other five "essential elements" to ensure they are not limiting factors.


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## woodsmaneh! (Mar 25, 2012)

you can do anything if you have the right knowledge


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## woodsmaneh! (Mar 25, 2012)

*Cleaning & Sterilizing Reusable Growing Media*
Aggregate media such as grow rocks, Geolite, Hydroton, etc. should be cleaned between crops to remove debris and roots that accumulated in the media. As well, any system parts that come in contact with nutrient solution, such as growing trays, feed/drain lines, water pump, etc., should be sterilized before putting the system back into use. Cleaned media can be sterilized at the same time simply by placing it in the system beforehand, or it can be sterilized separately. 
It's important to note that, in spite of sterilization, any remaining root fragments will begin to disintegrate and turn brown after approximately 2-3 weeks into the next growing cycle. This will leave a brown sediment on the reservoir floor and may tint the nutrient solution with a brown color as well. Thus the cleaning procedure outlined below is intended to minimize the number of root fragments remaining in the cleaned media. 

*Preparation*


During harvest, leave appx 2-3 inches of the plant's mainstem sticking out of the media to serve as a handle for subsequent processing of the root ball.
Perform the cleaning on the same day the system is put out of service, while the media is still wet and roots are still fresh. This will insure that the media sinks during the cleaning process.
 
*Cleaning*


While grasping the root ball by the main stem, hold it inside a suitable sized empty container and shake vigorously to dislodge the media particles. Large root balls can be very tight and easily hold more than a gallon of media, so you may need to first tear the roots on the outside of the ball so those on the inside are exposed and can be dislodged more easily. From the dislodged media, remove any obvious large clumps of roots.
Place a 5 gallon bucket in a bathtub or any suitable location with a drain. Then hook up a garden hose to your water supply and place the other end of the hose inside the bucket on the bottom. Turn on the water and allow it to constantly run so that it overflows the bucket top.
Slowly add the loose media to the bucket (with the water still running). The media will sink to the bottom while the remaining thousands of small root fragments will rise to the top where the current of flowing water will carry them over the edge of the bucket to the drain. Stir the media occasionally to release any fragments that may have become trapped under the media. When no more roots float to the top, the media is clean and can be returned to its container .
 
*Sterilizing*
Hydrogen peroxide (H2O2) is by far the most practical product to use for sterilizing aggregate media. Unlike system parts with smooth surfaces, media such as hydroton are designed with irregular surfaces and small pores meant to capture & store nutrient solution. As a result, bleach can be flushed from smooth system parts with one fresh-water rinse, but media requires several flushes before chlorine levels in the remaining solution become safe enough for plants. This is not a concern with H2O2 as one flush is enough to return media to a safe condition. And unlike bleach, because the weak H2O2 solution will naturally breakdown to a harmless condition when exposed to air for several hours, no rinsing is required if you don't need to replant right away. 
Because it is the least expensive, bleach may be more practical to use for the rest of your system. However, many find that the small savings doesn't outweigh the convenience of sterilizing both the system & media together at the same time and flushing only once, or not at all depending on the urgency to replant. 
To sterilize with H2O2, you can use the same 5 gallon bucket that was used to clean the media. Fill it with 4 gallons of water, then add 2 cups (16 oz) of the common drug store variety hydrogen peroxide, this is typically a 3% solution (check the label). For other strengths use a scaled down quantity. For example, if using a 30% strength use only 1/10 or 1.6 oz. See the H2O2 page for more. 
Place the container (with the media inside) into the H2O2 solution. After standing in the solution for 1 hour, remove it and let it drain back into the bucket. Rinse if needed, then repeat with the next container of media. 
[h=1]Hydrogen Peroxide
Uses & Dilutions[/h]At the end of this page is an article on Oxy-Plus copied from a Usenet post. The purpose of this page is to list plant related applications H2O2 products are commonly used for, and to provide dilutions for the three most popular strengths commonly available - 3%, 17.5% and 35%.


*About H2O2 Products*



The actual content of H2O2 in H2O2 products can vary considerably from product to product. The content is given as a percentage figure indicating how much H2O2 is actually contained within the product (also known as its purity or strength). You must read the label to know the purity of your product.
It should be noted that Oxy-Plus is a product name that is easy to confuse with other products. There is also an Oxy-Plus brand name product from Growth Technology with 17.5% H2O2 content, not the 35% content mentioned in the article on this page. It's believed the 35% solution has been revised since the article was written and is now a 17.5% solution carrying slightly modified instructions. However, there are still 35% products on the market. The dilutions from both the article and the revised instructions are compiled in the below tables along with dilutions for use with the more popular generic 3% hydrogen peroxide product commonly found in drug stores.
Oxygen-Plus is not the same as Oxy-Plus. In fact, both names seem to be commonly used with many H2O2 related products. I've seen an Oxy-Plus product meant to be taken internally by humans, another product to put in with your wash, and yet another as a mild plant food, and none stated the H2O2 content on the label. Make sure your product is suitable to be used with living plants for it may contain other ingredients harmful to plants. Look for good labeling, make sure you know which product you have and its H2O2 content.


*Uses and Dilutions*


Dilutions are given in milliliters (ml) per US Gallon and per Liter. In cases where less than one ml is used, drops will also be given as a practical alternative for dispensing such a small measure. 19 drops per ml will be used as the base, however, because drop size can vary with the dropper utensil being used it isn't very accurate. Limit the use of drops to mixing small volumes of 1 Liter or 1 US gallon or less, use milliliters whenever possible.

*Sterilization/Cleanup*
H2O2 Dilutions
 3%
17.5%
35%
 *US Gallon*
Liter
*US Gallon*
Liter
*US Gallon*
Liter
110.4ml
29.2ml
19ml
5ml
9.5ml
2.5ml
850ppm H2O2 (800ppm Oxygen + 50ppm Hydrogen)
 



*Increase oxygen content in hydro systems
2-3 times a week*
H2O2 Dilutions
 3%
17.5%
35%
 *US Gallon*
Liter
*US Gallon*
Liter
*US Gallon*
Liter
11.0ml
2.9ml
1.90ml
0.50ml
9.5 drops 
0.95ml
18 drops 
0.25ml
4.8 drops 
87ppm H2O2 (82ppm Oxygen + 5.2ppm Hydrogen)
 

Note: 30-50ppm seems to be safe for hydro systems/tanks,
and up to 100ppm may to be OK for a short period of time.
Use your best judgment.

*Increase oxygen content in hydro systems
on a daily basis*
H2O2 Dilutions
 3%
17.5%
35%
 *US Gallon*
Liter
*US Gallon*
Liter
*US Gallon*
Liter
5.5ml
1.45ml
0.95ml
18 drops
0.25ml
4.8 drops
0.475ml
9 drops 
0.125ml
2.4 drops
44ppm H2O2 (41ppm Oxygen + 2.6ppm Hydrogen)
 



*Seed Germination
Treating Rockwool
Misting Solution*
H2O2 Dilutions
 3%
17.5%
35%
 *US Gallon*
Liter
*US Gallon*
Liter
*US Gallon*
Liter
34.8ml
9.2ml
5.97ml
1.578ml
3ml
0.789ml
15 drops 
273ppm H2O2 (257ppm Oxygen + 16ppm Hydrogen)
 

If you want to further convert into ounces, cups, etc. use this liquid conversion chart.
[HR][/HR]​[h=2]The 35% article as posted to Usenet[/h]Oxy - Plus contains *35%* Hydrogen Peroxide (H2O2) in a stabilised form. H2O2 is highly oxygenating in action. It is a chemical which is fundamental to life itself, participating in many of the metabolic processes in plants and animals. When added to the nutrient tank it will quickly break down into pure water, releasing the extra Oxygen ion into the solution where it can be taken up by the roots in much the same way as nutrient ions.
In plants the extra Oxygen provided will massively stimulate protein production at the cellular level. This will greatly enhance the photosynthetic process, leading to bushier plants with larger leaves, thicker stems and shorter internodes. Plants will be stronger and leaves will be darker, thus collecting light with greater efficiency and further improving photosynthetic response.
Oxy - Plus has many applications in the greenhouse or growroom. It can be used to improve germination of seeds and to increase strike rates of cuttings. It can be added to the nutrient tank and also used as a Foliar feed. Finally it can be used at the end of the season to disinfect the system and to clear out decaying organic material from growing media.
Test Strips.
Used to monitor levels of Oxy-Plus in nutrient solutions. Strips are easy to use and show a wide range from 1 - 100 ppm H2O2. These readings will allow the easy monitoring and maintenance of effective levels of H2O2 in the nutrient tank. Optimum level for hydroponic systems is 30 - 100 ppm H2O2.
Growing with H202 *35%*
OXY-PLUS is just one of a number of high performance Growth Enhancers now available to the dedicated grower. These instructions are based on a range of agents, including Oxy-Plus which work best together. In all cases Oxy-Plus can be used on its own for the applications suggested. In all cases it is important to stick to the recommended dosage. Oxy-Plus is a very powerful chemical and higher doses can be harmful to plants.
MORE IS NOT ALWAYS BETTER

INSTRUCTIONS FOR USE
*Seed Germination*
To a Litre of lukewarm water add;
15 drops Oxy-Plus
5 mls ( 1 teaspoon) Nitrozyme
Stir thoroughly. Soak seeds in this solution for 24 hrs. before germinating in the usual way. Seeds treated in this way will germinate faster and produce more vigorous seedlings.
*Cuttings (Clones)*
Stock plant (mother).
Stock plant should be sprayed or misted with Nitrozyme about two weeks before cuttings are to be taken. This will produce a flush of vigorous new shoot growth and provide plenty of material for cuttings.

To each Litre of lukewarm water add;
5 mls ( 1 teaspoon) Nitrozyme
1 - 2 mls Agral.
15 drops Oxy-Plus

Mist stock plant thoroughly with this mixture. Apply when light levels are low, early morning is best time.
Treating RockWool
Take an appropriate amount of lukewarm water. Adjust pH to 5.5.
For each Litre add;
15 drops Oxy-Plus
5 mls Nitrozyme

Allow RockWool cubes to soak in this solution until thoroughly saturated. Set aside to drain.

Take cuttings in the usual way. Most species are propagated best from softwood tips. Selected material should show signs of healthy vigorous growth. Stems should be thick and firm and foliage should be dark green. We highly recommend Clonex Hormone Rooting Gel as the best product for root initiation.

Once all cuttings are in place, mist them thoroughly;
For misting solution,
to each Litre of lukewarm water add;
5 mls ( 1 teaspoon) Nitrozyme
1 - 2 mls Agral.
15 drops Oxy-Plus
To encourage speedy root initiation on your cuttings, it is necessary to pay attention to the environment in which this is taking place......Cuttings need to be kept in a very humid environment and will benefit from frequent misting. Best way to ensure ideal rooting environment is to use a propagator with a heated base and a high clear plastic cover. Keep cover on for at least three days then begin to open vents. Mist regularly with Nitrozyme Foliar as above.

*Hydroponic Systems*
To each 10 Litres of Tank Volume add;
5 mls ( 1 teaspoon) Nitrozyme
2.5 mls.Oxy-Plus
5 mls Earth Food
Stir thoroughly before circulating to plants.
Oxy Plus should be added to tank two or three times a week to maintain optimum levels of free Oxygen in the solution. Test strips are available to assist the grower in this (see your Hydroponic retailer).
[HR][/HR]​This info was included in the revised instructions, this is as good a place as any to include it.
Quote: "If it's convenient to add Oxy-Plus on a daily basis, then it should be added at the rate of 5ml per 20 Liters of tank volume."
The revised instructions are for use with the 17.5% Oxy-Plus product. For using on a daily basis with the 35% product, simply halve the quantities just mentioned to 2.5ml per 20 liters of tank volume)
[HR][/HR]​*Foliar Feeding Rocket Fuel*
Foliar feeding is the most efficient way to maximise benefits from these extraordinary natural growth enhancers. University studies have shown that correctly applied Foliar nutrition can be up to TEN times as useful to the plants as dry fertilisers. The following recipe is widely used in California where it is considered the ultimate growth booster and is affectionately known as Rocket Fuel.

To each Litre of water pH 6, slightly warmed, add the following ingredients, stirring or shaking thoroughly between each new addition.
1. 15 drops Oxy-Plus
This will remove any Chlorine and increase level of Oxygen availability, improving nutrient uptake and usage in plants.
2. 36 drops Agral.
3. 5 mls Nitrozyme
4. 30 mls Earth Food
Shake mixture thoroughly and mist the entire plant. Plants should be treated in this manner every two to three weeks and definitely no more than once a week. Foliar feeding should ALWAYS be carried out in low light, early morning or late evening. The above solution can also be used to water the root zone of plants. First dilute the mixture with four volumes of water. (One Litre of the above mixture will therefore make up to five Litres of watering solution).

*Cleanup*
Oxy-Plus can be used to clean and sterilise your hydroponic system and growing medium. It is a powerful and very aggressive liquid and it will effectively kill all pathogens and harmful bacteria. After application it will rapidly break down to harmless substances and there is no risk of damage to future crops. For this reason Oxy-Plus is a much better material for sterilisation than Hypochlorite.
If you are using a medium such as Perlite or expanded clay you will need to remove as many of the old roots as possible. You can then soak the medium in a concentrated solution of Oxy-Plus. This will oxidise organic matter in the medium and assist in its rapid decomposition. Remember to flush medium with fresh water before re-use. You can also make up Oxy-Plus in the tank and circulate it around the system to sterilise all the pipework, drippers etc. Once again remember to flush the system thoroughly with fresh water before installing new plants.
For cleanup solution
To each 10 Litres of Tank Volume add;
25 mls Oxy-Plus

*Attention*
Oxy-Plus is highly concentrated. The active ingredient is a volatile and aggressive chemical. Treat Oxy-Plus with great caution and handle with due care. KEEP OUT OF REACH OF CHILDREN.


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## oftheCosmos (Mar 29, 2012)

*Amazing thread and beautiful flowers 
Subbed +rep*


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## woodsmaneh! (Mar 29, 2012)

oftheCosmos said:


> *Amazing thread and beautiful flowers
> Subbed +rep*


Thanks for stopping by


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## woodsmaneh! (Mar 29, 2012)

*What is the difference between ppm and EC?*

[HR][/HR]​Total Dissolved Solids (TDS) is the best measurement of the nutrient concentration of a hydroponic solution. To estimate TDS, one can use a meter that measures the Electric Conductivity (EC) of a solution, and convert the number to TDS in parts per million (ppm). Many meters will do this conversion.

Total dissolved solids (TDS) is typically expressed in parts per million (ppm). It is a measurement of mass and determined by weighing, called a gravimetric analysis. A solution of nutrients dissolved in water at a strength of 700 ppm means that there are 700 milligrams if dissolved solids present for every liter of water. To accurately calculate total dissolved solids (TDS), one would evaporate a measured filtered sample to dryness, and weigh the residue. This type of measurement requires accurate liquid measurement, glassware, a drying oven, and a milligram balance. Example: 50 mL of the 700ppm solution would leave 35 mg of salt at the bottom of a crucible after drying.

Electrical Conductivity (EC) is expressed in siemens per centimeter (s/cm) or milliseimens per centimeter(ms/cm). It can be determined with an inexpensive hand held meter. Nutrient ions have an electrical charge, a whole number, usually a positive or negative 1, 2, or 3. EC is a measurement of all those charges in the solution that conduct electricity. The greater the quantity of nutrient ions in a solution, the more electricity that will be conducted by that solution. A material has a conductance of one siemens if one ampere of electric current can pass through it per volt of electric potential. It is the reciprocal of the ohm, the standard unit of electrical resistance. A siemens is also called a mho (ohm backwards).

For convenience, EC measurements often are converted to TDS units (ppm) by the meter.

The meter cannot directly measure TDS as described above, and instead uses a linear conversion factor to calculate it. Everyones nutrient mix is different, so no factor will be exact. The meter uses an approximate conversion factor, because the exact composition of the mix is not known. Conversion factors range from .50 to .72, *depending on the meter manufacturer, which do a good job of approximating a TDS calculation from the meters measurement of EC.

* All ppm pens actually measure the value based on EC and then convert the EC value to display the ppm value, having different conversion factors between differing manufacturers is why we have this problem communicating nutrient measurments between one another.

EC is measured in millisiemens per centimeter (ms/cm) or microsiemens per centimeter (us/cm).

One millisiemen = 1000 microsiemens.

EC and CF (Conductivity Factor) are easily converted between each other.
1 ms/cm = 10 CF

"The communication problem"...
So again, the problem is that different ppm pen manufacturers use different conversion factors to calculate the ppm they display. All ppm (TDS, Total Dissolved Solids) pens actually measure in EC or CF and run a conversion program to display the reading in ppm's.

There are three conversion factors which various manufacturers use for displaying ppm's...

USA 1 ms/cm (EC 1.0 or CF 10) = 500 ppm
European 1 ms/cm (EC 1.0 or CF 10) = 640 ppm
Australian 1 ms/cm (EC 1.0 or CF 10) = 700 ppm

For example,
Hanna, Milwaukee 1 ms/cm (EC 1.0 or CF 10) = 500 ppm
Eutech 1 ms/cm (EC 1.0 or CF 10) = 640 ppm
Truncheon 1 ms/cm (EC 1.0 or CF 10) = 700 ppm

Calculating the conversion factor
If your meter allows you to switch between EC and TDS units, your conversion factor can be easily determined by dividing one by the other.

Place the probe in the solution and read TDS in ppm. Change to EC on the meter and read EC in ms/cm.

Conversion factor = ppm / ec.
[Note: ms must be converted to us: One millisiemen = 1000 microsiemens (1.0 ms/cm = 1000.0 us/cm)

According to the chart below:
1.0 ms/cm = 500 ppm (USA Hanna)
1000 us/cm = 500 ppm

Conversion factor = ppm / (ms/cm * 1000)
.50 = 500ppm / (1000us/cm) ]

The answer is your meter's convertion factor and should be a number between 0.50 and 0.72 To improve accuracy, take ec and ppm readings from your res daily for about ten days. Average the conversion factors. The more data points that you use, the closer you will be to finding your true conversion factor.

When reporting your PPM in a thread, please give the conversion factor your meter uses. For example: 550 PPM @0.7 or give the reading in EC, which should be the same meter to meter.

It may also be advisable to give the starting value of your water; there is a huge difference between RO and distilled water with a PPM of approximately 0 and hard tap water of PPM 300 @.5 (notice the conversion factor so others can work out the EC) or well water with a conductance of 2.1 ms/cm.


A note to Organic Growers:
An EC meter has fewer applications for a soil grower because many organic nutrients are not electrically charged or are inert. Things like Superthrive or Fish Emulsion, blood meal, rock phosphate or green sand cannot be measured with a meter reliably when they are applied or in runoff. Meters can only measure electrically charged salts in solution.

"The solution"...
When reporting your PPM in a thread please give the conversion factor your meter uses for example 550 PPM @.7 or give the reading in EC (the EC shoul d be the same meter to meter).


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## woodsmaneh! (Mar 29, 2012)

Oxygenation, Air Pumps, Nutrient Uptake and Temperatures 

*Introduction: Why plant roots need oxygen*
Oxygen is an essential plant nutrient - plant root systems require oxygen for aerobic respiration, an essential plant process that releases energy for root growth and nutrient uptake. In many 'solution culture' hydroponic systems, the oxygen supplied for plant root uptake is provided mostly as dissolved oxygen (DO) held in the nutrient solution. If depletion of this dissolved oxygen in the root system occurs, then growth of plants, water and mineral uptake are reduced. Injury from low (or no) oxygen in the root zone can take several forms and these will differ in severity between plant types. Often the first sign of inadequate oxygen supply to the roots is wilting of the plant under warm conditions and high light levels. Insufficient oxygen reduces the permeability of the roots to water and there will be an accumulation of toxins, so that both water and minerals are not absorbed in sufficient amounts to support plant growth. This wilting is accompanied by slower rates of photosynthesis and carbohydrate transfer, so that over time, plant growth is reduced and yields are affected. If oxygen starvation continues, mineral deficiencies will begin to show, roots die back and plants will become stunted. If the lack of oxygen continues in the root zone, plants produce a stress hormone - ethylene, which accumulates in the roots and causes collapse of the root cells, at this stage pathogens such as pythium can easily take hold and destroy the plant. 

*Oxygen in Hydroponic Nutrient Solutions*
While its possible to measure the levels of dissolved oxygen in a hydroponic nutrient solution, its not carried out as often as EC and pH monitoring due to the cost of accurate DO (Dissolved Oxygen meters). However, if an effective method of aeration is continually being used, and solution temperatures are not reaching excessively high levels, then good levels of oxygenation in most systems can be achieved One of the most common and effective methods of oxygenation in hydroponic nutrient solutions is with the use of air pumps/machines and air stones.

*Air Pumps and Air Stones*
While there are a number of methods that can be used to introduce oxygen into a nutrient solution, many of these, such as ozone treatment, are expensive and not often used by smaller growers. One of the most practical and inexpensive, yet efficient ways of getting more dissolved oxygen into a plants root system is through forcing air into the nutrient. Air pumps are widely available in a range of sizes, from very small up to very large with capacity to run from one to many `air stones each introducing hundreds of tiny bubbles of fresh, oxygen rich air into the nutrient solution. 

*Why an Air Stone*
While an air pump tube alone can bubble air into a nutrient solution, oxygenation or the process of getting atmospheric oxygen dissolved into the liquid nutrient, is much more effective where many tiny bubbles of air are created, rather than a slow stream of larger bubbles. The greater the surface contact between the air bubbles and the nutrient, the more oxygen will diffuse into the nutrient solution and smaller bubbles create a far greater surface area than a few larger bubbles will. Air stones simply break up the air flow and distribute along the surface of the porous 'stone' so that many tiny bubbles are rapidly introduced into the nutrient. Depending on the size or dimensions of the nutrient reservoir into which air is being introduced for oxygenation, air stones of different shapes and sizes can be selected. For small rectangular tanks, long thin air stones (some up to 1 foot in length) can be placed on the base of the reservoir to distribute air bubbles and oxygen uniformly. A larger number of smaller, round, cylindrical or oval air stones placed at equal distance inside a nutrient pool or tank also ensure high levels of oxygenation. 
Air stones also have the benefit of acting as 'weights' which remain stable on the base, or in the lower layers of the nutrient tank - the further the bubbles have to travel to reach the surface of the nutrient, the more time oxygen has to diffuse into the liquid and the higher the rates of dissolved oxygen than can be obtained from an air pump and stone set up. 
For systems with multiple nutrient reservoirs or tanks, one large air pump with many outlets will allow oxygenation into all systems and it is always a good idea to buy an air machine and air stones larger than currently required so that aeration can be increased under warmer conditions or if the hydroponic system is later expanded. 

*Oxygen and Temperature Effects - Effective Aeration*
While forcing air bubbles deep down into the nutrient reservoir generally increases the dissolved oxygen levels in the nutrient, there is one other major factor to consider and that's the temperature of the air being pumped into the nutrient. As the temperature of a nutrient solution increases, its ability to hold dissolved oxygen decreases. So a cool nutrient solution may in fact hold twice as much oxygen at 'saturation level' than a warm solution. For example a nutrient solution at 45 F can hold around 12ppm of dissolved oxygen at 'saturation', (meaning it is the most it can hold), but the same nutrient solution at a temperature of 85 F will hold less than 7ppm at saturation. This means at a solution temperature of 85F there is much less dissolved oxygen available for the plants root system to take up. To complicate matters further, the requirement of the plants root system for oxygen at warmer temperatures, is many times greater than at cooler temperatures due to the increased rate of root respiration. So warm nutrients mean a very high oxygen requirement from the plants roots, but the nutrient can only hold very limited amounts of dissolved oxygen at saturation, no matter how much air is being bubbled into the solution. Ideally, nutrient solution temperatures for most plants should be run lower than the overall air temperature - this has many beneficial effects on plant growth and development. However, if overly warm air from the growing environment is pumped into an otherwise cool nutrient solution, the warm air will rapidly increase the temperature of the nutrient to that of the growing environment. If air is being pumped via an air machine with an intake close to lights or other heat sources then rapid heating of the nutrient will occur. On the other hand, cool air has the ability to reduce the temperature of the nutrient if sufficient levels are pumped in and thus result in a much more highly oxygenated solution for the plants roots. If keeping the nutrient solution temperature down seems to be a continual problem, checking the air inlet temperature of an air pump is a good idea. Overly warm nutrient solutions (ideally nutrient solutions should remain below 65 - 75 F) for most warm season, high light plants and well below 69 F for cool season can have serious effects on the plants root system. Apart from the increased oxygen requirement due to a much higher rate of root respiration which can rapidly result in oxygen starvation, high solution temperatures favour many of the root disease pathogens. Plant roots become highly 'stressed' when experiencing high temperatures, particularly if there is a large mis-match between the air and root temperature. Root stress slows the development of new roots, resulting in reserves inside the root tissue being `burned up during respiration faster than they are accumulated, and stress makes the root system in general more susceptible to disease attack. Keeping a check on nutrient temperature is vital, as is ensuring that air machines are not blasting hot air into the solution and cooking plant roots. Aeration is most effective when cool air is bubbled into a nutrient. 

*Oxygenation and Nutrient Uptake*
Healthy roots supplied with sufficient oxygen are able to absorb nutrient ions selectively from the surrounding solution as required. The metabolic energy which is required to drive this nutrient uptake process is obtained from root respiration using oxygen. In fact there can be a net loss of nutrient ions from a plants root system when suffering from a lack of oxygen (anaerobic conditions). Without sufficient oxygen in the root zone, plants are unable to take up mineral nutrients in the concentrations required for maximum growth and development. Maintain maximum levels of dissolved oxygen boosts nutrient uptake by ensuring healthy roots have the energy required to rapidly take up and transport water and mineral ions. 
Calcium is one important nutrient ion which has been shown to benefit from high levels of oxygenation in the hydroponic nutrient solution Calcium, unlike the other major nutrients is absorbed mostly by the root growing tips (root apex). The root apex has a large energy requirement for new cell production and growth and is therefore vulnerable to oxygen stress If root tips begin to suffer from a lack of oxygen, a shortage of calcium in the shoot will occur. This shortage of calcium makes the development of calcium disorders such as tip burn and blossom end rot of fruit more likely and severe under oxygen starvation conditions. High levels of oxygenation ensure healthy root tips are able to take the levels of calcium required for new tissue growth and development. 

*Conclusion*
While providing oxygenation with the use of air machines and stones is an excellent method of increasing the dissolved oxygen (DO) levels in a nutrient solution, the temperature of the air intake and nutrient solution must also be managed to ensure oxygen starvation in the root zone does not occur. Pumping hot air into a nutrient not only creates temperature stress in the root zone, it also results in less oxygen carrying capacity in the solution itself - a recipe for root suffocation that will rapidly affect the top portion of the plant as well. Getting oxygenation right means checking both aeration capacity of the equipment being chosen and temperatures in the nutrient and root zone.


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## woodsmaneh! (Mar 29, 2012)

*Low Maintenance Mothering
*
Stasis & Selective Light Intensity

Using clones of a favorite plant is the best way to perpetuate the traits we like most about that plant. It also helps bring some uniformity to a garden so we can rest assured that all the plants grow in the same manner and at the same rate. For the Sinsemilla cultivator one of the best things about using clones is that it removes the anxiety ridden step of sexing plants, eventually culling the males, then growing whatever females Mother Nature has seen fit to leave us with. Unlike seeds, using clones requires a living plant from which cuttings can be taken. While cuttings can be taken from a crop destined to be harvested, many people don't want to compromise their producers and will designate a separate plant to be the mother for their next generation of clones. Because a vegetative phase is more conducive to taking cuttings, and generally used for rooting them, a separate space is set up to isolate plants receiving a flowering photoperiod from those receiving a vegetative photoperiod. The vegetative space occupied by the mother plant(s) will need to be maintained separately. Timing the plant's growth in such a way as to deliver enough cuttings, at the right time, and of a good quality is of the essence. The need for cuttings develops as a crop nears harvest. Advance time must be allowed for the cuttings to root well so their placement in the system will coincide with the timely harvesting of the flowering plants. This means that a mother plant will be growing for almost the entire duration of a crop before her services are ever needed again. Under the wrong conditions this length of time (e.g. 60-90 days) can produce a mother plant that will easily outgrow its allotted space, or demand your time in order to maintain the growth within the space limitations. This hands-on maintenance usually takes the form of removing or redirecting growth. What's described here are two methods of _reducing_ growth so that the time spent using hands-on methods can be eliminated.


*The Stasis Photoperiod*


Vegetative photoperiods generally range from a constant 24 hours to 16 hours of light per day. Its goal is to prevent the plant from flowering, thus for mothers, providing good vegetative stock for cuttings. Needless to say 16 hours of light per day will produce less growth than more hours will, so for purposes of growth reduction fewer hours of light per day is preferable. Because the flowering response of cannabis is triggered by the duration of the dark phase, it will flower when it receives 12 hours of _uninterrupted darkness,_ but it will not flower with 12 hours of _interrupted_ darkness. Manipulating light timer settings in such a way as to provide 12 hours of light over a 24 hour period, but not permitting 12 hours of uninterrupted darkness to occur, can reduce growth by 25% when compared to the traditional 16 hour vegetative photoperiod without triggering the flowering response. A timer capable of 4 on/off cycles per day, using the settings in the following table, will produce such results.


Timer settings for a 24 hour period
beginning at 7pm
 *ON*
*OFF*
7 pm
6:00 am
9 am
9:20 am
1 pm
1:20 pm
4 pm
4:20 pm (off til 7 pm)



As you can see from the below graphic, over a 24 hour period these timer settings will provide 12 hours of light and 12 hours of darkness, but will not trigger flowering because no single dark phase is long enough to do so.



The above are examples of one timer schedule that's known to work well, others are indeed possible.​


*Selective Light Intensity*

Because a stasis photoperiod requires multiple on/off light cycles per day, it's best applied using fluorescent lighting, rather than stress HID lighting system components with so many daily on/off cycles. It also makes sense that if one wants to reduce growth that he would opt for lighting that provides fewer lumens. Unlike HID lighting, fluorescent lighting often uses multiple bulbs to distribute light over a given area. Configuring a multiple fluorescent lamp set-up so that each light can independently be turned on or off allows a grower to not only control the duration of the light per day with a stasis photoperiod, but to also control the light intensity.
Selective light intensity with fluorescents is nothing more than using as few tubes (less light) as needed to keep growth to a minimum during the times cuttings are not needed, and using more tubes (more light) just prior to taking cuttings so that shoots used for cuttings will be more robust and make for better clones. Turning off half of the available lamps during this time can reduce growth by 50%.
The combined growth reduction from using stasis and selective light intensity can approach 75%. The benefit is that the time spent on manual hands-on mother maintenance is replaced by the flick of a few switches. 

http://www.angelfire.com/cantina/fourtwenty/articles/mothering.htm


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## smok3y1 (Mar 31, 2012)

*You must spread some Reputation around before giving it to woodsmaneh! again.*

Thanks for the great thread! If you have anymore great articles please carry on posting alot of good information in them!!!


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## woodsmaneh! (Mar 31, 2012)

*Molasses and Plant Carbohydrates - b.com]Texas Plant & Soil Lab Report 
*
The following is an article I found on molasses and its use with plants. Thought others might find it useful, I did.

Molasses and Plant Carbohydrates
Sugars relating to plant functions for maximum economic production.
Texas Plant & Soil Lab, Inc., Texas Plant & Soil Lab (Home)

Environmental factors that affect when and how much sugar to use:
a. How much nitrate is in the soil, and plant sap (petiole test).
b. Soil moisture conditions.
c. Sunlight intensity.
d. Temperature.
e. Wind
f. Fruiting stage / load
g. Growth / vigor [shade lower leaves]

The right amount at the right time can improve fruiting and produce normal
plant growth with less attraction for disease and insects.

Needed for healthy plants - fruit production - plant development &
maturity.
Roots take nutrients from the soil and transport them up the stalk thru the
petiole (stem) to the leaves where the sunlight aids the production of
photosynthates (sugars are not the ONLY product of photosynthesis)
carbohydrates (C, H & O), principally glucose (C6H12O6) and then other sugars and photosynthates are formed.

Plant Sugars and other photosynthates are first translocated (boron is essential to the translocation) to a fruiting site. If fruit is not available, the sugars, along with excess nitrates, spur the rapid vegetative growth of the plant at the expense of creating fruiting bodies (first sink) for the storage of the sugars.

Once the proper balance of environmental factors (heat units, light intensity, soil moisture, nutrient balance, etc) are met, the fruiting buds form and then fruit formation gets the first crack at the sugar supply.

Any excess sugars are then translocated to the number two sink, (growing terminals,) to speed their growth. The left-over sugars, etc. then go to the number 3 sink, (the roots,) to aid their growth. Here the new root hairs take up nutrients to help continue the cycle of sugar and other photosynthate production, fruiting, growth of terminals and roots.

ADDED SUGARS CAN AID THE PLANT IN SEVERAL WAYS:
- MOLASSES is probably the best outside source of many sugars, such as table sugar, corn syrup and several more complex sugars such as polysaccharides found in humus products.
- Sugar can be added to the soil in irrigation water, drip & pivot being the most effective.

In the soil it can:

- Feed microbes to stimulate the conversion of nitrates to the more efficient NH2 form of N to synthesize protein more directly by the plants.

- The roots can directly absorb some of the sugars into the sap stream to supplement the leaf supply to fruit where it is most needed, and ALSO directly feed the roots for continued productive growth.

- This ADDED sugar can also help initiate fruiting buds in a steady-slow
fashion while maintaining normal growth.

-EXCESSIVE amounts of ADDED SUGARS applied foliarly can shock the
plant resulting in shortened growth internodes, increased leaf maturity & initiation of excess fruiting sites. This can be a short term effect lasting only a few days.

Pollination, soil moisture, nutrient balance and sufficiency as well as adequate light for photosynthate production decide how much of the induced fruit can mature.


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## Bonzo Mendoza (Apr 1, 2012)

woodsmaneh! said:


> Thanks for stopping by


baby I'm amazed


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## Benelli (Apr 5, 2012)

wow, great info. plus REP for you. time to get back to work...


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## Zoltan44x (Apr 6, 2012)

Excellent thread and the most beautiful rainbow pic at the end.


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## superoz (Apr 8, 2012)

One of the best Threads i have read here ! Congrats bro u are the bomb of Information.Took me two days to read all this advanced knowledge and digest , But has to be read again and again . bookmarked !!!!!!!


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## woodsmaneh! (Apr 9, 2012)

superoz said:


> One of the best Threads i have read here ! Congrats bro u are the bomb of Information.Took me two days to read all this advanced knowledge and digest , But has to be read again and again . bookmarked !!!!!!!



Thank you for stopping in and positive comments.


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## woodsmaneh! (Apr 21, 2012)

*
Hydrogen Peroxide Dilution Chart*

*Mixing 35% food grade hydrogen peroxide to get 3% hydrogen peroxide*
To make a gallon of 3% peroxide: In a clean gallon container, combine 1 and ¼ cups of 35% food grade hydrogen peroxide with 14 and ¾ cups of water.
To make 3% hydrogen peroxide from 35% hydrogen peroxide, the general mixing guideline is:* 1 part 35% hydrogen peroxide plus 11 parts water = 3% hydrogen peroxide*. You can use this guideline with any quantity you need to mix.
Heres the same thing I just said, but in the form of a Hydrogen Peroxide dilution chart:
*Peroxide dilution chart for mixing 35% hydrogen peroxide with water to get 3% hydrogen peroxide*

*USE THIS AMOUNT OF 35% HYDROGEN PEROXIDE**AND THIS AMOUNT OF WATER***TO MAKE THIS AMOUNT OF 3% HYDROGEN PEROXIDE*1 part11 parts12 parts1 and 1/4 cups14 and 3/4 cups1 gallon (16 cups)1 and 1/4 tablespoons3/4 cups + 2 and 3/4 tablespoons1 cup (16 tablespoons)1/4 cup + 1 tablespoon3 and 1/2 cups + 3 tablespoons1 quart (4 cups)
I cant think of a reason why youd want to mix more than a gallon of 3% peroxide, but perhaps Im missing something? (Please write and let me know if you mix larger quantities, Id be curious to know what you use the large amount of 3% for. Seems to me it would be easier to use 35% for anything that needs that much???)
*More how-to details and how to make it easier to do..*
I use an empty gallon apple juice bottle which Ive had for years. (It is glass. I consider glass to be acceptable for storing 3% hydrogen peroxide but NOT for 35%.)
To make measuring and mixing a gallon of 3% peroxide easier, do this:


Make a gallon of 3% hydrogen peroxide, as described in the peroxide dilution chart, above, by mixing 1 and 1/4 cups of 35% food grade hydrogen peroxide with 14 and 3/4 cups of water. Measure it out.
Use a permanent marker to make a mark on the outside of the bottle, where the level of the gallon of liquid fills the bottle up to.
From here on out, you can make 3% hydrogen peroxide every time this bottle is empty like this: *measure* 1 and 1/4 cups of 35% hydrogen peroxide, and pour it into the empty bottle. Then add enough water to fill up the bottle, up to the line.
*This eliminates having to measure and count out the 14 and ¾ cups of water each time!*
** What kind of WATER?*
In the hydrogen peroxide dilution chart, above, I just say water. But what kind of water?
That will depend on what you are planning to use the peroxide for. For most purposes, tap water will work.
Here is the exception: If you plan to use the peroxide as an oxygen supplement  to be ingested by anyone (including animals)  then you should consider using distilled water, or filtered water, if at all possible.
Any metals in water will combine with hydrogen peroxide. Ive read that this is bad stuff to ingest. Id like to know a lot more than I do about why, and what the level of risk is. I cant add a lot to this, other than to say that Ive read that this is risky. How risky I dont know. But it does make some sense: peroxide is an oxidant. Oxidizing metal creates rust. Drinking rust particles doesnt seem like a good idea.
Ive also read that it is bad to ingest peroxide in combination with iron supplements. The reason is the same: iron is a metal.
If you plan to ingest peroxide, you can consider this.

Site link for the above ^^^^
http://www.using-hydrogen-peroxide.com/peroxide-dilution-chart.html




*Mixing charts for gardening with hydrogen peroxide*

If you want to start gardening with hydrogen peroxide, you need to know how much peroxide to use. Here are charts to tell you how much!
*To water or mist plants, to soak seeds, to add to water used to wash sprouts:*


*TO THIS AMOUNT OF WATER**ADD THIS AMOUNT OF 3% HYDROGEN PEROXIDE**--OR-- ADD THIS AMOUNT OF 35% HYDROGEN PEROXIDE*1 cup1 and 1/2 teaspoons7 to 10 drops1 quart2 tablespoons1/2 teaspoon1 gallon1/2 cup2 teaspoons5 gallons2 and 1/2 cups3 tablespoons plus 1 teaspoon10 gallons5 cups6 tablespoons plus 2 teaspoons20 gallons10 cups3/4 cup plus 1 tablespoon plus 1 teaspoonbathtub (aprox 25 to 35 gallons) *12 to 17 cups1 to 1.5 cups
* bathtub sizes vary. It is okay to use more water and/or less peroxide.
*To spray on sick or fungusy plants:*


*TO THIS AMOUNT OF WATER**ADD THIS AMOUNT OF 3% HYDROGEN PEROXIDE**--OR-- ADD THIS AMOUNT OF 35% HYDROGEN PEROXIDE*1 cup1 tablespoon1/4 teaspoon1 pint2 tablespoons1/2 teaspoon1 quart1/4 cup1 teaspoon1 gallon1 cup1 tablespoon plus 1 teaspoon5 gallons5 cups6 tablespoons plus 2 teaspoons10 gallons10 cups3/4 cup plus 1 tablespoons plus 1 teaspoons20 gallons20 cups1 and 1/2 cups plus 2 tablespoons plus 2 teaspoons
*Please be mindful to choose the correct column in the chart depending on whether you are using 3% hydrogen peroxide or 35% hydrogen peroxide!!*


As you may notice, the amount of peroxide in the chart for sick and fungusy plants is twice as much as in the first chart. I have heard of people using stronger solutions, but more is *NOT* always better. So be careful, and when in doubt, stay safe. You can always apply more another day. If you decide to use a bit more, please make it only a *bit* more, don't get carried away. Gardening with hydrogen peroxide is great, but too much can harm your plants. 10% hydrogen peroxide is recommended as a week killer -- in other words *it will kill your plants at that concentration....*


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## woodsmaneh! (Apr 21, 2012)

Here are some shots with my usb scope I use it when I want to get close up like 400x and I can save the shots on my laptop. I have a few scopes that I use for different things will post shots of them in next post. It's handy as I do a lot of hydro so keeping an eye on roots is easy. My other scopes go from 120x to 30x.


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## woodsmaneh! (Apr 21, 2012)

here are my scopes the black one with the wire is the USB scope, the one with 2 eye pieces is from a fiber optical fiber lab and my new one the scope on the narrow stand is from a machine shop


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## Da Almighty Jew (Apr 21, 2012)

woodsmaneh i want to ask for your help on if i should start curing yet. I thought i would ask in here because i would get your attention and it is hard to get a good growers input. Here is my situation.

Ok so i have some buds that have been hanging up for 4 days and i think they feel like they are ready to cure. They are mostly dry on the outside but you can tell there is a little moisture in there and the stem bends, breaks but does not snap. Should i start curing these? 

I have other buds in the same room that are still very moist so im not thinking about curing those yet.

I keep my drying room at 66-68 deg and 45-55% humidity.

Also when i start curing how long do you need to burp jars for before you dont have to open them anymore.?


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## Adosbulc (Apr 21, 2013)

Some GREAT info here! Just thread through the whole post-wanted to bump it so others can see it aswell!


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