Soil-runoff coming in at 6.0-6.9 E.C, is that dangerous levels?

switch said:

Basically, i have been feeding like normal but my runoff is coming in extremely high in EC, the meter is working fine, does this mean that i can keep watering the plants with plain ph'd water until the runoff is down to between 0.5 and 1.0 EC, then start feeding again???

If the ec is high, does it mean that there is plenty of nutrients in the soil and i dont need to feed again for ages?? Or is this mis-leading?

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Whether you're growing hydro or in soil, the electrical conductivity (EC) and moisture of your medium are two key elements that should be manipulated to meet your needs. Both of these factors are controlling the same thing; the ability of a plant to uptake water and nutrients from the growth medium. (EC measures the level of fertilizer salts in the water.)
A plant grows by first dividing cells then expanding them, and in order to do this it requires water. By limiting the amount of water available to a plant you limit the expansion of cells. This can work for you by keeping your internodes close together, or against you by limiting bud growth. Both the amount of water you give your plants and the EC at which you grow them control the uptake of water.
A plant's roots act much like a pump, using osmotic pressure to move water into the plant. In order for this to work there must be a larger concentration of fertilizer salts in the plant's roots than in the soil or hydroponic solution, so when the medium's level of salt rises above the roots', the plant will wilt. Raising the salt level in the medium closer to that which is in the roots limits the water availability just the same as if we had provided less water.
During the vegetative stage we want our plants to form very tight internodes, especially under artificial lighting. By allowing the EC to drop below ideal during this stage we are wasting valuable space growing stem instead of bud. Most marijuana strains are happiest when grown at an EC of between 1.5 and 1.8, but different strains have different preferences. Try growing one of your plants using straight water for a week or so, you will see the internode length stretch dramatically compared to the ones on a regular fertilizer regime.

Hydroponic tomato growers sometimes will grow their transplants at extremely high EC's (up to 6 EC!) in order to get really nice stocky production plants. Please note that when doing this they use special nutrient formulas designed for this purpose, most of which have potassium to nitrogen ratios of 4:1, much higher than normal, as too much nitrate at this high an EC will easily damage a plant.
(Try this formula if you're interested: calcium nitrate 7 grams, potassium nitrate 0.095 grams, potassium sulphate 9.25 grams, mono potassium phosphate 2.2 gram, magnesium sulphate 5 grams, micromix .02 grams. Slowly raise your EC during veg stage, I would not recommend going above 3 or 4 EC. This is experimental! Do not try on all of your plants at once until you are sure your strain can handle it. All of these ingredients should be available at your local hydroponics store, it is usually called "six pack formula". Be sure to bring your EC back down once you enter floral stage, by the time tufts of pistils are visible you want to be at your ideal EC of 1.5-1.8.)
Try not to change the EC too quickly as a sharp drop can cause root damage. This also goes during your final flushing period when you want to eliminate all fertilizer from the medium ? lower the EC over a couple of days, as the sudden change in salt level will harm the roots.
When growing hydroponically, the only way of manipulating water availability is with the EC, while in soil we may also use the moisture level of the medium to the same ends. Many growers are under the mistaken impression that the EC and pH of their nutrient solution remains the same when applied to the soil. This in not the case, and you must test the soil in order to have a true
picture.

To test your soil, take a sample from the center of the root zone at the side of the pot (don't worry the torn roots will be fine). Mix the soil with 2 equal parts distilled water and let sit for 20 minutes. Once the time is up take an EC reading and multiply this number by 2.4 (this takes into account the dilution and the pore space factor) this will give you an accurate picture of the EC the roots are actually being exposed to. The pH should also be checked at this time. It is not feasible in soil to maintain an exact EC at all times, what we need to try and avoid is EC's climbing much above what we want and plants going for long periods with very low EC's.
A frequent mistake marijuana growers make is over-emphasizing the need for a plant grown in soil to dry out completely between waterings. Cannabis does like dry feet but this simply means that the root zone must not be kept extremely wet at all times. Keep in mind that if the soil has an EC of 1.8 and then dries out completely the amount of salt remains the same, causing the EC to double or more.
As a general rule, during the vegetative stage you should keep your plants a little on the drier side as this will restrict cell elongation, creating a shorter noded plant structure capable of creating a dense bud cluster in the floral stage. (Unless of course you are using the high EC method described above, in this case you must not let your soil get too dry because of the increased fertilizer level you will create.) Maintain this level of moisture into the first 14 to 20 days of 12/12 to minimize internode stretch.
As soon as early flowering begins you need to increase soil moisture to a nice evenly moist (not soaked) level to maximize bud expansion. Growing marijuana too dry during this stage will adversely affect your overall yield, as will having too high an EC in the medium.
In these times of government oppression we must make the most efficient use of available growing space in order to produce the copious amounts of cannabis necessary to overflow the boundaries placed upon us. Control your cannabis!

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switch said:

That is some extremely useful info, you should make a thread about that, it will help a lot of people!That probably explains why my plants are yellow and budding very sparsely, because I let em dry out too much and now the soil is clogged up with salts, causing nute lockup??? Can someone in the know confirm this?

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Temperature control The easiest and most under-used way to control internodal stretch is temperature control. Plant internodal length is directly related to the difference between day and night temperatures. The warmer your day cycle is as compared to your night cycle, the greater your internode length will be. The opposite also holds true; the closer your day and night temperatures, the shorter your internodes will be. Ever notice how as the warmer summer months approach, your plants begin to stretch? Part of this problem may lie in an overall hotter grow-room, but a larger factor is the increased difference between day and night temperatures.
Lets look at putting this to play in your grow room. Maximum temperatures should ideally never rise above 26C, so you must do everything you can to prevent your room getting too hot (run lights at night, use exhaust fans, air conditioners, etc). An ideal temperature range is 24-25C when the lights are on, and 22C when the lights are off.
The temperature technique is most effective under a 12/12 light regime, which is ideal as this is when cannabis stretches the most. When the light cycle is brought to 12/12 we will raise the night temperature to the daytime level of 24-25?C. Space heaters on timers work well for this, and max/min type thermometers are ideal for
tracking temperatures.


It is during the first 2-3 weeks of the flower cycle that most strains begin to lengthen internodes, making it a very important time to control temperature, as this is when the framework for future colas is built. After this 2-3 week window we need to drop the night temperature back down to 22C, as this is where the plant is happiest.

long internodes
As floral development begins we need to keep in mind that the total size of your buds is determined largely by average daily temperature, provided it does not exceed optimal. So if you are letting your day temperatures drop below 24C or your night drop below 22C, you are costing yourself in overall weight and harvest.

Once your buds have reached optimal size and and you have begun the flushing period, you may consider dropping temperature down to 17-19C for the final week or two. This drop in temperature triggers anthocyanin production, which intensifies the color of the floral clusters and makes for a showier bud, especially with "purple" varieties. This final temperature change is not always feasible and can be omitted.
For extreme height control you may even use warmer night temperature than day, but be very careful when running settings like this, as even a zero difference between night and day temperatures will lead to leaf chlorosis (yellowing) after 2-3 weeks.

Some things you will notice while using this technique are a change in the leaf angle, upwards during warm days and downwards during warm nights. There is also the chlorosis if this is done for too long. Neither of these symptoms is nutrient related and will fix themselves when the temperature is changed back.

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switch said:

Ph of my nutes is always 6.5. As is plain water, 6.5 always, right across the board. Have never done a soil ph test as i always assumed the soil SHOULD theroetically stay the same ph as the water/nutes that pass through it??

Indoor grow, using a 600hps for both stages. I keep my adjustawing never more than 16'' from the canopy. I like to keep it nice and close with a small fan blowing directly on the bulb. Temps vary, daytime is usually around 27/28c this time of year. Nighttime about 18/19c. I read in The Grow Bible that temperature fluctuations of 8c were fine.

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All plants need a plentiful supply of good clean water to grow. Tap water works ok but can often be high in alkalinity; if you are going to use tap water without a filter system then it is recommended that you leave tap water to stand for a couple of days to allow it to dechlorinate. You should also test its PH and make changes as necessary. Some growers prefer to use rain water, however, rainwater contains many pollutants and can vary wildly in its PH values and is therefore not recommended. It is possible to use tap water by providing optional calcium and magnesium components to the feed program, just check what amounts you have so far.
Supplying water to your plants is at the heart of your grow room. There are a whole range of automated watering systems to choose from.
If you are growing in soil and watering by hand your plants will need good drainage to enable flushing and avoid a build up of salts from the nutrients, they should not be left in standing water.


The exact frequency for watering your plant will vary according to size, strain, growth rate, temperature, size of pot and other variables. You should avoid saturating the plants while at the same time preventing them drying out. Put your finger an inch or two (2.5cm – 5cm) into the top of the soil. If this is dry then the plants need to be watered. With young plants this will be every few days. As the plants get bigger you will need to water more often with larger amounts. A large plant may require daily watering.
Observe the plants. Plants requiring water will begin to wilt and the leaves will droop. If you water when this happens your plants will revive within the hour. With practice, once you become familiar with your plant, you can catch it before wilting happens. Give enough water, directly onto the soil, so that it just begins to come out of the drainage holes at the base of the pot.
Water is used most efficiently if you give it during the plant’s morning photo period (remember its cycle may be different than the actual daylight cycle). A spray of the leaves during its evening is also beneficial. Remember to use water at room temperature to avoid shocking the plant.


pH is the measure of acidity of any given substance. A pH of 7.0 is totally neutral, 1.0 to 6.9 is acidic and 7.1 to 14.0 is alkaline. An increase in pH from 7 to 8 is actually a tenfold increase, so be aware! The average pH of American tap water is around 8.0 Marijuana responds best to a pH level of between 5.5 and 6.5 when it is grown hydroponically. There are products available known as pH Up and pH Down. These will help you to regulate the pH of water and nutrient solutions. If you are constrained by budget you can use baking powder to raise pH or vinegar to lower it but this is not advised. You need to note that it is natural for the pH level of a reservoir to climb over time as the plant takes up more water than nutrients. This will usually take between 5 and 10 days to move the pH up from 5.5 to 6.5.


Most growers use a continuous pH monitoring device, there are lots on the market but you should never totally rely on this one system. You should use a backup system to spot check and calibrate the original… if both are reading the same pH then all is good but if both are different you really need a third device to see which one is actually right!
Reverse Osmosis

These machines actually block molecule sized substances that can measure as low as 0.0005 microns. The systems have membranes with trillions of little holes and the water is pushed through them with two outputs, one of brine or waste water and the other of pure water. You want a nice even flow of water through the reverse osmosis machine at a rate of around 60 pounds per square inch; if you find the pressure in your flow gets too low then you need a back up pump to stabilize it. Reverse osmosis machines do waste a lot of water though at around 10 parts per 1 or 2 parts of pure water produced. These are complicated machines and we would advise that you look at systems that include both a booster and a permeate pump.

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