Beneficial Additives in Hydroponics! *A MUST READ*

I have previously stressed the point that plants will achieve optimum growth only after they have been provided with an ideal environment (temp, light, humidity etc) and ideal nutrition. I also stress the point that big yields do not come in bottles. That environment is king and a nutrient is only as good as the environment that it is used in.

That is not to say that some additives won’t enhance the plant’s capacity to achieve optimum yields.

For instance, plant nutrition purchased in fluid or powder form does not typically (ever) provide all of the elements that are available to plants in nature. Just one example of this is the absence of silica in nutrient formulas. Silica is an extremely common element in nature but is not incorporated into nutrient formulas due to high pH and insolubility. This means that the average nutrient formula can be improved upon somewhat with the addition of silica.

There are also other elements found in nature that aren’t commonly found in nutrient formulas. Because of this we are able to fully provide for the plant’s nutritional needs with careful use of beneficial nutritional additives.

In addition to this, some additives can enhance naturally occurring aspects of plant growth. Other additives can control what the plant does. In other cases additives can aid in plant health, reducing the incidence of disease and pathogens. For instance, products such as beneficial microbes, or sterilizing agents, which we’ll cover in depth in this chapter, are critical in any hydroponic system to ensure pathogens such as pythium and fusarium are controlled/prevented.

Anyway, let’s have a closer look at what I consider to be some of the more important/valuable beneficial additives. Let’s face it, with the vast array of additives on the market today, all growers have their own views with some using incredible amounts of additives and others using very few. Ultimately, each grower will make their own choices but for now let’s have an in depth look at beneficial additive science and why it is that I consider several additives of great value to growers/yields.


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Overview



Silicon (Si) is the second most common element on Earth after oxygen and is abundant in soils.

Siliconis abundant in all field grown plants, but it is not present in most hydroponicsolutions.

In plants, silicon strengthens cell walls, improving plant strength, health, and productivity.1


Silicon, deposited in cell walls of plants, has been found to improve heat and drought tolerance and increase resistance to insects and fungal infections. Silicon can help plants deal with toxic levels of manganese, iron, phosphorus and aluminium as well as zinc deficiency.

Thus, the beneficial effects of silicon (Si) are threefold: 1) it protects against insect and disease attack (Cherif et al. 1994; Winslow, 1992; Samuels, 1991), 2) it protects against toxicity of metals (Vlamis and Williams, 1967; Baylis et al. 1994), and 3) it benefits quality and yield of agricultural crops (Kathryn E Richmond et al, 2003).

Silica is excluded from hydroponic nutrient formulas because it has a high pH and is unable to remain soluble (hold/remain stable) in concentrated nutrient formulas.
Therefore, Si needs to be added to the nutrient tank as a separate element.

Benefits of Si
· Increased disease resistance
· Increased resistance to pathogenic airborne fungi (eg. Botrytis)
· Increased resistance to waterborne pathogens
· Increased resistance to insects/pests
· Increased strength in cell structure
· Increased stress tolerance
· Increased drought tolerance
· Increased salt tolerance
· Increased yields

THE SCIENCE



Silicon (Si) is not considered to be an essential plant nutrient because most plant species can complete their life cycle without it. However, Si is considered to be a beneficial element and some plant species can accumulate Si at concentrations higher than many essential macronutrients (Epstein, 1999).

A lack of knowledge about the role of silicon (Si) in horticultural crops became apparent with the change to soilless growing media (hydroponics) in the glasshouse industry in the Netherlands. It was found that in hydroponic systems the Si contents in plant tissue were significantly lower in comparison with crops grown in soil. Research was carried out on the effects of Si application in hydroponic systems. With cucumber, melon, courgette, strawberry, bean, and rose, the Si contents were increased as a result of the addition of Si into the root environment. Results in these trials showed that cucumber, rose, and courgette could benefit from enhanced Si concentration in the root environment, since total yield was increased and powdery mildew was suppressed. 2


Silica and Fungi Suppression (eg. Botrytis)



Si has been shown in numerous studies to suppress fungal pathogens such as Botrytis. In a study by Adatia et al (1986) conducted on cucumbers grown in recirculating hydroponic systems it was shown that despite regular applications of fungicide, outbreaks of the fungal disease occurred on most of the mature leaves of low Si cucumber plants, while the high Si plants remained almost completely free of fungal pathogens. The conclusion to this study noted:

“The addition of Si could be beneficial to cucumbers grown in areas where the local water supply is low in this element, especially when grown in recirculating solution or in a medium low in Si, e.g. peat.” 3


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Further research by Shettyet al (2011) demonstrated that Si treatment reduced powdery mildew development by inducing host defense responses in plants.4
It is believed that silicon deposition at sites of fungal pathogen penetration may be a common component of the host-defense response in a variety of plant families. 5

Silicon is also deposited in the cell walls of roots where it acts as a barrier against invasion by parasites and pathogens. 6

For instance, potassium silicate has been shown to act as a preventative against Pythium ultimum. 7



Studies have found that soluble Si polymerizes quickly and that disease development is suppressed only if Si is present in soluble form (Samuels et al., 1991b). To minimize disease development, Si must be provided continuously in the nutrient feed in hydroponic systems.8

Therefore, a continuous source of soluble siliconis very important to combat pathogens. This can be from constant feeding in hydroponics or from retention in the growing medium with soils or soilless mixes.

Optimum ppm of Si in Solution

Liquid Silicon as Si (not SiO2which is 46.743% Si and 53.25% O) is highly beneficial to plants in the range of 25-100 ppm in the nutrient solution. It is not included, at these levels, in any nutrient concentrates. It needs to be added as a separate component by the grower. Because potassium silicate products are highly alkaloid it is recommended to pre-dilute any Si product in eg. 5- 8L’s of water and pH adjust to 5.8- 6.0 before adding to the nutrient tank/reservoir.

We recommend Si use in coco substrate at the lower end of the scale – this being between 25 - 35ppm. In inert medias and water-based systems we recommend Si use at higher rates of between 50 – 75ppm.

Further, it has been shown that Si uptake is aided by the presence of fulvic acid in solution. 9

References

1."Silicon nutrition in plants" Plant Health Care,Inc.: 1. 12. Retrieved 1 July 2011.
2.W. Voogt and C. Sonneveld (2001) Silicon in horticultural crops grown in soilless culture http://dx.doi.org/10.1016/j.bbr.2011.03.031
3. M.H. Adatia and R.T. Besford (1986) The Effects of Silicon on Cucumber Plants Grown in Recirculating Nutrient Solution
4. R.Shetty, B. Jensen, N. P. Shetty, M. Hansen, C. W. Hansen, K. R. Starkey, H. J. L. Jorgensen (2011) Silicon induced resistance against powdery mildew of roses caused by Podosphaera pannosa
5. Pat Brown, Jim Menzies, and David Ehret (1992) Soluble Silicon Sprays Inhibit Powdery Mildew Development on Grape Leaves
6. Taiichiro Hattori, Shinobu Inanaga, Eiichi Tanimoto, Alexander Lux, Miroslava Luxová and Yukihiro Sugimoto (2003) Silicon-Induced Changes in Viscoelastic Properties of Sorghum Root Cell Walls

7. M. Cherif, N. Benhamous, J. G. Menzies, and R.R. Belanger (1992) Silicon induced resistance in cucumber plants against Pythium ultimum
8. Pat Bowen, Jim Menzies, and David Ehret (1992) Soluble Silicon Sprays Inhibit Powdery Mildew Development on Grape Leaves
9. Chen. C and Wang. X (2007) Sorption of Th (IV) to silica as a function of pH, humic/fulvic acid, ionic strength, electrolyte type.

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ADDITIONAL CHELATORS (eg. Amino Acids, Fulvic Acid, Citric Acid etc) IN SOLUTION​

In order to understand the benefits of chelation it is necessary to understand some theory around the subject. So, here we go!

Overview



The use of chelates in hydroponic nutrient formulation is critical for optimized nutrient uptake and transport. This is particularly true for the microelements such as Iron.

Micronutrients are crucial partners (cofactors) of enzymes in every metabolic function of the plant. Respiration, photosynthesis, protein synthesis, energy transfer, cell division and cell elongation are all dependent on an adequate supply of calcium, iron, copper, manganese, magnesium, zinc and other micronutrients.

Many microelements in their basic form are unavailable to the plant. This is largely due to the fact that metal microelements such as iron, copper and zinc are positively charged (cations) while the pores (openings) on the plants' leaves and roots are negatively charged. As a result, the positively charged microelements are repelled by the negatively charged plant pores. When a chelate is added with an element like iron it surrounds the microelement and changes the overall charge into a negative or neutral state allowing the element to enter the plant.

Another reason that some microelements require chelating is due to their stability in solution. For instance, iron (Fe) is a reactive metal. In concentrated solution it will react with other fertilizer elements, particularly phosphorus (P) to form an insoluble compound. It forms the compound iron(III) phosphate which is a solid precipitate in water, so it falls out of solution. To prevent this happening Fe used in fertilizers is usually provided in the chelated form.

A chelate describes a kind of organic chemical complex in which a metal ion is bonded/held so tightly that it cannot be changed through contact with other substances, which could convert it to an insoluble form. For instance, Iron (Fe) is a reactive metal. In concentrated solution it will react with other fertiliser elements, particularly phosphorus (P) to form an insoluble compound. Being insoluble iron cannot stay dissolved, so it falls out of solution. To prevent this happening, the iron (Fe) used in fertilizers is provided in chelated form, typically as the synthetic chelates EDTA, DTPA and/or EDDHA. Other than this, iron (Fe) is relatively unavailable to the plant due to the electrical charge that it carries and its reactions with the chemical composition of the root environment. Chelation, thus, makes iron more bioavailable and prevents reactions with other elements.

The typical chelates used in off the shelf hydroponic formulations are copper (Cu), zinc (Zn), Manganese (Mn), Iron (Fe). Nutrients may also contain chelated calcium (Ca), cobalt (Co), nickel (Ni), and magnesium (Mg).

Not all nutrients can be chelated. The positively charged cations, Iron, zinc, copper, manganese, calcium, potassium and magnesium can be chelated while other nutrients (the negatively charged anions) cannot.

CHELATED MINERALS VERSUS COMPLEXED MINERALS


Some nutrient elements only have the ability to be partially surrounded by a chelator/chelating agent and are referred to as a "complexes", while those that are capable of being completely surrounded are termed chelates.

Confusion and often contradictory information exists surrounding chelated and complexed minerals. Terms such as amino acid complexes, amino acid chelates, polysaccharide complexes, lignosulfonate complexes, and amino proteinates abound. In some cases chelates are referred to as “complexed” or “chelate complexes” while in other cases fertilizer producers wrongly promote complexed minerals as “chelated”. This only serves to confuse further. However, the difference between “chelated” and “complexed” can be understood via some basic principles.

ALL CHELATES ARE COMPLEXES - NOT ALL COMPLEXES ARE CHELATES


In order for a compound to be called a true chelating agent, it must have certain chemical characteristics. This chelating compound must consist of at least two sites capable of donating electrons (coordinate covalent bond) to the metal it chelates. For true chelation to occur the donating atom(s) must also be in a position within the chelating molecule so that a formation of a ring with the metal ion can occur.

The term “complexed” originates from combinations of minerals and organic compounds that do not meet the guidelines of a true chelate.

The key difference between a chelated mineral and complexed mineral is that chelates are relatively more stable under adverse conditions while complexes are less thermostable and release the atom quickly under adverse conditions.

Not all nutrients can be chelated. The positively charged cations iron, zinc, copper, cobalt, nickel, manganese, calcium, magnesium, and potassium can be chelated while the negatively charged anions such as phosphorous cannot.

While the negatively charged anions cannot be chelated they can be complexed via the use of donor atoms such as e.g. oxygen, nitrogen or sulphur. Amino acids such as glycine and/or lysergine are often used to complex the anions. Similarly, fulvic acid can be used to complex the negatively charged anions.

Both chelated and complexed minerals are more bioavailable than non-chelated and non-complexed minerals. This makes the use of additional organic (e.g. amino acid, fulvic acid) and inorganic chelators/complexers (eg, EDTA) highly beneficial in hydroponic solutions.

EDTA, DTPA, EDDHA: Synthetic Chelates



Well-formulated hydroponic nutrients ensure that there is a high level of nutrient availability in the correct forms and ratios. Nutrition that offers a diverse range of bioavailable elements will prove more effective than nutrition that has less diversity, particularly where trace elements (metals) are concerned. For this reason combinations of organic and synthetic chelates are demonstrated to benefit yields. What this means in simple terms is that for optimal nutrient bioavailability and uptake both synthetic and organic chelators should be present in solution.



This said…

The common types of chelates used by most hydro nutrient manufacturers are the synthetic chelates, EDTA (ethylenediaminetetraacetic acid) and to a lesser extent DTPA (Diethylene triamine pentaacetic acid). Chelates such as EDTA and DTPA have a high affinity for e.g. iron and generally form stable complexes with the metal across a pH range from 4 to 7.

Chelates have several points of attachment with which they "grasp" the trace element. EDTA has four connecting points while DTPA has five. Higher numbers of connection points isn’t always an advantage. In some cases the four connection points may hold the element too tightly, while in a different situation these may not hold it tight enough. For this reason, various chelates may prove better than others based on the ion that is chelated and the conditions in which the chelate is present.

For instance, the effectiveness of a chelating agent can depend on pH. For example, EDTA holds iron well up to pH 6, but between pH 6 and pH 8 it progressively loses iron and replaces it with calcium. In the case of iron Fe, EDTA is best suited to slightly lower than neutral pH levels while Fe DTPA is most effective at higher pH values. DTPA is more costly than EDTA and less soluble and is usually found in higher quality fertilizers. DTPA is stable up to a pH of 7.5 while EDTA is stable up to a pH of approximately 6.5.

The most effective of the synthetic chelating agents is ethylenediaminedihydroxy-phenylaceticacid (EDDHA). It is important to note that EDDHA can be formed only with iron and not with other essential microelements such as Cu, Zn, Mn etc. Iron EDDHA is the most stable of all the commonly available iron chelates. This synthetic chelate is held in a bond up to 100 times tighter than DTPA because it has six molecular bonds rather than five bonds. Typically EDDHA is only found in premium fertilizers because of its higher cost. EDDHA is stable up to pH 9.0 (pH range = 4- 9) but is not suitable for foliar applications due to EDDHA only being absorbed through the roots of the plant.

In most cases combinations of chelating agents can improve stability and broaden product effectiveness. That is, a mix/blend of EDTA, DTPA, EDDHA or EDTA and DTPA in formulation best ensures nutrient availability over a wide range of conditions, including those above or below optimal. For this reason, even in hydroponic growing environments where optimum pH (water temperatures etc) can be monitored and maintained there are benefits gained from using a blend of chelated elements in formulation.

Synthetic Chelators and Foliar Feeding



In spraying micro nutrient solutions on the foliage, there might be a danger in using a chelate (such as EDTA) as the chelate may bind to the calcium from the plant tissue (the middle lamella of the cells and the cytoplast membranes contain Ca). Free EDTA might extract the Ca from its sight in the leaf or root membranes and may inflict far more damage than the supply of the metal that is added and is intended to be beneficial. 1


In short, EDTA has a very high affinity for calcium.2As a result, the synthetic chelate will scavenge existing free calcium from the surrounding environment, including cell walls and membranes.

This has the potential to cause the collapse of the cell walls and the leakage of cell contents, leading to phytotoxicity effects.3


For this reason foliar sprays that contain synthetic chelators such as iron EDTA are best avoided. Foliar sprays that contain amino acids or lignosulfonate chelators/complexers, on the other hand, are highly recommended. We’ll talk more about these chelators/complexers shortly.

1. Meeting. Extracted from http://departments.agri.huji.ac.il/fieldcrops/topics_irrigation/uzifert/7thmeet.htm
2. Jeppsen, R. (1999) Advantages of Metal Amino Acid Chelates in Foliar Absorption. Proc. Albion’s International Conference on Plant Nutrition. 16-28.
3. Salisbury, F.B, and C.W. Ross. 1992. Plant Pathology Fourth Edition, (Belmont California: Wadsworth Publishing

Chelate Biochemistry – Organic vs. Synthetic



The permeability of the synthetic chelates has been shown to differ depending upon the size of their molecules. Larger molecules such as EDTA, DTPA and EDDHA will penetrate the root at a slower rate compared to natural chelating agents (Kannan, 1969). However, cell membranes do not have the capacity to absorb synthetic chelates. For the mineral to be absorbed into the cell, chelates must release the mineral outside of the cell. After the mineral has been released it becomes chelated again by organic acids such as citric acid, malonic acid, tartaric acid, and amino acids (e.g. glycine) that occur naturally within the plant. This secondary chelation process then enables nutrients to move freely inside the plant to areas where they are most needed.

Organic chelators differ to synthetic chelators. An organic chelate, unlike a synthetic chelate, can be uptaken, along with the nutrient element and enter the cell of the plant. This offers distinct advantages to nutrient uptake and translocation.

For this reason, the use of organic chelators can prove beneficial to yields.

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ORGANIC CHELATORS


​AMINO ACIDS​

Amino Acids – Overview



Amino acids are the "building blocks" of protein, without which the formation of any living tissue is impossible.

Amino Acids are fundamental ingredients in the process of Protein Synthesis. About 20 important Amino Acids are involved in the process of each function. Studies have shown that Amino Acids can directly or indirectly influence the physiological activities of the plant.

Amino acids can be taken up directly by the roots. 1Additionally, amino acids have been shown in numerous studies to be beneficial in foliar applications.2, 3, 4

Thus, amino acids used in fertilizer and foliar formulations can increase bioavailability and translocation of essential mineral elements.

Only L-Amino Acids have metabolic activity in plants. D - Amino Acids are not recognised by the ‘enzymatic locus’ (any of numerous proteins or conjugated proteins produced by living organisms and functioning as biochemical catalysts) and therefore cannot participate in protein synthesis.
L - Glycine & L - Glutamic Acid are known to be very effective chelating agents.

L – Glycine is now used to chelate minerals. These chelates are known as glycinates, proteinates, and/or amino proteinates.

GLYCINATES/ PROTEINATES

To touch on glycinate/amino proteinate theory.

Glycine is the simplest amino acid with a molecular weight of 75. Chelates of glycine with cations such as iron, zinc, and copper have been extensively studied.
Glycinates typically contain 2 moles of ligand (glycine) and one mole of metal. The plant recognises this molecule as a protein like nitrogen, allowing it to travel to the growing points such as flowers, fruit and berries where is it required.

Micro nutrients in glycinate/proteinate form have a very stable structure. They can be easily absorbed (uptaken) and directly join the biochemical processes in the plant.

BENEFITS



The requirement of amino acids/glycinates in essential quantities is well known to increase yield and overall quality of crops.

For instance, research conducted in USSR by Tronov and co-workers established that glycinates greatly stimulate the growth of plants. The results concluded that zinc glycinate increased the total, stem, root, and foliage weights by 194, 215, 254 and 147%, respectively. Respective effects of manganese glycinate were 79, 108, 110, and 15%.

Research has demonstrated:

1. Glycinates increase the availability of micronutrients compared to common synthetic chelates (e.g. EDTA, DTPA). 5

2. Crops tend to produce higher yields where glycinates are used.

Today, several hydro nutrient and additive manufacturers use glycinates in formulation. Among them – or those that I know of – are Advanced Nutrients, Cyco Platinum series and ourselves (Manic Botanix).

Refs

1. Wolf-Nicolas Fischer, Bruno André, Doris Rentsch, Sylvia Krolkiewicz, Mechthild Tegeder, Kevin Breitkreuz and Wolf B. Frommer (199 Amino acid transport in plants
2. A. Ilhami KÖKSAL, Hatice DUMANOGLU, Nurdan Tuna GÜNES, Mehmet AKTAS (199 The Effects of Different Amino Acid Chelate Foliar Fertilizers on Yield, Fruit Quality, Shoot Growth and Fe, Zn, Cu, Mn Content of Leaves in Williams Pear Cultivar (Pyrus communis L.)
3. Ashmead, H. (1986) World Nutritional Crisis in Agriculture, Foliar Feeding of Plants with Amino Acid Chelates.
4. Jeppsen, R. (1999) Advantages of Metal Amino Acid Chelates in Foliar Absorption. Proc. Albion’s International Conference on Plant Nutrition. 16-28.
5. Y.L Pan and D.W Wang EFFECTS OF IRON ON POTATO GROWTH. Research agronomists, Beijing Academy of Agriculture and Forest Science

Click to expand...

Commercial Humates are sourced from peat and coal formed over thousands or millions of years. They are formed during the coalification process from the degradation of organic material by microbial, chemical and geological action. Put simply, humates are various organic molecules of ancient compost.

‘Fulvic acid’ (FA) is the most important and active humate extract where hydroponics is concerned. It is water-soluble and is chemically active and readily available for uptake by the plant.

Fulvic acid increases the absorption capacity of plant roots, aids the cell building process and enhances the passage of poorly transported ions into and throughout the plant’s cells by acting as an efficient organic chelator/complexing agent in hydroponic solutions.

Fulvic Acid is a short chain molecule, which has a low molecular weight and soluble in both acid and alkali solutions/soils.

Typically, low-molecular-weight substances are 100% permeable to cell membranes, while high molecular-weight substances are not. Fulvic acid has a low molecular weight and therefore is absorbable by living organisms.

Fulvic acid forms four-point bonds with the elements it chelates, but unlike the synthetic agents it can be absorbed into the plant. This adds to the mobility of the nutrients. The nutrients chelated by fulvic acid can move more freely which prevents a number conditions like localized calcium deficiency that can happen due to low mobility of nutrients.

Fulvic acid can be most effective when the growing environment in the root zone is above or below optimal levels. Unlike some synthetic chelating agents fulvic acid retains its effectiveness under a range of conditions.

Studies show that fulvic acid provides for excellent translocation of microelements, such as iron, throughout the plant. When added to an iron chelate in one study it stimulated more growth and better utilization of the iron than with the synthetically chelated iron (Fe EDTA) alone. [SUP]1[/SUP]


In a study published by B.S Rauthan et al (2003) they describe the effects of fulvic acid treatments on the growth and nutrient content of hydroponically grown cucumber plants with:

“After six weeks, the plant tissues were analyzed for their mineral content, and the differences between fulvate treated and control plants were noted:“The application of 100 to 300 ppm of FA yielded highly significant increases (compared to controls) in concentrations of N, P, K, Ca, Mg, Cu, Fe and Zn in shoots and also in the N content of roots. Under these conditions, concentrations of all elements in the shoots, with the exception of Fe, more than doubled. Also, concentrations of N in roots greatly increased.... In just a six week growing cycle as was applied here, we can see that at the optimum concentration, fulvates enable the fullest expression of growth. It is as though fulvates dissolved in solution can “lubricate” and help to intercalate nutrients between plant cell membranes.”[SUP] 2[/SUP]

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In research conducted by Fabrizio Adani et al (199 trialing humates on hydroponically grown tomatoes it was shown that benefits to root and shoot growth were achieved (shoots: 8% and 9% increase over the control and roots: 18% and 16% increase over the control) with leonardite derived humates used at 50ppm. [SUP]3[/SUP]


FA use under conditions where adequate mineral nutrition exists consistently shows stimulation of plant growth when added to hydroponic nutrient solutions. Similar plant growth enhancements have been observed when FAs are applied to the foliage of plants grown in complete nutrient solutions. The degree of stimulation varies depending on the concentration of fulvic acid and on the quality/source of the fulvic acid.[SUP]4[/SUP]

Fulvic Acid Benefits



Enhances cell growth
Increases nutrient uptake
Increases nutrient transportation
Increases silica absorption
Stimulates plant immune system
Stimulates cell division
Enhances the permeability of cell membranes

Fulvic Acid Quality


The key to identifying a quality fulvic acid product is its’ colour. High quality fulvic acid (small molecule size) – i.e. most effective in hydroponic settings - is light yellow. Any product that is brown is far less suitable as it contains higher percentages of the larger molecule sized humic acid (which is not bioavailable to plants). See graph below.

Fulvic Acid - Optimum ppm in Solution
Research has demonstrated that optimum ppm for fulvic acid in hydro settings ranges between 25-300ppm (very dependent on what other chelators etc, etc, etc are present but let’s not get too complex for now). We recommend FA use at between 40-50ppm where standard, chelated hydroponic nutrients are used.

More on humates in hydroponics can be found here.

Refs

1. Chen and Stevenson (1986) Soil organic matter interactions with trace elements).
2. B. S. RAUTHAN and M. SCHNITZER. EFFECTS OF A SOIL FULVIC ACID ON THE GROWTH AND NUTRIENT CONTENT OF CUCUMBER (CUCUMIS SA TIVUS) PLANTS
3. Fabrizio Adani, Pierluigi Genevini, Patrizia Zaccheo & Graziano (199The effect of commercial humic acid on tomato plant growth and mineral nutrition
4. Day, K , Clapp, Charles , Vial, Ryan, Chen, Y , Palazzo, A, Bugbee, B, Tew, J (2003) Plant Growth Stimulation by Fulvic Acids

CITRIC ACID
​

Citric acid is one of the organic acids commonly used as chelating agents and similar to glycinate.

Citric Acid is a sequestering (chelator) and stabilizing agent.

Research has shown that citric acid acts as a more effective chelator in solution than the synthetic chelator EDTA where zinc, copper, and manganese are concerned. Plants grown in EDTA-containing nutrient solutions had lower biomass of roots, and especially shoots, in comparison to the plants grown in solution containing citrate (citrate is the conjugate base of citric acid).[SUP]1 [/SUP]



Citric Acid is a colourless crystalline organic compound and belongs to carboxylic acid family. It exists in all plants (especially in lemons and limes) and in many animal tissues and fluids. In biochemistry, it is involved in important metabolism of almost all living things; the Krebs cycle (also called citric acid cycle or tricarboxylic acid cycle), a part of the process by which living organisms (e.g. plants) convert food to energy. Citric acid works as a preservative (or as an antioxidant) and cleaning agent in nature. It is commercially obtained by fermentation process of glucose with the aid of the mold Aspergillus niger and can be obtained synthetically from acetone or glycerol.

Additionally, citric acid has been shown to have excellent buffering capacity when used/combined with carbonates/bicarbonates.

Citric acid can be easily used as an organic pH down and, therefore, a threefold benefit is obtained. I.e. 1) pH is corrected to optimum range, 2) additional chelation may occur, and 3) buffering (pH stability) is increased when carbonate/bicarbonate and citric acid are in solution.

Warning re using citric acid as pH down and/or for further chelation

Citric acid supports organic life. This means that where beneficial bacteria and fungi are used it aids in micro-proliferation (I.e. acts as food for beneficial bacteria and fungi and thus promotes microflora in solution). However, Citric acid is also one of algae’s favorite things to use as a food source. It not only drops the pH into a range that they enjoy it also is an organic acid, providing a food source of Carbon (C), Hydrogen (H) and Oxygen (O) for the organisms to feed on. Organic acids are a perfect food source to set off a fantastic bloom either by themselves or as a hidden addition in your fertilizer formula. However, it should be used in combination with beneficial bacteria and fungi and the tank/reservoir should be made light proof (algae requires light to grow).

Ref

1. Z. Rengel (2002) CHELATOR EDTA IN NUTRIENT SOLUTION DECREASES GROWTH OF WHEAT.
Conclusion


As chelating agents enable absorption of a variety of nutrients vital for optimum plant growth, growers should work with nutrients and additives that offer a range of chelating compounds. This means, the best working solutions (plant nutrition) will contain a combination of synthetic and organic chelators. This will ensure nutrient availability over a wide range of conditions, including those above or below optimal levels/ranges. Further, the correct use of chelators will ensure optimal uptake and translocation of key mineral nutrients, thereby increasing yields.

This said… A word of warning re chelates and organics in hydroponics.

It is important to note that where hydroponics is concerned, particularly water based systems (e.g. NFT, deep tank, and aeroponics) it’s important not to overdo it with organic matter or additives. In adding too much organics into the hydro system the proliferation of unwanted microbial life may potentially rob oxygen from the root zone creating a situation where roots are suffocated and pathogenic microbe numbers explode under oxygen starved conditions. This situation is far less pronounced in growing systems that utilize organic media (e.g. soil or coco substrate).

Another important factor where chelation is concerned is the simple rule “too much of a good thing is never a good thing” applies and only so much additional chelation will prove beneficial in nutrient uptake and translocation. Chelation is complex science and some caution is, therefore, advised.

Certainly, we highly recommend the use of fulvic acid in solution, along with perhaps some citric acid used for pH down. This said, Manic Botanix nutrients and additives are optimally chelated using synthetic chelates (EDTA, DTPA, EDDHA), amino acids, amino proteinates, citrates, fulvates etc.

That is, if you use our line of nutrients and additives, as advised, optimal chelation is assured.

Anyway, it’s starting to sound like a sales spiel so let’s move on….

Next up, PK additives.....
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Phosphorous and Potassium (PK, Potash etc)
​

PK BENEFITS

• Increased density and weight (Yield)
• Increased essential oil production
• Sweeter tasting fruit
• Increased flowering sites

Potassium and phosphorous are important elements in flowerset. By providing increased amounts of potassium and phosphorous to the plant at the right times it is possible to optimize flower growth and essential oil/resin production.

Potassium

Potassium is used in large quantities by plants to maintain ion balances within the cells, maintain osmotic pressure throughout the plant and activate enzymes; it is also required for protein synthesis. Potassium is the most important element in flower and fruit development.

Phosphorous

Phosphorus plays an essential role in photosynthesis; it helps with the formation of oils and helps convert light energy into chemical energy, resulting in optimum plant maturation and development. Phosphorous effects rapid growth and encourages bloom.

This said…


PK Additives and The High P Myth - The Overuse of Phosphorous in Hydroponics


It has been shown that phosphorous (P) is possibly overused by many hydroponic growers. Tissue tests conducted in 2003 by Advanced Nutrients through BC Research Inc on numerous cannabis strains demonstrated that cannabis plants require far less P than is present in many hydroponic nutrient formulations and additives. The tissue tests also demonstrated that N, Ca and K are required at far higher levels than P and P, while required at somewhat higher levels in bloom than grow (as is shown in numerous studies), is required at far lower levels than would be expected. Another surprising outcome was N requirements in flower (re cannabis) were higher than previously believed. These findings contradicted conventional beliefs among hydro industry professionals and others that high levels of phosphorous are required to achieve optimal flowerset in hydroponic settings (among other things). [SUP]1[/SUP]


In recent trials conducted by several US based medical growers, it was shown that optimal P levels in DTW/RTW coco were at approximately 60ppm during mid to late bloom. This figure was shown to be similar in soils – with as low as 40ppm of P in soil producing extremely good results.

While these trials lacked what would be considered standard scientific qualitative checks and measures (eg. no control was used to measure outcomes with higher and lower ranges of P in side-by-side trials) what became apparent over several months and several crop cycles was, 1) low P in solution (approx 20-25ppm) helped to reduce stretch and shorten internode gaps (setting up better plant structure) during the first weeks of the 12/12 flower cycle, 2) no yield benefits were obtained above 60ppm P and 3) resin production was optimal at 60ppm of P and seemed unaffected at even lower levels in both soil and coco (<40ppm). [SUP]2[/SUP]


Similar findings with tomato crops grown in soilless culture support these findings.

According to Spensley et al.,[SUP]3[/SUP] a typical nutrient solution for tomato production has the following composition: N: 150-200 ppm, P: 30- 40 ppm, K: 200-300 ppm, Mg: 40-50 ppm, Ca: 150-200 ppm and Fe: 5 ppm. Moreover, Winsor and Massey noticed that yield of tomato fruit was reduced significantly by low potassium concentration. [SUP]4[/SUP]


What these findings suggests is that many manufacturers of hydroponic nutrients and additives have their NPK profiles wrong and that an optimized PK additive should contain higher levels of K to P than is typically found in the vast majority of Potash products.

[HR][/HR]Coco Veg and Bloom Formula’s (Based on the Research of Yosemite Sam, IC Mag)


Coco Veg
150-24-150-166-70-25
N-P-K-Ca-Mg-Si

Coco Bloom
110-60-175-160-65-25
N-P-K-Ca-Mg-Si

Keep in mind that coco substrate requires higher levels of Ca and Mg than inert mediums so these numbers would differ from a formula developed for water based systems and/or inert medias such as rockwool. Factors such as genetics, crop type, growing method etc will also play an important role in an optimized nutrient regime.


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Evaluation of P in Hydroponic Working Solutions


We evaluated several off the shelf hydroponic nutrients at the same dilution rates to establish how many ppm of P (phosphorous) would be in working solution by average. The aim of the analysis was to establish roughly what ppm of P would be in working solution across a broad range of ECs as different nutrient brands are more concentrated than others and this reflects in EC at equivalent dilution rates. In all cases ppm of P equaled or exceeded 60ppm. The ppm data was calculated from lab analysis of concentrate formulas once diluted.

Samples (elemental P and not P as P[SUB]2[/SUB]O[SUB]5[/SUB])


AN Sensi Bloom 4ml/L = 81ppm P
AN Connoisseur Bloom 4ml/L = 90ppm P
H and G Coco 4ml/L = 60ppm P
Canna Coco 4ml/L = 64ppm
Canna Aqua Flores 4ml/L = 60.8ppm P

When considering that many hydroponic growers use further P through the use of P and K additives during flowerset this too needs to be factored into the P equation. For instance, with a product that contained PK 13- 14 %w/w listed as P[SUB]2[/SUB]O[SUB]5[/SUB] and K[SUB]2[/SUB]O with a specific gravity of 1.25, used at 1.5mL/L this would equate to an additional 104.8ppm of P in working solution. This would mean that if you were using eg. Canna Coco nutrient at 4ml/L and our example PK 13-14 at 1.5ml/L there would be approximately 168ppm of P in solution – or approximately three times the required levels of P that are optimal for coco substrate growing.

The Problem with Excessive Phosphorous in Solution

High levels of a particular nutrient can interfere with the availability and uptake of other nutrients. The nutrients which interfere with one another are referred to as antagonistic.

Excessive phosphorus will reduce the availability of iron, calcium, potassium, nitrogen, copper, and zinc. This is particularly true of the microelements iron, and zinc.

What this means is that the overuse of phosphorous in solution will starve out other important nutrients that are required for healthy growth/optimal yields.

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Iron​

Iron has special importance in biological redox systems involved with chlorophyll formation and protein synthesis.

Iron is essential in the enzyme system in plant metabolism (photosynthesis and respiration).

The enzymes involved include catalase, peroxidase, cytochrome oxidase, and other cytochromes. Fe is part of protein ferredoxin and is required in nitrate and sulfate reductions.

Fe is essential in the synthesis and maintenance of chlorophyll in plants and has been strongly associated with protein metabolism.

&#8203;Zinc​

Zinc is an integral component of many enzymes. Zinc plays a major role in protein synthesis and is involved with the carbohydrate metabolic processes. Zinc is also required for maintaining integrity of biomembranes and protecting membranes from oxidative damage from toxic oxygen radicals.

Zinc is important in the formation of the growth hormone auxin. Auxin is produced by shoot tips, and controls cell division, leaf and shoot growth and fruit development.

Zinc is also needed by leaf cells to form the green leaf pigment chlorophyll. Chlorophyll is needed for leaves to make sugars (photosynthesis).

Trace elements such as zinc are only needed in small quantities, but when they are in short supply, serious problems can occur.

Severely affected plants develop small, misshapen fruits of poor quality. This is due to poor cell division early in fruit development, and fruits not getting enough sugars from photosynthesis.



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Other than this…

Phosphorous in Combustible Crops



Burning phosphorus with sufficient oxygen results in the formation of phosphorus pentoxide (P[SUB]4[/SUB]O[SUB]10 [/SUB]but often simplified to P[SUB]2[/SUB]O[SUB]5 [/SUB]due to this being the simplest molecular breakdown of P pentoxide).

Phosphorus pentoxide is an irritant to the skin, mucous membranes, and respiratory tract/system (lungs etc) even at concentrations as low as 1 mg/m[SUP]3[/SUP]. What this means in simple terms is that if phosphorous is present in a combustible crop (after drying and curing) the produce when ingested, via inhalation, will be harsh and chemically tasting. This may have health implications on the end user if they are ingesting phosphorus pentoxide on a regular basis.

High End PK Additive Formulations



It’s worth noting that sulfur (S) as well as magnesium (Mg) and ammonium nitrogen (NH[SUB]4[/SUB]N) are also in demand by the plant during flowering.

In short…


Magnesium activates the plant enzymes needed for growth. Additional Mg in flowerset can prove beneficial to yields.

Low levels of ammonium nitrogen (NH[SUB]4[/SUB]N) can be beneficial for increasing flowering sites and yield weights in some flowering/fruiting crops (eg. tomatoes).

Sulfur plays a key role in plant metabolism and is a molecular building block for a number of proteins, hormones and vitamins. Rapidly growing plants can gain from additional S in nutrient and additive formulations.

For this reason a premium/optimal Potash product should contain Mg, NH[SUB]4[/SUB]N, and S, along with high levels of potassium and much lower levels of phosphorous.

Refs

1. Advanced Nutrients. The Great Phosphorous Myth Exposed.
2. IC Mag. The myth, of the high P myth. Trials conducted by Yosemite Sam, Spurr, and others. http://www.icmag.com/ic/showthread.php?t=191007
3. Spensley K., Winsor W., Cooper J., Nutrient film technique-crop production in flowing nutrient solution, Outlook of Agriculture (197
4. Majid FANDI*, Jalal MUHTASEB**, and Munir HUSSEIN (2010) EFFECT OF N, P, K CONCENTRATIONS ON YIELD AND FRUIT QUALITY OF TOMATO (SOLANUM LYCOPERSICUM L.) IN TUFF CULTURE

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Triacontanol (TRIA) has been realized as a potent plant growth promoting substance for a number of agricultural and horticultural crops.[SUP]1 [/SUP]

Triacontanol can be applied to the plant during any stage of growth, from seed or cutting to harvest day. Triacontanol is non-toxic to plants, animals, and humans at all levels within reason and is safe to use on consumable crops. Triacontanol can be co-applied with Auxins, Gibberellins, Cytokinins, and Brassinosteroids.

The Science

1-Triacontanol is a fatty alcohol of the general formula C[SUB]30[/SUB]H[SUB]62[/SUB]O, also known as melissyl alcohol or myricyl alcohol. It is found in plant cuticle waxes and in beeswax. Triacontanol is a plant growth regulator in the subclass of “growth stimulant” shown to increase yields in many plants, most notably C3 plants. [SUP]2[/SUP]
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C3 plants include wheat, rice, daisies, petunias, roses, fruit trees, conifers and cannabis. ALL C3 plants can benefit from TRIA applications, regardless of growing style or environmental conditions, although different types of C3 plants will have different optimum dosage rates of TRIA. Many investigators have shown that TRIA affects several basic metabolic processes including photosynthesis, nutrient uptake, and enzyme activity. [SUP]3[/SUP]
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Triacontanol has shown the ability to (somewhat) alleviate negative effects of stress induced by salinity toxicity, cold temperatures, and CO2 and light deprivation.

Applications of Triacontanol have been shown to increase both water and nutrient uptake, CO2 fixation, endogenous levels of Adenosine triphosphate (essential units of energy for all life), Rubisco Activase (often the limiting factor in C3 photosynthesis), chlorophyll a & b content and increased essential oil content of plants (not relative to trichome density).

Triacontanol applied to tomato plants as a foliar spray caused a significant increase in total yield and yield per plant. When triacontantol was added to the growth medium, only a temporary increase in yield and number of fruits was observed.
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TRIA applied as a foliar spray to tomato plants increased the total yield by 12% and the number of fruits from all plants by 25% as compared to the control group. However, TRIA added to the growth medium increased total yield by only 6% and the number of fruits by 3%. [SUP]4[/SUP]
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In research conducted by D. Skogen, et al (1981) two cultivars of Chrysanthemum morifolium, ‘Golden Horim’ and ‘Golden Miquel’, were cultivated in nutrient solution containing the growth regulator triacontanol. The dry weight of the whole plant and the shoot from both cultivars increased. The number of ‘inflorescences’ (a group of flowers growing from a common stem, often in a characteristic arrangement. Also called flower cluster) per plant and the number of flowers per inflorescence also increased in response to triacontanol treatment, which in turn enhanced the quality of flowers. The number of flowers of superior quality was more than doubled.[SUP]5[/SUP]

While research conducted by N. K. Srivastava et al (1989) on Opium Poppies treated with Triacontanol via foliar application demonstrated:

“Plant height, capsule number and weight, morphine content, CO 2
exchange rate, total chlorophyll and fresh and dry weight of the shoot were significantly maximum at 0 .01 mg/1 Tria. At the highest concentration (4mg/1) total chlorophyll, CO2 exchange rate and plant height were significantly inhibited. Thebaine (a crystalline, poisonous, and anodyne alkaloid from opium) and codeine contents remained unaffected at all the concentrations. The concentration of Fe, Mn, Cu in shoots were maximum at .01 and Zn at 0 .1 mg/l Tria. Increase in shoot weight, leaf area ratio and chlorophyll content were significantly correlated with morphine content…

(Concluding)…

The present investigation reveals that Tria at concentrations upto 0 .1 mg/1 significantly enhances various processes related to production physiology
in opium poppy . The primary processes in turn contribute significantly in
increasing overall yield of straw, capsule and morphine content .” [SUP]6[/SUP]

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In trials conducted on essential oil bearing plants (mint) by M. Naeem et al (2011) findings showed:

“Out of a large number of essential oil bearing plants, mint (Mentha arvensis L.) constitutes the most important source of therapeutic agents used in the alternative systems of medicine. The mint plant has marvelous medicinal properties. In view of enhancing growth, yield and quality of this medicinally important plant, a pot experiment was conducted according to simple randomized block design. The experiment was aimed at studying the effect of four concentrations of TRIA (10-0, 10-7, 10-6 and 10-5 M) on the performance of mint with regard to growth and other physiological attributes, crop yield and quality attributes and the yield and contents of active constituents of the plant. The growth and other physiological parameters as well as yield and quality attributes were studied at 100 and 120 DAP. The foliar application of TRIA at 10-6 M concentration significantly enhanced most of the growth and other physiological attributes, crop herbage yield and the yield and content of active constituents (menthol, L-methone, isomenthone and menthyl acetate) of mint at both the stages. However, the next higher concentration of TRIA (10-5 M) exhibited slightly negative effect and did not further increase the values of the attributes studied, but it proved significantly better than the control. Application of TRIA significantly enhanced the yield and content of all the active constituents… “ [SUP]7[/SUP]
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The only known negative side effect from TRIA other than over application is that it can suppress certain defence mechanisms that help ward off insect infestation. TRIA suppresses the production of certain proteinase inhibitors that are a main defensive mechanism against insect infestation. More often than not this effect is not noticeable, but we do not suggest applying TRIA to any plants that are having issues with an insect infestation.

Further to this, several factors can reduce the effectiveness of TRIA as a growth stimulator. Inhibitory compounds, which have been reviewed in detail, include long chain alcohols, morpholine (commonly found in distilled water from steam condensates), and phthalate esters, particularly from polyvinyl chloride tubing.[SUP]8[/SUP]
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When applying Triacontanol to the plant, it’s best to apply it to the foliage (as is shown in studies). Foliar applications of TRIA consistently have better improvements in growth and allow less use than applications of TRIA to the rhizosphere. There are several TRIA product patents claiming that adding cations with a valence of >1 (most notably calcium) improves the growth enhancing capabilities of TRIA. At least one of the mentioned patents says applications of the same cations to the rhizosphere before application had the same effect. However, to date, there has been no legitimate scientific experimentation to prove or disprove the possible TRIA/Ca synergy.

The best time to apply any products to the foliage of your plant is the beginning of the night cycle for your plants to allow minimum evaporation of your foliar spray. If growing indoors be sure to turn all fans off for a minimum of 6 hours, preferably until all leaves are dry. If growing outdoors try to apply spray on a night where there will be little wind. The higher the humidity the longer the spray will stay on the leaves and the better the penetration through the leaf cuticles will be.

References
1. M. Naeem, M. Masroor A. Khan, Moinuddin, Mohd. Idrees, Tariq Aftab (2011) Triacontanol-mediated regulation of growth and other physiological attributes, active constituents and yield of Mentha arvensis L.
2. B. Eriksen, M. K. Haugstad and S. Nilsen (1982) Yield of tomato and maize in response to foliar and root applications of triacontanol
3. Stanley Ries (1990) Triacontanol and Its Second Messenger9-b-L (+)-Adenosine as Plant Growth Substances
4. A. B. Eriksen, M. K. Haugstad and S. Nilsen (1982) Yield of tomato and maize in response to foliar and root applications of triacontanol
5. D. Skogen, A.B. Eriksen, S. Nilsen (1981) Effect of triacontanol on production and quality of flowers of Chrysanthemum morifolium Ramat
6. N .K. SRIVASTAVA** & SRIKANT SHARMA (1989) Effect of Triacontanol on photosynthesis, alkaloid content and growth in opium poppy (Papaver Somniferum L)
7. Naeem, M.; Khan, M; Moinuddin; Idrees, Mohd; Aftab, Tariq (2011) Triacontanol-mediated regulation of growth and other physiological attributes, active constituents and yield of Mentha arvensis L.

8. Ries SK (1985) Regulation of plant growth with triacontanol.
9. Stanley Ries (1990) Triacontanol and Its Second Messenger 9-b-L (+)-Adenosine as Plant Growth Substances
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AUXINS AND CYTOKININS
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Hormones are vital to plant growth and lacking them plants would be mostly a mass of undifferentiated cells. Because hormones stimulate or inhibit plant growth, many botanists also refer to them as plant growth regulators (PGRs). Botanists recognize six major groups of hormones: auxins, gibberellins, ethylene, cytokinins, abscisic acid, and brassinosteroids.

While all 6 groups of hormones are critical to plant growth, for reasons of simplification in this discussion, the two most important hormones, where indoor hydroponic gardening is concerned, are auxins and cytokinins.

Auxins
The term auxin is derived from the Greek word “auxein” which means to grow. Compounds are generally considered auxins if they can be characterized by their ability to induce cell elongation in stems and otherwise resemble indoleacetic acid (the first auxin isolated) in physiological activity. Auxins usually affect other processes in addition to cell elongation of stem cells but this characteristic is considered critical of all auxins and thus "helps" define the hormone (Arteca, 1996; Mauseth, 1991; Raven, 1992; Salisbury and Ross, 1992). Auxins also promote adventourous root initiation and growth and are shown to increase apical dominance/stretch.

Auxins cause several responses in plants:

• Bending toward a light source (phototropism)
• Downward root growth in response to gravity (geotropism)
• Stimulates cell elongation
• Promotes (via ethylene production) femaleness in dioecious flowers
• Stimulates growth of flower parts Fruit set and growth
• Promotes formation of adventitious roots
• Can induce fruit setting and growth in some plants

Cytokinins

Cytokinins are found in both plants and animals. They stimulate cell division and, in contrast to auxins, are shown to reduce apical dominance (stretch), among other things.

Cytokinin Functions
A list of some of the known physiological effects caused by cytokinins are listed below. The response will vary depending on the type of cytokinin and plant species (Davies, 1995; Mauseth, 1991; Raven, 1992; Salisbury and Ross, 1992).

• Stimulates cell division.
• Stimulates morphogenesis (shoot initiation/bud formation) in tissue culture.
• Stimulates the growth of lateral buds-release of apical dominance.
• Stimulates leaf expansion resulting from cell enlargement.
• May enhance stomatal opening in some species.
• Promotes the conversion of etioplasts into chloroplasts via stimulation of chlorophyll synthesis.

The Role of Auxins and Cytokinins in Plant Growth

Auxins and cytokinins are interrelated in terms of plant growth. By artificially shifting the balance of these hormones we are able to manipulate what the plant does. In simple terms, Introduce a cytokinin containing product (higher cytokinins to auxin ratio) the result will be more foliage growth and reduced apical dominance (stretch), while the Introduction of an auxin product (higher auxin to cytokinin ratio) will result in more cell elongation, apical dominance/stretch, and adventurous root growth.

For now let’s talk about auxins and their use in root and growth stimulants. We’ll cover more on cytokinins shortly.

Auxins

Auxin transport is required for important growth and developmental processes in plants, including gravity response and lateral root growth. Thus, one of the key roles of auxins is that they stimulate adventourous root growth.[SUP]1[/SUP]
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Products such as Canna Rhizotonic, House and Garden Algen etc thus contain auxins. Additionally, auxins (e.g. IBA, IAA, NAA) are the active in most rooting compounds in which cuttings are dipped during propagation (cloning). For instance, Clonex and other rooting compounds usually contain IBA (Indole-3-butyric acid) or NAA, or a combination of both.

Auxin containing products are ideal for early growth (when the plant is first introduced into the system) to ensure adventurous root development. This helps the plant to settle in early and aids in mineral element uptake. Through the right balance of auxins and the right form of auxins, along with other beneficial elements (e.g. kelp, triacontanol, vitamins, and cross-linked polyacrylate polymers) a product such as Manix Roots Xtreme can greatly enhance early growth rates and reduce stress when cuttings are first placed into high intensity lighting situations.

Ref:

1) Chambers. Science and Technology Dictionary. ISBN 1-85296-10-3

Cytokinins

Cytokinins are essential for the growth of intact and isolated plant organs and tissues. Their involvement in the processes of cell division, mobilization of inorganic and organic nutrients and senescence are well documented. The high levels of cytokinins in developing seeds and fruits are indicative of a function of this type of hormone during periods of active cell division.[SUP]1[/SUP]
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It is shown that sex expression in plants is regulated by gibberellins which are synthesized in leaves and cause male sex expression and by cytokinins which are synthesized in the roots and cause female sex expression.[SUP]2[/SUP]
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When the shoots of young hemp (Cannabis sativaL.) plants were cut off the roots, cultured as cuttings, and regenerating (adventitious) roots were removed as soon as appearing, ca. 80–90% of the plants became male (had staminate flowers) whereas if the roots were allowed to develop a similar percentage became female (pistillate flowers). Treatment of de-rooted cuttings with the synthetic cytokinin 6-benzylaminopurine (15 mg/l) restored the percent of female plants to ca. 80. It is suggested that the root system plays an essential role in sex expression in hemp and that this role is related to cytokinin synthesis in the root.[SUP]3[/SUP]

Cytokinins are essential for flower bud development in grapevines (Lavee 1989) and, the cytokinin concentration in phloem is critical to the induction of flowering of the long-day-plant Chenopodium murale (Nettle-leaved Goosefoot).[SUP]4[/SUP]
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Cytokinins are known to overcome apical dominance (stretch) by stimulating the growth of lateral and axillary buds, respectively (Faust 1989; Helgeson 1968; Leopold and Kriedemann 1975).

As short, squat plants, with close internodes are ideal in indoor growing situations (under lights) the use of cytokinins can prove beneficial in encouraging these traits. Further, as numerous studies have shown, the use of cytokinins stimulate cell division, resulting in higher yields.


The Synthetic Cytokinins – BAP, BA

6-Benzylaminopurine, benzyladenine or BAP is a first-generation synthetic cytokinin that elicits plant growth and development responses, setting blossoms and stimulating fruit richness by stimulating cell division.

Research by Paul T. Wismer et al (1995) showed that when Benzyladenine (BA), was used on apples in comparative trials against NAA, carbaryl, and daminozide, BA produced the best results of all the chemicals with increases in fruit size and weight. It was shown that BA increased the rate of cell layer formation in the fruit cortex, indicating that BA stimulated cortical cell division. The number of cells in an apple may be increased in three ways: 1) by more rapid cell division during the cell-division phase of fruit growth, 2) by extending cell division for a longer period than normal, or 3) by some combination of these two phenomena.[SUP]5[/SUP]
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Research by Kevin E. Crosby et al (1981) on soybean notes,

“Of the five cytokinins tested at 0.1 mm concentration in 1977, BA was found to be most effective in promoting fruit-set.”

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In the same research it was shown that BA increased soybean yields, hypothesizing that:

“BA may act by increasing the ability of the treated fruits to competitively mobilize nutrients. Shortages of assimilates, particularly during the period of fruit-set, may intensify nutrient competition between developing fruits and vegetative organs. This might cause abscission of young fruits deficient in substrate or hormones. Cytokinins are known to attract nutrients to sites of application.” [SUP]6[/SUP]

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BA to Reduce Apical Dominance (Stretch)



Apical dominance (stretch) is caused by the apical bud (top shoot of the plant) producing IAA (auxin) in abundance. Thus, a primary factor in the mechanism of apical dominance is a hormonal interaction between auxins and cytokinins. In simple terms apical dominance is antagonized by BA (cytokinin) which interferes with the abundance of IAA by increasing the naturally occurring cytokinin to auxin ratio. [SUP]7[/SUP]
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In research conducted by Nii et al (1986) 6-benzylamino purine (BA), was used as a foliar spray in orchard and potted plants to study its effect on branching and leaf development in peach trees, and to analyze the factors influencing its effectiveness, it was shown:

1) During the expansion of cells in peach leaves sprayed with BA, the number of chloroplasts per cell and the amount of chloroplast DNA increased with
the cell size, after this phase the chloroplast number per cell continued to increase, and 2) BA-treated trees were more compact than non BA treated trees and many branches of BA-treated shoots contributed to a less open growth habit.[SUP]8[/SUP]
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Similarly, in research conducted by Samanthi P. Herath et al (2004) on Hibiscus cannabinus L (Kenaf) it was shown that in BA treated plants supernumerary vegetative shoot buds were observed in and near the axillary buds. In the control plants (non BA treated plants) neither axillary nor adventitious buds developed. The results suggested that the treatment with BA reprogrammed the developmental fate of a large number of cells in the shoot apex of kenaf. Further, it reconfirmed the ability of BA to overcome the apical dominance of shoots.[SUP]9[/SUP]

Conclusion and Discussion

The correct useage of auxins and cytokinins used at varying ratios and times during the grow and flowering cycles can greatly stimulate desirable effects in plants. Auxins used in early grow, promote adventurous rooting, help relieve plant stress, and promote plant health/vigour.

Cytokinins, used during early bloom, can greatly aid in setting up a better plant structure (short squat plants with close internodes), and used thereafter can stimulate cell division (growth rates) and as a result increase yields.

Which brings us to our next point. Kelps as biostimulants – or as the case may be, more on auxins and cytokinins and other…. (next page)

References:

1. KEVIN E. CROSBY, LouIs H. AUNG, AND GLENN R. Buss (1981) Influence of 6-Benzylaminopurine on Fruit-Set and Seed Development in Two Soybean, Glycine max (L.) Merr. Genotypes'
2. M. Kh. Chailakhyan (1979) Genetic and Hormonal Regulation of Growth, Flowering, and Sex Expression In Plants
3. M. Kh. Chailakhyan and V. N. Khryanin (197 The role of roots in sex expression in hemp plants
4. T. Bubán (2000) The use of benzyladenine in orchard fruit growing: a mini review.
5. Paul T. Wismer and J.T.A. Proctor (1995) Benzyladenine Affects Cell Division and Cell Size during Apple Fruit Thinning
6. KEVIN E. CROSBY, LouIs H. AUNG, AND GLENN R. Buss (1980) Influence of 6 enzylaminopurine on Fruit-Set and Seed Development in Two Soybean, Glycine max (L.) Merr. Genotypes'
7. Gary J. Keever and Thomas J. Brass Presence of Offsets Reduces Hosta's Response to Benzyladenine http://www.ag.auburn.edu/hort/landscape/gary7.html
8. N. Nii, T. Kuroiwa (1986) Morphological and anatomical development of peach shoot and leaves as influenced by 6-benzylamino purine
9. Samanthi P. Herath, Takayuki Suzuki and Kazumi Hattori (2004) Light and Scanning Electron Microscopic Analysis of Benzyl Adenine Induced Multiple Shoot Regeneration in Kenaf (Hibiscus cannabinus L.)

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It is well documented that commercial seaweed preparations improve plant growth. Many of these effects have been attributed to the presence of growth substances, particularly the cytokinins, which are known to occur at relatively high levels in various seaweeds and commercial seaweed preparations.[SUP] 1[/SUP] Although, various kelp types will contain varying levels of auxin to cytokinin ratios. In some cases a certain kelp type will have high levels of cytokinins to much lower levels of auxins while in other instances the opposite will apply.

For instance, the addition of low concentrations of commercial kelp extract (Ecklonia maxima: Kelpak[SUP]®[/SUP]) in addition to fertiliser has proven to be beneficial in agriculture. It triggers rooting in field crops, increases yields and has other useful effects, such as parasite reduction. Its efficacy has been attributed to the fact that Kelpak[SUP]®[/SUP] is produced by a cold process, and has a high auxin/low cytokinin ratio.[SUP]2[/SUP]
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THE SCIENCE

Seaweed and seaweed-derived products have been widely used as amendments in crop production systems due to the presence of a number of plant growth stimulating compounds.[SUP]3[/SUP]
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Various kelp types are shown to contain carbohydrates, minerals, and trace elements, amino acids, complex polysaccharides, betaines, and growth hormones such as cytokinins and auxins at different levels. [SUP]4 [/SUP]
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In addition, kelp acts as a mild organic chelator of key mineral elements.

It has been estimated that there are about 9,000 species of macroalgae (kelp) broadly classified into three main groups. Brown seaweeds are the second most abundant group comprising about 2,000 species which reach their maximum biomass levels on the rocky shores of the temperate zones. They are the type most commonly used in agriculture. Among them Ascophyllum nodosum is the most widely researched. Ascophyllum nodosum (rockweed) is a brown seaweed known to grow abundantly in temperate countries such as Canada, France, Iceland, Ireland, Norway, and the United Kingdom.

Below is an analysis of an Ascophyllum nodosum kelp product that is produced in Canada.

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Table 1 Composition of Acadian marine plant extract powder 1–1–17
from Ascophyllum nodosum kelp
Physical data
Appearance Brownish-black crystals
Odor Marine color
Solubility in water 100%
pH 10.0–10.5
Typical analysis

Maximum moisture 6.5%
Organic matter 45–55%
Ash (Minerals) 45–55%
Total nitrogen (N) 0.8–1.5%
Available phosphoric acid (P2O5) 1–2%
Soluble potash (K2O) 17–22%
Sulfur (S) 1–2%
Magnesium (Mg) 0.2–0.5%
Calcium (Ca) 0.3–0.6%
Sodium (Na) 3–5%
Boron (B) 75–150 ppm
Iron (Fe) 75–250 ppm
Manganese (Mn) 5–20 ppm
Copper (Cu) 1–5 ppm
Zinc (Zn) 25–50 ppm
Carbohydrates Alginic acid, mannitol, laminarin
Amino acids (total 4.4%)
Alanine 0.32%
Arginine 0.04%
Aspartic acid 0.62%
Cystine 0.01%
Glutamic acid 0.93%
Glycine 0.29%
Histidine 0.08%
Isoleucine 0.26%
Leucine 0.41%
Lysine 0.16%
Methionine 0.11%
Phenylalanine 0.25%
Proline 0.28%
Serine 0.08%
Threonine 0.04%
Tyrosine 0.17%
Valine 0.28%
Tryptophan 0.07%

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Ascophyllum nodosum extracts contain various betaines and betaine-like compounds (Blunden and others 1986). In plants, betaines serve as a compatible solute that alleviates osmotic stress induced by salinity and drought stress; however, other roles have also been suggested (Blunden and Gordon 1986), such as enhancing leaf chlorophyll content of plants following their treatment with seaweed extracts (Blunden and others 1997). This increase in chlorophyll content may be due to a decrease in chlorophyll degradation (Whapham and others 1993). Yield enhancement effects due to improved chlorophyll content in leaves of various crop plants have been attributed to the betaines present in the seaweed (Genard and others 1991; Whapham and others 1993; Blunden and others 1997).

Numerous studies have revealed a wide range of beneficial effects of seaweed extract applications on plants, such as early seed germination and establishment, improved crop performance and yield, elevated resistance to biotic and abiotic stress, and enhanced postharvest shelf-life of perishable products (Beckett and van Staden 1989, Hankins and Hockey 1990; Blunden 1991; Norrie and Keathley 2006).

Seaweed extract increased fruit yield when sprayed on tomato plants during the vegetative stage, producing large sized fruits (30% increase in fresh fruit weight over the controls) with superior quality. [SUP]5[/SUP]
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In research conducted by C. M. Steveni et al (1992) on hydroponically grown barley it was shown that two treatments of Ascophyllum nodosum (Maxi Crop) incorporated either into the hydroponic solution or sprayed onto the plants at rates of 1ml per 3 litres resulted in faster growing plants with significant yield increases against controls not treated with Ascophyllum nodosum.

The research noting:

“ Spring barley (Hordeum vulgare cv. Triumph) was grown hydroponically over a 6-week period. Two treatments were incorporated either into the hydroponic solution or sprayed onto the plants at rates of 1 ml per 3 litres. The treatments applied were: (i) a seaweed concentrate prepared from Ascophyllum nodosum (L.) Le Jolis (marketed as Maxicrop Triple), (ii) a 'Trace element' treatment incorporating the micro and macro nutrients added to the seaweed extract base to produce the formulated product Maxicrop Triple and (iii) a control treatment. Irrespective of the mode of application, plants treated with Maxicrop Triple grew faster than plants under either of the two other treatments. Elevated growth rates were also found for the 'Trace element' treated plants when incorporated into the hydroponic solution.

At the final harvest, plants with Maxicrop Triple incorporated into the hydroponic solution showed increases from 56-63% over the control treatment for the growth characteristics measured. 'Trace element'-treated plants produced increases of between 25-45 %. When the treatments were sprayed the effect was less pronounced. Maxicrop Triple increased growth characters by 35-38% and the 'trace element' treatment gave increases in the range of 2-13%.” [SUP]6[/SUP]
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Seaweed components such as macro- and microelement nutrients, amino acids, vitamins, cytokinins, auxins, and abscisic acid (ABA)-like growth substances affect cellular metabolism in treated plants leading to enhanced growth and crop yield (Crouch and others 1992; Crouch and van Staden 1993a; Reitz and Trumble 1996; Durand and others 2003; Stirk and others 2003). Seaweed extracts are bioactive at low concentrations (diluted as 1:1000 or more) (Crouch and van Staden1993a). Although many of the various chemical components of seaweed extracts and their modes of action remain unknown, it is plausible that these components exhibit synergistic activity (Fornes and others 2002; Vernieri and others 2005).

Seaweed extracts have been shown to enhance plant defense against pest and diseases (Allen and others 2001). Besides influencing the physiology and metabolism of plants, seaweed products promote plant health by affecting the rhizosphere microflora. For this reason, kelp is shown to aid beneficial microbe colonization in hydroponic systems and soils.

Seaweeds and seaweed products are shown to enhance plant chlorophyll content (Blunden and others 1997). Application of a low concentration of Ascophyllum nodosum extract to soil or on foliage of tomatoes produced leaves with higher chlorophyll content than those of untreated controls. [SUP]7[/SUP]
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In research conducted by Stirk et al (2003) thirty-one seaweeds were tested for cytokinins. Findings showed:

“The cytokinin profiles were similar in all the macroalgae regardless of their taxonomy and growing locality. The main type of isoprenoid cytokinins present were zeatins with cis forms being more common than trans forms and isopentenyladenine (iP) derivatives. Only a few dihydrozeatin-type cytokinins were detected at very low levels in only nine species. Aromatic cytokinins were also present but at lower levels and were represented by benzyladenine (BA) and ortho- and meta-topolin derivatives. The topolins were present in greater diversity and concentrations than BA. For all the cytokinin types, the free bases, O-glucosides and nucleotides were the most common with no N-glucosides being detected and ribosides present at very low levels…”[SUP]8[/SUP]
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In later work, Stirk et al (2004) tested two seaweed concentrates of Ecklonia maxima and Macrocystis pyrifera. Both fresh and stored samples of the two seaweed concentrates were analysed for their endogenous cytokinin and auxin content.

Eighteen and nineteen different cytokinins were detected, respectively, in the two concentrates, with trans-zeatin-O-glucoside being the main cytokinin present.

Auxin-like activity was also detected in both concentrates with the E. maxima derived concentrate having higher biological activity, equivalent to 10[SUP]&#8722;5[/SUP]–10[SUP]&#8722;4[/SUP] M indole-butyric acid. Indole-3-acetic acid was the main auxin in both seaweed concentrates.[SUP]9 [/SUP]
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In research conducted by J. van Staden et al, it was shown that the seaweed concentrate Kelpak, made from Ecklonia maxima applied as a foliar spray or a root drench at transplanting, improved both the vegetative and reproductive growth of marigolds. Of particular significance is that the overall production of seeds (fruits) was increased by as much as 50 percent in some instances.[SUP]10[/SUP]
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Kelpak is a natural liquid extract of the fastest growing seaweed, Ecklonia maxima. It contains a level of 11mg/L of auxins and 31µg/ L of cytokinins (high auxins to cytokinin ratio). It is the only extract produced in the “Cold Cell Burst Method”. This method ruptures the cell walls releasing sap and vital plant hormones without any denaturing. In comparison to other seaweed products, Kelpak contains the highest levels of growth hormones auxins (indole-3-acetic acid, indole-3-carboxylic acid, indole-3-aldehyde, N,N-dimethyltryptamine and N-hydroxyethylphtalimide) and cytokins (transzeatin, ciszeatin, transribosylzeathin, dihydrozeatin, isopentenyladenosine and isopentenyladenine) at 11.0 mg/L of auxin and 0.031 mg/L of cytokinin. The high levels are preserved by the cold cell burst production process which is unique to Kelpak.

Which brings us to our next point…

KELPS – Quality, Types, Plant Species, Genetics, and Optimal Usage Rates and Times


Not all kelp products are of equal quality. For instance, it is generally asserted that powder/granular kelps are of inferior quality to liquid kelps (particularly cold pressed liquid products) due to the production process where dry products are dehydrated using caustic bases under high temperature and high pressure which disintegrates the kelp, removing some of the goodness. However, some extremely good dry products are also available such as Acadian™ (Ascophyllum nodosum) which is sourced and produced in Nova Scotia, Canada. For instance, in trials conducted in California on tomato cultivars, Acadian extracts indicated a range of beneficial responses from 10 to 50 percent increases in average fruit weight, a greater than 20 percent increase in total fruit number, a 50 percent increase in marketable yield, and a 30 percent increase in marketable fruit number. Slight increases in fruit diameter, average fruit weight, and brix were also found.[SUP]12
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Another factor that that will influence quality are kelp species and where the kelp comes from. For instance, kelps are known bioaccumulators of heavy metals and kelps deriving from polluted oceans can have high heavy metal content. These heavy metals can prove detrimental to plant health and be uptaken by the plant, thus entering the food chain.

Additionally, different kelp types possess different biostimulant qualities.

For instance, Ascophyllum nodosum (eg. Acadian), which has a high cytokinin to low auxin ratio, can prove superb for enhancing flower growth (size, firmness, and weight), while a high auxin to low cytokinin ratio kelp (eg. Kelpak which is produced using Ecklonia maxima) may prove detrimental when used in early flower due to high levels of auxins contributing to apical dominance/stretch and cell elongation (traits that are not desirable during the first 2-3 weeks of the flower cycle – or the “stretch phase” as it has become known).

Crop type plays an important role where kelps are concerned. For instance, an Ascophyllum nodosum based product (GOËMAR BM 86) was shown to reduce fruit firmness in two cultivars of strawberry[SUP]11[/SUP], while the same product was shown to increase firmness in apples in an earlier study.[SUP]13[/SUP]

Similarly, studies have also shown that individual cultivars of the same species may respond differently to treatments of seaweed extracts. For example, the same kelp type may improve the yield of one cultivar of potato but not another grown under the same conditions. [SUP]14[/SUP]
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Additionally, some kelp products are very effective biostimulants when used at the right times, and at the right levels, but may prove detrimental, or provide less benefits when used at too high or too low levels.

Therefore, kelp type, plant type, genetics, product quality, time of use, and usage rates all play an important role in outcomes.

Again, to repeat a point, let me stress something re the use of organics in hydroponic growing systems. It is important to note that where hydroponics is concerned, particularly water based systems (e.g. NFT, deep tank, and aeroponics) it’s important not to overdo it with organic matter or additives. In adding too much organics into the hydro system the proliferation of unwanted microbial life may potentially rob oxygen from the root zone creating a situation where roots are suffocated and pathogenic microbe numbers explode under oxygen starved conditions. This situation is far less pronounced in growing systems that utilize organic media (e.g. soil or coco substrate).

Leading to my next point…. Foliar feeding. (following page)

1) I. J. CROUCH', M. T. SMITH, J. VAN STADEN, M.J. LEWIS and G. V. HOAD (1991) Identification of Auxins in a Commercial Seaweed Concentrate
2) D. V. Robertson-Andersson, D. Leitao, J. J. Bolton, R. J. Anderson, A. Njobeni and K. Ruck (2006) Can Kelp Extract (KELPAK) be Useful in Seaweed Mariculture
3) Wajahatullah Khan, Usha P. Rayirath, Sowmyalakshmi Subramanian
Mundaya N. Jithesh, Prasanth Rayorath, D. Mark Hodges, Alan T. Critchley, James S. Craigie , Jeff Norrie, Balakrishan Prithiviraj (200 Seaweed Extracts as Biostimulants
of Plant Growth and Development
4) Wajahatullah Khan, Usha P. Rayirath, Sowmyalakshmi Subramanian
Mundaya N. Jithesh, Prasanth Rayorath, D. Mark Hodges, Alan T. Critchley, James S. Craigie , Jeff Norrie, Balakrishan Prithiviraj (200 Seaweed Extracts as Biostimulants
of Plant Growth and Development
5) Crouch IJ, van Staden J (1991) Evidence for rooting factors in a seaweed concentrate prepared from Ecklonia maxima.
6) C.M, Steveni, J. Norrington-Davies and S. D. Hankins (1992) Effect of seaweed concentrate on hydroponically grown spring barley
7) Wajahatullah Khan, Usha P. Rayirath, Sowmyalakshmi Subramanian
Mundaya N. Jithesh, Prasanth Rayorath, D. Mark Hodges, Alan T. Critchley, James S. Craigie , Jeff Norrie, Balakrishan Prithiviraj (200 Seaweed Extracts as Biostimulants
of Plant Growth and Development
W.A. Stirk, O. Novák, M. Strnad and J. van Staden (2003) Cytokinins in macroalgae
9) W. A. Stirk, G. D. Arthur, A. F. Lourens, O. Novák, M. Strnad and J. van Staden (2004) Changes in cytokinin and auxin concentrations in seaweed concentrates when stored at an elevated temperature
10) J. van Staden, S. J. Upfold & F. E. Drewes (1994) Effect of seaweed concentrate on growth and development of the marigold Tagetes patula
11) Agnieszka Masny , Alina Basaka and Edward Zurawicz (2004) EFFECTS OF FOLIAR APPLICATIONS OF KELPAK SL AND GOËMAR BM 86 PREPARATIONS ON YIELD AND FRUIT QUALITY IN TWO STRAWBERRY CULTIVARS
12) J. Norrie PhD (2000) Using Ascophyllum Marine Plant Extracts in Commercial Tomato Production
13) Szwonek E. 2003. GOËMAR BM 86 – wyci&#261;g nawozowy z alg morskich.
14) McHugh, D.J., Lawrence, T. (ed.), 2003. A guide to the seaweed industry. FAO Fisheries Technical Paper 441.
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Foliar Sprays/Foliar Feeding
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Foliar feeding refers to the application of fertilizers to a plant’s leaves.

In hydroponic systems nutrients are highly bioavailable and plants receive the large majority of nutrients very effectively through the roots.

This differs somewhat from soils where minerals are less bioavailable and can become locked due to the Cation Exchange Capacity (CEC) and Total Exchange Capacity (TEC) properties of various soil types. For instance, soil colloids tend to be negatively charged and like a magnet they attract positively charged elements (cations such as calcium etc) reducing their mobility in soil.

Other than this, clay and humus have electrostatic surface charges that attract the solution ions, and hold them. This holding capacity varies for the different clay types and clay-blends present in soil, and is very dependent of the proportion of clay+humus that is present in a particular soil. A way to increase CEC is to favor the formation of humus. In general, the higher the CEC, the higher the soil fertility.

Okay, I’ve possibly oversimplified things here – however, the long and short of it is that nutrients and far more bioavailable in hydroponic systems than they are in soils. This is just one of the reasons that hydroponic crops tend to produce larger yields. I.e. Hydroponics allows the plant to expend less energy in the pursuit of nutrients and to divert more energy towards plant growth. The result in increased plant size, better health and biomass (eg. plants grown in hydroponics tend to produce more nodes because of the optimum growing conditions involved etc).

So are there benefits to foliar feeding in hydroponics? Well yes! Certainly!

Ultimately, it depends upon your goals, your plants, and the condition of your plants. Here are several of the most common reasons why growers foliar feed.

Damaged Roots

Root damage can cause serious uptake problems in soils and soilless systems. If the roots are damaged this quickly results in nutrient deficiencies, as the roots are unable to uptake key critical nutrition. Foliar feeding can help correct these deficiencies.

Overcoming Deficiencies Caused by Inadequate Nutrition
The balance of factors in a hydroponic garden is very delicate, so it can be fairly easy for your plants to suffer a nutrient deficiency. Perhaps the nutrient balance isn't optimized, or the pH level is either too high or too low. In some cases too much of an element may be introduced via the overuse of an additive which results in one element locking out other key elements (eg. Too much phosphorous will lock out iron, zinc, and calcium etc).

To Give Your Plants a Boost
Something doesn't necessarily have to be wrong with your plants for you to choose to feed them with foliar fertilizer. Many choose foliar feeding for their plants simply to give them the extra nutrients that they need to grow to their maximum potential.

Some Elements are Better Delivered via Foliar Feeding (eg.Triacontanol, amino acids, complex carbohydrates etc)
In very simple terms, the Casparian strip is located inside each and every root and acts as a barrier that blocks or reduces the uptake of many elements or compounds except simple sugars (eg. glucose, sucrose, fructose[SUP]1[/SUP]), simple amino acids that the plant recognizes and nitrogen (e.g. glycine) or sulphur, and regular plant nutrients like nitrogen, calcium and potassium. Studies have indicated that plants cannot efficiently uptake some amino acids and complex carbohydrates through their roots. Root-based supplements or growth and flowering stimulants containing these elements are, for this reason, best applied via foliar application.

Additionally, it has been well documented in studies that some elements are more effectively delivered to the plant via foliar feeding. This applies to both plants grown in soils or soilless systems. For instance, it has been well documented in research that Triacontanol is best applied via foliar applications.

Foliar Feeding Is an Effective, Safe Way of Delivering Organics To Plants

As previously discussed, where hydroponics is concerned, particularly water based systems (e.g. NFT, deep tank, and aeroponics) it’s important not to overdo it with organic matter or additives. In adding too much organics into the hydro system the proliferation of unwanted microbial life may potentially rob oxygen from the root zone creating a situation where roots are suffocated and pathogenic microbe numbers explode under oxygen starved conditions.

For this reason, foliar feeding organic additives becomes a viable method to use organics in hydroponic settings without risk of overloading the solution with organic components. For instance, kelp is often used in foliar feeding formulations as it contains growth hormones and amino acids as well as macro&#8208; and micronutrients. Many of these hormones and amino acids are more readily absorbed through the foliage than the roots.

Ref


1) Saglio, P.H. and Xia, Jian-Hua (198 Characterization of the hexose transport system in maize root tips.

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Click to expand...

Beneficial microbe science is an extremely complex subject that is, too often, oversimplified by those with interests in selling beneficial bacteria and fungi products through the hydroponics industry. Just one of the practices that is common is manufacturers/suppliers present positive findings from soil-based research and apply this to an entirely different growing methodology –hydroponics - where, among other things, microflora, pH, EC, media matrix, microbial food levels, nutrient levels, and the bioavailability of nutrients are extremely different from soils. It is important to note that even in soil based research the benefits that a bacteria or fungi species may demonstrate in one soil type may not be replicated in another soil type. Additionally, many biocontrol agents perform well in the laboratory and green house conditions but fail to do so in the field.[SUP]1[/SUP] Similar outcomes are also demonstrated in soiless growing where inconsistencies arise between different systems .[SUP]2
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What is clear is that beneficial microbes offer hydroponic growers benefits beyond other methods of pathogen control/prevention. I.e. the use of beneficial microbes is not only demonstrated to control/eradicate pathogens but also to enhance yields through hormone stimulation, enzyme production and other mechanisms. The same cannot be said for sterilisation methods such as UV, ozone, monochloramine, chlorine and hydrogen peroxide.

Additionally, It is generally agreed that bio inoculants control diseases more stably under the better controllable conditions than in the open field. Thus, hydroponic systems offer a unique environment for control of pathogens since various parameters can be managed to favour friendly (beneficial) microorganisms over pathogenic bacteria and fungi.[SUP]3[/SUP]
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In the following material I have endeavoured to focus as much as possible on hydroponic specific content. The material covers just some of the ‘beneficials’ that have been shown to colonize efficiently in hydroponic growing environments and are proven to reduce plant disease and/or provide other benefits.

Root disease, root disease prevention, root disease cure, and sterilisation methods are among other subjects covered.

Terminology
Pythium is a specific type of organism but the term Pythium has become the generic name for describing a large number of water moulds or damping off fungi. For the purposes of this paper I will refer to many rhizosphere pathogens as Pythium. In other cases where a specific pathologen has been demonstrated to be eradicated or controlled by a given beneficial bacteria or fungi species I will refer to the pathogen using its scientific name. Other names, besides Pythium, that you will find are Fusarium oxysporum, Fusarium spp., Phytophthora spp etc.

spp. refers to species (plural). For instance, if you see Trichoderma spp. this refers to Trichoderma species

Host refers to the plant. I.e. The plant is a host for the beneficial bacteria or fungi

Bio inoculant - A formulation containing one or more beneficial bacterial or fungi strains

When referring to beneficial microbes or beneficial microbe products (bio inoculants) various terminology may be used. E.g. bio inoculant, beneficials, beneficial microbe products, friendly bacteria, beneficial bacteria and beneficial fungi. While the terminology isn’t scientifically correct this terminology is used because it is commonly used throughout the hydroponics retail sector (I.e.it is culturally appropriate to the readership).

Root Disease in Hydroponics (In Brief)

When science first conceived of hydroponics it was believed that the new artificial growing method would exclude soil borne pathogens. This was quickly disproven and it was soon discovered that a microflora, similar to that found in soils, rapidly established itself in hydroponic systems. Among the microflora were the plant pathogens Pythium, Phytophera and Fusarium.

Phytophera
Phytophthora (pronounced Fy-tof-thora - meaning plant destroyer) is a water mould, also known as an oomycete.

Phytophthora is an aggressive plant pathogen. When a plant is infected, it is unable to absorb nutrients.

Fusarium oxysporum
Fusarium oxysporum is a common soil fungus, and can become a pathogen causing a wide variety of wilt diseases in plants (usually called Fusarium wilts). Fusarium wilt can be identified with symptoms such as wilting, chlorosis, necrosis, premature leaf drop, browning of the vascular system, stunting, and damping-off.

Pythium
The most common root disease found in hydroponics is caused by Pythium. Pythium attacks the root system and severely limits the plant’s capacity to uptake food. What this ultimately means is an unhealthy crop and a low yield. In severe cases it can lead to crop death.

Pythium disease can be recognized by a brown root system that breaks away when pulled. This may also be accompanied by a musty smell as the root system decays.

Pythium can take hold of a weak, stressed crop far more easily than it can a healthy crop. Making sure that your plants remain healthy through the correct nutrition (particularly during heavy fruiting) and optimum conditions (air temp, water/nutrient temp, RH etc) will give your plants increased resistance against Pythium. I.e. plants grown in optimal conditions (i.e. optimal air temperature, optimal water/nutrient/media temperature, optimal nutrition, optimal RH) will be more resistant to root disease than plants that are subjected to stress as a result of less than optimal growing conditions.

Pythium spores are soil inhabitants. This is why hydroponics and soil don’t mix. Avoid introducing soil into your hydroponics environment! This means taking precautions such as not dragging soil from outdoors into your (indoor) growing environment on your shoes, clothes or hands.

Pythium are water moulds. Because of this, untreated water such as stream, dam, and shallow bore water are high-risk products. If you are going to use stream, dam or bore water in your system you will need to sterilise it prior to use. Rainwater should also be treated because of the likelihood of it collecting wind blown soil.

Managing disease suppression in hydroponics represents the best way of controlling Pythium. Three main strategies can be used: (1) increasing the level of suppressiveness by the addition of antagonistic microorganisms; (2) using a mix of microorganisms with complementary ecological traits and antagonistic abilities, combined with disinfection techniques; and (3) amending substrates and nutrient to favour the development of a beneficial microflora. [SUP]1[/SUP]
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Friendly Bacteria and Fungi in Hydroponic Settings
Hydroponic systems offer a unique environment for control of pathogens since various parameters can be managed to favour friendly (beneficial) microorganisms over pathogenic bacteria and fungi. Given this, the addition of beneficial bacteria and fungi in hydro systems, when handled correctly, promotes a dynamic microculture that prevents harmful organisms damaging the crop.

While the mechanisms that beneficial microbes use against pathogens are complex these mechanisms can be defined as:

Microbial antagonism
Microbial antagonism results from direct interactions between two microorganisms sharing the same ecological niche. Three main types of direct interaction may be characterized: parasitism, competition for nutrients or plant tissues, and antibiosis.

Parasitism
Parasitism of a plant pathogen by other microorganisms is a widely distributed phenomenon. It involves specific recognition between the antagonist and its target pathogen and several types of cell wall-degrading enzymes (CWDEs) that enable the parasite to penetrate the cell wall (hyphae) of the pathogen.

Competition for nutrients
Competition for nutrients is a general phenomenon regulating the dynamics of microorganisms sharing the same ecological niche and having the same physiological requirements when resources are limited. Competition for nutrients, especially for carbon, is common in as soils and other media, and is considered to be responsible for the phenomenon of fungistasis which is the inhibition of fungal spore germination. Competition for nutrients is one of the modes of action of many beneficial micros.

Antibiosis
Antibiosis is the antagonism resulting from the production by one microorganism of secondary metabolites toxic for other microorganisms. Antibiosis is a very common phenomenon responsible for the biocontrol activity of many beneficial microorganisms such as fluorescent Pseudomonas spp., Bacillus spp., Streptomyces spp. and Trichoderma spp. A given strain of beneficial microbe may produce several types of secondary metabolite, having different functions and effective against different species of fungal pathogens.

Induced resistance of the plant
Plants react to physical stresses such as heat, frost, drought, salt, and inoculation with pathogenic or nonpathogenic microorganisms by expressing defence reactions. These defence reactions are SAR (systemic acquired resistance) and ISR (induced systemic resistance). We’ll talk more about this in a moment.

Overview of Microbial Inoculants
Microbial inoculants are used in agriculture as soil amendments that use beneficial bacteria and fungi to promote plant health and nutrition. Various microbe species can be used as biological control agents and may provide effective activity against various pathogenic microorganisms. Just some examples:

Trichoderma harzianum has biocontrol potential against Botrytis cineria, Fusarium, Pythium and Rhizoctonia; Ampelomyces quisqualis, - a hyperparasite of powdery mildew. Bacillussubtillis has antifungal potential against Phytophthora parasitica Dast, Alternaria solani, Pythium aphanidermatum, C. gloeosporioides, Verticillium dahliae Klebahn, Fusariumoxysporum f.sp melongenae, Botrytis cinerea Pers, Fusarium oxysporum, and Lycopersici.[SUP]1[/SUP] Fluorescent pseudomonads produce “highly potent” broad spectrum antifungal molecules against various phytopathogens. [SUP]2[/SUP] Application of Trichoderma viride, Pseudomonas and Bacillus spp. have been found to substantially control seedling, root and stalk rots of maize caused by Fusarium graminearum. Pseudomonas cepacea has been found to inhibit a range of soil borne fungal pathogens including Fusarium graminearum, Fusarium moniliforme and M. phaseolina.[SUP]3[/SUP]Pseudomonas putida and Trichoderma atroviride have been found to promote the reproductive growth of tomato plants under typical hydroponic growing conditions,[SUP]4[/SUP] while numerous studies have demonstrated that rhizosphere bacteria can stimulate plant growth in both soils and hydroponic settings.

Foliar sprays can be used for leaf coverage and they are applied through irrigation to inoculate the soil. While they are applied to improve plant nutrition and health their exudates can also promote hormone production in plants, therefore promoting plant growth. Many of the beneficial bacteria and fungi form symbiotic relationships within the plant that are mutualistic. Roots themselves release exudates into the soil that are beneficial to the microorganisms which suggests a degree of co-evolution between microorganisms and plants that form the ecosystem of the rhizosphere.

The use of inoculants in agriculture has been shown to extend beyond their benefits as biological fertilizers. Research into the disease resistance of microbioinnoculants in crop species shows they can initiate systemic acquired resistance (SAR) to several common crop diseases.

In plants SAR is a resistance response that occurs following a previous localized exposure to a plant pathogen. Once stimulated SAR can provide resistance for several days to a wide variety of pathogens. When a plant recognizes a pathogen it induces a rapid defence response called the hypersensitive response (HR). HR results in localized cell or tissue death at the site of infection, which limits further spread of infection.

This localized response provides non specific resistance throughout the plant; a phenomenon known as systemic acquired resistance – SAR (Ryals et al 1996).

Plants produce salicylic acid as a result of the HR and this increase in concentration of salicylic acid is an activator of SAR. Research has shown that aspirin (acetyl salicylic acid) can work as a trigger for SAR.

There is also induced systemic resistance (ISR). ISR corresponds to the resistance induced by plant growth-promoting rhizobacteria involving the jasmonic acid (JA) and ethylene (ET) pathways. The two pathways are not independent and there are some commonalities between SAR and ISR. For example, both SAR and ISR are controlled by the same regulatory protein non-expressor in the plant. Cross-communication between defense pathways enables the plant to fine-tune its defense response. Based on recent research, the phenomenon of ‘priming’ defense appears to be a common feature of the plant’s immune system that offers protection against disease. When ISR is induced the plant shows a faster or greater activation of defense responses after infection.[SUP]5[/SUP]
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Put simply….

Beneficial microbes such as plant growth promoting bacteria (PGPB) and fungi can improve plant resistance to pathogens and even some insects by inducing
systemic defence responses. Beneficial bacteria and fungi exudates are recognized by the plant, which results in a mild activation of plant immune responses.

Plant Growth Promoting bacteria (PGPB) are considered to promote plant growth directly or indirectly. PGPB can exhibit a variety of characteristics responsible for influencing plant growth. The common traits include production of plant growth regulators (e.g. auxins), siderophores (iron chelating compounds), HCN (amino acid precursor) and antibiotics. Indole acetic acid (IAA) is one of the most physiologically active auxins. IAA is a common product of L-tryptophan metabolism by several microorganisms including PGPB. Microorganisms inhabiting rhizospheres of various plants are likely to synthesize and release auxin as secondary metabolites because of the rich supplies of substrates exuded from the roots compared with non-microbe inhabited soils.

There is evidence that the growth hormones produced by microbes can in some instances increase growth rates and improve yields of the host plants. It is also possible that microbes capable of phosphate solubilization may improve plant productivity both by hormonal stimulation and by supplying phosphate. However, because of the capacity of beneficial microbes to confer plant beneficial effects, efficient colonization of the plant environment is of utmost importance. This is often a fact that is greatly oversimplified by those with interests in selling beneficial microbe products to the agricultural and/or hydroponic sectors. One must consider that many microbes require optimal conditions in which to sufficiently produce benefits and in many instances soil-based research is used to substantiate the merits of bacteria and/or fungi benefits in hydroponics.

Take for example, Arbuscular Mycorrhizal Fungi (AMF) …

About Arbuscular Mycorrhizal Fungi (AMF)

The term "mycorrhiza" literally means fungus-root. It is estimated that 80 to 90 percent of all plant species form mycorrhiza. The relationship between plant and micorrhizae is a symbiosis, the main function of which, while complex, is the transfer of carbon produced by plants to fungi (sugars created in leaves of the plant move downward and into the fungal hyphae via the roots) and the transfer of nutrients acquired by fungi to plants (the plant receives phosphorus, nitrogen, potassium, and micronutrients such as copper, sulfur and zinc).

Elements that are critical in the plant/mycorrhizae symbiosis are CO[SUB]2[/SUB] concentration, nitrogen levels, phosphorous levels, soil matrix, pH and carbon.
Phosphorous, Nitrogen and AMF

One of the key functions of AM fungi is they increase the uptake of poorly soluble P sources, such as iron and aluminium phosphate and rock phosphates by converting non bioavailable phosphates in their organic form to inorganic, bioavailable H[SUB]2[/SUB]PO[SUB]4[/SUB][SUP]-[/SUP] (Pi) and HPO[SUB]4[/SUB][SUP]2-[/SUP] phosphorous.

AM fungi colonize the root cortex of the host plant in which the fungi are able to acquire organic carbon as food to build 'the infrastructure' for P uptake and transport. The mycorrhizal system is able to take up P more efficiently and transport P over longer distances than the plant root system, overcoming P depletion in soils.[SUP]1[/SUP]
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AM fungi also acquire substantial quantities of N from organic sources and play an important role in the nitrogen cycle, intercepting inorganic N released from decomposing organic matter before roots can acquire it and passing some of this on to plants as arginine (CH[SUB]2[/SUB]CH[SUB]2[/SUB]CH[SUB]2[/SUB]NH-C(NH)NH[SUB]2[/SUB]). Additionally, a plant ammonium (NH[SUB]4[/SUB] N) transporter that is mycorrhiza-specific and preferentially activated in arbusculated cells has recently been discovered, suggesting that N transfer to the plant may operate in a similar manner to P transfer. [SUP]2
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Pitched this way AM fungi sound impressive.

However…

The benefits of AM fungi are greatest in systems where inputs of phosphorous are low. Heavy usage of phosphorus fertilizer can inhibit mycorrhizal colonization and growth. As a soil's phosphorus levels available to a plant increases, the amount of phosphorus also increases in the plant's tissues, and carbon drain on the plant by the AM fungi symbiosis become non-beneficial to the plant. [SUP]3[/SUP]
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A comprehensive literature review conducted byKathleen K. Treseder (2004) concludes mycorrhizal abundance declines in response to adequate N (-15%) and P (-32%) fertilization by average across numerous studies.[SUP]4
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Under even moderate P levels that prevail in the majority of field crop systems, early season colonisation by AMF may often be parasitic, creating a carbon drain on crops and reducing yields.[SUP]5[/SUP]
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In research with AMF (Glomus intraradice), Schenck et al (1993) show citrus grown in adequate P environments had lower relative growth rates than non-mycorrhizal plants of equivalent P status.[SUP]6[/SUP] Similar findings have been established in other plant species.[SUP]7[/SUP]
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Author’s note: Carbon drain occurs when there is adequate available phosphorous, however, AMF continue to metabolise plant produced carbon thus placing unnecessary energy drain/burden on the host plants which are receiving low benefits via the mycorrhizae/plant symbiosis.

Hydroponics and AM Fungi
Research demonstrates:

1) The benefits of AM fungi are greatest in P deficient environments
2) Where adequate P is present AM fungi colonization is reduced (average 32%)
3) Bioavailable N plays a pivotal role in AM fungi colonization
4) Where high bioavailable N is present, AM fungi colonization is reduced (average 15%)
5) Yields may be detrimentally affected where adequate P exists (due to carbon drain)

H.J. Hawkins et al (2004) note that a nutrient medium containing a P concentration of 0.9 mM (27.876384ppm P) failed to produce viable mycorrhizal colonisation.[SUP]8[/SUP] Similar findings by G.Nagahashi (1996) demonstrates that mycorrhizae grown in the presence of P at 1.0mM (30.973ppm) showed significantly less hypal branching than in lower P environments.[SUP]9[/SUP]
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Conclusion


While the symbiosis between plants and AM fungi is complex and while more hydroponic specific research is needed, based on current knowledge it seems probable that any potential benefits of AM fungi in hydroponics is negated by the presence of high bioavailable P in hydroponic solutions. Additionally, high bioavailable N in hydroponic solutions likely reduces the efficiency of AM fungi further. It is also possible the presence of AM fungi in hydroponic settings may be detrimental to growth rates and yields as a result of carbon drain.

Back to the story…

The majority of soil living beneficial bacteria require oxygen for cellular respiration (also termed “oxidative metabolism”). Bacteria that require oxygen are classed as aerobes. Aerobes also require organic material or molecules (such as glucose) to produce energy. For this reason this class of bacteria are also called aerobic heterotrophs (i.e. aerobic heterotrophs are organisms that cannot live without free oxygen and do not produce their own food).

The main elements required for beneficial bacterial nutrition are C, H, O, N, S, P, K, Mg, Fe, Ca, Mn and traces of Zn, Cu and Mo.

‘Aerobic heterotrophs’ require a source of organic carbon, gaseous oxygen (air) and water along with the aforementioned mineral elements. Their source of energy is produced by the aerobic oxidation of organic material by metabolism to water and carbon dioxide. The energy released is stored in the phosphoanhydride bonds of ATP. When the energy is required it is released from ATP by hydrolysis. Certain environmental conditions are also required for the growth and division of bacteria like O[SUB]2[/SUB] concentration, pH and temperature.

ATP stands for Adenosine Tri-Phosphate. ATP consists of an adenosine molecule and three inorganic phosphates. ATP is the most important energy-transfer molecule in all living cells. ATP transports chemical energy within cells for metabolism. ATP is produced during photosynthesis and cellular respiration and used by enzymes and structural proteins in cellular processes, including biosynthetic reactions and cell division.

Phosphorous/phosphate plays a vital role in the ATP chain. Inorganic phosphorus in the form of the phosphate PO[SUB]4[/SUB][SUP]3-[/SUP] plays a major role in biological molecules DNA and RNA where it forms part of the molecular structure. Living cells use phosphate to transport cellular energy in the form of ATP. Nearly every cellular process that uses energy obtains it in the form of ATP. ATP -------> ADP (Adenosine Diphosphate) + Pi (orthophosphate) + energy.

For beneficial bacteria to survive in a hydroponic environment they will need ideal environmental conditions. Most hydroponic nutrients lack organic carbon sources for beneficial bacteria to survive. They can metabolise humic and fulvic extracts but one of the best sources of food for beneficial bacteria is molasses. Molasses typically contains ‘Total Digestable Nutrients’ (TDN) in excess of 60%, as well as containing a number of the major elements and trace elements required by bacteria, molasses is very high (50%+) in sugars. The sugars contained in molasses are an ideal source of carbon for heterotrophs. Cobalt and molybdenum, which are not usually listed in the typical analysis of molasses, will still be found in small traces. Another property of molasses, due to the high percentage of sugars, is its’ sticking ability when used in foliar sprays. Molasses, along with a wetting agent, increases the coverage and surface holding, optimising foliar nutrition. While discussing foliar sprays and biological inputs, saponins can be used as an organic wetting agent that not only reduces the surface tension of water (i.e. surfactant – surface active agent) it also has bio stimulating properties. Saponins are chemical compounds (phytochemicals) found in abundance in various plant species. To be specific they are amphipathic glycosides. The foaming ability of saponins is because of their surfactant like structure with hydrophillic (water soluble) and hydrophobic (fat soluble) chains. Their name is derived from the plant soapwort (genus Saponaria). Most commercial saponins are extracted from Yucca schidigera (Spanish Dagger) and Quillaja saponaria (the soap bark tree).

Two other prominent organic additives that act as microbial nutrients/stimulators and plant fertilisers are kelp and fish products.

It is important to note that where hydroponics is concerned, particularly water based systems (e.g. NFT and aeroponics) it’s important not to overdo it with organic matter or additives. In adding too much organics into the hydro system the proliferation of unwanted microbial life may potentially rob oxygen from the root zone creating a situation where roots are suffocated and pathogenic microbe numbers explode under oxygen starved conditions.

Fungi


Trichoderma spp. including T. harzianum, T. viride, T. koningii, T. hamatum and other spp.

Trichoderma spp. are free-living fungi that are very common in soil and root ecosystems. Recent discoveries demonstrate that they are opportunistic plant symbionts as well as parasites of other fungi. [SUP]1[/SUP]

For many years, the ability of these fungi to increase the rate of plant growth and development, including, especially, their ability to cause the production of more robust roots has been known. The mechanisms for these abilities are only just now becoming understood.

Trichoderma spp. show a high level of genetic diversity, and can be used to produce a wide range of products of commercial and ecological interest. They are prolific producers of extracellular proteins, and are best known for their ability to produce enzymes that degrade cellulose and chitin — although they also produce other useful enzymes.[SUP]2 [/SUP]In addition, different strains produce more than 100 different metabolites that have known antibiotic activities.[SUP]3[/SUP]

Trichoderma spp. have been used as biological controlagents against a wide range of pathogenic fungie.g. Rhizoctonia spp., Pythium spp., Botrytis cinerea, and Fusarium spp. Phytophthora palmivora, P. parasitica and different speciescan be used (e.g. T. harzianum, T. viride, T. virens)to control the various pathogens. Among them, Trichoderma harzianum is reported to be most widely used as an effective bio inoculant.

Some strains of Trichoderma are highly rhizosphere competent (able to colonize and grow on roots as they develop). The most efficient rhizosphere competent
strains can be added to soil or seeds by any method. Once they come into contact with the rhizosphere, they colonize the roots. If added as a seed treatment, the best strains will colonize root surfaces even when roots are deep below the soil surface. Trichoderma can colonize for long periods of time in the right environments, so colonization can occur throughout the duration of a crops life cycle. However, in less conducive environments Trichoderma colonization will prove less efficient and reapplication of the fungi is necessary.

To the authors knowledge various strains of Trichoderma control every pathogenic fungus for which control has been sought. However, in contrast to other fungi, Trichoderma spp. have been reported to have limited applications in biocontrol of pathogenic bacteria. An immediate explanation would be that bacteria generally have a faster growth rate (i.e. they multiply faster) than fungi.[SUP]4[/SUP]

This information becomes important when understanding that a broad-spectrum approach to preventing plant pathogens should be incorporated and species of both beneficial bacteria and fungi are likely the ideal. For instance, a good microbrial product should contain species of Bacillus spp. (bacteria) and Trichoderma spp (fungi). However, it isn’t a simple case of incorporating multiple strains of known to be beneficial bacteria and/or fungi as some species may outcompete others and the combinations may reduce overall efficiency. For instance, Pseudomonas fluorescens strain CHA0 which has demonstrated biofungicide qualities against a range of pathogens releases a compound (Phl) that has antibiotic activity against other beneficial microbes.[SUP]5[/SUP] Thus, Incompatibility of co-inoculants can arise because biocontrol agents may also inhibit the growth of each other as well as the target pathogen or pathogens.[SUP]6[/SUP]

Trichoderma spp. and Plant Immune Response

Localized and systemic induced resistance occurs in all or most plants due to among other things, response to attack by pathogenic microorganisms, physical damage due to insects and other factors, and the presence of non-pathogenic rhizobacteria.

Trichoderma penetrate the cells of the root system – this triggers a response in the plant that effectively `walls off’ the Trichoderma and prevents it getting any further into the living root tissue. In triggering this response, the plants natural defence mechanism is activated and a systemic resistance is induced. The relationship between Trichoderma and plant roots is an `opportunistic avirulent symbiotic relationship’ meaning even though the Trichoderma has gained entry to the plant tissue, it does not cause any disease or damage. Both plant and Trichoderma benefit from the symbiosis.

The plant gets protection, while the Trichoderma receives an ecological niche and food from the plant.

The Pathogens Pathogen

In addition to colonizing roots for food, Trichoderma spp. attack, parasitize and gain nutrition from other fungi. Since Trichoderma spp. grow and proliferate best when there are abundant healthy roots, they have evolved numerous mechanisms for both attack of other fungi and for enhancing plant and root growth.

One of the most effective methods of pathogenic fungi control exhibited by Trichoderma is `mycoparasitism’. In this process the Trichoderma detect other fungi, grow towards them, and attach and coil around the fungus, then produce enzymes that destroy the cell walls of the target fungus.

Trichoderma release two types of enzymes in their quest for sustenance – these are cellulase and chitinase. Cellulase enzymes break down cellulose which is a component of plant cells and organic matter. Chitinase breaks down chitin which is a structural component of fungal cell walls.

The production of chitinases has been implicated as a major cause of Trichodermas biocontrol activity against pathogenic fungi.[SUP]7[/SUP]

Viability and Benefits of Trichoderma Harzianum in Hydroponic Settings

T. harzianum are amongst the most effective of the beneficial microbes in hydroponic settings. Research demonstrates that where T. harzianum has been trialled in hydroponics their presence has controlled or eliminated all manner of pathogens in both inorganic and organic medias. This makes T.harzianum an obvious choice for hydroponic growers. Plant growth promoting benefits are also exhibited by some species of Trichoderma spp.

In research conducted in a controlled hydroponics system, Chet et al (2006) note an increase, at protein level, in the activity of chitinases, b-1,3-glucanases, cellulases and peroxidases in cucumber roots previously inoculated with T. harzianum strain T-203. The capability of T. harzianum to promote increased growth response was verified in the hydroponic system. A 30% increase in seedling emergence was observed and these plants exhibited a 95% increase in root area. Similarly an increase in P and Fe concentration was observed.[SUP]8[/SUP]

Similarly, research with T.harzianum strain T-203 conducted with cucumbers grown in an axenic (free from other microorganisms) hydroponic system demonstrated increased growth response as early as 5 days post-inoculation resulting in an increase of 25 and 40% in the dry weight of roots and shoots. Similarly, a “significant” increase in the concentration of copper, phosphorous, iron, zinc, manganese and sodium was observed in inoculated roots. In the shoots of these plants, the concentration of zinc, phosphorous and manganese increased by 25, 30 and 70%, respectively.[SUP]9[/SUP]

Ozbay et al note, T. harzianum strains T95 and T22 increased yield in the presence of measurable disease. Reduction of disease by the use of T. harzianum strains improved tomato yields between 6% and 37% in coir and between 2% and 25% in rockwool. However, Ozbay et al also note, T. harzianum had no effect on yield in the absence of the disease compared with an untreated and uninoculated control. Theses findings suggests that T. harzianum strains used in this experiment act only as biocontrol agents and, beyond this, offer no benefit to yields where disease is not present.[SUP]10[/SUP]

Conclusion
Trichoderma harzianum are shownacross a range of studies to be efficient biocontrol agents.

Additionally, some strains of Trichoderma harzianum are demonstrated to increase the uptake and concentration of a variety of nutrients (copper, phosphorus, iron, manganese and sodium) in hydroponic culture, even under axenic conditions. This increased uptake indicates an improvement in plant active-uptake mechanisms.

However, what is also demonstrated is species, among other factors, will determine whether benefits beyond efficient root disease prevention will be exhibited.

Other Info - Trichoderma spp and Enzymes

Cellulases (enzymes) produced by Trichoderma spp. are the most efficient enzyme system for the complete hydrolysis of cellulosic matter (e.g. decaying root matter) into glucose.[SUP]11[/SUP]

In research with Trichoderma asperellum, Brotman et al (200 note the majority of proteins released by T. asperellum could be classified as plant cell wall-degrading enzymes: cellulases (cellobiohydrolase, endoglucanase), hemicellulases (glucan 1,3-&#946;-glucosidase and arabinofuranosidases), and an aspartyl protease (an enzyme that breaks down proteins). glucoamylase, a starch-degrading enzyme, and swollenin, a protein first isolated from T. reesei were also detected.[SUP]12[/SUP]

Trichoderma viride, T. reesei T. harzianum[SUP]13[/SUP] and T. asperellum[SUP]14[/SUP] have been demonstrated to produce high levels cellulase enzymes.

Trichoderma in Coco Substrate

Inorganic substrates are more effectively colonized by bacteria, while organic substrates are more effectively colonized by fungi. While Trichoderma spp. have been shown to establish and proliferate in a range of mediums, colonization may be greater in organic mediums such as coconut coir. When coconut coir and rockwool were compared after inoculation with T. harzianum it was found that colonization was greater in the coco fibre, while the rockwool system contained the highest amount of fluorescent pseudomonads bacteria.[SUP]15[/SUP] When T.harzianum strains were applied at transplanting to the mediums coir and rockwool, Fusarium crown and root rot incidence of greenhouse-grown tomatoes was reduced up to 79% in coir slabs and up to 73% in rockwool slabs with yield increases of 6% and 37% in coir and between 2% and 25% in rockwool.[SUP]16[/SUP]

Materials that are high in lignocellulose are the organic medias, straw, wood bark, and coconut fibre. This makes coco fibre an ideal environment for Trichoderma spp. colonization.

Pesticide susceptibility

Trichoderma spp. possess an innate resistance to most agricultural chemicals, including fungicides, although strains differ in their resistance. Most manufacturers with registered Trichoderma products have extensive lists of susceptibilities or resistance to a range of pesticides.

Food for Fungi

Potatoe starch in particular makes a good food for fungi. When they breed fungi in the lab they use potatoe starch to stimulate Trichoderma colonization.
Fulvic/humic acid in solution has been demonstrated in numerous studies to aid micro colonisation in hydroponic settings.

Milk sugar (soluble dissaccharide lactose) has been demonstrated to benefit enzyme production by Trichoderma fungi.
Optimum Nutrient and Media Temperature for Trichoderma


Like many microbial species Trichoderma spp. has temperature optimums for rapid colonization and bioactivity. For most of the commonly applied species this is 25-30[SUP]o [/SUP]C (77-86 [SUP]o[/SUP]F) [SUP]([/SUP] with 28[SUP]o [/SUP]C (82.4 [SUP]o[/SUP]F) being the ideal. [SUP]18 [/SUP]If conditions are too cold, the colonization of Trichoderma will slow and even cease; if too warm, then die back may occur and the Trichoderma may become out competed, leaving the door open for other forms of microbial species to take hold.

However…

Optimum Water/Media Temp in Hydroponics vs. Optimum Water/Media Temp for Trichoderma

Often hydroponic growers attribute root browning/root disease to water borne pathogens (Pythium) when in fact one of the major causes of root browning is root zone oxygen starvation typically caused through overly warm nutrient or waterlogged media.

Nutrient salts don’t leak into the roots of the plant. Nutrient uptake is an active process which relies on several factors, one of which is that satisfactory levels of oxygen are available to the roots of the plant.

Roots “pump” nutrients from the outside of the root to the inside where they are transported to the leaves. This pumping process requires energy. The roots get their energy from respiration. In turn, respiration requires energy, which is achieved by burning sugar. Part of the sugar made in leaves by photosynthesis is transported to the roots to power the nutrient pumps.

Photosynthesis converts sugar and oxygen from carbon dioxide, nutrition and water using the energy from light.

Respiration is the opposite. Respiration makes energy by burning sugar (supplied by the leaves of the plant) and oxygen to make carbon dioxide. It is this energy that powers (among other things) the root nutrient pumps. In turn these pumps deliver the nutrition that is critical to sugar production within the plant.

Unlike sugar, oxygen is not transported from the leaves to the roots. This means that the roots must get their own oxygen.

If the roots can’t get sufficient amounts of oxygen (because of excessively warm water/nutrient or because there isn’t enough air space in the growing medium) their pumping capacity is significantly reduced. The result of this is that the plant becomes starved of critical nutrition.

While there are various factors that determine dissolved oxygen levels in water, it can be simply stated as fresh (non saline) water can hold 8.26 parts per million of oxygen at 25[SUP]O[/SUP]C (77 [SUP]O[/SUP]F), while at 20[SUP]O [/SUP]C (68 [SUP]O[/SUP]F), water can hold as much as 9.09 parts per million of oxygen. The colder water gets the more oxygen it can retain. The warmer water gets the less oxygen it can retain. However, if water is too cold nutrient uptake (hence growth rates) will be reduced.
Oxygen content and water temperature are inextricably linked. As water warms up it loses its capacity to hold oxygen. To avoid root rot as a result of oxygen starvation you will need to keep the nutrient temperature below 25 degrees C (recommended 20 –22°C = 68 – 71.6 °F). In addition to this, aeration of the nutrient is advised.
Given this information, it is best to maintain optimum oxygen temperatures in solution and media and compromise somewhat on optimum temperature for Trichoderma colonization.

Optimum pH for Trichoderma spp.


Optimum pH for Trichoderma fungi may vary between species, however fungi thrive in semi acidic conditions. Optimum cellulase production by Trichoderma harzianum is demonstrated at pH 5.0 – 6.0 with 5.5 being the ideal. Above pH 6.0 reduced cellulase production and, therefore, it is advisable that optimum pH for Trichoderma in hydro is 5.5 – 5.8.[SUP]19[/SUP]

Bacteria in Hydroponics – Bacillus and Pseudomonas spp

Beneficial bacteria, like beneficial fungi, form a symbiotic relationship with the plant (host). The bacteria benefit from the ecological niche provided by the plant, while the plant receives protection from the beneficial bacteria.

Plant growth–promoting rhizobacteria, most of which are Pseudomonas and Bacillus species, are applied to a wide range of agricultural crops to enhance growth and act as disease control.[SUP]1[/SUP]

Beneficial bacteria suppress pathogens by, among other things, producing hydrolytic enzymes and antibiotics.

Antibiotics

Antibiotics act as micro toxins that can, at low concentrations, poison or kill other microorganisms. It is shown that some antibiotics produced by bacteria are particularly effective against plant pathogens and the diseases they cause.[SUP]2[/SUP] It is this antibiotic production that plays a central role in disease control.[SUP]3[/SUP]

Additionally, these antibiotics are known to induce defence mechanisms in the host plant.[SUP]4[/SUP]

Bacillus subtilis is able to produce more than two dozen antibiotics with an amazing variety of structures.[SUP]5
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Biocontrol activity of Bacillus strains against multiple plant pathogens have been widely reported and well documented.[SUP]6[/SUP] Their success as a biocontrol agent is associated with the prominent property of producing lipopeptide antibiotics which exhibit wide spectrum antifungal activity.[SUP]7[/SUP]

Strains of Pseudomonas fluorescence have known biological control activity against certain soil-borne phytopathogenic fungi and are known to produce the antibiotic 2, 4-diacetylphloroglucinol (DAPG) which induces defence mechanisms in the host plant.[SUP]8[/SUP]

Hydrolytic Enzymes

There is a synergism between the micro toxins (antibiotics) and hydrolytic enzymes produced by bacteria. Firstly, the enzymes degrade the cell wall of the pathogen, and secondly, this enables the toxin to act more efficiently against the pathogen by gaining access at an intracellular level. I.e. bacteria are more able to effectively poison pathogens via the use of cell wall degrading enzymes.

Viability in Hydroponics

Pseudomonas putida strain PCL1760 has been demonstrated to have significant biological control over Fusarium oxysporum in eight independent laboratory experiments conducted in rockwool substrate.[SUP]9[/SUP]

Similarly Pseudomonas spp. and Bacillus spp. have been demonstrated to have control over Fusarium oxysporum in hydroponic settings.[SUP]10[/SUP]

In research with lettuce grown in recirculating gravel bed hydroponic systems Bacillis spp. were shown to control Pythium with Bacillis subtillis demonstrating the highest rate of control. Additionally, B. subtillis consistently enhanced the fresh leaf and root weight by 29.2 and 24.3% compared to the untreated control.[SUP]11[/SUP]

Research conducted in inorganic and organic hydroponic medias showed the stimulating effect of Pseudomonas putida and T. atroviride (Trichoderma atroviride) on the reproductive growth of tomato plants in both growing medias. The plant growth stimulation was most likely the result of numerous modes of action exhibited by each microorganism tested. This study concluded that Pseudomonas putida and T. atroviride could be used as plant growth-promoting microorganisms to improve the productivity of greenhouse tomato crops under hydroponic conditions in inorganic or organic media.[SUP]12[/SUP]

Pseudomonas putida strain PCL1760 has been shown to exercise significant biological control of tomato foot and root rot (TFRR), a disease caused by Fusarium oxysporum f. sp. radicis-lycopersici (Forl), in eight independent laboratory experiments in hydroponics (stonewool/rockwool substrate). Furthermore, its activity in stonewool was also tested in an industrial certified greenhouse with similar results. The research concluded that Pseudomonas putida strain PCL1760 acted as a bioinoculant via ‘‘competition for nutrients and niches” (CNN).[SUP]13[/SUP]

Optimum Temperature and pH for Bacillis subtillis

Bacteria species typically thrive best in pH neutral environments. Optimum pH for B. subtillis is 6.5 – 7.0. Optimum temperature is between 40– 47[SUP]0[/SUP]C. However, as noted with Trichoderma spp., always maintain optimum temperatures and pH for optimal plant growth in hydro systems. I.e. pH 5.5 – 6.0 and nutrient/media temp of 20 – 22[SUP]0[/SUP]C (68 – 71.6 °F)

Food for Bacteria


Bacteria thrives in a high carbon environment. Molasses has been shown to be a cost efficient source of providing this carbon.[SUP]14[/SUP]
Other sources of food are humates (fulvic and humic acid), kelp, and hydrolysed fish (fish emulsion).

Beneficial Bacteria and Fungi Product Quality

Benefical microbe products are generally formulated as wettable powders (WPs), dusts, granules and aqueous or oil based liquid products using different mineral and organic carriers.

Beneficial microbe products are sold and used, with or without legal registration, for the control of plant diseases. Bio inoculants are either marketed as standalone products or formulated as mixtures with other beneficial bacteria or fungi. Some products with bio inoculant properties may not be registered, and are sold instead as plant strengtheners or growth promoters without any specific claims regarding disease control.[SUP]15[/SUP]

There are several reputable companies that manufacture government registered products. Government registration ensures that products have been subject to trials and scrutiny where claims made about their efficiency are measured and proven. However, for the most part products sold through the agricultural sector largely remain unregistered or are registered with organic bodies (e.g. OMRI) where products aren’t subject to the same levels of scrutiny .[SUP]16[/SUP] Among other reasons that many products remain unregistered are cost of registration and the time required to have the registration approved.

High quality bio innoculants depend on having high concentrations of the microorganism(s), long shelf-life and a formulation appropriate to their use.

Variable results have been reported for all types of microbial products, whether liquid or dry, with variation in their effectiveness attributed to three main causes: (1) presence of an already satisfactory level of the beneficial microbes prior to inoculation; (2) poor survival of the beneficial microbes in their environment; and (3) low quality of the inoculant. Low quality inoculants can be defined as containing insufficient viable cells of the beneficial microbe/s, high numbers of contaminating micro- organisms, or both.[SUP]17[/SUP]

Olsen et al. (1995) found that only 1 of the 40 commercial North American beneficial products prepared from non-sterile peat contained more benefical microorganisms than contaminants. Contaminant microorganisms in non-sterile conditions often out-compete the beneficial organisms for space and nutrients and may also produce allelopathic (toxic) compounds. Manufacturers also risk incorporating pathogenic organisms into formulations when non-sterile carriers are used.[SUP]18[/SUP]

To manufacture a high quality microbial product, it is essential (among other things) that the carrier material is sufficiently sterilised. This allows for non-competitive multiplication and maintenance of the microorganisms in a nutrient rich environment.

Molasses and other microbial carriers commonly used for producing liquid beneficial products and peat granule, traditionally used for creating dry micro products, are unique in that they have a high initial ‘bio-burden’ (I.e. high number of contaminating microbes).

These factors dictate the use of autoclaving, in the case of liquids, and irradiation in the case of dry products, to achieve carrier sterility prior to introduction of the beneficial microbes to the carrier. However, while autoclaving or irradiation must be sufficient enough to achieve total ``kill'' of any contaminating microorganisms, it must not cause substrate/carrier breakdown, the creation of toxins, or adversely affect the carrier’s physical properties in another way. Only through “complete” sterilization can it be guaranteed that unwanted competitive microbes are eliminated from the carrier.[SUP]19[/SUP]

Some of the beneficial bacteria and fungi that are government registered in various countries

Bacteria


Burkholderia cepacia - Soil-borne fungi, nematodes
Pseudomonas fluorescens - Soil-borne fungi
P. syringae ESC-10, ESC-11 - Post-harvest fungi
P. chlororaphis - Soil-borne fungi
Bacillus subtilis - Soil-borne fungi
B. subtilis FZB24 - Soil-borne
B. subtilis KBC 1010 - Gray mold
B. subtilis GB03 - Soil-borne and wilt
B. subtilis GB07 - Soil-borne fungi
Rhizobium sp. KR181 - Bio fungicide
Streptomyces griseoviridis K61 - Various fungi

Fungi

Trichoderma polysporum, T. harzianum - Soil-borne fungi
T. harzianum KRL-AG2 - Soil-borne fungi
T. harzianum - Foliar fungi
T. harzianum, T. viride - Various
T. viride - Various
T. lignorum - Vascular wilt
Trichoderma spp - Soil-borne fungi
Ampelomyces quisqualis M-10 - Powdered mildew
Talaromyces flavus V117b - Soil-borne fungi
Gliocladium virens GL-21 - Soil-borne fungi
G. catenulatum - Soil-borne fungi
Fusarium oxysporum - non-pathogenic Pathogenic Fusarium

A number of companies are developing new products that are in the process of registration.

Spore Count and CFU (Colony Forming Units)



Spore count and cfu (colony forming units) are used to quantify the microbial content of a liquid or dry beneficial product. Spore count is used with fungi and cfu is used with bacteria. These units indicate the levels of microbes that are present in a given product.

A beneficial bacteria and/or fungi product should contain a level of bacteria or fungi sufficient to inoculate plants and produce gains. The required level of bacteria and/or fungi required cannot be established as a general standard because it varies from one species to another. While it is possible to undersupply beneficial microbes it is not possible to oversupply them. For this reason the higher the cfu and/or spore count the higher the quality of the product (put simply).

Other factors such as bacteria and fungi species (suitability) and contaminants must also be considered in the quality equation.

A quality beneficial bacteria and/or fungi product should list a guaranteed analysis of the cfu and/or spore count. Other things to look for are a use by date and actives.
Species Choice
While some species of fungi and bacteria are demonstrated to produce positive results in both hydroponics and soils (e.g. Trichoderma harzianum, Bacillis subtillis), other species (e.g. Mycorrhizae) may not produce such ubiquitous results. By understanding the science of beneficial bacteria and fungi in hydroponics one can more easily make informed purchasing decisions re products that will produce consistent results (given other factors are in check).

Liquids Products and Sporulation (suspended spores in solution)

Some years ago (2002) I wrote about beneficial bacteria and fungi and the potential they showed for disease control in hydro settings. One point I made was that liquid beneficial microbe products sold through the hydro industry should be avoided and preference should be given to dry micro products instead. This information was oversimplified and was largely based on the quality of liquid products available through the hydro retail sector at that time.

The science….

Bacteria must obtain nutrient materials necessary for their metabolic processes and cell reproduction from their environment. Thus in order microbes to thrive in their environment adequate food and oxygen must be present in solution and media.

A diverse group of gram positive bacteria (e.g. Bacillis spp.) and species of fungi (e.g. Trichoderma) are capable of sporulation as a means of surviving adverse conditions. These specialized bacteria and fungi are able to become dormant under stress and form spores which are resistant to many chemical as well as physical antibacterial measures. Bacterial spores are extremely stable, and resistant to heat, drying, light, disinfectants and other harmful agents than the original living bacterial organism. Spores may survive for many years.

When more suitable conditions present themselves, the spore germinates and again develops a similar cell to the one that originally formed the spore. This new cell, under favourable conditions of moisture, temperature, oxygen, pH and food supply, begins reproduction, antibiotic and enzyme production.

However, other species (gram negative) do not sporulate and their populations typically die out or are significantly reduced when faced with nutritional or oxygen stress.

Put simply - this means is if live sporulating microbes are added to a liquid product they will hibernate if and when faced with nutritional or oxygen stress. The suspended spores can then be regenerated (germinated) when placed in an environment such as a hydroponics system that provides a viable source of oxygen and food.

Other than this, quality liquid products are typically produced using spores that remain suspended due to the presence of antimicrobial preservatives (e.g. Kathon™) that while capable of killing live bacteria and fungi do not harm the more resistant spores.

While different microbes will germinate more readily than others a basic reference is that Bacillis subtillis will germinate within 24 hours of being added to the nutrient solution (fungi will typically germinate sooner).

Liquid products that contain sporulating bacteria and/or fungi are therefore very viable products when they are produced correctly.

Just some of the microbes that sporulate
• Trichoderma harzianum
• Trichoderma viride
• Trichoderma koningii
• Trichoderma polysporum
• Bacillus subtilis
• Bacillus laterosporus
• Bacillus licheniformus
• Bacillus megaterium
• Bacillus pumilus
• Arthrobotrys oligospora
• Hirsutella rhossiliensis
• Acremonium butyri

Dry Products – Storage

Dry products consist of spores (inactive bacteria and/or fungi) and a carrier medium. Dry products should be stored out of direct sunlight at between 4[SUP]o[/SUP]C and 10[SUP]o[/SUP]C in an airtight container. If the product becomes damp from air moisture the spores will become active and then die out when conditions are not suitable. This will greatly reduce product quality. Packets of bacteria/fungi should not be opened until they are ready to be used.

Water Quality and Beneficial Microbe Viability

Often mains water is treated with monochloramine to kill off undesirable microorganisms. The problem is that monochloramine does not discriminate between undesirable and beneficial microorganisms and therefore residual monochloramine in your tap water supply may also disrupt the viability of beneficial microbes in your hydroponic system (if you are using mains water – this does not apply to RO treated water where carbon filtration is incorporated). Monochloramine is reasonably stable and therefore can persist in tap water for some time. Varying levels of monochloramine can be present in tap water ranging from as low 0.2ppm to much higher; the EPA lists the maximum allowable limit as 4ppm while the World Health Organisation maximum allowable limit is 3ppm.

While both chlorine and monochloramine residuals decrease with time, monochloramine decreases more slowly than chlorine. Chlorine may take days to dissipate in a jug left on a counter and it will take much longer for monochloramine to dissipate. The decomposition rate will be faster when the water is exposed to air and sunlight. Chloramine, like chlorine, will eventually dissipate completely over time but this could take many days.

The easiest way to remove monochloramine from tap water is to first run it through an activated carbon filter. The activated carbon filter can reduce chloramine concentrations of 1 to 2 ppm to less than 0.1 ppm.

Which brings us to our next point… Water Sterilzation methods .....

Sterilization versus Beneficial Micros in Hydroponics
Sterilization is another means to prevent root disease in hydroponics.

Sterilization works by creating an entirely bio-devoid system. This means, sterilization eradicates microflora from the hydro system completely. I.e. by sterilising the nutrient you are killing both beneficial and pathogenic bacteria. UV, ozone, monochloramine, chlorine and hydrogen peroxide are commonly/widely used methods of sterilization in hydroponics.

Products such as Hydrogen Peroxide (Oxy Plus, Hy-Gen Peroxide), or Monochloramine (Pythoff) are useful sterilising agents. Because Pythium is a living organism, sterilization will kill the Pythium spores before they have a chance to enter the plant’s root zone.

It is important to note that both monochloramine and hydrogen peroxide act only as root disease preventatives. I.e. once root disease is present in the crop they are ineffective and other means for controlling the disease should be sort.

WARNING - DO NOT USE OXIDANTS WITH ORGANIC MEDIAS OR ORGANIC ADDITIVES: monochloramine, chlorine and hydrogen peroxide are not suitable for use where organic media (e.g. coco substrate) or organic additives are used.These products are oxidants and oxidants break down organic matter.

Monochloramine in Hydroponics

Inorganic chloramines such as monochloramine are formed when chlorine and ammonia are combined in water. One of the key uses for monochloramine is it is used for disinfecting mains water supplies.

Monochloramine is an oxidant. It kills bacteria by penetration of the cell wall and blockage of the metabolism. Monochloramine is considered to have moderate biocidal activity against bacteria.[SUP]1[/SUP] While there are more effective products available for eradicating bacteria (e.g. chlorine) these have been deemed unsuitable for use in treating mains water supplies due to the byproducts they form when interacting with organic matter.[SUP]2[/SUP] Monochloramine hydrolyses (breaks down) slowly in aqueous solutions, producing hypochlorite (at alkaline pH) or hypochlorous acid (at acid pH).[SUP]3[/SUP]

Research into the use of monochloramine in other areas suggests that where bacteria are able to attach to surfaces this provides a primary means for bacteria to survive disinfection. Research of K. pneumoniae grown in a high-nutrient medium attached to glass microscope slides demonstrated a 150-fold increase in disinfection resistance.[SUP]4
[/SUP]

Similar findings have been demonstrated in nursery fertigation systems where organic debris or particles prevented direct contact of chlorine (not to be confused monochloramine) with fungal propagules (Phytophthora spp.) and as a result reduced chlorine efficiency.[SUP]5[/SUP]
This may have implications in hydroponic systems where hosing, pipes, pots, drip emitters and, for that matter, media may offer pathogens protection.
Because monochloramine hydrolyzes (dissipates) slowly careful use is advised. I.e. monochloramine is an oxidant and overuse can result in build up, resulting in fine root hair burning, which will reduce nutrient uptake.

Use of Chlorine (not to be confused with monochloramine) in Hydroponics

A handy tip. Monochloramine sold through the hydro industry can be replaced by chlorine at greatly reduced cost.

Chlorine (Cl) is demonstrated to be a more effective sterilizing agent than monochloramine.[SUP]1[/SUP]

Research has demonstrated that 0.5ppm (780 mV) of chlorine in greenhouse irrigation systems at pH 6.0 eliminated Phytophthora sp., Fusarium sp. and bacteria within 0.5 minutes of contact time.[SUP]2 [/SUP]Chlorine efficiency is pH dependent and efficiency at pH 6.0 – 7.5 has been shown to be the ideal (maximum efficiency of chlorine is 6.5). Below pH 6.0 and toxic chlorine gas will be released. Because optimum pH in hydroponics is pH 5.8 – 6.0 this makes chlorine ideal as an effective and low cost sterilizing agent.

Products such as sodium hypochlorite (liquid typically 12.5% chlorine), calcium hypochlorite (bleaching powder/pool chlorine = approx 65% Cl), and chlorine dioxide are cheap sources of chlorine. Take for example calcium hypochlorite at 65% available chlorine. To achieve 0.5ppm chlorine in 100L of solution 0.08 grams would be required. This would mean that 250 grams of sodium hypochlorite would be good for 3125 treatments. The cost of 250grams of sodium hypochlorite is approximately £12.00 in the UK (in small volume purchased online – far cheaper in volume) or less than $20 USD. Now consider this; you would use only 14.6 grams a year to treat 100L every two days, so 17 years of chlorine treatment would cost less than $20.00 USD. When you consider that a 1L monochloramine product is sold through UK hydroponic stores for £30.00 - £34.99 ($49.00 -$57.00 USD) and is used at 0.2mL/L (50 treatments of 100L) the use of chlorine over monochloramine represents massive savings.

Chlorine - Potential Toxicity to Plants
Chlorine obviously has some potential toxicity (phytotoxicity) issues associated to plants, if used at excessive levels – as does monochloramine and hydrogen peroxide. Sensitive plants such as lettuce may be detrimentally affected if chlorine is present in solution at even 1ppm. Less sensitive plants will be tolerant to higher levels.
Research has demonstrated that 2ppm of chlorine at riser outlet, in fertigation systems poses little or no risk of toxicity to the majority of ornamental crops.[SUP]3 [/SUP]This indicates that treatment with 0.5ppm of chlorine poses very little risk to even sensitive plants.

Treatment
Chlorine hydrolyzes (dissipates) more quickly than monochloramine and, therefore, treatment should take place every two days. Directly after treatment the chlorinated nutrient should be cycled through the growing system to ensure pipes, pots, channels and media are adequately sterilized.

Measuring Chlorine in Solution

ORP Meters
It’s important to note that simply adding oxidants such monochloramine, chlorine and hydrogen peroxide to solution and hoping for the best can only be described as entering the realms of hydro cowboy country. Numerous factors will influence the levels of oxidant (e.g. temp, pH, ionic strength, organic content, dissipation rates, and existing chlorine or monochloramine in the water supply).

The most efficient means of accurately monitoring oxidant levels is through the use of an ORP meter.

ORP is a measurement of ‘Oxidation Reduction Potential’ (mV) most commonly used to measure the effectiveness of water disinfection systems using sanitizers such as chlorine, bromine, ozone, peroxyacetic acid, hydrogen peroxide etc. ORP standards have been long established for water sanitation and are recommended over ppm measurements with traditional test kits. ORP meters are relatively inexpensive (a handheld pen meter should set you back approximately $100 -150 USD) and easy to operate and should be an essential piece of equipment for people using a chlorination system in hydroponics. Optimal ORP for Pythium control with chlorine = 780 mV at pH 6.0

Desired Chlorine in Solution: 0.5ppm – 780 mV

Optimum pH for chlorine treatment in hydroponics: 6.0 (below pH 6.0 will release chlorine gas – above pH 6.0 is less than optimal for nutrient uptake)

Treatment: every two days – if using an ORP meter maintain at 780 mV

Safety Warnings: Calcium hydrochlorite CAS No: 7778-54-3 has strong oxidizing properties and is a corrosive. Handle with care and store in an airtight, lightproof, sealed container safely out of the reach of children.

Use our online calculator to establish chlorine ppm in solution with any given product. http://www.manicbotanix.com/calculators/dilution-concentration-calc.php

Hydrogen Peroxide (H[SUB]2[/SUB]O[SUB]2[/SUB]) In Hydroponics

Hydrogen peroxide, as with monochloramine and chlorine, is an oxidant. However, as a benefit it is also a disinfectant. The oxidant and disinfection mechanism of hydrogen peroxide is based on the release of free oxygen radicals:
H[SUB]2[/SUB]O[SUB]2[/SUB] &#8594; H[SUB]2[/SUB]O + O[SUB]2[/SUB]

Free radicals have both oxidising and disinfecting abilities.

Unlike monochloramine, hydrogen peroxide does not produce residues. I.e. Hydrogen peroxide is completely water-soluble.

Hydrogen peroxide hydrolyzes (dissipates) quickly and, therefore, treatment should take place every 2 days.

IMPORTANT NOTES: Sterilizing agents such as monochloramine, chlorine and hydrogen peroxide should not be used in conjunction with beneficial microbes. These compounds do not make a distinction between beneficial and harmful microbes and their use can result in killing off or reducing beneficial microbe numbers. If sterilization is used, it is important to reapply beneficial microbes when the sterilizing agent has completely hydrolyzed/dissipated.

WARNING - DO NOT USE OXIDANTS WITH ORGANIC MEDIAS OR ORGANIC ADDITIVES: monochloramine, chlorine and hydrogen peroxide are not suitable for use where organic media (e.g. coco substrate) or organic additives are used.These products are oxidants and oxidants break down organic matter.

Monochloramine and hydrogen peroxide should never be used together at the same time. Hydrogen peroxide is one method employed by water treatment experts to chase chlorine from mains water supplies. I.e. each product (monochloramine/hydrogen peroxide) renders the other inert.

Pythium – Cure

In 2002, in Edition 1 of Integral Hydroponics, I wrote about using Fongarid (active furalaxyl) as a cure for Pythium with:

“Once you have Pythium, control is not an easy matter. There are off the shelf fungicides that are available in Australia, but they need to be used with caution as they are systemic. I have found that Fongarid – a systemic fungicide that contains active furalaxyl – eradicates Pythium quite successfully. However, if Pythium is able to take hold in the crop this situation may change due to the reproductive cycle of the fungi (genetic mutations and more resistant spore types). For this reason prevention is a far smarter practice than cure.”

[End Quote]


My advice was based on two things. One, research by the CSIRO conducted in 1998 demonstrated the ability of furalaxyl to eradicate pythium [SUP]1[/SUP] and, two, through my own experiences with the product in hydroponics I had/have found that drenching coco coir with a 20ppm solution of furalaxyl for four hours cured Pythium and regenerated healthy root growth within days. To date I haven’t found a better product, hence, still recommending furalaxyl years later.

Warnings: Furalaxyl is systemic fungicide and should never be used
past week 3 of flower.

Use of furalaxyl will also add sodium (Na) to nutrient solution.

For this reason it is recommended that furalaxyl isn’t run constantly through the growing system. I.e. High levels of sodium are undesirable in solution.

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To stoned to even start reading that. Only posting so I can find it in the morning.

Warlock1369 said:

To stoned to even start reading that. Only posting so I can find it in the morning.

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LMAO! nice, It is loaded with scientific info on the benefits of additives. I learned a lot of interesting stuff that I didn't know. One thing that I learned was that Mycorrhizal Fungi can actually become a parasite sucking carbon from your plant if there is too much bio available P

I was always told it is Good no matter what. Now I know it can reduce yields if using mychorizh in a high available P environment, it will get the P from other sources and give it to your plant but bio avaiable P decreases colonization and just reduced the use.

I still need to read over it like 3 more times but this is jammed pack with need to know info if you use additives in your garden, synthetic or organic.

I am going to revise the format tomorrow. Arrange the subjects and highlight all the Topic subjects. I started getting tired and just throwing it together just to get it up.

I will make it much more easier to navigate tomorrow

calcium chloride additive

Calcium Chloride? Looked it up and it's used to reduce the freezing point of water and can be added straight to soil but isn't used a lot because it can easily burn the roots of the plant because it is a caustic salt

Alright I am home and am ready to organize this beast of a post so it is more appealing for people to read and find things in here that they like instead of blindly reading a massive post

Thank you for this thread! I will use it for reference! +rep

glad to hear the info is being read. i honestly thought the thread would just fall into oblivion. was hoping to get it stickied lol it needs to be organized better but RIU has a character limit but doesn't show it so i have to guess per page, and I am lazy lol

This is a BAMF.

great info. i have promoted the use of beneficials for a long time in hydro and have seen firsthand the difference in my plants. also the addition of silicon is one of the best things you can do for strong plants. after i started adding silicon i no longer had to support my branches.

OGEvilgenius said:

This is a BAMF.

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lol

superstoner1 said:

great info. i have promoted the use of beneficials for a long time in hydro and have seen firsthand the difference in my plants. also the addition of silicon is one of the best things you can do for strong plants. after i started adding silicon i no longer had to support my branches.

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Heck ya Beneficials make a noticeable difference as long as you don't over or under do it. Silicon is like body armor for your plants Makes them real stiff and sturdy and makes it harder for bugs and fungus to penetrate

This article was just an eye opener for me honestly

Who gave my thread only a 1 start rating :'(