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Beneficial Additives in Hydroponics

 

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 silicon in nutrient formulas. Silicon 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 silicon.

 

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.

 

Silicon and Hydroponics

 

For myself, I do not see silicon as a beneficial additive but, more so, as a must (an essential element) in any balanced/optimized nutrient regime.

 

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

 

Silicon is abundant in all field grown plants, but it is not present in most hydroponic solutions.

 

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).

 

Silicon is excluded from hydroponic nutrient formulas because it has a high pH and is unable to remain soluble (hold/remain stable) in concentrated nutrient solutions. 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 ‘quasi essential’ element for plants because its deficiency can cause various problems with respect to plant growth, development and reproduction. The addition of Si to hydroponic solutions exerts a number of beneficial effects on growth and yield of several plant species, which include improvement of leaf exposure to light, resistance to lodging, decreased susceptibility to pathogens and root parasites, and amelioration of abiotic stresses. Silicon can also alleviate imbalances between zinc and phosphorus supply. In general, dicot plants (e.g. tomato, cucumber, peppers) show a tissue accumulation of Si at about 0.5% or less.

 

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]

 

Si 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:

 

[Quote]

 

“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]

 

[End Quote]

 

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 silicon is 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

 

Research on optimum ppm of Si in hydroponic solutions tends to be somewhat variable. However, to generalize somewhat, hydroponic specific research has shown that different types of plants such as wheat, tomatoes and cucumbers react positively to a moderate addition of silicate ions.

 

Silicon as SiO2 (silicon dioxide), which is 46.743% Si and 53.25% O, has been shown in various studies to be beneficial to plants in the range of 50 -150 ppm in the nutrient solution. However, what is typically asserted as optimal SiO2 in hydroponic solutions is 100ppm, which equates to 46.7 ppm of Si.

 

However, there are several important things that you need to be aware of when using silicon in your hydroponics system.

 

Firstly, silicon has the tendency to react with other ions and if present at too high levels in the nutrient solution this can cause the precipitation (“drop out”) of other elements from solution. That is, silicates are relatively insoluble and the acidic pH in hydroponics can cause some precipitation of different reaction products of this ion with other ionic species present within the hydroponics solution. The silicate ions can also form silicic acid and start to polymerize into complex macromolecular structures. Basically, silicates in hydroponic solutions can act in unpredictable ways. For this reason, lower rates of use versus higher rates of use in hydroponic solution is advised.

 

Secondly, Si products typically are highly alkaline. Therefore, when added to solution they raise the solutions pH. As pH rises to above 8.0, the form that silica takes in solution changes from non-reactive, non-ionic monosilicic acid, to reactive, ionic polysilicic acids that react with other minerals and precipitate out of solution, giving a cloudy appearance. That is, at high pH of above 8 silica changes to a form that can react with other minerals and precipitate out of solution. The best way to prevent this is to add your Si additive to water (no nutrients – just water) outside of the nutrient tank/reservoir, and then lower the pH  to 5.5 – 5.8 before adding it to your hydroponic nutrient solution. Depending on how much ml of silicon is required and how concentrated the liquid product is, I tend to recommend prediluting the silicon in 5 – 8 litres (1 – 2 US gallons) of water and pH adjusting the solution (water + silicon) to 5.5 – 5.8 before adding it to the nutrient tank/reservoir. What I also recommend is to add this solution slowly over several hours. That is, add 20% of the solution and let this circulate into the nutrient. Then add another 20% an hour or so later etc.  While no research exists to support this practice as optimal in hydroponics, I have found that by adding the silicon to the nutrient tank/reservoir in this way minimizes the risk of nutrient precipitation.

 

Thirdly, after many years of using silicon products in hydroponics, I have found that like all other plant nutrients, too much Si in the root zone antagonizes other nutrients. For example, it has been shown that excessive levels of Si antagonizes iron and zinc. Other than this, it has been shown that silicon increases the oxiding power of the roots making Fe and Mn less soluble. Further, some research suggests that while the benefits of Si are seen when used at one level, when its’ use exceeded this ideal level, growth was negatively affected. What this really comes down to is that I tend to use silicon at full strength during grow and early bloom, but reduce the strength to about 65 % once the flowers begin to set (I.e. when the bulk of the internodes are formed and flowers/fruit begin swelling). I have found that this offers the best results and that too much Si in solution can negatively impact on optimal fruitset.

 

Therefore, I recommend Si use in RTW/DTW organic substrates (e.g. coco and sphagnum peat) at the lower end of the scale – this being between 20 (when flowers are setting) to 30ppm (or 42 – 64ppm as SiO2).

 

In inert medias and water-based systems I recommend Si use at a higher rate of 30 (during flowerset) to 46.7 ppm Si (or 64 – 100ppm as SiO2).


It is important to note that most hydroponic store sold liquid silicon (silicate) products are made using potassium silicate (K2SiO3). Potassium silicate contains 18.204% Si and 50.685% potassium (K). This means that by adding e.g. 30ppm of Si to solution we are adding 83.5 ppm of K to solution. The addition of potassium through the use of potassium silicate needs to be considered in any optimized nutrient regime.

 

The Si to K ratio of any potassium silicate product may vary. Therefore, it is advisable that you contact the manufacturer/supplier of the product and ask them how many ppm of Si (or SiO2) and K their recommended dilution rate contributes to the nutrient solution.

 

Fulvic Acid Aids Si Uptake

 

It has been shown that Si uptake is aided by the presence of fulvic acid in solution.[9]

NOTE: It is important to note that people use different terminology when specifying optimal silicon/silicate levels in solution. For example, it is typically asserted that optimal SiO2 (silicon dioxide) in hydroponic solutions is 100ppm. However, others may specify optimum ppm referring to Si (silicon), K2SiO3 (potassium silicate), or H4SiO4 (silicic acid). The various chemical references used will determine optimal ml per Ltr usage rates to achieve a given ppm of Si or SiO2 in solution.   Just be somewhat aware of this when looking at research or talking to hydroponic nutrient suppliers about their recommended usage rates and what this provides to the plants in terms of Si and other elements (e.g. K).

 

Converting between SiO2, K2SiO3, and H4SiO4

 

If you want to convert the ppm of Si to SiO2 ppm

 

Work out the percentage of Si in SiO2 – there is a molecule and mole calculator on the Manic Botanix website that does this for you. You simply enter in the ‘chemical formula’ of SiO2 (be sure to use subscript for the 2), enter 100% in the ‘purity of chemical box’, enter that you want 1 mole in the ‘moles required’ box (any number will actually do but 1 is just fine), hit calculate and the calculator will tell you that the SiO2 molecule consists of 46.743% silicon (Si) and 53.257% oxygen (O).

 

To convert:

 

1) Take the known percentage of Si in SiO2 and calculate that as a percentage of 1 – e.g. 46.743 (% Si in SiO2) x 1% = 0.46743 (be sure to use the percentage -%- button on the calculator)

2) Then take the amount of Si you want in ppm and divide it by the figure less than one.  E.g. 30 (ppm Si) divided by 0.46743 = 64.1807 (ppm SiO2)

 

Converting SiO2  ppm to Si ppm

 

This one is dead easy. Let’s say you want to convert the ppm of SiO2 to what this is in Si ppm.

 

1)     100 ppm (SiO2) = 46.743 ppm (Si) – i.e. 100 (ppm SiO2) x 46.743% (% Si in SiO2) = 46.743 (ppm Si)

 

These sums can be used for conversion between any chemical formulas, whether they be in ppm, grams, or ml. The unit doesn’t matter, just that the answer is in the same units or a conversion thereof (i.e. 100g or 0.1kg).

 

For example, if a manufacturer tells you that their recommended dilution rate for their potassium silicate (K2SiO3) product gives you 100ppm of potassium silicate in solution. To establish what this is in Si, you use the mole calculator on the Manic Botanix website and it will tell you that there is 18.204% Si in K2SiO3.

 

Therefore, to establish Si ppm from 100ppm of K2SiO3 – 100 (ppm K2SiO3) x 18.204% (%Si in K2SiO3) = 18. 204 ppm Si.

 

Knowing this, you would then be able to establish that the manufacturer’s recommended dilution rate is too low and would then be able to calculate what is required to achieve your sort after ppm in solution.

 

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.

 

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

 

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 example, the positively charged metal ions such as Zn+2, Mn+2, Cu+2 and Fe+2, readily react with negatively charged hydroxide ions (OH), making them unavailable to plants. OH ions are abundant in alkaline nutrient solutions, soils and substrates.   Therefore, metal chelation is important because it makes metal ions more stable and available to plants.

 

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.2 As 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.

 

ORGANIC CHELATORS

 

AMINO ACIDS

 

Amino Acids – Overview

Amino acids are the building blocks for proteins and also the products of their hydrolysis. Proteins are completely composed of linear chains of amino acids called polypeptides that are classed as either long or short (peptide). Polypeptides then form the large biological molecules called proteins, also called macromolecules. Thus, amino acids are fundamental ingredients in the process of protein synthesis (i.e. proteins are molecules which are constructed from even smaller molecules called amino acids – thus, all proteins are collections of amino acids).

 

About 20 important amino acids are involved in the process of each function. Besides the 20 amino acids used as precursors in protein synthesis, some 250 “nonprotein amino acids” are found in plants, in some botanical families in particular, and receive increasing attention with regard to their physiological and ecological roles (Vranova et al. 2011). They are also found in soil and peat extracts.[1] Studies have shown that amino acids can directly or indirectly influence the physiological activities of the plant. .

 

Even though plants have the inherent capacity to biosynthesize all of the amino acids that they require from nitrogen, carbon oxygen and hydrogen, the biochemical process is quite complex and energy consuming. Put simply, where amino acids and proteins are concerned, 20 amino acids must be synthesized by the plant in order for protein synthesis to occur. However, a challenge lies in the fact that proteins have a finite life span and must be constantly translated from m-RNA (which carries genetic information from DNA) in order for plant growth and development to continue. This means that there must be a ready supply of all 20 amino acids for protein synthesis and ultimately plant growth and development to occur. Therefore, the exogenous application of amino acids through addition to the nutrient, or applied via foliar spray, can aid the plant to save energy on this process. This energy can then be dedicated to better plant development during critical stages of growth.

 

To understand this energy saving process, nitrogen (N) containing amino acids such as glycine (C2H5NO2), alanine (CH₃CHCOOH), arginine (C6H14N4O2), tryptophan (C11H12N2O2), proline (C5H9NO2), histidine (C6H9N3O2) and lysine (C6H14N2O2) are shown to be uptaken and assimilated by some plants in large quantities. Some studies have indicated that where inorganic forms of nitrogen (e.g. nitrate nitrogen – NO3) and amino acids are present in soils and solutions plants uptake more N through amino acids than through inorganic sources of nitrogen. As a result, while the research is variable, some authors have suggested that plants possibly prefer organic amino acids as a source of nitrogen above inorganic forms of nitrogen.[2]

 

The next thing to understand is that when amino acids are provided to plants they are able to directly enter the plant as intact molecules and be translocated to the shoots. This requires less energy than when a plant is provided nitrogen through inorganic forms such as nitrate nitrogen. That is, when nitrate nitrogen (NO3–N) is provided to plants it first needs to be uptaken and translocated from the roots of the plant through the xylem. It is then absorbed by a mesophyll cell via one of the nitrate−proton symporters into the cytoplasm and reduced to nitrite (NO2) by nitrate reductase enzyme in the cytoplasm. From here the nitrite is reduced to ammonium (NH4) by nitrite reductase enzyme in the chloroplast, which is then incorporated into amino acids by the glutamine synthetase−glutamine− 2−oxoglutarate amidotransferase enzyme system, resulting in glutamine and, ultimately, other amino acids and their metabolites. The nitrate reductase enzyme activity is the limiting step of NO3 N conversion to amino acid synthesis (Campbell, 1999). In most plant species only a proportion of the absorbed nitrate is assimilated in the root, the remainder being transported upwards through the xylem for assimilation in the shoot where it is reduced and incorporated into amino acids (Forde, 2000).[3] See following image.

 

amino-acids-site

Image from Agricultural Science, Edited by Dr. Godwin Aflakpui: Xing-Quan Liu and Kyu-Seung Lee (2012). Effect of Mixed Amino Acids on Crop Growth

 

Looking at the nitrate nitrogen (NO3) to glutamate conversion process, we can see that plants need to process NO3 to NO2 to NH4+ and finally to an amino acid (glutamate), which ultimately becomes other amino acids and their metabolites. Therefore, while plants are adept at uptaking and using inorganic forms of nitrogen, the conversion to amino acids requires the plant to exert energy. However, plants can also uptake and use amino acids directly. This removes the need for the plant to convert NO3 to NO2, then NH4+ and finally into glutamate. Therefore, the energy required for this process can be directed elsewhere (i.e. this energy can be directed to other physiological plant functions such as biomass production).

 

Thus, exogenously applied amino acids have the capacity to enhance the nitrogen use efficiency of the plant. This in turn provides general stimulation to photosynthesis and plant growth.[1] Further, as amino acids enter the plant directly as nitrogen containing molecules, this takes away the need for the plant to convert NO3 into NO2, then NH4+ and finally into glutamate (an amino acid that ultimately converts into other amino acids and their metabolites).

 

While the science is extremely complex, involving enzymes, nitrogen and carbon metabolism, the Krebs cycle etc, amino acids also are shown to enhance the ability of uptake and assimilation of inorganic N by plants. This facilitates higher yields. That is, amino acids have positive effects on plant metabolism, including nitrogen and carbon metabolisms, primary and secondary metabolisms.[2] Most notably, several enzymes of the nitrate assimilation pathway – nitrate reduction and ammonium-to-amine conversion – are stimulated, and molecular analysis has indicated that this upregulation is achieved at the gene expression level, to a large extent. Enzymes of the Krebs cycle (energy production) are also stimulated, which is expected in any situation of enhanced synthesis and recycling of amino acids.

 

Studies of plants grown in hydroponics have shown that uptake of amino acid molecules from hydroponic solutions can occur at levels comparable to or in excess of inorganic sources of N. This is because, in hydroponics, the uptake of amino acids are maximized because unlike in soil, amino acids are readily bioavailable to plants, rather than being chemically or physically bound in soils or denatured. [3]

 

This makes amino acids an ideal part source of N and biostimulant in hydroponic growing situations.

 

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.

Amino Acids as Chelators and Complexers

 

This comes back to the material we have previously covered about chelators and complexers when discussing fulvic acid on page ….. and when talking about chelated and complexed nutrients on pages……

 

To summarize this material, chelators and complexors make nutrients more bioavailable to plants.

 

The positively charged cations, iron, zinc, copper, manganese, calcium, potassium and magnesium can be chelated while other nutrient ions, the negatively charged anions, nitrate nitrogen, chloride, sulphur and 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.

 

Both chelated and complexed minerals are more bioavailable than non-chelated and non-complexed nutrients. This makes the use of amino acids beneficial in hydroponic solutions due to their ability to chelate or complex nutrient ions.

 

Amino acids such as glycine act as chelators when they react with positively charged elements (cations) forming a strong chemical bond. To take a specific example, a chelate can be formed between the amino acid glycine (the chelator) and calcium (the mineral = Ca+). For this reason a hydroponic solution can often be improved by adding glycine.

 

Glycine, like other chelators also helps to stop precipitation of key elements from formulas. Its’ use therefore can prove beneficial in organic or inorganic/organic formulations both as a chelator to better facilitate the delivery of nutrients and as a stabilizer to hold nutrients in solution.

 

Glycine is perhaps of key importance in hydroponics because despite the capability of roots to take up a wide range of amino acids, it has been suggested that glycine is the only amino acid taken up rapidly, relative to inorganic nitrogen (e.g. nitrate nitrogen) due to its neutral charge and low molecular weight.[1] [2]

 

Glycine is the simplest amino acid with a molecular weight of 75. Glycine is used to produce glycine chelated micronutrients known as glycinates, proteinates and/or amino proteinates.

 

Glycinates contain 2 moles of ligand (glycine) and one mole of metal ion. 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. This offers distinct advantages because nutrients are literally delivered to the parts of the plant where they are most needed when chelated or complexed by glycine.

 

Research has demonstrated:

 

  1. Glycinates increase the availability of micronutrients compared to common
  2. Crops tend to produce higher yields where glycinates are used.

 

 

Benefits of Amino Acids in Hydroponics

 

  • Increased stress resistance
  • Increased salt tolerance
  • Beneficial to photosynthesis
  • Beneficial to the carbon and nitrogen cycle
  • Positive effects on plant metabolism
  • Beneficial to Krebs cycle
  • Increased protein synthesis
  • Increased cell division
  • Increased yields

[1] Kielland K. (1994) Amino acid absorption by arctic plants: implications for plant nutrition and nitrogen cycling. Ecology 75, 2373–2383.

[2] Lipson D.A. & Monson R.K. (1998) Plant-microbe competition for soil amino acids in the alpine tundra: effects of freeze-thaw and dry-rewet events. Oecologia 113, 406–414.

[1] Prof. Patrick du Jardin (2012) The Science of Plant Biostimulants –A bibliographic analysis, a Scientific Review of Biostimulants ordered by The European Commission

[2] Schiavon, M., Ertani, A. & Nardi, S, 2008. Effects of an Alfalfa Protein Hydrolysate on the Gene Expression

and Activity of Enzymes of the Tricarboxylic Acid (TCA) Cycle and Nitrogen Metabolism in Zea mays L.

Journal ofAgricultural and Food Chemistry, 56(24), pp.11800-11808: see also Maini, P., 2006. The experience of the first biostimulant , based on amino acids and peptides : a short retrospective review on the laboratory researches and the practical results. Fertilitas Agrorum, 1(1), pp.2943.

[3] The Rhizosphere: Biochemistry and Organic Substances at the Soil-Plant Interface 2nd Edition

Ed by Roberto Pinton, Zeno Varanini, Paolo Nannipieri:2009, CRC Press, Taylor and Francis Group pp. 118

[1] Prof. Patrick du Jardin (2012) The Science of Plant Biostimulants –A bibliographic analysis, a Scientific Review of Biostimulants ordered by The European Commission

[2] Xing-Quan Liu and Kyu-Seung Lee (2012) Effect of Mixed Amino Acids on Crop Growth

[3] Xing-Quan Liu and Kyu-Seung Lee (2012). Effect of Mixed Amino Acids on Crop Growth, Agricultural Science, Dr. Godwin Aflakpui (Ed.), ISBN: 978-953-51-0567-1, InTech, Available from:http://www.intechopen.com/books/agricultural-science/effect-of-mixed-amino-acids-on-crop-growth

 

 

FULVIC ACID (Humates)


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. 1

 

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:

 

[Quote]

 

“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.” 2

 

[End Quote]

 

In research conducted by Fabrizio Adani et al (1998) 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. 3

 

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.4

 

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 hydroponic applications ranges between 25-300ppm (very dependent on what other chelators are present but let’s not get too complex for now). I recommend FA use at between 40-50ppm where standard, chelated hydroponic nutrients are used.

 

If you need to work out how to achieve 40-50ppm of fulvic acid in solution you use this equation.

 

The Dilution Volume =                    The Concentration You Want  X   The Volume You Want

____________________________________________

The Concentration You Have

 

I.e. the equation is, the concentration you want times the volume you want, divided by the concentration you have. Actually, perhaps we need an example.

 

Strictly speaking this equation is used to establish how many ml or grams would be used to achieve a given ppm in solution.

 

V1 = C2 x V2

_______

C1

 

This comes from the dilution/concentration equation of  C1 x V1 =  C2 x V2

 

C stands for concentration and V stands for volume. 1 refers to stock, and 2 refers to diluted solution.

 

C1 = Initial Concentration (80,000mg/L)

V1 = Initial Volume (unknown)

C2 = Final Concentration (50mg/L = 50ppm)

V2 = Final Volume (1 Litre)

 

Let’s say that we had an 8% fulvic acid product that is listed as percentage weight by volume (%w/v) and we want to work out how much of our FA product is required to achieve 50ppm of FA in solution.

 

That’s 8 (%) x 1000 divided by 100 = 80g/L of FA in solution. I.e. 8% w/v equals 80 grams of FA per litre.

 

The next thing we need to do is to convert the units of measurement into ppm. Keep in mind that 1ppm equals 1mg/L and that ppm and mg/L are the same thing with different units of expression.

 

Keep in mind also that 1 gram = 1000mg or 1000ppm. (1000ppm in 1 Litre – parts per million is like a %age of something)

 

Therefore, 80g/L = 80,000mg/L = 80,000 ppm.

 

The initial volume is the amount that you need to make up to the final volume and the final volume is 1 litre.

 

Using the equation;  C1 x V1 = C2 x V2

 

80,000 x V1 = 50 x 1

 

V1 = 50 x 1 divided by 80,000

 

V1 = 0.000625 (Litres)

 

To Convert Litres to mL X 1,000

 

0.000625 x 1000 = 0.625 ml/L

 

Therefore, to achieve 50ppm of FA in solution you would need 0.625mL / Litre of an 8% w/v FA additive or 6.25ml per 10 litres.

 

This equation can be used for working out all sorts of dilution rates in order to achieve a given ppm, %w/v or mg/L in a final solution.

 

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 (1998)The 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).1

 

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….. (following page)