Every plant needs certain components—beyond soil, sun, rain and air—for them to grow. The basic components of living cells are proteins, which are formed from building block materials called amino acids.
Making amino acids available in appropriate quantities has long been known as a means to increase the yield and overall quality of crops. Amino acids are also an effective natural chelating agent.
Chelates (as well as amino acids) have been the subject of many discussions inside local hydroponic stores recently. Let’s take a look at both and see if we can gain a more clear understanding of their function and importance.
Chelating certain micronutrients is a popular topic when discussing the many fertilizers available for indoor gardeners. A technical discussion of chelates often requires a strong background in chemistry to understand, but the basic principle is really quite simple; they are a thin coating put around the nutrient, like the candy shell on an M&M.
Consider this—put the opposite poles of a magnet together and see how stuck these become. This is what happens when the negatively charged root tries to absorb the positively charged micronutrients.
What would help the root to be able to absorb the nutrient would be to somehow make the nutrient’s charge neutral, which is where the chelate or coating for the nutrient comes in. It’s like a blanket around the charged nutrient element and in effect creates a neutral charge, allowing the binding or fixing of the nutrient at the plant root or pore. Voilá—in it goes! Why do we do this?
For starters, the roots and leaves of plants are negatively charged (anions), while the trace elements (micronutrients) are positively charged (cations). Because of this polar difference in the electrical charge, the nutrient is ‘fixed’—or stuck outside of the plant root.
Another aspect that affects nutrition uptake by plants is related to precipitation. We are not talking about rain here, but a kind of nutrient tie-up. For example: a basic trace element like iron reacts to another element like ethyl alcohol (in the hydroxyl group) and forms insoluble ferric hydroxide.
In this case nature is taking a completely available form of iron and changing it to a form that is not. The result of this reaction is that the iron is now unavailable for absorption by the plant—it’s like it’s not in the soil at all.
Here’s a useful definition for chelation: chelation in soil increases nutrient availability to plants. Organic substances in the soil, either applied, or produced by plants or microorganisms, are natural chelating agents. The most important substances having this nature are hydroxamate siderophores, organic acids and amino acids.
Hydroxamate siderophores are naturally produced by soil microorganisms and are essential in natural ecosystems to make nutrients soluble and transport them (especially iron and copper) to plant roots.
To a certain degree the plant and the biology of the soil can work on this new modified element and once again make it available, but only in a very limited way. What we really want is to prevent this precipitation from happening in the first place and making the trace nutrient a complex by chelating it accomplishes this.
Although the beneficial bacteria that exist in the soil constitute another method of causing chelation and making plant nutrients more available, a little blanket of chelation placed around micronutrients—made from amino acids and other organic acids—is a very important added feature that most gardeners want to see in the nutrients they use.
Just how much of a positive impact on plants can chelation have? Research conducted in the USSR (by Tronov) indicated that glycinate, an amino acid, greatly stimulates the growth of plants. These results showed that zinc glycinate (zinc glycine chelate) increased total plant weight by between 147 per cent and 254 per cent.
Manganese glycinate (manganese glycine chelate) was almost as effective, increasing total plant weight by as much as 110 per cent. Now, these results are not going to be found in every application, but they do show how potentially beneficial micronutrient chelates can be in helping you to get the maximum yield from your crops.
The type of chelating agent you use is also a very important consideration. Some agents are too strong in bonding with the nutrient and can actually impede plant uptake, while others may be too weak and not able to prevent unwanted precipitation reactions.
Synthetic Chelates in Fertilizers
Many commercial fertilizers have one or more synthetic chelating agents: EDTA, DPTA and EDDHA are the most common.
- EDTA is the most economical and works best in soil with a lower pH (more acidic, below seven).
- DPTA is a special agent that is designed to work well in soils with a higher pH (more basic, above 7.5).
- EDDHA is the most expensive and the most effective among the synthetic group and has been shown to outperform EDTA and DPTA in studies.
In California, synthetic agents like EDTA, DPTA and EDDHA are allowed to be listed as chelates, while biological agents are required to be listed as complexes. Don’t be confused; these are all chelating agents, although each of them binds to the nutrient in a slightly different manner.
Biological Chelates in Fertilizers
There are compounds that occur naturally with the same beneficial effects on plant nutrition uptake, including fulvic and amino acids. These can be derived from a number of organic sources, like soy or corn protein.
Plants depend on these existing in the soil in order to help them process the nutrients they need to grow and stay healthy. Although synthetic chelating agents cannot be absorbed into plants, amino and fulvic acids can—a feature which adds to the mobility of nutrients within the plant.
The application of amino acids for foliar use is based on their requirement by plants in general and at critical stages of growth in particular. Plants absorb amino acids through stomas and this absorption is proportionate to environmental temperature.
Just getting these nutrients into your plants isn’t the end of the story. Once inside, the nutrients need to move. This translocation within the plant is essential to plant health and is one reason we want to make sure our plants get an adequate supply of calcium. Calcium plays a major role in nutrient movement within the plant and yet ironically tends to bind up many nutrients in the soil.
This is another reason that chelates play such an important part in plant yields, because there are going to be compounds and elements in the soil that the plant needs, but that also impede the availability of other nutrients.
An important issue here is to avoid over-fertilization. The right balance is what good nutrition is all about. You can see (just by the previous example) that too much calcium, or calcium in the wrong form, can be detrimental to the uptake of other nutrients.
Too much nitrogen is bad too, as it will cause what is often called leaf burn as the plant attempts to move the excess nutrient away from itself and out to the end of the leaves. This imbalance can actually kill your plants at extreme levels.
As conscientious gardeners we need to look for fertilizers that provide a broad cross section of nutrients. We need to employ complete fertilizers that include micro- as well as macronutrients, fertilizers based on scientific principles and techniques that help to make (and keep) the nutrients in the soil available to our plants.
Chelates employing amino acids are certainly in the forefront of this discussion and their application will help you to maintain the vigor and health of your indoor garden.