Chelation is a process that protects the integrity of nutrients. This is true for human nutrition and plant nutrition. Chelates, the actors in the chelation process, help increase the mobility of nutrients and help prevent their unwanted loss due to processes such as leaching or nutrient precipitation. Chelates have been likened to both an orange peel and a lobster’s claw in their form and function. The word “chelate” derives from the Greek word chelé, which means lobster’s claw.
The action of chelates can be likened to organic molecules encircling a metal nutrient like a claw embraces with its pincers. This marriage of organic molecules and metal nutrients is called a “ligand” or chelator. This embrace protects the metal nutrient from combining with other elements or from being lost through absorption. Like an orange peel, the ligand shields the nutrient within until it is ready for use.
What are Chelates and Chelating Agents?
To take this a step further from the above description, chelates are more like a ring system. This ring system is made up of a metal ion encapsulated by a “ring” of varying components derived from organic matter decomposition. The most commonly chelated metal ions are:
- Calcium (Ca)
- Magnesium (Mg)
- Iron (Fe)
- Cobalt (Co)
- Zinc (Zn)
- Manganese (Mn)
- Europium (Eu)
Once these metals have been swept up in this organic chemical process, their cationic characteristics have been compromised. They can be absorbed by plants since the chelate releases the metal ions slowly enough for plant uptake. This characteristic of chelated metals makes them useful in horticultural and agricultural applications as many metal ions would be prone to loss through leaching, runoff, or other chemical reactions. The chelated metals will essentially stay put and become useful to plants.
The chelating agents, or those components that spring forth from the naturally occurring decaying and decomposing processes of organic matter are numerous. These organic molecules can create several different types of bonds with a single metal ion. Natural chelating agents are organic substances either applied by or produced by plants or microorganisms. These include:
- organic acids
- amino acids
- sugar acids and derivatives
- poly flavonoids
- hydroxamate siderophores
- phytosiderophores (phyto: plant; siderophore: iron carrier)
Amino acids are often favored as chelating agents due to the numerous benefits they provide to plants and animals including ease of absorption. Essential amino acids work together by aiding structure function and enzymatic function as well as improving reproduction. Amino acids are thought by many sources to increase plant health, growth, and produce greater yields. They are therefore often used in agricultural applications.
There are numerous synthetic chelating agents as well. These synthetic and often proprietary chelating agents include such difficult to pronounce formulations as:
- Egtazic acid, also known as EGTA (ethylene glycol-bis (β-aminoethyl ether))
- Pentetic acid, also known as DPTA (diethylenetriaminepentaacetic acid)
- EDTA (Ethylenediaminetetraacetic acid)
And numerous others in existence and numerous more being developed…
Both classes of these chelating/complexing agents increase micronutrient (the metal ions) solubility and therefore usefulness to plants. It should be noted, however, that this process can occur naturally without any human intervention.
In the soil, plant roots can release natural chelates through their exudates.
Mugineic acid, (a non-protein amino acid) is a type of natural chelate called phytosiderophore. This is produced by various species of graminaceous (grassy) plants as they exhibit stress due to low-iron stress conditions. The exuded chelate then works by helping plants absorb nutrients in the root-solution-soil system. Such root-excreted chelates form a metal complex (i.e., a coordination compound) with a micronutrient ion in soil solution and approaches a root hair. The chelated micronutrient near the root hair releases the nutrient which finds its way to the root hair. The chelate is then free and becomes ready to complex with another micronutrient ion in the adjacent soil solution, amazingly having the ability to restart the cycle.
Source: Maximum Yield,04/01/2019,"Understanding Chelation in Plants"https://www.maximumyield.com/understanding-chelation-in-plants/2/17808