Chelation: What is it and the Different Types

What is Chelation

Plant nutrients are one of the environmental factors essential for crop growth and development. Nutrient management is crucial for optimal productivity in commercial crop production. Chelation of fertilisers offer a way to increase mineral effciency. Chelated nutrients are protected from oxidation, precipitation, and immobilization in certain conditions because the organic molecule (the ligand) can combine and form a ring encircling the nutrient. The pincer-like way the nutrient is bonded to the ligand changes its surface property and favours the uptake efficiency either through the soil or via foliar application.

Chelation keeps a nutrient from undesirable reactions in solution and soil. Chelated nutrients also facilitate nutrient uptake efficiency for foliar application because crop leaves are naturally coated with wax that repels water and charged substances. The organic ligand around the chelated micronutrient can penetrate the wax layer, thus increasing uptake.

Key benefits of Chelation:

  • Chelation neutralises the positive charge of cations to facilitate their easy entry via a negatively charged plant surface
  • It essentially involves avoiding a traffic jam (clogging of the stomates) to ensure easy entry
  • Chelation can involve a chemical or natural process

Type of Chelation

Chelates (or chelating agents) can be either chemical (synthetic) or natural.

Chemical Chelation

The ligands EDTA, DTPA, and EDDHA are often used in chelated fertiliser. The abundance of metal-complexing groups in EDTA, DTPA, and HEDTA permits a multiple number of metal-enclosing chelate rings to form—a condition promoting stability. All of the chelate rings which form include the metal in a fivemembered ring, a condition that imparts maximum stability. In general, chelating agents are molecules with metal-complexing groups arranged to produce a number of maximum stability chelate rings.

Natural Chelating Agents

The natural chelates are very small molecules, and consequently pass through the plant’s barriers including the cuticle, cell walls, and cell membranes maximizing absorption and assimilation. 

Natural Chelating Agents include:

  • Fulvic acid: is the most powerful natural chelating agent. Fulvic acids have a molecular size ranging from 1000 to 10,000, they are more chemically reactive. There small size means that they can rapidly enter the plant. Fulvic acid is a very effective carbon containing chelation agent which makes it ideal for a foliar additive. FA has a CEC of 1400
  • Amino acids: are all capable of chelation but the single most effective is Glycine. Glycine is the smallest amino acid and it can deliver minerals into the plant incredibly rapidly due to its tiny size
  • Kelp: contains mannitol another powerful chelating agent

Next time you apply foliar fertilisers make sure you use a natural chelating agent to make sure your plant absorbs these precious nutrients.