LFS:SoilWeb/Interactions Among Soil Components/Chelates

Structural formula for ferric gluconate (common iron chelate).

A chelate (from Greek chele = claw) is an organo-metal complex in which an organic molecule combines with a metal atom by way of two or more chemical bonds.

Organic molecules that chelate with metals include:

• Substances that are synthesized by roots

• Various humic substances that have multiple carboxyl groups

• Synthetic substances

Importance of chelates

• Dispersed and dissolved chelates readily release metal ions and contribute to nutrient metal availability. Fulvic acids form chelates which provide nutrients to plants.

• Undispersed (flocculated) and undissolved or excessively stable chelates, contribute to nutrient deficiency. Humic acids and humins form very stable chelates.

Siderophores

Under Fe-deficient conditions certain microbes and roots produce chelating ligands called siderophores. These ligands bond with Fe³⁺ and maintain relatively high concentrations of soluble iron.