Stability constant of Fe2+ chelates with soluble ligands from incubated soils

Summary The stability constants (log K) of Fe²⁺ chelates were determined on the basis of the shift in peak potential during the reduction of Fe²⁺ by a consortium of soluble ligands from incubated soils. Log K values ranged from 2.6 to 4.5. On average a change in pH of 1 unit induced a change in log K of 0.92 units. Aeration of the anaerobic decomposition products increased log K. The log K for Fe²⁺ chelates was about 0.8 units larger than that for Mn²⁺ chelates. It is considered that the chelation of ferrous iron plays an important role in the mobility and availability of iron to plants.