Forms, reactions and availability of iron in soils

Abstract

Abstract This paper discusses the forms and reactions of Fe in soils in relation to mechanisms of uptake by plants. Of all the forms of Fe in soil, the most reactive mobile (e.g. Fe complexes) and immobile (e.g. Fe(III) oxides) forms are the most likely to be utilized by plants. The behaviour of these forms, although influenced by pH, complexation and redox properties of the soil, is dominated by the insolubility of the hydrous ferric oxides. Uptake of Fe from both sources may be brought about by active uptake and secretion of protons and electrons (reductants). Of mechanisms, the significance of the Fe stress response in soils is undecided while contact reduction of insoluble Fe at the root‐soil interface is a plausible uptake mechanism which can be reconciled with many of the causes of Fe deficiency. Availability of Fe in soils would appear to depend on (a) the chemical nature and reactivity of the forms of Fe, (b) the physiological and morphological properties of plant roots, and (c) the Interaction at the root‐soil interface.