Distribution of different forms of iron in arid zone soils of Punjab, India

Abstract

Profiles of arid‐zone soils in Punjab, northwest India, were investigated for different forms of Fe, including total, diethylenetriamine penta‐acetic acid (DTPA)‐extractable, soil solution plus exchangeable Fe, Fe adsorbed onto inorganic sites, Fe bound by organic sites, and Fe adsorbed onto oxide surfaces. In general, the highest content of Fe was observed in the surface layers and then decreased in the lower layers. However, none of the forms of Fe exhibited any consistent pattern of distribution. Irrespective of the different fractions of Fe present, Fe content was higher in fine‐textured than in coarse‐textured soils. Soil pH, calcium carbonate, organic matter, and size fractions (clay and silt) had a strong influence on the distribution of different forms of Fe. Based upon the linear coefficient of correlation, the soil solution plus exchangeable Fe increased with increase in organic C and clay content. Iron adsorbed onto inorganic sites (crystalline) only increased with clay content. The fraction of...