Pedospheric attributes in distribution of total and DTPA-extractable Zn, Cu, Mn and Fe in Indo-Gangetic plains

Abstract The benchmark soils of the Indo-Gangetic plains show wide variability with respect to climate, profile development, and soil processes. We attempted to find out their relationships with the spatial distribution of reserve and available micronutrients (Zn, Cu, Fe, and Mn). For this, samples were drawn from genetic horizons of 20 benchmark profiles and total, diethylenetriamine penta-acetic acid (DTPA)-extractable micronutrients (Zn, Cu, Fe, and Mn) were determined. The total content varied from 23 to 99 mg kg −1 for Zn, from 10 to 64 mg kg −1 for Cu, from 1.5% to 4.5% for Fe, and from 169 to 627 mg kg −1 for Mn. These micronutrients reside in the finer fractions and content is high in aquic moisture regime, moderate in ustic moisture regime, and low in aridic moisture regime. Except in soils with fluventic or vertic properties, content of total Cu, Fe, and Mn followed the patterns of eluviation, illuviation, and leaching. Total Zn, on the other hand, had a close association with organic carbon content. The available micronutrient contents depended largely on organic carbon content. The correlation between total amounts of Cu, Fe, and Mn suggested that they occurred together. Although Soil Taxonomy is a morpho-genetic classification, its groupings could not explain spatial distribution of Zn, Cu, Fe, and Mn.