DTPA-extractable and total Zn, Cu, Mn, and Fe in Indian soils and their association with some soil properties

Abstract

Fifty-seven benchmark soils of India representing eight orders (Entisols, Inceptisols, Aridisols, Vertisols, Alfisols, Ultisols, Oxisols and Mollisols) were studied for the distribution of DTPA-extractable (representing plant available) forms and total contents of Zn, Cu, Mn and Fe in their surface horizons. Changes in pH, lime, organic matter, size fractions (clay) and soil moisture regime (pedoclimate) had a strong influence on the micronutrient distribution. Based upon the linear coefficients of correlation the DTPA-extractable: (1) Zn declined with a rise in pH and/or lime and with a fall in organic matter, and clay content, (2) Cu increased with an increase in organic matter, clay and total Cu content, and (3) Mn and Fe decreased with a rise in pH and/or lime content and with a fall in organic matter content. The total contents of Zn, Cu, Mn and Fe increased with lime and clay content. With a changing soil moisture regime from aquic to ustic and to aridic/torric, the pH and lime content increased, while organic matter content and clay content decreased. Accordingly, availability of Zn, Cu, Mn and Fe decreased as the soils became aridic; contrarily their total contents increased. Irrespective of the soil moisture regime, parent materials from which soils developed also influenced their total micronutrient contents. Based upon the DTPA-extractable micronutrients, only Zn deficiency is expected to be widespread (43 out of 57 soils) in Indian soils. The surface horizons of Alfisols, Vertisols, Aridisols and Inceptisols were represented by a larger number of Zn deficient soils.