ZINC ADSORPTION IN SOILS AS INFLUENCED BY DIFFERENT SOIL MANAGEMENT PRACTICES

Abstract

Zinc adsorption was studied in four soils (two Alfisols and two Inceptisols) under three different moisture regimens, viz., flooded-drying (FD), alternate wetting and drying (AWD), and preflooding (PF), each with and without added organic matter (0.50 and 0%). Results showed that the FD and AWD moisture treatments caused a marked decrease, whereas the PF treatment caused a marked increase, in the magnitude of Zn adsorption by the soils compared with controls (no moisture and no organic matter treatment). When organic matter was combined with all three moisture regime treatments, however, there was a significant increase in Zn adsorption compared with the no-organic matter control. Other adsorption-related parameters of the soils, such as adsorption maxima, bonding energy constant, free energy change for Zn, and Zn-hydroxide potential, affirmed the pattern of changes in Zn adsorption following such treatments. All such changes have been explained on the basis of the changes in soil physico-chemical properties, viz., pH, CaCO₃ equivalent, and Fe oxides as a result of treatments. Amorphous Fe oxides and soil pH were, however, found to play a major role in this regard. Results indicated the need for split application of Zn under AWD and FD regimes, but the reverse is true under PF treatments.