Chemical fractionation of zinc and its relationship with important properties of rice grown soils

Abstract

GPS based 90 representative surface soil samples were collected randomly from rice growing farmers’ fields to understand the distribution of Zn fractions. Five mechanistic Zn fraction i.e. Extractable Zn, carbonate Zn, organic Zn, amorphous Zn and residual Zn were determined and Total Zn was calculated as a sum of these five pools which ranged from 14.28 to 138.41 mg kg-1 with an average of 34.47 mg kg-1. Fractional distribution of Zn in these rice soils showed the order: RES-Zn > Org-Zn > WSEx-Zn > CO3-Zn > Ox-Zn. Correlation analysis showed that WSEx-Zn increased with SOC (r = 0.788) and silt+clay (r = 0.237).The fact that the chemistry of Zn in this set of soils appears to be dominated by the most stable fractions offers an explanation for the common notion held that majority of rice grown Navsari soils have low soil Zn test levels which accounts for low Zn bio-availability.