Sulfate formation and extraction from Red soil treated with micronized elemental sulfur fertilizer and incubated in closed and open systems

Abstract

Two extractants, 0.01 M CaCl2 and 0.01 M Ca(H2PO4)2, and two incubation systems, closed and open, were used to investigate the influence of granule dispersion and granule size on formation in a Red soil treated with a new micronized, granular S0 fertilizer at rates of 500 and 3000 mg kg−1 of S0. Sulfate production was significantly greater with dispersed micronized particles than for either the 1 to 2 mm or 2 to 4 mm intact granule size fractions. Increasing the dosage of S0 resulted in much greater formation from all particle sizes of S0. Quantities of extracted by 0.01 M Ca(H2PO4)2 generally exceeded those removed by 0.01 M CaCl2 in both the closed and open incubation systems. Levels of extractable recovered in the open incubation procedure were consistently much greater than those in closed incubation. In open incubation, extractable varied from 0.66 to 36.79 mg S/100 g soil and 1.35 to 65.02 mg S/100 g soil, respectively, for the 0.01 M CaCl2 and 0.01 M Ca(H2PO4)2 leaching solutions. With closed incubation, recoveries ranged from 0.15 to 12.08 mg S/100 g soil and 0.21 to 31.74 mg S/100 g soil in the 0.01 M CaCl2 and 0.01 M Ca(H2PO4)2 extracts, respectively. The average oxidation percentages measured by 0.01 M Ca(H2PO4)2 extraction were 27.9%, and 36.7% greater than those occurring with 0.01 M CaCl2 extraction, in closed and open incubation, respectively. Oxidation percentages for the dispersed S0 particles were significantly higher than for intact fertilizer S0 granules, which increased significantly with decreasing granule size. Oxidation percentages were significantly greater at the lower dosage rate of S0 fertilizer. Highly significant linear function relationships between cumulative formed by oxidation of S0 and the time of open incubation were found.