SULPHUR AVAILABILITY IN BRAZILIAN SOILS: EVALUATION OF NATIVE SULPHUR SUPPLYING POWER TO PLANTS

Abstract

An open incubation experiment was carried out in laboratory conditions using columns containing 50 g of soil from seven soils of the States of São Paulo, Minas Gerais and Goiás (Brazil), in presence and absence of liming. Soil columns were leached with KC1 0.01 M every other week during 14 weeks. A second greenhouse experiment was carried out with twelve soils from the same States. Corn (Zea mays L.) was grown in two successive croppings in presence of three rates of S (0, 20 and 40 ppm) applied as gypsunt. Total sulphur and carbon contents and sulphur mineralization potentials of the soils were correlated with sulphur absorption by corn plants. Total sulphur contents of soils showed no significant correlation with sulphur uptake (r=0.234 n.s.). Carbon content was significantly correlated with sulphur uptake in presence of liming (r=0.754, n=36), being lower in its absence (r=0.457, n=36). Sulphur mineralization potentials of soils were significantly correlated with sulphur uptake by corn in presence of liming (r=0.797, n=21), with no significance to its absence (r=0.373 n.s.). In joint analysis (no liming and liming) there was also a highly significant correlation (r=0.753, n=42). The best correlations of carbon contents and sulphur mineralization potentials of the soils with sulphur uptake in presence of liming can be accounted for by organic sulphur mineralization and inorganic S-S0₄= desorption.

KEY-WORDS: Carbon; sulphur; sulphur uptake; sulphur mineralization potentials.