SULPHUR AVAILABILITY IN BRAZILIAM SOILS: RESPONSE TO SULPHUR FERTILIZING IN PRESENCE AND AUSENCE OF LIMING

Abstract

A greenhouse experiment was carried out with surface samples of 12 soils from the States of São Paulo, Minas Gerais and Goiás (Brazil). Carbon (C) content varied from 0.50 to 3.03%, sulphur from 0.0104 to 0.0319% and clay varied from 8 to 60%. Corn (Zea mays L.) was grown in two successive croppings in presence of three rates of S (0, 20 and 40 ppm) applied as gypsum, previously incubated in presence and absence of lime. Dry matter production did not show significant difference due to the two croppings of the soils; sulphur uptake, otherwise, was thoroughly lower in the second cropping, indicating the depletion of native and applied sulphur. Sandy soils have a lower supplying power of sulphur due to its effective small reserve. Clayey soils, moreover “cerrado” soils with higher carbon contents, possess greater croppings and sulphur uptake potentials, provided the soil acidity is neutralized. Liming, besides its role as soil acidity neutralizer and as calcium and magnesium supplier, showed positive interaction with sulphur and a synergistic effect on the depletion of soils native sulphur. The rates of sulphur which maximized dry matter yield and sulphur absorption varied in the range of 20 to 70 ppm, being the highest requirements found in clayey soils with no liming.