Effects of gypsum and lime on perennial soybean grown in two acid soils

Abstract

In a green house experiment at Instituto de Zootecnia. Nova Odessa, SP, it was studied the effect of gypsum, dolomitic limestone, magnesium and sulphur on perennial soybean var. tinaroo grown in two acid soils: a Red-Yellow Podzolic soil, Laras variation from Nova Odessa County, and a Red€™ Yellow Latosol Terrace fase, collected in Pindamonhangaba County. Liming was performed in three levels none: Al³⁺ X 1,5; Al³⁺ X 3,0) Gypsum was studied in three levels, combined with liming levels and the amounths were based on the equivalence of calcium of dolomític limestone. It was included also some treatments where MgO was applied as MgO in the absence of lime, combined with levels of gypsum and others where S was applied as sodium sulphate, combined with the levels of lime, At planting time it was effected a basal fertilization with P, K, B, Cu, Zn and Mo. The treatments were set in -a Randomized Block Design with throe replications. The legume was grown in the fall time (February through June) and it was done two harvests, Both soils besides acidity problems and magnesium deficiency also showed sulphur deficiency for normal growth and nitrogen fixation by perennial soybean. Gypsum is source of sulphur, presented positive and significative effects on perennial soybean only when used after the elimination of the soil acidity problems and magnesium deficiency by the use of dolomitic limestone. Levels of gypsum in the absence of liming reduced dry matter yield and amount of nitrogen of soybean grown in the soil from Nova Odessa, but in the soil from Pindamonhangaba caused small increases in these parameters. Gypsumn application induced small decreases in me exchangeable aluminum and soil pH and increased exchangeable calcium in both soils studied.