Crescimento e acúmulo de fósforo pela soja cultivada em sucessão a diferentes gramíneas forrageiras adubadas com super fosfato triplo e fosfato reativo de arad

Abstract

The objective of this study was to evaluate the effect of the previous cultivation of different forage grasses fertilized with triple superphosphate (TSP) and reactive Arad phosphate (RAP) on growth, yield, and accumulation of P by soybean. Two experiments were carried out ; one in Haplic Cambisol typical tb distrophic, medium texture and the other in Red Latosol typical distrophic very clayey texture. For both experiments, the experimental design was a completely randomized one in a 4 x 2 + 2 factorial scheme; the previous crop being of four forage grasses utilized as cover plants in no-tillage system (Brachiaria decumbens Stapf - braquiária, Brachiaria brizantha Hochst Stapf - braquiarão, millet and forage sorghum) fertilized with two sources of P (RAP and TSP) and two additional treatments, which are the cultivation of soybean and bean plant without the previous growing of cover plants, and also fertilized with TSP and RAP. The plants were harvested after they had completed the development cycle. Grain and shoot dry matter yield and P accumulation in the shoot and in the grains of soybean were determined. The forage plants immobilized the P of TSP, reducing the residual effect for soybean. When forage grasses are fertilized with RAP, there is increased residual effect with increasing yield of soybean in succession to the cover plants, with exception for the growing in succession to Brachiaria brizanta.