The present work was carried out to evaluate in two different soils fertilized with different phosphorus sources the use of phosphorus and the soybean yield grown in succession to forage grasses. Two experiments were carried out using Inceptsol (Cambisol) and Oxisol (Latosol), using four dm³ pots with soil. The experimental were carried out in a completely randomized design in a 5 x 2 factorial scheme, the five treatments being of soil cover, represented by the previous cultivation of the four forage plants (Brachiaria decumbens, Brachiaria brizantha, Pennisetum glaucum and Sorghum bicolor), plus the soil without cultivation and two sources of P (Triple Superphosphate - TSP and Arad Reactive Phosphate - ARP). The cover forage plants were harvested in the flowering, being cultivated following on straw and root, the soybean as succession culture, the soybean was harvested after had completed the development cycle. In Inceptsol, when fertilized with the lower solubility (ARP) P source, the previous cultivation of the forage plants promoted larger growth, production and use of the residual effect of applied P in the soybean cultivated in succession; the same was not observed in Oxisol. For the soluble source (TSP), the previous cultivation of the forage grasses didn't affect those variables in the soybean cultivated in Inceptsol and, in a general way, in Oxisol, it was harmful, when compared with the treatment without cultivation. Among the forage grasses studied, a defined effect of their previous cultivation on the evaluating variables in the soybean cultivated in succession was not observed.
use of phosphorus; vegetable coverage; crop succession
