The use of phosphate fertilizer has promoted changes in phosphorus fractions and availability in soil, that highlights the requirement of more studies to understand phosphorus dynamics in soil, and to develop cultivation strategies to increase crop grain yield under phosphate fertilization. The work aimed to evaluate changes in soil phosphorus availability in sequential crop seasons, under effects of phosphate fertilizer sources and cover crop plants. The experiment was carried at Technological Federal University of Parana, Dois Vizinhos, PR, Brazil. The soil is a Ferralsol, with high level of available P. Experimental design was a factorial 3*8, in randomized blocks, with three replicates and 5*5 m plots. Treatments were composed of natural phosphate and soluble phosphate, and a control. During winter season, the seven cover crops were: vetch, white lupin, radish, ryegrass, black oat, clover and pigeon pea, and a witness with no cover crop. Brazilian Ferralsol, with high level of available P, does not increase plant grain yield with sources of phosphate fertilization. Available P in soil changes markedly with phosphate fertilization, especially in the surface layer (0-5 cm). Important results are expected in soil P availability after winter cover crops.
