Phosphorus fractions as a function of the use of phosphate fertilizers in different soil classes

Most Brazilian soils have low natural fertility. The main characteristic is phosphorus (P) deficiency and high P adsorption capacity. This creates the need to add phosphate mineral fertilizers, organic or organomineral. This addition can cause changes in P dynamics in the soil. Thus, the aim of this study was to evaluate the P fractions in the soil as a function of the application of organic fertilizer, organomineral and mineral phosphate, in different soil classes. The experimental design used was entirely randomized, in a 3x3 factorial scheme. The treatments consisted of three P sources (mineral, organic and organomineral phosphate) in three soil classes (RED LATOSOL Dystrophic, YELLOW ARGISOL Dystrophic and QUARTZARENIC NEOSOLS), cultivated with Glycine max and then with Urochloa (sin. Brachiaria) ruziziensis, in the same units. For the fractionation of P, a collection of all experimental units was performed 270 days after the implementation of the experiment. The organic fertilization with phosphate increased the total P of the soil, mainly the non-labile forms, while the mineral fertilization contributed to increases in the labile fractions of P in the soils. In sandy soils, labile P levels are higher.