Phosphate fertilizers and soybean yield in soils with different phosphate buffer capacities

The efficiency of three new phosphate fertilizers (test sources, TS) was assessed and compared to traditional P fertilizers in terms of nutrition and yield of soybeans, on three different soils: a Quartzarenic Neosol, a loamy dystrophic Red-Yellow Latosol, and a clayey dystrophic Red-Yellow Latosol. The greenhouse experiments, in a factorial layout of (2 x 4) + 8, compared two TS (TS1 and TS2) in four doses, with eight additional treatments for each soil [triple superphosphate with calcitic lime, triple superphosphate with dolomitic lime, triple superphosphate + TS1, triple superphosphate + TS2, magnesium thermophosphate, Araxa rock phosphate, TS3, and a control (no P)]. Based on the remaining-P analysis, different P doses were determined for each soil. P supply by TS1 and TS2 increased the yields of soybean dry matter and grain. The use of TS's, separately or in mixture with triple superphosphate, provided vegetative growth and production of soybean that is comparable to treatments with triple superphosphate and thermophosphate. The increase in the P capacity factor of the soil restricted the P uptake and contributed to a greater P use efficiency for soybean, leveling off the effect of the treatments.