Soil phosphorus fate and its lability after a long-term phosphorus fertilizer strategy in Brazilian Oxisol

We aimed to assess the changes in soil phosphorus (P) pools and legacy P after long-term phosphate fertilization. A field study was conducted for 12 years with cotton and soybean crop production in a yearly rotation. Treatments included initial P buildup with five rates (0, 50, 100, 150 and 200 kg ha(-1)of P2O5), and annual band-applied P at five rates (0, 30, 60, 90 and 120 kg ha(-1)of P2O5). Soil was sampled at 0-20 and 20-40 cm and analyzed for soil P pools via a sequential P fractionation scheme. Higher annual P rates (60, 90 and 120 kg ha(-1) of P2O5) improved significantly the residual soil P accumulation in labile fractions (+34, +53 and +67 mg kg(-1) of P, respectively), while no effect of initial P buildup was detected. The cumulative yield increased with annually banded fertilizer rates, with a peak under 91 kg ha(-1)of P2O5, representing a productivity of 4.11 Mg ha(-1) per year across the 12-year period. Thus, P accumulation from annual rates in labile fractions (13%, similar to 110 mg kg(-1) of P) represents promptly available P pool in the soil and may be considered for P fertilizer recommendation programs in crop production systems.