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.

Automated summary

This study evaluated changes in soil phosphorus pools and residual phosphorus after long-term phosphate fertilization. Results showed that higher annual phosphorus rates significantly improved residual soil phosphorus in labile fractions, while initial phosphorus buildup had no effect. The study suggests that the phosphorus accumulation in labile fractions from annual rates can be considered for phosphorus fertilizer recommendation in crop production systems.