ABSTRACT
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%, ~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.
Disclosure statement
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.