Phosphorus accumulation and depletion in soils in wheat-maize cropping systems : Modeling and validation

Abstract Long-term (over 15 years) winter wheat ( Triticum aestivum L.)–maize ( Zea mays L.) crop rotation experiments were conducted to investigate the accumulation of phosphorus (P) at five sites differing geographically and climatically in China. The results showed that, in soils without P added, the concentration of soil P extracted by 0.5 mol L −1 NaHCO 3 at pH 8.5 (Olsen-P) decreased with cultivation time until about 3 mg kg −1 , afterwards it remained constant. The trend of decrease in Olsen-P in soils without P added could be described by an exponential function of time. The concentration of Olsen-P in soils with P fertilizers increased with cultivation time and the model of accumulation of Olsen-P in soils could be described using P application rate, crop yield and soil pH. The accumulation rate of Olsen-P in the long-term wheat–maize crop rotation experiments was 1.21 mg kg −1  year −1 on average. If the target yield of wheat and maize is 10 ton ha −1 in the soil with pH 8, the increasing rates of Olsen-P in soils as estimated by the model will be 0.06, 0.36, 0.66, 0.95, 1.25 and 1.55 mg kg −1  year −1 when P application rates are 30, 40, 50, 60, 70 and 80 kg P ha −1  year −1 , respectively. The models of accumulation of Olsen-P in soils were validated independently and could be used for the accurate prediction of accumulation rate of Olsen-P in soils with wheat–maize rotation systems. Also the application of the model was discussed for best management of soil P in agricultural production and environment protection.