Build-up and utilization of phosphorus with continues fertilization in maize-wheat cropping sequence

Long-term phosphorus (P) fertilization in the maize-wheat cropping system in northwest India has led to a considerable build-up of Olsen-P concentrations in many fields that exceed the crop removal. Optimal P management in high Olsen-P soils is desirable to achieve sustainable crop production and reduce the fertilizer P inputs and risk of P transfer to water bodies. This study aimed at finding the impact of fertilizer P applications on crop yield, P uptake, P use efficiency, and P balance (P input minus P output) from a 10 years study on maize-wheat sequence having contrastingly different Olsen-P levels. The results revealed no response to both maize and wheat to P application rates beyond 13 kg ha(-1) in 'very high' P (VHP) (>50.0 kg ha(-1)) soils and 26 kg ha(-1) in 'high' P (HP) (22.5-50.0 kg ha(-1)) and 'medium' P (MP) (12.5-22.5 kg ha(-1)) soils. P fertilization, significantly enhanced average maize P uptake by 8% and 26% and wheat P uptake by 5% and 18% in VHP soils relative to HP and MP soils. The improved agronomic and recovery P efficiencies were obtained in VHP soils by reducing fertilizer P to 50% of the recommended fertilizer P (26 kg P ha(-1)). Without P application, the average Olsen-P declined at the rate of 3.43 kg P ha(-1) year(-1) in VHP soils leading to the highest negative P surplus in these soils. P fertilization rates of 26 kg P ha(-1) or above caused soil P build-up in loamy sand soils irrespective of Olsen-P status, thereby increase soil P surplus ranging from 13.4 to 67.0 kg P ha(-1). Therefore, for attaining optimum yields and P use efficiency under intensively cultivated maize-wheat cropping sequence, long-term P balance, P availability in different Olsen-P soils should be undertaken while formulating P recommendations.