Long-term impact of legume-inclusive diversification and nutrient management practices on phosphorus dynamics in alkaline Fluvisol

Abstract

Abstract An insight into the dynamics of soil phosphorus (P) pools with long-term cropping/management practices would help in designing efficient and sustainable management module(s). The study aimed to investigate the long-term impact of diversified rice-based rotations and variable nutrient management practices on the dynamic composition of P pools and their influence on systems’ base-crop productivity in an alkaline soil of Indo-Gangetic plain (Fluvisol). Treatments consisted of four rotations [rice–wheat (R–W), rice–wheat–mungbean (R–W–Mb), rice–wheat–rice–chickpea (R–W–R–C), rice–chickpea (R–C)] each with three nutrient treatments [control (CT), integrated nutrient management (INM), sole-chemical fertilizers (CF)]. Notably, R–C exhibited higher levels of bioavailable-P (soluble-P, Ca2-P, labile-Po), particularly in subsurface soil depth (0.2–0.4 m) compared to other rotations. Likewise, the inclusion of chickpea every alternate year (R–W–R–C) resulted in higher Ca2-P (40%), labile-Pi (15%), labile-Po (11%), and moderately labile Po (8%) compared to R–W rotation demonstrating an increased significance of chickpea in maintaining a favorable soil P regime in alkaline soil. Both R–C and R–W–R–C reduced the surface-to-subsurface depth ratio (SSBR) of soluble-P and Ca2-P while increasing the ratio for microbial biomass P. Even with a suboptimal fertilizer-P rate, INM significantly increased soluble-P (4–33%), labile-Po (13–17%), microbial biomass P (10–26%), moderately labile-Po (4–17%) compared to CF and exhibited higher SSBR values. Correlation analysis demonstrated the substantial influence of very-labile carbon, microbial and phosphatase activities on P availability. The treatment-induced changes in labile-P pools significantly influenced rice (base-crop) yields. In conclusion, chickpea-inclusive diversification and INM could be a sustainable approach to enhance P bioavailability and crop productivity in tropical rice soils.