Trade-offs and synergies in phosphorus release kinetics under hydrothermal conditions and nutrient management in a rice–wheat system

Despite sustained fertilizer inputs, the stabilization and release of phosphorus (P) within soil aggregates under varying hydrothermal conditions remain poorly understood in intensively cultivated rice–wheat (R-W) systems. In particular, mechanistic insights into how nutrient supply options regulate aggregate-associated total phosphorus (AATP) distribution and P-release kinetics across contrasting moisture–temperature regimes are limited. To address this gap, a 19-year long-term rice–wheat experiment at ICAR-IIFSR, Modipuram, India, was used to evaluate the effects of contrasting P–management strategies on AATP storage and phosphorus mineralization dynamics. Across nutrient treatments, AATP increased with aggregate size and declined with soil depth, with macro-aggregates storing approximately 20–25% more P than micro-aggregates. Integrated and organic nutrient management enhanced AATP concentrations by ~20–40% compared with mineral fertilizer and unfertilized control treatments across aggregate fractions. Phosphorus mineralization was strongly regulated by nutrient management, incubation time, and hydrothermal regime. Elevated temperature and submergence increased phosphorus mineralization rates by ~25–40% relative to field capacity conditions. Integrated nutrient strategies consistently showed 40–60% higher phosphorus mineralization rates and 30–50% greater P–release constants than conventional fertilizer management. Overall, the study demonstrates that long-term nutrient management interacts with soil aggregation and hydrothermal regimes to regulate trade-offs and synergies in P–stabilization and release in R-W systems. These findings provide quantitative, process-level evidence to inform P–management strategies aimed at improving use efficiency and long-term sustainability of intensive cereal-based agroecosystems.