Phosphorus supply increases nitrogen transformation rates and retention in soil: a global meta-analysis

Interactions between nitrogen (N) and phosphorus (P) are important for plant growth and ecosystem carbon (C) sequestration. While effects of N supply on P dynamics have been much studied, much less is known about the opposite (P-effect on N). We conducted a meta-analysis by compiling a total of 1734 individual experimental observations from 116 peer-reviewed publications to assess P-addition effects on soil N dynamics. Globally, P additions increased the soil total N (TN) pool, potentially as a result of enhanced plant and microbial immobilization and reduced N losses, with a stronger effect detected under longer duration of P addition (≥ 5 years). A coupled increase in soil organic C with TN signifies the fundamental role of exogenous P supply in enhancing soil C sequestration. Phosphorus addition accelerated some of the soil N cycling processes including gross N mineralization, gross nitrification, and denitrification, with the effect sizes varying among ecosystem types and increasing with P addition rates. Our results indicate the fundamental role of P in affecting soil N pools and processes, and highlight the efficacy of P supply in sequestering soil C and mitigating global C emission.