Modeling Long-Term Impacts of Phosphorus Fertilization Strategies on Maize Productivity and Soil P Dynamics in Calcareous Soils of North China Plain

The North China Plain (NCP), a major maize production region in China, faces critical challenges of P overuse under intensive farming, leading to soil P accumulation, leaching risks, and threats to groundwater quality and P resource sustainability. This study employed a parameter-calibrated APSIM model (v7.9) to simulate long-term effects (2007–2017) of eight P application rates (0–300 kg P 2 O 5 ha −1 ) on maize growth, P utilization, and soil P dynamics using field trial data from Quzhou Country (36.9°N, 115.0°E), Hebei Province, China. Results demonstrated that 71 kg P 2 O 5 ha −1 optimized maize productivity, achieving mean aboveground biomass and grain yields of 17.5 t ha −1 and 9.3 t ha −1 , respectively, with a P use efficiency (PUE) of 17%. Continuous P fertilization induced progressive accumulation of labile P (32 mg/kg under 75 kg P 2 O 5 ha −1 application rate vs. 40.8 mg/kg under 100 kg P 2 O 5 ha -1 application rate in 2017) and stable inorganic P pools, with P100 exceeding the environmental threshold (39.9 mg/kg) for calcareous soils. Post-cessation simulations (22 years) revealed that legacy P from 11-year P75 applications sustained maize yields at 8–10 t ha −1 for 12–13 years, despite labile P decreasing from 32.3 to 15.8 mg/kg. Model analysis highlighted limitations in APSIM’s current P module, which prioritizes adsorption-desorption over precipitation-dissolution mechanisms critical for calcareous soils. These findings provide a theoretical foundation for P reduction strategies in NCP maize systems.