Optimizing plastic film mulching and nitrogen fertilizer strategies for spring maize in Loess Plateau through field experiments and enhanced AquaCrop modeling

• Plastic film mulching (PM) enhanced spring maize yield and soil water and heat. • AquaCrop model improved using stage-specific temperature compensation under PM. • Improved model achieved higher accuracy in simulating canopy cover and biomass. • Optimal PM–nitrogen setup: full film 180 kg N dry years, wide film 225 kg N normal/wet. Plastic film mulching (PM) is widely used to improve soil temperature and moisture in rainfed agriculture, but the combined effects of PM proportions and nitrogen (N) fertilization on spring maize under different hydrological conditions remain unclear. We conducted a two-year field experiment (2021 and 2022) in the Loess Plateau and improved the AquaCrop model by incorporating stage-specific temperature-increase compensation coefficients for full and wide PM treatments. Results showed that PM increased soil temperature by 2.11–3.59°C and water content by 14.3–21.2% during the first 90 days after sowing, requiring compensatory temperature increases during the sowing-tasseling stage. The modification reduced normalized root-mean-square error values of canopy cover and biomass from 14.2 and 7.6% to 8.1 and 6.2%, respectively. Using 40 years of hydrological simulation, we identified the optimal PM–N combinations: FN180 (100% PM+180 kg N ha −1 ) for dry years to maximize precipitation use efficiency (+35.3%), and WN225 for normal and wet years to balance yield and nitrogen fertilizer agronomic use efficiency (>14 kg kg −1 ). Our results demonstrate that tailoring PM proportions and N rates to hydrological conditions enhances water–nutrient synergy, providing a climate-resilient management approach for sustainable maize production in semi-arid agroecosystems.