Optimizing irrigation strategies for wheat–maize rotation in the North China Plain under future climate Scenarios: Balancing water use, yield, and carbon intensity

The North China Plain (NCP), a major grain-producing region, is experiencing severe water scarcity and groundwater overexploitation, which threaten the sustainability of wheat–maize rotation. Optimizing irrigation management under future climate conditions is critical to sustain crop productivity while alleviating pressures on water resources and the agro-environment. This study employed the APSIM model to simulate the crop yields, water consumption (ET), and global warming potential (GWP) of a wheat–maize rotation system in the NCP from 1980 to 2060 under Shared Socioeconomic Pathways 2–4.5 (SSP245) and Shared Socioeconomic Pathways 5–8.5 (SSP585) scenarios. The APSIM model was calibrated and independently validated using observed crop yield data, achieving good performance (R2 = 0.71–0.80, nRMSE = 11.83%–17.08%) before being applied to long-term regional simulations. Five irrigation strategies were evaluated using the APSIM auto-irrigation module, where irrigation was triggered to replenish soil water up to the drained upper limit when soil moisture depletion reached 5 mm (W1), 15 mm (W2), 30 mm (W3), 45 mm (W4), and 60 mm (W5), respectively. The results showed that wheat yield is projected to increase by 19.6%–22.1% by the 2050 s. In contrast, maize yield shows a modest increase under SSP245 (+2.5%) but a slight decline under SSP585 (-1.0%). A comprehensive multi-criteria assessment further demonstrated that W3 irrigation strategy (30 mm threshold) consistently delivers the most favorable trade-offs among yield stability, irrigation water savings (24%) and GWP reduction (43%). This strategy dominated most cropping areas (65.0–80.3% for wheat and >85% for maize), with substantial regional water-saving potential (3.2–3.8 billion m3 for wheat and 9.6–10.0 billion m3 for maize) while maintaining minimal yield losses. This study provides process-based evidence to inform climate-adaptive irrigation management and promote sustainable agricultural development in the NCP.