Shifts in Sowing Dates and Water Management Promote High and Stable Potential Yield of Silage Maize in China: Implications for Quality Feed Intensification

Context: Filling China's massive forage gap requires intensified silage maize (Zea mays L.) production with high and stable yield. Modifying irrigation and sowing time comprise two practical, cost-effective measures for such intensification, yet their spatial effects remain insufficiently quantified. Methods: Using the APSIM Classic 7.10 version for Maize, calibrated with experimental data using a differential evolution algorithm, we assessed biomass yield potential, irrigation benefits, and sowing strategies at 10 km resolution across five regions in China (1980-2017). In addition, partial correlation analysis was employed to identify the climatic drivers of irrigation benefits, while sensitivity analysis was conducted to evaluate the effects of sowing date and climate variability on biomass yield. Results: Under full irrigation and non-nitrogen-limiting conditions, potential yield (Yp) exceeded 24 Mg/ha in Northeast (NE) and Northwest (NW) China, while rainfed potential (Yw) was highest in Southwest (SW; 20 Mg/ ha) and Southeast (SE; 18 Mg/ha). Irrigation expanded high-yield stable (HS) areas from low-yield unstable (LU) zones by 26%, particularly in arid and semi-arid northern zones, with impacts of irrigation modulated by mean annual precipitation (MAP) during growing season. Optimal sowing strategies varied by region and water regime: early sowing by 30 days most improved HS areas in North China Plain (NC; +49%), SE (+28%), and SW (+26%) under sufficient water, while NE and NW favored 20-day and 10-day advances, respectively. Under rainfed conditions, southern regions benefited from early sowing, whereas the north required moderate delays for yield stability. Sensitivity analysis further confirmed that sowing date dominated irrigated yield variability in the north, while precipitation and radiation were key limiting factors in rainfed northern (MAP < 650 mm) and southern (MAP > 1000 mm) zones, respectively. Conclusions: This study provides the first high-resolution national assessment of silage maize, offering a scientific basis for tailoring its deployment to regional climate constraints and water availability, thereby supporting resilient forage intensification under changing environmental conditions.