Irrigation and nitrogen management shape cropland efficiency-sustainability synergies in China.

INTRODUCTION: Cropland systems face the challenge of providing adequate nutrition while managing environmental constraints, such as climate change and water scarcity. In China, where agricultural production supports a large portion of the global population with limited land and water resources, achieving balance between efficiency and sustainability in cropland systems is a critical issue. OBJECTIVES: The purpose of this study is to develop a spatially explicit diagnostic framework that integrates crop production, calorie-output data, and environmental impact models to assess cropland efficiency (CE) and sustainability (CS) across regions and crop types in China. The study aims to identify how these two calorie-based performance dimensions interact and where they either reinforce or undermine each other. METHODS: Crop production data, life cycle assessment, water-footprint accounting and a coupling coordination degree (CCD) model were integrated to evaluate CE, CS and their coordination within a common analytical framework. Random forest models and SHapley Additive exPlanations (SHAP) were then used to characterize the non-linear associations of climate, soil, hydrogeology and management factors on CE, CS and CCD. RESULTS: CE and CS varied substantially across regions, crop types and water-supply conditions. In the Northwest, maximum calorie-based productivities reached about 55.01 kcal g-1N for NUE, 1.95 Mcal g-1 PO43--eq for eutrophication productivity and 2.08 Mcal m-3 for grey-water-footprint productivity. CE and CS were highly correlated nationally (R2 = 0.98), but their hotspots were not fully aligned: CE hotspots were concentrated mainly in Northeast and North China, whereas CS hotspots shifted towards South, Northeast and North China. Irrigation increased CE by roughly one-third in water-scarce Northwest and North China, but reduced GHG productivity by an average of about 13% across regions and by up to 48% in South China. Pulses showed consistently higher CE and CS than cereals and sugar crops. Nitrogen fertilization and irrigation intensity were the dominant management drivers, with positive effects at moderate levels but negative effects on CS and CCD when inputs became excessive. CONCLUSION: Improving cropland performance requires region- and crop-specific strategies, not uniform input expansion. Precision irrigation, balanced nutrient management, soil conservation and crop restructuring can improve the coordination between calorie-based efficiency and environmental sustainability when matched to local water availability, soil conditions, crop portfolios and socio-economic feasibility. The framework provides a transferable diagnostic approach for identifying efficiency-sustainability synergies and trade-offs, while local recommendations still require field validation, farmer-level economic assessment and policy implementation analysis.