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Crop Water Requirement and Utilization Efficiency-Based Planting Structure Optimization in the Southern Huang-Huai-Hai Plain

Optimizing planting structure that balances both high yield and water resources shortage is essential for developing efficient water-saving agriculture. To provide insights about the relationship between planting structure optimization and water resource constraint, crop water requirement, precipitation coupling degree, gross total water requirement and irrigation project metrics were calculated and analyzed with the dataset collected from 16 locations in Xuchang City, China. The strategy of reducing the planting proportion of high water-consumption crops and increasing low consumption and high precipitation coupling degree crops was adopted to determine a suitable water-saving planting scheme based on the IQR (interquartile range) method. Evapotranspiration had a decreasing trend from northwest to southeast areas. There were positive correlations between gross total water requirement (GTWR) and annual total yields (r = 0.825, p = 0.002), and between GTWR and proportion of vegetable planting areas (PVPA) (r = 0.734, p = 0.0101). The GTWR was negatively correlated with the ratio of water-saving irrigated areas to effective irrigated areas (RSEA), proportion of wheat planting areas (PWPA) and proportion of bean planting areas (PBPA), with coefficients of −0.787, −0.936 and −0.828, respectively. The planting proportion of winter wheat, summer maize, vegetables and flowers decreased by 8.8%, 25.8%, 16.2%, and 28.7%, respectively, while oil-beans and tubers increased by 62.4% and 95.6%, respectively. The irrigation water consumption was reduced by 5.2%, saving 3.25 × 107 m3 irrigation water without sacrificing economic benefits after adjusting for the whole region. Consequently, precipitation coupling degree, water-saving technology and historical planting habits should be considered when optimizing cropping distributions. This research provided a new theoretical basis and comprehensive approach for agriculture irrigation water management and regional planting structure optimization from a realistic perspective.