Water use efficiency and optimal supplemental irrigation in a high yield wheat field

Water shortage and unbalanced precipitation distribution are major problems threatening agricultural sustainability, especially winter wheat (Triticum aestivum L.) production, in the Huang-Huai-Hai Plain of China, and water-saving cultivation with limited irrigation is a promising technique in this region. An eight-year field study was conducted in this region from 2007 to 2015, with the same water and fertilizer management used in the sowing stage of winter wheat, which then received supplemental irrigation (SI) or no irrigation (rain-fed). The proportion of water consumption from jointing to maturity averaged 56% under rain-fed conditions, but reached 64% under the optimal SI conditions. The main water supply during the different growth periods that was suitable for achieving both high yield and high water use efficiency (WUE) had a nearly constant volume. The optimal seasonal SI amount decreased with an increasing natural water supply throughout the growing season, and its contributions to the seasonal evapotranspiration ranged from 11% to 44%. Significant regression relationships were observed among the main water supply at sowing, precipitation in different growth stages and rain-fed grain yield and between the optimal SI amounts needed from sprouting to jointing or from sprouting to anthesis and the rain-fed grain yield. These results provide important theoretical and technical support for on-demand irrigation by model forecasting. The results also indicated SI, as determined by simultaneously considering the precipitation change, soil water storage condition, and crop evapotranspiration status, is an important way to achieve high yield and conserve water in winter wheat.