Optimal Nitrogen Supply Improves Grain Yield and Resource Use Efficiency in Winter Wheat under Supplemental Irrigation

Water scarcity is a great challenge for wheat production. Recently, a new supplemental irrigation (SI) regime, which considers crop requirement and soil water storage, is being widely adopted for saving water in wheat fields. However, the effects of nitrogen (N) fertilization rates on wheat under this new SI regime have been rarely assessed. A two-year field experiment was conducted using four N rates (0, 180, 210, 240 kg ha(-1)) under SI to address the research gap. Compared to the conventional flood irrigation, SI increased the total dry matter accumulation at maturity and dry matter allocation to grain in post-anthesis phase, increasing grain yield. At 210 kg N ha(-1), the higher nitrogen use efficiency (NUE) and water use efficiency (WUE) were attained under SI than under conventional flood irrigation. For different N rates, soil water consumption from 80-120 cm soil layer was higher at 210 kg N ha(-1). The flag leaf water potential, Phi PSII, and Fv/Fm at 210 kg N ha(-1) during 14-28 days after anthesis were higher which resulted in high dry matter accumulation. The WUE and grain yield were higher at N rate of 210 kg ha(-1) treatment, which also recorded higher NUE than 240 kg N ha(-1) but lower than 180 kg N ha(-1). Therefore, 210 kg N ha(-1) with SI regime can be the optimum nitrogen and water management for increasing wheat yield, WUE and NUE in semiarid regions. (C) 2020 Friends Science Publishers