Effects of irrigation and fertilization on grain yield, water and nitrogen dynamics and their use efficiency of spring wheat farmland in an arid agricultural watershed of Northwest China

Inappropriate irrigation and nitrogen application had caused low water and nitrogen use efficiency and severe NO3--N leaching in spring wheat field in the Wuliangshuhai lake watershed (WLSLW) of Northwest China. Thus, aimed at determining the rational irrigation and nitrogen fertilization for spring wheat in this area, field experiments were carried out in the 2019 and 2020 seasons to investigate the effects of irrigation and nitrogen application on soil water and nitrogen status, grain yield, and water and nitrogen use efficiency. Three irrigation levels, i.e., 180, 315, and 450 mm (13, 12 and Ilk and three nitrogen fertilization rates, i.e., 170, 250, and 340 kg N ha(-1) (N3, N2 and N1) were respectively considered in the experiments. Results indicated that increasing irrigation depth increased root zone soil available water, and increasing nitrogen application could significantly enhance the available nitrogen content in root zone soils and the soil water utilization amount by wheat. Under the control treatment (I1N1), about 25-32% of the applied nitrogen was leached out of the root zone soils throughout the year. Compared to the control treatment, the I2N2 treatment could reduce NO3--N leaching by 32%, and increased the water use efficiency (WUE) and partial factor productivity of nitrogen fertilizer (PFPn) by 33% and 44%, respectively. In addition, the highest yield and net profit of 8078 kg ha(-1) and 1.82x10(4) Chinese Yuan ha(-1) was achieved by the I2N2 treatment, respectively, and it was 6% higher than that of the control treatment. Therefore, considering the grain yield, WUE, PFPn economic benefits and environmental impacts, the strategy of 315 mm irrigation and 250 kg N ha(-1) nitrogen application is recommended for spring wheat in the arid agricultural watershed of Northwest China and areas with similar conditions.

Automated summary

Inappropriate irrigation and nitrogen application can lead to low water and nitrogen use efficiency and severe NO3--N leaching in spring wheat fields. Adjusting irrigation depth and nitrogen application levels can improve soil water and nitrogen status, increase grain yield, and enhance water and nitrogen use efficiency. By optimizing irrigation and nitrogen fertilization, it is possible to achieve higher yields, economic benefits, and environmental sustainability.