Yield and water use responses of winter wheat to irrigation and nitrogen application in the North China Plain

With increasing water shortage resources and extravagant nitrogen application, there is an urgent need to optimize irrigation regimes and nitrogen management for winter wheat (Triticum aestivum L.) in the North China Plain (NCP). A 4-year field experiment was conducted to evaluate the effect of three irrigation levels (W1, irrigation once at jointing stage; W2, irrigation once at jointing and once at heading stage; W3, irrigation once at jointing, once at heading, and once at filling stage; 60 mm each irrigation) and four N fertilizer rates (N0, 0; N1, 100 kg N ha^?1; N2, 200 kg N ha^?1; N3, 300 kg N ha^?1) on wheat yield, water use efficiency, fertilizer agronomic efficiency, and economic benefits. The results showed that wheat yield under W2 condition was similar to that under W3, and greater than that under W1 at the same nitrogen level. Yield with the N1 treatment was higher than that with the N0 treatment, but not significantly different from that obtained with the N2 and N3 treatments. The W2N1 treatment resulted in the highest water use and fertilizer agronomic efficiencies. Compared with local traditional practice (W3N3), the net income and output-input ratio of W2N1 were greater by 12.3 and 19.5%, respectively. These findings suggest that two irrigation events of 60 mm each coupled with application of 100 kg N ha^?1 is sufficient to provide a high wheat yield during drought growing seasons in the NCP.