Effects of Irrigation and Polymer-Coated Urea on Water-Nitrogen Productivity and Yield of Winter Wheat

Optimal irrigation and nitrogen (N) fertilization play essential roles in improving crops yield, but the interactive effects of irrigation and controlled-release N fertilizer on yield, photosynthesis characterizes, water, and N productivity in winter wheat ( Triticum aestivum L.) were not well studied. A two-year field experiment was conducted with two types of N fertilizer (urea (U) and polymer-coated urea (PCU)) in combination with three irrigation levels ((traditional irrigation (100%I); 85% of traditional irrigation (85%I), and 70% of traditional irrigation (70%)) using the split-plot design. The N released from PCU was consistent with the N requirement of winter wheat, especially with 100% irrigation. Compared with U treatments, the nitrate N (NO 3 − -N) in 0–20 cm soil was improved after the jointing stage, while it was decreased in 80–120 cm soil by using PCU after wheat harvested. Compared with 70%I, the net photosynthetic rate ( P n ) of 100%I and 85%I were enhanced at the jointing and anthesis stage, and the grain yields improved by 1.9 ~ 16.3% and 3.8 ~ 30.2%, respectively. In addition, the application of PCU combined with 85% of traditional irrigation achieved higher water productivity, while the grain yields were nearly the same as 100% irrigation. Fifteen percent reduced irrigation combined with PCU was recommended as the optimal measure to obtain superior benefits for winter wheat growth in arid and semi-arid areas.