Effects of Nitrogen Reduction Under Limited Water Micro-Sprinkler Irrigation on Yield, Nitrogen Absorption and Utilization, and Nitrogen Apparent Balance of Winter Wheat

Reconciling high crop productivity with reduced resource inputs is a primary challenge for sustainable agriculture in water-scarce regions. This study evaluated the feasibility of reducing nitrogen (N) fertilizer application for winter wheat under limited micro-sprinkler irrigation in the Huang-Huai-Hai Plain, China. A field experiment compared five treatments: a non-fertilized and non-irrigated control (CK), conventional flood irrigation with standard N (FI), and limited micro-sprinkler irrigation (80 mm) with standard N (MI), a 20% N reduction (MI1), and a 40% N reduction (MI2). We analyzed grain yield, water and N use efficiency (WUE and NUE) and the apparent soil N balance. WUE in this study was expressed as grain yield per seasonal evapotranspiration (ET), and NUE was evaluated using agronomic indices. The results showed that the MI1 treatment maintained a high grain yield that was not significantly different from the high-input FI and MI treatments. This high yield was sustained by a compensatory mechanism involving enhanced post-anthesis N assimilation and increased extraction of deep soil water, which offset the reduced inputs. Consequently, MI1 significantly improved WUE, irrigation water use efficiency (IWUE), and NUE, while reducing the apparent soil N surplus by 74.5% compared to FI. In contrast, the greater N reduction (MI2) led to a significant yield penalty. In conclusion, a moderate (20%) reduction in N top-dressing under limited micro-sprinkler irrigation presents a viable strategy to maintain high wheat yield, simultaneously enhance resource-use efficiency, and markedly reduce environmental N losses.