This study investigates the optimization of basal-top-dressing nitrogen ratios for improving winter wheat grain yield, nitrogen use efficiency, water use efficiency, and physiological parameters under supplemental irrigation. A water-saving irrigation (SI) regime and a sufficient irrigation (UI) control were used. Four split-nitrogen regimes (10:0, 7:3, 5:5, and 3:7 basal-top-dressing ratios) were tested with a constant total nitrogen application of 240 kg ha⁻¹. The 5:5 ratio (N3) significantly increased grain yield, nitrogen use efficiency, and water use efficiency compared to other treatments under both SI and UI conditions. The improved yield was attributed to enhanced flag leaf photosynthetic capacity and grain-filling capacity. SI also increased water use efficiency compared to UI. The 5:5 basal-top-dressing nitrogen ratio with SI is recommended as an optimal fertigation strategy.

Zhen Zhang, Yongli Zhang, Yu Shi, Zhenwen Yu