Problem

Water deficiency is an important factor limiting wheat production in northern China. Fortunately, at present, one-off irrigation for wheat can be guaranteed in some drought-prone areas with the quick development of the high-standard construction of farmland in China, but the information about how to better utilize one-off irrigation is limited. Moreover, the interactive effects of irrigation, tillage, and nitrogen (N) rate on grain yield and water and N use efficiency in wheat are poorly understood.

Objective or research question

This study aimed to determine if and how one-off irrigation interacted with tillage and N fertilization to affect wheat productivity, resource use efficiency, and soil nitrate-N residues in a drought-prone area of China.

Methods

Using a split–split plot design with three replications, we conducted a three-year (2019–2022) field experiment at the intersection between the Loess Plateau and the Huang-Huai-Hai Plain in China. The main plots were assigned to two irrigation levels (non-irrigation and one-off irrigation), while three tillage methods (rotary tillage, sub-soiling, and plowing) and four N rates (0, 120, 180, and 240 kg N ha⁻¹, represented by N0, N120, N180, and N240, respectively) were assigned to the subplots and sub-subplots, respectively. Grain yield, plant N accumulation, water and N use efficiency, and soil nitrate-N residues were examined.

Results

One-off irrigation increased the grain yield, plant N accumulation, and water and N use efficiency, but decreased the soil nitrate-N residues in the 0–200 cm soil layer at wheat harvest. Although one-off irrigation, tillage, and N rate did not interactively affect grain yield and water and N efficiency, the improvement in one-off irrigation was considerably affected by N rate, and there was a significant interaction between tillage and the N rate on grain yield and water and N efficiency. One-off irrigation combined with sub-soiling and N180 improved grain yield and water use efficiency more than other treatment combinations in all three years. Furthermore, one-off irrigation combined with sub-soiling and N180 optimized plant N accumulation and the N harvest index, thus increasing grain N accumulation, N uptake efficiency, N agronomy efficiency, and N apparent use efficiency by 44.8%, 42.7%, 33.5%, and 55.1%, respectively, and decreased nitrate-N residue in the 0–200 cm soil by 14.2% compared with sub-soiling combined with N180 under non-irrigation, averaged across three years.

Conclusions

One-off irrigation combined with sub-soiling and N180 is an optimal strategy for high-yielding, high-efficient, and low soil nitrate-N residues of wheat in the drought-prone area.

Implications or significance

This study provides an important reference for manipulating tillage and N rate under one-off irrigation to improve grain yield and resource use efficiency in drought-prone areas.