Diversified rotation systems improve grain yield and water use efficiency of winter wheat under limited irrigation in the North China Plain

Diversifying crop rotation aims to balance production and ecological concerns. However, yield and water use efficiency (WUE) of crop in diversified rotation systems have not been well documented, especially under limited irrigation. Here, we conducted a 6-year experiment with five treatments: 1) wheat-maize cropping system (WM), as control; 2) WMME, spring maize → WM rotation; 3) WMML, spring millet → WM rotation; 4) WMMP, spring peanut → WM rotation; and 5) WMMS, spring soybean → WM rotation, to explore how diversified rotations affected yield and WUE of wheat. Results showed that approximately 60% higher precipitation during wheat growing season in Cycle 1 (2015–2017) resulted in yield increases by 33.8%–55.7% compared to those in Cycle 2 (2017–2019) and Cycle 3 (2019–2021). Grain yield and WUE of wheat were 16.7% and 9.6% higher in Cycle 1, 81.5% and 86.8% higher in Cycle 2, and 56.1% and 78.7% higher in Cycle 3 on average in diversified rotations compared to those in WM, respectively. Further analysis revealed that spike number and aboveground biomass were the main contributors to the increments, which can be explained by the increased evapotranspiration during the middle-late wheat growth stages (e.g., regreening, jointing, and anthesis) in diversified rotations. In general, diversified rotations enhanced synchronization of soil water supply with crop water demand by affecting the spatiotemporal dynamics of soil moisture under varied precipitation conditions, thereby increasing yield and WUE of wheat. Hence, diversified spring crops → WM rotations offer a sustainable and efficient strategy for enhancing wheat production and water conservation in dry areas.