Assessing the effects of precipitation and irrigation on winter wheat yield and water productivity in North China Plain

Achieving high crop yield with less irrigation is important to improve water productivity (WP) and irrigation water productivity (IWP) in water-limited regions in the North China Plain (NCP). Coupling the impacts of precipitation and irrigation on the crop yield is, therefore, an essential tool for understanding crop response to different water sources and forecasting irrigation water requirements. In this study, the CERES-Wheat model was used to simulate winter wheat yield, WP, and IWP under different irrigation schedules (no, deficit, full, and automatic irrigation) and three precipitation category years (wet, normal, and dry years). Results showed that the amount of precipitation fluctuated significantly over site-years, leading to considerably varied irrigation water requirements. For the wet year, deficit two irrigations at greening and jointing stages (treatment 11) alleviated water stress during key winter wheat growth periods, contributing to increasing biomass, yield, WP, and IWP. However, when reducing the irrigation amount by 50%, a significant increase in WP and a nonsignificant difference in yield were found at Fengqiu and Shangqiu. Two irrigation applications 11 improved pre-anthesis biomass and wheat yield while achieving high WP and IWP in normal and dry years (except for extreme drought conditions). The finding also indicated that the distribution of growing season precipitation exerted a significant impact on irrigation time. If the early season precipitation was low, shifting the irrigation to an earlier time to ensure pre-anthesis water requirements, which can synchronously achieve the goals of increasing WP and maintaining a higher yield. In conclusion, optimizing irrigation strategies to various precipitation conditions will be a promising and effective practice for wheat production and water conservation.