Responses of yield and WUE of winter wheat to water stress during the past three decades-A case study in the North China Plain

Improving grain yield and water use efficiency (WUE) under limited irrigation is very important for food security in water shortage regions. This paper summarized a long-term field experiment (from 1987 to 2015, 28 growing seasons of winter wheat) on the responses of winter wheat to different levels of water stress under the changing background of cultivars, soil fertility and weather conditions at a site in the North China Plain (NCP). The results showed that during the past 28 seasons soil organic matter and N contents were significantly increased at the experimental site and the atmospheric evaporation demand (ET0) was increased and seasonal rainfall was reduced. Although yield was continuously increased from 1987 to 2015 under irrigated condition, the yield of winter wheat under rain-fed condition decreased recently as compared with that during 2000s due to the higher ET0 and less seasonal rainfall. WUE was increased continuously from past to present, especially under water stress condition, indicating that the winter wheat used water more efficiently under the current growing conditions. This could be attributed to the increase in harvest index, improved N status in soil and the reduced soil evaporation. Overall, the sensitivity of grain yield to the fluctuation in seasonal ET was increased from 1980s to present. Yield reduction rate under water stress was greater under current growing conditions than that back in 1980s and 1990s. However, even with the changes in the responses to water stress, irrigation scheduling of one irrigation application from recovery to jointing for winter wheat could achieve relative stable yield and higher WUE through the 28 seasons and should be taken as optimized irrigation scheduling under limited water supply condition.