Modelling future climate change impacts on winter wheat yield and water use: A case study in Guanzhong Plain, northwestern China

Climate change in China would cause change into precipitation patterns and rise in temperature. The assessment of climate change impact on Chinese wheat production is needed for both rainfed and irrigated farming in order to maintain wheat self-sufficiency and to assure future food demand. The current study assesses the future trends of wheat yield in Guanzhong Plain, China by employing the calibrated Agricultural Production Systems sIMulator (APSIM)-wheat model and using the downscaled daily climate projections for 32 general circulation models (GCMs), under two representative concentration pathways (RCP 4.5 and RCP 8.5). Simulations were carried out for rainfed cropping and various levels of irrigation for future time windows of 2030s, 2060s, and 2090s. The climate projections show an overall gradual increase in future temperature and precipitation for the region. It was found that the climate change would shorten the growing period of winter wheat, as the flowering shifted back on an average by 8-18 days and 10-34 days, under RCP4.5 and RCP8.5, respectively. Similarly, maturity date shifted back on an average by 8-16 days and 10-32 days under RCP4.5 and RCP8.5, respectively. An improvement in the future rainfed winter wheat yield was noted for all simulation time periods, and the average yield increase was 6.75 %, 21.5 % and 26.5 % for 2030s, 2060s, and 2090s, respectively. Irrigation provided at a threshold of 10 % and 20 % of plant available water capacity (PAWC) was found suitable to be used as supplementary irrigation, and it resulted an overall improvement of 27 % in rainfed yield. Any increase in yield for irrigation provision beyond 20 % PAWC threshold was not statistically significant. It was found that the optimum irrigation amount with high water use efficiency (WUE) would range from 90 mm to 132 mm and up to 56 % of water can be saved by avoiding irrigation with thresholds over 20 % PAWC. These results could help policy makers and farmers to adapt accordingly in future, ensuring the sustainable and improved wheat production in this region.