An APSIM modified model under drought conditions to simulate winter wheat yield in North China

Abstract: Drought is one of the main agrometeorological disasters to affect the winter wheat yield in North China. The crop model is one of the main approaches to assessing the effect of drought on crop yield. However, it is urgent to improve the crop growth model under extreme weather and climate conditions (such as drought), due to the blur simulation of the crop yield. This study aims to more accurately simulate the crop yield under extreme weather conditions using the crop model. The validated agricultural production systems simulator (APSIM) was utilized to simulate the effect of different drought grades on the yield during the stage from the jointing to flowering and from flowering to maturity of winter wheat. The correction coefficient of APSIM was proposed for the effect of drought on wheat yield. 186 literatures and a total of 1876 pairs of observation data were collected, including irrigating, N application rate, crop yield, water use efficiency, and the number of stations. The crop water deficit index (CWDI) was selected as the agricultural drought index to divide into the different drought grades. The temporal and spatial distributions of drought were then analyzed using historical climate conditions and the future climate scenarios of SSP245 and SSP585. The modified APSIM model was used to evaluate the effect of the drought grades on the yield of winter wheat during the stage from jointing to flowering and from flowering to maturity. The results showed that the APSIM model underestimated the effect of drought winter wheat yield during the stage from jointing to flowering. The correction coefficients of light, medium, and heavy drought were 0.85, 0.91, and 0.85, respectively. The APSIM accurately simulated the effect of light and medium drought on the winter wheat yield during the stage from flowering to maturity, but overestimated the effect of heavy drought, with a correction coefficient of 1.33. Under historical and future climate scenarios, the decreasing spatial distribution was observed in the yield reduction rate of winter wheat from the north to the south. The negative impact of drought during the stage from flowering to maturity on the winter wheat was higher than that during the stage from jointing to flowering. Furthermore, the yield reduction rate caused by the light, medium and heavy drought under future climate scenarios was lower than that under historical climate conditions. The negative impact of drought was alleviated in the future climate scenarios on the winter wheat yield, compared with the historical climatic conditions. The finding can provide theoretical and practical significance for drought prevention and food security in North China.