Susceptibility Assessment of Winter Wheat, Barley and Rapeseed to Drought Using Generalized Estimating Equations and Cross-Correlation Function

Abstract

Due to the impact of drought on crop yield, the aim of this research is the susceptibility assessment of winter wheat, barley and rapeseed species to drought using Generalized Estimating Equations (GEE) and Cross-Correlation Function (CCF). For this objective, the climatic data of 10 synoptic stations in Iran from 1968 to 2017 (i.e., 50 years) were used. Then, the AquaCrop model was adopted to simulate annual yield (Ay) of the above-mentioned species. Also, the standardized precipitation evapotranspiration index (SPEI) was applied to assess drought conditions in selected constant and progressively increasing reference time periods, including 1-month, 3-month, 6-month and 12-month time scales (27 reference time periods) starting in October. For evaluating the accuracy of the GEE model, the correlation coefficients (CC) between simulated and predicted annual yields in selected species through the AquaCrop model and GEE model were used, respectively. The accuracy test of the GEE model showed that the CC between simulated and predicted annual yield of barley almost in all stations and all-time scales were significant at 0.01 level. Only in Birjand and Kerman stations the CC between simulated and predicted annual yield were significant at 0.05 level in 3.7% and 66.67% of time scales, respectively. Based on the GEE and CCF models in all stations, the susceptibility of rapeseed to drought was more than that of wheat, and the susceptibility of wheat was more than that of barley.