Sensitivity analysis of wheat yield based on growing degree days in different growth stages: Application of machine learning approach enhanced by grey systems theory.

•The wheat yield sensitivity to different stages of growth and various variables has been investigated.•Growing degree days (GDD) and crop coefficient (Kc) were introduced as crop-specific variables.•The mid-season stage was identified as the best time window.•By using the proposed approach, wheat yield can be achieved before the harvest season.