The results showed that precipitati

The results showed that precipitation had relative less impact on yields than SRD and temperature. Wheat at the stations was well irrigated. Yields were not sensitive to precipitation because the majority of the ˇ3in the multiple regression models were not statistically significant in Zones I–VII (Supporting Information). Wheat was prone to water-logging, insects and disease during rainy season and high precipitation reduced crop yields particularly during RGP.In Zone VI, temperature and SRD were quite high, which caused high evapotranspiration and water requirements. The results also showed that yields decreased with SRD increase in Zone I, Zone Vand Zone VII. Excess SRD can photoinhibit photosynthesis and maylead to photooxidative destruction of the photosynthetic apparatus (Long et al., 1994), such as in Zone V and high altitude Zone VII (Zhang and Tang, 2005). In Zone I, there was a negative correlation between SRD and minimum temperature, decreases of SRD benefited yields because of the associated reduction in frost occurrence. In addition, there is experimental evidence that yields of some crops can rise if small reductions in total radiation coincide with increases in diffuse radiation (Stanhill and Cohen, 2001).