Variations in wheat water requirement and climatic causes in arid regions of northwest China

Analysis of crop water requirement and its influencing factors are important for optimal allocation of water resources. However, research on variations of climatic factors and their contribution to wheat water requirement in Xinjiang is insufficient. In our study, daily meteorological data during 1961‒2017 in Xinjiang was collected. Penman-Monteith formula and crop coefficient method was adopted to calculate wheat water requirement. Mann-Kendall mutation test and grey correlation degree analysis were used to investigate variation characteristics and correlation degree between climatic factors and wheat water requirement. The results showed that wheat water requirement ranged from 511 to 548 mm (average = 529.5 mm). Spatial distribution of wheat water requirement in Xinjiang presented a pattern of "southeast > Northwest, east > west". Wheat water requirement in most areas of Xinjiang showed a decreasing trend. During the whole growth period of wheat, the top five climatic factors affecting wheat water requirement in Xinjiang were ET₀, T_max, T_mean, sunshine duration, and U_mean. Precipitation and relative humidity negatively impacted wheat water requirement, while reference crop evapotranspiration (ET₀), mean wind speed (U_mean), mean temperature (T_mean), maximum temperature (T_max), minimum temperature, and sunshine duration had positive effects. This study provides a comprehensive basis for the decision making of efficient agricultural water use and irrigation measures in Xinjiang.