Effect of water on yield of winter wheat at different growth phases

The characteristic of climate in North China is short of precipitation in winter and spring. Insufficient supply of water is a major factor affecting yield of winter wheat. The variation of yield caused by irrigation or drought at different stages is not alike. The relationship between them can be represented with water-yield reaction coefficient. Based on the experiment conducted in 2001 through 2004, yield of winter wheat has a marked positive correlation with precipitation at different stages after winter. The water-yield reaction coefficients increase with crop development, especially in turning green stage. The maximum occurs at head sprouting stage. Then it decreases slightly at milking stage. In order to raise water use efficiency of winter wheat, it is necessary to practice irrigation at elongating and head sprouting stages first and milking stage next.