Effects of irrigation on water balance, yield and WUE of winter wheat in the North China Plain

Limited precipitation restricts yield of winter wheat grown in the North China Plain (NCP). Irrigation experiments were conducted during different growing stages of winter wheat (Triticum aestivum L.) at Luancheng agro-ecology systems station of the Chinese Academy of Sciences during 1999/2000, 2000/2001 and 2001/2002 to identify suitable irrigation schedules for winter wheat. The aim was also to develop relationships between seasonal amounts of irrigation and yield, water-use efficiency (WUE), irrigation water-use efficiency (WUEi), net water-use efficiency (WUEet) and evapotranspiration (ET). A comparison of irrigation schedules for wheat suggested that for maximum yield in the NCP, 300 mm is an optimal amount of irrigation, corresponding to an ET value of 426 mm. Results showed that with increasing ET, the irrigation requirements of winter wheat increase as do soil evaporation but excessive amounts of irrigation can decrease grain yield, WUE, and WUEi. These results indicate that excessive irrigation might not produce greater yield or optimal economic benefit, thus, suitable irrigation schedules must be established.