Effects of Nitrogen Application on Yield and Water Use Efficiency of Winter Wheat in Semi-Humid Area of the Loess Plateau

Nitrogen fertilizer has been broadly applied in agriculture practice for a long term.The effects of nitrogen fertilizer on winter wheat yield and water use efficiency in the Loess Plateau of China were studied in two years.The nitrogen fertilizer application were set at four different levels,e.g.100 kg·hm-2(N100),200 kg·hm-2(N200),300 kg·hm-2(N300),and 400 kg·hm-2(N400),in the long-term field experiments,and 0 kg·hm-2(N0)was set as control.Soil water content and water use efficiency in 0~200 cm soil profile at different growth stages of winter wheat were analyzed.Results showed that grain yield,dry matter weight and water use efficiency(per unit grain yield and dry matter weight)of winter wheat under nitrogen application treatments(N100,N200,N300,and N400)were significantly larger than those of control(N0),while soil water content under all nitrogen treatments were comparatively less during each growth stage.Water consumption and yield under N100 and N200 treatments were consistently larger than those under N0 in the two experimental years,while N300 and N400 treatments showed less water consumption and lower yield,compared to N0.Furthermore,compared to N0,all nitrogen application treatments showed increased water use efficiency,either in‘per unit grain yield’or in‘per unit dry matter weight’,but both of them under N300 treatment had no significant difference with those under N200 and N400 treatments.In a conclusion,the treatment of N200 was found as an optimal nitrogen application scheme in semi-humid area of the Loess Plateau,regarding its comprehensive performance in yield and water use efficiency.