Effects of dairy effluents irrigation on yield and nitrogen use efficiency of winter wheat and soil nitrate nitrogen

【Objectives】Study on the effects of dairy effluents on grain yield, nitrogen use efficiency and soil nitrate contents will provide theoretical basis for the assessment of livestock effluents irrigation on farmland, so as to decrease the risk of nitrogen lose from livestock effluents.【Methods】 A field experiment using dairy effluents for irrigation in winter wheat was conducted successively for three years in the plain of North China. The study included five treatments with three replications: No fertilizer and irrigated with freshwater (CK); two irrigation with dairy effluents in wintering and filling stages, two freshwater irrigation, the total nitrogen brought with effluents was 160 kg/hm2 (T1); three irrigation with dairy effluents in wintering, jointing and filling stages, one freshwater irrigation in heading stage, the total nitrogen brought with effluents was 240 kg/hm2 (T2); four irrigation with dairy effluents in wintering, jointing, heading and filling stages, with total nitrogen brought with effluents of 320 kg/hm2 (T3); and farmer customized fertilization, inorganic compound fertilizer with 375 kg/hm2 after planting, and 600 kg/hm2 urea application at the wheat jointing stage and freshwater irrigation in wheat growing season(CF). The total irrigation quota was 830 m3/hm2, and the irrigation quantity was controlled by water Ultrasonic flow meters. The soil nitrite nitrogen content and winter wheat yield were investigated at harvest. 【Results】 1) The dairy effluents irrigation significantly increased the yield of winter wheat which was fluctuated with the input of nitrogen from the effluents, the highest yield was obtained in the three dairy effluents irrigations with the N input of 240 kg/hm2. 2) The nitrogen accumulation in plants and grains of wheat irrigated with effluents was significantly higher than those of the CK. In 2011 and 2012, there were no significant differences in the nitrogen accumulations in plants among the treatments, in 2013, however, those in T2 and T3 were significantly higher than in T1 and CF. 3) With the increasing of nitrogen brought by dairy effluents, the nitrogen recovery efficiency and nitrogen agronomic efficiency were decreased, with the average values of 48.57% and 37.15 kg/kg in T1, respectively. 4) After the harvest of winter wheat, the soil nitrate nitrogen accumulation in 0-100 cm layer was increased with the increasing of nitrogen amount of dairy effluents. The 0-100 cm layer of soil nitrate nitrogen accumulation in the T3 was significantly higher than those in T1 and T2.【Conclusions】 Dairy effluents irrigation significantly increases the grain yield of winter wheat. With the increase of nitrogen amount from dairy effluents, the nitrogen recovery efficiency and nitrogen agronomic efficiency of dairy effluents are decreased. The nitrate nitrogen accumulation in 0-100 cm soil layer is significantly enhanced with 320 kg/hm2 of nitrogen brought with the four irrigation of dairy effluents. This result indicates that most of nitrogen is not utilized by winter wheat, might leached into deep soil. Under the experiment conditions, considering comprehensively, the proper nitrogen amount brought with dairy effluent in winter wheat was 160-240 kg/hm2.