Effects of nitrogen application on grain yield, nitrogen utilization and balance of winter wheat under limited irrigation condition

Effects of different N application rates on grain yield and N utilization of winter wheat and soil N balance were studied using field experiment under water-limited irrigation during 2008-2009. The results show that spike numbers and per spike grains of winter wheat are significantly increased under N applications, while the 1000-grain weight is not significant increased. The relationships between grain yield, N uptake and the N application rates are parabolic, and grain yield and N uptake are reduced when N application rates exceed N 240 kg/ha. Soil NO-3-N is found at 0-20, 20-40, 40-60, 60-80 and 80-100 cm soil layers after the erecting stage of winter wheat. Soil NO-3-N contents are decreased with increase of soil layer depth under the same treatment, and are increased with increase of N application rates at the same layer. Soil NO-3-N accumulations decrease with winter wheat growth and development. Under the N0 and N120 treatments, there are NO-3-N deficiencies after the jointing stage and anthesis stage. In the harvest stage, soil residual N in 100 cm soil layer is the main part of surplus N, and soil lost N accounts for little percentage. With increase of N application rates, N utilization efficiency and N agronomy efficiency appear downtrend, while the N residual efficiency appears uptrend. Under this experiment condition, N application rates from N 180 to 220 kg/ha has good combinations of grain yield, N utilization efficiency and N residual efficiency. Therefore, the N 180-220 kg/ha are ideal N rates considering both economic benefit and environmental benefit under water-limited irrigation.