限水灌溉下施氮量对冬小麦产量、氮素利用及氮平衡的影响

2008~2009年通过大田试验,研究了限水灌溉条件下,不同施氮量对冬小麦产量、氮素利用、土壤硝态氮动态变化及氮素平衡的影响。结果表明,施用氮肥显著增加小麦穗数和穗粒数,对千粒重无显著影响。作物产量、吸氮量与施氮量均呈抛物线关系,施氮量超过N240 kg/hm2,产量和吸氮量随施氮量增加略有降低。小麦起身期后,0—100 cm土层都有硝态氮分布,且随土层深度增加而减少;相同土层则随施氮量的增加而增加。土壤硝态氮积累量随生育期推进而降低,N0和N120处理分别在拔节期和开花期后表现出氮素亏缺;成熟期,土壤表观盈余以残留为主,表观损失量占小部分。氮肥表观利用率、农学利用率随施氮量增加呈降低趋势,而氮素残留率随施氮量增加呈增加趋势。在本试验条件下,施氮量在N 180~220 kg/hm2水平可以达到产量、氮素表观利用率、氮素残留率的较好结合,是限水灌溉下兼顾经济效益与环境效益的适宜施氮量。

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.