In this paper,to solve the issues of unreasonable fertilizer application and lower nitrogen use efficiency, the effects of nitrogen rate on soil NO3 --N,yield and nitrogen use efficiency of maize were studied by using randomized block design started from 2011 to 2012.The results revealed that the yield increased with the increase of nitrogen rate and reached the highest grain yield of 4 922.22 kg·hm -2 under N rate of 180 kg·hm -2 in 2011 and 10 267.06 kg·hm -2 un-der N rate of 225 kg·hm -2 in 2012.The accumulation of NO3 --N at 200 cm soil layer was increased with nitrogen in-puts wad increased,peaking at 501 .65 kg·hm -2 in 2011 and 422.07 kg·hm -2 in 2012.The NO3 -1 -N accumulation at 0 ~200 cm soil layer of different nitrogen treatments varied significantly with planting year.The nitrogen use efficiency was increased and reached 25 .13% at nitrogen rate of 180 kg·hm -2 and then decreased.Optimum nitrogen rate can in-crease the yield and nitrogen use efficiency,reduce the soil accumulation of NO3 --N at 200 cm soil layer,thus reduc-ing the potential threat to the environment.%针对黄土高原半干旱区春玉米全膜双垄沟播栽培中施肥不科学和氮肥利用率低的问题，研究不同施氮量对春玉米产量、土壤硝态氮及氮肥利用率的影响。采用2011—2012年两年田间定位试验，设置0、135、180、225、270 kg·hm －2和360 kg·hm －2六个施氮量，探讨不同施氮水平对作物和环境的影响。结果表明，随施氮量的增加，玉米产量先增加后降低。2011年施氮量180 kg·hm －2时玉米子粒产量达到最大，为4922．22 kg·hm －2，显著高于 N135，与 N225、N270差异不显著；2012年施氮量225 kg·hm －2时，玉米子粒产量达到最大，为10267．06 kg·hm －2，与对照及其它施氮处理差异不显著。硝态氮累积量在200 cm 土层中随氮素投入量的增加而显著增加，随种植年限的增加各处理间差异增大。2011年 N180、N225、N270、N360处理间硝态氮累积量差异均不显著，但显著高于 N135处理；2012年各施氮处理间硝态氮累积量差异相互显著，N360累积量高达615．50 kg·hm －2。玉米氮肥吸收利用率随着施氮量的增加呈先增加后降低趋势，施氮量为180 kg·hm －2时，氮肥吸收利用率达到25．13％。适宜的施氮量能提高玉米产量及氮肥利用率，并且200 cm 土层内硝态氮累积量较低，对环境的潜在危害较小。
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