减量施氮对渭北旱地春玉米产量、氮素利用及土壤硝态氮含量的影响

为确定渭北旱地春玉米减肥增效的科学生产模式,于2016—2019年在陕西合阳县实施旱地春玉米田间定位施肥试验。以郑单958和陕单8806为试验品种,设置5个施氮量处理,分别为360(N₃₆₀,当地农户常规施氮量)、270(N₂₇₀)、150～180(N_150-180)、75～90(N_75-90)和0 kg·hm^-2 (N₀),分析减量施氮处理下春玉米产量、氮素吸收利用及硝态氮残留状况。结果表明: 1)与N₃₆₀处理相比,两个品种在N_150-180处理下籽粒产量增加0.9%～7.1%,吸氮量降低4.1%～4.6%,平均氮肥回收利用率、偏生产力和农学效率分别提高79.3%～83.6%、105.9%～157.7%和101.9%～114.1%;2)在高施氮量(大于180 kg·hm^-2)处理下,硝态氮残留量显著增加;降雨不足显著降低玉米需氮量,导致氮素残留量增加。经过4年定位试验0～200 cm土层硝态氮含量高达504.7～620.8 kg·hm^-2,在80～140 cm土层出现累积峰,存在硝态氮淋失风险。根据年际间玉米籽粒产量表现、肥料利用效率和硝态氮残留状况综合评价,渭北旱地春玉米田适宜氮肥用量为150～180 kg N·hm^-2。

Effects of reduced nitrogen application on yield,nitrogen utilization of spring maize and soil nitrate content in Weibei dryland,Northwest China

To get a scientific pattern for nitrogen-reducing and efficiency-increasing production of spring maize in Weibei dryland, we conducted an in-situ field experiment of spring maize (Zhengdan 958 and Shaandan 8806) under dryland farming from 2016 to 2019 in Heyang County, located in Weibei dryland of Shaanxi. There were five nitrogen (N) treatments, including 360 kg·hm^-2(N₃₆₀, a rate commonly adopted by local farm households), 270 kg·hm^-2(N₂₇₀), 150-180 kg·hm^-2(N_150-180), 75-90 kg·hm^-2(N_75-90) and 0 kg·hm^-2(N₀). We investigated the effects of reduced nitrogen application on maize yield, nitrogen uptake and utilization of spring maize and soil nitrate residue. The results showed that: 1) Maize yield of both varieties at N_150-180 was increased by 0.9%-7.1% and nitrogen uptake was decreased by 4.1%-4.6%, while average reco-very efficiency, partial-factor productivity and agronomic efficiency of N at N_150-180 were increased by 79.3%-83.6%, 105.9%-157.7%, and 101.9%-114.1% compared with those at N₃₆₀, respectively. 2) The contents of residual nitrate increased significantly when nitrogen application rate was more than 180 kg·hm^-2, while nitrogen uptake was significantly reduced under rainfall shortage, and thus resulted in increasing soil residual nitrogen. After four-year treatments, the residual nitrate was up to 504.7-620.8 kg·hm^-2 in 0-200 cm soil layer, with a peak in 80-140 cm soil layer. There was a risk of nitrate leaching. According to the comprehensive evaluation for annual yield, nitrogen use efficiency and soil nitrate residue, the optimum N application rate was recommended to be 150-180 kg N·hm^-2 for spring maize in Weibei dryland.