我国农牧交错区耕作方式与施氮量对小麦氮素利用的影响

在我国内蒙古自治区赤峰市农牧交错区研究了不同耕作方式及不同施氮量对小麦氮肥吸收利用和产量的影响.结果表明：长期实施保护性耕作使小麦对氮素的利用率提高3%～4%，减轻氮肥对农田环境的污染；保护性耕作有利于促进小麦对氮素的吸收，提高小麦产量.当施氮量由120 kg·hm^-2增加到360 kg·hm^-2时，小麦对氮素的吸收利用由36.5%降低为26%；氮素损失增加约5%，对应的氮素损失量则从60 kg·hm^-2增加到约200 kg·hm^-2，对环境的污染明显增加.小麦对上季残留氮素的利用受耕作方式影响较小，受上季施氮量影响较大，总体趋势为施氮量越高，小麦利用率越低，损失越多.经过两季小麦种植后，小麦-土壤系统回收的总氮素比例约为44%～50%，其中土壤残留氮素约占施氮量的13%～18%.

Effects of tillage mode and nitrogen application rate on nitrogen use efficiency of wheat in a farming-pasture zone of North China

A field experiment was conducted in a farming-pasture zone in Chifeng City of Inner Mongolia Autonomous Region, North China to investigate the effects of different tillage modes and nitrogen (N) application rates on the grain yield and nitrogen use efficiency (NUE) of winter wheat. The results showed that long term conservation tillage increased the wheat NUE by 3%-4%, and decreased the environmental pollution by fertilizer N. Conservation tillage promoted the N absorption by wheat, and increased the grain yield. When the N application rate increased from 120 kg·hm^-2 to 360 kg·hm^-2, the NUE decreased from 36.5% to 26%, fertilizer N loss increased by about 5%, i.e., the corresponding N loss was increased from 60 kg·hm^-2 to 200 kg·hm^-2, and the environmental N pollution increased markedly. The wheat NUE of the residual N in last season was less affected by tillage mode, but more affected by the N application rate in last season, with an overall tendency of the higher the N application rate in last season, the lower the NUE and the more the fertilizer N loss. After two seasons’ wheat planting, the proportion of the total nitrogen recovery by the wheat soil system was about 44%-50%, among which, the residual N in soil occupied about 13%-18% of applied N.