To get the optimum nitrogen (N) fertilization rate which could guarantee wheat yield and protect environment, we examined wheat yield, N use efficiency, apparent N loss and soil N balance in Weibei dryland with a 3-year field experiment. The results showed that annual wheat yield increased and then decreased as N application rate increased in all the years with different annual rainfall, but the cumulative apparent N use efficiency significantly decreased. Higher yield and N use efficiency were obtained at the fertilization rate of 150 kg·hm-2. Residual nitrate-N concentrations significantly increased with the increases of N application rate. When the N application rate was between 75 and 150 kg·hm-2, the apparent N loss and loss rate were nearly the same, but if N application rate was higher than 150 kg·hm-2, the apparent loss and loss rate significantly increased. In conclusion, N application rate at 150 kg·hm-2 in Weibei dryland could guarantee high yield and N use efficiency, and simultaneously maintain residual nitrate-N concentration and reduce apparent N loss.
为了明确渭北旱区兼顾冬小麦产量和环境效益的农田系统适宜氮肥用量,通过连续3年的田间试验,研究了冬小麦产量、氮肥利用效率、氮素表观损失和土壤氮素平衡对施氮量的响应.结果表明: 随着氮肥用量的增加,不同年份冬小麦产量均呈现先增加后降低的趋势,而累计氮肥表观利用率表现为显著降低趋势,3季冬小麦均在施氮150 kg·hm-2时达到相对较高的产量和氮肥表观利用率;随着施氮量的增加,氮肥残留显著增加,当施氮量在75～150 kg·hm-2时,表观损失量和损失率变化不明显,而施氮超过150 kg·hm-2,表观损失量和损失率显著增加.综合考虑保证冬小麦既可获得相对较高的产量和氮肥利用率,又能保持收获前后土壤硝态氮库的基本稳定,同时也可将氮肥表观损失降至较低水平,150 kg·hm-2是渭北旱区冬小麦较为合理的施氮量.
Keywords: Weibei dryland; environmental benefit; optimal N application rate; winter wheat; yield.