通过田间试验，研究了不同施氮量对大白菜产量、氮肥利用率、硝态氮残留量的影响。结果表明，施氮对大白菜有显著的增产作用，但随着施氮量的增加产量变化不大，产量对施氮量的反应呈平台模式。氮肥利用率在3.3%～12.6%，并且随施氮量的增加呈先增加后降低的趋势，在施氮量为656.4 kg/hm2(纯氮300 kg/hm2+有机肥12 000 kg/hm2)时，氮肥利用率和作物产量最高。合理控制氮肥用量会促进作物对土壤氮素的吸收。施氮可明显提高0~180 cm剖面土壤NO3--N的累积量，残留的NO3--N的分布随施氮量的增加而显著增加，并且随施氮量的增加残留深度下移，表现出明显的底层累积。各处理土壤氮均集中在0~100 cm土层中，100 cm土层以下，各处理氮含量渐趋一致。综合不同施氮量对大白菜产量以及环境指标的影响，在本试验肥力水平下，大白菜氮肥投入阈值为656.4 kg/hm2(纯氮300 kg/hm2+有机肥12 000 kg/hm2)时，能够兼顾作物高产与环境安全。

In order to provide evidence for reasonable use of nitrogen fertilizer， a field trial was carried out to examine the effects of the yield and the environmental effects of the chinese cabbage under open field cultivation during 2011 — 2012 . The results showed that the yield of chinese cabbage was highest at 656.4 kg/hm2(N 300 kg/hm2+organic manure 12 000 kg/hm2) . The nitrogen uptake by chinese cabbage increased with increasing N rate . With N application of 656.4 kg/hm2(N 300 kg/hm2+organic manure 12 000 kg/hm2)， the nitrogen uptaked was the highest . With N fertilizer rate increasing， the content of NO3--N in soil layers increased dramatically . With more than 656.4 kg/hm2 (N 300 kg/hm2+organic manure 12 000 kg/hm2) was supplied， soil NO3--N moved down obviously . N fertilizer residual amount increased with increased N fertilizer rate . The nitrogen use efficiency ranged from 3.3% to 12.6% under different rates of N fertilization . At the rate of 656.4 kgN/hm2(N 300 kg/hm2+organic manure 12 000 kg/hm2) could meet the chinese cabbage demand. These results suggest that the N application rates of 656.4 kg/hm2(N 300 kg/hm2+organic manure 12 000 kg/hm2)， would be optimal for the yield of chinese cabbage and a reduction in the risk of nitrate release into environment .

S634.1；S147.2

公益性行业(农业)科研专项“北方高原山地区面源污染监测与氮磷化肥投入阈值研究”(201003014-7)部分内容