中文摘要：

针对目前集约化农业生产中氮肥用量盲目偏高、氮素利用率低、土壤及肥料中氮素以温室气体N2O形式的排放量增加等问题,采用田间试验研究了不同氮肥水平（150、225、300kg·hm-2）配施双氰胺（DCD）对华北地区集约化农田冬小麦-夏玉米轮作系统N2O排放的影响,并分析了其经济效益.结果表明：在整个轮作系统中,不同氮水平配施DCD处理的N2O排放通量减小25.6%~32.1%,N2O年度累积排放量降低23.1%~31.1%.土壤N2O排放通量与表面温度和湿度均呈显著指数相关,且湿度对小麦季N2O排放的影响大于玉米季,而温度对玉米季的影响大于小麦季.施用DCD后,小麦、玉米产量分别增加16.7%~24.6%和29.8%~34.5%,两季作物经济收益平均增加7973.2元·hm-2.因此,合理氮肥用量配施DCD既可以保证作物产量、提高经济效益,又可以减少N2O排放.综合考虑环境效益与经济效益,本试验条件下中量氮肥配施双氰胺（N总量225 kg·hm-2）是一种适宜在华北地区推广的优良氮肥管理模式.

英文摘要：

Aiming at the problems of excessive and unreasonable fertilizer application, lower nitro- gen use efficiency, increasing N20 emission from soil and fertilizer in current intensified agricultural productions, a field experiment was conducted to study the effects of dicyandiamide （DCD） com- bined with nitrogen fertilizer application at different levels, i.e., 150, 225, 300 kg · hm-2, on N/O emission and relevant economic benefit in a typical winter wheat-summer maize rotation system in North China Plain. The results showed that DCD application decreased N20 emission fluxes and cu- mulative emissions by 25.6%-32.1% and 23.1%-31.1% in the year-round. There was a significant positive exponential correlation between N20 flux and soil surface temperature or soil moisture con- tent. The effect of soil moisture on N2O emission was stronger in wheat season than in maize season, while the effect of temperature on N2O emission was on the contrary. The yields of winter wheat and summer maize with DCD addition were increased by 16.7%-24.6% and 29.8%-34.5%, respective- ly, and the average economic income of two seasons was increased by 7973.2 yuan · hm-2. There- fore, appropriate rate of N fertilizer combined with DCD could not only increase crop yield and eco- nomic income, but also reduce N2O emission. Considering environmental and economic benefit un- der this experimental condition, DCD combined with nitrogen of moderate level （ total N amount 225 kg · hm-2） was a good nitrogen management mode in North China.