中文摘要：

以种植玉米（Zeamays）、大豆（Glycinemax）和水稻（Oryzasativa）的农田生态系统为研究对象，于2003年6～10月系统观测了N2O和CH4的排放、土壤温度和湿度以及相关的生物学因子。玉米和水稻分别施化肥氮300kg·hm^-2，大豆未施氮肥。研究结果表明，作物类型对农田N2O和CH4排放具有显著的影响。土壤-玉米系统、土壤-大豆系统和土壤-水稻系统的N2O季节性平均排放通量分别为620．5±57．6、338．0±7．5和238．8±13．6μg·m^-2·h^-1（N2O）。种植作物促进了农田生态系统的N2O排放，玉米地土壤和裸地土壤的N2O平均排放通量分别为364．2±11．7和163．7±10．5μg·m^-2·h^-1（N2O）。土壤-玉米系统、土壤-水稻系统、玉米地土壤和裸地土壤N2O排放受土壤温度的影响，与土壤湿度无显著统计相关，但受土壤温度和水分的综合影响。土壤-大豆系统N2O排放随作物绿叶干重的增加而指数增加，与土壤温度和水分条件无统计相关，由大豆作物自身氮代谢所产生的N2O-N季节总量约为6．2kg·hm^-2（N）。土壤-水稻系统CH4平均排放通量为1．7±0．1mg·m^-2·h^-1（CH4），烤田抑制了稻田CH4的排放。烤田前影响稻田CH4排放的主要因素是水稻生物量，烤田后的浅水灌溉及湿润灌溉阶段的CH4排放与土壤温度和水稻生物量无关。本研究未观测到旱作农田有吸收CH4的现象。

英文摘要：

To evaluate the effect of cropping system on N2O and CH4 emissions and to identify the key factors controlling the emissions, a field experiment was carried out in 2003 at Jiangsu Academy of Agricultural Sciences, Three crops of maize （Glycine max）, soybean （Zeamays） and rice （Oryza sativa ） were planted during the period from June to October. In addition, a bare soil plot was set up near the soybean-planted plot. Plots planted maize and rice received same amount of 300 kg · hm^ 2 （N）, and the plots of the soybean-planted and the bare soil did not receive nitrogen fertilizer. When taking gas samples, soil moisture, temperature and dry mass of green leaves and plants were also measured. Results showed that there was a significant difference （P〈0. 001） in the N2O and CH4 emissions from different plots. Seasonal N2O flux averaged 620. 5±57. 6μg ·m^-2 · h^-1 （N2O） for the maize-plan ted plot, 338.0±7.5 μg· m^-2·h^-1 （N2O） for the soybean-planted plot, and 238.8±13.6 μg· m^ 2 · h^-1 （N2O） for the rice-planted plot, respectively. Crop cultivation enhanced N2O emission from the soil. The maize planted soil emitted N2O with an average rate of 364. 2 11.7 μg · m^-2 · h^-1 （N2O）, while the average rate was 163. 7±10.5μg·m^-2 · h^-1 （N20） in the bare soil. Seasonal average of CH4 flux was 1.7±0.1 μg@ m^-2 · h^- 1 （CH4） in the rice-planted plot. No CH4 emission or uptake was found in the plots of maize-planted and soybeanplanted. A further investigation suggests that soil temperature determine the seasonal variation of N2O emissions from the plots of maize-planted, rice-planted and bare soil, as well as from the maize-planted soil. This determination can be well described by an exponential function. Though there was no significant correlation between N2O emission from the uplands and soil moisture, the N2O emission can be mathematically expressed by an exponential function that integrates soil temperature and moisture. We found that N2O emission from