小麦-玉米轮作田与菜地N2O排放的对比研究

应用静态箱/气相色谱法对旱地小麦-玉米轮作田和种菜历史超过20a的菜地进行了N2O排放的定位观测,分析了旱地和菜地生态系统N2O排放特征的差异,及施氮、土壤温度、土壤湿度和作物参与对两种农田系统N2O排放的不同影响。结果表明,不施氮情况下,旱地和菜地N2O排放通量分别为17.8±5.6和50.7±13.3μg m-2h-1,菜地N2O排放通量是旱地农田的3.1倍。在施氮(N 150 kg hm-2)情况下,菜地N2O排放系数较旱地高39.0%。粮食作物参与和蔬菜作物参与对增加各自农田生态系统N2O排放量的贡献无明显差异。旱地和菜地不同作物季N2O排放量的差异主要是由于作物生育期长短不同造成单位时间施肥强度存在差异。所以,根据作物生育期特点调节施肥量可能会减少农田生态系统N2O排放量,并且由于菜地各蔬菜生育期长短的差异更大,因此,菜地若能实现精量施肥,其N2O减排的潜力可能大于旱地农田。

Comparison study on N2O emissions from field under wheat-maize rotation system and field under vegetable cultivation

Stationary observation was performed during the period from October, 2006 to October, 2007 of N₂O emissions from a field under wheat-maize rotation and a field under vegetable cultivation for over 20 years, using the static chamber method/gas chromatograph technique. Characteristics of the emissions from the two ecosystems were analyzed for differences between the two and effects of the participating factors, such as N application, soil temperature, soil moisture and crops on the emissions. Results show that in CK (No N applied) the mean N₂O emission flux was 17.8?5.6 and 50.7?13.3 ?g m^-2 h^-1, respectively, from the wheat-maize ecosystem and the vegetable ecosystem. Clearly the flux from the latter was 3.1 times higher than that from the former. When N was applied at N150 kg hm^-2, the N₂O emission coefficient in the vegetable field was 39.0% higher than that in wheat-maize field. Plant participation was not responsible for higher N₂O emission from the vegetable ecosystem. The difference in N₂O emission flux between the two ecosystems in different crop growing seasons was attributed to the fact that the difference in life cycle between the crops led to difference in intensity of N application per unit time. Therefore, N₂O emission from the agro-ecosystems may be cut down by regulating N application rate in light of characteristics of the crop growing season, which vary sharply especially of vegetables. If precise fertilization can be adopted for vegetables, the potential of the vegetable field in reducing N₂O emission would be greater than that of the upland farm field.