太湖地区不同轮作模式对稻田温室气体(CH4和N2O)排放的影响

通过田间试验，研究了太湖地区不同轮作模式下稻季温室气体排放规律.结果表明: 水稻生长季CH₄排放呈先升高后降低趋势，CH₄排放主要集中在水稻生育前期，烤田后至水稻收获期间CH₄排放量较低；N₂O的排放主要集中在3次施肥及烤田期.稻季排放的CH₄对全球增温潜势(GWP)的贡献远高于N₂O，各处理所占比例为94.7%～99.6%，是温室气体减排的主要对象.不同轮作模式下，稻季CH₄排放总量及其GWP存在显著差异，表现为小麦-水稻>紫云英-水稻>休闲-水稻轮作；稻季N₂O排放总量及其GWP没有显著性差异.与不施肥处理相比，紫云英-水稻轮作模式下施加氮肥显著降低了CH₄排放量和GWP，但不同氮肥用量下的CH₄排放量和GWP没有显著性差异，而紫云英还田稻季施氮240 kg·hm^-2下的水稻产量却最高.综合经济效益和环境效益，紫云英还田稻季施氮240 kg·hm^-2下的增产减排综合效果更好，是值得当地推广的耕作制度.

Effects of different rotation systems on greenhouse gas (CH4 and N2O) emissions in the Taihu Lake region,China.

We conducted a greenhouse gas emissions study of different rice-based cropping systems in the Taihu Lake region. The results indicated that the seasonal CH₄ emission initially increased, but declined over time. CH₄ emission mainly occurred during the early stages of rice growth and decreased after the paddy soil dried. N₂O emission mainly occurred during the fertilizer application and paddy field drying stages. Compared with N₂O emission, CH₄ emission contributed significantly more to the global warming potential (GWP) during the rice season. The proportion of CH₄ emission to the total greenhouse gas emissions, which this study aimed to reduce, ranged from 94.7%-99.6%. CH₄ emissions and their GWP during the rice season varied significantly under different rotation systems, with the order of wheat-rice rotation>Chinese milk vetch-rice rotation>fallow rice rotation, while the N₂O emissions and their GWP exhibited no significant differences. Compared with no nitrogen fertilization, applying N fertilizer significantly reduced CH₄ emission and GWP of the Chinese milk vetch-rice rotation. However, CH₄ emission and GWP did not vary with N application rates. The rice yield was largest when the N application rate was 240 kg·hm^-2. Taking economic and environmental benefits into account, we found that a N application rate of 240 kg·hm^-2 and a straw return application of Chinese milk vetch not only reduced greenhouse gas emissions but also achieved the highest rice grain yield, which was recommended as a suitable cropping system for the Taihu Lake region.