太湖地区不同轮作模式对稻田温室气体(CH_4和N_2O)排放的影响

Effects of different rotation systems on greenhouse gas(CH_4 and N_2O) emissions in the Taihu Lake region,China

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CH_4排放呈先升高后降低趋势,CH_4排放主要集中在水稻生育前期,烤田后至水稻收获期间CH_4排放量较低;N_2O的排放主要集中在3次施肥及烤田期.稻季排放的CH_4对全球增温潜势(GWP)的贡献远高于N_2O,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CH_4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N_2O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CH_4排放量和GWP,但不同氮肥用量下的CH_4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.

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.