中国稻田CH_4和N_2O排放及减排整合分析

CH_4 and N_2O Emission from Rice Field and Mitigation Options Based on Field Measurements in China:An Integration Analysis

【目的】对中国有关稻田CH4和N2O排放试验结果进行整合分析,估算不同管理措施的减排潜力,为稻田CH4和N2O减排提供参考依据。【方法】通过建立中国稻田CH4和N2O排放的数据库,研究稻田CH4和N2O的排放特征,分析作用显著的影响因素,比较不同措施的减排效果。【结果】中国稻田CH4排放存在明显的地域性分布规律,主要表现为西南地区稻田CH4排放远高于其它地区。水稻生长季节水分管理方式、非水稻生长季水分状态、化肥氮投入量和有机物料对稻田CH4排放具有重要影响(P<0.05)。与淹水灌溉(CF)相比,前期淹水-中期晒田-淹水(F-D-F)、前期淹水-中期晒田-淹水-湿润灌溉(F-D-F-M)和间歇灌溉或完全湿润(M)降低稻田CH4排放的幅度分别为45%、59%和83%。与休闲期淹水(F)相比,采取冬闲期排干(SD)、稻旱轮作(LD)或旱-旱-稻轮作模式(TD),能降低稻田CH4排放42%—56%。不同有机添加物产生CH4的能力的顺序为:作物秸秆+厩肥(S+FM)>绿肥(GM)>厩肥(FM)>作物秸秆(S)>堆肥或沼渣(CM)。化学氮肥的种类对CH4排放有一定的影响,但特征不明显,而随着氮肥用量(N)的增加,CH4排放逐渐降低。当0<N≤150kgN·hm-2,150<N<250kgN·hm-2和≥250kgN·hm-2时,CH4排放较不施任何肥料降低12%、29%和65%。中国稻田N2O排放的地域性分布特征不明显。水稻生长季节水分管理方式、非水稻生长季水分状态和总氮投入量是影响N2O排放的最重要的因素(P<0.05)。与CF相比,F-D-F、F-D-F-M和M能够提高稻田N2O排放12%、140%和478%,而且在F-D-F、F-D-F-M模式下的氮肥N2O排放因子分别为0.43%和0.68%。不同非水稻生长季水分状态模式下N2O排放平均值表明,SD、LD和TD比F增加40%—110%的排放。【结论】稻田CH4和N2O排放的消长关系表现在水分管理、非水稻生长季节的水分状态和氮素的投入量等方面。合理的减排措施应基于二者的综合考虑。通过优化稻田水肥管理措施可降低稻田CH4和N2O排放的温室效应。

【Objective】 By integrated analyzing field experimental results about CH4 and N2O emissions from rice field in China,the authors estimated the mitigation potential of various factors controlling CH4 and N2O emissions in order to provide some suggestions for reducing them in paddy field.【Method】 A database of CH4 and N2O emissions from rice field in China was constructed in order to study the characteristics of two greenhouse gas emissions and analyze the factors which have a significant effect on them.【Result】 There clearly existed a zonal distribution law of CH4 emission in China,which showed that the CH4 emissions from Southwest of China were far more than other rice planting areas.It was considered that the factors controlling CH4 emission were water management regimes in rice growing period,water status of non-rice growing season,types of organic or synthetic nitrogen fertilizer and levels of chemical nitrogen fertilizer input（P0.05）.Compared to continuously flooded（F）,flooding-midseason drainage-reflooding（F-D-F）,flooding-midseason drainage-reflooding-moist intermittent irrigation,but without water logging（F-D-F-M）and alternative flooding and drainage after transplanting,or moister irrigation but without water logging（M）reduced CH4 emission by 45%,59% and 83%,respectively.Water status of non-rice growing season determined by cropping system also has a significant effect on CH4 emission.The mode of short drainage（SD）,long drainage（LD）,and two drainage（TD） could reduce CH4 emission by 42%-56% compared to flooded（F）.Simulated effect of organic amendments on CH4 emission from rice field was decreased in the order of crop straw ＋ farm manure（S＋FM）green manure（GM）farm manure（FM）crop straw（S） composted farm manure and biogas digestion（CM）.The effect of different types of chemical nitrogen fertilizer on CH4 emission was unclear.The CH4 emission decreased gradually with increasing chemical nitrogen fertilizer rate（N）.When N was 0N≤150 kg N·hm-2,150N250 kg N·hm-2 and N≥250 kg N·hm-2,CH4 emission was reduced by 12%,29% and 65% compared with treatment of non-fertilizer.There did not exist a zonal distribution law for N2O emission.The factors including water management regimes in rice growing period,the non-rice season water status,and total nitrogen fertilizer input were important for N2O emission（P0.05）.Compared to CF,the N2O emission was increased by 12%,140% and 478% under F-D-F,F-D-F-M and M.The nitrogen fertilizer-induced N2O emission factors were 0.43% and 0.68% in F-D-F and F-D-F-M,respectively.By analyzing the water status of non-rice growing season,the average N2O emission increased by 40%-110% under SD,LD and TD,compared to F.【Conclusion】 There was a trade-off relationship between emission of CH4 and N2O from rice field,appeared water management regimes in rice growing period,water status of non-rice growing season,and the amount of synthetic nitrogen fertilizer.Mitigation measurements in rice fields should be taken consideration comprehensively both of CH4 and N2O emissions.Global worming potential of CH4 and N2O emission from rice field could be reduced by optimizing water regime and fertilizer management.