农田土壤固碳措施的温室气体泄漏和净减排潜力

农田土壤固碳措施作为京都议定书认可的大气CO2减排途径受到了广泛关注.研究表明,农田土壤固碳措施在主要农业国家和全球都具有很大的固碳潜力.但是,实施农田土壤固碳措施有可能影响农业中化石燃料消耗和其他农业投入的CO2排放和非CO2温室气体排放.这些土壤碳库以外的温室气体排放变化可能抵消部分甚至全部土壤固碳效果,构成了农田土壤固碳措施的温室气体泄漏.因此,将土壤固碳和温室气体泄漏综合计算的净减排潜力成为了判定土壤固碳措施可行性的首要标准.综述总结了目前较受重视的一些农田措施(包括施用化学氮肥、免耕和保护性耕作、灌溉、秸秆还田、施用禽畜粪便以及污灌)的土壤固碳潜力,温室气体泄漏和净减排潜力研究成果.结果表明,温室气体泄漏可抵消以上措施土壤固碳效益的-241%～660%.建议在今后的研究中,应该关注土壤碳饱和、气候变化及土地利用变化对农田固碳措施温室气体泄漏和净减排潜力的评估结果的影响.

Researches on the greenhouse gas leakage and net mitigation potentials of soil carbon sequestration measures in croplands

Being recognized by the Kyoto Protocol, soil carbon sequestration and greenhouse gas mitigation in croplands have drawn broad attention. Previous studies showed that soil carbon sequestration measures might have considerable carbon sequestration potentials in the major agricultural countries and the whole world. However, the implementation of the soil carbon sequestration measures could affect the CO2 emission from the fossil fuel use and inputs in agriculture, and influence the non\|CO2 greenhouse gas emissions from the croplands. As the changes of the GHG emissions from outside the soil carbon pool can partly or even fully counteract the mitigation benefit of soil carbon sequestration, such changes are regarded as GHG leakage of soil carbon sequestration measures in croplands. As a result, the net mitigation potential, which concerns both soil carbon sequestration and leakage, turns to be the foremost criteria of the feasibility of a carbon sequestration measure. This paper reviewed several reputable farming practices (e.g., synthetic nitrogen fertilizer application, no\|tillage and conservation tillage, irrigation, straw return, manuring and sewage sludge application) for net mitigation based on their soil carbon sequestration and impacts on the GHG leakage. The results indicated that GHG leakage could offset -241%-660% of the soil carbon sequestration of the above\|mentioned measures. This review suggests more attention be paid to the influences of soil carbon saturation, climate change and land use change on GHG leakages and net mitigation potentials of soil carbon sequestration measures in croplands.