稻田秸秆还田:土壤固碳与甲烷增排

基于我国农田土壤有机质长期定位试验和稻田甲烷排放试验成果,将全国稻田划分为单季区和双季区.根据土壤有机质试验数据,分析了秸秆还田在我国两个稻田区的单季稻田、水旱轮作稻田和双季稻田的固碳潜力.同时根据我国稻田甲烷排放试验数据,采用取平均排放系数的方法,估算了我国稻田在无秸秆还田情况下的甲烷排放总量;结合IPCC推荐的方法和参数,估算了我国稻田秸秆还田后甲烷排放总量及增排甲烷的全球增温潜势.结果表明:在中国稻田推广秸秆还田的固碳潜力为10.48TgC.a-1,对减缓全球变暖的贡献为38.43TgCO2-eqv.a-1;但秸秆还田后稻田甲烷排放将从无秸秆还田的5.796Tg.a-1增加到9.114Tg.a-1;秸秆还田引起甲烷增排3.318Tg.a-1,其全球增温潜势达82.95TgCO2-eqv.a-1,为土壤固碳减排潜力的2.158倍.可见,推广秸秆还田后,中国稻田增排甲烷的温室效应会大幅抵消土壤固碳的减排效益,是一项重要的温室气体泄漏.

Straw return to rice paddy: Soil carbon sequestration and increased methane emission.

Based on the long term datasets of soil organic matter content and the observation data of rice paddies’ methane (CH₄) emission collected from the
 agricultural experiment stations across the country, the rice paddies in China were divided into single cropping and double cropping regions. The soil carbon s
equestration potential of straw return in three types of rice paddies in the tworegions, i.e., single cropping rice paddies, upland/paddy alternated rice pad
dies, and double cropping rice paddies, was evaluated, based on the datasets of soil oranic matter content; and the total CH₄ emission from  rice padd
ies without straw return was estimated, with reference to the experimental data of  paddies CH₄ emission and by the method of mean emission coefficient.
The total CH₄ emission from our paddies after straw return and the global warming potential of the increased CH₄ emission were also estimated by using the r
elated methods and parameters given by IPCC. It was estimated that the full popuarization of straw return to China’s rice paddies would sequester 10.48 Tg C·a^-1of C, and the contribution to the global warming mitigation was 38.43 Tg CO₂-eqv·a^-1.In the meanwhile, the CH₄  emission from our rice paddies would be increased from 5.796 Tg·a^-1 to 9.114 Tg·a^-1, and the increased 3.318 Tg·a^-1 of CH₄emission would lead to a global warming potential of82.95 Tg CO₂-eqv·a^-1, which was 2.158 times of the mitigation from carbon sequestration in rice paddies. Therefore, the increased CH₄ emission due to straw return should be regarded as an important greenhouse gas leakage, since it could greatly offset the mitigation benefits of soil carbon sequestration in China’s rice paddies.