Greenhouse gas emissions and mitigation measures in Chinese agroecosystems

Globally, CO 2, CH 4 and N 2O, contribute 60%, 15% and 5%, respectively, to the anthropogenic greenhouse effect. Atmospheric CO 2, CH 4 and N 2O are currently increasing by 0.5%, 1.1% and 0.3% per year, respectively. This paper reviews studies on greenhouse gas emission and mitigation measures in China in recent years. CH 4 emissions originate mainly from rice paddy fields, and are determined by soil characteristics, e.g., temperature, water content, pH and Eh conditions, and by land and crop management, e.g., land use, rice varieties and fertilizer application. Rice paddies emit N 2O in addition to CH 4, however, the N 2O and CH 4 emission patterns are quite different. Fertilization practices and field water conditions are major factors that control N 2O emissions. In order to minimize net greenhouse gas emissions from agricultural production systems, either sources of emissions must be reduced, or agricultural greenhouse gas sinks must be enhanced or newly created. Because the effects of greenhouse gas mitigation measures on each greenhouse gas are different, specific practices must be developed and adopted for the various gases. This paper discusses some promising greenhouse gas mitigation strategies to reduce net emissions from agroecosystems in China.