Greenhouse gas emissions and mitigation in rice agriculture

Rice paddies supply half the global population with staple food, but also account for ~48% of greenhouse gas (GHG) emissions from croplands. In this Review, we outline the characteristics of GHG emissions (CH 4 and N 2 O) from paddy soils, focusing on climate change effects and mitigation strategies. Global mean annual area-scaled and yield-scaled GHG emissions are ~7,870 kg CO 2 e ha −1 and 0.9 kg CO 2 e kg − 1 , respectively, with 94% from CH 4 . However, emissions vary markedly, primarily reflecting the impact of management practices. In particular, organic matter additions and continuous flooding of paddies both stimulate CH 4 emissions, whereas fertilizer N application rate is the most important driver of N 2 O emissions. Although contemporary changes in emissions are uncertain, future elevated [CO 2 ] and warming are projected to increase CH 4 emissions by 4–40% and 15–23%, respectively. Yet, integrated agronomic management strategies — including cultivar, organic matter, water, tillage and nitrogen management — offer GHG mitigation potential. In particular, new rice variety selection, non-continuous flooding and straw removal strategies reduce GHG emissions by 24%, 44% and 46% on average, respectively. However, approaches need to be optimized on the basis of seasonal CH 4 emission patterns, necessitating improved quantification and reduced uncertainty in regional and global GHG estimates, especially in low latitudes.