Dilemma of organic matter input to mitigate climate impact of rice paddies

Abstract

Soil can act as either a source or sink of atmospheric carbon (C). Organic matter application can sequester carbon dioxide (CO2) through negative emission technologies. However, in rice paddies, organic matter application can significantly increase methane (CH4) emissions, offsetting potential climate benefits. We compared the effects of organic matter types on net climate impact by quantifying annual gaseous fluxes and soil C stock changes with CO2 equivalents. All organic amendments increased CH4 emissions (7–30 Mg CO2-eq. ha−1) compared with the no organic matter treatment (NPK). However, the increases in soil C stock (9–11 Mg CO2-eq. ha−1) were insufficient to shift the system from a net C source to a net sink, even when combined with water management strategies. In contrast, biochar increased CH4 emissions but enhanced soil C stock, leading to a net negative emission effect without compromising rice productivity. Given that rice paddies account for about 11 % of anthropogenic CH4 emissions, organic matter application requires careful evaluation to avoid exacerbating climatic impacts. © 2025 Elsevier Ltd