Combined application of inorganic and organic fertilizers reduces global warming potential from rice paddy soil

Soil carbon sequestration and greenhouse gas (GHG) emissions are critical factors in assessing the climate impacts of fertilization practices in rice paddy systems. This study evaluated the effects of inorganic fertilizer, composted animal manure, and their combined application on soil organic carbon dynamics, GHG emissions, net ecosystem carbon budget (NECB), global warming potential (GWP), and greenhouse gas intensity (GHGI) in a rice paddy field in South Korea. The combined application of inorganic fertilizer and compost (NPK+CM) resulted in higher cumulative CH 4 and N 2 O emissions compared with single fertilization treatments. However, annual soil organic carbon change was positive only with the NPK+CM treatment, indicating enhanced soil carbon accumulation. Although greenhouse gas emissions alone suggested a higher warming impact with NPK+CM, net ecosystem carbon budget (NECB) analysis showed that this treatment achieved the greatest net carbon gain due to increased carbon inputs from fertilization and plant production. Consequently, the NPK+CM treatment exhibited the lowest net GWP among treatments. In addition, rice grain yield was highest and GHGI was lowest under the combined fertilization treatment, indicating improved production efficiency with reduced yield-scaled climate impact. These results demonstrate that evaluating fertilization practices based solely on greenhouse gas emissions may lead to misinterpretation of their overall climate impacts. An integrated assessment incorporating NECB, net GWP, and GHGI provides a more comprehensive framework for identifying climate-smart fertilization strategies that enhance crop productivity while mitigating global warming impacts in paddy soil systems.