Characteristics of greenhouse gas emissions from rice paddy fields in South Korea under climate change scenario RCP-8.5 using the DNDC model

Understanding the greenhouse gas (GHG) emission from rice paddy fields is essential to come up with appropriate countermeasure in response to global warming. However, GHG emissions from paddy fields in South Korea are not well characterized. The objectives of this study were to estimate the carbon dioxide (CO₂) and methane (CH₄) emissions from rice paddy fields in South Korea, under the Representative Concentration Pathway 8.5 (RCP-8.5) climate change scenario using the DNDC (i.e., DeNitrification-DeComposition) model at 1-km² resolution. The performance of the model was verified with field data collected using a closed chamber, which supports the application of the model to South Korea. Both the model predictions and field measurements showed that most (> 95%) GHG emissions occur in the cropping period, between April and October. As a baseline (assuming no climate change), the national sums of the CO2 and CH4 emissions for the 2020s and 2090s were estimated to be 5.8 × 10⁶ and 6.0 × 10⁶ t CO2-equivalents (CO2-eq) year^–1 for CO2 and 6.4 × 10⁶ and 6.6 × 10⁶ t CO₂-eq year^–1 for CH₄, respectively, indicating no significant changes over 80 years. Under RCP-8.5, in the 2090s, CH₄ emissions were predicted to increase by 10.7 × 10⁶ and 14.9 × 10⁶ t CO₂-eq year^–1, for a 10- or 30-cm tillage depth, respectively. However, the CO₂ emissions gradually decreased with rising temperatures, due to reduced root respiration. Deep tillage increased the emissions of both GHGs, with a more pronounced effect for CH₄ than CO₂. Intermittent drainage in the middle of the cropping season can attenuate the CH₄ emissions from paddy fields. The findings of this work will aid in developing nationwide policies on agricultural land management in the face of climate change.