Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Assessing Cumulative Nitrous Oxide Emissions during both Rice Cultivation and Fallow Phases: A Three-Year Case Study in South Korea

Version 1 : Received: 25 September 2023 / Approved: 26 September 2023 / Online: 27 September 2023 (10:44:40 CEST)

How to cite: Ju, O.; Kang, N.; Soh, H.; Park, J.-S.; Choi, E.-J.; Jeong, H.-C. Assessing Cumulative Nitrous Oxide Emissions during both Rice Cultivation and Fallow Phases: A Three-Year Case Study in South Korea. Preprints 2023, 2023091823. https://doi.org/10.20944/preprints202309.1823.v1 Ju, O.; Kang, N.; Soh, H.; Park, J.-S.; Choi, E.-J.; Jeong, H.-C. Assessing Cumulative Nitrous Oxide Emissions during both Rice Cultivation and Fallow Phases: A Three-Year Case Study in South Korea. Preprints 2023, 2023091823. https://doi.org/10.20944/preprints202309.1823.v1

Abstract

Rice cultivation serves as a significant anthropogenic source of methane (CH4), a primary greenhouse gas, and nitrous oxide (N2O), a secondary greenhouse gas. Although N2O emissions remain relatively small compared to CH4 emissions, they are remarkably affected by nitrogen-fertilized soil conditions during rice cultivation. To date, investigations are very limited concerning N2O emissions from rice cultivation in relation to environmental factors such as temperature, rainfall, and soil properties. In this case study, we investigated the characteristics of N2O emissions in the central region of South Korea, where a single rice cropping cycle occurs annually over a span of three years, from May 2020 to May 2023. We investigated the impact of variations in temperature and soil moisture on N2O emissions during rice cultivation. In this context, we attempted to discover the complex dynamics of N2O emissions by comparing longer fallow periods with the rice cultivation periods and extended non-dry periods with irrigated periods. We observed that extremely high N₂O flux events encountered during the fallow period appeared to have a substantial impact on the yearly cumulative N₂O emissions, surpassing the impact of cumulative N₂O emissions during the rice cultivation period. We found that high N₂O flux events arose not only from artificial nitrogen inputs but also due to temperature and soil moisture variations influenced by weather conditions. We concluded that assessing N₂O emissions solely based on the rice cultivation period would underestimate annual emissions. To prevent underestimation of N₂O emissions, continual gas collection throughout a year covering both rice cultivation and fallow phases is required in align with monitoring of varying temperature and soil moisture conditions. Based on our findings, we recommend that at least a three whole year evaluation period is needed to ensure estimation accuracy of N₂O emissions under varying nitrogen fertilization rates. Also, the findings from this study would help prepare a further revision or refinement of N2O emission factor from rice cultivation in the national greenhouse gas inventories defined by the inter-governmental panel on climate change (IPCC).

Keywords

nitrous oxide; rice paddy; nitrogen fertilization; soil moisture; weather condition

Subject

Environmental and Earth Sciences, Atmospheric Science and Meteorology

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