Changes in Methane Emission of Korean Rice Production Systems for the Last Two Decades and Suggestions for Methane Mitigation

Rice (Oryza sativa L.) paddy soils are major sources of methane (CH4) emission in the agricultural sector, and thus it is necessary to mitigate CH4 emission from paddy soils. In this review, we have investigated the changes in CH4 emission in South Korea for the last decades in relation with changes in rice cultivation area and rice production amount. We have also suggested managements for CH4 reduction in rice cultivation systems. During the last 25 years since 1998, rice cultivation area has decreased by 30.8% and total CH4 emission has also decreased by 33.5% accordingly. During the same period, total rice production has decreased by 23.8%, but rice production per unit area increased by 9.2% due to advances in agricultural technologies. The rice production per unit area was affected by rainfall (negatively) and air temperature (positively) in rice growing seasons, while CH4 emissions per unit area for the last 25 years (8.10 - 8.81 ton (CO2eq) ha-1) were not affected by weather conditions. However, CH4 emissions per unit rice production (1.57 - 1.97 ton (CO2eq) ton-1) were positively and negatively correlated with rainfall and air temperature, respectively, owing to the dependency of rice yield on weather conditions. Literature suggested that intermittent irrigation and shallow depth irrigation are effective in reducing CH4 emission while increasing rice yield and saving water uses. In addition, it was also reported that minimum and reduced tillage could also decrease CH4 emission while increasing soil organic carbon with marginal decreases in rice yield. Therefore, it may be possible to mitigate CH4 emission by employing theses irrigation and tillage methods while maintaining rice cultivation area for food security under climate change.Changes in (a) CH4 emission per unit rice yield of South Korea for the last two decades and its relation with (b) rainfall and (c) air temperature during rice cultivation season.