Changes in carbon stock in agricultural soils over 20 years in South Korea

In the carbon neutral era, soil carbon became more important. Soil carbon pools (2400 Gt) are about three times larger than atmospheric pools, and soil carbon sequestration can store large amounts of organic carbon. Soil carbon storage has been reported as an effective tool to mitigate climate change in various studies, including the IPCC. Among them, it is known that agricultural soil can sequester carbon every year through sustainable soil management. In this study, we investigated changes in soil carbon storage (excluding volcanic soils) using the results of the Monitoring Project on Agri-Environmental Quality in South Korea from 1999 to 2018. Land use was categorized into paddy, upland, orchards and greenhouses. The soil organic carbon content of cultivated land has increased steadily over the past two decades, with annual organic carbon increases of 0.16 g kg^-1 in paddy, 0.26 g kg^-1 in upland and 0.33 g kg^-1 in orchard, and 0.21 g kg^-1 in greenhouse. In the 2000s, the use of chemical fertilizers decreased and the amount of livestock manure compost increased, which seems to have increased soil organic carbon. As a result of calculating the total annual increase in soil organic carbon in the entire cultivated land, it was found that 770,000 tons of C were stored in the soil (0-20 cm) per year. This corresponds to about 11% (2.8 million tons CO_2-eq) of the 24.7 million tons CO_2-eq of Korea's agricultural and livestock greenhouse gas emissions in 2018. South Korea also presented a scenario to achieve carbon neutrality by 2050, but currently does not include a method for using carbon sequestration. Looking at changes in soil carbon over the past 20 years, we found that soil can make a significant contribution to carbon neutrality if we introduce soil management that increases soil carbon and quantify the carbon sequestration. Therefore, it is judged necessary to introduce a soil management method that can maximize the carbon sequestration of the soil.