Changes in the soil properties and quality of agricultural soils in South Korea over a period of 20 years

Until the 90s, South Korea was a heavily inorganic fertilizer agriculture system, but it has since shifted to eco-friendly agriculture that uses less fertilizer and more livestock manure compost. For sustainable agriculture, efforts are being made to improve soil quality and nutrient balance. In addition, changes in the agricultural environment are being monitored to build a D/B of soil properties. In this study, we summarized the changes in agricultural soil properties over the past 20 years in Korea and investigated the soil quality changes based on the soil quality assessment model developed in previous studies. Soil analysis results were used from the agricultural environment monitoring project from 1999 to 2022, excluding volcanic soils, and the analyzed properties were pH, EC, organic matter, available P₂O₅, and exchangeable cation (Ca, Mg, K). The land use types were categorized as paddy, upland, orchard, and plastic house, and the agricultural land area as of 2022 is 776 kha for paddy, 490 kha for upland, 130 kha for orchard, and 77 kha for plastic house. The pH has increased continuously, which is the impact of the national project to supply calcareous fertilizers to increase the low pH. EC is very high in the plastic house and is constantly increasing, with the same trend in free phosphoric acid. Due to the nature of the plastic house, it is protected from rainfall and large amounts of fertilizer are applied, so fertilizer is constantly incorporated into the soil. Soil organic matter has increased steadily over the past 20 years due to a government-supported project to compost excess livestock manure. The available P₂O₅ is the result of phosphorus in the soil from phosphate fertilizer use and large amounts of livestock manure. This is currently causing problems such as salt accumulation in the plastic house. After applying the soil quality assessment model to evaluate the soil quality, the soil quality score of the soil was found to be increasing. This is because we have reduced the use of fertilizers, increased the organic matter content of the soil by supplying compost, and supplied amendments to increase the pH to increase the overall soil fertility to an appropriate level. However, the soil quality indicators of facility cultivation sites were found to be low due to high EC and phosphate, and it is urgent to prepare and disseminate soil management measures to solve this problem. It is believed that the change in the direction of soil management of agricultural land at the national level over the past 20 years has had a positive effect on soil properties and soil quality, and in the future, soil management that can contribute to carbon neutrality and maintain adequate productivity while increasing soil quality in line with the carbon neutrality era is necessary.