Soil Chemical Properties of Citrus Orchards in Jeju

This study is conducted to be used as data for soil nutrient management and fertilizer application improvement by examining the chemical characteristics of citrus orchard soils in the Jeju region. The soil samples were collected from 50 sites of dark brown soils (DBS), 50 sites of very dark brown volcanic ash soils (VDBAS), and 50 sites of black volcanic ash soils (BVAS) in Jeju Island from February to March 2018. Soil chemical properties such as pH, organic matter, available phosphate (Av. P₂O5), exchangeable potassium (Ex. K), exchangeable calcium (Ex. Ca), exchangeable magnesium (Ex. Mg), and lime requirement were analyzed. The average pH of DBS, VDBAS, and BVAS were 5.4, 5.0, and 5.3, respectively. Organic matter contents were 42 g kg-1 for DBS, 98 g kg-1 for VDBAS, and 154 g kg-1 for BVAS, which showed that the darker the soil color, the higher the organic matter contents. Av. P₂O5 and Ex. K contents became lower as the soil color get darker, and the lime requirement became higher as the soil color get darker. When compared to the optimal range of ideal citrus orchard soils, the insufficient ratio of pH, Ex. Ca, and Mg were quite high, with more than 58% in all soils, thus requiring the use of calcium magnesium fertilizer. The excessive ratio of Av. P₂O5 and Ex. K were high in DBS with 90% and 62%, respectively, and the insufficient ratio of Av. P₂O5 and Ex. K in BVAS were high with 46% and 56%, respectively. As for the correlation between citrus orchard soil chemical components, the pH and Ex. cations (K, Ca, and Mg) showed a positive correlation, and the pH and lime requirement showed a negative correlation. Organic matter showed a negative correlation with Av. P₂O5 and a positive correlation with lime requirement. In conclusion, the fertilizer management of the soil in Jeju needs to be managed differently depending on the soil color.