Relationship Between Soil Physical Properties and Erodibility Factor of Jeju Black Volcanic Ash Soils Under a Rainfall Simulator Condition

Abstract

This study was conducted to determine the validity by comparing the soil erodibility factor (K) values, which were calculated by rainfall simulator conditions (Kobs) and in the Universal Soil Loss Equation (KUSLE) from eight sites of black volcanic ash soils (BVAS) in Jeju Island and developed a new soil erodibility factor equation based on the physical properties of BVAS. The KUSLE value showed negative values in BVAS, indicating other methods for soil erodibility estimation need to be developed. The Kobs value had a significant positive correlation with the runoff rate (p < 0.01) and positively correlated with fine sand (0.02 - 0.2 mm) and clay / (silt + very fine sand). A significant negative correlation was observed between the Kobs and silt (0.002 - 0.02 mm) (p < 0.05), saturated hydraulic conductivity (Ksat), and infiltration rate (p < 0.01), all of which indicate the effect of these physical properties on the soil erodibility factor. As a result of multiple regression analysis, K = - 0.1492 + 0.0036 runoff rate - 0.0908 Ksat + 0.0112 fine sand (0.02 - 0.2 mm) (R2 = 0.981, p < 0.01). Therefore, the developed equation may be used as the soil erodibility estimation for USLE to predict soil erosion in BVAS on Jeju Island. Multiple regression analysis for the soil erodibility factor value (K) calculation in black volcanic ash soils on Jeju Island. Model Variable† R2 Adjusted R2 Durbin- Watson Mean Square F Pr＞F 1 X1 0.8390 0.8122 2.17 0.13285 31.3 0.0014 2 X1․X2 0.9499 0.9299 2.52 0.07521 47.4 0.0006 3 X1․X2․X3 0.9894 0.9815 1.23 0.05222 124.5 0.0002 4 X1․X2․X3․X4 0.9965 0.9919 2.07 0.03945 215.2 0.0005 5 X1․X2․X3․X4․X5 0.9987 0.9954 1.20 0.03163 305.1 0.0033 6 X1․X2․X3․X4․X5․X6 1.0000 0.9999 2.68 0.02639 8174.3 0.0085 †123456