Study on Soil Erosion and Physical Characteristics of Jeju Volcanic Ash Soils Under a Rainfall Simulator Condition

Abstract

The objective of this study is to determine the effects of physical properties of soils on soil erosion under a rainfall simulator. The soil samples were collected from five sites of dark brown soil (DBS), six sites of very dark brown volcanic ash soil (VDBAS), and eight sites of black volcanic ash soil (BVAS) in Jeju Island. The rainfall simulator, which ran for 30 minutes at a slope gradient of 10%, determined the amounts of soil erosion, infiltrated water, and runoff water. The particle size distribution, water-stable aggregates distribution, bulk density, organic matter content, and saturated hydraulic conductivity in soils were analyzed as well. The amounts of soil erosion gradually increased and reached a steady state after 20 minutes. The amounts of soil erosion in BVAS were higher than that in other soils. It also correlated positively with the amounts of runoff water and related negatively to the amounts of infiltrated water. The amounts of soil erosion in DBS and BVAS had a significant negative correlation with some particle size fractions and saturated hydraulic conductivity (p<0.05). A significant positive correlation was observed between the amounts of soil erosion and the water-stable aggregates with the size smaller than 1 mm in DBS and VDVAS (p<0.05). The bulk density and organic matter content did not significantly affect the amount of soil erosion. These results concluded that the physical properties of soils affecting the amount of soil erosion varied among the color of soils in Jeju Island. It is suggested that the values of soil erodibility factor for the volcanic ash soils of Jeju Island need to be estimated with an alternative algorithm to predict the amount of soil erosion. Relationship between the amount of soil erosion and runoff (a) and infiltration water (b) in dark brown soil (▲ ), very dark brown volcanic ash soil (○), and black volcanic ash soil (●). **Significant difference at 1%, *Significant difference at 5%.