Effectiveness of different surface cover types in reducing runoff and soil erosion in oil palm catchments

Abstract

Soil losses from hill slopes in oil palm plantation in Sedenak Estate, Johor were measured using runoff plots and rainfall simulator. The plot was designed to be removable but the size was fixed at 0.8 x 3.75m. Four types of surface covers were applied for the plots i.e. half bare soil and grass cover (HGC), half bare soil and dry frond (HDF), fully grass cover (FG), and fully bare soil (BS). The effects of physical soil factors such as soil moisture and saturated hydraulics conductivity, Ks along with land slope were also evaluated. The rainfall simulator produced rainfall intensities between 90 and 160 mm/hr with durations from 45 to 60 min per run. BS exhibited the highest Ks value among all surface plots but the percentage of soil moisture on this surface was low. The results indicate that there are significant differences in runoff generation and soil loss production with respects to different types of surface cover. The lowest runoff coefficient (ROC) was produced on BS with the value of 52±15%, followed by HGC (58.2±0%), FG (78.5±7%) and HDF (86.3±12%).The highest average cumulative soil loss was from BS plot (806.8 t.h-1.yr-1) and the lowest from HGC (167.1 t.h-1.yr-1). Overall, surface cover such as grasses and dry fronds are effective measures in reducing risk of runoff and soil erosion.