Assessing the rice straw effects on the soil erosion rate in forest road cut slope embankments

Applying rice straw as mulch blanket on recently-established embankment is one way to reduce the environmental impact of sediment yields from forest roads embankments. Effectiveness of straw, however, is often unknown and it is unclear how the rate of application should vary with factors such as slope. In this study, the effects of the percentage of straw cover and slope gradient in the embankment of forest roads on the runoff volume and soil erosion were studied using rainfall simulator in plots of 1 m × 1 m dimension. Straw effects were quantified in four treatments of rice straw cover (0%, 30%, 60% and 90%), three treatments of slopes (0-15%, 16-30%, and 30-45%), with three replications in each giving a total of 36 experimental plots. Runoff and sediment from each plot were recorded every two minutes during the simulated rainfall of 65 mm/h intensity for 16 minutes. The 16-min simulations divided into eight simulation periods. The results showed that an increase in straw cover (based on length and amount) resulted in an impressive decrease in the runoff volume and soil erosion. Moreover, investigating the effect of slopes indicated that the runoff volume was significantly different between 0-15% and 15-30% slope classes. In terms of sediment concentration (g mL-1) and sediment (g), there were significant differences between the study slopes (various slopes and covers). The results showed that rice straw can decrease soil erosion up to 90% in road embankments and the rice straw with the length of 5 cm was the most economical choice to protect soil from erosions.