Effect of land use types and slope on soil Erodibility factor in Alborz province, Iran

ABSTRACT: Erodibility is the qualitative and quantitative statement of the intrinsic susceptibility of a specific soil to detachment and transfer by the rain water and runoff. In the present study, using the Wischmeierʹs nomograph and the corresponding equation, the erodibility status of the soil in Zidasht, located in Alborz province, was determined and the effect of slope on soil erodibility with different land uses was analyzed. First, three slope classes consisting of 3-8%, 8-18%, and 18-40% were chosen for land use units including pasture, dry land farming, andirrigated farming, and soil samples in three repetitions. The samples were used for organic matter measurement, soil gradation and texture analysis, and bulk density measurement. Erodibility for pasture land use increased with slope percentage, which is statistically significant at the p < 0.01 level. The same was true for dry land farming, i.e. erodibility increased significantly at the same p level with slope percentage. In the case of irrigated farming, lands with 8-18% slope had the highest erodibility;this shows a critical condition at this slope class. Lands with 18-40% slope had the lowest erodibility; this can be because of erosion at earlier times. In general, the results indicate that erodibility increases with slope percentage of lands with agricultural use. Without considering land use types, lands with 3-8% slopes had the lowest erodibility, while an increase in the slope led to an increased erodibility.