摘要：The direct measurement of erosion is very difficult and expensive. So use of erosion and sediment models is important to determine the amount of soil erosion. To determine the soil erodibility, has taken 300 soil samples from different fields with 0-12 cm depth that are located in the Aras sub watershed in North West of Iran in 2005-2006. The soil samples were analyzed and some factors such as soil texture , organic matter were measured. By use of the factors the other factors such as soil structure class, soil percolation class, total sand, fine sand, clay and silt percentage was measured. The study used the soil structure class and percolation to determine the soil erodibility. This study evaluates the effects of soil erodibility and the factors on sediments amount in the hydrological watersheds that have station to measure the sediment. Soil erodibility was measured by the formula follow this: 100K = 2.1M 1.4x0-4xz(12 - % OM)+3.25(S-2)+(P-3). Soil erodibility and some factors such as soil organic matter , fine sand percentage and soil structure class can predict the amount of soil erosion. Analysis of variance and the means comparisons with LSD test was done by MSTATC software. Linear correlation coefficients between different traits were done by SPSS software. The variance analysis results of the studied attributes showed that there is significant difference among the erodibility, fine sand and soil structure class. The studied location mean showed that Mashiran, Pole Almasi and Borran station in comparison the other locations, had the most erodibility. Soil erodibility cannot be the factor that has effect on the sediment producing in a station, alone. This factor must be evaluated with other factors such as soil organic matter, soil fine sand percentage, soil structure class, watershed area, topography and plant cover. In the prospective research, we should improve method to measure and calculate soil erodibility, strengthen the research on the mechanism of soil erodibility and conduct research on soil erodibility by both water and wind agents.
