Estimation of Soil erodibility factor of USLE model and its relationship with landscape features in some parts of Nazzlo-Chay basin, Iran

Soil erodibility is a dynamic aspect that varies over time and with plough, animal’s activities and biochemical factors resulting in a major environmental threat to the sustainability and productive capacity of agricultural areas. In Universal Soil Loss Equation (USLE), soil erodibility factor (K-factor), as an effective parameter in water erosion is a function of particle size distribution, organic matter, structure and permeability. In the present study, the spatial distribution of the amount of K-factor was investigated in the Nazlou Chai Watershed in Urmia, West Azerbaijan using geostatistics. Then soil samples were taken from 1 km by 1 km square grid over 64 location, and the amount of K-factor was calculated in the USLE model. The results showed that K-factor was ranged from 0.029 to 0.079 (T h MJ-1 mm -1). The spatial variation of K-factor was best fit to the exponential model and showed a moderate spatial structure. The studied soils were categorized in low and very low erodibility classes. The quantitative amounts of erodibility were categorized based on slope classes and the highest value observed for 5-8% slope that belongs to dry farming land use. Also K-factor showed various values in different hydrological groups, where group A showed the least and group D showed the highest amount. It seems that inappropriate soil management in both hilly areas and dry farming lands is one of the main causes of soil damage and an increase of soil erodibility.