Analyzing the Changes of Soil Erodibility Index (K) in the Soils of Arid Regions and the Effective Factors in Central Iran (Case Study: Yazd-Ardakan Plain)

One of the main factors of water erosion is the natural characteristics of the soil called «erodibility» or «detachability». The present study aims to analyze the variations of soil erodibility factor in differentplains and the factors related to it. Erodibility is one the key factors in some models of erosion and sediment such as Universal Soil Loss Equation (USLE), Revised USLE (RUSLE), and Modified USLE (MUSLE) and is a function of grain size distribution, organic matter, structure and infiltration. To this end, the index of soil erodibility was measured through field surveys in 37 spots in the faces of bare pediment, coalescing pediment, and concealed pediment plains using Wischmeier and Smith (1987) method. The infiltration of soil profile and the percentage of desert pavement in the field were measured as well. Soil grain size distribution, percentage of organic matter, soil structure, gravel volumetric content, lime, salinity, acidity, and sodium absorption rate were also measured in the laboratory. The statistical analysis indicated positive correlations of erodibility with silt, very fine sand (VFS), and negative correlation of this factor with gravel, sand, infiltration, organic matter, and lime. The results from Analysis of Variance (ANOVA) test also indicated that three factors of salinity, acidity, and sodium absorption rate are not significantly different in bare pediment, coalescing pediment, and concealed pediment plains. The results suggested that in natural conditions of soil surface, desert pavement plays its protective role and land use change through mixing the soil would thwart effect of the pavement. So, the erodibility of the soil in manipulated and mixed conditions increases up to 10 times.