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)

Abstract

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