Spatial variability of soil erodibility associated with lithology and topography

Today, water erosion is considered one of the most important forms of nature destruction, and the problems caused by it are inseparable problems of the country's watersheds. Among the numerous environmental factors affecting soil erodibility, lithology, topography and climate factors are the most important factors affecting soil erodibility. The purpose of this research is to investigate soil properties including number of drops impact (NDI), mean weight diameter of soil aggregates (MWD), soil penetration resistance (PR), soil cohesion (COH), saturated conductivity (Ks) and soil erodibility index (K). Therefore, six rock types (granite, limestone, ophiolite, shale, marl and sandstone) were selected in Razavi Khorasan province and sampling was done in three slope classes 0-10, 10-25 and more than 25% in 2021. In order to compare soil erodibility in similar rocks in different climates, limestone was selected in Tabas city (dry climate). The results showed that the average soil erodibility index and other indices have a significant difference (P<0.001). The results of measuring soil erodibility index in different slopes showed no significant erodibility index in three slope classes (sig=0.893, p<0.05). The comparison of the average soil erodibility in different climates in rocks similar to Paleogene limestone with a value of 0.83 in Tabas limestone and 0.96 (ton ha h / ha MJ mm) sarakhs limestone showed that the average soil erodibility in different climate has a significant difference (sig=0.023, p<0.05). The results of measuring CSEI index showed that the highest amount of reduction in erodibility reflected by this index is in granite with a value of 64% and the lowest value in shale with a value of 25%.