Relation between Atterberg Limits and Interrill Erodibility of Semi-arid Area in East Azerbaijan Province

Atterberg limits are indicators of soil moisture that show consistency of soil at various states. This study was conducted to investigate the relationship between interrill erodibility and soil Atterberg limits. For this reason 26 soil samples with contrasting properties were collected from four regions of East Azerbaijan province. The sand, silt and clay fractions were determined by the combined sieve- hydrometer method. Atterberg limits were determined according to the standard ASTM method (by Casagrande and hand rolling methods). A rainfall simulator with drainable tilting flume (1×0.5 m) at slope of 9% was employed and interrill erodibility coefficient of the soil (Ki) was calculated at 20, 37, and 47 mm/h rainfall intensities. Results showed that the effect of rainfall intensity on soil interrill erodibility coefficient was insignificant (P˃0.05). Regression relations between Ki and Atterberg limits and other soil properties were developed by STATISTICA software. Ki was estimated using clay, soil organic matter (SOM), sodium adsorption ratio (SAR) and pH as predictors and this regression model could explain 75% of the variance in Ki. Results also showed that there was a direct positive relationship between Atterberg limits and SOM and clay content of the soil. According to the results, the Atterberg limits couldn’t be a suitable predictor for estimating the interrill erodibility coefficient of the soils.