Assessment of aggregate stability and determination of instability mechanism of marly soils in Taleghan watershed

Due to the constraints in determining of soil susceptibility to water erosion or soil erodibility through field tests, use of laboratory methods on small soil samples, are easy to implement and far less expensive and time-consuming. among different laboratory methods based on the soil properties, those relating to aggregate stability have received much attention. In this study, by relying on observations and changes in the macroscopic scale of homogeneous work units in marly soils of taleghan watershed, with 3260 hectares in area, 84 points as the soil sampling points were selected.
In order to distinction between aggregate breakdown mechanisms and assessing of soil structural behavior in different environmental conditions, aggregate stability is measured with respect to three treatments fast wetting, slow wetting and stirring after pre-wetting using Le Bissonnais method. Results showed that aggregate breakdown mechanisms have a significant influence on aggregate stability. The instability main mechanism of marly soils in Taleghan watershed is slaking that caused by the compression of entrapped air during fast wetting and this situation can occur during rain storms on dry soils and irrigation flooding. So it seems that the method of agricultural land irrigation can be one of the most important soil erosion factors in the study area.