Effect of Initial Moisture on Runoff Generation and Soil Loss in Different Soil Textures under Simulated Rainfall Condition

The surface soil moisture content has an important and effective role in runoff generation and soil loss, especially in the arid and semiarid regions. For this purpose, an experiment to determine the effect of initial moisture on runoff and soil loss in two soil texture of loamy, sandy clay loam in intact land in the vicinity of the University of Zanjan was performed with four initial moisture levels (one, four, seven and 10 days). Field experiment as factorial in randomized block design was carried out in plot scale (6080cm) using a rainfall simulator. Twelve plots for each soil were installed on a uniform slope of seven percent and accordingly exposed to simulated rainfall with intensity of 55 mmh-1 for 30 min. The results showed that, significant difference was found in runoff generation (p0.05), high initial moisture aggregates in this soil resisted versus detachment by raindrops, while these changes were significant among the soil moisture levels of the sandy clay loam soil (p0.05) between soil loss and runoff generation under moisture levels in soils.