Experimental investigation of the aggregate breakdown and splash erosion in different conditions intensity and rainfall duration in selected soil of Dashtegol watershed of Masjed Soleyman

One of the major problems of soil erosion and related environmental impacts are damaging both within the region and outside the region is not negligible. Understanding the factors and processes affecting soil erosion and soil conservation strategy for the region to provide a healthy environment is essential. One of the most important processes in splash erosion is aggregate breakdown and producing the detached particles which are more easily transportable (24). This study was carried out to find the relationship between aggregate breaking down and splash erosion in laboratory conditions with Multiple Splash Set (MSS). The experiment was conducted as factorial based on completely randomized design with three replicates. The treatments were including duration of rainfall at levels (5, 10, 15 and 20 minute), rainfall intensity at two levels (1.5 and 2 mm.min-1) and two type of land use (forest and agriculture). Soil samples were collected from surface horizon (A) of each land uses for physico-chemical analyses. Soil properties including amount of organic matter, gypsum, CaCO3, particle size distribution and aggregate stability were measured. Soil aggregate stability index (mean weight diameter, MWD) were measured before treatment and compared with after treatment. The rates of splash erosion were measured using multivariate samples set (MSS). Splash erosion was measured by collecting the splashed particle. Analyses of the physical and chemical characteristics indicate that almost 50 percent of the particles in both land use is silt particles, which indicates the soil is susceptible to erosion. The results showed that with increasing rainfall duration and intensity the amount of splash erosion and aggregate breaking down were significantly increased (P<0.01).The results indicated with increasing rainfall intensity from 1.5 to 2 mm mim-1 splash erosion and aggregate breakdown increased 1.3 and 1.33 times. The amounts of splash erosion in two land uses were significantly different (P<0.01). The mean of splash erosion in agricultural and forest landuses was 29.37 and 25.56 g m-2 respectively. The results showed a significant positive correlation between splash erosion and aggregate breaking down (R2=0.96). The results also demonstrated splash erosion and aggregate breakdown increased significantly by increasing rainfall duration from 5 to 20 minutes. According to the results can be concluded that rainfall duration and intensity are important parameters to the process of splash erosion and degradation of soil aggregates. At the beginning time, splash erosion and breaking down of soil aggregate was low. The maximum amount of splash and aggregate breaking down in the range of 10-15 minutes after the rain, and then splash and breaking down was almost constant trend.