The Role of Surface Sealing on Sediment Concentration and Soil Loss in Laboratory Plots under Simulation of Subsequent Rainfalls

Soil is one of the most important national assets of any country. Since the effects of aggregate detachment and formation of surface sealing on increasing flood fertility, reducing soil fertility and increasing erosion is an important issue, the aim of this study was to investigate the role of surface sealing in sediment concentration and soil loss.

The present study was performed on two loamy-sandy and loamy-sandy-clay soil textures under the influence of three rainfall sequences with intensities of 50 and 90 mm h-1 and duration of 15 minutes at the intervals of 10 days in small erosion plots with dimensions of 0.5×0.5 m with a slope of 18%. Also, two weighted average indices of the diameter of soil grains and a three-dimensional scanner with an accuracy of 20 micrometers were used to measure the surface coating.

The results showed that rainfall sequence had a significant effect (p<0.01) on sediment concentration and soil loss. As a result of the sequence of rainfall, the loss of soil in the loamy-sandy texture increased by about 45% in the rainfall intensity of 50 mm h-1, while it decreased by 38% in the rainfall intensity of mm h-1, and in the loamy-sandy-clay texture respectively Rainfalls of 50 and 90 mm h-1 reduced soil loss by 5 and 67%, respectively. Sediment concentration also decreased after rainfall sequences. The results of measuring soil loss showed that, except in loamy-sandy texture at an intensity of 50 mm h-1, in both soils, the amount of soil loss decreased from the first rainfall to the third rainfall. The results of three-dimensional scanner at rainfall intensity of 50 mm h-1 showed that the soil surface roughness in loamy-sandy texture decreased from 1.30 to 1.18 mm and in loamy-sandy-clay texture decreased from 1.80 to 1.31 mm, but at rainfall intensity of 90 mm h-1, the soil surface roughness increased and the formation of surface sealing was prevented.

The results showed that soil surface roughness and surface sealing resulting from previous rainfall can change soil surface conditions and runoff and soil loss at the plot scale and the intensity of these changes is under the interaction of rainfall intensity and soil texture.