The Effect of Soil Air Entrapment on Soil Erosion During Simulated Rainfall
ABSTRACT THE effect of entrapped soil air on soil erosion during simulated rainfall was investigated. A rotating disc rainfall simulator generated laboratory rainstorms of 220 mm/h intensity with raindrop characteristics similar to those of natural rainfall. A test box containing a reconstructed tilled Hagerstown silty clay loam profile with a slowly permeable layer was used to evaluate the effect of soil air entrapment on runoff and erosion rates. Rainstorms of known intensity and duration were applied to the test box and the ensuing runoff was collected. The sediment-runoff water mixture, from each 15-s period, was analyzed with the results expressed as infiltration, runoff, and erosion rates and sediment concentrations. Although only 0.17% of the total energy available for erosion on land areas with a restricting layer originates from entrapped soil air acting upward at the soil surface, a comparison of erosion rates of air-vented and air-trapped treatments showed an increase in erosion rate of 66% due to air entrapment. Furthermore, soil air entrapment enhanced sediment concentration and runoff rate by 25 and 30%, respectively.