SEAL DEVELOPMENT AND INFILTRATION AS AFFECTED BY RAINFALL KINETIC ENERGY

The effect of rainfall kinetic energy levels and intensities on bare soil surfaces was investigated on two South Dakotan soils. The rainfall was simulated by a modified Purdue type infiltrometer. Six levels of kinetic energy were used in this study. Drop size distribution was measured by the flour method. Seginer's procedure (1965) was used to calculate drop velocities and the rainfall kinetic energy was subsequently calculated.;The modified Green-Ampt infiltration model by Chu (1984) was used after modification according to the concept of Childs (1969) to analyze the field data of Vienna loam and Lowry silt loam soils. The modified model gave a fair description of the infiltration rate.;A pronounced change in the condition of the soil surface was observed through the development of the seal and the decrease in the time to runoff, accumulative water after the runoff, final infiltration rate and the time to infiltrate 50 mm of water.;Protected surfaces were not affected by the rainfall kinetic energy levels in Vienna loam and the final infiltration rate remained as high as the application rate. Protected surfaces with stopping periods were affected by air entrapment, soil compaction, and slaking.;The time to runoff, the time to infiltrate 50 mm of water and the final infiltration rate were investigated under different rainfall kinetic energy levels and intensities. The effect of kinetic energy on seal formation was studied under different soil surface conditions.;Lowry silt loam was more susceptible to seal development from rainfall kinetic energy than Vienna loam. The rainfall sealing energy of Vienna loam was higher compared to Lowry silt loam. The measured energy parameter E(t) value for Vienna loam was 0.12 J/cm('2) and for Lowry silt loam was 0.07 J/cm('2). These values were consistent across the kinetic energy levels imposed and can be used to describe the soil seal.