The Effect of Soil Air Entrapment on Erosion

Abstract

ABSTRACT THE effects of soil air entrapment on erosion and infiltration were investigated by two laboratory studies, one with a fallow soil and one with a grass cover. Both the fallow soil and the grass cover experiment had a zone which restricted the downward movement of soil air. For the air-trapped treatments, soil air was trapped between the restrictive zone and an advancing wetting front produced by applying overland flow. Vent tubes permitted soil air to escape at the restrictive layer during the air-vented treatments. Trapping the soil air above the plow pan restricting zone increased the erosion rates an average of 530 and 180% during the overland flow application rates of 1.54 and 0.89 L/s-m, respectively. Fluctuations in the erosion rate correlated well with the fluctuations of soil air pressure. Infiltration rates decreased when soil air was entrapped. The decrease in cumulative infiltration depth averaged 55% for the low-flow treatments and 45% for the high-flow treatments. The effect of soil air entrapment on infiltration rates for the grass-cover treatments decreased as the grass cover developed and the soil's bulk density increased. The decreased infiltration rates, due to soil air trapping, averaged 74% for the initial overland flow event, 26% for an identical event 12 weeks later, and 10% 16 weeks later.