Wind Erosion Abrasion: Effects of Aggregate Moisture

AFTER rain showers, wind erodible-size particles on the surface dry rapidly and often begin abrading the surface aggregates and crust while the latter are still moist. The objectives of this investigation were to measure the abrasive loss rates of moist aggregates and develop prediction equations of the loss rates that would be useful in field studies as well as in development of complex wind erosion models. Accordingly, soil samples were obtained from four soils ranging from a sandy loam to a silty clay loam. Forty aggregates, 4, to 6 cm in diameter, were selected from each soil and then further subdivided by establishing four moisture levels with 10 aggregates at each level. Each aggregate was abraded in an enclosed chamber using a calibrated sandblasting nozzle. A stability test was also conducted on air-dried subsamples of each soil. In this test, 1.3 to 1.9 cm diameter aggregates were crushed to a fixed end point and the work done per unit mass (J/Kg) was measured. Test results showed that the slope of a regression line for the abrasion loss rate versus normalized moisture content varied in a systematic manner, as dry aggregate stability ranged from low to high. Thus, it was possible to develop a simple estimating equation to predict abrasion loss rate as a function of average dry aggregate crushing energy and aggregate moisture content.