Abstract
Maize was grown on erosion plots to test the relationships of soil exposure to soil loss. The effective ground cover of the crop canopy was estimated through dimensional calculation by assuming that the leaf array of the maize plant is rectangular in shape. Effective ground cover was negligible for the first week of growth but increased rapidly over the next three to four weeks during the period of exponential growth rate of the crop. Maximum ground cover was reached after six to seven weeks of growth. Prediction of soil loss in individual storms with the universal soil-loss equation was reasonably accurate when the soil was bare or nearly bare before crop growth was appreciable. Later in the growing season the predicted loss was always high compared to actual soil loss when an oil exposure factor was used in the equation instead of an empirical crop management factor. In windy storms the angle of incidence of rainfall into a tall canopy reduced the amount of oil exposed to direct raindrop impact, but this added factor did not fully explain the poor predictability of the soil exposure factor. Therefore, it was assumed that the growing crop provided other soil conserving factors in addition to canopy protection against direct raindrop impact.
