Date of Award
Master of Science
Plant, Soil and Environmental Sciences
Maxwell E. Springer
R. J. Lewis, W. L. Parker
The universal soil-loss prediction equation has served for several years as the guide to sound conservation planning on cropland. Up until now, its use for nonagricultural land has been limited. These limitations were due primarily to the lack of information on the soil erodibility factor values. In the past, these values were obtained through actual soil-loss measurements on only a few representative soils, to which other soils were compared. Undoubtedly, the method had quite a margin of error. Now, the development of the nomograph method has enabled the land user to obtain fast solutions to erodibility equations through computation of the erodibility factor at any given depth on any soil. In order to use the nomograph, one only needs to know five soil parameter values which can be obtained from routine laboratory determina-tions and standard soil profile descriptions. These five soil parameters are: percent silt plus very fine sand; percent sand greater than 0.10 millimeters; organic matter content; structure; and permeability. Once the erodibility factor is determined, it may be combined with five other major factors in the soil-loss prediction equation to predict annual soil loss on any given site. The other factors in the equation evaluate effects of rainfall pattern, slope length, slope steepness and shape, cover and management, and conservation practices on erosion. Forty-four soil series were selected on the basis of their representative physical characteristics, geographical location, and available laboratory data. The K-values calculated for these soils ranged from a low of 0.11 to a high of 0.69. As was anticipated, the soils in West Tennessee, containing more silt and less sand, exhibited the higher erodibility factor values. Also, large amounts of soil organic matter greatly decreased the erodibility factor values. The effects of soil structure and permeability were found to be significant enough to change individual erodibility predictions. After sediment yields were calculated on a portion of these representative soils, recommendations were given which if adopted would greatly reduce the volume of soil being lost by runoff.
Rhoton, Fred E., "Determination of erosion factors by the nomograph method and their use in soil-loss prediction on some Tennessee soils. " Master's Thesis, University of Tennessee, 1974.