Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Agricultural and Biosystems Engineering

First Advisor

T. S. Colvin


Soil erosion is an international problem that if not controlled will deprive humankind of life sustaining material from the soil. Working diligently to solve this serious problem, researchers have developed several mathematical and computer models, such as the USLE, the MUSLE, the RUSLE, and the WEPP. But, when applied to locations other than those in which they were developed, these models have not performed well;A laboratory apparatus was designed and developed to simulate the field conditions of water potential, as well as field flooding, slope, and water potential. The apparatus successfully duplicated water potential and slope of the field. Field conditions were imitated as closely as possible. Soil structure could not be duplicated identically because it was not possible to disturb the soil from the field and still maintain original soil tilth conditions;The apparatus performed well in initial experiments. Decreased water potential increased the shear strength of the soil. Tensiometers successfully measured soil water potential levels and were read by a pressure transducer;Soils of three textural classes (clay, silt, and sand), three tilth, or historical, conditions (grasses, corn-soybean rotations, and corn-corn rotations), and three water potentials (0, -5 and -15 cm) were studied. Soil in bins was exposed to the erosive power of running water;Runoff from webster (clay) soil from a grassed area had the lowest sediment concentration in the runoff water. On the average, sediment concentrations in runoff water from clay soils were less than those from either silty or sandy soil. Similarly, runoff from plots with -15 cm of water potential yielded less sediment than did plots at 0 cm of water potential. Relatively large sediment concentrations were observed for corn-soybean rotations compared to grass and corn-corn. On the whole, soils under grasses yielded lower sediment concentrations in runoff water than did soils under crop rotations.



Digital Repository @ Iowa State University,

Copyright Owner

Zahid Mahmood



Proquest ID


File Format


File Size

156 pages