Degree Type


Date of Award


Degree Name

Doctor of Philosophy




The subject of soil loss has attracted increased attention in recent years. There has been an abundance of literature on the importance of conserving this resource, and the consequences of depleting it. While some erosion is an inherent part of the farming process, and is a rational economic response to market and government generated economic factors, divergence of actual rates of erosion from economically determined optimum levels needs to be corrected. This dissertation examines the extent to which four different government policies can control soil loss, and thereby help sustain agricultural production over time;A regional-national recursive hybrid model is used to trace the path of net returns, crop production, and soil loss on Iowa farms over the twenty-year period, from 1980 to 2000. The regional linear programming model determines the level of crop production in Iowa. The econometric model estimates national levels of livestock production, as well as crop production in the U.S., excluding Iowa. Estimates obtained from these two components of the hybrid are added to determine national economic variables that are exogenous to the linear programming model. The Adjust sector adjusts yields and revises economic variables over time;The analysis indicates that mandatory controls on legally allowable levels of soil loss in Iowa at the 5 ton, or 10 ton level, or else controls of availability of nitrogenous fertilizer would result in a considerable reduction in soil loss over time. While net returns to land and management on Iowa farms would be slightly lower in 1980, higher net returns accrue as a result of all the policy measures under consideration between 1985-2000.



Digital Repository @ Iowa State University,

Copyright Owner

Aasha Kapur



Proquest ID


File Format


File Size

165 pages