Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Randy J. Killorn

Second Advisor

Thomas E. Loynachan


The management of nitrogen (N) applied to cropland has been the focus of much concern because of the increasing concentration of NO[subscript]3-N in surface and groundwater in recent years. Moreover, sustainable agricultural systems that rely on organic materials such as animal manure to supply a crop's N needs are growing in popularity. The potential for environmental contamination from improper management of these materials must be considered;Livestock confinement operations generate large amounts of animal manure and many have limited acreage where the manure can efficiently be applied. Additionally, it is expensive and time consuming to haul manure from areas of livestock confinement to cropland where the nutrients in the manure can be used. As a result large quantities of manure may be applied to limited areas, increasing the potential for environmental pollution;This dissertation describes results from two field experiments where liquid dairy, swine, and poultry manures and urea-ammonium nitrate (UAN) were applied for corn production. The objectives of this research were to evaluate changes in soil inorganic N (N[subscript] i) and determine the potential for NO[subscript]3-N contamination of surface and groundwater from the different systems. Grain yield was measured in an effort to determine differences in N utilization efficiency with different application methods;There were significant differences in soil NO[subscript]3-N with the different systems. Generally, systems where manure was injected will have a greater potential for NO[subscript]3-N movement to groundwater and systems where manure was broadcast over the surface increase the potential for movement into surface water. Corn yields were generally higher when the manure was injected;Soil electrical conductivity (EC) and pH were also measured. After three years there were no significant changes in residual values. Increases in EC were noted following manure application, around the time of seedling emergence and early seedling growth. Soil EC generally returned to initial levels before the next growing season. The elevated EC levels were not considered high enough to effect corn growth except near injection bands where the possibility of isolated areas with high EC values may occur. The application of manure had no significant effect on soil pH values.



Digital Repository @ Iowa State University,

Copyright Owner

Donald G. Wetterauer



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103 pages