Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Catherine L. Kling

Second Advisor

Joseph A. Herriges

Third Advisor

Jinhua Zhao


Increased use of nitrogen fertilizer in agricultural production has contributed to increased food production but also contributed to elevated concentration levels of nitrates in groundwater and surface water. High concentration levels of nitrates in drinking water supplied from groundwater and surface water have become a public concern because of their risks to human health.;One way to reduce nitrogen losses is to develop and apply technologies that enable farmers to more accurately match the amount and timing of fertilizer application to crop growth needs. It is best to apply nitrogen as close as possible to when crop needs it most, proper timing is most important with nitrogen fertilizer. Fall application of nitrogen increases the loss of nitrogen through denitrification, it also gives nitrogen time to leach through the root zone and into groundwater.;The first chapter gives overview of the timing of fertilizer application. The purpose of second chapter is to examine the effect of timing of fertilizer application on total amount of nitrogen fertilizer applied. The goals of the third chapter are twofold. First, it determines which factors influence the use of fall fertilizer application and conservation tillage in a modeling framework that recognizes the interrelationship between the two decisions. Second, it examines the implications of adopting these two practices for nitrogen productivity, which is measured by crop yield. The purpose of the forth paper is to develop a contract schedule to induce land-based nonpoint polluters to choose second-best input vectors for their soil type. Specifically, it concentrates on the issue of fall and spring nitrogen fertilizer application. It is assumed that the environmental agency can monitor the total amount of nitrogen applied; however, it cannot observe amounts of nitrogen applied in the fall and spring. Therefore, in addition to asymmetric information about soil type, this model also takes into account the moral hazard problem which appears because of unobserved actions taken by some farmers.



Digital Repository @ Iowa State University,

Copyright Owner

Mira Nurmakhanova



Proquest ID


OCLC Number




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File Size

132 pages