Degree Type


Date of Award


Degree Name

Doctor of Philosophy




Crop Production and Physiology; Sustainable Agriculture

First Advisor

Mary Wiedenhoeft


Over the period of 2009-2013, I compared the agronomic, economic, and ecologic performance of three distinct crop rotations at the Iowa State University Agronomy and Agricultural Engineering Research Farm in Boone County. One rotation represented the contemporary norm in Iowa, while the other two rotations included “alternative” crops (canola and wheat) and a forage legume green manure interseeding (red clover). The rotations were a corn-soybean (C-Sb) system, a system common to contemporary Iowa farming operations; and two “alternative” systems: corn-spring canola-winter wheat + red clover (C-SC-WW/RC) and corn-spring wheat-winter canola + red clover (C-SW-WC/RC). All three rotations included transgenic crops, applications of liquid swine manure, synthetic fertilizers, and chemical pesticides; though, I intended for biological N fixation by the red clover green manure and crop competitiveness with weeds to be more heavily relied on in the two alternative cropping systems. The overall purpose of this research project was to provide demonstrations of and more information about alternative, diverse cropping systems for farmers in Iowa. The objectives of this dissertation research were to determine: (i) whether red clover green manure could reduce reliance on purchased N fertilizer for corn production; (ii) the best combination of spring and winter varieties of wheat and canola in terms of yield and quality; and (iii) the financial and soil erosion dynamics among the three rotation systems studied. The alternative systems were not as competitive on a production or economical basis, but they did show tremendous promise in terms of reducing the potential for soil erosion and input costs associated with agriculture, compared to the contemporary C-Sb system common across Iowa.


Copyright Owner

Stefans Robert Gailans



File Format


File Size

116 pages