Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Plant Pathology and Microbiology

First Advisor

Charlie A. Martinson

Second Advisor

Gregory L. Tylka


The effects of application of swine manure and a comparable rate of inorganic fertilizer to corn on soybean cyst nematode, Heterodera glycines, population densities and soybean growth and yield the following year were studied in two two-year corn and soybean rotations. Soybean heights and yields were increased by manure and inorganic fertilizer that were applied the previous year in corn. Heterodera glycines egg population densities were reduced 48 to 64% in the two experiments after a year of corn. Egg population densities at corn harvest in both experiments were the same where manure or fertilizer was applied and in the untreated, planted control. Nutrient source and whether corn was or was not planted the first year had no influence on H. glycines egg population densities after soybean harvest the second year;In another set of four experiments, the effects of application of swine manure and inorganic fertilizer to soil prior to planting soybeans were evaluated. Both nutrient treatments reduced soybean plant population densities in three experiments and increased plant heights in all four experiments. Manure use increased or had no effect on soybean yield when compared to the untreated checks, but inorganic fertilizer reduced soybean yield in one experiment. H. glycines egg population densities in the soil at soybean harvest were either not different from or were greater than egg population densities in the untreated checks;In laboratory experiments, Heterodera glycines egg hatch was irreversibly inhibited when eggs were incubated in liquid swine manure and in deionized water exposed to vapors from manure. Hatch was inhibited when eggs were incubated in several components of manure, including the ionic salt components, volatile organic acids and aromatic organic compounds, and ammonium nitrate. Hatch inhibition by ammonium nitrate was reversible whereas hatch inhibition with the other compounds was irreversible. Indole vapors stimulated egg hatch. Another laboratory hatch study showed that leachate collected from soil amended with manure inhibited egg hatch relative to hatch in deionized water. Leachate from unamended soil stimulated egg hatch relative to hatch in deionized water. Egg hatch was reduced by contact with soil amended with manure and by volatiles from soil amended with manure.



Digital Repository @ Iowa State University,

Copyright Owner

Dean Alan Reynolds



Proquest ID


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152 pages