Increasing soybean yields through management and the role for nitrogen fixation

Title from PDF of title page (University of Missouri--Columbia, viewed on May 30, 2013).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Thesis advisor: Dr. Felix FritschiIncludes bibliographical references.M.S. University of Missouri--Columbia 2012."May 2012"A high yield soybean experiment was conducted to compare the management intensive practices of recent soybean record holder, Kip Cullers, to conventional production practices in 2008 to 2010. Preplant fertilizer applications of poultry litter and mineral fertilizers were compared for their effects on soybean yield and nodulation. While soybean yields increased between 2008 and 2010, preplant treatment differences were inconsistent. Soybean nodule weight, numbers, and size decreased over the three year experiment, but differences between poultry litter and mineral fertilizer applications did not occur. Foliar fertilizers, micronutrient, and irrigation applications were also studied, but did not have significant effects on soybean yield in this experiment. Overall, differences were not observed the high input treatments and conventional practices. To assess if changes have occurred in soybean nodulation capabilities and tolerance to mineral N over time, greenhouse and field experiments were conducted in 2010 and 2011 to survey soybean cultivars released from 1930 to 2002. Results from the field study demonstrate increased soybean yields with increasing cultivar release date, but similar trends in soybean nodulation, total N and leaf ureide concentrations were not observed. These experiments do not support a novel tolerance for N inhibition or loss of nodulation capabilities over time