Flipp, Amanda Marie2014-01-172014-01-172013-10https://hdl.handle.net/11299/162327University of Minnesota M.S. thesis. October 2013. Major: Applied Plant Sciences. Advisor: Gregg Johnson. 1 computer file (PDF); vi, 77 pages, appendices A-P.Studies were conducted in 2011 and 2012 at two sites at the Southern Research and Outreach Center in Waseca, MN to evaluate different combinations of row spacing, soybean varieties, and early season weed control treatments on giant ragweed, common lambsquarters, and tall waterhemp density, biomass, and seed production. The early season weed control treatments consisted of a pre-emergence herbicide, winter rye cover, and radish/pennycress cover mixture. Overall, a flumioxazin, acetochlor, or winter rye treatment were the most effective in reducing weed density, biomass, and seed production. These two treatments generally resulted in at least a 50% reduction in total weed density compared to the control. A flumioxazin or winter rye treatment resulted in no weed seed production of common lambsquarters at Site 1 in 2011, compared to 2018 seeds m-2 in the control. Results demonstrate the importance of early season weed control as part of a comprehensive weed management plan. Soybean row spacing and variety were not as effective in reducing weed density, biomass, and seed production. However, they were important as part of an integrated weed management strategy when used in combination with the winter rye cover crop and flumioxazin or acetochlor in controlling weeds in soybeans. A fully integrated approach is needed to control weeds, either to prevent herbicide resistant weeds or to manage herbicide resistant weeds.en-USAmaranthus retroflexus (Moq) Sauer (tall waterhemp)Ambrosia trifida L. (giant ragweed)Chenopodium album L. (common lambsquarters)Cover cropsIntegrated Weed ManagementRow spacingThesis or Dissertation