Chapter 1 assesses the effect of crop density and nitrogen immobilization on weed suppression and yields in an organic system where soybean [Glycine max (L.) Merr.] was no-till planted into a cereal rye mulch (Secale cereale L.). High soybean seeding rates promoted weed suppression, and yields were unaffected by low-nitrogen environments. Thus, results suggest that crop density is an important lever for optimizing weed suppression and that low soil nitrogen conditions may enhance weed suppression without reducing yields in soybean production.Chapter 2 evaluates the effect of multi-tactic weed management in establishing intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & Dewey], a burgeoning perennial grain crop. In this experiment, no single-tactic or combination of tactics suppressed weeds or increased grain yield relative to the untreated control. However, the experimental and analytical approach used in this study provides a framework for evaluating multi-tactic weed management and testing for synergistic interactions. Chapter 3 tests how soybean density and cereal rye mulch biomass suppress weeds and affect the functional diversity of weed communities. It determined that soybean density and cereal rye biomass interacted synergistically to promote weed suppression. However, soybean density and cereal rye biomass had differing effects on weed community functional diversity, suggesting that these management practices represent unique filters during weed community assembly. Consequently, this chapter shows that using multiple weed-management tactics can enable the suppression of diverse weed functional groups. Chapter 4 studies how phylogenetic relatedness affects cover crop-based weed suppression. Findings from this study demonstrate that cover crops can reduce up to 99% of weed biomass and change weed community structure by most intensely suppressing related weeds. However, only cover crops that overwintered affected weed community phylogenetic distance, suggesting that the emergence timing of cover crops relative to weeds might influence whether or not they select for particular weed phylogenetic groups. As such, this study helps develop cover crop-based weed management systems by demonstrating that the suppression of problematic weeds can be improved through the use of phylogenetically related cover crops that are established prior to weed emergence.