The diversity-productivity, diversity-invasibility, and diversity-stability hypotheses propose that increasing species diversity should lead, respectively, to increased average biomass productivity, invasion resistance, and stability. The diversity-productivity hypothesis expects that a more diverse system should be more productive than a less diverse system due to increased resource use efficiency or niche complementarity. Three hypotheses in the context of cover crop mixtures were tested to evaluate the effects of increasing cover crop mixture diversity on aboveground biomass, weed suppression, and biomass stability.