Allelopathy is the influence, usually detrimental, of one plant on another, where toxic substances are released when a plant dies or produced through decaying tissue. These secondary metabolites may establish direct or indirect impacts on populations of their own or different species. Allelopathy can a) affect the growth and yield of another crop (Batish et al. 2001) or b) develop autotoxicity, meaning chemicals expelled from plant residues of a species can hinder the growth of seedlings of the same species. Thus, if managed properly, allelopathy can be a great alternative in weed management.

Many of the cover crops seeded to protect the ground have allelopathic properties. Crops such as rye (Secale cereale L.), annual ryegrass (Lolium multiflorum L.), hairy vetch (Vicia villosa L.) and sunflower (Helianthus annuus L) have been shown to limit or reduce the growth of other plant species. Therefore, residues of these cover crops not only provide benefits to the soil but also help to reduce weed populations through allelopathy for the cash crops seeded in the season thereafter. In this experiment weeds were surveyed every two weeks after cover crop mix seeding to observe if allelopathic effects changed according to cover crop species or cover crop mixes. At the end of the season, plots were either roller-crimped or incorporated. The following growing season, canola, field pea and wheat will be sown perpendicular to the direction of these plots to observe if weed populations are still suppressed by the allelopathic effects of the cover crops and their mixes. Further, it will be assessed whether roller-crimping and incorporation impact weed suppression along with allelopathy.