Charles M. Geddes, Agriculture & Agri-Food Canada, Lethbridge, AB, CANADA, Andrea Cavalieri, 66 Dafoe Road, University of Manitoba, Winnipeg, MB, CANADA and Robert H Gulden, Department of Plant Science, University of Manitoba, Winnipeg, MB, Canada
Allelopathy is the chemical effect of one plant on another through the release of chemicals into the environment. Aqueous extracts of hairy vetch (Vicia villosa), fall rye (Secale cereale), and winter wheat (Triticum aestivum) were prepared using aboveground biomass to determine their allelopathic potential. Previous research indicated that aboveground biomass demonstrates greater allelopathic potential than belowground biomass. Vegetative and reproductive shoot biomass was extracted to evaluate the difference in allelochemical concentration between these developmental stages. Canola (Brassica napus), kochia (Kochia scoparia), lamb’s quarters (Chenopodium album), wheat (Triticum aestivum) and wild oat (Avena fatua) were used as model weed species to evaluate the allelopathic potential of the extracts on filter paper and in silty clay loam soil. Allelopathic potential was measured by determining the % germination and radicle elongation when imbibed with each extract relative to control treatments. Allelopathic effects varied widely among model weed species. In the presence of soil, extract efficacy was decreased throughout. Vegetative tissue extracts suppressed weed seed germination and radicle elongation more than reproductive tissue extracts. Wild oat germination and radicle elongation, as well as lamb’s quarters radicle elongation were stimulated by certain extracts in soil. The vegetative fall rye aboveground biomass extract displayed the greatest suppressive effect. Results indicate that the allelopathic effects were complex and dependent on extracted species, stage, medium, and model weed species in question. Further research on the allelopathic stimulation of radicle elongation of wild oat and lamb’s quarters warrants investigation.