Weed surveys in different tillage systems in southwestern Ontario field crops

Abstract

The survey was conducted after all weed-control measures had been carried out, and 82 weed species and groups of species were recorded. The most abundant weeds were green foxtail Setaria viridis, lamb's-quarters Chenopodium album, quack grass Agropyron repens, redroot pigweed Amaranthus retroflexus, common ragweed Ambrosia artemisiifolia and dandelion Taraxacum officinale. These weeds accounted for 54% of the total relative abundance. Weed communities in individual fields were highly variable. Most fields had <10 species, and nearly half of the fields had <6 weeds m-2. Yellow foxtail Setaria glauca, quack, grass spp. (Digitaria spp.), lamb's-quarters, green foxtail and chickweed Stellaria media, occurred at densities >100 plants or shoots m-2 in at least one field. Similar weed communities were found in fields that had different tillage histories. Annual weeds were found at higher densities and perennial weeds at lower densities in reduced tillage than in conventional tillage. Weeds were found at highest total densities in fields with no tillage. -from Authors