EFFECT OF AQUEOUS EXTRACTS OF CROP RESIDUES ON GERMINATION AND SEEDLING GROWTH OF TEN WEED SPECIES

摘要

Detrimental effects of residues from crops such as canola and lentils on subsequent crops have been observed in petri-dish bioassays and in the field. Suppression of wheat growth by canola and lentil residues has occurred, in producer fields, primarily in the area behind the combine where the residues are concentrated. Adequate straw spreading has permitted producers to grow wheat following canola and lentil crops. The effect of these and other crop residues on common weeds in western Canada has not been assessed. Aqueous extracts of the residues of six different crops were bioassayed for their effect on the germination and seedling growth of ten weeds common in western Canada. Extracts of lentil (Lens culinaris is Medic). oat (Avena sativa L.), canola (Brassica napus L.), and barley (Hordeum vulgare L.) were more toxic to flixweed (Descurainia sophia L. Webb), stinkweed (Thlaspi arvense L.), and downy brome (Bromus tectorum L.) than extract of canola was to wheat. The greater toxicity of these crop residues to flixweed, stinkweed, and downy brome than to wheal may permit selective management of these weeds in wheat. Flixweed, stinkweed, and downy brome are major winter annual weeds in winter wheat and usually require late fall or early spring herbicide treatments in no-tillage systems. Therefore, residues of canola, lentil, oat and barley have potential for reducing herbicide use in winter wheat production and in no-tillage direct seeding farming systems. Crop extracts were not toxic enough to affect the growth in the field of seven other weeds in this study.