A study of losses due to weeds in several crop zones of Manitoba

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McGregor, James Arthur
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The control of weeds is one of the oldest and still one of the most important problems connected with agriculture. Because we have always had weeds with us, there is a tendency to accept the situation as inevitable and one of the necessary evils connected with farming, consequently no sufficient, general, and concerted effort is being made to overcome the great loss which they cause. Yet the weed fight is one of the standard routine operations on the farm, and it represents a large proportion of the labor necessary to produce crops. No other single feature of farming requires such universal and unceasing attention as do weeds. The annual loss caused by weeds is enormous. As yet only a small amount of work of a definite nature has been done relative to the loss incurred. The following work has been undertaken to ascertain in a limited way the extent of some of these losses. Barnes and Hopkins in experimental work conducted withh tanks found that weeds were responsible for the removal in the first half of the growing season of more than half of the moisture conserved during the previous twelve months' treatment. This loss of moisture was directly reflected in the following crop of Wheat by reducing the yield over 50%. Barnes and Hopkins in experiments at Swift Current found that the yield of grain must suffer if the grain plants are obliged to compete with weeds for moisture. Experiments to determine the competitive effect of weeds were carried out by intentionally planting weed seeds with grain. Seeds of Russian Thistle, Stinkweed and Tumbling Mustard were used. The results obtained show a very depressing effect on the yield of grain growing in competition with weeds as compared to the weed free area. Similar results were obtained when weeds were allowed to grow upon land to be summerfallowed. Barnes and Hopkins found that the yield of Wheat sown the second year on land on which weeds had previously been planted with the Wheat was very greatly reduced. On weedy plots the yield was less than 25% of that on clean stubble land, Tumbling Mustard appearing to depress the yield to a greater extent than Russian Thistle or Stinkweed...