The use of herbicides for brush control in pastures of east-central Saskatchewan
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One of the main problems encountered with most methods of pasture improvement is the control of regrowth of young trees and shrubs which compete with grasses and legumes for moisture, nutrients, and sunlight. This paper reports on results from three timing experiments that used combinations of 2,4-D and dicamba and different patterns of herbicide application to control regrowth of woody plants in pastures of east-central Saskatchewan. The main woody plant species were aspen poplar, prickly rose, and western snowberry. The experiments were conducted during 1981 to 1989 in a community pasture located on a Waitville loam soil. The area had been cleared of trees and shrubs by bulldozing in the winter of 1979-80, prior to the start of the tests. In June of 1981 2,4-D ester or 2,4-D amine at 2.2 kg ha-1, plus dicamba at 1.5 kg ha-1, were foliar applied at full leaf expansion of the aspen poplar. Some treatments received repeated sprayings in the first year, second year, or in two consecutive years after the initial herbicide application. Other treatments studied included the application of 2,4-D tank mixtures with higher rates of dicamba, using a combination of fertilizer and herbicide, and using fertilizer alone. The results showed that herbicides were an effective method for controlling brush regrowth on pastures. The production of woody plant material was reduced by 52 to 98 %, while the production of grasses was increased nearly three-fold compared to untreated areas. When mixed with dicamba, application of 2,4-D ester was more effective for controlling undesirable plant species than the 2,4-D amine formulation. Using repeated herbicide applications improved the control of woody plants and improved the yields useable herbage. The highest yields of forage were obtained when herbicides and fertilizers were used in combination. Economic returns from brush control were generally highest for the one-time application of 2,4-D ester plus dicamba. Repeated herbicide applications, and application of a higher rate of dicamba, were not economically justified unless the value assigned to forage was very high. Under the conditions of this study, improving pasture productivity through application of fertilizer and herbicides in combination, or fertilizer alone, were less profitable than a one-time application of 2,4-D ester plus dicamba.
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