Legume Re-establishment in Pastures after the Application of Residual Herbicides.

Weeds can adversely affect livestock access to forage as well as reduce forage quantity and quality.  Integrated management of pastures and hayfields often require application of broadleaf weed herbicides for effective weed control. However producers are often hesitant to apply herbicides because of the effect the herbicides will have on forage legumes.  Many pasture weeds are best controlled by residual herbicides that will control later emerging seedlings of these and other weeds.  While these residual herbicides provide long-term weed control of a variety of weeds, they can adversely affect re-establishment of legumes in pastures if replanting occurs too soon after herbicide application.  Experiments were established in Nebraska, Missouri, Iowa, Kentucky, Pennsylvania, and Virginia over the past 4 years to assess legume re-establishment after fall and spring herbicide applications.  Our objective was to determine if forage legumes interseeded within 12 months after application of Milestone^® herbicide (aminopyralid) could be successfully established. Legumes evaluated included alfalfa, red clover, white clover, birdsfoot trefoil, annual lespedeza, and crimson clover.  Fall treatments included Milestone at 2, 4, 6, and 7 fluid ounces (fl oz) of product per acre, Tordon^® 22K herbicide (picloram) at 12 fl oz per acre and Grazon^® P+D herbicide (picloram+2,4-D) at 2 pints per acre.  Spring treatments included the same Milestone treatments as applied in the fall, ForeFront^® R&P herbicide (aminopyralid+2, 4-D) at 2 pints per acre, and 2, 4-D ester at 2 pints per acre.  Legumes were inter-seeded the spring of the year following application of the herbicide treatments.  All forage legumes successfully established at least 12 months after application of aminopyralid. 
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