Legume recovery in pastures following broadleaf weed control

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Invasive species are a widespread problem in pastures limiting forage production. While herbicides remain effective against weeds, herbicides also remove beneficial legumes known to increase production at minimal cost. Although prompt return of legumes is an important goal, the ability of legumes to re-establish in pastures following weed control depends on several factors. They include the rate of herbicide degradation following spraying, the presence of viable legume seeds in the soil, and the specific growing conditions needed to favor legume seedling emergence and growth under field conditions. We use a combination of field experiments (short and long-term) and complementary greenhouse trials to 1) quantify the degradation of two new herbicides (aminocyclopyrachlor and aminopyralid) with 'residual' properties, 2) assess their effect on the emergence and survival of two common legumes (alfalfa and white clover) following application, 3) evaluate the effect of environment (light and moisture) on legume seedling emergence, growth and survival, 4) document long-term changes in plant species composition of pasture following spraying, and 5) describe the soil seed bank in northern temperate pastures, including the abundance of legumes. Information will be used to assist growers to effectively re-establish legume and maintain productivity and pasture biodiversity.