Cover Crops and Conservation Tillage
for Soil Erosion Control on Cropland
Establishing Birdsfoot Trefoil or Crownvetch as a Living Mulch
General information - Establishing Birdsfoot Trefoil or Crownvetch as a Living Mulch
Crownvetch seedling growth is very slow, normally requiring 2 to 3 years to produce a well-established, vigorous stand. Birdsfoot trefoil, on the other hand, establishes more quickly, so it is seeded with crownvetch to provide quick cover until the crownvetch becomes well established. The conversion from birdsfoot trefoil to crownvetch may take 3 to 5 years. Normally the crownvetch seeding rate is 5 pounds per acre at a cost of $50 to $60 if seeded alone; but if crownvetch is seeded with birdsfoot trefoil, as little as 1 pound per acre of crownvetch seed can be used with 3 pounds per acre of birdsfoot trefoil, reducing the seed cost to about $20 per acre. Few growers can afford to take a field out of production while the cover crop is being established. Thus, seedings are best made in fields free of perennial difficult-to-control weeds, with IT or Clearfield corn and the Pursuit plus Basis herbicide mixture (Treatment 1, Table 2) for control of weed seedlings.
Perennial weeds, especially thistles, hedge and field bindweed, hemp dogbane, horsenettle, common milkweed and woody perennials are hard to control without legume cover crops and even more difficult with them. If perennial weeds are a problem, try to clean them up with Roundup or Touchdown and/or dicamba (Clarity) when no crop is present, typically in August or September the year before cover crop seeding. This usually is only possible after small grains or on conservation reserve land. Accent, Basis and Lightning have been found to be safe on crownvetch and birdsfoot trefoil and help control some of these problem weeds in corn.
A year before seeding the cover crops, apply lime to raise the soil pH to 6.2 to 7.0, and apply phosphorus and potassium to nourish both the crop and the cover crops. In the absence of a soil test, apply 200 pounds per acre of 10-30-10 starter fertilizer in the row or broadcast at the time of cover crop seeding. Make seedings with a broadcast seeder to the soil surface. Crownvetch and birdsfoot trefoil stands seem to be best when the seed is broadcast on the soil surface, but seedings may also be made with a drill or seeder in the same way any other legume is seeded. The birdsfoot trefoil should provide at least 75% ground cover by the end of the first growing season. A crownvetch stand of one plant per square yard after the first winter should be considered a success. Once the crownvetch becomes the dominant species, it should last indefinitely if treated properly.
If it is necessary to destroy the crownvetch stand, apply dicamba (Banvel or Clarity) or 2,4-D for 2 or 3 consecutive years while growing corn.