Controlling Summer Grasses In Alfalfa
How do you reduce the amount of foxtail and other weedy grasses in your hay? One way lets your alfalfa do all the work. If you keep your alfalfa thick and thrifty it will compete aggressively with invading foxtail. Thick initial stands and good soil fertility are needed. In addition, harvest alfalfa only after it begins to bloom or when new shoots appear at the base of the plants. Then alfalfa should regrow rapidly so foxtail doesn't get much time to become a problem.
Unfortunately, this method may be easier said than done, and it sacrifices some forage quality since harvest occurs after bloom begins. So this method may not solve all your problems.
Herbicides are another option. Roundup works great for Roundup Ready varieties. In regular alfalfa, two chemicals that control annual grasses are Select Max and Poast Plus. These herbicides work well on seedling grasses that are less than 4 inches tall, and alfalfa tolerates both herbicides very well. Another herbicide option is Gramoxone Extra. Gramoxone burns back top growth of all green plant material. This will kill most annuals like foxtail, but, it also can injure alfalfa regrowth that has already emerged. So, only use Gramoxone immediately after harvest and before new regrowth shoots appear. None of these herbicides have any soil residual activity, so good plant coverage is necessary and you may need to repeat the spraying if new weeds sprout.
If weedy grasses are a problem in your hay, thick and vigorous alfalfa stands and some well-chosen herbicides can help you get it under control.
[June 27th, 2008]
Dr. Bruce Anderson, Professor of Agronomy
Agronomy & Horticulture, University of Nebraska - Lincoln, Lincoln, NE