Wet soils in alfalfa fields right after cutting will certainly do one thing. It helps weeds and grasses grow. Let’s talk about what you can do about these weeds.
How do you reduce the amount of foxtail, crabgrass, pigweed and other weeds in your hay? The best way to start is to keep alfalfa thick and thrifty so it will compete aggressively with invading weeds. 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 weeds don’t get much time to become a problem.
Unfortunately, this method is easier said than done, and forage quality will be lower since harvest occurs after bloom begins.
Herbicides are another option. Roundup works great for Roundup Ready varieties. For conventional alfalfa varieties, 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. Neither of these herbicides has any soil residual activity, so good plant coverage is necessary and you may need to repeat the spraying if new grasses emerge.
For broadleaf weeds, Raptor and Pursuit are your best choices. They, too, need to be applied before weeds are 4 inches tall. Fortunately, both Raptor and Pursuit have some residual activity so you can apply them a little early and still get control of many later emerging weeds. They will, however, also set back your alfalfa just a little bit.
If weedy grasses or broadleaves are a problem in your hay, thick and vigorous alfalfa stands and some well-chosen herbicides can help you get it under control.
Bruce Anderson is a hay and forage professor at Nebraska Extension.