The bright yellow in your alfalfa fields might be an eyesore, but probably isn't a threat to your profits unless you try to get rid of it.
For four consecutive years, Jerry Doll, University of Wisconsin extension weed scientist, quality-tested dandelions in cut hay.
“On average, dandelions in the first cutting were four percentage points lower in protein,” he says. “In the second and third cuttings the difference wasn't statistically significant, but the dandelions averaged about a half point higher in protein than the alfalfa.”
That four-point protein difference in the first cutting is cheaper to make up with a feed supplement rather than controlling the dandelions with herbicides, says Doll.
“There's not a cost-effective way to control dandelions,” adds Roger Becker, University of Minnesota extension weed scientist. “The herbicides available don't give you complete control and are expensive. You have to ask yourself, why control them in the first place?”
Since dandelions are close to alfalfa in quality, Becker says the logical thing to do is leave them alone until you're ready to rotate the field.
“I try to talk people out of trying to control dandelions in alfalfa because they've got very good forage quality,” Becker says. “We're trying to get farmers to think of dandelions as an establishment or thinning indicator. They indicate that your alfalfa stand might not be what you really want. It might be time to go into rotation.”
Dandelions' only flaw may be their slow dry-down rate. A high level of dandelion contamination, maybe 30-40%, could add a half day to a day of drying time. That increases the probability curing hay will get rained on in the Great Lakes region, Becker states. The field could be harvested for silage rather than hay, if that's an option, to reduce the weather risk.
Herbicides haven't proven very cost-effective for dandelion control, but Doll says certain treatments may be justified if they get rid of other weeds, too.
“If you've got dandelions of consequence, you also probably have a little bit of quack, yellow rocket, hoary alyssum, brome or some other weed,” Doll says. “If you're willing to spend $20 or $25/acre targeting dandelions, and also take out the 15-20% grass and other weeds that are also out there, maybe you'll see a return on high-priced spring-dormant treatments like Sencor or Velpar.”
Roundup-Ready alfalfa, expected in a year or two, will give growers another dandelion control option. But it remains to be seen if Roundup will be more cost-effective than currently available herbicides.
“Dandelions are one of the tougher weeds for Roundup to control.” says Becker. “Grasses really kill forage quality; dandelions don't. Roundup will economically control grasses and improve forage quality. So use Roundup only for things that matter, and if dandelion presence is reduced, that's icing on the cake.”