Now a few weeks into spring, farmers are starting to take stock of their alfalfa stands and, in some cases, they’re concerned their stands didn’t survive a winter that saw low snow cover and a polar vortex early followed by heavy snow late.

David Combs of UW-Madison’s Department of Dairy Science said he has already had calls from farmers in the Madison area who have noticed their fields have been slow to green up. He said slow green-up was a problem last year in the Madison area and he wouldn’t be surprised if the same was the case this year.

“The question we get every year with our forages, like alfalfa, is, ‘Did it make it through the winter?’,” Combs said during an April 17 webinar hosted by Professional Dairy Producers of Wisconsin. “Slow green-up is a sign of injury, but it’s usually not a reason to take a crop out.”

Retired UW-Madison agronomy professor Dan Undersander identifies alfalfa winterkill risk factors as no snow cover, frost heaving, ice sheeting and the breaking of dormancy repeatedly during winter.

With that in mind, and with the state having seen several of those conditions over the course of the winter, Combs recommends farmers get out into their fields to get an idea of what they are dealing with this spring.

“Ideally, within the next week or so, we’d like to know what the level of damage in some of our stands is so we can make some decisions,” Combs said. “If we do determine that we’ve got significant damage to our alfalfa crop, what do we do? Our two options are keep the stand and try to figure out where to generate more forage if we’re going to be short or take that alfalfa stand out and replace it.”

Older alfalfa stands are more prone to winterkill than new seedings, Combs said. He said a stand that is two to three years old would ideally have five to six plants per square foot. He recommends taking a look at tap roots to assess damage. Brown, dehydrated roots indicate the plant is likely dead.

“The first step is getting out in the field when plants get about 4 to 6 inches tall and start digging up a few crowns in various areas of the field to try to assess damage,” Combs said.

He said Undersander’s research has shown that farmers need about 55 to 60 stems per square foot for maximum yield and that at about 40 stems per square foot, farmers see about a 25 percent reduction in yield.

“That’s kind of the cut point,” Combs said. “If we’re less than 40 stems per square foot, we know we’re losing 25 percent. That’s when we start thinking about taking that stand of alfalfa out and replace it with something else.”

Combs recommends farmers take a forage inventory and consider all options, including thickening alfalfa stands, cereal or cereal/pea forages or late-season plantings, depending on the amount of damage they are seeing. He added that with hay supplies tight, conditions aren’t favorable for those looking to buy hay.

“If you need forage to get through the summer months, you’re probably going to be looking at options to get a crop of forage to feed the dairy cattle, or at least dry cows and heifers, as soon as possible,” Combs said. “If we do have enough forage to get through the summer months, but the yield drag is going to hurt a little bit, maybe we need to consider replacing some winter-damaged stands of alfalfa with either corn or sorghum.”