Central Illinois alfalfa growers may see a lot of winter damage in fields this spring. Growers near Bloomington to Galesburg to parts north are finding heaving in alfalfa stands usually three to four years old, says Kevin Black, an agronomist with Growmark/FS based in Bloomington.
In one field, plants were consistently 4-6” out of the ground; some as much as 8-10” above ground, he says. “Most of the heaving was occurring on hilltops; we had ice sheeting and accumulated water.”
Heaving usually happens in heavy soils that hold moisture. Alternate freezing and thawing causes the soil to expand and contract, thereby pushing alfalfa taproots out of the ground.
“It’s going to impact a large number of growers” in that area, Black predicts. “I’ve got this gut feeling that a number of growers aren’t even aware of this yet. They’re just expecting that sometime soon their hay is going to green up. They’re more concerned about getting ready for their corn crops and have not yet visited their alfalfa fields. I’m afraid there’s going to be a lot more of this developing."
No grower calls have been fielded by Keith Johnson, extension forage agronomist at Purdue University in West Lafayette, IN, and he hasn’t seen any heaving in fields in that area. But he wouldn’t be surprised if alfalfa growers in areas of the state with heaving-prone fragipan soils find some damage.
“If you have not walked your fields, get out there – particularly if you have a soil that tends to be one that holds more water than some or has been saturated in late winter or early spring,” Johnson advises.
Ag agents in the southeastern corner of Iowa are seeing some heaving but not to the extent Illinois growers are experiencing, says Steve Barnhart, Iowa State University extension agronomist.
“The shorter the break between winter and spring, the fewer cyclings of freeze-thaws, freeze-thaws, and the less heaving, typically. So we generally don’t have as much problem as they do farther south,” Barnhart explains. Some alfalfa roots may be up to an inch out of the soil, he estimates.
It’s too early to know the condition of Wisconsin, Minnesota and Michigan alfalfa fields, says Dan Undersander, University of Wisconsin extension forage specialist, who will be checking his state’s alfalfa stands the second week of April.
If roots are only 1” or less out of the soil, Undersander says heaved plants will probably not winterkill. “People ask, ‘Should I go over it with a roller and push it back?’ The answer is ‘No.’ ” Those fields should survive to produce a normal yield.
But if plants heave above 1½”, the taproots are broken, Undersander says, and there’s little a grower can do but look for other land to establish a new stand.
“Basically,” adds Black, “when the plant moves that much, it shears all of the lateral roots off the taproots, so it’s rare for those plants to survive. But, realistically, I’ve seen cases where alfalfa heaves as much as 2” out of the ground and growers have been able to, being very careful, get as many as two cuttings. But they’re not great cuttings. All that does is buy them time until they can then, in late summer, establish new stands.”
The damaged field Black inspected showed no greenup at the crowns, he says. “I split a couple of upper taproots, and they’ve got that yellow, stringy look that’s typical of freeze-damaged alfalfa.” A nearby field with a little different drainage pattern looked “a little more normal and there was greenup starting down in the crowns,” Black says.
The grower of the severely damaged field spread grass seed “in the hope that the rainfall would be enough to get grass started and to keep the stand from being a weedy mess,” Black points out.
Undersander expresses a related concern: Growers who didn’t have the money to fertilize alfalfa last fall may have put their fields at risk of winterkill, especially with the Midwest’s repeated freezings and thawings.
"With low potassium we’re more likely to have winterkill than if our potassium has been at adequate levels. So that’s a strike against us.”
To see a photo of heaving damage taken by Black of that Bloomington alfalfa stand, as well as more information on heaving, click here . Click on Heaving Fact Sheet for University of Wisconsin recommendations.