Earlier this week after a series of storms and subfreezing temperatures swept through central Illinois, agronomist Ken Ferrie walked his March-planted soybean test plots south of the Bloomington area and didn’t like what he found.
“We had a substantial frost, reports of temperatures from 29 to 32 degrees, with the frost hanging around three hours or more,” Ferrie says. “Things are kind of crunchy in the grass this morning.”
That crunch underfoot translates into real damage in soybeans. Some plants, Ferrie says, are not going to make it.
“The worst hit are soybeans in the unifoliate stage or more and that were planted in our low ground,” he notes.
Illinois wasn’t the only state where soybeans were hit by frost. Weather reports from Monday and Tuesday indicate a late-season cold snap brought frost and freezing temperatures to at least four additional key soybean-producing states, impacting parts of Iowa, Indiana, Michigan and Ohio.
According to the USDA Crop Progress report released on April 20, roughly 12% of the national soybean crop had been planted. States like Illinois and Indiana were slightly ahead of their five-year averages, making crops there more vulnerable to this specific frost event.
Don’t Rush To Replant, Be Disciplined In Your Approach
Ferrie describes a clear set of visual cues growers can use to evaluate frost damage in their crop.
“Look for unifoliate leaves that are dark and deflated, and the cotyledons have a dark color,” he says. “The biggest telltale is the stem has no turgor pressure right below the cotyledons.”
He notes that those beans with discolored cotyledons and limited turgor pressure will require more time to see if they will refire at the cotyledon node.
Ferrie urges growers to take a systematic approach to evaluating frost-damaged soybeans with these four steps:
- Check bean growth stage and field position (low ground vs. higher areas).
- Inspect unifoliate leaves and cotyledons for dark, deflated tissue.
- Pinch stems just below the cotyledons to feel for turgor.
- Flag concerning areas and return in a couple of days to reevaluate survival and stand uniformity.
Once you’ve assessed damage, the questions then are, how many beans survived, and how uniform a stand remains?
Replant decisions, Ferrie emphasizes, should be based on surviving plant counts and uniformity, not on first impressions the morning after a frost. That will take a few days to assess.
Why Risk Planting Soybeans In March?
Ferrie addressed the broader strategy that put March-planted beans at risk in the first place — and why many growers benefit from planting early.
“Guys ask me why plant beans in March, when you can plant them April 15,” Ferrie says. “If you can plant them April 15, not much is gained. But if you get rained out at May 1 or later, you could definitely miss the early flowering window.”
That early flowering window, he notes, remains a key driver of soybean yield potential. The risk of frost is the tradeoff.
“So that risk of early planting and dealing with frost and the need to help them up with a hoe and things like that, that always needs to be weighed against missing the early flowering window,” he says.
Go Time For Planting More Soybeans
Ferrie says the next few days are a green light for planting soybeans in central Illinois.
“If you don’t have your full-season beans planted by April 24, you may want to switch to your shorter-season beans, giving them a better chance at early flowering. Our early flowering window is closing for these full-season beans,” he adds.
The freeze may claim some of the earliest soybeans, but Ferrie insists growers still have tools to protect yield — from switching maturities as key dates approach to making informed replant calls based on stand counts and plant response.
Younger soybeans typically handle the cold and frost better.
“Population is, here at the campus, the last emerging beans, still in the cotyledon stage, are in good shape,” he says. “And the beans that we plant in the covers are protected well.”
Ferrie’s message to farmers this week is clear: get out and assess your crop, but don’t rush to replant. “By the end of the week, we’ll know how rough this frost damage is, and we’ll reassess replanting decisions after that,” he says.
You can watch Ferrie’s brief video on how to assess soybean damage here.
