Heaving damage to alfalfa has been reported in several states in recent weeks.
The problem, caused when clay soils expand and contract while freezing and thawing, is serious in northern Missouri.
"I’ve never seen such carnage," says Rob Kallenbach, extension forage specialist at the University of Missouri-Columbia.
He reports a 70% kill rate in research plots seeded last fall. Heaving usually does the most damage to older plants with big taproots. This is the first time Kallenbach has seen heavy damage to young plants.
"Seedlings often float with the soil movement, but this year the small taproots were jacked entirely out of the ground," he says. "The plants are lying there, dead."
On older plants, he has seen the top 6" of taproots protruding above the soil surface.
"Those plants will be weak and may not recover," says Kallenbach. "They’re likely to be cut off below the growing point when the mower comes along."
He tells growers to examine their stands and make management decisions by mid-April. "Thinned stands will require intensive care this year."
His prescription for damaged stands: ensure sufficient fertility, control weeds to minimize competition, and delay the first harvest until past mid-bloom to let plants build carbohydrate reserves.
With delayed cutting you’ll sacrifice quality to gain stand life, says Kallenbach. Where heaving was an inch or less, it also may allow some plants to contract back into the ground, he adds.