Issue No. 3, Article 7/April 10, 2009
Responding to Alfalfa Heaving
Heaving, or the pushing of plants out of the ground, has been reported in several central Illinois alfalfa fields, most notably in the Bloomington to Peoria to Galesburg area.
Heaving is caused by the soil freeze-thaw cycles in late winter and early spring. It is most commonly observed on soils with high clay and high moisture content with poor percolation. If plants are heaved more than an inch, the crown and taproot are exposed to late-winter weather conditions and injury from mowing.
Heaving in alfalfa. (Photo courtesy Jeff Volenec, Purdue University).
In the future, leaving some plant residue on the soil surface helps insulate the soil and thus reduces the degree of soil freezing and thawing. Planting a cool-season grass with alfalfa will reduce heaving but will not eliminate it.
It is difficult to advise specifically, but if plants have heaved more than 1-1/2 inches, they most likely will not survive and stands should probably be terminated. If they have heaved less than an inch, the suggestion is to wait and observe how the plants grow. Do not use a cultipacker or similar implement to try to push plants back into the ground.
Dr. Dan Undersander, University of Wisconsin Extension forage agronomist, has written a new factsheet on Heaving in Alfalfa Fields, available online (Adobe PDF).--Jim Morrison