Managing Heaved Alfalfa Fields

Richard Leep, Tim Dietz, and Doo-Hong Min

Michigan State University Forage Agronomists

Heaving, or the pushing of plants out of the ground, has been reported in several Michigan alfalfa fields, most notably in the Central and Southern Michigan area. A photo of a field of heaved alfalfa in Central Michigan is provided below. Note several alfalfa plants that are heaved four inches or more that are already dead this spring.

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.

When heaving is observed, first dig a few plants to determine if the taproot is broken. Plants with broken taproots will likely green up and survive for a short time and then die when weather becomes warm and the soil dries. The length of time before plant death will depend on the length of taproot above the break and will range from green-up only (if tap root broken three to four inches below the soil surface) to sufficient growth for first crop (6 to 8 inches taproot) to growth until first dry spell (8 to 12 inches taproot).

Fields with over 1.5 inches heaving will likely have broken taproots and will also suffer significant

damage from harvesting equipment. These fields should likely be terminated immediately.

Fields with 1 inch or less heaving are likely to have unbroken taproots and may be salvageable for at

least the current year. These fields will likely have delayed greenup. The best recommendation is to do

nothing to the stands now. Do not go over the field with a roller or cultipacker in early spring to push the

crowns back into the soil. This will likely to do more damage than good. Plan on harvesting these fields later than normal (25% bloom) and to raise cutter bar at harvest sufficiently to clear crowns. Natural settling should occur during the year and, if plants are reseated, stands should survive until next year. Stands entering the winter with elevated crowns are likely to suffer above average winter injury and kill.