| April 2009 - Heaving Alfalfa |
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Heaving alfalfa Don McLean, Agronomist, FS PARTNERS When looking at alfalfa fields this spring take notice if there is any heaving. We are seeing significant heaving. Below is a picture of an alfalfa plant’s crown that have heaved up about 2 1/2 inches. The pictures were taken outside of Drayton on April 23rd. Many of the tap roots on the plants that are heaved have been broken and these plants will eventually die, if they haven’t already. 
Cause Heaving is caused by the lifting action of frost. Factors that increase the risk of frost heaving are: a late fall harvest which removes the layer of mulch and doesn’t allow for collection of snow, poorly drained or saturated soil and soil types like silt loams and clay loams tend to be at high risk. In plots at Ohio State University, a late fall harvest had alfalfa plants heaving 38% compared to only 5% on the area that was not harvested. What to do First assess the stand. Remember 1st year stand should have at least 11 plants/ft2, second year stand should have at least 8 plants/ft2. If the stand doesn’t have enough plants/ft2 you have a few options. The first one is to take the stand out and plant it to another crop. If you need the forage crop, then an option is to thicken it up with grasses, clovers or trefoil. Remember that in established stands of alfalfa, replanting alfalfa is not advised because of the autotoxicity affect of the alfalfa that is already there. If the alfalfa plants have heaved but are still alive, raising the cutter bar height is a good idea and will help prevent some mechanical injury to the crown. Using a packer or roller to push the crowns back into the ground will do a lot of damage to the plant and is not advised. With heaved stand, the longevity and productivity will ultimately be reduced. Sources of Info: OMAFRA Fact Sheet Ohio State University Extension |
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