Managing Alfalfa Winter Kill

An alfalfa field showing large patches with complete alfalfa winterkill in low elevation areas and standing thinning due to alfalfa winterkill throughout the field.

Each year in Wisconsin, alfalfa stands are at risk of being injured or killed by winter conditions. This year winter kill is impacting many farmers in Dodge County and across Wisconsin. Making winter kill even more of a challenge is that we are coming off a difficult harvest where many were not able to get fourth crop alfalfa or high quality corn silage harvested. This has put stockpiled forages at a premium and many are hoping to find relief with this year’s forage crops.

For farmers with alfalfa, the first step to take this year and every year, is to assess your stands. Stand assessments need to be made for each individual field, and alfalfa variety. How can you diagnose winter injury? Slow green up. Alfalfa fields should be nice and green at this point in the spring. If yours are still brown or is taking longer than your neighbors to green up, it’s time to check your stand for injury or death.  Do your plants have new shoots across the crown of the plant or are the shoots different lengths? This would indicate that part of the alfalfa root was killed or some bud on the crown were killed and need to be replaced by new buds. But the best way to determine winter injury is by digging up plants and examining roots. Healthy roots should be firm and white in color with little evidence of root rot. Winter killed roots will be brown, dehydrated and stringy. See UW Extension Publication A3620 for more details on evaluating root health.

If winter injury is evident in the field, the next step is determining stem density/potential yield. To do this, determine the number of stems in a square foot area, do this in multiple areas across the field and use the average. Fields with greater than 55 stems/sq. ft. – will not have limiting yield; 40-55 stems/sq. ft. – can expect some yield reduction; and fields with less than 39 stems/sq. ft. should consider replacing the stand.

If your stand needs replacement, there are many options still available. When reviewing stand replacement options you should ask yourself ‘What is the goal for your field?’. Do you need a spring forage? Are you looking for tonnage or feed value?  What is the return I am getting for my investment? Your best option is going to be the one that fits your farm needs the best. If it’s early forage, a small grain such as oats may be the answer. Need crude protein and palatability, add peas to the small grain. Tonnage – silage may be the best option, or maybe a sorghum-sudangrass, sudangrass, and pearl millet.  If you are looking for help and thinking about your options, call Amanda Young at the Dodge County Extension office at 920-386-3790; or talk with your agronomist and do not forget to keep you nutritionist in the loop.

Amanda Young

Dairy and Livestock Educator

University of Wisconsin Madison – Division of Extension


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