Management for Winter Injury and Winter Kill in Alfalfa

April 13, 2020

Every year established alfalfa stands have the potential for winter injury and winter kill. We have had a mild winter with some cold temperatures and some above freezing temperatures. However, the lack of snow cover is one of the main issues producers are worried about as the assess their alfalfa stands this spring. 

What could have caused my alfalfa plants to winter kill?

  • Stand age: Older stands are more likely to winter kill than younger plants.
  • Snow cover: Snow provides insulation to the plants and the crown. The crucial temperature region is two to four inches below the soil surface where a large part of the root structure is located. Stands that have at lease six inches of stubble left will be able to retain more snow cover and be less likely to winter injury.
  • Soil pH: Soils with a pH above 6.6 are less likely to experience winter injury.
  • Cutting management: Aggressive harvest schedules and shorter intervals between cuttings leave the alfalfa less time to accumulate carbohydrate levels in the root system before winter. This leaves the alfalfa plants more likely to winter injury.
  • Soil fertility: Stands planted in higher fertility soils are less likely to experience winter injury than those with low fertility.

When you are scouting your alfalfa stands look for these symptoms to assess if your field winter killed:

  • Compare you stand to other fields in the area. If you have spots that are greening up nicely and spots that are brown, it is time to check those brown stands for injury or death. 
  • Winter killed roots will have a gray appearance. Check if the roots are soft and brown in color, these are signs that your stand has winter injury.
  • Compare the shoots on the same plant, and if you notice that one set of shoots seems to be drastically out-growing others in terms of growth, the bud could be damaged from winter injury.

Evaluation of your alfalfa stand in the spring can be tricky. I have learned that “patience is a virtue” is a phrase that applies well when scouting and making decisions on your field. Deciding to rotate out of alfalfa or inter-seeding into an established alfalfa fields can be a hard decision. If you have any questions while you are evaluating your alfalfa stand this spring, give your product agronomist a call.

-Eric Solberg, Eastern Region Product Agronomist

Categories: alfalfa    

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