Alfalfa winter injury in Minnesota

Jared Goplen, Lisa Behnken, and Dan Martens

Photo 1. Severely winter-injured alfalfa in Carver County, 2013. Photo courtesy of Dave Nicolai

As the weather warms and the 2017 growing season gets rolling, it is time to evaluate alfalfa stands for winterkill and winter injury. There have been numerous reports of alfalfa fields across Minnesota with varying levels of winter injury and winterkill. Many reports are of low areas in the field suffering the greatest damage, with affected field areas ranging from 10 – 40%. Lack of snow cover along with cold temperatures, freezing and thawing in February, and ice sheeting are some possible causes for winter injury and winterkill this year.

Photo 2. Plants from left to right: 1) dead plant with soft root 2) asymmetrical growth, likely will not survive 3) new spring buds growing after winter injury. Plant will likely survive but be slightly delayed 4) Healthy plant with firm root and vigorous growth. Photo courtesy of Dan Martens.

Photo 3. Severely injured alfalfa roots. Photo courtesy of Dan Martens

To get an accurate assessment of winter injury, walk fields now to evaluate how the alfalfa plants are growing. Are all plants actively growing or do some look stunted compared to neighboring plants? Are only potions of the crowns growing? Check areas of the field that are greening up as well as the brown and slow growing areas. It is important to dig up some alfalfa plants to evaluate crown and root health. Healthy plants will be symmetrical, have a number of shoots, and will be off-white and turgid, similar to a potato. More details on evaluating an alfalfa stand, as well as a video tutorial can be found here:

• Alfalfa stand assessment: Is this stand good enough to keep? - University of  Wisconsin
• Assessing Alfalfa Stand Condition in the Spring - University of Wisconsin
• Alfalfa stand assessment (video) - University of Wisconsin

If the alfalfa field has a substantial area affected, there are a number of considerations to be made. Before making the decision to keep, terminate, or supplement the stand, it is important to evaluate forage and animal inventory as well as the various cropping and replant options. Whether a field should be rotated out of alfalfa or affected areas seeded to a supplemental forage crop will vary by operation. Resources to assist in crop management decisions can be found here:

• Alfalfa winter injury assessment and management - University of Minnesota
• Winter injury of alfalfa: Strategies for livestock producers - University of Minnesota
• Assessing alfalfa stands - University of Wisconsin

If alfalfa stands are thin or patchy and termination of the stand is not an option for your operation, there are a number of forage options to seed into winterkilled areas. Information on seeding into standing alfalfa can be found here:

• Seeding into an existing alfalfa stand - University of Wisconsin

Deciding how to manage a winterkilled or injured alfalfa field can be difficult and will add unexpected costs. However, walking fields, evaluating forage needs, considering options and making a plan now is critical to make a good decision for your farm. The resources provided will help you make the decision to keep or terminate the stand, seed supplemental forage, purchase additional forage, and/or plant new stands of alfalfa. The right answer for you will depend on your specific field and operation.

Resources related to alfalfa winter kill and winter injury, as well as other forage information can be found at the University of Minnesota Extension Forage website.