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Understanding Fall Dormancy and Winter Hardiness Ratings in Alfalfa

Understanding Fall Dormancy and Winter Hardiness Ratings in Alfalfa

Alfalfa is a big part of our crop rotations here in America’s Dairyland. Since it’s such a valuable crop to our dairy herds, it’s very important that we understand the meanings of fall dormancy and winter survival ratings. In a recent article in the Agri-View, Dan Undersander helped clarify these ratings.

Fall dormancy is simply a rating of alfalfa’s ability to grow in the fall. “The level of fall dormancy in an alfalfa is measured by the amount of regrowth after a Sept. 20 harvest. Fall dormancy scores run from 1 to 11, with 1 being the most fall dormant and 11 the least. Most alfalfa grown in Wisconsin has a fall dormancy of about 4,” states Undersander.

Higher fall dormancy numbers may have their advantages such as faster regrowth, but this also increases the chances of driving over new growth during the harvest process.

Winter hardiness is a rating of an alfalfa’s ability to survive the winter. Undersander says, “It [alfalfa] does this by hardening, meaning that membrane fatty acids become less saturated and more unsaturated. Alfalfa needs two weeks in the fall with fluctuating temperatures to harden before winter. That’s days with highs near 60 degrees Fahrenheit and lows close to 32 degrees.” Most alfalfa varieties used in Wisconsin have a winter hardiness score around 2. Varieties rated higher than that risk uneven green-up in the spring.

To read the full article, please click here.

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