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Extension > Agriculture > Crops > Forage Production > Establishment > Winter injury of alfalfa: putting the pieces together for livestock producers

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Winter injury of alfalfa: putting the pieces together for livestock producers

Jim Salfer, Dan Martens, Jim Paulson, Dave Nicolai, Phyllis Bongard

Figure 1. Severely winter-injured alfalfa in Carver County, 2013. Drought in 2012 may have predisposed this field to injury, since there was little regrowth after August. Photo courtesy of Dave Nicolai.

Reports of winter injury and winterkill of alfalfa continue to intensify across parts of southern Minnesota. As a result, livestock producers will need to carefully consider short and long-term inventory needs and then manage the damaged alfalfa to get as much productivity as possible.

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Figure 2. Healthy, firm, and off-white alfalfa roots. Source: Dan Undersander, University of Wisconsin.

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Figure 3. Significantly damaged (rating 4) and dead (rating 5) alfalfa roots. Source: Dan Undersander, University of Wisconsin.

Assessing alfalfa stand and damage

Assessing the alfalfa stand is the first step in determining the likelihood of producing feed. Is the stand dead or can it limp through 1st cutting or even the entire season? A healthy stand will have at least 55 stems per square foot and roots that are off-white and turgid, as seen in Figure 2.

In contrast, severely injured roots have large areas of root rot (rating 4 in Figure 3) and few shoots. Even dead roots (rating 5 in Figure 3) may send out a few shoots before the plant dies, so it is important to examine the roots when assessing the stand. Roots that are off-white, but spongy around the crown also indicate severe damage. Dig up plants in three or four representative areas of the field and split the roots to assess damage. Fewer than 40 stems per square foot indicate a poor stand and consideration for termination. However, in areas with severe winter injury, stands with less than 40 stems may be important for getting some early summer forage. The section on forage cropping options offers further discussion.

What percentage of the field has plants that are severely damaged or dead? The extent of this damage and forage needs will determine management options. For more information on assessing stands, see Alfalfa stand assessment: Is this stand good enough to keep?, an excellent resource from the University of Wisconsin and Maximizing Forage in Winter Injured and Killed Stands, Spring 2013.

How much forage is in inventory?

An inventory of the feed on hand along with anticipated summer and fall yields are important in determining feeding and cropping options. Work closely with your nutritionist to determine how many days of alfalfa and corn silage inventory are remaining. The Forage Inventory Management spreadsheet (95 K XLS) developed by University of Minnesota dairy specialists is a useful tool to plan for forage needs. Combine your inventory with an estimate of potential forage yields based on stand assessments for an overall estimate of the feed that will be available. Yield potential of stands with at least 55 stems per square foot should not be limited, but some reduction in yield would be expected with alfalfa densities between 40 and 55 stems per square foot. The University of Wisconsin recommends using stem counts to help estimate yield. Count stems per square foot and then multiply by 10 percent (0.10) to get a handle on yield potential. For example, 30 stems per square foot might mean a 3 ton yield potential. In a 3-cut system, forty percent (40%) of the yield may be taken in the first cutting. As a result, we might yield 1.2 tons per acre in the first cutting from a total 3 ton yield potential. It's very important to evaluate the condition of the roots to further assess whether these plants can continue to work toward that yield for first cutting or full season. Other options for enhancing alfalfa stands will be addressed below.

What are my feeding options if the inventory is short?

Adjusting rations is an option when the current or projected inventory is short:

What are my animal options?

An option for some producers may be to decrease animal inventory. This decision should be made with input from your management team, because reducing animal numbers can dramatically potentially compromise future profitability. The milk futures prices, feed futures prices and housing availability should all be taken into account when making this decision.

Figure 4. Damaged 1 year alfalfa stand (3.8 plants/sq.ft) that has been interseeded with alfalfa and grass, Carver County, May 2013. Photo courtesy of Dave Nicolai.

What are my forage cropping options?

Your long-term cropping and feeding strategies should not be compromised. Setting yourself up for a normal cropping year in 2014 while trying to meet this year's feed needs will be the most important goal. Use available acres to plan for adequate forage inventory, since it is easier to purchase grains than forages. Consider these ideas as you think about your cropping strategies:

Putting the pieces together

Careful planning will help reduce the economic impact of significant alfalfa winter injury. Work with your management team to assess the damage and develop a plan to meet this year's feed needs. Then set your goal to return to a normal cropping strategy for 2014 and maintaining long term farm profitability.

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