Alfalfa winter injury assessment and management

Many factors can contribute to winter damage of an alfalfa stand. All are important to consider when making spring assessments, and managing injured stands.

What affects alfalfa’s ability to survive winter

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Assessing winter injury

Regardless of winter conditions, it’s always recommended to closely assess stand health each spring. Winter injury may not be immediately apparent. You may be able to tell if there’s slow or uneven spring growth, or it could go undetected until after the first cut.

Root color and turgidity

The most direct way to assess spring plant health is root color and turgidity. Dig a few plants from representative areas of the field, and split the taproot down the center as in Figure 2.

Healthy roots will be off-white and turgid (firm and hydrated), as shown on the left. Damaged or winter-killed roots will be dark, dehydrated and ropey, as shown on the right.

alfalfa taproot
Figure 2: Healthy alfalfa taproot on the left and damaged taproots on the right.

Stem counts

For an early assessment of overall stand health and production potential, count the number of stems per square foot:

  • More than 55 stems: Density isn’t limiting to production.

  • 40 to 55 stems: Some reduction has occurred, but adequate production is still likely.

  • Less than 40 stems: You may need to consider termination or supplementary options.

Regrowth monitoring

If you’re concerned about winter injury, watch for slow or uneven regrowth and closely monitor regrowth following the first cut. Mild winter injury may cause reduced stem count or plant vigor.

Depending on plant health and the severity of the damage, production may decrease throughout the year or recover. Recognize every stand and every field is different and could require specific assessment and management planning.

Managing injured alfalfa stands

As you consider management options, remember injured alfalfa stands can exhibit delayed regrowth, but may be capable of recovering. Be careful not to rush into alternative options if you can maintain the stand for acceptable production.

Alternative approaches

If action is required, carefully consider the cost and expected benefit of alternatives with regard to the situation. You can interseed supplemental forages such as teff, annual ryegrass, and small grains into a thin stand or use it to cover any bad spots.

If a large percentage of the stand has been damaged, it may be more appropriate to terminate and plant silage corn or BMR sorghum instead. Read more about alternative options:

Reagan Noland, graduate student, College of Food, Agricultural and Natural Resource Sciences (CFANS); Doug Holen, former Extension educator; Craig Sheaffer, agronomist, CFANS and M. Scott Wells, Extension agronomist

Reviewed in 2018

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