Alfalfa winterkill: what now?

Jared Goplen, University of Minnesota Extension educator – crops

It is important to dig up some alfalfa plants to evaluate crown and root health

There have been reports of alfalfa stands across Minnesota with varying levels of winter injury and winterkill. Areas most-often affected include hilltops where crowns were exposed during the cold winter months and where extended flooding has occurred this spring. There have also been reports of frost heaves uprooting alfalfa crowns.

Alfalfa that has successfully made it through the winter should be starting to green up by now in most of the state, making stand evaluation more clear-cut. As you are walking fields, some questions to ask are:

    1. Are all plants actively growing or do some look stunted with patchy growth?
    2. Are only portions 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. Even slow-growing plants could recover if plants are symmetrical, have a number of shoots, and are off-white and turgid, similar to a potato. More details on evaluating an alfalfa stand can be found here:

Next steps

Steps to decide whether to keep, terminate, or supplement the stand include:

  1. Evaluate forage and animal inventory as well as your crop rotation and replant options. Given the high price of hay recently, purchasing additional forage is likely the least-attractive option1. Some fields should be rotated out of alfalfa and into another crop, like corn. Other fields could be supplemented by interseeding additional forages. The correct decision will vary by operation. Resources to assist in crop management decisions can be found here:
  2. If alfalfa stands are thin or patchy and termination of the stand is not an option, there are a number of forage options to seed into winterkilled areas. The best option for your operation may depend on seed and equipment availability as well as how many additional years are desired out of the stand. Several recommended options are listed in Table 1. Supplemental forages are ideally seeded with a no-till drill in the affected areas, but oftentimes conventional drills will work if the ground is somewhat soft.

 

 

Table 1. Several recommended forage options for interseeding into an existing alfalfa stand that has suffered winterkill or winter injury. The ideal option will vary by situation, including field condition, equipment and seed availability, and forage requirements.

Forage species Ideal use Yield potential
T DM /ac
Forage quality Seeding rate**
lbs/ac
Seeding depth
inches
Alfalfa ONLY if stand was established last year.
NOT recommended for older stands due to autotoxicity concerns.
3 – 5 Excellent Open areas: 12
Thin areas:
6 – 8
0.25 – 0.75
Small grains* Spotty or thin stands to be terminated after
this year. Likely best option if early-season
forage is a top priority.
1 – 3 Moderate to excellent 60 – 90 1.5 – 2
Sorghum-
sudangrass
Spotty or thin stands to be terminated after
this year when forage will be ensiled or if
interseeding is delayed until June. Could be
seeded following 1st cutting of alfalfa. If dry
hay is needed, substitute sudangrass (slightly
easier to dry).
2 – 3 Moderate 20 – 30 1 – 2
Small grain followed
by  sorghum-sudangrass*
Spotty or thin stands terminated after this year
and when forage will be ensiled. Could be used
for dry hay if harvested by the milk stage.
Likely provides both early and late-season tonnage.
3 – 5 Moderate See above 1 – 2
Italian/
Annual ryegrass
Spotty or thin stands with 1-2 years of
additional production desired. Best when
forage not baled for dry hay. Good yields
should be achieved by 2nd and later cuttings.
3 – 5 Good Open areas:
25-30
Thin areas:
5-10
0.25 – 0.75
Orchardgrass/
Tall fescue
Spotty or thin stands with 2 or more years of
additional production. Excellent fit for dry hay.
Not ideal for emergency forage as most yield is
late-season in the seeding year.
3 – 5 Good 5 – 10 0.25 – 0.75
Red clover Spotty or thin stands with 1-2 years of
additional production; can be chopped for
haylage or baleage or used as dry hay, but
drying can be somewhat difficult. Red Clover
will cause slobbers in horses.
2 – 4 Excellent 6 – 10 0.25 – 0.75

* Small grains could include a variety of small grains, including oats, barley, wheat, or spring triticale.
** Higher rates should be used if seed is broadcast.
Additional information: Seeding into standing alfalfa – University of Wisconsin

Deciding how to manage a winterkilled or injured alfalfa field adds unexpected costs and additional stress to the farming operation. Walking fields, evaluating forage needs, and making a plan now is critical to making the best decision for your farm. The resources provided here should help you make the decision to keep or terminate the stand, seed supplemental forage, purchase additional forage, and/or seed new alfalfa. The right answer for you will depend on your specific field and operation.

If you are feeling stressed this spring, don’t be afraid to ask for help. Helpful resources on how to deal with stress can be found at the Minnesota farm and rural stress website or by calling the Minnesota farm and rural helpline at 833-600-2670 x1.

For more information, visit the University of Minnesota Extension Forage website.

1If you do purchase forage or other supplemental feedstuffs, be aware of the source. Invasive weeds such as Palmer amaranth can be transported in the hay and feed supplements brought on-farm, with the most recent detections and infestations in Minnesota coming from sunflower screenings. Additional information can be found in this article, Take a proactive approach to managing Palmer amaranth in Minnesota crop production fields.

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