Exploring Options For Replanting Winterkilled Alfalfa

This past winter there were extreme temperature drops when there wasn’t much snow cover across Wisconsin. With alfalfa stands suffering some degree of winterkill, we need to consider replanting. Different options are appropriate depending on the farmer’s situation.

Option 1: Terminate The Current Stand Before First Cut

If there are <50 alfalfa stems per square foot there will not be enough alfalfa or grass to justify a spring cut. Most roots will have over 50% Fusarium root rot infection, along with clover root curculio feeding the field that should be rotated away from alfalfa. Autotoxicity will prevent a new alfalfa stand from establishing for about a year so it is best to till the field and plant another crop like corn silage for a year before replanting alfalfa.

Option 2: Take First Cut Only

Alfalfa plants killed by no snow cover and prolonged sub-zero weather.

If the alfalfa field is borderline, drilling in 1.5-2 bu/acre of oats can make some nice spring forage for first cut. Adding 50-75 lbs/acre of nitrogen and 10-15 lbs/acre of sulfur will increase tonnage and crude protein in most fields. Harvest at the soft dough stage for heifer/dry cow/beef feed or be-tween the flag leaf and boot stages for a higher quality feed for milk cows. Lay the windrows wide and flat to speed drying and use a tedder to spread out the wide windrows again a few hours after cutting if needed. There’s no need to run this alfalfa/oat silage mix through a conditioner. Try to chop a day after cutting and inoculate this mixed silage with a homolactic bacterial inoculant. Small grain silage should cut 1-1.25 inch in length compared to pure alfalfa silage cut at ~0.5 inch, especially if the silage is <30% dry matter.

Option 3: Take Multiple Cuts For 2019 Only

If additional feed is needed from a borderline alfalfa field for multiple cuts this season there are a couple of options.

  1. No-till drill 15-20 lbs/acre of annual or perennial ryegrass in the alfalfa field. Apply 75-100 lbs/acre of nitrogen, 15-20 lbs/acre of sulfur, along with phosphorous and potassium based on soil tests and a yield goal. If there’s enough moisture make another application of 50-75 lbs/acre of nitrogen prior to additional harvests.
  2. Drill in 1.5-2 bu/acre of oats and add some fertilizer for first cut. After first cutting, till the soil and plant a warm-season grass like teff (8-10 lbs/acre) or sorghum-sudangrass (20-30 lbs/acre) once the soil reaches 65°F Don’t harvest sorghum-sudangrass until it is at least 18- 20 inches tall to prevent prussic acid poisoning, which is not a concern with teff grass. Apply 50-75 lbs/acre of nitrogen, 10-15 lbs/acre of sulfur, along with phosphorous and potassium based on soil tests and a yield goal when planting the warm-season grass.

Option 4: Extend The Life Of The Stand By More Than One Season

If the life of an alfalfa stand needs to be extended beyond 2019 then it would be best to no-till drill either orchard grass (10 lbs/acre) or an endophyte-free tall fescue (15 lbs/acre) variety into the alfalfa field. Select a grass variety with a later heading date to improve the forage quality of the alfalfa-grass mixture. Use a similar fertility program as the recommendations for annual/perennial ryegrass. Ladino white clover (2-4 lbs/acre) or red clover (6-10 lbs/acre) can also be added to the stand to provide multiple years of forage, especially if the alfalfa has only died in some small areas of the field.

Risk Factors That Increase Winter Injury In Alfalfa

  • High fall soil moisture levels and poorly drained fields. Ice covered alfalfa plants.
  • Less than 6 inches of snow combined with temperatures below 5°F.
  • Temperature spikes over 40-50°F followed by rapid temperature drops to 10-20°F.
  • Late planted alfalfa fields (after Labor Day).
  • Alfalfa that hasn’t formed a crown prior to winter.
  • Alfalfa planted at less than 12-15 lbs/acre and/or north of its winter hardiness rating.
  • Low potassium test levels on alfalfa fields (<120 ppm), or alfalfa stands that are more than 3 years old.
  • Alfalfa harvested between Sept. 1 and Oct. 15 (5-6 weeks of uninterrupted growth after cutting).
  • Less than 6 inches of alfalfa stubble.
  • Alfalfa seed not treated with a fungicide seed treatment.
  • Competition from weeds or herbicide carryover will probably reduce alfalfa winter survival.

Alfalfa Fields That Should Be Taken Out Of Production After Evaluation

  • Poor early season growth and are brown longer than other fields.
  • Averages of <50 alfalfa stems per square foot.
  • Alfalfa shoots only growing on one side of the crown (bud injury), Figure 1.
  • 30% or more of the roots are rated at 3 or higher for Fusarium root rot, Figure 2.
  • There is clover root curculio damage on most roots, Figure 3.

Alfalfa fields at the highest risk of winterkill are greater than 3 years old, have low potassium levels, (<120 PPM), low pH (<6.6), have experienced flooding, have poor varietal disease ratings, and/or an aggressive cutting schedule.

Contact a Northside agronomist for consultation on the condition of your field and the best options for your situation.

Article adapted from Bill Verbeten, Division Agronomist, Helena Agri-Enterprises, LLC

Safe Handling of Chemicals

Farms have many chemicals that are used on them, perhaps even more so during spring. Fuels, pesticides, herbicides, fungicides and veterinary chemicals must be handled and stored with care. A few tips:

  • Follow manufacturer’s instructions.
  • Always wash your hands carefully after handling.
  • Remove soiled clothing before you enter your home as there is the possibility that chemical residue is on clothing or footwear.
  • Keep chemicals locked away and out of reach of children or unqualified individuals.
  • Take the time to wear appropriate protective gear like gloves and eye protection.

Safety precautions are necessary because exposure to chemicals can lead to health effects including headache, poisoning, nausea, respiratory illness, burns, cancers, and birth defects.

Helpful References:

University of Wisconsin: Evaluating and Managing Alfalfa Stands for Winter Injury
AgWeb: Considerations for Winter Injury and Winter Kill in Alfalfa
University of Minnesota: Alfalfa Winter Injury in Minnesota

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