Figure 1. Alfalfa winter kill in Beresford, South Dakota. Second year of establishment. Photo: S. Berg
Winter Kill in S.D. Alfalfa
This year lack of snow coverage along with up’s and down’s in temperatures have caused several issues with alfalfa stands in several locations in South Dakota. Where the damage has occurred, it is concentrated in areas of fields where ice sheets formed, water ponded, poor drainage, and not enough snow cover to insulate alfalfa against extreme temperatures. Late harvested stands that are three or more years old are showing more damage than younger ones’ under moderate management.
What to do?
If you find significant winterkill but decide to keep the stand anyways, here are a few options to increase forage production.
- For fields planted last year, intereseeding more alfalfa in thin spots is one feasible option.
- For older alfalfa stands, auto-toxicity and other problems could make interseeding alfalfa very risky.
- Add other species to keep forage production.
Replacing Alfalfa Stands: What are your options?
If the damaged alfalfa field was seeded more than two or three years ago, it is recommended to plant a different crop before planting alfalfa again to avoid auto-toxicity issues. Interseeding forage grasses or clovers will fill the gaps left by winterkilled alfalfa, preventing weed competition while yielding acceptable amounts of good quality forage.
- Red clover (Average seeding rate of 6-10 pounds per acre) can help prolong the life of alfalfa by an average of two years. This is a great option for producers that harvest their forage for haylage.
- Small grains and annual cool season grasses (Examples: Oats, wheat, rye, or triticale, annual or Italian ryegrass) can provide high quality forage fast, and prolong the stand life for one year.
- Interseed perennial grasses such as orchardgrass (5-10 pounds per acre), timothy (3-5 pounds per acre), or even tall fescue (4 pounds per acre) could enhance stands for two or more years depending on production but might take longer than annual grasses.
When assessing your fields, it is important to take roots samples and consider other factors that were mentioned in article on Alfalfa Winter Kill: Top Contributing Factors.
Winter Kill Management Guidelines
Wait until new growth is about 6 inches tall and count all stems longer than 2 inches within a one square foot area.
- Healthy Stands: Will have more than 55 stems per square foot, regardless of stand age.
- Intervention and decision making: Stem count is below 40 stems per square foot. Consider interseeding with some of the options suggested in this article.
When to keep or not your alfalfa stand?
Decision on whether to keep the stand should be based on the total area lost. There is a tendency that when fields have more than 50% alfalfa loss, starting over may be the best solution; whereas fields with less than 50% alfalfa loss may be worth salvaging for one additional year of production.
Figure 2. Another view of alfalfa winter kill in Southeastern S.D.