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Winter kill in alfalfa fields: What’s next?

BROOKINGS, S.D. – Alfalfa stands throughout South Dakota are showing signs of winter kill.

"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," said Karla A. Hernandez, SDSU Extension Forages Field Specialist.

Hernandez said that where damage has occurred, it is concentrated in areas of alfalfa fields where ice sheets formed, water ponded, there was 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," she said.

“This year, lack of snow coverage along with ups and downs in temperatures have caused several issues with alfalfa stands in several locations in South Dakota.” Karla A. Hernandez, SDSU Extension forages field specialist

Before making decisions, Hernandez recommends that growers first analyze the severity of damage. "When assessing your fields, it is important to take roots samples and consider other factors," she said, encouraging growers to read the iGrow.org article, Alfalfa Winter Kill: Top Contributing Factors, which can be found at this link: http://igrow.org/agronomy/other-crops/alfalfa-winter-injury-kill-top-contributing-factors/.

If an alfalfa field shows signs of winter kill, yet the grower wants to keep the field what should they do? Hernandez answers this question below.

1. For fields planted last year, consider interseeding alfalfa in thin spots.

2. For older alfalfa stands, auto-toxicity and other problems could make interseeding alfalfa very risky in this case add other species to keep forage production.

If an alfalfa field shows signs of winter kill and the grower decides to replace the alfalfa stand, what are their options? Hernandez addresses this question below.

"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," she said. "Interseeding forage grasses or clovers will fill the gaps left by winterkilled alfalfa, preventing weed competition while yielding acceptable amounts of good quality forage."

Some forages to consider include:

Red clover: Average seeding rate of 6 to 10 pounds per acre. Red clover 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," Hernandez said.

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: Orchard grass at a seeding rate of 5 to10 pounds per acre; timothy at a seeding rate of 3 to 5 pounds per acre or tall fescue, at a seeding rate of 4 pounds per acre.

"These perennial grasses could enhance stands for two or more years depending on production but might take longer than annual grasses," Hernandez said.

Other guidelines to following when treating alfalfa fields with winter kill:

1. Stem Counts: wait until new growth is about 6 inches tall and count all stems longer than 2 inches within a one square foot area.

a. Healthy Stands: will have more than 55 stems per square foot, regardless of stand age.

b. Intervention and decision making: stem count is below 40 stems per square foot. Consider interseeding with some of the options suggested in this article.

2. 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 percent of alfalfa loss, starting over may be the best solution; whereas fields with less than 50 percent alfalfa loss may be worth salvaging for one additional year of production.

–SDSU Extension