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Karla Hernandez, SDSU Extension forage field specialist, at a Forage Fiesta Field Day
SCOUT THE FIELD: In deciding if you should keep a winter damaged alfalfa stand or not, check stem density numbers, suggested Karla Hernandez, SDSU Extension forage field specialist.

Identifying and preventing winterkill

Forage Fiesta Field Day yields specific tips on preventing winterkill in alfalfa.

In livestock country, forages are the key to feed supplies. So keeping high quality forages growing in the field is crucial to producers. That’s why Karla Hernandez, South Dakota State University Extension forages field specialist, shared a primer for identifying and potentially preventing winterkill injury at a recent Forage Fiesta Field Day at the SDSU Southeast Research Station near Beresford, S.D.

There are several factors that can impact plants and lead to winter injury or death, says Hernandez. Older stands are more likely to winter-kill than younger plants. Soils with a pH level above 6.6 and soils that have a natural fertility are less likely to have winter injury. “Alfalfa varieties with superior winter hardiness ratings and a high disease resistance index are less likely to experience injury,” she says.

“Harvest frequency and timing of fall cutting will affect alfalfa winter hardiness,” says Hernandez. “The general trend shows that the shorter the interval between cuttings during the growing season, the greater risk there is from winter injury because an aggressive harvest schedule prevents the plant from storing carbohydrates in its root structure, which it will need to maintain health as it regrows.

“Stands where the last cutting of the season is taken between Sept. 1 and the middle of October are at the greatest risk as well, because plants didn’t have enough time to accumulate adequate carbohydrate levels in the root system before winter.”

CHOOSING VARIETIES: Alfalfa varieties with superior winter hardiness ratings and a high disease resistance index are less likely to experience injury, says SDSU Extension forage field specialist, Karla Hernandez.

Finally, snow cover provides insulation to the plants and the crown. “The crucial temperature region is two to four inches below the soil surface, where a large part of the root structure is located,” says Hernandez. “Stands that have at least six inches of stubble left will be able to retain more snow cover and be less susceptible to winter injury.”

Here are three ways Hernandez says you can identify winter kill.

• The stand is slow to green up in the spring. “Compare your stand to other fields in the area,” says Hernandez. “If you notice that some areas are starting to grow and other areas of your field are still brown, it is time to check those brown stands for injury or death.”

• Winterkilled roots will have a gray appearance. “If the root is soft and water can be easily squeezed from it, or if it has a brown color, these are possible signs of winter death related to cold weather,” she says.

• There is asymmetrical or uneven growth. “Compare the shoots on the same plant. If you notice that one set of shoots seems to be drastically outperforming another in terms of growth, it could be that winter cold has damaged the bud structure of your plants,” says Hernandez.

Replanting decision
The following is a stem density guide to replanting alfalfa.

For more information, contact Hernandez at karla.hernandez@sdsate.edu.

TAGS: Livestock
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