As spring arrives each year, it is important to pay attention to your alfalfa fields as they begin to green up and grow. It is time to look for signs of “winterkill.” Winterkill is the generic term used to describe death of an alfalfa stand from fall through spring. However, the name is misleading because most stand death happens during the spring. There are many reasons why alfalfa dies out over the winter and in the early spring. Each of our agronomists sounded the same message around the importance of checking stands for winterkill each spring.

Wisconsin update from Jacob Andrle, Sales Agronomist: Last fall, most of the state was wetter than normal and many stands were stressed all season long. With the cold weather we have had this winter, frost heaving could be an issue, especially on heavier textured soils that were saturated at freeze-up time at the start of winter. Fields with frost heaved plants or root damage can look normal after coming out of dormancy. However, plants will die off through the spring and summer. This loss of sufficient stand count will continue to occur as the haying season progresses. In this case, digging roots and checking for root damage can give you an idea of what to expect from that stand in the coming months, but I do suggest keeping an eye on it all summer long this year. There are areas of the state with no snow cover that could also see some winterkill issues with the abnormally cold temperatures we have been having.

Rotate or Leave it?

The decision to rotate a field can be hard to make with the irregular patterns of dead areas.The rule of thumb is rotate if the field falls below the average of 40 stems/square foot. We recommend using a larger size hoop than the simple 1-foot squares that are often available and used. A larger circle will give you a better representation. Be sure to sample several areas of the field until you feel comfortable with the numbers you are collecting.

Be sure to keep an eye on the stand quality throughout the summer as well. Additional mechanical damage from haying equipment to damaged crowns and taproots can cause additional loss throughout the summer, so keep that in mind.

If you have questions or would like help in this decision-making process, please contact your local Legend Seeds representative for guidance.

Examples of Winterkill Situations

Example of winterkill with crowns & taproot
Concerns: A few of the agronomists mentioned the crowns heaving or pushing out of the ground. See an example of this condition at right. When there is more than a half-inch of exposed root below the crown, then there is a very high probability that the taproot has been severed and the alfalfa plant will die shortly after greening up in the spring. Sometimes, the taproot gets severed deep enough that the plants will yield close to normal initially, but when cut for the first time the stand will never green up again.

Examples of winterkill from ponded water:

Example of winterkill from cold soil temperatures: