February 19, 2019

ALFALFA WINTERKILL: WINTER WEATHER AND IN-SEASON MANAGEMENT

By Rick Ancel – Forage Specialist  Rick.Ancel@agpartners.net

As I have been visiting customers this winter, a common question has been asked: “I have been seeing a lot of ice standing out in my fields, will my alfalfa die this winter?”

The reason this question is being asked is our unusual weather this winter thus far. A warm and mild winter was predicted for 2019, and this prediction has appeared to be accurate up until this recent stint of cold weather. As temperatures approach potentially record lows, we are fortunate to have accumulation of recent snowfall to help insulate alfalfa fields that were relatively bare only a few days ago. If recent snow had not fallen and temperatures were as cold as they are now, answering the above question may be easier.

Up until this time however, there were multiple freeze/thaw cycles that occurred causing accumulated snow to melt. It rained on bare fields, subsequently causing the icing in low areas of fields that are still visible today. The icing we are observing in alfalfa fields is causing concerns of winterkill. Dormant alfalfa still respires, and oxygen is a key component to cellular respiration. When an area of an alfalfa field is covered in ice, the plants cannot take in oxygen, eventually resulting in possible death of the affected plants.

So, is this the answer to the above question? Not necessarily, it is too early to tell. We will only know the answer to this question when fields break dormancy and affected areas are evaluated. Although weather is a factor that contributes to winter survival, it is not the only factor to consider.


Photo:  Michigan Farm Bureau

In-Season Management: Cutting Schedule, Fertility, Variety, and Stand Age

Cutting Schedule: Can I cut my alfalfa in November after its “dormant”? The answer to this is do not do it- unless you fully accept the risks. The exception to this rule is if you are desperately short on feed inventories, or you plan on terminating the stand. I have been on farms during the spring that have lost half of their hay crop because they cut late thinking their alfalfa was dormant. Unless you fall into one of the exceptions, do your best to have the last cutting completed by September- weather permitting of course.

Fertility: Applying potash regularly to an alfalfa stand will help with winter survival. 200 lbs. of potash should be applied after 1st and final cuttings. Late summer applications are critical to winter survival. These applications provide the potassium the plants use to store sugars and carbohydrates within the crown and roots. These carbohydrates are then used as an energy source for cellular respiration during winter dormancy and act as “anti-freeze” for plant cells.

Variety: Fall dormancy and winter hardiness should be considered when selecting alfalfa seed. Although recent breeding has allowed for greater winter hardiness with faster regrowth in the spring (less dormancy), these factors should still be considered. The lower the scores for both factors, the more dormant or winter-hardy they are. If winter-kill is a major concern, select a variety that scores below 2.0 in winter hardiness.

Additional Resources:

https://fyi.extension.wisc.edu/forage/evaluating-and-managing-alfalfa-stands-for-winter-injury/

https://forage.msu.edu/wp-content/uploads/2014/07/WI-A3620-IsThisAlfalfaStandGoodEnoughToKeep-Undersander-etal_2011.pdf

 

Please contact your local Ag Partners Agronomist or Nutritionist for further information.