WHAT IS WINTER INJURY?
Our harsh winter environment in northern New England can be surprisingly damaging to the plants we grow. Conditions like freeze/thaw events with fluctuating temperatures or desiccation due to lack of water can be a main driver for winter injury or winter kill. Perennial forage stands, particularly alfalfa, are no exception. Therefore, it is crucial to assess your forage fields early in the spring for signs of damage.
HOW TO DIAGNOSE IT:
First and foremost, it is most important to determine if your field(s) was impacted by the winter weather. Check your fields for…
- Stands that are slow to green up. If other fields in your area are starting to grow and yours are still brown those stands should be checked for injury or death.
- Uneven growth patterns as that may also indicate damage.
The best way to diagnose damage is by examining the plant roots in a suspect field. To do this, walk diagonally across a field and at regular intervals (every 4 to 5 paces) dig up a shovel full of plants (4 to 6 inches deep) and examine their roots. The roots of each plant should be firm and the interior color should be white or cream colored. If the roots are soft and the interior yellow to brownish in color it most likely was wintered killed. For alfalfa, the majority of crown buds should be white or pink and firm throughout the bud.
FOR FIELDS MODERATELY AFFECTED…
Winter injured stands will require different management than healthy stands if they are to stay in production. If winter injury is evident consider the following:
- Allow alfalfa plants to mature longer before cutting. This will help the plants rebuild needed energy for future production. Increasing the cutting height may also help stands recover. Lastly do not cut winter injured stands late in the fall this will allow them to build up more reserves before winter.
- If a significant loss of alfalfa was seen in a predominantly grass stand, then you could manage it for grass. This will work best if the grass species are predominated by tall growing species. If the grass is less than 10 inches tall, it may still be economical to apply 50 pounds of N per acre to boost yield and protein. If the grass stand is predominately lower yielding forage, you may want to consider replanting.
- If the alfalfa stand was only partially injured (25 to 50 %) interseeding (with a no-till or grain drill) with a quick germinating forage could provide additional production. When dealing with winter injured stands, it is particularly important to adequately fertilize and to control for weed competition.
FOR FIELDS SEVERELY AFFECTED…
If your stand was over 50 % killed, you may consider replanting. There are several forage choices depending on your needs or goals.
- Is your forage needed early/mid-summer? A small grain/field pea mixture will be the best choice. Harvest when the small grain is at late boot stage. This will allow enough time to replant the perennial forages during late summer if desired.
- Are you looking to optimize full season forage production? Corn silage will be the best choice for that. If corn silage is planted by the end of June, it will normally out yield most other forages however you risk lower quality forage.
- Are you planting mid-June to early July? Consider planting a summer annual grass. These forages should be harvested when they reach approximately 30 inches and will typically be harvested twice. Selecting varieties with the Brown Mid Rib (BMR) gene can increase the fiber digestibility of the forage.
For more information on winter injury, see the resources below:
- Evaluating and Managing Winter Forage Stands for Winter Injury, UVM: https://www.uvm.edu/sites/default/files/media/managing-forage-winter-injury.pdf
- Planning Ahead for Winter Injury in Forages, UNH: https://extension.unh.edu/resource/planning-ahead-winter-injury-forages
- Spring Oats Offer Fast Forage, Hay & Forage: https://hayandforage.com/article-4336-Spring-oats-offer-fast-forage.html
- Guide to Using Annual Forages in the Northeast: https://www.uvm.edu/sites/default/files/Northwest-Crops-and-Soils-Program/Articles_and_Factsheets/Annual_Forage_Guide_5.pdf