Even though it hasn’t been as cold this winter as in recent years, it’s still important to assess any alfalfa injury that your crop may have suffered. First, think about what type of winter your region experienced: Wet? Snowy? Bitter cold? Windy?
“In the Mid-Atlantic–Northeast region we’ve had a really mild winter, so I’m not expecting to see a lot of winter injury in our perennial crops this year,” said Jessica Williamson, assistant professor of forage management at Pennsylvania State University. “We haven’t started green-up yet, but it’s becoming milder and starting to warm up, so I’ll be out in the field in a few weeks.”
Diagnosing winter injury
An early indicator of winter injury is a late green-up of the alfalfa crop. Sometimes, a late fall harvest will set it behind in the spring.
“The crop isn’t as vigorous as other stands of alfalfa or other cool-season perennial forage,” she said. “If you notice that one particular stand is getting green significantly later than others, that’s a strong indicator that the field has experienced some winter injury.”
Another visual indicator is root damage. If you dig up some roots in early spring, ideally you’ll find healthy, solid, whitish- to creamish-colored roots. However, if a gray, soft, dry-feeling root is found, that’s a sign of winter damage as well.
Uneven or asymmetrical growth can mean some of the crowns have been killed. As the forage starts to grow and green-up in the spring and begins to fill in, if there’s a lot of uneven growth, you’ve likely not only had injury but also winter kill.
Evaluating your alfalfa stand
Start by looking at percentage of ground cover and correlate it with yield potential. With greater than 80% ground cover in the spring and good vigor, the crop should have excellent yield potential.
“If it’s a very young stand of alfalfa – in its first or second year of production – and it has a little bit of winter injury but you’re still getting 80% ground cover, you still have an excellent potential for yield,” Williamson explained. “We want to quantify that by about 25 to 30 plants per acre and 45 to 55 stems per square foot to really achieve an excellent yield potential.”
If you’re closer to 60% to 80% ground cover but the crop still has good vigor, it’s possible to have fair to good yield potential. This is an opportunity to determine what the operational goals are for the alfalfa stand and decide whether to interseed a perennial grass crop into the alfalfa to increase the overall yield potential or to completely renovate it by burning it down and planting another crop and then introducing alfalfa a year or two later.
If you’re in the 40% to 60% ground cover range and under 40 stems per square foot, expect about 50% to 60% of the stand’s yield potential. Again, consider your operational goals. If you need a pure stand of high-quality alfalfa, it’s time to replace the stand with another crop in the rotation.
Lessening winter injury
There are a few things you or Mother Nature can do to lessen winter injury.
• Snow cover. Many might think snow is bad for perennial or cool-season crops. But snow is actually a great insulator and can help prevent damage throughout the winter.
• Soil Fertility. Stands that are grown in the proper pH and have proper soil fertility going into the winter are less prone to experience winter injury.
• Stand age. Typically, younger stands (one-, two-, or three-year-old stands) are heartier and are less susceptible to winter injury than four- or five-year-old stands.
• Harvest management. Throughout the year but especially going into the fall, cutting timing can be another indicator of whether or not your stands are going to have winter injury. If you harvest late and the crop doesn’t have enough time to rebuild its carbohydrate stores going into the winter, it could result in winter injury.
If you suspect your alfalfa has experienced winter injury, it’s always a good idea to consult an agronomist or Extension agent to help identify the best approach moving forward for your operation.
Headline photo courtesy of the University of Wisconsin Forage Team.
To read more articles like this one:
Dairy Herd Management
Ryegrass an Option in Winter-Killed Alfalfa
How to Evaluate Winter Alfalfa Damage
Managing the Rotation from Alfalfa to Corn
Drovers
Time to Check for Winterkill Injury
Check if Lack of Snow Injured Alfalfa
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