As winter begins its slow trudge towards spring, winter injury and stand loss can be a concern for alfalfa growers in northern climates.
“It all depends on Mother Nature and what kind of weather she throws at you,” says Luke Wilson, Barenbrug USA’s Midwest territory manager, about the prevalence of alfalfa winterkill. “If you have a mild winter, you’re not going to see it as much.”
Wilson works with growers and dairy farmers across 12 states in the region. Based out of central Iowa, he says, he encounters two scenarios as the most common causes of winter injury in alfalfa stands. The first is a lack of snow cover during a bout of extremely cold temperatures. The second is an ice event that causes sheeting of ice over the field.
“Either of these situations for an extended period can damage the alfalfa plants,” says Wilson.
Along with weather, environmental factors such as a stand’s age, soil pH, soil fertility, cutting management, field traffic, and planting varieties not adapted to a region can also play into creating a perfect storm of winterkill in an alfalfa field.
The best way to diagnose winterkill or injury, says Wilson, is to dig up the roots (approx. 6 inches deep) in several locations across a field when the spring thaw begins. Depending on how far north producers are located, this timing could be anywhere from March to May. Healthy roots will appear white to cream in color and have a firm texture. Damaged plants will exhibit a grayish to brown color on the root and crown and have a mushy consistency.
“The other option is to wait until things green up,” says Wilson. “Compare a known healthy field to yours. If yours is delayed compared to others, you probably have some damage in that field. The thing with this method, though, is you have to react more quickly since you're waiting until later in the season.”
Experts say a good rule of thumb to follow is interseeding is justified when there are less than 4 to 5 healthy alfalfa plants per square foot left in a field. The route growers take will depend on their specific needs, says Wilson.
“If they don’t really need the feed and were going to tear up the field anyway, they might decide to rotate that field into another crop,” says Wilson. “However, if it was a field they were counting on for feed, then it’s probably more important they keep that stand in production and boost the yield in a different way.”
Whatever the case, Wilson explains injured stands will be slow to recover, so producers shouldn’t be in a hurry to tear up fields. As long as there are adequate plants remaining, it’s probably best to push the stand to get the most out of it this year.
In this situation, Wilson points out several forage options exist to do the trick. Interseeding annual forages can help stretch the stand through the current year while simultaneously boosting yield to ensure adequate feedstocks.
Small grains for forage, like oats and barley, and annual grasses such as Italian ryegrass work well as “emergency” options. If the window for spring planting has already passed, producers might want to consider a summer annual like sorghum-sudangrass.
In particular, Barenbrug’s Green Spirit, an Italian ryegrass blend, has proven itself to be a perfect emergency crop for this purpose.
“It’s very quick to establish and helps fill in those spots of damaged alfalfa or bare ground,” says Wilson. “And, it provides high-quality forage throughout the year without the need to change cutting schedules or anything.”
Green Spirit establishes best in early spring, says Wilson. Additionally, it is adapted to a wide range of soil types. However, it is ideally suited to higher moisture or irrigated situations in a cool-season climate.
Wilson notes, the recommended seeding rate for Green Spirit is between 15 to 25 pounds to the acre. When interplanting into an existing alfalfa stand, producers should drill seeds in a manner to stagger the placement of the seed with the other crop.
“The exact seeding rate will depend on how severe the damage,” says Wilson. “If it’s very severe, you will want to go heavier, close to 25 pounds per acre. If the damage is less and you’re just filling in some areas, then you can get away with 15 pounds to the acre.”
Once planted, Green Spirit usually provides forage in as little as six weeks. Typical plant heights reach around 12 to 18 inches, providing more than adequate forage for green chop, silage, and haylage harvesting options. Wilson points out Green Spirit does not dry down as well as perennial grasses like orchardgrass. Therefore, it is not recommended for dry hay production.
Another side perk of Green Spirit, says Wilson, is it’s proven to respond well to nitrogen. It works great with manure management and nutrient recycling. However, when interseeding into alfalfa stands producers should maintain manure application rates within parameters that are also ideal for the alfalfa in the stand.
Overall, Wilson says, “Green Spirit is a great fit for a person who just wants one more year out of an alfalfa stand. It’s a high-quality emergency forage to get you through the year until it’s time to rotate that field into a new crop.”
Author Byline: Written by Jesse Bussard, an agricultural writer based in Bozeman, MT.