Winter injury of alfalfa: Strategies for livestock producers
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If there’s significant alfalfa winter injury and winterkill, livestock producers must plan carefully to reduce the economic impact.
Assess the damage, work with your management team to carefully consider short- and long-term inventory needs, develop a plan to meet this year's feed needs and then manage the damaged alfalfa to get as much productivity as possible.
Aim to return to a normal cropping strategy next year and maintain the long-term profitability of your farm.
Determine damage extent and inventory needs
Assessing the alfalfa stand is the first step in determining how likely it is to produce feed (Figure 1). Is the stand dead or can it limp through first cutting or even the entire season?
Symptoms of damage
A healthy stand will have at least 55 stems per square foot and roots that are off-white and turgid, as shown in Figure 2.
In contrast, severely injured roots have large areas of root rot (rating 4 in Figure 3) and few shoots. Even dead roots (rating 5 in Figure 3) may send out a few shoots before the plant dies. This is why it’s important to examine the roots when assessing the stand.
Roots that are off-white, but spongy around the crown also indicate severe damage. Dig up plants in three or four representative areas of the field and split the roots to assess the damage.
How to assess damage
Fewer than 40 stems per square foot indicate a poor stand, and you should consider terminating it. However, in areas with severe winter injury, stands with less than 40 stems may be important for getting some early summer forage. View forage cropping options.
The best management approach will depend on what percent of a field is severely damaged or dead, as well as your forage needs.
For more guidance on assessing alfalfa stands, refer to:
To help guide feeding and cropping decisions, inventory the feed you have on hand along with anticipated summer and fall yields. Work closely with your nutritionist to determine how many days of alfalfa and corn silage inventory are remaining.
When planning for forage needs, the Forage Inventory Management spreadsheet developed by University of Minnesota dairy specialists is a useful tool. Combine your inventory with an estimate of potential forage yields based on stand assessments. This will give you an overall estimate of the feed that’ll be available.
Estimating yield potential
Yield potential for stands with at least 55 stems per square foot shouldn’t be limited. However, expect some yield reduction if your alfalfa densities are between 40 and 55 stems per square foot.
The University of Wisconsin recommends using stem counts to help estimate yield. Count stems per square foot, then multiply by 10 percent (0.10) to get a handle on yield potential.
For example, 30 stems per square foot might mean a 3 ton yield potential. In a three-cut system, 40 percent of the yield may be taken in the first cutting. As a result, we might yield 1.2 tons per acre in the first cutting from a total 3 ton yield potential. Be sure to evaluate the condition of the roots to further assess whether these plants can continue to work toward that yield for first cutting or full season.
Other options for enhancing alfalfa stands are addressed below.
What to do if you’re short on inventory
Adjusting rations is an option when the current or projected inventory is short.
If there’s a high amount of winter injury throughout Minnesota and Wisconsin, alfalfa supplies are likely to be tight and expensive. Sometimes purchasing hay is the most profitable option.
External sites that allow buyers and sellers to search for available hay lots include the Internet Hay Exchange and Craigslist. Print advertisements, personal contacts and hay auctions are also good resources.
Increase corn silage
If adequate corn silage inventory is available, increasing corn silage feeding is likely the best option. Cows can remain healthy and perform well on very high corn silage diets. Tips for supplementing high corn silage diets.
Re-balance rations using forage extenders
Work with your nutritionist to determine the cost and availability of forage-extending by-product feeds. The amount that can be fed will be based on other ration ingredients. Options might include:
Corn gluten feed.
Sweet corn silage.
For some producers, an option may be to decrease animal inventory.
Make this decision with input from your management team because reducing animal numbers can dramatically compromise future profitability. When making this decision, take milk futures prices, feed futures prices and housing availability into account.
Evaluate cow inventory
Are you dramatically overcrowded or are there unprofitable cows that should be culled? This is the easiest decision and should be done immediately.
Carefully evaluate decisions to cull productive cows. Typically, a productive cow in every stall is better than an empty stall, even if it means purchasing high-priced feed.
Evaluate heifer inventory
Are all heifers needed as replacements? If excess replacements are available, one option is to reduce how many heifers you have. If you can find a custom heifer raiser with feed and housing, consider having heifers custom-raised.
Try not to reduce future herd productivity by excessively culling herd replacements. An extreme option would be to cull all replacements and purchase springing heifers as needed. Don’t make this drastic decision without consulting with your veterinarian and considering genetic and biosecurity risks.
Don’t compromise your long-term cropping and feeding strategies. The most important goal is to set yourself up for normal cropping next year while trying to meet this year’s feed needs.
Use available acres to plan for adequate forage inventory, as it’s easier to purchase grains than forages. Consider the following ideas as you think about your cropping strategies.
Assess available acres
If limited acres are available for forage this year, it may limit flexibility and cropping strategies.
Plan for adequate corn silage
Corn silage provides the greatest dry matter and nutrient yields per acre. Don’t compromise corn silage inventory for the current feeding year.
Plant corn on alfalfa acres that can’t be salvaged
If the alfalfa has been winter-killed or significant injury occurred on a large percentage of your field, planting corn before July 1 will produce the most tonnage of any forage. The corn crop will also be able to take full nitrogen credit from the alfalfa.
BMR sorghum-sudangrass may be a good choice if you expect dry conditions and/or above-average temperatures.
Report any lost and damaged hay acres to the county Farm Service Agency Office. In areas with severe loss, FSA staff can use this information to evaluate whether county alfalfa crop loss merits a Department of Agriculture crop disaster declaration request.
Harvest alfalfa and follow with corn or soybeans
If a moderate percentage of the field has significant damage, you may decide to abandon the alfalfa after the first forage cutting. Then you can plant corn or soybean into the killed forage. Consider this approach if you need immediate feed.
Evaluate options on stands with partial winter injury
If a small to moderate percentage of the field has been affected, consider interseeding some fast-growing grass seed to increase yield (Figure 4). While this may not add much yield to the first crop harvest, yields for the subsequent harvests should be enhanced.
Drill-seed a 50-50 mix of Italian ryegrass and perennial ryegrass at 10 pounds per acre to a depth of 1/4 to 1/2 inch. Italian ryegrass has high feed value (neutral detergent fiber digestibility, or NDFD) and tends to remain productive through late summer.
For fields that’ll be salvaged beyond the current year, you may consider interseeding perennial grasses such as orchardgrass, perennial ryegrass or bromegrass.
Plant new alfalfa on other acres
Replace acres that you can’t salvage plus any stands that you’re keeping just for this year. Don’t seed a new alfalfa crop into an old stand, unless it’s less than a year old, due to autotoxicity concerns.
Before planting, make sure last year's herbicides don’t have any carryover concerns for alfalfa. Remember to check soil tests for pH and nutrient availability. View alfalfa fertilizer recommendations. A spring seeding should provide new alfalfa feed around July 1 with a second cutting likely in most areas, depending on rain.
There are several seeding options:
Direct seed with a small grain cover crop to harvest as forage near the end of June. If this hasn't worked well in the past, don’t risk compromising the alfalfa. Oats, barley or triticale with or without peas are all nurse crop options.
Direct seed with oats if needed for wind or water erosion. Kill oats with a grass herbicide (e.g., Poast or Select) when the oats are 6 to 8 inches tall to make the most of the alfalfa.
Direct seed alfalfa alone, if there are no significant wind or water erosion issues. Consider herbicide options if weeds are an issue. Roundup Ready alfalfa is also an option.
Seed small grains for forage harvest
After the small grains harvest, seed to brown midrib (BMR) sorghum-sudangrass for one or two cuttings. If fall-seeded alfalfa is a better option for you, consider using the field for manure applications after the small grains harvest, instead of seeding the sorghum-sudangrass.
Reviewed in 2018