Winter injury of alfalfa: putting the pieces together for livestock producers
On this page
- Assessing alfalfa stand and damage
- How much forage is in inventory?
- What are my feeding options if the inventory is short?
Figure 1. Severely winter-injured alfalfa in Carver County, 2013. Drought in 2012 may have predisposed this field to injury, since there was little regrowth after August. Photo courtesy of Dave Nicolai.
Reports of winter injury and winterkill of alfalfa continue to intensify across parts of southern Minnesota. As a result, livestock producers will need to carefully consider short and long-term inventory needs and then manage the damaged alfalfa to get as much productivity as possible.
Click image to expand
Figure 2. Healthy, firm, and off-white alfalfa roots. Source: Dan Undersander, University of Wisconsin.
Click image to expand
Figure 3. Significantly damaged (rating 4) and dead (rating 5) alfalfa roots. Source: Dan Undersander, University of Wisconsin.
Assessing alfalfa stand and damage
Assessing the alfalfa stand is the first step in determining the likelihood of producing feed. Is the stand dead or can it limp through 1st cutting or even the entire season? A healthy stand will have at least 55 stems per square foot and roots that are off-white and turgid, as seen 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, so it is 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 damage. Fewer than 40 stems per square foot indicate a poor stand and consideration for termination. However, in areas with severe winter injury, stands with less than 40 stems may be important for getting some early summer forage. The section on forage cropping options offers further discussion.
What percentage of the field has plants that are severely damaged or dead? The extent of this damage and forage needs will determine management options. For more information on assessing stands, see Alfalfa stand assessment: Is this stand good enough to keep?, an excellent resource from the University of Wisconsin and Maximizing Forage in Winter Injured and Killed Stands, Spring 2013.
How much forage is in inventory?
An inventory of the feed on hand along with anticipated summer and fall yields are important in determining feeding and cropping options. Work closely with your nutritionist to determine how many days of alfalfa and corn silage inventory are remaining. The Forage Inventory Management spreadsheet (95 K XLS) developed by University of Minnesota dairy specialists is a useful tool to plan for forage needs. Combine your inventory with an estimate of potential forage yields based on stand assessments for an overall estimate of the feed that will be available. Yield potential of stands with at least 55 stems per square foot should not be limited, but some reduction in yield would be expected with alfalfa densities 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 and 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 3-cut system, forty percent (40%) 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. It's very important 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 will be addressed below.
What are my feeding options if the inventory is short?
Adjusting rations is an option when the current or projected inventory is short:
- Purchase forage – With high amounts of winter injury throughout Minnesota and Wisconsin, alfalfa supplies are likely to remain tight and prices high. Class III milk futures for the remainder of the summer are over $18 per hundredweight (cwt), so purchasing some hay may be the most profitable option. Some external sites are available that allow buyers and sellers to search for available hay lots. Examples include the Internet Hay Exchange and Craig's List. Print advertisements, personal contacts, and hay auctions are also good resources.
- Increase corn silage – If adequate corn silage inventory is available, the best option is likely to increase corn silage feeding. Cows can remain healthy and perform well on very high corn silage diets. Some tips for supplementing high corn silage diets (18.9 K PDF) are available through the University of Wisconsin.
- Re-balance rations using forage extending by-product feeds – Work with your nutritionist to determine the cost and availability of forage extenders. The amount that can be fed will be based on other ration ingredients. Options might include cottonseed, corn gluten feed, wheat midds, soybean hulls, brewers grains, distillers grains, beet pulp, or sweet corn silage.
What are my animal options?
An option for some producers may be to decrease animal inventory. This decision should be made with input from your management team, because reducing animal numbers can dramatically potentially compromise future profitability. The milk futures prices, feed futures prices and housing availability should all be taken into account when making this decision.
- 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. Evaluate the decision of culling productive cows carefully. Typically having a productive cow in every stall is better than leaving a stall empty, 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 heifer numbers. 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 excess culling of herd replacements. An extreme option would be to cull all replacements and purchase springing heifers as needed. Do not make this drastic decision without consulting with your veterinarian and considering genetic and biosecurity risks.
Figure 4. Damaged 1 year alfalfa stand (3.8 plants/sq.ft) that has been interseeded with alfalfa and grass, Carver County, May 2013. Photo courtesy of Dave Nicolai.
What are my forage cropping options?
Your long-term cropping and feeding strategies should not be compromised. Setting yourself up for a normal cropping year in 2014 while trying to meet this year's feed needs will be the most important goal. Use available acres to plan for adequate forage inventory, since it is easier to purchase grains than forages. Consider these ideas as you think about your cropping strategies:
- Assess available acres to meet feed needs – Limited acres are available for forage this year, which may limit flexibility and cropping strategies.
- Plan for adequate corn silage – Corn silage provides the greatest dry matter and nutrient yields per acre. Do not compromise corn silage inventory for the 2013-2014 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 the 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 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 USDA crop disaster declaration request.
- If you need immediate feed, 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 corn or soybean can be planted into the killed forage.
- 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. While this may not add much yield to the first crop harvest, yields for the subsequent harvests should be enhanced. A 50/50 mix of Italian ryegrass and perennial ryegrass can be drill seeded at 10 pounds per acre to a depth of 1/4 to 1/2 inch. Italian ryegrass has high feed value (NDFD) and tends to remain productive through late summer. For fields that will be salvaged beyond 2013, interseeding perennial grasses such as orchardgrass, perennial ryegrass or bromegrass may be considered. University of Wisconsin has an excellent resource on Seeding in an Existing Alfalfa Stand.
- Plant new alfalfa on other acres – Replace acres that you cannot salvage plus any stands that you are keeping just for this year. Do not seed a new alfalfa crop into an old stand, unless it was less than a year old, due to autotoxicity concerns. (see Autotoxicity during re-establishment of alfalfa). Before planting, check to make sure that last year's herbicides don't have any carryover concerns for alfalfa. Remember to check soil tests for pH and nutrient suitability. A new fact sheet on Fertilizing Alfalfa in Minnesota is available from the University of Minnesota. A spring seeding should provide new alfalfa feed around July 1st 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, do not 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 the oats with a grass herbicide (ex. 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. See the New Alfalfa Seeding Weed Control Update from Penn State, but be sure to check the labels for Minnesota requirements. Roundup Ready alfalfa is also an option again.
- Seed small grains for forage harvest, then seed to brown midrib (BMR) sorghum-sudangrass for 1 or 2 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.
Putting the pieces together
Careful planning will help reduce the economic impact of significant alfalfa winter injury. Work with your management team to assess the damage and develop a plan to meet this year's feed needs. Then set your goal to return to a normal cropping strategy for 2014 and maintaining long term farm profitability.