When Is It Time For a New Alfalfa Stand?
You don’t have to plant your winter hardy alfalfa fields every year as you do with corn and soybeans. However, if you want consistently high yields for your own feeding needs or commercial alfalfa production, you can’t afford to let fields become unproductive.
In the Midwest, alfalfa fields begin to decline after the second year of production. According to Dan Undersander, University of Wisconsin Extension and research forage agronomist, often by as much as 17 percent from the first two years. (Source)
Stem count evaluation of alfalfa fields
The ultimate measure of the productivity of your alfalfa stand might be the tonnage you harvest, but that number will vary depending on weather and timing of your cutting.
You can also evaluate the health of your field in the fall after the last cutting or in the early spring using a stem count technique. You can expect full yield potential from a field with an average of 55 stems per square foot.
Michigan State University extension recommends using a marker—either a 17×17 inch square of PVC pipe or a 19-inch diameter metal ring—to designate a section that is 2 square foot in area. Count the number of alfalfa stems over 2 inches tall in that section. Repeat the process three or four times in representative areas of your alfalfa field.
Then calculate the number of stems per square foot by dividing your average count in half.
Research shows that fields with at least 55 stems per square foot can suffer some plant loss over the winter and still yield well in the following year.
Crown and root health evaluation of alfalfa fields
If the stem density is below 55 per square foot, and above 40, the stand may still be able to yield as it did the previous year. If plant health is good the plants are likely to survive the winter. To evaluate alfalfa crown and root health, you will want to look closely at the plants themselves.
Alfalfa Plant Health Rating
University of Wisconsin Extension offers photo examples of the rating system for evaluating alfalfa root and crown health in this article.
UW specialists recommend digging plants from three or four representative locations in the field. Be sure to include the top six inches of root. Examine the crowns for size, symmetry and the number of shoots present. Then cut the root lengthwise and check for rot or discoloration in the crown and root.
A plant with a rating of 0 will have a large symmetrical crown with many shoots and roots with few signs of discoloration. At a rating of 2, the crown will be smaller, less symmetrical with fewer shoots. There may be evidence of crown rot or vascular discoloration in the roots 3 to 4 inches deep. These plants still have a good chance of winter survival.
Ratings of 3 to 4 range from alfalfa plants with a weak crown and few roots, with significant crown rot and root discoloration that may still survive a mild winter. Unlike plants with few shoots and root rot affecting more than 50 percent of the root’s diameter. These are unlikely to survive any winter. Dead plants receive a 5 rating in this scale.
If more than 30 percent of your sample rates in category 4 in the fall, and your stem density is less than 55 plants per square foot, you are likely to experience significantly lower yields the next year, even without a winterkill incident.
Replacing weak alfalfa stands
If you have alfalfa stands that are showing the signs outlined above there are multiple approaches to take.
If extensive winter injury damages a field that had been in strong condition in the fall, the University of Wisconsin says one option is to increase yields without completely replacing the field elsewhere is by overseeding the field with forage species, which could include cereal grains (oats, beardless barley, wheat, triticale), annual or perennial ryegrasses, sorghum-sudangrass, orchardgrass or clovers. This could help extend the life of the field by a year or two dependent on the chosen forage variety. Some forage species include legumes such as:
- clover which provide a higher quality product for lactating dairy cattle,
- cereals and grasses may result in slightly lower quality but greater tonnage suitable for dry cows, bred heifers and other livestock
If the status of a field after the last fall cutting makes it obvious that the field should be replaced, the University of Minnesota recommends rotating into a new field to avoid autotoxicity in your alfalfa. This will allow the nitrogen benefits of the previous alfalfa stand to be used by corn the next year.
Choosing a new field for your replacement stand of alfalfa
- Strive to locate it where you have well-drained deep soils
- Avoiding hilltops, shallow and eroded soils, and fields where water is known to pool
- Soil sampling in your chosen field can identify nutrient deficiencies to guide perennial and annual applications
Spring seeding between April 15 and May 15 is most common throughout the U.S.. For our customers in northern Minnesota and similar areas, it is recommended to wait until May 1-30 to plant. Summer seeding dates may also be considered. Late July to early August decreases the need for herbicides, but carries risk of lack of soil moisture and growth time before winter.
Helping you choose the best alfalfa seed for your operation
It is important to select alfalfa varieties with adequate fall dormancy and disease resistance for your location.
Kussmaul’s alfalfa seed line-up includes registered traits.
- Traffic Tested®
- Roundup Ready®
- Hi-Gest® technologies
Winter hardy varieties with fall dormancy ratings from 3 to 5 provide options for a wide range of operations throughout the northern two-thirds of the United States. Offerings include proprietary genetics from multiple leading alfalfa breeding programs.
Our district sales managers are here to help you choose the right varieties for your alfalfa acres.
Find the sales manager for your region on our website here or download a complete catalog of Kussmaul seed. Included in the line up are; alfalfa, organic, conventional, traited and silage-specific corn hybrids; soybeans; forages, and wildlife mixes.