ARCHBOLD, Ohio – Deciding whether to reseed an alfalfa field is always a tough decision because of the expense of establishing a new crop.
However, there are several easy guidelines growers can use when evaluating whether it makes economic sense to keep a stand.
“Alfalfa growers and livestock producers need to get the maximum value per acre from their forage,” said Kirk Reese, technical information manager for Pioneer in Archbold, Ohio.
“To achieve that, check the health and population of stands, particularly those that are more than 4 years old.” To determine the alfalfa population, count the number of plants in one square foot at several locations throughout a field. According to Reese, the alfalfa population in an established stand should average at least five plants per square foot. “When it falls below that number consider plowing up the field and rotating out of alfalfa.”
Desired Plants Per Square Foot Based on Age of Stand
Age of Stand Condition of Stand
Good Fair Poor
New Seeding 25 15 <10
1 Year Old 12+ 8-12 <8
2 Years Old 8+ 5-8 <5
3 Years Old 6+ 4-6 <4
4 Years or More 4+ 3-5 <3
There is another evaluation method to consider. Recent research from Wisconsin by Dennis Cosgrove indicates that growers will get a more accurate reading if they count the number of stems in a square foot to determine when to plow down or interseed an alfalfa stand. This method is most useful for stands that have developed at least 6-10 inches of growth.
“If you have more than 55 stems per square foot, maximum yield can be expected,” said Cosgrove. “When stem counts drop below 40 stems per square foot, expect at least a 25 percent yield reduction. When this happens, consider replacing the stand.”
Reese also recommends checking the health of the stand by digging up plants and checking for crown and stem rots in the spring. If samples show some dark or discolored crowns or roots, then reseeding may be necessary, especially in older established stands.
Generally, the larger or less uniform a field, the greater the number of counts recommended in a year. For uniform fields 20 to 30 acres in size, count about 20 randomly chosen, square-foot areas and average the results.
Management. In addition to the plant stand, Reese recommends reviewing winter weather conditions. “Extreme cold may cause winter kill,” said Reese. “However, if there is adequate snow cover, it may not be as severe.”
Winter injury can range from total plant kill to reduced growth rate due to plant weakening. To determine cold injury and stand condition in early spring, dig plants and assess crown and taproot conditions.
Healthy taproots are creamy, white and firm in texture. “If there are good taproots and still evidence of bud growth from the crown, then the plant is likely recovering,” said Reese. “If taproots are spongy or watery and beginning to turn tan or yellow, the stand is likely severely cold-injured and deteriorating.”
If this is the case, Reese recommends checking the field again in about a week to confirm the assessment.
When reseeding is necessary, seedbed preparation and following proper management steps are key to producing a healthy alfalfa stand. Soil pH should measure between 6.8 and 7, phosphorous and potassium levels should be medium to high and the seed needs to be treated with a fungicide. Good seed-to-soil contact is critical and can be accomplished by either rolling or culti-packing prior to and after seeding alfalfa.
Certain crop rotations also help maximize alfalfa production. “There are many university studies that show planting continuous alfalfa is not as beneficial as planting alfalfa after a different crop,” said Reese.
Seed selection. Reese recommends growers look at several key factors when choosing an alfalfa variety. Those include winter hardiness, yield potential, a strong disease- and insect-resistance package and quality.
It’s important to look carefully at the total value package of each alfalfa variety,” said Reese. “Selecting varieties with a hardy or very hardy winter-hardiness rating is important as well as selecting those with a moderate resistant to highly resistant rating for Phytophthora root rot, fusarium wilt and Verticillium wilt to help ensure long stand life and a good return on investment for the grower.”
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