New growth on alfalfa. Photo credit: Creative Commons CC0; Pixabay.com
Old man winter still has some control of our weather, but he’s starting to lose his grip. In some parts of the state, alfalfa has broken winter dormancy. While fall evaluation of alfalfa stands is ideal, assessing stands in springtime can lead to more effective management decisions.
According to Dr. Dan Undersander, retired forage specialist at the University of Wisconsin, springtime stand assessment occurs in three parts:
- Are individual plants alive?
This assessment can begin as soon as the frost is out of the ground and continue until spring greenup occurs. The process is to dig a few plants 4 to 6 inches deep and look at the condition of the taproot. If the taproot is turgid (like a potato, leftmost plant), it is alive and healthy. If the root is browned, dehydrated, and ropey (like two plants on the right), it is dead or dying. This assessment can be repeated until greenup occurs and stand can be assessed on that basis.
Alfalfa taproot evaluation. Photo credit: University of Wisconsin
- Are plants injured?
Alfalfa forms buds in the fall for spring growth. If these buds are killed the plant must form new buds in the spring, delaying growth and reducing yield. The three taller stems in the picture (above line) are from buds formed in the fall and the shorter stems are from buds formed in the spring. The delayed, shorter growth will reduce yield of first cutting and then plants will recover. If you see this, consider management to reduce this in the future, such as adequate soil pH, fall application of potassium, more winter-hardy varieties.
Evaluation of winter injury by comparing fall versus springtime buds. The line in the photo separates fall buds (top growth) to spring buds (lower growth). Photo credit: University of Wisconsin.
- Are there thin spots in the field?
A healthy stand should have 55 stems/ft2. Early assessments, before stems are visible, may need to assess based on plant count. A high yielding alfalfa stands seeded last year should have 20 plants/ft2, counts as low as 12 will produce good yields, but result in shortened stand life. Stands seeded last spring or fall with less than 12 plants/ft2 should be disked and reseeded.
Thin stand (left) versus adequate stand (right). Photo credit: University of Wisconsin
A high yielding alfalfa stand over 1 year old should have at least 6 plants/ft2. If plant density is less than 6, oats (2 bu/a) or Italian ryegrass (10 lbs/a) can be overseeded to increase yield this year. The stand should be turned over either immediately or at end of year.
As I mentioned earlier, fall evaluation of stands is the preferred method. If you’d like to read more about that, check out the Wisconsin Factsheet. We’ll address that topic in Field Crop News again this upcoming fall.