From the Fields - Time to Check Alfalfa Stands!
by Jim Morrison
Extension Educator, Crop Systems
Rockford Extension Center, University of Illinois
Phone 815-395-5710; FAX 815-395-5726
Even if alfalfa stands were evaluated last fall, it will soon be time to assess the overwintering condition of that crop. Stand density at the beginning of the growing season is one estimate of the potential productivity of an alfalfa field.
In pure alfalfa fields there are two commonly used methods to evaluate alfalfa stand density: plant count or stem count.
The traditional approach, especially in the early spring, has been to count plants in a square foot area. As a general guide, the suggested number of plants per square foot is:
- Greater than 12 in the spring of the first production year
- Greater than 8 in the spring of the second production year
- Greater than 5 in the spring of the third production year
A similar recommendation for a spring evaluation states that a two-year old stand with 6 or fewer plants per square foot, or a three-year old stand with 3 or fewer plants per square foot will not produce well.
The preferred method of stand evaluation is a stem count per square foot. This approach has been shown to be a good indicator of potential yield. Stem counts can be taken when the plants are 4 to 6 inches or taller. Count any stem that would be cut at harvest. If there are fewer than 39 robust stems per square foot, consider tearing up the
With either method (plant count or stem count), make several "counts" across the field so a representative sampling is obtained. Include a health assessment of the alfalfa crown and root by digging up a number of plants from different areas of the field and then splitting them length-wise to determine crown and root vigor. Roots that exhibit disease or severe discoloration in the crown or more than a couple of inches below the crown may not produce well. Healthy roots will have firm, white tissue on the inside.
Alfalfa plants experiencing winter injury will exhibit these symptoms: slow green-up, shoots on only one side of the crown (asymmetrical growth), uneven growth, and root damage (mentioned above).
Many factors (forage inventory, cash flow, available land, etc.) need to be considered when making a decision to keep an alfalfa field, but assessing the stand density is an important one, and perhaps the starting point.