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Taking Another Look at Alfalfa

University of Minnesota Extension, Stearns County News
April 12, 2017         
Source:  Dan Martens, Extension Educator
University of Minnesota Extension
Stearns, Benton & Morrison Counties

Taking Another Look at Alfalfa
By Dan Martens, University of Minnesota Extension

FOLEY, Minn. (04/12/17) — Farmer and agronomy advisors continue to watch alfalfa fields to see how well they came through the winter. Here are some observations from digging out a few roots in a field near Foley on March 31. Some roots were firm with nice color. These will probably be OK.

Some roots (like the one pictured) had a more tan colored area for about 2 inches below the crown Some of these were getting soft, and juice could be squeezed from this part of the root. Fibrous strands would separate easily when the root was twisted. These plants will likely be lost. The root below this area was firm with more normal color.

Some roots were a little off-color, but still pretty firm. They might be OK; or they might decay further and be lost. This will be more obvious during the next week or two. With further decay, you might find that the outside layer of the root rubs loose pretty easily. 

There is probably a lot of variability around the area with how soils are warming up and drying out based on soil conditions, old crop residue, north/south slopes, low spots, varieties and other factors. Your past experience counts a lot.

Be thoughtful and patient. Sometimes roots turn soft and decay and dead plants are quite obvious. Sometimes alfalfa will grow to be 4 to 6 inches before they give up. Sometimes fall growth buds were damaged and it takes an extra time to get up and going. 

Plants that are 3 to 4 years old can have a brown core with enough firm tissue around the core to grow fine. This can be normal wear and tear from harvest, wheel traffic and other damage. The dark brown core you see now is NOT from injury during this past winter.

Farmers and agronomy advisors might use plant and/or stem counts to evaluate fields. Your common sense and past experience are significant.

For alfalfa that was seeded a year ago we might like to have 15 to 25 plants per square foot this spring. For older stands we might like to have 4 to 6 plants per square foot for good yield potential. Obviously this varies a lot with how well plants develop.

Stem counts might be more useful in the spring, if you can wait to make a decision long enough for stems to develop well. They don’t always start at the same time. A common scale for stem counts is that greater than 55 stems per square foot could have 100% yield potential; 45 to 50 stems at 80 to 90%; 30 to 40 stems at 50 to 70%; and less than 30 stems at less than 50%.

A chart in the North Central Alfalfa Management Guide shows that alfalfa with 55 stems per square foot might average 5.5 tons per acre; at 40 stems 4.5 tons; at 30 stems 3.5 tons. Obviously there are a lot of variables that determine potential and actual yields in a given field and a given year.

For counting purposes, a square foot is obviously12”x12”. A circle of stiff wire that is 27 inches long makes a square foot. Add what you need to tie the ends. A square 17”x17” is 2 square feet. A circle with a circumference of 60 inches is close to 2 square feet.

Internet users can find more information by doing a search for “Minnesota Extension Forage Production” and looking under the “Growth and Development” tab. You’re welcome to call with questions or information that might be useful.

In Stearns County call 255-6169 if a local call to St. Cloud or 1-800-450-6171; in Benton call 968-5077 if a local call to Foley or 800-964-4929; and in Morrison call 632-0161 if a local call to Little Falls or 1-866-401-1111.

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