Scouting Alfalfa
As you get ready to scout alfalfa fields this spring here is a checklist that can help.
Assessing Alfalfa
Determining alfalfa injury in mid- to late April is not easy because most plants will show some initial growth. This initial growth of injured plants comes from limited nutrient reserves in the roots.
Step 1: The key to early detection is digging and carefully examining the root system below the crown:

• Healthy plants have a firm root and will show initial growth from the crown.
• Injured roots are spongy and off-white to brown in color.
• The alfalfa roots can be a quick giveaway. In severe winterkill

areas, these will be extremely soggy as you dig them up.
Step 2: Cut the crown and root vertically:

• Healthy root tissue is firm and white. (In older stands, there is

usually some damage.)

• Moderately damaged roots will show some darkening and decay

in the upper part of the root. These plants will generally survive
if no more than 50% dark-brown discoloration.

• Severely damaged roots will show over 50% dark-brown

discoloration. These plants will likely not survive.

• Dead plants will have completely discolored and spongy roots.

Step 3: Determine the extent of the damage in the field:
• Check plants and roots in different areas of the field.
• Pay particular attention to low areas, compacted areas and
northwest slopes.
• Compile an average “healthy” stand/square foot.
Use the following table as a guide:

​*Stands in the “poor” category should be considered for renovating. Source: University of Minnesota.
Making the Decision
After assessing the amount of winter injury present, an economically sound decision should be made considering cost of reseeding, price of alfalfa, forage demand, etc.
Consider the following if keeping “borderline” stands:

• If grass makes up over half the stand, applying 40-50 lb. of

nitrogen may salvage an acceptable yield of dry matter for one
more year.

• Delaying the first cut to 50% bloom will help the roots build

adequate reserves for one more year of production.
Consider the following for renovation stands:

• A “good” stand of alfalfa plowed down is worth about 100 lb. of

nitrogen to corn, along with the added boost from the rotation
effect.

• Replanting alfalfa into a plowed alfalfa stand is not

recommended because of autotoxicity. The older the stand, the more likely this is to be a problem. If possible, wait at least one cropping season to avoid problems. It’s best not to attempt this if the stand was over three years old.

• Interseeding of a sparse stand with alfalfa is not recommended. 

 
Call Tom for an individual recommendation of your particular field and options. 574-536-6640