April 17, 2018 - 8:01am -- Anonymous

How did your alfalfa stand handle the winter?  Once we get some warmer weather and stands have 3-4 inches of growth, evaluate stand health by doing stem density counts and a root health assessment in at least 4-5 random areas per 25 acres.  Stem density counts provide an indication of the yield potential of the stand.  The following table is from the University of Wisconsin Extension publication A 3620; “Alfalfa Stand Assessment: Is this stand good enough to keep?” (https://bit.ly/2v9maZk)

Stem number/square foot

Expected result or action

Over 55

Stem density not limiting yield

40-55

Some yield reduction expected

Less than 39

Consider stand replacement

To assess root health, dig up five to six plant roots in four to five random locations and split them open.  A healthy root has a creamy white color and no to very little discoloration at the crown.  These plants have shoots evenly distributed across the crown of the plant. 

Discolored plant roots indicate a health problem.  They are a darker white, tending towards a tan color.  There may be obvious areas of root rot and crown rot that are a dark brown to black in color.  There may be streaks of brown running down the root.  These plants have fewer stems coming out of the crown and those stems may tend to be more numerous on one side of the crown as compared to the other.  These plants may not survive the entire production year, especially if we have a hot, dry year. 

In general if more than 30% of the roots that are dug and split have brown streaks running down the root and/or black areas of root/crown rot that cover greater than 30 to 50% of the roots diameter yield potential is significantly reduced.    The previously mentioned University of Wisconsin publication contains color photo illustrations of root health ratings.