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Spring Alfalfa Termination

Source: Nathan Drewitz, University of Minnesota Extension

Alfalfa stand assessments are potentially only a few weeks away.  I say “potentially” because the past weekend let us know that winter isn’t quite ready to be done.  However, the optimist in me believes that the snow is finished for remainder of the growing season.  This means that alfalfa should be coming out of dormancy shortly.  This also means that alfalfa fields will need to be watched for potential winter injury and death.  A recent article in the Minnesota Crop News by Extension Educators Scott Wells and Rodger Becker highlighted the critical aspects of alfalfa injury and assessment of stands.  These assessments start with digging a few plants and checking the health of crowns and finish with a stand assessment.  For those stands that are less than adequate (<40 stems per square foot), it may be time to consider alternative options or termination.  With alternative management, consider the cost and benefits of trying to maintain the stand versus termination.  For those stands that alternatives will not be cost effective to maintain, termination will be the next step. 

Spring termination does have its benefits as there is some potential for a late May harvest prior to termination and can provide soil cover to help prevent erosion.  Termination of alfalfa using herbicides is typically done using 2,4-D, dicamba, and glyphosate.  Check the label of the alfalfa variety that was planted for glyphosate resistant traits.  If you planted glyphosate resistant alfalfa, glyphosate application will not help with termination. Also, make sure to follow the herbicide label’s plant back restrictions on whatever crop you are planting following termination.  One other benefit is the potential nitrogen that comes from a terminated stand of alfalfa.  The amount of nitrogen present can be up to 200 pounds stored in the plant, and may be enough to supply corn planted in the first year following termination with its nitrogen requirements.  One disadvantage of spring termination is the decomposition of alfalfa and subsequent release of nitrogen may not be fast enough to supply the entire needs of the corn crop grown in the first year following termination.  Scout fields looking for Nitrogen deficiencies in the corn and supply extra Nitrogen where needed. 

Since corn is typically grown following alfalfa stand termination, be aware that delayed planting may be an issue.  Planting dates of corn usually happens prior to alfalfa reaching 4 inches tall which is around the height that herbicides are applied.  Plant back restrictions need to be followed in this situation and may require a couple of weeks before corn can be planted.  Alfalfa also uses water at a higher level than other crops.  Other options such as planting drought-tolerant corn hybrids should be considered in fields with limited in-season moisture.  For more information on Spring Alfalfa Termination visit the UMN Extension Website and look under Crop Production or call the Benton County Extension Office at (320) 968-5081.