Source: Nathan Drewitz, University of Minnesota Extension
FOLEY, Minn. (05/04/2022) — So far winter injury issues are not a concern for alfalfa stands throughout the region. We had plenty of snowfall through the winter months and for the most part temperatures have remained mild enough to prevent ice sheeting. This means that the larger concerns will be for stands that are starting to age and thin out due to other issues. This is one of those questions that comes up quite often. For those stands that are less than adequate (<40 stems per square foot), what are the alternative options or should the stand be terminated? 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. The disadvantage of this route is the decomposition of alfalfa and 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.
If you have questions on the above information, please feel free to email me at ndrewitz@umn.edu, or call at 608-515-4414. To receive future events, educational programming, and agronomic updates by email, signup at z.umn.edu/tricountysignup.