Assessing And Reacting To Alfalfa Winterkill

Assessing And Reacting To Alfalfa Winterkill

Last winter was tough on a lot of alfalfa fields and many suffered winterkill damage. Assessing your stands now and acting quickly can help you minimize long-term losses.

If you find significant winterkill, but decide to keep the stand anyway, consider these options to increase forage production:

  • For fields planted last year, simply interseed more alfalfa in thin spots.
  • For older fields, autotoxicity and other problems make interseeding alfalfa risky, but other species can be added.

Annuals like oats and Italian ryegrass can be interseeded right away, or plant summer annual grasses right after the first cutting.

Perennials like orchardgrass, festulolium, and red clover can bring long-term help, but won’t add much to this year’s production. If you do interseed, competition by the remaining alfalfa for sunlight could be a serious threat.  It only takes about one week of shading by a full alfalfa canopy to kill seedlings below.  About the only way to open up that canopy once it develops is to harvest the alfalfa extra early.  This will lower first harvest yield and may further weaken already stressed alfalfa plants, but it’s the only way to get enough sunlight to the new seedlings.

In some situations it might be better to wait until late summer to interseed. Alfalfa cut in late August or early September regrows more slowly than spring alfalfa, thus causing less competition. Interseeding right after that harvest has a better chance of succeeding, provided adequate moisture is available.

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