Assessing And Reacting To Alfalfa Winterkill

Assessing And Reacting To Alfalfa Winterkill

May 1, 2009

Last winter was tough on alfalfa and winterkill will reduce forage production in many alfalfa fields this year. Damage is quite common north of the Platte River this spring. If you haven't gotten out in your fields yet to assess potential damage, this would be a good time. Act quickly and properly to minimize long-term losses.

If you find significant winterkill but decide to keep the stand anyway, following are a few options to increase forage production.

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

Interseeding Other Species

Annuals like oats and Italian ryegrass can be interseeded right away and summer annual grasses can be planted after first cutting. Perennials like orchardgrass, festulolium, and red clover can provide a long-term benefit, but won't add much production this year.

If you do interseed, competition by the remaining alfalfa for sunlight will be a serious threat to success. 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 is to harvest the alfalfa early. This will lower first harvest yield and may further weaken already stressed alfalfa plants, but it will allow sunlight to reach the new seedlings.

Depending on the degree of winterkill, a better option might be to wait until late summer to interseed. Alfalfa cut by early September regrows more slowly than spring alfalfa and will cause less competition with new seedlings. Fall planting will have a better chance of succeeding, provided adequate moisture is available.

Bruce Anderson
Extension Forage Specialist