Purdue Explains Herbicide Use for Cover Crops

In a recent post, Purdue University researchers posted an article on the use of herbicides on cover crops. Herbicide manufacturers don’t address cover crops, per se, so Purdue is offering some new insights.

Here’s a portion of the article. Click here to see the entire article, which includes a chart with different cover crops and herbicides used for burndown.

One question that has been brought up in recent cover crop situations is replant timing when cover crops are planted after the use of residual herbicides used in corn or soybean. There are several plant species being promoted for the use of cover crops. Some of the plants include annual ryegrass, wheat, buckwheat, clovers, radish, cowpea and vetch. Information regarding effects or corn and soybean herbicides on these species is somewhat lacking. Herbicide label rotation restrictions often require substantial waiting periods before these species can be planted. These waiting periods are to assure that residual effects from the herbicide do not impact the following crop, the buyer (finished product) or livestock negatively. In some cases plants used as cover crops fall under the ‘other’ or ‘not listed’ category requiring the maximum duration before planting.

However, in recent conversations with the Office of the Indiana State Chemist we have learned the following. If the cover crop is not harvested, used as feed for livestock or sold in anyway and that the cover crop is terminated in the appropriate manner or left in the field, that the rotation restriction does not apply [personal communication Office of the Indiana State Chemist]. It comes down to the definition of a ‘crop’ and that a ‘cover crop’ is not really used as a ‘crop.’ Label rotation restrictions are in place for crops that are going to be harvested, cover crops are to be destroyed in the spring, left in the field or winter killed. The purpose is in having it there, but there is no finished product at the end of the season. However, because the company selling the herbicide does not recommend or approve a rotation other than the ones listed on the label, the company selling the herbicide is not liable for any injury or germination problems seen in the cover crop.

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2 Responses to Purdue Explains Herbicide Use for Cover Crops

  1. Mark Dodd says:

    I need additional information and advice. I want to interseed a covercrop in silage corn.
    But.. I do not know what herbicides that will work for me
    Rules are
    1. Non GMO seed
    2. No use of atrazine
    Can anyone give a recommendation on what kinds of herbicides to use in this case. Thanks Mark

    • Tim Buckley says:

      Mark,
      Interseeding annual ryegrass into corn at V5 is still in the early stages. Herbicide trials have been conducted by Penn State and ones are planned for the Midwest in 2015.

      Glyphosate for a burndown and Verdict (BASF product) preemerge has worked and is a popular option in Quebec. However it has not always worked- good stand in June but no annual ryegrass in August. Don’t know if it was residual herbicide or something else. Strongly encourage you to limit acres until we know more.

      Check out Penn State interseeding web site.

      Dan Towery
      AG Conservation Solutions
      765 490-0197

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