This field is home to eight cover crops: annual rye, radishes, crimson clover, cahaba vetch, triticale, turnips, blue lupine and volunteer wheat.

Addressing spring cover crop questions

I have had several questions through the winter on cover crop removal. I have experience with Austrian winter pea and annual ryegrass in some of my cover crop work at South Charleston at the OARDC Western Agricultural Research Station. Winter pea is easy — just apply your normal burndown of glyphosate, atrazine and favorite pre-emergent grass product for corn. My procedure was typically to plant, then immediately spray my burndown mixture, and this was very successful.

Annual ryegrass on the other hand was difficult. In reading the limited literature on control, it seems others have difficulty, too. The best nearby information I can find comes from the Weed Science group at Purdue University. I will quote below from a couple of their fact sheets.

From the Successful Cover Crop Termination with Herbicides bulletin, WS-50-W: www.extension.purdue.edu/extmedia/ws/ws-50-w.pdf. Annual ryegrass (Lolium multiflorum) has become a very popular cover crop throughout the Midwest. Do not confuse annual ryegrass with cereal rye (Secale cereal L.). Annual ryegrass can be an ideal cover crop because of its ability to rapidly germinate in the fall, grow aggressively in the spring, and add substantial root and forage mass to the soil profile.

However, this plant’s aggressive and competitive nature makes it a potential weed problem in production crops. The introduction of annual ryegrass as a cover crop in Indiana and the possibility of it escaping as a weed is a concern. Annual ryegrass has established itself as a weed in orchards, vineyards, and grain crops throughout the western and southern United States and is recognized by multiple scientific weed societies as an invasive weed species. Annual ryegrass is also able to quickly adapt to herbicide selection pressure. The international weed survey (www.weedscience.org) reports herbicide-resistant annual ryegrass populations in 10 states and across six herbicide modes of actions.

While you should take care when planning the termination for any cover crop, you should be especially vigilant when planning a termination application for a cover crop that includes annual ryegrass. Follow these guidelines for successful termination of annual ryegrass cover crops:

  • Apply herbicides when annual ryegrass plants are no taller than 6 inches.
  • Increase the herbicide rate if applying to annual ryegrass that is taller than 6 inches.
  • Make all efforts to terminate the annual ryegrass crop prior to jointing.
  • Use translocated herbicides to achieve complete ryegrass termination, including the plant’s underground reproductive structures.

Purdue completed some additional trial work in 2014 and reported this past fall on controlling Annual ryegrass with herbicides: https://www.extension.purdue.edu/extmedia/WS/WS-52-W.pdf.

Here I quote again from Purdue University weed scientists. Purdue research has shown, and we strongly recommend, that you use at least 1.25 pounds acid equivalent per acre of glyphosate (36 fluid ounces Roundup PowerMax) to terminate annual ryegrass. Under less-than-ideal conditions, rates of 2.5 pounds acid equivalent of glyphosate are preferred.

You may consider tank mixing herbicides to help control other weeds or cover crops present in the field. Purdue researchers evaluated a variety of tank mixes.

  • Mixing 1 ounce per acre of Sharpen with 1.25 pounds per acre of glyphosate provided the most consistent control of annual ryegrass at all application timings
  • Adding 2,4-D, dicamba, and Basis Blend did not increase or decrease termination efficacy compared to glyphosate alone
  • Adding a PS-II inhibiting herbicide (atrazine and metribuzin) can result in antagonism of glyphosate and fail to terminate the annual ryegrass.

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6 comments

  1. Jeff Sberna J&D FarmBuilt LLC,

    I find that Ag. publications only seems to publish articles more directed to no-till. farming. I have found that annual ryegrass can is surprisingly easy to turn under in the especially when applied during your primary tillage. When you chemically eradicate your cover crop you loose some of the major benefits of your cover crop.
    Jeff Sberna
    J&D FarmBuilt LLC.

  2. I hate to publicly disagree with Jeff Sberna, but the idea that plowing under a cover crop is the way to get the most benefit from it is absurd. That is 1950s thinking. Among many benefits of cover crops, the root growth adds organic matter to the soil. Plowing aerates the soil, with a net loss of organic matter. Some cover crops (but not annual ryegrass) can be killed by rolling at the right growth stage. Applying a herbicide does not “eradicate” a cover crop; the nutrient values and soil protection are still there. Learn more at the Apr. 6 field day (OhioNoTillCouncil.com).

  3. Another thing against Jeff’s advice – one of the big advantages of chemically terminating cover crops

  4. Here’s the rest of my comment – when you plow down a cover crop or disk it in – you immediately start to burn up the organic matter that you accumulated with all the fine roots associated with many of our grass cover crops. You want to build up your organic matter in the soil and you can’t do that with tillage. tillage encourages the bacteria populations in the soil to build up rapidly and attack the lush green cover crops. This results in the carbon in the soil being converted to C02 and that contributes to our greenhouse gas problem.

  5. I will side by side you theory anytime and I have.

  6. Anaerobic Bacteria

    aerobic-and-anaerobic-bacteria-1The first and most common bacteria would be the anaerobic bacteria, Obligate Anaerobes. They are capable of living in places void of O2 and most will die in the presence of oxygen. Some agile bacteria are Facultative Anaerobes. These are able to live both in and out of an oxygen laden atmosphere but they are rare microbes. Clostridium, for example, is one bacterial genes that does not need oxygen to survive. Everyone’s smelled anaerobic decomposition inside the refrigerator on occasions. So to, we have all smelled the offensive odor of this culprit coming from an old garbage can. Byproducts of their anaerobic decay involve hydrogen sulfide which smells like rotten eggs, butyric acid which smells like vomit, ammonia which will set our nostrils reeling, and vinegar. Anaerobic conditions foster pathogenic bacteria and kill off beneficial aerobic bacteria.

    .

    Aerobic Bacteria

    The second bacteria type and the most important for live organic horticulture, is the aerobic bacteria, or Obligate Aerobes. Though respiration is crucial to life, the precise function that oxygen plays to maintain life is not readily understood. Essentially, in a microorganism that is capable of using it, O2 enables food compounds to be totally digested. This ensures that every possible amount of energy will be used for maintaining the cell. So the aerobic bacteria have the advantage of metabolic efficiency. Aerobic bacteria can create twenty times more energy, with the equivalent amount of organic compounds, than anaerobic bacteria. What is more, aerobic bacteria aren’t generally known to produce horrible odors. One bacteria in the order of Actinomycetales, genus Streptomyces called actinomycetes, generate enzymes with volatile compounds which gives earth a fresh, clean smell. This is the good quality soil we smell when we instinctively hold a fist full of substrate up to our nose. Interesting how harmonious bacteria agree with us instinctually.
    I think this proves my point well and disproves yours.

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