Plant Cover Crops

Learning about the benefits of planting cover crops.

Chemical Use and Cover Crops

Can Cover Crops Become Weeds?

In a previous post I wrote that cover crops can suppress weeds.  And many farmers are planting them with that primary benefit in mind.

But, can cover crops become weeds?

Unfortunately, the answer is “yes, they can.”  Obviously we never want this to happen on our farm.  And with good management practices, we can lessen the possibility that it will.

Two species that require precise management are annual ryegrass and radishes. Both annual ryegrass  and radishes benefit the soil tremendously and have been shown to increase profit per acre, but both must be carefully managed as well. Specifically, there must be a comprehensive plan for terminating annual ryegrass. If you are not absolutely clear on how you are going to do this, you should not plant it. Likewise, with cover crop radishes, you need to be absolutely clear on what you are buying and when the seed should be planted.

It only takes a few annual ryegrass plants that produce seed to create a weed problem - especially if wheat is in the rotation.
It only takes a few annual ryegrass plants that produce seed to create a weed problem – especially if wheat is in the rotation.

This is why Hans Kok, from the Indiana Conservation Cropping Systems Initiative often tells farmers that are trying cover crops for the first time to start with a few acres of oats and radishes as a cover crop.  His thinking is that because both oats and radishes die over the winter that farmers will not have to worry about terminating the cover crop in the spring.  And I agree with Hans on this.

However, cover crops are becoming more popular and many producers are convinced that they are excellent at killing weeds and cover crops.  While Ag Chemical companies have shied away from making too many recommendations on killing cover crops, farmers are confident in their abilities to “figure it out” and make cover crops work on their farm.  Why use “boring” oats and radish?  Let’s use Annual Ryegrass!

Don’t get me wrong, Annual Ryegrass is a fabulous cover crop with tremendous value as a cover crop and forage.  But, it does take more management than many other cover crops.  Annual Ryegrass provides high reward with some additional risk.  On our home farm we sprayed our soybeans three times to make sure all annual ryegrass was killed.

Planting Radishes too early or planting the wrong Radish can create a problem with seed production on the radishes...and you don't want that!
Planting Radishes too early or planting the wrong Radish can create a problem with seed production on the radishes…and you don’t want that!

I’d love to hear your “formula” for annual ryegrass control. Have you noticed any difference with terminating annual ryegrass on different soil types? Different temperatures? Different additives? Different times of the day?

 

Cover Crops and Herbicide Carryover

University of Illinois Extension weed scientist Aaron Hager has published a couple of newsletter articles on the topic of herbicide carryover.  He will be publishing additional results in the future.

Be Aware of the Potential for Herbicide Carryover

and

Considerations for Fall-Seeded Small Grains

Thanks to Fred Iutzi, Manager, Value-Added Sustainable Development Center, Illinois Institute for Rural Affairs @ Western Illinois University for passing this information along.

Also see an excellent article starting on page 97 entitled Herbicide carryover concerns—Challenges from the drought will keep on coming written by Vince M. Davis, Department of Agronomy, UW-Madison/Extension.  Thanks to Rodney Hunt for making me aware of this article (and publication).

Terminating Cover Crops – Use Residual Herbicide

Terminating cover crops is part of the “stepped-up management” that using cover crops requires.  Over the past month I shot videos about killing annual ryegrass, killing crimson clover, and about the difference of killing cereal rye and annual ryegrass.  In each of the videos I examined the importance of killing the cover crop…and killing it dead.  Overall, most of the cover crop fields that I have seen had a very good burn down.  In more than a couple of instances it was obvious that the applicator missed a few (if not many) spots or strips.

Terminating Cover Crop Radishes

In the cover crop plots where Radishes were in the mix we now have plenty of Radishes in the corn!

But burndown is not all that we need to be concerned about.  In 2011 I saw photos from fields in Michigan that almost made my heart stop!

A corn field in southern Michigan had radishes that were taller than the knee high corn. And a field of soybeans had large radishes in it at harvest time.  Thankfully the corn field yield was not affected, but areas of the soybean field could not be be harvested.  At $12-13/bu soybeans that was an expensive lesson.

Applying glyphosate once a season without using a residual herbicide does not provide adequate weed control. These radishes germinated after the spring glyphosate application.

So how did these situations happen?  In both instances the producers used glyphosate for their burndown and did not  use (or had not yet used) residual herbicide.  Of course the radishes were not the only “weed” in the field, but it was the focus of the growers!

Terminating Cover Crops at Robison Farms

At Robison Farms in Central Indiana we have two issues going on in our fields this spring of 2012:

#1) Radishes are coming in the corn and soybeans, even though we did apply a residual herbicide!

#2) There are more annual ryegrass escapes than I’d ever like to see. We actually had very good burndown and we used residual herbicide too.  Note that these are NOT the only “weeds” that we have growing in the fields.  I cannot remember a year when we’ve seen so many winter annuals and broadleaf weeds survive residual herbicide.

My brother Don has been scouting our fields and he reports seeing ragweed, morning glory, cocklebur, Queen Anne’s lace,  and a variety of other broadleaf weeds across our 300 plus acres.  The weeds aren’t thick, but there are too many of them. So we’ve concluded that it is not “just the cover crops” that are escaping.

So what is the advice here?  Make a commitment to scout your fields for weeds, whether they be “cover crop species escapes” or other weed pressure.

  • Excellent weed control is vital for top profits in cash crops.
  • Use residual herbicide in corn and soybean fields.
  • Scout fields looking for escapes and other weed issues.
  • Terminate all escapes before they produce viable seed.
  • Realize that cover crop radishes do have hard seed and you most certainly will see radishes in the spring.
  • Oilseed crops (brassicas like radishes, turnips, rape, canola, kale, mustards) can stay viable in the soil for years. Scout each year in fields where you have had these brassicas.
  • Scout for brassicas later in the season as well.  This should not be an issue but don’t take a risk of losing acres of soybeans.  The soybean field in Michigan had no residual herbicide applied but the radishes that caused the problems came up later in the season (probably late July or early August gauging from their size at harvest).
  • In some years like 2012 (even if you did not use cover crops), you will have more weed pressure than other years.  Eliminating all weed pressure is important!
The casual drive-by look at this plot looks like we achieved a great kill on this annual ryegrass cover crop. The corn looks great, the grass looks brown and dead, but...
...in more than one area I found annual ryegrass "escapes" that are heading out or nearly heading out. These plants need to be sprayed right away so they will not produce viable seed.

 

Chemicals to Watch Out for when Planting Cover Crops

A few weeks ago I spoke at a meeting in Tipton County, IN about what chemicals to watch out for when a producer was following corn or soybeans with cover crops.

My instruction then and now is – “Follow the label” AND “talk to your chemical supplier” about what is safe for planting brassicas, clovers, peas and grasses.

And I want to make it very clear – I AM NOT A CHEMICAL EXPERT.  I will, however, search for answers. I’ve asked a few chemical companies for their help in getting some information out about how their chemicals work with cover crops, but I’m getting no response.

So here’s the protocol I’ve been following. Each time I get a chemical question,  I perform an internet search on that product, find the MSDS sheet, and then pass along the findings.  I’m glad to help and I’m thankful for the internet that helps me help producers.

However, we now have a few tools that can be quite helpful for all of us. 

My friends Hans Kok and Dan Perkins passed along this Corn and Soybean Herbicides and Fall Cover Crop Establishment (Penn State) chart that I believe most producers will find easy to read and helpful.

Another helpful article is from Kansas State which talks about chemical carryover after a failed corn crop.

There were also two excellent University of Wisconsin publications sent to me from Kevin Shelley who works with the UWEX Nutrient and Pest Management Program.

The first publication is Herbicide Persistence and Carryover, by Jed Colquhoun, which provides general information on persistence and the potential for carryover to a subsequent crop associated with herbicide chemical families as well as soils, environmental conditions, and management.

The other publication that Kevin sent is the PDF for A3646.  In the appendix, Table 2 provides a concise listing of the Planting Intervals for Rotational Crops associated with most of the herbicides used on field crops in Wisconsin.  It is based on label information from the products listed.  This may be somewhat useful for some of the species used as cover crops.

It’s time to plant cover crops in much of the Midwest, so let’s be sure that our chemical program from this past spring does not stand in the way of our success!

Photo diary- Corn after a cover crop (after corn)

“Planting this corn field was like planting into a garden” said my friend Dave.   He has been a ‘cover cropper” for six years now.  This year Dave no-tilled approximately 50% of his acres.  Dave is one of the most innovative guys I know…but he’s also “cautious”; he does not want to lose money!  That’s why Dave loves cover crops…using cover crops he has improved his profitability.  In this photo diary we will look at photos from April, May and June where Dave had a cover crop consisting of Oats/GroundHog Cover Crop Radish/AU Robin Crimson Clover.  The previous crop was corn.

An April view of the field with the AU Robin Crimson clover that over wintered. The oats and GroundHog Radishes had died out over the winter as expected.

 

A May photo of Crimson Clover that could not be killed yet because the field (and all other fields in the area) was too wet to spray. Normally by the date the photo was taken the Crimson Clover would have been dead and the corn would have been planted.

 

No-Till Corn on Corn planted into Oats and AU Robin Crimmson Clover