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The benefits and challenges of cover crops

This time of year I like to assess the previous growing season and see what lessons we can bring forward. The 2016 planting season started early and finished fast for most of our territory. One thing I noticed is now that cover crops have become more popular, growers are finding a few management challenges to consider.

There have been a several factors driving the adoption of cover crops. There is an incentive from local farm agencies ranging from $20 to $35 per acre, depending on what county you are in and what cover crop mix you plant. There is also increasing evidence of weed-control benefits from cover crops. And finally, I see an increase in general conservation efforts focused on runoff prevention and soil quality. Dr. Kevin Bradley and his team with the University of Missouri have been looking at cover crops for the past few years to determine what weed control benefits producers are seeing (you can see their work here:

In the past, I have mentioned on this page that using Italian ryegrass as a cover crop is a bad idea. That still holds true today. Italian rye can become a major weed with the ability to evade common control tactics, including evolving into a multiple herbicide-resistant plant. Although its growth characteristics are ideal for cover crops, its cons outweigh the pros.

During the spring of 2016, growers ran into challenges with cover crops planted the previous year. Some producers were planting into standing rye, partially killed rye, dead rye, clovers, etc. You name it, someone was doing it. This year these efforts worked. They worked better than I thought they would. I saw several fields planted in challenging conditions that ended up with ideal crop stands, emergence and weed control. I also saw several fields that looked much less than ideal. I am a firm believer that you need to have cover on fields in the off-season. I believe that cover crops allow us to meet that objective. I am, however, in favor of killing that cover crop before planting into it.

Here’s why. Early in the spring, it can take a while for cover crops to die from herbicide applications. I had the chance to walk a field this year and see something that I have only read in textbooks: a recently planted corn field where the corn was emerging, then dampening off. Upon further investigation, I found the grower had terminated the cereal rye, waited two weeks, and then planted corn. The trouble was with the corn that got planted at the base of cereal rye plants. These corn seedlings were dying off. As I looked over the field, I noted that the cereal rye was still green at the base. Cereal rye has been documented to have an allelopathic effect on corn. My recommendation is to avoid cereal rye before corn—use a different cover crop to avoid the risk of a yield hit. Additionally, if cereal rye is used before going into a non-corn crop, make sure the cereal rye is killed at least two weeks before planting the crop—not just sprayed two weeks prior. The cover crop should be dead, and I mean graveyard dead.

Another aspect that may be overlooked after a flourishing cover crop are the effects it might have at harvest. Last fall I got the opportunity to see some of the on-the-go learning that comes with cover-crop management. When it comes to cover crops, harvest disruption is something you probably don’t hear about too much. In this case, a cereal rye crop was balling up, causing a slower harvest than one would like. Of course, this wasn’t by design, but it was a struggle nonetheless.

Yes, I am a firm believer in cover crops. I believe they bring multiple benefits. It’s not just a soil conservation benefit, but moisture, weed control and organic matter, too.

A cover crop rotation can bring benefits, but there will be lessons along the way. Right now, agronomically speaking, I think we may have more questions than answers, but I believe you should give them a try. Start on a small field. Your top choice might be a highly erodible parcel or a field with the low organic matter. It’s a place to start.

There are a lot of resources available online, but this one will lead you down the right path:

If you have any further questions, please feel free to visit with your local MFA or AGChoice location.

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