A lot of farmers associate conservation tillage with strategies such as cover cropping. Are cover crops necessary when practicing conservation tillage? According to Jeremy Swanson, the cover crop equation depends a lot on your local conditions—the types of soil on your farm and the amount of organic matter you’re blessed with.

Cover Crops and Organic Matter

Cover crops could be a whole different discussion, but not one that I’m comfortable going into a lot of depth on—I’ll explain why in a minute. A lot of guys do associate cover crops with strategies such as no till, as they both fit under the umbrella of stuff that people from the city call “green.” However, as I’ve found, there’s no one-size-fits-all approach to lumping strategies that you should use together.

I’m still learning about cover crops and how to best use them, while we have other farmers in the FCLG—Jason Doebelin and Jake Hendricks, for example—who have used them a lot. In fact, I bet they’d tell you that you shouldn’t be no-tilling without them. To me, I think the use of cover crops may depend largely on where you are in the country and the properties of your soil. Where I’m at, we have soils with very high organic matter, so I don’t think cover crops are as critical here as they may be in other parts of the country. We’re very blessed with our soils here in north central Iowa and we probably take them for granted a bit.  

Warming Up the Soil for Growth

Basically, the longer you can keep something growing on your ground throughout the year—earlier and later than you typically would—the more nutrient cycling you have going on in your soil. That will promote overall soil health, with more active soil biology, and this will also help warm the ground up earlier in the spring. If the biology is waking up, moving, and active, they’re generating heat, which in turn will help germination and nutrient availability for your no-till crop. 

You can also make the weed control argument. If you’re trying to get away from those early-season herbicides to kill emerged weeds, cover crops can help suppress them. Of course, unless you’re going to cut and feed your cover crop, you end up using a herbicide anyway to kill off your cover crop. But there’s still an advantage there when you can curb those pesky early weeds. And then there’s the tillage effect. Take tillage radishes, for example. They help break up compaction and condition your soil. 

Caution with Cover Cropping Ahead of Corn

When it comes to how cover crops fit into a strip-till or no-till scenario, I think they are something you use more on the no-till side. It’s more of a strategy to use ahead of beans than ahead of corn, at least in my area. I think it’s easier to cover crop ahead of beans, which would be the no-till acres, for the weed suppression benefits. And cover crops don’t have the potential detrimental effects on the beans that some cover crops can have on corn. 

There’s two big risks planting cover crops ahead of corn. First, your cover crop can start using up available nitrogen that your corn crop will need. And if you kill your cover crop during a certain window relative to when you plant your corn, you risk causing issues with your corn germination and early-season development. 

From FCLG: Several researchers, such as those at the University of Nebraska-Lincoln, have suggested that some cover crops, such as cereal rye, can also have allelopathic effects on corn. This is where one plant releases chemicals that can negatively affect the development of another plant. However, these studies have been done in laboratories and don’t agree on a conclusion. And, researchers point out both that corn is a large seed and that allelopathic residue degrades quickly in the soil. The general advice is to terminate a cover crop ten to fourteen days before planting corn to avoid any issues.

Flying High: Aerial Cover Crop Application

In our area, we’ll have airplanes fly on ryegrass over the top of corn for fields that will grow beans the next season. This generally happens in September, starting around the first of the month. There are not a whole lot of different mixes that go on around here; at least we’re not as adventurous as farmers are in some other areas of the country. Some guys are starting to use drones instead to fly on the seed. 

The problem guys up here have with cover cropping into corn that’s standing is that, depending on whether you get a rain and how much of the seed gets caught up in the corn plants, you might end up with a spotty stand. Obviously, you’re not actually planting the seed into the ground as you would with a planter. 

The other option would be to use a drill, of course. I guess that’s one of the reasons that cover crops aren’t particularly popular around here. If you have to go buy a one-hundred-thousand-dollar drill to apply a cover crop, I’m not sure what kind of return you could really expect. You could look for an older cheap box drill, but are you going to cover two thousand acres with that? 

Back to Earth: Cover Crops Come Down to ROI

Around here it’s just tough to see the ROI with cover crops. We’re already so blessed with such high organic matter in our soils here—our soils are very forgiving. Maybe it’s something we should look at more, but there just isn’t a huge push for cover crops in our neighborhood. A lot of the advantages that cover crops bring don’t help us as much here as they would in other parts of the country. For example, if your organic matter wasn’t three feet deep on your fields, I could see where cover crops would be a better investment. 

For us (in Iowa), I don’t think cover crops are something to just brush off. On our farm we’ve learned how to be successful with strip till and reduced tillage. With cover crops, I think we need to keep learning. Is there a way to adopt cover crops and take them to another level where they would make more sense for our conditions? Can we use cover crops to reduce herbicide usage? Can we use them to access more nutrients in the soil and reduce the amount of fertilizer we apply? 

Those are more questions than answers, but, if you think about it, that’s how it should go. Let’s not just assume that we’re all doing the best. The more we learn, the more we can make the overall system better for our farms.