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The Illinois Nutrient Loss Reduction podcast explores efforts to reduce nutrients in Illinois waterways from agricultural runoff to municipal wastewater with host Todd Gleason and producers Rachel Curry, Nicole Haverback and Luke Zwilling with University of Illinois Extension.
Read the blog at extension.illinois.edu/nlr/blog.
NLRS 85
This episode of the Illinois Nutrient Loss Reduction Podcast examines the crucial role of timing in cover crop establishment through discussions with regional farmers Adam Dahmer, Brent Fowler, and Greg Thoren. The speakers emphasize that optimal seeding dates depend on geographic location and operational goals, highlighting tools such as the Midwest Cover Crops Council's county-specific seeding charts. The panel explains the biological mechanics of fall planting, where autumn-seeded crops enter survival mode to establish subsurface root systems below the frost line rather than producing top growth. They detail management strategies for various conditions, including adapting to late harvests, utilizing aerial seeding, combining cereal rye and winter wheat with oats or legumes for winter protection and soil health, and accounting for local weather challenges.
* Adam Dahmer, Williamson County, Illinois Farmer
* Greg Thoren, Jo Davies County, Illinois Farmer
* Brent Fowler, McDonough County, Illinois Farmer
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Todd Gleason: This is the Illinois Nutrient Loss Reduction Podcast, Episode 85, Cover Crop Conversations: When to Seed a Cover Crop. I’m University of Illinois Extension’s Todd Gleason. Today, in part four of our Cover Crop Conversation series, we examine the crucial role of timing when establishing a cover crop. We’ll hear again from Adam Dahmer of Southern Illinois, Brent Fowler from West Central Illinois, and Greg Thoren from the state’s Northwestern Driftless region.
In this segment, the farmers emphasize that an optimal seeding date is heavily dependent on geographic location and the specific agronomic goals of the operation. They’ll highlight practical tools, like the Midwest Cover Crops Council’s county-specific seeding charts, to guide these planting decisions. The panel explores the biological realities of fall planting, noting that autumn-seeded crops enter a survival mode focused on root establishment below the frost line. The three will detail how this subsurface root development is essential and provide practical management tips on strategies, seeding equipment, late harvest, companion crops, and harsh winter winds. We’ll begin in Southern Illinois with Adam Dahmer and work our way northward.
Adam Dahmer: Seeding date is extremely crucial, and it depends on where you’re at. The Midwest Cover Crops Council has a seeding date chart on their website that is an excellent tool. Each year is different. Like I stated, we got our beans planted much like double-crop beans last year—the end of June, first of July. And then we were able to drill ryegrass after that. Was I gambling? Absolutely. I’m not going to deny that. However, I was also paying attention to my warm soil temperatures that I still had going into the fall. Had I had a cooler, wetter fall, I would not have had success, and I would have had to pivot and change my plan.
Where I’m at geographically, and this stands true for most of the state, you can take cereal rye up into mid-November. You’re going to see minute top growth, but as long as your roots are below the frost line, your roots are going to continue to grow. Keep in mind, the reason we plant cover crops in the fall is because anything seeded in the fall—much like when you’re seeding pasture or hay ground—goes into survival mode. It is setting roots. That’s why we want to seed in the fall. When we plant in the spring, it goes to top growth because it’s chasing reproduction.
With the enhancement of cover crops in the soil, root growth is crucial because that’s where we pull about 56% of our organic matter. That’s how we work this ground and create better aggregate stability through root development. When it comes to seeding dates, you have to keep in mind that your legumes will shut off before your cereals. Crimson clover shuts off earlier than vetch in my area most of the time. Ryegrass, I can push into mid-October without any problem. Cereal rye, we take longer.
If I’m going in front of corn and I want to see crimson clover succeed, we’ll put oats in there with it. Spring oats, as a rule of thumb, grow pretty rapidly in the fall. What we’re doing is trying to protect the crown of that ryegrass or crimson clover from the cold, harsh winds. By those oats taking off and growing, we’re able to minimize the amount of cold weather kill because we have protected that plant. You have to adjust your seeding plan to make sure you are setting yourself up for success.
When it comes to a late harvest, guys have to remember there’s more than one way to get from point A to point B. That’s when we pull out our aerial seeding and get it established. Ideally, we harvest corn with four to six inches of growth on our cover crops. As soon as the sunlight hits it, it blows up and we’re happy. Do we have success every year? Absolutely not. But eight out of ten years, we have pretty good success.
Todd Gleason: That’s Adam Dahmer from Williamson County in deep Southern Illinois. We’ll move to West Central Illinois in just a moment. But first, if you’d like to find more from that Midwest Cover Crops Council tool, you can do so easily enough. The address online is midwestcovercrops.org. Now let’s hear from Brent Fowler and his discussion points for seeding a cover crop in the fall.
Brent Fowler: We used to worry about getting our cereal rye seeded as soon as we could until that picture of me standing in the chin-high rye happened. Now I’m not quite so paranoid about getting it seeded early. We try to do it as early as possible, but with cereal rye, which is what we use the most of, it also depends on what part of the state you’re in. Greg and Adam can definitely attest to that. Look how different the stories are going to be between the three of us. But in the middle of Illinois, we’ve seeded cereal rye in November. It doesn’t get very tall a lot of times in the wintertime, but it always seems to come back in the spring.
Todd Gleason: From Brent Fowler in West Central Illinois, we’ll now move to Greg Thoren in Jo Daviess County in the far northwestern part of the state.
Greg Thoren: I’ll keep it short and sweet. They covered this very nicely. Up here in Northwest Illinois, the answer to the question—not knowing exactly all the seedings and different things—is I agree that we’ve actually seeded cereal rye even the first couple days of January in particular years. That one year, I think there were only a couple of months we did not have the drill in the field. As far as the spring, we had an earlier spring too.
What we’ve seen this year, we have quite a number of acres of cereal rye with the dryness, and sometimes we’ll even use winter wheat as a cover crop. It’s not exposed above the ground; the root system is there. I definitely agree with Adam that these overwintering crops will put that root system down. They do not get much top growth. That’s how they’re designed. Depending on what was put down, if it was a winter cereal, it will be there in the spring. If you do have cereal rye, wheat, or triticale, it will grow and be there in the spring as long as your germination test on your seed was good. The quality of seed, of course, makes a difference.
What we try to do even after soybeans—and usually we harvest soybeans around the 25th of September on—is we’ll try to get the summer annuals with just a dab of wheat in there that will go into corn the following spring. We’ll try to get at least four or five different families in there, some legumes, and even some brassicas. We know we won’t get a tremendous amount of growth before frost, depending on when that might come any particular year. But we get the different families in there, and basically, you’re inoculating that soil. Even though you may not have that flush of real tall, lush growth, that seed and the roots will inoculate that soil. Biology-wise, it changes things enough that it is very advantageous for the corn crop the next year.
Todd Gleason: You’ve been listening to some practical advice on when to seed a cover crop. It’s part of our cover crops conversation series here on the Illinois Nutrient Loss Reduction Podcast. Our program is produced in collaboration with University of Illinois Extension’s Rachel Curry, Nicole Haverback, and Luke Zwilling. Until next time, I’m your host, Todd Gleason.