Planting a cover crop is becoming a more common decision for Midwest corn and soybean growers, but it is still far from routine. Nationally, U.S. farmers plant only 17.9 million acres to cover crops – approximately 4.7% of all croplands – according to the 2022 Census of Agriculture. The vast majority of fields still go bare after harvest.
That’s true in Iowa, as well, according to Iowa Farm Bureau. Farmers there seed about 3.87 million acres of cover crops in Iowa, roughly 16.7% of the state’s total corn and soybean cropland.
The gap there and elsewhere in the Midwest isn’t driven by farmer skepticism, according to Mark Licht, Iowa State Extension agronomist. Instead, he believes many farmers face unresolved practical questions: Which species fit where, and what can we realistically expect over time?
With some cover crops requiring planting as early as September, it’s not too early to be researching which cover crops are a good fit, he notes. Here are some considerations Licht addressed during a recent Iowa Learning Farms webinar.
Cover Crops Are a System Change, Not an Add-On
Licht says U.S. farmer interest in cover crops is clear, but the operational barriers are substantial. He stresses that they cannot simply be “bolted on” to an existing setup without shifting other variables. Adopting them successfully often means restructuring tillage systems, altering fertilizer programs, and adjusting herbicide use.
Because of this complexity, Licht urges farmers to start out using cover crops with specific management and agronomic goals for adoption. He argues you don’t “start with a pretty mix in a catalog” and then look for a use. Instead, you decide, for example: “I want erosion control and a soybean mulch,” or “I want something safer ahead of corn,” or “I want to tackle compaction,” then back from there into your selections. Here are some examples he referenced for consideration:
* Grasses/small grains for erosion and water quality
* Rye ahead of soybeans for biomass and mulch
* Oats/spring grains ahead of corn for fewer management headaches
* Brassicas for compaction
* Legumes where nitrogen contribution is a goal and herbicides allow
Keeping Mixes Simple and Focused
While complex cover crop mixtures are popular with farmers, Licht is not.He expressed some skepticism toward “kitchen-sink” blends available today.
“I personally am not a huge fan of a cover crop mixture that has more than five to 10 species,” he says.
Licht contends that when too many species are thrown together, the odds that all of them will work cooperatively to deliver their intended function drops sharply. He adds that large differences in seed size and density make it difficult to blend, meter and place seed evenly, which can leave some species too thin to matter.
Instead, he advocates for simple, targeted combinations aligned with clear goals. For erosion control, a small grain anchor like oats, rye, triticale, or wheat is good.
Ahead of corn, where growers want less risk of early-season competition, he would steer them toward a blend of oats, brassicas, and clovers rather than rye. Where nitrogen contribution is a priority and herbicide programs allow it, legumes such as crimson clover, hairy vetch, or red clover can be added to the mix.
Precision Seeding and Seeding Rates
Licht says that seeding details can make or break a cover crop stand. Small-seeded legumes like crimson and red clover need to be in the ground by early September to accumulate enough growth before winter frost. Furthermore, because their tiny seeds easily settle to the bottom of a drill box when mixed with large grains, broadcasting them requires careful calibration. Pairing them with intermediate-sized seeds, like radishes or hairy vetch, can improve uniformity.
Licht also challenges farmers to stop thinking about seeding rates for cover crops in terms of pounds per acre. Instead, he advises farmers to treat cover crops like cash crops, focusing on seeds per acre and pure live seed. The reason, he explains, is that stressful growing seasons can wildly alter seed sizes and germination percentages. Without testing seed and adjusting rates accordingly, a standard bushel may deliver far fewer viable plants than expected.
Timelines for Success: What to Expect
Licht encourages farmers to take time to understand what cover crops can offer in the short-term versus long-term biological benefits in soil health:
- Short term (1–4 years):
Farmers can expect visible improvements in nitrate capture, erosion control, infiltration and more “workable days,” especially when stands are well-established and management is dialed in. - Long term (5–10+ years):
Farmers can expect documented soil health improvements—organic matter, structure and measured infiltration.
Licht wants growers to see cover crops as a long-term system investment that delivers some fast payoffs in water and erosion, but that require time and management changes to show up in soil health data.
A Framework for First-Time Adopters
To navigate the learning curve with cover crops, Licht advises farmers to start small and isolate their trials. He recommends seeding about 20 acres on the home farm, ideally far enough from the main road that early missteps aren’t on public display, but close enough to watch carefully. This proximity lets growers experiment with seeding dates, termination timing, and adjustments to fertility or herbicides in a controlled way.
Ultimately, he notes, successful cover cropping requires a shift from a plug-and-play mindset to a systems-thinking approach. The growers most likely to stick with cover crops are those who treat the practice as a system change, start small, learn fast, and leave room for ongoing innovation.
