This article was originally published in the November issue of Illinois Field & Bean magazine.

Do cover crops work? That depends on the definition of “work,” according to Todd Steinacher, Illinois Certified Crop Advisor (CCA) and ILSoyAdvisor Content Coordinator. But that definition varies from farmer to farmer and even field to field.

“Cover crops can help farmers achieve a variety of goals, like stabilizing soil, suppressing weeds or reducing compaction,” says Steinacher. “But the cover crop has to do what it was intended to be considered successful.”

Steinacher, based in central Illinois, fields questions about cover crops every year, especiall as interest increases.

Survey data shows about two-thirds of Illinois farmers are aware and at least somewhat knowledgeable of cover crop management, according to Julie Armstrong, Executive Director of the Illinois Nutrient Research and Education Council (NREC). She reports Illinois cover crop acreage nearly doubled from 710,000 acres in 2017 to 1,410,000 acres in 2019 based on USDA data.

For those trends to continue, Steinacher stresses the importance of understanding the reasons for a cover crop and then managing toward those goals.

“Why do you want to use a cover crop?” he asks. “The answers help farmers figure out where to get more information and how to customize cover crops for their production systems.”

What can cover crops do?
Steinacher describes several goals cover crops can address, but he stresses that management is critical.

“Given their cover crop goals, farmers can select and implement a seed mix and planting and termination management strategies to meet those goals,” Steinacher says. “That process may require a bit of trial and error, but stated goals help farmers figure out what does and doesn’t work for them.”

For example, he explains that cover crops can help stabilize soils. That goal requires use of grass crops like ryegrass, with a root system that holds soil in place, no winter kill and spring longevity of above-ground vegetation, rather than tuber crops like radishes and turnips. But if the goal is addressing soil compaction, scavenging nitrogen to store it for the next crop or providing winter grazing for cattle, including tubers in a mixture of species will be much more effective than grasses alone.

If the goal is weed suppression, Steinacher says a cover crop that produces significant organic matter like ryegrass makes sense. Terminating it by crimping the ryegrass prior to or during planting lays down a mat of organic matter between crop rows to control weeds.

How do cover crop goals translate in the field?
“My initial reason for using cover crops was to protect fragile, sandy soils,” says Jeff O’Connor, who farms near Kankakee, Illinois. He has been incorporating cover crops into his production system for about a decade. “The concept was familiar to me, because my dad and grandfather both used cover crops for that reason.”

Steinacher notes that cover crops reduce all types of erosion common in Illinois. They minimize washouts and visible gully erosion from heavy rains. But cover crops also protect against hard-to-see or measure sheet erosion, which carries away a thin layer of organic matter even in flat fields.

“Once I felt I had success, fully protecting the soil from wind and water erosion, I noticed fields with cover crops had less weed pressure than others,” O’Connor says. That observation prompted him to use cover crops in more fields.

“I first chose to expand cover crops in a field that didn’t have road access,” he remembers. “Farming is very visual, and covercrops look different. That can be a hindrance to adoption. So, I started in a less noticeable field. Weed control improved there, so I continued to plant cover crops ahead of soybeans.”

His next discovery came when he looked at his soil through a microscope with a new employee from his local Soil and Water Conservation District in early spring.

“I was blown away by the activity in the soil,” O’Connor says. “I had no idea what was happening in the soil, but if I can keep my factory working through fall, winter and early spring, that’s betterfor soil productivity.”

Steinacher explains that soil microbials are active when soil temperature is above 50°F, but they need roots to feed on. He adds that cover crops build organic matter in soil, which acts as the sponge that holds all the nutrients and microbial life that gives soil flexibility and resiliency.

O’Connor has discovered these benefits helped him achieve other goals for his fields, like increasing water filtration rates and reducing nutrient loss.

“Wetter fields consistently dry out better than they used to,” he explains. “Year after year, I am finding that pattern drain fields have seedbeds that are ready to plant earlier in the spring. I believe that having cover crops as part of my system for years contributed to 2019 being my best year for soybeans despite the weather challenges.”

He adds that when he looks at his emerged cover crops, he can see where his striptilled corn left unused nitrogen. The cover crop pulls it out of the soil, preventing leaching.Research shows that nutrients scavenged by cover crops is typically available to the following crop in June or July.

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About the Author: Laura Temple