Adopting no-till and cover crops builds soil organic matter and shaves costs

Long before the carbon market emerged that offered economic incentives for farmers to adopt soil-conserving practices such as no-till and cover crops, Jack Boyer had already found the value of such practices.

In the mid-1990s, Boyer, a corn and soybean grower from Reinbeck, Iowa, started no-till planting his soybeans. No-till planting into commercial corn came later, as did his first on-farm experiments with cover crops.

The on-farm research showed him that cover crops could help him reduce chemical applications, cut nitrogen inputs, and eliminate the cost of cleaning buildups of eroded soil from waterways. All the while, cover crops were building soil organic matter.

"I initially switched from conventional tillage to no-till on soybeans to save labor," says Boyer. He and his wife, Marion, farm some 750 acres without outside help.

"I was also interested in moisture conservation because I initially farmed on really sandy soils," he says. "But now I farm highly productive soils."

Three-Pronged Goal

The Boyers' desire to leave soil in better shape than they found it inspired them to try cover crops. Most concerning was the degradation of soil organic matter after decades of tillage resulting from part of the farm's family history of being in a seed corn-soybean rotation.

The seed corn company for which the family grew seed required "black" soil conditions between the rows. "As a result, the soil had only 2.5% organic matter, as compared with 6% in the fencerows, where perennial grasses grew without soil disturbance," says Boyer.

A presentation at a conference inspired the idea that growing cover crops could build organic matter, even in tilled fields producing seed corn. "We had a three-pronged goal in growing cover crops," says Boyer. "We wanted them to build organic matter, control erosion, and improve nutrient cycling."

His first experiment with growing cover crops was to plant just 50 acres of annual ryegrass in seed corn. "I flew the ryegrass seed on in mid-September," he says. "It came up and looked good, growing 3 to 4 inches tall. But it froze out in winter. That's a problem for us because our goal is to have living roots in the soil as many days as possible."

Always committed to on-farm research, Boyer tried another trial the second year. He planted another 50 acres of annual ryegrass and an additional 50 acres of cereal rye in a different field. "The ryegrass froze out again," he says, "but the cereal rye grew up in the spring and grew rapidly after the temperature warmed to 50°F."

Thus, cereal rye became his go-to cover crop species, and today, 100% of the farm's acres grow a cover crop. A multispecies cover grows on a small acreage of land where Boyer grows cereal rye for harvesting the seed to use for his own cover crops. He also sells cover crop seed and uses some in the custom cover crop planting he does.

The July harvest of the rye for seed permits time for a warm-season multispecies cover crop mix to get established before winter and further build the soil. "I add rapeseed to the mix, and 25% of the rapeseed will overwinter; everything else will winter-kill," he says.

Boyer no-till plants all fields growing soybeans and commercial corn. He's also now able to use strip-till to plant seed corn because the production seed company relaxed tillage requirements.

Improved Soil Health

The combination of growing cover crops and reducing tillage has resulted in improved soil health. "Over the last 10 years we've seen soil organic matter increase by 1%," he says. "It now tests 3.5% organic matter, even on fields that are long-term seed-corn fields. Increasing organic matter improves water-holding capacity in the soil as well as increasing nutrient-holding capacity. It makes nutrients available for a longer period of time.

"Soil structure has improved, too," he says. "The soil used to have a plate-like structure, now it has a structure like cottage cheese. That allows more air into the soil, allowing more soil biology to live. And it allows water to infiltrate the soil."

Boyer noticed the benefits of improved water infiltration after just one year of growing cover crops. His early experiment with growing cereal rye was on a field that had been in a soybean-seed corn rotation for 70 years. "After a heavy rain, we would typically see water pooling on that field," he says. "But on the part of the field where we had 50 acres of cereal rye, there was no pooling after a big rain."

In addition to improved soil structure, "soil erosion is gone," he adds. "Before we grew cover crops, I'd have to clean out the waterways every seven years. I haven't had to clean them out at all since we started growing cover crops. That's money saved."

Another cost offset Boyer realized from growing a cover crop was the elimination of one herbicide application. In an on-farm trial conducted in cooperation with Practical Farmers of Iowa (PFI), he evaluated the effect of cover crops on weed control.

In one field he had strips of cover crops alternated with strips of no cover crops. All strips were to be no-till planted to soybeans. He terminated the cereal rye in some cover-crop strips 10 days before planting, and in other strips he terminated the rye 10 days after planting. "The rye was 24 inches tall when I planted the soybeans," he says.

In June, weed growth was evident in the soybeans planted where there was no cover crop but not in either of the two cover crop treatments. "At the end of June, I just sprayed the strips where there was no cover crop," he says. "That cost savings would have been more than enough to pay for the cost of the cover crop seed."

Boyer continued to experiment with letting the rye grow taller before terminating it. "I found that terminating the rye even when it was bigger resulted in no yield difference," he says. "The soybeans growing in the cover crops always looked like they were two weeks behind, but in the end there was no yield difference. My preference now is to plant soybeans into rye that's about 4 feet in height."

Reduced nitrogen use is another cost savings Boyer realizes from his no-till/cover crop system. "I've found that I can reduce by 40% the amount of nitrogen that I apply to corn," he says. "I believe the biological life in the soil is making the naturally occurring nitrogen more plant available. That savings more than pays for the cost of the cover crop seed."

Despite the reduced N use, Boyer has seen no decrease in yields in no-tilled commercial corn.

An additional potential savings results from nitrogen the cover crop scavenges and makes available to the subsequent crop. In a field trial Boyer did with PFI, he found that the cover crop captured 66 pounds per acre of N. "The cover crop prevents that amount of N from potentially leaching away," he says. "After terminating the cover crop in spring, the N then becomes available to the subsequent crop."

Reports of Boyer's and others' on-farm trials with PFI are at practicalfarmers.org/research/.

"I do public speaking on cover crops," adds Boyer, who was named a Soil Health Champion by the National Association of Conservation Districts. "By sharing my experiences — both good and bad — I hope I can help others learn to use cover crops to their advantage."

The new knowledge can help beginning no-till and cover crop users better position themselves to find possible opportunities in the carbon marketplace. "Adopting strip-till, no-till, cover crops, or finding ways to reduce N — each one of those is a step to get carbon credits," he says.