It’s been said that soil without biology is just geology—an accumulation of lifeless minerals unable to spawn healthy plant growth. And as intense monocropping production practices increasingly remove more life from the ground than they return, it sends that soil closer to fossilization via what conservationist Barry Fisher calls, “the spiral of degradation”: eroded, compacted and, eventually, dead.
But if a pair of Land Stewardship Project meetings held in southeastern Minnesota recently are any indication, a number of farmers don’t see such a downward plunge as written in stone. Fisher and other soil health experts at these meetings strongly encouraged the standing-room only crowds to return as much biology as possible to the ground beneath our feet. And in most cases, that means making it so living roots are present 365-days-a-year.
“So when in doubt, you plant,” said Fisher, who heads up the USDA Natural Resources Conservation Service’s Soil Health Division for the central part of the U.S. Until recently, he headed up a soil health partnership in Indiana that has made that state the leader in cover crop establishment.
Indeed, through presentations, panel discussions and networking, farmers participating in the southeastern Minnesota meetings focused on a key soil health improvement strategy that is based on Fisher’s advice: cover crops. During the past five years, there’s been a lot of excitement generated around the growing of these non-cash crops on corn and soybean fields before and after the regular growing season. These crops, which are often small grains such as cereal rye or brassicas such as tillage radish, have proven to be very effective at not only building soil health, but also keeping it from washing and blowing away in the first place. In fact, erosion control is the number one reason farmers begin experimenting with cover crops, according to Sarah Carlson, Midwest Cover Crops Coordinator for Practical Farmers of Iowa.
Fisher, who was long involved with promoting no-till farming in Indiana, said that in recent years farmers have noticed that not even this cutting edge system was enough to keep soil from eroding. No-till protects fields from disturbance, which is important, but it doesn’t always provide the biological activity needed to create stability within the profile. And once a soil is eroded, it’s difficult to do anything else with it.
“You can’t really build soils if there is erosion,” said Jay Fuhrer, a Natural Resources Conservation Service soil health expert in North Dakota. “You have to stabilize it first.”
That’s what southeastern Minnesota corn and soybean farmer Myron Sylling discovered a few years ago. His family transitioned to no-till in the 1990s to save time and soil on the rolling hills they farm near Spring Grove. It worked—at first. Then he started seeing significant soil loss during intense rainfalls in areas of the fields where there was concentrated flow of water. In the fall of 2012 Sylling borrowed a neighbor’s no-till drill and planted winter rye in those concentrated flow areas. The following spring, where Sylling had no-till corn with 100 percent residue cover, there was still erosion; on the cover cropped acres, he lost virtually no soil and weed control was better than before.
“Today we are doing 600 acres of cover crops on our farm operations,” Sylling told the meeting participants. “Our erosion issue is basically eliminated.”
This is particularly good news given that replicated trials are showing that cover cropping does not lower the yield of cash crops. Carlson shared the results of a seven-year study in Iowa showing that 38 out of 46 times corn and soybean yields were not significantly different when planted after a cereal rye cover crop. A handful of times, the cash crops actually saw an increase, and the yield hits only occurred in the first two years of the study, something Carlson blamed on “lack of experience” with cover crops.
The Iowa trials closely track results of a survey of 2,020 farmers from across the country that was released last month. During the 2015 crop year, survey respondents found corn yields and soybean yields, respectively, increased an average of 3.4 bushels and 1.5 acres per acre after cover crops were grown on the same field. It's a system that tends to build on itself: yield increases for corn rose to 8.3 bushels per acre after cover crops had been used for more than four years in a row on a field. In soybeans, the average yield gain increased from 0.1 bushel per acre after a single year in cover crops to 2.4 bushels after four years of cover crops.
Farmers and conservationists are also a fan of cover cropping’s ability to soak up excess nutrients such as nitrogen, keeping them from becoming water pollutants while making them available to growing plants later in the season.
If cover cropping does so much for the soil and has the potential to increase yields, then why are relatively so few farmers across the U.S. using it? Although there has been some recent growth in plantings, one estimate is only around 2 to 3 percent of cropland in states like Minnesota and Iowa are cover cropped on a regular basis, which tracks national statistics.
One issue is economics. Farmers who presented at the LSP meetings cautioned that producers need to budget in the cost of seed, fuel and time when considering cover crops. Jim Purfeerst, who has been using cover crops on his corn and soybean farm for the past few years, estimated that interseeding into his standing corn, for example, cost around $39 per acre. When he experimented with applying the seed with a helicopter, the cost went up to $65 an acre.
“In my mind, that’s too much money to have in these cover crops,” said Purfeerst, who farms near Faribault, Minn. “It might have been okay with $7 corn, but now where the commodity prices are at, we’ve got to get this down to $20 or $25 per acre to plant cover crops.”
Northern Iowa farmer Jack Boyer said one way to justify the expense of cover crops is to consider their ability to provide low-cost weed control. He estimates that cover cropping saved him $10 per acre last year in herbicide costs because it suppressed water hemp. A farmer also has to consider the cost of losing chemical inputs that are washed away from soil lacking cover crop protection.
One way to get economic value out of cover crops is through livestock grazing, something farmers in North Dakota’s Burleigh County have done quite effectively. Fuhrer, who helped develop a nationally recognized soil health team in that county, said that even crop farmers who don’t own livestock have added economic value to cover crops by partnering with their livestock-owning neighbors. The cover crops not only provide cheap feed for the livestock, but the animals build soil health further by depositing urine and feces while stomping biomass into the ground. “The livestock have been just a tremendous tool,” said Fuhrer. “I used to think they were important—now I think they’re essential.”
Kaleb Anderson agrees. When he came back to his family’s Goodhue, Minn., farm after college, he was looking for a way to get integrated into the existing business. Anderson saw an opportunity to utilize managed rotational grazing as a way to increase beef cattle production on a limited number of acres. He’s been experimenting with grazing cow-calf pairs on a multi-species cover crop mix to save haying costs and take pressure off his pasture during the hot part of the summer. Anderson has been happy with the results and wants to try drilling warm season annual cover crops into the farm’s pasture, which is dominated by cool season grasses. He’s also interested in incorporating cover crops into the corn and soybean rotation.
“Initially, I didn’t even look to get into this from a soil health perspective,” said Anderson. “I got into it from an attitude of I want to feed less hay, and I want to graze more.”
Fisher said farmers need to start looking at the ability of cover crops to build soil health as a way of creating the kind of organic matter that pays dividends into the future. Once that biology is jump-started, soil can start to create its own fertility. It can also begin utilizing moisture in a way that makes it possible to produce decent yields even under harsh weather conditions.
Since they are certified organic, farmers Jeff Gillespie and Rory Beyer have no other choice but to utilize such a natural source of fertility and weed control. “I think cover crops are just a natural fit with an organic system,” said Gillespie, who raises crops and livestock near Fountain, Minn. “I don’t have the luxury of all these other things I can add to my soil and so I need to have good soil health.”
Beyer, who milks cows, says having cover crops has helped him remain certified organic as well, and now he’s interested in building more fence and grazing these plants to take pressure off his pastures. It’s just one more way to, “harvest the sun as much as we can,” he said.
The bottom line: cover cropping is one of those practices that may be picked up with varying goals in mind. But, said Boyer, because it’s a practice that gets at the heart of good farming—soil health—it’s inevitable those motivations will evolve and expand.
“For me, the initial goal was to build organic matter, and erosion control and capturing nutrients came later,” he said. “As I learned more, they all became equally important.”
Brian DeVore is the editor of the Land Stewardship Letter.