WASECA, Minn. — Don Reicosky says that our agricultural production system of tillage and annual crops isn’t sustainable for the soil.
And it’s the soil upon which civilizations are built.
Reicosky, a retired Agricultural Research Service soil scientist, said he’s seeing subtle signs of soil degradation in the Corn Belt, where intensive agriculture has been practiced for 250 years.
One sign is eroded knobs in fields. With 30 years of moldboard plowing 18 inches of soil have moved from the knobs to other locations on the landscape, Reicosky said. As a result, it’s the less fertile subsoil that’s on top of the knobs.
Likewise, unprotected soil can erode quickly — in a rain event or windstorm for example. Unfortunately, it isn’t replaced quickly. It takes 500 to 1,000 years to develop one inch of soil, Reicosky said.
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"We are running out of soil we can’t afford to lose," he said, speaking at a September Soil Quality Workshop at the Southern Research and Outreach Center in Waseca.
What can be done to slow the degradation or even reverse it?
Reicosky advocates a more diverse four-crop rotation with a cover crop and alfalfa, minimal soil disturbance and continuous residue cover.
Yet, it’s a tough sell to add crops to the rotation when the federal government don’t subsidize alfalfa or perennial crops, he said. Farmers are doing exactly what government programs encourage them to do.
"Farmers are as smart as any group in the U.S., but they’re also driven by the bottomline," Reicosky said.
And when it comes to soil disturbance, equal or even greater hurdles exist. Farmers have been tilling the soil for generations. Culture and attitude support tillage. No till is a real challenge to establish on heavier soils.
In fact, it took 12 years of research at the soils lab in Morris to be able to get the same yield with no till as with conventional tillage, Reicosky said. For the first few years, no till yields were 5 percent to 7 percent less than conventional tillage.
Farmers can’t afford those kinds of yield losses on all their acres. That’s why Reicosky advocates a bit-by-bit approach. Take a small area and experiment with more diverse rotations, cover crops and perennial crops, he suggests.
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No till takes a higher level of management. There are timing differences for planting, harvesting and applying herbicide. For the first five to seven years, no-till land may need 10 pounds to 20 pounds of additional nitrogen because the residue sometimes ties it up.
The first year or two will be tough, Reicosky said, but after a time there will be fewer weeds as weed seeds aren't continually recycled. Fuel costs will decrease as there are fewer trips across the field than in a conventional tillage system.
Reicosky knows that society expects a lot from farmers — they are to produce food, fiber and fuel — but he adds a fourth demand: Protecting the environment.
"It’s a lot of responsibility for farmers," he said.
However, he said he thinks it’s possible for farmers to do all of the above through conservation agriculture, a term coined by the Food and Agriculture Organization of the United Nations. The three keys to conservation agriculture are minimal soil disturbance, continuous residue cover and diverse rotations with the use of cover crops.
Conservation agriculture allows farmers to intensify crop production without intensifying tillage, Reicosky said.
Conservation agriculture increases soil organic matter, a broad, generic term Reicosky applies to "residual plant material in various stages of decomposition and microbial biomass and all their bi-products." The key component of the organic matter is carbon.
Carbon is valuable and creates many environmental benefits, he said. For a time, farmers and ranchers were paid to sequester carbon in the soil through credits sold on the Chicago Climate Exchange. The exchange ceased about a year ago, lacking any federal energy legislation or an established economic value for sequestering carbon.
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Too much carbon as carbon dioxide in the atmosphere is believed to be a key factor in climate change, so holding it in the soil is one way to reduce human’s environmental footprint, while also increasing soil quality.
"The world is facing a trilemma of climate change, food insecurity (and) energy demand," Reicosky said. Managing the carbon cycle will address all three.
The many benefits of soil carbon sequestration include reduced soil erosion, improved water quality, decreased soil compaction and reduced air pollution.
"Soil carbon is a priceless key to the planet’s health and our environmental quality."
