It's no surprise that one of the fastest ways to reduce greenhouse gasses is to put more carbon in the soil. Now you may be able to make money doing that. The 2002 Farm Bill contains a provision to pay farmers for using ag practices that boost soil carbon content.
For the first half of the 20th century, farmers heavily tilled fields. They ripped open the land and allowed its organic matter to degrade into atmospheric carbon dioxide (CO2), a greenhouse gas. USDA estimates that as the soil degraded, soil carbon content in the Corn Belt fell by nearly half.
As farmers began to employ less-intensive tilling practices, soil carbon content started to rise. But there is still room for improvement. And with increasing concerns over global warming, the government plans to pay farmers to adopt carbon-friendly methods.
These methods include no-till, minimum-till, using cover crops, leaving roots in place, allowing crop residues to degrade, and spreading manure on the surface of farmland. So says Rattan Lal, director of the carbon management program at Ohio State University (OSU).
“We lost about 10-15 tons of carbon per acre throughout the Midwest,” he says. “We can put much of that back.”
The potential for U.S. farmland to absorb carbon is really quite good, says Ron Follett, soil scientist at USDA's soil plant nutrient research unit in Ft. Collins, CO.
The new government payment system hasn't been finalized, however. One proposal calls for fixed per-acre payments for adopting carbon storage methods. Another proposal calls for payments to vary according to the amount of carbon each farm recaptures.
The payments are, in effect, icing on the cake because soil carbon storage makes sense regardless of the implications for global climate.
“Soil becomes better as you put more carbon in it,” says Lal. The higher carbon content boosts yields, increases water-holding capacity and helps to minimize soil loss through erosion.
Adopting carbon-friendly methods should also cut input costs. Follett says there will be an immediate fuel savings of about 2 gallons/acre of diesel fuel because no-till systems eliminate cultivation.
Follett also agrees that yields should rise over time. But he cautions that there may be a break-in period of four to five years when yields decline somewhat as soil biology adapts to no till.
Rising CO2 boosts yields. A new study by OSU found rising levels of CO2 in the atmosphere will boost crop yields over the next century, in some cases substantially.
“If you're looking for a positive on rising CO2 levels, it's that ag production in some areas is bound to increase,” says Peter Curtis, professor of plant ecology at OSU. The process is already under way because atmospheric CO2 levels are rising rapidly, he says.
Soybeans will be one of the big winners, with yields expected to rise about 14%. Corn yields should increase by about 5%, the OSU analysis found.
To reach that conclusion, OSU researchers examined the findings of 159 studies done at Ohio State and other ag research institutions around the world.
But there is a hitch, Curtis says. Many plants grown in higher CO2 environments will have lower nitrogen content in their seeds, meaning they will have a lower nutritional content. Food animals that consume these plants will have to eat more of them to get the same nutrition.
For instance, the nutritional content of corn is expected to dip slightly, perhaps by several percentage points. That means cattle feeders would have to feed more for the same weight gains.
Legumes, such as soybeans, are an exception. Soybeans have the ability to increase the amount of nitrogen they take in as CO2 levels rise. Thus, while soybean yields will rise, soybeans won't suffer a loss of nutritional content, Curtis says.
Corn Belt soil carbon loss in the early 20th century: 50%.
Worldwide increase in atmospheric carbon since 1850: 170 billion metric tons.
Current annual worldwide atmospheric carbon increase: 3.8 billion tons a year.
Predicted 21st century atmospheric carbon increase: nearly 100%.
Potential reduction in U.S. carbon emissions from changes in farming and forest management: 27%/year.