Some scientists say an ice age was prevented thousands of years ago by the dawn of human agriculture – deforestation and farming released enough greenhouse gases into the atmosphere to prevent another global cool down, the theory goes.
Now, millennia later, researchers hope new farming techniques will put some of that carbon back into the ground and help stem the rising tide of global warming.
No-till agriculture, in which farmers don’t plow their fields anymore, is one practice said to promote carbon sequestration in the soil. Organic farming is another. Researchers here at the nonprofit Rodale Institute are now developing a hybrid “organic no-till” farming system that they say could sponge up more carbon than any other way of growing food.
The claim: If organic no-till agriculture were used successfully on all of the earth’s 3.5 billion tillable acres, it would absorb and sequester more than half of all present-day CO2 emissions every year, according to Rodale Institute research director Paul Hepperly.
At the same time, the practice would also curb soil erosion and the dangers of chemical runoff.
“No-till organic is probably one of the best systems for helping to sequester carbon,” says John Reganold, a soil scientist who has studied sustainable agriculture at Washington State University at Pullman for 25 years. “What Rodale is doing is the best of both worlds.”
Jeff Moyer, farm director at The Rodale Institute, says his quest for organic no-till began as a fortuitous accident 18 years ago. As part of an agricultural experiment, researchers had planted a field with a cover crop called hairy vetch. One end of the field wasn’t part of the experiment, though, so they just drove over it with tractors, crushing down the cover crop in the process.
Some time later, after the field had been planted with corn, Mr. Moyer noticed something interesting was happening where the tractors had trampled everything: Corn plants were growing through the crushed vetch crop, which now looked like a mat of brown cardboard and was acting as a sort of mulch.
“Everybody stood there and looked at it and went, ‘Wow, you did organic no-till,’ ” says Mr. Moyer. “So we’ve spent the last 18 years trying to figure out a system that will allow us to replicate that accident over and over and over again.”
The paradigm shift represented by organic no-till is that it strives to eliminate the use of both herbicides and tillage. But for it to work effectively, the cover crop suppressing the growth of weeds must be knocked down in just the right way and at just the right time. This lets a farmer plant cash crops directly through the cover crop at the same time it’s being rolled down.
In 2002, after experimenting for more than a decade with existing farm equipment, Mr. Moyer custom-engineered a corkscrewed roller-crimper that does the knockdown job from the front end of a tractor. The first roller-crimper prototype was built in a neighbor’s weld shop and now, seven years later, they are being sold commercially by an independent manufacturer. Dozens are being used across the country by agricultural researchers and early-adopter farmers.
Bill Mason, a farmer on Maryland’s Eastern Shore, is one such early adopter. His reason for the switch had nothing to do with carbon sequestration; he was drawn by another promise of organic no-till: better economics. Organic crops sell for more than conventionally raised ones, while no-till cuts down on tractor use, reducing a farmer’s fuel and labor costs.
In 2005, Mr. Mason purchased a 15-foot roller-crimper for $4,000 and decided to give it a try with a field of soybeans. He felt he was taking a gamble.
“When you go out and roll a 120-acre field down and pray that it’s going to work, it’s a good portion of your income,” he says. “You’re taking a little bit of risk there.”
Mr. Mason says his results for that first year were “excellent.” His organic soybean yield was as good as his best conventional yields had been, and he was able to reduce his pre-harvest trips across the field in a tractor from eight passes (plowing, harrowing, planting, and multiple rounds of rotary hoeing and cultivation) to just one. He figures he is saving about $50 per acre in fuel and machinery costs alone. He has been using organic no-till for three years now, and says he would recommend it to anybody, at least for soybeans.
Corn has been a different story. His results so far with this crop have been disappointing, plagued by insects and poor yields. Across the country, USDA-sponsored research into organic no-till has been conducted in Georgia, Iowa, Michigan, Mississippi, Pennsylvania, North Dakota, and California. Experimenting with different variables of climate, soil, and crop variety, researchers have reported results ranging from excellent to abject failure.
The Rodale Institute and others have found it’s only possible to no-till a field a few years in a row before more aggressive perennial weeds start to gain a foothold. Mr. Moyer has been tilling two or three times every five years at the Rodale farm. Still, that represents a reduction in tillage of 40 to 60 percent.
Research continues on perfecting organic no-till, which is still a work in progress.
The Rodale Institute made news in 2003 when it released research results from its Farming Systems Trial – the longest-running side-by side comparison of conventional and organic farming in the country – that showed its organic (tilled) cropland was sequestering 1,000 pounds of carbon per acre per year. The high number surprised soil scientists because it showed that organic farming – even though it relies on extensive tillage – was outperforming no-till farming in terms of storing carbon. Since then, additional studies by other soil researchers have arrived at the same conclusion.
Agricultural practices that promote carbon sequestration can be “stacked,” says Moyer, so the idea now is to combine them into one farming system for the best results. Rodale researchers say stacking no-till farming, organic farming, and composting has the potential to sequester 3,000 pounds of carbon per acre per year, ten times the amount typically achieved through no-till farming alone.
Lee Burras, a soil scientist at Iowa State University, agrees that agriculture can help fight global warming, but he is tempered in his view of how large a role it might play.
“Can it help mitigate? Yes,” he says. “Is it the long-term, major solution? No.”
Part of the reason organic and no-till farming are only temporary solutions, he says, is that the ability of soil to sponge up more and more carbon eventually runs out.
“My own work shows [that] the more beat-up [the soil] is to begin with, the better response you get subsequently with carbon sequestration,” he says. “But after 10 years, 20 years, maybe it’s 50 years, we’re going to plateau out.”
Another important question is how to get farmers to embrace new methods.
“Farmers are very conservative people by nature,” farm director Moyer says. “When you ask a farmer to adopt a new technology, they are literally risking the farm, their home, and their income on this new technology.”
The allure of reduced fuel costs and better prices for organic produce may not be enough. Mr. Hepperly, the Rodale Institute research director, says that for a switch-over to occur in this country, the government must enact a system that pays farmers to sequester carbon. Carbon trading is already being experimented with at the Chicago Climate Exchange and elsewhere. The Rodale Institute is advocating that such a trading system be enacted in the next farm bill in 2012.
“This will allow farmers to see a real economic motivation to resolving these core issues,” Hepperly says.
Mr. Burras concurs: “I strongly support the idea of green payments,” he says. “Any practice that results in better carbon sequestration results in better environmental quality across the board.”
How does organic no-till farming work?
One of the challenges of growing crops is controlling weeds, but different types of farmers come at the problem in different ways. “No-till” farmers use large amounts of chemical herbicides to kill weeds, but don’t plow the soil. “Organic” farmers plow and cultivate extensively – another way to manage weeds – but don’t use any herbicides. Although each method has its advantages, until recently it seemed they were incompatible: Organic farmers till often; “no-till” farmers use herbicides.
The key to organic no-till is that it relies instead on a third method of weed control: cover crops. Cover crops are planted between rotations of food crops and, besides holding soil in place and crowding out weeds, also serve to replenish soil nutrients.
For example, if an organic no-till farmer intends to plant corn in the spring, he might plant that field the previous autumn with a cover crop of hairy vetch. The hairy vetch will put nitrogen back into the soil (which is important, because corn requires a lot of nitrogen to grow) and also keep the ground covered through the winter.
In the spring, once the hairy vetch crop is in full bloom, the farmer will roll it down using a special piece of equipment called a roller-crimper attached to the front of a tractor. At the same time, a no-till planter attached to the back of the tractor will plant the corn crop.
When the cover crop dies, killed by the roller-crimper, it functions as a weed-suppressing mulch. If everything goes as planned, the corn will grow up through the mulch, while the weeds will be stifled.
Researchers point out that organic no-till is not necessarily an all-or-nothing proposition. No-till farmers can incorporate elements of it to reduce the amount of herbicide they use, and organic farmers can employ it to reduce their tillage.
The same concepts of organic no-till farming can be applied on a much smaller scale to home gardening, although the actual equipment and methods involved are different. Here’s a link to an organic gardening blog that describes how to do it.