Farmers Now Part of the Global Warming Solution as U.S. Agriculture Becomes
Net Carbon Sink
ARS News Service
Agricultural Research Service, USDA
May 17, 1999
Don Comis, (301) 504-1625, email@example.com
WASHINGTON, May 17, 1999--Sometime in the past 15 years, American farmers
turned an environmental corner, Agricultural Research Service Administrator
Floyd Horn announced today.
"A dramatic change in tillage techniques shifted U.S. farm soils from net
carbon dioxide producers to net accumulators of carbon--in the form of
valuable soil organic matter. This makes their soils more productive and
part of the potential global warming solution, rather than part of the
problem," Horn said. "American farmers have virtually abandoned the
moldboard plow used to break open the American West."
Horn said that Raymond R. Allmaras, a soil scientist with the U.S.
Department of Agriculture's Agricultural Research Service in St. Paul,
Minn., made these findings after a thorough search of published reports and
surveys for several major crops, comparing 1940 to 1990 conditions.
"These reports showed that, in 1980, 75 to percent of American farmers were
still using the plow. By 1993, a USDA survey showed that farmers used the
moldboard plow on only 6 to 9 percent of corn, soybean, and wheat fields,"
Horn said Allmaras used yield records to estimate amounts of crop parts that
would be left after harvest. "He also used long-term tillage experiments
conducted by himself and ARS colleagues nationwide. Dale E. Wilkins, an ARS
agricultural engineer in Pendleton, Oregon, assisted him in the study," Horn
Allmaras said that one of his tillage experiments showed there was no carbon
accumulation in soils during a 10-year period when corn and soybeans were
planted after annual plowing; another showed that abandoning the moldboard
plow produced distinct increases in soil carbon in as little as 10 years.
"The soil is storing more carbon that otherwise might be in the atmosphere
as carbon dioxide, which is one of the greenhouse gases thought to cause
global warming," Allmaras said. "The plow lifts and inverts an 8 to 12-inch
slice of soil, and also buries stubble and other unharvested crop residue
that was once on or near the surface. That places the residue deep in the
plow layer where different microbes live. These microbes convert the residue
to a form of carbon that readily converts to CO2, which can escape to the
atmosphere," he said.
As farmers put aside the plow, they leave more residue on the soil or within
a depth of 4 inches, Allmaras said. "For example, corn and grain sorghum
farmers are returning about twice as much residue than in 1940, and they are
keeping it on or near the surface. Here, the residue readily decays to
valuable organic matter, a more stable carbon compound and a key component
of the black, fertile prairie soil originally broken open by the plow. The
moldboard plow robbed the soils of the increased organic matter offered by
the yield increases since 1940," Allmaras said.
Allmaras said the dramatic shift away from the moldboard plow has altered
the farm landscape in another equally broad way: the reduced tillage and
increased organic matter in the soil has led to a looser, less erodible soil
that holds more water for crops. "This noticeable shift in the soil is the
main reason farmers have abandoned the moldboard plow," he said.
Horn added that farmers too often are criticized for causing environmental
problems. "Here's a case where they're definitely part of the solution, and
for that, they deserve a pat on the back," he said.
Scientific contact: Raymond R. Allmaras, ARS Soil and Water Management
Research Unit, St. Paul, MN, phone (617) 625-1742, firstname.lastname@example.org.
This item is one of the news releases and story leads that ARS Information
distributes on weekdays to fax and e-mail subscribers. You can also get the
latest ARS news on the World Wide Web at
* Feedback and questions to ARS News Service via e-mail: email@example.com.
* ARS Information Staff, 5601 Sunnyside Ave., Room 1-2251, Beltsville MD
20705-5128, (301) 504-1617, fax 504-1648.
To Unsubscribe: Email firstname.lastname@example.org with the command
"unsubscribe sanet-mg". If you receive the digest format, use the command
To Subscribe to Digest: Email email@example.com with the command
All messages to sanet-mg are archived at: