Plowing techniques affect global warming

by Mark Baumgarten

Farmers may now be doing more than simply feeding the world’s population. If University researcher Raymond Allmaras is correct, they are also helping stall global warming.
Allmaras’ research has shown that plowing practices releasing carbon dioxide are on the decline. According to the research, farmers have stumbled onto a method of storing the greenhouse gas instead of producing it.
“Sometime, maybe 10 years ago, instead of contributing to the greenhouse effect, farmers began to store carbon in their fields in the form of carbon sinks,” said Allmaras, a professor in the Department of Soil, Water and Climate. “This keeps the carbon from coming into contact with microbes that transform the carbon into carbon dioxide.”
The reason for the appearance of more carbons in soils used for agriculture, Allmaras said, is a change in the plowing methods of farmers.
The conventional method — moldboard plowing — lifts and inverts 12 inches of soil, burying a layer of residue containing carbon in the ground.
The buried residue is then subject to microbes, which are found deep in the soil. The microbes convert the residue into a form of carbon that will turn into carbon dioxide and escape into the atmosphere.
By using reduced tillage practices, which do not bury soil deeper than four inches, farmers have succeeded in keeping carbon away from the microbes. This carbon is then stored in the soil where it is less likely to become carbon dioxide.
The amount of moldboard plowing on U.S. farms has changed dramatically in the recent years. While 85 percent to 90 percent of corn, soybean and sorghum farmers used moldboard plowing before 1980, only 10 percent used the method of plowing in 1993.
But farmers who have changed their plowing techniques have had more than the environment on their minds; they are also interested in their pocketbooks.
“When the farmers get rid of the plows, they reduce erosion rates,” said Neal Eash, assistant professor at the University’s Southwest Experiment Station in Lamberton, Minn. “They also cut down on the amount of horsepower needed for the plowing. Both of these are cost-saving measures.”
“Moldboard plows are sitting among the trees on farms,” Allmaras said. “Farm equipment manufacturers barely even make or sell the plow anymore.”
But some in the industry don’t agree with Allmaras. Lance Larson, owner of Larson Implement in Cambridge, Minn., said farmers may be using them less often, but moldboard plows are still being bought.
“We’re not selling quite as many as we did 15 years ago, but we are definitely selling more than we did 10 years ago,” Larson said. “The plow is making a bit of a comeback. Farmers are realizing that they have to turn the ground over every once in a while.”
Some farmers are finding it infeasible to completely abandon plowing, despite the positive environmental effect.
“Reduced tillage is harder to manage for many farmers, and they don’t get as much yield as they do with moldboard plowing,” said Paul Porter, an associate professor in the College of Agricultural, Food, and Environmental Sciences who is currently working at the Southwest Experiment Station. “It’s hard to work the environmental factors into the equation, because we don’t put a value on environmental benefits like we do yields.”
But Allmaras believes a value needs to be put on the environmental service now provided by farmers.
“People who are carbon polluters should be paying those who store it,” Allmaras said. “I don’t know how it would be done, but it is something that needs to be looked into.”