One answer for cleaner air, water: better agricultural practices

December 17, 2000

Better management of agricultural lands in the United States could help reclaim the 100 to 300 million tons of carbon that escapes into the atmosphere each year, according to a researcher at Ohio State University.

Carbon is considered one of the key pollutants contributing to global warming.

Agricultural lands, which include crop, pasture and grazing lands, comprise about 42 percent of the total landmass of the United States. In the last 200 years, nearly 5 billion metric tons of carbon has been released into the atmosphere because of land use change, such as plowing, drainage and residue removal in the U.S., said Rattan Lal, a professor of natural resources at Ohio State. Each year, accelerated soil erosion releases about 15 million metric tons of carbon into the atmosphere in the United States alone.

"Soil can either be a source of, or a sink for carbon - it can either emit carbon or take it in," he said. "We need to start practicing ways to take it in. And we can do that by changing how we manage the land."

Lal presented his findings with John Kimble and Ronald Follett, both with the United States Department of Agriculture, on December 18 at the American Geophysical Union meeting in San Francisco.

"Agricultural land has the potential to sequester carbon while improving the quality of soil and the environment," Lal said. His suggestions for improving carbon sequestration in agricultural lands include:

Converting traditional plowing practices to conservation tillage
Growing cover crops during the winter, such as alfalfa and hay
Protecting marginal land (such as steep slopes) under the Conservation Reserve Program (CRP), a program that gives farmers financial incentive to set aside land unfit for agricultural use
Planting vegetation with deeper roots in order to control erosion
Controlling the grazing of cattle on the land - that is, limiting grazing to a certain portion of the land
Restoring degraded lands through planting and grazing management
Taking into consideration landscape type. For example, steep slopes shouldn't be cleared - doing so would only contribute to erosion

Draining and plowing both strip soil of its carbon content. But there are ways to turn soil into a carbon sink. In agricultural practices - and depending on the soil type - farmers could implement either no-till farming or crop rotation practices to reduce erosion. No-till farming means a farmer doesn't plow his fields between growing seasons.

The 5 billion tons of carbon lost to the atmosphere because of land mismanagement may seem like a drop in the bucket compared to the worldwide estimate of 260 billion tons of carbon emitted in the last two centuries from fossil fuel combustion. But worldwide, carbon emission from soil accounts for about one-third (60 to 90 billion tons) of the amount emitted by fossil fuels. Creating soil sinks for carbon would buy researchers time to figure out what to do about fossil fuels, which accelerate global warming, Lal said.

"Putting carbon back in the soil is truly a win-win situation," Lal said. "Carbon filters impurities from water and it also enriches soil (carbon-poor soil requires more fertilizers to produce the same yield as carbon-rich soil). More carbon sequestered in the soil means less erosion and, of course, less emission to the atmosphere."

Researchers have estimated the amount of carbon lost from soil during the last 200 years by comparing carbon amounts in the soil of undisturbed, forested areas to amounts in land that had been cleared for pasture or agriculture. "The difference in carbon content between the two is about 10 to 20 tons per acre," Lal said. "Adding that up state-by-state and country-by-country means a pretty significant amount of carbon has gone into the atmosphere."

It's far easier in the short run to change land management practices in order to reduce carbon emissions than it is to reclaim carbon from fossil fuels, Lal said.

"It's a question of how to put carbon back into the soil," he said. "It isn't as economical or effective to retrieve the carbon that has been taken from fossil fuel as it is to replenish the carbon in soil.

"But sequestering carbon in soil is only a short-term solution," Lal said. "Soil has a finite capacity to hold carbon. If these practices were adopted today, the 'sink' would be full in 25 to 50 years."

Lal's work is funded by the U.S. Department of Agriculture; the Natural Resources Conservation Service; the Department of Energy; American Electric Power; and Battelle Pacific.
-end-
Contact: Rattan Lal, 614-292-9069; Lal.1@osu.edu
Written by Holly Wagner, 614-292-8310; Wagner.235@osu.edu

Ohio State University

Related Global Warming Articles from Brightsurf:

The ocean has become more stratified with global warming
A new study found that the global ocean has become more layered and resistant to vertical mixing as warming from the surface creates increasing stratification.

Containing methane and its contribution to global warming
Methane is a gas that deserves more attention in the climate debate as it contributes to almost half of human-made global warming in the short-term.

Global warming and extinction risk
How can fossils predict the consequences of climate change? A German research team from Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), the Museum of Natural History Berlin and the Alfred Wegener Institute compared data from fossil and marine organisms living today to predict which groups of animals are most at risk from climate change.

Intensified global monsoon extreme rainfall signals global warming -- A study
A new study reveals significant associations between global warming and the observed intensification of extreme rainfall over the global monsoon region and its several subregions, including the southern part of South Africa, India, North America and the eastern part of the South America.

Global warming's impact on undernourishment
Global warming may increase undernutrition through the effects of heat exposure on people, according to a new study published this week in PLOS Medicine by Yuming Guo of Monash University, Australia, and colleagues.

Global warming will accelerate water cycle over global land monsoon regions
A new study provides a broader understanding on the redistribution of freshwater resources across the globe induced by future changes in the monsoon system.

Comparison of global climatologies confirms warming of the global ocean
A report describes the main features of the recently published World Ocean Experiment-Argo Global Hydrographic Climatology.

Six feet under, a new approach to global warming
A Washington State University researcher has found that one-fourth of the carbon held by soil is bound to minerals as far as six feet below the surface.

Can we limit global warming to 1.5 °C?
Efforts to combat climate change tend to focus on supply-side changes, such as shifting to renewable or cleaner energy.

Global warming: Worrying lessons from the past
56 million years ago, the Earth experienced an exceptional episode of global warming.

Read More: Global Warming News and Global Warming Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.