Beneficial Effects Of No-till Farming Depend Upon Future Climate Change

Growing plants take carbon dioxide from the air and store it ascarbon in their tissues. Most of this carbon is returned to theatmosphere as carbon dioxide when crops are harvested and consumed.Some carbon, however, can be permanently stored, or sequestered, in thesoil as organic matter. Changes in land management can potentiallyincrease the accumulation of organic carbon in soil.

The amount of carbon stored in soils also depends on how theclimate changes and how much carbon dioxide is in the atmosphere, sayresearchers from the University of Illinois at Urbana-Champaign and OakRidge National Laboratory in Tennessee.

"Our research focuses on the feasibility of differentsequestration schemes for reducing natural emissions of carbon dioxideor enhancing the natural uptake of atmospheric carbon dioxide," saidAtul Jain, a U. of I. professor of atmospheric sciences and lead authorof a paper published in the Oct. 12 issue of Geophysical ResearchLetters. "Converting from conventional plow tillage to no-till practiceis among the most cost-effective ways to reduce the buildup of carbondioxide in the atmosphere."

To study the effect of changes in climate and atmosphericcarbon dioxide on soil carbon sequestration, the researchers used a newEarth-system model called the Integrated Science Assessment Model.Developed by Jain and his graduate students, the model includes thecomplex physical and chemical interactions among carbon-dioxideemissions, climate change, carbon-dioxide uptake by plants and oceans,and changes in farming practices.

About 18 percent of cropland in the United States and about 30percent of cropland in Canada is under no-till, Jain said. By nottilling their fields, farmers can save labor and fuel costs, reducesoil erosion and preserve precious nutrients. No-till also increasesthe accumulation of soil organic carbon, thereby resulting insequestration of atmospheric carbon dioxide.

Changes in no-till land management were simulated with andwithout changes in climate and carbon dioxide levels over the period1981 to 2000. All model simulations were based upon the actual adoptionof no-till practices on U.S. and Canadian farms.

"Comparing the model results with and without changes in carbondioxide and climate allows us to estimate the impact of recent changesin climate and carbon dioxide on soil carbon sequestration," Jain said."Over the period 1981 to 2000, 868 million tons of carbon were storedin solids under no-till farming. Five percent of this carbon storagecomes about because climate change and increasing atmospheric carbondioxide accelerate carbon storage in soil. Future increases in no-tillcould sequester enough carbon to satisfy nearly one-fifth of the totalU.S. reduction in carbon-dioxide emissions called for by the KyotoProtocol."

The effects of climate change on carbon storage will vary fromplace to place because of differences in how soil moisture and soiltemperature change as the climate warms, Jain said. In general, incentral and western Canada, the eastern United States, and portions ofFlorida and Texas, carbon sequestration may increase. In other areas,such as Illinois, climate change will reduce the amount of sequesteredcarbon.

"Climate change will reduce the gains in the carbon storagefrom no-till in some areas, but there is still a net gain in storedcarbon," Jain said. "In the future, farmers could receive credit forthe carbon sequestered in their fields under a carbon-tradingarrangement such as has been proposed for the Kyoto Protocol."

Co-authors of the paper were Oak Ridge scientists Tristram West and Wilfred Post, and Illinois graduate student Xiaojuan Yang.

The U.S. Department of Energy funded the work.

Editor's note: To reach Atul Jain call 217-333-2128; e-mail: jain1@uiuc.edu.