Nebraska's farmland could help curb potential global warming by storing carbon and producers might harvest added income.

Steadily increasing atmospheric concentrations of carbon dioxide (CO2), a major greenhouse gas, have raised concerns about climate change. Reducing fossil fuel use is the long-term solution but won't happen quickly.

Storing, or sequestering, carbon in soil isn't a permanent solution but might buy time for broader efforts to cut fuel use. Major fossil fuel users might pay farmers or ranchers to store carbon and receive credit toward their CO2 emissions.

Carbon cycles through soil naturally. The challenge is to find ways to store more in soil. Through photosynthesis, plants convert CO2 into organic carbon compounds for growth and development. Carbon mostly enters the soil when plants die. Microbes decompose carbon-containing compounds, some of which become organic matter carbon. Eventually it recycles back into the air. Many farming practices that improve soil quality and boost crop yields also enhance carbon sequestration.

It sounds promising, but to be practical scientists must explore many questions about carbon sequestration.

Institute of Agriculture and Natural Resources scientists are heading a University of Nebraska interdisciplinary effort to provide answers, particularly about carbon sequestration potential in Nebraska's highly productive, irrigated cropping systems.

"We don't understand many of these processes or the upper limits of storage in irrigated systems," said Ted Elliott, director of UNL's School of Natural Resource Sciences.

Ken Cassman, head of the Department of Agronomy and Horticulture, and Shashi Verma, micrometeorologist, organized an interdisciplinary team with faculty from six UNL and UNO departments. Understanding the complexities of carbon sequestration demands this collaborative, holistic approach, Elliott said.

IANR recently received major U.S. Department of Energy grants for a comprehensive project to measure carbon sequestration at NU's Agricultural Research and Development Center near Mead. Starting next year, Verma and colleagues will set up instrumentation towers to measure how much CO2 enters and leaves fields.

NU is uniquely qualified for the task. Verma's team has worked nearly 20 years developing the technology and methods to precisely measure daily fluxes (uptake and release) of atmospheric gases.

"Once this is set up, you can call me in the morning and I can tell you the magnitudes of carbon fluxes in these fields the day before," Verma said.

The project's overall aim is to identify key factors controlling carbon sequestration in irrigated and dryland crop systems and to develop cost-effective management tactics to increase it.

"Nebraska is tailor-made for this research," Cassman said. "If we're going to talk about paying farmers to do this, we need to know how much is being stored and the production costs involved."

In related Nebraska Corn Board-funded research, researchers are testing existing simulation models that predict carbon sequestration rates based on yields, management and other factors to determine which work best under Nebraska's irrigated conditions. Eventually, they'll compare this information with state-of-the-art data from the CO2 measurement research.

Carbon sequestration is complex, but researchers hope to provide some answers within five years.

"Agriculture is a good candidate for carbon sequestration," Verma said. "It's one of those unique opportunities to benefit both the environment and farming."

– Vicki Miller

Carbon dioxide (CO2) is a major greenhouse gas. Through photosynthesis, plants convert CO2 to organic carbon compounds. Carbon cycles naturally through the soil. Increasing the amount of carbon stored in soil could buy time for more permanent solutions to ease the threat of climate change. IANR scientists are exploring the potential for carbon sequestration in Nebraska's irrigated agricultural systems.