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Real-Time Data Refines N2O Emission Estimates

Carbon dioxide may be the best-known culprit behind global climate change, but Agricultural Research Service (ARS) microbiologist Tim Parkin is keeping tabs on another gas as well: nitrous oxide.

“Nitrous oxide (N2O) can retain 300 times as much heat as carbon dioxide,” says Parkin, who works at the ARS National Soil Tilth Laboratory in Ames, Iowa.

The Intergovernmental Panel on Climate Change uses models to estimate N2O emissions, but better estimation methods are needed, according to Parkin. “We also need to know how N2O emissions vary with rainfall, soil conditions, and management practices,” he says.

Croplands are a significant source of N2O, but measuring soil N2O emissions is expensive and time consuming. So, as part of the ARS GRACEnet project (Greenhouse Gas Reduction through Agricultural Carbon Enhancement network), Parkin assembled a team that compared how accurately model simulations of N2O emissions from agricultural fields mirror actual emissions.

Other project collaborators included plant physiologist Tom Kaspar, laboratory director Jerry Hatfield, and AgCert scientists Marek Jarecki, Ray Jones, and Al Chan. AgCert, a subsidiary of the AES Corporation, based in Dublin, Ireland, produces and sells greenhouse gas emission credits from agricultural sources.

The team measured actual N2O emissions four times daily for several months from an experimental cornfield in Iowa. Following the same schedule, they estimated N2O emissions from the field using a computer model.

When comparing the two data sets, the researchers observed that the N2O emissions estimates generally paralleled the actual measurements, but the model underestimated peak events. In addition, there was a time lag between actual and simulated events.

Given their findings, the team concluded that the model still shows some promise for providing estimates of N2O emissions. But it needs refining and testing so those estimates will more closely mirror actual emissions data. With this additional work, the model could support scientists in fine-tuning their projections about global climate change.

“By comparing actual and estimated nitrous oxide emissions, we could pinpoint more accurate methods for identifying the range of agronomic factors and practices that contribute to global climate change,” Parkin says.—By Ann Perry, Agricultural Research Service Information Staff.

Timothy B. Parkin is in the USDA-ARS Air Quality of Agricultural Systems Research Unit, National Soil Tilth Laboratory, 2110 University Blvd., Ames, IA 50011-3120; phone (515) 294-6888, fax (515) 294-8125.

"Real-Time Data Refines N2O Emission Estimates" was published in the April 2009 issue of Agricultural Research magazine.

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