Methane as a Greenhouse Gas
CCSP Research Highlight 1

USDA

Do Croplands Increase or Decrease Atmospheric Methane?

USDA soil scientists are studying the effects of management practices and environment on methane emissions from croplands. A Minnesota study uses gas flux chambers to measure methane exchange between atmosphere and soil under different tillage and fertilizer treatments in corn/soybean rotations. A Colorado project studies the effects of crop selection, tillage system, and nitrogen fertilization on methane and nitrous oxide emissions on irrigated croplands.   Results suggest croplands destroy small quantities of atmospheric methane under drier growing conditions and emit small quantities under wetter growing conditions. Results on the effects of crop rotations, tillage practices, and fertilizer applications have been mixed.

Measuring effects of agricultural practices on atmosphere-soil methane exchange.

Understanding Methane Emissions from Livestock Operations:

USDA funds research to improve our understanding of methane emissions and dynamics from confined livestock operations. Kansas State University researchers have set up a meteorological tower with gas monitoring and other sensors at a commercial cattle feedlot in western Kansas to examine the vertical and horizontal movement of methane and other gases.   At Purdue University, researchers are using specialized facilities and methodologies to assess diet modifications and manure storage times on gas, odor, and dust emissions from confinement swine facilities. Researchers at Colorado State University are developing a process based model of gas and particulate emissions from confined dairy operations.

Confined feeding operations of cattle in Yuma, Arizona. [Photo by Jeff Vanuga; courtesy of USDA Natural Resources Conservation Service (NRCS)]

Methane Dynamics in Forested Wetlands:

Wetlands are thought to account for about 25 percent of the global methane flux. However, very little data exists on the dynamics of methane (and other trace greenhouse gases) in forested wetlands.   Management and restoration practices in these wetland systems affect the hydrology and carbon cycle and so too the methane and nitrous oxide dynamics. USDA research is characterizing methane fluxes in forested wetlands in the southeastern United States, and, quantifying how bottomland hardwood restoration affects trace gas emissions.   A soil biogeochemical model, Wetland-DNDC, is being developed to describe the carbon and trace gas dynamics in managed wetland forests.  

Forested wetland in the southeastern United States.