Farms, Fertilizers and Greenhouse Gas
Emissions By Ann
Perry December 9, 2009
Agricultural Research Service
(ARS) scientists are front and center in finding out how farming affects
emissions of the greenhouse gas nitrous oxide (N2O).
Experts already know that N2O emissions rise as applications of
nitrogen-based fertilizers increase. Microbiologist
Parkin, who works at the
National Laboratory for Agriculture and the Environment in Ames, Iowa, is
part of a team that is studying how different soils and different fertilizers
affect N2O emissions.
The researchers assessed the variation in the emissions of N2O, carbon
dioxide and methane from two different soil typesa sandy loam mix and a
clay soil. The two fertilizers used in the study were urea-ammonium nitrate
(UAN) and a liquid swine manure slurry.
They found that overall N2O emission levels were highest from soils
amended with swine manure slurry. High levels of N2O emissions were measured
from sandy loam soils amended either with UAN or slurry. But on the clay soils,
only those amended with slurryand not with UANhad elevated N2O
Venterea, who works at the
Soil and Water Management Research Unit in St. Paul, Minn., is also
studying N2O emission dynamics. He found that the amount of N2O emitted from
fields fertilized with anhydrous ammonia was on average twice as high as
emissions from fields fertilized with urea. The higher emissions from anhydrous
ammonia were likely derived from the conversion of ammonia to nitrate.
His findings also suggest that farmers using reduced tillage can
minimize N2O emissions by placing fertilizers below the upper 2 to 3 inches of
soil. This is because in a reduced tillage system, the microorganisms that
support N2O emissions are concentrated in the topmost soil layer.
Results from Parkin's research were published in the
Journal of Environmental
Quality in 2008. Venterea's work was published in
Biology in 2007 and the Journal of Environmental
Quality in 2005 and 2008.
more about this research in the November/December 2009 issue of
Agricultural Research magazine.
ARS is the principal intramural scientific research agency of the
U.S. Department of
Agriculture (USDA). The research supports the USDA priority of responding
to climate change.