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Impacts of Climate and Land Use Change on Soil Trace Gas Fluxes
Steve Del Grosso*
USDA ARS NPA SPNR, 2150 Centre Ave, Building D, Suite 100, Fort Collins, CO
Bill Parton
NREL-CSU, 1231 East Drive, Fort Collins, CO
| Agricultural soils are responsible for the majority
of nitrous oxide (N2O) emissions in the US and are also an important source
of ammonia (NH3) and nitric oxide and nitrogen dioxide (NOx) emissions.
With a global warming potential of ~300 times that of carbon dioxide (CO2),
N2O is an important greenhouse gas while NH3 and NOx contribute to ammonium
(NH4) and nitrate (NO3) in precipitation. The major factors that control
soil trace gas emissions are nitrogen (N) inputs, vegetation cover, soil
type, weather, and land management. To address how climate and land use
change impact soil trace gas fluxes, the DAYCENT biogeochemical model
was used to simulate N2O, NO3, and NH3 emissions for native vegetation
and cropping under current climate and projected climate change. Under
current climate, DAYCENT estimated N gas emissions are typically 4 to
8 times higher for intensive cropping than for native vegetation. Projecting
until the end of the present century, DAYCENT simulations suggest that
N gas emissions from corn/soy bean cropping in the central US will be
20-25% higher than under current weather and CO2 levels. However, the
potential to mitigate emissions from agricultural soils is very strong.
Recent data from irrigated corn cropping in Colorado suggests that using
nitrification inhibitors and time released fertilizer can reduce N2O emissions
by 50% or more compared to application of urea or urea ammonium nitrate,
which are the most common forms of N fertilizer. Reduced tillage intensity
provides an additional opportunity to mitigate soil greenhouse gas emissions
by storing carbon in soil.
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