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United States Department of Agriculture

Agricultural Research Service

Greenhouse Gas Emissions from Soils - Agricultural Management Impacts
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We are conducting field and lab studies aimed at quantifying and explaining fluxes of greenhouse gases and other trace gases from agricultural soils under differing management and climatic regimes.  While the dramatic increase in CO2 levels in the atmosphere since 1800 is well-known, parallel increases in CH4 and N2O have also occurred (see IPCC graph of these trends).


Field studies.


We measure CO2, N2O and CH4 fluxes using closed chamber methods and we also measure CO2 and NO fluxes using closed dynamic chambers. Current objectives of our field studies are to determine the impact of long-term tillage management and varying fertilizer practices on N2O and CH4 emissions in corn-soybean rotations in southeastern Minnesota.   Comprehensive assessment of the total greenhouse gas budget of reduced tillage agricultural systems must consider emissions of N2O and CH4, each of which have much higher global warming potentials than CO2.  Tillage intensity may also impact NO emissions, which can have various environmental and agronomic impacts.


Recent findings indicate that the effect of long-term reduced tillage on N2O emissions varied, in both magnitude and direction, depending on fertilizer practices (see graph of data).  Emissions of N2O following broadcast urea (BU) application were higher under no till (NT) and conservation tillage (CsT) compared to conventional tillage (CT).  In contrast, following anhydrous ammonia (AA) injection, N2O emissions were higher under CT and CsT compared to NT.  Emissions following surface urea ammonium nitrate (UAN) application did not vary with tillage (PDF file of Venterea, Burger, and Spokas. 2005, J. Environ. Qual. 34(5)). 


Lab studies.


We are conducting lab studies to determine the physical, chemical, and biological controls over production and consumption of NO and N2O in soils under different management and climatic regimes. For example, we have characterized the kinetics of NO and N2O production as a function of soil pH, nitrite (NO2-) concentration, soil water content, and temperature (Venterea et al. 2005 and Venterea, 2007).

Last Modified: 1/11/2010
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