PROGRAM TITLE:  	Reduction of N2O Emissions from Fertilizers
ACTIVITY STREAM:  	Process Studies
SCIENCE ELEMENT:  	Biogeochemical Dynamics

TENNESSEE VALLEY AUTHORITY (TVA)

SCIENTIFIC MERIT:  Emission factors for the various fertilizer types show 
great variation in the literature.  In particular, anhydrous ammonium 
fertilizer accounts for about 36 percent of fertilizer N applied in the U.S. but 
contributes approximately 70 percent of the gaseous N2O emissions from N 
fertilizers.  These emissions may be significant since they account for about 
50-100 million tons of CO2-equivalent.  Recent TVA soil efflux 
measurements of trace gases from non-irrigated corn indicate that the average 
rate of ammonium nitrate converted to N2O (2.96 percent) during a 1-month 
period is greater than values previously reported.  The objective of this work 
is to remove some of the uncertainties of the contribution of nitrogen 
fertilizers to greenhouse gas emissions by more accurately estimating N2O 
emissions from different types of fertilizers, including organic sources (e.g., 
manure), and determining what contributes to the variability in emission 
rates (such as the effects of timing of fertilizer application, placement of 
fertilizer, and rate of application).  The current uncertainty that surrounds 
these areas would be best served by a short-term (one- to three-year) research 
program that addresses these factors.  TVA's program is conducted in 
conjunction with support from university researchers and in cooperation 
with the USDA and the EPA as part of the Southern Oxidant Study.  The 
work is extensively reviewed by scientific workgroups and the results are 
published in the archival literature.  

STAKEHOLDERS:  This research program is linked to other elements of the 
USGCRP including climatic and hydrologic systems with the determination 
of ways to minimize groundwater contamination of nitrogen fertilizers and 
human interactions with an interest in environmentally sound agricultural 
practices and social and economic implications of actions that may limit the 
use of nitrogen fertilizers or may affect agricultural productivity as a result of 
low-emitting fertilizers.  This program will provide guidance and benefit to 
agriculture both in the U.S. and abroad.  TVA has had long-lasting relations 
with the fertilizer industry through its programs worldwide and through the 
International Fertilizer Development Center in Alabama.  In addition, other 
federal agencies (e.g., EPA, USDA) are currently partners in this work.  

POLICY RELEVANCE:  The reduction of N2O emissions associated with 
nitrogen fertilizers has short-term policy relevance.  If the preliminary 
emission rates are accurate, policy actions that encourage the use of urea and 
nitrogen fertilizers, believed to contribute significantly less to N2O emissions, 
rather than anhydrous ammonium sources could lead to significant 
reductions in the U.S. contribution of this greenhouse gas.  Better farming 
practices that are less favorable for denitrification could also lead to lower 
emissions of N2O.  A better understanding of the contribution of nitrogen 
fertilizer to global N2O emissions and the development of strategies that 
might reduce these emissions may help the Administration meet its goal of 
reducing greenhouse gases by the year 2000.  

PROGRAM CONTACTS:  James F. Meagher, TVA, P.O. Box 1010, Muscle 
Shoals, AL 35660, (205) 386-2342 (Programmatic); Frank C.Thornton, same 
address,(205) 386-3642 (Scientific).