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).