126-7Influence of Oxygen On Nitrous Oxide Production Via Nitrifier Denitrification.

See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: The Role of Soil Management in Influencing Nitrous Oxide Emissions and Microbial Processes
Monday, October 22, 2012: 2:45 PM
Duke Energy Convention Center, Room 204, Level 2

Xia Zhu1, Martin Burger2, Timothy A. Doane3 and William Horwath2, (1)Land, air and water resources, Univeristy of California davis, DAVIS, CA
(2)Land, Air and Water Resources, University of California Davis, Davis, CA
(3)LARW, UCDAVIS, DAVIS, CA
The development of mitigation strategies to reduce nitrous oxide (N2O) emission from soils is dependent on explaining the key biophysical factors affecting its production pathways. Nitrifier denitrification (ND), carried out by autotrophic ammonia oxidizers, produces N2O by oxidation of ammonia to nitrite which is then reduced to N2O. The existence of this pathway has long been established in pure culture, but has only recently been shown to be a significant source of N2O in soil, responding characteristically to soil moisture content. The main factor affecting the amount and pathway of N2O production, however, is the availability of oxygen (O2); this is usually associated indirectly with soil moisture status but has rarely been considered directly. The present work examined the interaction of fertilizer nitrogen source with O2 availability in influencing the production of N2O from ND in agricultural soil. This was studied in short-term incubations under a range of O2 content (21, 3, 0.5, and 0%) and two forms of fertilizer (urea and ammonium sulfate). A dual isotope (15N, 18O) approach was used to calculate the proportion of N2O arising from several possible pathways, including ND. Except at 0% O2, under which no N2O was derived from ammonium, the amount of N2O produced from ND increased as O2 availability decreased. Under reduced O2 availability (3 and 0.5%), ND was the dominant source of N2O in soil applied with urea, accounting for over 48% of the total produced. This contribution was greater than that from any other pathway, including fertilizer denitrification, nitrification-coupled denitrification, and nitrifier nitrification. At 21% O2, ND remained a significant source of N2O, with a greater contribution from ND observed following application of urea as compared to ammonium sulfate.
See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: The Role of Soil Management in Influencing Nitrous Oxide Emissions and Microbial Processes