The Influence of Nitrate, Nitrite, and Oxygen on the Composition of the Gaseous Products of Denitrification in Soil

Abstract [ 18 N]‐N 2 O produced by denitrification of 18 NO ‐ 3 in soil slurries readily exchanged with nonlabeled pools of added N 2 O. This supports the role of N 2 O as a free, obligate intermediate of denitrification in soils. The observation that N 2 O diffuses freely from the site of active denitrification in soils means that any factor which produces a change in the relative rate of N 2 O reduction compared to the rate of N 2 O production can alter the proportion of N 2 O and N 2 resulting. Increased concentration of NO 3 ‐ and NO 2 ‐ resulted in increased production of N 2 O relative to N 2 as the product of denitrification. The influence of NO 2 ‐ was much stronger than that of NO 3 ‐ , with low concentrations of NO 2 ‐ causing N 2 O to become a significant product of denitrification. This suggests that NO 2 ‐ , not NO 3 ‐ , may be the influential species. Additions of small quantities of O 2 (0.02 atm) caused a large decrease in denitrification activity and resulted in a significant increase in the N 2 O/N 2 ratio.