Increase in nitrous oxide production in soil induced by ammonium and organic carbon

Abstract

We observed that soil cores collected in the field containing relatively high NH ^sup+_inf4 and C substrate levels produced relatively large quantities of N₂O. A series of laboratory experiments confirmed that the addition of NH ^sup+_inf4 and glucose to soil increase N₂O production under aerobic conditions. Denitrifying enzyme activity was also increased by the addition of NH ^sup+_inf4 and glucose. Furthermore, NH ^sup+_inf4 and glocose additions increased the production of N₂O in the presence of C₂H₂. Therefore, we concluded that denitrification was the most likely source of N₂O production. Denitrification was not, however, directly affected by NH ^sup+_inf4 in anaerobic soil slurries, although the use of C substrate increased. In the presence of a high substrate C concentration, N₂O production by denitrifiers may be affected by NO ^sup-_inf3 supplied from NH ^sup+_inf4 through nitrification. Alternatively, N₂O may be produced during mixotrophic and heterotrophic growth of nitrifiers. The results indicated that the NH ^sup+_inf4 concentration, in addition to NO ^sup-_inf3 , C substrate, and O₂ concentrations, is important for predicting N₂O production and denitrification under field conditions.