AZIDE EFFECTS UPON N2O EMISSION AND TRANSFORMATIONS OF N IN SOILS

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Abstract
N2O emissions from soils under aerobic conditions were severalfold higher in the presence of azide (1 mM) than in its absence. Nitrogen, added either as NH4+ or NO3−, had no effect on the azide’s induced N2O production. Although the physiological basis by which azide induces the very high evolution of N2O remains unknown, it cannot be attributed to nitrification as a source of N2O emission in the presence of azide, the inhibitory effect of azide on the reduction of N2O to N2, or to the extensive destruction of azide by nitrite under the conditions of the present study. A possible explanation may lie in the stimulation of denitrification processes due to the azide’s role in the synthesis of denitrifying enzymes. This study has reconfirmed that, like N-serve and C2H2, azide (1 mM) is a very effective inhibitor of nitrification. However, azide had no effect on the oxidation of NO2− to NO3−, and was also shown not to be a general inhibitor of microbial activity. Key words: Denitrification, nitrification, dissimilatory nitrase reductase, denitrifying enzymes