A micrometeorological method for in situ denitrification measurements using acetylene inhibition

A method for acetylene inhibition measurements of denitrification in the field using micrometeorological techniques is presented. It is based on the monitoring of flux ratios from small (<5 m2) microplots. The method measures concentration profiles close to the surface, and from these the ratio of gradients, which can be assumed to be equal to the ratio of fluxes, is calculated. Acetylene has been shown to prevent the reduction of N2O to N2 by denitrifying bacteria, thereby increasing the flux of N2O by an amount equal to the N2 flux that would have been. By comparing the ratio of N2O fluxes from microplots with and without acetylene, an estimate of N2 production by denitrification was obtained. Field testing showed the technique to be practical and easily implemented. Under induced denitrifying conditions ratios of N2:N2O flux ranged from 0.42 to 31.4.