A micrometeorological method for in situ denitrification measurements using acetylene inhibition

A method for acetylene inhibition measurements of denitrification in the fi eld using micrometeorological techniques is presented. It is based on the m onitoring of flux ratios from small (<5 m(2)) microplots. The method measur es 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 cal culated. Acetylene has been shown to prevent the reduction of N2O to N-2 by denitrifying bacteria, thereby increasing the flux of N2O by an amount equ al to the N-2 flux that would have been. By comparing the ratio of N2O flux es from microplots with and without acetylene, an estimate of N-2 productio n by denitrification was obtained. Field testing showed the technique to be practical and easily implemented. Under induced denitrifying conditions ra tios of N-2:N2O flux ranged from 0.42 to 31.4. (C) 2000 Elsevier Science B. V. All rights reserved.