A TECHNIQUE FOR ESTIMATING DENITRIFICATION RATES AT DIFFERENT SOIL TEMPERATURES, WATER CONTENTS, AND NITRATE CONCENTRATIONS

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Abstract
Much of the mineral nitrogen loss during winter and early spring in central Alberta has been attributed to denitrification. However, the extent of this loss is site- and season-specific. In an attempt to use the results of more basic studies in the estimation of field denitrification, a simulation technique for denitrification was constructed as part of a more comprehensive agroecosystem model. As part of the larger model, the technique was fully coupled to submodels for carbon and nitrogen transformations and transport. In the technique, inter- and intra-horizon fluxes of oxygen in gaseous and soluble phases were simulated as oxygen moved from the atmosphere to sites of microbial respiration. A portion of the simulated demand for electron acceptors not met by oxygen at the microsites was met by nitrate, using a Michaelis-Menten function of rate versus nitrate concentration. The technique was tested against nitrate loss recorded under a range of controlled laboratory conditions. Recorded nitrate losses ranging from 0 to 3.0 μg N g−1 soil h−1 were reproduced by the technique across a range of temperatures, water contents, and nitrate concentrations. An interaction between temperature and water content on denitrification rate as observed elsewhere was also reproduced. However, the technique relies on an understanding of the distribution of soil organic matter among kinetic fractions in the simulated soil profile and upon the rates at which these fractions decompose. Thus, a process-based technique for the simulation of denitrification will require more detailed insight into soil carbon dynamics. © Williams & Wilkins 1991. All Rights Reserved.

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