AN EMPIRICAL-MODEL OF DENITRIFICATION

We used a simple empirical model to predict denitrification rates from measurements of bulk soil properties. Boundary analysis was used to d efine relationships between denitrification rate and each of air-fille d porosity, respiration rate and mineralizable-C content. The ratio of measured denitrifying enzyme activity to the maximum measured value w as used to account for variation in amounts of enzymes and numbers of denitrifiers in soil. Nitrate content had little effect on denitrifica tion rate and was excluded from the model. Because the model did not a ccount for microscale variability, it did not accurately predict rates in individual soil cores. Nevertheless, population means and distribu tions of predicted and measured values were similar. The seasonal patt erns of mean values of predicted and measured denitrification rates we re also similar over the second half of the sampling period, which ext ended from May to November. The model did not account for appreciable denitrification on three dates in May. This discrepancy indicated that environmental regulation of denitrification may not be uniform over t he season. The model was not sufficiently sensitive to factors influen cing episodic events.