Steady-state denitrification in aggregated soils: a mathematical model

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SUMMARY

A model is presented which calculates steady-state denitrification rates as a function of more readily-measured soil parameters: the soil moisture characteristic, the probability distributions of aggregate size and oxygen reduction potential, the nitrate concentration, and the moisture tension. The model does not depend on curve-fitting. It indicates that aggregates of intermediate size may be more efficient denitrifiers than very large ones. It provides a theoretical explanation for the reported observation of proportionality between denitrification rate and calculated anaerobic fraction of incubated soil cores. This proportionality extends over some five orders of magnitude and appears to be independent of moisture tension. Calculated whole-soil denitrification rates are affected principally by soil texture, structure and moisture tension, and less so by nitrate concentration. In addition to predicting denitrification rates, the model may be extended to predict the fraction of the gaseous products of denitrification emitted as nitrous oxide.

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