A Water Function Approximation to Degree of Anaerobiosis Associated With Denitrification

Using the acetylene blockage method, we measured denitrification gas flux at 64 locations along a 45-m transect on Yolo loam (Typic Xerorthents) soil, to develop an empirical function indirectly accounting for the degree of anaerobiosis in the field. The function was dependent upon the relative soil-water saturation. In addition to dentrification gas fluxes, we measured soil-water content, water-soluble organic carbon, and nitrate at all locations. The empirical water function was developed from a simple equation assuming that denitrification rate occurs according to a first-order reaction with respect to both nitrate and carbon. A water function was obtained that compared reasonably with other investigations. Using a fitted equation for the water function to calculate denitrification from measured values of water content, nitrate, and carbon resulted in a reasonable reconstruction of the denitrification spatial patterns and mean value. A rigorous test of the empirical function, however, will require extensive measurements for other soils and environmental situations.