Nitrate production is mainly heterotrophic in an acid dairy soil with high organic content in Australia.

A laboratory incubation experiment was conducted using the nitrification inhibitor acetylene and N isotope techniques in order to determine the relative significance of heterotrophic and autotrophic nitrification in three acid soils from different locations in Australia. The contribution of heterotrophic nitrification to total nitrification was found to vary from 20-88 % amongst the three soils. In the less acidic Glenormiston soil (pH 6.2, organic C content 5.6 %), nitrification was largely autotrophic with heterotrophic nitrification accounting for only 20 %. However, in the more acidic and higher organic C content Longworry soil (pH 4.8 and organic C content 9.3 %), heterotrophic nitrification was the predominant NO production pathway accounting for 88 % of total nitrification. [ABSTRACT FROM AUTHOR]