Nitrate production is mainly heterotrophic in an acid dairy soil with high organic content in Australia
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A laboratory incubation experiment was conducted using the nitrification inhibitor acetylene and 15N 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 (pHw 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 (pHw 4.8 and organic C content 9.3 %), heterotrophic nitrification was the predominant NO3 − production pathway accounting for 88 % of total nitrification.
KeywordsHeterotrophic nitrification Acetylene 15N isotope technique Acid soils
The authors would like to acknowledge the financial support by Incitec Pivot and the Australian Government Department of Agriculture through the Grains Research and Development Corporation.
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