Nitrification by Aspergillus flavus in sterilized soil

Abstract

The heterotrophic organism Aspergillus flavus has been shown to produce significant amounts of nitrate in sterile soil supplemented with sucrose and ammonium phosphate. Nitrate was produced in three soils sterilized by steam or by gamma irradiation, but in one soil (Honeoye silt loam, forest sample) considerably more nitrification occurred in the irradiated soil. The amount of nitrate produced by the fungus in soil was much less than that produced in liquid culture medium during the same incubation period, particularly in two of the three soils. Slight inhibition of nitrification occurred when water extracts of two soils were added to the liquid culture medium normally used for studying nitrification by A. flavus. However, the addition of small amounts of sterile soil to this culture medium markedly inhibited nitrification without apparently affecting the growth of the fungus.