Patterns Observed for the Oxidation of Ammonium to Nitrate by Soil Organisms

Abstract

AbstractAmmonium sulfate solutions were percolated for 28 days through samples from the top two horizons of 55 soils derived from several classes of glacial tills and through six calcareous horizons influenced by sodium. Four general nitrification patterns were observed:(I) Ammonium rapidly oxidized to nitrite which accumulated over a long period before being oxidized to nitrate. (II) Ammonium and the produced nitrite both rapidly oxidized. (III) Ammonium slowly oxidized to nitrate without nitrite appearing. (IV) Ammonium oxidation not detectable by either nitrite or nitrate formation.The occurrence of the four patterns was correlated with soil reaction and other acidity related properties. Nitrosomonas spp. and Nitrobacter spp. organism numbers and proliferation characteristics influenced by soil environment accounted for the four nitrification patterns observed except insufficient Nitrobacter spp. organisms were detected to produce the nitrate formed in type III soils.Nitrification patterns were modified by altering the soil properties and the number of nitrifying organisms consistent with the above interpretations. Ammonia, nitrite, nitrate, and pH affected Nitrobacter spp. lag in type I soils.