Organism specific denitrification in samples of an Udifluvent with different nitrate concentrations

Model experiments were carried out to elucidate the interrelations between the ratio of N₂O to N₂ gases released by the denitrification of different amounts of nitrate on the one hand and of the activity of bacterial populations on the other hand. Soil samples amended with 2 different amounts of nitrate were sterilized, inoculated with either their natural bacterial population or by strains of denitrifying soil bacteria and incubated anaerobically in gas‐tight flasks. Results of these experiments are: The composition of denitrification gases (N₂O, NO, N₂) was exclusively caused by the species of the active microorganism in the soil: the nitrate concentration only influenced the denitrification rate, but not the N₂O/N₂ ratio of each organism. The amounts of nitrite formed transitorily were also specific for the type of organism. These amounts of nitrite influenced neither the emission of N₂O (and NO) nor the ratio of N₂O to N₂ or of N₂O to consumption of nitrate. The N₂O formation depended primarily on the microbial soil population and secondly on the nitrate concentration in correlation with the type of the denitrifying population.