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:

• 1 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.
• 2 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.
• 3 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.