Specific features of determination of the net production of nitrous oxide by soils

The rate of the net nitrous oxide (N2O) production, the content of microbial biomass carbon (C-mic), and its portion in the total soil organic carbon (C-org) were determined in the samples from podzol, soddy-podzolic soils, gray forest soils, chernozems, burozems, and carbolithozems of natural, arable, and fallow ecosystems in Kostroma, Vladimir, Moscow, Kaluga, Voronezh oblasts, and Krasnodar region. The most sustainable N2O production was found in the soils enriched with glucose or its mixture with ammonium sulfate at 22A degrees C upon the preliminary incubation of the soil samples (7 days, 60% of water holding capacity). In the profiles of forest soils, a direct correlation was found between the N2O production and the C-mic content (r = 0.74, p a parts per thousand currency sign 0.05, n = 18). In the upper mineral layers (0-10 cm) of soddy-podzolic soils of the cropland, fallow, young, secondary and native forests, the inverse relationship between the N2O production and the C-mic content (r = -0.75, p a parts per thousand currency sign 0.05, n = 6) was observed. In a series of the fallowed, cultivated, and forest soils, the net N2O production decreased (239, 69, and 38 ng N2O-N x 10(-3)/g per h), and the C-mic content and C-mic: C-org ratio increased (181, 569, and 1020 mu g C/g; 1.4, 2.6, and 3.0%, respectively) attesting to the increasing N2O flux in the anthropogenically transformed ecosystems. The application of cycloheximide (20-50 mg/g) to the soil lowered the N2O production by 69-99%, which pointed to a significant contribution of fungi to this process. An approach to separate nitrification and denitrification in the soil using low concentrations of acetylene (1.8 Pa) was proposed. The conditions of preparation of the soil samples for sustainable detection of N2O production were specified. It was shown that this process is tightly related to the soil microbial biomass and its fungal component.