Specific features of determination of the net production of nitrous oxide by soils
2015
Ananyeva, N. D. | Ivashchenko, K. V. | Stolnikova, E. V. | Stepanov, A. L. | Kudei︠a︡rov, V. N.
The rate of the net nitrous oxide (N₂O) production, the content of microbial biomass carbon (Cₘᵢc), and its portion in the total soil organic carbon (Cₒᵣg) 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 22°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 Cₘᵢc content (r = 0.74, p ≤ 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 Cₘᵢc content (r = −0.75, p ≤ 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 × 10⁻³/g per h), and the Cₘᵢc content and Cₘᵢc: Cₒᵣg ratio increased (181, 569, and 1020 μg 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.
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