Seasonal and Depth-dependent Distribution of Denitrifying Bacteria and N₂O Emission Potential in Eastern Georgian Soils

Abstract

Background: Denitrifiers are not limited to free-living organisms. Some are part of biofilms and microbial aggregates in natural or engineered systems, such as wetlands, wastewater treatment plants, and bioreactors. In these environments, stratification of oxygen and nitrate concentrations facilitates microzones conducive to partial or complete denitrification. Aim: The present study aimed to explore the distribution of denitrifying bacteria and the emissions they produce are of great interest both from an agricultural and ecological perspective. From the soils we studied, it is possible to generalize and determine the general denitrifying activity in the soils of many countries. Methodology: The study was carried out at Department of Microbiology, Sukhumi State University during 2023-2024. Denitrifying bacteria were studied in the liquid phase of Giltai, the denitrification process was described by color reaction. For the quantitative calculation of denitrifiers in the liquid phase, we used the McCready system. Results: The quantitative composition of denitrifying bacteria distributed in brown, black soil, alluvial and anthropogenic soils of Eastern Georgia has been studied according to the depth of the studied soils (5,10,25 cm). Samples were taken in all four seasons of the year. The soil types and depths favorable for the spread of denitrifying bacteria have been determined. The influence of acidity, salinity, moisture, the amount of hydrolyzable nitrogen and the seasonality of the year on their number has been determined. Conclusion: The increase in denitrifiers in anthropogenic soils may be a result of increased moisture. The efficiency of the denitrification process is highest in alluvial soils, at neutral pH (7.0-7.4) and optimal moisture (20-30%). N₂O emissions may increase during the winter season.