Much attention has recently been paid to the study of carbon turnover, especially to the emission of carbon dioxide from the soil. This is related to the fact that CO2 significantly contributes to the greenhouse effect, and an increase in its concentration in the atmosphere can result in global climatic changes. Rhizospheric microorganisms enhance the decomposition of humus when they need additional mobilization of nutrients (particularly, of nitrogen) from soil organic matter, or hamper it upon competition with plants for the limited amount of nutrients