Effect of soil moisture on the destruction of phenanthrene and octadecane by a microbialplant association based on a red clover

The effect of soil moisture on the phenanthrene and octadecane destruction by the microbial-plant association based on meadow clover (Trifolium pratense L.) was studied. It was found that the greatest decrease in the concentration of hydrocarbons in the soil was observed with a periodic change in humidity from 25 to 35%. At the same time, the variants of experiments with constant soil moisture of 25 and 35% did not differ in the rate of decomposition of hydrocarbons. To explain the stimulating effect of periodic drying of the soil on the destruction of hydrocarbons, it has been suggested that this reduces the diffusion distance of root exudates. As a result, rhizosphere microorganisms in certain periods of time are outside the rhizosphere, outside the influence of organic substances of root exudates, which inhibit the oxidation of hydrocarbons due to catabolic repression. The studied soil moisture regimes did not affect the number of soil destructive microorganisms. The data obtained can be used in the development of methods for the purification of soils contaminated with hydrocarbons.