INFLUENCE OF NITROGEN ON MICROBIAL COLONIZATION OF THE BARLEY RHIZOSPHERE

Dynamics of the abundance of microorganisms belonging to different gro ups was studied in the rhizosphere and rhizoplane of barley with and w ithout addition of nitrogen. The dynamics of bacteria, actinomycetes, and fungi in the rhizosphere of the plants supplied with nitrogen were similar to the dynamics observed for the control plants. In the rhizo plane of nitrogen-amended plants, an increase in microbial number was initially observed, which indicates that in the rhizoplane nitrogen is a deficient resource as a result of competition between the plant and microorganisms. At the early stages of vegetation, the plants supplie d with nitrogen grew more slowly than the control ones, which can be e xplained by intense colonization of the root surface by microorganisms . Subsequently, the nitrogen-amended plants outstripped the growth of the control plants. The increase in microbial abundance in the plant r hizoplane in the presence of additional nitrogen should be taken into account when controlling both beneficial and phytopathogenic populatio ns of microorganisms.