The positive action of microbial preparation Microgumin on limitation by soil profile of biogenic elements and their compounds was proved in lysimetric experiments with spring barley. At the same time inoculation had promoted activation of nitrogen metabolism in plants which was proved by determination of plants’nitrate reductase’s activity and amino acids content in barley seeds.

The influence of plant growth regulator triman-1 on nitrogen fixing bacteria and nitrogen fixation process in barley root zone was studied in the laboratory and field conditions. It was shown that triman- 1 enhances associative nitrogen fixation activity when mineral nitrogen fertilizers (N30) was used. The use of triman-1 increases efficiency of associative symbiosis more effectively with the use of carboammonium salts rather than with ammonium nitrate.

The results of economical and energy efficiency studies of application of the microbial preparation Microgumin in the cultivation technologies of spring barley are presented. The influence of main factors on the formation of the efficiency indices was identified by the means of deterministic factor analysis. The high efficiency of Microgumin application was ensured due to the priority growth rates of yield level as compared to the costs increase.

The paper depicts the research results of development of bacteria of the nitrogen cycle in the root zone of winter wheat plants (variety Sonechko) under the use of microbial preparation Polymyxobacterin and different doses of mineral fertilizers. It was established that split application of fertilizers at doses that do not exceed N60P60K60 and pre-sowing seeds bacterization had optimized the composition of microbial associations in the root zone of plants. The increase of fertilizers doses was followed by the negative changes in the number of bacteria of different functional groups.