At the present time the main priorities in agricultural production in Ukraine and Russia are ecology of its branches, natural resources conservation, energy saving and economic efficiency. Therefore biotechnology of soybean, pea and other legumes breeding had been designed. It is based on the strategy of joint using of biological preparations by applying heterotrophic microorganisms of different action (symbiotic nitrogen fixing, phosphate mobilizing and growth-promoting activity, antagonistic activity to phytopathogens, entomocide activity to phytophagans), allowing to raise plant productivity, to protect the plants from pathogen infection, to control the quantity of phytophagans, and to get qualitative and ecologically safe products of plant-grower.

However, alternative ways of creation of the efficient plant–microbial systems and all-round studies of the mechanism of micro- and macro-partners interaction, conditions of their efficient functioning have a requirement in a further search. Special emphasis should be laid on the influence of phototrophic microorganisms – chyanobacteria on functional efficiency of the plant-microbial system. Chyanobacteria form a constant active part of soil biota, they are bound by a complex interaction with all its components, and take part in different processes in soil. Few studies have been examined the influence of biotechnology on soil-forming processes in agrocoenosis.

This work has investigated the influence of pre-sowing treatment seeds by microbial drugs on the basis of effective heterotrophic (nitrogen-fixing nodulating bacteria, growth-promoting and phosphate mobilizing microorganisms, and microorganisms-antagonists of the phytopathogenes) and phototrophic microorganisms (cyanobacteria) on changes of microbial cenoses and its functional structure (the number of the main ecological trophic groups of microorganisms, the ratio of mineralization and oliogotrophic indices) and seed productivity of legumes in the period of their growing in the steppe zone of Crimea.

It was found out that the phases of development of plants, legumes species and introduction of poly-functional preparations influenced the formation and functioning of microbial cenoses in the legumes rhizosphere.

The possibility of biological activity intensification in the rhizosphere of soil at different stages of legumes ontogenesis applying the heterotrophic and phototrophic microorganisms was proved. Usage of poly-functional preparations affected indices of mineralization, oliogotrophic and microbiological transformation of organic substance in the rhizosphere, but intensity of these processes was different depending on preparations.

Activation of microbiological transformation of organic substance in the rhizosphere soil was observed at the end of the legumes growing season, but the intensity of this process was different from according to the variants of bacterization: in the rhizosphere of peavine – in the variant of application Rhizobofit + Phosphoenterin + Biopolicid and mycorrhizal fungi with Rhizobofit, in the rhizosphere of soybean and pea – cyanobacterial consortium bacterization. Besides, application of biologies increased seed productivity of soybean, peavine and lentil by 0,30–0,48 t/ha and contents of protein in seeds by of 1-3%.

Key words: poly-functional preparations, legumes, soil microbiological processes, yield structure, seeds productivity, microbial cenosis.