Objective. Investigate the activity of biosynthesis of phytohormonal substances with nitrogen-fixing bacteria Bradyrhizobium japonicum and Azospirillum brasilense in pure and mixed culture. Methods. Microbiological, chromatographic, and mathematical. Results It has been established that the simultaneous cultivation of B. japonicum M-8 and A. brasilense 410 increases the content of gibberellins and cytokinins in the culture fluid of the test microorganisms. The content of gibberellic acid and isopentenylidene has increased most intensively in mixed culture compared with the pure culture of rhizobia. In the course of co-cultivation, the studied diazotrophs more intensively produced auxins compared to soybean rhizobia in pure culture, but less compared to pure culture of azospirilla. The highest level of abscisic acid that can inhibit the formation of nodules was found in A. brasilense 410 culture fluid, and it was lower when cultivating B japonicum M-8. However, the smallest amount of this phytohormone was found in the culture liquid of diazotrophs under their co-cultivation. The lowest ratio of auxin/cytokinin was found in B. japonicum M-8 and A. brasilense 410 culture fluid under their co-cultivation, which should positively influence the formation of a symbiotic system when interacting with soybean plants. Conclusion. A combination of cultivating rhizobia and azospirilla showed an increase in the amount of cytokinins and gibberellins in the culture fluid of the microorganisms, a decrease in the amount of abscisic acid and improvement in the auxin/cytokinin ratio compared to the values of the pure cultures of the nitrogen-fixing bacteria studied. An analysis of the quantitative parameters of the content of phytohormones suggests the feasibility of combining B. japonicum and A. brasilense in a mixed culture for the effective introduction of rhizobia in soybean agrocenosis.

The research of stabilizators influence on the growth, viability, nodulation activity and efficiency of Bradyrhizobium japonicum was conducted. It was found, that sodium alginate in a concentration of 0,2 % has a positive influence on a growth and functional activity of rhizobia. It was established in field experiments with soybean of Poltava cultivar that presowing seed bacterization with Bradyrhizobium japonicum, that were cultivated with given stabilizator, the area of assimilatory surface of leaves, number of nodules, their mass and nitrogen-fixing activity as well as plants productivity, were increasing.

The effectiveness of pre-sowing inoculation of winter wheat seeds with Agrobacterium radiobacter204, pre-activated with nanocarboxylates of metals, and the preparation Avatar (a complex of traceelements - metal nanocarboxylates), applied in combination and separately, was studied. The combinedapplication of bacterization and a complex of trace elements positively affects the microbiocenosis of therhizospheric soil of winter wheat: an increase in the number of ammonifiers (from 43.8% to 77.1%),nitrogen-fixing bacteria (from 2.7 to 3.5 times) was noted, while the number of micromycetes reduced.Pre-sowing bacterization and application of nanocarboxylates of metals contributes to the increase of thepotential nitrogen-fixing activity of rhizosphere soil and increase of wheat yield by 24.4% compared withthe control variant.

The paper describes the investigation results of economic and energy efficiency of microbial preparation Bactopaslon application in the technology of potato cultivation. The high efficiency of the studied biological product due to the advanced yield increase rates as compared to the increased costs was established.

Objective. Study the effect of the polysaccharide-protein complex on the efficiency of the use of the microbial preparation Ryzohumin for presowing and early bacterization of soybean seeds. Methods. Field experiment, microbiological, gas chromatography, mathematical statistics methods. Results. The influence of presowing bacterization of Suziria soybean variety on the formation of plant-microbial symbiosis with the use of Ryzohumin and simultaneous treatment of seeds with polysaccharide-protein complex (PPC) was studied. It was found that the highest number of nodules was in the variant with presowing bacterization using Ryzohumin with PPC: 4.5 times higher compared to control. In the variant with the use of PPC with early bacterization of seeds, the number of nodules on the roots of the plants was at the level of the variant with presowing bacterization using Ryzohumin (without PPC), although it was lower than the variant with presowing bacterization with the use of PPC. The largest weight of nodules was found during presowing bacterization using Ryzohumin and PPC treatment: it was on average 5.3 times higher compared to control during the years of studies. In the study of the influence of bacterization on the nitrogen-fixing activity of soybean nodule bacteria, its growth in all variants with bacterization was established. The highest activity was observed in the variant with presowing bacterization and treatment using PPC — 6,278.0 nmol C2H4/plant per hour, which is 2.7 times higher in comparison with the control parameters (without bacterization). With the early bacterization of seeds with Ryzohumin and PPC, the activity of nitrogen fixation was at the level of the variant with pre-sowing bacterization without PPC. On average, over the three years, the yield of soybean under pre-sowing bacterization was 3.33–3.43 t/ha, which is 29.6–33.5% higher than in the control, and early bacterization with Ryzohumin and PPC treatment provided an increase of 0.68 t/ha, which is 26.5% higher than in the control. Conclusion. Bacterization with Ryzohumin and simultaneous treatment with PPC helps to increase the weight and number of nodules on the roots of soybean plants both during pre-sowing and early bacterization of seeds. Formation of effective plant-microbial symbiosis provides an increased yield of soybeans up to 33.5% compared to the control variant. At the same time, early bacterization simultaneously with PPC provides an increased yield of 26.5%. The data obtained can be used to improve soybean cultivation technologies.