UDC 579:631.461:57.083.13 INFLUENCE OF SUBSTANCES OF DIFFERENT CHEMICAL COMPOSITION ON VIABILITY OF DIAZOTROPHS ON SEEDS OF AGRICULTURAL CROPS

The influence of carbohydrates, polyatomic alcohols, sodium chloride and compounds of protein nature on the safety of diazotrophs on seeds of agricultural crops has been studied. The most promising substances and their complexes to maintain the viability of nitrogen-fixing bacteria were determined. It has been established that the most effective are complexes of chemical compounds, because under their influence, the number of microbial cells on seeds was higher in comparison with other variants. The obtained study results can be used to develop new ways to increase the viability of useful soil microorganisms for their introduction into agrocenosis.

Seeds of agricultural crops were bacterized simultaneously with the use of chemicals. The initial bacterial count was 2*10 5 cells per seed. Bacterized seeds were stored without the access of light at 22 ± 2 ºC.
The obtained digital material was processed by the method of variation statistics using Excel and Statistica software, the probability of the difference was determined by Student t-test.
Results and discussion. Transition of diazotrophs to rest state and preserving under the effects of chemical compounds can be achieved by the use of chemicals that create stress conditions for microorganisms, but do not lead to the death of a bacterial cell (for example, polyhydric alcohols), as well as due to the protective effect of chemicals through the ability to form protective coating on the cell surface (for example, polymers and protein substances).
In the course of the study, it was found that the bacteria remained on seeds compared with the control variant under the action of different chemicals. Fig. 1 provides the results of study the viability maintaining of soybean rhizobia under the action of studied compounds.    From the data provided, it is seen that the number of viable cells was higher (both rhizobia and azospirilla) when using polymers, which can be explained by their protective effect.
In studying the maintenance of B. japonicum M-8 seeds, previously cultivated along with azospirilla, the highest positive effect on the viability of starch bacteria was found (Fig. 3), at the same time, under the effect of molasses the number of rhizobia was significantly lower compared with the other compounds throughout the storage period . After three months of storage, CSC 1 and CSC 2 were the most effective among the complexes. It was established that all studied substances contributed to the extension of the maintenance period of bacteria of the genus Azotobacter on marrow squash seeds (Fig. 4). It should be noted that throughout the storage period, the number of Azotobacter was higher under the action of protective

Fig. 4. Influence of chemical substances on safety of A. vinelandii and A. chroococcum М-70/2 (the total number of bacteria) on zucchini seeds.
During storage of R. leguminosarum 31 on pea seeds for three months, as well as in experiments with rhizobia and Azotobacter, rhizobia remained better compared to the control variant under the action of complex, which includes polymers, which can also be explained by their protective effect.
When using carbohydrates, pea rhizobia were better stored than in control, but the number of viable cells was smaller compared to variants in which the complex CSC 1 was used (Fig. 5): under its action, the number of bacteria after three months of storage exceeded control 6 times. Upon the storage of R. radiobacter 204 within three months, gelatine was effective (Fig. 6). Under the action of glucose, the number of bacteria on seeds in 7 days was the highest compared with other individual chemical compounds, but after 90 days the number of microorganisms was at level of control.
All chemical substances complexes were effective during the first month, but at the end of storage, CSC 1 was the most effective, since the number of diazotrophs studied exceeded the control variant by 7 times under its action. Therefore, it should be noted that after seed bacterization by nitrogen fixing microorganisms under storage within three months, there is a significant decrease in the number of viable cells of bacteria.
The addition of substances of different chemical nature does not completely stop this process, but it reduces its intensity. To preserve diazotrophs in the rest state on the seeds, it is expedient to use chemical substances complexes, since their effectiveness is much higher than the use of certain substances.