Immobilization and Survival of Plant Growth-Promoting Bacteria Streptomyces griseoviridis and Azotobacter sp

One of the problems in the production of microbial preparations for agriculture is the maintenance of bacterial viability. One of the methods of improving the viability is an immobilization in the carrier material. Immobilization of plant growth-promoting bacteria Streptomyces griseoviridis and Azotobacter sp. in the peat and experimental ceramic granules was studied. Bacterial viability in sterile aqueous suspension and in the immobilized state was tested during 10 months of storage at three different temperatures: 20 °C, 4 °C and -18 C. The peat and ceramic granules bound 49.3% and 47.8% of the added Azotobacter sp. and 26.7% and 8.2% of the added S. griseoviridis respectively. The number of bacterial colony-forming units (CFU) tended to increase during the first three days of storage at 4 C and 20 C in the suspension and in immobilized conditions and a gradual decrease of CFU was observed during storage of both bacteria with the exception of S. griseoviridiscontaining peat at 20 C. It is recommended to store immobilized S. griseoviridis in the peat at room temperature (20 C) and Azotobacter sp. in the peat at -18 C. Freezing had a good influence on the viability of Azotobacter sp. and is recommended for storage of Azotobacter sp. in the suspension and in the peat. In the case of immobilization in the ceramic granules, it is recommended to store both microbial preparations at a low temperature, best of all at -18 C. Bacterial suspensions in sterile water can be stored at 4 C.