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A b s t r a c tHerein we summarize the results of a comprehensive study aimed on the creation of liquid form of biological products for symbiotic and associative rhizobacteria. The objects of study were nodule bacteria from the rhizosphere of galegae (Rhizobium galegae), soybean (Bradyrhizobium japonicum) and associative rhizobacteria (Arthrobacter mysorens, Azospirillum brasilense, Agrobacterium radiobacter), as well as plants of soybean (Glycine max L.), barley (Hordeum L.), alfalfa (Medicago L.), etc. As carriers for bacteria, we used gamma-sterile peat, vermiculite and improved sterile liquid media on the basis of components of vegetable or synthetic origin, with the introduction of nutrients and stabilizers (humates, glycerine, potassium sorbate, carboxymethylcellulose, etc.). The efficacy of tested products and forms were compared in a biological survey carried out in different regions of the Russian Federation. Under the conditions of Leningrad Region the effectiveness was evaluated for the preparations based on recently used and perspective strains of alfalfa nodule bacteria Sinorhizobium meliloti. An optimized combination of stabilizers, nutrients and protective substrates provided a long-term storage and high efficiency of biological products. Nevertheless, plant nutrient media (bean broth) did not provide the required quality. Using bean medium for cultivation it is possible to obtain the desired titer of bacteria in the product, but their numbers are rapidly decreasing. Furthermore, preparations obtained with use of bean broth lose quality after 2-3 months after the beginning of storage because of extraneous microflora therein. The new forms of biochemicals designed on the basis of a synthetic nutrient medium can be stored at room temperature for at least 6 months, when sterile-packed in plastic bottles. High bacteria titer (3.6-4.2 billion CFU/ml of liquid formulation) was obtained after cultivation. It is shown that an improved liquid form has a high efficiency. Its application on leguminous plants increased grain yield by 20-40 % in soy, and by 15-25 % in peas. Productivity of cereal crops (wheat, barley) increased by 15-25 %, and the productivity of alfalfa was 20-45 % higher. A significant increase in crop quality was found to be due to higher protein content. The effectiveness of biological products considerably depended on agroecological conditions and biological features of the crops. Using different strains of nodule bacteria Sinorhizobium meliloti in the Leningrad Region allowed us to create the effective plantmicrobe systems. Thus on the sod-podzolic soil the strain A-4 was most effective providing yield increase by more than 25 %, while on sod-carbonate soil it was the strain A-5 which increased the productivity of alfalfa by 140 %.

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