Agrochemical and biological properties of soybean rhizosphere when applying seeds bacterization

The aim of the study is to evaluate the effect of pre-sowing bacterization of soybean seeds with strains of the biopreparation Rizotorfin on the agrochemical and biological properties of the rhizosphere. The study was conducted in the conditions of the southern forest-steppe of Western Siberia. The object of the study was new varieties bred by the Omsk Agrarian Scientific Center - Sibiriada and Sibiriada 20. The soil of the experimental plot is meadow-chernozem medium-deep heavy loamy with a humus content of 6.5 %. The study of the microbial pool of the meadow-chernozem soil was carried out in a field experiment to evaluate the effect of pre-sowing bacterization of seeds on the agrochemical and biological properties of the soybean rhizosphere. In the root zone, the content of nitrate nitrogen (N-NO3), the number of agronomically significant groups of microorganisms, and the direction of soil-microbiological processes were determined. Against the background of the use of microbiological preparations, the amount of nitrate nitrogen did not change significantly. The changes in amylolytic and saprotrophic microflora are presented, reflecting the direction of soil-microbiological processes in the rhizosphere of soybean varieties, where immobilization processes were predominant. Inoculation of Sibiriada 20 soybean seeds with Rizotorfin promoted activation of the soil organic matter transformation process, the transformation coefficient varied from 61.0 to 132.7, reaching maximum values when using strain BP 835. In the root zone, a significant increase in saprotrophic microflora was observed in the Sibiriada 20 variety when bacterizing seeds with Rizotorfin, strain 634 (72 % of the control). Microorganisms of the tested group in the rhizosphere of the Sibiriada variety experienced depression when introducing strains of symbiotic nitrogen fixers into the soil, the decrease was 32 and 63 % of the control, which may be due to the genotypic characteristics of the varieties. The activity of amylolytic microorganisms changed with a tendency similar to saprotrophic bacteria. The highest efficiency of inoculation on the yield of soybean grain was noted in 2022. In the extremely dry conditions of 2023, a reliable effect of the bacterization factor on crop productivity was revealed. The most effective strain for the Sibiriada variety was BP 634 (+0.44 t/ha), for the Sibiriada 20 variety - strain BP 835 (+0.42 t/ha).