Response of soybean for the use of the biodreparate of ACC-utilizing rhizobacteria

In addressing the improving ecology and resource saving it is essential to use environment-forming functions of legumes, which are highly symbiotrophic. In this regard, the search and the practical application of new microorganisms with multifunctional properties, which allow increasing the efficiency of legume cultivation due to the implementation of their symbiotic potential, is very promising. Of particular relevance in the context of climate change is the use of ACC-utilizing rhizobacteria, having a universal anti-stress effect on plants. The experiments studied the response of agro-cenosis of soybean cultivar Svapa to introduction of the promising ACC-utilizing rhizobacterial strain Pseudomonas oryzihabitans EP4 separately and in combination with the industrial strain of nodule bacteria Bradyrhizobium japonicum 634b at different levels of plant mineral nutrition (NPK 100% and NPK 70%). The results showed a stimulating effect ACC-utilizing rhizobacteria on the formation of soybeen nitrogen-fixing symbiosis. The combined introduction with rhizobia at a short nutritional background (NPK 70%) revealed maximum biological effect, allowing the plants to form larger nodules, having number, weight and nitrogenase activity by the 4.8, 6.6 and 3.4 times higher, respectively. It was found that a change in biometric and functional characteristics of plants and symbiotic photosynthetic activity was of conjugative nature as evidenced by the increase in the efficiency of photochemical reactions in soybean leaves, the intensity of the carbon dioxide absorption, as well as the increase in the area of assimilation surface, depending on the mineral background. Due to the better availability of plant nutrients the combined introduction of Ps. oryzihabitans EP4 and rhizobia contributed to obtaining the maximum crop yield of the studied variety, resulting in exceeded grain collection per hectare by 1.6 times. This in turn reduced the costs associated with application of mineral fertilizers by 30% without loss of yield, in which the proportion of nitrogen obtained from the air exceeded 34%.