Adaptability of the Sorghum Bicolor Rhizosphere Microbiocoenosis Inoculated by Microbial Agents in Southern Chernozem Soils

This paper examines the effect of presowing inoculation of Sorghum bicolor (L.) Moench seeds with a multifunctional microbial complex (MC) on the adaptability of its rhizosphere microbiocoenosis and crop yield in steppe conditions. The MC includes a number of bacterial strains (Paenibacillus рolуmуха P, Lelliottia nimipressuralis 32-3, and Agrobacterium radiobacter 204) and an association of endomycorrhizal fungi Rhizophagus sp. P3 from the collection of the Research Institute of Agriculture of Crimea. The study was performed in 2018–2020 as part of a stationary field experiment conducted to determine the applicability of no-tillage technologies in Crimean steppes. The microbiocoenosis structure was determined using standard abundance estimation techniques developed for various ecological–trophic microbial groups inhabiting the grain sorghum rhizosphere in the heading phase. The heatmap technique was used to visualize the obtained data. It is established that ammonifiers and micromycetes inhabiting the sorghum rhizosphere are resistant to arid conditions observed in 2018 and 2020. Amylolytics and pedotrophs feature the lowest activity levels in the rhizosphere compared to other groups. The proportion of effect caused by the grain sorghum inoculation with MC on the abundance of ecological–trophic groups varies from 1.3 to 9.0%. The MC application increases the abundance of ammonifiers, amylolytics, oligotrophs, pedotrophs, and micromycetes in the rhizosphere up to 4.0 times in years featuring moderate droughts. On average for 2018–2020, presowing inoculation of grain sorghum with MC boosted its yield by 0.23 t/ha (15%) in comparison with the control (no seed inoculation). Overall, the application of microbial preparations containing bioagent strains in the no-tillage farming system optimizes the rhizosphere microbiota functioning and increases the adaptive potential of plants to adverse environmental conditions.