Vast territories of Western Siberia (about 40%) are saline. On such lands, perennial grasses - phytomeliorants are mainly grown. The article presents the results of a four-year study of plant-microbial interactions in medium-sodium solonetz under fodder crop rotations with sweet yellow clover and awnless brome. The studies were conducted in the Baraba lowland, where crop rotations using layer-by-layer tillage were cultivated at the SSRIF (Siberian Scientific Research Institute of Feed) station for 33 years. In a six-field crop rotation with sweet clover in the first field, sweet clover of the Alsheevsky variety was sown with a cover crop – Sudan grass of the Novosibirskaya 84 variety; the second field was occupied by sweet clover; the third field was planted with Krasnoobsky oats. After that, everything was repeated all over again. In the crop rotation with rump, millet Kormovoe 45 was buried in the first field; in the second field, an awnless brome cultivar of the Siberian Scientific Research Institute of Agriculture -189 and millet were planted. Then the rump grew for four years. As a result of tillage and long-term exposure to phytomeliorant herbs in the 0–20 cm layer of medium solonetz, the biodiversity of bacteria has changed, the nitrification activity of the soil has increased by 1.9–2.3 times (primarily affecting the productivity of grasses cultivated in crop rotations). Under the sweet clover, the process of microbiological humus accumulation was activated. Using metagenomic analysis of 16S rRNA, four taxonomic groups of bacteria (phyla) were identified, significantly different from the virgin soil. In both crop rotations in the average solonetz, under the influence of agrobiological reclamation, the proportion of bacteria of the phylum firmicutes, mineralises of complex nitrogen-containing substances and producers of plant growth stimulants, as well as beta- and deltaproteobacteria, functionally associated with improving soil fertility, increased. Under the rump, the representation of Chloroflexi, indicators of soil density, significantly decreased.