In the thesis, based on complex of long-term stationary microbiological and molecular-biological studies of virgin and arable chernozems, it is proved that agrocenoses of the Left-Bank and Right-Bank Forest-Steppe, Northern Steppe of Ukraine preservation of microbial biodiversity and humus stage of soil is possible under prolonged use of soil conservation technologies of minimizing tillage, use of straw, green manures and fertilizers. The microbial transformation of organic matter of virgin and arable chernozems is studied, the mechanisms of loss and recovery of humus in these soils are established. By molecular-biological method the diversity of metagenome of prokaryotes of virgin and arable chernozem soils in Natural Reserve «Mikhailivska Tsilyna» is assessed. It is proved that human pressure on chernozem soils impoverishes their biodiversity, and under plowing the number of species of microorganisms compared to the virgin spot decreased almost in 2 times – from 145 to 86. The most extensive and complex structure of phylotype diversity of soil microorganisms was observed in the 0–20 cm soil layer under different-depth conservation tillage. It is represented by 7 major clusters of dominant genotypes belonging to members of 98 species, of which 31 % – uncultivated. Use of arable chernozem soils without fertilization leads to a gradual degradation of their microbiological properties, particularly evident under nonplowing (conservation) tillage, where there is accelerated growth of bacteria, especially those that are not cultivated on selective media. Fertilization changes direction of microbiological processes and restores fertility of chernozems. Organic and mineral fertilization system of soil creates in 3–5.7 times greater biodiversity of soil microorganisms compared to the option without fertilizers. Tillage systems, affecting the input and redistribution of crop residues and fertilizers residues in the tilled layer, change parameters and structure of phylotype diversity of soil microorganisms. The most extensive and complex structure of phylotype diversity of soil microorganisms is marked in the 0–20 cm soil layer under different-depth conservation tillage and is represented by 7 major clusters of dominant genotypes belonging to members of 98 species, of which 31 % – uncultivated. On options with plowing and shallow cultivation respectively were found 7 clusters, 57 species, 40 % and 8 clusters, 33 species, 18 % of uncultivated microorganisms. Plowing, unlike conservation tillage causes differentiation in 1.7 times of the number of microorganisms in the top 0–20 cm and lower 20–40 cm soil layers. Soil conservation technologies help to preserve humus stocks and ensure the reproduction of fertility of chernozem typical of the Forest-Steppe. Along with the quantitative, also the qualitative changes occurred in humus stage, that are most depending on fertilization. Restoration of humus in chernozem typical low-humus of the Forest-Steppe of Right-Bank Ukraine in conditions of intensive grain-beet crop rotation (40 % of hoed crops) is achieved by inputting of straw 1,2 t/ha + N12 + green manure + N78P68K68 per hectare of crop rotation area, due to the increase humus accumulation to 0.26 % and to decrease in content of non-hydrolyzed remaining to 15 %. The overall productivity of crops in the chernozem typical on 16-years use of various technologies war most dependent on the system of fertilization (up to 58 % compared to non-fertilized option) and less - on cultivation.
