The increase of soil fertility based on the definition of patterns of changes in soil processes and the formation of the crop for the use of microbial products and by-products of crops in crop rotation, different tillage systems. Methods. Field, laboratory, computational and statistical. Results. It is determined that the degree of destruction of plant residues of winter wheat for 3 months under the influence of decomposers increased in 2.2 -2.6 times in comparison with the control. The most intense decomposition of plant residues of wheat occurred under the influence of preparations Ekostern and Organik-balans (54.5 and 50.2% respectively); in the control -21.2%. Application of decomposers increased yield of spring barley on 0,01 -0,27 t/ha. For plowing the most effective were the following preparations: Organik-balans, Biodestruktor sterni, and Destruktor tselulozy, which provided an increase of yield on 0.15 -0.27 t/ha. For shallow tillage the best was Organik-balans. Conclusions. Application of the microbial preparationsdecomposers in the Southern Steppe is a pretty effective way to improve the biological activity of the soil and increase crop yields. Their effectiveness is vastly improved with sufficient moisture in the soil, whereby the degree of decomposition of plant residues increased by 2.2 -2.6 times in comparison with the control. In drought conditions, the decomposition of plant residues is less influenced by preparations-decomposers, and greater than the control only on 5.9 -20 absolute percent. The most intensive destruction of plant residues occurs during plowing, when they evenly incorporated throughout the whole depth of the arable soil layer. The use of chisel tillage at the same depth reduces the intensity of mineralization of plant residues on 5.3 -13.7 percent depending on the culture and moisture conditions of the soil, and use of the shallow subsurface tillage -on 18.7 -27.1%.