Meadow-chernozem soil biological activity depending on the tillage system and the chemicals use

The purpose of the study is to establish the direction of mobilization processes and quantitative changes in soil biota during long-term use of resource-saving treatments of meadow chernozem soil. The study was carried out in a long-term (established in 1973) stationary experiment in grain-fallow crop rotation (fallow - wheat - wheat - wheat - barley) under wheat (third after fallow) in the Omsk Agrarian Research Center in the southern forest-steppe of Western Siberia. The parameters of changes in the number of individual physiological groups of microorganisms and indicators of the biological activity of the meadow-chernozem soil under the third wheat after fallow under agricultural technologies with different levels of intensification, including the minimum-zero tillage system in crop rotation, were established. In separate periods of 2020 and 2021 with good soil moisture, the presence of a significant amount of plant residues in the variant with minimal-zero tillage, the number of oligonitrophils, phosphate-mobilizing bacteria increased to 200.0-451.0 million CFU/g. The use of complex chemicals significantly affected the number of nitrifying bacteria in the soil. The share of influence of the intensification factor in this case was 62.7 %. The largest amount of nitrifiers was observed when using complex chemicals (1.46-2.02 thousand CFU/g), as the intensity of tillage decreased, it decreased. The long-term minimization of the cultivation of the meadow-chernozem soil contributed to the accumulation of plant residues in the arable layer, which had a decisive influence on its biological properties. The total cumulative number of detected microorganisms on average for 2019-2021 was the highest with minimal tillage, exceeding plowing by 68.5 %. Over the years of research on the options for the use of means of intensification and against the control background, the highest grain yield was obtained with a moldboard tillage system, exceeding the minimum-zero one by 0.27 t/ha (9 %).