Relationships between the number of microorganisms and indicators of potential and effective fertility of gray forest soil for cultivation of white lupine and winter wheat

Aim. The study of the regularities of the formation of connections between separate groups of microorganisms in the composition of gray forest soil groups for the cultivation of white lupine and winter wheat with the use of different systems of fertilization, liming, plowing by-products of crop production and indicators of potential and effective fertility. Methods. Microbiological, laboratory-analytical, statistical. The research was carried out in the polygon monitoring system on the basis of the stationary experiment of the department of agro-soil science and soil microbiology of the NSC «Institute of Agriculture of NAAS» «Development and improvement of intensive technologies for growing agricultural crops on the basis of extended reproduction of soil fertility». Results. It was established that the number of microorganisms of many eco-trophic, systematic and functional groups, their physiological and biochemical activity, the intensity and direction of mineralization processes are correlated with the indicators of the potential fertility of the gray forest soil. The number of ammonifiers in the 0-20 cm soil layer correlates with the value of saline pH (r = 0.385), the content of nitrogen (–0.445), phosphorus (0.774), potassium (0.804); in the soil layer 20−40 cm: with hydrolytic acidity (–0.710), pH of salt (0.730), the content of mobile compounds of aluminum (–0.430), phosphorus (0.640), exchangeable calcium (0.506) and humus (0.505). The number of immobilizers of mineral nitrogen correlates in the 0–20 cm soil layer with the value of exchangeable acidity (0.338), the content of phosphorus (0.440), potassium (0.410), mobile compounds of aluminum (–0.386); in the 20-40 cm soil layer: with hydrolytic acidity (–0.403), saline pH (0.355), exchangeable acidity (–0.542), content of mobile compounds of aluminum (–0.575), nitrogen (–0.365). The total number of microorganisms in the 0–20 cm soil layer correlates with the content of nitrogen (–0.434), phosphorus (0.481), potassium (0.522), exchangeable magnesium (–0.418); in the soil layer 20-40 cm: with hydrolytic acidity (–0.493), pH of salt (0.520), the amount of exchangeable acidity (–0.359), the content of mobile aluminum compounds (–0.465), the content of phosphorus (0.368), exchangeable magnesium (–0.412), humus (0.352). The inverse nature of the relationship between the total number of microorganisms and the content of nitrogen compounds in the soil indicates that the legume culture of white lupine in the flowering stage no longer depends on the nitrogen content in the soil, consuming symbiotrophic nitrogen for growth and development. Conclusions. It has been established that the systems of diagnostic indicators of effective soil fertility for winter wheat and white lupine differ significantly, and it may be necessary to create different systems of diagnostic indicators for grain and leguminous crops, since they differ in plant physiology.