THE SPATIAL STRUCTURE OF GRAY FOREST SOIL BACTERIAL CENOSIS UNDER DIFFERENT CONDITIONS OF USE

Under the conditions of the stationary experiment (agrarian soils) and in the 22-year-old deposit areas, the state of microbiocenoses of individual horizons of gray forest soil: humusaccumulative (0-29 cm), illuvial (30-50 cm), transitional from illuvial horizon to solid (92-110 cm) was studied. It was established that the quantity and physiological and biochemical activity of the microorganisms of the studied ecological-trophic groups, the intensity and direction of the mineralization processes are changing by the soil profile. The nature and extent of such changes significantly depends on the way the soil is used.


Materials and methods.
The study was carried out on gray forest soil (experimental farm "Chabany" of Kyivo-Sviatoshynskyi district of the Region of Kyiv) in territorially close areas: 1soil removed from agricultural use in 1987; 2-3agrarian soils of the stationary experiment, which was laid in 1987. The studied variants with the system of soil cultivation traditional for the Forest-Steppe zone, with integrated pest, disease and weed protection and agrochemical loading of various intensity were studied: 2control, field crop rotation without the use of mineral and organic fertilizers (extensive agrarian soil); 3field crop rotation with mineral fertilizers N 96 P 108 K 112.5 at the background of plowing a crop production by-product (intense agrarian soil).
The number of microorganisms of certain ecological trophic groups was estimated by the method of seeding a soil suspension on the appropriate digestive media [7]. The intensity of the mineralization of nitrogen compounds was calculated according to E. N. Mishustin and E. V. Runov [8], pedotrophicity coefficientaccording to D. I. Nikitin and V. S. Nikitina [9], humus mineralization process activityby I. S. Demkina and B. N. Zolotariova [10].
The number of microorganism colonies was counted for 21 days, depending on the growth rate and physiological characteristics of microorganisms of certain ecological trophic groups.
Probability of bacterial colonies formation (BCF) was determined by S. Ishikuri and T Hattori method, described by P. A. Kozhevin et al. [11].
Results and discussion. According to Table 1, the soil of the horizon Ih contains much less microorganisms than the horizon He. Thus, the number of ammonifiers is reduced by 24.0 times in the Ih horizons of laylands, extensive agrarian soilby 38.5 times, intensive agrarian soilby 47.0 times. Similar indicators for pedotrophs are decreased by 28.6, 29.6 and 30.9 times, for cellulosolyticsby 28.0, 22.4 and 22.3, for polysaccharide-synthesizing microorganisms -by 42.0, 23.7 and 5.5 times. respectively. The obtained data partly confirm the results of L. M. Polianska et al. [1], which found that 20-40 cm layer of gray forest soil contains only 23 times less microorganisms than in the horizon 0-20 cm. However, according to the same authors, with the further deepening of the profile, the number of microorganisms almost does not change. Similar data on the total number of microorganisms by the same authors were also obtained for typical black soil. The results of our studies indicate a sharp decrease in the number of microorganisms with deepening to the horizon Pi: ammonifiers in the layland soilby 4,500 times, extensive agrarian soilby 9,800 times, intensive agrarian soilby 9,700 times compared with He horizon. observed with regard to immobilizers of mineral nitrogen, which are used in the metabolism of ammonifiers products: the maximum amount of nitrogen immobilizers is contained in intensive agrarian soilby 14.5 % more than in the layland, and by 6.92 times more than in the extensive agrarian soil ( Table 1).
Comparison of indicators of the layland Ih horizon with the extensive and intensive agrarian soils shows that the first contains more ammonifiers, pedotrophs, oligonitrophils, mineral nitrogen immobilizers, denitrifiers, mineral phosphate mobilizers, organic phosphates mobilizers, nitrifies, and streptomyces; layland Pi horizon contains more ammonifiers, pedotrophs, cellulolytics, oligonitrophils, mineral nitrogen immobilizers, and micromycetes (Table 1). This testifies to the existence of an effective substrate transport system down the profile to the lower horizons.
Therefore, the number of microorganisms in the layland soil is decreasing in the depth of the profile not so intensively, as in agrarian soils. At the same time, there is a pattern: if the number of microorganisms of a certain group in the upper layland horizon is smaller than in agrarian soils then in the Pi horizon their number exceeds the corresponding index of agrarian soil.
In the layland soil the intensity of decrease in the number of cellulolytics is higher than the indicators of extensive and intensive agrocenosesby 28.0 and 22.4 times, respectively. Perhaps this is due to the movement of soil in the process of plowing in agrocenoses, which contributes to the penetration of cellulose-containing substrates into deeper layers of soil. However, layland Pi horizon contains a larger number of cellulolytics than agrocenoses, and the rate of decline in number in the depth of the profile is minimal (5,000 times), in agrocenoses the rate of decrease in the number of cellulolytics is 13,500 and 23,100 times, respectively. Consequently, a sufficient amount of soluble cellulose derivatives, used by cellulolytics for growth, is transported through the capillary system of the layland soil to the depth of the profile. A similar pattern is observed regarding the number of ammonifiers, pedotrophs, micromycetes and microorganisms of other groups. Note. CFU*colony forming unit, Кr**coefficient of specific phosphoribilizing activity; -* − not determined Table 2. Note. -* − not determined

Probability of formation of microorganism colonies (λ, h -1 . 10 -2 ) and intensity indices of mineralization processes in gray forest soils of various uses
The data obtained by us on the more gradual decrease in the number of microorganisms in the layland soil, as compared with the agrarian soils, does not coincide with the data of T. H. Dobrovolska [4], according to which, a virgin (forest) soil is characterized by a sharp decrease in the number and variety of microorganisms in the soil profile compared with cultivated soils. According to our data, only the number of polysaccharide-synthesizing microorganisms, organic phosphates mobilizers and autochthonous microbiota decreases in depth of the profile from both agrocenoses (Table 1). Also, we had noted almost identical rates of decrease in the number of all studied variants of the use of soil microorganisms such as pedotrophs and oligonitrophils.
It is important to study the patterns of distribution of the micellar forms by the soil profile: the maximum rates of decrease in the number of micromycetes are characteristic for the profile of extensive agrocenosis, the minimumfor the intensive one. The rate of decrease in the number of streptomyces depends not only on the way of using the soil, but also from the horizon.
It should also be taken into account the existence of spores and conidia in these groups of microorganisms, which can be transported with capillary water and remain in anabiotic state for an extended period, sprouting on digest media.
Nitrifiers are characterised by a sharp decrease in the number by layland profile ( Table   1). As the microorganisms of this group belong to the strict aerobes, the marked feature indicates, first of all, the lack of oxygen content in the lower horizons of the layland profile. This is also confirmed by the maximum number of denitrifiers (anaerobes) in the layland Pi horizon.
The maximum amount of azotobacter is contained in the soil of extensive agrarian soil, in the soil of intensive agrarian soil it is present in small amounts, and it is absent in the layland soil. This pattern is confirmed by long-term observations. The study of the probability of formation of colonies has shown that the physiological state of microorganisms depends both on the horizon and on the way of using the soil (Table 2) 3. The intensity of mineralization of nitrogen compounds from He horizon to Ih horizon gradually decreases in the depth of the profile of layland and intensive agrarian soil. Ri horizon is characterized by a sharp decrease in the intensity of mineralization of nitrogen compounds: in the laylandby 6.9 times, in intensive agrarian soilby 2.5 times. For extensive agrarian soil, a low level of mineralization processes intensity is typical for He horizon.
The previously obtained data on the minimum activity of humus mineralization in all the horizons of the layland soil, the maximumin the extensive agrarian soil, have been confirmed.
Regardless of the type of soil use, there is a clear tendency to decrease in the activity of humus degradation down the profile.