The content of bacteria, yeasts and fungi in the soils of apple orchards in the north CCR

The aim of our research was to study the ratio of bacteria, yeast and fungi in soils occupied by apple orchards of different ages in the northern part of the Central Black Earth Region and fragmentarily in the Stavropol Territory. The research was carried out in 2015-2017 in fruit growing farms in the Tambov, Lipetsk, Penza regions and the Stavropol Territory. The objects of research were soils (typical chernozem, leached, podzolized, meadow-chernozem, chernozem-meadow, chernozem-moist-meadow and gray forest soils) under industrial apple orchards. The gardens were laid out according to 5x3, 6x4 and 6x8 m schemes on stocks 62-396, 54-118 and seed. The age of the surveyed gardens is from 15 to 89 years. In the waterlogged chernozem-meadow and chernozem-moist-meadow soils, the highest number of bacteria was noted, but the lowest number of fungi. The greatest amount of yeast and mold fungi (favorable for the apple rhizosphere micro flora) is noted in gray forest soils and podzolized chernozems. In the root layers of the near-stem strips of apple orchards, there were 2.3 times less bacteria, but 3.8 times more yeast and 4.4 times more fungi than in the aisles. There are more bacteria, yeast, and fungi in the humus horizon of the near-stem strips of old apple orchards than in the soils of younger orchards. As the age of the garden increases in the ratio “bacteria: yeast: fungi”, the proportion of yeast increases 2 times, and the proportion of fungi - 1.5 times. A year after stubbing the gardens in the 0-40 cm soil layer, the amount of molds becomes average between their content in the near-trunk strips and aisles. The death of trees on chestnut soil was noted where there were 5 times more bacteria, 2.5 times less yeast and 2 times less fungi.


Introduction
When designing intensive gardens, one should know its microbiological properties [1][2][3][4][5][6][7][8][9]. As a result of the accumulation of plant polyphenols in soils, the structure of the microbial community changes and soil fatigue sets in [2][3][4]. In the near-trunk strips, the presence of leaf litter determines the constant presence of cellulose-decomposing bacteria Enterobacter cloacae in the soil [3]. The use of herbicides in gardens strongly affects the genera of bacteria from the order Chthoniobacterales and reduces the  [11]. The presence of pathogenic bacteria in the soil (Klebsiella pneumonia, Shigella spp and E. Coil. Etc.) indicates soil contamination [13]. The bacteria Bacillus subtilis, Bacillus cereus, Pseudomonas aeruginosa and Escherichia coli in garden soils show resistance to a wide range of antibiotics and heavy metals such as zinc, copper and lead [6], and some bacteria (Lysinibacillus sp., Bacilldoco sp. And Rho .) even reduce the concentration of metals in the soil [5]. The bacteria of the genus Pseudomonas sp. strain HA-09 revealed a gene responsible for resistance to herbicides Glyphosate and Roundup [7]. Acidic soils have more bacteria, therefore fruit trees are more susceptible to diseases [10], but some bacteria (Acidobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes, Nitrospira, and Proteobacteria) increase the availability of calcium and magnesium for apple roots [17]. The rate of nitrogen conversion depends on the ratio of bacteria and fungi in the soil under trees [12][13]. The ratio of bacteria and fungi and their species diversity depends on the soil maintenance system in the apple orchard [15][16][17] and on the doses of organic fertilizers [18]. Vineyard soils have a higher species diversity of fungi than in other fruit plantations [11]. The biological activity of the soil is directly dependent on its density [8]. The deterioration of the physicochemical and morphological properties of soils between rows of gardens leads to a decrease in cellulolytic activity [16]. The pathogenic fungi Rhizoctoina solani, Pythium ultimum, Phytophthora cactorum, Fusarium oxysporum, Dematophora necatrix were found in the soils of old dying gardens, which, along with bacteria and actinomycetes, are greater than in the soil of young gardens [14]. The aim of our research was to study the ratio of bacteria, yeast and fungi in soils occupied by apple orchards of different ages in the northern part of the Central Black Earth Region and fragmentarily in the Stavropol Territory.

Materials and methods
The research was carried out in 2015-2017 in fruit growing farms in the Tambov, Lipetsk, Penza regions and the Stavropol Territory. The objects of research were soils (typical chernozem, leached, podzolized, meadow-chernozem, chernozem-meadow, chernozem-moist-meadow and gray forest soils) under industrial apple orchards. The main tracts of chernozems typical for apple orchards were located in OJSC "Dubovoe" of Petrovsky region, OJSC fruit nursery "Zherdevsky" of Zherdevsky region and SEC "Zemlyansky" of Inzhavinsky region of Tambov region. The humus horizons (A + AB) of the soils had an average thickness, the groundwater level was low (9 m). The main area of chernozems leached under apple orchards was concentrated in the FSUE Michurinskoye, the Komsomolets breeding farm in the Michurinsky district, in the Dubovoye OJSC of the Petrovsky district, the Snezhetok AO of the Pervomaisky district and the Zherdevsky fruit nursery. In terms of the thickness of the humus horizons, the soils are thick, the groundwater level was low (7 m). The main part of podzolized chernozems under apple orchards was located in FSUE Michurinskoye and Planeta Sady Plus LLC in Michurinsky District and Snezhetok AOO in Tambov Region. The soils had an average thickness of humus horizons, the groundwater level was low (7 m Soil sampling was carried out according to the methodological instructions of V.V. Zerling and L.A. Egorova [1]. The number of microorganisms in the soil was determined by sowing on nutrient media at a dilution of 10,000 and 100,000 times [2].

Results and Discussion
We found that in waterlogged soils (chernozem-meadow and chernozem-moist-meadow), the greatest number of bacteria was noted, but the least number of fungi. The greatest amount of yeast and mold fungi, which are very valuable for the root system of the apple tree, is noted in forest soils (gray forest and podzolized chernozems) (table 1).  A year after stubbing the orchard at Timiryazevo LLC in 2019, 1 g of leached chernozem was: 4 thousand CFU of bacteria in the 0-10 cm layer, 5970 thousand CFU of yeast and 115 thousand CFU of mushrooms, in the layer 10-40 cm respectively 6 thousand CFU of bacteria, 34704.5 thousand CFU of yeast and 373 thousand CFU of fungi.
The number of bacteria in the soil between rows increased with depth, and yeast and molds decreased. The number of bacteria and yeast in the soil of the near-trunk strips decreased with depth (table 2).  The soils of row spacing of apple orchards contained 2.3 times more bacteria, 3.8 times less yeast and 4.4 times less molds.
It was found that in the root layers of the soil of the near-stem strips of apple orchards that have entered full fruiting contains 6.8 CFU/g of bacteria, 12907 CFU/g of yeast and 572.8 CFU/g of fungi, that is, the ratio of "bacteria: yeast: fungi" will be 1: 1898: 84. In old apple orchards in the root zone of the soil of the near-stem strips, there were 8.3 CFU/g of bacteria, 28217 CFU/g of yeast and 1046 CFU/g of fungi, which is in a ratio of 1: 3400: 126.

Conclusion
Based on the foregoing:  In the waterlogged chernozem-meadow and chernozem-moist-meadow soils, the highest number of bacteria was noted, but the lowest number of fungi. The greatest amount of yeast and molds (favorable for the apple rhizosphere micro flora) is noted in gray forest soils and podzolized chernozems.  In the root layers of the near-stem strips of apple orchards, there were 2.3 times less bacteria, but 3.8 times more yeast and 4.4 times more fungi than in the aisles.  There are more bacteria, yeast, and fungi in the humus horizon of the near-stem strips of old apple orchards than in the soils of younger orchards. As the age of the garden increases in the ratio "bacteria: yeast: fungi", the proportion of yeast increases 2 times, and the proportion of fungi -1.5 times.
 A year after stubbing the gardens in the 0-40 cm soil layer, the amount of molds becomes average between their content in the near-trunk strips and aisles.  The death of trees on chestnut soil was noted where there were 5 times more bacteria, 2.5 times less yeast and 2 times less fungi.