The study investigates the effect of presowing treatment of spring wheat seeds (Triticum aestivum L.) with succinic and salicylic acids at concentrations of 10–5 M and 10–3 M with and without the use of a vacuum infiltrator. The obtained results showed a positive effect of seed treatment under conditions of vacuum pressure (0.9 atm, 15 min) on the development of coleoptile and seedling root on the seventh day of germination. In terms of the germination energy or vigor, exposure to a vacuum environment did not have a significant effect on the third day. In the stressful conditions of plant development under hyperthermia exposure, it was found that treatment of seeds with salicylic acid at a concentration of 10–3 M in a vacuum environment ensured the best result in that it reduced the stress load by suppressing catalase activity. Succinic acid at a concentration of 10–5 M proved to be the best option as a growth enhancer. In combination with the use of a vacuum environment, this treatment most significantly accelerated the development of the coleoptile and the root of the seedling on the seventh day of germination.

The optimal nutritional regime (application of the compound fertilizer at small doses), humidity and temperature conditions, and pH values (weakly alkaline) reduce the content of ascorbic acid (a protective antioxidant compound) in Solanum tuberosum L. tubers. Exogenous antioxidants (humic preparations) can be used to maintain the level of ascorbic acid in commercial products. Field experiments were conducted on two soil types and in two climatic regions (Voronezh and Moscow oblasts). The obtained data indicate that the application of humic preparations (Life Force Natural Humic Acids used in organic farming, Gumistar, and BIO-complex) and lichen-based Yagel-DETOX, both solely and in combination with the mineral fertilizer, maintains the ascorbic acid level (i.e., prevents its reduction) and increases the yield.

The effect of pre-sowing treatment of spring wheat seeds (Triticum aestivum L.) with succinic and salicylic acids at concentrations of 10–5 M and 10–3 M with and without the use of a vacuum infiltrator was studied. The obtained results showed a positive effect of seed treatment under conditions of rarefied pressure (0.9 atm, 15 min) on the development of coleoptile and seedling root on the 7th day of germination. On day 3 (when determining the germination energy), the effect of a rarefied medium did not reveal a significant effect. Under stressful conditions of plant development with hyperthermia, it was found that treatment of seeds with salicylic acid at a concentration of 10–3 M in a rarefied environment provided the best result in reducing stress load by suppressing catalase activity. Succinic acid at a concentration of 10–5 M proved to be the best option as a growth enhancer. Together with the use of a rarefied medium, such treatment most significantly accelerated the development of the coleoptile and the root of the seedling on the 7th day of germination.

The paper discusses the problem of reducing the content of ascorbic acid (as a plant-protective antioxidant compound in Solanum tuberosumL. potato tubers) while improving the nutritional regime - the use of complete mineral fertilizer in low doses, humidity and temperature conditions and physiologically optimal for potato growth pH values (weakly alkaline). The possibilities of using exogenous antioxidants (humic preparations) to maintain the level of ascorbic acid in commercial products are considered. Experimental data were obtained in f eld studies on two types of soils and in two climatic regions (Voronezh and Moscow regions). It has been shown that humic preparations can maintain the level of ascorbic acid as an independent top dressing, and against the background of full mineral fertilizer with an increase in yield.

In a model vegetation experiment (30 days), the responses of microbial communities of agro soddy-podzolic soil of two sites (Chashnikovo, Moscow oblast) with different organic carbon content (Corg 3.86 and 1.30%) to polymetallic pollution with heavy metals (HM) (Cu 660, Zn 1100, Pb 650 mg/kg) and treatment with biochar (5%) and lignohumate (0.25%). Classical microbiological culture-dependent analysis using Czapek agar and analysis of soil lipid profiles by gas chromatography–mass spectrometry revealed the differences in abundance colony forming units (CFUs), fungal and bacterial biomass, as well as in the diversity of cultivated fungi both in humus-rich and humus-poor soil. HMs did not have a significant effect on the number of CFUs and the number of cultural-morphological types of colonies, but reduced fungal and bacterial biomass in both soils; this decrease was more significant in a humus-poor soil. In addition, differences between the soils in the increase in the proportion of resistant melanized forms of fungi under the influence of HM in humus-rich (by 25.9%) and in humus-poor soil (by 45.7%) were observed. The sensitivity and universal significance of structural indicators as indicators of the stability of microbial complexes under chemical contamination of soils with different humus content were discussed. It was shown that the most sensitive and reliable indicators among the studied included the proportion of melanized fungi.

Reliable stable indicators are very important for assessing soil quality. This paper compares the dynamics of microbial parameters in two different soils (rich/poor in organic carbon), contaminated in laboratory experiments with an equal dose of heavy metals (HMs) after 30 and 90 days. For this purpose, the changes in the number, biomass, and taxonomic structure of bacterial and fungal communities were assessed in microcosm experiments using an organic carbon–rich ordinary chernozem (Ch-humus-rich soil) and a depleted carbon agrozem (Ag-humus-poor soil), spiked with high concentrations of a zinc, lead, and copper solution (1100 Zn + 660 Cu + 650 Pb mg per kg soil). At the 30th and 90th day from HM contamination, soil samples were collected for analyzing microbial community lipid markers by gas chromatography-mass spectrometry. The results show how both biomass and taxonomic structure of the bacterial and fungal communities analyzed were differently sensitive to HM contamination, depending on the type of soil. The Ag-humus-poor soil microbial community was significantly affected by the HM pollution with an increase in both fungi and bacteria and inside the latter several species changed their percentages. Differently, the Ch-humus-rich soil microbial community was not influenced by the HM addition. However, the negative impact of HM can manifest itself over time, so the microbial structure and its functioning cannot represent accurate indicators of the quality of all soil types. The results show that microbial characteristics should be taken into account only in a comprehensive assessment of soil quality in accordance with ISO 19,204:2017—soil quality TRIAD approach. This approach to environmental risk assessment combines biological data (from bioassay and ecological observations) with chemical analysis.

In this paper we present a sequential observation of the barley seed root system germination at early development stages. A target of research was a two-layer seedbed model. The model is constituted by the topsoil material from soddy-podzolic soils (Albic Glossic Retisols (Lomic, Cutanic)). The material contains two differently structured layers of seedbed: the over-seed layer (loose; 40% of the total pore volume-pore diameter 0.5–1.5 mm) and the subseed layer (compacted; fine-pored layer is dominated by soil pore diameter of 0.01–0.2 mm). Control of the root system development was sequentially conducted with the benefit of nondestructive testing (computed tomography), which bring an opportunity to receive detailed images of roots development with an accuracy up to 16 µm. The study found that during 7 days after planting the seed emerging root system doesn't depend on soil pore space structure surrounding the seed. The fact of a significant excess of the root diameter is noted in comparison with the diameters of soil pores, which indicates the ability of roots to push soil particles apart. It leads to an active pore space (pores-channels) formation.

Computed tomography allows quantifying the volume of elements of soil solids, pore space, and root system. It was possible to record the dynamics of changes in the soil pore volume space within the framework of a special physical model experiment with cultivation of barley seedlings for 7 days and tomographic imaging at key stages. The main goal was to quantify the structural changes in the development of root system and their dynamics. The experiment has been carried out in the samples of soddy-podzolic soil and chernozems; along with changes in the soil structure, changes in the structure of the microbial community have been recorded in the agrophysical system “germinating roots–pore space.” Models of the seedbed were created in plastic buckets with a volume of 3 cm3 with two layers: the subseminal layer compacted to 1.2 g/cm3 and the above-seed aggregated layer with a density of 0.7–0.8 g/cm3. Seeds of barley (Hordeum vulgare L.) of the Mikhailovskii variety were placed on the boundary of these layers. Soil water content was maintained close to the field capacity. As germination progressed from 3 to 7 days, a tomographic survey and a study of the microbiological community were carried out by gas chromatography-mass spectrometry. During this period, a decrease in the tomographic porosity in the subseminal layer and a change in the number of microorganisms, that mainly perform the destruction of complex carbon compounds, were recorded. Tomographic and microbiological studies have shown the interconnections between the processes occurring during seed germination and can be used to quantify the emerging root system.

An aggregate-forming effect of the microorganisms that modify a hydrophilic surface of minerals to an amphiphilic one was demonstrated in a model experiment: a sterile liquid medium was supplemented with the microorganism Bacillus velezensis washed off from river sand and with kaolinite, which contains potassium ions (up to 1%) in a sorbed state and in admixtures. An increase in the protein, carbon, and nitrogen contents was observable over two months of incubation; the C : N ratio reached a value close to 5. It was assumed that the microorganisms consuming potassium ion necessary for their vital activity produce protein compounds in the form of specific secretions of glycoprotein and polysaccharide natures. These compounds hydrophobized the surface of minerals (the contact angle increased from 20° to 40°), changed the specific surface area, and increased the share of microaggregate fractions (50–250 and 250–500 µm) by 5.4 and 1.5%, respectively. The incubation with B. velezensis hydrophobized the kaolinite surface as compared with the control specimens, most likely because of an amphiphilic nature of the microbial products. In turn, the hydrophobization of mineral surface induced a hydrophobic interaction between mineral particles thereby forming organomineral microaggregates.

The study of the effect of plants with different type of mycorrhizal symbiosis on carbon, nitrogen, and phosphorus transformation in soils is important in view of the necessity to predict changes in nutrient cycles upon transformation of the structure of plant communities under changing environmental conditions. The impact of dwarf shrubs ( Empetrum hermaphroditum , Vaccinium myrtillus , Vaccinium uliginosum , and Vaccinium vitis-idaea ) with ericoid mycorrhiza (ERM) and shrub ( Betula nana ) with ectomycorrhiza (ECM) on the properties of Umbric Leptosol of grass meadow in tundra of the Khibiny Mountains has been studied. It is shown that the presence of plants with ERM and ECM causes an increase in the content of labile mineral and organic phosphorus and of extractable organic nitrogen in soil and in the C/N ratio in the microbial biomass and a decrease in the content of nitrates, N-mineralization and nitrification activity, and the C/N and C/P ratios in the extractable organic matter. The increased activity of glucosidase, chitinase, and phosphatase testifies to high activity of exoenzymes of ERM fungi even in soil with high availability of inorganic nitrogen and phosphorus.

Barley seeds (Mikhailovsky sort) in a model physical experiment with a two-layer density soil bed (the range of soil density from 0.7 to 1.2 g/cm3) of silty loam arable soil (Albic Glossic Retisols (Lomic, Cutanic), Moscow Region) were placed for germination at the boundary of different-density layers at optimum moisture content. During the period from planting to 7-10 days. the dynamics of the root system development was studied using an x-ray microtomograph “Bruker SkyScan 1172G” (Belgium) while simultaneously studying the composition of soil biota, which was reconstructed from microbial markers (fatty acids and their derivatives).The roots of the germinating seed mastered the entire pore space of the soil, regardless of the density zones studied in experiments. The number of bacteria increases by the fifth day with a noticeable dominance of actinobacteria (aerobacteria Actinobacteria spp., Rhodococcus equi) and Firmicutes (anaerobes Ruminococcus sp.) due to the destruction of the seed coat with its subsequent decrease on the seventh day.

93 Effects of lignohumate and biochar on microbial communities in agricultural soils differing in organic matter content Terekhova V.A., Fedoseeva E., Pukalchik M.A., Ivanova A.E., Verkhovtseva N.V., Pozdnyakov L.А., Kulachkova S.A., Gorlenko M.V., Karpukhin M.M., Yakimenko O.S. Lomonosov Moscow State University, Moscow, Russia, vterekhova@gmail.com Severtsov Institute of Ecology and Evolution, Moscow, Russia Pirogov Russian National Research Medical University, Moscow, Russia Skolkovo Institute of Science and Technology, Moscow, Russia

Kaolinite suspensions were inoculated by microorganisms (Bacillus velezensis) for 2 months. During the period of inoculation the formation of microaggregates of a certain shape and size was traced by electron microscopy. During the experiment the initially predominant planar structure was partially transformed. The newly-formed large (up to 250 µm in diameter) organo-mineral aggregate-like particles were registered. We suppose that during the 2-month period of incubation B. velezensis microorganisms partially destroyed the crystal structure of minerals to obtain the vitally necessary potassium. The protein compounds produced by bacteria hydrophobized the surface of the minerals which resulted in the formation of organo-mineral aggregates by bonds of hydrophobic-hydrophilic interaction.

This study is focused on assessment of microbial community structure differences in urban soils by means of lipid analysis. Soil samples (0–20 cm deep topsoil layer) contaminated with trace metals to various extents were taken from six sites located in the rural part of the city of Kirov (Russia). The samples were measured for pH and total Pb, Ni, Cr, and Cd. To study the microbial community, microorganism markers (fatty acids) were extracted, which were then diagnosed by mass spectrometry. Nonmetric multidimensional scaling plots of soil communities showed relative dissimilarity in control and polluted soils. The total lipid content in control samples was found to be significantly higher than in polluted soil. The highest indicator value was assigned to Actinobacteria phylum, whose concentration decreased remarkably in polluted samples, and anaerobes Butyrivibrio sp. and Bifidobacterium sp. were regarded as an indicator for soils with relatively low pollution exposure. Microbial profiles were also indicative of selective enrichment with competent species (Desulfovibrio sp., Bacteroides fragilis, and Chlamydia sp.) in soil greatly contaminated with heavy metals. This study suggests that the method of lipid diagnostic can be highly indicative of soil microbial structure and thus it can be used as a quantitative measurement of urban soil biological quality.