The aim of the study was to exmine the effct of low rate of potassium humate application with and without fly ash (FA) on wheat roots rhizosphere bacteriobiome. Location and time of the study. The microplot field experiment was conducted in three replicates in randomized design in 2022 in Novosibirsk (Russia). Methods. Soil physical and chemical properties were determined by commonly used methods. Bacteriobiome structure and diversity were estimated by 16S rRNA genes (V3-V4 region) by metabarcoding. Results. The study revealed large bacteriobiome diversity: on average 2472 and 2330 operational taxonomic units (OTU) in bulk and rhizosphere soil< respectively. Overall 9120 OTE were found, belonging to 929 genera, 438 families, 416 orders, 104 classes and 37 phyla. A quarter of the total OTUs number belonged to the Proteobacteria phylum; Actinobacteria phylum ranked second in OTUs number (10%), whereas Firmicutes, Bacteroidetes and Acidobacteria each accounted for 8% of the total OTUs number. The Actinobacteria dominated in the relative abundance of the total number of sequence reads (38–41%), with Proteobacteria (25–28%) and Acidobacteria (10–13%) following. The treatment with potassium humate without fly ash did not influence the relative abundance of genera in the bulk soil, but increased twofold the relative abundance of the genus when combined with FA. In the rhizosphere soil bacteriobiome potassium humate without FA increased the Nocardioides relative abundance 1.8 times, whereas in combination with FA increased Sphingomonas and decreased Spartobacteria_gis relative abundance. Conclusions. Potassium humate treatment at a low rate resulted in small, but positive changes in soil and rhizosphere bacteriobiome despite the huge bacterial diversity, inherent for practically any soil, including the one used in this study. The effect of exogenic humate treatment involves a complex of various mechanisms, and detailed physiological and biochemical studies and meta-analysis of the published data are needed to understand the effect of low rate humate application on soil, plans and microorganisms.
Solutions of the contact problems of tooth gears with oblique teeth are presented without taking into account and taking into account the nonlinearrelationship between the elastic displacements of the teeth and the stresses arising in them. Expressions of the maximum contact stress and half-widthsof the contacting area are obtained for cases in which the Poisson's coefficients and the elasticity modules of the pinion and gear are not equal to each other. It is shown that the load capacity of the transmissions on contact stresses, taking into account the nonlinear relationship between the elastic deformations and stresses, is 11.4 % higher than that taking place without taking into account this nonlinearity. The proposed solutions are based on the new theory of the contact strength of elastically compressed bodies, developed by prof. A. P. Popov.
The article discusses some examples of incorrect methodology and terminology practice in soil research and publications. In particular, the authors draw attention to extremely inflated and unjustified use of the phrase “statistically significant”, to the controversy between the chemical determination and terminological definition of soil humus, to the inadequacy of using mass concentrations of chemical elements to inferring soil organic matter stoichiometry, to frequent interpreting empirical regression as if describing some conceptual relationship, to the principle impossibility to estimate bacteria and fungi numbers in soil by agar plate counts of colony-forming units. Based on the discussed examples, the authors conclude that the ease and the rate of the present-day communication flow will increasingly enhance the role of communication exchange in estimating the validity of results of a certain piece of scientific cognition, which will significantly increase the negative impact of consensuality, especially in soil science, as soil is one of the most complex natural bodies.
The amalgamation of mineral and targeted bacterial preparations represents a new generation of agricultural technology. Inoculation with combined preparations of microorganisms is more effective than inoculation with a single microorganism in stimulating plant growth by providing a more balanced diet for various crops. In this work, the effect of inoculation of 20 consortium variants on the yield indicators of three crops (wheat, buckwheat, corn) and the soil microbiome in the open field was investigated. The soil microbiome was defined by 16S rRNA sequences through NGS. Species richness of the soil microbial community (alpha diversity) was similar for all studied samples. Beta-diversity analysis revealed that the microbial diversity of three soil samples (C.bw, F.bw and Soil.bw) differed significantly from all others. At the phylum level, the number of Acidobacteriota and Firmicutes in these samples was increased. For the combination “Consortium C (Rothia endophytic GMG9 and Azotobacter chroococcum GMG39) - buckwheat”, a systemic positive improvement in all growth and yield indicators was observed. The soil of the site where buckwheat grew, inoculated by Consortium C, contained significantly more available phosphorus than all other soil samples. Such results can be explained both by the direct action of a consortium of phosphate-immobilizing and nitrogen-fixing bacteria and to acidification of the medium due to an increase in phylum Acidobacteriota bacteria in the soil.
The aim of the study. To estimate the influence of various metallurgical slags on the initial stages of plant growth and development. The study location and time. Vegetation experiment was conducted in laboratory where during 2 weeks plants were grown on mixed soil-slag substrates under favourable air temperature and humidit, substrate moisture and illumination rate of 1500 lux. Methodology. To conduct phytotoxicity testing we followed the protocol described by the federal standard GOST R ISO 22030-2009, using one species of the monocotyledonous plants (oats Avena sativa L., cultivar "Rovesnik") and one species of dicotyledonous plants (radish Raphanus sativus var. Sativus, cultivar "Saksa"). Four slags produced at the EVRAZ West Siberian plant by different technologies were used: white non-ferrous, blast furnace, converter and electrofurnace ones. The concentration of slags in soil-slag mixtures used as growth substrates, were 0 (soil);12.5; 25; 50 and 100% (pure slag). The data obtained were analyzed by descriptive statistics and correlation analysis. Main results. The growth and development of both radish and oats plants were not impeded by electrofurnace slag in all concentrations tested. The white non-ferrouswas found to be phytotoxic for both species in high concentrations only (50 and 100%). The converter and blast furnace slags had phytotoxic effect on radish only in their pure form, while for oats growth these slags were found to be harmful at 50% concentration. Conclusion. At the initial stages of plant growth and development three of the four studied metallurgical slags were found to have phytotoxic effect only in very concentrations in the substrates. Therefore to develop perspective technologies of slag use in recultivation we recommend to conduct longer vegetation and field experiments with lower slag concentrations for growing plants that can be really used for specific recultivation purpose, e.g. mixtures of legumes, grains and herbs, as well as woody bushes.
The aim of the study. The aim was to profile 16S rRNA gene diversity and to assess functional potential of bacterial assemblages in the rhizosphere of some unconventional vegetables grown in protected greenhouse conditions in West Siberia. Location and time of the study. Novosibirsk, Russia, 2016. Methodology. At the end of the growing season in the middle of September the rhizosphere soil was collected from the plants of wax gourd (Benincasa hispida), bitter melon (Momordica charantia), kiwano (Cucumis metuliferus) and cowpea (Vigna unguiculata) grown on peat-based substrate in a polyethylene-protected greenhouse that has been in operation for more than 40 years. The metagenomic DNA was extracted and amplified with V3-V4 primers for 16S rRNA genes, and the amplicons sequenced with Illumina MiSeq. The obtained OTUs tables were used to predict putative functions by running through the FAPROTAX database. Main results. The rhizosphere bacteriobiome was dominated by Proteobacteria (32±11% of the total number of sequence reads), Acidobacteria (23±7%) and Actinobacteria (18±3%) phyla, together accounting for about three quarters of the rhizosphere bacteriobiome. In total 20 bacterial phyla were found. The rhizosphere bacteriobiome was surprisingly diverse with Shannon index ranging 7.0–7.5. The number of the observed operational taxonomic units (OTUs) per sample was very high, ranging 4,500–4,900, and the potential number of OTUs estimated as 5,100–5,700; all those OTUs were evenly and equitably represented in the bacteriobiome, and dominance indices (Simpson dominance and Berger-Parker) were very low. The main dominant OTU represented Bradyrhizobiaceae family and accounted for just 1% on average. Overall the study identified 27 OTUs belonging to the Bradyrhizobiaceae family, but only four of them were ascribed to nitrogen fixation by FAPROTAX. Function prediction by FAPROTAX also suggested that bacteriobiome had a marked potential for the carbon cycle, denitrification, aromatic compound and plant polymer degradation, but no plant pathogens. The biggest difference in rhizosphere bacteriobiome diversity was observed between the bitter melon and the other three vegetable crops: bitter melon had much increased abundance of Arthrobacter and Sphingomonas as compared with wax gourd, kiwano and cowpea, and increased number of bacterial species associated with aromatic compounds degradation. Conclusion. Based on the finding that the studied rhizosphere bacteriobiomes were very diverse, we conclude that the crops were able to recruit diverse microbiota from the peat-based soil substrate, which, in its turn, means that diverse soil substrate microbiota has been sustained over several decades of the greenhouse operation. All crops apparently shaped distinct bacteriobiomes in their rhizosphere, which ideally should be included into studies of plant-associated bacterial diversity profiles for breeding and sustainable production.
Abstract The composition and structure of rhizosphere bacteriobiome of the husk tomato ( Physalis philadelphica Lam.) plants grown on Phaeozem in the open field in West Siberia, Russia (55°15’ NL, 83°31’ EL) were studied using Illumina MiSeq sequencing of the V3-V4 hypervariable region of 16S rRNA genes. In total 5898 OTUs (Operational Taxonomic Units) were found in the study, representing 20 phyla and 53 identified and 15 non-identified (below the phylum level) classes. The most OTU-rich phyla were Proteobacteria , Acidobacteria and Actinobacteria , their relative abundance in the total number of sequence reads being 26, 22 and 19%, respectively. Bacteroidetes , Gemmatimonadetes and Verrucomicrobia phyla each accounted for 2 ‒ 4%. The rest 14 of the identified phyla were quite negligible, contributing less than 0.5% each. At the OTUs level, the structure was very even and equitable, as only 7 OTUs had relative abundance ranging from 0.5 to 1.1%. The main dominant OTU represented Bradyrhizobiaceae family, implying the importance of nitrogen-fixing bacteria for plant growth and development without any mineral fertilisation. The dominance biodiversity index was very low (0.001), while Shannon index was rather high (7.5). We believe the presented husk tomato rhizosphere bacteriobiome, as the first study using new generation sequencing platform for this species, will help get a better picture of Solanaceae microbiomes in different environments, thus contributing to a more comprehensive understanding of shaping microbial communities by plant roots.
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