Organo-mineral Complexes Research Articles

ОЦЕНКА ЭФФЕКТИВНОСТИ ПРЕДПОСЕВНОЙ ОБРАБОТКИ СЕМЯН И ПОСЕВОВ БИОЛОГИЧЕСКИ АКТИВНЫМИ ВЕЩЕСТВАМИ НА ЯРОВОЙ ПШЕНИЦЕ В УСЛОВИЯХ ПРЕДКАМЬЯ РЕСПУБЛИКИ ТАТАРСТАН

The research was carried out in order to study the features of the effect of concentrated organomineral complex liquid fertilizers on the yield and grain quality of spring soft wheat. The work was carried out in 2020-2022 in the Republic of Tatarstan. The scheme of the experiment involved the study of the following options: without presowing seed treatment, herbicide in the tillering phase, insecticide in the booting phase (control); seed treatment with Batr Gum 0.5 l/t, herbicide + Batr Maks 1 l/ha in the tillering phase, insecticide + Batr Maks 1 l/ha in the booting phase; seed treatment with Chudozem 1 l/t, herbicide + Chudozem 2 l/ha in the tillering phase, insecticide + Chudozem 2 l/ha in the booting phase. Varieties Al Varis and Yoldyz were sown at a rate of 6 million viable seeds per 1 ha. Treatment of seeds with preparations Batr Gum and Chudozem increased field germination, and subsequent spraying of vegetative plants with the same preparations increased their safety for harvesting, the length of the stem and ear, the number of oats and grains in the ear. On average, over the years of research, the use of drugs provided an increase in the grain yield of the Al Varis variety at the level of 0.58 ... 0.60 t/ha, of the Yoldyz variety - 0.56 ... 0.58 t/ha. The use of Batr Maks contributed to the formation of spring wheat grains with the highest protein and gluten content in the experiment, as well as vitreousness in both varieties of soft wheat. The most economically profitable was the cultivation of the spring soft wheat variety Al Varis using the preparations Batr Gum and Batr Maks.

Stable C and N isotope abundances in water-extractable organic matter from air-dried soils as potential indices of microbially utilized organic matter

Stable carbon (C) and nitrogen (N) isotopes (13C and 15N) in water-extractable organic matter (WEOM) derived from air-dried soils may be applicable to elucidate the microbial decomposition of soil organic matter (SOM), which is crucial in terrestrial C cycles. A total of 40 soil samples were collected from a depth of 0–6 cm from a temperate broadleaved forest in Japan with vegetation succession from grassland approximately 150 years ago. Those soil samples were air-dried before the water extraction process and organic matter analysis. The C and N concentrations of WEOM were <3.6% of those of the bulk soil and were positively correlated with those of the bulk soil at a p-value of < 0.01. A positive correlation between the two fractions (i.e., WEOM and bulk soils) was also found for natural 13C and 15N abundances (δ13C and δ15N; p < 0.01). However, the C/N ratio of WEOM was slightly correlated with that of bulk soils, exhibiting a narrow range of values of ~10. Thus, those features of the WEOM were similar to the well-known features of microbial biomass. The δ13C and δ15N enrichments in WEOM relative to bulk soil, the difference in stable isotope abundances between bulk SOM and WEOM were negatively and positively correlated, respectively, with the concentrations of organo-mineral complexes and short-range order minerals (non-crystalline oxyhydroxides of aluminum and iron, allophane, imogolite, and allophane-like constituents), which play significant roles in SOM stabilization in soils. These relationships suggest that the stable isotopic enrichments in WEOM can be a good indicator of the microbial utilization of soil C and N under different substrate availabilities, which are crucial to SOM decomposition and decomposability substantially varying from local to global scales.

Functional additive based on natural premix in the diet of quails

The results of the experiment on the use of functional additive in the diet of growing quails on the basis of natural organomineral complex (sapropel) enriched with wheat bran, coniferous flour, pine nut shells and enzyme preparation Fitbest WP are presented. The experiment lasting 60 days was conducted according to the standard methodology on Japanese quails. For the experiment, two similar groups of 60 birds each (one control and one experimental group) were formed at one day of age. Both groups received basic mixed fodder corresponding to the physiological characteristics and age of the quails. In the ration of young animals of the experimental group 10% of the wheat mass was replaced by a functional additive consisting of sapropel (50%), wheat bran (20%), coniferous flour (15%) and pine nutshells (15%), enriched with the enzyme preparation Fitbest WP (100 g/t mixed fodder) designed to increase the absorption of phytate phosphorus. The birds were kept in a cage battery under the required microclimate conditions. The effect of feeding the experimental additive on the following indicators of quail chickens was studied: safety, average daily gain of live weight, meat productivity and meat quality, biochemical composition of blood. Introduction of the functional additive on the basis of natural premix (sapropel) into the mixed fodder of quails increased the safety of birds by 2.00%, live weight gain by 6.97% with no significant differences in the consumption of mixed fodder per unit production. The meat of the poultry that consumed the functional additive increased the dry matter content by 0.85%, ash by 0.61%, calcium and phosphorus by 1.05 and 1.30 times (p < 0.05). Intergroup differences in protein content and fat content were insignificant. Hematological parameters of quail chickens in the experimental groups corresponded to the physiological norm.

Using organo–mineral complex material to prevent the migration of soil Cd and As into crops: An agricultural practice and chemical mechanism study

The migration and transformations of Cd and As in soil are different, so it is difficult to simultaneously control them. In this study, an organo–mineral complex (OMC) material was prepared using modified palygorskite and chicken manure, the Cd and As adsorption capacities and mechanism of the OMC were explored, and the response of the crop to the OMC was clarified. The results show that the maximum Cd and As adsorption capacities of the OMC under pH values of 6–8 are 12.19 mg·g−1 and 5.07 mg·g−1, respectively. In the OMC system, the modified palygorskite contributed more to the adsorption of the heavy metals than the organic matter. Cd2+ may form CdCO3 and CdFe2O4, and AsO2− may form FeAsO4, As2O3, and As2O5 on the surfaces of the modified palygorskite. Organic functional groups such as hydroxyl, imino, and benzaldehyde groups can participate in the adsorption of Cd and As. The Fe species and carbon vacancy in the OMC system promote the conversion of As3+ into As5+. A laboratory experiment was conducted to compare five commercial remediation agents with OMC. Planting Brassica campestris in the OMC remediated soil with excessive contamination increased the crop biomass and decreased the Cd and As accumulation sufficiently to meet the current national food safety standards. This study emphasizes the effectiveness of OMC in preventing the migration of Cd and As into crops while promoting crop growth, which can provide a feasible soil management strategy for CdAs co-contaminated farmland soil.

Особенности трансформации микроэлементного состава почв города Ставрополя под влиянием урбогенеза

The article discusses the features of changes in the microelement composition of urban soils of the Stavropol agglomeration under the influence of urban genesis. Urban genesis, as a combination of technogenesis and landscape genesis on the territory of urban development, affects many aspects of soil functioning. Their physical properties, chemical composition, structure and mutual arrangement of genetic horizons change. Of particular relevance is the establishment of the specifics of the transformation of the microelement composition of urban soils in connection with the environmental hazard of a significant amount of trace elements classified as heavy metals. The city of Stavropol is characterized by a complex type of development, which combines one-story and multistory buildings, industrial infrastructure, and household facilities. This leads to the formation of multidirectional flows of pollutants, most of which enters the soil or subsoils. The presence of a clearly defined slope relief in the central part of the city causes the redistribution of silty fractions with water and air flows in an easterly direction. At the same time, differences in the nature of soil-forming rocks for different parts of the city largely change the pattern of differentiation of microelements in the soils of the city, associated with the peculiarities of their fixation in the composition of soil compounds. For the northwestern and central regions of the city, where Sarmatian limestone-shell rocks are exposed to the surface, calcium carbonates play a decisive role in the binding of trace elements in soils. In the soils of the southwestern and southern districts of the city, formed on loess-like loams, organomineral complexes of humic acids are of great importance in fixing microelements. In the bottoms of river valleys and gullies, formed by erosion products of Sarmatian clays, microelements in soils are present in silty fractions. Under the forest parks of the city, several dominant phases - carriers of microelements in soils are formed, depending on the predominance of one or another type of soil-forming deposits in different parts of the forest. In general, the features of the fixation of microelements in the soils of the Stavropol urban agglomeration are determined both by the natural characteristics of the territory and the specifics of the anthropogenic impact on the soil cover of pollutant flows.

Revealing the potential of organo-mineral complexes in agricultural application using bibliometrics

Organo-mineral complexes (OMCs) are referred to as biogeochemical black boxes and are widely thought to contribute to the long-term preservation of organic matter. However, the history and potential research directions of OMC research, as well as the deep applications of OMCs, have not been fully investigated. We conducted a comprehensive bibliometric study based on the Science Citation Index core database publications from 1959 to 2020 to fill this research gap in OMC studies. The results showed that a total of 751 publications involving OMCs (OMCPs) were published. There was a significant positive correlation between the frequency of international associations and the number of OMCPs. A dendrogram containing six categories and 130 keywords was constructed to represent the research content of OMCPs. In particular, the keyword co-occurrence analysis and a laboratory-scale practice jointly verified the feasibility of using silicate minerals and manure compost to produce synthetic OMCs. The life span prediction analysis revealed that the research on OMCs is in the climax stage, while the current number of studies is still less than 50% of the saturation amount. The two most potentially promising research directions are the use of OMCs in agriculture and pollutant control, which currently account for less than 30% and 25% of the saturation amount, respectively. This report clarified the research gap and predicted the development trend of OMC research using bibliometrics for the first time, and highlighted the importance of OMCs in improving agricultural production while stabilizing pollutant migration in agricultural soil.

Qualitative and Quantitative Changes in Soil Organic Compounds in Central European Oak Forests with Different Annual Average Precipitation

The various climate scenarios consistently predict warming and drying of forests in Hungary. Soils play a significant role in the long-term sequestration of atmospheric CO2, while in other cases they can also become net carbon emitters. Therefore, it is important to know what can be expected regarding future changes in the carbon storage capacity of soils in forests. We used precipitation gradient studies to solve this problem, using a type of “space–time” substitution. In this research, we primarily examined the quality parameters of soil organic matter (SOM) to investigate how climate change transforms the ratio of the main SOM compound groups in soils. For our studies, we applied elemental and 13C and 15N isotopic ratio analysis, NMR analysis, FT-IR spectra analysis, thermogravimetric and differential thermal analyses to measure SOM chemistry in samples from different oak forests with contrasting mean annual precipitation from Central Europe. Our results showed that soil organic carbon (SOC) was lower in soils of humid forests due to the enhanced decomposition processes and the leaching of Ca, which stabilizes SOM; however, in particular, the amount of easily degradable SOM compounds (e.g., thermolabile SOM, O-alkyl carbon, carboxylic and carbonyl carbon) decreased. In dry forest soils, the amount of recalcitrant SOM (e.g., thermostable SOM, alkyl carbon, aromatic and phenolic carbon and organo–mineral complexes stabilized by Ca increased, but the amount of easily degradable SOM increased further. The main conclusion of our study is that SOC can increase in forests that become drier, compensating somewhat for the decrease in forest plant biomass.

Polypropylene microplastics affect the distribution and bioavailability of cadmium by changing soil components during soil aging.

Compared with the widespread and serious heavy metal contamination in soils, microplastic pollution has gained attention only recently. Little is known about how microplastics affect the distribution of heavy metals in soils, especially across soil components level. In this study, a 180-day soil aging experiment and soil density fractionation were performed to investigate the effect of polypropylene (PP) microplastics on the binding behavior of cadmium (Cd) to solid components, i.e. particulate organic matter, organo-mineral complexes (OMC), and mineral. Results showed addition of 2-10% microplastics in soils induced the decomposition of OMC fraction by 10.88-23.10%. Compared to the control, the content of dissolved organic carbon increased, and pH, humic substances, and soil organic matter decreased with microplastics. After 180d of aging, the content of Cd in OMC fraction increased by 17.92%, while microplastics made Cd contents decline by 10.01-19.75%. The impacts strongly depended on the dose and surface characteristic of microplastics. Overall, PP microplastics increased the concentration of bioavailable Cd in soils via decreasing soil retention of Cd by the OMC fraction. These findings based on the solid components level will provide a new perspective for understanding microplastics effects on soil systems and pollutants.

Effects of Long-Term Application of Earthworm Bio-Organic Fertilization Technology on Soil Quality and Organo-Mineral Complex in Tea Garden

Soil quality is crucial for plant productivity and environmental quality sustainability. Applying bio-organic fertilizer to achieve sustainable agriculture has become popular. Tea garden soil which had been fertilized for 12 years was chosen for the study, and soil quality and microaggregate composition were studied. The results showed that earthworm bio-organic fertilizer treatment could increase the indicators of soil’s physical and chemical properties such as total carbon and total nitrogen in soil. Bio-organic fertilization technology could significantly increase the number and activity of soil microorganisms, and upgrade soil enzyme activity which was related to soil nutrients. Specifically, the activities of urease in soil were markedly enhanced due to the implication of bio-organic fertilizer. Additionally, SR-FTIR analysis revealed that clay minerals were connected as nuclei with the capacity to bind carbon, and that this interaction was aided by organic fertilization. Specifically, the replacement of chemical fertilizer with organic fertilizer can improve the ability of clay minerals and iron/aluminum/silicon oxides to protect aliphatic groups, polysaccharides and proteins. In conclusion, continuous organic amendments initialize a positive feedback loop for the maintenance of the organic–mineral complex in soils, which can contribute to enhanced soil organic carbon (SOC) storage. These results confirmed the feasibility of organic fertilizer for soil quality improvement in tea plantation ecosystems.

Elucidation of aniline adsorption-desorption mechanism on various organo-mineral complexes.

Complexes formed by organic matter and clay minerals, which are active components of soil systems, play an important role in the migration and transformation of pollutants in nature. In this study, humic-acid-montmorillonite (HA-MT) and humic-acid-kaolin (HA-KL) complexes were prepared, and their structures before and after the adsorption of aniline were analyzed. The aniline adsorption-desorption characteristics of complexes with different clay minerals and varying HA contents were explored using the static adsorption-desorption equilibrium method. Compared with the pristine clay minerals, the flaky and porous structure of the complexes and the aromaticity were enhanced. The adsorption of aniline on the different clay mineral complexes was nonlinear, and the adsorption capacity increased with increasing HA content. Additionally, the adsorption capacity of HA-MT was higher than that of HA-KL. After adsorption, the specific surface area of the complexes decreased, the surfaces became more complicated, and the aromaticity decreased because aniline is primarily adsorption onto the complexes via aromatic rings. Aniline was adsorbed onto the complexes via spontaneous exothermic physical adsorption. The amount of aniline desorbed from the complexes increased with increasing HA content, and a lag in desorption was observed, with a greater lag for HA-KL than for HA-MT.

ВЛИЯНИЕ ОРГАНО-МИНЕРАЛЬНОГО КОМПЛЕКСА ГУМИТОН С АЗОТНО-ФОСФОРНО-КАЛИЙНЫМ УДОБРЕНИЕМ НА ПРОДУКТИВНОСТЬ ГОРОХО-ОВСЯНОЙ СМЕСИ И ПЕРЕХОД 137Cs В РАСТЕНИЯ В УСЛОВИЯХ РАДИОАКТИВНОГО ЗАГРЯЗНЕНИЯ

In a vegetative experiment on soddy-podzolic sandy loamy soil, in which 137Cs was introduced, the effectiveness of use of the new organo-mineral complex Humiton and NPK on fodder crops was shown. With their combined use, the productivity of the green mass of the pea-oat mixture (1:1) increases by 49-65%, the accumulation coefficient of 137Cs decreases by 44 47%. The most effective option was the treatment of vegetative plants with Humiton against the background of the introduction of NPK.

ФІЗИКО-ХІМІЧНІ ДОСЛІДЖЕННЯ ЗБАГАЧЕНОЇ МОНТМОРИЛОНІТОМ ГЛИНИ ОКОЛИЦІ МІСТА ХМЕЛЬНИЦЬКОГО

The X-ray diffraction and complex thermal analysis show that the fraction of clay with the particle size ≤ 0.5×10–6 m from the Khmelnytskyi region is represented by the Ca–Mg-form of ferric-type montmorillonite. The mineral’s interlayer spacings are partially intercalated with natural organic matter. Based on the results of the photocolorimetry studies of the methylene blue dye sorption, the montmorillonite exchange capacity was defined and confirmed by thermogravimetric data. In terms of the dominant mineral’s ability to form organo-mineral complexes, it is recommended that studied clay be used for the environmental purposes as an engineering method of landfill protection against leachate by installing imprevious screens on these landfills.

Organo-mineral complexes in soil colloids: Implications for carbon storage in saline-alkaline paddy soils from an eight-year field experiment

The combination of organic carbon (OC) and reactive minerals is a crucial mechanism of soil carbon (C) storage, which is regulated by the formation of organo-mineral complexes on the surface of soil colloids. The effect of organic fertilizer on the storage mechanism of OC in soil colloids was studied through an 8-year field experiment, which included four treatments: i) no fertilization (control, CK), ii) only mineral N, P, and K fertilization (NPK), iii) NPK plus a low level (450 kg C ha-1 year-1) of organic fertilization (NPKC1), and iv) NPK plus a high level (900 kg C ha-1 year-1) of organic fertilization (NPKC2). The main results indicated that organic fertilizer addition significantly increased the content of aromatic-C, which was 158.7% and 140.0% higher in soil colloids than in bulk soil in the NPKC1 and NPKC2 treatments, respectively. X-ray photoelectron spectroscopy further demonstrated that the relative proportion of C=C group on the surface of soil colloids was increased by 20.1% and 19.1% in the NPKC1 and NPKC2 treatments, respectively, compared with the CK. In addition, compared with the NPK treatment, the content of reactive minerals (such as Fe and Al oxides) significantly increased with organic fertilization, which was positively correlated with C=C group in soil colloids. This indicates that aromatic-C may be retained by the formation of aromatic-mineral complexes with reactive minerals in soil colloids. Organic fertilization also significantly increased OC storage efficiency (OCSE), which was significantly higher in the NPKC1 treatment than in the NPKC2 treatment. Therefore, a moderate amount of organic fertilizer application is a better agronomic practice to increase OCSE and OC storage in saline-alkaline paddy soils.

Влияние органоминеральных питательных комплексов на урожайность малины (Rubus idaeus L.) в условиях Московского региона

The article presents the results of studies the influence of organomineral fertilizers complex «Beliy Zhemchug» on the yield and quality of raspberries (Rubus idaeus L.). The experiment was conducted on the Main Botanical Garden named after N.V. Tsitsin RAS territory, at the Laborato-ry of Cultivated Plants collection site. The objects of the study were the raspberry varieties ‘Zheltiy Guigant’, ‘Cascad’, ‘Solnishko’, ‘Novost’ Kuzmina’; organomineral complexes of fertilizers 'Beliy Zhemchug Antifreeze' (1% solution), 'Beliy Zhemchug Universalniy' (1% solution), 'Beliy Zhem-chug Drip' (1% solution), 'Beliy Zhemchug PhytoZatshita' (5% solution), 'Beliy Zhemchug StopKlop' (5% solution). Two-factor ANOVA did not show a significant effect of treatment with a phytomodulator on the raspberry fruits’ parameters. However, the fruits’ length, width and weight of ‘Zheltiy Guigant’ and ‘Cascad’ have been slightly increased, and the fruits have become more equal. ‘Solnishko’ showed a reverse reaction to the treatment. ‘Novost’ Kuzmina’ fruits parame-ters have been slightly increased while their uniformity have been reduced. The treatment had a positive effect on the sugar amount, fruits density and external evaluation. All these parameters are strongly directly related with fruits transportability, storage and original appearance retaining. Keywords: RASPBERRY, PRODUCTION, RUBUS IDAEUS L, CHEMICAL COMPLEX

Effects of application of horticultural soil amendments on decomposition, quantity, stabilisation and quality of soil carbon

Application of organic soil amendments is commonplace in horticulture to improve soil fertility. Whether this practice can also augment the soil carbon (C) pool has been of increasing interest in recent years. We used a controlled field experiment that has received annual applications of six different horticultural soil amendments for seven consecutive years. Each amendment was examined in terms of its contribution to bulk C and the distribution of C between theoretical pools, as defined by physical fractionation. Physical fractionation was combined with 13C nuclear magnetic resonance spectroscopy with cross-polarization and magic angle spinning (CPMAS NMR) analysis. Results indicated that the difference in total C concentration between treatments resulted from an increase in unprotected, free, particulate organic matter (fOM), rather than an increase in soil organic matter being occluded in aggregates or in organo-mineral complexes, and that C persisted in the fOM fraction as a result of accumulation in the alkyl C region. Unlike fresh litter or plant residues, organic amendments have undergone decomposition during the composting process (or during formation in the case of peat), in the absence of mineral soil components. This ex situ decomposition (and possible stabilization through acquired recalcitrance) could reduce the opportunity to become physically or chemically protected through association with the soil mineral phase following addition to soil. Carbon:Nitrogen (C:N) of amendment material likely influenced the rate of amendment decomposition. In addition, C:N determines the decomposition of plant litter inputs, as determined by the tea bag index.

Combined application of chemical fertilizer with green manure increased the stabilization of organic carbon in the organo-mineral complexes of paddy soil.

The influence of the combined application of chemical fertilizer with green manure on the stabilization of organic carbon (C) was explored in the organo-mineral complexes of paddy soil. The organo-mineral complexes were isolated from paddy soil treated with no fertilizer, chemical fertilizer alone, and chemical fertilizer combined with increasing amounts of Chinese milk vetch (CMV). The stability (reflected by mineralizable carbon proportion), the content and chemical composition of organic C, the Fe/Al oxides and their associated organic C in the organo-mineral complexes were investigated. The application of chemical fertilizer in combination with CMV significantly improved the stability of organic C in the organo-mineral complexes. The combined application of chemical fertilizer with CMV slightly decreased the proportion of O-alkyl C (easily decomposed) yet somewhat increased the proportions of carbonyl C and aromatic C (difficultly decomposed) and aromaticity index in the organo-mineral complexes. The treatments of chemical fertilizer combined with CMV showed more Fe oxides and Fe/Al-associated organic C and higher proportion of Fe/Al-associated organic C in the total organic C of the organo-mineral complexes. The mineralizable carbon proportion displayed significantly negative correlations with carbonyl C and Fe/Al oxide-associated organic C in the organo-mineral complexes. The Fe/Al oxides were likely to be preferentially bound with the aromatic C and carbonyl C in the organo-mineral complexes. Overall, the combined application of chemical fertilizer with CMV facilitated the association of difficultly decomposed carbon and Fe/Al oxides, which significantly improved the stabilization of organic C in the organo-mineral complexes ofpaddy soil.

Major, Trace and Rare Earth Element Distribution in Water, Suspended Particulate Matter and Stream Sediments of the Ob River Mouth

Ongoing climatic changes are influencing the volume and composition of the river waters that enter the Arctic Basin. This hydrochemical study was conducted within the mouth of the Ob River, which is one of the world’s largest rivers, providing 15% of the Arctic Ocean’s total intake. Concentrations of suspended and dissolved elements were determined using ICP–MS and ICP–AES. As compared to the world average values, the Ob river water had higher concentrations of dissolved P, As, Cu, Zn, Pb and Sb, i.e., the elements that form soluble organo-mineral complexes. The composition of suspended matter was characterized by low concentrations of most trace elements (Cd, Cr, Co, Cu, Mo, Al, Ni, Pb, V) due to their low contents in peat soils within the river drainage basin. Concentrations of dissolved forms were many times lower than concentrations of suspended forms in Al, Fe, Mn, Zn, Cr, Co, Ti, Sc, and all rare earth elements. Total concentrations of Ni, Cu, Bi, Pb, W in the river water increased by 2.5 to 4.2 times during the summer. The effects of climate change, which can cause an increase in the discharge of solid particles from thawing permafrost, are likely to lead to an increase in the discharge of certain elements into the Ob River estuary.

Organo-mineral complexes alter bacterial composition and induce carbon and nitrogen cycling in the rhizosphere.

It is widely thought that organo-mineral complexes (OMCs) stabilize organic matter via mineral adsorption. Recent studies have demonstrated that root exudates can activate OMCs, but the influence of OMCs on plant rhizosphere, which is among the most active areas for microbes, has not been thoroughly researched. In this study, a pot experiment using Brassica napus was conducted to investigate the effects of OMCs on plant rhizosphere. The result showed that OMC addition significantly promoted the growth of B. napus compared to the prevalent fertilization (PF, chemical fertilizer + chicken compost) treatment. Specifically, OMC addition increased the relative abundance (RA) of nitrogen-fixing bacteria and the bacterial α-diversity, and the operational taxonomic unit (OTU) group with RA > 0.5% in the OMC-treated rhizosphere was the result of a deterministic assembly process with homogeneous selection. Gene abundance related to nitrogen cycling and the soil chemical analysis demonstrated that the OMC-altered bacterial community induced nitrogen fixation and converted nitrate to ammonium. The upregulated carbon sequestration pathway genes and the increased soil microbial biomass carbon (23.68%) demonstrated that the bacterial-induced carbon storage in the rhizosphere was activated. This study shows that the addition of OMCs can influence the biogeochemical carbon and nitrogen cycling via regulating microorganisms in the rhizosphere. The findings provide fresh insights into the effects of OMCs on the biogeochemical cycling of important elements and suggest a promising strategy for improving soil productivity.

Structural Formation of Soil Concretes Based on Loam and Fly Ash, Modified with a Stabilizing Polymer Additive.

Finding new ways of recycling production waste to improve the characteristics of various building materials is an urgent scientific task. This article substantiates the possibility of the disposal of fly ash in the composition of soil concrete, which is used in the construction of the structural layers of road pavements, foundations of buildings and structures, as well as sites for various purposes. The scientific novelty lies in the fact that the structure formation of soil concretes based on loam and fly ash and modified with a stabilizing additive is being studied for the first time. It was found that the investigated fly ash, according to its hydraulic properties, is classified as latent active and can be introduced into the compositions of road soil concrete modified with additives of various resources. The effectiveness of the complex method of stabilization, due to changes in soil properties as a result of the use of the binding and stabilizing additives of polymer nature “Kriogelit”, is shown. It was found that the optimal content of binder and fly ash in the samples was 8 and 10 wt.%, respectively. It was established that the use of the stabilizing additive “Kriogelit” makes it possible to obtain soil concrete with the highest strength (compressive strength 2.5 MPa, flexural strength 0.5 MPa) and frost resistance of at least F15. The microstructure, the degree of dehydration and carbonization, and the phase composition of the initial raw mixtures and soil concretes stabilized with the addition of “Kriogelit” were studied by methods of scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, thermogravimetry, and infrared spectroscopy. It was shown that organo-mineral complexes, with the participation of polymer and montmorillonite, are formed in stabilized soil concrete. It was revealed that structure formation is accompanied by the physical adsorption of the polymer on active centers of silicate minerals, carbonization, and hydration–dehydration processes. It was found that the reason for the increase in the strength of stabilized soil concretes is the hydrophobization of the porous structure of minerals, as well as the formation of calcium oxide silicate and dicalcium hydrated silicate. By the method of performing biotests with the test objects Daphnia magna Straus and Chlorella vulgaris Beijer, it was proven that the developed road concretes modified with the stabilizing additive “Kriogelit” do not have an acute toxic effect on the test objects and are safe for the environment and human health.

Heterophase Synthesis of Humic Substances at Low Substrate Concentrations and Flow-Through Conditions

—Humic substances (HS) are heterogeneous and polydisperse compounds formed in soils, sediments and waters during the decay and transformation of organic residues (the process called humification). The role of extracellular free-radical condensation reactions (secondary synthesis) in the formation of HS is a subject of debate. Here we have studied the formation of HS from a mixture of monomers under the dynamic conditions and at low substrate concentrations in the presence of laccase from the fungus Coprinus comatus F-2940. Laccase was immobilized on kaolinite modified with aluminum hydroxide. We have investigated some properties of the enzyme, reactivity of phenolic acids and amino acids in the presence of laccase. The optimum of 2.6-dimethoxyphenol (2.6-DMP) oxidation by free laccase was at pH 6.0. Upon immobilization, it shifted to the acidic region (pH 4.4), the thermal stability decreased, however the kinetic parameters of 2.6-DMP oxidation remained unchanged. In terms of reactivity (% of substrate conversion by free laccase) the individual phenolic acids formed a series: caffeic (72) > ferulic (53) > gallic = syringic (43) > protocatechuic (5.5) > vanillic = p-hydroxybenzoic (0). In the mixture of phenolic acids, gallic acid was most efficiently oxidized (50%), while the other acids were oxidized in comparable amounts (13–17%). The conversion of phenolic acids increased in the presence of lysine. When a mixture of gallic, protocatechuic, syringic, ferulic acids (0.01 mM each) and lysine (0.02 mM) was passed through a flow-through microcolumn, immobilized laccase effectively oxidized the phenolic acids, the reaction products bound to the mineral phase, staining it dark. According to high performance liquid chromatography, the molecular weights of compounds extracted from the mineral phase did not exceed 900 Da, thus fulvic acid-like substances were formed. Results of the study suggest an important role of free-radical heterophase reactions in the formation of the molecular composition of the liquid phase and organo-mineral complexes.