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ABSTRACT Present review focuses on the most recent advances in the NMR of the coal‐derived humic and fulvic acids, covering exclusively the results of the liquid‐phase NMR and leaving apart an overwhelming amount of publications dealing with the solid‐state NMR investigations in this field (the latter are comprehensively reviewed elsewhere). Owing to the complexity of humic and fulvic acids together with other coal‐derived products, their 1H and 13C NMR spectra consist of a number of overlapping signals belonging to different hydrocarbon types. Comprehensive studies of humic and fulvic acids by means of NMR revealed characteristic functional groups of their composition together with spectral regions in which they resonate. Quantitative 1H and 13C NMR spectra characterize aromatic and saturated carbons spread over many structural moieties, which provides a solid guideline into molecular structure of humic and fulvic acids together with parent coal‐derived products. Nowadays, quantitative 13C NMR measurements yield information about a variety of structural parameters such as functional group distribution, aromaticity, degree of condensation of aromatic rings, and medium chain lengths together with many other more specific parameters. The structural NMR studies of the coal‐derived products are developing on a background of a marked progress in experimental and computational NMR. Discussed in the present review are the most recent advances in the liquid‐state NMR studies of the coal‐derived humic and fulvic acids together with their processing products. [ABSTRACT FROM AUTHOR]

The influence of biostimulant treatments on Passiflora species was assessed by observing changes in the growth and leaf functional compounds of plants exposed to humic acids (HAs) and seaweed extracts (SEs) to determine their optimal application doses. Four different concentrations of HA irrigation (0, 144, 192, and 285 mg·L-1 per pot assigned as HI-1, 2, 3, and 4, respectively), HA spraying (0, 96, 128, and 192 mg·L-1 as HS-1, 2, 3, and 4, respectively), SE irrigation (SI-1~4 at 0, 1, 1.33, and 2 g·L21 per pot, respectively), and SE spraying (SS-1~4 at 0, 0.5, 0.67, and 1 g·L21, respectively) treatments were applied to 'Tainung No. 1' and Passiflora suberosa cultivars every week to study their responses in plant growth traits and metabolites. Results show that leaf dry weight (DW) and root DW of 'Tainung No. 1' plants under SS-3 and HI-4 treatments, respectively, were significantly increased compared with controls. Both HI-3 and HS-3 treatments remarkably increased vine length, fresh weight (FW), and DW of leaves and shoots in P. suberosa plants compared with controls. Furthermore, 'Tainung No. 1' and P. suberosa plants respectively subjected to HI-2 and SS-4 treatments contributed to developing biostimulant applications for obtaining higher total phenol and flavonoid content per plant. Both Passiflora species are recommended for treatment with SS-4 and SE to maximize orientin and isovitexin content, and for all their beneficial applications and sustainable use in agriculture. [ABSTRACT FROM AUTHOR]

The main goal of the article is the creation and study of thermosensitive and wound-healing gelatin-alginate biopolymer hydrogels modified with humic acids. Their rheological properties, swelling and contraction behavior were experimentally investigated, elucidated using Fourier transform infrared spectroscopy and used to achieve the physiological melting point, which is necessary for successful drug delivery. It has been shown that in the gelatin-alginate-humic acid biopolymer hydrogels systems, it is possible to obtain a gel-sol transition temperature close to the physiological temperature of 37°C, which is important for drug delivery in the treatment of wounds. By changing the type and concentration of humic acids in the gelatin-alginate hydrogel, it turned out to be achievable to regulate the softening time of the gel on the human body in the range from 6 to 20 min, which provides the possibility of controlled prolonged delivery of drugs. Based on the study of the influence of calcium ions on the properties of humic acids and ion exchange, as well as the interaction of humic acids, sodium alginate and gelatin with the formation of tighter gel networks, approaches to regulate the rate of softening of hydrogels at physiological temperature and their swelling, which simulates the absorption of exudate, were proposed and implemented. In addition, low shrinkage of the hydrogel surface due to cross-linking of gelatin-alginate networks when modified with humic acids was experimentally confirmed, which is important for avoiding problems of wound contracture and contour deformations when using dressings for wound healing. Thus, the developed optimized innovative biopolymer hydrogels synergistically combine the outstanding properties of natural molecular polymers and humic acids and are promising for the creation of effective medicines for wound healing. [ABSTRACT FROM AUTHOR]

Poland is a major producer of various fruits, including strawberries. As growing consumer awareness of food quality, health, and wellbeing is increasing, farmers are receiving a new market opportunity for organic products of good quality. The integration of microbial solutions into agricultural practices can foster the transition of agricultural farms towards more resilient and sustainable production of quality food. The objective of this study was to assess the influence of novel microbial biopreparations (microbial fertilizing products) containing Bacillus sp., humic acids, and other organic compounds on the economic viability of three strawberry cultivars ('Honeoye', 'Vibrant', and 'Rumba') under organic farming conditions. This study was conducted in 2021 as a field experiment. Irrigated and non-irrigated strawberries were treated with five microbial fertilizing products (K2–K6). The single plot area was 16 m2, with a total of 144 plots. The adopted planting density of strawberries was 30,052 per hectare. K3 treatment was found to be the most universal microbial treatment in terms of positive impact on yields, with significant yield increase on both the non-irrigated (yield increase of 3.76 t·ha−1) and irrigated experiments (yield increase of 5.78 t·ha−1). The K4 treatment on the non-irrigated strawberries resulted in a yield increase of 4.96 t·ha−1, which at the same time had no effect on the yield of the irrigated experiment. On average, application of the K2–K6 combinations on the non-irrigated strawberries resulted in a yield increase from 13.4% (K2) to 33.5% (K4). The irrigated strawberries showed a yield increase from 3.9% (K4—non-significant yield increase) to as much as 36.1% (K3). The highest direct surplus for the non-irrigated strawberries was recorded for the K4 treatment (38,603 PLN·ha−1) and for K3 for the irrigated experiment (42,945 PLN·ha−1). The direct surplus for 'Rumba' and 'Vibrant' was higher than for 'Honeoye' on both the irrigated (22% and 53%, respectively) and non-irrigated (19% and 18%, respectively) experiments. The average profitability index for all tested non-irrigated and irrigated varieties improved when treated with microbial fertilizer products, with profitability indexes of 143.3–168.8% on the non-irrigated plantation and 129.2–169.7% on the irrigated plantation. The tested microbial fertilizing products proved to be valuable products to improve the productivity and economic effectiveness of organic strawberry production. At the same time, their use needs to be adapted to local plantation conditions. [ABSTRACT FROM AUTHOR]

The samples of humic acids (HAs), hymatomelanic acids (HmAs), humus acids (HuAs), and fulvic acids (FAs) and residual coals were obtained by extraction from brown coals of the Kansk-Achinsk and South Ural coal basins. The fractions of humic substances were studied using Fourier transform IR and 13C NMR (CPMAS) spectroscopy, technical analysis, and elemental analysis. It has been established that all fractions of humic substances had individual elemental and structural group compositions. [ABSTRACT FROM AUTHOR]

Information on the detection of the presence and potential for degradation of synthetic polymers (SPs) under various environmental conditions is of increasing interest and concern to a wide range of specialists. At this stage, there is a need to understand the relationship between the main participants in the processes of (bio)degradation of SPs in various ecosystems (reservoirs with fresh and sea water, soils, etc.), namely the polymers themselves, the cells of microorganisms (MOs) participating in their degradation, and humic substances (HSs). HSs constitute a macrocomponent of natural non-living organic matter of aquatic and soil ecosystems, formed and transformed in the processes of mineralization of bio-organic substances in environmental conditions. Analysis of the main mechanisms of their influence on each other and the effects produced that accelerate or inhibit polymer degradation can create the basis for scientifically based approaches to the most effective solution to the problem of degradation of SPs, including in the form of microplastics. This review is aimed at comparing various aspects of interactions of SPs, MOs, and HSs in laboratory experiments (in vitro) and environmental investigations (in situ) aimed at the biodegradation of polymers, as well as pollutants (antibiotics and pesticides) that they absorb. Comparative calculations of the degradation velocity of different SPs in different environments are presented. A special place in the analysis is given to the elemental chemical composition of HSs, which are most successfully involved in the biodegradation of SPs. In addition, the role of photo-oxidation and photoaging of polymers under the influence of the ultraviolet spectrum of solar radiation under environmental conditions on the (bio)degradation of SPs in the presence of HSs is discussed. [ABSTRACT FROM AUTHOR]

The study aimed to evaluate the effectiveness of the use of biostimulants, such as humic acid preparation, Seaweed algae extract and microbial preparation BaikalEM, on plant growth and yield. The impact of biostimulants on plant development and crop yields was studied on sugar beet (Beta vulgaris) and maize (Zea mays). To achieve this goal, field studies were conducted to compare different biostimulants in terms of germination and yield (total crop weight, weight of a single fruit, sugar, starch and protein content). The study was conducted in April-August 2023 in the Sumy district of the Sumy region. Standard agronomic methods, including soil cultivation, measurement of plant growth and yield parameters, and statistical processing of the data were used in the study. The results showed that humic acids and algae extract, when applied separately, provided the highest seed germination and yield. Among all the variants of combined application, the most significant increase in germination rates for beetroot was provided by treatment with a combination of Seaweed and Baikal-EM – 91.7%. For maize, Seaweed with humic acids and Seaweed with Baikal-EM are 92% each. The combination of Seaweed and humic acids had the best effect on the yield of both crops: 460.9 c/ha for beetroot (compared to 325 c/ha without treatment) and 61 c/ha for corn (41.5 c/ha without treatment). The microbial preparation Baikal also demonstrated a positive effect, but its results were lower, and it proved effective in combination with humic acids. The results obtained indicate the feasibility of using humic acids and algae extract to increase plant productivity, while Baikal can be useful for improving the general condition of soil and plants in combination with other fertilisers. [ABSTRACT FROM AUTHOR]

The study aimed to evaluate the effectiveness of the use of biostimulants, such as humic acid preparation, Seaweed algae extract and microbial preparation BaikalEM, on plant growth and yield. The impact of biostimulants on plant development and crop yields was studied on sugar beet (Beta vulgaris) and maize (Zea mays). To achieve this goal, field studies were conducted to compare different biostimulants in terms of germination and yield (total crop weight, weight of a single fruit, sugar, starch and protein content). The study was conducted in April-August 2023 in the Sumy district of the Sumy region. Standard agronomic methods, including soil cultivation, measurement of plant growth and yield parameters, and statistical processing of the data were used in the study. The results showed that humic acids and algae extract, when applied separately, provided the highest seed germination and yield. Among all the variants of combined application, the most significant increase in germination rates for beetroot was provided by treatment with a combination of Seaweed and Baikal-EM – 91.7%. For maize, Seaweed with humic acids and Seaweed with Baikal-EM are 92% each. The combination of Seaweed and humic acids had the best effect on the yield of both crops: 460.9 c/ha for beetroot (compared to 325 c/ha without treatment) and 61 c/ha for corn (41.5 c/ha without treatment). The microbial preparation Baikal also demonstrated a positive effect, but its results were lower, and it proved effective in combination with humic acids. The results obtained indicate the feasibility of using humic acids and algae extract to increase plant productivity, while Baikal can be useful for improving the general condition of soil and plants in combination with other fertilisers

The reducing capacity of humic acids (HA) was evaluated by the spectrophotometric method using Fe(III) complexes with organic and inorganic ligands as oxidizing agents, depending on the medium pH and reagent concentration. The maximum sensitivity of the method was observed at pH = 5 for Fe(III) complexes with α,α-bipyridyl and o-phenanthroline, as well as at pH = 9 for potassium hexacyanoferrate(III). The obtained results were supported by computational modeling of the complexation and dissociation processes. The number of available surface functional groups was found to decrease with an increase in the HA concentration due to the molecular aggregation, thus resulting in a lower reducing capacity. The formal redox potential of HA, measured by redox titration, ranged from 530–to 535 mV.

Heterogeneous systems including natural carbon matrices in the solid phase and aqueous solutions of low molecular weight organic compounds with positive and negative variations from ideality in the liquid phase are considered. The technical characterization of the considered supramolecular ensembles on the basis of brown coal of the Kara-Keche deposit (Kyrgyzstan), humic acids and humine extracted from it is given. Functional analysis of the samples was carried out using FTIR spectroscopy. The morphology of the surface of the considered carbon matrices has been investigated, in different points of which the local microelement composition has been established. An X-ray phase analysis of Kara-Keche brown coal and humic acids and humine extracted from it was carried out. The isothermal adsorption of bipolar molecules of glycine and urea, neutral D-glucose from aqueous solutions on solid carbon sorbents has been studied. An assumption has been made about the adsorption of low molecular weight organic compounds from aqueous solutions on humine and Kara-Keche coal in irregularities and pores of the carbon matrix of sorbents, for humic acids – on surface reaction centers. Due to its developed pore structure and resistance to acids and alkalis, humine from Kara-Keche coal is recommended for the purification of industrial wastewater from low molecular weight organic ecotoxicants.

Abstract Salinity stress poses a significant treat to crop yields and product quality worldwide. Application of a humic acid bio stimulant and grafting onto tolerant rootstocks can both be considered sustainable agronomic practices that can effectively ameliorate the negative effects of salinity stress. This study aimed to assess the above mentioned ameliorative effects of both practices on cucumber plants subjected to saline environments. To attain this goal a factorial experiment was carried out in the form of a completely randomized design with three replications. The three factors considered were (a) three different salinity levels (0, 5, and 10 dS m−1 of NaCl), (b) foliar application of humic acid at three levels (0, 100, and 200 mg L−1), and (c) both grafted and ungrafted plants. Vegetative traits including plant height, fresh and dry weight and number of leaf exhibited a significant decrease under increasing salinity stress. However, the application of humic acid at both levels mitigated these effects compared to control plants. The reduction in relative water content (RWC) of the leaf caused by salinity, was compensated by the application of humic acid and grafting. Thus, the highest RWC (86.65%) was observed in grafting plants with 0 dS m−1 of NaCl and 20 mg L−1 of humic acid. Electrolyte leakage (EL) increased under salinity stress, but the application of humic acid and grafting improved this trait and the lowest amount of EL (26.95%) was in grafting plants with 0 dS m−1 of NaCl and 20 mg L−1 of humic acid. The highest amount of catalase (0.53 mmol H2O2 g−1 fw min−1) and peroxidase (12.290 mmol H2O2 g−1 fw min−1) enzymes were observed in the treatment of 10 dS m−1 of NaCl and 200 mg L−1 humic acid. The highest amount of total phenol (1.99 mg g−1 FW), total flavonoid (0.486 mg g−1 FW), total soluble carbohydrate (30.80 mg g−1 FW), soluble protein (34.56 mg g−1 FW), proline (3.86 µg g−1 FW) was in grafting plants with 0 dS m−1 of NaCl and 200 mg L−1 of humic acid. Phenolic acids and phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) enzymes increased with increasing salinity and humic acid levels. Contrary to humic acid, salt stress increased the sodium (Na+) and chlorine (Cl−) and decreased the amount of potassium (K+) and calcium (Ca2+) in the root and leaf of ungrafted cucumber. However, the application 200 mg L−1 humic acid appeared to mitigate these effects, thereby suggesting a potential role in moderating physiological processes and improving growth of cucumber plants subjected to salinity stress. According to the obtained results, spraying of humic acid (200 mg L−1) and the use of salt resistant rootstocks are recommended to increase tolerance to salt stress in cucumber. These results, for the first time, clearly demonstrated that fig leaf gourd a new highly salt-tolerant rootstock, enhances salt tolerance and improves yield and quality of grafted cucumber plants by reducing sodium transport to the shoot and increasing the amount of compatible osmolytes.

Some biostimulant products provide proven benefits to plant production, potentially offering more environmentally friendly, sustainable, and natural inputs into production systems. However, the transference and predictability of known benefits between different growth environments, application protocols, and management systems are fraught with difficulty. In this study, we carried out carefully controlled glasshouse and in vitro assays with applications of humic acids, protein hydrolysates, and seaweed extract to compare the variability of biostimulant effects and dosage-dependent variations across diverse conditions, encompassing a sufficient range to comprehensively assess their full spectrum of impacts. The results demonstrated a clear trend of dosage-dependent effects with each biostimulant exhibiting a significant growth-promoting effect within a critical concentration range, but detrimental effects when the concentration fell outside this range. While substantial growth-promoting effects were observed under glasshouse conditions, biostimulant applications tended to be more sensitive and generally led to negative impacts in sterilised conditions. The combined use of biostimulants mostly resulted in detrimental and toxicological responses with only two combined treatments showing marginal synergistic effects. The findings demonstrated a complex interplay between biostimulants and the growth conditions of plants. Lack of knowledge of the indirect effects of different growth media may result in negative impacts of biostimulant applications and combinations of products outside narrow critical concentration ranges. [ABSTRACT FROM AUTHOR]

Phosphorus (P) retention in soils in the presence of organic matter (OM) has been, for years, a topic with no clear conclusions. Considering the important ecological functions of peatlands, the objective of this study is to examine the role of OM transformation in relation to P status in Histosols in the Oder Valley (Poland). Basic physical and chemical properties and the following P forms were determined in the organic horizons of 5 soil profiles from two habitats (eutrophic and dystrophic): total (Pt) and organic P (Po), available P (PM3), easily soluble P (PCaCl2), water-soluble P (PW), and fraction of Po in humic (Po_HA) and fulvic (Po_FA) acids after extraction with 0.5 mol L−1 NaOH. The results were statistically verified in both examined habitat groups separately. The higher values of mobile P forms were found in the upper organic horizons released from OM constituents as a result of their decomposition. The role of OM in P retention was strongly related to the activity of humic substances (HS): a higher Po percentage (6.9–99.4% of Po) was observed in dystrophic, whereas a lower (9.3–28.6% of Po) was observed in eutrophic Histosols. Humic acids played a dominant role in P retention compared to fulvic acids in most peat horizons, especially at pH < 5. The role of HA and FA in P retention was clearly dependent on forms found only in eutrophic Histosols. The important role of FA in P retention during OM transformation was confirmed by negative correlations between Po_FA and macronutrient ratios in both soil groups. The results confirm the variable role of OM in P retention, depending on soil environmental conditions and OM type (peat and moorsh). This may have important applications not only in areas of natural importance, for which the release of mobile P forms may be a threat, but also in agricultural areas where, for a change, we struggle to increase P availability. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the feasibility of using maize biomass for the phyto-stabilisation of iron-contaminated soils under conditions involving the application of humic acids (HAs). The biomass yield content of maize trace elements was analysed. In the absence of HAs, the first dose of Fe-stimulated plant biomass growth was compared to the absence of Fe contamination. The highest soil Fe contamination resulted in a very large reduction in maize biomass yield, with a maximum of 93%. The addition of HAs had a positive effect on plant biomass, with a maximum of 53%, and reduced the negative effect of Fe. There was an almost linear increase in maize biomass yield with increasing doses of HAs. Analogous changes were observed in dry matter content in maize. Soil treatment with Fe caused a significant increase in its content in maize biomass, with a maximum increase of three times in the series without HAs. There was also a decrease in Co, Cr and Cd content (by 17%, 21% and 44%, respectively) and an increase in Cu, Ni, Pb, Zn and Mn accumulation (by 32%, 63%, 75%, 97% and 203%, respectively). The application of HAs to the soil reduced the content of this trace element and its growth in the biomass of this plant under the influence of Fe contamination. They had a similar effect on other trace elements contained in the maize biomass. HAs contributed to a decrease in the level of most of the tested trace elements (except Ni and Pb) in the maize biomass. The reduction ranged from 11% (Cr and Mn) to 72% (Cd). The accumulation of Ni and Pb in the maize biomass was higher in the objects with HAs application than in the series without their addition. Humic acid application is a promising method for the reduction of the effects of soil Fe contamination on plants. [ABSTRACT FROM AUTHOR]

This paper studies the effect of different carbon sources on the electron transfer capacity(ETC) of humic substances(HS) during high-temperature composting of sewage sludge, using glucose and sucrose as external carbon sources,which are recoreded as CR1 and CR2. The electron donating capacity(EDC) and electron accepting capacity(EAC) of humic acid(HA) and fulvic acid(FA) are determined by electrochemical methods at different composting stages. Additionally, spectroscopic analysis techniques such as three-dimensional fluorescence spectroscopy, UV-visible spectroscopy, and Fourier transform infrared spectroscopy are employed to characterize the structural and compositional changes of HS. The results show that the EDC, EAC and RER of HS in CR1 and CR2 exhibit a continuous increasing trend during composting. Compared with CR1, CR2 has enhanced the ETC and RER of HA and FA, and has a better promotion effect on the EDC of HA and EAC of FA. Spectroscopic analysis reveals that CR2 facilitates the degradation of proteinaceous substances and the formation of humic-like and fulvic-like substances, with higher degrees of humification, aromatization, and oxygen-containing functional groups compared to CR1. Correlation analysis demonstrates that the increase in humic-like substances and aromatic compounds promote the enhancement of ETC and RER of HA. The increase in molecular weight, decrease in protein content, increase in humification degree, and formation of fulvic-like substances and aromatic compounds favor the enhancement of ETC and RER of FA. Therefore, the addition of sucrose can be an effective strategy to enhance the electron transfer capacity of composting humic substances when selecting carbon sources for sewage sludge composting. [ABSTRACT FROM AUTHOR]

Aims Understanding the inhibitory effects of natural organic substances on soil-borne pathogenic fungi and the relevant molecular mechanisms are highly important for future development of green prevention and control technology against soil-borne diseases. Our study elucidates the inhibitory effect of the combined application of humic acids (HAs) and chitosan on Alternariasolani and the light on the corresponding mechanism. Methods and Results The effect on A. solani growth by HAs incorporated with chitosan was investigated by plate culture and the corresponding mechanism was revealed using transcriptomics. The colony growth of A. solani was suppressed with the highest inhibition rate 33.33% when swine manure HAs was compounded with chitosan at a ratio of 1:4. Chitosan changed the colony morphology from round to irregularly. RNA-seq in the HAs and chitosan (HC) treatment revealed 239 differentially expressed genes compared with the control. The unigenes associated with enzymes activities related to growth and biological processes closely related to mycelial growth and metabolism were downregulated. RNA-seq also revealed that chitosan altered the expression of genes related to secondary metabolism, fungal cell wall formation and polysaccharide synthesis, and metabolism. Meanwhile, weighted gene co-expression network analysis showed that, genes expression in the module positively correlated with mycelial growth was significantly reduced in the HC treatment; and the results were verified by real-time quantitative polymerase chain reaction. Conclusions The co-inhibition effect of HAs and chitosan on A. solani is associated with downregulated genes expression correlated with mycelial growth. [ABSTRACT FROM AUTHOR]

Background: Most of the phosphorus (P) applied to low fertility, acidic tropical soils with high iron and aluminum oxide contents end up adsorbed to soil colloids and not available to crops. Diffusion of P from fertilizers was found to be facilitated by coating with humic substances and by soil moisture. Aim: However, there is still controversy on the effect of humic substances on soil P forms and diffusion, and there is a gap in the knowledge of how coating the fertilizer interacts with soil water. Methods: We studied P diffusion and availability from a conventional single superphosphate and a humic acid‐coated superphosphate in Petry dishes as affected by soil moisture and the effect of the distance of the fertilizer to the roots using a root‐matt methodology. Results: Coating single superphosphate with humic substances from leonardite (0.5%) and increasing water moisture resulted in improved P diffusion in the soil and plant P uptake. Maize dry matter increased by humic acid‐coated phosphate from 3% to 26%, depending on the distance from the fertilizer to the roots. Therefore, there is evidence of a lower P adsorption to soil colloids. The coated fertilizer increased labile P by 76% around the fertilizer granule, while higher levels of less labile P were observed with the use of conventional single superphosphate. Conclusion: All this resulted in facilitated P transport from the soil to the roots, which is important mainly in double‐cropped systems where the second crop is usually exposed to temporary drought. [ABSTRACT FROM AUTHOR]

The effect of barium ions on the biomineralization of calcium and magnesium ions is often overlooked when utilizing microbial-induced carbonate precipitation technology for removing barium, calcium, and magnesium ions from oilfield wastewater. In this study, Bacillus licheniformis was used to bio-precipitate calcium, magnesium, and barium ions. The effects of barium ions on the physiological and biochemical characteristics of bacteria, as well as the components of extracellular polymers and mineral characteristics, were also studied in systems containing coexisting barium, calcium, and magnesium ions. The results show that the increasing concentrations of barium ions decreased pH, carbonic anhydrase activity, and concentrations of bicarbonate and carbonate ions, while it increased the contents of humic acids, proteins, polysaccharides, and DNA in extracellular polymers in the systems containing all three types of ions. With increasing concentrations of barium ions, the content of magnesium within magnesium-rich calcite and the size of minerals precipitated decreased, while the full width at half maximum of magnesium-rich calcite, the content of O-C=O and N–C=O, and the diversity of protein secondary structures in the minerals increased in systems containing all three coexisting ions. Barium ions does inhibit the precipitation of calcium and magnesium ions, but the immobilized bacteria can mitigate the inhibitory effect. The precipitation ratios of calcium, magnesium, and barium ions reached 81–94%, 68–82%, and 90–97%. This research provides insights into the formation of barium-enriched carbonate minerals and offers improvements for treating oilfield wastewater. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) is one of the world's most important crops, but its productivity is at high risk as climate change increases the risk of water stress. Therefore, the development of mitigation strategies to combat water stress in agriculture is fundamental to ensure food security. Humic acids are known to have a positive effect on drought tolerance, but data on their efficacy under waterlogging are lacking. This study aimed to elucidate the effect of a new humic acid product, a by‐product of Ukrainian bentonite mining, on maize growth and nutrient status under waterlogging. Maize was grown for 9 weeks and three water stress treatments, which were applied for 14 days: waterlogging, alternating waterlogging and drought, and drought. On the day of stress application, the humic acid product (1% v/v) was applied to the leaves. Soil Plant Analysis Development (SPAD) values were recorded during the stress treatments. Plants were harvested after stressing ceased and fresh weight and P and Zn status were analyzed. Drought reduced shoot fresh weight, while it was unaffected under waterlogging. This is in contrast to SPAD readings, which showed a significant decrease over time under submergence, but not under drought. Under alternating stress, although SPAD values declined under waterlogging but stabilized when switched to drought, no growth reduction was apparent. Application of the humic acid product was ineffective in all cases. Although anthocyanin discoloration occurred under waterlogging stress, P deficiency, which is usually the main factor driving anthocyanin formation, was not the reason. Interestingly, Zn concentration decreased under waterlogging but not under the other stresses, which was alleviated by humic acid application. However, no effect of foliar‐applied humic acids was observed under alternating and drought stress. It can be concluded that the tested humic acid product has the potential to improve the Zn status of maize under waterlogging. [ABSTRACT FROM AUTHOR]

The initial brown coals, humic substances and their fractions obtained from them, as well as bitumen were characterized using technical and elemental analysis, Fourier infrared, 13C NMR spectroscopy. The component composition of the obtained bitumen and its fractions was studied using the chromatography-mass spectrometry method. It has been established that during the fractionation of humic substances, the main part of aromatic compounds is concentrated in humus acids. The data on the study of the phytostimulating activity of various fractions of humic substances and their mixtures with the saponified component of the resin of extraction bitumen, in relation to wheat seeds of the Aphrodite variety, are presented. A positive eff ect on the growth performance of the studied fractions of humic substances separately and when used together in a mixture with the saponified component of bitumen resin was shown. The phytoactivity index (PI) of the studied initial samples and their mixtures is in the range of 1.04–1.64. [ABSTRACT FROM AUTHOR]

Humic acids (HAs) produced during the landfill on Cr(VI) fate and their combined impact on the anaerobic digestion (AD) process has not yet been fully elucidated. This study systematically evaluated the interactions and mechanism of HAs on the AD of Cr(VI)-contaminated leachate. Results indicated that high concentrations of HAs (i.e., 200, 500, 1000 mg/L) detoxified the Cr(VI) on AD and the maximum methane production of 1011.63 ± 248.01 mL/g COD was obtained at 500 mg/L HAs, representing an 18.4% increase compared to the control group. Mechanistic studies demonstrated that high concentrations of HAs (i.e., C4-C5) detoxified the Cr(VI) on AD via adsorption and reduction, and the enhanced direct interspecies electron transfer (DIET) played an important role in methane production. The adsorption capacity (32.89 mg Cr(VI)/g HAs) was significantly higher than the granular sludge (3.29 mg Cr(VI)/g TS) and adsorbed Cr(VI) was reduced to less toxic Cr(III) due to the presence of functional groups of HAs (e.g., hydroxyl and phenolic groups), achieving detoxification of Cr(VI) on AD. The increase of viable microbial cells proved the detoxification of high HAs concentrations. Moreover, the increase in the abundance of Syntrophomonas and Methanosaeta has led to the higher methane production at high HAs concentration. [ABSTRACT FROM AUTHOR]

The possibility of extracting Cu compounds through adsorption using galvanic sludge modified with solutions of humic acids was investigated. The chemical and structural composition of rigid galvanic sludge from printed circuit board production was examined. The primary phase-forming element is Fe compounds in the form of β-FeOOH, constituting up to 45% of the sludge mass. X-ray phase analysis of the sludge revealed the presence of two main phases: akaganeite (β-FeOOH) and an atacamite-like crystalline phase of copper hydroxychloride (Cu(OH)3Cl) in quantities exceeding 10%. The conditions for leaching Cu compounds from the sludge and the effect of thermal treatment on the sludge adsorption capacity were determined. Copper was leached from galvanic sludge using an H2SO4 solution within the pH range of the equilibrium solution of 3–5.5. This allowed for the leaching of up to 97% of copper, with minimal dissolution of Fe compounds. The Cu concentration in the leaching solution reached 10–15 g/dm3, while the concentration of Fe ions did not exceed 1 mg/dm3, enabling the subsequent utilization of these solutions for Cu electroextraction. The modification of the sludge with humic acid solutions increases its adsorption capacity for copper ions by more than threefold. [ABSTRACT FROM AUTHOR]

While humic substances (HS) are recognized for their role in enhancing plant growth under abiotic stress by modulating hormonal and redox metabolisms, a key question remains: how do HS influence the microbiota associated with plants? This study hypothesizes that the effects of HS extend beyond plant physiology, impacting the plant-associated bacterial community. To explore this, we investigated the combined and individual impacts of HS and osmotic stress on tomato plant physiology and root endophytic communities. Tomatoes were grown within a sterile hydroponic system, which allowed the experiment to focus on seed-transmitted endophytic bacteria. Moreover, sequencing the 16S-ITS-23S region of the rrn operon (~4,500 bp) in a metabarcoding assay using the PNA-chr11 clamp nearly eliminated the reads assigned to Solanum lycopersicum and allowed the species-level identification of these communities. Our findings revealed that HS, osmotic stress, and their combined application induce changes in bacterial endophytic communities. Osmotic stress led to reduced plant growth and a decrease in Bradyrhizobium sp., while the application of HS under osmotic stress resulted in increased tomato growth, accompanied by an increase in Frigoribacterium sp., Roseateles sp., and Hymenobacter sp., along with a decrease in Sphingomonas sp. Finally, HS application under non-stress conditions did not affect plant growth but did alter the endophytic community, increasing Hymenobacter sp. and decreasing Sphingomonas sp. This study enhances the understanding of plant–endophyte interactions under stress and HS application, highlighting the significance of the vertically transmitted core microbiome in tomato roots and suggesting new insights into the mode of action of HS that was used as a biostimulant.

Abstract Background Traditional agriculture is on the front line of climate change, being most impacted by the increase in the intensity and frequency of extreme events, such as floods, drought and rising temperatures. Local ecological knowledge is a recognized keystone of successfully managed socioecological systems, but loss of soil fertility, water scarcity, incidence of diseases and decreased production due to climate change are linked to the greater vulnerability experienced by traditional farmers. Plant biostimulants are natural products used to stimulate nutrient uptake and efficiency by crops, increase tolerance to abiotic/biotic stress and improve quality without negative impacts on the environment if obtained from renewed sources. Humic substances are some of the most used plant biostimulants in agriculture and play a central role in plant adaptation. Materials and methods We reviewed and discussed a sample set of papers (n = 52) about humic substances to mitigate abiotic stress in crops using data basis from Web of Science (Clarivate Analytics), Scopus—IBM (International Business Machines Corporation), and Scielo (Scientific Electronic Library Online). Results The predominance of authors in the global south is notable, but it is not a coincidence, since this is where the effects of climate change will have the greatest impact. The mechanisms involved in the stress mitigation involve the activation of signaling factors, gene response induction, the accumulation of osmoprotective and anti-oxidant compounds, the induction of antioxidative metabolism, ion homeostasis, membrane transport and adjustment of hormonal balance. The intriguing question is: how can a complex mixture of molecules affect so many distinct effects on plants responsible for plant adaptation? Conclusions The complexity of humic substances challenges our knowledge method, but supramolecular chemistry may provide answers that enable us to broaden our understanding of the plant defense mechanisms modulated by these substances. Graphical Abstract

Background: Traditional agriculture is on the front line of climate change, being most impacted by the increase in the intensity and frequency of extreme events, such as floods, drought and rising temperatures. Local ecological knowledge is a recognized keystone of successfully managed socioecological systems, but loss of soil fertility, water scarcity, incidence of diseases and decreased production due to climate change are linked to the greater vulnerability experienced by traditional farmers. Plant biostimulants are natural products used to stimulate nutrient uptake and efficiency by crops, increase tolerance to abiotic/biotic stress and improve quality without negative impacts on the environment if obtained from renewed sources. Humic substances are some of the most used plant biostimulants in agriculture and play a central role in plant adaptation. Materials and methods: We reviewed and discussed a sample set of papers (n = 52) about humic substances to mitigate abiotic stress in crops using data basis from Web of Science (Clarivate Analytics), Scopus—IBM (International Business Machines Corporation), and Scielo (Scientific Electronic Library Online). Results: The predominance of authors in the global south is notable, but it is not a coincidence, since this is where the effects of climate change will have the greatest impact. The mechanisms involved in the stress mitigation involve the activation of signaling factors, gene response induction, the accumulation of osmoprotective and anti-oxidant compounds, the induction of antioxidative metabolism, ion homeostasis, membrane transport and adjustment of hormonal balance. The intriguing question is: how can a complex mixture of molecules affect so many distinct effects on plants responsible for plant adaptation? Conclusions: The complexity of humic substances challenges our knowledge method, but supramolecular chemistry may provide answers that enable us to broaden our understanding of the plant defense mechanisms modulated by these substances. [ABSTRACT FROM AUTHOR]

The principle of sustainable fertilisation in modern agriculture, which ensures that the soil is maintained in a fertile state requires the search for alternatives to manure fertilisation for products based on humic substances to increase the organic matter content of soils.The advantage of leonardite over conventional natural and organic fertilisers is mainly due to its high content of organic matter and humic substances (humic and fulvic acids). Leonardite, due to the presence of humic acids in it, can be suitable for soil amendment and yield of barley. In the conducted studies, the yield increase after adding Rosahumus fertilizer to the soil at a rate of 6 kg.ha−1 + NPK (Nitrogen, Phosphorus, Potasssium) was found to be 11% compared to the control (NPK).There were no changes in the Corg. content of the soil as a result of the application of Rosahumus fertilizer with NPK. The fertilizer only slightly modified the fractional composition of humus. In the future, we should expect an increase in the use of leonardite-derived humic substances in fertilizers and soil conditioners to stabilize soil organic matter. [ABSTRACT FROM AUTHOR]

Clear-cutting induces biogeochemical, ecological, and hydrological changes in the soil environment, especially in the conditions of climate change effect. This type of management affects soil carbon sequestration. In this paper, we generalize the effect of clear-cutting in mountainous mixed coniferous forests on the direction of organic matter transformation and the properties of humic substances. Soil samples of dystric Cambisols were taken two and ten years after clear-cutting (CC). Soil profiles located at the same elevation under forest cover without any harvesting were used as references. The contents of total organic carbon, total nitrogen, qualitative and quantitative characteristics of humic substances, as well as the mineralogical composition and the clay-associated C fraction, were analysed. Under mountainous conditions, clear-cutting in the mixed coniferous forest enhanced organic matter decomposition and decreased the low-molecular weight humic fraction. It also caused the accumulation of more stable humic acids, particularly in the upper soil horizons, and resulted in accumulation of humic substances with higher contents of C and O and lower H content in the first years after CC. Clear-cutting in the first two years reduced the aliphacity of humic acids in the topsoil. Ten years after harvesting, a significant increase in aliphacity in the Oa horizon confirmed organic matter recovery. Mixed coniferous forests are more resistant to biotic and abiotic disturbances, which is particularly important in the face of violent weather phenomena related to climate change. Thus, forest management plans should consider the conversion of spruce monocultures to mixed coniferous forests. [ABSTRACT FROM AUTHOR]

The lignin derivatives generated during pulping might be responsible for the suboptimal performance of anaerobic reactors during the treatment of pulping wastewater. However, the exact mechanisms by which these derivatives exert influence remain unclear. This study investigated the influence of lignin derivatives, simulated using humic acids (HAs), in anaerobic granular sludge (AnGS). Compared to the enzymes present during floc-bonding and granule-bonding, the HAs impeded the conversion of unhydrolyzed substrates into methane and caused considerable inactivation of free enzymes. Simultaneously, the HAs suppressed agglomeration and weakened the strength of the AnGS. Furthermore, calcium ions helped maintain the integrity of the sludge structure. Therefore, the inhibition of extracellular enzymes using lignin derivatives delays the methanation of unhydrolyzed substrates, resulting in a reduced biomass within AnGS reactors owing to sludge disintegration and biomass loss. This study serves as a reference for investigating the persistent risks originating from lignin derivatives associated with using anaerobic granular-sludge bed reactors to treat pulping wastewater. [ABSTRACT FROM AUTHOR]

Humic substances (HS) belong to a fairly common class of organic compounds in nature, which are a component of soils, peat, lignite and sapropels. Some properties of humates (salts of humic acids) make it possible to use them in various fields – crop production, animal production, well drilling and soil structuring. The biological and chemical activity of humic substances is well known. It is caused by the presence of such functional groups as carboxyl, hydroxyl, carbonyl, nitrogen- and sulfur-containing in the composition of GR macromolecules. This fact also serves as a basis for a more extensive study of other properties of GR, namely antioxidant activity. Purpose. Deepening and expanding the understanding of the biological and antioxidant activity of lignite humic (HA) and hymatomelanic (HmA) acids, determining its nature and evaluating the prospects of its use in little-studied processes of oxidation of organic and consumer substances. Methodology. The paper used a photocolorimetric method for determining the antiradical activity (ARA) of two components of humic substances of domestic lignite - humic and hymatomelanic acids. The antioxidant activity (AOA) of humic and hymatomelanic acids from lignite was determined using the gas volumetric method, evaluating the rate of reaction inhibition using the example of the initiated liquid-phase oxidation of cumene with oxygen. Findings. It was established that humic acids exhibit more pronounced antioxidant properties in the processes of radical-chain oxidation of hydrocarbons compared to hymatomelanic acids. The total AOA of HA is 1.68 relative units, which is almost three times higher than this figure for HmA (0.50). On the other hand, it has been experimentally proven that hymatomelanic acids have more pronounced antiradical properties than humic acids. ARA HmA is 0.90 relative units, which is approximately three times more than the similar value for HA (0.57). Originality. Despite the fact that a number of methods for determining the antiradical and antioxidant activity of low-molecular antioxidants and their mixtures have been developed, a method for determining these indicators for high-molecular native compounds has not yet been created. For the first time, a method for determining the antiradical effect of humic substances using the stable 2.2-diphenyl-1-picrylhydrazyl radical (DPPH) was proposed and experimentally tested. A method for determining the antioxidant activity of humic and hymatomelanic acids in hydrocarbon oxidation processes (on the example of cumulus) has been developed. The convenience and satisfactory reproducibility of the developed methods are shown. Practical value. The green-chemistry related development and application of drugs based on native and modified humic substances as polymers with adjustable redox properties (redox polymers) is a relevant direction of sustainable development of society. These substances are the basis for obtaining new medicines, plant protection products, new sorbents, preparations for the reclamation of territories contaminated with radionuclides, heavy metals, organic ecotoxicants, oil products, etc. [ABSTRACT FROM AUTHOR]

Samples of humic materials—humic acids and fulvic acids—derived from Tisul lignite (Kansk-Achinsk Basin) are investigated by ESR (electron spin resonance) spectroscopy. The concentration of free radicals declines in the following sequence: lignite, humic acids, fulvic acids. The proportion of aliphatic radicals increases in the same sequence. By simulation of the ESR spectra of the fulvic acids and comparison with the experimental spectra, natural complexes of fulvic acids with Fe3+ and Mn2+ ions are detected. By determining the splitting parameters in zero field (D and E), it is established that the complexes with Fe3+ have axial symmetry, with a complex multilevel structure. The internal coordination sphere of the complex consists of water molecules, whereas the external coordination sphere consists of oxygen-bearing fulvic acid groups. The calculated hyperfine structure constant of the experimental ESR spectra for the complexes with Mn2+ (79.7 G) is lower than the typical value for the octahedral Mn2+ complex [Mn(H2O)6]2+. That indicates partial replacement of the water molecules by oxygen-bearing functional groups of fulvic acids. [ABSTRACT FROM AUTHOR]

An interesting feedstock for energy purposes is plant biomass due to its renewability, widespread availability and relatively low cost. One plant with a high and versatile use potential is maize. Plants used for energy production can be grown in polluted areas, e.g., with iron. The aim of the study was to determine the effect of humic acids (HAs) on the yield, calorific value and other energy parameters and chemical composition of maize biomass applied as a phytostabiliser on iron-contaminated soil. The soil was contaminated with iron at 0, 250, 500 and 750 mg kg−1. The HAs were added to the soil in the following amounts: 0, 0.3, 0.6 and 0.9 g kg−1 of soil. Soil contamination with iron had relatively little effect on the heat of combustion and calorific value of biomass and very strongly reduced plant height (42%), dry matter yield (95%) and energy production of maize biomass (90%), the SPAD index at the fifth leaf unfolded stage (44%) (as opposed to the stem elongation stage), sodium, magnesium and phosphorus contents, and increased calcium, potassium and nitrogen contents of maize. The application of HAs to the soil had a positive and very large effect on both the height and biomass parameters studied, resulting in an increase in plant height (22%), dry matter yield (67%) and energy production from maize biomass (62%). Changes in the heat of combustion and calorific value of the biomass were minimal but positive. HAs contributed to a decrease in the value of the SPAD index during the stem elongation phase of maize and in the content of all macronutrients in maize biomass as a result of a reduction in the effect of iron on macronutrient content and to a significant increase in maize dry matter yield in plots with their application. The application of HAs appears to be an effective adjunct in the phytostabilisation of iron-contaminated soils by growing crops for energy purposes. [ABSTRACT FROM AUTHOR]

The interaction of humic acids (HAs) isolated from oxidized brown coal with the polyaromatic hydrocarbon naphthalene has been studied. The electron-donating properties of HAs were evaluated based on the intensity of electronic transitions in the UV region and calculated descriptors. The modification of the HA structure was carried out by mechanical activation (MA) under alkaline and oxidative conditions. A significant increase in the fraction of aromatic and oxidized fragments in the HA structure after MA under oxidative conditions increased the intensity of binding HAs to naphthalene. A significant increase in the adsorption capacity of mechanically activated HAs in a dispersive aqueous medium with naphthalene was demonstrated. [ABSTRACT FROM AUTHOR]

Humous and hymatomelanic acids are obtained by separating humic acids from Kansk-Achinsk and South Ural lignite. The yield of humic material is greatest for naturally oxidized lignite from the Tisul'sk field in Kansk-Achinsk Basin: 60.9% humic acids, 49.6% humous acids, and 11.3% hymatomelanic acids. The acid fractions are characterized by Fourier transform IR (FTIR) and 13C NMR (CPMAS) spectroscopy, as well as elemental and technical analysis. The elemental composition and structural group composition of the humic, humous, and hymatomelanic acids differ significantly. The composition of the humic acids is complex, with aromatic and aliphatic fragments. The hymatomelanic acids consist mainly of aliphatic fragments. The content of carbon and aromatic fragments is higher for humous acids, which are insoluble in alcohol, than for hymatomelanic acids. [ABSTRACT FROM AUTHOR]

The purpose of the study is to examine the main methods of obtaining fertilizers and optimizing processes. Using methods of analysis, comparison, and experimentation, three main approaches to obtaining fertilizers were identified: grinding and mixing with potassium hydroxide (KOH), ultrafine grinding with chemical additives, and a complex method for processing caustobioliths. Comparative analysis of the investigated methods allowed for identifying their advantages, disadvantages, and effectiveness. The key result was the ability to determine the most effective method for producing humate-containing fertilizers from brown coal, depending on specific production conditions and requirements. The results of the study showed that the ultrafine grinding process with chemical additions, such as urea and alkali metal hydroxides, showed promising potential for creating highly effective humate-containing fertilizers from brown coal, in addition to the comparative analysis. After thorough optimization, this technique showed improved fertilizer utilization and superior plant uptake, making it a strong contender for sustainable farming methods. Nevertheless, achieving optimal results requires detailed process parameter optimization. The study underscores the importance of using brown coal in humate-containing fertilizer production as an environmentally safe and sustainable approach. The results can contribute to further development and improvement of humate-containing fertilizer production methods, promoting sustainable agriculture and increased crop productivity. [ABSTRACT FROM AUTHOR]

• Inoculation with the UFRB FA72A2-1 isolate significantly improved corn growth. • Higher leaf nitrogen content, photosynthetic pigments and net photosynthesis were verified under inoculation with the isolate UFRB FA72A2-1. • Inoculations with UFRB FA34C2-2 and commercial strain, combined with the use of humic substances resulted in an increase in photosynthetic pigments and growth of corn plants. • The effects of humic substances are dose-dependent. This study investigates the morphophysiological traits and nutritional status of corn plants subjected to varying levels of humic substances, plant growth-promoting bacteria, and conventional fertilization. A controlled greenhouse experiment was conducted, involving the administration of diverse humic substance concentrations (0.0, 1.5, 3.0, 4.5, and 6.0 L ha−1), distinct bacterial strains (isolates UFRB FA72A2-1 + nitrogen supplementation, UFRB FA34C2-2 + nitrogen supplementation, and a commercial strain + nitrogen supplementation), alongside two control treatments (total nitrogen and cover), totaling 68 experimental plots. The evaluation encompassed parameters such as emergence percentage, emergence speed, emergence speed index, and emergence speed coefficient during the seedling emergence phase. Subsequently, the assessment extended to plant height, stem diameter, leaf count, leaf area, shoot biomass, root biomass, total dry mass, root volume, net photosynthesis, stomatal conductance, transpiration, as well as the quantification of total chlorophyll, carotenoids, nitrogen, and phosphorus content. Corn plants inoculated with the UFRB FA72A2-1 isolate exhibited superior growth, marked by elevated leaf nitrogen content, enhanced photosynthetic pigment concentration, and increased net photosynthesis. As for the UFRB FA34C2-2 and the commercial strain, the combined application of 1.5 and 3.0 L ha−1 of humic substances elevated the concentration of photosynthetic pigments and resulted in heightened stem height and diameter. Moreover, this combination contributed to an augmented total dry mass in the case of the commercial strain. Application of humic substances in isolation at these specified concentrations yielded a significant enhancement in net photosynthesis and shoot dry mass for corn plants. This study underscores the potential synergy between plant growth-promoting bacteria and humic substances in stimulating corn plant growth. The effect of the combined application of humic substances with plant growth-promoting bacteria depends on the dose of the humic substance and the species involved. [ABSTRACT FROM AUTHOR]

A recent study published data on the growth performance, relative weights of the organs of the gastrointestinal tract, liver histology, serum biochemistry, and hematological parameters for turkey poults fed an experimental diet contaminated with aflatoxin B1 (AFB1) and humic acids (HA) extracted from vermicompost. The negative effects of AFB1 (250 ng AFB1/g of feed) were significantly reduced by HA supplementation (0.25% w/w), suggesting that HA might be utilized to ameliorate the negative impact of AFB1 from contaminated diets. The present study shows the results of the remaining variables, as an extension of a previously published work which aimed to evaluate the impact of HA on the intestinal microbiota, gut integrity, ileum morphometry, and cellular immunity of turkey poults fed an AFB1-contaminated diet. For this objective, five equal groups of 1-day-old female Nicholas-700 turkey poults were randomly assigned to the following treatments: negative control (basal diet), positive control (basal diet + 250 ng AFB1/g), HA (basal diet + 0.25% HA), HA + AFB1 (basal diet + 0.25% HA + 250 ng AFB1/g), and Zeolite (basal diet + 0.25% zeolite + 250 ng AFB1/g). In the experiment, seven replicates of ten poults each were used per treatment (n = 70). In general, HA supplementation with or without the presence of AFB1 showed a significant increase (p < 0.05) in the number of beneficial butyric acid producers, ileum villi height, and ileum total area, and a significant reduction in serum levels of fluorescein isothiocyanate–dextran (FITC-d), a marker of intestinal integrity. In contrast, poults fed with AFB1 showed a significant increase in Proteobacteria and lower numbers of beneficial bacteria, clearly suggesting gut dysbacteriosis. Moreover, poults supplemented with AFB1 displayed the lowest morphometric parameters and the highest intestinal permeability. Furthermore, poults in the negative and positive control treatments had the lowest cutaneous basophil hypersensitivity response. These findings suggest that HA supplementation enhanced intestinal integrity (shape and permeability), cellular immune response, and healthier gut microbiota composition, even in the presence of dietary exposure to AFB1. These results complement those of the previously published study, suggesting that HA may be a viable dietary intervention to improve gut health and immunity in turkey poults during aflatoxicosis. [ABSTRACT FROM AUTHOR]

The multitude of beneficial properties of humic acids (HA), due, among other, to the presence of numerous functional groups in their structure, determines their increasing industrial use, not only in agriculture but also as feed components or ingredients in food supplements. The continuous increase in demand for these substances determines their high market value and prompts the search for efficient methods to isolate them from natural raw materials. However, in addition to the high isolation efficiency of humic acids, the quality aspect is equally important when selecting extraction methods, and the extraction method should not cause changes within the natural structure of the macromolecules. In the present study, a complex analysis of the application of low-intensity ultrasound-assisted extraction (LI-UAE) for the isolation of humic acids from peat was presented. Based on the fractional factorial design and statistical analysis, the influence of the parameters of the LI-UAE process on the efficiency of humic acids extraction with the use of NaOH and NH4OH solutions as extractants was described. The polynomial models, which defined the efficiency of the extraction process as a function of the most important parameters, were proposed, and the optimal extraction conditions were identified for both extactants tested. On the basis of the results, it was concluded that the use of ultrasound increases the amount of extracted humic acids, compared to the traditional process. Moreover, qualitative analysis of the products, using spectroscopic methods, did not show significant differences in the molecular structure of the humic acids, which were extracted in the processes studied. [ABSTRACT FROM AUTHOR]

Small floodplain lakes (SFLs), characterized by their diminutive size (

Relevance. The necessity to know the conditions and forms of W concentration in coals for solving a number of scientific and engineering problems at complex development of coal deposits. Aim. Complex estimation of W modes of occurrence in coal for development of measures for rational ecologically safe use of coal. Methods. Correlation analysis, scanning electron microscopy, infrared spectroscopy, coal group analysis, inductively coupled plasma mass spectrometry, instrumental neutron activation analysis. Results and conclusions. The modes of occurrence of W in coal were studied by a complex of methods. In the majority of W-enriched coal deposits, a negative significant correlation of its content in coal and coal ash with ash yield was found, indicating its association with organic matter. Using the method of coal group composition analysis, it was found that the main carrier and concentrator of W in the studied lignite deposits is organic matter. The contribution of the mineral phase in general in W-rich coals and in coals with its normal content does not exceed 20%, usually less than 5%. These conclusions are also confirmed by infrared spectroscopy data, according to which no more than 15% of the metal in the samples studied is associated with mineral phases. The association of W with high molecular humic acids predominates. In anomalously W-enriched lignites, the humic acid phase represents 76 to 88% of the gross metal content. The role of bitumen and low-molecular-weight humic acids in the balance of W is marginal at their different levels in the coals. Mineral phases of W are not characteristic of coal. Nano-microinclusions of scheelite, wolframite, hubnerite and ferberite were recorded as isolated occurrences. The main mineral phases are associated with Fe and Mn hydroxides, in which W is presented as a trace element in the amount of 1–5% together with other elements (Ge, As, etc.). In more metamorphosed bituminous and anthracite coals, authigenic mineral formations were found, represented by tungstite, phyllotungstite, native W and complex Fe-Mn-Ca-W-O mineral phases.

Abstract Maize (Zea mays L.) is one of the world's most important crops, but its productivity is at high risk as climate change increases the risk of water stress. Therefore, the development of mitigation strategies to combat water stress in agriculture is fundamental to ensure food security. Humic acids are known to have a positive effect on drought tolerance, but data on their efficacy under waterlogging are lacking. This study aimed to elucidate the effect of a new humic acid product, a by‐product of Ukrainian bentonite mining, on maize growth and nutrient status under waterlogging. Maize was grown for 9 weeks and three water stress treatments, which were applied for 14 days: waterlogging, alternating waterlogging and drought, and drought. On the day of stress application, the humic acid product (1% v/v) was applied to the leaves. Soil Plant Analysis Development (SPAD) values were recorded during the stress treatments. Plants were harvested after stressing ceased and fresh weight and P and Zn status were analyzed. Drought reduced shoot fresh weight, while it was unaffected under waterlogging. This is in contrast to SPAD readings, which showed a significant decrease over time under submergence, but not under drought. Under alternating stress, although SPAD values declined under waterlogging but stabilized when switched to drought, no growth reduction was apparent. Application of the humic acid product was ineffective in all cases. Although anthocyanin discoloration occurred under waterlogging stress, P deficiency, which is usually the main factor driving anthocyanin formation, was not the reason. Interestingly, Zn concentration decreased under waterlogging but not under the other stresses, which was alleviated by humic acid application. However, no effect of foliar‐applied humic acids was observed under alternating and drought stress. It can be concluded that the tested humic acid product has the potential to improve the Zn status of maize under waterlogging.

Abstract Background Iron oxide mineral–humic complexes serve as a reservoir of bioavailable Fe for plants, releasing metal ligands and providing Fe–humic complexes directly usable by plant Fe-uptake mechanisms. In this study, we synthesized and characterized goethite α-FeOOH (G) nanoparticles (NPs) intercalated in coal (GC) to estimate the bioactivity effect of humic acids (HA). The synthesized GC NPs were characterized by X-ray diffraction, scanning electron microscopy (SEM), Mössbauer spectroscopy, N2 adsorption–desorption Brunauer–Emmett–Teller (BET) specific surface area, zeta potential, hydrodynamic particle diameter, iron ions release, and a phytoassay method of root elongation using the higher plant Sinapis alba. Results X-ray diffraction revealed that G was the primary phase in both GC and GC–HA complexes. Mössbauer spectroscopy analysis identified a goethite-doped Fe2+-in the GC samples. The intercalation of G into the coal matrix increased the specific surface area of GC, enhancing its HA sorption capacity. In addition, GC–HA demonstrated superior plant growth stimulation compared to HA and GC alone, indicating its role in colloidal stability. In contrast to GC, GC–HA exhibited a more consistent and time-dependent release of Fe3+ and Fe2+. This sustained Fe release from GC–HA, coupled with the formation of Fe3+ and more bioavailable (soluble) Fe2+ humic complexes is a promising result in terms of iron nanofertilizers production. Conclusions The use of goethite nanoparticles intercalated within a coal matrix and subsequently complexed with HA contributes to prolonged phytoactivity by employing slowly released nutrient additives within the coal mesoporous matrix. Graphical Abstract

The stabilizing ability of humic acids isolated from reed fen peat of the Ryazan region in the relation to oil and petroleum products under various abiotic conditions of the aquatic environment has been studied. The applicability of the used biological products in conditions of low temperature and increased salinity of the medium is determined. The stabilizing ability of the developed biological products was determined by the transmittance of emulsions. It was found that in the condition of increased salinity, the transmission coefficient decreases by 5-24% relative to the control experiment for crude oil, diesel fuel and waste oil when using monocultural biological products. It was found that the use of polycultures in the composition of biological products significantly reduces the transmittance by 24-43% for “HAs from reed peat of the Ryazan region + Rhodococcus erythropolis S67 + Rhodococcus erythropolis X5” and 10-29% for “Humic acids of reed peat of the Ryazan region + Rhodococcus erythropolis S67 + Rhodococcus erythropolis X5 + Pseudomonas fluorescens 142NF”. The applicability of the studied biological products in conditions of low temperatures is confirmed by a decrease in the transmission coefficient to 68-73% for diesel fuel, to 60-64% for used synthetic engine oil and to 64-69% for crude oil. It was found that the transmission coefficient decreases in the series: “Humic acids of reed fen peat of the Ryazan region + Rhodococcus erythropolis X5” → “Humic acids of reed peat of the Ryazan region + Pseudomonas fluorescens 142NF” → “Humic acids from reed fen peat of the Ryazan region + Rhodococcus erythropolis S67”. It was revealed that the reduction of the transmission coefficient of oil emulsions occurs due to the combined use of humic acids isolated from reed peat of the Ryazan region and the association of bacteria (both when using 2 and 3 strains). The stabilizing ability of humic acids in conditions of increased salinity was comparable to it in conditions of reduced temperature. It has been established that cane humic acids of the Ryazan region can be used as a basis for biological products that stabilize oil and oil emulsions.

The application of humic substances (HSs) promotes bioactive effects in plants, stimulating growth and development, promoting against biotic and abiotic stresses and increasing agricultural productivity. There are countless examples of fertilizers and biostimulants made from HSs that are capable of being used to form state-of-the-art intelligent agricultural technologies with increased efficiency due to their versatility and structural richness. In recent years, the phytotechnics associated with HS application to foliage have improved, and the applications have been expanded to all plant groups; however, the studies are disaggregated and still scarce, hindering the integration of data and the implementation of this technology for researchers, technicians, and specialists. The objective of this review was to gather all possible evidence related to the ability of HSs to stimulate plant metabolism when applied to foliage. This review first addressed the characteristics of foliar application and HSs. Subsequently, studies were organized by plant groups: vegetables, grasses, legumes, fruit, oilseeds, and medicinal and ornamental plants. Regardless of the plant group, HS foliar application stimulated parameters such as biomass and plant height and increased levels of photosynthetic pigments and agricultural productivity. Foliar application promoted protection against stress events, increasing the activity of peroxidase (POX), catalase (CAT), and phenyl alanine ammonium lyase (PAL) enzymes. Fruit quality also improved with HS foliar application, especially the total sugar content and the amount of oil, protein, and fiber, among others. Based on this review, we propose studies that integrate new forms and technologies of HS foliar application to plants. Experiments with various sources of origin, plant types, and environments are necessary to standardize the application forms of these compounds. Thus, we conclude that HSs are a viable technology that is environmentally friendly and highly accessible to small farmers and family farmers.

Information on the detection of the presence and potential for degradation of synthetic polymers (SPs) under various environmental conditions is of increasing interest and concern to a wide range of specialists. At this stage, there is a need to understand the relationship between the main participants in the processes of (bio)degradation of SPs in various ecosystems (reservoirs with fresh and sea water, soils, etc.), namely the polymers themselves, the cells of microorganisms (MOs) participating in their degradation, and humic substances (HSs). HSs constitute a macrocomponent of natural non-living organic matter of aquatic and soil ecosystems, formed and transformed in the processes of mineralization of bio-organic substances in environmental conditions. Analysis of the main mechanisms of their influence on each other and the effects produced that accelerate or inhibit polymer degradation can create the basis for scientifically based approaches to the most effective solution to the problem of degradation of SPs, including in the form of microplastics. This review is aimed at comparing various aspects of interactions of SPs, MOs, and HSs in laboratory experiments (in vitro) and environmental investigations (in situ) aimed at the biodegradation of polymers, as well as pollutants (antibiotics and pesticides) that they absorb. Comparative calculations of the degradation velocity of different SPs in different environments are presented. A special place in the analysis is given to the elemental chemical composition of HSs, which are most successfully involved in the biodegradation of SPs. In addition, the role of photo-oxidation and photoaging of polymers under the influence of the ultraviolet spectrum of solar radiation under environmental conditions on the (bio)degradation of SPs in the presence of HSs is discussed.

Poland is a major producer of various fruits, including strawberries. As growing consumer awareness of food quality, health, and wellbeing is increasing, farmers are receiving a new market opportunity for organic products of good quality. The integration of microbial solutions into agricultural practices can foster the transition of agricultural farms towards more resilient and sustainable production of quality food. The objective of this study was to assess the influence of novel microbial biopreparations (microbial fertilizing products) containing Bacillus sp., humic acids, and other organic compounds on the economic viability of three strawberry cultivars (‘Honeoye’, ‘Vibrant’, and ‘Rumba’) under organic farming conditions. This study was conducted in 2021 as a field experiment. Irrigated and non-irrigated strawberries were treated with five microbial fertilizing products (K2–K6). The single plot area was 16 m2, with a total of 144 plots. The adopted planting density of strawberries was 30,052 per hectare. K3 treatment was found to be the most universal microbial treatment in terms of positive impact on yields, with significant yield increase on both the non-irrigated (yield increase of 3.76 t·ha−1) and irrigated experiments (yield increase of 5.78 t·ha−1). The K4 treatment on the non-irrigated strawberries resulted in a yield increase of 4.96 t·ha−1, which at the same time had no effect on the yield of the irrigated experiment. On average, application of the K2–K6 combinations on the non-irrigated strawberries resulted in a yield increase from 13.4% (K2) to 33.5% (K4). The irrigated strawberries showed a yield increase from 3.9% (K4—non-significant yield increase) to as much as 36.1% (K3). The highest direct surplus for the non-irrigated strawberries was recorded for the K4 treatment (38,603 PLN·ha−1) and for K3 for the irrigated experiment (42,945 PLN·ha−1). The direct surplus for ‘Rumba’ and ‘Vibrant’ was higher than for ‘Honeoye’ on both the irrigated (22% and 53%, respectively) and non-irrigated (19% and 18%, respectively) experiments. The average profitability index for all tested non-irrigated and irrigated varieties improved when treated with microbial fertilizer products, with profitability indexes of 143.3–168.8% on the non-irrigated plantation and 129.2–169.7% on the irrigated plantation. The tested microbial fertilizing products proved to be valuable products to improve the productivity and economic effectiveness of organic strawberry production. At the same time, their use needs to be adapted to local plantation conditions.

This study investigated the impact of fertilization treatments on mature, forty-year-old, fully productive olive trees (Olea europaea L. cv. Koroneiki) in two non-irrigated orchards featuring contrasting soil types: non-calcareous–acidic and calcareous–alkaline. Over three years (2019–2021), seven distinct treatments were applied, involving inorganic soil fertilizers (traditional strategy) and foliar applications of a liquid organic product containing fulvic and humic acids. Fertilization significantly influenced physiological parameters, such as mineral nutrition, photosynthetic pigments of olive leaves, fruit yield, and oil production per tree, revealing noteworthy effects influenced by soil types and their interactions with treatments. Statistical analysis highlighted specific treatments, indicating that the foliar application of the organic product once a year in alkaline soil or biannually in acidic soil resulted in the highest observed fruit yield and oil production per tree. Indeed, contrary to the control–unfertilized trees, specific fertilization strategies resulted in an average increase of up to 47% and 73% in fruit yield per tree and up to 96% and 100% in oil production per tree in acidic and alkaline soil, respectively. Furthermore, consistently high yields were correlated with constant high values of the chlorophyll a/chlorophyll b ratio (2.3–3.3 in August for acidic soil) and leaf chlorophyll a concentration (55–66 mg/100 g f.w. in August for alkaline soil). This novel finding underscores the crucial role of these factors as prerequisites for achieving superior fruit production. Our results emphasize the potential of integrating foliar organic fertilization as a complementary strategy to traditional soil-based approaches. This is particularly relevant under non-irrigated/rainfed cultural conditions, emphasizing the significance of considering alternative fertilization practices for optimized olive orchard management. [ABSTRACT FROM AUTHOR]

A study is performed of the maximum saturation of humic acids with Fe(III) ions when obtaining a complex humic sorbent. The complex sorbent HAmodFe retains 16.5 mmol/g of the functional groups of humic acids out of a total of 25 mmol/g that can participate in exchange reactions with metal ions. The maximum adsorption of Cd(II) by the sorbent is observed after 5 h of sorbate–sorbent contact and is 76 ± 2 mg/g. Extending the period of contact to 24 h results in the desorption of Cd(II) and the sorption exchange capacity of the sorbent drops to 55 ± 2 mg/g. The maximum adsorption of Cr(VI) is observed after 250 h of sorbate–sorbent contact. Having Cd(II) in the solution does not affect the sorption of Cr(VI) by the complex sorbent, which is 61 ± 1 mg/g. The rate of the adsorption of the considered metal ions is described by an equation of the pseudo-second order and is accompanied by mixed processes of diffusion. The redox potential of the falls 77 mV in the sorbent + Cr(VI) system and 38 mV in the sorbent + Cr(V) + Cd(II) system with a 250 h period of contact. [ABSTRACT FROM AUTHOR]

A model has been developed for the deposition of rare earth elements with yttrium, trace elements, and nonferrous metals in platform and activated structures of the Upper Amur region. Genetic types of lanthanide enrichment are considered; lanthanides are shown to concentrate nonuniformly in coal seams and in coal combustion products. Light rare earth elements predominate in coals. The capacity of peat and coal for metal extraction from aqueous solutions was proven. Criteria for a preliminary assessment of coal as a raw material for lanthanides were considered and prospects for their identification were analyzed. [ABSTRACT FROM AUTHOR]

Treatment of plants with mineral-organic concentrates has developed intensively in recent years. Fertilizers containing, among others, humus, L-amino acids, vitamins, chelates and metal complexes, macro-, micro- and meso-elements, organic matter and humic acids from the top organic layer of leonardite coal have a positive effect on plant growth and quality and seed yield. An experiment was conducted between 2019 and 2022 at the University of Agriculture in Kraków, in which the impact of mineral-organic concentrate on the seed yield and quality of perennial ryegrass (Lolium perenne L.) 2N Bokser (Hodowla Roślin Grunwald Ltd. Grupa IHAR, Grunwa, Poland) was determined. As part of the experiment, plants were sprayed with a mineral-organic product in three different doses: 1.0, 2.0 and 3.0 L·ha−1. The following parameters were examined: the number of generative shoots, the length of the flag leaf, seed yield, germination capacity and the weight of one thousand seeds. It turned out that the application of the concentrate with 3 L·ha−1 and 2 L·ha−1 led to a significant increase in the number of generative shoots and in seed yield, compared to control. In addition, seed germination capacity of fertilized plants was higher, with the greatest increase after the application of 3 L·ha−1. Moreover, the average weight of one thousand seeds was significantly higher in fertilized plants, compared to the control, and the largest increase was recorded in response to the highest dose. The results indicated a positive effect of the organic-mineral concentrate on perennial ryegrass development parameters and seed quality. [ABSTRACT FROM AUTHOR]