Carbon pools and microbial indicators in vineyard soils under organic and conventional fertilization in the São Francisco Valley, in a semi-arid tropical climate.

Soil management systems that do not prioritize conservation contribute to carbon (C) depletion in tropical environments. In the semi-arid region of Brazil, fruit farming has been a key driver for economic development, yet high agricultural yields depend on the use of costly inputs. We conducted a groundbreaking study in São Francisco Valley, northeastern Brazil, to investigate the effects of organic (OF) and synthetic fertilizers (CF) on carbon stock and stability, organic matter fractions, microorganismal carbon biomass (C-mic) and quality indexes, and C-CO2 emissions up to the 1 m of depth in grapevine soils. Additionally, we compared the fertilized soils with their nearby native vegetation under the Caatinga biome. Compared to native vegetation, the OF and CF grapevine soils store 33 Mg ha-1 in one year and 26 Mg ha-1 in two years of establishment, respectively. The total labile C stock was found to be 10.2 Mg ha-1 and 6.0 Mg ha-1 at a depth of 1 m. We observed the development of C-mic at 40-100 cm (approximately 280 mg kg-1) in the OF soil, which resulted in efficient C mineralization without disrupting microbial metabolism, which produced roughly 8.0 mg kg-1 day-1 of C-CO2. The isotopic signature shows that C3 plants partially influence carbon and nutrient cycling in deeper OF soil layers. The soil in OF exhibited a high concentration of carbonate equivalent (32 g kg-1) and calcium (6 g kg-1), which resulted in the protection of labile C from decomposition. The Cambisols of viticultural farm under organic fertilization exhibited a balance of humic and fulvic acids fractions of organic matter, consequently, a potential stability of C. Our findings show that organic fertilization based on cassava juice, fish amino acids, and straw combined with manure under intensive irrigation contributes to an increase in C storage and microbial indicators in the soil. Therefore, this type of fertilization could be employed as a sustainable management system in grape farming in the Brazilian Northeast to improve soil conditions and crop yield under harsh environmental conditions.

Enhancing carotenoid accumulation in Dunaliella bardawil by combined treatments with fulvic acid and optimized culture conditions.

Natural carotenoids from microalgae have received more attention as an alternative source. In this study, fulvic acid (FA), a plant growth regulator, was used to enhance carotenoid accumulation in microalgae Dunaliella bardawil rich in lutein. However, the addition of FA promoted pigment synthesis but also exhibited an inhibitory effect on biomass. Therefore, the optimization of culture conditions was performed to further enhance carotenoid accumulation, including high light stress (10,000 lx) and the two-stage cultivation comprising 1-aminocyclopropane-1-carboxylic acid (ACC) and FA. Under both culture conditions, the growth inhibition caused by FA was alleviated, leading to a further increase in the contents of chlorophylls and carotenoids. HPLC analysis revealed that the production of lutein, α-carotene and ß-carotene increased by 0.44-, 0.37- and 0.54-fold under the treatment of 400 mg/L FA with high light intensity and 0.91-, 1.15-0.29-fold under the two-stage cultivation comprising 11 mM ACC and 500 mg/L FA. Furthermore, algal cells under FA treatment and the two-stage cultivation stained with Bodipy505/515 emitted stronger fluorescence under a laser confocal microscope, suggesting that lipid accumulation was increased. Additionally, the transcription levels of carotenogenic genes were also found to be up-regulated by qRT-PCR. These results indicated an enhancement in both the storage capacity and synthesis of carotenoids in D. bardawil. This study revealed the potential application of plant growth regulators in promoting carotenoid accumulation in D. bardawil which could be further improved by optimizing the culture conditions, providing a reference for efficient carotenoid production in microalgae.

Fulvic Acid Enhances Nitrogen Fixation and Retention in Paddy Soils through Microbial-Coupled Carbon and Nitrogen Cycling.

Fulvic acid, the most soluble and active humic substance, is widely used as an agent to remediate contaminated soils and improve soil fertility. However, the influence of fulvic acid (FA), as a microbial carbon source, on carbon and nitrogen cycles in paddy soils remains elusive. Therefore, to investigate it, an incubation experiment was conducted. Gas analyses indicated that the carbon dioxide and methane emissions were enhanced in FA treatment, which increased up to 94.08-fold and 5.06-fold, respectively. 15N-labeling experiments revealed that nitrogen fixation capability was promoted (1.2-fold) to reduce the carbon and nitrogen imbalance due to fulvic acid amendment. Metagenomic analysis further revealed that gene abundances of degradation of lignin-like compounds, gallate degradation, methanogenesis, nitrogen fixation, and urea hydrolysis increased, while the bacterial ammonia oxidation and anaerobic ammonium oxidation decreased, caused by FA application. Metabolic reconstruction of metagenome-assembled genomes revealed that Azospirillaceae, Methanosarcinaceae, and Bathyarchaeota, with higher abundance in FA treatment, were the key microorganisms to maintain the carbon and nitrogen balance. The metabolic pathways of fulvic acid degradation and coupled nitrogen fixation and retention were constructed. Collectively, our results provided novel insights into the theoretical basis of the use of humic substances for reducing nitrogen fertilization and climate change.

Integrative transcriptome and metabolome analysis reveals the mechanism of fulvic acid alleviating drought stress in oat.

Drought stress inhibits oat growth and yield. The application of fulvic acid (FA) can improve the drought resistance of oats, but the corresponding molecular mechanism of FA-mediated drought resistance remains unclear. Here, we studied the effects of FA on the drought tolerance of oat leaves through physiological, transcriptomic, and metabolomics analyses, and identified FA-induced genes and metabolites related to drought tolerance. Physiological analysis showed that under drought stress, FA increased the relative water and chlorophyll contents of oat leaves, enhanced the activity of antioxidant enzymes (SOD, POD, PAL, CAT and 4CL), inhibited the accumulation of malondialdehyde (MDA), hydrogen peroxide (H2O2) and dehydroascorbic acid (DHA), reduced the degree of oxidative damage in oat leaves, improved the drought resistance of oats, and promoted the growth of oat plants. Transcriptome and metabolite analyses revealed 652 differentially expressed genes (DEGs) and 571 differentially expressed metabolites (DEMs) in FA-treated oat leaves under drought stress. These DEGs and DEMs are involved in a variety of biological processes, such as phenylspropanoid biosynthesis and glutathione metabolism pathways. Additionally, FA may be involved in regulating the role of DEGs and DEMs in phenylpropanoid biosynthesis and glutathione metabolism under drought stress. In conclusion, our results suggest that FA promotes oat growth under drought stress by attenuating membrane lipid peroxidation and regulating the antioxidant system, phenylpropanoid biosynthesis, and glutathione metabolism pathways in oat leaves. This study provides new insights into the complex mechanisms by which FA improves drought tolerance in crops.

Optimizing nitrogen fertilization in maize: the impact of nitrification inhibitors, phosphorus application, and microbial interactions on enhancing nutrient efficiency and crop performance.

Despite the essential role of nitrogen fertilizers in achieving high crop yields, current application practices often exhibit low efficiency. Optimizing nitrogen (N) fertilization in agriculture is, therefore, critical for enhancing crop productivity while ensuring sustainable food production. This study investigates the effects of nitrification inhibitors (Nis) such as Dimethyl Pyrazole Phosphate (DMPP) and Dimethyl Pyrazole Fulvic Acid (DMPFA), plant growth-promoting bacteria inoculation, and phosphorus (P) application on the soil-plant-microbe system in maize. DMPFA is an organic nitrification inhibitor that combines DMP and fulvic acid for the benefits of both compounds as a chelator. A comprehensive rhizobox experiment was conducted, employing varying levels of P, inoculant types, and Nis, to analyze the influence of these factors on various soil properties, maize fitness, and phenotypic traits, including root architecture and exudate profile. Additionally, the experiment examined the effects of treatments on the bacterial and fungal communities within the rhizosphere and maize roots. Our results showed that the use of Nis improved plant nutrition and biomass. For example, the use of DMPFA as a nitrification inhibitor significantly improved phosphorus use efficiency by up to 29%, increased P content to 37%, and raised P concentration in the shoot by 26%, compared to traditional ammonium treatments. The microbial communities inhabiting maize rhizosphere and roots were also highly influenced by the different treatments. Among them, the N treatment was the major driver in shaping bacterial and fungal communities in both plant compartments. Notably, Nis reduced significantly the abundance of bacterial groups involved in the nitrification process. Moreover, we observed that each experimental treatment employed in this investigation could select, promote, or reduce specific groups of beneficial or detrimental soil microorganisms. Overall, our results highlight the intricate interplay between soil amendments, microbial communities, and plant nutrient dynamics, suggesting that Nis, particularly DMPFA, could be pivotal in bolstering agricultural sustainability by optimizing nutrient utilization.

The combined effects of polystyrene nanoplastics and dissolved organic matter on the environmental bioavailability of carbamazepine.

The bioavailability of active pharmaceutical ingredients (APIs) plays a crucial role in determining the toxicity and risk of contaminants in the environment. However, the bioavailability of APIs in complex environmental matrices is still unclear. In this study, the combined effects of polystyrene nanoplastics (PS NPs) with various particle sizes (50, 100, and 1000 nm) and fulvic acid (FA) on the bioavailability of carbamazepine (CBZ) were investigated via negligible depletion solid-phase microextraction (nd-SPME) and Daphnia magna (D. magna) accumulation. The uptake kinetic study revealed that both PS NPs and FA reduced the elimination rate (k2) in most cases. The availability of CBZ to nd-SPME was determined by the hydrodynamic particle size of PS NPs, whereas the bioavailability to D. magna depended on the intrinsic particle size. The CBZ bioavailability was greater in co-exposed matrices due to the attenuated sorption of PS NPs to CBZ by FA modification. Notably, co-exposure of PS NPs and FA resulted in a higher bioaccumulation factor (BAF) of CBZ, probably due to the desorption and reabsorption of particle-associated CBZ. This study demonstrated that both PS NP particle size and FA binding affect the bioavailability of CBZ, and nd-SPME can mimic only the bioaccumulation of CBZ via diffusion.

Simultaneous removal of nitrate, copper, carbamazepine, and calcium from micropolluted water by fulvic acid through promotion of denitrification and microbial-induced calcium precipitation: Performance and mechanism.

In this paper, a study of the denitrification strain Cupriavidus sp. W12 was conducted to remove copper (Cu2+), carbamazepine (CBZ), and calcium (Ca2+) by microbial-induced calcium precipitation (MICP) after adding fulvic acid (FA). After the addition of 20 mg/L FA, the removal efficiencies of nitrate (NO3--N), Cu2+, CBZ, and Ca2+ reached 100.0 %, 98.7 %, 96.6 %, and 73.6 %, correspondingly and there was no accumulation of nitrite (NO2--N). FA stimulated the growth of strain W12, improved electron transfer activity, and facilitated the conversion of gaseous nitrogen. The research revealed that FA might enhance microbial activity and result in a more dense and porous structure of the biological precipitate. Cu2+ and CBZ were removed by co-precipitation and adsorption. As the initial report of FA promoting MICP to remove complex pollutants, this paper offers a theoretical foundation for NO3--N, Cu2+, CBZ, and Ca2+ remediation in micropolluted water.

Fulvic acid mediated highly efficient heterotrophic nitrification-aerobic denitrification by Paracoccus denitrificans XW11 with reduced C/N ratio.

Reducing the C/N ratio requirements for heterotrophic nitrification-aerobic denitrification (HNAD) is crucial for its practical application; however, it remains underexplored. In this study, a highly efficient HNAD bacterium, Paracoccus denitrificans XW11, was isolated. The HNAD characteristics of XW11 were studied, and the redox mediator fulvic acid (FA) was used to reduce the C/N requirements. Whole-genome sequencing revealed multiple denitrification genes in XW11; however, nitrification genes were not identified, because heterotrophic nitrification-related gene sequences were not included in the database. However, the nitrogen removal related enzyme activity test revealed complete nitrification and denitrification pathways. Reverse transcription PCR showed that the membrane-bound nitrate reductase (NarG), rather than the periplasmic nitrate reductase, was responsible for aerobic denitrification. The conventional nitrite reductase (NirS) also does not mediate nitrite denitrification. When the C/N ratio was 10, the ammonia removal efficiency of the Control was 71.71 % and the addition of FA increased it to 86.12 %. Transcriptomic analysis indicated electron flow from the carbon source to FA without proton transmembrane transport, and the presence of FA constructs another electron transfer system. The redox potential of oxidized FA/reduced FA is 0.3679 V, avoiding competition for electrons from Complex III. Thus, ammonia monooxygenase obtains electrons more easily, thereby promoting nitrification. The enzyme activity test of the nitrification process confirmed this view. In addition, NarG expression increased, and the denitrification process was enhanced. Overall, FA improved HNAD efficiency by facilitating electron transfer to the nitrogen dissimilation process, offering a novel approach to reduce the C/N requirement of HNAD.

Comparative analysis of soil organic carbon and soil properties in landscapes of Kerala: insights from the Western Ghats of India.

Soil organic carbon (SOC) is known to vary among different ecosystems and soilscapes, yet the degree of variation remains uncertain. Comparing SOC levels in undisturbed ecosystems like forests with those in gradually altered ecosystems can provide valuable insights into the impact of land use on carbon dynamics. This study aimed to evaluate the effects of different land uses on soil fertility parameters in the tropical region of Kerala, focusing on forests as well as cultivated agricultural landscape such as coconut, pepper, tapioca, acacia plantations, and mixed home garden cropping systems. Significant variations were observed among different crops and land use systems in terms of soil fertility. Forests exhibited the highest SOC content at 3.78 g kg-1, while acacia plantations showed the lowest at 0.76 g kg-1. Additionally, various soil properties such as different carbon fractions (e.g., humic acid, fulvic acid), total nitrogen, carbon, available nutrients, physical properties, aggregate size fractions, microbial biomass carbon, and spectral signatures differed significantly across the different land uses. These findings suggest a decline in soil fertility in altered ecosystems compared to adjacent forest soils, highlighting the vital role of forests in conserving natural resources and maintaining soil health. In addition, among the different landscapes studied, mixed cropping systems of home gardens sustained soil fertility better than monocropping systems. The observed variations in soil physicochemical properties among different land use types indicate a threat to sustainable crop production. Effective management practices aimed at improving soil fertility and sustaining crop production in these altered ecosystems are essential. This study highlights the importance of adopting appropriate management strategies to conserve soil health and ensure sustainable crop production in tropical landscapes like Kerala. The holistic approach adopted in this study, encompassing a wide range of soil fertility parameters across various land uses, along with its implications for sustainable land management, adds significant novelty and relevance to the existing literature on soil dynamics in tropical regions like Kerala.

Dietary fulvic acid improves immune, digestive and antioxidant parameters in juvenile white-leg shrimp (Litopenaeus vannamei) in a super-intensive system.

In the current study, the effects of dietary fulvic acid supplementation at levels of 0.5, 1 and 2% were examined in white-leg shrimp, Litopenaeus vannamei. A significant increase in the weight of the shrimp was observed in the group treated with 2% fulvic acid in comparison to the control group. This may have been associated with an increased digestive efficiency, with the food conversion ratio reducing from 2.4 to 1.9, and increased hepatopancreatic amylase, protease, and lipase enzyme activities. Enhanced activity of hemolymph superoxide dismutase was suggestive of an enhanced immune capacity, while hemolymph cell count increased by 16.4 and 13.6% in shrimp receiving diets supplemented with 1 and 2% fulvic acid, respectively. Additionally, the number of large granular cells increased by 37.3% and 40.8% relative to the control in these two groups. Furthermore, the lysozyme activity increased in shrimp receiving dietary supplementation of 1% and 2% fulvic acid by 16.7% and 24.7%, respectively. Phenol oxidase activity, which activates phagocytosis and encapsulation of invading pathogens, increased in all groups supplemented with fulvic acid, with the highest activity in the 1% fulvic acid group. Overall the present results suggest that fulvic acid is a promising feed additive for white-leg shrimp super-intensive culture.

Recycling aluminum from polyaluminum chloride sludge through acid dissolution and cation resin separation/purification.

To recycle aluminum (Al) from waterworks sludge resulting from polyaluminum chloride (PAC) used as coagulants, this study proposed an innovative strong acidic cation (SAC) exchange resin treatment strategy for Al separation from coexisting fulvic acid (FA) and heavy metals (HMs) in the H2SO4 leachate of PAC sludge. Fluorescence titration confirmed the breakdown of the Al-FA complex at pH 2.0, which facilitated Al separation from FA in the acidic leachate. The species distribution of the dissociated Al (i.e. Ala, Alb, and Alc) significantly influenced the adsorption of Al onto the cation exchange resin. The continuous release of H+ during the cation exchange reaction greatly promoted the transformation of dissociated Alc and Alb into Ala, thereby improving the adsorption of total Al. Moreover, the SAC resin column successfully separated the codissolved HMs from the Al in the leachate even at an influent pH of 2.8, which was attributed to the greater selectivity of the sulfonate groups on the cation exchange resin for free Al3+. The Al eluted from the exhausted resin with 1.1 M H2SO4 was collected as the recycled coagulant after proper pH adjustment. The Al adsorption capacity of the SAC resin decreased by approximately 5 % with each operation cycle and was regained by complete regeneration with 1.8 M H2SO4 after 5 cycles. Overall, the integrated efficiency of Al recovery from PAC sludge by H2SO4 acidification and SAC resin separation/purification reached 70.10 %. The recycled Al from sludge has a water treatment performance comparable to that of fresh PAC coagulant.

Fulvic acid application increases rice seedlings performance under low phosphorus stress.

BACKGROUND: Fulvic acid enhances plant growth and interacts synergistically with phosphate fertilizer to alleviate the agricultural production problem of low phosphorus fertilizer utilization efficiency. However, the underlying mechanism of its action remains poorly understood. In this study, we investigated the impact of fulvic acid application with varying concentrations (0, 40, 60, 80 and 120 mg/L) on rice performance in plants grown in a hydroponic system subjected to low phosphorus stress. The rice growth phenotypes, biomass, root morphology, phosphorus uptake, and the impact of fulvic acid on the rhizosphere environment of rice, were assessed. RESULTS: The findings showed that adding appropriate concentrations of exogenous fulvic acid could promote the growth performance of rice under low phosphorus stress. Particularly at T1 (40 mg/L) and T2 (60 mg/L) over the control effectively increased rice biomass by 25.42% and 24.56%, respectively. Fulvic acid treatments stimulated root morphogenesis, up-regulated phosphate transporter genes, and facilitated phosphorus absorption and accumulation. Especially T1 (20.52%), T2 (18.10%) and T3 (20.48%) treatments significantly increased phosphorus uptake in rice, thereby alleviating low phosphorus stress. Additionally, fulvic acid elevated organic acids concentration in roots and up-regulated plasma membrane H+-ATPase genes, promoting organic acids secretion. This metabolic alteration can also alleviate low phosphorus stress in rice. CONCLUSIONS: The effect of exogenous fulvic acid on physiological indicators is concentration-dependent under low phosphorus stress, enhances rice performance and reduces reliance on phosphorus fertilizer. This provides new insights to shed light on the mechanism of alleviating low phosphorus stress in rice through fulvic acid application, an eco-friendly tool.

Efficient extraction and formation mechanism of fulvic acid from lignite: Experimental and DFT studies.

Enhancing the coal-based fulvic acid (FA) yield through the effect of oxidation methods was of great importance. However, the realization of an efficient and environmentally friendly method for the preparation of FA, along with understanding of its formation mechanism, remains imperative. Herein, coal-based FA was prepared by oxidizing lignite with H2O2 and NaOH/KOH. The experimental data showed that ML lignite was pickled with HCl, metal ions such as iron, aluminum, and calcium can be removed, and this lignite is used as raw material, the reaction time was 150 min, the reaction temperature was 50 °C, and the volume ratio of H2O2 (30%) to KOH (3 mol/L) was 1:1, the effect of H2O2 and KOH on FA extraction was the best. The coal-based FA yield could reach 60.49%. The addition of silicone defoaming agent during the experiment resulted in a significant diminished the presence of bubbles and prevent the production of CO2. A decrease in N2 content was detected by GC. The FTIR, XPS, Py-GC/MS and other characterization results showed that FA has more polar functional groups (-COOH, -OH), and it contains more O-CO structure. Consequently, a greater quantity of FA molecules is generated during the reaction process. Moreover, the partial Gibbs free energies during the formation process of coal-based FA were calculated by density-functional theory (DFT). The highest energy required for free radicals was found to be between 1.3 and 1.7 eV. This study would provide theoretical support for exploring the FA formation process and the promotion of lignite humification by adding H2O2 or alkali to lignite.

U(VI) sorption on illite in the Co-existence of carbonates and humic substances.

The presence of carbonates or humic substances (HS) will significantly affect the species and chemical behavior of U(VI) in solution, but lacking systematic exploration of the coupling effect of carbonates and HS under near real environmental conditions at present. Herein, the sorption behavior of U(VI) on illite was systematically studied in the co-existence of carbonates and HS including both humic acid (HA) and fulvic acid (FA) by batch technique. The distribution coefficients (Kd) increased as function of time and temperature but decreased with increasing concentrations of initial U(VI), Ca2+, and Mg2+, as well as ion strength. At pH 2.0-10.5, the Kd values first increased rapidly and then decreased visibly, with its maximum value appearing at pH 5.0, owning to the changes in the interaction between illite and the dominant species of U(VI) from electrostatic attraction to electrostatic repulsion. The sorption was a heterogeneous, spontaneous, and endothermic chemical process, which could be well described by pseudo-second-order kinetic and Flory-Huggins isotherm models. When carbonates and HA/FA coexisted, the Kd values always increased first and then decreased as a function of pH, with the only difference for HA and FA being the key pH (pHkey) at which the promoting and inhibiting effects on the sorption of U(VI) onto illite undergo a transition. The carbonates and HS have a synergistic inhibitory effect on the U(VI) sorption onto illite at pH 7.8. FTIR and XPS spectra demonstrated that the hydroxyl groups on the illite surface and in the HS were involved in U(VI) sorption on illite in the presence of carbonates. These results provide valuable data for a deeper understanding of U(VI) migration in geological media.

Evaluation the role of insulin signaling pathway in reproductive toxicity of dispersed diesel particulate extract under environmental conditions.

Diesel particulate extract (DPE), which is a significant constituent of airborne particle pollution, has a strong association with the development of cancer and respiratory diseases. Fulvic acid (FA), a plentiful organic macromolecule found in water, has the capability to modify particle surface charge and adsorption capacity when combined with minerals. Nevertheless, there is a scarcity of data regarding the influence of their interaction on DPE toxicity. To examine the impact of environmental factor on the toxic effects of DPE, we used the Caenorhabditis elegans (C. elegans) model to investigate the reproductive toxicity of DPE and FA on insulin signaling pathway. C. elegans were subjected to a semi-fluid medium (NGG) containing different concentrations of DPE or DPE + FA in order to assess germline apoptosis and the expression of important genes in the insulin signaling pathway. Through several mutant strains, we found that daf-2, age-1, pdk-1, akt-1 and daf-16 were involved in DPE-induced apoptosis. Furthermore, and the expression levels of these genes significantly altered. The ratio of daf-16 translocation to nucleation, as well as the amount of reactive oxygen species (ROS), exhibited a dose-response relationship, however, the presence of FA could altered these effects. The results revealed that the insulin signaling pathway plays a vital role in mediating the harmful effects caused by DPE, whereas environmental factors have a substantial impact on its toxicity. Moreover, it was noted that semi-fluid medium could effectively replicate three-dimensional exposure circumstances closely resembling those observed in actual situations.

The protective effects and potential mechanisms of fulvic acid against ethanol-induced gastric mucosal injury in mice.

Fulvic acid (FA) is a kind of natural organic acids extracted from lignite, which is the active ingredient in Wujin oral liquid, a proprietary Chinese medicine used to treat gastric and duodenal ulcers. However, our understanding of the mechanisms of FA remains limited. Currently, the protection of FA and its mechanism were explored using the ethanol-induced gastric mucosal injury mouse model. The histopathological examinations showed FAs at three doses effectively reduced gastric congestion, oedema caused by ethanol, and prevented gastric epithelial cell fall-off. When compared to the model group, FAs reduced IL-1ß and IL-6 levels in serum, as well as IL-1ß, IL-6, TNF-α, and COX-2 expression levels in tissue. Furthermore, FAs significantly inhibited p65, P38 MAPK, and Erk1/2 phosphorylation in damaged gastric tissue. It was indicated FA has good protection against ethanol-induced gastric mucosa injuries in mice and this effect was related to NF-κB and MAPK signalling pathways.

Microbial community structure and carbon transformation characteristics of different aggregates in black soil.

Background: Previous research on whole-soil measurements has failed to explain the spatial distribution of soil carbon transformations, which is essential for a precise understanding of the microorganisms responsible for carbon transformations. The microorganisms involved in the transformation of soil carbon were investigated at the microscopic scale by combining 16S rDNA sequencing technology with particle-level soil classification. Methods: In this experiment,16S rDNA sequencing analysis was used to evaluate the variations in the microbial community structure of different aggregates in no-tillage black soil. The prokaryotic microorganisms involved in carbon transformation were measured before and after the freezing and thawing of various aggregates in no-tillage black soil. Each sample was divided into six categories based on aggregate grain size: >5, 2-5, 1-2, 0.5-1, 0.25-0.5, <0.25 mm, and bulk soil. Results: The relative abundance of Actinobacteria phylum in <0.25 mm aggregates was significantly higher compared to that in other aggregates. The Chao1 index, Shannon index, and phylogenetic diversity (PD) whole tree index of <0.25 mm aggregates were significantly smaller than those of in bulk soil and >5 mm aggregates. Orthogonal partial least-squares discrimination analysis showed that the microbial community composition of black soil aggregates was significantly different between <1 and >1 mm. The redundancy analysis (RDA) showed that the organic carbon conversion rate of 0.25-0.5 mm agglomerates had a significantly greater effect on their bacterial community structure. Moreover, humic acid conversion rates on aggregates <0.5 mm had a greater impact on community structure. The linear discriminant analysis effect size (LEfSe) analysis and RDA analysis were combined. Bradyrhizobium, Actinoplane, Streptomyces, Dactylosporangium, Yonghaparkia, Fleivirga, and Xiangella in <0.25 mm aggregates were positively correlated with soil organic carbon conversion rates. Blastococcus and Pseudarthrobacter were positively correlated with soil organic carbon conversion rates in 0.25-0.5 mm aggregates. In aggregates smaller than 1 mm, the higher the abundance of functional bacteria that contributed to the soil's ability to fix carbon and nitrogen. Discussion: There were large differences in prokaryotic microbial community composition between <1 and >1 mm aggregates. The <1 mm aggregates play an important role in soil carbon transformation and carbon fixation. The 0.25-0.5 mm aggregates had the fastest organic carbon conversion rate and increased significantly more than the other aggregates. Some genus or species of Actinobacteria and Proteobacteria play a positive role in the carbon transformation of <1 mm aggregates. Such analyses may help to identify microbial partners that play an important role in carbon transformation at the micro scale of no-till black soils.

Fulvic acid alleviates cadmium-induced root growth inhibition by regulating antioxidant enzyme activity and carbon-nitrogen metabolism in apple seedlings.

Introduction: Substantial previous studies have reported that fulvic acid (FA) application plays an important role in Chinese agricultural production. However, little is known about the mechanisms for using FA to increase apple trees resistance to Cd toxicity. In order to clarify the mechanism underlying FA alleviation in Cd-induced growth inhibition in apple seedlings. Methods: Herein, we treated M9T337 seedlings to either 0 or 30 µM/L Cd together with 0 or 0.2 g/L FA and analyzed the root growth, antioxidant enzyme activities, carbon (C) assimilation, nitrogen (N) metabolism, and C and N transport. Results: The results presented that, compared with CK (without Cd addition or FA spraying application), Cd poisoning significantly inhibited the root growth of apple seedlings. However, this Cd-induced root growth inhibition was significantly alleviated by FA spraying relative to the Cd treatment (Cd addition alone). On the one hand, the mitigation of inhibition effects was due to the reduced oxidative damage by enhancing antioxdiant enzyme (SOD, POD, and CAT) activities in leaves and roots. On the other hand, this growth advantage demonstrated compared to the Cd treatment was found to be associated with the strengthen of photosynthetic performance and the elevation of C and N metabolism enzymes activities. Meanwhile, we also found that under Cd stress condition, the distribution of C and N nutrients in apple seedlings was optimised by FA spraying application relative to the Cd treatment, according to the results of 13C and 15N tracing. Conclusion: Conclusively, our results suggested that the inhibitory effect of Cd on apple seedlings root growth was alleviated by FA through regulating antioxdiant capacities and C and N metabolism.

Effect of Exogenous Organic Matter on Phosphorus Forms in Middle-High Fertility Cinnamon Soil.

OBJECTIVES: To slow down the chemical fixation of phosphate fertilizer, reduce the risk of active phosphorus leaching, stimulate the inherent phosphorus resource activity of soil, and improve phosphorus supply capacity. METHODS: This study utilized a combination of field experiments and indoor chemical analysis. Six types of exogenous organic matter (fulvic acid, biochar, compound microbial fertilizer, high-energy microbial inoculum, pig manure-vermicompost, cow manure-vermicompost) were added based on conventional fertilization. The experiment was conducted under the wheat-maize rotation system in the Huang-Huai-Hai region. RESULTS: Compared with control (CK) without exogenous organic matter (EOM), all the other treatments with EOM had an enhancing effect on the available phosphorus of the cultivated soil. During the maize harvest, the combined application of biochar, pig manure-vermicompost and cow manure-vermicompost treatment significantly increased the content of available phosphorus in 0-20 cm soil by 45.87-56.59% compared with CK. The combined application of fulvic acid, biochar, pig manure-vermicompost and cow manure-vermicompost treatment significantly increased the content of Ca2-P in 0-20 cm soil by 34.04-65.14%. The content of Ca10-P in each treatment with EOM exhibited a lower level compared to CK. EOM could slow down the fixation of phosphorus to some degree. Correlation analysis revealed significant associations between Ca2-P, Ca8-P, Al-P, Fe-P, neutral phosphatase activity, acid phosphatase activity, and the available phosphorus content in the soil. The combined application of fulvic acid, biochar, and cow manure-vermicompost could enhance the activity of neutral and acid phosphatase in topsoil to a certain extent, thereby facilitating the conversion of phosphorus into highly available Ca2-P. EOM could enhance the soil phosphorus availability and decelerate the conversion of soil phosphorus into O-P and Ca10-P forms with low availability. Among all treatments, biochar exhibited the most pronounced efficiency in mitigating phosphorus leaching downward. CONCLUSIONS: All the EOMs had the potential to enhance the conversion of phosphorus into soluble phosphorus (Ca2-P), thereby mitigating the chemical fixation of soil phosphorus and ameliorating non-point source pollution caused by phosphorus. EOM enhanced the activity of neutral and acid phosphatase, which was beneficial to the conversion of organic phosphorus to inorganic phosphorus and increasing the content of available phosphorus. All EOMs had good effects on the retention of soil effective phosphorus, among which biochar had the best effect on retaining effective phosphorus in the tillage layer and blocking phosphorus leaching downward.

The effect of combining humic and fulvic acids poultice on wound healing in male rats.

Background: Finding new compounds to accelerate wound healing is critical today. Humic substances or fulvic acid each have anti-inflammatory properties. Aims and Objectives: The purpose of this study is to determine the effects of poultice 0.5% containing humic and fulvic acids on wound healing in male rats. Materials and Methods: An animal model was arranged by making a full-thickness skin wound was created in each rat. Animals were randomly divided into control, sham, and treatment groups. To investigate the effect of humic and fulvic acids combining poultice, the wound area and histological analyses of the number of inflammatory cells, fibroblasts, and angiogenesis were evaluated for 21 days. Results: The animals in the treated group showed higher wound healing percentage, angiogenesis, and fibroblast distribution compared with the control (P < 0.001). Moreover, the topical administration of humic and fulvic acids 0.5% poultice decreased the mean number of inflammatory cells significantly than the other groups (P < 0.001). Conclusion: The topical administration of a poultice containing humic and fulvic acid accelerated wound healing by increasing angiogenesis and fibroblast and reducing inflammatory cell distribution in a rat model.