Search Results (1,373)

Low-temperature pyrolysis around 250 °C represents a mild carbonization that differs from conventional high-temperature biochar production, and the role of pyrolysis duration under mild thermal conditions remains insufficiently understood. In this study, plant residues, including rice straw, sorghum leaves and stems, barley straw, and mixed woodchips, were converted into charred materials under low-temperature pyrolysis at 250 °C (4 h, 12 h) and compared with those produced at 500 °C (4 h). Pyrolysis at 250 °C (4 h) resulted in higher solid yields (51.9–72.8%) and higher recovery of carbon and nitrogen, whereas yields declined to 27.2–31.6% at 500 °C. Materials produced at 250 °C preserved abundant oxygen-containing functional groups, exhibited lower pH, and showed significantly higher cation exchange capacity (up to 93.68–119.91 cmol_c/kg at 12 h). Prolonged treatment at 250 °C enhanced humification, increasing the carbon extracted from humic acid by 25.3–237.9%, whereas humic substances were largely decomposed at 500 °C. Structural analyses indicated that low-temperature chars maintained reactive surface chemistry, while high-temperature chars showed greater aromaticity and porosity, particularly for wood-derived materials (378.5 m²/g). Overall, low-temperature pyrolysis produces functionally active carbon materials suitable for saline-sodic soil amendment and nutrient management, whereas 500 °C pyrolysis generates more aromatic and porous materials better suited for long-term carbon stability and physical soil conditioning. Full article

Plant-parasitic nematodes (PPNs) rank among the most economically destructive soilborne pathogens worldwide, causing annual crop losses estimated at USD 125–175 billion. Traditional management of plant parasitic nematodes has depended significantly on synthetic nematicides; however, increasing regulatory constraints, environmental pollution, and the rise of resistant nematode populations have generated an urgent need for sustainable alternatives. Humic substances (HS), comprising humic acids, fulvic acids, and humins derived primarily from leonardite and lignite, represent biologically active components of soil organic matter. Their different functional groups, like carboxylic, phenolic, and carbonyl groups, have direct nematicidal and nematostatic effects by stopping eggs from hatching, slowing down juvenile development, and lowering infectivity. They also indirectly improve soil structure, nutrient bioavailability, and the composition of the rhizosphere microbiome. Plant growth-promoting rhizobacteria (PGPR), particularly Bacillus spp. and Pseudomonas spp., suppress PPN populations through antibiotic biosynthesis, cuticle-degrading hydrolytic enzymes, nematostatic volatile organic compounds, and elicitation of induced systemic resistance (ISR). This review methodically analyzes the individual and synergistic processes by which HS and PGPR inhibit PPNs and enhance plant growth. Humic compounds strongly promote PGPR rhizosphere colonization, augmenting microbial metabolic activity and bioinoculant stability, hence producing combinatorial suppressive effects unattainable by either input independently. The combined HS-PGPR approach is reliable and environmentally sustainable for comprehensive nematode control, requiring multidisciplinary research to achieve global sustainable agriculture. Full article

Microbial inoculation is widely used to improve composting performance, yet its effectiveness hinges on inoculum composition, substrate characteristics, and composting technology, which remain poorly understood. This study compared single versus mixed inoculants across different substrates and assessed their interactions with biochar amendment and nanomembrane covering, focusing on organic matter transformation, inorganic nutrient dynamics, and biological pollution control. Mixed inoculation significantly improved heating performance in cattle manure compost compared to single strains (p < 0.05) and sustained thermophilic conditions in sludge-sawdust compost, but showed limited impact in chicken manure-sludge compost. It reduced humic acid (HA) accumulation in chicken manure-sludge compost (14.29% to −39.28%) while increasing HA content in sludge-sawdust compost (3.55–5.41 g/kg, p < 0.05). Inorganic nitrogen retention was enhanced; specifically NO₃⁻-N concentrations rose by 175.1–222.6% in the chicken manure-sludge and by 6.7–17.9% in the sludge-sawdust compost. Microbial community analysis indicated enrichment of inoculant strains during the thermophilic phase, supporting nitrogen conservation and humification. However, inoculation increased potential pathogenic bacteria by over 51.2% across all composts and enriched predicted antibiotic resistance genes (ARGs) by 9.9–22.96% in chicken manure-sludge compost, while reducing the membrane covering’s inhibitory effect on predicted ARGs (rebound by 29.5%). Moreover, we found that the predicted ARG profiles, derived from 16S-based PICRUSt2 functional inference, covaried strongly with microbial community structure, with environmental factors such as organic carbon shaping predicted ARG dynamics mainly through indirect effects on microbial communities. These findings highlight that while mixed inoculation boosts composting efficiency, it also raises biosafety concerns. Thus, a comprehensive evaluation integrating organic, inorganic, and biological perspectives is essential before promoting thermophilic inoculants. Full article

Insufficient oxidative capacity can limit humification during municipal sludge composting. This study comparatively evaluated two Fenton-like amendment systems, a homogeneous copper-based treatment (CH) and a heterogeneous nano-iron-based treatment (NFH), for their effects on composting performance, humification-related indices, spectroscopic characteristics, and bacterial community succession. Both amended treatments improved composting performance relative to the control, reaching higher peak temperatures (68.5 °C for CH and 70.3 °C for NFH) and prolonging the thermophilic phase. NFH also showed stronger moisture removal, with the final moisture content decreasing to 58.1%, compared with 65.1% in CH and 64.1% in the control. CH showed the highest apparent humic acid accumulation (1173 mg kg⁻¹), whereas NFH exhibited spectroscopic features commonly associated with lower E₄/E₆ ratios and more pronounced humic-like fluorescence characteristics. Ultraviolet–visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), and excitation–emission matrix fluorescence spectroscopy (EEM) analyses collectively indicated progressive transformation toward more aromatic and humified organic matter in the amended treatments. Bacterial community succession also differed across treatments, and several enriched taxa, including Rhodanobacter and Thermobifida, showed positive associations with reactive oxygen species (ROS)-related variables and humification indices. These results describe treatment-linked dynamics in humification and suggest corresponding changes in microbial succession during sludge composting, with potential implications for process outcomes. Full article

Here, the degradation of a β-blocker drug (Nadolol (NAD)) and real pharmaceutical wastewater was achieved using magnetized cow bone waste-derived char (MCBWC)–alginate hydrogel beads via a periodate (PI) activation system in a continuous-flow fluidized-bed photoreactor. The removal of NAD by PI-based degradation systems has not been previously reported, and the degradation of real industrial wastewater in continuous-flow photoreactors remains underexplored. The fabricated beads exhibited a high surface area of 78.58 m² g⁻¹, a total pore volume of 0.19 cm³ g⁻¹, and an effective integration of all composite components. The MCBWC–alginate hydrogel beads/PI/light degradation system degraded 71.47% of NAD, which was higher than that of the sole photocatalysis and PI activation systems. Further, the optimal operating condition could achieve a NAD degradation efficiency of 97.1% and a total organic carbon (TOC) removal efficiency of 82.78%. Furthermore, the degradation system demonstrated the non-formation of toxic iodinated byproducts. The hydrogel beads demonstrated high stability, where the NAD degradation efficiency slightly decreased by only 2.85% across five successive experiments. Singlet oxygen and iodine-based radicals contributed to NAD degradation more than other reactive species. Bicarbonate showed the highest suppressive effect on the degradation performance, while adding 10 mg L⁻¹ of humic acid decreased the degradation efficiency to 85.58%. The degradation system could further degrade other pharmaceuticals (e.g., ibuprofen, paracetamol, carbamazepine, tetracycline) and real pharmaceutical wastewater, attaining 78.37% degradation efficiency of NAD and 44.25% TOC mineralization. This study presents a stable, effective, and continuous degradation system that can be employed in real-world industrial wastewater treatment applications. Full article

This study investigated the effects of different straw return practices—no-tillage with straw mulching (SM), shallow tillage with straw incorporation (SS), and deep tillage with straw incorporation (DS)—on the content and structural characteristics of soil water-soluble organic carbon (WSOC) under a maize–soybean rotation in the black soil region in the Northeast of China. Compared with SM, SS and DS increased WSOC content by 39.0% and 28.8% in the 0~20 cm layer (p < 0.05), and by 28.4% and 8.5% in the 20–40 cm layer, respectively. Deep tillage combined with straw return reduced the WSOC/SOC ratio. The DS treatment exhibited the highest levels under maize straw incorporation, while SM treatment showed the highest levels under soybean straw incorporation. Spectral indices in both maize and soybean seasons—including the fluorescence index (FI, ranging from 1.53 to 1.57 in the maize season and from 1.53 to 1.67 in the soybean season), biological index (BIX, ranging from 0.84 to 1.79 in the maize season and from 0.61 to 0.74 in the soybean season), and humification index (HIX, ranging from 0.51 to 0.79 in the maize season and from 0.84 to 0.97 in the soybean season)—collectively indicated that WSOC predominantly consisted of microbially processed organic matter with a low degree of humification. PARAFAC modeling resolved two fluorescent components in maize season: C1 (humic acid-like substances, accounting for 34.8–54.9%) and C2 (Tryptophan-like substance, accounting for 45.1–65.2%), and two components in the soybean season: C1 (humic-like substances, 51.0–53.7%), and C2 (Fulvic acid-like substance 46.3–49.0%). Overall, deep straw return promotes soil humification but increases the structural complexity of WSOC. This systematic investigation provides mechanistic insights into how straw return practices regulate the quantity and quality of labile carbon pools in agricultural ecosystems over time. Full article

This article examines the scientific basis for using humic acids for the chemical stabilization of mineralized water prior to reverse osmosis. The need to develop alternative approaches to water pretreatment is due to the limited effectiveness of traditional antiscale reagents at high mineralization, as well as their potential environmental risks and the likelihood of secondary contamination of water systems. The article focuses on the mechanisms of interaction between humic acids and Ca²⁺ and Mg²⁺ hardness ions, which are mediated by complexation with carboxyl and phenolic functional groups. It is demonstrated that humic stabilization differs from classical softening and demineralization in that it is aimed not at the complete removal of dissolved salts, but at reducing the activity of ions involved in the formation of carbonate deposits. The potential advantages of this approach for reducing the scale-forming potential of water, improving the stability of reverse osmosis membranes, and extending inter-flushing intervals are discussed. The technological limitations associated with residual organic load, possible membrane fouling, the need to control total organic carbon, color and stability of the filter medium, as well as a pilot test of the proposed approach are considered. Full article

Soil salinization is one of the most severe forms of land degradation in arid and semi-arid regions, posing substantial threats to agroecosystem stability and food security. In this study, saline–alkali soil collected from the Wuding River Basin in Yulin, Shaanxi Province was used to construct a three-factor amendment system comprising superabsorbent polymers (SAP), biochar, and humic acid. A systematic assessment was conducted to elucidate their combined effects on soil water–salt transport and crop growth. Results from one-dimensional constant-head infiltration experiments using indoor soil columns demonstrated that the application of amendments significantly increased cumulative infiltration and improved the uniformity of wetting-front advancement. Specifically, the treatments regulated the redistribution of salts within the soil profile; while surface salinity reduction varied, the leaching efficiency was significantly enhanced in the A2B2C2 treatment. Soil bulk density (BD) showed dynamic fluctuations during the growth cycle, peaking at 1.628 cm⁻³ during the branching stage, while high-rate biochar (A3) reduced BD by up to 13.64% compared to the control by the initial flowering stage. Fitting results based on the Philip and Kostiakov models further indicated that the combined amendment strategy—particularly the A2B2C2 treatment (30 kg/ha SAP, 15,000 kg/ha biochar, and 600 kg/ha humic acid)—markedly enhanced both the initial infiltration rate and the steady infiltration capacity. Field experiments corroborated the indoor findings: plant height and dry biomass of Melilotus officinalis (L.)Lam. were significantly higher under amendment treatments than in the control, driven by improved water availability, mitigated salt stress, and enhanced soil structure. Single-factor and multi-factor interaction analyses revealed that SAP exerted pronounced effects during early growth stages, whereas biochar and humic acid contributed more substantially during the middle to late stages through sustained regulatory functions. Collectively, the results demonstrate that the combined application of SAP, biochar, and humic acid improves the water–salt regime of saline–alkali soils through a coupled “water–salt–structure–plant” mechanism, ultimately enhancing crop productivity. This study provides both theoretical insights and practical guidance for the amelioration of saline–alkali soils. Full article

The organic complexation of Cu²⁺ in aquatic systems dominates its chemical speciation, affecting its reactivity and bioavailability. Using voltammetry, we investigated Cu²⁺ organic complexing capacity (CuCC) in atmospheric samples, including water-soluble aerosol fraction, rainwater (wet-only deposition), and bulk deposition (wet and dry deposition), collected in a coastal marine area (National Park Brijuni, Adriatic Sea). The focus was on minimizing analytical interferences from surface-active substances (SAS) that accounted for up to 56% of dissolved organic carbon. Method optimization was performed using model SAS (humic-like substances, fulvic acid, and pollen-derived organic material), resulting in an optimal desorption potential of −1.4 V and the addition of 1 mg/L Triton X-100. Under these conditions, CuCC parameters of average ligand concentration and conditional stability constant of (209.8 ± 6.7) nM and log K = (10.2 ± 0.6) in water-soluble aerosol fraction, (117.1 ± 5.0) nM and log K = (9.6 ± 0.2) in rainwater, and (142.9 ± 4.1) nM and log K = (10.2 ± 0.2) in bulk deposition were determined. Atmospheric inputs represented a source of weak Cu-binding ligands for marine areas. In conclusion, short-term monitoring provided insight into the variability of different atmospheric inputs and offered a methodological basis for future long-term, more comprehensive studies. Full article

Drought is a major environmental constraint that disrupts photosynthetic processes. This study investigated the effects of foliar-applied commercial humic acid (HA) at different concentrations (1, 3 and 5 mg/mL) on the photosynthetic apparatus of sweet basil (Ocimum basilicum L. Italiano classico) under PEG-induced stress. The responses of the photosynthetic machinery were evaluated using chlorophyll a fluorescence analyses (JIP-test and PAM), leaf pigment composition, and assessments of membrane integrity. Drought stress caused pronounced alterations on both the donor and acceptor sides of photosystem II (PSII), including impaired Q_A⁻ reoxidation, reduced open PSII reaction centers (qP), diminished electron transport (ETo/RC, REo/RC), and substantial declines in performance indices (PI_ABS, PItotal). Energy dissipation increased (DI₀/RC), with regulated energy losses (Φ_NPQ) rising more strongly than non-regulated losses (Φ_NO). Drought also elevated oxidative stress markers (MDA and H₂O₂), leading to enhanced membrane injury. Among the tested concentrations, 5 mg/mL HA provided the most effective protection against drought stress. This treatment mitigated PEG-induced damage on both PSII donor and acceptor sides and increased the proportion of open reaction centers (qP). Improved PSII photochemistry corresponded with more efficient Q_A⁻ reoxidation, facilitated its interaction with plastoquinone, and caused the overall stabilization of photosynthetic functions under drought. The protective effects of HA were also evident for both PSI subpopulations. The enhanced tolerance was associated with the activation of antioxidant enzymes (CAT, SOD, APX) and the increased levels of anthocyanins and total phenolic content (TPC). In contrast, lower HA concentrations (1 and 3 mg/mL) provided insufficient protection. This study clearly demonstrates that HA enhances drought tolerance in basil in a concentration-dependent manner by protecting the structural and functional integrity of the photosynthetic apparatus, supporting its potential use as a foliar treatment to improve crop resilience under water-limited conditions. Full article

Miscanthus (Panicum virgatum L.), a biomass material known for its rapid growth and high biomass yield, is considered a suitable resource for producing biobased materials. Nevertheless, the dense and complex structure of Miscanthus hinders its full utilization. In this study, alkaline sulfite pretreatment of Miscanthus was carried out to separate the cellulosic fiber fraction and sulfonated lignin. Then, the fiber fraction was used to prepare biobased seedling pots via the wet foaming technique, and the maximum compressive strength of the prepared seeding pot could reach 1317 kPa. The surface coating of the seeding pot with wood wax oil further improved its hydrophobicity and water resistance. Furthermore, the resulting seedling pot with good biodegradability can be used to replace the petroleum-based plastic seedling pot, which could reduce plastic pollution. In addition, the fractionated sulfonated lignin was directly utilized as a fertilizer, showcasing a 6% increase in root and stem height of cabbage and a 15% rise in biomass (dry weight), compared to the humic acid treatment group. Therefore, this work offers a promising and sustainable strategy for the comprehensive utilization of Miscanthus, which can also be a beneficial reference for the better use of other kinds of lignocellulosic biomass. Full article

Low ambient temperatures severely restrict the start-up efficiency and microbial bioconversion of livestock manure during aerobic composting. To overcome this “cold-start” barrier, this study investigated the coupled effects of an easily accessible carbon source (molasses) and functional microbial inoculants (Streptomyces griseorubens JSD-1 and Paenarthrobacter nitroguajacolicus LDT1-8) on cattle manure composting. Results demonstrated that the combined strategy significantly expedited thermogenesis, achieving a peak temperature of 62.1 °C and extending the thermophilic phase (>50 °C) by 2 days. This enhanced microbial activity accelerated organic matter stabilization, increasing cellulose and hemicellulose degradation by 44.0% and 49.3%, respectively, and boosting humic acid content by 33.4% in treatment T7 (molasses + JSD-1 + LDT1-8). Amplicon sequencing revealed that the amendments reshaped microbial community structure, selectively enriching lignocellulose degradation and humification-driving taxa (e.g., Actinobacteriota and Mycothermus), leading to a more robust and modular metabolic network. Redundancy analysis confirmed that this directed succession was primarily driven by organic matter degradation and humic fraction accumulation. Overall, the combined application of molasses and microbial inoculants promoted temperature rise, lignocellulose degradation, and humification by reshaping microbial community structure, providing an effective strategy for improving cattle manure composting efficiency under low-temperature conditions. Full article

In containerized finished plant production, the effects of biostimulants in nursery practice are often judged primarily on the basis of visual condition, while a more precise interpretation of treatment response requires leaf-level physiological and rhizosphere-level indicators. The aim of our study was to determine how the humic- and fulvic acid-based BiStep biostimulant influences the physiological functioning and, in part, the rhizosphere enzyme activity of three deciduous ornamental shrub taxa widely used both in nursery finished plant production and in urban green space plantings, namely, Forsythia × intermedia ‘Beatrix Farrand’, Weigela florida ‘Eva Rathke’, and Viburnum opulus ‘Roseum’, under commercial container conditions. In the experiment, control and biostimulant treatments were compared. Treatment effects were evaluated on the basis of net photosynthesis (Pn); transpiration (E); chlorophyll content; stomatal density; stomatal length; and acid phosphatase (ACP), alkaline phosphatase (ALP), and β-glucosidase (GLUC) activities. For Pn, a significant taxon × treatment interaction was observed (p = 0.002). Pn showed taxon-dependent numerical changes under BiStep: values were 22.212 µmol CO₂ m⁻² s⁻¹ in F. intermedia, 4.182 µmol CO₂ m⁻² s⁻¹ in W. florida, and 3.370 µmol CO₂ m⁻² s⁻¹ in V. opulus, but pairwise differences from the control were not statistically significant. Transpiration also showed a significant taxon × treatment interaction (p < 0.001), although BiStep–control differences were not significant within taxa. Stomatal density increased significantly in F. intermedia and W. florida, while the BiStep–control difference was not significant in V. opulus. Chlorophyll content increased only in W. florida (from 699.6 to 924.4 µg g⁻¹ fresh weight), but this change was not statistically significant. ACP activity showed significant treatment and interaction effects (p = 0.0107; p = 0.00546), whereas ALP and GLUC did not show a consistent treatment response. Based on the results, the effect of BiStep was clearly taxon-dependent and functionally selective. Therefore, in nursery finished plant production and subsequent urban plant use, it should not be considered a universally effective input, but rather a biostimulant whose relevance depends on the specific physiological and rhizosphere-level response of the taxon. Full article

Investigating the application of sustainable agricultural approaches, such as the use of biostimulants, is considered more significant than ever, especially in the commercially important species Actinidia deliciosa L., in the face of climate change. In this work, the application of a glycine–betaine–proline-based biostimulant (GBP) and a humic and fulvic acid-based biostimulant (HF) was evaluated on the growth and metabolism of kiwi trees under field conditions. Total phenolic content, proline, and chlorophyll content were analyzed during the experiment. The metabolic data showed that the kiwi trees of the GBP treatment were more robust, as indicated by proline analysis (0.41 ± 0.09 µmol g⁻¹) compared to C (0.28 ± 0.06 µmol g⁻¹). This vigor of GBP treatment was also represented in leaf area (3943.17 ± 211.26 cm²), compared to the C (3484.01 ± 354.19 cm²). The implementation of biostimulants constitutes an ecological approach that can be integrated into biological crop management, as it is environmentally friendly, non-invasive to the ecosystem, and aims for crop resilience to biotic or abiotic stress. Full article

Conventional tillage, a soil preparation practice used to produce a fine seedbed, can disturb the soil profile by promoting soil compaction and soil organic matter (SOM) degradation. In contrast, conservation tillage, such as no-till, has the potential to sustain or increase SOM. This study aimed to (1) quantify soil organic carbon (SOC) content under conservation tillage and conventional tillage practices, (2) describe the degree of aromaticity of bioavailable SOC using fluorescence spectroscopy, and (3) correlate SOC quantity with nitrogen and phosphorus retention in soils. Fluorescence spectroscopy is a sensitive and non-destructive tool that allows for the assessment of bioavailable SOC quality related to the molecular structure, degree of aromaticity (cyclic molecules with carbon double bonds), and recalcitrance (difficulty of decomposition) of organic compounds. This study employed fluorescence excitation–emission matrices combined with parallel factor analysis (EEM-PARAFAC) to identify humic-like, fulvic-like, and protein-like substances. Data on agricultural management practices were collected from spring 2014 until fall 2017. We obtained soil samples (fall 2017) from farms in the Western Lake Erie Basin, Ohio, and performed geochemical characterization in the bulk soil and aqueous extraction. Our results showed that no-till and minimal tillage fields consistently had greater SOC and fluorescence intensity in the humic-like acids region when compared to conventional tilled fields (no-till: 34,000 mg TOC kg⁻¹; tilled six times: 16,000 mg TOC kg⁻¹). No-till enhanced SOC stabilization. In addition, conservation tillage practices retained the largest total nitrogen (no-till: 2800 mg TN kg⁻¹; tilled six times: 1350 mg TN kg⁻¹) and total phosphorus (no-till: 470 mg TP kg⁻¹; tilled six times: 250 mg TP kg⁻¹) concentrations at all studied depths (0–30 cm) when compared to conventional tilled fields. Conservation tillage promotes the accumulation of highly aromatic organic compounds favoring high cation exchange capacity, and NO₃⁻ and PO₄³⁻ retention and plant bioavailability. Full article