Search Results (423)

Intensive agriculture has intensified soil acidification in southern China, threatening crop productivity and ecosystem sustainability. Biochar can neutralize acidity, improve pH buffering, and enhance nutrient retention and microbial habitat in acidic soils. Accordingly, we produced biochars from pruned eucalyptus (ABC), camphora (ZBC), and guava (FBC) branches via pyrolysis at 500 °C. The three biochars were characterized by elemental analysis, Fourier Transform Infrared Spectroscopy (FTIR), and SEM (Scanning Electron Microscopy), and their effects on soil properties, enzyme activities, and bacterial communities were evaluated through a 56-day incubation experiment in an acidified, continuously cropped soil. Physicochemical characterization revealed that ZBC and FBC possessed more oxygen-containing functional groups and greater potential for pH buffering and nutrient release, whereas ABC exhibited higher aromaticity and structural stability. Biochar significantly increased soil pH by 0.62–1.42 units and improved nutrient availability and carbon pools (p < 0.05). Additionally, 4% ZBC increased urease and sucrase activities by 21.54% and 79.34%, respectively, while 2% FBC increased cellulase activity by 25.99%. High-throughput sequencing identified Acidobacteria and Proteobacteria as the dominant phyla; ZBC and FBC at 0.5% and 2% significantly increased Shannon and Chao1 indices. Redundancy analysis indicated that available potassium, pH, soil organic carbon, urease, sucrase, and cellulase were the primary drivers of bacterial community variation and positively associated with carbon-cycling phyla. These findings demonstrate that feedstock-specific biochar properties critically regulate soil biogeochemical processes, offering a sustainable strategy to remediate acidified soils and valorize agroforestry residues. Full article

Coal-based humic acid waste residue is a solid waste generated during the production of humic acid products. The extraction of coal-based humin (NHM) from such residues presents an effective approach for solid waste resource recovery. In this study, a novel calcium-based humin (Ca-NHM) was synthesized via a low-temperature-assisted method. The material was characterized and its cadmium passivation mechanism was investigated using scanning electron microscopy (SEM), zeta potential analysis (Zeta), carbon nuclear magnetic resonance (¹³C-CPMAS-NMR), and X-ray photoelectron spectroscopy (XPS). Soil incubation experiments were conducted to determine the actual cadmium adsorption capacity of coal-based humin in soils and to evaluate the stability of cadmium passivation. Plant cultivation experiments were carried out to verify the effects of coal-based humin on migration and transformation in soil, as well as on cadmium bioefficiency. The results showed that Ca-NHM passivated soil cadmium through multiple mechanisms such as ion exchange, electrostatic adsorption, complexation reactions, and physical adsorption. Compared with NHM, Ca-NHM exhibited a 69.71% increase in passivation efficiency, and a 2.44% reduction in cadmium leaching concentration. In Ca-NHM treatments, the above- and below-ground biomass of pakchoi increased by 18.06%, and 80.95%, respectively, relative to the control group. Furthermore, Ca-NHM enhanced the cadmium resistance of pakchoi, reduced the enrichment coefficient, activity coefficient, and activity-to-stability ratio in the above-ground portion of pakchoi, and maintained a transfer coefficient below 1, thereby alleviating cadmium toxicity. In summary, this study provides a theoretical foundation for understanding the mechanisms by which coal-based humin mitigates cadmium toxicity in pakchoi. Full article

The surface chemistry of biochar plays a pivotal role in the adsorption and stabilization of soil organic carbon (SOC); however, sorption-mediated mechanisms remain insufficiently understood for biochars derived from invasive plants. In this study, Solanum rostratum biomass, an aggressive invasive weed in northern China, was pyrolyzed at 400–600 °C in 2023 to produce biochars with varying surface functionalities and structural features. FTIR, Raman, XPS, and SEM analyses revealed that increasing pyrolysis temperature led to decreased oxygen-containing functional groups and enhanced aromatic condensation, reflecting a transition from hydrogen bonding to π–π and hydrophobic sorption mechanisms. Soil incubation experiments using sandy loam soil showed that biochar produced at 500 °C significantly increased the stable carbon pool (SCP) to 52.4%, compared to 30.6% in unamended soils. It also reduced cumulative CO₂ release from 1.74 mg g⁻¹ to 1.21 mg g⁻¹ soil, indicating improved carbon retention. Bacterial 16S rRNA gene sequencing revealed that biochar amendments significantly altered community composition and increased deterministic assembly, particularly under 500 °C biochar, suggesting a sorption-driven niche filtering effect. These findings demonstrate that S. rostratum-derived biochar, especially at intermediate pyrolysis temperatures, enhances both carbon sequestration and microbial habitat structure. This has direct implications for improving degraded soils in arid farming regions, offering a dual strategy for invasive biomass management and climate-resilient agriculture. Full article

Remediating cadmium (Cd) contamination in aquatic and terrestrial environments has become an urgent environmental priority. Biochar has been widely employed for heavy metal removal due to its wide availability, strong adsorption capacity, and potential for recycling agricultural waste. In this study, samples of alkali–Fe-modified biochar (Fe@NaOH-SBC, Fe@NaOH-HBC, and Fe@NaOH-MBC) were prepared from agricultural wastes (ginger straw, Sichuan pepper branches, and kiwi leaves) through NaOH and FeCl₃·6H₂O modification. A comprehensive characterization confirmed that the alkali–Fe-modified biochar exhibits a higher specific surface area, richer functional groups, and successful incorporation of the iron oxides Fe₃O₄ and α-FeOOH. The fitting parameter qmax from the Langmuir model indicates that the alkali–Fe modification of carbon significantly enhanced its maximum capacity for Cd²⁺ adsorption. Furthermore, a synergistic effect was observed between iron oxide loading and alkali modification, outperforming alkali modification alone. Furthermore, a 30-day soil incubation experiment revealed that the application of alkali–Fe-modified biochar significantly increased soil pH, SOM, and CEC while reducing the available cadmium content by 13.34–33.94%. The treatment also facilitated the transformation of highly bioavailable cadmium species into more stable, less bioavailable forms, thereby mitigating their potential entry into the food chain and the associated human health risks. Moreover, short-term spinach seed germination experiments confirmed that treatments with varying additions of alkali–Fe-modified biochar mitigated the inhibition of seed physiological processes by high concentrations of available cadmium to varying degrees. Overall, this study provides a sustainable and effective strategy for utilizing agricultural waste in the remediation of cadmium-contaminated water and soil systems. Full article

The vegetative mycelium of Pleurotus ostreatus (oyster mushroom) exhibits the ability to reduce nematode populations. This property may be utilized in integrated management programs targeting harmful nematodes such as Heterodera schachtii, a major pest of sugar beet crops. In addition to sugar beet, many other plant species serve as hosts for this nematode; susceptible plants promote H. schachtii development and population growth. Current control strategies rely on integrated plant protection methods, including the use of tolerant cultivars, fallowing, and trap crops such as oilseed radish and white mustard. This study aimed to determine whether sugar beet cv. Janetka or nematocidal plants—oilseed radish cv. Romesa and white mustard cv. Bardena—affect the nematocidal activity of P. ostreatus mycelium when applied together. Specifically, the influence of root or seed secretions from these plants on the activity of ten P. ostreatus mycelial strains was assessed using the model nematode Caenorhabditis elegans and the target pest H. schachtii. Experiments were conducted under laboratory conditions on water agar media colonized by P. ostreatus mycelium. Seeds or root exudates of the tested plants were applied to the mycelial surface. Following incubation, nematode mobility (C. elegans) and cyst entwining by the mycelium (H. schachtii) were evaluated, along with the ability of the mycelium to produce toxocysts. The results indicate that trap plants did not significantly alter the nematocidal activity of the mycelium. However, certain mycelial strains were slightly stimulated by seed diffusates or root exudates. Oilseed radish moderately influenced the nematocidal activity of four mycelial strains against C. elegans, whereas in the case of H. schachtii, similar effects were observed with white mustard. The mycelial elimination of H. schachtii occurred through cyst entwining, which was generally more effective in the presence of plant exudates. Overall, the findings demonstrate that incorporating trap crops such as oilseed radish cv. Romesa or white mustard cv. Bardena, as green manure in crop rotation systems, does not interfere with the nematocidal activity of P. ostreatus mycelium and simultaneously may enrich the soil with nutrients. The study further confirms that P. ostreatus maintains its ability to effectively entwine and eliminate H. schachtii cysts even in the presence of sugar beet, supporting its potential role as a biological control agent. To our knowledge, this is the first experiment that integrates the activities of trap plants and sugar beet with the nematocidal effects of P. ostreatus mycelium. Full article

Accurate evaluation of plant-available phosphorus (P) in flooded paddy soils requires consideration of redox dynamics and soil-specific properties. This study evaluated five soil P extraction methods, such as Truog, Bray 2, Mehlich 3, Olsen, and ascorbic acid-reduced Bray 2 (AR Bray 2), using soils collected from 20 paddy fields in a cold region of Japan that have received long-term fertilization. All four methods, except AR Bray 2, were conducted under air-dried and flooded incubation conditions. Additionally, we conducted pot experiments with the two rice cultivars to measure P uptake. Bray 2 extracted the highest amount of P (543.6–1045.4 mg P kg⁻¹). Incubation increased extractable P by factors of 2.4–4.9 with the Mehlich 3 and Truog methods, indicating enhanced P solubility under reduced conditions. The Olsen method showed minimal sensitivity to redox changes (−31.4 mg P kg⁻¹). Principal component and cluster analyses suggested three patterns of soil P behavior under changing redox conditions: (1) stable P extractability regardless of redox status; (2) increased P availability after incubation; and (3) P extractability depending on the extraction method used. These patterns were not explained by regional or taxonomic classifications. A comparison of soil extractions and P uptake indicated that no single method consistently predicted shoot P concentrations across all soils, suggesting that conventional P extraction methods may have limited ability in long-term fertilized paddy soils. Our findings demonstrate that soil-specific redox behavior and cultivar-specific P demand critically influence the effectiveness of standard P tests. Therefore, selecting diagnostic methods tailored to soil characteristics and crop requirements is essential for accurate P evaluation and sustainable fertilizer management in rice cultivation. Full article

Excessive copper (Cu) content in soil can affect plant growth and also cause damage to the soil ecosystem, making it one of the risk control projects for agricultural land soil pollution in China. Alternanthera philoxeroides exhibits stronger colonization ability in heavy metal-contaminated soil, but its physiological and ecological mechanisms of tolerance to excessive Cu remain unclear. A greenhouse incubation experiment was conducted to study the multifaced responses of A. philoxeroides to Cu stress at artificially augmented concentrations of 0, 250, 500, and 1000 mg kg⁻¹. The results showed that A. philoxeroides exhibited high tolerance to Cu²⁺, with a tolerance index (TI) exceeding 60%. As the Cu concentration increased from 0 mg kg⁻¹ to 500 mg kg⁻¹, root biomass and Cu concentration in the root increased. Additionally, soluble sugar (SS) and malondialdehyde (MDA) contents, and catalase (CAT) and peroxidase (POD) activities of A. philoxeroides continued to increase, whereas superoxide dismutase (SOD) enzyme activity, branch number, leaf area, and net photosynthetic rate kept declining. However, the trend of these indicators was opposite when Cu²⁺ concentrations were above 500 mg kg⁻¹, while the canopy area and underground root system of A. philoxeroides increased. These results suggested A. philoxeroides displayed a standing “silent” tolerance strategy to survive when soil copper was lower than 500 mg kg⁻¹ concentrations, and an “escape” strategy to avoid high copper stress by expanding the above- and below-ground areas of plants when soil copper concentrations were higher than 500 mg kg⁻¹. This study recommends the controlled utilization of A. philoxeroides for pollution remediation in Cu-contaminated soil areas where most local native plants are unable to survive. Full article

This study investigates the impact of tire wear particles (TWPs) and their dissolved organic matter (DOM) on soil DOM dynamics and heavy metal behavior. Through short-term incubation experiments under simulated natural conditions with TWPs of varying particle sizes, we analyzed ecological changes in soil. Using three-dimensional excitation–emission matrix (3D-EEM) spectroscopy coupled with parallel factor analysis, we monitored the photochemical properties and compositional evolution of soil dissolved organic matter. Results demonstrate that TWP amendment substantially alters soil DOM molecular characteristics, inducing a sharp decrease in protein-, carbohydrate-, and lipid-like components, the degradation of low-aromaticity unstable dissolved organic matter, and an overall increase in aromaticity. Furthermore, TWP input directly modified soil properties, triggering the transformation of soil aggregates: the proportion of large aggregates significantly decreased while that of small aggregates increased, thereby reducing overall aggregate stability. The bioaccessibility of heavy metals (HMs) (Cd, Cu, and Zn) extracted by CaCl₂ increased, primarily due to the release of endogenous metals from TWPs, compounded by the disruption of soil aggregates. In contrast, Pb tended to transform into more stable fractions under TWP stress, reducing its bioaccessibility. Further correlation analysis indicated that TWPs indirectly affected HM (Cd, Cu, and Zn) fractionation by influencing the soil dissolved organic matter properties and soil properties. This study provides a new perspective for elucidating the interplay between dissolved organic matter and HMs in urban soils, as mediated by tire wear particles (TWPs). Full article

The application of organic amendments is increasing in intensive modern agriculture. However, the impacts of organic amendments with distinct quality and quantity on soil mineral nitrogen (N) dynamics remain unclear. In this study, we performed a laboratory incubation experiment for 90 days to investigate the effects of organic amendments with different carbon-to-nitrogen ratios (C/N) (7, 119, 506) and application rates (2, 4, 6 g C kg⁻¹) on N mineralization–immobilization processes in calcareous cropland soil. The study showed that net N mineralization induced by low C/N amendment (rapeseed cake, 7) occurred in this soil. In contrast, net N immobilization was stimulated by glucose and high C/N organic amendments, including maize straw (C/N, 119) and cypress sawdust (C/N, 506). The immobilized N was in the order of glucose > maize straw > cypress sawdust regardless of application rates, which was ascribed to the discrepancy of their C availability. Both N mineralization and N immobilization increased with application rates during the incubation period. The net N mineralization from these organic amendments was significantly affected by C/N ratios (p < 0.001), application rates (p < 0.001), and their interaction (p < 0.001). The study indicated that organic amendments with a higher C/N ratio would promote soil N immobilization, which was further reinforced by higher application rates, thereby decreasing the risk of reactive N loss in calcareous soil. Full article

Cadmium (Cd) accumulation in cocoa poses a regulatory challenge for cacao producers in regions with naturally elevated soil Cd, such as Indonesia. This study evaluated the potential of soil-based and plant-based solutions to reduce Cd uptake in cacao. The efficacy of soil amendments was tested with two experiments: (1) a 12-week soil incubation tested lime, biochar, and lime–biochar mixtures at five rates on sandy clay loam and (2) a field trial evaluating zeolite applied at three rates (300, 600, and 900 kg ha⁻¹) with heat or alkali pretreatments. A third experiment evaluated the potential of four cacao genotypes and their rootstock–scion interactions to mitigate Cd uptake over the course of a 12-month nursery trial in Cd-augmented soil. In the incubation study, some lime and biochar treatments produced numerically lower soil Cd concentrations than the control (0.25 mg kg⁻¹), with final means as low as 0.15 mg kg⁻¹, but these differences were not statistically significant in this experiment. Application of zeolite in the field significantly reduced leaf and bean Cd levels (leaf: 0.35–0.50 mg kg⁻¹; bean: 0.25–0.75 mg kg⁻¹) compared to the control (p < 0.01). In the nursery experiment, average increases in leaf Cd concentrations from 6 to 12 months after spiking were lowest in rootstock MCC01 (1.46 mg kg⁻¹; p < 0.001) compared to higher increases in MCC02 (4.16 mg kg⁻¹) and Sulawesi 1 (3.53 mg kg⁻¹), indicating reduced Cd uptake by MCC01 across scions, while scion and interaction effects were not significant. Targeted soil amendments and specific rootstock–scion combinations are promising strategies to reduce Cd concentrations in cacao systems. Full article

Biochar produced from phosphorus (P)-rich feedstocks has often been promoted as an alternative P fertilizer. However, existing evidence has mainly been obtained from incubation experiments and field trials with a rather short duration, leaving uncertainty about whether repeated low-rate applications of biochar can meaningfully supply P and increase soil P pools over time. This study evaluates the agronomic effects of 10 years of application of biochar derived from plant biowaste (BIO) and bones (BC) at an application rate of 4 t ha⁻¹ yr⁻¹, compared with a mineral P fertilizer (MIN), compost application (COM), and a zero-P control. The application of P through BC and COM led to higher total soil P concentrations than the control. Changes in labile P pools (H₂O–P, NaHCO₃–P, Bray-P) were generally modest, but BC again tended to yield higher values relative to the other treatments. The ratio of organic to inorganic P was not influenced by fertilizer type. A clear effect of the amendments on maize yield was observed, with BC producing the highest yields among all amendments (6.4 t ha⁻¹; average 2020–2023), and yields were occasionally further increased when BC was combined with COM. The BIO treatments also achieved yields that were at least comparable to those of the MIN treatment (4.7 t ha⁻¹). Despite the limited effects on labile soil P pools, the amendments increased yields and can be considered effective substitutes for mineral P fertilizers at this application rate. Full article

Straw return is a potential practice for adsorbing salt and retaining moisture in saline–alkali soils. However, adverse climate conditions such as prolonged drought and cold winters shorten the effective structural turnover of returned straw biomass in soils. Furthermore, the rigid crystalline cell walls and recalcitrant lignin components of undecomposed plant residues lower the adsorption capacity towards salt. Here, we report the pretreatment of neutral oxalic acid to destroy the dense crystalline structure of cotton straw cellulose. Through laboratory experiments, combined with the changes in the structural and chemical properties of cotton straw, the optimal oxalic acid pretreatment (OAC) conditions were determined. Subsequently, the application effectiveness of OAC was evaluated via pot experiments and field trials. The optimal conditions of OAC were 0.2% dosage, 60 °C, and 24 h, displaying a maximum increase in salt absorption and water retention capacities of cotton straw materials, through exposing the hydroxyl network of cellulose and chemically hydrolyzing recalcitrant lignin. In the indoor potted plant experiments, the feasible application of oxalic acid pretreatment can be regarded as an active barrier, increasing soil moisture by 16–43% and reducing total salts by 23–26% in the topsoil (0–20 cm) within a 45-day laboratory incubation. Additionally, the OAC pretreatment had negligible adverse impacts on soil microbial communities. Moreover, some plant-beneficial microbes (e.g., Sphingomonadaceae and Gemmatimonadaceae) were stimulated, with their relative abundance increasing by 26–40% and 27–63%, respectively. Ultimately, under the pretreatment of oxalic acid-modified cotton straw salt-absorbing water-retention agent (OAC-SR), cotton seedling emergence rates, plant height, and biomass all increased to varying degrees across different concentrations of saline–alkali soil (0.05–1.0%) in the field. Then OAC-SR can be potentially applied to the process of cotton straw return to facilitate the turnover of straw structure in soil, enhance the salt-adsorption and water-retention capacities of returned straw, and provide a low-salt microenvironment for crop growth. This study demonstrates a further low-carbon and in situ applicable route to accelerate the destruction of cotton straw structure, thereby alleviating crop salt damage and promoting the green circular development of saline–alkali soil remediation. Full article

Returning straw to the soil is increasingly recognized as a sustainable practice that enhances soil fertility and promotes carbon sequestration. However, it can also accelerate the decomposition of soil organic carbon (SOC) and CO₂ emissions, raising concerns about carbon loss. This study aimed to clarify the biological and environmental drivers of SOC mineralization across soil depths in a semi-arid system. A 79-day incubation experiment was conducted using wheat straw applied at four rates (0, 3500, 7000, and 14,000 kg ha⁻¹) to soils from 0–10, 10–20, and 20–30 cm. Cumulative CO₂ release, SOC, dissolved organic carbon (DOC), and extracellular enzyme activities were quantified, and relationships were analyzed using correlation and structural equation modeling. Compared with the control, straw return increased cumulative CO₂ emissions by 48–126%, SOC by 9–21%, and DOC by 17–32%. Enzyme activities of β-glucosidase and N-acetylglucosaminidase were 25–64% higher under straw treatments. Structural modeling revealed that enzyme activity had a stronger direct effect on SOC mineralization than chemical properties. These results support the co-metabolism theory, stimulating microbial metabolism to enhance both straw- and native-SOC decomposition. Overall, straw return improves nutrient cycling but increases CO₂ emissions, underscoring the need for optimized management to balance soil fertility with carbon mitigation. Full article

Phosphorus (P) is a critical factor in enhancing agricultural yield improvement, but the over-application of P fertilizers has led to the widespread accumulation of ineffective P in soils worldwide. Artificial humic acid (AHA) has gained recognition as a new method for enhancing P effectiveness in soils. This study aims to explore the patterns and mechanisms underlying the effect of AHA on P effectiveness. A 60-day indoor incubation experiment was conducted using a soil column system, in which the soil was fractionated into five distinct particle size classes: 2 mm, 4 mm, 6 mm, 8 mm, and 10 mm. Findings revealed that AHA effectively promoted the accumulation of Olsen-P in fine-textured soils. Following the application of AHA, the fraction of particles with a size of 2 mm exhibited the highest increase in Olsen-P, at 15.4%, whereas the fraction with a size of 8 mm showed the lowest increase, at 0.2% relative to the control, at the 60th day. Additionally, AHA promoted the migration of HCl-P while enhancing the immobilization of Olsen-P. During the initial cultivation phase, the concentrations of HCl-P in the topsoil (0 cm) differed little from those in the deeper soil (40 cm). As cultivation progressed, the concentrations of NaOH-P and HCl-P in the 0 cm soil decreased more markedly than those at the 40 cm depth by the later cultivation stage. Finally, the structural equation modeling results indicated that among NaHCO₃-P, NaOH-P, and HCl-P, NaOH-P had the most significant effect on Olsen-P. These findings offer valuable insights into how AHA could be used to improve the effectiveness of P in soils. Full article

Rhizoctonia solani (Rs) and Sclerotinia sclerotiorum (Ss) are devastating pathogens of rice and rapeseed, contributing 20–69% and 10–50% of yield losses, respectively. These pathogens develop resistant overwintering and/or oversummering sclerotia, which serve as inocula for infection in the subsequent season under favorable conditions. The present study was designed to investigate the month-wise variation in microbial diversity by mixing Rs and Ss sclerotia separately in rice-rapeseed rotation field soil, thereby identifying key microbial players associated with specific sclerotia and their implications for subsequent crops. Therefore, we incubated 2.5 g of Rs and Ss sclerotia in 100 g of soil for 3 months to mimic the field conditions and subjected month-wise soil samples to 16S rRNA and ITS2 sequencing. Data analysis of bacterial communities revealed diversity, richness, and evenness in Ss treated soil samples compared to the control, while fungal communities exhibited less diversity. These results were also evident in PCoA and hierarchical clustering, where control and treated samples were scattered in 16S rRNA and ITS sequencing. Genus level diversity exhibited enrichment of bacterial genera with known beneficial potential, notably Acidibacter, Stenotrophobacter, Sphingomonas, Flavisolibacter, Gaiella, and Neobacillus in control. Beneficial bacterial genera such as Ramlibacter, Geomonas, Kofleria, Nitrospira, and Paraflavitalea were enriched in Ss treated soil samples. The addition of Ss and Rs sclerotia activated several beneficial fungi, notably Trichoderma, Talaromyces, Clonostachys in Ss treated samples, and Vermispora, Hyalorbilia, Mortierella, Lecanicillium in Rs treated samples. Additionally, Rs treated soil samples also activated pathogenic genera, including Typhula, Fusarium, and Rhizoctonia. Sclerotia in soil modulates the microbiome and activates beneficial and pathogenic microbes. During the off-season, the Sclerotinia inoculum pressure in the soil reduces, and it is safe to grow crops next season. Whereas, in the case of Rhizoctonia infected soil, it is suggested to avoid growing crops susceptible to wilt, root rot, and blight. However, field experiments to understand the pathogen–pathogen interactions around the sclerotiosphere require further exploration. Full article