Belowground microbes are emerging targets for ecosystem restoration. Understanding the assembly mechanisms of these microbial communities is critical for predicting ecosystem trajectories and optimizing restoration interventions. Arbuscular mycorrhizal fungi (AMF) are hypothesized to be key drivers of these eco-evolutionary dynamics as a crucial and unique functional group associating with approximately 80% of terrestrial plant species. However, relatively little empirical information is available on the role of AMF in the soil microbial community assembly. Here, we used Salix cupularis, a native pioneer shrub species of desertified alpine meadows, to investigate the temporal dynamics of soil rhizosphere microbial communities across a restoration chronosequence (5, 10, and 20 years), with a particular focus on the AMF community. The results showed that minimal changes occurred in bacterial community structure, whereas fungal community exhibited more pronounced shifts along the chronosequence. Bacterial community assembly was initially deterministic and then became stochastic, while fungal assembly was consistently stochastic. Shrub planting enhanced the complexity of both bacterial and fungal networks over time. Co-occurrence networks and Pearson correlation analysis revealed the "time-dependent" regulatory role of the AMF community in soil microbial assembly. AMF acted as an orchestrator in the 10th year after planting (the edge density of AMF peaking at 15.0) prior to the transition to a stable, ECM-dominated state in response to shifts in soil nutrient availability, particularly significant increases in MAOC and AP, as well as a decrease in DON. Our findings indicate that fungal communities exhibit higher sensitivity and highlight the dynamic regulatory function of AMF, especially under dual-mycorrhizal symbiosis. These results provide novel mechanistic insights into soil microbe trajectories, suggesting that targeted AMF inoculation is crucial for the early-to-mid establishment phase of restoring desertified alpine meadows.

Reliable extraction of high-quality DNA from ruminant faecal samples is essential for microbiome profiling, pathogen surveillance, and nutritional studies relevant to pastoral livestock systems. Faecal material from grazing sheep presents particular challenges due to high plant fibre content and the presence of PCR inhibitors. This study compares the performance of commercial soil and stool-specific DNA extraction kits for sheep faecal samples. Faecal samples were collected from eight adult Romney ewes grazing research pastures in New Zealand and processed in parallel using a stool and a soil-specific kit. DNA concentration and purity were assessed by NanoDrop spectrophotometry. The soil DNA kit yielded significantly higher DNA concentrations than the stool DNA kit (mean ± SD: 140.2 ± 65.1 ng µL−1 vs. 74.5 ± 36.4 ng µL−1; Wilcoxon signed-rank test, p = 0.0006), while purity ratios (A260/280 and A260/230) did not differ significantly between kits and met recommended thresholds for downstream sequencing. These results demonstrate that soil DNA extraction kits can provide superior DNA yields from sheep faecal samples without compromising purity, supporting their use in high-throughput ovine microbiome studies. These findings provide practical guidance for microbiome laboratories working with fibre-rich faecal matrices and support broader application of soil-oriented extraction protocols in ruminant microbiome research.

The Overseer model is widely used in New Zealand as a precision-agriculture-related tool for estimating nitrate (NO3−) leaching losses in agricultural systems. This study evaluated the accuracy of the Overseer model in predicting nitrate (NO3−) leaching through a two-year lysimeter experiment conducted at Woodhaven Gardens, New Zealand, under beetroot and pak choi cultivation. Seven distinct nitrogen (N) fertilizer treatments were applied to assess model performance. In year 1, Overseer overestimated NO3− leaching by an average of 45.2 kg N/ha (15.7%), and in year 2, the model overestimated by 35.2 kg N/ha (43.5%). A sensitivity analysis highlighted soil texture, impeded layer depth and crop residue incorporation as key drivers of leaching variability, underscoring the need for improved model calibration. Overseer performed reasonably well under lysimeter conditions, with a strong linear relationship (Pearson’s correlation coefficient r = 0.89, p < 0.0001) between measured and predicted values and explaining 77% of the variance (R2 = 0.77) in the observed data. The model predicted a baseline leaching loss of 39.4 kg N/ha/year even when measured losses were zero. Overseer demonstrates moderate reliability in predicting NO3− leaching under vegetable cropping systems but exhibits notable limitations in handling crop-specific N dynamics, soil hydrology, and fertilizer timing.

The ruminant gut microbiome is central to feed conversion efficiency, nutrient utilisation, and animal health, yet how pasture diversity and management shape its composition over time under real, working farm conditions remains poorly understood, as most previous studies have relied on short-term or more tightly controlled comparisons. A multi-year study (2022–2025) investigated gut microbial dynamics in cattle and sheep grazing on different pasture management systems; standard pastures under contemporary management (Std-Con), standard pastures under regenerative management (Std-Reg), diverse pastures under contemporary management (Div-Con), and diverse pastures under regenerative management (Div-Reg) at Massey University, Palmerston North, New Zealand, using 16S rRNA gene amplicon sequencing of faecal DNA. Microbial relative abundance remained broadly stable overall, with notable seasonal fluctuations. Faecalibacterium spp. were the most abundant taxon overall in both hosts, though its relative abundance varied seasonally and dropped below detection in cattle under the Std-Con treatment during winter (August 2023), where Bacteroides spp. became dominant instead. Alpha diversity was also stable across treatments for both hosts, however, a sharp decline was observed in Std-Con (1.6 ± 0.27) and Div-Con (1.6 ± 0.21) during winter (August 2023), while Div-Reg remained higher (2.3 ± 0.2) in cattle. Significant temporal signals were also detected in alpha diversity, with a peak across all treatments in cattle in spring (October 2022). In sheep, both regenerative treatments were higher in spring (November 2023) (Std-Reg: 2.59 ± 0.076, Div-Reg: 2.52 ± 0.077). Pairwise beta-diversity comparisons revealed significant divergence in microbial community composition between Std-Con and Div-Reg, most pronounced in cattle from December 2024 to April 2025 (p = 0.049–0.015) and in sheep from August to October 2023 (p = 0.003–0.001). These findings demonstrate that, under real, multi-year grazing conditions, seasonal effects played a greater role in shaping gut microbial dynamics than pasture treatment alone, with regenerative management buffering a marked winter decline in cattle. Future studies directly linking functional gene expression, forage-quality, and animal production data to microbiome composition within the same sampling framework are needed to determine whether these compositional shifts translate into measurable benefits for ruminant health and productivity.

Pasture systems strongly influence microbiome diversity in both soils and grazing ruminants, and their interactions through interconnected microbial exchange pathways. In temperate regions, grazed pasture systems are predominantly composed of perennial ryegrass-white clover, representing standard systems under contemporary management. However, sustainable alternatives such as regenerative agriculture, which emphasise diverse pasture species, are gaining attention. Diverse pastures, due to their varied root structures and nutritional composition, exert more pronounced effects on soil and ruminant microbiomes than standard swards. This review synthesises current knowledge on soil and ruminant gut microbiome responses to diverse pasture systems. Diverse swards enhance soil organic carbon and microbial abundance, while their varied nutrient profiles and bioactive compounds, together with ingested soil microbes during grazing, contribute to a more diverse and stable gut microbiome, potentially strengthening soil–gut microbial interactions. However, few omics-based studies have explored microbiome responses to pasture management, and none have simultaneously investigated soil and ruminant gut microbiomes under regenerative management. This review highlights these gaps and proposes future research directions, including integrated multi-omics approaches, to advance understanding of soil–gut microbiome dynamics, interactions, and functional roles within pasture-based agroecosystems.

Soil and ruminant gut microbiomes are linked within grazing pastoral systems, yet the strength and direction of these connections under different pasture management systems remain poorly understood. This study characterised bacterial communities in soil and faeces from cattle and sheep grazing standard and diverse pastures managed under contemporary and regenerative practices using 16 S rRNA gene sequencing. Shared bacterial taxa between soil and gut were identified, and their dominance patterns and soil–gut diversity relationships were evaluated using Spearman correlations and Procrustes analyses. Several taxa, including Prevotella copri, Faecalibacterium prausnitzii, Akkermansia muciniphila, Bacteroides uniformis, Clostridium perfringens and Fibrobacter succinogenes were commonly shared between soil and gut but were usually more prevalent in the gut, indicating predominant host‑associated dominance. Soil exhibited significantly greater bacterial alpha diversity than the gut across all treatments, and neither pasture diversity nor management significantly affected soil–gut alpha diversity differences or the contributions of shared taxa. Correlations between soil and gut alpha diversity were weak and non-significant, and correlations for beta diversity between soil and gut varied through time and among treatments without reaching significance. These findings indicate that, although soil–gut microbial connectivity exists, gut communities are primarily shaped by host-related ecological processes and internal filtering, with soil acting mainly as a diverse reservoir and sink for gut-derived taxa. This highlights that host-driven gut microbiomes primarily shape the soil–gut microbiome link, limiting the strong direct influence of pasture diversity or management.

Background The gut microbiome plays a key role in ruminant health, nutrient metabolism and performance. However, the influence of pasture diversity and management on gut microbiome dynamics remains poorly studied. Methods A multi-year study (2022–2025) was conducted to investigate gut microbial dynamics in cattle and sheep grazing on standard and diverse pastures managed under contemporary and regenerative practices. Faecal DNA was extracted, and 16S ribosomal RNA (16S rRNA) gene amplicon sequencing was utilised to characterise the gut microbiome, with taxonomic assignment based on the Greengenes 16S database. Results Microbial relative abundance remained broadly stable, with notable seasonal fluctuations. Diverse pastures promoted greater gut microbial abundance, dominated by Faecalibacterium prausnitzii , which showed both positive and negative associations with other co-occurring taxa. Regenerative management consistently supported higher alpha diversity, and pairwise beta-diversity comparisons revealed significant divergence in microbial community composition between standard-contemporary and diverse-regenerative pasture management systems. Conclusions These findings highlight that increased pasture diversity and regenerative management drive shifts in the ruminant gut microbiome that may foster improved animal health, productivity, and the long-term sustainability of grazing-based farming systems.

Soil compaction caused by uncontrolled machinery traffic is a major constraint to sustainable crop production. Controlled Traffic Farming (CTF), which restricts machinery movement to permanent lanes, has been practiced in New Zealand for more than a decade but has not been evaluated against Random Traffic Farming (RTF). This knowledge gap limits farmer awareness and adoption. This study hypothesized that CTF reduces soil compaction and improves soil physical properties compared with RTF. A one-year field experiment was conducted at Pukekohe, New Zealand, using annual ryegrass grown under CTF and RTF. Soil penetration resistance (PR), bulk density, total porosity, moisture content, and air-filled porosity were measured to a 40 cm depth. RTF increased soil PR relative to CTF across 10-40 cm. Bulk density was lower under CTF (0.96-1.03 g & centerdot;cm-3) than RTF (1.11-1.30 g & centerdot;cm-3), with improved total porosity (0.60-0.62 cm & centerdot;cm-3) and aeration (12-23 cm & centerdot;cm-3). CTF achieved a 5.7% higher bed-level yield. When scaled to the whole-field context, the productivity of tramlines contributed to 8% greater dry matter yield under CTF than RTF, indicating that the area allocated to tramlines did not negate the system-level productivity. This study provides the first New Zealand-specific empirical comparison of CTF and RTF to support adoption of CTF.

Shelterbelts along pasture boundaries are a natural, cost-effective, and sustainable solution to environmental challenges such as soil degradation and nutrient losses in New Zealand's pastoral systems. However, there's limited information on how shelterbelts affect nutrient dynamics in neighbouring pasture soils. Three field study sites, two dairy farms and one beef and sheep farm, consisting of the same soil type, were selected. Shelterbelts on the sites were composed of Pinus or Macrocarpa, or a mix of Macrocarpa and Willow. Soil samples were collected from each site, both with and without shelterbelts, at three transects for six distances (1 m, 5 m, 10 m, 20 m, 40 m, 80 m) and two soil depths (0-7.5 cm and 7.5-15 cm) in late spring 2023. Shelterbelts on all four farms significantly affected soil nutrient distribution in the adjacent area. Soils within 10 m of shelterbelts had higher total and Olsen phosphorus levels by up to 65 % and 80 %, respectively; the total and nitrate nitrogen levels increased by up to 64 % relative to control (no shelterbelt) soils. Shelterbelts increased soil organic carbon by up to 75 %. The macrocarpa and willow combined shelterbelt deposited around 17 Mg more C in the area tested compared to the control. These findings indicate that the shelterbelt with grazed pastures enhances phosphorus and nitrogen availability within the immediate vicinity. The inclusion of diverse species can contribute to the accumulation of topsoil carbon. Future research should focus on comparing more diverse tree species and improved grazing practices within shelterbelts to enhance the sustainability of the grazing farming system.

Intensive vegetable farming emits high nitrous oxide (N2O) due to traffic-induced compaction, highlighting the need for preventing nitrogen (N) losses through better traffic management. This study examined the effects of Controlled Traffic Farming (CTF) and Random Traffic Farming (RTF) on N2O emissions using intact soil cores (diameter: 18.7 cm; depth: 25 cm) collected from a vegetable production system in Pukekohe, New Zealand. Soil cores from CTF beds, CTF tramlines, and RTF plots were analysed under fertilised (140 kg N/ha) and unfertilised conditions. N2O fluxes were monitored over 58 days using gas chambers. The fertilised RTF system significantly (p < 0.05) increased N2O emissions (5.4 kg N2O–N/ha) compared to the unfertilised RTF system (1.53 kg N2O–N/ha). The emission from fertilised RTF was 46% higher than the maximum N2O emissions (3.7 kg N2O–N/ha) reported under New Zealand pasture conditions. The fertilised CTF system showed a 31.6% reduction in N2O emissions compared to fertilised RTF and did not differ significantly from unfertilised CTF. In general, CTF has demonstrated some resilience against fertiliser-induced N2O emissions, indicating the need for further investigation into its role as a greenhouse gas mitigation strategy.

Greenhouse gas (GHG) emissions during aerobic composting are unavoidable, but effective additives can significantly reduce emissions. Hence, this study intended to investigate the influence of different engineered biochar, modified with various materials (MgO, NaOH, Na2SiO3, and HNO3), on GHG emissions, bacterial community structure, and eco-efficiency during the co-composting process of chicken manure (CM) and bagasse. Six treatments were established, including a control (CK, a mixture of CM and bagasse), as well as treatments incorporating biochar (BC), MgO-biochar (MOBC), NaOH-biochar (SHBC), Na2SiO3-biochar (SSBC), and HNO3-biochar (NABC), respectively. These treatments underwent aerobic composting for 35 days. The findings show that engineered biochar significantly reduced GHG emissions compared to CK. Specifically, MOBC achieved a substantial 66.31 % reduction in cumulative NH3 emissions, while SHBC recorded the lowest cumulative N2O emissions. Furthermore, after composting, the MOBC treatment resulted in a significant increase of 75.72 % in amino acid nitrogen and an even more pronounced increase of 1516.02 % in amino sugar nitrogen. In contrast, the SSBC treatment led to increases of 66.81 % in amino acid nitrogen and 253.53 % in amino sugar nitrogen. The Mantel test revealed that the combination of Luteimonas, Persicitalea, and Taibaiella bacteria significantly influenced the levels of NH4+-N and organic nitrogen. Regarding GHG emissions and nitrogen retention, the ecoefficiency analysis demonstrated that MOBC exhibited superior performance, suggesting its potential as an effective material for enhancing the eco-efficiency of the co-composting process.

Cadmium (Cd) contamination in agricultural soils is one of the major environmental challenges globally. Biochar is a promising material for mitigating Cd pollution, but it carries the risk of increasing greenhouse gas emissions. Herein, we incorporate iron-based materials into biochar to simultaneously enhance soil nutrients, mitigate heavy metal contamination, and reduce greenhouse gas emissions. The results showed that the iron-modified biochar (FeBC) increased soil available potassium, alkali-hydrolyzable nitrogen and soil organic carbon. All materials promoted the formation of strongly bound Cd (FMO-Cd), with FeBC outperforming standalone iron or biochar by reducing soil Cd bioavailability by 17.0-44.9%. And the goethite-modified biochar (GBC) further enhanced iron plaque [FeO(OH)] formation, achieving the highest Cd reduction (80.4%) in rice grains. In addition, except for biochar and zero-valent iron, the other treatments significantly suppressed CH4 emission and stabilized CO2 and N2O. Among them, GBC treatment reduced the relative abundance of the mcrA gene, a CH4 emission-related gene, by 22.7%, ultimately leading to the highest reduction in CH4 emissions (26.3%). These findings suggest the potential of FeBC as soil amendments to improve soil nutrients and food safety, while reducing greenhouse gas emissions.

Inconsistent yield responses to inorganic phosphorus (P) fertilisers in tropical rice paddy soils remain a challenge. This study investigated the contributions of applied P fertilisers to soluble soil P and P transformation mechanisms in P-added paddy soils. An incubation study was conducted on three rice-growing soils (Ultisol, Alfisol, and Entisol) in Sri Lanka with and without single superphosphate (SSP), triple superphosphate (TSP), and urea. Dissolved reactive phosphorus (DRP) was measured over 112 days of submergence. Thermodynamic modelling and chemical P fractionation were employed to assess soil P transformations. Phosphorus-fertilised soils had significantly higher DRP concentrations (1.1–8.0 mg L−1) compared to controls at 7 days after submergence but DRP declined beyond 21 days (0.024–0.300 mg L−1). Single superphosphate increased DRP more than TSP, short-term. Urea did not affect DRP concentration. Ultisols exhibited the lowest DRP, while Alfisols maintained higher DRP than Ultisol which was near or above the critical concentration for rice (0.1 mg L⁻1) after 28 days. In Entisol, only SSP maintained DRP above 0.1 mg L−1. Modelling suggested Ca phosphates and Fe oxy(hydr)oxides dissolved during submergence. Released P may be resorbed by Fe/Al oxy(hydr)oxides and Ca minerals, with evidence of downward movement of dissolved P and its resorption onto Fe/Al and Ca minerals possibly due to saturation of P sorption sites in the topsoil layer. Low dissolved P in porewater may be linked to inherent soil characteristics, including low organic matter and high amorphous Fe and Al oxides. • Ultisols exhibited the lowest dissolved reactive P (DRP) concentrations in porewater. • Alfisols showed a slight increase in DRP over time, remaining at or above the critical concentration (0.1 mg L−1) for rice growth. • Only the single superphosphate added treatment in Entisol exceeded the 0.1 mg L−1 threshold. • Calcium phosphates and Fe(III) oxy(hydr)oxide dissolved and released P to porewater during the submergence. • The dissolved P leached and resorbed onto amorphous and crystalline Fe/Al oxy(hydr)oxides and Ca minerals.

This study investigates epoxy-lignite composite as a coating membrane for controlled-release fertilizers (CRFs). Two CRFs were developed by coating urea with different coating thicknesses, named Epox3 and Epox5. In urea dissolution test, the complete urea release took place in 144 and 408 h for Epox3 and Epox5, respectively. The coating percentage of Epox3 and Epox5 were 7.8% and 13.7%, respectively. Epox3 exhibited a surge in release of urea at around 130 h due to failure release. Scanning electron microscopy analysis verified the compact nature of the coating, revealing a distinct depression in the interface of urea and coating. The weak interactions between lignite and epoxy resin were confirmed by Fourier Transform Infrared Spectroscopy analysis. Thermal degradation of Epox5 occurred earlier than Epox3 as the former has higher epoxy content. Both CRFs showed high level of abrasion resistance. Effective porosity of Epox5 (12.28%) significantly (P < 0.05) lower than Epox3 (2.35%). The slower release of urea by Epox5 compared to Epox3 was attributed to the lower porosity, reduced water absorbency and the higher coating density resulting from the thicker coating layer. Fitted models with urea release from CRFs suggests that non-Fickian anomalous transport was the prominent mechanism for urea release.

In farmland shelterbelt systems, the decomposition and/or apoptosis of forest fine root litter could affect farmland soil properties at the tree-crop interface, particularly the soil nitrogen (N) cycling. However, how fine root litter affect the ammonia (NH3) and nitrous oxide (N2O) losses from farmland soil and the crop production is little known. A soil column experiment covering a whole rice season was conducted to evaluate the dynamics aforesaid in response to fine root litter of Populus (RP) and Metasequoia glyptostroboides (RM) with 0 and 240 kg ha(-1) N fertilizer input. Both RP and RM had minimal impact on NH3 and N2O emissions from soils without N input. At 240 kg N ha(-1) input, RP significantly (p < 0.05) increased total NH3 volatilization (including yield-scaled NH3 volatilization and emission factor) by 37.1%, while RM significantly (p < 0.05) decreased it by 18.1%. Both fine root litter significantly (p < 0.05) reduced the N2O emissions from paddy soil receiving 240 kg N ha(-1) by 22.7-27.1%. The reduction of N2O emission in N240 + RM was primarily attributed to higher topsoil ammonium-N but lower nitrate-N contents that indicating a reduced nitrification rate during the mid-season drainage stage. In addition, the decreases in soil AOA amoA (-39.4%) and nirS (-23.7%) gene copies explained the mitigating effect of RP on N2O emission. Regardless of N fertilizer application or not, there was no statistically significant difference in rice grain yield between treatments with and without fine root litter, although RM reduced grain yield by 11.2-14.9% compared to treatments without fine root litter. In conclusion, the impact of fine root litter on N emissions via NH3 and N2O depends on both N input rates and fine root types. RM simultaneously reduce reactive farmland soil N losses via NH3 and N2O in the tree-crop interface soils with N input.

Regenerative agricultural practices emphasize the use of diverse pasture species within sustainable agriculture production systems. The inclusion of a range of legume species in diverse pasture swards is likely to increase biological N fixation (BNF) across seasons, reducing the system’s reliance on synthetic N inputs. The present field study aims to quantify BNF in selected legume species within diverse pasture (combining 9 species) and standard pastures (ryegrass and clover combination) and assess their performance to identify the potential for improving N supply while maintaining year-round pasture quality. A year-round seasonal BNF was assessed by evaluating soil N status, nodulation patterns, plant composition, and conducting 15N natural abundance studies. The results revealed that the diverse pasture sward produced 5.4% more dry matter compared to the standard pasture, while soil mineral N (NO3−, NH4+) remained statistically similar between the two treatments. Nitrogen yield was 9.3% higher in the diverse pasture than in the standard pasture. 15N natural abundance analysis assessment revealed no substantial variation in BNF rates across treatments throughout the study. However, in contrast to standard pasture, the BNF rate in diverse pasture experienced a 3-fold increase from winter to summer, while the standard pasture exhibited a 1.5-fold increase. In both pasture systems, BNF increased with clover proportion up to 30%, indicating optimal fixation at moderate clover levels. The findings underscore the potential of diverse pastures when strategically managed to enhance seasonal BNF while sustaining pasture productivity.

Iron-carbon micro-electrolysis system is a promising method for promoting electron transfer in nitrate removal. However, many traditional approaches involving simple physical mixing inevitably suffered from the confined iron-carbon contact area and short validity period, leading to the overuse of iron. Here, a ceramsite-loaded microscale zero-valent iron (mZVI) and acidified carbon (AC) coupled-galvanic cell (CMC) was designed to support chemical, autotrophic and heterotrophic denitrification. Long-term experiments were conducted to monitor the nitrogen removal performance of denitrification reactors filled with CMC and thus optimized the denitrification performance by improving fabrication parameters and various operating conditions. The denitrification contributions test showed that the chemical denitrification pathway contributed most to nitrate removal (57.3%), followed by autotrophic (24.6%) and heterotrophic denitrification pathways (18.1%). The microbial analysis confirmed the significant aggregation of related denitrifying bacteria in the reactors, while AC promoted the expression of relevant nitrogen metabolism genes because of accelerated uptake and utilization of iron complexes. Meanwhile, the electrochemical analysis revealed a significantly improved electron transfer capacity of AC compared to pristine carbon. Overall, our study demonstrated the application of a novel mZVI-AC coupled material for effective nitrate removal and revealed the potential impact of CMC in the multipathway denitrification process. Graphical Abstract

The novel Fe-Mn oxide, microbe and biochar composite (FM-DB) synthesized by mixing Fe-Mn oxide, Cd(II)-resistant microbe inoculated biochar, was to simultaneously remediate the co-contamination of Cd and As. The adsorption behaviour and mechanism of Cd(II) and As(III) were studied by using adsorption experiments: the effects of the initial pH of solution, initial concentration of heavy metal, and addition order of Cd(II) and As(III) solutes on adsorption of FM-DB. The adsorption capacity for Cd and As was 59.27 and 84.73 mgkg-1, respectively. The results showed both antagonism and synergistic interaction behaviour of Cd(II) and As(III) adsorption. Synergistic effects was primarily governed by electrostatic interaction, biochemistry/specific adsorption and Cd-As co-precipitation. To investigate the FM-DB stabilization ability of heavy metal in two paddy soils, a 60-days soil incubation experiment was carried out. The pH of SY was significantly increased by 0.39-1.21 units with FM-DB addition, and the pH of FS remained relatively stable throughout the incubation periods. FM-DB significantly increased the DOC of the two soils by 40.57% and 18.16%, respectively. The BCR extraction was employed in this study to assess the transformation of unstable Cd and As into residual fractions. FM-DB significantly decreased the concentration of available Cd and As by 6.7%-20.4% and 8.7%-24.3%, respectively in SY, and by 4%-8% and 5.4%-25.2%, respectively in FS (p < .05). Thus, it is feasible to apply FM-DB to alleviate the Cd and As pollution in the environment.

This study examined the effectiveness of pristine biochar (BC) and Fe-functionalized biochar (FBC) in remediating As-Sb co-contaminated soil, and revealed the resulting impact on soil enzymatic activities and bacterial communities. Results from incubation experiments showed that the 1.5% FBC treatment reduced the bioavailable As and Sb concentration by 13.5% and 27.1%, respectively, in compared to the control, and reduced the proportion of specifically adsorbed and amorphous Fe-Mn oxide-bound metal(loid) fractions in the treated soil. Among the BC treatments, only the 1.5% BC treatment resulted in a reduction of bioavailable As by 11.7% and Sb by 21.4%. The 0.5% BC treatment showed no significant difference. The FBC achieved high As/Sb immobilization efficiency through Fe-induced electrostatic attraction, π-π electron donor-acceptor coordination, and complexation (Fe-O(H)-As/Sb) mechanisms. Additionally, the 1.5% FBC treatment led to a 108.2% and 367.4% increase in the activities of N-acetyl-β-glucosaminidase and urease in soils, respectively, compared to the control. Furthermore, it significantly increased the abundance of Proteobacteria (15.2%), Actinobacteriota (37.0%), Chloroflexi (21.4%), and Gemmatimonadota (43.6%) at the phylum level. Co-occurrence network analysis showed that FBC was better than BC in increasing the complexity of bacterial communities. Partial least squares path modeling further indicated that the addition of biochar treatments can affect soil enzyme activities by altering soil bacterial composition. This study suggests that FBC application offers advantages in simultaneous As and Sb immobilization and restructuring the bacterial community composition in metal(loid)-contaminated soil.

The beneficial utilization of potentially increasing urban green waste (UGW) is critical for sustainable urban development in China. In this study, UGW was pyrolyzed at different temperatures, and the resulting biochar was used to amend Cd-contaminated soils to grow cabbage. Our results showed that the Cd adsorption capacity of UGW-biochar was positively correlated with the surface area, O/C, and (O+N)/C value of biochar. Furthermore, UGW-biochar was incorporated into three Cd-contaminated soils, including one acidic soil and two neutral soils, to assess its impact on the availability of Cd. The most substantial reduction in the concentration of available Cd was observed in the acidic soil, of the three tested soils. In the neutral soils, a more substantial reduction was found in the heavily Cd-contaminated soil compared to the lightly Cd-contaminated soil. UGW-biochar amendments to the three Cd-contaminated soils resulted in an increase in the cabbage biomass in acidic soil, whereas in neutral soils, it increased in lightly contaminated soils but decreased in heavily contaminated soils. Additionally, the Cd bioaccumulation factor (BCF), translocation factor (TF), and removal efficiency (RE), as impacted by the biochar application, were calculated in the lightly Cd-contaminated soil-cabbage system. The BCF decreased from 5.84 to 3.80 as the dosage of the UGW-biochar increased from 0% to 3%, indicating that the UGW-biochar immobilized Cd and reduced its bioaccumulation in cabbage roots. Based on our investigations, UGW-biochar effectively immobilizes Cd by reducing its mobility and bioavailability in a lightly contaminated environment matrix.