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Prolonged wastewater irrigation in agriculture has led to the accumulation of heavy metals in soil, endangering both the soil quality and food safety, thereby posing a potential threat to human health through the consumption of contaminated crops. The present study aimed to enhance the yield of mustard (Brassica juncea L. cv. Varuna and NRCHB 101) plants and stabilize heavy metals (Cd, Cr, Ni, Cu, and Zn) in wastewater-irrigated soil using rice husk ash (RHA), rice mill by-product, collected from Chandauli region of Eastern Uttar Pradesh, India. Results demonstrated significant improvements in growth, biomass, physiology, and yield of mustard plant with increasing RHA application in wastewater irrigated soil (p ≤ 0.05). Heavy metal accumulation in different parts of mustard plants decreased as RHA application rate increased. Applying RHA at 2% in soil proved to be most effective in reducing Cd, Cr, Ni, Cu, and Zn accumulation in seeds by 29%, 29.6%, 23.1%, 21.3% and 20.1%, respectively in Varuna and 30.1%, 21.4%, 11.1%, 12.1%, and 28.5%, respectively in NRCHB 101cultivars. The present findings showed that RHA amendment in wastewater irrigated soil had reduced bioaccumulation of Cd, Cr, Ni, Cu, and Zn and consequently their toxicity in cultivated mustard plants. A novel application of RHA is unveiled in this research, offering a promising solution to promote sustainable agriculture and to reduce heavy metal associated health risks within the soil-mustard system. [Display omitted] • Effectiveness of rice husk ash amendment in soil-mustard system was investigated. • Rice husk ash application improved mustard growth in contaminated soil. • Soil pH and organic matter had negative relationships with heavy metals in seeds. • Use of Rice husk ash at the rate of 2% effectively reduced heavy metal in seeds. • Heavy metal contaminated soil can be remedied by using rice husk ash. [ABSTRACT FROM AUTHOR]

Biochar amendment for landfill soil cover has the potential to enhance methane removal efficiency while minimizing the soil depth. However, there is a lack of information on the response of biochar-mediated soil cover to the changes in configuration and operational parameters during the methane transport and transformation processes. This study constructed three biochar-amended landfill soil covers, with reduced soil depths from 75 cm (C2) to 55 cm (C3) and 45 cm (C4), and the control group (C1) with 75 cm and no biochar. Two operation phases were conducted under two soil moisture contents and three inlet methane fluxes in each phase. The methane removal efficiency increased for all columns along with the increase in methane flux. However, increasing moisture content from 10% to 20% negatively influenced the methane removal efficiency due to mass transfer limitation when at a low inlet methane flux, especially for C1; while this adverse effect could be alleviated by a high flux. Except for the condition with low moisture content and flux combination, C3 showed comparable methane removal efficiency to C2, both dominating over C1. As for C4 with only 45 cm, a high moisture content combined with a high methane flux enabled its methane removal efficiency to be competitive with other soil depths. In addition to the geotechnical reasons for gas transport processes, the evolution in methanotroph community structure (mainly type I methanotrophs) induced by biochar amendment and variations in soil properties supplemented the biological reasons for the varying methane removal efficiencies. • Biochar amendment enhanced the CH 4 removal capacity of landfill soil cover. • Thick soil cover with biochar benefited CH 4 removal at dry soil & low CH 4 flux. • Thin soil cover with biochar benefited CH 4 removal at wet soil & high CH 4 flux. • Evolution of type I methanotroph explained the varied CH 4 removal efficiencies. [ABSTRACT FROM AUTHOR]

Salinity stress poses a significant challenge to agriculture, impacting soil health, plant growth and contributing to greenhouse gas (GHG) emissions. In response to these intertwined challenges, the use of biochar and its nanoscale counterpart, nano-biochar, has gained increasing attention. This comprehensive review explores the heterogeneous role of biochar and nano-biochar in enhancing salt resilience in plants and soil while concurrently mitigating GHG emissions. The review discusses the effects of these amendments on soil physicochemical properties, improved water and nutrient uptake, reduced oxidative damage, enhanced growth and the alternation of soil microbial communities, enhance soil fertility and resilience. Furthermore, it examines their impact on plant growth, ion homeostasis, osmotic adjustment and plant stress tolerance, promoting plant development under salinity stress conditions. Emphasis is placed on the potential of biochar and nano-biochar to influence soil microbial activities, leading to altered emissions of GHG emissions, particularly nitrous oxide(N 2 O) and methane(CH 4), contributing to climate change mitigation. The comprehensive synthesis of current research findings in this review provides insights into the multifunctional applications of biochar and nano-biochar, highlighting their potential to address salinity stress in agriculture and their role in sustainable soil and environmental management. Moreover, it identifies areas for further investigation, aiming to enhance our understanding of the intricate interplay between biochar, nano-biochar, soil, plants, and greenhouse gas emissions. • Biochar & Nano-Biochar enhance plant and soil resilience to salt. • Both improve resilience via ion adsorption, nutrients, soil modification. • These amendments benefit soil microbes, aiding nutrient cycling & plant health. • Biochar & Nano-Biochar reduce GHGs via microbial processes in soil. [ABSTRACT FROM AUTHOR]

The marked salinity and alkaline pH of coastal saline soil profoundly impact the nitrogen conversion process, leading to a significantly reduced nitrogen utilization efficiency and substantial gaseous nitrogen loss. The application of soil amendments (e.g. biochar, manure, and gypsum) was proved to be effective for the remediation of saline soils. However, the effects of the three amendments on soil nitrogen transformation in soils with various salinity levels, especially on NH 3 volatilization and N 2 O emission, remain elusive. Here, we reported the effects of biochar, manure, and gypsum on NH 3 volatilization and N 2 O emission under four natural salinity gradients in the Yellow River Delta. Also, high-throughput sequencing and qPCR analysis were performed to characterize the response of nitrification (amoA) and denitrification (nirS , nirK , and nosZ) functional genes to the three amendments. The results showed that the three amendments had little effect on NH 3 volatilization in low- and moderate-salinity soils, while biochar stimulated NH 3 volatilization in high-salinity soils and reduced NH 3 volatilization in severe-salinity soils. Spearman correlation analysis demonstrated that AOA was significantly and positively correlated with the NO 3 −-N content (r = 0.137, P < 0.05) and N 2 O emissions (r = 0.174, P < 0.01), which indicated that AOA dominated N 2 O emissions from nitrification in saline soils. Structural equation modeling indicated that biochar, manure, and gypsum affected N 2 O emission by influencing soil pH, conductivity, mineral nitrogen content, and functional genes (AOA- amoA and nosZ). Two-way ANOVA further showed that salinity and amendments (biochar, manure, and gypsum) had significant effects on N 2 O emissions. In summary, this study provides valuable insights to better understand the effects of gaseous N changes in saline soils, thereby improving the accuracy and validity of future GHG emission predictions and modeling. • The amendments indirectly affected N 2 O emissions through influencing soil properties and functional genes. • Nitrososphaera AOA dominated N 2 O emissions from nitrification in saline soils. • Biochar and manure could reduce N 2 O emissions, while gypsum has the risk of increasing N 2 O emission in saline soils. • The amendments had little effect on NH 3 volatilization in saline soils. [ABSTRACT FROM AUTHOR]

The application of natural zeolites to improve soil quality and functioning has become highly popular, but we still miss information about the long-term effects on the soil due to its application. This study assesses the soil quality index (SQI) of three distinct agricultural soil systems 6–10 years after a single application of natural chabazite zeolite as a soil amendment. These soils exhibit different management practices: intensive arable (cereals), intensive perennial (pear) and organic perennial (olive). In the arable system, a zeolite application dosage of 5, 10 and 15 kg m−2 was tested and compared to unamended soil. In the two perennial systems, an application of 5 kg m−2 was tested against untreated reference sols. A set of 25 soil physical, chemical and biological parameters linked to soil health and quality were analysed at each experimental site. The dataset was investigated through Principal Component Analysis (PCA) to calculate the soil quality index (SQI) using linear scoring. In the arable-cereal field, the SQI doubled (0.3 to ca. 0.6 for all amendments) in chabazite-amended plots; a dose effect was not recognizable. In both perennial fields, the SQI was significantly higher in the chabazite-amended plots (5 kg m−2) with similar increases as compared to the arable-cereal field. At each site, the indicators selected by the PCA were different, indicating that chabazite addition impacted soil quality differently in each cropping system. Overall, the results highlighted a significant increase in soil quality with chabazite amendment, which confirms its potential for increasing soil health in the long-term. • We determined soil quality advances through long-term zeolite addition. • We evaluated 3 agricultural management systems based on 25 soil health indicators. • Zeolite addition increased soil quality in all three management systems. • Soil health indicators were specific for each agricultural management system. • An addition of 5 kg m−2 was sufficient for soil health advances. [ABSTRACT FROM AUTHOR]

Saline-alkali soil poses significant chanllenges to sustainable development of agriculture. Although biochar is commonly used as a soil organic amendment, its microbial remediation mechanism on saline-alkali soil requires further confirmation. To address this, we conducted a pot experiment using cotton seedlings to explore the potential remediation mechanism of rice straw biochar (BC) at three different levels on saline-alkaline soil. The results showed that adding of 2% biochar greatly improved the quality of saline-alkaline soil by reducing pH levels, electrical conductivity (EC), and water-soluble ions. Moreover, biochar increased the soil organic matter (SOM), nutrient availability and extracellular enzyme activity. Interestingly, it also reduced soil salinity and salt content in various cotton plant tissues. Additionally, biochar had a notable impact on the composition of the microbial community, causing changes in soil metabolic pathways. Notably, the addition of biochar promoted the growth and metabolism of dominant salt-tolerant bacteria, such as Proteobacteria, Bacteroidota, Acidobacteriota, and Actinobacteriota. By enhancing the positive correlation between microorganisms and metabolites, biochar alleviated the inhibitory effect of salt ions on microorganisms. In conclusion, the incorporation of biochar significantly improves the soil microenvironment, reduces soil salinity, and shows promise in ameliorating saline-alkaline soil conditions. [Display omitted] • 2% Biochar addition improved the microenvironment of saline-alkali soil by lowering EC and salt. • Biochar significantly reduced the relative abundance of Latescibacterota and Desulfobacterota. • Biochar stimulated the formation and metabolism of salt-tolerant dominant microbes. [ABSTRACT FROM AUTHOR]

Biochar is widely recognized as a soil amendment to reduce greenhouse gas emissions and enhance soil carbon storage in agroecosystems; however, the systematic focus on carbon balance and ecological benefits in cropping systems remains unclear in saline-alkali areas under water-saving irrigation. Here, a 2-yr field experiment with carbon footprint method was conducted to determine soil carbon budgets, biochar carbon efficiency performance, and the economic and ecological benefits of mulched drip-irrigated sorghum production, in an arid salinized region of Inner Mongolia, China. Corn straw-derived biochar dosages of 0 (CK), 15 (B15), 30 (B30), and 45 (B45) t hm−2 were just applied into the soil in the first crop growing season. A single application of biochar to soil significantly reduced CO 2 emissions for the current and subsequent crop-growing seasons, with 13.1%, 16.7%, and 12.5% reductions for B15, B30, and B45, respectively. Compared with the non-biochar control plots, B15, B30, and B45 also increased NPP by 36.7%, 38.4%, and 27.1%, respectively. The actual effects on improving net carbon sequestration for B15, B30, and B45 in the first year were higher than those in the second year, with mean increases of 1.27, 1.47, and 1.36 times, respectively; however, the efficiencies of biochar for fixing carbon per biochar dosage input for B15 were 72.8% and 64.1% higher than those of B30 and B45, respectively. Net profits were significantly improved by 57.2–87.1% by biochar treatments. The environmental benefits of biochar carbon trading revenues for B15, B30, and B45 increased by 105.9%, 162.1%, and 109.6%, respectively. The minimum observation for carbon productivity and the maximum measurements for both the economic and ecological benefits were B15. The B15 also significantly increased sorghum yield and grain number. Results demonstrate that biochar application in the current growing season helps reduce soil carbon emissions, increases net carbon sequestration for current and subsequent sorghum agroecosystems, and enhances net profit and ecological benefits. The optimal positive synergistic effect was observed at a biochar application rate of 15 t hm−2 for reducing soil carbon emissions, increasing crop production, and improving the ecological environment. • Carbon balances for sorghum production receiving the mulched drip-irrigation were systematically assessed. • Biochar single application decreased soil CO 2 emissions for the current and subsequent crop-growing seasons. • Net carbon sequestration and net primary productivity were significantly improved by biochar addition. • Biochar dosage 15 t hm−2 was suitable with better economic, environmental, and ecological benefits. [ABSTRACT FROM AUTHOR]

Metal(loid) contamination of agricultural soils has become an alarming issue due to its detrimental impacts on soil health and global agricultural production. Therefore, environmentally sustainable and cost-effective solutions are urgently required for soil remediation. Biochar, particularly nano-biochar, exhibits superior and high-performance capabilities in the remediation of metal(loid)-contaminated soil, owing to its unique structure and large surface area. Current researches on nano-biochar mainly focus on safety design and property improvement, with limited information available regarding the impact of nano-biochar on soil ecosystems and crop defense mechanisms in metal(loid)-contaminated soils. In this review, we systematically summarized recent progress in the application of nano-biochar for remediation of metal(loid)-contaminated soil, with a focus on possible factors influencing metal(loid) uptake and translocation in soil-crop systems. Additionally, we conducted the potential/related mechanisms by which nano-biochar can mitigate the toxic impacts of metal(loid) on crop production and security. Furthermore, the application of nano-biochar in field trials and existing challenges were also outlined. Future studies should integrate agricultural sustainability and ecosystem health targets into biochar design/selection. This review highlighted the potential of nano-biochar as a promising soil amendment for enhancing the remediation of metal(loid)-contaminated agricultural soils, thereby promoting the synthesis and development of highly efficient nano-biochar towards achieving environmental sustainability. • The direct and indirect effects of nano-biochar on metal(loid) immobilization were conducted. • Feedstock and doses of nano-biochar affect metal(loid) accumulation and translocation in crops. • Nano-biochar offers opportunities for soil remediation of metal(loid) contaminants and sustainable agriculture. [ABSTRACT FROM AUTHOR]

This study evaluate the effects of four organic soil amendments on soil. Physical, chemical and biochemical properties were compared to untreated and natural (not cultivated) soils in a semiarid region (Andalusia, Spain). A large set of physical, chemical biochemical properties and, the composition of bacterial communities; and overall soil quality index (SQI) were evaluated on soils treated with organic soil amendments of animal origin (compost from sheep and cow manure [CS] or chicken manure, [CK], vegetal origin (greenhouse crop residues [CC]), and vermicompost (CV). Immediately after application, the animal origin compost significantly increased pH, electrical conductivity (EC), and total nitrogen (TN) as well as the enzymatic activities associated with the carbon (C) cycle but decreased the richness and evenness of bacterial communities. After 3 months of treatment, all measured properties recovered except for EC, TN and dehydrogenase activity (whose increase was stable over time), as did bacterial richness, which remained lower. The vegetal-originating compost increased EC and pH whereas the other effects were not significant throughout the monitoring period. CV application did not affect soil properties. The SQI was the highest for soils treated with CK compost, both immediately after application and over time. The soil treatments with the other organic amendments did not result in a significantly different SQI over time compared to both untreated and natural sites. [Display omitted] • Compost of animal origin increases soil pH and electrical conductivity and enzymatic activities. • Compost of animal origin reduces bacteria richness and evenness. • Compost of vegetal origin only increases pH and electrical conductivity. • The soil quality index was the highest for compost of animal origin. [ABSTRACT FROM AUTHOR]

Gas-to-liquid (GTL) sludge is a specific wastewater treatment by-product, which is generated during the industrial process of natural gas conversion to transportation fuels. This least studied sludge is pathogen-free and rich in organic carbon and plant nutrients. Therefore, it can be reused for soil enhancement as a sustainable management strategy to mitigate landfill gas emissions. In this field study, we compared the performance of soil treatments with GTL sludge to the more conventional chemical fertilizers and cow manure compost for the cultivation of cotton under hyperarid conditions. After a complete growing season, GTL sludge application resulted in the enhancement of soil properties and plant growth compared to conventional inputs. As such, there was a significant dose-dependent increase of soil organic matter (4.01% and 4.54%), phosphorus (534 and 1090 mg kg−1), and cumulative lint yield (4.68 and 5.67 t ha−1) for GTL sludge application rates of 1.5% and 3%, respectively. The produced fiber quality was adequate for an upland cotton variety (Gossypium hirsutum var. MAY 344) and appeared more dependent on the prevailing climate conditions than soil treatments. On the other hand, the adverse effects generally related to industrial sludge reuse were not significant and did not affect the designed agro-environmental system. Accordingly, plants grown on GTL sludge-amended soils showed lower antioxidant activity despite significant salinity increase. In addition, the concentrations of detected heavy metals in soil were within the standards' limits, which did not pose environmental issues under the described experimental conditions. Leachate analysis revealed no risks for groundwater contamination with phytotoxic metals, which were mostly retained by the soil matrix. Therefore, recycling GTL sludge as an organic amendment can be a sustainable solution to improve soil quality and lower carbon footprint. To reduce any environmental concerns, an application rate of 1.5% could be provisionally recommended since a two-fold increase in sludge dose did not result in a significant yield improvement. [Display omitted] • Gas-to-liquid sludge is a carbon-rich by-product of GTL wastewater treatment. • GTL sludge land application mitigates the risks of landfill gas emissions. • GTL sludge improves soil and plant properties under hyperarid conditions. [ABSTRACT FROM AUTHOR]

The development of alginate-based composites in agriculture to combat nutrient loss and drought for sustainable development has drawn increasing attention in the scientific community. Existing studies are however scattered, and the retention and slow-release mechanisms of alginate-based composites are not well understood. This paper systematically reviews the current literature on the preparation, characterization, and agricultural applications of various alginate-based composites. The synthesis methods of alginate-based composites are firstly summarized, followed by a review of available analytical techniques to characterize alginate-based composites for the attainment of their desired performance. Secondly, the performance and controlling factors for agricultural applications of alginate-based composites are discussed, including aquasorb, slow-release fertilizer, soil amendment, microbial inoculants, and controlled release of pesticides for pest management. Finally, suggestions and future perspectives are proposed to expand the applications of alginate-based composites for sustainable agriculture. [Display omitted] • Preparation methods affect the physicochemical properties of alginate-based composites. • The selection of encapsulation object depends on the actual demand. • Alginate-based composites function as conditioners in agriculture. • Recommendations and future perspectives are proposed. [ABSTRACT FROM AUTHOR]

Soil quality deterioration and heavy metal contamination have greatly limited soil productivity in mining areas. As soil is a complex system with various properties and interactions, it is imperative to conduct a comprehensive investigation to understand the amendment's mechanisms at work in the soil in mining areas as well as effective ways to address its deteriorating quality. In this study, a potassium dihydrogen phosphate-modified maize straw-cow dung biochar (PBC) was applied as a soil amendment. Various physicochemical properties of the soil including organic matter, total nitrogen, available phosphorus, and pore characteristics were analyzed. This study also assessed soil-saturated water content and soil moisture characteristic curve. Lettuce biomass was measured and changes in various speciation of Pb and Cd in the soil, and the accumulation of Pb and Cd in lettuce were examined. Results showed that the addition of PBC increased soil organic matter, total nitrogen, and available phosphorus while reducing soil bulk density, it also increased soil porosity, saturated water content, and capillary water capacity. Soil structure analysis using CT scanning revealed that 3% PBC increased the macrospores volume fraction while 5% PBC made the pores more uniform. Lettuce biomass increased by 53.3%. 5% PBC resulted in a 56.79% and 38.30% reduction in Pb and a 44.56% and 16.60% reduction in Cd in roots and shoots of lettuce respectively. PBC facilitated the transformation of Pb and Cd from unstable fractions to stable fractions through complexation and precipitation. Overall, the addition of PBC effectively improved soil nutrients, porosity, and water-holding capacity, promoted plant growth, immobilized Pb and Cd, as well as reduced the bioavailability in contaminated-soil from mining areas. This study provides an effective strategy and a new perspective for the remediation of Pb–Cd-contaminated soils. [Display omitted] • An efficient method for the amendment of heavy metal-contaminated mining soil; • Soil water retention and pore structure has been improved by adding a phosphorus-modified biochar; • Soil saturated water content, organic matter, and total N content were the main factors affecting lettuce growth; • Increased Pb and Cd stable fractions restricted the migration of Pb and Cd from the soil to lettuce. • Lettuce biomass increased by 42.81–53.3%, while Pb and Cd contents reduced by 38.30–56.79% and 16.6–44.56%. [ABSTRACT FROM AUTHOR]

Here, tobermorite was prepared by a solvothermal technology using calcite and quartz with a mixed solvent of ethanol and water. Factors including reaction temperature, time and KOH content were studied to optimize the preparation procedure. To study the relationship between ethanol content-material structural characteristics-adsorption capacity, a series of materials were prepared in different mixed solvent proportions of ethanol and water, and their structural characteristics and adsorption capacity were compared. We found that the adsorption capacity of different samples for Pb2+ and Cd2+ was positively correlated with negatively correlated with the surface area and negatively correlated with the crystallinity of materials. Then, the material prepared by 30% ethanol solution (30-T) with the best adsorption performance was used for further research; the results were fitted by kinetic and thermodynamic models, and adsorbed materials were analyzed by various characterizations, suggesting that the adsorption process was ascribed to comprehensive pathways including ion exchange, chemical precipitation, and surface-complexation. Then, the 30-T was further used to remediate heavy metals contaminated soil, and the remediation effect was examined by the DTPA-extractable method and the European Community Bureau of Reference (BCR) sequential extraction method. The DTPA-extractable results showed that tobermorite observably reduced the bioavailability of Pb and Cd, and the BCR results suggested that the acid-soluble and reducible fractions of Pb and Cd were transformed to the oxidizable and residual fractions after remediation. In summary, tobermorite has great potential in the remediation of heavy metal polluted-aquatic environment/system and soil. • Tobermorite was successfully prepared in mixed solvent of ethanol and water. • Tobermorite was used to remove Pb2+ and Cd2+ in the water. • The adsorption mechanism was ascribed to comprehensive pathways. • The amendment reduced soil acidity and the bioavailable Pb and Cd in soil. • Tobermorite could translate Pb and Cd in soil to more stable fractions. [ABSTRACT FROM AUTHOR]

Phosphate fertilizers have been excessively applied in agricultural production, bringing the risk of phosphorus (P) loss to nearby river systems and low utilization efficiency. In this study, eggshell-modified biochars prepared by pyrolysis of eggshell and corn straw or pomelo peel were applied to soil for enhancing P immobilization and utilization. The structure and properties of modified biochars before and after P adsorption were analyzed using the Brunauer-Emmett-Teller (BET) nitrogen adsorption method, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The eggshell-modified biochar performed an excellent adsorption performance for P (up to 200 mg/g), which was well described by the Langmuir model (R2 > 0.969), showing monolayer chemical adsorption with homogenous surface. The Ca(OH) 2 appeared on the surface of eggshell modified biochars and changed to Ca 5 (PO 4) 3 (OH) and CaHPO 4 (H 2 O) 2 after P adsorption. The release of immobilized P by modified biochar increased with decreased pH. In addition, pot experiments of soybean indicated that the combined application of modified biochar and P fertilizer significantly increased the content of microbial biomass P in soil, raising from 4.18 mg/kg (control group) to 51.6–61.8 mg/kg (treatment group), and plants height increased by 13.8–26.7%. Column leaching experiments showed that P concentration in the leachate decreased by 97.9% with the modified biochar application. This research provides a new perspective that the eggshell-modified biochar could serve as a potential soil amendment for enhancing P immobilization and utilization. [Display omitted] • Modified biochar showed superior adsorption for P with a maximum of 200 mg/g. • The main adsorption mechanism for P on the modified biochar was Ca–P precipitation. • Microbial biomass P increased nearly 13 times and soil P leaching decreased 98.81%. [ABSTRACT FROM AUTHOR]

Soil amendments, including lime, biochar, industrial by-products, manure, and straw are used to alleviate soil acidification and improve crop productivity. Quantitative insight in the effect of these amendments on soil pH is limited, hampering their appropriate use. Until now, there is no comprehensive evaluation of the effects of soil amendments on soil acidity and yield, accounting for differences in soil properties. We synthesized 832 observations from 142 papers to explore the impact of these amendments on crop yield, soil pH and soil properties, focusing on acidic soils with a pH value below 6.5. Application of lime, biochar, by-products, manure, straw and combinations of them significantly increased soil pH by 15%, 12%, 15%, 13%, 5% and 17%, and increased crop yield by 29%, 57%, 50%, 55%, 9%, and 52%, respectively. The increase of soil pH was positively correlated with the increase in crop yield, but the relationship varied among crop types. The most substantial increases in soil pH and yield in response to soil amendments were found under long-term applications (>6 year) in strongly acidic (pH < 5.0) sandy soils with a low cation exchange capacity (CEC, <100 mmol c kg−1) and low soil organic matter content (SOM, <12 g kg−1). Most amendments increased soil CEC, SOM and base saturation (BS) and decreased soil bulk density (BD), but lime application increased soil BD (1%) induced by soil compaction. Soil pH and yield were positively correlated with CEC, SOM and BS, while yield declined when soils became compacted. Considering the impact of the amendments on soil pH, soil properties and crop yield as well as their costs, the addition of lime, manure and straw seem most appropriate in acidic soils with an initial pH range from <5.0, 5.0–6.0 and 6.0–6.5, respectively. [Display omitted] • Soil amendments increased soil pH and crop yield by ca. 13% and 36%, respectively. • Amendments increased soil CEC, OM and base saturation and decreased bulk density. • Lime is the most economical while biochar is the most expensive for raising pH. • Lime, manure and straw are recommended at pH < 5.0, 5.0–6.0 and 6.0–6.5, respectively. [ABSTRACT FROM AUTHOR]

Organic and inorganic soil amendments are used to increase crop yields and fertilizer efficiency, as well as to improve the physical and biological properties of soil, increase carbon sequestration, and restore contaminated and saline soils. The present study aimed to evaluate the effect of various zeolite composites mixed with either lignite or leonardite on the biomass production of spring wheat and rapeseed and their root morphology. A pot experiment involved the application of the following treatments: zeolite-carbon, zeolite-vermiculite composites, both mixed with lignite or leonardite, and a control treatment with no amendments. Inorganic composites were applied in a dose of 3% and 6%. The study also included an analysis of the root morphometric parameters and aboveground biomass of spring wheat and rapeseed. The lowest productivity was observed when both crops were not enriched with fertilizers or other amendments, 24.92 g per pot and 29.83 g per pot for spring wheat and rapeseed, respectively. The application of mineral fertilizers in combination with zeolite-carbon composite gave the highest aboveground biomass of spring wheat, 110.11 g per pot. Both zeolite-carbon and zeolite-vermiculite composites modified the morphological parameters of roots, with the control treatment showing the lowest root length and dry matter. Although mineral fertilization was found to have a positive impact root development in relation to untreated control, the treatment amended with zeolite-carbon composite and leonardite exhibited the highest root length and biomass of spring wheat. No other soil amendments improved the properties of rapeseed roots. [Display omitted] • Organic/inorganic composites were applied in spring wheat and rapeseed. • The lowest yield were obtained for Control. • Highest productivity was for mineral fertilization with zeolite-carbon composite. • Zeolite-carbon and zeolite-vermiculite increased root length and biomass. • The highest root length was for zeolite-carbon with leonardite. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is essential for most soil functions. Changes in land use from natural land to cropland disrupt long-established SOC balances and reduce SOC levels. The intensive use of chemical fertilisers in modern agriculture accelerates the rate of SOC depletion. Domestic organic residues (DOR) are a valuable source of SOC replenishment with high carbon content. However, there is still a lack of knowledge and data regarding whether and to what extent DOR can contribute to replenishing SOC. This paper aims to unpack the potential of DOR as a SOC source. Total SOC demand and annual SOC loss are defined and calculated. The carbon flow within different DOR management systems is investigated in three countries (China, Australia, and The Netherlands). The results show that the total SOC demand is too large to be fulfilled by DOR in a short time. However, DOR still has a high potential as a source of SOC as it can mitigate the annual SOC loss by up to 100%. Achieving this 100% mitigation requires a shift to more circular management of DOR, in particular, more composting, and direct land application instead of landfilling and incineration (Australia and China), or a higher rate of source separation of DOR (The Netherlands). These findings form the basis for future research on DOR recycling as a SOC source. [Display omitted] • Carbon in domestic organic residues is not enough to replenish carbon in soils. • More than half of domestic organic residues are not recycled to soils. • In China and Australia, landfill is the main cause of carbon loss in the system. • In the Netherlands, incineration causes the major carbon losses. • Transition to composting of organic residues could mitigate soil carbon loss. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) contamination poses a considerable threat to human health through grain enrichment and limits biological nitrogen fixation (BNF) in paddy fields. Biochar has shown great potential for agricultural soil remediation because it inactivates Cd, but uncertainties remain as to how biochar amendments affect BNF and grain N use efficiency in paddies. To elucidate these issues, we investigated the effects of biochar amendment on the structure and function of diazotrophic bacterial communities in different rice growth stages in Cd-contaminated paddy fields, and evaluated the contribution of BNF to grain N use efficiency under biochar amendment. The results showed that biochar amendment significantly increased the abundance of diazotrophic bacteria in the tillering and jointing stages. Furthermore, the community structure of soil diazotrophic bacteria markedly changed with biochar amendment, with a significant reduction in the abundances of Euryarchaeota , Desulfobacterales (Proteobacteria), and Sphingomonadales (Bacteroidetes) in the tillering stage. Changes in the soil carbon/nitrogen (C/N) ratio was the main factor driving diazotrophic microbial community characteristics caused by the release of available C from biochar at the tillering stage, rather than the Cd. Moreover, biochar amendment increased the efficiency of BNF (especially for autotrophic N 2 fixation) in the vegetative phase of rice growth. Notably, biochar amendment significantly decreased BNF efficiency during the filling stage and reduced grain N use efficiency. The limited available nutrients in biochar and the toxicity of polycyclic aromatics and phenols in biochar-derived dissolved organic matter were responsible for the varied impacts of biochar on BNF in different rice growth stages. For the first time, we report that biochar amendment in paddy soils reduces Cd toxicity but also inhibits BNF and thereby decreases N use efficiency. Therefore, before applying biochar to inactivate Cd in paddy fields, there should be a trade-off between agricultural production and ecological safety to achieve sustainable agriculture. [Display omitted] • Toxic polycyclic aromatics and phenols contained in biochar inhibit BNF. • The lower available nutrients in biochar limit N 2 primary assimilation efficiency. • Biochar amendment reduced the grain N use efficiency. • The toxicity of 0.154 mg kg−1 available Cd has no effect on the N use efficiency. • Biochar amendment reduced the contribution of BNF to grain N accumulation. [ABSTRACT FROM AUTHOR]

The use of organic amendments to enhance soil health is increasingly being identified as a strategy to improve residential landscapes while also reducing the need for external inputs (e.g., fertilizers, irrigation). Composted biosolids are a re-purposed waste product that can be used in organic amendments to improve the overall sustainability of a municipality by enhancing residential soil carbon content while simultaneously reducing waste materials. However, the biosolids-based feedstock of these compost products has the potential to be a source of organic contaminants. We conducted a laboratory-based soil column experiment to evaluate the potential for different commercially available compost products to act as a source of emerging organic contaminants in residential landscapes. We compared two biosolids-based compost products, a manure-based compost product, and a control (no compost) treatment by irrigating soil columns for 30 days and collecting daily leachate samples to quantify leaching rates of six hormones, eight pharmaceuticals, and seven per- and polyfluoroalkyl substances (PFAS). Detection of hormones and pharmaceuticals was rare, suggesting that compost amendments are likely not a major source of these contaminants to groundwater resources. In contrast, we detected three of the seven PFAS compounds in leachate samples throughout the study. Perfluorohexanoic acid (PFHxA) was more likely to leach from biosolids-based compost treatments than other treatments (p < 0.05) and perfluorobutane sulfonate (PFBS) was only detected in biosolids-based treatments (although PFBS concentrations did not significantly differ among treatments). In contrast, perfluorooctanoic acid (PFOA) was commonly detected across all treatments (including controls), suggesting potential PFOA experimental contamination. Overall, these results demonstrate that commercially available composted biosolids amendments are likely not a major source of hormone and pharmaceutical contamination. The detection of PFHxA at significantly higher concentrations in biosolids treatments suggests that biosolids-based composts may act as sources of PFHxA to the environment. However, concentrations of multiple PFAS compounds found in leachate in this study were lower than concentrations found in known PFAS hotspots. Therefore, there is potential for environmental contamination from PFAS leaching from composted biosolids, but leachate concentrations are low which should be considered in risk-benefit analyses when considering whether or not to use composted biosolids as an organic amendment to enhance residential soil health. • Compost amendments are used in residential landscapes to enhance soil health. • Biosolids can be a feedstock for compost but may contain organic contaminants. • The extent of organic contaminant leaching through residential soils is unknown. • Pharmaceuticals and hormones did not appear to leach from compost amendments. • Certain PFAS leached more from biosolids-based composts than other treatments. [ABSTRACT FROM AUTHOR]

Non-renewable phosphorus (P) resources are intensively declining and recyclable P is high in demand for agricultural sector. Biochar as a renewable source of P and its physicochemical properties may improve the nutrients condition in the soil for plant availability. This study was designed to evaluate the interaction of biochar with soil microbes in differently textured and P-limited soils for P availability, root colonization and nutrient uptake by plants. Onion plants were grown in two differently textured soils with two types of biochar, with or without P application, three microbially inoculated treatments and uninoculated control. Plants were grown for 65 days and root-shoot biomass, nutrient concentration and mycorrhizal root colonization were analyzed. The WinRhizo was used to evaluate root attributes such as length, surface area and volume of roots. Biochar addition enhanced the nutrient uptake and plant biomass in the presence of P and microbial inoculants. Root colonization was notably increased in biochar + mycorrhizal inoculated plants. Biochar and soil type interactions may develop a unique behavior of nutrient uptake, root colonization, plant growth and root attributes. Biochar in combination with microbial inoculants could be considered a potentially renewable source of P fertilizer. • Biochar and microbial inoculant were used to address soil P deficiency problem. • Different combinations were used as soil amendment for plant growth improvement. • 1% biochar addition in P limited soil enhanced P-uptake by plants. • 1% biochar with microbial inoculant increased plant biomass and root colonization. • Biochar with microbial inoculant might be a potentially renewable source of P fertilizer. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate the kinetics of methylparaben (MPB) and butylparaben (BPB) removal, two emerging pollutants with possible endocrine disrupting effects, from agricultural soil with and without amendment with compost from sewage sludge used as biostimulant. Compound removal is explained by a first-order kinetic model with half-life times of 6.5/6.7 days and 11.4/8.2 days, in presence/absence of compost, for MPB and BPB respectively. % R2 for the fitted model were higher than 96% in all cases. Additionally, isolation of bacteria capable to grow using MPB or BPB as carbon source was also carry out. Laboratory tests demonstrated the ability of these bacteria to biodegrade MPB and BPB from culture media in more than 95% in some cases. These strains showed high ability to biodegrade the compounds. Ten isolates, most of them related to Gram positive bacteria of the genus Bacillus , were identified by 16S rRNA gene sequencing. The study of the enzymatic activities of the isolates revealed both esterase (C4) and esterase-lipase activities. • Removal of methyl and butylparabens was investigated in soil and amended soil. • Bacteria able to biodegrade methyl and butylparabens were isolated from soils. • Most isolates using parabens as carbon source were related to Bacillus. • All bacterial isolates displayed esterase (C4) and esterase lipase enzyme activities. [ABSTRACT FROM AUTHOR]

Converting straw to biochar (BC) followed by successive application to soil has been increasingly suggested as a multi-win approach for soil fertility improvement, carbon (C) sequestration and efficient disposal of straw residues in intensive cropping agroecosystems. However, different soil types response differently in terms of crop growth and non-CO 2 greenhouse gas (GHG) emissions after BC application. Furthermore, few studies have comprehensively evaluated the net global warming potential (GWP) and net ecosystem economic benefits (NEEB) after long-term BC incorporation across representative soil types in China. A five-year outdoor column experiment was conducted using three rice-wheat rotated paddy soils and three millet-wheat rotated upland soils developed from different parent materials. Rice straw BC application rates of 0, 2.25 and 11.3 Mg ha−1 were used in each crop season with identical doses of NPK fertilizers. Compared with the no BC controls, BC significantly boosted crop growth, enhanced C sequestration, and decreased cumulative N 2 O and CH 4 emissions in all six soils over five rotation cycles. The response of the upland soils to BC was better in terms of crop growth and N 2 O mitigation, whereas the soil organic carbon (SOC) increment and CH 4 mitigation were less effective compared with the paddy soils. Net GWP decreased 0.6–19 fold after BC application; however, given the low trade price of CO 2 (0.21 × 103 CNY Mg−1), only a small contribution was made in terms of C costs to the NEEB. The BC-induced NEEB was mainly dependent on grain yield gains and BC costs. These findings highlight that widespread adoption of successive straw BC application to farmland requires an increase in crop yield and substantial lowering of the BC cost regardless of the soil type. From the standpoints of agronomics, environment and economics, acid upland soil shows most potential in terms of BC application. Image 1 • The viability of successive biochar applications to six soils over ten crop seasons was evaluated. • Biochar boosted crop growth, slowed GHG emissions and locked away C from six soil-crop systems. • The sustainability of straw biochar used depends on grain yield gains and biochar costs. • Biochar used in acid and upland soils were more potential compared to alkaline and paddy soils. [ABSTRACT FROM AUTHOR]

Due to the non-degradable nature of heavy metals (HMs), the industrial effluent, whether treated or untreated, carrying HMs, eventually end up into the water bodies, soil, and sediments. Numerous countermeasures were applied, but the use of ornamental plants for the stress mitigation associated with HMs on the environment is a neglected research domain. The composition of wastewater influences bioremediation strategies. As the wastewater is contaminated with multiple HMs, many lab studies, with the plants, failed in the industrial field. This work focuses on the potential of Nicotiana alata L. and Petunia hydrida L. against multiple HMs contaminated synthetic wastewater. To improve plant tolerance, soil amendments (biochar, compost, and moss, each at 5% v/v in soil) were used, individually and in combination. After 6 weeks of the exposure, plant physiological, biochemical and enzymatic parameters, as well as the distribution of HMs, (Cd, Cr, Cu, Pb, Mn, Ni, and Zn) in the plant (flower, leaves, root, and shoot) and soil, were measured. The HMs uptake positivity influenced the malondialdehyde content, hydrogen peroxide content and electrolyte leakage, while negatively to photosynthetic pigments, and resulted in increased catalase, guaiacol peroxidase, glutathione s-transferase, ascorbate peroxidase, while reduced superoxide dismutase activity. It was found that all amendments improved the plant growth by metal stabilization, and best results were obtained with the combined application of biochar + compost + moss. So, HMs stabilization can be achieved by growing ornamental plants, like Nicotiana alata L. and Petunia hydrida L. along with soil amendments. Image 1 • Heavy metal (HM) contents were quantified in selected industrial effluents. • Ornamental plants were tested against multi-HMs containing synthetic wastewater. • Biochar, compost, and peat moss reduced plant stress and metal mobility. • N. alata L. and P. hydrida L. were suitable for treatment of HMs in wastewater. [ABSTRACT FROM AUTHOR]

Rehabilitation of degraded drylands is challenged by environmental and anthropogenic constraints, such as limited availability of locally-sourced topsoil and poor quality alternative soil substrates. Current rehabilitation practices, at times, utilise inorganic soil amendments to improve the physicochemical and biological characteristics of reconstructed soil profiles. These approaches may be appropriate for dryland rehabilitation, but there is limited research available regarding the benefits of using these amendments. Here, we present a study in the Pilbara region of Western Australia, an arid landscape subject to intensive mining that currently uses inorganic soil amendments (gypsum and urea) in post-mining rehabilitation. The aim of this study was to assess the effectiveness of these amendments to (1) promote seed germination, seedling emergence and seedling growth across five plant species and, (2) re-instate soil quality in mine waste substrates. A series of glasshouse experiments assessed eight application combinations of these amendments in two alternative substrates and compared these to unamended substrates and topsoil. Soil amendments had a limited influence on seed germination, were detrimental to seedling emergence and resulted in increased seedling mortality. Mortality in the waste ranged from 2 to 61% but increased to 7–92% in amended waste. Seedling growth improved with high doses of amendments in waste, with a 1.3–5.6-fold increase across all plant species. Soil quality was relatively unaffected by amendments with soil nitrogen ranging from 0.01 to 0.08%, organic carbon from 0.01 to 0.12% and soil microbial activity from 2.3 to 2.4 ppm-CO 2 in the amended and unamended waste. The use of soil amendments in mine rehabilitation requires consideration of the trade-off between initial reductions in seedling recruitment and enhanced seedling development at later stages. Future rehabilitation should consider the timing of amendment application to avoid detrimental impacts on seedling recruitment and maximise the benefits to seedling growth. Image 10921 • Inorganic amendments were added to mine soils to assess plant and soil responses. • The percentage of germination and emergence of plants was highest in topsoil. • Plant responses to amendments varied across species and through plant life cycles. • Soil responses were similar across all mine soil treatments. • This study helps understand how agriculture practices can benefit arid restoration. [ABSTRACT FROM AUTHOR]

High N-fertilizer applications to conventional vegetable production systems are associated with substantial emissions of NH 3 , a key substance that triggers haze pollution and ecosystem eutrophication and thus, causing considerable damage to human and ecosystem health. While N fertilization effects on NH 3 volatilization from cereal crops have been relatively well studied, little is known about the magnitude and yield-scaled emissions of NH 3 from vegetable systems. Here we report on a 2-year field study investigating the effect of various types and rates of fertilizer application on NH 3 emissions and crop yields for a pepper-lettuce-cabbage rotation system in southwest China. Our results show that both NH 3 emissions and direct emission factors of applied N varied largely across seasons over the 2-year period, highlighting the importance of measurements spanning entire cropping years. Across all treatments varying from solely applying urea fertilizers to only using organic manures, annual NH 3 emissions ranged from 0.64 to 92.4 kg N ha−1 yr−1 (or 0.07–6.84 g N kg−1 dry matter), equivalent to 0.05–5.99% of the applied N. At annual scale, NH 3 emissions correlated positively with soil δ15N values, indicating that soil δ15N may be used as an indicator for NH 3 losses. NH 3 emissions from treatments fertilized partially or fully with manure were significantly lower compared with the urea fertilized treatment, while vegetable yields remained unaffected. Moreover, full substitution of urea by manure as compared to the partial substitution further reduced the yield-scaled annual NH 3 emissions by 79.0–92.4%. Across all vegetable seasons, there is a significant negative relationship between yield-scaled NH 3 emissions and crop N use efficiency. Overall, our results suggest that substituting urea by manure and reducing total N inputs by 30–50% allows to reduce NH 3 emissions without jeopardizing yields. Such a change in management provides a feasible option to achieve environmental sustainability and food security in conventional vegetable systems. [Display omitted] • Annual NH 3 emissions markedly varied with N fertilizer types and application rates. • Annual emission factors of NH 3 were with 0.05–5.99%, greatly lower as IPCC defaults. • Increases in soil δ15N values were positively correlated with annual NH 3 emissions. • Manure amendment-induced changes in NH 3 correlated negatively with organic N rates. • Fully substituting urea with manure resulted in lowest yield-scaled NH 3 emissions. [ABSTRACT FROM AUTHOR]

This paper aimed to highlight the succession of biochar addition for soil amendment and contaminants remediation during composting process. Biochar incorporated into the compost mixture promotes composting performance and enhances contaminants reduction. Co-composting with biochar for soil biota has been demonstrated via modified soil biological community abundance and diversity. On the other hand, adverse alterations to soil properties were noted, which had a negative impact on the communication of microbe-to-plant interactions within the rhizosphere. As a result, these changes influenced the competition between soilborne pathogens and beneficial soil microorganisms. Co-composting with biochar promoted the heavy metals (HMs) remediation efficiency in contaminated soils by around 66–95%. Notably, applying biochar during composting could improve nutrient retention and mitigate leaching. The adsorption of nutrients such as nitrogen and phosphorus compounds by biochar can be applied to manage environmental contamination and presents an excellent opportunity to enhance soil quality. Additionally, the various specific functional groups and large specific surface areas of biochar allow for excellent adsorption of persistent pollutants (e.g., pesticides, polychlorinated biphenyls (PCBs)) and emerging organic pollutants, such as microplastic, phthalate acid esters (PAEs) during co-composting. Finally, future perspectives, research gaps, and recommendations for further studies are highlighted, and potential opportunities are discussed. [Display omitted] • Biochar significantly enhanced soil amendment and remediation during co-composting. • Microbial community plays an important role in pollutants degradation during co-composting with biochar. • Co-composting with biochar can immobilize and reduce the bioavailable of heavy metals. • Persistent and emerging organic pollutants were degraded during co-composting with biochar. [ABSTRACT FROM AUTHOR]

Rice agriculture feeds over half the world's population, and paddy soils impact the carbon cycle through soil organic carbon (SOC) preservation and production of carbon dioxide (CO 2) and methane (CH 4), which are greenhouse gases (GHG). Rice husk is a nutrient-rich, underutilized byproduct of rice milling that is sometimes pyrolyzed or combusted. It is unresolved how the incorporation of these residues affects C dynamics in paddy soil. In this study, we sought to determine how untreated (Husk), low-temperature pyrolyzed (Biochar), and combusted (CharSil) husk amendments affect SOC levels, GHG emissions, and dissolved organic matter (DOM) chemistry. We amended Ultisol paddy mesocosms and collected SOC and GHG data for three years of rice grown under alternate wetting and drying (AWD) conditions. We also performed a greenhouse pot study that included water management treatments of nonflooded, AWD, and flooded. Husk, Biochar, and CharSil amendments and flooding generally increased SOC storage and CH 4 emissions, while nonflooded conditions increased N 2 O emissions and nonflooded and CharSil treatments increased CO 2 emissions. All amendments stored ∼0.15 kg C m−2 y−1 more SOC than CH 4 emissions (as CO 2 equivalents), but the combustion of husk to produce CharSil resulted in the net release of CO 2 which negates any SOC storage. UV–visible absorption/fluorescence spectroscopy from the pot study suggests that nonflooded treatment decreased DOM aromaticity and molecular size. Our data show that flooding and amendment of Husk and Biochar maximized C storage in the highly weathered rice paddy soil under study despite Husk increasing CH 4 emissions. Water management affected dissolved organic matter chemistry more strongly than amendments, but this requires further investigation. Return of rice husk that is untreated or pyrolyzed at low temperature shows promise to close nutrient loops and preserve SOC in rice paddy soils. [Display omitted] • Rice husk and husk biochar amendments were assessed for effects on soil C. • Husk amendments store a net 0.15 kg C m−2 y−1 despite increased CH 4 emissions. • High-temperature combustion of rice husk emits more C as CO 2 than it stores as SOC. • Water management affects DOM chemistry more than husk amendments. • Flooding paddy soil produces DOM that is more aromatic and larger. [ABSTRACT FROM AUTHOR]

Straw retention (SR) and organic fertilizer (OF) application contribute to improve soil quality, but it is unclear how the soil microbial assemblage under organic amendments mediate soil biochemical metabolism pathways to perform it. This study collected soil samples from wheat field under different application of fertilizer (chemical fertilizer, as control; SR, and OF) in North China Plain, and systematically investigated the interlinkages among microbe assemblages, metabolites, and physicochemical properties. Results showed that the soil organic carbon (SOC) and permanganate oxidizable organic carbon (LOC) in soil samples followed the trend as OF > SR > control, and the activity of C-acquiring enzymes presented significantly positive correlation with SOC and LOC. In organic amendments, bacteria and fungi community were respectively dominated by deterministic and stochastic processes, while OF exerted more selective pressure on soil microbe. Compared with SR, OF had greater potential to boost the microbial community robustness through increasing the natural connectivity and stimulating fungal taxa activities in inter-kingdom microbial networks. Altogether 67 soil metabolites were significantly affected by organic amendments, most of them belonged to benzenoids (Ben), lipids and lipid-like molecules (LL), and organic acids and derivatives (OA). These metabolites were mainly derived from lipid and amino acid metabolism pathways. A list of keystone genera such as stachybotrys and phytohabitans were identified as important to soil metabolites, SOC, and C-acquiring enzyme activity. Structural equation modeling showed that soil quality properties were closely associated with LL, OA, and PP drove by microbial community assembly and keystone genera. Overall, these findings suggested that straw and organic fertilizer might drive keystone genera dominated by determinism to mediate soil lipid and amino acid metabolism for improving soil quality, which provided new insights into understanding the microbial-mediated biological process in amending soil quality. [Display omitted] • Organic fertilizer had more potential to change microbiota assembly than straw. • The microbial network robustness in OF was greater than that in SR. • The assembly of microbiota motivated keystone taxa to mediate soil metabolism. • Amending soil quality mainly by regulating soil lipids and amino acids metabolism. [ABSTRACT FROM AUTHOR]

Biochar can directly hold cations in soil because of the negative charge that exists on its surfaces. Besides, improving soil cation exchange capacity, the negative charges on biochar surfaces can buffer acid soil by protonation and deprotonation mechanisms. Moreover, biochar ameliorates soil acidity due to the presence of oxides, carbonates, and hydroxides of its basic cations (Ca, Na, K, and Mg). Both biochar surface functional group and basic cation concentrations can be altered by modification with chemical agents which can affect its soil pH buffering capacity. However, the impact of modified biochar application on soil pH buffering capacity is still scanty. This study investigated the pH buffering capacity of acidic soil amended with three P-enriched modified Douglas fir biochars and compared this buffering capacity to amendment with untreated Douglas fir biochar. These three P-enriched biochars, were prepared by treating Douglas fir biochar (DFB), respectively, with: 1) anhydrous calcium chloride (CaCl 2) and potassium phosphate monobasic (KH 2 PO 4), 2) calcium carbonate (CaCO 3) and diammonium phosphate {(NH 4) 2 HPO 4 } and 3) an aqueous solution of magnesium sulfate (MgSO 4), potassium hydroxide (KOH) and potassium phosphate monobasic (KH 2 PO 4). The three P-enriched biochars were designated as CCPP, CAPP and MSPP, respectively. The soil pH buffering abilities were largely dependent on the added biochar's alkalinity and ash contents. The residual soil CEC was highly correlated (r ≥ 0.9), with the soil buffering capacity. Both alkalinity and pH buffering capacity improved following the order CCAP > CCPP > MSPP > DFB, while residual soil CEC followed the order CAPP > MSPP > CCPP > DFB. The pH buffering capacity of the soil after amendments with 10% CAPP, CCPP MSPP and BFB rose by 84.8, 58.3, 3.0 and 2.5%, respectively. Whereas MSPP had higher concentrations of K+ and Mg2+, greater concentrations of Ca2+ were present in CCAP and CCPP than MSPP. So, Ca2+ concentrations in biochar exerts a greater influence on alkalinity and buffering capacity than Mg2+ and K+ because of 1) its smaller effective hydration radius and larger charge density. 2) calcium hydroxide has a greater water solubility than magnesium hydroxide providing more available base. Since pH buffering capacity depends on cation exchange sites, soil additives containing Ca2+ are prone to create greater impacts than Mg2+ and K+ additives. [Display omitted] • P enriched biochar provided both liming and fertilization benefits. • Soil pH buffering abilities depended on biochar's alkalinity and ash contents. • Soil pH buffering capacity correlated (r ≥ 0.9) with the soil CEC. • Ca2+ exerts greater impacts on alkalinity and buffering capacity than Mg2+ and K+. [ABSTRACT FROM AUTHOR]

Examples of successful mine closure and acceptable regional transitioning of mining areas are scarce. The recent changes to the environmental, social and governance (ESG) obligations of mining companies should help to ensure that water and land resources as well as post-mining employment opportunities are considered as a part of mine closure. Integrating microalgae production into mine closure plans is a potential opportunity for mining companies to improve many ESG outcomes. Mine sites with sufficient suitable land and water resources in high solar radiation geographies may be able to economically grow microalgae to capture atmospheric CO 2 , re-purpose saline mine waters, treat acidic and near-neutral pH metalliferous waters as well as produce soil ameliorants (biofertiliser, biostimulants and/or biochar) to improve mine rehabilitation outcomes. Microalgae production facilities may also provide an alternative industry and employment opportunities to help transition regional mining towns that have become reliant on mining activities. The potential economic, environmental and social benefits of using mine-influenced water for microalgae production may offer an opportunity to successfully close and transition some mining landscapes. [Display omitted] • Microalgae production to improve ESG outcomes during mine closure. • Using brackish mine water for carbon capture and storage/utilisation. • Acidic, metalliferous and sulfate treatment by microalgae. • Converting microalgae to a biofertiliser or biochar for mine rehabilitation. • Post-mining employment opportunities in regional mining towns. [ABSTRACT FROM AUTHOR]

Here, we assess the effects of gypsum and local organic waste as amendments to non-weathered, filter-pressed bauxite residue (BR) to improve its properties and support plant growth. In addition, we monitored the leachate quality of the amended BR under progressive leaching that simulated precipitation conditions in Northern Brazil. Free-draining column tests consisting of BR amended with gypsum and organic waste, at 5% and 10% w/w, respectively, were leached for 8 weeks to assess the effects on the chemical composition of BR and the leachates. Adding gypsum to BR reduced the exchangeable sodium (Na) percentage (ESP) from approximately 79%–48%, whereas adding only organic waste had smaller effects on ESP (from ∼79% to ∼ 70%). The mean leachate pH ranged from 8.7 to 9.4 for the gypsum, and organic waste amended BR, while this was 10.3 in the leachate of the unamended BR. The treatments had similar trends of electrical conductivity throughout the experiments and were below 2 dS/cm after 8 weeks, when ∼1.700 mm simulated precipitation had leached. Aluminium (Al), Arsenic (As), and Vanadium (V) concentrations in leachates of BR with gypsum, either alone or in combination with organic waste, were significantly lowered than in leachate of non-amended BR. By contrast, metal concentrations increased if organic waste was added to BR. We conclude that amending BR with gypsum, in combination with organic waste, significantly improves the chemical properties of the solid phase and achieved rehabilitation goals for SAR and EC of the leachates after 8 weeks of leaching. However, despite high leaching rates, rehabilitation goals for pH and ESP were not achieved with gypsum either alone or combined with organic waste. [Display omitted] • Bauxite residue has physicochemical properties which are not suitable for plant growth. • Different remediation strategies were assessed in leaching column experiments. • Gypsum and organic waste promoted suitable physicochemical conditions for plant growth. • Al, As and V concentrations decreased substantially due to gypsum amendment. • Rehabilitation goals were hardly achieved in non-weathered bauxite residue. [ABSTRACT FROM AUTHOR]

Abstract The use of digestate as amendment for agricultural soils has already been proposed as an alternative to mineral fertilizers or undigested organic matter. However, little information is available concerning the effect of digestate atmospheric exposure on trace elements speciation and, consequently, on their mobility and bio-accessibility when digestate is stored in open tanks or handled before land spreading. In this study, we investigated at laboratory-scale the effect of digestate aeration on the distribution of Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se and W using the diffusive gradients in thin films technique (DGT)-based fractionation. For this purpose, experiments were performed to assess the variation in distribution between the labile, soluble and particulate fractions over time in digested sewage sludge during passive and forced aeration. Results showed that aeration promoted a dissolution of Al, As, Co, Cr, Cu, Fe, Mn, Mo and Pb, suggesting a possible increase in their mobility that may likely occur during storage in open tanks or handling before land spreading. Labile elements' fraction increased only during forced aeration (except for Fe and Mn), suggesting that their short-term bio-accessibility can increase only after significant aeration as the one assumed to occur when land spreading takes place. Graphical abstract Image 1 Highlights • Distribution trend of 14 trace elements was studied in digestate under air exposure. • DGT was used as trace elements fractionation tool to assess the labile fraction. • Aeration promoted dissolution of Al, As, Co, Cr, Cu, Fe, Mn, Mo and Pb. • Forced aeration promoted an increase of labile Al, As, Co, Mo, Ni, Sb, Se and W. • Al, As, Co, Cr, Cu, Fe, Mn and Pb were mainly present as particulate despite aeration. [ABSTRACT FROM AUTHOR]

Abstract Hydrothermal carbonization is a promising approach of biosolids management and its utilization as a soil amendment. This study evaluated the physical and chemical properties of hydrothermally converted biosolids (Sewchar) and its effect as a potential soil amendment on the growth of rice, beans, and radish. The germination experiment was conducted in a greenhouse in a randomized design using five Sewchar doses (0, 10, 20, 40 and 60 Mg ha−1). The results showed that hydrothermal carbonization influences the physicochemical properties of the biosolids, such as promoting pore structure and trace elements below the threshold values for use in agriculture. The spectroscopic techniques demonstrated higher presence of oxygen-containing functional groups (e.g., C O/O H) on surfaces of Sewchar than that of biosolids. The Sewchar doses of 10 Mg ha−1 and 60 Mg ha−1 yielded the highest dry biomass for beans and rice respectively. Increasing Sewchar doses negatively correlated with radish dry biomass, as indicated by linear regression equation fitting (p < 0.05). Thus, biomass responses to Sewchar application into the soil varied with Sewchar dose and type of plant. For a proper environmental management, a survey was conducted to assess farmers' perception and acceptance of Sewchar as a soil amendment. The survey revealed that younger farmers who had higher education qualifications were more prone to use Sewchar as soil amendment. Additionally, farmers who would not use Sewchar as soil amendment attributed the highest level of importance to economic criteria, such as fertilizer and freight prices. In the future, studies on a longer term under field conditions should be performed to elucidate the interactions between Sewchar and soil properties on plant growth and to ensure the safe use of Sewchar as a soil amendment. Highlights • Hydrothermal carbonization promoted pore structure development of biosolids. • Sewchar had higher O-containing functional groups and stability than biosolids. • Plant biomass response varied with Sewchar doses and type of plant. • Younger farmers are more prone to use Sewchar as a soil amendment. • Economic criteria were the most important for not using Sewchar as soil amendment. [ABSTRACT FROM AUTHOR]

Abstract Recent studies revealed the benefits of applying biochar in landfill final cover soil, such as adsorbing odorous compounds and promoting microbial methane oxidation. Most of these processes are related to the soil bacterial communities. However, the effects of biochar application on the overall bacterial community in newly established landfill cover soil are not yet understood, especially in field condition. The objective of the present field study is to investigate the effects of biochar on the diversity of soil bacterial community 3 months after incubation (short–term). Landfill final cover topsoil (0.6 m) was amended with 0 (control), 5, and 10% (w/w) of biochar derived from peanut–shell and wheat straw. Soil bacterial communities were analysed using the 16S rRNA–based T–RFLP approach. Biochar application significantly (p < 0.05) increased the diversity of soil bacterial communities. The Shannon diversity index of bacterial communities in soil amended with 5 and 10% of biochar was increased from 3.34 to 3.85 and 3.92, respectively. There were four bacterial phyla recorded found at both control and amended soils, namely Actinobacteria , Bacteroidetes , Firmicutes , and Proteobacteria. In addition, Gemmatimonadetes was found only in soil amended with 10% biochar. The interactions between soil bacterial communities and measured soil parameters including moisture content, electrical conductivity, total organic matter, total nitrogen and total phosphorus were found to be statistically non-significant (p > 0.05), according to the canonical correspondence analysis (CCA). This may be due to the highly heterogeneous nature of landfill soil. Results from this study revealed that short-term biochar application already altered the soil physicochemical properties and increased the diversity of soil bacterial communities. Highlights • The effects of biochar on bacterial community in landfill topsoil were studied. • Biochar application increased bacterial diversity three months after application. • The most abundant bacterial phylum was Firmicutes. • Gemmatimonadetes was only recorded in topsoil amended with 10% biochar. [ABSTRACT FROM AUTHOR]

Abstract The use of organic amendments is important for the sustainability of organic farming, with implications for soil organic matter turnover, nutrient cycling and greenhouse gases (GHGs) emissions to the atmosphere. Here, we investigated how long-term citrus organic farming influenced carbon sequestration and GHG emissions under organic and conventional management. We assessed the effects of management systems on soil organic matter dynamics and GHG emissions, focusing on N 2 O direct emissions from fertilizers. Soil stable isotope C and N compositions (0–100 cm) were used as parameters to assess changes in soil organic matter dynamics, with native forest as the reference. After the conversion from forest to orange orchard, stocks of soil C increased approximately 40 Mg ha−1, whereas stocks were similar in the organic and conventional treatments. Enrichment of 13C through the entire soil profile showed that organic matter from fertilizer replaced the original soil C by at least 20%, considering that poultry was fed only with C4 plants. By contrast, organic farming increased soil N stocks and inorganic N. Nitrogen emission factors for inorganic and organic fertilizers were 1.47 and 3.14, respectively. Organic management increased soil GHG emissions, primarily N 2 O emissions. Carbon emissions either as CO 2 or CH 4 were greater at the mid-rows than those under the crop canopy. We conclude that organic management did not promote C sequestration after six years of management. Moreover, organic management increased N 2 O emissions, and the GHG balance was more negative for organic than that for conventional farming when the ratio between crop harvest and emissions was determined. Graphical abstract Image 1 Highlights • Forest was converted into conventional citrus orchard 42 years before the study. • Studied orchards have the same history up to the partial conversion to the organic management. • Organic farming increased N but not C soil stocks compared to conventional system. • Added C in the organic management replaced the original soil organic matter. • N-N 2 O emission factor was 2-fold higher in the organic system. [ABSTRACT FROM AUTHOR]

Abstract The indiscriminate use of pesticides due to modern agricultural practices has received special attention from the scientific community to address the persistence, recalcitrance and multi-faceted toxicity of several pesticides. Pesticides are hazardous/toxic and can accumulate easily into non-target organisms including humans and other life forms. Several studies have been performed to investigate the effect of biochar addition for pesticide remediation. This review provides a comprehensive information on biochar amendment for the remediation of persistent organic pollutants such as pesticides. The types of pesticides and their hazards to life forms are briefly introduced before detailing biochar production, its characteristics and applications. Biochar addition in pesticide polluted environment offers the following advantages: (a) increases the soil water holding capacity, (b) improves aeration conditions in soil, and (c) provides habitat for the growth of microorganisms, thereby facilitating microbial community for metabolic activities and pesticide degradation. This paper also provides an up-to-date review on remediation of pesticides using biochar, the knowledge gaps and the future research directions in this field to evaluate the effect of biochar addition on agricultural and environmental performances. Graphical abstract Image Highlights • Recent findings published on pesticides remediation using biochar have been narrated. • Feedstock and pyrolysis conditions play vital role in case of biochar properties. • Long-term impacts regarding biochar application for remediation of pesticide(s) is essential. • Detailed studies are required to fill existing knowledge gaps prior to engineering application. [ABSTRACT FROM AUTHOR]

Abstract Mine soils often contain metal(loid)s that may lead to serious environmental problems. Phytoremediation, consisting in covering the soil with specific plants with the possible addition of amendments, represents an interesting way of enhancing the quality of mine soils by retaining contaminants and reducing soil erosion. In order to study the effect of an assisted phytoremediation (with willow and ryegrass) on the properties of soil pore water (SPW), we investigated the impact of amendment with biochar (BC) combined with the planting of willow and ryegrass on the behavior of several metal(loid)s (Pb, Zn, Ba, As, and Cd) in a mine soil. Data on the physicochemical parameters and concentrations of the different metal(loid)s in both SPW and in plant tissues of willow and ryegrass highlight the importance of BC for SPW properties in terms of reductions in soluble concentrations of Pb and Zn, although there was no effect on the behavior of As and Cd. BC also increased soluble concentrations of Ba, probably related to ion release by the BC. By improving major ions available in mine soil, BC improved the lifetime of plants and enhanced their growth. Plant development did not appear to significantly affect the physicochemical parameters of SPW. Willow and ryegrass growing on soil with BC incorporated Cd and Ba into their tissues. The influence of plants on the behavior of metal(loid)s was noticeable only for ryegrass growing in soil with 2% BC, where it modified the behavior of Pb and Ba. Highlights • Biochar leads to the reduction of Pb and Zn concentrations in soil pore water. • Biochar leads to the increase of Ba dissolved concentration in soil pore water. • Biochar does not influence the behavior of As and Cd. • Biochar improves physicochemical properties of soil pore water and nutrient status. • Ryegrass grown on soil with 2% biochar has slight influence on dynamics of Ba and Pb. [ABSTRACT FROM AUTHOR]

Abstract Problem soils are referred to as those with poor physical, chemical, and biological properties that inhibit or prevent plant growth. These poor properties may be a result of soil formation processes but are largely due to inappropriate farming practices or anthropogenic pollution. The world has lost a third of its arable land due to erosion and pollution in the past 40 years. Thus, there is an urgent need for improving and remediating problem soils. As a novel multifunctional carbon material, biochar has been widely used as a soil amendment for improving soil quality. Previous reviews have summarized the characteristics of biochar, the interactions with various soil contaminants, and the effects on soil quality, soil productivity, and carbon sequestration. Relatively limited attention has been focused on the effects of biochar amendment on plant growth in problem soils. As a result, a comprehensive review of literature in the Web of Science was conducted with a focus on the effects of biochar amendment on plant growth in problems soils. The review is intended to present an overview about problem soils, biochars as functional materials for soil amendment, how amended biochars interact with soils, soil microbes, and plant roots in remediation of problem soil and improve plant growth. Additionally, existing knowledge gaps and future directions are discussed. Information gathered from this review suggests that biochar amendment is a viable way of improving the quality of problem soils and enhancing crop production. It is anticipated that further research on biochar amendment will increase our understanding on the interactions of biochar with components of problem soils, speed up our effort on soil remediation, and improve crop production in problem soils. Highlights • Improving and remediating problem soils are in an urgent need. • Effects of biochar amendment on plant growth in problem soils are reviewed. • Key factors influence the biochar amendment to plant growth in problem soils are summarized. • Biochar amendment is a viable way of improving the quality of problem soils. [ABSTRACT FROM AUTHOR]

Abstract Water and organic amendments are the two most important factors that control methane (CH 4) emissions from rice fields, the combined effect of which on CH 4 emissions has been rarely studied. Thus, a field experiment in a split-plot design was conducted to investigate the combined effect of straw and water management on CH 4 emissions. Main plots had water treatments: continuous flooding (CF), flooding – midseason drying – flooding (FDF), and flooding for transplanting – rainfed (RF); and subplots had straw treatments: straw incorporated into soil (SI), straw mulching (SM), and without straw. Results showed that the presence of water layer led to substantial increase in CH 4 emissions which were enhanced by straw application. Cumulative CH 4 emissions were influenced by water, straw, and their interactions significantly (P < 0.05). The cumulative CH 4 emissions were 505.3, 241.2, and 56.5 kg ha−1 for CF, FDF, and RF, respectively. By contrast, SI under CF, FDF, and RF increased CH 4 emissions by 265.4, 271.4, and 175.6 kg ha−1, respectively. And SM under CF, FDF, and RF increased CH 4 emissions by 213.3, 112.8, and 14.6 kg ha−1, respectively. The results indicated that SM resulted in less CH 4 emissions compared with SI, especially in plots frequently with absence of water layer. Besides, SM had a potential to increase rice yield in rice paddies that had a lack of water. Therefore, in-season straw application should be avoided in lowland rice paddies, and straw mulching is practical in rice paddies lack of water. Highlights • Cumulative CH 4 emissions were influenced by water, straw, and their interactions. • Straw mulching resulted in less CH 4 emissions compared with straw incorporation. • In-season straw application should be avoided especially in lowland rice paddies. • Straw mulching is practical in rice paddies that have a lack of water. [ABSTRACT FROM AUTHOR]

Abstract A 32-week leaching column study was carried out in the greenhouse to investigate the effects of incorporation of gypsum, cattle manure, biosolids, gypsum plus cattle manure and gypsum plus biosolids into the topsoil layer (0–10 cm) on growth of Rhodes grass, and on root distribution and chemical and microbial properties in the topsoil and subsoil (10–30 cm) layers of seawater neutralized bauxite residues. The columns were leached for a period of 8 weeks prior to sowing Rhodes grass and during that time the bulk of the salts accumulated during seawater neutralization were leached out. The main cation leached was Na+ and the main balancing anions were Cl− and SO 4 2−. During this period the pH of leachates rose from 7 to 8 up to 9–10. At the end of the study, exchangeable Na and pH were lowered in the surface horizon by all treatments with a combination of gypsum plus organic amendments having the greatest effect. The latter treatments also caused a significant decrease in pH, extractable Al and exchangeable Na in the subsoil. Rhodes grass dry matter production followed the order Control < gypsum < cattle manure = gypsum plus cattle manure < biosolids = gypsum plus biosolids. Growth of roots into the subsoil layer was inhibited in the Control and gypsum treatments but when organic amendments were applied, 50% or more of root dry matter was recovered in the subsoil layer. It was concluded that incorporating a combination of gypsum and organic matter into the surface soil is an effective strategy for revegetation of bauxite residue. Highlights • The bulk of accumulated salts were leached over the first 5 leaching events. • The main cation leached was Na+ and the main balancing anions were Cl− and SO 4 2-. • Gypsum plus organic manures decreased pH, extractable Na and Al in the topsoil and subsoil layers. • Root growth into the subsoil layer was greatly promoted by addition of organic manures. • Shoot yields were greater for additions of cattle manure and biosolids than gypsum alone. [ABSTRACT FROM AUTHOR]

Abstract Current agriculture faces multiple challenges due to rapid increases in food demand and environmental concerns. Recently, biochar application in agricultural soils has attracted a good deal of attention. According to literature findings, biochar has proven to play various beneficial roles with respect to the enhancement of crop yield as a fertilizer and soil quality as a soil conditioner. It can further be used to remediate soil pollution as an adsorbent, while supporting the mitigation of greenhouse gases (GHGs) through the expansion of the soil carbon pool. The efficacy of biochar application on agricultural environments is found to be controlled by various factors such as pyrolysis temperature, feed stock, soil type, and biotic interactions. The combined effects of these factors may thus exert a decisive control on the overall outcome. Furthermore, the biochar application can also be proven to be detrimental in some scenarios. This review evaluates both the potential benefits and limitations of biochar application in agriculture soils. Highlights • Biochar-amended soils have promise in agro-environments due to the unique physiochemical characteristics of biochar. • Biochar has been proven to improve the yield, nutrition and management of disease and stress in plants. • Addition of biochar to soil can decrease emissions of GHGs (CO 2 and CH 4) from agriculture. • Potential limitations of biochar in agricultural soils must be taken into consideration prior its utilization. [ABSTRACT FROM AUTHOR]

The addition of organic residues to soil to increase its organic matter content is considered as a viable option for sustainable food production in soils sensitive to degradation and erosion. However, the recycling of these organic residues in agricultural soils needs to be previously appraised because they can modify the behaviour of pesticides when they are simultaneously applied in agricultural practices. This study evaluated the changes in the mobility and persistence of two herbicides, triasulfuron and prosulfocarb, after two repeated applications in field experimental plots in an unamended soil and one amended with green compost (GC) for seven months. Different factors were studied: i) soil without amendment (S), ii) soil amended with two doses of GC (∼12 t C ha −1 , S + GC1 and 40 t C ha −1 , S + GC2), and iii) soils unamended and amended with different irrigation conditions: non-irrigated and with additional irrigation (2.8 mm per week). After the first application of herbicides, the results initially indicated no significant effects of soil treatments or irrigation conditions for triasulfuron mobility in agreement with the residual concentrations in the soil profile. The effect of irrigation was noted after one month of herbicide application and the effect of the soil treatment was significant after two months because the persistence of triasulfuron in S + GC2 was maintained until 50% of the applied amount. For prosulfocarb, the influence of soil amendment was significant for the initial persistence of the herbicide in S + GC2, higher than in S or S + GC1, in agreement with its adsorption constants for this soil. However, dissipation or leaching of the herbicide over time was not inhibited in this soil. After the repeated application of herbicides, the influence of the treatment of soils and/or irrigation was significant for the leaching and dissipation of both herbicides. The initial dissipation/degradation or leaching of herbicides was higher than after the first application, although persistence was maintained after five months of application in amended soils for triasulfuron and in unamended and amended soils for prosulfocarb. The results confirm that high doses of GC increased the persistence of both herbicides. This practice may offer the possibility of applying a tailored dose of GC to soil for striking a balance between residual concentrations and the soil agronomic effect. [ABSTRACT FROM AUTHOR]

Certain agricultural practices, such as the repeated application of herbicides or organic amendments to soil, can influence herbicide dissipation. This research has studied the effects of two repeated applications of mesotrione, pethoxamid, and triasulfuron on their dissipation rates in unamended soil (S) and soil amended with green compost (S+GC) or sewage sludge (S+SS). The dissipation experiment has also included an evaluation of the adsorption of the three herbicides by soils and of changes in soil dehydrogenase activity (DHA). The adsorption of the three herbicides by amended soils (Kf range 0.83–2.98) was higher than by unamended soil (Kf range 0.20–0.64). The adsorption coefficients (Kd) of mesotrione and triasulfuron were higher for S+SS, while that of pethoxamid was higher for S+GC, but no relationship between values for the time to 50% degradation (DT 50 ) and adsorption coefficients could be determined. The repeated application of mesotrione decreased its dissipation rate in unamended soil (DT 50 increased from 4.75 to 8.15 days) and amended soils (DT 50 increased from 11.7 to 28.2 days in S+GC and from 17.7 to 37.9 in S+SS), whereas the repeated application of pethoxamid increased its dissipation rate in all the treatments, and the rate for triasulfuron increased only in amended soils. The highest DT 50 values for pethoxamid (12.3 days) and triasulfuron (57.1 days) were in S+GC, and the lowest in S+SS (8.35 and 24.7 days). Soil DHA was stimulated by the presence of GC in the soil and by the first application of mesotrione. The second application of mesotrione and pethoxamid positively affected soil DHA, but this did not occur for triasulfuron. The repeated applications of herbicides and soil organic amendments have different effects on herbicide dissipation, adsorption, and soil DHA, and they should be taken into account when assessing soil quality and other potential environmental implications of pesticide use. [ABSTRACT FROM AUTHOR]

Nanotechnology is increasingly being used to remediate polluted soil and water. However, few studies are available assessing the potential of nanoparticles to bind surface particles, decrease erosion, and minimize the loading of water pollutants from agricultural surface discharge. To investigate this potential, we treated in situ field plots with two practical surface application levels of anionic polyacrylamide (PAM only) with and without nanomagnetite (PAM-NM), examined soil physical properties, and evaluated the impact of this amendment on contaminant sorption and soil erosion control. Polyacrylamide and PAM-NM treatments resulted in 32.2 and 151.9 fold reductions in Mn 2+ , 1.8 and 2.7 fold for PO 4 3- -P, and 2.3 and 1.6 fold for NH 4 + -N, respectively, compared to the control. Thus, we found that the combination of PAM and NM, had an important inhibitory effect on NH 4 + -N and PO 4 3- -P transport from soil—pollutants which can contribute substantially to the eutrophication of surface water bodies. Additionally, since the treatment, especially at a high concentration of NM, was effective at reducing Mn 2+ concentrations in the runoff water, the combination of PAM and NM may be important for mitigating potential risks associated with Mn 2+ toxicity. Average sediment contents in the runoff monitored during the rainfall simulation were reduced by 3.6 and 4.2 fold for the low and high concentration PAM-NM treatments when compared to a control. This treatment was only slightly less effective than the PAM-only applications (4.9 and 5.9 fold, respectively). We report similar findings for turbidity of the runoff (2.6–3.3 fold for PAM only and 1.8–2.3 fold for PAM-NM) which was caused by the effects of both PAM and NM on the binding of surface particles corresponding to an increase in aggregate size and stability. Findings from this field-based study show that PAM-modified NM adsorbents can be used to both inhibit erosion and control contaminant transport. [ABSTRACT FROM AUTHOR]

Biochar can be an effective amendment for immobilizing heavy metals in contaminated soils but has variable effects depending on its chemical and physical properties and those of the treated soil. To investigate the range of biochar's effects on heavy metal accumulation in plants in responses to the variation of soil, biochar and plant, we carried out a meta-analysis of the literature that was published before March 2016. A total of 1298 independent observations were collected from 74 published papers. Results showed that across all studies, biochar addition to soils resulted in average decreases of 38, 39, 25 and 17%, respectively, in the accumulation of Cd, Pb, Cu and Zn in plant tissues. The effect of biochar on heavy metal concentrations in plants varied depending on soil properties, biochar type, plant species, and metal contaminants. The largest decreases in plant heavy metal concentrations occurred in coarse-textured soils amended with biochar. Biochar had a relatively small effect on plant tissue Pb concentrations, but a large effect on plant Cu concentrations when applied to alkaline soils. Plant uptake of Pb, Cu and Zn was less in soils with higher organic carbon contents. Manure-derived biochar was the most effective for reducing Cd and Pb concentrations in plants as compared to biochars derived from other feedstock. Biochar having a high pH and used at high application rates resulted in greater decreases in plant heavy metal uptake. The meta-analysis provides useful guidelines on the range of effects that can be anticipated for different biochar materials in different plant-soil systems. [ABSTRACT FROM AUTHOR]

Using batch-type experiments, chromium (Cr(VI)) and fluoride (F − ) sorption/desorption were studied in forest and vineyard soil samples, pyritic material, pine bark, oak ash, hemp waste and mussel shell, as well as on samples of forest and vineyard soil, and of pyritic material, individually treated with 48 t ha −1 of pine bark, oak ash, and mussel shell. Pine bark showed the highest Cr(VI) sorption (always > 97% of the concentration added) and low desorption (<1.5%). Pyritic material sorbed between 55 and 98%, and desorbed between 0.6 and 9%. Forest and vineyard soils, oak ash, mussel shell and hemp waste showed Cr(VI) sorption always < 32%, and desorption between 22 and 100%. Pine bark also showed the highest F − retention (sorption between 62 and 73%, desorption between 10 and 15%), followed by oak ash (sorption 60–69%, desorption 11–14%), forest soil (sorption 60–73%, desorption 19–36%), and pyritic material (sorption 60–67%, desorption 13–15%), whereas in vineyard sorption was 49–64%, and desorption 24–27%, and in hemp waste sorption was 26–36%, and desorption 41–59%. Sorption data showed better fitting to the Freundlich than to the Langmuir model, especially in the case of Cr(VI), indicating that multilayer sorption dominated. The addition of by-products to the forest and vineyard soils, and to the pyritic material, caused an overall increase in F − sorption, and decreased desorption. Furthermore, the pine bark amendment resulted in increases in Cr(VI) retention by both soils and the pyritic material. These results could be useful to favor the recycling of the by-products studied, aiding in the management of soils and degraded areas affected by Cr(VI) and F − pollution, and in the removal of both anions from polluted waters. [ABSTRACT FROM AUTHOR]

Nickel (Ni) contaminated soils pose a potential ecological risk to the environment, soil health, and quality of food produced on them. We hypothesized that application of miscanthus biochar (BC) and cationic zeolite (ZE) at various proportions into a Ni contaminated soil can efficiently immobilize Ni and reduce its bioavailability to sunflower ( Helianthus annuus L.) and maize ( Zea mays L.). An electroplating effluent contaminated soil was amended with BC and ZE, as sole treatments (2% w/w) and their combinations of various ratios (BC, ZE, BC25%ZE75%, BC50%ZE50% and BC75%ZE25%) for immobilization of Ni in the soil. Furthermore, the associated effects of these treatments on residual and DTPA-extractable Ni from the soil; concentrations of Ni in shoots, roots, and grain; growth, physiology, biochemistry and the antioxidant defence mechanisms of sunflower and maize were investigated. Results revealed that BC50%ZE50% treatment efficiently reduced DTPA-extractable Ni in the soil, Ni concentrations in shoots, roots, and grain, while improved selective parameters of both plants. Interestingly, the BC75%ZE25% treatment significantly improved the biomass, grain yield, physiology, biochemistry and antioxidant defense machinery, while decreased Ni oxidative stress in both sunflower and maize, compared to rest of the treatments. The results demonstrate that the BC50%ZE50% treatment can efficiently reduce Ni concentrations in the roots, shoots and grain of both sunflower and maize whereas, an improvement in biomass, grain yield, physiological, biochemical, and antioxidant defense machinery of both crops can only be achieved with the application of BC75%ZE25% treatment in a Ni contaminated soil. [ABSTRACT FROM AUTHOR]

The purpose of present study was to find out whether wood ash with a high pH value and neutralizing capacity reduces 137Cs uptake by forest plants many years after the radionuclide fallout. The effects of one-time point fertilisation with 137Cs-contaminated and uncontaminated wood ash alone or in combination with KCl on 137Cs transfer from soil to young leaves and green shoots of various dwarf shrubs and tree species were examined in a long-term fertilisation experiment (2012–2021) conducted in Bazar mixed forest, around 70 km from Chernobyl nuclear power plant. The results indicated minor effects of soil fertilisation, although there were differences between 137Cs uptake by species and years. Soil amendment with 137Cs-contaminated wood ash generally did not affect 137Cs uptake by young shoots and leaves of plants over the growing season in the first year and only slightly decreased T ag for 137Cs in the following years. The effect of a single application of 137Cs-uncontaminated wood ash on reducing 137Cs uptake by plants was generally negligible. Application of 137Cs-contaminated wood ash in combination with KCl reduced plant 137Cs uptake by about 45%, however, such reduction was only significant in some years for bilberry berries, young leaves and green shoots of lingonberry and alder buckthorn. Thus application of wood ash to 137Cs-contaminated forest soil many years after radionuclide fallout generally does not reduce 137Cs uptake by forest vegetation in a mixed forest ecosystem and this countermeasure should be applied with caution. [Display omitted] • Wood ash and KCl fertilisation don't result in consistent decrease of 137Cs uptake. • Effect of non-contaminated wood ash on 137Cs uptake was not detectable. • 137Cs-contaminated wood ash caused small or no response on 137Cs uptake. • 137Cs-contaminated wood ash + KCl decreases 137Cs uptake only marginally. • Fertilisation of forest soil with wood ash and KCl should be applied with cautions. [ABSTRACT FROM AUTHOR]

Land utilization of the biogas residue (BR) produced by anaerobic co-digestion of gentamicin mycelial residues (GMRs) and wheat straw is a promising method to achieve the deep recycling of GMRs. This study evaluated the feasibility and efficacy of application of using BR as a soil amendment by using a pot experiment. Results indicated that BR could improve the soil fertility better than commercial chicken manure fertilizer (CMF) in terms of the soil enzyme activities and nutrients supply. Random Forest (RF) model was applied to predict soil enzyme activities and identify key influencing factors. Combining the Random Forest (RF) model with the Three-dimensional Excitation–emission Matrix and Parallel Factor (3D-EEM-PARAFAC) analysis, revealing that humic-like substances provided by BR protected soil enzymes, thus improving soil fertility. Furthermore, gentamicin and antibiotic resistance genes (ARGs)/mobile genetic elements (MEGs) introduced by BR decreased greatly after cultivation, implying a low risk of antimicrobial resistance. This study suggested that reasonable application of BR could improve soil nutrients supply, soil enzyme activity and control antimicrobial resistance risk. [Display omitted] • BR increased the supply of soil nutrients and humic-acid substances. • BR performed better than CMF in the enhancement of soil enzyme activities. • RF model combined with EEM-PARAFAC was first applied in the cultivation process. • Microbial analysis indicated BR had more readily biodegradable matters than CMF. • Long cultivation cycle favored gentamicin degradation and ARGs attenuation. [ABSTRACT FROM AUTHOR]

Biochar, derived from unused biomass, is widely considered for its potential to deal with climate change problems. Global interest in biochar is attributed to its ability to sequester carbon in soil and to remediate aquatic environment from water pollution. As soil conditioner and/or adsorbent, biochar offers opportunity through a circular economy (CE) paradigm. While energy transition continues, progress toward low-emissions materials accelerates their advance towards net-zero emissions. However, none of existing works addresses CE-based biochar management to achieve carbon neutrality. To reflect its novelty, this work provides a critical overview of challenges and opportunities for biochar to promote CE and carbon neutrality. This article also offers seminal perspectives about strengthening biomass management through CE and resource recovery paradigms, while exploring how the unused biomass can promote net zero emissions in its applications. By consolidating scattered knowledge in the body of literature into one place, this work uncovers new research directions to close the loops by implementing the circularity of biomass resources in various fields. It is conclusive from a literature survey of 113 articles (2003–2023) that biomass conversion into biochar can promote net zero emissions and CE in the framework of the UN Sustainable Development Goals (SDGs). Depending on their physico-chemical properties, biochar can become a suitable feedstock for CE. Biochar application as soil enrichment offsets 12% of CO 2 emissions by land use annually. Adding biochar to soil can improve its health and agricultural productivity, while minimizing about 1/8 of CO 2 emissions. Biochar can also sequester CO 2 in the long-term and prevent the release of carbon back into the atmosphere after its decomposition. This practice could sequester 2.5 gigatons (Gt) of CO 2 annually. With the global biochar market reaching USD 368.85 million by 2028, this work facilitates biochar with its versatile characteristics to promote carbon neutrality and CE applications. [Display omitted] • 12% of CO 2 emissions by land use can be offset annually via biochar for soil enrichment. • By applying biochar for soil amendment, about 1/8 of CO 2 emissions can be minimized. • The production cost of biochar is 30% lower than that of activated carbon. • Global biochar market is projected to reach USD 368.85 million by 2028. • Biochar applications in different fields can sequester 2.5 gigaton of CO 2 annually. [ABSTRACT FROM AUTHOR]