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To investigate the effect of poly-γ-glutamic acid (γ-PGA) biopreparation on ameliorating coastal saline soil, three treatments were established: soil salt washed treatment (CK), soil salt washed with added γ-PGA (PGA), soil salt washed with added γ-PGA biopreparation (PGAB). This study determined the effects of γ-PGA on coastal saline soil by analyzing soil aggregate, soil evaporation, soil vertical water and salt distribution, and soil cation content, soil pH, soil nutrient content and soil microorganism quantity. Results showed that γ-PGA had an ameliorative effect on saline soil, with the PGAB treatment exhibiting the most pronounced ameliorative effect compared to CK. Adding PGAB reduced soil evaporation by 30.45 %, soil salt content by 27.91 %, meanwhile increasing plant height by 33.86 %, plant fresh weight by 98.54 %, soil aggregate diameter by 6.68 times, soil water content by 26.47 % (P < 0.05). Additionally, soil total nitrogen was increased by 50.0 % in PGAB treatment, and available nitrogen and phosphorus contents were increased by 1.68 times and 85.83 % (P < 0.05), respectively. Populations of soil-culturable bacteria and fungi of PGAB treatment increased by 65.96 % and 1.23 times, respectively (P < 0.05). After salt-washing process, adding PGAB improved soil physicochemical properties, which altered the ecological environment of rhizosphere soil and promoted plant growth. The results can provide a practical approach for ameliorating coastal saline soils.

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Theory questions the persistence of nonreciprocal interactions in which one plant has a positive net effect on a neighbor that, in return, has a negative net impact on its benefactor - a phenomenon known as antagonistic facilitation. We develop a spatially explicit consumer-resource model for belowground plant competition between ecosystem engineers, plants able to mine resources and make them available for any other plant in the community, and exploiters. We use the model to determine in what environmental conditions antagonistic facilitation via soil-resource engineering emerges as an optimal strategy. Antagonistic facilitation emerges in stressful environments where ecosystem engineers' self-benefits from mining resources outweigh the competition with opportunistic neighbors. Among all potential causes of stress considered in the model, the key environmental parameter driving changes in the interaction between plants is the proportion of the resource that becomes readily available for plant consumption in the absence of any mining activity. Our results align with theories of primary succession and the stress gradient hypothesis. However, we find that the total root biomass and its spatial allocation through the root system, often used to measure the sign of the interaction between plants, do not predict facilitation reliably.

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BACKGROUND: Poly-γ-glutamic acid (γ-PGA) is employed extensively in agriculture to enhance soil water retention; however, the underlying mechanism by which γ-PGA improves soil structure and soybean productivity in arid regions remains poorly understood. A micro-scale field experiment was conducted in the arid region of northwest China, employing five concentrations of γ-PGA to investigate its impacts on soybean yield, photosynthesis, and water-use efficiency, as well as soil aggregates and water distribution. The five levels of γ-PGA were 0 (CK), 10 (P1), 20 (P2), 40 (P3), and 80 kg ha-1 (P4). RESULTS: The results demonstrated that the application of γ-PGA significantly improved soybean yield, photosynthesis, and chlorophyll content. It resulted in a decrease in soil aggregate content with a maximum diameter of less than 0.053 mm and an increase in the stability of soil aggregates in the uppermost layer of the soil (0-30 cm). The application of γ-PGA significantly increased soil water content, particularly in the uppermost layer of the soil, and effectively reduced water consumption and improving water use efficiency in soybeans. Overall, the P3 treatment exhibited the most pronounced improvement of soybean yield, photosynthesis, water-use efficiency, as well as distribution of soil aggregates and water. The correlation matrix heatmap also revealed a strong correlation between improvement of soybean yield or photosynthesis at various γ-PGA application levels and the enhancement of soil stability or soil water content. CONCLUSION: The multivariate regression analysis revealed that an optimal application level of 46 kg ha-1 γ-PGA could enhance effectively both yield and water use efficiency of soybean in the arid region of northwest China. © 2024 Society of Chemical Industry.

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In recent years, the influx of business capital to rural areas, land transfer and adjustment in planting structure have led to the widespread of "non-grain production" of cultivated land in China, which threatens the "1.8 billion mu of arable land protection red line" as well as national food security. Both tillage layer stripped and unstripped are examples of "non-grain production" of cultivated land, which are detrimental to long-term food security because they might reduce soil fertility to varied degrees. In the former case, the original topsoil has been destroyed and the tillage layer is gone. In the latter, there may be impediments such as acidification and salinization. Domestic and international scholars have conducted extensive research on the improvement of degraded soils, including measures with guest soil and soil replacement, the reduction of soil barrier factors, biological fertilization and other measures. There are no systematic research results on the remediation of "non-grain production" of cultivated land. Using data from the National Statistical Yearbook data and literature analysis, we systematically summarized current status of "non-grain production" of cultivated land and key technologies for land improvement, recultivation and fertilization in China, and put forward future directions in this area.

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With the emergence of complex soil pollution problems, the combined contamination of heavy metals and microplastics (MPs) should not be overlooked. Particularly, the safe use of farmland soils deserves more attention. Passivators were commonly used for heavy metal-contaminated soil amelioration. However, the potential impact of MPs on this process is yet to be determined. Herein, the cadmium-contaminated paddy soil was collected to evaluate the effect of MPs on soil properties and bacterial community in soil amelioration. Two types of MPs were investigated, including conventional polyethylene (PE) and biodegradable polylactic acid (PLA). Both MPs decreased the available phosphorus content and bioavailability of cadmium in a similar way, while they changed the soil pH and nitrogen species in a different manner. Additionally, the high-dose PLA treatment induced a considerable decrease in soil pH (from ~5.4 to 3.6), with potential considerable release of carbon substrates and modification of bacterial community. Furthermore, for the ameliorated soil, it has a network structure of less complexity and stabilization, which resulted in greater disparities in the microbial community under different MP treatments. Profiling predicted functions provides insights into the potential correlations among bacterial activities and soil physicochemical properties. The study demonstrated that both PE and PLA could have significant effects on the soil amelioration process and pose a threat to agroecosystems.

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Saline and alkaline soils are a challenge for sustainable crop production. The use of organic and inorganic amendments is a common practice to increase the fertility of salt-affected soils that can trigger faster carbon (C) and nitrogen (N) cycling. We examined the effects of gypsum (Gyps), farm manure (Manure) and rice straw (Straw) on enzyme activities, organic matter mineralization and CO2 emissions in two salt-affected soils [Solonchak (saline); pH: 8, electrical conductivity (EC): 6.5, sodium adsorption ratio (SAR): 2.5, and Solonetz (alkaline sodic); pH: 8.9, EC: 1.6, SAR: 17]. Gypsum addition decreased soil pH up to 0.62 and 0.30 units, SAR 1.2 and 5.2 units, and EC 2.9 and 1.4 units in Solonchak and Solonetz, respectively. Dissolved organic C, microbial biomass C, dissolved organic N, mineral N (NO3- and NH4+), enzyme activities (urease, invertase, catalase, phosphatase, phenol-oxidase), alkali extractable phenols, and available phosphorous increased with the application of all amendments in both soils. Solonetz released more CO2 than Solonchak, whereas maximum CO2 emissions were common after manure application (3140 mg kg-1 in Solonchak, and 3890 mg kg-1 in Solonetz). We conclude that high SAR and low EC increase CO2 emissions through accelerated C and N cycling and manure decomposition in Solonetz soils.

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The wastes generated from the mining and processing of granite and marble stone are generally regarded as useless. However, these waste materials were used as the soil amendments for the first time. The functional groups, crystalline structure and micro-morphology of granite and marble wastes amendments (GMWA) were different from the original wastes demonstrated by X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR) and Scanning electron microscope-energy dispersive spectrometer (SEM-EDS) analyses. With the addition of the amendments, the cation exchange capacity, electrical conductivity and nutrient availability of the soil increased, and the extractable heavy metals of the soil reduced significantly. Under the condition of the addition of 3% amendments, 7.0%, 99.9%, 99.7% and 70.5% of Cu, Pb, Zn and Cd in exchangeable fractions in soil were transformed to the more stable Fe-Mn oxides- or carbonates-bounded fractions. Tessier method and correlation analysis showed that the reduction of extractable metals in the acidic paddy soil can be attributed to the adsorption of available SiO2, the co-precipitation induced by the elevated pH value, the complexation induced by Fe-Mn oxides and the cation exchange induced by mineral nutrients. This study provides a new strategy for resource recovery of waste stones and remediation of heavy metal-contaminated soil.

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Soil salinization is a critical environmental issue restricting agricultural production. Inner Mongolia is one of the areas with severe land salinization in China. This study aimed to investigate the effects of conditioning agent (containing marlstone and a range of enzymes) and cultivating Jerusalem artichoke on saline soils in Inner Mongolia. The effects of conditioner (0, 0.06 and 0.18 kg/m2) on soil physical, chemical and biological properties, including soil carbon fractions and microbiota in saline soils planted with Jerusalem artichoke, were characterized. The results showed that soil salinity was reduced significantly after cultivating Jerusalem artichoke and declined also after the conditioner addition. The application of conditioner increased the content of DOC (dissolved organic carbon), HFOC (heavy fraction organic carbon) and the content of aggregates >0.25 mm compared to the soil planted with Jerusalem artichoke alone. The relative abundance of halophilic bacteria such as Thioalkalivibrio and Thiohalobacter was greater in the CK (non-treated control). By contrast, the relative abundance of microorganisms with the carbon assimilation and nitrogen fixation capacities, such as Cyanobacteria and Rhodovulum, was greater in the conditioner-treated and Jerusalem artichoke-planted treatments. The planting of Jerusalem artichoke reduced soil salinity, increased soil organic carbon fractions, improved soil structure, and altered the soil microbial community, with the application of the conditioning agent enhancing these positive changes. The co-occurrence network structure of "Jerusalem artichoke-conditioner-saline soil-soil microorganism" was established, which provided scientific basis for Jerusalem artichoke-conditioner to improve saline soil.

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The aim of this study was to characterize the effects of cornstalk biomass amendments on microbial communities in bauxite residues (BRs) by phylogenetic analysis. Improvements in soil geochemical, physical, and biological properties were assessed to identify the major factors controlling microbial community development in BRs. After one year of incubation, the salinity and structure of the amended BRs had gradually improved, with pH dropping from 11.39 to 9.89, the exchangeable sodium percentage (ESP) dropping from 86.3% to 35.2%, and the mean weight diameter (MWD) rising from 0.12 mm to 0.38 mm. Further analysis of community level physiological profiles (CLPP) showed that the microbial utilization of different carbohydrates had shifted significantly, in addition to increases in the diversity index H' (0.7-7.34), U (2.16-3.14), and the average well color development (0.059-1.08). Over the one-year outside incubation, the dominant fungal phyla in the BRs had shifted gradually from Ascomycota (85.64%) to Ascomycota (52.07%) and Basidiomycota (35.53%), while the dominant bacterial phyla had shifted from Actinobacteria (38.47%), Proteobacteria (21.39%), and Gemmatimonadetes (12.72%) to Actinobacteria (14.87%), Proteobacteria (23.53%), and Acidobacteria (14.37%). Despite these shifts, microbial diversity remained lower in the amended BRs than in the natural soil. Further redundancy analysis indicated that pH was the major factor driving shifts in the bacterial community, while aggregates were the major factor driving shifts in the fungal community. This study demonstrated that amendment with cornstalk biomass shifted the microbial community in the BRs from halophilic groups to acidogenic groups by improving the soil environmental conditions.

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In the coastal zones, numerous ecological shelterbelt projects were conducted to protect against natural hazards. However, it is still not fully understood whether phytoremediation with native legume Albizzia julibrissin plantation can improve saline soil structural development or microbial community structure. In this study, a field experiment was conducted to investigate the responses of rhizosphere soil salinity, nutrients, bacterial community, and aggregate structure to A. julibrissin plantation in a recently reclaimed area along Zhejiang coast, China. After ~3-year plantation, rhizosphere soil pH and EC reduced to 8.25 and 0.14 dS·m-1, respectively, belonging to non-saline soil. Meanwhile, total organic carbon (TOC), permanganate-oxidizable carbon (POXC), total nitrogen (TN), alkali-hydrolyzable nitrogen (AN), and ammonium nitrogen (NH4+-N) were significantly increased in rhizosphere soil compared with bare land (P < 0.05). Consequently, rhizosphere soil had favorable habitat condition for copiotrophic bacterial taxa (e.g., Chloroflexi, Acidobacteria, and Bacteroidates), as well as high diversity, complex co-occurrence network, and catabolism related with nutrient cycling. The soil particle size of bare land was < 0.053 mm, while microaggregate (0.053-0.25 mm) and macroaggregate (0.25-2 mm) were formed in the rhizosphere and coupled with C accumulation and Fe removal. Soil aggregates were of great importance to soil fertility with more efficient bacterial network and biogeochemical cycles of nutrients. N-fixing Rhizobiales preferred to inhabit large soil particle and might primarily contribute to N accumulation. Generally, A. julibrissin was a suitable pioneer tree for mudflat reclamation projects, which effectively improved saline soil rhizosphere environment by reducing salinity, accumulating C and N, and promoting microbial community succession, as well as aggregate structure formation.

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Saline-sodic soils cover ∼10% of the global land surface and deliver various ecosystem services to human society in the arid/semiarid regions. Flue gas desulfurization gypsum (FGDG), a byproduct from coal-fired power plants, is widely used to ameliorate saline-sodic soils. Here, we aimed to quantify the impacts of FGDG application on multiple soil functions across climatic conditions, management practices, and soil types, and to explore how FGDG application affects plant productivity. We conducted a meta-analysis by compiling 2658 pairs of data points with and without FGDG application from 59 locations across China. We found that FGDG application significantly increased crop yield by 91.2% ± 22.5% (mean ± 95% CI) regardless of local climate and soil type, and improved soil quality by reducing soil exchangeable sodium percentage (ESP) by 37.4% ± 9.6% and pH by 8.1% ± 1.7%. Increases in soil productivity were strongly correlated with decreases in soil ESP and pH, suggesting that increases in soil productivity were due to alleviated stress for plant growth. Meanwhile, some heavy elements (e.g., Hg and Ni) increased after FGDG application, likely imposing threats to soil health. Overall, the FGDG application is effective in improving the quality and productivity of saline-sodic soils across China. Our findings suggest that simultaneous assessment of changes in soil water (e.g., water holding capacity and infiltration), nutrient transformation, soil organic matter dynamics, and microbial communities helps disentangle mechanisms that are responsible for optimizing ecosystem service provided by saline-sodic soils after FGDG amendment application.

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Saline-sodic soil is widely distributed around the world and has induced severe impacts on ecosystems and agriculture. Plant microbial desalination cell (PMDC) and soil microbial desalination cell (SMDC) were constructed to migrate excessive salt in the soil in this study. Compared with SMDC, PMDCs generated higher voltage ranging from 150 mV to 410 mV (500Ω) and the maximum power density reached 34 mW/m2. Higher desalinization efficiency was obtained by PMDCs, the soil conductivity reduced from initial 2.4 mS/cm to 0.4 ± 0.1 mS/cm and pH decreased from initial 10.4 to 8.2 ± 0.1. Soils desalination in PMDCs was achieved through multiple pathways, including ion migration in PMDCs driven by electrokinetic process, plant absorption and bioremediation by plant roots and anode microorganism activity. Geobacter was the dominant electrogenic bacteria at the PMDC anode. The electrochemical and desalinating performance of PMDCs was enhanced by plants and provided a new method for remediation of saline-sodic soil.

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The fungal community and soil geochemical, physical and biological parameters were analyzed, respectively, in bauxite residues (BRs) treated with organic matter and vermiculite/fly ash by phylogenetic analysis of ITS-18 S rRNA, community level physiological profiles (CLPP) and so on. The results indicated that after amendment of the BR, microbial utilization of carbohydrates and their enzyme activities were significantly increased, but fungal compositions at the phylum level were similar and dominated by the phylum of Ascomycota (82.05-98.96%, RA: relative abundance) after one year of incubation. The fungal taxa in the amended BR treatments, however, show significantly less alpha and beta diversity compared with the reference soils, although they still harbor a substantial novel taxon. The combined amendment of organic matter (OM) and vermiculite/fly ash significantly increases the fungal taxa at the genus and species level compared with solely OM amendment. The results of the following canonical correspondence analysis found that, over 90% variation of the fungal community could be explained by pH, OM and mean weight diameter (MWD) of aggregates; but the biological indicators, including urease (UR), dehydrogenase (DHA) and the value of average well color development (AWCD) could explain only 50% variation of the fungal flora in BRs. This paper indicated that resilience of fungal community in BRs was positively correlated with the BRs' improvement in fertility as well as biogeochemical properties, but alkalinity must be firstly decreased to the target level of BRs' rehabilitation.

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Globally soil salinity is one of the most devastating environmental stresses affecting agricultural systems and causes huge economic losses each year. High soil salinity causes osmotic stress, nutritional imbalance and ion toxicity to plants and severely affects crop productivity in farming systems. Freezing saline water irrigation and plastic mulching techniques were successfully developed in our previous study to desalinize costal saline soil. Understanding how microbial communities respond during saline soil amelioration is crucial, given the key roles soil microbes play in ecosystem succession. In the present study, the community composition, diversity, assembly and potential ecological functions of archaea, bacteria and fungi in coastal saline soil under amelioration practices of freezing saline water irrigation, plastic mulching and the combination of freezing saline water irrigation and plastic mulching were assessed through high-throughput sequencing. These amelioration practices decreased archaeal and increased bacterial richness while leaving fungal richness little changed in the surface soil. Functional prediction revealed that the amelioration practices, especially winter irrigation with saline water and film mulched in spring, promoted a community harboring heterotrophic features. ß-null deviation analysis illustrated that amelioration practices weakened the deterministic processes in structuring coastal saline soil microbial communities. These results advanced our understanding of the responses of the soil microbiome to amelioration practices and provided useful information for developing microbe-based remediation approaches in coastal saline soils.

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A great portion of Earth's freshwater and land resources are salt-affected and thus have restricted use or may become unsuitable for most human activities. Some of the recent scenarios warn that environmental salinization processes will continue to be exacerbated due to global climate change. The most relevant implications and side-effects in ecosystems under excessive salinity are destructive and long lasting (e.g. soil dispersion, water/soil hypersalinity, desertification, ruined biodiversity), often with non-feasible on site remediation, especially at larger scales. Agro-ecosystems are very sensitive to salinization; after a certain threshold is reached, yields and food quality start to deteriorate sharply. Additionally, salinity often coincides with numerous other environmental constrains (drought, waterlogging, pollution, acidity, nutrient deficiency, etc.) that progressively aggravate the threat to food security and general ecosystem resilience. Some well-proven, widely-used and cost-effective traditional ameliorative strategies (e.g. conservation agriculture, application of natural conditioners) help against salinity and other constraints, especially in developing countries. Remotely-sensed and integrated data of salt-affected areas combined with in situ and lab-based observations have never been so easy and rapid to acquire, precise and applicable on huge scales, representing a valuable tool for policy-makers and other stakeholders in implementing targeted measures to control and prevent ecosystem degradation (top-to-bottom approach). Continued progress in biotechnology and ecoengineering offers some of the most advanced and effective solutions against salinity (e.g. nanomaterials, marker-assisted breeding, genome editing, plant-microbial associations), albeit many knowledge gaps and ethical frontiers remain to be overcome before a successful transfer of these potential solutions to the industrial-scale food production can be effective.

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Environment-friendly disposal of coal fly ash (CFA) is essential for sustainable development and cleaner production of electricity in thermal power plants. Although CFA has been employed for soil amelioration, direct application of CFA to soil may pose risks such as heavy metal contamination. This study investigated recycling of CFA through a novel method, which employs the ultrasonic treatment of CFA before its application. Physico-chemical properties of refuse dump soil and CFA were analysed. Subsequently, the effect of ultrasonic treatment on the physico-chemical properties of CFA was investigated. Different ultrasonic parameters (ultrasonic frequency, time interval, and temperature) were studied using response surface methodology. Finally, plant growth experiments were conducted to verify the feasibility of using ultrasonically treated CFA (UTCFA) for soil amelioration. The results show that untreated CFA cannot be used for soil amelioration due to its unsuitable high pH (10.20) and threatening concentrations of trace elements (6.80 mg/kg for Cadmium and 109.75 mg/kg for Arsenic). Ultrasonic treatment increases the soil amelioration properties of CFA by decreasing pH (to 8.50-9.20), decreasing concentrations of Cadmium and Arsenic (satisfying GB 15618-2018), and improving the water-holding capacity of CFA (reducing water loss). Plant indicators confirm the feasibility of using UTCFA for soil amelioration and suggest that the optimum UTCFA proportion is 20%. This study is a benchmark for the utilisation of ultrasonic treatment to improve the soil amelioration properties of CFA.

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Planting rice is one of the effective ways to improve saline soils, but the underlying mechanisms are unknown. We studied basic soil properties (including pH, salt content, total nitrogen, etc.) and microbial diversity of the bare soil (salt content >4 g/kg, CK), the Suaeda (Suaeda glauca (Bunge) Bunge) soil (JP), and the soil in which rice (cv. Huaidao 5) grew for one (1Y) and three (3Y) years. The results showed that the soil salinity decreased in the order: CK > JP > 1Y > 3Y. The contents of soil organic matter, total nitrogen, dissolved organic carbon, readily oxidizable carbon, microbial biomass carbon, and particulate organic carbon were higher in 1Y and 3Y compared with CK. The Chao 1 index of soil microbiome diversity was about 1.20 times and 1.49 times higher in the soils after rice compared with JP and CK, respectively. Among the soil microorganisms, the top four abundant phyla were Proteobacteria, Chloroflexi, Bacteriodetes, and Firmicutes. In summary, planting rice decreased soil salinity, and increased the content of nutrients and diversity of microorganisms, thereby improving the saline soil.

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Immobilization is among the most-suitable strategies to remediate cadmium (Cd) contaminated sites. Organic additives (OAs) have emerged as highly efficient and environment-friendly immobilizers to eradicate Cd contamination in a wide range of environments. This review article is intended to critically illustrate the role of different OAs in Cd immobilization and to highlight the key findings in this context. Owing to the unique structural features (high surface area, cation exchange capacity (CEC), presence of many functional groups), OAs have shown strong capability to remediate Cd polluted soils by adsorption, electrostatic interaction, complexation and precipitation. Research data is compiled about the efficiency of different OAs (bio-waste, biochar, activated carbon, composts, manure, and plant residues) applied alone or in combination with other amendments in stabilization and renovation of contaminated sites. In addition to their role in remediation, OAs are widely advocated for being classical sources of essential plant nutrients and as agents to improve the soil health and quality which has also been focused in this review. OAs may contain considerable amounts of metals and therefore it becomes essential to assess their final contribution. Elimination of Cd contamination is essential to attenuate the contaminant effect and to produce the safe food. Therefore, deployment of environment-friendly remediation strategies (alone or in combination with other suitable technologies) should be adopted especially at early stages of contamination.

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It aimed to investigate and evaluate the soil amelioration process of bauxite residues with the amendments of organic materials from different sources. Wheat straw, poultry manure compost, and biosolids were chosen as the added organic materials. A series of essential soil properties were analyzed to evaluate the effects of organic materials on the soil amelioration of bauxite residue. The results indicated that organic amendments could obviously improve the texture of bauxite residues by increasing large aggregates contents, and elevating its organic matter content and fertility level (such as TN and TP). At the same time, organic additions were effective in reducing bauxite residues' salinity as pH, electrical conductivity and sodium content were obviously decreased in all rehabilitated treatments in comparison with control treatment. These improvements created sufficient conditions for a quick recovery of microbial communities in bauxite residues matrix. The maximum microbial biomass C increased to 0.642 g-C·kg-1, and the activities of urease, catalase, and invertase were massively elevated, especially for those after a year of rehabilitation, although alkali-phosphatase was kept a less level compared with other biological parameters. The further principal analysis and cluster analysis indicated that after 1 year of organic amendment, the improved bauxite residues matrix was very close to the reference soil based on the measured soil microbial properties. All the results suggested that organic amendment is an effective way to stimulate the soil amelioration of bauxite residues, and among the three amended organic materials, wheat straw and biosolid were better in improving the abiotic environmental conditions as well as biotic function recovery in soil amelioration of bauxite residue.

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Ever increasing volumes of biosolids (treated sewage sludge) are being produced by municipal wastewater facilities. This is a consequence of the continued expansion of urban areas, which in turn require the commissioning of new treatment plants or upgrades to existing facilities. Biosolids contain nutrients and energy which can be used in agriculture or waste-to-energy processes. Biosolids have been disposed of in landfills, but there is an increasing pressure from regulators to phase out landfilling. This article performs a critical review on options for the management of biosolids with a focus on pyrolysis and the application of the solid fraction of pyrolysis (biochar) into soil.

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