High-ash coal slime-based silica fertilizer (CSF) has the potential to provide mineral nutrients and passivate lead (Pb) in the soil to ensure the sustainable development of the coal industry and agriculture. This study investigated the performance and passivation mechanism of CSF, which contains potassium tobermorite and potassium silicate as the main components for soil improvement. Leaching experiments showed that low-crystalline muscovite was the only crystalline phase for CSF etching and that the silicon (Si), calcium (Ca), and potassium (K) in CSF had significant citric solubility. Soil cultivation and planting trials confirmed the ability of CSF to neutralize soil acidity, increase available soil Si and K, improve exchangeable Ca content, reduce the bioefficacy of Pb (exchangeable Pb by 19-75 % and carbonate-bound Pb by 6-18 %), and increase residual state Pb content. Compared to untreated Pb-contaminated soil, the 0.4 % CSF treatment reduced Pb in Chinese cabbage (Brassica rapa) by 25 % and increased plant biomass, Ca, and K by 37 %, 36 %, and 4 %, respectively. At the same time, soil pH increased by 0.58, and residual state Pb increased by 5 %. In CSF-treated soils, lead silicate is the dominant form of Pb present in the residual state. First-principle calculations showed that Pb3Si2O7 (cohesion energy -1.98 eV) formed by the passivation of Pb by CSF had greater stability in the soil compared to lead carbonate (PbCO3) (cohesion energy -1.38 eV) and lead sulfate (PbSO4) (cohesion energy -1.41 eV). This work shows the promising application of coal slime mineral fertilizers prepared using hydrothermal methods for soil improvement.

Due to the bioavailability and movement of antimony in trophic web, the overexploitation of antimony mine resulted in antimony contamination that harmed the ecology nearby, raising concerns for public health. Whereas, most researches focused on the removal of antimony in the aqueous instead of the immobilization of antimony in the soil. Herein, the immobilized performance of biochar (BC) loaded with nano zero-valent iron (nZVI-BC) on antimony in the soil near the smelting area was researched through pot experiments for the first time, and its stabilization mechanism on antimony was investigated by valent state variation of antimony. The results demonstrated that BC restricted the cation exchange capacity and catalase activity in the soil, while nZVI-BC had a favorable and negative impact on two variables, respectively. The nZVI-BC showed more stable immobilization capacity on antimony over time than BC, whose exchangeable speciation only marginally rose (2%-6%), although the exchangeable speciation of antimony fell both from 15% to 2% after adding the BC and nZVI-BC, The electron attraction force between nZVI-BC and antimony was also intensified owing to the oxidation-reduction process, which was considered as the stabilizing principle of nZVI-BC on antimony in soil. Furthermore, the decreased bioaccumulation factor for the perennial ryegrass (0.46-0.21) and Galinsoga parviflora Cav. (0.26-0.17) stated that the BC effectively mitigated the bioaccumulation risk of antimony.

The properties of different organic fertilizers and their potential for stabilizing toxic metals(loids) in soil have not been fully investigated. This study characterized and evaluated three organic fertilizers from different raw materials. The mushroom residue organic fertilizer (MO) had higher C, H, and O contents and more functional groups (-OH, C-H, and C = O). Its application significantly increased pH (1.00 ~ 1.32 units), organic matter (OM) content (26.58 ~ 69.11%), and cation exchange capacity (CEC) (31.52 ~ 39.91%) of soil. MO treatments can simultaneously reduce the bioavailable TCLP-Cd and TCLP-As in soil, solving the difficulties of remediating the combined Cd and As pollution. MO treatments inhibited the migration of Cd and As from soil to plant, promoting plant growth. Redundancy analysis (RDA) revealed that metal(loid) variations in plants were related to soil properties (40.09%) and TCLP-Cd/As (44.74%). Furthermore, the toxic metals(loids) risk assessment for all organic fertilizers was at safe levels. This study provided a valuable reference for choosing organic fertilizers and presented a novel option for the \"producing while remediating\" of farmlands with low pollution.

Rise in climate change-induced drought occurrences have amplified pollution of metal(loid)s, deteriorated soil quality, and deterred growth of crops. Rice straw-derived biochars (RSB) and cow manure-enriched biochars (CEB) were used in the investigation (at doses of 0%, 2.5%, 5%, and 7.5%) to ameliorate the negative impacts of drought, improve soil fertility, minimize arsenic pollution, replace agro-chemical application, and maximize crop yields. Even in soils exposed to severe droughts, 3 months of RSB and CEB amendment (at 7.5% dose) revealed decreased bulk density (13.7% and 8.9%), and increased cation exchange capacity (6.0% and 6.3%), anion exchange capacity (56.3% and 28.0%), porosity (12.3% and 7.9%), water holding capacity (37.5% and 12.5%), soil respiration (17.8% and 21.8%), and nutrient contents (especially N and P). Additionally, RSB and CEB decreased mobile (30.3% and 35.7%), bio-available (54.7% and 45.3%), and leachable (55.0% and 56.5%) fractions of arsenic. Further, pot experiments with Bengal gram and coriander plants showed enhanced growth (62-188% biomass and 90-277% length) and reduced arsenic accumulation (49-54%) in above ground parts of the plants. Therefore, biochar application was found to improve physico-chemical properties of soil, minimize arsenic contamination, and augment crop growth even in drought-stressed soils. The investigation suggests utilisation of cow manure for eco-friendly fabrication of nutrient-rich CEB, which could eventually promote sustainable agriculture and circular economy. With the increasing need for sustainable agricultural practices, the use of biochar could provide a long-term solution to enhance soil quality, mitigate the effects of climate change, and ensure food security for future generations. Future research should focus on optimizing biochar application across various soil types and climatic conditions, as well as assessing its long-term effectiveness.

Entisol soil is hard and compact in nature, rendering it high in bulk density, which influences root penetration adversely and thereby poor plant growth. In this experiment, used seven treatments in different combination in normal soil, were used as growth media for the Terminalia arjuna seedling. T3 (60% entisol) found the best as it gave the highest biomass in the species regardless of arbuscular mycorrhizal fungi (AMF) treatment. AMF treatment enhanced the growth and biomass of plants significantly in all the given treatments. AMF colonization observed a maximum in tertiary roots. T1 (100% entisol soil) exhibited the highest degree of AMF colonization in tertiary roots, resulting in the highest mycorrhiza dependency of plants for this soil. The addition of normal soil to entisol soil was found to decrease the bulk density, resulting in increased root diameter, and T3 plants exhibited the highest biomass and AMF compatibility for T. arjuna species. The T. arjuna plant\'s growth and biomass responded positively to AMF in all types of treatments. The plant\'s growth and biomass were highest in the T3 treatment, which had a bulk density of 1.50 g/cm3. In this study, we combined the entisol with mycorrhizal inoculation of the nursery growing medium to promote plant growth and biomass, improve the plant\'s ability to hold water and absorb nutrients, and lower the entisol\'s bulk density. The T. arjuna (Roxb) plant responds very favorably to mycorrhiza inoculation in nursery conditions with the entisol growth medium.

Proper management of wastewater treatment plant side streams in pulp and paper mills is a matter of great interest. This study evaluates the environmental impact of different strategies in the management of biosludge from pulp and paper mills in Finland through a Life Cycle Assessment methodology. The base industrial standard practice, biosludge incineration for energy recovery and ash landfill disposal (Scenario 1), was compared to the alternative process of hydrothermal carbonization. The hydrochar generated from hydrothermal carbonization was evaluated for energy recovery through incineration (Scenario 2), or for use in composting for nutrient recovery (Scenario 3). The results showed that the hydrothermal process improved the overall environmental performance of the sludge management, particularly in terms of energy consumption and greenhouse gas emissions. The use of hydrochar as a soil amendment in composting also resulted in a significant reduction on the environmental impact compared to the other two scenarios. Overall, this study highlights the potential of hydrothermal carbonization and hydrochar utilization as sustainable options for managing biosludge from pulp mills.

Rice straw breakdown is sluggish, which makes agricultural waste management difficult, however pretreatment procedures and cellulolytic fungi can address this issue. Through ITS sequencing, Chaetomium globosum C1, Aspergillus sp. F2, and Ascomycota sp. SM2 were identified from diverse sources. Ascomycota sp. SM2 exhibited the highest carboxymethyl cellulase (CMCase) activity (0.86 IU/mL) and filter-paper cellulase (FPase) activity (1.054 FPU/mL), while Aspergillus sp. F2 showed the highest CMCase activity (0.185 IU/mL) after various pretreatments of rice straw. These fungi thrived across a wide pH range, with Ascomycota sp. SM2 from pH 4 to 9, Aspergillus sp. F2, and Chaetomium globosum C1 thriving in alkaline conditions (pH 9). FTIR spectroscopy revealed significant structural changes in rice straw after enzymatic hydrolysis and solid-state fermentation, indicating lignin, cellulose, and hemicellulose degradation. Soil amendments with pretreated rice straw, cow manure, biochar, and these fungi increased root growth and soil nutrient availability, even under severe salt stress (up to 9.3 dS/m). The study emphasizes the need for a better understanding of Ascomycota sp. degradation capabilities and proposes that using cellulolytic fungus and pretreatment rice straw into soil amendments could mitigate salt-related difficulties and improve nutrient availability in salty soils.

In this study, a new eco-friendly urea-rich sodium alginate-based hydrogel with a slow-release nitrogen property was prepared, and its effectiveness was evaluated in the cultivation of tomato plants under different water stress levels. The structure and performance of the hydrogel were investigated by FTIR, XRD, TGA, DTG, and SEM. The swelling and release experiments showed that prepared urea-rich hydrogel exhibited a high-water holding capacity (412 ± 4 g/g) and showed a sustained and slow nitrogen release property. A greenhouse pot experiment was conducted using two hydrogel levels (0.1 and 0.5 wt%) under two water deficit levels (30 and 70 % based on required water irrigation). Germination tests indicated that the developed hydrogel fertilizer has no phytotoxicity and has a positive impact on the germination rate even under water deficit conditions. The application of hydrogel fertilizer at 0.5 wt% significantly (p > 0.05) enhanced plant growth parameters such as leaf number, chlorophyll content, stem diameter, and plant length compared to the control treatment. The magnitude of the responses to the hydrogel fertilizer application depended on the concentration of applied hydrogel fertilizer and stress severity with the most positive effects on the growth and yield of tomato observed at a level of 0.5 %. Tomato yield was significantly enhanced by 19.58 %-12.81 %, 18.58 %-22.02 %, and 39.38 %-43.18 % for the plant amended with hydrogel at 0.1-0.5 wt% and grown under water deficit levels of 0, 30, and 70 %, respectively, compared to the control treatment.

Excessive heavy metals in soils can threaten food security and soil health. New practical technology is urgently needed to remediate cadmium (Cd) contaminated paddies in many parts of the world. Chinese milk vetch (M), rice straw (R), and soil amendments can reduce Cd activity in soil; however, the mechanism underlying this reduction is not well understood. This study explored the impact of co-incorporation of milk vetch, rice straw, and either lime (L), sesbania biochar (B), or sepiolite on soil Cd bioavailability through field experiments. The results indicated that the rice grain Cd concentrations in soil treated with milk vetch + rice straw + fertilizer (MRF, 16.6 %), milk vetch + rice straw + fertilizer + sesbania biochar (MRFB, 50.1 %), and milk vetch + rice straw + fertilizer + lime (MRFL, 48.3 %) were significantly lower than those in soil treated with fertilizer (F). The acid-soluble Cd concentrations influenced rice grain Cd uptake and were 33.9 % and 47.5 % lower for the MRFB and MRFL treatments, respectively, than for F alone. A decrease in acid-soluble Cd (AciCd) was accompanied by a decrease in Eh and increases in pH, Fe2+, cation exchange capacity, and dissolved organic carbon. The MRFB treatment promoted iron plaque (IP) formation on the rice root surface. The relative abundances of Desulfobacterota and Verrucomicrobiota were higher for the MRFB treatment than for the other treatments. A partial least squares path model confirmed that Aci-Cd and low-crystalline IP (IP-Feh) influenced the rice grain Cd concentration.

Information about impacts of long-term biosolids application on soil microbial populations and functional groups and N cycling is important for evaluating soil health and agroecosystem sustainability under long-term biosolids application. Mine spoil plots received annual biosolids application from 1973 to 2010 at low (16.8 Mg ha-1 yr-1), medium (33.6 Mg ha-1 yr-1), and high rates (67.2 Mg ha-1 yr-1). A no-biosolids control received chemical fertilizer at the agronomic rate. Soil samples were collected in three seasons per year spanning 2003-2005 for measuring soil moisture, pH, soil organic C (SOC), total and extractable heavy metals (Cd, Cu, Ni, Zn), NO3-, N mineralization potential (NMP), microbial biomass C (MBC), and populations of three N-cycling bacteria (NCB) groups: ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and denitrifying bacteria (DNB). Soil samples were collected again in 2008 and 2010 for quantifying total and extractable heavy metals, and in 2018 (eight years after biosolids applications ended) for measuring SOC, MBC, NMP, and microbial respiration. During 2003-2005, mean MBC was 315, 554, 794, and 1001 mg kg-1 in the control, low, medium, and high biosolids treatments, respectively. Populations of NCB did not differ among treatments. Biosolids application increased total and extractable metal concentrations but the effect of biosolids rates were much lower on extractable than total concentrations. Soil extractable Cd and Cu concentrations decreased from medium to high applications, likely due to complexing with biosolids organic matter. Partial least squares regression analysis identified a strong positive effect on MBC of SOC and a weak negative effect of Cu, explaining the strong net positive effect of biosolids on MBC. In 2018, the medium and high biosolids treatments maintained higher SOC, MBC, NMP, and microbial respiration than the control. This study provided further evidence that long-term biosolids application has positive effects on soil microbes that persist for years after ending application.