Chemical fertilizer is widely used in agricultural fertilization, but over-fertilization has caused soil quality degradation. Some studies have shown that the application of organic fertilizer is beneficial to soil quality, but there are few studies researching the long-term organic fertilizer application effect on tea plantation soil. In this paper, we studied the physical and chemical properties and microbial communities of tea plantation soil through long-term field experiments by applying organic fertilizer with equal nitrogen amounts. The experiment showed that the soil’s physical and chemical properties were improved after long-term application of total organic fertilizer. Respectively, the soil organic matter (SOM), available potassium (K), available zinc (Zn), available copper (Cu), and pH were significantly enhanced, the soil bulk density was significantly increased, the water-stable aggregates were improved, the soil microbial diversity was increased. It was found that the main bacteria in tea soil were Proteobacteria, Acidobacteria, and Actinobacteria. Moreover, results from redundancy analysis showed t hat t he S OM ( p = 0 .001), A lkali h ydrolyzed n itrogen ( p = 0 .049) a nd p H ( p = 0 .008) h ad significant effects on the soil bacterial community composition. Thus SOM increased the relative richness of non-dominant bacteria, such as Bacteroidetes, Gemmatimonadestes, and Firmicutes. Overall, our results suggest that the use of organic fertilizer instead of chemical fertilizer could effectively improve the quality of tea plantation soil.

Background: Camellia sinensis is an important cash crop in southwestern China, with soil organic carbon playing a vital role in soil fertility, and microorganisms contributing significantly to nutrient cycling, thus both of them influencing tea tree growth and development. However, existing studies primarily focus on soil organic carbon, neglecting carbon fractions, and the relationship between soil organic carbon fractions and microbial communities is unclear. Consequently, this study aims to clarify the impact of different tea planting durations on soil organic carbon fractions and microbial communities and identify the main factors influencing microbial communities. It provides a theoretical basis for soil quality evaluation in the study area and scientific guidance for tea plantation management, thus fostering the region’s economic sustainability. Methods: This study selected tea plantations with different tea planting durations of 3–5 years (Y5), 12–16 years (Y15), 18–22 years (Y20), 40–42 years (Y40), and 48–50 years (Y50), as research subjects and adjacent uncultivated forest without a history of tea planting (CK) served as controls. Soil organic carbon (SOC), particulate organic carbon (POC), easily oxidizable organic carbon (EOC), dissolved organic carbon (DOC), microbial biomass carbon (MBC), and bacterial diversity were measured in the 0–20 cm and 20–40 cm soil layers, respectively. Results: Compared to the adjacent uncultivated forest (CK), the soil organic carbon (SOC), easily oxidizable carbon (EOC), particulate organic carbon (POC), and dissolved organic carbon (DOC) contents in a 40-year tea plantation significantly increased. Nonetheless, the microbial biomass carbon (MBC) content notably decreased. POC/SOC ratios rose with prolonged planting, signifying enhanced conversion of organic carbon into particulate forms. Bacterial community diversity peaked at 15 years and declined by 40 years post-planting and after tea planting dominated by Acidobacteriota, Chloroflexi, Proteobacteria, and Actinobacteriota in the tea garden. FAPROTAX analysis highlighted aerobic and anaerobic chemoheterotrophy, cellulolysis, and nitrogen fixation as key bacterial functions. POC and MBC significantly influenced bacterial community structure. In conclusion, tea plantation soil exhibited the highest organic carbon content at 40 years of tea planting, indicating strong carbon accumulation capacity. However, soil acidification in the tea plantation may affect changes in organic carbon and bacterial community. Therefore, in the tea planting process, it is necessary to improve the management system of tea plantations to ensure the maintenance of a good ecological environment in the tea plantation soil, thus achieving sustainable development of the tea industry in the region.

Red mud and phosphogypsum are by-products in the production process of aluminum manufacturing and phosphorus chemical industry respectively. PO₄³⁻, F⁻and Cd²⁺ in phosphogypsum and Na⁺ plasma in red mud will leach into water and soil after raining, which declines the ecological environment quality. Therefore, it is necessary to research the modification on red mud and phosphogypsum, and technologies of their soil substrates utilization. In this study, ferric chloride and sodium silicate were used to modify the red mud and phosphogypsum, and the control effect and mechanism of the modifiers on relevant pollutants were discussed. The study further explored the optimal ratio of this complex substrates and its growth effect on wheat grass through pot experiment. The results showed that the single modification process of ferric chloride on red mud reduced its pH value from 10.76 to 8.51–10.05, and improved its crystal and pore structure; while the Na₂SiO₃ treatment on phosphogypsum increased its pH value from 3.38 to 4.48–9.54, and significantly reduced the PO₄³⁻ (from 205.7 mg/L to 28.9 mg/L) and F⁻concentration (reduced to 3.77 mg/L) in the extraction. The relevant pollutants (pH, PO₄³⁻, F⁻ and heavy metal content) produced from the red mud and phosphogypsum modification complex (Spraying 1 mol/L FeCl₃ of 15% mass ratio in red mud and 1.4 mol/L Na₂SiO₃ of 10% mass ratio in phosphogypsum) with a mass ratio of 7:3 all meet the highest allowable concentration requirements in the comprehensive sewage discharge standard. The pot experiment of ryegrass planting with such modification complex cultivated the dry weight of 18.82g and plant height of 21.63cm at 40 days, which was comparable to the growth effect of ryegrass in fresh soil (dry weight 21.63g and plant height 21.35 cm at 40 days). The modification mechanism realized stable dealkalinization of red mud and stable curing of soluble PO₄³⁻ and F⁻ in phosphogypsum, which can be used as a soil-based substrate suitable for forage growth. And the optimizing ratio of modification complex even can be applied to soil and ecological remediation.

Electrolytic manganese slag (EMR) is a solid waste generated in the manganese hydrometallurgy process. It not only takes up significant land space but also contains Mn2+, which can lead to environmental contamination. There is a need for research on the treatment and utilization of EMR. Improved EMR substrate for Pennisetum sinese Roxb growth was determined in pot planting experiments. The study tested the effects of leaching solution, microorganisms, leaf cell structures, and growth data. Results indicated a substrate of 45% EMR, 40% phosphogypsum, 5% Hericium erinaceus fungi residue, 5% quicklime, and 5% dolomite sand significantly increased the available phosphorus content (135.54 +/- 2.88 mu g center dot g(-1)) by 17.95 times, compared to pure soil, and enhanced the relative abundance of dominant bacteria. After 240 days, the plant height (147.00 +/- 0.52 cm), number of tillers (6), and aerial dry weight (144.00 +/- 15.99g) of Pennisetum sinese Roxb increased by 5.81%, 200%, and 32.58%, respectively. Analyses of leaves and leaching solution revealed that the highest leaf Mn content (46.84 +/- 2.91 mu g center dot g(-1)) being 3.38 times higher than in pure soil, and the leaching solution Mn content (0.66 +/- 0.13 mu g center dot g(-1)) was lowest. Our study suggested P. sinese Roxb grown in an improved EMR substrate could be a feasible option for solidification treatment and resource utilization of EMR.

Manganese adsorptive removal is an important treatment process in constructed wetlands to deal with considerable amounts of tailing wastewater, many materials have been proposed for its removal. This work is aimed to examining the potential of biochars sorbent materials for removing Mn ions from manganese slag aqueous solutions by modified biochars. The biochars with different organic acid-Fe ratios were prepared; factors on Mn adsorption including mixing ratio, Fe adsorption rate, and the BET surface of the modified biochars were discussed and the sorption efficiency of Mn was investigated through column adsorption experiments. According to our study, it's clearly that loaded organic acid biochar with greater Fe content removed higher percent of Mn from the aqueous solution. Contents of Fe 2 O 3 (30-103%), Fe 3 O 4 (65-106%)and CaCO 3 (4-80%)increased after loaded with organic acid-Fe in the biochars. With the increasing Fe content (2.58-5.07%) in biochar, the BET surface area of the Citric Acid-Fe biochar composites decreased from 81 m 2 /g to 35 m 2 /g, while the EDTA-Fe biochar composites decreased from 96 m 2 /g to 22 m 2 /g. The fixed loaded Fe biochars mixtures had a reduction of 4.02% to 32.01% in Mn sorption contrasting with raw biochar. The modified biochars could be used to remove the Mn ions in the tailing wastewater.

As a highly effective acaricide, etoxazole is widely used in agricultural production, but its toxicological effects on soil organisms remain unclear. Based on nuclear magnetic resonance (NMR) metabolomics technology, in this study, we systematically investigated the sublethal responses of earthworms (Eisenia fetida) to etoxazole. The results showed that etoxazole exposure significantly altered the endogenous metabolic profiles in earthworms, with 19 and 20 metabolites significantly changed after 2 and 14 d of exposure, respectively. Trimethylamine N-oxide exhibited specific changes, indicating that it may be a potential biomarker for exposure to etoxazole. KEGG pathway analysis revealed that five metabolic pathways were notably affected after 2 and 14 days of etoxazole exposure. These pathways were primarily associated with energy conversion, protein and amino acid synthesis and metabolism, carbohydrate metabolism, and nucleic acid and DNA synthesis. Overall, etoxazole exposure notably altered the endogenous metabolic profiles of earthworms. This study was of great significance for comprehensively understanding the potential hazards that etoxazole poses to soil ecosystems and provides important information for environmental monitoring and ecological risk assessment.