Modified carbon-based microbial inoculum for improving saline-alkali soil as well as preparation method and application of modified carbon-based microbial inoculum

Abstract

The invention discloses a modified carbon-based microbial agent for improving saline-alkali soil as well as a preparation method and application thereof, and relates to the technical field of biology. The modified carbon-based bacterial agent is prepared from modified charcoal, bacillus marishii BM-C55 and bacillus velezensis IHRS7, and the modified charcoal-based bacterial agent is prepared from modified charcoal, bacillus marishii BM-C55, bacillus velezensis IHRS7 and bacillus velezensis IHRS7, and the modified charcoal-based bacterial agent is prepared from the modified charcoal, the bacillus marishii BM-C55 and the bacillus velezensis IHRS7. The bacillus velezensis BM-C55 and the bacillus velezensis IHRS7 are loaded in the modified biological carbon; the modified biochar is oxalic acid modified biochar. The modified carbon-based microbial agent provided by the invention can effectively improve saline-alkali soil, and has good effects of promoting plant growth under saline-alkali stress, improving saline-alkali soil quality and increasing soil microbial diversity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of biotechnology, in particular to a modified carbon-based microbial agent for improving saline-alkali soil and a preparation method and application thereof. BACKGROUND

[0002] Land salinization not only causes physiological water deficiency in plants, but also destroys soil structure, reduces soil microbial diversity and activity, and ultimately leads to a decrease in crop quality and productivity. Current measures to improve saline-alkali soil include physical, chemical, biological and water conservancy engineering methods. Physical and engineering methods are costly and require a large amount of fresh water, chemical amendments may cause secondary pollution, and biological improvement methods are easily affected by the environment. Therefore, there is an urgent need to develop more sustainable, low-cost and environmentally friendly improvement technologies.

[0003] In the improvement of saline-alkali soil, the synergistic effect of functional microbial agents and biochar carriers has attracted much attention. Biochar has abundant functional groups and can improve the survival and colonization of soil microorganisms as a carrier. At the same time, biochar reduces soil electrical conductivity by adsorbing salt ions, and functional bacteria regulate root exudates and secrete salt-tolerant substances to improve plant salt tolerance. Although biochar as a fixed carrier solves the limitations of free microbial agents and improves the survival rate of microorganisms. However, the original biochar has limitations in salt adsorption, which may exacerbate salinization. Therefore, optimizing the performance of biochar through modification strategies is the key to improving its efficiency in saline-alkali soil improvement. The present application aims to develop a new type of modified carbon-based microbial agent for application in saline-alkali soil improvement. SUMMARY

[0004] The purpose of the present application is to provide a modified carbon-based microbial agent for improving saline-alkali soil and a preparation method and application thereof to solve the problems existing in the prior art. The modified carbon-based microbial agent provided by the present application can effectively improve saline-alkali soil and has good effects on promoting plant growth under salt stress, improving saline-alkali soil quality and increasing soil microbial diversity.

[0005] To achieve the above-mentioned purpose, the present application provides the following solutions: The present application provides a modified carbon-based microbial agent for improving saline-alkali soil, which comprises modified biochar, Bacillus luchonensis (BM-C55) and Bacillus velezensis (IHRS7). Bacillus marisflavi Bacillus velezensis The Bacillus luchonensis BM-C55 and the Bacillus velezensis IHRS7 are loaded in the modified biochar. The modified biochar is oxalic acid-modified biochar. The modified biochar is oxalic acid-modified biochar. ​The preservation numbers of the Bacillus luchonensis BM-C55 and the Bacillus velezensis IHRS7 in the China General Microbiological Culture Collection Center are CGMCC No. 32788 and CGMCC No. 30948 respectively.

[0006] The application further provides a preparation method of the modified carbon-based microbial agent, comprising the steps of mixing the modified biochar and the microbial suspension, performing oscillation culture, and separating to obtain the modified carbon-based microbial agent. The microbial suspension contains the Bacillus luchonensis BM-C55 and the Bacillus velezensis IHRS7.

[0007] Further, in the microbial suspension, the quantity ratio of the Bacillus luchonensis BM-C55 and the Bacillus velezensis IHRS7 is 1:1.

[0008] Further, the temperature of the oscillation culture is 30 DEG C.

[0009] Further, the preparation method of the modified biochar comprises the step of mixing the biochar and an oxalic acid aqueous solution to perform a mixing reaction, so as to obtain the modified biochar.

[0010] Further, the concentration of the oxalic acid aqueous solution is 0.5 M. The mass-volume ratio of the biochar and the oxalic acid aqueous solution is 1 g:25 mL. The temperature of the mixing reaction is 30 DEG C, and the time is 7 h.

[0011] The application further provides the application of the modified carbon-based microbial agent in preparing a saline-alkali soil improvement product.

[0012] The application further provides a saline-alkali soil improvement product, comprising the modified carbon-based microbial agent.

[0013] The application further provides the application of the modified carbon-based microbial agent in improving saline-alkali soil.

[0014] The application further provides a method for improving saline-alkali soil, comprising the step of applying the modified carbon-based microbial agent to the saline-alkali soil.

[0015] The application discloses the following technical effects: The application takes oxalic acid modified biochar as a carrier to fix salt-tolerant growth-promoting strains, forms modified carbon-based microbial inoculants, and explores the application potential of the modified carbon-based microbial inoculants in improving the quality of coastal saline-alkali soil. The oxalic acid modified biochar not only significantly increases the specific surface area, but also increases the content of surface acid functional groups, provides more habitats for salt-tolerant growth-promoting bacteria, and improves the survival rate and colonization ability of the strains. The pot experiment shows that in the coastal saline-alkali soil, the application of modified carbon or functional microbial inoculants can effectively alleviate the adverse effects of salinization on wheat plants. The modified biochar and functional microbial inoculants show a synergistic effect, the modified carbon-based microbial inoculants can increase the biomass and physiological indicators of wheat, enhance the root activity, and improve the activity of antioxidant enzymes, which helps to enhance the stress resistance of wheat. At the same time, the soil pH and salt content are reduced, the soil fertility is improved, and the soil microbial diversity is increased. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described in the following are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0017] Figure 1 Na adsorption amount of biochar modified by different organic acids + Statistical diagram of Na adsorption amount Figure 2 Na adsorption amount of biochar prepared by different oxalic acid concentrations + Statistical diagram of Na adsorption amount Figure 3 Na adsorption amount of biochar prepared by different modification times + Statistical diagram of Na adsorption amount Figure 4 Na adsorption amount of biochar prepared by different modification temperatures + Statistical diagram of Na adsorption amount Figure 5 Na adsorption amount of biochar prepared by different material ratios + Statistical diagram of Na adsorption amount Figure 6 Response surface analysis diagram of the influence of two-factor interaction on Na adsorption rate of modified biochar + Modification concentration (A), material ratio (B) and modification time (C), wherein a) and b) are the interaction and contour map of modification concentration and material ratio, respectively; c) and d) are the interaction and contour map of modification concentration and modification time, respectively; e) and f) are the interaction and contour map of material ratio and modification time, respectively Figure 7SEM images of unmodified biochar (a), modified biochar (b), unmodified char-based microbial agent (c), and modified char-based microbial agent (d); Figure 8 The images show the FTIR spectra of biochar before and after modification. Figure 9 XPS chromatograms of unmodified biochar (A) and modified biochar (B); Figure 10 The images show the results of the detection of wheat phenotypic traits in different treatment groups; among them, (a) is an observation image of potted plants in each treatment group; (b) is a comparison image of whole wheat plants in each treatment group; (c) is a statistical chart of plant height in each treatment group; (d) is a statistical chart of plant weight in each treatment group; and (e) is a statistical chart of chlorophyll content in each treatment group. Figure 11 The graphs show the detection results of wheat enzyme activities in different treatment groups; (a) is a statistical graph of catalase activity in each treatment group; (b) is a statistical graph of peroxidase activity in each treatment group; (c) is a statistical graph of malondialdehyde activity in each treatment group; and (d) is a statistical graph of superoxide dismutase activity in each treatment group. Figure 12 The figures show the detection results of soil enzyme activities in different treatment groups; among them, (a) is a statistical graph of urease activity in each treatment group; (b) is a statistical graph of alkaline phosphatase activity in each treatment group; (c) is a statistical graph of sucrase activity in each treatment group; and (d) is a statistical graph of catalase activity in each treatment group. Figure 13 Statistical graph of Shannon index for different treatment groups; Figure 14 Statistical graphs of ACE indices for different treatment groups; Figure 15 A graph showing bacterial β-diversity analysis for different treatment groups; Figure 16 Bar chart showing the phylum-level species distribution for different treatment groups; Figure 17 Bar chart showing the genus-level species distribution for different treatment groups; Figure 18 Bar chart showing the significant gate distribution for different treatment groups; Figure 19 Graphs showing LEfSe analysis of microorganisms in different treatment groups; Figure 20 Diagrams showing the bacterial network structure of different treatment groups; Figure 21 A redundancy analysis diagram showing the relationship between the relative abundance of microbial phyla in soil samples and soil properties; Figure 22 A schematic diagram illustrating the mechanism of modified carbon-based bacterial agents in improving coastal saline-alkali soil. Detailed Implementation

[0018] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0019] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0020] Unless otherwise stated, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0021] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0022] The terms “comprising,” “including,” “having,” “containing,” etc., used in this invention are all open-ended terms, meaning that they include but are not limited to.

[0023] Example 1 1. Materials and Methods 1.1 Experimental Materials Biochar was prepared primarily from rice husks (pyrolyzed at 500-700℃) and purchased from Tangshan Zhongda Hanxing Environmental Remediation Co., Ltd. The ground, screened, and oven-dried biochar was used for modification. Plant enzyme activity kits were purchased from Suzhou Keming Biotechnology Co., Ltd. and Nanjing Construction Co., Ltd. Oxalic acid was purchased from Tianjin Yongda Co., Ltd.

[0024] Test strain Bacillus huanghaiense ( Bacillus marisflavi BM-C55 and Bacillus belesiensis ( Bacillus velezensisIHRS7 was isolated from saline-alkali soil in Hebei Province. Among them, Bacillus velezensis IHRS7 has been disclosed in patent document CN118956645A, entitled "A strain of Bacillus velezensis IHRS7 and its applications," and was deposited on June 14, 2024, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 30948. Bacillus huanghaiensis BM-C55 was deposited on November 25, 2024, at the China General Microbiological Culture Collection Center, located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 32788.

[0025] Coastal saline-alkali soil samples were collected from the saline-alkali coastal area of ​​Cangzhou (0-20 cm topsoil layer). Soil properties: pH 7.70; electrical conductivity (EC) 400 μS / cm. -1 Organic matter (OM), 21.6 g kg -1 Total nitrogen (TN), 1.25 g kg -1 Total phosphorus (TP), 1.26 g kg -1 Total potassium (TK) 22.5 g kg -1 ; and available phosphorus (AP), 19.0 mg kg -1 .

[0026] 1.2 Biochar Modification 1.2.1 Single-factor experiment (1) Under the conditions of a fixed material ratio of 1:25 (w / v), a modification temperature of 30℃, a modification time of 6 h, and an organic acid concentration of 0.5 M, biochar was modified with different organic acids to investigate the effect of different organic acid-modified biochar on Na+. + The effect of adsorption performance.

[0027] (2) Under the conditions of a material ratio of 1:25 (w / v), a modification temperature of 30℃, an organic acid of oxalic acid, and a modification time of 6 h, biochar was modified with different concentrations of organic acid to investigate the effect of different concentrations of oxalic acid on Na+. + The effect of adsorption performance.

[0028] (3) Under the conditions of a fixed material ratio of 1:25 (w / v), a modification temperature of 30℃, and oxalic acid as the organic acid with a concentration of 0.5 M, different modification times were set to modify biochar and investigate the effect of different modification times on Na + The effect of adsorption performance.

[0029] (4) Under the conditions of a fixed material ratio of 1:25 (w / v), a modification time of 6 h, and oxalic acid as the organic acid with a concentration of 0.5 M, different modification temperatures were set to modify biochar, and the effects of different modification temperatures on Na were investigated. + The effect of adsorption performance.

[0030] (5) Under the conditions of modification temperature of 30℃, modification time of 6h, organic acid of oxalic acid and concentration of 0.5 M, different material ratios were set for biochar modification treatment to explore the effect of different material ratios on Na + The effect of adsorption performance.

[0031] 1.2.2 Response Surface Box-Behnken Test Based on the results of single-factor experiments, a Box-Behnken response surface experimental design was adopted, with modification concentration, material ratio, and modification time as the three key factors. A three-level experimental scheme was set up, and a total of 17 experimental points were arranged for analysis.

[0032] 1.3 Preparation of carbon-based bacterial agents Modified carbon was prepared using the optimal preparation process obtained in section 1.2.

[0033] Modified charcoal of 30-80 mesh was obtained by sieving and sterilized at 121℃ for 30 min to obtain sterilized modified charcoal. A bacterial suspension was prepared by mixing *Bacillus huanghaiensis* BM-C55 and *Bacillus belyesense* IHRS7 at a 1:1 ratio, wherein the concentrations of both *Bacillus huanghaiensis* BM-C55 and *Bacillus belyesense* IHRS7 were 10. 8 CFU / mL. Sterile modified charcoal and bacterial suspension were mixed at a ratio of 1:20 (w / v) and incubated at 30℃ and 180 rpm for 4 h. After incubation, the mixture was separated using a 200-mesh sieve and washed three times with phosphate-buffered saline (PBS) solution to obtain the modified charcoal-based bacterial agent.

[0034] An unmodified carbon-based bacterial agent control was set up, prepared using the same method as the modified carbon-based bacterial agent, except that oxalic acid modification was not performed.

[0035] 1.3 Sample Characterization The morphology of the samples was observed using a scanning electron microscope (Zeiss Sigma 300) to verify the immobilization effect of functional strains on biochar or modified biochar. The number of functional strains immobilized on biochar or modified biochar was counted using the plate count method. Specific surface area (SSA) was measured using the multi-point N2 adsorption-desorption BET method on an automated gas adsorption analyzer (micromeritics, ASAP 2020, USA). Surface functional groups of the biochar samples were determined by Fourier transform infrared spectroscopy (FTIR, Thermo Scientific, Nicolet™ iS50, USA). Surface elements and functional groups of the samples were measured using X-ray photoelectron spectroscopy (XPS, Thermo Escalab 250 Xi, USA).

[0036] 1.4 Pot Experiment Five remediation reagents (T1: raw biochar; T2: modified biochar; T3: functional microbial agent; T4: carbon-based microbial agent; and T5: modified carbon-based microbial agent) and one control group (CK, no remediation reagent added) were set up in a pot experiment. 700 g of fresh coastal saline-alkali soil samples were placed in plastic pots (top diameter 12.7 cm, bottom diameter 10.9 cm, depth 9.5 cm) and then mixed thoroughly with the remediation reagents. The biochar addition was 2%, and the amount of microbial agent added was the same for all treatments. These treatments were incubated for 28 days in a greenhouse at 20–28℃. During soil incubation, distilled water was added to the soil to reach 60% field capacity. Wheat seeds were sown in the pots, 10 seeds per pot. 28 days after sowing, wheat plants were collected, washed with distilled water, and the aboveground parts were taken to measure plant height, fresh weight, dry weight, and chlorophyll content. Each treatment was replicated in triplicate.

[0037] 1.5 Analysis of Soil Physicochemical Properties and Enzyme Activity pH was measured using the potentiometric method (soil-to-water ratio 2.5:1); electrical conductivity (EC) was measured using a conductivity meter (soil-to-water ratio 5:1); soil organic matter content was measured using the oil bath heating potassium dichromate oxidation-volume method; total nitrogen was measured using the Kjeldahl distillation method; total phosphorus was measured using the hydrofluoric acid-perchloric acid digestion-molybdenum antimony colorimetric method; total potassium was measured using the hydrofluoric acid-perchloric acid digestion flame photometric method; available phosphorus was measured using 0.5 mol·L⁻¹. -1 NaHCO3 extraction (water-to-soil ratio 20:1), and determination by molybdenum antimony colorimetric method; determination of Na by atomic absorption spectrophotometry. + The concentration of sodium, the sodium adsorption ratio (SAR) is calculated as follows: .

[0038] Urease (UE) activity was determined using the sodium hypochlorite-phenol colorimetric method; sucrase (S-SC) activity was determined using the 3,5-dinitrosalicylic acid colorimetric method; catalase (CAT) activity was determined using the KMnO4 titration method; and alkaline phosphatase (ALP) activity was determined using the phosphomolybdicone benzidine colorimetric method. The enzyme activities of plant superoxide dismutase (SOD), malondialdehyde (MDA), and catalase (CAT) were determined using a test kit from Suzhou Keming Biotechnology Co., Ltd., and the peroxidase (POD) content was determined using a test kit from Nanjing Construction Co., Ltd., China.

[0039] 1.5 Analysis of Microbial Community Composition Soil DNA was extracted using the TGuide S96 magnetic bead method for soil genomic DNA extraction. The extracted DNA was used as a template for PCR amplification of the V3-V4 hypervariable region of bacterial 16S RNA. Bacterial amplification was performed using primers 338F / 806R. The amplification system was as follows: 95 °C pre-denaturation for 5 min; 25 cycles of 95 °C for 30 s, 50 °C for 30 s, and 72 °C for 40 s; and a final extension at 72 °C for 7 min. Detection was performed by 2% agarose gel electrophoresis. PCR products were recovered using 2% agarose gel electrophoresis, and the qualified PCR products were purified using VAHTS™ DNA Clean Beads. Library construction was performed using the TruSeq DNA Kit (Illumina). The fragment range and concentration of the library were detected using an Agilent 2100 Bioanalyzer. Libraries that passed the detection were sent to Beijing Biomarker Biotechnology Co., Ltd. for high-throughput sequencing using the Illumina NovaSeq6000 sequencing platform.

[0040] 1.6 Data Analysis Plant growth indicators and soil physicochemical indicators are expressed as mean and standard deviation. One-way ANOVA and Pearson correlation analysis were performed on the processed experimental data using statistical analysis software. Duncan's method was used to test for significant differences between treatments. P <0.05, P <0.01).

[0041] 2. Experimental Results 2.1 Results of Biochar Modification Process Optimization 2.1.1 Results of Single-Factor Experiment Different organic acid-modified biochar on its Na + Effects of different organic acid-modified biochar on Na+ adsorption performance + The effect of adsorption amount, such as Figure 1As shown. Under the conditions of a fixed material ratio of 1:25 (w / v), a modification temperature of 30℃, a modification time of 6 h, and a modification concentration of 0.5 M, modified biochar showed the effect of modifying Na... + The adsorption capacity of all three substances was significantly improved, with the improvement effect ranked as follows: oxalic acid > lactic acid > citric acid. Among these, oxalic acid adsorbed Na... + The concentration of oxalic acid was 259.04 mg / g, a significant increase of 27.27%. This may be because oxalic acid is more acidic, resulting in more pronounced hierarchical gaps and abundant surface pores in the modified biochar, which is conducive to the growth of Na+. + The adsorption of Na provides more adsorption sites. + The optimal organic acid for adsorption was determined to be oxalic acid.

[0042] Effect of oxalic acid concentration: The effect of different concentrations of oxalic acid-modified biochar on Na+ + The effect of adsorption amount, such as Figure 2 As shown. Under the conditions of a material ratio of 1:25 (w / v), a modification temperature of 30℃, an organic acid of oxalic acid, and a modification time of 6 h, the modified biochar showed a significant effect on Na+. + The adsorption capacity of all samples was significantly improved, showing an initial increase followed by a decrease, with the improvement effect ranked as follows: 0.5 M > 0.1 M > 1 M. Low concentrations of oxalic acid-modified biochar promoted its adsorption of Na+. + The adsorption of Na+ was inhibited by high concentrations of oxalic acid. This may be because the surface functional groups of biochar increase significantly at low concentrations, but surface functional group saturation occurs at high concentrations, affecting the adsorption of Na+ by the modified biochar. + Adsorption of Na. + The optimal oxalic acid concentration was determined to be 0.5 M based on the adsorption capacity.

[0043] Effect of modification time: The effect of oxalic acid-modified biochar on Na+ under different modification times + The effect of adsorption amount, such as Figure 3 As shown. When the modification time is 1 h-12 h, the modified biochar has a certain effect on Na. + The adsorption effect exhibited a peak-shaped curve, initially increasing and then decreasing with time, reaching a peak at 6 h, with significant differences. P <0.05), Na + The adsorption capacity was 259.04 mg / g. When the modification time was >6 h, the adsorption capacity of biochar Na... + The adsorption capacity showed a decreasing trend over time. This may be because long-term modification may cause oxalic acid or its byproducts to crystallize or precipitate on the surface of biochar, blocking pores and reducing effective adsorption sites.

[0044] Effect of modification temperature: Results are as follows Figure 4 As shown, when the modification temperature is 20-50℃, the modified biochar has a certain effect on Na. +The effect of adsorption exhibits a peak-shaped curve, initially increasing and then decreasing over time, reaching a peak at 30℃. Modified biochar is rich in carboxyl groups (-COOH), which can bind to sodium ions through ion exchange or coordination to form stable complexes. This chemical reaction can proceed efficiently at room temperature. Therefore, based on Na… + The optimal modification temperature was determined to be 30℃ based on the adsorption capacity.

[0045] Effect of solid-liquid ratio of biochar and oxalic acid: Modified biochar prepared with different material ratios on Na+ + The effect of adsorption capacity, such as Figure 5 As shown. When the material ratio is <1:25, the modified biochar has a significant effect on Na. + The adsorption capacity of modified biochar increases with increasing material ratio; when the material ratio > 1:25, the adsorption capacity of modified biochar for Na... + The adsorption capacity of modified biochar decreases with increasing material ratio. + The adsorption of Na first increases and then decreases with increasing material ratio, reaching a peak at a material ratio of 1:25. Therefore, according to Na... + The optimal material ratio for adsorption capacity was determined to be 1:25.

[0046] 2.1.2 Results of Box-Behnken Response Surface Experiment Based on the results of the single-factor experiments, a Box-Behnken response surface experimental design was adopted. The three key factors were modification concentration, material ratio, and modification time. A three-level experimental scheme was set up, and a total of 17 experimental points were arranged for analysis. The results are shown in Table 1.

[0047] Table 1 Response Surface Experimental Design and Results

[0048] Analysis of variance was performed on the data in Table 1. A quadratic multiple regression was used to fit the data using Design-Expert 13.0 software. A second-order polynomial regression model was used to represent the functional relationship between the scores and the independent variables, and a coding model was established: Na + The adsorption rate = +58.62 - 0.16×A - 1.03×B - 0.97×C - 0.26×A×B - 0.50×A×C - 0.67×B×C - 6.74×A² - 2.28×B² - 6.49×C². Actual equation model: Na +The adsorption rate is calculated as: -27.62 + 40.94X1 + 4.64X2 + 5.47X3 - 0.11X1×X2 - 0.25X1×X3 - 0.03X2×X3 - 33.28X1² - 0.09X2² - 0.32X3². In the coding model of this experiment, the coefficients of the quadratic terms are all negative, indicating the existence of a maximum point. Preliminary judgment suggests that this result aligns with the optimization objectives of this biochar modification process. Therefore, a variance analysis was subsequently performed on the experimental data, and the specific analysis results are shown in Table 2.

[0049] Table 2. Analysis of Variance of the Model

[0050] Note: * indicates statistical significance. P <0.05), ** indicates a significant difference ( P <0.01), *** indicates an extremely significant difference ( P <0.001).

[0051] The results of the significance analysis show that the model's P A value < 0.0001 indicates that the model difference is extremely significant and can accurately predict approximately 89.78% of the experimental results within the experimental range; lack of fit term P The value is 0.8695 ( P >0.05), indicating no statistically significant difference, further demonstrating a good model fit and small experimental error; the linear terms B (material ratio) and C (modification time) affect the modified biochar Na + The adsorption rates showed statistically significant differences. P <0.05), quadratic term B 2 Modified biochar Na + The adsorption rate is significantly affected ( P <0.01), quadratic term A 2 and C 2 Modified biochar Na + The adsorption rate is significantly affected ( P <0.001), while the interaction term affects the Na of modified biochar. + The adsorption rate was not significantly affected. P >0.05). Coefficient of determination R 2 =0.9879, indicating that the modified biochar has a positive effect on Na+. + The adsorption rate was significantly related to the three single-factor conditions investigated; the corrected coefficient of determination R² adj =0.9723, indicating that the model can explain 97.23% of the response value variation, which is relatively reliable. Judging from the F-value, these three factors affect the Na+ content of modified biochar. + The effect of adsorption rate is as follows: material ratio (B) > modification time (C) > modification concentration (A).

[0052] Three-dimensional response surface plots, by displaying the surface relationship between response values ​​and various influencing factors, can intuitively present the influence trend of the interaction of different influencing factors on the response values, as well as the range of change of the response values. This invention uses Design-Expert 13.0 software to analyze the interaction between three factors—modification concentration (A), material ratio (B), and modification time (C)—on the modified biochar Na. + The response surface methodology plot of the adsorption rate, as shown in the figure. Figure 6 As shown.

[0053] Modified biochar Na + The adsorption rate initially increases and then decreases within a certain range as the levels of various factors continuously increase. The response surface is entirely a downward-opening convex surface, indicating that the model has a maximum value. Figure 6 It can be seen that the steeper the slope of the curved surface, the denser the contour lines formed by the projection, indicating a greater interaction between the two factors. From Figure 6 It can be determined that the order of the interaction between the three factors of modification concentration (A), material ratio (B), and modification time (C) is AC > AB > BC.

[0054] 2.1.3 Determination of process parameters for modified biochar preparation Using Design-Expert 13.0 software analysis, combined with regression equations, response surfaces, and contour plots, the optimal preparation process parameters for modified biochar were determined: modification concentration 0.55 M, material ratio 1:24, modification time 7.21 h, and modification temperature 30℃. Under these optimal modification conditions, the modified biochar showed a significant effect on Na+. + The adsorption rate reached 58.77%. Considering the operability of the actual production process, the modified biochar preparation process was appropriately adjusted: the modification concentration was 0.5 M, the material ratio was 1:25, the modification time was 7 h, and the modification temperature was 30℃. Through Na… + Adsorption experiments were conducted to verify the accuracy of the model, and finally, Na was obtained. + The average adsorption rate was 58.47%, which is basically consistent with the predicted value (58.77%), indicating that the results are highly accurate and the preparation method of modified biochar optimized by this response surface methodology is feasible.

[0055] 2.1.4 Determination of the preparation method for carbon-based inoculants The carbon-based bacterial agent was prepared using the optimal preparation process determined in section 2.1.3. The specific method is as follows: 2 g of biochar was mixed with 50 mL of 0.5 M oxalic acid and incubated at 180 rpm at 30 °C for 7 h in a shaking incubator. The resulting biochar-acid mixture was centrifuged at 3000 g for 15 min to remove excess acid, and the biochar was washed with ultrapure water. This process was repeated three times to ensure complete removal of oxalic acid. After the washing process, the biochar was dried overnight in a hot air oven (60 ± 1 °C) to obtain modified char.

[0056] Modified charcoal of 30-80 mesh was obtained by sieving and sterilized at 121℃ for 30 min to obtain sterilized modified charcoal. A bacterial suspension was prepared by mixing *Bacillus huanghaiensis* BM-C55 and *Bacillus belyesense* IHRS7 at a 1:1 ratio, wherein the concentrations of both *Bacillus huanghaiensis* BM-C55 and *Bacillus belyesense* IHRS7 were 10. 8 CFU / mL. Sterile modified charcoal and bacterial suspension were mixed at a ratio of 1:20 (w / v) and incubated at 30℃ and 180 rpm for 4 h. After incubation, the mixture was separated using a 200-mesh sieve and washed three times with phosphate-buffered saline (PBS) solution to obtain the modified charcoal-based bacterial agent.

[0057] 2.2 Biochar modification and its effect on the activity of functional microbial agents Unmodified biochar has coarse pores, surface debris, and numerous small pores. Modified biochar retains the original physical morphology of rice husk biomass, with a smooth surface and increased pore size. Compared with unmodified original biochar, modified biochar increased the specific surface area, average pore size, and pore volume by 38.43%, 136.54%, and 383.33%, respectively (Table 3).

[0058] Table 3 BET analysis before and after biochar modification

[0059] FTIR spectroscopy revealed the chemical changes in the functional groups on the surface of the modified biochar, such as... Figure 8 As shown, the FTIR spectrum of biochar is in the range of 3000-3600 cm⁻¹. -1 1090cm -1 A broad band is observed at 1090 cm⁻¹, corresponding to the stretching vibration of the -OH group in the carboxyl group and the absorption peak of aliphatic CO, respectively. CO on the modified biochar surface shows an absorption peak at 1090 cm⁻¹. -1 The absorption peaks at the left and right edges broaden, and new characteristic vibrational bands appear. This may be due to the 1162 cm⁻¹ peak. -1 The characteristic peak, generated by COC-related glycosidic vibrations and the stretching vibrations resulting from -CH2 accumulation, can only be identified after acid modification. Furthermore, the modified biochar shows a peak at 1639 cm⁻¹. -1Corresponding to the stretching vibrations of aromatic C=C and C=O, 1735 cm -1 The characteristic vibrational bands of C=O functional groups corresponding to ester or ketone groups in rice husks increased in width after modification. This is because oxalic acid modification increases the number of C=O functional groups, which provide adsorption sites for salt ions in the modified biochar. These results indicate that oxalic acid modification increases the number of active functional groups on the biochar surface, particularly the O=CO functional groups, providing more active sites for salt ion adsorption and thus enhancing its adsorption capacity for salt ions. Figure 9 The XPS spectra further revealed the surface elemental composition and valence states of C and O on the biochar surface. Clearly, acid modification led to a significant increase in surface O content, indicating the presence of more OFGs (e.g., ester and carboxyl groups) on the modified biochar surface. High-resolution C1s XPS spectra showed three peaks at 284.8 eV, 286 eV, and 289 eV, representing C-C, C-O, and COOH functional groups, respectively. Compared to the original biochar, the modified biochar showed a new C=O functional group at 289 eV, with a content of 15.78%, indicating an increase in acidic functional groups on the modified surface. O1s XPS showed an increase in the number of -OH functional groups, from 73.34% to 92.93%.

[0060] Figure 7 show, Bacillus sp. successfully adhered to the surface and pore structure of biochar. Immobilization Bacillus sp. Plate counting method for measuring biochar Bacillus sp. is 9.0 × 10 8 The CFU / g and modified biochar concentrations are 12.2 × 10⁻⁶. 8 CFU / g. Salt-tolerant and growth-promoting strains are generally Bacillus species, with a diameter typically ranging from 0.5 to 5 μm, significantly larger than the pore size of biochar and modified biochar. This indicates that the strains are immobilized on the biochar carrier surface. Modified biochar provides numerous adsorption sites and protective cavities for Bacillus, and its larger specific surface area allows it to support a greater number of microorganisms. Therefore, the increased specific surface area and larger pore size of modified biochar are more beneficial for subsequent microbial immobilization.

[0061] 2.3 Effects of modified carbon-based inoculants on physiological and biochemical indicators of wheat under salt-alkali stress Under saline-alkali stress, plants experience physiological drought or a direct decrease in biomass due to high salinity and ion stress. For example... Figure 10The results showed that under saline-alkali conditions, biochar or modified biochar and compound microbial communities, whether applied alone or in combination, promoted the growth of wheat plants under salt stress. When modified biochar was applied, the plant height, fresh weight, and dry weight increased by 11.12%, 48.18%, and 32.07%, respectively, compared to the control group, while the functional microbial agents increased these by 18.41%, 39.06%, and 33.78%, respectively. Compared to the CK treatment, the T5 treatment significantly increased the plant height, chlorophyll content, aboveground fresh weight, and aboveground fresh weight by 25.58%, 25.51%, 57.89%, and 42.55%, respectively. This is likely because biochar, a carbon-based material, has a large surface area and high porosity, and contains nutrients such as carbon, nitrogen, phosphorus, and potassium, which can provide nutrients for plants. During the modification process, oxalic acid erosion and washing remove ash from the surface of biochar, expand pores and channels, thereby increasing pore size and specific surface area. Biochar-based microbial inoculants have a positive impact on the nutrient environment of plants and the diversity of root microorganisms. Biochar can adsorb and retain nutrients, forming a slow-release nutrient supply source. Simultaneously, biochar acts as a carrier, providing a favorable living environment for microorganisms, improving the growth of functional microorganisms in the soil, and thus promoting plant growth and development.

[0062] Abiotic stress can induce a surge in intracellular reactive oxygen species (ROS), producing large amounts of ROS. When cells initiate ROS scavenging mechanisms, they mobilize various intracellular antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), to increase their activity and remove excess ROS. Malondialdehyde (MDA) produced under salt stress and other accumulated peroxides can severely damage plant cells. Figure 11 The results showed that, compared with the control (CK), the MDA content of saline-alkali soil treated with modified biochar alone and the combined microbial community decreased by 30.62% and 57.54%, respectively. More importantly, the MDA content of saline-alkali soil treated with modified biochar-based microbial agents significantly decreased by 87.10%, further demonstrating the synergistic effect of modified biochar and functional microbial agents. Simultaneously, when modified biochar-based microbial agents were added to the soil, the activities of antioxidant enzymes (SOD, POD, and CAT enzymes) significantly increased, by 58.06%, 57.15%, and 12.58%, respectively. This suggests that oxidative stress in wheat plants may have been reduced, further mitigating the damage caused by salt stress. In conclusion, modified biochar-based microbial agents can significantly upregulate the expression of oxidative stress-related genes in plants, thereby reducing the damage caused by reactive oxygen species (ROS).

[0063] 2.4 Effects of modified carbon-based inoculants on the chemical properties and enzyme activity of saline-alkali soils Soil pH affects soil fertility through microbial activity, decomposition of minerals and organic matter, and the electrical properties of soil colloids. The chemical properties and enzyme activities of saline-alkali soils in each treatment group are shown in Tables 4 and 5. The results showed that soil pH decreased under treatments T2 and T5, with treatment T5 showing a significant decrease of 3.08%. This is because oxalic acid-modified biochar lowers pH and increases acidic functional groups, thereby reducing the application of alkaline substances to the soil. Biochar increases the amount of recalcitrant carbon in the soil to ensure the stability of the soil bacterial community and supplements organic carbon through the partial degradation of recalcitrant carbon, thus improving soil fertility. The organic matter content of the soil treated with added biochar was significantly higher than that of the control (CK) and T3, with treatments T4 and T5 showing significant increases of 152.02% and 152.31%, respectively. The addition of compound microbial communities had no significant effect on soil organic matter. Compared with the control (CK), application of T5 led to an increase of TN and AP contents of 18.25% and 24.04%, respectively, while TK contents decreased by 8.48%. Under environmental stress, biochar-based inoculants can promote photosynthetic capacity and biosynthesis of endogenous plant hormones in plants, leading to high uptake of TN, TP, and TK. Compared with the control (CK) treatment, AP content increased significantly by 10.96% and 23.04% in the T2 and T5 treatments, respectively. This indicates that biochar can provide phosphorus in a form easily absorbed by plants, thus addressing both short-term and long-term soil phosphorus deficiency. Furthermore, the sodium adsorption ratio (SAR) is commonly used to characterize Mg in soil. 2+ and Ca 2+ For exchangeable Na + The neutralizing effect of alkalization can predict the changing trends of the physicochemical properties of saline-alkali soils. The SAR value of the soil decreased after the application of biochar and modified carbon-based inoculants. Divalent metal cations (such as Ca) on the surface of biochar... 2+ Mg 2+ It can replace Na adsorbed in soil colloids. + This may be due to soil colloid Na. + The reason for the reduced free activity is that biochar has also been shown to reduce soil salinity by increasing soil porosity, reducing saline water upwelling, and accelerating salt leaching, thereby potentially reducing surface soil salt accumulation. This may contribute to the improvement of saline-alkali land by biochar. In summary, modified carbon-based microbial agents show that the synergistic effect of biochar and complex microbial communities can reduce soil pH and SAR, and increase soil organic matter, AP, and TN content.

[0064] Soil enzyme activity reflects microbial function, participates in many important biochemical processes, and is closely related to soil nutrients. Soil physicochemical properties such as pH, OM, AP, AN, and TN content can all significantly influence soil enzyme activity. Figure 12As shown, compared with the CK treatment, the urease and alkaline phosphatase activities in the soil under the T1 treatment were significantly increased by 2.48% and 9.29%, respectively. There was no significant difference in urease content between the T1 and T2 treatments, but both were higher than those under the T4 and T5 treatments. The alkaline phosphatase content and soil catalase also showed this trend under the T4 and T5 treatments. The study indicates that the application of carbon-based inoculants can increase the content of enzyme activities in the soil. This differs from the present invention, which may be because wheat is in a vigorous growth stage, with a rapid nutrient conversion rate and a high demand for soil nitrogen, resulting in a decrease in soil nitrogen content and a significant decrease in soil urease activity. The decrease in catalase activity may be because catalase activity is significantly positively correlated with pH, ​​and the application of modified biochar leads to a decrease in environmental pH. Soil sucrase content increased in all five treatments, with no significant difference between treatments. Among them, the T5 treatment showed a significant increase of 16.54% compared to the CK treatment.

[0065] Table 4. Concentration of salt ions in soil samples after CK and T1-5 treatments

[0066] Table 5 Effects of different treatments on soil chemical properties

[0067] 2.5 Effects on microbial community structure under saline-alkali stress This invention found that the combined application of modified biochar and functional microbial agents is beneficial in influencing microbial metabolic activities and significantly altering soil microorganisms. The effects of different treatments on soil microorganisms are shown in [see figure]. Figure 13-19 This invention, through alpha diversity analysis of soil microbial communities, revealed that the T5 treatment exhibited higher diversity. This indicates that bacteria possess the richest and most diverse taxonomic groups in saline-alkali soils. Bacteria are more sensitive to changes in the soil environment and prefer to grow in nutrient-rich soils. This could explain why bacterial community diversity was relatively high in the nutrient-rich T5 treatment.

[0068] PCoA analysis showed significant differences in bacterial community composition among different treatments. Compared to the control (CK), the T5 treatment exhibited the most significant difference in bacterial community composition, followed by the T4, T2, and T1 treatments. This indicates that the addition of biochar had the most significant impact on bacterial community composition. Proteobacteria (…) Proteobacteria ), Acidobacteria ( Acidobacteriota ), Bacillus phylum ( Gemmatimonadota ), Actinobacteria ( Actinobacteria Bacteroidetes ( Bacteroidota Firmicutes are the dominant phylum, accounting for over 70% of the total bacterial community. Notably, Firmicutes were more abundant in the T5 treatment. Further analysis revealed that Proteobacteria (…) Proteobacteria), Acidobacteria ( Acidobacteriota ), Actinobacteria ( Actinobacteria Significant differences were observed in bacteria from the four phyla (including Firmicutes, Firmicutes, and others) under different treatments. P Further analysis of the distribution of soil bacterial communities at the genus level (<0.05) revealed that the six most dominant taxa among genera with a relative abundance ≥1% mainly belonged to the phylum Proteobacteria ( ). Proteobacteria ), Acidobacteria ( Acidobacteriota ), Bacillus phylum ( Gemmatimonadota ), Actinobacteria ( Actinobacteria The T5 treatment significantly increased the abundance of Firmicutes, indicating that modified biochar improved the colonization of functional microorganisms. Increased abundance of Firmicutes in soil

[40] These bacteria can promote nutrient cycling and organic matter degradation, and also have good stress resistance and biological control effects. They can form a symbiotic relationship with plants, provide protection for plants, and thus promote the growth of wheat plants.

[0069] Minimum discriminant analysis (LDA) showed significant differences in phylum to genus classification (LDA > 3.5). Linear discriminant analysis (LefSe) results indicated significant differences among the 62 bacterial taxa across treatments. Among bacteria, the CK, T3, and T5 treatments showed the most significant differences, with the CK treatment group exhibiting the most pronounced differences. Vicinamibacterales , Xanthomonadaceae , Hymenobacter and Lysobacter Significant enrichment of bacterial genera, with Bacillus spp. being particularly abundant in the T3 treatment group. Gemmatimonas Significant enrichment was observed in Bacillus spp. in the T5 treatment group. Bacillus Bacteroides bacteroidales , Erysipelotrichales , Clostridia and Muribaculum The bacteria showed significant enrichment. This indicates that the modified carbon-based bacteria promoted the colonization of Bacillus in the soil.

[0070] 2.6 Effects on microbial networks under saline-alkali stress Based on the abundance and variation of each species in each sample, Spearman rank correlation analysis was performed, and data with correlations greater than 0.1 and p-values ​​less than 0.05 were selected to construct a correlation network. Figure 20 As shown, the parameters include the number of nodes, the number of edges, and modularity; specific values ​​for each parameter are shown in the table. In the six networks, bacteria belong to six main phyla: Proteobacteria (…). Proteobacteria ), Acidobacteria ( Acidobacteriota ), Bacillus phylum ( Gemmatimonadota ), Actinobacteria ( Actinobacteria ), Bacillus phylum ( Gemmatimonadota ) and Firmicutes ( FirmicutesT5 treatment adds Firmicutes to key nodes ( ). Firmicutes Bacillus belongs to the Firmicutes phylum, indicating that the addition of modified carbon-based inoculants is beneficial to their survival in the soil. Regarding bacteria, the number of edges, modules, network diameter, and average clustering coefficient of the soil microbial networks were similar across treatments; however, treatments T1 and T5 showed the highest number of points and modularity. The average path length increased in treatment T5, indicating that the addition of modified carbon-based inoculants increased the richness of soil microorganisms, strengthened interactions among them, and increased resistance to the external environment. Therefore, modified biochar and composite microbial communities, alone or in combination, can influence soil bacterial communities by recruiting specific key taxa.

[0071] 2.7 Relationship between wheat rhizosphere microorganisms and soil properties To explain the changes in soil microbial diversity under different amendments, the relationship between soil properties and microbial community structure was studied at the phylum level using RDA (Research-Based Analysis). Figure 21 The soil environmental factors in the first two main RDA axes, 1 and 2, represent 60.37% and 17.10% of the total variation in microbial composition, respectively. PC1 reflects the effects of soil N, SOM, SOD, and POD on plant growth (plant height and root length), while PC2 reflects the effects of pH, soil N and P, and salinity on microbial community structure. The control soil exhibits typical saline-alkali soil characteristics such as high soil salinity and poor soil nutrients. However, biochar significantly alleviates these problems mainly by improving exchangeable salt ion stress and increasing soil SOM, N, P, K, and antioxidant enzyme activity, especially the mitigation of exchangeable salt ion stress by modified biochar-based inoculants. This can be observed through the correlation between AP, SOM, AN, SOD, POD, sucrase, and plant height with soil salinity (…). p The negative correlation between Firmicutes and Bacteroidetes (<0.05) was confirmed in this invention. Bacteroidota The relative content of these compounds was positively correlated with SOM, AN, and AP, and negatively correlated with salinity. In conclusion, the addition of modified carbon-based inoculants altered the composition of soil microorganisms, and these changes may be related to changes in soil properties.

[0072] 2.8 Potential Mechanisms of Modified Carbon-Based Bacterial Agents in Improving Saline-Alkali Land Wheat plant growth showed significant differences among different treatments. Corn plants in the control soil could not grow normally due to high soil salinity and nutrient deficiency; however, the application of modified biochar, functional microbial agents, and modified carbon-based microbial agents significantly improved plant growth, especially the modified carbon-based microbial agents. This indicates that modified biochar, functional microbial agents, and modified carbon-based microbial agents can all improve the amelioration effect of coastal saline-alkali soil and promote wheat growth. The positive correlation between plant height and AP, SOM, AN, SOD, and POD further confirms this.

[0073] Example 2 1. Experimental Methods Three potted plant experiments were set up (the repair reagents were set as T5: modified carbon-based bacterial agent, T6: modified carbon-based bacterial agent-BM-C55, and T7: modified carbon-based bacterial agent-IHRS7, respectively) and one control group (CK, without the repair reagent).

[0074] The preparation method of the modified carbon-based bacterial agent of T5 is the same as that in section 2.1.4 of Example 1.

[0075] The preparation method of T6 modified carbon-based bacterial agent - BM-C55 is as follows: Sterilized modified carbon is prepared using method 2.1.4. Bacillus huanghaiense BM-C55 is prepared into a bacterial suspension (concentration 10). 8 The sterilized modified charcoal and bacterial suspension were mixed at a ratio of 1:20 (w / v) and incubated at 30°C and 180 rpm for 4 h. After incubation, the mixture was separated using a 200-mesh sieve and washed three times with phosphate-buffered saline (PBS) solution to obtain the modified charcoal-based bacterial agent -BM-C55.

[0076] The preparation method of T7 modified carbon-based bacterial agent - IHRS7 is as follows: Sterilized modified carbon is prepared using method 2.1.4. Bacillus belyeis IHRS7 is then formulated into a bacterial suspension (concentration 10). 8 The sterilized modified charcoal and bacterial suspension were mixed at a ratio of 1:20 (w / v) and incubated at 30°C and 180 rpm for 4 h. After incubation, the mixture was separated using a 200-mesh sieve and washed three times with phosphate-buffered saline (PBS) solution to obtain the modified charcoal-based bacterial agent - IHRS7.

[0077] The potted plant experiment is as follows: 700 g of fresh coastal saline-alkali soil samples were placed in plastic basins (top diameter 12.7 cm, bottom diameter 10.9 cm, depth 9.5 cm) and then mixed thoroughly with the remediation reagent. Biochar was added at a rate of 2%, and the amount of inoculant added was the same for all treatments. All treatments were incubated for 28 days in a greenhouse at 20–28°C. During soil incubation, distilled water was added to the soil to achieve 60% field capacity. Wheat seeds were sown in the basins, 10 seeds per basin. 28 days after sowing, wheat plants were collected, washed with distilled water, and the above-ground parts were used to measure plant height, fresh weight, dry weight, and chlorophyll content. Each treatment was replicated in triplicate.

[0078] 2. Experimental Results Table 6 shows the statistical results of wheat plant height, weight, and chlorophyll content in different treatment groups, and Table 7 shows the salt ion concentration in the soil samples after treatment. The results show that, compared with the modified carbon-based bacterial agent prepared by a single bacterium, the modified carbon-based bacterial agent prepared by combining Bacillus huanghaiensis BM-C55 and Bacillus belyes IHRS7 can effectively alleviate the effects of salt stress on wheat.

[0079] Table 6. Wheat plant height, fresh weight, and chlorophyll content in different treatment groups

[0080] Table 7. Concentration of salt ions in soil samples after CK and T5-7 treatments.

[0081] The potential mechanisms by which modified carbon-based microbial agents improve saline-alkali soil may include: (1) Modified biochar has a strong adsorption capacity, which can adsorb salt in saline-alkali soil, thereby reducing saline-alkali stress or alleviating plant stress response; (2) Modified carbon-based microbial agents contain rich nutrients (such as N and P), which can directly enhance soil fertility for plant growth. Among them, functional microbial agents can improve the salt tolerance of plants so that they can adapt to saline habitats, and can also improve saline-alkali soil by utilizing their interaction with host plants; (3) Modified biochar can provide a good living environment for soil microorganisms and microbial enzymes, improve the colonization of functional microbial agents, thereby alleviating the toxic effects of salt stress on wheat. In general, modified carbon-based microbial agents are a new type of soil conditioner that can improve soil fertility and plant nutrient absorption, thereby improving coastal saline-alkali soil and promoting wheat plant growth. Figure 22 ).

[0082] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A modified carbon-based microbial agent for improving saline-alkali land, characterized in that, Including modified biochar, Bacillus thuringiensis (Bacillus thuringiensis) Bacillus marisflavi BM-C55 and Bacillus belysinus ( Bacillus velezensis IHRS7; The Bacillus huanghaiensis BM-C55 and the Bacillus belyi IHRS7 were loaded in the modified biochar; The modified biochar is oxalic acid-modified biochar. The Bacillus huanghaiensis BM-C55 and Bacillus belyss IHRS7 have accession numbers of CGMCC No. 32788 and CGMCC No. 30948, respectively, at the China General Microbiological Culture Collection Center.

2. A method for preparing the modified carbon-based bacterial agent as described in claim 1, characterized in that, The process includes the steps of mixing modified biochar and bacterial suspension, culturing with shaking, and separating the modified biochar-based bacterial agent. The bacterial suspension contains the Bacillus huanghaiensis BM-C55 and the Bacillus belyssus IHRS7.

3. The preparation method according to claim 2, characterized in that, In the bacterial suspension, the ratio of Bacillus huanghaiensis BM-C55 to Bacillus belyi IHRS7 is 1:

1.

4. The preparation method according to claim 2, characterized in that, The temperature for the oscillation culture was 30°C.

5. The preparation method according to claim 2, characterized in that, The method for preparing the modified biochar includes the step of mixing and reacting biochar with an aqueous oxalic acid solution to obtain the modified biochar.

6. The preparation method according to claim 5, characterized in that, The concentration of the oxalic acid aqueous solution is 0.5 M; The mass-to-volume ratio of the biochar to the oxalic acid aqueous solution is 1 g: 25 mL; The mixing reaction was carried out at a temperature of 30°C for 7 hours.

7. The application of the modified carbon-based bacterial agent as described in claim 1 in the preparation of saline-alkali land improvement products.

8. A product for improving saline-alkali land, characterized in that, Includes the modified carbon-based bacterial agent as described in claim 1.

9. The application of the modified carbon-based bacterial agent as described in claim 1 in the improvement of saline-alkali land.

10. A method for improving saline-alkali land, characterized in that, The method includes the step of applying the modified carbon-based microbial agent of claim 1 to saline-alkali land.

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