Biochar-based immobilized microbial inoculum for promoting decomposition of litter and preparation method of biochar-based immobilized microbial inoculum

Abstract

The invention belongs to the field of microorganisms, and particularly relates to a biochar-based immobilized microbial agent for promoting litter decomposition and a preparation method thereof.The biochar-based immobilized microbial agent for promoting litter decomposition comprises a biochar-based culture medium and a microbial seed solution, the active ingredient of the microbial seed solution is phanerochaete chrysosporium, and the preservation number is SHBCC D13411. According to the invention, the adsorption efficiency of the microbial agent is enhanced through the iron-modified biochar, and a habitat suitable for development and reproduction is provided for microorganisms; on the other hand, the biochar has very strong hygroscopicity, water molecules can be adsorbed on the surface, and a suitable growth environment is provided for microorganisms, so that the microorganisms are promoted to decompose litters.

Description

Technical Field

[0001] The present invention belongs to the field of microorganisms, and in particular relates to a biochar-based immobilized bacterial agent for promoting the decomposition of litter and a preparation method thereof. Background Art

[0002] Litter refers to all organic matter produced by above-ground plant components within an ecosystem and returned to the ground surface, serving as a source of material and energy for decomposers, thereby maintaining ecosystem functions. Forest litter decomposition is the primary pathway for the transfer of carbon and nutrients from plants to the soil, and is a crucial link in the material cycle and energy flow within the ecosystem. It plays a vital role in maintaining soil fertility and promoting normal material circulation and nutrient balance in forest ecosystems. Litter decomposition involves physical, chemical, and biological processes, with the key to litter decomposition being the enzymatic hydrolysis of litter by microbial litterases and soil enzyme systems.

[0003] For long-term artificial management of afforestation tree species such as Chinese pine and larch, the stability and maintenance of soil fertility are very important. Promoting the decomposition of coniferous forest litter, increasing the rate of nutrient return, and maintaining soil fertility stability are one of the key issues in the sustainable management of artificial forests.

[0004] However, due to the inherent characteristics of coniferous forest litter: well-developed cuticle, mostly thick leathery, containing more difficult-to-decompose substances (such as lignin and cellulose, etc.), it is not conducive to microbial decomposition, nor is it conducive to precipitation leaching and damage by soil animals, and decomposition is slow; at the same time, there are fewer bacteria in the natural environment soil that degrade lignin. The main bacteria in the soil are Bacillus, which has a good decomposition effect on cellulose, but has difficulty decomposing lignin; in addition, free microorganisms are affected by the physical and chemical properties of litter and soil, resulting in low microbial content, poor biological activity and low decomposition efficiency in the litter layer. Therefore, it is necessary to develop a bacterial agent suitable for decomposing litter containing high lignin. Summary of the Invention

[0005] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a biochar-based immobilized bacterial agent for promoting the decomposition of litter and a preparation method thereof. The iron-modified biochar enhances the adsorption efficiency of the microbial agent, providing a habitat suitable for the development and reproduction of microorganisms; on the other hand, biochar has strong hygroscopicity and can adsorb water molecules on the surface, providing a suitable growth environment for microorganisms, thereby promoting the decomposition of litter by microorganisms.

[0006] The specific technical solution adopted in the present invention is:

[0007] A biochar-based immobilized bacterial agent for promoting the decomposition of litter, comprising a biochar-based culture medium and a microbial seed solution, wherein the active ingredient of the microbial seed solution is Phanerochaete chrysosporium, with a preservation number of SHBCCD13411.

[0008] Furthermore, the biochar-based culture medium comprises, by mass, 4-6 parts of melamine, 45-55 parts of iron-modified biochar, 25-35 parts of PDA culture medium and 12-16 parts of wheat bran.

[0009] Furthermore, the method for preparing the biochar-based culture medium comprises the following steps:

[0010] S1. Preparation of iron-modified biochar;

[0011] S201, adding melamine into water to obtain a melamine suspension;

[0012] S202, adding the iron-modified biochar to the melamine suspension and shaking, allowing it to stand to obtain a precipitate, and drying the precipitate to a constant weight to obtain material C;

[0013] S203, adjusting the pH value of the PDA culture medium to 4.5-4.8 using potassium dihydrogen phosphate;

[0014] S204, adding material C and wheat bran into PDA culture medium and mixing evenly, and obtaining biochar-based culture medium after sterilization.

[0015] Furthermore, in step S202, the ratio of the iron-modified biochar to the melamine suspension is 1:18-22.

[0016] Furthermore, the preparation method of the iron-modified biochar comprises the following steps:

[0017] S101, screening the bio-based raw materials, washing them, drying them at 55-65° C. for 45-50 hours, crushing them, and passing them through a 40-50 mesh sieve to obtain material A;

[0018] S102, Fe2(SO4)3·7H2O and material A were mixed and stirred in water, filtered to obtain a filter residue, and then the filter residue was dried to constant weight, ground, and passed through a 60-80 mesh sieve to obtain material B;

[0019] S103. Place material B in a heating furnace, pyrolyze it at 500-750° C. for 2-3 hours under the protection of nitrogen, and cool it to room temperature after pyrolysis to obtain iron-modified biochar.

[0020] Furthermore, in step S102, the Fe2(SO4)3·7H2O and material A are mixed and stirred in water at a mass ratio of 1:10-20.

[0021] A method for preparing a biochar-based immobilized bacterial agent for promoting litter decomposition, the method comprising the following steps:

[0022] S301. After inoculating and activating Phanerochaete chrysosporium, inoculate into liquid PDA culture medium and incubate at 26-28°C and 140-160 r·min -1 Cultivate in a culture vessel for 2-4 days to obtain a microbial seed solution;

[0023] S302, inoculating the biochar-based culture medium into the microbial seed solution, placing the culture medium in an incubator and continuing to culture for 4-5 days, then drying and grinding the bacterial agent in the incubator, and passing it through a 60-100 mesh sieve to obtain a biochar-based immobilized bacterial agent.

[0024] Furthermore, in step S302, 0.02 parts by mass of microbial seed liquid is added to each part by mass of the biochar-based culture medium.

[0025] A method for applying a biochar-based immobilized bacterial agent for promoting the decomposition of litter, wherein the biochar-based immobilized bacterial agent is evenly spread on the surface of a forest at an application rate of 10-20 kg / mu.

[0026] Furthermore, the biochar-based immobilized bacterial agent is subjected to coating and granulation treatment before spreading to form bacterial agent particles, and the bacterial agent particles are evenly spread on the surface of the forest land. The steps of the coating and granulation treatment are as follows:

[0027] A1. Prepare a coating solution by preparing 1.5-2 parts of chitosan, 0.8-1.2 parts of sodium alginate, 0.5-1 parts of polyvinyl alcohol, and 0.1-0.3 parts of magnesium stearate by weight;

[0028] A2. Add chitosan to an aqueous acetic acid solution and stir at 50-60° C. to form a viscous solution A;

[0029] A3. Dissolve sodium alginate in water, then shear and disperse at a speed of 1000-1200 r / min to form solution B. Add solution B to solution A, adjust the pH to 5.5-6.0, and stir to form a mixed solution.

[0030] A4. Add polyvinyl alcohol to water and stir at 90-95°C for 1-1.5 hours to form solution C. After solution C cools to below 30°C, add it to the mixed solution. Then, add magnesium stearate and ultrasonically disperse for 10-15 minutes to obtain a coating solution.

[0031] B. placing the biochar-based immobilized bacterial agent powder in a fluidized bed, starting the fluidized bed, and starting the spray gun after the biochar-based immobilized bacterial agent powder is fluidized and stabilized. The coating liquid is evenly sprayed onto the surface of the biochar-based immobilized bacterial agent powder by means of the spray gun to form a coating film;

[0032] C. After coating, dry the film. After the film solidifies, pass it through a 60-80 mesh sieve to form bacterial agent particles.

[0033] The beneficial effects of the present invention are:

[0034] 1. Phanerochaete chrysosporium is a known highly efficient lignin-degrading fungus. Compared with Bacillus sp., which mainly decomposes cellulose in natural soil, this fungal agent can specifically solve the problem of high lignin content and difficulty in decomposition in coniferous forest litter.

[0035] The Phanerochaete chrysosporium and the biochar carrier of the present invention produce a synergistic effect. On the one hand, the iron-modified biochar enhances the adsorption efficiency of microbial agents and anions such as phosphate by improving the carrier properties such as the specific surface area and pore volume of the biochar, while providing a habitat suitable for the development and reproduction of microorganisms, protecting the microorganisms from adverse factors such as soil pH fluctuations and heavy metal stress, and reducing the risk of microorganisms being exposed to external stress environments; on the other hand, the biochar has strong hygroscopicity and can adsorb water molecules on the surface, providing a suitable growth environment for microorganisms.

[0036] 2. The ratio of iron-modified biochar to melamine suspension in the present invention is 1:18-22, meaning the biochar culture medium has a C / N ratio of 20. This ratio is crucial for microbial fermentation and decomposition, promoting microbial growth and the expression and accumulation of exogenous proteins. Nitrogen is an essential nutrient for microbial growth and development and is easily immobilized and enriched by microorganisms. The C / N ratio in pine needles is as high as over 80. Adding melamine reduces this ratio and provides a nitrogen source for microbial growth. Phanerochaete chrysosporium is an important white-rot fungus with a strong lignin-degrading ability. It can invade wood cell cavities and release enzymes that degrade lignin and other wood components.

[0037] 3. In addition to changing the pore structure of biochar, the iron modification in the present invention can also improve the decomposition efficiency of lignin by Phanerochaete chrysosporium.

[0038] Phanerochaete chrysosporium is a typical lignin-degrading fungus. The synthesis and activity of key enzymes such as lignin peroxidase and manganese peroxidase secreted by it depend on iron (Fe 2+ / Fe 3+ ) as a cofactor, iron-modified biochar fixes iron in the biochar structure through the pyrolysis process, which can slowly release iron ions, provide essential trace elements for bacterial growth, directly promote the synthesis and catalytic efficiency of lignin-degrading enzymes, and thus accelerate the decomposition of litter.

[0039] 4. The biochar-based immobilized bacterial agent in the present invention needs to be coated and granulated before application, and then spread. When a drone is used for aerial spreading, the bacterial agent particles formed by coating and granulation can roll from the leaves or branches of the plant to the ground surface, and then fall on the surface of the litter, and will not stay on the surface of the plant. If it rains, the dissolved bacterial agent particles will also penetrate into the soil and decompose the litter in the inner layer of the soil. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. 1. Specific embodiments

[0042] The bio-based raw material described in the present invention is straw or peanut shell.

[0043] Example 1

[0044] S101, preparing iron-modified biochar, screening straw, washing it with deionized water 2-3 times, drying it at 60° C. for 48 h, and then crushing it through a 40-mesh sieve to obtain material A;

[0045] S102, Fe2(SO4)3·7H2O and material A were mixed in deionized water at a ratio of 1:15, with a stirring speed of 300 r / min and a stirring time of 24 h, and filtered to obtain a filter residue, which was then dried at 80°C to a constant weight, ground, and passed through a 60-mesh sieve to obtain material B;

[0046] S103, placing material B in a tubular atmosphere furnace, under nitrogen protection, heating to 650°C at a heating rate of 10°C / min, pyrolyzing for 2 hours, and naturally cooling to room temperature after pyrolysis to obtain iron-modified biochar;

[0047] S201, preparing a melamine suspension by adding 5 g of melamine to 1 L of deionized water;

[0048] S202, adding the iron-modified biochar to the melamine suspension, shaking, standing for 2 hours to obtain a precipitate, and drying the precipitate at 60° C. to a constant weight to obtain material C;

[0049] The ratio of iron-modified biochar to melamine suspension is 1:18-22;

[0050] S203, adjusting the pH value of the PDA culture medium to 4.5 using potassium dihydrogen phosphate;

[0051] S204, adding material C and wheat bran into the PDA culture medium and mixing them evenly, sterilizing them in a vertical high-pressure steam sterilizer with steam at 121° C. for 20 minutes, and then taking them out to obtain a biochar-based culture medium;

[0052] S301, after inoculating and activating Phanerochaete chrysosporium for 2 generations, inoculate into 100 ml of liquid PDA medium and incubate at 28°C and 150 r·min -1 The microorganism seed solution was prepared by expanding the culture in an air bath constant temperature oscillator for 3 days;

[0053] S302. The biochar-based culture medium is inoculated into the microbial seed solution at a ratio of 50:1, and the culture is continued in an air bath constant temperature oscillator for 4 days. The bacterial agent in the air bath constant temperature oscillator is then dried at a temperature below 40°C, ground, and passed through a 60-mesh sieve to obtain a biochar-based immobilized bacterial agent.

[0054] Example 2

[0055] S101, preparing iron-modified biochar, screening straw, washing it with deionized water 2-3 times, drying it at 60° C. for 48 h, and then crushing it through a 45-mesh sieve to obtain material A;

[0056] S102, Fe2(SO4)3·7H2O and material A were mixed in deionized water at a ratio of 1:10, with a stirring speed of 300 r / min and a stirring time of 24 h, and filtered to obtain a filter residue, which was then dried at 80°C to a constant weight, ground, and passed through a 70-mesh sieve to obtain material B;

[0057] S103, placing material B in a tubular atmosphere furnace, under nitrogen protection, heating to 500°C at a heating rate of 10°C / min, and pyrolyzing for 3 hours, and naturally cooling to room temperature after pyrolysis to obtain iron-modified biochar;

[0058] S201, preparing a melamine suspension by adding 5 g of melamine to 1 L of deionized water;

[0059] S202, adding the iron-modified biochar to the melamine suspension, shaking, standing for 2 hours to obtain a precipitate, and drying the precipitate at 60° C. to a constant weight to obtain material C;

[0060] The ratio of iron-modified biochar to melamine suspension was 1:18;

[0061] S203, adjusting the pH value of the PDA culture medium to 4.8 using potassium dihydrogen phosphate;

[0062] S204, adding material C and wheat bran into the PDA culture medium and mixing them evenly, sterilizing them in a vertical high-pressure steam sterilizer with steam at 121° C. for 20 minutes, and then taking them out to obtain a biochar-based culture medium;

[0063] S301, after inoculating and activating Phanerochaete chrysosporium for 2 generations, inoculate into 100 ml of liquid PDA medium and incubate at 28°C and 150 r·min -1The microorganism seed solution was prepared by expanding the culture in an air bath constant temperature oscillator for 2 days;

[0064] S302. The biochar-based culture medium is inoculated into the microbial seed solution at a ratio of 50:1, and the culture is continued in an air bath constant temperature oscillator for 2 days. The bacterial agent in the air bath constant temperature oscillator is then dried at a temperature below 40° C., ground, and passed through a 100-mesh sieve to obtain a biochar-based immobilized bacterial agent.

[0065] Example 3

[0066] S101, preparing iron-modified biochar, screening straw, washing it with deionized water 2-3 times, drying it at 60° C. for 48 h, and then crushing it through a 50-mesh sieve to obtain material A;

[0067] S102, Fe2(SO4)3·7H2O and material A were mixed in deionized water at a ratio of 1:20, with a stirring speed of 300 r / min and a stirring time of 24 h, and filtered to obtain a filter residue, which was then dried at 80°C to a constant weight, ground, and passed through an 80-mesh sieve to obtain material B;

[0068] S103, placing material B in a tubular atmosphere furnace, under nitrogen protection, heating to 750°C at a heating rate of 10°C / min, pyrolyzing for 2 hours, and naturally cooling to room temperature after pyrolysis to obtain iron-modified biochar;

[0069] S201, preparing a melamine suspension by adding 5 g of melamine to 1 L of deionized water;

[0070] S202, adding the iron-modified biochar to the melamine suspension, shaking, standing for 2 hours to obtain a precipitate, and drying the precipitate at 60° C. to a constant weight to obtain material C;

[0071] The ratio of iron-modified biochar to melamine suspension was 1:22;

[0072] S203, adjusting the pH value of the PDA culture medium to 4.6 using potassium dihydrogen phosphate;

[0073] S204, adding material C and wheat bran into the PDA culture medium and mixing them evenly, sterilizing them in a vertical high-pressure steam sterilizer with steam at 121° C. for 20 minutes, and then taking them out to obtain a biochar-based culture medium;

[0074] S301, after inoculating and activating Phanerochaete chrysosporium for 2 generations, inoculate into 100 ml of liquid PDA medium and incubate at 28°C and 150 r·min -1 The microorganism seed solution was prepared by expanding the culture in an air bath constant temperature oscillator for 2 days;

[0075] S302. The biochar-based culture medium is inoculated into the microbial seed solution at a ratio of 50:1, and the culture is continued in an air bath constant temperature oscillator for 2 days. The bacterial agent in the air bath constant temperature oscillator is then dried at a temperature below 40° C., ground, and passed through a 100-mesh sieve to obtain a biochar-based immobilized bacterial agent.

[0076] Comparative Example 1

[0077] The only difference between Comparative Example 1 and Example 1 is that the biochar in Comparative Example 1 uses ordinary biochar, and the specific preparation method is as follows:

[0078] S101, preparing biochar, screening straw, washing with deionized water 2-3 times, drying at 60° C. for 48 h, and then grinding through a 40-mesh sieve to obtain material A;

[0079] S102, stirring the material in deionized water at a stirring speed of 300 r / min for 24 h, filtering to obtain a filter residue, and then drying the filter residue at 80° C. to a constant weight, grinding it, and passing it through a 60-mesh sieve to obtain material B;

[0080] S103, placing material B in a tubular atmosphere furnace, under nitrogen protection, heating to 650°C at a heating rate of 10°C / min, pyrolyzing for 2 hours, and naturally cooling to room temperature after pyrolysis to obtain biochar;

[0081] S201, preparing a melamine suspension by adding 5 g of melamine to 1 L of deionized water;

[0082] S202, adding biochar to the melamine suspension and shaking, allowing it to stand for 2 hours to obtain a precipitate, and drying the precipitate at 60° C. to a constant weight to obtain material C;

[0083] The ratio of biochar to melamine suspension is 1:18-22;

[0084] S203, adjusting the pH value of the PDA culture medium to 4.5 using potassium dihydrogen phosphate;

[0085] S204, adding material C and wheat bran into the PDA culture medium and mixing them evenly, sterilizing them in a vertical high-pressure steam sterilizer with steam at 121° C. for 20 minutes, and then taking them out to obtain a biochar-based culture medium;

[0086] S301, after inoculating and activating Phanerochaete chrysosporium for 2 generations, inoculate into 100 ml of liquid PDA medium and incubate at 28°C and 150 r·min -1 The microorganism seed solution was prepared by expanding the culture in an air bath constant temperature oscillator for 3 days;

[0087] S302. The biochar-based culture medium is inoculated into the microbial seed solution at a ratio of 50:1, and the culture is continued in an air bath constant temperature oscillator for 4 days. The bacterial agent in the air bath constant temperature oscillator is then dried at a temperature below 40°C, ground, and passed through a 60-mesh sieve to obtain a biochar-based immobilized bacterial agent.

[0088] Comparative Example 2

[0089] The only difference between Comparative Example 2 and Example 1 is that the ratio of biochar to melamine suspension in Comparative Example 2 is 1:10, and the remaining steps are the same as in Example 1.

[0090] 2. Performance Testing

[0091] A 40-year-old Chinese pine plantation was selected as the test plot. Nine 1m*1m experimental plots were set for Examples 1-3, Comparative Examples 1-2, and a blank control (no bacterial agent was applied), with a total of 54 plots. The initial litter reserves were weighed and the initial lignin content was determined. The biochar-based immobilized bacterial agents obtained in Examples 1-3 and Comparative Examples 1-2 were then applied to each of the nine plots, with the application rate of the bacterial agent being 2‰ of the total litter volume. Three plots were then selected for sampling at 30d, 75d, and 120d, respectively. The samples were dried to constant mass and weighed to determine their mass loss rate and lignin content. The lignin content was determined by acid washing. The decomposition results are shown in Table 1.

[0092] Table 1

[0093]

[0094] It can be seen that the weight loss rate of Example 1 reached 25.89% at 120 days, which is 1.63 times that of the blank group, and the lignin content was 12.85%, which is 53.68% of the blank group. There was no significant difference between Examples 1, 2, and 3, and all were significantly greater than the blank group and Comparative Examples 1 and 2.

Claims

1. A biochar-based immobilized bacterial agent for promoting litter decomposition, characterized in that: The microbial agent comprises a biochar-based culture medium and a microbial seed solution. The active ingredient of the microbial seed solution is Phanerochaete chrysosporium, and the preservation number is SHBCC D13411.

2. The biochar-based immobilized bacterial agent for promoting litter decomposition according to claim 1, characterized in that: The biochar-based culture medium comprises, by mass, 4-6 parts of melamine, 45-55 parts of iron-modified biochar, 25-35 parts of PDA culture medium and 12-16 parts of wheat bran.

3. The biochar-based immobilized bacterial agent for promoting litter decomposition according to claim 1, characterized in that: The preparation method of the biochar-based culture medium comprises the following steps: S1. Preparation of iron-modified biochar; S201, adding melamine into water to obtain a melamine suspension; S202, adding the iron-modified biochar to the melamine suspension and shaking, allowing it to stand to obtain a precipitate, and drying the precipitate to a constant weight to obtain material C; S203, adjusting the pH value of the PDA culture medium to 4.5-4.8 using potassium dihydrogen phosphate; S204, adding material C and wheat bran into PDA culture medium and mixing evenly, and obtaining biochar-based culture medium after sterilization.

4. The biochar-based immobilized bacterial agent for promoting litter decomposition according to claim 3, characterized in that: The ratio of the iron-modified biochar to the melamine suspension in step S202 is 1:18-22.

5. The biochar-based immobilized bacterial agent for promoting litter decomposition according to claim 3, characterized in that: The preparation method of the iron-modified biochar comprises the following steps: S101, screening the bio-based raw materials, washing them, drying them at 55-65° C. for 45-50 hours, crushing them, and passing them through a 40-50 mesh sieve to obtain material A; S102, Fe2(SO4)3·7H2O and material A were mixed and stirred in water, filtered to obtain a filter residue, and then the filter residue was dried to constant weight, ground, and passed through a 60-80 mesh sieve to obtain material B; S103. Place material B in a heating furnace, pyrolyze it at 500-750° C. for 2-3 hours under the protection of nitrogen, and cool it to room temperature after pyrolysis to obtain iron-modified biochar.

6. The biochar-based immobilized bacterial agent for promoting litter decomposition according to claim 5, characterized in that: In step S102, the Fe2(SO4)3·7H2O and material A are mixed and stirred in water at a mass ratio of 1:10-20.

7. A method for preparing a biochar-based immobilized bacterial agent for promoting litter decomposition, for preparing the biochar-based immobilized bacterial agent for promoting litter decomposition according to claim 1, characterized in that: The preparation method of the biochar-based immobilized bacterial agent comprises the following steps: S301. After inoculating and activating Phanerochaete chrysosporium, inoculate into liquid PDA culture medium and incubate at 26-28°C and 140-160 r·min -1 Cultivate in a culture vessel for 2-4 days to obtain a microbial seed solution; S302, inoculating the biochar-based culture medium into the microbial seed solution, placing the culture medium in an incubator and continuing to culture for 4-5 days, then drying and grinding the bacterial agent in the incubator, and passing it through a 60-100 mesh sieve to obtain a biochar-based immobilized bacterial agent.

8. The method for preparing a biochar-based immobilized bacterial agent for promoting litter decomposition according to claim 7, characterized in that: In step S302, 0.02 parts by mass of microbial seed liquid is added to each part by mass of the biochar-based culture medium.

9. A method for applying a biochar-based immobilized bacterial agent for promoting litter decomposition, comprising applying the biochar-based immobilized bacterial agent for promoting litter decomposition according to claim 1, wherein: The biochar-based immobilized bacterial agent is evenly spread on the surface of the forest land at an application rate of 10-20 kg / mu.

10. A method for using a biochar-based immobilized bacterial agent to promote litter decomposition, characterized in that: The biochar-based immobilized bacterial agent is coated and granulated before being spread to form bacterial agent particles, and the bacterial agent particles are evenly spread on the surface of the forest. The steps of the coating and granulation treatment are as follows: A1. Prepare a coating solution by preparing 1.5-2 parts of chitosan, 0.8-1.2 parts of sodium alginate, 0.5-1 parts of polyvinyl alcohol, and 0.1-0.3 parts of magnesium stearate by weight; A2. Add chitosan to an aqueous acetic acid solution and stir at 50-60° C. to form a viscous solution A; A3. Dissolve sodium alginate in water, then shear and disperse at a speed of 1000-1200 r / min to form solution B. Add solution B to solution A, adjust the pH to 5.5-6.0, and stir to form a mixed solution. A4. Add polyvinyl alcohol to water and stir at 90-95°C for 1-1.5 hours to form solution C. After solution C cools to below 30°C, add it to the mixed solution. Then, add magnesium stearate and ultrasonically disperse for 10-15 minutes to obtain a coating solution. B. placing the biochar-based immobilized bacterial agent powder in a fluidized bed, starting the fluidized bed, and starting the spray gun after the biochar-based immobilized bacterial agent powder is fluidized and stabilized. The coating liquid is evenly sprayed onto the surface of the biochar-based immobilized bacterial agent powder by means of the spray gun to form a coating film; C. After coating, dry the film. After the film solidifies, pass it through a 60-80 mesh sieve to form bacterial agent particles.

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