A compound fertilizer for preventing and treating rice soil-borne diseases and a preparation method thereof

Abstract

This invention belongs to the field of agricultural biotechnology and fertilizer preparation technology, and more specifically relates to a compound fertilizer for the prevention and control of soil-borne diseases in rice and its preparation method. The compound fertilizer for the prevention and control of soil-borne diseases in rice provided by this invention has a four-layer gradient structure, consisting of a core, a middle layer, an isolation transition layer, and an outer layer from the inside out. The core includes urea, potassium dihydrogen phosphate, potassium chloride, potassium silicate, and chitosan oligosaccharides; the middle layer is a drug-loaded biochar slow-release layer; the isolation transition layer is formed by cross-linking sodium alginate and phytic acid; and the outer layer is a microbial protective layer. Through the core-shell-membrane multi-layer gradient structure design, physical isolation and sequential release of each component are achieved. The isolation transition layer effectively blocks direct contact between chemical fungicides and beneficial microorganisms, solving the problem of fungicide-microorganism interaction; at the same time, this structure ensures the orderly release of nutrients, fungicides, and microorganisms, matching the growth and disease occurrence patterns of rice.

Description

Technical Field

[0001] This invention belongs to the field of agricultural biotechnology and fertilizer preparation technology, and more specifically relates to a compound fertilizer for preventing and controlling soil-borne diseases of rice and its preparation method. Background Technology

[0002] Rice is frequently threatened by soil-borne diseases such as sheath blight, bakanae disease, and damping-off during its growth. Currently, the main methods for controlling these diseases include chemical pesticide spraying / seed dressing and traditional pesticide-fertilizer mixtures. However, long-term use of chemical pesticides leads to increased pathogen resistance and easily causes soil compaction, water pollution, and excessive pesticide residues in agricultural products. Traditional pesticide-fertilizer mixtures have significant drawbacks: First, there is cross-killing between pesticides and bacteria; if the formula contains beneficial microorganisms, high concentrations of chemical fungicides will directly kill the beneficial bacteria, leading to the failure of biological control. Second, there is asynchronous release; the nutrient release curve does not match the disease occurrence pattern and root absorption pattern, often resulting in excessively high concentrations in the early stages causing phytotoxicity, and insufficient concentrations in the later stages failing to prevent disease. Third, there is a lack of systematic approach; it only focuses on "killing" pathogens, neglecting to enhance the rice's own cell walls and induce acquired resistance to improve its intrinsic immunity. There is a lack of comprehensive technical solutions that can simultaneously address the challenges of "difficulty in coexisting chemical fungicides and beneficial microorganisms", "asynchronous release of nutrients and drug efficacy", and "limited effectiveness of single prevention and control methods". Summary of the Invention

[0003] To address the problems of existing technologies, such as the difficulty in coexisting chemical fungicides and beneficial microorganisms, the asynchronous release of nutrients and pesticides, and the limited range of control methods, this invention provides a compound fertilizer for the prevention and control of soil-borne diseases in rice and its preparation method. This fertilizer achieves the spatiotemporal separation and orderly release of chemical fungicides, beneficial microorganisms, immune inducers, and silicon nutrients, thus constructing a comprehensive four-in-one prevention and control system.

[0004] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention: provides a compound fertilizer for preventing and controlling soil-borne diseases of rice, comprising, by weight: The composition consists of 30-50 parts of nutrient components, 0.5-2.5 parts of bioactive components, 2-4 parts of bactericidal active components, 15-25 parts of carrier material, 2-5 parts of sustained-release coating components, and 1-2 parts of filler. The nutrient components include urea, potassium dihydrogen phosphate, potassium chloride, and potassium silicate; The bioactive components include Bacillus amyloliquefaciens spore powder and chitosan oligosaccharide; The bactericidal active ingredient is thifluzamide; The carrier material is zinc-doped porous biochar; The sustained-release coating components include sodium alginate, phytic acid, calcium chloride, and trehalose; The filler is talc.

[0005] Furthermore, the mass ratio of urea, potassium dihydrogen phosphate, potassium chloride, and potassium silicate is 35-45:25-35:18-28:7-12.

[0006] Furthermore, the mass ratio of Bacillus amyloliquefaciens spore powder to chitosan oligosaccharide is 55-70:30-45.

[0007] Furthermore, the viable bacteria content of the Bacillus amyloliquefaciens spore powder is ≥1.0×10⁻⁶. 11 cfu / g.

[0008] Furthermore, the mass ratio of sodium alginate, phytic acid, calcium chloride, and trehalose is 30-45:10-18:15-25:15-25.

[0009] Furthermore, the preparation steps of the zinc-doped porous biochar include: Rice husk powder is pulverized and passed through a 60-100 mesh sieve. It is then stirred for 30-60 minutes in 0.5-1.0 mol / L dilute hydrochloric acid at 50-60℃ with a solid-liquid ratio of 1:10-20 (g / mL). After washing until neutral, the powder is dried. It is then mixed with a 0.3-0.8 mol / L zinc sulfate solution at a solid-liquid ratio of 1:5-10 (g / mL). 5%-10% of the rice husk powder's mass of citric acid is added, and the mixture is stirred until homogeneous. Vacuum-assisted rotary impregnation is then performed for 2-3 hours, followed by solid-liquid separation. The solid portion is dried at 60-80℃ for 6-12 hours, and then subjected to low-temperature pre-carbonization, medium-temperature activation, and high-temperature carbonization. After cooling, the powder is ground and passed through a 200-300 mesh sieve. The undersize material is collected to obtain the zinc-doped porous biochar.

[0010] Optionally, the vacuum-assisted rotary impregnation treatment is performed by placing the sample in a rotary evaporator at 30-50 rpm and impregnating it at 50-60℃ and -0.05~-0.08 MPa.

[0011] Optionally, the heating rate of the low-temperature pre-carbonization is 1-2℃ / min, the temperature is 270-330℃, the holding time is 20-40min, and the protective atmosphere is nitrogen atmosphere.

[0012] Optionally, the intermediate-temperature activation is as follows: heating to 550-600℃ at a heating rate of 3-5℃ / min, using a protective gas mixture of nitrogen and water vapor, with a water vapor volume fraction of 5-10% (generated by nitrogen bubbling through a constant-temperature water bath), and holding at this temperature for 60-90 minutes.

[0013] Optionally, the heating rate of the high-temperature carbonization treatment is 3-5℃ / min, the temperature is 700-750℃, the holding time is 20-30min, and the atmosphere is a nitrogen atmosphere.

[0014] Zinc sulfate concentration (0.3-0.8 mol / L): If the concentration is too low, the zinc doping amount will be insufficient and the modification effect will be weak; if the concentration is too high, the zinc salt will easily lead to supersaturated crystallization on the surface, blocking the pores of the precursor.

[0015] The purpose of soaking in dilute hydrochloric acid is to remove some ash and impurities, expose more of the cellulose skeleton, and create more active sites for the subsequent uniform anchoring of zinc and pore formation.

[0016] Citric acid, as a green chelating agent and self-templating pore-forming agent, can form complexes with zinc ions to prevent zinc from agglomerating into lumps prematurely during subsequent drying and initial carbonization. On the other hand, it will completely decompose during carbonization, generating gas and leaving additional pores in the carbon skeleton.

[0017] The vacuum environment of vacuum-assisted rotary impregnation helps remove air from the pores of the raw material, allowing the impregnation liquid to penetrate more fully; rotation ensures uniform mixing and impregnation.

[0018] Low-temperature pre-carbonization causes the hemicellulose and cellulose in rice husks to decompose slowly, and citric acid decomposes and creates pores, initially forming a stable carbon skeleton and fixing zinc species to prevent their migration and aggregation.

[0019] The intermediate-temperature activation is also the pore-forming stage. A trace amount of water vapor is introduced for "mild gas phase activation". The water vapor undergoes a controlled gasification reaction with amorphous carbon at high temperature (C + H2O → CO + H2), which further etches and expands the pores, especially forming abundant mesopores and promoting the dispersion and activation of zinc species.

[0020] During the high-temperature graphitization stage, the steam supply is stopped and a pure nitrogen atmosphere is restored. The high temperature causes some carbon structures to undergo slight graphitization, which improves the chemical stability of the carrier material. At the same time, the zinc species are finally highly dispersed and firmly embedded in the carbon matrix in the form of zinc oxide nanoparticles.

[0021] The second technical solution of the present invention provides a method for preparing the above-mentioned compound fertilizer for preventing and controlling soil-borne diseases of rice, the steps of which include: The carrier material is mixed with an acetone solution containing a bactericidal active component at a concentration of 50-150 g / L, impregnated under vacuum, evaporated under reduced pressure, and dried to obtain the drug-loaded carrier. After pulverizing the nutrient components through an 80-120 mesh sieve, add chitosan oligosaccharide, mix evenly, adjust the moisture content to 15-25 wt%, granulate, and dry to obtain kernel particles; The drug carrier is mixed with 1-3% polyvinyl alcohol (PVA) aqueous solution in an equal mass ratio and then ground to form a uniform slurry. The core particles are coated with the slurry to obtain particles coated with an intermediate layer; A sodium alginate aqueous solution and a mixed crosslinking solution containing calcium chloride and phytic acid were prepared and sequentially sprayed onto the surface of the particles coating the intermediate layer to form a gel isolation film and then dried to obtain isolation layer particles. A bacterial suspension was prepared by mixing Bacillus amyloliquefaciens spore powder with a protective agent, sprayed onto the surface of the granules, and dried at 30-35°C. During the drying process, a filler was added to prevent the granules from sticking together, thus obtaining the compound fertilizer used to prevent soil-borne diseases of rice.

[0022] Furthermore, the parameters for the vacuum impregnation are: -0.08 MPa to -0.095 MPa, 2-4h, 25-35℃.

[0023] Furthermore, the parameters for the reduced pressure evaporation are: -0.06 MPa to -0.08 MPa, 30-40℃, to remove 95-100% of acetone.

[0024] Furthermore, the drying parameters are: drying to constant weight at ≤40℃ and ≤-0.095 MPa.

[0025] Furthermore, the particle size of the granulation is 2.0-3.5 mm.

[0026] Furthermore, the drying process involves drying at 60-70°C until the moisture content is ≤5wt%.

[0027] Furthermore, the coating process involves preheating the core particles to 35-40°C and fluidizing them, controlling the inlet air temperature to 40-50°C, the atomization pressure to 0.2-0.4 MPa, and the spraying rate to 5-15 mL / min, uniformly spraying the slurry onto the surface of the core particles, and then fluidizing and drying them at 40-50°C until the particle moisture content is ≤3%.

[0028] Furthermore, the preparation steps of the isolation layer particles include: preparing an aqueous solution of sodium alginate with a concentration of 1.5-2.5 wt%; preparing a mixed crosslinked aqueous solution containing 1-2 wt% calcium chloride and 0.3-0.8 wt% phytic acid; spraying the sodium alginate aqueous solution onto the surface of the particles coating the intermediate layer, then spraying the mixed crosslinked aqueous solution, followed by fluidization at 30-40℃ for 5-10 min, and then drying at 35-40℃ until the water content is ≤5 wt%, to obtain the isolation layer particles.

[0029] Furthermore, the protective agent is a pH 6.5-7.5 phosphate buffer containing 1-2 wt% trehalose, 0.1-0.3 wt% glycerol, and 0.5-1.0 wt% soluble starch.

[0030] Furthermore, the viable bacteria concentration of the bacterial suspension is 5.0 × 10⁻⁶. 8 -2.0×10 9 cfu / mL.

[0031] The present invention discloses the following technical effects: The compound fertilizer for controlling soil-borne diseases of rice provided by this invention has a four-layer gradient structure, consisting of a core, a middle layer, an isolation transition layer, and an outer layer from the inside out. The core includes urea, potassium dihydrogen phosphate, potassium chloride, potassium silicate, and chitosan oligosaccharides. The middle layer is a drug-loaded biochar slow-release layer. The isolation transition layer is formed by cross-linking sodium alginate, calcium chloride, and phytic acid. The outer layer is a microbial protective layer. Through the core-shell-membrane multi-layer gradient structure design, physical isolation and sequential release of each component are achieved. The isolation transition layer effectively blocks direct contact between chemical fungicides and beneficial microorganisms, solving the problem of cross-contamination between fungicides and pesticides. At the same time, this structure ensures the orderly release of nutrients, fungicides, and microorganisms, matching the growth and disease occurrence patterns of rice.

[0032] This invention utilizes a dense gel barrier membrane formed by the cross-linking of sodium alginate and phytic acid to effectively block the contact between chemical bactericides and beneficial microorganisms on the outer layer in physical space, thus avoiding the impact of chemical bactericides on beneficial microorganisms and significantly extending the duration of the biological control function.

[0033] The four-layer gradient structure design of this invention achieves the time-sequential synergistic release of each functional component through physical isolation and controlled-release properties of the materials: after fertilization, the readily available nutrients, silicon, and chitosan oligosaccharides in the core are rapidly released within 0-7 days, promoting seedling growth and inducing plant immunity in advance; the outer layer of Bacillus amyloliquefaciens then germinates and colonizes in the rhizosphere (approximately 3-20 days), establishing a biological control zone; while the middle layer of drug-loaded biochar, protected by the isolation layer, continuously and slowly releases thifluzamide during the critical period of disease occurrence (15-60 days), providing long-term chemical protection. This orderly release curve of 'immune induction—biological control—chemical control' perfectly matches the rice growth cycle and the occurrence pattern of soil-borne diseases, ensuring comprehensive control efficacy throughout the entire growth period while avoiding cross-killing of fungi and pesticides and early-stage phytotoxicity. Detailed Implementation

[0034] 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.

[0035] 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.

[0036] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been 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.

[0037] 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 readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0038] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0039] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of this invention are commercially available products.

[0040] Unless otherwise specified, room temperature and normal temperature in the specific embodiments of this invention refer to 20-30℃.

[0041] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0042] The zinc-doped porous biochar in the specific embodiment of the present invention is prepared by the following method: Rice husk powder was pulverized and passed through an 80-mesh sieve. It was then stirred for 40 minutes in 0.5 mol / L dilute hydrochloric acid at 50℃ at a solid-liquid ratio of 1:10 (g / mL). After washing until neutral, the powder was dried. Next, it was mixed with 0.5 mol / L zinc sulfate solution at a solid-liquid ratio of 1:8 (g / mL). Finally, 8% citric acid (by weight of the rice husk powder) was added, and the mixture was stirred thoroughly. The mixture was then placed in a rotary evaporator at 50 rpm and evaporated at 55℃ with a temperature of -0.05°C. Impregnated at MPa for 3 h, solid-liquid separation was performed. The solid part was dried at 70℃ for 8 h, and then heated to 300℃ at a heating rate of 2℃ / min under a nitrogen atmosphere and held for 30 min. The protective gas was then switched to a mixture of nitrogen and water vapor with a water vapor volume fraction of 5% (generated by nitrogen bubbling through a constant temperature water bath). The mixture was heated to 550℃ at a heating rate of 5℃ / min and held for 60 min. Finally, the mixture was heated to 700℃ at a heating rate of 5℃ / min under a nitrogen atmosphere and held for 20 min. After cooling, the mixture was ground and passed through a 300-mesh sieve. The undersize material was collected to obtain zinc-doped porous biochar.

[0043] In the technical solution of this invention, zinc doping is the core of functionalizing the biochar carrier. Zinc acts as a pore-forming agent during high-temperature carbonization, significantly increasing the specific surface area of ​​the biochar and optimizing its pore structure, thereby achieving efficient loading and long-term sustained release of thifluzamide. Simultaneously, zinc species (such as Zn) 2+ It possesses certain antibacterial activity, synergistically enhancing its effects with chemical fungicides and delaying drug resistance. Furthermore, zinc, as an essential trace element, provides nutrition to rice during the slow-release process, enhancing plant health and stress resistance, thus achieving a triple effect of carrier construction, efficacy enhancement, and nutrient supplementation.

[0044] In some specific embodiments, the present invention provides a compound fertilizer for preventing and controlling soil-borne diseases of rice, the preparation steps of which include: S1. Raw material preparation: 30-50 parts of nutrient components, 0.5-2.5 parts of bioactive components, 2-4 parts of bactericidal active components, 15-25 parts of carrier material, 2-5 parts of slow-release coating components, and 1-2 parts of filler; The nutritional components consist of urea, potassium dihydrogen phosphate, potassium chloride, and potassium silicate in a mass ratio of 35-45:25-35:18-28:7-12; the bioactive components consist of Bacillus amyloliquefaciens spore powder (commercially available) and chitosan oligosaccharides in a mass ratio of 55-70:30-45; the viable bacteria content of the Bacillus amyloliquefaciens spore powder is ≥1.0×10⁻⁶. 11 cfu / g; the bactericidal active ingredient is thifluzamide technical; the carrier material is zinc-doped porous biochar; the sustained-release coating components are sodium alginate, phytic acid, calcium chloride and trehalose in a mass ratio of 30-45:10-18:15-25:15-25; the filler is talc.

[0045] S2. Dissolve the bactericidal active component in acetone to prepare a drug with a concentration of 50-150 g / L. Mix the carrier material with the above drug, impregnate under vacuum (-0.08 MPa to -0.095 MPa, 2-4 h, 25-35℃), evaporate under reduced pressure (-0.06 MPa to -0.08 MPa, 30-40℃, remove 95-100% of acetone), and dry to constant weight at 40℃ and -0.095 MPa to obtain the drug-loaded carrier.

[0046] Vacuum impregnation is a crucial step in this process. Under vacuum conditions, air is extracted from the pores of the biochar. When atmospheric pressure is restored, the high-concentration drug solution from the outside is forced deep into the pores by the pressure difference, thus significantly improving the uniformity and loading of thifluzamide in the carrier. Controlling the drying temperature below 40°C is to prevent thermal decomposition or crystal transformation of thifluzamide at high temperatures, ensuring stable efficacy.

[0047] S3. After pulverizing the nutrient components through an 80-120 mesh sieve, add chitosan oligosaccharide, mix evenly, adjust the moisture content to 15-25 wt%, granulate (2.0-3.5 mm), and dry at 60-70℃ until the moisture content is ≤5 wt% to obtain kernel particles.

[0048] The core, serving as a fast-acting reservoir for fertilizer, directly affects the uniformity of subsequent coating due to its granulation strength and particle size. By controlling the material's moisture content, the core particles achieve suitable strength and surface roughness, facilitating both shaping and the adhesion of subsequent intermediate layer materials. Potassium silicate and chitosan oligosaccharides are uniformly dispersed in the nutrient matrix during this step, ensuring adequate silicon supply and immune-inducing function in the initial stages of fertilization.

[0049] S4. Mix the drug carrier with 1-3% polyvinyl alcohol (PVA) aqueous solution in equal mass ratio and grind to form a uniform slurry; S5. Preheat the core particles prepared in step S3 to 35-40℃ and fluidize them. Control the inlet air temperature to 40-50℃, the atomization pressure to 0.2-0.4 MPa, and the spraying rate to 5-15 mL / min. Spray the slurry from step S4 evenly onto the surface of the core particles, and then fluidize and dry them at 40-50℃ until the particle moisture content is ≤3%, to obtain particles coated with the intermediate layer.

[0050] S6. Prepare an aqueous solution of sodium alginate with a concentration of 1.5-2.5 wt%; prepare a mixed crosslinked aqueous solution containing 1-2 wt% calcium chloride and 0.3-0.8 wt% phytic acid; spray the sodium alginate aqueous solution onto the surface of the particles coated with the intermediate layer prepared in step S5, and then spray the mixed crosslinked aqueous solution onto the surface. Then, fluidize the mixture at 30-40°C for 5-10 min to form a gel isolation film, and then dry it at 35-40°C until the water content is ≤5 wt% to obtain the isolation layer particles.

[0051] This step is the core process for resolving the interaction between bacteria and antibiotics. Sodium alginate is a natural polymer that combines with calcium ions through coordination bonds to form an eggshell structure, thus rapidly gelling. This invention introduces phytic acid into the cross-linking solution. Phytic acid molecules contain multiple phosphate groups, which can further bind to the void sites in the sodium alginate network, filling the micropores of the gel network and significantly improving the density and barrier properties of the membrane. This ternary cross-linked network effectively blocks the outward diffusion of thifluamide molecules from the middle layer while allowing water molecules and small root exudates to pass through, providing a physical barrier for the survival of outer microorganisms.

[0052] S7. Mix Bacillus amyloliquefaciens spore powder with a pH 6.5-7.5 phosphate buffer containing 1-2 wt% trehalose, 0.1-0.3 wt% glycerol, and 0.5-1.0 wt% soluble starch to prepare a viable cell concentration of 5.0 × 10⁻⁶. 8 -2.0×10 9 A bacterial suspension of CFU / mL is sprayed onto the surface of the isolated particles in step S6 and dried at 30-35℃. During the drying process, a filler is added to prevent the particles from sticking together, thus obtaining a compound fertilizer for the prevention and control of soil-borne diseases in rice.

[0053] This embodiment constructs a material basis for "nutrient supply + disease control + soil improvement + root immune induction" through a specific combination of components. Urea, potassium dihydrogen phosphate, and potassium chloride serve as basic nutrients, collectively forming a readily available nitrogen, phosphorus, and potassium nutrient source to meet the nutritional needs of rice in its early growth stages. Potassium silicate, as a silicon fortifier, effectively strengthens the rice cell wall within the scope defined by this invention, forming a physical barrier to inhibit bacteria while simultaneously supplementing silicon nutrition. Chitosan oligosaccharide, as an immune inducer, preferably an oligosaccharide with a molecular weight less than 3000 Da, can induce systemically acquired resistance (SAR) in plants, activating the rice's own immune defense mechanism. Thifluzamide technical grade, as a chemical fungicide, has significant control effects on soil-borne diseases such as sheath blight. Zinc-doped porous biochar, as a functional carrier, not only possesses a high specific surface area and well-developed pore structure, effectively loading thifluzamide and achieving slow release, but its doped zinc element can also participate in plant growth metabolism and enhance photosynthesis. Bacillus amyloliquefaciens spore powder, as a beneficial microorganism, can colonize the rhizosphere and inhibit the growth of pathogens through biological competition. Sodium alginate, phytic acid, and calcium chloride are used as isolation layer materials to construct a dense gel isolation membrane, solving the problem of cross-infection between bacteria and drugs. Trehalose, as a protective agent, can protect the activity of microorganisms during drying and storage. Talc, as an anti-adhesion agent, prevents particles from sticking together during preparation and storage.

[0054] The compound fertilizer provided by this invention has a four-layer gradient structure. It is not a simple physical mixture, but rather a "core-shell-membrane" system with clearly defined functional zones and release sequences, constructed through a specific preparation process. The core logic of this structural design lies in utilizing physical spatial isolation to achieve the coexistence of chemical fungicides and beneficial microorganisms, and controlling the nutrient release rate through the properties of the interlayer materials. The core, serving as the skeleton of the entire particle, contains readily available nutrients, silicon, and immune inducers. During preparation, urea, potassium dihydrogen phosphate, and potassium chloride, as readily available nutrient sources, are mixed with potassium silicate and chitosan oligosaccharides to form the core. The main function of the core is to rapidly release nitrogen, phosphorus, and potassium nutrients in the early stages of fertilization to meet the growth needs of rice seedlings; simultaneously, the released potassium silicate strengthens the rice cell wall, forming a physical barrier, while the chitosan oligosaccharides induce systemically acquired resistance (SAR) in the plant, activating the immune mechanism in advance. The particle size of the core is typically controlled at 2-3 mm to ensure sufficient volume to hold nutrients and provide a basis for subsequent coating.

[0055] The intermediate layer is a drug-loaded biochar slow-release layer, coating the core surface. This layer is constructed from drug-loaded biochar powder and a binder (PVA solution) using a fluidized bed process. The drug-loaded biochar acts as a functional carrier, with its internal pores adsorbing the thifluzamide technical. When moisture permeates through the outer and insulating layers to reach the intermediate layer, the biochar's porous structure and zinc doping properties enable a slow-release effect on the fungicide, allowing it to be released continuously over a longer period. This matches the peak occurrence period of soil-borne diseases, achieving sustained chemical inhibition of pathogens.

[0056] The isolation transition layer, formed by the cross-linking of sodium alginate and phytic acid, is located between the intermediate and outer layers. This is the key structural design of this invention to solve the problem of cross-killing between bacteria and fungicides. The carboxyl groups on the sodium alginate molecular chain cross-link with calcium ions to form an egg-box structure, and the introduction of phytic acid further fills the pores of the gel network, forming a dense and selectively permeable physical barrier. This barrier can effectively prevent the diffusion of thifluzamide from the intermediate layer to the outer layer, preventing high concentrations of fungicides from contacting and killing Bacillus amyloliquefaciens on the outer layer. At the same time, this isolation layer has a certain degree of swelling capacity, allowing water and root exudates to pass through without affecting the activation of microorganisms on the outer layer.

[0057] The outer layer is a microbial protective layer, wrapped around the surface of the isolation transition layer. This layer is mainly composed of Bacillus amyloliquefaciens spore powder, trehalose, and talc. Trehalose acts as a protectant, protecting the cell membrane and protein activity of the bacteria in a dry environment; talc prevents particles from sticking together. The design of the outer layer allows beneficial bacteria to come into contact with the soil environment first after fertilization, rapidly germinating and colonizing the rhizosphere before the release of fungicides. They inhibit pathogens by competing for nutrients and space, and secreting antibacterial substances, thus forming a "bio-chemical" synergistic control with the subsequently released chemical fungicides.

[0058] Through the above four-layer gradient structure, the present invention realizes a comprehensive prevention and control system integrating "physical barrier (silicon) + chemical killing (thifluzamide) + biological competition (Bacillus) + immune induction (chitosan oligosaccharide)". Each component is isolated in space and released step by step in time, avoiding antagonistic effects and maximizing synergistic effects.

[0059] Example 1 The preparation steps of compound fertilizer used to prevent and control soil-borne diseases of rice include: S1. Raw material preparation: 44 parts of nutrient components, 1.5 parts of bioactive components, 3 parts of bactericidal active components, 20 parts of carrier material, 3.5 parts of sustained-release coating components, and 1.5 parts of filler; The nutritional components consist of urea, potassium dihydrogen phosphate, potassium chloride, and potassium silicate in a mass ratio of 45:30:25:10; the bioactive components consist of Bacillus amyloliquefaciens spore powder and chitosan oligosaccharides in a mass ratio of 60:30; and the viable bacteria content of the Bacillus amyloliquefaciens spore powder is ≥1.0×10⁻⁶. 11 CFU / g; the bactericidal active ingredient is thifluzamide technical; the carrier material is zinc-doped porous biochar; the sustained-release coating components are sodium alginate, phytic acid, calcium chloride and trehalose in a mass ratio of 37.5:12.5:20:17.5; the filler is talc.

[0060] S2. Dissolve the bactericidal active component in acetone to prepare a drug with a concentration of 100 g / L. Mix the carrier material with the above drug, impregnate under vacuum (-0.08 MPa, 3 h, 30 °C), evaporate under reduced pressure (-0.08 MPa, 35 °C, to remove about 95% of the acetone), and dry to constant weight at 40 °C and -0.095 MPa to obtain the drug-loaded carrier. S3. After pulverizing the nutrient components through a 100-mesh sieve, add chitosan oligosaccharide, mix evenly, adjust the moisture content to 20 wt%, granulate (between 2.0-3.5 mm), and dry at 65℃ until the moisture content is ≤5 wt% to obtain kernel particles; S4. Mix the drug carrier with a 2% polyvinyl alcohol (PVA) aqueous solution in an equal mass ratio and grind to form a uniform slurry; S5. Preheat the core particles prepared in step S3 to 35°C and fluidize them. Control the air inlet temperature to 45°C, the atomization pressure to 0.3 MPa, and the spraying rate to 10 mL / min. Spray the slurry from step S4 evenly onto the surface of the core particles, and then fluidize and dry them at 45°C until the particle moisture content is ≤3% to obtain particles coated with the intermediate layer. S6. Prepare a sodium alginate aqueous solution with a concentration of 2wt%; prepare a mixed crosslinked aqueous solution containing 1.5wt% calcium chloride and 0.5wt% phytic acid; spray the sodium alginate aqueous solution onto the surface of the particles coated with the intermediate layer prepared in step S5, and then spray the mixed crosslinked aqueous solution, and then fluidize at 35°C for 10 min to form a gel isolation film, and then dry at 35°C until the water content is ≤5wt% to obtain the isolation layer particles; S7. Mix Bacillus amyloliquefaciens spore powder with a pH 7.0 phosphate buffer containing 1.5 wt% trehalose, 0.2 wt% glycerol, and 0.8 wt% soluble starch to prepare a viable bacterial concentration of 10. 9 A bacterial suspension of CFU / mL was sprayed onto the surface of the isolated particles in step S6 and dried at 30°C. During the drying process, a filler was added to prevent the particles from sticking together, resulting in a compound fertilizer for the prevention and control of soil-borne diseases in rice.

[0061] Example 2 The preparation steps of compound fertilizer used to prevent and control soil-borne diseases of rice include: S1. Raw material preparation: 50 parts of nutrient components, 2.5 parts of bioactive components, 2 parts of bactericidal active components, 25 parts of carrier material, 5 parts of sustained-release coating components, and 2 parts of filler; The nutritional components consist of urea, potassium dihydrogen phosphate, potassium chloride, and potassium silicate in a mass ratio of 45:25:28:12; the bioactive components consist of Bacillus amyloliquefaciens spore powder and chitosan oligosaccharides in a mass ratio of 70:30; and the viable bacteria content of the Bacillus amyloliquefaciens spore powder is ≥1.0×10⁻⁶. 11 cfu / g; the bactericidal active ingredient is thifluzamide technical; the carrier material is zinc-doped porous biochar; the sustained-release coating components are sodium alginate, phytic acid, calcium chloride and trehalose in a mass ratio of 45:18:25:25; the filler is talc.

[0062] S2-S7, same as in Example 1.

[0063] Example 3 The preparation steps of compound fertilizer used to prevent and control soil-borne diseases of rice include: S1. Raw material preparation: 30 parts of nutrient components, 0.5 parts of bioactive components, 2 parts of bactericidal active components, 15 parts of carrier material, 2 parts of sustained-release coating components, and 2 parts of filler; The nutritional components consist of urea, potassium dihydrogen phosphate, potassium chloride, and potassium silicate in a mass ratio of 35:25:18:7; the bioactive components consist of Bacillus amyloliquefaciens spore powder and chitosan oligosaccharides in a mass ratio of 55:45; and the viable bacteria content of the Bacillus amyloliquefaciens spore powder is ≥1.0×10⁻⁶. 11cfu / g; the bactericidal active ingredient is thifluzamide technical; the carrier material is zinc-doped porous biochar; the slow-release coating components are sodium alginate, phytic acid, calcium chloride and trehalose in a mass ratio of 30:18:15:15; the filler is talc.

[0064] S2-S7, same as in Example 1.

[0065] Example 4 The preparation steps of compound fertilizer used to prevent and control soil-borne diseases of rice include: S1. Raw material preparation: 40 parts of nutrient components, 2 parts of bioactive components, 3 parts of bactericidal active components, 25 parts of carrier material, 3 parts of sustained-release coating components, and 2 parts of filler; The nutritional components consist of urea, potassium dihydrogen phosphate, potassium chloride, and potassium silicate in a mass ratio of 40:30:20:10; the bioactive components consist of Bacillus amyloliquefaciens spore powder and chitosan oligosaccharides in a mass ratio of 60:40; and the viable bacteria content of the Bacillus amyloliquefaciens spore powder is ≥1.0×10⁻⁶. 11 cfu / g; the bactericidal active ingredient is thifluzamide technical; the carrier material is zinc-doped porous biochar; the sustained-release coating components are sodium alginate, phytic acid, calcium chloride and trehalose in a mass ratio of 30:18:15:25; the filler is talc.

[0066] S2-S7, same as in Example 1.

[0067] Comparative Example 1 The preparation steps of compound fertilizer include: S1. Raw material preparation: 44 parts of nutrient components, 1.5 parts of bioactive components, 3 parts of bactericidal active components, 20 parts of carrier material, 3.5 parts of sustained-release coating components, and 1.5 parts of filler; The nutritional components consist of urea, potassium dihydrogen phosphate, potassium chloride, and potassium silicate in a mass ratio of 45:30:25:10; the bioactive components consist of Bacillus amyloliquefaciens spore powder and chitosan oligosaccharides in a mass ratio of 60:30; and the viable bacteria content of the Bacillus amyloliquefaciens spore powder is ≥1.0×10⁻⁶. 11 cfu / g; the bactericidal active ingredient is thifluzamide technical; the carrier material is zinc-doped porous biochar; the sustained-release coating components are sodium alginate, phytic acid, calcium chloride and trehalose in a mass ratio of 30-45:10-18:15-25:15-25; the filler is talc.

[0068] S2. Mix the raw materials shown in step S1 evenly to obtain compound fertilizer.

[0069] Comparative Example 2 The preparation steps of compound fertilizer (without an isolation layer) include: S1. Raw material preparation: 44 parts of nutrient components, 1.5 parts of bioactive components, 3 parts of bactericidal active components, 20 parts of carrier material, 0.7 parts of sustained-release coating components, and 1.5 parts of filler; The nutritional components consist of urea, potassium dihydrogen phosphate, potassium chloride, and potassium silicate in a mass ratio of 45:30:25:10; the bioactive components consist of Bacillus amyloliquefaciens spore powder and chitosan oligosaccharides in a mass ratio of 60:30; and the viable bacteria content of the Bacillus amyloliquefaciens spore powder is ≥1.0×10⁻⁶. 11 cfu / g; the bactericidal active ingredient is thifluzamide technical; the carrier material is zinc-doped porous biochar; the sustained-release coating component is trehalose; and the filler is talc.

[0070] S2. Dissolve the bactericidal active component in acetone to prepare a drug with a concentration of 100 g / L. Mix the carrier material with the above drug, impregnate under vacuum (-0.08 MPa, 3 h, 30 °C), evaporate under reduced pressure (-0.08 MPa, 35 °C, to remove about 95% of the acetone), and dry to constant weight at 40 °C and -0.095 MPa to obtain the drug-loaded carrier. S3. After pulverizing the nutrient components through a 100-mesh sieve, add chitosan oligosaccharide, mix evenly, adjust the moisture content to 20 wt%, granulate (between 2.0-3.5 mm), and dry at 65℃ until the moisture content is ≤5 wt% to obtain kernel particles; S4. Mix the drug carrier with a 2% polyvinyl alcohol (PVA) aqueous solution in an equal mass ratio and grind to form a uniform slurry; S5. Preheat the core particles prepared in step S3 to 35°C and fluidize them. Control the air inlet temperature to 45°C, the atomization pressure to 0.3 MPa, and the spraying rate to 10 mL / min. Spray the slurry from step S4 evenly onto the surface of the core particles, and then fluidize and dry them at 45°C until the particle moisture content is ≤3% to obtain particles coated with the intermediate layer. S6. Mix Bacillus amyloliquefaciens spore powder with a pH 7.0 phosphate buffer containing 1.5 wt% trehalose, 0.2 wt% glycerol, and 0.8 wt% soluble starch to prepare a viable bacterial concentration of 10. 9 A bacterial suspension of CFU / mL is sprayed onto the surface of the particles coated with the intermediate layer in step S5 and dried at 30°C. During the drying process, a filler is added to prevent the particles from sticking together, thus obtaining a compound fertilizer.

[0071] Comparative Example 3 The only difference from Example 1 is that the carrier material is rice husk charcoal obtained through conventional pyrolysis, and the preparation steps of this rice husk charcoal are as follows: Rice husk powder is crushed and passed through an 80-mesh sieve, placed in a muffle furnace, heated to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, held at that temperature for 120 minutes, cooled, ground, passed through a 300-mesh sieve, and the sieve-passing material is collected to obtain rice husk charcoal.

[0072] Comparative Example 4 The difference compared to Example 1 is that chitosan oligosaccharides are reduced in the raw materials.

[0073] Comparative Example 5 The difference compared to Example 1 is that potassium silicate is reduced in the raw materials.

[0074] Test case The compound fertilizers prepared in the examples and comparative examples were tested as follows: Experimental crop: rice, Wuyunjing 21.

[0075] Group settings: The compound fertilizers prepared in Examples 1-4 and Comparative Examples 1-5 were used as experimental groups; at the same time, a control group (CK) was set up (without spraying with sheath blight pathogen), which was treated with commercially available conventional rice compound fertilizer with N-P2O5-K2O of 24-0-5 and total nutrients of not less than 29%.

[0076] Each group consists of three plots, each plot being 15m in size. 2 .

[0077] Compound fertilizer application method: Apply as a base fertilizer once during transplanting, at a rate of 180 kg / hm² of pure nitrogen. 2 Conversion.

[0078] Spray at a concentration of 10 ppm 14 days after rice transplanting 6 A CFU / mL suspension of *Rhizoctonia solani* was sprayed at a rate of 60 mL / m³. 2 Spray the soil around the base of the rice plants and the root zone, and keep the field moist for 5 days after spraying.

[0079] On the day of rice transplanting (day 0) and 15 days after transplanting, rhizosphere soil was collected, and the number of Bacillus amyloliquefaciens (cfu / g dry soil) was determined by dilution plating method.

[0080] Pesticide residue determination: Soil samples were taken at 0, 7, 15, 30 and 60 days after transplanting, and the thifluzamide content was determined by HPLC.

[0081] Disease survey: Investigate the disease index of sheath blight during the tillering and jointing stages (100 plants were randomly surveyed in each plot).

[0082] Disease index = ∑(number of diseased plants at each level × relative level value) / (total number of plants surveyed × highest disease level) × 100.

[0083] Table 1 Correspondence between Disease Grade and Relative Grade Values Table 2 Data 15 days after transplanting Table 3 Comparison of timing release verification data between Example 1 and Comparative Example 1 Table 3 shows that the core fast-acting component in the initial Example 1 worked rapidly, with a chitosan oligosaccharide release rate as high as 85%. This design aims to preferentially activate the rice's own immune system before disease occurs, building the first line of biological defense. Meanwhile, the release rate of thifluzamide was controlled at 5%, providing a safe window for the outer layer of Bacillus amyloliquefaciens. In contrast, Comparative Example 1, lacking time control, allowed the fungicide to directly contact the microorganisms, resulting in the death of beneficial bacteria within 7-15 days (survival rate dropping below 10%), thus losing its biocontrol function.

[0084] Isolation and staggered release mechanism: During days 7-15, the thifluzamide release rate of Example 1 was only 25%, primarily relying on the barrier effect of the intermediate layer to ensure that the pesticide concentration in the rhizosphere soil remained below the safe threshold. This allowed Bacillus amyloliquefaciens to complete germination and rhizosphere colonization during this period, forming a biological barrier. In contrast, Comparative Example 2 (without an isolation layer), although not directly mixed, suffered from excessively rapid pesticide penetration due to the lack of a dense barrier of sodium alginate-phytic acid, resulting in a 55% decrease in the survival rate of beneficial bacteria during the critical colonization period. This demonstrates the crucial role of the isolation layer in resolving the problem of cross-contamination between bacteria and pesticides.

[0085] Precision strikes and long-term effectiveness: During the peak period of rice sheath blight (15-30 days), the release rate of thifluzamide in Example 1 reached a peak of 65%, while during the grain-filling period (30-60 days), the release rate remained above 90%, ensuring no nutrient deficiency or premature aging in the later stages. This release curve, which is low at the beginning and high at the end, effectively solves the problem of early efficacy loss and insufficient protection in the later stages associated with traditional fertilizers (Comparative Example 3).

[0086] Table 4 Comparison of agronomic traits and yield As can be seen from the data in Table 4: The yields of Examples 1-4 were maintained at 9280-9850 kg / hm. 2 In the high-level range, Example 1, with its optimal ratio, achieved better results in both effective panicle number and thousand-grain weight, indicating that its "core-shell-membrane" structure achieved the best balance in promoting tillering and panicle formation and grain filling.

[0087] Comparative Example 1 (physical blending) had the lowest yield (8040 kg / hm). 2 The results were even slightly higher than the blank control, directly confirming that direct mixing of chemical fungicides and beneficial microorganisms leads to "mutual killing of fungi and drugs," completely rendering the biological control function ineffective. Comparative Example 2 (without an isolation layer) showed a slight improvement, but due to the lack of a sodium alginate-phytic acid isolation layer, beneficial bacteria were still inhibited by the drug in the early stages of fertilization, resulting in a significantly lower number of effective panicles than in Example 1. Data from Comparative Example 3 (ordinary carrier) indicated that the lack of slow-release effect from zinc-doped porous biochar led to excessively rapid drug release, failing to cover the high-incidence period of diseases in the middle and late stages of rice growth, resulting in reduced yield in the later stages.

[0088] The yields of Comparative Example 4 (without chitosan oligosaccharides) and Comparative Example 5 (without potassium silicate) were between those of Comparative Example 3 and the Example. Comparative Example 4, lacking an immune inducer, exhibited insufficient systemic resistance and a slightly higher disease index. Comparative Example 5, lacking silicon fortification, had insufficient stem strength, which not only affected nutrient transport (resulting in a decrease in thousand-grain weight) but also increased the risk of lodging. These two sets of data strongly demonstrate that in the "nutrition + disease prevention + improvement + immunity" four-in-one system, each component is indispensable, collectively forming the synergistic effect basis of this invention.

[0089] In summary, the technical solution of the present invention has significant advantages in solving the problem of mutual killing between fungi and pesticides, achieving time-sequential synergistic release, and improving the overall stress resistance of crops.

[0090] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0091] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A compound fertilizer for preventing and controlling soil-borne diseases in rice, characterized in that, By weight, the components include: The composition consists of 30-50 parts of nutrient components, 0.5-2.5 parts of bioactive components, 2-4 parts of bactericidal active components, 15-25 parts of carrier material, 2-5 parts of sustained-release coating components, and 1-2 parts of filler. The nutrient components include urea, potassium dihydrogen phosphate, potassium chloride, and potassium silicate; The bioactive components include Bacillus amyloliquefaciens spore powder and chitosan oligosaccharide; The bactericidal active ingredient is thifluzamide; The carrier material is zinc-doped porous biochar; The sustained-release coating components include sodium alginate, phytic acid, calcium chloride, and trehalose; The filler is talc.

2. The compound fertilizer as described in claim 1, characterized in that, The mass ratio of urea, potassium dihydrogen phosphate, potassium chloride and potassium silicate is 35-45:25-35:18-28:7-12; And / or, the mass ratio of the Bacillus amyloliquefaciens spore powder to chitosan oligosaccharide is 55-70:30-45.

3. The compound fertilizer as described in claim 1, characterized in that, The viable bacterial content of the Bacillus amyloliquefaciens spore powder is ≥1.0×10⁻⁶. 11 cfu / g; And / or, the mass ratio of sodium alginate, phytic acid, calcium chloride and trehalose is 30-45:10-18:15-25:15-25.

4. The compound fertilizer as described in claim 1, characterized in that, The preparation steps of the zinc-doped porous biochar include: Rice husk powder is pulverized and passed through a 60-100 mesh sieve. It is then stirred for 30-60 minutes in 0.5-1.0 mol / L dilute hydrochloric acid at 50-60℃ with a solid-liquid ratio of 1:10-20 (g / mL). After washing until neutral, the powder is dried. It is then mixed with 0.3-0.8 mol / L zinc sulfate solution at a solid-liquid ratio of 1:5-10 (g / mL). 5%-10% of the rice husk powder's mass of citric acid is added, and the mixture is stirred until homogeneous. Vacuum-assisted rotary impregnation is then performed for 2-3 hours, followed by solid-liquid separation. The solid portion is dried at 60-80℃ for 6-12 hours, and then subjected to low-temperature pre-carbonization, medium-temperature activation, and high-temperature carbonization. After cooling, the powder is ground and passed through a 200-300 mesh sieve. The undersize material is collected to obtain the zinc-doped porous biochar.

5. The compound fertilizer as described in claim 4, characterized in that, The vacuum-assisted rotary impregnation process is as follows: the sample is placed in a rotary evaporator at 30-50 rpm and impregnated at 50-60℃ and -0.05~-0.08 MPa. And / or, the heating rate of the low-temperature pre-carbonization is 1-2℃ / min, the temperature is 270-330℃, the holding time is 20-40min, and the protective atmosphere is nitrogen atmosphere; And / or, the intermediate temperature activation is: heating to 550-600℃ at a heating rate of 3-5℃ / min, the protective gas being a mixture of nitrogen and water vapor, with a water vapor volume fraction of 5-10%, and holding at that temperature for 60-90min; And / or, the heating rate of the high-temperature carbonization treatment is 3-5℃ / min, the temperature is 700-750℃, the holding time is 20-30min, and the protective atmosphere is nitrogen atmosphere.

6. A method for preparing a compound fertilizer for preventing and controlling soil-borne diseases of rice according to any one of claims 1-5, comprising the following steps: The carrier material is mixed with an acetone solution containing a bactericidal active component at a concentration of 50-150 g / L, impregnated under vacuum, evaporated under reduced pressure, and dried to obtain the drug-loaded carrier. After pulverizing the nutrient components through an 80-120 mesh sieve, add chitosan oligosaccharide, mix evenly, adjust the moisture content to 15-25 wt%, granulate, and dry to obtain kernel particles; The drug-loaded carrier is mixed with 1-3 wt% of a polyvinyl alcohol aqueous solution in an equal mass ratio and then ground to form a uniform slurry. The core particles are coated with the slurry to obtain particles coated with an intermediate layer; Prepare an aqueous solution of sodium alginate and a mixed crosslinking solution containing calcium chloride and phytic acid, and spray them sequentially onto the surface of the particles that are coated with the intermediate layer to form a gel isolation film and dry it to obtain isolation layer particles; A bacterial suspension was prepared by mixing Bacillus amyloliquefaciens spore powder with a protective agent, sprayed onto the surface of the granules, and dried at 30-35°C. During the drying process, a filler was added to prevent the granules from sticking together, thus obtaining the compound fertilizer used to prevent soil-borne diseases of rice. The protective agent is a pH 6.5-7.5 phosphate buffer containing 1-2 wt% trehalose, 0.1-0.3 wt% glycerol, and 0.5-1.0 wt% soluble starch.

7. The preparation method according to claim 6, characterized in that, The parameters for vacuum impregnation are: -0.08 MPa to -0.095 MPa, 2-4 h, 25-35 °C; And / or, the parameters for the reduced pressure evaporation are: -0.06 MPa to -0.08 MPa, 30-40°C, to remove 95-100% of acetone; And / or, the drying parameters are: drying to constant weight at ≤40℃ and ≤-0.095 MPa.

8. The preparation method according to claim 6, characterized in that, The particle size of the granulation is 2.0-3.5 mm; And / or, the drying is performed at 60-70°C until the moisture content is ≤5wt%; And / or, the coating process is as follows: preheating the core particles to 35-40°C and fluidizing them, controlling the inlet air temperature to 40-50°C, the atomization pressure to 0.2-0.4 MPa, and the spraying rate to 5-15 mL / min, uniformly spraying the slurry onto the surface of the core particles, and then fluidizing and drying them at 40-50°C until the particle moisture content is ≤3wt%.

9. The preparation method according to claim 6, characterized in that, The preparation steps of the isolation layer particles include: preparing an aqueous solution of sodium alginate with a concentration of 1.5-2.5 wt%; preparing a mixed crosslinked aqueous solution containing 1-2 wt% calcium chloride and 0.3-0.8 wt% phytic acid; spraying the sodium alginate aqueous solution onto the surface of the particles coating the intermediate layer, then spraying the mixed crosslinked aqueous solution, followed by fluidization at 30-40℃ for 5-10 min, and then drying at 35-40℃ until the water content is ≤5 wt%, to obtain the isolation layer particles.

10. The preparation method according to claim 6, characterized in that, The viable bacteria concentration of the bacterial suspension is 5.0 × 10⁻⁶. 8 -2.0×10 9 cfu / mL.

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