Microbial fertilizer for improving soil structure and preparation method thereof

Abstract

The invention relates to the technical field of microbial fertilizers, in particular to a microbial fertilizer for improving a soil structure and a preparation method thereof, and the microbial fertilizer comprises the following components: microbial flora, a charcoal-based composite material, magnetic nanoparticles, a polymer water retention agent, a soil enzyme activator, peanut bran, molasses and a trace element supplement. By selecting and proportioning functional components such as various microbial florae, biochar-based composite materials, magnetic nanoparticles and the like, the invention aims to construct the microbial fertilizer with efficient nutrient utilization, excellent soil structure improvement capability and environmental adaptability, not only the instant effect of the fertilizer is concerned, but also the long-term benefit and ecological sustainability of the fertilizer are concerned, and the application prospect is wide. Powerful support is provided for green development of modern agriculture.

Description

Technical Field

[0001] The invention relates to the technical field of microbial fertilizers, and in particular to a microbial fertilizer for improving soil structure and a preparation method thereof. Background Art

[0002] With the rapid development of modern agriculture, the problems of soil quality decline and nutrient imbalance have become increasingly prominent, which has seriously affected the healthy growth of crops and the sustainable development of agriculture. In order to solve this problem, microbial fertilizers, as an environmentally friendly and efficient soil conditioner, have received widespread attention. Microbial fertilizers can improve the soil microecological environment and increase the utilization rate of soil nutrients by introducing beneficial microorganisms, thereby promoting crop growth.

[0003] However, traditional microbial fertilizers have many shortcomings in the preparation and application process. First, the types and quantities of microbial flora in traditional microbial fertilizers are limited, making it difficult to give full play to the synergistic effect of microorganisms, and the effect of improving soil structure is limited. Secondly, the nutrient release of traditional fertilizers is difficult to control, which easily leads to nutrient loss and waste, and cannot meet the needs of long-term crop growth. In addition, the additives and carrier materials in traditional fertilizers often lack functional design and cannot effectively improve the stability of fertilizers and nutrient utilization efficiency.

[0004] Therefore, we propose a microbial fertilizer for improving soil structure and a preparation method thereof to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a microbial fertilizer for improving soil structure and a preparation method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A microbial fertilizer for improving soil structure comprises the following components in parts by weight: 25-35 parts of microbial flora, 15-25 parts of biochar-based composite materials, 3-7 parts of magnetic nanoparticles, 8-12 parts of polymer water retaining agents, 3-7 parts of soil enzyme activators, 10-20 parts of peanut bran, 3-7 parts of molasses, and 8-12 parts of trace element supplements.

[0008] As the preferred technical solution:

[0009] The microbial fertilizer for improving soil structure as described above comprises the following components in parts by weight: 28 parts of microbial flora, 17 parts of biochar-based composite materials, 4 parts of magnetic nanoparticles, 9 parts of polymer water retaining agent, 5 parts of soil enzyme activator, 14 parts of peanut bran, 5 parts of molasses, and 9 parts of trace element supplement.

[0010] A microbial fertilizer for improving soil structure as described above, wherein the microbial flora includes photosynthetic bacteria, bacillus, and cellulose decomposing bacteria, the biochar-based composite material is made of charcoal and straw charcoal, the magnetic nanoparticles are made of magnetic materials, the magnetic materials include iron, cobalt, and nickel, and have superparamagnetism, the polymer water retaining agent is made of hydrophilic polymer materials, the hydrophilic polymer materials include polyacrylate and polyvinyl alcohol, the soil enzyme activator is one or more of humic acid and amino acids, and the trace element supplement contains phosphorus, potassium, manganese, copper, and iron.

[0011] The microbial fertilizer for improving soil structure as described above, the photosynthetic bacteria have a cell length of 1.5-3.0 microns and a diameter of 0.8-1.2 microns, the diameter of the spores of the bacillus is not less than 1 / 3 of the cell diameter, and the temperature range during spore formation is 25-40°C, the cellulolytic bacteria contain cellulase, and its enzyme activity is not less than 100U / mL in the pH range of 5.0-7.0; the particle size of the biochar in the biochar-based composite material is controlled to be 0.1-2mm; the saturation magnetization intensity of the magnetic nanoparticles is 50-100emu / g, the particle size of the particles is 10-100nm, and the particle surface is modified to have a Zeta potential of at least -15mV; the fat content of the peanut bran is 10-20% on a dry basis; the pH value of the molasses is controlled to be 4.5-5.5, and the viscosity of the molasses is 1000-3000cP at 25°C.

[0012] As described above, a microbial fertilizer for improving soil structure, in the biochar-based composite material, a biochar skeleton with a multi-level pore structure is designed, including macropores, mesopores and micropores; the magnetic nanoparticles have a core-shell structure, wherein the core layer provides magnetic function and the shell layer is used to load or modify other functional materials; in the soil enzyme activator, the enzyme activator material with recognition sites is prepared by molecular imprinting technology, which can selectively adsorb and activate target soil enzymes.

[0013] A microbial fertilizer for improving soil structure as described above, wherein the polymer water retaining agent has a three-dimensional network structure, contains hydrophilic groups including -COONa, -COOH, and OH, and absorbs water through molecular expansion caused by the dissociation of polymer electrolytes and ion repulsion. When the water in the gel is released, its water absorption capacity can still be restored as long as the molecular chain is not destroyed; functional minerals including apatite and potassium feldspar are introduced into the biochar-based composite material to construct a biochar-mineral composite skeleton; an orderly array of magnetic nanoparticles is constructed on the surface of the biochar-based composite material, and the directional movement and distribution of the microbial flora are achieved through external magnetic field manipulation, and the force of the external magnetic field on the magnetic nanoparticles is described by the magnetic field force:

[0014] F_m=\mu_0\chiVH\nablaH;

[0015] Where: F_m is the magnetic field force, mu_0 is the vacuum magnetic permeability, chi is the magnetic susceptibility of the magnetic nanoparticle, V is the volume of the particle, H is the strength of the external magnetic field, \nablaH is the gradient of the magnetic field strength;

[0016] The movement speed of the microbial flora v = \muF_m;

[0017] Among them, \mu is the mobility coefficient of the microbial flora;

[0018] The distribution of microbial flora is described by the diffusion equation:

[0019] \frac{\partialC}{\partialt}=D\nabla^2C-\nabla\cdot(vC);

[0020] Among them: \frac{\partialC}{\partialt} represents the rate of change of the concentration of the microbial flora C with time t. This is a partial derivative that describes how the concentration of the microbial flora changes with time at a given location. C is the concentration of the microbial flora, t is time, D is the diffusion coefficient, and v is the movement speed of the microbial flora.

[0021] The second aspect of the present invention provides a method for preparing a microbial fertilizer for improving soil structure, comprising the following steps:

[0022] S1: Mix the cultured Bacillus and cellulose decomposing bacteria, add molasses as a carbon source during the mixing process, and culture the mixed bacterial liquid in a constant temperature shaker for a period of time to allow the bacteria to fully adapt and form a stable mixture;

[0023] S2: Dispersing magnetic nanoparticles in sterile water to form a stable suspension, then adding photosynthetic bacterial solution to the suspension, and co-culturing in a weak magnetic field environment, so that the photosynthetic bacteria adhere to the surface of the magnetic nanoparticles through the guidance of the magnetic field to form a symbiotic system;

[0024] S3: Add the polymer water retainer into water and fully dissolve it to form a colloidal liquid. Then, add the photosynthetic bacteria liquid and the soil enzyme activator into the colloidal liquid in sequence and stir evenly. Through the bridging effect of the polymer water retainer, the photosynthetic bacteria and the soil enzyme activator form a stable composite system.

[0025] S4: crushing the peanut bran, mixing the crushed peanut bran with the trace element supplement to form a mixture rich in organic matter and trace elements, dispersing the biochar-based composite material in sterile water to form a suspension, and sequentially adding the Bacillus-cellulose decomposing bacteria mixture, the magnetic nanoparticle-photosynthetic bacteria symbiotic system, the photosynthetic bacteria-polymer water retaining agent-soil enzyme activator composite system, and the mixture of peanut bran and trace element supplement to the biochar suspension, and fully stirring to make each component evenly distributed on the biochar-based composite material;

[0026] S5: Drying the combined microbial fertilizer to remove excess water. After drying, sieving and packaging are performed to obtain the final microbial fertilizer product for improving soil structure.

[0027] As the preferred technical solution:

[0028] As described above, in the preparation method of a microbial fertilizer for improving soil structure, in S1, during the constant temperature shaking incubation process, a dynamic temperature and pH control strategy is implemented, and the temperature range gradually increases from 25°C to 35°C and then decreases to 25°C within 24 hours to simulate day and night changes; the pH value fluctuates within the range of ±0.5 from the initial 7.0 by automatically dripping acid and alkali solution, simulating the natural environment and enhancing the environmental adaptability of the bacteria.

[0029] The method for preparing a microbial fertilizer for improving soil structure as described above, wherein S4 comprises the following steps:

[0030] S41: First, peanut bran is selected as a raw material, and is crushed by a high-speed crusher, and the speed of the crusher is set to 2500-3000 rpm, and the crushed into particles with a particle size of less than 0.5 mm, and an anti-caking agent is added during the crushing process;

[0031] S42: Mix the crushed peanut bran with the trace element supplement using a double-screw mixer, set the mixing time to 30 minutes, and the mixing speed to medium speed. After the mixing is completed, take samples for quality inspection to ensure that the trace elements are evenly distributed in the peanut bran without local excess or deficiency.

[0032] S43: Dispersing the biochar-based composite material in sterile water using a high shear disperser for dispersion, setting the dispersion time to 20 minutes to ensure the formation of a stable suspension. During the dispersion process, a surfactant is added to reduce the surface tension of the biochar and improve its dispersibility in water;

[0033] S44: Slowly add the mixture prepared in step S42 to the biochar suspension prepared in step S43, and then add the Bacillus-cellulose decomposing bacteria mixture, the magnetic nanoparticle-photosynthetic bacteria symbiotic system, and the photosynthetic bacteria-polymer water retaining agent-soil enzyme activator composite system in sequence, and stir with a stirrer, set the stirring speed to 100-150 rpm, and the stirring time to 60 minutes to ensure that all components are evenly distributed on the biochar-based composite material.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] Bacillus can form spores to resist adverse environments, and produce a variety of enzymes to promote the decomposition of organic matter; cellulolytic bacteria can specifically decompose cellulose and convert it into usable substances such as glucose. After the two are combined, Bacillus provides protection and support for cellulolytic bacteria, and cellulolytic bacteria provide carbon sources and energy for Bacillus, jointly promoting the rapid decomposition of organic matter in the soil and the circulation of nutrients.

[0036] Magnetic nanoparticles can form a tiny magnetic field in the soil, affecting the growth and metabolic direction of microorganisms. Photosynthetic bacteria can photosynthesize and convert inorganic substances into organic substances. After the two are combined, magnetic nanoparticles can guide photosynthetic bacteria to move deeper into the soil and expand their distribution range. At the same time, the metabolic activities of photosynthetic bacteria can be regulated by magnetic nanoparticles, allowing them to use light energy more efficiently for photosynthesis. This symbiotic system can enhance the photosynthesis efficiency of the soil and increase the organic matter content and fertility of the soil.

[0037] Photosynthetic bacteria can photosynthesize and convert inorganic substances into organic substances; polymer water retainers can keep the water in the soil stable; soil enzyme activators can activate enzymes in the soil. After the three are combined, photosynthetic bacteria can use the water provided by the polymer water retainer to photosynthesize, and the activation of soil enzymes can accelerate the transformation and circulation of soil nutrients. This composite system can improve the organic matter content, water retention and nutrient utilization efficiency of the soil.

[0038] Microbial flora, biochar-based composite materials, and magnetic nanoparticles form a ternary system that combines the advantages of microbial flora, biochar-based composite materials, and magnetic nanoparticles. Microbial flora can decompose organic matter and release nutrients; biochar-based composite materials provide habitats and protection for microorganisms; and magnetic nanoparticles can guide microorganisms to move deep into the soil. The synergistic effect of the three can optimize the structure of soil microbial communities, improve soil biological activity and fertility, and promote nutrient circulation in the deep soil and improve soil structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is the bacterial phase at 3d of Example 4 of the present invention;

[0040] Figure 2 This is the bacterial phase at 7d of Example 4 of the present invention. DETAILED DESCRIPTION

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. In the event of a conflict, the definitions in the specification shall prevail. "When mass, concentration, temperature, time, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, regardless of whether the range is disclosed separately. For example, a range of 1-50 should be understood to include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91 6, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, any number, combination of numbers, or subrange, and all decimal values ​​between the above integers, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. With respect to subranges, "nested subranges" extending from any endpoint within the range are specifically contemplated. For example, nested subranges of the exemplary range 1-50 may include 1-10, 1-20, 1-30, and 1-40 in one direction, or 50-40, 50-30, 50-20, and 50-10 in the other direction."

[0042] The present invention is further explained below in conjunction with specific examples. The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0043] A microbial fertilizer for improving soil structure comprises the following components in parts by weight: 25-35 parts of microbial flora, 15-25 parts of biochar-based composite materials, 3-7 parts of magnetic nanoparticles, 8-12 parts of polymer water retaining agents, 3-7 parts of soil enzyme activators, 10-20 parts of peanut bran, 3-7 parts of molasses, and 8-12 parts of trace element supplements.

[0044] Among them, the microbial flora includes photosynthetic bacteria, Bacillus, and cellulose-decomposing bacteria. The biochar-based composite material is made of charcoal and straw charcoal. The magnetic nanoparticles are made of magnetic materials, and the magnetic materials include iron, cobalt, and nickel, and have superparamagnetism. The polymer water-retaining agent is made of hydrophilic polymer materials, and the hydrophilic polymer materials include polyacrylate and polyvinyl alcohol. The soil enzyme activator is one or more of humic acid and amino acids. The trace element supplement contains phosphorus, potassium, manganese, copper, and iron.

[0045] Specifically, the length of the photosynthetic bacteria is 1.5-3.0 microns and the diameter is 0.8-1.2 microns. The diameter of the spores of Bacillus is not less than 1 / 3 of the diameter of the bacteria, and the temperature range of spore formation is 25-40°C. The cells of the cellulose decomposing bacteria contain cellulase, and its enzyme activity is not less than 100U / mL in the pH range of 5.0-7.0; the particle size of the biochar in the biochar-based composite material is controlled to be 0.1-2mm; the saturation magnetization intensity of the magnetic nanoparticles is 50-100emu / g, the particle size of the particles is 10-100nm, and the surface of the particles is modified to have a Zeta potential of at least -15mV; the fat content of the peanut bran is 10-20% on a dry basis; the pH value of the molasses is controlled to be 4.5-5.5, and the viscosity of the molasses is 1000-3000cP at 25°C.

[0046] It should be noted that in biochar-based composite materials, a biochar skeleton with a multi-level pore structure is designed, including macropores, mesopores and micropores, to provide spaces of different scales for microbial habitation and nutrient storage; magnetic nanoparticles have a core-shell structure, in which the core layer provides magnetic function and the shell layer is used to load or modify other functional materials to achieve multifunctional integration; in soil enzyme activators, molecular imprinting technology is used to prepare enzyme activator materials with recognition sites, which can selectively adsorb and activate target soil enzymes; micro-nano structure regulation technology is introduced, including nanoimprinting and microfluidics, to precisely control the microstructure and morphology of fertilizers and optimize their interaction with soil and nutrient release behavior.

[0047] In the microbial fertilizer for improving soil structure, in order to realize the integrated application of the biochar-based composite material, magnetic nanoparticles, soil enzyme activator and micro-nano structure regulation technology, a specific embodiment is given below:

[0048] 1. Preparation of biochar-based composite materials

[0049] Raw material preparation: Sawdust is selected as the biomass source, and its particle size is controlled between 0.15 and 0.50 mm. Prepare a hydrogen peroxide solution with a mass concentration of 5% as an oxidant for the hydrothermal reaction. Hydrothermal reaction: Mix sawdust and hydrogen peroxide solution at a solid-liquid ratio of 1g:10mL, place in a hydrothermal reactor, and perform a hydrothermal reaction at 180°C for 24 hours to obtain hydrothermal charcoal. Pyrolysis treatment: Pyrolyze the hydrothermal charcoal at 800°C for 60 minutes in a nitrogen atmosphere to obtain a biochar skeleton with a multi-level pore structure. Among them, the macropore diameter is >50nm, the mesopore diameter is between 2 and 50nm, and the micropore diameter is <2nm.

[0050] 2. Preparation and Integration of Magnetic Nanoparticles

[0051] Core layer preparation: Fe was prepared by coprecipitation method 3 O 4 Nanoparticles are used as the core layer, and the average particle size is controlled at about 10nm to ensure that it has superparamagnetism. Shell coating: Polyethylene glycol is selected as the shell material, and the Fe 3 O 4 A uniform shell layer with a thickness of about 5nm is formed on the surface of the nanoparticles. Functional integration: Load or modify other functional materials on the shell layer, such as adding molecules containing functional groups such as carboxyl and amino groups to enhance their interaction with soil enzymes or microorganisms.

[0052] 3. Preparation and introduction of soil enzyme activators

[0053] Molecular imprinting technology: Using the target soil enzyme (such as urease, phosphatase) as the template molecule, the molecular imprinting technology is used to prepare the enzyme activator material with recognition sites. By optimizing the imprinting conditions and elution process, it is ensured that the activator can selectively adsorb and activate the target enzyme. Activator introduction: The prepared enzyme activator is mixed evenly with the biochar-based composite material so that the activator can be evenly distributed in the pore structure of the biochar.

[0054] 4. Application of Micro-Nano Structure Control Technology

[0055] Nanoimprinting: Nanoimprinting technology is used to create nanoscale patterns on the surface of biochar to increase its specific surface area and reactive sites. The imprinting depth is controlled between 50 and 100 nm. Microfluidics: Microfluidics technology is used to precisely control the microstructure and morphology of fertilizers. By adjusting parameters such as flow rate, temperature and pressure in the microchannel, the uniform distribution and size control of fertilizer particles can be achieved.

[0056] It should be noted that the polymer water retainer has a three-dimensional network structure, which contains hydrophilic groups, including -COONa, -COOH, and OH, so that it can absorb and store a large amount of water, and absorb water through the molecular expansion caused by the dissociation of polymer electrolytes and ion exclusion. When the water in the gel is released, as long as the molecular chain is not destroyed, its water absorption capacity can still be restored; in the biochar-based composite material, functional minerals, including apatite and potassium feldspar, are introduced to construct a biochar-mineral composite skeleton. This structure not only improves the mechanical strength and stability of the fertilizer, but also realizes the slow release function of nutrients to meet the needs of long-term crop growth; an orderly array of magnetic nanoparticles is constructed on the surface of the biochar-based composite material, and the directional movement and distribution of the microbial flora are realized through external magnetic field manipulation, and the soil microbial community structure is optimized. At the same time, this array structure can also enhance the soil's ability to adsorb nutrients and improve nutrient utilization efficiency. The force of the external magnetic field on the magnetic nanoparticles is described by the magnetic field force as follows:

[0057] F_m=\mu_0\chiVH\nablaH;

[0058] Where: F_m is the magnetic field force, mu_0 is the vacuum magnetic permeability, chi is the magnetic susceptibility of the magnetic nanoparticle, V is the volume of the particle, H is the strength of the external magnetic field, \nablaH is the gradient of the magnetic field strength;

[0059] The movement speed of the microbial flora v = \muF_m;

[0060] Among them, \mu is the mobility coefficient of the microbial flora;

[0061] The distribution of microbial flora is described by the diffusion equation:

[0062] \frac{\partialC}{\partialt}=D\nabla^2C-\nabla\cdot(vC);

[0063] Among them: \frac{\partialC}{\partialt} represents the rate of change of the concentration of the microbial flora C with time t. This is a partial derivative, which describes how the concentration of the microbial flora changes with time at a given location. C is the concentration of the microbial flora, t is time, D is the diffusion coefficient, and v is the movement speed of the microbial flora. During the diffusion process, if \frac{\partialC}{\partialt}>0, it means that the concentration of the microbial flora at this location increases with time; if \frac{\partialC}{\partialt}<0, it means that the concentration decreases with time; if \frac{\partialC}{\partialt}=0, it means that the concentration reaches a steady state and does not change with time.

[0064] In the microbial fertilizer for improving soil structure, a detailed embodiment is given below regarding the specific implementation of the polymer water retaining agent, functional minerals and magnetic nanoparticle array:

[0065] 1. Preparation and characteristics of polymer water retaining agent

[0066] Raw materials and preparation: Polyacrylate polymers are selected as the basic materials of water retaining agents. Through chemical cross-linking reactions, hydrophilic groups such as -COONa, -COOH, and OH are introduced into the polymer chain to form a three-dimensional network structure.

[0067] Performance data: The water retainer can absorb 500 times its own weight in water. Under normal soil conditions, the water retainer can slowly release water and continuously provide a moist environment for the soil for more than 30 days. When the water in the gel is released, its water absorption capacity can be restored to more than 85% of its original state if the molecular chain is not destroyed.

[0068] 2. Integration of biochar-based composites and functional minerals

[0069] Raw materials and preparation: Biochar is prepared by high-temperature pyrolysis using woody biomass as raw material. Functional minerals such as apatite and potassium feldspar are crushed into microparticles. Biochar is mixed with functional minerals and sintered at high temperature to form a biochar-mineral composite skeleton.

[0070] Performance data: The mechanical strength of the composite skeleton is increased by 30%, and the stability is significantly enhanced. The release rate of minerals in the soil is reduced by 40%, achieving the slow release function of nutrients. Crops can still maintain stable nutrient absorption within 60 days after fertilization.

[0071] 3. Construction and application of magnetic nanoparticle arrays

[0072] Preparation: Select Fe 3 O 4 As the basic material of magnetic nanoparticles, an orderly array of magnetic nanoparticles was constructed on the surface of biochar-based composite materials by chemical deposition.

[0073] Application and Effect: Under the action of external magnetic field, magnetic nanoparticles can realize the directional movement and distribution of microbial flora. The structure of soil microbial community is optimized, and the number of beneficial microorganisms increases by 30%. The soil's ability to adsorb nutrients is increased by 25%, and the nutrient utilization efficiency is significantly improved.

[0074] Embodiment 1

[0075] A microbial fertilizer for improving soil structure comprises the following components in parts by weight: 25 parts of microbial flora (photosynthetic bacteria, bacillus, cellulose decomposing bacteria; Shandong Siyang Biotechnology Co., Ltd.), 15 parts of biochar-based composite materials (charcoal, straw charcoal), 3 parts of magnetic nanoparticles, 8 parts of high molecular water retaining agent (polyacrylate), 3 parts of soil enzyme activator (humic acid; Shandong Suihua Biotechnology Co., Ltd.), 10 parts of peanut bran, 3 parts of molasses, and 8 parts of trace element supplement.

[0076] The embodiment also proposes a method for preparing a microbial fertilizer for improving soil structure, comprising the following steps:

[0077] S1: The cultured Bacillus and cellulose decomposing bacteria are mixed. During the mixing process, molasses is added as a carbon source to promote the symbiotic relationship between the two bacteria. The mixed bacterial liquid is cultured in a constant temperature shaker, the temperature is maintained at 28°C, the speed is set to 150rpm, and the culture time is continued for 24 hours to allow the bacteria to fully adapt and form a stable mixture;

[0078] S2: Use an ultrasonic disperser with a power of 200W and a treatment time of 5 minutes to disperse the magnetic nanoparticles in sterile water to form a stable suspension. Then, add the photosynthetic bacterial solution to the suspension and co-cultivate in a weak magnetic field environment. The magnetic field strength is maintained at 5mT for 12 hours. Through the guidance of the magnetic field, the photosynthetic bacteria adhere to the surface of the magnetic nanoparticles to form a symbiotic system.

[0079] S3: Add the polymer water retainer into water and fully dissolve it to form a colloidal liquid. Then, add the photosynthetic bacteria liquid and the soil enzyme activator into the colloidal liquid in sequence and stir evenly. The speed is set to 80 rpm and the stirring time is 30 minutes. Through the bridging effect of the polymer water retainer, the photosynthetic bacteria and the soil enzyme activator form a stable composite system.

[0080] S4: crushing the peanut bran to control the particle size to 0.1 mm so as to better mix with other components of the fertilizer, then uniformly mixing the crushed peanut bran with the trace element supplement to form a mixture rich in organic matter and trace elements, dispersing the biochar-based composite material in sterile water to form a suspension, and sequentially adding the Bacillus-cellulose decomposing bacteria mixture, the magnetic nanoparticle-photosynthetic bacteria symbiotic system, the photosynthetic bacteria-polymer water retaining agent-soil enzyme activator composite system, and the mixture of peanut bran and trace element supplement to the biochar suspension, and fully stirring at a speed of 150 rpm for 60 minutes to evenly distribute the components on the biochar-based composite material;

[0081] S5: Drying the combined microbial fertilizers, controlling the temperature at 40°C and the humidity below 30% for 12 hours. After drying, sieving and packaging are performed to obtain the final microbial fertilizer product for improving soil structure.

[0082] Embodiment 2

[0083] A microbial fertilizer for improving soil structure comprises the following components in parts by weight: 27 parts of microbial flora (photosynthetic bacteria, bacillus, cellulose decomposing bacteria), 18 parts of biochar-based composite materials, 4 parts of magnetic nanoparticles, 9 parts of polymer water retaining agents, 4 parts of soil enzyme activators, 12 parts of peanut bran, 4 parts of molasses, and 9 parts of trace element supplements.

[0084] The embodiment also proposes a method for preparing a microbial fertilizer for improving soil structure, comprising the following steps:

[0085] S1: The cultured Bacillus and cellulose decomposing bacteria are mixed. During the mixing process, molasses is added as a carbon source to promote the symbiotic relationship between the two bacteria. The mixed bacterial liquid is cultured in a constant temperature shaker, the temperature is maintained at 30°C, the speed is set to 160rpm, and the culture time is continued for 28 hours to allow the bacteria to fully adapt and form a stable mixture;

[0086] S2: Use an ultrasonic disperser with a power of 250W and a treatment time of 7 minutes to disperse the magnetic nanoparticles in sterile water to form a stable suspension. Then, add the photosynthetic bacterial solution to the suspension and co-cultivate in a weak magnetic field environment. The magnetic field strength is maintained at 6mT for 13 hours. Through the guidance of the magnetic field, the photosynthetic bacteria adhere to the surface of the magnetic nanoparticles to form a symbiotic system.

[0087] S3: Add the polymer water retainer into water and fully dissolve it to form a colloidal liquid. Then, add the photosynthetic bacteria liquid and the soil enzyme activator into the colloidal liquid in sequence and stir evenly. The speed is set to 90 rpm and the stirring time is 40 minutes. Through the bridging effect of the polymer water retainer, the photosynthetic bacteria and the soil enzyme activator form a stable composite system.

[0088] S4: crushing the peanut bran to control the particle size to 0.2 mm so as to better mix with other components of the fertilizer, then uniformly mixing the crushed peanut bran with the trace element supplement to form a mixture rich in organic matter and trace elements, dispersing the biochar-based composite material in sterile water to form a suspension, and sequentially adding the Bacillus-cellulose decomposing bacteria mixture, the magnetic nanoparticle-photosynthetic bacteria symbiotic system, the photosynthetic bacteria-polymer water retaining agent-soil enzyme activator composite system, and the mixture of peanut bran and trace element supplement to the biochar suspension, and fully stirring at a speed of 170 rpm for 70 minutes to evenly distribute the components on the biochar-based composite material;

[0089] S5: Drying the combined microbial fertilizers, controlling the temperature at 43°C, the humidity below 30%, and the drying time for 14 hours. After drying, sieving and packaging are performed to obtain the final microbial fertilizer product for improving soil structure.

[0090] Embodiment 3

[0091] A microbial fertilizer for improving soil structure comprises the following components in parts by weight: 29 parts of microbial flora (photosynthetic bacteria, bacillus, cellulose decomposing bacteria), 21 parts of biochar-based composite materials, 6 parts of magnetic nanoparticles, 11 parts of polymer water retaining agents, 6 parts of soil enzyme activators, 16 parts of peanut bran, 6 parts of molasses, and 11 parts of trace element supplements.

[0092] The embodiment also proposes a method for preparing a microbial fertilizer for improving soil structure, comprising the following steps:

[0093] S1: The cultured Bacillus and cellulose decomposing bacteria were mixed. During the mixing process, molasses was added as a carbon source to promote the symbiotic relationship between the two bacteria. The mixed bacterial liquid was cultured in a constant temperature shaker, the temperature was maintained at 31°C, the rotation speed was set to 180rpm, and the culture time lasted for 40 hours, so that the bacteria were fully adapted and formed a stable mixture;

[0094] S2: Use an ultrasonic disperser with a power of 300W and a treatment time of 8 minutes to disperse the magnetic nanoparticles in sterile water to form a stable suspension. Then, add the photosynthetic bacterial solution to the suspension and co-cultivate in a weak magnetic field environment. The magnetic field strength is maintained at 8mT for 15 hours. Through the guidance of the magnetic field, the photosynthetic bacteria adhere to the surface of the magnetic nanoparticles to form a symbiotic system.

[0095] S3: Add the polymer water retainer into water and fully dissolve it to form a colloidal liquid. Then, add the photosynthetic bacteria liquid and the soil enzyme activator into the colloidal liquid in sequence and stir evenly. The speed is set to 110 rpm and the stirring time is 50 minutes. Through the bridging effect of the polymer water retainer, the photosynthetic bacteria and the soil enzyme activator form a stable composite system.

[0096] S4: crushing the peanut bran to control the particle size to 0.3 mm so as to better mix with other components of the fertilizer, then uniformly mixing the crushed peanut bran with the trace element supplement to form a mixture rich in organic matter and trace elements, dispersing the biochar-based composite material in sterile water to form a suspension, and sequentially adding the Bacillus-cellulose decomposing bacteria mixture, the magnetic nanoparticle-photosynthetic bacteria symbiotic system, the photosynthetic bacteria-polymer water retaining agent-soil enzyme activator composite system, and the mixture of peanut bran and trace element supplement to the biochar suspension, and fully stirring at a speed of 210 rpm for 110 minutes to evenly distribute the components on the biochar-based composite material;

[0097] S5: Drying the combined microbial fertilizers, controlling the temperature at 47°C and the humidity below 30% for 21 hours. After drying, sieving and packaging are performed to obtain the final microbial fertilizer product for improving soil structure.

[0098] Embodiment 4

[0099] A microbial fertilizer for improving soil structure comprises the following components in parts by weight: 35 parts of microbial flora (photosynthetic bacteria, bacillus, cellulose decomposing bacteria), 25 parts of biochar-based composite materials, 7 parts of magnetic nanoparticles, 12 parts of polymer water retaining agents, 7 parts of soil enzyme activators, 20 parts of peanut bran, 7 parts of molasses, and 12 parts of trace element supplements.

[0100] The embodiment also proposes a method for preparing a microbial fertilizer for improving soil structure, comprising the following steps:

[0101] S1: The cultured Bacillus and cellulose decomposing bacteria are mixed. During the mixing process, molasses is added as a carbon source to promote the symbiotic relationship between the two bacteria. The mixed bacterial liquid is cultured in a constant temperature shaker, the temperature is maintained at 32°C, the speed is set to 200 rpm, and the culture time is continued for 48 hours to allow the bacteria to fully adapt and form a stable mixture;

[0102] S2: Use an ultrasonic disperser with a power of 400W and a treatment time of 10 minutes to disperse the magnetic nanoparticles in sterile water to form a stable suspension. Then, add the photosynthetic bacterial solution to the suspension and co-cultivate in a weak magnetic field environment. The magnetic field strength is maintained at 10mT for 16 hours. Through the guidance of the magnetic field, the photosynthetic bacteria adhere to the surface of the magnetic nanoparticles to form a symbiotic system.

[0103] S3: Add the polymer water retainer into water and fully dissolve it to form a colloidal liquid. Then, add the photosynthetic bacteria solution and the soil enzyme activator into the colloidal liquid in sequence and stir evenly. The speed is set to 120 rpm and the stirring time is 60 minutes. Through the bridging effect of the polymer water retainer, the photosynthetic bacteria and the soil enzyme activator form a stable composite system.

[0104] S4: crushing the peanut bran to control the particle size to 0.5 mm so as to better mix with other components of the fertilizer, then uniformly mixing the crushed peanut bran with the trace element supplement to form a mixture rich in organic matter and trace elements, dispersing the biochar-based composite material in sterile water to form a suspension, and sequentially adding the Bacillus-cellulose decomposing bacteria mixture, the magnetic nanoparticle-photosynthetic bacteria symbiotic system, the photosynthetic bacteria-polymer water retaining agent-soil enzyme activator composite system, and the mixture of peanut bran and trace element supplement to the biochar suspension, and fully stirring at a speed of 250 rpm for 120 minutes to evenly distribute the components on the biochar-based composite material;

[0105] S5: Drying the combined microbial fertilizers, controlling the temperature at 50°C, the humidity below 30%, and the drying time for 24 hours. After drying, sieving and packaging are performed to obtain the final microbial fertilizer product for improving soil structure.

[0106] Comparative Example 1

[0107] A microbial fertilizer for improving soil structure and a preparation method thereof are basically the same as those in Example 4, except that: in S1, during the constant temperature shaking incubation process, a dynamic temperature and pH control strategy is implemented, and the temperature range is gradually increased from 25°C to 35°C and then decreased to 25°C within 24 hours to simulate day and night changes; the pH value fluctuates within the range of ±0.5 from the initial 7.0 by automatically dripping acid and alkali solution, simulating the natural environment and enhancing the environmental adaptability of the bacteria.

[0108] Comparative Example 2

[0109] A microbial fertilizer for improving soil structure and a preparation method thereof are basically the same as those in Example 4, except that: S4 includes the following steps:

[0110] S41: First, high-quality peanut bran is selected as a raw material, and finely crushed by a crushing device, such as a high-speed crusher, and the speed of the crusher is set to 2500-3000 revolutions per minute to ensure that the peanut bran is evenly crushed into particles with a particle size of less than 0.5 mm, so as to increase its contact area with other fertilizer components. During the crushing process, a small amount of anti-caking agent, such as silicon dioxide, is added to prevent adhesion and agglomeration between peanut bran particles;

[0111] S42: Mix the crushed peanut bran with the pre-selected trace element supplement (such as zinc, copper, manganese, etc.) in a certain ratio (such as peanut bran: trace element = 10:1), use a double-screw mixer to mix, set the mixing time to 30 minutes, and the mixing speed to medium speed to ensure that the two materials are fully and evenly mixed. After the mixing is completed, take samples for quality inspection to ensure that the trace elements are evenly distributed in the peanut bran without local excess or deficiency;

[0112] S43: Select a biochar-based composite material with a high specific surface area and excellent adsorption performance, disperse the biochar-based composite material in sterile water at a ratio of 1:10, use a high shear disperser to disperse, set the dispersion time to 20 minutes to ensure the formation of a stable suspension, and during the dispersion process, add a surfactant (such as Tween-80) to reduce the surface tension of the biochar and improve its dispersibility in water;

[0113] S44: Slowly add the mixture rich in organic matter and trace elements (peanut bran and trace element supplement) prepared in step S42 to the biochar suspension prepared in step S43, and then add the pre-prepared Bacillus-cellulose decomposing bacteria mixture, magnetic nanoparticle-photosynthetic bacteria symbiotic system, and photosynthetic bacteria-polymer water retaining agent-soil enzyme activator composite system in sequence, and use a high-efficiency agitator to stir, set the stirring speed to 100-150 rpm, and the stirring time to 60 minutes to ensure that all components are evenly distributed on the biochar-based composite material. During the stirring process, the pH value and temperature of the mixed solution are monitored in real time to ensure that the integrated environment is stable, which is conducive to the activity and stability of each component.

[0114] Comparative Example 1

[0115] A microbial fertilizer for improving soil structure and a preparation method thereof are basically the same as those of Example 4, except that the addition of a mixture of Bacillus and cellulose decomposing bacteria is omitted during the preparation process.

[0116] Comparative Example 2

[0117] A microbial fertilizer for improving soil structure and a preparation method thereof are basically the same as those of the fourth embodiment, except that the addition of magnetic nanoparticles is omitted during the preparation process.

[0118] Comparative Example 3

[0119] A microbial fertilizer for improving soil structure and a preparation method thereof are basically the same as those in Example 4, except that the addition of a high molecular weight water retaining agent is omitted during the preparation process.

[0120] Comparative Example 4

[0121] A microbial fertilizer for improving soil structure and a preparation method thereof are basically the same as those of Example 4, except that the preparation steps are simplified, and steps S2 (co-cultivation of magnetic nanoparticles and photosynthetic bacteria) and S3 (mixing of a polymer water retaining agent with photosynthetic bacteria and a soil enzyme activator) are omitted during the preparation process.

[0122] The microbial fertilizers prepared in the above-mentioned Examples 1 to 4, Comparative Example 1, Comparative Example 2, and Comparative Examples 1 to 4 were tested:

[0123] Refer to GB / T 20238-2006 "Technical Specifications for Microbial Fertilizers"

[0124] Detection method: Determine the number of effective live bacteria in the fertilizer by plate count method or MPN method (maximum probable number method) to ensure that it meets the standard requirements.

[0125] Detection of microbial activity and soil enzyme activity

[0126] Testing standards: Please refer to the testing standards related to soil microorganisms and enzyme activity.

[0127] How to detect:

[0128] Ratio data: Measures soil respiration intensity and reflects microbial activity.

[0129] Interval data: Enzyme activity assays are used to quantify enzyme activity in soil.

[0130] Refer to GB / T 5716-2017 (Determination method of soil organic matter), GB / T 7859-1987 (Determination of soil pH value), etc.

[0131] Detection method: Determine the soil organic matter content, pH value and other physical and chemical properties through chemical analysis methods.

[0132] GB / T 26427-2010 (Detection of Bacillus cereus in feeds) and related cellulolytic bacteria detection standards.

[0133] Soil samples are collected and cultured using selective media to isolate Bacillus and cellulose-degrading bacteria. The bacterial species are further confirmed by microscopic observation, biochemical tests, and the number of bacteria is determined by colony counting. The ability to degrade cellulose can be determined by methods such as filter paper disintegration tests.

[0134] The results are shown in Table 1:

[0135] Table 1

[0136]

[0137]

[0138] From the above Table 1, it can be directly obtained that the effective viable count is one of the important indicators for measuring the quality of microbial fertilizers. From Example 1 to Example 4, we can see that the effective viable count gradually increases, which indicates that with the optimization of the formula and preparation method, the number of viable bacteria in the fertilizer has been effectively improved. Example 4 achieved the highest viable count of 5.0×10^8 CFU / g, which helps to enhance the effect of the fertilizer in soil improvement and plant growth promotion.

[0139] Soil respiration intensity is an important indicator reflecting soil microbial activity. From the data, it can be seen that the soil respiration intensity of Example 2 and Example 4 is relatively high, indicating that the microbial fertilizers in these two examples can better stimulate the activity of soil microorganisms and contribute to the biochemical process of the soil.

[0140] In terms of soil physical and chemical properties, the main focus was on organic matter content and pH value. Organic matter content: The organic matter content of all examples was 32%, showing the stability of the fertilizer in improving soil organic matter. pH value: The pH value of all examples was 7.0, indicating that the fertilizer has a good effect on maintaining a neutral soil environment, which is conducive to the growth of most plants and the activity of soil microorganisms.

[0141] All examples can completely decompose the filter paper within 7 days, showing good cellulose decomposition ability. This shows that the cellulose decomposing bacteria in the fertilizer are highly active and can effectively decompose the cellulose in the soil, releasing more nutrients for plant absorption.

[0142] Among Example 4 and Control Examples 1 and 2, Control Example 1 has the highest effective viable count, reaching 6.0×10^8CFU / g, which is higher than 5.0×10^8CFU / g of Example 4 and 5.5×10^8CFU / g of Control Example 2. This is because Control Example 1 adopts a dynamic temperature and pH control strategy, which enhances the environmental adaptability of the bacteria and promotes the proliferation of the bacterial colony.

[0143] The soil respiration intensity of Control Example 1 was the highest, at 30 μmolCO2 / g / h, indicating that its microbial activity was the strongest. Example 4 and Control Example 2 were 25 μmolCO2 / g / h and 28 μmolCO2 / g / h, respectively, both lower than Control Example 1. This is related to the higher number of viable bacteria in Control Example 1. The more viable bacteria there are, the more vigorous the microbial metabolic activity is, thereby increasing the soil respiration intensity.

[0144] In terms of organic matter content, the control example 1 has the highest content (34%), followed by the control example 2 (33%), and finally the embodiment 4 (32%). This shows that the fertilizers of the control examples 1 and 2 more effectively increase the organic matter content in the soil.

[0145] In terms of pH value, the pH value of Control Example 1 is 7.2, slightly higher than 7.0 of Example 4 and 7.1 of Control Example 2. This is related to the dynamic pH control strategy adopted in Control Example 1, which makes the soil pH value more neutral, which is conducive to the growth of most plants and the activity of microorganisms.

[0146] The cellulose decomposition rate of Control Example 1 was the fastest, and the filter paper could be completely decomposed in only 5 days, while Example 4 and Control Example 2 required 7 days and 6 days, respectively. This was related to the higher number of viable bacteria and optimized environmental conditions in Control Example 1, which increased the activity of cellulose-decomposing bacteria and thus accelerated the cellulose decomposition rate.

[0147] Reference Figure 1-2 In Example 4 and Comparative Example 1, where other conditions were the same, the addition of the Bacillus-cellulose decomposing bacteria mixture was omitted in Comparative Example 1. Impact: The effective viable bacteria count dropped to 3.5×10^8 CFU / g, and the soil respiration intensity and cellulose decomposition rate also decreased significantly, indicating that the absence of Bacillus and cellulose decomposing bacteria had a negative impact on the performance of the fertilizer.

[0148] The addition of magnetic nanoparticles was omitted in Comparative Example 2. Although the effective viable bacteria count was similar to that in Example 4, the soil respiration intensity and cellulose decomposition rate decreased, indicating that the magnetic nanoparticles played a role in improving microbial activity and promoting cellulose decomposition.

[0149] In comparative example 3, the addition of high molecular water retaining agent was omitted. The number of effective live bacteria decreased, the soil water content decreased by 10%, and the soil respiration intensity was also affected. This shows that high molecular water retaining agent plays an important role in maintaining soil moisture and microbial activity.

[0150] Comparative Example 4 simplifies the preparation steps, omitting the co-cultivation of magnetic nanoparticles and photosynthetic bacteria and the mixing of polymer water retaining agent, photosynthetic bacteria and soil enzyme activator. The effective viable bacteria count, soil respiration intensity and cellulose decomposition rate all decreased significantly, while the soil water content decreased by 15%. This shows that the omitted steps have an important impact on the overall performance of the fertilizer, especially affecting the activity of microorganisms and the water retention capacity of the soil.

[0151] By comparing the data of Example 4 with Comparative Examples 1 to 4, we can draw the following conclusions:

[0152] Importance of Bacillus and cellulolytic bacteria: The absence of these microorganisms will significantly reduce the effective live bacteria count and cellulose decomposition ability of the fertilizer, thus affecting the soil improvement effect.

[0153] The enhancing effect of magnetic nanoparticles: Although their absence will not significantly reduce the number of effective live bacteria, it will reduce the activity of microorganisms and the rate of cellulose decomposition, indicating that magnetic nanoparticles enhance the function of microorganisms in some way.

[0154] Key role of polymer water retainer: Omitting polymer water retainer resulted in decreased soil water content and reduced microbial activity, indicating that it is crucial in maintaining soil moisture environment and microbial activity.

[0155] Completeness of preparation steps: Simplifying the preparation steps will comprehensively affect the performance of the fertilizer, including microbial activity, soil respiration intensity, cellulose decomposition rate and soil water retention capacity, indicating that each step contributes to the performance of the final product.

[0156] The fertilizer of the present invention is composed of a variety of microbial flora (including photosynthetic bacteria, bacillus, cellulose decomposing bacteria), biochar-based composite materials, magnetic nanoparticles, polymer water retaining agents, soil enzyme activators, peanut bran and trace element supplements. Through specific preparation steps, including mixed cultivation of microorganisms, combination with biochar-based composite materials, etc., each component forms a stable composite system. In addition, advanced technologies such as dynamic temperature and pH control, fine crushing and efficient mixing are introduced to further improve the efficiency of the fertilizer.

[0157] By introducing efficient microbial flora, this technology can significantly increase the number of effective living bacteria in the soil, thereby improving the biological activity of the soil. These microorganisms can decompose organic matter, release nutrients, and promote plant growth.

[0158] The addition of biochar-based composites and magnetic nanoparticles helps improve the physical structure of the soil. Biochar provides a good microbial habitat, while magnetic nanoparticles can guide microorganisms deep into the soil, enhancing biological activity and nutrient cycling in the deep soil layer.

[0159] The use of polymer water retainers can effectively improve the water retention capacity of the soil, helping plants to survive and grow better under drought or seasonal drought conditions. Soil enzyme activators can activate enzymes in the soil, accelerate the conversion and utilization of nutrients, thereby improving the utilization rate of fertilizers and the nutrient absorption efficiency of plants.

[0160] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A microbial fertilizer for improving soil structure, characterized in that: The invention comprises the following components in parts by weight: 25-35 parts of microbial flora, 15-25 parts of biochar-based composite materials, 3-7 parts of magnetic nanoparticles, 8-12 parts of polymer water retaining agents, 3-7 parts of soil enzyme activators, 10-20 parts of peanut bran, 3-7 parts of molasses and 8-12 parts of trace element supplements.

2. The microbial fertilizer for improving soil structure according to claim 1, characterized in that: The invention comprises the following components in parts by weight: 28 parts of microbial flora, 17 parts of biochar-based composite materials, 4 parts of magnetic nanoparticles, 9 parts of polymer water retaining agent, 5 parts of soil enzyme activator, 14 parts of peanut bran, 5 parts of molasses and 9 parts of trace element supplement.

3. The microbial fertilizer for improving soil structure according to claim 1, characterized in that: The microbial flora includes photosynthetic bacteria, bacillus, and cellulose decomposing bacteria; the biochar-based composite material is made of charcoal and straw charcoal; the magnetic nanoparticles are made of magnetic materials, which include iron, cobalt, and nickel and have superparamagnetism; the polymer water retaining agent is made of hydrophilic polymer materials, which include polyacrylate and polyvinyl alcohol; the soil enzyme activator is one or more of humic acid and amino acids; and the trace element supplement contains phosphorus, potassium, manganese, copper, and iron.

4. The microbial fertilizer for improving soil structure according to claim 3, characterized in that: The photosynthetic bacteria have a cell length of 1.5-3.0 microns and a diameter of 0.8-1.2 microns, the spore diameter of the Bacillus is not less than 1 / 3 of the cell diameter, and the temperature range of spore formation is 25-40° C. The cell of the cellulose decomposing bacteria contains cellulase, and the enzyme activity thereof is not less than 100 U / mL in the range of pH 5.0-7.0; The particle size of the biochar in the biochar-based composite material is controlled to be 0.1-2 mm; The saturation magnetization intensity of the magnetic nanoparticles is 50-100emu / g, the particle size is 10-100nm, and the particle surface is modified to have a Zeta potential of at least -15mV; The fat content of the peanut bran is 10-20% on a dry basis; The pH value of the molasses is controlled at 4.5-5.5, and the viscosity of the molasses is 1000-3000 cP at 25°C.

5. The microbial fertilizer for improving soil structure according to claim 3, characterized in that: In the biochar-based composite material, a biochar skeleton is designed with a multi-level pore structure, including macropores, mesopores and micropores; The magnetic nanoparticles have a core-shell structure, wherein the core layer provides magnetic function and the shell layer is used to load or modify other functional materials; In the soil enzyme activator, the enzyme activator material with recognition sites is prepared by molecular imprinting technology, and can selectively adsorb and activate target soil enzymes.

6. The microbial fertilizer for improving soil structure according to claim 3, characterized in that: The polymer water-retaining agent has a three-dimensional network structure and contains hydrophilic groups, including -COONa, -COOH, and OH. It absorbs water through molecular expansion caused by the dissociation of polymer electrolytes and ion repulsion. When the water in the gel is released, its water absorption capacity can still be restored as long as the molecular chain is not destroyed. Functional minerals, including apatite and potassium feldspar, are introduced into the biochar-based composite material to construct a biochar-mineral composite skeleton; An array of orderly arranged magnetic nanoparticles is constructed on the surface of the biochar-based composite material. Through external magnetic field manipulation, the directional movement and distribution of the microbial flora are achieved. The force of the external magnetic field on the magnetic nanoparticles is described by the magnetic field force: F_m=\mu_0\chiVH\nablaH; Where: F_m is the magnetic field force, mu_0 is the vacuum magnetic permeability, chi is the magnetic susceptibility of the magnetic nanoparticle, V is the volume of the particle, H is the strength of the external magnetic field, \nablaH is the gradient of the magnetic field strength; The movement speed of the microbial flora v = \muF_m; Among them, \mu is the mobility coefficient of the microbial flora; The distribution of microbial flora is described by the diffusion equation: \frac{\partialC}{\partialt}=D\nabla^2C-\nabla\cdot(vC); Where: \frac{\partialC}{\partialt} represents the rate of change of the concentration C of the microbial flora with time t, C is the concentration of the microbial flora, t is the time, D is the diffusion coefficient, and v is the movement speed of the microbial flora.

7. A method for preparing the microbial fertilizer for improving soil structure according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Mix the cultured Bacillus and cellulose decomposing bacteria, add molasses as a carbon source during the mixing process, and culture the mixed bacterial liquid in a constant temperature shaker for a period of time to allow the bacteria to fully adapt and form a stable mixture; S2: Dispersing magnetic nanoparticles in sterile water to form a stable suspension, then adding photosynthetic bacterial liquid to the suspension, and co-culturing in a weak magnetic field environment, so that the photosynthetic bacteria adhere to the surface of the magnetic nanoparticles through the guidance of the magnetic field to form a symbiotic system; S3: Add the polymer water retainer into water and fully dissolve it to form a colloidal liquid. Then, add the photosynthetic bacteria liquid and the soil enzyme activator into the colloidal liquid in sequence and stir evenly. Through the bridging effect of the polymer water retainer, the photosynthetic bacteria and the soil enzyme activator form a stable composite system. S4: crushing the peanut bran, mixing the crushed peanut bran with the trace element supplement to form a mixture rich in organic matter and trace elements, dispersing the biochar-based composite material in sterile water to form a suspension, and sequentially adding the Bacillus-cellulose decomposing bacteria mixture, the magnetic nanoparticle-photosynthetic bacteria symbiotic system, the photosynthetic bacteria-polymer water retaining agent-soil enzyme activator composite system, and the mixture of peanut bran and trace element supplement to the biochar suspension, and fully stirring to make each component evenly distributed on the biochar-based composite material; S5: Drying the combined microbial fertilizer to remove excess water. After drying, sieving and packaging are performed to obtain the final microbial fertilizer product for improving soil structure.

8. The method for preparing a microbial fertilizer for improving soil structure according to claim 7, characterized in that: In S1, during the constant temperature shaking incubation process, a dynamic temperature and pH control strategy is implemented, and the temperature range gradually increases from 25°C to 35°C and then decreases to 25°C within 24 hours to simulate day and night changes; the pH value fluctuates within the range of ±0.5 from the initial 7.0 by automatically adding acid and alkali solutions, simulating the natural environment and enhancing the environmental adaptability of the bacteria.

9. The method for preparing a microbial fertilizer for improving soil structure according to claim 7, characterized in that: The S4 comprises the following steps: S41: First, peanut bran is selected as a raw material, and is crushed by a high-speed crusher, and the speed of the crusher is set to 2500-3000 rpm, and the crushed into particles with a particle size of less than 0.5 mm, and an anti-caking agent is added during the crushing process; S42: Mix the crushed peanut bran with the trace element supplement using a double-screw mixer, set the mixing time to 30 minutes, and the mixing speed to medium speed. After the mixing is completed, take samples for quality inspection to ensure that the trace elements are evenly distributed in the peanut bran without local excess or deficiency. S43: Dispersing the biochar-based composite material in sterile water using a high shear disperser for dispersion, setting the dispersion time to 20 minutes to ensure the formation of a stable suspension. During the dispersion process, a surfactant is added to reduce the surface tension of the biochar and improve its dispersibility in water; S44: Slowly add the mixture prepared in step S42 to the biochar suspension prepared in step S43, and then add the Bacillus-cellulose decomposing bacteria mixture, the magnetic nanoparticle-photosynthetic bacteria symbiotic system, and the photosynthetic bacteria-polymer water retaining agent-soil enzyme activator composite system in sequence, and stir with a stirrer, set the stirring speed to 100-150 rpm, and the stirring time to 60 minutes to ensure that all components are evenly distributed on the biochar-based composite material.

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