High-temperature-resistant bacterium-containing compound fertilizer and preparation method thereof

Abstract

The invention relates to the technical field of compound fertilizers, and provides a high-temperature-resistant bacteria-containing compound fertilizer and a preparation method thereof.The preparation method comprises the following steps that nanoscale freeze-dried bacterial powder is prepared from bacillus, bacillus stearothermophilus and rhodopseudomonas palustris; mixing the nano TiO2 modified SiO2 composite aerogel, diatomite, the modified charcoal, sepiolite and pullulan to prepare a microbial inoculum protection composite carrier; and mixing the freeze-dried bacterial powder with a carrier, and drying to obtain the micron-sized capsule bacterial agent. Uniformly mixing a reinforcing agent, a plasticizer and a stabilizer to prepare a performance regulator; the preparation method comprises the following steps: melting choline chloride-containing urea and monoammonium phosphate to prepare molten slurry; mixing the molten slurry with a compound fertilizer to form uniform slurry; and mixing the slurry with a micron-sized capsule microbial inoculum and a performance regulator, and granulating to obtain the high-temperature-resistant bacterium-containing compound fertilizer. By optimizing the adaptability of a microbial agent embedding carrier and a melting system, the technical bottleneck of conflict between high-temperature inactivation of the microbial agent and physical properties of a product is solved.

Description

Technical Field

[0001] This invention relates to the field of compound fertilizer technology, and more specifically, to a high-temperature resistant, bacteria-containing compound fertilizer and its preparation method. Background Technology

[0003] Microbial compound fertilizers, as a new type of green and ecological fertilizer, are favored by the market and farmers due to their advantages such as soil improvement, quality enhancement, yield increase, and eco-friendliness. They not only solve the pain points of traditional chemical fertilizers but also meet the needs of modern agricultural development. However, the difficulties in adding microorganisms to compound fertilizers, low microbial retention rates, and poor application effects have become major obstacles to the development of microbial compound fertilizers. For example, Chinese patent CN109516838A discloses a water-retaining and efficiency-enhancing compound fertilizer and its preparation method. This method uses a three-layer coating process, which is simple to prepare, low in cost, has good water absorption and retention, and a large number of microbial strains with high survival rates. However, it is limited to rotary drum or roller processes and cannot be added to high-tower or spray-drying processes. The process has high limitations, and the fertilizer product produced by this process is not fast-acting enough. Chinese Patent CN120717844A discloses a microbial compound fertilizer and its preparation method. This method involves forming a compound microbial solution by proportioning nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and biocontrol bacteria, and adding humic acid and L-glutamic acid as metabolic enhancers to achieve uniform coverage of the compound microbial solution on the fertilizer granule surface. However, humic acid, glutamic acid, and the microbial agent are highly susceptible to moisture absorption on the fertilizer granule surface, leading to problems such as product clumping, powdering, and decreased microbial effectiveness. Chinese Patent CN119841689A discloses a method for preparing a microbial compound fertilizer and a method for increasing the number of viable bacteria in fertilizer. This method involves spraying a liquid microbial agent onto the surface of fertilizer granules, and then mixing the sprayed product with a first powdered microbial agent to obtain the microbial compound fertilizer. This method can effectively increase the amount of bacteria added and the viable bacteria retention rate in the prepared microbial compound fertilizer. However, the microbial effectiveness of the product produced by this method is less than 70%, and the applicable process is limited, making it unsuitable for producing microbial compound fertilizer in high-temperature environments such as high-tower presses. Therefore, existing microbial compound fertilizers have problems such as limited processing technology, low effectiveness of microorganisms in the product, short survival time of microorganisms, easy powdering and clumping of the product, and unclear actual effect. Summary of the Invention

[0004] Based on the above problems, the purpose of this invention is to provide a high-temperature resistant bacterial compound fertilizer and its preparation method, which solves the technical bottleneck of the conflict between high-temperature inactivation of bacterial agents and physical properties of the product by optimizing the compatibility between the bacterial agent encapsulation carrier and the melting system.

[0005] The embodiments of the present invention are achieved through the following technical solutions: This invention provides a method for preparing a high-temperature resistant, microbial-containing compound fertilizer, comprising the following steps: S1. Preparation of micron-sized capsule bacterial agents S11. Nanoscale freeze-dried bacterial powder was prepared using Bacillus, thermophilic Bacillus stearothermophilus and Rhodopseudomonas palustris. S12. Preparation of microbial agent protective composite carrier: Nano-TiO2 modified SiO2 composite aerogel, diatomaceous earth, modified biochar, sepiolite, and pullulan polysaccharide are mixed to prepare microbial agent protective composite carrier. S13. Mix the freeze-dried bacterial powder obtained in S11 and the bacterial agent protective composite carrier obtained in S12, and then disperse them by ultrasonication to obtain microcapsules. Then, vacuum dry the microcapsules to obtain micron-sized capsule bacterial agent. S2, performance regulator The reinforcing agent, plasticizer, and stabilizer are mixed evenly to obtain a performance modifier; S3, compound fertilizer S31. Choline chloride and urea are mixed to obtain choline chloride-containing urea. S32. Melt urea containing choline chloride together with monoammonium phosphate to obtain a molten slurry; mix the molten slurry with compound fertilizer to form a homogeneous slurry; S33. Before the slurry enters the granulation nozzle, micron-sized capsule bacteria agent and performance regulator are added through a mixer and subjected to high-speed shear mixing to obtain a mixed slurry. S34. The mixed slurry is sprayed from a high tower and cooled and solidified during the falling process. After the granules are screened and tested and qualified, they are packaged to obtain high-temperature resistant bacterial compound fertilizer.

[0006] The present invention also provides a high-temperature resistant bacterial compound fertilizer, which is prepared by the above-described preparation method.

[0007] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects: 1. This invention utilizes the characteristic of choline chloride to lower the melting temperature of urea, allowing urea to reach a molten state at 70~80℃ without affecting the fluidity of the slurry. On the one hand, this reduces energy consumption and production costs, and on the other hand, it keeps the temperature within the range that bacteria can tolerate.

[0008] 2. This invention utilizes the high-temperature and salt-alkali resistance of functional bacteria, which are mixed with conventional strains in a certain proportion to improve the activity of the strains during the production and storage of compound fertilizers. Furthermore, a high-temperature resistant protective carrier is prepared by compounding nano-TiO2 modified SiO2 composite aerogel, calcined diatomaceous earth, modified biochar, sepiolite, and pullulan polysaccharide to encapsulate the strains, thereby preparing micron-sized capsule bacterial agents. This significantly improves the high-temperature tolerance of the strains during production, the stability during storage, and the stability and release effect during use.

[0009] 3. The addition of the performance regulator of this invention can improve the strength and roundness of the finished particles and prevent them from pulverizing, breaking or clumping during storage and transportation; at the same time, the short-time mixing process control shortens the high-temperature exposure time of the microbial agent to within the range of the microbial agent's tolerance time, solving the problem of activity loss in traditional processes.

[0010] 4. The preparation method of this invention reduces energy consumption, improves the fluidity of the slurry, prevents equipment blockage, enhances the high-temperature resistance of the strain, reduces the impact of the osmotic pressure difference of the compound fertilizer multi-salt system on the strain during storage, and can improve the strength and roundness of the finished product particles, solving the problem of producing microbial compound fertilizer under traditional high-tower high-temperature conditions; moreover, the produced finished product has high bacterial activity, effectively improves the soil microenvironment, promotes root growth, and significantly enhances crop stress resistance and fertilizer utilization. Detailed Implementation To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0011] The following is a detailed description of a high-temperature resistant bacterial compound fertilizer and its preparation method provided by an embodiment of the present invention.

[0012] In the production process of high-tower granulated compound fertilizer, the temperature of the molten slurry typically reaches 110-150℃, leading to a rapid loss of activity when microbial agents are added. To address this issue, existing technologies often employ coating or powdering after granulation; however, these methods suffer from problems such as poor adhesion of the microbial agent, easy detachment, and short survival time. Directly adding free microbial agents results in a survival rate of less than 10% due to high temperatures and easily disrupts slurry stability, affecting particle plasticity. Therefore, this invention addresses the technical bottleneck of the conflict between high-temperature inactivation of microbial agents and product physical properties by optimizing the compatibility between the microbial agent encapsulation carrier and the molten system. Specifically, this invention provides a method for preparing a high-temperature resistant microbial compound fertilizer, comprising the following steps: S1, Micron-sized Capsule Antibacterial Agent S11. Preparation of freeze-dried bacterial powder: ① Bacillus, thermophilic steatobacterium, and Rhodopseudomonas palustris are mixed at a ratio of 1.5~3.5:1:1, and the mixing temperature is controlled at 22~25℃, the mixing humidity at 20~30%, and the stirring speed is controlled at 100~150r / min. After thorough mixing, a combined bacterial agent is obtained. The Bacillus includes one or more of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus megaterium, and Bacillus licheniformis. ② Pre-freeze the combined bacterial agent at -15~-25℃ for 1~2h. After pre-freezing, transfer the sample to -70~-90℃ and place it for another 8~10h. Then take it out and put it into a freeze dryer for freeze drying to obtain freeze-dried sample. The freeze dryer temperature is -45~-55℃, the pressure is 50-60Pa, and the drying time is 16-18h. The segmented freezing method (-15~-25℃→-70~90℃) is mainly to finely control the ice crystal formation process in order to maximize the protection of the bioactivity of active ingredients. Specifically, pre-freezing controls ice crystal morphology, protects cell structure, and "softens" cell membranes to prevent ice crystals from piercing cells. Deep freezing hardens the cells, blocking biochemical reactions and completely freezing them to inhibit enzymatic reactions. Finally, sublimation removes ice crystals while preserving maximum porosity for rapid drying. After these two freezing stages, numerous ice crystal spaces have formed inside the sample. The freeze dryer removes these ice crystals through sublimation. Because the cells have lost most of their water during pre-freezing, their internal structure remains in a "void" state. The sublimation process removes the ice crystals from these voids, preserving the original cell morphology, allowing the dried bacterial agent to quickly regain its activity upon rehydration.

[0013] ③ Use a grinder to grind the freeze-dried sample into a fine powder. The grinder speed is 1500~2500 r / min and the grinding time is 10~20 min. After grinding, use a 200 mesh sieve to sieve and obtain freeze-dried bacterial powder. S12. Preparation of microbial agent protective composite carrier: Nano-TiO2 modified SiO2 composite aerogel, calcined diatomaceous earth, modified biochar, sepiolite, and pullulan polysaccharide are mixed in a carrier mixing tank at a mass ratio of 25~35:20~30:15~25:10~20:5~15. The stirring speed in the mixing tank is 100~150 r / min, the temperature in the tank is controlled at 40~50℃, and the humidity in the tank is controlled at 20~30%, thus obtaining the microbial agent protective composite carrier. The preparation method of nano-TiO2 modified SiO2 composite aerogel is as follows: (1) Pre-hydrolyzed silicon source: Mix silicon source, organic solvent (such as ethanol, propanol, etc., preferably ethanol), deionized water and a small amount of hydrochloric acid, and stir at 50~80℃ for 1~2h to partially hydrolyze the silicon source to obtain transparent SiO2 sol; the silicon source includes but is not limited to: tetraethoxysilane (TEOS), ethyltriethoxysilane, phenyltriethoxysilane, silicon tetrachloride, methyl orthosilicate, methyltrimethoxysilane, preferably tetraethoxysilane; (2) Preparation of titanium source solution: Mix TBOT and acetylacetone at a molar ratio of 1:1~2, stir thoroughly to chelate and slow down its hydrolysis rate, and then add organic solvent to dilute to obtain titanium source solution; wherein, the titanium source includes, but is not limited to: tetrabutyl titanate (TBOT) and tetraisopropyl titanate (TTIP), preferably tetrabutyl titanate; the organic solvent can be: acetylacetone, ethanol, propanol, preferably acetylacetone; (3) Mixing and co-gelling: The titanium source solution obtained in step (2) is slowly added dropwise to the SiO2 sol obtained in step (1), and the mixture is continuously stirred. Then, the pH of the system is adjusted to 4-5 with ammonia water to initiate the polycondensation reaction. The solution gradually thickens and is then placed in a mold to form a TiO2-SiO2 composite wet gel. (4) Aging: The TiO2-SiO2 composite wet gel was soaked in ethanol at 40~50℃ for 24~48h to strengthen the network; (5) Surface hydrophobic modification: replace the ethanol in the aging process with a trimethylchlorosilane / ethanol solution diluted with hexane, and immerse the gel at 40~60℃ for 24~36h; this step can replace the -Si-OH groups on the gel surface with -Si-CH3 to achieve hydrophobicity. (6) Post-treatment: The gel is then washed with an organic solvent (e.g., n-hexane) to remove residual modifiers and byproducts. The gel is then placed in a drying oven and gradually heated from room temperature to 120°C to slowly evaporate the solvent, finally obtaining a hydrophobic TiO2-SiO2 composite aerogel. The heating process is as follows: maintain at room temperature for 2 hours, maintain at 40°C for 12 hours, maintain at 60°C for 6 hours, maintain at 90°C for 6 hours, and maintain at 120°C for 2 hours. Among them, the preparation method of modified biochar can adopt existing technology, such as the content disclosed in CN110142023A: (1) Take corn stalks, wash them and dry them to constant weight; crush the stalks and sieve them to obtain stalk powder; put the stalk powder into a muffle furnace and pyrolyze it under oxygen-limited conditions of 300~700℃ for 5-7 h to obtain biochar; wash the biochar prepared above with deionized water and use nitric acid as a modifier, with the molar ratio of nitric acid to biochar being (1~5):1, and react under stirring conditions for 12-36 h, and finally wash it with deionized water until the pH is neutral, filter and dry to obtain modified biochar.

[0014] The bacterial agent protective composite carrier prepared in this invention constructs a porous microenvironment with high specific surface area, moderate mechanical strength, and adsorption and slow-release functions through a combination of nano-TiO2-SiO2 composite aerogel, calcined diatomaceous earth, modified biochar, sepiolite, and pullulan. Specifically, the combination of nano-TiO2-SiO2 aerogel and modified biochar provides abundant microporous structures and surface functional groups, which can increase the adsorption sites and bacterial load of the carrier. The hydrophobic structure of the aerogel helps to reduce the direct hydrolysis rate of the bacteria, significantly improving the adsorption capacity and fixation rate of the bacteria. The functional groups (such as carboxyl groups and phenolic hydroxyl groups) on the surface of biochar can form hydrogen bonds and π-π interactions with proteins or polysaccharides on the surface of the bacteria, stabilizing them. The microorganisms are stabilized; their highly hydrophobic porous structure can significantly reduce the rate of water penetration from the environment, achieving a slow-release effect; diatomaceous earth, after calcination, has a more stable surface pore structure, providing mechanical support and preventing the carrier from shattering during storage and transportation; sepiolite has a layered structure and microporous channels, with good water absorption and swelling properties. It can absorb water and swell to form a protective layer when the environment is dry, and release water when it is moist to maintain the appropriate activity of the microorganisms; pullulan, after dissolving in water, can form a transparent and flexible film. It forms a uniform adhesive layer on the surface of the carrier, which can fill the tiny pores between components, prevent the microorganisms from falling off, and maintain the humidity of the microenvironment through its good moisture retention properties, preventing harmful gases in the air from directly eroding the surface of the microorganisms.

[0015] S13. Mix the freeze-dried bacterial powder obtained in S11 and the bacterial agent protective composite carrier obtained in S12 at a mass ratio of 1:3~8, ultrasonically disperse at 10~30kHz for 10~20min, and then disperse through a microporous atomizing head to obtain microcapsules with a diameter of 100~200μm. Then place them in a vacuum dryer at 45-55℃ for 3~5h to obtain micron-sized capsule bacterial agent. This invention constructs a high-temperature resistant carrier for the microbial agent, physically encapsulating the bacteria within the carrier matrix to form a physical barrier. This allows the agent to form micron-sized capsules, protecting it from the effects of temperature during production and the osmotic pressure differences caused by the compound fertilizer's high salt content during storage. During drying, the carrier's moisture-retaining and hygroscopic properties create micro-capsules around the bacteria, preventing dehydration and inactivation. This microencapsulation effect significantly improves bacterial survival. The shell of the micron-sized capsules is primarily composed of nano-TiO2-SiO2 aerogel and modified biochar. These materials possess extremely high porosity and hydrophobicity. When the capsules come into contact with soil or water, moisture slowly penetrates the capsules via capillary action, gradually releasing and multiplying the bacteria, achieving slow release. Furthermore, the TiO2 layer on the capsule surface reflects ultraviolet light from the soil surface, preventing direct sunlight from killing the bacteria. Simultaneously, the photocatalytic properties of TiO2 degrade organic toxins on the soil surface, providing a more favorable environment for the bacteria.

[0016] S2, Performance modifier: Mix the reinforcing agent, plasticizer and stabilizer in a mass ratio of 1~3:2~4:4~6 and add them to the mixing tank. Set the mixing temperature to 45~55℃, the rotation speed to 100~150 r / min and the stirring time to 20~30min to obtain the performance modifier. Among them, the reinforcing agent can be selected from one or more of the following: nano-calcium carbonate, talc, bentonite, lithium stearate, and polyacrylamide; the plasticizer can be selected from one or more of the following: polyoxypropylene ethylene glycerol ether, polypropylene glycol, diphenyl glycol dipropyl ester, and hydrogenated dimer ester; the stabilizer can be selected from one or more of the following: sodium citrate, sodium phosphate, citric acid, lignin sulfonate, and polyvinylpyrrolidone. S3, compound fertilizer S31. Choline chloride and urea are mixed in a mixing tank at a mass ratio of 0.5~2:100~300. After uniform mixing, choline chloride-containing urea is obtained. By compounding choline chloride and urea and controlling the compounding ratio, a eutectic mixture can be stably formed. By utilizing the reconstruction of intermolecular forces, the original stable crystal structure of the two substances is destroyed, which greatly reduces the energy required for the system to melt, thereby reducing the melting temperature of urea. On the one hand, the slurry temperature can reach the tolerance range of the strain, and on the other hand, the energy consumption in the production process is reduced and equipment blockage is prevented. S32. Add urea containing choline chloride and monoammonium phosphate together to a melting tank to obtain a molten slurry. The temperature of the molten slurry is 60~80℃. Then, transfer the molten slurry to a secondary mixing tank and mix it with compound fertilizer (such as compound fertilizer containing at least two of the elements nitrogen, phosphorus, and potassium) to form a homogeneous slurry. At this point, the viscosity is ≤500 mPa. s; among which, the mass ratio of choline chloride urea, monoammonium phosphate, and compound fertilizer is 45~55:15~20:25~30; S33. Before the slurry enters the granulation nozzle, micron-sized encapsulated bacterial agent and performance regulator are added through a twin-screw mixer for 30-120 seconds, and high-speed shear mixing is performed at a speed of 2500-3500 r / min; wherein, the mass ratio of micron-sized encapsulated bacterial agent, performance regulator and slurry is 5-10:1-5:915-994. S34. The mixed slurry is sprayed through a high-tower sprayer, cooling and solidifying during the descent. The granules are then sieved (2-4mm in diameter), inspected, and packaged to obtain a high-temperature resistant, microbial-containing compound fertilizer. This step enhances the compatibility of the granulation and melting system, maintaining normal slurry flowability, preventing wall adhesion and equipment blockage, and improving the yield. It also improves the strength and roundness of the finished granules, preventing pulverization, breakage, or clumping during storage and transportation. Simultaneously, a short-time mixing process is used to shorten the high-temperature exposure time of the microbial agent to within its tolerance range, solving the problem of activity loss in traditional processes. This achieves stable coexistence of the microbial agent and the multi-salt system of the compound fertilizer without affecting the high-tower granulation process or the quality of the finished product. The finished product offers advantages such as soil improvement, increased fertilizer utilization, promotion of crop root growth, and enhanced crop disease resistance.

[0017] Example 1 - Preparation of nano-TiO2 modified SiO2 composite aerogel This embodiment provides a method for preparing nano-TiO2 modified SiO2 composite aerogel: (1) Pre-hydrolyzed silicon source: TEOS, ethanol, deionized water and 0.1 mol / L hydrochloric acid were mixed in a volume ratio of 1:4:0.9:2 and stirred at 65°C for 1 h to partially hydrolyze TEOS and obtain transparent SiO2 sol. (2) Preparation of titanium source solution: Mix TBOT and acetylacetone at a molar ratio of 1:2, stir and chelate thoroughly, and then add ethanol to dilute to obtain titanium source solution. The volume ratio of the mixture of TBOT and acetylacetone to ethanol is 1:8. (3) Mixing and co-gelling: The titanium source solution was slowly added to the SiO2 sol at a volume ratio of 4:1 and stirred continuously. Then, the pH of the system was adjusted to 4 with ammonia water. The solution gradually thickened and was then placed in a mold to form a TiO2-SiO2 composite wet gel. (4) Aging: The TiO2-SiO2 composite wet gel was soaked in ethanol at 45℃ for 24h for aging; (5) Surface hydrophobic modification: The TiO2-SiO2 composite wet gel was then soaked in a TMCS / ethanol solution diluted with hexane for 24 h for modification, and the system temperature was controlled at 50 °C to achieve hydrophobicity. The volume ratio of TMCS to ethanol was 1:1, and the volume ratio of hexane to TMCS / ethanol solution was 1:1. (6) Then wash the above composite gel with n-hexane. After washing, place the gel in a drying oven and gradually increase the temperature from room temperature to 120°C. Specifically, maintain at 40°C for 12 hours, at 60°C for 6 hours, at 90°C for 6 hours, and at 120°C for 2 hours. Slowly evaporate the solvent to finally obtain the hydrophobic TiO2-SiO2 composite aerogel.

[0018] Example 2 - Preparation of nano-TiO2 modified SiO2 composite aerogel The difference between this embodiment and embodiment 1 is that in step (2), TBOT and acetylacetone are mixed in a molar ratio of 1:1; in step (3), the pH of the system is adjusted to 5.0 with ammonia.

[0019] Example 3 - Preparation of Micron-sized Capsule-type Bacterial Agent This embodiment provides a method for preparing micron-sized capsule bacterial agents, including the following steps: (1) Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus stearothermophilus and Rhodopseudomonas palustris were mixed evenly in a bacterial agent mixing tank at a mass ratio of 1:1:1:1 (total viable count ≥200 billion / g), and the temperature in the bacterial agent mixing tank was controlled at 23℃, the humidity in the tank was controlled at 25%, and the speed of the mixer was controlled at 130r / min; The well-mixed bacterial agent was pre-frozen at -20℃ for 1.5 hours. After pre-freezing, the sample was transferred to -80℃ and placed for another 9 hours. Then, it was taken out and placed in a freeze dryer for freeze drying to obtain freeze-dried sample. The freeze dryer temperature was -50℃, the pressure was 55Pa, and the drying time was 17 hours. After drying, the freeze-dried sample was ground into a fine powder using a grinder at a speed of 2000 r / min for 15 min. After grinding, the sample was sieved through a 200-mesh sieve to obtain nano-sized freeze-dried bacterial powder. (2) Using the nano-TiO2 modified SiO2 composite aerogel provided in Example 1, the nano-TiO2 modified SiO2 composite aerogel, calcined diatomaceous earth, modified biochar, sepiolite, and pullulan polysaccharide were mixed in a carrier mixing tank according to the mass percentages of 30% nano-TiO2 modified SiO2 composite aerogel, 25% calcined diatomaceous earth, 20% modified biochar, 15% sepiolite, and 10% pullulan polysaccharide. The stirring speed in the mixing tank was 130 r / min, the temperature was controlled at 45℃, and the humidity in the tank was controlled at 25%, thus obtaining the bacterial agent protected composite carrier; wherein, the modified biochar was prepared according to the preparation method provided in Example 1 of CN110142023A; (3) The nano-scale freeze-dried bacterial powder and the bacterial agent protective composite carrier were mixed at a mass ratio of 1:5, and then ultrasonically dispersed (20kHz, 15min) and micro-atomized sprayed to form microcapsules with a diameter of 150μm. The microcapsules were then vacuum dried at 50℃ for 5h to obtain micron-sized capsule bacterial agents.

[0020] Example 4 - Preparation of Micron-sized Capsule-type Bacterial Agent The difference between this embodiment and Embodiment 3 is that it provides a method for preparing a micron-sized capsule bacterial agent, including the following steps: (1) Bacillus subtilis, Bacillus megaterium, Bacillus stearothermophilus and Rhodopseudomonas palustris were mixed evenly in a bacterial agent mixing tank at a mass ratio of 1:1:1:1 (total viable count ≥200 billion / g), and the temperature in the bacterial agent mixing tank was controlled at 22℃, the humidity in the tank was controlled at 25%, and the speed of the mixer was controlled at 130r / min; The well-mixed bacterial agent was placed in a -20℃ freezer for 2 hours for pre-freezing. After pre-freezing, the sample was transferred to a -90℃ freezer and placed for another 8 hours. Then, it was taken out and placed in a freeze dryer for freeze drying to obtain freeze-dried sample. The freeze dryer temperature was -55℃, the pressure was 60Pa, and the drying time was 17 hours. After drying, the freeze-dried sample was ground into a fine powder using a grinder at a speed of 2000 r / min for 10 min. After grinding, the sample was sieved through a 200-mesh sieve to obtain nano-sized freeze-dried bacterial powder. (2) Using the nano-TiO2 modified SiO2 composite aerogel provided in Example 2, the nano-TiO2 modified SiO2 composite aerogel, calcined diatomaceous earth, modified biochar, sepiolite, and pullulan polysaccharide were mixed in a carrier mixing tank according to the mass percentages of 30% nano-TiO2 modified SiO2 composite aerogel, 30% calcined diatomaceous earth, 15% modified biochar, 10% sepiolite, and 15% pullulan polysaccharide. The stirring speed in the mixing tank was 130 r / min, the temperature was controlled at 45℃, and the humidity in the tank was controlled at 25%, thus obtaining the bacterial agent protected composite carrier. (3) The freeze-dried bacterial powder and the bacterial agent protective composite carrier were mixed at a mass ratio of 1:5, and then ultrasonically dispersed (20 kHz, 15 min) and micro-atomized sprayed to form microcapsules with a diameter of 100 μm. Then, the microcapsules were vacuum dried at 45 °C for 5 h to obtain micron-sized capsule bacterial agents.

[0021] Example 5 - Preparation of Micron-sized Capsule-type Bacterial Agent The difference between this embodiment and Embodiment 3 is that it provides a method for preparing a micron-sized capsule bacterial agent, including the following steps: (1) Bacillus licheniformis, Bacillus amyloliquefaciens, Bacillus stearothermophilus and Rhodopseudomonas palustris were mixed evenly in a bacterial agent mixing tank at a mass ratio of 1:1:1:1 (total viable count ≥200 billion / g), and the temperature in the bacterial agent mixing tank was controlled at 25℃, the humidity in the tank was controlled at 25%, and the speed of the mixer was controlled at 150r / min; The well-mixed bacterial agent was placed in a -20℃ freezer for 1.5 hours for pre-freezing. After pre-freezing, the sample was transferred to a -80℃ freezer and placed for another 10 hours. Then, it was taken out and placed in a freeze dryer for freeze drying to obtain freeze-dried sample. The freeze dryer temperature was -55℃, the pressure was 60Pa, and the drying time was 18 hours. After drying, the freeze-dried sample was ground into a fine powder using a grinder at a speed of 2000 r / min for 15 min. After grinding, the sample was sieved through a 200-mesh sieve to obtain nano-sized freeze-dried bacterial powder. (2) Using the nano-TiO2 modified SiO2 composite aerogel provided in Example 1, the nano-TiO2 modified SiO2 composite aerogel, calcined diatomaceous earth, modified biochar, sepiolite, and pullulan polysaccharide were mixed in a carrier mixing tank according to the mass percentages of 35% nano-TiO2 modified SiO2 composite aerogel, 20% calcined diatomaceous earth, 15% modified biochar, 15% sepiolite, and 15% pullulan polysaccharide. The stirring speed in the mixing tank was 140 r / min, the temperature was controlled at 40℃, and the humidity in the tank was controlled at 30%, so as to obtain the bacterial agent protected composite carrier. (3) The freeze-dried bacterial powder and the bacterial agent protective composite carrier were mixed at a mass ratio of 1:5, and then ultrasonically dispersed (20 kHz, 15 min) and micro-atomized sprayed to form microcapsules with a diameter of 150 μm. Then, the microcapsules were vacuum dried at 50 °C for 5 h to obtain micron-sized capsule bacterial agents.

[0022] Example 6 - Preparation of performance modifier This embodiment provides a method for preparing a performance regulator, including the following steps: according to the mass percentage, 20% nano-calcium carbonate, 30% polyoxypropylene ethylene glycerol ether, and 50% sodium citrate are added to a stirring tank, the temperature is set to 50℃, the rotation speed is 130 r / min, and the mixture is stirred for 25 min to obtain a high-tower compound fertilizer granule performance regulator.

[0023] Example 7 - Preparation of performance modifier This embodiment provides a method for preparing a performance regulator, including the following steps: according to the mass percentage, 10% nano-calcium carbonate, 10% talc powder, 20% polyoxypropylene ethylene glycerol ether, 10% polypropylene glycol, 30% sodium citrate, and 20% sodium phosphate are added to a stirring tank, the temperature is set at 45℃, the rotation speed is 120 r / min, and the mixture is stirred for 30 min to obtain a high-tower compound fertilizer granule performance regulator.

[0024] Example 8 - Preparation of performance modifier This embodiment provides a method for preparing a performance regulator, including the following steps: according to the mass percentage, 10% nano-calcium carbonate, 10% bentonite, 20% polyoxypropylene ethylene glycerol ether, 10% diphenyl glycol dipropyl ester, 30% sodium citrate, and 20% citric acid are added to a stirring tank, the temperature is set at 55℃, the rotation speed is 110 r / min, and the mixture is stirred for 20 min to obtain a high-tower compound fertilizer granule performance regulator.

[0025] Example 9 - Preparation of Compound Fertilizer This embodiment provides a method for preparing a high-temperature resistant, microbial-containing compound fertilizer, including the following steps: (1) Choline chloride and urea are added to a mixing tank at a mass ratio of 1:200 and mixed evenly to obtain urea containing choline chloride; (2) Add choline chloride-containing urea and monoammonium phosphate together to a melting tank to obtain a molten slurry. The temperature of the molten slurry is 70℃. Then, transfer the molten slurry to a secondary mixing tank and mix it with phosphorus and potassium compound fertilizer. Stir to form a homogeneous slurry. At this time, the viscosity is ≤500 mPa. s; among which, the mass ratio of choline chloride-containing urea to monoammonium phosphate and potassium phosphate compound fertilizer is 50:20:30; (3) Before the slurry enters the granulation nozzle, the micron-sized capsule bacterial agent prepared in Example 3 and the performance regulator prepared in Example 6 are added through a twin-screw mixer, and the time is controlled at 90s, and high-speed shear mixing is performed at a speed of 3000r / min; wherein, the mass ratio of micron-sized capsule bacterial agent, performance regulator and slurry is 6:1:997. (4) The mixed slurry is sprayed through a high tower and cooled and solidified during the falling process. The particles are screened to obtain particles with a diameter of 2-4 mm. After passing the test, they are packaged to obtain high tower process bacterial compound fertilizer.

[0026] Example 10 - Preparation of Compound Fertilizer This embodiment provides a method for preparing a high-temperature resistant, microbial-containing compound fertilizer, including the following steps: (1) Choline chloride and urea are added to a mixing tank at a mass ratio of 1:300 and mixed evenly to obtain urea containing choline chloride; (2) Add choline chloride-containing urea and monoammonium phosphate together to a melting tank to obtain a molten slurry. The temperature of the molten slurry is 60℃. Then, transfer the molten slurry to a secondary mixing tank and mix it with phosphorus and potassium compound fertilizer. Stir to form a homogeneous slurry. At this time, the viscosity is ≤500 mPa. s; among which, the mass ratio of choline chloride-containing urea to monoammonium phosphate and potassium phosphate compound fertilizer is 55:20:25; (3) Before the slurry enters the granulation nozzle, the micron-sized capsule bacterial agent prepared in Example 4 and the performance regulator prepared in Example 6 are added through a twin-screw mixer, and the time is controlled at 100s, and high-speed shear mixing is performed at a speed of 3500r / min; wherein, the mass ratio of micron-sized capsule bacterial agent, performance regulator and slurry is 7:2:991; (4) The mixed slurry is sprayed through a high tower and cooled and solidified during the falling process. The particles are screened to obtain particles with a diameter of 2-4 mm. After passing the test, they are packaged to obtain high tower process bacterial compound fertilizer.

[0027] Example 11 - Preparation of Compound Fertilizer This embodiment provides a method for preparing a high-temperature resistant, microbial-containing compound fertilizer, including the following steps: (1) Choline chloride and urea are added to a mixing tank at a mass ratio of 1:300 and mixed evenly to obtain urea containing choline chloride; (2) Add choline chloride-containing urea and monoammonium phosphate together to a melting tank to obtain a molten slurry. The temperature of the molten slurry is 60℃. Then, transfer the molten slurry to a secondary mixing tank and mix it with phosphorus and potassium compound fertilizer. Stir to form a homogeneous slurry. At this time, the viscosity is ≤500 mPa. s; among which, the mass ratio of choline chloride-containing urea to monoammonium phosphate and potassium phosphate compound fertilizer is 55:20:25; (3) Before the slurry enters the granulation nozzle, the micron-sized capsule bacterial agent prepared in Example 4 and the performance regulator prepared in Example 6 are added through a twin-screw mixer, and the time is controlled at 100s, and high-speed shear mixing is performed at a speed of 3500r / min; wherein, the mass ratio of micron-sized capsule bacterial agent, performance regulator and slurry is 8:3:989; (4) The mixed slurry is sprayed through a high tower and cooled and solidified during the falling process. The particles are screened to obtain particles with a diameter of 2-4 mm. After passing the test, they are packaged to obtain high tower process bacterial compound fertilizer.

[0028] Example 12 The difference between this embodiment and embodiment 9 is that the mass ratio of the micron-sized capsule bacterial agent, performance regulator, and slurry is 9:4:987.

[0029] Example 13 The difference between this embodiment and embodiment 9 is that the mass ratio of the micron-sized capsule bacterial agent, performance regulator, and slurry is 10:5:985.

[0030] Comparative Example 1 The difference between this comparative example and Example 9 is that step (3) is not included.

[0031] Experimental Example 1 The melting temperature of urea obtained by compounding choline chloride and urea under different compounding ratios was experimentally determined. The results are shown in Table 1. Table 1 - Melting temperature and viscosity of choline chloride and urea in different blending ratios

[0032] As shown in Table 1, the melting temperature of urea can be significantly reduced by combining choline chloride and urea, with the reduction being particularly pronounced within a mass ratio range of 0.5–2:100–300. Furthermore, the viscosity data indicates that the choline chloride-urea mixture at this ratio exhibits good fluidity and does not stick to the walls after melting.

[0033] Experiment Example 2 The compound fertilizer granules prepared in Comparative Example 1 and Examples 9-13 were used as Experimental Groups 1-6. The strength of the compound fertilizer granules obtained in Experimental Groups 1-6 was tested according to GB / T 24890-2010 "Determination of Granular Strength in Compound Fertilizers". The agglomeration rate of the obtained compound fertilizer granules was tested according to the stacking test (10 bags of compound fertilizer were placed on a flat ground, stacked to the specified height according to normal storage method, and left to stand for 36 hours). At the same time, the number of effective viable bacteria in the compound fertilizer granules was tested. The results are shown in Table 2. Table 2 - Particle strength at different mass ratios

[0034] As shown in Table 2, although the compound fertilizer with added micron-sized encapsulated bacterial agent and performance regulator slightly decreased in granule strength, the significance analysis showed no significant impact on granule strength, meaning it had no significant effect on the overall quality of the compound fertilizer granules. After stacking tests, the fertilizer caking rate obtained in the embodiments of this invention was far below the industry's conventional control line, and there was virtually no pulverization or breakage, indicating that the compound fertilizer granules prepared by the method of this invention exhibit excellent compressive strength and anti-caking performance. The effective viable bacteria count of the compound fertilizer granules prepared in each embodiment group was ≥0.2 billion / g, and in Example 13 it reached as high as 1.03 billion / g, significantly better than the national standard. This indicates that the preparation method of the embodiments of this invention is stable and reliable, and the bacterial activity of the prepared compound fertilizer granules remains good. This makes it easier to form a dominant bacterial community after application to the soil, thereby effectively exerting functions such as phosphorus and potassium solubilization, achieving the expected effects of improving soil aggregate structure and promoting crop root growth.

[0035] Experimental Example 3 The compound fertilizer granules prepared in Comparative Example 1 and Examples 9-13 were used as experimental groups 1-6. A wheat pot experiment was conducted on the compound fertilizer granules obtained in experimental groups 1-6. The experimental method was as follows: A total of 7 treatment groups were set up, namely the blank control group (CK) and experimental groups 1-6. Each group had 3 replicates, randomly arranged (to avoid the influence of differences in environmental factors such as light and temperature on the experimental results). Each replicate contained one pot of wheat, and each pot was planted with 100 wheat seeds. 1g of compound fertilizer was weighed from each treatment group and evenly sprinkled on the surface of the pot. All potted plants were placed in the same greenhouse or experimental shed, and the environmental conditions were kept consistent: light duration was 12-14 h / d, light intensity was 3000-5000 lux; daytime temperature was maintained at 20-25℃, and nighttime temperature was maintained at 10-15℃; air humidity was maintained at 60%-70%; and the same amount of water was applied regularly. The wheat was sampled and tested after 15 days of growth. The detection method for the number of viable bacteria in the soil followed NY / T 798-2015 "Compound Microbial Fertilizers," and the effective viable bacteria count was determined using the dilution plate count method. The obtained data are shown in Table 3. Table 3 - Results of the compound fertilizer granule wheat pot experiment in each experimental group

[0036] As shown in Table 3, compared with the control group, the wheat treated with the compound fertilizer of this invention showed an increase in average plant height from 23.63 cm to 27.91 cm, an increase of approximately 18%, and an increase in average fresh weight from 0.23 g to 0.28 g. This simultaneous increase indicates that the compound fertilizer of this invention not only promotes cell elongation but also increases biomass accumulation, providing sufficient and balanced nutrient supply. The average root length significantly increased from 8.55 cm to 11.2 cm, an increase of over 30%, with a simultaneous increase in root weight. This significant improvement in root development indicates that the addition of micron-sized encapsulated microbial agents and performance regulators to the compound fertilizer of this invention led to the secretion of auxins or phosphorus- and potassium-solubilizing agents by the microorganisms within the fertilizer, thus significantly improving the rhizosphere microenvironment—an effect difficult to achieve with simple chemical fertilizers. In particular, the data on the number of effective viable bacteria in the soil clearly shows that, excluding soil background or environmental factors, the wheat treated with the compound fertilizer of the present invention all showed growth advantages due to the treatment with the compound fertilizer of the present invention. In experimental group 4 with the highest number of bacteria (0.38 billion / g), the sample with the highest plant height (27.91cm) and the longest root length (11.2cm) was also observed. Even in experimental group 3 with a relatively low number of bacteria (0.17 billion / g), its growth was significantly better than that of experimental group 1. This indicates that as long as the number of bacteria reaches a certain threshold (>0.1 billion / g), an effective bacterial community can be formed in the rhizosphere and play a role in promoting growth.

[0037] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-temperature resistant, microbial-containing compound fertilizer, characterized in that, Includes the following steps: S1. Preparation of micron-sized capsule bacterial agents S11. Nanoscale freeze-dried bacterial powder was prepared using Bacillus, thermophilic Bacillus stearothermophilus and Rhodopseudomonas palustris. S12. Preparation of microbial agent protective composite carrier: Nano-TiO2 modified SiO2 composite aerogel, diatomaceous earth, modified biochar, sepiolite, and pullulan polysaccharide are mixed to prepare microbial agent protective composite carrier. S13. Mix the freeze-dried bacterial powder obtained in S11 and the bacterial agent protective composite carrier obtained in S12, and then disperse them by ultrasonication to obtain microcapsules. Then, vacuum dry the microcapsules to obtain micron-sized capsule bacterial agent. S2, performance regulator The reinforcing agent, plasticizer, and stabilizer are mixed evenly to obtain a performance modifier; S3, compound fertilizer S31. Choline chloride and urea are mixed to obtain choline chloride-containing urea. S32. Melt urea containing choline chloride together with monoammonium phosphate to obtain a molten slurry; mix the molten slurry with compound fertilizer to form a homogeneous slurry; S33. Before the slurry enters the granulation nozzle, micron-sized capsule bacteria agent and performance regulator are added through a mixer and subjected to high-speed shear mixing to obtain a mixed slurry. S34. The mixed slurry is sprayed from a high tower and cooled and solidified during the falling process. After the granules are screened and tested and qualified, they are packaged to obtain high-temperature resistant bacterial compound fertilizer.

2. The method for preparing the high-temperature resistant bacterial compound fertilizer according to claim 1, characterized in that, S11 includes: S111. Mix Bacillus, thermophilic Bacillus stearothermophilus and Rhodopseudomonas palustris to obtain a combined bacterial agent; S112. The combined bacterial agent is pre-frozen in stages and then freeze-dried to obtain freeze-dried samples; S113. Grind and sieve the freeze-dried sample to obtain nano-scale freeze-dried bacterial powder.

3. The method for preparing the high-temperature resistant bacterial compound fertilizer according to claim 2, characterized in that, In S111, the mass ratio of Bacillus, thermophilic steatobacterium, and Rhodopseudomonas palustris is 1.5~3.5:1:

1.

4. The method for preparing the high-temperature resistant bacterial compound fertilizer according to claim 2, characterized in that, In S112: The combined bacterial agent is pre-frozen at -15~-25℃ for 1~2h. After pre-freezing, the sample is transferred to -70~-90℃ and placed for 8~10h. Then, it is taken out and placed in a freeze dryer for freeze drying to obtain freeze-dried sample. The freeze dryer temperature is -45~-55℃, the pressure is 50-60Pa, and the drying time is 16-18h.

5. The method for preparing the high-temperature resistant bacterial compound fertilizer according to claim 1, characterized in that, In S12, the mass ratio of the nano-TiO2 modified SiO2 composite aerogel, diatomaceous earth, modified biochar, sepiolite, and pullulan polysaccharide is 25~35:20~30:15~25:10~20:5~15; in S13, the freeze-dried bacterial powder and the bacterial agent protective composite carrier are mixed at a mass ratio of 1:3~8.

6. The method for preparing the high-temperature resistant bacterial compound fertilizer according to claim 1, characterized in that, In S12, the preparation method of the nano-TiO2 modified SiO2 composite aerogel is as follows: (1) Pre-hydrolyzed silicon source: The silicon source, organic solvent, deionized water and hydrochloric acid are mixed and hydrolyzed to obtain transparent SiO2 sol; (2) Preparation of titanium source solution: Mix titanium source with organic solvent, stir and chelate thoroughly, then add organic solvent to dilute to obtain titanium source solution; (3) Mixing and co-gelling: The titanium source solution obtained in step (2) is slowly added dropwise to the SiO2 sol obtained in step (1), and the mixture is continuously stirred. Then, the pH of the system is adjusted to 4-5 with ammonia water to initiate the polycondensation reaction. Then, the mixture is placed in a mold to form a TiO2-SiO2 composite wet gel. (4) Aging: The TiO2-SiO2 composite wet gel was soaked in an organic solvent for aging to strengthen the network; (5) Surface hydrophobic modification: Then the aged TiO2-SiO2 composite wet gel is soaked in the modifier for a period of time for modification; The modifier is a trimethylchlorosilane / ethanol solution diluted with n-hexane; (6) Post-treatment: The gel is then washed with an organic solvent and placed in a drying oven. The temperature is gradually increased from room temperature to slowly evaporate the solvent, thus obtaining nano-TiO2 modified SiO2 composite aerogel.

7. The method for preparing the high-temperature resistant bacterial compound fertilizer according to claim 1, characterized in that, In S2, the reinforcing agent, plasticizer and stabilizer are mixed in a mass ratio of 1~3:2~4:4~6.

8. The method for preparing the high-temperature resistant bacterial compound fertilizer according to claim 1, characterized in that, In S2, the reinforcing agent is one or more of the following: nano-calcium carbonate, talc, bentonite, lithium stearate, and polyacrylamide; the plasticizer is one or more of the following: polyoxypropylene ethylene glycerol ether, polypropylene glycol, diphenyl glycol dipropyl ester, and hydrogenated dimer ester; and the stabilizer is one or more of the following: sodium citrate, sodium phosphate, citric acid, lignin sulfonate, and polyvinylpyrrolidone.

9. The method for preparing the high-temperature resistant bacterial compound fertilizer according to claim 1, characterized in that, In S31, choline chloride and urea are mixed at a mass ratio of 0.5~2:100~300; in S32, the mass ratio of choline chloride-containing urea, monoammonium phosphate, and compound fertilizer is 45~55:15~20:25~30; in S33, the mass ratio of micron-sized capsule bacterial agent, performance regulator, and slurry is 5~10:1~5:915~994.

10. A high-temperature resistant, bacteria-containing compound fertilizer, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

Images