Multifunctional composite microbial fertilizer and preparation method thereof

Abstract

The application discloses a multifunctional composite microbial fertilizer and a preparation method thereof, and relates to the technical field of microbial fertilizer preparation, and comprises the following raw materials: modified organic carrier, slow-release nitrogen, phosphorus and potassium base material, composite bacillus agent, and microelement compound, and modified starch. In the application, the modified organic carrier is added, the rigid mineral pore skeleton is constructed by activating diatomite and sepiolite through L-malic acid, a large number of micropore storage sites are provided for the composite bacillus, a dynamic reversible polyphenol coordination gel network formed by the middle layer tannic acid and magnesium ions tightly locks the bacteria, and oxygen and moisture erosion is isolated in the storage and transportation stage; after the soil absorbs water, the coordination bond is slowly and gradually dissociated, time sequence regulation of the microbial environment is realized; the outer layer of sulfonated humic acid is physically anchored on the gel surface through pi-pi stacking and hydrogen bond under a weak alkaline environment, which not only blocks the invasion of external miscellaneous bacteria, but also provides wide-range pH buffering and heavy metal passivation functions.

Description

Technical Field

[0001] This invention relates to the field of microbial fertilizer preparation technology, and in particular to a multifunctional compound microbial fertilizer and its preparation method. Background Technology

[0002] Microbial fertilizers, also known as microbial inoculants, are a type of fertilizer product with functional microorganisms as their core and containing specific active strains. After being applied to the soil, they exert their fertilizing effect through the life activities of the microorganisms. Unlike chemical fertilizers, which directly provide large amounts of nitrogen, phosphorus, and potassium, they rely on beneficial bacteria to multiply and metabolize in the soil, fixing nitrogen from the air, decomposing insoluble phosphorus and potassium in the soil, secreting growth hormones, inhibiting pathogens, and improving soil aggregate structure and microecological environment. This promotes crop root development, improves nutrient utilization, enhances plant resistance, and ultimately achieves increased yield and quality, as well as sustainable soil use.

[0003] Traditional microbial fertilizers suffer from the following drawbacks: First, low survival rate of live bacteria and short shelf life. The bacteria rapidly inactivate during storage, with a survival rate of only 50% after 180 days. This means that while the live bacteria count meets standards at the time of production, it has significantly decreased by the time it reaches farmers, greatly reducing its effectiveness in the field. Second, uneven nutrient release and early-stage burst release that burns seedlings. Ordinary urea dissolves rapidly after being applied to the soil, releasing a large amount of nitrogen in a short period. This not only wastes nutrients and pollutes the environment but also creates a high osmotic pressure environment that inhibits or even kills beneficial bacteria, severely impacting the microbial efficacy of the fertilizer. Third, severe contamination by other microorganisms and poor product purity. Traditional microbial fertilizers are highly susceptible to contamination by other microorganisms during production and storage. Some traditional products have a contamination rate approaching the 30% upper limit of the standard. These contaminants compete with the target functional bacteria for nutrients and living space, weakening the competitive advantage of the effective bacteria and resulting in unstable field application effects. Therefore, this invention provides a multifunctional compound microbial fertilizer and its preparation method. Summary of the Invention

[0004] The main objective of this invention is to provide a multifunctional compound microbial fertilizer with high survival rate of live bacteria and low rate of contaminants after 180 days, and its preparation method, which is applied to a multifunctional compound microbial fertilizer and its preparation method.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a multifunctional compound microbial fertilizer, which comprises the following raw materials in parts by weight: 400-440 parts modified organic carrier, 378-418 parts slow-release nitrogen, phosphorus and potassium base material, 40-42 parts compound Bacillus inoculant, 29-31 parts micronutrient complex, and 10-12 parts modified starch.

[0006] The modified organic carrier uses well-rotted livestock and poultry manure, straw powder, and rapeseed cake as organic substrates, combined with harmlessly treated phosphogypsum as a mineral substrate, and undergoes gentle activation with L-malic acid to create pores and preserve sites, and tannic acid-Mg 2+ It is prepared by a three-level exclusive modification process of dynamic reversible gel coordination, physical anchoring and sealing in a weakly alkaline environment with sulfonated humic acid.

[0007] The modified organic carrier, relying on a three-level nested porous coordination structure, achieves efficient colonization, long-term retention, and barrier against contaminating microorganisms for functional bacteria, providing a stable microenvironment for bacterial survival and improving the shelf-life viable bacteria retention rate of the product. The modified urea in the slow-release nitrogen, phosphorus, and potassium base significantly alleviates the problem of excessive nitrogen release in traditional urea due to its multi-level gradient slow-release structure, steadily releasing nutrients while avoiding dehydration damage and activity inhibition of functional Bacillus spores caused by high nitrogen osmotic pressure, indirectly maintaining bacterial activity from a nutrient environment perspective. The modified starch, through a low-temperature weakly cross-linked flexible network, core-shell nano-resistance interface, and selective antibacterial system, further enhances the bacteria's salt resistance, antioxidant capacity, and anti-aging ability, inhibiting the growth of contaminating microorganisms. Simultaneously, it acts as a binding medium to ensure particle formation and serves as a cross-system ion coupling bridge, balancing the ion stability of the carrier and base phases and assisting in regulating the nutrient release rhythm. These three elements synergistically alleviate the common industry problems of easy inactivation of viable bacteria, uneven nutrient release, poor product stability, and large fluctuations in field effects in traditional microbial fertilizers.

[0008] Furthermore, the preparation of the modified organic carrier includes the following steps: A1. Mix industrial phosphogypsum and deionized water, set the speed to 200 rpm, and stir for 30 minutes to obtain a suspension. Put the suspension into a plate and frame filter press for filtration, set the pressure to 0.4 MPa, collect the filter cake, seal and stack the filter cake, mature at room temperature for 90 days, and pass it through a 100-mesh sieve to obtain harmless phosphogypsum.

[0009] A2. Mix and stir well-rotted livestock and poultry manure, straw powder and rapeseed cake at 130 rpm for 20 minutes to obtain a mixture. Crush the mixture through an 80-mesh sieve and adjust the moisture content of the sieved mixture to 52-56%. Let the adjusted mixture stand at room temperature for 12 hours, add compound matrine antibacterial agent and stir at 120 rpm for 10 minutes to obtain an organic base.

[0010] A3. Mix the organic substrate and the harmless phosphogypsum at a speed of 120 rpm for 15 minutes to obtain the composite substrate.

[0011] A4. Mix diatomaceous earth and sepiolite evenly, add L-malic acid aqueous solution and stir. Set the speed to 250 rpm and stir for 60 minutes. Add ammonia water dropwise to adjust the pH to 7.2-7.8, adjust the speed to 220 rpm and stir for 15 minutes to obtain material A. Mix material A with the composite substrate, set the speed to 120 rpm and stir for 15 minutes. Stop stirring and let it stand at room temperature and be sealed for aging for 18 hours to obtain rigid pore modified substrate.

[0012] A5. Mix deionized water, sodium alginate, tannic acid and magnesium chloride hexahydrate, set the temperature to 35℃, the speed to 180 rpm, and stir for 25 minutes to obtain material B. Add material B to the rigid pore modified substrate by atomization spraying and stir, set the atomization pressure to 0.20 MPa, the nozzle orifice diameter to 0.8 mm, the speed to 150 rpm, and stir for 20 minutes. Stop stirring and let it stand at room temperature for 24 hours under sterile conditions to obtain a multi-level pore modified composite substrate.

[0013] A6. Add ammonia water to the multi-porous modified composite substrate to adjust the pH to 8-9, turn on the stirrer, set the speed to 150 rpm, and stir for 10 minutes. Add the sulfonated humic acid aqueous solution to the multi-porous modified composite substrate through low-pressure atomization spray, set the atomization pressure to 0.18 MPa, the nozzle orifice diameter to 0.8 mm, the speed to 130 rpm, and stir for 12 minutes. Stop stirring, let it stand at room temperature and be sealed for aging for 8 hours. Air-dry the aged material C in the shade, set the wind speed to 0.8-1.2 m / s, and air-dry until the moisture content is 16-18%, to obtain the modified organic carrier.

[0014] Furthermore, the mass ratio of industrial phosphogypsum to deionized water in A1 is 1:2.

[0015] The mass ratio of decomposed livestock and poultry manure, straw powder, and rapeseed cake in A2 is 197.5:118.5:79.

[0016] The amount of the compound matrine antibacterial agent added is 0.3% of the mass of the mixture after standing at room temperature.

[0017] The mass ratio of organic substrate to harmless phosphogypsum in A3 is 395:25.

[0018] The mass concentration of the L-malic acid aqueous solution in A4 is 0.3%.

[0019] The mass ratio of diatomite to sepiolite is 2:1.

[0020] The total mass of the diatomaceous earth and sepiolite is in a solid-liquid ratio of 1:1.5 with the L-malic acid aqueous solution.

[0021] The ammonia concentration is 10%.

[0022] The mass ratio of material A to the composite substrate is 1:8.

[0023] The mass ratio of deionized water, sodium alginate, tannic acid, and magnesium chloride hexahydrate in A5 is 100:1.2:0.8:0.5.

[0024] The mass ratio of material B to the rigid porous modified substrate is 1:10.

[0025] The mass ratio of the sulfonated humic acid aqueous solution and the multi-level porous modified composite substrate in A6 is 1:5.

[0026] The mass concentration of the sulfonated humic acid aqueous solution is 2%.

[0027] The ammonia concentration is 10%.

[0028] The industrial phosphogypsum is selected from wet-process phosphoric acid by-products. It is a grayish-white homogeneous powder with no lumps or sand impurities. The initial moisture content is ≤12%, and the pH value is 6.0-7.5. The heavy metal content meets agricultural standards (total arsenic ≤15mg / kg, total lead ≤50mg / kg, total cadmium ≤3mg / kg, total mercury ≤2mg / kg). It is used after being filtered at 0.4MPa, aged at room temperature for 90 days, and sieved through a 100-mesh screen. There is no free acid residue, ensuring the stability of the carrier skeleton and no bacterial toxicity.

[0029] The decomposed livestock and poultry manure used is fully decomposed at high temperature, free of raw manure, odor, insect eggs, weeds, and seeds; organic matter content ≥45%, moisture content ≤30%, carbon-nitrogen ratio 25-30:1; seed germination index GI ≥70%, free of pathogens and antibiotic residues; after decomposition, it is crushed and homogenized to ensure a safe and stable nutritional environment for microbial colonization.

[0030] The straw powder is obtained by drying and pulverizing crop straw, preferably corn or wheat straw; the air-dried moisture content is ≤15%, and after pulverization, it is sieved through an 80-mesh sieve, with homogeneous fibers, no mold, and no mud or sand impurities; as an organic carbon source auxiliary material, it loosens the carrier structure and improves the porosity and air permeability.

[0031] The rapeseed cake is a low-temperature pressed defatted rapeseed cake, which completely removes anti-nutritional factors and is free from mold and rancidity. After being crushed, it is sieved through an 80-mesh screen, with a crude protein content of ≥35% and rich in organic matter, which can provide slow-release carbon and nitrogen nutrition for the long-term metabolism of microorganisms.

[0032] The compound matrine antibacterial agent is of agricultural grade, with an effective purity of ≥98% based on the core active ingredient matrine. The product is a commercially available standardized formulation, with the main active ingredients being a compound system of matrine, oxymatrine, and sophoridine. The proportion of components in commercial batches is fixed. It has specific inhibitory effects on molds, miscellaneous bacteria, and spoilage bacteria, but no inhibitory activity against functional strains of Bacillus. The addition amount is 0.3% of the mass of the mixture after standing.

[0033] The diatomaceous earth is a general-purpose porous diatomaceous earth for industrial and agricultural use. It is a white, lightweight powder with a SiO2 content of ≥85%. It has a fineness of 100 mesh, well-developed pores, and a large specific surface area. It is free of heavy metals and impurities and serves as a rigid pore-forming framework, suitable for L-malic acid-activated pore-forming processes.

[0034] The sepiolite is a fibrous, high-purity sepiolite mineral powder with a purity of ≥95% and a fineness of 100 mesh; it has strong adsorption properties, stable pore structure, and is resistant to acids and alkalis; it is strictly compounded with diatomaceous earth in a 2:1 mass ratio to synergistically construct a multi-level rigid bacterial storage pore.

[0035] The L-malic acid is food-grade L-malic acid with a purity of ≥99% and excellent water solubility. The concentration of the prepared aqueous solution is fixed at 0.3%, which gently acidifies and etches mineral pores, activating the structure without damaging the skeleton or the bacterial cells.

[0036] The ammonia solution is analytical grade dilute ammonia solution, with an industrially common 10% mass concentration; it is used for fine-tuning the pH of the system, with precise and controllable adjustment range, no residual toxicity, and is suitable for mineral activation and weakly alkaline substrate sealing processes.

[0037] The sodium alginate is of agricultural bonding and coating grade, with a viscosity of 150-400 mPa·s, and can be slowly dissolved in cold water; it has excellent film-forming and gelling properties, and can coordinate with magnesium ions to form a flexible gel network, which is suitable for pore-locking bacterial coating processes.

[0038] The tannic acid is a plant-derived, high-purity tannic acid with a purity ≥98%; it possesses excellent polyphenol coordination properties and can react with Mg. 2+ Dynamic reversible cross-linking forms a breathable, antibacterial, and slow-release gel structure.

[0039] The magnesium chloride hexahydrate is of analytical grade with a purity ≥99% and good water solubility; it serves as a metal coordination ion donor and crosslinks with tannic acid to construct a dynamic gel-based bacterial locking system.

[0040] The sulfonated humic acid is a highly active sulfonated modified humic acid with a water solubility of ≥95% and a humic acid content of ≥50%. It possesses strong ion exchange, pH buffering, and heavy metal passivation capabilities, making it suitable for surface physical anchoring and sealing processes.

[0041] Furthermore, the slow-release nitrogen, phosphorus, and potassium base material is composed of modified urea, monoammonium phosphate, potassium sulfate, and ultrafine talc powder mixed in a mass ratio of 202.5:95.8:89.25:10.45.

[0042] Furthermore, the preparation of the modified urea includes the following steps: B1. Heat the urea to 35-40℃, keep it warm for 20 minutes, and pass it through a 40-mesh sieve to obtain pretreated urea.

[0043] B2. Mix kaolin nanotubes and palygorskite evenly, add tartaric acid aqueous solution and stir. Set the speed to 220 rpm and stir for 30 minutes. Stop stirring and let stand for 25 minutes. Collect the bottom precipitate to obtain material D. Mix material D with pretreated urea and stir. Set the speed to 160 rpm and stir for 18 minutes to obtain modified urea intermediate.

[0044] B3. Mix deionized water, β-cyclodextrin, γ-polyglutamic acid and zinc citrate, set the temperature to 32℃, the speed to 170 rpm, and stir for 20 minutes to obtain material E. Add material E to the modified urea intermediate through low-pressure atomization and stir. Set the atomization pressure to 0.20 MPa, the nozzle orifice diameter to 0.8 mm, the speed to 140 rpm, and stir for 25 minutes. Stop stirring and let stand for 6 hours to obtain a double-layer membrane-coated slow-release urea intermediate.

[0045] B4. Add nano-cerium oxide and magnesium silicon calcium minerals sequentially to the double-layer membrane-coated slow-release urea intermediate and stir. Set the speed to 180 rpm and stir for 10 minutes. Stop stirring and let it stand at room temperature for 12 hours in a sealed environment. Pass it through a 40-mesh sieve to obtain modified urea.

[0046] The urea is agricultural grade premium urea with a total nitrogen content of ≥46.3%, white homogeneous granules, free from lumps and impurities; uniform particle size, suitable for low-temperature preheating sieving modification process, and used as a slow-release nitrogen source matrix.

[0047] The kaolin nanotubes are high-purity nanotube-shaped kaolin with a diameter of 20-50 nm, an aspect ratio of 20:1, and a purity of ≥95%. They have a large specific surface area, form dense films, and are suitable for acidification and activation to form a physical barrier layer.

[0048] The palygorskite is a high-purity fibrous palygorskite mineral powder with a fineness of 100 mesh and excellent adsorption performance; it is compounded with kaolin nanotubes at a mass ratio of 1:2 and forms a dense slow-release barrier layer after acidification.

[0049] The tartaric acid is an analytical grade reagent with a purity of ≥99%; a 0.2wt% low-concentration activation solution is prepared to gently etch the mineral surface and activate the adsorption sites without damaging the mineral framework structure.

[0050] The β-cyclodextrin is agricultural-grade β-cyclodextrin with a purity of ≥98%; it has molecular inclusion properties, which can encapsulate nutrients, block pores, and construct a slow-release barrier.

[0051] The γ-polyglutamic acid is a high-molecular-weight, water-soluble γ-polyglutamic acid with a molecular weight of 100,000-300,000 Da and a purity of ≥90%. It can complex with metal ions to form a membrane, which is highly flexible, anti-aging, and forms a double-layer controlled-release membrane.

[0052] The zinc citrate is food-grade zinc citrate with a purity of ≥98%; it provides zinc ion crosslinking sites, assists in polyglutamic acid film formation, and improves the density and stability of the film layer.

[0053] The nano-cerium oxide is high-purity rare earth nano-cerium oxide with a particle size of 30-50nm and a purity of ≥99.9%; it has excellent antioxidant, anti-aging, and UV resistance properties, stabilizes the coating structure, and delays the aging and cracking of the film layer.

[0054] The magnesium-silicon-calcium mineral is an agricultural composite magnesium-silicon-calcium powder with a fineness of 100 mesh. The main effective components, calculated as oxides, have the following content ranges: silicon dioxide (SiO2) ≥ 20.0%, calcium oxide (CaO) ≥ 25.0%, and magnesium oxide (MgO) ≥ 5.0%. It has well-developed pores and strong ion adsorption capacity; it can adsorb ammonium ions and slowly generate microcrystals in the soil, achieving stable nitrogen release over an ultra-long period.

[0055] Furthermore, the mass ratio of kaolin nanotubes to palygorskite in B2 is 1:2.

[0056] The total mass of the kaolin nanotubes and palygorskite and the solid-liquid ratio of the tartaric acid aqueous solution are 1:1.2.

[0057] The mass concentration of the tartaric acid aqueous solution is 0.2%.

[0058] The mass ratio of deionized water, β-cyclodextrin, γ-polyglutamic acid, and zinc citrate in B3 is 100:2:1.5:0.6.

[0059] The mass ratio of material E to the modified urea intermediate in B3 is 1:10.

[0060] The mass ratio of nano-cerium oxide, magnesium silicon calcium minerals, and bilayer membrane-coated slow-release urea intermediate in B4 is 0.405:1.62:200.475.

[0061] Furthermore, the compound Bacillus agent is composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus mucilaginosus, and Bacillus megaterium in a mass ratio of 5:3:2:1. The viable cell purity of each strain is ≥99%, free from contamination by other microorganisms; the total effective viable cell count is ≥20 billion CFU / g, with no antagonism between strains and complementary functions, and long-term survival after colonization in the pores of the adapted carrier.

[0062] The *Bacillus subtilis*, *Bacillus amyloliquefaciens*, *Paenibacillus mucilaginosus*, and *Bacillus megaterium* strains mentioned are all commercially available strains commonly used in the field of agricultural microbial fertilizers. They can be obtained through open purchase from the China General Microbiological Culture Collection Center (CGMCC) or other commercial microbial culture collection institutions. Specifically, the preservation number for *Bacillus subtilis* is CGMCC1.1391, for *Bacillus amyloliquefaciens* it is CGMCCNo.14934, for *Bacillus megaterium* it is CGMCCNo.17890, and for *Paenibacillus mucilaginosus* it can be purchased from commercial microbial agent suppliers (such as Shandong Yitai Biotechnology Co., Ltd.). All four strains are conventional agricultural microbial strains that are commercially available to the public, exhibit stable characteristics, and meet the requirements of NY / T798-2015 for compound microbial fertilizer strains.

[0063] The micronutrient complex is composed of chelated calcium, chelated magnesium, chelated iron, chelated zinc, chelated manganese, coordinated boron, and chelated molybdenum in a mass ratio of 35:25:15:12:10:2.5:0.5. The entire system uses an agricultural-grade stable chelating formulation with EDTA / small molecule amino acids as the double chelating ligands. The chelation rate is ≥95%, the water solubility is 100%, and there is no precipitation or free metal ions. It is suitable for weakly alkaline bacterial fertilizer systems, does not damage the activity of Bacillus subtilis, and does not cause salt damage stress.

[0064] The chelated calcium is EDTA-amino acid double chelated calcium, a white, free-flowing powder with an effective calcium content ≥10.0%; a moisture content ≤0.5%; and a pH value of 6.5-7.5. The chelated structure is stable, adaptable to a wide range of soil pH, avoids calcium solidification and inactivation, supplements the calcium required for crop cell wall synthesis, and gently optimizes the microenvironment for microbial survival, with no heavy metal residue.

[0065] The chelated magnesium is EDTA-amino acid double chelated magnesium, a white crystalline powder with an effective magnesium content ≥4.0%; moisture content ≤0.5%; pH value 6.0-7.5; it has strong chelation stability and is not easily fixed by soil colloids. As a core element for chlorophyll synthesis, it enhances photosynthetic efficiency and participates in the ion buffer balance of the system, helping to stabilize the microenvironment inside the particles.

[0066] The chelated iron is EDTA chelated iron (Fe-EDTA), a yellow and uniform powder with an effective iron content ≥12.0%; moisture content ≤0.5%; pH value 5.5-7.0; it has strong alkali resistance, does not fail or precipitate in weak alkali systems, can provide crops with iron for a long time, correct yellowing and chlorosis, and trace iron ions can help enhance the antioxidant activity of bacteria.

[0067] The chelated zinc is EDTA-amino acid double chelated zinc, a white fine powder with an effective zinc content ≥10.0%; moisture content ≤0.5%; pH value 6.0-7.5; the chelated zinc ions have high activity and high utilization rate, participate in the synthesis of endogenous hormones in crops, and can also assist in cross-linking and modifying the urea membrane structure, improving the stability of the slow-release system, and have no inhibitory effect on functional bacteria.

[0068] The chelated manganese is EDTA chelated manganese, a light pink uniform powder with an effective manganese content ≥8.0%; moisture content ≤0.5%; pH value 6.0-7.5; it has excellent water solubility and strong soil mobility, participates in crop photosynthesis and enzymatic metabolism, can enhance the system's antioxidant and anti-aging properties, and is suitable for long-term storage processes of microbial fertilizers.

[0069] The coordinated boron is organic coordinated boron (amino acid coordinated type), amino acid coordinated modified organic boron, soluble powder, with an effective boron content ≥8.0%; moisture content ≤0.5%, pH value 6.5-8.0; it adopts an amino acid coordination bonding structure to replace the traditional chelate structure, with stable chemical structure, suitable for weak alkaline preparation environment, no crystal precipitation, can promote crop flower bud differentiation and nutrient transport, and trace boron can optimize the stability of starch cross-linking network, which is in line with the index range of commercial mass production raw materials.

[0070] The chelated molybdenum is an amino acid chelated molybdenum, a grayish-white fine powder with an effective molybdenum content ≥1.0%; a moisture content ≤0.5%; and a pH value of 6.0-7.5. It has a highly stable chelated structure that is compatible with the metabolic needs of nitrogen-fixing bacteria, enhances the nitrogen-fixing activity of the bacterial community, and can achieve a long-lasting growth-promoting effect with extremely low addition amounts. It has no cumulative toxicity, and its parameters meet the conventional index range of agricultural-grade commercial chelated molybdenum.

[0071] Furthermore, the preparation of the modified starch includes the following steps: C1. Dry the starch at a set temperature of 40-45℃ for 30 minutes, then pass it through a 60-mesh sieve to obtain pretreated starch.

[0072] C2. Mix and stir borax decahydrate, mannitol and deionized water at 150 rpm for 15 minutes to obtain material F. Add material F to the pretreated starch by quantitative atomization spraying and stir. Set the atomization pressure to 0.18 MPa, the nozzle orifice diameter to 0.8 mm, the speed to 160 rpm, and stir for 12 minutes. Stop stirring, let stand and seal for maturation at 25-30℃ for 16 hours to obtain modified starch intermediate.

[0073] C3. A dispersion of silica-coated cerium dioxide core-shell nanoparticles was added to the modified starch intermediate by quantitative atomization spraying. The atomization pressure was set to 0.18 MPa, the nozzle orifice diameter to 0.8 mm, the rotation speed to 140 rpm, and the mixture was stirred for 15 minutes to obtain the composite starch intermediate.

[0074] C4. Add sodium hydroxide solution to the composite starch intermediate and adjust the pH to 7.5-8. Turn on the stirrer, set the speed to 130 rpm, and stir for 10 minutes. Add phytic acid aqueous solution through atomization and stir. Set the atomization pressure to 0.18 MPa, the nozzle orifice diameter to 0.8 mm, adjust the speed to 120 rpm, and stir for 10 minutes. Stop stirring and let it stand and be sealed for aging for 8 hours to obtain material G.

[0075] C5. Air-dry material G to control humidity. Set the ventilation speed to 0.8-1.2 m / s and control the humidity until the moisture content of material G is 12-15%. Add trehalose, glycerol and ascorbic acid and stir. Set the speed to 110 rpm and stir for 8 minutes to obtain modified starch.

[0076] The starch is food-grade corn starch, pure white and fine powder, free from mold and impurities; it is sieved through a 60-mesh screen, has a moisture content of ≤12%, stable gelatinization performance, and is suitable for low-temperature weak cross-linking modification process.

[0077] The decahydrate borax is analytical grade decahydrate borax with a purity ≥99%; it is cross-linked with mannitol at low temperature to construct a water-resistant, breathable, and water-retaining three-dimensional flexible starch network.

[0078] The mannitol is food-grade D-mannitol with a purity of ≥99%; it is a low-temperature weak cross-linking agent that regulates the cross-linking density of starch, ensuring that the network is breathable and does not clump, and is suitable for bacterial attachment and survival.

[0079] The silica-coated cerium dioxide core-shell nanoparticle dispersion is a silica-coated cerium dioxide core-shell nanoparticle dispersion with a solid content of 5 wt%, a particle size of 20-50 nm, a purity of ≥95%, and deionized water as the dispersion medium. It is stored at 4°C in the dark and purchased from Xi'an Qiyue Biotechnology Co., Ltd.

[0080] The sodium hydroxide used is analytical grade sodium hydroxide, prepared as a 5wt% low-concentration dilute solution; the weakly alkaline environment of the system is precisely fine-tuned to suit the phytic acid end-capping process, without causing damage to the bacterial cells due to excessive alkalinity.

[0081] The phytic acid is food-grade phytic acid, prepared as a 1.0 wt% aqueous solution; it selectively inhibits bacteria and caps the end, suppressing miscellaneous bacteria without damaging spore-forming bacteria, and also has ion chelation and auxiliary controlled release functions.

[0082] The trehalose mentioned is food-grade trehalose with a purity of ≥99%. It is a special stress protectant for microorganisms, which can stabilize the cell membrane structure of bacteria and improve the survival rate in extreme environments.

[0083] The glycerol is food-grade glycerol with a purity of ≥99%. It is a moisturizing and stress-resistant agent that maintains a moist and breathable environment in the starch system and buffers damage from salt stress and alternating wet and dry conditions.

[0084] The ascorbic acid is food-grade vitamin C with a purity of ≥99%. It is an antioxidant that scavenge free radicals in the system, provides long-lasting protection for bacterial activity, and delays system aging.

[0085] Furthermore, the mass ratio of borax decahydrate, mannitol, and deionized water in C2 is 10.1:6.5:132.8; The mass ratio of material F to pretreated starch is 1:5.

[0086] The mass ratio of the silica-coated cerium dioxide core-shell nanoparticle dispersion and the modified starch intermediate in C3 is 1:20.

[0087] The mass concentration of the silica-coated cerium dioxide core-shell nanoparticle dispersion is 5%.

[0088] The mass ratio of the complex starch intermediate to the phytic acid aqueous solution in C4 is 25:1.

[0089] The sodium hydroxide solution has a mass concentration of 5%.

[0090] The phytic acid aqueous solution has a mass concentration of 1%.

[0091] The mass ratio of material G, trehalose, glycerol and ascorbic acid is 10.89:0.055:0.033:0.022.

[0092] Secondly, the present invention provides a method for preparing a multifunctional compound microbial fertilizer, the method comprising the following steps: S1. The modified organic carrier, slow-release nitrogen, phosphorus and potassium base material, trace element complex and modified starch are added to the reactor in sequence and stirred. The stirring speed is set to 130 rpm and stirred for 20 minutes to obtain material H.

[0093] S2. Granulate the material using disc H. Set the disc tilt angle to 40°±2° and the disc rotation speed to 18 rpm. Feed the material continuously at a uniform speed and add water by atomization. Control the moisture content of the formed particles to 21-23% and the particle size to 2-4 mm. Cool the formed particles by air cooling. Set the air speed to 0.6-1 m / s and cool for 30 minutes to obtain cooled particles.

[0094] S3. The compound Bacillus agent is sprayed onto the cooled granules through sterile low-pressure atomization. The atomization pressure is set to 0.15MPa, the nozzle orifice diameter is 0.8mm, and the spraying is carried out at a uniform low speed over the entire area. The cooled granules are then dried with low-temperature hot air at a set temperature of 25-30℃ and a wind speed of 0.6-1m / s for 40-50 minutes. The 2-4mm standard granules are then sieved, and the fine powder is recycled and reprocessed to obtain a multifunctional compound microbial fertilizer.

[0095] The total amount of atomized clean water added in S2 is ≤ 3% of the total mass of material H.

[0096] The present invention has the following beneficial effects: 1. In this invention, a modified organic carrier is added. This carrier, through L-malic acid activation of diatomaceous earth and sepiolite, constructs a rigid mineral porous framework, providing numerous microporous storage sites for the composite Bacillus. The middle layer, a dynamic and reversible polyphenol coordination gel network formed by tannic acid and magnesium ions, tightly locks in the bacteria during storage and transportation, isolating them from oxygen and moisture erosion. As the soil absorbs water, the coordination bonds slowly and gradually dissociate, achieving temporal regulation of the microenvironment of the bacterial community. The outer layer, sulfonated humic acid, is physically anchored to the gel surface through π-π stacking and hydrogen bonding under weakly alkaline conditions, both blocking external bacterial contamination and providing a wide-range pH buffer and heavy metal passivation function. Simultaneously, the physical adsorption of ammonium ions by the carrier's mineral pores and the ion exchange performance of humic acid play a role in mitigating nitrogen release.

[0097] 2. This invention utilizes modified urea, which achieves gradient slow release of nitrogen through a three-stage synergistic process: The first stage involves tartaric acid-activated kaolin nanotubes and palygorskite forming a physical barrier layer on the urea particle surface, suppressing the peak nitrogen release during the seedling stage; the second stage involves β-cyclodextrin inclusion and γ-polyglutamic acid zinc ion complexation and locking to form a dual controlled-release membrane, ensuring stable nutrient release; the third stage involves nano-cerium oxide doping to inhibit membrane aging, and the adsorption of ammonium ions by magnesium-silicon-calcium mineral mesopores, which slowly generate magnesium ammonium phosphate microcrystals after soil introduction, achieving a long-term nitrogen supply of 90 to 180 days. Its core function is to provide stable nitrogen supply and eliminate high osmotic pressure stress, avoiding the dehydration damage and osmotic pressure shock caused by the high concentration of nitrogen resulting from the rapid release of ordinary urea. By optimizing the nutrient release rhythm, it indirectly creates a suitable soil microenvironment for microbial survival, achieving a two-way synergistic effect of nitrogen control and microbial protection.

[0098] 3. In this invention, modified starch is added, which constructs a three-dimensional flexible network with controllable density and water-resistant and breathable properties through low-temperature weak cross-linking of borax and mannitol, providing attachment sites and a breathable microenvironment for the bacteria. Silica-coated cerium dioxide core-shell nanoparticles uniformly fill the gaps in the network, constructing a dual-functional interface of physical salt resistance and rare earth anti-oxidation and anti-aging, providing long-term protection for the bacteria from high salt, oxidation, and high-temperature stress. Phytic acid atomization end-capping precisely inhibits contamination and bacteria without damaging functional Bacillus spores. Trehalose, glycerol, and ascorbic acid compound stress-resistance system further extends the survival period of the bacteria. Simultaneously, modified starch acts as a granulation binder to ensure granule formation and, after being activated by soil water absorption, becomes a key coupling medium mediating the cross-system migration of magnesium ions at the carrier end and zinc ions at the urea end, bridging the dual-system structure and balancing the ionic homeostasis within the granules. Its core functions are stress resistance and bacterial stabilization, contamination inhibition, binding, and cross-system coupling, serving as a secondary determining factor for the 180-day viable bacteria survival rate and contamination rate. Detailed Implementation

[0099] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0100] It should be noted that all raw materials used in the following experiments are commercially available.

[0101] The preparation methods of the modified organic carrier, modified urea, and modified starch in the following embodiments and comparative examples of the present invention are shown below. I. The preparation of the modified organic carrier includes the following steps: A1. Mix 25 parts of industrial phosphogypsum and 50 parts of deionized water, set the speed to 200 rpm, and stir for 30 minutes to obtain a suspension. Put the suspension into a plate and frame filter press for filtration, set the pressure to 0.4 MPa, collect the filter cake, seal and stack the filter cake, mature at room temperature for 90 days, and pass it through a 100-mesh sieve to obtain harmless phosphogypsum.

[0102] A2. Mix 197.5 parts of well-rotted livestock and poultry manure, 118.5 parts of straw powder, and 79 parts of rapeseed cake. Set the speed to 130 rpm and mix for 20 minutes to obtain a mixture. Crush the mixture and pass it through an 80-mesh sieve. Adjust the moisture content of the sieved mixture to 54%. Let the adjusted mixture stand at room temperature for 12 hours. Add 1.185 parts of compound matrine antibacterial agent and stir. Set the speed to 120 rpm and stir for 10 minutes to obtain an organic base.

[0103] A3. Mix 395 parts of organic substrate and 25 parts of harmless phosphogypsum, set the speed to 120 rpm, and mix for 15 minutes to obtain a composite substrate.

[0104] A4. Mix 35 parts of diatomaceous earth and 17.5 parts of sepiolite evenly, add 78.75 parts of 0.3% L-malic acid aqueous solution and stir at 250 rpm for 60 minutes. Add 10% ammonia solution to adjust the pH to 7.5, adjust the speed to 220 rpm and stir for 15 minutes to obtain material A. Mix 52.5 parts of material A with 420 parts of composite substrate, set the speed to 120 rpm and stir for 15 minutes. Stop stirring and let stand at room temperature for sealed aging for 18 hours to obtain rigid pore modified substrate.

[0105] A5. Mix 46.68 parts of deionized water, 0.56 parts of sodium alginate, 0.38 parts of tannic acid and 0.23 parts of magnesium chloride hexahydrate, and stir at 35°C and 180 rpm for 25 minutes to obtain material B. Add all of material B to 472.5 parts of rigid pore modified substrate by atomization spraying and stir. Set the atomization pressure to 0.20 MPa, nozzle orifice diameter to 0.8 mm, and speed to 150 rpm for 20 minutes. Stop stirring and let stand at room temperature for 24 hours under sterile conditions to obtain multi-level pore modified composite substrate.

[0106] A6. Add 10% ammonia solution to the multi-porous modified composite substrate to adjust the pH to 8.5. Turn on the stirrer, set the speed to 150 rpm, and stir for 10 minutes. Add 103.95 parts of 2% sulfonated humic acid aqueous solution to 519.75 parts of multi-porous modified composite substrate through low-pressure atomization spraying, set the atomization pressure to 0.18 MPa, the nozzle orifice diameter to 0.8 mm, the speed to 130 rpm, and stir for 12 minutes. Stop stirring, let stand at room temperature and seal for 8 hours for aging. Air-dry the aged material C in the shade, set the wind speed to 0.8-1.2 m / s, and air-dry until the moisture content is 17% to obtain the modified organic carrier.

[0107] II. The preparation of modified urea includes the following steps: B1. Heat 202.5 parts of urea to 38°C, keep warm for 20 minutes, and pass through a 40-mesh sieve to obtain pretreated urea.

[0108] B2. Mix 0.135 parts of kaolin nanotubes and 0.27 parts of palygorskite evenly, add 0.486 parts of 0.2% tartaric acid aqueous solution and stir. Set the speed to 220 rpm and stir for 30 minutes. Stop stirring and let stand for 25 minutes. Collect the bottom precipitate to obtain material D. Mix all material D with 202.5 parts of pretreated urea and stir. Set the speed to 160 rpm and stir for 18 minutes to obtain modified urea intermediate.

[0109] B3. Mix 20.29 parts of deionized water, 0.41 parts of β-cyclodextrin, 0.3 parts of γ-polyglutamic acid and 0.12 parts of zinc citrate, set the temperature to 32℃, the speed to 170 rpm, and stir for 20 minutes to obtain material E. Add all material E to 202.905 parts of modified urea intermediate through low-pressure atomization and stir. Set the atomization pressure to 0.20 MPa, the nozzle orifice diameter to 0.8 mm, the speed to 140 rpm, and stir for 25 minutes. Stop stirring and let stand for 6 hours to obtain a double-layer membrane-coated slow-release urea intermediate.

[0110] B4. Add 0.405 parts of nano-cerium oxide and 1.62 parts of magnesium silicon calcium minerals to 223.925 parts of double-layer membrane-coated slow-release urea intermediate and stir. Set the speed to 180 rpm and stir for 10 minutes. Stop stirring and let stand at room temperature for 12 hours in a sealed container. Pass through a 40-mesh sieve to obtain modified urea.

[0111] III. The preparation of modified starch includes the following steps: C1. Dry 10.879 parts of starch at a set temperature of 42℃ for 30 minutes, and then pass it through a 60-mesh sieve to obtain pretreated starch.

[0112] C2. Mix 0.219 parts of borax decahydrate, 0.141 parts of mannitol and 2.887 parts of deionized water and stir at 150 rpm for 15 minutes to obtain material F. Add all of material F to 10.879 parts of pretreated starch by quantitative atomization spraying and stir. Set the atomization pressure to 0.18 MPa, the nozzle orifice diameter to 0.8 mm, the speed to 160 rpm, and stir for 12 minutes. Stop stirring, let stand and seal for maturation, set the temperature to 25-30℃, and mature for 16 hours to obtain modified starch intermediate.

[0113] C3. 0.706 parts by mass concentration of 5% silica-coated cerium dioxide core-shell nanoparticle dispersion were added to 14.126 parts by mass of modified starch intermediate by quantitative atomization spraying. The atomization pressure was set to 0.18 MPa, the nozzle orifice diameter to 0.8 mm, the rotation speed to 140 rpm, and the mixture was stirred for 15 minutes to obtain the composite starch intermediate.

[0114] C4. Add 5% sodium hydroxide solution to 14.832 parts of composite starch intermediate and adjust the pH to 7.8. Turn on the stirrer, set the speed to 130 rpm, and stir for 10 minutes. Add 0.593 parts of 1% phytic acid aqueous solution through atomization and stir. Set the atomization pressure to 0.18 MPa, the nozzle orifice diameter to 0.8 mm, and the speed to 120 rpm. Stir for 10 minutes, stop stirring, and let stand and seal for aging for 8 hours to obtain material G.

[0115] C5. Air-dry material G to control humidity. Set the ventilation speed to 1 m / s and control the humidity until the moisture content of material G is 13.5%. Add 0.055 parts of trehalose, 0.033 parts of glycerol and 0.022 parts of ascorbic acid and stir. Set the speed to 110 rpm and stir for 8 minutes to obtain modified starch.

[0116] Example 1: A multifunctional compound microbial fertilizer, comprising the following raw materials by weight: 400 parts modified organic carrier, 378 parts slow-release nitrogen, phosphorus and potassium base material, 40 parts compound Bacillus inoculant, 29 parts micronutrient complex, and 10 parts modified starch.

[0117] The modified organic carrier uses well-rotted livestock and poultry manure, straw powder, and rapeseed cake as organic substrates, combined with harmlessly treated phosphogypsum as a mineral substrate, and undergoes gentle activation with L-malic acid to create pores and preserve sites, and tannic acid-Mg 2+ It is prepared by a three-level exclusive modification process of dynamic reversible gel coordination, physical anchoring and sealing in a weakly alkaline environment with sulfonated humic acid.

[0118] The slow-release nitrogen, phosphorus and potassium base material is composed of modified urea, monoammonium phosphate, potassium sulfate and ultrafine talc powder mixed in a mass ratio of 202.5:95.8:89.25:10.45.

[0119] The compound Bacillus agent is composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus mucilaginosus, and Bacillus megaterium in a mass ratio of 5:3:2:1.

[0120] The micronutrient complex is composed of chelated calcium, chelated magnesium, chelated iron, chelated zinc, chelated manganese, coordinated boron and chelated molybdenum in a mass ratio of 35:25:15:12:10:2.5:0.5.

[0121] A method for preparing a multifunctional compound microbial fertilizer, comprising the following steps: S1. The modified organic carrier, slow-release nitrogen, phosphorus and potassium base material, trace element complex and modified starch are added to the reactor in sequence and stirred. The stirring speed is set to 130 rpm and stirred for 20 minutes to obtain material H.

[0122] S2. Granulate the material using disc H. Set the disc tilt angle to 38° and the disc rotation speed to 18 rpm. Feed the material continuously at a uniform speed, add water by atomization, control the moisture content of the formed particles to 21%, and the particle size to 2 mm. Cool the formed particles by air cooling. Set the air speed to 0.6 m / s and cool for 30 minutes to obtain cooled particles.

[0123] S3. The compound Bacillus agent is sprayed onto the cooled granules through sterile low-pressure atomization. The atomization pressure is set to 0.15MPa, the nozzle orifice diameter is 0.8mm, and the spraying is carried out at a uniform low speed over the entire area. The cooled granules are then dried with low-temperature hot air at a set temperature of 25℃ and a wind speed of 0.6m / s for 40 minutes. The 2mm standard granules are then sieved, and the fine powder is recycled and reprocessed to obtain a multifunctional compound microbial fertilizer.

[0124] The total amount of atomized clean water added in S2 for atomized water replenishment is ≤ 3% of the total mass of material H.

[0125] A multifunctional compound microbial fertilizer was prepared, and the initial viable count (0-day viable count) of the sample was determined according to the dilution plate count method of NY / T2321-2013. Three parallel measurements were performed, and the values ​​from the three parallel measurements were 0.34, 0.37, and 0.37 billion / g, respectively. The average value was 0.36 billion / g, and the standard deviation was 0.02 billion / g, denoted as 0.36 ± 0.02 billion / g.

[0126] Example 2: A multifunctional compound microbial fertilizer, comprising the following components by weight: 420 parts modified organic carrier, 398 parts slow-release nitrogen, phosphorus and potassium base material, 41 parts compound Bacillus inoculant, 30 parts micronutrient complex, and 11 parts modified starch.

[0127] The modified organic carrier uses well-rotted livestock and poultry manure, straw powder, and rapeseed cake as organic substrates, combined with harmlessly treated phosphogypsum as a mineral substrate, and undergoes gentle activation with L-malic acid to create pores and preserve sites, and tannic acid-Mg 2+ It is prepared by a three-level exclusive modification process of dynamic reversible gel coordination, physical anchoring and sealing in a weakly alkaline environment with sulfonated humic acid.

[0128] The slow-release nitrogen, phosphorus and potassium base material is composed of modified urea, monoammonium phosphate, potassium sulfate and ultrafine talc powder mixed in a mass ratio of 202.5:95.8:89.25:10.45.

[0129] The compound Bacillus agent is composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus mucilaginosus, and Bacillus megaterium in a mass ratio of 5:3:2:1.

[0130] The micronutrient complex is composed of chelated calcium, chelated magnesium, chelated iron, chelated zinc, chelated manganese, coordinated boron and chelated molybdenum in a mass ratio of 35:25:15:12:10:2.5:0.5.

[0131] A method for preparing a multifunctional compound microbial fertilizer, comprising the following steps: S1. The modified organic carrier, slow-release nitrogen, phosphorus and potassium base material, trace element complex and modified starch are added to the reactor in sequence and stirred. The stirring speed is set to 130 rpm and stirred for 20 minutes to obtain material H.

[0132] S2. Granulate the material using disc H. Set the disc tilt angle to 40° and the disc rotation speed to 18 rpm. Feed the material continuously at a uniform speed, add water by atomization, control the moisture content of the formed particles to 22%, and the particle size to 3 mm. Cool the formed particles by air cooling. Set the air speed to 0.8 m / s and cool for 30 minutes to obtain cooled particles.

[0133] S3. The compound Bacillus agent is sprayed onto the cooled granules through sterile low-pressure atomization. The atomization pressure is set to 0.15MPa, the nozzle orifice diameter is 0.8mm, and the spraying is carried out at a uniform low speed over the entire area. The cooled granules are then dried with low-temperature hot air at a set temperature of 28℃ and a wind speed of 0.8m / s for 45 minutes. The granules are then screened to 3mm standard particles, and the fine powder is recycled and reprocessed to obtain a multifunctional compound microbial fertilizer.

[0134] The total amount of atomized clean water added in S2 for atomized water replenishment is ≤ 3% of the total mass of material H.

[0135] A multifunctional compound microbial fertilizer was prepared, and the initial viable count (0-day viable count) of the sample was determined according to the dilution plate count method of NY / T2321-2013. Three parallel measurements were performed, and the values ​​from the three parallel measurements were 0.36, 0.39, and 0.39 billion / g, respectively. The average value was 0.38 billion / g, and the standard deviation was 0.02 billion / g, denoted as 0.38 ± 0.02 billion / g.

[0136] Example 3: A multifunctional compound microbial fertilizer, comprising the following raw materials by weight: 440 parts modified organic carrier, 418 parts slow-release nitrogen, phosphorus and potassium base material, 42 parts compound Bacillus inoculant, 31 parts trace element complex, and 12 parts modified starch.

[0137] The modified organic carrier uses well-rotted livestock and poultry manure, straw powder, and rapeseed cake as organic substrates, combined with harmlessly treated phosphogypsum as a mineral substrate, and undergoes gentle activation with L-malic acid to create pores and preserve sites, and tannic acid-Mg 2+ It is prepared by a three-level exclusive modification process of dynamic reversible gel coordination, physical anchoring and sealing in a weakly alkaline environment with sulfonated humic acid.

[0138] The slow-release nitrogen, phosphorus and potassium base material is composed of modified urea, monoammonium phosphate, potassium sulfate and ultrafine talc powder mixed in a mass ratio of 202.5:95.8:89.25:10.45.

[0139] The compound Bacillus agent is composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus mucilaginosus, and Bacillus megaterium in a mass ratio of 5:3:2:1.

[0140] The micronutrient complex is composed of chelated calcium, chelated magnesium, chelated iron, chelated zinc, chelated manganese, coordinated boron and chelated molybdenum in a mass ratio of 35:25:15:12:10:2.5:0.5.

[0141] A method for preparing a multifunctional compound microbial fertilizer, comprising the following steps: S1. The modified organic carrier, slow-release nitrogen, phosphorus and potassium base material, trace element complex and modified starch are added to the reactor in sequence and stirred. The stirring speed is set to 130 rpm and stirred for 20 minutes to obtain material H.

[0142] S2. Granulate the material using disc H. Set the disc tilt angle to 42° and the disc rotation speed to 18 rpm. Feed the material continuously at a uniform speed, add water by atomization, and control the moisture content of the formed particles to 23% and the particle size to 4 mm. Cool the formed particles by air cooling. Set the air speed to 1 m / s and cool for 30 minutes to obtain cooled particles.

[0143] S3. The compound Bacillus agent is sprayed onto the cooled granules through sterile low-pressure atomization. The atomization pressure is set to 0.15MPa, the nozzle orifice diameter is 0.8mm, and the spraying is carried out at a uniform low speed over the entire area. The cooled granules are then dried with low-temperature hot air at a set temperature of 30℃ and a wind speed of 1m / s for 50 minutes. The 4mm standard granules are then sieved, and the fine powder is recycled and reprocessed to obtain a multifunctional compound microbial fertilizer.

[0144] The total amount of atomized clean water added in S2 for atomized water replenishment is ≤ 3% of the total mass of material H.

[0145] A multifunctional compound microbial fertilizer was prepared, and the initial viable count (0-day viable count) of the sample was determined according to the dilution plate count method of NY / T2321-2013. Three parallel measurements were performed, and the values ​​from the three parallel measurements were 0.35, 0.38, and 0.38 billion / g, respectively. The average value was 0.37 billion / g, and the standard deviation was 0.02 billion / g, denoted as 0.37 ± 0.02 billion / g.

[0146] Comparative Example 1: The difference between this comparative example and Example 1 is that: In this comparative example, a mixture of ordinary decomposed livestock and poultry manure, straw powder, and rapeseed cake was used as the organic carrier.

[0147] A multifunctional compound microbial fertilizer was prepared, and the initial viable count (0-day viable count) of the sample was determined according to the dilution plate count method of NY / T2321-2013. Three parallel measurements were performed, and the values ​​from the three parallel measurements were 0.33, 0.35, and 0.37 billion / g, respectively. The average value was 0.35 billion / g, and the standard deviation was 0.02 billion / g, denoted as 0.35 ± 0.02 billion / g.

[0148] Comparative Example 2: The difference between this comparative example and Example 1 is that: The controlled-release nitrogen, phosphorus, and potassium base material used in this comparative study uses unmodified urea.

[0149] A multifunctional compound microbial fertilizer was prepared. The initial viable count (0-day viable count) of the sample was determined according to the dilution plate count method of NY / T2321-2013. Three parallel measurements were performed, and the values ​​were 0.35, 0.38, and 0.39 billion / g, respectively. The average value was 0.37 billion / g, and the standard deviation was 0.02 billion / g, denoted as 0.37 ± 0.02 billion / g.

[0150] Comparative Example 3 differs from Example 1 in that: The starch used in this comparative example is unmodified starch.

[0151] A multifunctional compound microbial fertilizer was prepared, and the initial viable count (0-day viable count) of the sample was determined according to the dilution plate count method of NY / T2321-2013. Three parallel measurements were performed, and the values ​​from the three parallel measurements were 0.34, 0.37, and 0.38 billion / g, respectively. The average value was 0.36 billion / g, and the standard deviation was 0.02 billion / g, denoted as 0.36 ± 0.02 billion / g.

[0152] Performance testing: The multifunctional compound microbial fertilizer samples prepared in Examples 1, 2, 3, Comparative Examples 1, 2, and 3 were tested. The test data are recorded in Table 1 below: Table 1 - Sample Performance Tests of Multifunctional Compound Microbial Fertilizer

[0153] Based on the above data, the following conclusions can be drawn: The prepared multifunctional compound microbial fertilizer samples (3 bags per batch, 1 kg per bag, double-layered light-proof and moisture-proof sealed packaging) were placed in a constant temperature and humidity chamber (temperature 25℃±1℃, relative humidity 60%±5%). Samples were taken at 0, 30, 60, 90, 120, 150, and 180 days of storage. The effective viable bacteria count was determined according to the dilution plate count method in NY / T2321-2013 "Inspection Procedures for Microbial Fertilizer Products" (10g of solid sample was weighed and added to 100mL of sterile water with glass beads, shaken at 200r / min for 30min to prepare a basic bacterial suspension, serially diluted 1:10, spread on suitable culture medium plates, and counted after incubation at 30℃ for 48h). Each sample was tested in triplicate, and the results are expressed as mean ± standard deviation. The 180-day viable bacteria survival rate (%) = (number of viable bacteria on day 180 / number of viable bacteria on day 0) × 100% test method was used to test the 180-day viable bacteria survival rate of samples obtained from the multifunctional compound microbial fertilizers of Examples 1, 2, 3, Comparative Examples 1, 2, and 3.

[0154] The cumulative release rate calculation method according to GB / T23348-2009 "Slow-Release Fertilizers" was adopted, and the soil culture leaching method was used for testing: The microbial fertilizer samples from Examples 1-3 and Comparative Examples 1-3 were mixed evenly with air-dried and sieved soil (2mm) at a 1% application rate, and placed into a leaching column (5cm in diameter, 20cm in height). A layer of quartz sand was placed on top, and a layer of filter paper was placed at the bottom. Deionized water was used for leaching, with each leaching volume equivalent to 80% of the field capacity. Leaching was performed every 7 days, and the leachate was collected. The total nitrogen content of the leachate was determined according to GB / T8572, and the cumulative nitrogen release rate was calculated. Three replicates were set for each sample, and the results are expressed as mean ± standard deviation. The 90-day cumulative nitrogen release rate of the samples obtained from the multifunctional compound microbial fertilizers of Examples 1, 2, 3, Comparative Examples 1, 2, and 3 was tested using this method.

[0155] The determination of effective viable bacteria count and contamination rate was performed in accordance with Clause 5.2 of NY / T798-2015, and was conducted according to NY / T2321-2013: Bacterial contamination was determined using nutrient broth agar medium, and mold and other fungal contamination was determined using Martin medium or PDA medium; contamination rate (%) = (contamination count / total count) × 100%. Contamination rate was tested on the multifunctional compound microbial fertilizer samples of Examples 1-3 and Comparative Examples 1-3, with three replicates for each sample. Results are expressed as mean ± standard deviation. The contamination rate of the samples obtained from Examples 1, 2, 3, Comparative Examples 1, 2, and 3 were tested using the same testing method.

[0156] Modified organic carriers significantly improve the 180-day viable bacterial survival rate and reduce the contamination rate through a three-level nested structure (malic acid creating pores for bacterial storage, tannic acid-magnesium dynamic coordination gel for bacterial locking, and sulfonated humic acid physically anchoring for contamination suppression). Simultaneously, the mineral pores and humic acid ion exchange moderate nitrogen burst release. Modified urea, through a physical barrier layer, a dual controlled-release membrane, and nano-cerium oxide doping, ensures a stable and controllable 90-day cumulative nitrogen release rate, avoiding the osmotic pressure impact of high-concentration nitrogen on the bacteria and indirectly maintaining viable bacterial survival. Modified starch, through a borax-mannitol weak cross-linked network and core-shell nanoparticles for salt and antioxidant protection, significantly extends the bacterial survival period. Simultaneously, phytic acid's antibacterial and ion-coupling functions help reduce the contamination rate and regulate nitrogen release. These three components synergistically ensure the product's comprehensive performance of high viable bacterial count, slow-release nitrogen, and low contamination from three dimensions: bacterial storage, nitrogen control, and contamination suppression.

[0157] The higher the 180-day viable bacteria survival rate, the better. This directly reflects the ability of beneficial microorganisms to maintain activity during the 180-day storage and transportation period. A higher value indicates a more significant protective effect of the three-level dynamic nested structure of the carrier and the core-shell nano-coupled stabilizing agent on the bacteria. The lower the contamination rate, the better. This reflects the degree of contamination by non-target bacteria in the product. A lower value indicates stricter aseptic control in the production process and a smaller competitive disadvantage for effective bacteria. The cumulative nitrogen release rate of the product of this invention is stably controlled within the reasonable and optimal range of 64-70% over 90 days. There is no release peak in the early stage, a continuous and stable nitrogen supply in the middle stage, and sufficient slow-release nitrogen source is retained in the later stage to continuously supply crop growth. This not only avoids fertilizer damage and antibacterial problems caused by nitrogen burst release, but also ensures a balanced supply of nutrients throughout the crop's growth period, achieving a two-way synergy between efficient nutrient utilization and long-term bacterial survival.

[0158] Based on the above demonstrations, the present invention is significantly superior to the control group in terms of 180-day viable bacteria survival rate, 90-day nitrogen accumulation release rate, and miscellaneous bacteria rate.

[0159] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0160] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A multifunctional compound microbial fertilizer, characterized in that, The multifunctional compound microbial fertilizer comprises the following raw materials in parts by weight: 400-440 parts modified organic carrier, 378-418 parts slow-release nitrogen, phosphorus and potassium base material, 40-42 parts compound Bacillus inoculant, 29-31 parts micronutrient compound, and 10-12 parts modified starch. The modified organic carrier uses well-rotted livestock and poultry manure, straw powder, and rapeseed cake as organic substrates, combined with harmlessly treated phosphogypsum as a mineral substrate, and undergoes gentle activation with L-malic acid to create pores and preserve sites, and tannic acid-Mg 2+ It is prepared by a three-level exclusive modification process of dynamic reversible gel coordination, physical anchoring and sealing in a weakly alkaline environment with sulfonated humic acid.

2. The multifunctional compound microbial fertilizer according to claim 1, characterized in that, The preparation of the modified organic carrier includes the following steps: A1. Mix and stir industrial phosphogypsum and deionized water to obtain a suspension. Put the suspension into a plate and frame filter press for filtration, collect the filter cake, seal and stack the filter cake, mature it at room temperature, and sieve it to obtain harmless phosphogypsum. A2. Mix and stir well-rotted livestock and poultry manure, straw powder and rapeseed cake to obtain a mixture. Crush and sieve the mixture. Adjust the moisture content of the sieved mixture. Let the adjusted mixture stand at room temperature. Add compound matrine antibacterial agent and stir to obtain an organic base. A3. Mix the organic base and the harmless phosphogypsum at 120 rpm for 15 minutes to obtain the composite base. A4. Mix diatomaceous earth and sepiolite evenly, add L-malic acid aqueous solution and stir, add ammonia water dropwise and stir to obtain material A, mix material A with composite substrate, stop stirring, let stand at room temperature and seal for aging to obtain rigid pore modified substrate; A5. Mix deionized water, sodium alginate, tannic acid and magnesium chloride hexahydrate to obtain material B. Add material B to the rigid pore modified substrate by atomization spraying and stir. Stop stirring and let it stand at room temperature under sterile conditions to obtain a multi-level pore modified composite substrate. A6. Add ammonia water to the multi-level porous modified composite substrate, start stirring, add sulfonated humic acid aqueous solution to the multi-level porous modified composite substrate through low-pressure atomization spraying and stir, stop stirring, let stand at room temperature and seal for aging, and ventilate and air dry the aged material C to obtain the modified organic carrier.

3. The multifunctional compound microbial fertilizer according to claim 2, characterized in that, The mass ratio of industrial phosphogypsum to deionized water in A1 is 1:2; The mass ratio of decomposed livestock and poultry manure, straw powder, and rapeseed cake in A2 is 197.5:118.5:79; The compound matrine antibacterial agent is 0.3% of the mass of the mixture after standing. The mass ratio of organic substrate to harmless phosphogypsum in A3 is 395:25; The mass ratio of diatomite to sepiolite in A4 is 2:1; The total mass of the diatomaceous earth and sepiolite was mixed with the solid-liquid ratio of the L-malic acid aqueous solution at 1:1.

5. The mass ratio of material A to the composite substrate is 1:8; The mass ratio of deionized water, sodium alginate, tannic acid, and magnesium chloride hexahydrate in A5 is 100:1.2:0.8:0.

5. The mass ratio of material B to the rigid porous modified substrate is 1:10; The mass ratio of the sulfonated humic acid aqueous solution and the multi-level porous modified composite substrate in A6 is 1:

5.

4. The multifunctional compound microbial fertilizer according to claim 1, characterized in that, The slow-release nitrogen, phosphorus, and potassium base material is composed of modified urea, monoammonium phosphate, potassium sulfate, and ultrafine talc powder mixed in a mass ratio of 202.5:95.8:89.25:10.

45.

5. The multifunctional compound microbial fertilizer according to claim 4, characterized in that, The preparation of the modified urea includes the following steps: B1. Heat the urea, keep it at that temperature, and then sieve it to obtain pretreated urea; B2. Mix kaolin nanotubes and palygorskite evenly, add tartaric acid aqueous solution and stir, stop stirring, let stand, collect the bottom precipitate to obtain material D, mix material D with pretreated urea and stir to obtain modified urea intermediate; B3. Mix and stir deionized water, β-cyclodextrin, γ-polyglutamic acid and zinc citrate to obtain material E. Add material E to the modified urea intermediate through low-pressure atomization and stir. Stop stirring and let stand to obtain a double-layer membrane-coated slow-release urea intermediate. B4. Add nano-cerium oxide and magnesium silicon calcium minerals sequentially to the double-layer membrane-coated slow-release urea intermediate and stir. Stop stirring, let stand at room temperature and seal for aging, then sieve to obtain modified urea.

6. The multifunctional compound microbial fertilizer according to claim 5, characterized in that, The mass ratio of kaolin nanotubes to palygorskite in B2 is 1:2; The total mass of the kaolin nanotubes and palygorskite and the solid-liquid ratio of the tartaric acid aqueous solution are 1:1.2; The mass ratio of material D to pretreated urea is 1:500; The mass ratio of deionized water, β-cyclodextrin, γ-polyglutamic acid, and zinc citrate in B3 is 100:2:1.5:0.

6. The mass ratio of material E to the modified urea intermediate in B3 is 1:10; The mass ratio of nano-cerium oxide, magnesium silicon calcium minerals, and bilayer membrane-coated slow-release urea intermediate in B4 is 0.405:1.62:200.

475.

7. The multifunctional compound microbial fertilizer according to claim 1, characterized in that, The compound Bacillus agent is composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus mucilaginosus and Bacillus megaterium in a mass ratio of 5:3:2:

1. The trace element complex is composed of chelated calcium, chelated magnesium, chelated iron, chelated zinc, chelated manganese, coordinated boron and chelated molybdenum in a mass ratio of 35:25:15:12:10:2.5:0.

5.

8. The multifunctional compound microbial fertilizer according to claim 1, characterized in that, The preparation of the modified starch includes the following steps: C1. Dry the starch to obtain pretreated starch; C2. Borax decahydrate, mannitol and deionized water are mixed and stirred to obtain material F. Material F is added to pretreated starch by quantitative atomized spraying and stirred. Stirring is stopped and the mixture is left to stand and sealed for maturation to obtain modified starch intermediate. C3. A dispersion of silica-coated cerium dioxide core-shell nanoparticles was added to a modified starch intermediate by quantitative atomization spraying to obtain a composite starch intermediate; C4. Add sodium hydroxide solution to the composite starch intermediate, start stirring, add phytic acid aqueous solution through atomization and stir, stop stirring, let stand and seal for aging, and obtain material G; C5. Air-dry material G to remove moisture, add trehalose, glycerol and ascorbic acid and stir to obtain modified starch.

9. The multifunctional compound microbial fertilizer according to claim 8, characterized in that, The mass ratio of borax decahydrate, mannitol, and deionized water in C2 is 10.1:6.5:132.8; The mass ratio of material F to pretreated starch is 1:5; The mass ratio of the silica-coated cerium dioxide core-shell nanoparticle dispersion and the modified starch intermediate in C3 is 1:

20. The mass ratio of the complex starch intermediate to the phytic acid aqueous solution in C4 is 25:1; The mass ratio of material G, trehalose, glycerol and ascorbic acid is 10.89:0.055:0.033:0.

022.

10. A method for preparing a multifunctional compound microbial fertilizer according to any one of claims 1-9, characterized in that, The preparation method of the multifunctional compound microbial fertilizer includes the following steps: S1. The modified organic carrier, slow-release nitrogen, phosphorus and potassium base material, trace element complex and modified starch are added to the reaction vessel in sequence and stirred. The stirring speed is set to 130 rpm and stirred for 20 minutes to obtain material H. S2. Granulate the material using disc H. Set the disc tilt angle to 40°±2° and the disc rotation speed to 18 rpm. Feed the material continuously at a uniform speed and add water by atomization. Control the moisture content of the formed particles to 21-23% and the particle size to 2-4 mm. Cool the formed particles by air cooling. Set the air speed to 0.6-1 m / s and cool for 30 minutes to obtain cooled particles. S3. The compound Bacillus agent is sprayed onto the cooled granules through aseptic low-pressure atomization. The atomization pressure is set to 0.15MPa, the nozzle orifice diameter is 0.8mm, and the spraying is carried out at a uniform low speed over the entire area. The cooled granules are then dried with low-temperature hot air at a set temperature of 25-30℃ and a wind speed of 0.6-1m / s for 40-50 minutes. The 2-4mm standard granules are then sieved, and the fine powder is recycled and reprocessed to obtain a multifunctional compound microbial fertilizer. The total amount of atomized clean water added in S2 is ≤ 3% of the total mass of material H.

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