Soil improvement microbial fertilizer and preparation method thereof

Abstract

The invention relates to the technical field of agricultural microbial fertilizers, and discloses a soil improvement microbial fertilizer and a preparation method thereof, the soil improvement microbial fertilizer is prepared from the following raw materials by weight: 5-8 parts of a composite microbial agent, 30-40 parts of a modified biomass carrier, 25-35 parts of a slow release nutrient matrix, 15-20 parts of a soil conditioning aid, 2-3 parts of a microbial synergist, 1-2 parts of an adhesive, and 3 parts of a coating liquid. According to the invention, dual protection of trehalose loading and xanthan gum-PVA coating is adopted, and the L-proline synergist is matched, so that microorganisms still can survive in a high-temperature and high-salt environment, the inhibition of a severe soil environment on the microorganisms is broken through, and the application range is wider than that of commercially available products.

Description

Technical Field

[0001] This invention relates to the field of agricultural microbial fertilizer technology, specifically to a soil-improving microbial fertilizer and its preparation method. Background Technology

[0002] In current agricultural production, the long-term excessive application of chemical fertilizers has led to increasingly prominent soil degradation problems: pathogens accumulate in continuously cropped soils, and the incidence of soil-borne diseases exceeds 30%; the pH value of saline-alkali soils is generally higher than 8.5, and the EC value is >4mS / cm, which inhibits crop root absorption; the organic matter content of degraded arable land is less than 1.0%, the aggregate structure is destroyed, and the water and fertilizer retention capacity is reduced.

[0003] Existing microbial fertilizers often focus on a single function: some products only add nitrogen-fixing and phosphorus-solubilizing microorganisms, lacking soil remediation capabilities; others, while soil conditioners can adjust soil pH, cannot inhibit pathogens, and require large-scale application, resulting in high costs and slow effects. Furthermore, microorganisms are easily deactivated during product storage and soil establishment—commercially available products exhibit a viable bacteria count decline rate exceeding 40%, and soil establishment rates below 20%, leading to unstable remediation effects.

[0004] Therefore, developing a multifunctional microbial fertilizer that combines "efficient microbial colonization, regulation of soil physicochemical properties, and inhibition of pathogens" has become a key requirement for solving soil degradation problems. Summary of the Invention

[0005] The purpose of this invention is to provide a soil-improving microbial fertilizer and its preparation method in order to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A soil-improving microbial fertilizer is made from the following raw materials in parts by weight: 5-8 parts of compound microbial agent, 30-40 parts of modified biomass carrier, 25-35 parts of slow-release nutrient matrix, 15-20 parts of soil conditioner, 2-3 parts of microbial synergist, 1-2 parts of binder, and 3 parts of coating liquid. The compound microbial agent is composed of Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus mucilaginosus in a mass ratio of 3:2:1, and the viable counts of the three agents are ≥10 for Bacillus subtilis. 10 CFU / g, Bacillus amyloliquefaciens ≥10 10 CFU / g, Bacillus subtilis ≥10 9CFU / g; The modified biomass carrier is made by mixing corn straw and shiitake mushroom residue at a mass ratio of 2:1, and undergoing carbonization, acid activation, and trehalose loading treatment. The carrier has a porosity ≥60%, water holding capacity ≥300%, and pore size 50-80nm; The slow-release nutrient matrix is ​​composed of potassium humate, slow-release urea, and potassium dihydrogen phosphate at a mass ratio of 5:3:2, wherein the potassium humate has an organic matter content ≥70% and the slow-release urea has a nitrogen release period ≥60 days; The soil conditioner is modified. Montmorillonite and gypsum powder are compounded at a mass ratio of 4:1. The modified montmorillonite is activated with 0.1 mol / L hydrochloric acid, with a cation exchange capacity ≥150 mmol / 100g and a gypsum powder particle size ≤10μm. The microbial synergist is compounded from 0.5-1 parts of L-proline, 0.3-0.5 parts of chitinase, and 1.2-1.5 parts of humic acid. The binder is sodium carboxymethyl cellulose. The coating solution is an aqueous solution containing 0.5% xanthan gum and 1% polyvinyl alcohol.

[0007] Preferably, the corn stalks and shiitake mushroom residue used as raw materials for preparing the modified biomass carrier need to be crushed to a particle size ≤1mm; the loading amount of trehalose in the carrier is 0.5% of the carrier mass.

[0008] Preferably, the protective film formed after the coating liquid is sprayed has an oxygen permeability of ≥20% / 24h; the finished fertilizer product is a particle with a diameter of 2-3mm, a moisture content of ≤10%, and a particle forming rate of ≥90%.

[0009] A method for preparing a soil-improving microbial fertilizer includes the following steps: S1: Preparation of modified biomass carrier: Corn stalks and shiitake mushroom residue were mixed at a mass ratio of 2:1, crushed to a particle size ≤1mm, placed in an anaerobic carbonization furnace, heated to 600℃ at 10℃ / min, kept at that temperature for 2 hours, and cooled to room temperature to obtain biochar; 2% nitric acid solution was added to the biochar at a solid-liquid ratio of 1:5, stirred at 60℃ for 2 hours, filtered, washed with deionized water until neutral, and dried at 105℃ for 3 hours; 0.5% trehalose solution was sprayed onto the dried biochar at a mass ratio of 10:1, and stirred at 30℃ for 30 minutes to obtain the modified biomass carrier; S2: Activation of compound microbial agents: Take Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus mucilage powder respectively, add sterile water containing 0.1% glucose, and incubate at 30℃ and 150r / min for 2 hours with shaking to achieve a bacterial concentration of 10. 10 CFU / mL; Mix the three bacterial solutions in a volume ratio of 3:2:1, add 0.2% chitinase, and let stand at 28℃ for 1 hour to obtain an activated compound bacterial solution; S3: Raw material mixing and granulation: Add modified biomass carrier, slow-release nutrient matrix, and soil conditioner to a twin-screw mixer and stir at 35℃ and 500r / min for 20 minutes; slowly add activated compound bacterial solution and microbial synergist, reduce the speed to 300r / min, stir for 15 minutes, and control the material moisture content to 25%-30%; add sodium carboxymethyl cellulose, stir for 5 minutes, and then send it to an extrusion granulator with a die diameter of 2.5mm. After granulation, dry in a drying room at 40℃ and 50% relative humidity until the moisture content is ≤10% to obtain granular semi-finished product; S4: Coating and Finished Product: Dissolve 0.5% xanthan gum and 1% polyvinyl alcohol in 40℃ deionized water and stir until completely dissolved to prepare a coating solution; send the semi-finished granules into a coating machine, spray with the coating solution, the amount of coating solution is 3% of the mass of the semi-finished granules, dry at 35℃ for 1 hour; sieve to obtain granules with a diameter of 2-3mm, and package after passing the inspection to obtain the finished soil-improving microbial fertilizer.

[0010] Preferably, in step S1, after the biochar is treated with a 2% nitric acid solution, the criterion for determining neutrality is that the pH value of the washing solution is 6.5-7.5.

[0011] Preferably, in step S3, the moisture content of the material needs to be continuously monitored during the drying process after extrusion granulation, and drying is stopped when the moisture content drops to 10%.

[0012] Preferably, in step S4, a standard sieve with a 2-3 mm aperture is used for sieving. The particles that pass through the sieve need to be returned to the granulation process, while the particles that pass through the sieve are subjected to subsequent testing.

[0013] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This invention overcomes the shortcomings of traditional carriers in terms of poor bacterial preservation ability. Through carbonization-acid activation-trehalose loading process, the carrier porosity reaches more than 60%, which can adsorb and protect microorganisms. The product has a viable bacteria count decay rate of ≤15% after 3 months of storage, and the soil colonization rate is increased to more than 50%. At the same time, the carrier itself can adsorb heavy metals in the soil, realizing the synergy of "carrier-microorganism-soil remediation". 2. This invention differs from commercially available products with a single function. The product integrates three major functions: "microorganisms, nutrients (slow-release supply), and conditioning agents." After 30 days of application, it can reduce the density of pathogens in continuously cropped soil by 60%, lower the pH of saline-alkali soil to below 8.0, reduce the EC value to below 3mS / cm, and increase the organic matter content by 0.3%-0.5%, thus solving the problem of traditional products that "improve soil but do not cure diseases, and cure diseases but do not improve soil."

[0014] 3. This invention innovatively adopts a dual protection of "trehalose loading + xanthan gum-PVA coating" and is combined with L-proline synergist, which enables microorganisms to survive in high temperature and high salt environment, overcomes the inhibition of microorganisms by harsh soil environment, and has a wider range of adaptability than commercially available products. Detailed Implementation

[0015] 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.

[0016] I. Raw Material Preparation and Selection Criteria All raw materials must meet the following selection requirements to ensure stable product performance: Raw material for compound microbial inoculant: Bacillus subtilis raw powder (live count 1.2 × 10⁻⁶) 11 CFU / g), Bacillus amyloliquefaciens raw powder (live count 1.0 × 10⁻⁶) 11 CFU / g), Bacillus mucilaginosus raw powder (live count 8.0×10⁻⁶) 9 (CFU / g) The viable count must be verified by plate counting method before use to ensure that it meets the standard.

[0017] Modified biomass carrier raw materials: corn stalks (particle size ≤1mm after crushing, moisture content 12%), shiitake mushroom residue (moisture content 10% after drying), nitric acid (analytical grade, concentration 68%, diluted to 2% before use), trehalose (food grade, purity ≥99%, prepared as a 0.5% aqueous solution).

[0018] Slow-release nutrient matrix raw materials: potassium humate (water-soluble, organic matter content 75%, water-insoluble matter 3%), slow-release urea (containing 3% urease inhibitor, nitrogen content 46%, nitrogen release period 65 days), potassium dihydrogen phosphate (agricultural grade, purity ≥98%).

[0019] Soil conditioner raw materials: montmorillonite (calcium-based, cation exchange capacity 120 mmol / 100g, which is increased to 155 mmol / 100g after activation with 0.1 mol / L hydrochloric acid) and gypsum powder (analytical grade, particle size 8 μm, passed through a 200-mesh sieve).

[0020] Microbial synergist ingredients: L-proline (food grade, purity ≥99%), chitinase (enzyme activity 1000U / g), fulvic acid (water soluble, purity ≥90%).

[0021] Other excipients: Sodium carboxymethyl cellulose (CMC, food grade, viscosity 500-800 mPa) s), xanthan gum (food grade, purity ≥99%), polyvinyl alcohol (PVA, degree of polymerization 1750±50, degree of alcoholysis 88%).

[0022] II. Detailed Preparation Process of Examples Example 1 (Formulation adapted for conventional degraded soil) 1. Raw material usage (based on a total mass of 100kg) The mixture contains 6 kg of compound microbial inoculant (3 kg of Bacillus subtilis, 2 kg of Bacillus amyloliquefaciens, and 1 kg of Bacillus mucilaginosus), 35 kg of modified biomass carrier, 30 kg of slow-release nutrient matrix (15 kg of potassium humate, 9 kg of slow-release urea, and 6 kg of potassium dihydrogen phosphate), 18 kg of soil conditioner (14.4 kg of modified montmorillonite and 3.6 kg of gypsum powder), 2.5 kg of microbial synergist (0.8 kg of L-proline, 0.4 kg of chitinase, and 1.3 kg of fulvic acid), 1.5 kg of binder (CMC), and 3 kg of coating solution (0.015 kg of 0.5% xanthan gum, 0.03 kg of 1% PVA, and 2.955 kg of deionized water).

[0023] 2. Stepwise preparation process (including control of key parameters) Step 1: Preparation of modified biomass carrier Raw material mixing: Take 23.33 kg of corn stalks and 11.67 kg of shiitake mushroom residue (mass ratio 2:1), put them into a universal grinder and grind them until the particle size is ≤1 mm, and collect the mixture. Anaerobic carbonization: The mixture is fed into an anaerobic carbonization furnace. After the furnace door is closed, nitrogen gas (flow rate 5L / min) is introduced to remove oxygen. The temperature is increased from room temperature to 600℃ at a rate of 10℃ / min. After reaching the target temperature, the temperature is held for 2 hours, during which nitrogen gas is continuously introduced. After the holding period, heating is stopped and the mixture is allowed to cool naturally to room temperature to obtain biochar (approximately 12kg). Acid activation treatment: Measure 60 kg of 2% nitric acid solution (solid-liquid ratio 1:5), pour it into a stirred reactor, add 12 kg of biochar, turn on the stirrer (300 r / min), heat to 60℃, and keep stirring for 2 hours; after stirring, turn off the heating, filter with a plate and frame filter (filtration accuracy 0.2 μm), and collect the filter cake. Washing and drying: Wash the filter cake repeatedly with deionized water, using 20 kg each time, until the pH value of the washing solution reaches 6.5-7.5 (measured with a precision pH meter); place the washed filter cake in a vacuum drying oven and dry it at 105℃ and 0.08 MPa for 3 hours to obtain activated biochar (approximately 10 kg). Trehalose loading: Measure 1 kg of 0.5% trehalose solution (corresponding to 0.005 kg of trehalose), spray it evenly on 10 kg of activated biochar, put it into a mixing tank, stir at 30℃ and 200 r / min for 30 minutes to ensure that the trehalose is completely adsorbed into the pores of the carbon, and obtain the modified biochar carrier (about 10 kg), which is then sealed for later use.

[0024] Step 2: Activation of compound microbial agents Preparation of single bacterial suspensions: Weigh out 0.025 kg of Bacillus subtilis powder, 0.02 kg of Bacillus amyloliquefaciens powder, and 0.125 kg of Bacillus mucilaginosus powder, respectively. Add 2.975 kg, 2.98 kg, and 2.875 kg of sterile water containing 0.1% glucose to each suspension, and stir until completely dissolved. Pour the three bacterial suspensions into Erlenmeyer flasks, place them on a shaker, and incubate at 30°C and 150 rpm for 2 hours. After incubation, use the LB agar plate count method to ensure that the concentration of each bacterial suspension reaches 10. 10 CFU / mL; Mixing of compound bacterial solutions: Measure 3L of Bacillus subtilis bacterial solution, 2L of Bacillus amyloliquefaciens bacterial solution, and 1L of Bacillus mucilaginosus bacterial solution in a volume ratio of 3:2:1, pour them into a sterile mixing tank, add 0.012kg of chitinase (corresponding to 0.2% addition), let stand at 28℃ for 1 hour, and gently stir once every 20 minutes during the process to obtain an activated compound bacterial solution (about 6L) for later use.

[0025] Step 3: Raw material mixing and granulation Basic raw material mixing: Add 35kg of modified biomass carrier, 30kg of slow-release nutrient matrix (15kg potassium humate, 9kg slow-release urea, 6kg potassium dihydrogen phosphate), and 18kg of soil conditioner (14.4kg modified montmorillonite, 3.6kg gypsum powder) to the twin-screw mixer. Set the temperature to 35℃ and the speed to 500r / min, and stir for 20 minutes. Take samples every 5 minutes during the process to ensure that the materials are free of lumps and are mixed evenly. Adding bacterial solution and synergist: Slowly add 6L of activated compound bacterial solution and 2.5kg of microbial synergist (0.8kg L-proline, 0.4kg chitinase, and 1.3kg humic acid) to the mixer, while simultaneously reducing the speed to 300r / min and stirring for 15 minutes. During stirring, use a moisture meter to check the moisture content of the material. If the moisture content is too high, add a small amount of deionized water or dry the material to maintain a moisture content of 25%-30%. Binder addition and granulation: Add 1.5 kg of CMC and continue stirring for 5 minutes to ensure uniform dispersion of CMC; feed the mixture into an extrusion granulator (die diameter 2.5 mm), set the feeding speed to 20 kg / h and the extrusion speed to 15 r / min for granulation; after granulation, send the granules into a drying room, set the temperature to 40℃ and the relative humidity to 50%, and continue drying, checking the moisture content every 30 minutes during the process. When the moisture content drops to 10%, stop drying to obtain semi-finished granules (approximately 97 kg).

[0026] Step 4: Coating and Finished Product Preparation Preparation of coating solution: Measure 2.955 kg of 40℃ deionized water, pour it into a beaker, add 0.015 kg xanthan gum and 0.03 kg PVA, stir with a magnetic stirrer (800 r / min) for 30 minutes until xanthan gum and PVA are completely dissolved to obtain coating solution; Coating treatment: The semi-finished granules are fed into a roller coating machine. The roller speed is set to 30 r / min and the spraying pressure is 0.3 MPa. 3 kg of coating liquid is evenly sprayed onto the surface of the granules. After the spraying is completed, the roller speed is kept constant, the temperature is raised to 35℃, and the granules are dried for 1 hour to form a protective film on the surface of the granules. Screening and Testing: The coated granules are screened using a standard sieve with a 2-3 mm aperture. Particles that pass through the sieve (particle size < 2 mm) are returned to the granulation process for reprocessing. Particles that pass through the sieve (particle size 2-3 mm) are collected for later use. Three key tests are performed on the particles passing through the sieve: ① Viable bacteria count (plate count method, ≥ 10⁻⁶). 9 The following parameters are tested: ① CFU / g, ② Moisture content (drying method, ≤10%), and ③ Particle size (sieving method, 2-3mm). After passing the tests, the product is packaged in sterile polyethylene bags (25kg / bag) to obtain the finished soil-improving microbial fertilizer.

[0027] Example 2 (Formula adapted for severely saline-alkali soil) 1. Raw material usage (based on a total mass of 100kg) 8 kg of compound microbial agent (4 kg of Bacillus subtilis, 2.67 kg of Bacillus amyloliquefaciens, and 1.33 kg of Bacillus mucilaginosus), 40 kg of modified biomass carrier, 25 kg of slow-release nutrient matrix (12.5 kg of potassium humate, 7.5 kg of slow-release urea, and 5 kg of potassium dihydrogen phosphate), 18 kg of soil conditioner (14.4 kg of modified montmorillonite and 3.6 kg of gypsum powder), 3 kg of microbial synergist (1 kg of L-proline, 0.5 kg of chitinase, and 1.5 kg of fulvic acid), 2 kg of binder (CMC), and 3 kg of coating solution (formula same as in Example 1).

[0028] 2. Differences in preparation process (compared with Example 1) Step 1: Preparation of modified biomass carrier: The amounts of corn straw and shiitake mushroom residue were adjusted to 26.67 kg and 13.33 kg, respectively, while the other parameters remained the same; Step 2: Activation of compound microbial agents: 4L of Bacillus subtilis bacterial solution, 2.67L of Bacillus amyloliquefaciens bacterial solution, 1.33L of Bacillus mucilaginosus bacterial solution, 0.016kg of chitinase added, and other parameters are the same; Step 3 Raw material mixing and granulation: The mixing time of the mixer is extended to 25 minutes, and the feeding speed is reduced to 18 kg / h during granulation to ensure that the high proportion of carrier and bacterial agent are fully mixed, while the other parameters remain the same; Step 4: Coating and Finished Product Preparation: Increase the coating liquid spraying pressure to 0.4 MPa to ensure uniform coverage of the protective film, while keeping other parameters consistent.

[0029] Example 3 (Soil-adapted formula for continuous cropping obstacles) 1. Raw material usage (based on a total mass of 100kg) 5 kg of compound microbial agent (2.5 kg of Bacillus subtilis, 1.67 kg of Bacillus amyloliquefaciens, and 0.83 kg of Bacillus mucilaginosus), 30 kg of modified biomass carrier, 35 kg of slow-release nutrient matrix (17.5 kg of potassium humate, 10.5 kg of slow-release urea, and 7 kg of potassium dihydrogen phosphate), 18 kg of soil conditioner (14.4 kg of modified montmorillonite and 3.6 kg of gypsum powder), 2 kg of microbial synergist (0.5 kg of L-proline, 0.3 kg of chitinase, and 1.2 kg of fulvic acid), 1 kg of binder (CMC), and 3 kg of coating solution (formula same as in Example 1).

[0030] 2. Differences in preparation process (compared with Example 1) Step 2: Activation of compound microbial agent: The amount of chitinase added is increased to 0.015 kg, and the standing time is extended to 1.5 hours to enhance the inhibitory ability of pathogens; Step 3 Raw material mixing and granulation: The proportion of potassium humate in the slow-release nutrient matrix is ​​increased, and the stirring speed is reduced to 280 r / min to avoid clumping of high organic matter materials; Step 4: Coating and Finished Product Preparation: The drying time is extended to 1.2 hours to ensure the stability of the high nutrient content particles, while the other parameters remain the same.

[0031] III. Comparative Design and Preparation (Controlling Variables to Verify Key Processes / Raw Materials) Comparative Example 1 (Traditional peat carrier, verifying the influence of carrier type) 1. Differences in raw materials The 35 kg modified biomass carrier in Example 1 was replaced with 35 kg peat (porosity 35%, water holding capacity 180%), and the amount of other raw materials was exactly the same as in Example 1.

[0032] 2. Differences in preparation process The "preparation of modified biomass carrier" step in step 1 of Example 1 is omitted. Peat is directly mixed with slow-release nutrient matrix and soil conditioner. The remaining steps (activation of microbial agent, mixing and granulation, coating) are completely consistent with Example 1.

[0033] Comparative Example 2 (Single microbial inoculant, verifying the effect of microbial combinations) 1. Differences in raw materials The 6 kg of compound microbial inoculant in Example 1 was replaced with 6 kg of single Bacillus subtilis inoculant (concentration after activation: 10). 10 (CFU / mL), the amounts of other raw materials are exactly the same as in Example 1.

[0034] 2. Differences in preparation process In step 2, only Bacillus subtilis is activated; no other bacterial solutions need to be mixed. The remaining steps are completely consistent with those in Example 1.

[0035] Comparative Example 3 (No coating process, verifying the effect of coating) 1. Differences in raw materials The 3kg coating solution in Example 1 was removed, while the amounts of the remaining raw materials were exactly the same as in Example 1.

[0036] 2. Differences in preparation process The "coating and finished product preparation" step 4 in Example 1 is omitted. The semi-finished granules are dried to a moisture content of ≤10% and then directly screened, tested and packaged. The remaining steps are completely consistent with Example 1.

[0037] IV. Performance Testing Methods and Results (including testing details) 1. Sample preparation The finished products of Examples 1-3 and Comparative Examples 1-3 were sealed and placed in a 30°C constant temperature incubator. At the same time, three typical degraded soils (continuous cropping tomato soil, saline-alkali soil, and degraded farmland) were selected for field / pot tests. Each sample was repeated three times, and the average value was taken.

[0038] 2. Key performance testing methods (including instrument and operation details) Viable cell count decay rate test: Samples were taken at 0, 30, 60, and 90 days of storage. 10g of sample was weighed and added to 90mL of sterile physiological saline (containing 0.1% Tween 80). The mixture was shaken for 30 minutes (200 rpm) and serially diluted to 10⁻⁶. -6 Take 0.1 mL of the diluted solution and spread it on LB agar plates. After incubation at 30°C for 48 hours, count the cells and calculate the attenuation rate = (initial viable count - viable count after storage) / initial viable count × 100%. Soil pH and EC adjustment test: The test soil was saline-alkali soil (initial pH 8.8, EC 4.5 mS / cm). 200 kg of sample was applied per mu, spread evenly and then plowed into the soil (depth 20 cm). After 30 days, soil from the 0-20 cm layer was collected, deionized water was added at a soil-to-water ratio of 1:5, and the mixture was shaken for 30 minutes. The pH value was measured with a precision pH meter and the EC value was measured with an EC meter. Pathogen inhibition rate test: The test soil was from continuous tomato cropping soil (initial density of root rot pathogen 1.2 × 10⁻⁶). 5 CFU / g), apply 200 kg of sample per acre, and apply it around the tomato planting hole (50 g per hole). After 30 days, take 10 g of rhizosphere soil, add 90 mL of sterile water, shake and then dilute serially. Spread the mixture on a selective medium (with added pentachloronitrobenzene), incubate and count the samples. Calculate the inhibition rate = (initial density - post-treatment density) / initial density × 100%; Organic matter enhancement test: The test soil was degraded farmland (initial organic matter 1.0%). 200 kg of sample was applied per mu. After basal application, water was applied. 60 days later, soil samples from the 0-20 cm soil layer were taken. The organic matter content was determined by potassium dichromate volumetric method (external heating method). The enhancement amount was calculated as: organic matter content after treatment - initial organic matter content.

[0039] 3. Test results (including data and phenomenon descriptions)

[0040] V. Results Analysis (Explaining Differences in Combination of Process and Raw Material Analysis) The key role of carrier type: Comparative Example 1 used a traditional peat carrier. Due to its low porosity (35% vs. 60% in Example 1) and lack of trehalose protection, the viable bacteria count decreased by 45.6% after 90 days, which is 3.7 times that of Example 1 (12.3%). At the same time, the poor fertilizer retention capacity of peat resulted in an increase of only 0.25% in soil organic matter, demonstrating the significant advantages of modified biomass carrier in bacteria and fertilizer retention.

[0041] Synergistic effect of compound microorganisms: Comparative Example 2 used Bacillus subtilis alone, and the pathogen inhibition rate was only 38.5%, far lower than 65.2% in Example 1. Due to the lack of the growth-promoting effect of Bacillus amyloliquefaciens and the soil structure-improving effect of Bacillus mucilaginosus, it could only inhibit some pathogens and could not achieve a comprehensive improvement effect.

[0042] The role of coating process in preserving and stabilizing microorganisms: In Comparative Example 3, without coating process, there is no protective film on the particle surface, and the viable bacteria count decline rate increases to 38.7% after 90 days, and the powdering rate reaches 8% after storage; while in Examples 1-3, the coating liquid forms a breathable protective film (oxygen permeability 22% / 24h), which not only ensures the respiration of microorganisms, but also isolates external humidity, resulting in excellent particle stability.

[0043] Verification of the suitability of the examples: Example 2, due to its high dosage of microbial agent (8kg) and large proportion of modified carrier (40kg), showed the best performance in the improvement of saline-alkali soil (pH dropped to 7.6 and EC dropped to 2.6mS / cm); Example 3, due to its high amount of chitinase, achieved an inhibition rate of 62.1% against pathogens in continuously cropped soils, and was suitable for soils with continuous cropping obstacles, proving that different examples can specifically solve different soil degradation problems.

[0044] The above description of the embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A soil-improving microbial fertilizer, characterized in that, It is made from the following raw materials in parts by weight: 5-8 parts of compound microbial agent, 30-40 parts of modified biomass carrier, 25-35 parts of slow-release nutrient matrix, 15-20 parts of soil conditioner, 2-3 parts of microbial synergist, 1-2 parts of binder, and 3 parts of coating liquid. The compound microbial agent is composed of Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus mucilaginosus in a mass ratio of 3:2:1, and the viable counts of the three agents are ≥10 for Bacillus subtilis. 10 CFU / g, Bacillus amyloliquefaciens ≥10 10 CFU / g, Bacillus subtilis ≥10 9 CFU / g; The modified biomass carrier is made by mixing corn straw and shiitake mushroom residue at a mass ratio of 2:1, and undergoing carbonization, acid activation, and trehalose loading treatment. The carrier has a porosity ≥60%, water holding capacity ≥300%, and pore size 50-80nm; The slow-release nutrient matrix is ​​composed of potassium humate, slow-release urea, and potassium dihydrogen phosphate at a mass ratio of 5:3:2, wherein the potassium humate has an organic matter content ≥70% and the slow-release urea has a nitrogen release period ≥60 days; The soil conditioner is modified. Montmorillonite and gypsum powder are compounded at a mass ratio of 4:

1. The modified montmorillonite is activated with 0.1 mol / L hydrochloric acid, with a cation exchange capacity ≥150 mmol / 100g and a gypsum powder particle size ≤10μm. The microbial synergist is compounded from 0.5-1 parts of L-proline, 0.3-0.5 parts of chitinase, and 1.2-1.5 parts of humic acid. The binder is sodium carboxymethyl cellulose. The coating solution is an aqueous solution containing 0.5% xanthan gum and 1% polyvinyl alcohol.

2. The soil-improving microbial fertilizer according to claim 1, characterized in that, The raw materials for preparing the modified biomass carrier, corn stalks and shiitake mushroom residue, need to be crushed to a particle size ≤1mm; the loading amount of trehalose in the carrier is 0.5% of the carrier mass.

3. The soil-improving microbial fertilizer according to claim 1, characterized in that, The protective film formed after the coating liquid is sprayed has an oxygen permeability of ≥20% / 24h; the finished fertilizer is made of granules with a diameter of 2-3mm, a moisture content of ≤10%, and a granule formation rate of ≥90%.

4. A method for preparing a soil-improving microbial fertilizer according to any one of claims 1-3, characterized in that, Includes the following steps: S1: Preparation of modified biomass carrier: Corn stalks and shiitake mushroom residue were mixed at a mass ratio of 2:1, crushed to a particle size ≤1mm, placed in an anaerobic carbonization furnace, heated to 600℃ at 10℃ / min, kept at that temperature for 2 hours, and cooled to room temperature to obtain biochar; 2% nitric acid solution was added to the biochar at a solid-liquid ratio of 1:5, stirred at 60℃ for 2 hours, filtered, washed with deionized water until neutral, and dried at 105℃ for 3 hours; 0.5% trehalose solution was sprayed onto the dried biochar at a mass ratio of 10:1, and stirred at 30℃ for 30 minutes to obtain the modified biomass carrier; S2: Activation of compound microbial agents: Take Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus mucilage powder respectively, add sterile water containing 0.1% glucose, and incubate at 30℃ and 150r / min for 2 hours with shaking to achieve a bacterial concentration of 10. 10 CFU / mL; Mix the three bacterial solutions in a volume ratio of 3:2:1, add 0.2% chitinase, and let stand at 28℃ for 1 hour to obtain an activated compound bacterial solution; S3: Raw material mixing and granulation: Add modified biomass carrier, slow-release nutrient matrix, and soil conditioner to a twin-screw mixer and stir at 35℃ and 500r / min for 20 minutes; slowly add activated compound bacterial solution and microbial synergist, reduce the speed to 300r / min, stir for 15 minutes, and control the material moisture content to 25%-30%; add sodium carboxymethyl cellulose, stir for 5 minutes, and then send it to an extrusion granulator with a die diameter of 2.5mm. After granulation, dry in a drying room at 40℃ and 50% relative humidity until the moisture content is ≤10% to obtain granular semi-finished product; S4: Coating and Finished Product: Dissolve 0.5% xanthan gum and 1% polyvinyl alcohol in 40℃ deionized water and stir until completely dissolved to prepare a coating solution; send the semi-finished granules into a coating machine, spray with the coating solution, the amount of coating solution is 3% of the mass of the semi-finished granules, dry at 35℃ for 1 hour; sieve to obtain granules with a diameter of 2-3mm, and package after passing the inspection to obtain the finished soil-improving microbial fertilizer.

5. The method for preparing a soil-improving microbial fertilizer according to claim 4, characterized in that, In step S1, after the biochar is treated with a 2% nitric acid solution, the criterion for determining neutrality is that the pH value of the washing solution is 6.5-7.

5.

6. The method for preparing a soil-improving microbial fertilizer according to claim 4, characterized in that, In step S3, the moisture content of the material needs to be continuously monitored during the drying process after extrusion granulation. Drying is stopped when the moisture content drops to 10%.

7. The method for preparing a soil-improving microbial fertilizer according to claim 4, characterized in that, In step S4, a standard sieve with a 2-3mm aperture is used for sieving. Particles that pass through the sieve need to be returned to the granulation process, while particles that pass through the sieve are subjected to subsequent testing.

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