A heavy-crop-resistant composite microbial fertilizer with soil improvement function and a preparation method thereof

Abstract

The application provides an anti-cropping composite microbial fertilizer with soil improvement function and a preparation method thereof, and relates to the technical field of fertilizers.The preparation method comprises the following steps: step 1: selecting bacillus strains and trichoderma strains with anti-cropping effects, and sequentially completing strain activation, seed liquid expansion, and liquid-state fermentation in a fermentation tank to obtain single-bacterium fermentation liquor, and then mixing the single-bacterium fermentation liquor according to a proportion to obtain composite bacterial liquor; step 2: mixing soil improvement components and fertilizer conditioning components, crushing and sieving, adjusting the water content and the carbon-nitrogen ratio, and obtaining fertilizer base material; step 3: inoculating the composite bacterial liquor into the fertilizer base material, adding nutritional accessories, mixing, adjusting the carbon-nitrogen ratio again, and performing solid-state aerobic fermentation to obtain fermentation base material; and step 4: adding functional additives to the fermentation base material, uniformly mixing, and performing granulation, low-temperature drying and sieving to obtain the anti-cropping composite microbial fertilizer.The application can improve the heavy-cropping soil, cultivate the soil fertility, and promote stable yield and yield increase of crops.

Description

Technical Field

[0001] This invention relates to the field of fertilizer technology, specifically to a compound microbial fertilizer for resisting continuous cropping and its preparation method, which also has soil improvement functions. Background Technology

[0002] Under the long-term continuous cropping cultivation model of vegetables and fruit trees, the multiple cropping index remains high, and the soil is subjected to high-intensity consumption year after year, which can easily lead to continuous cropping obstacles: on the one hand, the soil organic matter is continuously depleted, the granular structure collapses, and physical and chemical deterioration problems such as compaction, acidification, high bulk density, and reduced water and fertilizer retention capacity occur; on the other hand, the rhizosphere microecology is unbalanced, soil-borne pathogens such as Fusarium oxysporum accumulate in large quantities, the abundance of beneficial microorganisms decreases sharply, and crops suffer from high incidence of wilt disease and root rot, and seedling death and rotting occur frequently.

[0003] In response to the soil deterioration and microecological imbalance caused by continuous cropping of vegetables and fruit trees, microbial compound fertilizer is a new type of ecological fertilizer that is scientifically compounded with beneficial microbial flora, organic matter and trace elements. Unlike traditional single chemical fertilizers, it has the advantages of biological activity, comprehensive nutrition, soil improvement and root protection, and green and long-lasting effects. It can be applied to reduce fertilizer and increase efficiency and restore soil in fields where vegetables are continuously cropped.

[0004] Existing microbial compound fertilizers, such as the compound microbial organic fertilizer and its preparation method disclosed in CN103113167A, have the following problems: 1. The types of soil amendment raw materials are limited, relying only on peat moss, potassium humate, and shell powder, resulting in a single coverage of soil amendment functions; 2. The substrate moisture content and carbon-nitrogen ratio were not specifically adjusted during the preparation process, which failed to provide a suitable growth environment for microbial growth and reproduction. Summary of the Invention

[0005] This invention provides a compound microbial fertilizer for resisting continuous cropping and a method for preparing the same, which has soil improvement function, in order to solve at least one of the technical problems mentioned in the background art.

[0006] To address the aforementioned technical problems, this invention discloses a method for preparing a compound microbial fertilizer for resisting continuous cropping that also has soil improvement functions, comprising the following steps: Step 1: Select Bacillus strains and Trichoderma strains with anti-replanting function, activate the strains and expand the seed liquid, and then inoculate them into a fermenter for liquid fermentation to obtain fermentation broth of each single strain. Mix the single strain fermentation broth according to the formula to obtain compound bacterial liquid. Step 2: Mix the soil amendment components and fertilizer conditioning components according to the formula, and adjust the moisture content and carbon-nitrogen ratio after crushing and sieving to obtain fertilizer base material; Step 3: Inoculate the compound bacterial solution into the fertilizer substrate, add nutrient additives, stir and mix, adjust the carbon-nitrogen ratio again, carry out solid-state aerobic fermentation, and obtain the fermented substrate after the fermentation is completed; Step 4: Add functional additives to the fermentation substrate, mix evenly, and then granulate, dry at low temperature, and screen to obtain a compound microbial fertilizer with soil improvement function to resist continuous cropping.

[0007] Preferably, the Bacillus strain is at least two of Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus polymyxa, and the Trichoderma strain is at least one of Trichoderma harzianum and Trichoderma viride.

[0008] Preferably, the ratio of total viable Bacillus strains to total viable Trichoderma strains is (3-5):1; the total viable bacteria concentration in the compound bacterial solution is ≥2×10⁻⁶. 9 CFU / mL.

[0009] Preferably, the soil amendment component is at least two of decomposed straw, humic acid, and peat moss; the fertilizer conditioning component is at least one of biochar, attapulgite, and diatomaceous earth; and the nutrient supplement is at least one of soybean meal, wheat bran, and corn flour.

[0010] Preferably, in step 2: 60-80 parts of soil amendment component and 15-25 parts of fertilizer conditioning component; the moisture content of the fertilizer base material after conditioning is 30%-45%, and the carbon-nitrogen ratio is (20-30):1; the carbon-nitrogen ratio is adjusted by supplementing carbon source auxiliary materials or nitrogen source auxiliary materials; The inoculation amount of the compound bacterial solution is 5% to 12% of the total mass of the fertilizer base material; the amount of nutrient additives added is 8% to 15% of the total mass of the fertilizer base material; and the amount of functional additives added is 2% to 5% of the fermentation base material.

[0011] Preferably, the functional additives include a binder and chelated trace elements, wherein the binder is at least one of sodium carboxymethyl cellulose and xanthan gum, and the chelated trace elements are at least one of chelated zinc, chelated boron, and chelated manganese.

[0012] Preferably, after obtaining the fermentation broth of each single strain in step 1, the process includes: Step 1-1: Cool the fermented Bacillus spp. and Trichoderma spp. fermentation broths to room temperature of 25-30°C, then mix the Bacillus spp. and Trichoderma spp. fermentation broths to make the ratio of live Bacillus spp. to Trichoderma spp. in the mixed basic compound bacterial solution reach (3-5):1. Steps 1-2: Add water-soluble wall materials to the basic composite bacterial solution in sequence: 2wt% to 4wt% gum arabic and 1wt% to 2wt% humic acid. Control the stirring speed to 60 to 100 r / min and stir and coat at room temperature in the dark for 2 to 4 hours to obtain the wall material-coated composite bacterial solution.

[0013] Preferably, step 2 includes: Step 2-1: Detect the viscosity of the composite bacterial solution coated with wall material, and the target viscosity range of the composite bacterial solution coated with wall material, and determine the normalized viscosity factor; Step 2-2: Mix the soil amendment components and fertilizer conditioning components according to the formula, crush and sieve, and then take samples to test the porosity of the material passing through the sieve. Step 2-3: Determine the first target moisture content based on the normalized viscosity factor and the porosity of the undersize material; adjust the moisture content of the undersize material obtained in Step 2-2 to the first target moisture content, and adjust the carbon-nitrogen ratio at the same time to obtain fertilizer base material; Steps 2-4: Determine the target spraying pressure for coating the composite bacterial solution based on the normalized viscosity factor and the porosity of the undersize material; Step 3 includes: spraying the inoculated compound bacterial solution into the fertilizer base material through atomized spraying based on the target spraying pressure, adding nutrient additives, stirring and mixing, adjusting the carbon-nitrogen ratio again, and carrying out solid-state aerobic fermentation. After the fermentation is completed, the fermented base material is obtained.

[0014] The present invention also discloses a compound microbial fertilizer for resisting continuous cropping that also has soil improvement function, which is prepared by the preparation method of the compound microbial fertilizer for resisting continuous cropping that also has soil improvement function.

[0015] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. Coating the compound functional bacteria with gum arabic and water-soluble humic acid at room temperature in the dark forms a slow-release protective layer on the bacterial surface. This effectively reduces damage to live bacteria caused by environmental stress during solid-state fermentation, storage, transportation, and initial soil application, significantly improving the strain's environmental tolerance and extending the colonization time and survival stability of beneficial bacteria in the rhizosphere. This ensures a sufficient number of live bacteria for stable soil improvement and disease control. Utilizing coating protection and porous carrier colonization technology, the effective action period of the rhizosphere live bacteria can reach 45-60 days, providing long-term soil improvement and control of soil-borne diseases. The absence of a post-mixing co-fermentation culture step allows the two types of bacteria to form a symbiotic adaptation system in advance. 2. Soil amendment components composed of decomposed straw, humic acid, and peat moss can rapidly increase soil organic matter content, provide long-term carbon source substrates for soil microorganisms, and promote the formation of soil aggregates. Mineral conditioning components such as biochar and attapulgite, with their porous structure and adsorption properties, can loosen the soil, reduce bulk density, and alleviate compaction and acidification. On the other hand, they can adsorb and fix beneficial bacteria and nutrients, reduce nutrient leaching, and prolong the colonization time of microbial communities in the rhizosphere.

[0017] 3. The fertilizer substrate provides a solid carrier for the microbial community, while the bran, soybean meal, and other nutrient supplements provide fast-acting carbon and nitrogen nutrition, solving the problems of insufficient nutrition and slow colonization of microorganisms in the early stage of pure organic substrate fermentation. With the carbon-nitrogen ratio precisely controlled to the optimal range of 20~30:1, the proliferation rate of beneficial bacteria can be increased, the fermentation cycle can be shortened by 3~5 days, the material can be decomposed more thoroughly, and after being applied to the soil, it can quickly activate the metabolic activity of rhizosphere microorganisms and accelerate the soil nutrient cycle.

[0018] 4. Bacillus subtilis and Bacillus amyloliquefaciens reproduce rapidly, quickly occupying rhizosphere niches and secreting lipopeptide antimicrobial substances to inhibit soil-borne pathogens. Trichoderma harzianum parasitizes pathogens through mycelial parasitism and lyses pathogen cell walls, while simultaneously inducing systemic disease resistance in crops. The two strains have complementary mechanisms of action, with an antimicrobial spectrum covering multiple core pathogens of continuous cropping, such as Fusarium, Phytophthora, and Rhizoctonia solani. They can specifically inhibit soil-borne pathogens such as Fusarium oxysporum in the rhizosphere, significantly reducing the incidence of continuous cropping diseases such as cucumber wilt, effectively alleviating seedling death and root rot caused by continuous cropping obstacles, reducing the use of chemical pesticides, and meeting the requirements of green agricultural production.

[0019] Sodium carboxymethyl cellulose and xanthan gum, as binders, can improve particle strength and reduce pulverization loss during storage, transportation and application. Chelated trace elements are not easily fixed by the soil and can be directly absorbed by crops, supplementing the micronutrients that are generally lacking in continuously cropped soils. At the same time, it avoids antagonistic reactions between metal elements and live bacteria, taking into account both particle shapeability and functional stability.

[0020] 5. Through the pathways of live bacteria protection, physical and chemical soil improvement, promotion of bacterial proliferation, disease control, and nutrient enhancement, this application can simultaneously increase soil organic matter content, reduce soil bulk density, and increase the activity of soil sucrase and other biological enzymes, thereby simultaneously improving soil physical and chemical properties and micro-ecological environment, solving the problems of soil compaction, soil fertility decline, and micro-ecological imbalance caused by continuous cropping, and ultimately achieving multiple benefits of soil fertility cultivation, healthy crop growth, and increased yield. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1This is a schematic diagram of the process of the present invention. Detailed Implementation

[0022] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0023] Furthermore, in this invention, the use of terms such as "first" and "second" is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions and features of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, such a combination should be considered non-existent and not within the scope of protection claimed by this invention.

[0024] The present invention provides the following embodiments: Example 1: This embodiment of the invention provides a method for preparing a compound microbial fertilizer for resisting continuous cropping that also has soil improvement functions, such as... Figure 1 As shown, it includes the following steps: Step 1: Select Bacillus strains and Trichoderma strains with anti-replanting function, activate the strains and expand the seed liquid, and then inoculate them into a fermenter for liquid fermentation to obtain fermentation broth of each single strain. Mix the single strain fermentation broth according to the formula to obtain compound bacterial liquid. Step 2: Mix the soil amendment components and fertilizer conditioning components according to the formula, then crush and sieve (60-120 mesh, preferably 80-100 mesh) to adjust the moisture content and carbon-nitrogen ratio to obtain fertilizer base material; Step 3: Inoculate the compound bacterial solution into the fertilizer substrate, add nutrient additives, stir and mix, adjust the carbon-nitrogen ratio again, carry out solid-state aerobic fermentation, and obtain the fermented substrate after the fermentation is completed; Step 4: Add functional additives to the fermentation substrate, mix evenly, and then granulate, dry at low temperature, and screen to obtain a compound microbial fertilizer with soil improvement function to resist continuous cropping.

[0025] The Bacillus strain is at least two of Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus polymyxa, and the Trichoderma strain is at least one of Trichoderma harzianum and Trichoderma viride.

[0026] The ratio of viable bacteria in the compound bacterial solution is: (3-5) viable bacteria of Bacillus strains to (3-5) viable bacteria of Trichoderma strains; the total viable bacteria concentration in the compound bacterial solution is ≥2×10⁻⁶. 9 CFU / mL.

[0027] The soil amendment component comprises at least two of decomposed straw, humic acid, and peat moss; the fertilizer conditioning component comprises at least one of biochar, attapulgite, and diatomaceous earth; and the nutrient supplement comprises at least one of soybean meal, wheat bran, and corn flour.

[0028] In step 2: 60-80 parts of soil amendment component and 15-25 parts of fertilizer conditioning component; the moisture content of the fertilizer base material after conditioning is 30%-45%, and the carbon-nitrogen ratio is (20-30):1; the carbon-nitrogen ratio is adjusted by supplementing carbon source auxiliary materials or nitrogen source auxiliary materials. The inoculation amount of the compound bacterial solution is 5% to 12% of the total mass of the fertilizer base material; the amount of nutrient additives added is 8% to 15% of the total mass of the fertilizer base material; and the amount of functional additives added is 2% to 5% of the fermentation base material.

[0029] The functional additives include a binder and chelated trace elements. The binder is at least one of sodium carboxymethyl cellulose and xanthan gum, and the chelated trace elements are at least one of chelated zinc, chelated boron, and chelated manganese.

[0030] In step 1, after obtaining the fermentation broth of each individual strain, the process includes: Step 1-1: Cool the fermented Bacillus spp. and Trichoderma spp. fermentation broths to room temperature of 25-30°C, then mix the Bacillus spp. and Trichoderma spp. fermentation broths to make the ratio of live Bacillus spp. to Trichoderma spp. in the mixed basic compound bacterial solution reach (3-5):1. Steps 1-2: Add water-soluble wall materials to the basic composite bacterial solution in sequence: 2wt% to 4wt% of gum arabic (gum arabic accounts for 1wt% to 2wt% of the mass of the basic composite bacterial solution) and 1wt% to 2wt% of water-soluble humic acid (water-soluble humic acid accounts for 1wt% to 2wt% of the mass of the basic composite bacterial solution). Control the stirring speed to 60 to 100 r / min, stir and coat at room temperature in the dark for 2 to 4 hours to obtain the wall material-coated composite bacterial solution. Specific implementation examples:

[0031] I. Experimental materials: Strains: Bacillus subtilis (ACCC11086), Bacillus amyloliquefaciens (ACCC11078), Trichoderma harzianum (ACCC30150).

[0032] Raw materials: Well-rotted corn stalks: 58.2% organic matter, 12.3% moisture content, carbon-nitrogen ratio 62.4:1; Humic acid powder: 62.7% free humic acid, 8.5% moisture content; Biochar: 40 mesh particle size, 42.6% porosity; Attapulgite: passed through 200 mesh, blue absorption 28.3g / 100g; Soybean meal, wheat bran, sodium carboxymethyl cellulose (CMC-Na), chelated zinc (EDTA-Zn), chelated boron (sugar alcohol chelated boron), and urea (nitrogen content 46.4%) are all commercially available industrial grade.

[0033] II. Preparation steps: Step 1: Preparation of compound bacterial solution: (1) Slant activation: Bacillus subtilis and Bacillus amyloliquefaciens, which were stored in cold storage, were inoculated into beef extract peptone slant medium: beef extract 3 g / L, peptone 10 g / L, NaCl (5 g / L), agar 20 g / L, pH 7.0-7.2, and incubated at 30℃ for 24 h. Microscopic examination showed that the bacterial cells were uniform in morphology and free of contaminants. The slant was considered qualified when it was covered with milky white single colonies. Trichoderma harzianum was inoculated into PDA slant medium: potato 200 g / L (boiled and filtered), glucose 20 g / L, agar 20 g / L, pH 6.0-6.5, and incubated at 28℃ for 48 h. The slant was considered qualified when it was covered with dense green conidia.

[0034] (2) Seed culture expansion: Pick 2 loops of fresh colonies from the slant and inoculate them into the corresponding liquid seed culture medium (200 mL / 500 mL shake flask): Bacillus seed culture: Remove agar from the culture medium, and keep the other components the same as the slant. Incubate at 30℃ and 180r / min on a shaker for 18h. Microscopic examination shows that the bacterial concentration meets the standard and there is no contamination by other bacteria. This is a qualified first-grade seed culture.

[0035] Trichoderma harzianum seed culture: Liquid PDA medium (agar-free), shaken at 28℃ and 160r / min for 28h, spore germination rate ≥92% and no contaminants were observed under a microscope, which is qualified as Grade I seed culture.

[0036] (3) Liquid fermentation in a fermenter: The primary seed liquid was inoculated into a 50L mechanically stirred fermenter at a 5% inoculation rate, with a total liquid volume of 35L. Aeration and stirring were carried out throughout the process, and samples were taken every 6 hours for microscopic examination and viable cell count. Bacillus subtilis: fermentation temperature 30℃, stirring speed 220 r / min, aeration rate 0.8 vvm, fermentation time 40 h, final measured viable count 1.28 × 10⁻⁶ 9 CFU / mL; Bacillus amyloliquefaciens: fermentation temperature 30℃, stirring speed 220 r / min, aeration rate 0.8 vvm, fermentation time 38 h, final measured viable count 1.22 × 10⁻⁶ 9 CFU / mL; Trichoderma harzianum: Fermentation temperature 28℃, stirring speed 180 r / min, aeration rate 0.6 vvm, fermentation time 50 h, final measured spore concentration 9.1 × 10⁻⁶ 8 CFU / mL. Three strains are fermented independently to avoid interspecies nutrient competition and metabolic antagonism.

[0037] (4) Step 1-1: Cool the fermented Bacillus subtilis fermentation broth, Bacillus amyloliquefaciens fermentation broth, and Trichoderma harzianum fermentation broth to room temperature of 28°C respectively; calculate the mixing volume according to the measured concentration of each single-strain fermentation broth, with the ratio of total viable Bacillus spp. to viable Trichoderma spp. = 4:1 (where the ratio of viable Bacillus subtilis to viable Bacillus amyloliquefaciens is approximately 1:1), mix them evenly under aseptic conditions to obtain the basic composite bacterial solution.

[0038] Steps 1-2: Add water-soluble wall materials sequentially to the basic composite bacterial solution: 3 wt% gum arabic and 1.5 wt% water-soluble humic acid. Maintain a stirring speed of 80 r / min and stir at room temperature in the dark for 3 hours to coat the solution, obtaining a composite bacterial solution coated with the wall material. The measured total viable bacteria concentration was 2.17 × 10⁻⁶. 9 CFU / mL, store temporarily at 4℃ protected from light, and use within 24 hours.

[0039] Step 2: Fertilizer base material preparation: Weigh out the following by weight: 62 parts decomposed corn stalks, 13 parts humic acid, 16 parts biochar, and 9 parts attapulgite.

[0040] (1) After mixing, put the mixture into a hammer mill for crushing, and pass it through an 80-mesh standard sieve to remove the hard core and clumps of straw; (2) Adjust the moisture content by spraying clean water, and adjust the initial moisture content to 38% by actual measurement; (3) The initial carbon-nitrogen ratio of the main material was 34.7:1. After adding 0.8 parts of urea and mixing, the carbon-nitrogen ratio was retested and found to be 26:1, which is in line with the optimal range for solid-state fermentation, and fertilizer base material was obtained.

[0041] Step 3: Solid-state aerobic fermentation: (1) The compound bacterial solution was sprayed into the base material at an inoculation rate of 8.2% of the total mass of the fertilizer base material, and 9.5% of wheat bran was added as a nutrient supplement. The mixture was sprayed and stirred 3 times to ensure that the bacterial solution and supplement were evenly dispersed. The carbon-nitrogen ratio of the mixed material was retested, and a small amount of urea was added to finely adjust it to 24.8:1, which is in line with the optimal range for solid-state fermentation. (2) The mixed materials are piled into a strip-shaped fermentation pile with a height of 1.2m and a width of 1.5m, and the ambient temperature is controlled at 28-32℃; (3) The fermentation cycle lasts for 10 days. The core temperature of the pile is monitored daily: On the second day, the pile temperature rises to 56℃ and is maintained at a high temperature above 55℃ for 72 hours (3 days); On the fourth day, the pile is turned over for the first time and the pile temperature drops to 51℃; On the seventh day, the pile is turned over for the second time and the pile temperature is 38℃; On the tenth day, the pile temperature drops to 30℃, the material is dark brown, has no ammonia smell, is soft and elastic to the touch, and is fully decomposed, thus obtaining the fermentation base material; (4) The moisture content of the material was 27.6% when fermentation was completed. Random sampling and testing showed no Escherichia coli or roundworm eggs, which met the standards for harmless organic fertilizer.

[0042] Step 4: Post-processing of finished products: (1) Spread the fermentation substrate to room temperature, add 3.2% of the total mass of functional additives (accounting for 3.2% of the total mass of the fermentation substrate): 2.1% sodium carboxymethyl cellulose and 1.1% chelated trace elements (chelated zinc: chelated boron = 1:1), and stir in a three-dimensional mixer for 15 minutes until uniform; (2) Granulation by roller extrusion to produce cylindrical particles with a diameter of 3-4 mm; (3) Dry with hot air at 48℃, take samples every 2 hours to measure moisture content, and stop drying when the moisture content reaches 17.8%; (4) The fine powder and lumps are removed by vibrating screen to obtain the finished product granules. The actual measured indicators of the finished product are: total number of effective viable bacteria 0.82 billion / g, organic matter mass fraction 45.7%, and moisture 17.8%.

[0043] III. Fertilizer Efficacy Verification Experiment: 1. Experimental Design: Experimental location: Greenhouse potted plants; the soil used in the experiment was taken from the 0-20cm topsoil of a greenhouse where cucumbers had been continuously grown for 6 years. Initial soil background values: organic matter 12.4 g / kg, bulk density 1.49 g / cm³, available nitrogen 87.2 mg / kg, available phosphorus 18.6 mg / kg, Fusarium oxysporum count 3.2 × 10⁻⁶. 4 CFU / g dry soil; Experimental treatment: Each pot contained 15 kg of air-dried soil and planted 2 cucumber seedlings (Jinyou No. 1) with 2 leaves and 1 heart. Each treatment group had 6 pots replicated. Routine water and fertilizer management was used, and the growth period was consistent.

[0044] ① Blank control group (CK): No fertilizer was applied; ②Commercially available control fertilizer group (T1): Apply ordinary commercial bio-organic fertilizer (0.5 billion live bacteria / g, 40% organic matter), with an application rate equivalent to 200 kg per mu, applied as base fertilizer in furrows; ③ Example group (T2) of the present invention: Apply the compound microbial fertilizer prepared in this example, with an application rate of 200 kg per mu, applied as base fertilizer in furrows.

[0045] 2. Measurement Indicators and Methods: Fusarium wilt disease index: During the peak fruiting period, the disease index was calculated based on a grading standard of 0 to 4. Soil physicochemical properties: Rhizosphere soil samples were taken at harvest time; organic matter was measured using the potassium dichromate method, and bulk density was measured using the ring sampler method. Soil microbial indicators: Fusarium oxysporum quantity was determined by dilution plate method, and soil sucrase activity was determined by colorimetric method; Yield: The cumulative yield per plant during the harvest period.

[0046]

[0047] Grade 0: The plant is completely healthy, with no disease spots or wilting; Grade 1: A small number of lower leaves are slightly yellowed, and the wilted area is less than 10% of the whole plant; Level 2: Leaves in the middle and lower parts of the plant turn yellow and wilt, with the affected area accounting for 10% to 30% of the entire plant; Level 3: More than half of the leaves are wilted and yellowed, with the affected area accounting for 30% to 60% of the entire plant; Level 4: The entire plant is severely wilted and dies, with the affected area exceeding 60% until the entire plant dies.

[0048] Cucumber Fusarium Wilt Disease Severity Index = Where i represents the i-th order, 4 in the denominator represents the 4-th order, and M represents the total number of plants surveyed. To investigate the total number of plants at level i in the total number of plants; The beneficial effects of this invention are as follows: 1. Coating the compound functional bacteria with gum arabic and water-soluble humic acid at room temperature in the dark forms a slow-release protective layer on the bacterial surface. This effectively reduces damage to live bacteria caused by environmental stress during solid-state fermentation, storage, transportation, and initial soil application, significantly improving the strain's environmental tolerance and extending the colonization time and survival stability of beneficial bacteria in the rhizosphere. This ensures a sufficient number of live bacteria for stable soil improvement and disease control. Utilizing coating protection and porous carrier colonization technology, the effective action period of the rhizosphere live bacteria can reach 45-60 days, providing long-term soil improvement and control of soil-borne diseases. The absence of a post-mixing co-fermentation culture step allows the two types of bacteria to form a symbiotic adaptation system in advance. 2. Soil amendment components composed of decomposed straw, humic acid, and peat moss can rapidly increase soil organic matter content, provide long-term carbon source substrates for soil microorganisms, and promote the formation of soil aggregates. Mineral conditioning components such as biochar and attapulgite, with their porous structure and adsorption properties, can loosen the soil, reduce bulk density, and alleviate compaction and acidification. On the other hand, they can adsorb and fix beneficial bacteria and nutrients, reduce nutrient leaching, and prolong the colonization time of microbial communities in the rhizosphere.

[0049] 3. The fertilizer substrate provides a solid carrier for the microbial community, while the bran, soybean meal, and other nutrient supplements provide fast-acting carbon and nitrogen nutrition, solving the problems of insufficient nutrition and slow colonization of microorganisms in the early stage of pure organic substrate fermentation. With the carbon-nitrogen ratio precisely controlled to the optimal range of 20~30:1, the proliferation rate of beneficial bacteria can be increased, the fermentation cycle can be shortened by 3~5 days, the material can be decomposed more thoroughly, and after being applied to the soil, it can quickly activate the metabolic activity of rhizosphere microorganisms and accelerate the soil nutrient cycle.

[0050] 4. Bacillus subtilis and Bacillus amyloliquefaciens reproduce rapidly, quickly occupying rhizosphere niches and secreting lipopeptide antimicrobial substances to inhibit soil-borne pathogens. Trichoderma harzianum parasitizes pathogens through mycelial parasitism and lyses pathogen cell walls, while simultaneously inducing systemic disease resistance in crops. The two strains have complementary mechanisms of action, with an antimicrobial spectrum covering multiple core pathogens of continuous cropping, such as Fusarium, Phytophthora, and Rhizoctonia solani. They can specifically inhibit soil-borne pathogens such as Fusarium oxysporum in the rhizosphere, significantly reducing the incidence of continuous cropping diseases such as cucumber wilt, effectively alleviating seedling death and root rot caused by continuous cropping obstacles, reducing the use of chemical pesticides, and meeting the requirements of green agricultural production.

[0051] Sodium carboxymethyl cellulose and xanthan gum, as binders, can improve particle strength and reduce pulverization loss during storage, transportation and application. Chelated trace elements are not easily fixed by the soil and can be directly absorbed by crops, supplementing the micronutrients that are generally lacking in continuously cropped soils. At the same time, it avoids antagonistic reactions between metal elements and live bacteria, taking into account both particle shapeability and functional stability.

[0052] 5. Through the pathways of live bacteria protection, physical and chemical soil improvement, promotion of bacterial proliferation, disease control, and nutrient enhancement, this application can simultaneously increase soil organic matter content, reduce soil bulk density, and increase the activity of soil sucrase and other biological enzymes, thereby simultaneously improving soil physical and chemical properties and micro-ecological environment, solving the problems of soil compaction, soil fertility decline, and micro-ecological imbalance caused by continuous cropping, and ultimately achieving multiple benefits of soil fertility cultivation, healthy crop growth, and increased yield.

[0053] In one embodiment, step 2 includes: Step 2-1: Detect the viscosity of the composite bacterial solution coated with wall material, and the target viscosity range of the composite bacterial solution coated with wall material, and determine the normalized viscosity factor; Step 2-2: Mix the soil amendment components and fertilizer conditioning components according to the formula, crush and sieve, and then take a sample to test the porosity of the material under the sieve (the material under the sieve after sieving). Step 2-3: Determine the first target moisture content based on the normalized viscosity factor and the porosity of the undersize material; adjust the moisture content of the undersize material obtained in Step 2-2 to the first target moisture content, and at the same time adjust the carbon-nitrogen ratio (carbon-nitrogen ratio is (20~30):1) to obtain fertilizer base material; Steps 2-4: Determine the target spraying pressure for coating the composite bacterial solution based on the normalized viscosity factor and the porosity of the undersize material; Step 3 includes: spraying the inoculated compound bacterial solution into the fertilizer substrate using atomized spraying based on the target spraying pressure, adding nutrient additives, stirring and mixing, adjusting the carbon-nitrogen ratio again (carbon-nitrogen ratio is (20-30):1), carrying out solid-state aerobic fermentation, and obtaining the fermented substrate after the fermentation is completed.

[0054] (1) In this embodiment, the target viscosity range (specifically 120-200 mPa·s (detection temperature 28℃)) matches the range of addition of gum arabic and water-soluble humic acid and the range of coating and stirring process defined by the present invention. Under the cross-linking state of the wall material corresponding to this viscosity (the same as the viscosity detection temperature corresponding to step 2-1), the wall material coating of the composite bacterial solution is qualified (the bacterial solution is left to stand at room temperature in the dark for 2 hours, without layering or visible precipitation, and the bottom precipitation volume accounts for ≤1% of the total liquid volume; the bacterial solution is left to stand at room temperature in the dark for 12 hours, and the viable bacteria attenuation rate is ≤10%; the water-soluble wall material protective layer outside the bacterial cells can be separated by aseptic gradient dilution, and viable bacteria can be accurately detected by plate counting method, and the viable bacteria attenuation rate can be calculated). The viscosity of the composite bacterial solution coated with the wall material was measured using a rotational viscometer at a constant temperature, with the measurement temperature controlled at the bacterial solution coating reaction temperature of 25–30°C (preferably 28°C). Normalized viscosity factor = (viscosity of the encapsulated composite bacterial solution detected in step 2-1 - minimum value of the target viscosity range) ÷ (maximum value of the target viscosity range - minimum value of the target viscosity range); If the calculated normalized viscosity factor is <0 or >1.0, the viscosity of the composite bacterial solution coated with the wall material is deemed unqualified, and the wall material dosage or coating stirring parameters need to be adjusted before retesting.

[0055] In this embodiment, the porosity of the undersize material is detected as follows: A graduated cylinder with a fixed nominal volume is selected, and the crushed and sieved material is allowed to fall freely into the graduated cylinder without vibration or pressing, and is allowed to fill naturally to the full mark; then, clean water is slowly added along the wall of the graduated cylinder until a continuous free liquid surface appears on the surface of the material and no obvious bubbles continue to overflow, at which point the addition of water is stopped, and the total volume of clean water added is read; the percentage value obtained by dividing the total volume of clean water added by the fixed total volume of the material in the graduated cylinder is the porosity of the undersize material.

[0056] (2) The first target moisture content is determined based on the normalized viscosity factor and the porosity of the undersize material, specifically as follows: Matching table for the first target moisture content range:

[0057] Note: The values ​​in the table represent the first target moisture content range for the corresponding parameters, and porosity refers to the porosity of the material under the sieve.

[0058] Target spray pressure range matching table:

[0059] Note: The values ​​in the table represent the target spray pressure range for the corresponding parameters.

[0060] The beneficial effects of the solution in this embodiment are as follows: 1. When gum arabic is combined with water-soluble humic acid, it forms a three-dimensional hydrophilic polymer wall material through hydrogen bonding and hydrophobic interactions. The degree of cross-linking of the wall material directly determines the density, water permeability, air permeability, and structural stability of the protective film: insufficient cross-linking results in a loose wall material structure that easily dissociates and falls off upon contact with water, failing to provide stress protection for the bacteria; excessive cross-linking leads to an overly compact polymer network, blocking the metabolic channels of the bacteria and inhibiting spore germination and activity. The macroscopic viscosity of the bacterial solution is related to the microscopic cross-linking degree of the wall material; therefore, the target viscosity range is used as the acceptable viscosity threshold range to accurately correspond to the stable structure of the wall material with appropriate cross-linking.

[0061] 2. The wetting angle determines whether the bacterial solution can spontaneously penetrate the matrix pores: the higher the viscosity of the bacterial solution, the greater the surface tension, and the higher the critical water content required to wet the matrix pores; the higher the carrier porosity, the stronger the capillary suction, and liquid phase wetting can be completed at a low water content. This scheme is based on the linkage of normalized viscosity factor (surface tension property of bacterial solution) + porosity (capillary adsorption property of matrix) to match the water content and regulate the ratio of gas and liquid phases inside the pores: high viscosity bacterial solution is paired with high porosity matrix to increase water content and reduce surface tension of bacterial solution, allowing bacterial solution to penetrate deep into the pores through capillary action; low viscosity bacterial solution is paired with low porosity dense matrix to reduce water content and avoid liquid phase saturation crowding out oxygen channels in the pores; the carbon-nitrogen ratio (20~30):1 is fixed simultaneously to match the carbon-nitrogen metabolism ratio of functional bacteria and maintain the basic nutrient balance of fermentation.

[0062] By utilizing the porous, sheltered microenvironment, it achieves integrated in-situ metabolism encompassing "settling-feeding-proliferation," shortening the fermentation cycle by 3-5 days and significantly increasing the biomass of the microbial community and the yield of antibacterial metabolites. After fermentation, the mature microbial community is protected by a multi-layered structure. When applied to continuously cropped soils, it can sustainably establish itself in the rhizosphere, degrade soil toxic substances, antagonize soil-borne pathogens such as Fusarium oxysporum, and simultaneously decompose straw organic matter to improve granular structure. 3. Normalized viscosity factor directly determines the nutrient chelation and local microenvironment regulation capabilities of the outer coating wall material of the microorganisms. Porosity reflects the proportion of internal space in the fertilizer substrate that can be used for microbial attachment, colonization, and storage of nutrients. By setting the spray pressure in conjunction with these two parameters, functional bacteria with different coating characteristics can be evenly dispersed and stably attached to the organic pore structure inside the substrate, allowing the coated bacteria and the organic carrier to be tightly integrated into a symbiotic whole.

[0063] The bacteria colonize the slow-release structure nested inside the fertilizer, relying on the dual buffer system of the wall material and pores to isolate the temperature and humidity fluctuations during storage. The live bacteria rely on the trace nutrients retained in the pores to maintain basic metabolism, which greatly improves the metabolic homeostasis of live bacteria during the shelf life of the finished fertilizer, and the attenuation rate of live bacteria is stably controlled within 10%.

[0064] After being applied to continuously cropped soil, the double-layered nested slow-release structure responds to changes in soil water and fertilizer in stages: the carrier pores first slowly release bulk organic nutrients, the bacterial cell wall material simultaneously complexes trace elements in the soil and buffers the acidification stress of continuously cropped soil, and the bacterial community continuously releases to the rhizosphere through the carrier's storage capacity, forming a long-lasting rhizosphere beneficial bacterial barrier. Unlike conventional fertilizers, which release live bacteria in a single application and quickly become ineffective after a short period of effectiveness, the slow-release structure of this invention can achieve a gradient and long-lasting release of nutrients, live bacteria, and antibacterial metabolites, extending the effective period of soil improvement and wilt disease control by 20-40 days.

[0065] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a compound microbial fertilizer for resisting continuous cropping that also has soil improvement functions, characterized in that: Includes the following steps: Step 1: Select Bacillus strains and Trichoderma strains with anti-replanting function, activate the strains and expand the seed liquid, and then inoculate them into a fermenter for liquid fermentation to obtain fermentation broth of each single strain. Mix the single strain fermentation broth according to the formula to obtain compound bacterial liquid. Step 2: Mix the soil amendment components and fertilizer conditioning components according to the formula, and adjust the moisture content and carbon-nitrogen ratio after crushing and sieving to obtain fertilizer base material; Step 3: Inoculate the compound bacterial solution into the fertilizer substrate, add nutrient additives, stir and mix, adjust the carbon-nitrogen ratio again, carry out solid-state aerobic fermentation, and obtain the fermented substrate after the fermentation is completed; Step 4: Add functional additives to the fermentation substrate, mix evenly, and then granulate, dry at low temperature, and screen to obtain a compound microbial fertilizer with soil improvement function to resist continuous cropping.

2. The preparation method according to claim 1, characterized in that: The Bacillus strain is at least two of Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus polymyxa, and the Trichoderma strain is at least one of Trichoderma harzianum and Trichoderma viride.

3. The preparation method according to claim 1, characterized in that: Based on the ratio of viable bacteria, the total viable bacteria count of Bacillus strains to the total viable bacteria count of Trichoderma strains is (3-5):1; the total viable bacteria concentration in the compound bacterial solution is ≥2×10⁻⁶. 9 CFU / mL.

4. The preparation method according to claim 1, characterized in that: The soil amendment component comprises at least two of decomposed straw, humic acid, and peat moss; the fertilizer conditioning component comprises at least one of biochar, attapulgite, and diatomaceous earth; and the nutrient supplement comprises at least one of soybean meal, wheat bran, and corn flour.

5. The preparation method according to claim 1, characterized in that: In step 2: 60-80 parts of soil amendment component and 15-25 parts of fertilizer conditioning component; the moisture content of the fertilizer base material after conditioning is 30%-45%, and the carbon-nitrogen ratio is (20-30):1; the carbon-nitrogen ratio is adjusted by supplementing carbon source auxiliary materials or nitrogen source auxiliary materials. The inoculation amount of the compound bacterial solution is 5% to 12% of the total mass of the fertilizer base material; the amount of nutrient additives added is 8% to 15% of the total mass of the fertilizer base material; and the amount of functional additives added is 2% to 5% of the fermentation base material.

6. The preparation method according to claim 1, characterized in that: The functional additives include a binder and chelated trace elements. The binder is at least one of sodium carboxymethyl cellulose and xanthan gum, and the chelated trace elements are at least one of chelated zinc, chelated boron, and chelated manganese.

7. The preparation method according to claim 1, characterized in that: After obtaining the fermentation broth of each single strain in step 1, the process includes: Step 1-1: Cool the fermented Bacillus spp. and Trichoderma spp. fermentation broths to room temperature of 25-30°C, then mix the Bacillus spp. and Trichoderma spp. fermentation broths to make the ratio of live Bacillus spp. to Trichoderma spp. in the mixed basic compound bacterial solution reach (3-5):

1. Steps 1-2: Add water-soluble wall materials to the basic composite bacterial solution in sequence: 2wt% to 4wt% gum arabic and 1wt% to 2wt% humic acid. Control the stirring speed to 60 to 100 r / min and stir and coat at room temperature in the dark for 2 to 4 hours to obtain the wall material-coated composite bacterial solution.

8. The preparation method according to claim 7, characterized in that: Step 2 includes: Step 2-1: Detect the viscosity of the composite bacterial solution coated with wall material, and the target viscosity range of the composite bacterial solution coated with wall material, and determine the normalized viscosity factor; Step 2-2: Mix the soil amendment components and fertilizer conditioning components according to the formula, crush and sieve, and then take samples to test the porosity of the material passing through the sieve. Step 2-3: Determine the first target moisture content based on the normalized viscosity factor and the porosity of the undersize material; adjust the moisture content of the undersize material obtained in Step 2-2 to the first target moisture content, and adjust the carbon-nitrogen ratio at the same time to obtain fertilizer base material; Steps 2-4: Determine the target spraying pressure for coating the composite bacterial solution based on the normalized viscosity factor and the porosity of the undersize material; Step 3 includes: spraying the inoculated compound bacterial solution into the fertilizer base material through atomized spraying based on the target spraying pressure, adding nutrient additives, stirring and mixing, adjusting the carbon-nitrogen ratio again, and carrying out solid-state aerobic fermentation. After the fermentation is completed, the fermented base material is obtained.

9. A compound microbial fertilizer for resisting continuous cropping, which also has soil improvement functions, is characterized in that, The compound microbial fertilizer for resisting continuous cropping and possessing soil improvement function is prepared using any one of the preparation methods described in claims 1-8.

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