Microbial soil conditioner as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of soil improvement, and particularly relates to a microbial soil conditioner as well as a preparation method and application thereof. The microbial soil conditioner comprises a compound microbial agent, an organic carrier and an auxiliary additive, the compound microbial agent is prepared from bacillus subtilis, bacillus amyloliquefaciens, paenibacillus mucilaginosus and bacillus licheniformis. By screening microbial strains with a synergistic effect and combining with an optimized organic carrier, the soil conditioner not only can effectively improve the physicochemical properties of soil, break soil hardening and regulate the pH value of the soil, but also can improve the fertility of the soil, promote the growth of crop roots and inhibit the reproduction of harmful pathogenic bacteria in the soil; the use amount of chemical fertilizers and pesticides is reduced. Meanwhile, the preparation method disclosed by the invention is simple in process, relatively low in cost and suitable for large-scale industrial production, and has a wide market application prospect.

Description

A microbial soil conditioner, its preparation method and application Technical Field

[0001] This invention belongs to the field of soil improvement technology, specifically relating to a microbial soil conditioner, its preparation method, and its application. Background Technology

[0002] Soil is the core carrier of agricultural production, and its quality directly affects crop growth, yield, quality, and agricultural ecological stability, making it crucial for ensuring national food security and sustainable agricultural development. In recent years, my country's agricultural modernization process has accelerated, but unreasonable farming practices such as excessive use of chemical fertilizers and pesticides and long-term continuous cropping have become widespread, leading to severe soil degradation and seriously hindering agricultural development.

[0003] Currently, soil quality problems in my country are characterized by diversity and complexity, mainly including: widespread soil compaction, leading to reduced soil porosity, decreased aeration and permeability, severely hindering crop root extension and nutrient absorption; regionalized and intensified soil salinization and acidification, disrupting soil pH balance, causing nutrient imbalances, and inhibiting crop physiological metabolism; and long-term continuous cropping and overuse of chemical fertilizers resulting in decreased soil organic matter content, nutrient imbalances, and a continuous decline in soil fertility, leading to insufficient supply of nitrogen, phosphorus, potassium, and micronutrients required for crop growth. Simultaneously, the large accumulation of harmful pathogens in the soil exacerbates soil-borne diseases, not only reducing crop yields but also affecting the quality and safety of agricultural products. These interconnected soil quality problems not only severely restrict the realization of crop production potential and reduce agricultural production efficiency but also may accumulate through the food chain, posing a potential threat to human health and further hindering the achievement of sustainable agricultural development goals.

[0004] To address the aforementioned issues, the development of efficient and environmentally friendly soil amendment technologies and products has become a research hotspot and urgent need in the agricultural field. Microbial soil conditioners, with their advantages of being environmentally friendly and pollution-free, having long-lasting effects, and simultaneously achieving soil conditioning and ecological restoration, are gradually replacing traditional chemical conditioners and have become the core direction of soil improvement, attracting widespread attention from the scientific research community and agricultural production sectors.

[0005] Existing microbial soil amendment products have many technical defects and are difficult to meet the comprehensive needs of large-scale agricultural production. The main defects are as follows: (1) The strains are single and the functions are limited. They can only achieve a single improvement target and cannot solve multiple soil problems at the same time; (2) The strain synergistic design is lacking. The composite strains are mostly simple mixtures, which are prone to antagonistic effects and the synergistic effect is difficult to exert; (3) The carrier formula is unreasonable. Most of them use single materials and lack targeted optimization, resulting in low survival rate and short action cycle of microorganisms in the soil; (4) The preparation process is complicated, with high requirements for equipment and parameters, and the production cost is high, which is not conducive to industrial mass production and widespread promotion.

[0006] In summary, existing microbial soil amendment products have drawbacks such as limited functionality, poor strain synergy, insufficient carrier compatibility, and high cost, making them unable to effectively solve the current diverse soil quality problems.

[0007] Therefore, screening synergistic compound microbial strains, optimizing carrier and auxiliary additive formulations, and developing microbial soil amendment products with comprehensive functions, significant improvement effects, low cost, and easy industrial production are of great practical significance and application value for solving soil degradation problems, improving crop yield and quality, and promoting sustainable agricultural development. Summary of the Invention

[0008] Based on the above technical background, the main objective of this invention is to provide a microbial soil conditioner, its preparation method, and its application, so as to overcome the shortcomings of the prior art.

[0009] To achieve the aforementioned objective, the technical solution adopted by the present invention includes: The first aspect of the present invention is to provide a microbial soil conditioner, wherein the microbial soil conditioner comprises the following raw materials in parts by weight: 5-15 parts by weight of compound microbial agent, 60-80 parts by weight of organic carrier, and 5-20 parts by weight of auxiliary additives.

[0010] Preferably, the microbial soil conditioner comprises the following raw materials in parts by weight: 10 parts by weight of compound microbial agent, 70 parts by weight of organic carrier, and 15 parts by weight of auxiliary additives.

[0011] Preferably, the compound microbial agent includes Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Bacillus subtilis var. amyloliquefaciens ratio of (2-3):(1-2):(1-2):(1-1.5), and the total viable count of the compound microbial agent is ≥1×10⁻⁶. 9 CFU / g.

[0012] More preferably, the viable count ratio of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Bacillus subtilis is 2.5:1.5:1.5:1.25, and the total viable count of the compound microbial agent is ≥1×10⁻⁶. 9 CFU / g.

[0013] Preferably, the organic carrier comprises the following raw materials in parts by weight: 30-40 parts by weight of decomposed straw, 20-30 parts by weight of compost, and 10-20 parts by weight of humus.

[0014] More preferably, the organic carrier comprises the following raw materials in parts by weight: 35 parts by weight of decomposed straw, 25 parts by weight of compost, and 15 parts by weight of humus.

[0015] Decomposed straw is rich in organic matter such as cellulose and hemicellulose, which can improve soil aeration and water retention; compost contains abundant organic matter and nutrients, which can enhance soil fertility; humus has good adsorption properties, which can fix microorganisms and nutrients, and improve the survival rate of microorganisms in the soil. The decomposed straw is obtained by high-temperature decomposition and crushing of at least one of corn straw and wheat straw. The particle size of the decomposed straw is 0.5-2 mm, which facilitates uniform mixing with other components.

[0016] The decomposed straw is decomposed corn straw or decomposed wheat straw.

[0017] The auxiliary additives include the following raw materials in parts by weight: 2-8 parts by weight of water-retaining agent, 1-5 parts by weight of slow-release agent, and 2-7 parts by weight of trace elements.

[0018] Preferably, the auxiliary additives include the following raw materials in parts by weight: 5 parts by weight of water-retaining agent, 3 parts by weight of slow-release agent, and 4 parts by weight of trace elements.

[0019] The water-retaining agent is one or both of sodium polyacrylate and polyacrylamide. This agent can absorb and retain moisture in the soil, improving its water retention capacity, and is particularly suitable for use in arid regions.

[0020] Preferably, the water-retaining agent is a mixture of sodium polyacrylate and polyacrylamide prepared in a mass ratio of (0.8-1.2):1.

[0021] More preferably, the water-retaining agent is a mixture of sodium polyacrylate and polyacrylamide prepared in a mass ratio of 1:1.

[0022] The slow-release agent is one or both of zeolite powder and bentonite. The above-mentioned diluent has good adsorption and slow-release properties, which can delay the release rate of nutrients and extend the product's effective period.

[0023] Preferably, the slow-release agent is a mixture of zeolite powder and bentonite, with a mass ratio of zeolite powder to bentonite of (1-3):1.

[0024] More preferably, the mass ratio of the zeolite powder to the bentonite is 1:1.

[0025] The trace elements include at least three of iron, zinc, manganese, copper, and boron, and each trace element exists in a chelated form. The chelated trace elements have high stability and bioavailability, and can meet the trace element requirements for crop growth.

[0026] Preferably, the trace elements include iron, zinc, manganese, copper, and boron.

[0027] The second aspect of this invention is to provide a method for preparing the microbial soil conditioner described in the first aspect of this invention. The preparation method includes the following steps: Step 1, culturing Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Bacillus subtilis respectively to obtain fermentation broths of each strain, mixing the fermentation broths of each strain, adding a protective agent, and spray drying to obtain a composite microbial agent; Step 2, pulverizing, sieving, and drying an organic carrier to obtain a pretreated organic carrier; Step 3, mixing the composite microbial agent obtained in Step 1, the pretreated organic carrier obtained in Step 2, and auxiliary additives to obtain the microbial soil conditioner.

[0028] The steps described above are described in detail below.

[0029] In step 1, the culture conditions for each strain were as follows: each strain was cultured in LB liquid medium at a temperature of 28–32℃, a pH of 6.5–7.5, a shaking frequency of 160–200 r / min, and a culture time of 24–48 h.

[0030] Preferably, the culture conditions for each strain are as follows: each strain is cultured in LB liquid medium at a temperature of 30°C, a pH of 7, a shaking frequency of 180 r / min, and a culture time of 36 h.

[0031] The protective agent is a mixture of sucrose and skim milk powder, wherein the mass ratio of sucrose to skim milk powder is (0.5-2):1.

[0032] Preferably, the mass ratio of sucrose to skim milk powder is 1:1.

[0033] The amount of the protective agent added is 5-10% of the total weight of the fermentation broth of each strain.

[0034] Preferably, the amount of the protective agent added is 7% of the total weight of the fermentation broth of each strain.

[0035] Protectants can improve the survival rate of microorganisms during the drying process.

[0036] The spray drying conditions are: inlet air temperature 180-200℃, outlet air temperature 80-90℃, and feed rate 20-35 mL / min.

[0037] Preferably, the spray drying conditions are: inlet air temperature 180-190℃, outlet air temperature 80-85℃, and feed rate 20-30 mL / min.

[0038] In step 2, the organic carrier is crushed and then passed through an 8-20 mesh sieve, preferably a 10 mesh sieve.

[0039] The drying conditions are as follows: first, dry mix for 5 to 15 minutes, then dry at 60 to 70°C until the moisture content of the organic carrier is 10 to 15%, and finally mix again for 3 to 10 minutes to ensure uniform mixing.

[0040] Preferably, the drying conditions are as follows: first, dry mix for 10 minutes, then dry at 65°C until the moisture content of the organic carrier is 10-15%, and finally mix again for 5 minutes. The dried organic carrier can reduce the impact of moisture on microbial activity.

[0041] In step 3, the stirring speed is 120-180 r / min, and the stirring time is 20-30 min.

[0042] Preferably, the stirring speed is 150 r / min and the stirring time is 25 min.

[0043] The obtained microbial soil conditioner was tested for viable bacteria count, moisture content, and pH value. After passing the tests, it was sealed and packaged to prevent the product from getting damp and the microorganisms from becoming inactive.

[0044] A third aspect of the present invention is to provide an application of the microbial soil conditioner described in the first aspect of the present invention in the field of soil improvement.

[0045] The microbial soil conditioner can be used to improve saline-alkali soil, acidified soil, or compacted soil.

[0046] The microbial soil conditioner is applied by broadcasting or furrowing, with an application rate of 200–500 kg / mu. This microbial soil conditioner can be used in combination with conventional fertilizers, with a mass ratio of 1:(1–2) between the microbial soil conditioner and conventional fertilizers.

[0047] In practical applications, the application rate can be adjusted according to the degree of soil degradation. For areas with more severe soil degradation, the application rate can be increased appropriately.

[0048] The beneficial effects of the present invention are as follows: (1) The soil conditioner of the present invention is composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis and Bacillus licheniformis. The strains have synergistic effects and can achieve functional complementarity. It can not only effectively improve the physical and chemical properties of the soil, break up soil compaction, and regulate soil pH, but also enhance soil fertility, promote crop root growth, inhibit the reproduction of harmful pathogens in the soil, and reduce the amount of chemical fertilizers and pesticides used.

[0049] (2) The organic carrier used in this invention is made by mixing decomposed straw, compost, and humus in a specific ratio. It can not only provide microorganisms with the nutrients and living environment required for growth, improve the survival rate and action cycle of microorganisms in the soil, but also improve soil permeability and water retention, and enhance soil fertility.

[0050] (3) The auxiliary additives used in this invention include water-retaining agents, slow-release agents and trace elements. Water-retaining agents can improve the soil's water retention capacity, slow-release agents can delay the release of nutrients and extend the product's action period, and trace elements can meet the needs of crop growth and further improve crop yield and quality.

[0051] (4) The preparation method of the present invention is simple and easy to operate, does not require complex equipment, has low cost, is suitable for large-scale industrial production, and has broad market application prospects. Attached Figure Description

[0052] Figure 1 shows the growth curves of each strain in the compound microbial agent; Figure 2 shows the pH value changes before and after the product of this invention improved saline-alkali soil; Figure 3 shows the comparison of wheat growth between the experimental group and the control group. Detailed Implementation

[0053] The present invention will now be described in detail, and its features and advantages will become clearer and more apparent from these descriptions.

[0054] The *Bacillus subtilis*, *Bacillus amyloliquefaciens*, *Bacillus mucilaginosus*, and *Bacillus licheniformis* used in this invention were isolated and screened through the following methods: 1) Sample collection: Select plots with long-term crop cultivation and good soil fertility, collect soil samples from the 0-20 cm surface layer, seal them in sterile sampling bags, and bring them back to the laboratory; 2) Enrichment culture: Weigh 10 g of soil sample, add 90 mL of sterile physiological saline, shake well to prepare a soil suspension, take 1 mL of the soil suspension and inoculate it into LB liquid medium, and culture it at 28-32℃ and 150-200 r / min for 24 h to enrich the strains; 3) Separation and purification: Take the enriched bacterial suspension and dilute it to 10⁻¹⁰ using a serial dilution method. -6 10 -7 10 -8Concentration gradients: 0.1 mL of each of the three concentration gradients was spread onto LB agar plates and incubated at 30℃ for 24–48 h. After single colonies appeared on the plates, different single colonies were selected based on their morphology, color, and size. The plates were then purified multiple times using the streak plating method to obtain pure strains. 4) Functional screening: The purified strains were functionally verified. *Bacillus subtilis* was tested for its antibacterial ability using the Oxford cup method, selecting strains with an inhibition zone diameter ≥15 mm. *Bacillus amyloliquefaciens* was tested for its amylase production ability using a starch hydrolysis test, selecting strains with a clear zone diameter to colony diameter ratio ≥2.0. *Bacillus colloidis* was tested for its phosphorus and potassium solubility using a phosphorus and potassium solubility test, selecting strains with a phosphorus / potassium solubility zone diameter to colony diameter ratio ≥1.8. *Bacillus licheniformis* was tested for its root growth promotion ability using a root growth promotion test, selecting strains that increased crop root fresh weight by ≥20%. 5) Synergistic effect verification: The selected strains were cultured in pairs and in multiples. The total number of viable bacteria and various functional indicators (antibacterial, enzyme production, phosphorus and potassium solubilization, growth promotion) of the mixed bacterial solution were measured. The combination of strains with no antagonistic effect and functional indicators that were better than those of single strains was selected to determine the final strain ratio of the compound microbial agent.

[0055] The selected strains have the following functions: *Bacillus subtilis* can produce antibiotics, inhibiting the growth of harmful pathogens in the soil, and also secretes various enzymes to promote the decomposition of organic matter in the soil. *Bacillus amyloliquefaciens* has a strong ability to produce amylase, decomposing starchy substances in the soil, releasing nutrients, and also has a certain degree of disease resistance. *Bacillus mucilaginosus* can decompose minerals such as phosphate and potassium in the soil, converting insoluble phosphorus and potassium into soluble nutrients, thus improving soil fertility. *Bacillus licheniformis* can regulate the soil microbial community structure, improve the soil microecological environment, and promote crop root growth.

[0056] The present invention is further illustrated below by specific examples. These examples are for illustrative purposes only and are not intended to limit the scope of the invention. All raw materials used in the embodiments of the present invention were commercially available.

[0057] Example 1: A microbial soil conditioner, composed of the following raw materials in parts by weight: 5 parts by weight of compound microbial agent, 80 parts by weight of organic carrier, and 15 parts by weight of auxiliary additives.

[0058] The compound microbial agent includes Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Bacillus subtilis. The viable count ratio of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Bacillus subtilis is 2:1:1:1, and the total viable count is 1×10⁻⁶. 9CFU / g; The organic carrier is a mixture of 30 parts by weight of decomposed corn stalks, 30 parts by weight of compost, and 20 parts by weight of humus. The particle size of the decomposed corn stalks is 0.5-1 mm; The auxiliary additives consist of 5 parts by weight of sodium polyacrylate, 3 parts by weight of zeolite powder, and 7 parts by weight of a chelated iron-zinc-manganese mixture.

[0059] The preparation method of the microbial soil conditioner includes the following steps: Step 1, preparation of compound microbial inoculant: Each strain is cultured separately using LB liquid medium (formulation: 10 g / L tryptone, 5 g / L yeast extract, 10 g / L NaCl, diluted with deionized water, autoclaved at 121℃ for 20 min, and adjusted to pH 6.5 after cooling). Among them, Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Bacillus subtilis are cultured at 28℃, pH 7, and constant temperature shaking at 180 r / min for 48 h, until the bacterial solution OD reaches the specified level. 600 Fermentation was terminated when the value was 1.8–2.0 (the growth curves of each microbial agent are shown in Figure 1), and the fermentation broth of each strain was obtained. The fermentation broth of each strain was mixed according to the above live cell count ratio, and 5% of the total weight of the fermentation broth of each strain was added as a protective agent of a mixture of sucrose and skim milk powder (sucrose:skim milk powder weight ratio = 1:1). The mixture was dried using a centrifugal spray dryer (inlet air temperature 180–190℃, outlet air temperature 80–85℃, feed rate 20–30 mL / min). The dried bacterial powder was collected to obtain the compound microbial agent.

[0060] Step 2, Pretreatment of organic carrier: The decomposed corn stalks, compost, and humus are crushed separately using a universal crusher and passed through a 10-mesh standard sieve (2mm aperture). They are then added to a double-spiral conical mixer in proportion, dry-mixed for 10 minutes, and then dried in a 60℃ forced-air drying oven until the moisture content is 10%. After drying, they are mixed again for 5 minutes to ensure uniformity, thus obtaining the pretreated organic carrier.

[0061] Step 3, Mixing and compounding: Add the compound microbial agent, pretreated organic carrier and auxiliary additives to the double helix conical mixer in sequence, set the speed to 150 r / min, and stir for 20 min. During this period, stop the machine every 5 min to check the mixing uniformity (using the five-point sampling method, the coefficient of variation of viable bacteria at each sampling point is ≤5% to be considered uniform), and the microbial soil conditioner is obtained.

[0062] Finished product testing and packaging: The testing is refined according to the GB 20287-2006 standard "Agricultural Microbial Agents". The specific steps are as follows: (1) Viable bacteria count test: Weigh 10 g of finished product sample (microbial soil conditioner), add it to 90 mL of sterile physiological saline, and place it on a shaker to shake for 30 min (speed 150 r / min) to prepare 10 -1The diluent was diluted to 10 using a gradient dilution method. -6 10 -7 For concentration gradients, 0.1 mL of each dilution was spread onto LB agar plates, with three replicates for each concentration gradient. After incubation at 30°C for 48 h, the viable counts were calculated, ensuring a viable count ≥ 1 × 10⁻⁶. 9 CFU / g; (2) Moisture content detection: Using the drying and weighing method, weigh 5 g of sample and place it in a weighing bottle that has been constant in weight. Dry it in a 105℃ forced-air drying oven for 4 h. After taking it out, put it in a desiccator to cool for 30 min and weigh it. Calculate the moisture content (moisture content = (weight before drying - weight after drying) / weight before drying × 100%). The moisture content must be ≤10%; (3) pH value detection: Weigh 5 g of sample and add it to 45 mL of deionized water. Stir well and let it stand for 30 min. Use a precision pH meter (accuracy 0.01) to measure the pH value of the supernatant. It must be in the range of 6.5 to 7.5; (4) Contamination rate detection: Select 10 of the viable bacteria count detection. -3 For the dilution plate, distinguish the target colony (based on the colony morphology of each strain) from the colony of other bacteria, count the number of other bacteria, and calculate the contamination rate (contamination rate = number of other bacteria / total number of colonies × 100%). The contamination rate must be ≤3%. After all indicators pass the test, vacuum pack the product in aluminum foil composite bags (vacuum degree ≤ -0.08 MPa), 5 kg per bag.

[0063] Application of microbial soil conditioner: It is used to improve saline-alkali soil. It is applied by broadcasting at a rate of 200 kg / mu. The microbial soil conditioner is used in combination with conventional fertilizer at a mass ratio of 1:1.

[0064] Example 2: A microbial soil conditioner, composed of the following raw materials in parts by weight: 15 parts by weight of compound microbial agent, 60 parts by weight of organic carrier, and 20 parts by weight of auxiliary additives.

[0065] The composite microbial agent includes Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Bacillus subtilis. The viable count ratio of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Bacillus subtilis is 3:2:2:1.5, and the total viable count is 2×10⁻⁶. 9 CFU / g; The organic carrier is a mixture of 40 parts by weight of decomposed wheat straw, 20 parts by weight of compost, and 10 parts by weight of humus. The particle size of the decomposed wheat straw is 1-2 mm. The auxiliary additives consist of 8 parts by weight of polyacrylamide, 5 parts by weight of bentonite, and 7 parts by weight of a chelated iron-zinc-copper-boron mixture.

[0066] The preparation method of the microbial soil conditioner includes the following steps: Step 1, preparation of compound microbial agent: Each strain is cultured separately in LB liquid medium (formula same as in Example 1, pH adjusted to 7.5) and cultured for 24 h under constant temperature shaking conditions of 32℃ and 200 r / min until the bacterial solution OD reaches the specified value. 600 Fermentation was terminated when the value was 2.0 to 2.2. The fermentation broths were mixed according to the formula, and 10% of the total weight of each fermentation broth was added as a protective agent of a mixture of sucrose and skim milk powder (sucrose:skim milk powder weight ratio = 2:1). The mixture was dried using a centrifugal spray dryer (inlet air temperature 190-200℃, outlet air temperature 85-90℃, feed rate 25-35mL / min). The bacterial powder was collected to obtain the compound microbial agent.

[0067] Step 2, Pretreatment of organic carrier: The decomposed wheat straw, compost, and humus are crushed using a universal crusher, passed through an 18-mesh standard sieve (1 mm aperture), and added to a double spiral conical mixer for dry mixing for 15 min. The mixture is then dried in a 70℃ forced-air drying oven until the moisture content is 15%. After drying, it is mixed again for 8 min to obtain the pretreated organic carrier.

[0068] Step 3, Mixing and compounding: Add the compound microbial agent, pretreated organic carrier and auxiliary additives to the double helix conical mixer in sequence, set the speed to 180 r / min, stir and mix for 30 min, and use the five-point sampling method to detect the mixing uniformity (coefficient of variation of viable bacteria ≤5%).

[0069] Finished product testing and packaging: The testing is detailed according to GB 20287-2006 standard, and the steps are as follows: (1) Viable bacteria count test: Weigh 10 g of sample (microbial soil conditioner) and add it to 90 mL of sterile physiological saline, shake for 30 min (rotation speed 150 r / min) to prepare 10 -1 Diluent, serially diluted to 10 -7 10 -8 Concentration gradients were established by spreading 0.1 mL of each dilution onto LB agar plates (three replicates per concentration), incubating at 30°C for 48 h, and counting the viable cells to ensure an average viable count ≥ 2 × 10⁻⁶. 9 CFU / g; (2) Moisture content detection: Weigh 5 g of sample into a constant weight weighing bottle, dry at 105℃ for 4 h, cool in a desiccator for 30 min and weigh. The calculated moisture content should be ≤15%; (3) pH value detection: Add 45 mL of deionized water to 5 g of sample, stir and let stand for 30 min, and then use a precision pH meter to measure the pH value of the supernatant. The pH value should be in the range of 6.5-7.5; (4) Bacterial contamination rate detection: Select 10 -3Diluent plates are used to distinguish and count target bacteria and other bacteria colonies, with the rate of other bacteria being ≤3%. After all indicators are qualified, the product is vacuum-packed in aluminum foil composite bags (vacuum degree ≤ -0.08 MPa), with each bag weighing 5 kg.

[0070] Application: Microbial soil conditioner is used to improve acidified soil. It is applied via trenching at a rate of 500 kg / mu. The microbial soil conditioner is mixed with conventional fertilizer at a mass ratio of 1:2. Example 3: The microbial soil conditioner is prepared in a similar manner to Example 1, except that it consists of the following raw materials in parts by weight: 10 parts by weight of compound microbial inoculant, 70 parts by weight of organic carrier, and 10 parts by weight of auxiliary additives. The specific composition and preparation method of the compound microbial inoculant, organic carrier, and auxiliary additives are the same as in Example 1.

[0071] Application of microbial soil conditioner: The microbial soil conditioner can be used to improve saline-alkali soil, acidified soil or compacted soil. It is applied by broadcasting or furrowing at a rate of 300 kg / mu and can be used in combination with conventional fertilizers at a mass ratio of 1:1.

[0072] After application, it can effectively improve soil structure, reduce soil compaction, regulate soil pH, and enhance soil fertility, thereby promoting crop root growth and increasing crop yield, and has a good soil improvement effect.

[0073] Comparative Example 1: The microbial soil conditioner was prepared in a similar manner to Example 1, except that the composite microbial agent used included Bacillus subtilis, Bacillus mucilaginosus, and Bacillus licheniformis. The viable count ratio of Bacillus subtilis, Bacillus mucilaginosus, and Bacillus licheniformis was 2:1:1, and the total viable count was 1×10⁻⁶. 9 CFU / g.

[0074] The microbial soil conditioner prepared in Comparative Example 1 was used to conduct soil improvement experiments on saline-alkali soil, acidified soil, and compacted soil. Three replicate plots were set up, each with an area of ​​20 m². 2 The wheat variety planted was Jimai 44. Except for the soil conditioner used, all other field management practices remained the same. After a complete growing season, soil bulk density, soil pH, soil organic matter content, wheat yield, and protein content were measured.

[0075] The results showed that, compared with conventional microbial soil amendment products, Comparative Example 1 improved the soil physicochemical properties to a certain extent, reduced soil bulk density, increased soil organic matter content, and improved wheat yield and quality. However, compared with Example 1 of the present invention, its adjustment range of pH value of saline-alkali soil and acidified soil was smaller, its improvement effect on compacted soil structure was not obvious, and the increase in wheat yield and protein content was lower than that of Example 1. The test results are shown in Table 1.

[0076] Analysis suggests that the compound microbial agent used in Comparative Example 1 lacked Bacillus amyloliquefaciens, resulting in insufficient nutrient transformation and microbial synergy, thus affecting the overall soil improvement effect.

[0077] Comparative Example 2 was prepared in a similar manner to Example 1, except that the composite microbial agent used included Bacillus amyloliquefaciens, Bacillus mucilaginosus, and Bacillus licheniformis. The viable count ratio of Bacillus amyloliquefaciens, Bacillus mucilaginosus, and Bacillus licheniformis was 1:1:1, and the total viable count was 1×10⁻⁶. 9 CFU / g. Using the microbial soil conditioner prepared in Comparative Example 2, soil improvement experiments were conducted on saline-alkali soil, acidified soil, and compacted soil according to the same experimental method as in Comparative Example 1. Each treatment had three replicate plots, each plot area being 20 m². 2 The crop types and field management practices remain consistent.

[0078] The experimental results showed that Comparative Example 2 improved the soil physicochemical properties to a certain extent, slightly reduced soil bulk density and increased soil organic matter content, and increased wheat yield and protein content compared with conventional microbial soil amendment products; however, the overall improvement effect was still significantly lower than that of Example 1. In particular, Comparative Example 2 had limited effect in inhibiting soil compaction, promoting crop root growth and increasing wheat yield. The test results are shown in Table 1.

[0079] The reason is that the compound microbial agent used in Comparative Example 2 lacks Bacillus subtilis, which weakens the ability to inhibit harmful soil microorganisms and the rhizosphere growth promotion effect, thus affecting the overall improvement performance.

[0080] Experimental Example 1: Effect Test. Three experimental fields were selected: saline-alkali soil, acidified soil, and compacted soil. Experimental groups (applied with the product of Example 1 of this invention (microbial soil conditioner)), Comparative Example 1, Comparative Example 2, and a control group (applied with conventional microbial soil conditioner products) were set up. The conventional microbial soil conditioner product is a commercially available compound microbial soil conditioner, and its main components and dosages are as follows: The conventional microbial soil conditioner product includes a compound microbial agent and an inorganic carrier. The compound microbial agent includes Bacillus subtilis and Bacillus amyloliquefaciens, with a viable count ratio of 1:1. The total viable count of the compound microbial agent is 1 × 10⁻⁶. 8 CFU / g; the inorganic carrier is a mixture of bentonite and diatomaceous earth, with a mass ratio of bentonite to diatomaceous earth of 3:2; in the conventional microbial soil improvement product, the amount of compound microbial agent added is 5% of the total mass of the product, and the remainder is inorganic carrier, without organic carrier, water-retaining agent, slow-release agent and trace element additive.

[0081] The application method and dosage of the conventional microbial soil amendment products were consistent with those of the experimental group. Each group had three replicate plots, each plot measuring 20 m². 2 The wheat variety planted was Jimai 44, and other field management practices were consistent. The experiment lasted for one growing season. Soil physicochemical properties, wheat yield, and quality indicators were measured. The test results are shown in Table 1 below. The pH changes before and after soil improvement in the experimental and control groups are shown in Figure 2. The final wheat ears obtained in the experimental and control groups are shown in Figure 3. Table 1

[0082] As can be seen from Table 1 and Figure 2, the microbial soil conditioner prepared by this invention can significantly reduce soil bulk density and improve soil compaction; adjust soil pH value, bringing the pH value of saline-alkali and acidified soils closer to the range suitable for crop growth (6.5-7.5); increase soil organic matter content and improve soil fertility; at the same time, the microbial soil conditioner described in this invention can significantly increase wheat yield and wheat protein content, improve wheat quality, and the improvement effect is significantly better than conventional microbial soil conditioner products.

[0083] To further verify the reliability of the experimental results, SPSS 26.0 software was used to perform analysis of variance on the experimental data (significance level α=0.05). The results showed that in saline-alkali soil, the P-values ​​for soil bulk density, pH value, organic matter content, wheat yield, and protein content between the experimental group and the control group were 0.021, 0.018, 0.025, 0.012, and 0.015, respectively, all less than 0.05; in acidified soil, the P-values ​​for the above indicators were 0.023, 0.016, 0.022, 0.010, and 0.013, respectively, all less than 0.05; and in compacted soil, the P-values ​​for the above indicators were 0.019, 0.032, 0.020, 0.009, and 0.011, respectively, all less than 0.05. These results indicate that there are significant differences between the experimental group and the control group, and the soil improvement and crop yield and quality enhancement effects of the microbial soil conditioner of this invention are statistically significant and not due to accidental factors.

[0084] As can be seen from Figure 3, after the soil was improved using the soil conditioner described in this invention, the wheat ears cultivated were fuller.

[0085] Experimental Example 2: Stability Test of Viable Bacteria Count under Different Storage Durations To clarify the storage stability of the microbial soil conditioner of this invention, the finished products of Examples 1 and 2 were selected as test objects. Two common storage conditions were set: (1) ambient temperature storage (25℃±2℃, relative humidity 60%±5%); (2) low temperature storage (4℃±1℃, relative humidity 60%±5%). Aluminum foil composite vacuum packaging was used as the standard packaging method. Viable bacteria counts were tested at storage days 0 (initial), 30, 60, 90, and 180. Three replicate samples were set at each time point. The detection method was the same as the viable bacteria count test steps for the finished product. The average viable bacteria count and survival rate (survival rate = viable bacteria count after storage / initial viable bacteria count × 100%) were calculated. The results are shown in Table 2 below: Table 2

[0086] A two-way ANOVA was performed on the data in Table 2 using SPSS 26.0 software (factor 1: storage conditions; factor 2: storage duration). The results showed that: (1) storage duration had a significant effect on the number of viable bacteria (P<0.01). As the storage time increased, the number of viable bacteria showed a slow downward trend. However, after 180 days (6 months), the viable bacteria in the two examples of products (microbial soil conditioner) still had a survival rate of ≥65% at room temperature and ≥79% at low temperature. After conversion, the viable bacteria survival rate met the requirement of ≥1×10⁻⁶ viable bacteria in GB 20287-2006. 8The requirements for CFU / g. (2) The survival rate of viable bacteria under low-temperature storage conditions was significantly higher than that under normal temperature storage (P<0.05). Among them, the survival rate of the product of Example 1 after 180 days of low-temperature storage was 14 percentage points higher than that under normal temperature storage, and the survival rate of the product of Example 2 was 14.5 percentage points higher, indicating that the low-temperature environment is more conducive to improving the survival rate of viable bacteria in the product. (3) Due to the higher initial viable bacteria count, the absolute value of viable bacteria count at each time point of the product of Example 2 under the same storage conditions was higher than that of the product of Example 1, and the stability performance was consistent. The above experimental data show that the microbial soil conditioner of the present invention has good storage stability and can meet the conventional storage and transportation needs in agricultural production.

[0087] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A microbial soil conditioner, characterized in that, The microbial soil conditioner comprises the following raw materials in parts by weight: 5-15 parts by weight of compound microbial agent, 60-80 parts by weight of organic carrier, and 5-20 parts by weight of auxiliary additives; the compound microbial agent comprises Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and the ratio of viable bacteria of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Bacillus licheniformis is (2-3):(1-2):(1-2):(1-1.5).

2. The microbial soil conditioner according to claim 1, characterized in that, The organic carrier comprises the following raw materials in parts by weight: 30-40 parts by weight of decomposed straw, 20-30 parts by weight of compost, and 10-20 parts by weight of humus.

3. The microbial soil conditioner according to claim 2, characterized in that, The decomposed straw is decomposed corn straw or decomposed wheat straw, and the particle size of the decomposed straw is 0.5 to 2 mm.

4. The microbial soil conditioner according to claim 1, characterized in that, The auxiliary additives include the following raw materials in parts by weight: 2-8 parts by weight of water-retaining agent, 1-5 parts by weight of slow-release agent, and 2-7 parts by weight of trace elements.

5. The microbial soil conditioner according to claim 4, characterized in that, The water-retaining agent is one or both of sodium polyacrylate or polyacrylamide; and / or, the slow-release agent is one or both of zeolite powder or bentonite; and / or, the trace elements include at least three of iron, zinc, manganese, copper, and boron, and each trace element exists in a chelated form.

6. A method for preparing the microbial soil conditioner according to any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: Step 1, Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Bacillus subtilis are cultured separately to obtain fermentation broths of each strain, the fermentation broths of each strain are mixed, a protective agent is added and spray-dried to obtain a composite microbial agent; Step 2, the organic carrier is pulverized, sieved, and dried to obtain a pretreated organic carrier; Step 3, the composite microbial agent obtained in Step 1, the pretreated organic carrier obtained in Step 2, and auxiliary additives are stirred and mixed to obtain a microbial soil conditioner.

7. The preparation method according to claim 6, characterized in that, In step 1, the culture conditions for each strain were as follows: each strain was cultured in LB liquid medium at a temperature of 28–32℃, a pH of 6.5–7.5, a shaking frequency of 160–200 r / min, and a culture time of 24–48 h.

8. The preparation method according to claim 6, characterized in that, In step 1, the protective agent is a mixture of sucrose and skim milk powder, and the mass ratio of sucrose to skim milk powder is (0.8-1.2):1; the amount of protective agent added is 5-10% of the total weight of the fermentation broth of each strain.

9. The preparation method according to claim 6, characterized in that, In step 2, the drying conditions are as follows: first dry mix for 5 to 15 minutes, then dry at 60 to 70°C until the moisture content of the organic carrier is 10 to 15%, and finally mix again for 3 to 10 minutes.

10. The application of the microbial soil conditioner according to any one of claims 1 to 5 in the field of soil improvement; the microbial soil conditioner can be used to improve saline-alkali soil, acidified soil or compacted soil.

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