Bacillus amyloliquefaciens and application thereof in preparation of liquid fertilizer

Abstract

The invention provides bacillus amyloliquefaciens and application of the bacillus amyloliquefaciens in preparation of a liquid fertilizer. The preservation number of the bacillus amyloliquefaciens is CGMCC (China General Microbiological Culture Collection Center) NO. 31787. The invention also discloses a microbial liquid bacterial fertilizer. The bacterial fertilizer is fermentation liquor containing bacillus amyloliquefaciens with the viable count of 1.0 * 10 < 9 > cfu / mL or more. The invention further discloses a preparation method of the liquid bacterial fertilizer and application of the liquid bacterial fertilizer in agricultural planting. The liquid bacterial fertilizer disclosed by the invention is good in storage stability, and can effectively inhibit plant germs, decompose nutrient substances, promote crop absorption, improve soil micro-ecology, prevent and control plant diseases and improve the yield and quality of crops. And the method is simple to use and environment-friendly, has important significance in promoting agricultural production and sustainable development of land resources, and has wide application prospects in agricultural production.

Description

Technical Field

[0001] The invention belongs to the technical field of functional microorganism screening and application, and specifically relates to a strain of Bacillus amyloliquefaciens and application thereof in the preparation of liquid fertilizer. Background Art

[0002] Fertilizer is an important material basis for agricultural development, but the long-term excessive use of chemical fertilizers has led to a series of soil problems: soil acidification and hardening, decreased fertility; reduced microbial communities in the soil, which is not conducive to the growth of crops; accumulation of heavy metal elements in the soil, which damages the ecology, etc. Excessive chemical residues in crops will further endanger human health. Therefore, it is urgent to reduce the application of chemical fertilizers, promote more green organic fertilizers and new microbial fertilizers, and improve the absorption and utilization rate of fertilizers by plants.

[0003] Microbial fertilizer is green and natural, and is a new type of environmentally friendly and efficient ecological fertilizer. Microbial fertilizer contains a large amount of organic matter, plant growth regulators, vitamins, trace elements, and rich mineral elements such as potassium, phosphorus, magnesium, and calcium. It is nutritious, highly active, and easily absorbed and utilized by plants. Functional bacteria reproduce in the soil, which can improve the physical and chemical properties and aggregate structure of the soil, increase the soil's ability to store water and fertilizer, reduce the application of chemical fertilizers, promote the growth of crops, and increase the yield and quality of agricultural products. Modern agriculture is gradually developing towards green and pollution-free ecological agriculture. The research and development of high-quality microbial fertilizers is in line with the national agricultural economic development strategy, and can also alleviate the problem of soil pollution caused by excessive application of chemical fertilizers.

[0004] The soil microecological environment is very important for the nutrition of plant roots. The beneficial microorganisms in the soil are directly involved in the degradation of organic matter in the soil, the formation of humus, the fixation of nitrogen, etc. The application of microbial fertilizers can help reconstruct a healthy soil microecology. During the growth and metabolism of microorganisms, they can secrete a variety of products such as plant growth hormones, antibiotics, bacteriocins, proteases, cellulases, etc., accelerate the degradation of organic matter into small molecular nutrients that can be absorbed by crops, inhibit pathogens in the soil to prevent and control plant diseases and insect pests, enrich mineral elements to supply the growth and development of crops, and improve the efficiency of plant absorption and utilization of nutrients, thereby improving the yield and quality of crops. There are two types of microbial fertilizers: solid and liquid. Liquid fertilizers are easy to use. They can be diluted with water and sprayed or watered. They are uniform, quick-dissolving, ready to use, and do not absorb moisture and agglomerate. Liquid fertilizers can directly act on the leaves and roots of crops, so they usually take effect quickly. At present, the common problem of microbial liquid fertilizer products in the industry is poor stability. As the storage time increases, the number of live bacteria will decrease significantly, and the efficacy will be significantly reduced. Summary of the invention

[0005] The present invention provides a strain of Bacillus amyloliquefaciens and its application in the preparation of liquid fertilizer, and provides the application of the strain in liquid bacterial fertilizer. The Bacillus amyloliquefaciens can effectively inhibit plant pathogens, decompose nutrients, promote crop absorption, prevent and control plant diseases, and improve the yield and quality of crops.

[0006] The present invention first provides a Bacillus amyloliquefaciens JRB-F6 strain, which has been deposited in the China General Microbiological Culture Collection Center on August 30, 2024, with a deposit number of CGMCCNO.31787 and a deposit address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing.

[0007] The rDNA sequence of the Bacillus amyloliquefaciens JRB-F6 strain is SEQ ID NO: 1.

[0008] The invention also provides an application of Bacillus amyloliquefaciens, which can be used to prepare liquid bacterial fertilizer, promote plant root growth, and prevent and control diseases and insect pests.

[0009] The Bacillus amyloliquefaciens strain of the present invention can also be used to prepare strain products, and the products have the effects of promoting the growth of plant roots and preventing and controlling diseases and insect pests.

[0010] The bacterial strain product is a liquid bacterial fertilizer, and a specific preparation method thereof is as follows:

[0011] 1) Inoculate the Bacillus amyloliquefaciens strain into LB medium, and culture at 37°C and 250 rpm for 18 h to prepare a seed solution;

[0012] 2) Inoculate the seeds into the fermentation medium at a volume ratio of 5%, and culture at 37°C and 250 rpm for 48 hours;

[0013] 3) Add 0.1% to 1% of stabilizer to the fermentation liquid to make microbial liquid fertilizer.

[0014] The stabilizer is any one of formic acid, acetic acid, citric acid or kasonite.

[0015] Furthermore, the added amount of citric acid is 0.02%.

[0016] The fermentation medium is composed of glucose as a carbon source, expanded soybeans as a nitrogen source, and 0.01% magnesium sulfate MgSO4 and 0.01% calcium chloride as inorganic salts, with a natural pH;

[0017] Furthermore, the fermentation medium contains 2% glucose, 3% puffed soybeans, 0.01% MgSO4, 0.01% calcium chloride, and natural pH.

[0018] The invention also provides application of the microbial fertilizer in agricultural planting.

[0019] The beneficial effects of the present invention are as follows:

[0020] (1) The Bacillus amyloliquefaciens JRB-F6 screened by the present invention can effectively inhibit plant pathogens such as tomato gray mold, cucumber powdery mildew, and grape white rot, and prevent and control plant diseases. The strain has high protease and cellulase activity, can promote the absorption of nutrients by crops, and has broad application prospects in the research of microbial liquid fertilizers.

[0021] (2) The Bacillus amyloliquefaciens JRB-F6 of the present invention has strong stress resistance and good storage stability. When the amount of citric acid added is 0.02%, the bacterial survival rate is 98.5% after storage for 3 months.

[0022] (3) The liquid bacterial fertilizer prepared by fermentation of Bacillus amyloliquefaciens JRB-F6 screened by the present invention is applied to agricultural planting, and the effect is obvious. When the liquid bacterial fertilizer of the present invention is applied to strawberry planting, the fresh weight, number of fruits and yield of the strawberry plants in the experimental group are increased compared with the control group. The incidence of strawberry plants in the experimental group is significantly reduced, and the sweetness of the fruit is improved, and the taste is better. When the liquid bacterial fertilizer of the present invention is applied to cucumber planting, the incidence of cucumbers in the experimental group is greatly reduced compared with the control group, and the yield-increasing effect is obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : Colony morphology of Bacillus amyloliquefaciens JRB-F6 on LB medium.

[0024] Figure 2 :Bacillus amyloliquefaciens JRB-F6 bacterial morphology under microscope. DETAILED DESCRIPTION

[0025] The invention provides a Bacillus amyloliquefaciens which has the function of degrading protein and cellulose, inhibiting pathogens and having strong stress resistance, and develops a microbial fertilizer with the function of preventing diseases and promoting growth.

[0026] The present invention is further described below by means of specific examples, but the protection scope of the present invention shall not be limited thereto.

[0027] Example 1: Isolation and screening of strains

[0028] The method for obtaining the Bacillus amyloliquefaciens JRB-F2 is as follows:

[0029] 1. Sample source:

[0030] Samples of rotten leaves, grass and soil near the vegetable greenhouse in Haiyang, Yantai City, Shandong Province.

[0031] 2. Strain isolation and screening:

[0032] Screen Bacillus from the collected samples. Weigh 5g of sample, add to 45mL of sterile saline, shake and mix for 20min to make an initial bacterial suspension. Take 5mL of bacterial suspension and place it in an 80-degree water bath, warm it for 10 minutes, cool it quickly, and then dilute the sample in 10-fold increments with saline. Select 3-5 appropriate dilutions, take 100μL of each and spread it on an LB medium plate, and culture it at 37 degrees overnight. Select 20 colonies with good growth and different morphologies on different plates, streak them on LB medium plates to separate them to obtain pure cultures, and name them with letters F1-20 respectively.

[0033] 3. Screening of protease production ability

[0034] The 20 selected bacterial strains were inoculated into LB liquid culture medium, cultured at 37°C for 72 hours, and the fermentation supernatant was obtained by centrifugation. The protease activity was tested. The results are shown in Table 1 below.

[0035] Table 1: Data table of protease activity determination of different strains

[0036]

[0037]

[0038] From the results in the above table, it can be seen that strains F1, F3, F6, and F19 have strong protease production capabilities, among which F6 has the highest enzyme activity.

[0039] 4. Screening of cellulase production ability

[0040] The 20 selected bacterial strains were inoculated into LB liquid culture medium, cultured at 37°C for 72 hours, and the fermentation supernatant was obtained by centrifugation. The cellulase activity was tested. The results are shown in Table 2 below.

[0041] Table 2: Cellulase activity assay of different strains

[0042] strain Cellulase activity (U / mL) strain Cellulase activity (U / mL) F1 43 F11 59 F2 16 F12 7 F3 21 F13 52 F4 13 F14 75 F5 105 F15 8 F6 132 F16 94 F7 46 F17 156 F8 58 F18 45 F9 82 F19 108 F10 6 F20 32

[0043] From the results in the above table, it can be seen that strains F5, F6, F17 and F19 have strong cellulase production capabilities.

[0044] 5. Screening of the ability to inhibit pathogens

[0045] (1) Preparation of test bacterial solution

[0046] The above 20 strains were inoculated into LB liquid culture medium respectively, cultured at 37°C for 72 h, 250 r / min, shaken for 72 h, centrifuged at 12000 r / min for 5 min, and the fermentation supernatant was obtained for use.

[0047] (2) Antibacterial ability analysis

[0048] The antibacterial performance of the common pathogens stored in our laboratory, including Botrytis cinerea, peanut root rot, corn leaf spot, cucumber powdery mildew, cucumber wilt, grape white rot, Candida albicans, Escherichia coli, Staphylococcus aureus, and Salmonella, was analyzed as indicator bacteria. The antibacterial ability of each strain was determined by the plate confrontation method, as shown in Table 3.

[0049] Table 3: Analysis of the inhibitory effects of each strain on pathogens

[0050]

[0051] From the above results, we can see that the F5, F6, F8, F14, and F19 strains have a good comprehensive inhibitory ability against several pathogenic bacteria, and will have a good application effect in the prevention and control of crop diseases. Combined with the protease and cellulase production capabilities of each strain, the F6 strain was finally selected as the target strain. The F6 strain was named JRB-F6 and further studied.

[0052] Example 2 Identification of strains

[0053] 1. Colony morphology identification

[0054] The colony morphology of JRB-F6 strain is as follows Figure 1 As shown: The colonies are round, milky white and opaque, with a rough and wrinkled surface that is not easy to pick up, and the colonies are stringy and have mucus.

[0055] 2. 16S rDNA Identification of Bacterial Species

[0056] After the strain was streaked on the LB plate, a single colony was picked and inoculated into LB liquid medium for 24 hours. The strain DNA was extracted using a bacterial genome extraction kit as a template for PCR amplification. The PCR reaction conditions were as follows: 98℃ pre-denaturation for 5 minutes, 95℃ for 30 seconds, 55℃ for 30 seconds, 72℃ for 30 seconds, 30 cycles, and 72℃ final extension for 10 minutes. The obtained PCR product was sequenced and compared with the known sequences in the Genbank database for homology. It was found that JRB-F6 was closest to Bacillus amyloliquefaciens.

[0057] The final strain obtained by screening was named Bacillus amyloliquefaciens JRB-F6, and was deposited in the China General Microbiological Culture Collection on August 30, 2024, with the deposit number CGMCC NO.31787, and the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0058] Figure 1 This is the colony morphology of Bacillus amyloliquefaciens JRB-F6 on LB medium. The colonies have nearly circular protrusions, irregular wrinkles on the surface, and are milky white and opaque. Figure 2 This is the bacterial morphology of the strain under a microscope. After culturing in LB medium for 24 hours, the bacteria are in the shape of thin rods; after culturing for 48 hours, endogenous spores appear in the bacteria, and the spores are located in the center of the bacteria.

[0059] Example 3 Optimization of fermentation conditions of Bacillus amyloliquefaciens JRB-F6

[0060] Seed culture medium: Seeds were cultured in LB medium at 37°C for 24 hours.

[0061] Fermentation medium: maltose 2%, beef extract 3%, MgSO4 0.01%, calcium chloride 0.01%, natural pH.

[0062] The following experiments were based on the existing fermentation medium to optimize the carbon and nitrogen sources and culture conditions.

[0063] 1. Cultivation temperature optimization

[0064] The strain was inoculated into LB medium at a 2% inoculum, cultured at 37°C for 24 h, then transferred to fermentation medium (30 / 250 mL) at a 5% inoculum, and cultured at 30°C, 34°C, and 37°C for 48 h, respectively, and the bacterial count and spore formation rate were measured.

[0065] Table 4: Effect of culture conditions on starch decomposition of Bacillus amyloliquefaciens JRB-F6

[0066] 30℃ 34℃ 37℃ Starch <![CDATA[1.88×10 9 (Spore rate: 0)]]> <![CDATA[1.25×10 9 (Spore rate: 0)]]> <![CDATA[1.91×10 9 (Spore rate: 0)]]>

[0067] From the results in Table 4, we can see that, excluding experimental errors, the temperature has little effect on this strain. 37°C was selected as the optimal culture temperature. However, under this culture condition, the spore rate at the end of fermentation was zero, which affected the storage of the product. From the known experimental results, we can see that in the absence of spores, the survival rate of the strain was only 10% after storage at room temperature for 1 month. Therefore, we continue to optimize the culture medium composition to increase the spore yield.

[0068] 2. Optimization of carbon and nitrogen sources for Bacillus amyloliquefaciens

[0069] 1) Carbon source optimization

[0070] The basic fermentation medium was used as a control, and sucrose, glucose, lactose, molasses, and bran were used as carbon sources to replace maltose in the basic medium, while other components remained unchanged, to explore the optimal carbon source. The strain of the present invention was inoculated into LB medium at a 2% inoculation amount, cultured at 37°C for 24h, transferred to the fermentation medium at a 6% inoculation amount (25 / 250ml), cultured at 37°C for 48h, and the bacterial count and spore rate were measured.

[0071] Table 5: Effect of carbon source on spore production rate of Bacillus amyloliquefaciens JRB-F6

[0072]

[0073]

[0074] When maltose, glucose and bran were used as carbon sources, a small amount of spores were produced. Combined with the amount of bacteria at the end of fermentation, glucose was selected as the carbon source for further optimization.

[0075] 2) Nitrogen source optimization

[0076] Using glucose as the carbon source, the beef extract in the basal culture medium was replaced by yeast powder, ammonium sulfate, ammonium chloride, urea, peptone, corn gluten powder, and puffed soybean powder, respectively, while keeping other ingredients unchanged, to explore the optimal nitrogen source. The results are shown in Table 6 below.

[0077] Table 6: Effect of carbon source on spore production rate of Bacillus amyloliquefaciens JRB-F6

[0078] Nitrogen source Bacteria Spore production rate Control (beef extract) <![CDATA[1.54×10 9 ]]> 12％ Yeast powder <![CDATA[1.31×10 9 ]]> 90％ Ammonium sulfate <![CDATA[5×10 5 ]]> 0 Ammonium chloride <![CDATA[6×10 5 ]]> 0 Urea <![CDATA[4.5×10 8 ]]> 30％ Peptone <![CDATA[7.8×10 8 ]]> 0 Corn Gluten Meal <![CDATA[3.4×10 7 ]]> 0 Expanded soybean powder <![CDATA[1.71×10 9 ]]> 88％ Yeast powder: urea = 1:2 <![CDATA[1.5×10 7 ]]> 5％

[0079] From the above results, it can be seen that the nitrogen source has a great influence on the growth of the strains. The bacterial amount of different nitrogen sources is obviously different, and the spore production rate is also different. When the nitrogen source is yeast powder, 90% of spores are produced in 48 hours, but yeast powder is expensive as a nitrogen source and is not conducive to large-scale production. When inorganic nitrogen sources and organic nitrogen sources are combined and fermented at a ratio of yeast powder: urea = 1:2, the bacterial amount and spore production rate are not high. The most suitable nitrogen source is puffed soybean powder. At the end of fermentation, the bacterial amount is high and the spore production rate is comparable to that of yeast powder. Therefore, the optimization is completed with puffed soybeans as the best nitrogen source and glucose as the best carbon source.

[0080] Example 4: Genetic stability analysis of Bacillus amyloliquefaciens JRB-F6

[0081] Bacillus amyloliquefaciens JRB-F6 was subcultured more than ten times to detect the stability of its enzyme production and antibacterial properties. The strain was fermented with LB for 48 hours, and the supernatant was obtained by centrifugation for evaluation. The indicator bacteria were tomato gray mold, cucumber powdery mildew, grape white rot, and Staphylococcus aureus. In the table below, JRB-F6 is the original strain, and JN is the strain after ten subcultures.

[0082] Table 7: Genetic stability data of Bacillus amyloliquefaciens JRB-F6

[0083]

[0084] From the above results, it can be seen that after multiple subcultures, the inhibitory ability of Bacillus amyloliquefaciens JRB-F6 against pathogenic bacteria is not much different, the stability of antibacterial performance is good, and the activity of protease and cellulase produced is also stable.

[0085] Example 5: Preparation of microbial liquid fertilizer

[0086] 1) Seed preparation: The Bacillus amyloliquefaciens JRB-F6 of the present invention was inoculated into LB medium, and cultured in a constant temperature shaker at 37 degrees for 18 hours to prepare a seed solution.

[0087] 2) Preparation of fermentation medium: 2% glucose, 3% puffed soybean, 0.01% MgSO4, 0.01% calcium chloride, natural pH, sterilization to obtain the fermentation medium.

[0088] 3) Inoculate the seeds into the fermentation medium at a volume ratio of 5%, and culture at 37 degrees and 250 r / min for 48 hours.

[0089] 4) After 48 h of fermentation, the number of live Bacillus amyloliquefaciens in the fermentation broth was detected to be 1.73×10 9 cfu / mL, and collect the fermentation liquid to obtain microbial liquid fertilizer.

[0090] Example 6: Storage stability experiment of liquid bacterial fertilizer

[0091] The storage stability experiment was conducted with the microbial liquid fertilizer prepared in Example 6. 100 mL of each fertilizer was taken, and 0.05% and 0.1% of formic acid, acetic acid, citric acid, and kason were added respectively. The sample without stabilizer was used as a blank control and stored at room temperature. The number of live bacteria in the fertilizer sample was detected by plate count method every other month, and the survival rate was calculated. The results are as follows:

[0092] Table 8: Storage stability data of liquid bacterial fertilizer

[0093] blank 0.1% Formic acid 0.1% acetic acid 0.1% citric acid 0.1% Kasson 1 month 93.6％ 95.3％ 100％ 100％ 98.4％ 2 months 70.5％ 88.5％ 97.5％ 99.8％ 92.6％ 3 months 45.3％ 64.8％ 91.6％ 98.6％ 80.9％

[0094] From the above results, it can be seen that adding a stabilizer to the microbial liquid fertilizer prepared by the present invention can stabilize the live bacteria therein at room temperature for 3 months, and the bacterial quantity remains basically unchanged. The most effective stabilizer is citric acid, followed by acetic acid and kason.

[0095] A further gradient experiment was conducted on the added concentration of citric acid, and the results are shown in Table 9 below.

[0096] Table 9: Effect of different addition amounts of citric acid on stability

[0097] 0.01% citric acid 0.02% citric acid 0.05% citric acid 0.1% citric acid 1 month 98.1％ 100％ 100％ 100％ 2 months 90.7％ 99.6％ 99.3％ 99.6％ 3 months 78.2％ 98.5％ 98.2％ 98.5％

[0098] It can be seen that when the amount of citric acid added reaches 0.02%, it has a good stabilizing effect on the bacteria. Therefore, 0.02% citric acid is the best stabilizer. After adding the stabilizer, it is necessary to adjust the pH to neutral with an appropriate amount of NaOH before use.

[0099] Example 7: Effect of microbial liquid fertilizer on strawberry growth

[0100] Experimental location: Haiyang strawberry greenhouse in Yantai City, Shandong Province

[0101] The prepared microbial liquid fertilizer was subjected to a field experiment, and the experimental scheme was as follows:

[0102] A strawberry greenhouse with normal growth of 2 mu was selected and randomly divided into a control group and an experimental group. The control group was fertilized conventionally, using two different fertilizers purchased from the market, and the experimental group used the microbial liquid fertilizer of the present invention, and the rest of the field management was the same. After the experiment, the weight, yield, incidence rate and sweetness of the strawberry plants in each experimental group were calculated.

[0103] Table 10: Effects of microbial liquid fertilizer on strawberry growth

[0104] Fresh weight (g / plant) Number of results (pieces / strain) Yield (g / plant) Incidence (%) Sweetness(%) Control group 1 14.0 6.5 21.8 41.0 15.85 Control group 2 16.6 7.3 26.2 30.7 16.88 Experimental Group 1 19.1 9.4 31.5 8.8 18.04 Experimental Group 2 18.9 9.3 30.8 8.2 18.13

[0105] As shown in Table 10 above, compared with the two control groups, the fresh weight, fruit number and yield of strawberry plants in the experimental group using the microbial liquid fertilizer of the present invention increased. The incidence of strawberry plants in the experimental group decreased significantly, and the sweetness of the fruit increased, and the taste was better.

[0106] Example 8 Effect of microbial liquid fertilizer on cucumber growth

[0107] Experimental location: Haiyang vegetable greenhouse in Yantai City, Shandong Province

[0108] A normal cucumber greenhouse with about 2 mu of growth was selected, with a cucumber spacing of 0.2 m and a row spacing of 1.5 m, and the cucumbers were randomly divided into a control group and an experimental group. The control group was fertilized conventionally, using two different fertilizers purchased from the market, and the experimental group used the microbial liquid fertilizer of the present invention, which was diluted 500 times and then irrigated, and the remaining planting conditions and field management were exactly the same. After the experiment, the yield and incidence were calculated, and the specific results are shown in Table 11 below.

[0109] Table 11: Effects of microbial liquid fertilizer on cucumber growth

[0110] deal with Incidence (%) Yield (kg / mu) Control group 1 21.35 4078 Control group 2 15.58 4584 Experimental Group 1 8.82 5106 Experimental Group 2 8.49 5079

[0111] From the above results, it can be seen that compared with the control group, the incidence of cucumber in the experimental group was greatly reduced, and the yield increase effect was obvious.

[0112] In summary, the Bacillus amyloliquefaciens JRB-F6 of the present invention can effectively inhibit plant pathogens such as tomato gray mold, cucumber powdery mildew, and grape white rot, has high protease activity and cellulase activity, can promote the absorption of nutrients by crops, and has good storage stability, and has broad application prospects in the research of microbial liquid fertilizer.

Claims

1. A strain of Bacillus amyloliquefaciens, characterized in that The deposit number of the Bacillus amyloliquefaciens is CGMCCNO.31787.

2. The Bacillus amyloliquefaciens according to claim 1, wherein The rDNA sequence of Bacillus amyloliquefaciens is SEQ ID NO:

1.

3. Use of the Bacillus amyloliquefaciens according to claim 1 in promoting plant root growth or preventing and controlling diseases and insect pests.

4. Use of the Bacillus amyloliquefaciens according to claim 1 in preparing liquid bacterial fertilizer.

5. A liquid bacterial fertilizer, characterized in that: The liquid bacterial fertilizer contains live bacteria of the Bacillus amyloliquefaciens according to claim 1.

6. The liquid bacterial fertilizer according to claim 5, characterized in that: The liquid bacterial fertilizer is further added with a stabilizer, and the stabilizer is any one or more of formic acid, acetic acid, citric acid or kason.

7. The liquid bacterial fertilizer according to claim 6, characterized in that: The stabilizer is citric acid, and the added amount is 0.02%.

8. The liquid bacterial fertilizer according to claim 5, characterized in that: The preparation method of the liquid bacterial fertilizer is as follows: 1) Inoculate the Bacillus amyloliquefaciens strain into LB medium, and culture at 37°C and 250 rpm for 18 h to prepare a seed solution; 2) Inoculate the seeds into the fermentation medium at a volume ratio of 5%, and culture at 37°C and 250 rpm for 48 hours; 3) Add 0.1% to 1% of stabilizer to the fermentation liquid to make microbial liquid fertilizer.

9. The liquid bacterial fertilizer according to claim 8, characterized in that The fermentation medium uses glucose as a carbon source, puffed soybeans as a nitrogen source, and is added with 0.01% magnesium sulfate MgSO4 and 0.01% calcium chloride as inorganic salts.

10. Use of the liquid bacterial fertilizer according to claim 5 in agricultural planting.

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