A microbial composition for water-soluble fertilizer and preparation method thereof

Abstract

The present invention relates to the field of microbial technology, and specifically to a microbial composition for water-soluble fertilizer and a preparation method thereof. The present invention immobilizes a microbial composite agent by modified biochar to obtain a modified microbial composite agent, and then modifies it with a coating material and an ascorbic acid aqueous solution respectively to obtain a microbial composition A and a microbial composition B, and the two are evenly mixed to obtain a microbial composition for water-soluble fertilizer. In the present invention, biochar can not only provide nutrients for microorganisms, but also create a relatively stable living environment; the coating materials are sodium alginate and ascorbic acid, which can further maintain the stability of biochar-immobilized microorganisms and reduce the impact of ultraviolet rays on microorganisms. The microbial composition for water-soluble fertilizer prepared in the present invention can effectively play the role of nitrogen fixation, phosphorus dissolution, disease and pest prevention and plant growth promotion, and has a broad application prospect compared with the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of microorganisms, and in particular to a microbial composition for water-soluble fertilizer and a preparation method thereof. Background Art

[0002] Water-soluble fertilizers are liquid or solid fertilizers that are dissolved or diluted in water and used for irrigation and fertilization, foliar fertilization, soilless cultivation, seed soaking and root dipping, etc. Since water-soluble fertilizers can be quickly dissolved in water and are more easily absorbed and utilized by crops, they can not only be formulated to contain growth elements such as nitrogen, phosphorus, and potassium required by crops, but also to prepare medium and trace and ultra-trace elements, so that the soil maintains the chemical composition of the original soil, improves the plant's own immune function, and resists various diseases and pests, thereby obtaining high-quality crops. Therefore, water-soluble fertilizers are the key to the transformation from traditional agriculture to modern agriculture, and the research, promotion and application of water-soluble fertilizer technology have far-reaching significance for the development of modern agriculture.

[0003] Microorganisms are a general term for a class of organisms including bacteria, viruses, fungi, etc., covering many types of beneficial and harmful organisms, and widely involved in many fields such as food, medicine, industry and agriculture, environmental protection, sports, etc. Microbial agents have the advantages of being green and pollution-free, leaving no residue after use, improving the soil ecological environment, inhibiting soil-borne diseases, and increasing soil nutrient activity. In recent years, microbial agents have begun to be widely used in agriculture. With the development of technology, the application of composite agents has gradually replaced the application of single agents. People have found that compounding microbial agents with different effects can combine the functions of different microbial agents, promote each other to enhance the growth-promoting effect, and improve the adaptability of microbial agents in different environments and improve the colonization effect of microorganisms.

[0004] At the same time, the composite microbial agent is combined with the composite fertilizer to make a biological fertilizer, which can simplify the application method of the microbial agent, increase the effect of the fertilizer, and improve the crop yield, and finally achieve the purpose of increasing fertilizer efficiency and increasing crop yield. For example, the patent technical document CN108675866A discloses a water-soluble microbial fertilizer for legume crops and a preparation method thereof, which includes the following steps: activating and culturing Rhodopseudomonas palustris and Phanerochaete chrysosporium, freeze-drying into powder after compounding, and making a composite microbial agent to directly compound with other nutrients. The invention can meet the nutrient needs of flower bud differentiation of legume crops, but the activity of the microbial agent in the water-soluble fertilizer needs to be further improved.

[0005] Therefore, according to the above-mentioned related technologies, it is urgent to develop a water-soluble fertilizer microbial composition and a preparation method thereof that can maintain microbial activity and promote plant growth. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a microbial composition for water-soluble fertilizer and a preparation method thereof, so as to solve the problem in the prior art that the microorganisms in water-soluble fertilizers are not highly active and are difficult to promote plant growth.

[0007] Based on the above purpose, the present invention provides a microbial composition for water-soluble fertilizer and a preparation method thereof.

[0008] A microbial composition for water-soluble fertilizer, comprising the following raw materials in parts by weight:

[0009] 65-75 parts of microbial composition A, 6.5-7.5 parts of microbial composition B;

[0010] The microbial composition A is prepared from the following raw materials in parts by weight: 25-35 parts of coating material and 40-50 parts of modified microbial composite bacterial agent;

[0011] The microbial composition B is prepared from the following raw materials in parts by weight: 5-8 parts of ascorbic acid aqueous solution and 2-5 parts of modified microbial composite bacterial agent;

[0012] The coating material is obtained by mixing sodium alginate and ascorbic acid;

[0013] The modified microbial composite agent is prepared from the following raw materials in parts by weight: 35-45 parts of modified biochar and 18-22 parts of the microbial composite agent;

[0014] The modified biochar is obtained by modifying the biochar with KOH.

[0015] Preferably, the preparation method of the modified biochar is as follows:

[0016] The biochar was soaked in a KOH solution with a mass fraction of 35%-40%, stirred for 12-13 hours, allowed to stand for 20-24 hours, dried at 110-120°C for 48-50 hours, cooled, washed twice with a 1 mol / L hydrochloric acid solution and deionized water, and then dried at 60-70°C for 3-4 hours to obtain modified biochar;

[0017] The mass ratio of the biochar to the KOH solution with a mass fraction of 40% is 1:4.5-5.5.

[0018] Preferably, the preparation method of the microbial composite agent is as follows:

[0019] Step A1. The primary seed solution of Bacillus subtilis and the primary seed solution of Bacillus licheniformis are inoculated into a fermentation tank containing NA liquid medium and cultured to obtain the secondary seed solution of Bacillus subtilis and the secondary seed solution of Bacillus licheniformis;

[0020] Step A2. The first seed solution of Bacillus Velez is inoculated into a fermenter containing NB liquid medium to obtain a second seed solution of Bacillus Velez;

[0021] Step A3. Inoculate the first-level seed solution of Pantoea into a fermenter containing LB liquid medium to obtain the second-level seed solution of Pantoea;

[0022] Step A4. The secondary seed solution of Bacillus subtilis, the secondary seed solution of Bacillus licheniformis, the secondary seed solution of Bacillus velezii, and the secondary seed solution of Pantoea are mixed evenly at an effective live bacterial count ratio of 2:0.5-1:2-3:0.5-1:1-2 to prepare a mixed bacterial solution;

[0023] Step A5. Centrifuge the mixed bacterial solution at 4000-5000 rpm for 15-20 min, discard the supernatant, collect the bacterial cells, and prepare a bacterial suspension with sterile water to obtain a microbial composite bacterial agent;

[0024] The NA liquid culture medium has a formula of: 3 g / L beef extract, 10 g / L peptone, 5 g / L NaCl, and a pH of 7.0-7.2;

[0025] The NB liquid culture medium formula is: beef extract 5g / L, peptone 10g / L, NaCl 5g / L, glucose 10g / L, pH 7.0-7.2;

[0026] The LB liquid culture medium formula is: 10 g / L tryptone, 5 g / L yeast powder, 10 g / L NaCl, and pH 7.0-7.2.

[0027] Preferably, the Bacillus subtilis primary seed solution and the Bacillus licheniformis primary seed solution in step A1 are cultured for 20-36 hours at 20-40° C., a stirring speed of 150-200 r / min, and an air volume of 0.7-1.3 vvm;

[0028] The first-level seed solution of Bacillus Velezii described in step A2 is cultured for 20-36 hours at 30-37° C., a stirring speed of 160-180 r / min, and an air volume of 0.7-1.3 vvm;

[0029] The Pantoea primary seed solution in step A3 is cultured for 16-24 hours at 30-37° C., a stirring speed of 160-180 r / min, and an air volume of 0.7-1.3 vvm.

[0030] Preferably, the preparation method of the Bacillus subtilis primary seed solution in step A1 is as follows:

[0031] The original strains of Bacillus subtilis and Bacillus licheniformis are inoculated into NA solid culture medium respectively, cultured at 20-40° C. for 20-36 hours to obtain activated strains, and then inoculated into NA liquid culture medium respectively, cultured at 20-40° C. and a shaking speed of 150-200 r / min for 20-36 hours to obtain Bacillus subtilis first-level seed liquid and Bacillus licheniformis first-level seed liquid;

[0032] The preparation method of the primary seed solution of Bacillus Velez subtilis described in step A2 is as follows:

[0033] The original strain of Bacillus Velez is inoculated into NB solid culture medium, cultured at 30-37° C. for 20-36 hours to obtain activated strains, and then inoculated into NB liquid culture medium, cultured at 30-37° C. and a shaking speed of 160-180 r / min for 20-36 hours to obtain a first-level seed solution of Bacillus Velez;

[0034] The preparation method of the Pantoea primary seed solution in step A3 is as follows:

[0035] The original strain of Pantoea was inoculated into LB solid medium, cultured at 30-37°C for 16-24 hours to obtain activated strains, and then inoculated into NB liquid medium, cultured at 30-37°C and a shaking speed of 160-180 r / min for 16-24 hours to obtain Pantoea primary seed solution;

[0036] The NA solid culture medium formula is: beef extract 3g / L, peptone 10g / L, NaCl 5g / L, agar 10g / L, pH 7.0-7.2;

[0037] The NB solid culture medium formula is: beef extract 5g / L, peptone 10g / L, NaCl 5g / L, glucose 10g / L, agar 12.0g / L, pH 7.0-7.2;

[0038] The LB solid culture medium formula is: 10 g / L tryptone, 5 g / L yeast powder, 10 g / L NaCl, 15 g / L agar, and pH is 7.0-7.2.

[0039] Preferably, the volume ratio of the Bacillus subtilis primary seed solution and the Bacillus licheniformis primary seed solution to the NA liquid culture medium in step A1 is 100:700-900;

[0040] The volume ratio of the Bacillus Velez primary seed solution to the NB liquid culture medium in step A2 is 100:700-900;

[0041] The volume ratio of the Pantoea primary seed solution to the LB liquid culture medium in step A3 is 100:700-900.

[0042] Preferably, the number of Bacillus subtilis in the secondary seed solution of Bacillus subtilis in step A1 is 5.5-7.2×10 10 cfu / mL;

[0043] The volume ratio of the mixed bacterial solution to sterile water in step A5 is 10-15:25-30.

[0044] Preferably, the preparation method of the coating material is as follows:

[0045] Adding sodium alginate and ascorbic acid to deionized water in sequence, heating and stirring at 50-60° C. for 20-30 minutes, to obtain a coating material;

[0046] The mass ratio of deionized water, sodium alginate and ascorbic acid is 8-10:10-15:3-4;

[0047] The preparation method of the ascorbic acid aqueous solution is as follows:

[0048] Add ascorbic acid to deionized water, heat and stir at 50-60° C. for 10-20 minutes to obtain an ascorbic acid aqueous solution;

[0049] The mass ratio of the deionized water to ascorbic acid is 3-7:8-12.

[0050] Preferably, the preparation method of the modified microbial composite agent is as follows:

[0051] Add modified biochar to the microbial composite agent, and place the conical flask in a constant temperature shaking incubator set at a temperature of 25-30°C and a rotation speed of 130-160r / min for culturing for 20-24h, take it out and let it stand for 2-3h, filter it, rinse it with sterile water, and filter it to obtain a modified microbial composite agent;

[0052] The preparation method of microbial composition A is as follows:

[0053] The modified microbial composite agent and the coating material are added to a 25-30°C constant temperature shaking box, shaken and stored for 6-7 hours, mixed evenly, and placed in a 25-30°C oven to dry for 2.5-3.5 hours to obtain a microbial composition A;

[0054] The preparation method of microbial composition B is as follows:

[0055] The modified microbial composite agent and ascorbic acid aqueous solution are added to a 25-30°C constant temperature shaking box, shaken and stored for 6-7 hours, mixed evenly, and placed in a 25-30°C oven to dry for 2.5-3.5 hours to obtain a microbial composition B modified by ascorbic acid aqueous solution.

[0056] A method for preparing a microbial composition for water-soluble fertilizer comprises the following steps:

[0057] The microbial composition A and the microbial composition B are mixed evenly to obtain the microbial composition for water-soluble fertilizer.

[0058] Beneficial effects of the present invention:

[0059] The invention provides a microbial composition for water-soluble fertilizer and a preparation method thereof. The invention fixes a microbial composite agent by modified biochar to obtain a modified microbial composite agent, and then modifies the modified microbial composite agent by a coating material and an ascorbic acid aqueous solution to obtain a microbial composition A and a microbial composition B, and the two are evenly mixed to obtain the microbial composition for water-soluble fertilizer.

[0060] In the present invention, the biochar modified by KOH has a larger specific surface area and a stronger adsorption capacity, the microbial composite agent can be dispersed on the surface and pores of the biochar, and the biochar can provide nutrients for the microorganisms and create a relatively stable living environment; the coating materials are sodium alginate and ascorbic acid, sodium alginate has good film-forming properties and can further maintain the stability of the biochar-immobilized microorganisms, and ascorbic acid is a light-blocking agent, which can absorb ultraviolet rays in the external environment and reduce the influence of ultraviolet rays on the microorganisms, and on the other hand, the carbonyl and hydroxyl groups contained in the molecule can form hydrogen bonds with the modified biochar to further improve the adsorption effect of sodium alginate and the modified biochar.

[0061] The microbial composition A in the present invention can stably exist in the fertilizer particles and has a long shelf life; ascorbic acid in the microbial composition B, as a strong reducing agent, can effectively protect the structure of the biochar from further oxidation, thereby maintaining the adsorption performance of the biochar and providing a more stable living environment for the microorganisms. The water-soluble fertilizer microbial composition prepared in the present invention can effectively play the role of nitrogen fixation, phosphorus dissolution, pest control and plant growth promotion, and has a wide application prospect compared with the prior art. DETAILED DESCRIPTION

[0062] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0063] The sources and properties of some of the raw materials used in the present invention are as follows:

[0064] Sodium alginate was purchased from Jiangsu Weizhirun Biotechnology Co., Ltd.; ascorbic acid was purchased from Wuhan Dingxintong Pharmaceutical Co., Ltd.; Bacillus subtilis was Bacillus subtilis subsp.subtilis, deposited in the General Microbiology Center of China National Microorganism Culture Collection, with a deposit number of CGMCC No.21826; Bacillus licheniformis was deposited in the General Microbiology Center of China National Microorganism Culture Collection, with a deposit number of CGMCC No.18082; Bacillus velez was Bacillus velez ZLP-101, deposited in the General Microbiology Center of China National Microorganism Culture Collection, with a deposit number of CGMCC No.20130; Pantoea was deposited in the General Microbiology Center of China National Microorganism Culture Collection, with a deposit number of CGMCC No.9359.

[0065] Embodiment 1: A method for preparing a microbial composition for water-soluble fertilizer, comprising the following steps:

[0066] S1. Take 1g of biochar and soak it in 4.5g of 40% KOH solution, stir it for 12h, let it stand for 20h, dry it at 110℃ for 50h, cool it, wash it twice with 1mol / L hydrochloric acid solution and deionized water, and then dry it at 60℃ for 4h to obtain modified biochar;

[0067] S2. Weigh 3 g of beef extract, 10 g of peptone, and 5 g of NaCl, add 1000 mL of distilled water, heat at 40°C until completely dissolved, adjust the pH to 7, add 10 g of agar, heat at 50°C until completely dissolved, filter, and sterilize at 121°C for 15 min to obtain NA solid culture medium; weigh 3 g of beef extract, 10 g of peptone, and 5 g of NaCl, add 1000 mL of distilled water, heat at 40-50°C until completely dissolved, adjust the pH to 7, filter, and sterilize at 121°C for 15 min to obtain NA liquid culture medium;

[0068] S3. Weigh 5 g beef extract, 10 g peptone, 5 g NaCl, and 10 g glucose, add 1000 mL of distilled water, heat at 40°C until completely dissolved, adjust the pH to 7, add 12 g agar, heat at 50°C until completely dissolved, filter, and sterilize at 121°C for 15 min to obtain NB solid culture medium; Weigh 5 g beef extract, 10 g peptone, 5 g NaCl, and 10 g glucose, add 1000 mL of distilled water, heat at 40°C until completely dissolved, adjust the pH to 7, filter, and sterilize at 121°C for 15 min to obtain NB liquid culture medium;

[0069] S4. Weigh 10 g of tryptone, 5 g of yeast powder, and 10 g of NaCl, add 1000 mL of distilled water, heat at 40°C until completely dissolved, adjust the pH to 7, add 15 g of agar, heat at 50°C until completely dissolved, filter, and sterilize at 121°C for 15 min to obtain LB solid culture medium; weigh 10 g of tryptone, 5 g of yeast powder, and 10 g of NaCl, add 1000 mL of distilled water, heat at 40°C until completely dissolved, adjust the pH to 7, filter, and sterilize at 121°C for 15 min to obtain LB liquid culture medium;

[0070] S5. The original strains of Bacillus subtilis and Bacillus licheniformis were inoculated into NA solid medium, cultured at 20°C for 36 hours to obtain activated strains, and then inoculated into NA liquid medium, cultured at 40°C and a shaking speed of 1200 r / min for 36 hours to obtain a first-level seed solution of Bacillus subtilis and a first-level seed solution of Bacillus licheniformis;

[0071] S6. The original strain of Bacillus Velez is inoculated into NB solid medium, cultured at 30° C. for 36 h to obtain activated strains, and then inoculated into NB liquid medium, cultured at 30° C. and a shaking speed of 180 r / min for 36 h to obtain a primary seed solution of Bacillus Velez;

[0072] S7. The original strain of Pantoea was inoculated into LB solid medium, cultured at 30°C for 24 hours to obtain activated strains, and then inoculated into NB liquid medium, cultured at 30°C and a shaking speed of 180 r / min for 24 hours to obtain the first-level seed solution of Pantoea;

[0073] S8. 100 mL of the primary seed solution of Bacillus subtilis and 100 mL of the primary seed solution of Bacillus licheniformis were inoculated separately into a fermenter containing 700 mL of NA liquid medium, and cultured for 36 h at 20 ° C, a stirring speed of 200 r / min, and an air volume of 1.3 vvm to obtain a secondary seed solution of Bacillus subtilis and a secondary seed solution of Bacillus licheniformis;

[0074] S9. Inoculate 100 mL of the primary seed solution of Bacillus Velez into a fermenter containing 700 mL of NB liquid medium, and culture for 36 h at 30 ° C, a stirring speed of 180 r / min, and an air volume of 1.3 vvm to obtain a secondary seed solution of Bacillus Velez;

[0075] S10. Inoculate 100 mL of Pantoea primary seed solution into a fermenter containing 700 mL of LB liquid medium, and culture for 24 h at 30° C., stirring speed 180 r / min, and air volume 1.3 vvm to obtain Pantoea secondary seed solution;

[0076] S11. The secondary seed liquid of Bacillus subtilis, the secondary seed liquid of Bacillus licheniformis, the secondary seed liquid of Bacillus velezii, and the secondary seed liquid of Pantoea are mixed in an effective living bacteria count ratio of 2:0.5:2:0.5:1 to prepare a mixed bacterial liquid;

[0077] S12. Centrifuge 10 mL of the mixed bacterial solution at 4000 rpm for 20 min, discard the supernatant, collect the bacteria, and prepare a bacterial suspension with 25 mL of sterile water to obtain a microbial composite bacterial agent;

[0078] S13. To 8 g of deionized water solution, 10 g of sodium alginate and 3 g of ascorbic acid were added successively, and the mixture was heated and stirred at 50 ° C for 30 min to obtain a coating material; 8 g of ascorbic acid was then added to 3 g of deionized water solution, and the mixture was heated and stirred at 50 ° C for 20 min to obtain an ascorbic acid aqueous solution;

[0079] S14. Add 35 g of modified biochar to 18 g of the microbial composite agent, and place the conical flask in an oscillating incubator at 25°C and a speed of 160 r / min for 24 h of oscillation culture. Take it out and let it stand for 2 h. After filtering, rinse with sterile water and filter to obtain a modified microbial composite agent.

[0080] S15. Add 40 g of the modified microbial composite agent and 25 g of the coating material to a 25°C constant temperature shaker, shake and store for 7 h, mix evenly, and place in a 25°C oven to dry for 3.5 h to obtain a microbial composition A loaded with the coating material;

[0081] S16. Add 2 g of the modified microbial composite agent and 5 g of ascorbic acid aqueous solution to a 25°C constant temperature shaker, shake and store for 6 h, mix well, and place in a 25°C oven to dry for 3.5 h to obtain a microbial composition B modified with ascorbic acid aqueous solution;

[0082] S17. Mix 65 g of microbial composition A and 6.5 g of microbial composition B evenly to obtain a microbial composition for water-soluble fertilizer.

[0083] Embodiment 2: A method for preparing a microbial composition for water-soluble fertilizer, comprising the following steps:

[0084] S1. Soak 1g in 5g of 40% KOH solution, stir for 12.5h, let stand for 22h, dry at 115℃ for 49h, cool, wash twice with 1mol / L hydrochloric acid solution and deionized water, and dry at 65℃ for 3.5h to obtain modified biochar;

[0085] S2. Weigh 3 g of beef extract, 10 g of peptone, and 5 g of NaCl, add 1000 mL of distilled water, heat at 45°C until completely dissolved, adjust the pH to 7.1, add 10 g of agar, heat at 55°C until completely dissolved, filter, and sterilize at 121°C for 15 min to obtain NA solid culture medium; Weigh 3 g of beef extract, 10 g of peptone, and 5 g of NaCl, add 1000 mL of distilled water, heat at 45°C until completely dissolved, adjust the pH to 7.1, filter, and sterilize at 121°C for 15 min to obtain NA liquid culture medium;

[0086] S3. Weigh 5 g beef extract, 10 g peptone, 5 g NaCl, and 10 g glucose, add 1000 mL of distilled water, heat at 45°C until completely dissolved, adjust the pH to 7.1, add 12 g agar, heat at 55°C until completely dissolved, filter, and sterilize at 121°C for 15 min to obtain NB solid culture medium; Weigh 5 g beef extract, 10 g peptone, 5 g NaCl, and 10 g glucose, add 1000 mL of distilled water, heat at 45°C until completely dissolved, adjust the pH to 7.1, filter, and sterilize at 121°C for 15 min to obtain NB liquid culture medium;

[0087] S4. Weigh 10 g of tryptone, 5 g of yeast powder, and 10 g of NaCl, add 1000 mL of distilled water, heat at 45°C until completely dissolved, adjust the pH to 7.1, add 15 g of agar, heat at 55°C until completely dissolved, filter, and sterilize at 121°C for 15 min to obtain LB solid culture medium; weigh 10 g of tryptone, 5 g of yeast powder, and 10 g of NaCl, add 1000 mL of distilled water, heat at 45°C until completely dissolved, adjust the pH to 7.1, filter, and sterilize at 121°C for 15 min to obtain LB liquid culture medium;

[0088] S5. The original strains of Bacillus subtilis and Bacillus licheniformis were inoculated into NA solid medium, cultured at 30°C for 28h to obtain activated strains, and then inoculated into NA liquid medium, cultured at 30°C and a shaking speed of 180r / min for 28h to obtain a primary seed solution of Bacillus subtilis and a primary seed solution of Bacillus licheniformis;

[0089] S6. The original strain of Bacillus Velez is inoculated into NB solid medium, cultured at 34° C. for 28 h to obtain activated strains, and then inoculated into NB liquid medium, cultured at 34° C. and a shaking speed of 170 r / min for 28 h to obtain a primary seed solution of Bacillus Velez;

[0090] S7. The original strain of Pantoea was inoculated into LB solid medium, cultured at 34°C for 20 hours to obtain activated strains, and then inoculated into NB liquid medium, cultured at 34°C and a shaking speed of 170 r / min for 20 hours to obtain the first-level seed solution of Pantoea;

[0091] S8. 100 mL of the primary seed solution of Bacillus subtilis and 100 mL of the primary seed solution of Bacillus licheniformis were inoculated separately into a fermenter containing 800 mL of NA liquid medium, and cultured for 28 h at 30 ° C, a stirring speed of 180 r / min, and an air volume of 1.0 vvm to obtain a secondary seed solution of Bacillus subtilis and a secondary seed solution of Bacillus licheniformis;

[0092] S9. Inoculate 100 mL of the primary seed solution of Bacillus Velez into a fermenter containing 800 mL of NB liquid medium, and culture for 28 h at 34 ° C, a stirring speed of 170 r / min, and an air volume of 1.0 vvm to obtain a secondary seed solution of Bacillus Velez;

[0093] S10. Inoculate 100 mL of Pantoea primary seed solution into a fermenter containing 800 mL of LB liquid medium, and culture for 20 h at 34°C, a stirring speed of 170 r / min, and an air volume of 1.0 vvm to obtain Pantoea secondary seed solution;

[0094] S11. The secondary seed liquid of Bacillus subtilis, the secondary seed liquid of Bacillus licheniformis, the secondary seed liquid of Bacillus velezii, and the secondary seed liquid of Pantoea are mixed and compounded at an effective living bacterial count ratio of 2:0.8:2.5:0.8:1.5 to prepare a mixed bacterial liquid;

[0095] S12. Centrifuge 13 mL of the mixed bacterial solution at 4500 rpm for 18 min, discard the supernatant, collect the bacterial cells, and prepare a bacterial suspension with 28 mL of sterile water to obtain a microbial composite bacterial agent;

[0096] S13. To 9 g of deionized water solution, 13 g of sodium alginate and 3.5 g of ascorbic acid were added successively, and the mixture was heated and stirred at 55 ° C for 25 min to obtain a coating material; 10 g of ascorbic acid was then added to 5 g of deionized water solution, and the mixture was heated and stirred at 55 ° C for 15 min to obtain an ascorbic acid aqueous solution;

[0097] S14. Add 40 g of modified biochar to 20 g of the microbial composite agent, and place the conical flask in an oscillating incubator at 28°C and a speed of 150 r / min for 22 h of oscillation culture. Take it out and let it stand for 2.5 h. After filtering, rinse with sterile water and filter to obtain a modified microbial composite agent.

[0098] S15. Add 45 g of the modified microbial composite agent and 30 g of the coating material to a 28°C constant temperature shaker, shake and store for 6.5 h, mix well, and place in a 28°C oven to dry for 3 h to obtain a microbial composition A loaded with the coating material;

[0099] S16. Add 4 g of the modified microbial composite agent and 7 g of ascorbic acid aqueous solution to a 28°C constant temperature shaker, shake and store for 6.5 h, mix well, and place in a 28°C oven to dry for 3 h to obtain a microbial composition B modified with ascorbic acid aqueous solution;

[0100] S17. Mix 70 g of microbial composition A and 7 g of microbial composition B evenly to obtain a microbial composition for water-soluble fertilizer.

[0101] Embodiment 3: A method for preparing a microbial composition for water-soluble fertilizer, comprising the following steps:

[0102] S1. Weigh 1g of biochar and soak it in 5.5g of 40% KOH solution, stir it for 13h, let it stand for 24h, dry it at 120℃ for 48h, cool it, wash it twice with 1mol / L hydrochloric acid solution and deionized water, and then dry it at 70℃ for 3h to obtain modified biochar;

[0103] S2. Weigh 3 g of beef extract, 10 g of peptone, and 5 g of NaCl, add 1000 mL of distilled water, heat at 50°C until completely dissolved, adjust the pH to 7.2, add 10 g of agar, heat at 60°C until completely dissolved, filter, and sterilize at 121°C for 15 min to obtain NA solid culture medium; weigh 3 g of beef extract, 10 g of peptone, and 5 g of NaCl, add 1000 mL of distilled water, heat at 50°C until completely dissolved, adjust the pH to 7.2, filter, and sterilize at 121°C for 15 min to obtain NA liquid culture medium;

[0104] S3. Weigh 5 g beef extract, 10 g peptone, 5 g NaCl, and 10 g glucose, add 1000 mL of distilled water, heat at 50°C until completely dissolved, adjust the pH to 7.2, add 12 g agar, heat at 60°C until completely dissolved, filter, and sterilize at 121°C for 15 min to obtain NB solid culture medium; Weigh 5 g beef extract, 10 g peptone, 5 g NaCl, and 10 g glucose, add 1000 mL of distilled water, heat at 50°C until completely dissolved, adjust the pH to 7.2, filter, and sterilize at 121°C for 15 min to obtain NB liquid culture medium;

[0105] S4. Weigh 10 g of tryptone, 5 g of yeast powder, and 10 g of NaCl, add 1000 mL of distilled water, heat at 50°C until completely dissolved, adjust the pH to 7.2, add 15 g of agar, heat at 60°C until completely dissolved, filter, and sterilize at 121°C for 15 min to obtain LB solid culture medium; weigh 10 g of tryptone, 5 g of yeast powder, and 10 g of NaCl, add 1000 mL of distilled water, heat at 50°C until completely dissolved, adjust the pH to 7.2, filter, and sterilize at 121°C for 15 min to obtain LB liquid culture medium;

[0106] S5. The original strains of Bacillus subtilis and Bacillus licheniformis were inoculated into NA solid medium, cultured at 40°C for 20 hours to obtain activated strains, and then inoculated into NA liquid medium, cultured at 40°C and a shaking speed of 150 r / min for 20 hours to obtain a primary seed solution of Bacillus subtilis and a primary seed solution of Bacillus licheniformis;

[0107] S6. The original strain of Bacillus Velez is inoculated into NB solid medium, cultured at 37° C. for 20 h to obtain activated strains, and then inoculated into NB liquid medium, cultured at 37° C. and a shaking speed of 160 r / min for 20 h to obtain a primary seed solution of Bacillus Velez;

[0108] S7. The original strain of Pantoea was inoculated into LB solid medium, cultured at 37°C for 16 hours to obtain activated strains, and then inoculated into NB liquid medium, cultured at 37°C and a shaking speed of 160 r / min for 16 hours to obtain the first-level seed solution of Pantoea;

[0109] S8. 100 mL of the primary seed solution of Bacillus subtilis and 100 mL of the primary seed solution of Bacillus licheniformis were inoculated separately into a fermenter containing 900 mL of NA liquid medium, and cultured for 20 h at 40 ° C, a stirring speed of 150 r / min, and an air volume of 0.7 vvm to obtain a secondary seed solution of Bacillus subtilis and a secondary seed solution of Bacillus licheniformis;

[0110] S9. Inoculate 100 mL of the primary seed solution of Bacillus Velez into a fermenter containing 900 mL of NB liquid medium, and culture for 20 h at 37° C., a stirring speed of 160 r / min, and an air volume of 0.7 vvm to obtain a secondary seed solution of Bacillus Velez;

[0111] S10. Inoculate 100 mL of Pantoea primary seed solution into a fermenter containing 900 mL of LB liquid medium, and culture for 16 h at 37°C, a stirring speed of 160 r / min, and an air volume of 0.7 vvm to obtain Pantoea secondary seed solution;

[0112] S11. The secondary seed liquid of Bacillus subtilis, the secondary seed liquid of Bacillus licheniformis, the secondary seed liquid of Bacillus velezii, and the secondary seed liquid of Pantoea are mixed in an effective living bacteria count ratio of 2:1:3:1:2 to prepare a mixed bacterial liquid;

[0113] S12. Centrifuge 15 mL of the mixed bacterial solution at 5000 rpm for 20 min, discard the supernatant, collect the bacteria, and prepare a bacterial suspension with 30 mL of sterile water to obtain a microbial composite bacterial agent;

[0114] S13. To 10 g of deionized water solution, 15 g of sodium alginate and 4 g of ascorbic acid were added successively, and the mixture was heated and stirred at 60 ° C for 20 min to obtain a coating material; 12 g of ascorbic acid was then added to 7 g of deionized water solution, and the mixture was heated and stirred at 60 ° C for 10 min to obtain an ascorbic acid aqueous solution;

[0115] S14. Add 45 g of modified biochar to 22 g of the microbial composite agent, and place the conical flask in an oscillating incubator at 30 ° C and a speed of 130 r / min for 20 h of oscillation culture. After taking it out, let it stand for 3 h, filter it, rinse it with sterile water, and filter it to obtain a modified microbial composite agent;

[0116] S15. Add 50 g of the modified microbial composite agent and 35 g of the coating material to a 30°C constant temperature shaker, shake and store for 6 h, mix evenly, and place in a 30°C oven to dry for 2.5 h to obtain a microbial composition A loaded with the coating material;

[0117] S16. Add 5 g of the modified microbial composite agent and 8 g of ascorbic acid aqueous solution to a 30°C constant temperature shaker, shake and store for 6 h, mix well, and place in a 30°C oven to dry for 2.5 h to obtain a microbial composition B modified with ascorbic acid aqueous solution;

[0118] S17. Evenly mix 75 g of the microbial composition A and 7.5 g of the microbial composition B to obtain a microbial composition for water-soluble fertilizer.

[0119] Comparative Example 1:

[0120] Compared with Example 1, this comparative example did not add modified biochar during the preparation of the microbial composition, and the remaining steps and parameters were the same, which will not be repeated in this comparative example. Finally, a microbial composition for water-soluble fertilizer was obtained.

[0121] Comparative Example 2:

[0122] Compared with Example 1, this comparative example only replaces the "coating material" with "an equal amount of ascorbic acid aqueous solution", and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally a microbial composition for water-soluble fertilizer is obtained.

[0123] Comparative Example 3:

[0124] Compared with Example 1, this comparative example only replaces the "ascorbic acid aqueous solution" with "an equal amount of coating material", and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally a microbial composition for water-soluble fertilizer is obtained.

[0125] Comparative Example 4:

[0126] Compared with Example 1, this comparative example did not add a coating material and an aqueous ascorbic acid solution during the preparation of the microbial composition, and the remaining steps and parameters were the same, which will not be repeated in this comparative example. Finally, a microbial composition for water-soluble fertilizer was obtained.

[0127] Comparative Example 5:

[0128] Compared with Example 1, this comparative example did not modify the biochar with 40% KOH by mass during the preparation of the microbial composition. The remaining steps and parameters were the same and will not be repeated in this comparative example. Finally, a microbial composition for water-soluble fertilizer was obtained.

[0129] Performance Test:

[0130] Yield increase test of crops:

[0131] The microbial compositions prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were mixed with organic fertilizers at a mass ratio of 1-2: 1000-1100 to obtain water-soluble fertilizers prepared by Examples 1 to 3 and Comparative Examples 1 to 5, wherein the organic matter in the organic fertilizers used was ≥ 15%, N ≥ 16%, P2O5 ≥ 12%, K2O ≥ 12%, and the number of effective live bacteria contained in the prepared fertilizers was ≥ 20 million / g. The water-soluble fertilizers prepared by Examples 1 to 3 and Comparative Examples 1 to 5 were diluted 800 times with water, and 5 kg was taken and evenly sprayed on one acre of corn and cucumber fields, and the yields of corn and cucumbers were counted;

[0132] Disease resistance test:

[0133] 1 g of the microbial composition prepared in Examples 1 to 3 and Comparative Examples 1 to 5 was respectively taken into 10 mL of sterile water to obtain an antibacterial agent. A plate confrontation method was adopted to select corn sheath blight and wheat smut as targets. In a plate with NA culture medium poured, parallel lines were drawn at positions 2.5 cm to the left and right of the center of the plate to inoculate the antibacterial agent, and then corn sheath blight and wheat smut were inoculated in the center of the plate and the plate was inverted for culture; a control group was set, and corn sheath blight and wheat smut were directly inoculated in the center of the plate without antibacterial bacteria. When the colony diameter of the pathogen in the control group grew to more than 2 / 3 of the plate diameter, the width of the antibacterial zone between the pathogen and the antibacterial bacteria in the treatment group was measured;

[0134] Antibacterial rate calculation formula:

[0135] Antibacterial rate (%) = (expanded diameter of control group - expanded diameter of treatment group) / expanded diameter of control group × 100%

[0136] Microbial activity test:

[0137] According to the "Microbial Fertilizer Product Testing Procedure" (NY / T2321-2013), 20 g of the water-soluble fertilizer prepared by Example 1 to Example 3 and Comparative Example 1 to Comparative Example 5 were placed in aluminum foil bags, sealed, and stored in a dry dark environment at room temperature and pressure. After 6 months, the effective viable count was tested by the plate count method;

[0138] Determination of nitrogen content by alkaline hydrolysis:

[0139] After the corn was harvested in the test of the yield-increasing performance of crops, five 20cm tillage layers of soil were collected in each group of test fields using the five-point method, and the debris was picked up. After the test soil of each group was fully mixed, the diagonal method was used for sampling. 50g was taken from each group and passed through a 16-mesh sieve. Then, the soil sample was placed in the outer chamber of the diffusion dish, and 30mL20g / L boric acid-indicator solution was added to the inner chamber. The soil sample was treated with 10mL1.0mol / L sodium hydroxide solution, and the diffusion dish was quickly sealed and placed in a 40±1℃ incubator for 24h. The diffusion dish was opened, and the ammonia in the inner chamber was titrated with a sulfuric acid standard solution. The alkaline nitrogen content in the soil was calculated by the volume of standard acid consumed by the titration.

[0140] Calculation formula of alkaline nitrogen content:

[0141] Alkaline hydrolysis nitrogen content (mg / kg) = C × (V-V0) × 14 × 10 3 / m

[0142] Where: C is the concentration of sulfuric acid standard solution (mol / L); V is the volume of sulfuric acid standard solution used for sample titration (mL); V0 is the volume of sulfuric acid standard solution used for blank test titration (mL); m is the mass of the sample (g).

[0143] Table 1 Summary of experimental data in Examples 1-3 and Comparative Examples 1-5

[0144]

[0145]

[0146] Data Analysis:

[0147] As can be seen from Table 1, the microbial composition for water-soluble fertilizer prepared by the present invention has higher activity, showing a higher effective viable count and pathogen inhibition rate, thereby making the crop yield high and the soil conditions good after the water-soluble fertilizer acts. This may be due to the fact that the biochar modified by KOH has a larger specific surface area and a stronger adsorption capacity, the microbial composite agent can be dispersed on the surface and pores of the biochar, and the biochar can not only provide nutrients for the microorganisms, but also create a relatively stable living environment; the coating material is sodium alginate and ascorbic acid, sodium alginate has good film-forming properties, which can further maintain the stability of the biochar-immobilized microorganisms, and ascorbic acid is a light-blocking agent. On the one hand, it can absorb ultraviolet rays in the external environment and reduce the impact of ultraviolet rays on microorganisms. On the other hand, the carbonyl and hydroxyl groups contained in the molecule can form hydrogen bonds with the modified biochar to further improve the adsorption effect of sodium alginate and modified biochar. Under the joint action of modified biochar, coating material and light-blocking agent, the microorganisms prepared by the present invention can exist stably and play an effective role.

[0148] As for Comparative Example 1, since modified biochar was not added in the preparation process of the microbial composition, its activity is poor as can be seen from Table 1. This may be because sodium alginate and ascorbic acid are well soluble in water, and the formed coating layer is easy to break. Only the coating material and the light-proof agent are used as microbial protective agents, and the protective effect on the microbial agent when the fertilizer is applied is insufficient. Therefore, the crop yield, pathogen inhibition rate, effective viable bacteria count and alkaline nitrogen content shown in Comparative Example 1 are worse than those in Example 1; Comparative Example 2 replaces the "coating material" with "an equal amount of ascorbic acid aqueous solution", and its activity is poor as can be seen from Table 1. This may be because the coating material is sodium alginate and ascorbic acid, and sodium alginate has good film-forming properties, which can further maintain the stability of biochar-immobilized microorganisms. On the one hand, ascorbic acid can absorb ultraviolet rays in the external environment and reduce the impact of ultraviolet rays on microorganisms; on the other hand, the carbonyl and hydroxyl groups contained in the molecule can form hydrogen bonds with modified biochar to further improve the adsorption effect of sodium alginate and modified biochar. The lack of coating material lacks a layer of protection for the microbial agent fixed on the modified biochar. Therefore, the crop yield, pathogen inhibition rate, effective viable bacteria count and alkaline nitrogen content shown in Comparative Example 2 are worse than those in Example 1; Comparative Example 3 replaces the "ascorbic acid aqueous solution" with "an equal amount of coating material", and it can be seen from Table 1 that its activity is poor. This may be because the ascorbic acid in the ascorbic acid-modified microbial composition B, as a strong reducing agent, can effectively protect the structure of the biochar from further oxidation, thereby Maintain the adsorption performance of biochar and provide a more stable living environment for microorganisms. Therefore, the crop yield, pathogen inhibition rate, effective viable bacteria count and alkaline nitrogen content shown in Example 3 are worse than those in Example 1; since no coating material and ascorbic acid aqueous solution were added in the preparation process of the microbial composition in Comparative Example 4, it can be seen from Table 1 that its activity is poor. This may be because the coating material and ascorbic acid aqueous solution are further used to protect the modified microbial composite bacterial agent. In the absence of a light shield, ultraviolet rays will directly harm the microorganisms and affect the activity; when there is no coating material, there are too many microorganisms attached to the surface of the modified biochar, and there will be fierce competition, resulting in a decrease in overall activity. Therefore, the crop yield, pathogen inhibition rate, effective viable bacteria count and alkaline nitrogen content shown in Comparative Example 4 are poor. The amount is worse than that in Example 1; since Comparative Example 5 did not modify the biochar with 40% KOH by mass during the preparation of the microbial composition, it can be seen from Table 1 that its activity is poor. This may be because the surface of the biochar may not be fully activated, the specific surface area of ​​the biochar is small, and the adsorption effect is insufficient, resulting in reduced microbial immobilization efficiency; and KOH is a strong base, which can promote the formation of oxygen-containing functional groups in the biochar, thereby affecting the formation of hydrogen bonds and other forces between sodium alginate, ascorbic acid and biochar, weakening the adsorption effect between the coating material, ascorbic acid aqueous solution and biochar, and poor stability of the living environment of the microbial agent. Therefore, the crop yield, pathogen inhibition rate, effective viable count and alkaline nitrogen content shown in Comparative Example 5 are worse than those in Example 1.

[0149] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0150] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A microbial composition for water-soluble fertilizer, characterized in that: It is composed of the following raw materials by weight: 65-75 parts of microbial composition A, 6.5-7.5 parts of microbial composition B; The microbial composition A is prepared from the following raw materials in parts by weight: 25-35 parts of coating material and 40-50 parts of modified microbial composite bacterial agent; The microbial composition B is prepared from the following raw materials in parts by weight: 5-8 parts of ascorbic acid aqueous solution and 2-5 parts of modified microbial composite bacterial agent; The coating material is obtained by mixing sodium alginate and ascorbic acid; The modified microbial composite agent is prepared from the following raw materials in parts by weight: 35-45 parts of modified biochar and 18-22 parts of the microbial composite agent; The modified biochar is obtained by modifying the biochar with KOH; The preparation method of the coating material is as follows: Adding sodium alginate and ascorbic acid to deionized water in sequence, heating and stirring at 50-60° C. for 20-30 minutes, to obtain a coating material; The preparation method of the microbial composite agent is as follows: Step A1. The primary seed solution of Bacillus subtilis and the primary seed solution of Bacillus licheniformis are inoculated into a fermentation tank containing NA liquid medium and cultured to obtain the secondary seed solution of Bacillus subtilis and the secondary seed solution of Bacillus licheniformis; Step A2. The first seed solution of Bacillus Velez is inoculated into a fermenter containing NB liquid medium to obtain a second seed solution of Bacillus Velez; Step A3. Inoculate the first-level seed solution of Pantoea into a fermenter containing LB liquid medium to obtain the second-level seed solution of Pantoea; Step A4. The secondary seed solution of Bacillus subtilis, the secondary seed solution of Bacillus licheniformis, the secondary seed solution of Bacillus velezii, and the secondary seed solution of Pantoea are mixed evenly at an effective live bacterial count ratio of 2:0.5-1:2-3:1-2 to prepare a mixed bacterial solution; Step A5. Centrifuge the mixed bacterial solution at 4000-5000 rpm for 15-20 min, discard the supernatant, collect the bacterial cells, and prepare a bacterial suspension with sterile water to obtain a microbial composite bacterial agent; The preparation method of the modified microbial composite agent is as follows: Add modified biochar to the microbial composite agent, and place the conical flask in a constant temperature shaking incubator set at a temperature of 25-30°C and a rotation speed of 130-160r / min for culturing for 20-24h. After taking it out, let it stand for 2-3h, filter it, rinse it with sterile water, and filter it to obtain a modified microbial composite agent.

2. The water-soluble fertilizer microbial composition according to claim 1, characterized in that: The preparation method of the modified biochar is as follows: The biochar was soaked in a KOH solution with a mass fraction of 35%-40%, stirred for 12-13 hours, allowed to stand for 20-24 hours, dried at 110-120°C for 48-50 hours, cooled, washed twice with a 1 mol / L hydrochloric acid solution and deionized water, and then dried at 60-70°C for 3-4 hours to obtain modified biochar; The mass ratio of the biochar to the KOH solution with a mass fraction of 40% is 1:4.5-5.

5.

3. The water-soluble fertilizer microbial composition according to claim 1, characterized in that: The Bacillus subtilis primary seed solution and the Bacillus licheniformis primary seed solution in step A1 are cultured for 20-36 hours at 20-40° C., a stirring speed of 150-200 r / min, and an air volume of 0.7-1.3 vvm; The first-level seed solution of Bacillus Velezii described in step A2 is cultured for 20-36 hours at 30-37° C., a stirring speed of 160-180 r / min, and an air volume of 0.7-1.3 vvm; The Pantoea primary seed solution in step A3 is cultured for 16-24 hours at 30-37° C., a stirring speed of 160-180 r / min, and an air volume of 0.7-1.3 vvm.

4. The water-soluble fertilizer microbial composition according to claim 1, characterized in that: The preparation method of the Bacillus subtilis primary seed solution in step A1 is as follows: The original strains of Bacillus subtilis and Bacillus licheniformis are inoculated into NA solid culture medium respectively, cultured at 20-40° C. for 20-36 hours to obtain activated strains, and then inoculated into NA liquid culture medium respectively, cultured at 20-40° C. and a shaking speed of 150-200 r / min for 20-36 hours to obtain Bacillus subtilis first-level seed liquid and Bacillus licheniformis first-level seed liquid; The preparation method of the primary seed solution of Bacillus Velez subtilis described in step A2 is as follows: The original strain of Bacillus Velez is inoculated into NB solid culture medium, cultured at 30-37° C. for 20-36 hours to obtain activated strains, and then inoculated into NB liquid culture medium, cultured at 30-37° C. and a shaking speed of 160-180 r / min for 20-36 hours to obtain a first-level seed solution of Bacillus Velez; The preparation method of the Pantoea primary seed solution in step A3 is as follows: The original strain of Pantoea was inoculated into LB solid culture medium, cultured at 30-37°C for 16-24 hours to obtain activated strains, and then inoculated into NB liquid culture medium, cultured at 30-37°C and a shaking speed of 160-180 r / min for 16-24 hours to obtain Pantoea primary seed solution.

5. The water-soluble fertilizer microbial composition according to claim 1, characterized in that: The volume ratio of the Bacillus subtilis primary seed solution and the Bacillus licheniformis primary seed solution to the NA liquid culture medium in step A1 is 100:700-900; The volume ratio of the Bacillus Velez primary seed solution to the NB liquid culture medium in step A2 is 100:700-900; The volume ratio of the Pantoea primary seed solution to the LB liquid culture medium in step A3 is 100:700-900.

6. The water-soluble fertilizer microbial composition according to claim 1, characterized in that: The number of Bacillus subtilis in the secondary seed solution of Bacillus subtilis in step A1 is 5.5-7.2×10 10 cfu / mL; The volume ratio of the mixed bacterial solution to sterile water in step A5 is 10-15:25-30.

7. The microbial composition for water-soluble fertilizer according to claim 1, characterized in that: The mass ratio of deionized water, sodium alginate and ascorbic acid is 8-10:10-15:3-4; The preparation method of the ascorbic acid aqueous solution is as follows: Add ascorbic acid to deionized water, heat and stir at 50-60° C. for 10-20 minutes to obtain an ascorbic acid aqueous solution; The mass ratio of the deionized water to ascorbic acid is 3-7:8-12.

8. The microbial composition for water-soluble fertilizer according to claim 1, characterized in that: The preparation method of microbial composition A is as follows: The modified microbial composite agent and the coating material are added to a 25-30°C constant temperature shaking box, shaken and stored for 6-7 hours, mixed evenly, and placed in a 25-30°C oven to dry for 2.5-3.5 hours to obtain a microbial composition A; The preparation method of microbial composition B is as follows: The modified microbial composite agent and ascorbic acid aqueous solution are added to a 25-30°C constant temperature shaking box, shaken and stored for 6-7 hours, mixed evenly, and placed in a 25-30°C oven to dry for 2.5-3.5 hours to obtain a microbial composition B modified by ascorbic acid aqueous solution.

9. A method for preparing a water-soluble fertilizer microbial composition according to any one of claims 1 to 8, characterized in that: The following steps are involved: The microbial composition A and the microbial composition B are mixed evenly to obtain the microbial composition for water-soluble fertilizer.

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