A compound microbial fertilizer and a preparation method thereof

Abstract

The application discloses a kind of composite microbial fertilizer and preparation method thereof, belong to fertilizer preparation technical field.The preparation method includes the following steps: fermentation nutrient solution, pretreatment coal-based solid waste and mineral potassium fertilizer are mixed and stirred according to the ratio of weight parts 20~24:5~7:9~11, after drying to moisture content reaches 16%~18%, the composite microbial fertilizer is obtained by granulation screening.The composite microbial fertilizer prepared by the preparation method of the application has good viable count and fertilizer efficiency performance, realizes the resource utilization of coal-based solid waste.

Description

Technical Field

[0001] This invention belongs to the field of fertilizer preparation technology, specifically relating to a compound microbial fertilizer and its preparation method. Background Technology

[0002] In agricultural production, fertilizer is a fundamental production material used extensively to supply the nutrients needed for crop growth and development and to improve soil nutrient status. Chemical fertilizers dominate the fertilizer application process, primarily due to their rapid dissolution and nutrient release, which can significantly increase yields in a short period. While chemical fertilizers offer the advantage of quick-acting action, the rapid development of modern agriculture has led to an increasing demand for fertilizers in farmland, resulting in significant harms from their use, including soil nutrient imbalances, soil depletion, and eutrophication of water bodies. In today's world, where environmental protection, sustainable agriculture, and pollution-free agriculture are increasingly emphasized, chemical fertilizers clearly cannot meet the requirements of environmentally friendly and sustainable development. Therefore, technological innovation and product development to produce environmentally friendly and efficient modern fertilizers are of great significance.

[0003] Coal is my country's primary energy source and an important chemical raw material, serving as the cornerstone of my country's energy security and industrial and supply chain security. However, the entire process of coal development and utilization inevitably generates a large amount of coal-based solid waste. Coal-based solid waste refers to various solid wastes generated during coal mining, processing, combustion, and conversion, mainly including coal gangue, fly ash, desulfurization gypsum, coal gasification ash, and coal liquefaction residue. These wastes, due to their heavy metal ion and other pollutant sources, have a significant impact on soil, water, and air pollution. Although coal-based solid waste poses a significant pollution problem, its structure contains mineral components and nutrients necessary for plant growth. If treated, it can be used as fertilizer for crops, which is of great significance for the resource utilization of coal-based solid waste and thus solving its environmental pollution problem. However, although coal-based solid waste contains nutrients needed by crops, the content is low, often making it unsuitable for direct use as fertilizer. Microorganisms play multiple key roles in the field of fertilizers, including nitrogen fixation, phosphorus and potassium solubilization, soil structure improvement, and crop stress resistance. They can not only significantly improve fertilizer utilization and reduce the amount of chemical fertilizer used, but also restore soil ecology and improve the quality of agricultural products, making them an important technical support for achieving sustainable agricultural development.

[0004] Therefore, it is of great significance to find ways to utilize coal-based solid waste and microorganisms to prepare compound microbial fertilizers that promote crop growth. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention mixes and granulates fermentation nutrient solution, pretreated coal-based solid waste, and mineral potassium fertilizer to obtain a compound microbial fertilizer, thereby solving the technical problems mentioned in the background art. Specifically, the technical solution of this invention includes the following:

[0006] One objective of this invention is to provide a method for preparing a compound microbial fertilizer, the method comprising the following steps:

[0007] Fermentation nutrient solution, pretreated coal-based solid waste and mineral potassium fertilizer are mixed and stirred in a weight ratio of 20~24:5~7:9~11, dried until the moisture content reaches 16%~18%, and then granulated and screened to obtain the compound microbial fertilizer.

[0008] Furthermore, the method for preparing the fermentation nutrient solution includes the following steps:

[0009] Bacillus subtilis was inoculated into LB solid medium and cultured at 30°C for 24 h to obtain activated Bacillus subtilis;

[0010] Activated Bacillus subtilis was inoculated into MRS liquid medium and cultured at 35°C until OD500. 600 The concentration of Bacillus subtilis seed culture was 0.6-0.7.

[0011] The Bacillus subtilis seed culture was inoculated into a fermentation medium and cultured at 35°C for 24-28 hours to obtain the fermentation nutrient solution.

[0012] Furthermore, the strain number of the Bacillus subtilis is CICC 24713.

[0013] Furthermore, the LB solid culture medium is prepared by mixing 10g tryptone, 5g yeast extract, 10g sodium chloride and 15g agar, dissolving in water and bringing the volume to 1L, adjusting the pH to 7.0, and finally sterilizing in an autoclave at 121°C for 20 minutes.

[0014] Furthermore, the MRS liquid culture medium is prepared by mixing 12g peptone, 9g beef extract, 2g yeast extract, 18g glucose, 2g potassium dihydrogen phosphate, 5g sodium acetate, 2g disodium hydrogen citrate, 0.2g magnesium sulfate and 0.04g manganese sulfate, dissolving in water and bringing the volume to 1L, adjusting the pH to 6.5, and finally sterilizing in an autoclave at 121°C for 20 minutes.

[0015] Furthermore, the method for preparing the fermentation medium includes the following steps:

[0016] The fermentation medium is prepared by mixing baijiu lees, soluble starch, magnesium sulfate heptahydrate, ferric chloride hexahydrate, and deionized water in a weight ratio of 90-95:10-15:0.2-0.4:0.02-0.04:100-105, adjusting the pH to 6.5-7.0, and then sterilizing at 121℃ for 20 minutes.

[0017] Furthermore, the inoculation amount of the Bacillus subtilis seed liquid into the fermentation medium is 5% to 7%.

[0018] Furthermore, the method for preparing the pretreated coal-based solid waste includes the following steps:

[0019] Coal-based solid waste and acid solution are mixed at a solid-liquid mass ratio of 1:6~7 and stirred at 100 r / min for 1 h~2 h. The mixture is then transferred to an ultrasonic disperser and treated at 600 W~700 W for 2 h~3 h. After filtration, filter cake is obtained, rinsed with deionized water, and dried at 55 °C for 24 h to obtain the pretreated coal-based solid waste.

[0020] Furthermore, the coal-based solid waste includes fly ash.

[0021] Furthermore, the acid solution includes a hydrochloric acid solution with a pH of 3 to 4.

[0022] Furthermore, the mineral potassium fertilizer includes potassium humate.

[0023] The second objective of this invention is to provide a compound microbial fertilizer.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] This invention first constructs a fermentation culture medium using distiller's grains, soluble starch, magnesium sulfate, and ferric chloride. Bacillus subtilis, which has phosphorus and potassium solubilizing properties, is then fermented in this medium to obtain a fermentation nutrient solution. Next, coal-based solid waste, fly ash, undergoes acid treatment combined with ultrasound-assisted leaching to reduce the heavy metal ion content and pollution levels. After leaching, the fly ash is filtered, washed, and dried to obtain pretreated coal-based solid waste. Finally, the fermentation nutrient solution, pretreated coal-based solid waste, and potassium fertilizer are mixed and granulated to obtain a compound microbial fertilizer. In this compound microbial fertilizer, Bacillus subtilis is pretreated and fermented in a culture medium rich in carbon and nitrogen sources such as cellulose, protein, and starch. This not only improves the fermentation efficiency of Bacillus subtilis but also, the inorganic metal ions magnesium and iron promote the production of more antibacterial and other active substances, enhancing the stress resistance and stability of Bacillus subtilis. This, in turn, increases the number of viable bacteria in the compound microbial fertilizer, thus promoting crop growth after fertilization. Fly ash is loose, porous, and has a large specific surface area, which increases soil porosity, thereby improving soil aeration and permeability, creating favorable space for root growth. Mineral potassium fertilizer can chelate with metal ions in the soil, reducing the fixation of phosphorus by these ions and converting unavailable phosphorus into available phosphorus. The synergistic effect of fly ash, Bacillus subtilis, and mineral potassium fertilizer significantly improves the fertilizer efficiency of the prepared compound microbial fertilizer, opening up a new path for the effective resource utilization of coal-based solid waste. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise stated, all raw materials and reagents used in this invention are commercially available or can be prepared by known methods.

[0028] Preparation Example 1

[0029] The LB solid culture medium is prepared as follows:

[0030] Weigh 10g tryptone, 5g yeast extract, 10g sodium chloride, and 15g agar using an electronic balance and add them to an Erlenmeyer flask. Add 500mL of deionized water and heat to 80℃, stirring until dissolved and thoroughly mixed. Then, add deionized water to bring the total volume to 1L, adjust the pH to 7.0, and finally place the flask in an autoclave. Heat to 121℃ and sterilize for 20 minutes. After sterilization, cool to room temperature before use.

[0031] Preparation Example 2

[0032] The preparation of MRS liquid culture medium is as follows:

[0033] Weigh out 12g peptone, 9g beef extract, 2g yeast extract, 18g glucose, 2g potassium dihydrogen phosphate, 5g sodium acetate, 2g disodium hydrogen citrate, 0.2g magnesium sulfate, and 0.04g manganese sulfate using an electronic balance. Add these ingredients to an Erlenmeyer flask, then add 500mL of deionized water and heat to 80°C while stirring until dissolved and mixed thoroughly. Next, add deionized water to bring the total volume to 1L, adjust the pH to 6.5, and finally place the flask in an autoclave and heat to 121°C for 20 minutes to sterilize. After sterilization, cool to room temperature before use.

[0034] Preparation Example 3

[0035] The fermentation medium is prepared as follows:

[0036] Weigh 90 parts by weight of baijiu lees, 10 parts by weight of soluble starch, 0.2 parts by weight of magnesium sulfate heptahydrate, 0.02 parts by weight of ferric chloride hexahydrate, and 100 parts by weight of deionized water, mix and stir evenly, then adjust the pH to 6.5, and then sterilize at 121℃ for 20 minutes to obtain the fermentation medium.

[0037] Preparation Example 4

[0038] The fermentation medium is prepared as follows:

[0039] Weigh 91 parts by weight of baijiu lees, 11 parts by weight of soluble starch, 0.24 parts by weight of magnesium sulfate heptahydrate, 0.024 parts by weight of ferric chloride hexahydrate, and 101 parts by weight of deionized water, mix and stir evenly, then adjust the pH to 6.5, and then sterilize at 121℃ for 20 minutes to obtain the fermentation medium.

[0040] Preparation Example 5

[0041] The fermentation medium is prepared as follows:

[0042] Weigh 92 parts by weight of baijiu lees, 12 parts by weight of soluble starch, 0.28 parts by weight of magnesium sulfate heptahydrate, 0.028 parts by weight of ferric chloride hexahydrate, and 102 parts by weight of deionized water, mix and stir evenly, then adjust the pH to 6.5, and then sterilize at 121℃ for 20 minutes to obtain the fermentation medium.

[0043] Preparation Example 6

[0044] The fermentation medium is prepared as follows:

[0045] Weigh 93 parts by weight of baijiu lees, 13 parts by weight of soluble starch, 0.32 parts by weight of magnesium sulfate heptahydrate, 0.032 parts by weight of ferric chloride hexahydrate and 103 parts by weight of deionized water, mix and stir evenly, then adjust the pH to 7.0, and then sterilize at 121℃ for 20 min to obtain the fermentation medium.

[0046] Preparation Example 7

[0047] The fermentation medium is prepared as follows:

[0048] Weigh 94 parts by weight of baijiu lees, 14 parts by weight of soluble starch, 0.36 parts by weight of magnesium sulfate heptahydrate, 0.036 parts by weight of ferric chloride hexahydrate, and 104 parts by weight of deionized water, mix and stir evenly, then adjust the pH to 7.0, and then sterilize at 121℃ for 20 minutes to obtain the fermentation medium.

[0049] Preparation Example 8

[0050] The fermentation medium is prepared as follows:

[0051] Weigh 95 parts by weight of baijiu lees, 15 parts by weight of soluble starch, 0.4 parts by weight of magnesium sulfate heptahydrate, 0.04 parts by weight of ferric chloride hexahydrate, and 105 parts by weight of deionized water, mix and stir evenly, then adjust the pH to 7.0, and then sterilize at 121℃ for 20 minutes to obtain the fermentation medium.

[0052] Preparation Example 9

[0053] The fermentation medium is prepared as follows:

[0054] Weigh 95 parts by weight of baijiu lees, 15 parts by weight of soluble starch, 1 part by weight of magnesium sulfate heptahydrate, 0.04 parts by weight of ferric chloride hexahydrate, and 105 parts by weight of deionized water, mix and stir evenly, then adjust the pH to 7.0, and then sterilize at 121℃ for 20 minutes to obtain the fermentation medium.

[0055] Preparation Example 10

[0056] The fermentation medium is prepared as follows:

[0057] Weigh 95 parts by weight of baijiu lees, 15 parts by weight of soluble starch, 0.4 parts by weight of magnesium sulfate heptahydrate, 0.1 parts by weight of ferric chloride hexahydrate, and 105 parts by weight of deionized water, mix and stir evenly, then adjust the pH to 7.0, and then sterilize at 121℃ for 20 minutes to obtain the fermentation medium.

[0058] Preparation Example 11

[0059] The fermentation medium is prepared as follows:

[0060] Weigh 105 parts by weight of baijiu lees, 15 parts by weight of soluble starch, 0.4 parts by weight of magnesium sulfate heptahydrate, 0.04 parts by weight of ferric chloride hexahydrate, and 105 parts by weight of deionized water, mix and stir evenly, then adjust the pH to 7.0, and then sterilize at 121℃ for 20 minutes to obtain the fermentation medium.

[0061] Preparation Example 12

[0062] The fermentation nutrient solution is prepared as follows:

[0063] On a clean bench, a loopful of Bacillus subtilis strain CICC 24713 was picked up with a sterilized inoculation loop and inoculated into the LB solid medium obtained in Preparation Example 1. The medium was then placed in a 30°C incubator and incubated statically for 24 hours to obtain activated Bacillus subtilis. Next, a loopful of activated Bacillus subtilis was inoculated into the MRS liquid medium obtained in Preparation Example 2 using a sterilized inoculation loop. The medium was then placed in a 35°C incubator and incubated with shaking at 100 rpm until OD (dose retardation) was achieved. 600 The Bacillus subtilis seed culture was obtained by adding 0.6 to the fermentation medium. The fermentation medium obtained in Preparation Example 3 was loaded into the fermenter, and the loading volume was controlled to be two-thirds of the total volume of the fermenter. Then, 5% of the volume of the fermentation medium in the fermenter was inoculated into the fermenter and mixed with the fermentation medium. The temperature of the fermenter was controlled at 35°C and cultured for 24 hours to obtain the fermentation nutrient solution.

[0064] Preparation Example 13

[0065] The fermentation nutrient solution is prepared as follows:

[0066] On a clean bench, a loopful of Bacillus subtilis strain CICC 24713 was picked up with a sterilized inoculation loop and inoculated into the LB solid medium obtained in Preparation Example 1. The medium was then placed in a 30°C incubator and incubated statically for 24 hours to obtain activated Bacillus subtilis. Next, a loopful of activated Bacillus subtilis was inoculated into the MRS liquid medium obtained in Preparation Example 2 using a sterilized inoculation loop. The medium was then placed in a 35°C incubator and incubated with shaking at 100 rpm until OD (dose retardation) was achieved. 600 The Bacillus subtilis seed culture was obtained with a concentration of 0.62. The fermentation medium obtained in Preparation Example 4 was loaded into the fermenter, and the loading volume was controlled to be two-thirds of the total volume of the fermenter. Then, 5% of the volume of the fermentation medium in the fermenter was inoculated into the fermenter and mixed with the fermentation medium. The temperature of the fermenter was controlled at 35°C, and the culture was timed for 25 hours to obtain the fermentation nutrient solution.

[0067] Preparation Example 14

[0068] The fermentation nutrient solution is prepared as follows:

[0069] On a clean bench, a loopful of Bacillus subtilis strain CICC 24713 was picked up with a sterilized inoculation loop and inoculated into the LB solid medium obtained in Preparation Example 1. The medium was then placed in a 30°C incubator and incubated statically for 24 hours to obtain activated Bacillus subtilis. Next, a loopful of activated Bacillus subtilis was inoculated into the MRS liquid medium obtained in Preparation Example 2 using a sterilized inoculation loop. The medium was then placed in a 35°C incubator and incubated with shaking at 100 rpm until OD (dose retardation) was achieved. 600 The Bacillus subtilis seed culture was obtained with a concentration of 0.64. The fermentation medium obtained in Preparation Example 5 was loaded into the fermenter, and the loading volume was controlled to be two-thirds of the total volume of the fermenter. Then, 6% of the volume of the fermentation medium in the fermenter was inoculated into the fermenter and mixed with the fermentation medium. The temperature of the fermenter was controlled at 35°C, and the culture was timed for 26 hours to obtain the fermentation nutrient solution.

[0070] Preparation Example 15

[0071] The fermentation nutrient solution is prepared as follows:

[0072] On a clean bench, a loopful of Bacillus subtilis strain CICC 24713 was picked up with a sterilized inoculation loop and inoculated into the LB solid medium obtained in Preparation Example 1. The medium was then placed in a 30°C incubator and incubated statically for 24 hours to obtain activated Bacillus subtilis. Next, a loopful of activated Bacillus subtilis was inoculated into the MRS liquid medium obtained in Preparation Example 2 using a sterilized inoculation loop. The medium was then placed in a 35°C incubator and incubated with shaking at 100 rpm until OD (dose retardation) was achieved. 600 The Bacillus subtilis seed culture was obtained with a concentration of 0.66. The fermentation medium obtained in Preparation Example 6 was loaded into the fermenter, and the loading volume was controlled to be two-thirds of the total volume of the fermenter. Then, 6% of the volume of the fermentation medium in the fermenter was inoculated into the fermenter and mixed with the fermentation medium. The temperature of the fermenter was controlled at 35°C, and the culture was timed for 27 hours to obtain the fermentation nutrient solution.

[0073] Preparation Example 16

[0074] The fermentation nutrient solution is prepared as follows:

[0075] On a clean bench, a loopful of Bacillus subtilis strain CICC 24713 was picked up with a sterilized inoculation loop and inoculated into the LB solid medium obtained in Preparation Example 1. The medium was then placed in a 30°C incubator and incubated statically for 24 hours to obtain activated Bacillus subtilis. Next, a loopful of activated Bacillus subtilis was inoculated into the MRS liquid medium obtained in Preparation Example 2 using a sterilized inoculation loop. The medium was then placed in a 35°C incubator and incubated with shaking at 100 rpm until OD (dose retardation) was achieved. 600The Bacillus subtilis seed culture was obtained with a concentration of 0.68. The fermentation medium obtained in Preparation Example 7 was loaded into the fermenter, and the loading volume was controlled to be two-thirds of the total volume of the fermenter. Then, 7% of the volume of the fermentation medium in the fermenter was inoculated into the fermenter and mixed with the fermentation medium. The temperature of the fermenter was controlled at 35°C, and the culture was timed for 28 hours to obtain the fermentation nutrient solution.

[0076] Preparation Example 17

[0077] The fermentation nutrient solution is prepared as follows:

[0078] On a clean bench, a loopful of Bacillus subtilis strain CICC 24713 was picked up with a sterilized inoculation loop and inoculated into the LB solid medium obtained in Preparation Example 1. The medium was then placed in a 30°C incubator and incubated statically for 24 hours to obtain activated Bacillus subtilis. Next, a loopful of activated Bacillus subtilis was inoculated into the MRS liquid medium obtained in Preparation Example 2 using a sterilized inoculation loop. The medium was then placed in a 35°C incubator and incubated with shaking at 100 rpm until OD (dose retardation) was achieved. 600 The Bacillus subtilis seed culture was obtained by adding 0.7% of the fermentation medium obtained in Example 8 into a fermenter, controlling the amount added to be two-thirds of the total volume of the fermenter. Then, 7% of the volume of the fermentation medium in the fermenter was inoculated into the fermenter and mixed with the fermentation medium. The temperature of the fermenter was controlled at 35°C, and the culture was timed for 28 hours to obtain the fermentation nutrient solution.

[0079] Preparation Example 18

[0080] The fermentation nutrient solution is prepared as follows:

[0081] The fermentation medium in Preparation Example 17 was replaced with the fermentation medium obtained in Preparation Example 9, and the rest of the preparation process was the same as in Preparation Example 17.

[0082] Preparation Example 19

[0083] The fermentation nutrient solution is prepared as follows:

[0084] The fermentation medium in Preparation Example 17 was replaced with the fermentation medium obtained in Preparation Example 10, and the rest of the preparation process was the same as in Preparation Example 17.

[0085] Preparation Example 20

[0086] The fermentation nutrient solution is prepared as follows:

[0087] The fermentation medium in Preparation Example 17 was replaced with the fermentation medium obtained in Preparation Example 11, and the rest of the preparation process was the same as in Preparation Example 17.

[0088] Preparation Example 21

[0089] The fermentation nutrient solution is prepared as follows:

[0090] On a clean bench, a loopful of Bacillus subtilis strain CICC 24713 was picked up with a sterilized inoculation loop and inoculated into the LB solid medium obtained in Preparation Example 1. The medium was then placed in a 30°C incubator and incubated statically for 24 hours to obtain activated Bacillus subtilis. Next, a loopful of activated Bacillus subtilis was inoculated into the MRS liquid medium obtained in Preparation Example 2 using a sterilized inoculation loop. The medium was then placed in a 35°C incubator and incubated with shaking at 100 rpm until OD (dose retardation) was achieved. 600 Bacillus subtilis seed culture was obtained with a concentration of 0.8. The fermentation medium obtained in Preparation Example 8 was loaded into the fermenter, and the loading volume was controlled to be two-thirds of the total volume of the fermenter. Then, 7% of the volume of Bacillus subtilis seed culture in the fermenter was inoculated into the fermenter and mixed with the fermentation medium. The temperature of the fermenter was controlled at 35°C, and the culture was timed for 28 hours to obtain the fermentation nutrient solution.

[0091] Preparation Example 22

[0092] The fermentation nutrient solution is prepared as follows:

[0093] On a clean bench, a loopful of Bacillus subtilis strain CICC 24713 was picked up with a sterilized inoculation loop and inoculated into the LB solid medium obtained in Preparation Example 1. The medium was then placed in a 30°C incubator and incubated statically for 24 hours to obtain activated Bacillus subtilis. Next, a loopful of activated Bacillus subtilis was inoculated into the MRS liquid medium obtained in Preparation Example 2 using a sterilized inoculation loop. The medium was then placed in a 35°C incubator and incubated with shaking at 100 rpm until OD (dose retardation) was achieved. 600 The Bacillus subtilis seed culture was obtained by adding 0.7. The fermentation medium obtained in Preparation Example 8 was loaded into the fermenter, and the loading amount was controlled to be two-thirds of the total volume of the fermenter. Then, 10% of the volume of the fermentation medium in the fermenter was inoculated into the fermenter with Bacillus subtilis seed culture and mixed with the fermentation medium. The temperature of the fermenter was controlled at 35°C and cultured for 30 hours to obtain the fermentation nutrient solution.

[0094] Preparation Example 23

[0095] The preparation of pretreated coal-based solid waste is as follows:

[0096] Weigh 10 parts by weight of fly ash and 60 parts by weight of hydrochloric acid solution with pH 4 and mix them together. Mix at 100 r / min for 1 hour. After treatment, transfer to an ultrasonic disperser and treat at 600 W for another 2 hours. After treatment, filter the cake and wash it repeatedly with deionized water until the pH of the washing liquid reaches neutral. Then, let it stand naturally in deionized water for 24 hours to settle. Take out the supernatant and dry the bottom sediment in a dryer at 55℃ for 24 hours to obtain pretreated coal-based solid waste.

[0097] Preparation Example 24

[0098] The preparation of pretreated coal-based solid waste is as follows:

[0099] Ten parts by weight of fly ash and 65 parts by weight of hydrochloric acid solution with a pH of 3 were weighed and mixed together at a speed of 100 r / min for 1.5 h. After treatment, the mixture was transferred to an ultrasonic disperser and treated at an ultrasonic power of 650 W for another 2.5 h. After treatment, the filter cake was collected by filtration and repeatedly washed with deionized water until the pH of the washing waste liquid reached neutral. Then, it was placed in deionized water to settle naturally for 24 h. The supernatant was taken out, and the bottom sediment was placed in a dryer at 55℃ and dried for 24 h to obtain pretreated coal-based solid waste.

[0100] Preparation Example 25

[0101] The preparation of pretreated coal-based solid waste is as follows:

[0102] Weigh 10 parts by weight of fly ash and 70 parts by weight of hydrochloric acid solution with pH 3 and mix them together at a speed of 100 r / min for 2 hours. After treatment, transfer the mixture to an ultrasonic disperser and treat it at an ultrasonic power of 700 W for another 3 hours. After treatment, filter the mixture and collect the filter cake. Rinse the filter cake repeatedly with deionized water until the pH of the rinsing waste liquid reaches neutral. Then, let it stand naturally in deionized water for 24 hours to settle. Take out the supernatant and dry the bottom sediment in a dryer at 55℃ for 24 hours to obtain pretreated coal-based solid waste.

[0103] Example 1

[0104] A method for preparing a compound microbial fertilizer specifically includes the following steps:

[0105] 20 parts by weight of the fermentation nutrient solution obtained in Preparation Example 12, 5 parts by weight of the pretreated coal-based solid waste obtained in Preparation Example 23, and 9 parts by weight of potassium humate were mixed and stirred evenly. The mixture was then dried until the moisture content reached 16%, transferred to a granulator for granulation, and screened through a 4.75 mm square hole sieve to obtain the compound microbial fertilizer.

[0106] Example 2

[0107] A method for preparing a compound microbial fertilizer specifically includes the following steps:

[0108] 20 parts by weight of the fermentation nutrient solution obtained in Preparation Example 13, 5 parts by weight of the pretreated coal-based solid waste obtained in Preparation Example 23, and 9 parts by weight of potassium humate were mixed and stirred evenly. The mixture was then dried until the moisture content reached 16%, transferred to a granulator for granulation, and screened through a 4.75 mm square hole sieve to obtain the compound microbial fertilizer.

[0109] Example 3

[0110] A method for preparing a compound microbial fertilizer specifically includes the following steps:

[0111] 22 parts by weight of the fermentation nutrient solution obtained in Preparation Example 14, 6 parts by weight of the pretreated coal-based solid waste obtained in Preparation Example 24, and 10 parts by weight of potassium humate were mixed and stirred evenly. The mixture was then dried until the moisture content reached 17%, transferred to a granulator for granulation, and screened through a 4.75 mm square hole sieve to obtain the compound microbial fertilizer.

[0112] Example 4

[0113] A method for preparing a compound microbial fertilizer specifically includes the following steps:

[0114] 22 parts by weight of the fermentation nutrient solution obtained in Preparation Example 15, 6 parts by weight of the pretreated coal-based solid waste obtained in Preparation Example 24, and 10 parts by weight of potassium humate were mixed and stirred evenly. The mixture was then dried until the moisture content reached 17%, transferred to a granulator for granulation, and screened through a 4.75 mm square hole sieve to obtain the compound microbial fertilizer.

[0115] Example 5

[0116] A method for preparing a compound microbial fertilizer specifically includes the following steps:

[0117] 24 parts by weight of the fermentation nutrient solution obtained in Preparation Example 16, 7 parts by weight of the pretreated coal-based solid waste obtained in Preparation Example 25, and 11 parts by weight of potassium humate were mixed and stirred evenly. The mixture was then dried until the moisture content reached 18%, transferred to a granulator for granulation, and screened through a 4.75 mm square hole sieve to obtain the compound microbial fertilizer.

[0118] Example 6

[0119] A method for preparing a compound microbial fertilizer specifically includes the following steps:

[0120] 24 parts by weight of the fermentation nutrient solution obtained in Preparation Example 17, 7 parts by weight of the pretreated coal-based solid waste obtained in Preparation Example 25, and 11 parts by weight of potassium humate were mixed and stirred evenly. The mixture was then dried until the moisture content reached 18%, transferred to a granulator for granulation, and screened through a 4.75 mm square hole sieve to obtain the compound microbial fertilizer.

[0121] Comparative Example 1

[0122] A method for preparing a compound microbial fertilizer specifically includes the following steps:

[0123] 24 parts by weight of the fermentation nutrient solution obtained in Preparation Example 18, 7 parts by weight of the pretreated coal-based solid waste obtained in Preparation Example 25, and 11 parts by weight of potassium humate were mixed and stirred evenly. The mixture was then dried until the moisture content reached 18%, transferred to a granulator for granulation, and screened through a 4.75 mm square hole sieve to obtain the compound microbial fertilizer.

[0124] Comparative Example 2

[0125] A method for preparing a compound microbial fertilizer specifically includes the following steps:

[0126] 24 parts by weight of the fermentation nutrient solution obtained in Preparation Example 19, 7 parts by weight of the pretreated coal-based solid waste obtained in Preparation Example 25, and 11 parts by weight of potassium humate were mixed and stirred evenly. The mixture was then dried until the moisture content reached 18%, transferred to a granulator for granulation, and screened through a 4.75 mm square hole sieve to obtain the compound microbial fertilizer.

[0127] Comparative Example 3

[0128] A method for preparing a compound microbial fertilizer specifically includes the following steps:

[0129] 24 parts by weight of the fermentation nutrient solution obtained in Preparation Example 20, 7 parts by weight of the pretreated coal-based solid waste obtained in Preparation Example 25, and 11 parts by weight of potassium humate were mixed and stirred evenly. The mixture was then dried until the moisture content reached 18%, transferred to a granulator for granulation, and screened through a 4.75 mm square hole sieve to obtain the compound microbial fertilizer.

[0130] Comparative Example 4

[0131] A method for preparing a compound microbial fertilizer specifically includes the following steps:

[0132] 24 parts by weight of the fermentation nutrient solution obtained in Preparation Example 21, 7 parts by weight of the pretreated coal-based solid waste obtained in Preparation Example 25, and 11 parts by weight of potassium humate were mixed and stirred evenly. The mixture was then dried until the moisture content reached 18%, transferred to a granulator for granulation, and screened through a 4.75 mm square hole sieve to obtain the compound microbial fertilizer.

[0133] Comparative Example 5

[0134] A method for preparing a compound microbial fertilizer specifically includes the following steps:

[0135] 24 parts by weight of the fermentation nutrient solution obtained in Preparation Example 22, 7 parts by weight of the pretreated coal-based solid waste obtained in Preparation Example 25, and 11 parts by weight of potassium humate were mixed and stirred evenly. The mixture was then dried until the moisture content reached 18%, transferred to a granulator for granulation, and screened through a 4.75 mm square hole sieve to obtain the compound microbial fertilizer.

[0136] (1) Fertilizer index verification

[0137] According to the "Compound Microbial Fertilizer NY / T798-2015", the viable count and pH of the compound microbial fertilizers obtained in Examples 1-6 and Comparative Examples 1-5 were tested (the fertilizer and water were mixed and stirred evenly at 25°C according to a mass ratio of 1:5 and then allowed to stand for 30 minutes before measurement). The results are shown in Table 1 below.

[0138]

[0139] (2) Fertilizer efficacy verification:

[0140] Mix 5 kg of soil and 100 g of compound microbial fertilizer evenly and fill the pot with a diameter of 35 cm and a height of 40 cm. Control the water holding capacity at 70 ± 2%. Sow corn seeds to a depth of 5 cm. Then, cultivate the plants in an environment with a humidity of 60 ± 5% and a temperature of 28 ± 2℃ for 50 days. Measure the fresh weight and plant height. The results are shown in Table 2 below.

[0141]

[0142] Based on Tables 1 and 2 above, the following conclusions can be drawn:

[0143] (1) As can be seen from Examples 1 to 6, the compound microbial fertilizer prepared by the present invention has good viable bacteria count and fertilizer effect.

[0144] (2) Comparative Example 1 shows that the number of viable bacteria in the fertilizer and the corresponding fertilizer efficiency are poor. This may be because although magnesium sulfate helps Bacillus subtilis to activate enzyme metabolism and improve energy metabolism, excessive magnesium sulfate may increase the osmotic pressure of the fermentation broth. The high osmotic pressure environment will force Bacillus subtilis to consume a lot of energy to synthesize or accumulate compatible solutes to maintain intracellular osmotic pressure balance. This will lead to energy diversion, reducing the energy used for cell growth and product synthesis, and ultimately resulting in a decrease in the growth rate of the bacteria. On the other hand, excessive magnesium ions may interfere with the absorption and utilization of other cations, disrupt the intracellular ion balance, affect signal transduction and inhibit enzyme activity, which may lead to abnormal cell morphology, cell membrane damage, and decreased vitality, thereby affecting the fertilizer efficiency.

[0145] (3) Comparative Example 2 shows that the number of viable bacteria in the fertilizer and the corresponding fertilizer effect are poor. This may be because although iron is a cofactor of many key enzymes and helps to improve the fermentation of Bacillus subtilis, excessive iron will lead to oxidative stress and the production of free radicals. These free radicals will attack and damage important biomolecules such as cell membrane lipids, proteins and DNA, causing oxidative damage and interfering with the normal metabolic activities of cells. This oxidative damage will inhibit the growth and reproduction of Bacillus subtilis and the vitality of the bacteria itself, resulting in poor fertilizer effect.

[0146] (4) Comparative Example 3 shows that the number of viable bacteria in the fertilizer and the corresponding fertilizer effect are poor. This may be because although the baijiu lees are rich in nutrients such as protein and amino acids, which are beneficial to the fermentation of microorganisms, too much baijiu lees may not only cause the fermentation medium to be too viscous, affecting oxygen diffusion and nutrient absorption, leading to slow growth of microorganisms, but also cause an imbalance in the carbon-nitrogen ratio, affecting the normal metabolism of Bacillus subtilis, thus resulting in poor fertilizer effect.

[0147] (5) Comparative Example 4 shows that the number of viable bacteria in the fertilizer and the corresponding fertilizer effect are poor. This may be because if the OD600 of the bacterial solution is too high when preparing the seed solution, the bacterial density may be too high. The high bacterial density may not only significantly increase the viscosity of the culture medium, affecting the stirring efficiency and oxygen transfer rate, but also cause the high-density bacteria to rapidly consume the dissolved oxygen in the culture medium, leading to the formation of an anaerobic environment, which affects the aerobic metabolism of Bacillus subtilis. In addition, high-density culture is prone to the accumulation of organic acids, which leads to a decrease in the pH of the culture medium, inhibiting the growth and metabolism of bacteria, and thus the fertilizer effect is poor.

[0148] (6) Comparative Example 5 shows that the number of viable bacteria in the fertilizer and the corresponding fertilizer effect are poor. This may be because, on the one hand, excessive inoculation leads to rapid proliferation of bacteria, which can easily consume a large amount of dissolved oxygen in a short period of time, forming a local anaerobic area, affecting the normal metabolism of bacteria. In addition, excessive inoculation can lead to the rapid accumulation of metabolic byproducts such as organic acids, which inhibits the growth and metabolism of bacteria. On the other hand, if the culture time is too long, more bacteria are prone to enter the death phase due to the rapid consumption of nutrients. The bacteria may undergo autolysis and become contaminated, weakening the activity and metabolic vitality of the bacteria, thus resulting in poor fertilizer effect.

[0149] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing a compound microbial fertilizer, characterized in that, The preparation method includes the following steps: Fermentation nutrient solution, pretreated coal-based solid waste and mineral potassium fertilizer are mixed and stirred in a weight ratio of 20~24:5~7:9~11, dried until the moisture content reaches 16%~18%, and then granulated and screened to obtain the compound microbial fertilizer. The preparation method of the fermentation nutrient solution includes the following steps: Bacillus subtilis was inoculated into LB solid medium and cultured at 30°C for 24 h to obtain activated Bacillus subtilis; Activated Bacillus subtilis was inoculated into MRS liquid medium and cultured at 35°C until OD500. 600 The concentration of Bacillus subtilis seed culture was 0.6-0.

7. The Bacillus subtilis seed culture was inoculated into a fermentation medium and cultured at 35°C for 24-28 hours to obtain the fermentation nutrient solution. The method for preparing the fermentation medium includes the following steps: The fermentation medium is prepared by mixing baijiu lees, soluble starch, magnesium sulfate heptahydrate, ferric chloride hexahydrate, and deionized water in a weight ratio of 90-95:10-15:0.2-0.4:0.02-0.04:100-105, adjusting the pH to 6.5-7.0, and then sterilizing at 121℃ for 20 minutes. The method for preparing the pretreated coal-based solid waste includes the following steps: Coal-based solid waste and acid solution are mixed at a solid-liquid mass ratio of 1:6~7 and stirred at 100 r / min for 1h~2h. Then, the mixture is transferred to an ultrasonic disperser and treated at 600W~700W for 2h~3h. The sediment is then collected and dried at 55℃ for 24h to obtain the pretreated coal-based solid waste. The amount of Bacillus subtilis seed liquid inoculated into the fermentation medium is 5% to 7% of the volume of the fermentation medium.

2. The method for preparing a compound microbial fertilizer according to claim 1, characterized in that, The strain number of the Bacillus subtilis is CICC 24713.

3. The method for preparing a compound microbial fertilizer according to claim 1, characterized in that, The coal-based solid waste includes fly ash.

4. The method for preparing a compound microbial fertilizer according to claim 1, characterized in that, The acid solution includes a hydrochloric acid solution with a pH of 3 to 4.

5. The method for preparing a compound microbial fertilizer according to claim 1, characterized in that, The mineral potassium fertilizer includes potassium humate.

6. A compound microbial fertilizer, characterized in that, The compound microbial fertilizer is prepared by the method for preparing a compound microbial fertilizer according to any one of claims 1 to 5.

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