Microbial fertilizer for promoting growth of plants in saline-alkali soil and preparation method of microbial fertilizer

Abstract

The invention relates to the technical field of agricultural soil improvement, and particularly discloses a microbial fertilizer for promoting growth of plants in saline-alkali soil and a preparation method. The microbial fertilizer comprises a compound microbial agent, a decomposed organic fertilizer, organic acid, a sulfuric acid compound, urea, seaweed meal, fruit and vegetable residues, earthworm soil, polyglutamic acid and biochar, and all the raw materials have a synergistic effect to form a stable system. The preparation method comprises the following steps: performing pre-activation and carrier adsorption on the microbial inoculum, pre-treating the raw materials, mixing, and performing segmented temperature control drying, conditioning acid integration, granulation and carbon dioxide induced after-ripening to finally obtain the finished product. The microbial fertilizer can be used for saline-alkali soil improvement and plant growth promotion, can relieve saline-alkali stress, provides guarantee for microbial colonization, improves the physical and chemical environment of soil, improves the fertility of the soil, and is stable in microbial activity. In addition, the preparation method can protect the activity of the microbial inoculum in the whole process, avoids inactivation of the microbial inoculum in the processing process, and is convenient to operate and convenient for industrial large-scale production.

Description

Technical Field

[0001] This application relates to the field of agricultural soil improvement technology, and more specifically, to a microbial fertilizer for promoting plant growth in saline-alkali land and its preparation method. Background Technology

[0002] Saline-alkali land is a widely distributed type of low-yield soil. Its high salt and high alkalinity properties damage soil aggregate structure and inhibit soil microbial activity, thereby affecting plant nutrient absorption and utilization. Microbial fertilizers, with their multiple functions of reducing salt content, improving soil quality, fixing nitrogen, and promoting growth, have become an important technical means for improving saline-alkali land. Currently, most related products are made by combining compound microbial agents with organic fertilizers and inorganic salts. They utilize the metabolic activities of functional bacteria to regulate soil ion balance, improve soil fertility, and provide support for crop growth in saline-alkali land.

[0003] However, existing microbial fertilizers for saline-alkali land generally suffer from a core problem: the functional microorganisms lack stability under saline-alkali stress, making it difficult for them to colonize and maintain their effects over the long term. On the one hand, the high osmotic pressure and high pH of saline-alkali land easily inhibit microbial metabolism and reproduction, leading to a rapid decline in their activity. On the other hand, conventional fertilizers lack targeted microbial protection mechanisms, and the functional microorganisms are easily inactivated by external factors during processing, storage, and field application. Ultimately, this prevents the fertilizer from fully realizing its soil-improving and efficiency-enhancing effects, failing to meet the actual needs of saline-alkali land improvement. Summary of the Invention

[0004] To address the problems of insufficient stability of functional microorganisms under saline-alkali stress, difficulty in long-term colonization, and inability to continuously exert soil-improving and growth-promoting effects in existing technologies, this application provides a microbial fertilizer for promoting plant growth in saline-alkali land and its preparation method.

[0005] In a first aspect, this application provides a microbial fertilizer for promoting the growth of plants in saline-alkali land, employing the following technical solution:

[0006] A microbial fertilizer for promoting plant growth in saline-alkali land comprises the following raw materials in parts by weight: 8-13 parts compound microbial agent, 5.2-6.0 parts decomposed organic fertilizer, 2.2-3.2 parts organic acid, 1.2-3.2 parts sulfuric acid compound, 1-16 parts urea, 4.2-5.2 parts seaweed powder, 2.8-3.2 parts fruit and vegetable residue, 2.8-3.2 parts earthworm soil, 0.5-1.5 parts polyglutamic acid, and 2-4 parts biochar.

[0007] By adopting the above technical solution, the compound microbial agent, as the core functional component, can play a fundamental role in reducing salinity, promoting growth, fixing nitrogen, and improving soil. Polyglutamic acid has good water retention and chelating properties, which can lock in soil moisture, chelate available nutrients in the soil, and reduce nutrient loss. Biochar has a rich porous structure and can serve as a carrier for microorganisms, adsorbing and immobilizing them, reducing their inactivation in saline-alkali environments. The combination of well-rotted organic fertilizer, seaweed powder, fruit and vegetable residues, and earthworm soil provides sufficient nutrition for microbial growth. Organic acids and sulfuric acid compounds synergistically regulate the soil's physical and chemical environment, alleviating saline-alkali stress. The various raw materials complement each other without antagonistic effects, ensuring the colonization and efficacy of microorganisms in saline-alkali land.

[0008] Preferably, the compound microbial agent is composed of fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis and aerobic denitrifying bacteria, and the mass ratio of the fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis and aerobic denitrifying bacteria is (1-2):(2-3):(1-1.5):(1-2):(0.5-1).

[0009] By employing the above technical solutions, halophilic bacteria can decompose salt ions in the soil, reducing soil salinity; Bacillus subtilis can secrete growth-promoting substances, promoting plant root development; aerobic denitrifying bacteria can convert excess nitrogen in the soil, reducing the adverse effects of soil nitrogen accumulation; fermenting bacteria can accelerate the decomposition of organic matter in the soil, providing nutritional support for other functional bacteria; and probiotics can improve the soil microecological environment and inhibit the reproduction of harmful bacteria. The specific ratio allows the metabolic activities of the five bacterial species to synergize and complement each other, and the metabolic products of the five species to promote each other, further enhancing the comprehensive efficacy of the compound microbial agent.

[0010] Preferably, the organic acid is one or more of linoleic acid, linolenic acid, and oxalic acid, and the sulfuric acid compound is one or two of ferrous sulfate and zinc sulfate.

[0011] By employing the above technical solutions, oxalic acid can regulate soil pH and alleviate soil alkalinity stress. Linoleic acid and linolenic acid can enhance the stability of microbial cell membranes, reduce damage to microbial cells caused by saline-alkali environments, and thus maintain microbial activity. Ferrous sulfate and zinc sulfate can replenish soil minerals such as iron and zinc. These minerals can act as coenzymes for microbial metabolism and, together with organic acids, form complexes, reducing the concentration of free salt ions in the soil and minimizing the toxic effects of salt on plants and microorganisms. The combination of organic acids and sulfuric acid compounds can prevent sudden changes in soil pH and reduce stimulation to microorganisms and plant roots.

[0012] Preferably, the composted organic fertilizer is made from livestock and poultry manure, straw and soybean meal through high-temperature composting, wherein the mass ratio of livestock and poultry manure, straw and soybean meal is (3-5):(2-3):(1-2).

[0013] By adopting the above technical solutions, livestock and poultry manure, rich in organic matter and nutrients such as nitrogen, phosphorus, and potassium, can directly provide nutrition for microorganisms and plants. Straw can increase the porosity of organic fertilizer, improve soil aeration and water retention, and enhance the fertilizer retention capacity of organic fertilizer. Soybean meal is rich in plant protein, which can be decomposed into small-molecule amino acids after composting, making it easy for microorganisms to absorb and utilize, and rapidly accelerating the colonization rate of microorganisms. Specific proportions can make the nutrient composition of organic fertilizer more balanced, and the high-temperature composting process can kill miscellaneous bacteria and insect eggs in the raw materials, avoiding adverse effects of harmful microorganisms on soil microecology and plant growth.

[0014] Secondly, this application provides a method for preparing a microbial fertilizer for promoting plant growth in saline-alkali land, employing the following technical solution:

[0015] A method for preparing a microbial fertilizer for promoting plant growth in saline-alkali land includes the following steps:

[0016] S1. Pre-activation of microbial agent and adsorption by carrier: The compound microbial agent is mixed with some seaweed powder and polyglutamic acid, added to nutrient solution for activation treatment, and then mixed with biochar for adsorption to obtain a biochar carrier loaded with microbial agent.

[0017] S2. Raw material pretreatment and mixing: The decomposed organic fertilizer, sulfuric acid compound, urea, residual seaweed powder, fruit and vegetable residue and earthworm soil are crushed separately, and then mixed and stirred with biochar carrier loaded with bacterial agent and deionized water to obtain the initial mixture.

[0018] S3. Segmented temperature-controlled drying and activation: The initial mixture is dried in segments under relatively low and relatively high temperature conditions to obtain an activated dry mixture.

[0019] S4. Conditioning and acid integration: Add deionized water and organic acid to the activated dry mixture, mix evenly, and maintain the integration reaction at a preset temperature for a period of time to obtain the conditioned wet mixture.

[0020] S5. Granulation and Induction of Post-Ripening: The conditioning wet mixture is granulated, and the resulting granules are placed in a preset temperature and humidity environment for post-ripening treatment. Air containing a low concentration of carbon dioxide is introduced at the beginning of the post-ripening treatment, and then the entire post-ripening process is completed to obtain microbial fertilizer.

[0021] By employing the above technical solutions, the microbial agent is first pre-activated, which awakens dormant microorganisms and enhances their metabolic activity. Then, the adsorption properties of biochar are used to fix the activated microbial agent in its porous structure, forming a stable loading system and reducing the inactivation of the microbial agent during subsequent processing. Pulverizing the raw materials increases the contact area, making the various components more uniformly mixed and facilitating the absorption and utilization of nutrients by microorganisms. Segmented temperature-controlled drying avoids damage to the activity of the microbial agent caused by single high-temperature drying, while simultaneously activating the components. Conditioning and acid integration allow organic acids and mineral elements to fully combine, while adjusting the material's moisture content, providing suitable conditions for subsequent granulation. Granulation improves the convenience of fertilizer storage and application, and low-concentration carbon dioxide-induced ripening promotes the adaptation of microorganisms to saline-alkali environments, extending their colonization time in the soil. Each step is interconnected, with each step providing suitable conditions for the next, ensuring the stability and sustained efficacy of the final product.

[0022] Preferably, in step S1, the activation treatment is performed at a temperature of 30-35°C for 1-2 hours; the nutrient solution is an aqueous solution containing yeast extract and potassium dihydrogen phosphate, and the amount added is 20-40% of the total mass of the bacterial agent and seaweed powder.

[0023] By adopting the above technical solutions, a suitable temperature can rapidly awaken microbial activity while avoiding high-temperature damage to the microbial agent. Sufficient activation time ensures full microbial recovery, preventing insufficient activation from affecting subsequent efficacy. Yeast extract provides microorganisms with carbon, nitrogen, and growth factors, meeting their nutritional needs during activation. Potassium dihydrogen phosphate regulates the osmotic pressure of the nutrient solution, reducing microbial cell dehydration and inactivation. Appropriate nutrient solution addition avoids nutrient overload leading to microbial metabolic disorders. Seaweed powder provides natural protective substances, synergistically forming a triple protection system with polyglutamic acid and biochar, reducing the activity loss of the microbial agent during subsequent processing.

[0024] Preferably, in step S2, the particle size of the pulverized material is 0.1-0.5 mm, the stirring speed is 150-200 r / min, and the stirring time is 50-65 min.

[0025] By adopting the above technical solutions, uniform particle size avoids uneven mixing of components and increases the contact area between raw materials and microbial agents, facilitating agent adhesion and nutrient absorption. Appropriate stirring speed ensures thorough mixing, preventing localized raw material concentration imbalances from adversely affecting agent activity. Sufficient stirring time ensures complete integration of the biochar carrier loaded with microbial agents with other raw materials, resulting in uniform distribution of the agent throughout the material system. A homogeneous material system avoids metabolic competition caused by excessively high local agent concentrations, ensuring stable agent activity and providing a good foundation for subsequent processes.

[0026] Preferably, in step S3, the relatively low temperature is 60-70℃ and the processing time is 2-3 hours; the relatively high temperature is 80-90℃ and the processing time is 1-2 hours; the initial mixture is spread to a thickness of 2-3 cm and is turned over during the processing.

[0027] By employing the above technical solutions, lower temperatures can slowly remove most of the free moisture in the initial mixture, reducing material clumping. Higher temperatures can further remove residual moisture and activate the components, while simultaneously breaking down the structure of harmful impurities in the raw materials and avoiding damage to the activity of the microbial agent from prolonged high-temperature treatment. Appropriate spreading thickness ensures uniform heating of the material, preventing insufficient drying of the lower layers. Turning and tossing further ensures uniform heating of all parts of the material, promotes the volatilization of volatile harmful substances, and allows the components in the material to fully contact, promoting uniform activation reactions and enhancing the activity of the dry mixture.

[0028] Preferably, in step S4, the preset temperature is 40-45℃, the maintenance period is 20-30 minutes, and the moisture content of the conditioned wet mixture obtained after conditioning is 25-30%.

[0029] By adopting the above technical solution, a suitable reaction temperature can promote the full complexation reaction between organic acids and mineral elements, accelerating the reaction rate while preventing the decomposition of the complex. Sufficient reaction time ensures the complexation reaction proceeds fully, allowing the mineral elements to remain stably in the material system, facilitating subsequent absorption and utilization by plants. A suitable moisture content gives the conditioned wet mixture good viscosity and flowability, meeting the requirements of the granulation process, preventing material adhesion and clumping or brittle particles, while also preventing the microbial agent from suffering drying stress and preventing damage to the microbial agent due to compression during subsequent granulation, further ensuring the activity of the microbial agent.

[0030] Preferably, in step S5, the particle size of the granulated particles is 2-4 mm; the preset temperature and humidity environment is 25-30℃ and 60-70%; the volume concentration of carbon dioxide in the introduced air is 0.5-1.5%, the aeration time is 24-48 hours, and the total time of the entire post-ripening process is 72-96 hours.

[0031] By adopting the above technical solutions, the appropriate particle size facilitates field application, avoiding slow dissolution or dusting during application that could reduce utilization. Suitable temperature and humidity provide favorable conditions for microbial ripening, promoting further microbial reproduction and increasing inoculant content, while preventing the growth of unwanted microorganisms or inhibition of microbial metabolism. Low-concentration carbon dioxide can moderately regulate the intensity of microbial metabolism, promoting the synthesis of metabolites adapted to saline-alkali environments and enhancing their resistance. Sufficient aeration time and ripening time ensure that carbon dioxide plays its full role, allowing microorganisms to fully adapt to the material environment, form a stable microbial community structure, and rapidly reproduce in saline-alkali soils, continuously improving soil quality and promoting growth.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. This application uses a compound microbial agent formulated in a specific mass ratio, and synergistically adds polyglutamic acid and biochar, which enables the microbial agent to more effectively perform multiple functions such as salt reduction, growth promotion, nitrogen fixation and soil improvement in saline-alkali land. At the same time, the water-retaining chelating properties of polyglutamic acid and the carrier adsorption effect of biochar together provide protection for microorganisms, significantly improving the stability and efficacy of fertilizer under stress.

[0034] 2. In this application, one or more of linoleic acid, linolenic acid, and oxalic acid are preferred as organic acids, and one or two of ferrous sulfate and zinc sulfate are preferred as sulfuric acid compounds. These components can regulate the soil ion balance and work together with other components in the raw materials to improve the physical and chemical properties of saline-alkali soil.

[0035] 3. In this application, it is preferred to use livestock and poultry manure, straw and soybean meal in a specific ratio to make organic fertilizer through high-temperature composting. Organic fertilizer can provide sufficient nutrients for microbial growth, improve soil aggregate structure, create a good soil environment for plant growth, and achieve the effect of improving soil fertility.

[0036] 4. The method of this application combines pre-activation of the microbial agent with adsorption on the carrier, and segmented temperature-controlled drying activation. Pre-activation can awaken the activity of microorganisms, biochar adsorption provides a protective carrier for microorganisms, and segmented temperature-controlled drying can remove moisture and avoid high temperature damage to the microbial agent. Therefore, the effect of maintaining the activity of the composite microbial agent is achieved.

[0037] 5. The method of this application, through granulation and low-concentration carbon dioxide-induced ripening, can improve the storage stability and ease of application of fertilizers, and carbon dioxide induction can regulate the metabolic state of microorganisms and enhance their adaptability to saline-alkali environments, thus achieving the effect of extending the shelf life of fertilizers and improving fertilizer efficiency. Attached Figure Description

[0038] Figure 1This is a flowchart of a method for preparing a microbial fertilizer for promoting plant growth in saline-alkali land, as provided in this application. Detailed Implementation

[0039] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0040] Technical Concept: Existing microbial fertilizers and preparation technologies for saline-alkali land plant growth suffer from a core problem: functional microorganisms struggle to establish stable colonization and maintain their efficacy under saline-alkali stress. This is primarily due to the high salt and alkali content of saline-alkali land, which inhibits microbial metabolism and reproduction, leading to rapid attenuation of inoculant activity. Furthermore, the raw material combinations lack synergy, the preparation process fails to protect inoculant activity, and some process steps are poorly designed, further exacerbating inactivation during processing, storage, and application, thus failing to meet the actual needs of saline-alkali land improvement.

[0041] This technical solution utilizes a composite microbial agent with specific components as the core functional carrier, synergistically adding polyglutamic acid and biochar. Leveraging the water-retaining chelating properties of polyglutamic acid and the porous adsorption effect of biochar, a protective system is constructed for the microorganisms. Simultaneously, it incorporates well-rotted organic fertilizer, organic acids, and other components to synergistically regulate the soil's physicochemical environment and provide sufficient nutrition. At the preparation process level, key steps such as pre-activation of the microbial agent, segmented temperature-controlled drying, and carbon dioxide-induced post-ripening are designed to protect the activity of the microorganisms throughout the process, awaken the metabolic capacity of the microbial agent, and promote its adaptation to the saline-alkali environment. Through the synergistic effect of raw materials and processes, stable colonization of microorganisms in saline-alkali land and sustained efficacy are achieved.

[0042] Example 1: This example provides a microbial fertilizer for promoting plant growth in saline-alkali land, made from the following raw materials in parts by weight: 10.5 parts compound microbial agent, 5.6 parts decomposed organic fertilizer, 3.0 parts organic acid, 2.2 parts sulfuric acid compound, 8.5 parts urea, 4.7 parts seaweed powder, 3.0 parts fruit and vegetable residue, 3.0 parts earthworm soil, 1.0 part polyglutamic acid, and 3.0 parts biochar.

[0043] The compound microbial agent consists of fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis, and aerobic denitrifying bacteria, with a mass ratio of 1.5:2.5:1.25:1.5:0.75 between the fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis, and aerobic denitrifying bacteria.

[0044] The preparation method of the compound microbial agent is as follows: freeze-dried powder strains of fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis, and aerobic denitrifying bacteria are inoculated into LB liquid medium. The fermenting bacteria and salt-solubilizing bacteria are cultured at 31℃ and 180 r / min with shaking for 24 h; the probiotics and Bacillus subtilis are cultured at 35℃ and 200 r / min with shaking for 18 h; and the aerobic denitrifying bacteria are cultured at 28℃ and 150 r / min in the dark with shaking for 36 h, yielding the desired results. The viable cell concentration of each bacterial suspension was determined using the plate count method. Then, the five bacterial suspensions were mixed thoroughly in a mass ratio of 1.5:2.5:1.25:1.5:0.75. 10% trehalose was added as a preservative to the mixed suspension, and after stirring to dissolve, the mixture was placed in a spray dryer. The inlet air temperature was controlled at 120℃ and the outlet air temperature at 60℃ for spray drying to obtain a composite microbial agent powder with a total viable cell count ≥1.0 × 10⁻⁶. 10 CFU / g;

[0045] Among them, oxalic acid is selected as the organic acid; ferrous sulfate is selected as the sulfuric acid compound.

[0046] Among them, the decomposed organic fertilizer is made from livestock and poultry manure, straw and soybean meal through high-temperature decomposition, and the mass ratio of livestock and poultry manure, straw and soybean meal is 4:2.5:1.5;

[0047] The preparation method of the decomposed organic fertilizer is as follows: weigh livestock and poultry manure, straw, and soybean meal according to a mass ratio of 4:2.5:1.5. Crush the straw to a particle size of 1-2 cm and the soybean meal to a particle size of 0.5 cm. Then mix them evenly with the livestock and poultry manure. Add deionized water to the mixture to adjust the moisture content to 58%. Pile the mixture into a pile with a length, width, and height of 3m × 2m × 1.5m for high-temperature decomposition. Start timing when the internal temperature of the pile reaches 65℃ and maintain this temperature range for 6 days of decomposition. Turn the pile over every 24 hours to ensure that all parts of the pile are heated evenly. Stop the decomposition when the pile temperature naturally drops to room temperature and the material is loose, dark brown, and has no obvious odor. Crush the decomposed material to a particle size of less than 0.5 cm to obtain the decomposed organic fertilizer.

[0048] The above-mentioned method for preparing a microbial fertilizer for promoting plant growth in saline-alkali land includes the following steps:

[0049] S1. Pre-activation of microbial agent and adsorption on carrier: The compound microbial agent is mixed with some seaweed powder and polyglutamic acid, added to nutrient solution for activation treatment, and then mixed with biochar for adsorption to obtain a biochar carrier loaded with microbial agent.

[0050] The activation treatment was carried out at a temperature of 32.5℃ for 1.5 hours. The nutrient solution was an aqueous solution containing yeast extract and potassium dihydrogen phosphate, with a yeast extract concentration of 5 g / L and a potassium dihydrogen phosphate concentration of 2 g / L. The amount of nutrient solution added was 30% of the total mass of the bacterial agent and seaweed powder. During the adsorption process, the mixture was continuously stirred for 10 minutes to ensure that the bacterial agent was uniformly loaded in the porous structure of the biochar.

[0051] S2. Raw material pretreatment and mixing: The decomposed organic fertilizer, sulfuric acid compound, urea, residual seaweed powder, fruit and vegetable residue and earthworm soil are crushed separately, and then mixed with biochar carrier loaded with bacterial agent and deionized water and stirred to obtain a preliminary mixture.

[0052] The crushing process was carried out using a universal crusher, and the particle size of the crushed material was 0.3 mm. The stirring speed was 175 r / min, and the stirring time was 57.5 min. The ambient temperature was controlled at 27.5℃ during the stirring process to avoid the temperature from affecting the activity of the microbial agent.

[0053] S3. Segmented temperature-controlled drying and activation: The initial mixture is dried in segments under relatively low and relatively high temperature conditions to obtain activated dry mixture.

[0054] The relatively low temperature was 65℃ and the processing time was 2.5 hours; the relatively high temperature was 85℃ and the processing time was 1.5 hours; the initial mixture was spread to a thickness of 2.5 cm; the mixture was turned over every 30 minutes during the process, with a turning depth of 1.2 cm, to ensure that the material was heated evenly and to remove bacteria and volatile harmful substances from the raw materials.

[0055] S4. Conditioning and Acid Integration: Add deionized water and organic acid to the activated dry mixture, mix evenly, and maintain the integration reaction at a preset temperature for a period of time to obtain a conditioned wet mixture.

[0056] The preset temperature was 42.5℃, and the holding time was 25 minutes. The moisture content of the conditioned wet mixture was 27.5%. Low-speed stirring was used during the integration reaction, with a rotation speed of 30 r / min, to promote the full complexation of organic acids and mineral elements.

[0057] S5. Granulation and Induction of Post-Ripening: The conditioning wet mixture is granulated, and the resulting granules are placed in a preset temperature and humidity environment for post-ripening treatment. Air containing a low concentration of carbon dioxide is introduced at the beginning of the post-ripening treatment, and then the entire post-ripening process is completed to obtain microbial fertilizer.

[0058] The granulation process uses a rotary drum granulator, producing granules with a diameter of 3mm. The preset temperature and humidity environment is 27.5℃ and 65% humidity. The volume concentration of carbon dioxide in the introduced air is 1.0%, and the ventilation time is 36 hours. The total time for the entire post-ripening process is 84 hours. During the post-ripening period, ventilation is carried out every 6 hours, with each ventilation lasting 12 minutes, to ensure the stable metabolic activity of microorganisms inside the granules.

[0059] Example 2: This example provides a microbial fertilizer for promoting plant growth in saline-alkali land, made from the following raw materials in parts by weight: 8 parts compound microbial agent, 5.2 parts decomposed organic fertilizer, 2.2 parts organic acid, 1.2 parts sulfuric acid compound, 1 part urea, 4.2 parts seaweed powder, 2.8 parts fruit and vegetable residue, 2.8 parts earthworm soil, 0.5 parts polyglutamic acid, and 2 parts biochar.

[0060] The compound microbial agent consists of fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis, and aerobic denitrifying bacteria, with a mass ratio of 1:2:1:1:0.5 between the fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis, and aerobic denitrifying bacteria.

[0061] The preparation method of the compound microbial agent is as follows: freeze-dried powder strains of fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis, and aerobic denitrifying bacteria are inoculated into LB liquid medium, respectively. The fermenting bacteria and salt-solubilizing bacteria are cultured at 29℃ and 160 r / min with shaking for 20 h; the probiotics and Bacillus subtilis are cultured at 35℃ and 200 r / min with shaking for 18 h; and the aerobic denitrifying bacteria are cultured at 28℃ and 150 r / min with shaking in the dark for 36 h. h, bacterial suspensions of each bacterial species were obtained separately. The viable cell concentration of each suspension was determined by plate counting. Then, the five bacterial suspensions were mixed evenly in a mass ratio of 1:2:1:1:0.5. Trehalose (10% by mass) was added to the mixed suspension as a preservative, stirred and dissolved, and then placed in a spray dryer. The inlet air temperature was controlled at 115℃ and the outlet air temperature at 58℃ for spray drying to obtain a compound microbial agent powder with a total viable cell count ≥1.0×10⁻⁶. 10 CFU / g;

[0062] Among them, linoleic acid was selected as the organic acid; zinc sulfate was selected as the sulfuric acid compound.

[0063] Among them, the decomposed organic fertilizer is made from livestock and poultry manure, straw and soybean meal through high-temperature decomposition, and the mass ratio of livestock and poultry manure, straw and soybean meal is 3:2:1;

[0064] The preparation method of the decomposed organic fertilizer is as follows: weigh livestock and poultry manure, straw, and soybean meal according to a mass ratio of 3:2:1. Crush the straw to a particle size of 1-2 cm and the soybean meal to a particle size of 0.5 cm. Then mix them evenly with the livestock and poultry manure. Add deionized water to the mixture to adjust the moisture content to 62%. Pile the mixture into a pile with a length, width, and height of 3m × 2m × 1.5m for high-temperature decomposition. Start timing when the internal temperature of the pile reaches 60℃ and maintain this temperature range for 8 days of decomposition. Turn the pile over every 12 hours during this period to ensure that all parts of the pile are heated evenly. Stop the decomposition when the pile temperature naturally drops to room temperature and the material is loose, dark brown, and has no obvious odor. Crush the decomposed material to a particle size of less than 0.5 cm to obtain the decomposed organic fertilizer.

[0065] The above-mentioned method for preparing a microbial fertilizer for promoting plant growth in saline-alkali land includes the following steps:

[0066] S1. Pre-activation of microbial agent and adsorption on carrier: The compound microbial agent is mixed with some seaweed powder and polyglutamic acid, added to nutrient solution for activation treatment, and then mixed with biochar for adsorption to obtain a biochar carrier loaded with microbial agent.

[0067] The activation treatment was carried out at a temperature of 30°C for 1 hour. The nutrient solution was an aqueous solution containing yeast extract and potassium dihydrogen phosphate, with a yeast extract concentration of 3 g / L and a potassium dihydrogen phosphate concentration of 1 g / L. The amount of nutrient solution added was 20% of the total mass of the bacterial agent and seaweed powder. During the adsorption process, the mixture was continuously stirred for 8 minutes to ensure that the bacterial agent was uniformly loaded in the porous structure of the biochar.

[0068] S2. Raw material pretreatment and mixing: The decomposed organic fertilizer, sulfuric acid compound, urea, residual seaweed powder, fruit and vegetable residue and earthworm soil are crushed separately, and then mixed with biochar carrier loaded with bacterial agent and deionized water and stirred to obtain a preliminary mixture.

[0069] The crushing process was carried out using a universal crusher, and the particle size of the crushed material was 0.1 mm. The stirring speed was 150 r / min, and the stirring time was 50 min. The ambient temperature was controlled at 25℃ during the stirring process to avoid the temperature being too high and affecting the activity of the microbial agent.

[0070] S3. Segmented temperature-controlled drying and activation: The initial mixture is dried in segments under relatively low and relatively high temperature conditions to obtain activated dry mixture.

[0071] The relatively low temperature is 60℃ and the treatment time is 2 hours; the relatively high temperature is 80℃ and the treatment time is 1 hour; the initial mixture is spread to a thickness of 2cm; the mixture is turned over every 30 minutes during the treatment process, with a turning depth of 1cm, to ensure that the material is heated evenly and to remove bacteria and volatile harmful substances from the raw materials.

[0072] S4. Conditioning and Acid Integration: Add deionized water and organic acid to the activated dry mixture, mix evenly, and maintain the integration reaction at a preset temperature for a period of time to obtain a conditioned wet mixture.

[0073] The preset temperature was 40℃, and the holding time was 20 minutes; the moisture content of the conditioned wet mixture was 25%; low-speed stirring was used during the integration reaction, with a rotation speed of 25 r / min, to promote the full complexation of organic acids and mineral elements.

[0074] S5. Granulation and Induction of Post-Ripening: The conditioning wet mixture is granulated, and the resulting granules are placed in a preset temperature and humidity environment for post-ripening treatment. Air containing a low concentration of carbon dioxide is introduced at the beginning of the post-ripening treatment, and then the entire post-ripening process is completed to obtain microbial fertilizer.

[0075] The granulation process uses a rotary drum granulator, resulting in granules with a diameter of 2mm. The preset temperature and humidity environment is 25℃ and 60% humidity. The volume concentration of carbon dioxide in the introduced air is 0.5%, and the ventilation time is 24 hours. The total time for the entire post-ripening process is 72 hours. During the post-ripening period, ventilation is carried out every 6 hours, with each ventilation lasting 10 minutes, to ensure the stable metabolic activity of microorganisms inside the granules.

[0076] Example 3: This example provides a microbial fertilizer for promoting plant growth in saline-alkali land, made from the following raw materials in parts by weight: 13 parts compound microbial agent, 6.0 parts decomposed organic fertilizer, 3.2 parts organic acid, 3.2 parts sulfuric acid compound, 16 parts urea, 5.2 parts seaweed powder, 3.2 parts fruit and vegetable residue, 3.2 parts earthworm soil, 1.5 parts polyglutamic acid, and 4 parts biochar.

[0077] The compound microbial agent consists of fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis, and aerobic denitrifying bacteria, with a mass ratio of 2:3:1.5:2:1 between the fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis, and aerobic denitrifying bacteria.

[0078] The preparation method of the compound microbial agent is as follows: freeze-dried powder strains of fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis, and aerobic denitrifying bacteria are inoculated into LB liquid medium, respectively. The fermenting bacteria and salt-solubilizing bacteria are cultured at 33℃ and 200 r / min with shaking for 28 h; the probiotics and Bacillus subtilis are cultured at 35℃ and 200 r / min with shaking for 18 h; and the aerobic denitrifying bacteria are cultured at 28℃ and 150 r / min with shaking in the dark for 36 h. h, bacterial suspensions of each bacterial species were obtained separately. The viable cell concentration of each bacterial suspension was determined by plate counting. Then, the five bacterial suspensions were mixed evenly in a mass ratio of 2:3:1.5:2:1. Trehalose (10% by mass) was added to the mixed bacterial suspension as a preservative. After stirring and dissolving, the mixture was placed in a spray dryer, and spray drying was performed with the inlet air temperature controlled at 125℃ and the outlet air temperature at 56℃ to obtain a compound microbial agent powder with a total viable cell count ≥1.0×10⁻⁶. 10 CFU / g;

[0079] Among them, linolenic acid was selected as the organic acid; ferrous sulfate was selected as the sulfuric acid compound.

[0080] Among them, the decomposed organic fertilizer is made from livestock and poultry manure, straw and soybean meal through high-temperature decomposition, and the mass ratio of livestock and poultry manure, straw and soybean meal is 5:3:2;

[0081] The preparation method of the decomposed organic fertilizer is as follows: weigh livestock and poultry manure, straw, and soybean meal according to a mass ratio of 5:3:2. Crush the straw to a particle size of 1-2 cm and the soybean meal to a particle size of 0.5 cm. Then mix them evenly with the livestock and poultry manure. Add deionized water to the mixture to adjust the moisture content to 52%. Pile the mixture into a pile with a length, width, and height of 3m × 2m × 1.5m for high-temperature decomposition. Start timing when the internal temperature of the pile reaches 70℃ and maintain this temperature range for 5 days of decomposition. Turn the pile over once every 24 hours to ensure that all parts of the pile are heated evenly. Stop the decomposition when the pile temperature naturally drops to room temperature and the material is loose, dark brown, and has no obvious odor. Crush the decomposed material to a particle size of less than 0.5 cm to obtain the decomposed organic fertilizer.

[0082] The above-mentioned method for preparing a microbial fertilizer for promoting plant growth in saline-alkali land includes the following steps:

[0083] S1. Pre-activation of microbial agent and adsorption on carrier: The compound microbial agent is mixed with some seaweed powder and polyglutamic acid, added to nutrient solution for activation treatment, and then mixed with biochar for adsorption to obtain a biochar carrier loaded with microbial agent.

[0084] The activation treatment was carried out at a temperature of 35℃ for 2 hours. The nutrient solution was an aqueous solution containing yeast extract and potassium dihydrogen phosphate, with a yeast extract concentration of 8 g / L and a potassium dihydrogen phosphate concentration of 3 g / L. The amount of nutrient solution added was 40% of the total mass of the bacterial agent and seaweed powder. During the adsorption process, the mixture was continuously stirred for 12 minutes to ensure that the bacterial agent was uniformly loaded in the porous structure of the biochar.

[0085] S2. Raw material pretreatment and mixing: The decomposed organic fertilizer, sulfuric acid compound, urea, residual seaweed powder, fruit and vegetable residue and earthworm soil are crushed separately, and then mixed with biochar carrier loaded with bacterial agent and deionized water and stirred to obtain a preliminary mixture.

[0086] The crushing process was carried out using a universal crusher, resulting in a particle size of 0.5 mm. The stirring speed was 200 r / min, and the stirring time was 65 min. The ambient temperature was controlled at 30℃ during the stirring process to avoid excessively high temperatures affecting the activity of the microbial agent.

[0087] S3. Segmented temperature-controlled drying and activation: The initial mixture is dried in segments under relatively low and relatively high temperature conditions to obtain activated dry mixture.

[0088] The relatively low temperature was 70℃ and the treatment time was 3 hours; the relatively high temperature was 90℃ and the treatment time was 2 hours; the initial mixture was spread to a thickness of 3cm; the mixture was turned over every 30 minutes during the treatment process, with a turning depth of 1.5cm, to ensure that the material was heated evenly and to remove bacteria and volatile harmful substances from the raw materials.

[0089] S4. Conditioning and Acid Integration: Add deionized water and organic acid to the activated dry mixture, mix evenly, and maintain the integration reaction at a preset temperature for a period of time to obtain a conditioned wet mixture.

[0090] The preset temperature was 45℃, and the holding time was 30 minutes; the moisture content of the conditioned wet mixture was 30%; and low-speed stirring at 35 r / min was used during the integration reaction to promote the full complexation of organic acids and mineral elements.

[0091] S5. Granulation and Induction of Post-Ripening: The conditioning wet mixture is granulated, and the resulting granules are placed in a preset temperature and humidity environment for post-ripening treatment. Air containing a low concentration of carbon dioxide is introduced at the beginning of the post-ripening treatment, and then the entire post-ripening process is completed to obtain microbial fertilizer.

[0092] The granulation process uses a rotary drum granulator, producing granules with a diameter of 4mm. The preset temperature and humidity environment is 30℃ and 70% humidity. The volume concentration of carbon dioxide in the introduced air is 1.5%, and the ventilation time is 48 hours. The total time for the entire post-ripening process is 96 hours. During the post-ripening period, ventilation is carried out every 6 hours, with each ventilation lasting 15 minutes, to ensure the stable metabolic activity of microorganisms inside the granules.

[0093] Comparative Example 1: The only difference between this comparative example and Example 1 is that polyglutamic acid is not added to the raw materials, while the types and amounts of the other raw materials are exactly the same as in Example 1.

[0094] Comparative Example 2: The only difference between this comparative example and Example 1 is that step S1 is omitted, and the composite microbial agent powder, all seaweed powder, polyglutamic acid, biochar and other raw materials are directly mixed in step S2.

[0095] Comparative Example 3: The only difference between this comparative example and Example 1 is that in step S5, no air containing CO2 is introduced during the post-curing process, and the post-curing is carried out for 84 hours under the same temperature and humidity.

[0096] Comparative Example 4: This comparative example differs from Example 1 only in that it uses a commercially available brand of general-purpose microbial fertilizer for improving saline-alkali land, wherein the total number of viable bacteria is ≥2.0×10⁻⁶. 8 CFU / g, organic matter content ≥45%, apply according to the recommended dosage and method in the product instructions, without adding any additional raw materials or adjusting the process.

[0097] Comparative Example 5: The only difference between this comparative example and Example 1 is that biochar was removed from the raw materials, while the types and amounts of the other raw materials are exactly the same as in Example 1.

[0098] Experiment 1: Determination of effective viable bacteria count and soil colonization rate in fertilizers. Following the standards NY / T3021-2016 "Determination of Effective Viable Bacteria Count in Microbial Fertilizers" and NY / T1109-2021 "General Rules for Bioassays of Microbial Fertilizers", typical moderately saline-alkali soil was selected, sieved through a 2 mm sieve, and then divided into uniformly sized flowerpots, with each pot containing the same amount of soil. Fertilizers from Examples 1-3 and Comparative Examples 1-5 were applied with equal amounts of pure nutrients. A blank control without fertilizer was also included. All treatments were replicated in triplicate. The soil was watered to 70% of its field capacity and maintained at this humidity. The effective viable bacteria count of each fertilizer sample was measured on the day of fertilization using the dilution plating method combined with the morphological characteristics of the target bacteria. Soil samples were collected at 7, 14, and 28 days after fertilization, and the colonization rate of the target functional bacteria in the soil was determined using the same plate counting method. The viable bacteria retention rate and soil colonization rate of each fertilizer treatment were calculated.

[0099] Experiment 2: Determination of pH and EC values ​​of saline-alkali soil. Following the standards NY / T1121.2-2006 "Soil Testing Part 2: Determination of Soil pH" and LY / T1251-1999 "Determination of Electrical Conductivity of Forest Soils," the potted plant treatment scheme and replication settings were identical to those in Experiment 1. Base soil samples were collected from each pot before fertilization, and soil samples from each treatment were collected again 28 days after fertilization. The soil samples were air-dried and passed through a 1 mm sieve. A soil suspension was prepared at a soil-to-water ratio of 1:5, thoroughly shaken, and then filtered. The soil pH was determined using the potentiometry method, and the soil EC value was determined using a conductivity meter. The measurement data for each treatment were recorded, and the average value and coefficient of variation were calculated.

[0100] Experiment 3 determined the germination rate and biomass of crops in saline-alkali land. Following the standards NY / T1107-2020 "Technical Regulations for Field Trials to Identify Fertilizer Effects" and GB / T3543.4-1995 "Seed Inspection Procedures for Crop Germination Tests," sunflower, a salt-tolerant crop, was selected as the test crop. The same potted treatment and replication settings as in Experiments 1 and 2 were used. An equal number of plump sunflower seeds were sown in each pot and placed in a light incubator. The incubation conditions were set as follows: 12 hours of light per day, 3000 lux light intensity, and 25℃ temperature; 12 hours of darkness per day and 20℃ temperature. Soil moisture was kept stable. The germination rate of each treatment was recorded on the 10th day after sowing. All plants were harvested on the 30th day after sowing, and the fresh weight of the above-ground parts was measured. The plants were then placed in an oven at 105℃ for 30 minutes to blanch, and then dried at 75℃ until constant weight. The dry weight of the above-ground parts was measured, and the average value of each treatment was calculated.

[0101] Table 1: Results of Fertilizer Effective Viable Bacteria Count and Soil Colonization Rate Measurement

[0102] Processing group Effective viable bacteria count (CFU / g) on ​​the day of fertilization Soil colonization number 7 days after fertilization (CFU / g dry soil) Soil colonization number 14 days after fertilization (CFU / g dry soil) Soil colonization number 28 days after fertilization (CFU / g dry soil) 28-day viable bacteria retention rate (%) Example 1 <![CDATA[1.2×10 10 ]]> <![CDATA[8.5×10 8 ]]> <![CDATA[7.2×10 8 ]]> <![CDATA[6.8×10 8 ]]> 56.7 Example 2 <![CDATA[1.0×10 10 ]]> <![CDATA[7.1×10 8 ]]> <![CDATA[6.0×10 8 ]]> <![CDATA[5.5×10 8 ]]> 55.0 Example 3 <![CDATA[1.5×10 10 ]]> <![CDATA[9.8×10 8 ]]> <![CDATA[8.5×10 8 ]]> <![CDATA[7.9×10 8 ]]> 52.7 Comparative Example 1 <![CDATA[9.5×10 9 ]]> <![CDATA[3.2×10 8 ]]> <![CDATA[2.1×10 8 ]]> <![CDATA[1.5×10 8 ]]> 15.8 Comparative Example 2 <![CDATA[8.2×10 9 ]]> <![CDATA[2.5×10 8 ]]> <![CDATA[1.3×10 8 ]]> <![CDATA[0.8×10 8 ]]> 9.8 Comparative Example 3 <![CDATA[1.1×10 10 ]]> <![CDATA[6.0×10 8 ]]> <![CDATA[4.2×10 8 ]]> <![CDATA[3.0×10 8 ]]> 27.3 Comparative Example 4 <![CDATA[2.5×10 8 ]]> <![CDATA[1.8×10 6 ]]> <![CDATA[1.0×10 6 ]]> <![CDATA[0.5×10 6 ]]> 20.0 Comparative Example 5 <![CDATA[9.0×10 9 ]]> <![CDATA[2.8×10 8 ]]> <![CDATA[1.6×10 8 ]]> <![CDATA[1.0×10 8 ]]> 11.1 Blank control - <![CDATA[1.2×10 5 ]]> <![CDATA[1.0×10 5 ]]> <![CDATA[0.8×10 5 ]]> -

[0103] Table 2: Results of pH and EC values ​​improvement effects on saline-alkali soils

[0104] Processing group pH value before fertilization pH value 28 days after fertilization pH decrease EC value before fertilization (mS / cm) EC value (mS / cm) 28 days after fertilization EC decrease (%) Example 1 8.6 7.3 1.3 6.8 3.2 52.9 Example 2 8.6 7.5 1.1 6.8 3.5 48.5 Example 3 8.6 7.2 1.4 6.8 3.0 55.9 Comparative Example 1 8.6 7.9 0.7 6.8 4.8 29.4 Comparative Example 2 8.6 8.1 0.5 6.8 5.2 23.5 Comparative Example 3 8.6 7.7 0.9 6.8 4.2 38.2 Comparative Example 4 8.6 8.0 0.6 6.8 5.0 26.5 Comparative Example 5 8.6 8.2 0.4 6.8 5.5 19.1 Blank control 8.6 8.5 0.1 6.8 6.6 2.9

[0105] Table 3: Results of Crop Emergence Rate and Biomass Measurement in Saline-Alkali Land

[0106] Processing group Emergence rate (%) Fresh weight of a single plant above ground (g) Dry weight of a single plant above ground (g) Dry matter accumulation rate (%) Example 1 92 38.5 8.2 21.3 Example 2 88 35.2 7.5 21.3 Example 3 95 42.1 9.0 21.4 Comparative Example 1 65 22.3 4.8 21.5 Comparative Example 2 58 18.5 4.0 21.6 Comparative Example 3 78 28.6 6.1 21.3 Comparative Example 4 62 20.1 4.3 21.4 Comparative Example 5 55 16.8 3.6 21.4 Blank control 32 8.2 1.8 21.9

[0107] As can be seen from Examples 1-3 and Comparative Example 1, and Tables 1-3, polyglutamic acid plays a key protective and synergistic role in the microbial fertilizer system. It can effectively maintain the activity of the compound microbial agent, help functional bacteria to colonize better in the soil, and also work with components such as biochar to improve the soil improvement effect, thereby creating more suitable conditions for crop growth.

[0108] As can be seen from Examples 1-3 and Comparative Example 2, and Tables 1-3, the pre-activation of microbial agents and the adsorption of the carrier are important steps to ensure the activity of microorganisms. Pre-activating the microbial agents and then adsorbing them through biochar can create a stable living environment for microorganisms, avoid damage to the microbial agents caused by subsequent mixing and drying processes, and thus allow the functional bacteria to play a better role, promoting soil property improvement and crop growth.

[0109] Based on Examples 1-3 and Comparative Example 3, and in conjunction with Tables 1-3, it can be seen that introducing low-concentration carbon dioxide during the post-ripening process can effectively regulate the metabolic state of microorganisms, help functional bacteria improve their adaptability to saline-alkali environments, promote their colonization and reproduction in the soil, and thus optimize soil pH and EC values, providing favorable conditions for crop emergence and growth.

[0110] As can be seen from Examples 1-3 and Comparative Example 4, and Tables 1-3, the microbial fertilizer of this application has significant advantages in raw material combination and preparation process. The specific ratio of compound microbial agent combined with functional adjuvants such as polyglutamic acid and biochar, combined with a series of processes such as pre-activation, segmented drying and CO2-induced ripening, can achieve the synergistic effect of microbial agent activity retention, soil improvement and crop growth promotion, which is difficult to achieve with conventional commercially available saline-alkali land improvement microbial fertilizers.

[0111] Based on Examples 1-3 and Comparative Example 5, and in conjunction with Tables 1-3, it can be seen that biochar, as a carrier of microorganisms, can effectively adsorb the functional bacteria in the compound microbial agent, reducing their loss during processing and application. At the same time, it can also adsorb salt ions in the soil and work with other components to regulate soil properties. The lack of biochar will directly affect the colonization effect of the microbial agent and the progress of soil improvement, thereby adversely affecting crop growth.

[0112] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A microbial fertilizer for promoting plant growth in saline-alkali land, characterized in that: The raw materials contain the following parts by weight: 8-13 parts compound microbial inoculant, 5.2-6.0 parts well-rotted organic fertilizer, 2.2-3.2 parts organic acid, 1.2-3.2 parts sulfuric acid compound, 1-16 parts urea, 4.2-5.2 parts seaweed powder, 2.8-3.2 parts fruit and vegetable residue, 2.8-3.2 parts earthworm soil, 0.5-1.5 parts polyglutamic acid, and 2-4 parts biochar.

2. The microbial fertilizer for promoting plant growth in saline-alkali land according to claim 1, characterized in that: The compound microbial agent is composed of fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis and aerobic denitrifying bacteria, and the mass ratio of the fermenting bacteria, salt-solubilizing bacteria, probiotics, Bacillus subtilis and aerobic denitrifying bacteria is (1-2):(2-3):(1-1.5):(1-2):(0.5-1).

3. The microbial fertilizer for promoting plant growth in saline-alkali land according to claim 1, characterized in that: The organic acid is one or more of linoleic acid, linolenic acid, and oxalic acid, and the sulfuric acid compound is one or two of ferrous sulfate and zinc sulfate.

4. A microbial fertilizer for promoting plant growth in saline-alkali land according to claim 1, characterized in that: The decomposed organic fertilizer is made from livestock and poultry manure, straw and soybean meal through high-temperature decomposition, wherein the mass ratio of livestock and poultry manure, straw and soybean meal is (3-5):(2-3):(1-2).

5. A method for preparing a microbial fertilizer for promoting plant growth in saline-alkali land, characterized in that, A microbial fertilizer for promoting plant growth in saline-alkali land as described in any one of claims 1-4, comprising the following steps: S1. Pre-activation of microbial agent and adsorption by carrier: The compound microbial agent is mixed with some seaweed powder and polyglutamic acid, added to nutrient solution for activation treatment, and then mixed with biochar for adsorption to obtain a biochar carrier loaded with microbial agent. S2. Raw material pretreatment and mixing: The decomposed organic fertilizer, sulfuric acid compound, urea, residual seaweed powder, fruit and vegetable residue and earthworm soil are crushed separately, and then mixed and stirred with biochar carrier loaded with bacterial agent and deionized water to obtain the initial mixture. S3. Segmented temperature-controlled drying and activation: The initial mixture is dried in segments under relatively low and relatively high temperature conditions to obtain an activated dry mixture. S4. Conditioning and acid integration: Add deionized water and organic acid to the activated dry mixture, mix evenly, and maintain the integration reaction at a preset temperature for a period of time to obtain the conditioned wet mixture. S5. Granulation and Induction of Post-Ripening: The conditioning wet mixture is granulated, and the resulting granules are placed in a preset temperature and humidity environment for post-ripening treatment. Air containing a low concentration of carbon dioxide is introduced at the beginning of the post-ripening treatment, and then the entire post-ripening process is completed to obtain microbial fertilizer.

6. A method for preparing a microbial fertilizer for promoting plant growth in saline-alkali land according to claim 5, characterized in that: In step S1, the activation treatment is carried out at a temperature of 30-35°C for 1-2 hours; the nutrient solution is an aqueous solution containing yeast extract and potassium dihydrogen phosphate, and its addition amount is 20-40% of the total mass of the bacterial agent and seaweed powder.

7. A method for preparing a microbial fertilizer for promoting plant growth in saline-alkali land according to claim 5, characterized in that: In step S2, the particle size of the pulverized material is 0.1-0.5 mm, the stirring speed is 150-200 r / min, and the stirring time is 50-65 min.

8. A method for preparing a microbial fertilizer for promoting plant growth in saline-alkali land according to claim 5, characterized in that: In step S3, the relatively low temperature is 60-70℃ and the processing time is 2-3 hours; the relatively high temperature is 80-90℃ and the processing time is 1-2 hours; the initial mixture is spread to a thickness of 2-3 cm and is turned over during the processing.

9. A method for preparing a microbial fertilizer for promoting plant growth in saline-alkali land according to claim 5, characterized in that: In step S4, the preset temperature is 40-45℃, and the maintenance period is 20-30 minutes; the moisture content of the conditioned wet mixture obtained after conditioning is 25-30%.

10. A method for preparing a microbial fertilizer for promoting plant growth in saline-alkali land according to claim 5, characterized in that: In step S5, the particle size of the granulated particles is 2-4 mm; the preset temperature and humidity environment is 25-30℃ and 60-70%; the volume concentration of carbon dioxide in the introduced air is 0.5-1.5%, the aeration time is 24-48 hours, and the total time of the entire post-ripening process is 72-96 hours.

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