A mineral biological organic-inorganic composite fertilizer and preparation method thereof

Abstract

The invention discloses a mineral biological organic-inorganic composite fertilizer and a preparation method thereof, and belongs to the technical field of fertilizers. The fertilizer of the invention is prepared from magnetic biochar, decomposed pig manure, minerals, modifiers, Litsea cubeba oil, chitosan, microbial agents, urea, superphosphate, and potassium sulfate. Heptafluorodecyltrimethoxysilane and sodium alginate with a mass ratio of 1:1 are used as modifiers to modify carbide slag, zeolite, and white mud, giving the coating film a controllable hydrophobic property. In acidic soils containing heavy metals, the slow-release performance of the fertilizer can be increased according to the acidity; the coating film materials used, carbide slag, zeolite, white mud and magnetic biochar, work synergistically, and the heavy metal adsorption effect is stronger; the microbial agent can significantly enhance the heavy metal adsorption and soil improvement effect of the microbial agent under the stimulation of ammonia water, and significantly improve the yield and quality of crops in acidic or heavy metal-contaminated land.

Description

Technical Field

[0001] The invention belongs to the technical field of bio-organic fertilizers, and in particular relates to a mineral bio-organic-inorganic composite fertilizer and a preparation method thereof. Background Art

[0002] Soil acidification is a manifestation of soil degradation. In recent years, due to high-intensity human activities, the speed of soil acidification has greatly accelerated, showing the characteristics of wide distribution, large area and high degree of acidification. Soil acidification not only affects fertility and nutrient content, but also weakens the soil buffering capacity, leading to soil compaction and degradation, which brings severe challenges to agricultural production. In addition, the soil acidification process further activates harmful substances such as heavy metals, changes the structural diversity of soil microorganisms, affects the ecological function of microorganisms and enzyme activity, thereby aggravating the harm to the ecological environment and agricultural production.

[0003] Heavy metals that contaminate soil mainly include mercury (Hg), cadmium (Cd), lead (Pb), chromium (Cr), metalloid arsenic (As) and other elements with significant biological toxicity, as well as zinc (Zn), copper (Cu), nickel (Ni) and other elements with certain toxicity. Compared with air pollution and water pollution, which can be directly judged by vision and smell, soil heavy metal pollution is often highly hidden and will not become prominent until several years, decades or even hundreds of years. Soil pollution, especially heavy metal pollution, is cumulative, has a slow migration rate, and has serious pollution consequences. Continuous enrichment leads to an increasingly larger pollution area, affecting soil properties and causing a decline in soil fertility.

[0004] If straw is not utilized, it will not only occupy a large amount of land resources but also seriously pollute the air quality due to its incineration; the industrial waste slag, carbide slag, has CaO as its main component. It is alkaline when dissolved in water. Long-term accumulation will cause land salinization and pollute groundwater; the industrial waste white mud has a high silicon content, and the silicon interferes with the recycling of alkali. The white mud is mainly used for paving roads or directly discharged into rivers.

[0005] CN110802107A2 adopts plant restoration technology, through the rotation and joint planting of kenaf and flax, activates the metal cadmium in the soil through heavy metal activators, and adsorbs the heavy metal cadmium in acidic soil. However, the adsorption effect of this technology on other heavy metals is not obvious, and the fertilizer used is only organic fertilizer with poor fertilizer efficiency. Therefore, straw waste, carbide slag, and white mud waste resources are used as raw materials to prepare a coated slow-release fertilizer combining organic fertilizer and inorganic fertilizer, which can effectively improve acidic soil and adsorb heavy metal substances, which is of great significance to agricultural development. Summary of the invention

[0006] The present invention overcomes the deficiencies of the prior art and discloses a mineral biological organic-inorganic composite fertilizer and a preparation method thereof. The fertilizer core of the present invention is organic fertilizer, decomposed pig manure and nitrogen, phosphorus and potassium fertilizers. Carbide slag, zeolite, white mud and magnetic biochar cross-linked and modified by genipin are used as coating materials. Heptadecafluorodecyltrimethoxysilane and sodium alginate with a mass ratio of 1:2 are used as modifiers to modify the carbide slag, zeolite and white mud powder. Microbial agents stimulated by ammonia water are also added, and fertilizer particles are coated with Litsea cubeba oil, thereby significantly improving the yield and quality of crops in acidic and heavy metal polluted land.

[0007] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0008] A mineral biological organic-inorganic composite fertilizer comprises the following raw materials in parts by weight: 30-50 parts of magnetic biochar, 15-25 parts of decomposed pig manure, 20-80 parts of minerals, 5-8 parts of modifiers, 6-12 parts of litsea cubeba oil, 1-5 parts of chitosan, 3-5 parts of microbial agents, 50-70 parts of urea, 30-50 parts of superphosphate and 25-40 parts of potassium sulfate.

[0009] Preferably, the minerals are carbide slag, zeolite and white mud in a mass ratio of 1:1:1.

[0010] Preferably, the modifier is heptadecafluorodecyltrimethoxysilane and sodium alginate in a mass ratio of 1:1.

[0011] Preferably, the microbial agent is obtained by mixing and modifying Trichoderma aculeatus, Saccharomyces cerevisiae and Verticillium dahliae in a mass ratio of 1:1:1 with an ammonia solution with a mass fraction of 0.05%.

[0012] More preferably, the Trichoderma aculeatus was purchased from the China General Microorganism Collection Center (CGMCC), with an address of No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, with a deposit number of CGMCC3.17461, and an original deposit date of August 27, 2014; the Saccharomyces cerevisiae was purchased from the China General Microorganism Collection Center (CGMCC), with an address of No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, with a deposit number of CGMCC2.5432, and an original deposit date of November 30, 2015; the Verticillium dahliae was purchased from the China General Microorganism Collection Center (CGMCC), with an address of No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, with a deposit number of CGMCC3.15299, and an original deposit number of May 21, 2013. The strains of the present invention can be purchased through the collection center without repeated preservation.

[0013] A method for preparing a mineral biological organic-inorganic composite fertilizer, the steps are as follows:

[0014] (1) Preparation of magnetic biochar:

[0015] The abandoned crop straw was rinsed with clean water, dried to a moisture content of ≤3%, crushed and passed through an 80-mesh sieve, put into a reactor, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, pyrolyzed at 600°C for 3h, cooled to 25°C, and ground through a 200-mesh sieve; the ground powder was added back into the reactor, 1 / 10 of the total volume of 0.75 mol / L ferrous sulfate heptahydrate solution was added, stirred evenly, 1 / 8 of the total volume of 30% hydrogen peroxide solution was added, heated to reflux at 85°C for 3h, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, and pyrolyzed for 3h to obtain magnetic biochar;

[0016] (2) Preparation of decomposed pig manure:

[0017] 30 kg of pig manure is aired for 3-5 days, the water content is controlled to be maintained at 40%, 5 kg of 30°C warm water is soaked to dissolve 2 kg of fermented EM stock solution, and stirred evenly; the pig manure is spread out, the fermented EM stock solution is soaked in warm water and placed for 2 hours, and then sprayed evenly on the surface of the pig manure at one time, the pig manure is piled up, and the surface is covered with a layer of straw, and covered and sealed with a plastic film, and the pig manure is dark brown and the temperature drops to 25°C to complete the decomposition, thereby obtaining decomposed pig manure;

[0018] (3) Preparation of microbial agents:

[0019] Trichoderma aculeatus, Saccharomyces cerevisiae, and Verticillium dahliae were cultured in soybean powder medium at 25°C, 28°C, and 25°C for 24 hours, respectively, and inoculated into LB medium at a 10% inoculum, and cultured at 25°C, 28°C, and 25°C with shaking until the bacterial concentration OD 600 ≈2.5, obtain fermentation broth of three bacteria, then mix them evenly in a mass ratio of 1:1:1 to obtain a mixed bacterial solution, add 30% of the volume of the mixed bacterial solution and a 0.05% ammonia solution by mass fraction, let it stand for 24 hours, and dry it to a water content of ≤3% to obtain a microbial agent;

[0020] The composition of the soybean powder culture medium is as follows: 5-10 parts of soybean powder, 1-5 parts of NaCl, 1-3 parts of CaCO3, 2-5 parts of peptone, and 5-10 parts of glucose by weight; the pH value of the soybean powder culture medium is 7.0-7.5;

[0021] (4) Preparation of activated hydrophobic controllable mineral powder:

[0022] The zeolite, carbide slag and white mud were dried separately, the water content was controlled to be ≤10%, and they were crushed and ground to pass through a 200-mesh sieve. The crushed zeolite, carbide slag and white mud powders were added to a reactor and stirred evenly. The zeolite, carbide slag and white mud powders were activated by microwave heating at 220-265°C for 35 minutes. Heptadecafluorodecyltrimethoxysilane was dissolved in a 50% ethanol solution at a volume ratio of 1:10, stirred evenly, and added to a reactor. Sodium alginate was added, and the mixture was heated at 60°C for 4 hours with stirring, and then dried to obtain an active hydrophobic controllable mineral powder.

[0023] (5) Preparation of hydrophobic controllable heavy metal adsorption coating membrane:

[0024] The magnetic biochar prepared in step (1) is added to a reactor, and the microbial agent prepared in step (3) and the activated hydrophobic controllable mineral powder prepared in step (4) are added in sequence, and stirred evenly; chitosan is dissolved in water to prepare a chitosan aqueous solution with a mass fraction of 15%, and the mixture is stirred evenly and added to the reactor, and magnetic stirring is performed at 20-28° C. for 5 h at a speed of 400 rpm, and ventilation drying is performed until the water content is ≤5% to obtain a hydrophobic controllable heavy metal adsorption coating;

[0025] (6) Granulation:

[0026] The decomposed pig manure prepared in step (2) is ventilated and dried to a moisture content of ≤3%, crushed and ground to pass through a 200-mesh sieve, mixed evenly with urea, superphosphate and potassium sulfate, granulated, and sieved to obtain particles with a particle size of 1-4.75 mm to obtain organic-inorganic mixed fertilizer particles;

[0027] (7) Encapsulation:

[0028] The organic-inorganic mixed fertilizer particles prepared in step (6) are placed in a disc granulator and preheated with hot air at 35-45°C for 5 minutes. A small amount of Litsea cubeba oil is sprayed on the organic-inorganic mixed fertilizer particles with a high-pressure spray gun to wet the surface of the particles without adhering to each other. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) is added to the disc granulator and rotated for 10 minutes. The remaining Litsea cubeba oil is then sprayed in and rotated for 20 minutes. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) can be coated on the surface of the organic-inorganic mixed fertilizer particles prepared in step (6) to obtain a mineral biological organic-inorganic composite fertilizer.

[0029] Preferably, the waste crop straw in step (1) is one or more of rice straw, wheat straw, corn straw, reed straw, peanut seedlings, sorghum stalks, and soybean straw.

[0030] Calcium carbide slag is industrial waste residue produced in the process of producing acetylene, polyvinyl chloride and polyvinyl alcohol using industrial calcium carbide. Its main component is CaO. Calcium carbide slag is alkaline when dissolved in water. Long-term accumulation will cause land salinization and pollute groundwater.

[0031] Zeolite is a hydrous alkali or alkaline earth metal aluminum silicate mineral with good adsorption and ion exchange properties for cations. It can adsorb metal ions with a specific surface area of ​​500-1000m 2 / g, has strong water absorption capacity.

[0032] White mud is industrial waste generated during the alkali recovery process of pulp and paper mills. Due to the high silicon content in white mud, silicon interferes with the recovery of alkali. The white mud is mainly used for paving roads or directly discharged into rivers.

[0033] The fertilizer core of the invention is organic fertilizer, mature pig manure and nitrogen, phosphorus and potassium fertilizers. Modified calcium carbide slag, zeolite, white mud and magnetic biochar are used as coating materials. Heptadecafluorodecyl trimethoxysilane and sodium alginate with a mass ratio of 1:2 are used as modifiers to modify calcium carbide slag, zeolite and white mud powder. Heptadecafluorodecyl trimethoxysilane has low surface energy and strong wetting ability. Hydrophobic groups with low surface energy are introduced into the surfaces of calcium carbide slag, zeolite and white mud, thereby reducing the surface energy of the coating film and enhancing the hydrophobic effect. Sodium alginate has pH sensitivity and can be used at pH values ​​of 6-11. It is relatively stable in aqueous solution, but will precipitate gel or coagulate when the pH is lower than 6 or higher than 11. Under acidic conditions, -COO- in sodium alginate will be converted into -COOH, the degree of ionization will be reduced, the hydrophilicity will be reduced, and the molecules will shrink; under alkaline conditions, -COOH will continue to dissociate into -COO-, the hydrophilicity will be increased, and the molecular chain will be extended. The hydroxyl and carboxyl active groups of sodium alginate are used to graft sodium alginate onto the surface of the coating composed of calcium carbide slag, zeolite, and white mud, and work together with the super hydrophobic material heptadecafluorodecyltrimethoxysilane of equal mass, not only The coating film is endowed with hydrophobic properties and has controllable adjustment. Especially in acidic soils containing heavy metals, the slow-release performance of the fertilizer can be increased according to the acidity. The carbide slag, zeolite, white mud and magnetic biochar in the coating film material of the present invention can improve the acidic soil and have obvious heavy metal adsorption and passivation effects; the magnetic biochar obtained by modifying the biochar increases its own specific surface area and increases the adsorption performance; the mass ratio of 1:1:1 of Trichoderma spinulosa, Saccharomyces cerevisiae and Verticillium dahliae is 0.05 The product is obtained by mixing and modifying % ammonia solution, which changes the structure of polysaccharides or proteins on the surface of the bacteria and dissolves some impurities that are not conducive to adsorption, exposing more binding sites to the bacteria. In addition, ammonia water dissolves hydrogen ions on the surface of the bacteria, which significantly increases the electronegative functional groups on the surface of the bacteria and increases the adsorption capacity of heavy metals. The decomposed pig manure plays a synergistic role as organic fertilizer and microbial cells, which has enhanced the anti-insect and antibacterial effects of microbial agents and played a role in repairing the soil. Chitosan, as a natural coating agent, forms a coating film with strong stability and good effect.

[0034] Beneficial Effects

[0035] The fertilizer core of the invention is organic fertilizer, decomposed pig manure and nitrogen, phosphorus and potassium fertilizers. Chitosan-modified carbide slag, zeolite, white mud and magnetic biochar are used as coating materials. Heptadecafluorodecyltrimethoxysilane and sodium alginate with a mass ratio of 1:1 are used as modifiers to modify carbide slag, zeolite and white mud powder. Microbial agents are also added, and fertilizer particles are coated with litsea cubeba oil. Compared with the prior art, the mineral biological organic-inorganic composite fertilizer produced by the invention has good slow-control performance and controllability, and can meet the growth requirements of crops in acidic soil containing heavy metals. The invention can meet all the needs of the industry; the coating film materials such as carbide slag, white mud and straw waste are the recycling of waste resources, and have good adsorption of heavy metals and improvement of acidic soil; the magnetic biochar obtained by modified biochar increases the specific surface area and improves the adsorption performance; low concentration of ammonia water stimulation enhances the heavy metal adsorption of microbial agents, and has strong anti-insect and antibacterial effects; the chitosan coating film used has good stability; the material selection and use of the invention are natural and environmentally friendly, and the synergistic coordination between the raw materials significantly improves the yield and quality of crops in acidic and heavy metal polluted land. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below in conjunction with specific embodiments:

[0037] Example 1

[0038] A mineral biological organic-inorganic composite fertilizer comprises the following raw materials in parts by weight: 30 parts of magnetic biochar, 15 parts of decomposed pig manure, 20 parts of minerals, 5 parts of modifiers, 6 parts of litsea cubeba oil, 1 part of chitosan, 3 parts of microbial agents, 50 parts of urea, 30 parts of superphosphate and 25 parts of potassium sulfate.

[0039] The minerals are carbide slag, zeolite and white mud in a mass ratio of 1:1:1.

[0040] The modifier is heptadecafluorodecyltrimethoxysilane and sodium alginate in a mass ratio of 1:1.

[0041] The microbial agent is obtained by mixing and modifying Trichoderma aculeatus, Saccharomyces cerevisiae and Verticillium dahliae in a mass ratio of 1:1:1 with an ammonia solution with a mass fraction of 0.05%.

[0042] The Trichoderma spinulosa was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.17461; the Saccharomyces cerevisiae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC2.5432; the Verticillium dahliae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.15299.

[0043] A method for preparing a mineral biological organic-inorganic composite fertilizer, the steps are as follows:

[0044] (1) Preparation of magnetic biochar:

[0045] The abandoned crop straw was rinsed with clean water, dried to a moisture content of ≤3%, crushed and passed through an 80-mesh sieve, put into a reactor, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, pyrolyzed at 600°C for 3h, cooled to 25°C, and ground through a 200-mesh sieve; the ground powder was added back into the reactor, 1 / 10 of the total volume of 0.75 mol / L ferrous sulfate heptahydrate solution was added, stirred evenly, 1 / 8 of the total volume of 30% hydrogen peroxide solution was added, heated to reflux at 85°C for 3h, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, and pyrolyzed for 3h to obtain magnetic biochar;

[0046] (2) Preparation of decomposed pig manure:

[0047] 30 kg of pig manure was aired for 3 days, the water content was controlled to be maintained at 40%, 2 kg of fermented EM stock solution was dissolved in 5 kg of 30°C warm water, and stirred evenly; the pig manure was spread out, the fermented EM stock solution was soaked in warm water and placed for 2 hours, and then sprayed evenly on the surface of the pig manure at one time, the pig manure was piled up, the surface was covered with a layer of straw, and covered and sealed with a plastic film, and the pig manure was dark brown and the temperature dropped to 25°C to complete the decomposition, thereby obtaining decomposed pig manure;

[0048] (3) Preparation of microbial agents:

[0049] Trichoderma aculeatus, Saccharomyces cerevisiae, and Verticillium dahliae were cultured in soybean powder medium at 25°C, 28°C, and 25°C for 24 hours, respectively, and inoculated into LB medium at a 10% inoculum, and cultured at 25°C, 28°C, and 25°C with shaking until the bacterial concentration OD 600 ≈2.5, obtain fermentation broth of three bacteria, then mix them evenly in a mass ratio of 1:1:1 to obtain a mixed bacterial solution, add 30% of the volume of the mixed bacterial solution and a 0.05% ammonia solution by mass fraction, let it stand for 24 hours, and dry it to a water content of ≤3% to obtain a microbial agent;

[0050] (4) Preparation of activated hydrophobic controllable mineral powder:

[0051] The zeolite, carbide slag and white mud were ventilated and dried respectively, the water content was controlled to be ≤10%, and then they were crushed and ground to pass through a 200-mesh sieve. The crushed zeolite, carbide slag and white mud powder were added to a reactor and stirred evenly. The mixture was activated by microwave heating at 220°C for 35 minutes. Heptadecafluorodecyltrimethoxysilane was dissolved in a 50% ethanol solution at a volume ratio of 1:10, stirred evenly, and added to a reactor. Sodium alginate was added, and the mixture was heated at 60°C for 4 hours with stirring, and then dried to obtain an active hydrophobic controllable mineral powder.

[0052] (5) Preparation of hydrophobic controllable heavy metal adsorption coating membrane:

[0053] The magnetic biochar prepared in step (1) is added to a reactor, and the microbial agent prepared in step (3) and the activated hydrophobic controllable mineral powder prepared in step (4) are added in sequence, and stirred evenly; chitosan is dissolved in water to prepare a chitosan aqueous solution with a mass fraction of 15%, and the mixture is stirred evenly and added to the reactor, and magnetic stirring is performed at 20-28° C. for 5 h at a speed of 400 rpm, and ventilation drying is performed until the water content is ≤5% to obtain a hydrophobic controllable heavy metal adsorption coating;

[0054] (6) Granulation:

[0055] The decomposed pig manure prepared in step (2) is ventilated and dried to a moisture content of ≤3%, crushed and ground to pass through a 200-mesh sieve, mixed evenly with urea, superphosphate and potassium sulfate, granulated, and sieved to obtain particles with a particle size of 1-4.75 mm to obtain organic-inorganic mixed fertilizer particles;

[0056] (7) Encapsulation:

[0057] The organic-inorganic mixed fertilizer particles prepared in step (6) are placed in a disc granulator and preheated with hot air at 35°C for 5 minutes. A small amount of Litsea cubeba oil is sprayed on the organic-inorganic mixed fertilizer particles with a high-pressure spray gun to wet the surface of the particles without adhering to each other. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) is added to the disc granulator and rotated for 10 minutes. The remaining Litsea cubeba oil is then sprayed in and rotated for 20 minutes. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) can be coated on the surface of the organic-inorganic mixed fertilizer particles prepared in step (6) to obtain a mineral biological organic-inorganic composite fertilizer.

[0058] The discarded crop straw in step (1) is rice straw.

[0059] Example 2

[0060] A mineral biological organic-inorganic composite fertilizer comprises the following raw materials in parts by weight: 40 parts of magnetic biochar, 20 parts of decomposed pig manure, 50 parts of minerals, 7 parts of modifier, 9 parts of litsea cubeba oil, 3 parts of chitosan, 4 parts of microbial agent, 60 parts of urea, 40 parts of superphosphate and 35 parts of potassium sulfate.

[0061] The minerals are carbide slag, zeolite and white mud in a mass ratio of 1:1:1.

[0062] The modifier is heptadecafluorodecyltrimethoxysilane and sodium alginate in a mass ratio of 1:1.

[0063] The microbial agent is obtained by mixing and modifying Trichoderma aculeatus, Saccharomyces cerevisiae and Verticillium dahliae in a mass ratio of 1:1:1 with an ammonia solution with a mass fraction of 0.05%.

[0064] The Trichoderma spinulosa was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.17461; the Saccharomyces cerevisiae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC2.5432; the Verticillium dahliae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.15299.

[0065] A method for preparing a mineral biological organic-inorganic composite fertilizer, the steps are as follows:

[0066] (1) Preparation of magnetic biochar:

[0067] The abandoned crop straw was rinsed with clean water, dried to a moisture content of ≤3%, crushed and passed through an 80-mesh sieve, put into a reactor, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, pyrolyzed at 600°C for 3h, cooled to 25°C, and ground through a 200-mesh sieve; the ground powder was added back into the reactor, 1 / 10 of the total volume of 0.75 mol / L ferrous sulfate heptahydrate solution was added, stirred evenly, 1 / 8 of the total volume of 30% hydrogen peroxide solution was added, heated to reflux at 85°C for 3h, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, and pyrolyzed for 3h to obtain magnetic biochar;

[0068] (2) Preparation of decomposed pig manure:

[0069] 30 kg of pig manure was aired for 4 days, the water content was controlled to be maintained at 40%, 2 kg of fermented EM stock solution was dissolved in 5 kg of 30°C warm water, and stirred evenly; the pig manure was spread out, the fermented EM stock solution was soaked in warm water and placed for 2 hours, and then sprayed evenly on the surface of the pig manure at one time, the pig manure was piled up, the surface was covered with a layer of straw, and covered and sealed with a plastic film, and the pig manure was dark brown and the temperature dropped to 25°C to complete the decomposition, thereby obtaining decomposed pig manure;

[0070] (3) Preparation of microbial agents:

[0071] Trichoderma aculeatus, Saccharomyces cerevisiae, and Verticillium dahliae were cultured in soybean powder medium at 25°C, 28°C, and 25°C for 24 hours, respectively, and inoculated into LB medium at a 10% inoculum, and cultured at 25°C, 28°C, and 25°C with shaking until the bacterial concentration OD 600 ≈2.5, obtain fermentation broth of three bacteria, then mix them evenly in a mass ratio of 1:1:1 to obtain a mixed bacterial solution, add 30% of the volume of the mixed bacterial solution and a 0.05% ammonia solution by mass fraction, let it stand for 24 hours, and dry it to a water content of ≤3% to obtain a microbial agent;

[0072] (4) Preparation of activated hydrophobic controllable mineral powder:

[0073] The zeolite, carbide slag and white mud were ventilated and dried respectively, the water content was controlled to be ≤10%, and the powders were ground and passed through a 200-mesh sieve. The crushed zeolite, carbide slag and white mud powders were added to a reactor and stirred evenly. The powders were activated by microwave heating at 240°C for 35 minutes. Heptadecafluorodecyltrimethoxysilane was dissolved in a 50% ethanol solution at a volume ratio of 1:10, stirred evenly, and added to a reactor. Sodium alginate was added, and the mixture was heated at 60°C for 4 hours with stirring, and then dried to obtain an active hydrophobic controllable mineral powder.

[0074] (5) Preparation of hydrophobic controllable heavy metal adsorption coating membrane:

[0075] The magnetic biochar prepared in step (1) is added to a reactor, and the microbial agent prepared in step (3) and the activated hydrophobic controllable mineral powder prepared in step (4) are added in sequence, and stirred evenly; chitosan is dissolved in water to prepare a chitosan aqueous solution with a mass fraction of 15%, and the mixture is stirred evenly and added to the reactor, and magnetic stirring is performed at 20-28° C. for 5 h at a speed of 400 rpm, and ventilation drying is performed until the water content is ≤5% to obtain a hydrophobic controllable heavy metal adsorption coating;

[0076] (6) Granulation:

[0077] The decomposed pig manure prepared in step (2) is ventilated and dried to a moisture content of ≤3%, crushed and ground to pass through a 200-mesh sieve, mixed evenly with urea, superphosphate and potassium sulfate, granulated, and sieved to obtain particles with a particle size of 1-4.75 mm to obtain organic-inorganic mixed fertilizer particles;

[0078] (7) Encapsulation:

[0079] The organic-inorganic mixed fertilizer particles prepared in step (6) are placed in a disc granulator and preheated with hot air at 40°C for 5 minutes. A small amount of Litsea cubeba oil is sprayed on the organic-inorganic mixed fertilizer particles with a high-pressure spray gun to wet the surface of the particles without adhering to each other. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) is added to the disc granulator and rotated for 10 minutes. The remaining Litsea cubeba oil is then sprayed in and rotated for 20 minutes. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) can be coated on the surface of the organic-inorganic mixed fertilizer particles prepared in step (6) to obtain a mineral biological organic-inorganic composite fertilizer.

[0080] The waste crop straw in step (1) is corn straw.

[0081] Example 3

[0082] A mineral biological organic-inorganic composite fertilizer comprises the following raw materials in parts by weight: 50 parts of magnetic biochar, 25 parts of decomposed pig manure, 80 parts of minerals, 8 parts of modifiers, 12 parts of litsea cubeba oil, 5 parts of chitosan, 5 parts of microbial agents, 70 parts of urea, 50 parts of superphosphate and 40 parts of potassium sulfate.

[0083] The minerals are carbide slag, zeolite and white mud in a mass ratio of 1:1:1.

[0084] The modifier is heptadecafluorodecyltrimethoxysilane and sodium alginate in a mass ratio of 1:1.

[0085] The microbial agent is obtained by mixing and modifying Trichoderma aculeatus, Saccharomyces cerevisiae and Verticillium dahliae in a mass ratio of 1:1:1 with an ammonia solution with a mass fraction of 0.05%.

[0086] The Trichoderma spinulosa was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.17461; the Saccharomyces cerevisiae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC2.5432; the Verticillium dahliae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.15299.

[0087] A method for preparing a mineral biological organic-inorganic composite fertilizer, the steps are as follows:

[0088] (1) Preparation of magnetic biochar:

[0089] The abandoned crop straw was rinsed with clean water, dried to a moisture content of ≤3%, crushed and passed through an 80-mesh sieve, placed in a reactor, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, pyrolyzed at 600°C for 3h, cooled to 25°C, and ground through a 200-mesh sieve; the ground powder was added back into the reactor, 1 / 10 of the total volume of 0.75 mol / L ferrous sulfate heptahydrate solution was added, stirred evenly, 1 / 8 of the total volume of 30% hydrogen peroxide solution was added, heated to reflux at 85°C for 3h, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, and pyrolyzed for 3h to obtain magnetic biochar;

[0090] (2) Preparation of decomposed pig manure:

[0091] 30 kg of pig manure was aired for 5 days, the water content was controlled to be maintained at 40%, 5 kg of 30°C warm water was soaked to dissolve 2 kg of fermented EM stock solution, and stirred evenly; the pig manure was spread out, the fermented EM stock solution was soaked in warm water and placed for 2 hours, and then sprayed evenly on the surface of the pig manure at one time, the pig manure was piled up, the surface was covered with a layer of straw, and covered and sealed with a plastic film, and the pig manure was dark brown and the temperature dropped to 25°C to complete the decomposition, thereby obtaining decomposed pig manure;

[0092] (3) Preparation of microbial agents:

[0093] Trichoderma aculeatus, Saccharomyces cerevisiae, and Verticillium dahliae were cultured in soybean powder medium at 25°C, 28°C, and 25°C for 24 hours, respectively, and inoculated into LB medium at a 10% inoculum, and cultured at 25°C, 28°C, and 25°C with shaking until the bacterial concentration OD 600 ≈2.5, obtain fermentation broth of three bacteria, then mix them evenly in a mass ratio of 1:1:1 to obtain a mixed bacterial solution, add 30% of the volume of the mixed bacterial solution and a 0.05% ammonia solution by mass fraction, let it stand for 24 hours, and dry it to a water content of ≤3% to obtain a microbial agent;

[0094] (4) Preparation of activated hydrophobic controllable mineral powder:

[0095] The zeolite, carbide slag and white mud were ventilated and dried respectively, the water content was controlled to be ≤10%, and they were crushed and ground to pass through a 200-mesh sieve. The crushed zeolite, carbide slag and white mud powder were added to a reactor and stirred evenly; microwave heating was performed at 265° C. for activation for 35 min; heptadecafluorodecyltrimethoxysilane was dissolved in a 50% ethanol solution at a volume ratio of 1:10, stirred evenly, and added to a reactor, sodium alginate was added, and the mixture was heated at 60° C. for 4 h and then dried to obtain an active hydrophobic controllable mineral powder;

[0096] (5) Preparation of hydrophobic controllable heavy metal adsorption coating membrane:

[0097] The magnetic biochar prepared in step (1) is added to a reactor, and the microbial agent prepared in step (3) and the activated hydrophobic controllable mineral powder prepared in step (4) are added in sequence, and stirred evenly; chitosan is dissolved in water to prepare a chitosan aqueous solution with a mass fraction of 15%, and the mixture is stirred evenly and added to the reactor, and magnetic stirring is performed at 20-28° C. for 5 h at a speed of 400 rpm, and ventilation drying is performed until the water content is ≤5% to obtain a hydrophobic controllable heavy metal adsorption coating;

[0098] (6) Granulation:

[0099] The decomposed pig manure prepared in step (2) is ventilated and dried to a moisture content of ≤3%, crushed and ground to pass through a 200-mesh sieve, mixed evenly with urea, superphosphate and potassium sulfate, granulated, and sieved to obtain particles with a particle size of 1-4.75 mm to obtain organic-inorganic mixed fertilizer particles;

[0100] (7) Encapsulation:

[0101] The organic-inorganic mixed fertilizer particles prepared in step (6) are placed in a disc granulator and preheated with hot air at 45°C for 5 minutes. A small amount of Litsea cubeba oil is sprayed on the organic-inorganic mixed fertilizer particles with a high-pressure spray gun to wet the surface of the particles without adhering to each other. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) is added to the disc granulator and rotated for 10 minutes. The remaining Litsea cubeba oil is then sprayed in and rotated for 20 minutes. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) can be coated on the surface of the organic-inorganic mixed fertilizer particles prepared in step (6) to obtain a mineral biological organic-inorganic composite fertilizer.

[0102] The waste crop straw in step (1) is soybean straw.

[0103] Comparative Examples 1-4

[0104] The composition and ratio of the modifier heptadecafluorodecyltrimethoxysilane and sodium alginate were changed, and other raw materials and preparation methods were the same as those in Example 3, and the corresponding comparative examples were obtained by mixing them in different mass ratios.

[0105] The composition of the modifier is shown in Table 1:

[0106] Table 1 Modifier composition (mass ratio)

[0107] Heptadecafluorodecyltrimethoxysilane Sodium alginate Comparative Example 1 1 0 Comparative Example 2 0 1 Comparative Example 3 1 2 Comparative Example 4 2 1

[0108] Comparative Example 5

[0109] A mineral biological organic-inorganic composite fertilizer comprises the following raw materials in parts by weight: 50 parts of magnetic biochar, 25 parts of decomposed pig manure, 80 parts of minerals, 8 parts of modifiers, 12 parts of litsea cubeba oil, 5 parts of chitosan, 5 parts of microbial agents, 70 parts of urea, 50 parts of superphosphate and 40 parts of potassium sulfate.

[0110] The minerals are carbide slag, zeolite and white mud in a mass ratio of 1:1:1.

[0111] The modifier is heptadecafluorodecyltrimethoxysilane and sodium alginate in a mass ratio of 1:1.

[0112] The microbial agent is obtained by mixing and modifying Trichoderma aculeatus, Saccharomyces cerevisiae and Verticillium dahliae in a mass ratio of 1:1:1 with an ammonia solution with a mass fraction of 0.05%.

[0113] The Trichoderma spinulosa was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.17461; the Saccharomyces cerevisiae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC2.5432; the Verticillium dahliae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.15299.

[0114] A method for preparing a mineral biological organic-inorganic composite fertilizer, the steps are as follows:

[0115] (1) Preparation of magnetic biochar:

[0116] The abandoned crop straw was rinsed with clean water, dried to a moisture content of ≤3%, crushed and passed through an 80-mesh sieve, placed in a reactor, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, pyrolyzed at 600°C for 3h, cooled to 25°C, and ground through a 200-mesh sieve; the ground powder was added back into the reactor, 1 / 10 of the total volume of 0.75 mol / L ferrous sulfate heptahydrate solution was added, stirred evenly, 1 / 8 of the total volume of 30% hydrogen peroxide solution was added, heated to reflux at 85°C for 3h, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, and pyrolyzed for 3h to obtain magnetic biochar;

[0117] (2) Preparation of decomposed pig manure:

[0118] 30 kg of pig manure was aired for 5 days, the water content was controlled to be maintained at 40%, 5 kg of 30°C warm water was soaked to dissolve 2 kg of fermented EM stock solution, and stirred evenly; the pig manure was spread out, the fermented EM stock solution was soaked in warm water and placed for 2 hours, and then sprayed evenly on the surface of the pig manure at one time, the pig manure was piled up, the surface was covered with a layer of straw, and covered and sealed with a plastic film, and the pig manure was dark brown and the temperature dropped to 25°C to complete the decomposition, thereby obtaining decomposed pig manure;

[0119] (3) Preparation of microbial agents:

[0120] Trichoderma aculeatus, Saccharomyces cerevisiae, and Verticillium dahliae were cultured in soybean powder medium at 25°C, 28°C, and 25°C for 24 hours, respectively, and inoculated into LB medium at a 10% inoculum, and cultured at 25°C, 28°C, and 25°C with shaking until the bacterial concentration OD 600 ≈2.5, obtaining fermentation broths of three bacteria, then mixing them evenly in a mass ratio of 1:1:1 to obtain a mixed bacterial solution, and drying to a water content of ≤3% to obtain a microbial agent;

[0121] (4) Preparation of activated hydrophobic controllable mineral powder:

[0122] The zeolite, carbide slag and white mud were ventilated and dried respectively, the water content was controlled to be ≤10%, and then they were crushed and ground to pass through a 200-mesh sieve. The crushed zeolite, carbide slag and white mud powder were added to a reaction kettle and stirred evenly; and activated by microwave heating at 265°C for 35 minutes;

[0123] Dissolve heptadecafluorodecyl trimethoxysilane in ethanol solution, stir evenly, add to the reaction kettle, add sodium alginate,

[0124] After heating at 60°C with stirring for 4 hours, the mixture was dried to obtain active hydrophobic controllable mineral powder;

[0125] (5) Preparation of hydrophobic controllable heavy metal adsorption coating membrane:

[0126] The magnetic biochar prepared in step (1) is added to a reactor, and the microbial agent prepared in step (3) and the activated hydrophobic controllable mineral powder prepared in step (4) are added in sequence, and stirred evenly; chitosan is dissolved in water to prepare a chitosan aqueous solution with a mass fraction of 15%, and the mixture is stirred evenly and added to the reactor, and magnetic stirring is performed at 20-28° C. for 5 h at a speed of 400 rpm, and ventilation drying is performed until the water content is ≤5% to obtain a hydrophobic controllable heavy metal adsorption coating;

[0127] (6) Granulation:

[0128] The decomposed pig manure prepared in step (2) is ventilated and dried to a moisture content of ≤3%, crushed and ground to pass through a 200-mesh sieve, mixed evenly with urea, superphosphate and potassium sulfate, granulated, and sieved to obtain particles with a particle size of 1-4.75 mm to obtain organic-inorganic mixed fertilizer particles;

[0129] (7) Encapsulation:

[0130] The organic-inorganic mixed fertilizer particles prepared in step (6) are placed in a disc granulator and preheated with hot air at 45°C for 5 minutes. A small amount of Litsea cubeba oil is sprayed on the organic-inorganic mixed fertilizer particles with a high-pressure spray gun to wet the surface of the particles without adhering to each other. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) is added to the disc granulator and rotated for 10 minutes. The remaining Litsea cubeba oil is then sprayed in and rotated for 20 minutes. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) can be coated on the surface of the organic-inorganic mixed fertilizer particles prepared in step (6) to obtain a mineral biological organic-inorganic composite fertilizer.

[0131] The waste crop straw in step (1) is soybean straw.

[0132] Compared with Example 3, this comparative example is different from Example 3 in that only the microbial agent selected in step (3) of the preparation method does not use an ammonia solution, and the rest of the operation process is exactly the same as Example 3.

[0133] Comparative Example 6

[0134] A mineral biological organic-inorganic composite fertilizer comprises the following raw materials in parts by weight: 50 parts of magnetic biochar, 25 parts of decomposed pig manure, 80 parts of minerals, 8 parts of modifiers, 12 parts of litsea cubeba oil, 5 parts of chitosan, 5 parts of microbial agents, 70 parts of urea, 50 parts of superphosphate and 40 parts of potassium sulfate.

[0135] The minerals are carbide slag, zeolite and white mud in a mass ratio of 1:1:1.

[0136] The modifier is heptadecafluorodecyltrimethoxysilane and sodium alginate in a mass ratio of 1:1.

[0137] The microbial agent is obtained by mixing and modifying Trichoderma aculeatus, Saccharomyces cerevisiae and Verticillium dahliae in a mass ratio of 1:1:1 with an ammonia solution with a mass fraction of 0.05%.

[0138] The Trichoderma spinulosa was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.17461; the Saccharomyces cerevisiae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC2.5432; the Verticillium dahliae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.15299.

[0139] A method for preparing a mineral biological organic-inorganic composite fertilizer, the steps are as follows:

[0140] (1) Preparation of biochar:

[0141] The abandoned crop straw is rinsed with clean water, dried to a moisture content of ≤3%, ground through an 80-mesh sieve, placed in a reactor, nitrogen is introduced to exhaust the air, the temperature is increased to 600°C at a heating rate of 5°C / min, pyrolyzed at 600°C for 3h, cooled to 25°C, and ground through a 200-mesh sieve to obtain biochar;

[0142] (2) Preparation of decomposed pig manure:

[0143] 30 kg of pig manure was aired for 5 days, the water content was controlled to be maintained at 40%, 5 kg of 30°C warm water was soaked to dissolve 2 kg of fermented EM stock solution, and stirred evenly; the pig manure was spread out, the fermented EM stock solution was soaked in warm water and placed for 2 hours, and then sprayed evenly on the surface of the pig manure at one time, the pig manure was piled up, the surface was covered with a layer of straw, and covered and sealed with a plastic film, and the pig manure was dark brown and the temperature dropped to 25°C to complete the decomposition, thereby obtaining decomposed pig manure;

[0144] (3) Preparation of microbial agents:

[0145] Trichoderma aculeatus, Saccharomyces cerevisiae, and Verticillium dahliae were cultured in soybean powder medium at 25°C, 28°C, and 25°C for 24 hours, respectively, and inoculated into LB medium at a 10% inoculum, and cultured at 25°C, 28°C, and 25°C with shaking until the bacterial concentration OD 600 ≈2.5, obtain fermentation broth of three bacteria, then mix them evenly in a mass ratio of 1:1:1 to obtain a mixed bacterial solution, add 30% of the volume of the mixed bacterial solution and a 0.05% ammonia solution by mass fraction, let it stand for 24 hours, and dry it to a water content of ≤3% to obtain a microbial agent;

[0146] (4) Preparation of activated hydrophobic controllable mineral powder:

[0147] The zeolite, carbide slag and white mud were ventilated and dried respectively, the water content was controlled to be ≤10%, and they were crushed and ground to pass through a 200-mesh sieve. The crushed zeolite, carbide slag and white mud powder were added to a reactor and stirred evenly; microwave heating was performed at 265° C. for activation for 35 min; heptadecafluorodecyltrimethoxysilane was dissolved in a 50% ethanol solution at a volume ratio of 1:10, stirred evenly, and added to a reactor, sodium alginate was added, and the mixture was heated at 60° C. for 4 h and then dried to obtain an active hydrophobic controllable mineral powder;

[0148] (5) Preparation of hydrophobic controllable heavy metal adsorption coating membrane:

[0149] The biochar prepared in step (1) is added to a reactor, and the microbial agent prepared in step (3) and the activated hydrophobic controllable mineral powder prepared in step (4) are added in sequence, and stirred evenly; chitosan is dissolved in water to prepare a chitosan aqueous solution with a mass fraction of 15%, and the mixture is stirred evenly and added to the reactor, and magnetically stirred for 5 hours at 20-28°C, at a speed of 400 rpm, and ventilated and dried to a water content of ≤5% to obtain a hydrophobic controllable heavy metal adsorption coating;

[0150] (6) Granulation:

[0151] The decomposed pig manure prepared in step (2) is ventilated and dried to a moisture content of ≤3%, crushed and ground to pass through a 200-mesh sieve, mixed evenly with urea, superphosphate and potassium sulfate, granulated, and sieved to obtain particles with a particle size of 1-4.75 mm to obtain organic-inorganic mixed fertilizer particles;

[0152] (7) Encapsulation:

[0153] The organic-inorganic mixed fertilizer particles prepared in step (6) are placed in a disc granulator and preheated with hot air at 45°C for 5 minutes. A small amount of Litsea cubeba oil is sprayed on the organic-inorganic mixed fertilizer particles with a high-pressure spray gun to wet the surface of the particles without adhering to each other. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) is added to the disc granulator and rotated for 10 minutes. The remaining Litsea cubeba oil is then sprayed in and rotated for 20 minutes. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) can be coated on the surface of the organic-inorganic mixed fertilizer particles prepared in step (6) to obtain a mineral biological organic-inorganic composite fertilizer.

[0154] Compared with Example 3, in this comparative example, only the biochar prepared in step (1) of the preparation method was not subjected to the magnetization process, and the rest of the operation process was exactly the same as that of Example 3.

[0155] Comparative Example 7

[0156] A mineral biological organic-inorganic composite fertilizer comprises the following raw materials in parts by weight: 50 parts of magnetic biochar, 25 parts of decomposed pig manure, 80 parts of minerals, 8 parts of modifiers, 12 parts of litsea cubeba oil, 5 parts of chitosan, 5 parts of microbial agents, 70 parts of urea, 50 parts of superphosphate and 40 parts of potassium sulfate.

[0157] The minerals are carbide slag and zeolite in a mass ratio of 1:1.

[0158] The modifier is heptadecafluorodecyltrimethoxysilane and sodium alginate in a mass ratio of 1:1.

[0159] The microbial agent is obtained by mixing and modifying Trichoderma aculeatus, Saccharomyces cerevisiae and Verticillium dahliae in a mass ratio of 1:1:1 with an ammonia solution with a mass fraction of 0.05%.

[0160] The Trichoderma spinulosa was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.17461; the Saccharomyces cerevisiae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC2.5432; the Verticillium dahliae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.15299.

[0161] A method for preparing a mineral biological organic-inorganic composite fertilizer, the steps are as follows:

[0162] (1) Preparation of magnetic biochar:

[0163] The abandoned crop straw was rinsed with clean water, dried to a moisture content of ≤3%, crushed and passed through an 80-mesh sieve, placed in a reactor, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, pyrolyzed at 600°C for 3h, cooled to 25°C, and ground through a 200-mesh sieve; the ground powder was added back into the reactor, 1 / 10 of the total volume of 0.75 mol / L ferrous sulfate heptahydrate solution was added, stirred evenly, 1 / 8 of the total volume of 30% hydrogen peroxide solution was added, heated to reflux at 85°C for 3h, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, and pyrolyzed for 3h to obtain magnetic biochar;

[0164] (2) Preparation of decomposed pig manure:

[0165] 30 kg of pig manure was aired for 5 days, the water content was controlled to be maintained at 40%, 5 kg of 30°C warm water was soaked to dissolve 2 kg of fermented EM stock solution, and stirred evenly; the pig manure was spread out, the fermented EM stock solution was soaked in warm water and placed for 2 hours, and then sprayed evenly on the surface of the pig manure at one time, the pig manure was piled up, the surface was covered with a layer of straw, and covered and sealed with a plastic film, and the pig manure was dark brown and the temperature dropped to 25°C to complete the decomposition, thereby obtaining decomposed pig manure;

[0166] (3) Preparation of microbial agents:

[0167] Trichoderma aculeatus, Saccharomyces cerevisiae, and Verticillium dahliae were cultured in soybean powder medium at 25°C, 28°C, and 25°C for 24 hours, respectively, and inoculated into LB medium at a 10% inoculum, and cultured at 25°C, 28°C, and 25°C with shaking until the bacterial concentration OD 600 ≈2.5, obtain fermentation broth of three bacteria, then mix them evenly in a mass ratio of 1:1:1 to obtain a mixed bacterial solution, add 30% of the volume of the mixed bacterial solution and a 0.05% ammonia solution by mass fraction, let it stand for 24 hours, and dry it to a water content of ≤3% to obtain a microbial agent;

[0168] (4) Preparation of activated hydrophobic controllable mineral powder:

[0169] The zeolite and carbide slag were ventilated and dried respectively, the moisture content was controlled to be ≤10%, and then crushed and ground to pass through a 200-mesh sieve. The crushed zeolite and carbide slag powders were added to a reactor and stirred evenly. The zeolite and carbide slag powders were activated by microwave heating at 265°C for 35 minutes. Heptadecafluorodecyltrimethoxysilane was dissolved in a 50% ethanol solution at a volume ratio of 1:10, stirred evenly, and added to a reactor. Sodium alginate was added, and the mixture was heated at 60°C for 4 hours with stirring, and then dried to obtain an active hydrophobic controllable mineral powder.

[0170] (5) Preparation of hydrophobic controllable heavy metal adsorption coating membrane:

[0171] The magnetic biochar prepared in step (1) is added to a reactor, and the microbial agent prepared in step (3) and the activated hydrophobic controllable mineral powder prepared in step (4) are added in sequence, and stirred evenly; chitosan is dissolved in water to prepare a chitosan aqueous solution with a mass fraction of 15%, and the mixture is stirred evenly and added to the reactor, and magnetic stirring is performed at 20-28° C. for 5 h at a speed of 400 rpm, and ventilation drying is performed until the water content is ≤5% to obtain a hydrophobic controllable heavy metal adsorption coating;

[0172] (6) Granulation:

[0173] The decomposed pig manure prepared in step (2) is ventilated and dried to a moisture content of ≤3%, crushed and ground to pass through a 200-mesh sieve, mixed evenly with urea, superphosphate and potassium sulfate, granulated, and sieved to obtain particles with a particle size of 1-4.75 mm to obtain organic-inorganic mixed fertilizer particles;

[0174] (7) Encapsulation:

[0175] The organic-inorganic mixed fertilizer particles prepared in step (6) are placed in a disc granulator and preheated with hot air at 45°C for 5 minutes. A small amount of Litsea cubeba oil is sprayed on the organic-inorganic mixed fertilizer particles with a high-pressure spray gun to wet the surface of the particles without adhering to each other. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) is added to the disc granulator and rotated for 10 minutes. The remaining Litsea cubeba oil is then sprayed in and rotated for 20 minutes. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) can be coated on the surface of the organic-inorganic mixed fertilizer particles prepared in step (6) to obtain a mineral biological organic-inorganic composite fertilizer.

[0176] Compared with Example 3, the minerals selected in this comparative example are only carbide slag and zeolite in a mass ratio of 1:1, and white mud is not used. The rest of the operation process is exactly the same as that of Example 3.

[0177] Comparative Example 8

[0178] A mineral biological organic-inorganic composite fertilizer comprises the following raw materials in parts by weight: 50 parts of magnetic biochar, 25 parts of decomposed pig manure, 80 parts of minerals, 8 parts of modifiers, 12 parts of litsea cubeba oil, 5 parts of chitosan, 5 parts of microbial agents, 70 parts of urea, 50 parts of superphosphate and 40 parts of potassium sulfate.

[0179] The minerals are carbide slag and white mud in a mass ratio of 1:1.

[0180] The modifier is heptadecafluorodecyltrimethoxysilane and sodium alginate in a mass ratio of 1:1.

[0181] The microbial agent is obtained by mixing and modifying Trichoderma aculeatus, Saccharomyces cerevisiae and Verticillium dahliae in a mass ratio of 1:1:1 with an ammonia solution with a mass fraction of 0.05%.

[0182] The Trichoderma spinulosa was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.17461; the Saccharomyces cerevisiae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC2.5432; the Verticillium dahliae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.15299.

[0183] A method for preparing a mineral biological organic-inorganic composite fertilizer, the steps are as follows:

[0184] (1) Preparation of magnetic biochar:

[0185] The abandoned crop straw was rinsed with clean water, dried to a moisture content of ≤3%, crushed and passed through an 80-mesh sieve, placed in a reactor, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, pyrolyzed at 600°C for 3h, cooled to 25°C, and ground through a 200-mesh sieve; the ground powder was added back into the reactor, 1 / 10 of the total volume of 0.75 mol / L ferrous sulfate heptahydrate solution was added, stirred evenly, 1 / 8 of the total volume of 30% hydrogen peroxide solution was added, heated to reflux at 85°C for 3h, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, and pyrolyzed for 3h to obtain magnetic biochar;

[0186] (2) Preparation of decomposed pig manure:

[0187] 30 kg of pig manure was aired for 5 days, the water content was controlled to be maintained at 40%, 5 kg of 30°C warm water was soaked to dissolve 2 kg of fermented EM stock solution, and stirred evenly; the pig manure was spread out, the fermented EM stock solution was soaked in warm water and placed for 2 hours, and then sprayed evenly on the surface of the pig manure at one time, the pig manure was piled up, the surface was covered with a layer of straw, and covered and sealed with a plastic film, and the pig manure was dark brown and the temperature dropped to 25°C to complete the decomposition, thereby obtaining decomposed pig manure;

[0188] (3) Preparation of microbial agents:

[0189] Trichoderma aculeatus, Saccharomyces cerevisiae, and Verticillium dahliae were cultured in soybean powder medium at 25°C, 28°C, and 25°C for 24 hours, respectively, and inoculated into LB medium at a 10% inoculum, and cultured at 25°C, 28°C, and 25°C with shaking until the bacterial concentration OD 600 ≈2.5, obtain fermentation broth of three bacteria, then mix them evenly in a mass ratio of 1:1:1 to obtain a mixed bacterial solution, add 30% of the volume of the mixed bacterial solution and a 0.05% ammonia solution by mass fraction, let it stand for 24 hours, and dry it to a water content of ≤3% to obtain a microbial agent;

[0190] (4) Preparation of activated hydrophobic controllable mineral powder:

[0191] The carbide slag and white mud were ventilated and dried respectively, the water content was controlled to be ≤10%, and then ground and passed through a 200-mesh sieve. The ground carbide slag and white mud powder were added to a reactor and stirred evenly. The mixture was activated by microwave heating at 265°C for 35 minutes. Heptadecafluorodecyltrimethoxysilane was dissolved in a 50% ethanol solution at a volume ratio of 1:10, stirred evenly, and added to a reactor. Sodium alginate was added, and the mixture was heated at 60°C for 4 hours with stirring, and then dried to obtain an active hydrophobic controllable mineral powder.

[0192] (5) Preparation of hydrophobic controllable heavy metal adsorption coating membrane:

[0193] The magnetic biochar prepared in step (1) is added to a reactor, and the microbial agent prepared in step (3) and the activated hydrophobic controllable mineral powder prepared in step (4) are added in sequence, and stirred evenly; chitosan is dissolved in water to prepare a chitosan aqueous solution with a mass fraction of 15%, and the mixture is stirred evenly and added to the reactor, and magnetic stirring is performed at 20-28° C. for 5 h at a speed of 400 rpm, and ventilation drying is performed until the water content is ≤5% to obtain a hydrophobic controllable heavy metal adsorption coating;

[0194] (6) Granulation:

[0195] The decomposed pig manure prepared in step (2) is ventilated and dried to a moisture content of ≤3%, crushed and ground to pass through a 200-mesh sieve, mixed evenly with urea, superphosphate and potassium sulfate, granulated, and sieved to obtain particles with a particle size of 1-4.75 mm to obtain organic-inorganic mixed fertilizer particles;

[0196] (7) Encapsulation:

[0197] The organic-inorganic mixed fertilizer particles prepared in step (6) are placed in a disc granulator and preheated with hot air at 45°C for 5 minutes. A small amount of Litsea cubeba oil is sprayed on the organic-inorganic mixed fertilizer particles with a high-pressure spray gun to wet the surface of the particles without adhering to each other. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) is added to the disc granulator and rotated for 10 minutes. The remaining Litsea cubeba oil is then sprayed in and rotated for 20 minutes. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) can be coated on the surface of the organic-inorganic mixed fertilizer particles prepared in step (6) to obtain a mineral biological organic-inorganic composite fertilizer.

[0198] Compared with Example 3, the minerals selected in this comparative example are only carbide slag and white mud with a mass ratio of 1:1, and zeolite is not used. The rest of the operation process is exactly the same as that of Example 3.

[0199] Comparative Example 9

[0200] A mineral biological organic-inorganic composite fertilizer comprises the following raw materials in parts by weight: 50 parts of magnetic biochar, 25 parts of decomposed pig manure, 80 parts of minerals, 8 parts of modifiers, 12 parts of litsea cubeba oil, 5 parts of chitosan, 5 parts of microbial agents, 70 parts of urea, 50 parts of superphosphate and 40 parts of potassium sulfate.

[0201] The minerals are zeolite and white mud in a mass ratio of 1:1.

[0202] The modifier is heptadecafluorodecyltrimethoxysilane and sodium alginate in a mass ratio of 1:1.

[0203] The microbial agent is obtained by mixing and modifying Trichoderma aculeatus, Saccharomyces cerevisiae and Verticillium dahliae in a mass ratio of 1:1:1 with an ammonia solution with a mass fraction of 0.05%.

[0204] The Trichoderma spinulosa was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.17461; the Saccharomyces cerevisiae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC2.5432; the Verticillium dahliae was purchased from China General Microorganism Collection Center (CGMCC), with an address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and a collection number of CGMCC3.15299.

[0205] A method for preparing a mineral biological organic-inorganic composite fertilizer, the steps are as follows:

[0206] (1) Preparation of magnetic biochar:

[0207] The abandoned crop straw was rinsed with clean water, dried to a moisture content of ≤3%, crushed and passed through an 80-mesh sieve, placed in a reactor, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, pyrolyzed at 600°C for 3h, cooled to 25°C, and ground through a 200-mesh sieve; the ground powder was added back into the reactor, 1 / 10 of the total volume of 0.75 mol / L ferrous sulfate heptahydrate solution was added, stirred evenly, 1 / 8 of the total volume of 30% hydrogen peroxide solution was added, heated to reflux at 85°C for 3h, nitrogen was introduced to exhaust the air, the temperature was increased to 600°C at a heating rate of 5°C / min, and pyrolyzed for 3h to obtain magnetic biochar;

[0208] (2) Preparation of decomposed pig manure:

[0209] 30 kg of pig manure was aired for 5 days, the water content was controlled to be maintained at 40%, 5 kg of 30°C warm water was soaked to dissolve 2 kg of fermented EM stock solution, and stirred evenly; the pig manure was spread out, the fermented EM stock solution was soaked in warm water and placed for 2 hours, and then sprayed evenly on the surface of the pig manure at one time, the pig manure was piled up, the surface was covered with a layer of straw, and covered and sealed with a plastic film, and the pig manure was dark brown and the temperature dropped to 25°C to complete the decomposition, thereby obtaining decomposed pig manure;

[0210] (3) Preparation of microbial agents:

[0211] Trichoderma aculeatus, Saccharomyces cerevisiae, and Verticillium dahliae were cultured in soybean powder medium at 25°C, 28°C, and 25°C for 24 hours, respectively, and inoculated into LB medium at a 10% inoculum, and cultured at 25°C, 28°C, and 25°C with shaking until the bacterial concentration OD 600 ≈2.5, obtain fermentation broth of three bacteria, then mix them evenly in a mass ratio of 1:1:1 to obtain a mixed bacterial solution, add 30% of the volume of the mixed bacterial solution and a 0.05% ammonia solution by mass fraction, let it stand for 24 hours, and dry it to a water content of ≤3% to obtain a microbial agent;

[0212] (4) Preparation of activated hydrophobic controllable mineral powder:

[0213] The zeolite and white mud were ventilated and dried respectively, the moisture content was controlled to be ≤10%, and then ground and passed through a 200-mesh sieve. The ground zeolite and white mud powder were added to a reactor and stirred evenly. The zeolite and white mud powders were activated by microwave heating at 265°C for 35 minutes. Heptadecafluorodecyltrimethoxysilane was dissolved in a 50% ethanol solution at a volume ratio of 1:10, stirred evenly, and added to a reactor. Sodium alginate was added, and the mixture was heated at 60°C for 4 hours with stirring, and then dried to obtain an active hydrophobic controllable mineral powder.

[0214] (5) Preparation of hydrophobic controllable heavy metal adsorption coating membrane:

[0215] The magnetic biochar prepared in step (1) is added to a reactor, and the microbial agent prepared in step (3) and the activated hydrophobic controllable mineral powder prepared in step (4) are added in sequence, and stirred evenly; chitosan is dissolved in water to prepare a chitosan aqueous solution with a mass fraction of 15%, and the mixture is stirred evenly and added to the reactor, and magnetic stirring is performed at 20-28° C. for 5 h at a speed of 400 rpm, and ventilation drying is performed until the water content is ≤5% to obtain a hydrophobic controllable heavy metal adsorption coating;

[0216] (6) Granulation:

[0217] The decomposed pig manure prepared in step (2) is ventilated and dried to a moisture content of ≤3%, crushed and ground to pass through a 200-mesh sieve, mixed evenly with urea, superphosphate and potassium sulfate, granulated, and sieved to obtain particles with a particle size of 1-4.75 mm to obtain organic-inorganic mixed fertilizer particles;

[0218] (7) Encapsulation:

[0219] The organic-inorganic mixed fertilizer particles prepared in step (6) are placed in a disc granulator and preheated with hot air at 45°C for 5 minutes. A small amount of Litsea cubeba oil is sprayed on the organic-inorganic mixed fertilizer particles with a high-pressure spray gun to wet the surface of the particles without adhering to each other. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) is added to the disc granulator and rotated for 10 minutes. The remaining Litsea cubeba oil is then sprayed in and rotated for 20 minutes. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) can be coated on the surface of the organic-inorganic mixed fertilizer particles prepared in step (6) to obtain a mineral biological organic-inorganic composite fertilizer.

[0220] The waste crop straw in step (1) is soybean straw.

[0221] Compared with Example 3, the minerals selected in this comparative example are only zeolite and white mud with a mass ratio of 1:1, and carbide slag is not used. The rest of the operation process is exactly the same as that of Example 3.

[0222] Detection experiment

[0223] 26 mu of acidic heavy metal contaminated brown soil land with similar soil environment at the location of 010 rural road in Anning Village, Dongmiao Township, Du'an Yao Autonomous County, Hechi City, Guangxi Zhuang Autonomous Region was selected as an experimental field for rice planting (rice purchased from Guangxi Zhuang Autonomous Region Nanning Liangnong Seed Co., Ltd. as Zhuangxiangyou 1205), and the 24 mu experimental field was divided into 12 portions, each with two mu. The seedlings after seedling cultivation were transplanted on March 27, 2021, with a row spacing of 30 cm and a plant spacing of 10-12 cm. Top dressing began 5 days after transplanting, and the fertilizers prepared in Examples 1-3 and Comparative Examples 1-9 were applied to the 12 experimental fields respectively. Fertilization was performed once, and only the fertilizers applied were different. The rest were the same daily rice field management, and the harvest was carried out on July 18, 2023. After harvest, soil from each component test field was sampled for experiments. The soil was sampled at a depth of 0-40 cm. Three samples were taken from each component test field for heavy metal detection. The Hg, As, Cd, Cr, Pb, Cu, Zn, and Ni content indicators after harvest were detected and averaged. The pH value changes of the acidic soil in each test field were detected and averaged. The soil without fertilizer was selected as a blank control. The specific test results are shown in Table 2:

[0224] Referring to the detection method of “Determination of Heavy Metals in Soil Quality-Aqua Regia Reflux Digestion Atomic Absorption Spectrometry” (NY / T 1613-2008), the contents of eight heavy metals, including Hg, As, Cd, Cr, Pb, Cu, Zn and Ni, were tested in the soil samples of the experimental field.

[0225] Table 2 Soil quality heavy metal detection table (unit: mg / kg)

[0226]

[0227]

[0228] According to the experimental test data, the mineral biological organic-inorganic composite fertilizer prepared in Examples 1-3 was applied, and compared with Comparative Examples 5-9 and a blank control group. The present invention has a significant improvement effect on acidic heavy metal soil. After applying the fertilizer of the present invention, the Hg content in the soil is about 0.06 mg / kg, which is reduced by 94%; the As content in the soil is about 5.1 mg / kg, which is reduced by 60%; the Cd content in the soil is about 0.1 mg / kg, which is reduced by 88%; the Cr content in the soil is about 32 mg / kg, which is reduced by 63%; the Pb content in the soil is about 8.9 mg / kg, which is reduced by 71%; the Cu content in the soil is about 12.15 mg / kg, which is reduced by 82%; the Zn content in the soil is about 46 mg / kg, which is reduced by 71%; the Ni content in the soil is about 19 mg / kg, which is reduced by 78%. After applying the fertilizer, the soil pH is increased from 4.8 to about 7, wherein the magnetic biochar, the microbial preparation blended with ammonia water, the carbide slag in the coating film component, the zeolite, The mutual promotion of white mud is an important factor in the adsorption of heavy metals.

[0229] According to the national standard "Slow-release Fertilizer" (GB / T 23348-2009), the fertilizers prepared in Examples 1-3 and Comparative Examples 1-9 were immersed in 25°C still water to test the nutrient release rate for 24 hours, 7 days, and 28 days. The specific test results are shown in Table 3.

[0230] Table 3 Product index comparison table

[0231]

[0232] As can be seen from Table 3, the mineral biological organic-inorganic composite fertilizers prepared in Examples 1-3 of the present invention have an average 24-hour nutrient release rate of 6%, a 7-day cumulative nutrient release rate of 18%, and a 28-day nutrient release rate of 43%. Therefore, the 24-hour nutrient release rate measured by the 25°C water immersion method of the present invention is less than or equal to 15%; the 28-day cumulative nutrient release rate is less than or equal to 80%, and the product meets national standards.

[0233] To further verify the fertilizer effect, field experiments were conducted:

[0234] Field experiment

[0235] Thirteen test plots of 26 mu of acidic heavy metal-contaminated brown soil with similar soil environment were selected at the location of 010 Township Road, Anning Village, Dongmiao Township, Du'an Yao Autonomous County, Hechi City, Guangxi Zhuang Autonomous Region. The per-mu yield, thousand-grain weight, and number of seedlings withered and died after harvesting of the fertilizers prepared by Examples 1-3 and Comparative Examples 1-10 were statistically analyzed. The specific test results are shown in Table 4:

[0236] Table 4 Rice harvest status

[0237]

[0238] According to Table 4, the mineral biological organic-inorganic composite fertilizer prepared by Examples 1-3 was compared with Comparative Examples 1-9. Only one seedling withered and died due to acidity and heavy metals, which was significantly better than the comparative example; the average thousand-grain weight of rice was 28.01 g, which was increased by 21.68%, and the grains were fuller; the average yield per mu was 746 kg, and the yield was increased by 23.1%, indicating that the mineral biological organic-inorganic composite fertilizer prepared by the present invention can better meet the nutrient demand of rice growth, significantly improve the utilization rate of fertilizer, improve the soil quality of acidic and heavy metal soils, promote the growth of rice in acidic and heavy metal contaminated soils, and increase the yield and quality of rice.

[0239] It should be noted that the above embodiments are only partial embodiments of the preferred methods of implementing the present invention, rather than all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

Claims

1. A mineral biological organic-inorganic composite fertilizer, characterized in that: The invention comprises the following raw materials in parts by weight: 30-50 parts of magnetic biochar, 15-25 parts of decomposed pig manure, 20-80 parts of minerals, 5-8 parts of modifiers, 6-12 parts of litsea cubeba oil, 1-5 parts of chitosan, 3-5 parts of microbial agents, 50-70 parts of urea, 30-50 parts of superphosphate and 25-40 parts of potassium sulfate; the minerals are carbide slag, zeolite and white mud in a mass ratio of 1:1:1; the modifier is heptadecafluorodecyltrimethoxysilane and sodium alginate in a mass ratio of 1:1; the microbial agent is obtained by mixing and modifying Trichoderma acanthosporum, Saccharomyces cerevisiae and Verticillium dahliae in a mass ratio of 1:1:1 with an ammonia solution with a mass fraction of 0.05%.

2. The mineral biological organic-inorganic composite fertilizer according to claim 1, characterized in that: The Trichoderma spinulosa ( Trichoderma asperellum ) is deposited as CGMCC3.17461; the brewer's yeast ( Saccharomyces cerevisiae ) is deposited as CGMCC2.5432; the dahlia verticillium ( Verticillium dahliae )'s deposit number is CGMCC3.15299.

3. The method for preparing the mineral biological organic-inorganic composite fertilizer according to any one of claims 1 to 2, characterized in that: Here are the steps: (1) Preparation of magnetic biochar: The discarded crop straw was rinsed with clean water, dried to a moisture content of ≤3%, crushed and passed through an 80-mesh sieve, placed in a reactor, nitrogen was introduced to exhaust the air, the temperature was raised to 600°C at a rate of 5°C / min, pyrolyzed at 600°C for 3h, cooled to 25°C, and ground through a 200-mesh sieve; The ground powder was added back into the reactor, 1 / 10 of the total volume of 0.75 mol / L ferrous sulfate heptahydrate solution was added, stirred evenly, 1 / 8 of the total volume of 30% hydrogen peroxide solution was added, heated to 85°C for reflux for 3 h, nitrogen was introduced to exhaust the air, the temperature was raised to 600°C at a rate of 5°C / min, and pyrolyzed for 3 h to obtain magnetic biochar; (2) Preparation of decomposed pig manure: 30 kg of pig manure is dried in the sun for 3-5 days, the water content is controlled to be maintained at 40%, 2 kg of fermented EM stock solution is dissolved in 5 kg of 30°C warm water, and stirred evenly; the pig manure is spread out, the fermented EM stock solution is soaked in warm water and placed for 2 hours, and then sprayed evenly on the surface of the pig manure at one time, the pig manure is piled up, and the surface is covered with a layer of straw, and covered and sealed with a plastic film. When the pig manure turns dark brown and the temperature drops to 25°C, the decomposition is completed, and the decomposed pig manure is obtained; (3) Preparation of microbial agents: Trichoderma aculeatus, Saccharomyces cerevisiae, and Verticillium dahliae were cultured in soybean powder medium at 25°C, 28°C, and 25°C for 24 hours, respectively, and inoculated into LB medium at a 10% inoculum, and cultured at 25°C, 28°C, and 25°C with shaking until the bacterial concentration OD 600 ≈2.5, obtain fermentation broth of three bacteria, then mix them evenly in a mass ratio of 1:1:1 to obtain a mixed bacterial solution, add 30% of the volume of the mixed bacterial solution and a 0.05% ammonia solution, let it stand for 24 hours, and dry it to a water content of ≤3% to obtain a microbial agent; (4) Preparation of active hydrophobic controllable mineral powder: The zeolite, carbide slag and white mud were dried separately, the water content was controlled to be ≤10%, and they were crushed and ground to pass through a 200-mesh sieve. The crushed zeolite, carbide slag and white mud powders were added to a reactor and stirred evenly. The powders were activated by microwave heating at 220-265°C for 35 minutes. The heptadecafluorodecyltrimethoxysilane in the modifier was dissolved in an ethanol solution with a mass concentration of 50% at a volume ratio of 1:10, stirred evenly, and added to the reactor. The sodium alginate in the modifier was added, and the mixture was heated at 60°C for 4 hours with stirring, and then dried to obtain an active hydrophobic controllable mineral powder. (5) Preparation of hydrophobic controllable heavy metal adsorption coating membrane: The magnetic biochar prepared in step (1) is added to a reactor, and the microbial agent prepared in step (3) and the active hydrophobic controllable mineral powder prepared in step (4) are added in sequence, and stirred evenly; chitosan is dissolved in water to prepare a chitosan aqueous solution with a mass fraction of 15%, and the solution is stirred evenly and added to the reactor, and magnetic stirring is performed at 20-28°C for 5 hours at a speed of 400 rpm, and ventilation drying is performed until the water content is ≤5% to obtain a hydrophobic controllable heavy metal adsorption coating film; (6) Granulation: The decomposed pig manure prepared in step (2) is ventilated and dried to a moisture content of ≤3%, crushed and ground to pass through a 200-mesh sieve, mixed evenly with urea, superphosphate and potassium sulfate, granulated, and sieved to obtain particles with a particle size of 1-4.75 mm to obtain organic-inorganic mixed fertilizer particles; (7) Encapsulation: The organic-inorganic mixed fertilizer particles prepared in step (6) are placed in a disc granulator and preheated with hot air at 35-45°C for 5 minutes. A small amount of Litsea cubeba oil is sprayed on the organic-inorganic mixed fertilizer particles with a high-pressure spray gun to wet the surface of the particles without adhering to each other. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) is added to the disc granulator and rotated for 10 minutes. The remaining Litsea cubeba oil is then sprayed in and rotated for 20 minutes. The hydrophobic controllable heavy metal adsorption coating film prepared in step (5) can be coated on the surface of the organic-inorganic mixed fertilizer particles prepared in step (6) to obtain a mineral biological organic-inorganic composite fertilizer.

4. The method for preparing the mineral biological organic-inorganic composite fertilizer according to claim 3, characterized in that: The waste crop straw in step (1) is one or more of rice straw, wheat straw, corn straw, reed straw, peanut seedlings, sorghum stalks, and soybean straw.

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