A biological organic fertilizer for repairing heavy metal cadmium in soil and its preparation method

Abstract

The present invention discloses a bio-organic fertilizer for repairing heavy metal cadmium in soil and a preparation method thereof, belonging to the technical field of organic fertilizers. It is made of the following raw materials in parts by weight: 7-12 parts of a composite microbial agent, 30-40 parts of modified biochar, 3-8 parts of sodium alginate, 6-8 parts of a chelating agent, and 60-80 parts of decomposed edible fungus residue; the composite microbial agent is made of potassium-solubilizing jelly-like bacillus MSSW02, Pseudomonas ayutans, and Bacillus afusii; the chelating agent is composed of calcium humate and nano-hydroxyapatite in a mass ratio of 100:3-5. The multi-component synergistic effect of the present invention effectively reduces the content of heavy metals in the soil, especially the content of heavy metal Cd. At the same time, it also contains rich organic matter, which can significantly improve the physical and chemical properties of the soil, improve the soil's water and fertilizer retention capacity, and promote crop growth; it has a good effect on repairing farmland soil with moderate to light cadmium pollution and a significant effect on promoting the growth of crops.

Description

Technical Field

[0001] The invention belongs to the technical field of bio-organic fertilizers, and particularly relates to a bio-organic fertilizer for repairing heavy metal cadmium in soil and a preparation method thereof. Background Art

[0002] "Agriculture is rooted in the land." Soil is an important natural resource and an important carrier of agriculture. Most of the vegetables, grains, and fruits that provide most of the nutrients needed by humans are produced in the soil. At the same time, the soil also carries about 90% of the pollutants in the environment. Soil contaminated by heavy metals is difficult to repair, especially heavy metals represented by Cd, Hg, As, etc. Once they enter the soil, they are continuously accumulated, reducing soil fertility, crop yields, and quality. Some of them are converted into alkyl compounds, and the more active parts are absorbed by plants and animals, accumulating in humans and livestock through the food chain, thereby endangering human health.

[0003] Studies have shown that soil cadmium contamination is associated with the long-term improper use of chemical fertilizers. According to statistics, phosphate fertilizers contain higher levels of cadmium than potassium and nitrogen fertilizers. Therefore, the long-term application of cadmium-containing phosphate fertilizers may cause soil cadmium contamination. Unlike traditional chemical fertilizers, bio-organic fertilizers are primarily derived from organic matter such as animal and plant residues and excrement. The use of organic fertilizers can effectively reduce the content of harmful heavy metals in the soil through microbial decomposition and conversion. Bio-organic fertilizers are also rich in organic matter. When applied to the soil, they increase soil porosity, improving aeration and water permeability. They provide a rich food source for soil microorganisms, promoting their reproduction. These microorganisms further decompose organic matter, releasing nutrients and improving soil fertility, further reducing the use of chemical fertilizers and reducing the heavy metal pollution caused by long-term use of chemical fertilizers. Therefore, bio-organic fertilizers offer significant advantages in controlling heavy metal contamination in soil.

[0004] Currently, there are many bio-organic fertilizers for remediating heavy metal-contaminated soils, but they also have many drawbacks. For example, single microbial agents are sensitive to environmental conditions. If soil conditions are unsuitable (such as extreme pH, drought, or excessive moisture), the microbial survival rate and activity are low, and the remediation effect is unstable. Traditional organic fertilizers lack specificity and are less effective at remediating heavy metal cadmium. The use of some raw materials (such as sewage sludge) may aggravate cadmium contamination. Therefore, there is an urgent need for a bio-organic fertilizer with excellent fixation and remediation effects on heavy metal cadmium in soil. Summary of the Invention

[0005] The present invention aims to provide a bio-organic fertilizer for remediating heavy metal cadmium in soil and a method for preparing the same. This invention constructs a ternary synergistic system of "functional microorganisms, modified biochar, and an organic chelating agent" to effectively reduce the content of heavy metals in soil, particularly Cd. The system also contains abundant organic matter, significantly improving soil physical and chemical properties, increasing its water and fertilizer retention capacity, and promoting crop growth. The fertilizer is effective in remediating farmland soil with moderate to mild cadmium contamination and significantly promoting crop growth.

[0006] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0007] A bio-organic fertilizer for repairing heavy metal cadmium in soil is prepared from the following raw materials in parts by weight: 7-12 parts of a composite microbial agent, 30-40 parts of modified biochar, 3-8 parts of sodium alginate, 6-8 parts of a chelating agent, and 60-80 parts of decomposed edible fungus residue; the composite microbial agent is prepared from potassium-solubilizing jelly-like Paenibacillus mucilaginosus MSSW02, Pseudomonas plecoglossicida, and Bacillus aryabhattai; the strain number of the potassium-solubilizing jelly-like Paenibacillus MSSW02 is CCTCC NO: M20231472, and it is deposited in the China Center for Type Culture Collection on August 14, 2023, at Wuhan University, Wuhan, China; the strain number of the Pseudomonas plecoglossicida is CGMCC No. 1.16111, purchased from the China General Microbiological Culture Collection on March 29, 2017, at No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The Bacillus argyi strain, CGMCC No. 1.15248, was purchased from the China General Microbiological Culture Collection on May 10, 2015, at No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The chelating agent is composed of calcium humate and nano-hydroxyapatite in a mass ratio of 100:3-5. The potassium-solubilizing jelly-like Paenibacillus MSSW02 used in this invention was deposited with the China Type Culture Collection as part of the patent application prior to the application date and was donated by the depositor, Hubei Maosheng Biological Co., Ltd. Both Pseudomonas ayutans and Bacillus argyi strains can be purchased through the collection's open catalog, eliminating the need for duplicate deposits.

[0008] Preferably, the calcium humate is prepared by the following method:

[0009] (1) Grind the weathered coal humic acid through a 100-mesh sieve to obtain humic acid powder, then add it to a 0.1 mol / L NaOH solution at a solid-liquid ratio of 1 g:10 ml, stir and react at 60 °C for 2 h, and centrifuge to obtain the supernatant to obtain an activated humic acid solution;

[0010] (2) Adjust the pH of the activated humic acid solution to 6.5, slowly add a 20% mass fraction of Ca(OH)2 suspension, stir evenly and react at 60°C for 4 hours. After the reaction is completed, collect the precipitate by centrifugation, wash with deionized water until no Ca²⁺ remains, dry at 60°C, and then crush through an 80-mesh sieve.

[0011] Preferably, the volume ratio of the activated humic acid solution to the Ca(OH)2 suspension in step (2) is 1:1.5.

[0012] Preferably, the composite microbial agent is prepared by the following method: potassium-solubilizing jelly-like Bacillus MSSW02, Pseudomonas ayutans, and Bacillus afusii are thawed and activated respectively, streaked on a plate and cultured in an incubator at 30°C for 48 hours, a loop of the cultured strain is placed in LB liquid culture medium, placed in a shaker at 30°C and 180 r / min and shaken for 24 hours to obtain a seed liquid; the seed liquids of the three strains are inoculated into 200 mL of TSB liquid culture medium at an inoculum size of 3%, and shaken and cultured at 30°C and 200 r / min for 72 hours to obtain a fermentation liquid; the three fermentation liquids are mixed in a volume ratio of 2:1:1 to obtain a composite microbial agent.

[0013] The LB liquid medium is composed of: 10.0 g / L tryptone, 5.0 g / L yeast extract, 10.0 g / L sodium chloride, pH 7.0; the TSB liquid medium is composed of: 17.0 g / L tryptone, 3.0 g / L soy peptone, 5.0 g / L sodium chloride, 2.5 g / L potassium hydrogen phosphate, pH 7.3.

[0014] Preferably, the modified biochar is prepared by the following method:

[0015] Step 1: Wash and dry the corn straw, crush it, put it into a muffle furnace, heat it to 600°C at a rate of 3°C / min under a nitrogen atmosphere, and calcine it at high temperature for 2 hours to obtain corn straw biochar;

[0016] Step 2: corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea, and deionized water are mixed in proportion and stirred evenly, heated to 80°C for reaction for 2 hours, and the mixture is naturally cooled to room temperature and then placed in an oven at 80°C for drying for 16 hours to obtain a dry product;

[0017] Step 3: The product obtained in step 2 is transferred into a tubular furnace and calcined at high temperature under a nitrogen atmosphere. After completion, the product is cooled to room temperature and washed three times with deionized water, dried and ground to obtain modified biochar.

[0018] Preferably, in step 2, the usage ratio of corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea and deionized water is 5g:0.002mol:0.001mol:0.1mol:200ml.

[0019] Preferably, the specific method of high-temperature calcination in step 3 is to increase the temperature to 800° C. at a heating rate of 10° C. / min and calcine for 2 hours.

[0020] Preferably, the decomposed edible fungus residue is prepared by the following method: discarded mushroom sticks after the cultivation of edible fungi such as oyster mushrooms, enoki mushrooms, and king oyster mushrooms are removed and crushed to obtain edible fungus residue, inoculated with EM bacteria accounting for 1% of the total weight of the edible fungus residue, mixed thoroughly, and water is added to adjust the moisture content of the mixture pile to 60-65%, composted and fermented, and the temperature of the mixture pile is controlled in the range of 50°C-65°C. After fermentation for 7-10 days, the fermentation product is dried and crushed to obtain the decomposed edible fungus residue.

[0021] Preferably, the effective viable count of the EM bacteria is ≥100 billion / gram.

[0022] The present invention also provides a method for preparing the above-mentioned bio-organic fertilizer for repairing heavy metal cadmium in soil, comprising the following steps:

[0023] S1: preparing a composite microbial agent and modified biochar respectively, and mixing the two in proportion to obtain a mixture;

[0024] S2: preparing calcium humate and mixing it with nano-hydroxyapatite in a certain proportion to obtain a chelating agent;

[0025] S3: preparing decomposed edible fungus residue;

[0026] S4: fully mix the decomposed edible fungus residue, the chelating agent and the mixture obtained in S1, prepare a solution of sodium alginate with a mass fraction of 1% and spray it evenly on the surface of the mixture, and granulate it with a granulator.

[0027] The present invention selects three dominant strains, namely, Paenibacillus jelly-like potassium-solubilizing MSSW02, Pseudomonas ayusi, and Bacillus argei, and uses them in a specific ratio. The strains act synergistically, and their metabolites can adsorb heavy metal ions in the soil, significantly reducing the content of the effective heavy metal Cd in the soil. Simultaneously, Paenibacillus jelly-like decomposes mineral phosphorus and potassium, Pseudomonas ayusi secretes organic acids to further dissolve phosphate, and Bacillus argei fixes nitrogen, while plant hormone substances secreted by Pseudomonas ayusi promote root absorption of nutrients. The three strains act synergistically, have complementary functions, are highly active, and have a long field action time.

[0028] Biochar has attracted widespread attention due to its abundance and renewability. However, the low specific surface area of ​​traditional biochar limits its adsorption activity. In order to increase the specific surface area and improve the performance of biochar, biochar is usually modified before use. This invention uses Fe-Ce-N three elements to modify corn straw biochar, and the micromorphology ( Figure 1 ) It can be seen that the surface of the modified biochar contains not only numerous micropores and nanoparticles, but also many filamentous carbon nanotubes, which greatly increases the specific surface area and porosity of the modified biochar, providing more active sites for the adsorption of heavy metal Cd ions. At the same time, the introduction of Fe-Ce-N doping enriches the surface functional groups, increases the complexing ability for heavy metal ions, and effectively reduces the biological effectiveness of heavy metal Cd in the soil.

[0029] The chelating agent used in the present invention is composed of calcium humate and nano-hydroxyapatite in a specific ratio. The Ca²⁺ released by calcium humate preferentially occupies the negative potential point of soil colloid, reducing the adsorption of Cd²⁺ by the soil. At the same time, the carboxyl and phenolic hydroxyl groups of humic acid form a stable complex with Cd²⁺; while nano-hydroxyapatite slowly releases PO4 in the soil. 3- , and Cd 2+ An extremely insoluble apatite-type precipitate is formed. The two work synergistically, and humic acid is adsorbed on the surface of nanohydroxyapatite through carboxyl groups (-COOH) to prevent it from agglomerating, thereby optimizing the dispersion and reaction microenvironment of nanohydroxyapatite, and further improving its chelation stability for heavy metal Cd in the soil.

[0030] The beneficial effects of the present invention are as follows: the bio-organic fertilizer comprises a composite microbial agent with specific functionalities, modified biochar, a chelating agent, and organic matter. Through multiple mechanisms, including microbial action, Cd²⁺-organic matter complexation, and biochar fixation, it synergistically reduces the bioavailability of Cd in the soil, while simultaneously reducing cadmium absorption and accumulation in crops, thereby improving food safety. Furthermore, the present invention can increase soil organic matter content, improve the soil's physical and chemical environment, and enhance soil fertility, significantly increasing crop yields and incomes. It is widely applicable to farmland with moderate to mild cadmium contamination. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Scanning electron micrographs of the modified biochar prepared in the present invention before and after modification, wherein a) is the biochar before modification, and b) is the biochar after modification;

[0032] Figure 2 is the content of available Pb in the soil of different treatment groups of the present invention;

[0033] Figure 3 is the available Cd content in the soil of different treatment groups of the present invention;

[0034] Figure 4 is the content of available Hg in the soil of different treatment groups of the present invention;

[0035] Figure 5 is the content of available As in the soil of different treatment groups of the present invention. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be further described below with reference to specific embodiments, but is not limited thereto. The strain number of the potassium-solubilizing jelly-like Paenibacillus MSSW02 used in the following examples of the present invention is CCTCC NO: M 20231472, deposited in the China Center for Type Culture Collection, and the deposit date is August 14, 2023; the strain number of Pseudomonas ayuensis is CGMCC No. 1.16111, purchased from the China General Microbiological Culture Collection Administration Center, and the deposit date is March 29, 2017; the strain number of Bacillus ardeis is CGMCC No. 1.15248, purchased from the China General Microbiological Culture Collection Administration Center, and the deposit date is May 10, 2015; the potassium-solubilizing jelly-like Paenibacillus MSSW02 used in the present invention has been deposited in the China Center for Type Culture Collection as a patent procedure before the application date and was donated by the depositor, Hubei Maosheng Biological Co., Ltd. for use; both the Pseudomonas ayuensis and the Bacillus ardeis strains can be purchased through the open catalog of the collection center without the need for repeated deposit.

[0037] Example 1

[0038] A bio-organic fertilizer for repairing heavy metal cadmium in soil is prepared from the following raw materials in parts by weight: 7 parts of a composite microbial agent, 30 parts of modified biochar, 3 parts of sodium alginate, 6 parts of a chelating agent, and 60 parts of decomposed edible fungus residue; the composite microbial agent is prepared from potassium-solubilizing Paenibacillus mucilaginosus MSSW02, Pseudomonas plecoglossicida, and Bacillus aryabhattai; the chelating agent is composed of calcium humate and nano-hydroxyapatite in a mass ratio of 100:3.

[0039] The calcium humate is prepared by the following method:

[0040] (1) Grind the weathered coal humic acid through a 100-mesh sieve to obtain humic acid powder, then add it to a 0.1 mol / L NaOH solution at a solid-liquid ratio of 1 g:10 ml, stir and react at 60 °C for 2 h, and centrifuge to obtain the supernatant to obtain an activated humic acid solution;

[0041] (2) The pH of the activated humic acid solution was adjusted to 6.5, and a 20% by mass Ca(OH)2 suspension was slowly added. The mixture was stirred evenly and reacted at 60°C for 4 h. After the reaction, the precipitate was collected by centrifugation, washed with deionized water until no Ca²⁺ residue was left, dried at 60°C, and then crushed through an 80-mesh sieve. The volume ratio of the activated humic acid solution to the Ca(OH)2 suspension was 1:1.5.

[0042] The composite microbial agent is prepared by the following method: potassium-solubilizing jelly-like bacillus MSSW02, Pseudomonas ayutans, and Bacillus aeruginosa are thawed and activated respectively, streaked on a plate and cultured in a 30°C incubator for 48 hours, a loopful of the cultured strains is placed in LB liquid culture medium, and the culture is shaken in a shaker at 30°C and 180 rpm for 24 hours to obtain a seed solution; the seed solutions of the three strains are respectively inoculated into 200 mL of TSB liquid culture medium at a 3% inoculum amount, and the culture is shaken at 30°C and 200 rpm for 72 hours to obtain a fermentation solution; and the three fermentation solutions are mixed in a volume ratio of 2:1:1 to obtain the composite microbial agent.

[0043] The modified biochar is prepared by the following method:

[0044] Step 1: Wash and dry the corn straw, crush it, put it into a muffle furnace, heat it to 600°C at a rate of 3°C / min under a nitrogen atmosphere, and calcine it at high temperature for 2 hours to obtain corn straw biochar;

[0045] Step 2: corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea, and deionized water are mixed in proportion and stirred evenly, heated to 80°C for reaction for 2 hours, and the mixture is naturally cooled to room temperature and then placed in an oven at 80°C for drying for 16 hours to obtain a dry product;

[0046] Step 3: The product obtained in step 2 was transferred into a tubular furnace, heated to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere, and calcined for 2 hours. After completion, it was cooled to room temperature and washed with deionized water three times, dried and ground to obtain modified biochar.

[0047] In step 2, the usage ratio of corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea and deionized water is 5g:0.002mol:0.001mol:0.1mol:200ml.

[0048] The decomposed edible fungus residue is prepared by the following method: discarded mushroom sticks after the cultivation of edible fungi such as oyster mushrooms, golden needle mushrooms, and king oyster mushrooms are removed from impurities and crushed to obtain edible fungus residue, EM bacteria accounting for 1% of the total weight of the edible fungus residue are inoculated, and after thorough mixing, water is added to adjust the moisture content of the mixture pile to 60-65%, composting and fermentation are carried out, and the temperature of the mixture pile is controlled within the range of 50°C-65°C. After fermentation for 7-10 days, the fermentation product is dried and crushed to obtain the decomposed edible fungus residue; the effective viable bacteria count of the EM bacteria is ≥100 billion / gram.

[0049] A method for preparing the above-mentioned bio-organic fertilizer for repairing heavy metal cadmium in soil comprises the following steps:

[0050] S1: preparing a composite microbial agent and modified biochar respectively, and mixing the two in proportion to obtain a mixture;

[0051] S2: preparing calcium humate and mixing it with nano-hydroxyapatite in a certain proportion to obtain a chelating agent;

[0052] S3: preparing decomposed edible fungus residue;

[0053] S4: fully mix the decomposed edible fungus residue, the chelating agent and the mixture obtained in S1, prepare a solution of sodium alginate with a mass fraction of 1% and spray it evenly on the surface of the mixture, and granulate it with a granulator.

[0054] Example 2

[0055] A bio-organic fertilizer for repairing heavy metal cadmium in soil is prepared from the following raw materials in parts by weight: 12 parts of a composite microbial agent, 40 parts of modified biochar, 8 parts of sodium alginate, 8 parts of a chelating agent, and 80 parts of decomposed edible fungus residue; the composite microbial agent is prepared from potassium-solubilizing Paenibacillus mucilaginosus MSSW02, Pseudomonas plecoglossicida, and Bacillus aryabhattai; the chelating agent is composed of calcium humate and nano-hydroxyapatite in a mass ratio of 100:5.

[0056] The calcium humate is prepared by the following method:

[0057] (1) Grind the weathered coal humic acid through a 100-mesh sieve to obtain humic acid powder, then add it to a 0.1 mol / L NaOH solution at a solid-liquid ratio of 1 g:10 ml, stir and react at 60 °C for 2 h, and centrifuge to obtain the supernatant to obtain an activated humic acid solution;

[0058] (2) The pH of the activated humic acid solution was adjusted to 6.5, and a 20% by mass Ca(OH)2 suspension was slowly added. The mixture was stirred evenly and reacted at 60°C for 4 h. After the reaction, the precipitate was collected by centrifugation, washed with deionized water until no Ca²⁺ residue was left, dried at 60°C, and then crushed through an 80-mesh sieve. The volume ratio of the activated humic acid solution to the Ca(OH)2 suspension was 1:1.5.

[0059] The composite microbial agent is prepared by the following method: potassium-solubilizing jelly-like bacillus MSSW02, Pseudomonas ayutans, and Bacillus aeruginosa are thawed and activated respectively, streaked on a plate and cultured in a 30°C incubator for 48 hours, a loopful of the cultured strains is placed in LB liquid culture medium, and the culture is shaken in a shaker at 30°C and 180 rpm for 24 hours to obtain a seed solution; the seed solutions of the three strains are respectively inoculated into 200 mL of TSB liquid culture medium at a 3% inoculum amount, and the culture is shaken at 30°C and 200 rpm for 72 hours to obtain a fermentation solution; and the three fermentation solutions are mixed in a volume ratio of 2:1:1 to obtain the composite microbial agent.

[0060] The modified biochar is prepared by the following method:

[0061] Step 1: Wash and dry the corn straw, crush it, put it into a muffle furnace, heat it to 600°C at a rate of 3°C / min under a nitrogen atmosphere, and calcine it at high temperature for 2 hours to obtain corn straw biochar;

[0062] Step 2: corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea, and deionized water are mixed in proportion and stirred evenly, heated to 80°C for reaction for 2 hours, and the mixture is naturally cooled to room temperature and then placed in an oven at 80°C for drying for 16 hours to obtain a dry product;

[0063] Step 3: The product obtained in step 2 was transferred into a tubular furnace, heated to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere, and calcined for 2 hours. After completion, it was cooled to room temperature and washed with deionized water three times, dried and ground to obtain modified biochar.

[0064] In step 2, the usage ratio of corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea and deionized water is 5g:0.002mol:0.001mol:0.1mol:200ml.

[0065] The decomposed edible fungus residue is prepared by the following method: discarded mushroom sticks after the cultivation of edible fungi such as oyster mushrooms, golden needle mushrooms, and king oyster mushrooms are removed from impurities and crushed to obtain edible fungus residue, EM bacteria accounting for 1% of the total weight of the edible fungus residue are inoculated, and after thorough mixing, water is added to adjust the moisture content of the mixture pile to 60-65%, composting and fermentation are carried out, and the temperature of the mixture pile is controlled within the range of 50°C-65°C. After fermentation for 7-10 days, the fermentation product is dried and crushed to obtain the decomposed edible fungus residue; the effective viable bacteria count of the EM bacteria is ≥100 billion / gram.

[0066] A method for preparing the above-mentioned bio-organic fertilizer for repairing heavy metal cadmium in soil comprises the following steps:

[0067] S1: preparing a composite microbial agent and modified biochar respectively, and mixing the two in proportion to obtain a mixture;

[0068] S2: preparing calcium humate and mixing it with nano-hydroxyapatite in a certain proportion to obtain a chelating agent;

[0069] S3: preparing decomposed edible fungus residue;

[0070] S4: fully mix the decomposed edible fungus residue, the chelating agent and the mixture obtained in S1, prepare a solution of sodium alginate with a mass fraction of 1% and spray it evenly on the surface of the mixture, and granulate it with a granulator.

[0071] Example 3

[0072] A bio-organic fertilizer for repairing heavy metal cadmium in soil is prepared from the following raw materials in parts by weight: 10 parts of a composite microbial agent, 35 parts of modified biochar, 6 parts of sodium alginate, 7 parts of a chelating agent, and 70 parts of decomposed edible fungus residue; the composite microbial agent is prepared from potassium-solubilizing Paenibacillus mucilaginosus MSSW02, Pseudomonas plecoglossicida, and Bacillus aryabhattai; the chelating agent is composed of calcium humate and nano-hydroxyapatite in a mass ratio of 100:4.

[0073] The calcium humate is prepared by the following method:

[0074] (1) Grind the weathered coal humic acid through a 100-mesh sieve to obtain humic acid powder, then add it to a 0.1 mol / L NaOH solution at a solid-liquid ratio of 1 g:10 ml, stir and react at 60 °C for 2 h, and centrifuge to obtain the supernatant to obtain an activated humic acid solution;

[0075] (2) The pH of the activated humic acid solution was adjusted to 6.5, and a 20% by mass Ca(OH)2 suspension was slowly added. The mixture was stirred evenly and reacted at 60°C for 4 h. After the reaction, the precipitate was collected by centrifugation, washed with deionized water until no Ca²⁺ residue was left, dried at 60°C, and then crushed through an 80-mesh sieve. The volume ratio of the activated humic acid solution to the Ca(OH)2 suspension was 1:1.5.

[0076] The composite microbial agent is prepared by the following method: potassium-solubilizing jelly-like bacillus MSSW02, Pseudomonas ayutans, and Bacillus aeruginosa are thawed and activated respectively, streaked on a plate and cultured in a 30°C incubator for 48 hours, a loopful of the cultured strains is placed in LB liquid culture medium, and the culture is shaken in a shaker at 30°C and 180 rpm for 24 hours to obtain a seed solution; the seed solutions of the three strains are respectively inoculated into 200 mL of TSB liquid culture medium at a 3% inoculum amount, and the culture is shaken at 30°C and 200 rpm for 72 hours to obtain a fermentation solution; and the three fermentation solutions are mixed in a volume ratio of 2:1:1 to obtain the composite microbial agent.

[0077] The modified biochar is prepared by the following method:

[0078] Step 1: Wash and dry the corn straw, crush it, put it into a muffle furnace, heat it to 600°C at a rate of 3°C / min under a nitrogen atmosphere, and calcine it at high temperature for 2 hours to obtain corn straw biochar;

[0079] Step 2: corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea, and deionized water are mixed in proportion and stirred evenly, heated to 80°C for reaction for 2 hours, and the mixture is naturally cooled to room temperature and then placed in an oven at 80°C for drying for 16 hours to obtain a dry product;

[0080] Step 3: The product obtained in step 2 was transferred into a tubular furnace, heated to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere, and calcined for 2 hours. After completion, it was cooled to room temperature and washed with deionized water three times, dried and ground to obtain modified biochar.

[0081] In step 2, the usage ratio of corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea and deionized water is 5g:0.002mol:0.001mol:0.1mol:200ml.

[0082] The decomposed edible fungus residue is prepared by the following method: discarded mushroom sticks after the cultivation of edible fungi such as oyster mushrooms, golden needle mushrooms, and king oyster mushrooms are removed from impurities and crushed to obtain edible fungus residue, EM bacteria accounting for 1% of the total weight of the edible fungus residue are inoculated, and after thorough mixing, water is added to adjust the moisture content of the mixture pile to 60-65%, composting and fermentation are carried out, and the temperature of the mixture pile is controlled within the range of 50°C-65°C. After fermentation for 7-10 days, the fermentation product is dried and crushed to obtain the decomposed edible fungus residue; the effective viable bacteria count of the EM bacteria is ≥100 billion / gram.

[0083] A method for preparing the above-mentioned bio-organic fertilizer for repairing heavy metal cadmium in soil comprises the following steps:

[0084] S1: preparing a composite microbial agent and modified biochar respectively, and mixing the two in proportion to obtain a mixture;

[0085] S2: preparing calcium humate and mixing it with nano-hydroxyapatite in a certain proportion to obtain a chelating agent;

[0086] S3: preparing decomposed edible fungus residue;

[0087] S4: fully mix the decomposed edible fungus residue, the chelating agent and the mixture obtained in S1, prepare a solution of sodium alginate with a mass fraction of 1% and spray it evenly on the surface of the mixture, and granulate it with a granulator.

[0088] Comparative Example 1

[0089] A bio-organic fertilizer for repairing heavy metal cadmium in soil is prepared from the following raw materials in parts by weight: 10 parts of a composite microbial agent, 35 parts of biochar, 6 parts of sodium alginate, 7 parts of a chelating agent, and 70 parts of decomposed edible fungus residue; the composite microbial agent is prepared from potassium-solubilizing Paenibacillus mucilaginosus MSSW02, Pseudomonas plecoglossicida, and Bacillus aryabhattai; the chelating agent is composed of calcium humate and nano-hydroxyapatite in a mass ratio of 100:4.

[0090] The calcium humate is prepared by the following method:

[0091] (1) Grind the weathered coal humic acid through a 100-mesh sieve to obtain humic acid powder, then add it to a 0.1 mol / L NaOH solution at a solid-liquid ratio of 1 g:10 ml, stir and react at 60 °C for 2 h, and centrifuge to obtain the supernatant to obtain an activated humic acid solution;

[0092] (2) The pH of the activated humic acid solution was adjusted to 6.5, and a 20% by mass Ca(OH)2 suspension was slowly added. The mixture was stirred evenly and reacted at 60°C for 4 h. After the reaction, the precipitate was collected by centrifugation, washed with deionized water until no Ca²⁺ residue was left, dried at 60°C, and then crushed through an 80-mesh sieve. The volume ratio of the activated humic acid solution to the Ca(OH)2 suspension was 1:1.5.

[0093] The composite microbial agent is prepared by the following method: potassium-solubilizing jelly-like bacillus MSSW02, Pseudomonas ayutans, and Bacillus aeruginosa are thawed and activated respectively, streaked on a plate and cultured in a 30°C incubator for 48 hours, a loopful of the cultured strains is placed in LB liquid culture medium, and the culture is shaken in a shaker at 30°C and 180 rpm for 24 hours to obtain a seed solution; the seed solutions of the three strains are respectively inoculated into 200 mL of TSB liquid culture medium at a 3% inoculum amount, and the culture is shaken at 30°C and 200 rpm for 72 hours to obtain a fermentation solution; and the three fermentation solutions are mixed in a volume ratio of 2:1:1 to obtain the composite microbial agent.

[0094] The biochar is prepared by the following method: corn stalks are washed, dried, crushed, placed in a muffle furnace, heated to 600° C. at a rate of 3° C. / min under a nitrogen atmosphere, and calcined at high temperature for 2 hours to obtain the biochar.

[0095] The decomposed edible fungus residue is prepared by the following method: discarded mushroom sticks after the cultivation of edible fungi such as oyster mushrooms, golden needle mushrooms, and king oyster mushrooms are removed from impurities and crushed to obtain edible fungus residue, EM bacteria accounting for 1% of the total weight of the edible fungus residue are inoculated, and after thorough mixing, water is added to adjust the moisture content of the mixture pile to 60-65%, composting and fermentation are carried out, and the temperature of the mixture pile is controlled within the range of 50°C-65°C. After fermentation for 7-10 days, the fermentation product is dried and crushed to obtain the decomposed edible fungus residue; the effective viable bacteria count of the EM bacteria is ≥100 billion / gram.

[0096] A method for preparing the above-mentioned bio-organic fertilizer for repairing heavy metal cadmium in soil comprises the following steps:

[0097] S1: preparing a composite microbial agent and biochar respectively, and mixing the two in proportion to obtain a mixture;

[0098] S2: preparing calcium humate and mixing it with nano-hydroxyapatite in a certain proportion to obtain a chelating agent;

[0099] S3: preparing decomposed edible fungus residue;

[0100] S4: fully mix the decomposed edible fungus residue, the chelating agent and the mixture obtained in S1, prepare a solution of sodium alginate with a mass fraction of 1% and spray it evenly on the surface of the mixture, and granulate it with a granulator.

[0101] This comparative example is basically the same as Example 3, except that the modified biochar is replaced by biochar.

[0102] Comparative Example 2

[0103] A bio-organic fertilizer for repairing heavy metal cadmium in soil is prepared from the following raw materials in parts by weight: 10 parts of a composite microbial agent, 35 parts of modified biochar, 6 parts of sodium alginate, 7 parts of a chelating agent, and 70 parts of decomposed edible fungus residue; the composite microbial agent is prepared from potassium-solubilizing Paenibacillus mucilaginosus MSSW02, Pseudomonas plecoglossicida, and Bacillus aryabhattai; and the chelating agent is calcium humate.

[0104] The calcium humate is prepared by the following method:

[0105] (1) Grind the weathered coal humic acid through a 100-mesh sieve to obtain humic acid powder, then add it to a 0.1 mol / L NaOH solution at a solid-liquid ratio of 1 g:10 ml, stir and react at 60 °C for 2 h, and centrifuge to obtain the supernatant to obtain an activated humic acid solution;

[0106] (2) The pH of the activated humic acid solution was adjusted to 6.5, and a 20% by mass Ca(OH)2 suspension was slowly added. The mixture was stirred evenly and reacted at 60°C for 4 h. After the reaction, the precipitate was collected by centrifugation, washed with deionized water until no Ca²⁺ residue was left, dried at 60°C, and then crushed through an 80-mesh sieve. The volume ratio of the activated humic acid solution to the Ca(OH)2 suspension was 1:1.5.

[0107] The composite microbial agent is prepared by the following method: potassium-solubilizing jelly-like bacillus MSSW02, Pseudomonas ayutans, and Bacillus aeruginosa are thawed and activated respectively, streaked on a plate and cultured in a 30°C incubator for 48 hours, a loopful of the cultured strains is placed in LB liquid culture medium, and the culture is shaken in a shaker at 30°C and 180 rpm for 24 hours to obtain a seed solution; the seed solutions of the three strains are respectively inoculated into 200 mL of TSB liquid culture medium at a 3% inoculum amount, and the culture is shaken at 30°C and 200 rpm for 72 hours to obtain a fermentation solution; and the three fermentation solutions are mixed in a volume ratio of 2:1:1 to obtain the composite microbial agent.

[0108] The modified biochar is prepared by the following method:

[0109] Step 1: Wash and dry the corn straw, crush it, put it into a muffle furnace, heat it to 600°C at a rate of 3°C / min under a nitrogen atmosphere, and calcine it at high temperature for 2 hours to obtain corn straw biochar;

[0110] Step 2: corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea, and deionized water are mixed in proportion and stirred evenly, heated to 80°C for reaction for 2 hours, and the mixture is naturally cooled to room temperature and then placed in an oven at 80°C for drying for 16 hours to obtain a dry product;

[0111] Step 3: The product obtained in step 2 was transferred into a tubular furnace, heated to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere, and calcined for 2 hours. After completion, it was cooled to room temperature and washed with deionized water three times, dried and ground to obtain modified biochar.

[0112] In step 2, the usage ratio of corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea and deionized water is 5g:0.002mol:0.001mol:0.1mol:200ml.

[0113] The decomposed edible fungus residue is prepared by the following method: discarded mushroom sticks after the cultivation of edible fungi such as oyster mushrooms, golden needle mushrooms, and king oyster mushrooms are removed from impurities and crushed to obtain edible fungus residue, EM bacteria accounting for 1% of the total weight of the edible fungus residue are inoculated, and after thorough mixing, water is added to adjust the moisture content of the mixture pile to 60-65%, composting and fermentation are carried out, and the temperature of the mixture pile is controlled within the range of 50°C-65°C. After fermentation for 7-10 days, the fermentation product is dried and crushed to obtain the decomposed edible fungus residue; the effective viable bacteria count of the EM bacteria is ≥100 billion / gram.

[0114] A method for preparing the above-mentioned bio-organic fertilizer for repairing heavy metal cadmium in soil comprises the following steps:

[0115] S1: preparing a composite microbial agent and modified biochar respectively, and mixing the two in proportion to obtain a mixture;

[0116] S2: preparing calcium humate to obtain a chelating agent;

[0117] S3: preparing decomposed edible fungus residue;

[0118] S4: fully mix the decomposed edible fungus residue, the chelating agent and the mixture obtained in S1, prepare a solution of sodium alginate with a mass fraction of 1% and spray it evenly on the surface of the mixture, and granulate it with a granulator.

[0119] This comparative example is basically the same as Example 3, except that the chelating agent contains only calcium humate.

[0120] Comparative Example 3

[0121] A bio-organic fertilizer for repairing heavy metal cadmium in soil is prepared from the following raw materials in parts by weight: 10 parts of a composite microbial agent, 35 parts of modified biochar, 6 parts of sodium alginate, 7 parts of a chelating agent, and 70 parts of decomposed edible fungus residue; the composite microbial agent is prepared from potassium-solubilizing Paenibacillus mucilaginosus MSSW02, Pseudomonas plecoglossicida, and Bacillus aryabhattai; and the chelating agent is nano-hydroxyapatite.

[0122] The composite microbial agent is prepared by the following method: potassium-solubilizing jelly-like bacillus MSSW02, Pseudomonas ayutans, and Bacillus aeruginosa are thawed and activated respectively, streaked on a plate and cultured in a 30°C incubator for 48 hours, a loopful of the cultured strains is placed in LB liquid culture medium, and the culture is shaken in a shaker at 30°C and 180 rpm for 24 hours to obtain a seed solution; the seed solutions of the three strains are respectively inoculated into 200 mL of TSB liquid culture medium at a 3% inoculum amount, and the culture is shaken at 30°C and 200 rpm for 72 hours to obtain a fermentation solution; and the three fermentation solutions are mixed in a volume ratio of 2:1:1 to obtain the composite microbial agent.

[0123] The modified biochar is prepared by the following method:

[0124] Step 1: Wash and dry the corn straw, crush it, put it into a muffle furnace, heat it to 600°C at a rate of 3°C / min under a nitrogen atmosphere, and calcine it at high temperature for 2 hours to obtain corn straw biochar;

[0125] Step 2: corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea, and deionized water are mixed in proportion and stirred evenly, heated to 80°C for reaction for 2 hours, and the mixture is naturally cooled to room temperature and then placed in an oven at 80°C for drying for 16 hours to obtain a dry product;

[0126] Step 3: The product obtained in step 2 was transferred into a tubular furnace, heated to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere, and calcined for 2 hours. After completion, it was cooled to room temperature and washed with deionized water three times, dried and ground to obtain modified biochar.

[0127] In step 2, the usage ratio of corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea and deionized water is 5g:0.002mol:0.001mol:0.1mol:200ml.

[0128] The decomposed edible fungus residue is prepared by the following method: discarded mushroom sticks after the cultivation of edible fungi such as oyster mushrooms, golden needle mushrooms, and king oyster mushrooms are removed from impurities and crushed to obtain edible fungus residue, EM bacteria accounting for 1% of the total weight of the edible fungus residue are inoculated, and after thorough mixing, water is added to adjust the moisture content of the mixture pile to 60-65%, composting and fermentation are carried out, and the temperature of the mixture pile is controlled within the range of 50°C-65°C. After fermentation for 7-10 days, the fermentation product is dried and crushed to obtain the decomposed edible fungus residue; the effective viable bacteria count of the EM bacteria is ≥100 billion / gram.

[0129] A method for preparing the above-mentioned bio-organic fertilizer for repairing heavy metal cadmium in soil comprises the following steps:

[0130] S1: preparing a composite microbial agent and modified biochar respectively, and mixing the two in proportion to obtain a mixture;

[0131] S2: preparing decomposed edible fungus residue;

[0132] S3: fully mix the decomposed edible fungus residue, nano-hydroxyapatite and the mixture obtained in S1, prepare a 1% by mass solution of sodium alginate and spray it evenly on the surface of the mixture, and granulate it with a granulator.

[0133] This comparative example is basically the same as Example 3, the only difference being that the chelating agent is only nano-hydroxyapatite.

[0134] Comparative Example 4

[0135] A bio-organic fertilizer for repairing heavy metal cadmium in soil is prepared from the following raw materials in parts by weight: 10 parts of a composite microbial agent, 35 parts of modified biochar, 6 parts of sodium alginate, and 70 parts of decomposed edible fungus residue; the composite microbial agent is prepared from potassium-solubilizing Paenibacillus mucilaginosus MSSW02, Pseudomonas plecoglossicida, and Bacillus aryabhattai; and the chelating agent is composed of calcium humate and nano-hydroxyapatite in a mass ratio of 100:4.

[0136] The composite microbial agent is prepared by the following method: potassium-solubilizing jelly-like bacillus MSSW02, Pseudomonas ayutans, and Bacillus aeruginosa are thawed and activated respectively, streaked on a plate and cultured in a 30°C incubator for 48 hours, a loopful of the cultured strains is placed in LB liquid culture medium, and the culture is shaken in a shaker at 30°C and 180 rpm for 24 hours to obtain a seed solution; the seed solutions of the three strains are respectively inoculated into 200 mL of TSB liquid culture medium at a 3% inoculum amount, and the culture is shaken at 30°C and 200 rpm for 72 hours to obtain a fermentation solution; and the three fermentation solutions are mixed in a volume ratio of 2:1:1 to obtain the composite microbial agent.

[0137] The modified biochar is prepared by the following method:

[0138] Step 1: Wash and dry the corn straw, crush it, put it into a muffle furnace, heat it to 600°C at a rate of 3°C / min under a nitrogen atmosphere, and calcine it at high temperature for 2 hours to obtain corn straw biochar;

[0139] Step 2: corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea, and deionized water are mixed in proportion and stirred evenly, heated to 80°C for reaction for 2 hours, and the mixture is naturally cooled to room temperature and then placed in an oven at 80°C for drying for 16 hours to obtain a dry product;

[0140] Step 3: The product obtained in step 2 was transferred into a tubular furnace, heated to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere, and calcined for 2 hours. After completion, it was cooled to room temperature and washed with deionized water three times, dried and ground to obtain modified biochar.

[0141] In step 2, the usage ratio of corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea and deionized water is 5g:0.002mol:0.001mol:0.1mol:200ml.

[0142] The decomposed edible fungus residue is prepared by the following method: discarded mushroom sticks after the cultivation of edible fungi such as oyster mushrooms, golden needle mushrooms, and king oyster mushrooms are removed from impurities and crushed to obtain edible fungus residue, EM bacteria accounting for 1% of the total weight of the edible fungus residue are inoculated, and after thorough mixing, water is added to adjust the moisture content of the mixture pile to 60-65%, composting and fermentation are carried out, and the temperature of the mixture pile is controlled within the range of 50°C-65°C. After fermentation for 7-10 days, the fermentation product is dried and crushed to obtain the decomposed edible fungus residue; the effective viable bacteria count of the EM bacteria is ≥100 billion / gram.

[0143] A method for preparing the above-mentioned bio-organic fertilizer for repairing heavy metal cadmium in soil comprises the following steps:

[0144] S1: preparing a composite microbial agent and modified biochar respectively, and mixing the two in proportion to obtain a mixture;

[0145] S2: preparing decomposed edible fungus residue;

[0146] S3: fully mix the decomposed edible fungus residue and the mixture obtained in S1, prepare a solution of sodium alginate with a mass fraction of 1% and spray it evenly on the surface of the mixture, and granulate it using a granulator.

[0147] This comparative example is basically the same as Example 3, except that it does not contain a chelating agent.

[0148] Comparative Example 5

[0149] A bio-organic fertilizer for repairing heavy metal cadmium in soil is prepared from the following raw materials in parts by weight: 10 parts of a composite microbial agent, 35 parts of modified biochar, 6 parts of sodium alginate, 7 parts of a chelating agent, and 70 parts of decomposed edible fungus residue; the composite microbial agent is prepared from potassium-solubilizing Paenibacillus mucilaginosus MSSW02, Pseudomonas plecoglossicida, and Bacillus aryabhattai; the chelating agent is composed of calcium humate and nano-hydroxyapatite in a mass ratio of 100:4.

[0150] The calcium humate is prepared by the following method:

[0151] (1) Grind the weathered coal humic acid through a 100-mesh sieve to obtain humic acid powder, then add it to a 0.1 mol / L NaOH solution at a solid-liquid ratio of 1 g:10 ml, stir and react at 60 °C for 2 h, and centrifuge to obtain the supernatant to obtain an activated humic acid solution;

[0152] (2) The pH of the activated humic acid solution was adjusted to 6.5, and a 20% by mass Ca(OH)2 suspension was slowly added. The mixture was stirred evenly and reacted at 60°C for 4 h. After the reaction, the precipitate was collected by centrifugation, washed with deionized water until no Ca²⁺ residue was left, dried at 60°C, and then crushed through an 80-mesh sieve. The volume ratio of the activated humic acid solution to the Ca(OH)2 suspension was 1:1.5.

[0153] The composite microbial agent is prepared by the following method: potassium-solubilizing jelly-like bacillus MSSW02, Pseudomonas ayutans, and Bacillus afusii are thawed and activated respectively, streaked on a plate, and cultured in a 30°C incubator for 48 hours, a loopful of the cultured strains is taken into LB liquid culture medium, and the culture is shaken in a shaker at 30°C and 180 r / min for 24 hours to obtain a seed liquid; the seed liquids of the three strains are respectively inoculated into 200 mL of TSB liquid culture medium at an inoculum size of 3%, and the culture is shaken at 30°C and 200 r / min for 72 hours to obtain a fermentation liquid; and the three fermentation liquids are mixed in a volume ratio of 1:1:1 to obtain the composite microbial agent.

[0154] The modified biochar is prepared by the following method:

[0155] Step 1: Wash and dry the corn straw, crush it, put it into a muffle furnace, heat it to 600°C at a rate of 3°C / min under a nitrogen atmosphere, and calcine it at high temperature for 2 hours to obtain corn straw biochar;

[0156] Step 2: corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea, and deionized water are mixed in proportion and stirred evenly, heated to 80°C for reaction for 2 hours, and the mixture is naturally cooled to room temperature and then placed in an oven at 80°C for drying for 16 hours to obtain a dry product;

[0157] Step 3: The product obtained in step 2 was transferred into a tubular furnace, heated to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere, and calcined for 2 hours. After completion, it was cooled to room temperature and washed with deionized water three times, dried and ground to obtain modified biochar.

[0158] In step 2, the usage ratio of corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea and deionized water is 5g:0.002mol:0.001mol:0.1mol:200ml.

[0159] The decomposed edible fungus residue is prepared by the following method: discarded mushroom sticks after the cultivation of edible fungi such as oyster mushrooms, golden needle mushrooms, and king oyster mushrooms are removed from impurities and crushed to obtain edible fungus residue, EM bacteria accounting for 1% of the total weight of the edible fungus residue are inoculated, and after thorough mixing, water is added to adjust the moisture content of the mixture pile to 60-65%, composting and fermentation are carried out, and the temperature of the mixture pile is controlled within the range of 50°C-65°C. After fermentation for 7-10 days, the fermentation product is dried and crushed to obtain the decomposed edible fungus residue; the effective viable bacteria count of the EM bacteria is ≥100 billion / gram.

[0160] A method for preparing the above-mentioned bio-organic fertilizer for repairing heavy metal cadmium in soil comprises the following steps:

[0161] S1: preparing a composite microbial agent and modified biochar respectively, and mixing the two in proportion to obtain a mixture;

[0162] S2: preparing calcium humate and mixing it with nano-hydroxyapatite in a certain proportion to obtain a chelating agent;

[0163] S3: preparing decomposed edible fungus residue;

[0164] S4: fully mix the decomposed edible fungus residue, the chelating agent and the mixture obtained in S1, prepare a solution of sodium alginate with a mass fraction of 1% and spray it evenly on the surface of the mixture, and granulate it with a granulator.

[0165] This comparative example is basically the same as Example 3, except that the volume ratio of the fermentation broth of the three strains in the preparation method of the composite microbial agent is different. Specifically, the potassium-soluble jelly-like Paenibacillus MSSW02, Pseudomonas ayutans, and Bacillus afusii were thawed and activated separately, and the plates were streaked and cultured in a 30°C incubator for 48 hours. A loop of the cultured strain was placed in LB liquid medium and placed in a shaker at 30°C and 180 r / min for 24 hours to obtain a seed solution; the seed solutions of the three strains were inoculated into 200 mL of TSB liquid medium at an inoculum size of 3%, and cultured at 30°C and 200 r / min for 72 hours to obtain a fermentation broth; the three fermentation broths were mixed in a volume ratio of 1:1:1 to obtain a composite microbial agent.

[0166] Comparative Example 6

[0167] A bio-organic fertilizer for repairing heavy metal cadmium in soil is prepared from the following raw materials in parts by weight: 10 parts of a composite microbial agent, 35 parts of modified biochar, 6 parts of sodium alginate, 7 parts of a chelating agent, and 70 parts of decomposed edible fungus residue; the composite microbial agent is prepared from potassium-solubilizing Paenibacillus mucilaginosus MSSW02, Pseudomonas plecoglossicida, and Bacillus aryabhattai; the chelating agent is composed of calcium humate and nano-hydroxyapatite in a mass ratio of 100:4.

[0168] The calcium humate is prepared by the following method:

[0169] (1) Grind the weathered coal humic acid through a 100-mesh sieve to obtain humic acid powder, then add it to a 0.1 mol / L NaOH solution at a solid-liquid ratio of 1 g:10 ml, stir and react at 60 °C for 2 h, and centrifuge to obtain the supernatant to obtain an activated humic acid solution;

[0170] (2) The pH of the activated humic acid solution was adjusted to 6.5, and a 20% by mass Ca(OH)2 suspension was slowly added. The mixture was stirred evenly and reacted at 60°C for 4 h. After the reaction, the precipitate was collected by centrifugation, washed with deionized water until no Ca²⁺ residue was left, dried at 60°C, and then crushed through an 80-mesh sieve. The volume ratio of the activated humic acid solution to the Ca(OH)2 suspension was 1:1.5.

[0171] The composite microbial agent is prepared by the following method: potassium-solubilizing jelly-like bacillus MSSW02, Pseudomonas ayutans, and Bacillus afusii are thawed and activated respectively, streaked on a plate and cultured in a 30°C incubator for 48 hours, a loopful of the cultured strains is taken and placed in LB liquid culture medium, and the culture is shaken in a shaker at 30°C and 180 r / min for 24 hours to obtain a seed liquid; the seed liquids of the three strains are respectively inoculated into 200 mL of TSB liquid culture medium at an inoculum size of 3%, and the culture is shaken at 30°C and 200 r / min for 72 hours to obtain a fermentation liquid; and the three fermentation liquids are mixed in a volume ratio of 1:2:1 to obtain the composite microbial agent.

[0172] The modified biochar is prepared by the following method:

[0173] Step 1: Wash and dry the corn straw, crush it, put it into a muffle furnace, heat it to 600°C at a rate of 3°C / min under a nitrogen atmosphere, and calcine it at high temperature for 2 hours to obtain corn straw biochar;

[0174] Step 2: corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea, and deionized water are mixed in proportion and stirred evenly, heated to 80°C for reaction for 2 hours, and the mixture is naturally cooled to room temperature and then placed in an oven at 80°C for drying for 16 hours to obtain a dry product;

[0175] Step 3: The product obtained in step 2 was transferred into a tubular furnace, heated to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere, and calcined for 2 hours. After completion, it was cooled to room temperature and washed with deionized water three times, dried and ground to obtain modified biochar.

[0176] In step 2, the usage ratio of corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea and deionized water is 5g:0.002mol:0.001mol:0.1mol:200ml.

[0177] The decomposed edible fungus residue is prepared by the following method: discarded mushroom sticks after the cultivation of edible fungi such as oyster mushrooms, golden needle mushrooms, and king oyster mushrooms are removed from impurities and crushed to obtain edible fungus residue, EM bacteria accounting for 1% of the total weight of the edible fungus residue are inoculated, and after thorough mixing, water is added to adjust the moisture content of the mixture pile to 60-65%, composting and fermentation are carried out, and the temperature of the mixture pile is controlled within the range of 50°C-65°C. After fermentation for 7-10 days, the fermentation product is dried and crushed to obtain the decomposed edible fungus residue; the effective viable bacteria count of the EM bacteria is ≥100 billion / gram.

[0178] A method for preparing the above-mentioned bio-organic fertilizer for repairing heavy metal cadmium in soil comprises the following steps:

[0179] S1: preparing a composite microbial agent and modified biochar respectively, and mixing the two in proportion to obtain a mixture;

[0180] S2: preparing calcium humate and mixing it with nano-hydroxyapatite in a certain proportion to obtain a chelating agent;

[0181] S3: preparing decomposed edible fungus residue;

[0182] S4: fully mix the decomposed edible fungus residue, the chelating agent and the mixture obtained in S1, prepare a solution of sodium alginate with a mass fraction of 1% and spray it evenly on the surface of the mixture, and granulate it with a granulator.

[0183] This comparative example is basically the same as Example 3, except that the volume ratio of the fermentation broth of the three strains in the preparation method of the composite microbial agent is different. Specifically, the potassium-soluble jelly-like Paenibacillus MSSW02, Pseudomonas ayutans, and Bacillus afusii were thawed and activated separately, and the plates were streaked and cultured in a 30°C incubator for 48 hours. A loop of the cultured strain was placed in LB liquid medium and placed in a shaker at 30°C and 180 r / min for 24 hours to obtain a seed solution; the seed solutions of the three strains were inoculated into 200 mL of TSB liquid medium at an inoculum size of 3%, and cultured at 30°C and 200 r / min for 72 hours to obtain a fermentation broth; the three fermentation broths were mixed in a volume ratio of 1:2:1 to obtain a composite microbial agent.

[0184] Comparative Example 7

[0185] A bio-organic fertilizer for repairing heavy metal cadmium in soil is prepared from the following raw materials in parts by weight: 10 parts of a composite microbial agent, 35 parts of modified biochar, 6 parts of sodium alginate, 7 parts of a chelating agent, and 70 parts of decomposed edible fungus residue; the composite microbial agent is prepared from potassium-solubilizing Paenibacillus mucilaginosus MSSW02, Pseudomonas plecoglossicida, and Bacillus aryabhattai; the chelating agent is composed of calcium humate and nano-hydroxyapatite in a mass ratio of 100:4.

[0186] The calcium humate is prepared by the following method:

[0187] (1) Grind the weathered coal humic acid through a 100-mesh sieve to obtain humic acid powder, then add it to a 0.1 mol / L NaOH solution at a solid-liquid ratio of 1 g:10 ml, stir and react at 60 °C for 2 h, and centrifuge to obtain the supernatant to obtain an activated humic acid solution;

[0188] (2) The pH of the activated humic acid solution was adjusted to 6.5, and a 20% by mass Ca(OH)2 suspension was slowly added. The mixture was stirred evenly and reacted at 60°C for 4 h. After the reaction, the precipitate was collected by centrifugation, washed with deionized water until no Ca²⁺ residue was left, dried at 60°C, and then crushed through an 80-mesh sieve. The volume ratio of the activated humic acid solution to the Ca(OH)2 suspension was 1:1.5.

[0189] The composite microbial agent is prepared by the following method: potassium-solubilizing jelly-like bacillus MSSW02, Pseudomonas ayutans, and Bacillus afusii are thawed and activated respectively, streaked on a plate and cultured in a 30°C incubator for 48 hours, a loopful of the cultured strains is taken into LB liquid culture medium, and the culture is shaken in a shaker at 30°C and 180 r / min for 24 hours to obtain a seed liquid; the seed liquids of the three strains are respectively inoculated into 200 mL of TSB liquid culture medium at an inoculum size of 3%, and the culture is shaken at 30°C and 200 r / min for 72 hours to obtain a fermentation liquid; and the three fermentation liquids are mixed in a volume ratio of 1:1:2 to obtain the composite microbial agent.

[0190] The modified biochar is prepared by the following method:

[0191] Step 1: Wash and dry the corn straw, crush it, put it into a muffle furnace, heat it to 600°C at a rate of 3°C / min under a nitrogen atmosphere, and calcine it at high temperature for 2 hours to obtain corn straw biochar;

[0192] Step 2: corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea, and deionized water are mixed in proportion and stirred evenly, heated to 80°C for reaction for 2 hours, and the mixture is naturally cooled to room temperature and then placed in an oven at 80°C for drying for 16 hours to obtain a dry product;

[0193] Step 3: The product obtained in step 2 was transferred into a tubular furnace, heated to 800°C at a heating rate of 10°C / min under a nitrogen atmosphere, and calcined for 2 hours. After completion, it was cooled to room temperature and washed with deionized water three times, dried and ground to obtain modified biochar.

[0194] In step 2, the usage ratio of corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea and deionized water is 5g:0.002mol:0.001mol:0.1mol:200ml.

[0195] The decomposed edible fungus residue is prepared by the following method: discarded mushroom sticks after the cultivation of edible fungi such as oyster mushrooms, golden needle mushrooms, and king oyster mushrooms are removed from impurities and crushed to obtain edible fungus residue, EM bacteria accounting for 1% of the total weight of the edible fungus residue are inoculated, and after thorough mixing, water is added to adjust the moisture content of the mixture pile to 60-65%, composting and fermentation are carried out, and the temperature of the mixture pile is controlled within the range of 50°C-65°C. After fermentation for 7-10 days, the fermentation product is dried and crushed to obtain the decomposed edible fungus residue; the effective viable bacteria count of the EM bacteria is ≥100 billion / gram.

[0196] A method for preparing the above-mentioned bio-organic fertilizer for repairing heavy metal cadmium in soil comprises the following steps:

[0197] S1: preparing a composite microbial agent and modified biochar respectively, and mixing the two in proportion to obtain a mixture;

[0198] S2: preparing calcium humate and mixing it with nano-hydroxyapatite in a certain proportion to obtain a chelating agent;

[0199] S3: preparing decomposed edible fungus residue;

[0200] S4: fully mix the decomposed edible fungus residue, the chelating agent and the mixture obtained in S1, prepare a solution of sodium alginate with a mass fraction of 1% and spray it evenly on the surface of the mixture, and granulate it with a granulator.

[0201] This comparative example is basically the same as Example 3, except that the volume ratio of the fermentation broth of the three strains in the preparation method of the composite microbial agent is different. Specifically, the potassium-soluble jelly-like Paenibacillus MSSW02, Pseudomonas ayutans, and Bacillus azadirachta were thawed and activated separately, and the plates were streaked and cultured in a 30°C incubator for 48 hours. A loop of the cultured strain was placed in LB liquid medium and placed in a shaker at 30°C and 180 r / min for 24 hours to obtain a seed solution; the seed solutions of the three strains were inoculated into 200 mL of TSB liquid medium at an inoculum size of 3%, and cultured at 30°C and 200 r / min for 72 hours to obtain a fermentation broth; the three fermentation broths were mixed in a volume ratio of 1:1:2 to obtain a composite microbial agent.

[0202] Fertilizer efficiency verification test

[0203] The experimental site was a slightly cadmium-contaminated farmland (total Cd content of 1.46 mg / kg) in Xiafan Village, Baisha Town, Huangshi City, Hubei Province. The soil type is red soil, and the heavy metal contents in the soil are available Pb 29.6 mg / kg, available Cd 0.69 mg / kg, available Hg 0.001 mg / kg, and available As 0.25 mg / kg. Other basic physical and chemical properties of the soil are shown in Table 1.

[0204] Table 1 Basic physical and chemical properties of soil

[0205]

[0206] Test crops: Rice, Ezhong No. 5.

[0207] Experimental method: A total of 12 treatment groups were set up in the experiment, namely, the treatment group of Example 3, the treatment groups of Comparative Examples 1 to 7, the treatment group of commercial organic fertilizer (purchased from Handan Yuanwo Fertilizer Co., Ltd., with an effective viable count of ≥ 200 million / g and an organic matter content of ≥ 50%), and a blank control group (no fertilizer was applied); each treatment group had an area of ​​40 m 2 Each treatment group applied the corresponding fertilizer at 200 kg / mu, plowed the soil after basal application, and applied fertilizer once at the tillering stage and heading stage respectively (the dosage was 50 kg / mu).

[0208] Survey Methods: Total rice yield in each group was surveyed at harvest. Additionally, 30 individual plants in each treatment group were randomly sampled for plant height, number of grains per ear, and 1,000-grain weight, with the average values ​​calculated. At harvest, five sampling points were used per plot. Rice grains were harvested, sun-dried, ground into rice grains, and then pulverized (ground) into brown rice flour. Pretreatment was performed using aqua regia prepared with concentrated hydrochloric acid and concentrated nitric acid. Cadmium content in the rice grains was determined using ICP-OES using the nitrification solution. Table 2 shows this information.

[0209] Table 2 Rice yield and composition in different treatment groups

[0210]

[0211] From the results in Table 2 above, it can be seen that the rice yield increased significantly after using the biological organic fertilizer of Example 3 of the present invention, which increased by 43.5% compared with the blank control and by 12.0% compared with the commercial organic fertilizer group. The yield components such as rice plant height, number of grains per panicle, and 1000-grain weight were also significantly better than those of Comparative Examples 1-7. The cadmium content of rice (0.08 mg / kg) was significantly lower than the national standard (GB 2762-2022, the Cd limit of rice is 0.2 mg / kg), while the cadmium content of rice obtained from Comparative Examples 1-7, the commercial organic fertilizer, and the blank control group was significantly higher than that of the treatment group of Example 3 of the present invention. This shows that the formula of the present invention reduces the cadmium content of rice by microbial action, Cd 2+ -Multiple mechanisms such as organic matter complexation and biochar fixation synergistically reduce the bioavailability of Cd in soil, while reducing the absorption and accumulation of Cd by crops, thereby improving food safety.

[0212] After rice harvest, surface soil samples (0-20 cm) were collected. Soil samples were collected from each treatment group using the S-shaped sampling method. When collecting soil, the soil drill was drilled to a depth of 20 cm at a time. Three replicates were collected from each treatment group. The three replicates from the same treatment group were combined into one sample. Visible debris such as gravel and plant roots were removed and the sample was brought back to the laboratory for determination of basic soil physical and chemical properties and the content of available heavy metals in the soil. The test results are shown in Table 3 and Figure 2-5 .

[0213] Table 3 Physical and chemical properties of soil under different treatments

[0214]

[0215] Can be drawn from the data of above-mentioned table 3, after using bio-organic fertilizer of the present invention, soil bulk density reduces, organic matter content significantly improves, and soil fertility and air permeability obviously improve.This is due to multi-component synergy in the present invention, the special structure that the microporous structure formed by modified biochar is combined with filamentous carbon nanotube, this kind of unique structure is more stable, is more conducive to protecting functional microorganisms and slow-release nutrients, and a large amount of beneficial microorganisms can activate soil activity, strengthen soil water and fertilizer conservation ability, improve soil pH, thus realize the effective improvement of soil.Reduce and change any one component in bio-organic fertilizer of the present invention, corresponding effect disappears or weakens.

[0216] from Figure 2-Figure 5The results show that compared with the blank control group, the content of heavy metals Pb, Cd, Hg, and As in the soil after the use of the bio-organic fertilizer of the present invention is reduced to varying degrees, among which the reduction of Pb, Hg, and As (Pb 13.5%, Hg 20%, and As 28%) is relatively small, while the content of available Cd is reduced by 84% compared with the blank control, which is much higher than that of comparative examples 1-7. Comparative example 1 uses unmodified biochar, which has a small specific surface area and a weak ability to adsorb and remove heavy metal ions. However, the modified biochar has a special microstructure and a greatly increased specific surface area, which is Cd. 2+ While providing a large number of physical adsorption sites, it can also improve the soil aggregate structure, enhance air permeability and drainage capacity, improve water retention through capillary action, and alleviate drought stress. As can be seen from Comparative Examples 2-4, the chelating agent made of calcium humate and nano-hydroxyapatite in a specific ratio has a significant synergistic effect. After changing the ratio of the two, the corresponding synergistic effect disappears or weakens. The raw material formula of the present invention is optimized by multiple mechanisms for the characteristics of Cd. The modified biochar has better adsorption and complexing effects on cadmium after modification. The chelating agent has a suitable ratio and synergistic effect. It constructs a stable "functional microorganism-modified biochar-organic chelating agent" ternary synergistic system with a large number of functional microorganisms, effectively reducing the content of effective heavy metal Cd in the soil. It also contains rich organic matter, which can significantly improve the physical and chemical properties of the soil, improve the soil's water and fertilizer retention capacity, and promote crop growth; it has a good effect on repairing farmland soil with moderate to light cadmium pollution and has a significant effect on promoting the growth of crops.

[0217] It should be noted that the above embodiments are only some of the preferred embodiments of the present invention, and not all of them. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.

Claims

1. A bio-organic fertilizer for repairing heavy metal cadmium in soil, characterized in that: The invention is prepared from the following raw materials in parts by weight: 7-12 parts of composite microbial agent, 30-40 parts of modified biochar, 3-8 parts of sodium alginate, 6-8 parts of chelating agent, and 60-80 parts of decomposed edible fungus residue; the composite microbial agent is composed of potassium-solubilizing jelly-like Paenibacillus MSSW02 ( Paenibacillus mucilaginosus MSSW02), Pseudomonas ayuensis ( Pseudomonas plecoglossicida ), Bacillus arguta ( Bacillus aryabhattai ) The fermentation broths of the three strains are mixed in a volume ratio of 2:1:1; the strain number of the potassium-solubilizing jelly-like Paenibacillus MSSW02 is CCTCC NO: M 20231472; the strain number of the Pseudomonas ayusi is CGMCC No. 1.16111; and the strain number of the Bacillus arguta is CGMCC No. 1.15248; the chelating agent is composed of calcium humate and nano-hydroxyapatite in a mass ratio of 100:3-5; The composite microbial agent is prepared by the following method: potassium-solubilizing jelly-like Paenibacillus MSSW02, Pseudomonas ayutans, and Bacillus afusii are thawed and activated respectively, streaked on a plate and cultured in a 30°C incubator for 48 hours, a loopful of the cultured strains is placed in LB liquid medium, and the culture is shaken in a shaker at 30°C and 180 rpm for 24 hours to obtain a seed solution; The seed liquid of the three strains was inoculated into 200 mL of TSB liquid culture medium at an inoculum size of 3%, and cultured at 30°C and 200 rpm for 72 hours to obtain fermentation liquid. The three fermentation liquids were mixed at a volume ratio of 2:1:1 to obtain a composite microbial agent. The modified biochar is prepared by the following method: Step 1: Wash and dry the corn straw, crush it, put it into a muffle furnace, heat it to 600°C at a rate of 3°C / min under a nitrogen atmosphere, and calcine it at high temperature for 2 hours to obtain corn straw biochar; Step 2: corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea, and deionized water are mixed in proportion and stirred evenly, heated to 80°C for reaction for 2 hours, and the mixture is naturally cooled to room temperature and then placed in an oven at 80°C for drying for 16 hours to obtain a dry product; Step 3: The product obtained in step 2 is transferred into a tubular furnace and calcined at high temperature under a nitrogen atmosphere. After completion, the product is cooled to room temperature and washed three times with deionized water, dried and ground to obtain modified biochar.

2. The bio-organic fertilizer for repairing heavy metal cadmium in soil according to claim 1, characterized in that The calcium humate is prepared by the following method: (1) Grind the weathered coal humic acid through a 100-mesh sieve to obtain humic acid powder, then add it to a 0.1 mol / L NaOH solution at a solid-liquid ratio of 1 g:10 ml, stir and react at 60 °C for 2 h, and centrifuge to obtain the supernatant to obtain an activated humic acid solution; (2) Adjust the pH of the activated humic acid solution to 6.5, slowly add a 20% mass fraction of Ca(OH)2 suspension, stir evenly and react at 60°C for 4 hours. After the reaction is completed, collect the precipitate by centrifugation, wash with deionized water until no Ca²⁺ remains, dry at 60°C, and then crush through an 80-mesh sieve.

3. The bio-organic fertilizer for repairing heavy metal cadmium in soil according to claim 2, characterized in that, The volume ratio of the activated humic acid solution to the Ca(OH)2 suspension in step (2) is 1:1.

5.

4. The bio-organic fertilizer for repairing heavy metal cadmium in soil according to claim 1, characterized in that In step 2, the usage ratio of corn straw biochar, Fe(NO3)3, Ce(NO3)3, urea and deionized water is 5g:0.002mol:0.001mol:0.1mol:200ml.

5. The bio-organic fertilizer for repairing heavy metal cadmium in soil according to claim 1, characterized in that The specific method of high-temperature calcination in step 3 is to increase the temperature to 800° C. at a heating rate of 10° C. / min and calcine for 2 hours.

6. The bio-organic fertilizer for repairing heavy metal cadmium in soil according to claim 1, characterized in that The decomposed edible fungus residue is prepared by the following method: discarded mushroom sticks after the cultivation of oyster mushrooms, golden needle mushrooms and king oyster mushrooms are removed and crushed to obtain edible fungus residue, EM bacteria accounting for 1% of the total weight of the edible fungus residue are inoculated, water is added after thorough mixing, the moisture content of the mixture pile is adjusted to 60-65%, composting and fermentation are carried out, the temperature of the mixture pile is controlled within the range of 50°C-65°C, and after fermentation for 7-10 days, the fermentation product is dried and crushed to obtain the decomposed edible fungus residue.

7. The bio-organic fertilizer for repairing heavy metal cadmium in soil according to claim 6, characterized in that The effective viable count of the EM bacteria is ≥100 billion / gram.

8. A method for preparing a bio-organic fertilizer for repairing heavy metal cadmium in soil according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: preparing a composite microbial agent and modified biochar respectively, and mixing the two in proportion to obtain a mixture; S2: preparing calcium humate and mixing it with nano-hydroxyapatite in a certain proportion to obtain a chelating agent; S3: preparing decomposed edible fungus residue; S4: fully mix the decomposed edible fungus residue, the chelating agent and the mixture obtained in S1, prepare a solution of sodium alginate with a mass fraction of 1% and spray it evenly on the surface of the mixture, and granulate it with a granulator.

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