Application of composite solid phosphate-solubilizing bacterial agent to remediation of cadmium-contaminated soil and improvement of soil quality

Abstract

The invention relates to the field of environment, resource utilization and agricultural biotechnology, in particular to application of a composite solid phosphate-solubilizing bacterial agent to remediation of cadmium-contaminated soil and improvement of soil quality, in the application, the composite solid phosphate-solubilizing bacterial agent comprises phosphate-solubilizing bacteria, bone black, a culture medium and an organic matrix; the phosphate solubilizing bacteria are pantoea agglomerans CT-3 and enterobacter hormaechei HS-6; the composite solid phosphate-solubilizing bacterial agent is applied to Cd-polluted soil, the bio-availability of Cd in the soil is reduced through synergy of pantoea agglomerans CT-3, enterobacter hormaechei HS-6 and micron-nano multi-stage bone black, and meanwhile, the soil quality is improved. On one hand, the application can effectively promote conversion of insoluble phosphate into soluble phosphate, so that the content of available phosphorus in soil is increased by 98.19%; on the other hand, soil heavy metal Cd can be fixed, so that the content of available Cd in the soil is reduced by about 52.50%, and the soil remediation agent has excellent Cd fixation capacity, can relieve Cd stress of crops, and has good application value in the aspects of farmland Cd pollution remediation, soil quality improvement and environmental protection.

Description

Technical Field

[0001] The present invention relates to the fields of environment, resource utilization and agricultural biotechnology, and particularly relates to the application of a composite solid phosphate-solubilizing bacterial agent in repairing cadmium-polluted soil and improving soil quality. Background Art

[0002] Soil cadmium (Cd) pollution has become a global environmental problem, imposing a heavy burden on the ecosystem, agricultural production and human health. In terms of sources, activities such as the discharge of industrial "three wastes", the unreasonable use of Cd-containing pesticides and fertilizers, and mining and smelting have caused a large amount of Cd elements to enter the paddy field ecosystem. As one of the main food crops in the world, rice has a strong ability to accumulate Cd.

[0003] Traditional Cd-polluted paddy soil remediation technologies, such as chemical leaching, can reduce the soil Cd content to a certain extent, but they will damage the soil structure, lead to a decline in soil fertility, and the use of chemical reagents is likely to cause secondary pollution; the soil replacement method is costly, extremely difficult to implement on a large scale, and will also damage the ecological environment of the soil-taking area. Therefore, the development of green, efficient, low-cost and sustainable remediation technologies is of great significance for the safe production of crops.

[0004] Phosphate-solubilizing bacteria (PSB) are a group of functional microorganisms that can convert insoluble phosphorus in the soil into available phosphorus that plants can absorb and utilize. They can participate in the nutrient cycling and transformation of the soil, increase the content of available soil nutrients, improve the soil microbial community structure, and enhance soil fertility and quality. For the remediation of soil heavy metal Cd pollution, as a bioremediation method, phosphate-solubilizing bacteria have lower costs compared to chemical remediation methods and will not cause secondary pollution. However, the growth and activity of phosphate-solubilizing bacteria are usually restricted by environmental factors, resulting in a significant reduction in the remediation effect.

[0005] In addition, microbial agents have gradually been used for the remediation of Cd-polluted soil. However, there are not many microbial agents that can be effectively used for the remediation of Cd-polluted soil, and the remediation effect is not prominent. Therefore, the development of microbial agents needs to be strengthened to enrich the microbial agent resources for Cd-polluted soil remediation and promote the remediation of Cd-polluted soil. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide the application of a composite solid phosphate-solubilizing bacterial agent in repairing cadmium-polluted soil and improving soil quality. The application of this composite solid phosphate-solubilizing bacterial agent in repairing cadmium-polluted soil and improving soil quality has remarkable effects in reducing the bioavailability of Cd and increasing the content of available soil phosphorus. The soil quality has been greatly improved, and it can maintain the soil ecological balance and promote plant growth by enhancing soil fertility.

[0007] To achieve the object of the above invention, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides an application of a composite solid phosphate-solubilizing bacterium agent in repairing cadmium-polluted soil and improving soil quality. The composite solid phosphate-solubilizing bacterium agent includes phosphate-solubilizing bacteria, bone charcoal, culture medium and organic matrix; the phosphate-solubilizing bacteria include Enterobacter hormaechei HS-6 and Pantoea agglomerans CT-3;

[0009] The classification name of Enterobacter hormaechei HS-6 is Enterobacter hormaechei, and it was deposited in the General Microbiology Center of the China Committee for Culture Collection of Microorganisms on October 19, 2023, with the deposit number CGMCC NO.: 28680;

[0010] The classification name of Pantoea agglomerans CT-3 is Pantoea agglomerans, and it was deposited in the General Microbiology Center of the China Committee for Culture Collection of Microorganisms on January 8, 2025, with the deposit number CGMCC NO.: 33335;

[0011] Applying the composite solid phosphate-solubilizing bacterium agent to cadmium-polluted soil, the biological availability of cadmium in the soil is synergistically reduced by Enterobacter hormaechei HS-6, Pantoea agglomerans CT-3 and bone charcoal, and the soil quality is improved at the same time.

[0012] Furthermore, the 16S rDNA gene sequence of Enterobacter hormaechei HS-6 is as shown in SEQ ID No.1;

[0013] The 16S rDNA gene sequence of Pantoea agglomerans CT-3 is as shown in SEQ ID No.2.

[0014] Furthermore, the particle size of the bone charcoal is 30nm to 2μm.

[0015] Furthermore, the organic matrix is at least one of wheat bran, rice straw or corn cob.

[0016] Furthermore, the application of the composite solid phosphate-solubilizing bacterium agent in repairing cadmium-polluted soil and improving soil quality includes the following steps:

[0017] S1. Preparation of micro-nano bone charcoal: Animal bones are pyrolyzed and then cooled, and micron-nano multi-stage bone charcoal is obtained by ball milling;

[0018] S2. Activation of strains: Enterobacter hormaechei HS-6 and Pantoea agglomerans CT-3 are respectively inoculated into LB culture medium, and then placed in a constant temperature shaker at 28°C and shaken at 180r / min until OD 600 = 0.6 - 0.8 to obtain HS-6 bacterial suspension and CT-3 bacterial suspension;

[0019] S3. Preparation of liquid inoculum: Mix the HS-6 bacterial suspension and CT-3 bacterial suspension obtained in step S2 to form a composite bacterial liquid. After irradiating and sterilizing the micron-nano multi-stage bone charcoal prepared in step S1, add it and the composite bacterial liquid to the NBRIP medium, and then place it in a constant temperature shaker at 28 °C and shake it at 180 r / min for 44 h to 50 h to obtain the liquid inoculum;

[0020] S4. Treatment of organic matrix carrier: After rinsing the organic matrix with deionized water, add deionized water covering the organic matrix to soak the organic matrix, and sterilize it under high temperature and high pressure to obtain the treated organic matrix carrier;

[0021] S5. Preparation of solid inoculum: Add the liquid inoculum obtained in step S3 to the organic matrix carrier obtained in step S4, and culture it at 28 °C for 2 d to 4 d to obtain the composite solid phosphorus-solubilizing bacterial inoculum;

[0022] S6. Remediation of Cd-contaminated soil: Apply the composite solid phosphorus-solubilizing bacterial inoculum to the Cd-contaminated soil.

[0023] Further, in step S1, heat the animal bone at a heating rate of 8 °C / min to 12 °C / min to 440 °C to 460 °C and pyrolyze it for 100 min to 140 min, and then cool it to obtain large bone charcoal. Use a ball mill to ball mill the large bone charcoal at 440 rpm to 460 rpm for 4 h to 6 h to obtain the micron-nano multi-stage bone charcoal; and / or

[0024] In the ball mill, use zirconia particles to ball mill the large bone charcoal, and add ethanol as a grinding aid; the weight ratio of the zirconia particles to the large bone charcoal is (15 - 20):1; the mass ratio of the ethanol to the large bone charcoal is (1.5 - 2):1.

[0025] Further, in step S2, the effective viable counts of the obtained HS-6 bacterial suspension and CT-3 bacterial suspension are 1×10 10 CFU / mL to 9×10 10 CFU / mL.

[0026] Further, in step S3, the mass-volume ratio of the bone charcoal to the NBRIP medium is 0.5% to 2.5%; and / or

[0027] The volume ratio of the HS-6 bacterial suspension to the CT-3 bacterial suspension is 1:1;

[0028] The inoculation amount of the composite bacterial liquid in the NBRIP medium is 1% of the volume percentage of the NBRIP medium; and / or

[0029] The dose of the irradiation sterilization is 3.0 kGy to 6.0 kGy.

[0030] Further, in step S4, after rinsing the organic matrix three times with deionized water, add deionized water covering the organic matrix and soak the organic matrix for 10 h to 20 h, and obtain the treated organic matrix carrier through high-temperature and high-pressure sterilization;

[0031] The conditions for the high-temperature and high-pressure sterilization are: 121 °C, 104 KPa, 20 min.

[0032] Further, in step S5, add the liquid bacterium agent obtained in step S3 to the organic matrix carrier obtained in step S4, seal it in a polyethylene bag, puncture 5 to 8 air holes on the surface of the polyethylene bag with a sterile needle, and then place it in a constant-temperature shaker at 28 °C and oscillate and culture it at 180 r / min for 2 d to 4 d to obtain the composite solid phosphorus-solubilizing bacterium agent;

[0033] In step S5, the mass ratio of the liquid bacterium agent to the organic matrix carrier is 15:(70 - 100);

[0034] In step S6, the mass ratio of the composite solid phosphorus-solubilizing bacterium agent to the Cd-contaminated soil is 3:(250 - 350).

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) The application of a composite solid phosphorus-solubilizing bacterium agent for repairing Cd-contaminated soil and improving soil quality according to the present invention, the composite solid phosphorus-solubilizing bacterium agent includes phosphorus-solubilizing bacteria, bone charcoal, a culture medium and an organic matrix; the phosphorus-solubilizing bacteria include Enterobacter hormaechei HS-6 and Pantoea agglomerans CT-3; when the composite solid phosphorus-solubilizing bacterium agent is applied to Cd-contaminated soil, Enterobacter hormaechei HS-6, Pantoea agglomerans CT-3 and bone charcoal synergistically reduce the bioavailability of Cd in the soil, and at the same time improve the soil quality and increase the content of available phosphorus in the soil. On the one hand, this application can effectively promote the conversion of insoluble phosphate into soluble phosphate, increasing the content of available phosphorus in the soil by 98.19%; on the other hand, it can fix the heavy metal Cd in the soil, reducing the content of available Cd in the soil by about 52.50%, having excellent Cd-fixing ability, and can relieve the Cd stress of crops (such as rice), and has good application value in the repair of farmland Cd pollution, improvement of soil quality and environmental protection.

[0037] (2) Application of a composite solid phosphate-solubilizing bacterium agent of the present invention in repairing cadmium-polluted soil and improving soil quality. Compared with the Cd pollution repair technologies in the prior art that only focus on a single mechanism, the application technology of the present invention is a combined repair technology synergistically using Enterobacter hormaechei HS-6, Pantoea agglomerans CT-3 and bone charcoal. Due to the rich pore structure, large specific surface area and strong ion exchange capacity of the micron-nano multi-stage bone charcoal in the phosphate-solubilizing bacterium agent, it can efficiently and rapidly adsorb Cd ions in the soil, has an excellent fixing ability for Cd in the soil, and can also provide a stable habitat and rich nutrients for Enterobacter hormaechei HS-6 and Pantoea agglomerans CT-3, protect Enterobacter hormaechei HS-6 and Pantoea agglomerans CT-3 from the influence of adverse environmental factors, enhance the survival ability and activity of Enterobacter hormaechei HS-6 and Pantoea agglomerans CT-3 in the polluted environment, and further improve the heavy metal repair ability of Enterobacter hormaechei HS-6 and Pantoea agglomerans CT-3. Therefore, the synergism of Enterobacter hormaechei HS-6, Pantoea agglomerans CT-3 and micron-nano multi-stage bone charcoal greatly improves the removal and fixation efficiency of Cd, greatly reduces the bioavailability of Cd in the soil, and reduces its harm to the ecological environment and crops. In addition, the metabolites produced by Enterobacter hormaechei HS-6 and Pantoea agglomerans CT-3 during the phosphate-solubilizing process can also form stable complexes or precipitates with Cd ions, further reducing the bioavailability of Cd. Therefore, compared with the method of using physical or chemical adsorption alone, the present invention has a more significant repair effect in reducing the bioavailability of Cd in the soil.

[0038] (3) Application of a composite solid phosphate-solubilizing bacterium agent of the present invention in repairing cadmium-polluted soil and improving soil quality. Compared with the traditional chemical repair method that easily causes drug residues and secondary pollution when using a large amount of chemical agents, the repair technology of the present invention uses Enterobacter hormaechei HS-6, Pantoea agglomerans CT-3 and micron-nano multi-stage bone charcoal, all of which are of natural origin or biodegradable materials, will not introduce harmful chemical substances into the soil, and are more friendly to the soil and the surrounding ecological environment. In addition, Enterobacter hormaechei HS-6 and Pantoea agglomerans CT-3 can also improve the soil microbial community structure, promote the growth and reproduction of beneficial microorganisms, and the micron-nano multi-stage bone charcoal can provide a good habitat environment for soil microorganisms, jointly maintaining the soil ecological balance, which is difficult to achieve by many traditional repair technologies. Therefore, the application of the present invention has the advantage of being green and environmentally friendly.

[0039] (4) Application of a composite solid phosphate-solubilizing bacterial agent of the present invention in repairing cadmium-polluted soil and improving soil quality. Since Enterobacter hormaechei HS-6 and Pantoea agglomerans CT-3 in the phosphate-solubilizing bacterial agent can convert insoluble phosphorus in the soil into available phosphorus, thereby increasing soil phosphorus nutrition, while micron-nano multi-level bone char can increase the pH value and cation exchange capacity of the soil, enhancing the water and fertilizer retention capacity of the soil. Therefore, the combination of the three can comprehensively improve soil fertility and create good nutritional conditions for crop growth.

[0040] (5) Application of a composite solid phosphate-solubilizing bacterial agent of the present invention in repairing cadmium-polluted soil and improving soil quality. Through Enterobacter hormaechei HS-6, Pantoea agglomerans CT-3 and micron-nano multi-level bone char, the three work together to reduce the toxic effect of Cd in the soil on crops and enhance the stress resistance of crops, which is a function not possessed by simple physical or chemical remediation technologies. On the other hand, micron-nano multi-level bone char is rich in various nutrient elements such as calcium, nitrogen, phosphorus, and magnesium, which are exactly the nutrients necessary for plant growth. Therefore, the micron-nano multi-level bone char of the present invention can also act as a fertilizer to supplement soil fertility, promote the healthy growth of crops, and thus improve agricultural productivity. In summary, the application of the present invention has advantages in promoting plant growth. Brief Description of the Drawings

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0042] Figure 1 It is a scanning electron micrograph of Enterobacter hormaechei HS-6 of the present invention.

[0043] Figure 2 It is a scanning electron micrograph of Enterobacter hormaechei HS-6 after its interaction with bone char of the present invention.

[0044] Figure 3 It is a scanning electron micrograph of Pantoea agglomerans CT-3 of the present invention.

[0045] Figure 4 It is a scanning electron micrograph of Pantoea agglomerans CT-3 after its interaction with bone char of the present invention.

[0046] Figure 5 It is a graph showing the measurement results of the soil pH value of samples collected at different time periods in different experimental groups.

[0047] Figure 6 It is a graph showing the measurement results of the soil cation exchange capacity of samples collected at different time periods in different experimental groups.

[0048] Figure 7 It is a graph showing the determination results of the available phosphorus content in the soil of samples collected at different time periods in different experimental groups.

[0049] Figure 8 It is a graph showing the determination results of the available Cd content in the soil of samples collected at different time periods in different experimental groups.

[0050] Figure 9 It is a graph showing the determination results of the catalase activity in the soil of samples collected at different time periods in different experimental groups.

[0051] Figure 10 It is a graph showing the determination results of the invertase activity in the soil of samples collected at different time periods in different experimental groups.

[0052] Figure 11 It is a graph showing the determination results of the urease activity in the soil of samples collected at different time periods in different experimental groups.

[0053] Figure 12 It is a graph showing the determination results of the acid phosphatase activity in the soil of samples collected at different time periods in different experimental groups.

[0054] Figure 13 It is a graph showing the determination results of the plant height of rice cultivated with soil samples from different experimental groups.

[0055] Figure 14 It is a graph showing the determination results of the root length of rice cultivated with soil samples from different experimental groups.

[0056] Figure 15 It is a graph showing the determination results of the fresh weight of the above-ground part of rice cultivated with soil samples from different experimental groups.

[0057] Figure 16 It is a graph showing the determination results of the fresh weight of the underground part of rice cultivated with soil samples from different experimental groups. Detailed implementation manner

[0058] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0059] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In the present invention, the singular forms of "a", "the" and "said" used in the embodiments and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0060] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0061] The medium formulations described in the following examples are as follows:

[0062] LB medium (g / L): peptone 10 g, yeast extract 5 g, NaCl 10 g, pH 7.0 - 7.2.

[0063] Solid LB medium: add 18 g - 20 g of agar powder to every 1 L of LB medium.

[0064] NBRIP medium (g / L): glucose 10 g, MgCl 2 ·6H 2 O 5 g, MgSO 4 ·7H 2 O 0.25 g, FeSO 4 ·7H 2 O 0.01 g, KCl 0.2 g, (NH 4 ) 2 SO 4 0.1 g, Ca 3 (PO 4 ) 2 5.0 g, pH 7.0 - 7.4.

[0065] Solid NBRIP medium: add 18 g - 20 g of agar powder to every 1 L of NBRIP - P medium.

[0066] Example 1

[0067] Application of a composite solid phosphate - solubilizing bacterium agent in repairing cadmium - contaminated soil and improving soil quality. The composite solid phosphate - solubilizing bacterium agent includes phosphate - solubilizing bacteria, bone char, medium and wheat bran. The phosphate - solubilizing bacteria include Enterobacter hormaechei HS - 6 and Pantoea agglomerans CT - 3. The classification name of Enterobacter hormaechei HS - 6 is Enterobacter hormaechei, which was deposited in the China General Microbiological Culture Collection Center on October 19, 2023, with the deposit number CGMCC NO.: 28680 and the deposit address: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. Among them, the scanning electron micrograph of Enterobacter hormaechei HS - 6 is as shown in Figure 1 shown. The classification name of Pantoea agglomerans CT - 3 is Pantoea agglomerans, which was deposited in the China General Microbiological Culture Collection Center on January 8, 2025, with the deposit number CGMCC NO.: 33335 and the deposit address: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. Among them, the scanning electron micrograph of Enterobacter hormaechei HS - 6 is as shown in Figure 3 shown.

[0068] The application applies a composite solid phosphate-solubilizing bacterium agent to Cd-polluted soil, and synergistically reduces the bioavailability of Cd in the soil and improves the soil quality through Enterobacter hormaechei HS-6, Pantoea agglomerans CT-3 and bone charcoal.

[0069] Among them, the 16S rDNA gene sequence of Enterobacter hormaechei HS-6 is shown in SEQ ID No.1. Among them, the length of the gene sequence is 1476.

[0070] Among them, the 16S rDNA gene sequence of Pantoea agglomerans CT-3 is shown in SEQ ID No.2. Among them, the length of the gene sequence is 1411.

[0071] In this example, the particle size of the bone charcoal is 30nm to 2μm.

[0072] The application of the composite solid phosphate-solubilizing bacterium agent for repairing Cd-polluted soil and improving soil quality includes the following steps:

[0073] S1. Preparation of micro-nano bone charcoal: The animal bone is heated to 450°C at a heating rate of 10°C / min and pyrolyzed for 120 min, and after cooling, large bone charcoal is obtained. The large bone charcoal is ball-milled in a ball mill at 450 rpm for 5 h to obtain micro-nano multi-stage bone charcoal;

[0074] Among them, in the ball mill, the large bone charcoal is ball-milled with zirconia particles, and ethanol is added as a grinding aid; the weight ratio of zirconia particles to large bone charcoal is 17:1; the mass ratio of ethanol to large bone charcoal is 1.8:1.

[0075] S2. Activation of strains: Enterobacter hormaechei HS-6 and Pantoea agglomerans CT-3 are respectively inoculated into LB medium, and then placed in a constant temperature shaker at 28°C and shaken at 180 r / min until OD 600 = 0.6 - 0.8 to obtain HS-6 bacterial suspension and CT-3 bacterial suspension; among them, the effective viable bacteria counts of the prepared HS-6 bacterial suspension and CT-3 bacterial suspension are 1×10 10 CFU / mL - 9×10 10 CFU / mL.

[0076] S3. Preparation of liquid bacterium agent: The HS-6 bacterial suspension and CT-3 bacterial suspension obtained in step S2 are mixed to form a composite bacterial solution. The micro-nano multi-stage bone charcoal prepared in step S1 is irradiated and sterilized and added to the NBRIP medium, and then placed in a constant temperature shaker at 28°C and shaken at 180 r / min for 48 h to obtain a liquid bacterium agent;

[0077] In this example, the mass-volume ratio of bone char to NBRIP medium is 0.5%; among them, the volume ratio of HS-6 bacterial suspension to CT-3 bacterial suspension is 1:1; the inoculation amount of the composite bacterial liquid in the NBRIP medium is 1% of the volume percentage of the NBRIP medium; in this example, the dose of irradiation sterilization is 5.0 kGy.

[0078] S4. Treatment of organic matrix carrier: After rinsing the organic matrix three times with deionized water, add deionized water covering the organic matrix and soak the organic matrix for 15 h, and obtain the treated organic matrix carrier through high-temperature and high-pressure sterilization; among them, the conditions for high-temperature and high-pressure sterilization are: 121 °C, 104 KPa, 20 min.

[0079] S5. Preparation of solid bacterial agent: Add the liquid bacterial agent obtained in step S3 to the organic matrix carrier obtained in step S4, seal it in a polyethylene bag, puncture 5 air holes on the surface of the polyethylene bag with a sterile needle, and then place it in a constant temperature shaker at 28 °C and shake it at 180 r / min for 3 d to obtain the composite solid phosphate-solubilizing bacterial agent; in this example, the mass ratio of the liquid bacterial agent to the organic matrix carrier is 15:85;

[0080] S6. Remediation of Cd-polluted soil: Apply the composite solid phosphate-solubilizing bacterial agent to the Cd-polluted soil. In this example, the mass ratio of the composite solid phosphate-solubilizing bacterial agent to the Cd-polluted soil is 3:300.

[0081] Example 2

[0082] An application of a composite solid phosphate-solubilizing bacterial agent in remediating Cd-polluted soil and improving soil quality. The difference between this example and Example 1 is that in step S3, the mass-volume ratio of bone char to NBRIP medium is 1%, the dose of irradiation sterilization is 3.0 kGy, and the shaking culture is for 44 h. The remaining conditions and methods of this example are the same as those of Example 1.

[0083] Example 3

[0084] An application of a composite solid phosphate-solubilizing bacterial agent in remediating Cd-polluted soil and improving soil quality. The difference between this example and Example 1 is that in this example, the organic matrix is rice straw; in step S3, the mass-volume ratio of bone char to NBRIP medium is 2%, the dose of irradiation sterilization is 4.0 kGy, and the shaking culture is for 46 h. The remaining conditions and methods of this example are the same as those of Example 1.

[0085] Example 4

[0086] Application of a composite solid phosphorus-solubilizing bacterium agent in repairing cadmium-polluted soil and improving soil quality. The difference between this example and Example 1 is that in this example, the organic matrix is corncob; in step S3, the mass-volume ratio of bone char to NBRIP medium is 2.5%, the dose of irradiation sterilization is 6.0 kGy, and the shaking culture is carried out for 50 h. The remaining conditions and methods in this example are the same as those in Example 1.

[0087] Example 5

[0088] Application of a composite solid phosphorus-solubilizing bacterium agent in repairing cadmium-polluted soil and improving soil quality. The difference between this example and Example 1 is that in this example, in step S1, preparation of micro-nano bone char: Animal bones are heated to 440 °C at a heating rate of 8 °C / min and pyrolyzed for 140 min, and after cooling, large pieces of bone char are obtained. The large pieces of bone char are ball-milled in a ball mill at 440 rpm for 6 h to obtain micro-nano multi-level bone char.

[0089] Among them, in the ball mill, zirconia particles are used to ball-mill the large pieces of bone char, and ethanol is added as a grinding aid; the weight ratio of zirconia particles to large pieces of bone char is 15:1; the mass ratio of ethanol to large pieces of bone char is 1.7:1.

[0090] The remaining conditions and methods in this example are the same as those in Example 1.

[0091] Example 6

[0092] Application of a composite solid phosphorus-solubilizing bacterium agent in repairing cadmium-polluted soil and improving soil quality. The difference between this example and Example 1 is that in this example, in step S1, preparation of micro-nano bone char: Animal bones are heated to 460 °C at a heating rate of 12 °C / min and pyrolyzed for 100 min, and after cooling, large pieces of bone char are obtained. The large pieces of bone char are ball-milled in a ball mill at 460 rpm for 4 h to obtain micro-nano multi-level bone char.

[0093] Among them, in the ball mill, zirconia particles are used to ball-mill the large pieces of bone char, and ethanol is added as a grinding aid; the weight ratio of zirconia particles to large pieces of bone char is 20:1; the mass ratio of ethanol to large pieces of bone char is 2:1; the dose of irradiation sterilization is 6.0 kGy.

[0094] The remaining conditions and methods in this example are the same as those in Example 1.

[0095] Example 7

[0096] Application of a composite solid phosphate-solubilizing bacterial agent in repairing cadmium-polluted soil and improving soil quality. The difference between this example and Example 1 is that in this example, in step S4, deionized water covering the organic matrix is added to soak the organic matrix for 10 h. In step S5, 6 air holes are pricked on the surface of the polyethylene bag with a sterile needle, and then it is placed in a constant temperature shaker at 28 °C and shaken at 180 r / min for 2 d to obtain the composite solid phosphate-solubilizing bacterial agent; in this example, the mass ratio of the liquid bacterial agent to the organic matrix carrier is 15:70. In step S6, the mass ratio of the composite solid phosphate-solubilizing bacterial agent to the Cd-polluted soil is 3:250.

[0097] The remaining conditions and methods of this example are the same as those of Example 1.

[0098] Example 8

[0099] Application of a composite solid phosphate-solubilizing bacterial agent in repairing cadmium-polluted soil and improving soil quality. The difference between this example and Example 1 is that in this example, in step S4, deionized water covering the organic matrix is added to soak the organic matrix for 20 h. In step S5, 8 air holes are pricked on the surface of the polyethylene bag with a sterile needle, and then it is placed in a constant temperature shaker at 28 °C and shaken at 180 r / min for 4 d to obtain the composite solid phosphate-solubilizing bacterial agent; in this example, the mass ratio of the liquid bacterial agent to the organic matrix carrier is 15:100. In step S6, the mass ratio of the composite solid phosphate-solubilizing bacterial agent to the Cd-polluted soil is 3:350.

[0100] The remaining conditions and methods of this example are the same as those of Example 1.

[0101] Experimental detection:

[0102] I. Scanning electron microscopy detection

[0103] Among them, for the scanning electron microscopy image of the strain Enterobacter hormaechei HS-6 of the present invention, please refer to Figure 1 . Among them, Figure 1 (b) is Figure 1 the partial enlarged view of the dashed box in Figure 1 (a). As

[0104] shown, Enterobacter hormaechei HS-6 is a rod-shaped bacterium 1 μm in length. Figure 2 In addition, for the scanning electron microscopy detection after Enterobacter hormaechei HS-6 acts on bone charcoal, please refer to Figure 2 (b) is Figure 2 the enlarged view of the dashed box part in Figure 2 (a). It can be seen from

[0105] Among them, for the scanning electron microscope image of the Pantoea agglomerans CT-3 strain of the present invention, please refer to Figure 3 . Among them, Figure 3 (b) is Figure 3 the partial enlarged view of the dashed box in Figure 3 (a). As

[0106] shown, Pantoea agglomerans CT-3 is a rod-shaped bacterium 1 μm in length. Figure 4 In addition, for the scanning electron microscope detection after the action of Pantoea agglomerans CT-3 and bone charcoal, please refer to Figure 4 (b) is Figure 4 the enlarged view of the dashed box part in Figure 4 (a). As can be seen from

[0107] II. Remediation of Cd-contaminated soil

[0108] 1. Soil collection

[0109] The soil for the experiment was collected from the surface soil of 0 cm - 20 cm in a paddy field in Huadu District, Guangzhou (latitude 23.415°, longitude 113.047°). Before use, the soil was air-dried, ground, and passed through a 2 mm sieve.

[0110] 2. Experimental sample design plan

[0111] The specific experimental sample design plan is shown in Table 1 below.

[0112] Table 1 Experimental sample design plan table

[0113]

[0114] For the four experimental groups in Table 1, each experimental group was set with four parallels. The total weight of the samples in each experimental group was 300 g, and they were placed in brown wide-mouth bottles for cultivation. The bottles were placed in a constant temperature environment of 25 °C, and water was supplemented daily to keep the moisture content constant at 60%. Soil samples were collected on the 0th day, 3rd day, 10th day, 18th day, and 30th day respectively, cold-dried, ground, and passed through a 100-mesh sieve for subsequent test work.

[0115] The samples of the above-mentioned experimental groups were respectively measured for soil pH, soil cation exchange capacity (CEC), soil available phosphorus content, soil available Cd content, and soil enzyme activity.

[0116] (I) Measuring the soil pH of the samples in different experimental groups

[0117] Samples designed according to Table 1 and collected at different time periods (each sample was set with four parallel samples) were used to determine the soil pH value respectively according to "Determination of Soil pH Value - Potentiometry" (HJ 962 - 2018). For the determination results, please refer to Figure 5 . Figure 5 In Figure 5 , the label "Cd" represents the Cd soil group, the label "Cd MNBC" represents the Cd MNBC soil group, and the label "Cd MNBC CT - 3&HS - 6" represents the Cd MNBC CT - 3&HS - 6 soil group.

[0118] From Figure 5 the determination results, it can be seen that the pH values of the samples in the blank control group and the Cd soil group at each sampling time period were approximately around 4.5, and the pH values of the samples in the Cd MNBC soil group and the Cd MNBC CT - 3&HS - 6 soil group at each sampling time period were around 6. This indicates that the soil with added bone char or added bone char, Pantoea agglomerans CT - 3, and Enterobacter hormaechei HS - 6 had an increased pH value compared to the blank control group, and could improve acidic soil.

[0119] In addition, Figure 5 in Figure 5 , the soil pH basically showed a trend of first increasing and then decreasing, reaching the highest at the 10th day, indicating that the increase in the soil pH value with the application of bone char or the application of bone char, Pantoea agglomerans CT - 3, and Enterobacter hormaechei HS - 6 was extremely significant.

[0120] A large number of studies have shown that in acidic soil (pH < 6), the activity of some phosphate - solubilizing bacteria may be inhibited, but in neutral (pH 6 - 7) or slightly alkaline (pH > 7) soil, the activity of many phosphate - solubilizing bacteria is relatively high, which is conducive to the release of phosphorus. Therefore, the application of a composite solid phosphate - solubilizing bacterial agent to repair cadmium - contaminated soil and improve soil quality can make the soil approach neutral, thereby increasing the activity of Pantoea agglomerans CT - 3 and Enterobacter hormaechei HS - 6, and promoting the increase of the available phosphorus content in the soil. Therefore, applying the composite solid phosphate - solubilizing bacterial agent of the present invention in the soil, combined with the effects of bone char, Pantoea agglomerans CT - 3, and Enterobacter hormaechei HS - 6, is beneficial to the survival of Pantoea agglomerans CT - 3 and Enterobacter hormaechei HS - 6 in paddy soil and better play the role of phosphorus solubilization.

[0121] (2) Determination of the soil cation exchange capacity of samples in different experimental groups

[0122] Samples designed according to Table 1 and collected at different time periods (each sample was set with four parallel samples) were used to determine the soil cation exchange capacity (CEC). For the determination results, please refer to Figure 6 . Among them, the determination of the soil cation exchange capacity was carried out according to "Determination of Soil Cation Exchange Capacity - Extraction with Hexaamminecobalt(III) Chloride - Spectrophotometry" (HJ 889 - 2017). Figure 6Among them, the label "Cd" represents the Cd soil group, the label "Cd MNBC" represents the Cd MNBC soil group, and the label "Cd MNBC CT-3&HS-6" represents the Cd MNBC CT-3&HS-6 soil group.

[0123] From Figure 6 the measurement results, it can be seen that for the samples of the Cd MNBC soil group and the Cd MNBC CT-3&HS-6 soil group at each sampling time period, compared with the blank control group and the Cd soil group, the soil cation exchange capacity has increased significantly. The soil cation exchange capacity basically shows a trend of first increasing and then decreasing, reaching the highest on the 10th day, indicating that the application of bone char or the application of bone char, Pantoea agglomerans CT-3 and Enterobacter hormaechei HS-6 has extremely significantly increased the soil cation exchange capacity.

[0124] (III) Measure the available phosphorus content of the soil samples in different experimental groups

[0125] Measure the available phosphorus content of the samples designed according to Table 1 and collected at different time periods (each sample is set with four parallel samples). For the measurement results, please refer to Figure 7 . Figure 7 Among them, the label "Cd" represents the Cd soil group, the label "Cd MNBC" represents the Cd MNBC soil group, and the label "Cd MNBC CT-3&HS-6" represents the Cd MNBC CT-3&HS-6 soil group.

[0126] From Figure 7 the measurement results, it can be seen that for the Cd MNBC soil group and the Cd MNBC CT-3&HS-6 soil group, compared with the blank control group and the Cd soil group, the available phosphorus content has increased significantly, indicating that the application of micron-nano multi-level bone char and phosphate-solubilizing bacteria in the soil can significantly increase the available phosphorus content of the soil. Interestingly, compared with the Cd MNBC soil group, the available phosphorus content of the Cd MNBC CT-3&HS-6 soil group increased by 16.51% on the 3rd day under the action of micron-nano multi-level bone char combined with Pantoea agglomerans CT-3 and Enterobacter hormaechei HS-6, indicating that under Cd pollution, the application of the present invention, namely micron-nano multi-level bone char, Pantoea agglomerans CT-3 and Enterobacter hormaechei HS-6 in synergy, can further increase the available phosphorus content of the soil. After 30 days, the available phosphorus content of the Cd MNBC CT-3&HS-6 soil group increased by 98.19%.

[0127] (IV) Measure the available Cd content of the soil samples in different experimental groups

[0128] Measure the available Cd content of the samples designed according to Table 1 and collected at different time periods (each sample is set with four parallel samples). For the measurement results, please refer to Figure 8 . Figure 8Among them, the label "Cd" represents the Cd soil group, the label "Cd MNBC" represents the Cd MNBC soil group, and the label "Cd MNBC CT-3&HS-6" represents the Cd MNBC CT-3&HS-6 soil group.

[0129] Among them, the determination of available Cd content in soil was carried out according to "Determination of 8 available elements in soil - Extraction with diethylenetriaminepentaacetic acid - Inductively coupled plasma optical emission spectrometry" (HJ 804-2016). Weigh 5.00 g of freeze-dried and sieved soil sample and place it in a 50 mL centrifuge tube. Add 20 mL of diethylenetriaminepentaacetic acid (DTPA)-calcium chloride (CaCl 2 2)-triethanolamine (TEA) extractant (pH 7.3), reciprocally oscillate and extract at room temperature at 160 r / min for 2 h, centrifuge, and filter the supernatant through a 0.22 μm filter membrane for determination.

[0130] From Figure 8 the determination results, it can be seen that compared with the Cd soil group, the available Cd contents of the Cd MNBC soil group and the Cd MNBC CT-3&HS-6 soil group were both significantly reduced. Especially, compared with the Cd MNBC soil group, the reduction degree of available Cd content in the Cd MNBC CT-3&HS-6 soil group was greater, indicating that the combined action of micron-nano multi-level biochar and Pantoea agglomerans CT-3 and Enterobacter hormaechei HS-6 had a better effect on reducing the available Cd content in soil. On the 3rd day, by comparing with the Cd soil group, it was found that the available Cd contents in the Cd MNBC soil group and the Cd MNBC CT-3&HS-6 soil group were reduced by 39.88% and 43.19% respectively. After 30 days of the action of micron-nano multi-level biochar combined with Pantoea agglomerans CT-3 and Enterobacter hormaechei HS-6, the available Cd content in the Cd MNBC CT-3&HS-6 soil group was reduced by 52.50%. According to Figure 8 analysis, in the Cd MNBC soil group and the Cd MNBC CT-3&HS-6 soil group, in the early stage (day 0 - 10), biochar may dominate Cd adsorption; in the middle stage (day 10 - 18), the biochemical regulation effect of phosphate-solubilizing bacteria was prominent, further strengthening Cd fixation; in the long term (day 18 - 30), the Cd MNBC CT-3&HS-6 soil group maintained lower Cd availability by continuously activating soil nutrients and optimizing the Cd form. It shows that the application of a composite solid phosphate-solubilizing bacteria agent of the present invention for repairing cadmium-polluted soil and improving soil quality can greatly reduce the available Cd content and has a more significant effect on reducing the biological availability of Cd in soil.

[0131] (V) Determine and compare the available Cd content in single-bacteria and double-bacteria samples

[0132] Prepare a single-strain phosphate-solubilizing agent as a comparative sample. Among them, the preparation of the single-strain phosphate-solubilizing agent is different from the preparation of the composite solid phosphate-solubilizing agent in Example 1 in that Pantoea agglomerans CT-3 is not used, and only Enterobacter hormaechei HS-6 is used. The remaining methods are the same as those in Example 1.

[0133] The design schemes of the single-strain and double-strain samples are shown in Table 2 below.

[0134] Table 2 Design scheme table of single-strain and double-strain experimental samples

[0135]

[0136] For the three experimental groups in Table 2, four parallels are set for each experimental group. The total weight of the samples in each experimental group is 300 g, and they are placed in brown wide-mouth bottles for cultivation. The bottles are placed in a constant temperature environment of 25 °C, and water is supplemented daily to keep the moisture content constant at 60%. Soil samples are collected on the 0th d, 3rd d, 10th d, 18th d, and 30th d respectively, cooled and dried, ground, passed through a 100-mesh sieve, and then the available Cd content in the soil is measured.

[0137] Compared with the Cd soil group, the available Cd content in the soil of the Cd MNBC HS-6 soil group and the Cd MNBC CT-3&HS-6 soil group decreased significantly, and the decrease is shown in Table 3 below.

[0138] Table 3 Data table of the decrease in available Cd content in the soil of single-strain and double-strain experimental samples

[0139]

[0140]

[0141] As can be seen from the data in Table 3, compared with the Cd MNBC HS-6 soil group, in the early stage (3rd d to 10th d), the degree of decrease in the available Cd content in the soil of the Cd MNBC HS-6 soil group is relatively large; in the long term (18th d to 30th d), the degree of decrease in the available Cd content in the soil of the Cd MNBC CT-3&HS-6 soil group is relatively large. It shows that the application of a composite solid phosphate-solubilizing agent for repairing cadmium-polluted soil and improving soil quality in the present invention has a more significant effect on long-term repair of Cd-polluted soil.

[0142] (VI) Measure the soil enzyme activities of samples in different experimental groups

[0143] Measure the soil catalase activity, sucrase activity, urease activity, and acid phosphatase activity of the samples designed according to Table 1 and collected at different time periods (four parallel samples are set for each sample) respectively. The measurement results are shown in Figure 9 、 Figure 10 、Figure 11 and Figure 12 。

[0144] Among them, the method for measuring soil enzyme activity is as follows: Use the kit of Isaku Co., Ltd. (China) according to the manufacturer's instructions, and use a multi-functional enzyme marker (Synergy HTX, BioTek, USA) to measure the activities of four typical soil enzymes, namely soil catalase, sucrase, urease, and acid phosphatase.

[0145] Figures 9 to 12 In, the label "Cd" represents the Cd soil group, the label "Cd MNBC" represents the Cd MNBC soil group, and the label "Cd MNBC CT-3&HS-6" represents the Cd MNBC CT-3&HS-6 soil group.

[0146] Among them, urease, sucrase, and catalase are important soil enzymes widely used to evaluate the impact of soil amendments on soil biological functions. Urease and sucrase are involved in the decomposition and mineralization of carbohydrates in the soil, providing nutrients for the growth of soil microorganisms and crops, while catalase can degrade H 2 O 2 in the soil, reducing its toxic effects on organisms. Figures 9 to 12 It can be seen that compared with the Cd soil group, the combination of micronano multi-stage biochar, Pantoea agglomerans CT-3, and Enterobacter hormaechei HS-6 can significantly increase the activities of catalase, sucrase, urease, and acid phosphatase in Cd-contaminated soil, by 13.30%, 340.38%, 473.29%, and 108.59% respectively.

[0147] In addition, acid phosphatase is a class of enzymes that catalyze the mineralization of soil organic phosphorus. The level of its activity directly affects the decomposition, transformation, and bioavailability of organic phosphorus in the soil, and is an indicator for evaluating the direction and intensity of soil phosphorus biotransformation. Acid phosphatase is significantly affected by the carbon and nitrogen contents, available phosphorus content, and pH of the soil. Therefore, the combination of micronano multi-stage biochar, Pantoea agglomerans CT-3, and Enterobacter hormaechei HS-6 enhanced the activity of acid phosphatase in Cd-contaminated soil, and this enhancement may be closely related to the unique properties of micronano multi-stage biochar. Biochar is an additional source of C and P elements, providing more suitable habitat conditions for Pantoea agglomerans CT-3 and Enterobacter hormaechei HS-6 in the soil and promoting their growth.

[0148] III. Experiment on Promoting Crop Growth

[0149] The selected rice variety is Xiuzhan 15. First, the rice is cultivated in a plant incubator. After 14 days of cultivation, rice seedlings of the same size are transplanted into four experimental group samples designed according to Table 1 for pot cultivation. Six parallel samples are set for each sample and placed at room temperature for a 28-day exposure experiment. The rice plants are harvested, and the plant height, root length, above-ground fresh weight, and underground fresh weight of the rice are measured respectively. The measurement results can be seen in Figure 13 , Figure 14 , Figure 15 and Figure 16 .

[0150] Figures 13 to 16 respectively. In

[0151] , the label "Cd" represents the Cd soil group, the label "Cd MNBC" represents the Cd MNBC soil group, and the label "Cd MNBC CT-3&HS-6" represents the Cd MNBC CT-3&HS-6 soil group. Figures 13 to 16 It can be seen from the measurement results of

[0152] that compared with the blank control group, the plant height, root length, above-ground fresh weight, and underground fresh weight of the rice cultivated in the Cd soil group are all significantly reduced, by 22.55%, 25.87%, 25.23%, and 32.00% respectively, indicating that the Cd-polluted soil seriously affects the growth of crops. Compared with the Cd soil group, both the Cd MNBC soil group and the Cd MNBC CT-3&HS-6 soil group significantly increase the plant height, root length, and above-ground fresh weight of the rice. Among them, compared with the Cd soil group, the plant height, root length, and above-ground fresh weight of the rice in the Cd MNBC CT-3&HS-6 soil group are increased by 16.05%, 31.99%, and 49.46% respectively. It shows that the application of a composite solid phosphate-solubilizing bacterium agent to repair Cd-polluted soil and improve soil quality can promote the healthy growth of crops and thus improve agricultural productivity.

[0153]

[0154]

Claims

1. An application of a composite solid phosphate-dissolving bacteria agent for repairing cadmium-contaminated soil and improving soil quality, characterized in that: The composite solid phosphate-dissolving bacteria agent comprises phosphate-dissolving bacteria, bone charcoal, culture medium and organic matrix; the phosphate-dissolving bacteria comprises Enterobacter holsteinii HS-6 and Pantoea agglomerans CT-3; The classification name of the Enterobacter hormaechei HS-6 is Enterobacter hormaechei, which was deposited in the General Microbiological Center of the China Microbiological Culture Collection Administration on October 19, 2023, with a deposit number of CGMCC NO.: 28680; The classification name of the Pantoea agglomerans CT-3 is Pantoea agglomerans, which has been deposited in the General Microbiological Center of the China Microbiological Culture Collection Administration on January 8, 2025, with a deposit number of CGMCCNO.: 33335; The composite solid phosphate-dissolving bacteria agent is applied to Cd-contaminated soil, and the bioavailability of Cd in the soil is synergistically reduced through Enterobacter hullii HS-6, Pantoea agglomerans CT-3 and bone char, while improving soil quality.

2. The use of a composite solid phosphate-dissolving bacteria agent for repairing cadmium-contaminated soil and improving soil quality as claimed in claim 1, characterized in that: The 16S rDNA gene sequence of the Enterobacter holmesii HS-6 is shown in SEQ ID No. 1; The 16S rDNA gene sequence of the Pantoea agglomerans CT-3 is shown in SEQ ID No.

2.

3. The use of a composite solid phosphate-dissolving bacteria agent for repairing cadmium-contaminated soil and improving soil quality as claimed in claim 1, characterized in that: The particle size of the bone char is 30nm-2μm.

4. The use of a composite solid phosphate-dissolving bacteria agent for repairing cadmium-contaminated soil and improving soil quality as claimed in claim 1, characterized in that: The organic matrix is ​​at least one of wheat bran, rice straw or corn cob.

5. The use of a composite solid phosphate-dissolving bacteria agent for repairing cadmium-contaminated soil and improving soil quality as claimed in claim 1, characterized in that: The application comprises the following steps: S1. Preparation of micro-nano bone charcoal: thermally crack animal bones, cool them, and then ball-mill them to obtain micron-nano multi-grade bone charcoal; S2. Activation of strains: Enterobacter HS-6 and Pantoea agglomerans CT-3 were inoculated into LB medium respectively, and then placed in a constant temperature shaker at 28°C and shaken at 180 r / min until OD 600 =0.6-0.8, to obtain HS-6 bacterial suspension and CT-3 bacterial suspension; S3, preparation of liquid bacterial agent: the HS-6 bacterial suspension and the CT-3 bacterial suspension obtained in step S2 are mixed to form a composite bacterial solution, the micron-nano multi-grade bone char obtained in step S1 is sterilized by irradiation and added to the NBRIP culture medium, and then placed in a constant temperature shaker at 28° C. and shaken at 180 r / min for 44 h to 50 h to obtain a liquid bacterial agent; S4, organic matrix carrier treatment: after washing the organic matrix with deionized water, add deionized water that covers the organic matrix to soak the organic matrix, and sterilize at high temperature and high pressure to obtain a treated organic matrix carrier; S5, preparation of solid bacterial agent: adding the liquid bacterial agent obtained in step S3 to the organic matrix carrier obtained in step S4, culturing at 28° C. for 2 to 4 days, to obtain the composite solid phosphate-dissolving bacterial agent; S6. Remediation of Cd-contaminated soil: applying the composite solid phosphate-dissolving bacteria agent to Cd-contaminated soil.

6. The use of a composite solid phosphate-dissolving bacteria agent for repairing cadmium-contaminated soil and improving soil quality as claimed in claim 5, characterized in that: In step S1, the animal bone is heated to 440°C to 460°C at a heating rate of 8°C / min to 12°C / min and thermally cracked for 100min to 140min, and then cooled to obtain a large piece of bone char, which is ball-milled in a ball mill at 440rpm to 460rpm for 4h to 6h to obtain micron-nano multi-grade bone char; and / or In the ball mill, zirconium oxide particles are used to ball-mill the bulk bone char, and ethanol is added as a grinding aid; the weight ratio of the zirconium oxide particles to the bulk bone char is (15-20):1; the mass ratio of the ethanol to the bulk bone char is (1.5-2):

1.

7. The use of a composite solid phosphate-dissolving bacteria agent for repairing cadmium-contaminated soil and improving soil quality as claimed in claim 5, characterized in that: In step S2, the effective viable counts of the prepared HS-6 bacterial suspension and CT-3 bacterial suspension were 1×10 10 CFU / mL~9×10 10 CFU / mL.

8. The use of a composite solid phosphate-dissolving bacteria agent for repairing cadmium-contaminated soil and improving soil quality as claimed in claim 5, characterized in that: In step S3, the mass volume ratio of the bone char to the NBRIP culture medium is 0.5% to 2.5%; and / or The volume ratio of the HS-6 bacterial suspension to the CT-3 bacterial suspension is 1:1; The inoculation amount of the composite bacterial liquid in the NBRIP medium is 1% of the volume percentage of the NBRIP medium; and / or The radiation sterilization dosage is 3.0 kGy to 6.0 kGy.

9. The use of a composite solid phosphate-dissolving bacteria agent for repairing cadmium-contaminated soil and improving soil quality as claimed in claim 5, characterized in that: In step S4, after washing the organic matrix three times with deionized water, adding deionized water that covers the organic matrix to soak the organic matrix for 10 hours to 20 hours, and sterilizing the organic matrix carrier with high temperature and high pressure; The conditions of high temperature and high pressure sterilization are: 121° C., 104 KPa, 20 min.

10. The use of a composite solid phosphate-dissolving bacteria agent for repairing cadmium-contaminated soil and improving soil quality as claimed in claim 5, characterized in that: In step S5, the liquid bacterial agent obtained in step S3 is added to the organic matrix carrier obtained in step S4, and the mixture is placed in a polyethylene bag and sealed, and 5 to 8 air holes are pierced on the surface of the polyethylene bag with a sterile needle, and then the mixture is placed in a constant temperature shaker at 28° C. and shaken at 180 r / min for 2 to 4 days to obtain the composite solid phosphate-dissolving bacterial agent; In step S5, the mass ratio of the liquid bacterial agent to the organic matrix carrier is 15:(70-100); In step S6, the mass ratio of the composite solid phosphate-dissolving bacteria agent to the Cd-contaminated soil is 3:(250-350).

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