Soil matrix containing mud cakes, preparation method of soil matrix and application of soil matrix in ecological restoration

Abstract

The invention relates to the technical field of ecology, and particularly discloses a soil matrix containing mud cakes, a preparation method of the soil matrix and application of the soil matrix in ecological restoration. The soil matrix comprises a solid mixture and water, wherein the solid mixture comprises 0.005%-0.01% of a growth-promoting nitrogen-fixing composite microbial agent, 20%-45% of an organic composite slow-release material, 25%-40% of a mud cake, 28%-42% of deep soil, 0.05%-0.1% of cationic polyacrylamide and 0.2%-0.4% of a vinyl acetate-vinyl versatate copolymer; the growth-promoting and nitrogen-fixing complex microbial inoculant comprises rhizobium, azotobacter chroococcum, bacillus megatherium and azospirillum brasilense; the organic composite slow-release material comprises an organic fertilizer, wood flour and a fertilizer. According to the method, a large number of mud cakes generated in projects such as hydroelectric development are fully utilized and developed into the matrix suitable for plant growth, a platform and a carrier are particularly provided for growth of plants on a slope, land resources are saved, and the method has the advantages of being high in operability, low in cost, good in ecological restoration effect and the like.

Description

Technical Field

[0001] The invention relates to the technical field of ecology, in particular to a soil matrix containing mud cakes and a preparation method thereof and application thereof in ecological restoration. Background Art

[0002] During the construction of the hydropower station, the excavation of various tunnels in the power station produced a large amount of sand and gravel aggregates. The wastewater generated by the sand and gravel processing system was recycled to produce a large amount of concentrated mud. The mud was pressurized to the filter press workshop by a slurry pump. The filter press workshop (plate and frame filter press) separated the mud into clean water and dried to form mud cakes. The main component of the mud cake is powdered rock, accounting for more than 90%. In addition, the chemical agents added to the wastewater treatment system make it difficult to recycle resources. An ordinary power station produces about 1,000 tons of mud cake per year. As a useless material in the work area, the mud cake is very complicated to dispose of and must be stored at designated locations, occupying a large amount of land resources and destroying the local ecological environment. In particular, in high-altitude areas that are very sensitive to the ecosystem, vegetation restoration is very difficult and the disposal cost is high. Since most of the mud cake is powdered fine sand, the physical structure is poor, the soil porosity is small, it is very difficult for plant seeds to germinate, and the cohesion is very small. If it is constructed on a slope, it is easy to cause slope instability and landslides, resulting in failure of ecological restoration. How to improve the resource utilization rate of waste stone powder in the work area has become an important issue to be solved in the work area.

[0003] In addition, in the process of building hydropower stations in high-altitude and ecologically fragile areas, the slopes are damaged to a certain extent, which will affect the diversity and integrity of the ecosystem. In view of the unique ecological restoration challenges of the plateau, poor soil, uneven precipitation, large temperature differences, etc., directly limit the necessary conditions for plant growth. In addition, the restoration of the ecosystem requires a large amount of planting soil, and the power station is generally located in a remote area. The planting soil resources available in the project area are very scarce, which is difficult to meet the needs of ecological restoration. Therefore, how to effectively achieve ecological restoration is also an urgent problem to be solved. Summary of the invention

[0004] One of the purposes of the present invention is to provide a soil matrix which can fully utilize the mud cake produced by the sand and gravel processing system and can provide a platform and carrier for plants, especially plants growing on slopes.

[0005] The present invention provides a soil matrix, comprising a solid mixture and water, wherein the solid mixture comprises, by mass percentage, 0.005%-0.01% of a growth-promoting nitrogen-fixing composite bacterial agent, 20%-45% of an organic composite slow-release material, 25%-40% of mud cake, 28%-42% of deep raw soil, 0.05%-0.1% of a cationic polyacrylamide, and 0.2%-0.4% of a vinyl acetate-vinyl versatate copolymer; The growth-promoting nitrogen-fixing composite bacterial agent includes rhizobium, round brown nitrogen-fixing bacteria, bacillus megaterium and nitrogen-fixing spirulina; the organic composite slow-release material includes organic fertilizer, wood powder and fertilizer.

[0006] The invention provides a soil matrix by combining specific components, which can fully utilize the mud cake produced by the sand and gravel processing system and provide a platform and carrier for plants, especially plants growing on slopes.

[0007] The invention specifically uses mud cakes and deep raw soil as raw materials, utilizes growth-promoting nitrogen-fixing composite bacteria agents and organic composite slow-release materials, and in the case of symbiosis with leguminous plants, fixes nitrogen in the air and converts it into its own nutrients, continuously provides energy for plants, and through the addition of specific components, namely cationic polyacrylamide and vinyl acetate-vinyl ester copolymer, the soil matrix can have ideal water storage and anti-scouring capabilities, providing a platform and carrier for plants to grow on slopes; the invention can make full use of a large amount of mud cakes generated in the process of hydropower development, save precious land resources, has the advantages of high operability and low cost, good ecological restoration effect, and can be widely promoted and applied.

[0008] The specific components in the present invention can be effectively matched. The specific growth-promoting nitrogen-fixing composite bacterial agent is composed of four bacterial agents, namely, rhizobia, round brown nitrogen-fixing bacteria, Bacillus megaterium and Azospirillum. Through the interaction between symbiotic nitrogen-fixing bacteria and autogenic nitrogen-fixing bacteria and legumes, the soil enzyme activity is improved, the nitrogen in the air is converted into soil nutrients, and the soil nutritional structure is improved; the organic composite slow-feeding material is composed of fermented organic fertilizer, organic matter and compound fertilizer. The effective time of compound fertilizer is generally about 3 months, the effective time of organic fertilizer is generally 6 months, and the fermentation time of organic matter is about 1 year. It can enable plants to continuously provide nutrients in the short, medium and long term, and combined with the nitrogen fixation ability of growth-promoting nitrogen-fixing bacteria and legumes, it can continuously provide nutrients for plants to meet the growth needs of plants; deep The soil structure of both the layer soil and the mud cake is heavy, the porosity is relatively small, and the physical structure is poor. The simple two components together make it difficult for plant seeds to germinate and grow. The polyacrylamide added in the present invention is a positively charged linear chain structure, which can tightly adsorb the negative charges in the deep soil, mud cake and organic fertilizer. In addition, the polyacrylamide solution has a certain cohesiveness, which can bond wood powder together, thereby forming a specific three-dimensional multiple network structure, which can promote the coagulation of large aggregates to form large pore channels, and can make the colloidal molecules between the mud cake and the deep soil form certain small pore channels, and in addition, the self-generated super water absorption of polyacrylamide can ensure the stability of the soil structure while making it have water storage and porosity, so as to be suitable for the growth of plants. Vinyl acetate-versatate vinyl ester copolymer has the characteristics of strong water solubility, and its molecules can be evenly distributed on the soil structure, which can slow down the volatilization of water molecules in the soil matrix of the present invention to a certain extent, so that the soil structure has a strong water retention capacity.

[0009] In the soil matrix of the present invention, the growth-promoting nitrogen-fixing composite bacterial agent includes, based on a mass fraction of 100%, 35% of rhizobia, 35% of round brown nitrogen-fixing bacteria, 15% of Bacillus megaterium, and 15% of Azospirillum; the effective live bacteria count of the growth-promoting nitrogen-fixing composite bacterial agent is ≥1 billion / g.

[0010] In the soil matrix of the present invention, the organic composite slow-fertilization material comprises, by mass fraction 100%, 25% organic fertilizer, 70% wood powder, and 5% fertilizer; The organic fertilizer is made by fermenting cow dung and then air-drying it. The particle size of the wood powder is ≤3 cm. The N and P in the fertilizer are 2 O 5 , K 2 O ratio is 10:20:20, and the total nutrient content is not less than 50%.

[0011] In the soil matrix of the present invention, the molecular weight of the cationic polyacrylamide is 8 million to 12 million Da.

[0012] In the soil matrix of the present invention, the particle size of the deep raw soil is less than 3 cm, the pH value is 5.5-8.5, and the salt content is ≤0.1%.

[0013] In the soil matrix of the present invention, powdered rocks account for more than 90% of the mud cake, and the particle size of the mud cake is less than 3 cm.

[0014] In the soil matrix of the present invention, the mud cake is a mud cake produced by a sand and gravel processing system; the preferred preparation method is: sand and gravel aggregates are processed by a sand and gravel processing system to obtain wastewater; the wastewater is recycled to obtain concentrated mud; the clear water in the concentrated mud is separated out, and the obtained solids are dried to obtain a mud cake.

[0015] As a specific implementation method, the specific preparation method of mud cake is as follows: when the sand and gravel processing system processes sand and gravel into the target particle size, it will generate production wastewater (aggregate washing wastewater) of the sand and gravel processing system, which will flow to the fine sand recovery workshop through the collection pipeline, and the fine sand and stone powder with a particle size greater than 0.16mm will be recovered through the fine sand recovery device to reduce the concentration of wastewater, and then it will flow to the auxiliary flow sedimentation tank after adding drugs in the dosing workshop, and the clear water and concentrated mud will be separated after sedimentation, and the mud will be pressurized to the filter press workshop through the slurry pump, and the mud will be separated into clear water and cement cake by the plate and frame filter press in the filter press workshop, and the cement cake will fall to the first floor of the filter press workshop for drying and storage, wherein the wastewater system is added with PAC (flocculant inorganic polyaluminum chloride), and the water content of cement cake before being formed is about 22%. The main component of the dried mud cake is powdered rock, accounting for more than 90% (there may also be residual chemicals added in the wastewater treatment system).

[0016] Preferably, the sand and gravel aggregates come from the excavated materials of various tunnels in the hydropower station during the construction process.

[0017] The organic fertilizer and wood powder can be directly purchased in the area where the project is implemented.

[0018] The deep raw soil in the present invention refers to the soil below 100 cm from the surface, which is seldom affected by the surface climate and is relatively compact, with very few weed seeds, and can be directly collected in the area where the project is implemented.

[0019] In the present invention, the soil matrix is ​​in a water-saturated state.

[0020] In the present invention, the amount of water included in the soil matrix is ​​preferably such that the soil matrix is ​​in a water-saturated state. Those skilled in the art can determine the amount of water based on common knowledge in the field.

[0021] Water saturation refers to the water content in the soil matrix reaching the maximum water holding capacity. The maximum water holding capacity is the moisture content when all the pores of the soil matrix are filled with water under natural conditions (that is, the maximum amount of water that can be absorbed by the soil matrix. If more water is added, the water will flow out of the soil matrix).

[0022] The present invention also provides a method for preparing the above soil matrix, which comprises: The mud cake, deep raw soil, vinyl acetate-vinyl versatate copolymer and organic composite slow-release material are fully mixed to prepare a mixture A; Fully dissolve cationic polyacrylamide in water to prepare solution B; Mixing the growth-promoting nitrogen-fixing composite bacterial agent with water to prepare solution C; The solution B and the mixture A are slowly stirred and mixed until the fluid state slowly changes into a solid state, and the stirring is stopped to obtain a premix 1; the premix 1 fully absorbs the solution C to prepare a premix 2; water is slowly added to the premix 2 until the maximum water holding capacity is reached to prepare a soil matrix.

[0023] In the method of the present invention, the concentration of cationic polyacrylamide in the solution B is 1.9-2.1‰; And / or, the solid-liquid ratio of the nitrogen-fixing composite bacterial agent to water in the solution C is 1 g:500 ml.

[0024] The invention also provides application of the soil matrix in ecological restoration.

[0025] The beneficial effects of the present invention are at least: The present invention utilizes the mud cake produced by the sand and gravel processing system to prepare a soil matrix suitable for application on the slope, providing a new idea for solving the problem of scarcity of topsoil in high-altitude and ecologically fragile areas, reducing secondary ecological damage and soil erosion, and promoting biodiversity restoration. At the same time, it also opens up a new way for the resource utilization of mud cake produced during the construction of power stations and other projects, solves the impact of mud cake on the ecological environment and the disposal cost, and demonstrates significant ecological and economic benefits. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that the following examples are provided only for the purpose of illustration and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0027] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are commercially available or prepared according to conventional methods in the art unless otherwise specified.

[0028] The growth-promoting nitrogen-fixing composite bacterial agent in the specific implementation mode of the present invention was purchased from Yangzhou Haicheng Biotechnology Co., Ltd., and the effective live bacteria count was ≥ 1 billion / g.

[0029] Organic fertilizer is made by fermenting cow dung (the fermentation bacteria is thermophilic stearic bacillus, the substrate is kept at a moisture content of 50%, the pH value is between 7-8, and it is fully fermented and decomposed) and then air-dried. The particle size of wood powder is ≤3cm. 2 O 5 , K 2 O in a ratio of 10:20:20 and a total nutrient content of 50%, purchased from Changfeng Chemical Co., Ltd.

[0030] The particle size of the mud cake is less than 3 cm, and rocks account for 90%.

[0031] The particle size of deep raw soil is less than 3 cm, the pH is 8.3, and the salt content is ≤0.1%.

[0032] Cationic polyacrylamide has a molecular weight of 10 million Da and was purchased from Aisen (Rudong) Chemical Co., Ltd.

[0033] Vinyl acetate-versatate copolymer was purchased from Aisen (Rudong) Chemical Co., Ltd.

[0034] Example 1 The present invention provides a method for preparing a slope soil matrix by using a mud cake produced by a sand and gravel processing system, comprising: The soil matrix includes a solid mixture and water. The solid mixture includes the following components in the following mass percentages: 0.005% of a growth-promoting and nitrogen-fixing compound bacterial agent, 45% of an organic composite slow-release material, 25% of a mud cake, 29.745% of deep raw soil, 0.05% of a cationic polyacrylamide, and 0.2% of a vinyl acetate-versatate copolymer.

[0035] Furthermore, the growth-promoting nitrogen-fixing composite bacterial agent includes, based on a mass fraction of 100%, 35% of rhizobia, 35% of round brown nitrogen-fixing bacteria, 15% of Bacillus megaterium, and 15% of Azospirillum.

[0036] Furthermore, the organic composite slow-release material includes, based on a mass fraction of 100%, 25% organic fertilizer, 70% wood powder, and 5% fertilizer.

[0037] The mud cake, deep raw soil, vinyl acetate-versatate copolymer and organic composite slow-release material are fully mixed to prepare mixture A; the required cationic polyacrylamide is injected into clean water to prepare a 2‰ solution, which must be fully stirred to completely dissolve the polyacrylamide to prepare solution B; the required growth-promoting and nitrogen-fixing composite bacteria agent is mixed with clean water at room temperature, and the solid-liquid ratio of the growth-promoting and nitrogen-fixing composite bacteria agent to the water is 1g:500ml to prepare solution C.

[0038] Solution B and mixture A were slowly stirred and mixed until the fluid state slowly turned into a solid state, and the stirring was stopped to obtain premix 1; premix 1 fully absorbed solution C to prepare premix 2. Water was slowly added to premix 2 until the maximum water holding capacity (water absorption saturation state) was reached to prepare a soil matrix.

[0039] Example 2 The present invention provides a method for preparing a slope soil matrix by using a mud cake produced by a sand and gravel processing system, comprising: The soil matrix includes a solid mixture and water. The solid mixture includes the following components in the following mass percentages: 0.01% of a growth-promoting and nitrogen-fixing composite bacterial agent, 20% of an organic composite slow-release material, 37.49% of a mud cake, 42% of deep raw soil, 0.1% of a cationic polyacrylamide, and 0.4% of a vinyl acetate-versatate copolymer.

[0040] Furthermore, the growth-promoting nitrogen-fixing composite bacterial agent includes, based on a mass fraction of 100%, 35% of rhizobia, 35% of round brown nitrogen-fixing bacteria, 15% of Bacillus megaterium, and 15% of Azospirillum.

[0041] Furthermore, the organic composite slow-release material includes, based on a mass fraction of 100%, 25% organic fertilizer, 70% wood powder, and 5% fertilizer.

[0042] The mud cake, deep raw soil, vinyl acetate-versatate copolymer and organic composite slow-release material are fully mixed to prepare mixture A; the required cationic polyacrylamide is injected into clean water to prepare a 2‰ solution, which must be fully stirred to completely dissolve the polyacrylamide to prepare solution B; the required growth-promoting and nitrogen-fixing composite bacteria agent is mixed with clean water at room temperature, and the solid-liquid ratio of the growth-promoting and nitrogen-fixing composite bacteria agent to the water is 1g:500ml to prepare solution C.

[0043] Solution B and mixture A were slowly stirred and mixed until the fluid state slowly turned into a solid state, and the stirring was stopped to obtain premix 1; premix 1 fully absorbed solution C to prepare premix 2. Water was slowly added to premix 2 until the maximum water holding capacity (water absorption saturation state) was reached to prepare a soil matrix.

[0044] Example 3 The present invention provides a method for preparing a slope soil matrix by using a mud cake produced by a sand and gravel processing system, comprising: The soil matrix includes a solid mixture and water. The solid mixture includes the following components in the following mass percentages: growth-promoting and nitrogen-fixing composite bacterial agent (0.0075%), organic composite slow-release material (24.6175%), mud cake (40%), deep raw soil (35%), cationic polyacrylamide (0.075%), and vinyl acetate-vinyl ester copolymer (0.3%).

[0045] Furthermore, the growth-promoting nitrogen-fixing composite bacterial agent includes, based on a mass fraction of 100%, 35% of rhizobia, 35% of round brown nitrogen-fixing bacteria, 15% of Bacillus megaterium, and 15% of Azospirillum.

[0046] Furthermore, the organic composite slow-release material includes, based on a mass fraction of 100%, 25% organic fertilizer, 70% wood powder, and 5% fertilizer.

[0047] The mud cake, deep raw soil, vinyl acetate-versatate copolymer and organic composite slow-release material are fully mixed to prepare mixture A; the required cationic polyacrylamide is injected into clean water to prepare a 2‰ solution, which must be fully stirred to completely dissolve the polyacrylamide to prepare solution B; the required growth-promoting and nitrogen-fixing composite bacteria agent is mixed with clean water at room temperature, and the solid-liquid ratio of the growth-promoting and nitrogen-fixing composite bacteria agent to the water is 1g:500ml to prepare solution C.

[0048] Solution B and mixture A were slowly stirred and mixed until the fluid state slowly turned into a solid state, and the stirring was stopped to obtain premix 1; premix 1 fully absorbed solution C to prepare premix 2. Water was slowly added to premix 2 until the maximum water holding capacity (water absorption saturation state) was reached to prepare a soil matrix.

[0049] Comparative Example 1 This comparative example provides a method for preparing a slope soil matrix using mud cakes produced by a sand and gravel processing system. The components and preparation steps are basically the same as those in Example 1, with the only difference being that the growth-promoting nitrogen-fixing composite bacterial agent is replaced with an equal-quality microbial agent 1 (the main component is composite polymyxa bacillus, with a live bacteria count of 20 billion / g, purchased from Shandong Xinfuwo Bioengineering Co., Ltd.).

[0050] Comparative Example 2 This comparative example provides a method for preparing a slope soil matrix using mud cakes produced by a sand and gravel processing system. The components and preparation steps are basically the same as those in Example 1, with the only difference being that the growth-promoting nitrogen-fixing composite bacterial agent is replaced with a composite microbial agent 2 of equal mass (the main components are Bacillus and actinomycetes, with a live bacteria count of 9.8 billion / g, purchased from Beihai Qiangxing Biotechnology Co., Ltd.).

[0051] Comparative Example 3 This comparative example provides a method for preparing a slope soil matrix using mud cakes produced by a sand and gravel processing system. The components and preparation steps are basically the same as those in Example 1, except that the organic composite slow-release material is replaced with a compound fertilizer of equal mass (nitrogen, phosphorus, and potassium in a ratio of 15:15:15, with a total nutrient content of not less than 45%, purchased from Stanley Agricultural Group Co., Ltd.) Comparative Example 4 This comparative example provides a method for preparing a slope soil matrix using mud cakes produced by a sand and gravel processing system. The components and preparation steps are basically the same as those in Example 1, with the only difference being that the vinyl acetate-versatate vinyl ester copolymer is replaced with an equal-quality water-retaining agent (the main component is a high-molecular water-absorbing resin, with an effective component of >99%, purchased from Henan Qiantelu Chemical Products Co., Ltd.).

[0052] Comparative Example 5 This comparative example provides a method for preparing a slope soil matrix using mud cakes produced by a sand and gravel processing system. The components and preparation steps are basically the same as those in Example 1, with the only difference being that cationic polyacrylamide is replaced with an adhesive 1 of equal mass (the main components are polyacrylic acid salt and polyacrylamide copolymer, with an effective ingredient content of more than 95%, purchased from Beijing Jinyuanyi Ecological Environment Industry Co., Ltd.).

[0053] Comparative Example 6 This comparative example provides a method for preparing a slope soil matrix using mud cakes produced by a sand and gravel processing system. The components and preparation steps are basically the same as those in Example 1, with the only difference being that cationic polyacrylamide is replaced with an equal mass of polyaluminium chloride (the main chemical component is aluminium oxide, with an effective substance content of 28%, purchased from Henan Jinyuan Water Treatment Materials Co., Ltd.).

[0054] Comparative Example 7 This comparative example provides a method for preparing a slope soil matrix using mud cakes produced by a sand and gravel processing system. The components and preparation steps are basically the same as those in Example 1, except that the amount of cationic polyacrylamide is changed from 0.05% to 0.3%, and the amount of deep raw soil is changed from 29.745% to 29.495%.

[0055] Comparative Example 8 This comparative example provides a method for preparing a slope soil matrix using mud cakes produced by a sand and gravel processing system. The components and preparation steps are basically the same as those in Example 1, except that the amount of vinyl acetate-versatate copolymer is changed from 0.2% to 0.6%, and the amount of deep raw soil is changed from 29.745% to 29.345%.

[0056] Experimental Example 1 This experimental example tests the soil substrates prepared in Examples 1-3 and Comparative Examples 1-8. The experimental results are shown in Table 1. Specifically: The testing method of porosity is: refer to LY / T1215-1999.

[0057] The test method for bulk density is: refer to NY / T1121.4-2006.

[0058] The test method for water holding capacity is: refer to NY / T1121.22-2010.

[0059] The test method for cohesion is: refer to GB / T50123-1999.

[0060] The test method for internal friction angle is: refer to GB / T50123-1999.

[0061] The germination rate test method is: 100 indigofera seeds are evenly placed in culture dishes filled with 5 cm of soil matrix, the culture dishes are placed in a seed germination box, maintain a certain humidity, set the temperature to 25°C, and after 14 days, the seed germination rate is counted according to the requirements of "Forest Seed Quality Grading" GB7908.

[0062] The test method of growth height is: the seedlings germinated from each soil matrix obtained in the germination rate experiment are planted in a planting experiment, and their growth height after 180 days is counted.

[0063] Table 1 Soil structure and plant growth conditions of each experimental group From the above results, it can be seen that the soil matrix prepared by using mud cake provided by the present invention has relatively large porosity, which is suitable for plant germination and growth, relatively small bulk density, large cohesion and internal friction angle, which is more conducive to the attachment and fixation of the soil matrix on the slope surface. If the soil bulk density is large, the gravity on the slope surface is large, which is greater than the shear resistance of the soil, and it is easy to slide from the slope surface, causing ecological restoration failure. The water holding capacity is large, and more water can be stored, especially in dry and hot valley areas, where rainfall is small and evaporation is large, which can save maintenance costs.

[0064] From the examples and comparative examples 7-8, it can be seen that if the amount of cationic polypropylene is too much and the charge it carries is too much, such as a large amount of residual colloid molecules after flocculation and precipitation, the adhesion is greatly increased, resulting in the deterioration of the physical structure of the soil matrix, the decrease of porosity, the increase of bulk density, the difficulty of plant germination, the deterioration of growth potential, and the serious impact on the growth height of the plant.

[0065] If the amount of vinyl acetate-versatate copolymer is too much, it will easily form a physical film on the surface of the soil matrix, hindering the exchange of the soil matrix with the outside air and water, resulting in very little oxygen content in the soil matrix. It is difficult for water to enter the soil during maintenance watering or rain, which seriously affects the germination rate and growth status of the plant.

[0066] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, these modifications or improvements made on the basis of not departing from the spirit of the present invention are all within the scope of the present invention.

Claims

1. A soil matrix, characterized in that: It comprises a solid mixture and water, wherein the solid mixture comprises, by mass percentage, 0.005%-0.01% of a growth-promoting nitrogen-fixing composite bacterial agent, 20%-45% of an organic composite slow-release material, 25%-40% of mud cake, 28%-42% of deep raw soil, 0.05%-0.1% of a cationic polyacrylamide and 0.2%-0.4% of a vinyl acetate-versatate vinyl ester copolymer; The growth-promoting nitrogen-fixing composite bacterial agent includes rhizobium, round brown nitrogen-fixing bacteria, bacillus megaterium and nitrogen-fixing spirulina; the organic composite slow-release material includes organic fertilizer, wood powder and fertilizer.

2. The soil matrix according to claim 1, characterized in that The growth-promoting nitrogen-fixing composite bacterial agent comprises, by mass fraction 100%, 35% of rhizobia, 35% of round brown nitrogen-fixing bacteria, 15% of Bacillus megaterium, and 15% of Azospirillum; The effective live bacteria count of the growth-promoting nitrogen-fixing composite bacterial agent is ≥ 1 billion / g.

3. The soil matrix according to claim 1 or 2, characterized in that The organic composite slow-release material includes, by mass fraction of 100%, 25% organic fertilizer, 70% wood powder, and 5% fertilizer; The organic fertilizer is made from cow dung fermented and then air-dried, the particle size of the wood powder is ≤3 cm, the ratio of N, P2O5 and K2O in the fertilizer is 10:20:20, and the total nutrient content is not less than 50%.

4. The soil matrix according to any one of claims 1 to 3, characterized in that The cationic polyacrylamide has a molecular weight of 8 million to 12 million Da; And / or, the particle size of the deep raw soil is less than 3 cm, the pH is 5.5-8.5, and the salt content is ≤0.1%.

5. The soil matrix according to any one of claims 1 to 4, characterized in that The powdered rocks in the mud cake account for more than 90%, and the particle size of the mud cake is less than 3 cm.

6. The soil matrix according to claim 5, characterized in that The mud cake is a mud cake produced by a sand and gravel processing system; the preferred preparation method is: sand and gravel aggregates are processed by a sand and gravel processing system to obtain wastewater; the wastewater is recycled and processed to obtain concentrated mud; the clear water in the concentrated mud is separated out, and the obtained solids are dried to obtain a mud cake.

7. The soil matrix according to any one of claims 1 to 6, characterized in that The soil matrix is ​​in a water-saturated state.

8. A method for preparing the soil matrix according to any one of claims 1 to 7, characterized in that: include: The mud cake, deep raw soil, vinyl acetate-vinyl versatate copolymer and organic composite slow-release material are fully mixed to prepare a mixture A; Fully dissolve cationic polyacrylamide in water to prepare solution B; Mixing the growth-promoting nitrogen-fixing composite bacterial agent with water to prepare solution C; The solution B and the mixture A are slowly stirred and mixed until the fluid state slowly changes into a solid state, and the stirring is stopped to obtain a premix 1; the premix 1 fully absorbs the solution C to prepare a premix 2; water is slowly added to the premix 2 until the maximum water holding capacity is reached to prepare a soil matrix.

9. The method according to claim 8, characterized in that The concentration of cationic polyacrylamide in the solution B is 1.9-2.1‰; And / or, the solid-liquid ratio of the nitrogen-fixing composite bacterial agent to water in the solution C is 1 g:500 ml.

10. Use of the soil matrix according to any one of claims 1 to 7 in ecological restoration.

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