Coal gangue-based improved soil and preparation method thereof

Abstract

The invention relates to the technical field of solid waste resourceful treatment, and discloses coal gangue-based improved soil and a preparation method thereof. The coal gangue-based improved soil comprises the following raw materials: coal gangue, sandy soil and a fermentation inoculant, the fermentation bacterial agent is prepared from bacillus subtilis SHBCC D11446, arbuscular mycorrhizal fungi SHBCC D24696, trichoderma viride SHBCC D10197 and bacillus velezensis GS02, and the preservation number of the bacillus velezensis GS02 is CCTCC (China Center for Type Culture Collection) NO: M 2025531. Phosphorus, potassium, nitrogen and organic matters in the coal gangue can be fully utilized, the prepared coal gangue-based improved soil has high nutrient substance content and low effective state heavy metal content, and meanwhile, the situation that the alkalinity and the salt content of the improved soil are greatly improved due to introduction of the coal gangue can be avoided; the improved soil can effectively promote plant growth.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource treatment, and in particular to a gangue-based improved soil and a preparation method thereof. Background Art

[0002] Gangue is a type of solid waste emitted during coal mining and coal washing, and is considered a type of mining solid waste. It is a dark-gray rock that is lower in carbon and harder than coal, and is produced in association with coal seams during coal formation. Gangue has a complex chemical composition, primarily consisting of inorganic and organic matter. The inorganic component primarily consists of oxides of silicon, aluminum, calcium, magnesium, and iron, such as SiO2, Al2O3, Fe2O3, CaO, and MgO. It also contains rare metals such as gallium, vanadium, titanium, and cobalt. These elements exist in the gangue as complex compounds, offering numerous possibilities for its comprehensive utilization.

[0003] Currently, the main uses for coal gangue include producing building materials, generating electricity, recovering coal and pyrite, land reclamation and backfilling, and preparing chemical products. However, due to certain technical limitations, the utilization rate of coal gangue is generally around 60-70%, resulting in low efficiency. For example, in patent CN118620630A, coal gangue is mixed with coal-to-liquid residue, followed by acid treatment and roasting. The mixture is then mixed with polyacrylamide, water, a monomer, and an initiator, followed by polymerization, standing, solid-liquid separation, and drying. The mixture is then mixed with polyethylene terephthalate, an ammonium bicarbonate solution, and a crosslinking agent, followed by crosslinking, solid-liquid separation, and drying. The resulting modified coal gangue can be used for soil improvement. This patent can reduce the risk of heavy metal leakage in coal gangue by covering the surface of coal gangue with a polymer with a three-dimensional network structure. However, coal gangue contains a large amount of phosphorus and potassium elements that are difficult to be absorbed and utilized by plants. The method of this patent cannot make effective use of these elements. In addition, the roasting process will also cause the loss of organic matter in the coal gangue. Summary of the Invention

[0004] To address the aforementioned technical issues, namely, the low utilization rate of gangue in existing methods for preparing improved soil using gangue, making it difficult to fully utilize the organic matter, phosphorus, and potassium therein, the present invention provides a gangue-based improved soil and a method for preparing the same. The present invention enables more complete utilization of the phosphorus, potassium, and organic matter in the gangue, and the resulting gangue-based improved soil has a higher nutrient content and a lower effective heavy metal content. Furthermore, the invention prevents the introduction of gangue from significantly increasing the alkalinity and salinity of the improved soil, enabling the improved soil to effectively promote plant growth.

[0005] The specific technical solutions of the present invention are: In a first aspect, the present invention provides a gangue-based improved soil, comprising the following raw materials: gangue, sandy soil, and a fermentation agent; the fermentation agent comprises Bacillus subtilis SHBCC D11446, arbuscular mycorrhizal fungus Rhizophagus irregularis SHBCC D24696, Trichoderma viride SHBCCD10197, and Bacillus velezensis GS02 with a deposit number of CCTCC NO: M 2025531.

[0006] In the fermentation bacteria used in the present invention, the information of each strain is as follows: (1) Bacillus velezensis GS02 is a new strain isolated from soil by the present invention team. Its deposit information is as follows: Name of depository: China Center for Type Culture Collection (abbreviated as "CCTCC"); Address of depository: Wuhan University, Wuhan, China; Deposit date: March 20, 2025; Deposit number: CCTCC NO: M 2025531.

[0007] (2) Bacillus subtilis SHBCC D11446 can be purchased from Shanghai Collection of Microorganisms (abbreviated as "SHBCC"). The information about this strain from SHBCC is as follows: Strain ID: SHBCC D11446; Other numbers: AS1.421; Chinese name: Bacillus subtilis SHBCC D11446 AS1.421.

[0008] (3) Arbuscular mycorrhizal fungus SHBCC D24696 can be purchased from Shanghai Collection of Microorganisms (SHBCC). The information about this strain from SHBCC is as follows: Strain ID: SHBCC D24696; Other numbers: PL112; Chinese name: Arbuscular Mycorrhiza PL112 SHBCC D24696=PL112; Latin name: Rhizophagus irregularis PL112.

[0009] (4) Trichoderma viride SHBCC D10197 can be purchased from Shanghai Collection of Microorganisms (SHBCC). The information about this strain from SHBCC is as follows: Strain ID: SHBCC D10197; Other numbers: NBRC 30546 = ATCC 26802; Chinese name: Trichoderma viride.

[0010] Among the aforementioned fermentation agents, Bacillus velezensis GS02, when fermented in a mixture of coal gangue, sand, and other raw materials, can immobilize heavy metals, reducing their available heavy metal content while increasing organic matter, total nitrogen, available phosphorus, and readily available potassium. It can also reduce the increase in soil alkalinity and salinity caused by the introduction of coal gangue. However, no strains of Bacillus velezensis have been reported to possess these combined capabilities.

[0011] The present invention uses a compound mixture of Bacillus velezensis GS02, Bacillus subtilis SHBCC D11446, arbuscular mycorrhizal fungus SHBCC D24696, and Trichoderma viride SHBCC D10197. The four strains can produce a synergistic effect, thereby achieving a better fermentation effect. The prepared gangue-based improved soil has higher organic matter, total nitrogen, available phosphorus, and available potassium contents, as well as lower available heavy metal contents. The invention also avoids excessive increases in alkalinity and salt content of the improved soil caused by the introduction of gangue. Therefore, the improved soil is more suitable for plant cultivation and effectively promotes plant growth. The utilization rate of the gangue is also increased, and the phosphorus, potassium, and organic matter therein are more fully utilized.

[0012] In addition, after the gangue is fermented with the bacterial agent of the present invention, its nutrients are activated, and it will have higher organic matter, available phosphorus, and available potassium contents. However, although the bacterial agent of the present invention can reduce soil compaction to a certain extent, it cannot completely solve the problem of gangue being prone to compaction when used as planting soil. Sandy soil has low organic matter content, lacks clay minerals, has a low cation exchange capacity (CEC), and poor fertilizer retention capacity, but has weak cohesion and good air permeability. The present invention combines gangue and sandy soil to improve the soil structure of the gangue-based improved soil, making it have better air permeability and a higher nutrient content.

[0013] Preferably, the coal gangue includes small-particle gangue, medium-particle gangue and large-particle gangue in a mass ratio of 30-50:30-40:15-30; the particle size of the small-particle gangue is not greater than 2 mm, the particle size of the medium-particle gangue is 2-6 mm (excluding 2 mm and 6 mm), and the particle size of the large-particle gangue is 6-10 mm (including 6 mm and 10 mm).

[0014] Small-particle gangue (d≤2mm) has a strong water-retention effect on plant roots. Medium-particle gangue (2mm<d<6mm) combines water retention and air permeability. Large-particle gangue (6mm≤d≤10mm) provides ventilation and dust and sand control. The present invention combines these three types of gangue in a specific ratio to make gangue-based improved soil more suitable for plant growth.

[0015] Preferably, the ratio of the viable cell counts of Bacillus subtilis SHBCC D11446, arbuscular mycorrhizal fungus SHBCC D24696, Trichoderma viride SHBCC D10197 and Bacillus velezensis GS02 is 1000:0.8-1.2:0.1-0.3:100-300.

[0016] Preferably, the mass of the fermentation agent is 0.1 to 1.5% of the mass of the coal gangue.

[0017] Preferably, the gangue-based improved soil further comprises the following raw materials: water retaining agent and organic fertilizer.

[0018] Furthermore, the water-retaining agent includes at least one of sodium polyacrylate, diatomaceous earth and perlite; the organic fertilizer includes at least one of manure fertilizer, green manure, compost fertilizer and commercial fertilizer; the mass of the water-retaining agent and organic fertilizer is 0.1-1% of the mass of the coal gangue.

[0019] Preferably, the particle size of the sand is less than 2 mm, and the mass of the sand accounts for 30-70% of the total mass of all raw materials.

[0020] In a second aspect, the present invention provides a method for preparing the gangue-based improved soil, comprising: mixing all raw materials and fermenting to obtain the gangue-based improved soil.

[0021] Preferably, before fermentation, the moisture content is adjusted to 15-25%; the fermentation temperature is 20-37° C., and the fermentation time is 10-30 days.

[0022] Preferably, the preparation steps of the fermentation agent include: inoculating Bacillus subtilis SHBCC D11446 and Bacillus velezensis GS02 into TSB culture medium, and inoculating arbuscular mycorrhizal fungi SHBCC D24696 and Trichoderma viride SHBCCD10197 into PDA culture medium, respectively; after expanding the culture, centrifuging the fermentation liquid at high speed, discarding the supernatant, collecting the bacterial mud, mixing the bacterial mud with a protective agent, and then freeze-drying to obtain bacterial powder of the four strains; and mixing the bacterial powders of the four strains to obtain the fermentation agent.

[0023] Preferably, the process of mixing all the raw materials includes the following steps: preparing the fermentation bacteria agent into a bacterial liquid, mixing it with coal gangue, adding a water retaining agent and an organic fertilizer, mixing well, and then mixing it with sand.

[0024] Furthermore, the method for preparing the fermentation agent into a bacterial solution is: mixing the fermentation agent and water in a mass ratio of 0.7 to 1.2:9.

[0025] Furthermore, before mixing the bacterial liquid with the coal gangue, the coal gangue is first crushed to a particle size of no more than 10 mm, and then the crushed coal gangue is divided into three categories through sorting and screening: particle size no more than 2 mm, particle size of 2 to 6 mm (excluding 2 mm and 6 mm), and particle size of 6 to 10 mm (including 6 mm and 10 mm), and mixed in a mass ratio of 30 to 50:30 to 40:15 to 30.

[0026] Compared with the prior art, the present invention has the following advantages: (1) The present invention uses a specific fermentation agent to carry out mixed fermentation of raw materials including coal gangue and sandy soil. The four strains of bacteria contained in the fermentation agent can produce a synergistic effect, thereby immobilizing heavy metals to a greater extent, activating phosphorus and potassium elements, and increasing the organic matter and total nitrogen content. It also avoids the introduction of coal gangue causing the alkalinity and salt content of the improved soil to increase too much. Not only can the improved soil obtained effectively promote plant growth, but it can also improve the utilization rate of coal gangue, so that the phosphorus, potassium and organic matter therein are more fully utilized.

[0027] (2) The present invention adopts a compound of three types of coal gangue particle sizes (d≤2mm, 2mm<d<6mm and 6mm≤d≤10mm), which can make the improved soil have better water retention and air permeability, thereby providing a more suitable soil environment for plant growth.

[0028] (3) The present invention can not only realize the large-scale resource disposal of coal gangue, but also solve the various environmental pollution problems caused by the accumulation of coal gangue, thereby creating new economic growth points and providing strong technical support for solving the problem of coal gangue treatment in coal mining areas. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to the embodiments.

[0030] Overall embodiment First, the present invention relates to a coal gangue-based improved soil, comprising the following raw materials: coal gangue, sandy soil, and a fermentation agent; the fermentation agent comprises Bacillus subtilis SHBCC D11446, arbuscular mycorrhizal fungus Rhizophagus irregularis SHBCC D24696, Trichoderma viride SHBCCD10197, and Bacillus velezensis GS02 with a preservation number of CCTCC NO: M 2025531.

[0031] In some specific embodiments, the coal gangue includes small-particle gangue, medium-particle gangue, and large-particle gangue in a mass ratio of 30-50:30-40:15-30; the particle size of the small-particle gangue is not greater than 2 mm, the particle size of the medium-particle gangue is 2-6 mm (excluding 2 mm and 6 mm), and the particle size of the large-particle gangue is 6-10 mm (including 6 mm and 10 mm).

[0032] In some specific embodiments, the ratio of the viable cell counts of Bacillus subtilis SHBCC D11446, arbuscular mycorrhizal fungus SHBCCD24696, Trichoderma viride SHBCC D10197, and Bacillus velezensis GS02 is 1000:0.8-1.2:0.1-0.3:100-300.

[0033] In some specific embodiments, the mass of the fermentation agent is 0.1-1.5% of the mass of the coal gangue.

[0034] In some specific embodiments, the particle size of the sand is less than 2 mm, and the mass of the sand accounts for 30-70% of the total mass of all raw materials.

[0035] In some specific embodiments, the gangue-based improved soil further comprises the following raw materials: a water-retaining agent and an organic fertilizer. The water-retaining agent comprises at least one of sodium polyacrylate, diatomaceous earth, and perlite, with a mass of 0.1-1% of the mass of the gangue. The organic fertilizer comprises at least one of manure, green manure, composted manure, and commercial fertilizer, with a mass of 0.1-1% of the mass of the gangue.

[0036] Secondly, the present invention relates to a method for preparing the gangue-based improved soil, comprising: mixing all raw materials and fermenting to obtain the gangue-based improved soil.

[0037] In some specific embodiments, before fermentation, the moisture content is adjusted to 15-25%; the fermentation temperature is 20-37° C., and the fermentation time is 10-30 days.

[0038] In some specific embodiments, the preparation step of the fermentation agent includes: inoculating Bacillus subtilis SHBCCD11446 and Bacillus velezensis GS02 into TSB culture medium, and inoculating arbuscular mycorrhizal fungi SHBCCD24696 and Trichoderma viride SHBCC D10197 into PDA culture medium, expanding culture at 25-30°C and 100-130 rpm / min for 20-24 hours, centrifuging the fermentation broth at high speed, discarding the supernatant, collecting the bacterial sludge, mixing the bacterial sludge with a protective agent, and then freeze-drying to obtain bacterial powder of the four strains; and mixing the bacterial powders of the four strains to obtain a fermentation agent.

[0039] In some specific embodiments, the process of mixing all raw materials includes the following steps: preparing the fermentation bacteria agent into a bacterial liquid, mixing it with coal gangue, adding a water-retaining agent and an organic fertilizer, mixing well, and then mixing it with sand.

[0040] In the above specific implementation manner, optionally or preferably: The method for preparing the fermentation agent into a bacterial solution is as follows: mixing the fermentation agent and water in a mass ratio of 0.7 to 1.2:9; Before mixing the bacterial liquid with the coal gangue, the coal gangue is first crushed to a particle size of no more than 10 mm, and then the crushed coal gangue is divided into three categories through sorting and screening: particle size no more than 2 mm, particle size of 2 to 6 mm (excluding 2 mm and 6 mm), and particle size of 6 to 10 mm (including 6 mm and 10 mm), and mixed in a mass ratio of 30 to 50:30 to 40:15 to 30. Specific embodiments The present invention is described below by way of specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit and scope of the inventive concept, any changes and advantages that can be imagined by those skilled in the art are included in the present invention, and the scope of protection of the present invention is defined by the appended claims and any equivalents thereof.

[0042] Example 1: Effects of microbial agents on the physical and chemical properties of gangue-based improved soil 1.1 Preparation of fermentation agent TSB medium was prepared as follows: 17.0 g tryptone, 3.0 g yeast extract, 5.0 g sodium chloride, 2.5 g potassium hydrogen phosphate, and 2.5 g glucose. The volume was made up to 1000 mL with distilled water, the pH was adjusted to 7.1-7.5, and the medium was sterilized at 121°C for 30 min.

[0043] The preparation method of PDA culture medium is as follows: 5 g potato powder, 20 g glucose, 15 g agar, dilute to 1000 mL with distilled water, and sterilize at 121°C for 30 min.

[0044] Bacillus subtilis SHBCC D11446 and Bacillus velezensis GS02 were inoculated into TSB medium, respectively, and arbuscular mycorrhizal fungi SHBCC D24696 and Trichoderma viride SHBCC D10197 were inoculated into PDA medium, respectively. The cultures were cultured at 28°C and 120 rpm / min for 24 h. The fermentation broth was then centrifuged at high speed (10,000×g, 10 min), the supernatant was discarded, and the bacterial sludge was collected. The bacterial sludge was mixed with a protective agent (a 15% (w / v) skim milk powder solution) and freeze-dried to obtain bacterial powders of the four strains: SHBCC D11446 powder, SHBCC D24696 powder, SHBCC D10197 powder, and GS02 powder.

[0045] SHBCC D11446 bacterial powder, SHBCC D24696 bacterial powder and SHBCC D10197 bacterial powder were mixed at a ratio of 1000:0.8:0.1 of viable bacteria to obtain fermentation agent GN3.

[0046] SHBCC D11446 bacterial powder, SHBCC D24696 bacterial powder, SHBCC D10197 bacterial powder and GS02 bacterial powder were mixed at a ratio of 1000:0.8:0.1:100 in terms of viable bacteria count to obtain fermentation agent GN4-min.

[0047] SHBCC D11446 bacterial powder, SHBCC D24696 bacterial powder, SHBCC D10197 bacterial powder and GS02 bacterial powder were mixed at a ratio of 1000:1.2:0.3:300 in terms of viable bacteria count to obtain the fermentation agent GN4-max.

[0048] 1.2 Strain antagonism experiment LB medium was prepared as follows: 10 g tryptone, 5 g yeast extract, 10 g sodium chloride, and 15 g / L agar. The volume was adjusted to 1000 mL with distilled water and sterilized at 121°C for 30 min. PDA medium was prepared as follows: 5 g potato extract, 20 g glucose, and 15 g agar. The volume was adjusted to 1000 mL with distilled water and sterilized at 121°C for 30 min. Before solidification, equal volumes of the above LB and PDA media were mixed. After solidification, LB / PDA composite medium was obtained.

[0049] Bacillus subtilis SHBCC D11446 and Bacillus velezensis GS02 were streaked in pairs with the arbuscular mycorrhizal fungus SHBCCD24696 and Trichoderma viride SHBCC D10197, respectively, on LB / PDA composite medium, without intersecting the lines. The lines were then incubated at 30°C for 4 days. Antagonism between the strains was determined based on the following criteria: if a sterile zone formed at the intersection of the two strains, it indicated a zone of inhibition between the two strains, indicating antagonism and incompatibility. If no sterile zone formed between the two strains, it indicated no antagonism and compatibility. The results (Table 1) indicate that the strains did not antagonize each other and did not interfere with each other's growth, thus allowing them to be combined as a composite inoculant.

[0050] Table 1 Results of strain antagonism experiments strain SHBCC D11446 SHBCC D24696 SHBCC D10197 GS02 SHBCC D11446 - - - SHBCC D24696 - - - SHBCC D10197 - - - GS02 - - - Note: “+” indicates positive, with antagonistic effect; “-” indicates negative, with no antagonistic effect.

[0051] 1.3 Preparation of gangue-based improved soil After the gangue is crushed to a particle size of no more than 10 mm, it is sorted and screened to select small-size gangue (d≤2 mm), medium-size gangue (2 mm < d < 6 mm) and large-size gangue (6 mm < d < 10 mm), and mixed in a mass ratio of 4:4:3 to obtain a gangue mixture.

[0052] SHBCC D11446 bacterial powder, SHBCC D24696 bacterial powder, SHBCC D10197 bacterial powder, GS02 bacterial powder, fermentation agent GN3, fermentation agent GN4-min and fermentation agent GN4-max were mixed with water at a mass ratio of 1:9 to obtain bacterial solutions.

[0053] Each bacterial solution was sprayed onto the gangue mixture at a mass ratio of 1:10 and stirred evenly to obtain Mixture A. Perlite water-retaining agent and commercial organic fertilizer (Xin Yangguang Organic Fertilizer, Changchun Xin Yangguang Organic Fertilizer Co., Ltd.) were added to Mixture A at a rate of 0.1% of the mass of the gangue mixture and stirred evenly to obtain Mixture B. Mixture B was mixed with sandy soil at a mass ratio of 7:3 and stirred evenly to obtain Mixture C. After adjusting the moisture content of Mixture C to 20%, it was fermented at 25°C for 10 days, during which time it was covered with a film to reduce water loss, to obtain gangue-based improved soil. An equal mass of water was used in the control group (CK) instead of bacterial solution.

[0054] 1.4 Physical and chemical properties testing of gangue-based improved soil The pH, electrical conductivity (EC), organic matter content, total nitrogen content, available phosphorus content, available potassium content and available heavy metal content of sandy soil and gangue-based improved soil prepared in each group were measured. The results are shown in Tables 2 and 3.

[0055] Table 2 Test results of physical and chemical indicators of gangue-based improved soil Table 3 Test results of effective heavy metal content in gangue-based improved soil According to Table 2 and Table 3, we can see that: (1) Compared with the CK group, the pH and EC values of the improved soil produced by the GS02 group were closer to those of sandy soil, with higher contents of organic matter, total nitrogen, available phosphorus, and available potassium, and lower contents of available heavy metals. This indicates that the strain can improve the excessive alkalinity and salinity of coal gangue, and has the functions of activating phosphorus and potassium, fixing nitrogen, and passivating heavy metals.

[0056] (2) Compared with the single bacteria and fermentation agent GN3 using four bacterial strains, the improved soils produced by the GN4-min and GN4-max groups had lower alkalinity, EC value, and available heavy metal content, as well as higher organic matter, total nitrogen, available phosphorus, and available potassium content. This indicates that the four bacterial strains in the fermentation agent of the present invention can produce a synergistic effect, achieving a better fermentation effect, resulting in a higher nutrient content in the obtained coal gangue-based improved soil and a greater reduction in the risk of heavy metal pollution in the soil.

[0057] Example 2: Performance of improved soil with different amounts of coal gangue added 2.1 Preparation of gangue-based improved soil After preparing four single bacterial powders according to the method in Example 1, SHBCC D11446 bacterial powder, SHBCCD24696 bacterial powder, SHBCC D10197 bacterial powder and GS02 bacterial powder were mixed at a ratio of 1000:1:0.2:200 in terms of viable bacteria count to obtain the fermentation agent GN4-mid.

[0058] After the gangue is crushed to a particle size of no more than 10 mm, it is sorted and screened to select small-size gangue (d≤2 mm), medium-size gangue (2 mm < d < 6 mm) and large-size gangue (6 mm < d < 10 mm), and mixed in a mass ratio of 4:4:3 to obtain a gangue mixture.

[0059] The fermentation agent GN4-mid and water were mixed in a mass ratio of 1:9 to produce a bacterial solution. The solution was then sprayed onto the gangue mixture at a mass ratio of 1:100 and tilled to mix thoroughly, resulting in Mixture A. Perlite water-retaining agent and commercial organic fertilizer (New Sunshine Organic Fertilizer, Changchun New Sunshine Organic Fertilizer Co., Ltd.) were added to Mixture A at a rate of 0.1% of the mass of the gangue mixture, and tilled to mix thoroughly, resulting in Mixture B. In Groups #1 to #3, Mixture B was mixed with sandy soil in mass ratios of 3:7, 1:1, and 7:3, respectively, and tilled to mix thoroughly, resulting in Mixture C. After adjusting the moisture content of Mixture C to 20%, the soil was fermented at 25°C for 10 days, with film covering applied to minimize water loss. This resulted in Gangue-based improved soils #1 to #3.

[0060] 2.2 Physical and chemical properties test of gangue-based improved soil The gangue-based improved soil samples prepared in Groups #1 to #3 were obtained by multi-point sampling, and their pH, electrical conductivity (EC), organic matter content, total nitrogen content, available phosphorus content, available potassium content, and available heavy metal content were measured. The results are shown in Tables 4 and 5.

[0061] Table 4 Test results of physical and chemical indicators of gangue-based improved soil Table 5 Test results of effective heavy metal content in gangue-based improved soil According to Tables 4 and 5, it can be seen that the pH and EC values of the gangue-based improved soils prepared in Groups #1 to #3 are still close to those of sandy soils, while the organic matter content, total nitrogen content, and available potassium content have been significantly improved, and the contents of various available heavy metals in the improved soils are all lower than the soil pollution risk values for agricultural land.

[0062] 2.3 Alfalfa planting experiment The gangue-based improved soil prepared in groups #1 to #3 was taken as the experimental group, the sandy soil was taken as the control group, and blank controls CK1 to CK3 were set up (the gangue-based improved soil of CK1 to CK3 was prepared according to groups #1 to #3, respectively, and the only difference from groups #1 to #3 was that the fermentation agent GN4-mid was not added). Alfalfa was used as the indicator crop, and the sowing density of each group was the same. After shallow soil covering, a field experiment was carried out for 30 days. Multi-point sampling was carried out on plant samples in each group, and plant height, root length and fresh weight were measured. The results are shown in Table 6.

[0063] Table 6 Alfalfa growth test results According to Table 6, we can see that: (1) When the improved soils of groups #1 to #3 were used, the average plant height and average fresh weight of alfalfa were significantly improved compared with those in sandy soil, indicating that the gangue-based improved soil prepared by the method of the present invention can promote plant growth.

[0064] (2) When the improved soils of groups #1 to #3 were used, the average plant height, average root length, and average fresh weight of alfalfa were significantly increased compared to the corresponding blank controls (CK1 to CK3). This indicates that fermentation treatment with the fermentation agent of the present invention can make the improved soil more suitable for plant growth.

[0065] 2.4 Buckwheat planting experiment The gangue-based improved soil prepared in Group #1 and Group #2 was used as the experimental group, and blank controls CK1 and CK2 were set up (the gangue-based improved soil of CK1 and CK2 was prepared according to Group #1 and Group #2, respectively, and the only difference from Group #1 and Group #2 was that the fermentation agent GN4-mid was not added). Buckwheat was used as the indicator crop. The sowing density of each group was the same. After shallow soil covering, a field experiment was conducted for 30 days. Multi-point sampling was carried out on plant samples in each group, and plant height, root length and fresh weight were measured. The results are shown in Table 7.

[0066] Table 7 Buckwheat growth test results Table 7 shows that the average plant height, average root length, and average fresh weight of buckwheat significantly increased when using the improved soils of Groups #1 and #2 compared to the corresponding blank controls (CK1 and CK2). This indicates that fermentation with the fermentation agent of the present invention can make the improved soil more suitable for plant growth.

[0067] Example 3: Effect of coal gangue particle size on improved soil properties 3.1 Preparation of gangue-based improved soil After preparing four single bacterial powders according to the method in Example 1, SHBCC D11446 bacterial powder, SHBCCD24696 bacterial powder, SHBCC D10197 bacterial powder and GS02 bacterial powder were mixed at a ratio of 1000:1:0.2:200 in terms of viable bacteria count to obtain the fermentation agent GN4-mid.

[0068] After the gangue is crushed to a particle size of no more than 10 mm, it is sorted and screened to select small-size gangue (d≤2 mm), medium-size gangue (2 mm < d < 6 mm) and large-size gangue (6 mm < d < 10 mm), and mixed in a mass ratio of 4:4:3 to obtain a gangue mixture.

[0069] After preparing the fermentation agent GN4-mid according to the method in Example 2, it was mixed with water in a mass ratio of 1:9 to obtain a bacterial solution. The bacterial solution was sprayed into the coal gangue mixture at a mass ratio of 1:100, and the mixture was tilled and mixed evenly to obtain Mixture A. Perlite water-retaining agent and commercial organic fertilizer (New Sunshine Organic Fertilizer, Changchun New Sunshine Organic Fertilizer Co., Ltd.) were added to Mixture A, with the addition amount of perlite water-retaining agent and commercial organic fertilizer each being 0.1% of the mass of the coal gangue mixture. The mixture was tilled and mixed evenly to obtain Mixture B. In Groups #1 to #3, Mixture B was mixed with sandy soil in a mass ratio of 7:3, respectively, and tilled and mixed evenly to obtain Mixture C. After adjusting the moisture content of Mixture C to 20%, it was fermented at 25°C for 10 days, during which time it was covered with a film to reduce water loss, to obtain Coal Gangue-Based Improved Soil #3.

[0070] In the above process, the gangue mixture was replaced with small-particle gangue (d≤2mm), medium-particle gangue (2mm<d<6mm) and large-particle gangue (6mm≤d≤10mm) of equal mass, and the other raw materials and steps remained unchanged, and gangue-based improved soils #4 to #6 were obtained respectively.

[0071] 3.2 Alfalfa planting experiment The gangue-based improved soil prepared in groups #3 to #6 was used as the experimental group. Alfalfa was used as the indicator crop. The sowing density of each group was the same. After shallow soil covering, a field experiment was conducted for 30 days. Multi-point sampling was carried out on plant samples in each group to measure plant height, root length and fresh weight. The results are shown in Table 8.

[0072] Table 8 Alfalfa growth test results coal gangue Average plant height (cm) Average root length (cm) Average fresh weight (g) #3 Gangue mixture 5.85 10.03 0.38 #4 Small-sized coal gangue 2.32 5.42 0.11 #5 Medium-sized coal gangue 2.85 5.35 0.121 #6 Large-size coal gangue 2.47 4.96 0.09 Table 8 shows that the difference between #4 to #6 and #3 lies in the different particle sizes of the coal gangue used. Compared with groups #4 to #6, the average plant height, average root length, and average fresh weight of alfalfa increased in the improved soil of group #3. This indicates that the combination of three coal gangue particle sizes (d ≤ 2 mm, 2 mm < d < 6 mm, and 6 mm ≤ d ≤ 10 mm) used in the present invention can provide a more suitable soil environment for plant growth.

[0073] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this disclosure pertains. Unless otherwise specified, the raw materials and equipment used herein are conventional in the art and can be obtained from conventional commercial sources. The methods used herein are conventional in the art, unless otherwise specified.

[0074] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A gangue-based improved soil, characterized in that: The raw materials include: coal gangue, sand, fermentation agent; the fermentation agent includes Bacillus subtilis ( Bacillus subtilis ) SHBCC D11446, arbuscular mycorrhizal fungi ( Rhizophagus irregularis ) SHBCC D24696, Trichoderma viride ( Trichoderma viride ) SHBCCD10197 and Bacillus velezinis with a deposit number of CCTCC NO: M 2025531 ( Bacillus velezensis )GS02.

2. The gangue-based improved soil according to claim 1, characterized in that: The coal gangue includes small-size coal gangue, medium-size coal gangue and large-size coal gangue in a mass ratio of 30~50:30~40:15~30; the particle size of the small-size coal gangue is not greater than 2 mm, the particle size of the medium-size coal gangue is 2~6 mm, and the particle size of the large-size coal gangue is 6~10 mm.

3. The gangue-based improved soil according to claim 1, characterized in that: The ratio of the viable bacteria counts of the Bacillus subtilis SHBCCD11446, the arbuscular mycorrhizal fungus SHBCC D24696, the Trichoderma viride SHBCC D10197 and the Bacillus velezensis GS02 is 1000:0.8-1.2:0.1-0.3:100-300.

4. The gangue-based improved soil according to claim 1 or 3, characterized in that: The mass of the fermentation agent is 0.1-1.5% of the mass of the coal gangue.

5. The gangue-based improved soil according to claim 1, characterized in that: It also includes the following raw materials: water retaining agent, organic fertilizer.

6. The gangue-based improved soil according to claim 5, characterized in that: The water-retaining agent includes at least one of sodium polyacrylate, diatomaceous earth and perlite; the organic fertilizer includes at least one of manure fertilizer, green manure, compost fertilizer and commercial fertilizer; the mass of the water-retaining agent and the organic fertilizer is 0.1-1% of the mass of the coal gangue.

7. The gangue-based improved soil according to claim 1, characterized in that: The particle size of the sand is less than 2 mm, and the mass of the sand accounts for 30-70% of the total mass of all raw materials.

8. A method for preparing the gangue-based improved soil according to any one of claims 1 to 7, characterized in that: include: After all the raw materials are mixed, fermentation is carried out to obtain coal gangue-based improved soil.

9. The preparation method according to claim 8, characterized in that Before fermentation, the moisture content is adjusted to 15-25%; the fermentation temperature is 20-37°C and the fermentation time is 10-30 days.

10. The preparation method according to claim 8, characterized in that The process of mixing all the raw materials includes the following steps: preparing the fermentation bacteria agent into a bacterial liquid, mixing it with coal gangue, adding a water retaining agent and an organic fertilizer, mixing well, and then mixing it with sand.

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