Soil activator for soil health restoration and preparation method thereof

Abstract

The application relates to the technical field of agricultural environmental materials, in particular to a soil activator for soil health repair and a preparation method thereof. The activator is prepared by compounding an organic matter matrix, a compound microbial flora, a mineral conditioner, a biological stimulant and a functional auxiliary agent in a specific proportion, and the preparation method comprises the following steps: organic matter matrix pretreatment, microbial flora propagation and fixation, mineral conditioner modification, polyglutamic acid biosynthesis and final compounding and low-temperature granulation. Through the synergistic effect of the triple repair mechanisms of physics, chemistry and biology, the application can systematically improve various degradation problems such as soil compaction, acidification, salinization and continuous cropping obstacles, significantly improve soil microbial diversity and crop yield, has the advantages of wide raw material sources, controllable process, long-lasting improvement effect and the like, and is suitable for ecological repair and health reconstruction of various degraded farmland soils.

Description

Technical Field

[0001] This invention relates to the field of soil conditioner technology, and in particular to a soil activator for soil health restoration and its preparation method. Background Technology

[0002] Soil is the foundation of human agricultural production. However, long-term high-intensity farming, excessive application of chemical fertilizers, and unreasonable irrigation have led to soil degradation problems such as compaction, acidification, salinization, and continuous cropping obstacles in large areas of farmland in my country. According to statistics, about one-third of the arable land in the country suffers from varying degrees of soil degradation, which seriously restricts food security and sustainable agricultural development.

[0003] Currently, soil degradation remediation technologies mainly fall into three categories: physical remediation, chemical remediation, and biological remediation. However, existing technologies generally suffer from the following shortcomings: First, they are single-function, with most products targeting only a specific type of degradation and failing to address complex degradation issues. Second, chemical remediation agents are prone to causing secondary pollution, and their long-term effects are unstable. Third, microbial inoculants have poor cell survival rates and field colonization capabilities, significantly reducing their practical application effectiveness. Fourth, there is a lack of systematic solutions that organically combine physical, chemical, and biological remediation methods.

[0004] Biochar, as a novel soil amendment material, has attracted widespread attention due to its porous structure and high adsorption performance. However, the application of single biochar has obvious limitations: on the one hand, ordinary plant-derived biochar is alkaline and can be applied directly to acidic soils, but may have adverse effects on neutral or alkaline soils. On the other hand, its pore structure is easily blocked by salts or fine particles, and its effect diminishes with long-term use. In addition, existing composite amendments mostly adopt simple physical mixing methods, which fail to give full play to the synergistic effect of each component.

[0005] Therefore, there is a need to develop a soil activator and its preparation method that can systematically remediate various degraded soils, improve physical structure, regulate chemical properties and enhance biological activity, and has controllable process and long-lasting effect. Summary of the Invention

[0006] To address the problems mentioned in the background section, this invention provides a soil activator for soil health restoration and its preparation method. This activator, through the scientific formulation of organic matrix, complex microbial community, mineral conditioner, biostimulant and functional adjuvant, and a unique preparation process, achieves systematic restoration of soil compaction, acidification, salinization and continuous cropping obstacles.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing a soil activator for soil health remediation, comprising the following steps: S1. Organic matrix pretreatment: Mix humic acid, biochar and decomposed straw or mushroom residue in a mass ratio, and crush to 60-80 mesh to obtain organic matrix. S2. Microbial community propagation and fixation: Bacillus subtilis, nitrogen-fixing bacteria, Trichoderma, and arbuscular mycorrhizal fungi were cultured to the logarithmic growth phase and then mixed in proportion to form a composite bacterial solution. The composite bacterial solution was then sprayed onto a sterilized biochar-diatomaceous earth composite carrier for adsorption and fixation. After being dried at room temperature until the moisture content was ≤15%, the immobilized microbial agent was obtained. The arbuscular mycorrhizal fungi was Glomus mosseae / Funneliformis mosseae, preservation information: BGC XJ01, purchased from the China Arbuscular Mycorrhizal Fungi Germplasm Bank (BGC). Propagation was carried out through a host plant (maize) pot culture method: maize seeds were sown in sterilized sand and inoculated with BGC XJ01 spore suspension. After culturing for 6-8 weeks, the substrate containing spores, mycelia, and infected root segments was harvested, cut into pieces, and passed through a 0.5 mm sieve to obtain AMF inoculum. S3. Modification of mineral conditioner: Sodium-based bentonite is dried and pulverized to 100 mesh, and shell powder or oyster shell powder is calcined at 800-900℃ for 1 hour to obtain modified mineral conditioner. S4. Polyglutamic acid biosynthesis: A two-step fermentation method is adopted. First, Bacillus subtilis and Bacillus natto are fermented in glucose and yeast extract culture medium for 3-4 days. Then, 15-25 g / L of sterilized straw powder is added and fermentation continues for 3-5 days. The fermentation product is centrifuged, precipitated with alcohol, and dried to obtain polyglutamic acid. S5. Final compounding and low-temperature granulation: The organic matrix obtained in step S1, the modified mineral conditioner obtained in step S3, the polyglutamic acid and functional additives obtained in step S4 are mixed in a predetermined ratio in steps, and finally the immobilized microbial agent obtained in step S2 is added. The mixture is then granulated at low temperature at 40-50℃ and dried until the moisture content is ≤12% to obtain granular soil activator.

[0008] Preferably, in step S1, the organic matrix comprises, by weight percentage: 20%-30% humic acid, 10%-15% biochar, and 15%-20% decomposed straw or mushroom residue, wherein the mass ratio of fulvic acid to humic acid in the humic acid is 2-3:1.

[0009] Preferably, in step S2, the effective viable count ratio of each strain in the composite microbial community is 4-6:2-3:1-2:0.5-1 according to Bacillus subtilis: nitrogen-fixing bacteria: Trichoderma: arbuscular mycorrhizal fungi, with a total effective viable count ≥500 million CFU / g.

[0010] Preferably, in step S2, the mass ratio of biochar to diatomite in the biochar-diatomite composite carrier is 6:4-8:2, and the composite carrier is sterilized at 121°C for 30 minutes before use.

[0011] Preferably, in step S3, the mineral conditioning agent comprises, by weight percentage: 10%-15% sodium bentonite, 5%-8% diatomaceous earth, and 3%-5% calcined shell powder or oyster shell powder.

[0012] Preferably, in step S4, the first fermentation temperature of the two-step fermentation method is 30-37℃, the second fermentation temperature is 28-35℃, and the molecular weight of the polyglutamic acid is 50-200kDa.

[0013] Preferably, in step S5, the specific operation of the stepwise mixing is as follows: first, mix the organic matrix and mineral conditioner at a speed of 300-400 rpm for 5-10 minutes, then add polyglutamic acid and functional additives at a speed of 200-300 rpm and mix for 3-5 minutes, and finally add immobilized microbial agent at a speed of 100-150 rpm and mix for 2-3 minutes.

[0014] Preferably, in step S5, the functional additives include, by weight percentage: 2%-3% seaweed extract and 1%-2% sodium lignosulfonate.

[0015] Preferably, the low-temperature granulation is performed by extrusion granulation or disc granulation, and the resulting particles have a diameter of 2-4 mm.

[0016] The present invention also provides a soil activator for soil health remediation prepared by the above method, the components and weight percentages of which are as follows, based on dry weight: organic matter matrix 35%-65%, compound microbial community 5%-10%, mineral conditioner 18%-28%, biostimulant 7%-11%, and functional adjuvant 3%-5%. The biostimulant is a mixture of potassium humate and polyglutamic acid, wherein potassium humate accounts for 5%-8% and polyglutamic acid accounts for 2%-3%. The activator has a pH value of 6.5-7.5, an electrical conductivity ≤1.5mS / cm, a particle size of 2-4mm, and a moisture content ≤12%.

[0017] The beneficial effects of this invention are: 1. In this invention, the organic matrix provides the soil with an abundant source of organic carbon and a stable porous structure. The fulvic acid in humic acid has a small molecular weight and high activity, which can quickly chelate harmful ions in the soil and promote the formation of aggregate structure. The black humic acid has a large molecular weight and strong stability, which can maintain the soil organic matter level for a long time. The porous structure of biochar not only provides an ideal habitat for microorganisms, but also adsorbs pollutants and excess nutrients in the soil, reducing loss. The decomposed straw or mushroom residue further supplements the easily decomposed organic matter and provides an energy source for microbial activities.

[0018] 2. In this invention, the composite microbial community is immobilized using a biochar-diatomaceous earth composite carrier, which significantly improves the survival rate and field colonization ability of the microorganisms. Bacillus subtilis can secrete a variety of antibacterial substances and enzymes to inhibit soil-borne pathogens. Nitrogen-fixing bacteria can convert atmospheric nitrogen into ammonia nitrogen that plants can utilize. Trichoderma has strong biocontrol activity and can antagonize a variety of soil-borne diseases. Arbuscular mycorrhizal fungi can form a symbiotic relationship with crop roots, expand the root absorption area, and enhance the plant's ability to absorb water and mineral nutrients. The synergistic cooperation of the four strains forms a complete biological regulation chain from nutrient transformation and disease control to growth promotion and efficiency enhancement.

[0019] 3. In this invention, the sodium-based bentonite in the mineral conditioner has extremely strong water absorption and swelling properties and cation exchange capacity, which can effectively improve the soil aggregate structure and enhance water and fertilizer retention performance. The porous structure of diatomaceous earth can regulate soil permeability and prevent compaction. After being calcined at 800-900℃, the calcium carbonate in the shell powder or oyster shell powder is completely decomposed into calcium oxide, which generates calcium hydroxide upon contact with water and releases highly active calcium ions, which can replace sodium ions on soil colloids, reduce the degree of soil alkalization, and supplement calcium elements at the same time.

[0020] 4. In this invention, polyglutamic acid, as a biostimulant, has a large number of carboxyl and amide groups on its molecular chain, which have extremely strong water absorption and chelation capabilities. It can form a water-retaining film in the soil, reduce water evaporation, and at the same time chelate trace elements such as potassium, calcium, and magnesium, thereby improving fertilizer utilization. Potassium humate directly stimulates crop root growth and enhances stress resistance. The synergistic effect of the two can significantly improve the crop's tolerance to adverse conditions such as salinity, drought, etc.

[0021] 5. In this invention, the stepwise mixing and low-temperature granulation process effectively protects the activity of microorganisms and heat-sensitive components. First, the organic matrix and mineral conditioner are mixed at high speed to ensure the uniformity of the basic framework. Then, biostimulants and adjuvants are added at medium speed to achieve uniform distribution of functional components. Finally, immobilized microbial agents are added at low speed to avoid damage to the cells by shear force. The low-temperature drying conditions of 40-50℃ ensure that the survival rate of microorganisms is ≥85%. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Unless otherwise specified, all raw materials used in this invention are commercially available products, and all microbial strains used are obtained from public collections such as the China General Microbiological Culture Collection Center (CGMCC). Specific strain numbers are as follows: Bacillus subtilis CGMCC 1.1630, Azotobacter chroococcum CGMCC 1.1031, Trichoderma harzianum CGMCC 3.4429, and Glomus mosseae (currently classified as Funneliformis mosseae), purchased from the China Arbuscular Mycorrhizal Fungi Germplasm Bank (BGC) of the Institute of Plant Nutrition and Resource Environment, Beijing Academy of Agricultural and Forestry Sciences, strain number BGC. XJ01 (National Science and Technology Resource Sharing Platform No.: 1511C0001BGCAM0016) can be obtained by ordering from the BGC open strain catalog. The inoculum is a sand mixture containing spores, infected root segments and mycelium, Bacillus natto CGMCC 1.1086.

[0024] Example 1: S1, Organic matrix pretreatment: Weigh out 250g of humic acid (fulvic acid: humic acid = 2.5:1), 125g of biochar (obtained from corn stalks by oxygen-limited pyrolysis at 500℃ and passed through an 80-mesh sieve), and 175g of fermented mushroom residue, totaling 550g (accounting for 55% of the total mass of the finished product). Put the three materials into a high-speed pulverizer and pulverize them to 60-80 mesh. Mix them evenly to obtain an organic matrix.

[0025] S2. Microbial community propagation and fixation: Bacillus subtilis, nitrogen-fixing bacteria, and Trichoderma were inoculated into their respective liquid culture media and cultured at 30℃ and 180 rpm until the logarithmic growth phase (approximately 24-48 hours). Arbuscular mycorrhizal fungi were propagated through a pot culture method using a host plant (corn): corn seeds were sown in sterilized sand and inoculated with BGC XJ01 spore suspension (obtained by suspending and filtering purchased sand inoculum with sterile water). After 8 weeks of culture, the roots and substrate were harvested, chopped, and passed through a 0.5 mm sieve to obtain a fungal agent containing spores and mycelia. The various fungal solutions were mixed according to the effective viable count ratio (Bacillus subtilis: nitrogen-fixing bacteria: Trichoderma: arbuscular mycorrhizal fungi = 5: 2.5: 1.5: 1), and the total viable count was adjusted to 5 × 10⁻⁶. 8 CFU / mL was used to obtain a compound bacterial solution.

[0026] Weigh 70g of biochar (same as S1) and 30g of diatomaceous earth (passed through a 200-mesh sieve), mix them, sterilize at 121℃ for 30 minutes, and use the mixture as a composite carrier. Spray the composite bacterial solution evenly onto the composite carrier at a solid-liquid ratio of 1g:2mL while stirring to ensure full adsorption of the bacterial solution. Spread the mixture at room temperature until the moisture content is ≤15% to obtain the immobilized microbial agent for later use.

[0027] S3, Mineral Conditioner Modification: Weigh out 120g of sodium bentonite (dried to 100 mesh), 65g of diatomaceous earth (passed through a 200-mesh sieve), and 40g of oyster shell powder (calcined at 850℃ for 1 hour beforehand), totaling 225g (accounting for 22.5% of the total mass of the finished product), mix them evenly, and obtain the modified mineral conditioner.

[0028] S4, Polyglutamic acid biosynthesis: Step 1 Fermentation: Prepare fermentation medium (30g / L glucose, 5g / L yeast extract, 20g / L sodium glutamate, 0.5g / L MgSO4·7H2O, 1g / L K2HPO4, pH 7.0), inoculate with Bacillus subtilis and Bacillus natto (2% each), and ferment for 3 days at 35℃ and 200rpm.

[0029] Second fermentation step: Add 20g / L of sterilized straw powder (passed through a 40-mesh sieve) to the first fermentation broth and continue fermentation at 30℃ and 180rpm for 4 days.

[0030] After fermentation, the fermentation broth was centrifuged at 8000 rpm for 20 minutes to remove the cells. Three volumes of anhydrous ethanol were added to the supernatant to precipitate polyglutamic acid. After standing overnight at 4°C, the precipitate was collected by centrifugation again and dried under vacuum at 50°C to constant weight to obtain crude polyglutamic acid (molecular weight about 120 kDa, yield about 13.5 g / L), which was then used for later use.

[0031] S5. Final compounding and low-temperature granulation: Take 550g of the organic matrix obtained from S1, 225g of the modified mineral conditioner obtained from S3, 25g of polyglutamic acid obtained from S4 (accounting for 2.5% of the total mass of the finished product), 70g of potassium humate (accounting for 7%), 25g of seaweed extract (accounting for 2.5%), and 15g of sodium lignosulfonate (accounting for 1.5%), for a total of 910g.

[0032] First, put the organic matrix and mineral conditioner into a three-dimensional mixer and mix at 350 rpm for 8 minutes. Then, add polyglutamic acid, potassium humate, seaweed extract and sodium lignosulfonate and mix at 250 rpm for 5 minutes. Finally, add 90g (9%) of the immobilized microbial agent obtained from S2 and mix at 120 rpm for 3 minutes.

[0033] The mixture is fed into a disc granulator, and an appropriate amount of deionized water (about 10%-15% of the material mass) is sprayed in. Granulation is carried out at 40-50℃, and the particle size is controlled at 2-4mm. After granulation, the mixture is dried in an airflow at 45℃ until the moisture content is ≤12%. The mixture is then sieved and graded to obtain the finished soil activator.

[0034] Product characteristics: The activator is a dark brown granule with a pH value of 6.89, an electrical conductivity of 1.21 mS / cm, a moisture content of 10.5%, and a particle size of 2-4 mm accounting for ≥90%.

[0035] Example 2: The difference from Example 1 is that the ratio of organic matrix in S1 is adjusted to: 200g humic acid, 150g biochar, and 200g decomposed straw, totaling 550g; the ratio of mineral conditioner in S3 is adjusted to: 100g sodium bentonite, 80g diatomaceous earth, and 45g shell powder, totaling 225g; and the molecular weight of polyglutamic acid in S4 is adjusted to approximately 80kDa (achieved by adjusting the fermentation time in the second step to 3 days). The remaining steps and parameters are exactly the same as in Example 1.

[0036] Example 3: The difference from Example 1 is that the amount of immobilized microbial agent added in S5 is adjusted to 50g (5% of the total mass of the finished product), and the amount of organic matrix added is adjusted to 590g (59%). The remaining steps and parameters are exactly the same as in Example 1. In this example, the effective viable count concentration of the immobilized microbial agent is adjusted to 9×10⁻⁶. 8 The total number of viable bacteria in the finished product is set at CFU / g to ensure that the total number of viable bacteria still meets the requirement of ≥500 million CFU / g. Example

[0037] The difference from Example 1 is that the amount of polyglutamic acid added in S5 is adjusted to 30g (3%), and the amount of potassium humate added is adjusted to 60g (6%). The remaining steps and parameters are exactly the same as in Example 1.

[0038] Comparative Example 1 The difference from Example 1 is that the addition of the microbial community in S2 is omitted, that is, no immobilized microbial agent is added in S5, and only an equal amount (90g) of biochar-diatomite composite carrier is used instead. The remaining steps and parameters are exactly the same as in Example 1.

[0039] Comparative Example 2 The difference from Example 1 is that the biosynthesis step of polyglutamic acid in S4 is omitted, that is, in S5, an equal amount (25g) of ordinary commercial polyglutamic acid (molecular weight of about 120kDa, purchased from a chemical company) is used instead, and the remaining steps and parameters are exactly the same as in Example 1.

[0040] Comparative Example 3 The difference from Example 1 is that the calcination treatment of the shell powder in S3 is omitted, that is, uncalcined oyster shell powder is used. The remaining steps and parameters are exactly the same as in Example 1.

[0041] Comparative Example 4 The difference from Example 1 is that in S5, a one-step mixing method is used (mixing all components at 350 rpm for 10 minutes at once) instead of stepwise mixing. The remaining steps and parameters are exactly the same as in Example 1.

[0042] Comparative Example 5 The difference from Example 1 is that no modifier was applied, and only an equal amount (1.5%) of clean water was used for treatment.

[0043] Performance testing methods and results: Potted plant experiment setup: The tested soil was collected from a vegetable greenhouse in Shouguang City, Shandong Province, which was affected by continuous cropping obstacles (tomatoes were grown there for 8 years). Its basic physicochemical properties were as follows: pH 5.83, electrical conductivity (EC) 0.98 mS / cm, organic matter content 8.72 g / kg, soil bulk density 1.46 g / cm3, root-knot nematode disease index 78, and wilt disease incidence rate 45%. Experimental design: Polyethylene plastic pots (top diameter × height = 25cm × 30cm) were used, each pot was filled with 5.0kg of soil. The soil activator prepared in Examples 1-4 and Comparative Examples 1-5 was mixed thoroughly with the soil at 1.5% of the soil dry weight. Each group had 3 replicates. Crop cultivation: Transplant one tomato seedling (variety: Jinpeng No. 1, seedling age 30 days) into each pot and manage it in a greenhouse in a conventional manner for a cultivation period of 90 days; Indicator measurement methods: Soil porosity: determined by the ring sampler method, referring to the "Determination of Physical Properties of Soil" (LY / T 1215-1999); Soil microbial diversity: High-throughput sequencing was used to determine the V3-V4 region of bacterial 16S rRNA genes, and the Shannon index was calculated. Tomato yield: The total fresh weight of mature fruits per pot (unit: g / pot); Tomato quality: Soluble solids content (%) was determined using a handheld refractometer, and vitamin C content (mg / 100g) was determined using the 2,6-dichlorophenolindophenol titration method. Disease survey: The root-knot nematode disease index was graded from 0 to 5, and the incidence rate of Fusarium wilt was calculated based on the proportion of infected plants. Microbial survival rate determination: Take 1g of immobilized microbial agent, add sterile physiological saline, shake and elute, spread and count, and calculate the survival rate by comparing with the number of viable bacteria in the initial bacterial solution.

[0044] The results are shown in Tables 1 and 2: Table 1. Results of soil physicochemical and biological property measurements (90 days after planting)

[0045] Table 2. Results of Tomato Yield, Quality, and Disease Survey (90 days after planting)

[0046] As shown in Tables 1 and 2, the soil activators prepared in the various embodiments of the present invention (especially Example 1) have a significant positive effect on various indicators of soils with continuous cropping obstacles, specifically as follows: Regarding soil physical structure, the soil porosity of Example 1 increased from the initial 42.3% to 53.6%, an increase of 26.7%, which was significantly better than the comparative examples (comparative example 1 was only 47.5%), indicating that the synergistic effect of organic matrix and mineral conditioner effectively improved soil aeration and permeability.

[0047] Regarding soil biological activity, the Shannon index of Example 1 increased from 3.15 to 4.93, an increase of 56.5%, while that of Comparative Example 1 (lacking microorganisms) was only 3.67 and that of Comparative Example 2 (lacking polyglutamic acid) was 4.38, which fully demonstrates the key role of the complex microbial community and polyglutamic acid in activating the soil microbial community.

[0048] Regarding soil chemical properties, Example 1 increased the soil pH from 5.83 to 6.81, which is close to neutral, effectively alleviating the acidification problem. The EC value decreased from 0.98 to 0.76 mS / cm, indicating that the salt was leached to a certain extent. The organic matter content increased from 8.72 g / kg to 17.56 g / kg, an increase of 101.4%, far exceeding the ratios.

[0049] In terms of crop yield and quality, the tomato yield of Example 1 reached 693.5g / pot, which was 62.0% higher than the blank control (Comparative Example 5) and 32.5% higher than the microbial-deficient Comparative Example 1. The soluble solids and vitamin C content were also significantly better than those of the comparative examples, indicating that the activator has a significant effect on increasing yield and improving quality.

[0050] In terms of disease control, Example 1 reduced the root-knot nematode disease index from 78 to 31 and the wilt disease incidence rate from 45% to 11%, with control effects of 60.3% and 75.6%, respectively, which were significantly better than the control ratios, demonstrating the synergistic biocontrol effect of the compound microbial community and biostimulants.

[0051] Although the effect of Comparative Example 4 (one-step mixing) was better than that of Comparative Examples 1-3, it was still lower than that of Example 1, indicating that the stepwise mixing process plays an important role in protecting microbial activity and ensuring uniform distribution of components.

[0052] In summary, the soil activator for soil health restoration provided by this invention, through the scientific formulation of organic matrix, complex microbial community, mineral conditioner, biostimulant and functional adjuvant, and a unique preparation process (microbial immobilization, in-situ fermentation of polyglutamic acid, stepwise mixing and low-temperature granulation), constructs a synergistic system of "physical improvement-chemical regulation-bioremediation". This system can not only systematically improve various degradation problems such as soil compaction, acidification, and continuous cropping obstacles, but also significantly improve crop yield and quality, effectively control soil-borne diseases, and provide a green, efficient and economically feasible technical approach for the healthy restoration and sustainable use of degraded farmland soil.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a soil activator for soil health remediation, characterized in that, Includes the following steps: S1. Mix humic acid, biochar and decomposed straw or mushroom residue in a mass ratio, and crush to 60-80 mesh to obtain an organic matrix. S2. After culturing Bacillus subtilis, nitrogen-fixing bacteria, Trichoderma and arbuscular mycorrhizal fungi to the logarithmic growth phase, they are mixed in proportion to the effective viable number to form a compound bacterial solution. The compound bacterial solution is then sprayed onto a sterilized biochar-diatomaceous earth composite carrier for adsorption and fixation. After drying at room temperature until the moisture content is ≤15%, an immobilized microbial agent is obtained. The arbuscular mycorrhizal fungi are propagated by the host plant pot culture method. After harvesting spores and infected root segments, they are ground and sieved to obtain the inoculum. S3. Dry sodium-based bentonite and pulverize it to 100 mesh, and calcine shell powder or oyster shell powder at 800-900℃ for 1 hour to obtain a modified mineral conditioner. S4. A two-step fermentation method is adopted. First, Bacillus subtilis and Bacillus natto are fermented in glucose and yeast extract culture medium for 3-4 days. Then, 15-25 g / L of sterilized straw powder is added and fermentation continues for 3-5 days. The fermentation product is centrifuged, precipitated with alcohol, and dried to obtain polyglutamic acid. S5. The organic matrix obtained in step S1, the modified mineral conditioner obtained in step S3, the polyglutamic acid and functional additives obtained in step S4 are mixed in a predetermined ratio in steps. Finally, the immobilized microbial agent obtained in step S2 is added, and the mixture is granulated at low temperature at 40-50℃ and dried until the moisture content is ≤12% to obtain granular soil activator.

2. The preparation method according to claim 1, characterized in that, In step S1, the organic matrix comprises, by weight percentage: 20%-30% humic acid, 10%-15% biochar, and 15%-20% decomposed straw or mushroom residue, wherein the mass ratio of fulvic acid to humic acid in the humic acid is 2-3:

1.

3. The preparation method according to claim 1, characterized in that, In step S2, the effective viable count ratio of each strain in the composite microbial community is 4-6:2-3:1-2:0.5-1 according to Bacillus subtilis: nitrogen-fixing bacteria: Trichoderma: arbuscular mycorrhizal fungi, with a total effective viable count ≥500 million CFU / g.

4. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of biochar to diatomite in the biochar-diatomite composite carrier is 6:4-8:2, and the composite carrier is sterilized at 121°C for 30 minutes before use.

5. The preparation method according to claim 1, characterized in that, In step S3, the mineral conditioning agent comprises, by weight percentage: 10%-15% sodium bentonite, 5%-8% diatomite, and 3%-5% calcined shell powder or oyster shell powder.

6. The preparation method according to claim 1, characterized in that, In step S4, the first fermentation temperature of the two-step fermentation method is 30-37℃, the second fermentation temperature is 28-35℃, and the molecular weight of the polyglutamic acid is 50-200kDa.

7. The preparation method according to claim 1, characterized in that, In step S5, the specific operation of the stepwise mixing is as follows: first, mix the organic matrix and mineral conditioner at a speed of 300-400 rpm for 5-10 minutes, then add polyglutamic acid and functional additives at a speed of 200-300 rpm and mix for 3-5 minutes, and finally add immobilized microbial agent at a speed of 100-150 rpm and mix for 2-3 minutes.

8. The preparation method according to claim 1, characterized in that, In step S5, the functional additives include, by weight percentage: 2%-3% seaweed extract and 1%-2% sodium lignosulfonate.

9. The preparation method according to claim 1, characterized in that, The low-temperature granulation is carried out by extrusion granulation or disc granulation, and the resulting particles have a diameter of 2-4 mm.

10. A soil activator for soil health remediation prepared by the method according to any one of claims 1-9, characterized in that, The components and weight percentages based on dry weight are as follows: organic matrix 35%-65%, immobilized microbial agent 5%-10%, mineral conditioner 18%-28%, biostimulant 7%-11%, and functional additives 3%-5%. The biostimulant is a mixture of potassium humate and polyglutamic acid, wherein potassium humate accounts for 5%-8% and polyglutamic acid accounts for 2%-3%. The activator has a pH value of 6.5-7.5, an electrical conductivity ≤1.5mS / cm, a particle size of 2-4mm, and a moisture content ≤12%.

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