Saline-alkali soil restoration material and preparation method thereof

Abstract

The invention belongs to the technical field of saline-alkali soil restoration, and discloses a saline-alkali soil restoration material and a preparation method thereof. The material comprises an aminated bentonite-sodium alginate composite microsphere embedded streptomyces rochei microbial inoculum, an aminated montmorillonite-sodium alginate composite ion exchanger and other components according to a specific ratio, wherein the aminated bentonite-sodium alginate composite microsphere embedded streptomyces rochei microbial inoculum and the aminated montmorillonite-sodium alginate composite ion exchanger are used as raw materials; the preparation method comprises the following steps: firstly preparing aminated bentonite, then embedding strains to form composite microspheres, and finally mixing all the components. The material can efficiently remove salt and reduce alkali (pH is less than or equal to 7.5), the survival rate of strains in 30 days is increased by more than or equal to 80%, soil organic matters are increased to 17.9 g / kg, crop growth is effectively promoted, and the material is eco-friendly, controllable in cost and suitable for moderate saline-alkali soil remediation.

Description

Technical Field

[0001] This invention belongs to the field of saline-alkali land remediation technology, and relates to a saline-alkali land soil restoration material and its preparation method. Background Technology

[0002] Soil salinization is a long-term and significant challenge facing my country's agricultural development and ecological restoration, especially in the arid and semi-arid northwest, the North China Plain, and coastal areas. Due to high salt content, high pH value, and compacted structure, salinized soils severely damage soil fertility and microbial community balance, making it difficult for crops to grow and even leading to the abandonment of arable land, posing a direct threat to national food security. Moreover, with unreasonable irrigation and climate change, secondary salinization problems are still intensifying, making efficient, long-term, and eco-friendly restoration technologies urgently needed.

[0003] To address the aforementioned issues, existing technologies have gradually formed four major technical directions: physical, chemical, biological, and composite improvement. However, each technical route has significant limitations in practical applications, making it difficult to achieve the comprehensive restoration goals of efficient desalination, stable alkali reduction, long-term fertilization, and ecological compatibility. Physical improvement technology was a commonly used method in the early stages, mainly adjusting soil structure through deep plowing, water leaching, or laying isolation layers. Although this technology can improve soil permeability to a certain extent, it requires large amounts of freshwater leaching, which not only consumes a lot of water resources but also easily leaches surface salts to deeper layers, causing secondary salinization. Furthermore, physical improvement alone cannot change the adsorption characteristics of soil colloids for sodium ions, and the restoration effect can only be maintained for 1-2 growth cycles, which is insufficient to meet the needs of long-term agricultural production.

[0004] Chemical remediation technologies achieve rapid reduction of salinity and alkalinity through ion exchange or acid-base neutralization, but these technologies have significant drawbacks: on the one hand, aminated clay, phosphogypsum, and other chemical remediation agents are expensive when used alone, making large-scale application uneconomical; on the other hand, long-term application of some chemical reagents can lead to soil colloid aggregation, which can exacerbate compaction, and the complexes formed with residual heavy metals in the soil may pollute groundwater, posing a significant ecological risk.

[0005] Biological soil improvement technology has become a research hotspot in recent years due to its environmental friendliness and long-term effectiveness. Its core principle is to utilize microbial metabolites (such as organic acids and extracellular polysaccharides) to neutralize alkalinity, improve soil structure, and simultaneously promote the degradation of organic matter. For example, microorganisms such as Streptomyces and Pseudomonas can lower soil pH by secreting organic acids and promote the decomposition of mature organic matter through extracellular enzymes, thereby enhancing soil fertility. However, existing biological soil improvement technologies still face two major bottlenecks: First, the selection of microbial strains is limited. Mainstream strains such as Bacillus subtilis and EM compound bacteria lack sufficient resistance in moderate to severe saline-alkali environments, resulting in low survival rates and difficulty in sustaining metabolic functions. Second, the encapsulation carriers have limited functions and cannot simultaneously provide ion exchange capacity, making it difficult to create a stable microenvironment for microorganisms, leading to the easy loss of microbial metabolites and soil nutrients.

[0006] Composite improvement technologies attempt to integrate the advantages of the above technologies, but existing composite technologies are mostly simple superpositions of single functional components, failing to form multi-component synergy: for example, they lack ion exchange components for active desalination, resulting in long remediation cycles and an inability to maintain soil fertility in the long term. Although simple biological + organic composite systems can increase organic matter content, their desalination efficiency is low, their remediation effect on moderately saline-alkali land is poor, and they are difficult to meet the needs of crop growth.

[0007] In summary, the shortcomings of existing saline-alkali land remediation technologies lie in the lack of a multifunctional material that can integrate salt-tolerant and highly efficient microbial strains, stress-resistant multifunctional carriers, and active ion exchange components. This results in low remediation efficiency, high costs, and a tendency for effects to rebound, failing to create a virtuous cycle of desalination, alkalinity reduction, and fertilization promotion. Therefore, developing a saline-alkali land soil restoration material that can specifically address the above problems, by selecting more salt-tolerant microbial strains, designing multifunctional composite encapsulation carriers, and synergistically incorporating ion exchange and organic fertilization components to achieve efficient, long-lasting, and low-cost remediation goals, has become an urgent need in the field of saline-alkali land management and is of great significance for promoting the sustainable utilization of saline-alkali land resources in my country. Summary of the Invention

[0008] To address the problems of insufficient microbial resistance, limited function of encapsulation carriers, and lack of multi-component synergy in existing saline-alkali land remediation technologies, which lead to low remediation efficiency, high costs, and easy rebound of effects, this invention selects the salt-tolerant Streptomyces loucheri, designs aminated bentonite-sodium alginate composite microspheres as a stress-resistant encapsulation carrier, and coordinates aminated montmorillonite ion exchanger, nano-hydroxyapatite-coated biochar, and decomposed fungal residue, etc., to achieve efficient desalination and alkali reduction of saline-alkali land, improve the survival stability of microbial strains, and provide long-term improvement in soil fertility and structure, ultimately providing an eco-friendly and cost-effective saline-alkali land remediation solution. Specifically, this invention provides the following technical solution.

[0009] First, this invention provides a soil restoration material for saline-alkali land, comprising the following components by weight: 25-35 parts of Streptomyces louchei inoculum encapsulated in aminated bentonite-sodium alginate composite microspheres; 15-25 parts of aminated montmorillonite-sodium alginate composite ion exchanger; 10-20 parts of corn cob biochar coated with nano-hydroxyapatite; 25-35 parts of fermented oyster mushroom residue; 3-5 parts of compound chelating agent; Sodium dodecylbenzenesulfonate (SDBS) 0.5~1.5 parts; The composite chelating agent is ethylenediaminetetraacetic acid-aminotrimethylenephosphonic acid, with a weight ratio of 1:1.

[0010] Furthermore, for the aforementioned saline-alkali soil restoration materials, the viable count of *Streptomyces loucheri* powder used to prepare aminated bentonite-sodium alginate composite microspheres for encapsulating *Streptomyces loucheri* inoculum is ≥1×10⁻⁶. 10 CFU / g.

[0011] Furthermore, for the aforementioned saline-alkali soil restoration materials, the molecular weight of the polyethyleneimine used to prepare aminated bentonite or aminated montmorillonite is 5000~6000.

[0012] Furthermore, for the aforementioned saline-alkali soil restoration materials, the degree of amination of aminated bentonite or aminated montmorillonite is ≥2.0%.

[0013] Furthermore, for the aforementioned saline-alkali soil restoration materials, the corn cob biochar coated with nano-hydroxyapatite has a specific surface area ≥600 m². 2 / g.

[0014] Furthermore, for the aforementioned saline-alkali soil restoration material, the particle size of the nano-hydroxyapatite is 50~100nm.

[0015] Furthermore, for the above-mentioned saline-alkali soil restoration materials, the organic matter content of the decomposed oyster mushroom residue is ≥40%.

[0016] On the other hand, the present invention provides a method for preparing the above-mentioned saline-alkali land soil restoration material, comprising: 1) Preparation of aminated bentonite-sodium alginate composite microspheres for encapsulating Streptomyces loucheri: Preparation of aminated bentonite: 200-400 mesh bentonite was mixed with deionized water to form a suspension. Polyethyleneimine was added, the mixture was stirred and the pH was adjusted to 6.5-7.2. After drying, the mixture was pulverized to 200 mesh to obtain aminated bentonite. 15-25 g of Streptomyces loucheri powder was added to a 4-6% sodium alginate solution and stirred to form a strain-sodium alginate suspension. 25-35 g of the prepared aminated bentonite was added and dispersed to form a strain-sodium alginate-aminated bentonite mixed system. The mixed system was dripped into a calcium chloride solution to solidify and form microspheres with a particle size of 1-2 mm. After drying, the microspheres were obtained. 2) Preparation of aminated montmorillonite-sodium alginate composite ion exchanger: Add 200-400 mesh montmorillonite and polyethyleneimine to deionized water at a weight ratio of 10-15:1, mix and modify, and then dry to obtain aminated montmorillonite; then mix it with sodium alginate at a weight ratio of 2-4:1, suspend it in deionized water, and drop calcium chloride solution into it to form microspheres with a diameter of 2-3 mm. After solidification and drying, the product is obtained. 3) Preparation of corn cob biochar coated with nano-hydroxyapatite: Carbonize corn cob at 750~850℃ for 1~3h, cool and pulverize to obtain biochar; Disperse biochar and nano-hydroxyapatite in 40~60% ethanol at a weight ratio of 4~6:1 using ultrasonication, and dry by rotary evaporation to obtain the final product. 4) Preparation of mature oyster mushroom residue: After crushing the residue, compost it with EM inoculant for 6-8 days, turning the pile once a day during the period. After fermentation, crush it to obtain mature mushroom residue. 5) Preparation of composite chelating agent: Ethylenediaminetetraacetic acid and aminotrimethylenephosphonic acid are mixed evenly in deionized water at a weight ratio of 1:1 and then dried to obtain the final product; 6) Mixed components: The prepared aminated bentonite-sodium alginate composite microspheres containing Streptomyces loucheri inoculant, aminated montmorillonite-sodium alginate composite ion exchanger, nano-hydroxyapatite-coated corn cob biochar, decomposed oyster mushroom residue, composite chelating agent, and sodium dodecylbenzene sulfonate are mixed according to the above proportions to obtain saline-alkali soil restoration material.

[0017] Furthermore, in step 1) of the above method, the solid-liquid ratio of bentonite to deionized water is 1:10~12, and the amount of polyethyleneimine added is 8~12% of the weight of bentonite.

[0018] Furthermore, in step 4) of the above method, the weight ratio of the inoculum residue to the EM inoculum agent is 25-30:1, and the viable count of the EM inoculum agent is ≥1×10⁻⁶. 9 CFU / g; adjust the moisture content to 55-65% before composting.

[0019] Compared with the prior art, the present invention, "a material for restoring saline-alkali land and its preparation method," has the following beneficial effects: 1. Enhance the stress resistance and survival stability of microorganisms to ensure the long-term effectiveness of bioremediation. This invention selects *Streptomyces loucherei*, a species with strong salt tolerance, and uses aminated bentonite-sodium alginate composite microspheres as an encapsulation carrier. Through the synergistic effect of the aminated groups on the carrier and the carboxyl groups on sodium alginate, a synergistic protective microenvironment of salt-alkali buffering, water retention, and nutrient supply is constructed for the bacterial strain. Specifically, the aminated bentonite can neutralize excess OH- in the soil. - The method stabilizes the pH of the microenvironment surrounding the microorganisms at 6.5-7.5, preventing inactivation due to high alkalinity. The composite microspheres have a water-absorbing effect in saline-alkali environments, maintaining the humid environment required for microbial survival, while the degradation products of the carrier provide a carbon source for the microorganisms. The *Streptomyces loucherei* strain of this invention exhibits a 30-day viable cell survival rate of ≥80%, effectively addressing the shortcomings of existing bioremediation technologies, such as insufficient strain resistance and easy attenuation of repair effects, thus ensuring the long-term stable performance of bioremediation.

[0020] 2. Desalination and alkali reduction, with remediation efficiency significantly superior to existing technologies. This invention constructs an active and efficient desalination system through a combination design of microsphere-encapsulated Streptomyces loucheri inoculum, a composite ion exchanger, and nano-hydroxyapatite-coated corn cob biochar. Specifically, the aminated montmorillonite-sodium alginate ion exchanger can be used to exchange amino groups (-NH3) through... + ) and carboxyl group (-COO) - Actively adsorbs Na from the soil + Cl - Harmful ions, etc. Nano-hydroxyapatite-coated corn cob biochar utilizes the porous structure of biochar to provide a living space for microorganisms, combined with the slow-release Ca from nano-hydroxyapatite. 2+ Promote the growth of Na in soil colloids + The replacement of the material was demonstrated in field trials. After 90 days of application of the material of this invention to moderately saline-alkali land, the soil pH dropped to 7.3 and the salt content dropped to 2.6 g / kg, improving desalination efficiency and significantly shortening the remediation cycle. This solved the shortcomings of existing technologies, such as low desalination efficiency and reliance on freshwater leaching.

[0021] 3. Effectively improves soil fertility and nutrient utilization while ensuring ecological safety. This invention introduces a fertilization-safety system using decomposed oyster mushroom residue and an EDTA-ATMP composite chelating agent: On the one hand, the decomposed oyster mushroom residue has a high organic matter content, and its degradation process continuously releases nitrogen, phosphorus, potassium, and trace elements into the soil, while promoting the formation of soil aggregates (reducing soil bulk density); on the other hand, the EDTA-ATMP composite chelating agent can chelate phosphorus (Pb) in the soil. 2+ Cd 2+ It removes heavy metal ions and prevents their migration to crops. Field trials showed that the soil organic matter content in the group using this invention increased from an initial 11.6 g / kg to 17.9 g / kg, significantly higher than the control group, helping to solve the problems of existing chemical amendments easily causing soil compaction and heavy metal pollution risks, as well as the insufficient improvement in fertility of single biological amendments.

[0022] 4. The multi-component system forms a virtuous cycle of desalination, alkali reduction, and fertilization promotion, resulting in outstanding comprehensive restoration effects. This invention achieves synergistic effects through functional complementarity, which is directly reflected in crop growth indicators: In Example 8, the wheat emergence rate of the group of this invention reached 97.6%, the average seedling height was 60.1 cm, and the average root length was 31.3 cm. The crop adaptability is significantly better than the existing compound improvement technology, proving that this invention achieves the simultaneous optimization effect of desalination, alkali reduction and fertilization, and breaks through the bottleneck of the single repair effect of the existing technology.

[0023] 5. It is eco-friendly and cost-controllable, with the potential for large-scale promotion and application. This invention fully considers both economic and ecological aspects in its raw material selection and preparation process: 1) The core carrier (bentonite, sodium alginate), biochar (prepared from corn cobs), and decomposed oyster mushroom residue are all low-cost and readily available raw materials. Corn cobs and oyster mushroom residue are agricultural waste, reducing raw material costs and achieving resource utilization of waste; 2) The preparation process requires no complex equipment. For example, aminated bentonite can be prepared through conventional stirring and drying, and the composite microspheres are solidified by peristaltic pump drip addition, suitable for industrial-scale mass production; 3) No high-risk chemical reagents are used throughout the process, and all components are biodegradable or absorbed by the soil, eliminating the risk of secondary pollution. Sodium dodecylbenzenesulfonate (SDBS) is used in small quantities, is low in cost, and enhances material dispersibility, further improving desalination and alkali reduction efficiency. Compared with existing technologies, this invention has low material costs and avoids the ecological risks of chemical modifiers (such as sulfur and calcium chloride), meeting the needs of large-scale agricultural production and ecological restoration in moderately saline-alkali areas. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Unless otherwise specified, the test methods in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0026] The Streptomyces loucherii mycelium powder described in this invention was purchased from Shandong Jinwanhua Fine Chemical Co., Ltd.

[0027] Example 1 This embodiment describes the preparation of Streptomyces loucheri inoculum encapsulated in aminated bentonite-sodium alginate composite microspheres.

[0028] 1. Preparation of Aminated Bentonite Take 100g of 200-400 mesh bentonite, add 1000mL of deionized water (solid-liquid ratio 1:10), and stir until a suspension is formed; Add 12g of polyethyleneimine (molecular weight 5500), stir at 35℃ and 200rpm for 40min, and adjust the pH to 7.0 with 1mol / L HCl during the process; After drying at 80℃, the material is pulverized to 200 mesh and the degree of amination is measured to be 3.3% (converted from nitrogen content determined by the Kjeldahl method). Aminated bentonite is then obtained and set aside for later use.

[0029] 2. Composite microspheres encapsulating Streptomyces loucherei Pretreatment of mycelial powder: Take Streptomyces loucheri mycelial powder (viable count ≥ 1 × 10⁻⁶) 10 20g of CFU / g was added to 200mL of 5% sodium alginate solution and stirred at 30℃ and 150rpm for 30min to prepare a bacterial-sodium alginate suspension. Composite dispersion: Add 30g of aminated bentonite to the above suspension, and ultrasonically disperse for 20min at 300W to form a uniform mixture of bacteria, sodium alginate, and aminated bentonite. Microsphere molding: The mixture is dripped into a 5% calcium chloride solution using a peristaltic pump and allowed to stand at 30°C for 2 hours to solidify, forming microspheres with a particle size of 1~2 mm; Drying and activation: After filtering the microspheres, dry them at 30°C until the moisture content is ≤10% to obtain the aminated bentonite-sodium alginate composite microsphere encapsulated Streptomyces loucheri inoculum.

[0030] Example 2 This embodiment describes the preparation of an aminated montmorillonite-sodium alginate composite ion exchanger.

[0031] 1. Preparation of Aminated Montmorillonite Take 200-400 mesh montmorillonite and add it to deionized water at a weight ratio of 10:1 with polyethyleneimine (molecular weight 5500). Set the solid-liquid ratio to 1:20, stir at 35℃ and 200 rpm for 40 min, dry at 80℃ and then pulverize to 200 mesh to obtain aminated montmorillonite (degree of amination 3.0%). 2. Composite spheres Aminated montmorillonite and sodium alginate were mixed at a weight ratio of 3:1 and suspended in deionized water to prepare a 5% concentration suspension. The suspension was then dripped into a 5% calcium chloride solution using a peristaltic pump to form microspheres with a diameter of 2-3 mm. The microspheres were allowed to stand at 30°C for 2 hours to solidify, filtered, and then dried at 60°C to obtain an aminated montmorillonite-sodium alginate composite ion exchanger.

[0032] Example 3 This embodiment describes the preparation of corn cob biochar coated with nano-hydroxyapatite.

[0033] 1. Preparation of corn cob biochar Corn cobs were crushed to 1-3 cm and carbonized at 800℃ for 2 hours under a nitrogen atmosphere (heating rate 5℃ / min). After cooling, the carbonized material was crushed to 200 mesh to obtain biochar, with a measured specific surface area of ​​640 m². 2 / g; 2. Nano-coating Biochar and nano-hydroxyapatite (particle size 50~100nm) were added to a 50% ethanol solution at a weight ratio of 5:1, the solid-liquid ratio was set to 1:15, ultrasonically dispersed for 30min, power 300W, and rotary evaporated at 80℃ for 12h to obtain nano-hydroxyapatite-coated corn cob biochar.

[0034] Example 4 This embodiment describes the preparation of fermented oyster mushroom residue.

[0035] Take oyster mushroom residue (crushed to less than 1cm), and add EM inoculant (live count ≥1×10⁻⁶) at a weight ratio of 30:1. 9 The moisture content was adjusted to 60% and composted at 55℃ for 7 days, with the pile turned over once a day during the period. After fermentation, the residue was crushed through an 80-mesh sieve to obtain mature oyster mushroom residue (the organic matter content was measured to be 62%).

[0036] Example 5 This embodiment describes the preparation of a composite chelating agent.

[0037] Ethylenediaminetetraacetic acid (EDTA) and aminotrimethylenephosphonic acid (ATMP) were dissolved in an appropriate amount of deionized water at a weight ratio of 1:1. The mixture was stirred at 35°C and 200 rpm for 40 minutes to ensure uniform mixing. After drying at 80°C, the mixture was pulverized to obtain a composite chelating agent (EDTA-ATMP).

[0038] Example 6 This embodiment describes the preparation of the saline-alkali land soil restoration material.

[0039] 300g of *Streptomyces loucherii* inoculant prepared in Example 1 (ammonia-sodium alginate composite microspheres), 200g of ammonium montmorillonite-sodium alginate composite ion exchanger prepared in Example 2, 150g of corn cob biochar coated with nano-hydroxyapatite prepared in Example 3, 300g of decomposed oyster mushroom residue prepared in Example 4, 40g of composite chelating agent prepared in Example 5, and 10g of SDBS were added to a double-helix mixer and stirred at 32℃ and 300rpm for 30min to obtain a grayish-brown powdery saline-alkali soil restoration material (overall moisture content ≤8%).

[0040] Example 7 This embodiment describes the survival rate test of the saline-alkali land soil restoration material at room temperature.

[0041] 1. Test Methods Take 30g of the embedded bacterial agent and dispense it into 3 sterile wide-mouth bottles (10g / bottle). Seal the bottle opening with breathable gauze (to avoid oxygen deficiency caused by sealing). Store in a room temperature incubator (25±1℃, relative humidity 50±5%). Take samples for testing at 0 days (initial), 15 days and 30 days of storage.

[0042] At each time point, 1g of the encapsulated bacterial agent was taken, added to 9mL of sterile physiological saline, and the microspheres were ground and broken (ensuring complete dispersion of the microspheres) to prepare 10... -1 Diluent; Serial dilution: Same as step 1, dilute to 10. -6 10 -7 10 -8 Concentration gradient; (3) Spread culture: Take 0.1 mL of diluted solution and spread it on Gao's No. 1 medium (formula: soluble starch 20 g / L, KNO3 1 g / L, K2HPO4・3H2O 0.5 g / L, MgSO4・7H2O 0.5 g / L, NaCl 0.5 g / L, FeSO4・7H2O 0.01 g / L, pH 7.2~7.4, sterilized at 121℃ for 20 min) plates, repeat 3 times, incubate at 30℃ for 7 days, and count the number of colonies.

[0043] Calculate the survival rate: Viable bacterial survival rate (%) = (Number of viable bacteria after storage / Number of viable bacteria after 0 days of storage) × 100% 2. Test Results The experimental results are shown in Table 1.

[0044] Table 1. Results of Survival Rate Measurement at Room Temperature

[0045] As shown in Table 1, the initial viable count of the bacterial powder in the saline-alkali soil restoration material was 6.2 × 10⁻⁶. 9 The CFU / g count was 4.7 × 10⁻⁶ after storage at room temperature (25±1℃) for 30 days. 9 The CFU / g survival rate reached 81.0%, ≥80%, indicating that the encapsulation technology described in this invention can effectively improve the stability of the strains during room temperature storage and solve the problems of short storage period and rapid activity decay of microbial agents in the prior art.

[0046] Example 8 This embodiment describes the field application effect of the saline-alkali land soil restoration material.

[0047] 1. Basic preparation for the experiment 1) Selection and division of experimental sites Experimental site selection: moderately saline-alkali land in Hekou District, Dongying City, Shandong Province. The soil type in this area is coastal saline soil.

[0048] Experimental plot area and division: A randomized block design was adopted, divided into 3 treatment groups, each with 3 replicate plots, and each plot area was 20m². 2 (4m×5m), with a 0.5m wide isolation ditch set between the small sections (to prevent moisture from crossing with the repair materials).

[0049] 2) Test materials Tested remediation material: The saline-alkali soil remediation material prepared in this invention was applied at a rate of 60 kg / mu (i.e., 1.8 kg / 20 m²). 2 (Community) preparation.

[0050] Reference material: The composite repair agent of CN106590684A was prepared according to Example 3.

[0051] The tested crop was the salt-tolerant wheat variety "Hangmai 802".

[0052] 3) Experimental grouping Control group: No repair materials were applied, only regular irrigation was performed, repeated 3 times, as a baseline reference; Control group: The control material repair agent was applied at a rate of 12 kg / mu (0.36 kg / 20m²). 2 In the small plot, till the soil to a depth of 20cm, irrigate as usual, and repeat 3 times; The invention group: Apply the repair material of this invention, till the soil to a depth of 20cm, irrigate as usual, and repeat 3 times.

[0053] 2. Test Procedure 1) Application of repair materials (Day 0) Application time: 10 days before wheat sowing (late March in spring, when the average daily temperature is 10-15℃, to avoid low temperature affecting microbial activity); Application method: Spread the remediation materials of each treatment group evenly on the surface of the plot, and use a small rotary tiller to till to a depth of 20cm to fully mix the remediation materials with the soil.

[0054] 2) Irrigation and field management (entire experiment) Irrigation Management: Day 1 after application: Irrigation water volume 1.5m³ 3 / 20m 2 In the community, ensure that the soil moisture content reaches 70% of field capacity to avoid loss of remediation materials and at the same time activate microbial activity; Irrigate once every 15 days thereafter, with each irrigation volume being 0.9m³. 3 / 20m 2 In residential areas, measures should be taken to prevent soil salinization caused by drought.

[0055] Crop planting: Sow wheat on the 10th day after application, at a seeding rate of 15 kg / mu (i.e., 0.45 kg / 20m²). 2 (In small plots), manual row sowing was carried out, ensuring that the sowing depth was 4±1cm.

[0056] Field management: Throughout the experiment, all groups underwent normal water and fertilizer management, manual weeding, and no diseases or pests occurred.

[0057] 3) Sample collection time Three sampling time points were set up, and soil samples from 0 to 20 cm were collected at each time point using a five-point sampling method: Time Point 1: Day 0, before applying remediation materials, initial soil samples were collected to determine basic physicochemical properties, including: pH (9.2), salinity (7.8 g / kg), organic matter content (11.6 g / kg), and soil bulk density (1.52 g / cm³). 3 ); Time point 2: Day 30, 30 days after the application of the remediation material, the short-term desalination effect of the present invention group was measured, including: pH (8.1), salt content (3.9 g / kg), organic matter content (16.3 g / kg), and soil bulk density (1.44 g / cm³). 3 ); Time point 3: Day 90, 90 days after the application of the repair material, i.e., the wheat seedling stage, to measure the long-term repair effect of each group (all indicators and crop growth indicators, see Table 2).

[0058] Sample processing procedure: Remove stones, roots, and other impurities from the collected fresh soil sample and divide it into two portions: Part 1 (approximately 500g): Air dry naturally to constant weight, grind and pass through a 10-mesh sieve (for bulk density and organic matter determination) and a 100-mesh sieve (for pH and salinity determination). Part 2 (approximately 200g): Store at 4°C for microbial viability determination (time points 2 and 3 only).

[0059] 3. Indicator Testing Methods 1) Soil pH value determination: Refer to NY / T 1121.2-2006, each sample is repeated 3 times, and the average value is taken.

[0060] 2) Soil salinity determination: Refer to NY / T 1121.16-2006, each sample is repeated 3 times, and the average value is taken.

[0061] 3) Determination of soil organic matter content: Refer to NY / T 1121.6-2006, repeat each sample 3 times, and take the average value.

[0062] 4) Soil bulk density determination: Refer to NY / T 1121.4-2006, repeat 3 times for each sample, and take the average value.

[0063] 5) Streptomyces loucherii activity test: Weigh 10.00g of fresh soil sample refrigerated at 4℃, add 90mL of sterile physiological saline (0.85% NaCl), shake for 30min (200rpm), and prepare 10 -1 Diluent; serially diluted to 10 -6 10 -7 10 -8Spread 0.1 mL of the diluted solution onto Gao's No. 1 medium; incubate at 30℃ for 7 days, count the colonies of *Streptomyces louchei*, and calculate the viable count using the formula: Viable bacteria count (CFU / g) = colony count × dilution factor / coating volume (L); each sample was repeated 3 times and the average value was taken.

[0064] 6) Crop growth index test (Day 90) Emergence rate: Test method: Avoiding the edge of the plot, select 3 1m seedlings in each plot. 2 For quadrats, count the actual number of seedlings that emerge within the quadrats and calculate the emergence rate using the formula: Emergence rate (%) = (Actual number of seedlings / Theoretical number of seedlings) × 100%, where: Theoretical number of seedlings = Quadrat area × Sowing density; Average seedling height: 10 wheat plants were randomly selected from each quadrat, and the height from the ground surface to the top of the plant was measured with a ruler (accurate to 0.1 cm), and the average value was taken; Average root length: The selected 10 wheat plants were dug up whole, the roots were washed to remove soil, and the length of the main root was measured with a ruler (accurate to 0.1cm). The average value was taken.

[0065] 4. Test Results The results of Day 90 are shown in Table 2.

[0066] Table 2. Test results of each group of indicators

[0067] As shown in Table 2, the restoration effect of the present invention on moderately saline-alkali land is significantly better than that of the blank group and the control group in terms of desalination and alkali reduction, soil structure optimization, fertility improvement, maintenance of microbial activity and crop adaptability.

[0068] Regarding the core desalination and alkali reduction effects, the soil pH in the group treated with this invention decreased to 7.3, and the salt content was 2.6 g / kg, indicating that the ion exchange of the aminated carrier improved the soil's physicochemical properties and was more efficient than existing chemical-biological composite desalination technologies. In terms of the synergistic improvement of soil structure and fertility, the soil bulk density in the group treated with this invention decreased to 1.31 g / cm³. 3 The organic matter content reached 17.9 g / kg, confirming that the composting of mature oyster mushroom residue combined with microbial extracellular metabolites promotes aggregation, thereby improving structure and enhancing fertility. Regarding microbial activity, the viable count of *Streptomyces loucherei* in this invention group was 1.2 × 10⁻⁶. 9 With CFU / g, wheat emergence rate reached 97.6%, average seedling height was 60.1 cm, and root length was 31.3 cm, showing a significant improvement. This demonstrates that the stress-resistant encapsulation carrier and the synergistic effect of multiple components can ensure the long-term effect of microorganisms, achieving a technological advancement in remediation from simple desalination to promoting crop growth.

[0069] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art through related deductions and substitutions based on the inventive concept, without inventive effort, are within the scope of protection of the present invention.

Claims

1. A soil restoration material for saline-alkali land, characterized in that, Based on parts by mass, it includes the following components: 25-35 parts of Streptomyces louchei inoculum encapsulated in aminated bentonite-sodium alginate composite microspheres; 15-25 parts of aminated montmorillonite-sodium alginate composite ion exchanger; 10-20 parts of corn cob biochar coated with nano-hydroxyapatite; 25-35 parts of fermented oyster mushroom residue; 3-5 parts of compound chelating agent; Sodium dodecylbenzenesulfonate 0.5~1.5 parts; The composite chelating agent is ethylenediaminetetraacetic acid-aminotrimethylenephosphonic acid, with a weight ratio of 1:

1.

2. The soil restoration material for saline-alkali land according to claim 1, characterized in that, The viable count of *Streptomyces loucheretia* powder used in the preparation of aminated bentonite-sodium alginate composite microspheres for encapsulating *Streptomyces loucheretia* is ≥1×10⁻⁶. 10 CFU / g.

3. The soil restoration material for saline-alkali land according to claim 1, characterized in that, The molecular weight of the polyethyleneimine used to prepare aminated bentonite or aminated montmorillonite is 5000-6000.

4. The soil restoration material for saline-alkali land according to claim 1, characterized in that, The degree of amination of aminated bentonite or aminated montmorillonite is ≥2.0%.

5. The soil restoration material for saline-alkali land according to claim 1, characterized in that, The corn cob biochar coated with nano-hydroxyapatite has a specific surface area ≥600 m². 2 / g.

6. The soil restoration material for saline-alkali land according to claim 1, characterized in that, The particle size of the nano-hydroxyapatite is 50~100nm.

7. The soil restoration material for saline-alkali land according to claim 1, characterized in that, The organic matter content of the fermented oyster mushroom residue is ≥40%.

8. A method for preparing a saline-alkali land soil restoration material as described in any one of claims 1 to 7, characterized in that, include: 1) Preparation of aminated bentonite-sodium alginate composite microspheres for encapsulating Streptomyces loucheri: Preparation of aminated bentonite: 200-400 mesh bentonite was mixed with deionized water to form a suspension. Polyethyleneimine was added, the mixture was stirred and the pH was adjusted to 6.5-7.

2. After drying, the mixture was pulverized to 200 mesh to obtain aminated bentonite. 15-25 g of Streptomyces loucheri powder was added to a 4-6% sodium alginate solution and stirred to form a strain-sodium alginate suspension. 25-35 g of the prepared aminated bentonite was added and dispersed to form a strain-sodium alginate-aminated bentonite mixed system. The mixed system was dripped into a calcium chloride solution to solidify and form microspheres with a particle size of 1-2 mm. After drying, the microspheres were obtained. 2) Preparation of aminated montmorillonite-sodium alginate composite ion exchanger: Add 200-400 mesh montmorillonite and polyethyleneimine to deionized water at a weight ratio of 10-15:1, mix and modify, and then dry to obtain aminated montmorillonite; then mix it with sodium alginate at a weight ratio of 2-4:1, suspend it in deionized water, and drop calcium chloride solution into it to form microspheres with a diameter of 2-3 mm. After solidification and drying, the product is obtained. 3) Preparation of corn cob biochar coated with nano-hydroxyapatite: Carbonize corn cob at 750~850℃ for 1~3h, cool and pulverize to obtain biochar; Disperse biochar and nano-hydroxyapatite in 40~60% ethanol at a weight ratio of 4~6:1 using ultrasonication, and dry by rotary evaporation to obtain the final product. 4) Preparation of mature oyster mushroom residue: After crushing the residue, compost it with EM inoculant for 6-8 days, turning the pile once a day during the period. After fermentation, crush it to obtain mature mushroom residue. 5) Preparation of composite chelating agent: Ethylenediaminetetraacetic acid and aminotrimethylenephosphonic acid are mixed evenly in deionized water at a weight ratio of 1:1 and then dried to obtain the final product; 6) Mixed components: The prepared aminated bentonite-sodium alginate composite microspheres containing Streptomyces loucheri inoculant, aminated montmorillonite-sodium alginate composite ion exchanger, nano-hydroxyapatite-coated corn cob biochar, decomposed oyster mushroom residue, composite chelating agent, and sodium dodecylbenzene sulfonate are mixed according to the proportions in claim 1 to obtain saline-alkali soil restoration material.

9. The preparation method according to claim 8, characterized in that, In step 1), the solid-liquid ratio of bentonite to deionized water is 1:10~12, and the amount of polyethyleneimine added is 8~12% of the weight of bentonite.

10. The preparation method according to claim 8, characterized in that, In step 4), the weight ratio of the inoculum residue to the EM inoculum is 25-30:1, and the viable count of the EM inoculum is ≥1×10⁻⁶. 9 CFU / g; adjust the moisture content to 55-65% before composting.

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