Composite improvement material for ecological restoration of saline-alkali land in plain area and preparation method thereof

Abstract

The application discloses a composite improvement material for ecological restoration of saline-alkali soil in plain areas and a preparation method thereof, belongs to the technical field of soil ecological restoration, and aims to solve the technical defects of poor adaptability, weak synergistic effect, easy salt return, repeated data parameters and existing technologies, and inability to meet the ecological restoration requirements of saline-alkali soil in plain areas. The preparation method comprises four steps of raw material pretreatment, grading mixing, post-treatment and quality detection, and is simple, controllable and free of three wastes. The application precisely adapts to the regional characteristics of saline-alkali soil in plain areas, all data parameters and calculation formulas avoid the existing technologies, realizes the synergistic promotion of desalination, alkali reduction, soil structure improvement and microbial community restoration, has stable and long-lasting improvement effect, has high utilization rate of active ingredients, is suitable for large-scale production and popularization and application, and can effectively realize long-term stable ecological restoration of saline-alkali soil in plain areas.

Description

Technical Field

[0001] This invention belongs to the field of soil ecological restoration technology, specifically relating to composite improvement materials for ecological restoration of saline-alkali land in plain areas and their preparation methods. It is applicable to soil desalination, alkali reduction, structural improvement and ecological restoration of mild, moderate and severe saline-alkali land in plain areas. It is particularly suitable for the regional characteristics of plain areas, such as shallow groundwater level, easy salt accumulation, severe soil compaction and weak ecological carrying capacity. It can achieve the synergistic promotion of soil physicochemical property optimization and vegetation community reconstruction, and avoid the technical defects of existing technologies, such as single improvement effect, poor synergy, easy salt return and high cost. Background Technology

[0002] Saline-alkali land in plains areas is mostly distributed in alluvial plains, coastal plains, and inland basin plains. The landform type belongs to the floodplain of the North China Plain and northwestern Shandong. It is influenced by natural factors such as flat terrain, shallow groundwater level (usually 0.5-3.0m), evaporation exceeding precipitation, and strong soil capillary action, as well as human factors such as unreasonable irrigation and extensive farming practices. The soil contains soluble salts (mainly...) , , , The accumulation of pollutants leads to an increase in soil pH, bulk density, and porosity, resulting in soil compaction, poor aeration, and a decline in water and fertilizer retention capacity. This, in turn, inhibits plant root growth, damages soil microbial community structure, and causes a decline in land productivity and ecological degradation, becoming a major bottleneck restricting the sustainable development of agriculture and ecological protection in plain areas.

[0003] Currently, saline-alkali land improvement technologies are mainly divided into four categories: physical improvement, chemical improvement, biological improvement, and composite improvement. Physical improvement (such as deep plowing, leaching, and mulching) can reduce surface salinity in the short term, but it involves large-scale engineering and water consumption, and cannot fundamentally solve the problems of soil alkalinity reduction and structural improvement, and is prone to secondary salinization. Chemical improvement (such as the application of gypsum, desulfurized gypsum, humic acid, etc.) can alleviate the harm of salinity through ion replacement or acid-base neutralization, but existing chemical improvement materials often have problems such as unreasonable component matching, weak synergistic effect, and short-term improvement effect. Some materials can also cause secondary soil pollution, and their specific adaptability to the plains with surface salt accumulation and shallow groundwater levels is poor. Biological improvement (such as planting salt-tolerant plants and applying microbial agents) is ecological and environmentally friendly, but the improvement cycle is long and the effect is slow, making it difficult to meet the needs of rapid ecological restoration of saline-alkali land in plains.

[0004] Existing composite soil amendment materials are mostly general-purpose and do not fully consider the regional characteristics of saline-alkali land in plains areas. They either focus on desalination while neglecting alkali reduction and soil structure improvement, or focus on chemical improvement while neglecting ecological compatibility. Furthermore, they suffer from drawbacks such as component redundancy, complex preparation processes, data parameters that overlap with existing technologies, and unstable improvement effects. They cannot achieve the synergistic effect of desalination, alkali reduction, soil structure improvement, soil fertility enhancement, and microbial community restoration, making it difficult to achieve the goal of long-term stable ecological restoration of saline-alkali land in plains areas. In addition, in existing preparation methods, insufficient raw material pretreatment, uneven mixing, and unreasonable control of reaction conditions lead to low utilization rates of active ingredients and unstable performance of the amendment materials, further affecting the improvement effect.

[0005] Therefore, given the specific characteristics of saline-alkali land in plain areas, developing a composite improvement material and its preparation method that is rationally composed, has no redundant components, exhibits significant synergistic effects, has a simple preparation process, stable performance, avoids the defects of existing technologies, and meets licensing requirements, and that integrates soil desalination, alkali reduction, structural improvement, and ecological restoration, has important practical significance and application value. Summary of the Invention

[0006] To address the shortcomings of existing composite improvement materials, such as poor adaptability, weak synergistic effects, easy salinization, unreasonable preparation processes, and data parameters that overlap with existing technologies, thus failing to meet the needs of ecological restoration of saline-alkali land in plain areas, this invention provides a composite improvement material for ecological restoration of saline-alkali land in plain areas and its preparation method. This composite improvement material has a simple composition with no additional components, can accurately adapt to the regional characteristics of saline-alkali land in plain areas, and achieves synergistic effects of desalination, alkali reduction, soil structure improvement, soil fertility enhancement, and microbial community restoration. The preparation process is simple, controllable, and has stable performance.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: a composite improvement material for ecological restoration of saline-alkali land in plain areas and its preparation method, characterized in that it is composed of the following raw materials in parts by weight, without any additional additives: 110-130 parts of modified desulfurized gypsum powder, 38-42 parts of potassium humate, 38-42 parts of biochar, 26-30 parts of oxalamide, 5.5-6.5 parts of polyglutamic acid, 1.2-1.6 parts of powdered composite microbial agent, and 1.2-1.6 parts of diatomaceous earth powder; The modified desulfurized gypsum powder is prepared using a citric acid-aluminum ion composite modification process. The preparation process involves: pulverizing the raw desulfurized gypsum ore, passing it through a 120-mesh sieve to remove impurities, adding 12-15% (by mass) of citric acid solution (concentration 1.8-2.2 mol / L) and 8-10% (by mass) of aluminum sulfate solution (concentration 0.9-1.1 mol / L), and stirring at a constant temperature of 48-52℃ for 3.8-4.2 hours. After the reaction, centrifuge to dehydrate (speed 3200-3400 r / min, time 18-22 min), drying the precipitate at 105-115℃ until the moisture content is ≤2.0%, pulverizing again, and passing it through a 150-mesh sieve to obtain the modified desulfurized gypsum powder. The modified desulfurized gypsum powder has a calcium ion dissolution rate ≥88%, a particle size ≤100 μm, and a specific surface area of ​​380-420 m² / g. The potassium humate has a particle size ≤85μm, a purity ≥98.5%, and a carboxyl group ( ) content ≥8.2mmol / g, hydroxyl ( The content is ≥5.8mmol / g, the pH value is 5.2-5.6, and it is sieved through a 100-mesh sieve after being pulverized; The biochar is prepared by staged pyrolysis of corn stalks under anaerobic conditions. The pyrolysis process is as follows: first, the corn stalks are crushed and dried to a moisture content ≤3.0%; then, under nitrogen protection, the temperature is increased from room temperature to 320-340℃ at a rate of 8-10℃ / min and held at this temperature for 1.8-2.2 hours; next, the temperature is increased to 580-620℃ at a rate of 6-8℃ / min and held at this temperature for 2.8-3.2 hours; after cooling to room temperature, the biochar is crushed and passed through a 100-mesh sieve. The biochar has a pH value of 7.8-8.2, a specific surface area of ​​480-520 m² / g, and a porosity of 58-62%. The oxalamide has a purity of ≥98.0%, a nitrogen content of ≥32.5%, and a particle size of ≤95μm. After being pulverized, it passes through a 110-mesh sieve. The polyglutamic acid has a purity of ≥94.0%, a molecular weight of 1.6-1.8 million Daltons, and a particle size of ≤90μm; The powdered compound bacterial agent is prepared by aseptically mixing Bacillus mucilaginosus and Bacillus laterosporus brevis in a mass ratio of 7:3, wherein the effective viable count of Bacillus mucilaginosus is ≥2.8×10⁻⁶. 9 CFU / g, effective viable count of Bacillus laterosporus brevis ≥2.8 × 10⁻⁶ 9 cfu / g; the powdered compound bacterial agent and diatomaceous earth powder are mixed evenly at a mass ratio of 1:1, and the effective viable bacteria count after mixing is ≥1.4×10⁻⁶. 9 cfu / g; The diatomaceous earth powder has a particle size ≤80μm, a specific surface area of ​​280-320m² / g, and a porosity of 68-72%. The particle size of each solid raw material in the composite modified material is ≤100μm, its pH value is 6.2-6.6, its bulk density is 0.88-0.92g / cm³, its porosity is 52-56%, and its cation exchange capacity is 28-32cmol / kg. The desalination rate, alkali reduction rate, soil aggregate stability, and microbial diversity improvement rate of the composite improvement material meet the calculation requirements of the following formulas, and the relevant indicators meet the standards: Soil desalination rate calculation formula: ,in Soil desalination rate (%) The soluble salt content (g / kg) in the topsoil layer (0-20cm) before improvement. To improve Soluble salt content (g / kg) in the topsoil layer (0-20cm) of Tianhou soil. This is the desalination correction factor (with a value range of 1.02-1.06). To improve the number of days; the soil desalination rate should be ≥58% after 30 days, ≥72% after 60 days, and ≥82% after 90 days; Formula for calculating soil alkalinity reduction rate: ,in Soil alkalinity reduction rate (%) To improve the soil pH level before, To improve Soil pH value after the moon The soil alkali reduction correction coefficient (range 1.03-1.07) is used; the soil alkali reduction rate is ≥48% after 30 days, ≥62% after 60 days, and ≥76% after 90 days. Formula for calculating soil aggregate stability: ,in Soil water-stable aggregate content (%) The mass (g) of water-stable aggregates with a particle size ≥ 0.25 mm. The mass (g) of water-stable aggregates with a particle size of 0.053-0.25 mm. The total mass (g) of the soil sample. The aggregate correction factor (range 1.01-1.05) indicates that the soil water-stable aggregate content is ≥48% 90 days after application. Formula for calculating the rate of improvement in microbial diversity: ,in The percentage increase in soil microbial diversity. The soil microbial diversity index before improvement. To improve Soil microbial diversity index, The microbial correction factor (range 1.04-1.08) shows that the soil microbial diversity increased by ≥148% 90 days after application.

[0008] Furthermore, the modified desulfurized gypsum powder comprises 115-125 parts by weight, potassium humate comprises 39-41 parts by weight, biochar comprises 39-41 parts by weight, oxamide comprises 27-29 parts by weight, polyglutamic acid comprises 5.8-6.2 parts by weight, powdered composite microbial agent comprises 1.3-1.5 parts by weight, and diatomaceous earth powder comprises 1.3-1.5 parts by weight; the calcium ion dissolution rate of the modified desulfurized gypsum powder is 89-91%, and the specific surface area is... The specific surface area of ​​the biochar is 490-410 m² / g, and its porosity is 59-61%. The nitrogen content of the oxalamide is 32.8-33.2%. The molecular weight of the polyglutamic acid is 1.65-1.75 million Daltons. The effective viable bacteria count after mixing the powdered compound bacterial agent with diatomaceous earth powder is 1.5-1.7 × 10⁻⁶ m² / g. 9 The specific surface area of ​​the diatomaceous earth powder is 290-310 m² / g, and the porosity is 69-71%. The pH value of the composite modified material is 6.3-6.5, the bulk density is 0.89-0.91 g / cm³, the porosity is 53-55%, and the cation exchange capacity is 29-31 cmol / kg.

[0009] Furthermore, the modified desulfurized gypsum powder has a citric acid solution concentration of 1.9-2.1 mol / L and is added at 13-14% of its mass; an aluminum sulfate solution concentration of 0.95-1.05 mol / L and is added at 8.5-9.5% of its mass; a constant temperature stirring reaction temperature of 49-51℃ and a reaction time of 3.9-4.1 h; a centrifugal dehydration speed of 3250-3350 r / min and a dehydration time of 19-21 min; a drying temperature of 108-112℃ and a moisture content of 1.5-1.8% after drying; and after further pulverization, it passes through a 150-mesh sieve with a particle size of 80-100 μm. The modified desulfurized gypsum powder has a calcium sulfate content ≥98.5%, an impurity content ≤1.5%, and is free of toxic and harmful impurities.

[0010] Furthermore, the moisture content of the corn stalks used for pretreatment in the biochar is 2.0-2.5%; the heating rate under nitrogen protection is 8.5-9.5℃ / min in the first stage, heating to 325-335℃, and the isothermal pyrolysis time is 1.9-2.1h; the second stage is 6.5-7.5℃ / min, heating to 590-610℃, and the isothermal pyrolysis time is 2.9-3.1h; the particle size after cooling to room temperature is 80-100μm, and the residue content after passing through a 100-mesh sieve is ≤0.3%; the biochar has a fixed carbon content ≥78%, an ash content ≤12%, a volatile matter content ≤10%, and no obvious mechanical impurities.

[0011] Furthermore, in the powdered compound bacterial agent, both *Bacillus mucilaginosus* and *Bacillus laterosporus* are activated strains. The activation process is as follows: the two strains are inoculated separately into LB medium and cultured with shaking at 32-36℃ and 180-220 r / min for 24-28 h to obtain activated strains. The effective viable count of the activated strains is ≥3.0 × 10⁻⁶. 9 The aseptic mixing process is carried out in a sterile operating table at a temperature of 20-24℃ and a humidity of 48-52%, with a colony count of ≤10 cfu / m³. The mixing time is 25-35 min, and the mixing uniformity is ≥99.5%. The moisture content of the powdered compound bacterial agent is ≤5.0%, the storage temperature is 15-25℃, and the shelf life is 6 months.

[0012] Furthermore, the desalination correction coefficient K1 of the composite amendment is 1.03-1.05, the alkali reduction correction coefficient K2 is 1.04-1.06, the aggregate correction coefficient K3 is 1.02-1.04, and the microbial correction coefficient K4 is 1.05-1.07. 30 days after application, the soil desalination rate is 59-61%, and the soil alkali reduction rate is 49-51%. 60 days after application, the soil desalination rate is 73-75%, and the soil alkali reduction rate is 63-65%. %%; 90 days after application, the soil desalination rate was 83-85%, the soil alkalinity reduction rate was 77-79%, the soil water-stable aggregate content was 49-51%, and the soil microbial diversity improvement rate was 150-155%; after improvement, the soluble salt content of the topsoil (0-20cm) was ≤2.5g / kg, the pH value was 7.2-7.8, the bulk density was 1.15-1.25g / cm³, and the porosity was 45-50%, meeting the growth needs of crops and herbaceous plants in plain areas.

[0013] Furthermore, the specific steps include: Step 1: Raw material pretreatment Modified desulfurized gypsum powder, potassium humate, biochar, oxamide, polyglutamic acid, powdered composite microbial agent, and diatomaceous earth powder were pretreated separately. The modified desulfurized gypsum powder was prepared in advance according to the preparation process described in claim 1 and tested to ensure it passed inspection before use. Potassium humate, oxamide, and polyglutamic acid were pulverized, sieved through corresponding mesh sizes to remove impurities, dried at 85-95℃ until the moisture content was ≤2.5%, and cooled to room temperature before use. Biochar was prepared according to the pyrolysis process described in claim 1 and tested to ensure it passed inspection before use. The powdered composite microbial agent and diatomaceous earth powder were mixed evenly at a mass ratio of 1:1, sealed under sterile conditions, and stored at an ambient temperature of 18-22℃ and a humidity of 45-55%. All pretreated raw materials underwent parameter testing, and only those that passed the testing were used in subsequent mixing steps; unqualified raw materials were prohibited from use. Step 2: Graded Mixing The graded mixing process is adopted, and the specific operation is as follows: First-stage mixing: The pretreated potassium humate, biochar, and oxamide are added to a twin-screw mixer. The mixer speed is adjusted to 280-320 r / min, the mixing temperature to 28-32℃, and the mixing time to 28-32 min, yielding the first mixture. The mixing uniformity is ≥98.5%. The formula for calculating mixing uniformity is: ,in Mixing uniformity (%) The standard deviation of the content of each component in the mixture. This represents the average content of each component in the mixture. Second-stage mixing: The pretreated modified desulfurized gypsum powder and polyglutamic acid are added to the first mixture. The mixer speed is adjusted to 380-420 r / min, the mixing temperature to 25-29℃, and the mixing time to 38-42 min to obtain the second mixture; the mixing uniformity is ≥98.5%. Third-stage mixing: The mixture of pretreated powdered compound microbial agent and diatomaceous earth powder is slowly added to the second mixture. The mixer speed is adjusted to 180-220 r / min, the mixing temperature is 18-22℃, and the mixing time is 48-52 min to obtain the crude composite modified material. The mixing uniformity is ≥99.0%. The temperature is monitored in real time during the mixing process to avoid the microbial agent from being deactivated due to excessive temperature. Step 3: Post-processing The crude composite modified material obtained in step 2 is crushed and passed through a 150-mesh sieve to remove coarse particulate impurities, with the content of coarse particulate impurities ≤0.5%. Then, it is sent to a low-temperature drying equipment and dried at 45-55℃ until the moisture content is ≤2.0% for 1.8-2.2 hours. After drying, it is cooled to room temperature (20-25℃) and parameters are tested. The test indicators include pH value, bulk density, porosity, cation exchange capacity, particle size distribution, number of viable bacteria, content of each component, desalination rate, and alkali reduction rate. After passing the test, it is sealed and packaged. Step 4: Quality Inspection Sampling and testing of the packaged composite modified materials shall be carried out at a sampling rate of 0.5% of each batch of products, with no less than 3 samples per batch. The testing items shall be the same as those in step 3. Only products that pass all tests shall be allowed to leave the factory. If there are any unqualified products, they shall be remixed and reprocessed until they pass the tests.

[0014] Further, in step 1, the drying temperature of potassium humate, oxalamide, and polyglutamic acid is 88-92℃, the drying time is 2.5-3.5h, and the moisture content after drying is 1.8-2.2%; after pulverization, potassium humate is passed through a 100-mesh sieve, oxalamide through a 110-mesh sieve, and polyglutamic acid through a 100-mesh sieve, and the content of residue on the sieve is ≤0.3%; the method for preparing the sterile environment is as follows: the operating table and surrounding environment are disinfected with ultraviolet light for 30-40min, followed by ventilation for 10-15min, and the mixing operation is carried out after the sterile environment is tested and found to meet the standards; the mixing time of the powdered compound bacterial agent and diatomaceous earth powder is 25-35min, the mixing speed is 120-140r / min, and the mixing uniformity is ≥99.5%.

[0015] Furthermore, in step 2, the first-stage mixing speed is 290-310 r / min, the mixing temperature is 29-31℃, the mixing time is 29-31 min, and the mixing uniformity is 98.8-99.2%; the second-stage mixing speed is 390-410 r / min, the mixing temperature is 26-28℃, the mixing time is 39-41 min, and the mixing uniformity is 98.8-99.2%; the third-stage mixing speed is 190-210 r / min, the mixing temperature is 19-21℃, the mixing time is 49-51 min, and the mixing uniformity is 99.2-99.6%; the stirring paddle speed of the double-helix mixer is adjustable from 0-500 r / min, the mixing chamber temperature is adjustable from 0-50℃, the mixing chamber has good sealing performance, and there is no dust leakage.

[0016] Further, in step 3, the crude composite modified material is pulverized at a speed of 2800-3200 r / min for 18-22 min, and then passed through a 150-mesh sieve with a particle size of 70-100 μm and a residue content of ≤0.3%. The low-temperature drying equipment operates at a temperature of 48-52℃ for 1.9-2.1 h, resulting in a moisture content of 1.5-1.8%. The sealed packaging uses breathable but waterproof non-woven fabric bags with a thickness of 0.12-0.15 mm, each weighing 25 kg. The product can be packaged in kilograms or 50 kg, with the product name, components, dosage, shelf life, and storage conditions clearly marked on the packaging. Storage conditions include a cool, dry, and well-ventilated area at a temperature of 15-25°C and a humidity of 40-60%, avoiding direct sunlight and high-temperature, high-humidity environments. The shelf life is 12 months. The preparation cycle of the method is 3-5 days, and each batch can produce 50-80 tons of composite modified material. No waste gas, wastewater, or waste residue is emitted during the preparation process. The utilization rate of the active ingredients in the composite modified material is ≥92%, calculated using the following formula: ,in The percentage represents the utilization rate of the active ingredient. The total content of active ingredients in the raw materials (g / kg). The total content of active ingredients (g / kg) in the composite modified material after preparation. This is a utilization rate correction factor (with a value range of 1.01-1.03).

[0017] This invention provides a composite amendment material for ecological restoration of saline-alkali land in plain areas and its preparation method, which has the following beneficial effects: With strong regional adaptability, it is precisely targeted at the regional characteristics of saline-alkali land in plains, such as shallow groundwater levels, easy salt accumulation on the surface, and severe soil compaction. Through precise component matching and parameter optimization, it achieves synergistic effects of desalination, alkali reduction, soil structure improvement, soil fertility enhancement, and microbial community restoration, avoiding the shortcomings of poor adaptability of existing general-purpose soil amendment materials. After application, the amendment material can quickly reduce surface soil salinity and pH value, while breaking up soil compaction, improving soil water and fertilizer retention capacity, creating a suitable environment for plant growth and microbial reproduction, and solving the technical problems of poor ecological restoration effect and easy salt return in saline-alkali land in plains.

[0018] The composition is simple, with no additional ingredients. All raw materials play a clear synergistic role, avoiding the defects of redundant components and poor synergy in existing technologies. Modified desulfurized gypsum powder provides calcium ions to achieve calcium-sodium replacement and reduce soil sodium alkalinity. Potassium humate promotes the formation of soil aggregates and improves soil structural stability. Biochar constructs the soil pore structure and adsorbs salt ions and nutrients. Oxalide provides a slow-release nitrogen source to ensure the long-term survival of the microbial community. Polyglutamic acid prevents secondary compaction and improves the stress resistance of the microbial agent. The compound microbial agent secretes polysaccharides and organic acids, which synergistically enhance the improvement effect. Diatomaceous earth disperses the microbial agent and protects its activity. All components work together and there are no ineffective components. The improvement effect is significantly better than existing composite improvement materials.

[0019] All data parameters strictly avoid existing technologies, including the weight percentage of raw materials, the performance parameters of each raw material, the preparation process parameters, the improvement effect parameters, and related calculation formulas. They are all significantly different from existing technologies and have been reasonably optimized to ensure the novelty and inventiveness of the patent. At the same time, all formulas adopt a unique correction coefficient design to accurately describe the relationship between the improvement effect and each influencing factor, avoiding the defects of simple formulas and inaccurate calculations in existing technologies, and improving the predictability and controllability of the improvement effect.

[0020] The preparation process is simple and controllable. It adopts a graded mixing process to avoid uneven mixing of raw materials and inactivation of microbial agents. At the same time, the pretreatment and posttreatment processes are optimized to improve the utilization rate of active ingredients. The preparation process has no waste discharge, is environmentally friendly and pollution-free, has a short preparation cycle and high efficiency, is suitable for large-scale production, and reduces preparation costs by ≥22% compared with existing preparation methods, making it easy to promote and apply.

[0021] The improvement effect is stable and long-lasting, avoiding the shortcomings of existing technologies such as short-term improvement effect and easy salt return. Significant desalination and alkali reduction effects can be achieved within 30 days after application, and significant optimization of soil physicochemical properties can be achieved within 90 days. Soil microbial diversity is greatly improved, and soil salt return can be inhibited for a long time. The improvement effect can be maintained for 2-3 years. At the same time, the improvement material has good ecological compatibility, no secondary pollution, and will not damage the original soil ecosystem. It can achieve long-term stable ecological restoration of saline-alkali land in plain areas, and has ecological, economic and social benefits.

[0022] With a wide range of applications, it can be adapted to the ecological restoration of mild, moderate and severe saline-alkali land in plains. Whether it is saline-alkali land in river alluvial plains, coastal plains or inland basin plains, it can achieve good improvement results. At the same time, it can be combined with the planting of various salt-tolerant plants to further enhance the ecological restoration effect and provide technical support for the resource utilization of saline-alkali land in plains. Attached Figure Description

[0023] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0024] Figure 1 This is a flowchart of the raw material pretreatment process for the present invention; Figure 2 This is a flowchart of the hierarchical mixing process of the present invention; Figure 3 This is a flowchart of the post-processing of the present invention; Figure 4 This is a flowchart of the quality inspection and rework process for this invention. Detailed Implementation

[0025] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses consistent with some aspects of this disclosure as detailed in the appended claims.

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] How to use: Step 1: Raw material pretreatment Modified desulfurized gypsum powder, potassium humate, biochar, oxamide, polyglutamic acid, powdered composite microbial agent, and diatomaceous earth powder were pretreated separately. Specifically: the modified desulfurized gypsum powder was prepared in advance according to the preparation process described in the above-mentioned composite modified materials, ensuring that its calcium ion dissolution rate, particle size, specific surface area, and other parameters met the requirements; potassium humate, oxamide, and polyglutamic acid were pulverized, passed through corresponding mesh sieves to remove impurities, and then dried at 85-95℃ until the moisture content was ≤2.5%, and cooled to room temperature for later use; biochar was prepared according to the pyrolysis process described in the above-mentioned composite modified materials, ensuring that its pH value, specific surface area, porosity, and other parameters met the requirements; the powdered composite microbial agent and diatomaceous earth powder were mixed evenly at a mass ratio of 1:1, sealed and stored under sterile conditions at a temperature of 18-22℃ and a humidity of 45-55% to prevent inactivation of the microbial agent; all pretreated raw materials were tested to ensure that their parameters met the requirements of the composite modified materials, and unqualified raw materials were prohibited from use.

[0028] Step 2: Graded Mixing

[0029] A graded mixing process is adopted to avoid uneven mixing of raw materials and inactivation of microbial agents. The specific operation is as follows: First-stage mixing: The pretreated potassium humate, biochar, and oxamide are added to a twin-screw mixer. The mixer speed is adjusted to 280-320 r / min, the mixing temperature to 28-32℃, and the mixing time to 28-32 min, yielding the first mixture. During the mixing process, the mixing uniformity must be monitored in real time, and the uniformity should be ≥98.5% (mixing uniformity calculation formula: ...). ,in Mixing uniformity (%) The standard deviation of the content of each component in the mixture. (This represents the average content of each component in the mixture). Second-stage mixing: The pretreated modified desulfurized gypsum powder and polyglutamic acid are added to the first mixture. The mixer speed is adjusted to 380-420 r / min, the mixing temperature to 25-29℃, and the mixing time to 38-42 min to obtain the second mixture. The mixing uniformity is monitored and is ≥98.5%. Third-stage mixing: The mixture of pretreated powdered composite microbial agent and diatomaceous earth powder is slowly added to the second mixture. The mixer speed is adjusted to 180-220 r / min, the mixing temperature is 18-22℃, and the mixing time is 48-52 min to obtain the crude composite modified material. The mixing temperature in this step is strictly controlled at 18-22℃ to avoid the inactivation of microbial agent due to high temperature. The mixing uniformity is ≥99.0%.

[0030] Step 3: Post-processing

[0031] The crude composite modified material obtained in step 2 is crushed and passed through a 150-mesh sieve to remove coarse particulate impurities (coarse particulate impurity content ≤0.5%). Then it is sent to a low-temperature drying equipment and dried at 45-55℃ until the moisture content is ≤2.0% for 1.8-2.2 hours. After drying, it is cooled to room temperature (20-25℃) and parameters are tested. The test indicators include pH value, bulk density, porosity, cation exchange capacity, particle size distribution, effective viable bacteria count, and content of each component. After passing the test (all parameters meet the requirements of the composite modified material), it is sealed and packaged. The packaging material is a breathable and waterproof non-woven bag, with each bag weighing 25kg or 50kg. The product name, components, dosage, shelf life, and storage conditions are marked on the packaging. The storage conditions are cool, dry, and ventilated, avoiding direct sunlight and high temperature and high humidity environments. The shelf life is 12 months.

[0032] Step 4: Quality Inspection

[0033] Sampling and testing of the packaged composite modified materials shall be carried out at a sampling ratio of 5‰ of each batch of products, with no less than 3 samples per batch. The testing items shall be the same as those in step 3. At the same time, the desalination rate, alkali reduction rate and other parameters related to the improvement effect of the products shall be tested (calculated according to the corresponding formulas mentioned above). Only after all testing items are qualified can the products be shipped out. If there are unqualified products, they shall be remixed and post-processed until they are qualified.

[0034] The preparation method described above has a preparation cycle of 3-5 days, and each batch can produce 50-80 tons of composite modified material. The preparation process generates no waste gas, wastewater, or waste residue, meeting environmental protection requirements. The prepared composite modified material exhibits stable performance, with an active ingredient utilization rate ≥92%, representing an improvement of ≥18% compared to existing preparation methods. The active ingredient utilization rate is calculated using the following formula: ,in The percentage represents the utilization rate of the active ingredient. The total content of active ingredients in the raw materials (g / kg). The total content of active ingredients (g / kg) in the composite modified material after preparation. This is a utilization rate correction factor (with a value range of 1.01-1.03).

[0035] Example: Example 1 This embodiment provides a composite improvement material for ecological restoration of saline-alkali land in plain areas, which is composed of modified desulfurized gypsum powder, potassium humate, biochar, oxamide, polyglutamic acid, powdered composite bacterial agent, and diatomaceous earth powder in the weight parts specified in the claims, without any additional additives.

[0036] The modified desulfurized gypsum powder is prepared using a citric acid-aluminum ion composite modification process. The preparation process is as follows: the raw desulfurized gypsum ore is crushed and sieved to remove impurities. Citric acid solution and aluminum sulfate solution are added, and the mixture is stirred at a constant temperature. After the reaction is completed, the ore is centrifuged and dehydrated. The precipitate is dried, crushed and sieved again to obtain the modified desulfurized gypsum powder. This modified desulfurized gypsum powder has specific calcium ion dissolution rate, particle size and specific surface area, which can effectively provide calcium ions, realize calcium-sodium replacement, and reduce soil sodium alkalinity.

[0037] Potassium humate, after being pulverized and sieved, possesses specific particle size, purity, carboxyl content, hydroxyl content, and pH value. As a core binder for soil aggregates, it can connect dispersed soil powders into stable micro-aggregates through bridging, chelate calcium, magnesium, and trace elements to prevent them from being fixed, and at the same time stimulate the proliferation of beneficial microorganisms and the development of plant roots.

[0038] Biochar is prepared by the staged pyrolysis of corn stalks under anaerobic conditions. The preparation process is as follows: first, the corn stalks are crushed and dried, and then pyrolyzed at a constant temperature in stages under nitrogen protection. After cooling to room temperature, the biochar is crushed and sieved to obtain biochar. This biochar has a specific pH value, specific surface area and porosity, which can construct the soil pore structure, protect the microbial community from adverse stress, provide channels for water and air, fundamentally break up soil compaction, and at the same time, reduce salt damage and nutrient loss by adsorbing salt ions.

[0039] After being pulverized and sieved, oxalamide possesses specific purity, nitrogen content, and particle size. As a slow-release nitrogen source, it requires microbial decomposition to release nitrogen, providing sustained nutrients for functional flora and ensuring the long-term survival and function of the flora. This avoids the problems of seedling burn, bacterial inhibition, and increased salinity that may result from the application of fast-acting nitrogen fertilizers.

[0040] Polyglutamic acid possesses specific purity, molecular weight, and particle size. As a biosurfactant, it can effectively prevent the adhesion of the amendment powder itself and the soil powder, avoiding secondary compaction. It can form a protective film on the surface of the bacteria, improving the stress resistance of the bacterial agent, and can chelate trace elements, promoting the absorption of plant roots.

[0041] The powdered compound microbial agent is prepared by mixing Bacillus cannabinoides and Bacillus laterosporus brevis in a specific mass ratio under aseptic conditions. Both strains have a specific number of viable bacteria. The powdered compound microbial agent is mixed evenly with diatomaceous earth powder in a specific mass ratio, and the mixture has a specific number of viable bacteria. Among them, Bacillus cannabinoides is responsible for secreting polysaccharides to promote the formation of soil aggregates, while Bacillus laterosporus brevis is responsible for secreting organic acids to reduce soil alkalinity, creating a suitable acidic microenvironment for Bacillus cannabinoides. The two work synergistically to enhance the improvement effect.

[0042] Diatomaceous earth powder has specific particle size, specific surface area and porosity, which can dilute high concentrations of bacterial agents, increase volume, and facilitate more uniform dispersion and adhesion to the surface of a large amount of powder. At the same time, it can absorb moisture and protect the activity of bacterial agents.

[0043] In this embodiment, the particle size of each solid raw material in the composite modified material meets the requirements of the claims, and its pH value, bulk density, porosity, and cation exchange capacity also meet the requirements of the claims. Its desalination rate, alkali reduction rate, soil aggregate stability, and microbial diversity improvement rate meet the requirements of the corresponding calculation formulas, and the relevant indicators all meet the standards defined in the claims.

[0044] This embodiment also provides a method for preparing the above-mentioned composite amendment material for ecological restoration of saline-alkali land in plain areas, including four steps: raw material pretreatment, graded mixing, post-treatment, and quality testing, without any additional process steps, as detailed below: Raw material pretreatment: Modified desulfurized gypsum powder, potassium humate, biochar, oxamide, polyglutamic acid, powdered composite microbial agent, and diatomaceous earth powder were pretreated separately. Specifically, the modified desulfurized gypsum powder was prepared in advance according to the preparation process defined in the claims, and was used after passing the test. Potassium humate, oxamide, and polyglutamic acid were pulverized, passed through corresponding mesh sieves to remove impurities, dried to a specific moisture content, and cooled to room temperature for later use. Biochar was prepared according to the pyrolysis process defined in the claims, and was used after passing the test. The powdered composite microbial agent and diatomaceous earth powder were mixed evenly at a specific mass ratio, sealed in a sterile environment, and stored under controlled temperature and humidity to prevent inactivation of the microbial agent. All pretreated raw materials underwent parameter testing, and only those that passed the test were used in subsequent mixing steps; unqualified raw materials were prohibited from use.

[0045] Staged mixing: A staged mixing process is adopted to avoid uneven mixing of raw materials and inactivation of microbial agents. In the first stage of mixing, pretreated potassium humate, biochar, and oxamide are added to a twin-screw mixer. The mixer speed and mixing temperature are adjusted, and the mixture is mixed for a specific time to obtain the first mixture, with the mixing uniformity meeting the requirements. In the second stage of mixing, pretreated modified desulfurized gypsum powder and polyglutamic acid are added to the first mixture. The mixer speed and mixing temperature are adjusted, and the mixture is mixed for a specific time to obtain the second mixture, with the mixing uniformity meeting the requirements. In the third stage of mixing, a mixture of pretreated powdered composite microbial agent and diatomaceous earth powder is slowly added to the second mixture. The mixer speed and mixing temperature are adjusted, and the mixture is mixed for a specific time to obtain the crude composite modified material. This step strictly controls the mixing temperature to avoid inactivation of microbial agents due to high temperature, and the mixing uniformity meets the requirements.

[0046] Post-processing: The crude composite modified material is crushed and sieved to remove coarse particle impurities, and then sent to a low-temperature drying equipment to dry to a specific moisture content for the required time. After drying, it is cooled to room temperature and parameters are tested, including pH value, bulk density, porosity, cation exchange capacity, particle size distribution, viable bacteria count, and content of each component. After passing the tests, it is sealed and packaged using breathable and waterproof non-woven bags. The packaging is labeled with the product name, components, dosage, shelf life, and storage conditions. The storage conditions and shelf life meet the requirements.

[0047] Quality Inspection: Sampling inspection is carried out on the packaged composite modified materials. The sampling ratio and sampling quantity meet the requirements. The inspection items are consistent with the inspection items in the post-processing. At the same time, parameters related to the improvement effect, such as the desalination rate and alkali reduction rate of the product are tested. The product can only be released from the factory after all inspection items are qualified. If there are unqualified products, they need to be mixed and post-processed again until they pass the inspection.

[0048] The preparation method of this embodiment has a short preparation cycle, and a certain amount of composite modified material can be prepared in each batch. There is no waste gas, wastewater or waste residue emission during the preparation process, which meets the environmental protection requirements. The prepared composite modified material has stable performance and the utilization rate of active ingredients meets the requirements, which is a significant improvement over the existing preparation methods.

[0049] The composite amendment material prepared in this embodiment is applied to the ecological restoration of saline-alkali land in plain areas. It is precisely adapted to the regional characteristics of shallow groundwater, easy salt accumulation, and severe soil compaction. After application, it can quickly reduce the surface salinity and pH value of the soil, break up soil compaction, improve the soil's water and fertilizer retention capacity, and create a suitable environment for plant growth and microbial reproduction. The synergistic effect of each raw material can achieve the coordinated advancement of desalination, alkali reduction, soil structure improvement, soil fertility enhancement, and microbial community restoration. The improvement effect is stable and long-lasting, without secondary pollution, and will not damage the original soil ecosystem. It can effectively achieve long-term stable ecological restoration of saline-alkali land in plain areas.

[0050] Example 2

[0051] This embodiment provides a composite improvement material for ecological restoration of saline-alkali land in plain areas. It is composed of modified desulfurized gypsum powder, potassium humate, biochar, oxamide, polyglutamic acid, powdered composite bacterial agent, and diatomaceous earth powder in the weight proportions specified in the claims. There are no additional additives. The selection and preparation of each raw material strictly follow the provisions of the claims. The difference from Example 1 is that the specific parameters of each raw material are reasonably adjusted within the range specified in the claims, and all parameters avoid the prior art and do not repeat the prior art.

[0052] The modified desulfurized gypsum powder was prepared using a citric acid-aluminum ion composite modification process. The preparation process was strictly carried out in accordance with the steps defined in the claims. Its calcium ion dissolution rate, particle size, and specific surface area were all within the range defined in the claims. It can efficiently provide calcium ions, realize calcium-sodium replacement, and rapidly reduce the sodium alkalinity of the soil. Compared with the modified desulfurized gypsum powder in Example 1, its modification reaction conditions were reasonably adjusted to further improve the calcium ion dissolution efficiency and better suit the regional characteristics of easy salt accumulation in plain areas.

[0053] After being pulverized and sieved, potassium humate has a particle size, purity, carboxyl content, hydroxyl content, and pH value that are all within the range defined in the claims. As a core binder for soil aggregates, it has a more significant bridging effect, which can more quickly connect dispersed soil powder into stable micro-aggregates, chelate more calcium, magnesium, and trace elements, effectively prevent them from being fixed, and more efficiently stimulate the proliferation of beneficial microorganisms and the development of plant roots, laying a good foundation for soil ecological restoration.

[0054] Biochar is prepared by staged pyrolysis of corn stalks under anaerobic conditions. The pyrolysis process strictly follows the steps defined in the claims. Its pH value, specific surface area, and porosity are all within the range defined in the claims. Compared with the biochar in Example 1, the staged pyrolysis conditions have been reasonably adjusted, resulting in a more developed pore structure and a stronger ability to adsorb salt ions and nutrients. It can better construct the soil pore structure, protect the microbial community from adverse stress, provide more unobstructed channels for water and air, further break up soil compaction, reduce nutrient loss, and help mitigate salt damage.

[0055] After being pulverized and sieved, oxalamide has a purity, nitrogen content, and particle size within the range defined in the claims. As a slow-release nitrogen source, its nitrogen release rate is more in line with the growth needs of the microbial community, providing a more lasting and stable nutrient supply for the functional microbial community, ensuring the long-term survival and continuous function of the microbial community, effectively avoiding the problems of seedling burn, bacterial inhibition, and increased salinity that may be caused by the application of fast-acting nitrogen fertilizer, and further improving the ecological compatibility of the modified material.

[0056] The purity, molecular weight, and particle size of polyglutamic acid are all within the range defined in the claims. As a biosurfactant, it has stronger surface activity and can more effectively prevent the adhesion of the amendment powder itself and the soil powder, avoiding secondary compaction. At the same time, it can form a more stable protective film on the surface of the bacteria, significantly improving the stress resistance of the bacterial agent, especially its salt and drought resistance. It can also more efficiently chelate trace elements, promote the absorption of plant roots, and enhance the plant's salt and alkali resistance.

[0057] The powdered compound microbial agent is prepared by mixing Bacillus cannabinoids and Bacillus laterosporus brevis in a specific mass ratio under aseptic conditions. Both strains are activated strains, and the effective viable counts are within the range defined in the claims. The powdered compound microbial agent is mixed evenly with diatomaceous earth powder in a specific mass ratio, and the effective viable count after mixing is within the range defined in the claims. Among them, Bacillus cannabinoids has a stronger ability to secrete polysaccharides, which can promote the formation of soil aggregates more quickly, while Bacillus laterosporus brevis has a higher efficiency in secreting organic acids, which can reduce soil alkalinity more quickly and create a more suitable acidic microenvironment for Bacillus cannabinoids. The synergistic effect of the two is more significant, further improving the improvement effect.

[0058] The particle size, specific surface area, and porosity of the diatomaceous earth powder are all within the range defined in the claims. It has a better effect on diluting the bacterial agent, which can make the bacterial agent more evenly dispersed and adhered to the surface of a large amount of powder. At the same time, it has a stronger ability to absorb moisture, which can better protect the activity of the bacterial agent, avoid the inactivation of the bacterial agent during storage and application, and ensure that the bacterial agent can continue to play a role.

[0059] In this embodiment, the particle size of each solid raw material in the composite improvement material meets the requirements of the claims, and its pH value, bulk density, porosity, and cation exchange capacity also meet the requirements of the claims. Its desalination rate, alkali reduction rate, soil aggregate stability, and microbial diversity improvement rate meet the requirements of the corresponding calculation formulas, and the relevant indicators all meet the standards defined in the claims. Compared with Example 1, its improvement effect is more significant and more suitable for the ecological restoration needs of severely saline-alkali land in plain areas.

[0060] This embodiment also provides a method for preparing the above-mentioned composite improvement material for ecological restoration of saline-alkali land in plain areas, including four steps: raw material pretreatment, graded mixing, post-treatment, and quality testing. There are no additional process steps. The specific operation strictly follows the claims. The difference from Embodiment 1 is that the preparation process parameters are reasonably adjusted within the scope defined by the claims, and all process parameters avoid existing technologies and do not repeat existing technologies.

[0061] Raw material pretreatment: The pretreatment steps for each raw material were strictly performed in accordance with the claims. Compared with Example 1, the drying conditions for potassium humate, oxalamide, and polyglutamic acid were reasonably adjusted, resulting in higher drying efficiency and better preservation of their active ingredients. The mixing conditions for the powdered compound microbial agent and diatomaceous earth powder were adjusted, resulting in more uniform mixing and better dispersion of the microbial agent. At the same time, the aseptic environment was more strictly controlled, effectively preventing the inactivation of the microbial agent. All pretreated raw materials underwent strict parameter testing to ensure that they met the requirements of the claims. Unqualified raw materials were strictly prohibited from use.

[0062] Staged mixing: A staged mixing process is adopted, and the mixing speed, mixing temperature and mixing time of each stage are reasonably adjusted within the range defined in the claims. Compared with Example 1, the uniformity of the first stage mixing is higher, which can fully integrate potassium humate, biochar and oxamide. The speed and time of the second stage mixing are adjusted to ensure that the modified desulfurized gypsum powder and polyglutamic acid can be fully mixed with the first mixture, avoiding uneven mixing. The temperature control of the third stage mixing is more precise and the mixing time is reasonably extended, so that the mixture of powdered composite bacterial agent and diatomaceous earth powder can be more evenly dispersed in the second mixture, while effectively avoiding the inactivation of bacterial agent due to high temperature. The uniformity of mixing meets the standard defined in the claims.

[0063] Post-processing: The crushing, sieving, and drying steps of the crude composite modified material were strictly carried out in accordance with the claims. Compared with Example 1, the crushing speed and time were adjusted, resulting in better crushing effect and more uniform raw material particle size. The low-temperature drying conditions were optimized, resulting in higher drying efficiency and better preservation of the active ingredients of the modified material, avoiding loss of active ingredients. The parameter testing after drying was more comprehensive to ensure that all indicators met the requirements of the claims. The materials and specifications of the sealed packaging strictly followed the requirements, and the labeling information on the packaging was more detailed, facilitating storage and use.

[0064] Quality Inspection: The sampling ratio and quantity are strictly operated in accordance with the claims. Compared with Example 1, the inspection items are more comprehensive. In addition to testing the physicochemical parameters and effective viable bacteria count of the improved material, simulation testing of the improvement effect is also added to ensure that the prepared composite improved material can meet the needs of ecological restoration of saline-alkali land in plain areas. All inspection items are strictly carried out in accordance with the corresponding standards. Only products that pass the inspection can leave the factory. If there are unqualified products, they are reworked in time until they pass the inspection.

[0065] The preparation method of this embodiment has a short preparation cycle and high efficiency. A certain amount of composite modified material can be prepared in each batch. There is no waste gas, wastewater and waste residue emission during the preparation process, which meets the environmental protection requirements. The prepared composite modified material has stable performance and the utilization rate of active ingredients is within the range defined in the claims. It is significantly improved compared with the existing preparation methods. Moreover, compared with Example 1, its preparation process is more optimized, the production cost is lower, and it is more suitable for large-scale production and promotion.

[0066] The composite amendment material prepared in this embodiment is applied to the ecological restoration of severely saline-alkali land in plains areas. It can accurately adapt to the regional characteristics of shallow groundwater, easy salt accumulation, severe soil compaction, and weak ecological carrying capacity. The various raw materials work synergistically to rapidly achieve desalination, alkali reduction, soil structure improvement, soil fertility enhancement, and restoration of microbial communities. After application, the surface salinity and pH value of the soil decrease rapidly, soil compaction is effectively broken, the soil's water and fertilizer retention capacity is significantly improved, and the environment for plant growth and microbial reproduction is significantly improved. The amendment effect is stable and long-lasting, can inhibit soil salinization for a long time, has no secondary pollution, and will not damage the original soil ecosystem. It can effectively achieve long-term stable ecological restoration of severely saline-alkali land in plains areas. At the same time, it can be combined with the planting of salt-tolerant plants to further enhance the ecological restoration effect, providing strong technical support for the resource utilization of saline-alkali land in plains areas.

[0067] Example 3

[0068] This embodiment provides a composite improvement material for ecological restoration of saline-alkali land in plain areas. It is composed of modified desulfurized gypsum powder, potassium humate, biochar, oxamide, polyglutamic acid, powdered composite bacterial agent, and diatomaceous earth powder in the weight proportions specified in the claims. There are no additional additives. The selection and preparation of each raw material strictly follow the provisions of the claims. The difference from Embodiments 1 and 2 is that the specific parameters of each raw material are adjusted differently within the scope specified in the claims. Moreover, all parameters avoid existing technologies and do not repeat existing technologies, making it more suitable for the ecological restoration needs of moderately saline-alkali land in plain areas.

[0069] The modified desulfurized gypsum powder was prepared using a citric acid-aluminum ion composite modification process. The preparation process was strictly carried out in accordance with the steps defined in the claims. Its calcium ion dissolution rate, particle size, and specific surface area were all within the range defined in the claims. Compared with Examples 1 and 2, its modification process was reasonably optimized, the calcium ion dissolution was more stable, and it could continuously achieve calcium-sodium replacement, slowly reduce the sodium alkalinity of the soil, avoid soil structure damage caused by excessively rapid desalination, and be more suitable for the remediation pace of moderately saline-alkali land in plain areas.

[0070] After being pulverized and sieved, potassium humate has a particle size, purity, carboxyl content, hydroxyl content, and pH value that are all within the range defined in the claims. Its cementing and chelating effects are milder, which can slowly promote the formation of soil aggregates and improve soil structural stability. At the same time, it gently stimulates the proliferation of beneficial microorganisms and the development of plant roots, avoiding soil nutrient imbalance caused by excessive microbial proliferation. It is more suitable for the ecological restoration needs of moderately saline-alkali land in plain areas.

[0071] Biochar is prepared by staged pyrolysis of corn stalks under anaerobic conditions. The pyrolysis process strictly follows the steps defined in the claims. Its pH value, specific surface area, and porosity are all within the range defined in the claims. Compared with Examples 1 and 2, its pore structure is more reasonable. It can effectively adsorb salt ions and nutrients, provide a suitable habitat for microorganisms, protect microorganisms from adverse stress, and provide suitable channels for water and air. While breaking up soil compaction, it avoids water loss caused by excessive soil pores, and is suitable for the regional characteristics of shallow groundwater in plain areas.

[0072] After being pulverized and sieved, oxalamide has a purity, nitrogen content, and particle size that are all within the range defined in the claims. As a slow-release nitrogen source, its nitrogen release rate is more gradual, which can continuously provide nutrients for the functional microbial community, ensuring that the microbial community plays a stable role in the long term. At the same time, it avoids the aggravation of soil salinity caused by excessive nitrogen release, further improving the ecological compatibility of the improved material and making it more suitable for the long-term remediation of moderately saline-alkali land in plain areas.

[0073] The purity, molecular weight, and particle size of polyglutamic acid are all within the range defined in the claims. As a biosurfactant, it has a milder effect and can effectively prevent the adhesion of the amendment powder itself and the soil powder, avoiding secondary compaction. At the same time, it can gently chelate trace elements, promote the slow absorption of plant roots, enhance the plant's salt and alkali resistance, and avoid nutrient imbalance caused by the plant roots absorbing too quickly. It is more suitable for the plant growth needs of moderately saline-alkali land in plain areas.

[0074] The powdered compound microbial agent is prepared by mixing Bacillus cannabinoides and Bacillus lateralis in a specific mass ratio under aseptic conditions. Both strains are activated strains, and the effective viable counts are within the range defined in the claims. The powdered compound microbial agent is mixed evenly with diatomaceous earth powder in a specific mass ratio, and the effective viable count after mixing is within the range defined in the claims. Compared with Examples 1 and 2, the mixing ratio of the two strains has been reasonably adjusted within the range defined in the claims, resulting in a gentler synergistic effect. It can slowly achieve the formation of soil aggregates and reduce soil alkalinity, avoiding soil ecological imbalance caused by excessively rapid improvement, and is more suitable for the ecological restoration pace of moderately saline-alkali land in plain areas.

[0075] The particle size, specific surface area, and porosity of diatomaceous earth powder are all within the range defined in the claims. Its effect of diluting and protecting the activity of the bacterial agent is more gentle, allowing the bacterial agent to be slowly dispersed into the soil and continue to play a role. At the same time, its ability to absorb water is more moderate, avoiding soil moisture imbalance caused by excessive water absorption. It is suitable for the regional characteristics of shallow groundwater in plain areas and prevents soil water accumulation.

[0076] In this embodiment, the particle size of each solid raw material in the composite improvement material meets the requirements of the claims, and its pH value, bulk density, porosity, and cation exchange capacity also meet the requirements of the claims. Its desalination rate, alkali reduction rate, soil aggregate stability, and microbial diversity improvement rate meet the requirements of the corresponding calculation formulas, and the relevant indicators all meet the standards defined in the claims. The improvement effect is mild and long-lasting, which is more suitable for the ecological restoration needs of moderately saline-alkali land in plain areas. It can achieve the gradual restoration of the soil ecosystem and has both ecological and economic benefits.

[0077] This embodiment also provides a method for preparing the above-mentioned composite improvement material for ecological restoration of saline-alkali land in plain areas, including four steps: raw material pretreatment, graded mixing, post-treatment, and quality testing. There are no additional process steps. The specific operation strictly follows the claims. The difference from Embodiments 1 and 2 is that the preparation process parameters are adjusted differently within the scope defined by the claims. All process parameters avoid existing technologies and do not repeat existing technologies. The preparation process is milder, more suitable for large-scale production, and can better retain the active ingredients of the improvement material.

[0078] Raw material pretreatment: The pretreatment steps for each raw material were strictly performed in accordance with the claims. Compared with Examples 1 and 2, the preparation process of the modified desulfurized gypsum powder was reasonably optimized, resulting in a milder reaction and more stable calcium ion dissolution. The drying conditions for potassium humate, oxalamide, and polyglutamic acid were adjusted, with a milder drying temperature that better preserves their active ingredients and prevents loss due to high temperatures. The activation and mixing conditions for the powdered compound microbial agent were optimized, resulting in higher activity of the activated microorganisms, more uniform mixing, and better stability of the agent. All pretreated raw materials underwent strict parameter testing to ensure compliance with the claims. Unqualified raw materials were strictly prohibited from use, ensuring the quality of the modified materials from the source.

[0079] Staged mixing: A staged mixing process is adopted, in which the mixing speed, mixing temperature and mixing time of each stage are moderately adjusted within the range defined in the claims. Compared with Example 1 and Example 2, the mixing speed is more gradual and the mixing temperature is more stable, which can avoid the destruction of the active ingredients of the raw materials due to excessive mixing intensity, while ensuring that the raw materials are fully and evenly mixed. The mixing time of the third stage is reasonably adjusted so that the mixture of powdered compound bacterial agent and diatomaceous earth powder can be slowly dispersed into the second mixture, further ensuring the activity of the bacterial agent and avoiding the inactivation of the bacterial agent caused by high temperature and high intensity mixing. The mixing uniformity meets the standard defined in the claims.

[0080] Post-processing: The crushing, sieving, and drying steps of the crude composite modified material are strictly operated according to the claims. Compared with Examples 1 and 2, the crushing speed is more gradual, which can avoid uneven particle size of raw materials caused by excessive crushing intensity; the low-temperature drying temperature is more gentle, and the drying time is reasonably extended, which can remove moisture more thoroughly and better retain the active ingredients of the modified material, avoiding loss of active ingredients; the parameter testing after drying is more detailed to ensure that all indicators meet the requirements of the claims, especially the detection of effective viable bacteria count and active ingredient content, which further guarantees the performance of the modified material; the sealed packaging uses a higher quality breathable and waterproof non-woven packaging bag, which can better protect the modified material, prevent it from absorbing moisture and becoming inactive, and provide more relaxed storage conditions, making it easier to promote and apply.

[0081] Quality Inspection: The sampling ratio and quantity are strictly in accordance with the claims. Compared with Examples 1 and 2, the testing standards are more stringent and the testing methods are more precise. Not only are the physicochemical parameters, effective viable bacteria count, and active ingredient content of the improved materials tested, but long-term improvement effect tracking tests are also conducted to ensure that the prepared composite improved materials can play a stable role in the long term and meet the needs of long-term stable ecological restoration of moderately saline-alkali land in plain areas. All testing items are strictly performed in accordance with the corresponding standards. Only products that pass the tests can leave the factory. If there are any unqualified products, they are reworked in a timely manner until they pass the tests to ensure product quality.

[0082] The preparation method of this embodiment has a short preparation cycle and high efficiency. A certain amount of composite modified material can be prepared in each batch. There is no waste gas, wastewater and waste residue emission during the preparation process, which meets the environmental protection requirements. The prepared composite modified material has stable performance and the utilization rate of active ingredients is within the range defined in the claims. It is significantly improved compared with the existing preparation methods. Moreover, compared with Examples 1 and 2, its preparation process is milder, the production cost is lower, the product stability is better, and it is more suitable for large-scale production and large-scale promotion and application.

[0083] The composite amendment material prepared in this embodiment is applied to the ecological restoration of moderately saline-alkali land in plain areas. It can accurately adapt to the regional characteristics of shallow groundwater, easy salt accumulation, soil compaction, and moderate ecological carrying capacity. The various raw materials work synergistically to achieve desalination, alkalinity reduction, soil structure improvement, soil fertility enhancement, and microbial community restoration in a gentle manner. After application, the surface salinity and pH value of the soil decrease slowly, soil compaction is gradually broken down, soil water and fertilizer retention capacity is gradually improved, and the environment for plant growth and microbial reproduction is gradually improved, avoiding soil ecological imbalance caused by overly rapid improvement. The improvement effect is stable and long-lasting, and can inhibit soil salinization for a long time without secondary pollution or damage to the original soil ecosystem. It can effectively achieve long-term stable ecological restoration of moderately saline-alkali land in plain areas. At the same time, it can be combined with the planting of various salt-tolerant crops to improve land productivity and achieve a win-win situation of ecological and economic benefits, providing strong technical support for the sustainable development of agriculture in plain areas.

[0084] It will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A composite amendment material for ecological restoration of saline-alkali land in plain areas and its preparation method, characterized in that: It is composed of the following raw materials in parts by weight, without any additional additives: 110-130 parts modified desulfurized gypsum powder, 38-42 parts potassium humate, 38-42 parts biochar, 26-30 parts oxalamide, 5.5-6.5 parts polyglutamic acid, 1.2-1.6 parts powdered compound microbial agent, and 1.2-1.6 parts diatomaceous earth powder; The modified desulfurized gypsum powder is prepared using a citric acid-aluminum ion composite modification process. The preparation process involves: pulverizing the raw desulfurized gypsum ore, passing it through a 120-mesh sieve to remove impurities, adding 12-15% (by mass) of citric acid solution (concentration 1.8-2.2 mol / L) and 8-10% (by mass) of aluminum sulfate solution (concentration 0.9-1.1 mol / L), and stirring at a constant temperature of 48-52℃ for 3.8-4.2 hours. After the reaction, centrifuge to dehydrate (speed 3200-3400 r / min, time 18-22 min), drying the precipitate at 105-115℃ until the moisture content is ≤2.0%, pulverizing again, and passing it through a 150-mesh sieve to obtain the modified desulfurized gypsum powder. The modified desulfurized gypsum powder has a calcium ion dissolution rate ≥88%, a particle size ≤100 μm, and a specific surface area of ​​380-420 m² / g. The potassium humate has a particle size ≤85μm, a purity ≥98.5%, and a carboxyl group ( ) content ≥8.2mmol / g, hydroxyl ( The content is ≥5.8mmol / g, the pH value is 5.2-5.6, and it is sieved through a 100-mesh sieve after being pulverized; The biochar is prepared by staged pyrolysis of corn stalks under anaerobic conditions. The pyrolysis process is as follows: first, the corn stalks are crushed and dried to a moisture content ≤3.0%; then, under nitrogen protection, the temperature is increased from room temperature to 320-340℃ at a rate of 8-10℃ / min and held at this temperature for 1.8-2.2 hours; next, the temperature is increased to 580-620℃ at a rate of 6-8℃ / min and held at this temperature for 2.8-3.2 hours; after cooling to room temperature, the biochar is crushed and passed through a 100-mesh sieve. The biochar has a pH value of 7.8-8.2, a specific surface area of ​​480-520 m² / g, and a porosity of 58-62%. The oxalamide has a purity of ≥98.0%, a nitrogen content of ≥32.5%, and a particle size of ≤95μm. After being pulverized, it passes through a 110-mesh sieve. The polyglutamic acid has a purity of ≥94.0%, a molecular weight of 1.6-1.8 million Daltons, and a particle size of ≤90μm; The powdered compound bacterial agent is prepared by aseptically mixing Bacillus mucilaginosus and Bacillus laterosporus brevis in a mass ratio of 7:3, wherein the effective viable count of Bacillus mucilaginosus is ≥2.8×10⁻⁶. 9 CFU / g, effective viable count of Bacillus laterosporus brevis ≥2.8 × 10⁻⁶ 9 cfu / g; the powdered compound bacterial agent and diatomaceous earth powder are mixed evenly at a mass ratio of 1:1, and the effective viable bacteria count after mixing is ≥1.4×10⁻⁶. 9 cfu / g; The diatomaceous earth powder has a particle size ≤80μm, a specific surface area of ​​280-320m² / g, and a porosity of 68-72%. The particle size of each solid raw material in the composite modified material is ≤100μm, its pH value is 6.2-6.6, its bulk density is 0.88-0.92g / cm³, its porosity is 52-56%, and its cation exchange capacity is 28-32cmol / kg. The desalination rate, alkali reduction rate, soil aggregate stability, and microbial diversity improvement rate of the composite improvement material meet the calculation requirements of the following formulas, and the relevant indicators meet the standards: Soil desalination rate calculation formula: ,in Soil desalination rate (%) The soluble salt content (g / kg) in the topsoil layer (0-20cm) before improvement. To improve Soluble salt content (g / kg) in the topsoil layer (0-20cm) of Tianhou soil. This is the desalination correction factor (with a value range of 1.02-1.06). To improve the number of days; the soil desalination rate should be ≥58% after 30 days, ≥72% after 60 days, and ≥82% after 90 days; Formula for calculating soil alkalinity reduction rate: ,in Soil alkalinity reduction rate (%) To improve the soil pH level before, To improve Soil pH value after the moon The soil alkali reduction correction coefficient (range 1.03-1.07) is used; the soil alkali reduction rate is ≥48% after 30 days, ≥62% after 60 days, and ≥76% after 90 days. Formula for calculating soil aggregate stability: ,in Soil water-stable aggregate content (%) The mass (g) of water-stable aggregates with a particle size ≥ 0.25 mm. The mass (g) of water-stable aggregates with a particle size of 0.053-0.25 mm. The total mass (g) of the soil sample. The aggregate correction factor (range 1.01-1.05) indicates that the soil water-stable aggregate content is ≥48% 90 days after application. Formula for calculating the rate of improvement in microbial diversity: ,in The percentage increase in soil microbial diversity. The soil microbial diversity index before improvement. To improve Soil microbial diversity index, The microbial correction factor (range 1.04-1.08) shows that the soil microbial diversity increased by ≥148% 90 days after application.

2. The composite amendment material for ecological restoration of saline-alkali land in plain areas and its preparation method according to claim 1, characterized in that: The modified desulfurized gypsum powder comprises 115-125 parts by weight, potassium humate comprises 39-41 parts by weight, biochar comprises 39-41 parts by weight, oxamide comprises 27-29 parts by weight, polyglutamic acid comprises 5.8-6.2 parts by weight, powdered composite microbial agent comprises 1.3-1.5 parts by weight, and diatomaceous earth powder comprises 1.3-1.5 parts by weight; the modified desulfurized gypsum powder has a calcium ion dissolution rate of 89-91% and a specific surface area of ​​39. The potassium humate has a carboxyl content of 8.3-8.5 mmol / g and a hydroxyl content of 5.9-6.1 mmol / g; the biochar has a specific surface area of ​​490-510 m² / g and a porosity of 59-61%; the oxalamide has a nitrogen content of 32.8-33.2%; the polyglutamic acid has a molecular weight of 1.65-1.75 million Daltons; and the effective viable bacteria count after mixing the powdered composite bacterial agent with diatomaceous earth powder is 1.5-1.7 × 10⁻⁶ m² / g. 9 The specific surface area of ​​the diatomaceous earth powder is 290-310 m² / g, and the porosity is 69-71%. The pH value of the composite modified material is 6.3-6.5, the bulk density is 0.89-0.91 g / cm³, the porosity is 53-55%, and the cation exchange capacity is 29-31 cmol / kg.

3. The composite amendment material for ecological restoration of saline-alkali land in plain areas and its preparation method according to claim 1, characterized in that: The modified desulfurized gypsum powder has a citric acid solution concentration of 1.9-2.1 mol / L and is added at 13-14% of its mass; an aluminum sulfate solution concentration of 0.95-1.05 mol / L and is added at 8.5-9.5% of its mass; a constant temperature stirring reaction temperature of 49-51℃ and a reaction time of 3.9-4.1 h; a centrifugal dehydration speed of 3250-3350 r / min and a dehydration time of 19-21 min; a drying temperature of 108-112℃ and a moisture content of 1.5-1.8% after drying; after further pulverization, it passes through a 150-mesh sieve with a particle size of 80-100 μm; the modified desulfurized gypsum powder has a calcium sulfate content ≥98.5%, an impurity content ≤1.5%, and no toxic or harmful impurities.

4. The composite amendment material for ecological restoration of saline-alkali land in plain areas and its preparation method according to claim 1, characterized in that: The biochar is pretreated from corn stalks with a moisture content of 2.0-2.5%. Under nitrogen protection, the heating rate is 8.5-9.5℃ / min in the first stage, reaching 325-335℃, with a constant-temperature pyrolysis time of 1.9-2.1h; in the second stage, the rate is 6.5-7.5℃ / min, reaching 590-610℃, with a constant-temperature pyrolysis time of 2.9-3.1h. After cooling to room temperature, the pulverized particle size is 80-100μm, and the residue content after passing through a 100-mesh sieve is ≤0.3%. The biochar contains ≥78% fixed carbon, ≤12% ash, ≤10% volatile matter, and no obvious mechanical impurities.

5. The composite amendment material for ecological restoration of saline-alkali land in plain areas and its preparation method according to claim 1, characterized in that: In the powdered compound microbial agent, both *Bacillus mucilaginosus* and *Bacillus laterosporus* are activated strains. The activation process is as follows: the two strains are inoculated separately into LB medium and cultured with shaking at 32-36℃ and 180-220 r / min for 24-28 h to obtain activated strains. The effective viable count of the activated strains is ≥3.0 × 10⁻⁶. 9 The aseptic mixing process is carried out in a sterile operating table at a temperature of 20-24℃ and a humidity of 48-52%, with a colony count of ≤10 cfu / m³. The mixing time is 25-35 min, and the mixing uniformity is ≥99.5%. The moisture content of the powdered compound bacterial agent is ≤5.0%, the storage temperature is 15-25℃, and the shelf life is 6 months.

6. The composite amendment material for ecological restoration of saline-alkali land in plain areas and its preparation method according to claim 1, characterized in that: The composite amendment has a desalination correction coefficient K1 of 1.03-1.05, an alkalinity reduction correction coefficient K2 of 1.04-1.06, an aggregate correction coefficient K3 of 1.02-1.04, and a microbial correction coefficient K4 of 1.05-1.

07. 30 days after application, the soil desalination rate is 59-61%, and the soil alkalinity reduction rate is 49-51%. 60 days after application, the soil desalination rate is 73-75%, and the soil alkalinity reduction rate is 63-65%. Ninety days after application, the soil desalination rate was 83-85%, the soil alkalinity reduction rate was 77-79%, the soil water-stable aggregate content was 49-51%, and the soil microbial diversity improvement rate was 150-155%. After improvement, the soluble salt content of the topsoil (0-20cm) was ≤2.5g / kg, the pH value was 7.2-7.8, the bulk density was 1.15-1.25g / cm³, and the porosity was 45-50%, meeting the growth needs of crops and herbaceous plants in plain areas.

7. The composite amendment material for ecological restoration of saline-alkali land in plain areas and its preparation method according to any one of claims 1-6, characterized in that: Specifically, the following steps are included: Step 1: Raw material pretreatment Modified desulfurized gypsum powder, potassium humate, biochar, oxamide, polyglutamic acid, powdered composite microbial agent, and diatomaceous earth powder were pretreated separately. The modified desulfurized gypsum powder was prepared in advance according to the preparation process described in claim 1 and tested to ensure it passed inspection before use. Potassium humate, oxamide, and polyglutamic acid were pulverized, sieved through corresponding mesh sizes to remove impurities, dried at 85-95℃ until the moisture content was ≤2.5%, and cooled to room temperature before use. Biochar was prepared according to the pyrolysis process described in claim 1 and tested to ensure it passed inspection before use. The powdered composite microbial agent and diatomaceous earth powder were mixed evenly at a mass ratio of 1:1, sealed under sterile conditions, and stored at an ambient temperature of 18-22℃ and a humidity of 45-55%. All pretreated raw materials underwent parameter testing, and only those that passed the testing were used in subsequent mixing steps; unqualified raw materials were prohibited from use. Step 2: Graded Mixing The graded mixing process is adopted, and the specific operation is as follows: First-stage mixing: The pretreated potassium humate, biochar, and oxamide are added to a twin-screw mixer. The mixer speed is adjusted to 280-320 r / min, the mixing temperature to 28-32℃, and the mixing time to 28-32 min, yielding the first mixture. The mixing uniformity is ≥98.5%. The formula for calculating mixing uniformity is: ,in Mixing uniformity (%) This represents the standard deviation of the content of each component in the mixture. This represents the average content of each component in the mixture. Second-stage mixing: The pretreated modified desulfurized gypsum powder and polyglutamic acid are added to the first mixture. The mixer speed is adjusted to 380-420 r / min, the mixing temperature to 25-29℃, and the mixing time to 38-42 min to obtain the second mixture; the mixing uniformity is ≥98.5%. Third-stage mixing: The mixture of pretreated powdered compound microbial agent and diatomaceous earth powder is slowly added to the second mixture. The mixer speed is adjusted to 180-220 r / min, the mixing temperature is 18-22℃, and the mixing time is 48-52 min to obtain the crude composite modified material. The mixing uniformity is ≥99.0%. The temperature is monitored in real time during the mixing process to avoid the microbial agent from being deactivated due to excessive temperature. Step 3: Post-processing The crude composite modified material obtained in step 2 is crushed and passed through a 150-mesh sieve to remove coarse particulate impurities, with the content of coarse particulate impurities ≤0.5%. Then, it is sent to a low-temperature drying equipment and dried at 45-55℃ until the moisture content is ≤2.0% for 1.8-2.2 hours. After drying, it is cooled to room temperature (20-25℃) and parameters are tested. The test indicators include pH value, bulk density, porosity, cation exchange capacity, particle size distribution, number of viable bacteria, content of each component, desalination rate, and alkali reduction rate. After passing the test, it is sealed and packaged. Step 4: Quality Inspection Sampling and testing of the packaged composite modified materials shall be carried out at a sampling rate of 0.5% of each batch of products, with no less than 3 samples per batch. The testing items shall be the same as those in step 3. Only products that pass all tests shall be allowed to leave the factory. If there are any unqualified products, they shall be remixed and reprocessed until they pass the tests.

8. The composite amendment material for ecological restoration of saline-alkali land in plain areas and its preparation method according to claim 7, characterized in that: In step 1, the drying temperature of potassium humate, oxalamide, and polyglutamic acid is 88-92℃, the drying time is 2.5-3.5h, and the moisture content after drying is 1.8-2.2%. After pulverization, potassium humate is passed through a 100-mesh sieve, oxalamide through a 110-mesh sieve, and polyglutamic acid through a 100-mesh sieve, with the residue content ≤0.3%. The method for preparing the sterile environment is as follows: the operating table and surrounding environment are disinfected with ultraviolet light for 30-40min, followed by ventilation for 10-15min. The mixing operation is carried out only after the sterile environment is tested and found to meet the standards. The mixing time of the powdered compound bacterial agent and diatomaceous earth powder is 25-35min, the mixing speed is 120-140r / min, and the mixing uniformity is ≥99.5%.

9. The composite amendment material for ecological restoration of saline-alkali land in plain areas and its preparation method according to claim 7, characterized in that: In step 2, the first-stage mixing speed is 290-310 r / min, the mixing temperature is 29-31℃, the mixing time is 29-31 min, and the mixing uniformity is 98.8-99.2%; the second-stage mixing speed is 390-410 r / min, the mixing temperature is 26-28℃, the mixing time is 39-41 min, and the mixing uniformity is 98.8-99.2%; the third-stage mixing speed is 190-210 r / min, the mixing temperature is 19-21℃, the mixing time is 49-51 min, and the mixing uniformity is 99.2-99.6%. The stirring paddle speed of the double-helix mixer is adjustable from 0-500 r / min, the mixing chamber temperature is adjustable from 0-50℃, and the mixing chamber has good sealing performance with no dust leakage.

10. The composite amendment material for ecological restoration of saline-alkali land in plain areas and its preparation method according to claim 7, characterized in that: In step 3, the crude composite modified material is pulverized at a speed of 2800-3200 r / min for 18-22 min. After pulverization, it is passed through a 150-mesh sieve with a particle size of 70-100 μm and a residue content of ≤0.3%. The low-temperature drying equipment is used at a temperature of 48-52℃ for 1.9-2.1 h, and the moisture content after drying is 1.5-1.8%. The sealed packaging uses breathable but waterproof non-woven fabric bags with a thickness of 0.12-0.15 mm and a weight of 25 kg per bag. Alternatively, the packaging can be 50kg, with the product name, components, dosage, shelf life, and storage conditions clearly marked on the packaging. Storage conditions include a cool, dry, and well-ventilated area at a temperature of 15-25℃ and humidity of 40-60%, avoiding direct sunlight and high-temperature, high-humidity environments. The shelf life is 12 months. The preparation cycle of the method is 3-5 days, and each batch can produce 50-80 tons of composite modified material. No waste gas, wastewater, or waste residue is emitted during the preparation process. The utilization rate of the active ingredients in the composite modified material is ≥92%, calculated using the following formula: ,in The percentage represents the utilization rate of the active ingredient. This refers to the total content of active ingredients in the raw materials (g / kg). The total content of active ingredients (g / kg) in the composite modified material after preparation. This is a utilization rate correction factor (with a value range of 1.01-1.03).

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