Acidified soil conditioner, preparation method thereof, and acidified soil improvement method

Abstract

This invention provides an acidified soil conditioner and its preparation method, as well as a method for improving acidified soil, belonging to the field of soil improvement technology. It includes: preparing a steel slag-phosphogypsum composite using steel slag and phosphogypsum; preparing MgO@biochar using crop straw; preparing microbial microcapsules by inoculating and culturing alkali-tolerant nitrogen-fixing bacteria and phosphate-solubilizing bacteria to obtain a mixed bacterial solution; uniformly mixing 45-55 parts of the steel slag-phosphogypsum composite, 10-20 parts of humic acid, and 2-4 parts of carboxymethyl cellulose, and granulating to obtain core particles; preparing a suspension using 15-25 parts of MgO@biochar, and spraying it onto the core particles to obtain coated particles; uniformly attaching 4-6 parts of microbial microcapsules to the surface of the coated particles to obtain the soil acidification conditioner. This invention utilizes a combination of solid waste and functional materials to achieve solid waste resource utilization and long-term release of alkaline substances; achieves core-shell slow release and multi-level regulation through core granulation and outer core coating; and solves the problem of room temperature storage for bacterial conditioners.

Description

Technical Field

[0001] This invention relates to the field of soil improvement technology, specifically to an acidified soil conditioner and its preparation method and method for improving acidified soil. Background Technology

[0002] Soil acidification is prevalent in southern my country, and severe acidification can lead to problems such as soil compaction, microbial imbalance, reduced fertility, decreased crop yields, and lower crop quality. Using soil conditioners is one of the main methods to improve soil acidification. Many types of soil conditioners are available, including organic, inorganic, and organic-inorganic composite types.

[0003] For example, Chinese patent application CN117925252A discloses a targeted aluminum control and acidified soil amendment material based on soil and material properties. It belongs to the organic-inorganic compound acidified soil amendment, which includes 40%~60% alkaline conditioner, 20%~40% organic materials and 30%~40% modified biochar by mass percentage. The formulation of this amendment is determined based on big data of soils with different acidification levels and various material properties, and the key parameters for the synergistic effect of aluminum control / acid inhibition / fertilization are optimized.

[0004] For example, Chinese patent application CN116948654A discloses an acidic soil conditioner based on calcium and magnesium supplementation. It mainly belongs to the category of inorganic acidified soil conditioners and includes the following components by weight: 40-80 parts of phosphorus tailings powder, 10-20 parts of silicon-based yellow phosphorus slag powder, and 5-20 parts of silicate minerals. It has a good improvement effect primarily on acidic red soils lacking calcium and magnesium.

[0005] For example, Chinese patent application document CN105331368A discloses a soil conditioner containing water-soluble small molecule organic matter. The soil conditioner containing water-soluble small molecule organic matter is obtained by acidifying and decomposing organic wastewater to obtain a liquid solution rich in water-soluble small molecule organic matter, then adding alkaline oxides, granulating and cooling, and then adding beneficial microorganisms.

[0006] However, although the various soil conditioners or soil amendments provided in the above literature can improve soil pH to a certain extent, their alkaline substances are easy to dissolve quickly, and the pH is prone to rebound after a sudden increase. They cannot effectively regulate and improve agricultural product yield in the long term. In addition, some existing bacterial amendments are difficult to store at room temperature. Summary of the Invention

[0007] The technical problem this invention aims to solve is to provide an acidified soil conditioner, its preparation method, and a method for improving acidified soil. The acidified soil conditioner provided by this invention achieves solid waste resource utilization and long-term release of alkaline substances through the composite of solid waste and functional materials; it achieves core-shell slow release and multi-level regulation through core granulation and outer core coating; and it achieves green preparation and precise control by incorporating technologies such as high-temperature calcination, ultrasonic-assisted impregnation, and nano-dispersion, while solving the problem of room-temperature storage for bacterial-containing conditioners. It features long-term release regulation, green and low-cost operation, high efficiency, precise control, and easy storage.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing an acidified soil conditioner, specifically comprising the following steps:

[0010] S1. Preparation of steel slag-phosphogypsum composite: Steel slag and phosphogypsum are mixed at a dry basis mass ratio of 3-5:1 and calcined at 1100-1200℃ for 1-2 hours under a CO2 atmosphere. After calcination, the material is rapidly cooled to below 200℃. Then, it is ground for 2-3 hours and sieved to obtain the final product. The introduction of a CO2 atmosphere during high-temperature calcination promotes the formation of calcium silicate (Ca2SiO4), and the rapid cooling operation after high-temperature calcination (such as water mist quenching) increases porosity and activity. The resulting steel slag-phosphogypsum composite is a highly active composite alkaline material.

[0011] S2. Preparation of MgO@biochar: (1) Crush crop straw into small pieces of 2-3 cm, heat it to 600-650 °C at 10-15 °C / min under N2 protection, pyrolyze for 2-3 hours, cool it, grind, pass and sieve to obtain biochar; (2) Immerse the biochar in magnesium salt solution with a solid-liquid ratio of 1:10-15, sonicate for 30-60 minutes, and then let it stand for 12-24 hours; (3) Dry the filtered material at 110-130 °C, and then calcine it at 500-550 °C for 3-5 hours to decompose the magnesium salt into nano MgO; wash the product with water until neutral, and dry it to obtain the product.

[0012] S3. Preparation of microbial microcapsules: (1) Inoculate alkali-tolerant nitrogen-fixing bacteria and phosphate-solubilizing bacteria in a 1:1 ratio into liquid culture medium and culture in a shaker at 30-40℃ and 150-180r / min for 48-60 hours to obtain a mixed bacterial solution with a bacterial concentration ≥1×10⁻⁶. 9 CFU / mL; (2) Mix the mixed bacterial solution with sodium alginate aqueous solution at a volume ratio of 1:4~6 to obtain a mixed solution. The mixed solution is then added to CaCl2 solution to solidify and form microspheres. The microspheres are then coated twice with chitosan acetic acid solution to obtain microbial microcapsules. After freeze-drying, they are stored for later use.

[0013] S4. Core granulation: Mix 45-55 parts of the steel slag-phosphogypsum composite obtained in S1, 10-20 parts of humic acid, and 2-4 parts of carboxymethyl cellulose evenly; spray in polyvinyl alcohol solution for granulation; dry after granulation to obtain core particles.

[0014] S5. Shell coating: 15-25 parts of MgO@biochar prepared in S2 are dispersed in a polylactic acid (PLA)-dichloromethane solution to obtain a suspension, and ultrasonically dispersed for 20-50 minutes; the core particles formed in S4 are placed in a fluidized bed and sprayed with the suspension at a rate of 0.2-0.3 mL / min to form a coating layer; after vacuum drying to remove residual solvent, coated particles are obtained.

[0015] S6. Microbial loading: 4-6 portions of microbial microcapsules prepared in S3 and the coated particles formed in S5 are put into a three-dimensional mixer with a speed of 30-40 r / min and a mixing time of 20-50 minutes to ensure that the microbial microcapsules are uniformly attached to the surface of the coated particles. The mixture is equilibrated at 40℃ and 30-40% humidity for 12-18 hours to obtain the soil conditioner for acidified soil.

[0016] Furthermore, in S3, a CaCl2 solution with a mass percentage of 1.5% is added dropwise to the mixed solution at a volume of 5 to 10 times to solidify and form microspheres; the obtained microspheres are first filtered to obtain microsphere particles, and then the microsphere particles are added to a chitosan acetic acid solution at a mass-volume ratio of 1:2~3 g / mL for secondary coating.

[0017] Furthermore, in step S4, the particle size is controlled to be 2~4mm, and after granulation, the particles are dried with hot air at 80~90℃ until the moisture content is ≤5%.

[0018] Furthermore, in step S5, the coating thickness is controlled at 200~300μm, and the vacuum drying conditions are 50~60℃ for 4~6 hours.

[0019] Preferably, the freeze-drying conditions in S3 are: pre-freezing at -40°C for 24 hours under a vacuum of 10 Pa.

[0020] Furthermore, the steel slag in S1 contains CaO ≥ 40%, MgO ≥ 8%, SiO2 ≥ 15%, heavy metals Cd ≤ 1 mg / kg, Hg ≤ 10 mg / kg, As ≤ 10 mg / kg, Cr ≤ 30 mg / kg, Pb ≤ 30 mg / kg, Fe ≤ 0.3%, and moisture content ≤ 5%.

[0021] The phosphogypsum has a purity of ≥90% and a soluble P2O5 content of ≤0.5%.

[0022] Furthermore, the crop straw in S2 is corn or rice straw, with a carbon content ≥40%, ash content ≤15%, fixed carbon ≥70% after pyrolysis and carbonization, and porosity ≥80%.

[0023] Furthermore, the magnesium salt is either magnesium nitrate or magnesium sulfate, with a purity ≥99.9%.

[0024] Furthermore, in S3, the alkali-tolerant nitrogen-fixing bacteria (Azotobacter chroococcum) strain has an effective viable count ≥ 2.5 billion / g; the phosphate-solubilizing bacteria (Bacillus megaterium) strain has an effective viable count ≥ 2.5 billion / g.

[0025] Preferably, in S3, the mass-volume concentration of the chitosan acetic acid solution is 0.5%~2% (w / v), and the acetic acid concentration is 1%~3%.

[0026] Furthermore, in S4, the humic acid is preferably extracted from lignite or weathered coal, with a humification index (HI) ≥ 60% and an E4 / E6 ratio ≤ 5.

[0027] Furthermore, in S4, the carboxymethyl cellulose has a purity of ≥95% and a viscosity of ≥1500 mPa·s (2% aqueous solution).

[0028] Furthermore, in S4, the polyvinyl alcohol has a degree of alcoholysis ≥98%, ash content ≤0.5%, and sodium acetate residue ≤0.1%.

[0029] Furthermore, in S5, the polylactic acid (PLA) has a molecular weight range of 100,000 to 150,000; and the dichloromethane has a purity of ≥99.9% and a residual moisture content of ≤0.01%.

[0030] Secondly, the present invention also provides an acidified soil conditioner prepared by the above method.

[0031] Furthermore, the soil acidification conditioner comprises the following raw materials in parts by weight:

[0032] The steel slag-phosphogypsum composite contains 45-55 parts, humic acid 10-20 parts, carboxymethyl cellulose 2-4 parts, MgO@biochar 15-25 parts, and microbial microcapsules 4-6 parts.

[0033] Thirdly, the present invention also provides a method for improving acidified soil, specifically, applying the acidified soil conditioner as described above 3 to 7 days before rice transplanting, with an application rate of 100 to 200 kg / mu, and after application, thoroughly tilling and mixing the top 20 to 30 cm of soil and watering it with sufficient water.

[0034] The present invention has the following beneficial effects:

[0035] (1) In terms of raw materials, it can realize the resource utilization of solid waste and the composite of functional materials.

[0036] The soil acidification amendment provided by this invention is made from raw materials such as alkali-tolerant nitrogen-fixing bacteria and phosphate-solubilizing bacteria, steel slag, phosphogypsum, magnesium nitrate, crop straw, humic acid, carboxymethyl cellulose, polyvinyl alcohol, polylactic acid (PLA), dichloromethane, liquid culture medium, sodium alginate, CaCl2, and chitosan. Its technical indicators are: CaO ≥ 15%, SiO2 ≥ 6%, MgO ≥ 3%, fixed carbon ≥ 5%, effective viable bacteria count ≥ 200 million / g, pH 8-10, particle size 2-5mm, alkaline substance release rate of 30-40% in 0-7 days, daily average alkaline substance release rate ≤ 5% after 7 days, daily alkaline substance release rate ≥ 0.5%, and release duration ≥ 90 days.

[0037] By calcining and activating steel slag (CaO / SiO2 source) and phosphogypsum (Ca / S source) under a CO2 atmosphere, highly active calcium silicate (Ca2SiO4) is generated, enabling the resource utilization of solid waste and the long-term release of alkaline substances. Furthermore, by loading nano-MgO (particle size ≤50nm) onto the surface of biochar using a magnesium nitrate impregnation-confined calcination method, the pH buffering capacity (specific surface area >300m²) is simultaneously enhanced. 2 / g). Alkali-tolerant nitrogen-fixing and phosphate-solubilizing bacteria were selected and bred. The sodium alginate-chitosan double encapsulation technology can solve the problem of bacterial survival in alkaline environments, with a bacterial survival rate of >90%.

[0038] (2) In terms of structure, it can achieve core-shell sustained release and multi-level regulation, and can achieve two-stage pH regulation. Specifically, it is reflected in:

[0039] Core-based rapid neutralization: The core of the steel slag-phosphogypsum composite can rapidly release Ca. 2+ / OH - It can raise the soil pH to neutral within 7 days.

[0040] Long-lasting slow-release outer shell: The outer shell of PLA-coated MgO@biochar gradually degrades with soil moisture, continuously releasing alkaline substances, maintaining pH stability, and achieving 180 days without rebound.

[0041] The porous structure of biochar provides colonization space for microorganisms, while humic acid can activate the activity of the microbial community, forming a symbiotic system of "carrier-nutrient-microbial community".

[0042] (3) In terms of process, it can achieve green preparation and precise control.

[0043] In the preparation of the steel slag-phosphogypsum composite, calcination of steel slag and phosphogypsum at 1200℃ in a CO2 atmosphere promotes the formation of Ca2SiO4, with a Ca2SiO4 content ≥60%, which improves the activity by 2 times compared to traditional lime. In the preparation of MgO@biochar, ultrasonic-assisted impregnation combined with low-temperature (500℃) calcination is used to achieve uniform dispersion of nanoparticles, resulting in a loading of ≥8%. Furthermore, freeze-drying combined with chitosan coating overcomes the limitation of cold chain transportation required for bacterial agents, and the bacterial activity loss is <10% after 6 months of storage at room temperature.

[0044] (4) In terms of the collaborative mechanism, it can achieve three-in-one repair.

[0045] First, chemical neutralization, alkaline substances (Ca) 2+ MgO, OH - Firstly, it can directly neutralize soil acidity; secondly, it uses physical adsorption, with the biochar pore structure locking in H+. + Al 3+ The three main methods are: ion remediation, bioremediation, and biological remediation. Functional microbial communities fix nitrogen and solubilize phosphorus, promoting organic matter accumulation and aggregate formation. Through this integrated approach of chemical, physical, and biological remediation, highly efficient remediation of acidified soils can be achieved.

[0046] (5) In terms of application value, it can achieve a win-win situation of low cost and ecological benefits.

[0047] The acidified soil conditioner provided by this invention uses 60% industrial solid waste as raw material, and the overall cost can be reduced by 30% compared with commercially available products. It meets the green "dual carbon" requirements, and each ton of product can absorb about 300 kg of steel slag and 100 kg of phosphogypsum, and reduce CO2 emissions by about 0.5 tons. One application can last for 2 to 3 years, and can simultaneously improve acidification and enhance soil fertility.

[0048] Therefore, the soil acidification amendment provided by this invention has the characteristics of long-term release regulation, green and low cost, high efficiency and precise control and easy storage. Attached Figure Description

[0049] Figure 1 This is a schematic flowchart illustrating the preparation method of the soil acidification amendment provided in this embodiment of the invention. Detailed Implementation

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0051] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0052] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0053] The main raw materials used in the following examples and their sources are as follows:

[0054] The alkali-tolerant nitrogen-fixing bacteria (Azotobacter chroococcum) strain was provided by Paul Timham (Weifang) Biotechnology Co., Ltd., with an effective viable count of 3.35 billion / g.

[0055] The phosphate-solubilizing bacteria (Bacillus megaterium) strain was provided by Shandong Yihao Biotechnology Co., Ltd., with an effective viable count of 2.82 billion / g.

[0056] The steel slag was provided by Hunan Valin Steel Group Co., Ltd., and contained the following components: CaO content 43.1%, MgO content 8.5%, SiO2 content 18.9%, heavy metals: Cd content 0.13 mg / kg, Hg content 0.26 mg / kg, As content 3.7 mg / kg, Cr content 16.2 mg / kg, Pb content 21.1 mg / kg, Fe content 0.15%, and moisture content 1.42%.

[0057] The phosphogypsum was supplied by Fuzhou Persian Gulf Chemical Co., Ltd., with a purity of 95.6% and a soluble P2O5 content of 0.06%.

[0058] Magnesium nitrate was supplied by Guangdong Daxiao Chemical Co., Ltd., with a purity of 99.98%.

[0059] The crop straw was provided by Hunan Wanmufeng Agricultural Technology Co., Ltd. It is rice straw with a carbon content of 43.1%, ash content of 11.6%, fixed carbon of 83% after pyrolysis and carbonization, and porosity of 88.3%.

[0060] The humic acid was provided by Shanxi Jiayou Humic Acid Technology Co., Ltd., with a humification index (HI) of 68.4% and an E4 / E6 ratio of 3.21.

[0061] Carboxymethyl cellulose was provided by Renqiu Jinyu Chemical Co., Ltd., with a purity of 98.9% and a viscosity ≥2604 mPa·s (2% aqueous solution).

[0062] Polyvinyl alcohol was provided by Shanghai Xinheng New Material Technology Co., Ltd., with a degree of alcoholysis of 99.1%, ash content of 0.26%, and sodium acetate residue of 0.02%.

[0063] Polylactic acid (PLA) was supplied by Suzhou Jiangcangfa Plastics Co., Ltd., with a molecular weight of 136,800.

[0064] The dichloromethane was supplied by Shanghai Denuo Chemical Co., Ltd., with a purity of 99.96% and a residual moisture content of 0.004%.

[0065] I. Preparation of Soil Acidification Conditioner

[0066] like Figure 1 As shown, the present invention provides a method for preparing an acidified soil conditioner, comprising the following steps:

[0067] S1. Preparation of steel slag-phosphogypsum composite: Steel slag and phosphogypsum are mixed at a dry basis mass ratio of 3~5:1. The mixture is placed in a rotary kiln and calcined at 1100~1200℃ for 1~2 hours. A CO2 atmosphere is introduced to promote the formation of calcium silicate (Ca2SiO4). After calcination, the material is quenched with water mist to below 200℃ to increase porosity and activity. The material is then ground in a ball mill for 2 hours and passed through a 100-mesh sieve to obtain a highly active composite alkaline material of steel slag-phosphogypsum.

[0068] The following preferred embodiment is used as an example. The specific parameters are as follows: the ratio of steel slag to phosphogypsum by dry weight is 3:1; the calcination condition is calcination at 1100℃ for 1 hour.

[0069] Preparation of S2, MgO@Biochar: Crop straw is crushed into 2-3 cm pieces, placed in a tube furnace, and heated to 600-650℃ at 10-15℃ / min under N2 protection for 2-3 hours. After cooling, it is ground and passed through a 200-mesh sieve to obtain biochar. The biochar is immersed in a 0.5 mol / L magnesium salt solution with a solid-liquid ratio of 1:10-15 and ultrasonically treated for 30-60 minutes, then allowed to stand for 12-24 hours. After filtration, the material is dried at 110-130℃ and then calcined at 500-550℃ for 3-5 hours to decompose Mg(NO3)2 into nano-MgO (particle size ≤50nm). The product is washed with water until neutral and dried for later use.

[0070] The following preferred embodiments are examples, and the specific parameters are as follows: the pyrolysis conditions are: heating to 600℃ at 10℃ / min and pyrolysis for 2 hours; magnesium nitrate is used as the magnesium salt; the solid-liquid ratio of biochar to magnesium salt solution is 1:10; ultrasonic treatment for 30 minutes, followed by standing for 12 hours; drying conditions are 110℃; calcination conditions are calcination at 500℃ for 3 hours, so that Mg(NO3)2 decomposes into nano MgO, and the specific surface area of ​​the obtained MgO@biochar is ≥300m² / g.

[0071] S3. Preparation of microbial microcapsules: Alkali-tolerant nitrogen-fixing bacteria and phosphate-solubilizing bacteria are inoculated into liquid culture medium at a ratio of 1:1~2 and cultured on a shaker at 30~40℃ and 150~180r / min for 48~60 hours to obtain a mixed bacterial suspension with a concentration ≥1×10⁻⁶. 9 CFU / mL; Mix the mixed bacterial culture with 2% sodium alginate solution at a volume ratio of 1:4~6 to obtain a mixed solution, and add it dropwise into a 1.5% CaCl2 solution with a mass percentage of 5~10 times the volume of the mixed solution to solidify and form microspheres with a particle size of 1~2mm; Filter the obtained microspheres to obtain microsphere particles, and then add the microsphere particles to a 0.5% chitosan acetic acid solution at a mass-volume ratio of 1:2~3g / mL for secondary coating to obtain microbial microcapsules, freeze-dry and store for later use. The freeze-drying conditions are: vacuum degree 10Pa, pre-freezing at -40℃ for 24 hours.

[0072] The following preferred embodiments are examples, and the specific parameters and conditions are as follows: the inoculation ratio of alkali-tolerant nitrogen-fixing bacteria to phosphate-solubilizing bacteria is 1:1; the conditions for liquid culture of bacterial solution are 30℃, 150r / min shaker culture for 48 hours; the volume ratio of mixed bacterial solution to sodium alginate solution is 1:4; the volume ratio of the mixed solution formed by mixed bacterial solution and sodium alginate solution to 1.5% CaCl2 solution is 1:10; the mass-volume ratio of microsphere particles to chitosan acetic acid solution is 1:2 g / mL.

[0073] S4. Core Granulation: The steel slag-phosphogypsum composite, humic acid, and carboxymethyl cellulose obtained in S1 are mixed evenly according to a preset ratio; a 2% polyvinyl alcohol solution is sprayed into the mixture using a disc granulator to control the particle size to 2~4mm; after granulation, the particles are dried with hot air at 80℃ until the moisture content is ≤5% to obtain the core particles.

[0074] S5. Shell Coating: The MgO@biochar prepared in S2 is dispersed in a polylactic acid (PLA)-dichloromethane solution to obtain a suspension, wherein the PLA concentration is 5% and the suspension concentration is 50~100g / L. The suspension is ultrasonically dispersed for 20 minutes. The core particles formed in S4 are placed in a fluidized bed, and the inlet air temperature is controlled at 40℃. The suspension is sprayed at a rate of 0.2~0.3mL / min to form a coating layer with a thickness of 200~300μm. After coating, the particles are treated in a vacuum drying oven at 50~60℃ for 4~6 hours to remove residual solvent and obtain coated particles.

[0075] The following preferred embodiments are examples, and the specific parameters are as follows: the spraying rate of the suspension is 0.2 mL / min; the drying conditions for the coated particles are treatment in a vacuum drying oven at 60°C for 4 hours.

[0076] S6. Microbial loading: The microbial microcapsules prepared in S3 and the coated particles formed in S5 are put into a three-dimensional mixer with a speed controlled at 30~40 r / min and a mixing time of 20~50 minutes to make the microcapsules uniformly adhere to the particle surface; the mixture is equilibrated at 40℃ and 30~40% humidity for 12~18 hours to obtain the acidified soil conditioner.

[0077] The following preferred embodiments are examples, and the specific parameters are as follows: the rotation speed is set to 30 r / min, and the mixing time is 20 minutes; the equilibrium conditions of the mixture after microcapsule loading are 40°C and 30% humidity for 12 hours.

[0078] The weight composition of the main components and the corresponding steps of the preparation method in each group of examples and comparative examples are shown in Table 1 below. The acidified soil conditioners obtained are respectively referred to as Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2.

[0079]

[0080] II. Comparative Experiment on the Application of Acidified Soil Conditioners

[0081] From June 2023 to November 2024, a paddy field experiment was conducted in a paddy field in a town in Hunan Province. The paddy field soil was yellow sandy mud, with total nitrogen of 1.14 g / kg, available nitrogen of 76.7 mg / kg, available phosphorus of 11.8 mg / kg, available potassium of 50.0 mg / kg, pH of 5.02, organic matter of 30.7 g / kg, and cation exchange capacity of 9.45 cmol (+) / kg. Two seasons of medium-season rice were planted in 2023 and 2024, for a total of two seasons. The rice variety was Zhulong Liangyou 1212, purchased from Yuan Longping High-Tech Agriculture Co., Ltd. The plot size was 3m × 7m (21m). 2 The fields are divided by 30cm high and 30cm wide ridges, with agricultural film laid on the ridges. Each plot is irrigated individually to prevent cross-contamination of water and fertilizer. The following treatment groups are set up:

[0082] Treatment 1 (Control): Planted according to local customs and methods;

[0083] Treatment 2: Apply 200 kg / 667 m³ of the soil conditioner prepared in Example 1 according to the application method of this invention. 2 (mu);

[0084] Treatment 3: Apply 200 kg / 667 m³ of the soil conditioner prepared in Example 2 according to the application method of this invention. 2 ;

[0085] Treatment 4: Apply 200 kg / 667 m³ of the soil conditioner prepared in Example 3 according to the application method of this invention. 2 ;

[0086] Treatment 5: Apply 200 kg / 667 m³ of the soil conditioner prepared in Comparative Example 1 according to the application method of this invention. 2 ;

[0087] Treatment 6: Apply 200 kg / 667 m³ of the soil conditioner prepared in Comparative Example 2 according to the application method of this invention. 2 .

[0088] Treatment 7: Apply 200 kg / 667 m³ of steel slag powder according to the application method of this invention. 2 .

[0089] Treatment 8: Apply 200 kg / 667 m³ of phosphogypsum powder according to the application method of this invention. 2 .

[0090] Each process is set to 3 repetitions, for a total of 24 cells.

[0091] The specific application method for treatments 2-8 is as follows: Apply once, 7 days before rice transplanting in the first year, thoroughly mix with the soil at a depth of 0-20cm and water thoroughly. Do not apply in the second year.

[0092] When the rice matures, yield will be measured. Soil samples will be collected from each plot at 90, 180, 360 and 540 days after the application of the soil conditioner for testing and analysis.

[0093] The methods for determining soil pH, available manganese, soil base saturation, and rice yield in the following experiments are as follows:

[0094] (1) Soil pH determination: Using water as the extractant, a small amount of soil was collected and mixed with water at a mass ratio of 2.5:1. The pH was determined by potentiometric method (refer to NY / T1377-2007).

[0095] (2) Determination of available manganese in soil: After extraction with a pH 7.3 diethylenetriaminepentaacetic acid-calcium oxide-triethanolamine (DTPA-CaCl2-TEA) buffer solution, the manganese was determined by ICP-MS (refer to NY / T 890-2004).

[0096] (3) Determination of soil base saturation: The total amount of exchangeable bases was determined by the 1 mol / L ammonium acetate exchange-neutralization titration method, the cation exchange capacity was determined by the ammonium acetate extraction titration method, and the base saturation was calculated (refer to LY / T 1243-1999, LY / T 1244-1999, LY / T 1247-1999).

[0097] (4) Rice yield measurement: Refer to the "Operation Specification for Rice Yield Measurement" (DB33 / T 2517-2022).

[0098] The test results are shown in Tables 2-5 below.

[0099]

[0100] Table 2 shows that: After 90, 180, 360, and 540 days, the soil pH of treatment 2 increased by 0.47, 0.39, 0.50, and 0.34 units compared to treatment 1, respectively; after 90, 180, 360, and 540 days, the soil pH of treatment 3 increased by 0.43, 0.42, 0.48, and 0.36 units compared to treatment 1, respectively; and after 90, 180, 360, and 540 days, the soil pH of treatment 4 increased by 0.45, 0.41, 0.5, and 0.35 units compared to treatment 1, respectively. The soil pH of treatment 5 increased by 0.42, 0.36, 0.36, and 0.22 units respectively at 90, 180, 360, and 540 days after application compared to treatment 1; the soil pH of treatment 6 increased by 0.47, 0.39, 0.44, and 0.29 units respectively at 90, 180, 360, and 540 days after application compared to treatment 1; and the soil pH of treatment 7 increased by 0.49, 0.32, 0.26, and 0.08 units respectively at 90, 180, 360, and 540 days after application compared to treatment 1.

[0101] Over time, the soil pH of treatments 2, 3, 4, 5, 6, and 7 showed a decreasing trend, but the rate of decrease, from smallest to largest, was: Treatment 2 / Treatment 3 / Treatment 4 < Treatment 6 < Treatment 5 < Treatment 7. At all time points, the soil pH of treatment 8 was lower than that of treatment 1. In the short term (within 90 days), the effects of treatments 2, 3, 4, 5, 6, and 7 were similar; however, in the longer term (180–540 days), the effects of treatments 5, 6, and 7 were significantly weaker than those of treatments 2 / 3 / 4. This indicates that applying the soil conditioner of this invention can effectively increase the pH of acidified soils, and the effect can be sustained for a relatively long time (two rice growing years).

[0102]

[0103] Table 3 shows that: After 90, 180, 360, and 540 days of application, the available manganese in the soil under treatment 2 decreased by 33.0%, 29.5%, 26.6%, and 23.9% compared to treatment 1, respectively; after 90, 180, 360, and 540 days of application, the available manganese in the soil under treatment 3 decreased by 31.4%, 28.9%, 27.9%, and 24.8% compared to treatment 1, respectively; and after 90, 180, 360, and 540 days of application, the available manganese in the soil under treatment 4 decreased by 32.1%, 28.2%, 27.2%, and 24.8% compared to treatment 1, respectively. Treatment 5 showed a decrease in available manganese in the soil compared to treatment 1 at 90, 180, 360, and 540 days after application, with reductions of 30.5%, 25.2%, 24.5%, and 15.3%, respectively. Treatment 6 showed a decrease of 32.4%, 27.5%, 26.3%, and 21.3%, respectively, compared to treatment 1 at the same time points. Treatment 7 showed a decrease of 33.3%, 19.7%, 12.4%, and 3.5%, respectively, compared to treatment 1 at the same time points. Over time, the available manganese in the soil increased in treatments 2, 3, 4, 5, 6, and 7, but the rate of increase was in the order of treatment 2 / 3 / 4 < treatment 6 < treatment 5 < treatment 7. Treatment 8 showed an increase in available manganese in the soil compared to treatment 1 at all time points. In a shorter period (within 90 days), the effects of treatments 2, 3, 4, 5, 6, and 7 were similar; however, in a longer period (180-540 days), the effects of treatments 5, 6, and 7 were significantly weaker than those of treatments 2, 3, and 4. This indicates that applying the soil acidifier of this invention can effectively reduce available manganese in the soil (a barrier to soil acidity) and the effect can be sustained for a relatively long time (two rice growing years).

[0104]

[0105] Table 4 shows that: After application, soil base saturation at 90, 180, 360, and 540 days in treatment 2 increased by 40.1%, 37.8%, 30.4%, and 31.7% compared to treatment 1, respectively; after application, soil base saturation at 90, 180, 360, and 540 days in treatment 3 increased by 41.0%, 37.3%, 31.1%, and 31.5% compared to treatment 1, respectively; and after application, soil base saturation at 90, 180, 360, and 540 days in treatment 4 increased by 40.7%, 36.6%, 30.7%, and 32.5% compared to treatment 1, respectively. Treatment 5 showed an increase in soil base saturation of 39.9%, 34.9%, 19.5%, and 16.7% compared to treatment 1 at 90, 180, 360, and 540 days after application, respectively. Treatment 6 showed an increase of 39.6%, 35.2%, 27.1%, and 28.5% compared to treatment 1 at the same time. Treatment 7 showed an increase of 42.0%, 16.5%, 3.5%, and 1.1% compared to treatment 1 at the same time. Over time, the soil base saturation of treatments 2, 3, 4, 5, 6, and 7 showed a decreasing trend, but the rate of decrease, from smallest to largest, was: Treatment 2 / Treatment 3 / Treatment 4 < Treatment 6 < Treatment 5 < Treatment 7. Treatment 8 showed a decrease in soil base saturation at all time points compared to treatment 1. In a shorter period (within 90 days), the effects of treatments 2, 3, 4, 5, 6, and 7 were similar; however, in a longer period (180-540 days), the effects of treatments 5, 6, and 7 were significantly weaker than those of treatments 2, 3, and 4. This indicates that applying the soil acidifier of this invention can effectively increase soil base saturation (an important indicator of soil fertility) and the effect can be sustained for a relatively long time (two rice growing years).

[0106]

[0107] Table 5 shows that: Treatment 2 increased rice yield by 15.3% and 12.5% ​​in the first and second years compared to Treatment 1, respectively; Treatment 3 increased rice yield by 16.9% and 14.4% in the first and second years compared to Treatment 1, respectively; Treatment 4 increased rice yield by 15.9% and 12.8% in the first and second years compared to Treatment 1, respectively; Treatment 5 increased rice yield by 6.9% and 5.0% in the first and second years compared to Treatment 1, respectively; Treatment 6 increased rice yield by 5.1% and 2.5% in the first and second years compared to Treatment 1, respectively; and Treatment 7 increased rice yield by 8.5% and -0.2% in the first and second years compared to Treatment 1, respectively. Treatment 8 resulted in a decrease in rice yield. This indicates that the application of the soil acidifier of this invention can effectively increase rice yield and the effect can be sustained for a relatively long period (two rice planting years).

[0108] In summary, after a single application of the soil conditioner of this invention, it can significantly increase soil pH and base saturation, reduce available manganese in the soil, and substantially increase rice yield over a relatively long period of time, demonstrating significant advantages. By employing a composite of solid waste and functional materials, it achieves the resource utilization of solid waste and the long-term release of alkaline substances; through core granulation and outer core coating, it achieves core-shell slow release and multi-level regulation; by incorporating technologies such as high-temperature calcination, ultrasonic-assisted impregnation, and nano-dispersion, it achieves green preparation and precise control, and solves the problem of room-temperature storage for bacterial-containing conditioners; it features long-term release regulation, green and low-cost operation, high efficiency, precise control, and easy storage.

[0109] The above description is only a part of the preferred embodiments of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an acidified soil conditioner, specifically comprising the following steps: S1. Preparation of steel slag-phosphogypsum composite: Steel slag and phosphogypsum are mixed at a dry basis mass ratio of 3~5:1, and calcined at 1100~1200℃ for 1~2 hours under CO2 atmosphere; after calcination, the material is rapidly cooled to below 200℃; then ground for 2~3 hours and sieved to obtain the final product. S2. Preparation of MgO@biochar: (1) Crush crop straw into small pieces of 2-3 cm, heat it to 600-650 °C at 10-15 °C / min under N2 protection, pyrolyze for 2-3 hours, cool it, grind and sieve it to obtain biochar; (2) Immerse the biochar in magnesium salt solution with a solid-liquid ratio of 1:10-15, sonicate it for 30-60 minutes and let it stand for 12-24 hours; (3) Dry the filtered material at 110-130 °C, and then calcine it at 500-550 °C for 3-5 hours to decompose the magnesium salt into nano MgO; The product is washed with water until neutral and then dried to obtain the final product. S3. Preparation of microbial microcapsules: (1) Inoculate alkali-tolerant nitrogen-fixing bacteria and phosphate-solubilizing bacteria at a ratio of 1:1~2 into liquid culture medium, and culture in a shaker at 30~40℃ and 150~180r / min for 48~60 hours to obtain a mixed bacterial solution with a bacterial concentration ≥1×10⁻⁶. 9 CFU / mL; (2) Mix the mixed bacterial solution with sodium alginate aqueous solution at a volume ratio of 1:4~6 to obtain a mixed solution. Add CaCl2 solution to the mixed solution to solidify and form microspheres. Coat the microspheres twice with acetic acid solution of chitosan to obtain microbial microcapsules. Freeze-dry and store for later use. S4. Core granulation: Mix 45-55 parts of the steel slag-phosphogypsum composite obtained in S1, 10-20 parts of humic acid, and 2-4 parts of carboxymethyl cellulose evenly; spray in polyvinyl alcohol solution for granulation; dry after granulation to obtain core particles. S5. Shell Coating: 15-25 parts of the MgO@biochar obtained in S2 are dispersed in a polylactic acid-dichloromethane solution to obtain a suspension, which is ultrasonically dispersed for 20-50 minutes. The molecular weight of the polylactic acid is in the range of 100,000-150,000. The core particles formed in S4 are placed in a fluidized bed and sprayed with the suspension at a rate of 0.2-0.3 mL / min to form a coating layer. After vacuum drying to remove residual solvent, the coated particles are obtained. S6. Microbial loading: 4-6 portions of microbial microcapsules prepared in S3 and the coated particles formed in S5 are put into a three-dimensional mixer with a speed of 30-40 r / min and a mixing time of 20-50 minutes to ensure that the microbial microcapsules are uniformly attached to the surface of the coated particles. The mixture is equilibrated at 40℃ and 30-40% humidity for 12-18 hours to obtain the soil conditioner for acidified soil.

2. The method for preparing the soil conditioner for acidified soil according to claim 1, characterized in that, In S3, a CaCl2 solution with a mass percentage of 1.5% is added dropwise to a mixed solution at a volume of 5 to 10 times to solidify and form microspheres. The microspheres are first filtered to obtain microsphere particles, and then the microsphere particles are added to a chitosan acetic acid solution at a mass-to-volume ratio of 1:2 to 3 g / mL for secondary coating.

3. The method for preparing the soil conditioner for acidified soil according to claim 1, characterized in that, In step S4, the particle size is controlled to be 2~4mm, and after granulation, the particles are dried with hot air at 80~90℃ until the moisture content is ≤5%.

4. The method for preparing the soil conditioner for acidified soil according to claim 1, characterized in that, In step S5, the coating thickness is controlled at 200~300μm, and the vacuum drying conditions are 50~60℃ for 4~6 hours.

5. The method for preparing the soil conditioner for acidified soil according to claim 1, characterized in that, The steel slag in S1 contains CaO ≥ 40%, MgO ≥ 8%, SiO2 ≥ 15%, heavy metals Cd ≤ 1 mg / kg, Hg ≤ 10 mg / kg, As ≤ 10 mg / kg, Cr ≤ 30 mg / kg, Pb ≤ 30 mg / kg, Fe ≤ 0.3%, and moisture content ≤ 5%. The phosphogypsum has a purity of ≥90% and a soluble P2O5 content of ≤0.5%.

6. The method for preparing the soil conditioner for acidified soil according to claim 1, characterized in that, S2 contains corn or rice straw with a carbon content ≥40%, ash content ≤15%, fixed carbon ≥70% after pyrolysis and carbonization, and porosity ≥80%. The magnesium salt is either magnesium nitrate or magnesium sulfate, with a purity of ≥99.9%.

7. The method for preparing the soil conditioner for acidified soil according to claim 1, characterized in that, In S3, the effective viable count of the alkali-tolerant nitrogen-fixing bacteria strain is ≥2.5 billion / g; the effective viable count of the phosphate-solubilizing bacteria strain is ≥2.5 billion / g.

8. The method for preparing the soil conditioner for acidified soil according to claim 1, characterized in that, In S4, the humic acid is extracted from lignite or weathered coal, with a humification index ≥60% and an E4 / E6 ratio ≤5; the carboxymethyl cellulose has a purity ≥95% and a viscosity ≥1500 mPa·s; the polyvinyl alcohol has a degree of alcoholysis ≥98%, ash content ≤0.5%, and sodium acetate residue ≤0.1%. In S5, the dichloromethane has a purity of ≥99.9% and a residual moisture content of ≤0.01%.

9. An acidified soil conditioner prepared by the method of any one of claims 1 to 8.

10. A method for improving acidified soil, characterized in that, Apply the soil conditioner described in claim 9 3 to 7 days before rice transplanting, at a rate of 100 to 200 kg / mu. After application, thoroughly till and mix the top 20 to 30 cm of soil and water it thoroughly.

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