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

Abstract

The invention provides an acidified soil conditioner, a preparation method thereof and an acidified soil improvement method, and relates to the technical field of soil improvement. Comprising the following steps: preparing a steel slag-ardealite compound from steel slag and ardealite; mgO charcoal is prepared from crop straw; carrying out inoculated culture on alkali-resistant nitrogen-fixing bacteria and phosphate solubilizing bacteria to obtain a mixed bacteria solution, and then preparing the microbial microcapsules; uniformly mixing 45-55 parts of a steel slag-ardealite compound, 10-20 parts of humic acid and 2-4 parts of carboxymethylcellulose, and granulating to obtain inner core particles; preparing suspension liquid from 15-25 parts of MgO and biochar, and spraying the suspension liquid outside the inner core particles to prepare coated particles; and 4-6 parts of microbial microcapsules are uniformly attached to the surfaces of the coated particles to obtain the soil acidification modifier. Solid waste and functional materials are compounded, so that solid waste recycling and long-acting release of alkaline substances can be realized; core-shell slow release and multi-stage regulation are realized through inner core granulation and outer core coating; and the problem of normal-temperature preservation of the bacterium-containing modifier can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of soil improvement, and in particular to an acidified soil conditioner, a preparation method thereof, and an acidified soil improvement method. Background Art

[0002] Soil acidification is widespread in southern my country, and severe soil acidification can lead to soil compaction, imbalanced microbial flora, reduced fertility, and decreased crop yields and quality. Using soil conditioners is one of the primary methods for addressing soil acidification. Numerous types of soil conditioners are available, including organic, inorganic, and organic-inorganic composites.

[0003] For example, Chinese patent application document CN117925252A discloses a targeted aluminum control and acidification soil improvement material based on soil and material properties. The material is an organic-inorganic composite acidification soil improver, comprising 40% to 60% alkaline conditioner, 20% to 40% organic material, and 30% to 40% modified biochar in mass percentage. The formula of the improver is based on big data of soils with different acidification degrees and various material properties, and the key parameters for the synergistic effect of aluminum control, acid resistance, and fertilization are preferably determined.

[0004] For example, Chinese patent application CN116948654A discloses an acidic soil conditioner based on calcium and magnesium supplementation. This inorganic acidifying soil conditioner comprises the following components by weight: 40-80 parts of phosphate tailings powder, 10-20 parts of silicon-based yellow phosphorus slag powder, and 5-20 parts of silicate minerals. This agent is particularly effective in improving acidic red soils that are deficient in 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, adding alkaline oxides, granulating and cooling, and then adding beneficial microorganisms.

[0006] However, although the various soil conditioners or soil improvers provided in the above literature can improve the soil pH to a certain extent, their alkaline substances are easily dissolved quickly, and the pH is prone to rebound after a sudden increase, making it impossible to accurately adjust and increase agricultural product yields in the long term. In addition, some existing bacterial-containing improvers are difficult to store at room temperature. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an acidified soil conditioner, a preparation method thereof, and an acidified soil improvement method. The acidified soil conditioner provided by the present invention realizes the resource utilization of solid waste and the long-term release of alkaline substances by compounding solid waste and functional materials; realizes core-shell slow release and multi-stage regulation by inner core granulation and outer core coating; realizes green preparation and precise control by incorporating high-temperature calcination, ultrasonic-assisted impregnation, nano-dispersion and other technologies, and solves the problem of room temperature storage of bacteria-containing conditioners. It has the characteristics of long-term release regulation, green and low cost, high efficiency, precise regulation and easy storage.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

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

[0010] S1. Preparation of steel slag-phosphogypsum composite: Mix steel slag and phosphogypsum in a dry weight ratio of 3:5:1. Calcine the mixture at 1100-1200°C for 1-2 hours under a CO₂ atmosphere. After calcination, the mixture is rapidly cooled to below 200°C, ground for 2-3 hours, and sieved. The introduction of CO₂ during high-temperature calcination promotes the formation of calcium silicate (Ca₂SiO₄). Rapid cooling (e.g., water mist quenching) after high-temperature calcination 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 segments of 2~3 cm, heat to 600~650℃ at 10~15℃ / min under N2 protection, pyrolyze for 2~3 hours, grind, filter and sieve after cooling to obtain biochar; (2) Immerse the biochar in a magnesium salt solution with a solid-liquid ratio of 1:10~15, ultrasonically treat for 30~60 minutes, and then let it stand for 12~24 hours; (3) After filtration, the material is dried at 110~130℃, and then calcined at 500~550℃ for 3~5 hours to decompose the magnesium salt into nano-MgO; the product is washed with clean water until neutral and dried.

[0012] S3. Preparation of microbial microcapsules: (1) Inoculate alkali-resistant nitrogen-fixing bacteria and phosphate-solubilizing bacteria into liquid culture medium at a ratio of 1:1, and culture at 30-40°C and 150-180 rpm for 48-60 hours to obtain a mixed bacterial solution with a bacterial solution concentration of ≥1×10 9 CFU / mL; (2) the mixed bacterial solution was mixed with a sodium alginate aqueous solution at a volume ratio of 1:4-6 to obtain a mixed solution, and the mixed solution was dropped into a CaCl2 solution to solidify and form microspheres; the microspheres were secondary coated with an acetic acid solution of chitosan to obtain microbial microcapsules, which were freeze-dried and stored for future use.

[0013] S4, core granulation: 45-55 parts of the steel slag-phosphogypsum composite prepared in S1, 10-20 parts of humic acid, and 2-4 parts of carboxymethyl cellulose are uniformly mixed; polyvinyl alcohol solution is sprayed into the mixture for granulation; and after granulation, the core particles are dried 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 the suspension is sprayed at a rate of 0.2-0.3 mL / min to form a coating layer; and the residual solvent is removed after vacuum drying to obtain coated particles.

[0015] S6. Microbial loading: 4 to 6 parts of the microbial microcapsules prepared in S3 and the coated particles formed by S5 are put into a three-dimensional mixer and the speed is controlled at 30 to 40 r / min for 20 to 50 minutes to allow the microbial microcapsules to evenly adhere to the surface of the coated particles; the mixed materials are balanced at 40 to 50°C and 30 to 40% humidity for 12 to 18 hours to obtain the acidified soil conditioner.

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

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

[0018] Furthermore, the coating layer thickness in step S5 is controlled to be 200-300 μm, and the vacuum drying condition is 50-60° C. for 4-6 hours.

[0019] Preferably, the freeze-drying conditions in S3 are pre-freezing at -40°C for 24 hours under a vacuum degree 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 of ≤0.5%.

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

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

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

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

[0026] Furthermore, in S4, the humic acid is preferably an extract of 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 an alcoholysis degree ≥ 98%, an ash content ≤ 0.5%, and a sodium acetate residue ≤ 0.1%.

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

[0030] In a second aspect, the present invention also provides an acidified soil conditioner prepared by the above method.

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

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

[0033] In a third aspect, 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 transplanting rice, with an application amount of 100 to 200 kg per mu. After application, the 20 to 30 cm soil layer on the surface of the cultivated land is fully rotary tilled and stirred and watered 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 combination of functional materials.

[0036] The soil acidifying agent provided by the present invention is made from raw materials such as alkali-resistant nitrogen-fixing 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 specifications include CaO ≥ 15%, SiO2 ≥ 6%, MgO ≥ 3%, fixed carbon ≥ 5%, effective viable bacteria count ≥ 200 million / g, pH 8-10, particle size 2-5 mm, alkaline substance release rate of 30-40% from 0 to 7 days, daily average alkaline substance release rate of ≤ 5% after 7 days, daily alkaline substance release rate ≥ 0.5%, and a release duration of ≥ 90 days.

[0037] By calcining and activating steel slag (CaO / SiO2 source) and phosphogypsum (Ca / S source) in a CO2 atmosphere, highly active calcium silicate (Ca2SiO4) is generated, which can achieve solid waste resource utilization and long-term release of alkaline substances. Nano-MgO (particle size ≤ 50nm) is loaded on the surface of biochar through magnesium nitrate impregnation-confined calcination method, and the pH buffering capacity is simultaneously enhanced (specific surface area> 300m 2 / g). Alkali-resistant nitrogen-fixing and phosphate-solubilizing bacteria were selected and bred, and sodium alginate-chitosan double encapsulation technology was used to 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-stage regulation, and can achieve dual-stage pH regulation. Specifically, it is reflected in:

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

[0040] Long-term sustained release of the shell: The shell layer of PLA-coated MgO@biochar gradually degrades with soil moisture, continuously releasing alkaline substances, maintaining pH stability, and achieving no rebound for 180 days.

[0041] Pores and microcapsules work together to carry bacteria. The porous structure of biochar can provide colonization space for microorganisms, and humic acid can activate the activity of the bacterial community, forming a "carrier-nutrient-bacteria" symbiotic system.

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

[0043] During the preparation of the steel slag-phosphogypsum composite, steel slag and phosphogypsum are calcined in a CO2 atmosphere at 1200°C, which can promote the formation of Ca2SiO4. The Ca2SiO4 content is ≥60%, which is twice the activity of traditional lime. During the preparation of MgO@biochar, ultrasound-assisted impregnation combined with low-temperature (500°C) calcination can achieve uniform dispersion of nanoparticles with a loading capacity of ≥8%. Freeze-drying combined with chitosan coating is also used to break through the limitation of cold chain transportation of bacterial agents. The bacterial activity loss after 6 months of storage at room temperature is <10%.

[0044] (4) In terms of coordination mechanism, it can achieve trinity repair.

[0045] One is chemical neutralization, alkaline substances (Ca 2+ ,MgO,OH - ) can directly neutralize soil acidity; secondly, physical adsorption, the pore structure of biochar locks H + 、Al 3+ ions; thirdly, bioremediation, where functional bacteria fix nitrogen and dissolve phosphorus, promoting the accumulation of organic matter and the formation of aggregate structures. Through a trinity of chemical, physical, and biological remediation methods, efficient remediation of acidified soils is achieved.

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

[0047] The acidified soil conditioner provided by the present invention uses 60% of industrial solid waste as raw materials, 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 consume about 300 kg of steel slag and 100 kg of phosphogypsum, which can reduce CO2 emissions by about 0.5 tons; a single application can last for 2 to 3 years, and can simultaneously achieve acidification improvement and soil fertility improvement.

[0048] Therefore, the soil acidification modifier provided by the present invention has the characteristics of long-term release regulation, green and low cost, high efficiency and precise regulation, and easy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic flow chart of a method for preparing a soil acidifying modifier provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0051] In these examples, parts and percentages are by mass unless otherwise indicated.

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

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

[0054] The alkali-resistant nitrogen-fixing bacteria (Azotobacter chroococcum) strain was provided by Paul Timhan (Weifang) Biotechnology Co., Ltd., with an effective viable bacterial 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 bacterial count of 2.82 billion / g.

[0056] The steel slag was provided by Hunan Valin Steel Group Co., Ltd., including: 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] Phosphogypsum was provided 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 provided by Guangdong Xiaoda Chemical Co., Ltd. with a purity of 99.98%.

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

[0060] 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 an alcoholysis degree of 99.1%, an ash content of 0.26%, and a sodium acetate residue of 0.02%.

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

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

[0065] 1. Preparation of acidifying soil 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 in a dry basis mass ratio of 3-5:1. The mixture is placed in a rotary kiln and calcined at 1100-1200°C for 1-2 hours. A CO2 atmosphere is introduced to promote the formation of calcium silicate (Ca2SiO4). After calcination, the material is rapidly cooled to below 200°C using water mist quenching to increase porosity and activity. The mixture is then ground in a ball mill for 2 hours and passed through a 100-mesh sieve to obtain a steel slag-phosphogypsum composite high-activity composite alkaline material.

[0068] The following preferred embodiments are examples, and the specific parameter conditions are: the dry mass ratio of steel slag to phosphogypsum is 3:1; and the calcination condition is calcination at 1100° C. for 1 hour.

[0069] Preparation of S2 and MgO@biochar: Crush crop straw into 2-3 cm segments, place in a tubular furnace, heat to 600-650°C at 10-15°C / min under N2 protection, pyrolyze for 2-3 hours, cool, grind and pass through a 200-mesh sieve to produce biochar; immerse the biochar in a 0.5 mol / L magnesium salt solution with a solid-liquid ratio of 1:10-15, ultrasonically treat for 30-60 minutes, and then let it stand for 12-24 hours; after filtration, dry the material at 110-130°C, and then calcine at 500-550°C for 3-5 hours to decompose Mg(NO3)2 into nano-MgO (particle size ≤50 nm); wash the product with clean water until neutral, dry it and set aside.

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

[0071] S3. Preparation of microbial microcapsules: Alkali-resistant nitrogen-fixing bacteria and phosphate-solubilizing bacteria were inoculated into liquid culture medium at a ratio of 1:1-2, and cultured in a shaking incubator at 30-40°C and 150-180 rpm for 48-60 hours to obtain a mixed bacterial solution with a bacterial solution concentration of ≥1×10 9 CFU / mL; the mixed bacterial liquid and 2% sodium alginate solution are mixed at a volume ratio of 1:4~6 to obtain a mixed solution, which is then dropped into a 1.5% CaCl2 solution with a mass percentage of 5~10 times the volume of the mixed solution to solidify into microspheres with a particle size of 1~2mm; the obtained microspheres are first filtered to obtain microsphere powder, and then the microsphere powder is added to an acetic acid solution with a mass percentage concentration of 0.5% chitosan at a mass volume ratio of 1:2~3g / mL for secondary coating to obtain microbial microcapsules, which are then freeze-dried and stored for future use. The freeze-drying conditions are: pre-freeze at -40°C for 24 hours under a vacuum degree of 10Pa.

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

[0073] S4, core granulation: the steel slag-phosphogypsum composite prepared in S1, humic acid, and carboxymethyl cellulose are uniformly mixed according to a preset ratio; a 2% polyvinyl alcohol solution is sprayed into the pellets using a disc granulator to control the particle size to 2-4 mm; after granulation, the pellets are dried with hot air at 80°C to a moisture content of ≤5% to obtain core particles.

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

[0075] The following preferred embodiments are examples, and the specific parameter conditions are as follows: the spraying rate of the suspension is 0.2 mL / min; the drying condition of the coated particles is to treat them 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 controlled rotation speed of 30-40 r / min and a mixing time of 20-50 minutes, so that the microcapsules are evenly attached to the surface of the particles; the mixed materials are balanced at 40-50°C and a humidity of 30-40% for 12-18 hours to obtain the acidified soil conditioner.

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

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

[0079]

[0080] 2. Comparative test of application of acidified soil conditioner

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

[0082] Treatment 1 (control): Planting according to local customary methods;

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

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

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

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

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

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

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

[0090] Each treatment was replicated three times, for a total of 24 plots.

[0091] Treatments 2-8 should be applied once seven days before transplanting rice in the first year. Mix thoroughly with the soil (0-20 cm) and water generously. No application is required in the second year.

[0092] When the rice is mature, the yield is measured, and soil samples are collected from each plot 90 days, 180 days, 360 days, and 540 days after the application of the amendment 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 extraction agent, collect a small amount of soil and mix the water and soil in a mass ratio of 2.5:1, and measure the pH using the potentiometric method (refer to NY / T1377-2007).

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

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

[0097] (4) Rice yield determination: refer to the “Operational Specification for Rice Yield Determination” (DB33 / T 2517-2022).

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

[0099]

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

[0101] Over time, the soil pH in Treatments 2, 3, 4, 5, 6, and 7 showed a downward trend, but the rate of decline ranked from smallest to largest: Treatment 2 / 3 / 4 < Treatment 6 < Treatment 5 < Treatment 7. The soil pH in Treatment 8 decreased at all time points compared to Treatment 1. Over a shorter period (less than 90 days), the effects of Treatments 2, 3, 4, 5, 6, and 7 were similar. Over a longer period (180-540 days), the effects of Treatments 5, 6, and 7 were significantly weaker than those of Treatments 2 / 3 / 4. This demonstrates that the application of the acidified soil conditioner of the present invention can effectively increase the pH of acidified soils, and the effect is sustained over a long period (two rice-growing years).

[0102]

[0103] As shown in Table 3, the soil available manganese in treatment 2 decreased by 33.0%, 29.5%, 26.6% and 23.9% compared with treatment 1 90 days, 180 days, 360 days and 540 days respectively; the soil available manganese in treatment 3 decreased by 31.4%, 28.9%, 27.9% and 24.8% compared with treatment 1 90 days, 180 days, 360 days and 540 days respectively; the soil available manganese in treatment 4 decreased by 32.1%, 28.2%, 27.2% and 24.8% compared with treatment 1 90 days, 180 days, 360 days and 540 days respectively. .2%; 90, 180, 360, and 540 days after application, soil available manganese in Treatment 5 decreased by 30.5%, 25.2%, 24.5%, and 15.3%, respectively, compared with Treatment 1; 90, 180, 360, and 540 days after application, soil available manganese in Treatment 6 decreased by 32.4%, 27.5%, 26.3%, and 21.3%, respectively, compared with Treatment 1; 90, 180, 360, and 540 days after application, soil available manganese in Treatment 7 decreased by 33.3%, 19.7%, 12.4%, and 3.5%, respectively, compared with Treatment 1. Over time, soil available manganese in Treatments 2, 3, 4, 5, 6, and 7 increased, but the rate of increase was Treatment 2 / 3 / 4 < Treatment 6 < Treatment 5 < Treatment 7. Soil available manganese in Treatment 8 increased at all time points compared with Treatment 1. Over a shorter period (less than 90 days), the effects of Treatments 2, 3, 4, 5, 6, and 7 were similar. Over a longer period (180 to 540 days), the effects of Treatments 5, 6, and 7 were significantly weaker than those of Treatments 2, 3, and 4. This suggests that the application of the acidifying soil conditioner of the present invention can effectively reduce available manganese in the soil (a barrier to soil acidity) and that the effect is sustainable over a longer period (two rice-growing years).

[0104]

[0105] As shown in Table 4, the soil base saturation of treatment 2 increased by 40.1%, 37.8%, 30.4% and 31.7% respectively 90 days, 180 days, 360 days and 540 days compared with treatment 1; the soil base saturation of treatment 3 increased by 41.0%, 37.3%, 31.1% and 31.5% respectively 90 days, 180 days, 360 days and 540 days compared with treatment 1; the soil base saturation of treatment 4 increased by 40.7%, 36.6%, 30.7% and 32.0% respectively 90 days, 180 days, 360 days and 540 days compared with treatment 1 .3%; 90, 180, 360, and 540 days after application, soil base saturation in Treatment 5 increased by 39.9%, 34.9%, 19.5%, and 16.7%, respectively, compared with Treatment 1; 90, 180, 360, and 540 days after application, soil base saturation in Treatment 6 increased by 39.6%, 35.2%, 27.1%, and 28.5%, respectively, compared with Treatment 1; 90, 180, 360, and 540 days after application, soil base saturation in Treatment 7 increased by 42.0%, 16.5%, 3.5%, and 1.1%, respectively, compared with Treatment 1. Over time, soil base saturation in Treatments 2, 3, 4, 5, 6, and 7 showed a decreasing trend, but the rate of decrease was Treatment 2 / 3 / 4 < Treatment 6 < Treatment 5 < Treatment 7. Soil base saturation in Treatment 8 decreased at all time points compared with Treatment 1. Over a shorter period (less than 90 days), the effects of Treatments 2, 3, 4, 5, 6, and 7 were similar. Over 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 suggests that the application of the acidified soil conditioner of the present invention can effectively increase soil base saturation (an important indicator of soil fertility) and that the effect is sustained over a long period (two rice-growing years).

[0106]

[0107] Table 5 shows that in Treatment 2, rice yields increased by 15.3% and 12.5% in the first and second years, respectively, compared to Treatment 1; in Treatment 3, rice yields increased by 16.9% and 14.4% in the first and second years, respectively; in Treatment 4, rice yields increased by 15.9% and 12.8% in the first and second years, respectively; in Treatment 5, rice yields increased by 6.9% and 5.0% in the first and second years, respectively; in Treatment 6, rice yields increased by 5.1% and 2.5% in the first and second years, respectively; and in Treatment 7, rice yields increased by 8.5% and -0.2% in the first and second years, respectively, compared to Treatment 1. Treatment 8 resulted in a reduction in rice yield. This demonstrates that the application of the acidified soil conditioner of the present invention can effectively increase rice yield, and the effect is sustained over a long period (two rice-growing years).

[0108] In summary, after applying the acidified soil conditioner of the present invention once, it can significantly improve the soil pH and base saturation, reduce the effective manganese in the soil, and greatly increase rice yield over a long period of time, with obvious effect advantages. By using solid waste and functional materials to compound, solid waste resource utilization and long-term release of alkaline substances are achieved; core-shell sustained release and multi-level regulation are achieved through inner core granulation and outer core coating; green preparation and precise control are achieved by integrating high-temperature calcination, ultrasonic-assisted impregnation, nano-dispersion and other technologies, and the problem of room temperature storage of bacterial-containing improvers is solved; it has the characteristics of long-term release regulation, green and low cost, high efficiency, precise regulation and easy storage.

[0109] The above descriptions are only some preferred embodiments of the present invention and are 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 in the scope of protection of the present invention.

Claims

1. A method for preparing an acidified soil conditioner, comprising the following steps: S1. Preparation of steel slag-phosphogypsum composite: steel slag and phosphogypsum are mixed in a dry weight ratio of 3-5:1, and calcined at 1100-1200° C. for 1-2 hours under a CO2 atmosphere; after calcination, the material is rapidly cooled to below 200° C.; then, the material is ground for 2-3 hours and sieved to obtain the composite; S2. Preparation of MgO@biochar: (1) Crush crop straw into small pieces of 2-3 cm, heat to 600-650℃ at 10-15℃ / min under N2 protection, pyrolyze for 2-3 hours, grind and sieve after cooling to obtain biochar; (2) Immerse the biochar in a magnesium salt solution with a solid-liquid ratio of 1:10-15, ultrasonically treat for 30-60 minutes, and then let it stand for 12-24 hours; (3) After filtration, dry the material at 110-130℃, and then calcine at 500-550℃ for 3-5 hours to decompose the magnesium salt into nano-MgO; The product is washed with clean water until neutral and dried; S3. Preparation of microbial microcapsules: (1) Inoculate alkali-resistant nitrogen-fixing bacteria and phosphate-solubilizing bacteria into liquid culture medium at a ratio of 1:1~2, and culture at 30~40℃ and 150~180r / min on a shaking table for 48~60 hours to obtain a mixed bacterial solution with a bacterial solution concentration of ≥1×10 9 CFU / mL; (2) the mixed bacterial solution and the sodium alginate aqueous solution were mixed in a volume ratio of 1:4-6 to obtain a mixed solution, and CaCl2 solution was added dropwise to the mixed solution to solidify and form microspheres; the microspheres were coated with chitosan acetic acid solution for the second time to obtain microbial microcapsules, which were freeze-dried and stored for future use; S4, core granulation: 45-55 parts of the steel slag-phosphogypsum composite prepared in S1, 10-20 parts of humic acid, and 2-4 parts of carboxymethyl cellulose are uniformly mixed; polyvinyl alcohol solution is sprayed into the mixture for granulation; and after granulation, the core particles are dried to obtain core particles; S5, shell coating: 15-25 parts of MgO@biochar prepared in S2 are dispersed in a polylactic acid-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 the suspension is sprayed at a rate of 0.2-0.3 mL / min to form a coating layer; and the residual solvent is removed after vacuum drying to obtain coated particles; S6. Microbial loading: 4 to 6 parts of the microbial microcapsules prepared in S3 and the coated particles formed by S5 are put into a three-dimensional mixer and the speed is controlled at 30 to 40 r / min for 20 to 50 minutes to allow the microbial microcapsules to evenly adhere to the surface of the coated particles; the mixed materials are balanced at 40 to 50°C and 30 to 40% humidity for 12 to 18 hours to obtain the acidified soil conditioner.

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

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

4. The method for preparing the acidified soil conditioner according to claim 1, wherein: The coating layer thickness in step S5 is controlled to be 200-300 μm, and the vacuum drying condition is 50-60° C. for 4-6 hours.

5. The method for preparing the acidified soil conditioner according to claim 1, wherein: 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 of ≤0.5%.

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

7. The method for preparing the acidified soil conditioner according to claim 1, wherein: In S3, the effective viable count of the alkali-resistant nitrogen-fixing bacteria species is ≥ 2.5 billion / g; the effective viable count of the phosphate-solubilizing bacteria species is ≥ 2.5 billion / g.

8. The method for preparing the acidified soil conditioner according to claim 1, wherein: In S4, the humic acid lignite or weathered coal extract has a humification index ≥ 60% and an E4 / E6 ratio ≤ 5; The carboxymethyl cellulose has a purity of ≥95% and a viscosity of ≥1500 mPa·s; the polyvinyl alcohol has an alcoholysis degree of ≥98%, an ash content of ≤0.5%, and a sodium acetate residue of ≤0.1%; In S5, the polylactic acid (PLA) has a molecular weight range of 100,000 to 150,000; the dichloromethane has a purity of ≥99.9% and a residual moisture of ≤0.01%.

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

10. A method for improving acidified soil, characterized in that: The acidified soil conditioner according to claim 9 is applied 3 to 7 days before rice transplanting at an application rate of 100 to 200 kg per mu. After application, the 20 to 30 cm soil layer on the surface of the cultivated land is fully rotary tilled and stirred and watered with sufficient water.

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