Expansion slow-release soil conditioner and preparation method thereof

Abstract

The invention discloses an expansion slow-release soil conditioner and a preparation method thereof, and relates to the technical field of soil conditioners. The swelling slow-release type soil conditioner is prepared from the following raw materials in parts by mass: bentonite, open-cell expanded perlite, polysuccinimide, bacillus mucilaginosus, ailanthus altissima, copper tailings, a biodegradable calcium silicate nano composite material, swelling type polymer microspheres, a slow-release type coated fertilizer, sodium alginate gel particles and a nanoscale bentonite compound. The fertilizer has super-strong water absorption expansibility, can significantly increase soil porosity and improve soil air permeability and water retention, is suitable for soil improvement in hardened soil and arid areas, controls the nutrient release speed through a coating technology, provides long-acting fertility supply, improves the fertilizer utilization rate, reduces the fertilization frequency and environmental pollution, and has a wide application prospect. The soil conditioner is suitable for soil improvement in arid regions, and further improves the water-retaining property and nutrient adsorption capacity of soil.

Description

Technical Field

[0001] The invention relates to the technical field of soil conditioners, and in particular to a swelling slow-release soil conditioner and a preparation method thereof. Background Art

[0002] With the rapid development of agricultural planting, people's quality of life has been significantly improved while meeting their basic needs for food and clothing. However, excessive reclamation, abuse of fertilizers and pesticides, and unreasonable farming methods have led to increasingly prominent problems such as serious degradation of soil fertility, imbalance of microbial flora, and soil acidification and compaction. The emergence of these problems not only reduces soil productivity, but also aggravates the deterioration of the ecological environment. In response to this situation, expansive slow-release soil conditioners came into being. This type of conditioner can effectively increase soil porosity and improve soil structure through its unique expansibility and slow-release properties, while slowly releasing nutrients to promote the recovery and balance of soil microorganisms, thereby repairing degraded soil, improving soil fertility, and providing strong support for sustainable agricultural development.

[0003] Although existing soil conditioners can increase soil water retention and air permeability, they have limited expansion properties and cannot significantly increase soil porosity. They have limited effects on improving compacted soil or clay soil, and are not convenient for fundamentally solving the problem of poor soil aeration. In addition, nutrients are released too quickly, resulting in inadequate absorption by crops and low fertilizer utilization. At the same time, their water retention capacity is limited and they are easily ineffective due to high temperature or acid-base environment, causing soil moisture to evaporate quickly and unable to maintain soil moisture for a long time.

[0004] Currently, no effective solution has been proposed for the problems in the related technologies. Summary of the invention

[0005] In view of the problems in the related art, the present invention proposes an expansive slow-release soil conditioner and a preparation method thereof to overcome the above-mentioned technical problems existing in the existing related art.

[0006] To this end, the specific technical solution adopted by the present invention is as follows: According to one aspect of the present invention, a swelling slow-release soil conditioner is provided, which is composed of the following raw materials in parts by weight: 480-520 parts of bentonite, 40-60 parts of open-pore expanded perlite, 60-80 parts of polysuccinimide, 0.5-1 parts of colloidal Bacillus, 12-16 parts of Ailanthus altissima, 45-55 parts of copper tailings, 40-45 parts of biodegradable calcium silicate nanocomposite materials, 12-18 parts of expandable polymer microspheres, 18-22 parts of slow-release coated fertilizers, 6-9 parts of sodium alginate gel particles and 10-14 parts of nano-grade bentonite composite materials.

[0007] Furthermore, the expandable polymer microspheres are composed of the following raw materials in parts by mass: 6 - 8 parts of sodium polyacrylate, 3 - 5 parts of cross - linker, 1 - 2 parts of initiator and 2 - 3 parts of surfactant.

[0008] Furthermore, the slow - release coated fertilizer is composed of the following raw materials in parts by mass: 10 - 12 parts of base fertilizer, 6 - 8 parts of coating material, 1 - 2 parts of plasticizer and 1 - 2 parts of binder.

[0009] Furthermore, the sodium alginate gel particles are composed of the following raw materials in parts by mass: 3 - 5 parts of sodium alginate, 2 - 3 parts of cross - linker, 0.5 - 1 part of thickener and 0.5 part of water.

[0010] Furthermore, the nano - sized bentonite composite is composed of the following raw materials in parts by mass: 5 - 8 parts of nano - silica, 3 - 5 parts of nano - clay and 2 - 3 parts of surface modifier.

[0011] Furthermore, the base fertilizer includes at least two of nano - ammonium sulfate, nano - phosphate fertilizer, controlled - release nitrogen fertilizer, plant - derived nitrogen fertilizer, nitrogen - phosphorus - potassium compound fertilizer or silicon - based fertilizer.

[0012] Furthermore, the coating material includes at least two of graphene coating, polylactic acid coating, polyurethane coating, nano - sodium alginate coating, polycaprolactone coating, carbon nanotube coating or polyethylene - plant fiber composite.

[0013] According to another aspect of the present invention, there is also provided a preparation method of an expandable and slow - release soil conditioner. The preparation method of the expandable and slow - release soil conditioner includes the following steps: S1. Respectively use a ball mill to crush bentonite, open - cell expanded perlite, copper tailings, biodegradable calcium silicate nanocomposite, and nano - sized bentonite composite to a particle size of less than 0.5 mm according to the preset parts by mass, and then use a hot - air circulation dryer to dry the Ailanthus altissima to a moisture content of less than 7%, and then use a ball mill to crush it to 50 - 80 mesh for standby; S2. Mix sodium polyacrylate, cross - linker, initiator and surfactant according to the preset parts by mass, and prepare expandable polymer microspheres by emulsion polymerization method. Dry and screen the prepared expandable polymer microspheres to obtain expandable polymer microspheres with uniform particle size; S3. Respectively mix the base fertilizer with the coating material, plasticizer and binder according to the preset parts by mass, and prepare slow - release coated fertilizer by fluidized - bed coating technology. Dry and screen the prepared coated fertilizer and then set it aside; S4. Mix sodium alginate, crosslinking agent, thickening agent and water according to the preset mass fractions respectively, prepare sodium alginate gel particles by spray drying method, dry and screen the prepared gel particles and reserve them for later use; S5. Use a double helix mixer to mix the pretreated bentonite, expanded perlite with open pores, copper tailings, biodegradable calcium silicate nanocomposite, nano-sized bentonite composite, Ailanthus altissima, expandable polymer microspheres, slow-release coated fertilizer, and sodium alginate gel particles, and add Bacillus mucilaginosus, continue to mix and stir for 10 - 15 minutes to obtain a mixture, and use an extrusion granulator to extrude the mixture into granular soil conditioner with a particle diameter of 2 - 4 mm; S6. Use a hot air circulation dryer to dry the granular soil conditioner at 60 - 80 °C until the moisture content is lower than 5%, and cool it to room temperature. Use a vibrating screen to screen the cooled granular soil conditioner, remove oversized or undersized particles, and package the screened granular soil conditioner into finished products.

[0014] Further, mix sodium polyacrylate, crosslinking agent, initiator and surfactant according to the preset mass fractions, prepare expandable polymer microspheres by emulsion polymerization method, dry and screen the prepared expandable polymer microspheres, and obtain expandable polymer microspheres with uniform particle size, including the following steps: S21. Use a high-speed mixer to add sodium polyacrylate, crosslinking agent, initiator and surfactant into deionized water, stir evenly to form a premixed solution, and add the premixed solution into an emulsifier, and emulsify for 10 - 15 minutes under the condition that the stirring speed is 1000 - 1500 r / min to form a stable emulsion; S22. Transfer the emulsion to a reaction kettle, under nitrogen protection, raise the temperature of the reaction kettle to 60 - 80 °C, and the reaction time is 2 - 3 hours; S23. After the reaction is completed, use a centrifuge to centrifuge and separate the reaction product to obtain expandable polymer microspheres, and wash the separated expandable polymer microspheres 3 - 5 times with deionized water in an ultrasonic cleaner to remove unreacted monomers and impurities; S24. Put the washed expandable polymer microspheres into a spray dryer, dry them at 60 - 80 °C until the moisture content is lower than 5%, and use a vibrating screen to screen the dried expandable polymer microspheres to obtain expandable polymer microspheres with uniform particle size.

[0015] Further, mix the basic fertilizer with coating material, plasticizer, and binder according to the preset mass fractions respectively, prepare slow-release coated fertilizer by fluidized bed coating technology, dry and screen the prepared coated fertilizer and reserve it for later use, including the following steps: S31. Use a vibrating sieve to screen the basic fertilizer to obtain fertilizer particles with uniform particle size, and add the screened fertilizer particles into a fluidized bed coating machine, and preheat them at 50-70 °C for 10-15 minutes to make the surface temperature of the fertilizer particles uniform; S32. Use a stirring reactor to dissolve the coating material in an organic solvent to form a uniform coating solution, and use a filter to filter the coating solution to remove undissolved impurities to ensure the uniformity of the solution; S33. Keep the preheated fertilizer particles in the fluidized bed coating machine, turn on the air flow of the fluidized bed to make the fertilizer particles in a suspended state, and use a spray nozzle to evenly spray the coating solution on the surface of the suspended fertilizer particles; S34. Set the coating temperature to 50-70 °C, and the coating time to 1-2 hours, and use an infrared thermometer and a thickness gauge to monitor the coating temperature and coating thickness in real time to ensure uniform coating; S35. Transfer the coated fertilizer particles to a hot air circulation dryer, dry them at 60-80 °C until the moisture content is less than 5%, and use a moisture meter to detect the moisture content of the coated fertilizer particles to ensure the drying effect; S36. Use a vibrating sieve to screen the dried coated fertilizer to obtain slow-release coated fertilizer with uniform particle size.

[0016] The beneficial effects of the present invention are as follows: 1. The present invention has super water absorption and swelling properties, can significantly increase soil porosity, improve soil aeration and water retention, is suitable for improving compacted soil and soil in arid areas, and controls the nutrient release rate through the coating technology to provide long-term fertilizer supply, improve fertilizer utilization rate, reduce fertilization frequency and environmental pollution. At the same time, it forms a gel when encountering water, can adsorb water and nutrients, enhance the water retention capacity of the soil, is suitable for improving soil in arid areas, enhances the function of bentonite through nanotechnology, further improves the water retention capacity and nutrient adsorption capacity of the soil, and has better performance and longer-lasting effect.

[0017] 2. The present invention has extremely strong water absorption and swelling properties, and its volume increases rapidly when encountering water, can effectively increase soil porosity, improve soil aeration and water permeability, has a porous structure, can adsorb water and nutrients, at the same time increase soil looseness, promote plant root growth, and the biodegradable calcium silicate nanocomposite material has the function of adjusting soil pH value, can neutralize acidic soil, improve soil chemical properties. At the same time, Ailanthus altissima has antibacterial effects, can inhibit pathogenic bacteria in the soil, reduce the occurrence of soil-borne diseases, and Bacillus mucilaginosus has the functions of decomposing phosphorus and potassium, can promote the transformation of insoluble nutrients in the soil, and improve nutrient utilization rate. Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for use in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0019] Figure 1 is a flowchart of a preparation method of an expanding and slow-release type soil conditioner according to an embodiment of the present invention. Detailed implementation manners

[0020] To further illustrate each embodiment, the present invention provides accompanying drawings. These accompanying drawings are a part of the disclosure of the present invention, mainly used to illustrate the embodiments, and can be used in conjunction with the relevant descriptions in the specification to explain the operation principle of the embodiments. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention.

[0021] According to an embodiment of the present invention, there is provided an expanding and slow-release type soil conditioner and a preparation method thereof.

[0022] The expanding and slow-release type soil conditioner according to an embodiment of the present invention is composed of the following raw materials in parts by mass: 480 - 520 parts of bentonite, 40 - 60 parts of open-cell expanded perlite, 60 - 80 parts of poly(succinimide), 0.5 - 1 part of Bacillus mucilaginosus, 12 - 16 parts of Ailanthus altissima, 45 - 55 parts of copper tailings, 40 - 45 parts of biodegradable calcium silicate nanocomposite, 12 - 18 parts of expanding polymer microspheres, 18 - 22 parts of slow-release coated fertilizer, 6 - 9 parts of sodium alginate gel particles, and 10 - 14 parts of nanoscale bentonite composite.

[0023] In this alternative embodiment, the expanding polymer microspheres are composed of the following raw materials in parts by mass: 6 - 8 parts of sodium polyacrylate, 3 - 5 parts of crosslinking agent, 1 - 2 parts of initiator, and 2 - 3 parts of surfactant.

[0024] In this alternative embodiment, the slow-release coated fertilizer is composed of the following raw materials in parts by mass: 10 - 12 parts of basic fertilizer, 6 - 8 parts of coating material, 1 - 2 parts of plasticizer, and 1 - 2 parts of adhesive.

[0025] In this alternative embodiment, the sodium alginate gel particles are composed of the following raw materials in parts by mass: 3 - 5 parts of sodium alginate, 2 - 3 parts of crosslinking agent, 0.5 - 1 part of thickening agent, and 0.5 part of water.

[0026] In this alternative embodiment, the nano-sized bentonite composite is composed of raw materials in the following parts by mass: 5-8 parts of nano-silica, 3-5 parts of nano-clay, and 2-3 parts of surface modifier.

[0027] In this alternative embodiment, the base fertilizer includes at least two of nano-ammonium sulfate, nano-phosphate fertilizer, controlled-release nitrogen fertilizer, plant-derived nitrogen fertilizer, nitrogen-phosphorus-potassium compound fertilizer, or silicon-based fertilizer.

[0028] In this alternative embodiment, the coating material includes at least two of graphene coating, polylactic acid coating, polyurethane coating, nano-sodium alginate coating, polycaprolactone coating, carbon nanotube coating, or polyethylene-plant fiber composite.

[0029] According to another embodiment of the present invention, as Figure 1 shown, a preparation method of an expandable and slow-release soil conditioner is also provided. The preparation method of the expandable and slow-release soil conditioner includes the following steps: S1. Respectively use a ball mill to crush bentonite, open-cell expanded perlite, copper tailings, biodegradable calcium silicate nanocomposite, and nano-sized bentonite composite to a particle size of less than 0.5 mm according to preset parts by mass, and then use a hot air circulation dryer to dry the Ailanthus altissima to a moisture content of less than 7%, and then use a ball mill to crush it to 50-80 mesh for standby; S2. Mix sodium polyacrylate, crosslinking agent, initiator, and surfactant according to preset parts by mass, and prepare expandable polymer microspheres by emulsion polymerization. Dry and screen the prepared expandable polymer microspheres to obtain expandable polymer microspheres with uniform particle size; S3. Respectively mix the base fertilizer with the coating material, plasticizer, and binder according to preset parts by mass, and prepare slow-release coated fertilizer by fluidized bed coating technology. Dry and screen the prepared coated fertilizer and set it aside; S4. Mix sodium alginate, crosslinking agent, thickening agent, and water according to preset parts by mass, and prepare sodium alginate gel particles by spray drying method. Dry and screen the prepared gel particles and set it aside; S5. Use a double-screw mixer to mix the pretreated bentonite, open-cell expanded perlite, copper tailings, biodegradable calcium silicate nanocomposite, nano-sized bentonite composite, Ailanthus altissima, expandable polymer microspheres, slow-release coated fertilizer, and sodium alginate gel particles, and add Bacillus mucilaginosus, and continue to mix and stir for 10-15 minutes to obtain a mixture. Use an extrusion granulator to extrude the mixture into granular soil conditioner, and the particle diameter is 2-4 mm; S6. Use a hot air circulation dryer to dry the granular soil conditioner at 60 - 80°C until the moisture content is less than 5%, and then cool it to room temperature. Use a vibrating sieve to screen the cooled granular soil conditioner to remove oversized or undersized particles, and then package the screened granular soil conditioner as a finished product.

[0030] To better understand the above technical solutions of the present invention, the following will be described in detail with specific embodiments.

[0031] Example 1 The swelling and slow-release type soil conditioner is composed of the following raw materials in parts by mass: 480 g of bentonite, 40 g of open-cell expanded perlite, 60 g of poly(succinimide), 0.5 g of Bacillus mucilaginosus, 12 g of Ailanthus altissima, 45 g of copper tailings, 40 g of biodegradable calcium silicate nanocomposite, 6 g of sodium polyacrylate, 3 g of crosslinking agent, 1 g of initiator, 2 g of surfactant, 10 g of basic fertilizer, 6 g of coating material, 1 g of plasticizer, 1 g of binder, 3 g of sodium alginate, 2 g of crosslinking agent, 0.5 g of thickener, 0.5 g of water, 5 g of nano-silica, 3 g of nano-clay and 2 g of surface modifier.

[0032] Example 2 The swelling and slow-release type soil conditioner is composed of the following raw materials in parts by mass: 520 g of bentonite, 60 g of open-cell expanded perlite, 80 g of poly(succinimide), 1 g of Bacillus mucilaginosus, 16 g of Ailanthus altissima, 55 g of copper tailings, 45 g of biodegradable calcium silicate nanocomposite, 8 g of sodium polyacrylate, 5 g of crosslinking agent, 2 g of initiator, 3 g of surfactant, 12 g of basic fertilizer, 8 g of coating material, 2 g of plasticizer, 2 g of binder, 5 g of sodium alginate, 3 g of crosslinking agent, 1 g of thickener, 0.5 g of water, 8 g of nano-silica, 5 g of nano-clay and 3 g of surface modifier.

[0033] Example 3 The swelling and slow-release type soil conditioner is composed of the following raw materials in parts by mass: 500 g of bentonite, 50 g of open-cell expanded perlite, 70 g of poly(succinimide), 0.75 g of Bacillus mucilaginosus, 14 g of Ailanthus altissima, 50 g of copper tailings, 42.5 g of biodegradable calcium silicate nanocomposite, 7 g of sodium polyacrylate, 4 g of crosslinking agent, 1.5 g of initiator, 2.5 g of surfactant, 11 g of basic fertilizer, 7 g of coating material, 1.5 g of plasticizer, 1.5 g of binder, 4 g of sodium alginate, 2.5 g of crosslinking agent, 0.75 g of thickener, 0.5 g of water, 6.5 parts of nano-silica, 4 g of nano-clay and 2.5 g of surface modifier.

[0034] Comparative Example: The swelling and slow-release type soil conditioner is composed of the following raw materials in parts by mass: 510 g of bentonite, 45 g of open-cell expanded perlite, 75 g of poly(succinimide), 0.6 g of Bacillus mucilaginosus, 13 g of Ailanthus altissima, 52 g of copper tailings, and 41 g of biodegradable calcium silicate nanocomposite.

[0035] It should be noted that: I. Experimental purpose: By comparing the performance of the swelling and slow-release type soil conditioners in Example 1, Example 2, Example 3 and the comparative example, verify the advantages of each example in terms of slow-release performance, swelling performance, soil improvement effect, etc.

[0036] II. Experimental method: Slow-release performance test: Mix the soil conditioners of each example and the comparative example with the soil respectively, measure the fertilizer release rate, and record the nutrient release amount within 30 days.

[0037] Swelling performance test: Immerse the soil conditioners of each example and the comparative example in water, and measure their swelling rate.

[0038] Soil improvement effect test: Apply the soil conditioners of each example and the comparative example to the experimental field, and measure the soil porosity, water retention and plant growth.

[0039] III. Experimental steps: 1) Slow-release performance test: Mix the soil conditioners of each example and the comparative example with the soil at a ratio of 1:10 respectively.

[0040] Regularly take samples to measure the nutrient content in the soil, and record the nutrient release amount within 30 days.

[0041] 2) Swelling performance test: Immerse the soil conditioners of each example and the comparative example in 100 mL of water respectively. After 24 hours, measure their volume change and calculate the swelling rate.

[0042] 3) Soil improvement effect test: Apply the soil conditioners of each example and the comparative example to the experimental field at a rate of 100 g per square meter.

[0043] Measure the soil porosity, water retention, and record the plant growth.

[0044] IV. Experimental results: Slow-release performance: Example 1: The nutrient release amount within 30 days is 85%.

[0045] Example 2: The nutrient release amount within 30 days is 80%.

[0046] Example 3: The nutrient release amount within 30 days is 82%.

[0047] Control example: The nutrient release amount within 30 days is 95%.

[0048] Swelling performance: Example 1: The swelling rate is 210%.

[0049] Example 2: The swelling rate is 220%.

[0050] Example 3: The swelling rate is 215%.

[0051] Control example: The swelling rate is 180%.

[0052] Soil improvement effect: Example 1: The soil porosity increases by 15%, the water retention capacity increases by 20%, and the plant growth height increases by 25%.

[0053] Example 2: The soil porosity increases by 18%, the water retention capacity increases by 22%, and the plant growth height increases by 28%.

[0054] Example 3: The soil porosity increases by 16%, the water retention capacity increases by 21%, and the plant growth height increases by 26%.

[0055] Control example: The soil porosity increases by 10%, the water retention capacity increases by 15%, and the plant growth height increases by 18%.

[0056] V. Experimental data comparison table: As shown in Table 1.

[0057] Table 1: Experimental data comparison table VI. Experimental conclusion: By comparing the experimental data, it can be seen that Example 1, Example 2, and Example 3 are superior to the control example in terms of slow-release performance, swelling performance, and soil improvement effect. The specific manifestations are as follows: Slow-release performance: The nutrient release amounts of Example 1, Example 2, and Example 3 are all lower than that of the control example, indicating better slow-release effects.

[0058] Swelling performance: The swelling rates of Example 1, Example 2, and Example 3 are all higher than that of the control example, indicating better swelling effects.

[0059] Soil improvement effect: The improvement effects of Example 1, Example 2, and Example 3 in terms of soil porosity, water retention capacity, and plant growth height are all superior to those of the control example.

[0060] In this alternative embodiment, sodium polyacrylate, a crosslinking agent, an initiator, and a surfactant are mixed according to preset mass parts, and expandable polymer microspheres are prepared by emulsion polymerization. Drying and screening the prepared expandable polymer microspheres to obtain expandable polymer microspheres with uniform particle sizes includes the following steps: S21. Add sodium polyacrylate, a crosslinking agent, an initiator, and a surfactant to deionized water using a high-speed stirrer, stir evenly to form a premixed solution, and add the premixed solution to an emulsifier. Emulsify for 10 - 15 minutes under the condition that the stirring speed is 1000 - 1500 r / min to form a stable emulsion; S22. Transfer the emulsion to a reaction kettle, and under nitrogen protection, raise the temperature of the reaction kettle to 60 - 80 °C, and the reaction time is 2 - 3 hours; S23. After the reaction is completed, centrifuge and separate the reaction product using a centrifuge to obtain expandable polymer microspheres, and wash the separated expandable polymer microspheres 3 - 5 times with deionized water in an ultrasonic cleaner to remove unreacted monomers and impurities; S24. Put the washed expandable polymer microspheres into a spray dryer and dry them at 60 - 80 °C until the moisture content is lower than 5%, and use a vibrating screen to screen the dried expandable polymer microspheres to obtain expandable polymer microspheres with uniform particle sizes.

[0061] In this alternative embodiment, a basic fertilizer is respectively mixed with a coating material, a plasticizer, and an adhesive according to preset mass parts, and a slow-release coated fertilizer is prepared by fluidized bed coating technology. Drying and screening the prepared coated fertilizer and then storing it for later use includes the following steps: S31. Screen the basic fertilizer using a vibrating screen to obtain fertilizer particles with uniform particle sizes, and add the screened fertilizer particles to a fluidized bed coater. Preheat at 50 - 70 °C for 10 - 15 minutes to make the surface temperature of the fertilizer particles uniform; S32. Dissolve the coating material in an organic solvent using a stirring reaction kettle to form a uniform coating solution, and filter the coating solution using a filter to remove undissolved impurities to ensure the uniformity of the solution; S33. Keep the preheated fertilizer particles in the fluidized bed coater, turn on the air flow of the fluidized bed to make the fertilizer particles in a suspended state, and use a spray nozzle to evenly spray the coating solution on the surface of the suspended fertilizer particles; S34. Set the coating temperature to 50 - 70 °C, and the coating time is 1 - 2 hours. Use an infrared thermometer and a thickness gauge to monitor the coating temperature and coating thickness in real time to ensure uniform coating; S35. Transfer the coated fertilizer granules to a hot air circulation dryer and dry them at 60 - 80 °C until the moisture content is lower than 5%. Use a moisture meter to detect the water content of the coated fertilizer granules to ensure the drying effect. S36. Use a vibrating screen to screen the dried coated fertilizer to obtain slow-release coated fertilizer with uniform particle size.

[0062] In summary, by means of the above technical solutions of the present invention, the present invention has extremely strong water absorption and swelling properties. After encountering water, its volume rapidly increases, which can effectively increase soil porosity, improve soil aeration and water permeability. It has a porous structure, can adsorb water and nutrients, and at the same time increase soil looseness, promote plant root growth. Moreover, the biodegradable calcium silicate nanocomposite has the function of adjusting soil pH value, can neutralize acidic soil, and improve soil chemical properties. At the same time, Ailanthus altissima has antibacterial effects, can inhibit pathogenic bacteria in the soil, and reduce the occurrence of soil-borne diseases. Bacillus mucilaginosus has the functions of decomposing phosphorus and potassium, can promote the transformation of insoluble nutrients in the soil, and improve nutrient utilization efficiency.

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A swelling slow-release soil conditioner, characterized in that: The expansive slow-release soil conditioner is composed of the following raw materials in parts by mass: 480-520 parts of bentonite, 40-60 parts of open-pore expanded perlite, 60-80 parts of polysuccinimide, 0.5-1 parts of colloidal Bacillus, 12-16 parts of Ailanthus altissima, 45-55 parts of copper tailings, 40-45 parts of biodegradable calcium silicate nanocomposite materials, 12-18 parts of expandable polymer microspheres, 18-22 parts of slow-release coated fertilizers, 6-9 parts of sodium alginate gel particles and 10-14 parts of nano-grade bentonite composite materials.

2. The swelling slow-release soil conditioner according to claim 1, characterized in that: The expanded polymer microspheres are composed of the following raw materials in parts by mass: 6-8 parts of sodium polyacrylate, 3-5 parts of cross-linking agent, 1-2 parts of initiator and 2-3 parts of surfactant.

3. A swelling slow-release soil conditioner according to claim 2, characterized in that: The slow-release coated fertilizer is composed of the following raw materials in parts by mass: 10-12 parts of basic fertilizer, 6-8 parts of coating material, 1-2 parts of plasticizer and 1-2 parts of adhesive.

4. The swelling slow-release soil conditioner according to claim 3, characterized in that: The sodium alginate gel particles are composed of the following raw materials in parts by mass: 3-5 parts of sodium alginate, 2-3 parts of cross-linking agent, 0.5-1 part of thickener and 0.5 part of water.

5. The swelling slow-release soil conditioner according to claim 4, characterized in that: The nano-bentonite composite is composed of the following raw materials in parts by weight: 5-8 parts of nano silicon dioxide, 3-5 parts of nano clay and 2-3 parts of surface modifier.

6. The swelling slow-release soil conditioner according to claim 5, characterized in that: The basic fertilizer includes at least two of nano-ammonium sulfate, nano-phosphate fertilizer, controlled-release nitrogen fertilizer, plant-derived nitrogen fertilizer, nitrogen-phosphorus-potassium compound fertilizer or silicon-based fertilizer.

7. The swelling slow-release soil conditioner according to claim 6, characterized in that: The coating material comprises at least two of graphene coating, polylactic acid coating, polyurethane coating, nano-sodium alginate coating, polycaprolactone coating, carbon nanotube coating or polyethylene-plant fiber composite.

8. A method for preparing a swelling slow-release soil conditioner, used for preparing the swelling slow-release soil conditioner described in claim 7, characterized in that: The preparation method of the swelling slow-release soil conditioner comprises the following steps: S1. Use a ball mill to grind bentonite, open-pore expanded perlite, copper tailings, biodegradable calcium silicate nanocomposite materials, and nano-grade bentonite composite materials according to preset mass fractions to a particle size of less than 0.5 mm for later use, and use a hot air circulation dryer to dry Ailanthus altissima to a moisture content of less than 7%, and then use a ball mill to grind it to 50-80 mesh for later use; S2, mixing sodium polyacrylate, a crosslinking agent, an initiator and a surfactant according to preset weight fractions, preparing expandable polymer microspheres by emulsion polymerization, drying and sieving the prepared expandable polymer microspheres to obtain expandable polymer microspheres with uniform particle size; S3, mixing the basic fertilizer with the coating material, the plasticizer, and the adhesive according to the preset mass fractions, preparing a slow-release coated fertilizer by fluidized bed coating technology, and drying and sieving the prepared coated fertilizer for later use; S4, respectively mixing sodium alginate, a cross-linking agent, a thickener and water according to preset weight fractions, preparing sodium alginate gel particles by spray drying, and drying and sieving the prepared gel particles for later use; S5, using a double-screw mixer to mix the pretreated bentonite, open-pore expanded perlite, copper tailings, biodegradable calcium silicate nanocomposite, nano-grade bentonite composite, Ailanthus altissima, expandable polymer microspheres, slow-release coated fertilizer, and sodium alginate gel particles, and adding colloidal Bacillus, continuing to mix and stir for 10-15 minutes to obtain a mixture, and using an extrusion granulator to extrude the mixture into a granular soil conditioner with a particle diameter of 2-4 mm; S6. Use a hot air circulation dryer to dry the granular soil conditioner at 60-80°C to a moisture content of less than 5%, and cool it to room temperature. Use a vibrating screener to screen the cooled granular soil conditioner to remove oversized or undersized particles, and package the screened granular soil conditioner into finished products.

9. The method for preparing a swelling slow-release soil conditioner according to claim 8, characterized in that: The method comprises the following steps: mixing sodium polyacrylate, a crosslinking agent, an initiator and a surfactant according to preset weight fractions, preparing expandable polymer microspheres by emulsion polymerization, drying and sieving the prepared expandable polymer microspheres, and obtaining expandable polymer microspheres with uniform particle size: S21, using a high-speed stirrer to add sodium polyacrylate, a cross-linking agent, an initiator and a surfactant to deionized water, stirring evenly to form a premixed solution, and adding the premixed solution to an emulsifier, emulsifying for 10-15 minutes at a stirring speed of 1000-1500 r / min to form a stable emulsion; S22, transferring the emulsion to a reactor, raising the temperature of the reactor to 60-80° C. under nitrogen protection, and reacting for 2-3 hours; S23, after the reaction is completed, the reaction product is centrifuged using a centrifuge to obtain expanded polymer microspheres, and the separated expanded polymer microspheres are washed 3-5 times with deionized water in an ultrasonic cleaning machine to remove unreacted monomers and impurities; S24, placing the washed expanded polymer microspheres into a spray dryer, drying at 60-80° C. until the moisture content is less than 5%, and using a vibrating sieving machine to sieve the dried expanded polymer microspheres to obtain expanded polymer microspheres with uniform particle size.

10. The method for preparing a swelling slow-release soil conditioner according to claim 8, characterized in that: The method comprises the following steps: mixing the basic fertilizer with the coating material, the plasticizer, and the adhesive according to the preset mass fractions, preparing the slow-release coated fertilizer by the fluidized bed coating technology, and drying and screening the prepared coated fertilizer for standby use: S31, using a vibrating screening machine to screen the basic fertilizer to obtain fertilizer particles with uniform particle size, and adding the screened fertilizer particles into a fluidized bed coating machine, and preheating at 50-70° C. for 10-15 minutes to make the surface temperature of the fertilizer particles uniform; S32, using a stirred reactor to dissolve the coating material in an organic solvent to form a uniform coating solution, and using a filter to filter the coating solution to remove undissolved impurities to ensure that the solution is uniform; S33, keeping the preheated fertilizer particles in a fluidized bed coating machine, turning on the air flow of the fluidized bed to suspend the fertilizer particles, and using a spray nozzle to evenly spray the coating solution on the surface of the suspended fertilizer particles; S34, the coating temperature is set to 50-70℃, the coating time is 1-2 hours, and an infrared thermometer and a thickness meter are used to monitor the coating temperature and coating thickness in real time to ensure uniform coating; S35, transferring the coated fertilizer particles to a hot air circulation dryer, drying them at 60-80°C until the moisture content is less than 5%, and using a moisture meter to detect the moisture content of the coated fertilizer particles to ensure the drying effect; S36. Using a vibrating screening machine to screen the dried coated fertilizer to obtain a slow-release coated fertilizer with uniform particle size.

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