Rice planting fertilizer and preparation method thereof

Abstract

The application discloses a kind of fertilizer for rice planting and its preparation method, the fertilizer is the particle with the triple structure of core-shell-outer functional layer, including: core layer, by 35±2 parts of polyurethane coated urea is constituted;Intermediate layer, is covered outside the core layer, by 25±2 parts of sulfur-coated urea is constituted;Outer layer, is covered outside the intermediate layer, and total weight is 40±5 parts.The application realizes the programmed release of nutrient by the triple structure design of "core-shell-outer functional layer", and outer layer mineral source humic acid potassium, composite silicon source and the like are rapidly dissolved and released, stimulate seedling root and provide early resistance ability;Intermediate layer sulfur-coated urea is degraded in tillering to early jointing stage, releases nitrogen and sulfur element, accurately interfaces rice first nitrogen uptake peak, and sulfur element activates nitrogen metabolic enzyme, improves nitrogen assimilation efficiency;Core layer polyurethane coated urea continuously releases nitrogen in late jointing to milk stage, effectively prevents late period from losing fertilizer.

Description

Technical Field

[0001] This application belongs to the field of rice cultivation technology, specifically relating to a fertilizer for rice cultivation and its preparation method. Background Technology

[0002] As a major food crop, high and stable rice yields are crucial for ensuring food security. Fertilization is one of the key agronomic measures affecting rice yield and quality. Currently, commonly used fertilizers in rice cultivation mainly include traditional compound fertilizers and various slow-release / controlled-release fertilizers.

[0003] Traditional compound fertilizers (such as NPK ternary compound fertilizers) release nutrients rapidly and in a concentrated manner, making it difficult to match the long growth cycle of rice, which lasts for several months and has different nutrient requirements at each stage. This often leads to nutrient excess in the early stages, causing excessive vegetative growth or seedling burn, while in the middle and later stages (especially from jointing to grain filling), insufficient nutrient supply leads to nutrient deficiency and premature senescence, ultimately affecting the number of grains per panicle and the thousand-grain weight. At the same time, a large amount of nutrients that are not absorbed in time (especially nitrogen) are lost through volatilization, leaching, or runoff, which not only reduces fertilizer utilization (nitrogen fertilizer utilization is usually only 30%-40%), but also causes serious agricultural non-point source pollution.

[0004] To overcome the above problems, slow-release / controlled-release fertilizer technology has been developed. Common slow-release fertilizers, such as polymer-coated urea and sulfur-coated urea, can delay the release of nitrogen. However, existing technologies mostly focus on the slow release of a single nutrient (mainly nitrogen), and their functions are relatively simple. In practical applications, there are the following limitations: (1) Single nutrient release mode: Most of them present a simple "slow-fast" or uniform release, which cannot accurately correspond to the two key nitrogen demand peaks of rice "tillering peak-jointing stage" and "late jointing-grain filling stage", as well as the urgent need for potassium, silicon and other elements in the seedling stage. (2) Low functional integration: It is difficult to achieve multiple functions such as slow release of nutrients, supplementation of micronutrients, soil improvement and disease resistance and growth promotion in the same particle. (3) Contradiction between structural stability and functional effectiveness: Some multi-layer structured fertilizers are prone to interlayer delamination (high brittleness) during preparation or transportation, or premature disintegration in the field, resulting in the failure of the designed phased release function. (4) Complex process and high cost: To achieve multi-layer coating, multiple sets of independent equipment or complex processes are often required, with numerous quality control points and high production costs, which restricts its large-scale promotion and application.

[0005] Therefore, there is an urgent need in this field for a new type of fertilizer that can accurately match the fertilizer requirements of rice throughout its entire growth period, integrate multiple functions, has a stable structure, and has a feasible preparation process, so as to maximize fertilizer utilization and minimize environmental impact while increasing yield. Summary of the Invention

[0006] This application provides a fertilizer for rice cultivation and its preparation method, aiming to solve the problems of existing technologies such as single nutrient release mode, low functional integration, and contradiction between structural stability and functional effectiveness.

[0007] In a first aspect, a fertilizer for rice cultivation, said fertilizer being granules with a triple structure of core-shell-outer functional layer, comprising, by weight:

[0008] The core layer consists of 35±2 parts of polyurethane-coated urea;

[0009] The intermediate layer, which covers the core layer, is composed of 25±2 parts of sulfur-coated urea.

[0010] The outer layer, which covers the middle layer, has a total weight of 40±5 parts, including 20±2 parts of mineral-derived potassium humate, 15±2 parts of composite silicon source, 2.5±0.5 parts of trace element composition, and 2.5±0.5 parts of binding and slow-release conditioning system.

[0011] Optionally, the polyurethane-coated urea has a coating thickness of 45-55 micrometers, and the sulfur-coated urea has a sulfur coating thickness of 30-40 micrometers and is covered with a microcrystalline wax sealant.

[0012] Optionally, the mineral-derived potassium humate contains not less than 60% water-soluble humic acid and not less than 12% potassium oxide.

[0013] Optionally, the composite silicon source is granulated by mixing calcined silicon-calcium-magnesium fertilizer and humic acid complexed silicon solution at a mass ratio of 95:5, wherein the silicon dioxide content is ≥35%.

[0014] Optionally, the trace element composition comprises ethylenediaminetetraacetic acid chelated zinc, borax, and ammonium molybdate.

[0015] Optionally, the bonding and slow-release conditioning system consists of modified starch adhesive and attapulgite.

[0016] Secondly, a method for preparing a fertilizer for rice cultivation includes the following steps:

[0017] S1: Preparation and pretreatment of core particles: Polyurethane-coated urea particles with a particle size of 2.8-3.2 mm are screened out, cleaned and dried to obtain core particles.

[0018] S2: Construction of the intermediate layer: Sulfur-coated urea is made into fine powder, and hydroxypropyl methylcellulose aqueous solution is used as a binder. The fine powder is coated onto the surface of the core particles through a fluidized bed bottom spray coating process. After drying and curing, the particle intermediate is obtained.

[0019] S3: Coating of the outer functional layer involves mixing mineral-derived potassium humate, composite silicon source, a combination of trace elements, and attapulgite to form a functional powder. Modified starch adhesive is used as a binder, and the functional powder is coated onto the surface of the granular intermediate through a fluidized bed top spraying process. After drying and sieving, fertilizer granules are obtained.

[0020] Optionally, in step S2, the concentration of the hydroxypropyl methylcellulose aqueous solution is 8-10%, and 3-5 parts of a polyethylene wax aqueous dispersion with a solid content of 40% are added to every 100 parts of the solution.

[0021] Optionally, in step S3, the modified starch adhesive has a solid content of 18-22%, and 5-8 parts of partially hydrolyzed polyvinyl alcohol and 1-2 parts of sodium alginate are simultaneously dissolved in every 100 parts of dry-based modified starch.

[0022] Optionally, after step S2 is completed, the particle intermediate is subjected to quality testing, and its friability is not higher than 1.0%, and the initial nitrogen dissolution rate after 7 days is less than 15%.

[0023] Compared with the prior art, this application has at least the following beneficial effects:

[0024] This application achieves programmed nutrient release through a triple structure design of "core-shell-outer functional layer". The outer layer contains mineral-derived potassium humate and composite silicon sources that are rapidly dissolved and released, stimulating seedling rooting and providing early stress resistance. The middle layer, sulfur-coated urea, degrades during the tillering to early jointing stage, releasing nitrogen and sulfur elements, precisely targeting the first nitrogen uptake peak of rice. The sulfur element also activates nitrogen metabolism enzymes, improving nitrogen assimilation efficiency. The core layer, polyurethane-coated urea, continuously releases nitrogen during the late jointing to grain-filling stage, effectively preventing nutrient deficiency in the later stages.

[0025] The multi-layered slow-release design of this application significantly reduces nitrogen volatilization and leaching losses. In particular, the synergistic effect of sulfur in the middle layer with silicon, potassium, and trace elements in the core and outer layers comprehensively improves nitrogen fertilizer utilization through multiple pathways, including promoting absorption (potassium humate), enhancing assimilation (sulfur), and strengthening transport and retention (silicon and potassium). At the same time, sufficient silicon enhances the silicification of plant epidermal cells, and works together with various micronutrients to enhance rice's resistance to diseases such as rice blast and sheath blight, as well as its lodging resistance.

[0026] This application scientifically integrates long-acting nitrogen sources, medium-acting sulfur and nitrogen sources, fast-acting growth-promoting and disease-resistant components (humic acid, silicon, potassium, and trace elements), and soil conditioning components (attapulgite soil) into a single particle. Farmers can meet the multi-faceted needs of rice for macro-, medium-, and micronutrients throughout its entire growth period with a single basal application, while simultaneously obtaining the additional benefits of promoting growth, disease resistance, and improving the rhizosphere microecology. This eliminates the hassle of multiple topdressing and foliar fertilizer applications and saves labor costs. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating a method for preparing fertilizer for rice cultivation, provided as an embodiment of this application.

[0028] Figure 2 This is a comparison table of nitrogen release curves.

[0029] Figure 3 This is a table comparing yield and nitrogen fertilizer utilization rate.

[0030] Figure 4 Table showing the relationship between rice stem strength and silicon content. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments.

[0032] This application provides a fertilizer for rice cultivation, comprising:

[0033] The fertilizer is a granular material with a triple structure of "core-shell-outer functional layer", and its composition by weight includes:

[0034] Core layer (long-lasting slow-release nitrogen source): Composed of 35±2 parts of polyurethane-coated urea. The core of the polyurethane-coated urea is ordinary urea, and the coating material is water-based polyurethane. The coating thickness is controlled at 45-55 micrometers to ensure that the initial nitrogen dissolution rate in still water (25℃) is less than 15% in 24 hours, and the cumulative release rate reaches more than 80% after 28 days. This core layer aims to provide a continuous and stable nitrogen supply for the reproductive growth of rice from the late jointing stage to the grain-filling stage, avoiding nutrient deficiency in the later stages.

[0035] The intermediate layer (medium-efficiency slow-release and sulfur-replenishing layer) consists of 25±2 parts of sulfur-coated urea. The sulfur-coated urea is prepared using a molten sulfur spraying process, with a sulfur coating thickness of 30-40 micrometers, and is coated with approximately 2% microcrystalline wax as a sealant. This layer covers the core layer, and its sulfur coating gradually degrades under the action of soil microorganisms, thereby releasing nitrogen and sulfur. The peak nitrogen release period is designed to occur from the tillering stage to the early jointing stage, coinciding with the first peak nitrogen uptake of rice. The sulfur content (calculated as S, not less than 10%) not only serves as a nutrient element but, more importantly, participates in the activation of key enzymes in nitrogen metabolism, promoting nitrogen assimilation and utilization, which is one of the key design features of this fertilizer in improving nitrogen fertilizer utilization efficiency.

[0036] Outer layer (growth-promoting, disease-resistant, and fast-acting functional layer): Total weight 40±5 parts, formed by the following components wrapped around the intermediate layer with an adhesive:

[0037] Potassium humate from mineral sources: 20±2 parts, preferably products obtained from weathered coal through refined purification and potassium activation processes, requiring a water-soluble humic acid content of not less than 60%, and potassium oxide ( The content is not less than 12%, and the pH value is 8.0-10.0. Its function is to rapidly dissolve to stimulate the root development of rice seedlings, improve the activity of rhizosphere microorganisms, and reduce nutrient fixation through chelation.

[0038] Composite silicon source: 15±2 parts. Composed of silicon dioxide (… This product is granulated by mixing calcined silicon-calcium-magnesium fertilizer (fineness greater than 200 mesh) with ≥35% silica content and humic acid complexed silicon solution (mass ratio 95:5). This component provides both fast-acting and long-lasting silicon, the key being the complexation state of silicate ions and humic acid, which can improve the mobility of silicon in the soil and the absorption efficiency of crops, thereby strengthening the silicification of plant epidermal cells. It is the main functional carrier for improving resistance to rice blast and lodging.

[0039] Micronutrient composition: 2.5 ± 0.5 parts. Specifically, it contains 1.5 parts of EDTA-chelated zinc (Zn content ≥ 15%), 0.8 parts of borax (B content ≥ 11%), and 0.2 parts of ammonium molybdate (Mo content ≥ 54%). This composition is premixed and ultra-finely pulverized (through 325 mesh) to ensure uniform distribution.

[0040] Binding and slow-release conditioning system: 2.5 ± 0.5 parts. It consists of biodegradable modified starch adhesive (70%) and porous attapulgite (30%). This system not only acts as a film-forming binder, but the adsorption properties of the attapulgite also provide a slight buffer for the initial release of nutrients from the outer layer, preventing excessive loss.

[0041] In one embodiment, a method for preparing fertilizer for rice cultivation is provided, comprising the following steps:

[0042] S1: Preparation and pretreatment of core particles. Commercially available qualified polyurethane-coated urea was selected as raw material. First, a double-layer vibrating screen was used for grading to accurately separate uniform particles with a particle size of 2.8-3.2 mm. Particles within this size range were then placed in a drum polisher, and dry air was introduced while rotating at low speed to remove surface dust and static electricity, resulting in clean and dry core particles for later use.

[0043] S2: Construction of the intermediate sulfur layer (slow-release nitrogen source II layer) includes the following steps:

[0044] S2.1: Powder processing: Ordinary sulfur-coated urea granules are initially crushed by a hammer mill and then finely crushed and classified by an air classifier mill to collect fine powder with a particle size distribution of 90-100 mesh (about 150-160 micrometers).

[0045] S2.2: Fluidized bed bottom spray coating: The core particles obtained in S1 are fed into a fluidized bed coating machine (e.g., a bottom spray Wurster chamber). Start the equipment, set the inlet air temperature to 60-65℃, and raise the material bed temperature to 52-58℃ and maintain it stable.

[0046] S2.3: Simultaneous powder and liquid spraying. Prepare an 8-10% aqueous solution of hydroxypropyl methylcellulose (HPMC) as a binder. Turn on the spray gun and spray the sulfur-coated urea fine powder and the atomized binder solution (atomization pressure 0.25-0.30MPa) into the fluidized bed simultaneously but independently. The powder is conveyed by a Venturi feeder. The ratio (mass ratio) of the liquid spraying rate to the powder spraying rate is controlled at 1:(4-5). It is necessary to ensure that the dry fine powder is adhered to the core particle surface that is slightly moistened by the atomized liquid droplets the moment it comes into contact with the core particle surface.

[0047] S2.4: Drying and curing: After coating to the predetermined weight, stop feeding and continue drying in a fluidized state at 55-60℃ for 10-15 minutes. Then discharge the material to obtain a particle intermediate with a dense sulfur-polymer composite layer on the surface. This intermediate needs to be allowed to stand and equilibrate in an environment below 40℃ for at least 2 hours to allow the coating layer to solidify and stabilize.

[0048] Furthermore, after step two is completed and the product has matured, the granular intermediate needs to undergo random sampling inspection of key quality indicators. The specific testing items and acceptance standards are as follows:

[0049] Friability: Weigh a certain amount (e.g., 50.0g) of the granular intermediate and place it in a friability tester (such as the drum instrument described in General Chapter 0923 of the Chinese Pharmacopoeia) and rotate it at 25 rpm for 10 minutes. After removal, sieve it through a 1.0mm sieve, collect and weigh the fine powder. Calculate the percentage of the fine powder weight to the total sample weight, which is the friability. The friability of a qualified granular intermediate should not exceed 1.0%. This indicator is used to evaluate the bonding strength between the sulfur coating layer and the core particles and the wear resistance.

[0050] Initial nitrogen dissolution rate: Accurately weigh a particle intermediate sample equivalent to 0.10 g of nitrogen and place it in a sealed container containing 200 mL of deionized water. Shake the sample at a frequency of 100 times / minute in a 25°C constant temperature water bath. After soaking for 7 days, immediately filter the sample and collect the filtrate. Determine the nitrogen content in the filtrate using the Kjeldahl method or distillation titration. Calculate the percentage of dissolved nitrogen relative to the total nitrogen content of the sample; this is the initial nitrogen dissolution rate after 7 days. The initial nitrogen dissolution rate after 7 days for qualified particle intermediates should be controlled below 15%. This indicator is used to characterize the sustained-release performance of the intermediate layer for nitrogen release, ensuring that its release pattern meets design requirements.

[0051] S3: Coating of the outer functional layer, specifically including:

[0052] S3.1: Premixing and micronization of functional powders: Weigh the mineral-derived potassium humate (passed through 100 mesh), composite silicon source (passed through 100 mesh), trace elements, and attapulgite filler according to the formula. First, place the attapulgite and all trace elements in a three-dimensional motion mixer and mix for 30 minutes to achieve preliminary dispersion and loading of trace components. Then, add this mixture, potassium humate, and composite silicon source to the mixer together. The total mixing time should not be less than 45 minutes to ensure overall uniformity. To further improve the coating uniformity, the mixed powder can be air-jet pulverized to make its median particle size (D50) reach 20-30 micrometers.

[0053] S3.2: Preparation of high-viscosity binder slurry: Slowly add modified starch (such as oxidized cross-linked starch) to warm water at 40-45℃, stir to dissolve, and prepare a colloidal solution with a solid content of 18-22%. After cooling, its viscosity (25℃, Brookfield RVT, rotor No. 4, 20 rpm) should not be less than ;

[0054] S3.3: Fluidized Bed Adhesion Granulation. The intermediate particles obtained in S2 are reintroduced into a fluidized bed using a top spray method. The ultrafine functional powder obtained in S3.1 and the high-viscosity starch adhesive prepared in S3.2 are sprayed together onto the surface of the particles in a vigorous fluidized state through a special dual-fluid nozzle (the powder and adhesive are mixed outside the nozzle) or through a tightly coupled parallel spray gun system. The inlet air temperature is controlled at 50-55℃, and the material temperature is maintained at 40-45℃. It is necessary to ensure instantaneous mixing and adhesion of the powder and adhesive to form a porous but strong composite functional layer.

[0055] S3.4: Low-temperature curing and sieving. After coating, fluidize and dry at ≤65℃ until the product moisture content is ≤2.0%. The dried particles are then sieved using a double-layer sieve (e.g., 3.5mm and 4.5mm apertures), and the qualified product with the middle particle size is taken. The material over the sieve is slightly crushed and returned to the system, while the fine powder under the sieve can be reused as recycled material.

[0056] S4: Post-processing and packaging. The qualified granules obtained in S3 are conveyed to a cooling drum and brought into counter-current contact with room temperature air to cool to a temperature difference of less than 5°C from the environment. They are then immediately vacuum-sealed or nitrogen-filled in aluminum-plastic composite film bags to prevent moisture absorption and clumping.

[0057] Furthermore, the adhesive system is designed and compounded differently for different functional layers, as detailed below:

[0058] The binder used for the intermediate layer (sulfur layer) coating is primarily an aqueous solution of hydroxypropyl methylcellulose (HPMC) at a concentration of 8-10% (w / w). To further enhance the structural stability of the sulfur coating in moist soil environments and regulate its dissolution rate, 3-5 parts of a polyethylene wax aqueous dispersion with a solid content of 40% can be added to every 100 parts of HPMC solution. This hydrophobic component forms a micro-hydrophobic network after the coating layer dries and forms a film, thereby moderately delaying water penetration and nutrient release.

[0059] The adhesive used for the outer functional layer is primarily modified starch adhesive with a solid content of 18-22%. To enhance the adhesion and retention of this hydrophilic colloid under humid conditions and the deliquescence resistance of the final particles, a compounding technique is employed. Specifically, 5-8 parts of partially hydrolyzed polyvinyl alcohol (PVA) with a degree of polymerization of 1700±50 and a degree of hydrolysis of 88%, and 1-2 parts of sodium alginate are simultaneously dissolved in every 100 parts of modified starch (dry basis). This compound system, after drying, forms a composite film that combines toughness and a certain degree of water resistance, ensuring firm adhesion of the outer functional powder and resisting short-term apparent moisture.

[0060] In one specific embodiment, the experimental process and results report of this scheme are provided. One test site is set up in the southern double-cropping rice area (Hunan) and the northern single-cropping rice area (Heilongjiang). The soil types are red soil and black soil, respectively, with medium basic fertility.

[0061] Set up 4 treatments, with each treatment repeated 3 times:

[0062] T1: Conventional compound fertilizer (control), applied twice according to local standard dosage (base fertilizer + top dressing).

[0063] T2: This application uses a three-layer structure fertilizer, applied as a single basal fertilizer, with a total nutrient content equal to the nitrogen content of T1;

[0064] T3: Core layer + intermediate layer fertilizer only (no outer functional layer);

[0065] T4: Only outer functional layer + ordinary urea (no sustained-release structure).

[0066] All treatments had the same total nitrogen, phosphorus, and potassium levels, and all field management measures were exactly the same except for fertilization. Growth indicators were recorded at each growth stage (tillering stage, jointing stage, heading stage, and grain-filling stage).

[0067] And detect the following data:

[0068] Fertilizer performance testing

[0069] Nutrient release curve determination (static water dissolution method, 25℃):

[0070] Samples were taken on days 1, 3, 7, 14, 28, and 56 to determine the release of nitrogen, potassium, and silicon.

[0071] Particle structure stability test:

[0072] Friability, compressive strength;

[0073] Microscopic observation of coating layer degradation under simulated soil temperature and humidity conditions.

[0074] Field growth index measurement

[0075] Tiller number, plant height, and chlorophyll content (SPAD value);

[0076] Root morphology (root length, root volume, root vitality);

[0077] Disease resistance: incidence of rice blast and sheath blight;

[0078] Lodging resistance: determination of internode strength at the base of the stem and silicon content.

[0079] Yield and quality measurement

[0080] Yield composition: number of effective ears, number of grains per ear, thousand-grain weight, and actual yield;

[0081] Rice quality: protein content, amylose content.

[0082] Environmental and Utilization Indicators

[0083] Nitrogen fertilizer utilization rate (using Tracer method);

[0084] Nitrogen loss: ammonia volatilization and leaching nitrogen collection and determination;

[0085] Changes in soil physicochemical properties: pH, organic matter, available silicon, and trace element content.

[0086] based on Figure 2 The data shows that T2 release is the most gradual, with a low dissolution rate in the early stage and continuous release in the middle and late stages, and it has the highest matching degree with the fertilizer requirement curve of rice.

[0087] based on Figure 3 The data shows that T2 has the highest yield, significantly improved nitrogen fertilizer utilization, and the lowest disease incidence, indicating that the three-layer structure has synergistic advantages in nutrient supply and disease resistance.

[0088] based on Figure 4 The data showed that T2 had the highest silicon content and the greatest stem strength, indicating that the composite silicon source and the slow-release structure jointly enhanced the lodging resistance.

[0089] The following conclusions can be drawn:

[0090] Nutrient release is highly matched with rice growth: the three-layer structure achieves precise fertilization by promoting root growth in the early stage, supplying nitrogen in the middle stage, and preventing senescence in the later stage;

[0091] Nitrogen fertilizer utilization rate is significantly improved: from the conventional 35% to 52%, and nitrogen loss is reduced;

[0092] The multi-functional integration has significant effects: it has obvious effects on disease resistance, lodging resistance and root promotion, and reduces the use of pesticides and topdressing.

[0093] One-time basal application is feasible: it can save labor and the number of fertilizations while ensuring yield.

[0094] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A fertilizer for rice cultivation, characterized in that, The fertilizer is a granular material with a triple structure of core-shell-outer functional layer, comprising, by weight: The core layer consists of 35±2 parts of polyurethane-coated urea; The intermediate layer, which covers the core layer, is composed of 25±2 parts of sulfur-coated urea. The outer layer, which covers the middle layer, has a total weight of 40±5 parts, including 20±2 parts of mineral-derived potassium humate, 15±2 parts of composite silicon source, 2.5±0.5 parts of trace element composition, and 2.5±0.5 parts of binding and slow-release conditioning system.

2. The fertilizer for rice cultivation according to claim 1, characterized in that, The polyurethane-coated urea has a coating thickness of 45-55 micrometers, and the sulfur-coated urea has a sulfur coating thickness of 30-40 micrometers and is covered with a microcrystalline wax sealant.

3. The fertilizer for rice cultivation according to claim 1, characterized in that, The mineral-derived potassium humate contains no less than 60% water-soluble humic acid and no less than 12% potassium oxide.

4. The fertilizer for rice cultivation according to claim 1, characterized in that, The composite silicon source is granulated by mixing calcined silicon-calcium-magnesium fertilizer and humic acid complexed silicon solution at a mass ratio of 95:5, wherein the silicon dioxide content is ≥35%.

5. The fertilizer for rice cultivation according to claim 1, characterized in that, The micronutrient composition comprises zinc chelated with ethylenediaminetetraacetic acid, borax, and ammonium molybdate.

6. The fertilizer for rice cultivation according to claim 1, characterized in that, The bonding and slow-release conditioning system consists of modified starch adhesive and attapulgite clay.

7. A method for preparing a fertilizer for rice cultivation, characterized in that, Includes the following steps: S1: Preparation and pretreatment of core particles: Polyurethane-coated urea particles with a particle size of 2.8-3.2 mm are screened out, cleaned and dried to obtain core particles. S2: Construction of the intermediate layer: Sulfur-coated urea is made into fine powder, and hydroxypropyl methylcellulose aqueous solution is used as a binder. The fine powder is coated onto the surface of the core particles through a fluidized bed bottom spray coating process. After drying and curing, the particle intermediate is obtained. S3: Coating of the outer functional layer involves mixing mineral-derived potassium humate, composite silicon source, a combination of trace elements, and attapulgite to form a functional powder. Modified starch adhesive is used as a binder, and the functional powder is coated onto the surface of the granular intermediate through a fluidized bed top spraying process. After drying and sieving, fertilizer granules are obtained.

8. The method for preparing fertilizer for rice cultivation according to claim 7, characterized in that, In step S2, the concentration of the aqueous hydroxypropyl methylcellulose solution is 8-10%, and 3-5 parts of a polyethylene wax aqueous dispersion with a solid content of 40% are added to every 100 parts of the solution.

9. The method for preparing fertilizer for rice cultivation according to claim 7, characterized in that, In step S3, the solid content of the modified starch adhesive is 18-22%, and 5-8 parts of partially hydrolyzed polyvinyl alcohol and 1-2 parts of sodium alginate are simultaneously dissolved in every 100 parts of dry-based modified starch.

10. The method for preparing fertilizer for rice cultivation according to claim 7, characterized in that, After step S2 is completed, the particle intermediate is subjected to quality testing. Its brittleness is not higher than 1.0%, and the initial nitrogen dissolution rate after 7 days is less than 15%.

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