Composite liquid water-soluble fertilizer and its production method

Abstract

This invention discloses a compound liquid water-soluble fertilizer and its production method, relating to the field of agricultural fertilizer preparation and application technology. The compound liquid water-soluble fertilizer, by weight, comprises the following components: 300 to 500 parts of macro-element fertilizer, 15 to 35 parts of micro-element fertilizer, 10 to 25 parts of organic chelating agent, 2 to 8 parts of surfactant, 50 to 150 parts of slow-release biostimulant dispersion, and 400 to 800 parts of water. This invention constructs a microcapsule structure, which forms a physical barrier, effectively blocking the osmotic impact of high-concentration inorganic salt ions in the liquid fertilizer and the erosion of acidic and alkaline environments, preventing the degradation of active ingredients, thereby ensuring the uniformity and effectiveness of the product during storage and transportation, and extending its shelf life.

Description

Technical Field

[0001] This invention relates to the field of agricultural fertilizer preparation and application technology, specifically to a compound liquid water-soluble fertilizer and its production method. Background Technology

[0002] Liquid water-soluble fertilizers are widely used in modern agriculture due to their comprehensive nutrient composition, high absorption and utilization rate, and suitability for integrated water and fertilizer systems such as sprinkler and drip irrigation. To further enhance crop resistance, promote root growth, and improve fruit quality, the industry often experiments with adding plant growth regulators or biostimulants to liquid water-soluble fertilizers containing nitrogen, phosphorus, and potassium. Existing compound liquid water-soluble fertilizers typically consist of macronutrient fertilizers such as urea, potassium dihydrogen phosphate, and potassium nitrate, as well as micronutrient fertilizers such as ethylenediaminetetraacetic acid (EDTA) chelated iron, EDTA chelated zinc, and EDTA chelated manganese, combined with conventional surfactants and water as solvents.

[0003] However, in actual production and application, directly incorporating biostimulants into high-concentration liquid water-soluble fertilizers faces severe technical challenges. First, liquid water-soluble fertilizers are essentially high-concentration inorganic salt electrolyte solutions with extremely high ionic strength and osmotic pressure. This high-salt environment strongly salts out organic hormone molecules, leading to reduced hormone solubility, aggregation, flocculation, precipitation, or side reactions with metal ions in the fertilizer, severely disrupting the homogeneity and stability of the fertilizer system. Second, liquid water-soluble fertilizers have a wide pH range and are often in acidic or alkaline environments. Many active hormones with specific molecular structures are highly susceptible to hydrolysis, ring-opening, or oxidative degradation under these conditions, resulting in rapid loss of efficacy during storage and transportation.

[0004] Furthermore, existing technologies mostly employ simple physical mixing or conventional emulsification techniques, which cannot effectively control the release rate of hormones after they enter the soil or come into contact with crop leaves. Free hormones are often released too rapidly in the initial stages of application, creating a burst release effect that can easily lead to excessive vegetative growth or even phytotoxicity. In the later stages of crop growth, the hormones are depleted or decomposed in the environment, failing to exert a sustained regulatory effect. Conventional microencapsulation technology often suffers from capsule wall rupture due to the large osmotic pressure difference between the inside and outside of the capsule wall when facing high-concentration salt solutions in liquid fertilizers, or swelling and dissolution due to the capsule material's intolerance to salt and alkali, making it difficult to achieve true physical isolation and slow-release protection. Therefore, there is an urgent need to develop a compound liquid water-soluble fertilizer and its production method that can resist high-salt and wide-pH environments, prevent hormone aggregation and degradation, and possess long-lasting slow-release function to solve the above-mentioned technical challenges. Summary of the Invention

[0005] The purpose of this invention is to provide a compound liquid water-soluble fertilizer and its production method, to solve the technical problems in the prior art where biostimulants are prone to salting out and agglomeration, chemical degradation, and rapid release after application leading to phytotoxicity or short-lasting fertilizer effect in liquid fertilizer matrices with high concentrations of inorganic salts and wide pH ranges. This invention aims to achieve long-term uniform and stable dispersion and controllable slow release of hormones in liquid water-soluble fertilizer systems, thereby improving the comprehensive utilization rate of fertilizers.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A compound liquid water-soluble fertilizer, by weight, comprises the following components: 300 to 500 parts of macro-element fertilizer, 15 to 35 parts of micro-element fertilizer, 10 to 25 parts of organic chelating agent, 2 to 8 parts of surfactant, 50 to 150 parts of slow-release biostimulant dispersion, and 400 to 800 parts of water. The raw materials for preparing the sustained-release biostimulant dispersion are composed of the following components in parts by weight: 5 to 30 parts of biostimulant, 30 to 80 parts of solvent, 0.5 to 1.5 parts of nonionic surfactant, 25 to 150 parts of gelling carrier material, 15 to 100 parts of crosslinking agent, 60 to 200 parts of coating material, 2 to 8 parts of plasticizer, 2 to 8 parts of film-forming aid, and 2 to 15 parts of dispersion stabilizing system. The biostimulant is (2R,3R,4R,5S)-6-(8-(2-(1H-indol-3-yl)-1-(naphth-1-yl)ethyl)-2-(benzylamino)-9H-purine-9-yl)hexane-1,2,3,4,5-pentaol.

[0007] Furthermore, the chemical structure of (2R,3R,4R,5S)-6-(8-(2-(1H-indol-3-yl)-1-(naphth-1-yl)ethyl)-2-(benzylamino)-9H-purin-9-yl)hexane-1,2,3,4,5-pentaol is as follows: .

[0008] Furthermore, the macro-element fertilizer is selected from one or more of urea, potassium nitrate, potassium dihydrogen phosphate, ammonium polyphosphate, and calcium ammonium nitrate.

[0009] Furthermore, the micronutrient fertilizer is selected from one or more of the following: ethylenediaminetetraacetic acid (EDTA) chelated iron, EDTA chelated zinc, EDTA chelated manganese, EDTA chelated copper, boric acid, and sodium molybdate.

[0010] Furthermore, the organic chelating agent is selected from one or more of disodium ethylenediaminetetraacetate, diethylenetriaminepentaacetic acid, citric acid, and tartaric acid.

[0011] Furthermore, the surfactant is selected from one or more of Tween-80, Span-60, alkyl glycosides, and sodium dodecylbenzenesulfonate.

[0012] Furthermore, the solvent is selected from one or more of water, ethanol, and propylene glycol.

[0013] Furthermore, the nonionic surfactant is selected from one or more of Tween-20, Span-80, polyoxyethylene castor oil, and alkyl glycosides.

[0014] Furthermore, the gelling carrier material is selected from one or more of sodium alginate, deacetylated chitosan, gelatin, sodium carboxymethyl cellulose, and hydroxypropyl starch.

[0015] Furthermore, the crosslinking agent is selected from one or more of calcium chloride, calcium sulfate, sodium tripolyphosphate, and glutaraldehyde.

[0016] Furthermore, the coating material is selected from one or more of polylactic acid-glycolic acid copolymer, polycaprolactone, polyvinyl alcohol, polyacrylic acid, lignin, paraffin emulsion, and silica sol.

[0017] Furthermore, the dispersion stabilization system includes a dispersant and an anti-settling agent.

[0018] Furthermore, the dispersant is selected from one or more of polyether-modified polysiloxane, sodium lignosulfonate, and sodium polycarboxylate.

[0019] Furthermore, the anti-settling agent is selected from one or more of xanthan gum, sodium bentonite, and hydroxypropyl methylcellulose.

[0020] Furthermore, the plasticizer is selected from one or more of glycerol, triethyl citrate, and dioctyl phthalate.

[0021] Furthermore, the film-forming aid is selected from one or more of polyethylene glycol 400, dibutyl phthalate, and dodecyl alcohol ester.

[0022] A method for producing a compound liquid water-soluble fertilizer includes the following steps: The first step is to add the water to the reaction vessel, heat it and start stirring, and then add the macro-element fertilizer, micro-element fertilizer, organic chelating agent and surfactant in the formula amount in sequence, and stir to dissolve until a uniform and transparent matrix fertilizer solution is formed for later use. The second step involves adding the biostimulant to the solvent, adding the nonionic surfactant, and dissolving it by ultrasonic assistance or stirring to obtain a hormone mother liquor. The third step involves dissolving the gelling carrier material in water to prepare a core aqueous solution, and then adding the hormone stock solution obtained in the second step to the core aqueous solution to mix and disperse it to form a drug-loaded precursor solution. The fourth step is to prepare a crosslinking bath solution containing the crosslinking agent, introduce the drug-loaded precursor solution obtained in the third step into the crosslinking bath by spraying, dripping or emulsification shearing, solidify to form drug-loaded microparticles, filter and collect the drug-loaded microparticles; The fifth step involves dispersing the coating material in solvent A, adding the plasticizer and film-forming aid to prepare a coating solution, placing the drug-loaded microparticles obtained in the fourth step in a fluidized bed or spray coating machine, spraying the coating solution for coating, and drying to obtain coated particles. The coated particles obtained in step 5 are washed to remove free hormones and residual cross-linking agents from the surface. The particles are then redispersed in water and a dispersion stabilization system of the formulation is added. The sustained-release biostimulant dispersion is obtained by low-shear homogenization dispersion treatment; the sustained-release biostimulant dispersion is obtained by high-pressure homogenization dispersion treatment; wherein the high-pressure homogenization pressure is 20 MPa to 50 MPa, and the homogenization is performed 2 to 3 times. Step 7: While stirring, add the slow-release biostimulant dispersion obtained in step 6 to the substrate fertilizer solution prepared in step 1, and stir until a compound liquid water-soluble fertilizer is formed.

[0023] Furthermore, the concentration of the core aqueous solution is 1% to 5% (w / v).

[0024] Furthermore, the concentration of the crosslinking bath solution is 1% to 10% (w / v), and the solvent is water.

[0025] Furthermore, solvent A is one or more of ethanol, acetone, and dichloromethane; when the coating material is an aqueous dispersion system (such as silica sol), solvent A is deionized water or a water-ethanol mixture. The amount of solvent A used is 5 to 20 times the weight of the coating material.

[0026] Furthermore, in the sixth step, the amount of water used is 1 to 5 times the weight of the coated particles (by weight) so that the solid content of the final sustained-release biostimulant dispersion is controlled within the range of 20% to 50%.

[0027] Furthermore, the heating temperature in the first step is 40 degrees Celsius to 60 degrees Celsius; and the shear rate for mixing and dispersing in the third step is 2000 rpm to 4000 rpm.

[0028] Furthermore, in the fourth step, the curing time is controlled to be 15 to 60 minutes; the average particle size of the drug-loaded particles collected in the fourth step is 1 micrometer to 30 micrometers or 50 micrometers to 1000 micrometers.

[0029] Furthermore, in the sixth step, the solid content of the slurry is adjusted to 20% to 50%.

[0030] Furthermore, the stirring time in the seventh step is 30 to 60 minutes.

[0031] This invention utilizes microencapsulation technology to synergistically solve the technical challenges of easy salting out, easy degradation, and uncontrollable release of biostimulants in high-concentration inorganic salt liquid fertilizers. Its specific mechanism of action is as follows: First, targeting the specific hydrophobic hormone molecule (2R,3R,4R,5S)-6-(8-(2-(1H-indol-3-yl)-1-(naphth-1-yl)ethyl)-2-(benzylamino)-9H-purine-9-yl)hexane-1,2,3,4,5-pentaol, a nonionic surfactant is used to emulsify and disperse it in the aqueous matrix of a gelling carrier. A crosslinking agent induces the formation of a dense three-dimensional network gel structure between the carrier molecular chains, thereby physically anchoring and initially encapsulating the hormone molecule at the microscale, restricting its free diffusion. Second, by coating the surface of the gel particles with a hydrophobic or semi-permeable membrane layer composed of materials such as polylactic acid-glycolic acid copolymer, polyvinyl alcohol, or polycaprolactone, a biostimulant targeting the high ionic strength matrix of the liquid fertilizer is constructed. The product employs a physical barrier that effectively blocks the penetration and impact of high concentrations of nitrogen, phosphorus, and potassium ions from external macronutrient fertilizer solutions on the internal hormones, preventing hormone aggregation and precipitation caused by strong electrolyte salting-out effects. It also isolates the active groups of hormone molecules from the chemical erosion caused by the acidic or alkaline environment of the matrix. Finally, a dispersion and stabilization system composed of polyether-modified polysiloxane and xanthan gum utilizes steric hindrance and the pseudoplastic rheological properties of liquids to overcome the gravitational sedimentation of coated particles in denser liquid fertilizers, ensuring a uniform and stable system. When the product is applied to crops, as the outer coating material biodegrades and swells on the soil or leaves, the internal cross-linked network gradually loosens due to environmental moisture, thereby eliminating the osmotic pressure difference between the inside and outside, enabling the hormone molecules to be released on demand and stably, exerting a long-lasting biostimulatory effect.

[0032] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention significantly improves the chemical stability of biostimulants in high-concentration liquid water-soluble fertilizer matrices by constructing a microcapsule structure. This structure forms a physical barrier, effectively blocking the osmotic impact of high-concentration inorganic salt ions in the liquid fertilizer and the corrosive effects of acidic and alkaline environments. It avoids the aggregation, precipitation, hydrolysis, or oxidative degradation of active ingredients due to salting out, thereby ensuring the uniformity and effectiveness of the product during storage and transportation, and extending its shelf life.

[0033] 2. This invention achieves long-term sustained release of biostimulants, effectively solving the phytotoxicity problem that may be caused by the sudden release of hormones in traditional liquid fertilizers and improving utilization efficiency. The hormones are locked in a microscopic three-dimensional network structure formed by a gelling carrier material, combined with the controlling effect of the outer coating material, allowing the hormones to be released steadily and continuously as the coating layer degrades and the cross-linked network loosens. This sustained-release mechanism avoids the risk of excessive crop growth or seedling burn caused by excessively high local concentrations in the early stages of application, while ensuring that crops receive continuous biostimulation regulation throughout their growth cycle, significantly improving the overall efficacy of the fertilizer.

[0034] 3. This invention solves the technical challenges of dispersing hydrophobic hormones and the easy sedimentation of solid particles through the synergistic effect of specific mother liquor solubilization technology and dispersion stabilization system. Pretreatment with solvents and surfactants improves the biocompatibility of poorly soluble hormones, and the suspension network constructed by dispersants and anti-settling agents effectively prevents flocculation and stratification of drug-loaded particles in the liquid medium. This not only endows the compound liquid water-soluble fertilizer with excellent physical suspension stability but also ensures its good flowability, enabling it to meet the application requirements of modern integrated water and fertilizer facilities such as drip irrigation and sprinkler irrigation, and preventing pipeline blockage. Attached Figure Description

[0035] Figure 1 The synthetic route for the biostimulant (2R,3R,4R,5S)-6-(8-(2-(1H-indol-3-yl)-1-(naphth-1-yl)ethyl)-2-(benzylamino)-9H-purine-9-yl)hexane-1,2,3,4,5-pentaol described in this invention is shown. Detailed Implementation

[0036] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Preparation Example 1 Preparation of biostimulant (2R,3R,4R,5S)-6-(8-(2-(1H-indol-3-yl)-1-(naphth-1-yl)ethyl)-2-(benzylamino)-9H-purin-9-yl)hexane-1,2,3,4,5-pentaol: first step: Raw material 1: 2,4-dichloro-5-nitropyrimidine; Raw material 2: (2R,3R,4R,5S)-6-aminohexane-1,2,3,4,5-pentaacetate; Intermediate 1: (2R,3R,4R,5S)-6-((2-chloro-5-nitropyrimidin-4-yl)amino)hexane-1,2,3,4,5-pentaacetate.

[0038] Add raw material 1 (5.00 g) and anhydrous DCM (100 mL) to the flask and stir until evenly dispersed. Cool the reaction flask to 0°C in an ice-water bath and stir for 10 minutes to reach thermal equilibrium. Then add DIPEA (5.39 mL). Dissolve raw material 2 (9.32 g) in anhydrous DCM (30 mL) and transfer to a constant pressure dropping funnel. At 0°C, control the dropping rate (approximately 1 drop / second) and slowly add the glycosamine solution to the pyrimidine solution, controlling the dropping temperature not to exceed 5°C. After the addition is complete, maintain 0°C and continue stirring for 1 hour, then remove the ice bath and allow the reaction system to naturally rise to room temperature for 3 hours. After the reaction is complete, pour the reaction solution into a separatory funnel and wash the organic phase successively with 1M HCl (50 mL), saturated NaHCO3 solution (50 mL), and saturated saline solution (50 mL). The organic phase was separated and dried with 10 g of anhydrous Na₂SO₄ for 30 minutes. The desiccant was removed by filtration, and the filter cake was washed with a small amount of DCM. The filtrate was concentrated by rotary evaporation under reduced pressure to obtain the crude product. The crude product was purified by rapid column chromatography using a gradient elution with a mixed solution of hexane and ethyl acetate (4:1 to 2:1). The fraction containing the target product was collected, evaporated to dryness, and vacuum dried overnight to obtain 10.24 g of intermediate 1.

[0039] Intermediate 1 1 HNMR (CDCl3):

[0040] Step Two: Intermediate 2: (2R,3R,4R,5S)-6-((5-amino-2-chloropyrimidin-4-yl)amino)hexane-1,2,3,4,5-pentaacetate.

[0041] To a round-bottom flask, add intermediate 1 (10.24 g), ethanol (80 mL), and water (20 mL) sequentially, stirring until evenly dispersed. Then, add solid ammonium chloride (5.43 g) to the reaction system, stirring until homogeneous. Next, add reduced iron powder (5.67 g) in small, repeated additions. Raise the temperature of the reaction system to 80°C and reflux for 3 hours. After the reaction is complete, cool the mixture to room temperature. Filter through a Buchner funnel lined with diatomaceous earth to remove unreacted iron powder and iron oxide sludge. Wash the filter cake with warm ethanol (3 × 20 mL). Concentrate the filtrate under reduced pressure by rotary evaporation to remove most of the ethanol. Add water (50 mL) and ethyl acetate (80 mL) to the residue, shaking to separate the layers. Extract the aqueous layer again with ethyl acetate (2 × 50 mL). Combine the organic phases and wash sequentially with saturated sodium bicarbonate solution (50 mL) and saturated brine (50 mL). Dry the organic phase with anhydrous sodium sulfate for 30 minutes. The desiccant was removed by filtration, and the filtrate was evaporated to dryness under reduced pressure at 40°C to obtain the crude product. Purification was performed using rapid silica gel column chromatography with a gradient elution of a mixture of petroleum ether and ethyl acetate (2:1 to 1:1). The fraction containing the target product was collected, evaporated to dryness under vacuum overnight, yielding 7.31 g of intermediate 2.

[0042] Intermediate 2 1 HNMR (CDCl3):

[0043] Step 3: Raw material 3: 3-(1H-indol-3-yl)-2-(naphth-1-yl)propionic acid; Intermediate 3: (2R,3R,4R,5S)-6-(8-(2-(1H-indol-3-yl)-1-(naphth-1-yl)ethyl)-2-chloro-9H-purin-9-yl)hexane-1,2,3,4,5-pentylpentaacetic acid ester.

[0044] Under a nitrogen atmosphere, intermediate 2 (7.31 g) and raw material 3 (12.47 g) were added to a flask, followed by anhydrous DMF (110 mL). The mixture was stirred until homogeneous. The reaction flask was cooled in an ice-water bath for 10 minutes. At 0°C, HOBt (4.53 g) and EDC·HCl (6.42 g) were added sequentially. DIPEA (9.7 mL) was slowly added dropwise, controlling the internal temperature to not exceed 5°C during the addition. The ice bath was removed, and the reaction system was allowed to rise naturally to room temperature, where it was stirred for 16 hours. After the reaction was complete, most of the DMF was removed by rotary evaporation under reduced pressure, yielding a viscous oily residue. Glacial acetic acid (150 mL) was added to the residue. A reflux condenser was attached, and the reaction system was heated to 110°C in an oil bath, with stirring for 6 hours. After the reaction was complete, the mixture was cooled to room temperature. Most of the acetic acid was removed by rotary evaporation under reduced pressure. The residue was dissolved in EtOAc (300 mL). The organic phase was washed slowly with saturated NaHCO3 aqueous solution (3 x 100 mL) until the pH of the aqueous phase was weakly alkaline (approximately 8). The organic phase was then washed with deionized water (100 mL) and saturated brine (100 mL) to separate the organic phase. The mixture was dried over anhydrous Na2SO4 for 30 minutes. The desiccant was removed by filtration, and the filtrate was concentrated under reduced pressure to obtain the crude product. Purification was performed using rapid silica gel column chromatography with a gradient elution of a mixture of petroleum ether and ethyl acetate (3:1 to 1:1). The fraction containing the target product was collected, evaporated to dryness, and then vacuum-dried overnight to obtain 10.28 g of intermediate 3.

[0045] Intermediate 3 1 HNMR (CDCl3):

[0046] Step 4: Raw material 4: Benzylamine; Intermediate 4: (2R,3R,4R,5S)-6-(8-(2-(1H-indol-3-yl)-1-(naphth-1-yl)ethyl)-2-(benzylamino)-9H-purin-9-yl)hexane-1,2,3,4,5-pentanolpentacetic acid ester.

[0047] Under a nitrogen atmosphere, intermediate 3 (10.28 g) was added to a flask, followed by anhydrous 1,4-dioxane (135 mL). The mixture was stirred until homogeneous, then triethylamine (3.75 mL) and starting material 4 (2.20 mL) were added sequentially, and the mixture was stirred until homogeneous. The reaction flask was placed in an oil bath preheated to 95°C and refluxed for 4 hours. After the reaction was complete, the reaction solution was cooled to room temperature. Most of the 1,4-dioxane was removed by rotary evaporation under reduced pressure. The resulting residue was dissolved in dichloromethane (150 mL) and transferred to a separatory funnel. The organic phase was washed sequentially with semi-saturated brine (100 mL × 2) and saturated brine (100 mL) to remove excess benzylamine and triethylamine hydrochloride. The organic phase was separated, dried over anhydrous sodium sulfate for 30 minutes, and filtered to remove the drying agent. The filtrate was concentrated under reduced pressure to obtain the crude product. Purification was performed using rapid silica gel column chromatography with gradient elution using a mixture of dichloromethane and methanol (100:1 to 40:1) as the mobile phase. The fraction containing the target product was collected, evaporated to dryness, and vacuum dried overnight to obtain 8.85 g of intermediate 4.

[0048] Intermediate 4 1 HNMR (CDCl3):

[0049] Step 5: Final product: Biostimulant (2R,3R,4R,5S)-6-(8-(2-(1H-indol-3-yl)-1-(naphth-1-yl)ethyl)-2-(benzylamino)-9H-purine-9-yl)hexane-1,2,3,4,5-pentaol.

[0050] Under a nitrogen atmosphere, intermediate 4 (8.85 g) and dichloromethane (DCM, 40 mL) were added to a flask and stirred until uniformly dispersed. Anhydrous methanol (80 mL) was added, followed by dropwise addition of NaOMe / MeOH solution (25% wt, 0.93 mL). The reaction was carried out at room temperature for 2 hours. After the reaction was complete, approximately 3.0 g of Amberlite-IR-120 (H+form) acidic ion exchange resin was added to the reaction solution to neutralize the sodium methoxide in the reaction system. Stirring was continued for 10 minutes until the pH paper showed neutrality. Subsequently, the resin was removed by vacuum filtration through a sintered glass funnel, and the filter cake was washed with a small amount of methanol / DCM (1:1, 20 mL × 2). The filtrates were combined and concentrated under reduced pressure using a rotary evaporator at 40°C in a water bath to remove most of the solvent, yielding the crude product. Purification was performed using rapid silica gel column chromatography with gradient elution of a mixture of dichloromethane and methanol (20:1 to 5:1) as the mobile phase. The fraction containing the target product was collected, evaporated to dryness, and vacuum dried overnight to obtain 5.49 g of biostimulant.

[0051] Biostimulants1 HNMR (CDCl3):

[0052] like Figure 1 As shown, the synthetic route of the biostimulant includes five reaction steps: the first step is to react 2,4-dichloro-5-nitropyrimidine with (2R,3R,4R,5S)-6-aminohexane-1,2,3,4,5-pentaacetate to obtain intermediate 1; the second step is to reduce intermediate 1 to obtain intermediate 2; the third step is to react intermediate 2 with 3-(1H-indol-3-yl)-2-(naphth-1-yl)propionic acid and cyclize it to obtain intermediate 3; the fourth step is to react intermediate 3 with benzylamine to obtain intermediate 4; and the fifth step is to deprotect intermediate 4 to obtain the target biostimulant.

[0053] Example 1 Preparation of a compound liquid water-soluble fertilizer: 1. Raw material components by weight: Macronutrient fertilizer: 150 parts urea, 100 parts potassium nitrate, 50 parts potassium dihydrogen phosphate, totaling 300 parts; Micronutrient fertilizer: 5 parts ethylenediaminetetraacetic acid (EDTA) chelated iron, 4 parts EDTA chelated zinc, 3 parts EDTA chelated manganese, 2 parts EDTA chelated copper, 0.5 parts boric acid, 0.5 parts sodium molybdate, totaling 15 parts; Organic chelating agent: 15 parts of disodium ethylenediaminetetraacetate; Surfactant: 3 parts Tween-80, 2 parts alkyl glycoside, totaling 5 parts; Sustained-release biostimulant dispersion: 100 parts (based on a solid content of 35%, including 35 parts of dry coated particles and 65 parts of water). Water: 600 servings.

[0054] The raw materials for preparing the sustained-release biostimulant dispersion are composed of the following raw material components in parts by weight (on a dry basis): Biostimulant (i.e., (2R,3R,4R,5S)-6-(8-(2-(1H-indol-3-yl)-1-(naphth-1-yl)ethyl)-2-(benzylamino)-9H-purin-9-yl)hexane-1,2,3,4,5-pentaol): 15 parts; Solvents (30 parts ethanol, 20 parts propylene glycol): 50 parts (which are mostly removed during subsequent drying and washing processes and are not included in the final dispersion weight). Nonionic surfactant: Tween-200.3 parts; gelling carrier material: 25 parts sodium alginate, 5 parts deacetylated chitosan, totaling 30 parts; Crosslinking agent: 20 parts calcium chloride (after participating in the crosslinking reaction, the excess part is removed in the washing step, and the final residue of about 5 parts is included in the dry weight). Coating material: 60 parts polylactic acid-glycolic acid copolymer, 15 parts polyvinyl alcohol, totaling 75 parts; Plasticizer: 1.5 parts triethyl citrate; Film-forming aid: 1.5 parts of polyethylene glycol 400; Dispersion stabilization system: 1.5 parts polyether modified polysiloxane, 0.9 parts xanthan gum, totaling 2.4 parts.

[0055] Material balance verification: All dry-based raw materials used in the above crosslinking and coating processes (15 parts biostimulant, 0.3 parts nonionic surfactant, 30 parts gelling carrier material, approximately 5 parts residual crosslinking agent, 75 parts coating material including PLGA and polyvinyl alcohol, 1.5 parts plasticizer, and 1.5 parts film-forming aid) are fully included in the dry weight. Theoretically, approximately 128.3 parts of dry-coated particles can be obtained. The solvent (ethanol and propylene glycol used to prepare the mother liquor, and the solvent system used for subsequent coating) is completely removed during fluidized drying and washing. To obtain 100 parts of the sustained-release biostimulant dispersion with a solid content of 35% as described in this example, 32.6 parts of the dry-coated particles were redispersed in 65 parts of deionized water, and 2.4 parts of a dry-based dispersion stabilization system were added to obtain 100 parts of the sustained-release biostimulant dispersion. The remaining dry-coated particles can be separately prepared into dispersions in the same proportion.

[0056] 2. Preparation method: Step 1: Preparation of the substrate fertilizer solution: Add 600 parts of deionized water to a reactor equipped with a stirring device and a heating mantle. Turn on the stirring and heat to 50°C, controlling the stirring speed at 200 rpm. Add the following ingredients in the specified amounts: urea, potassium nitrate, potassium dihydrogen phosphate, ethylenediaminetetraacetic acid (EDTA) chelated iron, EDTA chelated zinc, EDTA chelated manganese, EDTA chelated copper, boric acid, sodium molybdate, disodium EDTA, Tween-80, and alkyl glycosides. After adding all ingredients, continue stirring for 30 minutes until a homogeneous substrate fertilizer solution is formed. Let it stand for later use. The second step is the preparation of the hormone stock solution: 15 parts of biostimulant are added to a mixed solvent consisting of 30 parts of ethanol and 20 parts of propylene glycol, and 0.3 parts of Tween-20 are added as a solubilizer. The mixture is placed in an ultrasonic cleaner and ultrasonically assisted to dissolve for 15 minutes at a frequency of 40kHz and a power of 200W until it is evenly dispersed to form the hormone stock solution. The third step is the preparation of the drug-loaded precursor solution: 30 parts of the gelling carrier material were dissolved in 750 parts of deionized water to prepare a 4% (w / v) core aqueous solution. The solution was stirred in a 60°C water bath at 400 rpm for 2 hours until completely swollen and dissolved. The reaction system was then cooled to room temperature, and the hormone stock solution obtained in the second step was added. The solution was mixed and dispersed using a high-speed shear disperser at a shear rate of 3000 rpm for 20 minutes to form a uniformly dispersed drug-loaded precursor solution. Step 4: Solidification and molding of drug-loaded microparticles: Prepare a 5% (w / v) calcium chloride aqueous solution as the crosslinking bath solution, using deionized water as the solvent. The drug-loaded precursor solution obtained in Step 3 is added dropwise to the crosslinking bath solution at a flow rate of 5 mL / min using a peristaltic pump, controlling the drop height to 10 cm. The droplets solidify in the crosslinking bath to form drug-loaded microparticles. The solidification time is 30 minutes, and the stirring speed is controlled at 100 rpm to ensure uniform dispersion of the microparticles without breakage. After solidification, the drug-loaded microparticles are collected by filtration through a 200-mesh sieve and washed twice with deionized water to remove residual calcium chloride solution from the surface. The resulting drug-loaded microparticles are spherical, with an average particle size controlled within the range of 50 to 500 micrometers. Step 5, preparation of coated particles: 60 parts of polylactic acid-glycolic acid copolymer (PLGA) were dissolved in 360 parts of dichloromethane, and 15 parts of polyvinyl alcohol were added to 90 parts of deionized water (heated to 90°C to fully dissolve and then cooled to room temperature). The two phase solutions were mixed, and 1.5 parts of triethyl citrate were added as a plasticizer and 1.5 parts of polyethylene glycol 400 as a film-forming aid. The mixture was sheared at 3000 rpm for 15 minutes at 40°C using a high-shear emulsifier to obtain a uniform and stable W / O / W type coated emulsion (i.e., solvent A is a mixture of dichloromethane and water). The drug-loaded microparticles obtained in Step 4 were placed in a fluidized bed coating machine, with the inlet air temperature controlled at 45°C, the material temperature at 35°C, and the atomization pressure at 0.15 MPa. The above-mentioned coated emulsion was sprayed onto the microparticles using a bottom spray method for coating. After coating, the particles were further fluidized and dried at 40°C for 30 minutes (diochloromethane and water were completely evaporated during the fluidization process) to obtain coated particles with a dense composite film layer on the surface. Step 6: Preparation of the sustained-release biostimulant dispersion: The coated particles obtained in Step 5 were transferred to a washing vessel and washed three times with deionized water. After each wash, the particles were centrifuged (3000 rpm for 5 minutes) to thoroughly remove free hormones and residual cross-linking agents from the surface. Then, 32.6 parts of the washed, dry coated particles were resuspended in 65 parts of deionized water, and 2.4 parts of a dispersion stabilization system (polyether-modified polysiloxane and xanthan gum) were added. The mixture was dispersed using a low-shear mechanical stirrer at 300 rpm for 30 minutes. This low-shear process effectively prevented the breakage of the microcapsule structure and the leakage of the core hormone, maintaining the average particle size within the range of 50 to 500 micrometers, ultimately achieving a solid content of 35% (w / w) in the dispersion, resulting in a stable, suspended sustained-release biostimulant dispersion. Step 7, compounding of the liquid water-soluble fertilizer: While stirring, slowly add the slow-release biostimulant dispersion prepared in step 6 to the substrate fertilizer solution prepared in step 1, controlling the addition rate at 50 mL / min to avoid excessive local concentration leading to agglomeration. After the addition is complete, continue stirring for 45 minutes at a stirring speed of 150 rpm until a homogeneous and stable liquid water-soluble fertilizer is formed.

[0057] Example 2 A compound liquid water-soluble fertilizer was prepared following the steps of Example 1, except that the macro-element fertilizers were replaced with 100 parts urea, 120 parts ammonium polyphosphate, and 80 parts potassium dihydrogen phosphate; the organic chelating agent was replaced with 15 parts diethylenetriaminepentaacetic acid; the gelling carrier material was replaced with 30 parts gelatin; the crosslinking agent was replaced with 8 parts glutaraldehyde; and the coating material was replaced with 75 parts polycaprolactone. The remaining steps were the same as in Example 1. (Key parameters such as the amount of gelling carrier material in step three (30 parts) and the amount of coating material in step five (75 parts) are based on the corrected data from Example 1.) In the preparation process, in the third step, when dissolving gelatin in water to prepare the core aqueous solution, the water bath temperature needs to be controlled at 50℃; in the fourth step, glutaraldehyde aqueous solution is used as the crosslinking bath solution, and the curing time is controlled at 45 minutes; in the fifth step, polycaprolactone is dispersed in dichloromethane to prepare the coating liquid, and the fluidized bed inlet air temperature is controlled to not exceed 40℃. The solid content and stability of the final composite liquid water-soluble fertilizer are comparable to those of Example 1.

[0058] Example 3 The preparation of a composite liquid water-soluble fertilizer follows the steps of Example 1, except that the surfactant is replaced with 3 parts of Span-60 and 2 parts of sodium dodecylbenzenesulfonate, the solvent is replaced with 50 parts of water, the nonionic surfactant is replaced with 0.3 parts of polyoxyethylene castor oil, the gelling carrier material is replaced with 30 parts of sodium carboxymethyl cellulose, the crosslinking agent is replaced with 20 parts of sodium tripolyphosphate (after participating in the crosslinking reaction, the excess part is removed in the washing step, and the final residual of about 5 parts is included in the dry weight), the coating material is replaced with 75 parts of lignin, and the dispersion stabilization system is replaced with 1.5 parts of sodium lignin sulfonate and 0.9 parts of sodium bentonite, and the rest remains the same as in Example 1.

[0059] In the preparation process, in the second step, when using water as a solvent to prepare the hormone stock solution, the ultrasonic-assisted dissolution time was extended to 25 minutes to ensure sufficient dispersion of the biostimulant. In the fourth step, sodium tripolyphosphate aqueous solution was used as a cross-linking bath, utilizing the ionic cross-linking effect between sodium tripolyphosphate and sodium carboxymethyl cellulose to form drug-loaded microparticles, with the curing time controlled at 60 minutes. In the fifth step, lignin was dispersed in ethanol to prepare the coating solution. Due to the natural surface activity of lignin, a stable dispersion system could be formed without the addition of additional dispersants. The final composite liquid water-soluble fertilizer exhibits good anti-settling properties and is suitable for drip irrigation systems.

[0060] Example 4 The preparation of a composite liquid water-soluble fertilizer follows the steps of Example 1, except that the macro-element fertilizer is replaced with 100 parts of calcium ammonium nitrate, 100 parts of potassium nitrate, and 120 parts of ammonium polyphosphate; the organic chelating agent is replaced with 45 parts of citric acid (preferably added first and the pH of the system is adjusted to 3.5-4.5 to chelate calcium ions and inhibit phosphate precipitation); the gelling carrier material is replaced with 30 parts of hydroxypropyl starch; the crosslinking agent is replaced with 20 parts of calcium sulfate (after participating in the crosslinking reaction, the excess part is removed in the washing step, and the final residue of about 5 parts is included in the dry weight); the coating material is replaced with 75 parts of modified silica sol (based on SiO2, purchased from Zhejiang Yuda Chemical Co., Ltd., model XCS-30); the plasticizer is replaced with 1.5 parts of glycerol; the film-forming aid is replaced with 1.5 parts of dodecyl alcohol ester; and the dispersion stabilizing system is replaced with 1.2 parts of hydroxypropyl methylcellulose and 1.2 parts of sodium lignosulfonate.

[0061] In the preparation process, the first step involves dissolving citric acid in deionized water and adjusting the pH to 3.5-4.5, followed by the sequential addition of calcium ammonium nitrate, potassium nitrate, and ammonium polyphosphate, stirring until a homogeneous and transparent substrate fertilizer solution is formed. The fourth step uses a calcium sulfate aqueous solution as a crosslinking bath. In the fifth step, when using modified silica sol as a coating material, 75 parts of modified silica sol are dispersed in 450 parts of a water-ethanol mixed solvent (mass ratio 7:3, as solvent A), and glycerol and dodecyl alcohol ester are added to prepare the coating solution. Coating and drying are performed according to the spraying conditions described in Example 1, resulting in a continuous and dense inorganic-organic composite shell after drying. The sixth step uses hydroxypropyl methylcellulose as an anti-settling agent. The final composite liquid water-soluble fertilizer maintains excellent suspension stability even under high-temperature storage conditions.

[0062] Comparative Example 1 The preparation of a compound liquid water-soluble fertilizer follows the steps of Example 1, except that the slow-release biostimulant dispersion is replaced by the direct dissolution and addition of the biostimulant active ingredient, while the rest remains the same as in Example 1.

[0063] Specifically, in step seven, the preparation of the slow-release biostimulant dispersion in step six is ​​cancelled. Instead, 15 parts of the biostimulant (2R,3R,4R,5S)-6-(8-(2-(1H-indol-3-yl)-1-(naphth-1-yl)ethyl)-2-(benzylamino)-9H-purine-9-yl)hexane-1,2,3,4,5-pentaol are dissolved in a mixed solvent of ethanol and propylene glycol (mass ratio 3:2). After ultrasonic-assisted dissolution, the solution is added directly to the substrate fertilizer solution prepared in step one under stirring. The mixture is stirred for 45 minutes to obtain a compound liquid water-soluble fertilizer.

[0064] Comparative Example 2 The preparation of a compound liquid water-soluble fertilizer follows the steps of Example 1, except that the fifth step of preparing coated particles and the sixth step of preparing a slow-release biostimulant dispersion are replaced by directly using the drug-loaded microparticles obtained in the fourth step as the dispersion, while the rest remains the same as in Example 1.

[0065] Specifically, after collecting the drug-loaded microparticles in step four, the coating process in step five is omitted (i.e., coating is not performed using polylactic acid-glycolic acid copolymer, polyvinyl alcohol, triethyl citrate, and polyethylene glycol 400). The drug-loaded microparticles (average particle size of 50 to 500 micrometers) collected by filtration are directly washed according to the method in step six of Example 1, redispersed in 65 parts of deionized water, added to the dispersion stabilization system, and homogenized to obtain an uncoated biostimulant dispersion. Then, it is mixed with the substrate fertilizer solution in step seven.

[0066] Comparative Example 3 The preparation of a compound liquid water-soluble fertilizer follows the steps of Example 1, except that the biostimulant (2R,3R,4R,5S)-6-(8-(2-(1H-indol-3-yl)-1-(naphth-1-yl)ethyl)-2-(benzylamino)-9H-purine-9-yl)hexane-1,2,3,4,5-pentaol is replaced with an equal mass of 6-benzylaminopurine (6-BA), and the rest remains the same as in Example 1.

[0067] Specifically, in the second step, 15 parts of 6-benzylaminopurine are used to replace the biostimulant with the specific structure and added to a mixed solvent consisting of 30 parts of ethanol and 20 parts of propylene glycol. 0.3 parts of Tween-20 are added and the mixture is dissolved by ultrasound to form a hormone stock solution. The subsequent third to seventh steps are carried out according to the process described in Example 1 to obtain a composite liquid water-soluble fertilizer containing 6-benzylaminopurine.

[0068] Comparative Example 4 The preparation of a composite liquid water-soluble fertilizer follows the steps of Example 1, except that the dispersion stabilization system (1.5 parts of polyether-modified polysiloxane and 0.9 parts of xanthan gum) is replaced with an equal mass of sodium dodecylbenzenesulfonate (2.4 parts), and the homogenization process in step 6 is omitted. The rest is the same as in Example 1.

[0069] Specifically, in step six, after the washed coated particles are redispersed in 65 parts of deionized water, 2.4 parts of sodium dodecylbenzenesulfonate are added as a dispersant, and ordinary mechanical stirring (200 rpm, 30 minutes) is used instead of high-pressure homogenization to obtain a biostimulant dispersion; in step seven, the mixture is mixed with the substrate fertilizer solution according to Example 1 to obtain a compound liquid water-soluble fertilizer.

[0070] Performance testing: 1. Seed germination and seedling growth experiment: The crop tested was Chinese cabbage (Brassicarapa var. chinensis).

[0071] Experimental design: There were 9 treatments in total, including Examples 1-4, Comparative Examples 1-4 and water control (CK), with 4 replicates for each treatment and 20 plants per replicate.

[0072] Application method: Dilute each sample 500 times and spray the leaves at the three-leaf stage of the crop, ensuring that the liquid droplets are evenly applied to the leaf surface without dripping. Spray once every 7 days, for a total of 3 sprays. For the water control, spray an equal amount of deionized water.

[0073] Measurement indicators: Chlorophyll content: measured using a SPAD-502 chlorophyll meter, data are shown in Table 1; Biomass: Whole plants containing roots were taken, blanched at 105℃ and dried at 80℃ to constant weight, and the dry weight was measured. The data are shown in Table 1.

[0074] 2. Determination of stress resistance indicators: After the pak choi seedlings in each treatment group reached the four-leaf stage, they were transferred to an artificial climate chamber for low-temperature stress treatment. The low-temperature stress conditions were set as follows: daytime temperature 15℃ / nighttime temperature 8℃, photoperiod 12h / 12h (day / night), light intensity 3000 lux, and relative humidity 70%. After 7 days of continuous treatment, the penultimate true leaf (i.e., the fully expanded functional leaf) of each treatment group was collected, immediately flash-frozen in liquid nitrogen, and stored in an ultra-low temperature freezer at -80℃ for later use. Each treatment group was set up with 4 biological replicates, and the leaves of 10 plants were collected in each replicate and mixed to form a single sample. The free proline content in the leaves was determined by sulfosalicylic acid extraction, and the data are shown in Table 1.

[0075] Table 1

[0076] Note: Data are the mean ± standard deviation of four replicates; DW is dry weight; FW is fresh weight. Table 1 shows that, compared with the water control, treatments 1-4 significantly increased chlorophyll content (SPAD value) and dry biomass (DW), while reducing proline content under low-temperature stress. Specifically, the SPAD values ​​for treatments 1-4 were 46.2±1.9-49.2±2.3, DW was 3.92±0.15-4.38±0.20 g / plant, and proline content was 28.7±2.1-35.1±2.8 μg / gFW; while the SPAD value for the water control was 35.2±1.4, DW was 2.48±0.10 g / plant, and proline content was 46.3±3.8 μg / gFW. This indicates that the compound liquid water-soluble fertilizer of this invention can maintain chlorophyll levels in plant leaves and promote dry matter accumulation under low-temperature conditions, while mitigating osmotic / oxidative stress responses caused by low-temperature stress, thereby improving crop resistance.

[0077] Furthermore, compared with Examples 1-4, Comparative Examples 1-4 showed a smaller increase in chlorophyll content and biomass, and a less significant decrease in proline content: the SPAD values ​​of Comparative Examples 1-4 were 36.8±1.5-42.1±1.9, DW was 2.72±0.11-3.45±0.15 g / plant, and proline content was 39.2±2.9-44.5±3.6 μg / gFW. These results indicate that introducing biostimulants into the compound liquid water-soluble fertilizer system in the form of a slow-release dispersion as described in this invention is more beneficial for exerting a synergistic effect of growth promotion and stress resistance under low-temperature stress than directly adding or changing key components / processes in the comparative examples.

[0078] The increased SPAD value, increased DW, and decreased proline content indicate that the treatment of this invention can, under low-temperature conditions,: on the one hand, promote the maintenance of leaf chlorophyll content and the stability of photosynthetic system function, thereby increasing the formation of photosynthetic products and the accumulation of dry matter; on the other hand, reduce the degree of cell osmotic imbalance and membrane system damage caused by low-temperature stress, so that plants can maintain normal physiological state without accumulating large amounts of osmotic regulators such as proline. The results in Table 1, showing the highest SPAD value (49.2±2.3) and DW (4.38±0.20 g / plant) and the lowest proline content (28.7±2.1 μg / gFW) in Example 4, further illustrate that the technical solution of this invention can achieve better growth promotion and stress resistance effects.

[0079] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A compound liquid water-soluble fertilizer, characterized in that, By weight, the compound liquid water-soluble fertilizer comprises the following components: 300 to 500 parts of macro-element fertilizer, 15 to 35 parts of micro-element fertilizer, 10 to 25 parts of organic chelating agent, 2 to 8 parts of surfactant, 50 to 150 parts of slow-release biostimulant dispersion, and 400 to 800 parts of water. The raw materials for preparing the sustained-release biostimulant dispersion are composed of the following components in parts by weight: 5 to 30 parts of biostimulant, 30 to 80 parts of solvent, 0.5 to 1.5 parts of nonionic surfactant, 25 to 150 parts of gelling carrier material, 15 to 100 parts of crosslinking agent, 60 to 200 parts of coating material, 2 to 8 parts of plasticizer, 2 to 8 parts of film-forming aid, and 2 to 15 parts of dispersion stabilizing system. The biostimulant is (2R,3R,4R,5S)-6-(8-(2-(1H-indol-3-yl)-1-(naphth-1-yl)ethyl)-2-(benzylamino)-9H-purine-9-yl)hexane-1,2,3,4,5-pentaol; The gelling carrier material is selected from one or more of sodium alginate, deacetylated chitosan, gelatin, sodium carboxymethyl cellulose, and hydroxypropyl starch; The crosslinking agent is selected from one or more of calcium chloride, calcium sulfate, sodium tripolyphosphate, and glutaraldehyde; The coating material is selected from one or more of polylactic acid-glycolic acid copolymer, polycaprolactone, polyvinyl alcohol, polyacrylic acid, lignin, paraffin emulsion, and silica sol.

2. The compound liquid water-soluble fertilizer according to claim 1, characterized in that, The macro-element fertilizer is selected from one or more of urea, potassium nitrate, potassium dihydrogen phosphate, ammonium polyphosphate, and calcium ammonium nitrate. The micronutrient fertilizer is selected from one or more of the following: ethylenediaminetetraacetic acid (EDTA) chelated iron, EDTA chelated zinc, EDTA chelated manganese, EDTA chelated copper, boric acid, and sodium molybdate. The organic chelating agent is selected from one or more of disodium ethylenediaminetetraacetate, diethylenetriaminepentaacetic acid, citric acid, and tartaric acid; The surfactant is selected from one or more of Tween-80, Span-60, alkyl glycosides, and sodium dodecylbenzenesulfonate.

3. The compound liquid water-soluble fertilizer according to claim 1, characterized in that, The solvent is selected from one or more of water, ethanol, and propylene glycol; The nonionic surfactant is selected from one or more of Tween-20, Span-80, polyoxyethylene castor oil, and alkyl glycosides.

4. The compound liquid water-soluble fertilizer according to claim 1, characterized in that, The dispersion stabilization system includes a dispersant and an anti-settling agent; The dispersant is selected from one or more of polyether-modified polysiloxane, sodium lignosulfonate, and sodium polycarboxylate. The anti-settling agent is selected from one or more of xanthan gum, sodium bentonite, and hydroxypropyl methylcellulose; The plasticizer is selected from one or more of glycerol, triethyl citrate, and dioctyl phthalate; The film-forming aid is selected from one or more of polyethylene glycol 400, dibutyl phthalate, and dodecyl alcohol ester.

5. A method for producing a compound liquid water-soluble fertilizer as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The first step is to add the water to the reaction vessel, heat it and start stirring, and then add the macro-element fertilizer, micro-element fertilizer, organic chelating agent and surfactant in the formula amount in sequence, and stir to dissolve until a uniform and transparent matrix fertilizer solution is formed for later use. The second step involves adding the biostimulant to the solvent, adding the nonionic surfactant, and dissolving it by ultrasonic assistance or stirring to obtain a hormone mother liquor. The third step involves dissolving the gelling carrier material in water to prepare a core aqueous solution, and then adding the hormone stock solution obtained in the second step to the core aqueous solution to mix and disperse it to form a drug-loaded precursor solution. The fourth step is to prepare a crosslinking bath solution containing the crosslinking agent, introduce the drug-loaded precursor solution obtained in the third step into the crosslinking bath by spraying, dripping or emulsification shearing, solidify to form drug-loaded microparticles, filter and collect the drug-loaded microparticles; Fifth step: Disperse the coating material in solvent A, add the plasticizer and film-forming aid to prepare a coating solution, place the drug-loaded microparticles obtained in step four in a fluidized bed or spray coating machine, spray the coating solution for coating, and dry to obtain coated particles; wherein the solvent A is one or more of ethanol, acetone, dichloromethane, and water-ethanol mixed solvent, and its amount is 5 to 20 times the weight of the coating material; Step 6: Wash the coated particles obtained in Step 5 to remove free hormones and residual cross-linking agents from the surface. Then, redisperse the particles in water, add the prescribed amount of dispersion stabilization system, and obtain a sustained-release biostimulant dispersion through low-shear homogenization; obtain a sustained-release biostimulant dispersion through high-pressure homogenization; wherein the high-pressure homogenization pressure is 20 MPa to 50 MPa, and homogenization is performed 2 to 3 times. Step 7: While stirring, add the slow-release biostimulant dispersion obtained in step 6 to the substrate fertilizer solution prepared in step 1, and stir until a compound liquid water-soluble fertilizer is formed.

6. The method for producing compound liquid water-soluble fertilizer according to claim 5, characterized in that, The heating temperature in the first step is 40 to 60 degrees Celsius; the shear rate for mixing and dispersing in the third step is 2000 to 4000 rpm.

7. The method for producing compound liquid water-soluble fertilizer according to claim 5, characterized in that, In the fourth step, the curing time is controlled to be 15 to 60 minutes; the average particle size of the drug-loaded microparticles collected in the fourth step is 10 micrometers to 500 micrometers.

8. The method for producing compound liquid water-soluble fertilizer according to claim 5, characterized in that, In the sixth step, the solid content of the slurry is adjusted to 20% to 50%.

9. The method for producing compound liquid water-soluble fertilizer according to claim 5, characterized in that, The stirring time in step seven is 30 to 60 minutes.

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