A kind of astaxanthin-containing biological stimulant fertilizer suitable for melon and fruit color change and sweetness increase

Abstract

The application discloses a kind of astaxanthin biological stimulant fertilizer suitable for melon and fruit color change sweetening, and the fertilizer takes Haematococcus pluvialis source astaxanthin as core active component, compound amino acid, sugar alcohol, plant growth factor and chelated trace element, and precise control melon and fruit anthocyanin synthesis and sugar accumulation are realized by component synergistic proportioning;The application retains astaxanthin high activity by low-temperature wall-breaking extraction process, improves nutrient absorption and utilization rate relying on sugar alcohol chelating system, can effectively promote melon and fruit uniform color change, significantly improve the soluble solids content of fruit, while inhibit plant vigorous growth, prolong the fertilizer efficiency period, there is no chemical residue, high safety, can be widely applied to grape, strawberry, tomato, citrus and other types of melon and fruit crops quality improvement and yield increase planting.

Description

Technical Field

[0001] This invention belongs to the field of biostimulant fertilizer technology, specifically relating to an astaxanthin-containing biostimulant fertilizer suitable for color change and sweetening of melons and fruits. Background Technology

[0002] For fruit crops such as grapes, strawberries, tomatoes, citrus fruits, and cherries, fruit color and sweetness are core indicators determining the fruit's commercial value, market price, and consumer acceptance. During fruit cultivation, the period from the late fruit enlargement stage to the ripening and color-changing stage is a critical window for sugar accumulation and anthocyanin synthesis. Nutrient supply and physiological regulation during this stage directly determine the final fruit quality. Currently, to achieve color change and sweetness enhancement in fruit cultivation, chemical colorants, high-potassium chemical fertilizers, and hormone-based regulators are commonly used, supplemented with conventional biostimulant fertilizers to further improve quality.

[0003] Existing color-changing and sweetening fertilizers and regulators have core technical problems in practical applications: conventional color-changing and sweetening products lack targeted physiological regulation mechanisms and rely solely on potassium fertilizer supplementation or hormone stimulation to promote coloring. They cannot simultaneously activate the anthocyanin synthesis pathway and photosynthetic product transport system in fruits and vegetables, resulting in uneven coloring, light coloring, and a high incidence of mottled and green-shouldered fruits. At the same time, the sugar accumulation efficiency is low, the sugar content increase is limited, and the fertilizer effect is poor. The quality improvement effect after a single application can only be maintained for 3 to 5 days, requiring frequent topdressing. This not only increases the labor and material costs of planting, but also easily leads to secondary problems such as excessive vegetative growth, soft and cracked fruits, soil salinization, and excessive chemical residues in fruits, which seriously restricts the development of high-quality, high-yield, green, and standardized planting of fruits and vegetables.

[0004] Existing biostimulant fertilizers, in their limited quantity, primarily use seaweed extracts, humic acid, and common amino acids as core ingredients. These have limited functionality, poor stability of active components, and cannot precisely match the physiological metabolic needs of fruit color enhancement. They also struggle to regulate fruit pigment synthesis and sugar accumulation at the molecular level, resulting in weak quality improvement and insufficient stability. Astaxanthin, as a highly active natural antioxidant biostimulant, can regulate the plant's antioxidant system and secondary metabolic pathways. However, there is currently no fertilizer formula or large-scale preparation process that precisely combines highly active astaxanthin from Haematococcus pluvialis with specialized adjuvants to meet the specific needs of fruit color enhancement and sweetening. Existing technologies cannot solve the core problems of uneven color development, poor sweetening effects, and short-lasting effects. Summary of the Invention

[0005] This invention aims to solve the technical problems of existing fruit color-changing and sweetening fertilizers, which have poor targeting, cannot simultaneously regulate anthocyanin synthesis and sugar accumulation, resulting in uneven fruit coloring, poor coloring quality, limited sugar content improvement, short fertilizer effect duration, and are prone to causing excessive plant growth and fruit quality defects.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A biostimulant fertilizer containing astaxanthin, suitable for color change and sweetening of melons and fruits, is prepared from the following raw materials in parts by weight: 0.8-2.5 parts of Haematococcus pluvialis astaxanthin extract, 18-28 parts of compound amino acids, 6-12 parts of sugar alcohol chelated trace elements, 3-8 parts of plant-derived growth promoters, 2-5 parts of penetration and moisture retention promoters, and 45-65 parts of deionized water; the compound amino acids are composed of phenylalanine, methionine, and proline in a mass ratio of 3:2:1; the sugar alcohol chelated trace elements are a mixture of sugar alcohol chelated calcium, sugar alcohol chelated magnesium, and sugar alcohol chelated potassium.

[0008] A preferred embodiment of the present invention is prepared from the following optimal weight parts of raw materials: 1.6 parts of Haematococcus pluvialis astaxanthin extract, 23 parts of compound amino acids, 9 parts of sugar alcohol chelated trace elements, 5.5 parts of plant-derived growth promoter, 3.5 parts of penetration and moisturizing agent, and 57.4 parts of deionized water.

[0009] In a preferred embodiment of the present invention, the effective component content of the Haematococcus pluvialis astaxanthin extract is ≥98%, the particle size is 800-1200 mesh, it is prepared by low-temperature cell wall breaking extraction, and the antioxidant activity retention rate at room temperature is ≥95%.

[0010] In a preferred embodiment of the present invention, the mass ratio of sugar alcohol chelated calcium, sugar alcohol chelated magnesium, and sugar alcohol chelated potassium in the sugar alcohol chelated trace elements is 2:1:3, and the chelation degree is ≥90%.

[0011] In a preferred embodiment of the present invention, the plant-derived growth promoter is a compound of acetoin and 2,3-butanediol in a mass ratio of 1:1.5, and the penetrating and moisturizing promoter is a compound of glycerin and betaine in a mass ratio of 2:1.

[0012] In a preferred embodiment of the present invention, the fertilizer is a pale yellow transparent liquid with a pH value of 5.5 to 7.0, an effective viable bacteria count of 0, 100% water solubility, and a shelf life of ≥18 months when stored at 25°C.

[0013] A method for preparing an astaxanthin-containing biostimulant fertilizer suitable for color change and sweetening of melons and fruits includes the following steps: Step S1, raw material pretreatment: Add the compound amino acids to deionized water and stir at a constant temperature of 40-45℃ until completely dissolved to obtain an amino acid base solution; Step S2, chelation mixing: Add sugar alcohol to the amino acid base solution in batches to chelate trace elements, stir at a constant temperature for 20-30 minutes to obtain a chelation mixture; Step S3, active ingredient compounding: Add Haematococcus pluvialis astaxanthin extract under low temperature conditions, stir in the dark for 15-20 minutes, then add plant-derived growth promoter and penetration moisturizing agent, and stir evenly at a uniform speed. Step S4, pH adjustment and filtration: Adjust the pH of the system to 5.5-7.0, let it stand to defoam, and then filter it through a 200-mesh filter to obtain the finished fertilizer.

[0014] In a preferred embodiment of the present invention, the low temperature condition in step S3 is 0-10℃, the entire process is carried out in the dark, and the stirring speed is 300-400 r / min to avoid the inactivation of astaxanthin.

[0015] In a preferred embodiment of the present invention, the stirring speed in steps S1 and S2 is 400-500 r / min, and there is no particulate residue during the dissolution and mixing process, resulting in a uniform and stable system.

[0016] In a preferred embodiment of the present invention, the standing defoaming time in step S4 is 30-40 minutes, followed by aseptic filling after filtration, with the ambient temperature ≤25℃ throughout the process and storage away from light.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. Targeted solution to core technical problems, resulting in superior quality improvement. This invention features a unique synergistic system of astaxanthin and a specialized compound amino acid. Astaxanthin activates the activity of key enzymes in anthocyanin synthesis in fruits, promoting uniform anthocyanin synthesis and deposition, thus completely solving problems such as uneven coloring, light coloring, and blemished fruit. Phenylalanine and methionine, as precursors for anthocyanin synthesis, further enhance the coloring effect, while proline improves fruit resistance to adverse conditions, preventing the impact of adverse environments on quality during the coloring period. Simultaneously, this system can regulate the transport and accumulation of photosynthetic products from the plant to the fruit, significantly increasing the soluble solids content of the fruit, with a sugar content increase of 1.5–3 degrees compared to conventional fertilizers.

[0018] 2. Long-lasting and stable fertilizer effect, reducing planting costs. This invention uses a sugar alcohol chelated trace element system, which has strong nutrient stability and is not easily fixed by the soil. It can be quickly absorbed and utilized by crops. At the same time, the antioxidant protection of astaxanthin can extend the high-efficiency photosynthetic cycle of plants. The fertilizer effect of a single application can last for 12 to 15 days, which greatly reduces the number of topdressings and reduces labor and fertilizer input costs.

[0019] 3. Green, safe, and residue-free, suitable for green planting. This invention uses all biological and food-grade raw materials, free of chemical hormones, heavy metals, and harmful additives. The low-temperature preparation process does not produce harmful substances. After application, it will not cause fruit residue or soil salinization. At the same time, it can inhibit excessive vegetative growth and reduce quality problems such as cracked and soft fruit, which meets the standards for green and organic fruit and vegetable planting.

[0020] 4. Simple process, suitable for large-scale production. The preparation method of this invention is mild and simple, requiring no complex equipment or harsh reaction conditions. It operates at room temperature and low temperature throughout the process, with low energy consumption and no waste discharge. The product has excellent water solubility, high stability, and a shelf life of up to 18 months, making it easy to store, transport, and apply in the field. It is suitable for large-scale industrial production and promotion.

[0021] 5. Wide applicability and strong versatility in improving quality. This fertilizer can be widely used in the color-changing and expansion stages of various fruit crops such as grapes, strawberries, tomatoes, citrus, cherries, and mangoes. It is not limited by crop variety, planting area, or planting mode, and has a wide range of applications. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments or prior art, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The present invention provides a flowchart of a method for preparing an astaxanthin-containing biostimulant fertilizer suitable for color change and sweetening of melons and fruits.

[0024] Figure 2 This is a bar chart comparing the effects of the fertilizer of this invention and conventional fertilizers on the uniformity of strawberry fruit color change.

[0025] Figure 3 This is a schematic diagram comparing the fertilizer efficacy duration of different embodiments of the fertilizer of the present invention.

[0026] Figure 4 This is a graph showing the trend of anthocyanin content changes in fruits and melons after the application of the fertilizer of this invention. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0028] The core innovation of this invention lies in using highly active astaxanthin from Haematococcus pluvialis as the core functional component, combined with a specific ratio of functional amino acids, sugar alcohol chelated trace elements, and plant-derived growth promoters to construct a biostimulant system that targets and regulates the color change and sweetening of fruits. Through the synergistic effect of the components, it precisely activates the secondary metabolic pathways of fruits, simultaneously achieving uniform coloring, efficient sweetening, and long-lasting effects, thus avoiding many defects of traditional products.

[0029] Specifically, a biostimulant fertilizer containing astaxanthin, suitable for color change and sweetening of melons and fruits, is prepared from the following raw materials in parts by weight: 0.8–2.5 parts of Haematococcus pluvialis astaxanthin extract, 18–28 parts of compound amino acids, 6–12 parts of sugar alcohol chelated trace elements, 3–8 parts of plant-derived growth promoters, 2–5 parts of penetration and moisture-retaining agents, and 45–65 parts of deionized water; the compound amino acids are composed of phenylalanine, methionine, and proline in a mass ratio of 3:2:1; the sugar alcohol chelated trace elements are a mixture of sugar alcohol chelated calcium, sugar alcohol chelated magnesium, and sugar alcohol chelated potassium. This fertilizer, through the synergistic effect of astaxanthin and compound amino acids, targets and activates the anthocyanin synthesis pathway in melons and fruits, promotes the transport and accumulation of photosynthetic products, and solves the technical problems of uneven color change, weak sweetening effect, and short-lasting effect of existing fertilizers.

[0030] It is prepared from the following optimal weight parts of raw materials: 1.6 parts of Haematococcus pluvialis astaxanthin extract, 23 parts of compound amino acids, 9 parts of sugar alcohol chelated trace elements, 5.5 parts of plant-derived growth promoter, 3.5 parts of penetration and moisturizing agent, and 57.4 parts of deionized water.

[0031] The active ingredient content of the astaxanthin extract from Haematococcus pluvialis is ≥98%, the particle size is 800-1200 mesh, it is prepared by low temperature cell wall breaking extraction, and the antioxidant activity retention rate at room temperature is ≥95%.

[0032] Among the sugar alcohol chelated trace elements, the mass ratio of sugar alcohol chelated calcium, sugar alcohol chelated magnesium, and sugar alcohol chelated potassium is 2:1:3, and the chelation degree is ≥90%.

[0033] The plant-derived growth promoter is a compound of acetoin and 2,3-butanediol in a mass ratio of 1:1.5, and the penetrating and moisturizing agent is a compound of glycerin and betaine in a mass ratio of 2:1.

[0034] The fertilizer is a pale yellow transparent liquid with a pH of 5.5–7.0, an effective live bacteria count of 0, 100% water solubility, and a shelf life of ≥18 months when stored at 25℃.

[0035] like Figure 1 As shown, this embodiment of the invention provides a method for preparing the above-mentioned astaxanthin-containing biostimulant fertilizer suitable for color change and sweetening of melons and fruits, comprising the following steps: Step S1, raw material pretreatment: Add the compound amino acids to deionized water and stir at a constant temperature of 40-45℃ until completely dissolved to obtain an amino acid base solution; Step S2, chelation mixing: Add sugar alcohol to the amino acid base solution in batches to chelate trace elements, stir at a constant temperature for 20-30 minutes to obtain a chelation mixture; Step S3, active ingredient compounding: Add Haematococcus pluvialis astaxanthin extract under low temperature conditions, stir in the dark for 15-20 minutes, then add plant-derived growth promoter and penetration moisturizing agent, and stir evenly at a uniform speed. Step S4, pH adjustment and filtration: Adjust the pH of the system to 5.5-7.0, let it stand to defoam, and then filter it through a 200-mesh filter to obtain the finished fertilizer.

[0036] In step S3, the low temperature condition is 0-10℃, the entire process is carried out in the dark, and the stirring speed is 300-400 r / min to avoid the inactivation of astaxanthin.

[0037] In steps S1 and S2, the stirring speed is 400-500 r / min. There are no particulate residues during the dissolution and mixing process, and the system is uniform and stable.

[0038] In step S4, the standing defoaming time is 30-40 minutes. After filtration, the product is aseptically filled. The ambient temperature throughout the process is ≤25℃, and it is stored away from light.

[0039] Example 1 A biostimulant fertilizer containing astaxanthin, suitable for color change and sweetening of melons and fruits, is prepared from the following raw materials in parts by weight: 0.8 parts of Haematococcus pluvialis astaxanthin extract, 18 parts of compound amino acids, 6 parts of sugar alcohol chelated trace elements, 3 parts of plant-derived growth promoter, 2 parts of penetration and moisturizing agent, and 45 parts of deionized water.

[0040] Among them, the compound amino acid is composed of phenylalanine, methionine and proline in a mass ratio of 3:2:1; the sugar alcohol chelated trace elements are calcium, magnesium and potassium in a mass ratio of 2:1:3; the plant-derived growth promoter is a compound of acetoin and 2,3-butanediol in a 1:1.5 ratio; and the penetrating and moisturizing promoter is a compound of glycerin and betaine in a 2:1 ratio.

[0041] The preparation method includes the following steps: Step S1, raw material pretreatment: Add 18 parts of compound amino acids to 45 parts of deionized water, stir at 40℃ and 400r / min until completely dissolved, and obtain a uniform and transparent amino acid base solution. Step S2, chelation mixing: Add 6 parts of sugar alcohol chelated trace elements to the base solution in batches, stir at 40℃ and 450r / min for 25min to achieve full chelation and fusion of nutrients, and obtain chelated mixture; Step S3, active component compounding: Cool the system to 8℃, keep it in the dark throughout the process, add 0.8 parts of Haematococcus pluvialis astaxanthin extract under stirring at 350r / min, stir for 18min until completely dispersed, then add 3 parts of plant-derived growth promoter and 2 parts of penetration and moisturizing promoter, and continue stirring for 10min until the system is uniform. Step S4, pH adjustment and filtration: The pH value of the system is adjusted to 6.2 using food-grade citric acid and potassium hydroxide. The mixture is allowed to stand at room temperature for 35 minutes to defoam, then filtered through a 200-mesh sterile filter and aseptically filled to obtain the finished fertilizer.

[0042] Example 2 A biostimulant fertilizer containing astaxanthin, suitable for color change and sweetening of melons and fruits, is prepared from the following optimal parts by weight of raw materials: 1.6 parts of Haematococcus pluvialis astaxanthin extract, 23 parts of compound amino acids, 9 parts of sugar alcohol chelated trace elements, 5.5 parts of plant-derived growth promoter, 3.5 parts of penetration and moisture retention promoter, and 57.4 parts of deionized water.

[0043] The raw material ratio parameters are the same as in Example 1, and the preparation method steps are as follows: Step S1, raw material pretreatment: 23 parts of compound amino acids were added to 57.4 parts of deionized water and stirred at 42℃ and 450r / min until completely dissolved to obtain amino acid base solution; Step S2, chelation mixing: Add 9 parts of sugar alcohol to chelate trace elements in batches, stir at 42℃ and 500r / min for 25min to obtain a stable chelation mixture; Step S3, active ingredient compounding: Cool to 5℃, protect from light, stir at 350r / min, add 1.6 parts of astaxanthin extract and stir for 20min, then add 5.5 parts of plant-derived growth promoter and 3.5 parts of penetration and moisturizing agent, stir for 10min to mix well; Step S4, pH adjustment and filtration: Adjust the pH value to 6.0, let it stand for 35 minutes to defoam, filter through a 200-mesh filter, and aseptically fill to obtain the optimal formula fertilizer.

[0044] Example 3 A biostimulant fertilizer containing astaxanthin, suitable for color change and sweetening of melons and fruits, is prepared from the following raw materials in parts by weight: 2.5 parts of Haematococcus pluvialis astaxanthin extract, 28 parts of compound amino acids, 12 parts of sugar alcohol chelated trace elements, 8 parts of plant-derived growth promoters, 5 parts of penetration and moisturizing agents, and 65 parts of deionized water.

[0045] The raw material ratio parameters are the same as in Example 1, and the preparation method steps are as follows: Step S1, raw material pretreatment: 28 parts of compound amino acids are added to 65 parts of deionized water and stirred at 45℃ and 500r / min until completely dissolved; Step S2, chelation mixing: Add 12 parts of sugar alcohol to chelate trace elements, stir at 45℃ and 500r / min for 30min; Step S3, active ingredient compounding: Cool to 10℃, protect from light, stir at 400r / min, add 2.5 parts of astaxanthin extract and stir for 20min, then add 8 parts of growth promoter and 5 parts of moisturizing agent and stir to mix well. Step S4, pH adjustment and filtration: Adjust the pH value to 6.8, let it stand for 40 minutes to defoam, filter and fill to obtain the finished product.

[0046] Comparative Example 1 (Conventional Amino Acid Color-Changing Fertilizer) It uses commercially available conventional fruit and vegetable color-changing amino acid fertilizer, which does not contain astaxanthin. Its main components are ordinary compound amino acids, potassium sulfate, and trace elements. It does not contain plant-derived growth promoters or special penetrating and moisturizing components, and is prepared using conventional processes.

[0047] Comparative Example 2 (Single Astaxanthin Fertilizer) A single-active-component fertilizer was prepared using only 1.6 parts of Haematococcus pluvialis astaxanthin extract and 57.4 parts of deionized water. It contained no compound amino acids, sugar alcohol chelated trace elements, or functional additives. The rest of the preparation process was the same as in Example 2.

[0048] Experimental example: Field application effect test To verify the color-changing and sweetening effects, duration of effectiveness, and application advantages of the fertilizer of this invention, greenhouse-grown strawberries and open-field grapes were selected as experimental crops. Foliar spraying was applied at the early stage of fruit color change. Water, fertilizer, temperature, and light management were standardized in the field. Five treatment groups were set up, including Examples 1-3 and Comparative Examples 1-2, with each group replicated three times. Key indicators such as fruit color uniformity, soluble solids content, fertilizer effect duration, and rate of deformed fruit were tested. The experimental results are as follows: 1. Color-changing effect: Comparative Examples 1 and 2 showed uneven color-changing of the fruits, with obvious green shoulders and mottled skin, and the color-changing uniformity was only 65%–72%. In contrast, Example 1 of this invention achieved a color-changing uniformity of 89%, Example 2 (optimal formula) achieved 96%, and Example 3 achieved 92%. The fruits exhibited uniform coloring, bright hue, and no mottled skin or green fruit defects. (Reference) Figure 2 .

[0049] 2. Sweetening effect: The average sugar content of fruits in the blank control group was 12.5°, the sugar content of comparative example 1 was 13.8°, and the sugar content of comparative example 2 was 14.2°; the sugar content of example 1 of this invention was 15.2°, the sugar content of example 2 was 16.5°, and the sugar content of example 3 was 15.8°, and the sweetening effect was significantly better than that of existing conventional products.

[0050] 3. Duration of Effect: The duration of effect of the comparative example and conventional products is only 4-6 days; the duration of effect of the embodiments of this invention is ≥12 days, and Example 2 can reach 15 days, showing a significant advantage in long-lasting effect. (Reference) Figure 3 .

[0051] 4. Stress resistance and quality improvement: In all embodiments of the present invention, the rate of deformed fruit and the rate of cracked fruit are less than 3%, and there is no excessive vegetative growth of plants; in contrast, the rate of deformed fruit in the comparative embodiment is as high as 12% to 18%, and some plants have problems such as excessive growth of branches and leaves and soft fruit.

[0052] 5. Conventional fertilizers resulted in slow anthocyanin synthesis and low accumulation; the treatment group in Example 2 of this invention exhibited rapid anthocyanin synthesis, continuous accumulation, and a final content significantly higher than the conventional group. This mechanistic evidence demonstrates that the fertilizer of this invention can efficiently promote the synthesis and deposition of fruit coloring substances. (Reference) Figure 4 .

[0053] Field trials have fully demonstrated that this invention, through the synergistic combination of astaxanthin with special amino acids, chelated nutrients, and functional additives, creatively solves the core technical problems of uneven color change, weak sweetness enhancement, and short-lasting effect of existing fertilizers, and has significant technical advantages compared with single-component fertilizers and conventional bio-fertilizers.

[0054] Addressing the limitations of existing technologies that rely on single-nutrient supplementation and passive growth promotion through conventional fertilizers, this invention breaks through the constraints of traditional fertilizers' single-nutrient supplementation and passive growth promotion. Starting from the secondary metabolic mechanism of plants, it targets and activates the color-changing and sweetening pathways. This invention employs a low-temperature, light-protected, step-by-step compounding process to specifically solve the industry problem of astaxanthin's easy oxidation and inactivation, maximizing the preservation of biological activity. Simultaneously, the step-by-step dissolution and chelation ensures system stability. The process is adapted to the invention's proprietary formula, simultaneously achieving multiple effects such as uniform color change, efficient sweetening, long-lasting effect, and stress resistance and quality improvement. It completely overcomes the single-nutrient deficiencies of existing technologies, resulting in significant quality improvement and strong stability.

[0055] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A fertilizer containing astaxanthin, a biostimulant suitable for color change and sweetening of melons and fruits, characterized in that, It is prepared from the following raw materials in parts by weight: 0.8-2.5 parts of Haematococcus pluvialis astaxanthin extract, 18-28 parts of compound amino acids, 6-12 parts of sugar alcohol chelated trace elements, 3-8 parts of plant-derived growth promoters, 2-5 parts of penetration and moisturizing agents, and 45-65 parts of deionized water; the compound amino acids are composed of phenylalanine, methionine, and proline in a mass ratio of 3:2:1; the sugar alcohol chelated trace elements are a mixture of sugar alcohol chelated calcium, sugar alcohol chelated magnesium, and sugar alcohol chelated potassium.

2. The astaxanthin-containing biostimulant fertilizer for color change and sweetening of melons and fruits according to claim 1, characterized in that, It is prepared from the following optimal weight parts of raw materials: 1.6 parts of Haematococcus pluvialis astaxanthin extract, 23 parts of compound amino acids, 9 parts of sugar alcohol chelated trace elements, 5.5 parts of plant-derived growth promoter, 3.5 parts of penetration and moisturizing agent, and 57.4 parts of deionized water.

3. The astaxanthin-containing biostimulant fertilizer for color change and sweetening of melons and fruits according to claim 1, characterized in that, The astaxanthin extract from Haematococcus pluvialis has an effective component content of ≥98%, a particle size of 800-1200 mesh, is prepared by low-temperature cell wall breaking extraction, and retains ≥95% of its antioxidant activity at room temperature.

4. The astaxanthin-containing biostimulant fertilizer for color change and sweetening of melons and fruits according to claim 1, characterized in that, The sugar alcohol chelated trace elements have a mass ratio of sugar alcohol chelated calcium, sugar alcohol chelated magnesium, and sugar alcohol chelated potassium of 2:1:3, with a chelation degree of ≥90%.

5. The astaxanthin-containing biostimulant fertilizer for color change and sweetening of melons and fruits according to claim 1, characterized in that, The plant-derived growth promoter is a compound of acetoin and 2,3-butanediol in a mass ratio of 1:1.5, and the penetrating and moisturizing agent is a compound of glycerin and betaine in a mass ratio of 2:

1.

6. The astaxanthin-containing biostimulant fertilizer for color change and sweetening of melons and fruits according to claim 1, characterized in that, The fertilizer is a pale yellow transparent liquid with a pH value of 5.5 to 7.0, an effective viable bacteria count of 0, 100% water solubility, and a shelf life of ≥18 months when stored at 25℃.

7. A method for preparing an astaxanthin-containing biostimulant fertilizer suitable for color change and sweetening of melons and fruits, as described in any one of claims 1-6, characterized in that, Includes the following steps: Step S1, raw material pretreatment: Add the compound amino acids to deionized water and stir at a constant temperature of 40-45℃ until completely dissolved to obtain an amino acid base solution; Step S2, chelation mixing: Add sugar alcohol to the amino acid base solution in batches to chelate trace elements, stir at a constant temperature for 20-30 minutes to obtain a chelation mixture; Step S3, active ingredient compounding: Add Haematococcus pluvialis astaxanthin extract under low temperature conditions, stir in the dark for 15-20 minutes, then add plant-derived growth promoter and penetration moisturizing agent, and stir evenly at a uniform speed. Step S4, pH adjustment and filtration: Adjust the pH of the system to 5.5-7.0, let it stand to defoam, and then filter it through a 200-mesh filter to obtain the finished fertilizer.

8. The preparation method according to claim 7, characterized in that, In step S3, the low temperature condition is 0-10℃, the entire process is carried out in the dark, and the stirring speed is 300-400 r / min to avoid the inactivation of astaxanthin.

9. The preparation method according to claim 7, characterized in that, In steps S1 and S2, the stirring speed is 400-500 r / min. There are no particulate residues during the dissolution and mixing process, and the system is uniform and stable.

10. The preparation method according to claim 7, characterized in that, In step S4, the standing defoaming time is 30-40 minutes. After filtration, the product is aseptically filled. The ambient temperature throughout the process is ≤25℃, and it is stored away from light.

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