A liquid organic fertilizer for improving the quality of guava and its preparation method

Abstract

The present invention discloses a liquid organic fertilizer for improving the quality of guava and a preparation method thereof, belonging to the technical field of fertilizers. The raw materials of the liquid organic fertilizer include animal manure urine treatment liquid, diatom, compound microbial inoculum, trace element chelate (chelate of iron, zinc, copper, magnesium, boron, molybdenum and chitosan), stevia extract, 5-aminolevulinic acid, stabilizer, and surfactant. The above components act synergistically, can provide rich and comprehensive nutrients for guava, at the same time can improve the soil structure, inhibit the spread of pathogenic bacteria, improve the disease resistance of guava, improve the fertilizer absorption and utilization rate, increase the soluble sugar content and VC content of fruits, and improve the yield and quality of guava.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizers, and in particular to a liquid organic fertilizer for improving the quality of guava and a preparation method thereof. Background Art

[0002] Guava (Psidium guajava L.), also known as guava and guava, is a tropical and subtropical fruit with high nutritional value and market value. In recent years, with the improvement of consumers' requirements for food safety and quality, organic agriculture has developed rapidly, and organic fertilizers have played an increasingly important role in agricultural production because of their ability to improve soil health, increase crop nutrient absorption efficiency and improve fruit quality.

[0003] The traditional guava cultivation process mainly relies on chemical fertilizers and pesticides, which not only destroys the soil structure and reduces the activity of soil microorganisms, but also may cause environmental pollution and excessive food residues. At the same time, the long-term use of chemical fertilizers alone can easily lead to soil compaction and reduced fertility, which in turn affects the growth and yield of guava, and even affects the taste and nutritional value of the fruit.

[0004] Although the existing liquid organic fertilizers on the market have solved the above problems to a certain extent, most products have limited effects in promoting the maturity, sugar accumulation and yield of guava fruits. In addition, the preparation process of some organic fertilizers is complicated and the cost is high. In addition, due to the lack of effective biologically active substances, it is difficult to achieve a sustained and stable fertilization effect.

[0005] Therefore, developing a liquid organic fertilizer that can effectively improve the quality of guava, increase the sweetness of the fruit, improve the taste, and increase the yield of guava, and that is easy to prepare and low in cost has become a key issue that needs to be solved urgently. Summary of the invention

[0006] The purpose of the present invention is to provide a liquid organic fertilizer for improving the quality of guava and a preparation method thereof, so as to solve the problems existing in the above-mentioned prior art.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] One of the technical solutions of the present invention is a liquid organic fertilizer for improving the quality of guava. The raw materials include, by weight: 100-120 parts of animal manure treatment liquid, 3-5 parts of diatoms, 0.3-0.5 parts of composite microbial agents, 3-5 parts of trace element chelates, 2-4 parts of stevia extracts, 0.1-0.3 parts of 5-aminolevulinic acid, 3-5 parts of stabilizers, and 3-5 parts of surfactants; the trace element chelates are chelates of iron, zinc, copper, magnesium, boron, molybdenum and chitosan.

[0009] Further, the preparation method of the animal manure and urine treatment liquid comprises: heating animal manure and urine at 220 - 250 °C for 1 - 2 h to obtain a treated material; separating the solid and liquid of the treated material to obtain the animal manure and urine treatment liquid.

[0010] Further, the animal manure and urine are fresh pig manure and urine.

[0011] Pig manure and urine contain a large amount of organic substances and essential nutrient elements such as nitrogen, phosphorus, potassium, etc., which can provide sufficient nutrients for guava. The heating treatment can effectively kill harmful germs and eggs in pig manure and urine. After fermentation with a fermentation bacterium agent, under the synergistic action of strains, the organic substances in pig manure and urine are effectively degraded, and pig manure and urine are converted into high-quality liquid fertilizer.

[0012] Further, the diatom is Navicula.

[0013] Diatoms are rich in physiological active substances such as proteins, amino acids, inorganic salts, vitamins, alginic acid, and a small amount of enzymes, phytohormones, polyphenols, and polysaccharides, etc., which can provide rich and diverse nutrients for guava and improve the yield and quality of guava. In addition, diatoms and the compound microbial inoculum can form a dominant population around the roots of guava, inhibit the life activities of other harmful bacteria, and effectively improve the soil. The O2 produced during the photosynthesis of diatoms can well supply the metabolic activities of beneficial bacteria, and the CO2 quorum sensing signal molecules produced by beneficial bacteria can promote the assimilative growth of diatoms. The two symbiotically cooperate, can decompose the insoluble phosphorus and potassium fertilizers in the soil, produce various substances required by plants, and improve the yield and quality of guava.

[0014] Further, the compound microbial inoculum comprises Bacillus amyloliquefaciens, Bacillus mucilaginosus, Bacillus subtilis, and Trichoderma harzianum with a mass ratio of 1 - 3:1 - 3:1 - 2:1 - 2. That is, by mass ratio, Bacillus amyloliquefaciens: Bacillus mucilaginosus: Bacillus subtilis: Trichoderma harzianum = 1 - 3:1 - 3:1 - 2:1 - 2.

[0015] Further, the effective viable count of Bacillus amyloliquefaciens is 1 - 2×10 11 CFU / g, the effective viable count of Bacillus mucilaginosus is 1 - 3×10 10 CFU / g, the effective viable count of Bacillus subtilis is 1 - 3×10 10 CFU / g, and the effective viable count of Trichoderma harzianum is 1 - 3×10 10 CFU / g.

[0016] Bacillus amyloliquefaciens can dissolve compounds such as calcium phosphate, iron phosphate, and aluminum phosphate that are not easily absorbed in the soil, promote the dissolution and utilization of ineffective phosphorus in the soil, and can rapidly colonize and grow dominantly in the roots of guava.

[0017] After Bacillus mucilaginosus is applied to the soil, it reproduces and grows in the soil, which can play a role in nitrogen fixation, phosphorus solubilization, potassium solubilization and release of medium and trace elements, increase soil fertility and improve fertilizer utilization rate; during its metabolic process, it also produces various physiologically active substances such as gibberellin, indoleacetic acid, cytokinin, etc., enhancing the disease resistance and stress resistance of guava, increasing the yield of guava and improving the product quality; it can also form beneficial bacterial communities at the roots of guava, effectively inhibiting the reproduction of harmful and pathogenic microorganisms in the soil, and significantly reducing the occurrence of various soil-borne diseases.

[0018] During the growth process, Bacillus subtilis will produce active substances such as subtilin, polymyxin, nystatin, and gramicidin. These active substances have obvious inhibitory effects on harmful and pathogenic microorganisms; the phytase secreted by it can degrade most of the phytates in the soil, providing the nutrients needed for the growth of guava. At the same time, Bacillus subtilis can also produce auxin to promote the growth of guava fruits.

[0019] The growth hormone in Trichoderma harzianum can improve the photosynthesis efficiency of guava, increase the accumulation of photosynthetic products of guava, and thus promote the growth and development of guava. At the same time, the nutrients such as proteins, amino acids and trace elements contained in Trichoderma harzianum can also provide nutrients for guava, promote the healthy growth of guava, increase the sugar and vitamin content of the fruits, and thus improve the fruit quality. Moreover, various antibiotics in Trichoderma harzianum can also enhance the self-immunity of guava and improve the pest and disease resistance of guava.

[0020] The above-mentioned microbial agents cooperate synergistically, which can effectively improve the disease resistance of guava, improve the absorption and utilization of nutrients by guava, and further increase the yield and fruit quality of guava.

[0021] Furthermore, the stabilizer includes one or more of citric acid, sodium gluconate, sodium carboxymethyl cellulose and sodium hexametaphosphate; the surfactant is sodium dodecyl sulfate.

[0022] Furthermore, the preparation method of the trace element chelate includes: dissolving ferrous sulfate, zinc sulfate, copper sulfate, magnesium sulfate, borax, and ammonium molybdate in water, adjusting the pH to 7-8 to obtain a mixed solution A; dissolving chitosan in water to obtain a mixed solution B; dropping the mixed solution B into the mixed solution A, stirring and reacting for 10-12 h, then standing, centrifuging, and drying to obtain the trace element chelate.

[0023] Furthermore, the mass ratio of ferrous sulfate, zinc sulfate, copper sulfate, magnesium sulfate, borax, and ammonium molybdate is 3-5:5-8:1-2:2-3:3-5:2-3; the mass ratio of the sum of the masses of ferrous sulfate, zinc sulfate, copper sulfate, magnesium sulfate, borax, and ammonium molybdate to the mass of chitosan is 1:3-5.

[0024] Furthermore, the mixture B is added dropwise to the mixture A under stirring; the temperature of the stirring reaction is 30 - 40°C; the standing time is 20 - 24 h; when dissolving ferrous sulfate, zinc sulfate, copper sulfate, magnesium sulfate, borax, and ammonium molybdate in water, the ratio of the sum of the masses of ferrous sulfate, zinc sulfate, copper sulfate, magnesium sulfate, borax, and ammonium molybdate to the volume of water is 1 g: 90 - 100 mL; when dissolving chitosan in water, the mass - to - volume ratio of chitosan to water is 1 g: 8 - 10 mL; the rotation speed of the stirring is 150 - 200 rpm.

[0025] Two elements, iron and zinc, participate in the formation process of leaf chlorophyll, which can promote photosynthesis and increase the accumulation of organic substances inside the fruit; copper element can catalyze the formation of proteins and carbohydrates inside the fruit, improving the sugar content and taste of the fruit; magnesium is the main component of chlorophyll, which can promote photosynthesis and increase the accumulation rate of organic substances, thus promoting the swelling of the fruit; boron can not only promote the metabolism of calcium, but also promote the transfer of organic substances from the xylem to the phloem; molybdenum can promote the process of nitrogen metabolism in fruit trees, enhance the nitrogen absorption and utilization ability of plants, contribute to the growth and development of fruits, increase yield and quality. In addition, molybdenum can also promote the activation of enzyme systems in fruit trees, improving the taste and flavor of fruits; the use of chitosan can not only promote the growth of plants, but also significantly improve the quality of fruits, including increasing the soluble sugar content, VC content of fruits and maintaining the moisture of fruits. The chelate composed of iron, zinc, copper, magnesium, boron, molybdenum and chitosan can provide trace elements for guava in a long - term manner, effectively improving the yield and fruit quality of guava.

[0026] Furthermore, the preparation method of the stevia extract includes: crushing stevia, adding an ethanol solution and performing ultrasonic extraction for 4 - 6 h, filtering after the ultrasonic extraction ends, and concentrating and drying the filtrate to obtain the stevia extract.

[0027] Furthermore, the concentration of the ethanol solution is 65 - 75 vol%, and the mass - to - volume ratio of stevia to the ethanol solution is 1 g: 8 - 10 mL; the power of the ultrasonic extraction is 200 - 300 W.

[0028] The stevia extract is rich in various substances such as stevioside, amino acids, polypeptides, polysaccharides, organic acids, vitamins, etc. Among them, stevioside can be directly absorbed by guava without metabolic conversion, reducing the energy consumption of guava, increasing the accumulation of soluble sugars in fruits, and promoting the conversion of fruit acids into sugars in the pulp, thereby increasing the fruit sweetness. Amino acids, polypeptides, polysaccharides, organic acids, vitamins, etc. can stimulate the generation of fruit ester compounds, improving the fragrance.

[0029] As a plant growth regulator, 5-aminolevulinic acid not only participates in the regulation of plant growth and development, but also has physiological activities similar to plant hormones. It can accelerate the formation rate of chlorophyll synthase, increase the chlorophyll content, improve the photosynthetic efficiency, promote photosynthesis, and thus promote the growth and development of plants, and improve the yield and quality of guava. In addition, 5-aminolevulinic acid also has the effect of improving environmental stress tolerance, including low light tolerance, cold tolerance and salt tolerance, and improving fertilizer absorption capacity.

[0030] The second technical solution of the present invention: The preparation method of the above-mentioned liquid organic fertilizer for improving the quality of guava includes the following steps: Mix the animal manure treatment liquid, diatom and compound microbial inoculant, and perform aerobic fermentation treatment to obtain a fermentation liquid; add a trace element chelate, stevia extract, 5-aminolevulinic acid, stabilizer and surfactant to the fermentation liquid, and stir evenly to obtain the liquid organic fertilizer for improving the quality of guava.

[0031] Further, the temperature of the aerobic fermentation is 30-35°C; the time is 50-72h.

[0032] The third technical solution of the present invention: The application of the above-mentioned liquid organic fertilizer for improving the quality of guava in guava planting, the liquid organic fertilizer is applied once before the guava tree germinates and once after the flowers fall.

[0033] Further, the fertilization amount before germination is 6-10 kg / plant, and the fertilization amount after the flowers fall is 5-8 kg / plant.

[0034] Further, when the guava tree blooms and bears fruit multiple times a year, the liquid organic fertilizer is applied once after each flower falls.

[0035] The present invention discloses the following technical effects:

[0036] The present invention provides a liquid organic fertilizer for improving the quality of guava. The raw materials include animal manure treatment liquid, diatom, compound microbial inoculant, trace element chelate (chelates of iron, zinc, copper, magnesium, boron, molybdenum and chitosan), stevia extract, 5-aminolevulinic acid, stabilizer, surfactant. The above components act synergistically to provide rich and comprehensive nutrients for guava, and at the same time can improve the soil structure, inhibit the spread of pathogenic bacteria, improve the disease resistance of guava, improve the fertilizer absorption and utilization rate, increase the soluble sugar content and VC content of the fruit, and improve the yield and quality of guava.

[0037] The preparation method of the liquid organic fertilizer of the present invention is simple, and the main raw material is animal manure, with low cost, and is suitable for large-scale popularization and application. Specific embodiments

[0038] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be construed as a limitation on the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0041] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0042] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0043] The preparation method of the trace element chelate used in the following examples is as follows: Dissolve 4 g of ferrous sulfate, 6 g of zinc sulfate, 2 g of copper sulfate, 3 g of magnesium sulfate, 4 g of borax, and 3 g of ammonium molybdate in 2200 mL of water, adjust the pH to 7 to obtain a mixed solution A; dissolve 110 g of chitosan in 1100 mL of water to obtain a mixed solution B; drop the mixed solution B into the mixed solution A under stirring (150 rpm), continue stirring and reacting for 12 h after the dropping is completed, then let it stand for 24 h, centrifuge, and dry to obtain the trace element chelate.

[0044] The preparation method of the stevia extract used in the following examples is as follows: the sun-dried stevia (whole plant) is crushed to pass through a 60-mesh sieve, a 70 vol% ethanol solution is added at a solid-liquid ratio of 1 g:10 mL, and ultrasonic extraction is performed for 5 h at an ultrasonic power of 200 W. After the ultrasonic extraction is completed, the filtrate is filtered, and the filtrate is concentrated and dried to obtain the stevia extract.

[0045] The effective viable bacteria count of Bacillus amyloliquefaciens used in the following examples is 1×10 11 CFU / g, the effective number of viable bacteria of jelly-like Bacillus is 2×10 10 CFU / g, the effective number of viable bacteria of Bacillus subtilis is 2×10 10 CFU / g, the effective viable bacteria count of Trichoderma harzianum is 2×10 10 CFU / g; all are common commercially available products.

[0046] The stabilizer used in the following examples is citric acid, and the surfactant is sodium dodecyl sulfate.

[0047] The diatom used in the following examples is Navicula.

[0048] Example 1

[0049] A liquid organic fertilizer for improving the quality of guava, comprising the following raw materials by weight: 100 parts of animal manure treatment liquid, 3 parts of diatoms, 0.3 parts of composite microbial agents, 3 parts of trace element chelates, 2 parts of stevia extracts, 0.1 parts of 5-aminolevulinic acid, 3 parts of stabilizers and 3 parts of surfactants.

[0050] The preparation steps are as follows: animal manure treatment liquid, diatoms and composite microbial agents are mixed, and aerobic fermentation treatment is performed at a fermentation temperature of 30° C. and a fermentation time of 50 hours to obtain a fermentation liquid; trace element chelates, stevia extract, 5-aminolevulinic acid, a stabilizer and a surfactant are added to the fermentation liquid, and the mixture is stirred evenly to obtain a liquid organic fertilizer for improving the quality of guava.

[0051] The preparation method of the animal excrement and urine treatment liquid is as follows: heating fresh pig excrement and urine at 220° C. for 1 hour to obtain a treated material; and separating the treated material into solid and liquid to obtain the animal excrement and urine treatment liquid.

[0052] The composite microbial agent is prepared by mixing Bacillus amyloliquefaciens, Bacillus gelatinosa, Bacillus subtilis and Trichoderma harzianum in a mass ratio of 1:1:1:1.

[0053] Example 2

[0054] A liquid organic fertilizer for improving the quality of guava, comprising the following raw materials by weight: 110 parts of animal excrement treatment liquid, 4 parts of diatom, 0.4 parts of composite microbial agent, 4 parts of trace element chelate, 3 parts of stevia extract, 0.2 parts of 5-aminolevulinic acid, 4 parts of stabilizer and 4 parts of surfactant.

[0055] The preparation steps are as follows: animal manure treatment liquid, diatoms and composite microbial agents are mixed, and aerobic fermentation treatment is performed at a fermentation temperature of 33° C. and a fermentation time of 60 hours to obtain a fermentation liquid; trace element chelates, stevia extract, 5-aminolevulinic acid, a stabilizer and a surfactant are added to the fermentation liquid, and the mixture is stirred evenly to obtain a liquid organic fertilizer for improving the quality of guava.

[0056] The preparation method of the animal manure and urine treatment liquid is as follows: heating fresh pig manure and urine at 230° C. for 1.5 hours to obtain a treated material; and separating the treated material into solid and liquid to obtain the animal manure and urine treatment liquid.

[0057] The composite microbial agent is prepared by mixing Bacillus amyloliquefaciens, Bacillus gelatinosa, Bacillus subtilis and Trichoderma harzianum in a mass ratio of 1:1:2:2.

[0058] Example 3

[0059] A liquid organic fertilizer for improving the quality of guava, comprising the following raw materials by weight: 120 parts of animal manure treatment liquid, 5 parts of diatoms, 0.5 parts of composite microbial agents, 5 parts of trace element chelates, 4 parts of stevia extracts, 0.3 parts of 5-aminolevulinic acid, 5 parts of stabilizers and 5 parts of surfactants.

[0060] The preparation steps are as follows: animal manure treatment liquid, diatoms and composite microbial agents are mixed, and aerobic fermentation treatment is performed at a fermentation temperature of 35° C. and a fermentation time of 72 hours to obtain a fermentation liquid; trace element chelates, stevia extract, 5-aminolevulinic acid, a stabilizer and a surfactant are added to the fermentation liquid, and the mixture is stirred evenly to obtain a liquid organic fertilizer for improving the quality of guava.

[0061] The preparation method of the animal manure and urine treatment liquid is as follows: fresh pig manure and urine are heated at 250° C. for 2 hours to obtain a treated material; the treated material is separated into a solid and a liquid to obtain the animal manure and urine treatment liquid.

[0062] The composite microbial agent is prepared by mixing Bacillus amyloliquefaciens, Bacillus gelatinosa, Bacillus subtilis and Trichoderma harzianum in a mass ratio of 3:3:2:2.

[0063] Comparative Example 1

[0064] Same as Example 1, except that the use of diatoms is omitted.

[0065] Comparative Example 2

[0066] Same as Example 1, except that the use of stevia extract is omitted.

[0067] Comparative Example 3

[0068] Same as Example 1, except that the use of 5-aminolevulinic acid is omitted.

[0069] Comparative Example 4

[0070] Same as Example 1, except that the compound microbial inoculum is composed of Bacillus amyloliquefaciens, Bacillus mucilaginosus and Bacillus subtilis mixed in a mass ratio of 1:1:1.

[0071] Comparative Example 5

[0072] Same as Example 1, except that the preparation method of the trace element chelate is as follows: dissolve 4 g of ferrous sulfate, 6 g of zinc sulfate, 2 g of copper sulfate, 3 g of magnesium sulfate and 4 g of borax in 1900 mL of water, adjust the pH to 7 to obtain a mixed solution A; dissolve 95 g of chitosan in 950 mL of water to obtain a mixed solution B; drop the mixed solution B into the mixed solution A under stirring (150 rpm), continue stirring and reacting for 12 h after dropping, then stand for 24 h, centrifuge and dry to obtain the trace element chelate.

[0073] Test Example

[0074] Select an orchard of 4-year-old 'Pearl' guava with a row spacing of about 4×3 m in a certain place in Guangdong as the test field, randomly divide the experimental plots, and the area of each experimental plot is 100 m 2 , and the number of fruit trees in each experimental plot is the same. Conduct a fertilizer efficiency test on the liquid organic fertilizers prepared in Examples 1-3 and Comparative Examples 1-5. At the same time, set a control group (the control group applies retted and decomposed pig manure), and each test treatment has 3 replicates; before the 'Pearl' guava trees germinate, apply the fertilizer once by ditch application, 6 kg per plant; after the flowers fall, apply the fertilizer once again by ditch application, 5 kg per plant; other fertilization, watering and pest control management are carried out according to the conventional management method of 'Pearl' guava in this field (this is a conventional technical means in this field and is not the content protected by this invention patent, so it will not be elaborated here). Calculate the yield per mu after the first fruit maturity and measure the nutrient content in the fruits. The results are shown in Table 1.

[0075] Among them, the nutrient content mainly tests the soluble sugar content (anthrone method) and VC content (2,6-dichlorophenol indophenol titration method) of the fruits.

[0076] Table 1

[0077]

[0078] As can be seen from Table 1, when the liquid organic fertilizers prepared in Examples 1-3 of the present invention are used for guava cultivation, both the yield and quality of guavas are improved, which are not only better than those of each comparative example, but also better than those of the control group applying conventional organic fertilizers.

[0079] From the data comparison of Example 1 and Comparative Examples 1-5, it can be seen that the components in the liquid organic fertilizer of the present invention cooperate synergistically to achieve the best effect of improving the yield and quality of guavas. Omitting any one of the components will affect the final effect.

[0080] The above-described embodiments are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A liquid organic fertilizer for improving the quality of guava, characterized in that, By mass parts, the raw materials include: 100 - 120 parts of animal manure treatment liquid, 3 - 5 parts of diatomaceous earth, 0.3 - 0.5 parts of compound microbial inoculum, 3 - 5 parts of trace element chelate, 2 - 4 parts of stevia extract, 0.1 - 0.3 parts of 5 - aminolevulinic acid, 3 - 5 parts of stabilizer, and 3 - 5 parts of surfactant; the trace element chelate is a chelate of iron, zinc, copper, magnesium, boron, molybdenum and chitosan; The preparation method of the animal manure treatment liquid includes: heating the animal manure at 220 - 250 °C for 1 - 2 h to obtain a treated material; separating the solid and liquid of the treated material to obtain the animal manure treatment liquid; The compound microbial inoculum includes Bacillus amyloliquefaciens, Bacillus mucilaginosus, Bacillus subtilis and Trichoderma harzianum with a mass ratio of 1 - 3:1 - 3:1 - 2:1 - 2; The preparation method of the trace element chelate includes: dissolving ferrous sulfate, zinc sulfate, copper sulfate, magnesium sulfate, borax and ammonium molybdate in water, adjusting the pH to 7 - 8 to obtain a mixed solution A; dissolving chitosan in water to obtain a mixed solution B; dropping the mixed solution B into the mixed solution A, stirring and reacting for 10 - 12 h, then standing, centrifuging and drying to obtain the trace element chelate; The mass ratio of ferrous sulfate, zinc sulfate, copper sulfate, magnesium sulfate, borax and ammonium molybdate is 3 - 5:5 - 8:1 - 2:2 - 3:3 - 5:2 - 3; the mass ratio of the sum of the masses of ferrous sulfate, zinc sulfate, copper sulfate, magnesium sulfate, borax and ammonium molybdate to the mass of chitosan is 1:3 - 5; The preparation method of the stevia extract includes: crushing stevia, adding an ethanol solution and ultrasonically extracting for 4 - 6 h, filtering after the ultrasonic extraction ends, and taking the filtrate to be concentrated and dried to obtain the stevia extract; The preparation method of the liquid organic fertilizer for improving the quality of guava includes the following steps: mixing the animal manure treatment liquid, diatomaceous earth and compound microbial inoculum, and performing aerobic fermentation treatment to obtain a fermentation liquid; adding the trace element chelate, stevia extract, 5 - aminolevulinic acid, stabilizer and surfactant to the fermentation liquid and stirring evenly to obtain the liquid organic fertilizer for improving the quality of guava; The temperature of the aerobic fermentation is 30 - 35 °C; the time is 50 - 72 h; The animal manure is fresh pig manure urine.

2. The liquid organic fertilizer for improving the quality of guava according to claim 1, wherein The stabilizer includes one or more of citric acid, sodium gluconate, sodium carboxymethyl cellulose and sodium hexametaphosphate; the surfactant is sodium dodecyl sulfate.

3. Application of the liquid organic fertilizer for improving the quality of guava according to any one of claims 1-2 in guava cultivation, characterized in that, Apply the liquid organic fertilizer once each before the guava tree buds and after the flowers fall.

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