Fulvic acid type compound microbial organic fertilizer and preparation method thereof

Abstract

The invention relates to the technical field of research and development of organic fertilizers, and discloses a fulvic acid type compound microbial organic fertilizer and a preparation method thereof.The preparation method comprises the steps that on the basis of the nucleophilic addition reaction mechanism, diaminodibenzene-18-crown-6 ether and isocyano ethyl methacrylate serve as raw materials, and dimethacrylate ureido dibenzene-18-crown-6 ether is prepared; the dimethacrylate ureido crown ether calcium complex is prepared by recognizing and chelating a nutrient element calcium through crown ether; on the basis of a reaction mechanism of an aqueous solution polymerization method, fulvic acid is used as a raw material, acrylic acid and acrylamide are used as monomers, and a dimethacrylate urea-based crown ether calcium complex is used as a cross-linking agent, so that the fulvic acid-based water absorption and retention fertilizer is prepared. And uniformly mixing the fulvic acid-based water absorption and retention fertilizer, a chemical fertilizer and a compound microbial agent to prepare the fulvic acid type compound microbial organic fertilizer. The fertilizer has better water absorption and water retention performance, effectively overcomes the defect that calcium element is easy to generate antagonism with iron element and zinc element, and improves the utilization efficiency of the fertilizer.

Description

Technical Field

[0001] The present invention relates to the technical field of organic fertilizer research and development, and in particular to a fulvic acid-type composite microbial organic fertilizer and a preparation method thereof. Background Art

[0002] Compound microbial organic fertilizer is a living microbial product composed of microbial agents, inorganic nutrients and organic fertilizers. It can not only overcome the obstacles of continuous cropping in soil and enrich the soil microbial community, but also significantly promote crop growth, effectively prevent and control the occurrence of diseases, and increase crop yield and quality. It has broad application value and market prospects.

[0003] Research has found that biocontrol bacteria possess strong stress resistance, multiple functions, wide adaptability, and stable effects. Among them, Paenibacillus polymyxa is a highly stress-resistant biocontrol bacterium that is resistant to high temperatures, salinity, and humidity. It not only secretes antimicrobial substances such as lipids, proteins, and antibiotics, but also growth-promoting hormones. It has the functions of nitrogen fixation, phosphorus solubilization, and potassium solubilization, promoting the efficient use of nutrients by crops. Fulvic acid is a natural substance composed of organic macromolecular compounds. It promotes the formation of soil aggregate structure, improves soil biochemical properties, increases soil exchange capacity, enhances soil fertility, promotes crop growth, and enhances crop stress resistance, making it an ideal material for preparing organic fertilizers.

[0004] However, dryland farmland faces a mismatch between natural rainfall and the nutrient needs of crop growth. In existing technologies, the introduction of fertilizer water-retaining agents (SMAs) is an effective strategy. These agents, through their ability to absorb, retain, and retain water, coordinate soil moisture and nutrient supply, thereby improving crop water use efficiency and nutrient absorption capacity, ultimately increasing production and income.

[0005] In addition, the calcium element in the fertilizer is prone to antagonism with zinc and iron. Calcium will increase the pH value of the soil and convert iron from soluble divalent iron to difficult-to-absorb trivalent iron, resulting in reduced iron effectiveness. The high calcium environment will compete for the cation absorption sites of the plant roots, further hindering the absorption of iron. In addition, calcium and zinc compete for the absorption sites in the plant roots. High concentrations of calcium will inhibit the absorption of zinc, and there is also a competitive relationship between iron and zinc during the absorption process in the plant body. Summary of the Invention

[0006] The present invention provides a fulvic acid-based composite microbial organic fertilizer and a preparation method thereof. The fulvic acid-based water-absorbing and water-retaining fertilizer is prepared by an aqueous solution polymerization method using a newly developed dimethacrylate urea-type crown ether calcium complex as a cross-linking agent, fulvic acid as a raw material, acrylic acid and acrylamide as monomers. The fulvic acid-based water-absorbing and water-retaining fertilizer is then mixed with a chemical fertilizer and a composite microbial agent to prepare a fulvic acid-based composite microbial organic fertilizer.

[0007] To achieve the above object, the present invention adopts the following technical solution: a method for preparing fulvic acid-type composite microbial organic fertilizer, comprising the following steps:

[0008] Step 1: Based on the nucleophilic addition reaction mechanism, diaminodibenzo-18-crown-6 ether and isocyanoethyl methacrylate are used as raw materials to prepare dimethacrylate ureidodibenzo-18-crown-6 ether;

[0009] The crown ether in dimethacrylate urea-type crown ether calcium complex was prepared by recognizing and chelating the nutrient element calcium through the crown ether in dimethacrylate urea-type dibenzo-18-crown-6 ether.

[0010] Based on the reaction mechanism of aqueous solution polymerization, fulvic acid is used as raw material, acrylic acid and acrylamide are polymerization monomers, dimethacrylate urea-type crown ether calcium complex is used as cross-linking agent, and ammonium persulfate is used as initiator to prepare fulvic acid-based water-absorbing and water-retaining fertilizer.

[0011] Step 2: Using fulvic acid-based water-absorbing and water-retaining fertilizer, chemical fertilizer and compound microbial agent as raw materials, mixing them evenly to prepare fulvic acid-based compound microbial organic fertilizer.

[0012] Furthermore, the preparation method of diaminodibenzo-18-crown-6 ether is: based on the nitration reaction and reduction reaction mechanism, dibenzo-18-crown-6 ether, concentrated nitric acid and hydrazine hydrate are used as raw materials to prepare diaminodibenzo-18-crown-6 ether.

[0013] Furthermore, the fulvic acid-based composite microbial organic fertilizer comprises the following raw materials in parts by weight: 40-60 parts by weight of fulvic acid-based water-absorbing and water-retaining fertilizer, 16-24 parts by weight of inorganic fertilizer, and 25-35 parts by weight of composite microbial agent.

[0014] Furthermore, the inorganic fertilizer comprises the following raw materials in parts by weight: 2-4 parts by weight of urea, 5-7 parts by weight of sodium dihydrogen phosphate, 8-10 parts by weight of potassium sulfate, 0.5-1.6 parts by weight of magnesium sulfate, 0.2-0.8 parts by weight of ferric chloride and 0.3-0.6 parts by weight of zinc sulfate.

[0015] Furthermore, the composite microbial agent includes the following strains: Bacillus subtilis, Bacillus amyloliquefaciens, and Trichoderma harzianum.

[0016] The beneficial effects of the present invention are as follows:

[0017] Based on the nucleophilic addition reaction mechanism, dimethacrylate ureido dibenzo-18-crown-6 ether was prepared from diaminodibenzo-18-crown-6 ether and isocyanoethyl methacrylate.

[0018] Based on the recognition and chelation ability of the crown ether in dimethacrylate ureido dibenzo-18-crown-6 ether for the trace element calcium, a dimethacrylate ureido crown ether calcium complex was prepared.

[0019] Then, based on the reaction mechanism of aqueous solution polymerization, fulvic acid was used as the raw material, acrylic acid and acrylamide as the polymerization monomers, dimethacrylate urea-type crown ether calcium complex as the crosslinker, and ammonium persulfate as the initiator to prepare a fulvic acid-based water-absorbing and water-retaining fertilizer.

[0020] Finally, the fulvic acid-based water-absorbing and water-retaining fertilizer, chemical fertilizer and compound microbial agent are fully mixed to prepare the fulvic acid-based compound microbial organic fertilizer.

[0021] The experimental results show that the fulvic acid-based composite microbial organic fertilizer has good water absorption and water retention properties, can slow down the evaporation of soil moisture, and has a nutrient slow-release period of 75 days. The characteristic curve of the total nutrient slow-release performance is "S"-shaped, and it effectively overcomes the antagonistic effect between calcium and iron and zinc elements in the fertilizer. The organic components, inorganic nutrients and composite microorganisms work synergistically to significantly improve the fertilizer utilization efficiency and reduce the risk of nutrient loss. DETAILED DESCRIPTION

[0022] Example 1:

[0023] The preparation of fulvic acid-based water-absorbing and water-retaining fertilizer comprises the following steps:

[0024] (1) Preparation of dimethacrylate ureido dibenzo-18-crown-6 ether. The preparation mechanism is as follows: dimethacrylate ureido dibenzo-18-crown-6 ether is prepared by a nucleophilic addition reaction between the amino group in diaminodibenzo-18-crown-6 ether and the isocyanate group in isocyanoethyl methacrylate. The specific experimental steps are as follows: 2 g of dibenzo-18-crown-6 ether is placed in 40 mL of chloroform solution, mixed, 30 mL of acetic acid is added, and stirred at room temperature for 5 minutes. Subsequently, a mixed solution of concentrated nitric acid (1.4 mL) and acetic acid (4 mL) is added dropwise for 15 minutes. The mixture is stirred at 30°C for 1 hour, then heated under reflux for 3 hours, cooled to room temperature, filtered, and washed to obtain dinitrodibenzo-18-crown-6 ether.

[0025] 2 g of dinitrodibenzo-18-crown-6 ether was added to 50 mL of anhydrous ethanol, stirred magnetically and uniformly, purged with nitrogen, and after the air was expelled, 10% Pd / C catalyst (0.05 g) and 85% hydrazine hydrate (15 mL) were added, and the mixture was heated under reflux for 4 h, filtered, and the filtrate was collected and degassed with nitrogen. The filtrate was then placed in an ice-water bath to precipitate white crystals, which were then recrystallized with ethanol, washed with distilled water, filtered, and dried in vacuo at 60° C. for 5 h to obtain diaminodibenzo-18-crown-6 ether;

[0026] Under a nitrogen atmosphere, 3 g of diaminodibenzo-18-crown-6 ether was added to 50 mL of dimethyl sulfoxide and mechanically stirred until uniform. 2.4 g of isocyanoethyl methacrylate was then added. After the addition was complete, the temperature was raised to 50°C and stirred for 4 h. The mixture was then filtered, washed, and dried in a vacuum drying oven at 40°C for 6 h to prepare dimethacrylate ureidodibenzo-18-crown-6 ether.

[0027] The chemical structure of dimethacrylate ureido dibenzo-18-crown-6 ether is:

[0028]

[0029] (2) Preparation of dimethacrylate urea-type crown ether calcium complex, the specific experimental steps are as follows: 7 g of dimethacrylate urea-type dibenzo-18-crown-6 ether was ultrasonically dispersed in 500 mL of deionized water to form a uniform suspension, and then 2 g of calcium nitrate was added to the suspension, stirred for 4 h, and the solid material was centrifuged, washed, and vacuum-dried at 60° C. for 4 h to prepare dimethacrylate urea-type crown ether calcium complex;

[0030] (3) Preparation of fulvic acid-based water-absorbing and water-retaining fertilizer, the preparation mechanism of which is: based on the reaction mechanism of aqueous solution polymerization, fulvic acid is used as raw material, acrylic acid and acrylamide are polymerization monomers, dimethacrylate urea-type crown ether calcium complex is used as cross-linking agent, and ammonium persulfate is used as initiator to prepare fulvic acid-based water-absorbing and water-retaining fertilizer. The specific experimental steps are as follows: 3g of fulvic acid (purchased from Wuhan Jiyesheng Chemical Co., Ltd., CAS No. 479-66-3) is added to the reactor, and 18g of acrylic acid and 2g of acrylic acid are added. The mixture was stirred for 3 minutes, and then 0.3 g of dimethacrylate urea-type crown ether calcium complex was added. After stirring for 3 minutes, ammonium persulfate solution (1 g of ammonium persulfate was dissolved in 50 mL of distilled water) was added. The mixture was kept warm at 75 ° C for 4 hours. After the reaction was completed, the product was placed in a vacuum drying oven at 60 ° C for 10 hours to prepare a fulvic acid-based water-absorbing and water-retaining fertilizer.

[0031] Example 2:

[0032] The preparation of fulvic acid type compound microbial organic fertilizer comprises the following steps:

[0033] 50 parts by weight of fulvic acid-based water-absorbing and water-retaining fertilizer, 3 parts by weight of urea, 6 parts by weight of sodium dihydrogen phosphate, 9 parts by weight of potassium sulfate, 1 part by weight of magnesium sulfate, 0.5 parts by weight of ferric chloride and 0.5 parts by weight of zinc sulfate were mixed, and then 30 parts by weight of a composite microbial agent (purchased from Shanghai Banon Chemical Co., Ltd.) was added and mechanically stirred to obtain a fulvic acid-based composite microbial organic fertilizer.

[0034] Performance testing:

[0035] 1. According to NY / T 525-2021 "Organic Fertilizers", NY / T 305.1~305.4-1995 "Determination of Copper, Zinc, Iron and Manganese in Organic Fertilizers", and NY / T 4076-2022 "Determination of Calcium, Magnesium and Sulfur Content in Organic Fertilizers", the pH value (acidity and alkalinity), organic matter content, nitrogen content, phosphorus content, potassium content, iron content, zinc content, calcium content and magnesium content in fulvic acid type compound microbial organic fertilizer were determined. The test results were: pH value was 7.1, organic matter content was 49.92%, total nitrogen, phosphorus and potassium content was 8.36%, of which nitrogen content was 2.36%, phosphorus pentoxide was 3.55%, and potassium oxide was 2.45%; iron content was 1.7g / kg, zinc content was 2.1g / kg, magnesium oxide content was 0.336%, and calcium oxide content was 0.0765%.

[0036] 2. Water absorption rate test: Accurately weigh 1g of fulvic acid type compound microbial organic fertilizer, put it into a 0.15mm nylon mesh bag, seal it and place it in a beaker filled with 250mL distilled water, soak it at room temperature for a period of time (about 3h), take out the mesh bag, hang it until no water drips and it reaches a constant weight, weigh it, and calculate the water absorption rate W (g / g) of the fertilizer, W=T / T0-1, where T and T0 represent the mass of the fertilizer after full water absorption and swelling and the mass of the dry fertilizer, respectively. The test result is: the water absorption rate of fulvic acid type compound microbial organic fertilizer is 21.5g / g.

[0037] 3. Water retention performance test: accurately weigh 200g of dry soil that has passed through a 0.2mm sieve, mix it evenly with 6g of fulvic acid-type compound microbial organic fertilizer, and then put it into a 500mL beaker. Then add a certain amount of tap water to the beaker (based on the fact that there is no water on the soil surface and a small amount of water seeps out between the inner wall of the beaker and the soil when the beaker is tilted). Place it in a 35°C oven. Weigh the total mass of the beaker every 20h. At the same time, do a blank test (without adding fulvic acid-type compound microbial organic fertilizer, and other conditions are the same as above). Record the data and calculate the soil water retention rate P, P = Mi-M1 / M0-M1×100%, where M0 is the total mass (g) of the fertilizer and soil when fully absorbed and saturated with water; M1 is the total mass (g) of the dry soil and dry fertilizer; Mi is the total mass (g) of the soil and fertilizer when weighed at the ith hour;

[0038] The above test results are shown in Table 1 below;

[0039] Table 1 Water retention performance test results of fulvic acid type compound microbial organic fertilizer

[0040]

[0041]

[0042] The data in Table 1 indicate that the fulvic acid-based composite microbial organic fertilizer prepared by the present invention has good water retention capacity after application to the soil, slowing down soil moisture evaporation. During rainy days, the fertilizer stores excess water. During droughts, it slowly releases this stored water for absorption and utilization by plant roots, thereby reducing irrigation frequency and improving water utilization efficiency.

[0043] 4. At room temperature, seal the bottom of a 5cm diameter glass soil column tube with a 100-mesh sieve, place 25g of sand on the sieve, first fill it with 200g of air-dried soil without fertilizer, and compact it; then fill it with a mixture of 200g of soil and 10g of fulvic acid-type compound microbial organic fertilizer at the same compaction; then fill it with 200g of air-dried soil without fertilizer, and compact it; finally fill it with 25g of sand, and connect the bottom of the tube to a frosted three-necked bottle. Add 50mL of deionized water gradually until the soil moisture in the soil column is close to saturation. After 24 hours of incubation, the soil was rinsed with 100 mL of water to simulate the rainy conditions in the natural environment. Thereafter, the soil was leached once on the 3rd, 7th, 10th, 14th, 21st, 28th, 35th, 60th and 75th days, and the nitrogen, phosphorus and potassium nutrients in the leaching solution were determined. The results of the soil column leaching experiment showed that the fulvic acid type compound microbial organic fertilizer had a 75-day nutrient slow-release period, and the total nutrient slow-release performance characteristic curve was "S"-shaped. The fertilizer could release nutrients stably and persistently in the soil, significantly improving the nutrient supply efficiency and utilization rate.

[0044] In order to improve the antagonistic effect of calcium and iron / zinc, the present invention can also adopt the following implementation scheme:

[0045] Implementation Plan 1:

[0046] On the basis of Example 1, a fulvic acid-based water-absorbing and water-retaining fertilizer A is prepared, comprising the following steps:

[0047] (1) Preparation of dimethacrylate ureido-type crown ether iron complex, the specific experimental steps are as follows: 7g dimethacrylate ureido dibenzo-18-crown-6 ether was ultrasonically dispersed in 500mL deionized water to form a uniform suspension, and then 2g ferric chloride was added to the suspension, stirred for 4h, and the solid material was centrifuged, washed, and vacuum dried at 60°C for 4h to prepare dimethacrylate ureido-type crown ether iron complex;

[0048] (2) Preparation of a dimethacrylate ureido-type crown ether zinc complex, the specific experimental steps are as follows: 7 g of dimethacrylate ureido-dibenzo-18-crown-6 ether was ultrasonically dispersed in 500 mL of deionized water to form a uniform suspension, and then 2 g of zinc sulfate was added to the suspension, stirred for 4 h, and the solid material was centrifuged, washed, and vacuum-dried at 60° C. for 4 h to prepare a dimethacrylate ureido-type crown ether zinc complex;

[0049] (3) Preparation of fulvic acid-based water-absorbing and water-retaining fertilizer A, the preparation mechanism of which is: based on the reaction mechanism of aqueous solution polymerization, fulvic acid is used as raw material, acrylic acid and acrylamide are polymerization monomers, dimethacrylate urea-type crown ether iron complex and dimethacrylate urea-type crown ether zinc complex are cross-linking agents, and ammonium persulfate is used as initiator to prepare fulvic acid-based water-absorbing and water-retaining fertilizer A. The specific experimental steps are as follows: 3g of fulvic acid (purchased from Wuhan Jiyesheng Chemical Co., Ltd., CAS No. 479-66-3) is added to the reactor, and 18g of acrylic acid and 2g of acrylamide are added. amine, mix well, then place the reactor in an ice water bath and add 40% by mass sodium hydroxide solution while stirring for neutralization (neutralization degree is 90%), then add 0.15g of dimethacrylate urea-type crown ether iron complex and 0.15g of dimethacrylate urea-type crown ether zinc complex, stir for 3 minutes, add ammonium persulfate solution (1g of ammonium persulfate is dissolved in 50mL of distilled water), keep warm at 75℃ for 4h, and after completion of the reaction, place the product in a vacuum drying oven at 60℃ and dry it for 10h to prepare fulvic acid-based water-absorbing and water-retaining fertilizer A.

[0050] On the basis of Example 2, a fulvic acid-type composite microbial organic fertilizer A is prepared, comprising the following steps:

[0051] Mix 50 parts by weight of fulvic acid-based water-absorbing and water-retaining fertilizer A, 3 parts by weight of urea, 6 parts by weight of sodium dihydrogen phosphate, 9 parts by weight of potassium sulfate, 1 part by weight of magnesium sulfate, and 1 part by weight of calcium nitrate, then add 30 parts by weight of composite microbial agent (purchased from Shanghai Banon Chemical Co., Ltd.), and stir mechanically to obtain fulvic acid-based composite microbial organic fertilizer A.

[0052] Implementation Plan 2:

[0053] On the basis of Example 1, a fulvic acid-based water-absorbing and water-retaining fertilizer B is prepared, comprising the following steps:

[0054] (1) Preparation of dimethacrylate urea-type crown ether calcium complex, the specific experimental steps are as follows: 7 g of dimethacrylate urea-type dibenzo-18-crown-6 ether was ultrasonically dispersed in 500 mL of deionized water to form a uniform suspension, and then 2 g of calcium nitrate was added to the suspension, stirred for 4 h, and the solid material was centrifuged, washed, and vacuum-dried at 60° C. for 4 h to prepare dimethacrylate urea-type crown ether calcium complex;

[0055] (2) Preparation of dimethacrylate ureido-type crown ether iron complex, the specific experimental steps are as follows: 7g dimethacrylate ureido dibenzo-18-crown-6 ether was ultrasonically dispersed in 500mL deionized water to form a uniform suspension, and then 2g ferric chloride was added to the suspension, stirred for 4h, and the solid material was centrifuged, washed, and vacuum dried at 60°C for 4h to prepare dimethacrylate ureido-type crown ether iron complex;

[0056] (3) Preparation of a dimethacrylate ureido-type crown ether zinc complex, the specific experimental steps are as follows: 7 g of dimethacrylate ureido-dibenzo-18-crown-6 ether was ultrasonically dispersed in 500 mL of deionized water to form a uniform suspension, and then 2 g of zinc sulfate was added to the suspension, stirred for 4 h, and the solid material was centrifuged, washed, and vacuum-dried at 60° C. for 4 h to prepare a dimethacrylate ureido-type crown ether zinc complex;

[0057] (4) Preparation of fulvic acid-based water-absorbing and water-retaining fertilizer B, the preparation mechanism of which is as follows: based on the reaction mechanism of aqueous solution polymerization, fulvic acid is used as raw material, acrylic acid and acrylamide are polymerization monomers, dimethacrylate urea-type crown ether calcium complex, dimethacrylate urea-type crown ether iron complex and dimethacrylate urea-type crown ether zinc complex are cross-linking agents, and ammonium persulfate is used as initiator to prepare fulvic acid-based water-absorbing and water-retaining fertilizer B. The specific experimental steps are as follows: 3g of fulvic acid (purchased from Wuhan Jiyesheng Chemical Co., Ltd., CAS No. 479-66-3) is added to the reactor, 18g of acrylic acid and 2g of acrylamide are added , mix well, then place the reactor in an ice-water bath and add 40% by mass sodium hydroxide solution while stirring for neutralization (neutralization degree is 90%), then add 0.1g dimethacrylate urea-type crown ether calcium complex, 0.1g dimethacrylate urea-type crown ether iron complex and 0.1g dimethacrylate urea-type crown ether zinc complex, stir for 3min, add ammonium persulfate solution (1g ammonium persulfate is dissolved in 50mL distilled water), keep warm at 75℃ for 4h, after completion of the reaction, place the product in a 60℃ vacuum drying oven and dry for 10h to prepare fulvic acid-based water-absorbing and water-retaining fertilizer B.

[0058] On the basis of Example 2, a fulvic acid-type composite microbial organic fertilizer B is prepared, comprising the following steps:

[0059] Mix 50 parts by weight of fulvic acid-based water-absorbing and water-retaining fertilizer B, 3 parts by weight of urea, 6 parts by weight of sodium dihydrogen phosphate, 9 parts by weight of potassium sulfate, and 1 part by weight of magnesium sulfate, then add 31 parts by weight of composite microbial agent (purchased from Shanghai Banon Chemical Co., Ltd.), and stir mechanically to prepare fulvic acid-based composite microbial organic fertilizer B.

Claims

1. A method for preparing fulvic acid type composite microbial organic fertilizer, characterized in that: The following steps are involved: Step 1: Based on the nucleophilic addition reaction mechanism, diaminodibenzo-18-crown-6 ether and isocyanoethyl methacrylate are used as raw materials to prepare dimethacrylate ureidodibenzo-18-crown-6 ether; The crown ether in dimethacrylate urea-type crown ether calcium complex was prepared by recognizing and chelating the nutrient element calcium through the crown ether in dimethacrylate urea-type dibenzo-18-crown-6 ether. Based on the reaction mechanism of aqueous solution polymerization, fulvic acid is used as raw material, acrylic acid and acrylamide are polymerization monomers, dimethacrylate urea-type crown ether calcium complex is used as cross-linking agent, and ammonium persulfate is used as initiator to prepare fulvic acid-based water-absorbing and water-retaining fertilizer. Step 2: Using fulvic acid-based water-absorbing and water-retaining fertilizer, chemical fertilizer and compound microbial agent as raw materials, mixing them evenly to prepare fulvic acid-based compound microbial organic fertilizer.

2. The method for preparing a fulvic acid type composite microbial organic fertilizer according to claim 1, characterized in that: The preparation method of diaminodibenzo-18-crown-6 ether comprises the following steps: based on the nitration reaction and reduction reaction mechanism, dibenzo-18-crown-6 ether, concentrated nitric acid and hydrazine hydrate are used as raw materials to prepare diaminodibenzo-18-crown-6 ether.

3. The method for preparing a fulvic acid type composite microbial organic fertilizer according to claim 1, characterized in that: The chemical structural formula of the dimethacrylate ureido dibenzo-18-crown-6 ether is:

4. A fulvic acid-type composite microbial organic fertilizer prepared according to the method according to any one of claims 1 to 3, characterized in that: The fulvic acid-based composite microbial organic fertilizer comprises the following raw materials in parts by weight: 40-60 parts by weight of fulvic acid-based water-absorbing and water-retaining fertilizer, 16-24 parts by weight of inorganic fertilizer, and 25-35 parts by weight of composite microbial agent.

5. The fulvic acid type composite microbial organic fertilizer according to claim 4, characterized in that: The inorganic fertilizer comprises the following raw materials in parts by weight: 2-4 parts by weight of urea, 5-7 parts by weight of sodium dihydrogen phosphate, 8-10 parts by weight of potassium sulfate, 0.5-1.6 parts by weight of magnesium sulfate, 0.2-0.8 parts by weight of ferric chloride and 0.3-0.6 parts by weight of zinc sulfate.

6. The fulvic acid type composite microbial organic fertilizer according to claim 4, characterized in that: The composite microbial agent comprises the following strains: Bacillus subtilis, Bacillus amyloliquefaciens, and Trichoderma harzianum.

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