Microbial suspended fertilizer based on seaweed nano-zinc oxide and preparation method and application thereof

Abstract

This application relates to the field of microbial fertilizer technology, specifically to a microbial suspension fertilizer based on seaweed nano-zinc oxide, its preparation method, and its application. First, *Sargassum fusiforme* (seaweed) is washed, dried, and ground into powder, then mixed with water to form an algae slurry. Alginic acid lyase is added to the *Sargassum fusiforme* slurry to obtain an enzymatic hydrolysate. Then, the *Sargassum fusiforme* enzymatic hydrolysate is mixed with zinc acetate under heating conditions. The reaction product is centrifuged, washed, and calcined to obtain seaweed nano-zinc oxide particles. Finally, the nano-zinc oxide particles and adjuvants such as compound microbial agents are formulated into a microbial suspension fertilizer. By utilizing the reaction between *Sargassum fusiforme* enzymatic hydrolysate and zinc acetate, seaweed nano-zinc oxide with more uniform particle size can be obtained, and its photocatalytic and antibacterial properties are improved. Furthermore, the microbial suspension fertilizer prepared based on this seaweed nano-zinc oxide can promote crop growth, improve crop quality, and fortify grain zinc nutrition, making it suitable for various agricultural production applications.

Description

Technical Field

[0001] This application relates to the field of microbial fertilizer technology, specifically to a microbial suspension fertilizer based on seaweed nano zinc oxide, its preparation method, and its application. Background Technology

[0002] Zinc is an essential micronutrient for plant growth and development, playing a crucial role in various physiological processes such as photosynthesis, enzyme activity regulation, protein synthesis, and stress resistance formation. However, in current agricultural production, zinc deficiency in crops remains widespread due to low available zinc content in soil and limited migration and transformation efficiency of zinc in the soil-plant system. Existing agricultural zinc sources are mainly inorganic zinc compounds such as zinc sulfate or ordinary zinc oxide, which generally suffer from problems such as easy fixation and loss in the soil, low plant absorption efficiency, and significant influence of environmental conditions on application effectiveness, failing to meet the demands of modern agriculture for efficient and precise zinc nutrient supply. To improve the absorption and utilization efficiency of zinc in plants, nano-zinc oxide, with its small particle size, large specific surface area, and high bioactivity, is considered a promising new zinc source material. Nano-zinc oxide can be absorbed more efficiently by plants through foliar or rhizosphere pathways and, to some extent, also possesses biological effects such as promoting growth and inhibiting pathogenic microorganisms. Therefore, it can be applied in the agricultural field by formulating suspension fertilizers based on nano-zinc oxide. However, the actual application effect and environmental compatibility of nano zinc oxide suspension fertilizer in agriculture largely depend on the preparation method of nano zinc oxide and the structure and surface properties of the resulting material.

[0003] Currently, the preparation of nano-zinc oxide mainly relies on physical or chemical methods. These methods are typically energy-intensive and often require the use of strong alkalis or other chemical reagents during synthesis, potentially generating byproducts and posing certain environmental risks. While biological methods such as plant or algal extraction reduce chemical pollution to some extent, their reaction systems involve complex active components and limited controllability. The resulting nano-zinc oxide materials often suffer from uneven particle size distribution, insufficient stability, and inconsistency in function, thus affecting their practical effectiveness in agricultural applications.

[0004] Therefore, there is an urgent need to develop a method for preparing nano-zinc oxide suspension fertilizer that can achieve controllable synthesis of nano-zinc oxide under mild conditions and has environmental friendliness, structural stability and good agricultural application performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the primary objective of this application is to provide a microbial suspension fertilizer based on seaweed-derived nano-zinc oxide, its preparation method, and its application. This method uses seaweed as a functional medium to achieve the controllable synthesis of nano-zinc oxide under mild conditions, thereby obtaining nano-zinc oxide materials with good dispersibility, biocompatibility, and agricultural application potential. This addresses the problems of high energy consumption, insufficient environmental friendliness, and difficulty in controlling the material structure and properties of existing nano-zinc oxide preparation methods.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] In a first aspect, this application provides a microbial suspension fertilizer based on seaweed nano zinc oxide, comprising the following components by weight: 50-70 parts seaweed nano zinc oxide, 3-5 parts compound microbial agent, 4-6 parts penetrant, 1-3 parts wetting agent, 0.5-1.5 parts emulsifier, 1-3 parts defoamer, 0.5-1.5 parts dispersant, 1-3 parts antifreeze, 2-4 parts settling agent, 12-16 parts suspending agent, and 25-35 parts deionized water.

[0008] Preferably, the compound microbial agent is *Paenibacillus mucilaginosus*, *Azotobacter chroococcum*, or *Bacillus subtilis*. The following are preparation methods: The first method involves mixing subtilis in a mass ratio of 2:2:1; the second method involves mixing alkylphenol polyoxyethylene ether, organosilicon, and azone in a mass ratio of 2:1:1; the third method involves mixing o-aminobenzoyl hydrazine and 3-propanedithiol in a mass ratio of 1:1; the fourth method involves mixing Span S-40 and fatty alcohol polyoxyethylene ether in a mass ratio of 1:3; the fifth method involves mixing glycerol polyoxypropylene ether defoamer and organosilicon defoamer in a mass ratio of 1:1; the sixth method involves ethyl acetate; the seventh method involves mixing polyethylene glycol, glycerol, and urea in a mass ratio of 2:3:1; the eighth method involves mixing nano-sized silica, light calcium carbonate, and magnesium aluminum silicate in a mass ratio of 1:1:2; and the ninth method involves mixing xanthan gum and activated clay in a mass ratio of 3:5.

[0009] The compound microbial agents added to the suspension fertilizer include: Bacillus mucilaginosus (purchased from Shandong Yihao Biotechnology Co., Ltd.), which efficiently decomposes fixed phosphorus and potassium elements in the soil, converting insoluble nutrients into readily absorbable nutrients for crops; Azotobacter chrysophagus (purchased from Shandong Kuifeng Biotechnology Co., Ltd.), which fixes free nitrogen from the air, supplementing soil nitrogen nutrition; and Bacillus subtilis (purchased from Shaanxi Guangren Biotechnology Co., Ltd., model GR-ZHW), which improves the rhizosphere microecological environment of crops, inhibits the reproduction of harmful pathogens, stimulates root growth, and enhances nutrient absorption efficiency. The penetrant significantly reduces the surface tension of the solution, quickly penetrating the cuticle of crop leaves and the epidermal cells of roots, accelerating the penetration and absorption of seaweed nano-zinc oxide and nutrients, preventing nutrients from remaining on the crop surface and causing loss, and improving fertilizer utilization efficiency. Wetting agents effectively reduce the interfacial tension between solid and liquid, ensuring uniform wetting and full dispersion of seaweed nano-zinc oxide particles in the aqueous system, preventing particle agglomeration and clumping. They also enhance the spreading and adhesion of the microbial suspension fertilizer to crop leaves and roots, reducing droplet roll-off losses. Emulsifiers stabilize the interfacial structure between various organic adjuvants and inorganic particles, preventing stratification of the oil and aqueous phases and maintaining a uniform and stable suspension system. Defoamers specifically eliminate foam generated during stirring and mixing, preventing uneven mixing, insufficient particle dispersion, and overflow during filling. Dispersants further break down van der Waals forces between seaweed nano-zinc oxide particles, preventing particle sedimentation and agglomeration, and ensuring long-term uniform dispersion in the system. Antifreeze agents lower the freezing point of the microbial suspension fertilizer system, preventing freezing and particle agglomeration / demulsification at low temperatures. Flocculants moderately adjust the system density, working with suspending agents to form a stable suspension network, preventing light components from floating and heavy components from settling rapidly, reducing stratification, and ensuring uniform fertilizer composition after long-term storage. Suspension agents can improve the suspension stability and flowability of the system, ensuring that the particles remain uniformly suspended for a long time without affecting application and dilution due to excessive viscosity.

[0010] Secondly, this application provides a method for preparing a microbial suspension fertilizer based on seaweed nano-zinc oxide, comprising the following steps:

[0011] Wash and dry Sargassum fusiforme, grind it into powder, and add water to make Sargassum fusiforme algal slurry; add alginate lyase to the Sargassum fusiforme algal slurry for enzymatic hydrolysis, centrifuge, take the supernatant and filter to obtain Sargassum fusiforme enzymatic hydrolysate;

[0012] The enzymatic hydrolysate of Sargassum fusiforme was mixed with a zinc salt solution under heating and alkaline conditions. The reaction product was centrifuged, washed, and calcined to obtain seaweed-mediated synthesized seaweed nano-zinc oxide particles.

[0013] Microbial suspension fertilizer is prepared by mixing seaweed nano zinc oxide particles, compound microbial agents, penetrants, wetting agents, emulsifiers, defoamers, dispersants, antifreeze agents, flocculants, suspending agents, and deionized water in a certain proportion.

[0014] The average particle size of the obtained seaweed nano zinc oxide is 30~200nm, preferably 40~100nm.

[0015] Enzymatic hydrolysate obtained from seaweed through enzymatic hydrolysis is used as the reaction medium and regulating component, reacting with a zinc salt solution under heating and stirring conditions. The hydroxyl and carboxyl functional groups on the polysaccharides and oligosaccharide fragments contained in the seaweed hydrolysate can complex with zinc ions, thereby regulating the nucleation and growth process of the zinc-based precursor. Under alkaline conditions, zinc ions further hydrolyze to generate zinc hydroxide or basic zinc salt precursors. After separation, washing, and calcination, the precursors undergo dehydration and phase transformation, ultimately forming nano-zinc oxide particles. The preparation process can be completed under relatively mild conditions, and the particle size distribution and dispersion state of the obtained nano-zinc oxide can be controlled by adjusting the enzymatic hydrolysis conditions, zinc salt concentration, system pH, and calcination parameters.

[0016] Preferably, the particle size of the Sargassum fusiforme powder is 60-100 mesh, and the mass-to-volume ratio of Sargassum fusiforme powder to water in the Sargassum fusiforme slurry is (2-4):100; the alginate lyase is obtained by fermentation of Microbulbifer sp. SH-1 strain, whose preservation number is CGMCC No.16906.

[0017] The specific preparation method of alginate lyase is as follows: Microbulbifer sp. SH-1 bacterial culture is inoculated into a fermentation medium, and fermented at 28℃ with shaking for 12 hours to obtain the fermentation broth. Then, the supernatant is collected by centrifugation, purified, and filtered to obtain the alginate lyase. The fermentation medium has the following formula: sodium alginate 10 g / L, ammonium sulfate 5 g / L, magnesium sulfate 0.2 g / L, potassium dihydrogen phosphate 1 g / L, ferrous sulfate 0.02 g / L, sodium chloride 5 g / L, and pH 7.5–8.5.

[0018] Preferably, the specific conditions for enzymatic hydrolysis are as follows: the volume ratio of alginate lyase to Sargassum fusiforme slurry is (1~5):100; the hydrolysis temperature is 35~45℃; the pH is 8.0~9.0; and the hydrolysis time is 18~24h. The specific conditions for obtaining Sargassum fusiforme enzymatic hydrolysate by centrifugation and filtration of the supernatant are as follows: the centrifugation rate is 8000~9000rpm; the centrifugation time is 5~10min. The Sargassum fusiforme enzymatic hydrolysate is stored at 4℃.

[0019] Preferably, the zinc salt solution is a zinc acetate solution with a concentration of 0.1~0.2 mol / L; the volume ratio of the Sargassum fusiforme enzymatic hydrolysate to the zinc acetate solution is 1:(5~10); the mixing reaction conditions are: temperature 55~65℃, pH value 9.0~10.0, and magnetic stirring for 3~4 hours.

[0020] Preferably, the centrifugation conditions are: centrifugation at 9000~10000 rpm for 10~15 min; washing is performed 3 times with anhydrous ethanol; and calcination is performed at 400~500℃ for 1.5~2.5 h.

[0021] Preferably, the specific steps for preparing the microbial suspension fertilizer are as follows:

[0022] Seaweed nano zinc oxide and deionized water were placed in a reaction vessel and kept at a constant temperature of 35-40℃, stirred at a speed of 150-200 rpm for 25-30 minutes. Then, compound microbial agent, penetrant, wetting agent, emulsifier, defoamer, dispersant, antifreeze and flocculant were added in sequence, and stirring was continued for 50-60 minutes. Then, the suspending agent was added for the first time and stirred until the average particle size in the solution was less than 500 μm. Then, the suspending agent was added for the second time and stirred at 120-150 rpm for 50-60 minutes to obtain microbial suspension fertilizer.

[0023] Preferably, the mass ratio of the first added suspending agent to the second added suspending agent is 1:1.

[0024] Thirdly, this application relates to the application of a microbial suspension fertilizer based on seaweed nano zinc oxide, wherein the microbial suspension fertilizer is absorbed by crops through foliar spraying or rhizosphere application.

[0025] Specifically, applying low concentrations (0-100 mg / L) of seaweed-based nano-zinc oxide suspension fertilizer to Chinese cabbage can significantly increase biomass, improve root architecture, enhance photosynthetic capacity, increase the activity of the antioxidant system, and increase the content of soluble sugars and vitamin C. This is because zinc (Zn) is a key factor in the synthesis of auxin in plants; appropriate Zn supplementation can promote the synthesis of endogenous auxin, thereby improving root architecture. Simultaneously, as an important component of chloroplast structure and carbonic anhydrase, it can ensure the integrity of chloroplasts and enhance photosynthetic capacity. Similarly, Zn plays an important role in enhancing the activity of the antioxidant system and in the synthesis of soluble sugars and vitamin C. Therefore, seaweed-based nano-zinc oxide suspension fertilizer can achieve the above effects. However, since Zn is a heavy metal, excessive application can have a certain toxic effect on plants, inhibiting their growth.

[0026] This application has the following beneficial effects:

[0027] The formation of nano-zinc oxide is mediated by seaweed enzymatic hydrolysate, reducing the use of strong alkalis and harmful chemical reagents. Simultaneously, the active components in the seaweed enzymatic hydrolysate can regulate the nucleation and growth process of nano-zinc oxide, facilitating the acquisition of nano-zinc oxide with uniform particle size and good dispersibility. By compounding nano-zinc oxide with various adjuvants, seaweed nano-zinc oxide suspension fertilizer can be obtained, providing nutrient supply, inhibiting bacteria and promoting growth, and improving soil. Specifically, the combination of compound microbial agents and nano-zinc oxide utilizes the properties of microbial agents to improve the soil environment, supplement nitrogen, and synergize with zinc-promoted auxin synthesis to enhance crop root growth. Furthermore, the organic acids produced by microbial metabolism can promote the dissolution of seaweed nano-zinc oxide, improving zinc fertilizer utilization. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A flowchart illustrating a method for preparing seaweed nano-zinc oxide provided in this application.

[0030] Figure 2 X-ray diffraction patterns of seaweed nano-zinc oxide prepared in Example 1, Comparative Example 1 and Comparative Example 2, (a) overall pattern, (b) magnified view of the main diffraction peaks.

[0031] Figure 3 Fourier transform infrared spectra of seaweed nano zinc oxide and some intermediate products prepared in Examples 1, Comparative Examples 1 and 2, (a) spectra of nano zinc oxide and intermediate products in Comparative Examples 1 and 2, (b) spectra of nano zinc oxide and intermediate products in Comparative Examples 1 and 1.

[0032] Figure 4 The image shows the scanning electron microscope (SEM) morphology of the zinc oxide nanoparticles prepared in Example 1.

[0033] Figure 5 Wheat yield and grain zinc content in 2024-2025 under different fertilizer treatments: (a) wheat yield in 2024, (b) wheat yield in 2025, (c) wheat grain zinc content in 2024, and (d) wheat grain zinc content in 2025.

[0034] Figure 6 The cumulative zinc content in different parts of the body during different treatments with seaweed nano zinc oxide fertilizer.

[0035] Figure 7The effects of different seaweed nano zinc oxide fertilizer treatments on the amino acid content of grains. Detailed Implementation

[0036] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0037] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0038] The preparation method of the alginate lyase used in this application embodiment is as follows: Microbulbifer sp. SH-1 bacterial culture is inoculated into a fermentation medium, and fermented at 28°C with shaking for 12 hours to obtain a fermentation broth. Then, the supernatant is collected by centrifugation, purified, and filtered to obtain the alginate lyase. The fermentation medium has the following formula: sodium alginate 10 g / L, ammonium sulfate 5 g / L, magnesium sulfate 0.2 g / L, potassium dihydrogen phosphate 1 g / L, ferrous sulfate 0.02 g / L, sodium chloride 5 g / L, and pH 7.5–8.5.

[0039] The following specific embodiments further illustrate this point:

[0040] Example 1

[0041] like Figure 1 As shown in the figure, this embodiment provides a method for preparing seaweed nano-zinc oxide, including the following steps:

[0042] 1. Weigh 2.0g of Sargassum powder and place it in an Erlenmeyer flask. Add 100mL of water to disperse it and adjust the pH to 8.5. Add 5mL of alginate lyase and enzymatically hydrolyze it at a constant temperature of 40℃ for 24h. Centrifuge the hydrolysate at 8000rpm for 10min, take the supernatant and filter it to obtain Sargassum hydrolysate. Store it at 4℃ for later use.

[0043] 2. The enzymatic hydrolysate of Sargassum fusiforme was mixed with 0.1 mol / L zinc acetate solution at a volume ratio of 1:5 and reacted for 3 h under constant temperature magnetic stirring in a 60℃ water bath. After cooling, 0.1 mol / L NaOH solution was added dropwise to adjust the pH of the system to 10, thus obtaining a nano zinc oxide suspension.

[0044] 3. Centrifuge the nano zinc oxide suspension at 10,000 rpm for 10 min, discard the supernatant and take the precipitate, wash it three times with anhydrous ethanol and dry it, calcine it at 450℃ for 2 h and grind it to obtain the seaweed nano zinc oxide (SFEE-ZnO) prepared by the method described in Example 1.

[0045] Example 2

[0046] This embodiment provides a method for preparing seaweed nano-zinc oxide, including the following steps:

[0047] 1. Weigh 3.0g of Sargassum powder and place it in an Erlenmeyer flask. Add 100mL of water to disperse it and adjust the pH to 8.0. Add 3mL of alginate lyase and enzymatically hydrolyze it at a constant temperature of 35℃ for 20h. Centrifuge the hydrolysate at 8500rpm for 8min, take the supernatant and filter it to obtain Sargassum hydrolysate. Store it at 4℃ for later use.

[0048] 2. The enzymatic hydrolysate of Sargassum fusiforme was mixed with 0.15 mol / L zinc acetate solution at a volume ratio of 1:7.5 and reacted for 3.5 h under constant temperature magnetic stirring in a water bath at 55 ℃. After cooling, 0.1 mol / L NaOH solution was added dropwise to adjust the pH of the system to 9.5 to obtain a nano zinc oxide suspension.

[0049] 3. Centrifuge the nano zinc oxide suspension at 9500 rpm for 12 min, discard the supernatant and take the precipitate, wash it 3 times with anhydrous ethanol and dry it, calcine it at 400℃ for 1.5 h and grind it to obtain the seaweed nano zinc oxide prepared by the method described in Example 2.

[0050] Example 3

[0051] This embodiment provides a method for preparing seaweed nano-zinc oxide, including the following steps:

[0052] 1. Weigh 4.0g of Sargassum powder and place it in an Erlenmeyer flask. Add 100mL of water to disperse it and adjust the pH to 9.0. Add 1mL of alginate lyase and enzymatically hydrolyze it at a constant temperature of 45℃ for 18h. Centrifuge the hydrolysate at 9000rpm for 5min, take the supernatant and filter it to obtain Sargassum hydrolysate. Store it at 4℃ for later use.

[0053] 2. The enzymatic hydrolysate of Sargassum fusiforme was mixed with 0.2 mol / L zinc acetate solution at a volume ratio of 1:10 and reacted for 4 h under constant temperature magnetic stirring in a 65℃ water bath. After cooling, 0.1 mol / L NaOH solution was added dropwise to adjust the pH of the system to 9.0 to obtain a nano zinc oxide suspension.

[0054] 3. Centrifuge the nano zinc oxide suspension at 9000 rpm for 15 min, discard the supernatant and take the precipitate, wash it 3 times with anhydrous ethanol and dry it, calcine it at 500℃ for 2.5 h and grind it to obtain the seaweed nano zinc oxide prepared by the method described in Example 3.

[0055] Example 4

[0056] This embodiment provides a method for preparing a microbial suspension fertilizer based on seaweed nano-zinc oxide, including the following steps:

[0057] The seaweed nano-zinc oxide prepared in Example 1 and deionized water were placed in a reaction vessel and stirred at 200 rpm for 30 min at a constant temperature of 40°C. Then, the composite microbial agent, penetrant, wetting agent, emulsifier, defoamer, dispersant, antifreeze, and flocculant were added sequentially, and stirring was continued for 60 min. Then, the suspending agent was added for the first time, and stirring was continued until the average particle size in the solution was less than 500 μm. Then, the suspending agent was added for the second time, and stirring was carried out at 150 rpm for 60 min to obtain the suspension fertilizer prepared by the method described in Example 4. The mass ratio of the seaweed nano-zinc oxide, penetrant, wetting agent, emulsifier, defoamer, dispersant, antifreeze, flocculant, suspending agent, and deionized water was 50:5:2:1:2:1:2:3:14:30. The mass ratio of the first addition of suspending agent to the second addition of suspending agent was 1:1.

[0058] The composite microbial agent is prepared by mixing Bacillus mucilaginosus, Azotobacter chrysophagus, and Bacillus subtilis in a mass ratio of 2:2:1; the penetrant is prepared by mixing alkylphenol polyoxyethylene ether, organosilicon, and azone in a mass ratio of 2:1:1; the wetting agent is prepared by mixing o-aminobenzoyl hydrazine and 3-propanedithiol in a mass ratio of 1:1; the emulsifier is prepared by mixing Span S-40 and fatty alcohol polyoxyethylene ether in a mass ratio of 1:3; the defoamer is prepared by mixing glycerol polyoxypropylene ether defoamer and organosilicon defoamer in a mass ratio of 1:1; the dispersant is ethyl acetate; the antifreeze is prepared by mixing polyethylene glycol, glycerol, and urea in a mass ratio of 2:3:1; the settling agent is prepared by mixing nano-sized silica, light calcium carbonate, and magnesium aluminum silicate in a mass ratio of 1:1:2; and the suspending agent is prepared by mixing xanthan gum and activated clay in a mass ratio of 3:5.

[0059] Example 5

[0060] This embodiment provides a method for preparing a microbial suspension fertilizer based on seaweed nano-zinc oxide, including the following steps:

[0061] The seaweed nano-zinc oxide prepared in Example 2 and deionized water were placed in a reaction vessel and stirred at 38°C and 180 rpm for 28 min. Then, the composite microbial agent, penetrant, wetting agent, emulsifier, defoamer, dispersant, antifreeze, and flocculant were added sequentially, and stirring was continued for 55 min. Then, the suspending agent was added for the first time, and stirring was continued until the average particle size in the solution was less than 500 μm. Then, the suspending agent was added for the second time, and stirring was continued at 130 rpm for 55 min to obtain the suspension fertilizer prepared by the method described in Example 5. The mass ratio of the seaweed nano-zinc oxide, penetrant, wetting agent, emulsifier, defoamer, dispersant, antifreeze, flocculant, suspending agent, and deionized water was 60:4:1:0.5:1:0.5:1:2:15:25. The mass ratio of the first addition of suspending agent to the second addition of suspending agent was 1:1.

[0062] The composite microbial agent is prepared by mixing Bacillus mucilaginosus, Azotobacter chrysophagus, and Bacillus subtilis in a mass ratio of 2:2:1; the penetrant is prepared by mixing alkylphenol polyoxyethylene ether, organosilicon, and azone in a mass ratio of 2:1:1; the wetting agent is prepared by mixing o-aminobenzoyl hydrazine and 3-propanedithiol in a mass ratio of 1:1; the emulsifier is prepared by mixing Span S-40 and fatty alcohol polyoxyethylene ether in a mass ratio of 1:3; the defoamer is prepared by mixing glycerol polyoxypropylene ether defoamer and organosilicon defoamer in a mass ratio of 1:1; the dispersant is ethyl acetate; the antifreeze is prepared by mixing polyethylene glycol, glycerol, and urea in a mass ratio of 2:3:1; the settling agent is prepared by mixing nano-sized silica, light calcium carbonate, and magnesium aluminum silicate in a mass ratio of 1:1:2; and the suspending agent is prepared by mixing xanthan gum and activated clay in a mass ratio of 3:5.

[0063] Example 6

[0064] This embodiment provides a method for preparing a microbial suspension fertilizer based on seaweed nano-zinc oxide, including the following steps:

[0065] The seaweed nano-zinc oxide prepared in Example 3 and deionized water were placed in a reaction vessel and stirred at 150 rpm for 25 min at a constant temperature of 35°C. Then, the compound microbial agent, penetrant, wetting agent, emulsifier, defoamer, dispersant, antifreeze, and flocculant were added sequentially, and stirring was continued for 50 min. Then, the suspending agent was added for the first time, and stirring was continued until the average particle size in the solution was less than 500 μm. Then, the suspending agent was added for the second time, and stirring was continued at 120 rpm for 50 min to obtain the suspension fertilizer prepared by the method described in Example 6. The mass ratio of the seaweed nano-zinc oxide, penetrant, wetting agent, emulsifier, defoamer, dispersant, antifreeze, flocculant, suspending agent, and deionized water was 70:6:3:1.5:3:1.5:3:4:16:35. The mass ratio of the first addition of suspending agent to the second addition of suspending agent was 1:1.

[0066] The composite microbial agent is prepared by mixing Bacillus mucilaginosus, Azotobacter chrysophagus, and Bacillus subtilis in a mass ratio of 2:2:1; the penetrant is prepared by mixing alkylphenol polyoxyethylene ether, organosilicon, and azone in a mass ratio of 2:1:1; the wetting agent is prepared by mixing o-aminobenzoyl hydrazine and 3-propanedithiol in a mass ratio of 1:1; the emulsifier is prepared by mixing Span S-40 and fatty alcohol polyoxyethylene ether in a mass ratio of 1:3; the defoamer is prepared by mixing glycerol polyoxypropylene ether defoamer and organosilicon defoamer in a mass ratio of 1:1; the dispersant is ethyl acetate; the antifreeze is prepared by mixing polyethylene glycol, glycerol, and urea in a mass ratio of 2:3:1; the settling agent is prepared by mixing nano-sized silica, light calcium carbonate, and magnesium aluminum silicate in a mass ratio of 1:1:2; and the suspending agent is prepared by mixing xanthan gum and activated clay in a mass ratio of 3:5.

[0067] Comparative Example 1

[0068] Comparative Example 1 provides a method for preparing nano zinc oxide. The difference from Example 1 is that no Sargassum fusiforme hydrolysate is added during the preparation process. The remaining steps are the same as in Example 1 and will not be repeated here.

[0069] Comparative Example 2

[0070] Comparative Example 2 provides a method for preparing seaweed nano zinc oxide. Compared with Example 1, the difference is that no alginate lyase is added to extract Sargassum fusiforme. Instead, the water extract of Sargassum fusiforme is directly used in the next reaction. The remaining steps are the same as in Example 1 and will not be repeated here.

[0071] Comparative Example 3 provides a method for preparing microbial suspension fertilizer based on seaweed nano zinc oxide. Compared with Example 4, no compound microbial agent is added, and the remaining steps are the same as in Example 4, which will not be repeated here.

[0072] Explanation of the abbreviations for the materials in the test results: SFAE Sargassum water extract; SFEE Sargassum enzyme extract; nano zinc oxide prepared by C-ZnO comparative example 1; seaweed nano zinc oxide prepared by SFAE-ZnO comparative example 2; seaweed nano zinc oxide prepared by SFEE-ZnO example 1; nano zinc oxide intermediate prepared by Intermediate SFAE-ZnO comparative example 2; nano zinc oxide intermediate prepared by Intermediate SFEE-ZnO example 1; nano zinc oxide particles prepared by C-ZnO NPs comparative example 1; seaweed nano zinc oxide particles prepared by SFAE-ZnO NPs comparative example 2; seaweed nano zinc oxide particles prepared by SFEE-ZnO NPs example 1.

[0073] To demonstrate the performance of the seaweed-based nano-zinc oxide prepared according to the present application, XRD was used to test the diffraction patterns of C-ZnO, SFAE-ZnO, and SFEE-ZnO in the range of 20–80°. The test results are as follows: Figure 2 As shown; FTIR was used to scan the Fourier transform infrared spectra of C-ZnO, SFAE-ZnO, Intermediate SFAE-ZnO, SFAE, SFEE-ZnO, Intermediate SFEE-ZnO, and SFEE in the range of 500~4000 cm⁻¹. The test results are as follows. Figure 3 As shown; the particle morphology and particle size distribution of SFEE-ZnO NPs were observed using SEM, and the test results are as follows. Figure 4 As shown.

[0074] from Figures 2-4 The test results show that the product prepared in Example 1 of this application exhibits characteristic diffraction peaks corresponding to the ZnO crystal phase in XRD testing, and Zn-O related characteristic absorption is observed in FTIR, indicating that nano-zinc oxide can be prepared by the scheme of this application. From the SEM particle size distribution map and particle size morphology image, it can be seen that the nano-zinc oxide particles prepared in the example of this application have uniform particle size and concentrated particle size distribution, proving that the nano-zinc oxide particles prepared in this application are of good quality.

[0075] To verify the application effect of the seaweed-based nano zinc oxide suspension fertilizer prepared in this application in agriculture, a field plot experiment was conducted to test its effect on wheat yield and grain zinc fortification.

[0076] Field plot trials were conducted for two consecutive wheat growing seasons in 2023-2024 and 2024-2025. A randomized complete block design was used, with each plot measuring 16 m². Each treatment had replicate plots, and other field management practices were consistent with local conventional cultivation. A water control (CK) and zinc fertilizer treatment groups were established: T1 was ZnSO₄·7H₂O (1.33 g / L, 2.65 g / L, 5.30 g / L); T2 was chemically synthesized nano-zinc oxide (0.5 g / L, 1.0 g / L, 2.0 g / L); T3 was seaweed nano-zinc oxide suspension fertilizer prepared in Comparative Example 3 of this application (0.5 g / L, 1.0 g / L, 2.0 g / L); and T4 was seaweed nano-zinc oxide suspension fertilizer prepared in Example 4 of this application. Each treatment group was sprayed with foliar spray at the jointing, heading, and grain-filling stages, with a spraying rate of 40 L / mu. Before application, the treatment solution was ultrasonically dispersed (100W, 25kHz) for 30 min.

[0077] Test results are as follows Figure 5As shown, compared with CK and conventional zinc sulfate treatment (T1), the seaweed nano zinc oxide suspension fertilizer treatment prepared in Comparative Example 3 (T3) and the seaweed nano zinc oxide suspension fertilizer treatment prepared in Example 4 (T4) can increase the number of grains per ear, thousand-grain weight and grain yield of wheat in both growing seasons. The effect is more significant at an application concentration of 1.0 g / L (P<0.05), which proves that the seaweed nano zinc oxide prepared in this application has a better effect on promoting crop growth. At the same time, the growth-promoting effect of the suspension fertilizer prepared in Example 4 (T4) is better than that of Comparative Example 3 (T3). This is mainly because the compound microbial agent added in Example 4 (T4) can further promote the absorption of zinc fertilizer and the synthesis of auxin, thereby promoting crop growth.

[0078] like Figure 6 As shown, different zinc fertilizer treatments can increase the zinc accumulation in plants. Among them, the seaweed nano zinc oxide treatment (T3) prepared in Comparative Example 3 and the suspension fertilizer treatment (T4) prepared in Example 4 can significantly increase the zinc accumulation and its proportion in the grain, indicating that they are more conducive to the enrichment of zinc into the grain. Furthermore, the overall zinc content of the plants treated with the suspension fertilizer (T4) in Example 4 is significantly higher than that of the plants treated with the comparative example (T3).

[0079] like Figure 7 As shown, compared with CK, conventional treatment and Comparative Example 3 treatment, the suspension fertilizer (T4) prepared in Example 4 can improve the amino acid content of grains to varying degrees, thereby improving the quality of wheat.

[0080] In summary, the seaweed nano zinc oxide suspension fertilizer prepared in this application can effectively promote crop growth and increase crop yield, and has excellent application value in agriculture.

[0081] It should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application, and all such modifications and substitutions should be covered within the scope of the claims of this application.

Claims

1. A microbial suspension fertilizer based on seaweed-derived nano-zinc oxide, characterized in that, By weight, it includes the following components: 50-70 parts seaweed nano zinc oxide, 3-5 parts compound microbial agent, 4-6 parts penetrant, 1-3 parts wetting agent, 0.5-1.5 parts emulsifier, 1-3 parts defoamer, 0.5-1.5 parts dispersant, 1-3 parts antifreeze, 2-4 parts flocculant, 12-16 parts suspending agent, and 25-35 parts deionized water; The seaweed nano zinc oxide was obtained by reacting seaweed hydrolysate extracted by alginate lyase with zinc salt.

2. The microbial suspension fertilizer based on seaweed nano-zinc oxide according to claim 1, characterized in that, The composite microbial agent is prepared by mixing Bacillus mucilaginosus, Azotobacter chrysophagus, and Bacillus subtilis in a mass ratio of 2:2:1; the penetrant is prepared by mixing alkylphenol polyoxyethylene ether, organosilicon, and azone in a mass ratio of 2:1:1; the wetting agent is prepared by mixing o-aminobenzoyl hydrazine and 3-propanedithiol in a mass ratio of 1:1; the emulsifier is prepared by mixing Span S-40 and fatty alcohol polyoxyethylene ether in a mass ratio of 1:3; the defoamer is prepared by mixing glycerol polyoxypropylene ether defoamer and organosilicon defoamer in a mass ratio of 1:1; the dispersant is ethyl acetate; the antifreeze is prepared by mixing polyethylene glycol, glycerol, and urea in a mass ratio of 2:3:1; the settling agent is prepared by mixing nano-sized silica, light calcium carbonate, and magnesium aluminum silicate in a mass ratio of 1:1:2; and the suspending agent is prepared by mixing xanthan gum and activated clay in a mass ratio of 3:

5.

3. A method for preparing a microbial suspension fertilizer based on seaweed nano-zinc oxide as described in any one of claims 1-2, characterized in that, Includes the following steps: Wash and dry Sargassum fusiforme, grind it into powder, and add water to make Sargassum fusiforme algal slurry; add alginate lyase to the Sargassum fusiforme algal slurry for enzymatic hydrolysis, centrifuge, take the supernatant and filter to obtain Sargassum fusiforme enzymatic hydrolysate; The enzymatic hydrolysate of Sargassum fusiforme was mixed with a zinc salt solution under heating and alkaline conditions. The reaction product was centrifuged, washed, and calcined to obtain seaweed-mediated synthesized seaweed nano-zinc oxide particles. Microbial suspension fertilizer is prepared by mixing seaweed nano zinc oxide particles, compound microbial agents, penetrants, wetting agents, emulsifiers, defoamers, dispersants, antifreeze agents, flocculants, suspending agents, and deionized water in a certain proportion.

4. The method for preparing a microbial suspension fertilizer based on seaweed nano-zinc oxide according to claim 3, characterized in that, The particle size of the Sargassum fusiforme powder is 60-100 mesh, and the mass-to-volume ratio of Sargassum fusiforme powder to water in the Sargassum fusiforme slurry is (2-4):100g / mL; the alginate lyase is obtained by fermentation of Microbulbifer sp. SH-1 strain, and its preservation number is CGMCC No.16906.

5. The method for preparing a microbial suspension fertilizer based on seaweed nano-zinc oxide according to claim 3, characterized in that, The specific conditions for enzymatic hydrolysis are as follows: the volume ratio of alginate lyase to Sargassum fusiforme slurry is (1~5):100; the hydrolysis temperature is 35~45℃; the pH is 8.0~9.0; and the hydrolysis time is 18~24h. The specific conditions for obtaining Sargassum fusiforme enzymatic hydrolysate by centrifugation and filtration of the supernatant are as follows: the centrifugation speed is 8000~9000rpm; the centrifugation time is 5~10min. The Sargassum fusiforme enzymatic hydrolysate is stored at 4℃.

6. The method for preparing a microbial suspension fertilizer based on seaweed nano-zinc oxide according to claim 3, characterized in that, The zinc salt solution is a zinc acetate solution with a concentration of 0.1~0.2 mol / L; the volume ratio of the Sargassum fusiforme enzymatic hydrolysate to the zinc acetate solution is 1:(5~10); the mixing reaction conditions are: temperature 55~65℃, pH value 9.0~10.0, and magnetic stirring for 3~4 hours.

7. The method for preparing a microbial suspension fertilizer based on seaweed nano-zinc oxide according to claim 3, characterized in that, The centrifugation conditions are: centrifugation at 9000~10000 rpm for 10~15 min; washing is performed 3 times with anhydrous ethanol; calcination is performed at 400~500℃ for 1.5~2.5 h.

8. The method for preparing a microbial suspension fertilizer based on seaweed nano-zinc oxide according to claim 3, characterized in that, The specific steps for preparing the microbial suspension fertilizer are as follows: Seaweed nano zinc oxide and deionized water were placed in a reaction vessel and kept at a constant temperature of 35-40℃, stirred at a speed of 150-200 rpm for 25-30 minutes. Then, compound microbial agent, penetrant, wetting agent, emulsifier, defoamer, dispersant, antifreeze and flocculant were added in sequence, and stirring was continued for 50-60 minutes. Then, the suspending agent was added for the first time and stirred until the average particle size in the solution was less than 500 μm. Then, the suspending agent was added for the second time and stirred at 120-150 rpm for 50-60 minutes to obtain microbial suspension fertilizer.

9. The method for preparing a microbial suspension fertilizer based on seaweed nano-zinc oxide according to claim 8, characterized in that, The mass ratio of the first addition of suspending agent to the second addition of suspending agent is 1:

1.

10. An application of a microbial suspension fertilizer based on seaweed nano-zinc oxide as described in any one of claims 1-2, characterized in that, The microbial suspension fertilizer is absorbed by crops through foliar spraying or rhizosphere application.

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