Silica nano-composite fertilizer, preparation method and application thereof

Abstract

The application discloses silica nano composite fertilizer, a preparation method and application thereof, and belongs to the field of nanobiotechnology. The silica nano composite fertilizer is prepared by taking modified dendritic mesoporous silica as a carrier and loading ionic compounds. The silica nanoparticles prepared by the application have excellent nanometer size, and the formed nano organic fertilizer can better help the transportation of element ions in plants. After modification, the loading and penetration guiding effect of the silica nanoparticles is improved, so that the yield and quality of vegetables are improved, the transportation performance of various elements in the vegetables is improved, and the utilization rate of element fertilizers is improved.

Description

Technical Field

[0001] This invention relates to the field of nanobiotechnology, specifically to a silica nanocomposite fertilizer, its preparation method, and its application. Background Technology

[0002] In vegetable cultivation, calcium, magnesium, and sulfur are all essential nutrients for vegetable growth and development, playing a vital role in maintaining cell wall structure, improving photosynthetic efficiency, enhancing fruit quality, and strengthening resistance to adverse conditions. Calcium participates in pectin synthesis and cell membrane stability, significantly reducing the incidence of physiological diseases such as blossom-end rot in tomatoes, heart rot in cabbage, and fruit cracking in melons. Magnesium, as a core component of chlorophyll, directly affects crop photosynthesis and nitrogen metabolism; magnesium deficiency easily leads to chlorosis and yellowing of older leaves in vegetables, as well as a decline in yield and quality. Sulfur participates in the synthesis of proteins and endogenous substances, positively impacting the flavor and marketability of vegetables.

[0003] Currently, calcium formate is commonly used in production as a fast-acting organic calcium source due to its good water solubility, high absorption and utilization rate, and its combined effects of calcium supplementation and rhizosphere microenvironment regulation. Magnesium sulfate, with its dual nutrients of magnesium and sulfur, low cost, and good solubility, is widely used for correcting magnesium deficiency and supplementing nutrition in vegetables. However, in practical applications, there are still many technical problems with the application of these fertilizers alone or in combination: On the one hand, there is a significant absorption antagonism between calcium and cations such as magnesium and potassium. Excessive application of magnesium sulfate can easily inhibit the absorption and transport of calcium in vegetables, exacerbating calcium deficiency symptoms in fruits. On the other hand, calcium ions in calcium formate easily react with phosphate and sulfate ions to form insoluble precipitates, which not only reduces fertilizer efficiency but also easily causes blockage of drip irrigation systems. At the same time, long-term and excessive application of magnesium sulfate can easily lead to soil acidification and salt accumulation, thereby affecting the availability of trace elements such as iron and zinc. Calcium formate at high concentrations can easily burn young leaves, flowers, and fruits, requiring strict control of application time and concentration. In addition, under traditional fertilization methods, calcium and magnesium nutrients have poor mobility and uneven distribution in the soil, making it difficult to simultaneously meet the needs of vegetable vegetative and reproductive growth. This leads to nutrient waste and frequent physiological diseases, which restricts the high-quality and efficient production of vegetables.

[0004] Nano-silica, due to its large specific surface area, abundant pore structure, good chemical inertness, and excellent biocompatibility, is widely used as a carrier material and has significant application prospects in catalysis, adsorption, environmental remediation, biomedicine, and electronic materials. Utilizing nano-silica to support ionic compounds as fertilizers for vegetable production is one direction for achieving high-quality and efficient vegetable production. However, existing nano-silica surfaces are mainly composed of silanol groups (Si-OH), which have limited chemical activity. They can only form weak interactions with most supported ions, such as physical adsorption, weak electrostatic interactions, or hydrogen bonds, resulting in insufficient ion loading strength. During use, the loaded ions are prone to desorption and loss. Furthermore, it is difficult to balance the ion loading capacity with the structural stability of nano-silica. During loading, silanol groups compete for adsorption with supported ions, reaction solvents, and impurities in the system, further affecting the efficiency and stability of ion loading. Summary of the Invention

[0005] In view of the above-mentioned prior art, the purpose of this invention is to provide a silica nanocomposite fertilizer, its preparation method and application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a silica nanocomposite fertilizer, wherein the silica nanocomposite fertilizer uses modified dendritic mesoporous silica as a carrier and the loaded object is an ionic compound; The modified dendritic mesoporous silica was prepared by the following method: (1) Ammoniated dendritic mesoporous silica is obtained by amination treatment. (2) Add L-glutamic acid, EDC·HCl and NHS to MES buffer at pH 5.5, activate for 10-30 min, then adjust the pH of the system to 7.2-7.4, add aminated dendritic mesoporous silica, react at room temperature for 6-14 h to obtain glutamic acid modified dendritic mesoporous silica. (3) Glutamic acid-modified dendritic mesoporous silica was dispersed in Tris buffer at pH 8.5, tannic acid was added, and the mixture was stirred at room temperature for 2-6 hours. The modified dendritic mesoporous silica was then washed and dried.

[0007] Preferably, in step (2), the amount of L-glutamic acid added is 10-30% of the weight of dendritic mesoporous silica, the amount of EDC·HCl added is 10-20% of the weight of dendritic mesoporous silica, and the amount of NHS added is 5-15% of the weight of dendritic mesoporous silica.

[0008] Preferably, in step (3), the amount of tannic acid added is 10-30% of the weight of the glutamic acid-modified dendritic mesoporous silica.

[0009] Preferably, the ionic compound is selected from one or both of calcium formate or magnesium sulfate.

[0010] A second aspect of the present invention provides a method for preparing the above-mentioned silica nanocomposite fertilizer, comprising the following steps: Modified dendritic mesoporous silica was dispersed in a saturated solution of an ionic compound and stirred for 20-40 min. The solution was then centrifuged. The resulting precipitate was washed to remove unreacted substances, and the precipitate was freeze-dried to prepare silica nanocomposite fertilizer.

[0011] Preferably, the centrifugation speed is 14,000 rpm and the centrifugation time is 30 min.

[0012] Furthermore, the above preparation method also includes the step of slowly adding eucalyptus essential oil dropwise onto the surface of the freeze-dried precipitate, with 0.1g of eucalyptus essential oil added for every 1g of precipitate; stirring slowly for 2h, and removing residual volatile components under reduced pressure at 25℃.

[0013] When plant essential oils enter the dendritic mesoporous structure, they form hydrophobic microdomains and diffusion-restricting layers, reducing the initial explosive release of the ionic compounds and improving the wetting, spreading, and permeation transport properties of the formulation at biological interfaces. The dendritic mesoporous nano-silica provides a high specific surface area, large pore volume, and open radial channels, providing a structural basis for the efficient loading and migration release of the ionic compounds. The synergistic effect of these three elements significantly improves the loading retention, sustained-release performance, and permeation transport of the ionic compounds.

[0014] A third aspect of the present invention provides the application of the above-mentioned silica nanocomposite fertilizer in the following (1) or (2): (1) Improve the transport performance of calcium and magnesium elements in vegetables; (2) Prepare products that improve the transport performance of calcium and magnesium elements in vegetables.

[0015] In a fourth aspect, the present invention provides the application of the above-mentioned silica nanocomposite fertilizer in improving the quality of vegetables.

[0016] In the above applications, improving vegetable quality means: increasing the content of soluble sugars, soluble proteins, and vitamin C in vegetable leaves; and reducing the nitrate content.

[0017] The beneficial effects of this invention are: (1) The dendritic mesoporous nano-silica used in this invention has "several channels from the center to the surface, with a pore size of up to 20-30 nm", and "a specific surface area of ​​~1000 m² / g and a pore volume of ~2.0 ml / g". Commercially available mesoporous silica is usually two-dimensional hexagonal through-holes with small pore sizes (2-5 nm) and tortuous channels. In contrast, the dendritic structure in this invention has large pore sizes and open surfaces. This lays the physical foundation for subsequent loading of various trace elements and slow release.

[0018] This invention employs the co-modification of dendritic mesoporous nano-silica with tannic acid and glutamic acid, which synergistically enhances the loading capacity, sustained-release performance, and permeation transport performance of dendritic mesoporous nano-silica. The proposed mechanism is as follows: co-modification with tannic acid and glutamic acid constructs a composite functional layer with both carboxyl and polyphenolic hydroxyl sites on the carrier surface and pore area. Glutamic acid, through its carboxyl groups, associates or coordinates with metal cations in the loaded ionic compounds, increasing the retention of metal cations near the pore walls and pore openings. Tannic acid, through its polyphenolic hydroxyl groups, further provides multiple metal ion binding sites and forms an outer layer structure on the carrier surface with adhesive and diffusion-blocking effects, thereby reducing the loss and initial burst release of the ionic compounds during storage and use. The synergistic effect of these two modifiers enables dendritic mesoporous nano-silica to simultaneously possess high ionic compound loading capacity, good sustained-release performance, and superior interfacial deposition and permeation transport effects.

[0019] (2) The synthesis process of preparing silica nanocomposite sheets in this invention is simple to operate and has a high yield. The solvent is deionized water, which is safe and non-toxic. It has low equipment requirements, is environmentally friendly, and has broad market application prospects. Moreover, the silica nanocomposite fertilizer prepared by this invention has slow-release properties and excellent permeability, thereby achieving increased yield of crops. Attached Figure Description Figure 1 Scanning electron microscope (SEM) image of the dendritic mesoporous silica used in this embodiment of the invention.

[0020] Figure 2 Transmission electron microscopy (TEM) image of the dendritic mesoporous silica used in this embodiment of the invention.

[0021] Figure 3 N2 adsorption-desorption curves of dendritic mesoporous silica used in the embodiments of the present invention.

[0022] Figure 4 : Pore size distribution diagram of the dendritic mesoporous silica used in the embodiments of the present invention.

[0023] Figure 5The results of the slow-release performance study of the silica nanocomposite fertilizer prepared in Example 1 of this invention dispersed in buffer solutions of different pH values.

[0024] Figure 6 The images show the transport effects of fluorescently labeled modified dendritic mesoporous silica and unmodified dendritic mesoporous silica on pakchoi leaves at different time points. In the figures, A is a photograph of two pakchoi leaves under natural light; B is an image of a small animal without the addition of fluorescent material; C shows the spreading and penetration of fluorescently labeled unmodified dendritic mesoporous silica on the leaf surface at 5 s on the left and fluorescently labeled modified dendritic mesoporous silica on the right; D shows the spreading and penetration on the leaf surface at 10 s; E shows the spreading and penetration on the leaf surface at 15 s; and F shows the spreading and penetration on the leaf surface at 30 s.

[0025] Figure 7 The images show the transport effects of fluorescently labeled modified dendritic mesoporous silica and unmodified dendritic mesoporous silica on lettuce leaves at different time points. In the figures, A is a photograph of two lettuce leaves under natural light; B is an image of a small animal without the addition of fluorescent material; C shows the spreading and penetration of fluorescently labeled unmodified dendritic mesoporous silica on the leaf surface at 5 s on the left and fluorescently labeled modified dendritic mesoporous silica on the right; D shows the spreading and penetration on the leaf surface at 10 s; E shows the spreading and penetration on the leaf surface at 15 s; and F shows the spreading and penetration on the leaf surface at 30 s.

[0026] Figure 8 Effects of different treatments on the soluble sugar content of bok choy and lettuce.

[0027] Figure 9 The effects of different treatments on the soluble protein content of bok choy and lettuce.

[0028] Figure 10 The effects of different treatments on the vitamin C content of bok choy and lettuce.

[0029] Figure 11 The effects of different treatments on the nitrate content of bok choy and lettuce. Detailed Implementation

[0030] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0031] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0032] The test materials used in the embodiments of this invention, unless otherwise specified, are all conventional test materials in the art and can be purchased through commercial channels. Where specific experimental conditions and methods are not specified in the embodiments of this invention, they are generally performed under conventional conditions or according to the manufacturer's recommendations. Wherein: The dendritic mesoporous silica (DMSN) used in the examples was prepared by the following method: (1) Add 0.068 g of triethanolamine to 25 mL of purified water and place it at high temperature (80 °C) with magnetic stirring (350 rpm) for 30 min; then, add 380 mg of hexadecyl dimethyl ammonium bromide and 168 mg of sodium salicylate to the solution and continue stirring at high temperature for 1 h; then add 4 mL of tetraethyl orthosilicate to the mixture and continue stirring at high temperature for 2 h. (2) Centrifuge the solution prepared in step (1) at 11000 r / min for 30 min, discard the supernatant, collect the precipitate, and wash the precipitate three times with anhydrous ethanol. Dissolve the final precipitate in methanol and concentrated hydrochloric acid, then bathe it in water three times, and finally centrifuge and vacuum dry to obtain a white powder, which is dendritic mesoporous silica.

[0033] The scanning electron microscope morphology of the prepared dendritic mesoporous silica is as follows: Figure 1 As shown, the morphology under transmission electron microscopy is as follows: Figure 2 As shown. The N2 adsorption-desorption curve is as follows. Figure 3 As shown; the pore size distribution of the prepared dendritic mesoporous silica is as follows. Figure 4 As shown. The dendritic mesoporous silica prepared by this invention has a particle size mainly distributed in the range of 200-300 nm; the pore size is mainly distributed in the range of 20-30 nm, and the silica has a high-density mesoporous structure inside.

[0034] Example 1: Preparation of silica nanocomposite fertilizer 1. Preparation of modified dendritic mesoporous silica: (1) 100 mg of dendritic mesoporous silica was dispersed in 20 mL of anhydrous ethanol, and 0.2 mL of 3-aminopropyltriethoxysilane (APTES) was added. The mixture was stirred at 75 °C for 8 h. After the reaction, the mixture was washed three times with ethanol and dried under vacuum overnight to prepare aminated dendritic mesoporous silica (DMSN-NH2).

[0035] (2) Add 30 mg L-glutamic acid to MES buffer (pH 5.5), then add 15 mg EDC·HCl and 10 mg NHS, and activate at room temperature (25℃) for 20 min. Then adjust the pH of the system to 7.2-7.4, then add 100 mg of aminated dendritic mesoporous silica, and react at room temperature for 12 h; after the reaction, wash with water / ethanol alternately, and finally vacuum dry to obtain glutamic acid modified dendritic mesoporous silica; (3) Glutamic acid-modified dendritic mesoporous silica was dispersed in Tris buffer (pH 8.5), 30 mg of tannic acid was added, and the mixture was stirred at room temperature (25°C) for 4 h; it was washed with deionized water and vacuum dried to prepare modified dendritic mesoporous silica.

[0036] 2. Loaded ionic compounds: 100 mg of modified dendritic mesoporous silica was dispersed in 60 mL of calcium formate saturated solution and placed at room temperature (25 °C) and magnetically stirred (350 rpm) for 30 min. The solution was then centrifuged at 14000 rpm for 30 min. The resulting precipitate was washed three times with deionized water to remove unreacted substances. The precipitate was then freeze-dried for 48 h to prepare silica nanocomposite fertilizer (named Ca@DMSNs).

[0037] Example 2: Preparation of silica nanocomposite fertilizer 1. Preparation of modified dendritic mesoporous silica: The modified dendritic mesoporous silica was prepared using the same method as in Example 1.

[0038] 2. Loaded ionic compounds: 100 mg of modified dendritic mesoporous silica was dispersed in 60 mL of saturated magnesium sulfate solution and placed at room temperature (25 °C) with magnetic stirring (350 rpm) for 30 min. The solution was then centrifuged at 14000 rpm for 30 min. The resulting precipitate was washed three times with deionized water to remove unreacted substances. The precipitate was then freeze-dried for 48 h to prepare silica nanocomposite fertilizer (named Mg@DMSNs).

[0039] Example 3: Preparation of silica nanocomposite fertilizer 1. Preparation of modified dendritic mesoporous silica: The modified dendritic mesoporous silica was prepared using the same method as in Example 1.

[0040] 2. Loaded ionic compounds: 100 mg of modified dendritic mesoporous silica was dispersed in 60 mL of magnesium sulfate saturated solution + 60 mL of magnesium sulfate saturated solution, and magnetically stirred (350 rpm) at room temperature (25℃) for 30 min. The solution was then centrifuged at 14000 rpm for 30 min. The resulting precipitate was washed three times with deionized water to remove unreacted substances. The precipitate was then freeze-dried for 48 h to prepare silica nanocomposite fertilizer (named Ca / Mg@DMSNs).

[0041] Example 4: Preparation of silica nanocomposite fertilizer 1. Preparation of modified dendritic mesoporous silica: The modified dendritic mesoporous silica was prepared using the same method as in Example 1.

[0042] 2. Loaded ionic compounds: 100 mg of modified dendritic mesoporous silica was dispersed in 60 mL of calcium formate saturated solution and placed at room temperature (25 °C) with magnetic stirring (350 rpm) for 30 min. The solution was then centrifuged at 14000 rpm for 30 min. The resulting precipitate was washed three times with deionized water to remove unreacted substances and then freeze-dried for 48 h. Eucalyptus essential oil was slowly added dropwise to the surface of the freeze-dried precipitate, with 0.1g of eucalyptus essential oil added for every 1g of precipitate; the mixture was stirred slowly for 2 hours, and the residual volatile components were removed under reduced pressure at 25℃ to prepare silica nanocomposite fertilizer.

[0043] Comparative Example 1: 100 mg of unmodified dendritic mesoporous silica was dispersed in 60 mL of calcium formate saturated solution and placed at room temperature (25 °C) and magnetically stirred (350 rpm) for 30 min. The solution was then centrifuged at 14000 rpm for 30 min. The resulting precipitate was washed three times with deionized water to remove unreacted substances. The precipitate was then freeze-dried for 48 h to prepare silica nanocomposite fertilizer.

[0044] Comparative Example 2: 1. Preparation of modified dendritic mesoporous silica: (1) 100 mg of dendritic mesoporous silica was dispersed in 20 mL of anhydrous ethanol, and 0.2 mL of 3-aminopropyltriethoxysilane (APTES) was added. The mixture was stirred at 75 °C for 8 h. After the reaction, the mixture was washed three times with ethanol and dried under vacuum overnight to prepare aminated dendritic mesoporous silica (DMSN-NH2).

[0045] (2) Add 30 mg L-glutamic acid to MES buffer (pH 5.5), then add 15 mg EDC·HCl and 10 mg NHS, and activate at room temperature (25℃) for 20 min. Then adjust the pH of the system to 7.2-7.4, then add 100 mg of aminated dendritic mesoporous silica, and react at room temperature for 12 h. After the reaction, wash with water / ethanol alternately, and finally dry under vacuum to obtain glutamic acid modified dendritic mesoporous silica.

[0046] 2. Loaded ionic compounds: 100 mg of glutamic acid-modified dendritic mesoporous silica was dispersed in 60 mL of calcium formate saturated solution and placed at room temperature (25 °C) with magnetic stirring (350 rpm) for 30 min. The solution was then centrifuged at 14000 rpm for 30 min. The resulting precipitate was washed three times with deionized water to remove unreacted substances. The precipitate was then freeze-dried for 48 h to prepare silica nanocomposite fertilizer.

[0047] Comparative Example 3: 1. Preparation of modified dendritic mesoporous silica: (1) 100 mg of dendritic mesoporous silica was dispersed in 20 mL of anhydrous ethanol, and 0.2 mL of 3-aminopropyltriethoxysilane (APTES) was added. The mixture was stirred at 75 °C for 8 h. After the reaction, the mixture was washed three times with ethanol and dried under vacuum overnight to prepare aminated dendritic mesoporous silica (DMSN-NH2).

[0048] (2) Take 100 mg of aminated dendritic mesoporous silica (DMSN-NH2) and disperse it in Tris buffer (pH 8.5). Add 30 mg of tannic acid and stir at room temperature (25℃) for 4 h. Wash with deionized water and vacuum dry to prepare tannic acid modified dendritic mesoporous silica.

[0049] 2. Loaded ionic compounds: 100 mg of tannic acid-modified dendritic mesoporous silica was dispersed in 60 mL of calcium formate saturated solution and placed at room temperature (25 °C) with magnetic stirring (350 rpm) for 30 min. The solution was then centrifuged at 14000 rpm for 30 min. The resulting precipitate was washed three times with deionized water to remove unreacted substances. The precipitate was then freeze-dried for 48 h to prepare silica nanocomposite fertilizer.

[0050] Test Example 1: Load Performance Evaluation 1. Test method: The loading performance of the silica nanocomposite fertilizers prepared in Examples 1, 2, 1, 2, and 3 was determined using the following methods: Load factor (%) = (C0V0 - C1V1) / C0V0 × 100% In the formula: C0: Initial calcium / magnesium ion concentration; V0: Initial volume of calcium formate saturated solution or magnesium sulfate saturated solution; C1: The concentration of residual calcium / magnesium ions in the supernatant after centrifugation following the loading of ionic compounds; V1: Volume of supernatant after centrifugation following loading of ionic compounds.

[0051] 2. Test Results: The loading rates of ionic compounds in the silica nanocomposite fertilizers prepared in different embodiments and comparative examples are shown in Table 1.

[0052] Table 1: Results of Ionic Compound Loading Rate Measurement The results showed that modifying dendritic mesoporous silica with a combination of glutamic acid and tannic acid could synergistically improve the loading effect of dendritic mesoporous silica on ionic compounds.

[0053] Experimental Example 2: Study on sustained-release performance 1. Test method: The silica nanocomposite fertilizer prepared in Example 1 was dispersed in different pH buffer solutions (pH 6.5, pH 7.4, pH 8.2), shaken at 25°C, and samples were taken at different time points to detect the content of released ions and calculate the cumulative release rate of ions.

[0054] 2. Test Results: The results are as follows Figure 5 As shown, the results indicate that the silica nanocomposite fertilizer prepared by this invention exhibits slow-release properties of ionic compounds under different pH conditions.

[0055] Experimental Example 3: Permeability Performance Investigation 1. Test method: Dissolve 5 mg of FITC in 100 mL of deionized water. Add 5 mg of the modified dendritic mesoporous silica prepared in Example 1 and the unmodified dendritic mesoporous silica respectively. After thorough sonication, stir magnetically overnight at room temperature in the dark. Centrifuge the resulting mixture and wash the precipitate several times with deionized water to remove free FITC. The precipitate is the fluorescently labeled modified dendritic mesoporous silica and the fluorescently labeled unmodified dendritic mesoporous silica.

[0056] Take 20 mg of fluorescently labeled modified dendritic mesoporous silica and fluorescently labeled unmodified dendritic mesoporous silica and dilute them with 1000 mL of water to obtain fluorescently labeled modified dendritic mesoporous silica dilution (named FITC@modified silica) and fluorescently labeled unmodified dendritic mesoporous silica (named FITC@silica).

[0057] Leaves of well-developed lettuce and bok choy were selected, and equal amounts of FITC@modified silica and FITC@silica were sprayed onto the leaves respectively. Unadsorbed FITC@modified silica and FITC@silica were washed away. Paraffin sections were prepared, and the fluorescence distribution of FITC@modified silica and FITC@silica at various locations on the lettuce and bok choy leaves was observed using SLM.

[0058] 2. Test Results: Figure 6 The transport effects of FITC@modified silica and FITC@silica on pak choi leaves at different time points (using a small animal imager). Figure 7 Images show the transmission effects of FITC@modified silica and FITC@silica on lettuce leaves at different time points (using a small animal imaging system). The results indicate that with prolonged treatment time, the fluorescence intensity of FITC@modified silica is stronger, and the fluorescence distribution range is wider. This suggests that modifying dendritic mesoporous silica using a combination of glutamic acid and tannic acid can improve its permeability to leaves.

[0059] Experiment Example 4: Investigation into the impact on vegetable quality 1. Test method: After sowing, when the bok choy and lettuce have grown to three leaves and one bud, select bok choy and lettuce with basically the same growth rate for an experiment, with the following treatments: Treatment Group 1 (T1): The silica nanocomposite fertilizer prepared in Example 1 was diluted with water to make a diluted solution with a concentration of 167 mg / L, and then sprayed on the leaves. Treatment Group 2 (T2): The silica nanocomposite fertilizer prepared in Example 2 was diluted with water to make a diluted solution with a concentration of 168 mg / L, and then sprayed on the leaves. Treatment Group 3 (T3): The modified dendritic mesoporous silica prepared in Example 1 was diluted with water to prepare a diluted solution with a concentration of 100 mg / L, which was then sprayed on the leaves. Treatment group 4 (T4): Leaves were sprayed with a calcium formate solution at a concentration of 112 mg / L; Treatment group 5 (T5): Leaves were sprayed with a magnesium sulfate solution with a concentration of 114 mg / L; Control group (CK): Only water was sprayed.

[0060] Each treatment group was sprayed with an appropriate amount of water, enough to coat the leaves with water droplets without them falling off. After the same treatment time, the contents of soluble sugar, soluble protein, vitamin C, and nitrate in the leaves of bok choy and lettuce were determined. Soluble sugar was determined using the anthrone colorimetric method; soluble protein was determined using the Coomassie Brilliant Blue G-250 staining method; vitamin C content was determined using the molybdenum blue colorimetric method; and nitrate content was determined using the salicylic acid method.

[0061] 2. Test Results: The results are as follows Figures 8-11 As shown, the results indicate that compared with the application of calcium formate and magnesium sulfate, the application of the silica nanocomposite fertilizer prepared in this invention can increase the soluble sugar content, soluble protein content, and vitamin C content of bok choy and lettuce, and significantly reduce the nitrate content in the plants, thereby significantly improving the quality of the vegetables.

[0062] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A silica nanocomposite fertilizer, characterized in that, The silica nanocomposite fertilizer uses modified dendritic mesoporous silica as a carrier and ionic compounds as the loading material. The modified dendritic mesoporous silica was prepared by the following method: (1) Ammoniated dendritic mesoporous silica is obtained by amination treatment. (2) Add L-glutamic acid, EDC·HCl and NHS to MES buffer at pH 5.5, activate for 10-30 min, then adjust the pH of the system to 7.2-7.4, add aminated dendritic mesoporous silica, react at room temperature for 6-14 h to obtain glutamic acid modified dendritic mesoporous silica. (3) Disperse glutamic acid-modified dendritic mesoporous silica in Tris buffer at pH 8.5, add tannic acid, and stir at room temperature for 2-6 hours; The modified dendritic mesoporous silica was prepared by washing and drying.

2. The silica nanocomposite fertilizer according to claim 1, characterized in that, In step (2), the amount of L-glutamic acid added is 10-30% of the weight of dendritic mesoporous silica, the amount of EDC·HCl added is 10-20% of the weight of dendritic mesoporous silica, and the amount of NHS added is 5-15% of the weight of dendritic mesoporous silica.

3. The silica nanocomposite fertilizer according to claim 1, characterized in that, In step (3), the amount of tannic acid added is 10-30% of the weight of the glutamic acid-modified dendritic mesoporous silica.

4. The silica nanocomposite fertilizer according to claim 1, characterized in that, The ionic compound is selected from one or both of calcium formate or magnesium sulfate.

5. A method for preparing the silica nanocomposite fertilizer according to any one of claims 1-4, comprising the following steps: The modified dendritic mesoporous silica was dispersed in a saturated solution of an ionic compound and stirred for 20-40 min. The solution was then centrifuged. The precipitate was washed to remove unreacted substances, and then freeze-dried to prepare silica nanocomposite fertilizer.

6. The preparation method according to claim 5, characterized in that, The centrifugation speed was 14,000 rpm and the centrifugation time was 30 min.

7. The preparation method according to claim 5, characterized in that, The preparation method further includes the step of slowly adding eucalyptus essential oil dropwise onto the surface of the freeze-dried precipitate, with 0.1g of eucalyptus essential oil added for every 1g of precipitate; stirring slowly for 2h, and removing residual volatile components under reduced pressure at 25℃.

8. The application of the silica nanocomposite fertilizer according to any one of claims 1-4 in the following (1) or (2): (1) Improve the transport performance of calcium and magnesium elements in vegetables; (2) Prepare products that improve the transport performance of calcium and magnesium elements in vegetables.

9. The application of the silica nanocomposite fertilizer according to any one of claims 1-4 in improving vegetable quality.

10. The application according to claim 9, characterized in that, The improvement of vegetable quality is achieved by increasing the content of soluble sugars, soluble proteins, and vitamin C in vegetable leaves, and reducing the nitrate content.

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