A slow-release biological stimulant and a method for preparing the same

Abstract

The application discloses a slow-release biological stimulant and a preparation method thereof, and relates to the technical field of plant growth regulators. The specific preparation method is as follows: a biological stimulant composite microsphere carrier is prepared; seaweed extract and humic acid are dissolved in a phosphate buffer solution to obtain a biological stimulant solution; the biological stimulant composite microsphere carrier is immersed and adsorbed in the biological stimulant solution, and after separation, a slow-release biological stimulant intermediate is obtained; chitosan is dissolved in acetic acid, Tween-80 is added, and stirring is uniformly conducted to obtain a chitosan solution; the slow-release biological stimulant intermediate is added into the chitosan solution, ultrasonic oscillation is conducted to uniformly disperse the slow-release biological stimulant intermediate, then a crosslinking agent is added for reaction, and after centrifugation, washing and drying, the slow-release biological stimulant is obtained. The application can realize slow release of the biological stimulant, so that the biological stimulant can continuously and stably play a role in the plant growth cycle, the application frequency is reduced, and the labor intensity and cost are reduced.

Description

Technical Field

[0001] This invention relates to the field of plant growth regulator technology, specifically to a slow-release biostimulant and its preparation method. Background Technology

[0002] In the agricultural sector, biostimulants, as an important class of plant growth regulators, have received widespread attention in recent years. Biostimulants refer to materials containing certain substances or microorganisms that, when applied to plants or their rhizosphere, can stimulate natural plant processes, thereby improving nutrient absorption, nutrient utilization, resistance to abiotic stresses, and product quality. They are diverse, encompassing eight main categories: humic acids, complex organic compounds, beneficial chemical elements, inorganic salts (including phosphites), seaweed extracts, chitin and chitosan derivatives, antitranspirants, free amino acids, and other nitrogen-containing substances.

[0003] Biostimulants play many crucial roles in agricultural production. They can promote nutrient absorption by plants, significantly improve the efficiency of plants in uptake various nutrients from the soil, and allow fertilizers to be more effective; effectively improve the nutrient utilization efficiency of plants or the rhizosphere, and optimize the nutrient metabolism process of plants; enhance the ability of plants to resist abiotic stress, and help plants better cope with harsh environments such as drought, high temperature, low temperature, and salinity; improve crop quality, making agricultural products more advantageous in terms of taste, color, and nutritional composition; and also promote the effective absorption of nutrients in the soil or rhizosphere, improve the soil microecological environment, and create favorable soil conditions for plant growth.

[0004] However, a significant drawback of most commercially available biostimulants is their lack of sustained-release properties. This limits the effectiveness of a single application, requiring continuous application throughout the plant's growth cycle to maintain a sustained growth-promoting effect. Furthermore, the abundant microorganisms in the soil degrade biostimulants, significantly shortening their active period and making it difficult to guarantee their effective duration. This not only increases usage costs and labor input but also reduces the utilization efficiency of biostimulants. Summary of the Invention

[0005] The purpose of this invention is to provide a slow-release biostimulant and its preparation method to solve the technical problems mentioned in the background section. This invention enables the slow release of the biostimulant, allowing it to exert its effects continuously and stably throughout the plant growth cycle, reducing the frequency of application, labor intensity, and costs. Furthermore, the slow-release process also protects the biostimulant, effectively reducing degradation by external factors such as soil microorganisms, extending its active period, improving its utilization efficiency, and better meeting the needs of plant growth and development.

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

[0007] A method for preparing a sustained-release biostimulant includes the following steps:

[0008] S1. Preparation of biostimulant composite microsphere carrier;

[0009] S2. Dissolve seaweed extract and humic acid in phosphate buffer to obtain a biostimulant solution;

[0010] S3. The biostimulant composite microsphere carrier was impregnated and adsorbed by the biostimulant solution, and after separation, a sustained-release biostimulant intermediate was obtained.

[0011] S4. Dissolve chitosan in acetic acid, add Tween-80, stir well to obtain chitosan solution;

[0012] S5. Add the sustained-release biostimulant intermediate to the chitosan solution, disperse it evenly by ultrasonic vibration, then add the cross-linking agent to react, and after centrifugation, washing and drying, the product is obtained.

[0013] This invention prepares a sustained-release biostimulant by efficiently impregnating and adsorbing seaweed extract and humic acid onto a biostimulant composite microsphere carrier, achieving the loading and enrichment of the biostimulant. Then, a protective outer film is formed by the coating effect of chitosan solution, and a stable sustained-release structure is constructed through the cross-linking reaction of a cross-linking agent. Through the dual effects of carrier adsorption and chitosan coating, the release rate of the biostimulant is effectively slowed, extending its duration of action. The sustained-release process also protects the biostimulant, effectively reducing degradation by external factors such as soil microorganisms, prolonging its active period, improving its utilization efficiency, and better meeting the needs of plant growth and development. Simultaneously, the biocompatibility of chitosan and the synergistic effect of the carrier material enhance the stability and bioavailability of the biostimulant, reducing the loss and waste of active ingredients. Therefore, in application, it achieves continuous nourishment and regulation of crops, significantly improving the effect and possessing outstanding advantages of high efficiency, long-lasting effect, and stability.

[0014] Preferably, in step S2, the method for preparing the seaweed extract includes the following steps:

[0015] Brown or red algae are added, crushed, and then enzymatically hydrolyzed with cellulase and pectinase, followed by drying to obtain the final product.

[0016] Preferably, the mass ratio of cellulase to pectinase is 5:2 to 3.

[0017] Preferably, in step S2, the mass ratio of seaweed extract to humic acid is 2:3 to 6.

[0018] Preferably, in step S3, the impregnation and adsorption time is 10 to 18 hours.

[0019] Preferably, in step S5, the crosslinking agent is glutaraldehyde.

[0020] Preferably, in step S5, the crosslinking reaction time is 1 to 3 hours.

[0021] Preferably, in step S1, the preparation method of the biostimulant composite microsphere carrier includes the following steps:

[0022] Aluminum nitrate, cerium nitrate, and ytterbium chloride were dissolved in deionized water to obtain a mixed solution. Then, 2-phosphonobutane-1,2,4-tricarboxylic acid was added, and the mixture was heated to obtain a metal-organic complex solution.

[0023] Hexadecyltrimethylammonium bromide was added to a mixed solution of ethanol and water, then concentrated ammonia was added, and the mixture was dissolved by ultrasonic oscillation. Then, a metal-organic complex solution and tetraethyl orthosilicate solution were added, and the mixture was kept at a constant temperature for reaction. After centrifugation, washing, drying, and calcination, the biostimulant composite microsphere carrier was obtained.

[0024] In the technical solution of this invention, the preparation of the biostimulant composite microsphere carrier is first carried out by reacting the multidentate chelating agent 2-phosphonobutane-1,2,4-tricarboxylic acid with Al 3+ Ce 3+ Yb 3+ A thermodynamically stable polynuclear metal complex is formed, whose carboxyl / phosphonic acid groups effectively inhibit the hydrolysis and precipitation of metal ions. Subsequently, in a hexadecyltrimethylammonium bromide micelle template, the metal complex undergoes a co-condensation reaction with the silanol groups generated from the hydrolysis of tetraethyl orthosilicate. Under ammonia catalysis, a Si-O-Si framework is gradually formed, while metal ions in the metal complex are embedded into the silica network through MO-Si covalent bonds. Finally, calcination removes the organic components, achieving atomically dispersed doped hollow mesoporous silica with ternary metals. 3+ Doping imparts a positive charge to the carrier surface, creating an electrostatic attraction with the negatively charged seaweed extract; Ce 3+ / Ce 4+ The empty orbitals of the algae form coordination bonds with the phenolic hydroxyl groups of humic acid, utilizing this interaction to achieve the adsorption and binding of seaweed extract and humic acid. Furthermore, the Al-O-Ce bonds inhibit mesopore shrinkage, maintaining a uniform and stable mesopore size. 3+ The radius adaptability can alleviate Al 3+ With Ce 3+ The lattice mismatch leads to the formation of a thermally stable mesoporous structure, Yb 3+ Able to enable Al 3+ and Ce 3+Uniform dispersion within mesoporous silica helps enhance the adsorption and binding of biostimulants. For example... Figure 1 The image shows a SEM image of the biostimulant composite microsphere carrier prepared in this invention. It can be observed that the surface of the biostimulant composite microsphere carrier is smooth and flat.

[0025] Preferably, the biostimulant composite microsphere carrier is modified by grafting with 3-aminopropyltriethoxysilane.

[0026] The invention team discovered through experiments that the sustained-release performance of the prepared biostimulant composite microsphere carrier significantly decreased after exposure to external forces (such as extrusion and stirring). Further research revealed that this problem is closely related to the interaction between the interface of the biostimulant composite microsphere carrier and chitosan. When the sustained-release biostimulant encounters external force, the chitosan on the surface of the biostimulant composite microsphere carrier easily detaches. To further address this issue, the invention modifies the surface of the biostimulant composite microsphere carrier by grafting 3-aminopropyltriethoxysilane onto its surface, thus amylating it. The aminated biostimulant composite microsphere carrier can participate in the subsequent chitosan cross-linking reaction, thereby chemically binding the chitosan layer to the biostimulant composite microsphere carrier and enhancing the binding force, thereby solving the problem of decreased sustained-release performance of the biostimulant under external force.

[0027] A sustained-release biostimulant was prepared by the method described above.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. It enables the slow and continuous release of biostimulants, allowing them to exert a long-lasting effect throughout the plant's growth cycle, reducing the number of applications, lowering labor intensity and costs, and meeting the needs of plant growth and development.

[0030] 2. The slow-release structure effectively protects the formation of biostimulants, reduces degradation by external factors such as soil microorganisms, prolongs the activity cycle, and improves their stability and bioavailability, reducing the loss and waste of active ingredients and improving the effect of use.

[0031] 3. By grafting the biostimulant composite microsphere carrier with 3-aminopropyltriethoxysilane, it is chemically bonded to the chitosan layer, enhancing the interaction between the two and preventing the decrease in sustained-release performance caused by chitosan detachment under external force, thus ensuring stable sustained-release effect. Attached Figure Description

[0032] Figure 1 This is a SEM image of the biostimulant composite microsphere carrier prepared in this invention. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1: A method for preparing a sustained-release biostimulant, comprising the following steps:

[0035] Step 1: Weigh 0.5g aluminum nitrate, 0.3g cerium nitrate and 0.2g ytterbium chloride, dissolve them together in 200mL deionized water, and stir until completely dissolved to obtain a mixed solution; then add 1.0g 2-phosphonobutane-1,2,4-tricarboxylic acid to the mixed solution, raise the temperature of the system to 60℃, and continue stirring for 2h to obtain a metal-organic complex solution.

[0036] Mix 50 mL of ethanol with 50 mL of deionized water, then add 0.8 g of hexadecyltrimethylammonium bromide. Stir to disperse evenly, then add 5 mL of concentrated ammonia. Place the mixture in an ultrasonic instrument and sonicate for 15 min until completely dissolved. Then, add the prepared organometallic complex solution and 10 mL of tetraethyl orthosilicate solution (concentration 0.5 g / mL) sequentially. Control the system temperature at 40 °C and keep the reaction at this temperature for 4 h. After the reaction is complete, centrifuge (8000 r / min, 10 min), collect the precipitate, wash it three times alternately with deionized water and ethanol, dry it at 60 °C for 12 h, place it in a muffle furnace, raise the temperature to 450 °C at a rate of 5 °C / min, and calcine for 3 h to obtain the biostimulant composite microsphere carrier.

[0037] Weigh 5g of biostimulant composite microsphere carrier, add 300mL of 3% (w / w) 3-aminopropyltriethoxysilane ethanol solution, stir and react at 50℃ for 3h, centrifuge after reaction, wash 3 times with ethanol, dry at 60℃ for 8h to complete grafting modification treatment, and obtain aminated biostimulant composite microsphere carrier.

[0038] Step 2: Weigh 2g of brown algae and homogenize it into a paste using a tissue homogenizer. First, add 50mL of deionized water, then add 0.5g of cellulase and 0.25g of pectinase, stir well, and enzymatically hydrolyze at 45℃ for 4h. After that, place the enzymatic hydrolysate in a vacuum drying oven and dry it at 60℃ to constant weight. Grind it into powder to obtain seaweed extract.

[0039] Weigh 1.0g of seaweed extract and 2.8g of humic acid, add them together to 150mL of phosphate buffer (concentration 0.05mol / L, pH=7.0), and stir magnetically at 30℃ for 30min until completely dissolved to obtain a biostimulant solution.

[0040] Step 3: Weigh 2g of aminated biostimulant composite microsphere carrier, add it to 100mL of biostimulant solution, place it in a constant temperature water bath shaker at 30℃, and oscillate at 150r / min for 16h for impregnation and adsorption; after adsorption, separate the solid product by centrifugation (6000r / min, time 8min) to obtain the sustained-release biostimulant intermediate.

[0041] Step 4: Weigh 2g of chitosan and add it to 150mL of 2% acetic acid solution. Stir magnetically at 30℃ for 1h until completely dissolved. Then add 0.5mL of Tween-80 to the solution and continue stirring for 30min to ensure uniform mixing, thus obtaining the chitosan solution.

[0042] Step 5: Add 1.5g of the sustained-release biostimulant intermediate to the above 150mL chitosan solution, place it in an ultrasonic instrument, and sonicate for 20min at a power of 300W and a frequency of 40kHz. Then add 1.5mL of 25% glutaraldehyde solution, adjust the pH to 8.0, and magnetically stir the reaction at 30℃ for 2.5h. After the reaction is completed, centrifuge (8000r / min, 10min), collect the precipitate, wash it with deionized water until neutral, and then place it in a vacuum drying oven and dry it at 50℃ for 12h to obtain the sustained-release biostimulant.

[0043] Example 2: A method for preparing a sustained-release biostimulant, comprising the following steps:

[0044] Step 1: The preparation of the aminated biostimulant composite microsphere carrier is the same as in Example 1.

[0045] Step 2: Weigh 2g of brown algae and homogenize it into a paste using a tissue homogenizer. First, add 50mL of deionized water, then add 0.5g of cellulase and 0.25g of pectinase, stir well, and enzymatically hydrolyze at 45℃ for 4h. After that, place the enzymatic hydrolysate in a vacuum drying oven and dry it at 60℃ to constant weight. Grind it into powder to obtain seaweed extract.

[0046] Weigh 1.0g of seaweed extract and 2.0g of humic acid, add them together to 150mL of phosphate buffer (concentration 0.05mol / L, pH=7.0), and stir magnetically at 30℃ for 30min until completely dissolved to obtain a biostimulant solution.

[0047] Step 3: Weigh 2g of the amino-modified biostimulant composite microsphere carrier, add it to 100mL of biostimulant solution, place it in a constant temperature water bath shaker at 30℃, and oscillate at 150r / min for 12h for impregnation and adsorption; after adsorption, separate the solid product by centrifugation (6000r / min, 8min) to obtain the sustained-release biostimulant intermediate.

[0048] Step 4: Weigh 2g of chitosan and add it to 150mL of 2% acetic acid solution. Stir magnetically at 30℃ for 1h until completely dissolved. Then add 0.5mL of Tween-80 to the solution and continue stirring for 30min to ensure uniform mixing, thus obtaining the chitosan solution.

[0049] Step 5: Add 1.5g of the sustained-release biostimulant intermediate to the above 150mL chitosan solution, place it in an ultrasonic instrument, and sonicate for 20min at a power of 300W and a frequency of 40kHz. Then add 1.5mL of 25% glutaraldehyde solution, adjust the pH to 8.0, and magnetically stir the reaction at 30℃ for 1.5h. After the reaction is completed, centrifuge (8000r / min, 10min), collect the precipitate, wash it with deionized water until neutral, and then place it in a vacuum drying oven and dry it at 50℃ for 12h to obtain the sustained-release biostimulant.

[0050] Example 3: A method for preparing a sustained-release biostimulant, comprising the following steps:

[0051] Step 1: The preparation of the aminated biostimulant composite microsphere carrier is the same as in Example 1.

[0052] Step 2: Weigh 2g of brown algae and homogenize it into a paste using a tissue homogenizer. First, add 50mL of deionized water, then add 0.5g of cellulase and 0.25g of pectinase, stir well, and enzymatically hydrolyze at 45℃ for 4h. After that, place the enzymatic hydrolysate in a vacuum drying oven and dry it at 60℃ to constant weight. Grind it into powder to obtain seaweed extract.

[0053] Weigh 1.0g of seaweed extract and 2.5g of humic acid, add them together to 150mL of phosphate buffer (concentration 0.05mol / L, pH=7.0), and stir magnetically at 30℃ for 30min until completely dissolved to obtain a biostimulant solution.

[0054] Step 3: Weigh 2g of aminated biostimulant composite microsphere carrier, add it to 100mL of biostimulant solution, place it in a constant temperature water bath shaker at 30℃, and oscillate at 150r / min for 15h for impregnation and adsorption; after adsorption, separate the solid product by centrifugation (6000r / min, time 8min) to obtain the sustained-release biostimulant intermediate.

[0055] Step 4: Weigh 2g of chitosan and add it to 150mL of 2% acetic acid solution. Stir magnetically at 30℃ for 1h until completely dissolved. Then add 0.5mL of Tween-80 to the solution and continue stirring for 30min to ensure uniform mixing, thus obtaining the chitosan solution.

[0056] Step 5: Add 1.5g of the sustained-release biostimulant intermediate to the above 150mL chitosan solution, place it in an ultrasonic instrument, and sonicate for 20min at a power of 300W and a frequency of 40kHz. Then add 1.5mL of 25% glutaraldehyde solution, adjust the pH to 8.0, and react magnetically at 30℃ for 2h. After the reaction is complete, centrifuge (8000r / min, 10min), collect the precipitate, wash it with deionized water until neutral, and then place it in a vacuum drying oven and dry it at 50℃ for 12h to obtain the sustained-release biostimulant.

[0057] Example 4: A method for preparing a sustained-release biostimulant, comprising the following steps:

[0058] Step 1: The preparation of the aminated biostimulant composite microsphere carrier is the same as in Example 1.

[0059] Step 2: Weigh 2g of brown algae and homogenize it into a paste using a tissue homogenizer. First, add 50mL of deionized water, then add 0.5g of cellulase and 0.3g of pectinase, stir well, and enzymatically hydrolyze at 45℃ for 4h. After that, place the enzymatic hydrolysis product in a vacuum drying oven and dry it at 60℃ to constant weight. Grind it into powder to obtain seaweed extract.

[0060] Weigh 1.0g of seaweed extract and 3.0g of humic acid, add them together to 150mL of phosphate buffer (concentration 0.05mol / L, pH=7.0), and stir magnetically at 30℃ for 30min until completely dissolved to obtain a biostimulant solution.

[0061] Step 3: Weigh 2g of aminated biostimulant composite microsphere carrier, add it to 100mL of biostimulant solution, place it in a constant temperature water bath shaker at 30℃, and oscillate at 150r / min for 18h for impregnation and adsorption; after adsorption, separate the solid product by centrifugation (6000r / min, time 8min) to obtain the sustained-release biostimulant intermediate.

[0062] Step 4: Weigh 2g of chitosan and add it to 150mL of 2% acetic acid solution. Stir magnetically at 30℃ for 1h until completely dissolved. Then add 0.5mL of Tween-80 to the solution and continue stirring for 30min to ensure uniform mixing, thus obtaining the chitosan solution.

[0063] Step 5: Add 1.5g of the sustained-release biostimulant intermediate to the above 150mL chitosan solution, place it in an ultrasonic instrument, and sonicate for 20min at a power of 300W and a frequency of 40kHz. Then add 1.5mL of 25% glutaraldehyde solution, adjust the pH to 8.0, and react magnetically at 30℃ for 3h. After the reaction is complete, centrifuge (8000r / min, 10min), collect the precipitate, wash it with deionized water until neutral, and then place it in a vacuum drying oven and dry it at 50℃ for 12h to obtain the sustained-release biostimulant.

[0064] Example 5: A method for preparing a sustained-release biostimulant, comprising the following steps:

[0065] Step 1: The preparation of the aminated biostimulant composite microsphere carrier is the same as in Example 1.

[0066] Step 2: Weigh 2g of brown algae and homogenize it into a paste using a tissue homogenizer. First, add 50mL of deionized water, then add 0.5g of cellulase and 0.2g of pectinase, stir well, and enzymatically hydrolyze at 45℃ for 4h. After that, place the enzymatic hydrolysate in a vacuum drying oven and dry it at 60℃ to constant weight. Grind it into powder to obtain seaweed extract.

[0067] Weigh 1.0g of seaweed extract and 1.5g of humic acid, add them together to 150mL of phosphate buffer (concentration 0.05mol / L, pH=7.0), and stir magnetically at 30℃ for 30min until completely dissolved to obtain a biostimulant solution.

[0068] Step 3: Weigh 2g of the amino-modified biostimulant composite microsphere carrier, add it to 100mL of biostimulant solution, place it in a constant temperature water bath shaker at 30℃, and oscillate at 150r / min for 10h for impregnation and adsorption; after adsorption, separate the solid product by centrifugation (6000r / min, 8min) to obtain the sustained-release biostimulant intermediate.

[0069] Step 4: Weigh 2g of chitosan and add it to 150mL of 2% acetic acid solution. Stir magnetically at 30℃ for 1h until completely dissolved. Then add 0.5mL of Tween-80 to the solution and continue stirring for 30min to ensure uniform mixing, thus obtaining the chitosan solution.

[0070] Step 5: Add 1.5g of the sustained-release biostimulant intermediate to the above 150mL chitosan solution, place it in an ultrasonic instrument, and sonicate for 20min at a power of 300W and a frequency of 40kHz. Then add 1.5mL of 25% glutaraldehyde solution, adjust the pH to 8.0, and react magnetically at 30℃ for 1h. After the reaction is complete, centrifuge (8000r / min, 10min), collect the precipitate, wash it with deionized water until neutral, and then place it in a vacuum drying oven and dry it at 50℃ for 12h to obtain the sustained-release biostimulant.

[0071] Comparative Example 1

[0072] The difference between Comparative Example 1 and Example 1 is that aluminum nitrate is not added in step 1.

[0073] Comparative Example 2

[0074] The difference between Comparative Example 2 and Example 1 is that cerium nitrate is not added in step 1.

[0075] Comparative Example 3

[0076] The difference between Comparative Example 3 and Example 1 is that ytterbium chloride is not added in step 1.

[0077] Comparative Example 4

[0078] The difference between Comparative Example 4 and Example 1 is that the aminated biostimulant composite microsphere carrier in step 1 is replaced with ordinary unaminated biostimulant composite microspheres.

[0079] Comparison Example

[0080] The difference between the comparative example and Example 1 is that the aminated biostimulant composite microsphere carrier in step 1 is replaced with hollow mesoporous silica.

[0081] Performance testing:

[0082] 1. Adsorption performance test:

[0083] Humic acid adsorption test: Weigh 1.0 g of the sustained-release biostimulant intermediate prepared in each example and comparative example, add it to 50 mL of sodium pyrophosphate-sodium hydroxide desorption solution (0.05 M Na4P2O7 + 0.1 M NaOH), and sonicate at 25 °C for 16 h to completely desorb the adsorbed humic acid. Centrifuge the desorbed solution (8000 r / min, 10 min), take the supernatant, and measure the absorbance at 465 nm using a UV spectrophotometer. Calculate the concentration of humic acid in the desorption solution according to the humic acid standard curve, and then calculate the adsorption amount of humic acid. The formula is: Adsorption amount (mg / g) = (humic acid concentration in desorption solution × volume of desorption solution) / sample mass.

[0084] Seaweed extract adsorption capacity test: Weigh 1.0 g of the sustained-release biostimulant intermediate prepared in each example and comparative example, add 50 mL of phosphate buffer desorption buffer (0.1 M PBS, pH 7.2, containing 0.05% Tween 80), and shake at 150 rpm for 4 hours at 25 °C. After centrifugation (8000 rpm, 15 min), take the supernatant and detect it using HPLC-ELSD coupled with a TSKgel G4000PWXL column. The mobile phase was 0.1 M NaNO3 (0.8 mL / min), and the ELSD parameters were set to drift tube 45 °C and carrier gas 35 psi. The adsorption capacity was calculated based on the concentration difference of the liquid phase before and after adsorption: Q = (C0 - Cres) × V / m, unit mg / g.

[0085] 2. Anti-degradation performance test: Take 0.5g of each sample and mix it with 100g of fresh soil (containing natural microbial community). Add 50mL of deionized water to adjust the humidity to 60% and incubate at 25℃ in the dark. After 28 days, take samples, separate the residual biostimulants by ethanol extraction, and determine their content by high performance liquid chromatography. Calculate the residue rate (residue rate = determined content / initial content × 100%).

[0086] 3. External force stability test: Place 1.0g of each sample in a 250mL beaker, add 100mL of deionized water, and stir on a magnetic stirrer at 300r / min for 2h (simulating the external force in field construction operations). Then, determine the cumulative release rate after 168h according to the sustained-release performance test method. Calculate the sustained-release performance decay rate = (release rate after stirring - release rate without stirring) / release rate without stirring × 100%. The lower the decay rate, the smaller the impact of external force on the sustained-release performance and the better the stability.

[0087]

[0088] 4. Sustained-release performance test: Weigh 0.5 g of the sustained-release biostimulant samples prepared in each example and comparative example, and place them in dialysis bags. Place the dialysis bags in Erlenmeyer flasks containing 500 mL of phosphate buffer (0.05 mol / L, pH=7.0), and shake at 100 r / min in a 30℃ constant temperature water bath. Take 5 mL samples at 10 h, 24 h, and 48 h, and simultaneously add an equal volume of fresh buffer. Measure the absorbance of the sample solutions using a UV spectrophotometer, and calculate the cumulative release rate of the biostimulants (humic acid and seaweed extract) based on the standard curve.

[0089]

[0090] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a sustained-release biostimulant, characterized in that, Includes the following steps: S1. Preparation of amino-modified biostimulant composite microsphere carriers: Aluminum nitrate, cerium nitrate, and ytterbium chloride were dissolved in deionized water to obtain a mixed solution. Then, 2-phosphonobutane-1,2,4-tricarboxylic acid was added, and the mixture was heated to obtain a metal-organic complex solution. Hexadecyltrimethylammonium bromide was added to a mixed solution of ethanol and water, then concentrated ammonia was added, and the mixture was dissolved by ultrasonic oscillation. Then, a metal-organic complex solution and tetraethyl orthosilicate solution were added, and the mixture was kept at a constant temperature for reaction. After centrifugation, washing, drying and calcination, the biostimulant composite microsphere carrier was obtained. The biostimulant composite microsphere carrier was modified by grafting with 3-aminopropyltriethoxysilane to obtain an aminoated biostimulant composite microsphere carrier. S2. Dissolve seaweed extract and humic acid in phosphate buffer to obtain a biostimulant solution; S3. The aminated biostimulant composite microsphere carrier was added to the biostimulant solution for impregnation and adsorption. After separation, a sustained-release biostimulant intermediate was obtained. S4. Dissolve chitosan in acetic acid, add Tween-80, stir well to obtain chitosan solution; S5. Add the sustained-release biostimulant intermediate to the chitosan solution, disperse it evenly by ultrasonic vibration, then add glutaraldehyde crosslinking agent to react, and after centrifugation, washing and drying, the product is obtained.

2. The method for preparing a sustained-release biostimulant according to claim 1, characterized in that, In step S2, the preparation method of the seaweed extract includes the following steps: Brown or red algae are added, crushed, and then enzymatically hydrolyzed with cellulase and pectinase, followed by drying to obtain the final product.

3. The method for preparing a sustained-release biostimulant according to claim 2, characterized in that, The mass ratio of cellulase to pectinase is 5:2 to 3.

4. The method for preparing a sustained-release biostimulant according to claim 1, characterized in that, In step S2, the mass ratio of seaweed extract to humic acid is 2:3 to 6.

5. The method for preparing a sustained-release biostimulant according to claim 1, characterized in that, In step S3, the impregnation and adsorption time is 10 to 18 hours.

6. The method for preparing a sustained-release biostimulant according to claim 1, characterized in that, In step S5, the crosslinking reaction time is 1 to 3 hours.

7. A sustained-release biostimulant, characterized in that, It is prepared by the method described in any one of claims 1 to 6.

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