Coated slow-release solid water-soluble fertilizer as well as preparation method and application thereof

Abstract

The invention discloses a coated slow-release solid water-soluble fertilizer as well as a preparation method and application thereof. The coated slow-release solid water-soluble fertilizer comprises the following components in parts by weight: 15-20 parts of a nitrogen source, 8-12 parts of a phosphorus source, 15-25 parts of a potassium source, 3-8 parts of humic acid and 10-15 parts of charcoal powder, the composite material comprises the following components in parts by weight: 0.5-1.5 parts of functional microorganisms, 1-2 parts of microbial metabolite, 2-5 parts of seaweed extract and 5-8 parts of chitosan-gelatin composite material. The functional microorganisms are bacillus subtilis, bacillus licheniformis and azospirillum which are adsorbed on the charcoal powder. The coated slow-release solid water-soluble fertilizer provided by the invention has the effects of supplying nutrients and preventing and treating soil-borne diseases, achieves multiple effects by one fertilizer, and can improve the crop nutrient utilization rate, inhibit the soil-borne diseases and promote the diversity of soil microorganisms.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizers, and more particularly to a coated slow-release solid water-soluble fertilizer and a preparation method and application thereof. Background Art

[0002] Soil-borne diseases refer to pathogens such as fungi, bacteria, nematodes and viruses that live in the soil with diseased remains and attack crops from the roots or stems when conditions are right. Soil-borne diseases are an important factor restricting agricultural production and seriously affect crop yield and quality. Solid water-soluble fertilizers provide sufficient nutrition, enhance crop resistance, and reduce the occurrence of soil-borne diseases. At the same time, they are increasingly valued by agricultural growers because they can improve fertilizer utilization and promote ecological environmental protection. However, traditional solid water-soluble fertilizers often use chemical control methods. Although they can control soil-borne diseases to a certain extent, long-term use can easily lead to soil ecological imbalance, increased pathogen resistance, and adverse effects on the environment and human health.

[0003] As a new type of fertilizer, microbial fertilizer contains specific living microorganisms, which increase the nutrient supply of crops or promote crop growth through their life activities, increase yield, improve the quality of crops and the agricultural ecological environment. However, the activity of microorganisms is easily affected by environmental factors, and the nutrient release rate is difficult to synchronize with the needs of crops, so it is necessary to prepare it in the form of slow-release compound fertilizer. Chinese invention patent CN 107011071A discloses a slow-release microbial compound fertilizer and a preparation method, but the coating material of the patent adopts the traditional combination of gelatin and polyvinyl alcohol, which has limited functionality and environmental protection, and has not been studied in depth for the prevention and control of soil-borne diseases such as bacterial wilt and wilt. For this reason, it is urgently needed to develop a slow-release microbial compound fertilizer that can both promote the growth of crops and prevent and control soil-borne diseases of crops. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a coated slow-release solid water-soluble fertilizer and a preparation method thereof and application of the coated slow-release solid water-soluble fertilizer provided by the present invention.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions:

[0006] A coated slow-release solid water-soluble fertilizer comprises the following components in parts by weight: 15-20 parts of nitrogen source, 8-12 parts of phosphorus source, 15-25 parts of potassium source, 3-8 parts of humic acid, 10-15 parts of biochar powder, 0.5-1.5 parts of functional microorganisms, 1-2 parts of microbial metabolites, 2-5 parts of seaweed extracts, and 5-8 parts of chitosan-gelatin composite materials; the functional microorganisms are Bacillus subtilis, Bacillus licheniformis and Azospirillum adsorbed on the biochar powder.

[0007] The coated slow-release solid water-soluble fertilizer provided by the present invention has the effects of both nutrient supply and prevention and treatment of soil-borne diseases, achieving multiple effects with one fertilizer, and can improve crop nutrient utilization, inhibit soil-borne diseases and promote soil microbial diversity.

[0008] Furthermore, the preparation method of the functional microorganisms is: soaking biochar powder in a mixed bacterial liquid, filtering and drying after adsorption to obtain functional microorganisms; the effective live bacteria count in the mixed bacterial liquid is 80 million to 150 million CFU / g of Bacillus subtilis, 90 million to 130 million CFU / g of Bacillus licheniformis, and 90 million to 130 million CFU / g of Azospirillum.

[0009] There must be enough functional bacteria in the mixed bacterial solution. The appropriate concentration of bacteria can help enhance the diversity of soil microorganisms, competitively exclude pathogens, reduce the occurrence of soil-borne diseases such as bacterial wilt and wilt, and improve the disease resistance and growth vitality of crops. Ordinary straw can be burned into biochar powder. Functional microorganisms use the pore structure of biochar to provide attachment sites for composite microorganisms, promoting the growth of beneficial bacteria and certain functional bacteria. The adsorption and hydrolysis of signal molecules by biochar will affect the interspecies communication of microorganisms, thereby changing the structure of soil microbial communities. The combination of biochar and composite microorganisms can promote the reproduction of beneficial microorganisms, improve the diversity and function of microorganisms, and enhance the disease resistance of crops.

[0010] Furthermore, the microbial metabolite is at least one of a lactic acid bacteria metabolite and a Streptomyces secondary metabolite.

[0011] Lactic acid bacteria produce metabolites such as lactic acid and bacteriocins, while Streptomyces can produce a variety of polysaccharides, enzymes and plant hormones. These metabolites can promote the growth of crop roots, improve stress resistance and prevent diseases and pests.

[0012] Furthermore, the preparation method of the seaweed extract comprises: alkaline hydrolyzing the seaweed, and then fermenting and degrading the seaweed using a composite microbial enzyme.

[0013] The seaweed extract obtained by fermentation and degradation contains active substances such as alginate, polysaccharides and oligosaccharides. Seaweed extract can be used as a biostimulant to improve the adaptability of crops to environmental stress, enhance their stress resistance and resistance to diseases and pests, and enhance the effect of fertilizer.

[0014] Furthermore, the composite microbial enzyme comprises 32-38 wt% of cellulase, 13-18 wt% of pectinase, 10-16 wt% of hemicellulase, 10-15 wt% of amylase and 21-27 wt% of protease.

[0015] Different microbial enzymes have their own special fermentation methods and fermentation products. During the fermentation process, these enzymes interact and promote each other to produce various beneficial fermentation substances. After the seaweed is fermented by the composite microorganisms of the present application, the extract contains a variety of plant hormones and bioactive substances such as alginic acid, amino acids, polysaccharides, etc. The activity of these substances is enhanced after fermentation, which has a significant impact on the physiological process of crops and contributes to the healthy growth of crops.

[0016] Furthermore, the nitrogen source is at least one of urea, ammonium nitrate and ammonium bicarbonate.

[0017] Urea contains up to 46% nitrogen, ammonium nitrate contains about 34% nitrogen, and ammonium bicarbonate contains about 17% nitrogen. They can be quickly absorbed by crops after being applied to the soil. The above three substances as nitrogen sources can quickly replenish the nitrogen needed by crops in the soil, increase the nutrients in the crops, and improve the quality and taste of the crops.

[0018] Furthermore, the phosphorus source is at least one of phosphorus pentoxide, diammonium phosphate, monoammonium phosphate, and ammonium polyphosphate.

[0019] The above substances are suitable for various soils and crops as phosphorus sources. They can promote crop root development and flower bud differentiation, and improve crop yield and quality.

[0020] Furthermore, the potassium source is at least one of potassium chloride, potassium sulfate, potassium nitrate and potassium oxide.

[0021] Potassium chloride is relatively cheap and has good solubility, so it is suitable for field crops that are insensitive to chloride ions, such as wheat and corn. Potassium sulfate provides sulfur in addition to potassium, so it is suitable for crops that require more sulfur. Potassium nitrate is suitable for cash crops, such as tobacco, fruits, and vegetables. Potassium oxide has a high potassium content and is suitable as a potassium source for various crops that require high potassium content.

[0022] Furthermore, the particle size of the biochar powder is 50 to 500 μm.

[0023] The size of biochar particles has a certain influence on its adsorption performance. Generally speaking, the smaller the particles, the larger the specific surface area, so the adsorption performance will be better, but too small particles will also cause too many pores and defects, affecting its adsorption performance. Biochar particles with a size of 50 to 500 μm have a pore structure suitable for composite microorganisms, providing attachment sites for composite microorganisms, and can also enhance the activity of soil microorganisms and promote the growth of beneficial bacteria and certain functional bacteria.

[0024] Furthermore, the preparation method of the chitosan-gelatin composite material comprises:

[0025] Dissolving chitosan in 2wt% to 4wt% acetic acid solution to prepare a chitosan solution;

[0026] Dissolving gelatin in water to make it swell, and preparing a gelatin solution with a mass fraction of 1% to 10%;

[0027] The chitosan solution and the gelatin solution are mixed to obtain the chitosan-gelatin composite material.

[0028] Acetic acid solution is a weak acid, and a concentration of 2wt% to 4wt% has a suitable solubility for chitosan, and at the same time has a limited degradation effect on chitosan, which can maintain the high molecular weight of chitosan, thereby better exerting its biological activity and function. Gelatin fully swells in water, so that the prepared chitosan-gelatin composite material has a good slow-release fertilizer release effect, and improves the absorption and utilization rate of the components in the fertilizer by crops.

[0029] A method for preparing the above-mentioned coated slow-release solid water-soluble fertilizer comprises:

[0030] S1: mixing nitrogen source, phosphorus source, potassium source and humic acid powder to prepare core particles;

[0031] S2: adding functional microorganisms to microbial metabolic concentrate, adding carboxymethyl cellulose, polyethylene glycol and polyvinyl alcohol to prepare a suspended biochar mixture; spraying the suspended biochar mixture on the surface of the core particles to form a functional microbial coating;

[0032] S3: applying the chitosan-gelatin composite material to the surface of the functional microbial coating and curing it to form a coating layer;

[0033] S4: applying the seaweed extract on the surface of the coating layer to form a biostimulant coating to obtain a coated slow-release solid water-soluble fertilizer.

[0034] The coated slow-release solid water-soluble fertilizer of the present application includes a four-layer structure of core particles, functional microbial coating, coating layer and biostimulant coating from the inside to the outside. The core particles in the innermost layer can reduce nutrient loss and improve the long-term utilization rate of fertilizers. Among them, humic acid comes from organic matter such as weathered coal and lignite. Humic acid can form a stable complex with nitrogen, phosphorus and potassium elements, which is conducive to the slow release of nutrients and continuous absorption by crops, increases the absorption capacity of crops for nutrients such as nitrogen, phosphorus and potassium, promotes crop growth, and reduces nutrient loss. The functional microbial coating has an antibacterial effect, wherein carboxymethyl cellulose and polyethylene glycol make the suspended biochar mixture have good stability, and polyvinyl alcohol increases the bonding ability of the suspended mixture. The main function of the coating layer is to protect the inner layer components, control the release rate, and improve the fertilization effect. The functional microbial layer is located between the core particles and the coating layer, which can effectively resist the interference of the external environment on the functional microorganisms. Seaweed extract as a biostimulant coating can increase the granular structure of the coating layer in the outermost layer. The large pores between the granules are well supplied with oxygen, which can promote the activity of microorganisms inside the coating layer. In addition, the biostimulant coating can also promote crop growth and improve crop stress resistance, and can enhance the activity of various beneficial microorganisms in the soil, thereby enhancing crop stress resistance and resistance to pests and diseases, and enhancing the effect of fertilizers. The coated slow-release solid water-soluble fertilizer gradually decomposes and releases nutrients from the outer layer to the inner layer. On the one hand, it can continuously supply nutrients to crops, so that the internal nutrient release rate is synchronized with crop demand. On the other hand, it can gather beneficial microorganisms inside the coated fertilizer and in the soil, which has the effect of regulating microorganisms.

[0035] Furthermore, the moisture content of the core particles is lower than 2%.

[0036] The lower moisture content of the core particles can prevent the internal nutrients of the coated slow-release solid water-soluble fertilizer from being released too quickly, which is conducive to the slow release of nutrients and continuous absorption by crops, increasing the long-term absorption of nutrients such as nitrogen, phosphorus and potassium by crops, reducing nutrient loss, and improving the utilization rate of nutrients by crops.

[0037] An application of the above-mentioned coated slow-release solid water-soluble fertilizer in the supply of crop nutrition and the prevention and control of soil-borne diseases.

[0038] The present application utilizes sustained-release coating technology to organically combine humic acid, functional microorganisms, microbial metabolites and seaweed extracts, which can provide sufficient nutrient supply for crops. The functional microorganisms therein have significant effects on the prevention and control of soil-borne diseases, and can also enhance the diversity of beneficial microorganisms in the soil and improve the ability of crops to resist diseases, thus achieving the goal of one fertilizer with multiple effects.

[0039] Furthermore, the crops include at least one of pepper, tomato, cucumber, corn and eggplant.

[0040] Experiments have shown that the coated slow-release solid water-soluble fertilizer of the present invention has good yield-increasing and disease-resistance capabilities in peppers, tomatoes, cucumbers, corn, and eggplants. The fertilizer of the present application contains nutrients such as nitrogen, phosphorus, and potassium that peppers, tomatoes, cucumbers, corn, and eggplants usually need, and the fertilizer of the present application has a preventive and control effect on common pathogens in soil-borne diseases, and can be used in a variety of crops.

[0041] Furthermore, the soil-borne diseases include bacterial wilt and / or fusarium wilt.

[0042] Bacterial wilt, as a disease that widely affects a variety of crops, is caused by pathogens such as Pseudomonas solanacearum; wilt, also known as blight, is caused by pathogens such as Fusarium oxysporum. The Bacillus subtilis and Bacillus licheniformis in the functional microorganisms of this application can secrete antibiotics, enzymes and growth-promoting substances, effectively inhibiting the growth of soil-borne pathogens. Azospirillum provides an available nitrogen source through nitrogen fixation, creating more favorable nutrient conditions for plant growth. The three beneficial bacteria combined with biochar powder can synergistically enhance the diversity of soil microorganisms, competitively exclude pathogens of bacterial wilt and wilt, and improve the disease resistance of crops.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. The coated slow-release solid water-soluble fertilizer provided by the present invention has the effects of both nutrient supply and prevention and treatment of soil-borne diseases, achieving multiple effects with one fertilizer, and can improve crop nutrient utilization, inhibit soil-borne diseases and promote soil microbial diversification. It is beneficial to maintain the health of soil ecology, and the fertilizer efficiency is significantly increased. Specifically, humic acid, functional microorganisms, microbial metabolites and seaweed extracts are organically combined using slow-release coating technology to achieve a comprehensive improvement in fertilizer utilization, plant stress resistance and soil health. The fertilizer of the present application can sustainably release nutrients such as nitrogen, phosphorus and potassium during crop growth, reduce nutrient losses, and improve fertilizer utilization efficiency; functional microorganisms and their metabolites effectively enhance plant disease resistance and stress resistance by inhibiting pathogens, decomposing organic matter and improving rhizosphere microbial communities; seaweed extracts, as biostimulants, promote plant growth and improve resistance. In addition, humic acid and biochar powder optimize soil structure, enhance water and fertilizer storage capacity, and further improve soil health.

[0045] 2. Functional microorganisms use the pore structure of biochar to provide attachment sites for composite microorganisms, promoting the growth of beneficial bacteria and certain functional bacteria. The adsorption and hydrolysis of signal molecules by biochar will affect the interspecies communication of microorganisms, thereby changing the structure of soil microbial communities, promoting the reproduction of beneficial microorganisms, improving the diversity and function of microorganisms, maintaining the stability of soil ecological communities, and enhancing the disease resistance of crops. Bacillus subtilis and Bacillus licheniformis in functional microorganisms can secrete antibiotics, enzymes and growth-promoting substances, effectively inhibiting the growth of soil-borne pathogens. At the same time, Azospirillum provides available nitrogen sources through nitrogen fixation, creating more favorable nutrient conditions for crop growth. The synergy of three beneficial bacteria and biochar can enhance the diversity of soil microorganisms, competitively exclude pathogens, reduce the occurrence of soil-borne diseases such as bacterial wilt and wilt, and at the same time improve the disease resistance and growth vitality of crops. DETAILED DESCRIPTION

[0046] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Modifications or substitutions made to the methods, steps or conditions of the present invention without departing from the spirit and essence of the present invention are within the scope of protection of the present invention. Unless otherwise specified, the experimental materials, reagents, instruments, etc. used in the examples of the present invention are all commercially available; unless otherwise specified, all technical means in the examples of the present invention are conventional means well known to those skilled in the art.

[0047] Example 1

[0048] The present embodiment provides a method for preparing a coated slow-release solid water-soluble fertilizer, which is prepared using the following components: 15 kg of urea, 10 kg of monoammonium phosphate, 20 kg of potassium chloride, 5 kg of humic acid, 10 kg of biochar powder; 0.5 kg of mixed bacterial liquid; 2 kg of microbial metabolites; 3 kg of seaweed extract; and 6 kg of coating liquid.

[0049] The specific preparation method comprises the following steps:

[0050] S1. Preparation of core particles: urea, monoammonium phosphate, potassium chloride and humic acid powder are uniformly mixed, an appropriate amount of water is added, stirred into granules, and dried until the moisture content is less than 2% to obtain core particles.

[0051] S2. Preparation of functional microorganisms: Bacillus subtilis and Bacillus licheniformis are fermented by high dissolved oxygen liquid fermentation process. The fermentation medium contains glucose, peptone, corn steep liquor, pH value is 6.5-7.0, and cultured at 37°C for 48 hours. Stir and ventilate continuously to ensure rapid proliferation of bacteria, and finally obtain high concentrations of Bacillus subtilis and Bacillus licheniformis. The fermentation of Azospirillum uses sucrose as the carbon source, pH value is 6.8-7.2, and fermented at 28°C for 48-72 hours, with appropriate ventilation or slight stirring, and finally obtains highly active Azospirillum bacterial liquid. The above strain liquids are mixed to obtain a mixed bacterial liquid with effective live bacteria counts of 120 million CFU / g for Bacillus subtilis, 100 million CFU / g for Bacillus licheniformis, and 100 million CFU / g for Azospirillum. The straw is burned into 50-500μm biochar powder, and the mixed bacterial liquid is mixed and adsorbed with the sterilized biochar powder to obtain functional microorganisms.

[0052] S3. Preparation of microbial metabolites: The lactic acid bacteria fermentation medium uses glucose as the carbon source, and peptone, yeast extract and other nutrients are added. The pH value is controlled at 6.0-6.5, the fermentation temperature is 32°C, and the time is 48 hours. Maintain appropriate temperature and acidity during the fermentation process to promote the rapid growth of lactic acid bacteria and the efficient accumulation of lactic acid. During the fermentation process, lactic acid bacteria will produce metabolites such as lactic acid and bacteriocins. After the fermentation is completed, the bacteria are separated from the fermentation liquid by an industrial centrifuge or filtration equipment, and the fermentation liquid contains the metabolites of lactic acid bacteria. The fermentation liquid is further filtered using microfiltration membrane separation technology to remove residual bacteria and macromolecular impurities and purify the desired metabolites. The filtered fermentation liquid is concentrated under vacuum conditions to reduce the water content, increase the concentration of the active ingredients, and obtain a microbial metabolite concentrate.

[0053] S4. Preparation of suspended mixed solution: adding the functional microorganisms prepared in S2 to the microbial metabolite concentrate prepared in S3, and adding carboxymethyl cellulose and polyethylene glycol to suspend biochar particles, and adding polyvinyl alcohol to increase the bonding ability of the suspended mixed solution to obtain a suspended mixed solution.

[0054] S5. Functional microorganism spraying: spray the suspension mixture prepared in S4 at low temperature on the surface of the core particles prepared in S1 to form fertilizer particles with functional microorganism coating.

[0055] S6. Preparation of coating solution: Dissolve chitosan in 2% acetic acid solution, stir for 30 minutes to obtain chitosan solution; dissolve gelatin in deionized water, disperse by ultrasonic for 3 hours, and place at room temperature for 24 hours to fully swell to obtain a gelatin solution with a mass fraction of 10%. Mix the chitosan solution with the gelatin solution to obtain the coating solution of the chitosan-gelatin composite material.

[0056] S7. Slow-release coating treatment: preheat the fertilizer particles prepared in S5 at 35°C to 50°C, and then evenly spray or roll the coating liquid prepared in S6 on the surface of the functional microbial coating in a rotating drum or fluidized bed; solidify the coating by heating or drying to form a uniform coating layer.

[0057] S8. Preparation of seaweed extract: Wash the fresh seaweed, remove impurities, mince and homogenize, adjust the pH value of the homogenate, and perform pressurized alkaline hydrolysis to destroy the seaweed cell wall and release the internal components. Use a composite microbial enzyme containing 32% cellulase, 18% pectinase, 10% hemicellulase, 15% amylase, and 21% protease to ferment and degrade the seaweed after alkaline hydrolysis. The fermentation conditions are: temperature 32-37°C, pH value adjusted to about 6.5, reaction time 18-24 hours, moderate stirring to ensure full contact between the enzyme and the seaweed. Under the above conditions, the composite enzyme can efficiently decompose the seaweed cell wall to form a seaweed extract rich in nutrients and small molecules with biological activity.

[0058] S9. Biostimulant coating: The seaweed extract prepared in S8 is evenly sprayed on the surface of the coating layer formed in S7 to form a biostimulant coating to further enhance the fertilizer effect.

[0059] Example 2

[0060] The present embodiment provides a method for preparing a coated slow-release solid water-soluble fertilizer, which is prepared using the following components: 20 kg of urea, 8 kg of monoammonium phosphate, 25 kg of potassium nitrate, 8 kg of humic acid, 15 kg of biochar powder; 1 kg of mixed bacterial liquid; 1 kg of microbial metabolites; 5 kg of seaweed extract; and 8 kg of coating liquid.

[0061] The specific preparation method comprises the following steps:

[0062] S1. Preparation of core particles: urea, monoammonium phosphate, potassium nitrate and humic acid powder are uniformly mixed, an appropriate amount of water is added, stirred into granules, and dried until the moisture content is less than 2% to obtain core particles.

[0063] S2. Preparation of functional microorganisms: Bacillus subtilis and Bacillus licheniformis are fermented by high dissolved oxygen liquid fermentation process. The fermentation medium contains glucose, peptone, corn steep liquor, pH value is 6.5-7.0, and cultured at 37°C for 48 hours. Stir and ventilate continuously to ensure rapid proliferation of bacteria, and finally obtain high concentrations of Bacillus subtilis and Bacillus licheniformis. The fermentation of Azospirillum uses sucrose as the carbon source, pH value is 6.8-7.2, and fermented at 28°C for 48-72 hours, with appropriate ventilation or slight stirring, and finally obtains highly active Azospirillum bacterial liquid. The above strain liquids are mixed to obtain a mixed bacterial liquid with effective live bacterial counts of 150 million CFU / g for Bacillus subtilis, 9 million CFU / g for Bacillus licheniformis, and 13 million CFU / g for Azospirillum. The straw is burned into 50-500 μm biochar powder, and the mixed bacterial liquid is mixed and adsorbed with the sterilized biochar powder to obtain functional microorganisms.

[0064] S3. Preparation of microbial metabolites: The lactic acid bacteria fermentation medium uses glucose as the carbon source, and peptone, yeast extract and other nutrients are added. The pH value is controlled at 6.0-6.5, the fermentation temperature is 32°C, and the time is 48 hours. Maintain appropriate temperature and acidity during the fermentation process to promote the rapid growth of lactic acid bacteria and the efficient accumulation of lactic acid. During the fermentation process, lactic acid bacteria will produce metabolites such as lactic acid and bacteriocins. After the fermentation is completed, the bacteria are separated from the fermentation liquid by an industrial centrifuge or filtration equipment, and the fermentation liquid contains the metabolites of lactic acid bacteria. The fermentation liquid is further filtered using microfiltration membrane separation technology to remove residual bacteria and macromolecular impurities and purify the desired metabolites. The filtered fermentation liquid is concentrated under vacuum conditions to reduce the water content, increase the concentration of the active ingredients, and obtain a microbial metabolite concentrate.

[0065] S4. Preparation of suspended mixed solution: adding the functional microorganisms prepared in S2 to the microbial metabolite concentrate prepared in S3, and adding carboxymethyl cellulose and polyethylene glycol to suspend biochar particles, and adding polyvinyl alcohol to increase the bonding ability of the suspended mixed solution to obtain a suspended mixed solution.

[0066] S5. Functional microorganism spraying: spray the suspension mixture prepared in S4 at low temperature on the surface of the core particles prepared in S1 to form fertilizer particles with functional microorganism coating.

[0067] S6. Preparation of coating solution: Dissolve chitosan in 3% acetic acid solution, stir for 30 minutes to obtain chitosan solution; dissolve gelatin in deionized water, disperse by ultrasonic for 3 hours, and place at room temperature for 24 hours to fully swell to obtain 5% gelatin solution. Mix the chitosan solution with the gelatin solution to obtain the coating solution of the chitosan-gelatin composite material.

[0068] S7. Slow-release coating treatment: preheat the fertilizer particles prepared in S5 at 35°C to 50°C, and then evenly spray or roll the coating liquid prepared in S6 on the surface of the functional microbial coating in a rotating drum or fluidized bed; solidify the coating by heating or drying to form a uniform coating layer.

[0069] S8. Preparation of seaweed extract: Wash the fresh seaweed, remove impurities, mince and homogenize, adjust the pH value of the homogenate, and perform pressurized alkaline hydrolysis to destroy the seaweed cell wall and release the internal components. Use a composite microbial enzyme containing 38% cellulase, 13% pectinase, 16% hemicellulase, 10% amylase, and 27% protease to ferment and degrade the seaweed after alkaline hydrolysis. The fermentation conditions are: temperature 32-37°C, pH value adjusted to about 6.5, reaction time 18-24 hours, and moderate stirring to ensure full contact between the enzyme and the seaweed. Under the above conditions, the composite enzyme can efficiently decompose the seaweed cell wall to form a seaweed extract rich in nutrients and small molecules with biological activity.

[0070] S9. Biostimulant coating: The seaweed extract prepared in S8 is evenly sprayed on the surface of the coating layer formed in S7 to form a biostimulant coating to further enhance the fertilizer effect.

[0071] Example 3

[0072] The present embodiment provides a method for preparing a coated slow-release solid water-soluble fertilizer, which is prepared using the following components: 15 kg of urea, 8 kg of monoammonium phosphate, 15 kg of potassium chloride, 3 kg of humic acid, 10 kg of biochar powder; 0.5 kg of mixed bacterial liquid; 2 kg of microbial metabolites; 2 kg of seaweed extract; and 5 kg of coating liquid.

[0073] The specific preparation method comprises the following steps:

[0074] S1. Preparation of core particles: urea, monoammonium phosphate, potassium chloride and humic acid powder are uniformly mixed, an appropriate amount of water is added, stirred into granules, and dried until the moisture content is less than 2% to obtain core particles.

[0075] S2. Preparation of functional microorganisms: Bacillus subtilis and Bacillus licheniformis are fermented by high dissolved oxygen liquid fermentation process. The fermentation medium contains glucose, peptone, corn steep liquor, pH value is 6.5-7.0, and cultured at 37°C for 48 hours. Stir and ventilate continuously to ensure rapid proliferation of bacteria, and finally obtain high concentrations of Bacillus subtilis and Bacillus licheniformis. The fermentation of Azospirillum uses sucrose as the carbon source, pH value is 6.8-7.2, and ferments at 28°C for 48-72 hours, with appropriate ventilation or slight stirring, and finally obtains highly active Azospirillum bacterial liquid. The above strain liquids are mixed to obtain a mixed bacterial liquid with effective live bacterial counts of 80 million CFU / g for Bacillus subtilis, 13 million CFU / g for Bacillus licheniformis, and 9 million CFU / g for Azospirillum. The straw is burned into 50-500μm biochar powder, and the mixed bacterial liquid is mixed and adsorbed with the sterilized biochar powder to obtain functional microorganisms.

[0076] S3. Preparation of microbial metabolites: The lactic acid bacteria fermentation medium uses glucose as the carbon source, and peptone, yeast extract and other nutrients are added. The pH value is controlled at 6.0-6.5, the fermentation temperature is 32°C, and the time is 48 hours. Maintain appropriate temperature and acidity during the fermentation process to promote the rapid growth of lactic acid bacteria and the efficient accumulation of lactic acid. During the fermentation process, lactic acid bacteria will produce metabolites such as lactic acid and bacteriocins. After the fermentation is completed, the bacteria are separated from the fermentation liquid by an industrial centrifuge or filtration equipment, and the fermentation liquid contains the metabolites of lactic acid bacteria. The fermentation liquid is further filtered using microfiltration membrane separation technology to remove residual bacteria and macromolecular impurities and purify the desired metabolites. The filtered fermentation liquid is concentrated under vacuum conditions to reduce the water content, increase the concentration of the active ingredients, and obtain a microbial metabolite concentrate.

[0077] S4. Preparation of suspended mixed solution: adding the functional microorganisms prepared in S2 to the microbial metabolite concentrate prepared in S3, and adding carboxymethyl cellulose and polyethylene glycol to suspend biochar particles, and adding polyvinyl alcohol to increase the bonding ability of the suspended mixed solution to obtain a suspended mixed solution.

[0078] S5. Functional microorganism spraying: spray the suspension mixture prepared in S4 at low temperature on the surface of the core particles prepared in S1 to form fertilizer particles with functional microorganism coating.

[0079] S6. Preparation of coating solution: Dissolve chitosan in 4% acetic acid solution, stir for 30 minutes to obtain chitosan solution; dissolve gelatin in deionized water, disperse by ultrasonic for 3 hours, and place at room temperature for 24 hours to fully swell to obtain 1% gelatin solution. Mix the chitosan solution with the gelatin solution to obtain the coating solution of the chitosan-gelatin composite material.

[0080] S7. Slow-release coating treatment: preheat the fertilizer particles prepared in S5 at 40°C to 50°C, and then evenly spray or roll the coating liquid prepared in S6 on the surface of the functional microbial coating in a rotating drum or fluidized bed; solidify the coating by heating or drying to form a uniform coating layer.

[0081] S8. Preparation of seaweed extract: Wash the fresh seaweed, remove impurities, mince and homogenize, adjust the pH value of the homogenate, and perform pressurized alkaline hydrolysis to destroy the seaweed cell wall and release the internal components. Use a composite microbial enzyme containing 35% cellulase, 16% pectinase, 13% hemicellulase, 12% amylase, and 24% protease to ferment and degrade the seaweed after alkaline hydrolysis. The fermentation conditions are: temperature 32-37°C, pH value adjusted to about 6.5, reaction time 18-24 hours, moderate stirring to ensure full contact between the enzyme and the seaweed. Under the above conditions, the composite enzyme can efficiently decompose the seaweed cell wall to form a seaweed extract rich in nutrients and small molecules with biological activity.

[0082] S9. Biostimulant coating: The seaweed extract prepared in S8 is evenly sprayed on the surface of the coating layer formed in S7 to form a biostimulant coating to further enhance the fertilizer effect.

[0083] Comparative Example

[0084] A commercially available ordinary compound fertilizer with a nutrient element ratio of N:P:K=15:15:15 was selected for testing.

[0085] Experimental Example 1

[0086] Pepper seedlings with consistent growth were selected, and the test was carried out in a greenhouse. To ensure the consistency of the root growth environment, potted substrate cultivation was adopted, 10 trays were treated for each treatment, and 3 replicates were used for each treatment. The blank control group was treated without fertilization. Each embodiment and comparative example used fertilizer to mix soil for fertilization, and 20g of fertilizer was mixed into 10kg soil per tray. Other agronomic measures remained consistent. Leaf width, plant height, stem thickness, and chlorophyll content were measured 30d after fertilization. The measurement results are shown in Table 1. Different letters in the table represent different significant differences, a represents the strongest significance, and letters from a to e represent decreasing significance.

[0087] Table 1 Statistics on the growth of pepper seedlings

[0088]

[0089] From the results in Table 1, it can be seen that compared with the blank control group, the leaf width, plant height, stem thickness, and chlorophyll content of each embodiment showed a significant increasing trend. Among them, Example 2 contains functional microorganisms with a higher mass specific gravity, and the overall growth index of pepper increases most significantly. Compared with the blank control group, the leaf width, plant height, stem thickness, and chlorophyll content of Example 2 increased by 187.3%, 56.9%, 72.6%, and 16.9%, respectively; compared with the control group, the leaf width, plant height, stem thickness, and chlorophyll content of Example 2 increased by 32.3%, 14.8%, 13.1%, and 2.6%, respectively. The above results show that the coated slow-release solid water-soluble fertilizer prepared in this application has a good promoting effect on the growth of pepper seedlings, and the functional microorganisms have a greater effect on the growth of pepper seedlings.

[0090] Experimental Example 2

[0091] The number of culturable beneficial microorganisms in the rhizosphere soil of the pepper seedlings cultured in Experimental Example 1 was counted, and the statistical results are shown in Table 2. Different letters in the table represent different significant differences, a represents the strongest significance, and letters from a to e represent decreasing significance.

[0092] Table 2 Number of beneficial microorganisms that can be cultivated in the rhizosphere soil of pepper seedlings

[0093]

[0094]

[0095] From the results in Table 2, it can be seen that the fertilizers used in the examples all significantly increased the abundance of beneficial microorganisms in the rhizosphere soil of crops. Among them, Example 2 contains functional microorganisms with a higher mass specific gravity, and the number of culturable microorganisms in the rhizosphere soil of pepper seedlings is the most significant. Compared with the blank control group, the number of culturable bacteria, actinomycetes and fungi in Example 2 increased by 27.9%, 38.9%, 72.6% and 42.3%, respectively. The conventional compound fertilizer used in Comparative Example 1 did not significantly change the number of microorganisms in the rhizosphere soil of pepper seedlings compared to the blank control group.

[0096] It can be concluded that adding functional microorganisms to coated slow-release solid water-soluble fertilizers can enhance the disease resistance of plants through various mechanisms. Functional microorganisms quickly colonize in the rhizosphere of plants, occupy ecological sites, limit the living space and resources of pathogens, reduce their chances of infection, and promote the diversity of beneficial microorganisms in the roots of peppers. The increase in the diversity of microorganisms in the roots of peppers also provides a guarantee for enhancing the disease resistance of peppers. Some beneficial microorganisms can secrete antibacterial substances, such as antibiotics and enzymes, which can directly inhibit or kill pathogens and reduce the incidence of diseases. Beneficial microorganisms can activate the plant's defense system, improve its resistance to pathogens, and enhance disease resistance. The abundance of beneficial microorganisms can improve soil fertility, improve soil structure, promote the healthy growth of crops, and thus enhance their disease resistance.

[0097] Experimental Example 3

[0098] The effects of the fertilizers prepared in each embodiment and comparative example on the disease resistance of tomatoes were evaluated by field investigation. The test site was a general farmland in Zhu Village, Zengcheng, Guangzhou, and the soil type was loam. The test crop was tomato. The test set up 5 treatments, including Example 1, Example 2, Example 3, comparative example and blank control group, each with 100 plants, 5 repetitions, and 500 plants were investigated in each treatment. Regularly go to the field to observe and record the incidence of diseases throughout the growth period of tomatoes. Record the number of diseased plants in each treatment as a percentage of the total number of plants. According to the disease severity score, the disease index was calculated, and the statistical results are shown in Table 3.

[0099] Table 3 Number of diseased tomato plants

[0100]

[0101]

[0102] As can be seen from Table 3, the number of diseased tomato plants in the blank control group and the comparative example treatment accounted for 7.8% and 8.2% respectively, and the number of diseased trees in all the treatments of the examples showed a significant downward trend, among which the number of diseased plants in Example 2 accounted for the lowest, only 1.4%, and the number of diseased plants in Example 1 and Example 3 accounted for 3.4% and 3.0% respectively. The results confirmed that the treatment with the water-soluble fertilizer of the present application significantly reduced the incidence rate of diseases and the disease index, indicating that the fertilizer of the present application has the effect of enhancing the disease resistance of crops. The coated slow-release solid water-soluble fertilizer of the present application can be used for base fertilizer and topdressing, furrow application or for water-fertilizer integrated irrigation and fertilization, with a dosage of 10 to 15 kg per mu, which can significantly promote the growth of crops and reduce the spread of soil-borne diseases, and improve the stress resistance of crops.

[0103] Experimental Example 4

[0104] By measuring the effect of the fertilizer of the present invention on the quality of each part of the pepper seedlings, it is verified whether its slow-release performance can continuously and balancedly meet the nutrient requirements of crops in each growth period. The pepper pot test was carried out in a greenhouse from May to September 2024. Each pot was filled with 5kg of soil, and the soil was fertilized at a pure nitrogen rate of 180mg / kg. Two pepper seedlings were transplanted in each pot. The weight method was used to adjust the soil moisture during the culture period to keep the soil moisture content at 60% of the field water holding capacity. There are 5 treatments in total, including Example 1, Example 2, Example 3, Comparative Example and Blank Control Group, each treatment was repeated 3 times, and the weight of each part of the pepper seedlings after growth was recorded. The statistical results are shown in Table 4. Different letters in the table represent different significant differences, a represents the strongest significance, and letters from a to e represent decreasing significance.

[0105] Table 4 Weight of each part of pepper seedling

[0106]

[0107]

[0108] As shown in Table 4, different treatments have different effects on various organs and total dry weight of pepper plants. The overall performance of the dry weight of various organs of the plant is fruit>leaf stem>root. Example 2 performed best among all treatments, with the total dry matter weight being 154.8% and 60.4% higher than that of the blank control group and the comparative example. There were significant differences between the total dry matter weight of pepper and the dry matter weight of fruit in different fertilization treatments, and the overall performance was that the embodiment treatment was significantly better than the control no fertilization treatment and the comparative example treatment. The main reason is that ordinary compound fertilizers generally release a large amount of nutrients in a short period of time, but as time goes by, due to volatilization and leaching, in the later stage of growth, the nutrient supply is insufficient, and the overall growth status of the plant is lower than that of the slow-release fertilizer used in the embodiment. The coated slow-release solid water-soluble fertilizer of the present invention adopts materials and technologies for controlling and slowing the release of nutrients, which can achieve the persistent release of nutrients and maximize the utilization efficiency of fertilizers. At the same time, the organic combination of functional microorganisms, microbial metabolites and seaweed extracts broadens the source of nutrient absorption of crops and promotes the growth and yield increase of crops.

[0109] Similarly, applying the coated slow-release solid water-soluble fertilizer in the scheme of the present invention to the planting process of economic crops such as cucumbers, corn, eggplants, etc. also has a similar effect.

[0110] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, the above technical features can be freely combined without departing from the concept of the present invention, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the coverage of the claims of the present invention.

Claims

1. A coated slow-release solid water-soluble fertilizer, characterized in that: The invention comprises the following components in parts by weight: 15 to 20 parts of nitrogen source, 8 to 12 parts of phosphorus source, 15 to 25 parts of potassium source, 3 to 8 parts of humic acid, 10 to 15 parts of biochar powder, 0.5 to 1.5 parts of functional microorganisms, 1 to 2 parts of microbial metabolites, 2 to 5 parts of seaweed extracts, and 5 to 8 parts of chitosan-gelatin composite materials; the functional microorganisms are Bacillus subtilis, Bacillus licheniformis and Azospirillum adsorbed on the biochar powder.

2. The coated slow-release solid water-soluble fertilizer according to claim 1, characterized in that: The preparation method of the functional microorganisms is as follows: immersing biochar powder in a mixed bacterial solution, filtering and drying after adsorption to obtain the functional microorganisms; the effective live bacteria counts in the mixed bacterial solution are 80 million to 150 million CFU / g of Bacillus subtilis, 90 million to 130 million CFU / g of Bacillus licheniformis, and 90 million to 130 million CFU / g of Azospirillum.

3. The coated slow-release solid water-soluble fertilizer according to claim 1, characterized in that: The microbial metabolite is at least one of a lactic acid bacteria metabolite and a Streptomyces secondary metabolite.

4. The coated slow-release solid water-soluble fertilizer according to claim 1, characterized in that: The preparation method of the seaweed extract comprises: alkaline hydrolyzing the seaweed and then fermenting and degrading the seaweed using a composite microbial enzyme.

5. The coated slow-release solid water-soluble fertilizer according to claim 4, characterized in that: The composite microbial enzyme comprises 32-38 wt % of cellulase, 13-18 wt % of pectinase, 10-16 wt % of hemicellulase, 10-15 wt % of amylase and 21-27 wt % of protease.

6. The coated slow-release solid water-soluble fertilizer according to claim 1, characterized in that: The particle size of the biochar powder is 50 to 500 μm.

7. The coated slow-release solid water-soluble fertilizer according to claim 1, characterized in that: The preparation method of the chitosan-gelatin composite material comprises: Dissolving chitosan in 2wt% to 4wt% acetic acid solution to prepare a chitosan solution; Dissolving gelatin in water to make it swell, and preparing a gelatin solution with a mass fraction of 1% to 10%; The chitosan solution and the gelatin solution are mixed to obtain the chitosan-gelatin composite material.

8. A method for preparing a coated slow-release solid water-soluble fertilizer according to any one of claims 1 to 7, characterized in that: include: S1: mixing nitrogen source, phosphorus source, potassium source and humic acid powder to prepare core particles; S2: adding functional microorganisms to microbial metabolic concentrate, adding carboxymethyl cellulose, polyethylene glycol and polyvinyl alcohol to prepare a suspended biochar mixture; spraying the suspended biochar mixture on the surface of the core particles to form a functional microbial coating; S3: applying the chitosan-gelatin composite material to the surface of the functional microbial coating and curing it to form a coating layer; S4: applying the seaweed extract on the surface of the coating layer to form a biostimulant coating to obtain a coated slow-release solid water-soluble fertilizer.

9. The preparation method according to claim 8, characterized in that: The moisture content of the core particles is less than 2%.

10. Use of the coated slow-release solid water-soluble fertilizer according to any one of claims 1 to 7 in the supply of crop nutrition and the prevention and control of soil-borne diseases.

11. The use according to claim 10, characterized in that: The crops include at least one of pepper, tomato, cucumber, corn and eggplant.

12. The use according to claim 10, characterized in that: The soil-borne diseases include bacterial wilt and / or fusarium wilt.

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