A water-saving and growth-promoting seed coating agent for naked oats, its preparation method and application

Abstract

This invention belongs to the field of seed treatment technology and discloses a water-saving and growth-promoting seed coating agent for naked oats, its preparation method, and its application. The coating agent consists of, from the inside out, a biological buffer water-retaining layer, a low-dose ternary active slow-release layer, and a stress-resistant and wear-resistant film-forming layer. The inner layer uses a polysaccharide matrix and modified superabsorbent resin to construct a hydrogel micro-reservoir, physically blocking the agent and achieving water regulation. The middle layer employs a ternary compound nano-slow-release system of chemical pesticides, plant-derived substances, and biocontrol bacteria, providing broad-spectrum control of soil-borne diseases with low pesticide dosage. The outer layer combines high adhesion, wear resistance, stress resistance, and sowing fluidity. This invention addresses the characteristics of naked oat seeds—thin and smooth seed coats—and the low-temperature, dry planting environment, significantly reducing the risk of pesticide damage, improving coating adhesion and drought and cold resistance, adapting to mechanized sowing, and suitable for green production of naked oats in cold, arid northern regions.

Description

Technical Field

[0001] This invention belongs to the field of agricultural seed treatment technology, specifically relating to a water-saving and growth-promoting seed coating agent for naked oats, its preparation method and application. Targeting the characteristics of naked oat seeds—thin and smooth seed coats, and the low-temperature and arid planting environment—it can significantly reduce the risk of phytotoxicity, improve coating adhesion and drought and cold resistance, and is suitable for mechanized sowing. It is applicable to the green production of naked oats in the cold and arid regions of northern China. Background Technology

[0002] Naked oats (Avena nuda L.), also known as naked oats, are a specialty dual-purpose crop for both grain and forage in the cold, arid regions of northern my country. They are characterized by their tolerance to poor soil, strong resilience, and rich nutritional value. They are widely cultivated in Inner Mongolia, Gansu, the Bashang area of ​​Hebei, and northern Shanxi, and are extensively used in dryland agriculture, forage supply, desertification control, and aerial seeding for ecological restoration in mountainous areas. In recent years, with the increasing industrialization of naked oats, their planting scale has continuously expanded. However, many constraints exist in production, among which abiotic stresses and pest and disease damage during seed germination and seedling stages are key issues affecting yield and quality.

[0003] Seed coating technology is an important means to improve crop seedling resistance, control seedling diseases and pests, and achieve reduced pesticide use and increased efficiency. It involves coating the seed surface with a thin film containing active ingredients to achieve targeted application and sustained-release efficacy. However, naked oat seeds have unique biological characteristics that existing general-purpose seed coating agents are difficult to adapt to: First, naked oat seeds lack a protective husk, have a thin and delicate seed coat with high permeability, and high concentrations of chemicals in conventional seed coating agents can easily penetrate directly into the embryo, causing phytotoxicity, resulting in a reduction in germination rate of more than 10%, a significant increase in the rate of deformed seedlings, and seriously affecting seedling quality; Second, the smooth surface and thin waxy layer of naked oat seeds result in weak adhesion of conventional film-forming agents (such as polyvinyl alcohol and carboxymethyl cellulose), with a coating peeling rate as high as 20% or more. This not only causes loss of efficacy but also leads to poor seed flowability. Third, naked oat production areas are mostly arid and semi-arid high-altitude and cold regions. During spring sowing, they often encounter the dual stress of low temperature and drought. Existing seed coating agents mainly focus on the control of diseases and pests, lacking the active regulation function of drought and cold resistance. Seed germination is slow, seedling emergence is uneven, and seedling rate is low. In drought years, the field emergence rate is less than 60%. Fourth, naked oat seedlings are often affected by a combination of diseases such as smut, root rot, and oat cyst nematode. Conventional seed coating agents are mostly single agents or binary chemical compounds, with a single control target and limited efficacy. Moreover, the amount of chemical pesticides used is high, which does not meet the development requirements of green production of miscellaneous grains.

[0004] Currently, there are some research and patent publications related to oat seed coating agents and drought-resistant seed coating agents. For example, CN111543136A discloses a method for soaking naked oat seeds, in which naked oat seeds are soaked in a humic acid aqueous solution at 20-30℃ in the dark for 3-15 hours to obtain soaked oat seeds. Soaking naked oat seeds in humic acid aqueous solution can alleviate drought stress on naked oat seeds, thereby significantly improving the germination rate of naked oat seeds, increasing the plant height, aboveground dry matter weight, and photosynthetic efficiency of dryland naked oats, and thus increasing the yield of dryland oats. CN108684464A discloses a high-yield cultivation method for oats, which selects high-quality varieties that are drought-resistant, disease-resistant, and lodging-resistant, adopts a reasonable crop rotation system and soil preparation methods, and combines timely sowing, seedling stage and late management, including soil moisture control and fertilizer application, as well as seed treatment and disease prevention measures, to ensure healthy growth and high yield of oats. The specific seed treatment involves selecting plump, pure seeds free of mold, sun-drying them for 3-5 days before sowing, disinfecting them with 1% KMnO4 for 1-2 minutes, rinsing them thoroughly with clean water, and air-drying them naturally. Then, the seeds are treated with a mixture of 40% wettable powder and thiamethoxam suspension seed dressing agent to prevent oat smut. CN102365971B discloses a naked oat seed dressing agent and its preparation method. The weight percentage of the raw materials is as follows: thiamethoxam 15-20%; tebuconazole 0.05-0.1%; dispersant 2-7%; anti-caking agent 1-4%; suspending agent 1-6%; film-forming agent 0.1-3%; filler 1-10%; preservative 1-3%; colorant 3-5%; and the remainder is water. A water-based oat-specific seed coating agent using thiamethoxam and tebuconazole as active ingredients coats oat seeds through a suspension coating process. Utilizing the systemic properties of thiamethoxam and the bactericidal function of tebuconazole, a film is formed on the seed surface for continuous control of aphids and smut. This method boasts advantages such as high efficiency, low toxicity, ease of operation, and time and labor savings. However, this approach lacks a buffer structure designed for the thin and delicate nature of naked oat seeds. High-concentration agents directly contact the seed coat, posing a high risk of phytotoxicity. Furthermore, it lacks drought resistance and water retention capabilities, making it unsuitable for dryland planting environments. It also lacks systematic pest and disease control, offering limited functionality. Additionally, the coating film has insufficient mechanical strength and poor abrasion resistance, making it unsuitable for large-scale mechanized sowing. Moreover, under low-temperature and drought stress, its effect on seedling emergence is limited, making it unsuitable for the complex adverse conditions of high-altitude and cold dryland areas.

[0005] In addition, existing water-retaining seed coating agents generally suffer from the problem of difficulty in synergistic effect between water retention and slow release: the superabsorbent resin in the single-layer structure is prone to rupture after absorbing water and swelling, which leads to rapid release of the agent and failure to achieve long-term control; at the same time, the water-retaining material is mostly directly mixed in the coating matrix and cannot be stably fixed on the seed surface, and is easily lost with rainwater or irrigation water, resulting in a short water retention period.

[0006] Therefore, considering the seed characteristics and planting environment of naked oats, developing a water-saving and growth-promoting seed coating agent specifically for naked oats that combines low phytotoxicity, high adhesion, drought and cold resistance, and broad-spectrum control is an urgent need to improve the seedling quality of naked oats, achieve stable and increased yields, and promote green production. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned problems existing in the prior art and to provide a water-saving and growth-promoting seed coating agent for naked oats, its preparation method and application. Through the structural design of inner layer buffer water retention, middle layer slow release control, and outer layer stress resistance and wear resistance, it systematically solves the technical problems of severe pesticide damage, poor adhesion, weak stress resistance and single control of naked oat seed coating agents.

[0008] This invention provides a water-saving and growth-promoting seed coating agent specifically for naked oats. It consists of an inner biological buffer water-retaining layer, a middle low-dose ternary active slow-release layer, and an outer stress-resistant and wear-resistant film-forming layer, sequentially coating the surface of naked oat seeds from the inside out. The three layers work synergistically and complementaryly: the inner layer constructs a physical barrier and micro-reservoir system, simultaneously achieving pesticide protection and water regulation; the middle layer constructs a chemical-plant-biocontrol bacteria ternary slow-release system, achieving broad-spectrum control at low doses; and the outer layer constructs a highly adhesive and wear-resistant system, while also endowing the seeds with stress-regulating functions, making it suitable for mechanized sowing and high-altitude, cold, and arid environments.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a water-saving and growth-promoting seed coating agent for naked oats, comprising, from the inside out, an inner biological buffer water-retaining layer, a middle low-dose ternary active slow-release layer, and an outer stress-resistant and wear-resistant film-forming layer coated on the surface of naked oat seeds; by weight, the raw material composition of the inner biological buffer water-retaining layer is: 12-15 parts carboxymethyl chitosan, 0.5-1 part sodium hyaluronate, 3-5 parts chitosan oligosaccharide, 4-6 parts modified potassium polyacrylate superabsorbent resin, 2-3 parts sodium alginate, 0.5-1 part crosslinking agent, and deionized water to make up to 30-35 parts; the inner biological buffer water-retaining layer contains carboxymethyl chitosan, sodium hyaluronate, and sodium hyaluronate... Sodium hyaluronate and sodium alginate crosslink to form a continuous and dense hydrophilic polysaccharide film that adheres closely to the seed coat surface, forming a physical barrier that prevents direct contact between the middle layer of chemical agents and the seed embryo, thus reducing the risk of phytotoxicity from the root. At the same time, the polysaccharide matrix has excellent biocompatibility and will not irritate the seed coat. The superabsorbent resin fixed in the hydrogel network can quickly absorb and store soil moisture, and slowly release it during drought, forming a micro-reservoir around the seed, improving the availability of water around the seed, shortening the germination time, and increasing the emergence rate under drought conditions. Chitosan oligosaccharide, as a plant growth regulator, can induce the secretion of endogenous hormones in the seed through the seed coat, enhance seed germination vitality, and strengthen seedling resistance.

[0010] The raw material composition of the middle low-dose ternary active sustained-release layer, by weight, is as follows: 1.5-2.5 parts chemical fungicide, 1.1-1.7 parts plant-derived active ingredients, 2-4 parts biocontrol agent, 8-12 parts carboxymethyl oleoyl chitosan nanoparticles, 0.5-1 part dispersant, and deionized water to make up to 40-45 parts; wherein the chemical fungicide rapidly controls early seedling diseases, the plant-derived ingredients treat both pests and diseases and are low in toxicity and environmentally friendly, and the biocontrol agents provide long-lasting colonization and continuous control. The active ingredients complement each other's targets, resulting in synergistic effects. The amount of chemical pesticides used is reduced by more than 40% compared to conventional formulations, while the efficacy is significantly improved. The active ingredients are loaded into chitosan nanoparticles for slow release, avoiding sudden release of the pesticide and extending the duration of effectiveness throughout the seedling stage. At the same time, the nanocarrier can reduce the penetration of the pesticide into the inner layer, further reducing the risk of phytotoxicity. It can significantly reduce the amount of chemical pesticides used. The biocontrol bacteria and plant-derived components have good environmental compatibility, meeting the requirements of green production of miscellaneous grains, and have low toxicity to non-target organisms.

[0011] The outer stress-resistant and wear-resistant film-forming layer, by weight, comprises: 10-14 parts film-forming matrix, 1.5-3 parts stress-resistant active substance, 1-2 parts wear-resistant lubricant, and deionized water to make up to 20-25 parts. The compounded film-forming matrix tightly binds with the seed coat to form a continuous and tough outer film. Combined with the wear-resistant lubricant, it significantly improves the mechanical strength and wear resistance of the coating, reducing the coating shedding rate to less than 5%, meeting the requirements for transportation and mechanized sowing. The stress-resistant active substance is slowly released and absorbed by the seedlings, regulating cell physiological metabolism, enhancing the seedlings' drought and cold resistance, alleviating low-temperature drought stress, and improving seedling survival rate and seedling growth. The wear-resistant lubricant optimizes the surface fluidity of the seeds, giving the coated seeds good fluidity, preventing adhesion and blockage during mechanical sowing, and improving sowing accuracy and efficiency.

[0012] Furthermore, the modified potassium polyacrylate superabsorbent resin in the inner biological buffer water-retaining layer is a starch-grafted acrylic acid-modified potassium polyacrylate, with a deionized water absorption ratio of 300-500 times and a physiological saline water absorption ratio of 40-60 times. Compared with ordinary polyacrylate resin, the starch-grafted modification has better biocompatibility, stronger binding force with polysaccharide matrix, and better degradability, avoiding soil residue. The crosslinking agent is anhydrous calcium chloride. The sodium alginate and calcium ions crosslink in situ on the seed surface to form a three-dimensional hydrogel network, fixing the modified superabsorbent resin inside the network, forming an adsorption-storage-slow release micro-reservoir system. When the soil moisture is sufficient, the hydrogel network quickly absorbs and stores water; when the soil is dry, the stored water is slowly released, continuously supplying water for seed germination and effectively alleviating drought stress.

[0013] Furthermore, the chemical fungicide is a mixture of fludioxonil and difenoconazole at a mass ratio of (1~1.5):(0.5~1). Fludioxonil exhibits extremely high fungicidal activity against both seed-borne and soil-borne fungi, while difenoconazole has systemic activity. The combination of the two synergistically controls various fungal diseases such as smut, root rot, and damping-off. The plant-derived active ingredient is a mixture of matrine and allicin at a mass ratio of (0.8~1.2):(0.3~0.5). Matrine possesses both insecticidal and antibacterial activities, showing significant toxic effects against oat cyst nematodes and aphids. The active ingredient can inhibit a variety of pathogenic fungi and bacteria. The combination of the two supplements the control range of chemical agents while reducing dependence on chemical pesticides. The biocontrol agent is a 1:1 mass mixture of Paecilomyces lilacinus spore powder and Trichoderma harzianum spore powder. The viable count of both agents is ≥1 billion CFU / g. Paecilomyces lilacinus can parasitize nematode eggs and provide long-term control of cyst nematodes. Trichoderma harzianum controls soil-borne fungal diseases through competitive action, hyperparasitism, and induced resistance, while also promoting root growth. The synergistic effect of biocontrol agents, chemical agents, and plant-derived components can construct a rapid and long-lasting control system.

[0014] Furthermore, the carboxymethyl oleoyl chitosan nanoparticles have an average particle size of 100-200 nm and a drug loading rate of 15%-20%. The amphiphilic carboxymethyl oleoyl chitosan can self-assemble into nanoparticles, encapsulating chemical and plant-derived active ingredients internally to achieve sustained-release and controlled-release effects, thus prolonging the duration of efficacy. Simultaneously, the nanoparticles can enhance the penetration efficiency of the active ingredients, thereby strengthening the control effect. The dispersant is sodium lignosulfonate or sodium dodecylbenzenesulfonate, used to improve the stability of the suspension and prevent the active ingredients from settling and agglomerating.

[0015] Furthermore, in the outer stress-resistant and wear-resistant film layer, the film-forming matrix is ​​a mixture of hydroxypropyl methylcellulose and carboxymethyl chitosan in a mass ratio of (6~8):(4~6). Hydroxypropyl methylcellulose has good film-forming properties and high mechanical strength, while carboxymethyl chitosan has strong adhesion and can form a firm interface bond with the smooth naked oat seed coat. The film layer formed after the two are combined has strong adhesion and good toughness, effectively reducing the coating peeling rate. The stress-resistant active substance is a mixture of betaine, L-proline, and 5-aminolevulinic acid in a mass ratio of (1~2):(0.5~1):(0.2~0.5). Betaine and proline, as osmotic regulators, can enhance the osmotic pressure regulation capacity of seedling cells and strengthen drought and cold resistance; 5-ALA can increase the chlorophyll synthesis rate and antioxidant enzyme activity, alleviate the oxidative damage to seedlings caused by low temperature and drought stress, and improve the photosynthetic efficiency of seedlings; the wear-resistant lubricant is talc or fumed silica with a particle size of 2000-3000 mesh, which is filled in the film-forming matrix to improve the wear resistance of the film layer and reduce friction loss during transportation and sowing; at the same time, it improves the smoothness and fluidity of the seed surface, making it suitable for mechanized precision sowing and avoiding seed sticking and clogging.

[0016] Furthermore, the dry matter mass ratio of the inner biological buffer water-retaining layer, the middle low-dose ternary active slow-release layer, and the outer stress-resistant and wear-resistant film-forming layer is (30~35):(40~45):(20~25); after coating, the dry matter of the seed coating accounts for 2.5%~3.5% of the total mass of naked oat seeds, ensuring functionality while avoiding excessive coating thickness that could affect seed respiration.

[0017] To achieve the above objectives, the present invention also provides a method for preparing the above-mentioned water-saving and growth-promoting seed coating agent for naked oats, which employs a fluidized bed bottom spray coating process to form a three-layer structure through layer-by-layer coating, specifically including the following steps: (1) Seed pretreatment: Select naked oat seeds, remove impurities, chaff, broken and moldy seeds, obtain seeds with uniform particle size by sieving, preheat to 30~35℃, send to the material chamber of fluidized bed coating machine, and adjust parameters to make the seeds in a stable fluidized state. (2) Inner biological buffer water-retaining layer coating: Carboxymethyl chitosan, sodium hyaluronate, chitosan oligosaccharide, modified potassium polyacrylate superabsorbent resin, and sodium alginate are added to deionized water and stirred at room temperature for 2-3 hours until completely dissolved and dispersed to prepare the inner base liquid; calcium chloride is dissolved in deionized water to prepare a crosslinking liquid with a mass fraction of 1%-2%; the inner base liquid and crosslinking liquid are sprayed simultaneously using a dual-path atomization system to crosslink and solidify in situ on the seed surface to form a continuous and uniform biological buffer water-retaining layer; (3) Coating of the middle layer with low dose of ternary active sustained-release layer: Carboxymethyl oleoyl chitosan nanoparticles are dispersed in deionized water, and chemical bactericides, plant-derived active ingredients, biocontrol agents and dispersants are added in sequence. The mixture is dispersed by high-speed shearing for 15-20 min. Biocontrol agents are added and stirred evenly within 1 hour before use to obtain a middle layer coating suspension. The middle layer coating suspension is atomized and sprayed onto the inner layer surface. During the spraying process, the air inlet temperature is controlled not to exceed 32℃ to avoid inactivation of biocontrol agents. After spraying, the mixture is fluidized and dried for 5-10 min to form a dense ternary active sustained-release layer. (4) Coating the outer layer of stress-resistant and wear-resistant film: Add the film-forming matrix to deionized water and let it swell at room temperature for 12 hours until it is completely dissolved. Add the stress-resistant active substance and wear-resistant lubricant and stir evenly to obtain the outer coating liquid. Spray the outer coating liquid onto the surface of the middle layer. After spraying, heat it to 35~40℃ and fluidize and dry it for 10~15 minutes to make the film completely solidify. After cooling, the three-layer structure coated naked oat seeds are obtained.

[0018] Furthermore, in step (2), the inlet air temperature of the fluidized bed is 35~40℃, the atomization pressure is 0.2~0.3MPa, the spraying flow rate of the inner layer base liquid is 1.0~1.5mL / min, and the spraying flow rate of the crosslinking liquid is 0.3~0.5mL / min; during the coating process, the seed fluidization height is controlled at 15~20cm to ensure that each seed is evenly coated and does not stick together.

[0019] Furthermore, in step (3), the rotation speed of the high-speed shear is 8000~10000 r / min; the air inlet temperature during the spraying process is 30~32℃, the atomization pressure is 0.25MPa, and the coating liquid flow rate is 1.2~1.8mL / min; the temperature is strictly controlled to avoid the inactivation of biocontrol spores, while ensuring rapid solvent evaporation to avoid excessive seed imbibition.

[0020] Furthermore, in step (4), the air inlet temperature is 35~40℃, the atomization pressure is 0.2~0.3MPa, and the coating liquid flow rate is 1.5~2.0mL / min; the seed moisture content after drying is controlled at 8%~10% to ensure safe storage of the seeds.

[0021] This invention also provides the application of the water-saving and growth-promoting seed coating agent for naked oats in mechanized precision sowing and seedling protection and yield increase under drought stress in cold and dry farming areas in northern China. It is especially suitable for seedling protection and yield increase under drought stress with low temperature of 0~10℃ and soil relative moisture content ≤20%.

[0022] Compared with the prior art, the present invention has the following significant advantages: 1. The water-saving and growth-promoting seed coating agent for naked oats of this invention has a three-layer structure: an inner biological buffer water-retaining layer, a middle low-dose ternary active slow-release layer, and an outer stress-resistant and wear-resistant film-forming layer. The inner biological buffer water-retaining layer forms a continuous polysaccharide physical barrier, preventing direct contact between the middle layer agent and the seed embryo, reducing the risk of phytotoxicity by more than 80%. Under standard germination conditions, the seed germination rate is increased by more than 12% compared to conventional seed coating agents, with no deformed seedlings, germination vigor increased by more than 10%, and seedlings emerge uniformly. The outer compound film-forming matrix firmly bonds with the smooth seed coat, and with the addition of a wear-resistant lubricant, the coating shedding rate is reduced from more than 20% to less than 5%. At the same time, the seeds have excellent fluidity, making them suitable for mechanized precision sowing, increasing the sowing qualification rate by more than 15%, with no seed sticking or clogging, and the coating has strong adhesion, making it suitable for mechanized sowing. The inner micro-reservoir absorbs, stores, and slowly releases water, continuously supplying water for seed germination; the outer layer contains stress-resistant active substances that regulate cell osmotic pressure and the antioxidant system. Under the dual stresses of low temperature and drought, the seedling rate is increased by more than 20% compared to conventional seed coating agents, the emergence time is shortened by 2-3 days, and the root length and fresh weight of seedlings are significantly increased.

[0023] 2. The three-layer structure of the water-saving and growth-promoting seed coating agent for naked oats of this invention—comprising an inner biological buffer water-retaining layer, a middle low-dose ternary active slow-release layer, and an outer stress-resistant and wear-resistant film-forming layer—exhibits multiple synergistic effects. First, the inner physical barrier, combined with the middle nano-slow-release layer, provides dual control over the penetration of the agent into the seed embryo, minimizing phytotoxicity. Simultaneously, the inner hydrogel's water absorption and expansion does not cause the middle membrane to rupture, ensuring the stability of the slow-release system and achieving buffer-slow-release synergy. Second, the inner micro-reservoir continuously supplies water, while the outer stress-resistant factors regulate cell metabolism. Thanks, both enhance drought and cold resistance in a synergistic way from the two dimensions of water supply and cell tolerance, achieving a synergistic effect of water retention and stress resistance, which is far superior to the effect of water retention or stress resistance alone; third, the tough outer film-forming matrix protects the inner functional layer, preventing the water-retaining material in the inner layer and the active ingredients in the middle layer from falling off and being lost during transportation and sowing, ensuring the long-term effectiveness of the function, and achieving a synergistic effect of adhesion and stability; finally, the middle layer controls pests and diseases to prevent seedling damage, while the active ingredients in the inner and outer layers promote seedling growth and enhance stress resistance, comprehensively improving seedling growth and seedling survival rate.

[0024] 3. The combination of chemical fungicides, plant-derived active ingredients and biocontrol bacteria complements each other and enhances the effect. It achieves a control efficacy of over 85% against smut and root rot, and a reduction rate of over 70% against cyst nematodes. At the same time, the amount of chemical pesticides used is reduced by 40% compared with conventional formulas, and the effective period is extended by more than 30 days.

[0025] 4. Long-lasting and stable function: The three-layer structure protects the inner functional layer from loss of water-retaining materials and active ingredients; the nano-controlled release system ensures long-lasting activity in pest and disease control; the hydrogel network ensures stable water retention, with the effect lasting throughout the entire seedling stage. The preparation process is controllable and suitable for large-scale production. A fluidized bed bottom spraying process is used for layer-by-layer coating, resulting in high coating uniformity. Controllable process parameters enable large-scale continuous production and stable product quality. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein. The reagents used herein may be commercially available related products, and performance testing standards refer to industry or national standards.

[0028] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The term “and / or” as used herein includes all or any units and all combinations of one or more associated listed items.

[0029] The preparation methods for some of the materials used in the experiment are as follows: The modified potassium polyacrylate superabsorbent resin is a starch-grafted acrylic acid-modified potassium polyacrylate resin, and its preparation method is as follows: Corn starch was gelatinized in a 120℃ oven for 20 minutes, cooled, and then prepared into a 10% (w / w) starch paste under nitrogen protection. Acrylic acid monomer was added to the starch paste, and the neutralization degree of the acrylic acid was adjusted to 70%–75% with potassium hydroxide. The starch to acrylic acid mass ratio was 1:4–1:5. Ammonium persulfate (0.3%–0.5% of the monomer mass) and N,N'-methylenebisacrylamide (0.05%–0.08% of the monomer mass) were added sequentially. After stirring evenly, the mixture was heated to 55–60℃ and reacted at this temperature for 2.5–3 hours. The reaction product was then shredded, washed with ethanol, vacuum dried at 80℃, and pulverized through a 100-mesh sieve to obtain the final product. The resulting modified potassium polyacrylate superabsorbent resin had a deionized water absorption rate of 300–500 g / g and a physiological saline absorption rate of 40–60 g / g.

[0030] Carboxymethyl oleoyl chitosan nanoparticles have an average particle size of 100-200 nm and a drug loading rate of 15%-20%. They are prepared by self-assembly of amphiphilic modified chitosan, and the specific method is as follows: Chitosan with a degree of deacetylation ≥90% was dispersed in isopropanol, and a 40% sodium hydroxide solution was slowly added dropwise with stirring. The mixture was alkalized at 25°C for 2 hours. A chloroacetic acid to chitosan mass ratio of 1.2:1 was added to the isopropanol solution, and the mixture was heated to 60°C and reacted for 4 hours. After the reaction, the pH was adjusted to 7.0, and the mixture was precipitated with ethanol, washed, and vacuum dried at 60°C to obtain carboxymethyl chitosan with a carboxymethyl substitution degree of 0.8~1.0. The carboxymethyl chitosan was dissolved in deionized water, and the pH was adjusted to 8.0. A carboxymethyl chitosan to oleoyl chloride mass ratio of 3:1 was slowly added dropwise with oleoyl chloride, and the mixture was reacted at 30°C for 3 hours. After dialysis purification, the mixture was freeze-dried to obtain carboxymethyl oleoyl chitosan. The carboxymethyl oleoyl chitosan was dissolved in a phosphate buffer solution at pH 7.4 to prepare a 1% solution. An active ingredient ethanol solution was slowly added dropwise under ultrasonic dispersion, and the mixture was sonicated for another 10 minutes. The solution was then filtered through a 0.22 μm filter membrane to obtain drug-loaded nanoparticles.

[0031] Carboxymethyl chitosan was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No. 83512-85-0.

[0032] Example 1 The three-layer seed coating agent of this embodiment consists of an inner biological buffer water-retaining layer, a middle low-dose ternary active slow-release layer, and an outer stress-resistant and abrasion-resistant film-forming layer, which sequentially coat the surface of naked oat seeds from the inside out. The specific composition and preparation are as follows: Formulation composition (by mass parts): Inner biological buffer water-retaining layer (32 parts in total): 13 parts carboxymethyl chitosan, 0.8 parts sodium hyaluronate, 4 parts chitosan oligosaccharide, 5 parts modified potassium polyacrylate superabsorbent resin, 2.5 parts sodium alginate, 0.7 parts calcium chloride, and deionized water to make up to 32 parts. Middle layer low-dose ternary active sustained-release layer (43 parts in total): fludioxonil 1.2 parts, difenoconazole 0.8 parts, matrine 1.0 parts, allicin 0.4 parts, Paecilomyces lilacinus spore powder 1.25 parts, Trichoderma harzianum spore powder 1.25 parts, carboxymethyl oleoyl chitosan nanoparticles 10 parts, sodium lignosulfonate 0.6 parts, deionized water to make up to 43 parts; Outer anti-wear resistant film layer (25 parts in total): 7 parts hydroxypropyl methylcellulose, 5 parts carboxymethyl chitosan, 1.5 parts betaine, 0.8 parts L-proline, 0.3 parts 5-aminolevulinic acid, 1.5 parts talc, and deionized water to make up to 25 parts.

[0033] The dry matter ratio of the three layers is 32:43:25, and the dry weight of the coated seed coat accounts for 3.0% of the total seed weight.

[0034] A three-layer structure is formed by layering the coating material using a fluidized bed bottom spray coating process, as detailed below: (1) Seed pretreatment: Select naked oat seeds, sieve out impurities and broken grains, take uniform seeds with a particle size of 2.0~2.5mm, preheat to 32℃, weigh 1kg and send it into the material chamber of the fluidized bed coating machine, adjust the air intake to make the seed fluidization height stable at 18cm.

[0035] (2) Inner layer coating: Weigh the inner layer raw materials according to the formula, add carboxymethyl chitosan, sodium hyaluronate, chitosan oligosaccharide, superabsorbent resin and sodium alginate to deionized water, stir for 2.5h until completely dispersed to obtain the inner layer base liquid; prepare 1.5% calcium chloride crosslinking liquid; use dual-path atomizing nozzles for synchronous spraying, with an air inlet temperature of 38℃, atomization pressure of 0.25MPa, inner layer base liquid flow rate of 1.2mL / min, and crosslinking liquid flow rate of 0.4mL / min; after spraying, fluidize and dry for 5min to obtain inner layer coated seeds.

[0036] (3) Intermediate layer coating: Carboxymethyl oleoyl chitosan nanoparticles were dispersed in deionized water, and fludioxonil, difenoconazole, matrine, allicin, and sodium lignin sulfonate were added. The mixture was sheared at 10,000 r / min for 15 min. Biocontrol spore powder was added 30 min before spraying and stirred evenly to obtain an intermediate layer suspension. The air inlet temperature was adjusted to 31℃, the atomization pressure to 0.25 MPa, and the suspension flow rate to 1.5 mL / min. The suspension was then atomized and sprayed onto the inner layer surface. After spraying, the mixture was fluidized and dried at 30℃ for 8 min.

[0037] (4) Outer coating: Hydroxypropyl methylcellulose and carboxymethyl chitosan were added to deionized water and swollen for 12 hours. Betaine, proline, 5-ALA and talc were added and stirred evenly to obtain the outer coating solution. The air inlet temperature was adjusted to 38℃, the atomization pressure to 0.25MPa, and the coating solution flow rate to 1.8mL / min. After spraying, the solution was fluidized and dried at 40℃ for 12 minutes. The solution was discharged and cooled to obtain the coated seeds.

[0038] Example 2 The three-layer seed coating agent of this embodiment consists of an inner biological buffer water-retaining layer, a middle low-dose ternary active slow-release layer, and an outer stress-resistant and abrasion-resistant film-forming layer, which sequentially coat the surface of naked oat seeds from the inside out. The specific composition and preparation are as follows: Formulation composition (by mass parts): Inner biological buffer water-retaining layer (32 parts in total): 12 parts carboxymethyl chitosan, 0.5 parts sodium hyaluronate, 3 parts chitosan oligosaccharide, 6 parts modified potassium polyacrylate superabsorbent resin, 3 parts sodium alginate, 0.8 parts calcium chloride, and deionized water to make up to 32 parts. Middle layer low-dose ternary active sustained-release layer (43 parts in total): fludioxonil 1.2 parts, difenoconazole 0.8 parts, matrine 1.0 parts, allicin 0.4 parts, Paecilomyces lilacinus spore powder 1.25 parts, Trichoderma harzianum spore powder 1.25 parts, carboxymethyl oleoyl chitosan nanoparticles 10 parts, sodium lignosulfonate 0.6 parts, deionized water to make up to 43 parts; Outer anti-wear resistant film layer (25 parts in total): 7 parts hydroxypropyl methylcellulose, 5 parts carboxymethyl chitosan, 1.5 parts betaine, 0.8 parts L-proline, 0.3 parts 5-aminolevulinic acid, 1.5 parts talc, and deionized water to make up to 25 parts.

[0039] The dry matter ratio of the three layers is 32:43:25, and the dry weight of the coated seed coat accounts for 3.0% of the total seed weight.

[0040] A three-layer structure was formed by layering the fluidized bed bottom spray coating process, and the specific preparation method is the same as in Example 1.

[0041] Example 3 The three-layer seed coating agent of this embodiment consists of an inner biological buffer water-retaining layer, a middle low-dose ternary active slow-release layer, and an outer stress-resistant and abrasion-resistant film-forming layer, which sequentially coat the surface of naked oat seeds from the inside out. The specific composition and preparation are as follows: Formulation composition (by mass parts): Inner biological buffer water-retaining layer (32 parts in total): 13 parts carboxymethyl chitosan, 0.8 parts sodium hyaluronate, 4 parts chitosan oligosaccharide, 5 parts modified potassium polyacrylate superabsorbent resin, 2.5 parts sodium alginate, 0.7 parts calcium chloride, and deionized water to make up to 32 parts. Middle layer low-dose ternary active sustained-release layer (43 parts in total): fludioxonil 1.0 part, difenoconazole 0.5 part, matrine 1.2 part, allicin 0.5 part, Paecilomyces lilacinus spore powder 1.5 part, Trichoderma harzianum spore powder 1.5 part, carboxymethyl oleoyl chitosan nanoparticles 10 parts, sodium lignosulfonate 0.6 parts, deionized water to make up to 43 parts; Outer anti-wear resistant film layer (25 parts in total): 7 parts hydroxypropyl methylcellulose, 5 parts carboxymethyl chitosan, 1.5 parts betaine, 0.8 parts L-proline, 0.3 parts 5-aminolevulinic acid, 1.5 parts talc, and deionized water to make up to 25 parts.

[0042] The dry matter ratio of the three layers is 32:43:25, and the dry weight of the coated seed coat accounts for 3.0% of the total seed weight. The three-layer structure is formed by coating layer by layer using a fluidized bed bottom spray coating process, and the specific preparation method is the same as in Example 1.

[0043] Example 4 The three-layer seed coating agent of this embodiment consists of an inner biological buffer water-retaining layer, a middle low-dose ternary active slow-release layer, and an outer stress-resistant and abrasion-resistant film-forming layer, which sequentially coat the surface of naked oat seeds from the inside out. The specific composition and preparation are as follows: Formulation composition (by mass parts): Inner biological buffer water-retaining layer (32 parts in total): 13 parts carboxymethyl chitosan, 0.8 parts sodium hyaluronate, 4 parts chitosan oligosaccharide, 5 parts modified potassium polyacrylate superabsorbent resin, 2.5 parts sodium alginate, 0.7 parts calcium chloride, and deionized water to make up to 32 parts. Middle layer low-dose ternary active sustained-release layer (43 parts in total): fludioxonil 1.0 part, difenoconazole 0.5 part, matrine 1.2 part, allicin 0.5 part, Paecilomyces lilacinus spore powder 1.5 part, Trichoderma harzianum spore powder 1.5 part, carboxymethyl oleoyl chitosan nanoparticles 10 parts, sodium lignosulfonate 0.6 parts, deionized water to make up to 43 parts; Outer anti-wear resistant film layer (25 parts in total): 8 parts hydroxypropyl methylcellulose, 6 parts carboxymethyl chitosan, 2 parts betaine, 1 part L-proline, 0.5 parts 5-aminolevulinic acid, 2 parts talc, and deionized water to make up to 25 parts.

[0044] The dry matter ratio of the three layers is 32:43:25, and the dry weight of the coated seed coat accounts for 3.0% of the total seed weight. The three-layer structure is formed by coating layer by layer using a fluidized bed bottom spray coating process, and the specific preparation method is the same as in Example 1.

[0045] Comparative Example 1 This comparative example lacks an inner biological buffer water-retaining layer. Instead, the middle and outer layers are directly coated on the surface of naked oat seeds. The formulation and preparation process of the middle and outer layers are the same as in Example 1. The total dry weight of the coating accounts for 3.0% of the total seed weight.

[0046] Comparative Example 2 This comparative example uses a commercially available conventional naked oat seed coating agent with a single-layer structure. Specifically, it consists of 2 parts tebuconazole, 1 part imidacloprid, 8 parts polyvinyl alcohol, 1 part talc, and deionized water to make up the difference. It is prepared using a conventional coating process, and the dry weight of the coating accounts for 3.0% of the total seed weight.

[0047] Comparative Example 3 This comparative example lacks an outer stress-resistant and wear-resistant film layer, and only coats the inner and middle layers. The formulation and preparation process of the inner and middle layers are the same as in Example 1, and the total dry weight of the coating accounts for 3.0% of the total seed weight.

[0048] Comparative Example 4 This comparative example is a single-layer water-retaining seed coating agent. The water-retaining material, agent, and film-forming agent are mixed and coated in a single layer. The formula is as follows: 5 parts modified potassium polyacrylate superabsorbent resin, 1.2 parts fludioxonil, 0.8 parts difenoconazole, 12 parts hydroxypropyl methylcellulose, 1.5 parts talc, and deionized water is added to make up the difference. The coating is a single layer, and the dry weight of the coating accounts for 3.0% of the total seed weight.

[0049] Germination tests were conducted on the products of each embodiment and comparative example. The germination characteristics of seeds under different treatments are shown in Table 1. Table 1 shows that the germination potential and germination rate of Examples 1-4 of this invention were significantly higher than those of the comparative examples, and no deformed seedlings were observed. This indicates that the inner biological buffer layer effectively blocked the damage of the agent to the seed embryo, resulting in an extremely low risk of phytotoxicity. Specifically, the germination rate of Example 1 reached 94.7%, an increase of 3.2 percentage points compared to the blank naked seed and 16.1 percentage points compared to Comparative Example 2, demonstrating significant effectiveness. Comparative Example 1 lacked an inner layer, and the agent directly contacted the seed coat, resulting in a significant decrease in germination rate and a deformed seedling rate as high as 8.7%. This shows that the inner buffer layer is the core structure for reducing phytotoxicity. Comparative Example 2 showed the most severe phytotoxicity with the conventional seed coating agent, exhibiting the lowest germination rate and the highest deformed seedling rate. Comparative Example 4, with its single-layer water-retaining seed coating agent, also showed some phytotoxicity because the agent directly contacted the seed coat, and the superabsorbent resin absorbed water, promoting agent penetration and leading to an increased deformed seedling rate.

[0050] Table 1. Seed germination characteristics data under different treatments

[0051] The coating shedding rate was tested using the mechanical oscillation method, and the test results are shown in Table 2.

[0052] Table 2 Coating shedding rate under different treatments

[0053] As shown in Table 2, the coating peeling rates of Examples 1-4 were all below 5%, far lower than the 21.7% of Comparative Example 2, indicating that the outer anti-wear film layer significantly improved the coating adhesion and wear resistance. Among them, Example 4 had the highest content of outer film matrix and lubricant, and the lowest peeling rate, only 3.9%. Comparative Example 3 lacked an outer layer, and its peeling rate was as high as 18.6%, proving that the outer layer is the key to improving adhesion and wear resistance. Comparative Example 2 had the highest peeling rate of conventional seed coating agent, making it unsuitable for mechanized sowing. The peeling rate of the single-layer water-retaining seed coating agent in Comparative Example 4 was also relatively high, because the superabsorbent resin easily leads to a loose film structure and reduced wear resistance after absorbing water and swelling.

[0054] The water retention capacity was tested using a soil-simulated drought method. Specifically, air-dried sandy loam soil (passed through a 2mm sieve) was placed in plastic cups, 200g per cup. Ten coated seeds were sown at a depth of 2cm, and the soil was watered once until saturated. After weighing, the soil was placed in a 25℃ constant temperature incubator for natural drought. Soil moisture changes were recorded daily, and the number of days the soil moisture content within 1cm of the seeds remained above 15% was counted. Each treatment was replicated three times. The test results are shown in Table 3.

[0055] Table 3. Number of days of soil water retention under different treatments

[0056] As shown in Table 3, the water retention duration of the examples was significantly longer than that of the comparative examples. Example 2 had the highest content of superabsorbent polymer (SAP) in its inner layer, achieving a water retention period of 14.2 days, approximately three times that of the blank control, demonstrating the excellent water retention capacity of the inner micro-reservoir system. The water retention period of the single-layer water-retaining seed coating agent in Comparative Example 4 was shorter than that of the examples because the SAP in the single-layer structure easily migrates and is lost with moisture, failing to be stably fixed around the seeds, resulting in a short water retention period. In contrast, the SAP in the examples was fixed within a hydrogel network, making it less prone to loss and providing a longer-lasting water retention effect. The conventional seed coating agent in Comparative Example 2 had virtually no water retention function, and moisture was rapidly lost under drought conditions.

[0057] The product underwent stress resistance testing, and the results are shown in Table 4. Table 4 shows that under low-temperature drought stress (0~10℃, relative soil moisture content ≤20%), the germination rate and seedling growth indicators of the examples were significantly better than those of the comparative examples. Specifically, the germination rate of Example 4 reached 85.3%, an increase of 34.5 percentage points compared to the blank control and 32.9 percentage points compared to Comparative Example 2 with the conventional seed dressing agent, demonstrating that the synergistic effect of water retention and stress resistance in this invention significantly improves seedling survival under adverse conditions. Comparative Example 3 lacked an outer stress-resistant layer, resulting in a significantly lower germination rate, indicating that the outer layer of stress-resistant active substances plays an important role in improving seedling stress resistance. Comparative Example 1 lacked an inner water-retaining layer, resulting in insufficient water under drought conditions and the lowest germination rate. Comparative Example 4 only had water-retaining function and lacked stress resistance regulation, resulting in a lower germination rate than the examples, further confirming the synergistic effect of water retention and stress resistance in this application.

[0058] Table 4 Seedling growth indicators under low temperature and drought stress

[0059] Field trials of the product were conducted in dryland experimental fields with sandy loam soil, where oat smut, root rot, and cyst nematodes are prevalent annually. A randomized block design was used, with each plot measuring 20 m². 2 The study was conducted with three replicates. The incidence and disease index of root rot were investigated 50 days after sowing, the incidence of head smut was investigated at the heading stage, and the density of soil cyst nematodes was investigated at harvest. The control effect was calculated. The test results are shown in Table 5.

[0060] Table 5 Field pest and disease control effectiveness

[0061] As shown in Table 5, the control efficacy of the examples against the three pests and diseases was significantly better than that of the comparative examples. Example 3 had the highest content of biocontrol bacteria, achieving a 76.3% reduction rate against cyst nematodes. Example 1 showed the best overall control efficacy, with 87.2% control of smut, 83.5% control of root rot, and a 72.4% reduction rate against cyst nematodes, far exceeding that of the conventional seed dressing agent in Comparative Example 2. Comparative Example 2, a conventional seed dressing agent containing only chemical pesticides, had poor nematode control efficacy and a short duration of action, resulting in low overall control efficacy. Comparative Example 4, a single-layer structure agent with burst release, had a high concentration in the early stages but insufficient concentration in the later stages, resulting in poor control efficacy. Therefore, the ternary compound system of this invention achieves broad-spectrum control of fungal diseases and nematodes, and the amount of chemical pesticides used is far lower than that of conventional formulations, achieving the goal of reducing pesticide use while increasing efficiency.

[0062] In addition, the dialysis bag method was used to test the drug release performance. The specific operation was as follows: Coated seeds equivalent to 10 mg of fludioxonil were placed in a dialysis system containing 200 mL of pH 7.0 phosphate buffer, and the solution was shaken at a constant temperature of 25 °C. Samples were taken periodically to determine the concentration of fludioxonil in the solution, and the cumulative release rate was calculated.

[0063] Test results showed that in Example 1, the cumulative release rate of fludioxonil was 32.6% after 7 days and 78.5% after 28 days, exhibiting a stable and sustained release characteristic. In contrast, in Comparative Example 2, the cumulative release rate reached 68.3% after 7 days, and the release was almost complete after 28 days, indicating a significant burst release phenomenon. In Comparative Example 4, the single-layer water-retaining seed coating agent had a release rate of 75.2% after 7 days, showing an even more severe burst release. This indicates that the mid-layer nano-sustaining system effectively prolongs the duration of action of the agent and avoids the risk of burst release.

[0064] The test results from the above embodiments and comparative experiments show that the water-saving and growth-promoting seed coating agent for naked oats of the present invention, which consists of an inner biological buffer water-retaining layer, a middle low-dose ternary active slow-release layer, and an outer stress-resistant and wear-resistant film-forming layer, coated on the surface of naked oat seeds from the inside out, is significantly superior to existing technologies in terms of germination safety, coating adhesion, water retention and stress resistance, and pest and disease control. The synergistic effect of each layer effectively solves the multiple technical problems existing in naked oat seed coating agents, and has excellent application value and promotion prospects.

[0065] The preferred embodiments of the present invention have been described in detail above, and are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water-saving and growth-promoting seed coating agent specifically for naked oats, characterized in that, The inner biological buffer water-retaining layer, the middle low-dose ternary active slow-release layer, and the outer stress-resistant and wear-resistant film layer are sequentially coated on the surface of naked oat seeds from the inside out. The raw material composition of the inner biological buffer water-retaining layer by mass parts is as follows: 12-15 parts of carboxymethyl chitosan, 0.5-1 parts of sodium hyaluronate, 3-5 parts of chitosan oligosaccharide, 4-6 parts of modified potassium polyacrylate superabsorbent resin, 2-3 parts of sodium alginate, 0.5-1 parts of crosslinking agent, and deionized water to make up to 30-35 parts. The raw material composition of the middle low-dose ternary active sustained-release layer, by mass parts, is as follows: 1.5-2.5 parts of chemical bactericide, 1.1-1.7 parts of plant-derived active ingredients, 2-4 parts of biocontrol agent, 8-12 parts of carboxymethyl oleoyl chitosan nanoparticles, 0.5-1 parts of dispersant, and deionized water to make up to 40-45 parts. The outer anti-stress and wear-resistant film layer, by mass fraction, consists of: 10-14 parts film-forming matrix, 1.5-3 parts anti-stress active substance, 1-2 parts wear-resistant lubricant, and deionized water to make up to 20-25 parts.

2. The water-saving and growth-promoting seed coating agent for naked oats according to claim 1, characterized in that, The modified potassium polyacrylate superabsorbent resin in the inner biological buffer water-retaining layer is a starch-grafted acrylic acid-modified potassium polyacrylate, which has a deionized water absorption ratio of 300-500 times and a physiological saline water absorption ratio of 40-60 times; the crosslinking agent is anhydrous calcium chloride; the sodium alginate and calcium ions crosslink in situ on the seed surface to form a three-dimensional hydrogel network, which fixes the modified superabsorbent resin inside the network, forming an adsorption-storage-slow release micro-reservoir system.

3. The water-saving and growth-promoting seed coating agent for naked oats according to claim 1, characterized in that, The chemical fungicide is a mixture of fludioxonil and difenoconazole at a mass ratio of (1~1.5):(0.5~1); the plant-derived active ingredient is a mixture of matrine and allicin at a mass ratio of (0.8~1.2):(0.3~0.5); the biocontrol agent is a mixture of Paecilomyces lilacinus spore powder and Trichoderma harzianum spore powder at a mass ratio of 1:1, and the viable count of both agents is ≥1 billion CFU / g.

4. The water-saving and growth-promoting seed coating agent for naked oats according to claim 1, characterized in that, The average particle size of the carboxymethyl oleoyl chitosan nanoparticles is 100~200nm, and the drug loading rate is 15%~20%; the dispersant is sodium lignosulfonate or sodium dodecylbenzenesulfonate.

5. The water-saving and growth-promoting seed coating agent for naked oats according to claim 1, characterized in that, In the outer anti-stress and wear-resistant film layer, the film-forming matrix is ​​a compound of hydroxypropyl methylcellulose and carboxymethyl chitosan in a mass ratio of (6~8):(4~6); the anti-stress active substance is a compound of betaine, L-proline and 5-aminolevulinic acid in a mass ratio of (1~2):(0.5~1):(0.2~0.5); and the wear-resistant lubricant is talc or fumed silica with a particle size of 2000~3000 mesh.

6. The water-saving and growth-promoting seed coating agent for naked oats according to claim 1, characterized in that, The dry matter mass ratio of the inner biological buffer water-retaining layer, the middle low-dose ternary active slow-release layer, and the outer stress-resistant and wear-resistant film-forming layer is (30~35):(40~45):(20~25); after coating, the dry matter of the seed coating accounts for 2.5%~3.5% of the total mass of naked oat seeds.

7. A method for preparing a water-saving and growth-promoting seed coating agent for naked oats according to any one of claims 1 to 6, characterized in that, A three-layer structure is formed by layering the fluidized bed bottom spray coating process, specifically including the following steps: (1) Seed pretreatment: Select naked oat seeds, remove impurities, chaff, broken and moldy grains, screen and grade them, preheat to 30~35℃, and send them into the material chamber of the fluidized bed coating machine; (2) Inner biological buffer water-retaining layer coating: Carboxymethyl chitosan, sodium hyaluronate, chitosan oligosaccharide, modified potassium polyacrylate superabsorbent resin, and sodium alginate are added to deionized water and stirred until completely dissolved and dispersed to prepare the inner base liquid; calcium chloride is dissolved in deionized water to prepare a crosslinking liquid with a mass fraction of 1%~2%; the inner base liquid and crosslinking liquid are sprayed simultaneously using a dual-path atomization system to crosslink and solidify in situ on the seed surface to form a continuous biological buffer water-retaining layer; (3) Coating of the middle layer with low dose of ternary active sustained-release layer: Carboxymethyl oleoyl chitosan nanoparticles are dispersed in deionized water, and chemical bactericides, plant-derived active ingredients, biocontrol agents and dispersants are added in sequence. The mixture is sheared and dispersed at high speed for 15-20 min to obtain a uniform middle layer coating suspension. The middle layer coating suspension is atomized and sprayed onto the inner layer surface. During the spraying process, the air inlet temperature is controlled not to exceed 32℃. After the spraying is completed, the mixture is fluidized and dried for 5-10 min to form a ternary active sustained-release layer. (4) Coating the outer layer of stress-resistant and wear-resistant film: Add the film-forming matrix to deionized water, and after it swells completely, add the stress-resistant active substance and wear-resistant lubricant, and stir evenly to obtain the outer coating liquid; spray the outer coating liquid onto the middle layer surface by atomization, and after spraying, heat to 35~40℃ and fluidize and dry for 10~15 minutes. After discharge, the coated naked oat seeds are obtained.

8. The preparation method according to claim 7, characterized in that, In step (2), the inlet air temperature of the fluidized bed is 35~40℃, the atomization pressure is 0.2~0.3MPa, the spraying flow rate of the inner layer base liquid is 1.0~1.5mL / min, and the spraying flow rate of the crosslinking liquid is 0.3~0.5mL / min; during the coating process, the seed fluidization height is controlled at 15~20cm to ensure uniform coating.

9. The preparation method according to claim 7, characterized in that, In step (3), the rotation speed of the high-speed shear is 8000~10000 r / min; the air inlet temperature during the spraying process is 30~32℃, the atomization pressure is 0.25MPa, and the coating liquid flow rate is 1.2~1.8mL / min; the biocontrol agent is added to the suspension within 1 hour before spraying to avoid prolonged soaking leading to inactivation of live bacteria.

10. The application of the water-saving and growth-promoting seed coating agent for naked oats according to any one of claims 1 to 6 in the mechanized precision sowing of naked oats in cold and dry farming areas of northern China or in protecting seedlings and increasing yield under drought stress in northern China.

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