A seed pelleting agent and coating process

Abstract

This invention discloses a seed coating agent and coating process for seed pelleting, belonging to the field of seed coating technology. The seed coating agent comprises components such as a superabsorbent compound, brewer's residue, and attapulgite. The superabsorbent compound is a starch-acrylic acid-acrylamide terpolymer, formed through cross-linking with a mixture of non-degradable and degradable cross-linking agents, exhibiting both high water retention and easy penetration. This coating process, involving grafting solution preparation, mixed powder preparation, and layered coating treatment, is suitable for sowing in sandy areas of northern China during the non-rainy season. It solves problems such as seed germination due to water shortage, seedling death, premature germination preventing sowing, and nutrient deficiency, effectively improving seed germination rate, seedling survival rate, and stress resistance. It is suitable for forage planting and ecological restoration.

Description

Technical Field

[0001] This invention relates to the field of seed coating technology, and in particular to a seed pelleting agent and coating process. Background Technology

[0002] Hydrophilic colloids, as a class of organic substances that can dissolve, disperse, or swell in water, can alter the physical properties of aqueous solutions, such as thickening, emulsification, and stability. Their hydrophilic groups can bind tightly to water molecules through hydrogen bonds, and they have been widely used in various industries, including food, petrochemicals, and pharmaceuticals. With the development of agricultural technology, hydrophilic colloids and superabsorbent polymers are increasingly being applied to seed coating. These materials have a fast water absorption rate and high absorption capacity, and the absorbed water is not easily squeezed out by mechanical pressure, potentially solving the problem of water supply after seed sowing in arid regions. Among them, synthetic resin-based superabsorbent compounds, as novel functional polymer materials, have become a research hotspot in agriculture, forestry, horticulture, and desertification control due to their excellent water retention properties, providing new solutions for water-saving irrigation and improving crop germination rates.

[0003] Northern sandy areas are important regions for ecological restoration and forage cultivation in my country. However, these areas suffer from harsh climates, long non-rainy seasons, scarce rainfall, high evaporation rates, and predominantly sandy soils with extremely poor water retention. Furthermore, the soils are deficient in organic matter and trace elements, severely hindering forage cultivation and ecological restoration. Forage seeds generally have low thousand-seed weight and weak resilience. After sowing during the non-rainy season, rapid soil moisture loss often leads to insufficient seed water absorption, hindering radicle germination. Even if some seeds germinate, subsequent prolonged drought can cause bud drying or seedling withering. In addition, existing planting methods suffer from the problem of "pre-germinating seeds that cannot be sown," as prematurely germinated seeds struggle to adapt to the arid sandy environment, further increasing planting risks. Seeds used for grassland ecological restoration often face the challenge of not being able to be artificially irrigated, resulting in extremely low seed survival rates. This has become a core bottleneck for ecological restoration and livestock development in northern sandy areas.

[0004] To alleviate the above problems, existing technologies attempt to apply gelatin, common superabsorbent polymers, and other similar materials to seed coating. By coating the seed surface with a seed coating agent containing superabsorbent materials and nutrients, the aim is to improve water retention capacity and nutrient supply levels. However, existing technologies still have many key shortcomings: First, the structural design of superabsorbent materials is unreasonable, and the water absorption coefficient is difficult to meet the long-term water retention needs of sandy land. Moreover, the network constructed by a single cross-linking agent either has poor water retention durability or forms a hard shell that hinders the breakthrough of the radicle, failing to balance "continuous water retention" and "easy breakthrough". Second, the seed coating agent formulation lacks specificity, fails to optimize nutrient ratios based on the growth needs of forage grasses, and does not effectively utilize low-cost organic matter. This makes it difficult to accurately compensate for the deficiencies of sandy soils and results in high coating costs. Third, the coating process is imperfect, failing to address the core pain point of "germination before sowing". Furthermore, the process parameters have poor adaptability, easily leading to problems such as coating peeling, insufficient adhesion, or excessive thickness compressing the seeds. Fourth, the design of the stress resistance system is lacking, failing to optimize for the dual stresses of salinity and drought in sandy lands, resulting in a low survival rate of seedlings under harsh conditions.

[0005] Therefore, developing a seed pelleting agent and coating process that combines high water retention, easy penetration, nutrient synergy, strong stress resistance, and adaptability to the needs of non-rainy season sowing and ecological restoration in northern sandy areas has become an urgent technical problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a seed pelleting agent and coating process.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a seed pelleting agent comprising the following components by weight percentage: superabsorbent compound: 25%-35%, beer lees: 5%-7%, attapulgite: 20%-30%, potassium dihydrogen phosphate: 6%-10%, ammonium molybdate: 0.08%-0.12%, borax: 0.15%-0.25%, copper sulfate: 0.08%-0.12%, manganese sulfate: 0.08%-0.12%, zinc sulfate: 0.08%-0.12%, with the balance being talc powder.

[0008] Preferably, the seed coating agent further includes sodium naphthenate at 50-70 ppm based on the total weight of the seed coating agent.

[0009] Preferably, the superabsorbent compound is a starch-acrylic acid-acrylamide terpolymer, which is formed by crosslinking with a mixed crosslinking agent.

[0010] More preferably, the mixed crosslinking agent is a mixture of a non-degradable crosslinking agent and a degradable crosslinking agent.

[0011] More preferably, the non-degradable crosslinking agent is N,N'-methylenebisacrylamide, and the degradable crosslinking agent is polyethylene glycol diacrylate with an average molecular weight of ≈700; Preferably, the method for preparing the superabsorbent compound includes the following steps: (1) Add high branched starch to distilled water, heat to 85-95℃, stir for 15-25 min to obtain gelatinized starch solution; add acrylic acid to KOH aqueous solution under stirring until the pH of the system is neutral to obtain acrylic acid neutralized solution; (2) Cool the gelatinized starch solution and the acrylic acid neutralization solution to 35-45℃ and mix them. Then add acrylamide, ammonium persulfate, sodium bisulfite and mixed crosslinking agent in sequence. Stir for 8-15 min until the mixture is uniform. Keep the temperature at 38-42℃ and stir for 20-30 min to obtain the precursor of the super water-absorbing compound. (3) Pour the superabsorbent compound precursor into a tray, spread it evenly, and then send it into a channel drying device for drying. After cooling to room temperature, crush it and pass it through a 120-mesh sieve to obtain the superabsorbent compound.

[0012] More preferably, the method for preparing the superabsorbent compound includes the following steps: (1) Add high branched starch to distilled water, heat to 90°C, stir for 20 min to obtain gelatinized starch solution; add acrylic acid to KOH aqueous solution under stirring until the pH of the system is neutral to obtain acrylic acid neutralized solution; (2) After cooling the gelatinized starch solution and the acrylic acid neutralization solution to 40°C, mix them, then add acrylamide, ammonium persulfate, sodium bisulfite and mixed crosslinking agent in sequence, stir for 10 min until they are mixed evenly, keep the temperature at 40°C and stir for 25 min to obtain the precursor of the super water-absorbing compound. (3) Pour the superabsorbent compound precursor into a tray, spread it evenly, and then send it into a channel drying device for drying. After cooling to room temperature, crush it and pass it through a 120-mesh sieve to obtain the superabsorbent compound.

[0013] Preferably, in the preparation method of the superabsorbent compound, the weight ratio of high branched starch, acrylic acid, acrylamide, ammonium persulfate, sodium bisulfite and mixed crosslinking agent is 1:0.4-0.6:0.6-0.8:0.01-0.014:0.006-0.01:0.04-0.06.

[0014] More preferably, in the method for preparing the superabsorbent compound, the weight ratio of high branched starch, acrylic acid, acrylamide, ammonium persulfate, sodium bisulfite and mixed crosslinking agent is 1:0.5:0.6:0.012:0.008:0.05.

[0015] Preferably, the weight ratio of high amylopectin to distilled water in (1) is 1:8-12.

[0016] More preferably, the weight ratio of high amylopectin to distilled water in (1) is 1:10.

[0017] Preferably, the concentration of the KOH aqueous solution in (1) is 20-40 wt%.

[0018] More preferably, the concentration of the KOH aqueous solution in (1) is 30 wt%.

[0019] Preferably, in the mixed crosslinking agent in (2), the weight ratio of non-degradable crosslinking agent to degradable crosslinking agent is 4-7:1-3.

[0020] More preferably, in the mixed crosslinking agent in (2), the weight ratio of non-degradable crosslinking agent to degradable crosslinking agent is 7:3.

[0021] Furthermore, the present invention also provides a coating process for a seed coating agent, comprising the following steps: S1. Add the superabsorbent compound to distilled water and stir until dissolved to obtain a grafting solution for later use; add the superabsorbent compound, brewer's residue, attapulgite, potassium dihydrogen phosphate, sodium naphthenate, ammonium molybdate, borax, copper sulfate, manganese sulfate, zinc sulfate, and talc to a double-helix conical mixer and stir at 200-300 r / min for 20-30 min to obtain a seed pelleting agent for later use; S2. Add attapulgite clay, talc powder and grafting solution to a high-speed mixer and stir at 800-1000 r / min for 10-20 min to obtain a mixed powder for later use. S3. Add the seeds to the water chestnut-type coating pan and stir at 30-40 r / min. Spray the grafting solution with a pneumatic spray gun. While spraying the grafting solution, add the mixed powder. Control the addition time of the mixed powder to 15-25 min to obtain the coated seed precursor. Take it out and dry it at 40-50℃. Then put it back into the water chestnut-type coating pan and continue to spray the grafting solution. At the same time, add the seed pelleting agent until the seed weight increases by 13-17 times to obtain the coated seeds. S4. Continue to add talcum powder to the water chestnut coating pan and stir until the surface of the coated seeds is smooth. Add pigment and stir until the color is uniform. Then dry and cool to room temperature to complete the coating process.

[0022] Preferably, the concentration of the superabsorbent compound in the grafting solution in S1 is 4.5 wt%.

[0023] Preferably, the weight ratio of attapulgite, talc, and grafting solution in S2 is 1:1:0.08-0.12.

[0024] Preferably, the weight ratio of seeds to mixed powder in S3 is 1:0.45-0.55.

[0025] Preferably, when the mixed powder is added in S3, the spraying rate of the pneumatic spray gun is 3-5 g / min, and when the seed pelleting agent is added, the spraying rate is 20-60 g / min.

[0026] Preferably, the addition rate of the seed pelleting agent in S3 is 20-60 g / min.

[0027] Preferably, the amounts of talc and pigment added in S4 are 18%-22% and 0.4%-0.6% respectively, based on the weight of the seeds in S3.

[0028] Preferably, the mechanism of action of the seed pelleting agent and coating process of the present invention is explained as follows: This invention addresses the core pain points of forage seeds during non-rainy season sowing in northern sandy areas through "construction of a highly absorbent functional system, synergistic effect of multiple components, and adaptation of coating technology," specifically solving the problems of "water shortage and seedling death, germination restriction due to coating, and insufficient nutrients for growth" in forage seeds. The specific solutions are as follows: The superabsorbent compound serves as the core functional carrier of the seed coating agent. The highly branched starch used in this process undergoes gelatinization, which disrupts its crystalline structure, allowing the molecular chains to expand and expose numerous hydroxyl active sites, providing a stable backbone for subsequent monomer grafting. Acrylic acid, neutralized to neutral with KOH aqueous solution, forms potassium acrylate. Its carboxyl groups (-COOK) possess strong hydrophilicity and can tightly bind to water molecules through hydrogen bonds. Meanwhile, the amide groups (-CONH2) provided by acrylamide enhance the stability of the polymer chain, preventing chain collapse after water absorption. Both are initiated by a Redox system formed from ammonium persulfate and sodium bisulfite. Free radical copolymerization occurs, grafting onto starch molecular chains to form a core structure of "starch backbone - hydrophilic side chains"; in the mixed crosslinking agent, N,N'-methylenebisacrylamide, as a non-degradable crosslinking agent, constructs a rigid framework for the three-dimensional network, ensuring that it does not disintegrate after water absorption, while polyethylene glycol diacrylate (average molecular weight ≈700), as a degradable crosslinking agent, introduces weak points in the ether bonds, which can slowly break under the action of soil microorganisms, so that the coating forms a loose structure during the seed germination period, which not only ensures high water absorption performance, but also solves the problem of traditional coating hard shells hindering the breakthrough of the radicle, achieving a balance between "water retention and stability and easy breakthrough"; The synergistic effect of the various components of the seed coating agent further enhances its functional adaptability. The three-dimensional hydrophilic network of the superabsorbent compound is the core of its continuous water retention, which can quickly absorb and lock in water after the first rain in northern sandy areas, reducing the risk of seedling death due to water shortage. Beer residue not only reduces the cost of the seed coating agent, but its rich organic matter can also slowly release nutrients, forming a nutrient supply system with potassium dihydrogen phosphate, ammonium molybdate, borax and other trace elements. The content of borax and ammonium molybdate is customized to meet the high boron requirements of forage grasses, effectively compensating for the lack of nutrients in sandy soils. Attapulgite and talc are compounded in a 1:1 ratio. The layered structure of attapulgite enhances the coating's adhesion and sand-fixing ability, while talc optimizes the coating's fluidity. The two work together to make the coating neither easy to fall off nor harden, ensuring the seeds' breathability. Sodium naphthenate, as a stress-resistance adjuvant, can enhance the drought and salt-alkali resistance of seeds and seedlings, complementing the water-retention function of the superabsorbent compound, further improving the survival rate of seedlings in sandy environments. The combined design of grafting solution and mixed powder constructs a highly efficient coating adhesion-water retention integrated system. The grafting solution is a 4.5wt% aqueous solution of a superabsorbent compound, with its concentration precisely controlled. It serves as a binding medium to ensure that the mixed powder and seed coating agent adhere tightly to the seed surface, while also supplementing water retention capacity through its own hydrophilic groups, preventing excessive evaporation of water during the coating process. During the preparation of the mixed powder, attapulgite, talc, and grafting solution are mixed at a weight ratio of 1:1:0.08-0.12. The grafting solution evenly penetrates into the gaps between the powder particles, forming moist and highly fluid particles. This avoids the flying and uneven adhesion caused by adding dry powder, and also forms a uniform thin film layer during the coating process. The porous structure formed in the inner coating stage ensures the air permeability required for seed germination, while the dense structure of the outer coating enhances water retention and sand fixation effects, achieving a structural balance of "air permeability-water retention." The coating process is implemented in stages. During the preparation of the coating precursor, the addition time of the mixed powder is controlled at 15-25 minutes, and the spraying rate of the grafting solution is 3-5 g / min. This ensures that a uniform initial coating layer forms on the surface of each seed. After drying, a stable precursor is formed, which not only fixes the initial coating structure but also avoids the accumulation of seed coating agent during subsequent coating. In the final coating stage, the seed coating agent is added at a rate of 20-60 g / min, matching the spraying rate of the grafting solution at 20-60 g / min. This allows the seed coating agent to uniformly coat the surface of the precursor under the action of the binding medium, until the seed weight increases by 13-17 times. This weight gain ratio ensures the water retention capacity and nutrient reserves of the coating layer without compressing the seed due to excessive coating thickness. The talc added in the post-treatment stage further optimizes the smoothness of the coating surface, reducing mechanical wear and drift risks during sowing. The pigments facilitate the differentiation of different coated seeds, improving the convenience of field application. This invention ensures "continuous water retention and easy breakthrough" through the molecular structure design of highly absorbent compounds. The multi-component seed coating agent achieves integrated "water retention, nutrient supply, and stress resistance" through multi-component synergy. The coating process ensures efficient implementation of the function through parameter control. All three are adapted to the environmental characteristics of low temperature, drought, poor soil, and strong winds in northern sandy areas. This allows seeds to obtain water, nutrients, and structural protection throughout the entire cycle from seed imbibition, germination, emergence, to seedling growth. Ultimately, this solves the core technical problem of sowing during the non-rainy season and improves germination rate and seedling survival rate.

[0029] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention constructs a three-dimensional network using a mixture of non-degradable and degradable crosslinking agents. The non-degradable crosslinking agent maintains a stable framework, ensuring no disintegration after water absorption and long-term water retention. The degradable crosslinking agent introduces weak points in the ether bonds, allowing the coating to form a loose structure during seed germination, preventing a hard shell from hindering radicle growth. The molecular structure of the starch-acrylic acid-acrylamide terpolymer further enhances chain segment stability, reducing collapse after water absorption and significantly improving the continuity of water supply during seed germination, solving the problem of balancing water retention and breakthrough in traditional superabsorbent materials.

[0030] 2. This invention reduces costs and provides slow-release organic matter by adding beer waste residue. The precise ratio of potassium dihydrogen phosphate and various trace elements specifically compensates for the nutrient deficiencies in sandy soils, meeting the key needs for forage growth. Sodium naphthenate and superabsorbent compounds complement each other, enhancing the drought and salt tolerance of seeds and seedlings. The combination of attapulgite and talc optimizes the coating's adhesion and flowability, preventing detachment and compaction, ensuring seed respiration and breathability, and comprehensively improving seedling survival potential.

[0031] 3. The grafting solution concentration used in this invention is scientifically controlled, possessing both binding and water-retaining functions. This is matched to the addition rate of the seed coating agent and mixed powder, preventing insufficient binding or excessive moisture and clumping. The step-by-step coating and precursor drying process ensures a uniform and dense coating layer on the surface of each seed, guaranteeing sufficient water retention and nutrient reserves without compressing the seed due to excessive coating thickness. The pretreatment design of the mixed powder reduces dry powder dispersion and uneven adhesion, improves coating uniformity and mechanical stability, and reduces losses during transportation and sowing.

[0032] 4. The technical solution of this invention specifically addresses the core pain points of sandy areas, such as drought, low rainfall, infertile soil, and high stress resistance requirements. Through the deep integration of water retention systems, nutrient supply, stress resistance design, and process adaptation, it provides stable protection for seeds throughout the entire growth cycle, from imbibition and germination to seedling growth. It improves the survival rate and yield of forage grass planting without the need for additional complex irrigation or fertilization measures, reducing planting costs and labor intensity, while also contributing to the ecological restoration of northern sandy areas and the sustainable development of animal husbandry, demonstrating broad application prospects. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0034] Preparation example: The specific preparation method of superabsorbent compounds includes the following steps: (1) Add 100g of high amylopectin to 1kg of distilled water, heat to 90℃, stir for 20min to obtain gelatinized starch solution; add 50g of acrylic acid to a 30wt% KOH aqueous solution under stirring until the pH of the system is neutral to obtain acrylic acid neutralized solution; (2) After cooling the gelatinized starch solution and the acrylic acid neutralization solution to 40°C, mix them together, and then add 60g acrylamide, 1.2g ammonium persulfate, 0.8g sodium bisulfite and 5g mixed crosslinking agent (a mixture of N,N'-methylenebisacrylamide and polyethylene glycol diacrylate in a weight ratio of 7:3) in sequence. Stir for 10min until the mixture is uniform, keep the temperature at 40°C and stir for 25min to obtain a high water-absorbing compound precursor. (3) Pour the superabsorbent compound precursor into a tray, spread it evenly, and then send it into a channel drying device for drying. After cooling to room temperature, crush it and pass it through a 120-mesh sieve to obtain the superabsorbent compound.

[0035] Comparative Preparation Example 1: The difference between Comparative Preparation Example 1 and the Preparation Example is that the mixed crosslinking agent is replaced with N,N'-methylenebisacrylamide.

[0036] Comparative Preparation Example 2: The difference between Comparative Preparation Example 2 and Preparation Example 2 is that the mixed crosslinking agent is replaced with polyethylene glycol diacrylate.

[0037] Comparative Preparation Example 3: The difference between Comparative Preparation Example 3 and the Preparation Example is that no acrylamide is added.

[0038] Comparative Preparation Example 4: The difference between Comparative Preparation Example 4 and the Preparation Example is that ammonium molybdate and borax are not added.

[0039] Example 1: A specific coating process for a seed pelleting agent, comprising the following steps: S1. Add the superabsorbent compound to distilled water and stir until dissolved to obtain a grafting solution with a concentration of 4.5 wt%, set aside; add 25% of the superabsorbent compound prepared according to the preparation example, 5% beer waste residue, 20% attapulgite, 6% potassium dihydrogen phosphate, 50 ppm sodium naphthenate, 0.08% ammonium molybdate, 0.15% borax, 0.08% copper sulfate, 0.08% manganese sulfate, 0.08% zinc sulfate, and the balance being talc powder to a double helical conical mixer, stir at 200 r / min for 20 min, and then remove to obtain a seed pelleting seed coating agent, set aside; S2. Add attapulgite clay, talc powder and grafting solution to a high-speed mixer at a weight ratio of 1:1:0.08, stir at 800 r / min for 10 min to obtain a mixed powder for later use; S3. Add 100g of seeds to a water chestnut-type coating pan and stir at 30r / min. Spray the grafting solution with a pneumatic spray gun at a spraying rate of 5g / min. While spraying the grafting solution, add 45g of mixed powder and control the addition time of the mixed powder to 15min to obtain the coated seed precursor. After taking it out, dry it at 40℃, put it back into the water chestnut-type coating pan, and continue to spray the grafting solution at a rate of 20g / min. At the same time, add the seed pelleting agent at a rate of 20g / min until the seed weight increases 13 times to obtain the coated seeds. S4. Add 18g of talcum powder to the water chestnut coating pan and continue stirring until the surface of the coated seeds is smooth. Add 0.4g of pigment and stir until the color is uniform. Then dry the seeds and cool them to room temperature to complete the coating process.

[0040] Example 2: A specific coating process for a seed pelleting agent, comprising the following steps: S1. Add the superabsorbent compound to distilled water and stir until dissolved to obtain a grafting solution with a concentration of 4.5 wt%, set aside; add 30% of the superabsorbent compound prepared according to the preparation example, 6% of brewer's waste, 25% of attapulgite, 8% of potassium dihydrogen phosphate, 60 ppm of sodium naphthenate, 0.1% of ammonium molybdate, 0.2% of borax, 0.1% of copper sulfate, 0.1% of manganese sulfate, 0.1% of zinc sulfate, and the balance of talc powder to a double helical conical mixer, stir at 260 r / min for 25 min, and then remove to obtain a seed pelleting seed coating agent, set aside; S2. Add attapulgite clay, talc powder and grafting solution to a high-speed mixer at a weight ratio of 1:1:0.1, stir at 900 r / min for 15 min to obtain a mixed powder for later use; S3. Add 100g of seeds to a water chestnut-type coating pan and stir at 35r / min. Spray the grafting solution with a pneumatic spray gun at a spraying rate of 4g / min. While spraying the grafting solution, add 50g of mixed powder and control the addition time of the mixed powder to 20min to obtain the coated seed precursor. After taking it out, dry it at 45℃, put it back into the water chestnut-type coating pan, and continue to spray the grafting solution at a rate of 40g / min. At the same time, add the seed pelleting agent at a rate of 40g / min until the seed weight increases 15 times to obtain the coated seeds. S4. Add 20g of talcum powder to the water chestnut coating pan and continue stirring until the surface of the coated seeds is smooth. Add 5g of pigment and stir until the color is uniform. Then dry the seeds and cool them to room temperature to complete the coating process.

[0041] Example 3: A specific coating process for a seed pelleting agent, comprising the following steps: S1. Add the superabsorbent compound to distilled water and stir until dissolved to obtain a grafting solution with a concentration of 4.5 wt%, set aside; add 35% of the superabsorbent compound prepared according to the preparation example, 7% beer waste residue, 30% attapulgite, 10% potassium dihydrogen phosphate, 70 ppm sodium naphthenate, 0.12% ammonium molybdate, 0.25% borax, 0.12% copper sulfate, 0.12% manganese sulfate, 0.12% zinc sulfate, and the balance talc powder to a double helical conical mixer and stir at 300 r / min for 30 min, then remove to obtain a seed pelleting seed coating agent, set aside; S2. Add attapulgite clay, talc powder and grafting solution to a high-speed mixer at a weight ratio of 1:1:0.12, stir at 1000 r / min for 20 min to obtain a mixed powder for later use; S3. Add 100g of seeds to a water chestnut-type coating pan and stir at 40r / min. Spray the grafting solution with a pneumatic spray gun at a spraying rate of 3g / min. While spraying the grafting solution, add 55g of mixed powder and control the addition time of the mixed powder to 25min to obtain the coated seed precursor. After taking it out, dry it at 50℃, put it back into the water chestnut-type coating pan, and continue to spray the grafting solution at 60g / min. At the same time, add the seed pelleting agent at a rate of 60g / min until the seed weight increases 17 times to obtain the coated seeds. S4. Add 22g of talcum powder to the water chestnut coating pan and continue stirring until the surface of the coated seeds is smooth. Add 6g of pigment and stir until the color is uniform. Then dry the seeds and cool them to room temperature to complete the coating process.

[0042] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the superabsorbent compound prepared according to the preparation example is replaced with the superabsorbent compound prepared according to Comparative Preparation Example 1.

[0043] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the superabsorbent compound prepared according to the preparation example is replaced with the superabsorbent compound prepared according to Comparative Preparation Example 2.

[0044] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that the superabsorbent compound prepared according to the preparation example is replaced with the superabsorbent compound prepared according to Comparative Preparation Example 3.

[0045] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that the superabsorbent compound prepared according to the preparation example is replaced with the superabsorbent compound prepared according to Comparative Preparation Example 4.

[0046] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that beer waste and sodium naphthenate are not added in S1.

[0047] Comparative Example 6: The difference between Comparative Example 6 and Example 2 is that no mixed powder is added in S3.

[0048] Performance testing: 1. Water absorption and retention capacity test of superabsorbent compounds: Take 1g of each of the superabsorbent compounds prepared in the preparation example and comparative preparation examples 1-3, and place them in four 1000ml beakers, labeled A (preparation example), B (comparative preparation example 1), C (comparative preparation example 2), and D (comparative preparation example 3). Add 500ml of distilled water (simulating a rain-permeable environment) and 500ml of tap water (containing 0.3% salt, pH=8.5, simulating the actual soil moisture environment) to each beaker, respectively. Soak in a constant temperature environment of 25℃ for 24h, stirring once every 6h (30s each time). After the soaking time is reached, filter through a 120-mesh filter and let stand for 10min. The weight of the gel was then weighed, and the water absorption weight was calculated as gel weight - initial sample weight. For the water retention capacity test, the filtered gel containing distilled water was placed in a constant temperature and humidity chamber at 30℃ and 40% humidity (simulating the arid environment of sandy land). The remaining weight of the gel was weighed after 24h, 48h, and 72h, and the water retention rate was calculated as remaining gel weight / initial gel weight × 100%. The experimental results are shown in Table 1.

[0049] Table 1. Test results of water absorption and retention capacity of superabsorbent compounds

[0050] 2. Coating Water Retention Durability Test: Alfalfa seeds were coated according to the coating processes described in Examples 1-3 and Comparative Examples 1-6. 500 coated seeds of each type were sown in cylindrical containers (15cm thick, with a waterproof membrane at the bottom) containing the same weight of dry sandy soil (5% moisture content). After sowing, each container was watered with 100ml of distilled water and then placed in a constant temperature and humidity chamber at 30℃ and 35% humidity (simulating a dry environment in the sandy soil during the non-rainy season). On day 1 and day 30 after watering, the moisture content at a depth of 5cm in the soil was measured using a soil moisture sensor. The water retention durability of the coating was calculated as: (Moisture content on day 30 / Moisture content on day 1) × 100%. The experimental results are shown in Table 2.

[0051] 3. Test on the radicle breakthrough performance of coated seeds: Alfalfa seeds were coated according to the coating process of Examples 1-3 and Comparative Examples 1-6. 1000 coated seeds and 1000 uncoated blank alfalfa seeds (control group) were taken and evenly sown in seedling pots (50 seeds per pot) filled with northern sandy soil (sand:soil = 7:3, moisture content 15%). The pots were placed in an artificial climate chamber to simulate the sandy environment (daytime temperature 20-25℃, nighttime temperature 8-12℃, light 12h / d, humidity 50%-60%). The number of seeds with radicle breakthrough after sowing was observed and recorded daily. The radicle breakthrough rate within 7 days was calculated as: number of seeds with breakthrough / total number of seeds sown × 100%. At the same time, the number of radicle malformations (bending, breakage) after breakthrough was counted and the malformation rate was calculated. The experimental results are shown in Table 2.

[0052] Table 2. Test results of water retention durability and radicle breakthrough performance of coated seeds.

[0053] 4. Seedling growth and stress resistance test: Alfalfa seeds were coated according to the coating process of Examples 1-3 and Comparative Examples 3-5. 1000 coated alfalfa seeds were sown in seedling trays simulating saline-alkali sandy soil in northern China (salt content 0.4%, pH=9.0) and placed in an artificial climate chamber (daytime temperature 22-28℃, nighttime temperature 10-15℃, light 14h / d, humidity 45%-55%) without additional watering (simulating drought stress during the non-rainy season). Germination rate was recorded within 20 days after sowing. When seedlings reached the 3-leaf stage, plant height and root length were measured as growth indicators. Chlorophyll content and proline content in seedling leaves were also measured. The experimental results are shown in Table 3.

[0054] Table 3 Results of seedling growth and stress resistance tests

[0055] Data Analysis: This invention achieves a comprehensive improvement in water absorption and retention capacity, radicle breakthrough performance, seedling growth, and stress resistance through structural optimization of the superabsorbent compound, synergistic effects of multiple seed coating agents, and precise adaptation of the coating process. The superabsorbent compound in the preparation example and the coated seeds in Example 2 showed the best performance in all tests, while the comparative preparation examples and comparative examples all had varying degrees of shortcomings in performance due to the lack of core components or improper process parameters, which fully verifies the rationality and superiority of the technical solution of this invention.

[0056] As can be seen from the experimental data in Table 1, the superabsorbent compound in the prepared example exhibits the best performance. This is likely due to the synergistic design of the mixed crosslinking agent and the starch-acrylic acid-acrylamide terpolymer. In the mixed crosslinking agent, the non-degradable crosslinking agent constructs a stable three-dimensional network framework, ensuring that it does not disintegrate after water absorption. The ether bonds introduced by the degradable crosslinking agent do not affect the contact between the hydrophilic groups and water molecules. The combination of the two ensures both water absorption space and structural stability. In the terpolymer, the amide groups of acrylamide provide support for the polymer chain segments, preventing the chain segments from collapsing after water absorption, further enhancing the synergistic effect of water absorption and retention. In comparison, the comparative preparation example using only non-degradable crosslinking agents had a reduced water absorption capacity due to its overly dense network structure, which limited the role of hydrophilic groups. The comparative preparation example using only degradable crosslinking agents had an initial water absorption capacity close to that of the prepared example, but the crosslinking network was prone to loosening due to the breakage of ether bonds, resulting in faster water loss and a significant decrease in water retention durability. The comparative preparation example without added acrylamide had insufficient polymer chain stability due to the lack of structural support from amide groups, and its water absorption and retention performance were inferior to that of the prepared example.

[0057] As can be seen from the experimental data in Table 2, the coated seeds of Example 2 showed outstanding performance in terms of water retention durability and radicle breakthrough performance. This may be because: the design of the mixed cross-linking agent of the superabsorbent compound maintains the structural stability required for long-term water retention through the non-degradable cross-linking agent, while the degradable cross-linking agent makes the coating form a loose structure during germination, reducing the resistance to radicle breakthrough; the addition of the mixed powder enhances the integrity and adhesion of the coating, preventing the coating from falling off or cracking; the concentration of the grafting solution is matched with the addition rate of the seed coating agent and the mixed powder to ensure that the coating is uniform and dense, locking in moisture without compressing the seeds. In comparison, the control group using pure non-degradable crosslinking agent superabsorbent compound had a hard shell coating, increased resistance to root breakthrough, significantly reduced breakthrough rate, and a markedly higher deformity rate. The control group using pure degradable crosslinking agent superabsorbent compound had a loose coating structure, easy water loss, and a significant decrease in water retention durability. The control group using binary copolymer superabsorbent compound had insufficient water retention stability, which disrupted the balance between water retention and breakthrough, resulting in weakened performance in both aspects. The control group without added mixed powder lacked necessary structural support, making the coating prone to detachment and collapse, and had the lowest water retention durability and root breakthrough rate. The control group without added specific trace elements, organic matter, or stress-resistant additives had performance in these two aspects that were similar to those in Example 2, as they did not affect the core structure of the coating or the design related to water retention and breakthrough.

[0058] As can be seen from the experimental data in Table 3, the seedlings in Example 2 exhibited the best growth and stress resistance, thanks to the synergistic effect of the seed coating components and the continuous water-retaining effect of the superabsorbent compounds. The hydrophilic network constructed by the superabsorbent compounds continuously locks in moisture, providing a stable water environment for seedling growth; the organic matter rich in beer waste slowly releases nutrients, forming a comprehensive nutrient supply system with potassium dihydrogen phosphate and various trace elements, meeting the needs of seedling growth; sodium naphthenate, as a stress-resistance adjuvant, enhances the seedlings' adaptability to drought and saline-alkali environments, while the precise ratio of trace elements further promotes chlorophyll synthesis and root development. Each comparative example exhibited significant shortcomings due to the lack of core functional components: the comparative example using a binary copolymer superabsorbent compound showed poor growth and stress resistance due to insufficient water retention and uneven nutrient release, resulting in unstable water and nutrient supply to the seedlings; the comparative example without added ammonium molybdate and borax suffered from stunted growth and reduced stress resistance due to the lack of essential micronutrients for forage growth, hindered chlorophyll synthesis, and reduced photosynthesis; the comparative example without added brewer's residue and sodium naphthenate showed lower growth and stress resistance compared to Example 2 due to insufficient organic matter leading to nutrient deficiency and the lack of stress-resistant adjuvants, making it difficult to adapt to harsh environments; the uncoated control group, lacking water retention and structural protection, had the lowest deformity rate due to unimpeded growth, but its bacon breakthrough rate was significantly lower than that of Example 2.

[0059] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A seed coating agent for seed pelleting, characterized in that, The composition includes the following components by weight percentage: superabsorbent polymer: 25%-35%, beer residue: 5%-7%, attapulgite: 20%-30%, potassium dihydrogen phosphate: 6%-10%, ammonium molybdate: 0.08%-0.12%, borax: 0.15%-0.25%, copper sulfate: 0.08%-0.12%, manganese sulfate: 0.08%-0.12%, zinc sulfate: 0.08%-0.12%, with the balance being talc. The seed coating agent also includes 50-70 ppm of sodium naphthenate based on the total weight of the seed coating agent; The superabsorbent compound is a starch-acrylic acid-acrylamide terpolymer, which is formed by cross-linking with a mixed cross-linking agent; The hybrid crosslinking agent is a mixture of non-degradable crosslinking agents and degradable crosslinking agents; The non-degradable crosslinking agent is N,N'-methylenebisacrylamide, and the degradable crosslinking agent is polyethylene glycol diacrylate with an average molecular weight of ≈700.

2. The seed pelleting agent according to claim 1, characterized in that, The method for preparing the superabsorbent compound includes the following steps: (1) Add high branched starch to distilled water, heat to 85-95℃, stir for 15-25 min to obtain gelatinized starch solution; add acrylic acid to KOH aqueous solution under stirring until the pH of the system is neutral to obtain acrylic acid neutralized solution; (2) Cool the gelatinized starch solution and the acrylic acid neutralization solution to 35-45℃ and mix them. Then add acrylamide, ammonium persulfate, sodium bisulfite and mixed crosslinking agent in sequence. Stir for 8-15 min until the mixture is uniform. Keep the temperature at 38-42℃ and stir for 20-30 min to obtain the precursor of the super water-absorbing compound. (3) Pour the superabsorbent compound precursor into a tray, spread it evenly, and then send it into a channel drying device for drying. After cooling to room temperature, crush it and pass it through a 120-mesh sieve to obtain the superabsorbent compound.

3. The seed pelleting agent according to claim 2, characterized in that, In the preparation method of the superabsorbent compound, the weight ratio of high branched starch, acrylic acid, acrylamide, ammonium persulfate, sodium bisulfite and mixed crosslinking agent is 1:0.4-0.6:0.6-0.8:0.01-0.014:0.006-0.01:0.04-0.

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4. The seed pelleting agent according to claim 2, characterized in that, The weight ratio of high amylopectin to distilled water in (1) is 1:8-12; the concentration of KOH aqueous solution is 20-40wt%.

5. The seed pelleting agent according to claim 2, characterized in that, In the mixture of (2), the weight ratio of non-degradable crosslinking agent to degradable crosslinking agent is 4-7:1-3.

6. The coating process of the seed pelleting agent according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Add the superabsorbent compound to distilled water and stir until dissolved to obtain a grafting solution for later use; add the superabsorbent compound, brewer's residue, attapulgite, potassium dihydrogen phosphate, sodium naphthenate, ammonium molybdate, borax, copper sulfate, manganese sulfate, zinc sulfate, and talc to a double-helix conical mixer and stir at 200-300 r / min for 20-30 min to obtain a seed pelleting agent for later use; S2. Add attapulgite clay, talc powder and grafting solution to a high-speed mixer and stir at 800-1000 r / min for 10-20 min to obtain a mixed powder for later use. S3. Add the seeds to the water chestnut-type coating pan and stir at 30-40 r / min. Spray the grafting solution with a pneumatic spray gun. While spraying the grafting solution, add the mixed powder and control the addition time of the mixed powder to 5-10 min to obtain the coated seed precursor. After taking it out, dry it at 40-50℃, put it back into the water chestnut-type coating pan, continue to spray the grafting solution, and add the seed pelleting agent at the same time until the seed weight increases by 13-17 times to obtain the coated seeds. S4. Continue to add talcum powder to the water chestnut coating pan and stir until the surface of the coated seeds is smooth. Add pigment and stir until the color is uniform. Then dry and cool to room temperature to complete the coating process.

7. The coating process of the seed pelleting agent according to claim 6, characterized in that, The concentration of the superabsorbent compound in the grafting solution in S1 is 4.5 wt%.

8. The coating process of the seed pelleting agent according to claim 6, characterized in that, The weight ratio of attapulgite, talc, and grafting solution in S2 is 1:1:0.08-0.

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9. The coating process of the seed pelleting agent according to claim 6, characterized in that, The weight ratio of seeds to mixed powder in S3 is 1:0.45-0.55; the spraying rate of the pneumatic spray gun when adding mixed powder is 3-5 g / min, the spraying rate when adding seed pelleting agent is 20-60 g / min, and the addition rate of seed pelleting agent is 20-60 g / min.

10. The coating process of the seed pelleting agent according to claim 6, characterized in that, The amounts of talc and pigment added in S4 are 18%-22% and 0.4%-0.6% respectively, based on the weight of the seeds in S3.

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