Special seedling raising substrate for fully-degradable tobacco seedling raising tray as well as preparation method and application of seedling raising substrate

Abstract

The invention provides a seedling substrate special for a fully-degradable tobacco seedling tray and a preparation method and application of the seedling substrate. The problems that components of an existing seedling substrate cannot be completely degraded, and nutrient release is not matched with tobacco requirements are solved. The seedling raising substrate is composed of 85%-97.5% of a tobacco special base substrate and 2.5%-15% of a high-nitrogen organic fertilizer, the base substrate is formed by mixing decomposed rice husks, coco coir and a temperature and humidity response type chitosan-sodium alginate coated biochar composite material according to the ratio of 30: 40: 30, the volume weight is 0.24-0.28 g.cm <-3 >, and the total porosity is 82%-86%; the high-nitrogen organic fertilizer is prepared by composting and fermenting livestock and poultry manure, soybean meal and straw and then adding humic acid and amino acid powder. The system solves the three technical bottlenecks of fertilizer shortage in the initial stage, loosening in the middle stage and difficult transplanting in the later stage of a fully-degradable seedling raising plate, the survival rate of tobacco seedlings reaches 97.8-99.6% and is remarkably superior to that of a control group containing mineral filler, and an environment-friendly and efficient seedling raising solution is provided for the tobacco industry.

Description

Technical Field

[0001] This invention belongs to the field of agricultural biomaterials, specifically relating to a fully degradable seedling substrate for tobacco seedling trays, its preparation method, and its application. Background Technology

[0002] In the tobacco seedling industry, fully biodegradable seedling trays are gradually replacing traditional plastic seedling trays due to their environmental friendliness and direct transplanting capabilities. However, the specialized seedling substrates used in their production need to balance physical structural stability, nutrient supply capacity, and synergistic degradation characteristics with fully biodegradable materials, which places higher demands on substrate formulation and preparation processes.

[0003] Patent application CN105706882A discloses a tomato seedling substrate, which is composed of 45% mushroom residue, 15% peat moss, 25% vermiculite, and 15% perlite in a volume ratio, with the addition of a certain amount of nitrogen, phosphorus, and potassium fertilizer. This substrate uses agricultural waste mushroom residue as its main material, achieving resource reuse, and its physicochemical properties meet the growth needs of tomato seedlings. However, this solution is mainly designed for tomato crops and does not consider the special requirements of tobacco seedlings for substrate bulk density, porosity, and initial nutrient release rate. Furthermore, its components include non-degradable inorganic minerals (such as vermiculite and perlite), which may remain in the soil during the application of fully degradable seedling trays, affecting the overall environmental performance of the degradation system. Patent application CN116349576A discloses a general-purpose seedling substrate, composed of vermiculite, perlite, peat moss, and coconut coir in a mass ratio of 4:1:1:2, and compounded with biological agents (Bacillus subtilis and fluopyram) and a specific proportion of fertilizer components. This substrate enhances disease resistance by introducing bio-agents and is suitable for a variety of crops. However, this approach still relies heavily on peat and non-degradable mineral fillers, which is inconsistent with the core concept of "fully degradable" seedling trays. In addition, its bio-agent combination is mainly aimed at southern root-knot nematodes, and is not effective in controlling common tobacco seedling diseases (such as damping-off and seedling blight), and does not consider the impact of substrate degradation on microbial activity.

[0004] In summary, while existing patents have made progress in the substitution of raw materials, nutrient regulation and functionalization of seedling substrates, there are still problems such as the substrate components not being completely degradable, insufficient crop specificity and weak synergy with the degradable tray when adapted to the application scenario of fully degradable tobacco seedling trays. There is still no dedicated seedling substrate solution that takes into account environmental friendliness, tobacco growth needs and synchronous degradation characteristics with the fully degradable tray. Summary of the Invention

[0005] One of the objectives of this invention is to provide a seedling substrate specifically for fully degradable tobacco seedling trays, its preparation method, and its application, aiming to solve the problems of incomplete degradation of components and mismatch between nutrient release and tobacco seedling needs when adapting existing seedling substrates to fully degradable tobacco seedling trays.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a seedling substrate specifically for fully degradable tobacco seedling trays, which is composed of the following components by mass percentage: 85%-97.5% tobacco-specific base substrate and 2.5%-15% high-nitrogen organic fertilizer; the tobacco-specific base substrate is obtained by mixing decomposed rice husks, coconut coir, and temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material in a mass ratio of 30:40:30, with a bulk density of 0.24-0.28 g·cm³. -3 The total porosity is 82%-86%, the pH value is 5.5-6.0, and the electrical conductivity (EC) value is 800-1000 μS·cm. -1 The high-nitrogen organic fertilizer is prepared by high-temperature aerobic composting and fermentation of livestock and poultry manure, soybean meal, and straw in a mass ratio of 50:30:20 for 15-20 days, followed by the addition of 3%-5% humic acid and 2%-4% amino acid powder, which are then mixed, dried, and the mixture has a nitrogen content of not less than 4.5%, a pH value of 7.0-7.5, and an EC value of 9.5-11.0 mS·cm. -1 ; The temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material has a temperature phase transition threshold of 32±1℃ and a humidity response range of 40%-80%RH, and its surface is loaded with a concentration of 1×10 7 -5×10 7 The plant rhizosphere growth-promoting bacteria (PGPR) complex, CFU / g, comprises Bacillus amyloliquefaciens FZB42 and Pseudomonas putida KT2440, with a viable count ratio of 3:1.

[0007] According to the present invention, the seedling substrate contains no non-degradable mineral fillers such as vermiculite, perlite, or peat; all components are biodegradable in soil, and its physical structure parameters are highly compatible with the root development needs of tobacco seedlings. By controlling the proportion of high-nitrogen organic fertilizer added, the substrate maintains an EC value of 600-1000 μS·cm in the early stages of seedling cultivation. -1 Within a certain range, it meets the nutrient requirements for tobacco seed germination while avoiding the inhibition of seedling growth due to excessive nutrient leaching. In addition, during the field degradation process of this substrate and fully degradable seedling trays prepared with sugarcane bagasse or rice straw, its degradation rate is coordinated with the disintegration cycle of the trays (complete disintegration within 45 days after transplanting), and no residues are formed that interfere with root penetration.

[0008] In some embodiments, the decomposed rice husks in the tobacco-specific base matrix have a particle size of 0.5-2 mm, the coconut coir fibers have a length of 2-5 mm, and the temperature and humidity responsive chitosan-sodium alginate coated biochar composite material has a particle size of 0.2-1 mm. The three are mixed and then steam-sterilized at a temperature of 121°C for 30 minutes.

[0009] In some embodiments, the preparation method of the temperature and humidity responsive chitosan-sodium alginate coated biochar composite material includes the following steps: (a) Biochar was prepared by pyrolyzing corn stalks at 450°C for 4 hours under limited oxygen conditions. The biochar was then pulverized and passed through a 0.2-1 mm sieve, washed with 1% HCl solution, and then washed with deionized water until neutral. (b) Chitosan with a degree of deacetylation ≥90% was prepared into a 5% working solution using a 1% acetic acid solution, and sodium alginate was prepared into a 3% aqueous solution separately. Under the conditions of an ice bath at 4°C and vigorous stirring at 500 rpm, sodium alginate solution was added dropwise to the chitosan solution at a rate of 2 mL / min to maintain the pH of the system at 5.0±0.2, forming a pre-complexed solution. The biochar obtained in step (a) was immersed in the pre-complexed solution and stirred at 60 rpm for 30 minutes. (c) Add N-isopropylacrylamide (NIPAM) and acrylic acid (AA) monomer (mass ratio (95-97):(3-5)), 0.5% azobisisobutyronitrile (AIBN) and 0.2% N,N'-methylenebisacrylamide (MBA) to the system, adjust the pH to 5.5±0.2, and polymerize in a water bath at 60°C for 2 hours under nitrogen protection to obtain biochar loaded with temperature-sensitive polymer; (d) The biochar loaded with the temperature-sensitive polymer was rinsed three times with deionized water and then freeze-dried at -50°C for 24 hours. (e) Mix Bacillus amyloliquefaciens FZB42 and Pseudomonas putida KT2440 at a viable count ratio of 3:1 to prepare a solution. The bacterial suspension was evenly sprayed onto the surface of the product from step (d) and left to stand at 4°C for 12 hours. (f) Freeze-dry at -50℃ for 12 hours to obtain a temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material with PGPR complex bacteria on the surface. Its temperature phase transition threshold is 32±1℃ and its humidity response range is 40%-80%RH.

[0010] The temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material has a dual environmental response mechanism: (1) Temperature responsiveness: When the ambient temperature is below 32℃, the NIPAM-AA copolymer chains extend to form a hydrophilic hydration layer, adsorbing and locking free water in the biochar pores, inhibiting the nutrient dissolution rate, and keeping the EC value stable at a high level (800-1000 μS·cm).-1 This meets the "slow demand" during the tobacco germination period; when the temperature rises above 32℃ (the rapid growth period of tobacco), the polymer chains contract to release and lock in moisture and expand the micropores, dissolving the undissolved nutrients accumulated in the pores in a pulsed release, so that the EC value is precisely reduced to 500-550 μS·cm within 30 days. -1 This matches the "fast demand" stage.

[0011] (2) Humidity responsiveness: When the relative humidity is <40%, the micropores on the material surface shrink to form a protective film, reducing the water evaporation rate by 35%-42%; when the humidity is >80%, the micropores expand to accelerate water release, avoiding root hypoxia caused by excessive substrate moisture.

[0012] The PGPR complex microbial community enhances the technical effect through the following mechanisms: (i) Bacillus amyloliquefaciens FZB42 secretes surfactants to promote the directional migration of nutrients in the pores of biochar, increase the EC value, and significantly improve the "mid-term looseness" problem; (ii) Pseudomonas putida KT2440 produces siderophores to chelate metal ions on the surface of biochar, expanding the pH buffer range of the matrix to 5.2-6.3, effectively inhibiting the incidence of tobacco damping-off disease; (iii) The two strains work together to form a biofilm network, which enhances the tensile strength of the roots and reduces the breakage rate during the rolling operation.

[0013] In some embodiments, during the preparation of the high-nitrogen organic fertilizer, the initial C / N ratio of the compost is adjusted to 20-25:1, the moisture content is controlled at 55%-65%, the compost is turned over every 3 days, and the fermentation temperature is maintained at 55℃-70℃.

[0014] In some embodiments, the humic acid in the high-nitrogen organic fertilizer is potassium fulvic acid, and the amino acid powder is a hydrolyzed product of soybean protein, with a free amino acid content of not less than 80%.

[0015] In some embodiments, the seedling substrate needs to be adjusted to a moisture content of 50%-60% before use and allowed to stand for 24 hours to allow the moisture to be evenly distributed.

[0016] Secondly, the present invention provides a method for preparing the above-mentioned fully degradable tobacco seedling tray-specific seedling substrate, comprising the following steps: S10: The decomposed rice husks, coconut coir, and temperature and humidity responsive chitosan-sodium alginate coated biochar composite material are crushed to the specified particle size range and mixed in a mass ratio of 30:40:30 to obtain a tobacco-specific base matrix. S20: Mix livestock and poultry manure, soybean meal, and straw, adjust the C / N ratio to 20-25:1, and the moisture content to 55%-65%. Inoculate with 0.2%-0.5% high-temperature composting bacteria and carry out aerobic composting fermentation for 15-20 days, turning the pile every 3 days during the period. After fermentation, dry the pile until the moisture content is below 15%. S30: Add 3%-5% humic acid and 2%-4% amino acid powder (by mass of total material) to the dry material obtained in step S20, mix evenly, and pulverize through a 2 mm sieve to obtain high-nitrogen organic fertilizer. S40: Mix the tobacco-specific basic substrate obtained in step S10 with the high-nitrogen organic fertilizer obtained in step S30 at a mass ratio of 85:15, 90:10, 92.5:7.5, 95:5 or 97.5:2.5, mix evenly, adjust the moisture content to 50%-60%, and let stand for 24 hours to obtain the fully degradable tobacco seedling tray-specific seedling substrate.

[0017] According to the present invention, this preparation method, by precisely controlling the ratio of the basic substrate to high-nitrogen organic fertilizer, ensures that the EC value of the final seedling substrate falls within the range of 600-1000 μS·cm. -1 The ideal range of salinity satisfies the nutrient requirements for tobacco seed germination while avoiding high salt stress. Furthermore, all raw materials are renewable agricultural waste or natural organic matter, and the entire preparation process requires no addition of chemically synthesized fertilizers or non-degradable inorganic fillers, ensuring the overall biodegradability of the substrate and the fully degradable seedling tray after field application.

[0018] In some embodiments, in step S10, the decomposed rice husks are obtained by drying rice processing by-products at 60°C, pulverizing them, and passing them through a 0.5-2 mm sieve; the coconut coir is desalinated commercial coconut coir, washed with water until the EC value is below 1.0 mS·cm. -1 Dry and store for later use.

[0019] In some embodiments, in step S20, the high-temperature composting microbial agent is a compound microbial agent of Bacillus spp. and Actinomyces spp., with a viable count of not less than 1×10⁻⁶. 8 CFU / g.

[0020] In some embodiments, in step S30, the drying is carried out using a low-temperature drying method, with the temperature not exceeding 60°C and the time being 8-12 hours, in order to retain the active substances in the organic fertilizer.

[0021] In some embodiments, in step S40, a twin-shaft paddle mixer is used for mixing at a speed of 20-30 rpm for a mixing time of 10-15 minutes.

[0022] Thirdly, the present invention provides a method for applying the above-mentioned fully degradable tobacco seedling tray-specific seedling substrate in tobacco seedling cultivation, comprising the following steps: T10: The seedling substrate is filled into a fully degradable tobacco seedling tray made of sugarcane bagasse or rice straw fiber through vacuum filtration and shaped with the addition of 0.2% nano-anti-mildew agent and 0.5% biodegradable modified MUF wet strength agent, and compacted to a bulk density of 0.26-0.28 g·cm³. -3 ; T20: Sow fresh tobacco seeds of the current year, 1-2 seeds per hole, cover with a thin layer of substrate, and cultivate in a greenhouse with an ambient temperature controlled at 25℃-30℃ and a relative humidity of 70%-85%; T30: During the seedling stage, maintain the substrate moisture content at 50%-60%. When the tobacco seedlings grow to 65 days old, stop watering for 5 days to control water usage, causing the plants to wilt physiologically but keeping the stems and leaves flexible. T40: After water control is completed, the entire tray of tobacco seedlings is transferred to the field in a "rolled-up" manner for "integrated pot and seedling transplanting" without removing the trays; T50: After transplanting, the seedling trays degrade synchronously with the growth of tobacco seedlings in the soil, completely disintegrating within 45 days, allowing roots to penetrate freely.

[0023] According to the present invention, this application method fully utilizes the synergistic effect of fully degradable seedling trays and specialized substrates. In the early stage of seedling cultivation, an appropriate amount of high-nitrogen organic fertilizer in the substrate provides stable nutrients, avoiding rapid nutrient leaching caused by the high porosity structure of the plant fiber trays; during the seedling stage, water control treatment enhances the overall toughness of the trays and plants, enabling seamless transplanting; after transplanting, the substrate and trays degrade synchronously, leaving no residue and promoting root expansion in the soil.

[0024] In some embodiments, in step T10, the fully degradable tobacco seedling tray has external dimensions of 524 mm × 330 mm × 60 mm, 126 holes, a layout of 9 × 14 grids, and a single hole depth of 45-50 mm.

[0025] In some embodiments, in step T20, the seeds are disinfected by soaking in a 0.1% potassium permanganate solution for 15 minutes before sowing, rinsed with clean water, and then dried for later use.

[0026] In some embodiments, during step T30, if extreme high temperatures (>35°C) occur during water control, a moisturizing spray can be applied in the evening, with a single spray volume not exceeding 5 mL·m. -2 .

[0027] In some embodiments, during step T40, the "rolling blanket" operation involves slowly rolling the blanket along the long side of the acupuncture plate, with a roll diameter of not less than 20 cm, to avoid mechanical damage.

[0028] In some embodiments, in step T50, the soil pH of the transplanting plot is 5.5-7.0, and the organic matter content is not less than 20 g·kg⁻¹. -1 Apply sufficient base fertilizer before transplanting.

[0029] According to this invention, the system solves the three major technical bottlenecks that have long existed in tobacco seedling cultivation using fully degradable seedling trays: "initial nutrient deficiency, mid-stage looseness, and late-stage difficulty in transplanting," through the synergistic optimization of material selection, structural design, and substrate formulation. Sugarcane bagasse fiber is a preferred raw material due to its high yield, low cost, and moderate fiber length; the special substrate precisely regulates nutrient release through gradient compounding of organic fertilizers; and the water control process effectively improves transplant adaptability, forming a complete technical closed loop.

[0030] In summary, this invention, by constructing a three-in-one technical system of "specialized substrate - fully degradable seedling tray - supporting agronomy", has for the first time realized the efficient, stable and environmentally friendly application of fully degradable seedling trays in tobacco production, and provides a practical and feasible technical path to solve the "white pollution" problem caused by traditional plastic seedling trays.

[0031] The beneficial effects of this invention are: (1) The seedling substrate provided by the present invention uses fully biodegradable components and contains no non-biodegradable mineral fillers. It ensures that it completely disintegrates within 45 days after field application, along with sugarcane bagasse or rice straw seedling trays, without any residue interfering with root penetration. This effectively solves the problem of "white pollution" caused by traditional plastic seedling trays and provides an environmentally friendly alternative for the tobacco industry.

[0032] (2) The substrate used in this invention maintains the EC value stably at 600-1000 μS·cm by precisely controlling the proportion of high-nitrogen organic fertilizer added (2.5%-15%). -1 The ideal range satisfies the continuous nutrient requirements of tobacco seeds during germination while avoiding seedling growth inhibition caused by high salt stress and excessive nutrient leaching. Simultaneously, its physical structural parameters (bulk weight 0.24-0.28 g·cm³) are suitable. -3 With a total porosity of 82%-86% and a pH of 5.5-6.0, it is highly compatible with tobacco root development, significantly improving the survival rate in the early stage of seedling cultivation and ensuring the healthy growth of tobacco seedlings.

[0033] (3) The temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material used in this invention constructs an environmental response system that precisely matches the growth needs of tobacco through the synergistic design of NIPAM-AA temperature-sensitive copolymer and chitosan-sodium alginate composite layer. The temperature phase change threshold of 32±1℃ is highly consistent with the rapid growth period of tobacco, reducing the water evaporation rate. The EC value change curve changes from the monotonous decrease of the traditional matrix to a precise three-stage regulation of "high-medium-low" (850→510→330μS·cm). -1First, it solves the problem of "initial nutrient deficiency and mid-term looseness"; second, it innovatively loads a compound microbial community (3:1) of Bacillus amyloliquefaciens FZB42 and Pseudomonas putida KT2440, which improves the tensile strength of the root system and reduces the rate of root roll breakage through the biofilm network, while also reducing the incidence of damping-off disease; third, it can still maintain high substrate moisture content and high survival rate under extreme climatic conditions (32.5℃ / RH 35%-45%), realizing a three-in-one technical closed loop of "intelligent material response - microbial activity maintenance - crop demand matching", providing core support for the fully degradable seedling system.

[0034] (4) The method provided by this invention, combined with water-controlled transplanting technology, enhances plant resilience and achieves "pot-seedling integration" non-destructive mat transplanting, completely overcoming the long-standing technical difficulties of "initial nutrient deficiency, mid-term looseness, and late-term difficulty in transplanting" in fully degradable seedling trays. The entire system is based on the resource utilization of agricultural waste, and the preparation process does not require chemically synthesized fertilizers or non-degradable additives. This not only reduces production costs but also promotes the rapid expansion of tobacco seedling roots in the soil, ultimately forming an efficient, stable, and environmentally friendly tobacco seedling solution, providing a practical and feasible technical path for the sustainable development of the tobacco industry. Detailed Implementation

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0036] As described in the background section above, existing tobacco seedling substrates mostly rely on non-degradable mineral fillers (such as vermiculite and perlite) or peat. When used in conjunction with fully degradable seedling trays, problems such as component residues, nutrient release mismatch, and unstable physical structure arise. To solve these problems, this invention provides a seedling substrate specifically for fully degradable tobacco seedling trays, its preparation method, and its application. By using entirely biodegradable organic raw materials, precisely controlling the ratio of the base substrate to high-nitrogen organic fertilizer, and employing a dedicated agronomic operation process, a systematic synergy between the substrate, seedling tray, and transplanting process is achieved.

[0037] In a first aspect, the present invention provides a seedling substrate specifically for fully degradable tobacco seedling trays, which is composed of the following components by mass percentage: 85%-97.5% tobacco-specific base substrate and 2.5%-15% high-nitrogen organic fertilizer; the tobacco-specific base substrate is obtained by mixing decomposed rice husks, coconut coir, and temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material in a mass ratio of 30:40:30, with a bulk density of 0.24-0.28 g·cm³. -3 The total porosity is 82%-86%, the pH value is 5.5-6.0, and the electrical conductivity (EC) value is 800-1000 μS·cm. -1The high-nitrogen organic fertilizer is prepared by high-temperature aerobic composting and fermentation of livestock and poultry manure, soybean meal, and straw in a mass ratio of 50:30:20 for 15-20 days, followed by the addition of 3%-5% humic acid and 2%-4% amino acid powder, which are then mixed, dried, and the mixture has a nitrogen content of not less than 4.5%, a pH value of 7.0-7.5, and an EC value of 9.5-11.0 mS·cm. -1 .

[0038] According to the present invention, the seedling substrate contains no non-degradable mineral fillers such as vermiculite, perlite, or peat; all components are biodegradable in soil, and its physical structure parameters are highly compatible with the root development needs of tobacco seedlings. By controlling the proportion of high-nitrogen organic fertilizer added, the substrate maintains an EC value of 600-1000 μS·cm in the early stages of seedling cultivation. -1 Within a certain range, it meets the nutrient requirements for tobacco seed germination while avoiding the inhibition of seedling growth due to excessive nutrient leaching. In addition, during the field degradation process of this substrate and fully degradable seedling trays prepared with sugarcane bagasse or rice straw, its degradation rate is coordinated with the disintegration cycle of the trays (complete disintegration within 45 days after transplanting), and no residues are formed that interfere with root penetration.

[0039] In some embodiments, the tobacco-specific base matrix contains decomposed rice husks with a particle size of 0.5-2 mm, coconut coir fibers with a length of 2-5 mm, and temperature-humidity responsive chitosan-sodium alginate-coated biochar composite material with a particle size of 0.2-1 mm. The mixture is then steam-sterilized at 121°C for 30 minutes. The decomposed rice husks are obtained from rice processing by-products dried at 60°C, pulverized, and passed through a 0.5-2 mm sieve; the coconut coir is desalinated commercial coconut coir, washed with water until the EC value is below 1.0 mS·cm. -1 Dry and store for later use.

[0040] In some embodiments, during the preparation of the high-nitrogen organic fertilizer, the initial C / N ratio of the compost is adjusted to 20-25:1, the moisture content is controlled at 55%-65%, the compost is turned over every 3 days, and the fermentation temperature is maintained at 55℃-70℃. The high-temperature composting agent is a compound agent of Bacillus spp. and Actinomyces spp., with a viable count of not less than 1×10⁻⁶. 8 The inoculum concentration is CFU / g, and the inoculum amount is 0.2%-0.5% of the total material mass. After fermentation, the material is dried until the moisture content is below 15%. The drying method is low-temperature drying, with the temperature not exceeding 60℃ and the time being 8-12 hours, in order to retain the active substances in the organic fertilizer.

[0041] In some embodiments, the humic acid in the high-nitrogen organic fertilizer is potassium fulvate, and the amino acid powder is a hydrolyzed product of soybean protein, with a free amino acid content of not less than 80%. 3%-5% potassium fulvate and 2%-4% hydrolyzed soybean protein amino acid powder are added to the dried compost material, mixed evenly, and then pulverized through a 2 mm sieve to obtain the finished high-nitrogen organic fertilizer.

[0042] In some embodiments, the seedling substrate needs to be adjusted to a moisture content of 50%-60% before use and allowed to stand for 24 hours to allow the moisture to be evenly distributed. Mixing is performed using a twin-shaft paddle mixer at a speed of 20-30 rpm for 10-15 minutes to ensure thorough homogenization of the base substrate and the high-nitrogen organic fertilizer.

[0043] Secondly, the present invention provides a method for preparing the above-mentioned fully degradable tobacco seedling tray-specific seedling substrate, comprising the following steps: S10: The decomposed rice husks, coconut coir, and temperature and humidity responsive chitosan-sodium alginate coated biochar composite material are crushed to the specified particle size range and mixed in a mass ratio of 30:40:30 to obtain a tobacco-specific base matrix. S20: Mix livestock and poultry manure, soybean meal, and straw, adjust the C / N ratio to 20-25:1, and the moisture content to 55%-65%. Inoculate with 0.2%-0.5% high-temperature composting bacteria and carry out aerobic composting fermentation for 15-20 days, turning the pile every 3 days during the period. After fermentation, dry the pile until the moisture content is below 15%. S30: Add 3%-5% humic acid and 2%-4% amino acid powder (by mass of total material) to the dry material obtained in step S20, mix evenly, and pulverize through a 2 mm sieve to obtain high-nitrogen organic fertilizer. S40: Mix the tobacco-specific basic substrate obtained in step S10 with the high-nitrogen organic fertilizer obtained in step S30 at a mass ratio of 85:15, 90:10, 92.5:7.5, 95:5 or 97.5:2.5, mix evenly, adjust the moisture content to 50%-60%, and let stand for 24 hours to obtain the fully degradable tobacco seedling tray-specific seedling substrate.

[0044] According to the present invention, this preparation method, by precisely controlling the ratio of the basic substrate to high-nitrogen organic fertilizer, ensures that the EC value of the final seedling substrate falls within the range of 600-1000 μS·cm. -1 The ideal range of salinity satisfies the nutrient requirements for tobacco seed germination while avoiding high salt stress. Furthermore, all raw materials are renewable agricultural waste or natural organic matter, and the entire preparation process requires no addition of chemically synthesized fertilizers or non-degradable inorganic fillers, ensuring the overall biodegradability of the substrate and the fully degradable seedling tray after field application.

[0045] Thirdly, the present invention provides a method for applying the above-mentioned fully degradable tobacco seedling tray-specific seedling substrate in tobacco seedling cultivation, comprising the following steps: T10: The seedling substrate is filled into a fully degradable tobacco seedling tray made of sugarcane bagasse or rice straw fiber through vacuum filtration and shaped with the addition of 0.2% nano-anti-mildew agent and 0.5% biodegradable modified MUF wet strength agent, and compacted to a bulk density of 0.26-0.28 g·cm³. -3 The fully biodegradable tobacco seedling tray has external dimensions of 524 mm × 330 mm × 60 mm, 126 holes, a layout of 9 × 14 grids, and a single hole depth of 45-50 mm. T20: Sow fresh tobacco seeds of the current year, 1-2 seeds per hole, cover with a thin layer of substrate, and cultivate in a greenhouse with an ambient temperature controlled at 25℃-30℃ and a relative humidity of 70%-85%; before sowing, soak the seeds in a 0.1% potassium permanganate solution for 15 minutes for disinfection, rinse with clean water and dry for later use. T30: During the seedling stage, maintain the substrate moisture content at 50%-60%. When the seedlings reach 65 days of age, stop watering for 5 days to control water usage, causing physiological wilting of the plants while keeping the stems and leaves flexible. If extreme high temperatures (>35℃) occur during the water control period, spray moisture in the evening, with a single spray volume not exceeding [amount missing]. ; T40: After water control is completed, the entire tray of tobacco seedlings is transferred to the field in a "rolled-up" manner for "integrated pot and seedling transplanting" without removing the trays; when "rolling up" the trays, slowly roll them up along the long side of the tray, with a roll diameter of not less than 20 cm to avoid mechanical damage. T50: After transplanting, the seedling trays degrade synchronously with the growth of the tobacco seedlings in the soil, completely disintegrating within 45 days, allowing roots to penetrate freely; the soil pH of the transplanting site should be 5.5-7.0, and the organic matter content should not be less than 20 g·kg⁻¹. -1 Apply sufficient base fertilizer before transplanting.

[0046] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Example 1

[0047] S10: Well-rotted rice husks (particle size 0.5-2 mm), desalted coconut coir (fiber length 2-5 mm), and temperature-humidity responsive chitosan-sodium alginate-coated biochar composite material (particle size 0.2-1 mm) were mixed in a mass ratio of 30:40:30 and steam-sterilized (121℃, 30 min) to obtain a tobacco-specific base matrix. The bulk density was measured to be 0.26 g·cm³. -3 Total porosity 84%, pH 5.7, EC 920 μS·cm -1 ; The preparation method of the temperature and humidity responsive chitosan-sodium alginate coated biochar composite material includes the following steps: (a) Biochar was prepared by pyrolyzing corn stalks at 450°C for 4 hours under limited oxygen conditions. The biochar was then crushed and passed through a 0.5 mm sieve, washed with 1% HCl solution, and then washed with deionized water until neutral. (b) Chitosan with a degree of deacetylation ≥90% was prepared into a 5% working solution using a 1% acetic acid solution, and sodium alginate was prepared into a 3% aqueous solution separately. Under the conditions of an ice bath at 4°C and vigorous stirring at 500 rpm, sodium alginate solution was added dropwise to the chitosan solution at a rate of 2 mL / min to maintain the pH of the system at 5.0±0.2, forming a pre-complexed solution. The biochar obtained in step (a) was immersed in the pre-complexed solution and stirred at 60 rpm for 30 minutes. (c) Add N-isopropylacrylamide (NIPAM) and acrylic acid (AA) monomer (mass ratio 97:3), 0.5% azobisisobutyronitrile (AIBN) and 0.2% N,N'-methylenebisacrylamide (MBA) to the system, adjust the pH to 5.5±0.2, and polymerize in a water bath at 60°C for 2 hours under nitrogen protection to obtain biochar loaded with temperature-sensitive polymer; (d) The biochar loaded with the temperature-sensitive polymer was rinsed three times with deionized water and then freeze-dried at -50°C for 24 hours. (e) Mix Bacillus amyloliquefaciens FZB42 and Pseudomonas putida KT2440 at a viable count ratio of 3:1 to prepare a 1×10⁻⁶ solution. 8 CFU / mL bacterial suspension was evenly sprayed onto the surface of the product in step (d) and allowed to stand at 4°C for 12 hours. (f) Freeze-dry at -50℃ for 12 hours to obtain a temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material with PGPR complex bacteria on the surface. Its temperature phase transition threshold is 32±1℃ and its humidity response range is 40%-80%RH.

[0048] S20: Mix chicken manure, soybean meal, and wheat straw in a ratio of 50:30:20, add water to adjust the C / N ratio to 22:1, and maintain a moisture content of 60%. Inoculate with a Bacillus-Actinomyces compound inoculant (0.3%, viable count 1.2 × 10⁻⁶). 8 (CFU / g), piled up for fermentation for 18 days, turning the pile every 3 days, fermentation temperature 58-68℃, dried at 60℃ for 10 hours to a moisture content of 12%; S30: Add 4% potassium humate and 3% soybean protein hydrolyzed amino acid powder (free amino acid content 82%) to the dry material, mix thoroughly using a twin-shaft paddle mixer (25 rpm, 12 min), pulverize and pass through a 2 mm sieve to obtain high-nitrogen organic fertilizer with a nitrogen content of 4.8%, pH 7.2, and EC 10.2 mS·cm. -1 ; S40: Mix the basic substrate with high-nitrogen organic fertilizer at a ratio of 95:5, mix for 15 min, add water to adjust the moisture content to 55%, and let stand for 24 h to obtain the seedling substrate with an EC value of 850 μS·cm. -1 ; T10-T50: Fill sugarcane bagasse fully biodegradable seedling trays (126 cells, 48 ​​mm depth per cell), sow Yunyan 87 seeds, control watering for 5 days, then roll up the trays and transplant to Yunnan red soil (pH 6.2, organic matter 22 g·kg⁻¹). -1 The seedling trays completely disintegrated 45 days after transplanting, with a survival rate of 98.5%. Example 2

[0049] Except for the addition ratio of high-nitrogen organic fertilizer being 10% (90% of the base substrate), the rest is the same as in Example 1. Example 3

[0050] Except for the addition ratio of high-nitrogen organic fertilizer being 15% (basic substrate 85%), the rest is the same as in Example 1. Example 4

[0051] Except for the addition ratio of high-nitrogen organic fertilizer being 2.5% (basic substrate 97.5%), the rest is the same as in Example 1. Example 5

[0052] Except for strictly controlling the particle size of the temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material to the lower limit of 0.2 mm (passing through a 200-mesh sieve), the rest is the same as in Example 1. Example 6

[0053] Except for adjusting the particle size of the temperature and humidity responsive chitosan-sodium alginate coated biochar composite material to the upper limit of 1.0 mm (passing through an 18-mesh sieve), the rest is the same as in Example 1. Example 7

[0054] Except for adjusting the C / N ratio of the compost to the lower limit of 20:1, the rest is the same as in Example 2 (the proportion of high-nitrogen organic fertilizer added is 10%). Example 8

[0055] Except for adjusting the C / N ratio of the compost to the upper limit of 25:1, the rest is the same as in Example 4 (the proportion of high-nitrogen organic fertilizer added is 7.5%). Example 9

[0056] Except for extending the water control treatment to the maximum of 7 days, the rest is the same as in Example 4 (the proportion of high-nitrogen organic fertilizer added is 7.5%).

[0057] Comparative Example 1 A commercially available peat moss:vermiculite:perlite = 6:3:1 mixed substrate (containing non-degradable components) was used and placed in the same fully degradable seedling trays. The remaining operations were the same as in Example 1.

[0058] Comparative Example 2 Unfermented rice husks were used instead of fermented rice husks in the base substrate, and the rest was the same as in Example 1.

[0059] Comparative Example 3 5% vermiculite (total percentage) was added to the base matrix, and the rest was the same as in Example 1. The trace amount of non-degradable filler formed a physical barrier, causing the roots to deflect at the degradation interface, proving that even a small amount of mineral filler can disrupt the degradation continuity, highlighting the necessity of fully degradable components.

[0060] Comparative Example 4 The proportion of high-nitrogen organic fertilizer added was 20% (exceeding the range of 2.5%-15%), and the rest was the same as in Example 1. Excessive organic fertilizer led to an imbalance in the C / N ratio (measured at 18:1), and the continuous accumulation of salt caused high salt stress, confirming the key role of the patent-limited proportion in avoiding salt stress.

[0061] Comparative Example 5 The basic substrate ratio was adjusted to 40:30:30 (rice husk: coconut coir: temperature and humidity responsive chitosan-sodium alginate coated biochar composite material), with the rest being the same as in Example 1. Excessive rice husk resulted in a dense structure, and the anaerobic environment reduced the number of lateral roots by 42.7%, verifying the optimization value of the 30:40:30 ratio for the physical structure.

[0062] Comparative Example 6 The water control treatment was shortened to 3 days (below the lower limit of 5 days), and the rest was the same as in Example 4 (the proportion of high-nitrogen organic fertilizer added was 7.5%). This proves that insufficient water control leads to insufficient structural strength, highlighting the necessity of 5 days as the lower limit of the process.

[0063] Comparative Example 7 The water control treatment was extended to 10 days (exceeding the 7-day upper limit), with the rest remaining the same as in Example 4 (the proportion of high-nitrogen organic fertilizer added was 7.5%). This demonstrates that prolonged water control exceeds the plant's tolerance threshold, verifying the scientific validity of setting 7 days as the upper limit for the process.

[0064] Comparative Example 8 Except for replacing the temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material with biochar that is only coated with chitosan-sodium alginate but does not contain temperature-sensitive polymer (preparation method: skip step (c) of temperature-sensitive polymer synthesis and proceed directly to steps (d)-(f)), the rest is the same as in Example 1.

[0065] Comparative Example 9 Except for replacing the temperature and humidity responsive chitosan-sodium alginate coated biochar composite material with ordinary biochar loaded with the same amount of PGPR but without a coating layer (preparation method: steps (b)-(d) are omitted, and the PGPR bacterial suspension is directly sprayed onto the surface of ordinary biochar), the rest is the same as in Example 1.

[0066] The specific performance test items for each embodiment and comparative example are as follows: 1.45-day residual rate: determined according to GB / T 38082-2019, samples were taken every 5 days after transplanting, dried, weighed, and the residual percentage was calculated. 2. EC value monitoring: The conductivity of the 1:5 water extract was determined according to the standard method of NY / T 1121.2-2006, and monitored every 10 days during the seedling stage. 3. Tray breakage rate: The proportion of seedling trays damaged during transplanting is visually estimated; 4. Survival rate: The percentage of tobacco seedlings that survived 30 days after transplanting was statistically analyzed; 5. Temperature response test: Take 5g of dry composite material sample and place it in a constant temperature and humidity chamber. After stabilizing at 25℃ for 24 hours, record the moisture content every 2 hours. Then raise the temperature to 35℃ and maintain it for 24 hours, and record the moisture content every 2 hours.

[0067] 6. Humidity response test: Place the sample in a sealed test chamber, first use a desiccant to stabilize the ambient humidity at 40%RH for 12 hours, and record the amount of moisture released per unit time; then use a humidifier to increase the humidity gradient to 80%RH (increase by 10% every 2 hours), and measure the moisture release rate simultaneously.

[0068] 7. PGPR Activity Retention Test Method: On days 7 and 14 after transplanting, 10 tobacco seedlings were randomly selected. The substrate within a 2cm radius around the roots was carefully excavated, and the root surface microorganisms were washed away with sterile physiological saline. The eluent was collected as the test sample. The eluent was serially diluted and spread on a specially prepared selective medium (containing 100 mg / L nalidixic acid and 50 mg / L actinomycete ketone). After incubation at 28°C for 48 hours, the colony count was recorded. The number of viable bacteria per gram of rhizosphere substrate was calculated using colony forming units (CFU).

[0069] 8. Extreme climate adaptability test (simulation of continuous drought in Yunnan): daily average temperature 32.5℃, relative humidity 35%-45%.

[0070] The results are shown in Table 1:

[0071] As shown in Table 1, the experimental data demonstrate that the temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material of this invention exhibits significant technical advantages. Regarding degradation performance, Examples 1-9 all achieved complete degradation within 45 days (0% residue), while Comparative Example 1, containing mineral fillers, had a residue rate of 65%, and even Comparative Example 3, with only 5% vermiculite added, had a residue of 5.3%, fully demonstrating the necessity of a fully biodegradable design. Precise control of the high-nitrogen organic fertilizer ratio (2.5%-15%) is crucial for system performance. Examples 2-4 maintained stable EC values ​​within this range, with seedling survival rates all exceeding 97.8%; however, Comparative Example 4 exceeded this range, resulting in a severely excessive EC value and a sharp drop in survival rate to 72.4%, verifying the scientific validity of the patented specified ratio.

[0072] The temperature and humidity response characteristics of the material are the core innovation of this invention. The temperature response (moisture content change <22.5%) and humidity response (release rate adjustment ratio >2.3:1) of Examples 1-9 are significantly better than the control group, forming a stark contrast to Comparative Example 8 (without temperature-sensitive polymer) and Comparative Example 9 (without coating layer). In particular, Example 1 exhibits a moisture content change of only 18.7%, enabling the matrix to intelligently regulate moisture and nutrient supply under different environmental conditions. This environmental responsiveness directly translates into practical application advantages: under simulated continuous drought conditions in Yunnan (daily average temperature 32.5℃, relative humidity 35%-45%), the extreme climate survival rate of Example 1 reaches 97.6%, nearly 9 percentage points higher than Comparative Example 9.

[0073] The protective effect of the coating structure on microbial activity is equally crucial. In Examples 1-9, PGPR activity was maintained at 5.9 × 10⁻⁶ days post-transplantation. 6 -8.5×10 6 CFU / g, which is the value of Comparative Example 9 (2.1 × 10⁻⁶). 5 The biochar concentration was more than 28 times higher than that of the control group (CFU / g). This highly active microorganism not only effectively inhibited the occurrence of diseases, but also significantly improved the structural stability through the biofilm network it formed, reducing the breakage rate of the seedbed to 0.7-1.5%, while the breakage rate of the control group 6, which had insufficient water control, was as high as 18.7%. The synergistic optimization of biochar particle size (0.2-1 mm), basic substrate ratio (30:40:30), and C / N ratio (20-25:1), combined with a precise water control process of 5-7 days, jointly solved the industry problems of "initial nutrient deficiency, mid-term looseness, and difficulty in transplanting" in fully degradable seedling trays, achieving a balance between environmental friendliness and high-efficiency seedling cultivation.

[0074] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A seedling substrate specifically for fully degradable tobacco seedling trays, characterized in that, It is composed of the following components by mass percentage: 85%-97.5% tobacco-specific base matrix and 2.5%-15% high-nitrogen organic fertilizer; the tobacco-specific base matrix is ​​obtained by mixing decomposed rice husks, coconut coir, and temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material in a mass ratio of 30:40:30, with a bulk density of 0.24-0.28 g·cm³. -3 The total porosity is 82%-86%, the pH value is 5.5-6.0, and the electrical conductivity (EC) value is 800-1000 μS·cm. -1 The high-nitrogen organic fertilizer is prepared by high-temperature aerobic composting and fermentation of livestock and poultry manure, soybean meal, and straw in a mass ratio of 50:30:20 for 15-20 days, followed by the addition of 3%-5% humic acid and 2%-4% amino acid powder, which are then mixed, dried, and the mixture has a nitrogen content of not less than 4.5%, a pH value of 7.0-7.5, and an EC value of 9.5-11.0 mS·cm. -1 ; The temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material has a temperature phase transition threshold of 32±1℃ and a humidity response range of 40%-80%RH, and its surface is loaded with a concentration of 1×10 7 -5×10 7 The plant rhizosphere growth-promoting bacteria complex, comprising Bacillus amyloliquefaciens FZB42 and Pseudomonas putida KT2440, with a viable count ratio of 3:

1.

2. The seedling substrate for a fully degradable tobacco seedling tray according to claim 1, characterized in that, The tobacco-specific base matrix contains decomposed rice husks with a particle size of 0.5-2 mm, coconut coir fibers with a length of 2-5 mm, and temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material with a particle size of 0.2-1 mm. The three are mixed and then steam-sterilized at 121°C for 30 minutes. The preparation method of the temperature and humidity responsive chitosan-sodium alginate coated biochar composite material includes the following steps: (a) Biochar was prepared by pyrolyzing corn stalks at 450°C for 4 hours under limited oxygen conditions. The biochar was then crushed and passed through a 0.2-1 mm sieve, washed with 1% HCl solution, and then washed with deionized water until neutral. (b) Chitosan with a degree of deacetylation ≥90% was prepared into a 5% working solution using a 1% acetic acid solution, and sodium alginate was prepared into a 3% aqueous solution separately. Under the conditions of an ice bath at 4°C and vigorous stirring at 500 rpm, sodium alginate solution was added dropwise to the chitosan solution at a rate of 2 mL / min to maintain the pH of the system at 5.0±0.2, forming a pre-complexed solution. The biochar obtained in step (a) was immersed in the pre-complexed solution and stirred at 60 rpm for 30 minutes. (c) Add N-isopropylacrylamide and acrylic acid monomer, 0.5% azobisisobutyronitrile and 0.2% N,N'-methylenebisacrylamide in a mass ratio of (95-97):(3-5) to the system, adjust the pH to 5.5±0.2, and polymerize in a water bath at 60°C for 2 hours under nitrogen protection to obtain biochar loaded with temperature-sensitive polymer; (d) The biochar loaded with the temperature-sensitive polymer was rinsed three times with deionized water and then freeze-dried at -50°C for 24 hours. (e) Mix Bacillus amyloliquefaciens FZB42 and Pseudomonas putida KT2440 at a viable count ratio of 3:1 to prepare a 1×10⁻⁶ solution. 8 CFU / mL bacterial suspension was evenly sprayed onto the surface of the product in step (d) and allowed to stand at 4°C for 12 hours. (f) Freeze-dry at -50℃ for 12 hours to obtain a temperature and humidity responsive chitosan-sodium alginate-coated biochar composite material with PGPR complex bacteria on the surface. Its temperature phase transition threshold is 32±1℃ and its humidity response range is 40%-80%RH.

3. The seedling substrate for a fully degradable tobacco seedling tray according to claim 1, characterized in that, In the preparation process of the high-nitrogen organic fertilizer, the initial C / N ratio of the compost is adjusted to 20-25:1, the moisture content is controlled at 55%-65%, the compost is turned over every 3 days, and the fermentation temperature is maintained at 55℃-70℃; the humic acid in the high-nitrogen organic fertilizer is potassium fulvic acid, and the amino acid powder is a hydrolyzed product of soybean protein, with a free amino acid content of not less than 80%. The seedling substrate needs to be adjusted to a moisture content of 50%-60% before use and left to stand for 24 hours to allow the moisture to be evenly distributed.

4. A method for preparing a fully degradable tobacco seedling tray-specific seedling substrate, characterized in that, The preparation of the fully degradable tobacco seedling tray-specific seedling substrate according to any one of claims 1-3 includes the following steps: S10: The decomposed rice husks, coconut coir, and temperature and humidity responsive chitosan-sodium alginate coated biochar composite material are crushed to the specified particle size range and mixed in a mass ratio of 30:40:30 to obtain a tobacco-specific base matrix. S20: Mix livestock and poultry manure, soybean meal, and straw, adjust the C / N ratio to 20-25:1, and the moisture content to 55%-65%. Inoculate with 0.2%-0.5% high-temperature composting bacteria and carry out aerobic composting fermentation for 15-20 days, turning the pile every 3 days during the period. After fermentation, dry the pile until the moisture content is below 15%. S30: Add 3%-5% humic acid and 2%-4% amino acid powder (by mass of total material) to the dry material obtained in step S20, mix evenly, and pulverize through a 2 mm sieve to obtain high-nitrogen organic fertilizer. S40: Mix the tobacco-specific basic substrate obtained in step S10 with the high-nitrogen organic fertilizer obtained in step S30 at a mass ratio of 85:15, 90:10, 92.5:7.5, 95:5 or 97.5:2.5, mix evenly, adjust the moisture content to 50%-60%, and let stand for 24 hours to obtain the fully degradable tobacco seedling tray-specific seedling substrate.

5. The method for preparing a fully degradable tobacco seedling tray-specific seedling substrate according to claim 4, characterized in that, In step S10, the decomposed rice husks are obtained by drying rice processing by-products at 60℃, pulverizing them, and passing them through a 0.5-2 mm sieve; the coconut coir is desalinated commercial coconut coir, washed with water until the EC value is below 1.0 mS·cm. -1 Dry and store for later use.

6. The method for preparing a fully degradable tobacco seedling tray-specific seedling substrate according to claim 4, characterized in that, In step S20, the high-temperature composting inoculant is a compound inoculant of Bacillus and Actinomycetes, with a viable count of not less than 1×10⁻⁶. 8 CFU / g.

7. The method for preparing a fully degradable tobacco seedling tray-specific seedling substrate according to claim 4, characterized in that, In step S30, the drying process uses a low-temperature drying method, with the temperature not exceeding 60°C and the time being 8-12 hours, in order to retain the active substances in the organic fertilizer.

8. The method for preparing a fully degradable tobacco seedling tray-specific seedling substrate according to claim 4, characterized in that, In step S40, the mixing is carried out using a twin-shaft paddle mixer with a rotation speed of 20-30 rpm and a mixing time of 10-15 minutes.

9. The application of a seedling substrate specifically for a fully degradable tobacco seedling tray according to any one of claims 1-3, characterized in that, Includes the following steps: T10: The seedling substrate is filled into a fully degradable tobacco seedling tray made of sugarcane bagasse or rice straw fiber through vacuum filtration and shaped with the addition of 0.2% nano-anti-mildew agent and 0.5% biodegradable modified MUF wet strength agent, and compacted to a bulk density of 0.26-0.28 g·cm³. -3 ; T20: Sow fresh tobacco seeds of the current year, 1-2 seeds per hole, cover with a thin layer of substrate, and cultivate in a greenhouse with an ambient temperature controlled at 25℃-30℃ and a relative humidity of 70%-85%; T30: During the seedling stage, maintain the substrate moisture content at 50%-60%. When the tobacco seedlings grow to 65 days old, stop watering for 5 days to control water usage, causing the plants to wilt physiologically but keeping the stems and leaves flexible. T40: After water control is completed, the entire tray of tobacco seedlings is transferred to the field in a "rolled-up" manner for "integrated pot and seedling transplanting" without removing the trays; T50: After transplanting, the seedling trays degrade synchronously with the growth of tobacco seedlings in the soil, completely disintegrating within 45 days, allowing roots to penetrate freely.

10. The application of the seedling substrate specifically for fully degradable tobacco seedling trays according to claim 9, characterized in that, In step T10, the external dimensions of the fully degradable tobacco seedling tray are 524 mm × 330 mm × 60 mm, the number of holes is 126, the layout is 9 × 14 grids, and the depth of a single hole is 45-50 mm. In step T20, before sowing, the seeds are soaked in a 0.1% potassium permanganate solution for 15 minutes for disinfection, rinsed with clean water, and then dried for later use. In step T30, if the temperature exceeds 35℃ during the water control period, a moisturizing spray can be applied in the evening, with a single spray volume not exceeding 5 mL / m³. -2 ; In step T40, the "rolling blanket" operation is performed by slowly rolling up the blanket along the long side of the acupuncture plate, with a roll diameter of not less than 20 cm, to avoid mechanical damage. In step T50, the soil pH of the transplanting site should be 5.5-7.0, and the organic matter content should be no less than 20 g·kg⁻¹. -1 Apply sufficient base fertilizer before transplanting.

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