A method for making a biocontrol pepper blight seedling substrate using solid waste

Abstract

The present application relates to a kind of methods for making biocontrol pepper blight seedling substrate with solid waste.The effect of trichoderma in preventing and treating pepper blight in the prior art is greatly influenced by environment and has poor stability.The method comprises: mixing organic solid waste raw materials with auxiliary materials, adding phosphogypsum for aerobic composting once fermentation, cooling to below 45 DEG C to obtain an organic carrier; inoculating trichoderma into the organic carrier, and carrying out secondary fermentation below 45 DEG C until the number of trichoderma in the product and the seed germination index meet the standards.The present application optimizes the physicochemical properties of the carrier by phosphogypsum, and realizes efficient colonization of trichoderma in the organic carrier by secondary fermentation.The prepared substrate can significantly reduce the number of pepper pythium, the comprehensive disease prevention rate of pepper blight reaches 77% to 85%, the yield increases by 20.0% to 45.2%, and realizes effective combination of waste resource utilization and disease control.

Description

Technical Field

[0001] This invention relates to the fields of agricultural solid waste resource utilization and biological control of plant diseases. Specifically, it relates to a method for producing a biocontrol substrate for pepper blight seedlings using solid waste. Background Technology

[0002] Phytophthora blight of peppers is a devastating soil-borne disease caused by Phytophthora capsici. The pathogen can remain dormant in the soil for extended periods, and once suitable temperature and moisture conditions are met, it rapidly infects the pepper root system, causing plant wilting and death, resulting in significant economic losses for pepper cultivation. With the adjustment of agricultural industrial structure and the expansion of greenhouse vegetable cultivation, continuous cropping of peppers is becoming increasingly common, leading to a year-on-year increase in the incidence and severity of Phytophthora blight. In current agricultural production practices, chemical control remains the primary means of controlling Phytophthora blight. Although it is fast-acting, the long-term and excessive use of chemical pesticides not only leads to pesticide resistance in pathogens, reducing control effectiveness, but also disrupts the soil microbial community structure, causing pesticide residues and environmental pollution, threatening food safety. Therefore, developing environmentally friendly and long-lasting biological control technologies, especially utilizing antagonistic microorganisms to control soil-borne diseases, has become a research hotspot and development direction in this field.

[0003] In existing technologies, using Trichoderma for the biological control of pepper blight is a common approach. Trichoderma, as an important biocontrol fungus, possesses rapid growth, strong competitive ability, the ability to produce various antimicrobial substances, and hyperparasitic mechanisms, exhibiting significant antagonistic effects against various plant pathogenic fungi. Conventional methods typically involve preparing Trichoderma into powders, granules, or liquid inoculum, which are then applied directly to the soil or used for root drenching before pepper planting or at the early stages of disease. For example, some existing technologies disclose a wettable powder of Trichoderma harzianum for controlling pepper blight through spraying or root drenching. However, these existing technologies have significant drawbacks in practical application: after direct application of Trichoderma to the soil, due to the complexity of the soil environment, such as soil type, pH, temperature, humidity, and competition from native microorganisms, the exogenously introduced Trichoderma often fails to effectively colonize and form a dominant community in the pepper rhizosphere. This results in unstable disease control efficacy, is highly dependent on site conditions, and is difficult to replicate effectively in field applications.

[0004] To improve the colonization effect of microbial inoculants, existing technologies have also developed solutions that utilize organic materials as carriers to carry biocontrol bacteria. For example, well-rotted livestock and poultry manure or agricultural waste compost is used as a carrier, adsorbed or mixed with Trichoderma spores before being applied to the soil. While this approach improves the microenvironment for Trichoderma spores to some extent and increases the initial survival rate, it still has shortcomings. First, although conventional compost carriers provide basic nutrients, their physical structure (such as porosity and water retention) and chemical properties (such as pH and salinity) are often not entirely suitable for the long-term survival and reproduction of Trichoderma spores, resulting in limited carrier carrying capacity. Second, after being applied to the soil, such carriers are prone to rapid degradation or have their ecological niches usurped by other microorganisms, failing to provide a continuous shelter for Trichoderma spores. This causes the population density of biocontrol bacteria in the rhizosphere to decline rapidly over time, making it difficult to maintain sustained inhibitory ability against Phytophthora capsici throughout the entire growth period. Furthermore, most existing carrier preparation processes only focus on the fermentation and composting process, lacking targeted regulation based on the colonization needs of biocontrol bacteria, and failing to achieve an organic combination of carrier construction and functional bacteria cultivation.

[0005] In summary, how to construct a seedling substrate that can both utilize solid waste for resource recovery and provide a suitable habitat for biocontrol bacteria, significantly improving their planting efficiency and stability in the rhizosphere of chili peppers, is a key technical problem that urgently needs to be solved in the field of biological control of chili pepper diseases. Summary of the Invention

[0006] To address the technical problems existing in the background art, such as the difficulty in soil colonization of current Trichoderma preparations, the significant influence of site environment on disease control efficacy, poor stability, and the unsuitability of conventional organic carriers for long-term survival of biocontrol bacteria, this invention provides a method for preparing a biocontrol seedling substrate for pepper blight using solid waste. This invention combines organic solid waste fermentation technology with biocontrol bacteria cultivation technology, utilizing phosphogypsum as a conditioner to optimize the carrier environment, thus constructing a seedling substrate that ensures efficient Trichoderma colonization and sustained biocontrol function.

[0007] The present invention provides a method for making a biocontrol seedling substrate for pepper blight using solid waste, comprising the following steps: (1) Organic carrier preparation: organic solid waste raw materials and auxiliary materials are mixed, and phosphogypsum is added as a conditioner for aerobic composting fermentation. When the fermentation temperature enters the cooling stage and the temperature is below 45°C, the first fermentation is completed to obtain an organic carrier; (2) Secondary bio-fermentation: Trichoderma is inoculated into the organic carrier obtained in step (1), and secondary fermentation is carried out under the condition that the fermentation temperature is below 45°C until the number of Trichoderma in the fermentation product reaches the preset threshold and the seed germination index meets the standard, thereby obtaining a biocontrol seedling substrate for pepper blight.

[0008] In the above technical solution, the preparation of the organic carrier in step (1) is the foundation of the entire method. This invention uses organic solid waste as the main raw material, which not only realizes the resource utilization of waste but also provides carbon and nitrogen sources for Trichoderma. Adding phosphogypsum as a conditioner is one of the key features of this invention. Phosphogypsum can not only adjust the pH of the mixture and neutralize the alkaline substances produced during fermentation, creating a suitable pH environment for subsequent Trichoderma colonization, but also improve the physical structure of the material, increase porosity, and facilitate aeration. The high temperature generated during aerobic composting fermentation can kill pathogens and weed seeds, ensuring the safety of the carrier. Controlling the primary fermentation to end at a cooling stage below 45℃ is to avoid over-fermentation leading to the depletion of organic matter, while also ensuring that the carrier temperature is suitable for subsequent Trichoderma inoculation, preventing high temperatures from killing functional bacteria.

[0009] Further, in step (1), the organic solid waste raw material includes cow dung, and the auxiliary material includes crop straw; the carbon-nitrogen ratio of the mixed organic solid waste raw material and auxiliary material is adjusted to 30-35, and the moisture content is adjusted to 60%-65%. The carbon-nitrogen ratio is a key parameter affecting the composting fermentation rate and the degree of decomposition. Controlling the carbon-nitrogen ratio between 30 and 35 can ensure the activity of microorganisms in decomposing organic matter, enabling the fermentation process to heat up quickly and achieve thorough decomposition. The moisture content is directly related to the metabolic activities of microorganisms and the aeration of the compost pile. A moisture content of 60%-65% can meet the needs of microbial life activities and ensure sufficient oxygen diffusion space within the compost pile, preventing the formation of an anaerobic environment.

[0010] Furthermore, in step (1), the amount of phosphogypsum added is 10% to 15% of the dry weight of the mixture of organic solid waste raw materials and auxiliary materials. The amount of phosphogypsum added is precisely calculated. If the amount added is too low, it will be difficult to effectively adjust the pH value of the carrier and improve the physical structure; if the amount added is too high, it may introduce too much acidic substances or heavy metal risks, affecting the growth of pepper seedlings. This ratio range has been verified by a large number of experiments and can achieve the best balance between adjusting the physicochemical properties and ensuring the safety of the substrate.

[0011] Furthermore, the inoculation amount of Trichoderma in step (2) is 1‰ to 2‰ of the dry weight of the organic carrier. The control of the inoculation amount is directly related to the initial density and final colonization effect of Trichoderma in the carrier. Too low an inoculation amount may cause Trichoderma to be at a disadvantage in competition with other indigenous microorganisms, making it difficult to form a dominant microbial community; too high an inoculation amount will increase production costs and may lead to fierce competition for nutrients due to excessive population density, which is not conducive to the survival of the fungi.

[0012] Furthermore, during the secondary fermentation process described in step (2), the pile is turned over every two days. Turning over increases the oxygen supply within the carrier, removes excess carbon dioxide and heat, promotes the uniform distribution and growth of Trichoderma in the carrier, and prevents localized high temperatures or hypoxia from inhibiting Trichoderma activity.

[0013] Furthermore, the preset threshold mentioned in step (2) is when the number of Trichoderma fungi reaches 0.2 × 10⁻⁶. 8 cfu / g ~ 0.5 × 10 8 CFU / g; the seed germination index meeting the standard means that the seed germination index is greater than or equal to 70%. The amount of Trichoderma is a core indicator for measuring the biocontrol ability of the substrate; reaching this level ensures that the substrate, after being applied to the soil, has an effective antagonistic effect against Phytophthora capsici. The seed germination index is an important indicator for evaluating the maturity and toxicity of the substrate; a germination index greater than 70% indicates that the substrate is fully decomposed, contains no phytotoxic substances, and is suitable for the growth of chili seedlings.

[0014] Furthermore, in step (2), when obtaining the biocontrol substrate for seedlings against Phytophthora in peppers, the moisture content of the fermentation product is controlled to be less than 30%. A lower moisture content helps to inhibit the growth of miscellaneous bacteria, prolongs the shelf life of the substrate, facilitates the storage and transportation of the product, and also ensures that the substrate has suitable bulk density and porosity, which is beneficial for seedling operation.

[0015] Furthermore, the aerobic composting fermentation described in step (1) adopts windrow composting, with the windrow pile dimensions being 2m long, 1.5m wide, and 1.5m high. During the fermentation process, a centrifugal fan is used for ventilation, with a ventilation volume of 1610 m³ / h. 3 / h~2844 m 3 / h. Windlass composting has a simple structure, is easy to operate, and is suitable for large-scale production. Specific compost dimensions and ventilation parameters are optimized to ensure sufficient oxygen supply and uniform temperature distribution within the compost, thereby obtaining a high-quality organic carrier with uniform physicochemical properties.

[0016] This invention also provides a biocontrol seedling substrate for pepper blight prepared according to any one of the above methods, the substrate comprising fermented organic solid waste, phosphogypsum, and colonized Trichoderma, wherein the effective viable count in the substrate is 0.2 × 10⁻⁶. 8 cfu / g ~ 0.5 × 10 8 The cfu / g, fecal coliform count, ascarid egg mortality rate, and heavy metal content meet the requirements of NY525-2021 standards. This substrate integrates the functions of biocontrol and seedling substrate, achieving functional integration.

[0017] Furthermore, the physicochemical properties of the biocontrol substrate for pepper blight seedling cultivation are as follows: pH value of 6.5–7.5, and bulk density of 0.6 g / cm³.3 ~0.8 g / cm 3 The total porosity is 75%–85%. This range of physicochemical properties is suitable for the root development of chili seedlings, possessing both good water and fertilizer retention capacity and sufficient aeration, which can promote the vigorous growth of chili seedlings.

[0018] The present invention has the following beneficial effects: (1) Because the present invention adopts a two-step process of "one-time aerobic composting fermentation + two-time biological fermentation", and inoculates Trichoderma in the second fermentation stage, Trichoderma can reproduce and colonize in large quantities in a pretreated and stable organic carrier. Compared with the prior art of directly applying Trichoderma to the soil or simply mixing organic materials, the number of Trichoderma in the substrate prepared by the present invention is as high as 0.2×10 8 cfu / g ~ 0.5 × 10 8 The concentration of cfu / g and the presence of a suitable microecological environment provided by the carrier allow Trichoderma to quickly form a protective layer in the rhizosphere of peppers after transplanting, significantly improving the planting efficiency and disease resistance stability, with a comprehensive disease prevention rate of 77% to 85%.

[0019] (2) By adding phosphogypsum as both an acidic and physical conditioner, the problem that the alkaline nature of organic waste compost is unfavorable for Trichoderma growth was effectively solved. The addition of phosphogypsum stabilized the substrate pH between 6.5 and 7.5, which is the optimal pH range for Trichoderma growth and also suitable for chili seedling growth. Simultaneously, phosphogypsum improved the substrate's pore structure, maintaining a bulk density of 0.6–0.8 g / cm³. 3 With a total porosity of 75% to 85%, it is conducive to both aeration and water retention, providing an ideal physical environment for the survival of Trichoderma and the development of pepper roots.

[0020] (3) This invention utilizes agricultural solid waste such as cow dung and straw, as well as industrial waste from phosphogypsum, as raw materials to achieve the circular agriculture goal of "treating waste with waste". On the one hand, it disposes of a large amount of accumulated organic waste and phosphorus chemical waste residue, reducing environmental pollution; on the other hand, it transforms waste into high-value-added biocontrol seedling substrate, reducing production costs and having significant ecological and economic benefits.

[0021] (4) The substrate prepared by this invention integrates seedling cultivation and disease prevention functions, making it convenient to use. Farmers can introduce biocontrol bacteria during the seedling cultivation process, eliminating the need for additional root irrigation or pesticide application during transplanting, thus simplifying agricultural operations and reducing labor intensity. Simultaneously, transplanting with the substrate avoids damage to the seedling roots during transplanting, shortens the seedling recovery period, and improves the transplant survival rate. Chili pepper yield increases by 20.0%–45.2% compared to conventional seedling substrates.

[0022] (5) The method of this invention has clear process parameters, standardized operation, and strong reproducibility. By strictly controlling key parameters such as fermentation temperature, ventilation volume, turning frequency, and inoculation amount, the standardized and large-scale production of biocontrol seedling substrate has been achieved, and the product quality is stable and reliable, providing strong technical support for the safe and efficient production of the chili industry. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the invention.

[0024] This invention provides a method for producing a biocontrol seedling substrate for pepper blight using solid waste. The method comprises three core stages: raw material pretreatment and mixing, primary aerobic composting fermentation, and secondary bio-fermentation. By constructing a specific microbial habitat, utilizing organic solid waste as a nutrient carrier, and phosphogypsum as a physicochemical conditioner, combined with aerobic fermentation and bio-culture technology, a functional seedling substrate containing a high density of Trichoderma fungi is ultimately prepared. The design logic of the entire process is as follows: First, through primary fermentation, unstable organic waste is transformed into a stable humic carrier, eliminating pathogens and weed seeds, and phosphogypsum is used to adjust the pH and physical structure. Then, during the cooling stage, biocontrol Trichoderma fungi are inoculated, and secondary propagation and colonization are carried out using the remaining nutrients on the carrier and a suitable environment, making Trichoderma fungi the dominant microbial group in the carrier, thereby achieving the biocontrol function against pepper blight.

[0025] The following details each step and its key process parameters: I. Preparation of organic carriers (steps S1-S4) The preparation of organic carriers is a fundamental step in the method of this invention, and its core lies in providing a suitable physicochemical environment for the subsequent colonization of Trichoderma.

[0026] Raw Material Selection and Proportioning (S1): This invention uses the solid portion of cow manure after solid-liquid separation as the main raw material. Cow manure is rich in organic matter and nitrogen. After solid-liquid separation, it has a suitable moisture content and a loose structure, which facilitates aeration. The auxiliary material is crop straw, such as corn straw or wheat straw, which needs to be crushed into small pieces of 1-5 cm. The main function of the straw is to adjust the carbon-nitrogen ratio (C / N) of the mixture and improve the porosity of the compost pile. When mixing cow manure and straw, the C / N ratio of the mixed organic material needs to be precisely controlled to be adjusted to 30-35. This range is the optimal C / N ratio range for microbial metabolism. If the C / N ratio is too high (e.g., >40), microbial growth is limited by the nitrogen source, fermentation temperature rises slowly, and the degree of decomposition is low. If the C / N ratio is too low (e.g., <25), excess nitrogen source easily leads to ammonia volatilization, causing nitrogen loss and producing odor. At the same time, excessively high concentrations of ammonia may inhibit the subsequent growth of Trichoderma. The moisture content should be controlled between 60% and 65%, which is the optimal humidity range for aerobic microbial activity. Too low a moisture content (<50%) will cause microbial metabolism to stagnate and the pile to dry out; too high a moisture content (>70%) will clog the material's pores, creating an anaerobic environment, producing foul odors, and is detrimental to maintaining high temperatures. In practice, a touch test can be used to determine the appropriate moisture content: when the material is squeezed in the hand, it clumps together; water stains remain between the fingers but do not completely drip off; when the hand is released, the material disperses.

[0027] Addition of phosphogypsum (S2): Add phosphogypsum to the uniformly mixed organic materials at 10%–15% of the dry weight of the organic material mixture. Phosphogypsum is a byproduct of phosphate chemical industry, is acidic, and its main component is calcium sulfate dihydrate. In this invention, phosphogypsum plays several key roles: First, as an acid conditioner, the composting process of cow manure produces alkaline substances due to ammoniation, leading to an increase in pH value, often reaching above 8.0, while the suitable pH environment for Trichoderma is slightly acidic to neutral (pH 5.5-7.0). Adding phosphogypsum can effectively neutralize the alkaline products during the composting process, stabilizing the pH value of the carrier within the suitable range of 6.5–7.5 for Trichoderma growth. Second, the calcium ions in phosphogypsum can combine with organic matter, promoting the formation of humus and improving the colloidal stability of the carrier. Furthermore, calcium sulfate crystals can improve the physical structure of the carrier, increase the number of aggregates, regulate bulk density and porosity, and make the matrix more loose and breathable. The amount added should be strictly controlled between 10% and 15%. If it is less than 10%, the effect of adjusting pH and improving structure will not be obvious. If it is more than 15%, it may introduce excessive acidic substances, causing the carrier to become too acidic. In addition, the trace amounts of heavy metals and fluorides in phosphogypsum may have an accumulation risk and must be controlled within a safe range.

[0028] Aerobic composting fermentation (S3): Rapid maturation and fermentation are carried out using windrow composting. The pile dimensions are set at 2m long × 1.5m wide × 1.5m high. This size ensures sufficient heat capacity to maintain high temperature while facilitating mechanical turning. Forced ventilation is achieved using centrifugal fans during fermentation, with the ventilation volume controlled between 1610-2844 m³ / h. 3 / h, frequency 35-50Hz. Ventilation is a key control parameter for aerobic fermentation. Insufficient ventilation will lead to anaerobic conditions inside the pile, producing harmful gases such as hydrogen sulfide; excessive ventilation will remove too much heat and moisture, preventing the pile temperature from reaching the high-temperature stage. By combining regular turning (once every 6 days) with forced ventilation, sufficient oxygen supply and uniform temperature distribution inside the pile can be ensured. The aerobic fermentation process is divided into three stages: heating, high temperature, and cooling. In the heating stage, thermophilic bacteria are active, decomposing easily degradable organic matter, and the pile temperature rises rapidly; in the high-temperature stage (temperature >50℃, lasting 5-7 days), thermophilic bacteria become the dominant bacteria, not only accelerating the decomposition of recalcitrant organic matter, but more importantly, effectively killing pathogens, parasite eggs, and weed seeds, achieving the harmlessness of the material.

[0029] Determination of the end of primary fermentation (S4): After the fermentation process of heating up to high temperature is completed, the cooling stage begins. This invention specifically stipulates that the primary fermentation process is completed when the temperature drops below 45℃. Choosing 45℃ as the endpoint is based on the biological characteristics of *Trichoderma*: although *Trichoderma* has good heat resistance, it will be inactivated or die if exposed to high temperatures (>50℃) for extended periods. If fermentation ends at the high-temperature stage, the carrier temperature will be too high for direct inoculation; if the temperature is allowed to drop to room temperature, fermentation will be over-fermented, organic matter will be depleted, and the carrier density will increase, which is not conducive to the subsequent propagation of *Trichoderma*. At this point, the moisture content of the fermentation product is approximately 45% by mass, which retains some moisture for *Trichoderma* utilization while allowing for further moisture adjustment. The obtained product is the primary fermentation organic carrier, which is stable, highly harmless, and retains nutrients suitable for *Trichoderma* growth.

[0030] II. Secondary bio-fermentation process (steps S5-S8) Secondary bio-fermentation is the core step in achieving biocontrol function in this invention. Its purpose is to successfully inoculate Trichoderma and propagate and colonize it in large quantities in the carrier.

[0031] Trichoderma inoculation (S5): The inoculation target is the organic material carrier after primary fermentation. The inoculation amount is based on 1-2‰ of the dry weight of the carrier. Trichoderma inoculum is usually in the form of spore powder or granules, which needs to be premixed evenly with a small amount of carrier before being sprinkled into a large pile and evenly distributed by turning the pile. The choice of inoculation amount is crucial: if the inoculation amount is too low (<1‰), the initial density of Trichoderma in the carrier is low, making it difficult to quickly gain dominance in competition with native microorganisms, resulting in a long colonization period, and it may even be inhibited by contaminating microorganisms; if the inoculation amount is too high (>2‰), although it can quickly form a dominance, it significantly increases production costs, and the high density of mycelium in the limited nutrient space will lead to fierce competition, which may cause premature aging or autolysis of the mycelium. The Trichoderma selected in this invention is preferably Trichoderma harzianum, which has a strong antagonistic effect on Phytophthora capsici, and has a fast growth rate and high sporulation.

[0032] Fermentation Condition Control (S6): After inoculation, the second fermentation stage begins, and temperature control is crucial at this stage. Throughout the process, the fermentation temperature must be strictly controlled below 45℃. Unlike the primary fermentation, the secondary fermentation does not aim to kill unwanted microorganisms with high temperatures, but rather to create the optimal growth environment for *Trichoderma*. If the temperature exceeds 45℃, ventilation must be increased immediately or the pile must be turned to lower the temperature. During the secondary fermentation, turning is performed (every two days), more frequently than during the primary fermentation. This frequent turning is not only for oxygen supply but also to break up the mycelium, promoting the even spread of *Trichoderma* spores among the carrier particles and achieving multi-point colonization.

[0033] Fermentation endpoint determination (S7): The endpoint of secondary fermentation is determined by two indicators: First, the biosafety indicator, with a seed germination index (GI value) ≥ 70%. The GI value reflects the phytotoxicity of the compost product; a low GI value indicates the presence of substances that inhibit seed germination (such as small-molecule organic acids, ammonia, etc.), while a GI value ≥ 70% indicates that the carrier has been fully decomposed and is non-toxic to plants. Second, the functional microbial count indicator, with an effective viable count of Trichoderma reaching 0.2–0.5 × 10⁻⁶. 8 CFU / g. This is a critical threshold for ensuring biocontrol effectiveness. When the number of *Trichoderma* fungi in the carrier reaches this level, it means that *Trichoderma* has successfully colonized and formed a dominant microbial community. The detection method uses the dilution plate method, with counting on selective culture media. Simultaneously, the moisture content of the second fermentation product must be controlled to be less than 30% by mass. A low-moisture environment is conducive to *Trichoderma* spores entering a dormant state, extending the shelf life of the substrate, and preventing "spore burn" or mold growth due to microbial metabolic heat generation during storage and transportation.

[0034] III. Preparation of seedling substrate for biocontrol of pepper blight (steps S9-S12) After completing the above steps, the obtained fermented material is the biocontrol substrate for seedling cultivation of pepper blight. This substrate must meet the following quality indicators: Hygiene indicators (S9): Fecal coliform count, ascaris egg mortality rate, and heavy metal content meet the quality standards of NY525-2021 "Organic Fertilizer". This ensures the safety of the substrate in agricultural applications and prevents secondary pollution to the soil environment or agricultural products.

[0035] Functional indicator (S10): The effective viable count of Trichoderma is stable at 0.2–0.5 × 10⁻⁶. 8 cfu / g. This high bacterial density ensures that the substrate can quickly form a protective layer in the rhizosphere of peppers after being applied to the soil, inhibiting the infection of Phytophthora capsici through multiple mechanisms such as nutrient competition, hyperparasitism, and secretion of antibacterial substances.

[0036] Physicochemical properties (S11-S12): pH value is stable between 6.5 and 7.5, which is the optimal pH range for pepper seedling growth and Trichoderma survival. Bulk density is 0.6–0.8 g / cm³. 3 The total porosity is between 75% and 85%, with aeration porosity around 45% and water-holding porosity around 30%. This "granular structure" ensures both good water and fertilizer retention capacity of the substrate and sufficient oxygen supply for root respiration, preventing root rot caused by waterlogging. The addition of phosphogypsum plays a crucial physical conditioning role, improving upon the shortcomings of simple cow manure compost, such as easy compaction and insufficient porosity.

[0037] Working principle and process: The substrate prepared in this invention works as follows: First, during the seedling stage, chili seeds are sown in the substrate. The loose structure of the substrate facilitates seed germination and root development, while the abundant humus provides ample nutrients. Simultaneously, the high concentration of Trichoderma spores in the substrate germinates in a moist environment, and the mycelium rapidly covers the surface of the substrate particles, forming a mycorrhizal zone. Second, when the chili seedlings are transplanted to the field, the roots carry the substrate clumps containing Trichoderma into the soil. This "transplanting with fungi" method avoids the death of fungi caused by poor soil conditions when directly applying fungicides to the soil. The substrate clumps act as a "sanctuary" and "replenishment station" for Trichoderma, enabling it to survive and proliferate continuously in the rhizosphere soil of the chili peppers. Furthermore, *Trichoderma* controls pepper blight through multiple mechanisms: first, competition—*Trichoderma* grows rapidly, quickly consuming rhizosphere space and nutrients, and seizing infection sites from *Phytophthora*; second, hyperparasitism—*Trichoderma* recognizes and entangles with *Phytophthora* hyphae, secreting cell wall-degrading enzymes (such as chitinase and glucanase) to dissolve the pathogen's cell wall; and third, antibiotics—*Trichoderma* secretes antibiotic-like substances to directly inhibit *Phytophthora* growth. Finally, the phosphogypsum component in the substrate continuously regulates the rhizosphere pH, inhibiting the germination of acid-loving *Phytophthora* spores, and provides calcium to strengthen pepper cell walls, thus improving plant disease resistance. Specific Implementation Example 1: Biocontrol seedling substrate for pepper blight without added phosphogypsum Location of implementation: Yunnan Agricultural University, Kunming, Yunnan Province. Raw materials: sawdust (auxiliary material), chicken manure (main material). Mixing: The sawdust and chicken manure are mixed according to a C / N ratio of 30, and the total mass of the mixture is 2 tons. The moisture content of the initial fermentation is adjusted to 60%. Primary fermentation: The primary fermentation is carried out according to the high temperature composting method, using windrow composting and turning the pile regularly. When the fermentation pile completes the heating-high temperature process, the primary fermentation process is completed when the temperature is less than 45℃ during the cooling stage. Secondary fermentation: After the primary fermentation is completed, Trichoderma harzianum inoculant is added at 2‰ of the dry weight of the fermentation material. After mixing evenly, fermentation continues. The pile is turned every 2 days. Fermentation is stopped when the temperature approaches or reaches room temperature (ambient temperature), and secondary fermentation is completed. Product characteristics: (1) Hygiene indicators: Fecal coliform count 10 / g, Ascaris egg mortality rate 100%, heavy metal indicators meet the requirements of NY525-2021 standard. (2) Physical properties: The bulk density of the matrix is ​​0.70 g / cm³. 3 The total porosity was 82%, the aeration porosity was 48%, the water-holding porosity was 23%, and the pH value was 7.4. (3) Functional indicators: The number of effective live Trichoderma was 0.35×10 8 cfu / g. (4) Degree of decomposition: Germination index (GI value) 105%. This example served as a control group to verify the feasibility of the basic process, but the pH value was too high (7.4), which, although within the acceptable range, deviated slightly from the optimal growth of Trichoderma, and the water-holding porosity in the physical structure was too low.

[0039] Example 2: Biocontrol seedling substrate for pepper blight with added phosphogypsum (preferred embodiment of the present invention) Location of implementation: Yunnan Agricultural University, Kunming, Yunnan Province. Raw materials: sawdust (auxiliary material), chicken manure (main material), phosphogypsum (conditioner). Ingredients: sawdust and chicken manure are mixed according to a C / N ratio of 30, and phosphogypsum is added at 15% of the dry matter of organic materials. The total mass of the mixture is 2 tons, and the moisture content of the initial fermentation is adjusted to 60%. Primary fermentation: Primary fermentation is carried out according to the high temperature composting fermentation method. When the fermentation pile completes the heating-high temperature process, the primary fermentation process is completed when the temperature is less than 45℃ during the cooling stage. Secondary fermentation: After the primary fermentation is completed, 2‰ Trichoderma harzianum is added per kilogram of fermentation material, and fermentation continues, accompanied by turning the pile. When the temperature approaches or reaches room temperature (ambient temperature), fermentation is stopped, and secondary fermentation is completed. Product characteristics: (1) Hygiene indicators: fecal coliform count 6 / g, ascarid egg mortality rate 100%, heavy metal indicators meet the requirements of NY525-2021 standard. (2) Physical properties: The bulk density of the matrix is ​​0.80 g / cm³. 3The total porosity was 85%, the aeration porosity was 54%, the water-holding porosity was 31%, and the pH value was 6.8. (3) Functional indicators: The number of effective live Trichoderma was 0.48×10 8 cfu / g. (4) Decomposition degree: Germination index (GI value) 109%. Compared with Example 1, Example 2, by adding phosphogypsum, lowered the pH value to 6.8, which is more suitable for the growth of Trichoderma, and the number of effective viable bacteria increased by 37%. At the same time, the water-holding porosity increased to 31%, the water retention capacity was enhanced, which is more conducive to the cultivation of chili seedlings.

[0040] Example 3: Application Effect Verification Experiment Location: Vegetable planting base in Jinning Town, Jinning District, Kunming City, Yunnan Province. Experimental Design: Treatment Group T1: Chili seedlings grown using the biocontrol seedling substrate for blight prevention prepared in Example 1 (without phosphogypsum added) were transplanted (transplanted with the seedling substrate). Treatment Group T2: Chili seedlings grown using the biocontrol seedling substrate for blight prevention prepared in Example 2 (with phosphogypsum added) were transplanted (transplanted with the seedling substrate). Control Group CK: Chili seedlings grown using conventional chili seedling substrate (transplanted with the seedling substrate). All other post-transplant management of the chili seedlings was the same throughout the experiment. Results Analysis: 1. Rhizosphere Trichoderma colonization: Sampling and testing during the vigorous growth period showed that the gene copy number of Trichoderma rhizosphere in the T1 treatment group increased by 104.6% compared to the control (CK); the gene copy number of Trichoderma rhizosphere in the T2 treatment group increased by 163.2% compared to the CK. The results indicate that the substrate of this invention can significantly increase the colonization of Trichoderma in the rhizosphere, and the treatment group with added phosphogypsum showed even better results, indicating that the optimized pH environment and physical structure promoted the survival and reproduction of Trichoderma.

[0041] 2. Disease control effect: The overall disease control rate of Phytophthora blight in peppers reached 80.5% in the T1 treatment group and 85% in the T2 treatment group. The CK group showed a higher incidence rate. This demonstrates that the Trichoderma colonized in the substrate effectively inhibited the infection of Phytophthora capsici.

[0042] 3. Yield and Value: Compared with the control (CK), the T1 treatment group showed a 23.4% increase in chili pepper yield and a 26.2% increase in value; the T2 treatment group showed a 43.4% increase in yield and a 45.2% increase in value. The significant increase in yield was attributed to reduced disease losses and the beneficial effects of the substrate's good physical and chemical properties on plant growth.

[0043] Alternative embodiments and parameter discussion Based on the above embodiments, those skilled in the art can also adjust the parameters according to actual conditions, and these adjustments all fall within the protection scope of this invention: 1. Raw Material Substitution: Organic solid waste is not limited to cow manure and chicken manure; pig manure, sheep manure, or municipal sludge and fermented food waste products can all be used as the main raw material. Rice husks and mushroom residue can be used as auxiliary materials instead of straw. The key is to adjust the C / N ratio to the range of 30-35. If sludge is used, special attention must be paid to heavy metal testing to ensure compliance with standards.

[0044] 2. Strain Substitution: Trichoderma strains are not limited to Trichoderma harzianum; strains such as Trichoderma viride and Trichoderma echinosporum, which have antagonistic effects against Phytophthora, are also suitable. The inoculum amount can be adjusted according to the activity of the inoculum agent. If the spore germination rate is high, the inoculum amount can be appropriately reduced to 1‰; if the inoculum agent has been stored for a long time and its activity has decreased, the inoculum amount can be increased to 2.5‰ (exceeding this range requires verification through preliminary experiments).

[0045] 3. Process Parameter Adjustment: The turning frequency of the primary fermentation can be adjusted according to the ambient temperature. During the high-temperature period in summer, the turning interval can be shortened to 4-5 days to prevent the pile from overheating; in winter, it can be extended to 7-8 days to maintain warmth. Temperature control during secondary fermentation is crucial. If the ambient temperature is too low (<10℃), covering and insulation measures should be taken to maintain the pile temperature above 20-30℃ to facilitate the growth of Trichoderma. If the ambient temperature is too high (>35℃), ventilation and heat dissipation should be strengthened to prevent the pile temperature from exceeding 45℃.

[0046] 4. Dosage of phosphogypsum: For acidic raw materials (such as some industrial waste), phosphogypsum may be added little or no; for highly alkaline raw materials (such as fresh chicken manure), the dosage of phosphogypsum may be increased to 18%, but the pH value of the final matrix must be monitored to ensure it is between 6.5 and 7.5, and the fluorine content must be tested to see if it exceeds the standard.

[0047] Boundary Description The substrate prepared by the method of this invention is mainly used for chili seedling cultivation and transplanting, but its application to other crops is not excluded. For example, this substrate is also suitable for seedling cultivation of solanaceous crops such as tomatoes and eggplants, and it also has a certain preventive effect against soil-borne diseases such as bacterial wilt and Fusarium wilt. However, when applied to calcium-sensitive crops, attention should be paid to the potential impact of calcium ions in phosphogypsum. In addition, the survival period of Trichoderma in the substrate is affected by storage conditions; it is recommended to store it in a cool, dry place and use it within 3 months after production to ensure the best disease prevention effect.

[0048] The above description is merely a preferred embodiment of the present invention and does not limit the scope of the patent. Any equivalent structural or procedural modifications made based on the content of this specification, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this invention.

Claims

1. A method for producing a biocontrol seedling substrate for pepper blight using solid waste, characterized in that, The method includes the following steps: (1) Organic carrier preparation: Mix organic solid waste raw materials with auxiliary materials, and add phosphogypsum as a conditioner for aerobic composting fermentation. When the fermentation temperature enters the cooling stage and the temperature is below 45℃, the first fermentation is completed to obtain an organic carrier; (2) Secondary bio-fermentation: Inoculate Trichoderma into the organic carrier obtained in step (1), and continue secondary fermentation under the condition that the fermentation temperature is below 45℃ until the number of Trichoderma in the fermentation product reaches the preset threshold and the seed germination index meets the standard, to obtain a biocontrol pepper blight seedling substrate.

2. The method according to claim 1, characterized in that, In step (1), the organic solid waste raw material includes cow dung, and the auxiliary material includes crop straw; the carbon-nitrogen ratio of the organic solid waste raw material and the auxiliary material after mixing is adjusted to 30-35, and the moisture content is adjusted to 60%-65%.

3. The method according to claim 1, characterized in that, In step (1), the amount of phosphogypsum added is 10% to 15% of the dry weight of the mixture of organic solid waste raw materials and auxiliary materials.

4. The method according to claim 1, characterized in that, The inoculation amount of Trichoderma in step (2) is 1‰ to 2‰ of the dry weight of the organic carrier.

5. The method according to claim 1, characterized in that, During the secondary fermentation process described in step (2), the pile is turned over every two days.

6. The method according to claim 1, characterized in that, The preset threshold mentioned in step (2) is when the number of Trichoderma fungi reaches 0.2 × 10⁻⁶. 8 cfu / g ~ 0.5 × 10 8 cfu / g; the seed germination index meeting the standard means that the seed germination index is greater than or equal to 70%.

7. The method according to claim 1, characterized in that, When obtaining the biocontrol seedling substrate for pepper blight in step (2), the moisture content of the fermentation product should be controlled to be less than 30%.

8. The method according to claim 1, characterized in that, The aerobic composting fermentation described in step (1) adopts windrow composting, with the windrow pile dimensions being 2m long, 1.5m wide, and 1.5m high. During the fermentation process, a centrifugal fan is used for ventilation, with a ventilation volume of 1610m³. 3 / h~2844 m 3 / h.

9. The method according to any one of claims 1 to 8, characterized in that, The physicochemical properties of the biocontrol substrate for pepper blight seedling cultivation are as follows: pH value of 6.5–7.5, bulk density of 0.6 g / cm³. 3 ~0.8 g / cm 3 The total porosity is 75%–85%.

10. A biocontrol seedling substrate for pepper blight prepared according to any one of claims 1 to 9, characterized in that, The substrate comprises fermented organic solid waste, phosphogypsum, and colonized Trichoderma fungi, with an effective viable count of 0.2 × 10⁻⁶. 8 cfu / g ~ 0.5 × 10 8 The cfu / g, fecal coliform count, ascarid egg mortality rate, and heavy metal content meet the requirements of NY525-2021 standard.