A substrate for preventing and treating soil pests and a method for preparing the same

Abstract

This invention discloses a substrate for controlling soil-borne diseases and pests and its preparation method, belonging to the field of soil-borne disease and pest control and agricultural cultivation technology. The substrate for controlling soil-borne diseases and pests is prepared from the following raw materials by weight percentage: 50%-60% plant fiber substrate, 20%-30% diatomaceous earth, 5%-10% a complex of matrine and azadirachtin, 4%-8% humic acid chelated zinc and iron, 1%-3% compound microbial powder, and 1%-3% carboxymethyl chitosan. This invention uses plant fiber as a carrier, combining physical barrier agents, plant-derived insect repellents, microbial flora, and mineral elements. It achieves soil-borne disease and pest control through a triple mechanism of physical barrier, chemical repellency, and biological antagonism, while also improving soil structure and promoting crop growth. It is suitable for seedling cultivation and planting of greenhouse vegetables and flowers, as well as agricultural soil improvement.

Description

Technical Field

[0001] This invention relates to the fields of soil pest and disease control and agricultural cultivation technology, and more specifically, to a substrate for controlling soil pests and diseases and its preparation method. Background Technology

[0002] The active ingredients extracted from the roots and seeds of the legumes *Sophora flavescens* or *Sophora alopecuroides* belong to the quinolone alkaloid class, mainly containing matrine and oxymatrine (total alkaloid content ≥90%). This extract is effective against aphids (95% efficacy), spider mites (90% efficacy), and root-knot nematodes (soil treatment), among other pests. Azadirachtin, extracted from the seeds, leaves, and bark of the neem tree (*Azadirachta indica*), has its main active ingredient being a tetracyclic triterpenoid compound. Azadirachtin is effective against over 200 pests, such as aphids, whiteflies, and lepidopteran larvae, and is safe for beneficial insects (such as bees and ladybugs). As a highly effective and environmentally friendly plant-derived biological pesticide, the core value of azadirachtin lies in its unique advantages of being naturally derived, ecologically compatible, and unlikely to induce resistance.

[0003] According to a 2025 report by the Food and Agriculture Organization of the United Nations (FAO), soil-borne diseases will reduce crop yields by 23% globally, with the proportion of pesticide-resistant root-knot nematodes rising to 35% (a significant increase from 18% in 2020). Existing technologies have the following problems: ① Microbial carriers suffer inactivation rates exceeding 45% due to ultraviolet radiation; ② Physical control methods damage the natural microporous structure of diatomaceous earth (crystallinity ≤80%); ③ Chemical compounding easily leads to the risk of excessive pesticide residues in the soil.

[0004] According to a 2024 report, the main problems currently faced include: global annual losses due to soil-borne diseases amount to approximately US$22 billion, and the annual growth rate of root-knot nematode infestation area reaches 12%; long-term use of chemical pesticides has led to increased pathogen resistance; the effectiveness of single application of biological agents is unstable (sensitive to humidity and temperature); physical control (such as steam sterilization) is energy-intensive and disrupts the soil microecology; and existing technologies have failed to effectively resolve the contradiction between physical control with diatomaceous earth and the preservation of microbial activity (diatomaceous earth has strong water absorption, leading to dehydration and death of microorganisms).

[0005] Existing technological shortcomings:

[0006] Microbial carriers: UV inactivation rate >45%, field survival rate <30%; Physical control: High-temperature carbonization destroys the microporous structure of diatomaceous earth (reducing the specific surface area by 60%). Chemical compound: There is a risk of pesticide residue exceeding the standard (0.05 mg / kg chlorpyrifos residue was detected).

[0007] Technical contradiction: The physical control of diatomaceous earth (microporous adsorption of toxic proteins) is incompatible with the preservation of microbial activity (dehydration mortality rate >50%).

[0008] Therefore, how to develop a substrate for preventing and controlling soil diseases and pests and its preparation method is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0009] In view of this, the present invention provides a substrate for preventing and controlling soil diseases and pests and a method for preparing the same.

[0010] A substrate for preventing and controlling soil diseases and pests, by weight percentage, is prepared from the following raw materials: 50%-60% plant fiber substrate, 20%-30% diatomaceous earth, 5%-10% a compound of matrine and azadirachtin, 4%-8% humic acid chelated zinc and iron, 1%-3% compound microbial powder, and 1%-3% carboxymethyl chitosan.

[0011] Furthermore, the plant fiber substrate is coconut coir or straw fiber.

[0012] The beneficial effects of adopting the above-mentioned further technical solutions are: it can make full use of agricultural and forestry waste fiber resources, the resulting matrix material is lightweight, has good water retention and air permeability, and is biodegradable, while providing space for microorganisms to attach and grow.

[0013] Furthermore, the particle size of the diatomaceous earth is 50-80 mesh.

[0014] The beneficial effects of adopting the above-mentioned further technical solutions are: this particle size range has the highest mechanical damage rate to nematodes (up to 95.2%) and the highest adsorption rate of toxic proteins (up to 92%), thus achieving the best physical control effect.

[0015] Furthermore, in the complex of matrine and azadirachtin, the mass ratio of matrine to azadirachtin is 3:1, and the mass ratio of humic acid, ferrous sulfate, and zinc sulfate in the humic acid chelate zinc and iron is 10:3.5:3.

[0016] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: the nerve paralysis time of pests is the shortest under this ratio; when used in combination with diatomaceous earth, the adsorption rate of toxic proteins can be increased to more than 89%, and the synergistic control effect is significant.

[0017] Furthermore, in the composite microbial powder, the ratio of viable bacteria of *Trichoderma harzianum*, *Bacillus subtilis*, and *Paecilomyces lilacinus* is 5:3:2, and the total viable bacteria content of the composite microbial powder is ≥5×10⁻⁶. 9 CFU / g.

[0018] The beneficial effects of adopting the above-mentioned further technical solution are as follows: This ratio was obtained through orthogonal experimental screening. When this ratio is used, the viable bacteria count can reach 5.8 × 10⁻⁶ after 30 days. 9 With a CFU / g and a synergistic effect index of 1.89, the parasitic-antagonistic-colonizing functional network formed is highly complementary, resulting in excellent long-lasting control of the product.

[0019] Furthermore, the carboxymethyl chitosan has a molecular weight of 5-10 kDa and a degree of substitution ≥0.65.

[0020] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: low molecular weight, high degree of substitution chitosan has both good water solubility and film-forming properties. It can form a dense protective layer to coat the bacteria during the low-temperature curing process, which can increase the survival rate of microorganisms to 95.3%. At the same time, it can achieve the slow release of active ingredients and extend the product's shelf life to 6-8 months.

[0021] This invention also provides a method for preparing a substrate for preventing and controlling soil-borne diseases and pests, comprising the following steps: (1) Weigh out each raw material according to the substrate for preventing and controlling soil diseases and pests; (2) Raw material pretreatment: The plant fiber substrate is washed with deionized water to remove impurities, then dried, crushed, sieved, sterilized under high pressure steam, and then naturally cooled to room temperature for use. (3) Mixing stage: The plant fiber substrate, diatomaceous earth, matrine and azadirachtin complex, and humic acid chelated zinc and iron are mixed evenly to obtain a mixture; (4) Inoculation and fermentation: The mixture obtained in step (3) is added to the compound microbial powder for anaerobic fermentation to obtain the fermentation product; (5) Low-temperature solidification: The fermentation product obtained in step (4) is added to carboxymethyl chitosan, frozen and thawed to obtain microcapsules; glassy microcapsules are formed with an encapsulation rate of ≥95% and a glass transition temperature Tg=-12℃±1℃; (6) Packaging: Adjust the moisture content of the microcapsules obtained in step (5) and perform aseptic packaging.

[0022] Furthermore, in step (2), the product is dried at 60°C until the moisture content is ≤10%, pulverized to a particle size of 2-5 mm, passed through an 8-mesh sieve, and sterilized under high pressure steam at 121°C for 20 minutes.

[0023] Furthermore, in step (4), the anaerobic fermentation temperature is 28℃±2℃, the anaerobic fermentation time is 48 hours, and the pH value is monitored and maintained at 6.0-7.0 during the anaerobic fermentation process.

[0024] Furthermore, in step (5), the temperature is lowered to -18℃±2℃ at a rate of 5℃ / min for freezing and shaping, the freezing time is 2-4h, the humidity is controlled to be ≤30%±5% RH during the freezing process, and the temperature is raised to 25℃ at a rate of 2℃ / min during thawing, the thawing time is 20-25min; The beneficial effects of adopting the above-mentioned further technical solutions are as follows: The present invention forms glassy microcapsules through a low-temperature curing process of -18℃±2℃. The chitosan film layer can isolate the hygroscopic effect of diatomaceous earth, thereby increasing the survival rate of microorganisms to 89.5%. At the same time, it retains the natural microporous structure of diatomaceous earth (specific surface area ≥25 m² / g), achieving a synergistic effect of physical damage to nematodes and biological antagonism of microorganisms. It breaks through the technical bottleneck of existing technologies where diatomaceous earth absorbs moisture, leading to dehydration and death of bacteria. The product's shelf life can be extended from the conventional 3-4 months to 6-8 months.

[0025] In step (6), the moisture content of the microcapsules obtained in step (5) is adjusted to 35% ± 2%.

[0026] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: By strictly controlling the moisture content of the microcapsules at 35%±2%, the vitreous microcapsules can maintain their structural integrity during storage and transportation. This avoids both the dissolution of the capsule shell or premature activation of microorganisms due to excessive moisture and the brittleness of the capsule shell due to insufficient moisture, thereby extending the product shelf life to more than 12 months. It is also more suitable for field operations that are ready to use immediately after opening the bag.

[0027] Compared with the prior art, the present invention has the following beneficial effects: This invention relates to a cultivation substrate, a composite functional material for agricultural cultivation. Using plant fibers as a carrier, it incorporates physical barrier agents, plant-derived insect repellents, microbial flora, and mineral elements. Through a triple mechanism of physical damage, chemical repellency, and biological antagonism, it achieves soil pest and disease control while simultaneously improving soil structure and promoting crop growth. This substrate also possesses circular economy attributes; it is biodegradable after disposal, and the diatomaceous earth can be recycled and reused. This composite substrate is suitable for seedling cultivation and planting of greenhouse vegetables and flowers, as well as for improving agricultural soils.

[0028] In this agricultural cultivation substrate, diatomaceous earth and the matrine-azapine complex synergistically enhance pest and disease control: the sharp edges of diatomaceous earth mechanically damage the cuticle of nematodes, while its micropores adsorb pathogenic toxins; the plant-derived insect repellent interferes with the nerve conduction of pests. The combined use of these two agents shortens the paralysis time of nematodes to one-third of the control group, significantly improving control efficiency. Furthermore, chitosan derivatives synergistically enhance the survival rate of microbial communities through film formation protection (by 40%), strengthening the persistence of the biological antagonistic effect.

[0029] This invention achieves a synergistic effect of "1+1+1>3" through a triple-mechanism synergistic design, key process breakthroughs, and scientific ratio optimization. It is not a simple addition of existing raw materials. The specific inventiveness is reflected in the following aspects: I. Triple Mechanisms Working Together to Overcome the Technical Bias of "Simple Superposition": This invention is the first to integrate physical damage (diatomaceous earth), chemical repellency (matrine-azadirachtin), and biological antagonism (microbial community) into a systemic solution: Diatomaceous earth penetrates the 12.3±1.5μm mechanically torn cuticle of nematodes (61.4% efficacy alone, 76% toxin adsorption rate); diatomaceous earth significantly improves the dispersibility of plant extracts (contact angle reduced by 22°), and the survival rate of bacterial communities under chitosan film protection increases by 40%; Matrine-aridin complex (3:1 ratio) interferes with nerve conduction (paralysis time alone is 1 / 2 of the control group); Microbial flora (5:3:2 ratio) inhibits pathogens through parasitic competition (58.2% efficacy alone).

[0030] The combined use of the three products produces a super synergistic effect: the nematode control efficacy reaches 92.3% (super synergistic effect 18.7%), the paralysis time is shortened to 1 / 3 of the control group, the toxic protein adsorption rate is increased to 92%, and the duration of effect is extended to 6-8 months, overcoming the technical bias of "simple mixing of raw materials".

[0031] II. Low-temperature curing process resolves the technical contradiction of "diatomaceous earth-microorganism compatibility": Addressing the core contradiction in existing technologies where "diatomaceous earth absorbs moisture, leading to microbial dehydration and death (mortality rate > 50%)", this invention innovatively adopts the following approach: The -18℃±2℃ low-temperature curing process (cooling rate 5℃ / min±1℃) forms glassy microcapsules (Tg=-12℃±1℃, encapsulation rate ≥95%), avoiding ice crystal damage caused by traditional freezing and structural damage caused by high temperature.

[0032] The carboxymethyl chitosan film layer (molecular weight 5-10 kDa) isolates the hygroscopic effect of diatomaceous earth, increasing the survival rate of microorganisms to 89.5% (compared to only 30%-45% in existing technologies), which is 1.9-2.9 times higher than existing technologies (30%-45%).

[0033] This process simultaneously preserves the natural microporous structure of diatomaceous earth (specific surface area ≥25 m² / g) and "microbial activity protection," achieving a synergy between physical damage and biological activity, which is a key problem that has not been solved by existing technologies.

[0034] Traditional low-temperature treatment (such as freezing at -40℃) can preserve the structure of diatomaceous earth (99.1% crystallinity), but the microbial survival rate is only 81.2%; high-temperature drying (80℃) causes damage to the microporous structure of diatomaceous earth (a 60% decrease in specific surface area), and the survival rate of live bacteria is only 43.7%. Furthermore, existing technologies fail to address the core problem of "diatomaceous earth absorbing moisture leading to microbial dehydration and death," resulting in a generally lower field survival rate of microorganisms than 45%. Comparative experiments show that the low-temperature curing process of this invention is superior to traditional methods: Live bacteria survival rate: increased from 81.2% (traditional freezing) to 95.3%; Nematode control efficacy: increased from 86.1% (traditional freezing) to 92.3%; Duration of effectiveness: Extended to 6-8 months, far exceeding the 3-4 months of existing technologies.

[0035] In summary, although existing technologies have attempted low-temperature processing, they have not achieved systematic optimization of "process parameters-material protection-functional synergy". This invention, by targeting the "diatomaceous earth-microorganism compatibility contradiction", proves that its low-temperature curing process is not a simple follow-up to existing technologies, but rather a creative improvement.

[0036] III. Scientific proportioning and optimization to achieve complementary functions: Compound microbial powder formulation: The optimal formulation of 5:3:2 (Trichoderma harzianum: Bacillus subtilis: Paecilomyces lilacinus) was selected through L9(3³) orthogonal experiment, with a viable count of 5.8 × 10⁻⁶ after 30 days. 9 CFU / g (other formulations only 3.2-4.5×10) 9 The synergistic effect index was 1.89 (far exceeding the 1.12-1.43 of other ratios).

[0037] The combination ratio of matrine to azadirachtin (3:1) shortened the paralysis time to 53.6% of that of the single-drug group and increased the adsorption rate of toxic proteins by 16.2%-32.4%.

[0038] IV. The application effect is significantly better than that of a single raw material or a simple mixture: Nematode control efficacy: 92.3% (diatomaceous earth alone 61.4%, plant extract alone 58.2%, microorganism alone 58.2%). Duration of effectiveness: 6-8 months (3-4 months with existing technology); 88.7% control efficacy against Fusarium wilt disease; Crop yield increased by 27%, and the heavy metal content met the NY / T 2118-2022 standard.

[0039] In summary, this invention solves the technical problems of "simple superposition of raw materials without synergy" and "poor compatibility between diatomaceous earth and microorganisms" in the prior art through mechanism synergy, process innovation and ratio optimization, and produces unexpected technical effects. It has outstanding substantive features and significant progress, and is not a simple mixture of existing raw materials. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] The matrine-azadirachtin complex of the present invention is obtained by mixing matrine and azadirachtin at a mass ratio of 3:1 until homogeneous. The humic acid chelate of zinc and iron of the present invention is obtained by mixing humic acid, zinc sulfate, and ferrous sulfate in water until homogeneous, followed by drying.

[0042] Example 1 The preparation method of the substrate for preventing and controlling soil-borne diseases and pests includes the following steps: (1) Weigh each raw material: Plant fiber substrate: 60kg coconut coir fiber, 25kg diatomaceous earth with a particle size of 50-80 mesh, 6kg of a compound of matrine and azadirachtin (mass ratio of matrine to azadirachtin is 3:1), 4kg of humic acid chelated zinc and iron (mass ratio of humic acid, ferrous sulfate and zinc sulfate is 10:3.5:3), and compound microbial powder (the ratio of viable bacteria of Trichoderma harzianum, Bacillus subtilis and Paecilomyces lilacinus is 5:3:2, and the total viable bacteria content of the compound microbial powder is ≥5×10 9 3 kg of CFU / g and 2 kg of carboxymethyl chitosan (molecular weight 5-10 kDa, degree of substitution ≥0.65); (2) Raw material pretreatment: The plant fiber substrate is washed with deionized water to remove impurities, then dried at 60°C until the moisture content is ≤10%, crushed to a particle size of 2-5mm and passed through an 8-mesh sieve, sterilized under high pressure steam at 121°C for 20 minutes, and then naturally cooled to room temperature for use. (3) Mixing stage: The plant fiber substrate, diatomaceous earth, matrine and azadirachtin complex, and humic acid chelated zinc and iron are mixed evenly to obtain a mixture; (4) Inoculation and fermentation: The mixture obtained in step (3) is added to the compound microbial powder and anaerobic fermented at 28℃±2℃ for 48 hours to obtain the fermentation product. During the anaerobic fermentation process, the pH value is monitored and maintained at 6.0-7.0. (5) Low temperature solidification: The fermentation product obtained in step (4) is added to carboxymethyl chitosan and cooled to -18℃±2℃ at a rate of 5℃ / min for freezing and shaping. The freezing time is 3 hours, and the humidity is controlled at 30%±5% RH during the freezing process. When thawing, the temperature is increased to 25℃ at a rate of 2℃ / min and the thawing time is 25min to obtain microcapsules. (6) Packaging: Adjust the moisture content of the microcapsules obtained in step (5) to 35% ± 2% and perform aseptic packaging.

[0043] The substrate is packaged in 40L bags for greenhouse tomato seedling cultivation in plug trays. When using, adjust the substrate pH to the applicable range (5.5-6.5) and EC value (≤2.0 mS / cm). For alkalinity adjustment, use 1-6 mol / L NaOH or quicklime (2-4 kg per cubic meter of substrate); for acidity adjustment, use 1-6 mol / L HCl or ferrous sulfate (1 g / L solution spray). According to a 2024 study in the *Journal of Horticulture*, the highest nematode egg hatching inhibition rate was observed at pH 5.5-6.5.

[0044] Results: 60 days after transplanting, the nematode infection rate decreased to 8% (compared to 76% in the control group), and the yield increased by 27%. Growth promotion effect: The root length of tomato seedlings increased by 40%, and the chlorophyll SPAD value increased by 25%.

[0045] Example 2 (1) Weigh each raw material: Plant fiber substrate: 56 kg coconut coir fiber, 25 kg diatomaceous earth with a particle size of 50-80 mesh, 8 kg of a compound of matrine and azadirachtin (mass ratio of matrine to azadirachtin is 3:1), 5 kg of humic acid chelated zinc and iron (mass ratio of humic acid, ferrous sulfate and zinc sulfate is 10:3.5:3), and compound microbial powder (the ratio of viable bacteria of Trichoderma harzianum, Bacillus subtilis and Paecilomyces lilacinus is 5:3:2, and the total viable bacteria content of the compound microbial powder is ≥5×10 9 3 kg of CFU / g and 3 kg of carboxymethyl chitosan (molecular weight 5-10 kDa, degree of substitution ≥0.65); (2) Raw material pretreatment: The plant fiber substrate is washed with deionized water to remove impurities, then dried at 60°C until the moisture content is ≤10%, crushed to a particle size of 2-5mm and passed through an 8-mesh sieve, sterilized under high pressure steam at 121°C for 20 minutes, and then naturally cooled to room temperature for use. (3) Mixing stage: The plant fiber substrate, diatomaceous earth, matrine and azadirachtin complex, and humic acid chelated zinc and iron are mixed evenly to obtain a mixture; (4) Inoculation and fermentation: The mixture obtained in step (3) is added to the compound microbial powder and anaerobic fermented at 28℃±2℃ for 48 hours to obtain the fermentation product. During the anaerobic fermentation process, the pH value is monitored and maintained at 6.0-7.0. (5) Low temperature solidification: The fermentation product obtained in step (4) is added to carboxymethyl chitosan and cooled to -18℃±2℃ at a rate of 5℃ / min for freezing and shaping. The freezing time is 3 hours, and the humidity is controlled at 30%±5% RH during the freezing process. When thawing, the temperature is increased to 25℃ at a rate of 2℃ / min and the thawing time is 25min to obtain microcapsules. (6) Packaging: Adjust the moisture content of the microcapsules obtained in step (5) to 35% ± 2% and perform aseptic packaging.

[0046] The resulting substrate, after testing, showed a nematode control effect of 91.8%, with a viable bacterial count of 5.7 × 10⁻⁶ after 30 days. 9 CFU / g, with an effective period of over 6 months.

[0047] Example 3 (1) Weigh each raw material: Plant fiber substrate: 58 kg coconut coir fiber, 25 kg diatomaceous earth with a particle size of 50-80 mesh, 8 kg of a compound of matrine and azadirachtin (mass ratio of matrine to azadirachtin is 3:1), 4 kg of humic acid chelated zinc and iron (mass ratio of humic acid, ferrous sulfate and zinc sulfate is 10:3.5:3), and compound microbial powder (the ratio of viable bacteria of Trichoderma harzianum, Bacillus subtilis and Paecilomyces lilacinus is 5:3:2, and the total viable bacteria content of the compound microbial powder is ≥5×10 9 2 kg of CFU / g, 3 kg of carboxymethyl chitosan (molecular weight 5-10 kDa, degree of substitution ≥0.65); Steps (2)-(6) are the same as in Example 2.

[0048] The nematode control effect of the substrate obtained in this embodiment was 92.1%, and the viable bacterial count was 5.9 × 10⁻⁶ after 30 days of culture. 9 CFU / g can help increase crop yield by up to 25%. This embodiment, together with the foregoing embodiments, demonstrates that within the ratio range claimed by this invention, the substrate can achieve excellent soil pest and disease control effects through a triple synergistic mechanism.

[0049] Effect Experiment: Experiment 1. The effect of cooling rate on the process: Based on Example 1, the cooling rate of low-temperature curing in step (5) was changed, while other steps and parameters remained unchanged. The integrity, encapsulation efficiency, and applicability of the microcapsules are shown in Table 1; Table 1

[0050] Experiment 2. Through scientific orthogonal experimental design and multi-dimensional verification, this invention proves that the ratio of the compound microbial powder (Trichoderma harzianum: Bacillus subtilis: Paecilomyces lilacinus = 5:3:2) is not a simple selection, as specifically demonstrated below: I. Orthogonal experiment to screen data: Based on Example 1, the ratio of Trichoderma harzianum: Bacillus subtilis: Paecilomyces lilacinus was changed, while other steps and parameters remained unchanged.

[0051] Three mixing ratios (1:1:1, 5:3:2, and 3:5:2) were compared using an L9(3³) orthogonal experiment. The results showed that: The 5:3:2 ratio (of this invention) achieved a nematode control efficacy of 92.3% ± 1.8%, significantly higher than the control ratios (1:1:1 group 72.5% ± 2.3%, 3:5:2 group 81.7% ± 2.1%), with an efficacy increase of 27.3%. The number of live bacteria reached 5.8 × 10⁻⁶ after 30 days. 9 CFU / g, compared to other ratios (3.2-4.5×10⁻⁶). 9 CFU / g increased by 81.3%; The synergistic effect index is 1.89 (super-addition effect 89%), which is much higher than the 1.12-1.43 of other ratios.

[0052] II. Verification of Functional Collaboration Mechanism This ratio creates a "parasitic-antagonistic-colonizing" network through the complementary effects of the three bacterial groups: Trichoderma harzianum (50%): Parasitic nematode eggs (parasitism rate 78%), the hyphae's ability to penetrate the eggshell is 2.3 times higher than other ratios; Bacillus subtilis (30%): secreted antimicrobial peptides (inhibition zone diameter 15.6 mm), with a yield 42% higher than the 1:1:1 group; Purple lilacinus (20%): competes for ecological niches (increases rhizosphere colonization rate by 40%), and forms a spatial occupancy synergy with the first two fungi.

[0053] Comparative experiments showed that other ratios exhibited poor synergistic effects due to imbalances in the microbial community, resulting in functional overlap (e.g., excessive proliferation of Bacillus subtilis inhibiting Trichoderma activity) or niche vacancies (e.g., insufficient proportion of Paecilomyces lilacinus). In contrast, the 5:3:2 ratio achieved functional complementarity through ratio optimization, proving it to be the optimal combination selected through scientific screening, rather than a simple mixture.

[0054] Experiment 3 Field Application: The substrate from Example 1 was mixed with field soil at a 1:3 ratio, and tested after cucumbers were planted for 60 days. 1. Root-knot nematode density: 2.8 nematodes / g soil (control group: 31.5 nematodes / g soil); 2. Microbial diversity index (Shannon): 7.21 (control group: 5.83); 3. Key innovation verification: XRD analysis showed that the crystallinity of diatomaceous earth remained at 98.7% after low-temperature curing (≤80% in the high-temperature treatment group).

[0055] Experiment 4 Diatomite Particle Size Screening Experiment (Table 2): Based on Example 1, the diatomite particle size was changed, while other steps and parameters remained the same.

[0056] (1) Four groups of substrates: Group a has a particle size of 80-100 mesh, Group b has a particle size of 50-80 mesh, Group c has a particle size of 30-50 mesh, and Group d is the control group without diatomaceous earth; (2) Detection results of nematode damage rate: The adsorption rate of pathogen toxin protein in the 50-80 mesh group reached 92%, and the damage rate reached 95.2%.

[0057] Table 2. Diatomite particle size screening data

[0058] Experiment 5: Comparative experiment on the synergistic effect of matrine, azadirachtin and diatomaceous earth: Based on Example 1, the types of raw materials were changed, the total amount remained the same, and other steps and parameters remained the same.

[0059] Table 3 Comparison of nematode control effects of different component combinations

[0060] Comparative data on the synergistic effects of matrine, azadirachtin, and diatomaceous earth (see Table 3).

[0061] Control group 1 (diatomaceous earth only): nematode control effect 61.4%, paralysis time 45±3.2 min, toxic protein adsorption rate 76% (single mechanism of physical damage). Control group 2 (matrine-azapine only): nematode control effect 58.2%, paralysis time 28±2.5 min, toxic protein adsorption rate 68% (single chemical repellency mechanism). Control group 3 (diatomaceous earth + matrine-azapine): After synergy, the prevention and control effect increased to 83.7%, the paralysis time was shortened to 15±1.8 min, and the toxic protein adsorption rate reached 89% (physical-chemical synergy). Control group 4 (three-in-one): After the superimposed microbial parasitic competition mechanism, the prevention and control effect reached 92.3%, the paralysis time was further shortened to 9±1.2 min, and the toxic protein adsorption rate was 92% (Table 3).

[0062] The entire component of this invention works synergistically: the physical-chemical-biological triple mechanism achieves a prevention and control effect of 92.3% (1+1+1>3), a live bacteria survival rate of 95.3% (resolving compatibility issues), and extends the sustained-release half-life to 35 days (see Table 3).

[0063] Experimental conclusions: The combined use of diatomaceous earth and matrine-azapine significantly improved the nematode control effect by 36.4%-43.8% compared to the single-drug combination, shortened the paralysis time to 53.6% of the single-drug group, and increased the toxic protein adsorption rate by 16.2%-32.4%, showing a significant synergistic effect. The combined use of the three (with added microorganisms) further improved the control effect by 10.3% compared to the binary combination, verifying the synergistic effect of the triple mechanism.

[0064] Experiment 6 Comparison of Low-Temperature Curing Processes (Creative Verification): Based on Example 1, the low-temperature curing process was changed, while other steps and parameters remained unchanged.

[0065] Table 4 Comparison data of low-temperature curing processes (key differences from existing technologies)

[0066] Table 5 Comparison of Shelf Life (Data after 6 months)

[0067] Experiment 7 Environmental Safety Verification: Table 6

[0068] Experiment 8: Original data from the potted plant comparison experiment: Table 7

[0069] Inventiveness Demonstration: Pot experiments showed that the nematode control efficacy of the substrate of this invention (92.3%) was significantly higher than that of single mechanisms (diatomaceous earth alone 61.4%, matrine-azadirachtin alone 58.2%) and commercially available products (73.5%). In particular, the combined use of matrine-azadirachtin and diatomaceous earth produced a synergistic effect: the control effect was improved by 36.4%-43.8% compared to using either alone, the paralysis time was shortened from 28±2.5 min to 15±1.8 min, and the toxic protein adsorption rate increased from 68%-76% to 89%. This demonstrates that the triple mechanism synergy (physical damage + chemical slow release + biological antagonism) achieved through the low-temperature solidification process produced unexpected technical effects, and is not a simple superposition of existing raw materials. Compared with existing technologies, this invention, for the first time, solves the compatibility contradiction between diatomaceous earth and microorganisms (survival rate increased to 89.5%) and extends the effective period to 6-8 months, possessing outstanding substantive features and significant progress.

[0070] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A substrate for preventing and controlling soil-borne diseases and pests, characterized in that, It is prepared from the following raw materials by mass percentage: 50%-60% plant fiber substrate, 20%-30% diatomaceous earth, 5%-10% complex of matrine and azadirachtin, 4%-8% humic acid chelated zinc and iron, 1%-3% compound microbial powder, and 1%-3% carboxymethyl chitosan.

2. The substrate for preventing and controlling soil pests and diseases according to claim 1, characterized in that, The plant fiber substrate is coconut coir or straw fiber.

3. The substrate for preventing and controlling soil pests and diseases according to claim 1, characterized in that, The diatomaceous earth has a particle size of 50-80 mesh.

4. The substrate for preventing and controlling soil pests and diseases according to claim 1, characterized in that, In the complex of matrine and azadirachtin, the mass ratio of matrine to azadirachtin is 3:1, and the mass ratio of humic acid, ferrous sulfate, and zinc sulfate in the humic acid chelate zinc and iron is 10:3.5:

3.

5. The substrate for preventing and controlling soil pests and diseases according to claim 1, characterized in that, In the compound microbial powder, the ratio of viable bacteria of *Trichoderma harzianum*, *Bacillus subtilis*, and *Paecilomyces lilacinus* is 5:3:2, and the total viable bacteria content of the compound microbial powder is ≥5×10⁻⁶. 9 CFU / g.

6. The substrate for preventing and controlling soil-borne diseases and pests according to claim 1, characterized in that, The carboxymethyl chitosan has a molecular weight of 5-10 kDa and a degree of substitution ≥0.

65.

7. A method for preparing a substrate for preventing and controlling soil-borne diseases and pests, characterized in that, Includes the following steps: (1) Weigh each raw material according to any one of claims 1-6 for the substrate for preventing and controlling soil diseases and pests; (2) Raw material pretreatment: The plant fiber substrate is washed with deionized water to remove impurities, then dried, crushed, sieved, sterilized under high pressure steam, and then naturally cooled to room temperature for use. (3) Mixing stage: The plant fiber substrate, diatomaceous earth, matrine and azadirachtin complex, and humic acid chelated zinc and iron are mixed evenly to obtain a mixture; (4) Inoculation and fermentation: The mixture obtained in step (3) is added to the compound microbial powder for anaerobic fermentation to obtain the fermentation product; (5) Low-temperature solidification: The fermentation product obtained in step (4) is added to carboxymethyl chitosan, frozen and thawed to obtain microcapsules; (6) Packaging: Adjust the moisture content of the microcapsules obtained in step (5) and perform aseptic packaging.

8. The method for preparing a substrate for preventing and controlling soil-borne diseases and pests according to claim 7, characterized in that, In step (2), the product is dried at 60°C until the moisture content is ≤10%, pulverized to a particle size of 2-5 mm, passed through an 8-mesh sieve, and sterilized under high pressure steam at 121°C for 20 minutes.

9. The method for preparing a substrate for preventing and controlling soil-borne diseases and pests according to claim 7, characterized in that, In step (4), the anaerobic fermentation temperature is 28℃±2℃, the anaerobic fermentation time is 48 hours, and the pH value is monitored and maintained at 6.0-7.0 during the anaerobic fermentation process.

10. The method for preparing a substrate for preventing and controlling soil-borne diseases and pests according to claim 7, characterized in that, In step (5), the temperature is lowered to -18℃±2℃ at a rate of 5℃ / min for freezing and shaping. The freezing time is 2-4h, and the humidity is controlled to be ≤30%±5% RH during the freezing process. When thawing, the temperature is raised to 25℃ at a rate of 2℃ / min, and the thawing time is 20-25min. In step (6), the moisture content of the microcapsules obtained in step (5) is adjusted to 35% ± 2%.

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