Biochar-based slow-release nematicidal granule as well as preparation method and use method thereof

Abstract

The invention discloses charcoal-based slow-release nematicidal granules as well as a preparation method and a use method thereof, and belongs to the technical field of pest control. Comprising the following raw materials in parts by mass: 2.8-8.2 parts of 95% abamectin B2; 55.6-61.1 parts of biochar with a water content of 8-12%; 12 parts of 2-4% dilute sulfuric acid; 13.5 to 40 parts of dimethyl formamide with the concentration of 99%; 15 parts of a binder; 5 parts of a stabilizer; 1 part of an embedding agent; and 12 parts of water. The biochar-based slow-release nematicidal granule provided by the invention can effectively control the harm of root-knot nematode to crops such as tobacco, is safe to the crops, and can effectively guarantee the yield of agricultural products; in addition, by using the control technology, the dosage of chemical nematicide can be effectively reduced, and the purposes of reduction and synergism of chemical pesticide are achieved.

Description

Technical Field

[0001] This invention belongs to the field of pest control technology, and particularly relates to a biochar-based slow-release nematicide granule and its preparation and application method. Background Technology

[0002] Plant root-knot nematodes ( Meloidogyne Tobacco (spp.) is one of the important factors affecting crop yield and quality. Tobacco is an important economic crop in China, especially in the mountainous areas of southwest China, and is also a traditional pillar industry in many regions. In recent years, due to limited arable land resources, the problem of continuous tobacco cropping has become very prominent. Coupled with inadequate soil conservation measures, soil-borne diseases such as tobacco root-knot nematode disease have become very serious in some tobacco-growing areas. Root-knot nematode disease is a typical soil-borne disease with a hidden pathogen, strong resistance, and is difficult to eradicate in agricultural production. Tobacco root-knot nematodes not only directly damage tobacco plants, causing wilting, yellowing, stunted growth, and even death of the entire plant, but can also induce tobacco bacterial wilt (…). Ralstonia solanacearum ) and black shank ( Phytophthora parasitica var. nicotianae Other soil-borne diseases, such as , have become one of the major soil-borne diseases in the tobacco-growing areas of southwestern my country.

[0003] Currently, there is extensive research both domestically and internationally on the chemical, physical, and biological control of tobacco root-knot nematodes. Relatively speaking, soil chemical fumigation is the most thorough and effective method; however, its high cost and severe damage to the soil's microecological environment make it difficult to widely apply fumigants such as dazomet in tobacco fields. With the gradual elimination or restriction of highly polluting, persistent, and toxic chemical nematicides (such as aldicarb and carbofuran), the scientific utilization of existing nematicides is crucial, and the development of pesticide slow-release technology is an important research direction for reducing pesticide use. Furthermore, the ever-increasing costs of labor and agricultural inputs are becoming increasingly important factors restricting the profitability of flue-cured tobacco cultivation. Therefore, reducing the frequency and amount of pesticide application in flue-cured tobacco production is particularly important for improving the quality and efficiency of tobacco production.

[0004] Avermectin B2 is a high-yield strain obtained in my country through high-throughput screening technology. , The strains of the component, their fermentation broth The component content increased by about 40%. The component content increased by 90-94%; avermectin B2 has good nematicidal effect, low dosage, and relatively low price, with the active ingredient avermectin... It can be metabolized into more active avermectin by soil microorganisms. Therefore, it has a long residual effect in the soil.

[0005] To improve the effectiveness of the existing nematicide avermectin B2, this invention uses tobacco stem biochar as a slow-release adsorption carrier and adds specific binders, stabilizers and coating agents to develop a biochar-based slow-release nematicide granule containing avermectin B2. This related technology has not been reported in China. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to develop a biochar-based sustained-release nematicide granule with porous structure, strong adsorption, stable properties and good sustained-release effect, as well as its preparation and application method, which can overcome the shortcomings of the prior art.

[0007] The technical solution of the present invention is: a biochar-based slow-release nematicide granule, comprising the following raw materials in parts by weight: 95% abamectin B2: 2.8~8.2 parts; 8~12% water content biochar: 55.6~61.1 parts; 2~4% dilute sulfuric acid: 12 parts; 99% dimethylformamide: 13.5~40 parts; binder: 15 parts; stabilizer: 5 parts; encapsulating agent: 1 part; water: 12 parts.

[0008] The aforementioned biochar-based slow-release nematicide granules are composed of the following raw materials in parts by weight: 95% abamectin B2: 5.5 parts; 8-12% water content biochar: 58.3 parts; 3% dilute sulfuric acid: 12 parts; 99% dimethylformamide: 26.5 parts; binder: 15 parts; stabilizer: 5 parts; encapsulating agent: 1 part; water: 12 parts.

[0009] The aforementioned biochar-based slow-release nematicide granules refer to tobacco stem biochar.

[0010] The aforementioned biochar-based slow-release nematicide granules use bentonite as the binder.

[0011] The aforementioned biochar-based sustained-release nematicide granules contain glycerol or β-cyclodextrin as the stabilizer.

[0012] The aforementioned biochar-based slow-release nematicidal granules contain sodium alginate or polyvinyl alcohol as the encapsulating agent.

[0013] The aforementioned biochar-based sustained-release nematicide granules are prepared by following these steps after the raw materials are prepared according to their weight: ① First, dissolve 95% avermectin B2 technical grade in dimethylformamide and set aside; ② Treat the tobacco stem biochar with 2-4% dilute sulfuric acid spray to adjust the pH of the tobacco stem biochar to between 8.0 and 9.0, and then dry the acid-treated tobacco stem biochar to a moisture content of 15-20%; ③ Spray the abamectin B2 dimethylformamide solution prepared in step ① evenly onto the tobacco stem biochar treated with acid in step ②, while spraying and stirring simultaneously. Stir for 10-15 minutes, then place it in a room temperature of 15-30℃, in a dark and ventilated environment to dry, controlling the liquid content to 20-25%, and set aside for later use. ④ Crush the tobacco stem biochar that adsorbed abamectin B2 in step ③ to a particle size smaller than 20 mesh, then add bentonite and stir thoroughly until uniform; ⑤ Add glycerin based on step ④, stir thoroughly, and then extrude and granulate to prepare granules; ⑥ Dissolve sodium alginate in water to make a 10% sodium alginate aqueous solution, and dry the granules in step ⑤ in the dark until the liquid content is 25~30%, and then use sodium alginate aqueous solution for uniform spray coating treatment. ⑦ Dry the granules from step ⑥ in a dark environment until the surface is dry and no longer sticky, and the product is obtained.

[0014] The aforementioned biochar-based slow-release nematicide granules are applied in tobacco fields by applying them in holes before tobacco transplanting, at a rate of 3-6 g / plant.

[0015] Compared with existing technologies, this invention utilizes the porous, strong adsorption, and stable properties of biochar, and adds specific binders, stabilizers, and coating agents to achieve the effect of slow-release pesticides. This aligns with the development direction of modern agriculture and also promotes the maintenance of a healthy soil ecological environment.

[0016] Specifically, the present invention has the following advantages and positive effects: 1. The present invention provides a biochar-based slow-release nematicide granule, wherein the nematicide active ingredient is a highly efficient and low-toxicity nematicide, which is relatively safe for the environment; the slow-release adsorption carrier is plant-derived biochar, which is derived from nature and has a large adsorption capacity, which can effectively control the stable release of the nematicide active ingredient in the soil, maintain an appropriate pesticide dosage in the plant rhizosphere soil for a longer period of time, and the slow-release material is safe and friendly to the soil environment.

[0017] 2. The biochar-based slow-release nematicide granules provided by this invention have a good control effect on tobacco root-knot nematode disease. The efficacy is long-lasting and the slow-release effect is excellent. For most annual crops, it generally only needs to be used once per growing season. At the same time, the product of this invention contains biochar, which can effectively improve the physical and chemical properties of the soil, adsorb and passivate heavy metals, and play a certain role in improving crop yield and quality.

[0018] 3. The biochar-based slow-release nematicide granules provided by this invention can effectively control the damage caused by root-knot nematodes to crops such as tobacco. They are safe for crops and can effectively improve the yield and quality of agricultural products. Furthermore, using this control technology can effectively reduce the amount of nematicide used, achieving the goal of reducing pesticide use while increasing efficiency. Attached Figure Description

[0019] Figure 1 Release dynamics of abamectin B2 in soil from different formulations of biochar-based nematicide granules; Figure 2 The effect of different formulations of biochar-based nematicide granules on the number of rhizosphere bacteria in tobacco; Figure 3 The effect of different formulations of biochar-based nematicide granules on the number of rhizosphere fungi in tobacco; Figure 4 The effects of different formulations of biochar-based nematicide granules on the number of actinomycetes in the tobacco rhizosphere. Detailed Implementation

[0020] The following is a detailed description with reference to the accompanying drawings and embodiments: Example 1: Preparation of Biochar-Based Sustained-Release Nematicide Granules Raw material ratio: 5.5 kg of 95% abamectin B2 technical grade, 26.5 kg of 99% dimethylformamide, 12 kg of 3% dilute sulfuric acid, 58.3 kg of tobacco stem biochar (moisture content 8%~12%, pH≤9.5), 15 kg of bentonite as binder, 5 kg of glycerol as stabilizer, 1 kg of sodium alginate as encapsulating agent, and 12 kg of water.

[0021] After preparing the above-mentioned raw materials, the preparation method of biochar-based slow-release nematicide granules is completed according to the following processing steps: (1) First, dissolve 5.5 kg of 95% abamectin B2 technical material in 26.5 kg of 99% dimethylformamide and set aside; (2) Weigh 58.3 kg of tobacco stem biochar, spray it with 3% dilute sulfuric acid to adjust the pH value to between 8.0 and 9.0, and then dry it until the moisture content is 18%; (3) Spray the abamectin B2 dimethylformamide solution from step (1) evenly onto the tobacco stem biochar after acid treatment in step (2). Spraying and stirring are carried out simultaneously. Stir for 12 minutes, then place it in a room temperature of 15~30℃, in a dark and ventilated environment to dry, and control the liquid content to 22% for later use. (4) Crush the biochar after adsorbing the drug in step (3), pass it through a 20-mesh sieve, then add 15 kg of bentonite and stir thoroughly for 5 minutes; (5) Add 5 kg of glycerin on the basis of step (4), stir thoroughly for 5 minutes, and then extrude and granulate to form particles with a diameter of 4 mm and a length of 4-6 mm. (6) Dissolve 1 kg of sodium alginate in water to make a 10% aqueous solution. Dry the granules in step (5) in the dark until the liquid content is 25-30%. Then, use 10 kg of sodium alginate aqueous solution for uniform spray coating treatment. (7) Dry the granules in (6) in a dark environment until the surface is dry and there is no sticking and the total weight is 100 kg to obtain the product.

[0022] Example 2: Preparation of Biochar-Based Sustained-Release Nematicide Granules Raw material ratio: 2.8 kg of 95% abamectin B2 technical grade, 13.5 kg of 99% dimethylformamide, 12 kg of 4% dilute sulfuric acid, 61.1 kg of tobacco stem biochar (moisture content 8%~12%, pH≤9.5), 15 kg of bentonite, 5 kg of glycerin, 1 kg of sodium alginate, and 12 kg of water.

[0023] After preparing the above-mentioned raw materials, the preparation method of biochar-based slow-release nematicide granules is completed according to the following processing steps: (1) First, dissolve 2.8 kg of 95% abamectin B2 technical material in 13.5 kg of 99% dimethylformamide and set aside; (2) Weigh 61.1 kg of tobacco stem biochar, spray it with 12 kg of dilute sulfuric acid to adjust the pH value to between 8.0 and 9.0, and then dry it until the moisture content is 18%; (3) Spray the abamectin B2 dimethylformamide solution from step (1) evenly onto the tobacco stem biochar after acid treatment in step (2). Spraying and stirring are carried out simultaneously. Stir for 12 minutes, then place it in a room temperature of 15~30℃, in a dark and ventilated environment to dry, and control the liquid content to 22% for later use. (4) Crush the biochar after adsorbing the drug in step (3), pass it through a 20-mesh sieve, then add 15 kg of bentonite and stir thoroughly for 5 minutes; (5) Add 5 kg of glycerin on the basis of step (4), stir thoroughly for 5 minutes, and then extrude and granulate to form particles with a diameter of 4 mm and a length of 4-6 mm; (6) Dissolve 1 kg of sodium alginate in water to make a 10% aqueous solution. Dry the granules in step (5) in a dark environment until the liquid content is 25-30%, and then use sodium alginate aqueous solution for uniform spray coating treatment. (7) Dry the granules in (6) in a dark environment until the surface is dry and there is no sticking and the total weight is 100 kg to obtain the product.

[0024] Example 3: Preparation of Biochar-Based Slow-Release Nematicide Granules Raw material ratio: 8.2 kg of 95% abamectin B2 technical grade, 40 kg of 99% dimethylformamide, 12 kg of 2% dilute sulfuric acid, 55.6 kg of tobacco stem biochar (moisture content 8%~12%, pH≤9.5), 15 kg of bentonite, 5 kg of glycerin, 1 kg of sodium alginate, and 12 kg of water.

[0025] After preparing the above-mentioned raw materials, the preparation method of biochar-based slow-release nematicide granules is completed according to the following processing steps: (1) First, dissolve 8.2 kg of 95% abamectin B2 technical material in 40 kg of 99% dimethylformamide and set aside; (2) Weigh 55.6 kg of tobacco stem biochar, spray it with 12 kg of 2% dilute sulfuric acid to adjust the pH value to between 8.0 and 9.0, and then dry it until the moisture content is 18%; (3) Spray the abamectin B2 dimethylformamide solution from step (1) evenly onto the tobacco stem biochar after acid treatment in step (2). Spraying and stirring are carried out simultaneously. Stir for 12 minutes, then place it in a room temperature of 15~30℃, in a dark and ventilated environment to dry, and control the liquid content to 22% for later use. (4) Crush the biochar after adsorbing the drug in step (3), pass it through a 20-mesh sieve, then add 15 kg of bentonite and stir thoroughly for 5 minutes; (5) Add 5 kg of glycerin on the basis of step (4), stir thoroughly for 5 minutes, and then extrude and granulate to form particles with a diameter of 4 mm and a length of 4-6 mm. (6) Dissolve 1 kg of sodium alginate in water to make a 10% aqueous solution. Dry the granules in step (5) in a dark environment until the liquid content is 25-30%, and then use sodium alginate aqueous solution for uniform spray coating treatment. (7) Dry the granules in (6) in a dark environment until the surface is dry and there is no sticking and the total weight is 100 kg to obtain the product.

[0026] Example 4: Field control efficacy of abamectin B2 biochar-based granules against tobacco root-knot nematode disease (1) Tested nematicide granules The experiment included three formulations: Formula XA, with the following raw material ratio: 5.5 kg of 95% abamectin B2 technical grade, 26.5 kg of 99% dimethylformamide, 12 kg of 3% dilute sulfuric acid, 58.3 kg of tobacco stem biochar (moisture content 8%~12%, pH≤9.5), 15 kg of bentonite, 5 kg of glycerin, 1 kg of sodium alginate, and a certain amount of water for later use; Formula XB has the following raw material ratio: 5.5 kg of 95% abamectin B2 technical grade, 26.5 kg of 99% dimethylformamide, 12 kg of 3% dilute sulfuric acid, 58.3 kg of tobacco stem biochar (moisture content 8%~12%, pH≤9.5), 15 kg of bentonite, 5 kg of β-cyclodextrin, 1 kg of polyvinyl alcohol, and the remainder is water; Formula XC has the following raw material ratio: 5.5 kg of 95% abamectin B2 technical grade, 26.5 kg of 99% dimethylformamide, 12 kg of 3% dilute sulfuric acid, 58.3 kg of tobacco stem biochar (moisture content 8%~12%, pH≤9.5), 15 kg of bentonite, 5 kg of glycerin, 1 kg of polyvinyl alcohol, and the remainder is water.

[0027] The processing technology of formulations XA, XB and XC is the same as that of Examples 1-3. The content of abamectin B2 in formulations XA, XB and XC exceeds 5%.

[0028] In formulations XB and XC, polyvinyl alcohol replaced sodium alginate in XA as the encapsulating agent, and β-cyclodextrin replaced glycerol in XA as the stabilizer in formulation XB. A control (CK) was also included, which received no caustic agents.

[0029] (2) Test methods The experiment was conducted in Heishitou Town, Weining County, Guizhou Province, in fields where root-knot nematode disease had previously been severe. The locally promoted tobacco variety Yunyan 87 was used. A randomized block design was employed, with three replicates per plot, each containing 60 plants (3 rows of 20 plants each). Plant spacing was 0.55 m, and row spacing was 1.1 m. All treatments were applied at a dose of 4 g / plant in the planting hole before transplanting. Other management practices followed local standard practices.

[0030] The base fertilizer (9:13:22) was applied at a rate of 40 kg / mu, applied in planting holes before transplanting and mixed thoroughly with the soil. Seedling fertilizer (15:8:7) was applied at a rate of 2.5 kg / mu, diluted with water and applied within two days after transplanting. Specialized topdressing fertilizer (13:0:26) was applied at a rate of 20 kg / mu, applied dry approximately 30 days after planting. Preventive measures against soil-borne diseases other than root-knot nematodes were uniformly implemented throughout the experimental area.

[0031] (3) Survey methods The survey was conducted on both above-ground and below-ground parts, with each plant as a unit of classification. The number of diseased plants in each treatment was recorded in detail, and each plant was classified according to its disease severity, with the disease index and control efficacy calculated.

[0032] Grading standards for the above-ground parts of tobacco plants during the growing season (early harvesting and curing stage): Grade 0: Plants grow normally; Grade 1: Plants grow basically normally, but the leaf edges or tips turn yellow, but are not withered; Grade 3: Plants are 1 / 4 to 1 / 3 shorter than healthy plants, or the leaf tips are slightly withered; Grade 5: Plants are 1 / 3 to 1 / 2 shorter than healthy plants, or most leaves have withered edges or tips, or have withered yellow spots; Grade 7: Plants are more than 1 / 2 shorter than healthy plants, all leaves have withered edges or tips, or have withered yellow spots; Grade 9: Plants are severely stunted, and all leaves are basically withered.

[0033] Grading standards for root survey at maturity (end of harvesting and roasting): Grade 0: normal roots, no visible root knots; Grade 1: fewer than 1 / 4 of roots have a small number of root knots; Grade 3: 1 / 4 to 1 / 3 of roots have root knots; Grade 5: 1 / 3 to 1 / 2 of roots have root knots; Grade 7: more than 1 / 2 of roots have root knots, and a small number of secondary roots have root knots; Grade 9: all roots (including secondary roots) are covered with root knots.

[0034] (4) Test results Biochar-based slow-release nematicide granules were applied at 4.0 g / plant during tobacco transplanting, and the control efficacy was investigated once at the beginning of the curing season (July 22, 2024) and once at the end of the curing season (August 23, 2024) (see Table 1). The results showed that treatment XA had the best control efficacy among the three formulations, with a control efficacy of 52.76% against tobacco root-knot nematodes at the beginning of the curing season and 61.96% at the end of the curing season. Formulations XB and XC also showed some effectiveness.

[0035] Table 1. Control efficacy of different formulations of biochar-based nematicide granules against tobacco root-knot nematode disease.

[0036] Example 5: Release dynamics of the active ingredient of abamectin B2 biochar-based granules in the rhizosphere soil of tobacco plants (1) Tested nematicide granules The tested nematicidal granules were the three formulations (formulations XA, XB, and XC) from Example 4. A control (CK) was also set up, in which no nematicidal agent was applied.

[0037] (2) Test methods The experiment was conducted at the Tobacco Science and Technology Park in Heishitou Town, Weining County, Guizhou Province. The field treatment method was the same as in Example 2. After applying the biochar-based nematicide granules, rhizosphere soil samples were collected at 1, 2, 3, and 4 months to test the abamectin B2 content in the soil. During soil collection, three tobacco plants with similar growth were taken from each plot (one plant per row, avoiding the ends of each row). Approximately 500 g of soil was collected from each plant. After thoroughly mixing the soil sample from each plot, another 500 g was collected, sealed in a collection bag, and kept for later use.

[0038] (3) Detection method of avermectin B2 ① Sample preparation: Take 10 g of soil sample into a 50 mL centrifuge tube, add 25 mL of analytical grade acetonitrile (add 2 mL of water to the soil sample), extract ultrasonically for 30 min, add 2.5 g of sodium chloride, centrifuge at 8000 r / min for 5 min, and let stand for 10 min. Accurately pipette 10 mL of organic phase into a round-bottom flask, evaporate to near dryness in a water bath at 50℃, add 2 mL of dichloromethane-methanol solution (95:5 v / v) to dissolve, prewash the NH2 column with 5 mL of dichloromethane-methanol solution, discard the eluent, then add the dissolved sample concentrate, collect the eluent in a 20 mL centrifuge tube, wash the round-bottom flask with 2 mL of dichloromethane-methanol solution and transfer to the purification column, repeat 3 times, evaporate all collected eluent to near dryness by nitrogen blowing, dissolve the residue in chromatographic grade acetonitrile-water solution (90:10 v / v) and make up to 1 mL, filter through a 0.22 μm filter membrane, and prepare for analysis.

[0039] ②Chromatographic conditions: Instrument: Shimadzu LC40, mass spectrometer 8045; Column: Agilent Eclipseplus C18, 1.8 μm, 2.1×100 mm; Chromatographic separation conditions: Column temperature: 40°C, flow rate: 0.300 mL / min, run time: 3 min, injection volume: 2µL; Mobile phase: 0.1% formic acid water + methanol = 10 + 90; Mass spectrometry conditions: ESI source, positive ion MRM mode.

[0040] (4) Test results The test results showed that the highest concentrations of pesticides in the soil were observed one month after application for all three treatments, decreased significantly at two months, and stabilized at three and four months. Treatment XB showed significantly higher release at one month compared to the other treatments, while treatment XA had a relatively higher concentration in the later stages. Furthermore, treatment XA exhibited the best control efficacy among the three treatments, possibly related to its higher pesticide concentration in the soil during the later root-knot nematode pathogen invasion period (generally two months after planting). Treatment XB, due to its excessive release in the early stages, resulted in a lower pesticide concentration in the soil than XA in the later stages, thus exhibiting less control efficacy. Treatment XC had a lower pesticide content in the soil in the later stages, resulting in poorer control efficacy. In summary, treatment XA, with its higher soil pesticide concentration during the root-knot nematode pathogen invasion period, showed relatively better efficacy.

[0041] Example 6: Effects of abamectin B2 biochar-based granules on the safety of major microbial communities and invertebrate communities in tobacco fields (1) Tested nematicide granules The tested nematicidal granules were the three formulations (formulations XA, XB, and XC) from Example 4. A control (CK) was also set up, in which no nematicidal agent was applied.

[0042] (2) Test methods ① Field design The treatment method for field biochar-based nematicide granules is the same as in Example 4.

[0043] ② Microbial testing Soil collection: After applying the nematicide granules, rhizosphere soil samples were collected at 1, 2, 3, and 4 months. Three tobacco plants with similar growth were taken from each plot (one plant per row, avoiding the ends of each row). Approximately 500 g of soil was collected from each plant. The soil samples from each plot were thoroughly mixed, and then another 500 g was collected, sealed in a collection bag, and kept for later use.

[0044] Test culture media: PDA medium was used for fungal isolation: 200 g potato, 15 g agar, 20 g glucose, 1000 mL water. NA medium was used for bacterial isolation: 3.0 g beef extract, 5.0 g NaCl, 10.0 g peptone, 15-20 g agar, 1000 mL water, pH 7.2-7.5. Modified Gao's No. 1 medium was used for actinomycete isolation: purchased from a reagent company.

[0045] Serial dilution of soil samples: Weigh 10g of sample (accurate to 0.01g), add to 100mL of sterile water containing glass beads, let stand for 20min, then shake thoroughly on a rotary shaker at 200 rpm for 30min to obtain the soil stock solution. Using a sterile pipette, pipette 100μL of the above soil stock solution bacterial suspension, add 900μL of sterile water, and dilute at a ratio of 10... n A series of dilutions were performed to obtain 10... -1 10 -2 10 -3 10 -4 10 -5 Soil suspension diluted to a certain ratio.

[0046] Isolation and culture of soil microorganisms: Three consecutive appropriate dilutions were taken from each sample. 0.1 mL of soil suspension at each dilution was added to a pre-prepared solid culture medium plate. The suspension was spread evenly on the surface of the medium using a spreader. Each dilution was repeated three times and cultured under suitable conditions.

[0047] Colony counting: Bacteria were counted after 24 hours of culture, fungi after 48 hours of culture, and actinomycetes after 7 days of culture. Plates with a dilution of 20-300 colonies were used as the counting standard to count the number of viable bacteria isolated.

[0048] ③ Invertebrate survey methods Each plot was surveyed at 4-6 points (plants), with each soil sample measuring 0.5 m (length) × 0.4 m (width) × 0.3 m (depth). The survey was conducted twice. In the first survey (late July 2024), the species and quantity of invertebrates on one side of the tobacco plant ridge were first counted. Then, the invertebrate populations in the soil were investigated layer by layer using a small shovel. In the second survey (late August 2024), the species and quantity of invertebrates on one side of the tobacco plant ridge were first counted again. Then, the tobacco plants were uprooted, the root zone soil was quickly shaken off, and the invertebrate populations in the soil were investigated layer by layer using a small shovel. Finally, the results of the two surveys were combined to analyze the impact of each treatment on the invertebrate community.

[0049] For small social insects such as ants, they are graded based on visual count, with the following grading standards: 1 (1-5 insects); 2 (6-20 insects); 3 (21-100 insects); 4 (101-500 insects); 5 (501 or more insects). Grade 1 is equivalent to 1 insect in other insects, and so on.

[0050] (3) Test results ① Impact on the microbial community like Figure 2 The effects of different nematicide granules on the number of bacteria in the tobacco rhizosphere were investigated. The results showed that the bacterial counts of all treatments were lower than the control, indicating a certain impact on the bacterial community. The differences between the treatments and the control were more significant at 1 month and 4 months, while the differences were less significant at 2 and 3 months. There were no significant differences among the three treatments at 1 month, but at 4 months, the bacterial count in treatment XC was significantly lower than that in treatments XA and XB.

[0051] like Figure 3 The effects of different nematicide granules on the number of fungi in the tobacco rhizosphere were investigated. The results showed that the number of fungi in each treatment was lower than that in the early stage (1-3 months), while the number of fungi in the XC treatment was higher than that in the control at the fourth month. Among the three treatments, the number of fungi in the XC treatment was the lowest in the first 1-2 months, but the number of fungi in the XC treatment was significantly higher than that in the XA and XB treatments at the fourth month.

[0052] like Figure 4 To investigate the effects of different treatments on the abundance of actinomycetes in the tobacco rhizosphere, the results showed that the abundance of actinomycetes in each treatment was lower than that in the control from 2 to 4 months, indicating a certain impact on the actinomycete community. The difference between the treatments and the control was more significant in the 4th month. There were no significant differences among the three treatments from 1 to 3 months, but at 4 months, the abundance of actinomycetes in treatment XA was significantly lower than that in treatments XB and XC.

[0053] ② Impact on invertebrate communities Statistical results showed that, compared with the control (CK), there was no significant difference in the total number of pest subcommunities after the application of each nematicide granule treatment. The number of pests after treatments XA, XB, and XC were 102, 85, and 101, respectively. Statistical results on the neutral invertebrate subcommunity in the tobacco field showed that, compared with the control (CK), treatments XA and XB had no significant effect on the total number of neutral animals, but treatment XC had a greater effect. Treatments XA and XB had no significant effect on the neutral animal subcommunity. Statistical results on the effect on the number of natural enemies in the tobacco field showed that, compared with the control (CK), treatment XA had no significant effect on natural enemies, with a number of 81. Treatments XB and XC had some impact, especially on spiders. Overall analysis indicated that treatment XA had no significant effect on the natural enemy subcommunity.

[0054] Furthermore, compared to the control (CK), XA treatment had no effect on the population size of major invertebrate communities, and the population size was higher than that of the control treatment. The invertebrate population after XC treatment was 162 individuals, significantly lower than the control's 195 individuals, but the difference was not statistically significant. XC treatment had a more significant impact on the population sizes of spiders, millipedes, and tenebrionid beetles, and also a significant impact on natural enemies. In conclusion, XA treatment has no significant impact on invertebrate populations, making it the safest treatment for tobacco fields.

[0055] Table 2. Effects of different formulations of biochar-based nematicide granules on major invertebrate communities.

[0056] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A biochar-based sustained-release nematicide granule, characterized in that: The raw materials consist of the following parts by weight: 95% abamectin B2: 2.8~8.2 parts; 8~12% water content biochar: 55.6~61.1 parts; 2~4% dilute sulfuric acid: 12 parts; 99% dimethylformamide: 13.5~40 parts; binder: 15 parts; stabilizer: 5 parts; encapsulating agent: 1 part; water: 12 parts.

2. The biochar-based sustained-release nematicide granule according to claim 1, characterized in that, The raw materials consist of the following parts by weight: 95% abamectin B2: 5.5 parts; 8-12% water content biochar: 58.3 parts; 3% dilute sulfuric acid: 12 parts; 99% dimethylformamide: 26.5 parts; binder: 15 parts; stabilizer: 5 parts; encapsulating agent: 1 part; water: 12 parts.

3. The biochar-based sustained-release nematicide granules according to claim 1 or 2, characterized in that: The biochar mentioned is tobacco stem biochar.

4. The biochar-based sustained-release nematicide granule according to claim 3, characterized in that: The binder is bentonite.

5. The biochar-based sustained-release nematicide granule according to claim 4, characterized in that: The stabilizer is glycerol or β-cyclodextrin.

6. The biochar-based sustained-release nematicide granule according to claim 5, characterized in that: The encapsulating agent is sodium alginate or polyvinyl alcohol.

7. The method for preparing the biochar-based sustained-release nematicide granules as described in claim 6, characterized in that: After preparing the raw materials by weight, proceed with the following steps: ① First, dissolve 95% avermectin B2 technical grade in dimethylformamide and set aside; ② The tobacco stem biochar was sprayed with 2-4% dilute sulfuric acid to adjust the pH of the tobacco stem biochar to between 8.0 and 9.

0. The adjusted tobacco stem biochar was then dried to a moisture content of 15-20%. ③ Spray the abamectin B2 dimethylformamide solution prepared in step ① evenly onto the tobacco stem biochar treated with acid in step ②, while spraying and stirring simultaneously. Stir for 10-15 minutes, then place it in a room temperature of 15-30℃, in a dark and ventilated environment to dry, controlling the liquid content to 20-25%, and set aside for later use. ④ Crush the tobacco stem biochar that adsorbed abamectin B2 in step ③ to a particle size smaller than 20 mesh, then add bentonite and stir thoroughly until uniform; ⑤ Add glycerin based on step ④, stir thoroughly, and then extrude and granulate to prepare granules; ⑥ Dissolve sodium alginate in water to make a 10% sodium alginate aqueous solution, and dry the granules in step ⑤ in the dark until the liquid content is 25~30%, and then use sodium alginate aqueous solution for uniform spray coating treatment. ⑦ Dry the granules from step ⑥ in a dark environment until the surface is dry and no longer sticky, and the product is obtained.

8. The method of using the biochar-based sustained-release nematicide granules as described in claim 7, characterized in that: The application method in tobacco fields is to apply it in holes before transplanting tobacco plants, with an application rate of 3-6 g / plant.

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