Method for reducing pesticide residues of cowpeas

Abstract

The invention provides a method for reducing pesticide residues of cowpeas, and belongs to the technical field of cowpea cultivation. The method comprises the steps of seed pretreatment, soil preparation and sowing, seedling stage management and flowering stage management. In the seedling stage management, when 4-5 true leaves exist in the cowpea seedling stage, a control agent is sprayed to cowpea plants, and the control agent is composed of deionized water and a pesticide slow-release agent; the preparation method of the pesticide slow-release agent comprises the following steps: spraying a modifier onto biochar, raising the temperature for reaction, filtering, washing and drying to obtain modified biochar; placing matrine and acetamiprid in an ethanol solution to obtain a medicament mixed solution; adding the modified charcoal into the pesticide mixed solution, uniformly stirring, heating to 33-37 DEG C, adding lysine and arginine, uniformly stirring, adding carboxymethyl cellulose, and drying to obtain the pesticide slow-release agent. By planting the cowpeas through the method, pesticide residues in the cowpeas can be reduced, the yield can be increased, and the content and taste of vitamin C are guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of cowpea cultivation, and particularly relates to a method for reducing cowpea pesticide residues. Background Art

[0002] Cowpea, commonly known as carob, ginger bean, and ribbon bean, is an annual twining, herbaceous vine or nearly erect herb of the Fabaceae family and the genus Vigna. It is widely planted in the Yangtze River Basin and the south and is one of the main vegetable varieties in summer and autumn. Cowpea has the advantage of low sugar content, so it is suitable for obese people. Cowpea has low sodium content and is rich in dietary fiber and vitamins. It is suitable for patients with kidney disease. It can also maintain normal digestive gland secretion and gastrointestinal motility, improve the body's resistance to viruses, and enhance the body's immune function.

[0003] During the cultivation of cowpea, aphids, whiteflies, powdery mildew, rust and other pests and diseases are prone to occur, and the continuous cropping of cowpeas also aggravates the severity of pests and diseases, making prevention and control more difficult; the commonly used method is to apply pesticides, fertilizers, etc. to prevent and control pests and diseases. Although it can prevent and control pests and diseases to a certain extent, the large amount of pesticides and fertilizers used and the frequent use of drugs will increase the drug resistance of insects, making the prevention and control effect reduce year by year, and more chemical agents are likely to cause pesticide residues on cowpeas, resulting in excessive pesticide residues, affecting the edible value of cowpeas, endangering food safety and health, and also causing negative impacts on the environment.

[0004] In the process of planting cowpea, the existing technology generally includes the following methods to reduce pesticide residues: One is to reduce the use of pesticides and fertilizers, but this will increase the incidence of pests and diseases, ultimately reducing the yield of cowpeas and affecting profits; or change the timing and location of drug use, but it cannot effectively reduce pesticide residues in cowpeas; The second is to use the degradation bacteria in the microbial agent to degrade the pesticide residues, but there will be problems such as incomplete degradation, relatively single type of degraded pesticides, and high degradation costs; Third, by applying soil conditioners, the fertility and antibacterial ability of the soil can be improved, thereby improving the growth quality of cowpeas, reducing the probability of cowpeas being infected by pathogens, and increasing the survival rate of seeds, reducing the probability of infection, thereby reducing the amount of pesticides used; for example, CN117378447A discloses a low-pesticide cowpea planting method, which specifically discloses selecting a sowing ground and trimming it, sowing cowpea seeds in the sowing ground, applying organic fertilizers in sequence, laying ground film, building a greenhouse in the sowing ground, and setting insect-proof enclosures around the greenhouse, setting insect-attracting lamps in the greenhouse, and then releasing aphid wasps in the greenhouse, and after the cowpea seedlings grow to 3-4cm, breaking the film in sequence, setting up frames, applying compound fertilizers, and dripping pesticides on the roots of the seedlings, applying soil conditioners after the cowpeas grow to the flowering and pod-setting stage, and then releasing green wasps in the greenhouse, that is, completing the planting; The method in this patent solves the technical problems of high pesticide residues in cowpea cultivation and susceptibility to pests and diseases. In the process of planting cowpea, the germination rate reaches 97.48%, the survival rate reaches 95.62%, and the pesticide residue is reduced to 0.15 mg / kg. However, the cowpeas obtained by this planting method have a high incidence of powdery mildew, a low yield, a low vitamin C content, and a low nutritional value. Summary of the invention

[0005] In order to solve the technical problems existing in the prior art, the present invention provides a method for reducing pesticide residues in cowpea, which effectively reduces the pesticide residues in cowpea, reduces the incidence of cowpea diseases and pests, increases yield, and ensures the vitamin C content in cowpea.

[0006] In view of the above technical problems, the present invention adopts the following technical solutions: A method for reducing cowpea pesticide residues, including seed pretreatment, land preparation and sowing, seedling management, and flowering management, the specific operations are as follows: 1. Seed pretreatment Select cowpea seeds with full grains and no damage, soak them in a 0.11-0.15wt% potassium permanganate solution for 13-18 minutes, take them out and wash them, then soak them in deionized water at a temperature of 23-27°C for 3.8-4.2 hours, add aminoethyl hexanoate and Tween 20 after soaking, stir, continue soaking at 23-27°C for 2.2-2.8 hours, take them out, wash them, and dry them to obtain pretreated cowpea seeds; The mass ratio of the cowpea seeds, potassium permanganate solution, deionized water, ammonium ethyl hexanoate and Tween 20 is 48-52:980-1020:980-1020:0.10-0.14:0.12-0.15.

[0007] 2. Land preparation and sowing First, apply basal fertilizer to the soil, apply 638-642kg of decomposed cow dung, 3.4-3.6kg of potassium humate, 0.8-1.2kg of borax, 13-15kg of diammonium phosphate, and 16-18kg of potassium sulfate per mu. After the application, plough the soil to a depth of 28-33cm. Then spread the improver, spread 26-30kg per mu. After spreading, plough the soil again to a depth of 20-25cm. After raking and leveling, build ridges and cultivate on the ridges. Each ridge has 2 rows, the plant spacing is 30-32cm, the row spacing is 58-62cm, and 2 seeds are sown in each hole. The preparation method of the improver includes preparing biochar, preparing a primary improver, and a compounding step, which is specifically as follows: a. Preparation of biochar After cleaning and drying the corn stalks, put them into a muffle furnace, heat them to 417-423°C at a rate of 4.8-5.2°C / min in a nitrogen atmosphere, and keep them warm for 1.8-2.2 hours. After the insulation is completed, wait for them to return to room temperature naturally, grind them to a particle size of 18-22 μm, and obtain biochar; The corn stalk has a length of 0.8-1.2 mm and a diameter of 0.4-0.6 mm; b. Preparation of primary improver The biochar is put into an ethanol solution, polyethylene glycol monolaurate is added, the temperature is raised to 63-67°C, and the mixture is stirred for 28-32 minutes. After the stirring is completed, the mixture is filtered out and washed, and then placed in a reaction vessel. Dimethyl sulfoxide is introduced and stirred evenly. Humic acid and modified coconut fiber are added and stirred. The stirring speed is controlled to be 174-185 rpm. While stirring, the temperature is raised to 116-123°C at a rate of 0.8-1.2°C / min, and then concentrated sulfuric acid is added and stirred for 11.8-12.3 hours. After the reaction is completed, a primary improver is obtained. The mass volume ratio of the biochar, ethanol solution, polyethylene glycol monolaurate, dimethyl sulfoxide, humic acid, and modified coconut fiber is 13.0-13.5 g: 126-135 g: 1.2-1.4 g: 1270-1330 mL: 4.6-4.8 g: 1.5-1.7 g; The mass concentration of the ethanol solution is 18-22%; The preparation method of the modified coconut fiber comprises the following steps: placing the coconut fiber in an ethanol solution, stirring evenly, adding hexadecyltrimethylammonium bromide and kH560, raising the temperature to 60-64° C., keeping the temperature and stirring for 3.8-4.2 hours, filtering, washing and drying to obtain the modified coconut fiber; The mass ratio of the coconut fiber, ethanol solution, hexadecyltrimethylammonium bromide and kH560 is 8.3-8.7:88-92:0.76-0.83:0.90-0.95; The mass concentration of the ethanol solution is 30-34%.

[0008] c. Compound The primary modifier is placed in an ethanol solution, diethylenetriaminopropyltrimethoxysilane and γ-aminopropyltriethoxysilane are added, and the mixture is stirred at 58-62°C for 3.7-4.3 hours. After the reaction is completed, polyacrylamide and glutaraldehyde are added, and the mixture is stirred at 30-35°C for 1.4-1.7 hours. After the reaction is completed, the mixture is filtered, washed, and dried to obtain the modifier. The mass ratio of the primary modifier, ethanol solution, diethylenetriaminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, polyacrylamide and glutaraldehyde is 9.7-10.3:98-102:0.3-0.5:0.8-1.2:3.5-4.0:4.8-5.2; The mass concentration of the ethanol solution is 23-28%.

[0009] 3. Management during the seedling stage When the cowpea seedlings have 4-5 true leaves, spray the cowpea plants with the control agent, controlling the spraying amount to 115-123g per plant; The control agent is a mixture of deionized water and a pesticide slow-release agent, and the mass ratio of the deionized water to the pesticide slow-release agent is 1000:0.80-0.85; The preparation method of the control agent is as follows: spraying the modifier onto the biochar, controlling the spraying rate to be 2.8-3.2 g / min, raising the temperature to 60-64°C, stirring and reacting for 4.8-5.2 hours after the spraying is completed, filtering, washing and drying after the reaction is completed to obtain the modified biochar; placing matrine and acetamiprid in an ethanol solution, stirring evenly, and obtaining a mixed agent liquid; adding the modified biochar to the mixed agent liquid, performing homogenization treatment, the homogenization time is 4.8-5.2 minutes, the homogenization pressure is 2.7-3.0 MPa, after the homogenization is completed, heating to 33-37°C at a rate of 0.4-0.6°C / min, adding lysine and arginine, stirring evenly, adding carboxymethyl cellulose, stirring evenly, and drying to obtain a pesticide slow-release agent; The biochar is the biochar prepared in the step of preparing the improver; The modifier is composed of 34-36wt% ethanol solution, triethanolamine dodecyl sulfate and kH792, and the mass ratio of the 34-36wt% ethanol solution, triethanolamine dodecyl sulfate and kH792 is 100:0.8-1.2:1.3-1.6; The mass ratio of the modifier to the biochar is 108-112:12.3-12.7; The mass ratio of matrine, acetamiprid and ethanol solution is 0.6-0.8:0.8-1.0:990-1010; The mass concentration of the ethanol solution is 38-42%; The mass ratio of the reagent mixture, modified biochar, lysine, arginine, and carboxymethyl cellulose is 98-102:11.2-11.7:1.8-2.2:1.5-1.7:5.6-6.0; 4. Flowering period management At the beginning of flowering, 4.8-5.2 kg / mu of urea and 12.3-12.7 kg / mu of nitrogen, phosphorus and potassium compound fertilizers were applied to cowpea plants, and topdressing was performed every 7 days for a total of 3 times. After the first inflorescence is pod-forming, nutrient solution was applied every 3 days for a total of 2 times, with 145-155 g per plant. The nitrogen-phosphorus-potassium compound fertilizer has a nitrogen content of 14-16%, a phosphorus pentoxide content of 14-16%, and a potassium oxide content of 17-22%; The nutrient solution is a mixture of deionized water, ferrous sulfate, cupric sulfate, betaine and ammonium molybdate, and the mass ratio of the deionized water, ferrous sulfate, cupric sulfate, betaine and ammonium molybdate is 1000:3.3-3.7:4.0-4.4:4.8-5.3:3.7-4.2.

[0010] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The method for reducing cowpea pesticide residues of the present invention is mainly achieved through two aspects. First, the growth performance of crops is enhanced, the stress resistance of plants is improved, and the probability of plant diseases and insects is reduced, thereby reducing the application of pesticides; second, pesticides are coated by membrane coating technology to form a membrane structure on the surface of the pesticide package, which can not only achieve the sustained release of pesticides, increase the effective period of pesticides, and reduce the amount of pesticides used, but also reduce the penetration of pesticides into plants and reduce pesticide residues; the specific method is to first use an improver to improve the soil, use biochar as an improved matrix, and under the catalysis of concentrated sulfuric acid, the biochar, humic acid and coconut fiber are firmly cross-linked, and the obtained primary improver has a large adsorption capacity and a stable structure, and the humic acid contains more hydroxyl, carboxyl and other groups, which can adsorb heavy metals, pesticide residues and the like in the soil, so that pollutants and the like in the soil do not migrate to the plants, the primary improver is amino-modified, and then cross-linked again with glutaraldehyde, thereby improving the stability of the improver , which can effectively improve the soil aggregate structure, improve the soil permeability, balance the nutrients in the soil, promote the growth and development of plants, thereby improving the germination of cowpea seeds and the growth of seedlings, improving the stress resistance and growth rate of crops, promoting the absorption of nutrients by plants, improving the quality of cowpea fruits, increasing the content of nutrients, and enhancing the taste. In the seedling stage, the plants are sprayed with pesticide control agents, wherein the pesticide control agent is a membrane coating technology for coating the pesticide, specifically, the pesticide is adsorbed into the pore structure of the biochar, and then carboxymethyl cellulose is added, the carboxyl group of which can be combined with the amino group of the modified biochar, and the carboxymethyl cellulose has good adhesion, which improves the stability of the pesticide slow-release agent, thereby avoiding direct contact between the plant and the pesticide, and reducing the amount of pesticide applied, improving the persistence of the pesticide, and ultimately increasing the yield of cowpea, reducing the incidence of pests and diseases, reducing pesticide residues, improving the quality and taste of cowpea, and reducing crude fiber content; 2. When the method of the present invention is used to plant cowpea, during the growth period of cowpea, the incidence of aphids is 0.5-0.8%, the incidence of powdery mildew is 0.8-1.3%, and the incidence of rust is 1.2-1.5%; 3. The method of the present invention is used to plant cowpea, and the yield per mu is 2210.3-2218.4 kg, and the average single pod weight is 28.0-28.6 g; 4. The method of the present invention is used to plant cowpea, and the vitamin C content of the cowpea is 25.8-26.3 mg / 100g, and the crude fiber content is 0.91-0.98 g / 100g; 5. When the method of the present invention is used to plant cowpea, the pesticide residue in the cowpea is 0.08-1.11 mg / kg. DETAILED DESCRIPTION

[0011] In order to more clearly understand the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described.

[0012] Example 1 1. Seed pretreatment Select 50g of cowpea seeds with full grains and no damage, put them into 1000g of 0.13wt% potassium permanganate solution for soaking, the soaking time is 15min, take them out and wash them, then put them into 1000g of deionized water for soaking, the soaking temperature is 25℃, the soaking time is 4.0h, after the soaking, add 0.12g of aminoethyl hexanoate and 0.13g of Tween 20 for stirring, continue soaking at 25℃ for 2.0h, after the soaking, take them out, wash and dry them to obtain the pretreated cowpea seeds.

[0013] 2. Land preparation and sowing First, apply base fertilizer to the soil, apply 640kg of decomposed cow dung, 3.5kg of potassium humate, 1.0kg of borax, 14kg of diammonium phosphate, and 17kg of potassium sulfate per mu. After the application, plough the soil to a depth of 28-33cm, then spread the improver, spread 28kg per mu, and plough the soil again after spreading to a depth of 20-25cm. After raking and leveling, build ridges and cultivate on the ridges, with 2 rows per ridge, 30-32cm plant spacing, 58-62cm row spacing, and 2 seeds per hole. The preparation method of the improver includes preparing biochar, preparing a primary improver, and a compounding step, which is specifically as follows: a. Preparation of biochar The corn stalks were cleaned and dried, and then placed in a muffle furnace. The temperature was raised to 420°C at a rate of 5.0°C / min under a nitrogen atmosphere, and the temperature was kept for 2.0 hours. After the temperature was kept, the corn stalks were naturally restored to room temperature and ground to a particle size of 20 μm to obtain biochar. The corn stalk has a length of 1.0 mm and a diameter of 0.5 mm; b. Preparation of primary improver 13.2 g of biochar was added to 130 g of 20 wt% ethanol solution, 1.3 g of polyethylene glycol monolaurate was added, the temperature was raised to 65 ° C, and the mixture was stirred for 30 min. After the stirring was completed, the mixture was filtered out and washed, and then placed in a reaction vessel. 1300 mL of dimethyl sulfoxide was introduced and stirred evenly. Then, 4.7 g of humic acid and 1.6 g of modified coconut fiber were added and stirred. The stirring speed was controlled to 180 rpm. While stirring, the temperature was raised to 120 ° C at a rate of 1.0 ° C / min, and then concentrated sulfuric acid was added and stirred for 12.0 h. After the reaction was completed, a primary improver was obtained; The preparation method of the modified coconut fiber is as follows: 8.5 g of coconut fiber is placed in 90 g of 32 wt% ethanol solution, after stirring evenly, 0.80 g of hexadecyltrimethylammonium bromide and 0.92 g of kH560 are added, the temperature is raised to 62° C., the mixture is stirred at the temperature for 4.0 h, and the modified coconut fiber is obtained by filtering, washing and drying. c. Compound Place 10.0g of the primary improver in 100g of 25wt% ethanol solution, add 0.4g of diethylenetriaminopropyltrimethoxysilane and 1.0g of γ-aminopropyltriethoxysilane, and stir to react at 60°C for 4.0h. After the reaction, add 3.7g of polyacrylamide and 5.0g of glutaraldehyde, and stir to react at 32°C for 1.5h. After the reaction, filter, wash, and dry to obtain the improver.

[0014] 3. Management during the seedling stage When the cowpea seedlings have 4-5 true leaves, spray the cowpea plants with the control agent, controlling the spraying amount to 120g per plant; The control agent is a mixture of deionized water and a pesticide slow-release agent, and the mass ratio of the deionized water to the pesticide slow-release agent is 1000:0.82; The preparation method of the control agent is as follows: 110g of the modifier is sprayed onto 12.5g of biochar, the spraying rate is controlled to be 3.0g / min, after the spraying is completed, the temperature is increased to 62°C, the reaction is stirred for 5.0h, and after the reaction is completed, the modified biochar is obtained by filtering, washing, and drying; 0.7g of matrine and 0.9g of acetamiprid are placed in 1000g of 40wt% ethanol solution, and the mixture is stirred evenly to obtain a mixed agent liquid; 11.5g of the modified biochar is added to 100g of the mixed agent liquid, and homogenization is performed, the homogenization time is 5.0min, the homogenization pressure is 2.8MPa, after the homogenization is completed, the temperature is increased to 35°C at a rate of 0.5°C / min, 2.0g of lysine and 1.6g of arginine are added, and the mixture is stirred evenly, and then 5.8g of carboxymethyl cellulose is added, and the mixture is stirred evenly and dried to obtain a pesticide slow-release agent; The biochar is the biochar prepared in the step of preparing the improver; The modifier is composed of 35wt% ethanol solution, triethanolamine dodecyl sulfate and kH792, and the mass ratio of the 35wt% ethanol solution, triethanolamine dodecyl sulfate and kH792 is 100:1.0:1.4.

[0015] 4. Flowering period management At the beginning of flowering, 5.0 kg / mu of urea and 12.5 kg / mu of nitrogen, phosphorus and potassium compound fertilizer were applied to cowpea plants, and topdressing was performed every 7 days for a total of 3 times; after the first inflorescence was pod-bearing, nutrient solution was applied every 3 days for a total of 2 times, with 150 g per plant; The nitrogen-phosphorus-potassium compound fertilizer has a nitrogen content of 15%, a phosphorus pentoxide content of 15%, and a potassium oxide content of 20%; The nutrient solution is a mixture of deionized water, ferrous sulfate, cupric sulfate, betaine and ammonium molybdate, and the mass ratio of the deionized water, ferrous sulfate, cupric sulfate, betaine and ammonium molybdate is 1000:3.5:4.2:5.0:4.0.

[0016] Example 2 1. Seed pretreatment 48 g of cowpea seeds with full grains and no damage were selected, and soaked in 980 g of 0.11 wt% potassium permanganate solution for 13 min. The seeds were taken out and washed, and then soaked in 980 g of deionized water at 23 ° C for 3.8 h. After the soaking, 0.10 g of aminoethyl hexanoate and 0.12 g of Tween 20 were added for stirring, and the seeds were continued to be soaked at 23 ° C for 2.2 h. After the soaking, the seeds were taken out, washed, and dried to obtain the pretreated cowpea seeds.

[0017] 2. Land preparation and sowing First, apply base fertilizer to the soil, apply 638kg of decomposed cow dung, 3.4kg of potassium humate, 0.8kg of borax, 13kg of diammonium phosphate, and 16kg of potassium sulfate per mu. After the application, plough the soil to a depth of 28-33cm, then spread the improver, spread 26kg per mu, and plough the soil again after spreading to a depth of 20-25cm. After raking and leveling, build ridges and cultivate on the ridges, with 2 rows per ridge, 30-32cm plant spacing, 58-62cm row spacing, and 2 seeds per hole. The preparation method of the improver includes preparing biochar, preparing a primary improver, and a compounding step, which is specifically as follows: a. Preparation of biochar The corn stalks were cleaned and dried, and then placed in a muffle furnace. The temperature was raised to 417°C at a rate of 4.8°C / min under a nitrogen atmosphere, and the temperature was kept for 1.8 hours. After the temperature was kept, the corn stalks were naturally restored to room temperature and ground to a particle size of 18 μm to obtain biochar. The corn stalk has a length of 0.8 mm and a diameter of 0.4 mm; b. Preparation of primary improver 13.0g of biochar was added to 126g of 18wt% ethanol solution, 1.2g of polyethylene glycol monolaurate was added, the temperature was raised to 63°C, and the mixture was stirred for 28min. After the stirring was completed, the mixture was filtered out and washed, and then placed in a reaction vessel. 1270mL of dimethyl sulfoxide was introduced and stirred evenly. Then, 4.6g of humic acid and 1.5g of modified coconut fiber were added and stirred. The stirring speed was controlled to be 174rpm. While stirring, the temperature was raised to 116°C at a rate of 0.8°C / min, and then concentrated sulfuric acid was added and stirred for 12.3h. After the reaction was completed, a primary improver was obtained. The preparation method of the modified coconut fiber is as follows: 8.3 g of coconut fiber is placed in 88 g of 30 wt% ethanol solution, after stirring evenly, 0.76 g of hexadecyltrimethylammonium bromide and 0.90 g of kH560 are added, the temperature is raised to 60° C., the mixture is stirred at the temperature for 4.2 hours, and the modified coconut fiber is obtained by filtering, washing and drying. c. Compound 9.7 g of the primary improver was placed in 98 g of a 23 wt% ethanol solution, 0.3 g of diethylenetriaminopropyltrimethoxysilane and 0.8 g of γ-aminopropyltriethoxysilane were added, and the mixture was stirred and reacted at 58°C for 3.7 h. After the reaction, 3.5 g of polyacrylamide and 4.8 g of glutaraldehyde were added, and the mixture was stirred and reacted at 30°C for 1.7 h. After the reaction, the improver was obtained by filtering, washing and drying.

[0018] 3. Management during the seedling stage When the cowpea seedlings have 4-5 true leaves, spray the cowpea plants with the control agent, controlling the spraying amount to 115g per plant; The control agent is a mixture of deionized water and a pesticide slow-release agent, and the mass ratio of the deionized water to the pesticide slow-release agent is 1000:0.80; The preparation method of the control agent is as follows: spraying 108g of a modifier onto 12.3g of biochar, controlling the spraying rate to be 2.8g / min, raising the temperature to 60°C after the spraying, stirring and reacting for 4.8h, filtering, washing and drying after the reaction, to obtain modified biochar; placing 0.6g of matrine and 0.8g of acetamiprid in 990g of a 38wt% ethanol solution, stirring evenly, to obtain a mixed agent solution; adding 11.2g of the modified biochar to the 98g mixed agent solution, homogenizing, the homogenizing time is 4.8min, the homogenizing pressure is 2.7MPa, after the homogenization is completed, heating to 33°C at a rate of 0.4°C / min, adding 1.8g of lysine and 1.5g of arginine, stirring evenly, adding 5.6g of carboxymethyl cellulose, stirring evenly, and drying to obtain a pesticide slow-release agent; The biochar is the biochar prepared in the step of preparing the improver; The modifier is composed of 34wt% ethanol solution, triethanolamine dodecyl sulfate and kH792, and the mass ratio of the 34wt% ethanol solution, triethanolamine dodecyl sulfate and kH792 is 100:0.8:1.3.

[0019] 4. Flowering period management At the beginning of flowering, the cowpea plants were fertilized with 4.8 kg urea per mu and 12.3 kg NPK compound fertilizer per mu, applied once every 7 days for a total of 3 times; after the first inflorescence was pod-bearing, nutrient solution was applied once every 3 days for a total of 2 times, with 145 g per plant; The nitrogen-phosphorus-potassium compound fertilizer has a nitrogen content of 14%, a phosphorus pentoxide content of 14%, and a potassium oxide content of 17%; The nutrient solution is a mixture of deionized water, ferrous sulfate, cupric sulfate, betaine and ammonium molybdate, and the mass ratio of the deionized water, ferrous sulfate, cupric sulfate, betaine and ammonium molybdate is 1000:3.3:4.0:4.8:3.7.

[0020] Example 3 1. Seed pretreatment Select 52g of cowpea seeds with full grains and no damage, put them into 1020g of 0.15wt% potassium permanganate solution for soaking, the soaking time is 18min, take them out and wash them, then put them into 1020g of deionized water for soaking, the soaking temperature is 27℃, the soaking time is 4.2h, after the soaking, add 0.14g of aminoethyl hexanoate and 0.15g of Tween 20 for stirring, continue soaking at 27℃ for 1.8h, after the soaking, take them out, wash and dry them to obtain the pretreated cowpea seeds.

[0021] 2. Land preparation and sowing First, apply base fertilizer to the soil, apply 642kg of decomposed cow dung, 3.6kg of potassium humate, 1.2kg of borax, 15kg of diammonium phosphate, and 18kg of potassium sulfate per mu. After the application, plough the soil to a depth of 28-33cm, then spread the improver, spread 30kg per mu, and plough the soil again after spreading to a depth of 20-25cm. After raking and leveling, build ridges and cultivate on the ridges, with 2 rows per ridge, 30-32cm plant spacing, 58-62cm row spacing, and 2 seeds per hole. The preparation method of the improver includes preparing biochar, preparing a primary improver, and a compounding step, which is specifically as follows: a. Preparation of biochar The corn stalks were cleaned and dried, and then placed in a muffle furnace. The temperature was raised to 423°C at a rate of 5.2°C / min under a nitrogen atmosphere, and the temperature was kept for 2.2 hours. After the temperature was kept, the corn stalks were naturally restored to room temperature and ground to a particle size of 22 μm to obtain biochar. The corn stalk has a length of 1.2 mm and a diameter of 0.6 mm; b. Preparation of primary improver 13.5 g of biochar was added to 135 g of 22 wt% ethanol solution, 1.4 g of polyethylene glycol monolaurate was added, the temperature was raised to 67 ° C, and the mixture was stirred for 32 min. After the stirring was completed, the mixture was filtered out and washed, and then placed in a reaction vessel. 1330 mL of dimethyl sulfoxide was introduced and stirred evenly. Then, 4.8 g of humic acid and 1.7 g of modified coconut fiber were added and stirred. The stirring speed was controlled to 185 rpm. While stirring, the temperature was raised to 123 ° C at a rate of 1.2 ° C / min, and then concentrated sulfuric acid was added and stirred for 11.8 hours. After the reaction was completed, a primary improver was obtained; The preparation method of the modified coconut fiber is as follows: 8.7 g of coconut fiber is placed in 92 g of 34 wt% ethanol solution, after stirring evenly, 0.83 g of hexadecyltrimethylammonium bromide and 0.95 g of kH560 are added, the temperature is increased to 64° C., the mixture is stirred at the temperature for 3.8 hours, and the modified coconut fiber is obtained by filtering, washing and drying. c. Compound Place 10.3 g of the primary improver in 102 g of 28 wt% ethanol solution, add 0.5 g of diethylenetriaminopropyltrimethoxysilane and 1.2 g of γ-aminopropyltriethoxysilane, and stir to react at 62°C for 4.3 h. After the reaction, add 4.0 g of polyacrylamide and 5.2 g of glutaraldehyde, and stir to react at 35°C for 1.4 h. After the reaction, filter, wash, and dry to obtain the improver.

[0022] 3. Management during the seedling stage When the cowpea seedlings have 4-5 true leaves, spray the cowpea plants with the control agent, controlling the spraying amount to 123g per plant; The control agent is a mixture of deionized water and a pesticide slow-release agent, and the mass ratio of the deionized water to the pesticide slow-release agent is 1000:0.85; The preparation method of the control agent is as follows: 112g of the modifier is sprayed onto 12.7g of biochar, the spraying rate is controlled to be 3.2g / min, after the spraying is completed, the temperature is increased to 64°C, the reaction is stirred for 5.2h, and after the reaction is completed, the modified biochar is obtained by filtering, washing and drying; 0.8g of matrine and 1.0g of acetamiprid are placed in 1010g of 42wt% ethanol solution, and the mixture is stirred to obtain a mixed agent; 11.7g of the modified biochar is added to the 102g mixed agent solution, and homogenization is performed, the homogenization time is 5.2min, the homogenization pressure is 3.0MPa, after the homogenization is completed, the temperature is increased to 37°C at a rate of 0.6°C / min, 2.2g of lysine and 1.7g of arginine are added, and after stirring, 6.0g of carboxymethyl cellulose is added, and after stirring, the mixture is dried to obtain a pesticide slow-release agent; The biochar is the biochar prepared in the step of preparing the improver; The modifier is composed of 36wt% ethanol solution, triethanolamine dodecyl sulfate and kH792, and the mass ratio of the 36wt% ethanol solution, triethanolamine dodecyl sulfate and kH792 is 100:1.2:1.6.

[0023] 4. Flowering period management At the beginning of flowering, the cowpea plants were fertilized with 5.2 kg urea per mu and 12.7 kg NPK compound fertilizer per mu, applied once every 7 days for a total of 3 times; after the first inflorescence was pod-forming, nutrient solution was applied once every 3 days for a total of 2 times, with 155 g per plant; The nitrogen-phosphorus-potassium compound fertilizer has a nitrogen content of 16%, a phosphorus pentoxide content of 16%, and a potassium oxide content of 22%; The nutrient solution is a mixture of deionized water, ferrous sulfate, cupric sulfate, betaine and ammonium molybdate, and the mass ratio of the deionized water, ferrous sulfate, cupric sulfate, betaine and ammonium molybdate is 1000:3.7:4.40:5.3:4.2.

[0024] Comparative Example 1 Based on Example 1, the changes are as follows: In the preparation method of the improver, the step of preparing the primary improver is to place the biochar in a reaction container, introduce 1300 mL of dimethyl sulfoxide, stir evenly, add 4.7 g of humic acid and 1.6 g of coconut fiber, stir, control the stirring speed to 180 rpm, stir evenly, and obtain the primary improver; The preparation method of the control agent is as follows: 0.7g of matrine and 0.9g of acetamiprid are placed in 1000g of 40wt% ethanol solution, and stirred evenly to obtain a mixed agent solution; 11.5g of biochar is added to 100g of the mixed agent solution, and homogenization is performed, the homogenization time is 5.0min, the homogenization pressure is 2.8MPa, and after the homogenization is completed, drying is performed to obtain a pesticide slow-release agent; The biochar is the biochar prepared in the step of preparing the improver; The rest of the operations are the same.

[0025] Comparative Example 2 Based on Example 1, the changes are as follows: In the method for preparing the improver, the compounding step is omitted and the obtained primary improver is the improver; The preparation method of the control agent is as follows: 0.7g of matrine and 0.9g of acetamiprid are placed in 1000g of 40wt% ethanol solution, and stirred to obtain a mixed agent solution; 100g of the mixed agent solution is heated to 35°C at a rate of 0.5°C / min, 2.0g of lysine and 1.6g of arginine are added, and stirred to obtain a pesticide slow-release agent; The rest of the operations are the same.

[0026] Experimental Testing A base was selected in Shouguang City, Weifang City, Shandong Province as an experimental base, which was divided into 5 plots, each of which was 3 mu, and recorded as A1-A5. Then, cowpea was planted according to the methods of Examples 1-3 and Comparative Examples 1-2 to reduce the pesticide residue in cowpea. The variety of cowpea was cowpea 60, and the rest was managed according to general production and planting. During the growth cycle of cowpea, the incidence of aphids, powdery mildew and rust was counted. After harvesting, the yield per mu and average single pod weight were counted. The vitamin C content, crude fiber content and pesticide residue content of cowpea were measured. The test results are as follows:

[0027] The method for reducing cowpea pesticide residues of the present invention is mainly achieved through two aspects. First, the growth performance of crops is enhanced, the stress resistance of plants is improved, and the probability of plant diseases and insects occurring is reduced, thereby reducing the application of pesticides; second, pesticides are coated by membrane coating technology to form a membrane structure on the surface of the pesticide package, which can not only achieve the slow release of pesticides, increase the effective period of pesticides, reduce the amount of pesticides used, but also reduce the penetration of pesticides into plants and reduce pesticide residues; the specific method is to first use an improver to improve the soil, use biochar as an improved matrix, and under the catalysis of concentrated sulfuric acid, the biochar, humic acid and coconut fiber are firmly cross-linked, so that the primary improver has a large adsorption capacity and a stable structure, and the humic acid contains more hydroxyl groups, carboxyl groups and the like, which can adsorb heavy metals, pesticide residues and the like in the soil, so that pollutants and the like in the soil do not migrate to the plants, the primary improver is amino-modified, and then glutaraldehyde is used for cross-linking again, thereby improving the stability of the improver. The improvement can effectively improve the soil aggregate structure, increase soil permeability, balance nutrients in the soil, and promote plant growth and development, thereby improving the germination of cowpea seeds and the growth of seedlings, improving the stress resistance and growth rate of crops, promoting the absorption of nutrients by plants, improving the quality of cowpea fruits, increasing the content of nutrients, and enhancing the taste. In the seedling stage, the plants are sprayed with pesticide control agents, wherein the pesticide control agent is a membrane coating technology for coating the pesticide, specifically, the pesticide is adsorbed into the pore structure of biochar, and then carboxymethyl cellulose is added, the carboxyl group of which can be combined with the amino group of the modified biochar, and the carboxymethyl cellulose has good adhesion, which improves the stability of the pesticide sustained-release agent, thereby avoiding direct contact between the plant and the pesticide, and reducing the amount of pesticide applied, improving the persistence of the pesticide, and ultimately increasing the yield of cowpea, reducing the incidence of diseases and pests, reducing pesticide residues, reducing crude fiber content, and improving the quality and taste of cowpea.

[0028] In comparative example 1, in the step of preparing the improver, biochar is directly mixed with humic acid and coconut fiber to prepare the primary improver. The dispersibility of biochar and coconut fiber is poor, and the binding force between biochar and humic acid is poor, and a stable cross-linked structure cannot be formed. In the compounding step, the binding between biochar and aminosilane coupling agent is not strong. When cross-linking is performed with glutaraldehyde, the improver obtained by cross-linking has an unstable structure and a small adsorption capacity, and cannot effectively adsorb heavy metal ions and pesticide residues in the soil, thereby failing to effectively improve the soil and further failing to effectively promote the growth of plants. When preparing the control agent, only biochar is used to load the pesticide, and the loading is uneven. The pesticide cannot be completely adsorbed into the pores, so that the pesticide cannot play a long-term role, and the incidence of pests and diseases is increased. In addition, the pesticide directly contacts the plant itself, which increases the pesticide residue, and ultimately reduces the yield and fruit quality, and the taste is poor. In Comparative Example 2, the compounding step was omitted in the step of preparing the improver, and the primary improver was directly used for improvement. The stability of the improver was insufficient, and the improvement effect on the soil was poor, which affected the development and growth of cowpea to a certain extent. In addition, in the process of preparing the control agent, the loading of the modified biochar on the pesticide was omitted, which affected the long-term effect of the biochar. There was also an incomplete coating of the pesticide by carboxymethyl cellulose, which increased the pesticide residues, and ultimately caused a certain degree of decline in yield and quality, and a poor taste.

[0029] Unless otherwise specified, all ratios and percentages described in the present invention are by mass ratios and percentages are by mass percentages.

[0030] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for reducing cowpea pesticide residues, characterized in that: It includes seed pretreatment, land preparation and sowing, seedling management, and flowering management steps; The land preparation and sowing steps include spreading the improver into the soil at a rate of 26-30 kg per mu, plowing again after spreading, raking and leveling, building ridges, and cultivating on the ridges; The method for preparing the improver includes preparing biochar, preparing a primary improver, and a compounding step; The step of preparing the primary improver is to put the biochar into an ethanol solution, add polyethylene glycol monolaurate, raise the temperature to 63-67°C, keep warm and stir for 28-32 minutes, filter out and wash after the stirring, put it in a reaction container, introduce dimethyl sulfoxide, stir evenly, add humic acid and modified coconut fiber to stir, control the stirring speed to 174-185rpm, raise the temperature to 116-123°C at a rate of 0.8-1.2°C / min while stirring, then add concentrated sulfuric acid to stir and react for 11.8-12.3h, and obtain the primary improver after the reaction is completed; The compounding step comprises placing the primary improver in an ethanol solution, adding diethylenetriaminepropyltrimethoxysilane and γ-aminopropyltriethoxysilane, stirring and reacting at 58-62° C. for 3.7-4.3 hours, adding polyacrylamide and glutaraldehyde, stirring and reacting at 30-35° C. for 1.4-1.7 hours, filtering, washing and drying after the reaction, and obtaining the improver; The seedling stage management step is to spray the cowpea plants with a control agent when the cowpea seedlings have 4 to 5 true leaves, controlling the spraying amount of each plant to be 115 to 123 g, wherein the control agent is a mixture of deionized water and a pesticide slow-release agent; The preparation method of the pesticide slow-release agent comprises the following steps: spraying a modifier onto biochar, controlling the spraying rate to be 2.8-3.2 g / min, raising the temperature to 60-64°C after the spraying, stirring and reacting for 4.8-5.2 hours, filtering, washing and drying after the reaction, and obtaining modified biochar; placing matrine and acetamiprid in an ethanol solution, stirring evenly, and obtaining a mixed agent solution; adding the modified biochar to the mixed agent solution, and homogenizing the solution; after the homogenization, raising the temperature to 33-37°C at a rate of 0.4-0.6°C / min, adding lysine and arginine, stirring evenly, adding carboxymethyl cellulose, stirring evenly, and drying to obtain the pesticide slow-release agent.

2. A method for reducing cowpea pesticide residues according to claim 1, characterized in that: The land preparation and sowing steps are as follows: firstly, applying base fertilizer to the soil, applying 638-642kg of decomposed cow dung, 3.4-3.6kg of potassium humate, 0.8-1.2kg of borax, 13-15kg of diammonium phosphate, and 16-18kg of potassium sulfate per mu; after the application, ploughing is performed, and the ploughing depth is 28-33cm; then, 26-30kg of the improver is spread per mu; after the spreading, ploughing is performed again, and the ploughing depth is 20-25cm; after raking and leveling, ridges are built, and cultivation is carried out on the ridges, with 2 rows per ridge, 30-32cm plant spacing, 58-62cm row spacing, and 2 seeds are sown in each hole.

3. The method for reducing cowpea pesticide residues according to claim 1, characterized in that: In the preparation method of the improver, the step of preparing biochar is: after cleaning and drying the corn stalks, put them into a muffle furnace, heat them to 417-423°C at a rate of 4.8-5.2°C / min under a nitrogen atmosphere, and keep them warm for 1.8-2.2h. After the insulation is completed, wait for them to naturally return to room temperature, grind them to a particle size of 18-22μm, and obtain biochar; The corn stalk has a length of 0.8-1.2 mm and a diameter of 0.4-0.6 mm.

4. The method for reducing cowpea pesticide residues according to claim 1, characterized in that: In the preparation method of the improver, in the step of preparing the primary improver, the mass volume ratio of the biochar, ethanol solution, polyethylene glycol monolaurate, dimethyl sulfoxide, humic acid, and modified coconut fiber is 13.0-13.5g:126-135g:1.2-1.4g:1270-1330mL:4.6-4.8g:1.5-1.7g; The mass concentration of the ethanol solution is 18-22%.

5. The method for reducing cowpea pesticide residues according to claim 1, characterized in that: The preparation method of the modified coconut fiber comprises the following steps: placing the coconut fiber in an ethanol solution, stirring evenly, adding hexadecyltrimethylammonium bromide and kH560, raising the temperature to 60-64° C., keeping the temperature and stirring for 3.8-4.2 hours, filtering, washing and drying to obtain the modified coconut fiber; The mass ratio of the coconut fiber, ethanol solution, hexadecyltrimethylammonium bromide and kH560 is 8.3-8.7:88-92:0.76-0.83:0.90-0.95; The mass concentration of the ethanol solution is 30-34%.

6. The method for reducing cowpea pesticide residues according to claim 1, characterized in that: In the compounding step, the mass ratio of the primary modifier, the ethanol solution, diethylenetriaminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, polyacrylamide and glutaraldehyde is 9.7-10.3:98-102:0.3-0.5:0.8-1.2:3.5-4.0:4.8-5.2; The mass concentration of the ethanol solution is 23-28%.

7. The method for reducing cowpea pesticide residues according to claim 1, characterized in that: In the seedling management step, the mass ratio of the deionized water and the pesticide slow-release agent in the control agent is 1000:0.80-0.85; In the method for preparing the pesticide slow-release agent, the biochar is the biochar prepared in the step of preparing the improver; The modifier is composed of 34-36wt% ethanol solution, triethanolamine dodecyl sulfate and kH792, and the mass ratio of the 34-36wt% ethanol solution, triethanolamine dodecyl sulfate and kH792 is 100:0.8-1.2:1.3-1.6; The mass ratio of the modifier to the biochar is 108-112:12.3-12.7; The mass ratio of matrine, acetamiprid and ethanol solution is 0.6-0.8:0.8-1.0:990-1010; The mass concentration of the ethanol solution is 38-42%; The mass ratio of the reagent mixture, modified biochar, lysine, arginine, and carboxymethyl cellulose is 98-102:11.2-11.7:1.8-2.2:1.5-1.7:5.6-6.0; The homogenization process has a homogenization time of 4.8-5.2 min and a homogenization pressure of 2.7-3.0 MPa.

8. The method for reducing cowpea pesticide residues according to claim 1, characterized in that: The seed pretreatment step comprises: selecting cowpea seeds with full grains and no damage, soaking them in a 0.11-0.15wt% potassium permanganate solution for 13-18 minutes, taking them out and washing them, and then soaking them in deionized water at a soaking temperature of 23-27° C. for 3.8-4.2 hours. After the soaking, adding aminoethyl hexanoate and Tween 20 for stirring, and continuing to soak at 23-27° C. for 2.2-2.8 hours. After the soaking, taking them out, washing them, and drying them to obtain pretreated cowpea seeds; The mass ratio of the cowpea seeds, potassium permanganate solution, deionized water, ammonium ethyl hexanoate and Tween 20 is 48-52:980-1020:980-1020:0.10-0.14:0.12-0.

15.

9. The method for reducing cowpea pesticide residues according to claim 1, characterized in that: The flowering management step is as follows: at the beginning of flowering, fertilizing the cowpea plants with urea at a rate of 4.8-5.2 kg / mu and nitrogen, phosphorus and potassium compound fertilizer at a rate of 12.3-12.7 kg / mu, applying once every 7 days, for a total of 3 times; after the first inflorescence is pod-bearing, nutrient solution is applied once every 3 days, for a total of 2 times, and 145-155 g is applied to each plant; The nitrogen-phosphorus-potassium compound fertilizer has a nitrogen content of 14-16%, a phosphorus pentoxide content of 14-16%, and a potassium oxide content of 17-22%; The nutrient solution is a mixture of deionized water, ferrous sulfate, cupric sulfate, betaine and ammonium molybdate, and the mass ratio of the deionized water, ferrous sulfate, cupric sulfate, betaine and ammonium molybdate is 1000:3.3-3.7:4.0-4.4:4.8-5.3:3.7-4.2.

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