A biochar-based bacterial agent for preventing and controlling soil-borne diseases of solanaceous vegetables and a preparation method thereof

Abstract

The present invention provides a biochar-based bacterial agent for preventing and treating soil-borne diseases of solanaceous vegetables and a preparation method thereof. The biochar-based bacterial agent includes biochar and a biocontrol strain YW-1 with a preservation number of CGMCC NO.20620 loaded on the biochar. The biocontrol strain YW-1 is inoculated into a culture medium to obtain a fermentation broth, the fermentation broth is loaded on silicon-rich biomass and Fenton reaction treated sludge co-pyrolysis biochar, and then the biochar containing the biocontrol strain YW-1 is obtained by centrifugation, and then brewer's grains and sucrose are added as high-temperature protective agents, and after fluidized bed drying treatment, a starch-chitosan complex is finally added as a synergist and an adhesive, and then extruded and granulated to prepare a product. The preparation method of the biochar-based bacterial agent prepared by the present invention is simple, can provide a good habitat for biocontrol bacteria, prolong the storage time of the biocontrol bacteria in the prepared biochar-based bacterial agent, and has a good effect on promoting the growth of solanaceous vegetables and preventing and controlling diseases such as wilt, bacterial wilt and blight, and has a good development and application prospect.

Description

Technical Field

[0001] The invention relates to the field of microorganisms, and in particular to a biochar-based bacterial agent for preventing and controlling soil-borne diseases of solanaceous vegetables and a preparation method thereof. Background Art

[0002] Facility agriculture is a modern agricultural production method that comprehensively applies engineering equipment technology, biotechnology and environmental technology to create a suitable environment for the growth and development of animals and plants and realize the production of animals and plants. The development of facility vegetables not only alleviates the contradiction between production seasonality and consumption balance, but also can use facility cultivation to produce high-end vegetables, famous and special vegetables, seasonal vegetables, and increase the variety of vegetables to meet the consumption needs of different levels of society. my country has become the country with the largest area of ​​facility agriculture in the world, and it is still growing at a rate of about 10% per year. However, since the development of facility vegetables, there are also problems that cannot be ignored while growing rapidly. Facility vegetable cultivation has the characteristics of frequent soil cultivation, high degree of intensiveness, high multiple cropping index, and single variety. There are widespread phenomena of continuous cropping obstacles such as soil deterioration, rampant pests and diseases, and reduced quality, which seriously affect the production of vegetables and farmers' income. After analyzing facility cultivation under various conditions, many scholars at home and abroad believe that the aggravated soil-borne pests and diseases are the main cause of continuous cropping obstacles.

[0003] At present, the measures for the prevention and control of soil-borne diseases and insect pests of greenhouse vegetables mainly rely on chemical pesticides, which will not only cause serious environmental pollution, but also lead to excessive residues of toxic chemicals in vegetables, causing serious harm to human health. The use of soil antagonistic microorganisms to control soil-borne diseases can not only be carried out in situ, but also be harmless to humans and animals and environmentally friendly. Therefore, the development and application of biocontrol agents (fertilizers) have attracted the attention of more and more scholars. The inventor has previously screened a biocontrol strain YW-1 (deposited in the General Microbiological Center of the China Microbiological Culture Collection Administration Committee, with a deposit number of CGMCC NO.20620) that effectively prevents and treats a variety of soil-borne diseases such as melon wilt, tomato and pepper bacterial wilt, and pepper blight, and has been granted a patent (ZL202011229617.2). However, like the common biocontrol agents (fertilizers) on the market, this patented product is directly packaged as a finished product after liquid fermentation, which has problems such as inconvenient application and transportation and weak ability to keep alive. In addition, due to the rapid loss of liquid nutrient medium after application, the colonization effect of biocontrol bacteria is significantly reduced in a short period of time. If suitable carrier materials are selected to adsorb beneficial microorganisms and suitable processes and methods are sought to prepare solid microbial fertilizers, a good habitat can be provided for beneficial microorganisms, the effect of biocontrol agents (fertilizers) can be further enhanced, and a larger range of applications and efficacy can be achieved. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a biochar-based biocontrol agent for preventing and controlling soil-borne diseases of solanaceous vegetables. The present invention is improved on the basis of the existing authorized invention patent (ZL202011229617.2), by screening biochar, making full use of the adsorption function of biochar and the special elements it contains, adding biocontrol bacteria, preparing a biochar-based biocontrol agent with a long-lasting effect, and using it to prevent and control soil-borne diseases of solanaceous vegetables.

[0005] The present invention is achieved through the following technical solutions:

[0006] A biochar-based bacterial agent for preventing and controlling soil-borne diseases of solanaceous vegetables, the biochar-based bacterial agent comprising biochar and a biocontrol strain YW-1 loaded on the biochar.

[0007] A further improvement of the present invention is that the initial loading amount of the biocontrol strain YW-1 on the biochar is 8.0×10 8 -1.0×10 9 cfu / g.

[0008] A further improvement of the present invention is that the preservation number of the biocontrol strain YW-1 is CGMCC NO.20620.

[0009] A method for preparing a biochar-based bacterial agent for preventing and controlling soil-borne diseases of solanaceous vegetables comprises the following steps:

[0010] (1) drying biomass or mixing the dried biomass with sludge treated by Fenton reaction at a mass ratio of 5:1 to 10:1, followed by anaerobic pyrolysis to prepare biochar, and passing the prepared biochar through a 60-mesh sieve;

[0011] (2) The biocontrol strain YW-1 was inoculated into liquid activation medium and the strain concentration was 9×10 8 cfu / mL or above fermentation broth;

[0012] (3) the biochar prepared in step (1) is mixed evenly with the fermentation liquid of the biocontrol bacterium YW-1 prepared in step (2) at a ratio of 1:10 to 1:5 (w / v), and then the mixture is cultured at 28 to 35° C. and 160 to 200 rpm for 6 to 12 h, and then a high temperature protective agent is added, followed by high-speed (5000 rpm) centrifugation for 20 min, and the residue is dried at 40 to 45° C. until the water content is less than 10%; (4) the biochar loaded with the biocontrol bacterium YW-1 prepared in step (3) and the granulation auxiliary agent are placed in an extrusion granulator at a mass ratio of 9:1 to 9.5:0.5 for granulation, and the finished particle diameter is 3 to 5 cm, and the final bacterial strain concentration is 8.0×10 8 cfu / g or above biochar-based bacterial agent.

[0013] A further improvement of the present invention is that in step (1), the anaerobic pyrolysis condition is heating at a temperature of 400 to 500° C. for 1 to 2 hours.

[0014] A further improvement of the present invention is that in step (2), the composition of the liquid activation culture medium is 10-15 g / L of peptone, 5-10 g / L of yeast powder, 2-3 g / L of sodium chloride, 2-3 g / L of sodium carboxymethyl cellulose, 2-3 g / L of chitin, 1-1.5 g / L of ferric sulfate and 1-1.5 g / L of potassium dihydrogen phosphate.

[0015] A further improvement of the present invention is that in step (2), the culture conditions of the biocontrol strain YW-1 are 26-30° C. and 160-200 rpm for 24-48 hours.

[0016] A further improvement of the present invention is that in step (3), the high temperature protective agent is a mixture of brewer's grains and sucrose, trehalose or lactose, the mixing mass ratio of which is 3:1 to 2:1, and the brewer's grains are dried at 105 to 110°C and crushed through a 60-mesh sieve.

[0017] A further improvement of the present invention is that in step (4), the granulation auxiliary agent is a starch-chitosan composite, and the starch-chitosan composite is a composite obtained by mixing starch and chitosan in a mass ratio of 3:2 to 4:1 and heating the mixture at 120 to 140° C. for 60 to 120 minutes.

[0018] A method for using a biochar-based bacterial agent for preventing and controlling soil-borne diseases of solanaceous vegetables, wherein the agent is applied to the root soil after the vegetables are transplanted or sown and seedlings emerge, and the application amount is 1 to 2 g per plant.

[0019] The biomass refers to agricultural wastes including rice husks, rice straws, wheat straws, etc., with a silicon content of more than 5%. The sludge treated by Fenton reaction refers to the sludge from urban sewage treatment plants treated with H2O2 and FeSO4, i.e., using H2O2 and FeSO4 to 2+ The strong oxidizing property of Fenton sludge oxidizes organic compounds such as carboxylic acids, alcohols, and esters in the sludge into inorganic forms. In Fenton sludge, the iron content is between 15-20% and the organic matter is between 25-30%.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The present invention uses biochar obtained by pyrolysis of silicon-rich biomass and sludge treated by Fenton reaction as a carrier. The advantage is that during the pyrolysis process, the rich alkali metals contained in the sludge treated by Fenton reaction catalyze the silicon-rich biomass to generate biochar with rich pore structure, which can provide a good habitat for the biocontrol bacteria YW-1; the biochar prepared from silicon-rich biomass has a strong texture, which can enhance the hardness of biochar-based fertilizer particles, prolong the shelf life of biochar-based bacterial agents, and facilitate the storage and transportation of finished products; the sludge treated by Fenton reaction contains the Fe element required for the growth of the biocontrol bacteria, which can meet the demand of the biocontrol bacteria for Fe and enhance the control effect of the product;

[0022] (2) In view of the specificity of the biocontrol bacterium YW-1, the present invention develops a fermentation medium with better effect based on the characteristics of the biocontrol bacterium on the basis of the traditional LB medium, and can obtain the biocontrol bacterium YW-1 fermentation liquid with the maximum number of viable bacteria in a short period of time;

[0023] (3) Brewer's grains are rich in protein and fiber, which can play a good protective role in the spray drying process and can replace traditional skim milk powder as a drying protective agent, thus turning waste into treasure and reducing production costs to the greatest extent;

[0024] (4) The present invention uses a starch-chitosan composite, which is rich in carbon and nitrogen elements and can be used as an energy source for biocontrol bacteria, thereby enhancing the colonization and reproduction of biocontrol bacteria. In addition, the starch-chitosan composite has a specific antibacterial effect only on solanaceous fruit pathogens and is non-toxic to biocontrol bacteria.

[0025] (5) The biocontrol bacteria YW-1 has good control effects on a variety of soil-borne diseases of Solanaceae vegetables and can produce obvious growth-promoting effects. Compared with the liquid biocontrol agents available on the market, this product provides an excellent living environment for the biocontrol bacteria YW-1 through measures such as culture medium improvement, carrier screening, dehydration protection agent innovation, and granulation process optimization, thereby significantly extending the survival time of the biocontrol bacteria, ultimately making this product have more excellent control and growth-promoting effects. DETAILED DESCRIPTION

[0026] In order to make the technical means, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0027] Example 1: Comparison of the effects of different LB culture media on the amplification and cultivation of biocontrol bacteria YW-1

[0028] The biocontrol bacteria YW-1 strain stored in the glycerol tube in the -80℃ refrigerator was taken out, streaked on the LB solid medium for activation, and cultured overnight in a 30℃ incubator. The activated strain was inoculated into LB liquid medium and different modified LB medium, and cultured at 28℃ and 180rpm for 24h to obtain liquid biocontrol bacteria YW-1 fermentation liquid. The number of viable bacteria was calculated by the dilution plate method. The results are shown in Table 1:

[0029] Table 1 Comparison of the effects of different culture media on the amplification and cultivation of biocontrol bacteria YW-1

[0030]

[0031] + and - indicate the addition and non-addition of the substance, respectively.

[0032] From the results in Table 1, it can be seen that the improved LB liquid culture medium significantly increased the number of viable bacteria, among which LB4 had the best effect.

[0033] Example 2: Comparison of the effects of different carriers in preparing solid bacterial agents

[0034] (1) The biocontrol bacteria YW-1 stored in the glycerol tube in the -80°C refrigerator was taken out, streaked on LB solid medium for activation, and cultured in a 30°C incubator overnight. The activated strain was inoculated into the above-mentioned LB3 liquid medium and cultured at 30°C and 180 rpm for 24 h to obtain a liquid biocontrol bacteria YW-1 fermentation broth (effective viable count of 1.10×10 9 cfu / mL);

[0035] (2) Grind the rice straw biochar, diatomaceous earth, zeolite and kaolin through a 60-mesh sieve, add 20% to the fermentation liquid of the biocontrol bacteria YW-1, continue culturing for 6 hours, then add a mixture of brewer's grains and sucrose at a mass ratio of 10:1 (the mass ratio of brewer's grains to sucrose in the mixture is 3:1), and finally centrifuge at 5000 rpm for 20 minutes, discard the supernatant, and obtain a residue;

[0036] (3) The obtained residue was placed in a fluidized bed dryer and dried at 45° C. for 0.75 h to control the moisture content to 8%, thereby obtaining a carrier loaded with the biocontrol bacteria YW-1;

[0037] (4) The obtained carrier loaded with biocontrol bacteria YW-1 was mixed with starch and chitosan composite in a mass ratio of 9:1, and then put into an extrusion granulator for granulation. The speed was set to 60 rpm and the pressure was set to 6 MPa to obtain a finished product with a particle diameter of about 4 cm. Finally, the bacterial strain concentration was 8.0×10 8 Biochar-based bacterial agents above cfu / g;

[0038] (5) The finished products were placed in an incubator at 28°C and the number of viable bacteria was determined by the dilution plate method after 3, 7, 28, 72, 150 and 360 days respectively;

[0039] (6) A greenhouse pot experiment was also used to test the efficacy of solid YW-1 biocontrol agent against bacterial wilt of tomatoes and peppers. Tomato and pepper seedlings were grown in plug trays and transplanted when they had 3 to 4 true leaves. The treatment group was treated with 0.1 g of solid biocontrol agent mixed with 10 mL of water during root application, while the control group was treated with clean water. One week after transplanting, 10 7 cfu / mL Ralstonia solanacearum 3721 suspension 10mL. Each treatment group has 12 strains, repeated three times. Under the conditions of temperature 25-28℃, relative humidity 60%, light 12h / 12h, the disease level was investigated after 4 weeks of cultivation, and the control effect was calculated.

[0040] As shown in Table 2, the number of effective live bacteria in the fertilizer of solid biocontrol agents prepared with different types of carriers decreased to varying degrees after 28 days of storage compared with the initial number. Among them, the number of effective live bacteria in the solid biocontrol agents prepared with attapulgite, zeolite and kaolin as carriers decreased the most, while the rice straw biochar-based agent changed the least, indicating that rice straw biochar is the most suitable carrier for the solid biocontrol agent YW-1.

[0041] Table 2 Changes in active colonies of solid bacterial agents prepared with different carriers (10 8 cfu / g)

[0042]

[0043] Table 3 Control effect of solid bacterial agents prepared with different carriers (%)

[0044]

[0045] Example 3: Comparison of the effects of different types of biochar in preparing solid inoculants

[0046] (1) The biocontrol bacteria YW-1 stored in the glycerol tube in the -80°C refrigerator was taken out, streaked on LB solid medium for activation, and cultured in a 30°C incubator overnight. The activated strain was inoculated into the above-mentioned LB3 liquid medium and cultured at 30°C and 180 rpm for 24 h to obtain a liquid biocontrol bacteria YW-1 fermentation broth (1.1×10 9 cfu / mL);

[0047] (2) Poplar wood chips, rice straw, sludge treated by Fenton reaction, and a mixture of the latter two (mass ratio of 10:1) were subjected to anaerobically pyrolysis in a horizontal tube furnace at a pyrolysis temperature of 500°C for 1 h. The obtained biochar was ground through a 60-mesh sieve and added to the fermentation broth of biocontrol bacteria YW-1 at a rate of 20%. The culture was continued for 6 h, and then a mixture of brewer's grains and sucrose (the mass ratio of brewer's grains to sucrose was 3:1) was added at a mass ratio of 10:1. Finally, the mixture was centrifuged at 5000 rpm for 20 min, and the supernatant was discarded to obtain a residue.

[0048] (3) placing the obtained residue in a fluidized bed dryer and drying it at 45° C. for 0.75 h to control the moisture content to 8%, thereby obtaining a carrier loaded with the biocontrol bacteria YW-1;

[0049] (4) The obtained carrier loaded with biocontrol bacteria YW-1 was mixed with the starch-chitosan complex at a mass ratio of 9.5:0.5, and granulated in an extrusion granulator with a speed of 60 rpm and a pressure of 6 MPa to obtain a finished product with a particle diameter of about 4 cm. The final bacterial concentration was 8.0×10 8 Biochar-based bacterial agents above cfu / g;

[0050] (5) The finished products were placed in an incubator at 28°C and the number of viable bacteria was determined by the dilution plate method after 3, 7, 28, 72, 150 and 360 days respectively;

[0051] (6) A greenhouse pot experiment was also used to test the efficacy of solid YW-1 biocontrol agent against tomato bacterial wilt. Tomato seedlings were grown in plug trays and transplanted when they had 3 to 4 true leaves. The treatment group was treated with 0.1 g of solid biocontrol agent mixed with 10 mL of water during root application, while the control group was treated with clean water. One week after transplanting, 10 7 cfu / mL Ralstonia solanacearum 3721 suspension 10mL. Each treatment group has 12 strains, repeated three times. Under the conditions of temperature 25-28℃, relative humidity 60%, light 12h / 12h, the disease level was investigated after 4 weeks of cultivation, and the control effect was calculated.

[0052] Table 4 Changes in active colonies of solid inoculants prepared with different biochar carriers (10 8 cfu / g)

[0053]

[0054] Table 5 The control effect of solid bacterial agents prepared with different carriers on tomato bacterial wilt (%)

[0055]

[0056] As shown in Tables 4 and 5, compared with poplar wood chip biochar, rice straw sawdust can not only carry more biocontrol bacteria, but also maintain a high level of live bacteria within 360 days. The biochar prepared from Fenton reaction sludge is not suitable as a carrier of biocontrol bacteria YW-1 due to its high content of inorganic matter. However, the co-pyrolysis biochar of rice straw and Fenton reaction sludge can adsorb more biocontrol bacteria YW-1 and maintain a high level of live bacteria. More importantly, the control effect on tomato seedlings was maintained at more than 63% after 360 days of storage.

[0057] Example 4: Effects of different high temperature protective agents and drying conditions on viable bacteria rate

[0058] (1) The biocontrol bacteria YW-1 stored in the glycerol tube in the -80°C refrigerator was taken out, streaked on LB solid medium for activation, and cultured in a 30°C incubator overnight. The activated strain was inoculated into the above-mentioned LB3 liquid medium and cultured at 30°C and 180 rpm for 24 h to obtain a liquid biocontrol bacteria YW-1 fermentation broth (1.1×10 9 cfu / mL);

[0059] (2) The mixture of rice straw and Fenton reaction treated sludge (mass ratio of 10:1) was subjected to anaerobically pyrolysis in a horizontal tube furnace at a pyrolysis temperature of 500°C for 1 h. The obtained biochar was ground through a 100-mesh sieve and added to the fermentation broth of biocontrol bacteria YW-1 at a rate of 20%. The culture was continued for 6 h. The mixture was then mixed with one of the following: skimmed milk powder, sucrose, brewer's grains, a mixture of skimmed milk powder and sucrose (mass ratio of skimmed milk powder to sucrose was 3:1), and a mixture of brewer's grains and sucrose (mass ratio of brewer's grains to sucrose was 3:1) at a mass ratio of 10:1. The mixture was finally centrifuged at 5000 rpm for 20 min, and the supernatant was discarded to obtain a residue.

[0060] (3) The obtained residue was placed in a fluidized bed dryer and dried at 40, 45 or 50° C. for 0.5, 1 or 2 h to control the moisture content to about 8%, thereby obtaining a carrier loaded with the biocontrol bacterium YW-1; (4) The above dilution plate method was used to determine the number of viable bacteria before and after drying, and the viable bacterial rate (%) was calculated.

[0061] Table 6 Effect of different high temperature protective agents and drying conditions on viable bacteria rate (%)

[0062]

[0063] As shown in Table 6, compared with skimmed milk powder, sucrose and their mixture, the number of live bacteria in the mixture of brewer's grains and sucrose can be maintained above 80% after drying for 1 hour at a temperature of 40-50°C.

[0064] Example 5: Comparison of the control effects of different granulation adjuvants on biochar-based bacterial agents

[0065] (1) The biocontrol bacteria YW-1 stored in the glycerol tube in the -80°C refrigerator was taken out, streaked on LB solid medium for activation, and cultured in a 30°C incubator overnight. The activated strain was inoculated into the above-mentioned LB3 liquid medium and cultured at 30°C and 180 rpm for 24 h to obtain a liquid biocontrol bacteria YW-1 fermentation broth (1.1×10 9 cfu / mL);

[0066] (2) The mixture of rice straw and Fenton reaction treated sludge (mass ratio 10:1) was subjected to anaerobically pyrolysis in a horizontal tube furnace at a pyrolysis temperature of 500°C for 1 hour. The obtained biochar was ground through a 100-mesh sieve and added to the fermentation broth of biocontrol bacteria YW-1 at a rate of 20%. The culture was continued for 6 hours, and then centrifuged at 5000 rpm for 20 minutes to obtain a residue.

[0067] (3) the obtained residue was placed in a fluidized bed dryer and dried at 45° C. for 0.75 h to control the moisture content to about 8%, thereby obtaining a carrier loaded with the biocontrol bacteria YW-1;

[0068] (4) The obtained carrier loaded with biocontrol bacteria YW-1 was mixed with chitosan, starch, a starch-chitosan complex with a mass ratio of 5:1, a starch-chitosan complex with a mass ratio of 3:1, and a starch-chitosan complex with a mass ratio of 1:1 in a mass ratio of 9:1 to 9.5:0.5, and granulated in an extrusion granulator with a speed of 60 rpm and a pressure of 6 MPa to obtain a finished product with a particle diameter of about 4 cm;

[0069] (5) A greenhouse pot experiment was used to test the efficacy of biochar-based YW-1 biocontrol agent against bacterial wilt of tomatoes and peppers. Tomato seedlings were grown in plug trays and transplanted when they had 3 to 4 true leaves. The treatment group was treated with 0.1 g of solid agent mixed with 10 mL of water during root application, while the control group was treated with clean water. One week after transplanting, 10 7 cfu / mL Ralstonia solanacearum 3721 suspension 10mL. Each treatment group has 12 strains, repeated three times. Under the conditions of temperature 25-28℃, relative humidity 60%, and light 12h / 12h, the disease level was investigated after 4 weeks of cultivation, and the disease severity and control effect were calculated.

[0070] Table 7 Control effect of solid bacterial agents prepared with different granulation adjuvants (%)

[0071]

[0072] As shown in Table 7, compared with chitosan, starch and their mixtures of 5:1 and 1:1, the chitosan / starch mixture of 3:1 is better for controlling tomato and pepper bacterial wilt.

[0073] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A biochar-based bacterial agent, characterized in that: The biochar-based bacterial agent includes biochar and a biocontrol strain YW-1 loaded on the biochar; The biochar-based bacterial agent is prepared by the following steps: (1) Mixing rice straw and sludge treated by Fenton reaction at a mass ratio of 10:1 and performing anaerobic pyrolysis to prepare biochar, and filtering the prepared biochar through a 60-mesh sieve; (2) The biocontrol strain YW-1 was inoculated into a liquid activation medium and the strain concentration was 9×10 8 cfu / mL or above fermentation broth; (3) the biochar prepared in step (1) is mixed evenly with the fermentation liquid of the biocontrol bacteria YW-1 prepared in step (2) at a ratio of 1:10 to 1:5 (w / v), and the mixture is cultured at 28 to 35°C and 160 to 200 rpm for 6 to 12 hours, and then a high temperature protective agent is added and centrifuged, and the residue is dried at 40 to 45°C until the moisture content is less than 10%; (4) The biochar loaded with biocontrol bacteria YW-1 prepared in step (3) and the granulation auxiliary agent are placed in an extrusion granulator at a mass ratio of 9:1 to 9.5:0.5 for granulation. The diameter of the finished granules is 3 to 5 cm, and the final bacterial concentration is 8.0×10 8 Biochar-based bacterial agents above cfu / g; The biocontrol strain YW-1 has a deposit number of CGMCC NO.20620; In step (3), the high temperature protective agent is a mixture of brewer's grains and sucrose, trehalose or lactose, the mixing mass ratio of which is 3:1-2:1, and the brewer's grains are dried at 105-110°C and crushed through a 60-mesh sieve; In step (4), the granulation auxiliary agent is a starch-chitosan complex, and the starch-chitosan complex is a complex obtained by mixing starch and chitosan in a mass ratio of 3:2-4:1 and heating the mixture at 120-140° C. for 60-120 min.

2. A biochar-based bacterial agent according to claim 1, characterized in that: The initial loading amount of the biocontrol strain YW-1 on biochar was 8.0×10 8 -1.0×10 9 cfu / g.

3. A biochar-based bacterial agent according to claim 1, characterized in that: In step (1), the anaerobic pyrolysis condition is heating at a temperature of 400-500° C. for 1-2 h.

4. A biochar-based bacterial agent according to claim 1, characterized in that: In step (2), the composition of the liquid activation culture medium is 10-15 g / L peptone, 5-10 g / L yeast powder, 2-3 g / L sodium chloride, 2-3 g / L sodium carboxymethyl cellulose, 2-3 g / L chitin, 1-1.5 g / L iron sulfate and 1-1.5 g / L potassium dihydrogen phosphate.

5. The biochar-based bacterial agent according to claim 1, characterized in that: In step (2), the culture conditions of the biocontrol strain YW-1 are 26-30°C and 160-200 rpm for 24-48 hours.

6. A method for using the biochar-based bacterial agent as claimed in claim 1, characterized in that: Apply to the root soil after vegetable transplanting or sowing, with an application rate of 1-2g per plant.

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