Compound probiotic bacterial fertilizer for regulating growth of platycodon grandiflorum and application of compound probiotic bacterial fertilizer

Abstract

The invention provides a compound probiotic bacterial fertilizer for regulating growth of platycodon grandiflorum and application of the compound probiotic bacterial fertilizer, and belongs to the field of microbial fertilizers. The compound probiotic bacterial fertilizer is prepared from a microbial agent JG-002, platycodon grandiflorum root exudates and a carrier; the mass ratio of the microbial agent JG-002 to the platycodon root exudates to the carrier is 100: (1-5): (10-20); the microbial agent JG-002 is composed of bacillus subtilis, bacillus licheniformis and bacillus laterosporus according to the viable count ratio of 5: 3: 2; the carrier is humic acid, sodium alginate and calcium chloride, and the mass ratio of the humic acid to the sodium alginate to the calcium chloride is (3-5): (2-3): (1-2); the compound probiotic bacterial fertilizer disclosed by the invention has a biological antagonism effect, and can effectively inhibit growth and reproduction of pathogenic microorganisms such as fusarium in soil, reduce the incidence rate of root rot of platycodon grandiflorum and solve successive cropping obstacles.

Description

Technical Field

[0001] The present invention belongs to the field of microbial fertilizers, and specifically relates to a compound probiotic fertilizer for regulating the growth of Platycodon grandiflorus and its application. Background Art

[0002] Platycodon grandiflorus, as an important medicinal plant, has long been threatened by continuous cropping obstacles and root rot. Traditional continuous cropping leads to an imbalance in the soil microbial flora, which in turn inhibits plant growth, and the yield reduction can reach 30%-50%.

[0003] Continuous planting of Platycodon grandiflorus can cause a large accumulation of pathogenic microorganisms such as Fusarium spp. in the soil, while the numbers of beneficial microorganisms such as nitrogen-fixing bacteria and phosphate-solubilizing bacteria decrease significantly, disrupting the balance of the soil microbial community. Research shows that in Platycodon grandiflorus fields with continuous cropping for more than 3 years, the ratio of fungi / bacteria in the rhizosphere soil increases, which is positively correlated with the occurrence of root rot. Continuous cropping also leads to a decrease in soil organic matter content, increased soil compaction, and a decline in nutrient utilization efficiency. For example, the preferential absorption of potassium by Platycodon grandiflorus easily causes potassium depletion in the soil, further affecting the disease resistance of plants.

[0004] Currently, the solutions to the above problems include crop rotation / fallow and chemical control. However, using crop rotation / fallow for soil ecological restoration takes 2-3 years, with a long cycle, and a large amount of land cannot be fully utilized, resulting in resource waste; although chemical control can inhibit pathogenic bacteria in the short term, long-term use will cause pathogenic bacteria to develop drug resistance, pesticide residues to pollute groundwater, and damage soil biodiversity. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a compound probiotic fertilizer for regulating the growth of Platycodon grandiflorus, which is composed of a microbial inoculant JG-002, Platycodon grandiflorus root exudates, and a carrier; The mass ratio of the microbial inoculant JG-002, Platycodon grandiflorus root exudates, and the carrier is 100:1-5:10-20; The microbial inoculant JG-002 is composed of Bacillus subtilis (Bacillus subtilis GYH20240327-1), Bacillus licheniformis, and Bacillus laterosporus in a viable count ratio of 5:3:2; The strain preservation number of the Bacillus subtilis is: CCTCC NO: M2025520, the preservation date is: March 18, 2025; the preservation unit: China Center for Type Culture Collection; the preservation address: No. 299, Bayi Road, Wuchang District, Wuhan City, Hubei Province.

[0006] The carrier is humic acid, sodium alginate, and calcium chloride, and the mass ratio of the humic acid, sodium alginate, and calcium chloride is 3-5:2-3:1-2.

[0007] Preferably, the preparation method of the Platycodon grandiflorum root exudates is as follows: S21. Take sterile Platycodon grandiflorum seedlings and cultivate them in sterilized quartz sand, and supply 1 / 2 Hoagland nitrogen-free nutrient solution for 30 - 40 days; S22. Uproot the Platycodon grandiflorum seedlings together with their roots, wash the roots with sterile deionized water, collect the washing solution, and the washing solution contains beneficial substances such as Platycodin D, ferulic acid, and sucrose; S23. Filter the washing solution through a 200 - mesh sieve and concentrate it to 1 / 10 of the original volume to obtain a concentrated solution; S24. Freeze-dry the concentrated solution to obtain PRE powder, which is the Platycodon grandiflorum root exudates.

[0008] Preferably, the preparation method of the compound probiotic fertilizer is as follows: S31. Dissolve sodium alginate and humic acid in water and stir evenly to form a colloidal solution; S32. Uniformly disperse the microbial inoculant JG - 002 and the Platycodon grandiflorum root exudates in the colloidal solution to obtain a mixed colloidal solution; S33. Drop the mixed colloidal solution into calcium chloride solution for solidification to form compound probiotic fertilizer particles; S34. Dry the compound probiotic fertilizer particles below 40°C to obtain the compound probiotic fertilizer.

[0009] Preferably, in step S21, the cultivation environment maintains a temperature of 25 ± 2°C and a light of 16 h / day.

[0010] Preferably, in step S33, the mass concentration of the calcium chloride solution is 2%.

[0011] On the other hand, the present invention provides the application of the above compound probiotic fertilizer for preventing and treating Platycodon grandiflorum root rot, alleviating Platycodon grandiflorum continuous cropping obstacles, and / or promoting Platycodon grandiflorum root development and plant growth.

[0012] Preferably, the compound probiotic fertilizer is mixed with organic fertilizer in a mass ratio of 1:15 - 25 and then prepared into a compound fertilizer for use. The usage method is as follows: base-apply or top-dress the fertilizer before sowing or during the growth period of Platycodon grandiflorum, and the dosage per mu is 50 - 100 kg.

[0013] Preferably, the organic fertilizer is a granular organic fertilizer made from crop straws and livestock and poultry manure after fermentation and composting.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The compound probiotic fertilizer in the present invention is composed of Bacillus subtilis, Bacillus licheniformis, and Bacillus laterosporus in specific proportions, and has a biological antagonistic effect. It can effectively inhibit the growth and reproduction of pathogenic microorganisms such as Fusarium in the soil, reduce the incidence of Platycodon grandiflorum root rot, and effectively solve the problem of continuous cropping obstacle of Platycodon grandiflorum.

[0015] 2. Long-term continuous cropping will lead to the imbalance of soil microbial flora, the reduction of beneficial microorganisms, the enrichment of pathogenic microorganisms, the decrease of soil organic matter content, and the decline of nutrient utilization efficiency. The compound probiotic fertilizer provided by the present invention can increase the number of beneficial microorganisms in the soil, improve the microbial community structure, and alleviate the continuous cropping obstacle; the probiotics in the compound probiotic fertilizer can also decompose organic substances, release nutrients, improve soil fertility, provide sufficient nutrition for the growth of Platycodon grandiflorum, help the roots of Platycodon grandiflorum better absorb nutrients and water, promote root development and plant growth, and thus further alleviate the continuous cropping obstacle.

[0016] 3. The present invention replaces the traditional chemical control method by biological control means, reduces the usage amount of chemical pesticides, and reduces the pollution risk of pesticide residues to groundwater and soil environment.

[0017] 4. The PRE in the compound probiotic fertilizer provided by the present invention contains beneficial substances such as Platycodin D, ferulic acid, and sucrose, and these substances have a direct promoting effect on the growth of Platycodon grandiflorum, and can stimulate root development and plant growth.

[0018] 5. As a chemotactic signal molecule, PRE can form a clear concentration gradient in the rhizosphere soil, enabling the microbial inoculant JG-002 to perceive and respond to this signal, thereby migrating the microbial inoculant JG-002 towards the roots and surrounding areas of Platycodon grandiflorum. This not only increases the number of beneficial microorganisms around the roots, but also optimizes the soil microbial community structure, creating a more favorable microecological environment for plant roots.

[0019] 6. PRE can attract microorganisms such as Bacillus to form a close symbiotic relationship with the roots of Platycodon grandiflorum, which helps Platycodon grandiflorum absorb nutrients and nutrient elements in the soil more efficiently; at the same time, the aggregation of microorganisms around the roots can also enhance the stress resistance of plants, improve the abilities of drought resistance, cold resistance, pest and disease resistance, etc., thus promoting the healthy growth of plants.

[0020] 7. The present invention uses humic acid-sodium alginate to form a colloidal solution, loads the microbial inoculant JG-002 and PRE, and then drops it into calcium chloride solution to solidify into compound probiotic fertilizer particles, enabling the microbial inoculant JG-002 and PRE to slowly dissolve and release in humic acid-sodium alginate. At the same time, it can reduce the damage of ultraviolet rays and chemical fertilizers to the bacterial cells and PRE, extend the validity period, significantly reduce the fertilization frequency, and improve the utilization rate of the inoculant. Description of the Drawings

[0021] Figure 1 are the per - mu yields of three groups of Platycodon grandiflorum; Figure 2 are the saponin contents of three groups of Platycodon grandiflorum; Figure 3 are the flavonoid contents of three groups of Platycodon grandiflorum; Figure 4 are the numbers of bacteria measured in the root - zone soil of three groups of Platycodon grandiflorum; Figure 5 are the numbers of actinomycetes measured in the root - zone soil of three groups of Platycodon grandiflorum; Figure 6 are the numbers of fungi measured in the root - zone soil of three groups of Platycodon grandiflorum; Figure 7 are the determination results of sucrase in the roots of three groups of Platycodon grandiflorum; Figure 8 are the determination results of urease in the roots of three groups of Platycodon grandiflorum; Figure 9 are the determination results of cellulase in the roots of three groups of Platycodon grandiflorum; Figure 10 are the determination results of protease in the roots of three groups of Platycodon grandiflorum; Figure 11 are the determination results of catalase in the roots of three groups of Platycodon grandiflorum; Figure 12 are the numbers of Fusarium in the root - zone soil of three groups of Platycodon grandiflorum; Figure 13 is the picture of Platycodon grandiflorum planted in the JG - 002 group in Experiment 1; Figure 14 is the picture of Platycodon grandiflorum planted in the PT group in Experiment 1; Figure 15 is the picture of Platycodon grandiflorum planted in the Pcontrol group in Experiment 1. Specific implementation mode

[0022] In the examples, the Bacillus licheniformis used was purchased from Beihai Yiqiang Biotechnology Co., Ltd., the Bacillus laterosporus was purchased from Guangxi Nongbao Bio - engineering Co., Ltd., and the Bacillus subtilis was isolated from yogurt.

[0023] Example 1 A compound probiotic fertilizer for regulating the growth of Platycodon grandiflorum, which is composed of a microbial inoculant JG - 002, Platycodon grandiflorum root exudates, and a carrier; The mass ratio of the microbial inoculant JG - 002, Platycodon grandiflorum root exudates, and the carrier is 100:1:10; The microbial inoculant JG - 002 is composed of Bacillus subtilis, Bacillus licheniformis, and Bacillus laterosporus according to the viable - cell number ratio of 5:3:2; The preservation number of the Bacillus subtilis strain is: CCTCC NO: M2025520, and the preservation date is: March 18, 2025; The carrier is humic acid, sodium alginate, and calcium chloride, and the mass ratio of humic acid, sodium alginate, and calcium chloride is 3:2:1.

[0024] Moreover, the preparation method of the Platycodon grandiflorum root exudates is as follows: S21. Take sterile Platycodon grandiflorum seedlings and cultivate them in sterilized quartz sand, and supply 1 / 2 Hoagland nitrogen-free nutrient solution for 30 days; S22. Uproot the Platycodon grandiflorum seedlings, wash the roots with sterile deionized water, and collect the washing solution; S23. Filter the washing solution through a 200-mesh sieve and concentrate it to 1 / 10 of the original volume to obtain a concentrated solution; S24. Freeze-dry the concentrated solution to obtain PRE powder, which is the Platycodon grandiflorum root exudates.

[0025] Moreover, the preparation method of the compound probiotic fertilizer is as follows: S31. Dissolve sodium alginate and humic acid in water and stir evenly to form a colloidal solution; S32. Uniformly disperse the microbial inoculant JG-002 and the Platycodon grandiflorum root exudates in the colloidal solution to obtain a mixed colloidal solution; S33. Drop the mixed colloidal solution into the calcium chloride solution for solidification to form compound probiotic fertilizer particles; S34. Dry the compound probiotic fertilizer particles at a temperature below 40°C to obtain the compound probiotic fertilizer.

[0026] Moreover, in step S21, the cultivation environment maintains a temperature of 25°C and a light of 16 h / day.

[0027] Moreover, in step S33, the mass concentration of the calcium chloride solution is 2%.

[0028] Example 2 A compound probiotic fertilizer for regulating the growth of Platycodon grandiflorum, which is composed of a microbial inoculant JG-002, Platycodon grandiflorum root exudates, and a carrier; The mass ratio of the microbial inoculant JG-002, Platycodon grandiflorum root exudates, and the carrier is 100:5:20; The microbial inoculant JG-002 is composed of Bacillus subtilis, Bacillus licheniformis, and Bacillus laterosporus according to the viable bacteria count ratio of 5:3:2; The preservation number of the Bacillus subtilis strain is: CCTCC NO: M2025520, and the preservation date is: March 18, 2025; The carrier is humic acid, sodium alginate, and calcium chloride, and the mass ratio of humic acid, sodium alginate, and calcium chloride is 5:3:2.

[0029] Moreover, the preparation method of the root exudates of Platycodon grandiflorum is as follows: S21. Take sterile Platycodon grandiflorum seedlings and cultivate them in sterilized quartz sand, and supply 1 / 2 Hoagland nitrogen-free nutrient solution for 30 - 40 days; S22. Uproot the Platycodon grandiflorum seedlings, rinse the roots with sterile deionized water, and collect the rinsing solution; S23. Filter the rinsing solution through a 200-mesh sieve and concentrate it to 1 / 10 of the original volume to obtain a concentrated solution; S24. Freeze-dry the concentrated solution to obtain PRE powder, which is the root exudates of Platycodon grandiflorum.

[0030] Moreover, the preparation method of the compound probiotic fertilizer is as follows: S31. Dissolve sodium alginate and humic acid in water and stir evenly to form a colloidal solution; S32. Uniformly disperse the microbial inoculant JG-002 and the root exudates of Platycodon grandiflorum in the colloidal solution to obtain a mixed colloidal solution; S33. Drop the mixed colloidal solution into the calcium chloride solution for solidification to form compound probiotic fertilizer granules; S34. Dry the compound probiotic fertilizer granules at a temperature below 40°C to obtain the compound probiotic fertilizer.

[0031] Moreover, in step S21, the cultivation environment maintains a temperature of 27°C and a light of 16 h / day.

[0032] Moreover, in step S33, the mass concentration of the calcium chloride solution is 2%.

[0033] Example 3 A compound probiotic fertilizer for regulating the growth of Platycodon grandiflorum, which is composed of a microbial inoculant JG-002, root exudates of Platycodon grandiflorum, and a carrier; The mass ratio of the microbial inoculant JG-002, root exudates of Platycodon grandiflorum, and the carrier is 100:3:15; The microbial inoculant JG-002 is composed of Bacillus subtilis, Bacillus licheniformis, and Bacillus laterosporus according to the live bacteria number ratio of 5:3:2; The strain preservation number of Bacillus subtilis is: CCTCC NO: M2025520, and the preservation date is: March 18, 2025; The carrier is humic acid, sodium alginate, and calcium chloride, and the mass ratio of humic acid, sodium alginate, and calcium chloride is 4:2.5:1.5.

[0034] Moreover, the preparation method of the root exudates of Platycodon grandiflorum is as follows: S21. Take sterile Platycodon grandiflorum seedlings and cultivate them in sterilized quartz sand, and supply 1 / 2 Hoagland nitrogen-free nutrient solution for 35 days; S22. Uproot the Platycodon grandiflorum seedlings, rinse the roots with sterile deionized water, and collect the rinsing solution; S23. Filter the rinsing solution through a 200-mesh sieve and concentrate it to 1 / 10 of the original volume to obtain a concentrated solution; S24. Freeze-dry the concentrated solution to obtain PRE powder, which is the root exudates of Platycodon grandiflorum.

[0035] Moreover, the preparation method of the compound probiotic fertilizer is as follows: S31. Dissolve sodium alginate and humic acid in water and stir evenly to form a colloidal solution; S32. Uniformly disperse the microbial inoculant JG-002 and the root exudates of Platycodon grandiflorum in the colloidal solution to obtain a mixed colloidal solution; S33. Drop the mixed colloidal solution into calcium chloride solution for solidification to form compound probiotic fertilizer particles; S34. Dry the compound probiotic fertilizer particles below 40 °C to obtain the compound probiotic fertilizer.

[0036] Moreover, in step S21, the culture environment maintains a temperature of 26 °C and a light of 16 h / day.

[0037] Moreover, in step S33, the mass concentration of the calcium chloride solution is 2%.

[0038] Example 4 Mix the compound probiotic fertilizer prepared in Example 3 with organic fertilizer in a mass ratio of 1:20 to prepare a compound fertilizer.

[0039] Moreover, the organic fertilizer is a granular organic fertilizer made from crop straws and livestock and poultry manure through fermentation and composting.

[0040] Experimental part

[0041] Experiment 1 In Meilihe Town, Yuanbaoshan District, Chifeng City, Inner Mongolia, the same piece of land was selected and three experimental fields were set up to study the effects of different fertilizers on the growth of Platycodon grandiflorum. During the period from 2022 to 2024, in April of each year, farm manure was applied as the base fertilizer to the three experimental fields, and then Platycodon grandiflorum was planted. In August, different fertilization treatments were carried out on the three experimental fields: one group was not fertilized as the control group (control), one group was applied with organic fertilizer (PT) at 80 kg / mu, and the other group was applied with the compound probiotic fertilizer (JG-002) prepared in Example 4 of the present invention at 80 kg / mu. In October of each year, Platycodon grandiflorum was harvested, and the experiment was carried out continuously for three years.

[0042] Among the Platycodon grandiflorum samples harvested in 2024, we randomly selected three groups of Platycodon grandiflorum for observation. The results of the JG-002 group are as Figure 13 shown, and no symptoms of root rot were found. In contrast, the Platycodon grandiflorum in the PT group and the control group showed root rot problems to varying degrees, as Figure 14 and Figure 15 shown.

[0043] In addition, the yield per mu, saponin content, and flavonoid content of the three groups of Platycodon grandiflorum were measured and recorded continuously for three years. The results are as Figures 1 - 3 shown in Table 1-3. It can be seen that, compared with the PT group and the control group, applying the compound probiotic fertilizer prepared by the present invention (JG-002 group) can significantly promote the growth of Platycodon grandiflorum, improve the yield and quality of Platycodon grandiflorum. Particularly importantly, after continuous cropping with the compound fertilizer of the present invention for three years, the yield per mu, saponin content, and flavonoid content of Platycodon grandiflorum were not affected and even increased, which fully shows that the compound fertilizer of the present invention can effectively solve the problem of continuous cropping obstacles of Platycodon grandiflorum.

[0044] Table 1 Results of yield per mu

[0045] Table 2 Results of saponin content

[0046] Table 3 Results of flavonoid content

[0047] Experiment 2 The numbers of bacteria, actinomycetes, and fungi in the root soil of the three groups of Platycodon grandiflorum in Experiment 1 were measured respectively. The results are shown in Tables 4-6 and Figures 4 - 6, The analysis results show that, compared with the PT group and the control group, the compound fertilizer provided by the present invention (JG-002 group) can increase the number of beneficial microorganisms in the soil and improve the microbial community structure; the probiotics in the compound fertilizer can also decompose organic substances, release nutrients, improve soil fertility, provide sufficient nutrition for the growth of Platycodon grandiflorum, and help the roots of Platycodon grandiflorum better absorb nutrients and water, promoting root development and plant growth.

[0048] Meanwhile, compared with the Control group and the PT group, after three consecutive years of cropping with JG-002 treatment, the numbers of bacteria, actinomycetes and fungi in the soil all showed a significant improvement trend. This result indicates that the compound fertilizer provided by the present invention can not only effectively increase the number of beneficial microorganisms in the soil, but also help solve the problem of continuous cropping obstacles of Platycodon grandiflorum.

[0049] Table 4 Results of bacterial number determination

[0050] Table 5 Results of actinomycete number determination

[0051] Table 6 Results of fungal number determination

[0052] Experiment 3 The soil enzyme activities of the roots of the three groups of Platycodon grandiflorum in Experiment 1 were measured respectively, and the results are shown in Tables 7-11 and Figures 7 - 11 as shown. It can be clearly seen that, compared with the PT group and the Control group, the activities of sucrase, urease, cellulase, protease and catalase in the JG-002 group are all significantly increased. This result fully indicates that the compound fertilizer of the present invention can effectively improve the activities of various soil enzymes in the soil of Platycodon grandiflorum roots.

[0053] In addition, further analysis shows that after three consecutive years of cropping, compared with the Control group and the PT group, the soil enzyme content in the JG-002 group did not show an obvious decrease, and the activities of some enzymes even showed an increasing trend, further verifying the long-term improvement effect of the compound fertilizer of the present invention on soil enzyme activities and being able to effectively solve the problem of continuous cropping obstacles of Platycodon grandiflorum.

[0054] Table 7 Results of sucrase determination

[0055] Table 8 Results of urease determination

[0056] Table 9 Results of cellulase determination

[0057] Table 10 Protease assay results

[0058] Table 11 Catalase assay results

[0059] Experiment 4 The number of Fusarium in the root soil of the three groups of Platycodon grandiflorum in Experiment 1 was measured respectively, and the results are shown in Table 12 and Figure 12 , and analyzing the data in Table 12 and Figure 12 It can be seen that compared with the PT group and the Control group, the number of harmful bacteria Fusarium in the soil of the JG-002 group has decreased, proving that the prepared compound fertilizer can effectively inhibit the growth and reproduction of pathogenic microorganisms such as Fusarium in the soil and reduce the incidence of Platycodon grandiflorum root rot. Particularly significantly, after three consecutive years of cropping, compared with the Control group and the PT group, the number of Fusarium in the soil of the JG-002 group has further decreased. This result indicates that the compound fertilizer of the present invention can not only inhibit the growth and reproduction of Fusarium, reduce the incidence of Platycodon grandiflorum root rot, but also effectively solve the problem of continuous cropping obstacle of Platycodon grandiflorum.

[0060] Table 12 Fusarium number assay results

[0061] In summary, for the Platycodon grandiflorum planted by adopting the technical scheme of the present invention, after three consecutive years of cropping, its per mu yield, saponin content, and flavonoid content are all higher than those of the Control group and the PT group. The beneficial bacteria (bacteria, actinomycetes, fungi) in the root soil are all more than those of the Control group and the PT group, and the harmful bacteria Fusarium has decreased. At the same time, no root rot has occurred. It can be proved that the technical scheme of the present invention can effectively prevent and control Platycodon grandiflorum root rot, alleviate the continuous cropping obstacle of Platycodon grandiflorum, and at the same time promote the root development and plant growth of Platycodon grandiflorum.

Claims

1. A composite probiotic fertilizer for regulating the growth of Platycodon grandiflorum, characterized in that: The composite probiotic fertilizer is made of microbial agent JG-002, Platycodon grandiflorum root secretions, and a carrier; The mass ratio of the microbial agent JG-002, Platycodon grandiflorum root secretions, and the carrier is 100: 1-5: 10-20; The microbial agent JG-002 is composed of Bacillus subtilis, Bacillus licheniformis and Bacillus laterosporus in a ratio of 5:3:2 in terms of viable bacteria count; The strain deposit number of the Bacillus subtilis is: CCTCC NO: M2025520, and the deposit date is: March 18, 2025; The carrier is humic acid, sodium alginate and calcium chloride, and the mass ratio of the humic acid, sodium alginate and calcium chloride is 3-5:2-3:1-2.

2. A composite probiotic fertilizer for regulating Platycodon grandiflorum growth as claimed in claim 1, characterized in that: The preparation method of the Platycodon grandiflorum root exudates is as follows: S21, take sterile Platycodon grandiflorum seedlings and cultivate them in sterilized quartz sand, supply 1 / 2 Hoagland nitrogen-free nutrient solution and cultivate for 30-40 days; S22, uprooting the Platycodon grandiflorum seedlings, washing the roots with sterile deionized water, and collecting the washing liquid; S23, filtering the flushing liquid through a 200-mesh sieve and concentrating it to 1 / 10 of the original volume to obtain a concentrated solution; S24. Freeze-drying the concentrated solution to obtain PRE powder, i.e., Platycodon grandiflorum root exudates.

3. A composite probiotic fertilizer for regulating Platycodon grandiflorum growth as claimed in claim 1, characterized in that: The preparation method of the composite probiotic fertilizer is as follows: S31, dissolving sodium alginate and humic acid in water and stirring evenly to form a colloidal solution; S32, uniformly dispersing the microbial agent JG-002 and the Platycodon grandiflorum root secretions in the colloidal solution to obtain a mixed colloidal solution; S33, adding the mixed colloidal solution dropwise into the calcium chloride solution to solidify, thereby forming composite probiotic fertilizer particles; S34, drying the composite probiotic fertilizer particles at a temperature below 40° C. to obtain a composite probiotic fertilizer.

4. A composite probiotic fertilizer for regulating Platycodon grandiflorum growth as claimed in claim 2, characterized in that: In step S21, the culture environment is maintained at a temperature of 25±2° C. and a light intensity of 16 h / day.

5. A composite probiotic fertilizer for regulating Platycodon grandiflorum growth as claimed in claim 3, characterized in that: In step S33, the mass concentration of the calcium chloride solution is 2%.

6. The use of the composite probiotic fertilizer according to any one of claims 1 to 5, characterized in that: Used to prevent and control Platycodon root rot, alleviate Platycodon continuous cropping problems and / or promote Platycodon root development and plant growth.

7. The use of the composite probiotic fertilizer according to claim 6, characterized in that: The composite probiotic fertilizer is mixed with organic fertilizer in a mass ratio of 1:15-25 to prepare a composite fertilizer for use.

8. The use of the composite probiotic fertilizer according to claim 7, characterized in that: The usage is as follows: Apply fertilizer as base before sowing or as topdressing during the growing season, with a dosage of 50-100kg per mu.

9. The use of the composite probiotic fertilizer according to claim 8, characterized in that: The organic fertilizer is a granular organic fertilizer made from crop straw and livestock and poultry excrement through fermentation and composting.

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