A compound microbial inoculant and its application

Abstract

The present invention provides a compound microbial inoculant and its application, belonging to the technical field of agricultural microorganisms. Specifically, it is a compound microbial inoculant, which comprises the following components: Streptomyces microflavus, Bacillus firmus, Trichoderma longibrachiatum, welan gum, and fucoidan oligosaccharide. The compound microbial inoculant provided by the present invention can effectively colonize in saline-alkali soil, and is more conducive to colonizing around the roots, especially the colonization effect around the roots of gramineous plants is better; and it can effectively increase the root proliferation of crops in saline-alkali soil, especially the root proliferation effect of gramineous crops is better, and effectively reduces the dead seedling rate of corn seedlings when planting corn in saline-alkali soil.

Description

Technical Field

[0001] The present invention belongs to the technical field of agricultural microorganisms, and particularly relates to a compound microbial inoculant and its application. Background Art

[0002] China currently has approximately 550 million mu of various salinized land resources that can be utilized. Among them, the total area of salinized land with agricultural utilization prospects is 185 million mu, including 32 million mu of various unimproved salinized arable lands with obstacles, and 153 million mu of currently unused and newly formed salinized wastelands. Currently, the area of salinized land with good agricultural development value and the potential for agricultural improvement and utilization in the near future is 100 million mu, which is concentrated in five major regions: Northeast, central and northern, Northwest, coastal, and North China. Among them, the Northeast salinized area is 30 million mu, the Northwest salinized area is 30 million mu, the central and northern salinized area is 15 million mu, the coastal salinized area is 15 million mu, and the North China salinized area is 10 million mu. From the perspective of the provinces (autonomous regions) where it is distributed, it is mainly concentrated and distributed in 18 provinces, municipalities, and autonomous regions such as Jilin, Ningxia, Inner Mongolia, Hebei, Xinjiang, and Jiangsu.

[0003] Saline-alkali land is likely to cause dehydration of crop cells, interfere with the absorption of nutrients by crops, and lead to a decrease in soil air permeability and water permeability. These hazards will seriously affect the yield of crops, ultimately resulting in a significant reduction in crop yield and a decrease in food production. There are many reports on compound microbial fertilizers suitable for saline-alkali land in the prior art.

[0004] Chinese patent document CN112374939A (application number: 202011294268.2) discloses a compound microbial-coated long-acting saline-alkali land improvement fertilizer and its preparation method, including: saline-alkali land improvement materials, coating materials, compound microbial inoculants, compound fertilizer, and soil; the saline-alkali land improvement materials include acidic substances and gypsum, and the coating materials include coating substances, adsorbents, and binders.

[0005] Chinese patent document CN114804977A (application number: 202210377004.6) discloses a special compound microbial fertilizer for saline-alkali land and its preparation method. The compound microbial fertilizer includes a carrier and compound microorganisms; the carrier includes the following components in mass percentage: humic acid, attapulgite powder, and the balance is organic fertilizer; the compound microorganisms include Paenibacillus polymyxa and Bacillus velezensis.

[0006] Chinese patent document CN112458010A (application number: 202011315418.3) discloses a solid composite microbial inoculum for improving saline-alkali soil and its application, which includes composite microorganisms and porous materials. The composite microorganisms include Aspergillus glaucus, Talaromyces flavus, Trichothecium roseum, Lactobacillus delbrueckii, Candida utilis, and Halobacterium sp. The porous material is at least one of zeolite powder, ceramic powder, brick powder, and furnace ash.

[0007] Chinese patent document CN112625690A (application number: 202011381554.2) discloses a composite microbial porous material for inhibiting the return of saline-alkali in saline-alkali soil and its application. The composite inoculum includes Talaromyces flavus, Trichothecium roseum, Verticillium chlamydosporium, Trichoderma viride, Lactobacillus acidophilus, and Bacillus subtilis. The porous material is at least one of zeolite powder, activated carbon powder, straw ash, brick powder, ceramic powder, furnace slag powder, and volcanic rock powder.

[0008] In the prior art, there are many reports on composite microbial fertilizers for saline-alkali soil. However, when applying composite microbial fertilizers in saline-alkali soil, affected by the saline-alkali soil environment, it is very difficult for the applied microbial inoculum to colonize effectively in the soil for a long time. Summary of the Invention

[0009] In view of the deficiencies of the prior art, the present invention provides a composite microbial inoculum and its application.

[0010] The technical solution of the present invention is as follows:

[0011] A composite microbial inoculum, comprising the following components: Streptomyces microflavus, Bacillus firmus, Trichoderma longibrachiatum, welan gum, and fucoidan oligosaccharide.

[0012] Preferably according to the present invention, by weight, 1-5 parts of welan gum, 0.5-2 parts of fucoidan oligosaccharide, 5-10 parts of Streptomyces microflavus, 5-15 parts of Bacillus firmus, and 5-10 parts of Trichoderma longibrachiatum.

[0013] Further preferably, the effective viable count of Streptomyces microflavus is not less than 10 billion / g; the effective viable count of Trichoderma longibrachiatum powder is not less than 50 billion / g; the effective viable count of Bacillus firmus is not less than 50 billion / g.

[0014] Preferably according to the present invention, the strain number of Streptomyces microflavus in the China Center for Agricultural Culture Collection is ACCC40909, the strain number of Bacillus firmus in the China Center for Agricultural Culture Collection is ACCC03123, and the strain number of Trichoderma longibrachiatum in the China Center for Agricultural Culture Collection is ACCC 32522.

[0015] Preferably according to the present invention, the preparation method of Streptomyces microflavus includes the following steps:

[0016] ① Inoculate the Streptomyces microflavus strain into a liquid activation medium, and under the condition of 28 - 32 °C, obtain liquid seeds through shake flask culture for 48 - 72 h.

[0017] ② Inoculate the liquid seeds prepared in step ① into a solid fermentation medium at an inoculation amount of 5% - 20% by volume fraction, and adopt shallow pan solid fermentation. Regulate the pH to 7.0 - 7.5, the ventilation ratio to 1:(0.8 - 1.5), and culture at 28 - 32 °C for 72 - 96 h. After the culture is completed, the material is dried and pulverized to obtain Streptomyces microflavus.

[0018] Further preferably, in step ①, each liter of the liquid activation medium contains the following components: 20 - 25 g of soluble starch, 1 - 1.5 g of potassium nitrate, 0.5 - 1 g of sodium chloride, 0.5 - 1 g of dipotassium hydrogen phosphate, 0.5 - 1 g of magnesium sulfate, 0.5 - 1 g of ferrous sulfate, and the balance is water;

[0019] In step ②, the components of the solid fermentation medium are as follows by weight: 1 - 5 parts of soybean meal, 5 - 10 parts of starch, 40 - 50 parts of wheat bran; 20 - 30 parts of rice husk; 1 - 5 parts of glucose, 1 - 5 parts of ammonium sulfate, 1 - 2 parts of magnesium sulfate, 1 - 2 parts of ferrous sulfate; 30 - 40 parts of water.

[0020] According to the preference of the present invention, the preparation method of Bacillus firmus includes the following steps:

[0021] (1) Inoculate the Bacillus firmus strain into a liquid activation medium, and under the condition of 28 - 30 °C, obtain liquid seeds through shake flask culture for 24 - 48 h.

[0022] (2) Inoculate the liquid seeds prepared in step (1) into a liquid fermentation medium at an inoculation amount of 2% - 5% by volume fraction, regulate the pH value to 6.5 - 7.5, the ventilation ratio to 1:(0.5 - 1), and the rotation speed to 150 - 250 revolutions per minute. Culture at 28 - 30 °C for 24 - 48 h to obtain a bacterial liquid;

[0023] (3) Spray - dry the bacterial liquid prepared in step (2) to obtain Bacillus firmus.

[0024] Further preferably, in step (1), each liter of the liquid activation medium contains the following components: 6 - 8 g of tryptone, 4 - 7 g of yeast powder, 3 - 5 g of glucose, 1 - 3 g of calcium phosphate, 6 - 10 g of sodium chloride, and the balance is water;

[0025] In step (2), the components of the liquid fermentation medium per liter are as follows: 8-12 g of corn flour, 10-15 g of soybean cake powder, 5-10 g of molasses solution, 1-5 g of fish meal, 1-5 g of yeast powder, 5-10 g of sodium chloride, 0.1-0.25 g of magnesium sulfate, 0.1-0.25 g of manganese sulfate, 0.1-0.2 g of ferrous sulfate, 3-6 g of calcium phosphate, and the balance is water.

[0026] Preferably according to the present invention, the preparation method of Trichoderma longibrachiatum includes the following steps:

[0027] Ⅰ. Inoculate the Trichoderma longibrachiatum strain into a liquid activation medium, and under the condition of 25-28 °C, obtain liquid seeds through shake flask culture for 48-72 h;

[0028] Ⅱ. Inoculate the liquid seeds prepared in step Ⅰ into a solid fermentation medium at an inoculation amount of 5%-15% by volume fraction, and adopt shallow pan solid fermentation. Control the pH at 4.5-6.5, the ventilation ratio at 1:(0.5-1), and culture at 25-28 °C for 72-96 h. After the culture is completed, the material is dried and pulverized to obtain Trichoderma longibrachiatum.

[0029] More preferably, in step Ⅰ, the components of the liquid activation medium per liter are as follows: 5-10 g of potato leaching powder, 20-35 g of glucose, 0.05-0.15 g of chloramphenicol, and the balance is water;

[0030] In step Ⅱ, the components of the solid fermentation medium are as follows by weight: 1-5 parts of soybean meal, 5-10 parts of starch, 40-50 parts of bran, 20-30 parts of rice husk, 1-5 parts of glucose, 1-5 parts of ammonium sulfate, 1-2 parts of magnesium sulfate, and 30-40 parts of water.

[0031] The preparation method of the above composite microbial inoculant includes the following steps:

[0032] Mix Streptomyces microflavus, Bacillus firmus, Trichoderma longibrachiatum, welan gum and fucoidan oligosaccharide according to the corresponding weight parts to obtain the composite microbial inoculant.

[0033] The application of the above composite microbial inoculant in crop planting and soil improvement.

[0034] Preferably according to the present invention, the application of the composite microbial inoculant in crop planting in saline-alkali land and saline-alkali land soil improvement.

[0035] Preferably according to the present invention, the crop is a gramineous crop.

[0036] More preferably, the crop is corn, wheat or rice.

[0037] Even more preferably, the crop is corn or rice.

[0038] Beneficial effects

[0039] The composite microbial inoculant provided by the present invention can be effectively colonized in saline-alkali land, and is more conducive to colonizing around the roots, especially with better colonization effect around the roots of gramineous plants; and can effectively increase the root proliferation of crops in saline-alkali land, especially with better proliferation effect on the roots of gramineous crops, effectively reducing the dead seedling rate of corn seedlings when planting corn in saline-alkali land. Detailed implementation manners

[0040] The technical solutions of the present invention will be further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto.

[0041] Reagents and drugs involved in the embodiments are all ordinary commercially available products without special instructions; experimental operations involved in the embodiments are all conventional operations in the art without special instructions.

[0042] Bacillus firmus ACCC 03123, Trichoderma longibrachiatum ACCC 32522, Streptomyces microflavus ACCC 40909, Trichoderma viride ACCC 31988, Streptomyces microflavus ACCC 41155 are preserved in the China Center for Type Culture Collection of Agricultural Microorganisms and can be purchased therefrom.

[0043] Example 1

[0044] The preparation method of Bacillus firmus ACCC 03123 includes the following steps:

[0045] Inoculate the Bacillus firmus strain into a liquid activation medium, and obtain liquid seeds after shake flask culture at 28 - 30 °C for 28 h;

[0046] Inoculate the prepared liquid seeds into a liquid fermentation medium at an inoculation amount of 5% by volume fraction, adjust the pH value to 6.5 - 7.5, the aeration ratio to 1:1, and the rotation speed to 250 revolutions per minute, and culture at 28 - 30 °C for 48 h to obtain a bacterial liquid.

[0047] Spray dry the obtained bacterial liquid using a spray drying device to obtain Bacillus firmus bacterial powder with a viable count of 50 billion / g.

[0048] Each liter of the above liquid activation medium contains the following components: 8 g of tryptone, 5 g of yeast powder, 4 g of glucose, 1 g of calcium phosphate, 6 g of sodium chloride, and the balance is water.

[0049] Each liter of the above liquid fermentation medium contains the following components: 8 g of corn flour, 10 g of soybean cake powder, 5 g of molasses liquid, 2.5 g of fish meal, 2 g of yeast powder, 5 g of sodium chloride, 0.15 g of magnesium sulfate, 0.2 g of manganese sulfate, 0.1 g of ferrous sulfate, 3 g of calcium phosphate, and the balance is water.

[0050] Preparation method of Trichoderma longibrachiatum ACCC 32522, comprising the following steps:

[0051] Inoculate the Trichoderma longibrachiatum strain into a liquid activation medium, and under the condition of 25 - 28 °C, obtain liquid seeds through shake flask culture for 48 h;

[0052] Inoculate the prepared liquid seeds into a solid fermentation medium at an inoculation amount of 10% by volume fraction, adopt shallow pan solid fermentation, regulate the pH to 4.5 - 6.5, the ventilation ratio to 1:0.8, and culture at 25 - 28 °C for 96 h. After the culture is completed, the material is dried and pulverized to obtain Trichoderma longibrachiatum powder, and the viable count of the bacteria is 50 billion / g.

[0053] Each liter of the above liquid activation medium contains the following components: 5 g of potato leaching powder, 20 g of glucose, 0.05 g of chloramphenicol, and the balance is water.

[0054] The components of the above solid fermentation medium are as follows by weight: 5 parts of soybean meal, 7.5 parts of starch, 40 parts of bran; 25 parts of rice husk; 1.5 parts of glucose, 1.5 parts of ammonium sulfate, 1 part of magnesium sulfate, and 35 parts of water.

[0055] Preparation method of Streptomyces microflavus ACCC 40909, comprising the following steps:

[0056] Inoculate the Streptomyces microflavus strain into a liquid activation medium, and under the condition of 28 - 32 °C, obtain liquid seeds through shake flask culture for 60 h;

[0057] Inoculate the prepared liquid seeds into a solid fermentation medium at an inoculation amount of 15% by volume fraction, adopt shallow pan solid fermentation, regulate the pH to 7.0 - 7.5, the ventilation ratio to 1:1, and culture at 28 - 32 °C for 72 h. After the culture is completed, the material is dried and pulverized to obtain Streptomyces microflavus powder, and the viable count of the bacteria is 10 billion / g.

[0058] Each liter of the above liquid activation medium contains the following components: 22 g of soluble starch, 1.2 g of potassium nitrate, 0.5 g of sodium chloride, 0.6 g of dipotassium hydrogen phosphate, 0.5 g of magnesium sulfate, 0.5 g of ferrous sulfate, and the balance is water;

[0059] The components of the above solid fermentation medium are as follows by weight: 3 parts of soybean meal, 10 parts of starch, 45 parts of bran; 20 parts of rice husk; glucose

[0060] 3 parts, 1 part of ammonium sulfate, 1.5 parts of magnesium sulfate, 2 parts of ferrous sulfate, and 40 parts of water.

[0061] Example 2

[0062] A compound microbial inoculant, comprising the following components by weight: 5 parts of welan gum, 2 parts of fucoidan oligosaccharide, 8 parts of Streptomyces microflavus, 10 parts of Bacillus firmus, and 9 parts of Trichoderma longibrachiatum.

[0063] Streptomyces microflavus, Bacillus firmus, Trichoderma longibrachiatum were prepared in Example 1.

[0064] Example 3

[0065] A compound microbial inoculant comprises the following components in parts by weight: 1 part of welan gum, 1 part of fucoidan oligosaccharide, 5 parts of Streptomyces microflavus, 15 parts of Bacillus firmus, 5 parts of Trichoderma longibrachiatum.

[0066] Streptomyces microflavus, Bacillus firmus, Trichoderma longibrachiatum were prepared in Example 1.

[0067] Example 4

[0068] A compound microbial inoculant comprises the following components in parts by weight: 3 parts of welan gum, 0.5 part of fucoidan oligosaccharide, 7 parts of Streptomyces microflavus, 6 parts of Bacillus firmus, 8 parts of Trichoderma longibrachiatum.

[0069] Streptomyces microflavus, Bacillus firmus, Trichoderma longibrachiatum were prepared in Example 1.

[0070] Comparative Example 1

[0071] It is different from Example 2 in that Bacillus velezensis CGMCC 1.923 is used instead of Bacillus firmus, and others are the same.

[0072] Comparative Example 2

[0073] It is different from Example 2 in that Trichoderma viride ACCC 31988 is used instead of Trichoderma longibrachiatum, and others are the same.

[0074] Comparative Example 3

[0075] It is different from Example 2 in that Streptomyces microflavus ACCC 41155 is used instead of Streptomyces microflavus ACCC40909, and others are the same.

[0076] Application Example 1

[0077] Pot experiments were carried out using the compound microbial inoculants prepared in Examples 2-4 and Comparative Examples 1-3. The soil of saline-alkali land was taken for pot experiments, and the soil of saline-alkali land was sterilized at high temperature. Pot experiments were carried out using the seedlings of corn and pepper.

[0078] The amount of soil used was 5 kg / pot, and the amount of the compound microbial inoculant in the soil was 1 g / pot. No other fertilizers were applied, and sterilized water was used for watering. The total amount of initial microorganisms in the pot and the total amount of microorganisms in the soil of the crop roots after 30 days of planting were detected using the GB20287-2006 standard. The results of the corn pot experiment are shown in Table 1, and the results of the pepper pot experiment are shown in Table 2.

[0079] The detection results of the fresh weight of the roots of the crops planted for 30 days are shown in Table 3.

[0080] Table 1

[0081]

[0082] Table 2

[0083]

[0084] Table 3

[0085]

[0086]

[0087] Application Example 2

[0088] Select a saline-alkali paddy field in Jiejicun, Tailai Town, Tailai County, Qiqihar City, Heilongjiang Province. Rice variety: Dongnong 428. Test method: Prepare the test field by plowing and fertilizing, and level the land.

[0089] Use the compound microbial inoculants prepared in Examples 2-4 and Comparative Examples 1-3 to conduct a planting experiment. There are 3 parallel replicates for each treatment, 20 square meters for each parallel, and they are arranged in a randomized block design. The application rate of the compound microbial inoculant is 20 kg / mu, and it is applied by basal tillage; the rest of the field management is the same. For the blank control, no inoculant is applied. Detect the microbial content and the fresh weight of the roots at 70 days after planting, as shown in Tables 4 and 5.

[0090] Table 4

[0091]

[0092] Table 5

[0093]

[0094] Application Example 3

[0095] Select a saline-alkali land in Guozhuang Village, Encheng Town, Pingyuan County, Dezhou City, Shandong Province to plant corn. The variety is Zhengdan 958.

[0096] Test method: Prepare the test field by plowing and fertilizing, and level the land.

[0097] Use the compound microbial inoculants prepared in Examples 2-4 and Comparative Examples 1-3 to conduct a planting experiment. There are 3 parallel replicates for each treatment, 20 square meters for each parallel, and 100 holes are sown in each parallel plot. They are arranged in a randomized block design. The application rate of the compound microbial inoculant is 20 kg / mu, and it is applied by basal tillage; the rest of the field management is the same. For the blank control, no inoculant is applied. After 7 days of sowing, count the emergence rate of each plot, and after the three-leaf stage, count the dead seedling rate of each plot, as shown in Table 6.

[0098] Table 6

[0099]

[0100] The composite microbial inoculant provided by the present invention can effectively colonize in saline-alkali land, and is more conducive to colonizing around the roots, especially with better colonization effect around the roots of gramineous plants; and can effectively increase the root proliferation of crops in saline-alkali land, especially with better proliferation effect on the roots of gramineous crops, and effectively reduce the dead seedling rate of corn seedlings when planting corn in saline-alkali land.

Claims

1. A compound microbial inoculum, characterized in that, It consists of the following components: Streptomyces microflavus ACCC 40909, Bacillus firmus ACCC 03123, Trichoderma longibrachiatum ACCC 32522, welan gum, and alginate oligosaccharide; The composite microbial inoculant, by weight, is: 1 - 5 parts of welan gum, 0.5 - 2 parts of alginate oligosaccharide, 5 - 10 parts of Streptomyces microflavus ACCC 40909, 5 - 15 parts of Bacillus firmus ACCC 03123, and 5 - 10 parts of Trichoderma longibrachiatum ACCC 32522; The effective viable count of Streptomyces microflavus ACCC 40909 is not less than 10 billion / g, the effective viable count of the Trichoderma longibrachiatum ACCC 32522 bacterial powder is not less than 50 billion / g, and the effective viable count of Bacillus firmus ACCC 03123 is not less than 50 billion / g.

2. The composite microbial inoculum according to claim 1, wherein The preparation method of Streptomyces microflavus ACCC 40909 includes the following steps: ① Inoculate the Streptomyces microflavus ACCC 40909 strain into a liquid activation medium, and under the conditions of 28 - 32 °C, obtain liquid seeds through shake flask culture for 48 - 72 h; ② Inoculate the liquid seeds prepared in step ① into a solid fermentation medium at an inoculation amount of 5% - 20% by volume fraction, and adopt shallow pan solid fermentation. Adjust the pH to 7.0 - 7.5, the ventilation ratio to 1:(0.8 - 1.5), and culture at 28 - 32 °C for 72 - 96 h. After the culture is completed, the material is dried and pulverized to obtain Streptomyces microflavus ACCC 40909.

3. The composite microbial inoculum according to claim 2, wherein In step ①, each liter of the liquid activation medium contains the following components: 20 - 25 g of soluble starch, 1 - 1.5 g of potassium nitrate, 0.5 - 1 g of sodium chloride, 0.5 - 1 g of dipotassium hydrogen phosphate, 0.5 - 1 g of magnesium sulfate, 0.5 - 1 g of ferrous sulfate, and the balance is water; In step ②, the components of the solid fermentation medium by weight are as follows: 1 - 5 parts of soybean meal, 5 - 10 parts of starch, 40 - 50 parts of wheat bran; 20 - 30 parts of rice husk; 1 - 5 parts of glucose, 1 - 5 parts of ammonium sulfate, 1 - 2 parts of magnesium sulfate, 1 - 2 parts of ferrous sulfate; 30 - 40 parts of water.

4. The composite microbial inoculum according to claim 1, characterized in that, The preparation method of Bacillus firmus ACCC 03123 includes the following steps: (1)Inoculate the Bacillus firmus ACCC 03123 strain into a liquid activation medium, and under the conditions of 28 - 30 °C, obtain liquid seeds through shake flask culture for 24 - 48 h; (2)Inoculate the liquid seeds prepared in step (1) into a liquid fermentation medium at an inoculation amount of 2% - 5% by volume fraction, adjust the pH value to 6.5 - 7.5, the ventilation ratio to 1:(0.5 - 1), and the rotation speed to 150 - 250 revolutions per minute, and culture at 28 - 30 °C for 24 - 48 h to obtain a bacterial liquid; (3)Spray - dry the bacterial liquid prepared in step (2) to obtain Bacillus firmus ACCC 03123.

5. The composite microbial inoculum according to claim 4, wherein In step (1), each liter of the liquid activation medium contains the following components: 6 - 8 g of tryptone, 4 - 7 g of yeast powder, 3 - 5 g of glucose, 1 - 3 g of calcium phosphate, 6 - 10 g of sodium chloride, and the balance is water; In step (2), the components of the liquid fermentation medium per liter are as follows: 8-12 g of corn flour, 10-15 g of soybean cake powder, 5-10 g of molasses solution, 1-5 g of fish meal, 1-5 g of yeast powder, 5-10 g of sodium chloride, 0.1-0.25 g of magnesium sulfate, 0.1-0.25 g of manganese sulfate, 0.1-0.2 g of ferrous sulfate, 3-6 g of calcium phosphate, and the balance is water.

6. The composite microbial inoculant according to claim 1, wherein The preparation method of Trichoderma longibrachiatum ACCC 32522 comprises the following steps: Ⅰ. Inoculate the Trichoderma longibrachiatum ACCC 32522 strain into a liquid activation medium, and under the condition of 25-28 °C, obtain liquid seeds through shake flask culture for 48-72 h; Ⅱ. Inoculate the liquid seeds prepared in step Ⅰ into a solid fermentation medium at an inoculation amount of 5%-15% by volume fraction, adopt shallow pan solid fermentation, adjust the pH to 4.5-6.5, the aeration ratio to 1:(0.5-1), and culture at 25-28 °C for 72-96 h. After the culture is completed, the material is dried and crushed to obtain Trichoderma longibrachiatum ACCC 32522.

7. The composite microbial inoculant according to claim 6, wherein, In step Ⅰ, the components of the liquid activation medium per liter are as follows: 5-10 g of potato leaching powder, 20-35 g of glucose, 0.05-0.15 g of chloramphenicol, and the balance is water; In step Ⅱ, the components of the solid fermentation medium are as follows by weight: 1-5 parts of soybean meal, 5-10 parts of starch, 40-50 parts of wheat bran, 20-30 parts of rice husk, 1-5 parts of glucose, 1-5 parts of ammonium sulfate, 1-2 parts of magnesium sulfate, and 30-40 parts of water.

8. The preparation method of the compound microbial inoculant according to any one of claims 1-7 comprises the following steps: Mix Streptomyces microflavus ACCC 40909, Bacillus firmus ACCC 03123, Trichoderma longibrachiatum ACCC 32522, welan gum and fucoidan oligosaccharide according to the corresponding weight parts to obtain the compound microbial inoculant.

9. The application of the compound microbial inoculant according to any one of claims 1-7 in the planting of gramineous crops in saline-alkali land and the improvement of saline-alkali land soil.

10. The application according to claim 9, wherein The crops are corn and rice.

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