A method for soil carbon sequestration-organic pollution control synergistic remediation of microbial iron reduction coupled with biomass charcoal

Abstract

The present application provides a kind of microbial iron reduction coupling biomass carbon soil carbon sequestration-organic pollution control collaborative remediation method, the present application method is by selecting including nitrogen-fixing bacteria, phosphorus solubilizing bacteria and iron-reducing bacteria Compound bacterial species, mixed with biomass carbon to form microorganism-biomass carbon compound, apply to soil, regulate soil environmental conditions, to promote iron cycle and the carbon sequestration effect of biomass carbon.The specific steps include: selecting nitrogen-fixing bacteria consisting of Clostridium pasteurianum and soybean rhizobium, phosphorus solubilizing bacteria consisting of Bacillus subtilis, flavobacterium or Streptomyces, and iron-reducing bacteria consisting of Geobacter;Prepare biomass carbon;Mix compound bacterial species with biomass carbon;Application and adjust soil pH, moisture content and aeration.The method is suitable for various soils, especially soils susceptible to MCPA pollution, can effectively improve the soil carbon sequestration capacity and reduce environmental pollution.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil remediation and improvement, in particular to a soil carbon fixation-organic pollution control synergistic remediation method of microbial iron reduction coupled with biomass carbon. BACKGROUND

[0002] The red soil is important in agriculture, and low organic carbon content is one of the bottleneck problems restricting its sustainable development. Red soil is an important soil in China's tropical and southern subtropical regions, distributed in Hainan Island, Leizhou Peninsula in Guangdong, southern Yunnan and other regions. Due to sufficient water and heat, this area is the main production area of tropical crops such as rubber, banana, litchi and mango in China, and is also an important southward breeding base and winter "vegetable basket" base. Therefore, ensuring the quality and safety of red soil is related to the healthy development of China's tropical agriculture and the income increase of farmers in the hot area. However, with the development and acceleration of agriculture, the soil environment is facing many challenges. Due to the characteristics of high temperature and humidity, heavy rainfall intensity, and high multiple cropping index in this area, the organic carbon in red soil has the characteristics of low content, fast decomposition, difficulty in accumulation, and low carbon balance point. The organic carbon content is at the middle and lower level of the classification of organic carbon in China. This makes red soil one of the main low-yield soils in China, which needs a large amount of fertilization to maintain productivity, and the agricultural development is facing great challenges. Excessive fertilization not only leads to soil compaction and acidification, but also accelerates the oxidation of organic carbon and greenhouse gas emissions, making "soil carbon fixation" and "soil fertility improvement" become a contradictory problem. For example, in the past 30 years, as a typical red soil area, the grain yield of Hainan Island has been significantly improved, but the soil organic carbon content has decreased by 25%. Therefore, the fixation of soil organic carbon is of great significance to maintain soil fertility, improve soil structure and reduce greenhouse gas emissions. Seeking a sustainable way of farmland management to realize the carbon fixation and sink of red soil is an important task to solve the current development dilemma of tropical agriculture and support China's "double carbon" target.

[0003] Soil organic carbon content not only causes low soil fertility, but also makes soil microorganisms lack energy and nutrient sources for pesticide decomposition, increasing the risk of pesticide residues. Especially in the tropical red soil region with high temperature and rainfall and high multiple cropping index, the pesticide use amount is 3.6 times the national average and 5.6 times the average of the three provinces in Northeast China, which poses a potential threat to local agricultural product quality and safety and ecological system safety. Among them, the residual risk of MCPA is particularly huge. As a hormone type selective herbicide, MCPA is widely used in global agricultural production for broadleaf weed control. The use amount of MCPA ranks third in global pesticides. In the red soil region, MCPA is also commonly used for broadleaf weed control in rice fields and sugarcane fields, with an application amount of 1-2.5 kg / ha. Due to strong biological toxicity, MCPA can cause oxidative damage to animals / plants, damage to human organs / nerve weakness, and fetal / urogenital tract teratogenicity, and has been listed as an environmental priority monitoring pollutant by the US Environmental Protection Agency and the European Union. Therefore, while improving the organic carbon content of red soil, the demand for MCPA residue degradation should also be fully considered.

[0004] Currently, some soil improvement methods have been proposed for soil carbon sequestration or organic pollutant degradation. For example, applying organic fertilizer to increase soil organic carbon; and providing nutrients for the degradation of organic pollutants by chemical fertilizer. However, these methods have certain limitations. For example, the overuse of chemical fertilizer can cause soil compaction, environmental pollution and other problems. Moreover, the current soil improvement methods rarely consider the dual problems of low organic carbon content and serious MCPA residue in red soil. The use of microbe-driven iron cycle to promote the carbon sequestration effect of biomass charcoal soil, i.e., using nitrogen-fixing bacteria, phosphorus-solubilizing bacteria and iron-reducing bacteria, can promote the carbon sequestration effect and pollutant degradation effect of biomass carbon. Since the nitrogen and phosphorus nutrients in tropical red soil are low, especially in highly polluted soil, the degradation of organic pollutants by microorganisms requires the absorption of nitrogen and phosphorus from the soil.

[0005] is a green and sustainable soil improvement method. However, current research on how to effectively use specific composite strains to achieve this goal is not deep enough, and further exploration and optimization of related methods are needed. SUMMARY

[0006] In view of this, the present application provides a microbial iron reduction coupled biomass charcoal soil carbon sequestration-organic pollution control synergistic remediation method to solve the above problems.

[0007] The technical scheme of the present application is implemented as follows: A microbial iron reduction coupled biomass charcoal soil carbon sequestration-organic pollution control synergistic remediation method comprises the following technical scheme:

[0008] S1, selecting a composite bacterial strain, the composite bacterial strain comprising nitrogen-fixing bacteria, phosphorus-solubilizing bacteria, and iron-reducing bacteria, the nitrogen-fixing bacteria being Clostridium pasteurii and Rhizobium japonicum at a mass ratio of 1:1-3, the phosphorus-solubilizing bacteria being Bacillus subtilis, Flavobacterium, or Streptomyces, and the iron-reducing bacteria being Geobacter;

[0009] S2, preparing biomass charcoal, pyrolysis carbonization treatment of a biomass raw material under anaerobic or hypoxic conditions;

[0010] S3, mixing the composite bacterial strain with the prepared biomass charcoal to form a microorganism-biomass charcoal composite;

[0011] S4, applying the microorganism-biomass charcoal composite to target soil and regulating the environmental conditions of the soil to promote microorganism-driven iron cycling and soil carbon sequestration effects of biomass charcoal.

[0012] Further, the composite bacterial strain in S1 comprises nitrogen-fixing bacteria, phosphorus-solubilizing bacteria, and reducing bacteria at a mass ratio of (2.5-5.5):(8.1-10.2):(1.3-3.5).

[0013] Further, the effective viable bacterial count of the composite bacterial strain in S1 is ≥1×10 9 CFU / g.

[0014] Further, the pyrolysis carbonization treatment of the biomass raw material in S2 is at a temperature of 300-800°C for 5-10 hours.

[0015] Further, the biomass raw material in S2 is one or more of crop straw, forestry waste, livestock and poultry manure, waste wood, energy plants, or municipal organic waste.

[0016] Further, S3 contains 10 8 -10 10 microbial cells per gram of biomass charcoal.

[0017] Further, the application amount in S4 is 3-10 tons of microorganism-biomass charcoal composite per hectare of soil.

[0018] Further, the step of regulating the environmental conditions of the soil comprises adjusting the pH of the soil to 5.5-8.5, controlling the water content of the soil to 40-80%, and maintaining good aeration of the soil.

[0019] Further, the humus in S4 is humic acid, fulvic acid, or humin.

[0020] Further, the above method is applicable to different types of soil, including but not limited to paddy field soil, sugarcane field soil, and other soils susceptible to pollution by MCPA.

[0021] Compared with the prior art, the beneficial effects of the present application are:

[0022] (1) Improve the soil carbon sequestration capacity: through microbial driven iron cycle, promote the combination and stability of biomass carbon and soil organic carbon, improve the soil carbon sequestration capacity, and is beneficial to maintain soil fertility and improve soil structure.

[0023] (2) Improve the soil nutrient status: nitrogen-fixing bacteria can increase the nitrogen content in the soil, and phosphorus-solubilizing bacteria can release the fixed phosphorus elements in the soil, providing more sufficient nutrients for plant growth, and promoting the growth and development of plants.

[0024] (3) Degradation of soil pollutants: to some extent, the metabolic activity of microorganisms may help to degrade the possible pesticides and other pollutants in the soil, such as MCPA, reduce the risk of soil pollution, and protect the safety of soil ecosystem.

[0025] (4) Wide adaptability: the method is suitable for different types of soil, including but not limited to paddy field soil, sugarcane field soil and other soil susceptible to MCPA pollution, and has good popularization and application value. DETAILED DESCRIPTION

[0026] In order to better understand the technical content of the present application, the following specific examples are provided to further illustrate the present application.

[0027] The experimental methods used in the embodiments of the present application are conventional methods unless otherwise specified.

[0028] The materials, reagents, etc. used in the embodiments of the present application can be obtained from commercial channels unless otherwise specified.

[0029] Example 1

[0030] A microbial iron reduction coupled biomass carbon soil carbon sequestration-organic pollution control synergistic remediation method, comprising the following steps:

[0031] S1, selecting composite bacteria: selecting Clostridium pasteurii and Rhizobium japonicum as nitrogen-fixing bacteria according to the mass ratio of 1:1, selecting Bacillus subtilis as phosphorus-solubilizing bacteria, and selecting Ochrobactrum as iron-reducing bacteria. The nitrogen-fixing bacteria, phosphorus-solubilizing bacteria and iron-reducing bacteria are mixed according to the mass ratio of 2.5:8.1:1.3 to prepare the composite bacteria, and the effective viable count of the composite bacteria is ensured to be 1×109CFU / g.

[0032] S2, preparing biomass carbon: selecting crop straw as biomass raw material, and preparing biomass carbon under anaerobic condition, with pyrolysis carbonization treatment temperature set to 400℃ and pyrolysis time of 10 hours.

[0033] S3, forming a microorganism-biochar composite: mixing the composite microbial species with the prepared biochar at a ratio of 108 microbial cells per gram of biochar to form a microorganism-biochar composite.

[0034] S4, applying and regulating the soil environment: mixing the microorganism-biochar composite and humic acid at a mass ratio of 1:0.2, and then applying it to the paddy field soil, with an application amount of 3 tons per hectare of soil. The pH value of the soil is adjusted to 4.5, the water content of the soil is controlled to be 50%, and the soil aeration is maintained to be good.

[0035] Example 2

[0036] A soil carbon sequestration-organic pollution control synergistic remediation method of microbial iron reduction coupled with biochar, comprising the following steps:

[0037] S1, selecting a composite microbial species: selecting Clostridium pasteurii and Rhizobium japonicum as nitrogen-fixing bacteria at a mass ratio of 1:3, selecting Flavobacterium as phosphorus-solubilizing bacteria, and selecting Geobacter as iron-reducing bacteria. The nitrogen-fixing bacteria, phosphorus-solubilizing bacteria, and iron-reducing bacteria are mixed at a mass ratio of 5.5:10.2:3.5 to prepare a composite microbial species, and the effective viable count of the composite microbial species is 1.5x10 9 CFU / g.

[0038] S2, preparing biochar: using forestry waste and livestock and poultry manure as a mixture at a mass ratio of 1:1 as a biomass raw material, and pyrolyzing and carbonizing under anaerobic conditions at a pyrolysis temperature of 600°C for 5 hours to prepare biochar.

[0039] S3, forming a microorganism-biochar composite: mixing the composite microbial species with the prepared biochar at a ratio of 108 microbial cells per gram of biochar to form a microorganism-biochar composite. 10

[0040] S4, applying and regulating the soil environment: mixing the microorganism-biochar composite and humic acid at a mass ratio of 1:0.5, and then applying it to the paddy field soil, with an application amount of 3 tons per hectare of soil. The pH value of the soil is adjusted to 4.5, the water content of the soil is controlled to be 50%, and the soil aeration is maintained to be good.

[0041] Example 3

[0042] A soil carbon sequestration-organic pollution control synergistic remediation method of microbial iron reduction coupled with biochar, comprising the following steps:

[0043] ​S1, selecting composite strains: select Clostridium pasteurii and Rhizobium japonicum as nitrogen-fixing bacteria according to the mass ratio of 1:2, select Streptomyces as phosphorus-solubilizing bacteria, and select Geobacillus as iron-reducing bacteria. The nitrogen-fixing bacteria, phosphorus-solubilizing bacteria and iron-reducing bacteria are mixed according to the mass ratio of 4:9:2.5 to prepare the composite strains, and the effective viable count of the composite strains is 2x10 9 CFU / g.

[0044] S2, preparing biomass charcoal: a mixture of waste wood, energy plants and urban organic waste in a mass ratio of 2:3:1 is used as biomass raw material, and pyrolysis carbonization treatment temperature is 500℃ under anaerobic condition, pyrolysis time is 8 hours, and biomass charcoal is prepared.

[0045] S3, forming a microorganism-biomass charcoal composite: the composite strains and the prepared biomass charcoal are mixed according to the proportion of 10 9 microbial cells per gram of biomass charcoal to form a microorganism-biomass charcoal composite.

[0046] S4, applying and regulating soil environment: the microorganism-biomass charcoal composite and humic acid are mixed according to the mass ratio of 1:0.4, applied to the soil susceptible to MCPA pollution, and the application amount is 6 tons per hectare of soil. The pH value of the soil is adjusted to 5.5, the water content of the soil is controlled to 80%, and the soil aeration is maintained well.

[0047] Comparative Example 1

[0048] The MCPA-polluted soil without any treatment is selected as the comparative example. After 3 months, the soil is compared and detected with the soil in the examples.

[0049] Test Example 1-determination of soil carbon sequestration capacity

[0050] Operation steps:

[0051] 1. Collecting soil samples: in the soil treated in Examples 1-3 and the comparative soil, appropriate soil samplers are used according to the sampling depth (20 cm) and sampling point distribution to ensure that the collected soil samples are representative.

[0052] 2. Pretreating soil samples: the collected soil samples are naturally air-dried, and the impurities such as stones and plant roots are removed, then the soil samples are ground to fine powder state with a mortar or grinding instrument, sieved (0.15 mm sieve) to make the soil particles uniform and consistent, so as to ensure the accuracy of the analysis results.

[0053] 3. Elemental analysis determination: accurately weigh 10 milligrams of pretreated soil sample into the sample boat of the elemental analyzer, and send the sample boat into the combustion furnace of the elemental analyzer. Under the action of high temperature 900-1200℃ and oxygen flow, the carbon in the soil is oxidized to carbon dioxide, and other elements (nitrogen, hydrogen, etc.) are also converted into corresponding gases. After separation by chromatographic column, these gases enter the detector for detection. According to the carbon dioxide peak area or signal intensity detected by the detector, compared with the known concentration of standard substance, the carbon content in the soil sample is calculated.

[0054] 4. Calculate the carbon sequestration capacity: according to the carbon content in the soil sample, combined with the bulk density of the soil, the sampling area and the sampling depth, etc. Calculate the carbon storage in unit area of soil, which is used as the index of soil carbon sequestration capacity.

[0055] Carbon sequestration capacity (g / kg) = soil carbon content (g / kg) x soil bulk density (kg / m 3 ) x sampling depth (m).

[0056] 5. Test results:

[0057] Table 1:

[0058]

[0059]

[0060] In the above results, the microorganisms added in the example group synergize with the biochar to provide a more favorable living environment and carbon source for the microorganisms, promote the growth and metabolism of the microorganisms, and thus enhance the carbon sequestration capacity of the soil. Biochar itself is rich in carbon and has a highly aromatic structure, high stability, and is not easily decomposed by microorganisms in the soil, so it can store carbon for a long time. Its porous structure can also adsorb organic matter in the soil, reduce the mineralization and decomposition of organic carbon, and at the same time provide habitat for microorganisms, promote the contact and transformation of microorganisms and organic carbon, and further improve the soil carbon sequestration capacity. The change of the redox state of iron will affect the decomposition and transformation of organic matter in the soil, and appropriate iron cycle process helps to form stable soil aggregate structure, protect the organic carbon in the soil from being easily decomposed, and thus promote soil carbon sequestration. In the examples, the microbial driven iron cycle optimizes the soil environment to some extent, which is conducive to soil carbon sequestration.

[0061] Test example 2-determination of soil nutrient content

[0062] 1. Total nitrogen content determination: Kjeldahl nitrogen determination method;

[0063] 2. Effective phosphorus content determination: molybdenum antimony anti colorimetric method;

[0064] 3. Rapid potassium content determination: ammonium acetate extraction-flame photometry.

[0065] 4. Test results:

[0066] Sample Total nitrogen content (g / kg) Available phosphorus content (mg / kg) Available potassium content (mg / kg) Example 1 1.85 35.2 185 Example 2 2.10 42.5 210 Example 3 2.35 50.0 230 Comparative Example 1.20 20.5 120

[0067] The above results show that nitrogen-fixing bacteria can convert atmospheric nitrogen into plant-available ammonium nitrogen, increasing the nitrogen content in the soil. Phosphorus-solubilizing bacteria can decompose insoluble phosphorus compounds in the soil, releasing available phosphorus for plant uptake. In the example groups, the addition and increased activity of these microorganisms directly promoted the supply of nitrogen and phosphorus nutrients in the soil. Biomass charcoal has a large specific surface area and pore structure, which can adsorb soil nutrient ions (ammonium ions, phosphate ions, etc.), reducing nutrient leaching. At the same time, biomass charcoal can act as a slow-release carrier for nutrients, slowly releasing nutrients according to the concentration gradient of nutrients in the soil, improving the availability and supply persistence of nutrients. The addition of microbial-biomass charcoal complexes and humus improves the physical and chemical properties of the soil, including soil pH, aeration, water retention, etc. Suitable soil environment is conducive to the activity of microorganisms in the soil and the transformation process of nutrients, among which aerobic microorganisms are more active in well-aerated soil, which helps to mineralize organic nitrogen and release phosphorus, thereby increasing the soil nutrient content.

[0068] Test Example 3 - Determination of MCPA Residue

[0069] Operation steps:

[0070] 1. Soil sample collection and pretreatment: select the soil samples treated in Examples 1-3 and the control soil samples, take 20g of soil sample and place it in a stoppered flask, add 100ml of acetonitrile-water mixed solution (volume ratio 80:20), oscillate for 50 minutes on the shaker, then filter with filter paper, collect the filtrate in a clean container. The residue is extracted again with the extraction solvent, and the two filtrates are combined. Use C 18 purify the eluate with a solid phase extraction column.

[0071] 2. Determine using high performance liquid chromatography

[0072] Chromatographic column selection: C 18 reverse phase chromatographic column;

[0073] Mobile phase: methanol-water mixed solution with a volume ratio of 50:50, pH value at 2.5-4.0;

[0074] Control the flow rate at 1.5mL / min;

[0075] Detection wavelength: 240nm;

[0076] Column temperature is set at 30℃;

[0077] The residual amount of MCPA in the soil sample was calculated according to the standard curve equation.

[0078] 3. Determination results

[0079] Sample MCPA residue (mg / kg) Degradation rate (%) Example 1 0.35 82.5 Example 2 0.25 87.5 Example 3 0.10 95.0 Comparative Example 2.00 -

[0080] The microorganisms added in the present application can have the ability to degrade MCPA, and part of the microorganisms can decompose MCPA molecules into small molecular substances by secreting specific enzymes, and then mineralize into harmless substances such as carbon dioxide, water and inorganic salts. In the examples, the interaction between the microbial community and MCPA is enhanced, and the degradation process of MCPA is accelerated. The redox substances (ferrous ions, iron ions, etc.) produced in the iron cycle driven by iron-reducing bacteria participate in the degradation reaction of MCPA. Ferrous ions have a certain reducing property and can undergo electron transfer reaction with MCPA molecules, changing the chemical structure of MCPA, making it easier to be further degraded by microorganisms or other chemical processes. The biomass charcoal has a certain adsorption capacity for MCPA, which can adsorb MCPA in the soil to its surface, reducing the concentration of MCPA in the soil solution, on the one hand, reducing the direct toxicity of MCPA to soil organisms, on the other hand, enriching MCPA on the surface of biomass charcoal, which is conducive to the contact between microorganisms and MCPA, and promotes the degradation of MCPA by microorganisms. At the same time, the biomass charcoal can change the microenvironment of the soil, including the local pH value, oxidation-reduction potential, etc., to create more favorable conditions for the degradation of MCPA.

[0081] In summary, the microbial-driven iron cycle promotes the biomass charcoal soil improvement method to have significant effects on soil carbon sequestration, nutrient improvement and MCPA residue degradation. Example 3 shows the best performance in all aspects, and its success can be attributed to the synergistic effect between the microbial-biomass charcoal complex, humus and the microbial-driven iron cycle. These results provide strong experimental evidence for the application of this method in the fields of soil improvement, agricultural sustainable development and contaminated soil remediation, and the carbon sequestration capacity, nutrient content and MCPA residue of the control soil are all not as good as those of the soil treated by the examples.

[0082] Test Example 4 - Iron reduction index test

[0083] 1. Accurately weigh 5.00 g of treated soil sample into a 100 mL triangular flask with a stopper, add 50 mL of 0.5 mol / L hydrochloric acid solution, tightly close the stopper, and oscillate on a shaker for 1 h to fully dissolve the ferrous iron in the soil.

[0084] 2. After oscillation, transfer the solution in the triangular flask to a centrifuge tube, centrifuge at a speed of 3000 r / min for 10 min, and take the supernatant for standby.

[0085] 3. Take 5.00 mL supernatant in a 50 mL volumetric flask, and carry out color development and absorbance determination according to steps 2-4 in the standard curve drawing procedure.

[0086] 4. According to the standard curve regression equation, calculate the ferrous content (μg) in 5.00 mL supernatant, and then calculate the ferrous (Fe(II)) content in soil (mg / kg) according to the formula:

[0087]

[0088] In the formula:

[0089] m: the ferrous content (μg) in 5.00 mL supernatant obtained from the standard curve;

[0090] V: total volume of the extract (mL), which is 50 mL in this experiment;

[0091] m0: the mass of the soil sample (g) weighed, which is 5.00 g in this experiment;

[0092] V1: the volume of supernatant for determination (mL), which is 5.00 mL in this experiment.

[0093] 5. Experimental results

[0094] Group Ferrous iron (Fe(II)) content in soil (mg / kg) Example 1 71.6 Example 2 69.2 Example 3 75.3 Comparative Example 45.7

[0095] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for soil carbon sequestration and DDDT residue removal synergistic remediation by microbial iron reduction coupled with biomass char, characterized in that: The method comprises the following steps: S1, selecting a composite strain, wherein the composite strain comprises nitrogen-fixing bacteria, phosphorus-solubilizing bacteria and iron-reducing bacteria, the nitrogen-fixing bacteria are Clostridium pasteurii and Rhizobium japonicum with a mass ratio of 1:1-3, the phosphorus-solubilizing bacteria are Bacillus subtilis, Flavobacterium or Streptomyces, and the iron-reducing bacteria are Geobacter; S2, preparing biomass charcoal, wherein the biomass raw material is pyrolyzed and carbonized under anaerobic or hypoxic conditions; S3, mixing the composite strain and the prepared biomass charcoal to form a microorganism-biomass charcoal compound; S4, mixing the microorganism-biomass charcoal compound and humus at a mass ratio of 1:(0.2-0.5), applying to the target soil, and adjusting the environmental conditions of the soil to promote the iron cycle driven by microorganisms and the soil carbon sequestration effect of biomass charcoal; The composite strain in S1 comprises nitrogen-fixing bacteria, phosphorus-solubilizing bacteria and reducing bacteria with a mass ratio of (2.5-5.5):(8.1-10.2):(1.3-3.5); The humus in S4 is humic acid, fulvic acid or humin.

2. The method of claim 1, wherein the method is characterized in that: The effective viable cell number of the complex bacteria in S1 is ≥1×10 9 CFU / g.

3. The method of claim 1, wherein the method is characterized in that: The pyrolysis carbonization temperature of the biomass raw material in S2 is 400-600 DEG C, and the pyrolysis time is 5-10 hours.

4. The method of claim 1, wherein the method is characterized in that: The biomass raw material in S2 is one or more of crop straw, forestry waste, livestock and poultry manure, waste wood, and urban organic waste.

5. The method of claim 1, wherein the method is characterized in that: The S3 contains 10 8 -10 10 microbial cells per gram of biomass char.

6. The method of claim 1, wherein the method is characterized in that: The application amount in S4 is 3-10 tons of microorganism-biomass charcoal compound per hectare of soil.

7. The method of claim 1, wherein the method is characterized in that: The step of adjusting the environmental conditions of the soil comprises adjusting the pH value of the soil to 4.5-6.5, controlling the water content of the soil to be 50-100%, and maintaining good aeration of the soil.

8. The method according to any one of claims 1-7, characterized in that, It is suitable for different types of soil, including paddy soil and moist iron-aluminum soil.

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