High-efficiency modified biochar-based organic fertilizer and preparation method thereof

Abstract

The application discloses a kind of high-efficiency modified biochar-based organic fertilizer and its preparation method, agricultural waste is used as raw material, using step-by-step double modification and straw carbon buffer secondary load design: first, biochar is activated by phosphoric acid and neutralized pH, then form porous coating layer by using lignin-starch compound;After straw carbon pre-adsorption, compound microbial inoculum is loaded on double modified biochar, and the adsorption-activation-supply-improvement synergistic closed loop is constructed.The application solves the problems of existing organic fertilizer modification conflict, low survival of bacteria, nutrient loss and soil hardening, and has simple process, low cost, easy industrialization, nutrient slow release, microbial inoculum activation and soil improvement function, and wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of agricultural fertilizer technology, specifically relating to a highly efficient modified biochar-based organic fertilizer and its preparation method. Background Technology

[0002] With the development of green agriculture, biochar-based organic fertilizers are widely used due to their advantages in both soil improvement and nutrient supply. However, existing products generally have functional defects. Conventional biochar has insufficient surface active sites and a simple pore structure, resulting in low loading capacity for microbial agents and poor protection. After being applied to the soil, live bacteria are easily inactivated, leading to insufficient sustained fertilizer effect. At the same time, direct application of biochar to microbial agents is prone to problems such as weak binding and excessively rapid nutrient release. Some modification processes use high-temperature treatment, which can easily destroy the activity of microbial agents, making it difficult to balance the stability of the carrier structure and the survival rate of microorganisms.

[0003] Furthermore, existing organic fertilizers mostly employ simple physical blending without stepwise activation and gentle coating modification of biochar. The carrier's pore structure has poor compatibility with the microbial agent, failing to achieve slow release of the agent and buffering of the soil environment. Traditional processes suffer from harsh modification conditions, unreasonable raw material ratios, and short microbial agent survival periods, resulting in limited effectiveness in promoting phosphorus dissolution, nitrogen fixation, and soil improvement, failing to meet the long-term, high-efficiency, and environmentally friendly fertilization needs of modern agriculture. Therefore, developing a highly efficient modified biochar-based organic fertilizer with gentle activation, composite cross-linking coating, and stable microbial agent loading has become an urgent technical problem to be solved in this field. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a highly efficient modified biochar-based organic fertilizer and its preparation method. This organic fertilizer achieves carrier structure optimization through mild activation and composite cross-linking coating, resulting in stable microbial agent loading and long survival period. It also possesses long-acting fertilizer release, soil improvement, and growth-promoting and efficiency-enhancing functions, thus meeting the green, long-lasting, and efficient fertilization needs of field and facility agriculture.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A high-efficiency modified biochar-based organic fertilizer, wherein the organic fertilizer is prepared from the following raw materials in parts by weight:

[0007] 50-80 parts corn cob-based biochar, 6-12 parts lignin, 2-4 parts starch, 5-15 parts micron-sized straw biochar, and 10-25 parts phosphate-solubilizing bacteria-nitrogen-fixing bacteria compound inoculant.

[0008] The corn cob-based biochar is pre-activated with phosphoric acid, neutralized with pH and washed, and then coated with lignin-starch to form a modified biochar carrier. The lignin and starch are compounded at a mass ratio of 3:1 and cross-linked to form a porous coating layer. The compound microbial agent and micron-sized straw biochar form a microbial-char buffer complex and are loaded on the surface and pores of the modified biochar carrier.

[0009] Optionally, the phosphoric acid activation process uses a 5% (w / w) aqueous solution of phosphoric acid, and after activation, the phosphoric acid is neutralized to pH 6.5-7.0 using a 1% (w / w) sodium bicarbonate solution.

[0010] Optionally, the micron-sized straw biochar has a particle size of 5-10 μm, and the concentration of live bacteria in the compound microbial agent is 1.0 × 10⁻⁶. 8 -5.0×10 9 CFU / mL.

[0011] Optionally, the total amount of lignin and starch added accounts for 15%-20% of the mass of corn cob-based biochar.

[0012] Optionally, the preparation method of the aforementioned high-efficiency modified biochar-based organic fertilizer is as follows:

[0013] S1. Add 5% (w / w) phosphoric acid aqueous solution to corn cob-based biochar at a liquid-to-solid ratio of 10:1 (mL / g), activate at 40-50℃ and 100-200rpm for 1-1.5h, then adjust the pH of the system to 6.5-7.0 with 1% (w / w) sodium bicarbonate solution, filter, wash and dry for later use.

[0014] S2. Add lignin and starch to the biochar treated in step S1 at a mass ratio of 3:1, mix evenly, and then crosslink the mixture at 35-40℃ and 150-250rpm for 2-3 hours to form a porous coating layer, thus obtaining the modified biochar carrier.

[0015] S3. Add micron-sized straw biochar to the composite bacterial solution at a solid-liquid ratio of 1:5 (g / mL), and pre-adsorb at a constant temperature of 25℃ and 80-120rpm for 1 hour to form a bacterial-char buffer complex.

[0016] S4. Mix the modified biochar carrier with the bacteria-char buffer complex at a mass ratio of 3:1, dry at 30-40℃ and vacuum degree of 0.06-0.08MPa until the moisture content is ≤10%, and then sieve to obtain the finished product.

[0017] Optionally, the drying temperature in step S1 is 50-70℃, and the drying time is 2-3 hours.

[0018] The beneficial effects of this invention are as follows: The highly efficient modified biochar-based organic fertilizer microbial agent prepared by this invention has excellent stability, with a survival period of ≥30 days in the soil, significant phosphorus solubilization and nitrogen fixation effects, and an increase in available phosphorus of more than 20%; through mild activation and composite cross-linking to form an adaptable pore structure, the microbial agent achieves stable loading and slow release of nutrients, resulting in long-lasting fertilizer effect; biochar and straw char synergistically improve the soil, enhancing water and fertilizer retention and buffering capacity; the process is mild, without high-temperature inactivation, the raw materials are reasonable, and it is easy to scale up production, combining long-lasting effect, environmental protection and economy. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] Example 1: This Example 1 describes a highly efficient modified biochar-based organic fertilizer, prepared from the following raw materials in parts by weight:

[0021] 60 parts corn cob-based biochar, 9 parts lignin, 3 parts starch, 10 parts micron-sized straw biochar, and 20 parts phosphate-solubilizing bacteria-nitrogen-fixing bacteria compound inoculant.

[0022] The preparation method of corn cob-based biochar is as follows:

[0023] S1. Take corn cob raw material, wash it with clean water, dry it at 60℃ to constant weight and then crush it; weigh an appropriate amount of powder, put it in a covered crucible, seal it, put it in a box-type resistance furnace, and pyrolyze it at 500℃ for 1.5h.

[0024] S2. After naturally cooling to room temperature, remove the ash, grind and sieve to obtain 60-100 mesh corn cob-based biochar. Seal and store in a desiccator for later use.

[0025] The preparation method of micron-sized straw biochar is as follows:

[0026] S1. Take wheat straw without mold, wash it with clean water, dry it at 70℃ until the moisture content is ≤8%, then crush it and pass it through a 20-mesh sieve; weigh the sieved powder and place it in a sealed crucible, put it into a box-type resistance furnace, heat it to 550℃ at 5℃ / min under limited oxygen conditions, and keep it at the temperature for 2 hours for carbonization.

[0027] S2. After naturally cooling to room temperature, the powder is pulverized using an ultra-micro pulverizer, and the particle size is detected by a laser particle size analyzer. 5-10μm powder is collected, sealed, and stored in a desiccator for later use.

[0028] The preparation method of the phosphate-solubilizing bacteria-nitrogen-fixing bacteria composite inoculant is as follows:

[0029] S1. Select single colonies of activated phosphate-solubilizing bacteria (Priestella megaterium, CGMCC 1.833) and nitrogen-fixing bacteria (Azotobacter chrysophagus, ACCC 11103) and inoculate them into LB liquid medium. Incubate at 37°C and 180 rpm for 24 h to obtain single-strain bacterial suspensions.

[0030] S2. After determining the viable cell concentration using the plate count method, the two bacterial solutions were mixed at a 1:1 mass ratio, and the total concentration was adjusted to 2.0 × 10⁻⁶ in sterile LB medium. 8 CFU / mL, refrigerate at 4℃ for later use.

[0031] This embodiment describes a method for preparing a high-efficiency modified biochar-based organic fertilizer, with the following specific preparation steps:

[0032] S1. Take the treated corn cob-based biochar and add 5% (w / w) phosphoric acid aqueous solution at a liquid-to-solid ratio of 10:1 (mL / g). Activate the biochar at 45℃ and 150 rpm for 1.2 h. Then adjust the pH of the system to 6.8 with 1% (w / w) sodium bicarbonate solution. After filtration, wash the biochar three times with deionized water and dry it at 60℃ for 2.5 h to obtain the activated biochar.

[0033] S2. Add lignin and starch (mass ratio 3:1) to the dried biochar in step S1, mix evenly, and then crosslink at 38℃ and 200rpm for 2.5h to form a porous coating layer and obtain the modified biochar carrier.

[0034] S3. Take micron-sized straw biochar and add phosphate-solubilizing bacteria-nitrogen-fixing bacteria compound inoculant at a solid-liquid ratio of 1:5 (g / mL). Pre-adsorb at 25℃ and 100rpm constant temperature shaking for 1 hour to form bacteria-char buffer complex.

[0035] S4. Mix the modified biochar carrier and the bacteria-char buffer complex evenly at a mass ratio of 3:1, and vacuum dry at 35℃ and 0.07MPa until the moisture content is ≤10%. Pass the mixture through a 20-mesh sieve to obtain the high-efficiency modified biochar-based organic fertilizer product.

[0036] Example 2: This Example 2 describes a highly efficient modified biochar-based organic fertilizer, prepared from the following raw materials in parts by weight:

[0037] 70 parts corn cob-based biochar, 9 parts lignin, 3 parts starch, 10 parts micron-sized straw biochar, and 20 parts phosphate-solubilizing bacteria-nitrogen-fixing bacteria compound inoculant.

[0038] The preparation methods of corn cob-based biochar, micron-sized straw biochar, and phosphate-solubilizing bacteria-nitrogen-fixing bacteria composite inoculant are the same as in Example 1;

[0039] The preparation method of a high-efficiency modified biochar-based organic fertilizer in this embodiment is the same as that in Example 1, except that the amount of corn cob-based biochar is adjusted to 70 parts.

[0040] Example 3: This Example 3 describes a highly efficient modified biochar-based organic fertilizer, prepared from the following raw materials in parts by weight:

[0041] 60 parts corn cob-based biochar, 9 parts lignin, 3 parts starch, 10 parts micron-sized straw biochar, and 20 parts phosphate-solubilizing bacteria-nitrogen-fixing bacteria compound inoculant.

[0042] The preparation methods for corn cob-based biochar, micron-sized straw biochar, and phosphate-solubilizing bacteria-nitrogen-fixing bacteria composite inoculant are the same as in Example 1, except that the total viable bacteria concentration is adjusted to 1.0 × 10⁻⁶ in the preparation of the phosphate-solubilizing bacteria-nitrogen-fixing bacteria composite inoculant. 9 CFU / mL;

[0043] The preparation method of the high-efficiency modified biochar-based organic fertilizer in this embodiment is the same as that in Example 1.

[0044] Comparative Example 1: The organic fertilizer of Comparative Example 1 was prepared from the following parts by weight of raw materials:

[0045] 60 parts corn cob-based biochar, 9 parts lignin, 3 parts starch, 10 parts micron-sized straw biochar, and 20 parts phosphate-solubilizing bacteria-nitrogen-fixing bacteria compound inoculant.

[0046] The preparation methods of corn cob-based biochar, micron-sized straw biochar, and phosphate-solubilizing bacteria-nitrogen-fixing bacteria composite inoculant are the same as in Example 1;

[0047] The preparation method of organic fertilizer in this comparative example is the same as that in Example 1, except that phosphoric acid activation and neutralization washing are not performed in step S1.

[0048] Comparative Example 2: The organic fertilizer of Comparative Example 2 was prepared from the following parts by weight of raw materials:

[0049] 60 parts of corn cob-based biochar, 10 parts of micron-sized straw biochar, and 20 parts of phosphate-solubilizing bacteria-nitrogen-fixing bacteria compound inoculant.

[0050] The preparation methods of corn cob-based biochar, micron-sized straw biochar, and phosphate-solubilizing bacteria-nitrogen-fixing bacteria composite inoculant are the same as in Example 1;

[0051] The preparation method of the organic fertilizer in this comparative example is the same as that in Example 1, except that lignin and starch are not added.

[0052] Performance testing

[0053] 1. Viable bacteria count / strain survival rate test

[0054] Referring to the microbial detection method (GB 20287-2006), the test steps for viable bacteria count and strain survival rate are as follows: Take 10g each of the organic fertilizer finished products (stored for 0 days), 30 days, and 60 days of storage from Examples 1-3 and Comparative Examples 1-2, add 90mL of sterile physiological saline, and place in a shaker at 200rpm for 30min to prepare 10 -1 Diluent was used to serially dilute the sample to 10 μL using a gradient dilution method. -7 Concentration gradient, selected as 10 -5 10 -6 10 -7 Three dilutions were used, with 0.1 mL of bacterial suspension evenly spread onto LB agar plates. Each dilution was set up in triplicate. The plates were incubated at 37°C for 24 hours. The number of colonies on the plates was counted. The total number of viable bacteria in the sample was calculated using the formula: "Effective viable bacteria count (CFU / g) = average colony count × dilution factor × 10". At the same time, the number of viable individual bacteria of nitrogen-fixing bacteria and phosphate-solubilizing bacteria was counted separately using specific culture media (Ashbe nitrogen-free medium for nitrogen-fixing bacteria and Mongkina organic phosphorus medium for phosphate-solubilizing bacteria). The survival rate of the strains was calculated as (number of viable bacteria after 30 days / 60 days of storage ÷ number of viable bacteria after 0 days of storage) × 100%. The final result was the average of the three parallel experiments.

[0055] Table 1. Test data on viable bacterial count / strain survival rate of different samples.

[0056]

[0057] The total number of viable bacteria and the number of viable nitrogen-fixing and phosphate-solubilizing bacteria in Examples 1-3 of this invention after 30 and 60 days of storage were significantly higher than those in Comparative Examples 1 and 2. The survival rate of the strain in Example 1 after 60 days reached 75.0%, while that in Comparative Example 2 without coating protection was only 14.3%. This indicates that phosphoric acid activation and lignin-starch coating structure can significantly improve the survival stability and long-term storage capacity of microorganisms in fertilizer systems.

[0058] 2. Nitrogen fixation capacity test

[0059] Nitrogen fixation capacity was determined using the acetylene reduction method (ARA). The experimental steps were as follows: 5g of each of the organic fertilizer samples from Examples 1-3 and Comparative Examples 1-2 were weighed and placed in 50mL serum bottles. 20mL of sterile nitrogen-free culture medium (Assab medium) was added. After sealing, 10% of the air in the bottle was evacuated using a syringe, and an equal volume of acetylene gas was injected. The serum bottles were then incubated in a constant temperature shaking incubator at 28℃ and 150rpm for 48h. After incubation, the amount of ethylene produced in the bottle was determined using gas chromatography (Porapak Q column, column temperature 60℃, detector temperature 120℃, injection port temperature 100℃, carrier gas nitrogen). A blank control group (containing only nitrogen-free culture medium and acetylene, without organic fertilizer samples) was also set up. The nitrogenase activity of the samples was calculated using the ethylene standard curve, expressed as the number of micromoles (μmol C2H4·g) of ethylene produced per gram of organic fertilizer per hour. -1 ·h -1 () indicates nitrogen fixation capacity. Three parallel experiments were set up for each sample, and the final result was the average value.

[0060] Table 2. Test data on nitrogen fixation capacity of different samples

[0061]

[0062] The nitrogenase activities of Examples 1-3 were all significantly higher than those of the comparative examples, with Example 1 showing the highest nitrogenase activity (1.86 μmol C2H4·g). -1 ·h -1 The lack of phosphate activation in Comparative Example 1 and the lack of coating protection in Comparative Example 2 resulted in a significant decrease in the activity of nitrogen-fixing bacteria, indicating that the carrier modification and strain protection strategy of the present invention can significantly improve the nitrogen fixation efficiency of nitrogen-fixing bacteria.

[0063] 3. Phosphorus solubilization capacity test

[0064] The phosphorus solubilization capacity was determined using the molybdenum-antimony colorimetric method. The experimental steps were as follows: 2g of each of the organic fertilizer samples from Examples 1-3 and Comparative Examples 1-2 were weighed and placed in 250mL Erlenmeyer flasks. 100mL of 0.5mol / L hydrochloric acid solution was added, and the samples were extracted for 2 hours at 28℃ and 180rpm in a constant temperature shaking incubator. After extraction, the samples were filtered through quantitative filter paper, and 5mL of the filtrate was placed in a 50mL volumetric flask. 10mL of molybdenum-antimony colorimetric reagent was added, and the solution was diluted to the mark with distilled water. After shaking well, the solution was incubated at 25℃ in the dark for 30 minutes. A blank control group (containing only 0.5mol / L hydrochloric acid solution and colorimetric reagent, without organic fertilizer sample) was set up. The absorbance was measured at 700nm using a UV-Vis spectrophotometer. The content of available phosphorus (calculated as P2O5) in the samples was calculated using the phosphorus standard curve. The effective phosphorus content (mg P2O5·kg) was expressed as the number of milligrams of available phosphorus per kilogram of organic fertilizer. -1() indicates phosphorus solubility. Three parallel experiments were set up for each sample, and the final result was the average value.

[0065] Table 3. Data on phosphorus solubilization capacity of different samples

[0066]

[0067] The available phosphorus content of Examples 1-3 is superior to that of Comparative Examples 1 and 2, with Example 1 having an available phosphorus content of 218.6 mg P₂O₅·kg⁻¹. -1 It was much higher than that of the uncoated comparative example 2 (76.5 mg P2O5·kg⁻¹). -1 This indicates that the modified biochar carrier and coating structure can effectively protect phosphate-solubilizing bacteria and enhance their phosphate-solubilizing activity and nutrient release capacity.

[0068] 4. Fertilizer nutrient content test

[0069] Referring to the methods specified in the national standard for organic fertilizer NY / T 525-2021, the fertilizer nutrient content testing steps are as follows: 2g of each of the organic fertilizer samples from Examples 1-3 and Comparative Examples 1-2 (dried to constant weight at 105℃ and pulverized through a 2mm sieve) were weighed, and the organic matter content was determined using the potassium dichromate oxidation-external heating method. After digesting the samples with sulfuric acid-hydrogen peroxide, the total nitrogen content was determined using the Kjeldahl method, the total phosphorus content was determined using the molybdenum-antimony colorimetric method, and the total potassium content was determined using the flame photometry method. The total nutrient content (N+P2O5+K2O) was calculated. 5g of the sample was dried to determine the moisture content, and another 10g of the sample was added to 100mL of distilled water and shaken for 30min. The pH value of the extract was then measured using a pH meter. Three parallel experiments were set up for all indicators, and the final result was the average value.

[0070] Table 4. Nutrient content test data of different fertilizer samples

[0071]

[0072] The organic matter and total nutrient content of Examples 1-3 were higher than those of Comparative Examples 1 and 2, and the pH value was within the suitable range of 6.7-6.9, which meets the requirements of the NY / T 525-2021 organic fertilizer standard. This indicates that phosphoric acid activation treatment can optimize the adsorption and fertilizer retention performance of biochar and improve the overall nutrient level of fertilizer.

[0073] 5. Specific surface area test

[0074] Approximately 0.2 g of biochar carrier samples from Examples 1-3 and Comparative Examples 1-2 were taken and vacuum degassed at 150 °C for 6 h to remove adsorbed impurities. After cooling, the samples were tested using a fully automated specific surface area and porosity analyzer. The nitrogen adsorption-desorption isotherm was measured at 77 K liquid nitrogen temperature. The specific surface area was calculated using the BET model, and the average pore size and total pore volume were calculated using the BJH model. Each sample was tested three times, and the average value was taken as the final result.

[0075] Table 5. Specific surface area test data for different samples

[0076]

[0077] The specific surface area and total pore volume of Examples 1-3 were significantly greater than those of Comparative Examples 1 and 2, with Example 1 having a specific surface area of ​​286.3 m². 2 / g, while the comparative example 1 without phosphate activation had a value of only 164.2m. 2 / g, demonstrating that phosphoric acid activation can effectively construct a well-developed porous structure, providing sufficient sites for microbial loading and nutrient adsorption.

[0078] 6. Pot experiment

[0079] Wheat seedlings with uniform growth (three-leaf and one-heart stage) were transplanted into pots with a diameter of 20cm and a height of 25cm. Each pot contained 5kg of air-dried soil that had passed through a 2mm sieve. A blank control group (without organic fertilizer), Example 1-3 groups, and Comparative Example 1-2 groups were set up, with 10 pots replicated in each group. Each fertilization group was fertilized once with 5g of organic fertilizer per kilogram of soil as basal fertilizer, which was evenly mixed into the soil before transplanting the seedlings. The blank control group was transplanted without fertilization. During the experiment, the soil moisture content was uniformly controlled at 60%-70% of field capacity. After 60 days of cultivation in a greenhouse with natural light, the plant height and aboveground dry weight of wheat plants were measured. At the same time, the aboveground parts of the plants were collected, dried, crushed, and digested. The total nitrogen content was determined by the Kjeldahl method, and the total phosphorus content was determined by the molybdenum-antimony colorimetric method. The average values ​​of each group were calculated, and the differences were analyzed for significance.

[0080] Table 6. Data from potted plant experiments with different samples

[0081]

[0082] The wheat plant height, aboveground dry weight, and total nitrogen content of the treated plants in Examples 1-3 were all higher than those of the blank control, Comparative Example 1, and Comparative Example 2. Example 1 showed the best growth-promoting effect, indicating that the organic fertilizer of the present invention can effectively supply nitrogen nutrients and promote crop growth. Its comprehensive application effect is significantly better than that of the unmodified or uncoated comparative samples.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-efficiency modified biochar-based organic fertilizer, characterized in that, The organic fertilizer is prepared from the following raw materials in parts by weight: 50-80 parts corn cob-based biochar, 6-12 parts lignin, 2-4 parts starch, 5-15 parts micron-sized straw biochar, and 10-25 parts phosphate-solubilizing bacteria-nitrogen-fixing bacteria compound inoculant. The corn cob-based biochar is pre-activated with phosphoric acid, neutralized with pH and washed, and then coated with lignin-starch to form a modified biochar carrier. The lignin and starch are compounded at a mass ratio of 3:1 and cross-linked to form a porous coating layer. The compound microbial agent and micron-sized straw biochar form a microbial-char buffer complex and are loaded on the surface and pores of the modified biochar carrier.

2. The high-efficiency modified biochar-based organic fertilizer according to claim 1, characterized in that, The phosphoric acid activation process uses a 5% (w / w) aqueous solution of phosphoric acid, and after activation, it is neutralized to pH 6.5-7.0 using a 1% (w / w) sodium bicarbonate solution.

3. The high-efficiency modified biochar-based organic fertilizer according to claim 1, characterized in that, The micron-sized straw biochar has a particle size of 5-10 μm, and the concentration of live bacteria in the compound microbial agent is 1.0 × 10⁻⁶. 8 -5.0×10 9 CFU / mL.

4. The high-efficiency modified biochar-based organic fertilizer according to claim 1, characterized in that, The total amount of lignin and starch added accounts for 15%-20% of the mass of corn cob-based biochar.

5. A method for preparing a high-efficiency modified biochar-based organic fertilizer, used to prepare the high-efficiency modified biochar-based organic fertilizer according to any one of claims 1-4, characterized in that, The specific preparation method is as follows: S1. Add 5% (w / w) phosphoric acid aqueous solution to corn cob-based biochar at a liquid-to-solid ratio of 10:1 (mL / g), activate at 40-50℃ and 100-200rpm for 1-1.5h, then adjust the pH of the system to 6.5-7.0 with 1% (w / w) sodium bicarbonate solution, filter, wash and dry for later use. S2. Add lignin and starch to the biochar treated in step S1 at a mass ratio of 3:1, mix evenly, and then crosslink the mixture at 35-40℃ and 150-250rpm for 2-3 hours to form a porous coating layer, thus obtaining the modified biochar carrier. S3. Add micron-sized straw biochar to the composite bacterial solution at a solid-liquid ratio of 1:5 (g / mL), and pre-adsorb at a constant temperature of 25℃ and 80-120rpm for 1 hour to form a bacterial-char buffer complex. S4. Mix the modified biochar carrier with the bacteria-char buffer complex at a mass ratio of 3:1, dry at 30-40℃ and vacuum degree of 0.06-0.08MPa until the moisture content is ≤10%, and then sieve to obtain the finished product.

6. The method for preparing a high-efficiency modified biochar-based organic fertilizer according to claim 5, characterized in that, The drying temperature in step S1 is 50-70℃, and the drying time is 2-3 hours.

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