Humic acid polypeptide double-effect compound fertilizer based on microbial fermentation and preparation method thereof

Abstract

The invention discloses a humic acid polypeptide double-effect compound fertilizer based on microbial fermentation and a preparation method thereof, and relates to the technical field of agricultural fertilizers. The fertilizer comprises the following components in percentage by mass: 10-30% of humic acid, 5-20% of polypeptide, 30-50% of nitrogen phosphorus and potassium elements, 2-5% of medium trace elements, 1-3% of a microbial agent and the balance of an auxiliary agent. Functional synergy of the humic acid and the polypeptide is realized through microbial fermentation, effective addition and long-term stability of the polypeptide in the fertilizer are ensured, and the composite technology not only retains respective advantages of the humic acid and the polypeptide, but also exerts the synergistic effect of the humic acid and the polypeptide, so that the comprehensive effect of the fertilizer is improved. According to the invention, the humic acid is combined with various nutrient elements to form the compound fertilizer which has the biological activity of the humic acid and is rich in various nutrient elements, and the fertilizer can be quickly dissolved in soil and directly absorbed and utilized by crop roots, so that the utilization rate of the fertilizer is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural fertilizers, in particular to a humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation and a preparation method thereof. Background Art

[0002] The current state of agricultural compound fertilizers is characterized by strong industry demand and continued market growth, but it also faces pressure from transformation and upgrading, as well as environmental protection requirements. In recent years, with the development of the agricultural industry and adjustments to planting structures, the product structure and formulation of compound fertilizers have also been evolving. The scale of my country's compound fertilizer market continues to grow, and functional compound fertilizers have begun to be gradually accepted by a large number of professional growers in China.

[0003] Fertilizers containing soluble humic acid, such as water-soluble humic acid fertilizers, are extracted from raw materials such as peat, lignite, and weathered coal through a complex process. These fertilizers dissolve rapidly in water and are efficiently absorbed and utilized by plant roots or leaves. Humic acid has multiple benefits, including improving soil structure, enhancing its ability to retain water and fertilizer, promoting plant root growth, enhancing photosynthesis, and improving crop resistance to stress. Furthermore, humic acid can combine with various nutrients to form complexes that are easily absorbed by plants, thereby increasing nutrient utilization.

[0004] Polypeptide compound fertilizers are based on chemical fertilizers but incorporate metalloproteinases and precious trace elements such as rare earth elements, which are crucial for crops. These fertilizers can meet the growth needs of a wide variety of crops, improving fertilizer utilization, improving soil quality, boosting crop immunity, and promoting crop development and growth. Polypeptide compound fertilizers also regulate nutrient absorption, effectively preventing excessive crop growth, regulating the balance between vegetative and reproductive growth, and preventing various physiological diseases caused by calcium deficiency.

[0005] In the existing technology, traditional fertilizers have problems such as low utilization rate and easy environmental pollution. The interaction mechanism between humic acid and polypeptides in compound fertilizers is still unclear, and the synergistic effect of the two has not been fully explored. Therefore, we proposed a humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation and its preparation method to solve the above problems.

[0006] The above information disclosed in this background technology is only for enhancing understanding of the background technology of the present invention and therefore it may contain information that does not constitute the prior art that is already known to a person of ordinary skill in the art. Summary of the Invention

[0007] The purpose of the present invention is to provide a humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation and a preparation method thereof, so as to solve the problems raised by the above background technology.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a humic acid and polypeptide dual-effect compound fertilizer based on microbial fermentation, comprising the following components in mass percentage: 10% to 30% humic acid, 5% to 20% polypeptide, 30% to 50% nitrogen, phosphorus and potassium, 2% to 5% trace elements, 1% to 3% microbial agent, and the remainder auxiliary agent.

[0009] Preferably, the humic acid is a highly active humic acid extracted from weathered coal, with a purity of ≥85%.

[0010] Preferably, the polypeptide is derived from soybean meal enzymatic hydrolysate and has a molecular weight of 500 to 1500 Da.

[0011] Preferably, the nitrogen, phosphorus and potassium elements are compounded by urea, potassium dihydrogen phosphate and potassium sulfate in proportion, wherein N:P2O5:K2O=3:3:2.

[0012] Preferably, the trace elements include chelated compounds of calcium, magnesium, zinc and boron.

[0013] Preferably, the microbial agent is a composite flora of Bacillus subtilis and Bacillus amyloliquefaciens, with a viable cell count of ≥ 2×10 9 CFU / g.

[0014] Preferably, the auxiliary agent includes a dispersant, a binder and a pH adjuster.

[0015] The present invention also provides a method for preparing the above-mentioned humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation, comprising the following steps:

[0016] Step 1. Humic acid pretreatment: preferably weathered coal is crushed and passed through a 100-mesh sieve, a 5% potassium hydroxide solution (solid-to-liquid ratio of 1:8) is added, and the mixture is stirred at 85°C for 2 hours. The supernatant is centrifuged and the pH is adjusted to 2.0 with hydrochloric acid to precipitate humic acid. After drying, a humic acid powder with a purity of ≥85% is obtained;

[0017] Step 2. Preparation of polypeptide: After crushing soybean meal, add 3 times its weight of water, adjust the pH to 7.0, add 1.5% composite protease, and hydrolyze at 50℃ for 4 hours. After inactivating the enzyme, centrifuge and collect the supernatant, spray dry to obtain polypeptide powder;

[0018] Step 3. Activation of the bacterial strains: Inoculate Bacillus subtilis and Bacillus amyloliquefaciens into liquid culture medium at a ratio of 1:1 and incubate at 37°C for 24 hours to obtain a seed solution (viable bacterial count ≥ 5 × 10^8 CFU / mL);

[0019] Step 4. Solid-state fermentation compounding: the humic acid powder of step 1 and the polypeptide powder of step 2 are mixed in a mass ratio of 2:1, 10% wheat bran is added as a carrier, 20% seed liquid is inoculated, the moisture content is adjusted to 45%, and fermented at 35° C. for 72 hours, turning the compost every 12 hours, and the pH at the fermentation end point is 6.5-7.0;

[0020] Step 5. Fertilizer compounding: The fermentation product of step 4 is mixed with nitrogen, phosphorus, potassium raw materials, and trace elements in proportion, 1.5% to 2.5% carboxymethyl cellulose is added as a binder, and 0.5% to 2% dispersant is added, and the pH of the system is adjusted to 6.8 to 7.2;

[0021] Step 6. Granulation and drying: The compounded fertilizer is extruded into granules with a diameter of 2 to 4 mm using a twin-screw extruder, and then dried in a fluidized bed at 50°C to a moisture content of ≤5%;

[0022] Step 7. Post-processing: Encapsulate the microbial agent in trehalose-starch microcapsules, mix the dried particles with the microbial agent to avoid high-temperature inactivation, and finally seal and package the product.

[0023] Preferably, in step 3, the liquid culture medium contains 20 g / L glucose and 10 g / L peptone.

[0024] Preferably, in step 6, the extrusion granulation temperature is ≤ 60°C.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention realizes the functional synergy of humic acid and polypeptide through microbial fermentation, ensuring the effective addition and long-term stability of polypeptide in fertilizer. This composite technology not only retains the respective advantages of humic acid and polypeptide, but also exerts their synergistic effect, thereby improving the comprehensive effect of fertilizer.

[0027] (2) The present invention combines humic acid with a variety of nutrients to form a composite fertilizer that has both the biological activity of humic acid and is rich in a variety of nutrients. This fertilizer can dissolve quickly in the soil and be directly absorbed and utilized by crop roots, greatly improving the utilization rate of the fertilizer.

[0028] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the preparation process of the present invention. DETAILED DESCRIPTION

[0030] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] The humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation includes the following components in percentage by mass:

[0032] Humic acid 10% to 30%, preferably highly active humic acid extracted from weathered coal, with a purity of ≥85%;

[0033] 5% to 20% polypeptide, derived from soybean meal enzymatic hydrolysate, with a molecular weight of 500 to 1500 Da;

[0034] 30% to 50% of nitrogen, phosphorus and potassium elements, which are compounded by urea, potassium dihydrogen phosphate and potassium sulfate in proportion, wherein N:P2O5:K2O=3:3:2;

[0035] 2% to 5% of trace elements, including chelated compounds of calcium, magnesium, zinc, and boron;

[0036] Microbial agent 1% to 3%, a composite flora of Bacillus subtilis and Bacillus amyloliquefaciens, with a viable count of ≥ 2 × 10 9 CFU / g;

[0037] The remaining auxiliary agents include dispersants, binders and pH regulators; the dispersant can be sodium lignin sulfonate or sodium polyacrylate; the binder can be carboxymethyl cellulose; and the pH regulator can be potassium hydroxide or citric acid.

[0038] The preparation method of humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation comprises the following steps:

[0039] Step 1. Humic acid pretreatment: preferably weathered coal is crushed and passed through a 100-mesh sieve, a 5% potassium hydroxide solution (solid-to-liquid ratio of 1:8) is added, and the mixture is stirred at 85°C for 2 hours. The supernatant is centrifuged and the pH is adjusted to 2.0 with hydrochloric acid to precipitate humic acid. After drying, a humic acid powder with a purity of ≥85% is obtained;

[0040] Step 2. Preparation of polypeptide: After crushing soybean meal, add 3 times its weight of water, adjust the pH to 7.0, add 1.5% composite protease, and hydrolyze at 50℃ for 4 hours. After inactivating the enzyme, centrifuge and collect the supernatant, spray dry to obtain polypeptide powder;

[0041] Step 3. Activation of bacteria: Inoculate Bacillus subtilis and Bacillus amyloliquefaciens into liquid culture medium (containing 20 g / L glucose and 10 g / L peptone) at a ratio of 1:1, and culture at 37°C for 24 hours to obtain seed solution (viable bacteria count ≥ 5 × 10 8 CFU / mL);

[0042] Step 4. Solid-state fermentation compounding: the humic acid powder of step 1 and the polypeptide powder of step 2 are mixed in a mass ratio of 2:1, 10% wheat bran is added as a carrier, 20% seed liquid is inoculated, the moisture content is adjusted to 45%, and fermented at 35° C. for 72 hours, turning the compost every 12 hours, and the pH at the fermentation end point is 6.5-7.0;

[0043] Step 5. Fertilizer compounding: The fermentation product of step 4 is mixed with nitrogen, phosphorus, potassium raw materials, and trace elements in proportion, 1.5% to 2.5% carboxymethyl cellulose is added as a binder, and 0.5% to 2% dispersant is added, and the pH of the system is adjusted to 6.8 to 7.2;

[0044] Step 6. Granulation and drying: The compounded fertilizer is extruded into granules with a diameter of 2 to 4 mm using a twin-screw extruder at a temperature of ≤ 60°C, and then fluidized bed dried at 50°C to a moisture content of ≤ 5%;

[0045] Step 7. Post-processing: Encapsulate the microbial agent in trehalose-starch microcapsules, mix the dried particles with the microbial agent to avoid high-temperature inactivation, and finally seal and package the product.

[0046] Experiment 1: Optimization of the ratio of humic acid to polypeptide

[0047] Example 1

[0048] Humic acid 20%, polypeptide 10%, nitrogen, phosphorus and potassium 40%, trace elements 3%, microbial agents 2%, auxiliary agents 25%, including dispersants, binders and pH regulators; the dispersant is sodium lignin sulfonate; the binder is carboxymethyl cellulose; the pH regulator is potassium hydroxide.

[0049] Step 1. Humic acid pretreatment: preferably weathered coal is crushed and passed through a 100-mesh sieve, a 5% potassium hydroxide solution (solid-to-liquid ratio of 1:8) is added, and the mixture is stirred at 85°C for 2 hours. The supernatant is centrifuged and the pH is adjusted to 2.0 with hydrochloric acid to precipitate humic acid. After drying, a humic acid powder with a purity of ≥85% is obtained;

[0050] Step 2. Preparation of polypeptide: After crushing soybean meal, add 3 times its weight of water, adjust the pH to 7.0, add 1.5% composite protease, and hydrolyze at 50℃ for 4 hours. After inactivating the enzyme, centrifuge and collect the supernatant, spray dry to obtain polypeptide powder;

[0051] Step 3. Activation of bacteria: Inoculate Bacillus subtilis and Bacillus amyloliquefaciens into liquid culture medium (containing 20 g / L glucose and 10 g / L peptone) at a ratio of 1:1, and culture at 37°C for 24 hours to obtain seed solution (viable bacteria count ≥ 5 × 10 8 CFU / mL);

[0052] Step 4. Solid-state fermentation compounding: the humic acid powder of step 1 and the polypeptide powder of step 2 are mixed in a mass ratio of 2:1, 10% wheat bran is added as a carrier, 20% seed liquid is inoculated, the moisture content is adjusted to 45%, and fermented at 35° C. for 72 hours, during which the compost is turned every 12 hours. The pH at the fermentation end point is 6.8;

[0053] Step 5. Fertilizer compounding: The fermentation product of step 4 is mixed with nitrogen, phosphorus, potassium raw materials, and trace elements in proportion, 1.5% to 2.5% carboxymethyl cellulose is added as a binder, and 0.5% to 2% dispersant is added, and the pH of the system is adjusted to 6.8 to 7.2;

[0054] Step 6. Granulation and drying: The compounded fertilizer is extruded into granules with a diameter of 2 to 4 mm using a twin-screw extruder at a temperature of ≤ 60°C, and then fluidized bed dried at 50°C to a moisture content of ≤ 5%;

[0055] Step 7. Post-processing: Encapsulate the microbial agent in trehalose-starch microcapsules, mix the dried particles with the microbial agent to avoid high-temperature inactivation, and finally seal and package the product.

[0056] Example 2

[0057] The difference from Example 1 is: 15% humic acid, 15% polypeptide, 40% nitrogen, phosphorus and potassium elements, 3% trace elements, 2% microbial agent, and 25% auxiliary agent.

[0058] In step 4, the humic acid powder of step 1 and the polypeptide powder of step 2 are mixed in a mass ratio of 1:1.

[0059] Example 3

[0060] The difference from Example 1 is that: humic acid 24%, polypeptide 8%, nitrogen, phosphorus and potassium elements 40%, trace elements 3%, microbial agent 2%, and auxiliary agent 23%.

[0061] In step 4, the humic acid powder of step 1 and the polypeptide powder of step 2 are mixed in a mass ratio of 3:1.

[0062] Evaluation Metrics:

[0063] Soil improvement: organic matter content, cation exchange capacity (CEC); organic matter content was determined using the potassium dichromate oxidation method (GB9834-88); cation exchange capacity was determined using the ammonium acetate exchange method (NY / T 1121.5-2006);

[0064] Fertilizer efficiency: crop yield; field measurement, 3 replicates and average;

[0065] Microbial activity: the number of phosphate-solubilizing bacteria and nitrogen-fixing bacteria in the soil; determined by the selective culture medium plate count method.

[0066] The results are shown in Table 1 below.

[0067] Table 1. Results of each evaluation index in Experiment 1

[0068]

[0069] Result analysis: In Example 1, soil organic matter increased by 25%, crop yield was the highest, and the synergy between soil improvement and fertilizer efficiency was the best.

[0070] Experiment 2: Fermentation temperature and humidity optimization

[0071] Example 4

[0072] The difference from Example 1 is that: in step 4, the water content is adjusted to 30%, and fermentation is carried out at 30° C. for 72 hours.

[0073] Example 5

[0074] The difference from Example 1 is that: in step 4, the water content is adjusted to 60%, and fermentation is carried out at 40° C. for 60 hours.

[0075] Evaluation Metrics:

[0076] Fermentation efficiency: humic acid-polypeptide complex formation rate; infrared spectroscopy quantitative analysis of humic acid-polypeptide characteristic peak area ratio;

[0077] Bacterial activity: viable bacterial count (CFU / g) in fermentation product; plate spread method, LB medium, culture at 37°C for 24 h;

[0078] Functional substance retention rate: peptide molecular weight distribution; HPLC molecular weight distribution analysis, calculation of the proportion of undegraded peptides.

[0079] The results are shown in Table 2 below.

[0080] Table 2. Results of evaluation indicators in Experiment 2

[0081] project Complex formation rate (%) <![CDATA[Viable cell count (×10 9 CFU / g)]]> Peptide retention rate (%) Fermentation product enzyme activity (U / g) Example 4 78±4 0.8±0.1 85±3 120±10 Example 1 92±3 1.2±0.2 95±2 185±15 Example 5 65±5 0.5±0.1 72±4 90±8

[0082] Result analysis: In Example 1 (35°C / 45%), the humic acid-polypeptide complex formation rate reached 92%, and the number of viable bacteria was ≥1×109 CFU / g, indicating that 35℃ / 45% is the optimal growth condition for the bacterial flora, and the bacterial flora metabolic activity and complex formation rate are the highest.

[0083] Experiment 3: Optimization of pH control at the fermentation endpoint

[0084] Example 6

[0085] The difference from Example 1 is that the pH at the fermentation end point in step 4 is 6.0.

[0086] Example 7

[0087] The difference from Example 1 is that the pH at the fermentation end point in step 4 is 7.5.

[0088] Evaluation Metrics:

[0089] Product stability: The morphology of humic acid and polypeptide binding; observed by SEM electron microscopy, 5-point scale: 1 = loose, 5 = dense;

[0090] Microbial adaptability: The content of organic acids in the fermentation broth as metabolites of the microbial community; the total content of citric acid, oxalic acid, etc. is determined by high performance liquid chromatography;

[0091] Durability of fertilizer effect: nutrient release rate in field trials; simulated soil extraction method to measure nitrogen, phosphorus and potassium release rate.

[0092] The results are shown in Table 3 below.

[0093] Table 3. Results of evaluation indicators in Experiment 3

[0094]

[0095]

[0096] Result analysis: In Example 1 (pH 6.8), humic acid and polypeptide were tightly bound, the organic acid secretion was the highest, and the pH was close to the optimal pH for bacterial metabolism. Organic acid secretion promoted the sustained release of nutrients, the sustained release was the best, and the bacterial adaptability and product stability were the best.

[0097] Experiment 4: Optimization of granulation drying temperature

[0098] Example 8

[0099] The difference from Example 1 is that step 6 is fluidized bed drying at 40°C.

[0100] Example 9

[0101] The difference from Example 1 is that step 6 is fluidized bed drying at 60°C.

[0102] Evaluation Metrics:

[0103] Physical properties of particles: hardness, disintegration rate; particle hardness was measured using a universal material testing machine in accordance with GB / T15496-2008 standard; disintegration rate simulated soil moist conditions, and the complete disintegration time was recorded;

[0104] Microbial survival rate: viable bacterial count (CFU / g) of the embedded microbial agent, plate count of the embedded microbial agent, and comparison of viable bacterial counts before and after drying;

[0105] Retention of heat-sensitive substances: The degradation rate of peptides was quantitatively analyzed by SDS-PAGE electrophoresis.

[0106] The results are shown in Table 4 below.

[0107] Table 4. Results of evaluation indicators in test 4

[0108] project <![CDATA[Particle hardness (N / mm 2 )]]> Disintegration rate (min) Live bacteria survival rate (%) Peptide degradation rate (%) Example 8 15±2 >60 98±1 2±0.5 Example 1 20±3 45±5 92±2 2±0.5 Example 9 25±4 20±3 75±5 15±2

[0109] Result analysis: In Example 1 (50° C.), the particle disintegration rate was moderate, the microbial survival rate was ≥90%, the polypeptide degradation rate was <5%, and the balance between the particle physical properties and the microbial survival rate was optimal, avoiding high temperature damage to the polypeptide structure.

[0110] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0111] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation, characterized in that: The invention comprises the following components in percentage by mass: 10% to 30% of humic acid, 5% to 20% of polypeptide, 30% to 50% of nitrogen, phosphorus and potassium elements, 2% to 5% of medium and trace elements, 1% to 3% of microbial agent and the remainder of auxiliary agent.

2. The humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation according to claim 1, characterized in that: The humic acid is preferably high-activity humic acid extracted from weathered coal, with a purity of ≥85%.

3. The humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation according to claim 1, characterized in that: The polypeptide is derived from soybean meal enzymatic hydrolysis products and has a molecular weight of 500 to 1500 Da.

4. The humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation according to claim 1, characterized in that: The nitrogen, phosphorus and potassium elements are compounded by urea, potassium dihydrogen phosphate and potassium sulfate in proportion, wherein N:P2O5:K2O=3:3:

2.

5. The humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation according to claim 1, characterized in that: The trace elements include chelated compounds of calcium, magnesium, zinc and boron.

6. The humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation according to claim 1, characterized in that: The microbial agent is a composite flora of Bacillus subtilis and Bacillus amyloliquefaciens, with a viable bacterial count of ≥2×10 9 CFU / g.

7. The humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation according to claim 1, characterized in that: The auxiliary agents include dispersants, binders and pH regulators.

8. The method for preparing the humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation according to any one of claims 1 to 7, characterized in that: The steps include: Step 1. Humic acid pretreatment: preferably weathered coal is crushed and passed through a 100-mesh sieve, a 5% potassium hydroxide solution is added, and the mixture is stirred at 85°C for 2 hours. The supernatant is centrifuged and the pH is adjusted to 2.0 with hydrochloric acid to precipitate humic acid. Humic acid powder with a purity of ≥85% is obtained after drying. Step 2. Preparation of polypeptide: After crushing soybean meal, add 3 times its weight of water, adjust the pH to 7.0, add 1.5% composite protease, and hydrolyze at 50℃ for 4 hours. After inactivating the enzyme, centrifuge and collect the supernatant, spray dry to obtain polypeptide powder; Step 3. Activation of the bacterial strains: inoculate Bacillus subtilis and Bacillus amyloliquefaciens into liquid culture medium at a ratio of 1:1, and culture at 37°C for 24 hours to obtain seed solution; Step 4. Solid-state fermentation compounding: the humic acid powder of step 1 and the polypeptide powder of step 2 are mixed in a mass ratio of 2:1, 10% wheat bran is added as a carrier, 20% seed liquid is inoculated, the moisture content is adjusted to 45%, and fermented at 35° C. for 72 hours, turning the compost every 12 hours, and the pH at the fermentation end point is 6.5-7.0; Step 5. Fertilizer compounding: The fermentation product of step 4 is mixed with nitrogen, phosphorus, potassium raw materials, and trace elements in proportion, 1.5% to 2.5% carboxymethyl cellulose is added as a binder, and 0.5% to 2% dispersant is added, and the pH of the system is adjusted to 6.8 to 7.2; Step 6. Granulation and drying: The compounded fertilizer is extruded into granules with a diameter of 2 to 4 mm using a twin-screw extruder, and then dried in a fluidized bed at 50°C to a moisture content of ≤5%; Step 7. Post-processing: Encapsulate the microbial agent in trehalose-starch microcapsules, mix the dried particles with the microbial agent to avoid high-temperature inactivation, and finally seal and package the product.

9. The method for preparing the humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation according to claim 8, characterized in that: In step 3, the liquid culture medium contains 20 g / L glucose and 10 g / L peptone.

10. The method for preparing the humic acid polypeptide dual-effect compound fertilizer based on microbial fermentation according to claim 8, characterized in that: In step 6, the extrusion granulation temperature is ≤ 60°C.

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