Multifunctional biological source liquid medical fertilizer and preparation method thereof
By extracting and compounding multiple active ingredients from agricultural waste, a multifunctional bio-based liquid fertilizer was prepared, solving the problems of low resource utilization and environmental pollution. This achieved a highly efficient and environmentally friendly compounding of fertilizer ingredients, improving the control effect and yield capacity of crops.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUNAN SHENLONG TECHNOLOGY CO LTD
- Filing Date
- 2026-02-06
- Publication Date
- 2026-05-12
Abstract
Description
Technical Field
[0001] This invention belongs to the field of fertilizer technology, specifically a multifunctional bio-based liquid fertilizer and its preparation method. Background Technology
[0002] With the advancement of sustainable agricultural development, the excessive use of traditional fertilizers and pesticides has led to increasingly prominent problems such as soil degradation, environmental pollution, and agricultural product safety, necessitating the development of multifunctional green fertilizer and pesticide products that combine nutrient supply and ecological safety. Currently, the resource utilization of agricultural waste has become a research hotspot. For example, shrimp shells are rich in protein and chitin, but existing extraction processes often target only single components, resulting in low resource utilization and the generation of acidic and alkaline wastewater that can easily cause secondary pollution. Meanwhile, while the technology for combining biostimulants and biopesticides has been explored, each component often relies on independent sources, leading to high production costs and a lack of systematic synergistic design. Furthermore, the recycling technology for production wastewater is still immature, and the treatment of large amounts of acidic and alkaline wastewater increases the environmental burden and production costs. Therefore, how to achieve high-value conversion of all components of agricultural waste through integrated processes and recycle wastewater for the extraction and compounding of active ingredients, developing efficient and environmentally friendly multifunctional liquid fertilizers, has become a key issue that urgently needs to be addressed in the field of agricultural technology. Summary of the Invention
[0003] To address the aforementioned technical problems, this invention provides a method for preparing a multifunctional bio-based liquid fertilizer, comprising the following steps: S1. Mix shrimp shell powder and dilute nitric acid and stir. After solid-liquid separation, a first precipitate and a first liquid are obtained. The first precipitate is washed with deionized water. Then, the washed first precipitate is mixed with ethanol and soaked. After drying, decalcified and degreased shrimp shell powder is obtained. The first liquid and washing water are recovered and mixed to obtain residual nitric acid liquid. S2. The decalcified and defatted shrimp shell powder is enzymatically hydrolyzed using a compound protease, and the solid-liquid separation yields an amino acid solution and chitin residue. S3. The chitin residue and potassium hydroxide are mixed and reacted, and the solid and liquid are separated to obtain a second precipitate and a second liquid. The second precipitate is washed with deionized water and then dried to obtain chitosan residue. The second liquid and washing water are recovered and mixed to obtain potassium hydroxide residue. S4. The chitosan residue is enzymatically hydrolyzed using chitosan hydrolase, and the chitosan oligosaccharide solution is obtained by ultrafiltration membrane filtration. S5. The lignite is crushed, sieved, and dried to obtain lignite powder. The lignite powder and the potassium hydroxide residue are mixed and stirred. Solid-liquid separation is performed to obtain potassium humate crude solution. The nitric acid residue is added to it, stirred and filtered to obtain potassium humate precipitate and a third liquid. The pH of the third liquid is adjusted to 7.5~8.0 using the potassium hydroxide residue to obtain potassium humate pure solution. S6. Mix the amino acid solution, the chitosan oligosaccharide solution, and the potassium humate pure solution according to a preset ratio, add a buffer and stir evenly to obtain a premixed solution, then add abamectin microcapsules and surfactant, stir and filter to obtain a multifunctional bio-based liquid fertilizer.
[0004] Specifically, step S1 involves mixing the shrimp shell powder with 0.8-1.2 mol / L nitric acid at a solid-liquid ratio of 1 g: (12-15) mL and stirring for 1-1.5 h. After solid-liquid separation, the first precipitate and the first liquid are obtained. The first precipitate is washed with deionized water until the pH of the washing water is 6-6.5. Then, the washed first precipitate is mixed with 95 wt% ethanol at a solid-liquid ratio of 1 g: (8-10) mL and soaked for 1-1.5 h. After drying, the decalcified and degreased shrimp shell powder is obtained. The first liquid and the washing water are recovered and mixed to obtain the remaining nitric acid liquid. Specifically, step S2 involves mixing the decalcified and defatted shrimp shell powder with deionized water at a solid-liquid ratio of 1g:(20~25)mL, adjusting the pH to 7.5~8.2, then adding a complex protease equivalent to 0.7%~1.2% of the mass of the decalcified and defatted shrimp shell powder, and enzymatically hydrolyzing at 53~60℃ and a stirring speed of 200~220rpm for 7~9h, then heating to 85~90℃ and holding for 12~15min to inactivate the enzyme, and then centrifuging at 3000~3500rpm to obtain a supernatant and chitin residue. The supernatant is then concentrated to obtain the amino acid solution, wherein the concentration of free amino acids in the amino acid solution is greater than or equal to 100g / L. The complex protease is prepared by mixing alkaline protease and neutral protease at a mass ratio of 1:(1.2~1.5). Specifically, step S3 involves mixing the chitin residue and an 8.5-11 mol / L potassium hydroxide solution at a solid-liquid ratio of 1 g: (14-16) mL, reacting at 95-98°C for 4-5 hours, separating the solid and liquid to obtain the second precipitate and the second liquid, washing the second precipitate with deionized water until the pH of the washing water is 7.2-7.8, drying the second precipitate to obtain chitosan residue, recovering the second liquid and the washing water and mixing them to obtain potassium hydroxide residue. Specifically, step S4 involves mixing the chitosan residue and 1 wt% acetic acid solution at a solid-liquid ratio of 1 g: 20 mL and adjusting the pH to 5.0-5.5. Then, adding chitosan hydrolase with an activity of 1000-5000 U / g, equivalent to 1.0%-3.0% of the mass of the chitosan residue, and hydrolyzing at 48-52°C and 180-200 rpm for 5-6 hours. The enzyme is then inactivated by heating to 85°C and holding for 20 minutes. Finally, the mixture is filtered through a 5-10 kDa ultrafiltration membrane to obtain the chitosan oligosaccharide solution, wherein the chitosan oligosaccharide content of the solution is greater than or equal to 40 g / L.
[0005] Specifically, step S5 involves pulverizing and sieving the lignite, drying it at 105-110℃ for 2-2.5 hours to obtain lignite powder, mixing the lignite powder and the residual potassium hydroxide solution at a solid-liquid ratio of 1g:(5-15)mL, stirring at 80-85℃ for 2-2.5 hours, and centrifuging to obtain crude potassium humate solution; adjusting the pH of the crude potassium humate solution to 1.8-2.7 using the residual nitric acid solution, stirring and allowing it to stand, then filtering to obtain potassium humate precipitate and a third liquid; adjusting the pH of the third liquid to 7.5-8.0 using the residual potassium hydroxide solution, concentrating it to obtain pure potassium humate solution, wherein the fulvic acid content of the pure potassium humate solution is greater than or equal to 40g / L.
[0006] In step S6, mixing the amino acid solution, the chitosan oligosaccharide solution, and the potassium humate pure solution according to a preset ratio specifically involves mixing the amino acid solution, the chitosan oligosaccharide solution, and the potassium humate pure solution in a volume ratio of (10~20):(40~80):(40~80), and the buffer is a 0.3wt%~0.8wt% citric acid-sodium citrate buffer.
[0007] Step S6 further includes adding 1.0% to 5.0% of the avermectin microcapsules and 0.2% to 0.5% of the surfactant to the premixed solution. The avermectin microcapsules have a drug loading rate of greater than or equal to 70%, and the surfactant is composed of Tween 80 and Span 80 in a mass ratio of 2:1. To address the aforementioned technical problems, the present invention also provides a multifunctional bio-based liquid fertilizer, which is prepared by the above-mentioned method for preparing multifunctional bio-based liquid fertilizer.
[0008] This invention reduces acid and alkali emissions pollution and lowers costs through a closed-loop acid-base design. It improves the stability and activity of the compound by purifying potassium humate and enriches the nutritional functions of the fertilizer and pesticide through the utilization of by-products. Ultimately, it achieves a four-in-one effect of "nematode resistance, growth promotion, nutrient supplementation, and soil improvement". It achieves a high root-knot nematode inhibition rate and a high crop yield increase rate while being environmentally friendly and low-cost. Detailed Implementation
[0009] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0010] This invention provides a method for preparing a multifunctional bio-based liquid fertilizer, comprising the following steps: S1. Mix shrimp shell powder and dilute nitric acid and stir. After solid-liquid separation, a first precipitate and a first liquid are obtained. The first precipitate is washed with deionized water. Then, the washed first precipitate is mixed with ethanol and soaked. After drying, decalcified and degreased shrimp shell powder is obtained. The first liquid and washing water are recovered and mixed to obtain residual nitric acid liquid. Shrimp shell powder is obtained by washing fresh shrimp shells, drying them at 50-60℃ until the moisture content is less than or equal to 8%, crushing them, passing them through a 60-80 mesh sieve, and collecting the sieve-passing material.
[0011] S2. The decalcified and defatted shrimp shell powder is enzymatically hydrolyzed using a compound protease, and the solid-liquid separation yields an amino acid solution and chitin residue. S3. The chitin residue and potassium hydroxide are mixed and reacted, and the solid and liquid are separated to obtain a second precipitate and a second liquid. The second precipitate is washed with deionized water and then dried to obtain chitosan residue. The second liquid and washing water are recovered and mixed to obtain potassium hydroxide residue. The recovered nitric acid residue contains sufficient H2O. + It can meet the requirements for potassium humate precipitation, and the recovered potassium hydroxide residue contains sufficient OH-. - It can meet the needs of lignite treatment, pH adjustment and compound fine-tuning without the need for additional acid or alkali, which reduces pollution and lowers costs.
[0012] S4. The chitosan residue is enzymatically hydrolyzed using chitosan hydrolase, and the chitosan oligosaccharide solution is obtained by ultrafiltration membrane filtration. S5. The lignite is crushed, sieved, and dried to obtain lignite powder. The lignite powder and the potassium hydroxide residue are mixed and stirred. Solid-liquid separation is performed to obtain potassium humate crude solution. The nitric acid residue is added to it, stirred and filtered to obtain potassium humate precipitate and a third liquid. The pH of the third liquid is adjusted to 7.5~8.0 using the potassium hydroxide residue to obtain potassium humate pure solution. After purification, potassium humate exhibits improved stability and enhanced activity in compound formulations. Removing large-molecule potassium humate results in a more uniform molecular weight of potassium humate, improving its compatibility with amino acids and chitosan oligosaccharides. It also eliminates the risk of precipitation due to hydrogen bond aggregation, and the smaller-molecule potassium humate exhibits stronger chelating ability and life-promoting properties.
[0013] S6. Mix the amino acid solution, the chitosan oligosaccharide solution, and the potassium humate pure solution according to a preset ratio, add a buffer and stir evenly to obtain a premixed solution, then add abamectin microcapsules and surfactant, stir and filter to obtain a multifunctional bio-based liquid fertilizer.
[0014] By combining multiple components, the fertilizer and pesticide are made more comprehensive in nutrition and have a better growth-promoting effect. Potassium nitrate (an acid-base neutralization byproduct) is an essential nutrient for crops. It works synergistically with amino acids and potassium humate to improve crop absorption efficiency and stress resistance, resulting in a significant increase in crop yield.
[0015] Example 1 Fresh shrimp shells were taken, washed, and dried at 55°C until the moisture content was 7%. After crushing, the shells were passed through a 60-mesh sieve, and the sieve residue was collected. 10 kg of shrimp shell powder was weighed out. The shrimp shell powder and 1 mol / L nitric acid were mixed at a solid-liquid ratio of 1 g: 15 mL and stirred for 1.5 h. After centrifugation, the first precipitate and the first liquid were obtained. The first precipitate was washed with deionized water until the pH of the washing water was 6.2. Then, it was soaked in 51 L of 95% ethanol for 1.5 h. After centrifugation to separate the ethanol, the shells were dried at 60°C to obtain 5.4 kg of decalcified and degreased shrimp shell powder. The first liquid and the washing water were combined to obtain 185 L of residual nitric acid liquid. The concentration of nitric acid in the residual nitric acid liquid was 0.46 mol / L. The decalcified and defatted shrimp shell powder was mixed with deionized water at a solid-liquid ratio of 1g:25mL, and the pH was adjusted to 8.0. Then, 48g of complex protease (the complex protease was prepared by mixing alkaline protease and neutral protease at a mass ratio of 1:1.5) was added. The mixture was enzymatically hydrolyzed at 58℃ and 220rpm for 9h. The temperature was raised to 90℃ and kept at 12min to inactivate the enzyme. Then, the mixture was centrifuged at 3500rpm to obtain a supernatant and 3.9kg of chitin residue (dry basis). The supernatant was concentrated to obtain 14L of amino acid solution, in which the concentration of free amino acids was 106g / L. The chitin residue and 10 mol / L potassium hydroxide were mixed at a solid-liquid ratio of 1 g: 15 mL and reacted at 98 °C for 5 h. After solid-liquid separation, a second precipitate and a second liquid were obtained. The second precipitate was washed with deionized water until the pH of the washing water was 7.5. Then, the second precipitate was dried to obtain 3.1 kg of chitosan residue (dry basis). The second liquid and washing water were recovered and mixed to obtain 130 L of potassium hydroxide residue. The concentration of potassium hydroxide in the potassium hydroxide residue was 4.5 mol / L. The chitosan residue and 1 wt% acetic acid solution were mixed at a solid-liquid ratio of 1 g: 20 mL and the pH was adjusted to 5.2. Then, chitosan hydrolase with an activity of 5000 U / g, equivalent to 1.2% of the mass of the chitosan, was added. The mixture was enzymatically hydrolyzed at 50°C and 190 rpm for 6 h. The temperature was then raised to 85°C and held for 20 min to inactivate the enzyme. The mixture was then filtered through a 6 kDa ultrafiltration membrane and concentrated to obtain 60 L of the chitosan oligosaccharide solution, with a chitosan oligosaccharide content of 50 g / L. Lignite was pulverized and passed through a 100-mesh sieve, then dried at 110℃ for 2.5 hours. 10 kg of lignite powder was weighed and mixed with the residual potassium hydroxide solution at a solid-liquid ratio of 1 g: 10 mL. The mixture was stirred at 85℃ for 2.5 hours and centrifuged at 4000 rpm for 20 minutes to obtain 95 L of crude potassium humate solution (pH 12.5). The residual nitric acid solution was slowly added dropwise to adjust the pH of the crude potassium humate solution to 2.2. The mixture was stirred for 30 minutes and allowed to stand for 60 minutes before being filtered through a 0.45 μm ceramic membrane to obtain 115 L of third liquid. The residual potassium hydroxide solution was slowly added dropwise to adjust the pH of the third liquid to 7.8 to obtain 117 L of pure potassium humate solution. After concentration, 58 L of pure potassium humate solution with a humic acid content of 51 g / L was obtained.
[0016] A premixed solution was prepared by mixing 14L of the amino acid solution, 60L of the chitosan oligosaccharide solution, and 58L of the potassium humate solution. 0.6kg of citric acid-sodium citrate buffer was added, and the mixture was stirred evenly. Then, 3kg of abamectin microcapsules (with a drug loading rate of 80%) and 0.3kg of surfactant (prepared from Tween 80 and Span 80 at a mass ratio of 2:1) were added. The mixture was stirred at 3000rpm for 10min and filtered through a 0.45μm filter to obtain a multifunctional bio-based liquid fertilizer.
[0017] Example 2 Obtain a certain tomato variety "Da Mingxing", transplant it at the four-leaf stage, and inoculate each pot with 1000 root-knot nematode eggs; Five pots were treated with 500 times diluted solution of the multifunctional bio-based liquid fertilizer in Example 1 at a rate of 200 mL per pot as the experimental group, and five pots were treated with water at a rate of 200 mL per pot as the control group. After 30 days, the experimental group had an average of 7.5 root knots, while the control group had an average of 54.7 root knots. The relative control efficacy of the experimental group was 86.3%. Compared with the control group, the experimental group of tomatoes showed a 45.8% increase in plant height, a 92.3% increase in fresh weight of underground parts, and a 38.5% increase in fruit yield.
[0018] Comparative Example 1 Unlike Example 1, after the shrimp shell powder undergoes decalcification with nitric acid, a chitosan extraction step is performed first, followed by an amino acid liquid preparation step.
[0019] Comparative Example 2 Unlike Example 1, in the step of preparing potassium humate using lignite powder, no subsequent purification operation is performed after obtaining the crude potassium humate solution. In the step of preparing multifunctional bio-based liquid fertilizer, pure potassium humate solution is used instead of crude potassium humate solution.
[0020] Comparative Example 3 Unlike Example 1, the step of preparing the multifunctional bio-based liquid fertilizer does not involve adding pure potassium humate solution.
[0021] Comparative Example 4 Unlike Example 2, the experimental group was treated with the liquid fertilizer from Comparative Example 1; After 30 days, the experimental group had an average of 15.4 root knots, while the control group had an average of 54.7 root knots. The relative control efficacy of the experimental group was 71.8%. Compared with the control group, the experimental group of tomatoes showed a 37.5% increase in plant height, a 76.9% increase in fresh weight of underground parts, and a 31.3% increase in fruit yield.
[0022] Comparative Example 5 Unlike Example 2, the experimental group was treated with the liquid fertilizer from Comparative Example 2. After 30 days, the experimental group had an average of 7.8 root knots, while the control group had an average of 54.7 root knots. The relative control efficacy of the experimental group was 85.7%. Compared with the control group, the experimental group of tomatoes showed a 15.7% increase in plant height, a 23.5% increase in fresh weight of underground parts, and a 9.6% increase in fruit yield.
[0023] Comparative Example 6 Unlike Example 2, the experimental group was treated with the liquid fertilizer from Comparative Example 3; After 30 days, the experimental group had an average of 9.6 root knots, while the control group had an average of 54.7 root knots. The relative control efficacy of the experimental group was 82.4%. Compared with the control group, the experimental group of tomatoes showed a 14.2% increase in plant height, a 6.3% increase in fresh weight of underground parts, and a 5.1% increase in fruit yield.
[0024] Comparative Example 7 Unlike Example 2, the experimental group was prepared by treating the plants with 200 mL of abamectin diluted solution at the same concentration as in Example 1, while the control group was prepared by treating the plants with 200 mL of water per pot.
[0025] After 30 days, the experimental group had an average of 21.4 root knots, while the control group had an average of 54.7 root knots. The relative control efficacy of the experimental group was 60.9%. Compared with the control group, the experimental group of tomatoes showed an 8.1% increase in plant height, a 5.2% increase in fresh weight of underground parts, and a 4.5% increase in fruit yield.
[0026] This invention reduces acid and alkali emissions pollution and lowers costs through a closed-loop acid-base design. It improves the stability and activity of the compound by purifying potassium humate and enriches the nutritional functions of the fertilizer and pesticide through the utilization of by-products. Ultimately, it achieves a four-in-one effect of "nematode resistance, growth promotion, nutrient supplementation, and soil improvement". It achieves a high root-knot nematode inhibition rate and a high crop yield increase rate while being environmentally friendly and low-cost.
[0027] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.
Claims
1. A method for preparing a multifunctional bio-based liquid fertilizer, characterized in that, Includes the following steps: S1. Mix shrimp shell powder and dilute nitric acid and stir. After solid-liquid separation, a first precipitate and a first liquid are obtained. The first precipitate is washed with deionized water. Then, the washed first precipitate is mixed with ethanol and soaked. After drying, decalcified and degreased shrimp shell powder is obtained. The first liquid and washing water are recovered and mixed to obtain residual nitric acid liquid. S2. The decalcified and defatted shrimp shell powder is enzymatically hydrolyzed using a compound protease, and the solid-liquid separation yields an amino acid solution and chitin residue. S3. The chitin residue and potassium hydroxide are mixed and reacted, and the solid and liquid are separated to obtain a second precipitate and a second liquid. The second precipitate is washed with deionized water and then dried to obtain chitosan residue. The second liquid and washing water are recovered and mixed to obtain potassium hydroxide residue. S4. The chitosan residue is enzymatically hydrolyzed using chitosan hydrolase, and the chitosan oligosaccharide solution is obtained by ultrafiltration membrane filtration. S5. The lignite is crushed, sieved, and dried to obtain lignite powder. The lignite powder and the potassium hydroxide residue are mixed and stirred. Solid-liquid separation is performed to obtain potassium humate crude solution. The nitric acid residue is added to it, stirred and filtered to obtain potassium humate precipitate and a third liquid. The pH of the third liquid is adjusted to 7.5~8.0 using the potassium hydroxide residue to obtain potassium humate pure solution. S6. Mix the amino acid solution, the chitosan oligosaccharide solution, and the potassium humate pure solution according to a preset ratio, add a buffer and stir evenly to obtain a premixed solution, then add abamectin microcapsules and surfactant, stir and filter to obtain a multifunctional bio-based liquid fertilizer.
2. The method for preparing a multifunctional bio-based liquid fertilizer according to claim 1, characterized in that, Specifically, step S1 involves mixing the shrimp shell powder with 0.8-1.2 mol / L nitric acid at a solid-liquid ratio of 1 g: (12-15) mL and stirring for 1-1.5 h. After solid-liquid separation, the first precipitate and the first liquid are obtained. The first precipitate is washed with deionized water until the pH of the washing water is 6-6.
5. Then, the washed first precipitate is mixed with 95 wt% ethanol at a solid-liquid ratio of 1 g: (8-10) mL and soaked for 1-1.5 h. After drying, the decalcified and degreased shrimp shell powder is obtained. The first liquid and the washing water are recovered and mixed to obtain the remaining nitric acid liquid.
3. The method for preparing a multifunctional bio-based liquid fertilizer according to claim 1, characterized in that, Step S2 specifically involves mixing the decalcified and defatted shrimp shell powder with deionized water at a solid-liquid ratio of 1g:(20~25)mL, adjusting the pH to 7.5~8.2, then adding a complex protease equivalent to 0.7%~1.2% of the mass of the decalcified and defatted shrimp shell powder, and enzymatically hydrolyzing at 53~60℃ and a stirring speed of 200~220rpm for 7~9h, then heating to 85~90℃ and holding for 12~15min to inactivate the enzyme, and then centrifuging at 3000~3500rpm to obtain a supernatant and chitin residue. The supernatant is then concentrated to obtain the amino acid solution, wherein the concentration of free amino acids in the amino acid solution is greater than or equal to 100g / L. The complex protease is prepared by mixing alkaline protease and neutral protease at a mass ratio of 1:(1.2~1.5).
4. The method for preparing a multifunctional bio-based liquid fertilizer according to claim 1, characterized in that, Specifically, step S3 involves mixing the chitin residue with an 8.5-11 mol / L potassium hydroxide solution at a solid-liquid ratio of 1 g: (14-16) mL, reacting at 95-98°C for 4-5 hours, separating the solid and liquid to obtain the second precipitate and the second liquid, washing the second precipitate with deionized water until the pH of the washing water is 7.2-7.8, drying the second precipitate to obtain chitosan residue, recovering the second liquid and the washing water and mixing them to obtain potassium hydroxide residue.
5. The method for preparing a multifunctional bio-based liquid fertilizer according to claim 1, characterized in that, Step S4 specifically involves mixing the chitosan and a 1 wt% acetic acid solution at a solid-liquid ratio of 1 g: 20 mL and adjusting the pH to 5.0-5.
5. Then, adding chitosan hydrolase with an activity of 1000-5000 U / g, equivalent to 1.0%-3.0% of the mass of the chitosan, and hydrolyzing at 48-52°C and a stirring speed of 180-200 rpm for 5-6 hours. The temperature is then raised to 85°C and held for 20 minutes to inactivate the enzyme. Finally, the mixture is filtered through a 5-10 kDa ultrafiltration membrane to obtain the chitosan oligosaccharide solution, wherein the chitosan oligosaccharide content of the solution is greater than or equal to 40 g / L.
6. The method for preparing a multifunctional bio-based liquid fertilizer according to claim 1, characterized in that, Step S5 specifically involves crushing and sieving the lignite, drying it at 105-110℃ for 2-2.5 hours to obtain lignite powder, mixing the lignite powder and the residual potassium hydroxide solution at a solid-liquid ratio of 1g:(5-15)mL, stirring at 80-85℃ for 2-2.5 hours, and centrifuging to obtain crude potassium humate solution; adjusting the pH of the crude potassium humate solution to 1.8-2.7 using the residual nitric acid solution, stirring and allowing it to stand, then filtering to obtain a third precipitate and a third liquid; adjusting the pH of the third liquid to 7.5-8.0 using the residual potassium hydroxide solution, concentrating it to obtain pure potassium humate solution, wherein the fulvic acid content in the pure potassium humate solution is greater than or equal to 40g / L.
7. The method for preparing a multifunctional bio-based liquid fertilizer according to claim 1, characterized in that, In step S6, mixing the amino acid solution, the chitosan oligosaccharide solution, and the potassium humate pure solution according to a preset ratio specifically involves mixing the amino acid solution, the chitosan oligosaccharide solution, and the potassium humate pure solution in a volume ratio of (10~20):(40~80):(40~80), and the buffer is a 0.3wt%~0.8wt% citric acid-sodium citrate buffer.
8. The method for preparing a multifunctional bio-based liquid fertilizer according to claim 1, characterized in that, Step S6 further includes adding 1.0% to 5.0% of the avermectin microcapsules and 0.2% to 0.5% of the surfactant to the premixed solution. The avermectin microcapsules have a drug loading rate of greater than or equal to 70%, and the surfactant is composed of Tween 80 and Span 80 in a mass ratio of 2:
1.
9. A multifunctional bio-based liquid fertilizer, characterized in that, The multifunctional bio-based liquid fertilizer is prepared by the preparation method of the multifunctional bio-based liquid fertilizer according to any one of claims 1 to 8.