Straw biological carbonization-based fulvic acid fertilizer as well as preparation method and application thereof

Abstract

The invention relates to the technical field of fertilizers, and discloses a fulvic acid fertilizer based on straw biological carbonization as well as a preparation method and application of the fulvic acid fertilizer based on straw biological carbonization, and the preparation method comprises the following steps: carrying out mild carbonization treatment on a straw raw material to prepare carbonized straws; mixing the carbonized straws with a metal complexing agent to prepare pretreated carbonized straws; modifying the pretreated carbonized straws by using a surfactant so as to obtain modified straws; the modified straw is mixed with water, protease is added for degradation treatment, extraction is conducted through a hydrothermal method, and finally fulvic acid enrichment liquid is obtained; mixing the fulvic acid enrichment liquid, the modified straw and the bio-based polymer, and performing extrusion forming and drying to obtain the fulvic acid fertilizer based on straw biological carbonization. The method not only improves the extraction efficiency of fulvic acid and the slow release performance of the fertilizer, but also improves the stability, solubility and mechanical strength of the fertilizer.

Description

Technical Field

[0001] The present invention relates to the technical field of fertilizers, and in particular to a fulvic acid fertilizer based on straw biocharization, and a preparation method and application thereof. Background Art

[0002] With the growth of global population and the increase in agricultural production demand, the use of fertilizers continues to rise. Although fertilizers play an important role in increasing agricultural output, their excessive use has brought many environmental problems, such as soil degradation, groundwater pollution and air pollution. Therefore, the development of efficient, environmentally friendly and sustainable fertilizers has become an important topic in the current agricultural science and technology field. In order to solve the negative effects of traditional fertilizers, more and more research is focused on the development of bio-based fertilizers, slow-release fertilizers and functional fertilizers.

[0003] As an organic fertilizer, fulvic acid fertilizer has attracted widespread attention due to its good soil improvement effect, plant growth promotion effect and environmentally friendly characteristics. Fulvic acid is a natural product transformed from organic matter by microorganisms or chemical methods. It has multiple functions such as promoting plant growth, improving soil fertility, and improving soil structure. It improves the absorption of water and nutrients by plants by improving soil moisture retention capacity, enhancing soil aeration, and promoting the activity of soil microorganisms. However, fulvic acid fertilizer still faces some challenges in practical applications, such as low fulvic acid extraction efficiency, uneven fertilizer release, and poor stability.

[0004] Therefore, an innovative solution is urgently needed to improve the performance and application effect of fulvic acid fertilizers. Summary of the invention

[0005] In view of this, the present invention proposes a fulvic acid fertilizer based on straw biocharization and a preparation method and application thereof, aiming to improve the extraction efficiency of fulvic acid, improve the release characteristics of the fertilizer, and at the same time enhance the stability of the fertilizer and reduce the production cost.

[0006] The present invention proposes a method for preparing fulvic acid fertilizer based on straw biocharization, comprising:

[0007] The straw raw material is lightly carbonized to obtain carbonized straw;

[0008] The carbonized straw is mixed with a metal complexing agent to obtain pretreated carbonized straw; wherein the metal complexing agent is composed of a complex formed by a natural plant extract and a metal salt;

[0009] Using a surfactant to modify the pretreated carbonized straw to obtain modified straw;

[0010] The modified straw is mixed with water, and then protease is added to degrade the mixture, and then a fulvic acid enriched solution is obtained by hydrothermal extraction;

[0011] The fulvic acid enriched liquid, modified straw and bio-based polymer are mixed, extruded and dried to obtain the fulvic acid fertilizer based on straw biochar.

[0012] Preferably, the temperature of the slight carbonization treatment is 200-400°C.

[0013] Preferably, the preparation method of the metal complexing agent comprises:

[0014] Mixing oak bark with water and performing evaporation extraction to obtain the natural plant extract;

[0015] The natural plant extract and the metal salt solution are mixed and reacted to obtain the metal complexing agent.

[0016] Preferably, the metal salt solution is a zinc ion solution.

[0017] Preferably, the preparation method of the surfactant comprises:

[0018] The coconut oil and the sodium hydroxide solution are mixed, stirred and reacted at a temperature of 75±3° C., and the reaction product is dried to obtain the surfactant.

[0019] Preferably, the molar ratio of the coconut oil to the sodium hydroxide solution is 1-1.5:3.

[0020] Preferably, the method for preparing the bio-based polymer comprises:

[0021] Adding sodium alginate into deionized water to dissolve it, thereby obtaining a sodium alginate solution;

[0022] The calcium chloride solution and the sodium alginate solution are mixed and reacted, and stirring is maintained during the reaction, and a gel is obtained after gelation is completed;

[0023] The gel is solidified and then dried to obtain the bio-based polymer.

[0024] Preferably, the proteases are cellulases and lignin degrading enzymes.

[0025] The present invention also proposes a fulvic acid fertilizer based on straw biocharization, and the fulvic acid fertilizer based on straw biocharization is prepared by the above-mentioned preparation method of fulvic acid fertilizer based on straw biocharization.

[0026] The present invention also proposes an application of the above-mentioned fulvic acid fertilizer based on straw biocharization in improving soil and / or promoting plant growth.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The invention relates to a method for preparing fulvic acid fertilizer, which achieves multiple advantages through slight carbonization of straw, modification of a metal complexing agent and a surfactant and synergistic effects of a bio-based polymer.

[0029] Compared with the prior art, the present invention has the following significant beneficial effects:

[0030] 1. Improve the extraction efficiency of fulvic acid

[0031] In the preparation process of traditional fulvic acid fertilizer, straw is usually used directly to extract fulvic acid, but the extraction efficiency is low. The present invention treats the straw by slight carbonization, so that part of the organic matter (such as cellulose and lignin) is pyrolyzed and converted into a form that is easier to extract. This process significantly improves the extraction rate of fulvic acid, thereby increasing the yield and quality of the final fertilizer.

[0032] 2. Improve the slow-release performance and stability of fertilizers

[0033] Traditional fulvic acid fertilizers often cause the fertilizer effect to drop rapidly due to the rapid release of nutrients. The present invention uses a metal complexing agent to form a stable complex between metal ions and organic acids and phenolic substances in fulvic acid, thereby controlling the release rate of nutrients in the fertilizer. Compared with traditional methods, the fertilizer of the present invention can achieve a longer sustained release effect, reduce excessive loss of fertilizer, and improve the durability and use efficiency of the fertilizer.

[0034] 3. Improve fertilizer solubility and dispersibility

[0035] Many traditional fertilizers have the problem of uneven dissolution, resulting in inconsistent nutrient release. The present invention effectively improves the solubility and dispersibility of fertilizer particles in water by using surfactants, reduces the adsorption force between fertilizer particles, and ensures that the fertilizer can be evenly dissolved and slowly release nutrients during use. This modification method significantly improves the solubility of fertilizers and the nutrient absorption efficiency of plants.

[0036] 4. Improve the mechanical strength and compressive resistance of fertilizers

[0037] Traditional fertilizers are prone to breakage during transportation and storage, resulting in fertilizer loss. The bio-based polymers in the present invention can effectively solidify and strengthen fertilizer particles, showing higher mechanical strength and compression resistance. The bio-based polymers tightly bind the fertilizer components to prevent the particles from breaking, thereby improving the stability and service life of the fertilizer.

[0038] 5. Improve environmental friendliness and biodegradability

[0039] Traditional chemical fertilizers have caused a significant burden on the environment, such as soil acidification, groundwater pollution and other problems. In contrast, the bio-based polymer used in the present invention has good biodegradability and can reduce the pollution of fertilizers to the environment. In addition, the slight carbonization of straw reduces energy consumption in the production process and reduces waste emissions. Compared with traditional chemical fertilizers, the fertilizer of the present invention is more in line with the development needs of green and sustainable modern agriculture.

[0040] 6. Reduce production costs

[0041] Compared with deep carbonization, the slight carbonization treatment in the present invention can effectively reduce energy consumption and production costs. The carbonization temperature is low and the required time is short, which saves a lot of energy and improves the utilization rate of straw. In addition, through the reasonable application of metal complexing agents, surfactants and bio-based polymers, the fertilizer performance can be significantly improved without significantly increasing the cost, and the overall production cost can be reduced.

[0042] 7. Improve soil fertility and crop growth

[0043] Compared with traditional fertilizers, the fulvic acid fertilizer prepared by the present invention can better improve soil fertility, increase the effective content of nutrients such as nitrogen, phosphorus, potassium, and significantly promote crop growth. For example, the examples show that the use of the fertilizer of the present invention can significantly increase crop plant height, leaf area and dry weight, indicating that its promoting effect on plant growth is more significant.

[0044] 8. Better nutrient release control

[0045] The present invention achieves more precise nutrient release control through the synergistic effect of metal complexing agents and bio-based polymers, avoiding excessive loss or instantaneous excessive release of nutrients in traditional fertilizers, thereby improving the fertilizer efficiency and nutrient absorption efficiency of crops. This controlled release characteristic ensures that crops obtain a balanced nutrient supply during the growth cycle, avoiding the problem of excess or insufficient nutrition.

[0046] In summary, the beneficial effect of the present invention is that multiple properties of fulvic acid fertilizer are optimized through the comprehensive application of slightly carbonized straw, metal complexing agent, surfactant and bio-based polymer. Compared with the prior art, the present invention not only improves the extraction efficiency of fulvic acid and the slow-release performance of fertilizer, but also improves the stability, solubility and mechanical strength of fertilizer, reduces production costs, and meets environmental protection requirements. Overall, the present invention provides an efficient, green and sustainable fertilizer production method with significant market application potential and environmental benefits. DETAILED DESCRIPTION

[0047] The exemplary embodiments of the present disclosure will be described in more detail below. Although the exemplary embodiments of the present disclosure are shown below, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to be able to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0048] Example 1

[0049] 1. Preparation of metal complexing agent

[0050] 1. Extraction of natural plant extracts

[0051] Use about 500g of dried oak bark as raw material, cut into appropriate small pieces to increase the extraction surface area. Place the cut oak bark into the extraction chamber of the distiller, ensuring that it is separated from the water and can be directly contacted by steam. Add distilled water 3 times the weight of the oak bark into the distiller. Start the steam generator, heat the water to boiling, and the steam passes through the plant material and takes away the volatile compounds in it. After the steam is cooled through the condenser, the condensate is collected in a receiving container. The distillation time is 3 hours.

[0052] The water and oil components are separated by a separatory funnel, and the water in the extract can be separated by evaporation or natural sedimentation to obtain pure natural plant extracts.

[0053] 2. Complexation of natural plant extracts with zinc ions

[0054] (1) Preparation of zinc solution

[0055] Zinc sulfate preparation: Dissolve 7.3 g of zinc sulfate in deionized water and adjust the final volume to 500 ml.

[0056] (2) Complexation reaction between zinc ions and plant extracts

[0057] The prepared natural plant extract with a concentration of about 10% is mixed with the zinc solution (volume ratio is 1:1). After the pH is adjusted to a range of 4.0-5.5, the mixture is stirred to allow it to react fully. The complexation reaction is carried out at room temperature and the reaction time is at least 30 minutes.

[0058] After the reaction is completed, the separated complex is dried to obtain a zinc-plant complex, namely a metal complexing agent.

[0059] 2. Preparation of surfactant

[0060] Add sodium hydroxide solid to 250 ml water and stir until completely dissolved to obtain a sodium hydroxide solution with a concentration of 30%. Weigh 500 g of coconut oil, mix the coconut oil and sodium hydroxide solution in a molar ratio of 1:3, and heat to 75±3°C in a reactor. Continue stirring to allow the reaction to proceed fully for 2 hours until the oil is completely saponified. The triglycerides in the coconut oil are decomposed into glycerol and fatty acid salts under the action of sodium hydroxide. After the reaction is completed, cool to room temperature to obtain a reaction product. Wash the reaction product with hot water and dry it to obtain a surfactant.

[0061] 3. Preparation of Bio-based Polymers

[0062] 10g sodium alginate is added to 200ml deionized water and stirred at room temperature using a stirrer until the sodium alginate is completely dissolved to form a transparent sodium alginate solution with a pH value of 4-5. During the dissolution process, a few drops of 0.15% acetic acid are added to help the sodium alginate dissolve better.

[0063] 10g of calcium chloride is dissolved in 200ml of deionized water to form a calcium chloride solution. The calcium chloride solution and the sodium alginate solution are mixed and reacted, and stirring is maintained during the reaction to ensure uniform crosslinking. The reaction time is 10 minutes. After the gelation is completed, the gel obtained by the reaction is washed with deionized water to remove excess calcium ions. The gel is placed in cold water and soaked for 24 hours to help it completely solidify. The formed sodium alginate gel is cut into small pieces and placed in an oven at a temperature of 60-80°C until it is completely dry to obtain a bio-based polymer.

[0064] Example 2 Preparation of fulvic acid fertilizer based on slightly carbonized straw

[0065] 1. Straw preparation and slight carbonization

[0066] 1. Raw materials

[0067] Corn stalks are selected as the main raw material, which is rich in cellulose and lignin.

[0068] 2. Carbonization conditions

[0069] The straw was placed in a carbonization furnace at a controlled temperature of 300°C for 1.5 hours. After slight carbonization, a carbon-based structure rich in active functional groups was formed on the surface of the straw, which could improve the extraction effect of fulvic acid.

[0070] 2. Metal complexing agent treatment

[0071] The carbonized straw was mixed with a metal complexing agent solution (concentration of 0.5 mol / L), the pH was adjusted to 5.0, and the mixture was stirred for 2 hours. The metal complexing agent can remove harmful metal impurities in the straw and promote the release of fulvic acid.

[0072] 3. Modification of natural surfactants

[0073] The surfactant is mixed with the metal complex treated straw and stirred for at least 1 hour to ensure that the surfactant and the straw fully react.

[0074] 4. Hydrothermal Extraction of Fulvic Acid

[0075] The modified straw was mixed with water at a mass ratio of 1:5, and after adding cellulase and lignin degradation enzyme (enzyme activity: 300U / g) for degradation, it was treated by hydrothermal method, and the reaction temperature was set at 180°C and the reaction time was 3 hours. The extract was centrifuged to remove solid matter and obtain fulvic acid enriched solution.

[0076] 5. Solidification and fertilizer preparation

[0077] The extracted fulvic acid is mixed with the residue of modified straw, and a bio-based polymer is added as a curing agent, the curing agent ratio is 10% (mass ratio). The mixture is made into granular fertilizer by extrusion molding, and dried at 40° C. to a water content of less than 5%.

[0078] Example 2 Preparation of fulvic acid fertilizer based on slightly carbonized straw

[0079] 1. Straw preparation and slight carbonization

[0080] 1. Raw materials

[0081] Wheat straw was selected as the main raw material.

[0082] 2. Carbonization conditions

[0083] The straw is placed in a carbonization furnace at a controlled temperature of 300°C for 1 hour. After slight carbonization, a carbon-based structure rich in active functional groups will form on the surface of the straw, which can improve the effect of fulvic acid extraction.

[0084] 2. Metal complexing agent treatment

[0085] The carbonized straw was mixed with a metal complexing agent solution (concentration of 0.5 mol / L), the pH was adjusted to 5.0, and the mixture was stirred for 2 hours. The metal complexing agent can remove harmful metal impurities in the straw and promote the release of fulvic acid.

[0086] 3. Modification of natural surfactants

[0087] The surfactant is mixed with the metal complex treated straw and stirred for at least 1 hour to ensure that the surfactant and the straw fully react.

[0088] 4. Hydrothermal Extraction of Fulvic Acid

[0089] The modified straw was mixed with water at a mass ratio of 1:5, and after adding cellulase and lignin degradation enzyme (enzyme activity: 300U / g) for degradation, it was treated by hydrothermal method, and the reaction temperature was set at 180°C and the reaction time was 3 hours. The extract was centrifuged to remove solid matter and obtain fulvic acid enriched solution.

[0090] 5. Solidification and fertilizer preparation

[0091] The extracted fulvic acid is mixed with the residue of modified straw, and a bio-based polymer is added as a curing agent, the curing agent ratio is 10% (mass ratio). The mixture is made into granular fertilizer by extrusion molding, and dried at 40° C. to a water content of less than 5%.

[0092] Example 3 Preparation of fulvic acid fertilizer based on slightly carbonized straw

[0093] 1. Straw preparation and slight carbonization

[0094] 1. Raw materials

[0095] Rice straw was selected as the main raw material.

[0096] 2. Carbonization conditions

[0097] The straw is placed in a carbonization furnace at a controlled temperature of 250°C for 1 hour. After slight carbonization, a carbon-based structure rich in active functional groups will form on the surface of the straw, which can improve the effect of fulvic acid extraction.

[0098] 2. Metal complexing agent treatment

[0099] The carbonized straw was mixed with a metal complexing agent solution (concentration of 0.5 mol / L), the pH was adjusted to 5.5, and the mixture was stirred for 2 hours. The metal complexing agent can remove harmful metal impurities in the straw and promote the release of fulvic acid.

[0100] 3. Modification of natural surfactants

[0101] The surfactant is mixed with the metal complex treated straw and stirred for at least 1 hour to ensure that the surfactant and the straw fully react.

[0102] 4. Hydrothermal Extraction of Fulvic Acid

[0103] The modified straw was mixed with water at a mass ratio of 1:5, and after adding cellulase and lignin degradation enzyme (enzyme activity: 300U / g) for degradation, it was treated by hydrothermal method, and the reaction temperature was set at 160°C and the reaction time was 4 hours. The extract was centrifuged to remove solid matter and obtain fulvic acid enriched solution.

[0104] 5. Solidification and fertilizer preparation

[0105] The extracted fulvic acid is mixed with the residue of modified straw, and a bio-based polymer is added as a curing agent, the curing agent ratio is 10% (mass ratio). The mixture is made into granular fertilizer by extrusion molding, and dried at 40° C. to a water content of less than 5%.

[0106] Comparative Example 1

[0107] This comparative example does not use a metal complexing agent, and the rest is the same as Example 1.

[0108] Comparative Example 2

[0109] This comparative example does not use a surfactant, and the rest is the same as Example 1.

[0110] Comparative Example 3

[0111] This comparative example does not use bio-based polymer, and the rest is the same as Example 1.

[0112] Test Example 1

[0113] Performance tests and practical application tests were performed on Examples 1-3 and Comparative Examples 1-3.

[0114] 1. Performance test methods and standards

[0115] 1. Mechanical properties test

[0116] Purpose: To evaluate the curing effect and compressive strength of polymers in fertilizers.

[0117] Test method: The compressive strength of fertilizer granules was measured using a compression test (universal materials testing machine).

[0118] Standard: According to the application requirements of fertilizer granules, the compressive strength is usually required to be greater than 2MPa (not easy to break, suitable for storage and transportation).

[0119] 2. Water solubility test

[0120] Purpose: To evaluate the dissolution rate and controlled release performance of fertilizers in soil.

[0121] Test method: Soak the fertilizer granules in deionized water and measure the amount of fertilizer dissolved at fixed time intervals (1 hour, 6 hours, 24 hours).

[0122] Standard: Control the dissolution rate of the fertilizer so that no more than 50% dissolves within 24 hours to achieve a slow-release effect.

[0123] 3. Fertilizer release rate test

[0124] Purpose: To test the ability of fertilizer to be slowly released in the soil.

[0125] Test method: Place fertilizer granules in the soil, take samples regularly and measure the concentration of nutrients (nitrogen, phosphorus, potassium) in the soil.

[0126] Standard: According to the standard fertilizer release curve, the fertilizer is required to release 40%-50% within 7 days and the total release rate reaches 80% within 30 days.

[0127] 4. Biodegradability test

[0128] Purpose: To test the degradation rate of polymers and their impact on the environment.

[0129] Test method: Fertilizer granules are buried in the soil, samples are taken regularly and the residues are analyzed to determine the extent of polymer degradation.

[0130] Standard: Biodegradation rate requires at least 50% degradation within 90 days.

[0131] 2. Practical application test methods and standards

[0132] 1. Soil improvement effect test

[0133] Objective: To evaluate the effect of fertilizers on improving soil structure and nutrient content.

[0134] Testing method: Fertilizer is applied to actual soil samples and the soil is tested for pH, fertility (nitrogen, phosphorus, potassium content) and organic matter content.

[0135] Standard: The nitrogen, phosphorus and potassium content of the soil is required to increase by 10%-20%, and the soil pH value is maintained between 6-7 (suitable for the growth of most crops).

[0136] 2. Crop growth test

[0137] Objective: To evaluate the effect of fertilizers on crop growth.

[0138] Test method: Apply fertilizer to different crops (wheat, corn), and regularly measure crop height, leaf area, dry weight and other indicators.

[0139] Standard: After fertilization, crop height, leaf area, etc. should increase by 15%-30%, and crop dry weight should increase by 10%-20%.

[0140] 3. Results

[0141] The performance test results of Examples 2-4 and Comparative Examples 1-3 are shown in Table 1.

[0142] Table 1

[0143]

[0144] The actual application test results of Examples 2-4 and Comparative Examples 1-3 are shown in Table 2.

[0145] Table 2

[0146]

[0147] As can be seen from Table 1 and Table 2, the fertilizer products of Examples 2-4 are superior to Comparative Examples 1-3 in terms of mechanical properties, water solubility, fertilizer release rate and biodegradability. Specifically, the compressive strength of Examples 2-4 is higher than 3.4MPa, while the compressive strength of Comparative Examples 1-3 is lower than 3MPa, indicating that the polymer curing effect in the examples is better and more suitable for storage and transportation. In the water solubility test, the 24-hour dissolution amount of Examples 2-4 is lower than 50%, while the dissolution amount of Comparative Examples 1-3 is higher than 50%, indicating that the fertilizer in the examples has a better slow-release effect. The fertilizer release rate test shows that the release rate of Examples 2-4 within 30 days is higher than 83%, while the release rate of Comparative Examples 1-3 is lower than 82%, indicating that the fertilizer release rate in the examples is more in line with the standard requirements. The results of the biodegradability test show that the biodegradation rate of Examples 2-4 is higher than 52%, while the degradation rate of Comparative Examples 1-3 is lower than 51%, indicating that the polymer in the examples has better environmental friendliness.

[0148] In actual application tests, the soil fertility improvement effect and crop growth promotion effect of Examples 2-4 are better than those of Comparative Examples 1-3. The soil fertility improvement test shows that the increase in nitrogen, phosphorus and potassium content of Examples 2-4 is higher than 10%, while the increase in Comparative Examples 1-3 is lower than 10%, indicating that the fertilizers in the examples can more effectively improve soil structure and nutrient content. The results of crop growth tests show that the increase in plant height, leaf area and dry weight of crops in Examples 2-4 is higher than 15%, while the increase in Comparative Examples 1-3 is lower than 15%, which further confirms the significant promotion effect of the fertilizers in the examples on crop growth.

[0149] In summary, the fertilizer products of Examples 2-4 performed well in both performance tests and practical application tests, and were better than Comparative Examples 1-3, proving the positive effects of the addition of the metal complexing agent, surfactant and bio-based polymer on the fertilizer performance.

[0150] Exploration of principle mechanism:

[0151] The principle mechanism involved in the present invention is mainly reflected in the interaction of the four aspects of straw slight carbonization, metal complexing agent, surfactant and bio-based polymer and their modification effect on fulvic acid fertilizer. These treatment methods affect the performance of fertilizer from the chemical, physical and biological perspectives, and the specific mechanism is analyzed from the following aspects:

[0152] 1. Mechanism of slight carbonization of straw

[0153] Structural changes: Light carbonization heats the straw to a moderate temperature, causing some of its organic matter (such as cellulose, lignin, etc.) to undergo pyrolysis and transform into substances with a higher carbon content (such as biochar). This not only changes the physical structure of the straw, but also improves its chemical stability and reduces the content of harmful components (such as certain volatile organic compounds and impurities).

[0154] Improve the extraction efficiency of fulvic acid: Carbonized straw has more surface activity, which can effectively adsorb fulvic acid precursors and promote the formation and extraction of fulvic acid. The porosity of the internal structure of carbonized straw increases, making it easier for fulvic acid molecules to embed into it, thus improving the extraction efficiency.

[0155] Stability and degradability: The carbonized straw structure is more compact and stable, which can improve the stability of fulvic acid and make the fertilizer have better storage performance. In addition, the carbonized straw degrades more slowly, avoiding the rapid loss of fertilizer.

[0156] 2. Mechanism of action of metal complexing agents

[0157] Complexation of metal ions: Metal complexing agents form complexes with metal ions, thereby improving the slow-release properties of fertilizers. These complexes can effectively control the release rate of metal ions, making them stable in fertilizers.

[0158] Enhance the nutrient release of fertilizers: Metal chelating agents can form stable complexes with phenols, carboxyl and other functional groups in fulvic acid, making the release of fulvic acid more stable and avoiding the instantaneous excessive release of nutrients in the fertilizer, thereby improving the sustainability of fertilizer efficiency and plant absorption and utilization rate.

[0159] Promote soil microbial activity: Metal chelators have good biological activity in the soil, which can promote the growth of certain beneficial microorganisms in the soil, enhance soil health, and thus help the development of plant roots and nutrient absorption.

[0160] 3. Mechanism of action of surfactants

[0161] Improve the dispersibility of fertilizer particles: When surfactants act in fertilizers, their molecular structure contains both hydrophilic and hydrophobic groups, which can reduce the surface tension between fertilizer particles and improve the dispersibility and solubility of fertilizer particles in water. In this way, surfactants can ensure that the nutrients in the fertilizer are evenly released into the soil.

[0162] Regulating the release behavior of fertilizers: Surfactants slow down the release of active ingredients in fertilizers by changing the dissolution rate of fertilizer particles. This slow-release effect is achieved by combining with the surface of fertilizer particles to form a hydrophobic layer or film, thereby slowing down the dissolution rate of fertilizers and avoiding premature loss of nutrients.

[0163] Promoting the compatibility of soil and fertilizer: Surfactants can also improve the interaction between fertilizer and soil particles, allowing fertilizer to be better dispersed and interact with water and minerals in the soil, enhancing the soil's ability to absorb nutrients.

[0164] 4. Mechanism of action of bio-based polymers

[0165] Promoting fertilizer solidification: Bio-based polymers in fertilizers are mainly combined with other components (such as metal ions, fulvic acid, etc.) through cross-linking reactions or physical adsorption to form a stable structure. These polymers can condense fertilizer particles together, enhance the mechanical strength and compression resistance of fertilizers, and prevent them from breaking during transportation and use.

[0166] Improve the controlled release of fertilizers: Bio-based polymers can form a complex with fulvic acid to form a film or colloidal structure, thereby slowing down the release rate of the active ingredients in the fertilizer. This not only improves the efficiency of fertilizer use, but also avoids nutrient loss.

[0167] Biodegradability: Since bio-based polymers generally have good biodegradability, they can gradually decompose in the soil, thereby reducing environmental pollution, and can provide continuous nutrient support during the plant growth cycle. Bio-based polymers have good adaptability to soil microorganisms and plant roots, which helps to improve soil structure and effectively utilize fertilizer nutrients.

[0168] 5. Summary of the overall mechanism

[0169] Combining the action mechanisms of the above four key components, the core principle mechanism of the present invention is to form a stable, slow-release and environmentally friendly fulvic acid fertilizer through the synergistic effect of slight carbonization of straw, metal chelating agent, surfactant and bio-based polymer.

[0170] Slight carbonization increases the stability and porosity of the straw, facilitates the extraction of fulvic acid, and improves the durability of the fertilizer.

[0171] Metal chelating agents regulate the release rate of nutrients in fertilizers and improve the sustainability of fertilizer effectiveness by forming complexes with fulvic acid.

[0172] Surfactants improve the dispersibility and solubility of fertilizer particles, delay the release of fertilizer, and avoid premature loss of nutrients.

[0173] Bio-based polymers enhance the mechanical strength of fertilizers, improve the solidification of fertilizers, and are biodegradable, meeting environmental protection requirements.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing fulvic acid fertilizer based on straw biochar, characterized in that: include: The straw raw material is lightly carbonized to obtain carbonized straw; The carbonized straw is mixed with a metal complexing agent to obtain pretreated carbonized straw; wherein the metal complexing agent is composed of a complex formed by a natural plant extract and a metal salt; Modifying the pretreated carbonized straw using a surfactant to obtain modified straw; The modified straw is mixed with water, and then protease is added to degrade the mixture, and then a fulvic acid enriched solution is obtained by hydrothermal extraction; The fulvic acid enriched liquid, modified straw and bio-based polymer are mixed, extruded and dried to obtain the fulvic acid fertilizer based on straw biochar.

2. The method for preparing fulvic acid fertilizer based on straw biochar according to claim 1, characterized in that: The temperature of the slight carbonization treatment is 200-400°C.

3. The method for preparing fulvic acid fertilizer based on straw biochar according to claim 1, characterized in that: The preparation method of the metal complexing agent comprises: Mixing oak bark with water and performing evaporation extraction to obtain the natural plant extract; The natural plant extract and the metal salt solution are mixed and reacted to obtain the metal complexing agent.

4. The method for preparing fulvic acid fertilizer based on straw biochar according to claim 3, characterized in that: The metal salt solution is a zinc ion solution.

5. The method for preparing fulvic acid fertilizer based on straw biochar according to claim 1, characterized in that: The preparation method of the surfactant comprises: The coconut oil and the sodium hydroxide solution are mixed, stirred and reacted at a temperature of 75±3° C., and the reaction product is dried to obtain the surfactant.

6. The method for preparing fulvic acid fertilizer based on straw biochar according to claim 5, characterized in that: The molar ratio of the coconut oil to the sodium hydroxide solution is 1-1.5:

3.

7. The method for preparing fulvic acid fertilizer based on straw biochar according to claim 1, characterized in that: The method for preparing the bio-based polymer comprises: Adding sodium alginate into deionized water to dissolve it, thereby obtaining a sodium alginate solution; The calcium chloride solution and the sodium alginate solution are mixed and reacted, and stirring is maintained during the reaction, and a gel is obtained after gelation is completed; The gel is solidified and then dried to obtain the bio-based polymer.

8. The method for preparing fulvic acid fertilizer based on straw biochar according to claim 1, characterized in that: The proteases are cellulase and lignin degrading enzymes.

9. A fulvic acid fertilizer based on straw biochar, characterized in that: The fulvic acid fertilizer based on straw biochar is prepared by the preparation method of the fulvic acid fertilizer based on straw biochar according to any one of claims 1 to 8.

10. Use of the fulvic acid fertilizer based on straw biochar according to claim 9 in improving soil and / or promoting plant growth.

Images