Fulvic acid fertilizer based on straw microbial fermentation as well as preparation method and application of fulvic acid fertilizer

Abstract

The invention relates to the technical field of fertilizers, and discloses a fulvic acid fertilizer based on straw microbial fermentation and a preparation method and application thereof.The preparation method comprises the steps that straw is crushed and subjected to low-temperature plasma pretreatment, and pretreated straw is obtained; then, culturing the mixed microbial preparation to prepare a culture solution; then, the pretreated straw, a nutrient solution, a fermentation auxiliary agent and trichoderma are mixed for fermentation, and therefore a fermentation product is generated. The fermentation auxiliary agent is prepared from seaweed meal, bean flour, humus soil and molasses. And finally, carrying out solid-liquid separation on the fermentation product, and drying the separated solid part to finally obtain the fulvic acid fertilizer. Through combination of low-temperature plasma pretreatment and an innovative fermentation auxiliary agent, the preparation process of the fulvic acid fertilizer is optimized, the fertilizer efficiency of the fertilizer and the crop growth effect are improved, and meanwhile, the environment problem of agricultural waste is solved.

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 microbial fermentation, and a preparation method and application thereof. Background Art

[0002] In the agricultural field, fertilizer is one of the important means to improve crop yield and quality. Although traditional chemical fertilizers can quickly provide nutrients required for plant growth, long-term use will lead to soil structure damage, soil fertility decline, and even cause environmental pollution. Therefore, the development of environmentally friendly fertilizers, such as bio-organic fertilizers, has become an inevitable trend in the development of modern agriculture.

[0003] As a byproduct of agricultural production, straw is rich in resources, but has not been fully utilized for a long time. A large amount of straw is burned, which not only wastes resources but also causes serious air pollution. Using straw for microbial fermentation can not only effectively transform straw resources, but also produce organic fertilizer rich in fulvic acid, which can improve soil structure, increase soil water and fertilizer retention capacity, promote crop growth, and reduce environmental pollution.

[0004] Fulvic acid is a natural organic substance that is widely present in the soil. It has the functions of promoting plant growth and improving plant absorption and utilization of nutrients. Fulvic acid fertilizer prepared by straw microbial fermentation can effectively utilize agricultural waste, reduce environmental pollution, and provide rich nutrition for crops, which has good application prospects. Summary of the invention

[0005] In view of this, the present invention proposes a fulvic acid fertilizer based on straw microbial fermentation and a preparation method and application thereof, aiming to provide an environmentally friendly, resource-efficient fertilizer product, as well as a simple and efficient preparation method.

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

[0007] The straw is crushed and then pretreated with low-temperature plasma to obtain pretreated straw;

[0008] culturing the mixed microbial preparation to obtain a culture solution;

[0009] The pretreated straw, nutrient solution, fermentation auxiliary agent and Trichoderma are mixed and fermented to obtain a fermentation product; wherein the fermentation auxiliary agent includes seaweed powder, soybean powder, humus soil and molasses;

[0010] The fermentation product is subjected to solid-liquid separation, and the separated solid is dried to obtain the humic acid fertilizer.

[0011] Preferably, the straw is crushed and then pretreated with low-temperature plasma to obtain the pretreated straw, comprising:

[0012] Physically crushing the straw to obtain straw particles with a particle size of 1-5 mm;

[0013] The straw particles are placed in a low-temperature plasma device for pretreatment at a temperature between 30 and 50° C. for a treatment time of 10 to 30 minutes;

[0014] During the plasma treatment, the applied voltage is 2-5 kV, the frequency is 20-50 kHz, and the plasma treatment gas is air or nitrogen.

[0015] Preferably, the mixed microbial preparation comprises Pseudomonas aeruginosa, Klebsiella and lactic acid bacteria.

[0016] Preferably, the mixed microbial preparation is cultured to obtain a culture solution, comprising:

[0017] The bacillus, Klebsiella and lactic acid bacteria were inoculated into the culture medium at a ratio of 3:3:1, and cultured at a temperature of 30±2°C and a pH of 6.5-7.5 until the bacterial solution reached 1×10 6 Up to 1×10 8 CFU / mL.

[0018] Preferably, the components of the culture medium include humic acid, glucose, amino acids, complex nitrogen sources, seaweed extracts, potassium sulfate, potassium dihydrogen phosphate, trace element solutions, plant extracts and organic acids;

[0019] Wherein, the plant extract is soybean extract; and the organic acid is citric acid.

[0020] Preferably, the mass ratio of each component of the fermentation auxiliary agent is:

[0021] The mass ratio of the seaweed powder, soybean powder, humus and molasses is 5:1-2:1-2:1-2;

[0022] The total mass of the fermentation auxiliary agent is 2.5%-4% of the straw.

[0023] Preferably, the temperature of the fermentation process is controlled between 30-45° C., the humidity is maintained between 50%-70%, and the fermentation period is 15-30 days.

[0024] Preferably, the solid-liquid separation is performed by centrifugal separation or vacuum filtration, and the separated solid portion is dried at a temperature of 50-70° C. for 6-12 hours to obtain the humic acid fertilizer.

[0025] The present invention also provides a fulvic acid fertilizer, which is prepared according to the above-mentioned method for preparing fulvic acid fertilizer based on straw microbial fermentation.

[0026] The invention also proposes an application of the fulvic acid fertilizer in plant growth.

[0027] From a microscopic perspective, the principle mechanism of the fulvic acid fertilizer preparation scheme of the present invention includes the following key aspects:

[0028] 1. Microscopic mechanism of low-temperature plasma pretreatment

[0029] Straw surface modification: Low-temperature plasma undergoes physical and chemical reactions with the straw surface through high-energy electrons and free radicals, destroying the surface structure of the straw, increasing its roughness and porosity, and exposing more reaction sites.

[0030] Chemical bond breaking and functional group introduction: Plasma can break the chemical bonds (such as CC bonds, CH bonds) in the lignin, cellulose and hemicellulose molecules in the straw, and introduce polar groups such as hydroxyl (OH) and carboxyl (COOH), thereby enhancing the hydrophilicity of the straw and the adhesion ability of microorganisms.

[0031] Improve biodegradability: After plasma treatment, the structure of the straw is partially depolymerized, the lignin barrier is weakened, and the accessibility of cellulose and hemicellulose is improved, providing more favorable conditions for the degradation and utilization of microorganisms.

[0032] 2. Synergistic mechanism of fermentation adjuvants

[0033] Seaweed powder: rich in active substances such as brown algae polysaccharide, mannitol, iodine, etc., which can activate the metabolic activity of microorganisms and enhance their fermentation ability; at the same time, its decomposition products can serve as precursors of fulvic acid and increase the production of fulvic acid.

[0034] Soy flour: provides rich protein and amino acids, acts as a nitrogen source to promote microbial growth, and improves the nitrogen balance in the fermentation system.

[0035] Humus soil: Contains natural humus and trace elements, which can stabilize the pH value of the fermentation environment and provide a natural habitat for microorganisms, further increasing the organic matter content of humic acid fertilizer.

[0036] Molasses: As a carbon source, it provides energy that can be quickly utilized by microorganisms and promotes fermentation efficiency; at the same time, its metabolites help form the molecular structure of fulvic acid.

[0037] 3. Synergistic mechanism of fermentation microorganisms

[0038] Pseudomonas rod-shaped:

[0039] Cellulolysis: It can secrete cellulase and xylanase to quickly degrade cellulose and hemicellulose and release usable sugars.

[0040] Metabolites: The generated organic acids (such as oxalic acid and citric acid) can further degrade lignin and improve the overall degradation efficiency of the fermentation system.

[0041] Klebsiella:

[0042] Nitrogen fixation: It has the function of nitrogen fixation, which can increase the nitrogen content of the fermentation system and promote the growth and metabolism of microorganisms.

[0043] Synergistic effect: It cooperates with other bacteria to secrete fulvic acid precursors and optimize the production pathway of fulvic acid.

[0044] Lactic acid bacteria:

[0045] Organic acid production: Lactic acid bacteria produce lactic acid through carbohydrate metabolism, which regulates the acidic environment of the fermentation system, inhibits the growth of harmful microorganisms, and improves the stability of fulvic acid.

[0046] Auxiliary function: The cell wall decomposing enzymes produced during the metabolism of lactic acid bacteria can further promote the degradation of straw.

[0047] 4. Mechanism of promotion of culture medium and trace elements

[0048] Nutritional supply:

[0049] Amino acids and complex nitrogen sources provide efficient nitrogen for microorganisms, promoting the synthesis of proteins and enzymes;

[0050] Glucose provides quick energy and supports microbial metabolism;

[0051] Plant extracts (such as flavonoids in licorice) have antioxidant and metabolic effects, optimizing microbial fermentation efficiency.

[0052] Trace element regulation:

[0053] Iron (Fe) is involved in regulating the activity of oxidoreductases;

[0054] Manganese (Mn) and zinc (Zn) are cofactors of many enzymes;

[0055] Boron (B) and molybdenum (Mo) play an important role in cell wall formation and nitrogen metabolism of microorganisms.

[0056] 5. Chemical mechanism of fulvic acid production

[0057] Molecular transformation pathway:

[0058] During the fermentation process, microorganisms decompose the polysaccharides, lignin and proteins in the straw and convert them into precursor compounds of fulvic acid, such as small molecule organic acids, polyphenol compounds, etc.

[0059] The precursor compounds are further condensed and oxidized to form fulvic acid molecules with various functional groups (such as carboxyl and phenolic hydroxyl groups).

[0060] Structural optimization:

[0061] The organic acids and phenolic substances produced during the fermentation process can promote the diversification of fulvic acid molecules, improve their activity and stability in the soil.

[0062] 6. Crop growth promotion mechanism

[0063] Soil Improvement:

[0064] Fulvic acid can chelate metal ions (such as iron and zinc) in the soil, improving the effectiveness of nutrients;

[0065] Improve the ability of soil aggregate formation and improve soil structure.

[0066] Promotes root development:

[0067] The active functional groups in fulvic acid can stimulate the division and elongation of crop root cells and enhance the root system's ability to absorb water and nutrients.

[0068] Enhance stress resistance:

[0069] Fulvic acid can activate the antioxidant enzyme system of crops and improve their resistance to drought, disease and salinity.

[0070] Summary: The fulvic acid fertilizer preparation scheme of the present invention improves the preparation efficiency and product performance through the synergistic effect of multiple microscopic mechanisms from raw material pretreatment, microbial fermentation to the final fertilizer function formation, provides scientific support for the resource utilization of agricultural waste, and significantly enhances the effect of fulvic acid fertilizer on crop growth and soil improvement.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] 1. Low-temperature plasma pretreatment enhances the degradability of straw: Pretreatment of straw with low-temperature plasma technology significantly improves the hydrophilicity and biodegradability of straw, providing a better substrate for microbial fermentation. This process not only shortens the fermentation cycle, but also improves the yield and quality of the final fulvic acid.

[0073] 2. Innovative fermentation adjuvant combination: The present invention combines a variety of natural organic substances such as seaweed powder, soybean powder, humus and molasses as composite fermentation adjuvants. These substances interact with each other during the microbial fermentation process, providing rich nutrients and growth-promoting factors, significantly improving the metabolic activity of microorganisms, and thus increasing the organic matter content and fertilizer efficiency of fulvic acid fertilizer.

[0074] 3. Synergistic effect of lactic acid bacteria: Introducing lactic acid bacteria into fermentation microorganisms can promote the production of organic acids and enhance the stability and biological activity of fulvic acid. Lactic acid bacteria help optimize the structure of microbial populations, improve the acid-base balance of the soil, and promote the absorption of nutrients by crops.

[0075] 4. Applicable to various straw raw materials: The preparation method of fulvic acid fertilizer provided by the present invention can be widely applied to various types of straw raw materials such as corn straw, wheat straw and rice straw. This provides more options for the effective utilization of agricultural waste and helps reduce the pollution of straw to the environment.

[0076] 5. Significant soil improvement effect: The humic acid fertilizer prepared by the present invention can effectively improve the soil structure, increase the content of soil organic matter, enhance the water retention and air permeability of the soil, thereby improving soil fertility and creating a better environment for crop growth.

[0077] 6. Improve crop growth and yield: After applying the humic acid fertilizer of the present invention, the root development, plant height and leaf area of ​​crops are significantly increased, thereby accelerating the growth rate of crops and enhancing stress resistance. Compared with the prior art, this fertilizer has a more significant effect and is more conducive to the healthy growth of crops.

[0078] 7. Environmental friendliness and sustainability: This method uses agricultural waste (straw) as the main raw material, which is in line with the development concept of sustainable agriculture. It also reduces the cost of agricultural waste treatment and avoids the use of any harmful chemical additives, thus meeting environmental protection requirements.

[0079] The present invention optimizes the preparation process of fulvic acid fertilizer through low-temperature plasma pretreatment and innovative fermentation auxiliary agent combination, improves the fertilizer efficiency and crop growth effect of the fertilizer, and at the same time helps to solve the environmental problems of agricultural waste, providing a more environmentally friendly and efficient solution for agricultural production. DETAILED DESCRIPTION

[0080] 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.

[0081] Example 1 Preparation of culture medium

[0082] The raw materials include humic acid, glucose, amino acids, complex nitrogen sources, seaweed extracts, potassium sulfate, potassium dihydrogen phosphate, trace element solutions, plant extracts and organic acids.

[0083] Equipment includes culture bottles, stirrers, pH meters, autoclaves, etc.

[0084] Follow the steps below to prepare the culture medium:

[0085] 1. Preparation of seaweed extract: Clean the brown algae, remove seawater impurities and salt, cut into small pieces and put into water, keep the water temperature at 70±3℃, and heat and extract for about 40 minutes. Stir slightly during the extraction process to promote the dissolution of the active ingredients. After the extraction is completed, filter the liquid, remove the residue and dry it, and the powder obtained is the seaweed extract.

[0086] 2. Preparation of plant extract: After cleaning, cut the licorice root into small pieces, take 500 ml of 70% ethanol for every 100 g of licorice root, mix, seal and place in a cool place, shake once every 24 hours, soak for 72 hours, after the extraction is completed, filter with filter paper or gauze to remove plant residues; concentrate the filtered ethanol extract at low temperature using an evaporator, and then dry the concentrate into powder to obtain the plant extract.

[0087] 3. Preparation of trace element solution:

[0088] 2.78g of iron sulfate, 0.151g of manganese sulfate, 0.0807g of zinc sulfate, 0.01596g of copper sulfate, 0.06159g of ammonium molybdate, 0.00775g of cobalt sulfate and 0.006183g of boric acid were added to about 50mL of deionized water and stirred until completely dissolved. Each solution was mixed one by one to ensure that the solution of each element was completely dissolved, and then the mixed solution was diluted to a total volume of 1000mL using deionized water. The pH of the trace element solution was adjusted to 5-7 using hydrochloric acid and sodium hydroxide solution to obtain a final trace element solution.

[0089] 4. Mix humic acid, glucose, amino acid (glutamic acid), complex nitrogen source (urea), seaweed extract, potassium sulfate, potassium dihydrogen phosphate and trace element solution in a mass ratio of 15:5:1:1:0.5:5:3:0.3, add appropriate amount of distilled water and stir evenly.

[0090] 5. Adjust the pH value of the mixture to between 6.5-7.5 to meet the growth requirements of microorganisms.

[0091] 6. Sterilize the mixed culture medium solution under high temperature and high pressure to ensure that there is no contamination by other microorganisms.

[0092] 7. After sterilization, cool the culture medium to room temperature and then add appropriate amounts of plant extracts and organic acids to provide the nutrients required for microbial growth and promote their metabolism.

[0093] 8. Finally, pour the prepared culture medium into the culture bottle and prepare to inoculate the mixed microbial preparation.

[0094] Through the above steps, a culture medium suitable for the growth of Pseudomonas, Klebsiella and lactic acid bacteria can be obtained, laying a good foundation for the subsequent microbial fermentation process.

[0095] Example 2 Preparation of fulvic acid fertilizer using corn stalks as raw materials

[0096] Pretreatment of corn stalks: First, the corn stalks were physically crushed to obtain stalk particles with a particle size of 1-5 mm. These stalk particles were then placed in a low-temperature plasma device for pretreatment, with the treatment temperature set at 40°C and the treatment time set at 20 minutes. During the plasma treatment process, the applied voltage was 3 kV, the frequency was 35 kHz, and the plasma treatment gas was air.

[0097] Cultivation of mixed microbial preparations: Pseudomonas aeruginosa, Klebsiella pneumoniae and lactic acid bacteria were inoculated into the culture medium at a ratio of 3:3:1, and cultured at a temperature of 30±2°C and a pH of 6.5-7.5 until the bacterial liquid reached 1×10^7 CFU / mL.

[0098] Fermentation process: pre-treated corn stalks, nutrient solution, fermentation aids and Trichoderma are mixed and fermented. The mass ratio of each component of the fermentation aid is seaweed powder: soybean powder: humus soil: molasses = 5:1.5:1.5:1.5, and the total mass of the fermentation aid is 3% of the stalks. The temperature of the fermentation process is controlled at 35°C, the humidity is maintained at 60%, and the fermentation cycle is 20 days.

[0099] Solid-liquid separation and drying: The fermentation product is centrifuged and the separated solid part is dried at a drying temperature of 60°C for 8 hours to obtain humic acid fertilizer.

[0100] Through the above steps, humic acid fertilizer using corn straw as raw material was successfully prepared. The fertilizer is rich in organic matter and microbial metabolites, which can effectively improve soil structure and enhance soil fertility.

[0101] Example 3 Preparation of fulvic acid fertilizer using wheat straw as raw material

[0102] Pretreatment of wheat straw: The wheat straw was physically crushed to obtain straw particles with a particle size of 1-5 mm. These straw particles were placed in a low-temperature plasma device for pretreatment, with the treatment temperature set at 45°C and the treatment time set at 15 minutes. During the plasma treatment process, the applied voltage was 4 kV, the frequency was 40 kHz, and the plasma treatment gas was nitrogen.

[0103] Cultivation of mixed microbial preparation: The mixed microbial preparation was cultured according to the method in Example 2.

[0104] Fermentation process: pre-treated wheat straw, nutrient solution, fermentation aid and Trichoderma are mixed and fermented. The mass ratio of each component of the fermentation aid is seaweed powder: soybean powder: humus soil: molasses = 5:1:1:2, and the total mass of the fermentation aid is 4% of the straw. The temperature of the fermentation process is controlled at 40°C, the humidity is maintained at 70%, and the fermentation cycle is 25 days.

[0105] Solid-liquid separation and drying: The fermentation product is separated by vacuum filtration, and the separated solid part is dried at a drying temperature of 65°C for 10 hours to obtain humic acid fertilizer.

[0106] Through the above steps, humic acid fertilizer using wheat straw as raw material was successfully prepared, which has a good soil improvement effect and can promote crop growth.

[0107] Example 4 Preparation of fulvic acid fertilizer using rice straw as raw material

[0108] Pretreatment of rice straw: The rice straw was physically crushed to obtain straw particles with a particle size of 1-5 mm. These straw particles were placed in a low-temperature plasma device for pretreatment, with the treatment temperature set at 35°C and the treatment time set at 25 minutes. During the plasma treatment process, the applied voltage was 2 kV, the frequency was 25 kHz, and the plasma treatment gas was air.

[0109] Cultivation of mixed microbial preparation: The mixed microbial preparation was cultured according to the method in Example 2.

[0110] Fermentation process: pre-treated rice straw, nutrient solution, fermentation aid and Trichoderma are mixed and fermented. The mass ratio of each component of the fermentation aid is seaweed powder: soybean powder: humus soil: molasses = 5:2:2:1, and the total mass of the fermentation aid is 2.5% of the straw. The temperature of the fermentation process is controlled at 30°C, the humidity is maintained at 50%, and the fermentation cycle is 30 days.

[0111] Solid-liquid separation and drying: The fermentation product is centrifuged and the separated solid part is dried at a drying temperature of 55°C for 9 hours to obtain humic acid fertilizer.

[0112] Through the above steps, humic acid fertilizer using rice straw as raw material was successfully prepared, which can effectively improve the water and fertilizer retention capacity of the soil and promote the healthy growth of crops.

[0113] Test Example 1

[0114] The comprehensive performance test of the fulvic acid fertilizer prepared based on corn straw, wheat straw and rice straw raw materials in Examples 2-4 was carried out, and the test method is as follows:

[0115] Fulvic acid content: The acid dissolution method is used and the measurement is carried out using a UV-visible spectrophotometer, and quantitative analysis is performed based on the characteristic absorption peak of fulvic acid.

[0116] pH value: Use a pH meter to directly measure the pH value of the fertilizer aqueous solution.

[0117] Organic matter content: The organic matter content is determined by the ash method.

[0118] Nitrogen, phosphorus and potassium contents: conventional chemical analysis methods were used, with nitrogen content being determined by the Kjeldahl method, and phosphorus and potassium contents being determined by spectrophotometry and flame photometry, respectively.

[0119] The results are shown in Table 1.

[0120] Table 1

[0121]

[0122] As shown in Table 1, the three fulvic acid fertilizers prepared based on different straw raw materials all showed good results in terms of main performance indicators. The fulvic acid content of corn straw fulvic acid fertilizer was the highest, reaching 18.5%, indicating that it had a high degree of humification and potential soil improvement ability. The fulvic acid content of wheat straw fulvic acid fertilizer was slightly lower, at 16.3%, but its organic matter content was the lowest, at 35.7%, which may mean that it decomposed faster in the soil. The fulvic acid content of rice straw fulvic acid fertilizer was 17.0%, and the organic matter content was 38.5%, which was between the first two.

[0123] In terms of pH value, the three fertilizers are all slightly acidic, with pH values ​​of 6.2, 6.1 and 6.3 respectively, which is conducive to the growth of most crops, because most crops grow better in slightly acidic to neutral soil. Nitrogen, phosphorus and potassium are the three essential nutrients for plant growth. From the data in the table, it can be seen that the nitrogen, phosphorus and potassium contents of the three fertilizers have reached a certain level. The nitrogen content is determined by Kjeldahl nitrogen determination, and the phosphorus and potassium contents are determined by spectrophotometry and flame photometry respectively. The phosphorus and potassium contents of rice straw humic acid fertilizer are the highest, at 0.90% and 1.3% respectively, which may help improve the yield and quality of crops.

[0124] In general, all three humic acid fertilizers have good comprehensive performance, and the appropriate fertilizer type can be selected according to the needs of different crops and soil conditions. For example, rice straw humic acid fertilizer may be a better choice for crops that require more phosphorus and potassium nutrients. Corn straw humic acid fertilizer may be more suitable for soil improvement that requires a higher humus content.

[0125] Comparative Example 1

[0126] The preparation method is the same as that of Example 2, except that no low-temperature plasma pretreatment is performed, and only physical crushing is performed.

[0127] Comparative Example 2

[0128] The preparation method is the same as in Example 2, the only difference being that no fermentation aid is added.

[0129] Comparative Example 3

[0130] The preparation method is the same as that of Example 2, the only difference being that the mixed microbial preparation does not contain lactic acid bacteria, and only uses Pseudomonas aeruginosa and Klebsiella in a ratio of 3:7.

[0131] Test Example 2

[0132] Corn was selected as the experimental crop to conduct effect tests on Example 2 and Comparative Examples 1-3. The test results of soil improvement effect, crop growth effect, and fulvic acid content are shown in Tables 2-4, respectively.

[0133] Table 2

[0134]

[0135]

[0136] Table 3

[0137] Experimental Group Root length (cm) Plant height (cm) Leaf area (cm2) Example 2 25.4 50.5 55.2 Comparative Example 1 22.3 47.0 50.3 Comparative Example 2 21.0 45.1 48.1 Comparative Example 3 23.5 48.2 51.3

[0138] Table 4

[0139] Experimental Group Fulvic acid content (g / L) Example 2 15.6 Comparative Example 1 13.5 Comparative Example 2 12.9 Comparative Example 3 14.2

[0140] As shown in Tables 2-4, the soil improvement effect, crop growth effect and fulvic acid content of Example 2 are better than those of Comparative Examples 1-3. Specifically, the soil organic matter content, soil pH value, soil water retention capacity, root length, plant height, leaf area and fulvic acid content of Example 2 are higher than those of other comparative examples, which shows that the preparation method adopted in Example 2, including low-temperature plasma pretreatment, addition of fermentation adjuvant and use of a mixed microbial preparation (lactic acid bacteria, Pseudomonas rod-shaped and Klebsiella) in a specific proportion, has a significant positive effect on soil improvement and crop growth. Comparative Example 1 did not undergo low-temperature plasma pretreatment, Comparative Example 2 did not add fermentation adjuvant, and Comparative Example 3 did not use lactic acid bacteria, all of which led to a decrease in the improvement effect and crop growth indicators. Therefore, it can be concluded that the preparation method of Example 2 is more effective in soil improvement and crop growth promotion.

[0141] 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 microbial fermentation, characterized in that: include: The straw is crushed and then pretreated with low-temperature plasma to obtain pretreated straw; culturing the mixed microbial preparation to obtain a culture solution; The pretreated straw, nutrient solution, fermentation auxiliary agent and Trichoderma are mixed and fermented to obtain a fermentation product; wherein the fermentation auxiliary agent includes seaweed powder, soybean powder, humus soil and molasses; The fermentation product is subjected to solid-liquid separation, and the separated solid is dried to obtain the humic acid fertilizer.

2. The method for preparing fulvic acid fertilizer based on straw microbial fermentation according to claim 1, characterized in that: The straw is crushed and then pretreated with low-temperature plasma to obtain pretreated straw, including: Physically crushing the straw to obtain straw particles with a particle size of 1-5 mm; The straw particles are placed in a low-temperature plasma device for pretreatment at a temperature between 30 and 50° C. for a treatment time of 10 to 30 minutes; During the plasma treatment, the applied voltage is 2-5 kV, the frequency is 20-50 kHz, and the plasma treatment gas is air or nitrogen.

3. The method for preparing fulvic acid fertilizer based on straw microbial fermentation according to claim 1, characterized in that: The mixed microbial preparation comprises Pseudomonas aeruginosa, Klebsiella and lactic acid bacteria.

4. The method for preparing fulvic acid fertilizer based on straw microbial fermentation according to claim 3, characterized in that: When the mixed microbial preparation is cultured to obtain the culture fluid, it includes: The bacillus, Klebsiella and lactic acid bacteria were inoculated into the culture medium at a ratio of 3:3:1, and cultured at a temperature of 30±2°C and a pH of 6.5-7.5 until the bacterial solution reached 1×10 6 Up to 1×10 8 CFU / mL.

5. The method for preparing fulvic acid fertilizer based on straw microbial fermentation according to claim 4, characterized in that: The components of the culture medium include humic acid, glucose, amino acids, complex nitrogen sources, seaweed extracts, potassium sulfate, potassium dihydrogen phosphate, trace element solution, plant extracts and organic acids; Wherein, the plant extract is soybean extract; and the organic acid is citric acid.

6. The method for preparing fulvic acid fertilizer based on straw microbial fermentation according to claim 1, characterized in that: The mass ratio of each component of the fermentation auxiliary agent is: The mass ratio of the seaweed powder, soybean powder, humus and molasses is 5:1-2:1-2:1-2; The total mass of the fermentation auxiliary agent is 2.5%-4% of the straw.

7. The method for preparing fulvic acid fertilizer based on straw microbial fermentation according to claim 1, characterized in that: The temperature of the fermentation process is controlled between 30-45°C, the humidity is maintained between 50%-70%, and the fermentation period is 15-30 days.

8. The method for preparing fulvic acid fertilizer based on straw microbial fermentation according to claim 1, characterized in that: The solid-liquid separation is carried out by centrifugal separation or vacuum filtration, and the separated solid part is dried at a temperature of 50-70° C. for 6-12 hours to obtain the humic acid fertilizer.

9. A fulvic acid fertilizer, characterized in that: The fulvic acid fertilizer is prepared according to the method for preparing fulvic acid fertilizer based on straw microbial fermentation according to any one of claims 1 to 8.

10. Use of the fulvic acid fertilizer according to claim 9 in plant growth.

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