Method for preparing humic acid fertilizer synergist based on biological-chemical activated weathered coal

Abstract

The invention discloses a method for preparing a humic acid fertilizer synergist based on biological-chemical activated weathered coal, and relates to the technical field of humic acid fertilizer synergists. The method comprises the following steps: mixing bacillus subtilis, trichoderma harzianum and phanerochaete chrysosporium stock seeds to obtain a complex microbial inoculant, and activating the weathered coal by using the complex microbial inoculant to obtain biologically activated weathered coal; mixing the biologically activated weathered coal with potassium hydroxide and paper pulp lignin liquid, and performing chemical solid-phase activation under a heating condition to obtain an activated product, namely the humic acid fertilizer synergist. Through synergism of biological activation and chemical activation, the content of humic acid, organic matters and fulvic acid in the humic acid fertilizer synergist can be obviously increased, so that growth and development of rape are facilitated. Moreover, the weathered coal is activated by adopting the paper pulp lignin liquid, and meanwhile, the resource utilization of the paper pulp lignin liquid and the high-order conversion of the weathered coal are realized, so that the method has great practical significance.

Description

Technical Field

[0001] This invention relates to the field of humic acid fertilizer synergists, and in particular to a method for preparing humic acid fertilizer synergists based on bio-chemical activated weathered coal. Background Technology

[0002] Weathered coal, as an abundant low-rank coal resource, suffers from drawbacks such as high moisture content, easy weathering in air, low calorific value, and difficulty in storage and transportation. These drawbacks severely limit its industrial utilization. Studies have shown that weathered coal contains as much as 30%-80% humic acid; therefore, extracting humic acid from weathered coal is of great significance for enhancing its added value.

[0003] Currently, methods for extracting humic acid from weathered coal include hydrothermal extraction, chemical acid / alkali precipitation, and microbial transformation. Hydrothermal extraction attempts to extract humic acid by disrupting the macromolecular structure of weathered coal; however, this method is energy-intensive, requires sophisticated equipment, and excessively high temperatures may damage some active functional groups in the humic acid, leading to reduced biostimulatory activity in the final product, which is detrimental to agricultural applications. Chemical acid / alkali precipitation utilizes the reaction of acid / alkali with weathered coal at a certain temperature to activate its inert structure, converting insoluble humic substances into soluble humic acid. While this method is efficient, it generates significant waste and energy consumption. Microbial transformation utilizes the metabolic activities of microorganisms to decompose and transform macromolecular organic matter in weathered coal, thereby releasing and enriching humic acid. However, microbial growth and transformation are time-consuming, making it difficult to meet the needs of large-scale production. Therefore, existing methods for extracting humic acid from weathered coal have limitations in terms of economic cost, environmental friendliness, and production efficiency. Pulp lignin liquor is a waste liquid generated during the papermaking process. Conventional methods for treating lignin liquor, such as alkali recovery technology or alkali lignin preparation technology, require the evaporation and concentration of large quantities of lignin liquor before further processing, resulting in high production costs. Research indicates that pulp lignin liquor can be combined with brewing waste and nitrogen, phosphorus, and potassium (NPK) to prepare solid compound fertilizers rich in humic acid. The humic acid extracted from pulp lignin liquor can be used as an additive in chemical fertilizers. Therefore, combining the resource utilization of pulp lignin liquor with the advanced conversion process of weathered coal has significant practical implications.

[0004] In the prior art, CN106478187A discloses a compound fertilizer synergist, prepared by mixing lignite, water, NaOH, and mixed amino acid salts, and then adding a compound microbial community (Phanerochaete chrysosporium, Trichoderma harzianum, and Bacillus subtilis) for fermentation. This patent creates a strongly alkaline environment by adding 10%-50% (by weight) NaOH to the lignite. In this environment, the compound microbial community, especially Phanerochaete chrysosporium and Trichoderma harzianum, has weak alkali tolerance, resulting in a negligible number of microorganisms actually available for degradation and transformation during the subsequent fermentation process.

[0005] Therefore, it is particularly necessary to develop a humic acid fertilizer synergist using pulp lignin liquor and weathered coal as raw materials, which can combine the resource utilization of pulp lignin liquor with the advanced conversion process of weathered coal, and also increase the content of effective components in the resulting humic acid fertilizer. Summary of the Invention

[0006] In view of the above-mentioned prior art, the purpose of this invention is to provide a method for preparing humic acid fertilizer synergists based on bio-chemical activated weathered coal.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a humic acid fertilizer synergist based on bio-chemically activated weathered coal, comprising the following steps: (1) After mixing weathered coal and plant straw, a mixture is obtained; a compound microbial agent is added to the mixture for fermentation to obtain bio-activated weathered coal; The compound microbial agent is made by mixing Bacillus subtilis fermentation powder, Trichoderma harzianum fermentation powder and Protozoa chrysospora original culture fermentation powder in a mass ratio of 1:(0.5-1.5):(0.5-1.5); (2) Add potassium hydroxide and pulp lignin solution to bio-activated weathered coal in sequence and stir to obtain a precursor; heat the precursor to react, cool after reaction, and crush it to pass through a 100-mesh sieve while it is dry. Collect the solid to obtain humic acid fertilizer enhancer.

[0008] Preferably, in step (1), the Bacillus subtilis fermentation powder is prepared by the following method: Bacillus subtilis seed liquid is inoculated into Bacillus subtilis fermentation medium and cultured at 27-32℃, aeration rate of 160-200L / h, and 150-250rpm until the spore rate is 30%-50%. After stopping fermentation, the fermentation liquid is centrifuged, collected, and spray-dried to obtain Bacillus subtilis fermentation powder.

[0009] Furthermore, the inoculation amount of Bacillus subtilis seed liquid is 4%-6% of the volume of Bacillus subtilis fermentation medium.

[0010] Furthermore, the composition of the Bacillus subtilis fermentation medium is as follows: glucose 10-20 g / L; peptone 8-12 g / L; yeast extract 4-6 g / L; (NH4)2SO4 2-4 g / L; KH2PO4 1-3 g / L; K2HPO4·3H2O 1-3 g / L; MgSO4·7H2O 0.5-1.5 g / L; MnSO4·H2O 0.02-0.04 g / L; CaCl2 0.1-0.3 g / L; FeSO4·7H2O 0.01-0.03 g / L, with a pH of 7.0-7.2.

[0011] As a preferred method, in step (1), the Trichoderma harzianum fermentation powder is prepared by the following method: Trichoderma harzianum seed liquid is inoculated into a fermentation medium containing wheat bran, fermented in the dark at 28-32℃ for 7 days, centrifuged after fermentation, the fermentation liquid is collected, and spray-dried to obtain Trichoderma harzianum fermentation powder.

[0012] Furthermore, the inoculation volume of Trichoderma harzianum seed culture is 10%-20% of the volume of the fermentation medium containing wheat bran.

[0013] Furthermore, the fermentation medium containing wheat bran consists of: 600-1000 g wheat bran, 100-200 g soybean meal, 8-12 g KH2PO4, 1.5-2.5 g MgSO4·7H2O, 25-35 g gypsum, and 6-10 g NH4NO3, with water added to a final volume of 1000 mL.

[0014] As a preferred method, in step (1), the original fermentation powder of *Phanerochaete chrysosporium* is prepared by the following method: the original seed liquid of *Phanerochaete chrysosporium* is inoculated into a fermentation medium containing wheat bran, fermented in the dark at 28-32℃ for 7 days, centrifuged after fermentation, the fermentation liquid is collected, and spray-dried to obtain the original fermentation powder of *Phanerochaete chrysosporium*.

[0015] Furthermore, the inoculation volume of the original seed liquid of *Phanerochaete chrysosporium* is 10%-20% of the volume of the fermentation medium containing wheat bran.

[0016] Furthermore, the fermentation medium containing wheat bran consists of: 600-1000 g wheat bran, 100-200 g soybean meal, 8-12 g KH2PO4, 1.5-2.5 g MgSO4·7H2O, 25-35 g gypsum, and 6-10 g NH4NO3, with water added to a final volume of 1000 mL.

[0017] Preferably, in step (1), the preservation number of Bacillus subtilis is ATCC 6051, the preservation number of Trichoderma harzianum is CBS 226.95, and the preservation number of the original species of Protozoa chrysospora is ATCC 24725.

[0018] Preferably, in step (1), the plant straw is one or more of soybean straw, peanut straw, and corn straw.

[0019] Preferably, in step (1), the mass ratio of weathered coal to plant straw is 10:(2-4).

[0020] Preferably, in step (1), the mass ratio of the compound microbial agent to the mixture is 1:(40-60).

[0021] Preferably, in step (1), the fermentation temperature is 23-26℃ and the fermentation time is 15-25 days.

[0022] As a preferred option, in step (2), the mass ratio of bio-activated weathered coal, potassium hydroxide and pulp lignin solution is 100:(6-10):(15-25).

[0023] Preferably, in step (2), the stirring temperature is 60-80℃ and the stirring time is 60-80min.

[0024] Preferably, in step (2), the heating temperature is 180-200℃ and the reaction time is 25-35min.

[0025] In a second aspect, the present invention provides a humic acid fertilizer synergist prepared by the above-described preparation method.

[0026] In a third aspect, the present invention provides the application of the above-mentioned humic acid fertilizer synergist in promoting rapeseed development.

[0027] The beneficial effects of this invention are: This invention uses a mixture of Bacillus subtilis, Trichoderma harzianum, and Protozoa chrysospora as a compound microbial agent. First, weathered coal is activated using this compound microbial agent to obtain bio-activated weathered coal. Then, the bio-activated weathered coal is mixed with potassium hydroxide and pulp lignin solution, and chemical solid-phase activation is performed under heating conditions. The activation product is a humic acid fertilizer synergist. This invention, through the synergistic effect of biological and chemical activation, can significantly increase the content of humic acid, organic matter, and fulvic acid in the humic acid fertilizer synergist, thereby benefiting the growth and development of rapeseed. Furthermore, this invention uses pulp lignin solution to activate weathered coal, simultaneously realizing the resource utilization of pulp lignin solution and the high-level transformation of weathered coal, which is of great practical significance. In addition, this invention, using the synergistic treatment of weathered coal with biological and chemical activation to obtain humic acid materials, has a synergistic effect in improving the plant height and root length of rapeseed. Detailed Implementation

[0028] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0029] In existing technologies, weathered coal and lignin liquor from pulp are common industrial byproducts. Direct discharge of these substances not only causes environmental pollution but also wastes energy. Therefore, these two materials can be recycled and reused to "turn waste into treasure," creating economic value and solving environmental problems.

[0030] Based on this, the present invention provides a method for preparing a humic acid fertilizer synergist using weathered coal and pulp lignin liquor as raw materials. Specifically, a compound microbial agent is first prepared using Bacillus subtilis, Trichoderma harzianum, and Protozoa chrysospora. Then, this compound microbial agent is used to bio-activate the weathered coal, yielding bio-activated weathered coal. Next, potassium hydroxide and pulp lignin liquor are used to chemically activate the bio-activated weathered coal, resulting in the humic acid fertilizer synergist. During the bioactivation process, the compound microbial agent forms a highly efficient micro-ecosystem through physical penetration of mycelia, synergistic degradation of enzymes (lignin / cellulose / protease, etc.) and mutual benefit of metabolites, which significantly improves the activation efficiency and product diversity of weathered coal and enhances its environmental adaptability.

[0031] In the chemical activation process, a two-step activation method using potassium hydroxide and pulp lignin solution is employed. First, K... + The insertion and etching processes create a carbon framework with ultra-high specific surface area and hierarchical porosity. + H in oxygen-containing functional groups in weathered coal + Ion exchange occurs, causing K + Deeper distributed within the structure of weathered coal, the intense chemical reactions create an extremely large specific surface area. Potassium hydroxide activation creates numerous defects and unsaturated bonds on the carbon skeleton surface; these sites are highly chemically reactive and readily react with other substances. The lignin liquor of pulp contains abundant lignin and hemicellulose, along with many trace elements such as calcium and magnesium. Large organic molecules like lignin and hemicellulose, in solution or molten state, permeate and partially fill the pores created by potassium hydroxide, and then... 2+ and Mg 2+Under the catalytic action of potassium hydroxide and pulp lignin solution, the macromolecular organic matter that has penetrated into the pores undergoes better pyrolysis and carbonization to modify and expand the pore structure. Simultaneously, the water vapor and carbon dioxide generated during pyrolysis and carbonization further react and etch the carbon skeleton. Furthermore, the lignin and other components in the pulp lignin solution can increase soil porosity and improve the soil's water and fertilizer retention capacity. Therefore, the humic acid obtained through the two-step synergistic activation method using potassium hydroxide and pulp lignin solution typically has a higher specific surface area and total pore volume, a more optimized pore size distribution, and richer nutrient content than humic acid obtained using either potassium hydroxide or pulp lignin solution alone. This results in better water solubility, acid solubility, and anti-flocculation properties, making it more suitable as a semi-finished raw material for fertilizer deep processing and direct agricultural application.

[0032] This invention utilizes a bio-chemical synergistic activation process. First, it leverages the degradation effect of a compound microbial agent to activate weathered coal, avoiding the inactivation of the agent caused by directly introducing it into a strongly alkaline environment. Through biological pretreatment, the coal-based carbon chains are enzymatically broken down into highly active small-molecule carbon chains, increasing oxygen-containing functional groups. Potassium hydroxide is then added for further chemical activation, making the carbon chain functional groups free and water-soluble, thus improving their functionality and reducing the salinity and environmental impact of the final humic acid fertilizer synergist.

[0033] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0034] The experimental materials used in the embodiments of this invention are all conventional experimental materials in the art and can be purchased through commercial channels.

[0035] In this invention, the spore rate is calculated based on microscopic counting, and the calculation formula is as follows: Spore rate (%) = [N_spores / (N_vegetative+N_spores)] × 100%; In the formula, N_spores represents the number of spores observed under a microscope, and N_vegetative represents the number of vegetative cells observed under a microscope.

[0036] Bacillus subtilis, with accession number ATCC 6051, was purchased from Shandong Agricultural University Fertilizer Technology Co., Ltd.; Trichoderma harzianum, with accession number CBS 226.95, was purchased from Shandong Hezhong Kangyuan Biotechnology Co., Ltd.; Phanerochaete chrysosporium, with accession number ATCC 24725, was purchased from Shanghai Xuanke Biotechnology Co., Ltd.; weathered coal was purchased from Inner Mongolia Xinzhongshenglihe Fertilizer Co., Ltd.; and pulp lignin liquor, a waste liquid generated from the alkaline pulping process in the papermaking industry, was found to have a solid content of 42%.

[0037] The method for preparing Bacillus subtilis seed culture is as follows: Bacillus subtilis is inoculated into LB liquid medium and activated by culturing at 30℃ for 12h. The activated Bacillus subtilis is then inoculated into LB medium at an inoculation rate of 5% (volume ratio) and cultured at 30℃ with shaking for 15h to obtain Bacillus subtilis seed culture.

[0038] The method for preparing Trichoderma harzianum seed culture is as follows: Trichoderma harzianum is inoculated into PDA plate medium and cultured at 30℃ for 7 days to activate it. The activated Trichoderma harzianum is then inoculated into PDA liquid medium at an inoculation rate of 15% (volume ratio) and cultured at 30℃ and 160 rpm for 4 days to obtain Trichoderma harzianum seed culture.

[0039] The preparation method of *Phanerochaete chrysosporium* seed culture is as follows: *Phanerochaete chrysosporium* is inoculated into PDA plate medium and cultured at 30℃ for 7 days to activate it. The activated *Phanerochaete chrysosporium* is then inoculated into PDA liquid medium at an inoculation rate of 15% (volume ratio) and cultured at 30℃ and 160 rpm for 4 days to obtain *Phanerochaete chrysosporium* seed culture.

[0040] Example 1: (1) Bacillus subtilis seed culture was inoculated into Bacillus subtilis fermentation medium at an inoculation rate of 5% (volume ratio). The culture was carried out at 30℃, aeration rate of 180L / h, and 200rpm until the spore rate reached 40%. After stopping the fermentation, the culture was centrifuged and the fermentation liquid was collected. After spray drying, Bacillus subtilis fermentation powder was obtained. The composition of Bacillus subtilis fermentation medium was as follows: glucose 15g / L; peptone 10g / L; yeast powder 5g / L; (NH4)2SO4 3g / L; KH2PO4 2g / L; K2HPO4•3H2O 2g / L; MgSO4•7H2O 1g / L; MnSO4•H2O 0.03g / L; CaCl2 0.2g / L; FeSO4•7H2O 0.02g / L, pH 7.1. Trichoderma harzianum seed culture was inoculated into a fermentation medium containing wheat bran at an inoculation rate of 15% (volume ratio), and fermented in the dark at 30°C for 7 days. After fermentation, the fermentation liquid was collected by centrifugation and spray-dried to obtain Trichoderma harzianum fermentation powder. The original seed liquid of *Phanerochaete chrysosporium* was inoculated into a fermentation medium containing wheat bran at an inoculation rate of 15% (volume ratio). It was fermented in the dark at 30°C for 7 days. After fermentation, the liquid was centrifuged, collected, and spray-dried to obtain the original fermentation powder of *Phanerochaete chrysosporium*. The fermentation medium containing wheat bran consists of: 800 g wheat bran, 150 g soybean meal powder, 10 g KH2PO4, 2 g MgSO4•7H2O, 30 g gypsum, and 8 g NH4NO3, with water added to a final volume of 1000 mL. A compound microbial agent was prepared by mixing Bacillus subtilis fermentation powder, Trichoderma harzianum fermentation powder and Protozoa chrysospora original culture fermentation powder in a mass ratio of 1:1:1. (2) Soybean straw, peanut straw and corn straw are mixed in a mass ratio of 1:1:1 to obtain plant straw; weathered coal and plant straw are mixed in a mass ratio of 10:3 to obtain a mixture; the mixture and compound microbial agent are mixed in a mass ratio of 50:1 and fermented at 25°C for 20 days to obtain bio-activated weathered coal. (3) Heat the bio-activated weathered coal to 60°C, add potassium hydroxide and pulp lignin solution in sequence and stir for 60 min to obtain the precursor. The mass ratio of bio-activated weathered coal, potassium hydroxide and pulp lignin solution is 100:8:20. Place the precursor at 180°C for 30 min and cool it after the reaction. Immediately after drying, crush it to pass through a 100-mesh sieve and collect the solid to obtain the humic acid fertilizer synergist.

[0041] Example 2: (1) Bacillus subtilis seed culture was inoculated into Bacillus subtilis fermentation medium at an inoculation rate of 4% (volume ratio). The culture was carried out at 27℃, aeration rate of 160L / h, and 150rpm until the spore rate reached 30%. After stopping the fermentation, the culture was centrifuged and the fermentation broth was collected. After spray drying, Bacillus subtilis fermentation powder was obtained. The composition of Bacillus subtilis fermentation medium was as follows: glucose 10g / L; peptone 8g / L; yeast powder 4g / L; (NH4)2SO4 2g / L; KH2PO4 1g / L; K2HPO4•3H2O 1g / L; MgSO4•7H2O 0.5g / L; MnSO4•H2O 0.02g / L; CaCl2 0.1g / L; FeSO4•7H2O 0.01g / L, pH 7.01. Trichoderma harzianum seed culture was inoculated into a fermentation medium containing wheat bran at an inoculation rate of 10% (volume ratio), and fermented in the dark at 28°C for 7 days. After fermentation, the fermentation liquid was centrifuged, collected, and spray-dried to obtain Trichoderma harzianum fermentation powder. The original seed liquid of *Phanerochaete chrysosporium* was inoculated into a fermentation medium containing wheat bran at an inoculation rate of 10% (volume ratio). It was fermented in the dark at 28°C for 7 days. After fermentation, the liquid was centrifuged, collected, and spray-dried to obtain the fermentation powder of *Phanerochaete chrysosporium*. The fermentation medium containing wheat bran consists of: 600 g wheat bran, 100 g soybean meal powder, 8 g KH2PO4, 1.5 g MgSO4•7H2O, 25 g gypsum, and 6 g NH4NO3, with water added to a final volume of 1000 mL. A compound microbial agent was prepared by mixing Bacillus subtilis fermentation powder, Trichoderma harzianum fermentation powder and Protozoa chrysospora original culture fermentation powder in a mass ratio of 1:0.5:0.5. (2) Soybean straw, peanut straw and corn straw are mixed in a mass ratio of 1:1:1 to obtain plant straw; weathered coal and plant straw are mixed in a mass ratio of 10:2 to obtain a mixture; the mixture and compound microbial agent are mixed in a mass ratio of 40:1 and fermented at 23°C for 15 days to obtain biologically activated weathered coal. (3) Heat the bio-activated weathered coal to 70°C, add potassium hydroxide and pulp lignin solution in sequence and stir for 70 min to obtain the precursor. The mass ratio of bio-activated weathered coal, potassium hydroxide and pulp lignin is 100:6:15. Place the precursor at 190°C for 25 min to react. After the reaction, cool it and immediately crush it through a 100-mesh sieve while it is dry. Collect the solid to obtain the humic acid fertilizer synergist.

[0042] Example 3: (1) Bacillus subtilis seed culture was inoculated into Bacillus subtilis fermentation medium at an inoculation rate of 6% (volume ratio). The culture was carried out at 32℃, aeration rate of 200L / h, and 250rpm until the spore rate reached 50%. After stopping the fermentation, the culture was centrifuged and the fermentation liquid was collected. The fermentation liquid was spray-dried to obtain Bacillus subtilis fermentation powder. The composition of Bacillus subtilis fermentation medium was as follows: glucose 20g / L; peptone 12g / L; yeast powder 6g / L; (NH4)2SO4 4g / L; KH2PO4 3g / L; K2HPO4•3H2O 3g / L; MgSO4•7H2O 1.5g / L; MnSO4•H2O 0.04 g / L; CaCl2 0.3 g / L; FeSO4•7H2O 0.03 g / L, pH 7.2. Trichoderma harzianum seed culture was inoculated into a fermentation medium containing wheat bran at an inoculation rate of 20% (volume ratio), and fermented in the dark at 32°C for 7 days. After fermentation, the fermentation liquid was collected by centrifugation and spray-dried to obtain Trichoderma harzianum fermentation powder. The original seed liquid of *Phanerochaete chrysosporium* was inoculated into a fermentation medium containing wheat bran at an inoculation rate of 15% (volume ratio). It was fermented in the dark at 32°C for 7 days. After fermentation, the liquid was centrifuged, collected, and spray-dried to obtain the original fermentation powder of *Phanerochaete chrysosporium*. The fermentation medium containing wheat bran consists of: 1000 g wheat bran, 200 g soybean meal powder, 12 g KH2PO4, 2.5 g MgSO4•7H2O, 35 g gypsum, 10 g NH4NO3, and water to a final volume of 1000 mL. A compound microbial agent was prepared by mixing Bacillus subtilis fermentation powder, Trichoderma harzianum fermentation powder and Protozoa chrysospora original culture fermentation powder in a mass ratio of 1:1.5:1.5. (2) Soybean straw, peanut straw and corn straw are mixed in a mass ratio of 1:1:1 to obtain plant straw; weathered coal and plant straw are mixed in a mass ratio of 10:4 to obtain a mixture; the mixture and compound microbial agent are mixed in a mass ratio of 60:1 and fermented at 26℃ for 25 days to obtain biologically activated weathered coal. (3) Heat the bio-activated weathered coal to 80°C, add potassium hydroxide and pulp lignin solution in sequence and stir for 80 min to obtain the precursor. The mass ratio of bio-activated weathered coal, potassium hydroxide and pulp lignin solution is 100:10:25. Place the precursor at 200°C for 35 min and cool it after the reaction. While it is dry, crush it to pass through a 100-mesh sieve and collect the solid to obtain the humic acid fertilizer synergist.

[0043] Comparative Example 1: The difference between this comparative example and Example 1 is that only the weathered coal undergoes biological activation treatment. That is, biologically activated weathered coal is prepared using the method of Example 1 and used as a humic acid fertilizer synergist.

[0044] Comparative Example 2: The difference between this comparative example and Example 1 is that only the weathered coal undergoes chemical activation treatment. The specific preparation method is as follows: Weathered coal was heated to 60°C, and potassium hydroxide and pulp lignin solution were added sequentially and stirred for 60 minutes to obtain a precursor. The mass ratio of weathered coal, potassium hydroxide and pulp lignin solution was 100:8:20. The precursor was placed at 180°C for 30 minutes to react. After the reaction, it was cooled and immediately pulverized through a 100-mesh sieve while dry. The solid was collected to obtain the humic acid fertilizer synergist.

[0045] Comparative Example 3: Weathered coal and potassium hydroxide were mixed at a mass ratio of 100:8 and then crushed to obtain activated weathered coal, which was used as an synergist for humic acid fertilizer.

[0046] Experimental Example 1: Component Detection The components of the humic acid fertilizer synergists prepared in Example 1 and Comparative Examples 1-3 were tested, with weathered coal set as a control group. The results are shown in Table 1. Water-soluble humic acid in the samples was tested using the volumetric method in GB / T 11957-2001 "Determination of Humic Acid Yield in Coal", with tertiary water used instead of sodium pyrophosphate alkaline solution; all other operations were the same. Organic matter was tested according to the method in NY / T525-2021 "Organic Fertilizers"; water-insoluble matter content was tested according to the method in HG / T3278-2018 "Sodium Humate"; and fulvic acid content was tested according to the method in HG / T5334-2018 "Potassium Fulvicate".

[0047] Table 1. Physicochemical properties of the fertilizers prepared in Example 1 and Comparative Examples 1-3 Table 1 shows that the humic acid fertilizer synergist prepared using the synergistic method of biological and chemical activation in this invention contains 56.23% water-soluble humic acid, 70.12% organic matter, 19.26% water-insoluble matter, and 40.32% fulvic acid. In contrast, the fertilizers prepared in Comparative Examples 1-3 contain 40.65%-43.90% humic acid, 40.79%-44.90% organic matter, 34.66%-35.32% water-insoluble matter, and 1.86%-12.77% fulvic acid. Therefore, the effective component content of the humic acid fertilizer synergist prepared by this invention is significantly higher than that of the fertilizers in other groups.

[0048] Experiment Example 2: Pot Experiment The tested soil was typical brown soil from Shandong province, with moderate fertility (organic matter content approximately 0.8%–1.0%, pH 6.5–7.5). After being collected from the field, the soil was air-dried, crushed, and sieved through a 2 mm sieve to remove stones and plant residues, and then thoroughly mixed before use.

[0049] The rapeseed variety tested was "Luyou No. 1", which was sown on September 16, 2024 and harvested on November 18, 2024.

[0050] A total of 5 processes are set up, and each process is repeated 3 times, as follows: Control group: Only weathered coal was applied; Treatment group 1: The humic acid fertilizer synergist prepared in Example 1 was applied; Treatment group 2: The humic acid fertilizer synergist prepared in Comparative Example 1 was applied; Treatment group 3: The humic acid fertilizer synergist prepared in Comparative Example 2 was applied; Treatment group 4: The humic acid fertilizer synergist prepared in Comparative Example 3 was applied; The specific steps are as follows: The test soil and humic acid fertilizer synergist were mixed evenly at a mass ratio of 10000:1 and then filled into potted containers (25 cm in diameter and 20 cm in height), with 5.0 kg of the mixture per pot. 6–8 seeds were sown per pot. After emergence, seedlings were thinned to 3 plants per pot, maintaining a uniform spacing of approximately 3–5 cm to ensure adequate growing space for each plant. The same management practices were maintained across the experimental groups. At harvest, the entire rapeseed plant was dug up, avoiding root damage. The roots were gently washed with clean water to remove any soil residue. Nine plants were measured for each treatment, and plant height, root length, root volume, aboveground dry weight, and underground dry weight were measured. The results are shown in Table 2.

[0051] Among these methods, a ruler was used to measure plant height and root length; Root volume: The root volume is determined by the displacement method. Specifically, the root system is completely immersed in a graduated cylinder filled with water, and the volume V1 of the water level rise is recorded. After the root system is removed, the volume V2 of the remaining water is recorded. The difference in volume is the root volume. Dry weight of aboveground parts / dry weight of underground parts: Place the aboveground parts (stems and leaves) / underground parts in an oven at 105°C for 30 minutes to kill the green, then adjust to 80°C to dry to constant weight (until the difference between two weighings is <0.001g), weigh with a balance, and record as dry weight of aboveground parts / dry weight of underground parts.

[0052] Table 2 Properties of rapeseed in different treatment groups As shown in Table 2, after applying the humic acid fertilizer synergist prepared according to this invention, compared with the control group, the plant height increased by 2.5 cm, the root length increased by 4.45 cm, and the root volume increased by 0.245 cm³. 3 The above-ground dry weight increased by 1.0 g / plant, and the underground dry weight increased by 0.131 g / plant. After applying the humic acid fertilizer synergist prepared in Comparative Examples 1-3, plant height increased by 1.05-1.26 cm, root length increased by 1.98-2.33 cm, and root volume increased by 0.102-0.116 cm³. 3 The aboveground dry weight increased by 0.39-0.5 g / plant, and the underground dry weight increased by 0.103-0.110 g / plant. This demonstrates that the humic acid fertilizer synergist obtained by bio-chemical synergistic activation of weathered coal in this invention has a promoting effect on improving rapeseed development.

[0053] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing humic acid fertilizer synergists based on bio-chemical activation of weathered coal, characterized in that, Includes the following steps: (1) After mixing weathered coal and plant straw, a mixture is obtained; a compound microbial agent is added to the mixture for fermentation to obtain bio-activated weathered coal; The compound microbial agent is made by mixing Bacillus subtilis fermentation powder, Trichoderma harzianum fermentation powder and Protozoa chrysospora original culture fermentation powder in a mass ratio of 1:(0.5-1.5):(0.5-1.5); (2) Add potassium hydroxide and pulp lignin solution to bio-activated weathered coal in sequence and stir to obtain a precursor; heat the precursor to react, cool after reaction, and crush it to pass through a 100-mesh sieve while it is dry. Collect the solid to obtain humic acid fertilizer enhancer.

2. The method for preparing humic acid fertilizer synergists based on bio-chemical activated weathered coal as described in claim 1, characterized in that, In step (1), the Bacillus subtilis yeast powder is prepared by the following method: Bacillus subtilis seed culture was inoculated into Bacillus subtilis fermentation medium and cultured at 27-32℃, aeration rate of 160-200L / h, and 150-250rpm until the spore rate was 30%-50%. After stopping fermentation, the fermentation liquid was centrifuged, collected, and spray-dried to obtain Bacillus subtilis fermentation powder. The inoculation volume of Bacillus subtilis seed culture is 4%-6% of the volume of Bacillus subtilis fermentation medium.

3. The method for preparing humic acid fertilizer synergists based on bio-chemical activated weathered coal as described in claim 1, characterized in that, In step (1), the Trichoderma harzianum yeast powder is prepared by the following method: Trichoderma harzianum seed culture was inoculated into a fermentation medium containing wheat bran and fermented in the dark at 28-32℃ for 7 days. After fermentation, the fermentation liquid was centrifuged, collected, and spray-dried to obtain Trichoderma harzianum fermentation powder. The inoculation volume of Trichoderma harzianum seed culture is 10%-20% of the volume of fermentation medium containing wheat bran.

4. The method for preparing humic acid fertilizer synergists based on bio-chemical activated weathered coal as described in claim 1, characterized in that, In step (1), the original fermentation powder of *Plasmodium chrysosporium* was prepared by the following method: the original seed liquid of *Plasmodium chrysosporium* was inoculated into a fermentation medium containing wheat bran, fermented in the dark at 28-32℃ for 7 days, centrifuged after fermentation, the fermentation liquid was collected, and spray-dried to obtain the original fermentation powder of *Plasmodium chrysosporium*. The inoculation volume of the original seed liquid of *Phanerochaete chrysosporium* is 10%-20% of the volume of the fermentation medium containing wheat bran.

5. The method for preparing humic acid fertilizer synergists based on bio-chemical activated weathered coal as described in claim 1, characterized in that, The preservation number of Bacillus subtilis is ATCC 6051, the preservation number of Trichoderma harzianum is CBS 226.95, and the preservation number of the original species of Protozoa chrysospora is ATCC 24725.

6. The method for preparing humic acid fertilizer synergists based on bio-chemical activated weathered coal as described in claim 1, characterized in that, In step (1), the mass ratio of weathered coal to plant straw is 10:(2-4), the mass ratio of compound microbial agent to mixture is 1:(40-60), the fermentation temperature is 23-26℃, and the fermentation time is 15-25 days.

7. The method for preparing humic acid fertilizer synergists based on bio-chemical activated weathered coal as described in claim 1, characterized in that, In step (2), the mass ratio of bio-activated weathered coal, potassium hydroxide and pulp lignin solution is 100:(6-10):(15-25).

8. The method for preparing humic acid fertilizer synergists based on bio-chemical activated weathered coal as described in claim 1, characterized in that, In step (2), the stirring temperature is 60-80℃ and the stirring time is 60-80min; the heating temperature is 180-200℃ and the reaction time is 25-35min.

9. The humic acid fertilizer synergist prepared by the preparation method according to any one of claims 1-8.

10. The application of the humic acid fertilizer synergist according to claim 9 in promoting rapeseed development.

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