Method for preparing high-activity bio-organic fertilizer from caragana microphylla and organic fertilizer

Abstract

The invention discloses a method for preparing a high-activity bio-organic fertilizer from caragana microphylla and the organic fertilizer, and belongs to the technical field of agricultural waste recycling and bio-fertilizers. Aiming at the technical problems that caragana microphylla branch residues are high in lignification degree, contain many inhibitors and are difficult to efficiently decompose and convert into a high-activity fertilizer, the method provided by the invention comprises the following steps: crushing and drying caragana microphylla branches, pulverizing, mixing with dilute sulphuric acid and laccase, soaking at a high temperature, and neutralizing to obtain activated slurry; compounding a composite functional bacterial agent in a specific proportion; mixing the slurry, a microbial agent and a nitrogen source, and sequentially performing high-temperature aerobic fermentation and medium-temperature anaerobic fermentation with molasses and sodium selenite to obtain a fermented material; and finally mixing with a functional additive to prepare the fertilizer. The prepared fertilizer is rich in organic matters, humic acid, high-activity functional bacteria and stable organic selenium, and is suitable for improving soil, promoting crop growth and improving the quality of agricultural products.

Description

Technical Field

[0001] This invention relates to the field of agricultural waste resource utilization and bio-fertilizer technology. More specifically, this invention relates to a method for preparing highly active bio-organic fertilizer using *Caragana korshinskii* and the organic fertilizer itself. Background Technology

[0002] Caragana korshinskii, also known as Caragana sinica, is a leguminous shrub widely cultivated in arid and semi-arid regions of Northwest and North my country. As a pioneer plant for windbreak and sand fixation and soil and water conservation, Caragana korshinskii possesses strong resilience and abundant biomass. Each year, through methods such as coppicing and rejuvenation, a large amount of Caragana korshinskii branch residue is generated. If this residue is not effectively utilized, it not only represents a huge waste of biomass resources, but its accumulation can also pose a fire hazard. Therefore, transforming Caragana korshinskii into high-value-added products is a key way to achieve a win-win situation for both ecological and economic benefits, and is of great significance for promoting regional circular agriculture and rural revitalization.

[0003] Converting agricultural waste into bio-organic fertilizer is one of the mainstream directions of resource utilization. Bio-organic fertilizer not only provides organic matter and various nutrients to the soil, but its functional microorganisms can also improve the soil microecology, inhibit soil-borne diseases, and promote crop growth. However, converting highly lignified and structurally unique shrub waste such as Caragana korshinskii branches into high-quality bio-organic fertilizer faces far more severe technical challenges than ordinary straw materials. Caragana korshinskii stems have an exceptionally dense fiber structure, with lignin tightly cross-linked with cellulose and hemicellulose, forming a natural physical barrier. At the same time, as a plant of arid regions, Caragana korshinskii often accumulates a large amount of phenolic and tannin secondary metabolites, which have significant inhibitory or toxic effects on microorganisms. This makes Caragana korshinskii branches extremely difficult to decompose under natural conditions, and also results in problems such as long fermentation cycles, difficulty in raising temperatures, incomplete decomposition, and low activity of the final product when conventional composting fermentation technology is directly applied.

[0004] Numerous technological explorations have been undertaken regarding the pretreatment and bioconversion of lignocellulosic waste. In pretreatment, common physical methods (such as crushing and steam explosion) are energy-intensive, while chemical methods (such as acid and alkali treatment) easily cause environmental pollution and nutrient loss. Biological pretreatment (such as using white-rot fungi) has a very long cycle. In fermentation processes, single aerobic or anaerobic fermentation is commonly used. Aerobic fermentation facilitates rapid degradation and temperature rise, but results in significant organic matter mineralization loss and difficulty in nutrient preservation. Anaerobic fermentation is beneficial for nutrient preservation and humic synthesis, but it has a long cycle and weak initial degradation ability of lignocellulosic materials. Regarding the use of microbial agents, existing technologies either rely on environmental strains from diverse sources with unstable effects, or attempt long-term domestication of single strains (such as certain lignin-degrading bacteria). The former is inefficient, while the latter involves complex processes, poor reproducibility, and the domesticated strains often have limited functions, making it difficult to address the complex multi-stage and multi-objective requirements of Caragana korshinskii degradation. In addition, most existing technologies focus on achieving the harmlessness or matrix transformation of waste, with insufficient attention paid to the high-activity functional design of the final product, that is, how to make fertilizer not only rich in organic matter through process control, but also stably carry a high number of functional live bacteria and have specific functions such as stress resistance and growth promotion.

[0005] In summary, there are still a series of significant shortcomings in the preparation of bio-organic fertilizer from the residues of Caragana korshinskii branches: these include a lack of targeted pretreatment methods, insufficient synergy in fermentation processes, imperfect design of functional microbial agents, and a lack of focus on high activity and functionalization of the final product. These shortcomings make it difficult for existing methods to efficiently convert Caragana korshinskii branches into high-value bio-organic fertilizer with stable quality and outstanding functions. Therefore, there is an urgent need for an innovative and systematic technical solution to overcome the technical bottlenecks caused by the inherent characteristics of Caragana korshinskii branch residues and achieve high-value resource utilization. Summary of the Invention

[0006] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0007] Another objective of this invention is to provide a method for preparing highly active bio-organic fertilizer using Caragana korshinskii. This method utilizes acid-enzyme synergistic pretreatment to efficiently break down the stubborn structure of Caragana korshinskii and degrade biological inhibitors. Combined with customized compound microbial agents and a two-stage coupled fermentation process, it significantly improves conversion efficiency and decomposition degree. The resulting fertilizer has both highly active microbial flora and stable organic selenium form, resulting in long-lasting fertilizer effect and outstanding function.

[0008] To achieve these objectives and other advantages according to the present invention, a method for preparing highly active bio-organic fertilizer using *Caragana korshinskii* is provided, comprising: S1. The raw material, the residue of Caragana twigs, is first coarsely crushed and then preliminarily dried until the moisture content is less than 12%. Then, it is ultra-finely crushed to prepare Caragana twig micro powder with a particle size of more than 150 mesh. The Caragana twig micro powder is mixed with a 3-5% dilute sulfuric acid solution and laccase at a mass ratio of 1:2-3:0.05-0.15. After soaking at 120-150℃ for 40-60 minutes, the pH of the system is neutralized to 6.5-7 using a 20% sodium hydroxide solution. After solid-liquid separation, activated Caragana twig slurry is obtained. S2. Weigh out Bacillus laterosporus, Bacillus subtilis, Bacillus licheniformis, Bacillus licheniformis, and Saccharomyces cerevisiae liquid according to the live bacteria ratio of 3~5:2~3:2~3:0.5~1:1, activate them separately, and then compound them to prepare a compound functional bacterial agent; mix the compound functional bacterial agent with Aspergillus fumigatus at a mass ratio of 60~80:1, and then fix them together in sodium alginate-gelatin-biochar composite gel to make bacterial-enzyme co-solidified microspheres with a diameter of 1~3 mm; S3. The activated Caragana slurry obtained in step S1, the bacteria-enzyme co-solidified microspheres obtained in step S2, urea, and ammonium sulfate are mixed in a ratio of 100~120:8~12:3~6:1 and then subjected to high-temperature aerobic fermentation and mesophilic anaerobic fermentation in sequence to obtain fermented material. S4. Mix the fermentation material obtained in step S3 with functional additives to prepare the highly active bio-organic fertilizer; In step S3, high-temperature aerobic fermentation is carried out in a fermenter at a temperature of 50-55℃ and an aeration rate of 1.0-1.5 VVM (aeration volume per minute per unit liquid volume). Fermentation continues until the ratio of water-soluble organic carbon to total organic carbon in the material reaches 0.25-0.35. Mesophilic anaerobic fermentation is carried out in a closed fermentation tank. During mesophilic anaerobic fermentation, 5-8% molasses and 0.1-0.3% sodium selenite are added to the total weight of the Caragana korshinskii powder. The fermentation is carried out under anaerobic conditions at 38-42℃ for 100-120 hours.

[0009] In step S1, this application introduces laccase in the preparation of bio-organic fertilizer from *Caragana korshinskii*, and it works synergistically with dilute sulfuric acid at high temperature. Traditional pretreatment techniques for treating lignocellulose typically separate or simply connect physical / chemical methods with biological methods, resulting in low efficiency, long cycles, or conflicting conditions. For example, acid treatment aims to break down the structure, but strong acids and high temperatures denature and completely inactivate most enzyme preparations, while enzyme treatment is mostly carried out under mild conditions, making it difficult to address the stubborn structure of *Caragana korshinskii* alone. This application overcomes this technical bias by placing laccase in a specific environment of dilute acid and high temperature. Laccase is not only not completely destroyed, but it also produces a unique synergistic effect with dilute acid hydrolysis: dilute acid rapidly destroys the crystal structure and hemicellulose of cellulose, providing more accessible attack sites for laccase, while laccase precisely oxidizes and degrades lignin fragments dissolved under acidic conditions and aromatic inhibitors such as phenols and tannins unique to *Caragana korshinskii*. Specifically, as a drought-resistant shrub, *Caragana korshinskii* is rich in secondary metabolites such as phenolic acids, flavonoids, and tannins. These are important defense mechanisms against pests, diseases, and environmental stresses, but they also pose a challenge for microbial fermentation. While conventional acid, alkali, or physical pretreatment can break down the structure, their effectiveness in removing small-molecule inhibitors dissolved in the aqueous phase is limited. These inhibitors can then enter subsequent fermentation stages, severely inhibiting the activity of functional microorganisms, leading to slow fermentation start-up and a high failure rate. The laccase added in this application targets and eliminates this biological inhibition. Laccase is a highly efficient phenol oxidase that can efficiently catalyze the polymerization or degradation of this inhibitor into harmless substances in the specific acidic, high-temperature microenvironment provided in this application, achieving biological detoxification of the fermentation substrate. This creates a clean and easily attackable substrate environment for the subsequently introduced compound functional microorganisms, a crucial prerequisite for ensuring that *Caragana korshinskii* can be efficiently and stably biotransformed into highly active fertilizer.

[0010] In step S2, a specific process for preparing bacteria-enzyme co-solidified microspheres is as follows: Sodium alginate and gelatin are dissolved in warm water to form a homogeneous colloidal solution. At the same time, biochar powder (particle size <200 mesh) is uniformly dispersed in the solution to form a gel aqueous solution. The mass and volume of each component in the gel aqueous solution meet the following requirements: sodium alginate 1.5~2.5% (i.e. 1.5~2.5g / 100mL), gelatin 0.8~1.5%, and biochar powder 1.0~3.0%. The prepared compound functional microbial agent suspension and Aspergillus fumigatus were mixed evenly at a mass ratio of 60-80:1 to form a microbial-enzyme mixed suspension. This mixture was then thoroughly mixed with a gel aqueous solution under ice bath conditions to form a homogeneous gel-microbial-enzyme slurry. Finally, the slurry was sprayed into a coagulation bath containing calcium ions (calcium chloride solution). Sodium alginate and calcium ions underwent ion exchange, instantly forming a gel film on the droplet surface, thus embedding and fixing the internal microorganisms and enzymes to form moist gel microspheres. By controlling the dropping speed and pore size, microspheres with a diameter of 1-3 mm were obtained. The microspheres were removed from the coagulation bath and washed with buffer solution to obtain the microbial-enzyme co-solidified microspheres. Confining the compound functional microbial agent and Aspergillus fumigatus (cellulase) within a limited gel microsphere space allows the oligosaccharides and glucose products generated by cellulase degradation of fibers to be rapidly and in situ absorbed and utilized by the adjacent functional bacteria within the microsphere. This significantly shortens the material transport distance, achieving seamless integration of enzymatic hydrolysis and microbial utilization, and greatly improving substrate conversion rate and energy efficiency. Furthermore, the sodium alginate-gelatin-biochar composite gel forms a semi-permeable three-dimensional network barrier, which effectively blocks some macromolecular inhibitors from direct contact with internal bacterial enzymes, while allowing the diffusion of small molecule substrates and products. This directly addresses the challenges of numerous inhibitors and harsh fermentation environments in the Caragana korshinskii system, ensuring successful fermentation and high product activity.

[0011] This application designs a composite functional microbial agent composed of five specific microorganisms in precise proportions. This agent represents a rational integration of functional modules targeting the entire biotransformation process of *Caragana korshinskii*: *Bacillus laterosporus* and *Bacillus subtilis* form a degradation module, primarily targeting the rapid degradation of cellulose and hemicellulose, providing a basic carbon source and energy; *Bacillus licheniformis* forms a detoxification and adaptation module, specifically added to address the characteristics of *Caragana korshinskii*. *Bacillus licheniformis* can secrete a variety of enzymes that tolerate and degrade complex aromatic compounds, linking with the laccase function in pretreatment to continue clearing residual inhibitors during fermentation and enhancing the overall stress resistance of the microbial community; and *Bacillus licheniformis* forms a growth-promoting and nutrient conversion module, responsible for solidification... Nitrogen, phosphorus solubilization, and secretion of plant growth hormones directly convert degradation products into nutrients and stimulants usable by plants, enhancing the biological value of fertilizers. Saccharomyces cerevisiae forms a metabolic regulation and synergistic module, rapidly consuming some oxygen through its metabolic activities, assisting in creating a micro-anaerobic environment, and promoting anaerobic fermentation. Simultaneously, its metabolic products (such as vitamins and sterols) stimulate the growth of other bacteria, acting as a microbial community activator. All of the above-mentioned microbial agents are commercially available and, after being compounded according to the specific live bacteria ratio specified in this application, ensure that the functional modules of the composite functional agent can coexist stably and cooperate efficiently in a competitive environment, forming a stable and efficient synthetic microbial colony. The above-mentioned composite functional microbial agent provides a microbial colony for the complex composition of Caragana korshinskii, integrating all key biological functions from primary substrate decomposition and toxic substance detoxification to nutrient conversion and product synthesis. This ensures that the most suitable microorganisms dominate each stage from fermentation initiation to deep composting, thereby achieving controllable and efficient fermentation processes and stable product quality. In particular, the addition of Bacillus licheniformis directly addresses the challenge of residual inhibitors in Caragana korshinskii, which is a crucial factor in ensuring the successful colonization and efficacy of this specialized compound microbial agent on the Caragana korshinskii substrate.

[0012] Preferably, the specific activation steps in step S2 include: culturing and activating each bacterial agent in physiological saline containing 0.1-0.2% yeast extract and 0.05% magnesium sulfate heptahydrate at 35-37°C for 30-40 minutes.

[0013] Preferably, the specific steps in step S4 for preparing the highly active bio-organic fertilizer by mixing the fermented material obtained in step S3 with functional additives include: Add potassium humate (2-4% by dry weight), calcium alginate gel particles (1-2% by dry weight), and diatomaceous earth (0.3-0.6% by dry weight) to the fermentation material obtained in step S3, and mix them evenly. After drying the mixture at a temperature below 50°C until the moisture content is below 18%, it is granulated by extrusion granulation to produce particles with a particle size of 3-5 mm, which is the high-activity bio-organic fertilizer.

[0014] Preferably, after the mixture is dried to a moisture content of less than 18%, a composite binder is added to the dried mixture at a dry basis weight of 0.5 to 1.5%. The composite binder is a mixture of soluble starch and sodium lignosulfonate in a mass ratio of 2 to 3:1.

[0015] Preferably, the dry basis weight of the fermentation material is calculated using the following method: Dry basis weight of fermentation material = weight of fermentation material × (1-W1), where W1 is the immediate moisture content of the fermentation material, which is measured by a near-infrared moisture analyzer through rapid sampling from the fermentation material; The dry basis weight of the dried mixture is calculated using the following method: Dry basis weight of the dried mixture = weight of the dried mixture × (1-W2), where W2 is the immediate moisture content of the dried mixture, which is measured by a near-infrared moisture analyzer through rapid sampling from the dried mixture.

[0016] Preferably, in step S1, during ultrafine grinding, 1-3% (by dry weight) of ammonium bicarbonate from the remaining dry weight of the raw material, *Caragana korshinskii* branches, is added to the preliminarily dried, coarsely ground *Caragana korshinskii* branches for further ultrafine grinding. *Caragana korshinskii* fibers are not only dense in structure, but their surfaces are often deposited with silica cells and a hydrophobic waxy layer, forming a double barrier. When ammonium bicarbonate and coarse *Caragana korshinskii* powder undergo intense mechanical shearing, impact, and friction, the local temperature of the system rises, inducing a decomposition reaction of ammonium bicarbonate to generate NH3, CO2, and gaseous H2O. This decomposition process occurs instantaneously on the newly formed surface of the broken fibers during grinding. The newly generated ammonia and carbon dioxide gases, under immense mechanical force, enter along the microcracks and weak points of the *Caragana korshinskii* fibers, generating instantaneous pressure that physically expands or tears the fiber bundles, making their structure more porous and significantly reducing the crystallinity and density of the fibers. This facilitates the subsequent penetration of acids and enzymes, allowing dilute sulfuric acid and laccase to contact the substrate more quickly and deeply, greatly improving the brewing efficiency. The ammonia gas produced by the decomposition of ammonium bicarbonate, as a weakly alkaline gas, can slightly soften and corrode some of the silica and lignin on the fiber surface, weakening its barrier strength. Simultaneously, the release of carbon dioxide helps form tiny gas-solid interfaces, altering the material's flowability and preventing the ultrafine powder from re-agglomerating due to static electricity and oils, ensuring a more uniform Caragana korshinskii powder with a larger specific surface area. Finally, the nitrogen-containing components introduced by the addition of ammonium bicarbonate are partially adsorbed or bound to the material, providing a trace, slow-release nitrogen source for subsequent fermentation, helping to regulate the initial carbon-nitrogen ratio and promoting early microbial colonization.

[0017] Preferably, during mesophilic anaerobic fermentation in step S3, the molasses and sodium selenite are added in two batches: 40-60 wt% molasses and 20-30 wt% sodium selenite are added during mesophilic anaerobic fermentation, and the remaining molasses and sodium selenite are added after 48-60 hours of mesophilic anaerobic fermentation.

[0018] Preferably, the timing of adding the remaining molasses and sodium selenite is determined by monitoring the gas production rate in the closed fermentation tank: Connect the sealed fermentation tank to a wet gas flow meter to continuously measure and record the cumulative gas production of the sealed fermentation tank, and calculate the hourly gas production rate in real time. When the gas production rate reaches its peak, if the gas production rate monitored for 6-8 hours is lower than 80% of the peak value, add the remaining molasses and sodium selenite.

[0019] If all the molasses (a highly readily available carbon source) is added at the start of anaerobic fermentation, the fermenting microorganisms will enter a brief but intense metabolic burst. During this phase, the carbon source is rapidly consumed for growth and basal metabolism, producing large amounts of organic acids, leading to a rapid drop in pH. However, the inorganic selenium (Se) in sodium selenite... 4+ The process by which molasses is absorbed by microorganisms and converted into organic selenium (such as selenoamino acids) is a relatively slow secondary metabolic process that requires specific reductases and energy. When the molasses added at once is quickly depleted, the microbial community will prematurely enter a period of metabolic stagnation or death due to carbon source shortage. At this time, the bioconversion process of selenium is often incomplete or inefficient, resulting in low organic selenium content and unstable conversion rate in the final product. To resolve the contradiction between the difficulty in synchronizing and maximizing carbon source metabolism and selenium bioconversion, this application introduces molasses and sodium selenite into the fermentation system in batches. The purpose of the first addition is to start-up and acclimatization. An appropriate amount of readily available carbon source ensures that microorganisms quickly establish a dominant anaerobic community and create an active fermentation environment. At the same time, the pre-addition of a portion of sodium selenite allows the microbial community to sense and gradually adapt to the presence of selenium, initiating the expression of relevant selenium tolerance and converting enzyme systems, preparing physiologically for subsequent efficient conversion, and avoiding the initial shock of high concentrations of selenium. The purpose of the second addition is to stimulate and accelerate the process. After the microorganisms have completed community building and have initially adapted to the selenium environment, new carbon and selenium sources are added. At this point, the fresh carbon source reignites the activity of microorganisms in the metabolic plateau phase, providing ample energy and reducing power; while the supplemented selenium source is efficiently directed to the already initiated selenium conversion metabolic pathway. This carbon source relay ensures that the microbial community maintains high metabolic activity during the long later stages of anaerobic fermentation, specifically for driving the energy-intensive selenium bioconversion reaction, thereby significantly improving the selenium organication efficiency and total conversion rate.

[0020] In the anaerobic fermentation of Caragana korshinskii materials, biogas (mainly methane and carbon dioxide) is the ultimate gaseous product of microbial decomposition of organic matter. The biogas production rate directly and sensitively reflects the macroscopic metabolic intensity of the entire microbial community in converting the substrate into the final product. The peak rate signifies the zenith of the main metabolic phase driven by the initial addition of molasses; a subsequent continuous decline in the rate clearly indicates that this portion of the substrate is nearing depletion, and the overall metabolic activity of the microbial community begins to decline. The secondary addition window provided in this application is a crucial stage in the transition of the microbial community from substrate-sufficient metabolism to substrate-scarce dormancy, achieving the most significant activity restart effect with minimal intervention cost, maximizing the utilization efficiency of the supplemented carbon and selenium sources.

[0021] Preferably, when adding the remaining molasses and sodium selenite, the remaining molasses and sodium selenite are mixed evenly at 40~42°C and kept warm for later use.

[0022] The present invention further claims protection for a highly active bio-organic fertilizer, which is prepared by the method described above for preparing highly active bio-organic fertilizer using Caragana korshinskii.

[0023] The present invention has at least the following beneficial effects: Firstly, this invention achieves the simultaneous breakdown of the lignocellulosic structure and efficient degradation of biological inhibitors at high temperatures through the synergistic effect of acid and laccase. Combined with targeted compound microbial agents, it significantly improves the bioavailability of Caragana korshinskii, making subsequent fermentation more thorough and significantly shortening the cycle, thus fundamentally solving the technical bottleneck of low Caragana korshinskii conversion rate. Secondly, by introducing ammonium bicarbonate to assist in ultra-fine grinding and optimizing the fermentation process, this invention greatly increases the material reaction contact area and couples efficient aerobic and anaerobic fermentation stages, so that the decomposition of organic matter and the synthesis of humic substances can achieve an efficient balance, significantly improving the nutrient conversion efficiency and fertilizer maturity of unit raw materials. Thirdly, the present invention adopts a phased feeding strategy based on dynamic monitoring of gas production rate, accurately grasps the inflection point of fermentation metabolism to supplement nutrition, effectively maintains the continuous high activity of microbial community, not only promotes the bioconversion and enrichment of selenium, but also ensures the stability and efficiency of fermentation process, and improves the stability of product functional components. Fourth, this invention further endows the final granular product with excellent compressive strength, slow-release properties and water retention capacity by scientifically compounding functional additives and optimizing the molding process. At the same time, the premixing and heat preservation operation ensures the uniform distribution of functional components, so that the fertilizer can play a long-term and stable role in improving and promoting growth in the soil.

[0024] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can implement it based on the description.

[0026] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0027] Example 1 Raw materials: Residual Caragana twigs collected after coppicing and rejuvenation, with an average moisture content of 45%.

[0028] Preparation of activated Caragana korshinskii pulp: The remaining Caragana korshinskii branches were first coarsely pulverized to a length of 1-2 cm and dried at 85℃ until the moisture content was 10%. The dried coarsely pulverized material was then fed into an ultrafine pulverizer and pulverized until more than 95% of the material could pass through a 150-mesh sieve to obtain Caragana korshinskii micro powder. 100 kg of Caragana korshinskii micro powder was weighed and mixed with 250 kg of 4% (w / w) dilute sulfuric acid solution preheated to 60℃ and 5 kg of laccase (enzyme activity 50,000 U / g). The mixture was transferred to a reactor equipped with stirring and heating and reacted at 135℃ for 50 min. After the reaction was completed, a 20% (w / w) sodium hydroxide solution was slowly added while stirring to neutralize the pH of the system to 6.8. After neutralization, solid-liquid separation was performed, and the solid fraction obtained was the activated Caragana korshinskii pulp.

[0029] Preparation of the compound functional microbial agent: Weigh out the following liquids: *Bacillus brevis*, *Bacillus subtilis*, *Bacillus licheniformis*, and *Saccharomyces cerevisiae*, ensuring a viable cell ratio of 4:2.5:2.5:0.8:1. Take each liquid separately and incubate it at 36°C for 35 min with physiological saline containing 0.15% yeast extract and 0.05% magnesium sulfate heptahydrate. After activation, mix the liquids thoroughly to obtain a compound functional microbial agent suspension. Mix the compound functional microbial agent with *Aspergillus fumigatus* at a mass ratio of 60:1 and immobilize them together in a sodium alginate-gelatin-biochar composite gel to form microspheres with a diameter of 3 mm.

[0030] Coupled fermentation: Take the activated Caragana korshinskii pulp (100 kg on a dry basis) prepared above, mix it evenly with the prepared bacteria-enzyme co-solidified microspheres (8 kg of dry bacteria), 4 kg of urea, and 1 kg of ammonium sulfate, put it into a fermenter, control the temperature of the fermenter at 52℃, introduce sterile air at a rate of 1.2 L / (L·min) and stir, and carry out high-temperature aerobic fermentation until the ratio of water-soluble organic carbon to total organic carbon in the material reaches 0.25.

[0031] All the materials after high-temperature aerobic fermentation were transferred to a closed fermentation tank. Molasses and sodium selenite, equivalent to 6% of the total weight of the Caragana micro powder, were added first and stirred evenly. The mixture was then allowed to ferment at 40°C under anaerobic conditions for 120 hours to obtain fully decomposed fermented material.

[0032] Functionalized granulation: Potassium humate (3% by dry weight), calcium alginate gel particles (1.5% by dry weight), and diatomaceous earth (0.5% by dry weight) are added sequentially to the fermented material and mixed evenly under low-speed stirring. The mixture is dried at 45°C until the moisture content is 16%. Then, a composite binder (a mixture of soluble starch and sodium lignosulfonate in a mass ratio of 2.5:1) is added at 1% by dry weight of the dried mixture and mixed evenly. The mixture is then extruded into regular granules with a diameter of 4mm at room temperature. After low-temperature drying and sieving, the high-activity bio-organic fertilizer product is obtained.

[0033] Example 2 Raw materials: Same as in Example 1.

[0034] Preparation of activated Caragana korshinskii pulp: The dried coarsely pulverized material is put into an ultra-fine pulverizer, and at the same time, 2% by dry weight of ammonium bicarbonate of the remaining Caragana korshinskii branches is added and pulverized until more than 95% of the material can pass through a 150-mesh sieve. The rest is the same as in Example 1.

[0035] Preparation of compound functional microbial agents: Same as in Example 1.

[0036] Coupled fermentation: Same as in Example 1.

[0037] Functionalized granulation molding: Same as in Example 1.

[0038] Example 3 Raw materials: Same as in Example 1.

[0039] Preparation of activated Caragana korshinskii pulp: Same as in Example 1.

[0040] Preparation of compound functional microbial agents: Same as in Example 1.

[0041] Coupled fermentation: During mesophilic anaerobic fermentation, the molasses and sodium selenite are added in two batches. During mesophilic anaerobic fermentation, 40wt% molasses and 20wt% sodium selenite are added. The remaining molasses and sodium selenite are mixed evenly at 40°C and kept warm for later use. When the mesophilic anaerobic fermentation reaches 60h, the remaining molasses and sodium selenite are added. The rest is the same as in Example 1.

[0042] Functionalized granulation molding: Same as in Example 1.

[0043] Example 4 Raw materials: Same as in Example 1.

[0044] Preparation of activated Caragana korshinskii pulp: Same as in Example 1.

[0045] Preparation of compound functional microbial agents: Same as in Example 1.

[0046] Coupled fermentation: During mesophilic anaerobic fermentation, the molasses and sodium selenite were added in two stages. For mesophilic anaerobic fermentation, 40 wt% molasses and 20 wt% sodium selenite were added. The remaining molasses and sodium selenite were mixed evenly at 40°C and kept warm for later use. The cumulative gas production was monitored and the real-time gas production rate was calculated by connecting a wet gas flow meter. When the gas production rate reached its peak, and after 7 consecutive hours of monitoring showed that the gas production rate was below 80% of the peak (at which point it was the 52nd hour after fermentation began), the remaining molasses and sodium selenite were added. The rest of the process was the same as in Example 1.

[0047] Functionalized granulation molding: Same as in Example 1.

[0048] Example 5 Raw materials: Same as in Example 1.

[0049] Preparation of activated Caragana korshinskii pulp: Same as in Example 2.

[0050] Preparation of compound functional microbial agents: Same as in Example 1.

[0051] Coupled fermentation: Same as in Example 4.

[0052] Functionalized granulation molding: Same as in Example 1.

[0053] Comparative Example 1 In preparing activated Caragana korshinskii pulp, no laccase was added. Instead, Caragana korshinskii powder was soaked in a dilute sulfuric acid solution. The amount of dilute sulfuric acid solution used was the same as in Example 1, and the remaining steps were the same as in Example 1.

[0054] Comparative Example 2 Coupled fermentation was carried out using a single Bacillus lateralis, and the total number of viable bacteria added was the same as the total number of viable bacteria in the compound bacterial agent in Example 1. The remaining steps were the same as in Example 1.

[0055] Comparative Example 3 The high-temperature aerobic fermentation stage in the coupled fermentation was omitted. The activated Caragana korshinskii pulp, compound functional microbial agent, urea and ammonium sulfate were mixed and then directly subjected to mesophilic anaerobic fermentation with the same parameters as in Example 1 (6% molasses and 0.2% sodium selenite were added at once). The total fermentation time was still controlled at 120h, and the remaining steps were the same as in Example 1.

[0056] Comparative Example 4 In the coupled fermentation process, 0.2% sodium selenite was omitted during the mesophilic anaerobic fermentation stage. Only molasses equivalent to 6% of the total weight of the Caragana korshinskii powder was added for fermentation. The remaining steps were the same as in Example 1.

[0057] The organic matter content, humic acid content, effective viable bacteria count, and seed germination index of the bio-organic fertilizers obtained in Examples 1-5 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

[0058] Table 1 Results of Bio-organic Fertilizer Parameter Testing As shown in Table 1, the method of this application has significant advantages in improving the organic matter, humic acid, viable bacteria count, and seed germination index of biomass organic fertilizer. From the overall data trend, the indicators of Examples 1-5 are significantly better than those of Comparative Examples 1-4, with Example 5 showing the most outstanding performance, achieving an organic matter content of 48.5%, a humic acid content of 18.5%, an effective viable bacteria count as high as 260 million / g, and a seed germination index of 96%. This fully demonstrates the effectiveness and synergy of the pretreatment-inoculant-fermentation-forming whole-chain technology solution constructed in this application. Examples 2, 4, and 5, based on Example 1, gradually introduced optimization measures such as ammonium bicarbonate-assisted pulverization, multi-stage feeding, and dynamic monitoring of gas production rate, resulting in a step-by-step improvement in various indicators, ultimately achieving comprehensive optimization of fertilizer quality.

[0059] Examples 1-5 all employed microbial-enzyme co-solidification microsphere technology, which achieved two main functions: First, it created a spatially sequential synergistic effect, enabling the sugars produced by cellulase degradation to be rapidly utilized in situ by the functional bacteria within the microspheres, greatly improving substrate conversion efficiency. Second, it formed a microenvironmental protection effect; the composite structure of gel and biochar effectively buffered inhibitors, pH fluctuations, and mechanical shear forces in the fermentation system, providing a stable working environment for the bacteria and enzymes. This is another important reason why all examples significantly surpassed traditional simple mixing processes (such as Comparative Example 2) in terms of viable cell count and overall fertilizer efficiency.

[0060] Comparative Example 1, without the use of laccase, showed an organic matter content of only 42.5%, a humic acid content as low as 10.5%, an effective viable bacteria count reduced to 125 million / g, and a seed germination index of only 80%. This demonstrates the crucial role of laccase in the pretreatment stage. As a drought-resistant shrub, *Caragana korshinskii* is rich in lignin and secondary metabolites such as phenols and tannins. These substances not only physically hinder microbial contact but also chemically inhibit microorganisms. While traditional acid treatment can destroy the fiber structure, it has limited effectiveness in removing liquid-soluble biological inhibitors. This application introduces laccase into a high-temperature, acidic environment. Under these specific conditions, laccase remains active and can precisely catalyze the oxidation of these aromatic inhibitors, polymerizing or degrading them into harmless substances, thus achieving biological detoxification of the substrate. This creates a clean and easily attacked substrate environment for the subsequent colonization and fermentation of compound functional microbial agents, fundamentally solving the historical problems of slow fermentation start-up, high failure rate, and low maturity of *Caragana korshinskii*, thereby significantly improving the organic matter conversion efficiency and the biosafety of the final product (high germination index).

[0061] Comparative Example 2, using a single *Bacillus laterosporus* strain for fermentation, showed a sharp drop in viable cell count to 0.80 billion / g and a humic acid content of only 13.0%. The biotransformation of *Caragana korshinskii* is a complex, multi-stage, and multi-objective process involving multiple stages such as lignocellulose degradation, detoxification, nutrient conversion, and humic substance synthesis. This application designed a complex microbial community comprising *Bacillus laterosporus* (cellulose degradation), *Bacillus subtilis* (hemicellulose degradation), *Bacillus licheniformis* (detoxification and stress resistance), *Bacillus mucilaginosa* (nitrogen fixation, phosphorus solubilization, and growth promotion), and *Saccharomyces cerevisiae* (metabolic regulation and synergy), and set precise viable cell ratios to ensure that the most suitable microbial functional modules dominate each stage of fermentation, from primary decomposition to deep composting, forming a stable symbiotic and cooperative relationship among the microbial communities. In contrast, single-strain microorganisms have limited functionality, cannot meet the full-process transformation needs of complex substrates, and are easily inactivated in competitive environments, resulting in low fermentation efficiency and a single functional product.

[0062] Comparative Example 3 omitted the high-temperature aerobic fermentation stage and directly carried out anaerobic fermentation, resulting in a humic acid content of only 8.5% and a seed germination index as low as 75%. This invention sequentially combines high-temperature aerobic fermentation (55-60℃) with mesophilic anaerobic fermentation (38-42℃). In the aerobic stage, under sufficient oxygen and high temperature, aerobic microorganisms rapidly degrade easily decomposable organic matter in the *Caragana korshinskii* pulp, generating heat to maintain the high temperature, effectively killing pathogens and weed seeds, and providing a large amount of energy for microbial metabolism. This stage mainly achieves rapid mineralization of organic matter and preliminary material composting. Subsequently, the anaerobic stage begins. Under hypoxic conditions and suitable temperature, anaerobic and facultative anaerobic microorganisms dominate the process, and their metabolic pathways are more conducive to the synthesis and accumulation of complex and stable organic matter such as humic acid, while simultaneously carrying out the biotransformation of trace elements such as selenium. This two-stage coupling achieves an efficient connection between rapid decomposition and deep synthesis, achieving an optimal balance between organic matter decomposition and humic substance synthesis, thereby obtaining a high-quality fermented material with high humic acid content and complete composting (high germination index). Comparative Example 4, without the addition of sodium selenite, still exhibited comparable organic matter and humic acid content to the Example, with a germination index as high as 90%. This indicates that the addition of selenium did not interfere with the basic fermentation process, demonstrating the good compatibility of the process described in this invention. This provides a reliable foundation for the production of selenium-enriched functional fertilizers, enabling flexible switching between the production of ordinary fertilizers and functional fertilizers.

[0063] The lignin removal rate and organic selenium conversion rate of the methods in Examples 1-5 and Comparative Examples 1-4 were further tested, and the results are shown in Table 2.

[0064] Table 2 Results of lignin removal rate and organic selenium conversion rate As shown in Table 2, the lignin removal rate of all examples was significantly higher than that of the comparative example, reaching a maximum of 69.0% (Example 5); the organic selenium conversion rate was significantly improved in Examples 3, 4, and 5, which adopted the multi-feeding strategy, reaching a maximum of 78.5% (Example 5).

[0065] Efficient lignin removal is the primary challenge for the successful conversion of *Caragana korshinskii*. Comparative Example 1 (without laccase) achieved a lignin removal rate of only 41.0%, while Example 1 reached 66.5%, due to the synergistic pretreatment of dilute sulfuric acid and laccase. The lignin in *Caragana korshinskii* is tightly cross-linked with cellulose and hemicellulose, forming a robust natural barrier. Dilute sulfuric acid can effectively hydrolyze hemicellulose at high temperatures, disrupting the cellulose crystal structure, but this chemical treatment has limited effect on lignin itself, especially on dissolved phenolic fragments. The laccase introduced in this application is a multi-copper oxidase, unique in that it maintains catalytic activity under the harsh conditions of acidity (pH regulated by acid) and high temperature (120-150°C) provided by this invention. In this microenvironment, dilute sulfuric acid first opens the cellulose structure, exposing lignin; subsequently, laccase efficiently catalyzes the oxidation of dissolved lignin fragments and small-molecule phenolic inhibitors, causing them to polymerize or break down, thereby significantly reducing the biotoxicity of the substrate and increasing the accessible surface area. Example 2 further introduces ammonium bicarbonate-assisted ultrafine grinding. During mechanical grinding, it decomposes in situ to generate gas, physically expanding and tearing the fibers, resulting in finer particle size and a larger specific surface area. This provides more attack sites for enzymes, thereby increasing the lignin removal rate to 68.0%~69.0%. Through a three-stage pretreatment strategy of physical expansion-chemical decomposition-biodegradation, the stubborn structure of *Caragana korshinskii* is systematically broken down, clearing the biggest obstacle for subsequent microbial fermentation. It is important to emphasize that efficient pretreatment only creates great possibilities for fermentation, while the key to transforming these possibilities into high efficiency lies in the core role of the microbial-enzyme co-fixed microspheres during subsequent fermentation. The cellulose and other accessible carbon sources released during pretreatment are efficiently and directionally converted into microbial cells and metabolites through the spatially sequential synergistic mechanism of enzymatic hydrolysis and microbial utilization within the co-fixed microspheres. This drives the material and energy flow of the entire fermentation system, providing a fundamental guarantee for the high quality of lignin removal and final conversion into fertilizer.

[0066] Comparative Example 4 (without selenium addition) served as a blank control; lignin removal was acceptable, but no selenium conversion was observed. Example 1, using a one-time addition of molasses and sodium selenite, achieved an organic selenium conversion rate of 58.0%. However, Examples 3, 4, and 5, employing a phased addition strategy, saw conversion rates jump to 70.0%, 76.0%, and 78.5%, respectively. This is because the phased addition resolved the temporal contradiction between carbon source metabolism and selenium biotransformation. Inorganic selenium (Se in sodium selenite) 4+The absorption and conversion of selenium into organic selenium (such as selenomethionine) by microorganisms is a secondary metabolic process that requires a large amount of reducing power and energy. If all readily available carbon sources (molasses) are added at the beginning of anaerobic fermentation, the microorganisms will prioritize growth and metabolism, quickly depleting the carbon source and entering the decline phase, at which point the selenium conversion process has not yet been fully completed. In this application, molasses and sodium selenite are added in two stages: the first addition (a portion of the total amount) is used to start fermentation, establish a dominant anaerobic bacterial community, and enable the microorganisms to activate the selenium tolerance mechanism; the timing of the second addition is crucial. Example 3 uses fixed-time-point feeding, while Examples 4 and 5 go a step further by monitoring the gas production rate in real time using a wet gas flow meter. The gas production rate is a sensitive indicator reflecting the overall metabolic activity of the entire anaerobic microbial community. When the gas production rate reaches its peak and then continues to decline to below 80% of the peak, it indicates that the carbon source added in the first stage is about to be depleted, and the microbial activity enters a downward trend. At this point (as in Example 4 at 52h), a second feeding is performed, which can most effectively reactivate microbial activity and efficiently guide the supplemented carbon and selenium sources to the ready selenium conversion metabolic pathway, thereby maximizing the efficiency of selenium organicification.

[0067] Soil improvement and growth promotion effect experiment: Three experimental groups were set up: CK group (blank control, no fertilizer), CF group (using commercially available ordinary bio-organic fertilizer with a viable bacteria count of not less than 0.5 billion / g), and TF group (using highly active bio-organic fertilizer prepared in Example 5). A pot experiment was conducted in typical loam soil in Northwest China for 60 days, with a fertilizer application rate of 1.5 kg / m³. 2 The soil physicochemical properties were measured after the experiment, as shown in Table 3.

[0068] Table 3 Soil physicochemical indicators As shown in Table 3, the highly active bio-organic fertilizer prepared in Example 5 has significant advantages in improving soil physicochemical properties. Compared with the blank control (CK group) and commercially available ordinary bio-organic fertilizer (CF group), the soil bulk density of the TF group decreased from 1.32 g / cm³ in the CF group. 3 Further reduced to 1.25 g / cm³ 3 This indicates that the soil is more porous; the content of water-stable aggregates larger than 0.25 mm increased significantly from 41.5% in the CF group to 52.8%, indicating a significant enhancement in soil structural stability; soil porosity and field water holding capacity increased from 45.8% and 24.5% to 50.3% and 28.7%, respectively, reflecting a simultaneous improvement in soil aeration, permeability, and water retention capacity; cation exchange capacity (CEC) increased from 14.0 cmol. + / kg increased to 17.8 cmol + / kg, signifying a significant enhancement in soil fertility retention; most notably, the available selenium content surged from 0.06 mg / kg in the CF group to 0.85 mg / kg, representing a leap in magnitude. This is due to two main reasons. First, the synergistic effect of acid-enzyme pretreatment and the compound functional microbial agent. The pretreatment efficiently broke down the stubborn fibrous structure of *Caragana korshinskii* and degraded bioinhibitors such as phenols, providing a highly accessible clean substrate for subsequent functional microorganisms. In the compound microbial agent, *Bacillus laterosporus* and *Bacillus subtilis* are responsible for rapidly degrading organic matter, and their metabolites, along with the microbial cells themselves, become the core cementing substances for forming soil aggregates. Polysaccharides produced by *Bacillus spp.* and other bacteria further promote the stability of the aggregates, collectively leading to a chain reaction of improved soil structure, including decreased bulk density, increased aggregate content, and increased porosity. Second, the high humic acid content and active microorganisms in the product continuously act on the soil. Humic acid itself has a huge specific surface area and functional groups, which can significantly improve the soil's CEC and water retention capacity. Highly active functional microbial communities, after being applied to the soil, continue to multiply, and their metabolic activities continuously produce substances that promote aggregate formation and activate the soil's inherent nutrients, resulting in a dynamic and continuous improvement effect. Thirdly, through a phased application and dynamic monitoring process, sodium selenite is efficiently converted into organic selenium by microorganisms and remains stably present in the fertilizer. When the fertilizer is applied to the soil, these organic selenium forms are easily adsorbed by soil colloids and have high bioavailability, thus significantly increasing the soil's available selenium content and laying a solid foundation for the production of selenium-rich agricultural products.

[0069] In summary, the method for preparing highly active bio-organic fertilizer using Caragana korshinskii provided by this invention addresses the core challenge of high-value utilization of Caragana korshinskii resources. It involves pretreatment cell wall breaking, construction of compound microbial agents, coupling of fermentation processes to precise process control. Its ultimate goal is not only to achieve the harmless treatment of Caragana korshinskii waste, but also to transform it into a high-value-added bio-organic fertilizer with high organic matter, high humic acid, highly active functional microbial communities, and rich in stable organic selenium. This fertilizer plays a lasting and prominent role in improving soil, promoting crop growth, and enhancing the quality of agricultural products, truly achieving a unity of ecological and economic benefits.

[0070] The number of devices and processing scale described herein are for simplification of the invention. Applications, modifications, and variations of the method for preparing highly active bio-organic fertilizer using *Caragana korshinskii* and the organic fertilizer products thereof will be readily apparent to those skilled in the art.

[0071] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for preparing highly active bio-organic fertilizer using Caragana korshinskii, characterized in that, include: S1. The raw material, the residue of Caragana twigs, is first coarsely crushed and then preliminarily dried until the moisture content is less than 12%. Then, it is ultra-finely crushed to prepare Caragana twig micro powder with a particle size of more than 150 mesh. The Caragana twig micro powder is mixed with a 3-5% dilute sulfuric acid solution and laccase at a mass ratio of 1:2-3:0.05-0.

15. After soaking at 120-150℃ for 40-60 minutes, the pH of the system is neutralized to 6.5-7 using a 20% sodium hydroxide solution. After solid-liquid separation, activated Caragana twig slurry is obtained. S2. Weigh out Bacillus laterosporus, Bacillus subtilis, Bacillus licheniformis, Bacillus licheniformis, and Saccharomyces cerevisiae liquid according to the live bacteria ratio of 3~5:2~3:2~3:0.5~1:1, activate them separately, and then compound them to prepare a compound functional bacterial agent; mix the compound functional bacterial agent with Aspergillus fumigatus at a mass ratio of 60~80:1, and then fix them together in sodium alginate-gelatin-biochar composite gel to make bacterial-enzyme co-solidified microspheres with a diameter of 1~3 mm; S3. The activated Caragana slurry obtained in step S1, the bacteria-enzyme co-solidified microspheres obtained in step S2, urea, and ammonium sulfate are mixed in a ratio of 100~120:8~12:3~6:1 and then subjected to high-temperature aerobic fermentation and mesophilic anaerobic fermentation in sequence to obtain fermented material. S4. Mix the fermentation material obtained in step S3 with functional additives to prepare the highly active bio-organic fertilizer; In step S3, high-temperature aerobic fermentation is carried out in a fermenter at a temperature of 50-55℃ and an aeration rate of 1.0-1.5VVM, until the ratio of water-soluble organic carbon to total organic carbon in the material reaches 0.25-0.

35. Mesophilic anaerobic fermentation is carried out in a closed fermentation tank. During mesophilic anaerobic fermentation, 5-8% of molasses and 0.1-0.3% of sodium selenite are added to the total weight of the Caragana korshinskii powder, and the fermentation is carried out under anaerobic conditions at 38-42℃ for 100-120 hours.

2. The method for preparing highly active bio-organic fertilizer using *Caragana korshinskii* as described in claim 1, characterized in that, The specific activation steps in step S2 include: culturing each bacterial agent in physiological saline containing 0.1-0.2% yeast extract and 0.05% magnesium sulfate heptahydrate at 35-37°C for 30-40 minutes.

3. The method for preparing highly active bio-organic fertilizer using *Caragana korshinskii* as described in claim 1, characterized in that, The specific steps in step S4 of preparing the highly active bio-organic fertilizer by mixing the fermented material obtained in step S3 with functional additives include: Add potassium humate (2-4% by dry weight), calcium alginate gel particles (1-2% by dry weight), and diatomaceous earth (0.3-0.6% by dry weight) to the fermentation material obtained in step S3, and mix them evenly. After drying the mixture at a temperature below 50°C until the moisture content is below 18%, it is granulated by extrusion granulation to produce particles with a particle size of 3-5 mm, which is the high-activity bio-organic fertilizer.

4. The method for preparing highly active bio-organic fertilizer using *Caragana korshinskii* as described in claim 3, characterized in that, After the mixture is dried to a moisture content of less than 18%, a composite binder is added to the dried mixture at a dry basis weight of 0.5 to 1.5%. The composite binder is a mixture of soluble starch and sodium lignosulfonate in a mass ratio of 2 to 3:

1.

5. The method for preparing highly active bio-organic fertilizer using *Caragana korshinskii* as described in claim 4, characterized in that, The dry basis weight of the fermentation material is calculated as follows: Dry basis weight of fermentation material = weight of fermentation material × (1-W1), where W1 is the immediate moisture content of the fermentation material, which is measured by a near-infrared moisture analyzer by rapid sampling from the fermentation material; The dry basis weight of the dried mixture is calculated as follows: Dry basis weight of the dried mixture = weight of the dried mixture × (1-W2), where W2 is the immediate moisture content of the dried mixture, which is measured by a near-infrared moisture analyzer by rapid sampling from the dried mixture.

6. The method for preparing highly active bio-organic fertilizer using *Caragana korshinskii* as described in claim 1, characterized in that, In step S1, during ultrafine grinding, 1-3% of ammonium bicarbonate by dry weight of the remaining raw material Caragana twigs is added to the preliminarily dried coarsely ground Caragana twigs to carry out ultrafine grinding together.

7. The method for preparing highly active bio-organic fertilizer using *Caragana korshinskii* as described in claim 1, characterized in that, In step S3, during mesophilic anaerobic fermentation, the molasses and sodium selenite are added in two batches. During mesophilic anaerobic fermentation, 40-60 wt% molasses and 20-30 wt% sodium selenite are added. After 48-60 hours of mesophilic anaerobic fermentation, the remaining molasses and sodium selenite are added.

8. The method for preparing highly active bio-organic fertilizer using *Caragana korshinskii* as described in claim 7, characterized in that, The timing of adding the remaining molasses and sodium selenite was determined by monitoring the gas production rate in the closed fermentation tank. Connect the sealed fermentation tank to a wet gas flow meter to continuously measure and record the cumulative gas production of the sealed fermentation tank, and calculate the hourly gas production rate in real time. When the gas production rate reaches its peak, if the gas production rate monitored for 6-8 hours is lower than 80% of the peak value, add the remaining molasses and sodium selenite.

9. The method for preparing highly active bio-organic fertilizer using *Caragana korshinskii* as described in claim 1, characterized in that, When adding the remaining molasses and sodium selenite, mix the remaining molasses and sodium selenite evenly at 40~42℃ and keep warm for later use.

10. A highly active bio-organic fertilizer, characterized in that, The highly active bio-organic fertilizer is prepared using the method described in any one of claims 1 to 9, which utilizes *Caragana korshinskii* to prepare highly active bio-organic fertilizer.

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