Water-soluble fertilizer for promoting propagation of soil microorganisms

Abstract

The invention discloses a water-soluble fertilizer for promoting soil microorganism propagation, and relates to the field of fertilizer preparation, the water-soluble fertilizer comprises the following functional units: a core fertilizer unit, a microorganism signal unit and an environmental response type carrier unit; the microbial signal unit comprises a microbial chemotactic starting factor consisting of key precursor substances of root exudates, namely L-arabinose and gamma-aminobutyric acid according to a mass ratio of (1: 0.5)-(1: 2); the environmental response type carrier unit is nano ferroferric oxide / porous silicon dioxide bifunctional particles coated with humic acid-lignin composite gel, and the swelling degree of the humic acid-lignin composite gel is sensitive to the change of the pH value within the range of 5.0-7.0; the method is used for solving the technical problems that in the prior art, a microbial stimulation means lacks accuracy and controllability, cannot actively respond to dynamic changes of a rhizosphere environment, and is difficult to realize directional propagation and efficient function excitation of beneficial microorganisms.

Description

Technical Field

[0001] This invention relates to the field of fertilizer preparation, specifically to a water-soluble fertilizer that promotes the proliferation of soil microorganisms. Background Technology

[0002] Soil microorganisms are core drivers of the health and function of farmland ecosystems, playing an irreplaceable role in organic matter decomposition, nutrient cycling and transformation, soil structure improvement, and plant disease suppression. Therefore, promoting the proliferation and enhanced activity of beneficial soil microorganisms through agricultural management measures has become an important pathway to achieving green and sustainable agricultural development. While conventional fertilization strategies aim to provide nutrients to crops, they often fail to adequately consider the targeted regulation needs of the rhizosphere microbial community, resulting in the ineffective activation of microbial functional potential.

[0003] Fertilizer improvements designed to promote soil microorganisms mainly focus on the following aspects: First, adding specific types of microbial inoculants to conventional water-soluble fertilizers; second, incorporating natural organic stimulants such as humic acid and seaweed extracts into fertilizer formulations to provide carbon sources for microbial growth or stimulate their metabolism; and third, achieving slow-release of nutrients through physical granulation or coating technologies to provide a more sustained nutrient environment for microbial activity. These methods have had a positive impact on the microbial community to some extent, but their mechanisms of action are mostly passive supply or general stimulation.

[0004] The aforementioned existing technologies still have significant limitations: First, directly added microbial agents are prone to inactivation or lack competitiveness in complex soil environments, making it difficult to achieve stable colonization and propagation. Second, common organic additives lack precise "signals" to guide key rhizosphere microorganisms, failing to efficiently initiate the chemotaxis and proliferation processes of beneficial microorganisms. Third, conventional slow-release technologies are mostly time- or moisture-triggered, unable to respond to dynamic changes in the rhizosphere microenvironment, such as pH fluctuations or root exudate signals, resulting in a mismatch between nutrient release and microbial needs in time and space. Finally, existing technologies lack an intelligent means to actively regulate the release of microbial stimuli based on controllable external conditions (such as light and heat), making precise management of the microbial propagation process difficult. Therefore, developing an intelligent fertilizer that can precisely respond to the rhizosphere environment and actively regulate on demand is of great significance for improving the efficiency of soil microbial management. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a water-soluble fertilizer that promotes the proliferation of soil microorganisms, so as to solve the technical problems in the prior art that the microbial stimulation methods lack precision and controllability, cannot actively respond to dynamic changes in the rhizosphere environment, and are difficult to achieve directional proliferation and efficient functional stimulation of beneficial microorganisms.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a water-soluble fertilizer that promotes the proliferation of soil microorganisms, characterized in that it comprises the following functional units: a core fertilizer unit, a microbial signaling unit, and an environmentally responsive carrier unit; the microbial signaling unit comprises a microbial chemotactic initiator composed of L-arabinose and γ-aminobutyric acid, key precursors of root exudates, in a mass ratio of 1:0.5 to 1:2; the environmentally responsive carrier unit is a nano-ferric oxide / porous silica bifunctional particle coated with a humic acid-lignin composite gel, and the swelling degree of the humic acid-lignin composite gel is sensitive to changes in pH value within the range of 5.0-7.0; the environmentally responsive carrier unit is used to load the microbial chemotactic initiator and trace elements.

[0007] The present invention is further configured such that the core fertilizer unit is a source of macronutrients nitrogen, phosphorus and potassium, wherein the phosphorus source includes ammonium polyphosphate, and the P2O5 provided by ammonium polyphosphate accounts for 20%-40% of the total phosphorus; the potassium source includes potassium dihydrogen phosphate and potassium citrate, and the potassium provided by potassium citrate accounts for 5%-15% of the total potassium based on K2O.

[0008] The present invention is further configured such that, in the nano-iron oxide / porous silica bifunctional particles, nano-iron oxide serves as the core and porous silica serves as the outer shell, with an overall particle size of 50-200 nm and a specific surface area of ​​200-400 m² / g; the humic acid-lignin composite gel is coated on the surface of the nano-iron oxide / porous silica bifunctional particles through a cross-linking reaction, with a coating thickness of 10-50 nm.

[0009] The present invention is further configured such that the preparation method of the humic acid-lignin composite gel is as follows: potassium humate and alkali lignin are dissolved in water at a mass ratio of (2-4):1, and reacted with crosslinking agent N,N'-methylenebisacrylamide in the presence of an initiator to form a hydrogel, which is then dried and pulverized to obtain the hydrogel; the swelling degree of the composite gel at pH=5.0 is 1.5-3 times that at pH=7.0.

[0010] The present invention is further configured such that the fertilizer also contains 0.02%-0.1% by mass of a near-infrared photothermal conversion agent, wherein the near-infrared photothermal conversion agent is a carboxyl-modified copper-based chalcogenide nanosheet, the maximum absorption wavelength of which is located in the near-infrared region of 800-1100 nm.

[0011] The present invention is further configured such that the mass ratio of the microbial chemotactic initiator to the environmentally responsive carrier unit is 1:5 to 1:20; the trace elements exist in chelated form and are preloaded in the porous structure of the environmentally responsive carrier unit, and the trace elements include iron, zinc and copper, with a molar ratio of 1:0.3 to 0.6 to 0.1 to 0.3.

[0012] The present invention is further configured such that the fertilizer is in the form of core-shell structured particles with a diameter of 1-3 mm, wherein the "core" is a dense mixture containing the core fertilizer unit and the near-infrared photothermal conversion agent, and the "shell" is a porous coating layer constructed by an adhesive for the environmentally responsive carrier unit loaded with the microbial chemotactic initiation factor and the trace elements.

[0013] The present invention is further configured such that it also includes a method for preparing a soil microbial propagation water-soluble fertilizer: S1: Preparation of a load-type environmentally responsive carrier: The microbial chemotactic initiator and the trace element solution are mixed with the environmentally responsive carrier unit, and vacuum impregnation and adsorption are performed. After drying, a carrier loaded with active substances is obtained. S2: Preparation of core particles: The components of the core fertilizer unit are dry-mixed with the near-infrared photothermal conversion agent, and then the core is formed by extrusion granulation or rolling granulation; S3: Constructing a core-shell structure: The loaded environmentally responsive carrier obtained in S1 is uniformly dispersed in an adhesive solution to form a coating slurry. The core obtained in S2 is coated using a fluidized bed bottom spray coating process to form a porous shell. S4: Low-temperature curing and sieving: The coated granules are dried and cured at a temperature below 50°C, and then sieved to obtain the finished product.

[0014] The present invention is further configured such that: the fertilizer is applied to the root zone soil of the crop; when rapid microbial propagation is required, the root zone soil is intermittently irradiated with a near-infrared light source with a center wavelength of 980nm, each irradiation lasting 1-5 minutes, with an interval of not less than 30 minutes; the near-infrared photothermal conversion agent converts light energy into heat energy, causing the composite gel shell of the environmentally responsive carrier unit to shrink and accelerate the release of the loaded substance, while locally and gently raising the temperature by 2-5°C to simulate the rhizosphere heating effect.

[0015] In summary, the present invention has the following main beneficial effects: By designing an intelligent fertilizer system integrating "signal guidance," "environmental response," and "externally controlled release," this invention can precisely, efficiently, and controllably promote the directional proliferation of target soil microorganisms. Specifically, it utilizes a specific ratio of microbial chemotactic initiation factors to simulate root signals, actively guiding beneficial microorganisms to aggregate in the rhizosphere; through a pH-sensitive composite gel carrier, the core stimulating substances can intelligently respond to dynamic changes in the rhizosphere microenvironment and be released; and it innovatively introduces a near-infrared photothermal conversion mechanism, enabling the microbial proliferation process to be activated and enhanced non-contactly and on demand through external light, achieving a leap from "passive supply" to "active response and regulation," thereby significantly improving the efficiency and reliability of microbial fertilizers. Attached Figure Description

[0016] Figure 1 This is a diagram illustrating the method steps of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, so that those skilled in the art can implement the present invention. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the scope of protection of the present invention.

[0018] This invention provides a water-soluble fertilizer for soil microbial propagation with rhizosphere response and photothermal regulation functions. The core design concept of this fertilizer is to integrate basic nutrient supply, specific microbial signal guidance, and intelligent environmental response release mechanism, and to achieve on-demand activation through an external physical field, thereby achieving targeted, efficient, and controllable propagation promotion of the target beneficial microbial community.

[0019] The specific composition, structure and function of fertilizers The fertilizer of this invention is a multi-unit integrated system, and its specific composition is as follows: Core Fertilizer Unit This unit is responsible for providing the basic macronutrients of nitrogen, phosphorus, and potassium. The nitrogen source can be one or a combination of urea, ammonium nitrate, potassium nitrate, ammonium sulfate, monoammonium phosphate, and diammonium phosphate, to ensure both rapid and sustained supply. The phosphorus source must include ammonium polyphosphate, which not only provides phosphorus nutrition but also has the function of chelating and maintaining the activity of trace elements due to its long-chain structure; the phosphorus pentoxide provided by ammonium polyphosphate accounts for 20% to 40% of the total phosphorus mass in the fertilizer. The potassium source is provided by potassium dihydrogen phosphate and potassium citrate; based on potassium oxide, potassium citrate provides 5% to 15% of the total potassium mass. The introduction of potassium citrate not only supplements potassium nutrition but also its citrate ions can serve as beneficial organic ligands. The total nutrient content of this core fertilizer unit, i.e., the sum of nitrogen, phosphorus pentoxide, and potassium oxide, is preferably controlled between 35% and 55%.

[0020] Microbial signaling unit The core functional component of this unit is the microbial chemotactic initiator. This factor consists of two key root exudate precursors: L-arabinose and γ-aminobutyric acid (GABA). They are combined in a specific mass ratio, ranging from 1:0.5 to 1:2 (L-arabinose to GABA). For example, ratios of 1:0.8, 1:1, or 1:1.5 can be used. L-arabinose is a chemotactic carbon source for many beneficial microorganisms, while GABA is an important signaling molecule between roots and microorganisms. Their synergistic effect effectively mimics the signaling characteristics of healthy plant root exudates, actively attracting and activating target microorganisms such as arbuscular mycorrhizal fungi, phosphate-solubilizing bacteria, and biocontrol actinomycetes to aggregate in the rhizosphere and initiate their proliferation program.

[0021] Environmentally responsive carrier unit This unit is a smart carrier system with pH-responsive release characteristics, used to load and control the release of the aforementioned microbial chemotactic initiation factors and trace elements.

[0022] The carrier matrix is ​​a type of nano-sized, porous silica bifunctional particle. This particle exists in a core-shell structure: the core consists of nano-sized, magnetic iron oxide particles with a diameter of approximately ten to twenty nanometers; the outer shell is a porous silica layer with abundant mesoporous structure. After preparation via sol-gel encapsulation, the overall particle size range of this bifunctional particle is fifty to two hundred nanometers, and its specific surface area is as high as two hundred to four hundred square meters per gram. This large specific surface area provides it with excellent loading capacity.

[0023] Intelligent Response Coating Layer: A humic acid-lignin composite gel is further coated onto the surface of the aforementioned bifunctional particles via chemical cross-linking. The preparation process of this composite gel is as follows: Potassium humate and alkali lignin are dissolved together in deionized water at a mass ratio ranging from 2:1 to 4:1, for example, 2.5:1 or 3:1. Under an inert atmosphere and stirring conditions, a redox initiator system composed of potassium persulfate and sodium bisulfite is added, along with the cross-linking agent NN-methylenebisacrylamide. The reaction system temperature is maintained at 60-70 degrees Celsius, and the reaction is continued for 2-4 hours to form a three-dimensional network structure hydrogel. After the reaction, the gel is crushed, washed, and dried at a low temperature below 60 degrees Celsius or freeze-dried to obtain the final composite gel powder. This composite gel is firmly coated onto the surface of the bifunctional particles through surface modification or in-situ polymerization, forming a uniform coating layer with a thickness of approximately 10-50 nanometers.

[0024] The key characteristic of this humic acid-lignin composite gel is its highly sensitive swelling behavior to the concentration of hydrogen ions in the environment, i.e., pH value. Specifically, in a slightly acidic environment with a pH of 5.0, the swelling degree of the gel—the ratio of its volume or mass after absorbing water to its dry state—is 1.5 to 3 times that in a neutral environment with a pH of 7.0. This characteristic means that when fertilizer is applied to the active rhizosphere microzone in a slightly acidic environment, the gel layer absorbs water and swells, expanding the pores of its internal network, thereby accelerating the diffusion and release of its internal load; while in non-rhizosphere or neutral soil areas, the gel relatively shrinks, and the release is slow. This achieves intelligent response and targeted release to changes in the pH of the rhizosphere microenvironment.

[0025] Loading Contents: This environmentally responsive carrier unit is used to load two components: first, the aforementioned microbial chemotactic initiator, a mixture of L-arabinose and γ-aminobutyric acid; and second, trace elements in chelated form, including iron, zinc, and copper, with their molar ratio controlled at 1:0.3 to 0.6:0.1 to 0.3 (e.g., 1:0.4:0.2). EDTA chelates or amino acid chelates are preferably used to ensure their stability and availability in soil.

[0026] Loading ratio: The mass ratio between microbial chemotactic initiators and environmentally responsive carrier units should be controlled within the range of 1:5 to 1:20, for example, 1:8 or 1:15. This ratio ensures sufficient carrier capacity to load and control the release of signaling factors, while avoiding excessive dilution of the fertilizer's effective nutrient content due to excessive carrier.

[0027] Near-infrared photothermal conversion agent To endow the fertilizer of this invention with externally controllable, on-demand activation capabilities, a small but crucial near-infrared photothermal conversion agent is added to the fertilizer composition, accounting for 0.02% to 0.1% of the total fertilizer mass. This conversion agent is a copper-based chalcogenide nanosheet with a carboxylated surface modification, such as copper sulfide nanosheets or copper selenide nanosheets. Surface modification imparts good hydrophilicity and dispersion stability. The maximum light absorption wavelength of this nanosheet is located in the near-infrared spectral region of 800 to 1100 nanometers, a band that has a certain penetration ability into soil and is safe for plant tissues. Its function is to efficiently convert received near-infrared light energy into heat energy.

[0028] Final physical dosage form structure The aforementioned functional units are integrated into a physically stable core-shell structure particle through a specific process. The particle has a diameter of 1.0 to 3.0 millimeters.

[0029] Core: A dense solid particle formed by uniformly mixing all components of the core fertilizer unit with a near-infrared photothermal conversion agent and then granulating it. It constitutes the main body and mass center of the particle, providing basic nutrients and carrying out the photothermal conversion function.

[0030] Shell: A porous coating layer composed of environmentally responsive carrier units loaded with microbial chemotactic initiation factors and trace elements, bonded together with adhesives such as aqueous polyvinyl alcohol or polyacrylate dispersions. This shell covers the core, and its porous structure allows water and soil solutions to permeate, thereby initiating the responsive release process of the carrier units within the shell.

[0031] Fertilizer preparation methods The preparation of the fertilizer of this invention is a systematic process, which mainly includes three stages: carrier activation and loading, core molding, and core-shell structure construction.

[0032] First, the carrier activation and loading process was carried out. A predetermined amount of environmentally responsive carrier unit powder, namely, nano-porous silica bifunctional particles coated with humic acid-lignin composite gel, was weighed. The microbial chemotactic initiator L-arabinose and γ-aminobutyric acid were mixed in a certain proportion and dissolved in deionized water with a predetermined molar ratio of iron, zinc, and copper trace element chelates to prepare an active loading solution. The carrier powder was added to the loading solution while stirring, and the mixture was then transferred to a vacuum container. A vacuum was drawn to above -0.095 MPa and maintained for 20 to 40 minutes to ensure the active solution fully penetrated the mesopores and gel network of the carrier particles. After releasing the vacuum, gentle stirring was continued for 1 to 2 hours to ensure adsorption equilibrium. The solid material was obtained by filtration or centrifugation and then vacuum-dried at 40 to 50 degrees Celsius to constant weight, finally obtaining the carrier loaded with the active substance, denoted as the environmentally responsive carrier.

[0033] Next, the core particles are prepared. Accurately weigh all the nitrogen and phosphorus sources (including ammonium polyphosphate), and potassium sources (including potassium dihydrogen phosphate and potassium citrate) required for the core fertilizer unit according to the formula. Add the calculated amount of near-infrared photothermal conversion agent powder. Put all solid materials into a high-efficiency mixer for thorough dry mixing until homogeneous. Then, add an appropriate amount of pure water or a 5% polyethylene glycol solution as a wetting binder to the homogeneous powder, and produce wet particles with a particle size of approximately 0.8 to 2.5 mm in a mixing granulator or extrusion granulator. Transfer the wet particles to a fluidized bed dryer and dry them at an inlet temperature of 80 to 100 degrees Celsius to obtain dried core particles with a moisture content of less than 1.0% and a certain mechanical strength.

[0034] Finally, the core-shell structure was constructed. The aforementioned prepared loaded environmentally responsive carrier powder was slowly added to a binder solution, such as a 5% aqueous solution of polyvinyl alcohol, and dispersed uniformly using a high-speed shear emulsifier to form a stable coating slurry. The dried core particles were placed in the hopper of a fluidized bed bottom spray coating machine, and the equipment was started to keep the particles in a stable suspension state under hot air fluidization. The inlet air temperature was controlled at 60 to 80 degrees Celsius, and the material temperature was maintained at 40 to 50 degrees Celsius. Using a bottom spray nozzle, the coating slurry was continuously and uniformly sprayed onto the surface of the fluidized core particles at an atomization pressure of 0.2 to 0.4 MPa. By monitoring the particle size growth in real time, the coating weight gain was controlled until the target particle diameter reached 1.0 to 3.0 mm, thereby forming a uniform porous shell layer outside the core. After coating, the inlet air temperature was reduced to about 45 degrees Celsius, and fluidized drying continued for 30 to 60 minutes to allow the binder in the shell layer to completely solidify and set. Finally, the granules are removed, and the products with the required particle size are selected by vibrating sieve. They are then sealed in moisture-proof packaging to obtain the finished fertilizer described in this invention.

[0035] Fertilizer application methods The application of this fertilizer requires specific methods to fully leverage its intelligent regulation advantages. First, during critical crop growth periods, such as pre-sowing land preparation, seedling transplanting, or when the root system needs recovery from stress, the fertilizer should be applied directly to the crop root zone soil. Trench application, hole application, or mixing with the root zone soil are recommended, with an application rate of two to five kilograms per acre per application. Irrigation should be carried out immediately after fertilization, or the fertilizer should be applied directly through a drip irrigation system to ensure sufficient contact between the fertilizer particles and soil moisture, initiating its initial release process.

[0036] When agricultural producers need to actively and rapidly stimulate or enhance the propagation of microorganisms, such as when low temperatures in early spring lead to low microbial activity, or when potential risks of soil-borne diseases are detected and it is necessary to strengthen the biocontrol microbial population in advance, external light regulation technology can be used for intervention. A near-infrared light source with an emission center wavelength of 980 nanometers should be used, and this wavelength must match the maximum absorption band of the near-infrared photothermal conversion agent added to the fertilizer. The light source should be aimed at the soil surface in the root zone of the fertilized crop. Irradiation should be conducted in an intermittent mode, with each irradiation lasting one to five minutes, and the interval between irradiations not less than thirty minutes. One to three cycles of irradiation treatment can be performed daily, depending on actual needs.

[0037] During this irradiation process, near-infrared light penetrates the soil surface and is absorbed by the near-infrared photothermal converter in the fertilizer granules, converting it into heat energy. This thermal effect produces a dual positive effect: First, the heat is conducted to the humic acid-lignin composite gel shell of the environmentally responsive carrier unit, causing the gel to undergo thermal shrinkage and deformation, and accelerating internal water convection, thereby dramatically increasing the release rate of the microbial chemotactic initiation factors and trace elements it carries, forming a high concentration of signal and nutrient stimulation peaks in the rhizosphere within a short period of time; Second, this local thermal effect can gently raise the soil temperature in the rhizosphere micro-domain by two to five degrees Celsius. This temperature rise simulates the natural rhizosphere heating phenomenon produced by vigorous plant root metabolism or active microbial decomposition, which can significantly enhance the overall metabolic activity and proliferation rate of the soil microbial community. The intervention of external light allows the timing and intensity of microbial proliferation to be flexibly controlled by humans as needed, realizing precise and intelligent management of soil microorganisms.

[0038] In summary, this invention provides an intelligent water-soluble fertilizer integrating basic nutrient supply, specific signal guidance, environmental response release, and external physical field regulation. This fertilizer precisely guides beneficial microorganisms to aggregate in the rhizosphere through a chemotactic initiator composed of L-arabinose and γ-aminobutyric acid; it utilizes a pH-sensitive humic acid-lignin composite gel to encapsulate the nanocarrier, achieving intelligent response release of active substances to changes in the acidity and alkalinity of the rhizosphere microenvironment; and by introducing a near-infrared photothermal conversion agent and constructing a core-shell structure, the microbial propagation process can be actively activated on demand by external near-infrared light. This invention fundamentally changes the traditional passive supply mode of microbial fertilizers, solving the technical problems of missing signal guidance, mismatch between release and demand, and uncontrollable process in existing technologies. It achieves targeted, efficient, and artificially intervened propagation promotion of beneficial soil microbial communities, significantly improving the reliability and application efficacy of microbial fertilizers.

[0039] Although embodiments of the present invention have been shown and described, these specific embodiments are merely explanations of the invention and are not intended to limit it. The specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. After reading this specification, those skilled in the art may make modifications, substitutions, and variations to the embodiments as needed without departing from the principles and spirit of the invention, but such modifications, substitutions, and variations are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A water-soluble fertilizer that promotes the proliferation of soil microorganisms, characterized in that, It includes the following functional units: core fertilizer unit, microbial signaling unit, and environmentally responsive carrier unit; The microbial signaling unit comprises a microbial chemotactic initiator consisting of L-arabinose and γ-aminobutyric acid, key precursors of root exudates, in a mass ratio of 1:0.5 to 1:

2. The environmentally responsive carrier unit is a nano-iron oxide / porous silica bifunctional particle coated with humic acid-lignin composite gel, and the swelling degree of the humic acid-lignin composite gel is sensitive to changes in pH value within the range of 5.0-7.

0. The environmentally responsive carrier unit is used to load the microbial chemotactic initiation factor and trace elements.

2. The soil microbial propagation water-soluble fertilizer according to claim 1, characterized in that, The term includes: The core fertilizer unit consists of sources of macronutrients nitrogen, phosphorus, and potassium. Among them, the phosphorus source includes ammonium polyphosphate, and the P2O5 provided by ammonium polyphosphate accounts for 20%-40% of the total phosphorus. The potassium source includes potassium dihydrogen phosphate and potassium citrate, and the potassium provided by potassium citrate accounts for 5%-15% of the total potassium, calculated as K2O.

3. The soil microbial propagation water-soluble fertilizer according to claim 1, characterized in that, The term includes: In the nano-iron oxide / porous silica bifunctional particles, nano-iron oxide serves as the core and porous silica serves as the outer shell. The overall particle size is 50-200nm and the specific surface area is 200-400 m² / g. The humic acid-lignin composite gel is coated on the surface of the nano-iron oxide / porous silica bifunctional particles through a cross-linking reaction, with a coating thickness of 10-50 nm.

4. The soil microbial propagation water-soluble fertilizer according to claim 1 or 3, characterized in that, The method for preparing humic acid-lignin composite gel is as follows: Potassium humate and alkali lignin were dissolved in water at a mass ratio of 2:1 to 4:1, and reacted with the crosslinking agent N,N'-methylenebisacrylamide in the presence of an initiator to form a hydrogel, which was then dried and pulverized to obtain the product. The swelling degree of this composite gel at pH=5.0 is 1.5-3 times that at pH=7.

0.

5. The soil microbial propagation water-soluble fertilizer according to claim 1, characterized in that, The fertilizer also contains 0.02%-0.1% by mass of a near-infrared photothermal conversion agent, which is a carboxyl-modified copper-based chalcogenide nanosheet with a maximum absorption wavelength in the near-infrared region of 800-1100 nm.

6. The soil microbial propagation water-soluble fertilizer according to claim 1, characterized in that, The term includes: The mass ratio of the microbial chemotactic initiator to the environmentally responsive carrier unit is 1:5 to 1:20; The trace elements exist in chelated form and are preloaded in the porous structure of the environmentally responsive carrier unit. The trace elements include iron, zinc, and copper in a molar ratio of 1 to 0.3 to 0.6 to 0.1 to 0.

3.

7. The soil microbial propagation water-soluble fertilizer according to claim 1 or 5, characterized in that, The fertilizer is formulated as core-shell structured particles with a diameter of 1-3 mm. The "core" is a dense mixture containing the core fertilizer unit and the near-infrared photothermal conversion agent, and the "shell" is a porous coating layer constructed by an adhesive for the environmentally responsive carrier unit loaded with the microbial chemotactic initiation factor and the trace elements.

8. A method for preparing a water-soluble fertilizer for soil microbial propagation as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: Preparation of a load-type environmentally responsive carrier: The microbial chemotactic initiator and the trace element solution are mixed with the environmentally responsive carrier unit, and vacuum impregnation and adsorption are performed. After drying, a carrier loaded with active substances is obtained. S2: Preparation of core particles: The components of the core fertilizer unit are dry-mixed with the near-infrared photothermal conversion agent, and then the core is formed by extrusion granulation or rolling granulation; S3: Constructing a core-shell structure: The loaded environmentally responsive carrier obtained in S1 is uniformly dispersed in an adhesive solution to form a coating slurry. The core obtained in S2 is coated using a fluidized bed bottom spray coating process to form a porous shell. S4: Low-temperature curing and sieving: The coated granules are dried and cured at a temperature below 50°C, and then sieved to obtain the finished product.

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