A synergistic organic-inorganic compound microbial agent for promoting rice yield increase and a preparation method thereof

Abstract

This invention relates to the field of organic-inorganic composite microbial agent manufacturing technology, and discloses a synergistic organic-inorganic composite microbial agent for promoting rice yield and its preparation method. The method includes: forming a negatively charged active interface by adjusting the pH of an organic carrier; constructing a gradient stable structure using two multivalent metal cations with different coordination abilities; anchoring microorganisms and inorganic nutrients in situ at the interface in the form of ion bridges; and finally solidifying at low temperature. This invention, through the pre-constructed chemical structure during the manufacturing stage, enables each functional component to form an indivisible synergistic unit, thereby avoiding functional dissociation and mismatch of action timing caused by physical erosion in the soil, and establishing an intrinsic response relationship between nutrient supply and microbial demand.

Description

Technical Field

[0001] This invention relates to a synergistic organic-inorganic compound microbial agent for promoting rice yield and its preparation method, belonging to the field of organic-inorganic compound microbial agent manufacturing technology. Background Technology

[0002] In the field of manufacturing organic-inorganic compound microbial agents, combining organic carriers, inorganic nutrients, and beneficial microorganisms into the same particle is a recognized technical strategy to achieve their synergistic effect. To this end, physical methods such as mechanical mixing and spray granulation are commonly used in this field to polymerize the components that have undergone independent pretreatment. The main goal is to obtain granular products with uniform composition and sufficient physical strength to meet the requirements of storage, transportation, and mechanized application.

[0003] However, when these physically manufactured products are applied to the dynamic aquatic environment of paddy fields, the mismatch between the manufacturing method and the application conditions leads to functional deficiencies. The manufacturing method only achieves the physical aggregation of the components in the product form, without establishing a stable functional connection between the components. When the particles come into contact with water, the water-soluble, fast-acting inorganic nutrients will quickly dissolve and migrate with the water flow, spatially separating from the microorganisms still attached to the organic carrier. At the same time, the microorganisms need a certain start-up time to go from dormancy to activity. This time lag causes them to miss the window of opportunity to utilize the fast-acting nutrients, making it difficult to achieve the synergistic goals preset during manufacturing due to the functional dissociation of the components in the application environment.

[0004] To slow nutrient loss, the industry has also adopted coating or enhanced adhesion methods to improve the physical integrity of particles. However, these improvements are still limited to macroscopic physical structure, i.e., slowing down the overall disintegration rate of particles. The core problem that this approach fails to solve is that once components dissolve from particles, they remain independent units in the soil microenvironment, following their inherent physicochemical migration laws. The functional separation between them remains unchanged. Specifically, existing technologies mainly have the following shortcomings: 1. Separation of functional components, i.e., the spatial separation of water-soluble nutrients and microbial carriers under the action of soil water flow, hindering synergistic effects; 2. Mismatch of action sequence, i.e., the rapid loss of readily available nutrients and the slow activation of microorganisms are mismatched in time, reducing the effectiveness of nutrient utilization; 3. Lack of functional connection, i.e., the manufacturing process fails to provide an inherent stable connection for the interaction of each component in the soil microenvironment. Therefore, the technical problem to be solved by this invention is how to provide a manufacturing method that can pre-construct a structurally stable and functionally integrated micro-unit during the fertilizer granule preparation stage, in which inorganic nutrients, microorganisms and organic carriers are inseparable, so that the release of nutrients can be directly linked to the life activities of microorganisms. Summary of the Invention

[0005] This invention provides a synergistic organic-inorganic compound microbial agent for promoting rice yield and its preparation method. Its main purpose is to solve the problem that the components of the compound microbial agent manufactured by physical mixing in the prior art are easily separated in the soil, have a mismatched action sequence, and lack an inherent functional connection.

[0006] To achieve the above objectives, the present invention provides a method for preparing a synergistic organic-inorganic compound microbial agent for promoting rice yield increase, comprising the following steps performed in sequence:

[0007] Step a: The organic carrier containing organic acid functional groups is placed in a weakly alkaline chemical environment with a pH of 7.5 to 8.5 to form a negatively charged active colloidal interface on the surface of the organic carrier.

[0008] Step b: Mix an aqueous suspension containing microorganisms and inorganic nutrients with a solution containing first-type polyvalent metal cations and second-type polyvalent metal cations to obtain a mixture, wherein the second-type polyvalent metal cations have a stronger coordination ability with the organic acid functional groups on the surface of the organic carrier than the first-type polyvalent metal cations.

[0009] Step c: The mixture obtained in step b is applied to the negatively charged active colloidal interface in step a. Through interfacial complexation between the first type of multivalent metal cations and the active colloidal interface, a basic ionic cross-linking network resistant to physical erosion is constructed on the surface of the organic carrier. The second type of multivalent metal cations are used to form coordination locking sites in the basic ionic cross-linking network that specifically respond to chelating agents in plant root exudates. In this way, microorganisms and inorganic nutrients are anchored together on the surface of the organic carrier to form a composite structure.

[0010] Step d: The composite structure is subjected to a temperature below 50°C. Low-temperature drying is used to solidify the composite structure formed by interfacial complexation.

[0011] Preferably, the organic carrier is a mixture of rapeseed oil cake and humic acid; the first type of polyvalent metal cation is calcium ion; and the second type of polyvalent metal cation is zinc ion or manganese ion.

[0012] Preferably, in step a, while placing the organic carrier in a weakly alkaline chemical environment, a chemical reducing agent is also added to pre-convert the quinone functional groups on the surface of the organic carrier into reduced hydroquinone groups, thereby forming an antioxidant microenvironment at the interface.

[0013] Preferably, in step b, the first type of multivalent metal cation and the second type of multivalent metal cation are provided together in the form of a pre-prepared water-soluble heteronuclear metal complex precursor containing the two metal ions.

[0014] Preferably, in step c, the molar amount of the first type of multivalent metal cations Molar amount of organic acid functional groups on the surface of organic carrier The ratio is limited to a subsaturated range, which satisfies: ,in, Represents the total molar amount of type I multivalent metal cations. It represents the total molar amount of organic acid functional groups provided by the organic carrier and participating in the complexation.

[0015] Preferably, the microorganisms in step b include at least one of Bacillus subtilis and Bacillus mucilaginosus; the anchored microorganisms in step c are in a dormant state; the inorganic nutrients in step b include phosphate or sulfate; in step c, the phosphate or sulfate anions in the inorganic nutrients form slightly soluble precipitates with the first type of polyvalent metal cations and the second type of polyvalent metal cations, and are locked in situ in the forming complex structure.

[0016] Preferably, the chemical reducing agent is sodium sulfite or ascorbic acid.

[0017] Preferably, the water-soluble heteronuclear metal complex precursor is a calcium-zinc-citrate complex or a calcium-manganese-citrate complex prepared by reacting a base containing calcium ions with an oxide containing zinc ions or manganese ions with citric acid in an aqueous solution.

[0018] Preferably, in step c, the mixture is sprayed onto the surface of the organic carrier in a dynamically stirred state in the form of atomization; in step d, low-temperature drying continues until the final moisture content of the composite structure is less than 10%.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. By adjusting the pH of an organic carrier containing organic acid functional groups to form a negatively charged active colloidal interface, and then applying a suspension containing microbial inorganic nutrients and polyvalent metal cations onto it, a manufacturing method different from traditional physical mixing is established. In this method, the organic carrier is no longer just an inert filler, but a reactive framework. Its surface activated functional groups, through bridging with polyvalent metal cations, fix the microbial cells and inorganic nutrient anions in situ, forming a composite structure in which the three are tightly bound together by chemical forces with the organic carrier as the framework. This allows each component to form a stable synergistic unit in the manufacturing stage before being applied to the soil, avoiding the problems of spatial separation of functional components and mismatch of action time caused by physical erosion of traditional fertilizers in the soil.

[0021] 2. Based on the formed composite structure, the inorganic nutrients inside do not exist in a simple physical form, but are locked on the colloidal interface where microorganisms reside in the form of slightly soluble precipitates or complexes by polyvalent metal cations. This structure makes the nutrient release rate no longer mainly dependent on its own solubility, but directly related to the life activities of microorganisms. The organic acids produced by microbial metabolism will locally change the pH of the interfacial microenvironment, thereby affecting the balance of ion complexation. This establishes an intrinsic response relationship between nutrient supply and microbial demand, so that nutrients can be released gradually according to the activity level of microorganisms, realizing the synchronization of nutrient supply timing with the needs of crop rhizosphere microorganisms.

[0022] 3. When a chemical reducing agent is added to the organic carrier while pH adjustment is being performed in step a, this method also utilizes the quinone structure of humic acid in the organic carrier during the construction of the composite structure. The introduced reducing agent pre-converts the quinone groups at the carrier interface into reduced hydroquinone groups, which gives the final composite structure its organic framework long-lasting antioxidant capacity. During subsequent storage and transportation, oxygen penetrating the particles will preferentially react with the more reactive hydroquinone groups, thereby providing a continuous and spontaneous biochemical protective microenvironment for the dormant microbial cells fixed on the interface, avoiding the decline in the number of viable bacteria caused by oxidative stress damage.

[0023] 4. When the polyvalent metal cation in step c contains at least two metal cations with significantly different coordination abilities to organic acid functional groups, such as using calcium and zinc ions simultaneously, a gradient-stability locking system is formed inside the composite structure constructed by this method. The calcium ion with weaker coordination ability forms a basic ion cross-linking network that resists physical erosion, while the zinc ion with stronger coordination ability forms a few but stable coordination locking points. This structure exhibits high tolerance to non-specific acidic signals such as hydrogen ions commonly present in the soil environment, avoiding premature particle disintegration. It also exhibits a specific response to multidentate chelating agents such as citric acid, which are unique to plant root exudates. This is because the affinity of these chelating agents for zinc ions is sufficient to destroy the key coordination locking points, thereby triggering the accelerated disintegration of the entire structure. This achieves targeted release of functional components in the rhizosphere microdomain, enabling the product to maintain its on-demand release characteristics even in complex soil environments such as acidic or alkaline conditions. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the preparation and functional release process of the compound microbial agent of the present invention;

[0025] Figure 2 This is a graph showing the experimental data on the impact of the key stoichiometry of the present invention on product performance;

[0026] Figure 3This is a schematic diagram of the four-stage intelligent release mechanism of the compound microbial agent of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] This invention discloses a synergistic organic-inorganic composite microbial agent for promoting rice yield and its preparation method. The purpose is to pre-form a synergistic organic-inorganic composite microbial agent with integrated structure and function in the manufacturing stage through chemical construction. The overall process mainly includes the preparation and application of chemically activated functional component suspension on the surface of organic carrier, interfacial complexation and anchoring based on multivalent metal cations, and final low-temperature curing. By controlling the chemical conditions of each stage, the final granular microbial agent forms an indivisible unit among its internal functional components, thereby avoiding the separation of components due to physical erosion and the mismatch of their action sequence in soil application.

[0029] In one specific embodiment, the initial step of the preparation method, namely step a, involves the pretreatment of the organic carrier serving as the basic framework. To change the situation where the organic carrier merely acts as an inert physical filler, this method places the organic carrier containing organic acid functional groups in a weakly alkaline chemical environment with a pH value of 7.5 to 8.5. The organic carrier is preferably a mixture of rapeseed oil cake and humic acid, wherein rapeseed oil cake provides the basic organic matter, while humic acid is rich in a large number of carboxyl and phenolic hydroxyl functional groups. Under this pH condition, these organic acid functional groups undergo a deprotonation reaction, thereby forming a stable layer at the solid-liquid interface of the organic carrier particles. The negatively charged active colloidal interface transforms the organic carrier from a mere physical filler into a pre-designed reaction framework for subsequent chemical reactions. To improve product shelf-life stability, while adjusting the pH of the organic carrier in step a, a chemical reducing agent can be added to the system. This reducing agent is preferably sodium sulfite or ascorbic acid. Its mechanism lies in the fact that the humic acid component in the organic carrier contains quinone functional groups on its surface. The introduced reducing agent, in a weakly alkaline environment, pre-converts these quinone functional groups into more chemically reactive reduced hydroquinone groups. This process allows the carrier to... The interface has pre-stored reducing capacity, ensuring that during subsequent storage and transportation, oxygen penetrating the particles will preferentially react with hydroquinone groups and be consumed. This provides a continuous antioxidant microenvironment for the dormant microorganisms anchored at this interface, preventing the decline in viable cell count due to oxidative stress. The next step, b, involves the preparation of a functional component suspension. The purpose of this step is to integrate the microorganisms and inorganic nutrients to be anchored into a unified liquid system. In this step, an aqueous suspension containing microorganisms and inorganic nutrients is mixed with a system containing first-type multivalent metal cations and second-type multivalent metal cations. The solutions of cations are mixed to obtain a mixture in which the microorganisms may include at least one of Bacillus subtilis and Bacillus mucilaginosus, which exist in a dormant state. The inorganic nutrients may include phosphates or sulfates commonly used in agricultural production. The coordination ability of the second type of polyvalent metal cations to the organic acid functional groups on the surface of the organic carrier is stronger than that of the first type of polyvalent metal cations. For example, the first type of polyvalent metal cation may be selected as calcium ions, while the second type of polyvalent metal cation may be selected as zinc ions or manganese ions with stronger coordination ability. This gradient selection of different cation coordination abilities is the basis for constructing the subsequent responsive release structure.

[0030] To address the issue of uneven microstructure distribution that may occur during the co-spraying of two independent metal salt solutions in large-scale industrial production due to random competitive reactions, in a preferred embodiment, the first and second type of multivalent metal cations in step b are provided together in the form of a pre-prepared water-soluble heteronuclear metal complex precursor containing both metal ions. For example, a chemically stable calcium-zinc-citrate complex or calcium-manganese-citrate complex can be prepared by reacting a calcium-containing alkali, such as calcium hydroxide, with an oxide containing zinc or manganese ions, such as zinc oxide, in an aqueous solution with citric acid. Using this single precursor solution ensures that the two metal ions are simultaneously transported to the reaction interface in a precise stoichiometric ratio inherent within the molecule, thereby guaranteeing the functional uniformity and reliability of the final product. The subsequent step c is a crucial step in forming the composite structure of this invention. In this step, the mixture obtained in step b is continuously sprayed in atomized form onto the surface of the organic carrier treated in step a, which is under dynamic stirring. The polyvalent metal cations in the mixture undergo interfacial complexation with the negatively charged active colloidal interface on the surface of the organic carrier, thereby anchoring the microbial cells and inorganic nutrients in the suspension to the surface of the organic carrier, forming a composite structure. Specifically, the first type of polyvalent metal cation with relatively weak coordination ability, namely calcium ions, will form ionic cross-links with a large number of organic acid functional groups, constructing a basic ionic cross-linking network on the surface of the organic carrier that resists the physical erosion of conventional soil water flow. The second type of polyvalent metal cation with stronger coordination ability, namely zinc ions or manganese ions, ... Ions, within this basic network, form a few but chemically extremely stable coordination bonds with some organic acid functional groups, constituting coordination locking points that specifically respond to certain chelating agents in plant root exudates. This gradient-stabilized structure allows the microbial agent particles to maintain structural integrity in conventional soil environments. However, when they come into contact with multidentate chelating agents such as citric acid secreted by rice roots, the affinity of these chelating agents for zinc or manganese ions is sufficient to destroy the key coordination locking points, thereby triggering the accelerated disintegration of the entire structure and achieving the targeted release of functional components in the rhizosphere microdomain.

[0031] To achieve the targeted disintegration properties mentioned above, in step c, the stoichiometric ratio of the key components was limited, specifically the molar amount of the first type of multivalent metal cations. Molar amount of organic acid functional groups on the surface of organic carrier The ratio is limited to a subsaturated range, which must satisfy the following: ,in, Represents the total molar amount of type I multivalent metal cations. This represents the total molar amount of organic acid functional groups provided by the organic carrier and participating in the complexation. The basis for setting this range is that if the ratio is below 0.33, the density of the formed ionic cross-linking network is insufficient, the physical stability of the composite structure in the soil water environment decreases, and it is prone to premature disintegration. Conversely, if the ratio is above 0.5, the cross-linking network is too dense and stable, and even when in contact with plant root exudates, which act as strong metal ion chelators, its structural disintegration response becomes sluggish, failing to release nutrients and microorganisms in a timely manner. Therefore, limiting this ratio to a subsaturated range is a necessary engineering means to enable the composite structure to maintain structural stability in a conventional soil water environment and to achieve targeted structural disintegration in the rhizosphere microdomain. Furthermore, during the complexation process in step c, the inorganic nutrients in step b are also fixed in situ through chemical action. Specifically, the inorganic... Phosphate or sulfate anions in nutrients react with type I and type II polyvalent metal cations in the system to form slightly soluble precipitates, such as calcium phosphate or zinc phosphate, which are then locked in situ within the forming complex structure. This structure means that the release rate of inorganic nutrients no longer depends primarily on their own solubility, but is directly related to the stability of the entire complex structure and the life activities of microorganisms. For example, organic acids produced by microbial metabolism can locally alter the pH of the interfacial microenvironment, thereby affecting the balance of ion complexes. Thus, a responsive relationship is established between nutrient supply and microbial demand. The final step, d, involves low-temperature drying of the formed composite structure to ultimately solidify the composite structure formed by the interfacial complexation. To protect the biological activity of the anchored microbial cells, the drying process is carried out at temperatures below 50°C. The process is carried out at a specific temperature and continues until the final water content of the composite structure is less than 10%. This step gently removes water from the system, allowing the composite structure of organic carrier-metal ions-microorganisms-inorganic nutrients, which self-assembles in the liquid phase, to be stably solidified, forming the final granular product. The synergistic organic-inorganic composite microbial agent obtained directly by the above preparation method is a granular composite structure. The composite structure microscopically contains an organic carrier as a core and an interfacial complex layer that completely covers the surface of the organic carrier core. The interfacial complex layer contains microorganisms, inorganic nutrients, first-type polyvalent metal cations, and second-type polyvalent metal cations. The microorganisms and inorganic nutrients are anchored to the surface of the organic carrier core through the first-type and second-type polyvalent metal cations to form a basic ionic cross-linking network and a gradient stable structure with coordination locking points that specifically respond to chelating agents in plant root exudates.

[0032] In one specific embodiment, to obtain a composite microbial agent possessing both structural stability and targeted responsiveness, a preparation scheme comprising the following components and process parameters is provided: an organic carrier core, composed of 500g rapeseed oil cake and 500g humic acid (dry basis), wherein the total molar amount of organic acid functional groups available from 1000g of the organic carrier at pH 8.5 is determined by potentiometric titration. The concentration is 2.0 mol; the functional suspension consists of 1500 mL deionized water, 100 g potassium dihydrogen phosphate (as inorganic nutrient), 50 g dormant Bacillus subtilis powder, and a metal cation precursor solution. The metal cation precursor solution contains 0.4 mol calcium hydroxide. With 0.1 mol zinc oxide The reaction was carried out in a sufficient amount of aqueous citric acid solution to obtain a clear calcium-zinc-citrate complex precursor solution, which provides a first-class multivalent metal cation for the subsequent interfacial complexation step. Its total molar amount It is 0.8 mol; and provides a second type of multivalent metal cation. Its total molar amount is 0.1 mol. Therefore, the ratio of the molar amount of the first type of polyvalent metal cations to the molar amount of the organic acid functional groups on the surface of the organic support is... The value was set to 0.4, falling within the range of 0.33 to 0.5. In this technical solution, the roles and interrelationships of each core component are defined as follows: the organic carrier (a mixture of rapeseed oil cake and humic acid) serves as the reaction framework; its surface carboxyl and phenolic hydroxyl functional groups are deprotonated in an environment of pH 7.5 to 8.5, forming a negatively charged reaction interface, providing anchoring points for subsequent ion complexation; the first type of multivalent metal cation... As a basic structural building agent, it undergoes interfacial complexation with the organic acid functional groups on the surface of the organic carrier, forming a basic ionic cross-linking network covering the entire carrier surface. The main function of this network is to provide the composite structure with macroscopic stability against the physical erosion of soil water flow; second type of multivalent metal cations Its coordination ability with organic acid functional groups is stronger than In the basic ionic cross-linked network, a few chemically stable coordination locking sites are formed. These locking sites are crucial for coordination in conventional soil environments. It is not sensitive, but it has a specific response to multidentate chelating agents (such as citric acid) in plant root exudates.

[0033] Example 1: In a typical southern acidic red soil rice-growing area, during the early tillering stage after rice transplanting, the region experienced continuous and concentrated heavy rainfall. For organic-inorganic compound microbial agents manufactured using conventional physical mixing methods, the readily available nitrogen and potassium nutrients in the granules dissolved rapidly under the washout of rainwater and were lost with the surface runoff. Meanwhile, microorganisms such as Bacillus subtilis attached to the organic carrier, which require a certain activation time from dormancy to activity, had already lost a large amount of readily available nutrients by the time they began to proliferate and exert their effects in the new environment. This resulted in slow growth of rice seedlings and yellowing of leaves. Simultaneously, the lost nutrients... The influx of bacteria into surrounding water bodies caused eutrophication. Under the same soil and climate conditions, the application of the synergistic organic-inorganic composite microbial agent prepared by the method of this invention resulted in a granular composite structure. Due to the interfacial complexation of each functional component, it was anchored to the surface of the organic carrier core, forming a basic ionic cross-linking network constructed by the first type of polyvalent metal cation calcium ions. This network maintained its structural integrity under the physical scouring of heavy rainfall, stably retaining microorganisms and inorganic nutrients such as phosphates that were fixed in situ in the rhizosphere soil of rice, thus avoiding spatial separation of functional components and immediate loss of nutrients.

[0034] As rice roots grow, their root tips secrete organic acids such as citric acid and malic acid. When these root secretions, which act as strong metal ion chelators, come into contact with the surface of the composite structure, they react with a few but stable coordination-locking sites formed by zinc ions, a type II polyvalent metal cation, within the complex structure. Due to the affinity of these chelators for zinc ions, they are sufficient to disrupt the key coordination-locking sites, thereby triggering the accelerated disintegration of the entire gradient-stabilized structure. This process allows the immobilized microorganisms and inorganic nutrients to be released in a concentrated manner at the most active absorption interface of the rice roots, thus synchronizing nutrient supply with crop demand in both time and space. Ultimately, in this application scenario, rice grows vigorously during the tillering stage, with well-developed root systems and dark green leaves. Field soil nutrient monitoring data shows that the effective phosphorus concentration in the rhizosphere region remains at a high level, while the nitrogen and phosphorus contents at the field drainage outlets are significantly lower than those in the control area where conventional fertilizers were applied. The application of the composite structure meets the crop's nutritional needs while reducing the impact of nutrient loss on the surrounding environment.

[0035] Example 2: To verify the effect of the composite structure prepared by the method of the present invention on nutrient retention and plant growth, the following pot simulation experiment was set up. Acidic red soil was used as the cultivation substrate and filled into polyethylene experimental flower pots of uniform size. The test crop was rice. The entire experiment was conducted in a greenhouse to maintain consistent environmental conditions such as temperature, light, and humidity to eliminate interference from non-experimental factors. This experiment set up five treatment groups, namely: the experimental group, which used the synergistic organic-inorganic composite microbial agent prepared by the complete method of the present invention, wherein the molar amount of the first type of polyvalent metal cation was... Molar amount of organic acid functional groups on the surface of organic carrier The ratio was set to 0.4; Control group 1 consisted of the same material components as the experimental group, which were physically and mechanically mixed without pH adjustment and chemical complexation steps; Control group 2 used the preparation method of this invention, but in step b, only the first type of polyvalent metal cation calcium ions were used, without adding the second type of polyvalent metal cation zinc ions; Control group 3 used the complete preparation method of this invention, but... and The ratio was set to 0.2; control group 4 used the complete preparation method of this invention, but with... and The ratio is set to 0.7.

[0036] In each treatment group, fertilizer was evenly applied to the potting substrate according to the equivalent nitrogen application rate. On the 7th day after fertilization, a simulated heavy rainfall leaching test was conducted on all potted plants. That is, an equal amount of deionized water was evenly applied to the surface of each potting substrate, and all leachate was collected. The concentration of phosphorus in the leachate was determined by inductively coupled plasma atomic emission spectrometry. Afterward, the rice was cultivated for 90 days, and the agronomic traits of the plants were recorded regularly. At the end of the experiment, the aboveground parts were harvested, dried, and weighed to obtain biomass data. The leaching test and crop growth data are summarized in Table 1.

[0037] Table 1: Comparison of nutrient leaching and crop growth data in different treatment groups.

[0038]

[0039] Referring to Table 1, the phosphorus concentration data of the leachate show that the phosphorus loss in the experimental group was 1.8 mg / L, while that in control group 1 was 15.6 mg / L, indicating that the physical mixture without chemical complexation cannot effectively retain water-soluble nutrients. The phosphorus loss in control group 2 was 5.3 mg / L, higher than that in the experimental group, showing that the lack of coordination locking sites for the formation of second-type polyvalent metal cations reduces the stability of the overall structure. Control group 3, due to... and The ratio was 0.2, lower than the optimal range, indicating insufficient ionic cross-linking network and a phosphorus loss of 12.8 mg / L. The phosphorus loss in control group 4 was 2.1 mg / L, close to the experimental group, but its crop growth data, especially the number of effective tillers and aboveground dry weight, were lower than the experimental group, indicating excessive phosphorus loss. and While the ratio enhances structural stability, it also reduces the structure's responsiveness to plant root exudates, affecting the timely release of nutrients. Considering growth indicators such as plant height, effective tiller number, and aboveground dry weight, all values ​​in the experimental group were higher than those in all control groups. This result corresponds to the lowest nutrient loss rate and the release characteristics regulated by the gradient-stabilized structure. The experimental data show that the preparation method of this invention, by constructing a specific chemical structure and controlling the stoichiometry of key components within a defined subsaturated range, can maintain nutrient stability while responding to crop rhizosphere signals for release, thereby improving nutrient utilization efficiency and crop biomass.

[0040] To verify the protective effect of adding a chemical reducing agent in step a on the microbial activity of the composite structure, a comparative experiment was set up. Experimental sample group A used the complete preparation method of the experimental group in Example 2, i.e., ascorbic acid was added as a chemical reducing agent in step a. Comparative sample group B used the exact same preparation method as experimental sample group A, but without adding any chemical reducing agent in step a. Both groups of samples were heated at 30°C. Accelerated storage tests were conducted under conditions of 75% relative humidity. After 6 months of storage, the number of viable bacteria in the two groups of samples was determined by plate counting. The results showed that the decay rate of viable bacteria in experimental group A was lower than that in control group B. This data indicates that the antioxidant microenvironment pre-formed on the interface of the organic carrier by adding a chemical reducing agent effectively protects the fixed dormant microorganisms from oxidative stress damage during long-term storage.

[0041] Example 3: This example combines Figures 1 to 3 This paper describes a synergistic organic-inorganic compound microbial agent for promoting rice yield and its preparation method. Figure 1 As shown, the process begins in the raw material supply stage, where organic carriers and chemical reagents are fed into the activated organic carrier unit to form intermediate D1 activated organic carrier. Simultaneously, microorganisms, inorganic nutrients, and polyvalent metal cations are fed into the functional suspension preparation unit to form intermediate D2 functional suspension. Subsequently, intermediates D1 and D2 enter the interfacial complexation stage to generate wet composite structure D3. This wet structure undergoes low-temperature curing and molding treatment to obtain the final product D4 granular bacterial agent. After the final product enters the application environment of rice fields, its internal targeted release functional components are triggered by root exudate chelating agents, thereby releasing nutrients and microorganisms into the application environment.

[0042] like Figure 2 As shown, the horizontal axis of the graph represents the ratio of the molar amount of type I polyvalent metal cations to the molar amount of organic acid functional groups on the surface of the organic support, i.e. / The ratio, with the ordinate representing the phosphorus leaching rate (%), is plotted on two curves. The solid line marked with circles represents the structural stability test results under deionized water leaching conditions, showing that the phosphorus leaching rate increases with... / The ratio increases and then decreases sharply before leveling off, while the dashed line marked with a triangle represents the target responsiveness test results under citric acid leaching conditions, showing that the phosphorus leaching rate is... / The ratio begins to decrease significantly after it exceeds 0.5; both curves together reveal that when... / When the ratio is in the range of 0.33 to 0.5, the composite structure can simultaneously maintain high structural stability in conventional aquatic environments and high targeting responsiveness in chelating agent environments.

[0043] like Figure 3 As shown, the mechanism revolves around a core synergistic unit that cycles through the process. Step 1, interface activation, involves adjusting the pH to create a charged reaction interface on the organic carrier. Subsequently, in step 2, chemical construction, the interface is activated by... and The ion bridges and coordination locking sites formed by the multivalent metal cations represented by the cation anchor the functional components, thus entering step 3 to stabilize and wait, forming a structurally stable particulate product to resist physical erosion. Finally, in step 4, the intelligent release stage, the root system signal triggers the structural disintegration and releases nutrients in a coordinated manner. The released components then affect the pH of the rhizosphere microenvironment, providing feedback to the interface state in step 1, thereby forming a functional closed loop.

[0044] Example 4: This example provides a standardized engineering calibration procedure for determining the preferred subsaturation range of the preparation method of the present invention when applied to a novel organic carrier containing organic acid functional groups. This procedure is used to determine the molar amount of the first type of polyvalent metal cation. Molar amount of organic acid functional groups on the surface of the new organic carrier The proportional relationship between them; first, the new organic carrier is characterized to determine its A certain mass of dried organic carrier sample was taken and suspended in deionized water. The pH value of the solution was monitored using a pH meter with a resolution of 0.01 pH units. Under continuous stirring, the suspension was potentiometrically titrated with a sodium hydroxide standard solution of known concentration. The titration endpoint was set at pH 8.5. Based on the volume and concentration of sodium hydroxide standard solution consumed, the total molar amount of organic acid functional groups that can participate in the reaction under this pH condition per unit mass of organic carrier was calculated. Subsequently, based on the measured... Value, prepare a series of test samples, in which, except and Apart from the systematic change in the ratio, all other components and process parameters remain consistent with the above. The ratio is set as a gradient, starting from 0.1 and increasing in increments of 0.1 to 0.8, thereby obtaining a mixture containing... and Eight groups of composite structure particle samples with ratios of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8, respectively.

[0045] Next, two performance tests were conducted on each of the eight groups of samples. The first test was a structural stability test, in which a fixed mass of sample particles was placed in a chromatography column filled with quartz sand, eluted with deionized water at a constant flow rate, and all eluent was collected within a specified time. The concentration of phosphorus in the eluent, used as a tracer, was then measured. The second test was a target responsiveness test, using the same apparatus and operating procedures, but replacing the eluent with a solution containing a specific concentration of citric acid. The concentration of phosphorus in the eluent was then measured within the same time period. Finally, the data obtained from the two tests were analyzed. and When the ratio is below 0.3, the phosphorus leaching rate in the structural stability test shows a jump; when the ratio is above 0.6, the phosphorus leaching rate in the targeting responsiveness test shows a sharp drop. By using the inflection point of these two test data changes, an optimal subsaturation range that balances structural stability and targeting responsiveness can be determined for this new organic carrier.

[0046] Example 5: To verify the structural stability and response specificity of the composite structure of the present invention in different soil pH environments, the composite structure particles containing calcium and zinc ions prepared by the above method were placed in two buffer solutions simulating soil chemical environments for testing. The first solution had a pH of 4.5 to simulate an acidic soil environment. After immersing the particles in the acidic solution, swelling of the particles was observed, but the core structure remained intact, accompanied by a very low level of phosphorus release. This is because the hydrogen ions in the solution can interact with some of the weaker basic ionic cross-linking network formed by the first type of polyvalent metal cation calcium ions, but not enough to destroy the more chemically stable coordination locking sites formed by the second type of polyvalent metal cation zinc ions and organic acid functional groups. Therefore, the core of the composite structure is preserved, avoiding premature non-targeted release of functional components.

[0047] The second solution has a pH of 8.5 to simulate an alkaline soil environment. The composite structure particles are pre-wetted in the alkaline solution, and then a solution containing citric acid is added to simulate contact with plant roots. After the addition of citric acid, it was observed that the particles changed from a stable state to structural disintegration, accompanied by a large release of phosphorus. This phenomenon occurs because of the targeted disintegration mechanism of the composite structure. Its triggering does not mainly depend on the acidity brought by root exudates, but on the strong coordination abstraction ability of citric acid and other multidentate chelating agents on the second type of polyvalent metal cation zinc ions. This coordination abstraction is still effective in an alkaline environment, thereby destroying the key coordination locking sites and triggering the synergistic disintegration of the structure. Thus, the gradient stabilization structure of this invention enables the composite microbial agent to maintain its structural stability and targeted release function in soils with different chemical conditions.

[0048] Example 6: In the large-scale production of synergistic organic-inorganic composite bacterial agents, to ensure a constant stoichiometric ratio of the gradient stable structure composed of two different polyvalent metal cations on each particle, and to avoid the microscopic distribution inhomogeneity caused by co-spraying with independent ion sources, this example provides a standardized engineering procedure for preparing a water-soluble heteronuclear metal complex precursor. This precursor, in the form of a single component, provides an ion source for subsequent interfacial complexation. The procedure is performed in a stainless steel reactor equipped with a heating mantle and a mechanical stirrer. First, a calculated amount of citric acid hydrate is added to deionized water, and the temperature is raised to 60°C. Stir until completely dissolved to form a clear citric acid solution. Then, while maintaining the solution temperature and continuous stirring, precisely weighed zinc oxide powder and calcium hydroxide powder meeting industrial grade I standards are slowly and synchronously added to the citric acid solution according to a preset calcium-zinc molar ratio. After the addition is complete, the temperature of the reaction system is maintained at 70°C. The reaction was stirred continuously for 2 hours until no visible solid particles remained in the reactor and the system became a homogeneous and clear solution. This was taken as the endpoint of the reaction.

[0049] After the reaction is complete, heating is stopped and the solution is cooled to room temperature. After sampling, the concentrations of calcium and zinc ions in the solution are detected by inductively coupled plasma atomic emission spectrometry to verify the consistency of their molar ratio with the feed ratio, and the final concentration of the precursor solution is calibrated. The calcium-zinc-citrate complex solution prepared by this procedure is stable and can be directly used as a raw material in the spraying process in step c. By using this single-component precursor, the first type of polyvalent metal cations and the second type of polyvalent metal cations are uniformly delivered to the active colloidal interface of the organic carrier at a constant stoichiometric ratio, thereby ensuring the batch-to-batch stability of the final product function.

[0050] To further verify the necessity and non-obviousness of the present invention in achieving synergistic effects of functional components through specific chemical structures, the following comparative examples are provided.

[0051] Comparative Example 1: In this comparative example, an organic carrier (a mixture of 500g rapeseed oil cake and 500g humic acid), inorganic nutrients (100g potassium dihydrogen phosphate), microorganisms (50g dormant Bacillus subtilis powder), and metal salts (equivalent to 0.8mol calcium ions and 0.1mol zinc ions) were used. However, steps a, b, c, and d of this invention were not performed. Instead, the conventional mechanical mixing and physical granulation method mentioned in the background art was used. Specifically, all the above-mentioned dry powdered materials were placed in a V-type mixer for thorough mechanical mixing until the appearance color was uniform. Then, using water as a wetting agent, granules with a particle size comparable to those in the experimental group of Example 2 were prepared by a disc granulator. Finally, the granules were granulated to a particle size of less than 50 μm. The product was dried until the final moisture content was less than 10%. Performance test and results: The granular product obtained in this comparative example was compared with the test group sample in Example 2 under the same potted plant simulation test conditions. The test methods and data recording methods were consistent with those in Example 2. The data obtained are shown in the table below.

[0052] Table 2: Comparison of nutrient leaching and crop growth data between Comparative Example 1 and the experimental group.

[0053]

[0054] Conclusion and analysis: The test results show that the phosphorus concentration of the leachate of Comparative Example 1 is as high as 16.5 mg / L, which is higher than that of the experimental group (1.8 mg / L). This confirms that the water-soluble inorganic nutrients inside the granules prepared by conventional physical mixing will dissolve and be lost in large quantities when they are washed away by water. Correspondingly, after 90 days, the plant height, effective tiller number, and aboveground dry weight of the granules are significantly lower than those of the experimental group, and even slightly lower than those of the control group 1 in Example 2.

[0055] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a synergistic organic-inorganic compound microbial agent for promoting rice yield increase, characterized in that, This includes the steps performed in the following order: Step a: The organic carrier containing organic acid functional groups is placed in a weakly alkaline chemical environment with a pH of 7.5 to 8.5 to form a negatively charged active colloidal interface on the surface of the organic carrier. Step b: Mix an aqueous suspension containing microorganisms and inorganic nutrients with a solution containing first-type polyvalent metal cations and second-type polyvalent metal cations to obtain a mixture, wherein the second-type polyvalent metal cations have a stronger coordination ability with the organic acid functional groups on the surface of the organic carrier than the first-type polyvalent metal cations. Step c: The mixture obtained in step b is applied to the negatively charged active colloidal interface in step a. Through interfacial complexation between the first type of multivalent metal cations and the active colloidal interface, a basic ionic cross-linking network resistant to physical erosion is constructed on the surface of the organic carrier. The second type of multivalent metal cations are used to form coordination locking sites in the basic ionic cross-linking network that specifically respond to chelating agents in plant root exudates. In this way, microorganisms and inorganic nutrients are anchored together on the surface of the organic carrier to form a composite structure. Step d: The composite structure is dried at a low temperature below 50°C to solidify the composite structure formed by interfacial complexation. Furthermore, the organic carrier is a mixture of rapeseed oil cake and humic acid; the first type of polyvalent metal cation is calcium ion; the second type of polyvalent metal cation is zinc ion or manganese ion; In step c, the molar amount of the first type of multivalent metal cations Molar amount of organic acid functional groups on the surface of organic carrier The ratio is limited to a subsaturated range, which satisfies: ,in, Represents the total molar amount of type I multivalent metal cations. It represents the total molar amount of organic acid functional groups provided by the organic carrier and participating in the complexation.

2. The method for preparing a synergistic organic-inorganic compound microbial agent for promoting rice yield increase according to claim 1, characterized in that, In step a, while the organic support is placed in a weakly alkaline chemical environment, a chemical reducing agent is also added to pre-convert the quinone functional groups on the surface of the organic support into reduced hydroquinone groups.

3. The method for preparing a synergistic organic-inorganic compound microbial agent for promoting rice yield increase according to claim 1, characterized in that, In step b, the first type of multivalent metal cation and the second type of multivalent metal cation are provided together in the form of a pre-prepared water-soluble heteronuclear metal complex precursor containing the two metal ions.

4. The method for preparing a synergistic organic-inorganic compound microbial agent for promoting rice yield increase according to claim 1, characterized in that, In step b, the microorganisms include at least one of Bacillus subtilis and Bacillus mucilaginosus; in step c, the anchored microorganisms are in a dormant state; in step b, the inorganic nutrients include phosphate or sulfate; in step c, the phosphate or sulfate anions in the inorganic nutrients form slightly soluble precipitates with the first type of polyvalent metal cations and the second type of polyvalent metal cations, and are locked in situ in the forming complex structure.

5. The method for preparing a synergistic organic-inorganic compound microbial agent for promoting rice yield increase according to claim 2, characterized in that, The chemical reducing agent is sodium sulfite or ascorbic acid.

6. The method for preparing a synergistic organic-inorganic compound microbial agent for promoting rice yield increase according to claim 3, characterized in that, Water-soluble heteronuclear metal complex precursors are calcium-zinc-citrate complexes or calcium-manganese-citrate complexes prepared by reacting a base containing calcium ions with an oxide containing zinc or manganese ions in an aqueous solution of citric acid.

7. The method for preparing a synergistic organic-inorganic compound microbial agent for promoting rice yield increase according to claim 1, characterized in that, In step c, the mixture is sprayed onto the surface of the organic carrier in a dynamically stirred state in the form of atomization; in step d, low-temperature drying continues until the final moisture content of the composite structure is less than 10%.

8. A synergistic organic-inorganic composite microbial agent obtained by the preparation method according to any one of claims 1 to 7, characterized in that, The microbial agent is a granular composite structure, which includes: an organic carrier core; an interfacial complexing layer completely covering the surface of the organic carrier core; the interfacial complexing layer contains microorganisms, inorganic nutrients, first-class polyvalent metal cations, and second-class polyvalent metal cations. The microorganisms and inorganic nutrients are anchored to the surface of the organic carrier core through the first-class and second-class polyvalent metal cations to form a basic ionic cross-linking network and a gradient stable structure with coordination locking points that specifically respond to chelating agents in plant root exudates.

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