Heavy metal and pest dual-effect regulation type organic fertilizer and preparation process thereof

Abstract

The present application relates to the technical field of functional fertilizer, and discloses a heavy metal and pest and disease double-effect regulation type organic fertilizer and a preparation process thereof, the fertilizer is a granule with a core-inner layer coating-outer layer coating three-layer structure; the core is made of a composite passivation functional body, an organic nutrient substrate and a binder; the composite passivation functional body is a flavone modified functionalized biological porous carrier loaded with strontium ion doped nano-hydroxyapatite, used for fixing soil heavy metals and regulating rhizosphere microecology; the inner layer coating is made of wood vinegar, and the outer layer coating is made of chitosan oligosaccharide and sodium alginate; the layered structure realizes time sequence release of immune inducer, and synergistically induces plant resistance. Through specific structure design and component synergy, the present application realizes three effects of heavy metal fixation, rhizosphere microecology regulation and plant pest and disease induced resistance, and the effect is clear.

Description

Technical Field

[0001] This invention relates to the field of functional fertilizer technology, and in particular to organic fertilizers with dual effects in regulating heavy metals and pests and diseases, and their preparation process. Background Technology

[0002] In current agricultural production, soil heavy metal pollution and frequent plant diseases and pests are two major factors restricting crop yield and quality. To address soil heavy metal pollution, existing technologies typically employ passivating agents, such as phosphate materials, lime, or biochar, to reduce the bioavailability of heavy metals through adsorption, precipitation, or complexation. However, these passivating agents are often applied through simple physical mixing with soil or fertilizers, frequently resulting in uneven distribution in the soil, easy loss or premature consumption of active components, leading to low passivation efficiency and insufficient duration of effect.

[0003] To reduce the use of chemical pesticides, utilizing exogenous inducers to stimulate systemic resistance in plants has become an important strategy for pest and disease control. Substances such as chitosan oligosaccharides and wood vinegar have been shown to act as signaling molecules to induce defensive responses in plants. However, these inducers are chemically unstable in the soil environment and are easily degraded. If they are directly mixed with fertilizers, their release process is uncontrollable, typically exhibiting a one-time, explosive release, making it difficult to match with the critical periods in the plant growth cycle where resistance induction is needed. This limits the stability and effectiveness of their application.

[0004] In existing technologies, compound functional fertilizers developed to simultaneously address the above two problems are mostly prepared by simply mechanically blending various functional materials. This preparation method fails to address the potential antagonistic effects between functional components, nor can it achieve the sequential release of different functional components according to their mechanisms of action. For example, passivation requires the components to remain stable in the soil for a long period, while resistance induction may require specific signaling molecules to be preferentially released at specific time points. Therefore, simple blending cannot create synergistic effects, and the effectiveness of each component is limited. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an organic fertilizer that can simultaneously achieve effective fixation of heavy metals in soil and induce resistance regulation of plant diseases and pests, as well as its corresponding preparation process.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0007] In the first aspect, this application provides a dual-effect organic fertilizer that regulates both heavy metals and pests and diseases, employing the following technical solution:

[0008] A dual-effect organic fertilizer for regulating heavy metals and pests, comprising granules with a layered structure, wherein, by weight, the granules contain:

[0009] 100 core samples;

[0010] The inner coating covering 5 to 15 parts of the core; and

[0011] An outer membrane of 2.5 to 5.0 parts covering the inner membrane;

[0012] The core comprises the following components in parts by weight:

[0013] Composite passivation functional body: 5-15 parts;

[0014] Organic nutrient substrate: 73-83 parts;

[0015] Adhesive: 1-5 parts;

[0016] The inner coating is made of wood vinegar;

[0017] The outer coating is made of chitosan oligosaccharide and sodium alginate.

[0018] By adopting the above technical solution, the fertilizer's specific three-layer physical structure and the chemical functions of each layer's components work synergistically. Firstly, the composite passivation functional body within the fertilizer core, containing strontium-doped nano-hydroxyapatite, utilizes multiple pathways such as ion exchange, surface complexation, and co-precipitation to remove heavy metal ions (such as Cd) from the soil. 2+ Firstly, the core, inner membrane, and outer membrane of this fertilizer are fixed in its lattice or surface, reducing its bioavailability. Secondly, the physical structure of this fertilizer, consisting of a core, inner membrane, and outer membrane, enables the sequential release of functional components in the soil moisture environment. After application to the soil, the outermost chitosan oligosaccharide membrane first slowly dissolves and releases, acting as a plant immune signaling molecule recognized by the plant roots, initiating the plant's acquired resistance. Subsequently, the inner wood vinegar membrane is released; its contained organic acids and other substances not only regulate the rhizosphere microenvironment but also act as another type of immune-inducing signaling molecule, synergistically enhancing the effect with the previously released chitosan oligosaccharide. This structure ensures that different functional components act on the target system at the appropriate time and at effective concentrations, avoiding potential interactions or reduced activity that might occur due to direct contact before release.

[0019] Preferably, the composite passivation functional body is a flavonoid-modified bioporous carrier loaded with strontium ion-doped nano-hydroxyapatite.

[0020] By employing the above technical solution, strontium ion-doped nano-hydroxyapatite is in situ loaded onto a flavonoid-modified functionalized bioporous carrier. On the one hand, the large specific surface area and porous structure of the bioporous carrier provide dispersed attachment sites for the nano-hydroxyapatite, increasing its contact area and reactivity with heavy metal ions in the soil. On the other hand, the flavonoids immobilized on the carrier surface, as chemical signaling molecules, can directionally regulate the structure and activity of the rhizosphere microbial community, promote the proliferation of beneficial microorganisms (such as phosphorus-solubilizing and potassium-solubilizing bacteria), and further improve the rhizosphere environment through microbial metabolic activities, thereby indirectly improving the plant's health and nutrient absorption efficiency.

[0021] Preferably, the flavonoid-modified functionalized bioporous carrier is composed of mesoporous biochar and flavonoids immobilized thereon; the flavonoids are quercetin and / or rutin; and / or, the mesoporous biochar is prepared by pyrolysis of rice husks at a temperature of 450–650°C.

[0022] By employing the above technical solution, the mesoporous biochar prepared at a specific pyrolysis temperature possesses a suitable pore size distribution and functional groups, which is beneficial for the stable immobilization of flavonoids and the subsequent loading of nano-hydroxyapatite. Quercetin or rutin was chosen as the modifier because of their definite microbial regulatory functions.

[0023] Secondly, this application provides a preparation process for a dual-effect organic fertilizer that regulates both heavy metals and pests and diseases, employing the following technical solution:

[0024] A preparation process for a dual-effect organic fertilizer for regulating heavy metals and pests as described above includes the following steps:

[0025] (a) Core preparation: The composite passivation functional body, organic nutrient matrix and binder are mixed evenly, then granulated and dried to obtain core particles;

[0026] (b) Inner coating: The core particles obtained in step (a) are placed in a fluidized bed and an inner coating liquid is sprayed to form an inner coating.

[0027] (c) Outer coating: On the basis of particles that have formed an inner coating, an outer coating liquid is sprayed to form an outer coating.

[0028] By employing the above technical solution, this preparation process precisely constructs a functional gradient layered structure for the fertilizer through step-by-step operations. Step (a) prepares a stable core component with heavy metal fixation and rhizosphere regulation functions; steps (b) and (c) utilize fluidized bed coating technology, sequentially spraying different coating solutions to achieve physical isolation and orderly coating of the inner and outer functional layers. This process ensures that the final product possesses the aforementioned time-sequential release characteristics, providing structural assurance for achieving its dual efficacy. The process parameters are controllable, have good repeatability, and are suitable for industrial production.

[0029] Preferably, the composite passivation functional body used in step (a) is prepared by the following steps: dispersing a flavonoid-modified functionalized bioporous carrier in water to form a suspension, then adding calcium salt and strontium salt to the suspension under stirring, and adding phosphate solution dropwise to carry out an in-situ precipitation reaction, and obtaining the reaction product after aging, separation and drying.

[0030] By employing the above-mentioned technical solution and using an in-situ precipitation method, strontium ion-doped nano-hydroxyapatite is directly generated on the surface and within the pores of a flavonoid-modified functionalized bioporous carrier. Compared to simple physical mixing, this preparation method forms a tighter bonding interface, ensuring the structural stability of the composite passivated functional body in the soil environment and preventing the rapid detachment or loss of active components.

[0031] In summary, the present invention has at least one of the following beneficial technical effects:

[0032] 1. The organic fertilizer provided by this invention can effectively fix heavy metals in the soil through a composite passivation functional body in its core. This functional body loads strontium ion-doped nano-hydroxyapatite in situ onto a bioporous carrier, increasing the specific surface area and reaction sites of the active components. Through mechanisms such as ion exchange and surface complexation, it reduces the bioavailability of heavy metals in the soil, thereby reducing the absorption of heavy metals by crops.

[0033] 2. This invention achieves the sequential release of functional components through a precisely constructed three-layer physical structure: core, inner membrane, and outer membrane. The outer chitosan oligosaccharide and the inner wood vinegar, acting as plant immune-inducing signaling molecules, can be released sequentially in a preset order, synergistically acting on the plant roots to initiate and maintain the plant's systemic acquired resistance, thereby achieving the purpose of regulating pests and diseases. Furthermore, it avoids the reduction in activity of the active components due to direct contact during storage and the initial application period.

[0034] 3. This invention achieves targeted regulation of the rhizosphere microecology of plants by modifying flavonoids onto a bioporous carrier in the fertilizer core. Flavonoids, as chemical signals, can regulate the community structure and activity of beneficial rhizosphere microorganisms, promote nutrient transformation and absorption, improve soil health, and fundamentally enhance plant growth potential and tolerance to biotic and abiotic stresses, forming a beneficial synergistic effect with inactivation and resistance-inducing functions. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the scope of protection of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

[0036] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0037] Earthworm castings: Commercially available, organic fertilizer grade, with the following physicochemical indicators: organic matter content 40-45%, total nutrients (calculated as N+P2O5+K2O) ≥5.0%, pH 7.0-7.5.

[0038] Mineral-derived humic acid: Commercially available, in powder form, with the following physicochemical properties: water-soluble humic acid content ≥70%, pH 8.0~9.0.

[0039] Wood vinegar concentrate: commercially available, forestry grade, with the following physicochemical properties: pH 2.5-3.5, total organic acid content (calculated as acetic acid) 3-7% (w / v).

[0040] Sodium alginate: CAS No.: 9005-38-3; commercially available, food grade, its 1% aqueous solution has a viscosity of 200-500 mPa·s at 20℃, and is used as a film-forming agent.

[0041] Chitosan oligosaccharide: The chitosan oligosaccharide used in this invention is a mixture of oligomers prepared by enzymatic hydrolysis or acid hydrolysis of chitosan. Its key performance parameters are: number average molecular weight (Mn) range of 500 to 3000 Da, degree of deacetylation ≥ 90.0%.

[0042] Flavonoid-modified functionalized bioporous carrier: a non-commercially available substance, the specific preparation method of which is detailed in Preparation Example 1.

[0043] Composite passivation functional body: Not a commercially available material; its specific preparation method is detailed in Preparation Example 2.

[0044] Preparation Example 1:

[0045] This preparation example provides a method for preparing flavonoid-modified functionalized bioporous carriers, including the following steps:

[0046] 1) Preparation of mesoporous biochar:

[0047] 1 kg of dry, clean rice husks were placed in a tube furnace and heated to 550 °C at a heating rate of 10 °C / min under nitrogen protection (nitrogen flow rate of 200 mL / min). The mixture was then kept at this temperature for 2 hours for constant-temperature pyrolysis. After naturally cooling to room temperature, the carbonized product was removed, ground using a pulverizer, and passed through a 150-mesh sieve to obtain mesoporous biochar powder.

[0048] 2) Surface finishing:

[0049] Accurately weigh 1.0 g of quercetin and dissolve it in 1 L of anhydrous ethanol to prepare a modification solution with a concentration of 1.0 g / L. Weigh 300 g of the mesoporous biochar powder obtained in step (1) and add it to 9 L of the above modification solution to make the solid-liquid ratio 1:30 (g:mL). Stir the reaction continuously with a magnetic stirrer at 40 °C for 18 hours.

[0050] 3) Product post-processing:

[0051] After the reaction was completed, the solid product was collected by vacuum filtration. The solid product was washed four times with anhydrous ethanol to thoroughly remove unsupported quercetin. The washed solid was dried in a vacuum oven at 70°C for 10 hours to obtain flavonoid-modified functionalized bioporous carrier powder, which was then sealed and stored for later use.

[0052] Preparation Example 2:

[0053] This preparation example provides a method for preparing a composite passivation functional body, including the following steps:

[0054] 1) Carrier dispersion:

[0055] Weigh 100g of the flavonoid-modified functionalized bioporous carrier powder prepared in Preparation Example 1, add it to 1L of deionized water, and sonicate it for 30 minutes at a power of 200W and a frequency of 30kHz to form a uniform suspension.

[0056] 2) In-situ precipitation reaction:

[0057] Weigh 35.4g of calcium nitrate tetrahydrate and 3.5g of strontium nitrate, dissolve them in 500mL of deionized water to prepare a calcium-strontium mixed solution (solution A); separately weigh 13.2g of diammonium hydrogen phosphate, dissolve it in 500mL of deionized water to prepare a phosphorus source solution (solution B). Add solution A to the biochar suspension from step (1) and stir until homogeneous. While stirring continuously, use a peristaltic pump to slowly add solution B dropwise to the mixed suspension at a rate of 5mL / min. During the dropwise addition, use 1.0mol / L sodium hydroxide solution to adjust and maintain the pH of the reaction system at 10.5.

[0058] 3) Aging:

[0059] After the addition is complete, the mixed slurry is stirred and reacted in a 50°C water bath for 24 hours for aging.

[0060] 4) Product post-processing:

[0061] After aging, the slurry was filtered. The filter cake was repeatedly washed with deionized water until the filtrate was neutral, and then washed twice with anhydrous ethanol. The resulting filter cake was vacuum dried at 70°C for 12 hours, and finally ground to obtain composite passivation functional powder, which was then sealed and stored for later use.

[0062] Example 1

[0063] This embodiment provides a method for preparing an organic fertilizer that has both heavy metal passivation and pest and disease control effects, including the following steps:

[0064] 1) Core fabrication:

[0065] Weigh 10 kg of the composite passivated functional powder prepared in Preparation Example 2, 73 kg of earthworm castings, 5 kg of mineral humic acid, and 2 kg of calcium lignosulfonate. Place the above materials in a horizontal mixer and mix for 15 minutes until homogeneous. Feed the mixture into a roller extrusion granulator for granulation, controlling the average particle size to be 3.0 mm. Dry the resulting wet granules in hot air at 60°C to reduce the particle moisture content to 20%.

[0066] 2) Layered coating:

[0067] The 90 kg core particles obtained in step (1) were fed into a fluidized bed coating machine.

[0068] Inner coating: The fluidized bed inlet air temperature was set to 70℃ to stabilize the particle bed temperature at 45℃. The wood vinegar stock solution was diluted 2 times with deionized water to serve as the inner coating solution. It was then sprayed evenly onto the particle surface through an atomizing spray gun at a rate of 15 mL / min / kg, with a total coating solution of 4.5 kg.

[0069] Outer Coating: After the inner coating is completed, switch to the coating solution. Prepare the outer coating solution: Dissolve 3 kg of chitosan oligosaccharide and 1 kg of sodium alginate in water, bringing the volume to 50 L. Set the fluidized bed inlet air temperature to 65℃, stabilize the particle bed temperature at 40℃, and spray the outer coating solution at a rate of 15 mL / min / kg until complete.

[0070] 3) Post-processing:

[0071] The coated fertilizer granules were air-dried at 45℃ until the total moisture content of the finished product was below 10%. The dried granules were then piled at room temperature for 5 days to mature. Finally, the finished product with a particle size in the range of 2.0 to 4.0 mm was collected by sieving through a drum screen, yielding approximately 100 kg of final product.

[0072] Example 2

[0073] This embodiment is basically the same as embodiment 1, except that:

[0074] In the preparation of the composite passivation functional body (Preparation Example 2), the molar ratio of Sr / (Sr+Ca) in the calcium-strontium mixed solution (Solution A) was adjusted to 5%.

[0075] In step 1), the amount of composite passivation functional body used is 5 kg, the amount of earthworm castings used is 78 kg, the amount of mineral humic acid used is 5 kg, and the amount of calcium lignosulfonate used is 2 kg.

[0076] The remaining preparation steps and parameters are the same as in Example 1.

[0077] Example 3

[0078] This embodiment is basically the same as embodiment 1, except that:

[0079] In step 1), the amount of composite passivation functional body used is 15 kg, the amount of earthworm castings used is 68 kg, the amount of mineral humic acid used is 5 kg, and the amount of calcium lignosulfonate used is 2 kg.

[0080] The remaining preparation steps and parameters are the same as in Example 1.

[0081] Example 4

[0082] This embodiment is basically the same as embodiment 1, except that:

[0083] In the preparation of flavonoid-modified functionalized bioporous carriers (Preparation Example 1), 1) the preparation step of mesoporous biochar, the pyrolysis temperature was set to 450℃; (2) the surface modification step, the flavonoid used was rutin.

[0084] The remaining preparation steps and parameters are the same as in Example 1.

[0085] Example 5

[0086] This embodiment is basically the same as embodiment 1, except that:

[0087] In the preparation of flavonoid-modified functionalized bioporous carriers (Preparation Example 1), the pyrolysis temperature of the mesoporous biochar preparation step was set to 650℃.

[0088] The remaining preparation steps and parameters are the same as in Example 1.

[0089] Example 6

[0090] This embodiment is basically the same as embodiment 1, except that:

[0091] In step 2) of layered coating:

[0092] Inner coating: The wood vinegar stock solution was diluted 1:1 with deionized water and used as the inner coating solution. A total of 8 kg of this coating solution was sprayed.

[0093] Outer coating: The outer coating solution is formulated as follows: Dissolve 2 kg of chitosan oligosaccharide and 0.5 kg of sodium alginate in water and bring the volume to 50 L.

[0094] The remaining preparation steps and parameters are the same as in Example 1.

[0095] Comparative Example 1:

[0096] Compared to Example 1, the difference is that no layered coating is performed. All solid components used for core preparation and coating in Example 1 (composite passivation functional body, earthworm castings, mineral humic acid, calcium lignosulfonate, chitosan oligosaccharide, sodium alginate) and wood vinegar stock solution are added to a horizontal mixer for physical dry mixing before granulation, and then directly granulated to the final product.

[0097] Comparative Example 2:

[0098] The difference from Example 1 lies in the use of a different functional passivation material in the core preparation. A physical mixture (10 kg by weight) of ordinary, unmodified mesoporous biochar (prepared as in step 1 of Example 1) and commercially available ordinary nano-hydroxyapatite powder was used instead of the composite passivation functional body in Example 1. All other preparation steps and parameters were the same as in Example 1.

[0099] Comparative Example 3:

[0100] Compared to Example 1, the difference lies in the absence of a functionally graded layered structure, but the coating is retained. The inner coating solution (diluted wood vinegar) and the outer coating solution (chitosan oligosaccharide solution) from Example 1 are pre-mixed evenly, and then used as a single coating solution for a one-time spray coating of the core particles. All other preparation steps and parameters are the same as in Example 1.

[0101] Comparative Example 4:

[0102] The difference from Example 1 is that in Preparation Example 1, surface modification in step 2) was not performed; that is, unmodified mesoporous biochar was used to prepare the composite passivation functional body. All other preparation steps and parameters were the same as in Example 1.

[0103] Comparative Example 5:

[0104] The difference from Example 1 is that in Preparation Example 2, strontium nitrate is not added to solution A in step (2), i.e., a composite passivation functional body without strontium ion doping is prepared. The remaining preparation steps and parameters are the same as in Example 1.

[0105] Comparative Example 6:

[0106] The difference from Example 1 is that a simple physical mixing method using existing technology was employed. 78 kg of commercially available ordinary organic fertilizer (equivalent to the total nutrient substrate of earthworm castings + humic acid in Example 1) was mixed with 10 kg of the composite passivated functional body from Preparation Example 2 and granulated. For field application, 12.5 kg of a commercially available aqueous mixture of chitosan oligosaccharide and wood vinegar (with a solids content equivalent to Example 1) was diluted and applied together with the fertilizer.

[0107] Test Example 1: Evaluation of Heavy Metal Passivation Performance

[0108] The testing steps are as follows:

[0109] 1) Preparation and aging of simulated contaminated soil: Take uncontaminated wet soil (type: sandy loam), air-dry it, and then pass it through a 2mm sieve. Weigh the sieved, air-dried soil and calculate the required Cd based on the soil weight. 2+ The amount of Cd added was uniformly sprayed and mixed in the form of Cd(NO3)2 solution, so that the final exogenous Cd concentration in the soil was 5.0 mg / kg. The soil moisture content was adjusted to 60% of field capacity, and the soil was placed in a 25℃ constant temperature incubator for 30 days in the dark.

[0110] 2) Sample preparation and incubation: The aged contaminated soil was divided into portions, each weighing 1 kg. Fertilizer samples prepared in Examples 1-6 and Comparative Examples 1-6 were weighed and added to each portion of soil at a ratio of 1% of the dry soil weight (i.e., 10 g per portion), and mixed thoroughly. A separate portion of contaminated soil without any added fertilizer was used as a blank control. Each treatment was replicated in triplicate. All soil samples were placed in a 25°C incubator, maintaining a moisture content of 60% of field capacity, and incubated for 60 days.

[0111] 3) Extraction and determination of available heavy metals: After cultivation, soil samples were taken from each treatment, air-dried, and ground through a 100-mesh sieve. 10.0 g of soil sample was accurately weighed and placed in a 50 mL centrifuge tube. 20.0 mL of DTPA extraction solution (0.005 mol / L DTPA + 0.01 mol / L CaCl2 + 0.1 mol / L TEA, pH 7.3) was added. The mixture was horizontally shaken at 180 rpm for 2 hours at 25℃. After shaking, the solution was filtered through rapid filter paper. The concentration of Cd in the filtrate was determined using inductively coupled plasma mass spectrometry (ICP-MS).

[0112] Data calculation: The passivation rate (%) of heavy metals is calculated according to the following formula: Passivation rate = [(effective Cd content in blank control group - effective Cd content in treatment group) / effective Cd content in blank control group] × 100%.

[0113] The test results are shown in Table 1:

[0114] Table 1: Effects of different treatments on the content of DTPA-extractable Cd in soil and passivation rate

[0115] Processing group DTPA-extractable Cd content (mg / kg) passivation rate (%) Blank control 5.23 0 Example 1 0.71 86.4 Example 2 1.14 78.2 Example 3 0.6 88.5 Example 4 0.82 84.3 Example 5 0.75 85.7 Example 6 0.91 82.6 Comparative Example 1 2.38 54.5 Comparative Example 2 3.81 27.2 Comparative Example 3 1.95 62.7 Comparative Example 4 1.33 74.6 Comparative Example 5 1.19 77.2 Comparative Example 6 4.12 21.2

[0116] Table 1 shows that the DTPA-extractable Cd content in the soil of treatment groups 1-6 was lower than that of the blank control group and the comparative treatment groups 1-6, and the highest passivation rate was obtained. This result is related to the specific composition of the composite passivation functional body inside the fertilizer core. In this functional body, strontium ion-doped nano-hydroxyapatite fixes Cd through ion exchange and co-precipitation. 2+ Meanwhile, the mesoporous biochar carrier provides physical adsorption sites. The combination of these mechanisms enables efficient fixation of bioavailable Cd in soil. Data from Examples 2-6 show that effective Cd fixation can be achieved by changing the amount of components or the type of raw materials within the defined parameter range.

[0117] Comparing Example 1 with Comparative Examples 2 and 6, the latter two, which used physical mixtures of common components or field mixing, showed significantly lower passivation rates than Example 1. This indicates that the Cd fixation capacity of the composite structure formed by loading strontium-doped nano-hydroxyapatite onto a modified biochar support via in-situ precipitation is not simply the arithmetic sum of the capacities of each component. Comparing Example 1 with Comparative Examples 1 and 3, Comparative Example 1 used a mixed coating solution for granulation of all components, and Comparative Example 3 showed significantly lower passivation rates than Example 1. This confirms the necessity of a functionally graded layered structure for maintaining the activity of the core passivated functional body, which prevents direct contact between the core functional body and the outer active material.

[0118] Comparing Example 1 with Comparative Examples 4 and 5, the technological contribution of specific components can be confirmed. The passivation rate of Comparative Example 5 (undoped Sr) is lower than that of Example 1, indicating that Sr ion doping alters the crystal structure of hydroxyapatite, increasing its resistance to Cd. 2+ The passivation rate of Comparative Example 4 (without flavonoid modification) was also lower than that of Example 1, indicating that the changes in the surface chemical properties of the biochar carrier by flavonoids have a synergistic effect on the stability of the entire passivation system and the final Cd fixation effect.

[0119] Test Example 2: Evaluation of Plant Immune Induction Activity

[0120] The testing steps are as follows:

[0121] 1) Experimental Preparation and Seedling Raising: Tomato (variety: Zhongza 9) was selected as the indicator plant. Seedling substrate was filled into 10cm × 10cm seedling pots. Three seeds were sown in each pot. When the seedlings reached two leaves and a central bud, thinning was performed, leaving one healthy seedling of uniform growth in each pot. All seedlings were placed in a light incubator with the following conditions: temperature 25℃ / 18℃ (day / night), light 14h / d, and relative humidity 70%.

[0122] 2) Sample treatment: Treatment was carried out when the tomato seedlings reached the four-leaf-one-heart stage. The fertilizer samples prepared in Examples 1-6 and Comparative Examples 1-6 were mixed evenly with the substrate at a ratio of 1:100 (w / w) and applied to the nutrient pots. A separate group without any fertilizer was set up as a blank control. Each treatment was repeated in triplicate.

[0123] 3) Pathogen inoculation: Continue culturing for 7 days after treatment. Prepare a spore suspension of *Botrytis cinerea*, and adjust its concentration to 1 × 10⁻⁶ using a hemocytometer. 6 spores / mL. The spore suspension was evenly sprayed onto the leaves of the tomato plants using a spray method, until the leaf surface was covered with droplets.

[0124] 4) Sample Collection and Enzyme Activity Assay: 48 hours after inoculation, the 3rd to 4th functional leaves from the top of each treatment plant were collected. 0.5 g of fresh leaf was accurately weighed and added to 5 mL of pH 7.8 phosphate buffer, and the mixture was homogenized under ice bath conditions. The homogenate was centrifuged at 4℃ and 12000 r / min for 15 minutes, and the supernatant was used as the crude enzyme solution. The activities of peroxidase (POD) and polyphenol oxidase (PPO) in the supernatant were determined using a spectrophotometer via the guaiacol method and catechol method, respectively.

[0125] The test results are shown in Table 2:

[0126] Table 2. Effects of different treatments on the activity of defensive enzymes in tomato leaves after inoculation:

[0127] Processing group <![CDATA[POD activity (U·g -1 ·min -1 )]]> <![CDATA[PPO activity (U·g -1 ·min -1 )]]> Blank control 51.4 112.7 Example 1 152.8 358.1 Example 2 134.6 321.5 Example 3 161.2 373.4 Example 4 148.5 340.9 Example 5 155 366.2 Example 6 127.9 295.3 Comparative Example 1 73.1 145.8 Comparative Example 2 115.6 253 Comparative Example 3 96.7 218.6 Comparative Example 4 121.3 289.4 Comparative Example 5 131.8 317.7 Comparative Example 6 62.5 128.9

[0128] Table 2 shows that, compared with the blank control group and each comparative group, the activities of peroxidase and polyphenol oxidase in the tomato leaves of the treatment groups in Examples 1–6 were all at higher levels. This result indicates that specific components in the fertilizer sample, after being recognized by the plant, activated the plant's defense response signaling pathways, leading to an increase in the synthesis of defense-related proteins. These active substances originate from the wood vinegar and chitosan oligosaccharides on the outer layer of the fertilizer granules; they act as signaling molecules, directly affecting the plant roots.

[0129] The comparison results between Example 1 and Comparative Examples 1 and 3 confirm the necessity of the functionally graded layered structure. The enzyme activities of the treatment groups in Comparative Example 1 (all components physically dry-mixed) and Comparative Example 3 (coating solution mixed and then sprayed once) were significantly lower than those in Example 1. This indicates that the specific structure formed by the layered coating ensures the preferential release of external active substances (wood vinegar, chitosan oligosaccharides) after fertilizer application, avoiding physicochemical reactions with the core functional units before release, which would lead to reduced activity. This sequential release is a prerequisite for achieving efficient induction of plant defense responses.

[0130] The comparison between Example 1 and Comparative Example 4 confirmed the contribution of specific components to the overall effect. The enzyme activity in the Comparative Example 4 (core biochar without flavonoid modification) treatment group was lower than that in Example 1, indicating that the surface chemistry of the core component also affects the final biological effect. Although wood vinegar and chitosan oligosaccharides are direct signaling molecules, the flavonoid-modified biochar carrier may indirectly affect the plant's absorption efficiency or response intensity to signaling molecules by regulating the rhizosphere environment, thereby creating a synergistic effect among the components and collectively leading to the enzyme activity levels measured in the examples.

[0131] Test Example 3: Evaluation of the time-sequential release characteristics of functional components

[0132] The testing steps are as follows:

[0133] 1) Experimental setup and preparation: The static water immersion method was used. Take several 250mL stoppered conical flasks and add 100mL of deionized water to each flask.

[0134] 2) Sample preparation and soaking: Accurately weigh 10.0 g of each of the fertilizer granules prepared in Example 1, Comparative Example 1, and Comparative Example 3, and add them to conical flasks containing deionized water. Seal immediately and start timing. Place all conical flasks in a constant temperature shaker at 25°C and shake at a low speed of 50 r / min to simulate diffusion in a static water environment.

[0135] 3) Timed sampling: At time points of 0.5h, 2h, 8h, 24h, 72h, and 168h, 5mL of supernatant was taken from each conical flask, filtered through a 0.45μm filter membrane, and stored for analysis. After each sampling, 5mL of deionized water was added to the conical flask to maintain a constant total liquid volume.

[0136] 4) Component determination:

[0137] Total organic acid determination: The total organic acid content in the supernatant was determined by acid-base titration and used as an indicator of wood vinegar release.

[0138] Chitosan oligosaccharide determination: The concentration of chitosan oligosaccharide was determined by ultraviolet spectrophotometry, based on the absorbance value after the reaction of chitosan oligosaccharide with a specific colorimetric reagent.

[0139] 5) Data Calculation: Based on the measured concentration and total liquid volume, calculate the cumulative release rate of the functional components at each time point. Cumulative Release Rate (%) = (Total amount of components released at the current time point / Total content of that component in the fertilizer sample) × 100%.

[0140] The test results are shown in Table 3:

[0141] Table 3. Cumulative release rate (%) of functional components in fertilizers under different treatments:

[0142] Time (h) Example 1 - Total Organic Acids Example 1 - Chitosan Oligosaccharide Comparative Example 1 - Total Organic Acids Comparative Example 1 - Chitosan Oligosaccharide Comparative Example 3 - Total Organic Acids Comparative Example 3-Chitosan Oligosaccharide 0.5 45.3 6.8 21.7 18.5 32.6 30.1 2 78.1 15.2 24.1 22.8 48.9 45.4 8 91.5 28.7 26.3 25 65.7 64.3 24 94.6 53.4 28.9 27.6 82.1 83.5 72 95.8 81.9 30.1 29.5 86.4 87 168 96.2 92.5 31.5 30.8 87.3 88.1

[0143] Table 3 objectively demonstrates the release behavior of functional components in fertilizer granules with different structures in an aquatic environment. For the sample in Example 1, total organic acids (representing the inner coating) were rapidly released in the initial stage (0.5–8 h), with a cumulative release rate exceeding 90% after 8 hours; while the release of chitosan oligosaccharides (representing the outer coating) showed obvious delayed and slow-release characteristics, reaching a release rate of over 50% only after 24 hours. This significant difference in release curves intuitively confirms the existence of a functional gradient stratified structure within the fertilizer granules, enabling the time-sequential release of components.

[0144] Comparing the results of Example 1 and Comparative Example 1, both functional components in Comparative Example 1 (physical dry mixing of all components) exhibited extremely low release rates with no significant difference. This indicates that after physical mixing, most of the active components are encapsulated inside the fertilizer granules and cannot be effectively released. Comparing the results of Example 1 and Comparative Example 3, the release curves of the two components in Comparative Example 3 (one-time spraying after mixing of coating liquid) basically overlapped, both showing rapid release and loss of temporal sequence. This further confirms that only through a specific stepwise coating process can a structure with internal and external functional separation be constructed.

[0145] This physical structure, constructed through a layered coating process, forms the basis for achieving the desired technical effect. This structure ensures that the outer layer (such as chitosan oligosaccharide) forms a physical barrier, allowing the inner layer (such as wood vinegar) to come into contact with the external environment only after its dissolution and release, thus creating a sequential release pattern. This sequential release characteristic directly corresponds to the heavy metal fixation effect and plant defense response induction effect observed in Test Examples 1 and 2, demonstrating the causal relationship between structure and function.

[0146] Test Example 4: Evaluation of the Effect of Rhizosphere Microecological Regulation

[0147] The testing steps are as follows:

[0148] 1) Experimental Preparation and Sample Processing: The experiment adopted the pot method. The fertilizer samples prepared in Examples 1-6 and Comparative Examples 1-6 were mixed evenly with 2 kg of sieved and air-dried moist soil at a ratio of 1:100 (w / w) and placed in plastic flower pots. A separate group without any fertilizer was set up as a blank control. Each treatment was set up in triplicate.

[0149] 2) Planting and Cultivation: Transplant one tomato seedling of uniform growth (four-leaf stage) into each pot. Place all pots in a greenhouse for routine cultivation and management for 30 days.

[0150] 3) Rhizosphere soil sampling: After cultivation, remove the plant intact and gently shake off the loose soil attached to the roots. Use a sterile brush to collect the soil tightly attached to the root surface; this is the rhizosphere soil sample. Mix the three replicate rhizosphere soil samples from the same treatment thoroughly.

[0151] 4) Soil enzyme activity assay:

[0152] Urease activity assay: The sodium phenolate-sodium hypochlorite colorimetric method was used. 5.0 g of fresh rhizosphere soil sample was accurately weighed, and 10% urea solution and pH 6.7 phosphate buffer were added. The sample was incubated at 37℃ for 24 hours. The amount of ammonium nitrogen produced in the culture medium was measured.

[0153] Phosphatase activity assay: The disodium phenyl phosphate colorimetric method was used. 5.0 g of fresh rhizosphere soil sample was accurately weighed, and disodium phenyl phosphate solution and a modified universal buffer solution at pH 6.5 were added. The sample was incubated at 37°C for 2 hours. The phenol content generated in the solution was then determined.

[0154] The test results are shown in Table 4:

[0155] Table 4. Effects of different treatments on enzyme activity in tomato rhizosphere soil:

[0156] Processing group <![CDATA[Urease activity (mg NH4 + -N·g -1 ·24h -1 )]]> <![CDATA[Phosphatase activity (mg C6H5OH·g -1 ·2h -1 )]]> Blank control 0.18 1.27 Example 1 0.62 4.81 Example 2 0.53 3.98 Example 3 0.69 5.23 Example 4 0.58 4.66 Example 5 0.65 4.95 Example 6 0.59 4.47 Comparative Example 1 0.25 1.83 Comparative Example 2 0.31 2.15 Comparative Example 3 0.39 2.88 Comparative Example 4 0.42 3.19 Comparative Example 5 0.59 4.72 Comparative Example 6 0.21 1.54

[0157] Table 4 objectively reflects the effects of different treatments on the activity of rhizosphere soil enzymes. The urease and phosphatase activities in treatment groups 1–6 were significantly higher than those in the blank control group and the comparative groups. Soil enzyme activity is a key indicator for evaluating the overall activity of soil microbiota; the increase in urease and phosphatase activity indicates an acceleration of nitrogen and phosphorus transformation cycles in the soil, respectively. This result demonstrates that the fertilizer provided by this technical solution can effectively regulate the rhizosphere microenvironment and promote the proliferation and metabolic activities of beneficial microorganisms.

[0158] This effect is directly related to the specific design of the fertilizer core components. The functionalized bioporous carrier in the core has its surface modified with flavonoids. Flavonoids act as chemical signaling molecules in the soil environment, influencing the chemotaxis and colonization behavior of specific microorganisms. Simultaneously, the porous structure of the mesoporous biochar itself provides a physical shelter for microorganisms to attach and reproduce, while the organic nutrient matrix within the core (such as earthworm castings) provides a continuous carbon and energy source for the colonized microbial community. The combination of these three elements constitutes the basis for the targeted regulation of beneficial rhizosphere microorganisms.

[0159] Comparing the data from Example 1 and Comparative Example 4 (core biochar without flavonoid modification), the enzyme activity in the Comparative Example 4 treatment group, although increased, was significantly lower than that in Example 1. This directly confirms that flavonoid surface modification plays a decisive role in regulating microbial activity. Comparing Example 1 and Comparative Example 1 (all components physically dry-mixed), the increase in enzyme activity in Comparative Example 1 was very small, indicating that disordered physical mixing cannot form stable micro-regions conducive to microbial growth, and may even inhibit activity due to local chemical imbalance. Therefore, it is precisely the specific combination of flavonoid-modified functionalized carriers and organic nutrient substrates, existing in a stable core structure, that achieves effective and targeted regulation of the rhizosphere microecology.

[0160] In summary, the experimental results of Test Examples 1 to 4 confirm the technical effects that this technical solution can achieve from multiple perspectives.

[0161] Data from Test Example 1 shows that the fertilizer prepared using the method described in the examples exhibits a significantly higher passivation rate for DTPA-extractable Cd in the soil compared to the comparative examples. This effect is directly related to the composite passivation functional body within its core, which consists of a flavonoid-modified bioporous carrier and in-situ generated strontium-doped nano-hydroxyapatite. Compared to samples using ordinary physical mixtures (Comparative Example 2) or lacking specific modification / doping components (Comparative Examples 4 and 5), the passivation performance of the examples demonstrates the necessity of their specific structure.

[0162] Data from Test Example 3 confirms that the functional gradient structure constructed through the layered coating process enables the sequential release of components; that is, components in the inner coating are preferentially and rapidly released, while components in the outer coating exhibit delayed and slow release. This physical release characteristic directly corresponds to the biological results of Test Example 2. In Test Example 2, the plant defense enzyme activity in the treatment group was significantly higher than that in the physical dry mixing (Comparative Example 1) or mixed coating (Comparative Example 3) treatment groups, neither of which achieved sequential release of components. This indicates that a specific layered structure is the structural basis for ensuring that external signaling molecules effectively induce plant defense responses.

[0163] Furthermore, data from Test Example 4 showed a significant increase in rhizosphere soil enzyme activity in the treatment group. The difference in enzyme activity compared to Comparative Example 4, which used an unmodified flavonoid-based biochar core, confirms the direct role of the flavonoid-modified porous biocarrier in regulating rhizosphere microecological activity. The overall results demonstrate that by combining specific core component design with a functionally graded hierarchical structure, the dual technical effects of heavy metal fixation and plant physiological process regulation were ultimately achieved.

[0164] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A dual-effect organic fertilizer for regulating heavy metals and pests and diseases, characterized in that, The particles are stratified particles, and by weight, the particles comprise: 100 core samples; The inner coating covering 5 to 15 parts of the core; and An outer membrane of 2.5 to 5.0 parts covering the inner membrane; The core comprises the following components in parts by weight: Composite passivation functional material: 5-15 parts; Organic nutrient substrate: 73-83 parts; Adhesive: 1-5 parts; The inner coating is made of wood vinegar; The outer coating is made of chitosan oligosaccharide and sodium alginate; The composite passivation functional body is a functionalized bioporous carrier modified with flavonoids from nano-hydroxyapatite loaded with strontium ions. The flavonoid-modified functionalized bioporous carrier consists of mesoporous biochar and flavonoids immobilized thereon.

2. The dual-effect organic fertilizer for regulating heavy metals and pests according to claim 1, characterized in that, The particles comprise, by weight: The core consists of 100 parts, which are composed of 10 parts composite passivation functional body, 78 parts organic nutrient matrix and 2 parts binder; Five inner coating layers; and 4.4 parts of the outer coating.

3. The dual-effect organic fertilizer for regulating heavy metals and pests according to claim 1, characterized in that, The flavonoids are quercetin and / or rutin; and / or, the mesoporous biochar is prepared by pyrolysis of rice husks at a temperature of 450–650°C.

4. A preparation process for a dual-effect regulating organic fertilizer for heavy metals and pests as described in any one of claims 1-3, characterized in that, Includes the following steps: (a) Core preparation: The composite passivation functional body, organic nutrient matrix and binder are mixed evenly, then granulated and dried to obtain core particles; (b) Inner coating: The core particles obtained in step (a) are placed in a fluidized bed and an inner coating liquid is sprayed to form an inner coating. (c) Outer coating: On the basis of particles that have formed an inner coating, an outer coating liquid is sprayed to form an outer coating.

5. The preparation process according to claim 4, characterized in that, The composite passivation functional body used in step (a) is prepared by the following steps: a flavonoid-modified functionalized bioporous carrier is dispersed in water to form a suspension, then calcium salt and strontium salt are added to the suspension under stirring, and phosphate solution is added dropwise to carry out an in-situ precipitation reaction. The reaction product is obtained after aging, separation and drying.

6. The preparation process according to claim 5, characterized in that, The flavonoid-modified functionalized bioporous carrier is prepared by the following steps: mesoporous biochar powder is added to an ethanol solution containing flavonoids, and the mixture is stirred at 30-50°C for 12-24 hours. The reaction product is obtained after separation, washing and drying.

7. The preparation process according to claim 4, characterized in that, In step (b), the temperature of the granular bed of the fluidized bed is controlled at 40-50°C; and / or, in step (c), the temperature of the granular bed of the fluidized bed is controlled at 35-45°C.

8. The preparation process according to claim 4, characterized in that, In step (a), the granulation is carried out using a roller extrusion granulator, and the average particle size is controlled to be 2.0 to 4.0 mm; and / or, after step (c), the preparation process further includes a step of low-temperature air drying and maturation of the coated fertilizer granules.