Microbial fertilizer for preventing soil compaction and method for preparing the same
Through the synergistic effect of microporous mineral framework carriers and functional microbial communities, an anti-compaction aggregate structure is constructed in situ, which solves the long-term and sustainable problems of soil compaction and realizes the stability of soil structure and the long-term function of microorganisms.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NORTHEAST AGRICULTURAL UNIVERSITY
- Filing Date
- 2026-03-03
- Publication Date
- 2026-06-05
Smart Images
Figure CN122145245A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fertilizer technology. More specifically, this invention relates to a microbial fertilizer for preventing soil compaction and a method for preparing the same. Background Technology
[0002] Soil compaction is a common soil degradation problem under the long-term intensive farming conditions of modern agriculture. Its physical nature is manifested in the collapse of soil pores, the destruction of soil aggregate structure, and an abnormal increase in soil compressive strength. This deterioration of physical properties will produce a series of chain reactions, including directly restricting the normal penetration and growth of crop roots (i.e., the so-called "stunted growth"), severely hindering water infiltration and effective exchange of rhizosphere gases, and ultimately leading to a significant decrease in fertilizer utilization and a significant reduction in crop yield.
[0003] Currently, the main technical means to prevent or alleviate soil compaction in agricultural production rely on the addition of exogenous substances, including the large-scale application of traditional organic fertilizers and biochar, or the use of mineral conditioners such as gypsum and no-till conditioners, as well as some conventional microbial agents. Although these technologies can improve soil bulk density or aeration to some extent in the short term, they still have obvious limitations in terms of long-term mechanisms.
[0004] First, existing physical or chemical soil amendments generally suffer from poor structural stability. Most amendments rely primarily on the simple physical filling of soil pores with exogenous organic matter, failing to fundamentally rebuild the soil framework. The resulting loose structure is highly susceptible to disintegration after frequent wet-dry cycles, freeze-thaw cycles, or mechanical compaction in the field. Furthermore, under long-term chemical stress from fertilizer application, the effects of these amendments tend to diminish, leading to recurring soil compaction and a lack of sustainability.
[0005] Secondly, the functional design of existing microbial fertilizers suffers from singularity and randomness. Conventional microbial agents mostly focus on the transformation of soil nutrients (such as phosphorus and potassium solubilization) or the direct secretion of hormones to promote growth, lacking a systematic design targeting the "formation and stabilization process of soil physical structure". Even if some microorganisms can secrete extracellular polymers (EPS) with cementing effects, their cementing process in the soil is often randomly distributed, making it difficult to form a continuous, directional aggregate framework system with high compaction resistance.
[0006] Therefore, existing technologies cannot meet the needs of modern agriculture for deep soil structure restoration. There is an urgent need to develop a new type of fertilizer and its preparation method based on the core mechanism of microbial-induced soil structure construction. This fertilizer can construct a stable and self-healing aggregate structure system in situ in the soil through a specific induction mechanism, thereby fundamentally solving the problem of soil compaction. Summary of the Invention
[0007] The purpose of this invention is to provide a microbial fertilizer for preventing soil compaction and its preparation method. Through the synergistic effect of structure-induced functional bacterial communities, microporous mineral framework carriers and controllable cementation precursor matrices, a granular structure that is resistant to compaction and wet-dry cycle damage is constructed in situ in the soil, thereby inhibiting the occurrence of soil compaction in the long term.
[0008] To achieve these objectives and other advantages according to the present invention, a microbial fertilizer for preventing soil compaction is provided, comprising the following raw materials in parts by weight: 25-40 parts of microporous mineral framework carrier, 8-15 parts of structure-inducing functional microbial community, 20-35 parts of controllable release cementitious precursor matrix, 3-8 parts of aggregate stabilizing regulator and 1-4 parts of trace mineral activating component.
[0009] Preferably, the microporous mineral framework carrier is modified zeolite or calcined diatomaceous earth; The preparation process of modified zeolite includes the following steps: Natural zeolite is crushed and screened to obtain particles with a particle size distribution in the range of 0.1~2.0mm; the screened particles are then subjected to airflow washing to remove the dust attached to the surface and prevent it from clogging the pores; then it is rinsed with deionized water 3~5 times until the washing liquid is clear and free of turbidity, and the water is drained. Prepare a hydrochloric acid solution with a concentration of 0.5~1.0 mol / L as the activation solution. Mix the cleaned zeolite particles with the activation solution at a solid-liquid ratio of 1:2.5 and soak at room temperature for 2~4 hours at a speed of 30~50 rpm. The activation solution was drained, and the zeolite particles were repeatedly rinsed with deionized water. During this process, the pH value of the effluent was monitored in real time until the pH stabilized in the neutral range of 6.5 to 7.5. The moistened zeolite particles were dried at 105℃ to 120℃ to constant weight to obtain a microporous mineral framework carrier. The preparation process of calcined diatomaceous earth includes the following steps: Diatomaceous earth is crushed and screened to obtain particles with a particle size distribution in the range of 0.1~2.0mm; the screened particles are then subjected to airflow washing to remove the dust attached to the surface and prevent it from clogging the pores; then it is rinsed with deionized water 3~5 times until the washing liquid is clear and free of turbidity, and the water is drained. The cleaned diatomaceous earth particles were calcined at 450℃ to constant weight to obtain a microporous mineral framework carrier.
[0010] Preferably, the structure-inducible functional microbial community is composed of Bacillus mucilaginosus and Trichoderma harzianum in a mass ratio of 3:1, or of Bacillus subtilis and Trichoderma koningii in a mass ratio of 2:1.
[0011] Preferably, the controlled-release cementitious precursor matrix is composed of oxidized starch, soy protein isolate powder and sodium humate in a mass ratio of 12:10:3, or is composed of dextrin, corn gluten powder and calcium lignosulfonate in a mass ratio of 3:2:1.
[0012] Preferably, the pellet stabilizer is polyglutamic acid or sodium alginate.
[0013] Preferably, the trace mineral activating component is composed of magnesium sulfate and chelated calcium in a 1:1 mass ratio, or is composed of calcium nitrate, ammonium molybdate, and manganese sulfate in a 1:1:1 mass ratio.
[0014] The present invention also provides a method for preparing the above-mentioned microbial fertilizer for preventing soil compaction, comprising the following steps: S1. Inoculate the structure-inducible functional microbial community onto the surface and internal pores of the microporous mineral framework carrier, adjust the water content, and carry out directional domestication culture under constant temperature and humidity conditions until the formation of the biofilm initiation layer is detected on the surface of the microporous mineral framework carrier, thus obtaining the carrier-microbial system. S2. Under low shear stirring conditions, the controllable release cementing precursor matrix is introduced into the carrier-microorganism system in the form of powder or slurry. The coating layer is formed on the outer layer of the microporous mineral framework carrier by physical adsorption, electrostatic adsorption or bioadhesion, and the coating system is obtained. S3. Add agglomerate stabilizer and trace mineral activator to the coating system, mix evenly, so that each component combines with the coating layer to obtain a mixture. S4. The mixture is subjected to low-temperature granulation or direct low-temperature drying to control the final moisture content of the finished product between 8% and 15%, thus obtaining a microbial fertilizer that prevents soil compaction.
[0015] Preferably, S1 specifically includes the following steps: One to two hours before inoculation, the structure-inducible functional bacterial culture raw materials were mixed according to a set ratio, and then added to sterile physiological saline containing 0.2% sucrose. The mixture was then activated in a shaker at 30°C and 100 rpm for 45 minutes to prepare a culture with a total effective viable count ≥ 5.0 × 10⁻⁶. 9 CFU / mL bacterial suspension; The microporous mineral framework carrier is placed into a temperature-controlled drum mixer, and the drum is started to rotate at a low speed of 10-15 rpm. The bacterial suspension is evenly sprayed onto the surface of the microporous mineral framework carrier using an atomizing nozzle with a particle size of 10-30 μm. The spray volume is controlled so that the final water content of the microporous mineral framework carrier reaches 35%-40%. Seal the mixer door, adjust the internal temperature to 28℃~32℃, and maintain the relative humidity at 85%~90%; incubate statically for 12~24 hours. Sampling is performed at regular intervals, and the samples are observed using scanning electron microscopy or staining microscopy. When a continuous network of sticky substances is observed in the mineral pores and on the surface, and the microorganisms change from a dispersed state to a microcolony aggregated state, the biofilm initiation layer is considered to have been successfully constructed.
[0016] Preferably, S2 specifically includes the following steps: The controlled-release cementitious precursor matrix raw materials are mixed in a set ratio, ultra-finely pulverized, and passed through a 300-mesh sieve to ensure that the powder particle size is <50μm; At a rotation speed of 20-35 rpm, the controlled-release cemented precursor matrix was added to the carrier-microorganism system in multiple portions, with each addition being 20% of the total amount of the controlled-release cemented precursor matrix and the interval between two additions being 5-8 min. When the surface of the particles changes from wet and sticky to slightly dry, and there is no obvious powder falling off when pressed, the coating system is obtained.
[0017] Preferably, S3 specifically includes the following steps: Prepare an aqueous solution of a pellet stabilizer containing trace mineral activating components, and atomize and spray it onto the surface of the particles in the coating system that maintains a rolling state to obtain a mixture. S4 specifically includes the following steps: The mixture is fed into a fluidized bed dryer, the inlet air temperature is set to 35℃~45℃, the air speed is controlled to keep the particles in a slightly boiling state, and the drying is carried out for 30~45 minutes. When the moisture content of the finished product is reduced to 8%~15%, the heating is stopped immediately. Cold air below 20°C is introduced to rapidly cool the particles, inducing microorganisms to enter a deep dormant state; after the finished product is graded by a vibrating screen, it is vacuum or nitrogen-filled sealed packaging within 30 minutes.
[0018] The present invention has at least the following beneficial effects: First, this invention can construct stable, anti-compaction aggregate structures in situ within the soil, fundamentally inhibiting soil compaction. A microporous mineral framework provides a stable physical support structure, while structure-induced functional microbial communities form a biofilm initiation layer in the carrier pores and surface. Under the continuous action of a controllable release cementing precursor matrix, a multi-scale cementing structure is induced, transforming soil particles from a loose state into a aggregate system with a stable spatial structure. This effectively reduces the risk of soil compaction under external compaction and repeated wet-dry cycles.
[0019] Secondly, this invention significantly improves the stability of aggregate structure to wet-dry cycles and mechanical disturbances, extending the duration of its anti-soil compaction effect. Through the rigid support of the mineral framework, the flexible connection of the microbial cementing network, and the synergistic effect of aggregate stabilizing agents, the formed aggregate structure is less prone to short-term disintegration under alternating wet-dry conditions and tillage disturbances. This overcomes the problems of short-lived improvement effects and rapid decay with environmental changes in existing technologies, achieving structural stability over a longer period.
[0020] Third, this invention improves the colonization efficiency and survival stability of functional microorganisms in soil, ensuring the continuous performance of their structure-inducing effect. The microporous mineral framework carrier provides a closed and stable microenvironment for the functional microbial community. The construction of the biofilm initiation layer enhances the adhesion of microorganisms to the carrier and soil particles, effectively reducing the impact of environmental stress on microbial activity and preventing rapid inactivation or loss of functional microorganisms after application, thereby ensuring their long-term performance of structure-inducing and cementing effects in the soil.
[0021] Fourth, the preparation process of this invention is mild and the components have strong synergistic effects, making it promising for industrial application. The preparation process of the microbial fertilizer adopts low-temperature acclimatization, low-shear coating, and low-temperature drying processes, avoiding the damage to microbial activity and material structure caused by high temperature or strong chemical treatment. The process is controllable and has good repeatability, making it suitable for large-scale production and practical agricultural applications, achieving a stable anti-caking effect without significantly increasing production costs.
[0022] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description
[0023] Figure 1 This is a flowchart of the preparation process of the present invention; Figure 2 This is a scanning electron microscope image of the biofilm initiation layer in Example 1 of the present invention; Figure 3 This is a growth rate diagram of the functional bacterial community in Example 1 of the present invention; Figure 4 This is a graph showing the EPS growth rate in Embodiment 1 of the present invention; Figure 5 This is a graph showing the growth rate of the functional bacterial community in Example 2 of the present invention; Figure 6 This is a graph showing the EPS growth rate in Embodiment 2 of the present invention; Figure 7 These are scanning electron microscope images of soil pores after field application in Example 1, Comparative Example 1, and the control group of the present invention. Detailed Implementation
[0024] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.
[0025] It should be noted that, unless otherwise specified, the experimental methods described in the following implementation plan are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified.
[0026] <Example 1> 1. Product formula (by weight parts): Structure-inducible functional microbial community: 10 parts (Bacillus mucilaginosus powder: Trichoderma harzianum powder = 3:1); Microporous mineral framework carrier: 30 parts (modified zeolite with a particle size of 0.5~1.0 mm); Controlled-release cementitious precursor matrix: 25 parts (12 parts oxidized starch + 10 parts soy protein isolate + 3 parts sodium humate). Aggregate stabilizer: 5 parts (polyglutamic acid); Trace mineral activating component: 2 parts (magnesium sulfate: chelated calcium = 1:1); Additives: Bentonite (appropriate amount, used to adjust granulation viscosity).
[0027] 2. Preparation process steps, such as Figure 1 As shown, it includes: S1. Preparation of microporous mineral framework carriers: Physical sorting and purification: Natural zeolite ore is selected and pulverized by an air jet mill. Particles with a diameter strictly distributed within the range of 0.5~1.0mm are then screened through a vibrating screen. The screened particles are then subjected to air jet washing to remove surface dust (<0.05mm) to prevent clogging of the pores. The particles are then rinsed three times with deionized water until the washing liquid is clear and free of turbidity, and then drained. Acid etching and pore enlargement: Prepare a 0.5 mol / L hydrochloric acid solution as the activation solution. Add the cleaned zeolite particles and the activation solution to an enamel-lined reactor at a solid-liquid ratio of 1:2.5. Turn on the anchor stirrer (40 rpm) and treat at 25°C for 3 hours. This process utilizes the acid solution to dissolve carbonate impurities in the zeolite pores and etch the pore walls, increasing the specific surface area of the carrier by approximately 25% and exposing more silanol active sites, providing "anchor points" for microbial attachment. Neutralization and thermal activation: Drain the acid solution and rinse the zeolite particles repeatedly with running water until the pH of the washing solution stabilizes at 6.8-7.2. Spread the moistened zeolite particles evenly in a stainless steel tray and place it in a tunnel oven to dry at 115℃ for 120 minutes (at which point the weight is constant and the moisture content is <1%). This step not only removes physically adsorbed water but also completely sterilizes the carrier, creating a sterile "core framework" for subsequent inoculation.
[0028] S2. Targeted loading and biofilm domestication of structure-induced functional microbial communities: Bacterial resuscitation: Weigh out Bacillus mucilaginosus powder and Trichoderma harzianum powder, mix them, and add them to sterile physiological saline containing 0.2% sucrose. Activate the mixture in a shaker at 30℃ and 100 rpm for 45 min to prepare a solution with a concentration of approximately 5.0 × 10⁻⁶. 9 High-concentration bacterial suspension at CFU / mL; Deep colonization inoculation: The microporous mineral framework carrier prepared in S1 is placed into a temperature-controlled drum mixer, and the drum is started to rotate at a low speed of 12 rpm. The bacterial suspension is evenly sprayed onto the carrier surface using a pressure atomizing nozzle (pressure 0.3 MPa, atomized particle size 10-30 μm), controlling the spray volume to ensure the final moisture content of the carrier reaches 38%. Tiny droplets carrying microorganisms are drawn into the deep mesopores of the carrier by capillary force, achieving "deep colonization." Solid-phase microecological acclimatization: After inoculation, the mixing chamber door is closed, the temperature inside the chamber is adjusted to 30°C, and the relative humidity is maintained at 85%; static culture is carried out for 18 hours; during this period, microorganisms begin to germinate and secrete initial extracellular polysaccharides (EPS) using the microenvironment within the pores of the carrier. EPS acts as a biological glue to firmly adhere the bacterial cells to the carrier wall. Determination of the biofilm initiation layer: Samples were taken every 2 hours and observed using a scanning electron microscope (SEM) (e.g., ...). Figure 2 (As shown in the figure) When a continuous network of sticky substances is observed in the pores and on the surface of the mineral, and the microorganisms change from a dispersed state to a micro-colony aggregated state, it is determined that the "biofilm initiation layer" has been constructed. At this time, the resistance of the microbial community is significantly enhanced, and it is ready to enter the matrix coating stage.
[0029] S3. In-situ low-shear coating of controlled-release cementitious precursor matrix: Matrix micronization: Oxidized starch, soy protein isolate and sodium humate are mixed and pulverized through an air jet mill and passed through a 300-mesh sieve to ensure that the powder particle size is <50μm, so as to ensure the uniformity and density of the coating. Establishment of a low-shear fluidization field: The carrier loaded with bacteria is put into a drum mixer (a disc granulator can also be used), and the rotation speed is strictly controlled at 25 rpm to establish a "low-shear rolling flow field". This rotation speed can ensure that the material is fully tumbled and control the frictional shear force between particles below the threshold of biofilm damage, thus protecting the fragile biofilm structure formed in the S2 stage. Layered powder coating: Utilizing the bioadhesiveness (wetting biofilm) on the surface of the carrier in the S2 stage, the precursor matrix micro powder is added in small amounts multiple times; each addition is 20% of the total amount, with an 8-minute interval between two adjacent additions, so that the powder is adsorbed, wetted and compacted by the moisture and EPS on the surface of the carrier during rolling. Coating layer structure quality control: As the matrix layers wrap around the carrier particles, the particle size gradually increases, forming a ternary concentric structure of "mineral core - biofilm layer - nutrient matrix shell"; when the particle surface changes from wet and sticky to slightly dry, and there is no obvious powdering phenomenon when pressed, it indicates that the precursor matrix has been tightly bound to the outer layer of the carrier through physical adsorption and biological adhesion.
[0030] In the later stages of the S3 coating process, an appropriate amount of bentonite can be added according to the viscosity of the material to adjust the adhesion of the system and improve the granulation properties in the subsequent granulation or drying process.
[0031] S4. Functional component blending and surface strengthening: Crosslinking agent atomization: Polyglutamic acid (γ-PGA) was dissolved in deionized water to prepare a γ-PGA strengthening solution with a mass-volume fraction of 8% (w / v). Magnesium sulfate and chelated calcium were then added and stirred thoroughly until completely dissolved to obtain the functional strengthening solution. The strengthening solution was uniformly sprayed onto the surface of the coated particles obtained in stage S3 using pressure atomization. The atomization pressure was controlled at approximately 0.3 MPa, allowing the strengthening solution to cover the outer layer of the particles in the form of microdroplets. γ-PGA molecules formed a continuous polymer network structure on the particle surface, and in the Mg... 2+ With Ca 2+ Under the induction of [a specific substance], an ionic cross-linking reaction occurs, constructing a flexible and stable surface reinforcement layer. This surface reinforcement layer improves the overall resistance to wet-dry cycles and mechanical stability of the particles without damaging the internal "mineral core-biofilm layer-nutrient matrix shell" structure. At the same time, after being applied to the soil, it can gradually swell and release γ-PGA and mineral ions, further promoting the formation and stability of soil aggregate structure.
[0032] In-situ surface crosslinking: While keeping the drum rotating, the prepared strengthening liquid is atomized and sprayed onto the surface of the coated particles. Ca in the solution... 2+ It undergoes an in-situ cross-linking reaction with PGA and proteins on the particle surface, rapidly forming a flexible, semi-permeable mesh gel membrane, which improves particle strength. This mesh membrane not only seals off internal nutrients to prevent loss, but also endows the finished particles with "breathing ability" in the soil's wet-dry cycle (i.e., absorbing water and expanding without disintegrating, and losing water and shrinking without breaking), significantly improving the compaction resistance of the aggregate structure.
[0033] S5. Low-temperature drying and finished product packaging: Low-temperature fluidized bed drying: The wet granules treated with S4 are fed into a fluidized bed dryer, with the inlet air temperature set at 40℃ and the air velocity controlled to keep the granules in a slightly boiling state; drying for 45 minutes to harden the outermost cross-linked film, while reducing the moisture content of the finished product to 12%. Cooling and packaging: Cool the particles rapidly by introducing cold air below 20°C for 15 minutes to help microorganisms survive; after the finished product is graded by a 1.5mm mesh screen, it is vacuum sealed within 30 minutes.
[0034] <Example 2> 1. Product formula (by weight parts): Structure-inducible functional microbial community: 12 samples (Bacillus subtilis: Trichoderma koningii = 2:1); Microporous mineral framework carrier: 35 parts (calcined diatomaceous earth with a particle size of 0.2~0.8 mm); Controlled-release cementitious precursor matrix: 30 parts (15 parts dextrin + 10 parts corn gluten powder + 5 parts calcium lignosulfonate). Aggregate stabilizer: 6 parts (sodium alginate); Trace mineral activating components: 3 parts (calcium nitrate: ammonium molybdate: manganese sulfate = 1:1:1).
[0035] 2. Preparation process steps: S1. Preparation of microporous mineral framework carriers: Diatomaceous earth is crushed and screened to obtain particles with a particle size distribution in the range of 0.1~2.0mm; the screened particles are then subjected to airflow washing to remove dust adhering to the surface and prevent micro powder from clogging the pores; subsequently, it is rinsed 4 times with deionized water until the washing liquid is clear and free of turbidity, and the water is drained. The cleaned diatomaceous earth particles were calcined at 450℃ to constant weight to obtain higher porosity and rigidity, thus producing a microporous mineral framework carrier.
[0036] S2. Targeted loading and biofilm domestication of structure-induced functional microbial communities: The method is basically the same as in Example 1, except that the structure-inducing functional flora is replaced with Bacillus subtilis and Trichoderma koningii. During solid-phase microecological acclimatization, the incubation temperature in the chamber is lowered to 28°C and the static incubation time is extended to 24 hours to adapt to the growth characteristics of Trichoderma koningii and ensure that the mycelium fully extends in the pores.
[0037] S3. In-situ low-shear coating of controlled-release cementitious precursor matrix: It is basically the same as in Example 1, except that the raw materials of the precursor matrix are replaced with dextrin, corn gluten powder and calcium lignin sulfonate.
[0038] S4. Functional component blending and surface strengthening: It is basically the same as in Example 1, except that the agglomerate stabilizer is replaced with sodium alginate and the trace mineral activating components are replaced with calcium nitrate, ammonium molybdate and manganese sulfate.
[0039] S5. Low-temperature drying and finished product packaging: The process is basically the same as in Example 1, except that the temperature is kept below 38°C during the drying process to prevent heat damage to the Trichoderma kangaroo mycelium.
[0040] <Comparative Example> Comparative Example 1 (Common Microbial Agent): An equal amount of structure-inducible functional microbial community (same as in Example 1) was directly loaded onto talc powder (without microporous structure) (loading method is the same as in Example 1), without adding cementing precursor matrix and agglomeration stabilizer.
[0041] Comparative Example 2 (Carrier-free organic fertilizer): Controlled-release cementitious precursor matrix and functional microbial community (both the same as in Example 1) were mixed and fed into a disc granulator, and the rotation speed was controlled at 25 rpm for direct granulation, without microporous mineral skeleton carrier.
[0042] Comparative Example 3 (Aseptic Physical Modification): Contains only microporous mineral framework carrier, precursor matrix and trace mineral activating components, sterilized at high temperature, free of active microorganisms, mixed and fed into a disc granulator, with the rotation speed controlled at 25 rpm for direct granulation.
[0043] <Microbial Growth-ESP Secretion Test> Method for determining the growth rate of functional microbial communities: Structure-inducible functional microbial communities were inoculated into liquid culture medium with a controlled-release cementitious precursor matrix as the main carbon source and cultured at 30±1 ℃ with shaking at 150 r·min⁻¹. Samples were taken at 0, 6, 12, 18, and 24 h, serially diluted, and spread onto selective culture media. After colony formation, colony-forming units (CFUs) were counted. A linear regression was performed with culture time as the x-axis and ln(CFUs) as the y-axis. The slope of the regression was the specific growth rate of the functional microbial community, used to characterize its growth capacity.
[0044] Method for determining EPS growth rate: During the cultivation of functional bacteria, samples were taken at different time points. The culture medium was centrifuged at 8000 r·min⁻¹ for 10 min to remove bacteria and collect the supernatant. Three volumes of anhydrous ethanol were added to the supernatant, and the mixture was allowed to stand at 4 ℃ for 12 h to precipitate extracellular polymers (EPS). The precipitate was collected by centrifugation and redissolved in deionized water. The total polysaccharide content was determined using the phenol-sulfuric acid method. With the cultivation time as the independent variable and the EPS mass concentration as the dependent variable, the change in EPS content at adjacent time points was calculated and divided by the time interval to obtain the EPS growth rate, which serves as an indicator for evaluating the extracellular polymer production capacity of functional bacteria.
[0045] The growth rate of the functional microbial community in Example 1 is as follows: Figure 3 As shown, the EPS growth rate is as follows Figure 4 As shown; the growth rate of the functional bacterial community in Example 2 is as follows. Figure 5 As shown, the EPS growth rate is as follows Figure 6 As shown.
[0046] from Figures 3-6 It is easy to see that the logarithmic growth phase of the functional microbial community and the peak period of EPS secretion are basically synchronized (spatial-temporal matching). During the colonization process, the microorganisms gradually degrade the precursor substrate and transform it in situ into a highly viscous bio-cement, avoiding the problems of excessively rapid decomposition leading to excessively strong cementation in the early stage and insufficient cementation in the later stage, or excessively slow decomposition leading to failure of early structure construction, as seen in traditional organic fertilizers. This achieves a deep coupling between plant nutrition and soil improvement functions.
[0047] <Field Application Effect Testing and Evaluation> 1. Overview of the test site: The experimental site was located in a high-yield experimental field in Dezhou City, Shandong Province, where maize had been continuously cropped for a long period. The soil type was alluvial soil with a heavy clay texture. Years of rotary tillage had resulted in a shallow topsoil layer (12-15 cm), a thick plow pan, severe soil compaction, and a bulk density as high as 1.45 g / cm³. 3 .
[0048] 2. Experimental Design: Apartment size: 30m² 2 The randomized block arrangement is repeated 3 times.
[0049] Application method: Apply fertilizer before corn sowing, combined with rotary tillage. The fertilizer application rate in the example and comparative examples is 80 kg / mu. The CK (control) area is treated with only an equal amount of chemical fertilizer.
[0050] Test period: one crop growing season (approximately 110 days).
[0051] 3. Test Results: After harvest, soil samples were taken from the 0-20cm topsoil layer for testing. The results are shown in the table below: The soil samples were observed using SEM electron microscopy. The SEM scanning parameters were as follows: Magnification: Approximately 8000× (for observing the surface and pore structure of soil aggregates); Accelerating voltage: 5 kV; Sample preparation: The soil is first dried, crushed, and then metal-sprayed (such as with gold or platinum) before scanning; Working distance: 8~15 mm; Example 1, Scanning electron micrographs of soil pores after field application in Comparative Example 1 and blank control are shown below. Figure 7 As shown.
[0052] Based on the data in the table above and Figure 7 It is not difficult to see from the display: 1. Improved Bulk Density and Porosity: The bulk density of the soil treated in Examples 1 and 2 was significantly reduced (approximately 16% lower than the control), and the porosity exceeded 50%. Comparing the results of Comparative Example 2 (without a carrier) (bulk density 1.35), it can be seen that the soil, lacking microporous mineral framework support and only having cementing material, was still easily re-compacted under irrigation and mechanical operations. This demonstrates the importance of the "mineral framework support" in this invention.
[0053] 2. Aggregate stability: The water-stable aggregate content of Example 1 was as high as 56.8%, which was significantly better than the 32.5% of Comparative Example 1 (common bacterial agent). This indicates that if microorganisms are applied alone, without specific precursor nutrient substrates (cementing raw materials) and carrier protection, it is difficult for microorganisms to form a large amount of continuous biocement in situ.
[0054] 3. Synergy between biological and physical processes: Although Comparative Example 3 (sterile) added minerals and organic matter, it lacked the active weaving and cementing transformation effects of microorganisms, resulting in limited improvement. This confirms that the "structure-induced functional microbial community" in this invention is the core driving force for aggregate formation, while the mineral carrier and matrix are the material basis for its function.
[0055] 4. Increased yield: Due to the fundamental improvement in soil physical structure, the root penetration resistance is greatly reduced (more than 40% less compaction than CK). The corn yield in Example 1 increased by 20.7% compared to CK and by 12.9% compared to ordinary inoculants.
[0056] In summary, this invention achieves the organic coupling of microorganisms, mineral carriers, and cementing matrix through a unique preparation process, which has significant and irreplaceable technical advantages in preventing soil compaction.
[0057] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.
Claims
1. A microbial fertilizer for preventing soil compaction, characterized in that, The raw materials include the following parts by weight: 25-40 parts of microporous mineral framework carrier, 8-15 parts of structure-inducing functional microbial community, 20-35 parts of controllable release cementing precursor matrix, 3-8 parts of aggregate stabilizing regulator and 1-4 parts of trace mineral activating component.
2. The microbial fertilizer as described in claim 1, characterized in that, The microporous mineral framework carrier is modified zeolite or calcined diatomite. The preparation process of modified zeolite includes the following steps: Natural zeolite is crushed and screened to obtain particles with a particle size distribution in the range of 0.1~2.0mm; the screened particles are then subjected to airflow washing to remove the dust attached to the surface and prevent it from clogging the pores; then it is rinsed with deionized water 3~5 times until the washing liquid is clear and free of turbidity, and the water is drained. Prepare a hydrochloric acid solution with a concentration of 0.5~1.0 mol / L as the activation solution. Mix the cleaned zeolite particles with the activation solution at a solid-liquid ratio of 1:2.5 and soak at room temperature for 2~4 hours at a speed of 30~50 rpm. The activation solution was drained, and the zeolite particles were repeatedly rinsed with deionized water. During this process, the pH value of the effluent was monitored in real time until the pH stabilized in the neutral range of 6.5 to 7.
5. The moistened zeolite particles were dried at 105℃ to 120℃ to constant weight to obtain a microporous mineral framework carrier. The preparation process of calcined diatomaceous earth includes the following steps: Diatomaceous earth is crushed and screened to obtain particles with a particle size distribution in the range of 0.1~2.0mm; the screened particles are then subjected to airflow washing to remove the dust attached to the surface and prevent it from clogging the pores; then it is rinsed with deionized water 3~5 times until the washing liquid is clear and free of turbidity, and the water is drained. The cleaned diatomaceous earth particles were calcined at 450℃ to constant weight to obtain a microporous mineral framework carrier.
3. The microbial fertilizer as described in claim 2, characterized in that, The structure-induced functional microbial community is composed of Bacillus mucilaginosus and Trichoderma harzianum in a mass ratio of 3:1, or Bacillus subtilis and Trichoderma koningii in a mass ratio of 2:
1.
4. The microbial fertilizer as described in claim 2, characterized in that, The controlled-release cementitious precursor matrix is composed of oxidized starch, soy protein isolate powder and sodium humate in a mass ratio of 12:10:3, or dextrin, corn gluten powder and calcium lignosulfonate in a mass ratio of 3:2:
1.
5. The microbial fertilizer as described in claim 2, characterized in that, The aggregate stabilizer is polyglutamic acid or sodium alginate.
6. The microbial fertilizer as described in claim 2, characterized in that, The trace mineral activating component is composed of magnesium sulfate and chelated calcium in a 1:1 mass ratio, or of calcium nitrate, ammonium molybdate, and manganese sulfate in a 1:1:1 mass ratio.
7. The method for preparing microbial fertilizer for preventing soil compaction as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Inoculate the structure-inducible functional microbial community onto the surface and internal pores of the microporous mineral framework carrier, adjust the water content, and carry out directional domestication culture under constant temperature and humidity conditions until the formation of the biofilm initiation layer is detected on the surface of the microporous mineral framework carrier, thus obtaining the carrier-microbial system. S2. Under low shear stirring conditions, the controllable release cementing precursor matrix is introduced into the carrier-microorganism system in the form of powder or slurry. The coating layer is formed on the outer layer of the microporous mineral framework carrier by physical adsorption, electrostatic adsorption or bioadhesion, and the coating system is obtained. S3. Add agglomerate stabilizer and trace mineral activator to the coating system, mix evenly, so that each component combines with the coating layer to obtain a mixture. S4. The mixture is subjected to low-temperature granulation or direct low-temperature drying to control the final moisture content of the finished product between 8% and 15%, thus obtaining a microbial fertilizer that prevents soil compaction.
8. The preparation method according to claim 7, characterized in that, S1 specifically includes the following steps: One to two hours before inoculation, the structure-inducible functional bacterial culture raw materials were mixed according to a set ratio, and then added to sterile physiological saline containing 0.2% sucrose. The mixture was then activated in a shaker at 30°C and 100 rpm for 45 minutes to prepare a culture with a total effective viable count ≥ 5.0 × 10⁻⁶. 9 CFU / mL bacterial suspension; The microporous mineral framework carrier is placed into a temperature-controlled drum mixer, and the drum is started to rotate at a low speed of 10-15 rpm. The bacterial suspension is evenly sprayed onto the surface of the microporous mineral framework carrier using an atomizing nozzle with a particle size of 10-30 μm. The spray volume is controlled so that the final water content of the microporous mineral framework carrier reaches 35%-40%. Seal the mixer door, adjust the internal temperature to 28℃~32℃, and maintain the relative humidity at 85%~90%; incubate statically for 12~24 hours. Sampling is performed at regular intervals, and the samples are observed using scanning electron microscopy or staining microscopy. When a continuous network of sticky substances is observed in the mineral pores and on the surface, and the microorganisms change from a dispersed state to a microcolony aggregated state, the biofilm initiation layer is considered to have been successfully constructed.
9. The preparation method according to claim 7, characterized in that, S2 specifically includes the following steps: The controlled-release cementitious precursor matrix raw materials are mixed in a set ratio, ultra-finely pulverized, and passed through a 300-mesh sieve to ensure that the powder particle size is <50μm; At a rotation speed of 20-35 rpm, the controlled-release cemented precursor matrix was added to the carrier-microorganism system in multiple portions, with each addition being 20% of the total amount of the controlled-release cemented precursor matrix and the interval between two adjacent additions being 5-8 minutes. When the surface of the particles changes from wet and sticky to slightly dry, and there is no obvious powder falling off when pressed, the coating system is obtained.
10. The preparation method according to claim 7, characterized in that, S3 specifically includes the following steps: Prepare an aqueous solution of a pellet stabilizer containing trace mineral activating components, and atomize and spray it onto the surface of the particles in the coating system that maintains a rolling state to obtain a mixture. S4 specifically includes the following steps: The mixture is fed into a fluidized bed dryer, the inlet air temperature is set to 35℃~45℃, the air speed is controlled to keep the particles in a slightly boiling state, and the drying is carried out for 30~45 minutes. When the moisture content of the finished product is reduced to 8%~15%, the heating is stopped immediately. Cold air below 20°C is introduced to rapidly cool the particles, inducing microorganisms to enter a deep dormant state; after the finished product is graded by a vibrating screen, it is vacuum or nitrogen-filled sealed packaging within 30 minutes.