Organic silicon functional compound fertilizer capable of improving saline-alkali soil for long time and preparation method of organic silicon functional compound fertilizer

Abstract

The invention relates to the technical field of soil improvement and novel fertilizers, in particular to an organic silicon functional compound fertilizer capable of improving saline-alkali soil for a long time and a preparation method of the organic silicon functional compound fertilizer. The method aims at solving the problems that the survival rate of a microbial agent is suddenly reduced under saline-alkali stress in a saline-alkali area, the flora colonization period is not matched with the material degradation rate, the improvement effect lacks long-term effect, and salt return is prone to occurring. A three-layer coating structure is adopted, the inner layer is a sodium alginate-chitosan micro-capsule, the middle layer contains a humic acid loaded slow-release carbon source material, the outer layer is organic silicon modified zeolite, meanwhile, a multi-stage release carrier system is constructed, and poly (butylene succinate) is selected as a short-period degradation carrier to promote rapid propagation of the microbial inoculum, so that the slow-release carbon source material is prepared. The organic silicon modified starch is used as a medium-period carrier to support the requirement of a flora in a stable period, and the cross-linked organic silicon resin is used as a long-period material to form a deep salt-resistant skeleton, so that the saline-alkali soil can be improved for a long time, salt return is inhibited, and the salt-tolerant growth and yield of crops can be improved by one-time application.

Description

Technical Field

[0001] This invention relates to the fields of soil improvement and novel fertilizer technology, and in particular to an organosilicon functional compound fertilizer that can effectively improve saline-alkali land over a long period of time and its preparation method, which is especially suitable for improving soil organic matter in high saline-alkali areas. Background Technology

[0002] The improvement of saline-alkali soils is a crucial aspect of agricultural production and ecological restoration. Saline-alkali soils, characterized by high salt content, high alkalinity, poor soil structure, and nutrient deficiencies, hinder crop growth. Traditionally, saline-alkali land management has primarily employed engineering measures, chemical amendments, and biological methods. For example, digging drainage ditches and leaching with large amounts of water reduces soil salinity, while applying gypsum, sulfur, acidic substances, and other agents neutralizes alkalinity and improves soil physicochemical properties. However, chemical amendments often focus solely on reducing salinity levels, with limited impact on restoring soil microbial flora and rhizosphere ecology. Biological amendments include planting salt-tolerant plants for ecological restoration and applying microbial agents to improve soil. However, in high-salt environments, the survival rate and function of common microbial agents are severely inhibited, often resulting in difficulty in long-term colonization in the soil.

[0003] In recent years, novel organosilicon functional fertilizers have demonstrated excellent effects in the improvement of saline-alkali land. The introduction of organosilicon materials into fertilizers promotes soil aggregate formation and increases porosity, thereby accelerating salt leaching and slowing the accumulation of deep salts on the surface. Simultaneously, organosilicon elements can enhance crop salt tolerance and improve the root growth environment. However, most commercially available organosilicon amendments or functional fertilizers require frequent application to maintain their effectiveness. Once application ceases, salt leached down by rainwater may migrate back to the surface with rising groundwater levels, causing a "salinization" phenomenon and weakening the sustainability of the improvement. Furthermore, some functional fertilizers containing microorganisms suffer from a lack of effective protection and continuous nutrient supply; the live bacteria die rapidly under saline-alkali stress, and a single application cannot sustain the entire growing season. On the other hand, the introduction of controlled-release fertilizer technology promises to extend the duration of amendment action, but if the release cycle of the controlled-release carrier does not match the growth cycle of the microbial agent, it will also affect the effectiveness of the microbial community.

[0004] Therefore, there is an urgent need for a new fertilizer system that integrates the functions of "microbial remediation + controlled release + organosilicon improvement". Summary of the Invention

[0005] The purpose of this invention is to provide an organosilicon functional compound fertilizer and its preparation method that can effectively improve saline-alkali land over a long period, thereby efficiently solving problems such as the sharp drop in the survival rate of microbial agents, the mismatch between the colonization cycle of microorganisms and the degradation rate of materials, and the lack of long-term improvement effect and easy salt return under saline-alkali stress in saline-alkali areas. The problem of the sharp drop in the survival rate of microbial agents is solved by a three-layer encapsulation of microbial microcapsules; the problem of the mismatch between the colonization cycle and the degradation rate of materials is solved by an organosilicon-humic acid complex; and the problem of salt return is solved by constructing a core layer-propagation layer-stabilization layer-salt-inhibiting layer.

[0006] The specific technical solution is as follows:

[0007] An organosilicon functional compound fertilizer capable of long-term improvement of saline-alkali land and its preparation method are as follows:

[0008] S1: Three-layer encapsulated microbial microcapsules.

[0009] S11: Mix the salt-tolerant bacterial agent (Trichoderma harzianum) with sodium alginate solution at a ratio of 1:2.5 to 1:3.5 (w / v), and then stir at low speed to obtain a mixture with a sodium alginate solution concentration of 2%. Use a syringe to drop the mixture into a 0.18 mol / L CaCl2 solution and magnetically stir to solidify it into gel microspheres. Transfer the microspheres to a 0.3 mol / L CaCl2 solution and continue to magnetically stir to solidify for 10 min. Finally, transfer the microspheres to a 1% (w / v) chitosan solution (chitosan is dissolved in 1% acetic acid) and gently stir for 15 min. Then wash the microcapsules with sterile water to obtain sodium alginate-bacterial agent gel microspheres.

[0010] S12: Dissolve PLGA in dichloromethane at 4°C, add activated humic acid powder first, then add 0.5% (w / w) triethyl citrate plasticizer, and ultrasonically disperse for 10 min to prepare a 5% (w / w) PLGA-humic acid solution. Immerse the sodium alginate-bacterial agent gel microspheres prepared in S11 into the PLGA-humic acid solution for 30 s, drain, and then dry and solidify.

[0011] S13: Zeolite powder was mixed with KH550 silane coupling agent and reacted at 75℃ for 2 hours at pH=5 to prepare a silanized zeolite suspension. Then, the microspheres with the middle layer coating were placed in a fluidized bed and coated with the silanized zeolite suspension. Finally, the coated microcapsules were vacuum dried at 40℃ until the water content was ≤5%, thus preparing microbial microcapsules with a three-layer coating process.

[0012] S2: Synthesis of organosilicon-humic acid complex.

[0013] S21: Add humic acid to a reaction vessel filled with nitrogen, add deionized water at a solid-liquid ratio of 1:3, and stir to prepare a homogeneous humic acid suspension.

[0014] S22: Slowly add epoxy-modified polymethylsiloxane to the humic acid suspension prepared in S21, then heat to 80°C and stir to form a viscous mixture.

[0015] S23: Nano-SiO2 was added to the reaction system in three portions. The nano-SiO2 was treated with KH-550 at a mass fraction of 0.1%, with each portion spaced 10 minutes apart. The temperature was maintained at 80°C, and the reaction was stirred for 2 hours at a stirring rate of 400 rpm. The system became an elastic gel. Finally, heating was stopped, and the temperature was cooled to below 40°C. The gel was then transferred to a crusher and pulverized at 10°C through a 100-mesh sieve to prepare the organosilicon-humic acid composite.

[0016] S3: Four-stage concentric granulation.

[0017] S31: Put the nitrogen, phosphorus and potassium compound fertilizer into the rotary drum granulator and preheat it to 55°C; then spray a 5% MgCl2 solution and roll magnesium ammonium phosphate onto the surface of the nitrogen, phosphorus and potassium compound fertilizer, and then quickly dry it to form a dense core to obtain core layer granules.

[0018] S32: PBS particles were added to ethyl acetate at a solid-liquid ratio of 1:4. The mixture was heated to 50°C in a water bath with magnetic stirring. Then, the microbial microcapsules prepared in S13 were added, and the temperature was maintained at 40°C. The mixture was homogenized to form a uniform suspension, followed by ultrasonic treatment to prepare a PBS-ethyl acetate suspension. The core layer particles prepared in S31 were transferred to a fluidized bed, preheated to 40°C for 10 min, and then the PBS-ethyl acetate suspension was sprayed onto the core particles to form a porous propagation carrier. Finally, hot air drying was performed to form a uniform porous structure on the surface of the core particles, resulting in particles encapsulated by the propagation layer.

[0019] S33: Pregelatinized starch was mixed with deionized water and gelatinized at 60℃ for 30 min. Then, KH-550 diluted with ethanol at a 1:1 ratio was added dropwise, and the mixture was reacted at 65℃ for 2 h. Finally, it was spray-dried to prepare organosilicon-modified starch. The organosilicon-humic acid composite prepared in S23 was added to an ethanol aqueous solution and stirred in a water bath. Then, it was homogenized to obtain a non-agglomerated slurry with a solid content controlled at 40%. The particles coated with the propagation layer prepared in S32 were preheated at 55℃ for 10 min. Then, the slurry was coated using a roller coating machine and finally cured and dried in a stepped manner to obtain particles coated with a stable layer.

[0020] S34: Slowly add cross-linked silicone resin to ethanol, controlling the temperature to ≤30℃, stir until completely dissolved, add DBTL, and ultrasonically disperse to obtain a homogeneous resin solution. The particles coated with the stabilizing layer prepared in S33 are then subjected to ion exchange to eliminate surface static electricity, followed by high-pressure spraying of the resin solution; finally, a stepped thermosetting process is performed to obtain particles coated with a salt-barrier layer.

[0021] S4: Processing and packaging: Drying in a fluidized bed at 40℃ for 30 min, then cooling to 20℃. Polyurethane resin and diatomaceous earth are added to an ethanol solution to prepare a 25% solids content ethanol solution. The particles coated with the salt-barrier layer prepared in S34 are then coated with a 25% solids content ethanol solution using a polyurethane coating machine, and dried at 40℃ for 10 min to prepare an organosilicon functional compound fertilizer.

[0022] Furthermore, the mass-to-volume ratio of the salt-tolerant bacterial agent and the sodium alginate solution described in S11 is 1:2.5 to 1:3.5, wherein the concentration of the sodium alginate solution is 2%.

[0023] The low-speed stirring described in S11 has the following parameters: rotation speed 300 rpm, duration 10 min.

[0024] The magnetic stirring curing described in S11 has the following parameters: rotation speed 100 rpm, duration 10 min.

[0025] The mass ratio of PLGA to humic acid described in S12 is 2.5:1 to 3.5:1.

[0026] The drying and curing process described in S12 has the following parameter settings: primary curing temperature 50℃, duration 10min; secondary curing temperature 45℃, duration 10min.

[0027] The KH-550 silane coupling agent described in S13 is 1.5 to 2% of the mass of zeolite powder.

[0028] The fluidized bed described in S13 has the following parameter settings: inlet air temperature 50-55℃, atomization pressure 0.2MPa.

[0029] Furthermore, the humic acid described in S21 accounts for 70-78% of the total mass of the composite.

[0030] The stirring described in S21 has the following parameters: temperature 60℃, duration 30min, and stirring speed 300rpm.

[0031] The epoxy-modified polymethylsiloxane described in S22 accounts for 20-30% of the total mass of the composite.

[0032] The stirring described in S22 has the following parameters: stirring speed 200 rpm, duration 40 min.

[0033] The nano-SiO2 described in S23 accounts for 2-4% of the total mass of the composite.

[0034] Furthermore, the potassium nitrogen phosphate described in S31 accounts for 85-90% of the mass of the core layer.

[0035] The MgCl2 solution described in S31 is used in an amount of 10% of the core layer mass.

[0036] The magnesium ammonium phosphate described in S31 accounts for 10-15% of the mass of the core layer.

[0037] The rapid drying described in S31 has the following parameter settings: temperature 300℃, duration 50min.

[0038] The magnetic stirring described in S32 has the following parameters: duration 30 min, stirring speed 300 rpm.

[0039] The homogenizer described in S32 has the following parameter settings: rotation speed 9000~11000rpm, duration 5~10min.

[0040] The homogeneous suspension described in S32 has a total solid content of 20%, with PBS accounting for 70% of the solid content and microbial microcapsules accounting for 30% of the solid content.

[0041] The ultrasonic treatment described in S32 has the following parameter settings: 35-45 kHz, duration 8-12 min.

[0042] The spraying parameters described in S32 are as follows: spray gun pressure 0.2MPa, spray rate 20mL / min, and atomizing air flow rate 15L / min.

[0043] The hot air drying described in S32 has the following parameter settings: inlet air temperature 40℃, air velocity 1.5m / s, and duration 25min.

[0044] Furthermore, in the preparation of the organosilicon-modified starch described in S33, the mass ratio of pregelatinized starch, KH-550, and deionized water is 50:3:100.

[0045] The organosilicon-humic acid complex and organosilicon-modified starch described in S33 have a mass ratio of 0.5:1 to 1.5:1.

[0046] The ethanol-water solution described in S33 has a volume ratio of ethanol to water of 6:4.

[0047] The water bath stirring described in S33 has the following parameters: temperature 45℃, duration 20min, and stirring speed 500rpm.

[0048] The homogenizer described in S33 has the following parameter settings: rotation speed 8000 rpm, duration 3 min.

[0049] The roller coating machine described in S33 has the following parameter settings: rotation speed 65 r / min, spray gun pressure 0.15 MPa, slurry feed rate 15 mL / kg·min, and hot air temperature 60℃.

[0050] The stepped curing and drying process described in S33 has the following parameter settings: the first stage is hot air drying at 60℃ for 15 minutes, and the second stage is constant temperature drying at 65℃ for 25 minutes.

[0051] The homogeneous resin solution described in S34 contains 20-30% cross-linked silicone resin by mass, 0.2-0.5% DBTL by mass, and the remainder is anhydrous ethanol.

[0052] The ultrasonic dispersion described in S34 has the following parameter settings: frequency 40kHz, duration 10min.

[0053] The high-pressure spraying described in S34 has the following parameter settings: spraying pressure 0.35MPa, wind speed 1.2m / s, base coat coverage 60%, and top coat coverage 40%.

[0054] The stepped thermosetting process described in S34 has the following parameter settings: pre-curing temperature 40℃, duration 5min; main curing temperature 60℃, duration 30min; curing temperature 25℃, duration 12h.

[0055] Furthermore, the mass ratio of the polyurethane resin to diatomaceous earth described in S4 is 19:1.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] 1. By encapsulating salt-alkali resistant composite bacterial agents in the inner layer of sodium alginate-chitosan microcapsules, and the middle layer containing slow-release carbon source material loaded with humic acid, the bacterial agents are provided with continuous nutrition, thus solving the problem of low survival rate of microbial agents under salt and alkali stress.

[0058] 2. By constructing a multi-stage release carrier system, PBS was used as a short-cycle degradation carrier to promote the rapid propagation of the bacterial agent, while organosilicon-modified starch was used as a medium-cycle carrier to support the needs of the bacterial community during the stable period, thus solving the problem of mismatch between the colonization cycle of the bacterial community and the degradation of the material.

[0059] 3. The protective network formed by the organosilicon resin-humic acid network membrane solves the problem of insufficient sustainability of the improvement effect and achieves a longer-lasting fertilizer effect. Attached Figure Description

[0060] Figure 1 This is a flowchart of a preparation method for an organosilicon functional compound fertilizer that can effectively improve saline-alkali land over a long period of time.

[0061] Figure 2 This is a comparison chart of the 7-day survival rate of the microbial agent and the material degradation matching degree of the slow-release fertilizers prepared in Examples 1-5 and Comparative Examples 1-3.

[0062] Figure 3This is a comparison chart showing the decrease in soil electrical conductivity, salt return rate, and increase in organic matter of the slow-release fertilizers prepared in Examples 1-5 and Comparative Examples 1-3.

[0063] Figure 4 This is a schematic diagram of an organosilicon functional compound fertilizer that can effectively improve saline-alkali land over a long period of time. Detailed Implementation

[0064] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0065] This invention proposes an organosilicon functional compound fertilizer capable of long-term improvement of saline-alkali land and its preparation method. This invention solves problems such as low survival rate of microbial agents and mismatch between microbial colonization cycle and material degradation through functional layering, material synergy, and process optimization. Specifically, it consists of a core layer for slow-release of basic nutrients, a propagation layer for protecting and promoting microbial activity and reproduction, a stabilizing layer for resisting saline-alkali stress, and a salt-barrier layer for physically isolating salt ions. Specifically, the inner layer consists of sodium alginate-chitosan microcapsules encapsulating salt-alkali resistant compound microbial agents, a middle layer containing humic acid-loaded slow-release carbon source material to provide continuous nutrition for the microbial agents, and an outer layer of zeolite for adsorbing sodium ions. These three layers encapsulate the microbial agents and constitute the microbial microcapsules. (See attached...) Figure 1 The diagram shows a method for preparing an organosilicon functional compound fertilizer that can effectively improve saline-alkali land over a long period. The detailed core technical solution is as follows:

[0066] 1. Three-layer encapsulated microbial microcapsules

[0067] 1.1 Inner Layer Preparation

[0068] Salt-tolerant bacteria (Trichoderma harzianum) were mixed with sodium alginate solution and stirred at low speed to ensure uniform dispersion of the bacteria, resulting in a mixture. The mixture was then added dropwise to a low-concentration CaCl2 solution to avoid rapid cross-linking and surface hardening. The mixture was then magnetically stirred to solidify and prepare microspheres. The microspheres were then transferred to a high-concentration CaCl2 solution to enhance their mechanical strength and were further magnetically stirred to solidify. Finally, the microspheres were transferred to a chitosan solution containing acetic acid and stirred. Chitosan solution was chosen because chitosan and sodium alginate form a polyelectrolyte composite membrane through electrostatic interaction, which enhances the stability of the microcapsules and improves surface hydrophilicity. The microcapsules were then washed with sterile water to obtain sodium alginate-bacterial agent gel microspheres.

[0069] 1.2 Middle Coating

[0070] PLGA was dissolved in dichloromethane at 4°C. Activated humic acid powder was added first, followed by triethyl citrate plasticizer. The mixture was then ultrasonically dispersed. PLGA provided a hydrophobic barrier, humic acid enhanced nutrient supply to microorganisms, and triethyl citrate improved film-forming flexibility, thus preparing a 5% (w / w) PLGA-humic acid solution. The prepared sodium alginate-bacterial agent gel microspheres were immersed in the PLGA-humic acid solution, drained, and then dried in stages. Staged drying was performed to avoid rapid evaporation of the PLGA solvent at high temperatures, which could cause microcapsule collapse or cracking.

[0071] 1.3 Outer Coating

[0072] Zeolite powder was mixed with KH-550 silane coupling agent to prepare a silanized zeolite suspension. KH-550 can modify the hydroxyl groups on the zeolite surface, enhancing the interfacial bonding with the PLGA layer, while the zeolite provides ion exchange capacity. Then, the microspheres with the middle layer coating were placed in a fluidized bed and coated with the silanized zeolite suspension.

[0073] 2. Synthesis of organosilicon-humic acid complex

[0074] 2.1 Pre-dispersion treatment

[0075] Humic acid was added to the reaction vessel (which was filled with nitrogen for protection throughout the process). Humic acid was chosen because of its dominant ion exchange and water retention functions. Deionized water was added and stirred to prepare a homogeneous humic acid suspension.

[0076] 2.2 Organosilicon blends

[0077] Epoxy-modified polymethylsiloxane was slowly added to the humic acid suspension prepared above. The epoxy-modified polymethylsiloxane provides hydrophobic segments and reactive epoxy groups, which crosslink with the carboxyl groups of humic acid to form a network structure. Then, the mixture was heated to 80°C and stirred to form a viscous mixture. The temperature of 80°C was chosen because this temperature promotes the ring-opening of epoxy groups and the grafting reaction with humic acid.

[0078] 2.3 Nano-crosslinking reaction

[0079] Nano-SiO2 was added to the reaction system in three portions. The nano-SiO2 was treated with KH-550 at a mass fraction of 0.1%. KH-550 treatment was used because it can improve the dispersibility of SiO2 and form Si-O-Si bonds with the organosilicon chains on the surface, thereby enhancing the mechanical strength of the composite. The nano-SiO2 was added in three portions to avoid the agglomeration of nanoparticles and to ensure uniform dispersion in the gel network. Stirring made the system an elastic gel.

[0080] 2.4 Processing

[0081] Heating was stopped, the mixture was cooled, and then the gel was transferred to a crusher and pulverized at a low temperature of 10°C through a 100-mesh sieve. The low temperature was to prevent the degradation of humic acid, thus preparing an organosilicon-humic acid composite.

[0082] 3. Four-stage concentric granulation

[0083] 3.1 Core Layer Fabrication

[0084] Nitrogen, phosphorus, and potassium compound fertilizer is fed into a rotary drum granulator and preheated to 55°C. Then, a 5% MgCl2 solution is sprayed on it. The MgCl2 solution is sprayed to react with the phosphates in the compound fertilizer to form a slow-release skeleton structure. At the same time, magnesium ammonium phosphate is rolled and wrapped on the surface of the nitrogen, phosphorus, and potassium compound fertilizer. Then, it is quickly dried to form a dense core, resulting in core layer granules. The rapid drying is to prevent the premature release of nutrients.

[0085] 3.2 Preparation of propagation layer

[0086] PBS particles were added to ethyl acetate, heated in a water bath, and magnetically stirred. Then, the prepared microbial microcapsules were added, and the temperature was maintained at 40°C. The mixture was homogenized to form a uniform suspension, followed by ultrasonic treatment to prepare a PBS-ethyl acetate suspension. PBS provides a carbon source for the microorganisms, while ethyl acetate is a low-boiling-point solvent that readily evaporates to form a porous structure. The magnesium ammonium phosphate-coated compound fertilizer core particles were transferred to a fluidized bed, preheated, and then the PBS-ethyl acetate suspension was sprayed onto the core particles to form a porous propagation carrier. Finally, hot air drying was performed, resulting in a uniform porous structure on the surface of the core particles. This porous structure facilitates the colonization and propagation of the microbial community, yielding particles coated with a propagation layer.

[0087] 3.3 Preparation of the stabilizing layer

[0088] Pregelatinized starch was mixed with water and stirred until gelatinized. Then, KH-550 diluted with ethanol was added dropwise. The reason for adding KH-550 is that it can modify starch to enhance hydrophobicity and synergistically improve the resistance to salt and alkali erosion with the organosilicon-humic acid complex. Finally, the mixture was spray-dried to prepare organosilicon-modified starch. The organosilicon-humic acid complex and organosilicon-modified starch prepared above were added to an ethanol aqueous solution, stirred in a water bath, and then processed by a homogenizer to obtain a non-agglomerated slurry. The particles with the propagation layer completed were preheated, and then the slurry was coated. Finally, the particles were cured and dried in a stepped manner at 60°C and 65°C to obtain particles with a stable layer. The stepped curing was chosen because the 60°C pre-curing can remove the solvent, while the 65°C promotes the cross-linking of organosilicon to strengthen the film layer.

[0089] 3.4 Preparation of Salt Barrier Layer

[0090] Crosslinked silicone resin was slowly added to anhydrous ethanol and stirred until completely dissolved. DBTL was then added, and the mixture was ultrasonically dispersed to obtain a homogeneous resin solution. The particles coated with the stabilizing layer were then subjected to ionization to eliminate surface static electricity. The resin solution was then sprayed under high pressure, followed by a stepped thermosetting process (40℃ pre-curing, 60℃ main curing, and 25℃ aging) to obtain particles coated with a salt-barrier layer. The 40℃ pre-curing prevented solvent retention, the 60℃ process completed the crosslinking reaction, and the 25℃ aging eliminated internal stress.

[0091] 4. Outermost membrane

[0092] 4.1 Processing

[0093] The product was dried in a fluidized bed at 40°C for 30 minutes, and then cooled to 20°C. The 40°C drying temperature was chosen to avoid damage to microorganisms and organic components due to high temperature.

[0094] 4.2 Outermost layer construction

[0095] Polyurethane resin and diatomaceous earth were added to an ethanol solution to prepare an ethanol solution with a solid content of 25%. The particles encapsulated in the salt-barrier layer were then coated with a polyurethane coating machine to produce an organosilicon functional compound fertilizer.

[0096] Example 1

[0097] An organosilicon functional compound fertilizer capable of long-term improvement of saline-alkali land and its preparation method are as follows:

[0098] Table 1 Main Raw Materials

[0099]

[0100]

[0101]

[0102]

[0103] S1: Three-layer encapsulated microbial microcapsules.

[0104] S11: Mix Trichoderma harzianum and sodium alginate solution at a ratio of 1:3 (w / v) and stir at low speed of 300 rpm for 10 min to obtain a mixture; use a syringe to drop the mixture into 0.18 mol / L CaCl2 solution and stir magnetically at 100 rpm for 10 min to solidify and form gel microspheres; transfer the microspheres to 0.3 mol / L CaCl2 solution and continue to stir magnetically for 10 min to solidify; finally, transfer the microspheres to 1% (w / v) chitosan solution (chitosan dissolved in 1% acetic acid) and stir gently for 15 min; then wash the microcapsules with sterile water to obtain sodium alginate-bacterial agent gel microspheres.

[0105] S12: Dissolve PLGA in dichloromethane at 4°C, add activated humic acid powder first, then add 0.5% (w / w) triethyl citrate plasticizer, and ultrasonically disperse for 10 min. The mass ratio of PLGA to humic acid is 3:1, preparing a 5% (w / w) PLGA-humic acid solution. Immerse the prepared sodium alginate-bacterial agent gel microspheres in the PLGA-humic acid solution for 30 s, drain, and then dry and solidify at 50°C for 10 min, followed by drying and solidification at 45°C for 10 min.

[0106] S13: Zeolite powder was mixed with KH-550 silane coupling agent and reacted at 75℃ for 2 hours at pH=5 to prepare a silanized zeolite suspension, wherein the mass of KH-550 was 1.75% of the mass of the zeolite powder. Then, the microspheres with the middle layer coating were placed in a fluidized bed and coated with the silanized zeolite suspension. The fluidized bed parameters were set as follows: inlet air temperature 53℃, atomization pressure 0.2MPa. Finally, the coated microcapsules were vacuum dried at 40℃ until the moisture content was ≤5%, thus preparing microbial microcapsules with a three-layer coating process.

[0107] S2: Synthesis of organosilicon-humic acid complex.

[0108] S21: Add humic acid to the reaction vessel (filled with nitrogen for protection throughout the process), add deionized water at a solid-liquid ratio of 1:3, and then stir at 60°C for 30 minutes at a stirring speed of 300 rpm to prepare a homogeneous humic acid suspension.

[0109] S22: Slowly add epoxy-modified polymethylsiloxane to the humic acid suspension prepared above, then heat to 80°C and stir to form a viscous mixture. Stirring parameters: stirring speed 200 rpm, duration 40 min.

[0110] S23: Nano-SiO2 treated with 0.1% KH-550 by mass was added to the reaction system in three portions, with an interval of 10 min between each addition. The temperature was maintained at 80℃, and the reaction was stirred for 2 hours at a stirring rate of 400 rpm. The system became an elastic gel. Finally, heating was stopped, and the temperature was cooled to below 40℃. The gel was then transferred to a crusher and pulverized at 10℃ through a 100-mesh sieve to prepare the organosilicon-humic acid composite.

[0111] S3: Four-stage concentric granulation.

[0112] S31: Put the nitrogen, phosphorus and potassium compound fertilizer into the rotary drum granulator and preheat it to 55℃; then spray a 5% MgCl2 solution, while rolling magnesium ammonium phosphate around the surface of the nitrogen, phosphorus and potassium compound fertilizer, and then quickly dry it to form a dense core, thus obtaining core layer granules. The amount of MgCl2 solution is 10% of the core layer mass, the nitrogen, phosphorus and potassium compound fertilizer accounts for 87% of the core layer mass, and the magnesium ammonium phosphate accounts for 13% of the core layer mass. The rapid drying parameters are set as follows: temperature 300℃, duration 50min.

[0113] S32: Add PBS particles to ethyl acetate, controlling the solid-liquid ratio at 1:4. Heat in a water bath to 50°C, magnetically stir for 30 min at a stirring speed of 300 rpm, then add the microbial microcapsules prepared above, maintain the temperature at 40°C, and homogenize to form a uniform suspension. The total solid content of the suspension is 20%, PBS accounts for 70% of the solid content, and microbial microcapsules account for 30% of the solid content. Homogenizer parameters: speed 10000 rpm, duration 7 min. Then, ultrasonic treatment is performed to prepare a PBS-ethyl acetate suspension. Ultrasonic treatment parameters: 40 kHz, duration 10 min. Transfer the magnesium ammonium phosphate-coated compound fertilizer core particles to a fluidized bed, preheat at 40°C for 10 min, and then spray the PBS-ethyl acetate suspension onto the core particles to form a porous propagation carrier. Spraying parameters: spray gun pressure 0.2 MPa, spray rate 20 mL / min, atomizing air flow rate 15 L / min. Finally, hot air drying is performed to form a uniform porous structure on the surface of the core particles, resulting in particles wrapped in a propagation layer. The parameters are set as follows: air inlet temperature 40℃, air velocity 1.5m / s, and drying time 25min.

[0114] S33: Pregelatinized starch was mixed with water and gelatinized at 60℃ for 30 min. Then, KH-550 diluted with ethanol (1:1) was added dropwise, and the mixture was reacted at 65℃ for 2 h. Finally, it was spray-dried to prepare organosilicon-modified starch. The mass ratio of pregelatinized starch, KH-550, and deionized water was 50:3:100. The organosilicon-humic acid composite prepared above was added to an ethanol-water solution at a mass ratio of 1:1 (ethanol:water volume ratio of 6:4). The mixture was stirred in a water bath at 45℃ for 20 min at a stirring speed of 500 rpm. Then, it was homogenized to obtain a non-agglomerated slurry with a solid content controlled at 40%. The homogenizer parameters were set as follows: rotation speed 8000 rpm, duration 3 min. The particles coated with the propagation layer were preheated at 55℃ for 10 min. Then, the slurry was coated using a roller coating machine. Finally, it was cured and dried in a stepwise manner to obtain particles coated with a stable layer. The parameters for the roller coating machine are as follows: roller speed 65 r / min, spray gun pressure 0.15 MPa, slurry feed rate 15 mL / kg·min, hot air temperature 60℃. The parameters for the stepped curing and drying are as follows: first stage hot air drying at 60℃ for 15 min, second stage constant temperature at 65℃ for 25 min.

[0115] S34: Slowly add methyl silicone resin to anhydrous ethanol, controlling the temperature ≤30℃, and stir until completely dissolved. Add DBTL and ultrasonically disperse to obtain a homogeneous resin solution. The mass percentage of methyl silicone resin is 25%, the mass percentage of DBTL is 0.35%, and the remainder is anhydrous ethanol. Ultrasonic dispersion parameters: 40kHz, duration 10min. The particles coated with the stabilizing layer are then destatically removed using an ionizer, followed by high-pressure spraying of the resin solution. The parameters are: spraying pressure 0.35MPa, air velocity 1.2m / s, bottom layer spraying amount 60%, top layer spraying amount 40%. Finally, a stepped thermosetting process is performed to obtain particles coated with a salt-barrier layer. The stepped thermosetting parameters are: pre-curing temperature 40℃, duration 5min; main curing temperature 60℃, duration 30min; curing temperature 25℃, duration 12h.

[0116] S4: Processing and Packaging. The product is dried in a fluidized bed at 40℃ for 30 min, then cooled to 20℃. Polyurethane resin and diatomaceous earth are added to an ethanol solution at a mass ratio of 19:1 to prepare an ethanol solution with a solid content of 25%. The salt-barrier layer of the granules is coated with a polyurethane coating machine, and then dried at 40℃ for 10 min to prepare an organosilicon functional compound fertilizer.

[0117] Example 2

[0118] The composition and preparation process are the same as in Example 1, except that:

[0119] In step S12 of the preparation process, the mass ratio of PLGA to humic acid is 2.5:1. All other steps are the same.

[0120] In the preparation process S13, the KH-550 silane coupling agent is 1.5% of the zeolite powder mass, and the other components are the same.

[0121] In the preparation process S21, humic acid accounts for 70% of the total mass of the composite, while other components are the same.

[0122] In the preparation process S22, the epoxy-modified polymethylsiloxane accounts for 28% of the total mass of the composite, and the other components are the same.

[0123] In the preparation process S23, the mass percentage of nano-SiO2 in the composite is 2% of the total mass, and the other components are the same.

[0124] In the S31 preparation process, potassium nitrogen phosphate accounts for 85% of the core layer mass, magnesium ammonium phosphate accounts for 15% of the core layer mass, and other components are the same.

[0125] In the preparation process S32, the homogenizer parameters were set as follows: rotation speed 9000 rpm, duration 5 min; the ultrasonic treatment parameters were set as follows: 35 kHz, duration 8 min, and other steps were the same.

[0126] In the preparation process S33, the mass ratio of organosilicon-humic acid complex to organosilicon-modified starch is 0.5:1, and other components are the same.

[0127] In the preparation process S34, the mass percentage of methyl silicone resin is 20%, the mass percentage of DBTL is 0.2%, and the remainder is anhydrous ethanol, with other components being the same.

[0128] Example 3

[0129] The composition and preparation process are the same as in Example 1, except that:

[0130] In the preparation process, the mass ratio of PLGA to humic acid in S12 is 3.5:1. All other steps are the same.

[0131] In the preparation process S13, the KH-550 silane coupling agent is 2% of the zeolite powder mass, and the other components are the same.

[0132] In the preparation process S21, humic acid accounts for 78% of the total mass of the composite, while other components are the same.

[0133] In the preparation process S22, the epoxy-modified polymethylsiloxane accounts for 20% of the total mass of the composite, and the other components are the same.

[0134] In the preparation process S23, the mass percentage of nano-SiO2 in the composite is 2% of the total mass, and the other components are the same.

[0135] In the S31 preparation process, potassium nitrogen phosphate accounts for 90% of the core layer mass, magnesium ammonium phosphate accounts for 10% of the core layer mass, and other components are the same.

[0136] In the preparation process S32, the homogenizer parameters were set as follows: rotation speed 11000 rpm, duration 10 min; the ultrasonic treatment parameters were set as follows: 45 kHz, duration 12 min, and other steps were the same.

[0137] In the preparation process S33, the mass ratio of organosilicon-humic acid complex to organosilicon-modified starch is 1.5:1, and other components are the same.

[0138] In the preparation process S34, the mass percentage of methyl silicone resin is 30%, the mass percentage of DBTL is 0.5%, and the remainder is anhydrous ethanol, with other components being the same.

[0139] Example 4

[0140] The composition and preparation process are the same as in Example 1, except that:

[0141] In the preparation process, the mass ratio of PLGA to humic acid in S12 is 2.7:1. All other steps are the same.

[0142] In the preparation process S13, the KH-550 silane coupling agent is 1.6% of the zeolite powder mass, and the other components are the same.

[0143] In the preparation process S21, humic acid accounts for 72% of the total mass of the composite, while other components are the same.

[0144] In the preparation process S22, the epoxy-modified polymethylsiloxane accounts for 24% of the total mass of the composite, and the other components are the same.

[0145] In the preparation process S23, the mass percentage of nano-SiO2 in the composite is 4% of the total mass, and the other components are the same.

[0146] In the S31 preparation process, potassium nitrogen phosphate accounts for 86% of the core layer mass, magnesium ammonium phosphate accounts for 14% of the core layer mass, and other components are the same.

[0147] In the preparation process S32, the homogenizer parameters were set as follows: rotation speed 9500 rpm, duration 6 min; the ultrasonic treatment parameters were set as follows: 38 kHz, duration 9 min, and other steps were the same.

[0148] In the preparation process S33, the mass ratio of organosilicon-humic acid complex to organosilicon-modified starch is 0.8:1, and other components are the same.

[0149] In the preparation process S34, the mass percentage of methyl silicone resin is 23%, the mass percentage of DBTL is 0.25%, and the remainder is anhydrous ethanol, with other components being the same.

[0150] Example 5

[0151] The composition and preparation process are the same as in Example 1, except that:

[0152] In the preparation process, the mass ratio of PLGA to humic acid in S12 is 3.3:1. All other steps are the same.

[0153] In the preparation process S13, the KH-550 silane coupling agent is 1.85% of the zeolite powder mass, and the other components are the same.

[0154] In the preparation process S21, humic acid accounts for 76% of the total mass of the composite, while other components are the same.

[0155] In the preparation process S22, the epoxy-modified polymethylsiloxane accounts for 22% of the total mass of the composite, and the other components are the same.

[0156] In the preparation process S23, the mass percentage of nano-SiO2 in the composite is 2% of the total mass, and the other components are the same.

[0157] In the S31 preparation process, potassium nitrogen phosphate accounts for 88% of the core layer mass, magnesium ammonium phosphate accounts for 12% of the core layer mass, and other components are the same.

[0158] In the preparation process S32, the homogenizer parameters were set as follows: rotation speed 10500 rpm, duration 9 min; the ultrasonic treatment parameters were set as follows: 42 kHz, duration 11 min, and other steps were the same.

[0159] In the preparation process S33, the mass ratio of organosilicon-humic acid complex to organosilicon-modified starch is 1.3:1, and other components are the same.

[0160] In the preparation process S34, the mass percentage of methyl silicone resin is 28%, the mass percentage of DBTL is 0.35%, and the remainder is anhydrous ethanol, with other components being the same.

[0161] Comparative Example 1

[0162] The composition and preparation process are the same as in Example 1, except that:

[0163] The S1 three-layer coating of microbial microcapsules in the preparation process was removed, and humic acid was directly applied to the bacterial agent. The other steps were the same.

[0164] Comparative Example 2

[0165] The composition and preparation process are the same as in Example 1, except that:

[0166] In step S33 of the preparation process, the organosilicon-humic acid complex is removed, and only organosilicon-modified starch is used as the coating. The other steps are the same.

[0167] Comparative Example 3

[0168] The composition and preparation process are the same as in Example 1, except that:

[0169] Magnesium ammonium phosphate is removed from step S31 of the preparation process; the other steps remain the same.

[0170] The preparation of PBS-ethyl acetate solution is removed from step S32 of the preparation process; the other steps remain the same.

[0171] Based on Examples 1-5 and Comparative Examples 1-3, samples were taken from the microbial microcapsules prepared in S13 and the humic acid-coated bacterial agent in Comparative Example 1 for bacterial agent survival rate testing: the plate colony counting method was used for testing. The microcapsules were placed in 0.3% NaCl and pH 8.5 buffer solution, referring to the standard GB / T20287-2006 "Agricultural Microbial Agents", with five parallel groups and the average value was taken.

[0172] Based on Examples 1-5 and Comparative Examples 1-3, samples of the slow-release fertilizer prepared by S4 were taken, and the initial soil was selected from saline-alkali land in Hebei Province. The material degradation matching degree test was carried out: the degradation rate was determined by molecular weight method, with three parallel groups and the average value was taken, referring to the standard GB / T 23881-2009 "Determination of final aerobic biodegradation capacity of materials under controlled composting conditions - Method for determining carbon dioxide released - Part 1: General method"; the colonization rate was determined by three parallel groups and the average value was taken, referring to the standard NY / T1536-2025 "Technical Specification for Field Experiment and Effect Evaluation of Microbial Fertilizers".

[0173] Based on Examples 1-5 and Comparative Examples 1-3, saline-alkali land in Hebei Province was used as the initial soil to determine the colonization period of microbial communities. A field-based experiment was conducted with three parallel groups, and the average value was taken. The determination was carried out in accordance with the standard NY / T 1535-2007 "Technical Specifications for Field Trials of Microbial Fertilizers".

[0174] Based on Examples 1-5 and Comparative Examples 1-3, saline-alkali land in Hebei Province was used as the initial soil, and its electrical conductivity was measured. After adding compound fertilizer prepared by S4 for one year, the soil electrical conductivity was measured again. Field positioning test was conducted, and the measurement was carried out with reference to standard NY / T1121.18-2006 "Soil Testing Part 18: Determination of Electrical Conductivity of Soil Water Leachate".

[0175] Based on Examples 1-5 and Comparative Examples 1-3, saline-alkali land in Hebei Province was used as the initial soil. The total soluble salt content was measured. After adding compound fertilizer prepared by S4, the salt return rate was measured one year later. The measurement was carried out in accordance with the standard GB / T 32737-2016 "Specification for Dynamic Monitoring of Soil Salinity in Saline-Alkali Land".

[0176] Based on Examples 1-5 and Comparative Examples 1-3, the increase in soil organic matter was determined using the potassium dichromate oxidation-external heating method, referring to standard NY / T 1121.6-2006 "Determination of Soil Organic Matter".

[0177] The specific test results are shown in Tables 2 and 3:

[0178] Table 2 Performance Comparison of Examples 1-5 and Comparative Examples 1-3

[0179]

[0180] Note: Material degradation matching degree is defined as degradation rate / colonization rate.

[0181] Table 3 Soil feedback data after 12 months for Examples 1-5 and Comparative Examples 1-3

[0182]

[0183]

[0184] The comparison results above show that Example 1 has the best overall performance, with the highest 7-day survival rate of the microbial agent. This is because the three-layer coating provides a strong salt-resistant barrier; the propagation layer and stabilization layer synergistically control the slow release of microorganisms, ensuring the matching of the material degradation cycle; the colonization cycle of the microbial community is as long as 120 days, which meets the crop growth cycle; the salt-blocking layer and the core layer form an ion-blocking network, ensuring a low soil salinity return rate after one year, thus eliminating the need for multiple fertilizations. The overall performance of Examples 2 to 5 is slightly lower than that of Example 1, indicating that excellent extraction results were still achieved under a large range of parameter variations. Comparative Example 1 lacks the three-layer coating, and the microbial agent is directly exposed to the saline-alkali environment, resulting in a sharp drop in the survival rate of the microbial agent. Comparative Example 2 lacks the organosilicon-humic acid complex, and the stabilization layer has no slow-release function, resulting in a shortened colonization cycle to 90 days and an increased salinity return rate. Comparative Example 3 removes the magnesium ammonium phosphate core layer and the PBS propagation layer, resulting in a microbial burst release and a significantly increased salinity return rate.

[0185] In summary, as can be seen from the above embodiments and comparative examples, the organosilicon functional compound fertilizer provided by the present invention, which can effectively improve saline-alkali land in the long term, is significantly superior to traditional solutions in saline-alkali land. This is attributed to the innovative construction of a three-layer structure consisting of microbial microcapsules, an organosilicon-humic acid complex, a core layer, a propagation layer, a stabilizing layer, and a salt-blocking layer. This solves the problems of drastic drop in the survival rate of microbial agents, mismatch between the colonization cycle of the microbial community and the degradation rate of the material, and lack of long-term improvement effect and easy salt return in saline-alkali areas.

Claims

1. An organosilicon functional compound fertilizer capable of long-term improvement of saline-alkali land, characterized in that: An organosilicon functional compound fertilizer capable of long-term improvement of saline-alkali land comprises, from the inside out, a core layer, a propagation layer, a stabilizing layer, a salt-blocking layer, and an outermost layer. The core layer is composed of nitrogen, phosphorus, and potassium compound fertilizer and magnesium ammonium phosphate. The propagation layer consists of three layers of microbial microcapsules and PBS. The stabilizing layer consists of an organosilicon-humic acid complex and organosilicon-modified starch. The salt-blocking layer consists of cross-linked organosilicon resin and DBTL. The outermost layer consists of polyurethane and diatomaceous earth.

2. The organosilicon functional compound fertilizer for long-term improvement of saline-alkali land according to claim 1, characterized in that: The core layer, wherein the nitrogen-phosphorus-potassium compound fertilizer accounts for 85-90% of the core layer mass, and the magnesium ammonium phosphate accounts for 10-15% of the core layer mass, and its structure is magnesium ammonium phosphate coated with nitrogen-phosphorus-potassium compound fertilizer; The propagation layer, wherein the PBS accounts for 70% of the mass of the propagation layer, and the three-layer encapsulated microbial microcapsules account for 30% of the mass of the propagation layer, and its structure is that the PBS encapsulates the three-layer encapsulated microbial microcapsules. The stabilizing layer, wherein the mass ratio of the organosilicon-humic acid composite to the organosilicon-modified starch is 0.5:1 to 1.5:1; its structure is that the organosilicon-humic acid composite and the organosilicon-modified starch are used as a mixed slurry coating. The salt barrier layer comprises 20-30% by mass of cross-linked silicone resin, 0.2-0.5% by mass of DBTL, and the remainder being anhydrous ethanol. Its structure is a coating of cross-linked silicone resin and DBTL. The outermost layer contains polyurethane resin in a mass ratio of 19:1 to diatomaceous earth, and its structure consists of a mixture of polyurethane resin and diatomaceous earth followed by coating.

3. The organosilicon functional compound fertilizer for long-term improvement of saline-alkali land according to claim 1, characterized in that: The three-layer microbial microcapsules consist of an inner layer of salt- and alkali-resistant bacterial microspheres encapsulated in sodium alginate gel, a middle layer of PLGA-humic acid coating, and an outer layer of silanized zeolite powder coating.

4. The organosilicon functional compound fertilizer for long-term improvement of saline-alkali land according to claim 1, characterized in that: The organosilicon-humic acid composite comprises, by mass percentage: 70-78% humic acid, 20-30% epoxy-modified polymethylsiloxane, and 2-4% nano-SiO2.

5. The organosilicon functional compound fertilizer for long-term improvement of saline-alkali land according to claim 1, characterized in that, The components of the compound fertilizer, by mass percentage, include: 30-35% nitrogen-phosphorus-potassium compound fertilizer, 12-15% epoxy-modified polymethylsiloxane, 4.5-6% polybutylene succinate, 8-10% sodium alginate-bacterial microcapsules, 20-25% humic acid, 7-10% organosilicon-modified starch, 3-5% cross-linked organic resin, and 5-8% zeolite.

6. The method for preparing the organosilicon functional compound fertilizer capable of long-term improvement of saline-alkali land according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Three-layer encapsulated microbial microcapsules; S11: Mix the salt-tolerant bacterial agent with sodium alginate solution and stir at low speed to obtain a mixture; add the mixture dropwise to 0.18 mol / L CaCl2 solution and stir magnetically to solidify and form gel microspheres; transfer the microspheres to 0.3 mol / L CaCl2 solution and continue to stir magnetically to solidify for 10 min; finally, transfer the microspheres to a chitosan solution with 1% acetic acid by mass and gently stir for 15 min; wash the microcapsules with sterile water to obtain sodium alginate-bacterial agent gel microspheres. S12: Dissolve PLGA in dichloromethane at 4℃, add activated humic acid powder first, then add 0.5% (w / w) of triethyl citrate plasticizer, and ultrasonically disperse for 10 min to prepare a 5% (w / w) PLGA-humic acid solution; immerse the sodium alginate-bacterial agent gel microspheres prepared in S11 into the PLGA-humic acid solution for 30 s, drain, and then dry and solidify to obtain PLGA-humic acid coated microspheres; S13: Zeolite powder was mixed with KH-550 silane coupling agent and reacted at 75℃ for 2 hours under pH=5 conditions to prepare a silanized zeolite suspension; then the microspheres prepared in S12 were placed in a fluidized bed and coated with the silanized zeolite suspension; finally, the coated microcapsules were vacuum dried at 40℃ until the water content was ≤5% to prepare microbial microcapsules with a three-layer coating process. S2: Synthesis of organosilicon-humic acid complex; S21: Add humic acid to a nitrogen-filled reactor, add deionized water at a solid-liquid ratio of 1:3, and stir to prepare a homogeneous humic acid suspension. S22: Slowly add epoxy-modified polymethylsiloxane to the humic acid suspension prepared in S21, then heat to 80°C and stir to form a viscous mixture; S23: Nano-SiO2 was added to the reaction system in three portions. The nano-SiO2 was treated with KH-550 at a mass fraction of 0.1%, with each portion spaced 10 minutes apart. The temperature was maintained at 80°C, and the reaction was stirred for 2 hours at a stirring rate of 400 rpm. Finally, heating was stopped, and the mixture was cooled to below 40°C. The gel was then transferred to a crusher and pulverized at 10°C through a 100-mesh sieve to prepare the organosilicon-humic acid composite. S3: Four-stage concentric granulation; S31: Preheat the nitrogen, phosphorus and potassium compound fertilizer to 55℃; then spray a 5% MgCl2 solution, while rolling magnesium ammonium phosphate around the surface of the nitrogen, phosphorus and potassium compound fertilizer, and then quickly dry it to form a dense core, thus obtaining core layer particles. S32: PBS particles were added to ethyl acetate at a solid-liquid ratio of 1:

4. The mixture was heated to 50°C in a water bath and magnetically stirred. Then, the microbial microcapsules prepared in S13 were added and the temperature was maintained at 40°C. The mixture was homogenized to form a uniform suspension, followed by ultrasonic treatment to prepare a PBS-ethyl acetate suspension. The core layer particles prepared in S31 were transferred to a fluidized bed and preheated at 40°C for 10 minutes. Then, the PBS-ethyl acetate suspension was sprayed onto the core particles to form a porous propagation carrier. Finally, the particles were dried with hot air to form a uniform porous structure on the surface of the core particles, resulting in particles coated with the propagation layer. S33: Mix pregelatinized starch with deionized water, stir and gelatinize at 60℃ for 30 min, then add KH-550 diluted with ethanol 1:1 dropwise, react at 65℃ for 2 h, and finally spray dry to prepare organosilicon modified starch. The organosilicon-humic acid composite prepared by S23 and organosilicon-modified starch were added to an ethanol aqueous solution, stirred in a water bath, and then processed by a homogenizer to obtain a non-agglomerated slurry with a solid content controlled at 40%. The particles coated with the propagation layer prepared by S32 were preheated at 55°C for 10 min, then coated with the slurry, and finally cured and dried in a stepwise manner to obtain particles coated with a stable layer. S34: Slowly add cross-linked silicone resin to ethanol, control the temperature ≤30℃, stir until completely dissolved, add DBTL, and ultrasonically disperse to obtain a homogeneous resin solution; use an ionizer to eliminate static electricity on the particle surface of the particles coated with the stabilizing layer prepared in S33, and then perform high-pressure spraying of the resin solution; finally, perform step-by-step thermosetting to obtain particles coated with a salt barrier layer. S4: Processing and Packaging. The granules prepared by S34 are dried in a fluidized bed at 40°C for 30 min and then cooled to 20°C. Polyurethane resin and diatomaceous earth are added to an ethanol solution to prepare an ethanol solution with a solid content of 25%. The granules coated with the salt barrier layer prepared by S34 are coated with an outermost layer using a polyurethane coating machine. The spray solution is an ethanol solution with a solid content of 25%, and the mixture is dried at 40°C for 10 min to prepare an organosilicon functional compound fertilizer.

7. The method for preparing an organosilicon functional compound fertilizer capable of long-term improvement of saline-alkali land according to claim 6, characterized in that: The salt-tolerant bacterial agent and sodium alginate solution described in S11 have a mass-to-volume ratio of 1:2.5 to 1:3.5, wherein the concentration of sodium alginate solution is 2%. The low-speed stirring described in S11 has the following parameter settings: 300 rpm for 10 min. The magnetic stirring curing described in S11 has the following parameter settings: rotation speed 100 rpm, duration 10 min; The mass ratio of PLGA to humic acid described in S12 is 2.5:1 to 3.5:

1. The drying and curing process described in S12 has the following parameter settings: primary curing temperature 50℃, duration 10min; secondary curing temperature 45℃, duration 10min. The KH-550 silane coupling agent described in S13 is 1.5 to 2% of the zeolite powder by mass; The fluidized bed described in S13 has the following parameter settings: inlet air temperature 50-55℃, atomization pressure 0.2MPa.

8. The method for preparing an organosilicon functional compound fertilizer capable of long-term improvement of saline-alkali land according to claim 6, characterized in that: The stirring described in S21 has the following parameters: temperature 60℃, duration 30min, and stirring speed 300rpm. The stirring described in S22 has the following parameters: stirring speed 200 rpm, duration 40 min.

9. The method for preparing an organosilicon functional compound fertilizer capable of long-term improvement of saline-alkali land according to claim 6, characterized in that: The rapid drying described in S31 has the following parameter settings: temperature 300℃, duration 50min; The magnetic stirring described in S32 has the following parameter settings: duration 30 min, stirring speed 300 rpm; The homogenizer described in S32 has the following parameter settings: rotation speed 9000~11000rpm, duration 5~10min; The ultrasonic treatment described in S32 has the following parameter settings: 35-45kHz, duration 8-12min; The spraying described in S32 has the following parameter settings: spray gun pressure 0.2MPa, spraying rate 20mL / min, and atomizing air flow rate 15L / min; The hot air drying described in S32 has the following parameter settings: inlet air temperature 40℃, air velocity 1.5m / s, and duration 25min.

10. The method for preparing an organosilicon functional compound fertilizer capable of long-term improvement of saline-alkali land according to claim 6, characterized in that: The organosilicon-modified starch described in S33 is prepared with a mass ratio of pregelatinized starch, KH-550, and deionized water of 50:3:

100. The ethanol-water solution described in S33 has a volume ratio of ethanol to water of 6:

4. The water bath stirring described in S33 has the following parameters: temperature 45℃, duration 20min, stirring speed 500rpm. The homogenizer described in S33 has the following parameter settings: rotation speed 8000 rpm, duration 3 min; The coating described in S33 has the following parameter settings: rotation speed 65 r / min, spray gun pressure 0.15 MPa, slurry feed rate 15 mL / kg·min, and hot air temperature 60℃. The stepped curing and drying described in S33 has the following parameter settings: the first stage is 60℃ hot air drying for 15 minutes, and the second stage is 65℃ constant temperature for 25 minutes. The ultrasonic dispersion described in S34 has the following parameter settings: frequency 40kHz, duration 10min; The high-pressure spraying described in S34 has the following parameter settings: spraying pressure 0.35MPa, wind speed 1.2m / s, base coat coverage 60%, and top coat coverage 40%. The stepped thermosetting process described in S34 has the following parameter settings: pre-curing temperature 40℃, duration 5min; main curing temperature 60℃, duration 30min; curing temperature 25℃, duration 12h.

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