Compound fertilizer with nitrogen fertilizer slow-release and biocontrol functions and preparation method thereof

Abstract

The application discloses a kind of compound fertilizer with nitrogen fertilizer slow-release and biocontrol function and preparation method, it is related to microbial compound fertilizer field, including the following components: nitrogen source carrier, physical net trapping material, 3,4-dimethyl pyrazole phosphate, biocontrol component, binder.A kind of preparation method, including the following steps: after silanization modification treatment is carried out to attapulgite, with polyglutamic acid aqueous solution mixed reaction, obtain self-assembly gel;Bacillus subtilis is embedded and handled, rhamnolipid is pre-emulsified, chitosan oligosaccharide is crosslinked with boric acid treatment, and is blended;Nitrogen source carrier is heated to melt, add self-assembly gel, mix evenly;Temperature control, add 3,4-dimethyl pyrazole phosphate, and keep warm reaction;Cooling, add the blend obtained in step S200, binder, mix evenly;Extrusion granulation, after fluidized bed drying, slow-release coating is carried out, and the target compound fertilizer is obtained.The application makes disease control efficiency to improve to 89.2%, and blocks nitrosomonas AMO enzyme activity for 120 days.

Description

Technical Field

[0001] This invention relates to the field of microbial compound fertilizer technology, specifically to a compound fertilizer with both slow-release nitrogen fertilizer and biocontrol functions, and its preparation method. Background Technology

[0002] In China's agricultural production, the application of quick-acting nitrogen fertilizers such as urea accounts for more than 55% of the total amount of chemical fertilizers. However, the loss of ammonia volatilization in paddy fields is as high as 24-45%, and the area of ​​groundwater pollution exceeding the standard caused by nitrate nitrogen leaching reaches 150 million mu.

[0003] Traditional technologies mainly use physical slow-release methods such as sulfur coating and resin coating to delay nitrogen release, but they have the following problems: sulfur coatings decompose rapidly under flooded conditions and lack the ability to inhibit soil microbial nitrification, thus failing to block the biological transformation chain from ammonium nitrogen to nitrate nitrogen.

[0004] The nitrification inhibition effect is unsatisfactory. First-generation chemical inhibitors, represented by dicyandiamide (DCD), can inhibit the activity of nitrifying monocytogenes, but their half-life is only 5-7 days, and high-dose application leads to soil acidification. Second-generation specific inhibitors, such as DMPP (3,4-dimethylpyrazole phosphate), achieve targeted inhibition through competitive binding to ammonia monooxygenase (AMO), but have significant drawbacks: temperature dependence (effective for approximately 28 days at 25℃, with inhibition decreasing by 50% above 30℃); lack of physical protection mechanisms, resulting in over 40% loss through runoff after rainfall.

[0005] In current agricultural production, disease control relies on chemical pesticides, which are applied separately from fertilizers. This results in a survival rate of less than 15% for Bacillus subtilis in the highly permeable environment of chemical fertilizers. The peak nutrient demand of crops overlaps with the disease outbreak period, but applying pesticides in multiple applications increases labor costs by more than 30%. Although "pesticide-fertilizer mixtures" have appeared on the market, they are mostly physical mixtures. While saponins isolated from sorghum roots have the potential to inhibit nitrification, their extraction cost is high, making industrialization difficult.

[0006] In summary, there is an urgent need to develop a synergistic system that integrates physical preservation, chemical inhibition, and biological regulation into a triple slow-release mechanism, and can form multiple biocontrol functions such as microbial antagonism, metabolite inhibition, and plant immune activation, so as to fundamentally break through the bottleneck of nitrogen fertilizer utilization efficiency. Summary of the Invention

[0007] The purpose of this invention is to provide a compound fertilizer that combines slow-release nitrogen fertilizer and biocontrol functions, as well as a preparation method thereof, thereby improving the problem of the separation of fertilizer and biocontrol agent functions in existing compound fertilizers.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A compound fertilizer that combines slow-release nitrogen fertilizer and biocontrol functions, comprising the following components by weight:

[0010] Nitrogen source carrier: 70-85 parts, physical netting material: 15-25 parts, 3,4-dimethylpyrazole phosphate: 0.1-1 parts, biocontrol component: 2.3-13 parts, adhesive: 0.5-3 parts;

[0011] The nitrogen source carrier includes urea: 53-64 parts, ammonium sulfate: 17-21 parts; the biocontrol components include Bacillus subtilis: 0.3-2 parts, Bacillus subtilis metabolites: 1-5 parts, chitosan oligosaccharide: 0.5-3 parts, and rhamnolipid: 0.5-3 parts.

[0012] The physical trapping material includes silanized modified attapulgite-polyglutamic acid complex gel; the Bacillus subtilis metabolite is a concentrated powder of antibacterial substances extracted through liquid fermentation, with a surfactant content ≥15%.

[0013] The silanized modified attapulgite-polyglutamic acid gel of this invention forms a pH-responsive network. At pH > 7, the swelling ratio is 3.0-3.5 (volume expansion of 300-350%), and the release of NH4 is controlled through electrostatic adsorption and pore size retention. + DMPP is embedded in the gel pores, with a retention rate of >85% in dryland soils (>75% in paddy fields) after 60 days, significantly inhibiting DMPP loss. The Bacillus subtilis metabolites (antimicrobial lipopeptide concentrate extracted by in vitro fermentation) contain ≥15% surfactant and ≥8% iturin A, taking effect within 2 hours of application to ensure early control efficacy; after colonization, the live bacteria continuously secrete antimicrobial substances for 7 days, and the two work synergistically to shorten the disease control window to 5 days; DMPP blocks AMO enzyme activity, and the metabolites inhibit bacterial proliferation, jointly maintaining nitrification inhibition for >120 days.

[0014] This invention utilizes the metabolites of Bacillus subtilis to disrupt the cell membrane of bacteria and DMPP to block AMO enzyme activity, thereby synergistically reducing ammonia volatilization and effectively improving nitrogen utilization. The live bacteria reproduce and secrete iturin to inhibit bacteria, and the metabolites disrupt the cell membrane of pathogens, thus highly improving disease control efficacy. It achieves a three-in-one approach of nitrogen control, antibacterial action, and immune activation, solving the problem of functional separation between fertilizers and biocontrol agents.

[0015] A preparation method, applicable to the preparation of the compound fertilizer with both nitrogen fertilizer slow-release and biocontrol functions, includes the following steps:

[0016] S100. After silanizing modification of attapulgite, it is mixed with polyglutamic acid aqueous solution to obtain gel.

[0017] S200: Bacillus subtilis is encapsulated, rhamnolipin is pre-emulsified, and chitosan oligosaccharide is cross-linked with boric acid and then blended.

[0018] S300: Heat the nitrogen source carrier to melt, add the self-assembled gel, and mix evenly; control the temperature, add 3,4-dimethylpyrazole phosphate, and keep the reaction at the temperature; cool down, add the blend and binder obtained in step S200, and mix evenly.

[0019] After S400 extrusion granulation and fluidized bed drying, slow-release coating is carried out to obtain the target compound fertilizer.

[0020] The silanization modification of attapulgite was carried out using the existing technology CN201110350307.0.

[0021] In the preparation method of this invention, in step S200, Bacillus subtilis is embedded with trehalose-skimmed milk to form a glassy protective layer that resists the osmotic pressure of molten urea; boric acid crosslinks chitosan, increasing the temperature resistance from 60℃ to 130℃; rhamnolipid is pre-emulsified to form a liquid crystal phase, enhancing the dissolution efficiency against fungal cell membranes. The pre-emulsified rhamnolipid acts as a lubricant in blending with the embedded Bacillus subtilis, effectively reducing extrusion pressure, improving cell survival rate, and preventing the embedded cells from rupturing during granulation. In step S300, a three-step temperature control method is used: high-temperature gelation, temperature-controlled addition of DMPP to avoid thermal decomposition; addition of biocontrol components after cooling to ensure activity retention >95%, preventing inactivation of biocontrol components in molten urea; and silanization modification is completed before gel formation, pre-mixing the gel with DMPP to allow DMPP to be chemically adsorbed into the network pores, forming physical protection and achieving a slow-release effect.

[0022] The compound fertilizer prepared by this invention achieves dual controlled release through polylactic acid coating and gel network; the rapid disease prevention effect of metabolites and the long-term disease prevention effect of live bacteria work synergistically, and the crop's disease prevention efficacy can reach 88.9% in 60 days; in addition, it is beneficial to improve the soil, and the gel degradation promotes the formation of aggregates and increases the content of water-stable aggregates in the soil.

[0023] Further, in step S100, the mass ratio of the modified attapulgite to polyglutamic acid is 9~11:1; the relative molecular mass of the polyglutamic acid is 10000~15000 g / mol; the mass fraction of the polyglutamic acid aqueous solution is 25~32%, and the reaction temperature is 55~65℃.

[0024] Further, in step S200, the method for embedding Bacillus subtilis includes the following: adjusting the pH of the embedding solution to 6.8-7.2, sterilizing it, mixing it with Bacillus subtilis, shaking it at room temperature for 30-35 minutes, and then freeze-drying it.

[0025] The embedding solution comprises the following components by weight: 20-25 parts trehalose, 8-12 parts skim milk powder, 4-6 parts monosodium glutamate, 0.05-0.12 parts ascorbic acid, and 70-75 parts water; the mass ratio of trehalose to Bacillus subtilis cells is 2.8-3.2:1.

[0026] Further, the sterilization conditions are: temperature 120~125℃, time 15~20min; after cooling to 20~25℃, add Bacillus subtilis dry cells.

[0027] Further, in step S200, the chitosan oligosaccharide is cross-linked with a 0.09-0.11 wt% boric acid solution, and the rhamnolipid is pre-emulsified with water at a mass ratio of 2.5-3.5:1, and then mixed with the embedded bacterial cells and the cross-linked chitosan oligosaccharide.

[0028] Further, in step S300, the nitrogen source carrier is heated to 130~135℃, the gel is added, and the mixture is stirred for 8~12 min; at 60~70℃, 3,4-dimethylpyrazole phosphate is added, and the reaction is maintained for 10~15 min; the temperature is lowered to 40~50℃, and the Bacillus subtilis metabolites, the blend obtained in step S200, and the binder are added and mixed evenly.

[0029] Furthermore, in step S400, the particle size of the compound fertilizer obtained by extrusion granulation is 2~3mm, and the temperature of fluidized bed drying is 35~50℃.

[0030] Further, in step S400, the method for sustained-release coating includes the following: dissolving polylactic acid in dichloromethane to prepare a solution, adding tributyl citrate and mixing evenly, and spraying a film thickness of 45~55μm; the inlet air temperature is 38~42℃ and the atomization pressure is 0.65~0.75MPa.

[0031] Furthermore, the mass ratio of polylactic acid to compound fertilizer is 0.5~0.7:100, the solid-liquid ratio of polylactic acid to dichloromethane is 7.5~8.5:100, and the mass ratio of polylactic acid to tributyl citrate is 100:1~1.5.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] This invention utilizes a silanized gel network to encapsulate DMPP and employs physical adsorption to effectively reduce ammonia volatilization loss and improve nitrogen utilization efficiency, meeting the nitrogen requirements of crops at different stages of their growth cycle. The synergistic effect of live bacteria encapsulation and metabolites increases disease control efficacy to 89.9% over 60 days and blocks AMO enzyme activity in Nitrosomonas for up to 120 days. This compound fertilizer is suitable for use in field crops such as corn and rice.

[0034] DMPP: 3,4-Dimethylpyrazole phosphate. Detailed Implementation

[0035] Example 1

[0036] The embedding solution comprises the following components: 22g trehalose, 10g skim milk powder, 5g monosodium glutamate, 0.1g ascorbic acid, and 72g water; the mass ratio of trehalose to Bacillus subtilis cells is 3:1.

[0037] The method for embedding Bacillus subtilis includes the following steps: adjusting the pH of the embedding solution to 7, setting the temperature to 123℃, and the time to 18 min; cooling to 22℃, mixing thoroughly with Bacillus subtilis, and adsorbing by shaking at room temperature for 33 min; drying at 4℃ for 1 h, drying at -20℃ for 2 h, and quick-freezing at -40℃ for 5 min.

[0038] Example 2

[0039] The embedding solution comprises the following components: 20g trehalose, 8g skim milk powder, 4g monosodium glutamate, 0.05g ascorbic acid, and 70g water; the mass ratio of trehalose to Bacillus subtilis cells is 2.8:1.

[0040] The method for embedding Bacillus subtilis includes the following steps: adjusting the pH of the embedding solution to 6.8, setting the temperature to 120℃, and the time to 15 min; cooling to 20℃, mixing thoroughly with Bacillus subtilis, and adsorbing by shaking at room temperature for 30 min; drying at 4℃ for 1 h, drying at -20℃ for 2 h, and quick-freezing at -40℃ for 5 min.

[0041] Example 3

[0042] The embedding solution comprises the following components: 25g trehalose, 12g skim milk powder, 6g monosodium glutamate, 0.12g ascorbic acid, and 75g water; the mass ratio of trehalose to Bacillus subtilis cells is 3.2:1.

[0043] The method for embedding Bacillus subtilis includes the following steps: adjusting the pH of the embedding solution to 7.2, setting the temperature to 125℃, and the time to 20 min; cooling to 25℃, mixing thoroughly with Bacillus subtilis, and adsorbing by shaking at room temperature for 35 min; drying at 4℃ for 1 h, drying at -20℃ for 2 h, and quick-freezing at -40℃ for 5 min.

[0044] Comparative Example 1

[0045] Live Bacillus subtilis bacteria that have not undergone encapsulation treatment.

[0046] The viable counts of Bacillus subtilis in Examples 1-3 and Comparative Example 1 were ≥5 × 10⁻⁶. 10 CFU / g.

[0047] Table 1 shows the encapsulation effect parameters of Bacillus subtilis in Examples 1-3 and Comparative Example 1.

[0048] Table 1. Parameters of Bacillus subtilis encapsulation effect in Examples 1-3

[0049] Test Project Example 1 Example 2 Example 3 Comparative Example 1 Molten urea tolerance (survival rate at 130℃ / 10min) 96.2% 94.8% 97.1% 11.5% Granulation pressure survival rate (50MPa extrusion) 90.3% 88.7% 91.5% 36.2% Survival rate after 6 months of storage (sealed at 40°C) 84.5% 82.1% 85.9% 4.3% Rhizosphere colonization rate (CFU / g soil, 30 days after sowing) <![CDATA[2.3×10 7 ]]> <![CDATA[1.9×10 7 ]]> <![CDATA[2.6×10 7 ]]> <![CDATA[3.1×10 5 ]]> Efficacy of sheath blight control (60 days) 87.3% 85.4% 88.1% 45.6% Soil Iturin concentration (μg / g) 15.7 13.2 16.9 0.8

[0050] As shown in Table 1, after encapsulating Bacillus subtilis with trehalose and skim milk powder in Examples 1-3 of this invention, the survival rate of Bacillus subtilis at 130℃ / 10min during compound fertilizer preparation reached 97.1%, significantly higher than the 11.5% survival rate of unencapsulated Bacillus subtilis in Comparative Example 1; the survival rate at 50MPa granulation pressure reached 91.5%, significantly higher than the 36.2% of Comparative Example 1; the survival rate after 6 months of sealed storage at 40℃ reached 85.9%, significantly higher than the 4.3% of Comparative Example 1; and the rhizosphere colonization rate 30 days after sowing was 1.9~2.6×10⁻⁶. 7 It is significantly better than the 3.1 × 10⁻⁶ of Comparative Example 1. 5 .

[0051] When the Bacillus subtilis treated with the embedding method in Examples 1-3 was applied to corn fields, the control efficacy against sheath blight was 85.4%-88.1% after 60 days, significantly higher than the 45.6% of the control group. This indicates that the embedded bacteria continuously secrete Iturin A in the rhizosphere, inhibiting the mycelial fusion of the pathogen. During the testing period, the soil Iturin A concentration remained at 13.2-16.9 μg / g, significantly higher than the 0.8 μg / g of control group 1.

[0052] Example 4

[0053] A compound fertilizer that combines slow-release nitrogen fertilizer and biocontrol functions comprises the following components:

[0054] Nitrogen source carrier: 780g, physical netting material: 200g, 3,4-dimethylpyrazole phosphate: 0.6g, biocontrol component: 80g, binder: 18g;

[0055] The nitrogen source carrier includes urea: 600g, ammonium sulfate: 180g; the biocontrol components include Bacillus subtilis BS-5: 12g, Bacillus subtilis metabolites: 30g, chitosan oligosaccharide: 20g, and rhamnolipid RL-02: 18g.

[0056] Physical trapping materials include silanized modified attapulgite-polyglutamic acid complex gel.

[0057] The Bacillus subtilis metabolite is a concentrated powder of antibacterial substances extracted through liquid fermentation, with a surfactant content of 18%.

[0058] A preparation method, applicable to the preparation of the compound fertilizer with both nitrogen fertilizer slow-release and biocontrol functions, is characterized by comprising the following steps:

[0059] S100, silanized modified attapulgite clay and polyglutamic acid aqueous solution are mixed at a mass ratio of 10:1 and reacted at 60℃ to obtain a self-assembled gel; the relative molecular mass of polyglutamic acid is 12000 g / mol; the mass fraction of the polyglutamic acid aqueous solution is 28%.

[0060] S200. Bacillus subtilis was encapsulated according to the method of Example 1. Chitosan oligosaccharide was cross-linked with 0.1 wt% boric acid. Rhamnollipid was pre-emulsified with water at a mass ratio of 3:1 and then mixed with the encapsulated bacterial cells and cross-linked chitosan oligosaccharide.

[0061] S300: Heat the nitrogen source carrier to 132°C, add the self-assembled gel, and stir for 10 min; at 65°C, add 3,4-dimethylpyrazole phosphate and keep the reaction temperature for 12 min; cool to 45°C, add Bacillus subtilis metabolites, the blend obtained in step S200, and binder, and mix evenly.

[0062] The compound fertilizer obtained by S400 extrusion granulation has a particle size of 2.5 mm, and the fluidized bed drying temperature is 43℃.

[0063] Sustained-release coating: Polylactic acid is dissolved in dichloromethane to prepare a solution, and tributyl citrate is added and mixed evenly. The coating thickness is 50μm; the inlet air temperature is 40℃ and the atomization pressure is 0.7MPa.

[0064] The mass ratio of polylactic acid to compound fertilizer is 0.6:100, the solid-liquid ratio of polylactic acid to dichloromethane is 8:100, and the mass ratio of polylactic acid to tributyl citrate is 100:1.2.

[0065] Example 5

[0066] A compound fertilizer that combines slow-release nitrogen fertilizer and biocontrol functions comprises the following components:

[0067] Nitrogen source carrier: 700g, physical netting material: 150g, 3,4-dimethylpyrazole phosphate: 1g, biocontrol component: 23g, binder: 5g;

[0068] The nitrogen source carriers include urea: 530g and ammonium sulfate: 170g; the biocontrol components include Bacillus subtilis BS-5: 3g, Bacillus subtilis metabolites: 1g, chitosan oligosaccharide: 5g, and rhamnolipid RL-02: 5g.

[0069] Physical trapping materials include silanized modified attapulgite-polyglutamic acid complex gel.

[0070] The Bacillus subtilis metabolite is a concentrated powder of antibacterial substances extracted through liquid fermentation, with a surfactant content of 15%.

[0071] A preparation method, applicable to the preparation of the compound fertilizer with both nitrogen fertilizer slow-release and biocontrol functions, is characterized by comprising the following steps:

[0072] S100, silanized modified attapulgite clay and polyglutamic acid aqueous solution are mixed at a mass ratio of 9:1 and reacted at 55℃ to obtain a self-assembled gel; the relative molecular mass of polyglutamic acid is 10000 g / mol; the mass fraction of the polyglutamic acid aqueous solution is 25%;

[0073] S200. Bacillus subtilis was encapsulated according to the method of Example 1. Chitosan oligosaccharide was cross-linked with 0.1 wt% boric acid. Rhamnolliposide was pre-emulsified with water at a mass ratio of 2.5:1 and then mixed with the encapsulated bacterial cells and cross-linked chitosan oligosaccharide.

[0074] S300: Heat the nitrogen source carrier to 130°C, add the self-assembled gel, and stir for 8 min; at 60°C, add 3,4-dimethylpyrazole phosphate, and keep the reaction at this temperature for 10 min; cool to 40°C, add Bacillus subtilis metabolites, the blend obtained in step S200, and the binder, and mix thoroughly.

[0075] The particle size of the compound fertilizer obtained by S400 extrusion granulation is 2mm, and the fluidized bed drying temperature is 35℃.

[0076] Sustained-release coating: Polylactic acid is dissolved in dichloromethane to prepare a solution, and tributyl citrate is added and mixed evenly. The coating thickness is 45μm; the inlet air temperature is 38℃ and the atomization pressure is 0.65MPa.

[0077] The mass ratio of polylactic acid to compound fertilizer is 0.5:100, the solid-liquid ratio of polylactic acid to dichloromethane is 7.5:100, and the mass ratio of polylactic acid to tributyl citrate is 100:1.

[0078] Example 6

[0079] A compound fertilizer that combines slow-release nitrogen fertilizer and biocontrol functions comprises the following components:

[0080] Nitrogen source carrier: 850g, physical netting material: 250g, 3,4-dimethylpyrazole phosphate: 10g, biocontrol component: 130g, binder: 30g;

[0081] The nitrogen source carrier includes urea: 640g, ammonium sulfate: 210g; the biocontrol components include Bacillus subtilis BS-5: 20g, Bacillus subtilis metabolites: 50g, chitosan oligosaccharide: 30g, and rhamnolipid RL-02: 30g.

[0082] Physical trapping materials include silanized modified attapulgite-polyglutamic acid complex gel.

[0083] The Bacillus subtilis metabolite is a concentrated powder of antibacterial substances extracted through liquid fermentation, with a surfactant content of 20%.

[0084] A preparation method, applicable to the preparation of the compound fertilizer with both nitrogen fertilizer slow-release and biocontrol functions, is characterized by comprising the following steps:

[0085] S100, silanized modified attapulgite clay and polyglutamic acid aqueous solution were mixed at a mass ratio of 11:1 and reacted at 65℃ to obtain a self-assembled gel; the relative molecular mass of polyglutamic acid was 15000 g / mol; the mass fraction of the polyglutamic acid aqueous solution was 32%.

[0086] S200. Bacillus subtilis was encapsulated according to the method of Example 1. Chitosan oligosaccharide was cross-linked with 0.1 wt% boric acid. Rhamnolliposide was pre-emulsified with water at a mass ratio of 3.5:1 and then mixed with the encapsulated bacterial cells and cross-linked chitosan oligosaccharide.

[0087] S300: Heat the nitrogen source carrier to 135°C, add the self-assembled gel, and stir for 12 min; at 70°C, add 3,4-dimethylpyrazole phosphate and keep the reaction at this temperature for 15 min; cool to 50°C, add Bacillus subtilis metabolites, the blend obtained in step S200, and the binder, and mix thoroughly.

[0088] The particle size of the compound fertilizer obtained by S400 extrusion granulation is 3mm, and the fluidized bed drying temperature is 50℃.

[0089] Sustained-release coating: Polylactic acid is dissolved in dichloromethane to prepare a solution, and tributyl citrate is added and mixed evenly. The coating thickness is μm; the inlet air temperature is 42℃ and the atomization pressure is 0.75MPa.

[0090] The mass ratio of polylactic acid to compound fertilizer is 0.7:100, the solid-liquid ratio of polylactic acid to dichloromethane is 8.5:100, and the mass ratio of polylactic acid to tributyl citrate is 100:1.5.

[0091] In Examples 4-6, the method for cross-linking chitosan oligosaccharides with boric acid includes the following steps:

[0092] Step 1: Raw material preparation: Prepare a 10% (w / v) aqueous solution of chitosan oligosaccharide, a 0.1wt% aqueous solution of boric acid, and a 0.5mol / L strong oxidizing agent;

[0093] Step 2: Add 0.1wt% boric acid solution to the chitosan oligosaccharide solution at a volume ratio of 1:1, add sodium hydroxide to adjust the pH to 8.5~9.0, and shake in a water bath at 45±2℃ for 90 min.

[0094] Comparative Example 2

[0095] In Example 4, the physical trapping material was replaced with an equal amount of ordinary bentonite. Other components, parameters, and preparation methods were the same as in Example 4.

[0096] Comparative Example 3

[0097] The 3,4-dimethylpyrazole phosphate was omitted, and Bacillus subtilis BS-5 was increased to 18g. Other components, parameters, and preparation methods were consistent with those in Example 4.

[0098] Comparative Example 4

[0099] In step S300 of the preparation method, the biocontrol component is added directly at 132°C. Other components, parameters and preparation methods are the same as in Example 4.

[0100] The performance parameters of the compound fertilizers prepared in Examples 4-6 and Comparative Examples 2-5 for corn planting (calcareous brown soil) are shown in Table 2.

[0101] Table 2 Performance parameters of the compound fertilizers prepared in Examples 4-6 and Comparative Examples 2-5 for corn planting

[0102] parameter Example 4 Example 5 Example 6 Comparative Example 2 Comparative Example 3 Comparative Example 4 Ammonia volatilization loss (kg / ha) 10.2 12.4 9.8 28.7 15.8 11.3 Nitrogen utilization rate (%) 78.3 75.6 80.1 41.3 63.7 70.1 Sheath blight control efficacy (28 days, %) 91.2 90.1 92.6 70.3 65.5 83.2 Sheath blight control efficacy (60 days, %) 88.4 87.3 88.9 35.2 43.1 47.4 Sheath blight control efficacy (120 days, %) 81.2 80.1 85.2 12.4 15.1 14.2 Biocontrol component activity retention rate (%) 97 95 98 97 97 42 Nitrate nitrogen leaching loss (kg / ha) 15.1 17.5 14.3 44.2 24.3 18.9 Soil pH fluctuation (Δ) 0.15 0.18 0.13 0.52 0.25 0.20

[0103] As shown in Table 2, the compound fertilizers prepared in Examples 4-6 were used for field corn planting.

[0104] Examples 4-6 employ alkylated gels and silanized gels to adsorb NH4. + >90%, pH-responsive swelling and delayed release reduced ammonia volatilization loss to 9.8 kg / ha, and nitrogen utilization increased to over 75%; in Comparative Example 2, replacing the alkylated gel with ordinary bentonite increased ammonia volatilization loss to 28.7-9.8 kg / ha, resulting in low nitrogen utilization of only 41.3%.

[0105] Examples 4-6 used alkylated gels with DMPP embedded in the gel pores, synergistically inhibiting nitrifying bacteria with their metabolites. The control efficacy against sheath blight (28 days) was ≥90%, and the control efficacy against sheath blight (60 days) was ≥87%. In Comparative Example 2, ordinary bentonite failed to form a three-dimensional network, preventing DMPP from embedding in the pores and leading to easy loss. Initially, the exposed DMPP could inhibit nitrification along with the metabolites, but after 20 days, the DMPP was almost completely lost, resulting in a control efficacy against sheath blight (28 days) of only 70.3%. By 60 days, only the metabolites secreted by the implanted Bacillus subtilis were used for nitrification inhibition, resulting in a control efficacy against sheath blight (60 days) of only 35.2%.

[0106] In Comparative Example 3, without DMPP, only the amount of Bacillus subtilis BS-5 was increased. At the time of 28 days of sheath blight control efficacy, only the metabolites secreted by Bacillus subtilis inhibited nitrification, resulting in a control efficacy of only 65.5% at 28 days. At 60 days, only the metabolites secreted by the implanted Bacillus subtilis inhibited nitrification, resulting in a control efficacy of only 43.1% at 60 days.

[0107] In Comparative Example 4, in step S300 of the preparation method, the biocontrol component was directly added at 132℃, which resulted in the high temperature killing of Bacillus subtilis metabolites and Bacillus subtilis. Initially, nitrification inhibition was achieved by DMPP and residual Bacillus subtilis secreted metabolites. Due to the embedding of DMPP into the gel pores, at 28 days, DMPP and its metabolites inhibited nitrifying bacteria, maintaining 83.2%. At 60 days, due to the low survival rate of Bacillus subtilis during implantation, the metabolites decreased sharply, and the residual DMPP inhibited nitrifying bacteria, resulting in a disease control efficacy of only 47.4% (at 60 days).

[0108] In this invention, the efficacy against sheath blight is still >80% after 120 days.

[0109] Examples 4-6 employ a gradient cooling process to add biocontrol components, resulting in a biocontrol component activity retention rate >95%, while in Comparative Example 4, the high-temperature addition resulted in a biocontrol component activity retention rate of only 42%.

[0110] Examples 4-6 achieved a dual blocking effect of gel-DMPP embedded gel network and metabolite antibacterial activity, reducing nitrate leaching loss in the nitrification chain to as low as 14.3-17.5 kg / ha; soil pH fluctuation was as low as 0.13, significantly better than comparative examples 2-4.

[0111] In this invention, the gel-DMPP embedded gel network, Bacillus subtilis metabolites, Bacillus subtilis live bacteria encapsulation, and the addition of biocontrol components through gradient cooling synergistically ensure that the compound fertilizer of this invention achieves a triple slow-release mechanism of physical preservation, chemical inhibition, and biological regulation, and can form a synergistic system with multiple biocontrol functions such as microbial antagonism, metabolite antibacterial activity, and plant immune activation.

Claims

1. A compound fertilizer that combines slow-release nitrogen fertilizer and biocontrol functions, characterized in that, By weight, it includes the following components: Nitrogen source carrier: 70-85 parts, physical netting material: 15-25 parts, 3,4-dimethylpyrazole phosphate: 0.1-1 parts, biocontrol component: 2.3-13 parts, adhesive: 0.5-3 parts; The nitrogen source carrier includes urea: 53-64 parts, ammonium sulfate: 17-21 parts; the biocontrol components include Bacillus subtilis: 0.3-2 parts, Bacillus subtilis metabolites: 1-5 parts, chitosan oligosaccharide: 0.5-3 parts, and rhamnolipid: 0.5-3 parts. The physical trapping material includes silanized modified attapulgite-polyglutamic acid complex gel; the Bacillus subtilis metabolite is a concentrated powder of antibacterial substances extracted through liquid fermentation, with a surfactant content ≥15%; A preparation method, applicable to the preparation of the compound fertilizer with both nitrogen fertilizer slow-release and biocontrol functions, includes the following steps: S100. After silanizing modification of attapulgite, it is mixed with polyglutamic acid aqueous solution to obtain gel. S200: Bacillus subtilis is encapsulated, rhamnolipin is pre-emulsified, and chitosan oligosaccharide is cross-linked with boric acid and then blended. S300: Heat the nitrogen source carrier to melt, add the gel, and mix evenly; control the temperature, add 3,4-dimethylpyrazole phosphate, and keep the reaction at the temperature; cool down, add Bacillus subtilis metabolites, the blend obtained in step S200, and the binder, and mix evenly. After S400 extrusion granulation and fluidized bed drying, slow-release coating is carried out to obtain the target compound fertilizer.

2. The compound fertilizer according to claim 1, characterized in that, In step S100, the mass ratio of modified attapulgite to polyglutamic acid is 9~11:1; the relative molecular mass of the polyglutamic acid is 10000~15000 g / mol; the mass fraction of the polyglutamic acid aqueous solution is 25~32%; and the reaction temperature is 55~65℃.

3. The compound fertilizer according to claim 1, characterized in that, In step S200, the method for embedding Bacillus subtilis includes the following steps: adjusting the pH of the embedding solution to 6.8-7.2, sterilizing it, mixing it with Bacillus subtilis, shaking it at room temperature for 30-35 minutes, and then freeze-drying it. The embedding solution comprises the following components by weight: 20-25 parts trehalose, 8-12 parts skim milk powder, 4-6 parts monosodium glutamate, 0.05-0.12 parts ascorbic acid, and 70-75 parts water; the mass ratio of trehalose to Bacillus subtilis cells is 2.8-3.2:

1.

4. The compound fertilizer according to claim 3, characterized in that, Sterilization conditions: temperature 120~125℃, time 15~20min; after cooling to 20~25℃, add Bacillus subtilis dry cells.

5. The compound fertilizer according to claim 1, characterized in that, In step S200, chitosan oligosaccharide is cross-linked with boric acid solution, rhamnolipid is pre-emulsified with water at a mass ratio of 2.5~3.5:1, and then mixed with the embedded bacterial cells and cross-linked chitosan oligosaccharide.

6. The compound fertilizer according to claim 1, characterized in that, In step S300, the nitrogen source carrier is heated to 130~135℃, and the self-assembled gel is added and stirred for 8~12 min; at 60~70℃, 3,4-dimethylpyrazole phosphate is added and the reaction is kept at this temperature for 10~15 min; the temperature is lowered to 40~50℃, and Bacillus subtilis metabolites, the blend obtained in step S200, and the binder are added and mixed evenly.

7. The compound fertilizer according to claim 1, characterized in that, In step S400, the particle size of the compound fertilizer obtained by extrusion granulation is 2~3mm, and the temperature of fluidized bed drying is 35~50℃.

8. The compound fertilizer according to claim 1, characterized in that, In step S400, the method for sustained-release coating includes the following: dissolving polylactic acid in dichloromethane to prepare a solution, adding tributyl citrate and mixing evenly, and spraying a film thickness of 45~55μm; the inlet air temperature is 38~42℃ and the atomization pressure is 0.65~0.75MPa.

9. The compound fertilizer according to claim 8, characterized in that, The mass ratio of polylactic acid to compound fertilizer is 0.5~0.7:100, the solid-liquid ratio of polylactic acid to dichloromethane is 7.5~8.5:100, and the mass ratio of polylactic acid to tributyl citrate is 100:1~1.5.