Controlled-release nitrogen blended fertilizer and preparation method and application thereof

Abstract

This invention provides a controlled-release nitrogen blended fertilizer, its preparation method, and its application, belonging to the field of organic fertilizer technology. The controlled-release nitrogen blended fertilizer of this invention comprises nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, micronutrient fertilizer, and microbial inoculant. The nitrogen fertilizer has a multi-layered core-shell structure, consisting of a urea core layer, a first coating layer, an intermediate urea interlayer, a second coating layer, and an outer urea layer. This nitrogen fertilizer structure enables a three-stage gradient release of nitrogen, matching the nitrogen requirements of crops throughout their entire growth cycle. The microbial inoculant, composed of Bacillus subtilis and Trichoderma harzianum, has synergistic effects in promoting growth, preventing disease, and activating soil nutrients. This fertilizer is suitable for field crops such as corn, wheat, and rice. A single basal application can significantly improve nitrogen utilization, crop yield, and quality, showing promising application prospects.

Description

Technical Field

[0001] This invention relates to the field of organic fertilizer technology, specifically to a controlled-release nitrogen blended fertilizer, its preparation method, and its application. Background Technology

[0002] Nitrogen fertilizer is a core nutrient for ensuring high and stable yields of grain crops. However, large amounts of nitrogen are lost through ammonia volatilization, leaching, and runoff, leading to environmental problems such as eutrophication of water bodies, soil degradation, and greenhouse gas emissions. To improve nitrogen use efficiency, controlled-release fertilizers are gradually replacing conventional nitrogen fertilizers, but existing controlled-release nitrogen blended fertilizers still have significant technical shortcomings.

[0003] Most current mainstream controlled-release nitrogen fertilizers use a single coating material and a single controlled-release mechanism, resulting in a fixed nitrogen release rate. This makes it difficult to match the dynamic nitrogen requirements of crops throughout their entire growth cycle, often leading to insufficient nitrogen supply during the seedling stage, nutrient deficiency or excessive nutrient loss in the mid-to-late growth stages, thus limiting yield and quality improvement. Furthermore, the coating materials are mainly non-degradable petrochemical resins, which accumulate in the soil over long-term, damaging soil aggregate structure, causing compaction and reduced permeability, forming microplastic pollution, and threatening farmland ecological security.

[0004] Existing blended fertilizer products are mostly simple combinations of readily available nitrogen and ordinary controlled-release nitrogen, lacking gradient release design, and generally not coupled with modified carriers, microbial agents, and biodegradable binding systems, resulting in weak nutrient regulation capabilities and limited functionality. In addition, traditional coating processes are complex and costly, making them difficult to adapt to the simplified, one-time basal application needs of field crops, thus hindering large-scale promotion and application.

[0005] Therefore, developing new controlled-release nitrogen blended fertilizers with adjustable controlled-release properties, biodegradable coatings, and precise matching of nitrogen release with crop nutrient requirements is of great practical significance for improving nitrogen fertilizer utilization, reducing environmental risks, and supporting the development of green agriculture. Summary of the Invention

[0006] The purpose of this invention is to provide a controlled-release nitrogen blended fertilizer, its preparation method, and its application. The controlled-release nitrogen blended fertilizer provided by this invention can achieve nitrogen gradient release, improve fertilizer utilization, and has the effect of improving quality and increasing yield.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a controlled-release nitrogen blended fertilizer, comprising the following raw materials in parts by weight: 35-45 parts nitrogen fertilizer, 10-20 parts phosphate fertilizer, 12-25 parts potassium fertilizer, 1-5 parts micronutrient fertilizer, and 0.5-2 parts microbial agent; the nitrogen fertilizer has a multi-layer encapsulated core-shell structure, consisting of, from the inside out: a urea core layer, a first coating layer, an intermediate urea interlayer, a second coating layer, and an outer urea layer; the first coating layer comprises polyurethane, epoxidized soybean oil, chitosan, and Tween-80; the second coating layer comprises modified starch, polylactic acid, potassium humate, and Tween-80.

[0009] Preferably, the mass ratio of the urea core layer, the intermediate urea interlayer, and the outer urea layer is (2-3):(2-3):(4-6).

[0010] Preferably, the phosphate fertilizer is at least one of monoammonium phosphate and diammonium phosphate.

[0011] Preferably, the potassium fertilizer is at least one of potassium chloride and potassium sulfate.

[0012] Preferably, the micronutrient fertilizer includes at least one of zinc sulfate, borax, magnesium sulfate, and ferrous sulfate.

[0013] Preferably, the microbial agent is composed of Bacillus subtilis XJ8 and Trichoderma harzianum DTZJ0125.

[0014] The present invention also provides a method for preparing the controlled-release nitrogen blended fertilizer according to the above, comprising: sequentially spraying a first coating liquid, urea, a second coating liquid, and urea onto the surface of urea granules to obtain nitrogen fertilizer; and mixing nitrogen fertilizer, phosphate fertilizer, potassium fertilizer, micronutrient fertilizer and microbial agent to obtain controlled-release nitrogen blended fertilizer.

[0015] Preferably, the mass ratio of polyurethane, epoxidized soybean oil, chitosan and Tween-80 in the first coating solution is (30-35):(5-10):(2-4):(0.8-1.2); and the mass ratio of modified starch, polylactic acid, potassium humate and Tween-80 in the second coating solution is (8-12):(5-12):(4-7):(0.8-1.2).

[0016] The present invention also provides an application of the above-mentioned controlled-release nitrogen blended fertilizer in crop cultivation, wherein the crops include corn, wheat, and rice.

[0017] Preferably, the application rate of the controlled-release nitrogen blended fertilizer is 30-50 kg / mu.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention provides a controlled-release nitrogen blended fertilizer, comprising: nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, micronutrient fertilizer, and microbial inoculant; the nitrogen fertilizer has a multi-layered core-shell structure, consisting of, from the inside out: a urea core layer, a first coating layer, an intermediate urea interlayer, a second coating layer, and an outer urea layer; the microbial inoculant is composed of Bacillus subtilis XJ8 and Trichoderma harzianum DTZJ0125.

[0020] This invention provides a nitrogen fertilizer that achieves three-stage nitrogen release: fast-acting, medium-acting, and long-acting. In the early stage, it meets the needs of greening and seedling emergence; in the middle stage, it supports vegetative growth; and in the later stage, it ensures grain filling and fruit setting. It does not cause nutrient deficiency or excessive release throughout the entire process, significantly reducing ammonia volatilization, leaching, and runoff losses. This can significantly improve fertilizer utilization. The controlled-release cycle covers the entire growth period of crops, reducing the need for topdressing. The microbial inoculant also has the functions of inhibiting bacteria and preventing diseases, activating nutrients, promoting root growth and strengthening plants, and improving soil, thereby increasing crop yield and quality.

[0021] The controlled-release nitrogen blended fertilizer of this invention releases nitrogen stably under static water conditions at 25℃, with no explosive release in the early stage and sufficient supply in the middle and late stages; field application can significantly improve rice yield, grain quality and nitrogen, phosphorus and potassium nutrient utilization rate. Detailed Implementation

[0022] A controlled-release nitrogen blended fertilizer comprises the following raw materials in parts by weight: 35-45 parts nitrogen fertilizer, 10-20 parts phosphate fertilizer, 12-25 parts potassium fertilizer, 1-5 parts micronutrient fertilizer, and 0.5-2 parts microbial agent; the nitrogen fertilizer has a multi-layer encapsulated core-shell structure, consisting of, from the inside out: a urea core layer, a first coating layer, an intermediate urea interlayer, a second coating layer, and an outer urea layer; the first coating layer comprises polyurethane, epoxidized soybean oil, chitosan, and Tween-80; the second coating layer comprises modified starch, polylactic acid, potassium humate, and Tween-80.

[0023] The preferred mass ratio of the urea core layer, the intermediate urea interlayer, and the outer urea layer in this invention is (2-3):(2-3):(4-6), and more preferably 2.5:2.5:5.

[0024] The phosphate fertilizer described herein is preferably at least one of monoammonium phosphate and diammonium phosphate; the potassium fertilizer is preferably at least one of potassium chloride and potassium sulfate; and the micronutrient fertilizer preferably includes at least one of zinc sulfate, borax, magnesium sulfate, and ferrous sulfate.

[0025] The microbial agent of the present invention is preferably composed of Bacillus subtilis XJ8 and Trichoderma harzianum DTZJ0125.

[0026] The present invention also provides a method for preparing the controlled-release nitrogen blended fertilizer according to the above, comprising: sequentially spraying a first coating liquid, urea, a second coating liquid, and urea onto the surface of urea granules to obtain nitrogen fertilizer; and mixing nitrogen fertilizer, phosphate fertilizer, potassium fertilizer, micronutrient fertilizer and microbial agent to obtain controlled-release nitrogen blended fertilizer.

[0027] The preferred method for preparing the nitrogen fertilizer of the present invention includes: heating urea granules, sequentially spraying a first coating liquid, a urea solution, a second coating liquid, and another urea solution, and then curing the mixture to obtain nitrogen fertilizer; the preferred mass ratio of polyurethane, epoxidized soybean oil, chitosan, Tween-80, and acetic acid aqueous solution in the first coating liquid is (30-35):(5-10):(2-4):(0.8-1.2):(65-75), more preferably 32:8:3:1:70; the preferred method for preparing the first coating liquid includes: mixing chitosan with an acetic acid aqueous solution of 1%-3% by mass to obtain a chitosan solution, sequentially mixing epoxidized soybean oil with Tween-80 and polyurethane, adding the chitosan solution, and emulsifying at 1000-2000 rpm for 10-20 min to obtain the first coating liquid; the second coating liquid contains modified starch and polylactic acid. The preferred mass ratio of potassium humate, Tween-80, and water is (8-12):(5-12):(4-7):(0.8-1.2):(65-75), more preferably 10:8:5.5:1:70; the preferred method for preparing the second coating solution includes: mixing modified starch with 40%-50% of the total water mass and heating to 85-95℃ for 20-30 min to obtain a gelatinized liquid; mixing potassium humate with 8%-10% of the total water mass to obtain a potassium humate solution; mixing polylactic acid and ethyl acetate at a mass ratio of 1:(2-4), adding Tween-80, adding the remaining water at 2000-3000 rpm, emulsifying for 10-20 min, removing ethyl acetate by vacuum distillation to obtain an emulsion; mixing the gelatinized liquid, potassium humate solution, and emulsion, homogenizing under high pressure to obtain the second coating solution.

[0028] The first coating solution of this invention forms a tough inner coating on the surface of the urea core. With polyurethane as the main framework, a hydrophobic and water-resistant membrane is constructed to regulate the rate of water penetration and nitrogen diffusion. Epoxidized soybean oil is used for toughening modification to improve the impact resistance and rupture resistance of the membrane. Chitosan provides biocompatibility and mild antibacterial properties, improving the adhesion between the membrane and the urea interface. Tween-80 is used as an emulsifying dispersant to ensure uniform spreading of the coating solution and continuous, defect-free film formation.

[0029] The second coating solution forms a bio-based, biodegradable outer coating outside the inner coating and the intermediate urea layer. Modified starch and polylactic acid gradually degrade over time, achieving controlled release in the early stages. Potassium humate combines nutrient enhancement with film modification, improving soil buffering capacity, promoting root growth and plant vigor, and enhancing the film's water and fertilizer retention capacity. Tween-80 ensures the homogeneity and stability of the coating solution, resulting in a uniform and complete film formation. The second coating solution provides an initial controlled-release barrier, reducing the risk of initial explosive urea release, stabilizing the early nitrogen release rate, preventing seedling burn and rapid nitrogen loss, and providing a stable substrate for the intermediate urea layer. The synergistic effect of the dual-coating system extends the nitrogen release cycle to 120 days, matching the nitrogen requirements of corn, wheat, and rice throughout their entire growth cycle.

[0030] The nitrogen fertilizer of this invention has a structure of urea core - first coating - middle urea interlayer - second coating - outer urea layer, forming a three-stage supply of fast-acting, medium-acting and long-acting nitrogen fertilizer. In the early stage, it meets the needs of greening and seedling emergence; in the middle stage, it supports vegetative growth; and in the later stage, it ensures grain filling and fruit setting. It does not cause nutrient deficiency or excessive release throughout the entire process, and significantly reduces ammonia volatilization, leaching and runoff losses. The nitrogen utilization rate is significantly higher than that of ordinary urea and single-layer coated urea. The controlled release period covers the entire growth period of crops, reducing the need for topdressing.

[0031] This invention relates to Bacillus subtilis XJ8, which can colonize the rhizosphere, secrete lipopeptide-based antibacterial substances to inhibit soil-borne pathogens such as Fusarium and Pythium; activate insoluble phosphorus and potassium in the soil, improving nutrient availability; and promote the production of metabolites (auxins, cytokinins) to stimulate root development and improve soil aggregate structure. Trichoderma harzianum DTZJ0125 can control fungal diseases, promote root meristem and nutrient absorption, degrade soil autotoxic substances, and alleviate continuous cropping obstacles. Trichoderma harzianum DTZJ0125 promotes root growth and nutrient absorption, while Bacillus subtilis XJ8 enhances nutrient activation efficiency. The combined use of these two can improve fertilizer utilization and crop growth, enhance organic matter conversion, improve soil permeability, and increase crop resistance and control soil-borne diseases.

[0032] The present invention also provides an application of the above-mentioned controlled-release nitrogen blended fertilizer in crop planting; the crops include corn, wheat and rice; the preferred method of applying the controlled-release nitrogen blended fertilizer is basal application, and the preferred amount of basal application is 30-50 kg / mu, more preferably 40 kg / mu.

[0033] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] Unless otherwise specified, the following embodiments are all conventional methods.

[0035] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0036] Bacillus subtilis XJ8, sourced from the China Agricultural Microbial Culture Collection Center, strain number ACCC60429; Trichoderma harzianum DTZJ0125, sourced from the China Agricultural Microbial Culture Collection Center, strain number ACCC30371.

[0037] Polyurethane, sourced from Jining Letian Arts & Crafts Co., Ltd., model HYW-108; epoxidized soybean oil, sourced from Guangzhou Suixin Chemical Co., Ltd., CAS No. 8013-07-8; chitosan, sourced from Shanxi Shangshan Biotechnology Co., Ltd., item number SSW-386; modified starch (esterified starch), sourced from Guangdong Huimei Starch Technology Co., Ltd., model HM-368; polylactic acid, sourced from Anhui Fengyuan Biotechnology Co., Ltd., model FY604; ethyl cellulose, sourced from Shandong Liaocheng Ahua Pharmaceutical Co., Ltd., model EC20; corn starch, sourced from Xi'an Hongyao Pharmaceutical Excipients Co., Ltd., CAS No. 9005-25-8; polyvinyl alcohol (polyvinyl alcohol 1788), sourced from Zhongnuo Environmental Protection Technology (Guangdong) Co., Ltd.; sodium alginate, sourced from Hubei Sanxin Biotechnology Co., Ltd., model SX0911.

[0038] Example 1

[0039] (1) Preparation of nitrogen fertilizer

[0040] 1) First coating solution

[0041] Accurately weigh 32 parts polyurethane, 8 parts epoxidized soybean oil, 3 parts chitosan, 1 part Tween-80, and 70 parts 2% acetic acid aqueous solution according to the following weight proportions;

[0042] Chitosan was mixed with an aqueous acetic acid solution to obtain a chitosan solution; epoxidized soybean oil was mixed with Tween-80 and polyurethane in sequence, and then added to the chitosan solution. The mixture was emulsified at 1500 rpm for 15 min to obtain the first coating solution.

[0043] 2) Second coating solution

[0044] Accurately weigh 10 parts modified starch, 8 parts polylactic acid, 5.5 parts potassium humate, 1 part Tween-80 and 170 parts water according to the specified weight.

[0045] Modified starch was mixed with 45% of the total water mass and heated to 90°C for 25 min to gelatinize, resulting in a gelatinized liquid. Potassium humate was mixed with 20% of the total water mass to obtain a potassium humate solution. Polylactic acid and ethyl acetate were mixed at a mass ratio of 1:3, Tween-80 was added, and the remaining water was added at 2500 rpm. The mixture was emulsified for 15 min, and the ethyl acetate was removed by vacuum distillation to obtain an emulsion. The gelatinized liquid, potassium humate solution, and emulsion were mixed to obtain a mixed liquid. The mixture was concentrated under reduced pressure to half the volume of the mixed liquid and homogenized twice under high pressure at 30 MPa to obtain a second coating solution.

[0046] 3) Nitrogen fertilizer

[0047] Urea granules (urea core layer) are placed in a fluidized bed and preheated at 58°C for 8 minutes. The first coating liquid is heated to 45°C and sprayed onto the surface of the urea granules. It is then cured at 60°C for 12 minutes to form the first coating layer. Urea powder is sprinkled into the fluidized bed and adheres to the surface of the first coating layer. It is then cured at 60°C for 3 minutes to form the intermediate urea interlayer. The second coating liquid is sprayed and cured at 60°C for 12 minutes to form the second coating layer. Urea powder is then sprinkled into the fluidized bed and adheres to the surface of the second coating layer. After curing at 60°C for 8 minutes, it is dried at 65°C to a moisture content of 1.46 wt% to obtain nitrogen fertilizer.

[0048] The mass ratio of the dry matter of the urea core layer, the first coating layer, the intermediate urea interlayer, the dry matter of the second coating layer, and the outer urea layer is 2.5:0.6:2.5:0.8:5.

[0049] (2) Preparation of controlled-release nitrogen blended fertilizer

[0050] Accurately weigh the following raw materials according to their weight proportions: 40 parts nitrogen fertilizer, 15 parts monoammonium phosphate, 18 parts potassium chloride, 0.8 parts zinc sulfate, 0.5 parts borax, 1.2 parts magnesium sulfate, 0.5 parts ferrous sulfate, and 1.2 parts microbial inoculant; wherein, the microbial inoculant consists of Bacillus subtilis XJ8 and Trichoderma harzianum DTZJ0125, and the spore concentration of Bacillus subtilis XJ8 in the microbial inoculant is 7 × 10⁻⁶. 8 The spore concentration of Trichoderma harzianum DTZJ0125 is 8 × 10⁶ spores / g. 7 pcs / g;

[0051] The above raw materials are mixed and stirred at 18 rpm for 10 minutes to obtain controlled-release nitrogen blended fertilizer.

[0052] Example 2

[0053] (1) Preparation of nitrogen fertilizer

[0054] 1) First coating solution

[0055] Accurately weigh 30 parts polyurethane, 5 parts epoxidized soybean oil, 2 parts chitosan, 0.8 parts Tween-80, and 65 parts of 1% acetic acid aqueous solution according to the following weight proportions;

[0056] Chitosan was mixed with an aqueous acetic acid solution to obtain a chitosan solution; epoxidized soybean oil was mixed with Tween-80 and polyurethane in sequence, and then added to the chitosan solution. The mixture was emulsified at 1000 rpm for 20 min to obtain the first coating solution.

[0057] 2) Second coating solution

[0058] Accurately weigh 8 parts modified starch, 5 parts polylactic acid, 4 parts potassium humate, 0.8 parts Tween-80 and 150 parts water according to the specified weight.

[0059] Modified starch was mixed with 40% of the total water mass and heated to 85°C for 30 min to gelatinize, resulting in a gelatinized liquid. Potassium humate was mixed with 15% of the total water mass to obtain a potassium humate solution. Polylactic acid and ethyl acetate were mixed at a mass ratio of 1:2, Tween-80 was added, and the remaining water was added at 2000 rpm. The mixture was emulsified for 20 min, and the ethyl acetate was removed by vacuum distillation to obtain an emulsion. The gelatinized liquid, potassium humate solution, and emulsion were mixed to obtain a mixture. The mixture was concentrated under reduced pressure to half the volume of the mixture and homogenized three times under high pressure at 20 MPa to obtain the second coating solution.

[0060] 3) Nitrogen fertilizer

[0061] Urea granules (urea core layer) are placed in a fluidized bed and preheated at 55°C for 10 minutes. The first coating liquid is heated to 40°C and sprayed onto the surface of the urea granules. After curing at 55°C for 15 minutes, the first coating layer is formed. Urea powder is sprinkled into the fluidized bed and adheres to the surface of the first coating layer. After curing at 55°C for 5 minutes, the intermediate urea interlayer is formed. The second coating liquid is sprayed and cured at 55°C for 15 minutes to form the second coating layer. Urea powder is sprinkled into the fluidized bed and adheres to the surface of the second coating layer. After curing at 55°C for 10 minutes, the mixture is dried at 60°C to a moisture content of 1.65 wt% to obtain nitrogen fertilizer.

[0062] The mass ratio of the dry matter of the urea core layer, the first coating layer, the intermediate urea interlayer, the dry matter of the second coating layer, and the outer urea layer is 2:0.5:2.5:0.7:5.5.

[0063] (2) Preparation of controlled-release nitrogen blended fertilizer

[0064] Accurately weigh the following raw materials according to their weight proportions: 35 parts nitrogen fertilizer, 10 parts diammonium phosphate, 12 parts potassium sulfate, 0.25 parts zinc sulfate, 0.15 parts borax, 0.45 parts magnesium sulfate, 0.15 parts ferrous sulfate, and 0.5 parts microbial inoculant; wherein, the microbial inoculant consists of Bacillus subtilis XJ8 and Trichoderma harzianum DTZJ0125, and the spore concentration of Bacillus subtilis XJ8 in the microbial inoculant is 5 × 10⁻⁶. 8 The spore concentration of Trichoderma harzianum DTZJ0125 is 6 × 10⁶ spores / g. 7 pcs / g;

[0065] The above raw materials are mixed and stirred at 15 rpm for 12 minutes to obtain controlled-release nitrogen blended fertilizer.

[0066] Example 3

[0067] (1) Preparation of nitrogen fertilizer

[0068] 1) First coating solution

[0069] Accurately weigh 35 parts polyurethane, 10 parts epoxidized soybean oil, 4 parts chitosan, 1.2 parts Tween-80, and 75 parts of 3% acetic acid aqueous solution according to the following weight proportions;

[0070] Chitosan was mixed with an aqueous acetic acid solution to obtain a chitosan solution; epoxidized soybean oil was mixed with Tween-80 and polyurethane in sequence, and then added to the chitosan solution. The mixture was emulsified at 2000 rpm for 10 min to obtain the first coating solution.

[0071] 2) Second coating solution

[0072] Accurately weigh 12 parts modified starch, 12 parts polylactic acid, 7 parts potassium humate, 1.2 parts Tween-80 and 200 parts water according to the specified weight.

[0073] Modified starch was mixed with 50% of the total water mass and heated to 95°C for 20 min to gelatinize, resulting in a gelatinized liquid. Potassium humate was mixed with 25% of the total water mass to obtain a potassium humate solution. Polylactic acid and ethyl acetate were mixed at a mass ratio of 1:4, Tween-80 was added, and the remaining water was added at 3000 rpm. The mixture was emulsified for 10 min, and the ethyl acetate was removed by vacuum distillation to obtain an emulsion. The gelatinized liquid, potassium humate solution, and emulsion were mixed to obtain a mixed liquid. The mixture was concentrated under reduced pressure to half the volume of the mixed liquid and homogenized once under high pressure at 35 MPa to obtain a second coating solution.

[0074] 3) Nitrogen fertilizer

[0075] Urea granules (urea core layer) are placed in a fluidized bed and preheated at 60°C for 5 minutes. The first coating liquid is heated to 50°C and sprayed onto the surface of the urea granules. The mixture is then cured at 65°C for 10 minutes to form the first coating layer. Urea powder is sprinkled into the fluidized bed and adheres to the surface of the first coating layer. The mixture is then cured at 65°C for 2 minutes to form the intermediate urea interlayer. The second coating liquid is then sprayed and cured at 65°C for 10 minutes to form the second coating layer. Urea powder is then sprinkled into the fluidized bed and adheres to the surface of the second coating layer. After curing at 65°C for 5 minutes, the mixture is dried at 70°C to a moisture content of 1.17 wt% to obtain nitrogen fertilizer.

[0076] The mass ratio of the dry matter of the urea core layer, the first coating layer, the intermediate urea interlayer, the dry matter of the second coating layer, and the outer urea layer is 3:0.8:3:1:4.

[0077] (2) Preparation of controlled-release nitrogen blended fertilizer

[0078] Accurately weigh the following raw materials according to their weight proportions: 45 parts nitrogen fertilizer, 20 parts monoammonium phosphate, 25 parts potassium chloride, 1.25 parts zinc sulfate, 0.75 parts borax, 2.25 parts magnesium sulfate, 0.75 parts ferrous sulfate, and 2 parts microbial inoculant; wherein, the microbial inoculant consists of Bacillus subtilis XJ8 and Trichoderma harzianum DTZJ0125, and the spore concentration of Bacillus subtilis XJ8 in the microbial inoculant is 1×10⁻⁶. 9 The spore concentration of Trichoderma harzianum DTZJ0125 is 1×10⁶ spores / g. 8 pcs / g;

[0079] The above raw materials are mixed and stirred at 18 rpm for 10 minutes to obtain controlled-release nitrogen blended fertilizer.

[0080] Comparative Example 1

[0081] Unlike Example 1, the nitrogen fertilizer is not coated. The nitrogen fertilizer is prepared by mixing urea, the dry matter of the first coating layer, and the dry matter of the second coating layer in a mass ratio of 10:0.6:0.8 and drying at 65°C to a moisture content of 1.71 wt% to obtain the nitrogen fertilizer.

[0082] The first coating layer consists of polyurethane, epoxidized soybean oil, chitosan, and Tween-80 in a mass ratio of 32:8:3:1; the second coating layer consists of modified starch, polylactic acid, potassium humate, and Tween-80 in a mass ratio of 15:8:7:1.

[0083] Comparative Example 2

[0084] Unlike Example 1, the preparation method of the first coating solution is as follows: accurately weigh 32 parts by weight of ethyl cellulose, 8 parts by weight of triethyl citrate, 3 parts by weight of glyceryl monostearate, 1 part by weight of Span-60, 30 parts by weight of anhydrous ethanol and 70 parts by weight of water.

[0085] Ethyl cellulose, triethyl citrate, glyceryl monostearate, and Span-60 were added to anhydrous ethanol and mixed to obtain an organic phase. Water was heated to 40°C, and the organic phase was added to the water while stirring at 1500 rpm. The mixture was emulsified for 20 min, and then distilled under reduced pressure to remove the anhydrous ethanol, yielding the first coating solution.

[0086] Comparative Example 3

[0087] Unlike Example 1, the preparation method of the second coating solution is as follows: accurately weigh 20 parts corn starch, 6 parts polyvinyl alcohol, 2 parts sodium alginate, 10 parts potassium humate, 1 part Span-60, 0.3 parts calcium chloride and 70 parts water according to the following weight parts;

[0088] Mix 45% of the total water mass with corn starch, heat to 90℃, and gelatinize for 25 minutes to obtain a gelatinized liquid; mix 20% of the total water mass with polyvinyl alcohol and stir at 90℃ to obtain a polyvinyl alcohol solution; mix 15% of the total water mass with potassium humate and Span-60 to obtain a potassium humate solution; mix the remaining water with calcium chloride to obtain a calcium chloride solution; mix the gelatinized liquid, polyvinyl alcohol solution, and potassium humate solution sequentially, add the calcium chloride solution while stirring at 200 rpm, continue stirring for 7 minutes, and homogenize twice at 50℃ and 25 MPa pressure to obtain a second coating liquid.

[0089] Comparative Example 4

[0090] Unlike Example 1, the microbial inoculant consisted solely of Bacillus subtilis XJ8, with a spore concentration of 7.8 × 10⁻⁶ in the inoculant. 8 per g.

[0091] Comparative Example 5

[0092] Unlike Example 1, the microbial inoculant consisted solely of Trichoderma harzianum DTZJ0125, with a spore concentration of 7.8 × 10⁻⁶ spores. 8 per g.

[0093] Experimental Example 1

[0094] Nitrogen fertilizer slow release test

[0095] The slow-release effect of nitrogen fertilizer in Examples 1-3 and Comparative Examples 1-3 was tested respectively.

[0096] The specific testing method is as follows:

[0097] Accurately weigh 10g of each nitrogen fertilizer sample, put it into a dialysis bag (molecular weight cutoff 8000-14000Da), and tie the bag tightly to ensure no leakage.

[0098] Place the dialysis bag into a 250mL Erlenmeyer flask containing 200mL of deionized water and incubate at 25℃.

[0099] Samples were taken at 5, 10, 20, 35, 55, 80, 105, and 120 days after standing. The total nitrogen concentration in the extract was determined by the Kjeldahl method, and the cumulative nitrogen release rate was calculated. Each sample was tested in triplicate, and the average value was taken.

[0100] Nitrogen cumulative release rate (%) = (total nitrogen mass in extract / total nitrogen mass in nitrogen fertilizer sample) × 100%.

[0101] The cumulative nitrogen release rates of nitrogen fertilizers in Examples 1-3 and Comparative Examples 1-3 at different time points are shown in Table 1.

[0102] Table 1. Results of cumulative nitrogen release rate (%) of different nitrogen fertilizers

[0103]

[0104] As shown in Table 1, Examples 1-3 exhibit typical three-stage controlled-release characteristics: the initial release rate is 16.53%-19.13% in the first 5 days, meeting the nitrogen requirements of crop seedlings without explosive release; from 10 to 80 days, a stable release stage is reached, with the cumulative release rate increasing from 27.31%-30.89% to 79.66%-84.18%, matching the nutrient requirements of field crops during vegetative growth; and long-term release is completed in 105-120 days, with a final release rate of 96.54%-98.30%, covering the entire growth period. This is due to the combined effect of the multi-layered core-shell structure and double-coating system of the fertilizer in this invention: the first coating uses polyurethane as a framework to achieve water-resistant controlled release, and the second coating uses modified starch and polylactic acid biodegradable materials to achieve gradient nitrogen release through gradual degradation.

[0105] Comparative Example 1, an uncoated physical nitrogen fertilizer mixture, showed a 35.68% release rate after 5 days and near-complete release after 120 days, lacking controlled-release capability and easily causing seedling burn and nitrogen loss. Comparative Example 2, after replacing the first coating material, showed controllable release in the early stages, but membrane stability decreased later, with a sharp increase in the release rate after 80 days, reaching 98.68% after 120 days, indicating failure of long-term controlled-release. Comparative Example 3, by changing the second coating component, showed decreased membrane integrity and degradation coordination, with a 5-day release rate of 34.23%, deviating from crop requirements. These data indicate that a multi-layered core-shell structure and dual-functional coating are key to achieving stable, long-lasting, and crop-matched nutrient supply; single coating, material replacement, or no coating can not achieve the ideal controlled-release effect.

[0106] Experimental Example 2

[0107] Rice planting test

[0108] The effects of controlled-release nitrogen blended fertilizers from Examples 1-3 and Comparative Examples 1-5 on rice growth indicators were tested respectively.

[0109] Trial period: June 2025 to November 2025

[0110] Experimental location: Dongxin Farm Experimental Base, Lianyungang Academy of Agricultural Sciences.

[0111] Test soil: The test site was selected in a representative plot with uniform fertility, flat terrain, and convenient transportation. The soil nutrient status of the test field was investigated before the experiment.

[0112] Test fertilizers: Controlled-release nitrogen blended fertilizers from Examples 1-3 and Comparative Examples 1-5

[0113] The tested crop and variety: The tested rice variety was 9you210.

[0114] Machinery tested: harrowing machine, ditching machine.

[0115] Experimental treatment:

[0116] The experiment included 10 treatments, each with 3 replicates, using a randomized block design. The plot area for each replicate was 21 m². 2 The plant measures 7 meters long and 3 meters wide. Isolation and protective rows must be set up between different treatments. In rice experiments, plastic film was used to separate different treatments, with single irrigation and single row placement to prevent cross-irrigation and cross-drainage.

[0117] Treatment 1: Apply controlled-release nitrogen blended fertilizer as per Example 1 at a rate of 40 kg / mu as basal fertilizer;

[0118] Treatment 2: Apply controlled-release nitrogen blended fertilizer as a base fertilizer according to Example 2 at a rate of 40 kg / mu;

[0119] Treatment 3: Apply controlled-release nitrogen blended fertilizer as a base fertilizer according to Example 3 at a rate of 40 kg / mu;

[0120] Treatment 4: Apply controlled-release nitrogen blended fertilizer at a ratio of 1 at a base application rate of 40 kg / mu;

[0121] Treatment 5: Apply controlled-release nitrogen blended fertilizer at a ratio of 2 at a base application rate of 40 kg / mu;

[0122] Treatment 6: Apply 40 kg / mu of controlled-release nitrogen blended fertilizer at ratio 3 as basal application;

[0123] Treatment 7: Apply controlled-release nitrogen blended fertilizer at a ratio of 40 kg / mu as basal application;

[0124] Treatment 8: Apply 40 kg / mu of controlled-release nitrogen blended fertilizer at a ratio of 5 as basal application;

[0125] Treatment 9: Apply 40 kg / mu of compound fertilizer (15-15-15) and 15 kg / mu of urea as basal fertilizer, and apply 20 kg / mu of urea as top dressing for heading.

[0126] Treatment 10: Blank (no fertilizer applied).

[0127] Necessary field management should be carried out during the planting period, including disease and pest control, weeding, etc. Except for fertilization, other field management measures are the same in all plots, especially the crop variety, planting density, and seedling age should be kept consistent.

[0128] Field management: Except for the different fertilization measures, the other field management measures such as irrigation, weeding, pest and disease control, and chemical control are the same for each plot and conform to local production habits. They are completed by a designated person on the same day.

[0129] Measurement Indicators and Results

[0130] Rice growth indicators:

[0131] (1) Yield and quality assessment: During the harvest period, the yield, thousand-grain weight, and quality of rice were measured and assessed to analyze the impact of fertilizer on rice yield and quality.

[0132] The effects of different treatments on rice yield factors and grain quality are shown in Table 2.

[0133] Table 2. Effects of different treatments on yield factors and grain quality of rice.

[0134]

[0135] As shown in Table 2, the treatments in Examples 1-3 exhibited the best overall performance, with yields ranging from 678.53 to 702.18 kg / mu, with Example 1 reaching a peak yield of 702.18 kg / mu. The number of grains per panicle ranged from 160.28 to 164.36, the thousand-grain weight from 23.45 to 23.79 g, and the number of panicles per mu from 183,000 to 187,500. The rice production indicators of Examples 1-3 were significantly higher than those of the control group and the conventional multi-stage fertilization. This is because the gradient release of nitrogen met the nutrient requirements of rice during the critical tillering and grain-filling stages, and the combined effect of microbial agents promoted growth and inhibited bacterial growth, ensuring robust plant growth. Furthermore, the chalkiness of the brown rice in Examples 1-3 was 10.43%-11.79%, significantly lower than that of the conventional fertilization and control groups, indicating superior grain appearance quality.

[0136] Comparative Examples 1-3 showed decreased yield per acre, increased chalkiness, and reduced quality due to nitrogen release imbalance. Comparative Examples 4 and 5, lacking either *Trichoderma harzianum* or *Bacillus subtilis*, exhibited lower yields and quality than the examples, indicating a synergistic effect between the two bacteria in improving rice yield and quality. These results demonstrate that blended fertilizers composed of multi-layered controlled-release nitrogen, composite microorganisms, and balanced nutrients can achieve high yield and quality with a single basal application, replacing traditional multi-application fertilization and simplifying field production.

[0137] (2) Fertilizer utilization rate assessment: The yield, total nitrogen uptake of the aboveground parts of the plant, and fertilizer application amount of each group were measured to calculate the fertilizer utilization rate.

[0138] The method for testing fertilizer utilization rate is as follows:

[0139] Soil samples were collected before fertilization and after harvest, and physical indicators such as soil bulk density were measured to assess the impact of fertilizer on soil physical indicators.

[0140] Fertilizer utilization rate (%) = (Total nutrients absorbed by crops in the fertilized area - Total nutrients absorbed by the control crop) / Total nutrients in the applied fertilizer × 100%.

[0141] Where: Total nutrients absorbed by crops in the fertilized area = yield of the fertilized area × nutrient absorption required to produce 100 kg of economic yield under fertilization / 100;

[0142] Total nutrients absorbed by crops in the unfertilized area = yield of the unfertilized area × nutrient absorption required to produce 100 kg of economic yield without fertilizer / 100;

[0143] Nutrient absorption per 100kg of economic yield = (grain yield × grain nutrient content + stem and leaf yield × stem and leaf nutrient content) / grain yield × 100.

[0144] The results of fertilizer application rates and nutrient utilization rates in rice under different treatments are shown in Table 3.

[0145] Table 3. Fertilizer application rate and nutrient utilization rate of rice under different treatments

[0146]

[0147] As shown in Table 3, the nitrogen utilization rates of Examples 1-3 were 54.35%-57.17%, phosphorus utilization rates were 25.85%-27.52%, and potassium utilization rates were 55.71%-58.38%, which were the highest in the group. This is mainly due to the precise controlled release of the multi-layer coating, which reduces ammonia volatilization, leaching, and runoff loss, thereby improving nitrogen capture efficiency; the compound microbial agent also functions effectively, with Bacillus subtilis activating insoluble phosphorus and potassium in the soil, and Trichoderma harzianum promoting root nutrient absorption, thus achieving a synergistic effect of nitrogen, phosphorus, and potassium.

[0148] Comparative Example 1, lacking a controlled-release structure, suffered severe nitrogen loss and reduced utilization rate, with phosphorus and potassium utilization rates declining simultaneously. Comparative Examples 2-3 exhibited poor compatibility of coating materials, resulting in an imbalance between membrane controlled release and degradation, leading to low nutrient utilization. Comparative Examples 4-5, with their single strains lacking complementary functions, showed weakened nutrient activation and absorption-promoting capabilities, lower than the treatment with the compound microbial agent. This indicates that the combined use of two strains has a synergistic effect in improving nitrogen, phosphorus, and potassium absorption, and neither can be omitted. These results demonstrate that multilayer controlled-release nitrogen systems and compound microbial agents are key to improving fertilizer utilization, significantly enhancing nitrogen, phosphorus, and potassium utilization rates. They offer significant advantages in reducing fertilizer application, mitigating non-point source pollution, and improving farmland ecological security, providing data support for the research and promotion of green and efficient fertilizers.

[0149] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A controlled-release nitrogen fertilizer blend fertilizer, characterized by, The raw materials include the following parts by weight: 35-45 parts nitrogen fertilizer, 10-20 parts phosphate fertilizer, 12-25 parts potassium fertilizer, 1-5 parts micronutrient fertilizer, and 0.5-2 parts microbial inoculant. The nitrogen fertilizer has a multi-layered core-shell structure, consisting of, from the inside out: a urea core layer, a first coating layer, an intermediate urea interlayer, a second coating layer, and an outer urea layer; the first coating layer includes polyurethane, epoxidized soybean oil, chitosan, and Tween-80; the second coating layer includes modified starch, polylactic acid, potassium humate, and Tween-80.

2. The controlled-release nitrogen fertilizer of claim 1, wherein the controlled- release nitrogen fertilizer is a fertilizer having a nitrogen content of 5% to 20% by weight. The mass ratio of the urea core layer, the intermediate urea interlayer, and the outer urea layer is (2-3):(2-3):(4-6).

3. The controlled-release nitrogen fertilizer of claim 1, wherein the controlled- release nitrogen fertilizer is a fertilizer having a nitrogen content of 5% to 20% by weight. The phosphate fertilizer is at least one of monoammonium phosphate and diammonium phosphate.

4. The controlled-release nitrogen fertilizer of claim 1, wherein the controlled- release nitrogen fertilizer is a fertilizer having a nitrogen content of 5% to 20% by weight. The potassium fertilizer is at least one of potassium chloride and potassium sulfate.

5. The controlled-release nitrogen fertilizer of claim 1, wherein the controlled- release nitrogen fertilizer is a fertilizer having a nitrogen content of 5% to 30% by weight. The micronutrient fertilizer includes at least one of zinc sulfate, borax, magnesium sulfate, and ferrous sulfate.

6. The controlled-release nitrogen fertilizer of claim 1, wherein the controlled- release nitrogen fertilizer is a fertilizer having a nitrogen content of 5% to 20% by weight. The microbial agent consists of Bacillus subtilis XJ8 and Trichoderma harzianum DTZJ0125.

7. A method for preparing the controlled-release nitrogen blended fertilizer according to any one of claims 1-6, characterized in that, include: The surface of urea granules is sequentially coated with a first coating solution, urea, a second coating solution, and urea to obtain nitrogen fertilizer. Nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, micronutrient fertilizer and microbial agent are mixed to obtain controlled-release nitrogen blended fertilizer.

8. The production method according to claim 7, characterized by, The mass ratio of polyurethane, epoxidized soybean oil, chitosan and Tween-80 in the first coating solution is (30-35):(5-10):(2-4):(0.8-1.2); the mass ratio of modified starch, polylactic acid, potassium humate and Tween-80 in the second coating solution is (8-12):(5-12):(4-7):(0.8-1.2).

9. The use of the controlled-release nitrogen fertilizer of any one of claims 1-6 in the cultivation of crops, characterized in that, The crops mentioned include corn, wheat, and rice.

10. Use according to claim 9, characterized in that, The controlled-release nitrogen blended fertilizer is applied at a rate of 30-50 kg / mu.

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