Nitrogen-phosphorus-potassium balanced compound fertilizer containing alginic acid chelating carrier and preparation method of nitrogen-phosphorus-potassium balanced compound fertilizer

Abstract

The invention relates to the technical field of compound fertilizers, and discloses a nitrogen-phosphorus-potassium balanced compound fertilizer containing an alginic acid chelating carrier, which comprises the following raw materials by weight: urea, monocalcium phosphate, potassium sulfate compounded potassium chloride, alginic acid, medium trace elements, a slow release regulator, a bioactive substance, diatomite, gamma-polyglutamic acid and a coating material. According to the nitrogen-phosphorus-potassium balanced compound fertilizer containing the alginic acid chelating carrier and the preparation method of the nitrogen-phosphorus-potassium balanced compound fertilizer, the alginic acid microporous gel carrier prepared by gamma-ray irradiation degradation and electrostatic spinning technologies has an ultra-large specific surface area and a nanoscale microporous structure, and can efficiently adsorb basic nutrients such as nitrogen, phosphorus and potassium and medium trace elements to form a stable chelating system; by combining a slow-release regulator composed of carboxymethyl chitosan and humic acid and a multilayer coating design of a urease inhibitor, a nitrification inhibitor, PLA microcapsules and fatty acid calcium, nutrient loss is reduced, and the utilization rate of the fertilizer is remarkably increased.

Description

Technical Field

[0001] The invention relates to the technical field of compound fertilizers, in particular to a nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier and a preparation method thereof. Background Art

[0002] Compound fertilizer refers to a chemical fertilizer containing two or more nutrients among nitrogen, phosphorus and potassium. Compound fertilizer has the advantages of high nutrient content, few by-components and good physical properties. It plays a very important role in balanced fertilization, improving fertilizer utilization and promoting high and stable yields of crops. However, it also has some disadvantages. For example, its nutrient ratio is always fixed, while the types, quantities and ratios of nutrients required by different soils and different crops are different. Alginic acid is a natural polysaccharide uronic acid found in the cell walls of brown algae such as kelp and giant kelp. It can be used in compound fertilizers to improve the fertilizer's efficiency. For example, the invention patent with announcement number CN115073234A discloses a compound fertilizer containing alginic acid and a preparation method thereof, which comprises 1 part of urea, ammonium phosphate, potassium chloride, alginate, hypromellose K10045-5, hypromellose K4M, and 100 parts of sphaerocarp. The invention provides a surface layer and a core layer, and uses different weight ratios of hypromellose K100 and hypromellose K4M in the core layer and the surface layer, so that the surface layer releases nutrients quickly and the core layer releases nutrients slowly. Therefore, the nutrient elements can be released over a long period of time to meet the nutritional needs of crops at different growth stages and increase crop yields.

[0003] However, in the above invention, the yield can be increased by adding alginate to the compound fertilizer, but due to the insufficient amount added: only 8-15 parts, a continuous carrier cannot be formed, and the alginate is not functionalized, resulting in a single function of alginate. At the same time, the distribution is unreasonable: the surface alginate is only 0.25-0.35 times that of the core layer, and the early root-promoting and stress-resistant functions are lost, resulting in poor fertilizer efficiency of the compound fertilizer. Therefore, a nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelated carrier and a preparation method thereof are proposed to solve the above problems. Summary of the Invention

[0004] (1) Technical problems solved In response to the shortcomings of the existing technology, the present invention provides a nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier and a preparation method thereof, which has the advantages of improving the fertilizer effect of alginate in compound fertilizers and solving the problems of single effect and poor fertilizer efficiency.

[0005] (2) Technical solution To achieve the above-mentioned purpose of improving the fertilizer effect of alginic acid in compound fertilizers, the present invention provides the following technical solution: a nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginic acid chelate carrier, comprising the following raw materials in proportions by weight: 40-60 parts of urea, 18-20 parts of calcium dihydrogen phosphate, 16-18 parts of potassium sulfate and potassium chloride, 20-30 parts of alginic acid, 3-9 parts of trace elements, 11-18 parts of a slow-release regulator, 0.5-2 parts of a bioactive substance, 3-5 parts of diatomaceous earth, 0.5-1 part of gamma-polyglutamic acid, and a coating material; Coating material: 1~2 parts of urease inhibitor, 1~2 parts of nitrification inhibitor, 2~3 parts of polylactic acid PLA microcapsule and 3~6 parts of fatty acid calcium solution.

[0006] Preferably, the raw material of the alginic acid is enzymatically hydrolyzed seaweed extract, which is rich in bioactive substances such as seaweed polysaccharides, mannitol, and betaine. The alginic acid is irradiated with γ rays at a rate of 0.5 to 20 kGy / h to degrade the macromolecules into small molecular active fragments, and then the microporous gel structure is prepared by electrospinning technology.

[0007] Preferably, the secondary elements are composed of EDTA-chelated zinc, iron, manganese, copper, boron, molybdenum and magnesium sulfate heptahydrate, and the sustained-release regulator is composed of 8 to 10 parts of carboxymethyl chitosan and 5 to 10 parts of humic acid.

[0008] Preferably, the bioactive substance consists of polyaspartic acid, gibberellin and seaweed polysaccharide extract.

[0009] Another technical problem to be solved by the present invention is a method for preparing a nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier, comprising the following steps: S1. Raw material pretreatment: S1.1. Take the enzymatic hydrolyzed extract of brown algae (Ascophyllum nodosum / Sargassum) (alginic acid content ≥ 35%) and dilute it to 15% concentration by adding pH 6.8 phosphate buffer; S1.2, Irradiation degradation: Irradiation with a cobalt-60 gamma ray source (dose rate 0.5-20 kGy / h, total dose 8-15 kGy) to reduce the molecular weight from 200 kDa to 20-30 kDa; S1.3, Electrospinning: Mix the degradation solution with 8% PVA solution at a ratio of 1:3 and inject into a spinning machine (voltage 18 kV, receiving distance 15 cm) to form a nanofiber gel network with a diameter of 1-5 μm. S1.4. Freeze drying: Quickly freeze at -40°C and then vacuum dry to obtain an alginate microporous gel carrier with a specific surface area > 300 m² / g for later use; S2. Basic nutrients and carrier compound: S2.1. Solid-phase mixing: pulverize urea through a 100-mesh sieve, pre-dry calcium dihydrogen phosphate to a water content of <0.5%, and pulverize magnesium sulfate heptahydrate through an 80-mesh sieve. Mix the mixture with potassium sulfate and potassium chloride in a double-screw conical mixer to obtain a solid-phase mixture. S2.2, Liquid phase loading: Dissolve EDTA-chelated trace elements (2 parts Zn / Fe / Mn / Cu + 1 part borax + 1 part ammonium molybdate) in 40°C warm water and spray onto the solid phase mixture; S2.3, Carrier Adsorption: Add the alginate microporous carrier obtained in step S1, and start a high-speed shearing machine (1200 rpm) to embed the nutrients into the micropores to obtain a mixture; S3. Construction of sustained-release system and granulation: S3.1. Preparation of adhesive solution: dissolve carboxymethyl chitosan, humic acid and γ-polyglutamic acid in 5% citric acid solution to form an adhesive with a solid content of 12-15%; S3.2, drum granulation: Place the mixture from step S2.3 into a drum granulator (inclination angle 35°, speed 18 rpm), spray the binder liquid into the granulator, and granulate. S3.3. Addition of bioactive substances: spray ethanol suspension containing polyaspartic acid, gibberellin, and seaweed polysaccharide in sequence at the late stage of granulation; S4, multi-layer coating and post-processing: S4.1, Inner layer slow-release coating: The granulated fertilizer granules are placed in a bottom spray fluidized bed, and the inhibitor layer and the PLA microcapsule layer are sprayed in sequence, wherein: Inhibitor layer: methanol solution of urease inhibitor + nitrification inhibitor; PLA microcapsule layer: polylactic acid dissolved in acetone solution; S4.2. Outer hydrophobic coating: Spray fatty acid calcium solution (fatty acid calcium: water = 1:3-5 parts). During spraying, control the inlet air temperature at 75-85°C and the particle temperature ≤45°C. S4.3, Anti-caking treatment: Coat the coated fertilizer particles with diatomaceous earth as an isolation agent. After coating, tumble them in hot air at 38-42°C for 10 minutes; S4.4, Ripening and Screening: Ripen the fertilizer granules after coating with the release agent in a 45-55°C aging device for 24 hours, pass through a 2-4 mm sieve, and control the moisture content to ≤1.5% to obtain compound fertilizer granules.

[0010] Preferably, the speed of the double-helix conical mixer in step S2.1 is controlled at 25 rpm / min, the mixing time is 12-16 min, the liquid-to-solid ratio of the binder in step S3.2 is 1:2.5, and the particle size of the particles after granulation is controlled at 2-4 mm.

[0011] Preferably, the concentration of the ethanol suspension in step S3.3 is 0.3-7%, and the atomized particle size of the PLA microcapsule layer sprayed in step S4.1 is 50-80 μm.

[0012] (3) Beneficial effects Compared with the prior art, the present invention provides a nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier and a preparation method thereof, which has the following beneficial effects: 1. This nitrogen, phosphorus, and potassium balanced compound fertilizer containing an alginate chelate carrier and its preparation method. The alginate microporous gel carrier, prepared by gamma-ray irradiation degradation and electrospinning technology, has an ultra-large specific surface area and nanoscale microporous structure, and can efficiently adsorb basic nutrients such as nitrogen, phosphorus, and potassium, as well as trace elements, to form a stable chelate system. Combined with a slow-release regulator consisting of carboxymethyl chitosan and humic acid, and a multi-layer coating design of urease inhibitors, nitrification inhibitors, PLA microcapsules, and fatty acid calcium, it can achieve a dynamic balance from rapid nutrient supply to slow release, reduce nutrient loss (such as nitrogen volatilization and phosphorus and potassium fixation), and significantly improve fertilizer utilization.

[0013] 2. This nitrogen, phosphorus, and potassium balanced compound fertilizer containing an alginate chelate carrier and its preparation method, in which trace elements (zinc, iron, manganese, etc.) and bioactive substances (polyaspartic acid, gibberellins, seaweed polysaccharides, etc.) in EDTA chelate form avoid antagonistic reactions between elements through the synergistic effect of the chelate carrier, thus meeting the nutritional needs of plants at different growth stages; at the same time, substances such as alginate derivatives and polyglutamic acid can promote root development and nutrient absorption, enhancing the plant's ability to convert nutrients.

[0014] 3. The nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier and its preparation method can enzymatically hydrolyze bioactive substances such as seaweed polysaccharides, mannitol, and betaine in seaweed extracts, and synergize with gibberellins and other substances to stimulate plant cell division, enhance photosynthesis, and improve plant resistance to drought, pests and diseases, and other adversities; substances such as γ-polyglutamic acid and polyaspartic acid can also improve the soil microenvironment, promote the activity of beneficial microorganisms, and indirectly help plant growth.

[0015] 4. This nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier and its preparation method use degradable PLA microcapsules and fatty acid calcium as coating materials, reducing the residual pollution of traditional chemical coating agents; the slow-release system reduces environmental problems such as soil acidification and water eutrophication caused by excessive nutrient release, meeting the needs of green agricultural development. DETAILED DESCRIPTION

[0016] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0017] Example 1: A nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier, comprising the following raw materials in the following proportions by weight: 50 parts of urea, 19 parts of calcium dihydrogen phosphate, 17 parts of potassium sulfate and potassium chloride, 25 parts of alginate, 5.6 parts of trace elements, 15 parts of a slow-release regulator, 1.05 parts of a bioactive substance, 4 parts of diatomaceous earth, 0.7 parts of gamma-polyglutamic acid, and a coating material; Coating material: 1.5 parts of urease inhibitor, 1.5 parts of nitrification inhibitor, 2.5 parts of polylactic acid PLA microcapsule and 5 parts of fatty acid calcium solution.

[0018] It should be noted that the raw material of alginate is enzymatically hydrolyzed seaweed extract, which is rich in bioactive substances such as seaweed polysaccharides, mannitol, betaine, etc. It is irradiated with γ rays at 14kGy / h to degrade the macromolecules into small molecular active fragments, and then prepared through electrospinning technology to form a microporous gel structure.

[0019] Among them, the secondary elements are composed of EDTA-chelated zinc, iron, manganese, copper, boron, molybdenum and magnesium sulfate heptahydrate, including EDTA-Zn: 0.6 parts, EDTA-Fe: 0.8 parts, EDTA-Mn: 0.5 parts, EDTA-Cu: 0.2 parts, borax: 0.4 parts, ammonium molybdate: 0.1 parts, magnesium sulfate heptahydrate: 3 parts, the sustained-release regulator is composed of 9 parts of carboxymethyl chitosan and 7 parts of humic acid; the biologically active substances are composed of 0.4 parts of polyaspartic acid, 0.05 parts of gibberellins and 0.5 parts of seaweed polysaccharide extract.

[0020] A method for preparing a nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier comprises the following steps: S1. Raw material pretreatment: S1.1. Take the enzymatic hydrolyzed extract of brown algae (Ascophyllum nodosum / Sargassum) (alginic acid content ≥ 35%) and dilute it to 15% concentration by adding pH 6.8 phosphate buffer; S1.2, Irradiation degradation: Irradiation with a cobalt-60 gamma ray source (dose rate 14 kGy / h, total dose 10 kGy) reduces the molecular weight from 200 kDa to 22 kDa; S1.3, Electrospinning: The degradation solution was mixed with 8% PVA solution at a ratio of 1:3 and injected into a spinning machine (voltage 18 kV, receiving distance 15 cm) to form a nanofiber gel network with a diameter of 2.5 μm. S1.4. Freeze drying: Quickly freeze at -40°C and then vacuum dry to obtain an alginate microporous gel carrier with a specific surface area > 300 m² / g for later use; S2. Basic nutrients and carrier compound: S2.1. Solid-phase mixing: urea was pulverized and passed through a 100-mesh sieve, calcium dihydrogen phosphate was pre-dried to a moisture content of <0.5%, magnesium sulfate heptahydrate was pulverized and passed through an 80-mesh sieve, and then mixed with potassium sulfate and potassium chloride in a double-helix conical mixer to obtain a solid-phase mixture. The speed of the double-helix conical mixer was controlled at 25 rpm / min, and the mixing time was 12 min. S2.2, Liquid phase loading: Dissolve EDTA-chelated trace elements (2 parts Zn / Fe / Mn / Cu + 1 part borax + 1 part ammonium molybdate) in 40°C warm water and spray onto the solid phase mixture; S2.3, Carrier Adsorption: Add the alginate microporous carrier obtained in step S1, and start a high-speed shearing machine (1200 rpm) to embed the nutrients into the micropores to obtain a mixture; S3. Construction of sustained-release system and granulation: S3.1. Preparation of adhesive solution: dissolve carboxymethyl chitosan, humic acid and γ-polyglutamic acid in 5% citric acid solution to form an adhesive with a solid content of 12%; S3.2, Drum Granulation: The mixture from step S2.3 was placed in a drum granulator (inclination angle 35°, speed 18 rpm), and a binder was sprayed in to granulate the mixture. The liquid-to-solid ratio of the binder was 1:2.5, and the particle size after granulation was controlled to be 2 mm. S3.3. Addition of bioactive substances: In the later stage of granulation, ethanol suspension containing polyaspartic acid, gibberellin, and seaweed polysaccharide is sprayed in sequence, wherein the concentration of the ethanol suspension is 0.8%; S4, multi-layer coating and post-processing: S4.1, Inner layer slow-release coating: The granulated fertilizer granules are placed in a bottom spray fluidized bed, and the inhibitor layer and the PLA microcapsule layer are sprayed in sequence, wherein: Inhibitor layer: methanol solution of urease inhibitor + nitrification inhibitor; PLA microcapsule layer: polylactic acid dissolved in acetone solution, wherein the spray atomized particle size of the PLA microcapsule layer is 50 μm; S4.2. Outer hydrophobic coating: Spray fatty acid calcium solution (fatty acid calcium: water = 1:2 parts). During spraying, control the inlet air temperature at 75°C and the particle temperature ≤ 45°C. S4.3, Anti-caking treatment: Coat the coated fertilizer particles with diatomaceous earth as an isolation agent. After coating, tumble them in 38°C hot air for 10 minutes; S4.4, Ripening and Screening: Ripen the fertilizer granules coated with the release agent in a 45°C aging device for 24 hours, pass through a 2mm sieve, and control the moisture content to ≤1.0% to obtain compound fertilizer granules.

[0021] In this embodiment, weight reduction without reducing production is achieved by controlling chlorine (25%) + medium amount of humic acid (7 parts).

[0022] Example 2: A nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier, comprising the following raw materials in proportions by weight: 55 parts of urea, 20 parts of calcium dihydrogen phosphate, 18 parts of potassium sulfate and potassium chloride, 28 parts of alginate, 7.3 parts of trace elements, 18 parts of a slow-release regulator, 1.28 parts of a bioactive substance, 5 parts of diatomaceous earth, 0.9 parts of gamma-polyglutamic acid, and a coating material; Coating material: 2 parts of urease inhibitor, 2 parts of nitrification inhibitor, 3 parts of polylactic acid PLA microcapsule and 6 parts of fatty acid calcium solution.

[0023] It should be noted that the raw material of alginate is enzymatically hydrolyzed seaweed extract, which is rich in bioactive substances such as seaweed polysaccharides, mannitol, betaine, etc. It is irradiated with γ rays at 15kGy / h to degrade the macromolecules into small molecular active fragments, and then prepared through electrospinning technology to form a microporous gel structure.

[0024] Among them, the secondary elements are composed of EDTA-chelated zinc, iron, manganese, copper, boron, molybdenum and magnesium sulfate heptahydrate, including EDTA-Zn: 0.7 part, EDTA-Fe: 1.0 part, EDTA-Mn: 0.6 part, EDTA-Cu: 0.3 part, borax: 0.5 part, ammonium molybdate: 0.2 part, magnesium sulfate heptahydrate: 4 parts, the sustained-release regulator is composed of 10 parts of carboxymethyl chitosan and 8 parts of humic acid; the biologically active substances are composed of 0.5 parts of polyaspartic acid, 0.08 parts of gibberellins and 0.7 parts of seaweed polysaccharide extract.

[0025] A method for preparing a nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier comprises the following steps: S1. Raw material pretreatment: S1.1. Take the enzymatic hydrolyzed extract of brown algae (Ascophyllum nodosum / Sargassum) (alginic acid content ≥ 35%) and dilute it to 15% concentration by adding pH 6.8 phosphate buffer; S1.2, Irradiation degradation: Irradiation with a cobalt-60 gamma ray source (dose rate 15 kGy / h, total dose 12 kGy) reduces the molecular weight from 200 kDa to 25 kDa; S1.3, Electrospinning: Mix the degradation solution with 8% PVA solution at a ratio of 1:2.5 and inject into a spinning machine (voltage 18 kV, receiving distance 15 cm) to form a nanofiber gel network with a diameter of 3 μm; S1.4. Freeze drying: Quickly freeze at -40°C and then vacuum dry to obtain an alginate microporous gel carrier with a specific surface area > 300 m² / g for later use; S2. Basic nutrients and carrier compound: S2.1. Solid-Phase Mixing: Grind urea through a 100-mesh sieve, pre-dry calcium dihydrogen phosphate to a moisture content of <0.5%, and grind magnesium sulfate heptahydrate through an 80-mesh sieve. Mix the mixture with potassium sulfate and potassium chloride in a double-helix conical mixer to obtain a solid-phase mixture. The speed of the double-helix conical mixer is controlled at 25 rpm / min, the mixing time is 14 min, and the mixing uniformity is >98%. S2.2, Liquid phase loading: Dissolve EDTA-chelated trace elements (2 parts Zn / Fe / Mn / Cu + 1 part borax + 1 part ammonium molybdate) in 40°C warm water and spray onto the solid phase mixture; S2.3, Carrier Adsorption: Add the alginate microporous carrier obtained in step S1, and start a high-speed shearing machine (1200 rpm) to embed the nutrients into the micropores to obtain a mixture; S3. Construction of sustained-release system and granulation: S3.1. Preparation of adhesive solution: dissolve carboxymethyl chitosan, humic acid and γ-polyglutamic acid in 5% citric acid solution to form an adhesive with a solid content of 13%; S3.2, Drum Granulation: The mixture from step S2.3 was placed in a drum granulator (inclination angle 35°, speed 18 rpm), and a binder was sprayed in to granulate the mixture. The liquid-to-solid ratio of the binder was 1:2.5, and the particle size after granulation was controlled to be 3 mm. S3.3. Addition of bioactive substances: In the later stage of granulation, ethanol suspension containing polyaspartic acid, gibberellin, and seaweed polysaccharide is sprayed in sequence, wherein the concentration of the ethanol suspension is 0.9%; S4, multi-layer coating and post-processing: S4.1, Inner layer slow-release coating: The granulated fertilizer granules are placed in a bottom spray fluidized bed, and the inhibitor layer and the PLA microcapsule layer are sprayed in sequence, wherein: Inhibitor layer: methanol solution of urease inhibitor + nitrification inhibitor; PLA microcapsule layer: polylactic acid dissolved in acetone solution, wherein the spray atomized particle size of the PLA microcapsule layer is 65μm; S4.2. Outer hydrophobic coating: Spray fatty acid calcium solution (fatty acid calcium: water = 1:4 parts). During spraying, control the inlet air temperature at 80°C and the particle temperature ≤ 45°C. S4.3, Anti-caking treatment: Coat the coated fertilizer particles with diatomaceous earth as an isolation agent, then tumble in 40°C hot air for 10 minutes; S4.4, Ripening and Screening: Ripen the fertilizer granules coated with the release agent in a 50°C aging device for 24 hours, pass through a 3mm sieve, and control the moisture content to ≤1.1% to obtain compound fertilizer granules.

[0026] In this example, the high-activity substance (1.28 parts) + thickened PLA film (3 parts) prolongs the fertilizer effect until the harvest period.

[0027] Example 3: A nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier, comprising the following raw materials in the following proportions by weight: 45 parts of urea, 18 parts of calcium dihydrogen phosphate, 16 parts of potassium sulfate and potassium chloride, 30 parts of alginate, 7.1 parts of trace elements, 18 parts of a slow-release regulator, 1.63 parts of a bioactive substance, 3 parts of diatomaceous earth, 1 part of gamma-polyglutamic acid, and a coating material; Coating material: 1 part of urease inhibitor, 1 part of nitrification inhibitor, 2 parts of polylactic acid PLA microcapsules and 4 parts of fatty acid calcium solution (1.5 parts on dry basis).

[0028] It should be noted that the raw material of alginate is enzymatically hydrolyzed seaweed extract, which is rich in bioactive substances such as seaweed polysaccharides, mannitol, betaine, etc. It is irradiated with γ rays at 10kGy / h to degrade the macromolecules into small molecular active fragments, and then prepared through electrospinning technology to form a microporous gel structure.

[0029] Among them, the secondary elements are composed of EDTA-chelated zinc, iron, manganese, copper, boron, molybdenum and magnesium sulfate heptahydrate, including EDTA-Zn: 0.5 parts, EDTA-Fe: 0.7 parts, EDTA-Mn: 0.4 parts, EDTA-Cu: 0.1 parts, borax: 0.3 parts, ammonium molybdate: 0.1 parts, magnesium sulfate heptahydrate: 5 parts, the sustained-release regulator is composed of 8 parts of carboxymethyl chitosan and 10 parts of humic acid; the biologically active substances are composed of 0.6 parts of polyaspartic acid, 0.03 parts of gibberellins and 1.0 parts of seaweed polysaccharide extract.

[0030] A method for preparing a nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier comprises the following steps: S1. Raw material pretreatment: S1.1. Take the enzymatic hydrolyzed extract of brown algae (Ascophyllum nodosum / Sargassum) (alginic acid content ≥ 35%) and dilute it to 15% concentration by adding pH 6.8 phosphate buffer; S1.2, Irradiation degradation: Irradiation with a cobalt-60 gamma ray source (dose rate 15 kGy / h, total dose 10 kGy) to reduce the molecular weight from 200 kDa to 25 kDa; S1.3, Electrospinning: The degradation solution was mixed with 8% PVA solution at a ratio of 1:3 and injected into a spinning machine (voltage 18 kV, receiving distance 15 cm) to form a nanofiber gel network with a diameter of 2.5 ± 0.5 μm; S1.4. Freeze drying: Quickly freeze at -40°C and then vacuum dry to obtain an alginate microporous gel carrier with a specific surface area > 300 m² / g for later use; S2. Basic nutrients and carrier compound: S2.1. Solid-phase mixing: urea was pulverized and passed through a 100-mesh sieve, calcium dihydrogen phosphate was pre-dried to a moisture content of <0.5%, magnesium sulfate heptahydrate was pulverized and passed through an 80-mesh sieve, and then mixed with potassium sulfate and potassium chloride in a double-helix conical mixer to obtain a solid-phase mixture. The speed of the double-helix conical mixer was controlled at 25 rpm / min, and the mixing time was 14 min. S2.2, Liquid phase loading: Dissolve EDTA-chelated trace elements (2 parts Zn / Fe / Mn / Cu + 1 part borax + 1 part ammonium molybdate) in 40°C warm water and spray onto the solid phase mixture; S2.3, Carrier Adsorption: Add the alginate microporous carrier obtained in step S1, and start a high-speed shearing machine (1200 rpm) to embed the nutrients into the micropores to obtain a mixture; S3. Construction of sustained-release system and granulation: S3.1. Preparation of adhesive solution: dissolve carboxymethyl chitosan, humic acid and γ-polyglutamic acid in 5% citric acid solution to form an adhesive with a solid content of 15%; S3.2, Drum Granulation: Place the mixture from step S2.3 into a drum granulator (inclination angle 35°, speed 18 rpm), spray the binder liquid into the granulator, and granulate the granules. The liquid-to-solid ratio of the binder liquid is 1:2.5, and the particle size after granulation is controlled to be 3.0 ± 0.5 mm. S3.3. Addition of bioactive substances: In the later stage of granulation, ethanol suspension containing polyaspartic acid, gibberellin, and seaweed polysaccharide is sprayed in sequence, wherein the concentration of the ethanol suspension is 0.5%; S4, multi-layer coating and post-processing: S4.1, Inner layer slow-release coating: The granulated fertilizer granules are placed in a bottom spray fluidized bed, and the inhibitor layer and the PLA microcapsule layer are sprayed in sequence, wherein: Inhibitor layer: methanol solution of urease inhibitor + nitrification inhibitor; PLA microcapsule layer: polylactic acid dissolved in acetone solution, wherein the spray atomized particle size of the PLA microcapsule layer is 80 μm; S4.2. Outer hydrophobic coating: Spray fatty acid calcium solution (fatty acid calcium: water = 1:5 parts). During spraying, control the inlet air temperature at 80°C and the particle temperature ≤ 45°C. S4.3, Anti-caking treatment: Coat the coated fertilizer particles with diatomaceous earth as an isolation agent. After coating, tumble them in 42°C hot air for 10 minutes; S4.4, Ripening and Screening: Ripen the fertilizer granules coated with the release agent in a 50°C aging device for 24 hours, pass through a 4mm sieve, and control the moisture content to ≤1.2% to obtain compound fertilizer granules.

[0031] In this embodiment, zero potassium chloride + high humic acid (10 parts) + seaweed polysaccharide (1 part) are used to simultaneously improve soil resistance.

[0032] Comparison of Examples:

[0033] All three embodiments achieve the goal of "high load (urea adsorption capacity > 110 mg / g) + sustained-release synergy (R² > 0.98) + low-temperature active protection" to meet the needs of differentiated working conditions.

[0034] The beneficial effects of the present invention are as follows: the alginate microporous gel carrier prepared by gamma-ray irradiation degradation and electrospinning technology has an ultra-large specific surface area and nano-scale microporous structure, and can efficiently adsorb basic nutrients such as nitrogen, phosphorus, potassium and trace elements to form a stable chelate system; the multi-layer coating design of the combination of carboxymethyl chitosan and humic acid as a slow-release regulator, as well as a urease inhibitor, a nitrification inhibitor, PLA microcapsules and fatty acid calcium can achieve a dynamic balance from rapid nutrient supply to slow release, reduce nutrient loss (such as nitrogen volatilization and phosphorus and potassium fixation), and significantly improve fertilizer utilization; EDTA chelates trace elements (zinc, iron, manganese, etc.) and bioactive substances (polyaspartic acid, gibberellins, seaweed polysaccharides, etc.) through the synergistic effect of the chelate carrier, avoiding antagonistic reactions between elements. It meets the nutritional needs of plants at different growth stages; at the same time, substances such as alginate derivatives and polyglutamic acid can promote root development and nutrient absorption, and enhance the plant's ability to convert nutrients; bioactive substances such as seaweed polysaccharides, mannitol, and betaine in enzymatic seaweed extracts, synergistically with gibberellins, can stimulate plant cell division, enhance photosynthesis, and improve plant resistance to adversities such as drought, pests and diseases; substances such as γ-polyglutamic acid and polyaspartic acid can also improve the soil microenvironment, promote the activity of beneficial microorganisms, and indirectly assist plant growth; by using degradable PLA microcapsules and fatty acid calcium as coating materials, the residual pollution of traditional chemical coating agents is reduced; the slow-release system reduces environmental problems such as soil acidification and water eutrophication caused by excessive nutrient release, which is in line with the needs of green agricultural development.

[0035] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier, characterized in that: The invention comprises the following raw materials in proportion by weight: 40-60 parts of urea, 18-20 parts of calcium dihydrogen phosphate, 16-18 parts of potassium sulfate and potassium chloride, 20-30 parts of alginic acid, 3-9 parts of trace elements, 11-18 parts of sustained-release regulator, 0.5-2 parts of bioactive substance, 3-5 parts of diatomaceous earth, 0.5-1 part of gamma-polyglutamic acid and coating material; Coating material: 1~2 parts of urease inhibitor, 1~2 parts of nitrification inhibitor, 2~3 parts of polylactic acid PLA microcapsule and 3~6 parts of fatty acid calcium solution.

2. The nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier according to claim 1, characterized in that: The raw material of the alginate is enzymatically hydrolyzed seaweed extract, which is rich in bioactive substances such as seaweed polysaccharides, mannitol, and betaine. The alginic acid is irradiated with γ rays at 0.5 to 20 kGy / h to degrade the macromolecules into small molecular active fragments, and then prepared through electrostatic spinning technology to form a microporous gel structure.

3. The nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier according to claim 1, characterized in that: The intermediate elements are composed of EDTA-chelated zinc, iron, manganese, copper, boron, molybdenum and magnesium sulfate heptahydrate, and the sustained-release regulator is composed of 8-10 parts of carboxymethyl chitosan and 5-10 parts of humic acid.

4. The nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier according to claim 1, characterized in that: The biologically active substance consists of polyaspartic acid, gibberellin and seaweed polysaccharide extract.

5. A method for preparing a nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier, characterized in that: The following steps are involved: S1. Raw material pretreatment: S1.

1. Take the enzymatic hydrolyzed extract of brown algae (Ascophyllum nodosum / Sargassum) (alginic acid content ≥ 35%) and dilute it to 15% concentration by adding pH 6.8 phosphate buffer; S1.2, Irradiation degradation: Irradiation with a cobalt-60 gamma ray source (dose rate 0.5-20 kGy / h, total dose 8-15 kGy) to reduce the molecular weight from 200 kDa to 20-30 kDa; S1.3, Electrospinning: Mix the degradation solution with 8% PVA solution at a ratio of 1:3 and inject into a spinning machine (voltage 18 kV, receiving distance 15 cm) to form a nanofiber gel network with a diameter of 1-5 μm. S1.

4. Freeze drying: Quickly freeze at -40°C and then vacuum dry to obtain an alginate microporous gel carrier with a specific surface area > 300 m² / g for later use; S2. Basic nutrients and carrier compound: S2.

1. Solid-phase mixing: pulverize urea through a 100-mesh sieve, pre-dry calcium dihydrogen phosphate to a water content of <0.5%, and pulverize magnesium sulfate heptahydrate through an 80-mesh sieve. Mix the mixture with potassium sulfate and potassium chloride in a double-screw conical mixer to obtain a solid-phase mixture. S2.2, Liquid phase loading: Dissolve EDTA-chelated trace elements (2 parts Zn / Fe / Mn / Cu + 1 part borax + 1 part ammonium molybdate) in 40°C warm water and spray onto the solid phase mixture; S2.3, Carrier Adsorption: Add the alginate microporous carrier obtained in step S1, and start a high-speed shearing machine (1200 rpm) to embed the nutrients into the micropores to obtain a mixture; S3. Construction of sustained-release system and granulation: S3.

1. Preparation of adhesive solution: dissolve carboxymethyl chitosan, humic acid and γ-polyglutamic acid in 5% citric acid solution to form an adhesive with a solid content of 12-15%; S3.2, drum granulation: Place the mixture from step S2.3 into a drum granulator (inclination angle 35°, speed 18 rpm), spray the binder liquid into the granulator, and granulate. S3.

3. Addition of bioactive substances: spray ethanol suspension containing polyaspartic acid, gibberellin, and seaweed polysaccharide in sequence at the late stage of granulation; S4, multi-layer coating and post-processing: S4.1, Inner layer slow-release coating: The granulated fertilizer granules are placed in a bottom spray fluidized bed, and the inhibitor layer and the PLA microcapsule layer are sprayed in sequence, wherein: Inhibitor layer: methanol solution of urease inhibitor + nitrification inhibitor; PLA microcapsule layer: polylactic acid dissolved in acetone solution; S4.

2. Outer hydrophobic coating: Spray fatty acid calcium solution (fatty acid calcium: water = 1:3-5 parts). During spraying, control the inlet air temperature at 75-85°C and the particle temperature ≤45°C. S4.3, Anti-caking treatment: Coat the coated fertilizer particles with diatomaceous earth as an isolation agent. After coating, tumble them in hot air at 38-42°C for 10 minutes; S4.4, Ripening and Screening: Ripen the fertilizer granules after coating with the release agent in a 45-55°C aging device for 24 hours, pass through a 2-4 mm sieve, and control the moisture content to ≤1.5% to obtain compound fertilizer granules.

6. The method for preparing a nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier according to claim 5, characterized in that: In step S2.1, the rotation speed of the double-helix conical mixer is controlled at 25 rpm / min, and the mixing time is 12-16 min. In step S3.2, the liquid-to-solid ratio of the adhesive solution is 1:2.5, and the particle size of the granules after granulation is controlled at 2-4 mm.

7. The method for preparing a nitrogen, phosphorus and potassium balanced compound fertilizer containing an alginate chelate carrier according to claim 6, characterized in that: The concentration of the ethanol suspension in step S3.3 is 0.3-7%, and the spray atomization particle size of the PLA microcapsule layer in step S4.1 is 50-80 μm.

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