Intelligent controlled-release fertilizer for corn and preparation method thereof

Abstract

The invention discloses a method for preparing a special intelligent controlled-release fertilizer for corn, and belongs to the field of new fertilizer production. The invention mixes nitrogen and phosphorus nutrient response signal substances with fertilizer raw materials and extrude them into large-particle fertilizers, then coats them, improves the coating process, and designs them according to the nutrient demand and demand period of corn and combines the pressing and coating of corn nutrient response signal substances to make a new controlled-release fertilizer. The fertilizer delays the release of nutrients, solves the problem of difficulty in topdressing in the late growth period of corn, has a release period of about 50 to 60 days, greatly improves nutrient utilization, can save fertilizer by 30% to 50%, and has a yield-increasing effect, with huge economic, social and ecological benefits.

Description

Technical Field

[0001] The invention relates to a special intelligent controlled-release fertilizer for corn and a preparation method thereof, and belongs to the field of new fertilizer production. Background Art

[0002] In recent years, chemical fertilizers have played an important role in ensuring my country's food security and stabilizing and increasing crop yields. However, traditional chemical fertilizers have low conversion efficiency in the soil. For example, nitrogen fertilizers are easily volatilized and lost with surface runoff, and phosphorus fertilizers are easily fixed, resulting in low nutrient utilization rates of traditional chemical fertilizers. In addition, one-time fertilization of traditional chemical fertilizers cannot meet the nutrient needs of crops throughout their entire growth period, and excessive one-time application may cause root damage and seedling burns, waste of fertilizer resources, and serious environmental pollution.

[0003] Maize is one of the most important cereal crops in the world, ranking second only to wheat in terms of planting area and yield, and has extremely high added value. Maize exhibits a complex root system architecture and shows a large degree of genomic diversity. Therefore, maize is an excellent model for exploring the relationship between root architecture, gene regulation, and their interaction with the rhizosphere microbiota.

[0004] Nowadays, although controlled-release fertilizers have improved fertilizer utilization to a certain extent, they still restrict the green development of agriculture and the fertilizer industry: 1. Traditional controlled-release fertilizers only rely on the thickness of the coating to regulate the release of fertilizer nutrients, lack innovation in the targeted and precise regulation of nutrients, and only emphasize the supply of fertilizers to crops and soils, ignoring the intelligent response and mutual feedback cascade synergistic effect between fertilizer nutrients and crop root systems. 2. The nutrient supply of traditional fertilizers does not match the nutrient demand of crops at different growth stages. For corn production and cultivation, the incoordination between fertilizer nutrient release and corn fertilizer requirement period cannot meet the large demand for nutrients of corn in the large trumpet period: when corn does not need a lot of nutrients, fertilizers release nutrients into the soil, but when corn urgently needs nutrients, they do not release them, which eventually causes the vegetative growth and reproductive growth of corn to stagnate and the yield to decline. 3. The coating process of traditional controlled-release fertilizers mostly adopts the drum coating process. During heating and curing, the fertilizer particles are constantly sticking, tearing, and repairing in the drum, resulting in uneven distribution of the film material on the fertilizer surface and poor fertilizer nutrient controlled release effect. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the object of the present invention is to provide a special intelligent controlled-release fertilizer for corn and a preparation method thereof.

[0006] The present invention uses nitrogen, phosphorus and potassium fertilizer raw materials and nutrient response signal substances as fertilizer cores after mixed extrusion granulation, and improves the final film quality and controlled release performance by enhancing the crosslinking density of polyester polyol and isophorone diisocyanate, improving the coating process, etc. The present invention can synchronously release fertilizer nutrients and nitrogen and phosphorus nutrient response signal substances according to the law of nutrient absorption of corn throughout the growth period, thereby realizing the intelligence of fertilizer.

[0007] Compared with traditional chemical fertilizers, the present invention can save 30%-50% of fertilizer and has the effect of increasing production. It can also utilize the existing seed-fertilizer co-seeding technology to accurately sow large-particle intelligent coated controlled-release fertilizers near the corn root system without damaging the roots or burning the seedlings, thus saving labor costs and having huge economic, social and ecological benefits.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] In a first aspect, the present invention provides a smart controlled-release fertilizer for corn, comprising a fertilizer core and a coating material coated on the surface of the fertilizer core;

[0010] The fertilizer core is composed of fertilizer raw materials, nitrogen response signal substance A and phosphorus response signal substance B;

[0011] The nitrogen response signal substance A is a flavonoid compound or a derivative thereof; the phosphorus response signal substance B is a monosaccharide or a derivative thereof or an isomer thereof.

[0012] The nitrogen response signal substance A is one or a mixture of apigenin, luteolin, luteolin 7-rutin, apigenin-7-O-glucuronide, isovitexin, quercetin, epigallocatechin, gentiana, 4',7-dimethoxy-5-hydroxyflavone, and genistein; the phosphorus response signal substance B is one or a mixture of fructose, fructose alcohol, lactulose, and fructose diacetone.

[0013] In a second aspect, the present invention provides a method for preparing the above-mentioned intelligent controlled-release fertilizer for corn, comprising the following steps:

[0014] (1) mixing fertilizer raw materials, nitrogen response signal substance A and phosphorus response signal substance B uniformly, and then extruding them into spherical fertilizer cores;

[0015] (2) The coating material is coated on the surface of the spherical fertilizer core and solidified to prepare the corn-specific intelligent controlled-release fertilizer.

[0016] Preferably, the coating material is obtained by mixing a modified bio-based polyester polyol C obtained by grafting a bio-based polyester polyol with blocked isophorone diisocyanate.

[0017] The bio-based polyester polyol is prepared by the following method:

[0018] The liquefied plant straw and organic dicarboxylic acid are mixed evenly in a weight ratio of 100: (25-225), and 0.01% to 0.1% of tetraisobutyl titanate as a catalyst is added to the total weight of the raw materials. The mixture is stirred continuously for 2 to 10 hours at 120°C to 280°C and the rotation speed is 100 rpm to 180 rpm. After sufficient reaction, the reaction vessel is evacuated, and then dry high-purity N2 is introduced to remove the by-product water, and the bio-based polyester polyol is obtained after cooling.

[0019] Preferably, the organic dicarboxylic acid is one or a mixture of isopropylmalonic acid, allylmalonic acid, diethylmalonic acid, butylmalonic acid, propylmalonic acid, benzylmalonic acid, cyclopentylmalonic acid, 3-thiophenemalonic acid, dipropylmalonic acid, cinnamylmalonic acid, phenylsuccinic acid, and DL-benzylsuccinic acid.

[0020] The modified bio-based polyester polyol C is prepared by the following method:

[0021] Mix the bio-based polyester polyol and sulfuric acid in a weight ratio of (20-40):1.2, and continue stirring at 100-200°C, then add 5-15g of auxiliary agent D and continue stirring for 1-5h at a speed of 100-200rpm to obtain modified bio-based polyester polyol C;

[0022] Preferably, the auxiliary agent D is one or a mixture of hydroxypropyl methylcellulose, carboxymethyl cellulose calcium, cellulose acetate butyrate, cellulose acetate phthalate, cyanoethyl cellulose, and cellulose triacetate.

[0023] The blocked isophorone diisocyanate is prepared by the following method:

[0024] Add 10-15g of isophorone diisocyanate and 15%-85% of the weight fraction of the blocking agent E into the reaction kettle at room temperature, and stir continuously at 100rpm-550rpm for 0.5h-2.5h. Then continue blocking at room temperature for 1-6.5h to obtain blocked isophorone diisocyanate;

[0025] Preferably, the end-capping agent E is one or a mixture of chloroacetaldehyde sodium bisulfite, disodium hydrogen phosphate, diammonium hydrogen phosphate, tetrabutylammonium dihydrogen phosphate, sodium hydrogen sulfate, potassium hydrogen sulfate, tetramethylammonium hydrogen sulfate, and tetraethylammonium hydrogen sulfate.

[0026] Preferably, the coating material is coated on the surface of the spherical fertilizer core using a lifting immersion circulation device, the lifting immersion circulation device comprising: an oil bath pot for containing the coating material, a funnel for containing the fertilizer core is provided above the oil bath pot, and the funnel can slide up and down along the fixed rod.

[0027] The method for coating the surface of a spherical fertilizer core with a coating material using a lifting immersion circulation device comprises the following steps:

[0028] (1) The coating material is placed in an oil bath and heated to 40°C to 45°C and maintained constant to form a blended coating liquid. A funnel containing spherical fertilizer cores is lowered along a fixed rod into the blended coating liquid. After being fully immersed, the funnel rises along the fixed rod and leaves the oil bath containing the blended coating liquid, thereby obtaining fertilizer cores immersed in the blended coating liquid.

[0029] (2) The temperature of the blower is raised to 50°C to 80°C, so that the blended coating liquid coated on the surface of the spherical fertilizer core is rapidly solidified to form a film.

[0030] The coating material accounts for 0.5% to 3% of the weight of the intelligent coated controlled-release fertilizer for corn. The release period is about 50 to 60 days; the first release peak is reached at about 20 days, during which the fertilizer nutrients are released by about 10 to 20%; the second release peak is reached at about 45 days, during which the fertilizer nutrients are released by about 55 to 65%; the third release peak is reached at about 55 days, during which the fertilizer nutrients are released by about 15 to 35%.

[0031] Beneficial effects of the present invention:

[0032] (1) The present invention adds nitrogen and phosphorus nutrient response signal substances to the fertilizer core according to the nutrient demand of corn during the entire growth period, mixes and extrude into large-particle fertilizer, selects large-particle fertilizer of corresponding size according to the nutrient demand of each corn plant, and obtains corn-specific intelligent coated controlled-release fertilizer after coating. The fertilizer is accurately applied near the corn root system through the existing seed and fertilizer co-seeding technology, and synchronously and continuously releases nutrient signal substances and fertilizer nutrients according to the law of corn nutrient absorption during the entire growth period. The fertilizer nutrient signal substance can greatly improve the ability of plants to absorb and utilize nutrients: for example, some fertilizer nutrient signal substances can make plants maintain hunger and directly promote the absorption of nutrients by plants; some fertilizer nutrient signal substances can indirectly help corn absorb and utilize nutrients in the soil by reorganizing specific microbial communities in the corn rhizosphere and recruiting some beneficial microbial communities, thereby achieving the effect of increasing production.

[0033] For example, some nitrogen response signal substances A can enrich the Oxalis bacteria around the corn root system, which will promote the elongation of the lateral roots of the corn root system to improve the ability of corn to capture nitrogen under nitrogen deficiency. For example, some phosphorus response signal substances B can recruit phosphate-solubilizing bacteria near the corn root system, and can also be used as energy substances to increase the number of phosphate-solubilizing bacteria and improve the efficiency of corn in using inorganic phosphorus in the soil.

[0034] After the fertilizer is coated, the release of nutrients in the fertilizer is delayed, avoiding problems such as root damage and seedling burning, fertilizer resource waste and serious environmental pollution caused by excessive fertilizer application at one time.

[0035] (2) The present invention can synchronously release fertilizer nutrients and nitrogen and phosphorus nutrient signal response substances according to the law of nutrient absorption of corn throughout its growth period. The addition of nitrogen and phosphorus nutrient response signal substances can not only directly improve the nutrient capture ability of corn, but also indirectly promote the absorption of nutrients by corn by recombining specific microbial communities in the rhizosphere of corn and recruiting beneficial microbial communities, which has a certain yield-increasing effect.

[0036] Spherical large-particle fertilizer can be made by pressing small-particle fertilizer raw materials in a certain proportion according to the fertilizer requirement of corn during the entire growth period, which reduces the amount of chemical fertilizer used and the production and pressing process is green and pollution-free.

[0037] The additive D improves the stability of the polyol network structure after being grafted with the polyester polyol through the copolymerization reaction between the hydroxyl groups, and increases the degree of crosslinking between the polyol and isophorone diisocyanate, thereby improving the controlled release performance of the fertilizer nutrients.

[0038] (3) The present invention provides a special coating process, in which a lifting immersion circulation device replaces the traditional drum. The end-capping agent E is introduced, and the active hydrogen atoms of E itself react with -NCO- of isophorone diisocyanate to generate a closed polyurethane product with weak internal chemical bonds. The chemical reaction is reversible, and at a higher temperature, the reaction tends to release -NCO- and the end-capping agent. Compared with the traditional drum coating process, this process has the advantages of fast curing speed, simple process, low cost, and more uniform distribution of the film material on the fertilizer surface.

[0039] (4) The present invention can synchronously release fertilizer nutrients and nitrogen and phosphorus nutrient signal response substances according to the law of nutrient absorption of corn throughout its growth period, emphasizing the mutual feedback cascade synergistic effect between the crop rhizosphere, root system and fertilizer, and realizing targeted and precise regulation of nutrients.

[0040] (4) The fertilizer utilization rate of the present invention is significantly improved, which can save 30% to 50% of fertilizer and increase production. The existing seed and fertilizer co-seeding technology can be used to accurately sow large-particle intelligent coated controlled-release fertilizer near the corn root system, saving labor costs and having huge economic, social and ecological benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 : Electron microscope photos of the coated controlled-release fertilizer membrane shell; a is a surface photo of the fertilizer membrane shell without the additive D; c is a cross-sectional photo of the fertilizer membrane shell without the additive D; b is a surface photo of the fertilizer membrane shell with the additive D; d is a cross-sectional photo of the fertilizer membrane shell with the additive D.

[0042] Figure 2 : Release curve of nitrogen and phosphorus nutrient signal response substances of the coated controlled-release fertilizer prepared in Example 2 of the present invention.

[0043] Figure 3 : Comparison and analysis of the nutrient release curve of the coated controlled-release fertilizer prepared in Example 2 of the present invention and the nutrient absorption rate curve of corn during the growth period; the results show that the nutrient release trend of the intelligent controlled-release fertilizer of the present invention is relatively synchronized with the nutrient absorption trend of corn. Wherein V1: seedling stage; V6: jointing stage; V 12 : trumpet stage; VT: tasseling stage; R1: silking stage; R3: milky stage; R6: full maturity stage; a is a comparative analysis diagram of the cumulative release curve of nitrogen fertilizer of coated controlled-release fertilizer and the nitrogen absorption rate curve during the growth period of corn, b is a comparative analysis diagram of the cumulative release curve of phosphorus fertilizer of coated controlled-release fertilizer and the phosphorus absorption rate curve during the growth period of corn; c is a comparative analysis diagram of the cumulative release curve of potassium fertilizer of coated controlled-release fertilizer and the potassium absorption rate curve during the growth period of corn.

[0044] Figure 4 : Nitrogen, phosphorus and potassium nutrient release curves of the coated controlled-release fertilizer prepared in Example 1 of the present invention at 25°C; wherein a is the nitrogen release rate curve, b is the phosphorus release rate curve, and c is the potassium release rate curve.

[0045] Figure 5 : Nitrogen, phosphorus and potassium nutrient release curves of the coated controlled-release fertilizer prepared in Example 2 of the present invention at 25°C. Where a is the nitrogen release rate curve, b is the phosphorus release rate curve, and c is the potassium release rate curve.

[0046] Figure 6 : Nitrogen, phosphorus and potassium nutrient release curves of the coated controlled-release fertilizer prepared in Example 3 of the present invention at 25°C. Where a is the nitrogen release rate curve, b is the phosphorus release rate curve, and c is the potassium release rate curve.

[0047] Figure 7 : Schematic diagram of the structure of the lifting type immersion circulation device of the present invention; a is a schematic diagram of the overall structure of the lifting type immersion circulation device, b is a schematic diagram of the lifting mechanism structure, and c is a schematic diagram of the funnel structure;

[0048] Among them, 1. bottom plate, 2. constant temperature heating device, 3. oil bath pot, 4. funnel, 5. circular pores, 6. lifting plate, 7. hot blower, 8. connecting plate, 9. threaded slider, 10. screw rod, 11. protective shell, 12. motor; 9 and 10 constitute the fixing rod. DETAILED DESCRIPTION

[0049] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0050] As mentioned above, traditional controlled-release fertilizers have the following problems: 1. Traditional controlled-release fertilizers only rely on the thickness of the coating to regulate the release of fertilizer nutrients, lack innovation in targeted and precise nutrient regulation, and only emphasize the supply of fertilizers to crops and soil, ignoring the intelligent response and mutual feedback cascade synergistic effect between fertilizer nutrients and crop root systems. 2. The nutrient supply of traditional fertilizers does not match the nutrient demand of crops at different growth stages: Since traditional fertilizers release nutrients quickly in the early stage, fertilizer nutrients are released into the soil when the demand for nutrients is not high in the early stage of crop growth, resulting in a waste of fertilizer resources. 3. The coating process of traditional controlled-release fertilizers mostly adopts the drum coating process. During heating and curing, the fertilizer particles are constantly adhered, torn, and repaired in the drum, resulting in uneven distribution of the film material on the fertilizer surface and poor fertilizer nutrient controlled release effect.

[0051] Based on the shortcomings of traditional controlled-release fertilizers, the present invention provides a method for preparing a smart controlled-release fertilizer for corn. In one embodiment of the present invention, a method for preparing a smart controlled-release fertilizer for corn is provided, comprising the following steps:

[0052] Nitrogen response signal substance A and phosphorus response signal substance B are uniformly mixed into the fertilizer core, and the fertilizer core is extruded into a spherical fertilizer core on an extruder.

[0053] The nitrogen response signal substance A is one or a mixture of several of apigenin, luteolin, luteolin 7-rutin, apigenin-7-O-glucuronide, isovitexin, quercetin, epigallocatechin, gentiana strychnine, 4',7-dimethoxy-5-hydroxyflavone, and genistein;

[0054] The phosphorus response signal substance B is one of fructose, fructose alcohol, lactulose, and fructose diacetone, or a mixture of several of them.

[0055] The partial nitrogen response signal substance A used in the present invention can reorganize the specific microbial community in the corn rhizosphere, recruit the Oxalobacteraceae bacteria near the corn rhizosphere to regulate the development of corn lateral roots and promote the capture of nitrogen.

[0056] The partial phosphorus response signal substance B used in the present invention can not only recruit soil phosphate-solubilizing bacteria but also serve as an energy substance to increase the number of phosphate-solubilizing bacteria to indirectly improve the ability of corn root mycelium to activate organic phosphorus.

[0057] The liquefied plant straw and organic dicarboxylic acid are mixed evenly in a weight ratio of 100: (25-225), and 0.01% to 0.1% of tetraisobutyl titanate as a catalyst is added to the total weight of the raw materials. The mixture is stirred continuously for 2 to 10 hours at 120°C to 280°C and the rotation speed is 100 rpm to 180 rpm. After sufficient reaction, the reaction vessel is evacuated, and then dry high-purity N2 is introduced to remove the by-product water, and the bio-based polyester polyol is obtained after cooling.

[0058] The organic dicarboxylic acid is one or a mixture of isopropylmalonic acid, allylmalonic acid, diethylmalonic acid, butylmalonic acid, propylmalonic acid, benzylmalonic acid, cyclopentylmalonic acid, 3-thiophenemalonic acid, dipropylmalonic acid, cinnamylmalonic acid, phenylsuccinic acid, and DL-benzylsuccinic acid.

[0059] Since the molecular weight of the plant straw liquefied polyol obtained after the plant straw liquefaction is low, the cross-linking degree of the polyurethane generated by the reaction is low and cannot meet the expected controlled release requirements. Therefore, the present invention modifies the plant straw liquefied polyol: the purpose of the modification is to generate a bio-based polyester polyol with rich ester groups and flexible structural design, which can give the polyurethane excellent wear resistance, elasticity, flexibility, etc.

[0060] Bio-based polyester polyol and sulfuric acid are poured into a three-necked flask at a weight ratio of (20-40):1.2 and stirred continuously at 100-200°C, then 5-15g of auxiliary agent D is added and stirred continuously for 1-5h at a speed of 100-200rpm to obtain modified bio-based polyester polyol C. The auxiliary agent D is one or a mixture of hydroxypropyl methylcellulose, carboxymethyl cellulose calcium, cellulose acetate butyrate, cellulose acetate phthalate, cyanoethyl cellulose, and cellulose triacetate.

[0061] In order to further improve the stability of the polyol network structure, increase the degree of crosslinking between the polyol and isophorone diisocyanate, and improve the nutrient release characteristics of the controlled-release fertilizer, the present invention grafts the polyol by copolymerizing the hydroxyl groups of the auxiliary agent D with the polyester polyol.

[0062] Add 10-15g of isophorone diisocyanate and 15%-85% of the weight fraction of blocking agent E into a reaction kettle at room temperature, stir continuously at 100rpm-550rpm for 0.5h-2.5h, and then continue blocking at room temperature for 1-6.5h to obtain blocked isophorone diisocyanate.

[0063] The end-capping agent E is one or a mixture of chloroacetaldehyde sodium bisulfite, disodium hydrogen phosphate, diammonium hydrogen phosphate, tetrabutylammonium dihydrogen phosphate, sodium hydrogen sulfate, potassium hydrogen sulfate, tetramethylammonium hydrogen sulfate, and tetraethylammonium hydrogen sulfate.

[0064] In the present invention, the active hydrogen atom of the end-capping agent E can react with -NCO- of isophorone diisocyanate at 40° C. to generate a blocked polyurethane product with a weak internal chemical bond. The chemical reaction is reversible, and at a higher temperature, the reaction tends to release -NCO- and the end-capping agent.

[0065] The modified bio-based polyester polyol C and blocked isophorone diisocyanate are uniformly mixed at a mass ratio of (0.6-1.2):1 at room temperature to obtain a coating material.

[0066] In order to improve the quality of the coating, the present invention designs a lifting type immersion circulation device to coat the coating material on the surface of the spherical fertilizer core. The structural schematic diagram of the lifting type immersion circulation device is shown in FIG. Figure 7 As shown, it includes a bottom plate 1, a constant temperature heating device 2 is installed above the bottom plate 1, an oil bath pot 3 for containing coating materials is installed above the constant temperature heating device 2, a funnel 4 for containing fertilizer cores is arranged above the oil bath pot 3, and the funnel 4 can slide up and down along the fixed rod.

[0067] The fixed rod includes a screw rod 10 and a threaded slider 9. The screw rod 10 is vertically installed above the base plate 1. A motor 12 is fixedly installed on the top of the screw rod 10. The threaded slider 9 that can slide up and down is installed on the screw rod 10. The protective shell 11 forms a accommodating cavity to wrap the screw rod 10 and the threaded slider 9. A connecting plate 8 is installed on one side of the threaded slider 9. A lifting plate 6 with a circular hollow is fixedly installed on the front section of the connecting plate 8. The circular hollow part of the lifting plate 6 is used to install a conical funnel 4 with a circular gap 5. The hot blower 7 is installed below the lifting plate 6.

[0068] The method of coating the surface of a spherical fertilizer core with a coating material using a lifting immersion circulation device comprises the following steps:

[0069] (1) placing the coating material in an oil bath 3 and heating it to 40°C to 45°C and maintaining a constant temperature to form a blended coating liquid, then placing the spherical fertilizer core in a funnel 4 with a hole diameter of less than 1 mm of a lifting immersion circulation device, adjusting the threaded slider 9 downward by the motor 12, thereby driving the lifting plate 6 downward, so that the funnel 4 containing the spherical fertilizer core is fully immersed in the oil bath 3 containing the blended coating liquid, and adjusting the threaded slider 9 upward by the motor 12 again, thereby driving the lifting plate 6 upward, so that the funnel 4 containing the spherical fertilizer core leaves the oil bath 3 containing the blended coating liquid;

[0070] (2) Turn on the hot blower 7 to remove excess blended coating liquid on the surface of the spherical fertilizer core at 25° C., and increase the blower temperature to 50° C. to 80° C. so that the blended coating liquid can be quickly solidified on the surface of the spherical fertilizer core to form a film. Repeat steps (1) and (2) 3 to 5 times to obtain a large-particle intelligent coated controlled-release fertilizer for corn with a controlled-release period of about 50 to 60 days.

[0071] Compared with the traditional drum coating process, the coating process involved in the present invention is simpler, has low cost, fast curing speed, and more uniform distribution of the film material on the fertilizer surface.

[0072] Corn, as one of the most important cereal crops in the world, exhibits a complex root system structure and a large degree of genomic diversity. Corn is prone to nitrogen and phosphorus deficiency during planting, and even after the application of controlled-release fertilizers, the improvement effect is not obvious. This is due to the fact that nitrogen and phosphorus nutrients are easily lost and fixed in the soil and the limited ability of corn to absorb nutrients. In addition, corn often releases nutrient signal substances when it needs nutrients. These nutrient signal substances will keep corn hungry, directly promote the absorption of nutrients by corn, and recruit some special microbial communities, which will indirectly assist plants in obtaining nutrients. Based on the above, the present invention designs a new type of intelligent controlled-release fertilizer for corn: the fertilizer can synchronously release fertilizer nutrients and nitrogen and phosphorus nutrient signal response substances according to the law of nutrient absorption by corn throughout the growth period, so as to achieve the effect of increasing production. The present invention adopts nitrogen and phosphorus nutrient signal substances mixed with nitrogen, phosphorus and potassium fertilizers as the fertilizer core, and then encapsulates it, which can not only regulate the release rate of nitrogen, phosphorus and potassium nutrients, but also synchronously release fertilizer nutrient signal substances to promote the absorption of nutrients by corn.

[0073] The ingenuity of the present invention lies in:

[0074] For the first time, nitrogen and phosphorus nutrient signal response substances were mixed with fertilizer raw materials, granulated and coated to make controlled-release fertilizers. Fertilizer-crop-crop root system is closely linked. While delaying the release of fertilizer nutrients, the continuously released nitrogen and phosphorus nutrient signal response substances will also be sensed by the plant roots, keeping the crops hungry, directly promoting the crop's absorption of nutrients or recruiting beneficial soil microorganisms to indirectly improve the crop's ability to capture nutrients.

[0075] The advantages of the present invention over traditional controlled-release fertilizers are:

[0076] 1. First, nitrogen and phosphorus response signal substances were introduced on the basis of traditional controlled-release fertilizers, changing the traditional mode of controlled-release fertilizers that only rely on coating thickness to regulate nutrient release: the partial nitrogen response signal substance A can enrich the Oxalobacteraceae around the corn root system and promote the development and elongation of the lateral roots of the corn root system to increase corn yield under nitrogen deficiency; the partial phosphorus response signal substance B can not only provide energy for microorganisms, but also recruit phosphate-solubilizing bacteria near the corn root system to improve the utilization efficiency of inorganic phosphorus in the soil by corn. 2. The problem of low crosslinking degree of the existing polyurethane film shell was improved, and the auxiliary agent D was introduced to improve the stability of the polyol network structure through copolymerization between hydroxyl groups, increase its crosslinking degree with isophorone diisocyanate, and improve the nutrient release characteristics of the controlled-release fertilizer. 3. The release curves of nitrogen, phosphorus response signal substances and fertilizer nutrients are fitted with the fertilizer requirement curve during the growth period of corn, which to a certain extent solves the problem that the nutrient supply of traditional fertilizers does not match the nutrient demand of crops in different growth periods. 4. The traditional coating process is improved. In the existing drum coating process, during the heating and curing process, the fertilizer particles rotate continuously in the drum, and the adhesion, tearing and repairing process continue to occur. The film material is not evenly distributed on the fertilizer surface, resulting in poor fertilizer nutrient controlled release effect. The present invention adopts a lifting immersion automatic circulation device combined with a capping agent E, which is low in cost and simple to operate, and the film material is more evenly distributed on the fertilizer surface.

[0077] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific embodiments.

[0078] The test materials used in the examples and comparative examples of the present invention are all conventional test materials in the art and can be purchased through commercial channels. The experimental methods without detailed conditions are carried out in accordance with conventional test methods or the operating instructions recommended by the supplier. Among them:

[0079] The plant straw liquefaction method is an existing method in the prior art, for example, it can be prepared by referring to the method of the document "Siloxane and polyether dual modification improves hydrophobicity and interpenetrating polymer network of bio-polymer for coated fertilizers with enhanced slow release characteristics, 2018.06.061". The document was published by our laboratory. The plant straw liquefaction method in the document is the same as the present invention, but the liquefied straw catalyst used in the document is concentrated sulfuric acid, and the catalyst is replaced by tetraisobutyl titanate in the present invention.

[0080] The plant straw may be any existing plant straw, and corn straw is used in the embodiments and comparative examples of the present invention.

[0081] Example 1: A method for preparing a smart controlled-release fertilizer for corn

[0082] 1. Preparation of spherical fertilizer core:

[0083] The fertilizer core is composed of fertilizer raw materials, nitrogen response signal substance A, and phosphorus response signal substance B;

[0084] The fertilizer raw material is composed of urea, diammonium phosphate and potassium sulfate powder mixed in a weight ratio of 4:2:1;

[0085] The nitrogen response signal substance A is composed of apigenin, luteolin and apigenin 6-C-glucuronide mixed in a weight ratio of 1:1:1.

[0086] The phosphorus response signal substance B is composed of fructose and fructose alcohol mixed in a weight ratio of 1:1.

[0087] First, 0.9 g of nitrogen response signal substance A and 60 g of phosphorus response signal substance B are uniformly mixed into 1 kg of fertilizer raw material, and then mixed into 1000 kg of fertilizer raw material for secondary mixing to obtain a fertilizer core, which is then extruded into a spherical fertilizer core on an extruder.

[0088] 2. Preparation of coating materials:

[0089] (1) 100 g of liquefied plant straw and 25 g of organic dicarboxylic acid (the organic dicarboxylic acid is obtained by mixing isopropyl malonic acid, allyl malonic acid, diethyl malonic acid, and butyl malonic acid in a weight ratio of 1:1:1:1) are uniformly mixed, and 0.01% of tetraisobutyl titanate as a catalyst is added to the total weight of the mixed raw materials. The mixture is stirred continuously for 2 h at 120° C. and a speed of 100 rpm. After sufficient reaction, the reaction container is evacuated, and then dry high-purity inert gas (N2) is introduced to remove by-product water, and the bio-based polyester polyol is obtained after cooling.

[0090] (2) Pour 20 g of bio-based polyester polyol and 1.2 g of sulfuric acid into a three-necked flask and stir continuously at 100° C. Then add 5 g of auxiliary agent D (auxiliary agent D is hydroxypropyl methylcellulose and carboxymethyl cellulose calcium mixed in a weight ratio of 1:1 as auxiliary agent D) and continue stirring for 1 h at a speed of 100 rpm to obtain modified bio-based polyester polyol C.

[0091] (3) Add 10 g of isophorone diisocyanate and 15% by weight of a blocking agent E (blocking agent E is a mixture of sodium chloroacetaldehyde bisulfite and disodium hydrogen phosphate in a weight ratio of 1:1) into a reaction kettle at room temperature, and stir continuously at 100 rpm for 0.5 h. Then continue blocking at room temperature for 1 h to obtain blocked isophorone diisocyanate.

[0092] (4) At room temperature, 10 g of modified bio-based polyester polyol C and 10 g of blocked isophorone diisocyanate were mixed to obtain a coating material.

[0093] 3. Adoption Figure 7 The lifting type immersion circulation device shown in the figure is used for coating treatment, and the specific method is as follows:

[0094] (1) 10 g of coating material is placed in an oil bath and heated to 40° C. and maintained constant to form a blended coating liquid, and then the spherical fertilizer core is placed in a funnel with a hole diameter of less than 1 mm of a lifting immersion circulation device, and the threaded slider is adjusted by a motor to descend, thereby driving the lifting plate to descend, so that the funnel containing the spherical fertilizer core is fully immersed in the oil bath containing the blended coating liquid, and the threaded slider is adjusted by the motor to rise again, thereby driving the lifting plate to rise, so that the funnel containing the spherical fertilizer core leaves the oil bath containing the blended coating liquid;

[0095] (2) Turn on the hot blower at 25°C to remove excess blended coating liquid on the surface of the spherical fertilizer core, and increase the blower temperature to 55°C to allow the blended coating liquid to quickly solidify on the surface of the spherical fertilizer core to form a film, which accounts for about 0.5% of the total weight of the fertilizer. Repeat (1) and (2) for 3 times to obtain a large-particle intelligent coated controlled-release fertilizer for corn with a controlled-release period of about 50 days.

[0096] Embodiment 2:

[0097] 1. Preparation of spherical fertilizer core:

[0098] The fertilizer core is composed of fertilizer raw materials, nitrogen response signal substance A, and phosphorus response signal substance B;

[0099] The fertilizer raw material is composed of urea, diammonium phosphate and potassium sulfate powder mixed in a weight ratio of 4:2:1;

[0100] The nitrogen response signal substance A is composed of isovitexin and quercetin mixed in a weight ratio of 1:1.

[0101] The phosphorus response signal substance B is composed of fructose, fructose alcohol and lactulose mixed in a weight ratio of 1:1:1.

[0102] First, 0.9 g of nitrogen response signal substance A and 60 g of phosphorus response signal substance B are uniformly mixed into 1 kg of fertilizer raw material, and then mixed into 1000 kg of fertilizer raw material for secondary mixing to obtain fertilizer cores, which are then extruded into spherical fertilizer cores on an extruder.

[0103] 2. Preparation of coating materials:

[0104] (1) 100 g of liquefied plant straw and 25 g of organic dicarboxylic acid (the organic dicarboxylic acid is cyclopentylmalonic acid, 3-thiophenemalonic acid, dipropylmalonic acid, and cinnamylmalonic acid mixed in a weight ratio of 1:1:1:1 as the organic dicarboxylic acid) are mixed evenly, and 0.05% of tetraisobutyl titanate as a catalyst accounting for the total weight of the raw materials is added, and the mixture is continuously stirred at 200° C. for 5 h at a speed of 130 rpm. After sufficient reaction, the reaction vessel is evacuated, and then dry high-purity N2 is introduced to remove by-product water, and the bio-based polyester polyol is obtained after cooling.

[0105] (2) Pour 30 g of bio-based polyester polyol and 1.2 g of sulfuric acid into a three-necked flask and stir continuously at 150° C. Then add 10 g of auxiliary agent D (auxiliary agent D is cellulose acetate butyrate and cellulose acetate phthalate mixed in a weight ratio of 1:1) and continue stirring for 2.5 h at a speed of 150 rpm to obtain modified bio-based polyester polyol C.

[0106] (3) Add 10 g of isophorone diisocyanate and 50% by weight of blocking agent E (blocking agent E is tetrabutylammonium dihydrogen phosphate and sodium hydrogen sulfate mixed in a weight ratio of 1:1 as blocking agent E) into a reaction kettle at room temperature, and stir continuously at 300 rpm for 1.5 h. Then continue blocking at room temperature for 3 h to obtain blocked isophorone diisocyanate.

[0107] (4) 10 g of modified bio-based polyester polyol C and 10 g of blocked isophorone diisocyanate were mixed uniformly at room temperature to obtain a coating material.

[0108] 3. Adoption Figure 7 The lifting type immersion circulation device shown in the figure is used for coating treatment, and the specific method is as follows:

[0109] (1) 10 g of coating material is placed in an oil bath and heated to 45° C. and maintained constant to form a blended coating liquid, and then the spherical fertilizer core is placed in a funnel with a hole diameter of less than 1 mm of a lifting immersion circulation device, and the threaded slider is adjusted by a motor to descend, thereby driving the lifting plate to descend, so that the funnel containing the spherical fertilizer core is fully immersed in the oil bath containing the blended coating liquid, and the threaded slider is adjusted by the motor to rise again, thereby driving the lifting plate to rise, so that the funnel containing the spherical fertilizer core leaves the oil bath containing the blended coating liquid;

[0110] (2) Turn on the hot blower at 25°C to remove excess blended coating liquid on the surface of the spherical fertilizer core, and increase the blower temperature to 50°C to allow the blended coating liquid to quickly solidify on the surface of the spherical fertilizer core to form a film, which accounts for about 0.5% of the total weight of the fertilizer. Repeat (1) and (2) operations 4 times to obtain a large-particle intelligent coated controlled-release fertilizer for corn with a controlled-release period of about 55 days.

[0111] Example 3: Preparation method of a smart controlled-release fertilizer for corn

[0112] 1. Preparation of spherical fertilizer core:

[0113] The fertilizer core is composed of fertilizer raw materials, nitrogen response signal substance A, and phosphorus response signal substance B;

[0114] The fertilizer raw material is composed of urea, diammonium phosphate and potassium sulfate powder mixed in a weight ratio of 4:2:1;

[0115] The nitrogen response signal substance A is obtained by mixing apigenin, eugenol and apigenin 6-C-glucuronide in a weight ratio of 1:1:1, and the phosphorus response signal substance B is obtained by mixing fructose and fructose diacetone in a weight ratio of 1:1.

[0116] First, 0.9 g of nitrogen response signal substance A and 60 g of phosphorus response signal substance B are evenly mixed into 1 kg of fertilizer raw material, and then mixed into 1000 kg of fertilizer raw material for secondary mixing to obtain a fertilizer core, which is then extruded into a spherical fertilizer core on an extruder.

[0117] 2. Preparation of coating materials:

[0118] (1) 100 g of liquefied plant straw and 25 g of organic dicarboxylic acid (phenylsuccinic acid and DL-benzylsuccinic acid are mixed in a weight ratio of 1:1 as the organic dicarboxylic acid) are uniformly mixed, and 0.1% of tetraisobutyl titanate as a catalyst is added to the total weight of the mixed raw materials. The mixture is stirred continuously for 10 h at 280° C. and a speed of 180 rpm. After sufficient reaction, the reaction vessel is evacuated, and then dry high-purity N2 is introduced to remove by-product water, and the bio-based polyester polyol is obtained after cooling.

[0119] (2) Pour 40 g of bio-based polyester polyol and 1.2 g of sulfuric acid into a three-necked flask and continue stirring at 200° C. Then add 15 g of auxiliary agent D (auxiliary agent D is cyanoethyl cellulose and triacetate cellulose mixed in a weight ratio of 1:1 as auxiliary agent D) and continue stirring for 5 h at a speed of 200 rpm to obtain modified bio-based polyester polyol C.

[0120] (3) Add 10 g of isophorone diisocyanate and 85% by weight of blocking agent E (blocking agent E is obtained by mixing tetramethylammonium hydrogen sulfate and tetraethylammonium hydrogen sulfate in a weight ratio of 1:1) into a reaction kettle at room temperature, and stir continuously at 550 rpm for 2.5 hours. Then continue blocking at room temperature for 6.5 hours to obtain blocked isophorone diisocyanate.

[0121] (4) 10 g of modified bio-based polyester polyol C and 10 g of blocked isophorone diisocyanate were mixed uniformly at room temperature to obtain a coating material.

[0122] 3. Adoption Figure 7 The lifting type immersion circulation device shown in the figure is used for coating treatment, and the specific method is as follows:

[0123] (1) 10 g of coating material is placed in an oil bath and heated to 40° C. and maintained constant to form a blended coating liquid, and then the spherical fertilizer core is placed in a funnel with a hole diameter of less than 1 mm of a lifting immersion circulation device, and the threaded slider is adjusted by a motor to descend, thereby driving the lifting plate to descend, so that the funnel containing the spherical fertilizer core is fully immersed in the oil bath containing the blended coating liquid, and the threaded slider is adjusted by the motor to rise again, thereby driving the lifting plate to rise, so that the funnel containing the spherical fertilizer core leaves the oil bath containing the blended coating liquid;

[0124] (2) Turn on the hot blower at 25°C to remove excess blended coating liquid on the surface of the spherical fertilizer core, and increase the blower temperature to 65°C to allow the blended coating liquid to quickly solidify on the surface of the spherical fertilizer core to form a film, which accounts for about 0.5% of the total weight of the fertilizer. Repeat (1) and (2) for 5 times to obtain a large-particle intelligent coated controlled-release fertilizer for corn with a controlled-release period of about 60 days.

[0125] Comparative Example 1: No coating treatment was performed, and no nitrogen or phosphorus response signal substances were added to the fertilizer core.

[0126] The fertilizer core is composed of fertilizer raw materials;

[0127] The fertilizer raw material is composed of urea, diammonium phosphate and potassium sulfate powder mixed in a weight ratio of 4:2:1; the fertilizer raw material is extruded into a spherical fertilizer core on an extruder.

[0128] Comparative Example 2: The coating material of the present invention was used for coating treatment, and no nitrogen or phosphorus response signal substances were added to the fertilizer core.

[0129] 1. Preparation of spherical fertilizer core:

[0130] The fertilizer core is composed of fertilizer raw materials;

[0131] The fertilizer raw materials are prepared by mixing urea, diammonium phosphate and potassium sulfate powder in a weight ratio of 4:2:1; and then extruding them into spherical fertilizer cores on an extruder.

[0132] 2. The preparation of the coating material and the coating treatment method are the same as in Example 2.

[0133] Comparative Example 3: The coating material of the present invention is used for coating treatment, and only nitrogen response signal substance A is added to the fertilizer core.

[0134] 1. Preparation of spherical fertilizer core:

[0135] The fertilizer core is composed of fertilizer raw materials and nitrogen response signal substance A.

[0136] The fertilizer raw material is composed of urea, diammonium phosphate and potassium sulfate powder mixed in a weight ratio of 4:2:1;

[0137] The nitrogen response signal substance A is composed of isovitexin and quercetin mixed in a weight ratio of 1:1.

[0138] First, 0.9 g of nitrogen response signal substance A is uniformly mixed into 1 kg of fertilizer raw material, and then mixed into 1000 kg of fertilizer raw material for secondary mixing to obtain a fertilizer core, which is then extruded into a spherical fertilizer core on an extruder.

[0139] 2. The preparation of the coating material and the coating treatment method are the same as in Example 2.

[0140] Comparative Example 4: The coating material of the present invention is used for coating treatment, and only the phosphorus response signal substance B is added to the fertilizer core.

[0141] 1. Preparation of spherical fertilizer core:

[0142] The fertilizer core is composed of fertilizer raw materials and phosphorus response signal substance B.

[0143] The fertilizer raw material is composed of urea, diammonium phosphate and potassium sulfate powder mixed in a weight ratio of 4:2:1;

[0144] The phosphorus response signal substance B is composed of fructose, fructose alcohol and lactulose mixed in a weight ratio of 1:1:1.

[0145] First, 60 g of phosphorus response signal substance B is uniformly mixed into 1 kg of fertilizer raw material, and then mixed into 1000 kg of fertilizer raw material for secondary mixing to obtain a fertilizer core, which is then extruded into a spherical fertilizer core on an extruder.

[0146] 2. The preparation of the coating material and the coating treatment method are the same as in Example 2.

[0147] Test example:

[0148] Planting experiments were conducted using the intelligent controlled-release fertilizers for corn prepared in Examples 1-3 of the present invention and the fertilizers prepared in Comparative Examples 1-4.

[0149] The test field is located in Linzi District, Zibo City, Shandong Province (E 118°13′, N 36°57′). The soil type for the test is tidal soil (subclass), which is a lime-colored moist embryonic soil in the Chinese soil system classification. The corn variety is "Zhengdan 958". Sowing was carried out on June 24, and the seeds and fertilizers were sown at the same time; the experiment set up 7 treatments, and the fertilizers prepared by comparative examples 1-4 and examples 1-3 were applied respectively, and the application rate of the fertilizers was 650kg / ha.

[0150] After sowing, each treatment was managed according to farmers' habits such as field watering, pesticide application and weeding, and the management conditions of each treatment were consistent. Soil samples and plant samples were collected on the 22nd, 33rd, 55th and 101st days (7.16, 7.27, 8.18 and 10.3) after fertilization and sowing, and the yield was measured and harvested in early October. The aboveground plant samples were taken on the 22nd, 33rd, 55th and 101st days after planting, and 3 holes of aboveground plants were taken from each plot. The aboveground fresh weight was weighed and the data was recorded. Then, the aboveground plant sample of 1 hole close to the average value was brought back to the laboratory, put into 105℃ for 20min, and then completely dried in an 80℃ oven (48h) to constant weight, weighed and recorded, and the aboveground biomass was calculated.

[0151] Fifteen corn plants were harvested in each plot, and corn cobs and aboveground straw were harvested. Three rows of aboveground straw made one bundle, and each row of corn cobs made one bag. One stalk of corn was taken, and the fresh weight was weighed again and brought back to the laboratory. The straw was sterilized at 105 degrees and dried at 80 degrees. The dry weight of the straw was weighed, and the straw biomass was calculated. Corn cobs (5 plants) from the third row were taken back to the laboratory for air drying, and the dry weight of the corn cobs was weighed. The corn cobs were threshed, and the number of kernels on five cobs was counted separately. The weight of corn cobs and kernels was weighed to calculate the corn yield. The corn cobs were ground and the total nitrogen was determined. Then five portions of corn cobs and five portions of kernels were taken, dried at 80 degrees, weighed, and the kernel biomass and corn cob biomass were calculated.

[0152] Take the air-dried corn kernels, 100 kernels from each plot, and weigh them, which is the 100-kernel weight.

[0153] The corn yield, biomass, number of kernels per ear, and 100-kernel weight were counted. The experiment was repeated three times, and the results were averaged. Microsoft Excel 2016 and SPAS Statistics 26 software were used to count, analyze, and process the relevant data. Origin 2023 was used to draw graphs and tables. The results are shown in Table 1:

[0154] Table 1: Corn yield results of different fertilizer applications

[0155]

[0156] Note: The means in the same column were compared using Duncan multiple comparisons. The numbers with the same lowercase letters at the end indicated no significant difference (P<0.05).

[0157] It can be seen from Table 1 that the biomass, number of grains per ear, 100-grain weight, yield and other indicators of the corn treated with the fertilizers of Examples 1-3 are significantly improved compared with the corn treated with the fertilizers of Comparative Examples 1-4. The results show that adding the nitrogen response signal substance and the phosphorus response signal substance of the present invention to the fertilizer raw materials can improve the release effect of the fertilizer raw materials themselves, increase the yield of crops, and have a synergistic effect.

[0158] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A smart controlled-release fertilizer for corn, characterized in that: It comprises a fertilizer core and a coating material coated on the surface of the fertilizer core; The fertilizer core is composed of fertilizer raw materials, nitrogen response signal substance A and phosphorus response signal substance B; The nitrogen response signal substance A is one or more of apigenin, luteolin, isovitexin, quercetin, and euphorbia cerifera; The phosphorus response signal substance B is one or more of fructose, fructose alcohol, lactulose, and fructose diacetone; The method for preparing the intelligent controlled-release fertilizer for corn comprises the following steps: (1) mixing the fertilizer raw material, the nitrogen response signal substance A and the phosphorus response signal substance B uniformly, and then extruding them into a spherical fertilizer core; (2) coating the coating material on the surface of the spherical fertilizer core and solidifying it to prepare a smart controlled-release fertilizer for corn; The coating material is obtained by mixing a modified bio-based polyester polyol C obtained by grafting a bio-based polyester polyol with blocked isophorone diisocyanate; The modified bio-based polyester polyol C is prepared by the following method: The bio-based polyester polyol and sulfuric acid are mixed uniformly in a weight ratio of (20-40): 1.2, and stirred continuously at 100° C. to 200° C. Then, 5-15 g of an auxiliary agent D is added and stirred continuously for 1 to 5 hours at a speed of 100 to 200 rpm to obtain a modified bio-based polyester polyol C; The auxiliary agent D is one or more of hydroxypropyl methylcellulose, carboxymethyl cellulose calcium, cellulose acetate butyrate, cellulose acetate phthalate, cyanoethyl cellulose, and cellulose triacetate; The blocked isophorone diisocyanate is prepared by the following method: Add 10-15 g of isophorone diisocyanate and 15%-85% by weight of a blocking agent E to a reaction kettle at room temperature, stir continuously at 100 rpm to 550 rpm for 0.5 h to 2.5 h, and then continue blocking at room temperature for 1 to 6.5 h to obtain blocked isophorone diisocyanate; The end-capping agent E is one or more of chloroacetaldehyde sodium bisulfite, disodium hydrogen phosphate, tetrabutylammonium dihydrogen phosphate, sodium hydrogen sulfate, tetramethylammonium hydrogen sulfate, and tetraethylammonium hydrogen sulfate.

2. The intelligent controlled-release fertilizer for corn according to claim 1, characterized in that: The bio-based polyester polyol is prepared by the following method: The liquefied plant straw and the organic dicarboxylic acid are mixed evenly in a weight ratio of 100:(25-225), and 0.01%-0.1% of tetraisobutyl titanate as a catalyst is added to the mixture at a total weight of the mixed raw materials. The mixture is stirred continuously at 120°C-280°C for 2-10 hours at a rotation speed of 100rpm-180rpm. After sufficient reaction, the reaction vessel is evacuated, and then dry high-purity N2 is introduced to remove by-product water, and bio-based polyester polyol is obtained after cooling.

3. The intelligent controlled-release fertilizer for corn according to claim 2, characterized in that: The organic dicarboxylic acid is one or a mixture of isopropylmalonic acid, allylmalonic acid, diethylmalonic acid, butylmalonic acid, cyclopentylmalonic acid, 3-thiophenemalonic acid, dipropylmalonic acid, cinnamylmalonic acid, phenylsuccinic acid, and DL-benzylsuccinic acid.

4. The intelligent controlled-release fertilizer for corn according to claim 1, characterized in that: The coating material is coated on the surface of the spherical fertilizer core by using a lifting immersion circulation device to coat the coating material on the surface of the spherical fertilizer core; The lifting type immersion circulation device comprises: an oil bath pot for containing the coating material, a funnel for containing the fertilizer core is arranged above the oil bath pot, and the funnel can slide up and down along the fixed rod.

5. The intelligent controlled-release fertilizer for corn according to claim 4, characterized in that: The method of coating the coating material on the surface of the spherical fertilizer core using the lifting immersion circulation device comprises the following steps: (1) placing the coating material in an oil bath and heating it to 40° C. to 45° C. and maintaining a constant temperature to form a blended coating liquid, and lowering a funnel containing a spherical fertilizer core along a fixed rod into the blended coating liquid. After being fully immersed, the funnel rises along the fixed rod and leaves the oil bath containing the blended coating liquid, thereby obtaining a fertilizer core immersed in the blended coating liquid; (2) The temperature is raised to 50°C to 80°C, so that the blended coating liquid coated on the surface of the spherical fertilizer core is rapidly solidified to form a film.

6. The intelligent controlled-release fertilizer for corn according to claim 1, characterized in that: The coating material accounts for 0.5% to 3% of the weight of the intelligent coated controlled-release fertilizer dedicated to corn.

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