Synergistic urea and preparation method thereof

Abstract

The invention discloses synergistic urea and a preparation method thereof, and belongs to the technical field of controlled-release fertilizers. On the basis that the urease inhibitor and the nitrification inhibitor are adopted as synergists, the coating technology is combined, and the utilization rate of urea is greatly increased. Moreover, urea particles are subjected to double-layer coating, so that the release rate of urea in soil is slowed down, nutrient loss is reduced, the fertilizer efficiency is more lasting, the utilization rate of urea is greatly improved, crop income and yield increase is promoted, and the planting benefit is improved. In addition, the preparation method of the synergistic urea provided by the invention is simple in steps, coating of a coating liquid for multiple times is omitted, and the dosage of the coating liquid is small.

Description

Technical Field

[0001] The invention belongs to the technical field of controlled-release fertilizers, and in particular relates to a synergistic urea and a preparation method thereof. Background Art

[0002] Urea is suitable for various soils and plants, and has the advantages of being easy to store, convenient to use, and having little damage to the soil. At present, urea used in agriculture is usually instant fertilizer, which will dissolve and transform quickly in water and soil, resulting in an overall utilization rate of urea nitrogen of only 30-35%. Therefore, improving the utilization rate of urea has become a top priority in the current agricultural market.

[0003] Based on the principle that urea is rapidly converted under the action of urease and nitrification occurs under nitrifying bacteria, the urea utilization rate can be improved by adding urease inhibitors and nitrification inhibitors to urea. In addition, coating urea with polymers or other materials is also a common method to improve the urea utilization rate. On this basis, the prior art also proposes a method of combining urease inhibitors, nitrification inhibitors and coating technology. For example, patent CN116283422A discloses a nitrogen fertilizer synergist improved double-layer coated controlled release urea and a preparation method thereof, which first coats the urea surface with a nitrification inhibitor and a urease inhibitor, then coats the polymer coating to form an inner coating, then mixes the mesoporous nano-silica loaded with sodium selenate with a sodium alginate solution, and forms an outer gel membrane shell on the urea surface, thereby achieving the purpose of regulating the release of nitrogen and the conversion and utilization of nitrogen in the soil. However, the addition of the enhancer in this patent requires the coating of the nitrification inhibitor solution first, and then the addition of the urease inhibitor powder after the water has completely evaporated. At the same time, when preparing the inner coating and the outer gel membrane shell, the coating liquid needs to be repeatedly coated many times, which has the problems of cumbersome steps and large amount of coating liquid.

[0004] Therefore, how to provide a synergistic urea with simple preparation steps and small amount of coating material has become a technical problem that technical personnel in this field need to solve urgently. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a synergistic urea and a preparation method thereof. The preparation method of the synergistic urea provided by the present invention has simple steps, eliminates the need for multiple coatings of coating liquid, improves the utilization rate of urea, and is environmentally friendly.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing enhanced urea, comprising the following steps:

[0008] (1) dissolving a urease inhibitor and a nitrification inhibitor in a phosphoric acid solution to obtain a synergist mixed solution; adding urea granules into a coating machine, and then uniformly spraying the synergist mixed solution onto the surface of the urea granules through the coating machine;

[0009] (2) adding an intermediate coating slurry to a coating machine, and uniformly mixing the intermediate coating slurry with urea particles to form an intermediate coating layer; the intermediate coating slurry is a mixture of zinc oxide, calcium oxide, sodium alginate and water;

[0010] (3) spraying an adhesive onto the surface of the urea particles by a coating machine, and after the surface of the urea particles is evenly covered with the adhesive, adding diatomaceous earth and mixing evenly to form an outer coating layer to obtain the enhanced urea.

[0011] Preferably, in step (1), the mass ratio of the urease inhibitor, the nitrification inhibitor and the phosphoric acid solution is (1-3):(1-3):(28-36); and the mass concentration of the phosphoric acid solution is 42-55%.

[0012] Preferably, in step (1), the urease inhibitor is one or both of N-butylthiophosphoric acid triamide and phenylphosphorodiamidate.

[0013] Preferably, in step (1), the nitrification inhibitor is one or more of 3,4-dimethylpyrazole phosphate, 3,5-dimethylpyrazole phosphate, and 2-chloro-6-trichloromethylpyridine.

[0014] Preferably, in step (1), the spraying amount of the synergist mixture is 0.005-0.025% of the mass of the urea granules.

[0015] Preferably, in step (2), the amount of the intermediate layer coating slurry added is 0.02-0.05% of the mass of the urea particles.

[0016] Preferably, in step (2), the mass ratio of zinc oxide, calcium oxide, sodium alginate and water is (3-6):(3-6):(8-13):(40-55).

[0017] Preferably, in step (3), the binder is one or both of polyvinyl alcohol and ethyl cellulose.

[0018] Preferably, in step (3), the spraying amount of the binder is 0.05-0.08% of the mass of the urea granules, and the added amount of diatomaceous earth is 0.2-0.4% of the mass of the urea granules.

[0019] The present invention also provides synergistic urea prepared by the preparation method described in the above technical scheme.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] Firstly, the present invention prepares a synergist mixed solution by dissolving a urease inhibitor and a nitrification inhibitor in a phosphoric acid solution, wherein the urease inhibitor and the nitrification inhibitor work together to improve the utilization rate of urea, and the phosphoric acid solution as a binder can make the urease inhibitor and the nitrification inhibitor adhere to the surface of urea particles, eliminating the process of spraying the urease inhibitor and the nitrification inhibitor in steps, and the phosphoric acid solution can also provide phosphorus elements for crops. Secondly, the present invention uses an intermediate coating slurry mixed with zinc oxide, calcium oxide, sodium alginate and water to prepare the intermediate coating layer, wherein the zinc oxide and calcium oxide not only achieve the purpose of controlling the release rate of urea as coating materials, but also provide trace elements such as zinc and calcium for crops, and the use of sodium alginate can further control the release rate of urea, reduce the loss rate of nitrogen, and work together with zinc oxide and calcium oxide to improve the utilization rate of urea. Finally, the present invention forms an outer coating layer by first spraying an adhesive on the surface of urea particles and then adding diatomaceous earth and mixing them evenly. The adhesive can coat the diatomaceous earth on the surface of urea particles, and the porous structure of the diatomaceous earth can slowly release urea into the soil, thereby increasing the fertilizer effect period and improving the utilization rate of urea.

[0022] The present invention uses urease inhibitors and nitrification inhibitors as synergists, combined with coating technology, to greatly improve the utilization rate of urea. In addition, the present invention double-coates urea particles, slows down the release rate of urea in the soil, reduces nutrient loss, makes fertilizer effect more lasting, greatly improves the utilization rate of urea, promotes crop income and yield, and improves planting benefits.

[0023] The preparation method of the enhanced urea provided by the invention has simple steps, saves the need for multiple coatings of coating liquid, and uses less coating liquid. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific implementation methods.

[0026] The embodiment of the present invention provides a method for preparing enhanced urea, comprising the following steps:

[0027] (1) dissolving a urease inhibitor and a nitrification inhibitor in a phosphoric acid solution to obtain a synergist mixed solution; adding urea granules into a coating machine, and then uniformly spraying the synergist mixed solution onto the surface of the urea granules through the coating machine;

[0028] The present invention prepares a synergist mixed solution by dissolving a urease inhibitor and a nitrification inhibitor in a phosphoric acid solution, wherein the urease inhibitor and the nitrification inhibitor work together to improve the utilization rate of urea, and the phosphoric acid solution serves as a binder to enable the urease inhibitor and the nitrification inhibitor to adhere to the surface of urea particles, thereby eliminating the process of spraying the urease inhibitor and the nitrification inhibitor in steps, and the phosphoric acid solution can also provide phosphorus elements for crops.

[0029] (2) adding an intermediate coating slurry to a coating machine, and uniformly mixing the intermediate coating slurry with urea particles to form an intermediate coating layer; the intermediate coating slurry is a mixture of zinc oxide, calcium oxide, sodium alginate and water;

[0030] The present invention adopts an intermediate coating slurry composed of zinc oxide, calcium oxide, sodium alginate and water to prepare the intermediate coating layer, wherein the zinc oxide and calcium oxide not only achieve the purpose of controlling the urea release rate as coating materials, but also provide trace elements such as zinc and calcium for crops, and the use of sodium alginate can further control the urea release rate, reduce the nitrogen loss rate, and simultaneously improve the utilization rate of urea by working together with zinc oxide and calcium oxide.

[0031] (3) spraying an adhesive onto the surface of the urea particles by a coating machine, and after the surface of the urea particles is evenly covered with the adhesive, adding diatomaceous earth and mixing evenly to form an outer coating layer to obtain the enhanced urea.

[0032] The present invention forms an outer coating layer by first spraying an adhesive onto the surface of urea particles and then adding diatomaceous earth and mixing them evenly. The adhesive can coat the diatomaceous earth on the surface of the urea particles, and the porous structure of the diatomaceous earth can slowly release urea into the soil, thereby increasing the fertilizer effect period and improving the utilization rate of urea.

[0033] In a preferred embodiment, in step (1), the mass ratio of the urease inhibitor, the nitrification inhibitor and the phosphoric acid solution is (1-3): (1-3): (28-36), preferably (2-3): (2-3): (30-34); the mass concentration of the phosphoric acid solution is 42-55%, preferably 45-52%. The synergist mixture in the present invention uses phosphoric acid solution as the main raw material, and a small amount of urease inhibitor and nitrification inhibitor are added, thereby reducing the amount of the synergist.

[0034] In a preferred embodiment, in step (1), the urease inhibitor is one or two of N-butyl thiophosphoric acid triamide NBPT and phenyl phosphorodiamidate PPD, preferably N-butyl thiophosphoric acid triamide and phenyl phosphorodiamidate, and the mass ratio of N-butyl thiophosphoric acid triamide to phenyl phosphorodiamidate is (3-5): (1-3).

[0035] In a preferred embodiment, in step (1), the nitrification inhibitor is one or more of 3,4-dimethylpyrazole phosphate, 3,5-dimethylpyrazole phosphate, and 2-chloro-6-trichloromethylpyridine, preferably one or two of 3,4-dimethylpyrazole phosphate and 2-chloro-6-trichloromethylpyridine.

[0036] In a preferred embodiment, in step (1), the spraying amount of the synergist mixed solution is 0.005-0.025% of the mass of the urea particles, preferably 0.008-0.020%. The present invention appropriately reduces the spraying amount of the synergist mixed solution, combined with double-layer coating, to achieve the purpose of greatly improving urea utilization.

[0037] In a preferred embodiment, in step (1), the synergist mixture is evenly sprayed onto the surface of urea particles at room temperature, and the spraying is performed by an atomizing device of a coating machine.

[0038] In a preferred embodiment, in step (1), the particle size of the urea granules is 1.5-3 mm.

[0039] In a preferred embodiment, in step (2), the amount of the intermediate coating slurry added is 0.02-0.05% of the mass of the urea granules, preferably 0.025-0.048%. The present invention controls the amount of the intermediate coating slurry added within the above range, which not only appropriately prolongs the fertilizer effect period of urea, but also ensures the release of the inner layer synergist and urea granules.

[0040] In a preferred embodiment, in step (2), the mass ratio of zinc oxide, calcium oxide, sodium alginate and water is (3-6):(3-6):(8-13):(40-55), preferably (4-6):(4-6):(9-11):(43-52).

[0041] In a preferred embodiment, in step (3), the binder is one or both of polyvinyl alcohol and carboxymethyl cellulose. The binder in the present invention is used to bond diatomaceous earth to the surface of urea particles. By using a water-soluble binder, the use of organic solvents to avoid harm to the human body and the environment.

[0042] In a preferred embodiment, in step (3), the amount of the adhesive sprayed is 0.05-0.08% of the mass of the urea granules, preferably 0.055-0.075%, and the amount of the adhesive sprayed is based on the mass of the adhesive solution. The present invention controls the amount of adhesive sprayed within the above range, which ensures the binding force between the diatomite and the urea granules on the one hand, and the slow release of the substances in the middle coating layer on the other hand; increasing the amount of adhesive on this basis will not only fail to coat more diatomite on the surface of the urea granules, but will hinder the release of the substances in the middle coating layer, the synergist and the urea granules, and fail to give full play to the fertilizer effect of the synergistic urea.

[0043] In a preferred embodiment, in step (3), the amount of diatomaceous earth added is 0.2-0.4% of the mass of the urea granules, preferably 0.3-0.4%. The present invention uses diatomaceous earth as the outer coating layer, which can not only achieve the effect of slow release, but also play the role of moisturizing, loosening the soil, and promoting the growth of crops in the soil; controlling the amount of diatomaceous earth added within the above range can achieve the purpose of slow release of urea granules and avoid waste of diatomaceous earth.

[0044] In a preferred embodiment, in step (3), the particle size of the diatomaceous earth is 300-500 mesh.

[0045] The present invention also provides synergistic urea prepared by the preparation method described in the above technical scheme.

[0046] The enhanced urea provided by the invention can prolong the residence time of urea nitrogen and its conversion products in the soil, which is beneficial to the absorption and utilization of fertilizer nitrogen by crops.

[0047] The room temperature in the embodiments of the present invention refers to "25±2°C".

[0048] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0049] Example 1

[0050] A method for preparing enhanced urea, the specific steps are as follows:

[0051] (1) 2 kg of N-butylthiophosphoric acid triamide NBPT and 2 kg of 3,4-dimethylpyrazole phosphate were dissolved in 32 kg of a phosphoric acid solution having a mass concentration of 48%, and the mixture was stirred thoroughly to prepare a synergist mixture.

[0052] (2) 100 kg of urea granules with a particle size of 2 mm are placed in a material barrel of a coating machine, and then the synergist mixture in step (1) is placed in the atomizing device of the coating machine at a rate of 0.01% of the mass of the urea granules. The urea granules in the material barrel are turned on and rolled, and the synergist mixture is evenly sprayed onto the surface of the urea granules through the atomizing device of the coating machine at room temperature.

[0053] (3) 4 kg of zinc oxide, 4 kg of calcium oxide, 9 kg of sodium alginate and 43 kg of water were mixed and stirred thoroughly to obtain an intermediate coating slurry; the intermediate coating slurry was added into a material barrel at a rate of 0.025% of the mass of the urea particles, the urea particles in the material barrel were mixed with the intermediate coating slurry for 3 hours, and then dried at 50° C. for 1 hour, thereby forming an intermediate coating layer on the surface of the urea particles.

[0054] (4) placing polyvinyl alcohol in hot water at 68° C. to fully dissolve it, thereby obtaining a polyvinyl alcohol solution with a mass concentration of 2%; placing the polyvinyl alcohol solution in an atomizing device of a coating machine at a concentration of 0.055% of the mass of urea particles, and spraying the polyvinyl alcohol solution evenly onto the surface of the urea particles through the atomizing device of the coating machine at room temperature; after the surface of the urea particles is evenly covered with the polyvinyl alcohol solution, adding diatomaceous earth with a particle size of 300-500 meshes into a material barrel at a concentration of 0.3% of the mass of the urea particles, and mixing the diatomaceous earth and the urea particles for 2.5 hours by rotating the material barrel to form an outer coating layer, thereby obtaining enhanced urea.

[0055] Example 2

[0056] A method for preparing enhanced urea, the specific steps are as follows:

[0057] (1) 3 kg of phenyl phosphorodiamidate PPD and 3 kg of 3,4-dimethylpyrazole phosphate were dissolved in 36 kg of a 55% phosphoric acid solution, and the mixture was stirred thoroughly to prepare a synergist mixture.

[0058] (2) 100 kg of urea granules with a particle size of 1.5 mm are placed in a material barrel of a coating machine, and then the synergist mixture in step (1) is placed in the atomizing device of the coating machine at a rate of 0.02% of the mass of the urea granules. The urea granules in the material barrel are turned on and rolled, and the synergist mixture is evenly sprayed onto the surface of the urea granules through the atomizing device of the coating machine at room temperature.

[0059] (3) 3 kg of zinc oxide, 3 kg of calcium oxide, 8 kg of sodium alginate and 50 kg of water were mixed and stirred thoroughly to obtain an intermediate coating slurry; the intermediate coating slurry was added into a material barrel at a rate of 0.045% of the mass of the urea particles, the urea particles in the material barrel were mixed with the intermediate coating slurry for 3.5 hours, and then dried at 55° C. for 1 hour, thereby forming an intermediate coating layer on the surface of the urea particles.

[0060] (4) placing carboxymethyl cellulose in hot water at 55° C. to fully dissolve it, thereby obtaining a carboxymethyl cellulose solution with a mass concentration of 2%; placing the above carboxymethyl cellulose solution in an atomizing device of a coating machine at a concentration of 0.062% of the mass of urea particles, and spraying the carboxymethyl cellulose solution uniformly onto the surface of the urea particles through the atomizing device of the coating machine at room temperature; after the surface of the urea particles is uniformly covered with the carboxymethyl cellulose solution, adding diatomaceous earth with a particle size of 300-500 meshes into a material barrel at a concentration of 0.2% of the mass of the urea particles, and mixing the diatomaceous earth and the urea particles for 2.5 hours by rotating the material barrel to form an outer coating layer, thereby obtaining enhanced urea.

[0061] Example 3

[0062] A method for preparing enhanced urea, the specific steps are as follows:

[0063] (1) 1.5 kg of N-butylthiophosphoric acid triamide NBPT and 3 kg of 3,5-dimethylpyrazole phosphate were dissolved in 28 kg of a phosphoric acid solution having a mass concentration of 42%, and the mixture was stirred thoroughly to prepare a synergist mixture.

[0064] (2) 100 kg of urea granules with a particle size of 3 mm are placed in a material barrel of a coating machine, and then the synergist mixture in step (1) is placed in the atomizing device of the coating machine at a rate of 0.025% of the mass of the urea granules. The urea granules in the material barrel are turned on and rolled, and the synergist mixture is evenly sprayed onto the surface of the urea granules through the atomizing device of the coating machine at room temperature.

[0065] (3) 5 kg of zinc oxide, 3 kg of calcium oxide, 12 kg of sodium alginate and 40 kg of water were mixed and stirred thoroughly to obtain an intermediate coating slurry; the intermediate coating slurry was added into a material barrel at a rate of 0.048% of the mass of the urea particles, the urea particles in the material barrel were mixed with the intermediate coating slurry for 3 hours, and then dried at 50° C. for 1 hour, thereby forming an intermediate coating layer on the surface of the urea particles.

[0066] (4) placing carboxymethyl cellulose in hot water at 55° C. to fully dissolve it, thereby obtaining a carboxymethyl cellulose solution with a mass concentration of 2%; placing the above carboxymethyl cellulose solution in an atomizing device of a coating machine at a concentration of 0.072% of the mass of urea particles, and spraying the carboxymethyl cellulose solution evenly onto the surface of the urea particles through the atomizing device of the coating machine at room temperature; after the surface of the urea particles is evenly covered with the carboxymethyl cellulose solution, adding diatomaceous earth with a particle size of 300-500 meshes into a material barrel at a concentration of 0.34% of the mass of the urea particles, and mixing the diatomaceous earth and the urea particles for 2.5 hours by rotating the material barrel to form an outer coating layer, thereby obtaining enhanced urea.

[0067] Example 4

[0068] A method for preparing enhanced urea, the specific steps are as follows:

[0069] (1) 2 kg of N-butylthiophosphoric acid triamide NBPT and 2 kg of 2-chloro-6-trichloromethylpyridine were dissolved in 28 kg of a 42% phosphoric acid solution, and the mixture was stirred thoroughly to prepare a synergist mixture.

[0070] (2) 100 kg of urea granules with a particle size of 3 mm are placed in a material barrel of a coating machine, and then the synergist mixture in step (1) is placed in the atomizing device of the coating machine at a rate of 0.018% of the mass of the urea granules. The urea granules in the material barrel are turned on and rolled, and the synergist mixture is evenly sprayed onto the surface of the urea granules through the atomizing device of the coating machine at room temperature.

[0071] (3) 5 kg of zinc oxide, 3 kg of calcium oxide, 12 kg of sodium alginate and 40 kg of water were mixed and stirred thoroughly to obtain an intermediate coating slurry; the intermediate coating slurry was added into a material barrel at a rate of 0.03% of the mass of the urea particles, the urea particles in the material barrel were mixed with the intermediate coating slurry for 3 hours, and then dried at 50° C. for 1 hour, thereby forming an intermediate coating layer on the surface of the urea particles.

[0072] (4) placing carboxymethyl cellulose in hot water at 55° C. to fully dissolve it, thereby obtaining a carboxymethyl cellulose solution with a mass concentration of 2%; placing the above carboxymethyl cellulose solution in an atomizing device of a coating machine at a concentration of 0.072% of the mass of urea particles, and spraying the carboxymethyl cellulose solution evenly onto the surface of the urea particles through the atomizing device of the coating machine at room temperature; after the surface of the urea particles is evenly covered with the carboxymethyl cellulose solution, adding diatomaceous earth with a particle size of 300-500 meshes into a material barrel at a concentration of 0.34% of the mass of the urea particles, and mixing the diatomaceous earth and the urea particles for 2.5 hours by rotating the material barrel to form an outer coating layer, thereby obtaining enhanced urea.

[0073] Example 5

[0074] A method for preparing enhanced urea, the specific steps are as follows:

[0075] (1) 2 kg of N-butylthiophosphoric acid triamide NBPT, 1 kg of phenyl phosphorodiamidate PPD, and 3 kg of 3,4-dimethylpyrazole phosphate were dissolved in 32 kg of a phosphoric acid solution having a mass concentration of 48%, and the mixture was fully stirred to prepare a synergist mixture.

[0076] Steps (2) to (4) are the same as in Example 1.

[0077] Comparative Example 1

[0078] The difference from Example 1 is that step (3) is omitted, and the other steps are the same as Example 1.

[0079] Comparative Example 2

[0080] The difference from Example 1 is that step (4) is omitted, and the other steps are the same as Example 1.

[0081] Comparative Example 3

[0082] The difference from Example 1 is that in step (3), the intermediate layer coating slurry is added to the material barrel at 0.07% of the mass of the urea particles, and the other steps are the same as Example 1.

[0083] Comparative Example 4

[0084] The difference from Example 1 is that in step (4), a polyvinyl alcohol solution at 0.1% of the mass of the urea particles is placed in the atomizing device of the coating machine, and the other steps are the same as Example 1.

[0085] Comparative Example 5

[0086] The difference from Example 1 is that in step (4), diatomaceous earth with a particle size of 300-500 mesh is added to the material barrel at 0.1% of the mass of urea particles, and the other steps are the same as Example 1.

[0087] Field trials

[0088] The experiment was carried out in an experimental field in Lushunkou District, Dalian City from 2023 to 2024. The soil type was brown soil, the pH value of the topsoil was 8.2, the organic matter was 21.34g / kg, the total nitrogen was 1.87g / kg, the total phosphorus was 1.82g / kg, and the total potassium was 25.40g / kg.

[0089] The Nongda 108 corn was selected as the test object and planted in mid-April. The area of ​​each test plot was 5m×5m, and the plots were randomly arranged. Fertilization was carried out at the seedling stage, the large bell stage and the filling stage, and the fertilizer application rate was 15kg / mu each time. After the corn matured, 30 corn plants were randomly selected from each plot for agronomic traits and yield determination. The results are shown in Tables 1 and 2. The nitrogen content of the plants and grains was measured after air drying, and the nitrogen fertilizer utilization rate was calculated. The results are shown in Table 3.

[0090] Table 1 Biological morphology of corn treated with enhanced urea in Examples 1-5 and Comparative Examples 1-5

[0091] Plant height / cm Stem diameter / cm Spike length / cm Bald tip / cm Number of unfilled particles Example 1 264 2.61 20.1 0.52 8 Example 2 269 2.67 20.4 0.49 7 Example 3 281 2.75 21.9 0.42 4 Example 4 272 2.68 21.5 0.48 5 Example 5 274 2.71 21.3 0.45 6 Comparative Example 1 237 2.45 16.3 2.23 20 Comparative Example 2 233 2.42 15.7 2.45 21 Comparative Example 3 251 2.53 17.8 1.97 18 Comparative Example 4 248 2.50 17.3 2.23 19 Comparative Example 5 242 2.47 16.9 2.15 19 Blank group 226 2.36 13.4 2.92 26

[0092] Note: No fertilizer was applied to the blank group.

[0093] As can be seen from Table 1, the corn treated with the synergistic urea in Example 3 has the best effect in terms of plant height, stem thickness, ear length, bald tip and number of incomplete grains, which are 55 cm and 8.5 cm higher than those without fertilization, respectively, and the number of bald tip and incomplete grains is reduced by 2.5 cm and 22, respectively. In Comparative Example 1, the intermediate coating layer is omitted compared to Example 1, and the plant height and ear length of corn are reduced by 27 cm and 3.8 cm, respectively, compared to Example 1, and the number of bald tip and incomplete grains is increased by 1.71 cm and 12, respectively, compared to Example 1, indicating that the presence of the intermediate coating layer can improve the utilization rate of urea, thereby promoting the growth of corn. Compared with Example 1, Comparative Example 2 omitted the outer coating layer, and the plant height and ear length of corn were reduced by 31 cm and 4.4 cm respectively compared with Example 1, and the number of bald tips and incomplete grains increased by 1.93 cm and 13 respectively compared with Example 1, indicating that the outer coating layer will affect the utilization rate of urea granules, thereby affecting the growth of corn. Comparative Example 3 increased the amount of the middle layer coating slurry added, Comparative Example 4 increased the amount of polyvinyl alcohol solution sprayed, and Comparative Example 5 reduced the amount of diatomaceous earth added. Compared with Example 1, the plant height and ear length of corn in the three comparative examples were reduced to varying degrees, and the number of bald tips and incomplete grains increased, indicating that changing the above parameters will affect the utilization rate of urea granules, thereby affecting the growth of corn.

[0094] Table 2 Corn yields treated with enhanced urea in Examples 1-5 and Comparative Examples 1-5

[0095] Number of grains per ear Thousand-grain weight / g Yield kg / mu Example 1 576 297 902 Example 2 582 302 915 Example 3 599 321 934 Example 4 592 315 927 Example 5 593 314 921 Comparative Example 1 502 278 867 Comparative Example 2 496 275 863 Comparative Example 3 531 287 882 Comparative Example 4 523 283 878 Comparative Example 5 518 280 871 Blank group 423 254 819

[0096] Note: No fertilizer was applied to the blank group.

[0097] As can be seen from Table 2, the 1000-grain weight of corn treated with the enhanced urea in Example 3 can reach 321g, and the yield can reach 934kg / mu, which is 115kg higher than the blank group without fertilization, with an increase of 14.04%. Compared with Example 1, the 1000-grain weight of Comparative Examples 1-5 was reduced by 19g, 22g, 10g, 14g, and 17g, respectively, and the yield was reduced by 35kg, 39kg, 20kg, 24kg, and 31kg, respectively, indicating that the enhanced urea prepared by the preparation method provided by the present invention can significantly improve the utilization rate of urea, thereby increasing the yield of corn.

[0098] Table 3 Nitrogen absorption and utilization rate of corn treated with urea in Examples 1-5 and Comparative Examples 1-5

[0099]

[0100]

[0101] Note: No fertilizer was applied to the blank group.

[0102] It can be seen from Table 3 that the nitrogen absorption of the corn stalks and the nitrogen absorption of the kernels treated with the enhanced urea in Examples 1-5 are higher than those without fertilization, and the nitrogen fertilizer utilization rate of Example 1 is increased by 6.17-10.82% compared with the control group, indicating that the enhanced urea provided by the present invention prolongs the residence time of urea nitrogen and its conversion products in the soil, which is beneficial to the absorption and utilization of fertilizer nitrogen by corn plants.

[0103] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing synergistic urea, characterized in that: The following steps are involved: (1) dissolving a urease inhibitor and a nitrification inhibitor in a phosphoric acid solution to obtain a synergist mixed solution; adding urea granules into a coating machine, and then uniformly spraying the synergist mixed solution onto the surface of the urea granules through the coating machine; (2) adding an intermediate coating slurry to a coating machine, and uniformly mixing the intermediate coating slurry with urea particles to form an intermediate coating layer; the intermediate coating slurry is a mixture of zinc oxide, calcium oxide, sodium alginate and water; (3) spraying an adhesive onto the surface of the urea particles by a coating machine, and after the surface of the urea particles is evenly covered with the adhesive, adding diatomaceous earth and mixing evenly to form an outer coating layer to obtain the enhanced urea.

2. The method for preparing the enhanced urea according to claim 1, characterized in that: In step (1), the mass ratio of the urease inhibitor, the nitrification inhibitor and the phosphoric acid solution is (1-3):(1-3):(28-36); and the mass concentration of the phosphoric acid solution is 42-55%.

3. The method for preparing the enhanced urea according to claim 1 or 2, characterized in that: In step (1), the urease inhibitor is one or both of N-butylthiophosphoric acid triamide and phenylphosphorodiamidate.

4. The method for preparing the enhanced urea according to claim 1 or 2, characterized in that: In step (1), the nitrification inhibitor is one or more of 3,4-dimethylpyrazole phosphate, 3,5-dimethylpyrazole phosphate, and 2-chloro-6-trichloromethylpyridine.

5. The method for preparing the enhanced urea according to claim 1, characterized in that: In step (1), the spraying amount of the synergist mixed solution is 0.005-0.025% of the mass of the urea granules.

6. The method for preparing the enhanced urea according to claim 1, characterized in that: In step (2), the amount of the intermediate layer coating slurry added is 0.02-0.05% of the mass of the urea particles.

7. The method for preparing the enhanced urea according to claim 1, characterized in that: In step (2), the mass ratio of zinc oxide, calcium oxide, sodium alginate and water is (3-6):(3-6):(8-13):(40-55).

8. The method for preparing the enhanced urea according to claim 1, characterized in that: In step (3), the binder is one or both of polyvinyl alcohol and ethyl cellulose.

9. The method for preparing the enhanced urea according to claim 1, characterized in that: In step (3), the spraying amount of the binder is 0.05-0.08% of the mass of the urea granules, and the added amount of diatomaceous earth is 0.2-0.4% of the mass of the urea granules.

10. The synergistic urea prepared by the preparation method according to any one of claims 1 to 9.

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