Nitrification inhibitor and preparation method thereof, and stable urea and preparation method thereof

Abstract

The invention provides a nitrification inhibitor and a preparation method thereof as well as stable urea and a preparation method thereof, and relates to the technical field of fertilizers. The nitrification inhibitor provided by the invention is prepared from the following components in percentage by mass: 20 to 45 percent of 3, 4-dimethyl pyrazole phosphate (DMPP), 30 to 70 percent of amino acid and the balance of auxiliaries, the auxiliary agent is one or more of polysaccharide, polyvinylpyrrolidone, poloxamer and carbomer. According to the invention, the DMPP and the amino acid are compounded, the amino acid is used as a stabilizer of the DMPP, so that the stability of the DMPP can be remarkably improved, and meanwhile, the polymer additive is used as an adhesive, so that the stability of the DMPP can be further improved. The nitrification inhibitor provided by the invention has excellent stability; the stable urea can be obtained by adopting an endogenous adding mode and adding the stable urea into the urea with relatively low loss, and the stable urea has multiple effects of improving the urea utilization rate, improving the crop quality, improving the soil biological environment, improving the soil fertility and the like.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizers, and in particular to a nitrification inhibitor and a preparation method thereof, and stable urea and a preparation method thereof. Background Art

[0002] Nitrification inhibitors are a general term for a class of microbial active substances that can inhibit nitrosating bacteria and other microorganisms in the soil. + To NO 2- 、NO 3- The nitrification inhibitor is used in combination with nitrogen fertilizers to inhibit the activity of nitrifying bacteria, inhibit nitrite, nitrification, and denitrification, so that the applied amide and ammonium nitrogen can be converted into NH4 + -N exists in the form of nitrogen for crops to use, thereby improving fertilizer efficiency and reducing nitrogen fertilizer losses due to leaching and denitrification of nitrate and nitrite nitrogen, thereby improving nitrogen fertilizer utilization.

[0003] 3,4-Dimethylpyrazole phosphate (DMPP) is a new type of nitrification inhibitor developed in Germany. Experiments show that adding 1% to ammonium nitrogen fertilizer or urea can achieve efficient nitrification inhibition. There are many reports on the compounding technology of DMPP and nitrogen fertilizer. For example, the relevant technology makes DMPP into a solution, sprays it on the surface of urea particles during the urea granulation process to make urea with an inhibitor coating. Practice has shown that the formula used has a large loss of DMPP during the urea granulation process due to its easy decomposition at high temperature, and the loss can reach up to 80%. At the same time, DMPP only exists on the surface of urea, and its ability to improve the long-term effect of urea is weak. The relevant technology discloses a stable nitrification inhibitor, which is obtained by mixing the nitrification inhibitor DMPP with a protective colloid into a solution and then spray drying it. Compared with the former technical solution, the stability of DMPP in this formula is improved, but it still causes a large amount of DMPP volatilization loss during the high-temperature spray drying process. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a nitrification inhibitor and a preparation method thereof and stable urea and a preparation method thereof. The nitrification inhibitor provided by the present invention can significantly improve the stability of 3,4-dimethylpyrazole phosphate (DMPP).

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a nitrification inhibitor, which is composed of the following components in percentage by mass: 20-45% of 3,4-dimethylpyrazole phosphate, 30-70% of amino acid and the balance of auxiliary agent;

[0007] The auxiliary agent is one or more of polysaccharide, polyvinyl pyrrolidone, poloxamer and carbomer.

[0008] Preferably, the nitrification inhibitor is composed of the following components in percentage by mass: 25-45% of 3,4-dimethylpyrazole phosphate, 45-50% of amino acid and the remainder of auxiliary agent.

[0009] Preferably, the amino acid is one or more of polyglutamic acid, polyaspartic acid, aspartic acid, glutamic acid, glycine and 5-aminolevulinic acid.

[0010] Preferably, the polysaccharide is one or more of sodium carboxymethyl cellulose, carboxymethyl cellulose, ethyl cellulose and hydroxyethyl cellulose.

[0011] The present invention provides a method for preparing the nitrification inhibitor described in the above technical solution, comprising the following steps:

[0012] Mixing 3,4-dimethylpyrazole phosphate, amino acid, auxiliary agent and solvent to obtain a mixed solution;

[0013] The mixed solution is spray-dried to obtain the nitrification inhibitor.

[0014] Preferably, the solvent is one or more of N-methylpyrrolidone, ethanol, water and tetrahydrofuran.

[0015] Preferably, the spray drying temperature is 90-140°C.

[0016] The present invention provides a stable urea, comprising urea and a nitrification inhibitor, wherein the nitrification inhibitor is the nitrification inhibitor described in the above technical scheme or the nitrification inhibitor prepared by the preparation method described in the above technical scheme.

[0017] Preferably, the mass of 3,4-dimethylpyrazole phosphate in the nitrification inhibitor is 1-5% of the mass of urea.

[0018] The present invention provides a method for preparing the stable urea described in the above technical solution, comprising the following steps:

[0019] mixing the nitrification inhibitor with molten urea to obtain a mixture;

[0020] The mixed material is granulated to obtain the stable urea.

[0021] The present invention provides a nitrification inhibitor, which is composed of the following components in percentage by mass: 20-45% of 3,4-dimethylpyrazole phosphate, 30-70% of amino acid and the remainder of auxiliary agent; the auxiliary agent is one or more of polysaccharide, polyvinyl pyrrolidone, poloxamer and carbomer. The present invention compounded 3,4-dimethylpyrazole phosphate (DMPP) with amino acid, wherein the amino acid is used as a stabilizer of DMPP, and the stability of DMPP can be significantly improved by chelation between DMPP and amino acid, and at the same time, the polymer auxiliary agents in polysaccharide, polyvinyl pyrrolidone, poloxamer and carbomer are used as adhesives to further improve the stability of DMPP. Therefore, the nitrification inhibitor provided by the present invention has excellent stability; at the same time, the amino acid added to the nitrification inhibitor of the present invention is a type of biostimulant, which, as a fertilizer synergistic substance, has multiple effects such as increasing crop yield, improving crop quality, improving fertilizer utilization rate and reducing environmental risks, so that the nitrification inhibitor provided by the present invention also has multiple effects such as improving crop quality, improving soil biological environment and improving soil fertility.

[0022] The present invention provides a method for preparing the nitrification inhibitor described in the above technical solution, comprising the following steps: mixing the nitrification inhibitor, amino acid and auxiliary agent with a solvent to obtain a mixed solution; spray drying the mixed solution to obtain the nitrification inhibitor. The present invention uses amino acid as a stabilizer for DMPP, and the high-temperature loss of DMPP during the spray drying process is small, which can significantly improve the stability of DMP-type nitrification inhibitors. The results of the embodiment show that after spray drying at 90 to 140°C, the loss rate of 3,4-dimethylpyrazole phosphate is less than 20.4%, and can be as low as 4.8%.

[0023] The present invention provides a stable urea, which is composed of urea and a nitrification inhibitor, wherein the nitrification inhibitor is the nitrification inhibitor described in the above technical solution or the nitrification inhibitor prepared by the preparation method described in the above technical solution. The present invention can use an endogenous addition method to uniformly add the nitrification inhibitor to urea particles with low loss, thereby obtaining a stable urea with uniform inhibitor distribution, which has multiple functions such as improving fertilizer stability, improving urea utilization, improving crop quality, improving soil biological environment, and improving soil fertility. DETAILED DESCRIPTION

[0024] The present invention provides a nitrification inhibitor, which is composed of the following components in percentage by mass: 20-45% of 3,4-dimethylpyrazole phosphate, 30-70% of amino acid and the remainder of auxiliary agent, and the sum of the percentage by mass of each component is 100%;

[0025] The auxiliary agent is one or more of polysaccharide, polyvinyl pyrrolidone, poloxamer and carbomer.

[0026] In the present invention, the raw materials involved are all commercially available products well known in the art.

[0027] In terms of mass percentage, the components of the nitrification inhibitor provided by the present invention include 20-45% of 3,4-dimethylpyrazole phosphate (DMPP), which can be 20%, 25%, 28%, 30%, 33%, 35%, 40% or 45%, preferably 25-45%.

[0028] In terms of mass percentage, the components of the nitrification inhibitor provided by the present invention include 30-70% amino acids, which may be 33%, 37%, 42%, 43%, 45%, 50%, and preferably 45-50%. In the present invention, the amino acid is preferably one or more of polyglutamic acid, polyaspartic acid, aspartic acid, glutamic acid, glycine and 5-aminolevulinic acid, the molecular weight of the polyglutamic acid is preferably 17000-23000Da, which may be 20000Da, and the molecular weight of the polyaspartic acid is preferably 4250-5750Da, which may be 5000Da. The present invention uses amino acids as stabilizers for DMPP, and the stability of DMPP can be significantly improved by chelating between DMPP and amino acids. When the amino acid is polyglutamic acid or polyaspartic acid, DMPP can be stabilized by coupling a large number of carboxyl groups in the polymerized amino acid. At the same time, due to the characteristics of the polymer, DMPP can be wrapped in the internal cavity, cross-linked with each other to form a stable spatial network structure, further improving the stability of DMPP. Moreover, the combined application of amino acids and urea not only increases crop yields but also improves crop quality. It also plays an important role in improving soil biological environment and increasing soil fertility.

[0029] In terms of mass percentage, the components of the nitrification inhibitor provided by the present invention include the remainder of the auxiliary agent. In the present invention, the auxiliary agent is one or more of polysaccharide, polyvinyl pyrrolidone, poloxamer and carbomer, and the polysaccharide is preferably one or more of sodium carboxymethyl cellulose, carboxymethyl cellulose, ethyl cellulose and hydroxyethyl cellulose; the polyvinyl pyrrolidone is preferably K30; the molecular weight of the carbomer is preferably 240-320Da, which may be 280Da; the molecular weight of the sodium carboxymethyl cellulose is preferably 4250-5750Da, which may be 5000Da; the molecular weight of the carboxymethyl cellulose is preferably 170-230Da, which may be 200Da; the molecular weight of the ethyl cellulose is preferably 425-575Da, which may be 500Da; the molecular weight of the hydroxyethyl cellulose is preferably 620-850Da, which may be 700 or 800Da. In the present invention, the auxiliary agent acts as a binder and can further improve the stability of DMPP.

[0030] The present invention provides a method for preparing the nitrification inhibitor described in the above technical solution, comprising the following steps:

[0031] Mixing 3,4-dimethylpyrazole phosphate, amino acid, auxiliary agent and solvent to obtain a mixed solution;

[0032] The mixed solution is spray-dried to obtain the nitrification inhibitor.

[0033] The present invention mixes 3,4-dimethylpyrazole phosphate, amino acid and auxiliary agent with solvent to obtain a mixed solution. In the present invention, the solvent is preferably one or more of N-methylpyrrolidone, ethanol, water and tetrahydrofuran. When the solvent is several of N-methylpyrrolidone, ethanol, water and tetrahydrofuran, it can be a mixed solvent of water and ethanol, a mixed solvent of water and N-methylpyrrolidone, and a mixed solvent of tetrahydrofuran and ethanol. The present invention has no special requirements for the amount of the solvent, and the 3,4-dimethylpyrazole phosphate, amino acid and auxiliary agent can be completely dissolved. When the solvent is several of N-methylpyrrolidone, ethanol, water and tetrahydrofuran, the present invention has no special requirements for the ratio of each solvent, and can be mixed in any proportion.

[0034] After obtaining the mixed solution, the present invention spray-dries the mixed solution to obtain the nitrification inhibitor. In the present invention, the temperature of the spray drying is preferably 90 to 140°C, and can be 90°C, 100°C, 110°C, 120°C, 130°C or 140°C. After the spray drying, a nitrification inhibitor powder is obtained. In the present invention, the particle size of the nitrification inhibitor powder is preferably 8 to 20 μm. The present invention uses amino acids as stabilizers for DMPP, and the high-temperature loss of DMPP during the spray drying process is small.

[0035] The present invention provides a stable urea, comprising urea and a nitrification inhibitor, wherein the nitrification inhibitor is the nitrification inhibitor described in the above technical solution or the nitrification inhibitor prepared by the preparation method described in the above technical solution. In the present invention, the mass of 3,4-dimethylpyrazole phosphate in the nitrification inhibitor is preferably 1-5% of the mass of urea, and can be 1%, 2%, 3%, 4% or 5%. The stable urea provided by the present invention has good fertilizer stability, high urea utilization rate, and multiple functions such as improving crop quality, improving soil biological environment and improving soil fertility.

[0036] The present invention provides a method for preparing the stable urea described in the above technical solution, comprising the following steps:

[0037] mixing the nitrification inhibitor with molten urea to obtain a mixture;

[0038] The mixed material is granulated to obtain the stable urea.

[0039] In the present invention, the nitrification inhibitor is mixed with molten urea, that is, the nitrification inhibitor is added to the urea in an endogenous manner, and the DMPP and amino acid in the nitrification inhibitor are uniformly dispersed in the urea, and granulation is performed to obtain stable urea granules. In the present invention, the granulation method is preferably mixed extrusion granulation.

[0040] The traditional method of compounding DMPP with nitrogen fertilizer is usually to spray the nitrification inhibitor on the surface of urea. The disadvantage is that the fertilizer effect of urea is unstable, the release is very slow in the early stage, and it loses its effect quickly in the later stage. There is also a part of technology that simply mixes the nitrification inhibitor with urea before use or applies it to various soils together with urea. Since DMPP and urea exist independently in the soil, this method has a weak ability to improve the long-term effect of urea. The present invention adds the nitrification inhibitor to the molten urea in an endogenous manner, which can ensure the uniform distribution of the nitrification inhibitor in the urea particles. At the same time, the nitrification inhibitor provided by the present invention has low loss, which can significantly improve the stability of fertilizer effect and effectively improve the utilization rate of urea.

[0041] In order to further illustrate the present invention, the nitrification inhibitor and its preparation method and the stable urea and its preparation method provided by the present invention are described in detail below in combination with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0042] The “parts” in each example are all “parts by mass”.

[0043] Example 1

[0044] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate, 50 parts of polyglutamic acid (molecular weight 20000Da), and 25 parts of polyvinylpyrrolidone (K30).

[0045] Preparation method: 3,4-dimethylpyrazole phosphate, polyglutamic acid and polyvinyl pyrrolidone are dissolved in an ethanol aqueous solution, and spray-dried at 90°C to obtain nitrification inhibitor powder.

[0046] The nitrification inhibitor powder prepared in Example 1 is recorded as Product 1.

[0047] Example 2

[0048] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate, 50 parts of glutamic acid, and 25 parts of polyvinyl pyrrolidone (K30).

[0049] Preparation method: 3,4-dimethylpyrazole phosphate, glutamic acid and polyvinyl pyrrolidone are dissolved in a mixed solvent of tetrahydrofuran and ethanol, and spray-dried at 90°C to obtain nitrification inhibitor powder.

[0050] The nitrification inhibitor powder prepared in Example 2 is recorded as Product 2.

[0051] Example 3

[0052] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate, 50 parts of polyaspartic acid (molecular weight 5000Da), and 25 parts of polyvinylpyrrolidone (K30).

[0053] Preparation method: 3,4-dimethylpyrazole phosphate, polyaspartic acid and polyvinyl pyrrolidone are dissolved in an ethanol aqueous solution, and spray-dried at 90°C to obtain nitrification inhibitor micropowder.

[0054] The nitrification inhibitor powder prepared in Example 3 is recorded as Product 3.

[0055] Example 4

[0056] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate, 50 parts of aspartic acid, and 25 parts of polyvinyl pyrrolidone (K30).

[0057] Preparation method: 3,4-dimethylpyrazole phosphate, aspartic acid and polyvinyl pyrrolidone are dissolved in an ethanol aqueous solution, and spray-dried at 90°C to obtain nitrification inhibitor powder.

[0058] The nitrification inhibitor powder prepared in Example 4 is recorded as Product 4.

[0059] Example 5

[0060] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate, 50 parts of 5-aminolevulinic acid, and 25 parts of polyvinylpyrrolidone (K30).

[0061] Preparation method: 3,4-dimethylpyrazole phosphate, 5-aminolevulinic acid and polyvinyl pyrrolidone are dissolved in a mixed solvent of water and N-methylpyrrolidone, and spray-dried at 120°C to obtain nitrification inhibitor powder.

[0062] The nitrification inhibitor powder prepared in Example 5 is recorded as Product 5.

[0063] Example 6

[0064] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate, 50 parts of polyglutamic acid (molecular weight 20000Da), and 25 parts of sodium carboxymethyl cellulose (molecular weight 5000Da).

[0065] Preparation method: 3,4-dimethylpyrazole phosphate, polyglutamic acid and sodium carboxymethyl cellulose are dissolved in an ethanol aqueous solution and spray-dried at 90°C to obtain nitrification inhibitor powder.

[0066] The nitrification inhibitor powder prepared in Example 6 is recorded as Product 6.

[0067] Example 7

[0068] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate, 50 parts of polyglutamic acid (molecular weight 20000Da), and 25 parts of ethyl cellulose (molecular weight 500Da).

[0069] Preparation method: 3,4-dimethylpyrazole phosphate, polyglutamic acid and ethyl cellulose are dissolved in a mixed solvent of water and N-methylpyrrolidone, and spray-dried at 100°C to obtain nitrification inhibitor powder.

[0070] The nitrification inhibitor powder prepared in Example 7 is recorded as Product 7.

[0071] Example 8

[0072] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate, 50 parts of polyglutamic acid (molecular weight 20000Da), and 25 parts of carboxymethyl cellulose (molecular weight 200Da).

[0073] Preparation method: 3,4-dimethylpyrazole phosphate, polyglutamic acid and carboxymethyl cellulose are dissolved in ethanol aqueous solution, and spray-dried at 95°C to obtain nitrification inhibitor powder.

[0074] The nitrification inhibitor powder prepared in Example 8 is recorded as Product 8.

[0075] Example 9

[0076] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate, 50 parts of polyglutamic acid (molecular weight 20000Da), and 25 parts of carbomer (molecular weight 280Da).

[0077] Preparation method: 3,4-dimethylpyrazole phosphate, polyglutamic acid and carbomer are dissolved in an ethanol aqueous solution, and spray-dried at 90°C to obtain nitrification inhibitor powder.

[0078] The nitrification inhibitor powder prepared in Example 9 is recorded as Product 9.

[0079] Example 10

[0080] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate, 50 parts of polyglutamic acid (molecular weight 20000Da), and 25 parts of hydroxyethyl cellulose (molecular weight 736Da).

[0081] Preparation method: 3,4-dimethylpyrazole phosphate, polyglutamic acid and hydroxyethyl cellulose are dissolved in an ethanol aqueous solution and spray-dried at 100°C to obtain nitrification inhibitor powder.

[0082] The nitrification inhibitor powder prepared in Example 10 is recorded as Product 10.

[0083] Embodiment 11

[0084] Raw materials: 45 parts of 3,4-dimethylpyrazole phosphate, 45 parts of polyglutamic acid (molecular weight 20000Da), and 10 parts of polyvinylpyrrolidone (K30).

[0085] Preparation method: 3,4-dimethylpyrazole phosphate, polyglutamic acid and polyvinyl pyrrolidone are dissolved in an ethanol aqueous solution, and spray-dried at 90°C to obtain nitrification inhibitor powder.

[0086] The nitrification inhibitor powder prepared in Example 11 is recorded as Product 11.

[0087] Example 12

[0088] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate, 50 parts of polyglutamic acid (molecular weight 20000Da), and 25 parts of polyvinylpyrrolidone (K30).

[0089] Preparation method: 3,4-dimethylpyrazole phosphate, polyglutamic acid and polyvinyl pyrrolidone are dissolved in ethanol aqueous solution, and spray-dried at 140°C to obtain nitrification inhibitor powder.

[0090] The nitrification inhibitor powder prepared in Example 12 is recorded as Product 12.

[0091] Comparative Example 1

[0092] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate and 25 parts of polyvinyl pyrrolidone (K30).

[0093] Preparation method: 3,4-dimethylpyrazole phosphate and polyvinyl pyrrolidone are dissolved in ethanol aqueous solution, and spray-dried at 90°C to obtain nitrification inhibitor powder.

[0094] The nitrification inhibitor powder prepared in Comparative Example 1 is recorded as Product 13.

[0095] Comparative Example 2

[0096] Raw materials: 25 parts of 3,4-dimethylpyrazole phosphate, 50 parts of polyglutamic acid (molecular weight 20000Da).

[0097] Preparation method: 3,4-dimethylpyrazole phosphate and polyglutamic acid are dissolved in ethanol aqueous solution, and spray-dried at 90°C to obtain nitrification inhibitor powder.

[0098] The nitrification inhibitor powder prepared in Comparative Example 2 is recorded as Product 14.

[0099] Determination of the content of 3,4-dimethylpyrazole phosphate in the nitrification inhibitor powder prepared in each embodiment:

[0100] The content of 3,4-dimethylpyrazole phosphate in nitrification inhibitor powder was determined by high performance liquid chromatography (Bao Wankui, Huang Junming, Han Yansong, et al. Research on the method of determining 3,4-dimethylpyrazole phosphate in fertilizer by high performance liquid chromatography [J]. Chinese Soil and Fertilizer, 2021, (03): 354-358.), and the results are shown in Table 1.

[0101] Table 1 3,4-dimethylpyrazole phosphate content in nitrification inhibitor powders prepared in various examples

[0102] product Amino Acids Additives Theoretical content, % Actual content, % Loss rate, % Product 1 Polyglutamic acid Polyvinylpyrrolidone 25 23.8 4.8 Product 2 Glutamate Polyvinylpyrrolidone 25 22.7 9.2 Product 3 Polyaspartic acid Polyvinylpyrrolidone 25 23.7 5.2 Product 4 Aspartic acid Polyvinylpyrrolidone 25 22.5 10 Product 5 5-Aminolevulinic acid Polyvinylpyrrolidone 25 19.9 20.4 Product 6 Polyglutamic acid Sodium Carboxymethyl Cellulose 25 22.8 8.8 Product 7 Polyglutamic acid Ethyl cellulose 25 22.7 9.2 Product 8 Polyglutamic acid Carboxymethyl cellulose 25 22.6 9.6 Product 9 Polyglutamic acid Carbomer 25 21.3 15.0 Product 10 Polyglutamic acid Hydroxyethyl Cellulose 25 22.4 10.4 Product 11 Polyglutamic acid Polyvinylpyrrolidone 45 41.1 8.6 Product 12 Polyglutamic acid Polyvinylpyrrolidone 25 23 8.0 Product 13 / Polyvinylpyrrolidone 50 27.5 45 Products 14 Polyglutamic acid / 33.3 26.5 20.4

[0103] It can be seen from the above results that amino acids and high molecular polymers have a good stabilizing effect on 3,4-dimethylpyrazole phosphate.

[0104] Embodiment 13

[0105] Samples 1 to 3 were added to molten urea (the added amount (calculated as the content of DMPP in each sample) was 5% of the urea quality), and mixed extrusion granulation was performed to obtain stable urea granules.

[0106] Sample 1: the nitrification inhibitor powder prepared in Example 1; Sample 2: the solution obtained by dissolving DMPP, amino acid and polyvinyl pyrrolidone in ethanol aqueous solution in Example 1; Sample 3: DMPP powder.

[0107] The internal addition loss rate of 3,4-dimethylpyrazole phosphate was determined, and the test results are shown in Table 2.

[0108] Table 2 Loss rate of DMPP added to urea

[0109]

[0110]

[0111] It can be seen from the above results that when the nitrification inhibitor powder prepared in Example 1 is added to molten urea, the loss rate of 3,4-dimethylpyrazole phosphate is much lower than the loss rate when the DMPP powder is added to molten urea.

[0112] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A nitrification inhibitor, characterized in that: It is composed of the following components in percentage by mass: 20-45% of 3,4-dimethylpyrazole phosphate, 30-70% of amino acid and the balance of auxiliary agent; The auxiliary agent is one or more of polysaccharide, polyvinyl pyrrolidone, poloxamer and carbomer.

2. The nitrification inhibitor according to claim 1, characterized in that The invention is composed of the following components in percentage by mass: 25-45% of 3,4-dimethylpyrazole phosphate, 45-50% of amino acid and the balance of auxiliary agent.

3. The nitrification inhibitor according to claim 1 or 2, characterized in that: The amino acid is one or more of polyglutamic acid, polyaspartic acid, aspartic acid, glutamic acid, glycine and 5-aminolevulinic acid.

4. The nitrification inhibitor according to claim 1 or 2, characterized in that: The polysaccharide is one or more of sodium carboxymethyl cellulose, carboxymethyl cellulose, ethyl cellulose and hydroxyethyl cellulose.

5. The method for preparing the nitrification inhibitor according to any one of claims 1 to 4, characterized in that: The following steps are involved: Mixing 3,4-dimethylpyrazole phosphate, amino acid, auxiliary agent and solvent to obtain a mixed solution; The mixed solution is spray-dried to obtain the nitrification inhibitor.

6. The preparation method according to claim 5, characterized in that: The solvent is one or more of N-methylpyrrolidone, ethanol, water and tetrahydrofuran.

7. The preparation method according to claim 5, characterized in that: The spray drying temperature is 90-140°C.

8. A stable urea, characterized in that: The invention comprises urea and a nitrification inhibitor, wherein the nitrification inhibitor is the nitrification inhibitor according to any one of claims 1 to 4 or the nitrification inhibitor prepared by the preparation method according to any one of claims 5 to 7.

9. The stable urea according to claim 8, characterized in that The mass of 3,4-dimethylpyrazole phosphate in the nitrification inhibitor is 1-5% of the mass of urea.

10. The method for preparing stable urea according to claim 8 or 9, characterized in that: The following steps are involved: mixing the nitrification inhibitor with molten urea to obtain a mixture; The mixed material is granulated to obtain the stable urea.

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