CN112174729A

CN112174729A - High-concentration liquid slow-release nitrogen fertilizer and preparation method thereof

Info

Publication number: CN112174729A
Application number: CN202011039998.8A
Authority: CN
Inventors: 王仁宗; 汪志; 操素芬; 陈日远
Original assignee: Hubei Forbon Technology Co Ltd
Current assignee: Hubei Forbon Technology Co Ltd
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2021-01-05
Also published as: MA52718A1; MA52718B1

Abstract

The invention discloses a high-concentration liquid slow-release nitrogen fertilizer and a preparation method thereof, wherein the liquid slow-release nitrogen fertilizer consists of 40-80 parts of urea, 18-50 parts of formaldehyde, 1-15 parts of alkali compounds, 1-15 parts of amine compounds, 1-15 parts of ammonia water, 0.001-1 part of medium and trace element-containing substances and 0.01-5 parts of bio-stimulin. The preparation method comprises the following steps: the components are sequentially added into a reaction kettle to be subjected to a series of reactions to prepare the high-concentration liquid slow-release nitrogen fertilizer. The liquid slow-release nitrogen fertilizer contains medium and trace element substances and biostimulant, and can promote root growth, chlorophyll synthesis and improve crop quality; the fertilizer is directly sprayed on the leaf surfaces of plants, has the characteristics of quick effect, intermediate effect and slow effect, and improves the effective utilization rate of the nitrogen fertilizer to 50 percent; can be mixed with water and pesticide at will and directly sprayed on crops, thus solving the problem of uneven spreading of the traditional solid fertilizer and greatly reducing nitrogen loss and volatilization. Overcomes the defect of insufficient nitrogen source supply in the early stage of urea-formaldehyde resin, and solves the problems of large dosage, short lasting time, high loss rate, environmental pollution and the like of the traditional urea.

Description

High-concentration liquid slow-release nitrogen fertilizer and preparation method thereof

Technical Field

The invention relates to a high-concentration liquid slow-release nitrogen fertilizer and a preparation method thereof, in particular to a preparation method of a high-nitrogen-content liquid slow-release nitrogen fertilizer. Belongs to the technical field of fertilizers.

Background

The fertilizer is an important element influencing agricultural production, agricultural quality and agricultural health, is 'grain' of various crop grains, and is used for cultivating about 20% of people in the world by 7% of cultivated land in the world in China, so that the function of the fertilizer is unavailable.

The nitrogen fertilizer which is the first of three elements (nitrogen, phosphorus and potassium) for crop fertilization is one of the most important agricultural production input products, and has very important effects on crop yield increase, soil fertility and agricultural product quality improvement. From the average level of the whole world, the nitrogen fertilizer accounts for 60 percent of the total amount of the fertilizer, the proportion of the nitrogen fertilizer is far higher than the average level in the production condition of the fertilizer in China, the nitrogen fertilizer is the most consumed fertilizer in China, the importance of the nitrogen fertilizer prompts a plurality of farmers to apply the nitrogen fertilizer in large quantity, but due to the lack of scientific fertilizing methods, the low quality of the fertilizer and other reasons, the comprehensive utilization rate of the fertilizer in China is low, and a large amount of fertilizer nutrients are lost. Although nitrogen fertilizer is applied to some areas, the phenomenon of insufficient nitrogen fertilizer dosage still exists, the problem of how to improve the utilization rate of the nitrogen fertilizer becomes urgent to be solved, and the low utilization rate of the fertilizer can also cause a series of problems, such as resource waste, environmental pollution, increase of production cost and the like.

Currently, the main source of nitrogen fertilizer is also urea, which contains 46% available nitrogen and is commonly used as a plant nutrient. Urea is very soluble in water and can rapidly provide available nitrogen to plants in any form, whether liquid or solid. However, urea is very low in utilization, and has problems of phytotoxicity, plant burning and the like during use.

For the above reasons, formulated phytonutrient upgrades of urea, such as liquid slow-release urea-formaldehyde nitrogen fertilizers, have been used to slowly supply nitrogen to soil and avoid phytotoxicity and plant burning in the event of excess phytonutrients. Urea formaldehyde resin fertilizers provide a more controlled way of releasing nitrogen values in order to hopefully more effectively tailor the availability of nitrogen to time course nitrogen requirements. It is believed that the nitrogen loss normally associated with rapid release nitrogen fertilizers can be reduced.

Aiming at the prior art, when liquid slow-release nitrogen fertilizers pursue high solid content to maximize the total nitrogen value, the liquid nitrogen fertilizers have the problems of stability, poor slow-release effect and poison to plants caused by rapid nitrogen release in the early stage.

Patent WO9415890a1 describes a method and composition for a semicarbazide-formaldehyde fertilizer that utilizes an ammonia compound to inhibit the urea-formaldehyde polymerization reaction and reduce the formation of hot water insoluble nitrogen, and an ammonium compound to participate in the reaction to form a controlled release compound, which has the problem that when the conversion of urea nitrogen to cold water insoluble nitrogen is relatively low, when the semicarbazide-formaldehyde fertilizer is applied in large quantities to the soil, most of the nitrogen is rapidly released, thereby causing toxicity to the plant. Patent US4252785 describes a controlled release composition which is a microporous controlled release composition having at least about 20% by weight of a solid low molecular weight urea formaldehyde resin based on the total weight of the composition, wherein the molar ratio of urea to formaldehyde is about 2: 1, said resin comprising at least one active material therein for a sustained period of time when said resin is in an aqueous medium, at least about 3.5: 1 and at least one active material is releasable from the resin. The technical scheme has the problems that the slow release period of the synthetic urea-formaldehyde resin is too long, so that the nitrogen source is absorbed for the early stage of plants to generate influence, and when the minimum molar ratio of urea to formaldehyde is 2: below 1, the product is a useless liquid formed under very unstable and often explosive conditions. Higher than 3.5: 1, the product is too hard to allow diffusion from the interior, and is also difficult to form. Patent WO0216458a2 describes a controlled release urea formaldehyde liquid fertilizer resin having a nitrogen content of at least 28 wt% and a method for making the same, which is useful as a fertilizer, contains at least 50% controlled release nitrogen, and provides stable phosphate and potassium salts. The technical scheme has the problems that the influence factor of handicraft fluctuation is large, and the solution stability is only 2 months. Patent US6306194 states that the controlled release urea-formaldehyde liquid fertilizer resin has a high nitrogen level, which is a controlled release liquid urea-formaldehyde fertilizer with a nitrogen content of at least 31% and a process for its manufacture. The technical scheme has the problems of higher nitrogen concentration but poorer slow release effect. Patent WO2019209919a1 describes a fertilizer composition with slow release of nitrogen compounds and a method for forming the same, the solution being a method for forming a fertilizer composition with slow release of nitrogen compounds by a melt process. The method includes mixing a crystalline polyethylene wax with urea and formaldehyde to form a molten methylene urea mixture. The contents of the molten methylene urea mixture react to form the slow release nitrogen compound. This solution presents problems that the reduced reaction kinetics caused by the resin modifier can favor the formation of the desired short chain methylene urea reaction products, including the monomethylenediurea MDU and the 5, 6-dimethyl-2-thiouracil DMTU, and the formation of longer chain cold water insoluble nitrogen compounds. Patent WO8403503a1 describes an improved fertilizer product and processes for making and using the same, the solution being a method of preparing a controlled release fertilizer product containing increased levels of sustained release nitrogen, comprising the steps of mixing a portion of a water soluble thermoplastic binder with a urea-formaldehyde condensate and a pH adjusting agent. The amount of pH adjusting agent should be sufficient to provide a pH of the shaped fertilizer product in the range of 6 to 12. Subjecting the mixture to conditions including temperature and pressure to produce a shaped fertilizer product. The obtained formed fertilizer product comprises the slow-release nitrogen with the same amount as the urea-formaldehyde condensate in the mixture, and the technical scheme has the problems that the reaction process is greatly influenced by temperature, and the prepared urea-formaldehyde condensate product has large stability fluctuation. Patent US4409015 describes a flowable liquid fertilizer containing suspended water-insoluble nitrogen, the solution being a two-stage process for the preparation of an aqueous dispersion of a urea-formaldehyde condensation product, comprising: in the first stage, formaldehyde and urea are reacted together in a molar ratio of formaldehyde to urea of about 2.5 to 1 to about 4.7 to 1. The presence of a condensation catalyst until methanol tolerance is within a range such that the condensate is clear and remains clear after one year of storage at room temperature, substantially free of precipitated reaction species, forming an intermediate reaction product, which then enters a second stage, reacting the intermediate reaction product with an additional amount of urea such that the total molar ratio of urea to formaldehyde is in the range of 0.8 to 1 to about 1.7 to 1, about 70 ℃ at an acidic pH and an elevated temperature of no more than until the amount of water-insoluble nitrogen present in the reaction mixture is about 15% to about 35%, based on the total amount of nitrogen in the system. The technical scheme has the problems that the reaction process condition is long in route and difficult to accurately control. Patent US5449394 describes a non-polymer concentrated ammonia, urea, formaldehyde liquid fertilizer, the technical scheme is a method for preparing a liquid non-polymer controlled-release nitrogen plant food composition, by condensation reaction of 1 molecule of ammonia, 2 molecules of urea and 3 molecules of formaldehyde in an alkali buffer aqueous solution, controlling the pH to be 7 and the temperature to be 100 ℃, the technical scheme has the problems of poor slow-release effect and cannot effectively improve the utilization rate of nitrogen. Patent EP3090993a1 describes a method for preparing nitrogen fertilizers, which is a method for preparing liquid nitrogen fertilizers having a weight content of 20-32% of at least 10 tons of nitrogen fertilizers in a batch reactor, said method comprising at least gradually adding an ammonia solution to a formaldehyde and urea solution within at least 15 minutes to control the temperature of the reaction medium to gradually rise to 80-95 ℃, which has the problems of stability, large influence of formaldehyde and urea addition, and low production efficiency. Patent US4781749 describes a polymethylene urea fertilizer solution, which is a two-step process for the preparation of transparent, storage-stable, controlled-release, polymethylene urea nitrogen fertilizer solutions. In the first stage, urea is reacted with a molar excess of formaldehyde at a temperature of 75-100 ℃ at a near neutral pH provided by a buffer such as sodium bicarbonate in the presence of an ammonium compound until the formaldehyde is substantially converted to methylene moieties. In the second stage, the methylene moiety is reacted with additional urea and ammonium compound at a temperature of 75-100 ℃ in a near neutral buffer solution having a pH between 6.9 and 8.5 until substantially urea is added. Converted to water-soluble branched polymethylene urea. The optimum first stage molar ratio of urea to formaldehyde is from 0.483 to 0.518 to 1, while the optimum second stage ratio is from 1.3 to 1.5 moles of urea per mole of formaldehyde. Polymethylene ureas comprise a number of water-soluble compounds containing from 2 to 4 methylene moieties, from 2 to 5 urea moieties, and from 0 to 2 ammonia moieties, including several different structural isomers of the same empirical formula. The product exhibits controlled nitrogen nutrient release in plants due to the two-step process which provides low urea, ammonia and methylol urea concentrations. This technical solution has the problem that a small amount of polymeric urea formaldehyde, which affects storage stability, is present in the reaction product. Patent US 2955390 describes the production of a plant nutrient mixture in the form of urea from urea and UF-85 in the presence of potassium hydroxide in alkaline condition at 90 c, which solution presents the problem of the fact that the plant nutrient mixture product produced is generally substantially unstable in a relatively short time after 24 hours, and that after a while too much water evolves, which results in an unstable whole solution system. Patent US3462256 describes the preparation of an aqueous solution of 80-90% partially reacted urea and formaldehyde by adding ammonia to an aqueous mixture of partially reacted urea and formaldehyde at 70 c, which solution has the problem that the prepared transparent liquid is only stable for 30 days at 20-25 c. Patent US4304588 describes concentrated, storage-stable aqueous solutions of nitrogen-containing compounds obtained by reacting urea with formaldehyde, in which the product obtained consists essentially of monomethyl urea (MMU), small amounts of monomethyl-ene-diurea (MDU) and unreacted urea. The sustained-release tablet also contains a large amount of Hexamethylenetetramine (HMT), and the technical scheme has the problems of poor sustained-release effect and poor stability. Patent US4781749 states that reacting 1.5-2.5 moles of formaldehyde per mole of urea, which is lower than the initial molar ratio of 5-4 moles of formaldehyde per mole of urea, maintains the pH in near neutral conditions (6.9-8.5) throughout the reaction, the condensed UF chains have a lower solubility than methylolated urea and can proceed with the problem of leading to an extremely slow release, and the crop cannot make efficient use of the nitrogen source.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a high-concentration nitrogen content liquid slow-release nitrogen fertilizer and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a high-concentration liquid slow-release nitrogen fertilizer comprises the following components in parts by mass: the components consist of urea, formaldehyde aqueous solution, alkali compounds, amine compounds, ammonia water, medium and trace element-containing substances and biological stimulin; wherein the ratio of urea: 40-80 parts; 35-55% of formaldehyde aqueous solution by mass: 18-50 parts; alkali compounds: 1-15 parts; amine compounds: 1-15 parts; ammonia water with mass concentration of 20-28%: 1-15 parts; medium trace element-containing substance: 0.001-1 part; biological stimulin: 0.01-5 parts of total nitrogen content of 18-37 percent.

The medium trace element-containing substance is one or a mixture of more than two of iron ethylenediaminetetraacetic acid (EDTA iron), EDTA copper, EDTA zinc, EDTA manganese, boric acid, sodium molybdate, ammonium molybdate, magnesium sulfate, calcium formate, calcium acetate and calcium lignosulphonate.

The biological stimulin is one or a mixture of more than two of humic acid, polypeptide and free amino acid.

The water-insoluble substance of the humic acid is less than or equal to 0.5 percent, the particle size is less than or equal to 5 mu m, and the hard water resistance is more than or equal to 30.

The amino acids are one or a mixture of more than two of leucine, lysine, phenylalanine, isoleucine, valine, threonine, methionine, tryptophan, arginine and glutamine.

The amine compound is one or a mixture of more than two of diethylamine, triethylamine, diethanolamine, triethanolamine, monoammonium sulfate and diammonium phosphate.

The alkali compound is one or a mixture of more than two of sodium carbonate, sodium hydroxide, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, sodium formate, potassium acetate and sodium acetate.

The ratio of quick-acting nitrogen, intermediate-acting nitrogen and slow-acting nitrogen in the high-concentration liquid slow-release nitrogen fertilizer is 1-2: 1-2: 1.5-3.

A preparation method of a high-concentration liquid slow-release nitrogen fertilizer is characterized by comprising the following steps:

(1) mixing and stirring a certain mass part of 35-55% formaldehyde aqueous solution and urea in a reaction kettle at room temperature, wherein the stirring time is controlled to be 10-20min, and the stirring speed is controlled to be 500-;

(2) adding a certain mass part of ammonia water with the mass concentration of 20-28% into the mixed solution obtained in the step (1) for stirring, controlling the temperature to be 60-70 ℃, controlling the time to be 5-10min, and controlling the stirring speed to be 500-; wherein in the ammonia water adding process, the pH control range is 8-11;

(3) adding a certain mass part of amine compound into the mixed solution obtained in the step (2), and stirring, wherein the temperature is controlled to be between 70 and 90 ℃, the time is controlled to be between 20 and 30min, and the stirring speed is controlled to be 500-1000 r/min; wherein, in the adding process of the amine compound, the pH value is controlled within the range of 8-11;

(4) adding a certain mass part of alkali compounds into the mixed solution obtained in the step (3) for stirring, adding the alkali compounds for 3 times, continuing stirring for 60-90min after the addition is finished, controlling the temperature to be 75-100 ℃, and controlling the stirring speed to be 500-1000 r/min; wherein the pH control range is 8-11 in the alkali compound adding process;

(5) after the reaction in the step (4) is finished, cooling, and controlling the temperature to be 30-40 ℃;

(6) sequentially adding one or a mixture of more than two of EDTA iron, EDTA copper, EDTA zinc, EDTA manganese, boric acid, sodium molybdate, ammonium molybdate, magnesium sulfate, calcium formate, calcium acetate and calcium lignosulfonate into the transparent solution obtained in the step (5), and fully stirring for 20-30min at the stirring speed of 500-1000 r/min;

(7) adding a certain mass part of bio-stimulin into the solution obtained in the step (6), fully stirring for 20-30min, and controlling the stirring speed at 500-;

(8) and finally, cooling to room temperature to prepare the high-concentration liquid slow-release nitrogen fertilizer.

Compared with the prior art, the high-concentration liquid slow-release nitrogen fertilizer prepared by the invention has the following advantages:

1. the high-concentration liquid slow-release nitrogen fertilizer overcomes the defect of insufficient nitrogen source supply in the early stage of the urea formaldehyde slow-release granular fertilizer, and solves the problems of large urea dosage, short lasting time, high loss rate, environmental pollution and the like; the liquid slow-release nitrogen fertilizer is directly sprayed on plant leaf surfaces, has higher nutrient absorption rate, has the characteristics of quick effect, medium effect and slow effect, can continuously provide nutrients for crops for a long time, effectively improves the nitrogen element absorption rate, and avoids environmental pollution.

2. The high-concentration liquid slow-release nitrogen fertilizer prepared by the invention simultaneously contains unreacted ammonia water, urea and hydroxymethyl urea and methylene urea with different molecular chain lengths, the unreacted urea and the ammonia water can immediately play a role and are quick-acting parts, quick-acting nitrogen can take effect after leaf spraying, and more importantly, the quick-acting nitrogen of the parts can not burn leaf surfaces. The ingredients of the hydroxymethyl urea and the methylene urea which are synthesized into different molecular chain lengths are middle-effect and slow-effect parts, can be attached to the leaf surfaces of plants to slowly release nitrogen elements, and can be continuously absorbed by the plants for a long time to play a role, and the lasting period can reach 60-90 days to the maximum.

3. The high-concentration liquid slow-release nitrogen fertilizer prepared by the invention is safe to crops due to no leaf burning when being sprayed on the leaf surfaces, solves the problem of uneven spreading of solid chemical fertilizers, can be sprayed by combining an unmanned aerial vehicle, saves time, labor and force, can greatly reduce nitrogen loss and volatilization, protects the surrounding environment, reduces the loss of nitrogen fertilizer, improves the benefit, and improves the utilization rate by 50 percent compared with the traditional nitrogen fertilizer.

4. The amine compound used in the invention is one or a mixture of more than two of diethylamine, triethylamine, diethanolamine, triethanolamine, monoammonium sulfate and diammonium phosphate; by adding a large amount of urea, ammonia water and amine compounds, the nitrogen content in the slow release fertilizer can reach 26-35%, and the slow release fertilizer has higher nitrogen content and better fertilizer efficiency than other slow release fertilizers.

5. The salt index of the high-concentration liquid slow-release nitrogen fertilizer is less than or equal to 1.5, and the soil hardening and salinization are favorably reduced; various trace elements are adopted to promote root growth and chlorophyll synthesis and improve the quality of crops;

6. the high-concentration liquid slow-release nitrogen fertilizer has excellent water dispersibility and stability, and the storage period is 12-36 months; can be mixed with most pesticide products, directly sprayed on crops, and can provide nonflammable plant food nitrogen when applied to leaves of living plants, thereby improving the wetting and spreading performance of the liquid medicine, reducing the drift and further improving the pesticide effect and the fertilizer effect.

Detailed Description

The present invention will be further described with reference to examples. The raw materials of each example were purchased directly.

Example 1:

the liquid slow-release nitrogen fertilizer comprises 65 parts of urea, 43 parts of 35% formaldehyde aqueous solution with mass concentration, 3 parts of potassium hydroxide, 3 parts of monoammonium sulfate, 10 parts of 28% ammonia water with mass concentration, 0.82001 parts of medium trace element-containing substances and 2 parts of biostimulant, wherein the medium trace element-containing substances comprise 0.1 part of ferric EDTA, 0.01 part of copper EDTA, 0.1 part of zinc EDTA, 0.01 part of manganese EDTA, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate, and the biostimulant comprises 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine, and the preparation method comprises the following steps:

(1) mixing and stirring 43 parts of 35% formaldehyde aqueous solution and 65 parts of urea in a reaction kettle at room temperature, wherein the stirring time is controlled for 20min, and the stirring speed is controlled for 500 r/min;

(2) adding 10 parts of ammonia water with the mass concentration of 28% into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 65 ℃, controlling the time to be 10min, and controlling the stirring speed to be 500 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 3 parts of monoammonium sulfate into the mixed solution in the step (2), stirring, controlling the temperature to be 80 ℃, controlling the time to be 25min, and controlling the stirring speed to be 500 r/min; wherein in the process of adding the monoammonium sulfate, the PH control range is 8-11;

(4) adding 3 parts of potassium hydroxide into the mixed solution obtained in the step (3) for stirring, adding potassium hydroxide slowly for 3 times, continuing stirring for 60min after the addition is finished, controlling the temperature to be 85 ℃, and controlling the stirring speed to be 500 r/min; wherein, in the process of adding the potassium hydroxide compound, the PH control range is 8-11;

(5) after the reaction in the step (4) is finished, cooling, and controlling the temperature to be 35 ℃;

(6) adding 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate into the transparent solution obtained in the step (5) in sequence, fully stirring for 30min, and controlling the stirring speed to be 500 r/min;

(7) adding 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine into the solution obtained in the step (6), fully stirring for 30min, and controlling the stirring speed to be 500 r/min;

(8) finally, cooling to room temperature to prepare the high-concentration liquid slow-release nitrogen fertilizer.

And detecting the liquid slow-release nitrogen fertilizer.

(1) The detection results are as follows:

(2) evaluation of stability

The product is stable after being placed for 16 months, and white floccules do not appear.

Example 2:

the liquid slow-release nitrogen fertilizer comprises 70 parts of urea, 43 parts of 55% formaldehyde aqueous solution by mass, 3 parts of potassium hydroxide, 3 parts of triethanolamine, 10 parts of 20% ammonia water by mass, 0.82001 parts of medium trace element-containing substances and 2 parts of biostimulant, wherein the medium trace element-containing substances comprise 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate, and the biostimulant comprises 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine; the preparation method comprises the following steps:

(1) mixing and stirring 43 parts of formaldehyde aqueous solution with the mass concentration of 55% and 70 parts of urea in a reaction kettle at room temperature, wherein the stirring time is controlled for 20min, and the stirring speed is controlled for 1000 r/min;

(2) adding 10 parts of ammonia water with the mass concentration of 20% into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 65 ℃, controlling the time to be 10min, and controlling the stirring speed to be 1000 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 3 parts of triethanolamine into the mixed solution obtained in the step (2), stirring, controlling the temperature to be 75 ℃, controlling the time to be 30min and controlling the stirring speed to be 1000 r/min; wherein in the adding process of the triethanolamine compound, the PH control range is 8-11;

(4) adding 3 parts of potassium hydroxide into the mixed solution obtained in the step (3) for stirring, adding potassium hydroxide slowly for 3 times, continuing stirring for 70min after the addition is finished, controlling the temperature to be 79 ℃, and controlling the stirring speed to be 1000 r/min; wherein, in the process of adding the potassium hydroxide compound, the PH control range is 8-11;

(5) after the reaction in the step (4) is finished, cooling, and controlling the temperature to be 30 ℃;

(6) adding 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate into the transparent solution obtained in the step (5) in sequence, fully stirring for 20min, and controlling the stirring speed to be 1000 r/min;

(7) adding 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine into the solution obtained in the step (6), fully stirring for 25min, and controlling the stirring speed to be 1000 r/min;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

The product is stable after being placed for 12 months, and white floccules do not appear.

Example 3:

the liquid slow-release nitrogen fertilizer comprises 75 parts of urea, 43 parts of 45% formaldehyde aqueous solution with mass concentration, 3 parts of potassium hydroxide, 3 parts of triethanolamine, 10 parts of 25% ammonia water with mass concentration, 0.82001 parts of medium trace element-containing substances and 2 parts of biostimulant, wherein the medium trace element-containing substances comprise 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate, and the biostimulant comprises 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine; the preparation method comprises the following steps:

(1) mixing and stirring 43 parts of 45 mass percent formaldehyde aqueous solution and 75 parts of urea in a reaction kettle at room temperature, wherein the stirring time is controlled for 15min, and the stirring speed is controlled for 800 r/min;

(2) adding 10 parts of 25% ammonia water into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 65 ℃, the time to be 8min and the stirring speed to be 800 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 3 parts of triethanolamine into the mixed solution obtained in the step (2), stirring, controlling the temperature to be 75 ℃, controlling the time to be 25min and controlling the stirring speed to be 800 r/min; wherein in the adding process of the triethanolamine compound, the PH control range is 8-11;

(4) adding 3 parts of potassium hydroxide into the mixed solution obtained in the step (3) for stirring, adding potassium hydroxide slowly for 3 times, continuing stirring for 75min after the addition is finished, controlling the temperature to be 85 ℃, and controlling the stirring speed to be 800 r/min; wherein, in the process of adding the potassium hydroxide compound, the PH control range is 8-11;

(6) adding 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate into the transparent solution obtained in the step (5) in sequence, fully stirring for 25min, and controlling the stirring speed to be 800 r/min;

(7) adding 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine into the solution obtained in the step (6), fully stirring for 20min, and controlling the stirring speed at 800 r/min;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

The product is stable after being placed for 15 months, and white floccules do not appear.

Example 4:

the liquid slow-release nitrogen fertilizer comprises 75 parts of urea, 43 parts of 35% formaldehyde aqueous solution with mass concentration, 3 parts of potassium bicarbonate, 3 parts of diethylamine, 10 parts of ammonia water with mass concentration of 22%, 0.82001 parts of medium trace element-containing substances and 2 parts of biostimulant, wherein the medium trace element-containing substances comprise 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate, and the biostimulant comprises 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine; the preparation method comprises the following steps:

(1) mixing and stirring 43 parts of 35% formaldehyde aqueous solution and 75 parts of urea in a reaction kettle at room temperature, wherein the stirring time is controlled for 10min, and the stirring speed is controlled for 700 r/min;

(2) adding 10 parts of 22% ammonia water into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 60 ℃, controlling the time to be 7min, and controlling the stirring speed to be 700 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 3 parts of diethylamine into the mixed solution obtained in the step (2), stirring, controlling the temperature to be 75 ℃, controlling the time to be 25min and controlling the stirring speed to be 700 r/min; wherein the pH control range is 8-11 in the process of adding the diethanolamine compound;

(4) adding 3 parts of potassium bicarbonate into the mixed solution obtained in the step (3), stirring, slowly adding the potassium bicarbonate for 3 times, continuously stirring for 65min after the addition is finished, controlling the temperature to be 85 ℃, and controlling the stirring speed to be 700 r/min; wherein, in the process of adding the potassium bicarbonate compound, the PH is controlled within the range of 8-11;

(6) adding 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate into the transparent solution obtained in the step (5) in sequence, fully stirring for 25min, and controlling the stirring speed to 700 r/min;

(7) adding 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine into the solution obtained in the step (6), fully stirring for 25min, and controlling the stirring speed at 700 r/min;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

The product is stable after being placed for 10 months, and white floccule does not appear.

Example 5:

the liquid slow-release nitrogen fertilizer comprises 75 parts of urea, 43 parts of 40% formaldehyde aqueous solution by mass, 3.5 parts of potassium hydroxide, 3 parts of triethanolamine, 12.5 parts of ammonia water by mass at a concentration of 24%, 0.82001 parts of medium trace element-containing substances and 2 parts of biostimulant, wherein the medium trace element-containing substances comprise 0.1 part of ferric EDTA, 0.01 part of copper EDTA, 0.1 part of zinc EDTA, 0.01 part of manganese EDTA, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate, and the biostimulant comprises 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine; the preparation method comprises the following steps:

(1) mixing and stirring 43 parts of 40% formaldehyde aqueous solution and 75 parts of urea in a reaction kettle at room temperature, wherein the stirring time is controlled for 20min, and the stirring speed is controlled for 1000 r/min;

(2) adding 12.5 parts of ammonia water with the mass concentration of 24% into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 65 ℃, controlling the time to be 10min, and controlling the stirring speed to be 1000 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 3 parts of triethanolamine into the mixed solution obtained in the step (2), stirring, controlling the temperature to be 75 ℃, controlling the time to be 25min and controlling the stirring speed to be 1000 r/min; wherein in the adding process of the triethanolamine compound, the PH control range is 8-11;

(4) adding 3.5 parts of potassium hydroxide into the mixed solution obtained in the step (3) for stirring, slowly adding the potassium hydroxide for 3 times, continuously stirring for 70min after the potassium hydroxide is added, controlling the temperature to be 85 ℃, and controlling the stirring speed to be 1000 r/min; wherein, in the process of adding the potassium hydroxide compound, the PH control range is 8-11;

(6) adding 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate into the transparent solution obtained in the step (5) in sequence, fully stirring for 25min, and controlling the stirring speed to be 1000 r/min;

(7) adding 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine into the solution obtained in the step (6), fully stirring for 30min, and controlling the stirring speed to be 1000 r/min;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

The product is stable after being placed for 20 months, and white floccule does not appear.

Example 6:

the liquid slow-release nitrogen fertilizer comprises 75 parts of urea, 43 parts of 50% formaldehyde aqueous solution with mass concentration, 3 parts of potassium hydroxide, 15 parts of triethylamine, 13.5 parts of 25% ammonia water with mass concentration, 0.82001 parts of medium trace element-containing substances and 2 parts of biostimulant, wherein the medium trace element-containing substances comprise 0.1 part of ferric EDTA, 0.01 part of copper EDTA, 0.1 part of zinc EDTA, 0.01 part of manganese EDTA, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate, and the biostimulant comprises 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine; the preparation method comprises the following steps:

(1) mixing and stirring 43 parts of 50% formaldehyde aqueous solution and 75 parts of urea in a reaction kettle at room temperature, wherein the stirring time is controlled for 15min, and the stirring speed is controlled for 500 r/min;

(2) adding 13.5 parts of 25% ammonia water into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 60 ℃, controlling the time to be 5min, and controlling the stirring speed to be 500 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 15 parts of triethylamine into the mixed solution obtained in the step (2) for stirring, controlling the temperature to be between 70 and 90 ℃, controlling the time to be 20min and controlling the stirring speed to be 500 r/min; wherein in the adding process of the triethylamine compound, the PH control range is 8-11;

(4) adding 3 parts of potassium hydroxide into the mixed solution obtained in the step (3), stirring, adding potassium hydroxide slowly for 3 times, continuing stirring for 69min after the addition is finished, controlling the temperature to be 75 ℃, and controlling the stirring speed to be 500 r/min; wherein, in the process of adding the potassium hydroxide compound, the PH control range is 9-11;

(6) adding 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate into the transparent solution obtained in the step (5) in sequence, fully stirring for 20min, and controlling the stirring speed to be 500 r/min;

(7) adding 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine into the solution obtained in the step (6), fully stirring for 20min, and controlling the stirring speed to be 500 r/min;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

The product is stable after being placed for 14 months, and white floccules do not appear.

Example 7:

the liquid slow-release nitrogen fertilizer comprises 75 parts of urea, 43 parts of formaldehyde aqueous solution with the mass concentration of 37%, 3 parts of potassium hydroxide, 10 parts of diammonium phosphate, 14.5 parts of ammonia water with the mass concentration of 20%, 0.82001 parts of medium trace element-containing substances and 2 parts of biostimulant, wherein the medium trace element-containing substances comprise 0.1 part of ferric EDTA, 0.01 part of copper EDTA, 0.1 part of zinc EDTA, 0.01 part of manganese EDTA, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate, and the biostimulant comprises 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine; the preparation method comprises the following steps:

(1) mixing and stirring 43 parts of formaldehyde aqueous solution with the mass concentration of 37% and 75 parts of urea in a reaction kettle at room temperature, wherein the stirring time is controlled for 10min, and the stirring speed is controlled for 500 r/min;

(2) adding 14.5 parts of ammonia water with the mass concentration of 20% into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 60 ℃, controlling the time to be 5min, and controlling the stirring speed to be 500 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 10 parts of diammonium phosphate into the mixed solution obtained in the step (2), and stirring at the temperature of 80 ℃ for 20min and at the stirring speed of 500 r/min; wherein the pH control range is 8-11 in the process of adding the diammonium phosphate compound;

(4) adding 3 parts of potassium hydroxide into the mixed solution obtained in the step (3) for stirring, adding potassium hydroxide slowly for 3 times, continuing stirring for 80min after the addition is finished, controlling the temperature to be 85 ℃, and controlling the stirring speed to be 500 r/min; wherein, in the process of adding the potassium hydroxide compound, the PH control range is 8-11;

(6) adding 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium acetate into the transparent solution obtained in the step (5) in sequence, fully stirring for 20min, and controlling the stirring speed to be 500 r/min;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

Example 8:

the liquid slow-release nitrogen fertilizer comprises 75 parts of urea, 43 parts of 35% formaldehyde aqueous solution by mass concentration, 3.5 parts of potassium bicarbonate, 13.5 parts of diethylamine, 12 parts of ammonia water by mass concentration of 28%, 0.82001 parts of medium trace element-containing substance and 2 parts of biostimulant, wherein the medium trace element-containing substance comprises 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate, and the biostimulant comprises 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine; the preparation method comprises the following steps:

(1) mixing and stirring 43 parts of 35% formaldehyde aqueous solution and 75 parts of urea in a reaction kettle at room temperature, wherein the stirring time is controlled for 15min, and the stirring speed is controlled for 500 r/min;

(2) adding 12 parts of 28% ammonia water into the mixed solution obtained in the step (1), and stirring at 65 ℃ for 5min and at a stirring speed of 500 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 13.5 parts of diethylamine into the mixed solution in the step (2), stirring, controlling the temperature to be 80 ℃, controlling the time to be 20min, and controlling the stirring speed to be 500 r/min; wherein in the adding process of the diethylamine compound, the PH control range is 8-11;

(4) adding 3.5 parts of potassium bicarbonate into the mixed solution obtained in the step (3) for stirring, slowly adding the potassium bicarbonate for 3 times, continuously stirring for 75min after the addition is finished, controlling the temperature to be 85 ℃, and controlling the stirring speed to be 500 r/min; wherein, in the process of adding the potassium bicarbonate compound, the PH is controlled within the range of 8-11;

(6) adding 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium lignosulfonate into the transparent solution obtained in the step (5) in sequence, fully stirring for 20min, and controlling the stirring speed to be 500 r/min;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

Example 9:

the liquid slow-release nitrogen fertilizer comprises 75 parts of urea, 43 parts of 35% formaldehyde aqueous solution with mass concentration, 3 parts of potassium hydroxide, 15 parts of triethanolamine, 10.5 parts of ammonia water with mass concentration of 20%, 0.82001 parts of medium trace element-containing substances and 2 parts of biostimulant, wherein the medium trace element-containing substances comprise 0.1 part of ferric EDTA, 0.01 part of copper EDTA, 0.1 part of zinc EDTA, 0.01 part of manganese EDTA, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate, and the biostimulant comprises 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine; the preparation method comprises the following steps:

(2) adding 10.5 parts of ammonia water with the mass concentration of 20% into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 65 ℃, controlling the time to be 5min, and controlling the stirring speed to be 500 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 15 parts of triethanolamine into the mixed solution obtained in the step (2), stirring, controlling the temperature to be between 90 ℃, controlling the time to be 20min and controlling the stirring speed to be 500/min; wherein in the adding process of the triethanolamine compound, the PH control range is 8-11;

(4) adding 3 parts of potassium hydroxide into the mixed solution obtained in the step (3) for stirring, adding the potassium hydroxide slowly for 3 times, continuing stirring for 90min after the addition is finished, controlling the temperature to be between 75 ℃, and controlling the stirring speed to be 500 r/min; wherein, in the process of adding the potassium hydroxide compound, the PH control range is 9-11;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

The product is stable after being placed for 9 months, and white floccule does not appear.

Example 10:

the liquid slow-release nitrogen fertilizer comprises 75 parts of urea, 43 parts of 50% formaldehyde aqueous solution by mass concentration, 3 parts of potassium bicarbonate, 14.5 parts of triethanolamine, 10 parts of ammonia water by mass concentration of 20%, 0.82001 parts of medium trace element-containing substances and 2 parts of biostimulant, wherein the medium trace element-containing substances comprise 0.1 part of ferric EDTA, 0.01 part of copper EDTA, 0.1 part of zinc EDTA, 0.01 part of manganese EDTA, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate, and the biostimulant comprises 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine; the preparation method comprises the following steps:

(1) mixing and stirring 43 parts of 50% formaldehyde aqueous solution and 75 parts of urea in a reaction kettle at room temperature, wherein the stirring time is controlled for 10min, and the stirring speed is controlled for 500 r/min;

(2) adding 10 parts of ammonia water with the mass concentration of 20% into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 65 ℃, controlling the time to be 5min, and controlling the stirring speed to be 500 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 14.5 parts of triethanolamine into the mixed solution obtained in the step (2), stirring, controlling the temperature to be 70 ℃, the time to be 20min and the stirring speed to be 500 r/min; wherein in the adding process of the triethanolamine compound, the PH control range is 8-11;

(4) adding 3 parts of potassium bicarbonate into the mixed solution obtained in the step (3), stirring, slowly adding the potassium bicarbonate for 3 times, continuing stirring for 65min after the addition is finished, controlling the temperature to be between 90 ℃, and controlling the stirring speed to be 500 r/min; wherein, in the process of adding the potassium bicarbonate compound, the PH is controlled within the range of 8-11;

(7) adding 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine into the solution obtained in the step (6), fully stirring for 25min, and controlling the stirring speed to be 500 r/min;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

Example 11:

the liquid slow-release nitrogen fertilizer comprises 75 parts of urea, 43 parts of 45% formaldehyde aqueous solution by mass, 3 parts of potassium hydroxide, 12.5 parts of triethanolamine, 13.5 parts of 28% ammonia water by mass, 0.82001 parts of medium trace element-containing substances and 2 parts of biostimulant, wherein the medium trace element-containing substances comprise 0.1 part of ferric EDTA, 0.01 part of copper EDTA, 0.1 part of zinc EDTA, 0.01 part of manganese EDTA, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate, and the biostimulant comprises 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine; the preparation method comprises the following steps:

(1) mixing and stirring 43 parts of 45 mass percent formaldehyde aqueous solution and 75 parts of urea in a reaction kettle at room temperature, wherein the stirring time is controlled for 10min, and the stirring speed is controlled for 500 r/min;

(2) adding 13.5 parts of ammonia water with the mass concentration of 28% into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 70 ℃, controlling the time to be 5min, and controlling the stirring speed to be 500 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 12.5 parts of triethanolamine into the mixed solution obtained in the step (2), stirring, controlling the temperature to be between 70 and 90 ℃, controlling the time to be 20min, and controlling the stirring speed to be 500 r/min; wherein in the adding process of the triethanolamine compound, the PH control range is 8-11;

(4) adding 3 parts of potassium hydroxide into the mixed solution obtained in the step (3) for stirring, adding potassium hydroxide slowly for 3 times, continuing stirring for 65min after the addition is finished, controlling the temperature to be between 80 ℃, and controlling the stirring speed to be 500 r/min; wherein, in the process of adding the potassium hydroxide compound, the PH control range is 8-11;

(6) adding 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid and 0.00001 part of sodium molybdate into the transparent solution obtained in the step (5) in sequence, fully stirring for 25min, and controlling the stirring speed to be 500 r/min;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

Example 12:

the liquid slow-release nitrogen fertilizer comprises 75 parts of urea, 43 parts of 35% formaldehyde aqueous solution with mass concentration, 3 parts of potassium hydroxide, 8.8 parts of triethanolamine, 14.5 parts of 28% ammonia water with mass concentration, 0.82001 parts of medium trace element-containing substances and 2 parts of biostimulant, wherein the medium trace element-containing substances comprise 0.1 part of ferric EDTA, 0.01 part of copper EDTA, 0.1 part of zinc EDTA, 0.01 part of manganese EDTA, 0.1 part of boric acid, 0.00001 part of sodium molybdate and 0.5 part of calcium formate, and the biostimulant comprises 0.5 part of leucine, 0.5 part of lysine, 0.5 part of methionine and 0.5 part of arginine; the preparation method comprises the following steps:

(1) mixing and stirring 43 parts of 35% formaldehyde aqueous solution and 75 parts of urea in a reaction kettle at room temperature, wherein the stirring time is controlled for 10min, and the stirring speed is controlled for 500 r/min;

(2) adding 14.5 parts of 28% ammonia water into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 65 ℃, controlling the time to be 10min, and controlling the stirring speed to be 500 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 8.8 parts of triethanolamine into the mixed solution obtained in the step (2), stirring at 90 ℃, for 20-30min, and controlling the stirring speed at 500 r/min; wherein in the adding process of the triethanolamine compound, the PH control range is 9-10;

(4) adding 3 parts of potassium hydroxide into the mixed solution obtained in the step (3) for stirring, adding potassium hydroxide slowly for 3 times, continuing stirring for 85min after the addition is finished, controlling the temperature to be between 100 ℃, and controlling the stirring speed to be 500 r/min; wherein, in the process of adding the potassium hydroxide compound, the PH control range is 8-11;

(5) after the reaction in the step (4) is finished, cooling, and controlling the temperature to be 40 ℃;

(6) adding 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese and 0.1 part of boric acid into the transparent solution obtained in the step (5) in sequence, fully stirring for 30min, and controlling the stirring speed at 500 r/min;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

Example 13

The liquid slow-release nitrogen fertilizer comprises 40 parts of urea, 50 parts of 35% formaldehyde aqueous solution by mass, 1 part of sodium hydroxide, 1 part of sodium formate, 0.5 part of triethanolamine, 0.5 part of triethylamine, 14 parts of ammonia water with the mass concentration of 28%, 1 part of medium trace element-containing substance and 5 parts of arginine, wherein the medium trace element-containing substance comprises 0.1 part of ferric EDTA, 0.01 part of copper EDTA, 0.1 part of zinc EDTA, 0.01 part of manganese EDTA, 0.1 part of boric acid, 0.1 part of magnesium sulfate, 0.08 part of calcium acetate and 0.5 part of calcium formate, and the preparation method comprises the following steps:

(1) mixing and stirring 50 parts of 35% formaldehyde aqueous solution and 40 parts of urea in a reaction kettle at room temperature, wherein the stirring time is controlled for 20min, and the stirring speed is controlled for 800 r/min;

(2) adding 14 parts of 28% ammonia water into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 65 ℃, controlling the time to be 10min, and controlling the stirring speed to be 800 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 0.5 part of triethanolamine and 0.5 part of triethylamine into the mixed solution in the step (2) for stirring, controlling the temperature to be 80 ℃, controlling the time to be 25min and controlling the stirring speed to be 800 r/min; wherein in the adding process of the triethanolamine and the triethylamine, the PH control range is 8-11;

(4) adding 1 part of sodium hydroxide and 1 part of sodium formate into the mixed solution obtained in the step (3), stirring, adding the sodium hydroxide and the sodium formate slowly for 3 times, continuing stirring for 60min after the addition is finished, controlling the temperature to be 85 ℃, and controlling the stirring speed to be 800 r/min; wherein, in the process of adding sodium hydroxide and sodium formate, the PH control range is 8-11;

(6) adding 0.1 part of EDTA iron, 0.01 part of EDTA copper, 0.1 part of EDTA zinc, 0.01 part of EDTA manganese, 0.1 part of boric acid, 0.1 part of magnesium sulfate, 0.08 part of calcium acetate and 0.5 part of calcium formate into the transparent solution obtained in the step (5) in sequence, fully stirring for 30min, and controlling the stirring speed to be 800 r/min;

(7) adding 5 parts of arginine into the solution obtained in the step (6), fully stirring for 30min, and controlling the stirring speed at 800 r/min;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

The product is stable after being placed for 6 months, and white floccule does not appear.

Example 14

The liquid slow-release nitrogen fertilizer comprises 80 parts of urea, 18 parts of formaldehyde aqueous solution with the mass concentration of 55%, 1 part of sodium hydroxide, 1 part of monoammonium sulfate, 1 part of ammonia water with the mass concentration of 28%, 0.001 part of EDTA copper and 0.01 part of methionine, and the preparation method comprises the following steps:

(1) mixing 18 parts of formaldehyde aqueous solution with the mass concentration of 55% and 80 parts of urea in a reaction kettle at room temperature, stirring for 20min, and controlling the stirring speed at 700 r/min;

(2) adding 1 part of 28% ammonia water into the mixed solution obtained in the step (1), stirring, controlling the temperature to be 65 ℃, controlling the time to be 10min, and controlling the stirring speed to be 700 r/min; wherein in the ammonia water adding process, the PH control range is 8-11;

(3) adding 1 part of monoammonium sulfate into the mixed solution in the step (2), stirring, controlling the temperature to be 80 ℃, controlling the time to be 25min, and controlling the stirring speed to be 700 r/min; wherein in the process of adding the monoammonium sulfate, the PH control range is 8-11;

(4) adding 1 part of sodium hydroxide into the mixed solution obtained in the step (3) for stirring, adding sodium hydroxide slowly for 3 times, continuing stirring for 60min after the addition is finished, controlling the temperature to be 85 ℃, and controlling the stirring speed to be 500 r/min; wherein the PH control range is 8-11 in the adding process of the sodium hydroxide compound;

(6) sequentially adding 0.001 part of EDTA copper into the transparent solution obtained in the step (5), fully stirring for 30min, and controlling the stirring speed at 700 r/min;

(7) adding 0.01 part of methionine into the solution obtained in the step (6), fully stirring for 30min, and controlling the stirring speed at 700 r/min;

The liquid slow-release nitrogen fertilizer is detected,

(1) the detection results are as follows:

(2) evaluation of stability

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims

1. A high-concentration liquid slow-release nitrogen fertilizer comprises the following components in parts by mass: the components consist of urea, formaldehyde aqueous solution, alkali compounds, amine compounds, ammonia water, medium and trace element-containing substances and biological stimulin; wherein the ratio of urea: 40-80 parts; 35-55% of formaldehyde aqueous solution by mass: 18-50 parts; alkali compounds: 1-15 parts; amine compounds: 1-15 parts; ammonia water with mass concentration of 20-28%: 1-15 parts; medium trace element-containing substance: 0.001-1 part; biological stimulin: 0.01-5 parts of total nitrogen content of 18-37 percent.

2. The high-concentration liquid slow-release nitrogen fertilizer according to claim 1, wherein: the medium trace element-containing substance is one or a mixture of more than two of iron ethylenediaminetetraacetic acid (EDTA iron), EDTA copper, EDTA zinc, EDTA manganese, boric acid, sodium molybdate, ammonium molybdate, magnesium sulfate, calcium formate, calcium acetate and calcium lignosulphonate.

3. The high-concentration liquid slow-release nitrogen fertilizer according to claim 1, wherein: the biological stimulin is one or a mixture of more than two of humic acid, polypeptide and free amino acid.

4. The high-concentration liquid slow-release nitrogen fertilizer according to claim 3, wherein: the water-insoluble substance of the humic acid is less than or equal to 0.5 percent, the particle size is less than or equal to 5 mu m, and the hard water resistance is more than or equal to 30.

5. The high-concentration liquid slow-release nitrogen fertilizer according to claim 3, wherein: the amino acids are one or a mixture of more than two of leucine, lysine, phenylalanine, isoleucine, valine, threonine, methionine, tryptophan, arginine and glutamine.

6. The high-concentration liquid slow-release nitrogen fertilizer according to claim 1, wherein: the amine compound is one or a mixture of more than two of diethylamine, triethylamine, diethanolamine, triethanolamine, monoammonium sulfate and diammonium phosphate.

7. The high-concentration liquid slow-release nitrogen fertilizer according to claim 1, wherein: the alkali compound is one or a mixture of more than two of sodium carbonate, sodium hydroxide, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, sodium formate, potassium acetate and sodium acetate.

8. The high-concentration liquid slow-release nitrogen fertilizer according to claim 1, wherein: the ratio of quick-acting nitrogen, intermediate-acting nitrogen and slow-acting nitrogen in the high-concentration liquid slow-release nitrogen fertilizer is 1-2: 1-2: 1.5-3.

9. The method for preparing a high concentration liquid slow release nitrogen fertilizer according to any one of claims 1 to 8, comprising the steps of: