JPH0867591A - Urea-based compound fertilizer and its production - Google Patents

Abstract

PURPOSE: To obtain a compound fertilizer effective for solving various problems such as soil improvement, humification promotion and nutrient supply and having an effect meeting various purposes by mixing urea melt containing a specific sulfate with fused phosphate and cooling the liquid droplet of the mixture. CONSTITUTION: This granular urea-based compound fertilizer is produced by melting and mixing urea with salts under criteria of urea 100 pts.wt. - potassium chloride 10 pts.wt. at 115 deg.C, urea 100 pts.wt. - potassium chloride 10 pts.wt. - potassium sulfate 2 pts.wt. at 113 deg.C, urea 100 pts.wt. - potassium chloride 10 pts.wt. calcium sulfate 6 pts.wt. at 108 deg.C or urea 100 pts.wt. - potassium chloride 10 pts.wt. - magnesium sulfate 10 pts.wt. at 100 deg.C in ammonia gas atmosphere under pressure (5-12kg/cm<2> ), incorporating the produced molten product with 45-75wt.% (based on the total composition) of fused phosphate containing 95% fraction having an average particle diameter of <=0.3mm, ejecting the obtained slurry through a nozzle in the form of liquid droplets at an ambient temperature of 5-30 deg.C and a flow rate of 8-16m/sec and solidifying the droplets at a temperature lower than the melting point of the slurry by about 5 deg.C by an upward air flow having a temperature lower than the temperature of the malt mixture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound chemical fertilizer mainly composed of urea and molten phosphorus fertilizer and a method for producing the same. More specifically, it has functions such as soil improvement and plant nutrient supply,
The present invention relates to a urea-based compound chemical fertilizer capable of rationalizing fertilization and improving the utilization rate of fertilizer, and a method for producing the same.

[0002]

2. Description of the Related Art Fertilizers have various application methods depending on the purpose. For example, so-called soil making, which is a general term for soil improvement, is often carried out during the period when there are no crops in the fields from after the crop is harvested until about 30 days before the start of crop cultivation. For the purpose of improvement, improvement of van soil soil, promotion of agglomeration of soil particles, etc., alkaline phosphorus materials such as fused phosphorus fertilizer and slag silicate fertilizer are used.

When making soil, a large amount of material is scattered (100-
Since it is 200 kg / 10 a) and it requires a spraying labor, a material that is effective in a small amount is required. Usually, the fertilizer used for this is in the form of sand or a granulated product, but the particle size of this granulated product is as wide as 0.5 to 5 mm, and it is difficult to apply it evenly in actual fields. However, there is a problem that powdering is seen and workability is poor in the work by. Recently, the number of new open fields is small and the number of operations on stable soil is increasing, so there is a demand for materials that are easy to apply and have stable and sustainable effects.

In addition, as the mechanization of farming work progresses and the work area of combine harvesters increases dramatically, the utilization of rice straw, which is the residue of harvested crops, is increasing. Making soil is an important issue.

For the purpose of accelerating the ripening of rice straw, a method of spraying microbial cells directly on the paddy field is performed. But,
After cutting the rice straw, the components such as nitrogen and phosphoric acid necessary for microbial growth are insufficient, and the effect of promoting ripening is not sufficiently exerted.

To promote ripening with fertilizer components, lime nitrogen,
Straw-ripening-promoting fertilizers and the like are used, but lime-nitrogen is supplied only with the nitrogen source necessary for microbial growth, and the phosphoric acid source is insufficient, so that the ripening-promoting effect is not sufficiently exerted. As the straw-ripening-promoting fertilizer, one containing nitrogen, phosphoric acid, and magnesia necessary for microbial growth is used, but it is desired to develop a chemical fertilizer with higher functionality.

[0007] The chemical fertilizer used for the nutritional supply of crops is
It is a fertilizer that is used from immediately before the crop cultivation period until harvest, and is divided into basic fertilizer and top fertilizer.

As the basic fertilizer, the full-layer fertilizer applied by hand is generally used, but mechanical spraying has been frequently performed, and there has been a demand for a fertilizer suitable for a spraying machine.

The basic fertilizer is applied from about 30 days before the start of cultivation to the time of planting, and a chemical fertilizer containing three elements of nitrogen, phosphoric acid and potassium is used. There is a difference in the utilization rate of each fertilizer.

Full-layer fertilization is a method of applying before the cultivation period. If the period from application of fertilizer to planting is long, loss of fertilizer components and loss due to soil fixation occur, but the characteristic is that the duration of fertilization is long, and the utilization rate is generally 40 to 50% nitrogen and phosphoric acid. 20%, Kali 50-60%
It is supposed to be.

Side fertilization is 2 to 5 cm wide from the root of the crop,
It is a method to apply fertilizer locally (high concentration) to the stripes at a depth of 3 to 5 cm. Usually, uniform grain size is used to reduce unevenness in fertilization. Is said to improve by about 10 to 20%.

[0012] Further, as an effect of lateral fertilization, labor saving (fertilization +
Simultaneous work on rice planting), improvement of utilization rate of fertilizer, promotion of initial growth, prevention of water pollution (prevention of fertilizer runoff, prevention of water quality deterioration), etc., which has a high utilization rate recently due to environmental problems such as prevention of water pollution. Fertilization is increasing.

In order to ensure the effect of these lateral fertilizer applications, the form of the fertilizer used for this is such that the components of each particle are uniform and soluble, more spherical, smooth on the surface, and harder. It is desirable that the fertilizer used has features such as high yield, no generation of powder, etc., and a large true specific gravity of each particle for uniform fertilizer supply.
Granulated chemical fertilizer, slow-release fertilizer, coated fertilizer, paste fertilizer, etc. are considered.

Top fertilizer is a fertilizer applied to supplement the nutrient deficiency of crops according to the growth condition during the cultivation period, and granulated chemical fertilizer is used. The application method is usually carried out by mechanical power such as a power spreader. However, there is a demand for a shape that enables easy spraying and uniform spraying, and it is desired that the fertilizing effect be promptly exhibited and sustained.

At present, an example of the shape of a typical material used for full-layer fertilizer application / side-row fertilizer application is particle size: particle size 2 to 3.36.
mm has a thickness of about 83%, 3.3-4 mm has a thickness of about 17%, hardness: about 6 kg / grain, and bulk specific gravity: about 0.85.

Recently, the number of coated fertilizers has increased remarkably as a fertilizer exclusively for side strips, but this fertilizer has a particle size of 2 to 4 mm, and the elution and fertilizing effect of fertilizer components can be arbitrarily adjusted. The elution type that meets the cultivation conditions of is supplied.

The coated fertilizer is produced by spray-coating a granular material with a coating material composed of a thermosetting phenolic resin and talc of a mineral substance by a rotating drum, a rotating pan, and a fluidized bed, and heat-treating the granulated material to harden the resin. are doing.

[0018]

The object of the present invention is to solve the problems of soil improvement (soil preparation), ripening promotion, nutrient supply, and the like, and to provide a compound fertilizer having the effect of meeting multiple purposes at the same time. To provide.

[0019]

Means for Solving the Problems As a result of intensive research on the production of a urea-based chemical fertilizer capable of accommodating agricultural mechanization as a chemical fertilizer, the present inventors have found that urea,
The present invention has been completed by discovering a highly functional urea-based chemical fertilizer which mainly comprises molten phosphorous fertilizer, and which contains potassium salt or other microelements and other trace elements, and which meets the official standards of fertilizers, and a method for producing the same.

That is, the present invention provides a mixture of molten urea and molten phosphorus fertilizer, or a molten mixture containing potassium chloride or potassium chloride and one or more sulfates selected from the group consisting of potassium sulfate, calcium sulfate and magnesium sulfate. The present invention relates to a method for producing a urea-based chemical fertilizer characterized by cooling droplets of a mixed melt of urea and molten phosphorous fertilizer.

Further, the urea-based chemical fertilizer produced by such a method can be obtained by coating glass-like molten phosphorus fertilizer with urea or urea containing other fertilizing components, and has various characteristics described later. It was found to be a chemical fertilizer. Next, the present invention will be described in more detail.

The urea-based chemical fertilizer of the present invention is produced by heating and melting a raw material containing urea. Urea has a melting point (132.7 ° C)
When heated above, a urea condensate (biuret) is produced. This biuret has the chemical formula NH ₂ CONHCONH ₂
It is a substance harmful to crops that can be produced by separating one molecule of ammonia from the condensation product of two molecules of urea, and it is an official standard according to Article 3 of the Fertilizer Control Law (maximum amount of harmful components allowed to be contained (%) In the chemical fertilizer, the biuret nitrogen is 0.01 or less per content rate of 1% of the total amount of the largest main components of nitrogen, phosphoric acid and potassium. In order to suppress the formation of such biuret at the time of melting the raw material urea, a method of adding salts such as potassium salt and lowering the melting temperature by the eutectic phenomenon of these and urea has been conventionally known.

The salts used in the present invention are potassium chloride and one or more of sulfates such as potassium, calcium and magnesium. Molten phosphorous fertilizer is obtained, for example, by pyrolyzing phosphate rock, and is a glassy substance containing phosphoric acid, silicic acid, magnesium, calcium, etc. The shape is sandy with some protrusions, so handle with care. It costs.

The use ratio of these raw materials is appropriately determined depending on the intended chemical fertilizer, but potassium chloride 0 to 18,
Other salts are 0 to 3.5, molten phosphorus fertilizer is 45 to 75 (all are wt%), and the balance is urea. Further, as the other salts, one or more sulfates such as potassium, calcium and magnesium are used, and when these are used, the proportion thereof is 0 to 10 wt% with respect to the amount of urea.

In the present invention, first, urea and a predetermined amount of salts are mixed and heated and melted. The melting temperature varies depending on the type and amount of salt used. In this case, of course, it melts at a temperature lower than the melting temperature of urea alone, but in any case, it is sufficient that the mixture of urea and salts maintains the molten state, and if the temperature is raised more than necessary, the efficiency of the subsequent cooling process will be improved. It is not preferable also from the viewpoint of, and usually, the melting point of the material to be melted is preferably within + 2 ° C.

The melting temperature used as a guide in the present invention is urea (1
00 parts by weight) -potassium chloride (10 parts by weight) system: 115
C, urea (100 parts by weight) -potassium chloride (10 parts by weight) -potassium sulfate (2 parts by weight) system: 113 ° C., urea (100 parts by weight) -potassium chloride (10 parts by weight) -calcium sulfate (6 parts by weight) ) System: 108 ° C., urea (100 parts by weight) -potassium chloride (10 parts by weight) -magnesium sulfate (10 parts by weight) system: 100 ° C.

A predetermined amount of molten phosphorus fertilizer is added to the obtained melt. The molten phosphorous fertilizer is a vitreous powder (crushed body), about 95% of which has an average particle size of 0.3 mm or less, does not dissolve in the melt of urea and salts, and does not melt in the melt. It becomes a slurry-like mixture in which powder is mixed. Naturally, the viscosity varies depending on the amount of the molten phosphorous fertilizer mixed, but in the present invention, the total amount of the molten phosphorous fertilizer is 45%.
It is preferable to use an amount of ˜75 wt%. The ratio of the molten phosphorous fertilizer used in the present invention is such that the viscosity of the mixture with the molten urea becomes an appropriate slurry state (viscosity 100 to 1500 cp) when the mixture is treated as droplets.

The content of the molten phosphorus fertilizer used in the present invention is 9 to 15% when converted to P ₂ O ₅ . For example, in the method of granulating using the surface tension of molten urea, urea:
The powder ratio (slurry concentration) naturally has an upper limit and a lower limit.
Based on the amount of urea, the lower limit is urea: powder = 25:
At about 75, the viscosity becomes so high that the operation becomes difficult and the target granulation yield cannot be obtained. Also, the upper limit is urea: powder = 4
At about 5:56, the viscosity of the slurry is too low, and the ratio of particles having a particle size of less than 2 mm increases, so that the target granulation yield cannot be obtained.

In the case of paddy rice, for example, the required nutrient amount is 30
% Is said to be supplied from fertilizers, but in terms of the utilization rate of phosphoric acid in such actual application, the content ratio of the above-mentioned molten phosphorous fertilizer is appropriate, and it also includes potassium. It can be said that the range of chemical fertilizers is appropriate from the aspect of the balance of nitrogen, phosphorus and potassium.

The slurry-like mixture is cooled as droplets. For this cooling, for example, the slurry-like mixture is jetted from an outlet having an appropriate diameter and scattered as droplets to be cooled and solidified in the cooling section to form a granular material. The cooling at this time is generally performed by blowing a gas having a temperature lower than the melt temperature, for example, air from the lower portion of the cooling unit to bring the gas into contact with the droplets of the melt to cool the melt. The slurry solidifies at a temperature about 5 ° C. lower than the melting point, but in order to reduce latent heat by 5 degrees, it is important to improve the dispersibility of the droplets because the droplets are spherical and have a small surface area. It is necessary to properly adjust the temperature and flow rate of. Normally, the temperature is 5 to 30 ° C (atmospheric temperature), and the flow rate is 8 to 1.
It is about 6 m / sec.

The diameter of the air outlet at this time is appropriately determined depending on the size of the target chemical fertilizer, but a diameter of 2 to 5 mm is a standard. The pressure at which the melt is blown out is not particularly limited, but is about 4 to 8 Kg / cm ² .

The particle size of the above-mentioned chemical fertilizer can be adjusted by changing the viscosity of the slurry, the diameter of the slurry outlet, the outlet pressure and the like.

As described above, when urea is heated above its melting point, a urea condensate (biuret) is produced. As a means for suppressing the production of this biuret, there is the following method.

That is, this is a method of adding a small amount of water (5 wt% or less) to urea. By adding such water, a rapid temperature rise is suppressed and biuret formation can be suppressed.
Furthermore, the generation of biuret can be suppressed by melting the inside of the urea dissolving tank in an ammonia gas atmosphere. In particular,
In the case of a urea-fused phosphorus fertilizer-based fertilizer, the decomposition reaction of urea can be suppressed by heating under pressure in an ammonia gas atmosphere.

In this method, a mixture of urea and molten phosphorus fertilizer is pressurized under an ammonia gas atmosphere, and urea is melted in a state where the void portion of the mixture is replaced with ammonia gas. Although the pressurization at this time depends on the temperature and the holding time, the production of biuret can be sufficiently suppressed at 5 Kg / cm ² or more, but usually 5 to 5
It is about 12 Kg / cm ² . According to this method, it is not necessary to add a eutectic component for lowering the melting temperature of urea. The slurry of the obtained melt is cooled in the same manner as described above to obtain granular chemical fertilizer.

By the method as described above, a chemical fertilizer containing nitrogen, phosphorus, potassium, etc., in which harmful components are below the official standard and about 65% or more of which is adjusted to a particle size of 2 to 4 mm, is obtained. The characteristics of the obtained chemical fertilizer will be described below.

1. Uniformity of components of each particle: molten urea,
Since powdered molten phosphorus fertilizer is added to Kali salt and solidified, the surface of the molten phosphorus fertilizer is coated with urea, and each particle of the fertilizer is obtained as a uniform component composition.

2. Solubility: As a result of the test by the disintegration test method of the granulated fertilizer, the residual rate of 0% in the water disintegration test and the residual rate of 0% in the soil disintegration test were judged to be good. Is.

3. Shape: nearly spherical, angle of repose 36-38
Was relatively large.

4. Surface condition: The surface is coated with urea, and the surface is glossy.

5. Hardness: Harder than the conventional one with 8 kg / grain or more and no generation of powder.

6. The true specific gravity of the particles is 1.9 to 2.26 and the bulk specific gravity is 1.1 to 1.25, which is larger than that of the conventional one.

7. Color tone: greenish.

8. Smell: None.

The methods of measuring these characteristics are as follows.

Angle of repose: Measured from the height of the mountain and the width of the bottom formed when it was gently dropped from a funnel having a height of 30 cm. Hardness: Measured with a Kiya type hardness meter, and calculated as an average value of 50 grains. Bulk specific gravity: Obtained from the weight when filled in a container of 1 liter. True specific gravity: Calculated from the blending ratio of each raw material.

[0047]

INDUSTRIAL APPLICABILITY According to the production method of the present invention, it is possible to produce a urea-based chemical fertilizer having a high fertilizing effect in which the generation of biuret due to urea is suppressed.

The urea-based chemical fertilizer produced according to the present invention has high spraying accuracy because of characteristics such as shape and hardness. Therefore,
It can be sprayed evenly, has less uneven fertilization, and can reduce variations in fertilizing effect during dissolution. In addition, the use of this fertilizer improves the three-phase structure of the soil (solid phase, liquid phase, gas phase) and promotes soil preparation and rice straw ripening. Further, since this fertilizer has a fertilization form required for lateral fertilization, it can be fertilized evenly near the roots of crops, and the loss such as volatilization, leaching and fixing of components can be reduced. In particular, since it is spherical, the surface area is small and the contact area with the soil is small, so that soil fixation is reduced. Furthermore, since the form of phosphoric acid is soluble unlike phosphorous ammonium, the absorption utilization rate of crops is improved.

Particularly, the chemical fertilizer containing 45 to 75 wt% of the total amount of the molten phosphorus fertilizer can be applied to all the above-mentioned situations of soil improvement, promotion of rice straw ripening, and use of the chemical fertilizer as the basic fertilizer.

Generally, phosphorus-containing chemical fertilizers are manufactured on the assumption that they are water-soluble. This is because it is applied immediately before the cultivation of the plant and the purpose is to improve the fertilizing effect by increasing the phosphoric acid concentration. However, in this form, phosphoric acid binds to aluminum components in the soil and the like, and it cannot be said that the utilization efficiency for crops is necessarily high. On the other hand, since the molten phosphorus fertilizer is soluble in soil, it is used for crops by contact dissolution, and since it is in the form of calcium-type phosphoric acid, it is difficult to fix it in soil. When the molten phosphorus fertilizer particles and hydrogen soil colloid come into contact with each other, calcium and magnesium on the surface of the particles are exchanged with hydrogen ions, and phosphoric acid is eluted and immediately absorbed from plant roots. As is clear from the test examples described later, since the phosphoric acid absorption amount is relatively large as described above, the application amount may be small, the nutrient absorption amount is large, and the fertilizer utilization rate is high.

The urea-based chemical fertilizer produced according to the present invention has low solidification property, high hardness, and little generation of powder, and is suitable in terms of transportation, storage and spraying work of this fertilizer, and especially by mechanical spraying. Highly adaptable. In addition, since the fertilizer obtained in the present invention is in a form in which all the constituents are used for crops, the fertilizer utilization rate is high and the future use constituents are hardly washed away, so that the river is less polluted.

[0052]

EXAMPLES The present invention will be described below with reference to examples.

Urea, fused phosphorus fertilizer, potassium component, etc. were used in the proportions shown in Table 1. The total amount of raw materials is 80 kg. Urea (commercial granular urea), potassium component and the like (24 mesh or less) were mixed and heated and melted under the atmospheric pressure at the temperature shown in Table 1. In Examples 1 and 5, urea and molten phosphorus fertilizer were mixed in advance and heated under a nitrogen atmosphere at 6 kg / cm ² until the urea was completely melted.

The obtained melts other than those in Examples 1 and 5 were mixed with molten phosphorus fertilizer (95% or less under 100 mesh sieve) to form a slurry, which was spray-granulated, that is, on the upper part of the cooling tank. Pressure of the slurry from the installed nozzle with a diameter of 2.54 mm 6.
It is jetted at 2 Kg / cm ² , and the temperature is 12 ° C from the bottom of the cooling tank.
The cooling air was sent at a flow rate of 13 to 14 m / sec and brought into contact with the droplets of the slurry to cool and solidify the droplets to obtain a fertilizer having the properties shown in Table 2. The obtained fertilizer was classified (particle size 2 to 4 mm) to obtain a product. (In the table, T means "total", TN represents total nitrogen, and BN represents the content of biuretous nitrogen ... The same applies hereinafter).

[0055]

[Table 1]

[0056]

[Table 2-1]

[0057]

[Table 2-2]

The urea-based chemical fertilizers obtained in Examples 2 and 3 were used to test fertilization accuracy. The method of implementation is to put each test fertilizer into the hopper of the side-row fertilizer rice transplanter 6-row, set the fertilizer supply scale of side-row fertilizer to 10, and perform the planting operation.
The fertilization accuracy was obtained by measuring the amount of fertilizer that dropped on each line when continuously planting 500 strains. As a result, it can be seen that the fertilizer of the present invention has a high machine spraying adaptability of ± 0.43% (Example 2) and ± 0.45% (Example 3). The rice transplanter used was an Iseki riding rice transplanter (6 rows planted, type PA650), and the row spacing was 30 cm × the plant spacing was 18,16,14,12 cm, and 14 to 23 minutes / 10 a.

Similarly, the urea-based chemical fertilizer of the present invention was used to test the solidification property, hardness, and pulverization rate. For the caking test, the sample was packed in a cylinder having an inner diameter of 5 cm, pressurized to 1 Kg / cm ² , left for 2 weeks, taken out, and passed through a 5 mesh screen to measure the caking rate. The hardness was measured using a Kiya type hardness tester. The pulverization rate was obtained by dropping the sample 10 times from a height of 1.5 m and passing it through a 28-mesh sieve to measure the pulverization rate at the ratio under the sieve.

The results are shown in Table 3. The results show that the fertilizer of the present invention has high hardness, low pulverization rate and high mechanical spraying adaptability. Furthermore, it shows resistance to impact during transportation and storage (stacking).

Table 3 shows the results of measuring the specific gravity. From this result, it is understood that the urea-based chemical fertilizer of the present invention has a large bulk specific gravity, can effectively use more of the hopper capacity of the spraying machine, can reduce the number of times of supplying the fertilizer, and can save labor of the spraying work.

[0062]

[Table 3]

The urea-based chemical fertilizer obtained in Example 2 and a control group without addition of materials were set up to carry out a test for promoting ripening of rice straw.
The test method was to use rice straw after combine harvesting, and set 500 kg of rice straw as one ward in three wards. Rice straw was divided into 5 equal parts and accumulated in 5 steps, and in the material addition section, 1 equivalent amount of material was applied to the upper part of each step and 1 ton of water was irrigated. The test period is about 2 in winter
For a month, the carbon ratio and component composition at the start and end were measured. The chemical composition of the used rice straw and the results are shown in Tables 4 and 5, respectively. (In the table, T-C represents total carbon.) The urea-based chemical fertilizer of the present invention had a dry matter residual rate of about 10% less in two months than in the control group. Less dry matter remaining indicates that ripening has progressed.
Regarding the carbon ratio, the number of test plots was 24 compared with 49.8 in the control plots, and the lower carbon percentage is an index showing that ripening has progressed. From the dry matter residual rate and the carbon rate, it can be seen that the urea-based chemical fertilizer has a high effect of promoting ripening.

Comparing the component composition of rice straw at the end of the test, the test plot exceeded all the components in comparison with the control plot, and especially the concentration of magnesia and phosphoric acid was high, and the fertilizer of the present invention had a high soil-making effect. I understand.

From these facts, it can be said that the fertilizer of the present invention is a urea-based chemical fertilizer, which is an effective material having a high simultaneous effect of soil making and rice straw ripening promotion.

[0066]

[Table 4]

[0067]

[Table 5]

Using the chemical fertilizer obtained in Example 3, a rice cultivation test was conducted. The place is a paddy field in Wakuya-cho, Toda-gun, Miyagi Prefecture, the variety is Toyonishiki, and the chemical fertilizer obtained in Example 3 as the basic fertilizer (guaranteed component (%): nitrogen 13.8, phosphoric acid 10.5, Kari 1
0.5) was used, and commercially available No. 284 (guaranteed component (%): nitrogen 12, phosphoric acid 18, potassium 14) was used as a comparative example. Also, as the fertilizer, Nitrogen Kasei Kasei No. 68 (guaranteed component (%): Nitrogen 16 and Kali 18 was used. Application rate (basic fertilizer)
Was used so as to be 4 Kg / 10a in terms of nitrogen. Example: Basal fertilizer 29.0 kg / 10a, panicle manure 9.5 kg / 10a, Comparative example: Basal fertilizer 33.3 kg / 10a, panicle fertilizer 9.5 kg / 10a. .

The applied amount (Kg / 10a) is shown in Table 6 and the nutrient absorption amount (Kg / 10a) is shown in Table 7.

[0070]

[Table 6]

[0071]

[Table 7]

Further, a growth study (Table 8), a maturity study (Table 9), a dry matter weight (Table 10), a nitrogen concentration and a nitrogen absorption amount (Table 11) are shown respectively.

From the results shown in Tables 7 to 10, the growth status and the nutrient absorption status can be grasped, and the factors affecting the yield and quality can be confirmed.

[0074]

[Table 8]

[0075]

[Table 9]

[0076]

[Table 10]

[0077]

[Table 11]

Absorption of each nutrient / maturity (Kg / 10a) (Table 1
2) and yield survey (Table 13) are shown respectively. From the results shown in the table, it is understood that the chemical fertilizer of the present invention has a large absorption of each component of phosphoric acid, potassium, and silicic acid into plants, and has a large fertilizing effect. In particular, it can be seen that phosphoric acid has a large content in the ear and contributes to the increase in yield and the quality (grade) of the harvest.

[0079]

[Table 12]

[0080]

[Table 13]

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Claims (6)

[Claims] 1. A mixture of molten urea and molten phosphorus fertilizer, or molten urea containing potassium chloride or potassium chloride and one or more sulfates selected from the group consisting of potassium sulfate, calcium sulfate and magnesium sulfate. A method for producing a urea-based chemical fertilizer characterized by cooling droplets of a mixture with a fertilizer. 2. The urea-based chemical conversion according to claim 1, wherein droplets of a mixture of molten urea and molten phosphorus fertilizer, which are obtained by melting urea mixed with molten phosphorus fertilizer in an ammonia gas atmosphere, are cooled. Fertilizer manufacturing method. 3. The method according to claim 2, wherein the melting is performed under a pressure of 5 Kg / cm ² or more. 4. The method according to claim 1, wherein a molten phosphorous fertilizer containing boron and manganese is used. 5. A urea-based chemical fertilizer, which is obtained by coating molten phosphorous fertilizer with urea, or with urea containing potassium or at least one of potassium, calcium and magnesium, and having a hardness of 8.
kg / grain or more, true specific gravity 1.92 to 2.26 g / cm ³ , bulk specific gravity 1.1 to 1.25 g / cm ³ , repose angle 36 to 38 degrees, and at least 65% of average diameter 2 to 4 mm Spherical urea chemical fertilizer. 6. The urea-based chemical fertilizer according to claim 5, wherein the molten phosphorus fertilizer is 45 to 75 wt% of the whole.