JP5970963B2 - Short-term eluting coated granular fertilizer - Google Patents

Description

  The present invention relates to a coated granular fertilizer in which a resin is coated on a water-soluble granular fertilizer, and particularly to a short-term dissolution type coated granular fertilizer.

  In recent years, more labor-saving and more efficient fertilizers and their usage have been demanded from the viewpoints of environmental impacts caused by the runoff of the eluted components of granular fertilizers and labor savings associated with the aging of agricultural workers. Under such a background, various elution-adjusted fertilizers have been proposed and put into practical use.

  The elution control type fertilizer is a coated granular fertilizer in which elution of internal components is controlled by coating the surface of the granular fertilizer with an organic or inorganic water-permeable coating material. Among them, those using organic coating materials such as resins have a better elution control function, and those using such organic coating materials occupy the mainstream of coated granular fertilizers.

  Generally, when the coated granular fertilizer is immersed in water, the water gradually permeates the coating film and enters the inside of the coated granular fertilizer to dissolve the elution component of the water-soluble granular fertilizer. The dissolved elution component permeates the coating film and elutes out of the coating film. At this time, the coating film suppresses the permeation of water and components. Eventually, the coating film expands due to water absorption, thereby promoting elution.

  Various types of resins are used as the coating material, but thermosetting resins such as urethane resins have high coating strength, high water resistance, ease of control of elution characteristics, and do not use solvents. The present applicant also disclosed in Patent Document 1 a granular fertilizer whose surface is obtained from (A) an aromatic polyisocyanate and castor oil or a castor oil derivative polyol. A coated granular fertilizer is disclosed in which the obtained isocyanate group-terminated prepolymer is coated with (B) a castor oil or castor oil derivative polyol and (C) an amine-based polyol and cured with a film made of a polyurethane resin.

  Among the above coating materials, water-soluble coated granular fertilizers have elution patterns such as long-term elution type, short-term elution type, and sigmoid type depending on the elution control period and elution characteristics. It is required to finely adjust the elution pattern.

  For example, in Patent Document 2, when the coated granular fertilizer is produced by coating the surface of the granular fertilizer with a coating material containing a polymer compound, the minor axis / major axis ratio is 0.80 to 0.95. The manufacturing method of the coated granular fertilizer characterized by using a granular fertilizer is disclosed, The initial elution of a fertilizer component is prevented by using this coated granular fertilizer.

Patent Document 3 discloses that a film containing synthetic resin as a main component is covered on the surface of core material particles containing fertilizer as an active ingredient and having a “circularity coefficient” of 0.7 or more. A characteristic time-dissolved coated granular fertilizer is disclosed, and the use of the granular coated granular fertilizer improves the function of suppressing the initial dissolution of fertilizer components. The “circularity coefficient” is calculated by: circularity coefficient = (4π × projection area of particle) / (length of contour of particle projection diagram) ² .

  Moreover, in patent document 4, when manufacturing a coated granular fertilizer by coat | covering the surface of a granular fertilizer with a coating material, the granulated fertilizer used as a raw material uses the granulated particle | grains selected by the selection machine. A method for producing a coated granular fertilizer is described, and a fertilizer effect type fertilizer that elutes at a predetermined time has been proposed.

JP-A-10-265288 Japanese Patent Laid-Open No. 9-030884 Japanese Patent Laid-Open No. 10-158084 JP-A-2005-060119

  As described above, the elution control type fertilizer is required to finely adjust the elution control period, suppresses elution after application (hereinafter sometimes referred to as “initial elution”), and is applied. The thing which shows 80 mass% or more of elution in the after arbitrary period (for example, 7th-200th) is calculated | required.

  Among them, it is difficult to achieve a short-term elution type elution pattern that exhibits elution of 80% by mass or more particularly in a short period (for example, 7 to 40 days). Although a method of increasing the water permeability of the coating film by increasing the hydroxyl equivalent weight of the coating film is known, the above method tends to cause a pinhole defect or the like in the coating film. There was a problem that the initial elution could not be suppressed.

  Accordingly, an object of the present invention is to obtain a coated granular fertilizer having a short-term dissolution property capable of exhibiting a short-term dissolution type dissolution pattern without impairing suppression of initial dissolution.

  In the conventional coated granular fertilizer, a method is adopted in which a water-soluble granular fertilizer to be coated is made closer to a sphere, thereby forming a uniform coating film with few defects on its surface and suppressing unintentional elution. Yes. However, if it is attempted to achieve a short-term elution pattern with the above method, the entire coating film must be thinned, and as a result, it becomes difficult to suppress defects in the coating film. Could not be suppressed. Therefore, the present inventors can form a coating film having a non-uniform thickness by using fertilizer particles having irregularities on the surface unlike conventional ones, and in the coated granular fertilizer showing a short-term elution type elution pattern, It was found that elution can be suppressed.

  That is, the present invention is a coated granular fertilizer in which a coating film is formed on the surface of a water-soluble granular fertilizer, wherein 80% by mass or more per unit mass of the fertilizer particle group used for coating is the volume of fertilizer particles (V1), The unevenness coefficient (V1 / V2) calculated by the volume (V2) of a sphere having a diameter R when the length (R) connecting any two points on the surface of the fertilizer particle is maximum is 0. A short-term eluting coated granular fertilizer, characterized in that a coating film is formed on a surface having irregularities in the range of 0.05 to 0.6.

  By forming a coating film on the particles having the above shape, a coating film having a non-uniform film thickness is formed on the surface of the particles. Due to the non-uniform coating film, it is easy to elute from the part where the film thickness is relatively thin, and the elution period is adjusted by controlling the film thickness and film quality of this thin film part. It becomes possible.

  The volume (V1) of the fertilizer particles was determined by measuring the mass of the fertilizer particles and calculating V1 from the specific gravity. In addition, R estimated a plurality of maximum lengths of the fertilizer particles, measured with a micrometer to determine the maximum length, and calculated a volume V2 of a sphere having the calculated R as a diameter.

  The short-term eluting coated granular fertilizer of the present invention exhibits a short-term eluting type elution pattern without impairing suppression of initial elution.

The schematic diagram explaining the volume and maximum length of a fertilizer particle. Schematic explaining the manufacturing process of fertilizer particles. The figure showing the uneven | corrugated coefficient and dispersion | distribution of the ammonium chloride particle | grains of an Example. The figure showing the uneven | corrugated coefficient and dispersion | distribution of the ammonium chloride particle | grains of a comparative example.

  The short-term eluting coated granular fertilizer of the present invention is one in which a coating film having a non-uniform film thickness is formed on the surface of fertilizer particles by using fertilizer particles having irregularities on the surface, thereby suppressing initial dissolution. Since the surface of the fertilizer particles has irregularities, the film thickness of the recesses is large at the time of coating, and the film thickness of the protrusions becomes thin, so that it is easy to form a film with a nonuniform film thickness. The convex portion may be formed by adding other particles to spherical fertilizer particles, and it becomes easy to form a non-uniform coating film by this convex portion.

  In the present invention, the unevenness on the surface of the fertilizer particles is defined by an “unevenness coefficient” obtained by measuring the shape of the particles. A method of calculating the unevenness coefficient will be described with reference to FIG. First, the mass of a sample of one fertilizer particle is measured, and the volume V1 is calculated from the known specific gravity of the fertilizer. Next, a plurality of maximum lengths connecting two arbitrary points on the surface of the fertilizer particles are estimated, measured with a micrometer, and the maximum length among the plurality of measured values is R. Next, the volume V2 of the sphere having the diameter of R obtained is calculated. The ratio (V1 / V2) of the obtained volume V1 and volume V2 is defined as the unevenness coefficient.

  The granular particles have a shape in which the unevenness coefficient is in a range of 0.05 to 0.6, and by setting the unevenness coefficient to the above value, initial elution can be suppressed and desired elution is performed. It becomes easy to obtain a pattern. Moreover, Preferably it is good also as 0.05-0.5.

  The coating film covers the surface of the fertilizer particles, and gradually permeates water and suppresses the dissolution of the fertilizer particles dissolved in water to the outside of the coating film. The average film thickness of the coating film is not particularly limited, but an average film thickness that can suppress the permeation of water over the elution period is good. When the water permeability of the coating film is high, it is necessary to increase the film thickness, and when it is low, the film thickness may be thin. In particular, when fertilizer particles having a particle diameter of 1 to 20 mm are used, the elution performance can be suitably adjusted by setting the average film thickness to 1 to 200 μm.

  The short-term eluting coated granular fertilizer of the present invention preferably has a portion that is ½ or less of the average film thickness with respect to the average film thickness of the coating film. Here, the “average film thickness” refers to the average value of the film thickness of the coated fertilizer particle group. In the coating film, the film portion whose film thickness deviates from the average film thickness may be thicker than the average film thickness or thinner than the average film thickness. When the portion is a thick film, the thick film portion is less likely to be eluted. On the other hand, when the portion is a thin film, the thin film portion is likely to be eluted. The film thickness of the film portion is preferably ½ or less, more preferably ¼ or less of the average film thickness. The film thickness of the film part is less than the average film thickness, so that the entire coating film can be preferentially eluted from the thin film part without reducing the film thickness, and the initial dissolution and short-term dissolution pattern can be achieved simultaneously. Is possible. The thickness of the part may be determined according to a desired elution pattern.

  In the present invention, the cross section of the coated fertilizer particles was observed with a scanning electron microscope, and the thickness of the coating film was measured. The thickness of the coating film was measured every 10 ° around the center of the cross section of the coated fertilizer particles, and the average film thickness of the fertilizer particle group was determined by repeating this 30 samples. Next, the thickness of the fertilizer particle group is thinner than the average film thickness from the number of measurement points at which the film thickness is 1/2 or less and the number of measurement points at which 1/4 or less is obtained with respect to the obtained average film thickness. The proportion of parts was determined.

  Moreover, it is preferable that the said thin film part is 0.2 to 20% with respect to the surface area of the whole coating film of a fertilizer particle group. If it exceeds 20%, the elution area increases and it becomes difficult not only to suppress initial elution but also to achieve a desired elution pattern. Moreover, it is more preferable that it is 0.2 to 10% with respect to the surface area of the whole coating film, since the elution area decreases and the initial elution can be more easily suppressed.

  The short-term dissolution pattern was achieved by simultaneously achieving a dissolution rate of fertilizer components in water at 25 ° C of 40% by mass or less in 3 days and 80% by mass or more in 21 days. The linear elution pattern is shown up to a rate of 80% by mass. Therefore, even if the elution rate is 80% by mass or more in 21 days, those that exceed 40% by mass in 3 days and the initial elution cannot be suppressed are not suitable for the present invention.

  The fertilizer particles may be water-soluble, and the particle diameter is preferably 1 to 20 mm, more preferably 1 to 10 mm. The particle diameter is represented by the opening of a test sieve measured by a sieving method, and may be a directly measured value, an equivalent diameter converted to a sphere, or an indirectly measured value. The mesh can be easily selected by sieving with a sieve of 1 to 20 mm.

  Examples of the fertilizer particles include at least one fertilizer or composite selected from the group consisting of urea, ammonium sulfate, ammonium sulfate, ammonium nitrate, potassium chloride, potassium sulfate, potassium nitrate, sodium nitrate, potassium phosphate, ammonia phosphate, and lime phosphate. Examples include fertilizers and organic fertilizers.

  As described above, the coating film only needs to be able to gradually permeate water and suppress elution of the eluted components to the outside of the coating film. For example, thermosetting resin such as polyurethane resin, alkyd resin, epoxy resin, phenol resin, melamine resin, thermoplastic resin such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, acrylic resin, ABS resin, natural rubber, rosin, etc. Natural resins, silicone resins, waxes and the like can be used, and polyurethane resins are preferably used because elution characteristics are particularly easy to control.

  The coating film may be a single layer or a film in which multiple layers are laminated, and each layer may use the same type of film or may change the water permeability of the coating film using different types of films. Moreover, this coating film may contain arbitrary 3rd resin, an inorganic substance, a vegetable oil, a catalyst, etc. in this coating film in order to adjust the intensity | strength, elution characteristic, etc. of a coating film.

  Furthermore, the surface of the coating film may be treated with an inorganic powder for the purpose of preventing mutual fixation between the short-term eluting coated granular fertilizers. Examples of the inorganic powder include talc, sulfur, calcium carbonate, silica, zeolite, diatomaceous earth, clay, and metal oxide, and these may be used alone or in combination.

  The fertilizer particles of the present invention can be obtained, for example, by the following method (see FIG. 2). First, fertilizer raw material and water are mixed to form a slurry, and a pair of press rolls each having a plurality of hemispherical depressions with a diameter of 3 mm are charged with about 2-3 times the volume of the depressions. Press to harden to obtain plate fertilizer. The obtained plate-shaped fertilizer has a spherical portion molded by the above-described depression and a portion in which the excess portion protruding from the depression is molded into a plate shape. Next, fertilizer particles are obtained from both sides of the plate-shaped fertilizer by applying an impact using a hammer, a unrolling roll, or the like. At this time, the portion molded into the plate shape propagates the applied impact to the spherical portion, and the spherical portion is easily cracked or deformed, thereby obtaining the fertilizer particles of the present invention. In addition, when the fertilizer particle | grains obtained using the said method were measured, the uneven | corrugated coefficient became the range of 0.05-0.6, and the average value of the uneven | corrugated coefficient became about 0.3.

  As a method for producing the short-term eluting coated granular fertilizer of the present invention, the entire fertilizer particles can be coated by adding a coating material for forming a coating film to the fertilizer particles in a fluidized state or a rolling state. The In the case of the present invention, the short term which is the object when containing particles having a roughness coefficient of 0.05 to 0.6, 80 mass% or more per unit mass of the fertilizer particle group used for coating, preferably 90 mass% or more. It is desirable because an elution pattern can be achieved.

  A device such as a fluidized bed or a spouted bed can be used for fluidizing the fertilizer particles, and a device such as a rotating pan or a rotating drum can be used for rolling. By making the fertilizer particles into a fluid state or a rolling state, a coating film can be continuously formed on the surface of the fertilizer particles.

  When the fertilizer particles are in a fluidized state or a rolling state, it is preferable to preheat the fertilizer particles for a certain period of time with hot air or the like. At this time, the preheating time and the preheating temperature may be appropriately adjusted so that the amount of water and the temperature of the fertilizer particles are such that the water content of the fertilizer particles does not greatly affect the coating material.

  As a method for adding the coating material to the granular fertilizer in a fluidized state or a rolling state, any material that can be efficiently dispersed and added may be used, and examples thereof include spraying and dripping. The spray addition method is preferably used because a desired coating film can be formed. When the coating material is a liquid material such as a resin, the coating material preferably has a low viscosity, for example, preferably 0.1 to 200 mPa · s at the coating temperature. When the viscosity of the coating material is 200 mPa · s or more, it is difficult to cover the entire surface of the coating film with the coating material, which causes pinhole defects in the coating film and makes it difficult to suppress initial elution.

  Hereinafter, the present invention will be described by way of examples. In addition, this invention is not limited to a following example.

  First, fertilizer particles were created. First, 94% by mass of ammonium chloride and 6% by mass of water were mixed, and a fertilizer raw material made into a slurry was added to a pair of press rolls having a plurality of hemispherical indentations with a diameter of 3 mm and the volume of the indentations was doubled. Then, a plate-like ammonium chloride was obtained by pressing with a press roll. Next, it was broken from both sides of the plate-like ammonium chloride using a pair of unwinding rolls while intermittently giving impacts to obtain uneven ammonium chloride particles (Group A).

  Moreover, after evaporating the water | moisture content of the fertilizer particle | grains obtained by the said method as a comparative example, it rolls and sizes in a rolling device, Spherical ammonium chloride particle | grains (B Group).

Next, the shape of the ammonium chloride particles was measured, and the unevenness coefficient was calculated. The measurement was performed on uneven ammonium chloride particles (Group A) and spherical ammonium chloride particles (Group B), and the calculation was performed with the specific gravity of the ammonium chloride particles being 1.53 g / cm ³ . The unevenness coefficient (V1 / V2) is obtained from the result of measuring the shape, and the results of 20 samples are shown in Table 1 (Group A) and Table 2 (Group B), with one fertilizer particle as one sample, and FIG. (Group A) and FIG. 4 (Group B) show the distribution of the unevenness coefficient when measuring about 2 to 3 g of the sample. The average unevenness coefficient of Group A shown in Table 1 was 0.28, and the average unevenness coefficient of Group B shown in Table 2 was 0.62. Moreover, as shown in FIG. 3, 100% by mass of the fertilizer particles of Group A was in the range of the unevenness coefficient 0.05-6, but the fertilizer particles of Group B were in the range of the unevenness coefficient 0.05-6. The amount was about 47% by mass.

  Next, a coating film was formed on the surface of the ammonium chloride particles. The coating material used for forming the coating film is described below.

(Coating material used)
[Coating material A]
Urethane resin liquid prepared so that the following components 1 and 2 are isocyanate group / hydroxyl group = 1.0.
(Component 1)
MDI-modified castor oil (isocyanate group-terminated prepolymer in which castor oil is mixed with an excess amount of MDI so that the mass of isocyanate groups is 19% by mass of the total mass)
(Component 2)
Mixed liquid in which a and b are mixed at a molar ratio of hydroxyl group = 8: 2 a: Castor oil (hydroxyl value 160 mgKOH / g)
b: propylene oxide adduct of ethylenediamine (ratio of propylene oxide / nitrogen atom; 2.2, hydroxyl value; 760 mgKOH / g)

[Coating material B]
The urethane resin liquid which prepared the component 1 and the component 2 similar to the said coating | covering material A so that it might become isocyanate group / hydroxyl group = 0.8.

[Example 1]
While charging 1.2 kg of ammonium chloride particles (particle size 2.0-10.0 mm) having an average irregularity coefficient of 0.28 in the A group into a drum type rolling coating apparatus having a diameter of 300 mm, while rolling at 20 rpm, The temperature of the granular ammonium chloride was kept at 70 ° C. by a hot air generator.

  Next, in order to form the first coating layer, the coating material A (31.4 g in total) was added into the apparatus over 10 seconds.

  Next, 5 minutes after the addition of the first coating layer, as the second coating layer, the same component and the same amount of the coating material A as the first layer are added to the apparatus over 10 seconds, Five minutes after the addition of the second coating layer, the same component and the same amount of coating material A as the second layer were added to the apparatus over 10 seconds as the third coating layer.

  Further, 5 minutes after the addition of the third layer, the coating material B (13.5 g in total) was added to the apparatus over 10 seconds as the fourth coating layer. Seven minutes after the addition of the coating material B, the fourth coating layer almost lost its tackiness, and the coated ammonium chloride particles did not stick to each other.

  Next, it was rolled for 30 minutes to cure the coating film on the ammonium chloride. This was cooled to room temperature (about 25 ° C.) to obtain the intended short-term eluting coated granular fertilizer. At this time, the average film thickness of the ammonium chloride particle group was 26 μm, indicating a short-term elution pattern.

  The film thickness of the obtained short-term eluting coated granular fertilizer was measured and listed in Table 3.

[Measurement of film thickness]
The cross section of the obtained sample was observed with a scanning electron microscope, and the thickness of the coating film was measured. At this time, those having pinhole defects in which the coating film was locally lost were excluded as defective products.

[Example 2]
A short-term eluting coated granular fertilizer was obtained by the same method as in Example 1 except that the total amount of the coating material A in the first layer, the second layer, and the third layer was 23.9 g. At this time, the average film thickness of the ammonium chloride particle group was 26 μm, and the initial elution could be suppressed, and a short-term elution type elution pattern was shown.

[Comparative Example 1]
While charging 1.2 kg of ammonium chloride particles (particle size 2.8 to 4.0 mm) having an average unevenness coefficient of 0.62 in the group B into a drum-type rolling coating apparatus having a diameter of 300 mm, while rolling at 20 rpm, The ammonium chloride temperature was maintained at 70 ° C. by a hot air generator.

  Next, in order to form the first coating layer, the coating material A (13.7 g in total) was added into the apparatus over 10 seconds.

  Next, 5 minutes after the addition of the first coating layer, the same component and the same amount of coating material A as the first layer were added to the apparatus over 10 seconds as the second coating layer.

  Further, 5 minutes after the addition of the second layer, the coating material B (total 6.9 g) was added to the apparatus over 10 seconds as the third coating layer. Seven minutes after the addition of the coating material B, the third coating layer almost lost its tackiness, and the coated ammonium chlorides did not stick to each other.

  Next, it was rolled for 30 minutes to cure the coating film on the ammonium chloride. This was cooled to room temperature (about 25 ° C.) to obtain a short-term eluting coated granular fertilizer. At this time, the average film thickness of the ammonium chloride particle group was 16 μm and showed a short-term elution type elution pattern. However, many defects occurred in the coating film, and initial elution could not be suppressed.

[Comparative Example 2]
A short-term eluting coated granular fertilizer was obtained in the same manner as in Comparative Example 1 except that the total amount of the coating material A in the first layer and the second layer was 18.0 g. At this time, the average film thickness of the ammonium chloride particle group was 20 μm, and the initial elution could be suppressed, but the short-term elution type elution pattern was not shown.

[Comparative Example 3]
A short-term eluting coated granular fertilizer was obtained in the same manner as in Comparative Example 1 except that the amount of the coating material A added in the first layer and the second layer was 20.8 g in total. At this time, the average film thickness of the ammonium chloride particle group was 24 μm, and the initial elution could be suppressed, but the short-term elution type elution pattern was not shown.

[Dissolution test]
The obtained short-term eluting coated granular fertilizer was reduced and subjected to a dissolution test. The results are shown in Table 4. In the dissolution test, 12.5 g of the reduced short-term dissolution coated granular fertilizer was collected, put into 250 cc ion-exchanged water, stored in a thermostatic bath at 25 ° C., taken out after a predetermined time, and eluted in water. The eluted components were determined quantitatively. Table 2 shows the elution rate (mass%) of ammonium chloride when 1 day, 3 days, 7 days, 14 days, 21 days, 28 days, and 35 days have passed.

  From Example 1 and Example 2, by using fertilizer particles having an unevenness coefficient of 0.05 to 0.6, a desired coating film can be formed on the surface of the fertilizer particles, and the initial dissolution of the short-term eluting coated granular fertilizer It was found that a short-term elution pattern was achieved.

  Moreover, Comparative Example 1 to Comparative Example 3 were elliptical and had no conspicuous unevenness on the surface, and the unevenness coefficient was 0.62.

  Further, Comparative Example 1 aims at a short-term dissolution pattern similar to that of Example 1 and Example 2, but although the average film thickness is smaller than that of Example 1 and Example 2, the Example Although an elution pattern eluting for a longer time than 1 was shown and a long-term elution pattern equivalent to that of Example 2 was shown, initial elution could not be suppressed. Further, in Comparative Example 1, due to the thin film thickness, many defects of the coating film occurred during coating, and it was difficult to suppress initial elution.

  In Comparative Example 2, the initial elution was suppressed to the same extent as in Examples 1 and 2, but the average film thickness was smaller than in Examples 1 and 2 as in Comparative Example 1. Nevertheless, an elution pattern eluting for a longer time than in Example 1 and Example 2 was shown. Further, the coating film was uniformly coated as compared with Example 1, Example 2 and Comparative Example 1.

  Comparative Example 3 shows an average film thickness comparable to that of Example 1 and Example 2, and is excellent in suppressing initial elution, while being similar to Comparative Example 1 and Comparative Example 2, The elution pattern eluting for a longer time than that of Example 1 and Example 2 was shown. Further, as in Comparative Example 2, the coating film was uniformly coated.

  From the above, by forming coated granular fertilizer using fertilizer particles with an unevenness coefficient of 0.05 to 0.6, it becomes possible to form a portion thinner than the average film thickness in the coating film, suppressing initial elution However, it became clear that a short-term elution pattern could be achieved.

R Maximum length of fertilizer particles V1 Volume of fertilizer particles V2 Volume of sphere with diameter R

Claims (6)

A coated granular fertilizer having a coating film formed on the surface of a water-soluble granular fertilizer,
The coated granular fertilizer is obtained by forming a coating film on the surface of a group of fertilizer particles containing 80% by mass or more per unit mass of fertilizer particles having irregularities on the surface,
The fertilizer particles having irregularities are the volume of a sphere having a diameter R (R) when the fertilizer particle volume (V1) and the length (R) connecting any two points on the surface of the fertilizer particle are maximized (R). V2) and the unevenness coefficient (V1 / V2) calculated in the range of 0.05 to 0.6 ,
The short-term eluting coated granular fertilizer, characterized in that the coating film has a thin film portion that is ½ or less of the average film thickness with respect to the average film thickness of the coating film . 2. The short-term eluting coated granular fertilizer according to claim 1, wherein a portion of the thin film of the coating film is 0.2 to 20% with respect to a surface area of the entire coating film of the coated particle group. 3. The short-term eluting coated granular fertilizer according to claim 1, wherein the fertilizer particles have a particle diameter of 1 to 20 mm, and the coating film has an average film thickness of 1 to 200 μm. The short-term elution according to any one of claims 1 to 3, wherein a component elution rate for 3 days in water at 25 ° C is 40% by mass or less, and a component elution rate for 21 days is 80% by mass or more. Coated granular fertilizer. It is a manufacturing method of the short-term eluting covering granular fertilizer in any one of Claims 1 thru | or 4, Comprising: The process which makes the said fertilizer particle group a fluid state or a rolling state, This fertilizer of a fluid state or a rolling state A method for producing a short-term eluting coated granular fertilizer, comprising the step of coating a particle group by adding a coating material. The fertilizer particles,
A step of obtaining a plate-shaped fertilizer by putting a slurry-like fertilizer raw material into a pair of press rolls having a hemispherical depression, and pressing and solidifying the volume of the depression 2-3 times;
The method for producing a short-term eluting coated granular fertilizer according to claim 5, wherein the method is obtained through a step of applying impact from both sides of the plate-shaped fertilizer.

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