Coated granular fertilizer

Abstract

The present invention aims to provide a coated granular fertilizer that is degradable, has good dissolution control, and is impact-resistant, which can suppress the premature dissolution of fertilizer components after application using a spreader such as a side-dressing fertilizer applicator. [Solution] A coated granular fertilizer comprising granular urea and a coating film covering the granular urea, wherein the coating film contains a hardened vegetable oil, and the hardened vegetable oil has a melting point of 60°C or more and 100°C or less, and the angle of repose of the coated granular fertilizer is 29 degrees or less.

Description

Technical Field

[0001] The present invention relates to coated granular fertilizers.

Background Art

[0002] Coated granular fertilizers have advantages such as controlling the elution of fertilizer components and being able to maintain their efficacy once applied, thereby reducing the number of applications.

[0003] For example, the coated granular fertilizer described in Patent Document 1 has a film made of a petroleum-based wax that is decomposable in a fertilization environment such as soil for the purpose of reducing the environmental load.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a coated granular fertilizer having decomposability, good elution controllability, and impact resistance that can suppress the early elution of fertilizer components after application using a spreader such as a side-dressing machine.

Means for Solving the Problems

[0006] The present inventors have found that in a coated granular fertilizer comprising granular urea and a film coating the granular urea, and the film containing vegetable hardened oil, the above problems can be solved by setting the angle of repose of the coated granular fertilizer within a specific range.

[0007] That is, the coated granular fertilizer according to the present invention may have the following constituent aspects, but is not limited thereto. [1] The device comprises granular urea and a coating that covers the granular urea. The aforementioned coating contains a hydrogenated vegetable oil, The aforementioned hardened vegetable oil has a melting point of 60°C or higher and 100°C or lower, and is a coated granular fertilizer. A coated granular fertilizer in which the angle of repose of the coated granular fertilizer is 29 degrees or less. [2] The coated granular fertilizer according to [1], wherein the oil absorption rate of the granular urea is 0.4% or more and 1.0% or less. [3] The coated granular fertilizer according to [1] or [2], wherein the aforementioned hydrogenated plant oil is at least one selected from the group consisting of hydrogenated castor oil, hydrogenated rapeseed oil, and hydrogenated soybean oil. [4] The coated granular fertilizer according to [3], wherein the aforementioned hardened plant oil is hardened castor oil. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a coated granular fertilizer that is degradable, has good dissolution control properties, and has impact resistance that can suppress the premature dissolution of fertilizer components after application using a spreader such as a side-dressing fertilizer applicator. [Modes for carrying out the invention]

[0009] The coated granular fertilizer according to the present invention will be described below.

[0010] The coated granular fertilizer comprises granular urea and a coating film that covers the granular urea.

[0011] The coated granular fertilizer contains granular urea.

[0012] The granular urea is a granular material containing a urea component. The granular urea may be a granular material in which the urea component is granulated alone, or it may be a granular material containing the urea component and any additives. Examples of such optional additives include anti-flotation agents, composition uniformity promoters, effect-enhancing agents, colorants, and granulation promoters.

[0013] The average particle diameter of the granular urea is not particularly limited and may be 0.1 to 15.0 mm, may be 0.5 to 10 mm, or may be 1 to 5 mm. The average particle diameter of the granular urea can be measured according to the procedure described in the column of Examples below.

[0014] The circularity coefficient of the granular urea may be 0.6 to 1.0, or may be 0.7 to 0.9. The circularity coefficient of the granular urea can be measured according to the procedure described in the column of Examples below.

[0015] The aspect ratio of the granular urea may be 1.0 to 1.3, or may be 1.0 to 1.2. The aspect ratio of the granular urea can be measured according to the procedure described in the column of Examples below.

[0016] The angle of repose of the granular urea may be 31 degrees or less, may be 25 to 31 degrees, or may be 30 to 31 degrees. The angle of repose of the granular urea can be measured according to the procedure described in the column of Examples below.

[0017] The oil absorption rate of the granular urea may be 0.1 to 1.0%, may be 0.4 to 1.0%, or may be 0.5 to 0.9%. The oil absorption rate of the granular urea can be measured according to the procedure described in the column of Examples below.

[0018] The granular urea having an average particle diameter, circularity coefficient, aspect ratio, angle of repose, and oil absorption rate within specific ranges can be produced by the procedure described in the column of Examples below.

[0019] The coating contains vegetable hardening oil.

[0020] The vegetable hardened oil can be obtained by a method of adding hydrogen to a natural or synthetic vegetable oil containing unsaturated fatty acid triglyceride to saturate the unsaturated bonds of the unsaturated fatty acid triglyceride. The vegetable hardened oil can also be obtained by chemical synthesis. Examples of the vegetable hardened oil include castor hardened oil, rapeseed hardened oil, soybean hardened oil, palm hardened oil, peanut hardened oil, jojoba hardened oil, cottonseed hardened oil, and coconut hardened oil.

[0021] The vegetable hardened oil has appropriate degradability in a fertilization environment such as soil. Specifically, since the vegetable hardened oil is not immediately decomposed in the fertilization environment, the elution control property can be exhibited in the coating. Furthermore, the vegetable hardened oil is decomposed at an appropriate rate such that its residual in the fertilization environment does not pose a problem. That is, the coated granular fertilizer provided with the coating containing the vegetable hardened oil is excellent in both degradability and elution control property. The degradability of the vegetable hardened oil can be measured according to the procedure described in the column of the examples below.

[0022] The vegetable hardened oil is solid at 25°C. The melting point of the vegetable hardened oil is 60°C or higher and 100°C or lower, and may be 80°C or higher and 90°C or lower. The vegetable hardened oil with such a melting point can be melted by heating, and thus can be handled in a liquid state without using a solvent. Furthermore, when using the vegetable hardened oil with such a melting point, during the production of the coated granular fertilizer, sticking can be prevented between the coated granular fertilizers or between the coated granular fertilizer and the rotary tank, and the productivity of the coated granular fertilizer becomes good. The productivity of the coated granular fertilizer can be measured according to the procedure described in the column of the examples below. The freezing point of the vegetable hardened oil is 60°C or higher and 100°C or lower, and may be 80°C or higher and 90°C or lower. Although the melting point and the freezing point generally have the same value, in the vegetable hardened oil, the melting point may be higher than the freezing point.

[0023] The aforementioned hydrogenated plant oil has low viscosity. By including a hydrogenated plant oil with low viscosity in the coating of the coated granular fertilizer, clumping of the coated granular fertilizers together during manufacturing and storage can be suppressed, resulting in good adhesion of the coated granular fertilizer. The adhesion of the coated granular fertilizer during storage can be measured according to the procedure described in the Examples section below.

[0024] The aforementioned hydrogenated plant oil has lower water vapor permeability compared to biodegradable resins, making it superior in terms of improving the control of leaching of fertilizer components. The aforementioned hydrogenated plant oil has higher fluidity when melted by heating compared to biodegradable resins, which makes it less likely for caking to occur during the production of the coated granular fertilizer, resulting in good manufacturability of the coated granular fertilizer.

[0025] The content of the hydrogenated vegetable oil in the coating may be 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more.

[0026] The coating may contain only one of the hydrogenated vegetable oils, or it may contain two or more. The coating may contain at least one selected from the group consisting of hydrogenated castor oil, hydrogenated rapeseed oil, and hydrogenated soybean oil.

[0027] The coated granular fertilizer preferably does not contain biodegradable resins. Examples of biodegradable resins include polylactic acid, polyhydroxyalkanoate, polybutylene adipate terephthalate, polycaprolactone, polybutylene succinate, polyethylene succinate, polyvinyl alcohol, polyglycolic acid, polyaspartic acid, cellulose fatty acid ester, and polybutylene succinate adipate.

[0028] Preferably, the coating does not contain a resin that is not biodegradable. Examples of resins that are not biodegradable include thermoplastic resins and thermosetting resins. Examples of thermoplastic resins include olefin resins, diene resins, and polyvinyl chloride. Examples of olefin resins include polyethylene, polypropylene, polybutene, polystyrene, ethylene-propylene copolymer, butene-ethylene copolymer, butene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, and ethylene-carbon monoxide copolymer. Examples of diene resins include butadiene copolymer, isoprene polymer, chloroprene polymer, butadiene-styrene copolymer, and styrene-isoprene copolymer. Examples of thermosetting resins include epoxy resin, alkyd resin, phenol resin, urea resin, melamine resin, and silicone resin.

[0029] The coating may contain any additives. Examples of such additives include antibacterial agents. The content of the additives in the coating is, for example, 0.1 to 10% by mass.

[0030] The mass ratio of the granular fertilizer to the coating may be 1:0.1 or more and 1:0.5 or less.

[0031] The thickness of the coating is typically 30 to 500 μm. The thickness of the coating can be measured by observing a cross-section passing through the center of the coated granular fertilizer using a scanning electron microscope (Hitachi High-Tech Corporation, SU-3800) in BSE mode. Alternatively, it can be determined by drawing 10 line segments perpendicular to the coating for each piece of coated granular fertilizer and averaging their lengths.

[0032] The method for producing the coated granular fertilizer comprises a first step of putting the granular urea into a rolling state, and a second step of adding the hardened vegetable oil to the rolling granular urea. In the second step, the hardened vegetable oil can be dissolved in a solvent or heated and melted before being added to the granular urea. The method of adding the heated and melted hardened vegetable oil to the granular urea is preferable from the viewpoint of reducing environmental impact because it does not use a solvent. The heating and melting temperature is higher than the melting point of the hardened vegetable oil and may be 70°C, 80°C, 90°C, or 105°C.

[0033] The method for producing the coated granular fertilizer may include a step of adding a lubricant such as liquid paraffin or other optional components between the first and second steps. The step of adding other optional components may be carried out under heating conditions. The method for producing the coated granular fertilizer may also include a step of adding an optional additive such as a surfactant or an anti-caking agent to the surface of the obtained coated granular fertilizer after the third step.

[0034] The angle of repose of the coated granular fertilizer may be 29 degrees or less, 26 to 29 degrees, or 28 to 29 degrees. The angle of repose of the coated granular fertilizer can be measured according to the procedure described in the Examples section below.

[0035] The coated granular fertilizer can be used for cultivating crops in paddy fields, such as grasses. The coated granular fertilizer may be applied to paddy fields alone or as part of a compound fertilizer with other fertilizers.

[0036] In this specification, the initial dissolution rate E1 of the fertilizer components when the coated granular fertilizer is left standing in water at a concentration of 2.5 g / 100 mL for 7 days is referred to as the initial dissolution rate. The initial dissolution rate can be measured according to the procedure described in the Examples section below. The dissolution controllability of the coated granular fertilizer can be evaluated based on the value of E1. The coated granular fertilizer satisfies the condition E1 < 25 (%). In this specification, the elution rate E3 of the fertilizer components when the coated granular fertilizer is left standing in water at a concentration of 2.5 g / 100 mL for 42 days is referred to as the mid-term elution rate. The mid-term elution rate can be measured using the same procedure as the initial elution rate described in the Examples section below. The elution control performance of the coated granular fertilizer can also be evaluated based on the value of E3. A value of less than 40% can be considered to indicate good mid-term elution control performance.

[0037] The coated granular fertilizer can be spread onto the soil using a spreader such as a side-dressing fertilizer applicator.

[0038] In this specification, the elution rate E2 of the fertilizer components obtained when the coated granular fertilizer is applied using a side-dressing fertilizer applicator (Yanmar Co., Ltd., YK6D), promptly recovered, and then left to stand in water for 7 days in the same manner as described above, is referred to as the elution rate after initial mechanical application. The E2 of the coated granular fertilizer can be measured according to the procedure described in the Examples section below. The impact resistance of the coated granular fertilizer can be evaluated based on the value of E2-E1. The coated granular fertilizer satisfies the condition E2-E1 < 25 (%). In this specification, the elution rate E4 of the fertilizer components obtained when the coated granular fertilizer is applied using a side-dressing fertilizer applicator (Yanmar Co., Ltd., YK6D), promptly recovered, and then left to stand in water for 42 days in the same manner as described above, is referred to as the elution rate after mechanical fertilization in the intermediate period. The impact resistance of the coated granular fertilizer in the intermediate period can be measured using the same procedure as the impact resistance of the initial period, which will be described in the Examples section below. The impact resistance of the coated granular fertilizer can also be evaluated based on the value of E4-E3. Impact resistance can also be evaluated as good when E4-E3 is less than 45%.

[0039] When the coated granular fertilizer is spread onto the soil using the spreader, the coated granular fertilizer may collide with each other inside the spreader or with the inner wall of the spreader, causing impact to the fertilizer. The coated granular fertilizer can suppress the premature leaching of fertilizer components even in such cases. The mechanism by which these effects are achieved is not fully understood, and it is thought that various factors are involved, but one possible mechanism is as follows. The coated granular fertilizer is thought to have good rolling properties inside the spreader because its angle of repose is within a specific range, making it less susceptible to damage to the coating due to collisions between the coated granular fertilizer particles. This is thought to suppress the premature leaching of fertilizer components after application using a spreader such as a side-dressing fertilizer applicator. [Examples]

[0040] The present invention will be described in more detail below with reference to examples, but the present invention is not limited by the following examples.

[0041] [Granular urea] Granular urea obtained from Qatar Fertiliser Company and China Blue Chemical Limited was separated using a soybean sorting machine (Minoru Sangyo Co., Ltd., DS-1) (sample amount: 5g, inclination angle: 20 degrees, sorting time: 60 seconds) to prepare granular urea 1-7 and comparative granular urea 1, with the following values ​​for average particle size, circularity coefficient, aspect ratio, angle of repose, and oil absorption rate. Granular urea 1: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 26 degrees, oil absorption rate 0.17% Granular urea 2: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 28 degrees, oil absorption rate 0.16% Granular urea 3: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 30 degrees, oil absorption rate 0.88% Granular urea 4: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 31 degrees, oil absorption rate 0.65% Granular urea 5: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 31 degrees, oil absorption rate 0.57% Granular urea 6: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 31 degrees, oil absorption rate 0.51% Granular urea 7: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 32 degrees, oil absorption rate 0.17% Comparison granular urea 1: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 32 degrees, oil absorption rate 0.16% [Vegetable hydrogenated oil] Castor Oil Hydrogenated Oil, manufactured by Ito Oil Co., Ltd., melting point 80-90°C (hereinafter referred to as Castor Oil Hydrogenated Oil 1). Yokozeki Oil & Fat Industry Co., Ltd.'s "Highly Hydrogenated Rapeseed Oil," melting point 67°C (hereinafter referred to as "highly hydrogenated rapeseed oil"). [Petroleum-based wax] "HNP-51" manufactured by Nippon Seiro Co., Ltd. (hereinafter referred to as paraffin wax). "Sazol C80" manufactured by Kato Yoko Co., Ltd. (hereinafter referred to as FT Wax) [Plant-based wax] "Refined Carnauba Wax No. 2" manufactured by Kato Yoko Co., Ltd. (hereinafter referred to as "carnauba wax") "Refined Candelilla Wax" manufactured by Kato Yoko Co., Ltd. (hereinafter referred to as "candelilla wax") [others] Lunac S-98 (hereinafter referred to as stearic acid), manufactured by Kao Chemical Co., Ltd. Nissan Electrol WEP-5 (hereinafter referred to as fatty acid ester), manufactured by NOF Corporation. "Calcol 220-80" (hereinafter referred to as behenyl alcohol), manufactured by Kao Chemical Co., Ltd.

[0042] [Example 1] Granular urea 1 (1000 parts by mass) was placed in a rotating tank and turned. The granular urea 1 was then heated to approximately 70°C with hot air, after which liquid paraffin (MORESCO White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was added, and the tank was turned for 5 minutes. The paraffin-coated granular urea 1 was kept in a rolling state, and castor hydrogenated oil 1 (210 parts by mass) heated and melted at 105°C was added. The rolling state was maintained under heating conditions for 3 minutes or more. The mixture was then cooled to near room temperature to obtain coated granular fertilizer (hereinafter referred to as coated granular fertilizer 1).

[0043] [Examples 2-7] In Examples 2 to 7, coated granular fertilizers were obtained in the same manner as in Example 1, except that one of granular urea 2 to 7 was used instead of granular urea 1 (hereinafter, these will be referred to as coated granular fertilizers 2 to 7).

[0044] [Comparative Example 1] In Comparative Example 1, a coated granular fertilizer was obtained in the same manner as in Example 1, except that comparative granular urea 1 was used instead of granular urea 1 (hereinafter referred to as comparative coated granular fertilizer 1).

[0045] [Comparative Example 3] Granular urea (1000 parts by mass) was placed in a rotating tank and turned. The granular urea was then heated to approximately 70°C using hot air, after which liquid paraffin (MORESCO White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was added, and the tank was turned for 5 minutes. Paraffin-coated granular urea was kept in a rolling state, and FT wax (210 parts by mass) heated and melted at 105°C was added. The rolling state was maintained under heating conditions for 3 minutes or more. After that, it was cooled to near room temperature to obtain coated granular fertilizer (hereinafter referred to as comparative coated granular fertilizer 3).

[0046] [Comparative Example 4] Coated granular fertilizer was obtained in the same manner as in Comparative Example 3, except that carnauba wax was used instead of FT wax (hereinafter referred to as Comparative Coated Granular Fertilizer 4).

[0047] [Comparative Examples 5-6] A coated granular fertilizer was obtained in the same manner as in Comparative Example 3, except that paraffin wax or stearic acid was used instead of FT wax, and the heating temperature of the granular urea was set to 55°C (hereinafter, these will be referred to as Comparative Coated Granular Fertilizer 5 or 6, respectively).

[0048] [Evaluation of average particle size, circularity coefficient, and aspect ratio of granular urea] Granular urea 1 was placed on a glass slide and photographed at a magnification of approximately 20x, matching the size of the granular urea 1, with approximately 5-10 particles per field of view. An optical microscope (HRX-01, manufactured by Hirox Co., Ltd.) was used for the imaging. When placing the granular urea 1 on the glass slide, care was taken to ensure that the granular urea 1 particles did not come into contact with each other and that the contrast between the background color and the granular urea 1 particles was strong, in order to make the outline of the granular urea 1 clear. For the captured images of granular urea 1, the simple recognition tool (data acquisition mode: color difference, tolerance: 72) of the image analysis particle size distribution measurement software (Mac-View, manufactured by Mountec Co., Ltd.) was used to automatically recognize the contours of granular urea 1, perform image analysis, and measure the particle size (Heywood diameter), circularity coefficient (4π × area × perimeter), and aspect ratio (major axis / minor axis). Here, the major axis is defined as the maximum distance between two points on the surface of granular urea 1 captured in the image. The minor axis is defined as the maximum length of the line segment perpendicular to the major axis. The particle size, circularity coefficient, and aspect ratio were measured for 100 or more particles. The average values ​​of these measurements were defined as the average particle size, circularity coefficient, and aspect ratio, respectively. The average particle size, circularity coefficient, and aspect ratio were measured for granular urea 2-7 and comparative granular urea 1 using the same method.

[0049] [Evaluation of the angle of repose of granular urea and coated granular fertilizers] 375g of granular urea 1 was added to a 500mL cylindrical stainless steel container. The opening of the container was sealed with a smooth, rigid plate (material: SUS, dimensions: 50cm or more in length, 50cm or more in width), and the container and plate were inverted. The container was then pulled straight up at a speed of approximately 1cm / second. The angle between the inclined surface of the resulting conical deposit of granular urea 1 and the plate was measured from all four sides, and the average value was defined as the angle of repose. The angles of repose of granular urea 2-7 and comparative granular urea 1 were measured using the same method. The angles of repose of the coated granular fertilizers 1-7 and comparative coated granular fertilizer 1 were also measured using the same method.

[0050] [Evaluation of oil absorption rate of granular urea] 20g of granular urea 1 was added to a 200mL PP cup and left to stand in a 70°C incubator for 1 hour. 20mg of liquid paraffin was added to the cup and stirred with a spatula for 1 minute (Step 1). The mixture was again left to stand in a 70°C incubator for 30 minutes to allow the 20mg of liquid paraffin to be absorbed by the granular urea 1 (Step 2). The cup was removed from the incubator, and a small amount of granular urea 1 was firmly squeezed and visually checked to see if liquid paraffin adhered to a glove (Step 3). Steps 1-3 were repeated until liquid paraffin adhered to the glove. Based on the amount of liquid paraffin added up to just before Step 3, when adhesion of liquid paraffin to the glove was confirmed, the saturated oil absorption rate was calculated using Formula 1 below. The saturated oil absorption rate was measured three times, and the average value was defined as the oil absorption rate. The oil absorption rates of granular ureas 2-7 and comparative granular urea 1 were measured in the same manner.

[0051] [Mathematics 1] Saturation oil absorption rate (%) = (Total amount of liquid paraffin added (g) / Mass of granular urea (g)) × 100

[0052] [Evaluation of the decomposition properties of hydrogenated plant oils, petroleum-based waxes, etc.] (Method for preparing evaluation samples) Ten g each of the samples shown in Table 1, such as hydrogenated vegetable oil and petroleum-based wax, was placed in a constant temperature incubator set to 105°C and melted. The molten samples were cast onto a glass plate using a film applicator (Allgood Co., Ltd., 600 μm gap), cooled and solidified at room temperature, and a film with a thickness of approximately 300 μm was created. (Evaluation method) 20g of soil (collection site: Kasai City, Hyogo Prefecture) was placed in a 50mL plastic cup. A test specimen was prepared by cutting a 2cm square, approximately 100mg in size from the prepared film and weighing it (M1). The test specimen was placed on top of the soil, and 20g of soil was added on top. The specimen was then lightly tapped on the ground about 10 times to pack it. This plastic cup and a water-filled cup for moisture retention were placed on a tray, put into a plastic bag, and the opening was lightly tied. The tray was placed in a constant temperature incubator set to 28°C, and the weight of the cup was measured every half month from the start of the test. If a change was observed, water was added using a spray bottle. After one month, the test specimen was collected, lightly washed, and thoroughly dried at room temperature for at least one night. The mass of the test specimen was measured (M2), and the mass loss rate (W = M2 / M1 × 100 (%)) was calculated. (Evaluation Criteria) A: Mass reduction rate W is 20% or more but less than 40% B: Mass loss rate W is 10% or more but less than 20%, or 40% or more but less than 60% C: Mass loss rate W is less than 10% or 60% or more. A rating of A indicates that the coated granular fertilizer has good decomposition properties as a coating. The results are shown in Table 1.

[0053] [Table 1]

[0054] [Evaluation of the manufacturability of coated granular fertilizers] (Evaluation method) The degree of adhesion between coated granular fertilizers or between coated granular fertilizers and the rotating tank during the production of coated granular fertilizers 1-7 and comparative coated granular fertilizer 1 was visually evaluated. The results are shown in Tables 2 and 4. (Evaluation Criteria) ○: Almost no adhesion occurred between the coated granular fertilizers themselves or between the coated granular fertilizers and the rotating tank. ×: Significant adhesion occurred between the coated granular fertilizers themselves or between the coated granular fertilizers and the rotating tank.

[0055] [Table 2]

[0056] [Evaluation of the adhesive properties of coated granular fertilizers during storage] (Evaluation method) 50g of the coated granular fertilizer 1 was placed in a cylindrical container, and a 5kg weight was placed on top of it. The container was then left undisturbed in a constant temperature chamber set to 40°C for 24 hours. After that, the coated granular fertilizer 1 was removed from the container, and the degree of adhesion between the granular fertilizer particles was visually evaluated. The results are shown in Table 3. (Evaluation Criteria) ○: Almost no adhesion occurred between the coated granular fertilizers. ×: Significant adhesion occurred between the coated granular fertilizers.

[0057] [Table 3]

[0058] [Initial elution rate] 2.5g of coated granular fertilizer 1 (60-80 granules) was placed in a sample bottle, 100mL of water was added, and the mixture was left to stand at 25°C. After 7 days, 0.6mL of water was taken from the sample bottle, and the urea concentration was measured using a UV-Vis spectrophotometer (UV-1900i, manufactured by Shimadzu Corporation). Based on the measured urea concentration, the urea elution rate E1 (%) from coated granular fertilizer 1 was calculated. The results are shown in Table 4. E1 was similarly calculated for coated granular fertilizers 2-7 and comparative coated granular fertilizer 1. (Evaluation Criteria) A: Dissolution rate E1 is less than 13% B: Dissolution rate E1 is 13% or more and less than 25% C: Dissolution rate E1 is 25% or higher A rating of A or B indicates good initial dissolution control.

[0059] [Initial impact resistance] This coated granular fertilizer 1 was spread using a side-dressing fertilizer applicator (Yanmar Co., Ltd., YK6D) and then collected. The collected coated granular fertilizer 1 (2.5g, 60-80 granules) was placed in a sample bottle, 100mL of water was added, and it was left to stand at 25°C. After 7 days, the urea concentration was measured using the same method as above. Based on the measured urea concentration, the elution rate E2 (%) after initial mechanical fertilization was calculated. E2 was similarly calculated for coated granular fertilizers 2-7 and comparative coated granular fertilizer 1. The initial impact resistance was evaluated based on the E2-E1 value. The results are shown in Table 4. (Evaluation Criteria) A: E2-E1 is less than 15% B: E2-E1 is between 15% and less than 25% C:E2-E1 is 25% or more A rating of A or B indicates good impact resistance.

[0060] [Table 4]

Claims

1. The device comprises granular urea and a coating that covers the granular urea. The aforementioned coating contains a hydrogenated vegetable oil, The aforementioned hardened vegetable oil has a melting point of 60°C or higher and 100°C or lower, and is a coated granular fertilizer. A coated granular fertilizer in which the angle of repose of the coated granular fertilizer is 29 degrees or less.

2. The coated granular fertilizer according to claim 1, wherein the hydrogenated plant oil is at least one selected from the group consisting of hydrogenated castor oil, hydrogenated rapeseed oil, and hydrogenated soybean oil.

3. The coated granular fertilizer according to claim 2, wherein the aforementioned hardened plant oil is hardened castor oil.

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