JPH10101465A - Controlled release fertilizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a controlled release fertilizer capable of arbitrarily controlling the elution rate of the fertilizer component and free from spoiling the environment by combining the fertilizer component and mineral component with a biodegradable polymer or a plastic component using it as the main component. SOLUTION: This controlled release fertilizer is a complex solid where the fertilizer component and the mineral are combined with the plastic comprising the biodegradable polymer or the plastic comprising it as the main component. In addition to the biodegradable plastic, its plasticizer (e.g.: polyol compound, phthalic acid ester, etc.) can be used in the plastic component. The component ratio of the mineral component/the biodegradable ratio (weight ratio) is about 5/95 to 99/1. For example, a bulk material of hydrated silicate mineral and siliceous material are preferred as the mineral component. A biodegradable polyester, a biodegradable polyamide, chitin or chitosan compound, chemically modified starch, physically modified starch, etc., are cited as the biodegradable polymers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a sustained release fertilizer which is a composite solid. Here, controlled release (Controlled-Rel
“Ease property” is used in a broad sense including slow-acting and slow-acting properties.

[0002]

2. Description of the Related Art Fertilizer components are indispensable for growing crops, and fertilizers having various forms containing various fertilizer components have been developed and used. How efficiently these fertilizers are used in crops is an important point of the application method, and a uniform application cannot provide a sufficient effect.

[0003] For example, in rice cultivation, which is a major crop in Japan, the yield of nitrogen, phosphoric acid, potassium and other fertilizer elements is controlled at each stage of growth. Providing such a topdressing technique only with an immediate-acting fertilizer is extremely complicated in agricultural work, which is against the trend of labor saving in recent years. In addition, frequent application tends to cause excessive application, which causes problems such as concentration disturbance to crops and eutrophication of rivers and lakes due to the lost fertilizer components.

As a countermeasure against such a problem, various proposals have been made to use sustained-release fertilizers.

[0005] Among these, examples of the method for imparting sustained release by the fertilizer preparation form include a fertilizer handbook (4th edition,
Coating of solid fertilizers described on page 165 of the (Corporation of Agriculture, Mountains and Villages) and water-soluble solid fertilizers with water-resistant / hydrophobic polymers such as phenolic resin, olefin resin, paraffin wax, and olefin wax. Sustained-release fertilizers having a multilayer structure have been proposed (JP-A-63-147889, 55-16116, JP-B-2).
-23515, 6-74198, JP-A-5-857
No. 83 publication).

However, all of the above cases have the following problems.

That is, in the case of the above-mentioned solid fertilizer, it is difficult to gradually release a water-soluble fertilizer component which is an immediate effect into water or soil under control. In the case of the solid fertilizer, the sustained-release property depends on the relative decrease in the elution surface area due to granulation, the matrix effect of peat as a base (binder effect), and the effect of preventing fixation of phosphoric acid. For this reason, the sustained release effect is insufficient, and the effect of the application environment is large,
It is difficult to control the sustained release.

[0008] In the case of the above-mentioned sustained-release fertilizer, the sustained-release property depends on elution of fertilizer components from pinholes or cracks in the coating, and control of these pinholes or cracks in the production process. Is difficult. For this reason, it is difficult to accurately control the elution of the fertilizer component. Furthermore, when the above-mentioned synthetic resin or the like is used as a coating material and / or a fertilizer binder, they remain in the environment without being decomposed, causing soil and water pollution.

In view of the above, it has been proposed to use a water-soluble polymer such as polyvinyl alcohol, polyethylene glycol, starch, carboxymethylcellulose, etc. as a binder. And it is difficult to achieve sufficient sustained release.

In view of the above, a so-called biodegradable polymer in which a biodegradable polymer, which has been actively developed in recent years, is used as a coating material or a matrix (base material) and a fertilizer component is dispersed in the plastic component. Various types of sustained-release solid fertilizers for release systems have been proposed (JP-A-5-97561,
Nos. 6-15718, 7-33569, 7-31597
No. 6, 8-2989).

[0011]

However, when a biodegradable polymer is used as a coating agent, the above-mentioned difficulty in controlling elution by coating with a water-resistant / hydrophobic polymer has not been solved at all.

When a biodegradable polymer is used as a coating agent, the sustained release function depends only on the biodegradability of the polymer.
For this reason, in an actual application environment, the dissolution rate fluctuates greatly, so that it is difficult to obtain a stable dissolution rate. Further, since the dissolution rate of the fertilizer component changes largely before and after the start of decomposition, the degree of freedom in controlling the dissolution rate is small.

In view of the above, it is an object of the present invention to provide a sustained-release fertilizer which can control the elution rate of fertilizer components arbitrarily and does not pollute the environment.

[0014]

Means for Solving the Problems In view of the above problems, the present inventors have made intensive efforts for development, and as a result, mixed fertilizer components with mineral components and biodegradable polymers to dissolve biodegradable polymers. Or by plasticizing by heating,
A controlled release fertilizer having the following composition was conceived.

[0015] The sustained-release fertilizer which is a composite solid, wherein the fertilizer component and the mineral component are combined and complexed with a plastic component mainly composed of a biodegradable polymer. .

[0016]

The sustained-release fertilizer which is the composite solid of the present invention is a fertilizer component and a mineral component which are combined and combined with a biodegradable polymer-based or plastic-based component. As a result, the following operations and effects are achieved.

The basic function is that the elution of the fertilizer component is caused by the penetration of water from the filled pores of the mineral component.

In the initial stage of application, the voids are filled with a biodegradable polymer, so that the dissolution rate is limited to a certain level. Then, as the biodegradable polymer is decomposed with the passage of time, the eluted voids are expanded, and the fertilizer components inside are eluted.

Furthermore, even if most of the biodegradable polymer is lost, the sustained release property remains due to the fertilizer component adsorption effect and the matrix effect of the mineral powder. Will be maintained. Up to this point, the biodegradable polymer retains its function as a binder, preventing a rapid change in the dissolution rate due to the collapse of the solid form of the fertilizer, and after the final disappearance, only the mineral powder, which is essentially the soil component, remains collapsed Therefore, it does not pollute the environment.

The dissolution rate of the sustained-release fertilizer of the present invention is as follows:
Type of mineral component, particle size, type of biodegradable polymer,
Fine control is possible depending on the decomposition rate, the composition ratio of both the mineral component and the biodegradable polymer, and does not depend only on the decomposition of the biodegradable polymer.

Therefore, the influence of the fluctuation of the decomposition rate of the biodegradable polymer due to the difference in the application environment can be minimized.

Further, if necessary, the volume of the solid fertilizer /
It is also possible to combine with known dissolution control techniques such as adjustment of the surface area ratio and use of slow-release fertilizer components, and a solid sustained-release fertilizer having an arbitrary dissolution rate can be easily obtained. Therefore, it is also possible to prepare a sustained-release fertilizer having a plurality of different dissolution rates and fertilizer components, and to obtain the effect of applying the fertilizer under optimum conditions to the crop with minimal effort by applying the sustained-release fertilizer. Is also possible.

[0023]

[Detailed description of means]

A. The sustained-release fertilizer that is a composite solid according to the present invention is a fertilizer component and a mineral component that are combined and combined with a plastic component mainly composed of a biodegradable polymer or a biodegradable polymer. Here, the mode of compounding is the type and particle size of the mineral component and the plastic component (biodegradable polymer)
It is presumed that at least the fertilizer component is dispersed in the composite phase formed of the mineral component and the plastic component (the plastic component is a discontinuous phase or a continuous phase), although it depends on the ratio of the fertilizer.

Hereinafter, the fertilizer component, mineral powder, biodegradable polymer and plasticizer used in the present invention will be described in detail.
These components of the present invention are selected from substances that are harmless to the plants and the environment to which they are applied, and / or are used in an amount that does not cause harm. In the following description, a blending unit is a weight unit unless otherwise specified.

(1) Fertilizer components include nitrogenous fertilizers such as ammonium sulphate, salt ammonium, ammonium nitrate, urea, acetaldehyde condensed urea, isobutyraldehyde condensed urea, lime superphosphate, lime heavy superphosphate, molten fertilizer, etc. Phosphoric fertilizers, potassium fertilizers such as sulfated potassium and chlorided potassium, organic fertilizers such as fish cake, bone meal, soybean oil cake, and rapeseed oil cake, ternary compound fertilizers such as phosphoric acid and potassium phosphate, calcareous fertilizers, Siliceous fertilizer, magnesia fertilizer,
Manganese fertilizers, boron fertilizers, trace element compound fertilizers and the like can be mentioned, and these can be used alone or in combination of two or more.

As the form of the fertilizer component, any form provided as a solid or liquid, such as a powder, a granule, a paste, a slurry, and a solution, can be used.

(2) The mineral component is not particularly limited, but the hydrated silicate mineral aggregate and the siliceous raw material have a shape-forming property,
It is desirable from the viewpoint of the ability to retain fertilizer components and the effect on vegetation.

Examples of the hydrated silicate mineral aggregate include kaolin, kibushi clay, gairome clay, white silica, soft silica, furnace silica, perlite (pearlite), and the like.
Bentonite, zeolite, radiolite (diatomaceous earth) and the like can be cited, and these can be used alone or in combination of two or more.

The forms of these mineral components are powder, sphere,
Regardless of scaly, plate, thin, fiber, etc., it may be a crushed piece. Usually, the average particle size is 500 μm or less. If the particle size is too large, the moldability of the composition is poor, and it is difficult to obtain a sufficient sustained release effect, so that it is difficult to achieve the object of the present invention. The lower limit of the particle size of the mineral component is not particularly limited, but usually,
0.1 μm, preferably 0.5 μm.

Since the particle size of the mineral powder is related to the dissolution rate, it is large when a fast dissolution rate is desired, and small when a very slow dissolution rate is desired. Control the speed.

(3) Biodegradable polymers include highly modified biodegradable starch: low-substituted esterified and / or etherified starch, low-grade chemically and / or physically modified starch such as dextrin and alpha starch; Chemically and fermented synthetic polyesters and their biodegradable copolymers, such as water-resistant high-substituted esterified and / or etherified starch, graft-polymerized starch (polymerized end-blocking type and non-blocking type) ... polylactic acid, polycaprolactone, poly Biodegradable polyamides and biodegradable copolymers such as hydroxybutyrate / valeate, polyhydroxyalkanoate, etc. Biodegradable copolymers such as low molecular weight nylon, etc. Cellulose derivatives… Carboxymethyl cellulose, hydroxyethyl cellulose, cellulose acetate, etc. Biopolymers and derivatives thereof… Guar gum, alginic acid, cereal gluten, chitin, chitosan, Zein, gelatin, xanthan gum, pullulan, and derivatives thereof, and the like can be mentioned, complex to use one or two or more kinds of these. Particularly, among the above, highly degradable biodegradable starch, particularly starch ester having an ester group carbon number of 2 to 18 and a degree of ester substitution of 1.0 to 2.9, has a biodegradability rate, water resistance, etc. It is desirable from the viewpoint of affinity with the component of the above.

The starch ester can be obtained by various known methods. In particular, a vinyl ester described in JP-A-8-188601 is used as an esterification reagent and an esterification catalyst is used in a non-aqueous solvent. The starch ester obtained by the method of reacting with the starch gives a good effect as satisfying the above physical properties at low cost.

As the above-mentioned graft-polymerized starch, the present applicant has previously filed Japanese Patent Application No. 7-44487 (Japanese Unexamined Patent Application Publication No.
-) And Japanese Patent Application No. 7-133873 (JP-A-Hei), respectively.
The following esterified vinyl ester graft polymerized starch and esterified polyester grafted polymerized starch can be suitably used (both cited in claim 1).

"A starch to which polyvinyl ester is grafted together with esterification, wherein the corresponding acid for the esterification is one of saturated and unsaturated fatty acids having 2 to 18 carbon atoms and aromatic carboxylic acids. Or at least two kinds, wherein the corresponding acid of the polyvinyl ester is one of a saturated / unsaturated fatty acid having 2 to 18 carbon atoms and an aromatic carboxylic acid.
The species or two or more species are selected. "A starch which has been grafted with a polyester together with the esterification, wherein the corresponding acid for the esterification is one or two types of saturated / unsaturated fatty acids having 2 to 18 carbon atoms and aromatic carboxylic acids. The polyester selected from the above is a ring-opened polymer of a lactone selected from one or two or more kinds having 4 to 12 ring members, and the terminal hydroxyl group is substantially ester-blocked. " In order to achieve this, at least one of the substances is hardly soluble or insoluble in water, and / or a known water-proofing agent may be used as long as the biodegradability of the biodegradable polymer is not impaired. desirable.

(4) The biodegradable polymer can be used as needed, that is, from the viewpoint of promoting the plasticization of the biodegradable polymer, together with the biodegradable polymer plasticizer. . The mixing ratio of the plasticizer to the biodegradable polymer is usually 0 to 100 parts with respect to 100 parts of the biodegradable polymer.

It is desirable that the above-mentioned plasticizer has biodegradability also for the purpose of the invention, and it is possible to use one or more of the following examples in combination.

(A) polyol compound: ethylene glycol, polyethylene glycol, glycerin, polyglycerin, etc .; (b) phthalic acid ester: dimethyl / diethyl /
(C) phthalic acid ester derivatives such as dibutyl di (2-ethylhexyl). And di (n-octyl) phthalate ... ethyl phthalyl ethyl glycolate, ethyl phthalyl ethyl butyrate, etc., (d) aliphatic monobasic acid Esters: butyl oleate, glycerin monostearate, glycerin diacetate, triacetin, tripropionin, sucrose octaacetate, etc. (e) Aliphatic monobasic ester derivatives: methyl acetyl ricinoleate, acetyl citrate triethyl, etc., (f) Aliphatic dibasic acid ester: dibutyl adipate, di-n-hexyl adipate, dioctyl sebacate, etc. (g) Aromatic carboxylic acid ester: trioctyl trimellitate, diethylene glycol benzoate, octyl oxybenzoate, etc., (h) phosphorus Acid ester: tributyl phosphate, N acid tricresyl, (i)
Epoxy plasticizers, epoxidized soybean oil, epoxidized castor oil, alkyl epoxy stearate, etc. (j) Polymeric plasticizers: various liquid rubbers, polyterpene resins, low to medium molecular weight linear polyesters, etc. The mixing ratio (weight ratio) of the mineral component and the biodegradable polymer in the present invention is usually the former / the latter = 5/95 to 99 /
1, preferably in the range of 30/70 to 90/10. When the compounding ratio is extremely lean to biodegradable polymer,
The sustained release function will depend only on the biodegradable polymer, and conversely, if the composition is extremely rich in mineral powder, the binder effect and the elution suppression effect of the fertilizer component due to the biodegradable polymer will be insufficient. In such a case, the object of the present invention cannot be sufficiently achieved.

Within the above range, the dissolution rate can be further reduced by generally increasing the blending ratio of the biodegradable polymer.

B. The method for producing the sustained-release fertilizer of the present invention is performed as follows.

The fertilizer component, mineral powder, biodegradable polymer and, if necessary, a plasticizer or the like, in a dry state, or using water or an organic solvent as a medium, optionally with heating and / or cooling. Mix and knead uniformly underneath.

The kneaded material is extruded, press-formed,
Cast molding, molding by known molding techniques such as injection molding, or, or fluidized granulation, rolling granulation, granulation by known granulation techniques such as crushing granulation, further heating, if necessary, After drying, it becomes a composite solid.

The shape and size of the solid sustained-release fertilizer composition may be granular, spherical, cylindrical, prismatic, disk-shaped, pile-shaped, etc.
It can be selected in consideration of the convenience at the time of application, the fertilizer component content per molded product, and the difference in elution rate due to the volume / surface area ratio, and the like, and is not particularly limited.

There are no particular restrictions on the production conditions of the present fertilizer composition other than the temperature conditions during production. That is, some of the fertilizer components and biodegradable polymers used in the present invention undergo thermal decomposition or thermal degradation at high temperatures,
Inevitably, the product temperature at the time of mixing and kneading, at the time of molding and at the time of drying is controlled to be lower than the thermal decomposition or thermal degradation temperature of the component.

[0044]

EXAMPLES Examples and comparative examples for verifying the present invention will be described below, but they do not limit the present invention in any way.

A. Preparation of biodegradable polymer (1) Acetylated starch: high amylose corn starch 2
5 g is suspended in 200 g of DMSO (non-aqueous organic solvent), gelatinized by heating to 80 ° C. with stirring and maintaining at 80 ° C. for 20 minutes. To this solution, 20% of sodium hydrogencarbonate (catalyst) is added, and while maintaining at 80 ° C., 12 g of vinyl acetate (vinyl ester) is added, and the mixture is reacted at that temperature for 1 hour. Thereafter, the reaction solution is poured into tap water, and pulverized and washed with high-speed stirring to obtain a starch ester precipitate, which is filtered and dried to prepare an acetylated starch. The degree of substitution of this acetylated starch is 2.
It was 5.

B. Preparation of sustained-release fertilizer Each sustained-release fertilizer of Examples 1-6 and Comparative Examples 1-3 was prepared according to the following method.

<Example 1> In the composition 1 shown in Table 1,
Georgia kaolin (average particle size: 2μ) as mineral powder
m), using polycaprolactone (manufactured by Union Carbide, trade name: TONE787) as a biodegradable polymer, triacetin (manufactured by Daihachi Chemical) as a plasticizer, and using a plastmill (Toyo Seiki 30C150 type) as a plasticizer.
After mixing and kneading at ° C, the mixture was molded at 120 ° C by a hot press to obtain a prismatic (30 × 10 × 4 mm) sustained-release fertilizer.

Example 2 In the composition 2 shown in Table 1,
Georgia kaolin (average particle size: 2μ) as mineral powder
m), using the above acetylated starch as a biodegradable polymer, and ethylphthalylethyl glycolate (trade name # 10, manufactured by Daihachi Chemical Co., Ltd.) as a plasticizer, in the same manner as in Example 1 to give sustained release of the same shape. A fertilizer was obtained.

Example 3 In Formula 3 shown in Table 1,
Using the same mineral powder, biodegradable polymer, and plasticizer as in Example 2, a sustained-release fertilizer having the same shape was obtained in the same manner as in Example 1.

Example 4 In Formula 4 shown in Table 1,
Using the same mineral powder, biodegradable polymer and plasticizer as in Example 2, after mixing and kneading at 90 ° C. using a plastmill,
It was molded at 90 ° C. by a hot press, and further dried at 75 ° C. for 3 hours in a hot air circulation type drier to obtain a sustained-release fertilizer having the same shape as that of Example 1.

Example 5 In Formulation 5 shown in Table 1,
Using zeolite (average particle size: 2 μm) as a mineral powder, the above-mentioned acetylated starch as a biodegradable polymer, and triacetin (produced by Daihachi Chemical) as a plasticizer, a sustained release of the same shape in exactly the same manner as in Example 4. Got fertilizer.

Example 6 Perlite (average particle size: 50 μm) was used as the mineral powder in Example 3 in place of georgia kaolin, and a sustained-release fertilizer having the same shape was obtained in exactly the same manner.

Example 7 In the composition 6 shown in Table 1,
Georgia kaolin (average particle size 2μ) as mineral powder
m), using acetylated polycaprolactone-grafted acid-treated corn starch (acetyl substitution degree 2.4, molar substitution degree of graft group 2.5, graft group end blocking rate 80%) as a biodegradable polymer, In the same manner, a sustained-release fertilizer having the same shape was obtained.

Comparative Example 1 An EVA resin (trade name: Evatate H5010, manufactured by Sumitomo Chemical Co., Ltd.) was used instead of the biodegradable polymer in Example 7, and a sustained-release fertilizer having the same shape was obtained in the same manner as described below. .

Comparative Example 2 Gelatin akaolin (average particle size: 2 μm) was used as the mineral powder in Formulation 7 (excluding the coating agent) shown in Table 1, and plastomill was used.
After mixing and kneading at 0 ° C., the mixture was molded at 90 ° C. by a hot press, and further dried at 75 ° C. for 3 hours in a hot air circulating drier to obtain a molded product having the same shape as in Example 1. A biodegradable polymer, polycaprolactone (manufactured by Union Carbide, trade name TONE78) was added to the obtained composition as a coating agent.
The operation of spraying and drying the hot chloroform solution of 10% concentration in 7) was repeated to finally obtain a sustained-release fertilizer having the same shape as that of Example 1 having a coating film having a thickness of about 700 μm.

<Comparative Example 3> In the formulation 8 shown in Table 1,
Using the same biodegradable polymer and plasticizer as in Example 1, a sustained-release fertilizer having the same shape was obtained in the same manner as in Example 1.

B. Evaluation Test Each of the sustained release fertilizers prepared as described above was subjected to evaluation tests for the following items.

(1) Dissolution rate test (a) Dissolution rate under aseptic conditions Two fertilizer compositions of Examples 1 to 7 and Comparative Examples 1 and 2 were used for 20 tests.
It was immersed in 0 mL of sterile distilled water, allowed to stand at 25 ° C. on a sealed stopper, and the electric conductivity of the supernatant was measured with an electric conductivity meter (Toa Denpa Kogyo Co., Ltd.
(M-20E type), and the elution rate of the fertilizer component was determined by the following equation. Table 2 shows the obtained results.

<Calculation formula of dissolution rate> Dissolution rate (%) = A / B × 100 A: Electric conductivity per 1 g of sample (mS / cm · g) B: Electric conductivity per 1 g of sample at 100% elution (Theoretical value, mS / cm · g) (b) Elution rate under environmental model conditions for implementation Two fertilizer compositions of Examples 1 to 7 and Comparative Examples 1.2 were used for 19 samples.
Immerse in 0 mL of sterile distilled water, inoculate 10 mL of flooded paddy field (Hekinan City, Aichi Prefecture), leave at 25 ° C on the stopper, and determine the total nitrogen content of the supernatant using a modified salicylic acid-decomposed Kjeldahl method. It was measured over time and the elution rate of the nitrogen component was determined by the following equation. Table 3 shows the obtained results.

<Calculation formula of dissolution rate> Dissolution rate (%) = C / D × 100 C: Total nitrogen amount per 1 g of sample (g / g) D: Total nitrogen amount per 1 g of sample at 100% elution (theoretical (Value, g / g) (2) Disintegration test The fertilizer compositions of Examples 1 to 7 and Comparative Example were buried in a field (Hekinan City, Aichi Prefecture) at a depth of 5 cm, excavated after a predetermined period, and examined for disintegration. . Table 4 shows the obtained results.

C. Discussion of test results From Tables 2 and 3, the sustained-release fertilizer of each example has a suppressed initial dissolution of the fertilizer component, and until the entire fertilizer component is dissolved, a stable dissolution rate according to the setting by blending. It can be seen that the effect of the application environment on the sustained release is small while maintaining it. Also, from Table 4, each sustained-release fertilizer is from six months to
One year later, it can be seen that it has almost completely collapsed.

On the other hand, the sustained release fertilizer of Comparative Example 1 has the same performance as that of the present embodiment in sustained release, but does not disintegrate in the environment. Further, the sustained-release fertilizers of Comparative Examples 2 and 3 have significantly different elution properties under aseptic conditions and environmental model conditions, and the application conditions, particularly the soil microflora, etc. have a large effect on the elution speed, and the stable fertilizer application effect is high. It turns out that it is difficult to obtain.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

[Table 3]

[0066]

[Table 4]

Claims (8)

[Claims] 1. A sustained-release fertilizer which is a composite solid body, wherein a fertilizer component and a mineral component are combined and complexed with a biodegradable polymer-based or plastic-based component. And controlled release fertilizer. 2. The sustained-release fertilizer according to claim 1, wherein the plastic component comprises a plasticizer in addition to a biodegradable polymer. 3. The biodegradable polymer comprises one or more selected from the group consisting of a biodegradable polyester, a biodegradable polyamide, a chitin or chitosan compound, a chemically modified starch, and a physically modified starch. The sustained-release fertilizer according to claim 1, wherein 4. The method according to claim 1, wherein the chemically modified starch has 2 to 18 carbon atoms.
The sustained-release fertilizer according to claim 3, which is a starch ester having an ester constituent group of the formula (1) and a degree of ester substitution in the range of 1.0 to 2.9. 5. The starch ester is obtained by using a vinyl ester having an ester group carbon number of 2 to 18 as an esterification reagent and reacting with a starch together with an esterification catalyst in a non-aqueous organic solvent. 5. The method according to claim 4, wherein
The sustained-release fertilizer according to the above. 6. The chemically modified starch is a vinyl ester and / or polyester graft polymerized starch whose polymerization end is not ester-blocked or partially or completely ester-blocked. 3. The sustained-release fertilizer according to 3. 7. The sustained-release fertilizer according to claim 1, wherein the mineral component is an aggregate of hydrated silicate minerals or a siliceous raw material. 8. The sustained-release fertilizer according to claim 1, wherein the composition ratio (weight ratio) of the mineral component to the biodegradable polymer is in the range of former / latter = 5/95 to 99/1. .