Solid culture medium and method for cultivating plants

Abstract

To provide a solid culture medium for hydroponic cultivation that exhibits improved anti-algal effects, and a method for cultivating plants using such a solid culture medium.SOLUTION: According to one embodiment of the present invention, a solid culture medium for hydroponic cultivation includes a culture medium body, and an opaque film disposed on an upper surface of the culture medium body. The culture medium body is provided with a recess formed by depressing the upper surface, the recess being configured to receive a plant seed or seedling. The opaque film is provided with a through-hole at a position overlapping the recess when the solid culture medium is viewed from above, and at least a portion of an inner edge of the through-hole is positioned inside an outer edge of the recess.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a solid medium for hydroponics and a method for cultivating plants using the solid medium.

Background Art

[0002] When cultivating plants by hydroponics, a solid medium called a growing bed or a germination bed is immersed in water or a nutrient solution to germinate or grow the plants supported on the solid medium (see, for example, Patent Document 1). The germination bed described in Patent Document 1 is a solid medium made of urethane sponge, and a recess for sowing is provided on its upper surface. Further, in the above germination bed, in order to facilitate the downward growth of the roots of the plants, a cut is formed from the bottom of the recess, and the cut extends to the bottom surface of the germination bed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in hydroponics using a solid medium, algae, i.e., green algae, may propagate on the surface of the solid medium (especially the upper surface which faces upward when the solid medium is in use). Such propagation of algae may lead to the adhesion of algae to the cultivated plants and the resulting deterioration of the quality of the plants.

[0005] As a means for suppressing the growth of algae on the upper surface of the solid medium, for example, it is conceivable to cover the upper surface of the solid medium (specifically, the medium main body) with an opaque film or the like. To adopt this means, holes are made in the film so that the growth of the plants germinated in the recesses is not hindered by the above-mentioned film, and the film is attached to the upper surface of the medium main body so that the holes overlap with the recesses. Such a solid medium with a film is required to be configured so as to obtain a higher algae prevention effect.

[0006] The present invention has been made in view of the above circumstances, and aims to solve the problems of the prior art, and specifically, to provide a solid medium for hydroponic cultivation with an improved algae prevention effect. In addition, the present invention aims to provide a method for cultivating plants that can appropriately cultivate plants using the above-mentioned fixed medium.

Means for Solving the Problems

[0007] In order to achieve the above object, the solid medium of the present invention is a solid medium for hydroponic cultivation, comprising a medium main body and an opaque film disposed on the upper surface of the medium main body. A recess is formed by indenting the upper surface, and a recess into which plant seeds or seedlings can enter is provided in the medium main body. In the opaque film, a through-hole is provided at a position overlapping the recess when the solid medium is viewed from above, and at least a part of the inner edge of the through-hole is located inside the outer edge of the recess. By using the solid medium of the present invention configured as described above, the growth of algae on the surface of the solid medium in hydroponic cultivation can be more effectively suppressed.

[0008] Further, the inner edge of the through-hole and the outer edge of the recess may be circular, and the diameter of the circle formed by the inner edge of the through-hole may be smaller than the diameter of the circle formed by the outer edge of the recess. With the above configuration, a configuration in which the inner edge of the through-hole is located inside the outer edge of the recess can be easily realized.

[0009] Alternatively, the opaque film may include a white layer and a black layer disposed closer to the culture medium main body than the white layer. Or, the upper surface may be a black surface, and the opaque film may be a white film. In this case, the algae prevention effect on the surface of the solid culture medium can be further improved.

[0010] Further, the solid culture medium of the present invention may further have an adhesive layer between the culture medium main body and the opaque film. With the above configuration, it is possible to suppress the detachment of the opaque film from the culture medium main body.

[0011] Also, in the above configuration, it is more preferable that a gap is formed between the adhesive layer and the opaque film. In this case, the algae prevention effect on the surface of the solid culture medium can be further improved.

[0012] Also, an opaque film having the same number of through holes as the recesses provided on the upper surface may be disposed on the upper surface of the culture medium main body. With the above configuration, even when the number of recesses on the upper surface of the culture medium main body increases, the generation of algae on the surface of the solid culture medium can be appropriately suppressed.

[0013] Also, at least a part of the edge portion adjacent to the inner edge of the through hole in the opaque film may be joined to the inner peripheral surface of the recess to cover the inner peripheral surface. With the above configuration, the algae prevention effect on the surface of the solid culture medium can be further improved.

[0014] Further, in order to solve the above-mentioned problems, the plant cultivation method of the present invention is characterized in that the lower part of the solid culture medium corresponding to any of the above-described configurations is immersed in water or a nutrient solution, and the plant is cultivated by a hydroponic cultivation method. According to this method, the plant can be appropriately cultivated by a hydroponic cultivation method while suppressing the generation of algae on the surface of the solid culture medium.

Effects of the Invention

[0015] According to the present invention, a solid medium capable of more effectively suppressing the generation of algae on the surface of the solid medium is realized. Further, plants can be appropriately cultivated by a hydroponic cultivation method using the solid medium.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0017] One embodiment of the present invention (hereinafter, this embodiment) will be specifically described with reference to the accompanying drawings. However, the embodiments described below are examples given for ease of understanding of the present invention, and do not limit the present invention. That is, the present invention can be changed or improved from the embodiments described below without departing from the gist thereof. Further, equivalents thereof are included in the present invention.

[0018] Also, in this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. Also, in this specification, when explaining the position, posture, orientation, etc. of each component, it shall be explained assuming the normal use state. For example, the vertical direction (specifically, the Z direction described later) of the solid medium of this embodiment corresponds to the vertical direction.

[0019] Hereinafter, the XYZ directions are defined as three mutually orthogonal directions. Among them, the vertical direction of the solid medium of the present embodiment is the Z direction, the upper side is the “+Z side”, and the lower side is the “-Z side”. Further, the plane (cross section) perpendicular to the vertical direction of the solid medium is the XY plane. Also, the cross section (longitudinal section) orthogonal to the cross section, specifically, the I-I cross section in FIG. 2, is the YZ plane.

[0020] In the following description, “viewed in plan” means viewing the solid medium or the medium main body described later from the +Z side (that is, above).

[0021] [Configuration example of the solid medium according to the present embodiment] The solid medium 10 of the present embodiment is a solid medium for hydroponic cultivation. Specifically, it is used as a germination bed for germinating plant seeds or as a growing bed (seedling bed) for growing plant seedlings. The plant to be cultivated is, for example, an edible plant such as a vegetable or an ornamental plant such as a flower, and is harvested after cultivation and shipped as a product.

[0022] During the cultivation period of the plant, the solid medium 10 is used in a state where light for photosynthesis is irradiated on its upper part and its lower part is immersed in water or a nutrient solution (hereinafter, nutrient solution, etc.). The nutrient solution, etc. soaks into the lower part of the solid medium 10 and rises toward the upper part of the solid medium 10 by capillary action and the suction force of the plant. Note that the light irradiated on the solid medium 10 is not limited to artificial light, and may be sunlight, or may be irradiated using a combination of artificial light and sunlight.

[0023] As shown in FIG. 1, the solid medium 10 has a predetermined three-dimensional shape, and includes a medium main body 12 which is the main part of the solid medium 10, and an opaque film 20 disposed on the upper surface (+Z side surface) of the medium main body 12. The shape of the solid medium 10 may be, for example, a cube shape shown in FIG. 1, or a column shape such as a cylinder, or a barrel shape. Each dimension of the solid medium 10 may be set to a suitable value according to the number of seeds sown in the solid medium 10, or the size and number of seedlings held in the solid medium 10. Hereinafter, a solid medium 10 having a cube shape with a side length of about 30 mm will be described as an example.

[0024] The medium body 12 is made of a porous material having water absorbency (liquid absorbency), and is formed of, for example, urethane sponge, foam, or fiber mat, and is molded to have the same three-dimensional shape as the solid medium 10. Examples of the material constituting the medium body 12 include foamed resins such as polyurethane resin, phenol resin, polyester resin, polyethylene resin, and polystyrene, and fiber materials such as rock wool, coconut husk, perlite, peat moss, vermiculite, rice husk, bark, and coir mat. Among these, urethane resin, phenol resin, and rock wool are preferable, and phenol resin is particularly preferable. The water absorption rate of the material constituting the medium body 12 is preferably 50 to 99.9%, more preferably 70 to 99%, and still more preferably 80 to 98%.

[0025] Also, as shown in FIGS. 2 and 3, a recess 16 is provided on the +Z side surface (hereinafter, the upper surface 14) of the medium body 12. The recess 16 is formed by denting the upper surface 14 in a substantially hemispherical shape as shown in FIG. 3. During the cultivation period, the seeds or seedlings of the plant enter the recess 16. That is, when cultivating the plant, it is sown in the recess 16, or a part of the seedling is held (accommodated) in the recess 16. Although the recess 16 does not actually appear in the top view shown in FIG. 2, the recess 16 is illustrated by a dashed line in FIG. 2 for reasons such as showing the positional relationship with the through hole 26 described later.

[0026] In the present embodiment, one recess 16 is provided at the center of the upper surface 14 in one medium body 12, but the present invention is not limited to this, and two or more recesses 16 may be provided on the upper surface 14. Further, the depth of the recess 16 is preferably set to a depth such that the seeds or seedlings do not fall out of the recess 16. The depth of the recess 16 is the distance from the open end of the recess 16 to the deepest part of the recess 16 in the Z direction.

[0027] Also, as shown in FIG. 2, in this embodiment, the shape (planar shape) of the recess 16 in a plan view is circular. In other words, the shape formed by the outer edge of the recess 16 is a circle. Note that the planar shape of the recess 16 is not limited to a circle, and other shapes such as a triangle, a quadrilateral, other polygons, an ellipse, and an irregular shape may also be used.

[0028] Also, in this embodiment, as shown in FIG. 3, in the culture medium main body 12, a slit-shaped cut 18 extending from the upper surface 14 to the bottom surface (-Z side end surface) of the culture medium main body 12 is provided. The cut 18 is provided for the purpose of facilitating the downward extension of the roots of the seedlings when growing the seedlings of plants in the solid culture medium 10. The shape of the cut 18 in a plan view may be a plus (+) shape as shown in FIG. 2, or a minus (-) shape.

[0029] The opaque film 20 is used for the purpose of suppressing the generation of algae on the surface of the solid culture medium 10 (specifically, the surface on the +Z side), and is attached to the upper surface 14 of the culture medium main body 12 as shown in FIG. 3. If the upper surface 14 of the culture medium main body 12 is exposed, there is a possibility that algae may be generated by the irradiation of light on the exposed portion. However, the generation of algae can be suppressed by covering the upper surface 14 with the opaque film 20. In addition, by covering the upper surface with the opaque film 20, an increase in various bacteria can be suppressed in the same way as algae.

[0030] Here, the opaque measure (index value) is the reflectance and / or transmittance with respect to visible light (the wavelength range of visible light is assumed to be 400 to 700 nm), and these values can be measured by known measurement methods. Specifically, they can be measured by a known spectrophotometer and reflectance measuring device. The reflectance of the opaque film 20 is preferably 90% or more. Also, the transmittance of the opaque film is preferably 2% or less.

[0031] Note that the measure of opacity may be qualitative content. For example, when the film is laminated on white paper on which a black circle with a diameter of about 10 mm is drawn, the opacity may be evaluated by whether the above black circle can be visually recognized from above the film.

[0032] Examples of the material of the opaque film 20 include resins, plant fibers including paper, and metal thin films. Examples of the resin film include films made of films such as polyurethane, polyethylene, vinyl chloride, and PLA (Poly-Lactic Acid). It is preferable to use a non-water-permeable film.

[0033] In addition, the opaque film 20 of the present embodiment has a structure having a plurality of layers as shown in FIG. 4, and includes a white layer 22 located on the uppermost side (+Z side) and a black layer 24 disposed on the side of the culture medium body 12 (-Z side) rather than the white layer 22. The white layer 22 imparts light reflectivity to the opaque film 20, and the black layer 24 imparts light absorptivity to the opaque film 20. The white layer 22 and the black layer 24 are each constituted by containing a pigment or a dye in the base material of the film. Note that the opaque film 20 can be created, for example, by applying a black material to a white film or applying a white material to a black film. Further, the opaque film 20 may be created by applying a white material to one side of the film and applying a black material to the opposite side. Furthermore, the opaque film 20 may be created by laminating or adhering a white film and a black film. The method for creating the opaque film 20 is not limited to the methods described above, and any creation method may be used as long as one side of the film is white and the opposite side is black.

[0034] Furthermore, as shown in FIGS. 1 to 3, through holes 26 are formed in the opaque film 20. The through holes 26 are provided for the purpose of putting plant seeds or seedlings into the recess 16 in a state where the opaque film 20 is attached to the culture medium body 12. In the present embodiment, the shape of the through hole 26 is circular in plan view. In other words, the inner edge of the through hole 26 forms a circle. Note that the planar shape of the through hole 26 is not limited to a circle, and other shapes such as a triangle, a quadrangle, other polygons, an ellipse, and an irregular shape may also be used.

[0035] In the opaque film 20 of the present embodiment, the through-hole 26 is provided at a position overlapping with the recess 16 in a plan view. That is, the through-hole 26 is continuous with the recess 16 in the Z direction, and the opaque film 20 is attached to the culture medium main body 12 in a state where the existence range of the recess 16 and the existence range of the through-hole 26 overlap in the XY direction. Thereby, even after the opaque film 20 is attached to the culture medium main body 12, seeds or seedlings of plants can be smoothly put into the recess 16 through the through-hole 26.

[0036] Furthermore, in the present embodiment, as shown in FIG. 2, the diameter of the circle formed by the inner edge of the through-hole 26 is smaller than the diameter of the circle formed by the outer edge of the recess 16. Furthermore, as shown in FIG. 2, in a plan view, the opaque film 20 is attached to the culture medium main body 12 in a state where the entire inner edge of the through-hole 26 is located inside the outer edge of the recess 16.

[0037] More specifically, in a plan view, the opaque film 20 is attached to the culture medium main body 12 in a state where the circle formed by the inner edge of the through-hole 26 and the circle formed by the outer edge of the recess 16 are arranged concentrically. Therefore, as shown in FIG. 3, an edge portion (hereinafter also referred to as an adjacent edge portion 28) adjacent to the inner edge of the through-hole 26 in the opaque film 20 is located inside the outer edge of the recess 16 in the radial direction of the through-hole 26 and protrudes in a flange shape.

[0038] As described above, since the adjacent edge portion 28 is located inside the outer edge of the recess 16, the area of the upper surface 14 of the culture medium main body 12 covered by the opaque film 20 increases. Specifically, among the inner peripheral surface of the recess 16, the periphery of the outer edge of the recess 16 can be covered by the adjacent edge portion 28. Thereby, since the area of the upper surface 14 of the culture medium main body 12 irradiated with light can be reduced, the generation of algae on the surface of the solid culture medium 10 can be effectively suppressed.

[0039] In addition, if the adjacent edge portion 28 is located outside the outer edge of the recess 16 by chance, when the adjacent edge portion 28 is warped, the area other than the recess 16 on the upper surface 14 is exposed, and there is a possibility that light irradiates the area and algae are generated. On the contrary, since the adjacent edge portion 28 is located inside the outer edge of the recess 16 as in the present embodiment, even if the adjacent edge portion 28 is warped by chance, the area of the upper surface 14 other than the recess 16 that is exposed can be minimized as much as possible. Thereby, the generation of algae can be suppressed more effectively. Furthermore, in the solid medium 10 with seeds in the recess 16, when the seeds try to jump out of the recess 16 unintentionally, the adjacent edge portion 28 projecting in a flange shape locks the seeds and can prevent the seeds from jumping out.

[0040] In the present embodiment, one recess 16 is provided in the medium main body 12 for one solid medium 10. Correspondingly, one through hole 26 is provided in the opaque film 20. On the other hand, as described above, two or more recesses 16 may be provided on the upper surface 14 of one medium main body 12. In that case, an opaque film 20 having the same number of through holes 26 as the recesses 16 provided on the upper surface 14 may be arranged on the upper surface 14 of the medium main body 12. Further, as described above, each through hole 26 overlaps with the corresponding recess 16 in a plan view, and the inner edge of each through hole 26 is preferably located inside the outer edge of the corresponding recess 16.

[0041] The opaque film 20 is fixed to the upper surface of the medium main body 12 with an adhesive. In other words, as shown in FIG. 4, an adhesive layer 30 is provided between the back surface of the opaque film 20 (that is, the surface facing the medium main body 12) and the medium main body 12. The adhesive layer 30 is composed of an adhesive applied to the back surface of the opaque film 20 and / or the upper surface 14 of the medium main body 12, and is formed by curing the adhesive after the opaque film 20 is joined to the medium main body 12.

[0042] As the adhesive that constitutes the adhesive layer 30, known adhesives can be used. For example, those containing an epoxy resin as the main component and capable of firmly bonding the opaque film 20 to the culture medium main body 12 are suitable. In addition, examples of components that can be contained in addition to the epoxy resin include silicone compounds, polyol compounds such as polypropylene glycol, and urethane resins.

[0043] Also, when the opaque film 20 is joined to the culture medium main body 12, the above-mentioned adhesive is in an uncured state and has fluidity. Therefore, part of the adhesive flows into the culture medium main body 12 and impregnates the urethane or the like that constitutes the culture medium main body 12. As a result, as shown in FIG. 4, a gap 32 is formed between the adhesive layer 30 and the opaque film 20. By such a gap 32 intervening between the adhesive layer 30 and the opaque film 20, the portion of these interfaces that is in contact with the gap 32 becomes dry. As a result, it becomes difficult for the nutrient solution or the like that has penetrated into the culture medium main body 12 to reach the portion where the gap 32 is formed, so that the generation of algae that easily occurs in a wet state can be more effectively suppressed.

[0044] By the way, during the cultivation period of plants, a culture medium sheet 40 composed of a plurality of the above-mentioned solid culture media 10 connected in series is used in the period from sowing to the first transplantation. As shown in FIG. 5, the culture medium sheet 40 is rectangular in plan view and is formed by arranging two or more solid culture media 10 in each of the X and Y directions.

[0045] In addition, as shown in FIG. 5, the culture medium sheet 40 is provided with grid-shaped cutting lines 42. Each cutting line 42 is formed intermittently in a perforated shape and defines the boundary of each solid culture medium 10 that constitutes the culture medium sheet 40. In other words, two adjacent solid culture media 10 in the culture medium sheet 40 are adjacent via the cutting line 42. Specifically, among the cut portions (perforations) and non-cut portions alternately arranged on the cutting line 42, they are connected by the non-cut portions.

[0046] Then, by cutting a part of the culture medium sheet 40 along the cutting line 42 and separating it from the remaining part in the culture medium sheet 40, one solid culture medium 10 can be obtained. With such a configuration, the culture medium sheet 40 is divided into a plurality of solid culture media 10 during transplantation, and after transplantation, the individual solid culture media 10 are used in a state of being separated from each other. Note that the culture medium sheet 40 corresponds to an embodiment of the solid culture medium of the present invention, similar to the individually separated solid culture media 10.

[0047] Next, as a method for manufacturing the solid culture medium 10 according to the present embodiment, the manufacturing procedure of the above-described culture medium sheet 40 will be described with reference to FIG. 6. To manufacture the culture medium sheet 40, first, as shown in the left diagram in FIG. 6, a raw sheet of the opaque film 20 (hereinafter referred to as the film raw sheet 44) is cut into a rectangular shape of a predetermined size. Then, as shown in the central diagram in FIG. 6, grid-shaped perforations 46 are formed in the film raw sheet 44, and through holes 26 are drilled in the central portion of each unit region partitioned by the perforations 46. Note that at this stage, an adhesive is applied to the back surface of the film raw sheet 44, and a release paper (not shown) is further attached.

[0048] Next, as shown in the upper right diagram in FIG. 6, a raw sheet of the culture medium main body 12 (hereinafter referred to as the culture medium raw sheet 48) is cut into a rectangular shape of a predetermined size. Then, grid-shaped perforations 50 are formed in the culture medium raw sheet 48, and in each unit fragment partitioned by the perforations 50, the central portion of the upper surface is recessed in a substantially hemispherical shape to provide a recess 16. Here, the pitch (interval) of the perforations 50 in the culture medium raw sheet 48 is set to be the same size as the pitch (interval) of the perforations 46 in the film raw sheet 44. Furthermore, in each unit fragment, slit-shaped cuts 18 are formed at the same position as the recess 16.

[0049] Next, as shown in the lower right figure in FIG. 6, the release paper is peeled off from the film stock 44, and the film stock 44 is attached to the upper surface of the culture medium stock 48 (the surface on which the recess 16 is formed). At this time, the film stock 44 is positioned with respect to the culture medium stock 48 so that the perforations 46 provided in the film stock 44 and the perforations 50 provided in the culture medium stock 48 coincide, and the film stock 44 is overlaid on the culture medium stock 48, and these stocks are joined together.

[0050] Then, when the adhesive interposed between the film stock 44 and the culture medium stock 48 hardens and the adhesive layer 30 is formed, the culture medium sheet 40 is completed. In order to cultivate plants by a hydroponic method using the solid culture medium 10 manufactured by the above procedure, as in general hydroponics, the plants are cultivated while immersing the lower part of the solid culture medium 10 in water or nutrient solution. According to such a method of cultivating plants, by using the above-described solid culture medium 10, plants can be appropriately cultivated while suppressing the generation of algae on the surface of the culture medium.

[0051] [Regarding the algae prevention effect of the solid culture medium according to the present embodiment] In order to confirm the algae prevention effect of the solid culture medium 10 according to the present embodiment, Tests 1 to 5 were conducted. In Test 1, a solid culture medium configured by attaching an opaque film having a white layer and a black layer to a urethane culture medium body was used, specifically corresponding to the solid culture medium 10 of the present embodiment. In Test 2, a solid culture medium configured by attaching an opaque film having only a white layer to a urethane culture medium body was used. Regarding the opaque films of the solid culture media used in Tests 1 and 2, the reflectance with respect to visible light was 90%, and the transmittance of visible light was 0% in Test 1 and 2% in Test 2.

[0052] In Tests 3 to 5, solid culture media having a structure different from that of the solid culture medium of the present invention were used. Specifically, in Test 3, a solid culture medium configured by attaching a white semi-transparent film to a urethane culture medium body was used. In Test 4, a solid culture medium configured by painting the upper surface of a urethane culture medium body white was used. In Test 5, a conventional solid culture medium consisting only of a urethane culture medium body was used. In addition, the reflectance of the semi-transparent film provided in the solid medium used in Test 3 with respect to visible light was 60%, and the transmittance of visible light was 35%. Further, the light reflectances on the surface of the solid medium used in Tests 4 and 5, that is, on the upper surface of the urethane medium body, were 60% and 30%, respectively.

[0053] In each test, with the lower part of the solid medium immersed in the nutrient solution stored up to a water depth of 2 cm in a container (not shown), one seed of leaf lettuce was placed in the recess provided on the upper surface of the medium body, and cultivation was carried out for 10 days. On each day during the cultivation period, light was irradiated from a white LED (Light Emitting Diode) installed above the solid medium at 200 μmol / m 2 for 16 hours, and the light was turned off for 8 hours. Also, during the cultivation period, the temperature of the experimental environment was maintained at 23 ± 2°C, the humidity was maintained at 75 ± 10% RH, and the CO2 concentration was maintained at approximately 1500 ppm.

[0054] In each test, after 10 days of cultivation, the degree of algal growth on the surface of the solid medium was evaluated based on the coloring of the solid medium surface. Specifically, the closer the surface color was to white, the more the algal growth was suppressed, and the darker the green color was, the more algae had grown. Note that the degree of algal growth was evaluated according to the following four-level criteria A to D. A: The surface of the solid medium is white (algal growth is almost completely suppressed). B: The surface of the solid medium is slightly green, but no green colonies are observed. C: Green colonies are observed on the surface of the solid medium. D: The number of green colonies observed on the surface of the solid medium is remarkable. A colony is an area where algae have continuously grown on the surface of the solid medium and has a length of 1 mm or more. The experimental results are shown in Table 1 below.

[0055]

Table 1

[0056] From the above results, it was found that by using an opaque film having a reflectance of 90% or more and a transmittance of 2% or less with respect to visible light, the generation of algae on the surface of the solid medium can be effectively suppressed.

[0057] [Regarding Other Embodiments] So far, the solid medium of the present invention and the method for cultivating plants using the solid medium have been described. However, the above embodiments are merely examples, and other examples are also conceivable.

[0058] In the above embodiment, it was assumed that the opaque film 20 is attached to the medium main body 12 by the adhesive layer 30. However, the means for attaching (joining) the opaque film 20 to the medium main body 12 is not particularly limited. For example, the opaque film 20 may be attached to the medium main body 12 by heat fusion using a heat sealer and an ultrasonic welding machine without using an adhesive.

[0059] Also, in the above embodiment, it was assumed that the opaque film 20 has a white layer 22 and a black layer 24, and the white layer 22 is overlapped above the black layer 24 (in other words, the black layer 24 is disposed closer to the medium main body 12 than the white layer 22). However, it is not limited thereto. For example, the opaque film 20 may be a film that is white on both sides, has no black layer, and is composed only of the white layer. In this case, the upper surface 14 of the medium main body 12 is preferably a black surface. As a method for making the upper surface 14 of the medium main body 12 a black surface, a method of applying a black paint to the upper surface 14 may be used, or a method of forming the upper part of the medium main body 12 using a black material may also be used.

[0060] In the above-described embodiment, in the state where the opaque film 20 is attached to the culture medium main body 12, among the opaque film 20, the edge portion (adjacent edge portion 28) adjacent to the inner edge of the through-hole 26 is located inside the outer edge of the recess 16 and protrudes in a flange shape. However, the present invention is not limited to this, and as in the solid culture medium 10A shown in FIG. 7, at least a part of the adjacent edge portion 28 may be curved in an arc shape along the inner circumferential surface of the recess 16 and joined to the inner circumferential surface to cover the region. In this case, it is possible to avoid light from being irradiated to the region of the inner circumferential surface of the recess 16 where the adjacent edge portion 28 is joined, and effectively suppress the generation of algae in that region.

[0061] In the above-described embodiment, in a plan view, the entire inner edge of the through-hole 26 is located inside the outer edge of the recess 16, and the opaque film 20 is attached to the culture medium main body 12. However, the opaque film 20 may be attached to the culture medium main body 12 such that at least a part of the inner edge of the through-hole 26 is located inside the outer edge of the recess 16. In other words, the inner edge of the through-hole 26 may include a portion located outside the outer edge of the recess 16. However, from the viewpoint of more preferably achieving the effects of the present invention described above, it is preferable that 1 / 2 or more of the inner edge of the through-hole 26 is located inside the outer edge of the recess 16. More preferably, the entire inner edge is located inside the outer edge of the recess 16 as in the above-described embodiment.

Explanation of Reference Numerals

[0062] 10, 10A Solid culture medium 12 Culture medium main body 14 Upper surface 16 Recess 18 Notch 20 Opaque film 22 White layer 24 Black layer 26 Through-hole 28 Adjacent edge portion 30 Adhesive layer 32 Void 40 Culture medium sheet 42 Cutting line 44 Film web 46 stitches 48 base fabric 50 stitches

Claims

1. A solid medium for hydroponic cultivation, comprising: a medium body, and an opaque film disposed on the upper surface of the medium body, a recess formed by denting the upper surface and into which seeds or seedlings of plants can enter is provided in the medium body, in the opaque film, a through hole is provided at a position overlapping the recess when the solid medium is viewed from above, A solid medium in which at least a part of the inner edge of the through hole is located inside the outer edge of the recess.

2. The inner edge of the through hole and the outer edge of the recess are circular, The solid medium according to claim 1, wherein the diameter of the circle formed by the inner edge of the through hole is smaller than the diameter of the circle formed by the outer edge of the recess.

3. The solid medium according to claim 1, wherein the opaque film includes a white layer and a black layer disposed closer to the medium body side than the white layer.

4. The upper surface is a black surface, The solid medium according to claim 1, wherein the opaque film is a white film.

5. The solid medium according to claim 1, further having an adhesive layer between the medium body and the opaque film.

6. The solid medium according to claim 5, wherein a gap is formed between the adhesive layer and the opaque film.

7. The solid medium according to claim 1, wherein an opaque film having the same number of through holes as the recess provided in the upper surface is disposed on the upper surface of the medium body.

8. The solid medium according to claim 1, wherein at least a part of the edge portion adjacent to the inner edge of the through hole in the opaque film is joined to and covers the inner peripheral surface of the recess.

9. A method for cultivating a plant, comprising submerging the lower part of the solid medium according to any one of claims 1 to 8 in water or a nutrient solution and cultivating the plant by a hydroponic cultivation method.

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