Plant cultivation system, plant cultivation method

Abstract

Provided are a plant cultivation system and a plant cultivation method. By inhibiting the propagation of algae, the proliferation of bacteria in a nutrient solution can be inhibited. A plant cultivation system (1) has: a cultivation tank (21) that infuses a nutrient solution (61) to cultivate a plant (3); a storage tank (43) that stores the nutrient solution; a first drain path (45) that is connected to the cultivation tank to cause the nutrient solution to overflow at a prescribed water level and drain from the cultivation tank to the storage tank; a second drain path (47) that is connected to a vicinity of a bottom of the cultivation tank (21) to drain the nutrient solution (61) from the cultivation tank (21); a drain valve (49) that opens and closes the second drain path (47); a sterilization device (53) that is provided to a water supply path (55) of the nutrient solution (61) to perform sterilization processing on the nutrient solution (61) that is drained from the cultivation tank (21); and the water supply path (55) that supplies the nutrient solution (61) that has been subjected to the sterilization processing to the cultivation tank (21).

Description

Technical Field

[0001] The disclosed embodiments relate to plant cultivation systems and plant cultivation methods. Background Technology

[0002] Patent Document 1 describes a drain pipe structure for a nutrient solution tank that circulates the nutrient solution sequentially using a water supply pipe and a drain pipe. In this drain pipe structure, the drain pipe is configured to extend upward from the bottom wall of the nutrient solution tank, allowing the nutrient solution to overflow from its upper opening for drainage. Furthermore, a small hole is formed near the bottom wall that connects the inside and outside of the pipe, through which drainage also occurs.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2021-145569

[0004] In the aforementioned prior art, sufficient drainage cannot be achieved through the small holes. Therefore, it is difficult to suppress the growth of algae in the nutrient solution tank, which may lead to the proliferation of bacteria in the nutrient solution. Summary of the Invention

[0005] The present invention was made in view of such problems, and its object is to provide a plant cultivation system and method that can inhibit the proliferation of bacteria in nutrient solution by inhibiting the reproduction of algae.

[0006] To address the aforementioned issues, according to one aspect of the present invention, a plant cultivation system is provided, comprising: a cultivation trough for irrigating plants with nutrient solution; a storage tank for storing the nutrient solution; a first drainage path connected to the cultivation trough, allowing the nutrient solution to overflow from the cultivation trough to the storage tank at a predetermined water level; a second drainage path connected near the bottom of the cultivation trough for discharging the nutrient solution from the cultivation trough; a valve for opening and closing the second drainage path; a sterilization device disposed in the storage tank or the nutrient solution water path for sterilizing the nutrient solution discharged from the cultivation trough; and a water supply path for supplying the sterilized nutrient solution to the cultivation trough.

[0007] Furthermore, according to another aspect of the present invention, a plant cultivation method is applied, comprising: infusing a nutrient solution into a cultivation tank for cultivating plants; causing the nutrient solution in the cultivation tank to overflow and be discharged at a predetermined water level; discharging the nutrient solution from near the bottom of the cultivation tank; sterilizing the nutrient solution discharged from the cultivation tank; and supplying the sterilized nutrient solution to the cultivation tank.

[0008] Invention Effects

[0009] According to the plant cultivation system of the present invention, the proliferation of bacteria in the nutrient solution can be inhibited by inhibiting the reproduction of algae. Attached Figure Description

[0010] Figure 1 This is a diagram illustrating an example of the overall structure of a plant cultivation system according to an embodiment.

[0011] Figure 2 This is a diagram illustrating an example of plant flow in a plant cultivation system.

[0012] Figure 3 This is a perspective view showing an example of the structure of a cultivation shelf.

[0013] Figure 4 This is a diagram illustrating an example of the direction of plant flow in a cultivation shelf.

[0014] Figure 5 This is a side view showing an example of the overall structure of a cultivation shelf.

[0015] Figure 6 This is a perspective view showing an example of the overall structure of the transfer device.

[0016] Figure 7 This is an explanatory diagram showing an example of the nutrient solution supply and drainage structure of a plant cultivation system.

[0017] Figure 8 This is a top view showing an example of the structure of a cultivation trough, along with tracks, retaining devices, and plants.

[0018] Figure 9 This is a top view showing an example of the structure of a cultivation trough along with its tracks and holding devices.

[0019] Figure 10 This is a top view showing an example of the structure of a cultivation trough.

[0020] Figure 11 Is with Figure 10 The XI-XI section is equivalent to a cross-sectional view.

[0021] Figure 12 This illustrates an example of a structure that holds the device and the track together. Figure 8 A cross-sectional view corresponding to section XII-XII.

[0022] Figure 13 This is a flowchart illustrating an example of the processing steps performed by the control device.

[0023] Figure 14 This is a top view showing an example of the structure of a cultivation trough in a modified example where the second drainage channel is connected to the cultivation trough on the downstream side of the first drainage channel.

[0024] Figure 15 This is a top view showing an example of the structure of a cultivation trough in a modified example where the water supply line and the second drainage line are connected to the cultivation trough at a diagonal position.

[0025] Figure 16 This is a top view showing an example of the structure of a cultivation trough in a modified example that connects the second drainage channel to each water tank section.

[0026] Figure 17 Is with Figure 16 A sectional view corresponding to sections XVII-XVII.

[0027] Figure 18 This is a top view showing an example of the structure of a cultivation trough in a modified example that connects the first drainage channel, the second drainage channel, the water supply channel, and each water tank section.

[0028] Figure 19 This is a cross-sectional view showing an example of the structure of a downstream water tank in a modified example where an inclined section is provided at the bottom of the cultivation trough.

[0029] Figure 20 This is a top view showing an example of the structure of a downstream water tank in a modified example where the wall of the cultivation trough narrows toward the second drainage channel.

[0030] Figure 21 This is a top view showing an example of the structure of a cultivation trough in a modified example where a second drainage channel is also provided in the upstream side pool.

[0031] Figure 22 This is an explanatory diagram illustrating an example of the nutrient solution supply and drainage structure of a plant cultivation system in a modified example where a second drainage channel is also provided in the upstream pool.

[0032] Figure 23 This is a block diagram illustrating an example of the hardware structure of a control device.

[0033] Label Explanation

[0034] 1. Plant cultivation system

[0035] 3. Plants

[0036] 5. Holding device (an example of an accessory device)

[0037] 7. Cultivation shelves

[0038] 11. Transfer device (an example of an accessory device)

[0039] 21 Cultivation troughs

[0040] 21A Cultivation Trough

[0041] 21B Cultivation Trough

[0042] 23. Track (an example of a support device)

[0043] 43 Storage tank

[0044] 45. Drainage Channel 1

[0045] 47. Second Drainage Channel

[0046] 49. Drain valve (valve)

[0047] 51. Circulating pump (pump)

[0048] 53. Sterilization device

[0049] 55 Water supply line

[0050] 59. Control devices (first control device, second control device)

[0051] 61 Nutrient Solution

[0052] 65. Upstream side pool

[0053] 65a bottom

[0054] 67 Downstream side pool

[0055] 67a Bottom

[0056] 67c Wall

[0057] 67d Inclined section

[0058] 69 sink department

[0059] 95 Third Drainage Channel

[0060] 97 Drain valve Detailed Implementation

[0061] The embodiments will now be described with reference to the accompanying drawings. Furthermore, to facilitate the explanation of the various structures of the plant cultivation system, directions such as up, down, left, right, front, and back shown in the figures are sometimes appropriately used, but the orientation and position of each structure are not limited.

[0062] <1. Overall Structure of a Plant Cultivation System>

[0063] Reference Figure 1 and Figure 2 An example of the overall structure of the plant cultivation system of this embodiment will be described. Furthermore, in Figure 1 and Figure 2 The detailed diagrams of the individual components are omitted, and the overall structure of the system is shown schematically.

[0064] like Figure 1 and Figure 2As shown, the plant cultivation system 1 is a system in which a plant 3, the object of cultivation, is held in a holding device 5, and the holding device 5 is moved within a cultivation shelf 7 at predetermined intervals, thereby allowing the plant 3 to grow and be harvested. The plant 3 is, for example, a leafy vegetable. Alternatively, other plants besides vegetables, such as foliage plants, can also be cultivated.

[0065] The plant cultivation system 1 includes multiple holding devices 5, cultivation shelves 7, a loading device 9, a transfer device 11, a harvesting robot 13, and a unloading device 15. Within the cultivation shelves 7, the holding devices 5, which hold the plants 3, move at predetermined intervals, thereby allowing the plants 3 to grow. Furthermore, the plant cultivation system 1 may have multiple cultivation shelves 7, not just one.

[0066] like Figure 2 As shown, the loading device 9, for example, loads a holding device 5, which holds a plant 3 that has germinated from sown seeds, into the plant cultivation system 1. The loading device 9 is, for example, a conveyor. The holding device 5 loaded by the loading device 9 is transferred to the cultivation shelf 7 by a transfer device 11 located behind the cultivation shelf 7. Alternatively, the loading device 9 can also be an unmanned transport vehicle (AGV), for example, where an operator can use a trolley or the like to load the plant.

[0067] The transfer devices 11 are respectively arranged on the front and rear sides of the cultivation shelf 7. Each transfer device 11 transfers the holding device 5 from the shelf portion toward the shelf portion at both the front and rear ends of the cultivation shelf 7. In addition, the transfer device 11 arranged at the rear of the cultivation shelf 7 transfers the holding device 5, which is transported by the loading device 9 as described above, to the cultivation shelf 7. The transfer device 11 arranged at the front of the cultivation shelf 7 transfers the holding device 5, which holds the plant 3 growing in the cultivation shelf 7, to the harvesting robot 13.

[0068] like Figure 1 As shown, the harvesting robot 13 has a hand 17, which is used to hold the plant 3 and store it in a container 19. The container 19 is, for example, a plastic basket, a shipping container, etc.

[0069] The removal device 15 carries the container 19 containing the plant 3 and removes it from the plant cultivation system 1. The removal device 15 is, for example, an unmanned transport vehicle (AGV) that travels along a pre-set route to transport the container 19. Alternatively, the removal device 15 can also be a conveyor, or an operator can use a trolley or the like for removal.

[0070] <2. Structure of the cultivation shelf>

[0071] Reference Figures 2-5 An example of the structure of cultivation shelf 7 will be described.

[0072] like Figures 2-5 As shown, in the cultivation shelf 7, multiple layers (e.g., 8 layers) of shelf sections 7a are arranged in a multi-layered manner in the vertical direction. Figure 5 As shown, each shelf section 7a is equipped with a cultivation trough 21 for injecting nutrient solution to cultivate plants 3. Figures 2-4 (Illustration omitted). Multiple tracks 23 are arranged roughly horizontally along the front-to-back direction on the upper part of the cultivation trough 21. (See diagram). Figure 3 and Figure 4 As shown in the schematic diagram, multiple tracks 23 are arranged side by side in the left-right direction in each shelf section 7a, and the tracks 23 are configured to be approximately parallel.

[0073] The track 23 (an example of a support device) supports a plurality of retaining devices 5 so that they can move along the length direction (in this example, the front-back direction). The track 23 is configured to supply retaining devices 5 from one side in the front-back direction, thereby pushing and sliding other supported retaining devices 5 toward the other side in the front-back direction.

[0074] The number of shelves 7a in the cultivation shelf 7 is not particularly limited; however, in this embodiment, an example of 8 shelves will be described. Figure 3 and Figure 4 As shown, for ease of explanation, regarding the layers of the shelf section 7a of the cultivation shelf 7, the bottommost layer is appropriately referred to as layer A, the topmost layer as layer B, and the second to seventh layers from the top are collectively referred to as layer C. Layer A has one shelf section 7a, layer B has one shelf section 7a, and layer C has six shelf sections 7a. Figure 4 In the example shown, a relatively large number (e.g., 8) of tracks 23 are provided on shelf section 7a of layer A. A smaller number (e.g., 6) of tracks 23 are provided on shelf section 7a of layer B. A smaller number (e.g., 4) of tracks 23 are provided on shelf section 7a of layer C than on layer B.

[0075] like Figure 5 As shown, multiple light sources 25 for irradiating the plants 3 are provided above the shelf portion 7a of the cultivation shelf 7. Each light source 25 extends in the left-right direction and is disposed on the lower surface of a support plate 27, which is respectively disposed above each shelf portion 7a. The light sources 25 are arranged at predetermined intervals in the front-back direction. The type of light source 25 is not particularly limited, but in order to promote photosynthesis of the plants 3, LEDs, fluorescent lamps, etc., may be used.

[0076] Figure 2 and Figure 4 An example is shown of the direction of movement of the plant 3 (holding device 5) on each shelf portion 7a of the cultivation shelf 7. Additionally, Figure 4The symbol SY1 indicates the direction of movement of plant 3 from the front to the back, and the symbol SY2 indicates the opposite direction of movement of plant 3 from the back to the front. For example... Figure 2 and Figure 4 As shown, in layer A, plant 3 moves from the rear to the front in each track 23. In layer B, plant 3 moves from the front to the rear in each track 23. In layer C, in each layer, plant 3 moves from the rear to the front in each track 23.

[0077] The transfer device 11 located at the front of the cultivation shelf 7 performs the transfer (transplanting) of plants 3 (including holding device 5) from layer A to layer B, and the transfer (harvesting) of plants 3 from layer C to harvesting robot 13. During transplanting, the transfer device 11 also performs left-right allocation along with the vertical movement of the plants 3. Furthermore, the transfer device 11 located at the rear of the cultivation shelf 7 performs the transfer (transplanting) of plants 3 from the loading device 9 to layer A, and the transfer (transplanting) of plants 3 from layer B to layer C. During transplanting, the transfer device 11 also performs left-right allocation along with the vertical movement of the plants 3.

[0078] In the above movement path, as the plants are transferred in the order of layer A → layer B → layer C, the track spacing in the left and right directions gradually widens. This allows for dense cultivation in layer A (where the track spacing is narrowest) during the seedling stage, when the overall size of the plant 3 is smaller than that of the holding container 5. Then, the plants are moved in the order of layer B → layer C, with the track spacing gradually widening. This allows for increasing the track spacing according to the stages of significant growth of each plant 3. As a result, the entire area of ​​the cultivation shelf 7 can be efficiently utilized in the cultivation of the plant 3.

[0079] Furthermore, the structure of the cultivation shelf 7 described above is just one example and is not limited to the above. For example, the number of shelf sections 7a of the cultivation shelf 7 (the number of cultivation troughs 21 supported by the cultivation shelf 7) may be more than eight, or it may be an odd number. In addition, the multiple shelf sections 7a are not limited to being arranged side by side in the vertical direction, but may also be arranged side by side in the horizontal direction.

[0080] <3. Structure of the transfer device>

[0081] Reference Figure 6 An example of the structure of the transfer device 11 will be described. Additionally, in Figure 6 As an example, a transfer device 11 is shown positioned on the front side of the cultivation shelf 7; however, the transfer device 11 on the rear side has the same structure. Figure 6 In the center, the positive X-axis corresponds to the right, the negative X-axis corresponds to the left, the positive Y-axis corresponds to the back, the negative Y-axis corresponds to the front, the positive Z-axis corresponds to the top, and the negative Z-axis corresponds to the bottom.

[0082] like Figure 6 As shown, the transfer device 11 has a base 29, a gate-shaped support frame 31 disposed on the base 29, an actuator 33 disposed on the support frame 31, and a hand 35.

[0083] The support frame 31 has: a pair of columns 31a, which are arranged opposite each other in the X-axis direction on the base 29 along the Z-axis direction; and a generally horizontal beam 31b, which is erected on the upper end of the pair of columns 31a in the X-axis direction.

[0084] Actuator 33 has an X-axis unit 37, a Z-axis unit 39, and a Y-axis unit 41. X-axis unit 37 has a beam 37a, a slider 37b, and an X-axis motor 37c. Beam 37a is mounted generally horizontally between a pair of supports 31a in the X-axis direction. Slider 37b is movably supported on beam 37a in the X-axis direction. X-axis motor 37c is mounted, for example, at the left end of beam 37a, and drives slider 37b in the X-axis direction.

[0085] Z-axis unit 39 includes a beam 39a, a slider 39b, and a Z-axis motor 39c. The upper end of beam 39a is supported on beam 31b in a manner movably in the X-axis direction, and beam 39a is fixed to slider 37b. Slider 39b is movably supported on beam 39a in the Z-axis direction. Z-axis motor 39c is mounted, for example, on the lower end of beam 39a, and drives slider 39b in the Z-axis direction.

[0086] Y-axis unit 41 includes a beam 41a, a slider 41b, and a Y-axis motor 41c. Slider 41b is fixed to slider 39b. Beam 41a is supported by slider 41b to allow free movement in the Y-axis direction. Y-axis motor 41c is mounted, for example, at the front end of beam 41a and drives beam 41a in the Y-axis direction.

[0087] In actuator 33, when the slider 37b is driven in the X-axis direction by the X-axis motor 37c, the beam 39a moves in the X-axis direction, and consequently, the beam 41a moves in the X-axis direction. When the slider 39b is driven in the Z-axis direction by the Z-axis motor 39c, the beam 41a moves in the Z-axis direction. When the slider 41b and the beam 41a are driven relative to each other in the Y-axis direction by the Y-axis motor 41c, the beam 41a moves in the Y-axis direction. Thus, actuator 33 causes beam 41a to move in the three axial directions of the X, Y, and Z axes.

[0088] Hand 35 is mounted at the rear end of beam 41a of actuator 33 to hold the retaining device 5. Actuator 33 moves beam 41a in three axial directions, causing hand 35 to move in three directions: front-back (length direction of track 23), left-right (parallel arrangement direction of track 23), and up-down (stacked direction of shelf 7a, height direction).

[0089] During harvesting, the transfer device 11 removes the retaining device 5 holding the grown plant 3 from the track 23 of layer C and hands it over to the harvesting robot 13. At this time, the transfer device 11 holds the retaining device 5 located at the end of the track 23 from both sides with its hand 35 and pulls it out of the track 23. During transplanting, the transfer device 11 holds the retaining device 5 located at the end of the track 23 of the moving source from both sides with its hand 35 and pulls it out of the track 23. Then, the retaining device 5 held by the hand 35 is moved to the end of the track 23 at the moving destination and inserted into the track 23. At this time, the hand 35 pushes in by one pitch amount (the length of the retaining device 5 in the front-back direction) in the Y-axis direction (back-to-back direction) while holding the retaining device 5. As a result, the inserted retaining device 5 and the multiple retaining devices 5 supported on the track 23 can slide by one pitch amount. In this way, the transfer device 11 moves the entire column of multiple retaining devices 5 supported on the track 23 at the insertion destination of the retaining device 5 in the transport direction. After insertion, the hand 35 is released, releasing the grip of the retaining device 5. In addition, in the track 23 at the moving destination of the retaining device 5, before the retaining device 5 is inserted from one end, the retaining device 5 is pulled out from the other end, forming a gap of one pitch at the other end.

[0090] <4. Nutrient solution supply and drainage structure of plant cultivation system>

[0091] Reference Figure 7 An example of the nutrient solution supply and drainage structure of plant cultivation system 1 will be described.

[0092] like Figure 7 As shown, the plant cultivation system 1 includes a cultivation trough 21, a storage trough 43, a first drainage channel 45, a second drainage channel 47, a drainage valve 49, a circulation pump 51, a sterilization device 53, a water supply channel 55, a water supply valve 57, and a control device 59.

[0093] Cultivation troughs 21 are respectively provided on the eight shelf sections 7a constituting the aforementioned layers A, B, and C. Nutrient solution 61 is poured into each cultivation trough 21 and stored therein to cultivate plants 3, which are held by a movable holding device 5 supported by rails 23.

[0094] The storage tank 43 stores the nutrient solution discharged from the cultivation tank 21 through the first drainage channel 45 and the second drainage channel 47. The storage tank 43 is a tank that can temporarily store the nutrient solution, and it can also be composed of multiple tanks connected together.

[0095] One end of the first drainage channel 45 branches off and connects to each cultivation trough 21, while the other end converges and connects to the storage tank 43. The connection between the first drainage channel 45 and the cultivation trough 21 is configured to allow the nutrient solution 61 to overflow, thereby maintaining the water level in the cultivation trough 21 at a predetermined height (see below). Figure 11 Nutrient solution 61 in cultivation trough 21 is discharged to storage tank 43 via first drainage channel 45. Alternatively, the storage tank 43 side of the first drainage channel 45 may not be merged, and each cultivation trough 21 and storage tank 43 may be connected by a separate first drainage channel 45.

[0096] One end of the second drainage path 47 branches off and connects to the vicinity of the bottom of each cultivation trough 21, while the other end merges and connects to the storage tank 43. The nutrient solution 61 in the cultivation trough 21 is not discharged from the second drainage path 47 when the drain valve 49 is closed, but is discharged to the storage tank 43 via the second drainage path 47 when the drain valve 49 is open. The second drainage path 47 can also be configured to have a drainage capacity (e.g., cross-sectional area, length, gradient, etc.) greater than the water supply capacity of the circulation pump 51 via the water supply path 55. Alternatively, the storage tank 43 side of the second drainage path 47 can be connected to each cultivation trough 21 and the storage tank 43 using a separate second drainage path 47, without merging with the storage tank 43 side. Furthermore, the storage tank 43 side of the second drainage path 47 can also be configured to connect to the storage tank 43 via the first drainage path 45 (merging with the first drainage path 45). By merging the second drainage path 47 and the first drainage path 45, the total length of the piping can be shortened.

[0097] Drain valves 49 are respectively installed on multiple second drainage channels 47 after the branch, and open and close the second drainage channels 47 respectively. In addition, the drainage volume can also be adjusted by the opening degree of the drain valves 49. The opening and closing (including the opening degree) of the drain valves 49 is controlled by the control device 59.

[0098] A circulation pump 51 (an example of a pump) supplies nutrient solution 61 stored in the storage tank 43 to the cultivation tank 21 via a water supply line 55. The drive of the circulation pump 51 is controlled by a control device 59. For example, an inverter or similar device can be used to variably control the rotational speed (supply rate of nutrient solution 61) of the circulation pump 51. Furthermore, for example, multiple circulation pumps 51 can be provided for each cultivation tank 21. In this case, by making the rotational speed of each circulation pump 51 variable, the supply rate of nutrient solution 61 to each cultivation tank 21 can be adjusted.

[0099] A sterilization device 53 is installed in the water supply line 55 (an example of a water line) to sterilize the nutrient solution 61 discharged from the cultivation tank 21 via the first drainage line 45 and the second drainage line 47. The sterilization device 53 can perform sterilization by individually or in combination with any one of ozone, ultraviolet light, a catalyst, electrolyzed water, heating, or a chemical agent (such as hypochlorous acid). Furthermore, the sterilization device 53 can also remove and separate bacteria using a membrane (filter). In this case, it does not kill or inactivate bacteria, but it does remove and separate bacteria from the nutrient solution 61. Additionally, the location of the sterilization device 53 is not limited to the water supply line 55; it can also be installed in the storage tank 43 to sterilize the stored nutrient solution 61. Alternatively, a circulating water path for sterilization can be connected to the storage tank 43, and the sterilization device 53 can be installed in this circulating water path. The sterilization device 53 can also be installed midway through the first drainage path 45 or the second drainage path 47. The operation of the sterilization device 53 (e.g., the start or stop of sterilization) is controlled by the control device 59. Furthermore, the sterilization device 53 can also be operated by an operator.

[0100] One end of the water supply line 55 branches off and connects to each cultivation trough 21, while the other end converges and connects to the storage tank 43 via the sterilization device 53 and the circulation pump 51. The nutrient solution 61, sterilized by the sterilization device 53, is supplied to each cultivation trough 21 via the water supply line 55. Furthermore, the nutrient solution 61 is not supplied to cultivation troughs 21 where the water supply valve 57 is closed, but rather to cultivation troughs 21 where the water supply valve 57 is open.

[0101] Water supply valves 57 are respectively installed on multiple water supply lines 55 after the branch, and open and close the water supply lines 55 respectively. In addition, the water supply volume can also be adjusted by the opening degree of the water supply valves 57. The opening and closing (including the opening degree) of the water supply valves 57 is controlled by the control device 59.

[0102] Control device 59 (an example of the first control device and the second control device) controls the drain valve 49, circulation pump 51, sterilization device 53, water supply valve 57, etc. For example, the control is performed as follows: Control device 59 normally opens water supply valve 57 and closes drain valve 49, turns on sterilization device 53, and drives circulation pump 51. As a result, nutrient solution 61 supplied to cultivation tank 21 is poured into cultivation tank 21, discharged to storage tank 43 through first drainage path 45 for sterilization, and then supplied to cultivation tank 21 for circulation.

[0103] In the plant cultivation system 1, from a hygiene perspective, it is necessary to inhibit the proliferation of bacteria in the nutrient solution 61. Therefore, as described above, the nutrient solution 61 is sterilized while being circulated. However, the nutrient solution 61 discharged from the cultivation tank 21 via the first drainage channel 45 mainly becomes the supernatant, and therefore, the nutrient solution 61 tends to stagnate near the bottom of the cultivation tank 21. As a result, algae may grow. In particular, a light source 25 is provided on the cultivation shelf 7 to allow the plants 3 to grow, so algae easily proliferate in the illuminated portion of the cultivation tank 21. When algae proliferate in the nutrient solution 61, algae are more resistant to ultraviolet light, ozone, etc., used in the sterilization process than bacteria. Therefore, the sterilization process may not be able to adequately remove the proliferating algae. Furthermore, algae become a habitat for bacteria, and algae become an obstacle to the sterilization effect (e.g., reduced ozone consumption, reduced ultraviolet transmittance, etc.), thereby reducing the effectiveness of the sterilization process. Therefore, it may not be possible to adequately inhibit the proliferation of bacteria in the nutrient solution 61.

[0104] Therefore, the control device 59 opens the drain valve 49 at a preset time, discharging the nutrient solution 61 through the second drain path 47. This allows the nutrient solution 61 near the bottom of the cultivation tank 21 to be discharged, eliminating sedimentation. As a result, algae growth and bacterial proliferation are inhibited.

[0105] Furthermore, the control device 59 also controls the circulation pump 51 to supply nutrient solution 61 to the cultivation tank 21 when the drain valve 49 is opened. That is, the circulation pump 51 continues to operate even when draining from the second drain passage 47. As a result, nutrient solution 61 is continuously supplied to the cultivation tank 21 even when draining from the second drain passage 47, which can flush away the nutrient solution 61 near the bottom of the cultivation tank 21 and effectively eliminate the sedimentation of nutrient solution 61.

[0106] Furthermore, the control device 59 can also control the circulation pump 51 by increasing its rotational speed when the drain valve 49 is open, compared to when the drain valve 49 is closed (normally). In this case, the flow rate of the nutrient solution 61 flowing in the cultivation tank 21 can be increased compared to normal, thus further improving the effect of eliminating sedimentation of the nutrient solution 61.

[0107] Furthermore, the control device 59 controls the drain valves 49, each corresponding to one of the multiple cultivation troughs 21, to open at different times for each cultivation trough 21. This allows for drainage from the second drainage path 47 at different times for each cultivation trough 21, thus reducing the capacity of the storage tank 43, the circulation pump 51, and the output of the sterilization device 53 compared to drainage from multiple cultivation troughs 21 at once. As a result, the plant cultivation system can be miniaturized and its cost reduced.

[0108] Furthermore, the control device 59 can also perform the following control: opening the drain valve 49 at the time when the auxiliary equipment of the plant cultivation system 1 operates, as predetermined by the above-mentioned pre-set timing. "Auxiliary equipment" includes, for example, the transfer device 11 and the holding device 5. Specifically, the control device 59 can also perform the following control: opening the drain valve 49 at the time when the holding device 5 (plant 3) moves due to the operation of the transfer device 11. "The time when the holding device 5 moves" is, for example, when the transfer device 11 removes the holding device 5 from the end of the track 23 during transplanting or harvesting, or when the transfer device 11 inserts the holding device 5 into the end of the track 23. When the holding device 5 (plant 3) moves, flow occurs in the nutrient solution 61, flushing away impurities and sediments in the cultivation tank 21. Therefore, by discharging from the second drain 47 at the above-mentioned timing, impurities and sediments can be efficiently discharged.

[0109] Furthermore, the control device 59 can also adjust the timing interval for opening the drain valve 49 based on whether the auxiliary equipment of the plant cultivation system 1 is activated. For example, when the auxiliary equipment is not activated, it can discharge from the second drain 47 at regular intervals (e.g., every 15 minutes, every 30 minutes, etc.), and when the auxiliary equipment is activated, it can discharge at the timing corresponding to the activation, as described above. This effectively maintains the water quality of the nutrient solution 61 and improves the inhibition of algae growth and bacterial proliferation.

[0110] Furthermore, for example, a water quality meter for measuring the water quality of the nutrient solution 61 can be installed in the cultivation tank 21, the first drainage channel 45, or the storage tank 43, and the control device 59 can control the flow by opening the drain valve 49 at a predetermined time based on the measured water quality value. For example, turbidity, ultraviolet transmittance, electrical conductivity, pH (hydrogen ion concentration), BOD (biochemical oxygen demand), COD (chemical oxygen demand), DO (dissolved oxygen), SS (suspended solids), etc., can be measured, and the drain valve 49 can be opened when these measured values ​​are higher than (or lower than) a predetermined threshold.

[0111] <5. Structure of the cultivation trough>

[0112] Reference Figures 8-11 An example of the structure of cultivation trough 21 will be described. Figure 8 This is a top view showing an example of the structure of the cultivation trough 21 together with the track 23, the retaining device 5, and the plant 3. Figure 9 This is a top view showing an example of the structure of the cultivation trough 21 together with the track 23 and the holding device 5. Figure 10 This is a top view showing an example of the structure of the cultivation trough 21. Furthermore, Figure 11 Is with Figure 10 A cross-sectional view corresponding to section XI-XI. Additionally, in Figures 8-10 As an example, the structure of the cultivation trough 21 of layer C with 4 tracks 23 (water tanks) is shown. However, except for the number of tracks 23 (water tanks), the cultivation troughs 21 of layers A and B have the same structure.

[0113] like Figure 10 As shown, the cultivation trough 21 has an upstream water tank 65, a downstream water tank 67, and multiple water trough sections 69. The upstream water tank 65 is a generally rectangular, open-top water trough when viewed from above. A cylindrical pipe 71 is provided at the bottom 65a of the upstream water tank 65, extending upwards for a predetermined length through the bottom 65a. The pipe 71 is located, for example, near the rear end of the upstream water tank 65 at approximately the center in the left-right direction. A water supply passage 55 is connected to one end of the lower part of the pipe 71, through which nutrient solution 61 is supplied. According to the above structure, the water supply passage 55 is connected to the rear end of the cultivation trough 21 (an example of one end).

[0114] Furthermore, the connection method of the water supply line 55 to the cultivation trough 21 is not limited to the above-described method. For example, the water supply line 55 may also be connected to an opening formed at the bottom 65a of the upstream water tank 65, or it may be connected to the wall of the upstream water tank 65. In addition, the water supply line 55 may be laid in the upper part of the upstream water tank 65 to supply nutrient solution 61 from the top.

[0115] The downstream pool 67 is a roughly rectangular, open-topped trough when viewed from above. Figure 11As shown, a cylindrical pipe 63 is provided at the bottom 67a of the downstream water tank 67, extending upwards for a predetermined length through the bottom 67a. The pipe 63 is located, for example, near the front end, approximately to the right of the center position in the left-right direction of the downstream water tank 67. At the lower end of the pipe 63, a first drainage channel 45 is connected to one side. Nutrient solution 61 in the cultivation trough 21 overflows through the upper opening 63a of the pipe 63, thereby maintaining a predetermined water level, and flows out into the first drainage channel 45, discharging from the cultivation trough 21 into the storage tank 43. According to the above structure, the first drainage channel 45 is connected near the front end of the cultivation trough 21 (an example near the end of the other side).

[0116] Furthermore, the connection method of the first drainage channel 45 relative to the downstream pool 67 (the structure of the overflow section) is not limited to the above-described method. For example, it can also be configured such that a weir is formed by cutting off a part of the wall 67c of the downstream pool 67, so that the nutrient solution 61 overflowing from the weir flows into the first drainage channel 45.

[0117] Furthermore, an opening 67b is formed at the bottom 67a of the downstream water tank 67. The opening 67b is located near the front end, approximately to the left of the center of the downstream water tank 67, arranged side-by-side with the pipe 63 at a predetermined interval in the left-right direction. At the lower end of the opening 67b, the second drainage passage 47 is connected to one side. When the drain valve 49 is open, the nutrient solution 61 in the cultivation trough 21 is discharged from the cultivation trough 21 to the storage tank 43 via the second drainage passage 47. According to the above structure, the second drainage passage 47 is connected to the cultivation trough 21 at a position further forward than the center (an example of the other side). Furthermore, the location where the second drainage passage 47 connects to the cultivation trough 21 is not limited to the bottom 67a; it can be located, for example, near the bottom, such as the lower end of the wall 67c of the downstream water tank 67.

[0118] Multiple water troughs 69 are arranged side-by-side in a left-right direction, connecting the upstream water tank 65 and the downstream water tank 67. Each water trough 69 extends along the direction of movement of the plant 3 (in this example, the front-back direction) and is divided accordingly. Each water trough 69 is a rectangular water trough with an open top, for example, a long strip, viewed from above, and its two ends communicate with the upstream water tank 65 and the downstream water tank 67. Within the water trough 69, nutrient solution 61 is poured from the upstream water tank 65 toward the downstream water tank 67 in the direction of arrow 73. That is, in the cultivation trough 21, the rear side becomes the upstream side of the flow direction of the nutrient solution 61, and the front side becomes the downstream side of the flow direction of the nutrient solution 61. The same number of water troughs 69 are provided as the track 23. That is, the cultivation trough 21 in layer A is provided with, for example, 8 water tank sections 69, the cultivation trough 21 in layer B is provided with, for example, 6 water tank sections 69, and the cultivation trough 21 in layer C is provided with, for example, 4 water tank sections 69.

[0119] like Figure 9 As shown, a track 23 is provided on the upper part of each water tank section 69, and multiple retaining devices 5 are supported so that they can move in the front-to-back direction. Figure 8 and Figure 9 As shown, the retaining device 5 holds each plant 3 individually. Furthermore, in the plant cultivation system 1, one or more spacers are inserted between the retaining devices 5 according to the growth status of the plants 3, thereby adjusting the spacing of the retaining devices 5 in the front-to-back direction. Figure 8 and Figure 9 In the example shown, as spacers, such as components shared with the holding device 5, i.e., the holding devices 5 that are not holding the plant 3 in an empty state are inserted one by one between the holding devices 5 that hold the plant 3. According to the above structure, the second drainage channel 47 is connected to the area in the cultivation trough 21 where the track 23 is laid (an example of the area holding the plant 3) on the front side (an example of the other side).

[0120] <6. Maintain the structure of equipment and tracks>

[0121] Reference Figure 12 An example of the structure of the retaining device 5 and the track 23 will be described. Additionally, Figure 12 Is with Figure 8 A cross-sectional view corresponding to section XII-XII.

[0122] like Figure 12 As shown, the device 5 holds the plant 3 one plant at a time. That is, the device 5 and the plant 3 have a one-to-one relationship. Furthermore, "one plant" here refers to a single individual that has grown from a single seed. For example, as shown... Figure 12 As shown in plant 3, a plant in which multiple (or one) leaves 3b are supported by a stem 3a and aggregate into a single individual is a single plant. Furthermore, in the case where multiple stems 3a exist through branches, etc., and their roots 3c are connected and aggregate into a single individual, a plant in this manner is a single plant.

[0123] The retaining device 5 has a symmetrical shape in both the left-right and front-back directions. Therefore, the retaining device 5 has directional interchangeability, allowing it to be used in both the forward and reverse directions in the front-back direction (i.e., the direction of movement). The retaining device 5 is integrally molded from a material with high sliding properties (e.g., resin, or metal, etc.) and is configured to slide relative to the track 23 supporting the retaining device 5.

[0124] The retaining device 5 has a main body 75, a retaining cylinder 77, a hole 79, and a guide plate 81. The left and right edges of the main body 75 are held by the hands 35 of the transfer device 11. The retaining cylinder 77 is formed at the center of the main body 75 and has a hole 79 that extends vertically. The guide plate 81 is a pair of flat plate-shaped portions protruding upwards from the upper surface of the main body 75, arranged side-by-side at two locations in the left and right directions, separated by the upper opening of the hole 79. Furthermore, the retaining device 5 is not limited to being integrally formed and may be composed of multiple parts.

[0125] like Figure 12 As shown, the track 23 is disposed on the upper part of the water tank portion 69. The track 23 and the water tank portion 69 are integrally molded from a material with high sliding properties (e.g., resin, or metal). Alternatively, the track 23 and the water tank portion 69 can be composed of separate parts. The track 23 has a pair of upper track plates 23a extending in the front-rear direction, and a pair of lower track plates 23b extending in the front-rear direction below the upper track plates 23a. The main body 75 of the retaining device 5 is housed in the space 85 between the upper track plates 23a and the lower track plates 23b. The guide plate portion 81 of the retaining device 5 is housed between the pair of upper track plates 23a.

[0126] The water tank 69 has a pair of side wall portions 69a extending in the front-rear direction, and a bottom wall portion 69b extending in the front-rear direction across the lower ends of the pair of side wall portions 69a. The water tank 69 is an elongated water tank with a generally U-shaped cross-section that is open at the top, and it stores nutrient solution 61 inside.

[0127] The stem 3a of the plant 3, which grows from the seed in the culture medium 87, is held in place by the hole 79 of the holding device 5 filled with culture medium 87. The roots 3c of the plant 3 are immersed in the nutrient solution 61 in the water tank 69 through the lower opening of the hole 79, and the leaves 3b bulge upwards toward the track 23 through the upper opening of the hole 79 to grow. As the culture medium 87, a gel-like culture medium such as agar can be used, or a solid culture medium such as sponge, polyurethane, or asbestos can be used.

[0128] <7. Processing Steps of the Control Device>

[0129] Reference Figure 13 An example of a processing step (plant cultivation method) performed by control device 59 will be described.

[0130] In step S10, the control device 59 closes the drain valve 49 and opens the water supply valve 57. At this time, the drain valve 49 and water supply valve 57 corresponding to all the cultivation troughs 21 of the plant cultivation system 1 can be opened and closed. If only a part of the cultivation trough 21 is being irrigated with nutrient solution 61, the drain valve 49 and water supply valve 57 corresponding to only that part of the cultivation trough 21 can be opened and closed.

[0131] In step S20, the control device 59 drives the circulation pump 51 to supply the nutrient solution 61 stored in the storage tank 43 to the cultivation tank 21 via the water supply passage 55. Thus, the nutrient solution 61 is stored in the cultivation tank 21, and when it reaches the specified water level, it is discharged into the storage tank 43 via the first drainage passage 45 for circulation.

[0132] In step S30, the control device 59 begins sterilization using the sterilization device 53. Alternatively, if the sterilization device 53 is operated by an operator, step S30 is not required.

[0133] In step S40, the control device 59 determines whether a predetermined time has been reached to open any one of the drain valves 49 provided for the plurality of cultivation tanks 21. As described above, the predetermined time may be, for example, the time for the operation of the auxiliary equipment of the plant cultivation system 1, or a certain time interval (e.g., every 15 minutes, every 30 minutes, etc.). In addition, the predetermined time is set to be different for each cultivation tank 21. This step is repeated until the predetermined time is reached (step S40: No), and if the predetermined time is reached (step S40: Yes), the process proceeds to the next step S50.

[0134] In step S50, the control device 59 opens the drain valve 49 at a predetermined time for a specified period. As a result, the nutrient solution 61 in the cultivation tank 21 is discharged into the storage tank 43 via the second drain passage 47. The predetermined time is, for example, a time preset to discharge the entire amount of stored nutrient solution 61 based on the volume of the cultivation tank 21 and the drainage capacity of the second drain passage 47.

[0135] In step S60, the control device 59 determines whether to stop the plant cultivation system 1. For example, if the system is being maintained or the operator has performed a stop operation (step S60: Yes), the process ends. On the other hand, if no stop operation has been performed (step S60: No), the process returns to step S40 and repeats steps S40 to S60.

[0136] The processing steps described above are just one example. At least some of the steps can be deleted or modified, and steps other than those described above can be added. Furthermore, the order of at least some of the steps can be changed, or multiple steps can be combined into one step.

[0137] <8. Effects of the Implementation Method>

[0138] As described above, the plant cultivation system 1 of this embodiment includes: a cultivation trough 21, which is filled with nutrient solution 61 to cultivate plants 3; a storage tank 43, which stores the nutrient solution 61; a first drainage channel 45, which is connected to the cultivation trough 21 to allow the nutrient solution 61 to overflow from the cultivation trough 21 to the storage tank 43 at a predetermined water level; a second drainage channel 47, which is connected to the vicinity of the bottom of the cultivation trough 21 to discharge the nutrient solution 61 from the cultivation trough 21; a drain valve 49, which opens and closes the second drainage channel 47; a sterilization device 53, which is installed in the water supply channel 55 of the nutrient solution 61 to sterilize the nutrient solution 61 discharged from the cultivation trough 21; and a water supply channel 55, which supplies the sterilized nutrient solution 61 to the cultivation trough 21.

[0139] In the plant cultivation system 1, from a hygiene perspective, it is necessary to inhibit the proliferation of bacteria in the nutrient solution 61. Therefore, the nutrient solution 61 is sterilized while being circulated. However, the nutrient solution 61 discharged from the cultivation tank 21 via the first drainage channel 45 mainly becomes the supernatant, and thus, the nutrient solution 61 tends to stagnate near the bottom of the cultivation tank 21. When algae proliferate in the nutrient solution 61 due to stagnation, algae generally have higher tolerance to ultraviolet light and ozone used in the sterilization process than bacteria. Therefore, the sterilization process may not be able to adequately remove the proliferating algae. Consequently, algae become a habitat for bacteria, and algae become an obstacle to the sterilization effect (e.g., reduced ozone consumption, reduced ultraviolet transmittance, etc.), thus reducing the effectiveness of the sterilization process. Therefore, it may not be possible to adequately inhibit the proliferation of bacteria in the nutrient solution.

[0140] In this embodiment, a second drainage channel 47, which is opened and closed by a drain valve 49, is connected to the bottom of the cultivation tank 21. By opening the drain valve 49, the nutrient solution 61 near the bottom of the cultivation tank 21 can be discharged. This eliminates the sedimentation of the nutrient solution 61 in the cultivation tank 21 and inhibits the growth of algae that are highly resistant to sterilization treatment. As a result of inhibiting algae growth, the sterilization effect based on the sterilization device 53 is improved, and the proliferation of bacteria can be suppressed.

[0141] Alternatively, in this embodiment, the second drainage path 47 may be connected to the storage tank 43, and nutrient solution 61 may be discharged from the cultivation tank 21 to the storage tank 43. In this case, the sterilization device 53 may also sterilize the nutrient solution 61 discharged from the cultivation tank 21 via the first drainage path 45 and the second drainage path 47.

[0142] In this case, the nutrient solution 61 discharged from the second drainage channel 47 can be sterilized and recycled without being discharged outside the system, thus reducing the amount of new nutrient solution 61 supplied (reducing the amount of nutrient solution 61 wasted). Therefore, it can help save costs related to nutrient solution 61 and alleviate concerns about environmental impact.

[0143] In addition, in this embodiment, the plant cultivation system 1 may also include: a circulation pump 51 that supplies nutrient solution 61 stored in storage tank 43 to the cultivation tank 21 via a water supply passage 55; and a control device 59 that controls the circulation pump 51. In this case, the control device 59 may control the circulation pump 51 to supply nutrient solution 61 to the cultivation tank 21 when the drain valve 49 is closed, and also to supply nutrient solution 61 to the cultivation tank 21 when the drain valve 49 is open.

[0144] In this embodiment, when the drain valve 49 is closed, the nutrient solution 61 stored in the storage tank 43 is discharged from the cultivation tank 21 only through the first drain path 45, and the nutrient solution 61 is supplied to the cultivation tank 21 by the circulation pump 51, whereby the nutrient solution 61 is circulated. Furthermore, when the drain valve 49 is open and the nutrient solution 61 is discharged through the second drain path 47, the circulation pump 51 is maintained, continuously supplying the nutrient solution 61 to the cultivation tank 21. Therefore, compared to the case where the supply of nutrient solution 61 to the cultivation tank 21 stops when the nutrient solution 61 is discharged from the second drain path 47, the nutrient solution 61 near the bottom of the cultivation tank 21 can be flushed away, improving the effect of eliminating sedimentation of the nutrient solution 61. In addition, by adjusting the water supply and drainage volume, the drain valve 49 can be kept open at all times, continuously discharging nutrient solution 61 from both the first drain path 45 and the second drain path 47, and maintaining a constant water level. In this case, the nutrient solution 61 in the cultivation tank 21 can be completely replaced and circulated, thus preventing sedimentation and further enhancing the inhibitory effect on algae reproduction and bacterial proliferation.

[0145] Furthermore, in this embodiment, the plant cultivation system 1 may also be configured such that when the drain valve 49 is open, the supply of nutrient solution 61 increases compared to when the drain valve 49 is closed. For example, the control device 59 may also control the circulation pump 51 in such a way that when the drain valve 49 is open, the supply of nutrient solution 61 is increased compared to when the drain valve 49 is closed.

[0146] In this case, when the nutrient solution 61 is discharged through the second drainage channel 47, the flow rate of the nutrient solution 61 flowing in the cultivation tank 21 can be increased compared with the usual situation, thus further improving the effect of eliminating sedimentation of the nutrient solution 61.

[0147] Furthermore, in this embodiment, the second drainage path 47 may also be configured to have a drainage capacity greater than the water supply capacity of the circulation pump 51 via the water supply path 55.

[0148] In this case, when discharging through the second drainage channel 47, the water level in the cultivation tank 21 can be gradually lowered and all the nutrient solution 61 can be discharged without stopping the circulation pump 51 and continuously supplying it to the cultivation tank 21. Because the nutrient solution 61 can be continuously supplied and the cultivation tank 21 can be kept empty, impurities and other debris retained at the bottom can be flushed away, thus cleaning the cultivation tank 21 thoroughly.

[0149] In addition, in this embodiment, the water supply path 55 may also be connected to the vicinity of the end of one side (e.g., the rear side) of the cultivation trough 21, the first drainage path 45 may also be connected to the vicinity of the end of the other side (e.g., the front side) of the cultivation trough 21, and the second drainage path 47 may also be connected to the cultivation trough 21 at a position on the other side (e.g., the front side) of the cultivation trough 21, which is closer to the center.

[0150] Compared to the upstream side of the nutrient solution 61 flow direction, sedimentation of the nutrient solution 61 is more likely to occur in the cultivation tank 21 on the downstream side. In this embodiment, the nutrient solution 61 supplied to the cultivation tank 21 flows from one side (e.g., the rear side) to the other side (e.g., the front side) and is discharged from the first drainage channel 45. By connecting the second drainage channel 47 to the cultivation tank 21 on the side opposite to the center (e.g., the front side), the nutrient solution 61 near the bottom of the cultivation tank 21 can be discharged at a position downstream of the nutrient solution 61 flow direction. This effectively eliminates sedimentation of the nutrient solution 61.

[0151] In addition, in this embodiment, the second drainage channel 47 may also be connected to a position in the cultivation trough 21 on the other side (e.g., the front side) than the area where the plant 3 is held.

[0152] In the area of ​​the cultivation tank 21 where the plant 3 is held, impurities can easily accumulate, such as due to the sinking of roots, leaves, or other parts of the plant 3 into the nutrient solution 61. Therefore, downstream of this area, impurities transported by the flow of the nutrient solution 61 tend to settle. In this embodiment, the nutrient solution 61 near the bottom of the cultivation tank 21 can be discharged downstream of the area where the plant 3 is held. This effectively removes sediment and improves the water quality of the nutrient solution 61.

[0153] In addition, in this embodiment, the plant cultivation system 1 may also have a cultivation shelf 7 that supports multiple cultivation troughs 21. In this case, the second drainage path 47 may be connected to the multiple cultivation troughs 21 respectively, and the drainage valves 49 may be respectively provided in the multiple second drainage paths 47.

[0154] In this case, for example, the nutrient solution 61 can be discharged according to the time difference set for each cultivation tank 21, thus reducing the capacity of the storage tank 43.

[0155] In addition, in this embodiment, the plant cultivation system 1 may also have a control device 59 for controlling the opening and closing of the drain valve 49. In this case, the control device 59 may also control the drain valve 49 to be closed under normal conditions and to be opened at a predetermined time.

[0156] In this case, the opening time of the drain valve 49 can be adjusted so that discharge does not occur from the second drain 47 under normal circumstances, but is discharged from the second drain 47 when the probability of discharging impurities is high. As a result, the water quality of the nutrient solution 61 can be improved, and the inhibition effect on algae reproduction and bacterial proliferation can be enhanced.

[0157] In addition, in this embodiment, the control device 59 can also control the drain valve 49 to open at different times for each cultivation trough 21.

[0158] For example, if the nutrient solution 61 of multiple cultivation tanks 21 is discharged at one time and stored in the storage tank 43, the necessary capacity increases, resulting in a larger storage tank 43. In this embodiment, the nutrient solution 61 is discharged at different times for each cultivation tank 21, thus reducing the capacity of the storage tank 43, the circulation pump 51, and the output of the sterilization device 53. As a result, the plant cultivation system 1 can be miniaturized and cost-effective.

[0159] In addition, in this embodiment, the control device 59 can also control the drain valve 49 to open at a timed interval when the auxiliary equipment of the plant cultivation system 1 is activated.

[0160] In the plant cultivation system 1, when the auxiliary equipment operates, the plant 3 moves within the cultivation tank 21. As the plant 3 moves, flow occurs in the nutrient solution 61, flushing away impurities and sediments within the cultivation tank 21, increasing the likelihood of discharge through the second drainage channel 47. In this embodiment, discharge is performed at the timing of the auxiliary equipment's operation through the second drainage channel 47, thus efficiently removing impurities and sediments. Therefore, the water quality of the nutrient solution 61 is improved, enhancing the inhibition of algae growth and bacterial proliferation.

[0161] In addition, in this embodiment, the plant cultivation system 1 may also include: a plurality of holding devices 5 that hold the plants 3; and a track 23 disposed on the upper part of the cultivation trough 21 to support the plurality of holding devices 5 so that they can move. In this case, the control device 59 may also control the drain valve 49 to open at a time when the holding devices 5 move.

[0162] When the holding device 5 moves, flow occurs in the nutrient solution 61 into which the roots of the plant 3 are immersed. Impurities and sediments in the water tank 69 of the cultivation trough 21 are flushed downstream to the water pool 67, increasing the likelihood that they can be discharged through the second drainage channel 47. In this embodiment, discharge is performed through the second drainage channel 47 at regular intervals as the holding device 5 moves, thus efficiently removing impurities and sediments. Therefore, the water quality of the nutrient solution 61 can be improved, enhancing the inhibition effect on algae growth and bacterial proliferation.

[0163] In addition, in this embodiment, the plant cultivation system 1 may also have a transfer device 11, which removes the holding device 5 from the end of the track 23 and transfers it to another track 23. In this case, the control device 59 may also control the drain valve 49 at the timing when the transfer device 11 removes the holding device 5 from the track 23.

[0164] When the holding device 5 is removed from the end of the track 23, impurities and sediments in the water tank 69 are flushed into the downstream water pool 67, increasing the likelihood that they can be discharged through the second drainage channel 47. In this embodiment, discharge is performed through the second drainage channel 47 at the time when the transfer device 11 removes the holding device 5 from the track 23, thus efficiently discharging impurities and sediments. Therefore, the water quality of the nutrient solution 61 can be improved, and the inhibitory effect on algae reproduction and bacterial proliferation can be enhanced.

[0165] Furthermore, in this embodiment, the control device 59 can also change the timing interval for opening the drain valve 49 based on whether the auxiliary equipment is activated.

[0166] In this case, for example, discharge can be made from the second drainage channel 47 at certain time intervals when the auxiliary equipment is not in operation, and discharge can be made at timed intervals corresponding to the operation of the auxiliary equipment. As a result, the water quality of the nutrient solution 61 can be well maintained, and the inhibition effect of algae reproduction and bacterial proliferation can be improved.

[0167] <9. Variations>

[0168] The disclosed implementation methods are not limited to those described above, and various modifications can be made without departing from their main idea and technical concept. Examples of such modifications will be described below.

[0169] (9-1. The case where the second drainage channel is connected to a point downstream of the first drainage channel)

[0170] For example, the second drainage channel 47 can be connected to the cultivation trough 21 at a position downstream of the first drainage channel 45.

[0171] Figure 14 An example of the structure of the cultivation trough 21 in this modified example is shown. For example... Figure 14 As shown, a pipe 63 is installed at approximately the center position of the bottom 67a of the downstream water tank 67 in both the left-right and front-back directions. An opening 67b is formed near the front end of the pipe 63 at approximately the center position in the left-right direction. That is, the opening 67b is located on the downstream side of the pipe 63 (in this example, the front side; another example is on the other side). A first drainage passage 45 is connected to the lower part of the pipe 63, and a second drainage passage 47 is connected to the opening 67b.

[0172] According to this modified example, the nutrient solution 61 is discharged from the bottom via the second drainage channel 47 at a position further downstream than the connection point of the first drainage channel 45. Therefore, the entire cultivation tank 21 can easily discharge the nutrient solution 61. This further improves the effect of eliminating sedimentation.

[0173] (9-2. The case where the water supply line and the second drainage line are connected to the diagonal position of the cultivation trough)

[0174] For example, the water supply line 55 and the second drainage line 47 can be connected to the vicinity of one corner on one side and the other corner on the other side of the cultivation trough 21, respectively.

[0175] Figure 15 An example of the structure of the cultivation trough 21 in this modified example is shown. For example... Figure 15 As shown, the cultivation trough 21 is configured with a rectangular upstream water tank 65 and a rectangular downstream water tank 67 connected by multiple water tank sections 69, forming an overall roughly rectangular shape. A pipe 71 is provided near, for example, the left rear corner (an example of a corner on one side) of the upstream water tank 65. A water supply passage 55 is connected to the pipe 71. An opening 67b is formed near, for example, the right front corner (an example of a corner on the other side) of the downstream water tank 67. A second drainage passage 47 is connected to the opening 67b. The location of the pipe 63 connected to the first drainage passage 45 is not particularly limited, but it is typically located approximately at the center of the downstream water tank 67.

[0176] According to this modified example, nutrient solution 61 is supplied near one corner of the diagonal position in the cultivation tank 21, and nutrient solution 61 is discharged at the bottom near the other corner of the diagonal position. Therefore, the nutrient solution 61 can be flushed away from the entire cultivation tank 21. This further improves the sediment removal effect.

[0177] (9-3. Connection of the second drainage channel to each water tank section)

[0178] In the above embodiment, the cultivation trough 21 is configured such that an upstream water tank 65 and a downstream water tank 67 are connected by a plurality of water tank sections 69, and the downstream water tank 67 is connected to a first drainage passage 45 and a second drainage passage 47. However, the structure of the cultivation trough 21 is not limited to the above-described manner. For example, it may be configured such that the downstream water tank 67 is not provided, and the second drainage passage 47 is connected to the plurality of water tank sections 69 respectively.

[0179] Figure 16 and Figure 17 An example of the structure of the cultivation trough 21A in this modified example is shown. Figure 16 This is a top view showing an example of the overall structure of the cultivation trough 21A. Figure 17 Is with Figure 16 A sectional view corresponding to sections XVII-XVII. Additionally, in Figure 16 and Figure 17 As an example, the structure of a cultivation trough 21A with a C layer having four water tank sections 69 is illustrated. However, apart from the different number of water tank sections 69, the cultivation troughs 21A with A layer and B layer can also be designed with the same structure.

[0180] like Figure 16 As shown, the cultivation trough 21A has an upstream water tank 65, multiple water tank sections 69, and a water guide pipe 89. Figure 16 and Figure 17 As shown, a weir 91 is formed at the downstream end (front end in this example) of each water tank 69. The nutrient solution 61 within the water tank 69 overflows from the upper end of the weir 91, thereby maintaining a predetermined water level and flowing out through the guide pipe 89. The guide pipe 89 is a semi-cylindrical component with an open upper portion, and its lower end (not shown) is connected to the first drainage channel 45. The nutrient solution 61 flowing out of the guide pipe 89 is discharged into the storage tank 43 via the first drainage channel 45.

[0181] Near the downstream end of each water tank 69, a dam section 93, for example, widening in the left-right direction, is provided. Nutrient solution 61, blocked by the dam section 91, is retained in the dam section 93. A track 23 is provided in the area from the rear end of the water tank 69 to the rear side of the dam section 93, with the top of the dam section 93 open. Figure 17 As shown, an opening 93b is formed at the bottom 93a of the dam section 93, and the lower part of the opening 93b is connected to one end of a second drainage channel 47. Thus, the second drainage channel 47 is connected to a plurality of water tank sections 69. Furthermore, drain valves 49 are respectively provided in the plurality of second drainage channels 47. When the drain valves 49 are opened, the nutrient solution 61 in each water tank section 69 is discharged into the storage tank 43 via the second drainage channel 47.

[0182] According to this modified example, the downstream pool where the water tanks 69 converge at the downstream side can be omitted from the cultivation trough, thus enabling the cultivation trough 21A to be miniaturized. Consequently, the plant cultivation system 1 can be miniaturized. Furthermore, nutrient solution 61 can be discharged for each water tank 69, thus allowing for localized discharge, for example, only for water tanks 69 in the cultivation trough 21A that are heavily soiled. In addition, by setting a time difference for discharging nutrient solution 61 for each water tank 69, the capacity of the storage tank 43 can be further reduced.

[0183] (9-4. Connection of the first drainage line, the second drainage line, the water supply line, and each water tank section)

[0184] For example, it can also be configured so that there are no upstream water tank 65 and downstream water tank 67, but multiple water tanks 69 are respectively connected to the first drainage channel 45, the second drainage channel 47 and the water supply channel 55.

[0185] Figure 18 An example of the structure of the cultivation trough 21B in this modified example is shown. For example... Figure 18 As shown, the cultivation trough 21B has multiple water tank sections 69. At the upstream end (rear end in this example) of each water tank section 69, a water supply section 99 that widens in the left-right direction is provided. A cylindrical pipe 71 is provided in the water supply section 99 and connected to one end of the water supply passage 55, through which nutrient solution 61 is supplied.

[0186] Each water tank 69 has a dammed section 93, for example, widened in the left-right direction, at its downstream end (front side in this example). Nutrient solution 61 is retained in the dammed section 93. A track 23 is provided in the area from the front side of the water supply section 99 to the rear side of the dammed section 93, with the water supply section 99 and the dammed section 93 open above each other. An opening 93b is formed at the bottom 93a of the dammed section 93, and the lower part of the opening 93b is connected to one end of a second drainage channel 47. Furthermore, a pipe 63 connected to a first drainage channel 45 is provided in the dammed section 93. Thus, the nutrient solution 61 in the water tank 69 overflows at the upper opening 63a of the pipe 63, thereby maintaining a predetermined water level and flowing out into the first drainage channel 45, discharging from the water tank 69 into the storage tank 43. Drain valves 49 are respectively provided in the second drainage channels 47 connected to each dammed section 93. The drain valve 49 is opened, thereby discharging the nutrient solution 61 in each water tank 69 into the storage tank 43 via the second drain passage 47.

[0187] According to this modified example, both the upstream and downstream water tanks can be omitted from the cultivation trough, thus enabling the cultivation trough 21B to be miniaturized. Consequently, the plant cultivation system 1 can be miniaturized. Furthermore, nutrient solution 61 can be supplied or discharged to each water tank section 69, thus, for example, nutrient solution 61 can be supplied only to the necessary water tank sections 69 in the cultivation trough 21B, or discharged only to the heavily soiled water tank sections 69, enabling localized water supply and drainage.

[0188] (9-5. Case where an inclined section is provided at the bottom of the cultivation trough)

[0189] For example, an inclined section can be provided at the bottom of the cultivation trough 21, and the second drainage channel 47 can be connected to the lowest position of the inclined section.

[0190] Figure 19 An example of the structure of the downstream water tank 67 of the cultivation trough 21 in this modified example is shown. Additionally, in Figure 19 The diagram of the first drainage channel 45 and the pipe 63 connected to the first drainage channel 45 is omitted. Figure 19 As shown, the bottom 67a of the downstream pool 67 has an inclined portion 67d, for example, whose height decreases towards the center side in the left-right direction. An opening 67b is formed at approximately the center position in the left-right direction of the bottom 67a. A second drainage channel 47 is connected to the opening 67b. According to this structure, the second drainage channel 47 is connected to the lowermost position of the inclined portion 67d.

[0191] According to this modified example, the nutrient solution 61 flows naturally toward the second drainage channel 47 due to gravity, thus enabling efficient discharge of the nutrient solution through the second drainage channel 47. Furthermore, algae, impurities, and other debris that easily settle at the bottom of the cultivation tank 21 can be effectively collected and discharged together with the nutrient solution 61.

[0192] (9-6. Case where the cultivation trough has a wall that narrows towards the second drainage channel)

[0193] For example, the cultivation trough 21 may be provided with a wall that narrows towards the connection point of the second drainage channel 47.

[0194] Figure 20 This illustrates an example of the structure of the downstream water tank 67 in the cultivation trough 21 of this modification. For example... Figure 20 As shown, the downstream pool 67 has a wall 67c, which narrows at the connection point (opening 67b) of the nutrient solution 61 flow path toward the second drainage channel 47. Furthermore, the shape of the wall 67c is not limited to... Figure 20 The approximate triangular shape shown can be, for example, a trapezoidal shape, an arc shape, or a shape in which the flow path narrows towards the opening 67b.

[0195] According to this modified example, the flow of nutrient solution 61 can be guided to the second drainage channel 47, thus enabling efficient discharge of nutrient solution 61 via the second drainage channel 47. Furthermore, by increasing the flow rate of nutrient solution 61, the sediment removal effect can be further improved. In addition, algae, impurities, etc., that easily settle at the bottom of the cultivation tank 21 can be effectively collected and discharged together with the nutrient solution 61.

[0196] (9-7. The case where a drainage channel is also installed in the upstream pool)

[0197] In the above embodiment, the first drainage path 45 and the second drainage path 47 are connected to the downstream side water tank 67 of the cultivation trough 21. However, in addition to the downstream side water tank 67, a drainage path may also be connected to the upstream side water tank 65.

[0198] Figure 21 An example of the structure of the cultivation trough 21 in this modified example is shown. For example... Figure 21 As shown, an opening 65b is formed approximately at the center in the left-right direction near, for example, the front end of the bottom 65a of the upstream pool 65. A third drainage passage 95 (see below) is connected to the lower part of the opening 65b. Figure 22 The end of one side of the cultivation trough 21. According to the above structure, the third drainage channel 95 is connected to a position in the cultivation trough 21 that is further back (one side) than the area where the track 23 is laid (an example of the area where the plant 3 is held). Furthermore, the location where the third drainage channel 95 connects to the upstream water tank 65 is not limited to the bottom 65a; for example, it can be near the bottom, such as the lower end of the wall of the upstream water tank 65. Other structures of the cultivation trough 21 are the same as those described in the aforementioned embodiment (…). Figure 10 Since they are the same, the explanation is omitted.

[0199] Figure 22 This illustrates an example of the nutrient solution supply and drainage structure of the plant cultivation system 1 in this modified example. For example... Figure 22 As shown, one end of the third drainage channel 95 branches off and connects to the bottom of each cultivation trough 21 on the upstream side, while the other end merges and connects to the storage tank 43. The nutrient solution 61 in the cultivation trough 21 (especially the upstream water tank 65) is not discharged from the third drainage channel 95 when the drainage valve 97 is closed, but is discharged to the storage tank 43 via the third drainage channel 95 when the drainage valve 97 is open. Alternatively, the storage tank 43 side of the third drainage channel 95 may not merge, and separate third drainage channels 95 may be used to connect each cultivation trough 21 and the storage tank 43. Drainage valves 97 are respectively provided on the multiple branched third drainage channels 95, allowing for the opening and closing of each third drainage channel 95. The drainage volume can also be adjusted by the opening degree of the drainage valves 97. The opening and closing (including the opening degree) of the drainage valves 97 is controlled by the control device 59.

[0200] According to this modified example, in addition to discharging the nutrient solution 61 from the bottom of the cultivation tank 21 on the downstream side of the area where the plant 3 is held, the nutrient solution 61 can also be discharged from the bottom of the cultivation tank 21 on the upstream side of the area where the plant 3 is held. As a result, impurities and sediments generated on the upstream side of the cultivation tank 21 can be discharged, which can further improve the inhibitory effect on algae reproduction and bacterial proliferation.

[0201] (9-8. Others)

[0202] The above describes the scenario where drainage from the second drainage path 47 is stored in the storage tank 43 and circulated. However, for example, drainage from the first drainage path 45 can also be stored in the storage tank 43 and circulated, while drainage from the second drainage path 47 is discharged outside the plant cultivation system 1. Alternatively, the destination of drainage from the second drainage path 47 can be switched to either the storage tank 43 or outside the system. Thus, drainage from the second drainage path 47, which is dirtier than drainage from the first drainage path 45, can be discharged outside the system, thereby further improving the water quality of the nutrient solution 61.

[0203] Alternatively, the nutrient solution 61 can be stored in the cultivation tank 21 without being circulated normally, and if necessary, the drain valve 49 can be opened to discharge it into the storage tank 43 via the second drain passage 47.

[0204] Furthermore, the above describes the situation where the plant 3 is held in place by the holding device 5, moving along the track 23 provided on the cultivation trough 21 and growing. However, it is also possible to configure the plant 3 to be placed without moving it. For example, a system can be configured such that multiple plants 3 are held in place by a holding device such as a tray, and the holding device is placed on the upper part of the cultivation trough 21 for a specified period of time, thereby allowing them to grow.

[0205] <10. Example of Hardware Structure of Control Device>

[0206] Reference Figure 23 An example of the hardware structure of the control device 59 will be described. Additionally, in... Figure 23 The diagrams omitted the structures related to the function of supplying power to the motor (omitted) of the circulating pump 51.

[0207] like Figure 23 As shown, the control device 59 includes, for example, a CPU 901, a ROM 903, RAM 905, an ASIC or FPGA, an application-specific integrated circuit 907, an input device 913, an output device 915, a recording device 917, a driver 919, a connection port 921, and a communication device 923. These structures are connected to each other via a bus 909 and an input / output interface 911 in a manner that enables signal transmission.

[0208] The program can be pre-recorded in a recording device such as ROM 903, RAM 905, or hard disk 917.

[0209] The program can also be temporarily or non-temporarily (permanently) recorded on a removable recording medium 925 such as a floppy disk, various CD / MO disks, DVDs, or semiconductor memory. This recording medium 925 can also be provided as so-called packaged software. In this case, the program recorded on these recording media 925 can also be read by the drive 919 and recorded in the recording device 917 via the input / output interface 911, bus 909, etc.

[0210] The program can also be pre-recorded on a download site, other computer, other recording device, etc. (not shown). In this case, the program is transmitted via a network NW such as a LAN or the Internet, and the communication device 923 receives the program. Moreover, the program received by the communication device 923 can also be recorded in the aforementioned recording device 917 via the input / output interface 911, bus 909, etc.

[0211] The program can also be pre-recorded on a suitable external connection device 927. In this case, the program can also be transferred via a suitable connection port 921 and recorded in the recording device 917 via an input / output interface 911, bus 909, etc.

[0212] CPU 901 executes various processes according to the program recorded in the recording device 917, thereby realizing the above-mentioned... Figure 13 The control content shown is as follows. For example, the CPU 901 can directly read the program from the recording device 917 and execute it, or it can temporarily load it into the RAM 905 and then execute it. For example, when the CPU 901 receives a program via the communication device 923, the driver 919, or the connection port 921, it can also directly execute the received program without recording it in the recording device 917.

[0213] CPU 901 can also perform various processing as needed, for example, based on signals and information input from input devices 913 such as mouse, keyboard, microphone (not shown).

[0214] CPU 901 may output the results of the above processing from output devices such as display devices and voice output devices 915. CPU 901 may also send the processing results via communication device 923 or connection port 921 as needed. CPU 901 may also record the processing results in the above-mentioned recording device 917 or recording medium 925.

[0215] In the above explanation, the use of terms such as "perpendicular," "parallel," and "plane" does not imply a strict interpretation. These terms allow for design and manufacturing tolerances and errors, meaning "substantially perpendicular," "substantially parallel," and "substantially plane," respectively.

[0216] In the above explanation, when there are descriptions of appearance such as "same," "identical," "equal," or "different," these descriptions are not strictly defined. These terms allow for design and manufacturing tolerances and errors, and mean "substantially the same," "substantially identical," "substantially equal," or "substantially different."

[0217] For example, in the presence of a threshold (refer to) Figure 13 When the flowchart, benchmark value, etc., are recorded as the value or division value that serves as the prescribed judgment benchmark, the difference between their "same", "equal", "different" and other terms is a strict meaning.

[0218] In addition to those already described above, methods based on the above embodiments and variations can also be appropriately combined and utilized. Furthermore, although not all examples have been given, the above embodiments and variations can be implemented with various modifications without departing from their spirit.

[0219] The problems and effects to be solved by the above-described embodiments and modifications are not limited to those described above. Through the embodiments and modifications, problems not described above can also be solved and effects not described above can be achieved. Sometimes, only a part of the described problems are solved, or only a part of the described effects are achieved.

Claims

1. A plant cultivation system, comprising: A cultivation trough, which is filled with nutrient solution to cultivate plants; A storage tank for storing the nutrient solution; The first drainage channel is connected to the cultivation tank, allowing the nutrient solution to overflow from the cultivation tank to the storage tank at a specified water level. The second drainage channel is connected to the vicinity of the bottom of the cultivation trough and discharges the nutrient solution from the cultivation trough; A valve that opens and closes the second drainage path; A sterilization device is installed in the storage tank or the water path of the nutrient solution to sterilize the nutrient solution discharged from the cultivation tank. The water supply system supplies the nutrient solution, which has undergone the sterilization treatment, to the cultivation tank. The second control device controls the opening and closing of the valve; Multiple holding devices that hold the plant; and A support device, disposed on the upper part of the cultivation trough, supports the plurality of retaining devices so that they can move. The second control device controls the valve to be closed under normal conditions and to be opened at a predetermined time, so that the nutrient solution is discharged from the second drain at the time when the holding device is moved.

2. The plant cultivation system according to claim 1, wherein, The second drainage channel is connected to the storage tank, and discharges the nutrient solution from the cultivation tank to the storage tank. The sterilization device sterilizes the nutrient solution discharged from the cultivation tank via the first drainage channel and the second drainage channel.

3. The plant cultivation system according to claim 1, wherein, The plant cultivation system also has: A pump, which supplies the nutrient solution stored in the storage tank to the cultivation tank via the water supply line; and A first control device controls the pump. The first control device controls the pump to supply the nutrient solution to the cultivation tank when the valve is closed, and also controls the pump to supply the nutrient solution to the cultivation tank when the valve is open.

4. The plant cultivation system according to claim 3, wherein, The plant cultivation system is configured such that when the valve is open, the supply of nutrient solution to the cultivation tank is increased compared to when the valve is closed.

5. The plant cultivation system according to claim 4, wherein, The first control device controls the pump in such a way that when the valve is open, the supply of the nutrient solution is increased compared to when the valve is closed.

6. The plant cultivation system according to any one of claims 3 to 5, wherein, The second drainage path is configured to have a drainage capacity greater than the water supply capacity of the pump via the water supply path.

7. The plant cultivation system according to claim 1, wherein, The water supply line is connected to one end of the cultivation trough. The first drainage channel is connected to the vicinity of the other end of the cultivation trough. The second drainage channel is connected to the cultivation trough at a position on the other side of the central part.

8. The plant cultivation system according to claim 7, wherein, The second drainage channel is connected to the cultivation trough at a position on the other side of the area where the plant is held.

9. The plant cultivation system according to claim 7 or 8, wherein, The second drainage channel is connected to a position on the other side of the first drainage channel.

10. The plant cultivation system according to claim 7 or 8, wherein, The cultivation trough is shaped like a quadrilateral when viewed from above. The water supply path and the second drainage path are respectively connected to the vicinity of one corner on one side and the other corner on the other side of the cultivation trough.

11. The plant cultivation system according to any one of claims 1 to 5, wherein, The plant cultivation system also includes cultivation shelves that support multiple cultivation troughs. The second drainage channel is connected to each of the plurality of cultivation troughs. The valves are respectively installed in multiple of the second drainage channels.

12. The plant cultivation system according to any one of claims 1 to 5, wherein, The cultivation trough has multiple water tank sections extending along the direction of plant movement and being divided into them. The second drainage channel is connected to each of the plurality of water tanks. The valves are respectively installed in multiple of the second drainage channels.

13. The plant cultivation system according to any one of claims 1 to 5, wherein, The bottom of the cultivation trough has an inclined portion. The second drainage channel is connected to the lowest position of the inclined section.

14. The plant cultivation system according to any one of claims 1 to 5, wherein, The cultivation trough has a wall that narrows as the flow path of the nutrient solution narrows toward the connection point of the second drainage path.

15. The plant cultivation system according to claim 1, wherein, The plant cultivation system also includes cultivation shelves that support multiple cultivation troughs. The second drainage channel is connected to each of the plurality of cultivation troughs. The second control device controls the valve to open at different time intervals for each of the cultivation tanks.

16. The plant cultivation system according to claim 1 or 15, wherein, The second control device controls the valve to open at a timed interval when the attached equipment of the plant cultivation system is activated.

17. The plant cultivation system according to claim 1, wherein, The plant cultivation system also includes a transfer device that removes the holding device from the end of the support device and transfers it to other support devices. The second control device controls the valve to open at a timed interval when the transfer device removes the holding device from the support device.

18. The plant cultivation system according to claim 16, wherein, The second control device changes the timing interval for opening the valve based on whether the auxiliary equipment is activated.

19. The plant cultivation system according to any one of claims 1 to 5, wherein, The water supply line is connected to one end of the cultivation trough. The first drainage channel is connected to the vicinity of the other end of the cultivation trough. The second drainage channel is connected to the cultivation trough at a position on the other side of the area where the plants are held. The plant cultivation system also has a third drainage channel, which is connected to the bottom of the cultivation trough at a position on one side of the area where the plant is held, and discharges the nutrient solution from the cultivation trough.

20. A method for cultivating plants, comprising: Nutrient solution is poured into the cultivation tank for the plant. The nutrient solution in the cultivation tank is discharged by overflowing at a specified water level; The nutrient solution is discharged from near the bottom of the cultivation tank; The nutrient solution discharged from the cultivation tank is sterilized. The nutrient solution, after undergoing the sterilization treatment, is supplied to the cultivation tank; The multiple retaining devices for holding the plant are supported so that they can move; The control valve is normally closed and opens at a predetermined time to discharge the nutrient solution from the bottom of the cultivation tank during the time the holding device moves, wherein the valve opens and closes the drainage path for discharging the nutrient solution from the bottom of the cultivation tank.

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