WO2023132314A1

WO2023132314A1 - Nutrient solution discharge device used in plant cultivation system

Info

Publication number: WO2023132314A1
Application number: PCT/JP2022/048463
Authority: WO
Inventors: 基広山根
Original assignee: 株式会社Gac
Priority date: 2022-01-07
Filing date: 2022-12-28
Publication date: 2023-07-13
Also published as: JP2023101083A; JP7062323B1

Abstract

Provided is a nutrient solution discharge device for discharging a nutrient solution flowing in a cultivation tank without staying in a plant cultivation system for cultivating a plant in the cultivation tank containing the nutrient solution. This device includes a set of a first drainage part and a second drainage part. The first drainage part has a first drainage port at a height of the required liquid level of the nutrient solution necessary for plant cultivation. The second drainage part has a second drainage port at a height that is lower than the required liquid level and that can maintain at least the minimum liquid level necessary for plant survival even when the supply of nutrient solution is stopped. The second drainage part has a drainage pipe having the second drainage port and a sheath pipe covering the drainage pipe. The sheath pipe has one end located above the second drainage port and the other end at least a part of which is in contact with the bottom surface of the cultivation tank and in which one or more openings are provided for taking the nutrient solution in the cultivation tank into the interior, and the aforesaid one end is placed at a position higher than the first drainage port.

Description

Nutrient discharge device used in plant cultivation system

The present invention relates to the artificial cultivation of plants, and more specifically, to a discharge device that discharges the nutrient solution flowing in a cultivation tank for hydroponic cultivation of plants from the cultivation tank.

Plants, including vegetables and flowers, are generally produced by outdoor or indoor soil cultivation methods (open, semi-closed, or completely closed soil cultivation methods). However, the soil cultivation method has problems such as the fact that the harvest is dependent on the season and weather, the occurrence of continuous crop failure, and the risk of diseases caused by pests. In contrast to such soil cultivation methods, in recent years, an indoor artificial cultivation method has been put into practical use, in which plants are cultivated indoors using hydroponics.

There are various methods of hydroponic culture, but the most commonly used method uses a flowing nutrient solution to supply nutrients to the roots of plants. It is divided into a method and a submerged type hydroponics method. The thin-film type hydroponics method is a method in which a nutrient solution, in which nutrients necessary for plant growth are dissolved in water, is thinly poured down on a flat surface with a gentle slope, and plants are cultivated using the nutrient solution. The thin-film type hydroponics system hinders root elongation, which may cause problems in plant growth.

On the other hand, the submerged hydroponics method is a method in which a nutrient solution is supplied to a cultivation tank where plants are grown so that the plant roots are immersed in the nutrient solution. Compared to the thin film type hydroponics method, the submerged hydroponics method uses a large amount of nutrient solution, so the water depth is deep, root growth is not hindered, and changes in nutrient concentration and liquid temperature are gentle. Therefore, it has the characteristics of being easy to manage. The present invention relates to the latter, the submerged hydroponic system, and hereinafter, hydroponic culture refers to submerged hydroponic culture. The inventor of the present application has proposed a flood-type hydroponic culture in Patent Document 1.

Patent Document 1 proposes a plant cultivation system for performing submerged hydroponics. In this plant cultivation system, as shown in FIGS. 3 and 4 of Patent Document 1, a nutrient solution S for cultivating plants is supplied from a nutrient solution supply path 45 to the cultivation tank 10 and allowed to flow in one direction. , is discharged from the drain port 16 . The drainage port 16 consists of a first drainage port 16a and a second drainage port 16b. The first drainage port 16 a is an opening provided so as to be positioned on the same plane as the bottom surface of the cultivation tank 10 . The second drainage port 16b is provided so that the outflow port of the nutrient solution S is positioned near the water surface of the nutrient solution S. As shown in FIG.

Patent Document 2 proposes a water level control mechanism used in aquaculture/cultivation equipment. This water level adjustment mechanism consists of a water level adjustment pipe and a rack that covers the outside of the pipe, and the water is drained from the opening provided below the rack, so that the organic matter in the lower part of the water tank can be sucked up and discharged by the water flow. It is said to be possible.

JP 2015-84750 A Japanese Patent No. 3069847

The drainage method proposed in Patent Document 1 has the following problems.
If the drainage port 16a, which is a mere opening, is arranged on the bottom surface of the cultivation tank 10, the nutrient solution S near the drainage port 16a is preferentially drained, and the nutrient solution S is drained from the drainage port 16a in the cultivation tank 10. The nutrient solution S in a distant place may stay. If the nutrient solution S stays in this manner, the plant will not grow and may wither because the nutrient solution S in the stagnant portion will rot. In addition, since the amount of the nutrient solution S discharged from the drainage port 16b is reduced, the upper layer of the nutrient solution S in the cultivation tank 10 is not discharged smoothly and stays there, and the roots of the plants may rot.

In addition, when the power supply to the plant cultivation system is stopped due to a power outage, a failure, or the like, and the nutrient solution S is no longer properly supplied to the cultivation tank 10, the cultivation tank is discharged from the drainage port 16a arranged on the bottom surface of the cultivation tank 10. All of the nutrient solution S in 10 is discharged and the nutrient solution S falls below the required liquid level. Then, the plants cultivated in the cultivation tank 10 may wither. If a nutrient solution control system using, for example, a solenoid valve is adopted so that the supply of the nutrient solution S and the discharge of the nutrient solution S can be stopped automatically in the event of a power failure or malfunction, such a problem can be solved. can be used, but the introduction cost increases.

When the water level adjusting device proposed in Patent Document 2 is used alone in a plant cultivation system, the nutrient solution S is discharged only from the opening provided at the bottom of the plant, so the upper layer in the cultivation tank 10 stagnation of the nutrient solution S may occur, causing a problem in uniform discharge of the entire nutrient solution S. As in the case of Patent Document 1, when the upper layer of the nutrient solution S stays in the cultivation tank 10, the nutrient solution S may rot and the roots of the plants may rot.

In order to solve the above problems, the present invention provides a plant cultivation system for cultivating plants in a cultivation tank containing a nutrient solution, in which the entire nutrient solution flowing in the cultivation tank can be discharged uniformly without stagnation. It is an object of the present invention to provide a nutrient solution discharge device capable of

The present invention provides a nutrient solution discharge device for discharging the nutrient solution flowing in the cultivation tank. The device comprises a set of a first drain and a second drain. The first drainage part has a first drainage port at a required liquid level of a nutrient solution required for plant cultivation. The second drainage part has a second drainage port at a height that is lower than the required liquid level and that can maintain at least the minimum liquid level necessary for plant survival even when the supply of the nutrient solution is stopped. The second drainage part has a drainage tube having a second drainage port and a sheath tube covering the drainage tube. The sheath pipe is at least partially in contact with one end located above the second drainage port and the bottom surface of the cultivation tank, and is provided with one or more openings for taking in the nutrient solution in the cultivation tank. and the other end of the connector. One end is positioned higher than the first drainage port.

It is preferable that one or more spacers are provided between the outer surface of the drainage tube and the inner surface of the sheath tube. Also, the one or more spacers are preferably attached to the outer surface of the drain.

It is preferable that the total opening area of one or more openings of the sheath tube is smaller than the opening area of the second drainage port.

In one embodiment, the first drainage part and the second drainage part are preferably arranged side by side in a direction transverse to the direction of flow of the nutrient solution downstream of the flow of the nutrient solution. In another embodiment, the first drain and the second drain are juxtaposed downstream of the flow of the nutrient solution and in the same direction as the direction of flow of the nutrient solution, the second drain It is preferably arranged downstream of the drainage part of the.

According to the nutrient solution discharge device according to the present invention, it is possible to uniformly discharge the entire nutrient solution without causing partial stagnation of the nutrient solution in the cultivation tank, and to properly discharge the nutrient solution in the event of a power failure or malfunction. Even when an adequate supply is impossible, the liquid level of the nutrient solution in the cultivation tank does not drop below the liquid level necessary for the survival of the plants, and these functions can be realized at low cost. .

1 is a schematic general view of a plant cultivation system using a drainage device according to an embodiment of the present invention; FIG. 1 is a schematic side cross-sectional view of a cultivation tank of a plant cultivation system using a drainage device according to an embodiment of the present invention; FIG. 4 is an exploded perspective view of a first drainage part (overflow pipe) of the drainage device according to one embodiment of the present invention; FIG. FIG. 4 is an exploded perspective view of a second drainage part (drainage tube) of the drainage device according to one embodiment of the present invention; 1 is a plan view of a cultivation tank showing an arrangement example of a first drainage part and a second drainage part of a drainage device according to an embodiment of the present invention; FIG.

(Overview of plant cultivation system)
FIG. 1 shows a schematic diagram of a plant cultivation system 1 in which a nutrient solution discharge device according to one embodiment of the present invention is used. The plant cultivation system 1 includes a house 60, one or a plurality of cultivation tanks 10 housed in the house 60 for cultivating plants, and a modified air production means 20 for producing the modified air RA. The reformed air RA produced is air that has been reformed to have a higher oxygen content. In FIG. 1, the reformed air producing means 20 is provided outside the house 60, but it may be provided inside the house 60. FIG.

In the cultivation tank 10, single or multi-item plants are supported by supports (floats), and a nutrient solution S containing nutrients for growing the plants flows inside. The cultivation tank 10 is supported by a support frame 19, for example. When a variety of plants are cultivated, it is preferable to have a multi-stage configuration so as to be able to cope with the types of plants and the time until harvest. Roots of plants to be cultivated are immersed in the nutrient solution S in the cultivation tank 10 . The nutrient solution S is supplied with reformed air RA. Facilities such as a nutrient solution tank 41 are buried in the underground portion of the house 60 .

In the plant cultivation system 1, leafy vegetables such as spinach and leaf lettuce; fruit vegetables such as tomatoes, eggplants and cucumbers; head vegetables such as Chinese cabbage, cabbage and lettuce; Flowers and the like can be cultivated throughout the year as a single item or multiple items. In addition, when cultivating a variety of plants in the plant cultivation system 1, it is possible to simultaneously cultivate plants of different growth stages from immediately after germination to harvest.

The plant cultivation system 1 is configured such that the nutrient solution S, in which the same nutrients are mixed so as to be homogeneous throughout, is constantly circulated in a constant state between all the cultivation tanks 10 . As the nutrient solution S, the nutrient solution S with the same components is continuously used regardless of the type of plant, the stage of growth, and the time of cultivation, and water and/or nutrients are replenished by the amount reduced by evaporation and absorption by the plant. Just

The components contained in the nutrient solution S are not particularly limited, and any nutrient solution used in general hydroponics can be used. The nutrient solution S contains, for example, ammonia nitrogen, water-soluble phosphoric acid, nitrate nitrogen, water-soluble potassium, calcium nitrate, water-soluble magnesium, water-soluble manganese, water-soluble boron, water-soluble iron, water-soluble copper, It may contain water-soluble molybdenum and water-soluble zinc. The state of the nutrient solution S, that is, at least the values of parameters such as dissolved oxygen concentration (DO), electrical conductivity (EC), temperature Ts, hydrogen ion concentration exponent (pH), and oxidation-reduction potential (ORP) are generally constant. managed to be maintained.

FIG. 2 is a schematic side view showing an example of the cultivation tank 10 and peripheral equipment using the nutrient solution discharge device 16 according to one embodiment of the present invention. The cultivation tank 10 has a bottom surface 10a and side surfaces 10b and 10c, and is configured such that the nutrient solution S flows in one direction at a predetermined speed. A support substrate 11 is floated on the liquid surface of the nutrient solution S, and the support substrate 11 is provided with a plurality of openings 12 . A cultivation pot 13 containing a culture medium 14 is placed in the opening 12 . The types and shapes of the supporting substrate 11, the openings 12, and the cultivation pots 13 can be appropriately selected according to the type of plant to be cultivated, and are not limited to those shown in FIG.

The length, width and depth of the cultivation tank 10 are determined according to the type and amount of plants cultivated in each cultivation tank 10 and the scale of the cultivation facility. roots and stems can maintain their original growth shape. The cultivation tank 10 has a width of about 1000 mm and a depth of about 200 mm for leaf vegetables, and a width and depth of about 300 mm for fruit vegetables such as eggplants and tomatoes. , and headed vegetables such as lettuce, those having a width and depth of about 200 mm are used. The length of the cultivation tank 10 is appropriately set according to the scale of the greenhouse 60 for any plant, and may be about 50 cm for a short one and about 100 m for a long one, for example.

A nutrient solution S is supplied to the cultivation tank 10 from a supply route 45 . The nutrient solution S supplied from the supply port 45a flows in the cultivation tank 10 in the direction of the arrow in FIG.

An air pipe 34 and an air supply unit 36 are provided inside the cultivation tank 10 . The reformed air RA is supplied to the air supply section 36 through the air pipe 34 , and the reformed air RA is supplied to the nutrient solution S from the air supply section 36 . Although the air supply part 36 is not limited, it is preferably a hollow cylindrical porous body obtained by firing ceramics at a high temperature.

A nutrient solution discharge device 16 is provided in the cultivation tank 10 , and the nutrient solution S that has flowed through the cultivation tank 10 is discharged from the discharge device 16 . The drain device 16 consists of two

drains

16A, 16B. The first drainage part 16A is provided so that the outlet for the nutrient solution S is positioned at the same height as the liquid surface of the nutrient solution S. As shown in FIG. The second drainage part 16B is provided with an outlet for the nutrient solution S at a position slightly lower than the outlet of the first drainage part 16A. The details of the ejection device 16 will be described later.

The nutrient solution S discharged from the cultivation tank 10 passes through the discharge paths 46a and 46b and preferably enters the discharge side tank 41 buried in the ground. The nutrient solution S in the discharge side tank 41 is supplied to a supply side tank 44 preferably buried in the ground through a pipe 43 by a circulation pump (not shown). The nutrient solution S in the supply-side tank 44 is supplied to the cultivation tank 10 from the supply port 45a through the supply path 45 by a supply pump (not shown). The supply path 45 may be provided with a valve (not shown) for opening and closing the path, if necessary, so that the supply amount of the nutrient solution S can be controlled more precisely.

(Nourishing solution discharge device)
3 and 4 show a nutrient solution discharge device 16 according to the present invention. FIG. 3 is an exploded perspective view of the first drainage part 16A, and FIG. 4 is an exploded perspective view of the second drainage part 16B.

The first drainage part 16A has a nutrient solution S overflow function. That is, the first drainage part 16A is configured so that the nutrient solution S supplied to the cultivation tank 10 from the supply port 45a of the supply path 45 is at a liquid level of the nutrient solution S necessary for cultivating the plant in the cultivation tank 10, In other words, the "required liquid level" can be maintained.

The first drainage part 16A includes a hollow pipe socket 16A1 that fits into an opening provided in the bottom surface 10a of the cultivation tank 10, and an overflow pipe 16A2 that is inserted into the socket 16A1 from above. The socket 16A1 is connected to the discharge path 46a.

The overflow pipe 16A2 is a hollow pipe, and has a drainage port A21 (first drainage port) at its upper end. The height of the drainage port A21 is set to be the same as the required liquid level of the nutrient solution S. The height of the drainage port A21 (that is, the required liquid level) varies depending on the plant to be cultivated, but for example, it is about 3 mm to 5 mm below the boundary between the root and stem of the plant cultivated in the cultivation tank 10. preferable. By discharging the nutrient solution S from the overflow pipe 16A2, mainly the upper layer of the nutrient solution S in the cultivation tank 10 (the nutrient solution flowing at the height where the dense part of the roots of the plant is located) is retained. It can be discharged smoothly.

The lower end of the overflow pipe 16A2 is inserted into the socket 16A1. The upper end of the discharge path 46a is inserted into the socket 16A1 from below. Therefore, the nutrient solution S that has entered the overflow pipe 16A2 through the drain port A21 is discharged to the nutrient solution tank 41 via the discharge path 46a.

The second drainage part 16B has a function of moving mainly the lower layer portion of the nutrient solution S in the cultivation tank 10 in its own direction and discharging it. In addition, even when the supply of the nutrient solution S is stopped due to a power failure or the like, the second drainage part 16B has a function of maintaining at least the liquid level of the nutrient solution S necessary for the survival of the plant, that is, the "minimum liquid level". have. The lowest liquid level varies depending on the type of plant to be cultivated, but for example, it is preferably the liquid level at which about half of the roots of the plants cultivated in the cultivation tank 10 are immersed in the nutrient solution S, and the liquid level is higher than that. If it drops, the roots may dry out.

The second drainage part 16B includes a socket 16B1 that fits into an opening provided in the bottom surface 10a of the cultivation tank 10, and a drainage pipe 16B2 that is inserted into the socket 16B1 from above. The socket 16B1 is connected to the discharge path 46b.

The drain pipe 16B2 is a hollow pipe, and has a drain port B21 (second drain port) at its upper end. The height of the drainage port B21 is set to be lower than the required liquid level. Moreover, the height of the drainage port B21 is such that the minimum liquid level can be maintained even when the supply of the nutrient solution S to the cultivation tank 10 is stopped. Although the height of the drain port B21 is not limited, it is preferably arranged at a position 20 mm to 30 mm lower than the required liquid level and the drain port A21. When the height of the drainage port B21 is higher than the required liquid level and the position 20 mm lower than the drainage port A21, the nutrient solution S entering from the notch B34 of the sheath tube 16B3 described later becomes difficult to rise to the drainage port B21. Discharge of the liquid S may be hindered. If the height of the drainage port B21 is lower than the required liquid level and the position 30 mm lower than the drainage port A21, the liquid level may drop too much in the event of a power failure or malfunction, making it impossible to maintain the life of the plant.

The drainage pipe 16B2 is covered with a sheath pipe 16B3. The sheath tube 16B3 is a hollow pipe with one end B31 and the other end B33 both open. One end B31 is located above the drainage port B21 and is set to be higher than the drainage port A21 of the overflow pipe 16A2. When the end portion B31 is at a position lower than the drain port A21, the nutrient solution S discharged from the end portion B31 at a position higher than the notch B34 of the sheath tube 16B3 described later is discharged through the notch B34. Not only does it become impossible to maintain the required liquid level, but the amount of nutrient solution S passing through the notch B34 decreases, so the force that draws the nutrient solution S in the lower layer of the cultivation tank 10 weakens.

At the other end B33 of the sheath tube 16B3, one or more openings B34 are formed in the circumferential direction of the side surface B32. In the embodiment of FIG. 4 the openings are formed as three notches B34. Since the three notches B34 are formed in the other end B33, at the other end B33, part of the end surface contacts the bottom surface 10a of the cultivation tank 10, and the part with the notch B34 contacts the bottom surface 10a. It becomes an opening without opening. The shape of the notch B34 is not limited to a quadrangle as shown in FIG. 4, and may be a polygon or a part of a circle. Moreover, the number of notches B34 is not limited to three, and may be two or less, or may be four or more.

The nutrient solution S in the cultivation tank 10 is discharged from the second drainage part 16B by being pumped. Specifically, the nutrient solution S enters the inside of the sheath tube 16B3 through the notch B34 arranged adjacent to the bottom surface 10a of the cultivation tank 10. As shown in FIG. The nutrient solution S that has entered the sheath tube 16B3 rises between the inner surface of the sheath tube 16B3 and the outer surface of the side surface B22 of the drainage tube 16B2, and is discharged from the drainage port B21. The nutrient solution S flows downward inside the drainage pipe 16B2 and is discharged to the nutrient solution tank 41 via the discharge path 46b. A valve 47 (see FIG. 2) is preferably provided in the discharge path 46b. The valve 47 can be used to appropriately set the amount of the nutrient solution S discharged from the drain pipe 16B2.

The three cutouts B34 are determined so that the total opening area thereof is smaller than the opening area of the drainage port B21. Therefore, the flow velocity of the nutrient solution S when passing through the notch B34 is faster than the flow velocity when passing through the drain port B21. Therefore, compared with the drainage method used in Patent Document 1, even the nutrient solution S far from the second drainage part 16B can be drawn and drained. It is possible to prevent stagnation. The size of the notch B34 is not limited, but if it is too small, the notch B34 may be clogged with foreign matter and obstruct drainage. The nutrient solution S in the lower layer in the cultivation tank 10 becomes difficult to move.

The one or more openings formed in the other end B33 of the sheath tube 16B3 are limited to notches formed in the height direction from the end surface of the end B33 as shown in FIG. not. For example, it may be an opening formed in the side surface B32 at a position slightly separated from the end surface in the height direction of the sheath tube 16B3. The shape of the opening at this time is also not limited, and may be square or circular, for example.

One or more spacers B23 are erected on the outer surface of the side surface B22 of the drainage pipe 16B2. The spacer B23 is provided to maintain an appropriate distance between the drainage tube 16B2 and the sheath tube 16B3 and prevent movement of the sheath tube 16B3 during drainage. The positions and number of spacers B23 are not limited. In FIG. 4, four spacers B23 are provided at approximately the center in the height direction of the outer surface of the side surface B22 at regular intervals in the circumferential direction. For example, three or five or more spacers B23 may be provided in the circumferential direction of the drain pipe 16B2, and two or more rows may be provided in the height direction.

Although the spacer B23 is provided on the outer surface of the side surface B22 in FIG. 4, it is not limited to this, and may be provided on the inner surface of the sheath tube 16B3, for example. Also, the size of the spacer B23 is not limited. For example, the height (vertical length) of the spacer B23 may be the same as the height of the side surface B22 of the drainage pipe 16B2, and the width of the spacer B23 (that is, the length of protrusion from the outer surface of the side surface B22) It is sufficient if the gap between the liquid tube 16B2 and the sheath tube 16B3 can be properly maintained to prevent unnecessary movement of the sheath tube 16B3 during liquid discharge.

Materials for the first drainage part 16A and the second drainage part 16B are not particularly limited. Resin is preferred.

(Example of layout and size of nutrient solution discharge device)
FIG. 5 shows an example of the position where the discharging device 16 is arranged in the cultivation tank 10. As shown in FIG.
FIG. 5(a) shows an arrangement example of the discharging device 16 in a typical cultivation tank 10 (about 1000 mm wide and about 200 mm deep) used for cultivating leaf vegetables. The discharge device 16 is arranged near the side surface 10c of the cultivation tank 10 downstream in the flow direction of the nutrient solution S. In this example, the first drainage part 16A and the second drainage part 16B are arranged side by side in a direction crossing the direction in which the nutrient solution S flows.

The first drainage part 16A and the second drainage part 16B are arranged such that the centers of the respective drainage ports A21 and B21 are about 180 mm from the side surface 10b and about 250 mm from the side surface 10c. The inner diameter of the overflow pipe 16A2 that constitutes the first drainage portion 16A is 100 mm. The inner diameter of the drainage tube 16B2 that constitutes the second drainage part 16B is 100 mm, and the inner diameter of the sheath tube 16B3 is 200 mm.

FIG. 5(b) shows an arrangement example of the discharging device 16 in a typical cultivation tank 10 (about 300 mm in width and depth) used for cultivating fruit vegetables such as eggplants and tomatoes. The discharge device 16 is arranged near the side surface 10c of the cultivation tank 10 downstream in the flow direction of the nutrient solution S. In this example, the first drainage part 16A and the second drainage part 16B are arranged side by side in the same direction as the direction in which the nutrient solution S flows. 16A downstream.

The distance between the first drainage part 16A and the second drainage part 16B and the distance between the second drainage part 16B and the side surface 10c are both preferably about 250 mm. The inner diameter of the overflow pipe 16A2 that constitutes the first drainage portion 16A is 100 mm. The inner diameter of the drainage tube 16B2 that constitutes the second drainage part 16B is 100 mm, and the inner diameter of the sheath tube 16B3 is 200 mm.

FIG. 5(c) shows an arrangement example of the discharging device 16 in a typical cultivation tank 10 (about 200 mm in width and depth) used for head cultivation such as lettuce. The discharge device 16 is arranged near the side surface 10c of the cultivation tank 10 downstream in the flow direction of the nutrient solution S. In this example, as in the example of FIG. 5B, the first drainage part 16A and the second drainage part 16B are arranged side by side in the same direction as the direction in which the nutrient solution S flows. The liquid section 16B is arranged downstream of the first drainage section 16A.

It should be noted that the first drainage part 16A and the second drainage part 16B are preferably arranged in a direction that intersects the flow of the nutrient solution S as shown in FIG. 5(a). Furthermore, it is more preferable that both are arranged as far apart as possible. In the case of the cultivation tank 10 having a narrow width as shown in FIGS. However, in this case, it is preferable that the second drainage section 16B, which draws the nutrient solution S with a stronger force, be arranged downstream of the first drainage section 16A.

The distance between the first drainage part 16A and the second drainage part 16B and the distance between the second drainage part 16B and the side surface 10c are both preferably about 180 mm. Also, the inner diameter of the overflow pipe 16A2 of the first drainage portion 16A is 50 mm. The inner diameter of the drainage tube 16B2 of the second drainage part 16B is 50 mm, and the inner diameter of the sheath tube 16B3 is 100 mm.

1 plant cultivation system 10 cultivation tank 11 support 12 opening 13 pot 14 culture medium 16 discharge device 16A first discharge part 16A1 socket 16A2 overflow pipe A21 drain port (first drain port)
16B second discharge part 16B1 socket 16B2 drain pipe B21 drain port (second drain port)
B22 Side B23 Spacer 16B3 Sheath tube B31 Closed end (one end)
B32 side surface B33 open end (other end)
B34 notch (opening)
20 reformed air production means 30 reformed air supply means 34 air pipe 36 air supply section 40 nutrient solution circulation means 41 discharge side tank 41a, 41b liquid receiving port 41c liquid transfer port 43 pipe 44 supply side tank 45 supply path 46a, 46b Discharge path 47 Valve 60 House RA Reformed air S Nutrient solution

Claims

In a plant cultivation system for cultivating plants in a cultivation tank containing a nutrient solution, a nutrient solution discharge device for discharging the nutrient solution flowing in the cultivation tank,
a first drainage part having a first drainage port at a required liquid level of a nutrient solution required for plant cultivation;
a second drainage part having a second drainage port at a height that is lower than the required liquid level and that can maintain at least the minimum liquid level necessary for the survival of the plant even when the supply of the nutrient solution is stopped; prepared,
The second drainage part is
a drainage pipe having the second drainage port;
At least a part of the bottom surface of the cultivation tank is in contact with one end located above the second drainage port and higher than the first drainage port, and the nutrient solution in the cultivation tank is taken into the inside (1). and a sheath tube covering said drain tube, the other end being provided with one or more openings.
The nutrient solution discharge device according to claim 1, wherein one or more spacers are provided between the outer surface of the drain pipe and the inner surface of the sheath pipe.
The nutrient solution discharge device according to claim 2, wherein the one or more spacers are attached to the outer surface of the drain pipe.
The nutrient solution draining device according to any one of claims 1 to 3, wherein the one or more openings have a total opening area smaller than the opening area of the second drainage port. .
The first drainage part and the second drainage part are arranged downstream of the flow of the nutrient solution in a direction transverse to the direction of flow of the nutrient solution,
The nutrient solution discharge device according to any one of claims 1 to 4.
The first drainage part and the second drainage part are arranged downstream of the flow of the nutrient solution in the same direction as the direction of flow of the nutrient solution,
wherein the second drain is arranged downstream of the first drain;
The nutrient solution discharge device according to any one of claims 1 to 4.