Plant cultivation device

Abstract

A plant cultivation device according to the present invention is provided in a closed plant factory for cultivating plants indoors where sunlight is blocked, the plant cultivation device comprising: a cultivation tray that holds a nutrient solution containing water and a fertilizer, and holds a plant of which roots are immersed in the nutrient solution; and a nutrient solution tank that supplies additional nutrient solution to the cultivation tray. The nutrient solution in the cultivation tray is held by the cultivation tray without being circulated.

Description

Plant cultivation equipment

[0001] The present invention relates to a plant cultivation device used for performing hydroponics without using soil in a plant factory or the like.

[0002] In closed plant factories and the like that shield sunlight and cultivate plants using artificial light such as LED light sources instead of sunlight, hydroponics, which uses a nutrient solution instead of soil, has become mainstream. Hydroponics include a spray method in which the nutrient solution is directly sprayed in a mist form onto the roots of plants using a spray nozzle, but the mainstream hydroponics is a circulation method in which the nutrient solution is circulated through pool-like channels called cultivation beds (or cultivation trays) that are several meters to 20 meters long. For example, Patent Document 1 discloses a nutrient solution supplying device for a conventional plant cultivation facility.

[0003] This recirculating hydroponic system uses a pump to supply fertilizer dissolved in water to the plant roots through a supply nozzle on the surface of the cultivation bed, circulating the solution throughout the cultivation bed. This facilitates direct root absorption and also provides dissolved oxygen, promoting plant growth. However, because the roots are constantly moving due to the flow of the nutrient solution, plant waste and allelopathic substances leach from the roots into the cultivation bed. Their accumulation can lead to growth inhibition and soiling of the cultivation bed. For this reason, the nutrient solution in the cultivation beds must be periodically renewed (replaced). A recirculating nutrient solution tank is installed to hold a volume of renewal nutrient solution equivalent to the volume of the cultivation bed. In large-scale facilities, tens of tons of nutrient solution must be discharged at a time, resulting in a waste of water resources and significant environmental risks, such as the nitrogen and phosphate fertilizers contained in the nutrient solution contributing to eutrophication.

[0004] Furthermore, automation has recently been implemented in large-scale plant factories to compensate for labor shortages. One method of automation is to use short, easily transportable cultivation trays, approximately 1.5 m in length, and to transport the cultivation trays while circulating nutrient solution in the same manner as described above. This method aims to improve work efficiency by transporting the cultivation trays according to the growth of the plants. However, automation presents challenges, such as the nutrient solution spilling out of the supply port of the cultivation tray or spilling from the cultivation tray during transport due to the cultivation trays being transported with nutrient solution still in the tray, which can cause breakdowns in the automated machinery.

[0005] Furthermore, spillage of the nutrient solution can lead to contamination of the plants being cultivated, and problems arise in terms of hygiene management, such as an increase in the number of live bacteria, which means that the space where the cultivation trays are placed needs to be cleaned frequently, resulting in other issues such as an increased workload.

[0006] Japanese Patent Application Laid-Open No. 2005-021065

[0007] In order to solve the above problems, the present invention provides a new hydroponic cultivation method that does not circulate nutrient solution and a cultivation device used for the method, which dramatically improves the efficiency of fertilizer and water use in a closed plant factory where plants are cultivated using artificial light such as an LED light source in a room that is shielded from sunlight.

[0008] In contrast to conventional circulating concentration management in which the nutrient solution is circulated during plant cultivation in a plant factory and the concentration is controlled based on EC (electrical conductivity), the present invention aims to dramatically improve the utilization efficiency of the nutrient solution containing fertilizer and water and to make it easier to transport cultivation trays during automation by using a non-circulating speed management method in which the nutrient solution is not circulated but is instead adjusted to an appropriate concentration and applied.

[0009] A plant cultivation device according to one embodiment of the present invention is a plant cultivation device for use in a closed plant factory where plants are cultivated indoors and shielded from sunlight, and includes a cultivation tray that holds a nutrient solution containing water and fertilizer and that holds plants with their roots immersed in the nutrient solution, and a nutrient solution tank that supplies additional nutrient solution to the cultivation tray, and the nutrient solution in the cultivation tray is held in the cultivation tray without being circulated.

[0010] This type of cultivation device and cultivation method using the same device eliminates the need to prepare circulating nutrient solution, which reduces the amount of nutrient solution used by about half compared to conventional circulation-type cultivation devices and methods. In addition, the amount of waste solution discharged can be reduced or eliminated, providing an environmentally friendly cultivation device and method.

[0011] Preferably, the above-described cultivation device further comprises a control unit that controls the supply of additional nutrient solution from the nutrient solution tank to the cultivation tray, and the control unit supplies the additional nutrient solution from the nutrient solution tank to the cultivation tray at a predetermined timing.

[0012] According to such a cultivation device and a cultivation method using the same device, it is possible to provide a plant cultivation device and method that can manage the nutrient solution relatively easily compared to conventional methods.

[0013] In the above-described cultivation device, the electrical conductivity of the nutrient solution and the additional nutrient solution is preferably approximately twice the electrical conductivity of the nutrient solution in a conventional circulation-type cultivation device that circulates water in the cultivation trays.

[0014] In the above-mentioned cultivation device, the electrical conductivity of the nutrient solution and the additional nutrient solution is preferably 2.0 S / cm or more and 2.4 S / cm or less.

[0015] According to such a cultivation device and a cultivation method using the same device, the cultivation device of the present invention, which differs from conventional circulation-type cultivation devices, can appropriately manage the proportion of fertilizers, etc. contained in the nutrient solution.

[0016] In the above-described cultivation device, preferably, the nutrient solution tank is capable of supplying two or more additional nutrient solutions, each having a different fertilizer concentration and / or composition, to the cultivation tray, and the control unit supplies one of the two or more additional nutrient solutions to the cultivation tray at a predetermined timing in accordance with the growth of the plant held in the cultivation tray.

[0017] According to such a cultivation device and a cultivation method using the same device, the ratio of fertilizer and the like contained in the nutrient solution can be appropriately controlled.

[0018] According to one embodiment of the plant cultivation device of the present invention, compared to conventional circulation-type cultivation devices and methods, it is not necessary to prepare nutrient solution for circulation, so the amount of nutrient solution used can be reduced by about half. Also, it is possible to reduce or eliminate the amount of waste solution discharged.

[0019] FIG. 1 is a conceptual diagram of a plant cultivation device according to an embodiment.

[0020] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiment described below is merely a specific example for carrying out the present invention, and is not to be construed as limiting the present invention.

[0021] As described above, the plant cultivation device of this embodiment is a new hydroponic cultivation method that does not circulate nutrient solution and dramatically improves the efficiency of fertilizer and water use in a closed plant factory where plants are cultivated using artificial light such as an LED light source in a room that is shielded from sunlight, and is also a cultivation device used for this method.

[0022] As shown in FIG. 1 , a plant cultivation device 1 in this embodiment includes a cultivation tray 2, a nutrient solution tank 3, and a control unit 4. In a plant factory, a large number of cultivation trays 2 are arranged in a cultivation area of ​​a cultivation shelf, and each of these cultivation trays 2 is movable using an arm or the like. When supplying nutrient solution (additional nutrient solution, described below) to the cultivation tray 2, the cultivation tray 2 is moved to a nutrient solution supply area where the nutrient solution tank 3 and the control unit 4 are arranged. In the nutrient solution supply area, nutrient solution is supplied from the nutrient solution tank 3 under the control of the control unit 4, and then the cultivation tray 2 is returned to the cultivation area where it was originally placed. This configuration eliminates the need to provide a nutrient solution tank 3 for each cultivation tray 2, enabling space-saving and efficient arrangement and providing various advantages, such as easier nutrient solution management.

[0023] The cultivation tray 2 used for cultivation has a width of, for example, about 70 cm, a length of 130 cm, and a depth of 5 cm. A nutrient solution 21 is poured into the cultivation tray 2, and the nutrient solution 21 is retained for cultivating the plants 23 to be cultivated. A cultivation panel 22 having an array of holes each about 2.5 cm in diameter for planting the plants 23 is provided on top of the cultivation tray 2. In one example of a plant factory, many of these cultivation devices 1 are arranged lengthwise and widthwise on cultivation shelves, and the plants 23 are irradiated from above with an artificial light source such as an LED, and cultivated in a room where the temperature, humidity, and carbon dioxide concentration are controlled to constant levels.

[0024] In the nutrient solution supply area, nutrient solution is supplied to the cultivation tray 2 through a nozzle from a nutrient solution tank 3 containing nutrient solution prepared to an appropriate fertilizer concentration under the control of a control unit 4, which functions as an automatic nutrient solution supply device. The control unit 4 is, for example, a semiconductor device such as a microcomputer or a computer such as a PC running predetermined software. For convenience, the nutrient solution held and supplied by the nutrient solution tank 3 is sometimes referred to as "additional nutrient solution" to distinguish it from the nutrient solution 21 held in the cultivation tray 2 at the start of cultivation. The cultivation tray 2 holds the nutrient solution 21 to be supplied to the plants 23, just like a conventional cultivation bed. However, because it is smaller in size than a conventional cultivation bed, it is referred to as a "cultivation tray," and there is no significant difference between the two. Because of its relatively small size, the cultivation tray 2 can be transported relatively easily between the cultivation area and the nutrient solution supply area.

[0025] The nozzle of the nutrient solution tank 3 is equipped with a water level sensor, which allows additional nutrient solution to be supplied to the cultivation tray 2 so as to maintain a desired water level. However, the nutrient solution tank 3 does not supply additional nutrient solution to the cultivation tray 2 as needed to maintain the water level, but rather supplies a predetermined amount of additional nutrient solution to the cultivation tray 2 at a predetermined timing, as described below.

[0026] A plurality of nutrient solution tanks 3 are provided to change the concentration and / or composition of the fertilizer contained in the supplemental nutrient solution supplied according to the growth stage of the plants 23. Specifically, as shown in this embodiment, two nutrient solution tanks 31 and 32 are provided. For appropriate management of the plants 23, it is preferable to divide the concentration and / or composition of the fertilizer contained in the nutrient solution 21 into three or more levels, as described below. That is, it is preferable that the cultivation device 1 be configured to include two or more nutrient solution tanks 3 so that the nutrient solution 21 is first supplied to the cultivation tray 2 and then two types of supplemental nutrient solution can be automatically supplied to the cultivation tray 2 at predetermined times. Note that the configuration and method are not limited to these, and the configuration and method may be changed depending on the plants 23 to be cultivated. The concentration and / or composition of the fertilizer in the nutrient solution 21 or the supplemental nutrient solution may be referred to as the "fertilizer concentration."

[0027] The control unit 4 controls the supply of additional nutrient solution from the nutrient solution tank 3 to the cultivation tray 2 at a predetermined timing, for example. More specifically, for example, the control unit 4 measures the number of days since the start of cultivation using an internal or external timer, and supplies a predetermined amount of additional nutrient solution from the nutrient solution tank 31 to the cultivation tray 2 10 days after the start of cultivation, and then supplies a predetermined amount of additional nutrient solution from the nutrient solution tank 32 to the cultivation tray 2 7 days later. As described above, when additional nutrient solution is supplied from the nutrient solution tank 31 or 32 to the cultivation tray 2, the cultivation tray 2 is moved from the cultivation area to the nutrient solution supply area. That is, the cultivation tray 2 is moved to the nutrient solution supply area at a first timing and supplied with additional nutrient solution (first additional nutrient solution) from the nutrient solution tank 31, and at a second timing and supplied with additional nutrient solution (second additional nutrient solution) from the nutrient solution tank 32. At the start of cultivation, the cultivation tray 2 is manually supplied with nutrient solution 21 appropriate for the initial stage of cultivation. The supply (replenishment) of the nutrient solution 21 to the cultivation tray 2 is not performed at any other times than the above.

[0028] In conventional circulating hydroponic systems, the nutrient solution is circulated, causing a flow of the nutrient solution, and plants absorb necessary fertilizer components from this flowing nutrient solution through their roots. In contrast, in the cultivation device 1 of this embodiment, which employs a non-circulating cultivation method in which the nutrient solution 21 is not circulated, the nutrient solution does not circulate or flow, resulting in a decrease in the amount of nutrient solution absorbed by the roots. To compensate for this behavior, in the cultivation device 1 of this embodiment, the fertilizer concentration of the nutrient solution 21 and the additional nutrient solution supplied from the nutrient solution tank 3 is increased to approximately twice that of the conventional circulating system.

[0029] Specifically, in the conventional circulation type configuration, the fertilizer concentration of the nutrient solution 21 was adjusted by measuring the electrical conductivity (EC) of the nutrient solution 21 with a sensor, and the electrical conductivity (EC) was controlled by a control unit to be about 1 S / cm.

[0030] On the other hand, in the cultivation device 1 of this embodiment, the electrical conductivity (EC) of the nutrient solution 21 and the additional nutrient solution in the nutrient solution tank 3 is set to 2.0 S / cm or more and 2.4 S / cm or less, with a center of 2.2 S / cm being ±0.2 S / cm, and the fertilizer concentration of the additional nutrient solution supplied from the nutrient solution tank 3 and the fertilizer concentration of the nutrient solution 21 are controlled by the control unit 4 so that they are about twice as high as those of the conventional circulation system. The fertilizer concentration of the additional nutrient solution in the nutrient solution tank 3 is prepared to have a fertilizer concentration appropriate for each growth stage of the plants 23, so that additional nutrient solution can be supplied in accordance with the growth of the plants 23.

[0031] As a result, in the cultivation device 1 of this embodiment, the plant 23 can absorb an appropriate amount of fertilizer components through its roots, allowing the plant 23 to grow at the same rate as in the conventional method.

[0032] [Example of a Method for Cultivating Leaf Lettuce Using the Cultivation Apparatus 1] In the non-circulating cultivation method of the cultivation apparatus 1 of this embodiment, the amount of nutrient solution 21 in the cultivation tray 2 is not maintained constant, and therefore, the amount of nutrient solution 21 decreases as the plants 23 grow. In the early stages of cultivation after planting the plants 23, the decrease in the amount of nutrient solution 21 is gradual because the plants 23 are still small. For example, when cultivating leaf lettuce using this method, it is not necessary to add nutrient solution 21 until around the 10th day. After about the 7th to 10th day, nutrient solution (additional nutrient solution) prepared to the concentration and composition for the middle cultivation period is supplied to the cultivation tray 2 from the nutrient solution tank 3, and cultivation is continued. In the middle cultivation period, the amount of nutrient solution 21 decreases within about 5 to 7 days, and at this timing, nutrient solution (additional nutrient solution) prepared to the concentration and composition suitable for the later cultivation period is supplied to the cultivation tray from the nutrient solution tank 3. In the later cultivation period, leaf lettuce grows exponentially, and reaches a harvest size exceeding 100 g fresh weight in about 3 to 5 days. At this time, only a small amount of the nutrient solution 21 remains in the cultivation tray 2.

[0033] In the example of leaf lettuce grown using the non-recycle method of this embodiment, the stems above ground tend to be thicker and the overall shape is sturdy, whereas in the case of the conventional recycle method, the stems tend to be leggy, resulting in different plant shapes.

[0034] Furthermore, with this non-circulating system, the nutrient solution 21 is always stationary and the water level of the nutrient solution 21 drops (changes) as the plant grows, resulting in the development of many root hairs. Furthermore, as the roots are not moving, there is less stress, and waste products are less likely to elute from the roots, so the roots remain white, eliminating the phenomenon of root browning and waste products eluting into the nutrient solution 21, which is seen with the circulating system.

[0035] As described above, the cultivation device 1 according to one embodiment of the present invention is a cultivation device for plants in a closed plant factory where plants are cultivated indoors shielded from sunlight, and includes a cultivation tray 2 and a nutrient solution tank 3. The cultivation tray 2 holds a nutrient solution 21 containing water and fertilizer, and holds plants 23 with their roots immersed in the nutrient solution 21. The nutrient solution tank 3 supplies additional nutrient solution to the cultivation tray 2. The nutrient solution 21 in the cultivation tray 2 is held in the cultivation tray 2 without being circulated.

[0036] The cultivation device 1 further includes a control unit 4 that controls the supply of additional nutrient solution from the nutrient solution tank 3 to the cultivation tray 2. The control unit 4 supplies the additional nutrient solution from the nutrient solution tank 3 to the cultivation tray 2 at a predetermined timing.

[0037] In addition, in the above-described cultivation device 1, the electrical conductivity of the nutrient solution 21 and the additional nutrient solution is set to be approximately twice that of the nutrient solution in a conventional circulation-type cultivation device that circulates water in the cultivation trays. This electrical conductivity is preferably set to be 2.0 S / cm or more and 2.4 S / cm or less.

[0038] In the above-described cultivation device 1, the nutrient solution tank 3 includes a first nutrient solution tank 31 that holds a first additional nutrient solution, and a second nutrient solution tank 32 that holds a second additional nutrient solution that has a different fertilizer concentration and / or composition from the first additional nutrient solution. The control unit 4 supplies the first additional nutrient solution from the first nutrient solution tank 31 to the cultivation tray 2 at a first timing in accordance with the growth of the plants 23 held in the cultivation tray 2, and supplies the second additional nutrient solution from the second nutrient solution tank 32 to the cultivation tray 2 at a second timing.

[0039] According to the cultivation apparatus 1 of the present invention and the cultivation method using the same apparatus, the cultivation trays 2 are independent of each other, and a non-circulating system is used in which the nutrient solution 21 is not circulated, and the rate at which the nutrient solution 21 is appropriately replenished according to the growth of the plants 23 is managed, so that the remaining amount of nutrient solution 21 can be reduced to almost zero at the time of harvest, and the nutrient solution 21 can be used without waste. Therefore, the amount of nutrient solution 21 used is less than half that of the conventional circulating cultivation system, and furthermore, no wastewater is produced, making this an environmentally friendly cultivation system.

[0040] DESCRIPTION OF SYMBOLS 1: Cultivation device 2: Cultivation tray 21: Nutrient solution 22: Cultivation panel 23: Plant 3, 31, 32: Nutrient solution tank 4: Control device

Claims

1. A plant cultivation device in a closed plant factory where plants are cultivated indoors and shielded from sunlight, comprising: a cultivation tray that holds a nutrient solution containing water and fertilizer and that holds plants with their roots immersed in the nutrient solution; and a nutrient solution tank that supplies additional nutrient solution to the cultivation tray, wherein the nutrient solution in the cultivation tray is held in the cultivation tray without being circulated.

2. The plant cultivation device according to claim 1, further comprising a control unit that controls the supply of additional nutrient solution from the nutrient solution tank to the cultivation tray, wherein the control unit supplies the additional nutrient solution from the nutrient solution tank to the cultivation tray at a predetermined timing.

3. The plant cultivation device according to claim 1, wherein the electrical conductivity of the nutrient solution and the additional nutrient solution is approximately twice the electrical conductivity of the nutrient solution in a conventional circulation-type cultivation device that circulates water in the cultivation tray.

4. The plant cultivation device according to claim 1, wherein the electrical conductivity of the nutrient solution and the additional nutrient solution is 2.0 S / cm or more and 2.4 S / cm or less.

5. The cultivation device according to claim 2, wherein the nutrient solution tank includes a first nutrient solution tank that holds a first additional nutrient solution, and a second nutrient solution tank that holds a second additional nutrient solution that has a different fertilizer concentration and / or composition from the first additional nutrient solution, and the control unit supplies the first additional nutrient solution from the first nutrient solution tank to the cultivation tray at a first timing and supplies the second additional nutrient solution from the second nutrient solution tank to the cultivation tray at a second timing in accordance with the growth of the plants held in the cultivation tray.

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