Hydroponic cultivation system and hydroponic cultivation method

Abstract

To provide a hydroponic cultivation device and a hydroponic cultivation method that enable optimal lighting and liquid fertilizer supply for efficient plant growth.SOLUTION: The present invention provides a hydroponic cultivation device, comprising: an LED light source for hydroponic cultivation that combines a white LED having a light intensity in the 470 to 600 nm wavelength range of 75% or less of the peak light intensity of blue light emitted in the 440 to 460 nm wavelength range, a red LED emitting in the 650 to 670 nm wavelength range, a near-ultraviolet LED emitting in the 400 to 410 nm wavelength range, and a near-infrared LED emitting in the 730 to 740 nm wavelength range; a water level control mechanism for adjusting the level of liquid fertilizer relative to the roots of a cultivated plant; and a water flow control mechanism capable of intermittently applying a flow of liquid fertilizer to the roots.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a hydroponic cultivation apparatus and a hydroponic cultivation method used for hydroponic cultivation of plants, particularly vegetables such as leafy vegetables, fruit vegetables, and herbs.

Background Art

[0002] In the hydroponic cultivation of plants, technological development is underway to create light optimal for plant growth using artificial light sources by LED lighting and to grow plants efficiently. By promoting plant growth, the cultivation period can be shortened, the harvest rotation rate can be increased, or the harvest amount obtained in the same period can be increased. Therefore, there has been a demand for a hydroponic cultivation apparatus and a hydroponic cultivation method that can irradiate light of the required wavelength with an optimal spectral distribution according to the plant variety and growth stage, and can supply liquid fertilizer that promotes plant growth.

[0003] Therefore, the following hydroponic cultivation LED lighting devices have been proposed. Patent Document 1 discloses a plant cultivation LED lighting device provided with a white LED having an emission spectrum continuous in a wavelength range of at least 450 to 700 nm, a red LED having at least one peak in a wavelength range of 600 to 700 nm, a far-red LED having at least one peak in a wavelength range of 700 to 800 nm, and an ultraviolet LED having at least one peak in a wavelength range of 350 to 425 nm. Also disclosed is a switch for individually energizing ON / OFF these single-color LEDs. However, only the emission spectrum of the light source that can be irradiated by the combination of these four light sources is shown, and no technology for enhancing the effect of the entire hydroponic cultivation apparatus including the supply of liquid fertilizer is disclosed.

[0004] Patent Document 2 discloses an LED lighting device for plant cultivation consisting of a white LED with a color temperature of 4500K, an ultraviolet LED with a peak wavelength of 380nm, a red LED with a peak wavelength of 660nm, and a far-red LED with a peak wavelength of 730nm. However, the luminescence intensity of each LED is fixed by the number of LED chips arranged, and there is a problem in that it is difficult to flexibly adjust the emission spectrum according to the type of plant and growth stage.

[0005] Patent Document 3 discloses a hydroponic cultivation apparatus and method comprising a seedbed with a distinctive shape, a cultivation board that houses the seedbed, and a cultivation tub on which the cultivation board is placed at the upper end, with the cultivation tub connected by water supply and drainage pipes, allowing for repeated cycles of full and dry conditions. However, there are no particular limitations on the light source used for illumination, and no information is provided regarding the illumination of light effective for plant growth.

[0006] These prior art technologies had problems in that high growth efficiency could not be achieved because the emission wavelength range and emission intensity of each LED light source that constitutes the lighting necessary for plant growth were not necessarily optimized, and the method of supplying liquid fertilizer that promotes the secretion of growth hormones necessary for promoting plant growth was not optimized. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2021-119743 [Patent Document 2] Japanese Patent Publication No. 2021-058141 [Patent Document 3] Japanese Patent Publication No. 2019-075998 [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention aims to provide a hydroponic cultivation apparatus and method that enable the supply of optimal lighting and liquid fertilizer for efficient plant growth. [Means for solving the problem]

[0009] The hydroponic cultivation apparatus according to the present invention comprises a hydroponic LED light source that combines a white LED whose light intensity in the wavelength range of 470 to 600 nm is 75% or less of the peak light intensity of blue light emitted in the wavelength range of 440 to 460 nm, a red LED that emits light in the wavelength range of 650 to 670 nm, a near-ultraviolet LED that emits light in the wavelength range of 400 to 410 nm, and a near-infrared LED that emits light in the wavelength range of 730 to 740 nm, a water level control mechanism for adjusting the water level of liquid fertilizer to the roots of the cultivated plant, and a water flow control mechanism capable of intermittently supplying a water flow of liquid fertilizer to the roots, wherein the water flow control mechanism is equipped with a liquid delivery pipe having a liquid fertilizer ejection hole near the roots. The water flow control mechanism delivers liquid at predetermined time intervals, spraying water from nozzles to provide a water flow of liquid fertilizer to the roots, the strength of the water flow being sufficient to shake the roots, and the duration of the water flow being the sum of the time during which the water level of the liquid fertilizer increases, the time during which the inflow and delivery of liquid fertilizer continues even after the water level becomes constant in the full-water state, and the time during which the water level decreases as the liquid fertilizer flows out. This method is characterized by intermittently supplying water to the roots while irradiating them with the aforementioned LED light source for hydroponics.

[0010] The aforementioned LED light source for hydroponics is characterized in that the ratio of the luminescence intensity of the red region to the blue region is 2.0 or higher, the ratio of the luminescence intensity of the near-ultraviolet region to the blue region is 0.2 to 0.4, and the ratio of the luminescence intensity of the near-infrared region to the blue region is 0.7 to 0.9.

[0011] An LED lighting fixture on which the aforementioned LED light source for hydroponics is arranged, and For hydroponics A key feature is that the DC power supply for the LED light source is configured to be separable.

[0012] A single DC power supply for the aforementioned hydroponic LED light source is used to power multiple LED lighting fixtures in a single cultivation area.

[0013] The aforementioned LED light source for hydroponics is characterized by the addition of a dimming mechanism, including an on / off function, to its DC power supply.

[0014] The hydroponic cultivation method according to the present invention uses a white LED in which the light intensity in the wavelength range of 470 to 600 nm is 75% or less of the peak light intensity of blue light emitting in the wavelength range of 440 to 460 nm, a red LED emitting in the wavelength range of 650 to 670 nm, a near-ultraviolet LED emitting in the wavelength range of 400 to 410 nm, and a near-infrared LED emitting in the wavelength range of 730 to 740 nm, a hydroponic cultivation LED light source combined with them, a water level control mechanism for adjusting the water level of the liquid fertilizer with respect to the roots of the cultivated plants, and a water flow control mechanism having a liquid delivery pipe having ejection holes capable of intermittently supplying a water flow of the liquid fertilizer to the roots. near the root In the hydroponic cultivation method using a hydroponic cultivation device including a water flow control mechanism, during the light irradiation by the hydroponic cultivation LED light source, a water shortage state in which only the tip of the root is immersed in the liquid fertilizer by the water level control mechanism, and a flowing water state in which the root is wetted by supplying the water flow of the liquid fertilizer by the water flow control mechanism and at the same time a physical stimulus is applied to the root by the water flow are repeated. The water flow of liquid fertilizer provided by the water flow control mechanism is supplied by the water flow control mechanism at predetermined time intervals and ejected from the nozzles to the roots, the strength of the water flow is sufficient to shake the roots, and the duration of the water flow is the sum of the time during which the water level of the liquid fertilizer increases, the time during which the inflow and supply of liquid fertilizer continues even after the water level has stabilized in the full water state, and the time during which the water level decreases as the liquid fertilizer flows out. It is characterized by this.

[0015] The frequency of intermittently supplying the water flow of the liquid fertilizer is a frequency of once every 30 minutes or less, and the time for supplying the water flow of the liquid fertilizer once is 1 to 10 minutes.

Effect of the Invention

[0016] According to the present invention, it is possible to provide a hydroponic cultivation device and a hydroponic cultivation method capable of promoting the growth of plants by intermittently stimulating the roots of plants with a water flow to activate the secretion of growth hormones while providing illumination that optimizes the wavelength range components and emission intensity of light necessary for plant growth.

Brief Description of the Drawings

[0017] [Figure 1] It is a figure which shows an example of the emission spectrum of the LED light source used for the hydroponic cultivation device which concerns on this invention. [Figure 2] It is a figure which shows the structure of the DC power supply of the LED light source used for the hydroponic cultivation device which concerns on this invention. [Figure 3]It is a diagram showing the growth curves of plants cultivated using the hydroponic cultivation device according to the present invention when lighting is performed by changing the configuration of the LED light source. [Figure 4] It is a diagram for explaining an embodiment of a water flow control mechanism used in the hydroponic cultivation device according to the present invention. [Figure 5] It is a diagram for explaining another embodiment of a water flow control mechanism used in the hydroponic cultivation device according to the present invention.

Mode for Carrying Out the Invention

[0018] Hereinafter, an explanation will be given based on an embodiment of the hydroponic cultivation device and the hydroponic cultivation method according to the present invention.

[0019] Plants grow by absorbing light through photoreceptor chlorophyll present in chloroplasts, taking in carbon dioxide and water, and converting them into sugars through photosynthesis. In photosynthesis by chlorophyll, light in the wavelength range of mainly 400 to 700 nm is used, but particularly has absorption peaks in the red region around 660 nm and the blue region around 450 nm, so red light and blue light are effective for photosynthesis.

[0020] Therefore, the LED light source of the hydroponic cultivation device according to the present invention has a white LED with less emission of wavelength components other than the red light and blue light effective for the above photosynthesis in the emission spectrum of the white LED, and the light intensity in the wavelength region of 470 to 600 nm is 75% or less of the peak light intensity of the blue light emitting in the wavelength range of 440 to 460 nm, and a red LED having an emission spectrum in the wavelength range of 650 to 670 nm as basic components.

[0021] On the other hand, in addition to chlorophyll related to photosynthesis, plants have photoreceptors such as phytochrome, cryptochrome, and phototropin that collect light environment information necessary for plant growth, and it is known that the secretion of hormones is activated by the light to which each photoreceptor responds and plays an important role in plant growth.

[0022] For example, plant growth is further promoted by stimulating the roots, which activates the plant's own secretion of growth hormones. Assuming that the source substances of growth hormones are produced in the leaves, we investigated the effects of LEDs with various emission wavelength ranges on plant growth, in addition to the white and red LED light sources mentioned above. As a result, we confirmed that plant growth is significantly promoted by adding, for example, a near-ultraviolet LED with an emission peak at 406 nm and a near-infrared LED with an emission peak at 735 nm.

[0023] Based on these experimental results, it is believed that near-ultraviolet and near-infrared light also play an important role in plant growth, similar to photosynthesis by blue and red light. Therefore, in addition to the basic components consisting of the white LED and red LED described above, a near-ultraviolet LED having an emission spectrum in the wavelength range of 400-410 nm and a near-infrared LED having an emission spectrum in the wavelength range of 730-740 nm were added as components to the LED light source of the hydroponic cultivation apparatus according to the present invention.

[0024] Preferably, the emission intensity of each emission peak is such that the ratio of emission intensity of the red region emission peak to the blue region emission peak is 2.0 or higher, the ratio of emission intensity of the near-ultraviolet region emission peak to the blue region emission peak is 0.2 to 0.4, and the ratio of emission intensity of the near-infrared region emission peak to the blue region emission peak is 0.7 to 0.9.

[0025] As an example of an embodiment of the present invention, a hydroponic LED light source was constructed using one or more of the following: a white LED whose light intensity in the wavelength range of 470 nm to 600 nm is 75% or less of the peak light intensity of blue light emitted at 450 nm; a red LED having an emission peak at 660 nm; a near-ultraviolet LED with a peak wavelength of 406 nm; and a near-infrared LED with a peak wavelength of 735 nm. The emission spectrum is shown in Figure 1.

[0026] The emission spectrum 1 of the LED light source used in the hydroponic cultivation apparatus according to the present invention will be explained with reference to Figure 1. The emission spectrum 1 of the LED light source has a near-ultraviolet peak 11 from a near-ultraviolet LED, a blue peak 12 from a white LED, a red peak 13 which is a combination of the red peak from the white LED and the red peak from the red LED, and a near-infrared peak 14 from a near-infrared LED.

[0027] The magnitudes of each emission peak were adjusted so that the emission intensity ratio of the 660nm red light peak to the 450nm blue light peak was 2.5, the emission intensity ratio of the entire 470-600nm region of the white LED to the 450nm blue light peak was 0.7 or less, the emission intensity ratio of the 406nm near-ultraviolet light peak to the 450nm blue light peak was 0.3, and the emission intensity ratio of the 735nm near-infrared light peak to the 450nm blue light peak was 0.7.

[0028] While LED lighting is generally considered to have a long lifespan, the cultivation environments of hydroponics and plant factories present harsh conditions for LED lighting fixtures. Even if the LED chip itself has a long lifespan, malfunctions in the DC power supply built into the lighting fixture can negate the LED's inherent long lifespan. More specifically, electrolytic capacitors are commonly used to convert AC commercial power to DC, but electrolytic capacitors are susceptible to heat and humidity, resulting in an extremely short lifespan compared to LED chips. Since the environment in hydroponics is harsh for electrical components, a short lifespan for LED lighting fixtures, which represent a high proportion of the cost of cultivation equipment, leads to increased cultivation costs.

[0029] LED lighting fixtures typically have an LED module containing multiple LED chips and a DC power supply integrated inside the fixture. However, the above problem can be solved by housing the DC power supply as an external power supply for the lighting fixture in a highly moisture-resistant package. This eliminates the effects of heat generated by the LEDs and the high humidity of the cultivation equipment, extending the lifespan of both the LED lighting fixture and the DC power supply, and preventing an increase in cultivation costs. Furthermore, even if the DC power supply fails, there is the advantage that only the DC power supply needs to be replaced, rather than having to replace the entire expensive LED lighting fixture.

[0030] Figure 2 shows a block diagram of the DC power supply used for the LED light source in the hydroponic cultivation apparatus according to the present invention. The system uses a commercial AC power supply 21 to supply DC power to an LED lighting fixture 25, which is a modularized unit containing at least one or more types of LEDs arranged to obtain the emission spectrum shown in Figure 1. This DC power supply is provided through a timer 22 that sets the light / dark periods to adjust the circadian rhythm of the plants, and an AC / DC converter 23. A single cultivation area 26 containing multiple lighting fixtures is driven by a single DC power supply. In the example shown in Figure 2, six LED lighting fixtures 25 are placed in one cultivation area 26. Furthermore, a dimming function 24, including an on / off function described later, is placed between the AC / DC converter 23 and the LED lighting fixture 25.

[0031] In cultivation, as plants grow, the distance between the leaves and the lighting fixtures decreases, and the light intensity perceived by the leaves increases with growth. For example, if the light intensity is adjusted to the early stages of growth, i.e., when the seedlings are short, the light intensity may become too strong in the later stages of growth. At that time, growth disorders such as tip burn, where the leaf tips turn black, may occur. Therefore, a dimming function including an on / off function was added to the DC power supply shown in Figure 2. This makes it possible to control the on / off state and dim the light for each LED, allowing unnecessary types of LEDs to be turned off or the light intensity to be adjusted to the optimal level according to growth. This reduces power consumption and prevents growth disorders, resulting in reduced cultivation costs through power savings and improved cultivation yield.

[0032] The LED light source of the hydroponic cultivation apparatus according to the present invention can be used at all stages of the growth of cultivated plants. However, generally, only water and temperature are important during the germination stage, and light is hardly needed. Therefore, using the on / off function of the dimming function of the DC power supply of the LED light source of the hydroponic cultivation apparatus according to the present invention, it is possible to illuminate only the white LED and turn off the other LED light sources. This makes it possible to save power by not turning on LED light sources other than the white LED.

[0033] Generally, LED light sources can be equipped with dimming functions using various methods. One example of a means of achieving dimming is to change the switching duty cycle of a switching power supply. Normally, as described above, the DC power supply is also located inside the lighting fixture, so when the output of the light source is large, the components of the switching power supply also become large, which leads to the problem of the entire lighting fixture becoming large. However, in the LED light source used in the hydroponic cultivation device according to the present invention, the DC power supply is configured to be externally independent, so the lighting fixture is not constrained by the size limitations of the power supply.

[0034] Typical methods for supplying and circulating nutrient solution in hydroponic systems involve configuring the nutrient solution storage area, water supply and drainage channels, and cultivation containers to ensure circulation. For example, a siphon and overflow pipe are used to connect cultivation containers, allowing excess nutrient solution from one container to be circulated to others.

[0035] The hydroponic cultivation method according to the present invention is characterized by a cultivation method that stimulates the roots by irradiating them with light of wavelengths effective for plant growth while simultaneously intermittently supplying water to the roots to promote the secretion of growth hormones. This cultivation method is characterized by repeatedly alternating between a drought state in which only the tips of the roots are submerged in liquid fertilizer, and a flowing water state in which the roots are wet with liquid fertilizer and at the same time physically stimulated by the water flow.

[0036] In a drought condition where only the tips of the roots are submerged in liquid fertilizer and the rest is exposed to the air and dry, the roots tend to grow more easily than usual, and the efficiency of absorbing water and fertilizer components increases. In addition, the aerial roots, being in direct contact with the air, take in oxygen directly from the air, improving the efficiency of oxygen absorption.

[0037] On the other hand, intermittently wetting the roots with liquid fertilizer and then agitating them with a water current stimulates the growth hormone-secreting tissue at the base of the roots, thereby promoting the secretion of growth hormone. However, if near-ultraviolet and near-infrared light, which are necessary for producing the source substances of growth hormone, are not present, the effect on growth hormone secretion will be small. Therefore, it is necessary to stimulate the roots with a water current from the liquid fertilizer and irradiate them with near-ultraviolet and near-infrared light simultaneously.

[0038] In hydroponic cultivation systems, a water level control mechanism is provided to control the distance between the roots and the nutrient solution surface in order to achieve a drought state where only the tips of the roots are in contact with the liquid surface. One example of such a water level control mechanism is to install an overflow pipe or siphon and adjust the water level by changing the height of the drain outlet. However, other methods include increasing or decreasing the supply of nutrient solution to raise or lower the liquid level, or raising or lowering the cultivation board on which the plants are mounted relative to the liquid level, and the system is not limited to these methods.

[0039] Furthermore, the water flow control mechanism for supplying liquid fertilizer to the roots may include methods such as supplying water to the cultivation container from a water pump at predetermined time intervals, or placing a liquid delivery pipe with liquid fertilizer ejection holes near the roots of each plant and supplying liquid at predetermined time intervals, with the water flowing out of the ejection holes. It is also possible to utilize the increase or decrease in water level due to the inflow and outflow of liquid fertilizer between cultivation containers via an overflow pipe or siphon, and is not limited to these methods. In any case, whether the water level of the liquid fertilizer increases or decreases due to the inflow and outflow of liquid fertilizer, or whether the water level is kept constant by a water level control mechanism, a state in which water flow is generated is defined as a flowing water state.

[0040] In the hydroponic cultivation method according to the present invention, the frequency of the water flow of intermittently supplied liquid fertilizer is not particularly limited, but excessive water flow may damage the roots. Therefore, the strength of the water flow should be such that it can provide physical stimulation to the tissues that secrete growth hormones in the roots, that is, a water flow strong enough to shake the roots. The frequency of water flow is counted as one cycle of inflow and outflow of liquid fertilizer, that is, one cycle from a dry state to a full state and back to a dry state, or one cycle from a full state to a dry state and back to a full state. Furthermore, the duration of water flow is defined as the total time of time during which the water level of the liquid fertilizer increases due to inflow through the overflow pipe or siphon, or delivery by the water pump, as well as the time during which inflow or siphon inflow or delivery by the water pump continues even after the water level has stabilized in a full state, and the time during which the water level decreases as the liquid fertilizer flows out through the overflow pipe or siphon. As defined above, when defining the period and duration of the water flow, a frequency of water flow of once every 30 minutes or less is preferable, and the duration of each water flow is preferably in the range of 1 to 10 minutes.

[0041] In the present invention, the type of plant is not particularly limited, but it is preferable to apply it to leafy vegetables, fruit vegetables, herbs, grains, etc. Examples of vegetables include, but are not limited to, leaf lettuce, garden lettuce, curly lettuce, lamb's lettuce, romaine lettuce, endive, Lollo Rosso, arugula lettuce, frilly lettuce, green leaf lettuce, ssamjang, and other types of lettuce; Asteraceae vegetables such as garland chrysanthemum; Morning glory vegetables such as spinach; Rosaceae vegetables such as strawberries.

[0042] (Example 1) As one embodiment of the hydroponic cultivation apparatus according to the present invention, a type of green leaf lettuce called sanchu was cultivated using the hydroponic cultivation apparatus 3 shown in Figure 4. In this embodiment, an overflow pipe 40 and siphon 41, used for discharging liquid fertilizer from the cultivation container 31 to other cultivation containers, and an overflow pipe 42 and siphon 43, used for supplying liquid fertilizer from yet another cultivation container to the cultivation container 31, were used as a water level control mechanism and a water flow control mechanism, and the system repeatedly switched between a water flow state in which the roots were submerged in liquid fertilizer and a drought state in which only the tips of the roots were submerged in liquid fertilizer. The water flow occurs once every 30 minutes, and each flow lasts for 10 minutes. Figure 3 shows the cultivation curves for the LED light source of the present invention, used in the LED lighting fixture 25 used for light irradiation, when only white LEDs and red LEDs are used, when near-ultraviolet LEDs are added, and when near-infrared LEDs are added. The horizontal axis represents the number of cultivation days from sowing, and the vertical axis represents the weight per plant. The light intensity on the cultivation board surface at this time, when all white LEDs, red LEDs, near-ultraviolet LEDs, and near-infrared LEDs are combined, has a photosynthetic photon flux density of 120 μmol·m². -2 ·s -1 Furthermore, Timer 22 was set so that the light period was 85% and the dark period was 15%.

[0043] Specifically, by connecting the cultivation container 31 with an overflow pipe 40 and a siphon 41, excess liquid fertilizer in the cultivation container 31 flows out through the overflow pipe 40 and siphon 41, and similarly, liquid fertilizer flows in from other cultivation containers through the overflow pipe 42 and siphon 43. When the liquid fertilizer level rises, drainage begins when the water level reaches the drain outlet 400 of the overflow pipe 40, and the water level does not rise any further, so the overflow pipe 40 functions as a water level control mechanism for a full water level 36. At this time, the water level is set so that the roots 34 of the buds 33 supported on the cultivation board 35 are completely submerged in the liquid fertilizer. A valve 44 provided in the siphon 41 functions as part of the water flow control mechanism, and when the valve 44 is opened, drainage begins through the drain outlet 410 of the siphon 41 and the water level drops, and when the water level reaches the drain outlet 410 of the siphon 41, drainage stops, so it functions as a water level control mechanism for a drought state 37 where only the tips of the roots are submerged in the liquid fertilizer. The height of the drain outlets for the overflow pipe 40 and siphon 41 can be adjusted as needed.

[0044] Thus, as long as liquid fertilizer flows in and out through the overflow pipe 40 and siphon 41, a water flow is generated by the movement of liquid fertilizer within the cultivation container 31, which can shake the roots of the cultivated plants and provide physical stimulation. In this embodiment, the frequency of water flow due to the inflow of liquid fertilizer from a dry state to a full state, the water flow in the full state, and the water flow due to the outflow of liquid fertilizer from a full state to a dry state was once every 30 minutes. The duration of the water flow due to the inflow and outflow of liquid fertilizer was adjusted to 10 minutes.

[0045] (Example 2) As another embodiment of the present invention, lettuce was cultivated using the hydroponic cultivation apparatus 30 according to the present invention shown in Figure 5. The LED lighting fixture 25 and light irradiation conditions used were the same as in Example 1. In the hydroponic cultivation apparatus 30 shown in Figure 5, overflow pipes 45 and 46 were used as a water level control mechanism, and the liquid supply pipe 47 was used as a water flow control mechanism, repeatedly switching between a water flow state in which the entire root was submerged in liquid fertilizer and a drought state in which only the tips of the roots were submerged in liquid fertilizer.

[0046] Specifically, by connecting the cultivation container 32 using two overflow pipes 45 and 46 with drain outlets at different heights, excess liquid fertilizer in the cultivation container 32 flows out through the overflow pipes 45 and 46, functioning as a water level control mechanism. On the other hand, liquid fertilizer is supplied from the supply pipe 47 using a water flow pump 49, and the water flow pump 49 functions as a water flow control mechanism by adjusting the flow rate of the water flow pump 49 to control the strength of the water flow. When the liquid fertilizer level rises and reaches the drain outlet 450 of the overflow pipe 45, the water level does not rise any further, so the overflow pipe 45 functions as a water level control mechanism for the full water level 36. When liquid fertilizer is introduced from the supply pipe 47 using a water pump, water flow is continuously supplied to the roots 34 until the water level reaches the full flow state 36, and even after the water level reaches the full flow state 36, as long as the water level is kept constant by drainage from the drain outlet 450 of the overflow pipe, which can shake the roots 34 of the cultivated plant and provide physical stimulation. When the valve 48 of the overflow pipe 46 is opened from a full-water flow state, the liquid fertilizer water level drops to the position of the drain outlet 460 of the overflow pipe 46 and stops at the water level 37 of the dry state. In this embodiment, the frequency of water flow due to the inflow of liquid fertilizer from a low-water state to a full-water state, water flow in the full-water state, and water flow due to the outflow of liquid fertilizer from a full-water state to a low-water state was once every 30 minutes. Furthermore, the duration of water flow due to the inflow and outflow of liquid fertilizer was adjusted to 10 minutes.

[0047] The results of Example 1 and Example 2, in which lettuce was cultivated according to the present invention, along with the results in the absence of intermittent water flow to the roots, which is a characteristic of the present invention, are shown in Table 1.

[0048] [Table 1]

[0049] The light intensity in a typical plant factory using standard white LEDs is 200 μmol·m². -2 ·s -1 It is around that level, and recently it has been around 300 μmol·m -2 ·s -1Sometimes, a strong light source is used. Under such conditions, in a typical plant factory, the cultivation rate is generally such that 70-100g of green leaf lettuce per plant can be obtained in about 40 days from sowing.

[0050] In contrast, in one embodiment of the hydroponic cultivation method according to the present invention, the light intensity is 120 μmol·m -2 ·s -1 Despite being about half the level of a typical plant factory, in Example 1, with water flow, 90-110g per plant was obtained in 38 days with white LEDs alone, 135-150g per plant in 38 days with the addition of red LEDs, 135-150g per plant in 34 days with the addition of near-ultraviolet LEDs, and 135-150g per plant in 30 days with the addition of near-infrared LEDs. This shows that adding near-ultraviolet and near-infrared light in addition to blue and red light significantly improved the growth rate. In Example 2, with water flow, 100-120g per plant was obtained in 38 days with white LEDs alone, 135-150g per plant in 36 days with the addition of red LEDs, 135-150g per plant in 32 days with the addition of near-ultraviolet LEDs, and 135-150g per plant in 28 days with the addition of near-infrared LEDs. This shows that adding near-ultraviolet and near-infrared light in addition to blue and red light significantly improved the growth rate. In the absence of water flow, the results showed that growth was 70-90g in 40 days with white LEDs alone, 90-110g in 40 days with the addition of red LEDs, 100-120g in 40 days with the addition of near-ultraviolet LEDs, and 100-120g in 40 days with the addition of near-infrared LEDs. These results indicate that growth is promoted when water flow is provided to the roots, and that a particularly significant effect is obtained when irradiated with near-ultraviolet and near-infrared light.

[0051] From the results in Table 1, it is thought that when red LED light is added to white LED light, the presence of water flow promotes root elongation and activation of the roots through oxygen absorption by aerial roots, thus promoting growth compared to when there is no water flow. Furthermore, when red LED light and near-ultraviolet LED light are added to white LED light, growth is clearly promoted when there is water flow. This is thought to be because near-ultraviolet LED light generates growth hormone precursors in the leaves, and the stimulation of the roots by water flow promotes the secretion of hormones in the roots, thus promoting growth. Moreover, when red LED light, near-ultraviolet LED light, and near-infrared LED light are added to white LED light, it is thought that the presence of near-infrared light also generates growth hormone precursors, and the secretion of growth hormones in the roots by water flow is promoted, resulting in further growth promotion. [Industrial applicability]

[0052] One embodiment of the present invention provides a hydroponic cultivation apparatus and method that can concentrate light in the wavelength range necessary for photosynthesis and photomorphogenesis in plants, thereby more effectively promoting plant growth. Furthermore, the intermittent water flow promotes the secretion of growth hormones in the roots, enabling even greater growth promotion, and thus providing a hydroponic cultivation system with high cultivation efficiency and energy efficiency. [Explanation of symbols]

[0053] 1. Emission spectrum of an LED light source for a hydroponic cultivation system according to the present invention. 11 Wavelength components of near-ultraviolet light from near-ultraviolet LEDs 12 Wavelength components of blue light from a white LED 13. Wavelength components of red light from a white light LED and wavelength components of red light from a red light LED 14 Wavelength components of near-infrared light from near-infrared LEDs 2. Block diagram of the DC power supply for the LED light source for the hydroponic cultivation apparatus according to the present invention. 21 Commercial AC power supply 22 Timer 23 AC / DC Converters 24. Dimming function including on / off function 25 LED lighting fixtures 26 One cultivation area 3. Hydroponic cultivation system of Example 1 30 Hydroponic cultivation system of Example 2 31 Cultivation container of Example 1 32 Cultivation container for Example 2 33 buds 34 Root 35 Cultivation Boards 36. Water level when the water is flowing at full capacity. 37 Water level during drought 40 Overflow pipe 41 Siphon 400 Overflow pipe drain 410 Siphon drain 42 Overflow pipe from other growing containers 43 Siphon from other growing containers 44. Siphon valve 45 Overflow pipe 1 46 Overflow pipe 2 450 Overflow pipe 1 drain 460 Overflow pipe 2 drain 47 Liquid supply pipe 48 Valve for overflow pipe 2 49 Water flow pump

Claims

1. A hydroponic LED light source is provided, which combines a white LED whose light intensity in the 470-600 nm wavelength range is 75% or less of the peak light intensity of blue light emitted in the 440-460 nm wavelength range, a red LED that emits light in the 650-670 nm wavelength range, a near-ultraviolet LED that emits light in the 400-410 nm wavelength range, and a near-infrared LED that emits light in the 730-740 nm wavelength range. It comprises a water level control mechanism for adjusting the water level of liquid fertilizer to the roots of a cultivated plant, and a water flow control mechanism capable of intermittently supplying a water flow of liquid fertilizer to the roots, The water flow control mechanism includes a liquid delivery pipe having a liquid fertilizer ejection hole near the root, The water flow control mechanism delivers liquid at predetermined time intervals, and sprays water from the nozzle to provide a water flow of liquid fertilizer to the roots. The strength of the water flow is such that it shakes the roots. The duration of the water flow is the sum of the time during which the liquid fertilizer level increases, the time during which the inflow or flow of liquid fertilizer continues even after the water level has stabilized in the full-water state, and the time during which the liquid fertilizer flows out and the water level decreases. A hydroponic cultivation apparatus characterized by intermittently supplying water flow to the roots while irradiating them with the aforementioned LED light source for hydroponics.

2. The hydroponic cultivation apparatus according to claim 1, characterized in that the ratio of the luminescence intensity of the red region to the blue region of the LED light source for hydroponics is 2.0 or more, the ratio of the luminescence intensity of the near-ultraviolet region to the blue region is 0.2 to 0.4, and the ratio of the luminescence intensity of the near-infrared region to the blue region is 0.7 to 0.

9.

3. The hydroponic cultivation apparatus according to claim 1 or 2, characterized in that the LED lighting fixture on which the aforementioned hydroponic LED light source is arranged and the DC power supply for the hydroponic LED light source are configured to be separable.

4. The hydroponic cultivation apparatus according to claim 3, characterized in that a single DC power supply for the aforementioned hydroponic LED light source drives multiple LED lighting fixtures in a single cultivation area together.

5. The hydroponic cultivation apparatus according to claim 3, characterized in that a dimming function including an on / off function is added to the DC power supply of the aforementioned LED light source for hydroponics.

6. A hydroponic LED light source is provided, which combines a white LED whose light intensity in the 470-600 nm wavelength range is 75% or less of the peak light intensity of blue light emitted in the 440-460 nm wavelength range, a red LED that emits light in the 650-670 nm wavelength range, a near-ultraviolet LED that emits light in the 400-410 nm wavelength range, and a near-infrared LED that emits light in the 730-740 nm wavelength range. In a hydroponic cultivation system that includes a water level control mechanism for adjusting the water level of liquid fertilizer to the roots of a cultivated plant, and a water flow control mechanism equipped with a liquid delivery pipe having ejection holes near the roots that can intermittently supply a flow of liquid fertilizer to the roots, While light irradiation is performed by the aforementioned LED light source for hydroponics, the water level control mechanism repeatedly switches between a dry state in which only the tips of the roots are submerged in the nutrient solution and a flowing state in which the roots are wet by applying a water flow from the nutrient solution through the water flow control mechanism, while simultaneously applying physical stimulation to the roots with the water flow. The water flow of liquid fertilizer supplied by the water flow control mechanism is delivered by the water flow control mechanism at predetermined time intervals and ejected from the ejection holes to the roots. The strength of the water flow is such that it shakes the roots. The hydroponic cultivation method is characterized in that the duration of the water flow is the sum of the time during which the water level of the liquid fertilizer increases, the time during which the inflow or flow of liquid fertilizer continues even after the water level has stabilized in the full-water state, and the time during which the water level decreases due to the outflow of liquid fertilizer.

7. The hydroponic cultivation method according to claim 6, characterized in that the frequency of intermittently supplying the liquid fertilizer is once every 30 minutes or less, and the duration of each supply of the liquid fertilizer is 1 to 10 minutes.

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