Nutrient solution for cultivating vegetables and method for producing vegetables

Abstract

To improve the taste of vegetables.SOLUTION: A vegetable production method comprises a first step, a second step, a third step, a fourth step, and a fifth step. Therein: in the first step, seeding is performed; in the second step, a cotyledon is caused to sprout from a seed in a first period; in the third step, the vegetable is grown in a second period subsequent to the first period; in the fourth step, the vegetable is further grown in a third period subsequent to the second period; and in the fifth step, the vegetable is harvested; and in the third step, in at least a part of the second period, the vegetable is grown irradiated with first light having a maximum value of a light intensity in a wavelength range of 420 to 490 nm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for producing vegetables and lettuce.

Background Art

[0002] As a method for producing plants in place of general soil cultivation, hydroponics is known (see, for example, the descriptions in Patent Documents 1 to 5).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding the production of vegetables by hydroponics, there is room for improvement in terms of improving the taste of the vegetables.

Means for Solving the Problems

[0005] A method for producing vegetables is disclosed.

[0006] One aspect of the method for producing vegetables includes a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, sowing is carried out. In the second step, cotyledons are made to emerge from the seeds during a first period. In the third step, the vegetables are grown during a second period following the first period. In the fourth step, the vegetables are further grown during a third period following the second period. In the fifth step, the vegetables are harvested. In the latter stage of the second period, the vegetables are irradiated with a first light having a first maximum value of light intensity in the wavelength range of 420 nm to 490 nm and the maximum value of light intensity in the wavelength range of 500 nm to 600 nm being smaller than the first maximum value. During the first period, the early stage of the second period, and the third period, the vegetables are grown by irradiating them with a second light having a second maximum value of light intensity in the wavelength range of 590 nm to 650 nm, having a peak light intensity smaller than the second maximum value in the wavelength range of visible light of 500 nm or less, and the average value of light intensity in the wavelength range of 490 nm to 540 nm being smaller than the peak light intensity.

Advantages of the Invention

[0007] For example, the taste of the vegetables can be improved.

Brief Description of the Drawings

[0008]

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Figure 13

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the first embodiment will be described with reference to the drawings. In the drawings, parts having the same configuration and function are denoted by the same reference numerals, and redundant descriptions will be omitted in the following description. The drawings are schematically shown. From Fig. 2(a) to Fig. 9(b), a right-handed XYZ coordinate system is attached. In this XYZ coordinate system, the longitudinal direction along the horizontal direction of the lighting device 10 is the +X direction, the short-side direction along the horizontal direction of the lighting device 10 is the +Y direction, and the upward direction as the direction orthogonal to both the +X direction and the +Y direction is the +Z direction.

[0010] <1. First Embodiment> <1-1. Outline of Hydroponic Cultivation of Vegetables> As shown in Fig. 1, the period of hydroponic cultivation of vegetables has, for example, a first period P1, a second period P2, and a third period P3. The vegetables to be hydroponically cultivated (also referred to as cultivated target vegetables) include, for example, leafy vegetables such as lettuce.

[0011] The first period P1 is the period (also referred to as the germination period) from the timing of sowing (time T0) to the timing of starting seedling raising including germination (time T1). The timing of sowing is the timing of sowing seeds on the seedbed. For example, sponges, polyurethanes, non-woven fabrics, etc. are applied to the seedbed. The timing of germination is the timing when cotyledons emerge from the seeds on the seedbed. For example, when the cultivated target vegetable is lettuce, the cotyledons are dicotyledons. The length L1 of the period from sowing to seedling raising including germination for lettuce is, for example, about 7 days.

[0012] The second period P2 is the period from the timing of starting seedling raising including germination (time T1) to the timing (time T3) a predetermined number of days before the timing of harvesting (time T4). This second period P2 is the period when the vegetables mainly grow (also referred to as the main growth period). The second period P2 is divided into, for example, a first half period (also referred to as the second A period) P2a and a second half period (also referred to as the second B period) P2b.

[0013] The second A period P2a corresponds to the period of growing seedlings (also referred to as the seedling raising period). For example, when the target vegetable for cultivation is lettuce, the length L2a of the seedling raising period is set to about 7 to 14 days. At the timing (time T2) when the second A period P2a ends, an operation of expanding the interval between the seedlings after raising (also referred to as the interval expansion operation) is performed. The interval expansion operation aims to reduce the inhibition of photosynthesis caused by the overlapping of leaves due to growth between adjacent vegetables and to expand the room for growth. As the interval expansion operation, for example, an operation of transplanting the seedlings after raising from the seedbed to the medium adjusted according to growth (also referred to as planting) is performed. As the medium, for example, sponge, polyurethane, or non-woven fabric is adopted. At the time of planting, for example, the intervals between the seedlings such as the plant interval and the row interval are adjusted. The interval expansion operation can also be realized by dividing the seedbed and expanding the interval between the seedlings, or by thinning the seedlings without performing the planting of transplanting the seedlings from the seedbed to the medium.

[0014] The second B period P2b is the period of growing vegetables from the seedlings with the expanded interval (also referred to as the cultivation growth period). For example, when the target vegetable for cultivation is lettuce, the length L2b of the cultivation growth period is set to about 10 to 16 days.

[0015] The third period P3 is the period of further growing vegetables before harvesting (also referred to as the immediate pre-harvest period). The immediate pre-harvest period is the period of a predetermined number of days before harvesting the vegetables. The length L3 of the immediate pre-harvest period is set to about 1 to 7 days, for example. For example, when the target vegetable for cultivation is lettuce, the length L3 is set to about 4 to 7 days.

[0016] From the above, the method for producing vegetables by hydroponics has, for example, the first step S1 to the fifth step S5 that are performed in order. The first step S1 is the step of sowing seeds. The second step S2 is the step of causing cotyledons to emerge from the seeds in the first period P1. The third step S3 is the step of growing the vegetables in the second period P2 following the first period P1. The fourth step S4 is the step of further growing the vegetables in the third period P3 following the second period P2. The fifth step S5 is the step of harvesting the vegetables. When performing such hydroponics, the seedbed and the culture medium are each located in a container such as a cultivation tray in which a culture solution (also referred to as a nutrient solution) for growing vegetables is stored. A solution in which the components of a fertilizer suitable for the situation are dissolved is applied to the nutrient solution. Also, during the germination period, for example, by supplying water from above the seeds sown on the seedbed, the germination in which cotyledons emerge from the seeds is promoted.

[0017] <1-2. Configuration of the Cultivation Site in Hydroponics> At the timing of sowing, for example, as shown in FIGS. 2(a) and 2(b), a plurality of seeds 32a are arranged at appropriate intervals on a seedbed 31a located in the upper recess of a cultivation container 30a. For the container 30a, for example, a cultivation tray or the like is applied. This cultivation tray has, for example, a rectangular outer shape when viewed in plan from above downward (-Z direction). This container 30a is in a state in which a nutrient solution for growing vegetables is stored. For this reason, the seedbed 31a is in a state of being immersed in the nutrient solution. Also, for example, a plurality of lighting devices 10 are arranged on a support 34 located above the container 30a. The plurality of lighting devices 10 are arranged, for example, at appropriate intervals so as to be parallel to each other. Electric power is supplied to each lighting device 10 via, for example, a power supply 33.

[0018] In the first period P1 as the germination period, for example, as shown in FIG. 2(b), without using sunlight, the light sources of the respective lighting devices 10 are made to emit light for about 12 to 16 hours per day, and the light emitted from the respective lighting devices 10 is irradiated onto a plurality of seeds 32a. Further, water is supplied to the plurality of seeds 32a. Thereby, germination from each seed 32a is promoted. As a result, for example, as shown in FIGS. 3(a) and 3(b), cotyledons emerge from the plurality of seeds 32a respectively, and a plurality of vegetable seedlings 32b can be obtained. In FIGS. 2(b), 3(b), 4(b), 5(b) and 6(b), for the light emitted from the respective lighting devices 10, the traveling direction of the light is indicated by a two-dot chain line arrow, and the outer edge of the light is drawn by a two-dot chain line.

[0019] In the second period P2a as the seedling raising period, for example, as shown in FIGS. 4(a) and 4(b), further, without using sunlight, the light sources of the respective lighting devices 10 are made to emit light for about 12 to 16 hours per day, and the light emitted from the respective lighting devices 10 is irradiated onto a plurality of vegetable seedlings 32b. Thereby, for example, the growth of the plurality of vegetable seedlings 32b is promoted.

[0020] When the seedling raising period ends, for example, the seedlings 32b of a plurality of vegetables are replanted by transplantation. Here, for example, as shown in FIGS. 5(a) and 5(b), the seedlings 32b of a plurality of vegetables that will become the cultivation target vegetables 32c are arranged at appropriate intervals in the culture medium 31b located in the upper recess of the cultivation container 30b. Hereinafter, the vegetable seedlings 32b and the cultivation target vegetables 32c are also collectively referred to as "vegetables" as appropriate. For the container 30b, for example, a cultivation tray or the like is applied. This cultivation tray has, for example, a long rectangular outer shape when viewed in plan from above in the downward (-Z direction). In the examples of FIGS. 5(a) and 5(b), four long containers 30b are arranged in a substantially parallel state. A nutrient solution for growing vegetables is stored in each container 30b. For this reason, the culture medium 31b is in a state of being immersed in the nutrient solution. Further, for example, a plurality of lighting devices 10 are arranged on the support 34 located above the container 30a. The plurality of lighting devices 10 are arranged so as to be parallel to each other at appropriate intervals. In the examples of FIGS. 5(a) and 5(b), the longitudinal direction of each lighting device 10 is, for example, orthogonal to the longitudinal direction of the container 30b. Electric power is supplied to each lighting device 10 via the power supply 33.

[0021] In the second B period P2b as the cultivation growth period, for example, as shown in FIG. 5(b), without using sunlight, the light sources of the respective lighting devices 10 are caused to emit light for about 12 to 16 hours per day, and the light emitted from each lighting device 10 is irradiated onto the plurality of cultivation target vegetables 32c. Thereby, the growth of the plurality of cultivation target vegetables 32c is promoted.

[0022] In the third period P3 as the period immediately before harvesting, for example, as shown in FIG. 6(b), without using sunlight, the light sources of the respective lighting devices 10 are caused to emit light for about 12 to 16 hours per day, and the light emitted from each lighting device 10 is irradiated onto the plurality of cultivation target vegetables 32c. Thereby, as shown in FIGS. 6(a) and 6(b), the growth of the plurality of cultivation target vegetables 32c is promoted.

[0023] Here, for example, the distances between the plurality of lighting devices 10 and the seeds 32a, the vegetable seedlings 32b, or the target vegetables 32c to be cultivated may be changed to appropriate distances.

[0024] In addition, for the plurality of lighting devices 10, for example, light sources that emit light having mutually different spectra may be applied between the first period P1, the second A period P2a, the second B period P2b, and the third period P3. Also, for the plurality of lighting devices 10, for example, light sources that emit light having mutually different spectra may be applied between the second A period P2a and the second B period P2b.

[0025] According to the method for producing vegetables by hydroponics as described above, the target vegetables 32c can be grown without using sunlight.

[0026] <1-3. Configuration of Lighting Device> As shown in FIGS. 7(a), 7(b), and 8, the lighting device 10 includes, for example, a housing 11, a wiring board 12, a plurality of light sources 1, and a light-transmissive substrate 13.

[0027] <1-3-1. Housing> The housing 11 has, for example, a long rectangular parallelepiped outer shape having a longitudinal direction along the +X direction, and has an opening facing the -Z direction. The housing 11 has, for example, a function of holding the light-transmissive substrate 13 and a function of dissipating the heat generated by the light source 1 to the outside. As the material of the housing 11, for example, metals such as aluminum, copper or stainless steel, plastics or resins are applicable. The housing 11 has, for example, a long main body portion 21 having a bottom portion 21a and a pair of holding portions 21b, and two lid portions 22. The bottom portion 21a has, for example, a longitudinal direction along the +X direction. The pair of holding portions 21b have, for example, a longitudinal direction along the +X direction in a state of hanging down in the -Z direction from both ends in the width direction (+Y direction) of the bottom portion 21a. For this reason, the main body portion 21 has an opening facing the -Z direction (downward) and openings located at both ends in the +X direction (longitudinal direction). The two lid portions 22 are, for example, in a state of closing the openings located at both ends in the +X direction (longitudinal direction) of the main body portion 21. Further, each holding portion 21b has, for example, a groove portion extending along the +X direction for holding the light-transmissive substrate 13 in the vicinity of the end portion in the -Z direction. In other words, the pair of groove portions are positioned so as to face each other. The length of the housing 11 in the longitudinal direction (+X direction) is, for example, about 100 millimeters (mm) to 2000 mm.

[0028] <1-3-2. Wiring Substrate> The wiring substrate 12 is, for example, located in a state of being fixed to the housing 11 within the housing 11. The wiring substrate 12 is, for example, in a state of being fixed to the surface facing the -Z direction within the housing 11. As the wiring substrate 12, for example, printed circuit boards such as rigid substrates, flexible substrates or rigid-flexible substrates are applicable.

[0029] <1-3-3. Light Source> The plurality of light sources 1 are, for example, mounted on the wiring substrate 12 within the housing 11 and are located in a state of being arranged in a straight line along the longitudinal direction of the housing 11. As shown in FIGS. 9(a) and 9(b), the light source 1 has, for example, a substrate 2, a light-emitting element 3, a frame body 4, a sealing member 5 and a wavelength conversion member 6.

[0030] <<Substrate 2>> Substrate 2 is, for example, an insulating substrate. For the material of substrate 2, for example, ceramics such as alumina or mullite, or glass ceramics, etc. are applicable. For the material of substrate 2, composite materials such as a material in which multiple types of ceramics are mixed, or a material in which ceramics and glass ceramics are mixed may also be applicable. Here, for example, if a polymer resin in which fine particles of metal oxide are dispersed is applied to the material of substrate 2, the thermal expansion coefficient of this substrate 2 can be appropriately adjusted. Further, substrate 2 has, for example, a conductor (also referred to as a wiring conductor) that electrically connects the inside and the outside of this substrate 2. For the material of the wiring conductor, for example, conductive materials such as tungsten, molybdenum, manganese, or copper are applicable. The wiring conductor can be produced, for example, by applying a metal paste obtained by adding an organic solvent to powder such as tungsten in a predetermined pattern to a ceramic green sheet that becomes substrate 2, and laminating and firing a plurality of ceramic green sheets. For example, if a plating layer such as nickel or gold is deposited on the surface of the wiring conductor, oxidation of the wiring conductor can be reduced. Further, if a metal reflection layer is positioned in a state of being separated from the wiring conductor and the plating layer on the surface facing the -Z plane of substrate 2, the reflection layer can efficiently reflect light in the -Z direction. For the material of the reflection layer, for example, aluminum, silver, gold, copper, or platinum, etc. are applicable. The wiring pattern of substrate 2 is, for example, in a state of being electrically connected to the wiring pattern of wiring substrate 12 via solder or a conductive adhesive. Thereby, for example, a signal from wiring substrate 12 is transmitted to light-emitting element 3 via substrate 2, and light-emitting element 3 can emit light. Electric power is supplied to wiring substrate 12 via wiring from a power source provided outside.

[0031] <<Light-emitting element 3>> The light-emitting element 3 is, for example, in a state of being mounted on the substrate 2. The light-emitting element 3 is electrically connected, for example, via a brazing material or solder or the like on a gold plating layer adhered to the surface of a wiring conductor on the substrate 2. For the light-emitting element 3, for example, a light-emitting diode (LED) capable of emitting light outward in response to recombination of electrons and holes in a pn junction region using a semiconductor is applied. The light-emitting element 3 has a translucent substrate and a light semiconductor layer located on the translucent substrate. For the translucent substrate, for example, a substrate capable of growing a light semiconductor layer using a chemical vapor deposition method such as metalorganic chemical vapor deposition or molecular beam epitaxy is applied. For the material of the translucent substrate, for example, sapphire, gallium nitride, aluminum nitride, zinc oxide, zinc selenide, silicon carbide, silicon, or zirconium diboride or the like is applied. The thickness of the translucent substrate is, for example, about 50 micrometers (μm) to 1000 μm. The light semiconductor layer has, for example, a first semiconductor layer, a light-emitting layer, and a second semiconductor layer. The first semiconductor layer is located, for example, on the translucent substrate. The light-emitting layer is located, for example, on the first semiconductor layer. The second semiconductor layer is located, for example, on the light-emitting layer. For the materials of the first semiconductor layer, the light-emitting layer, and the second semiconductor layer, for example, nitride semiconductors as III-V group semiconductors, gallium phosphide, gallium arsenide, or the like are applied. The nitride semiconductor includes, for example, gallium nitride, aluminum nitride, or indium nitride or the like. The thickness of the first semiconductor layer is, for example, about 1 μm to 5 μm. The thickness of the light-emitting layer is, for example, about 25 nanometers (nm) to 150 nm. The thickness of the second semiconductor layer is, for example, about 50 nm to 600 nm. The light-emitting element 3 having such a configuration can emit excitation light in a wavelength range of about 370 nm to 420 nm, for example.

[0032] <<Frame body 4>> The frame body 4 is positioned, for example, so as to surround the light-emitting element 3 on the substrate 2. For the material of the frame body 4, for example, a resin material mixed with powder is applied. For the powder material, for example, ceramic materials or porous materials such as aluminum oxide, titanium oxide, zirconium oxide, or yttrium oxide, or metal oxides such as aluminum oxide, titanium oxide, zirconium oxide, or yttrium oxide are applied. The frame body 4 is, for example, in a state of being laminated on the substrate 2 and connected to the substrate 2 via resin or the like. The frame body 4 is positioned, for example, so as to surround the light-emitting element 3 without contacting the light-emitting element 3. The inner wall surface of the frame body 4 is positioned, for example, so as to expand outward from the end in the +Z direction toward the end in the -Z direction. In other words, the inner wall surface of the frame body 4 is inclined with respect to the Z axis such that, for example, the cross-section along the XY plane of the space inside the frame body 4 expands as it progresses in the -Z direction. In this case, for example, the inner wall surface of the frame body 4 functions as a surface (also referred to as a reflection surface) that reflects the excitation light emitted from the light-emitting element 3. Here, for example, when the frame body 4 is viewed in plan with the +Z direction facing up, if the shape of the inner wall surface of the frame body 4 is circular, the reflection surface can reflect the light emitted by the light-emitting element 3 in all directions. Further, the inner wall surface of the frame body 4 has, for example, a metal layer and a metal plating layer (also referred to as a plated metal layer) that covers this metal layer on the inner peripheral surface of the frame body 4 which is a sintered body. Here, for example, metals such as tungsten, molybdenum, copper, or silver are applied to the material of the metal layer. For the plated metal layer, for example, nickel or gold or the like is applied. Such a plated metal layer can, for example, reflect the light emitted by the light-emitting element 3. In other words, in this case, the inner wall surface of the frame body 4 can serve as a reflection surface that reflects the light emitted by the light-emitting element 3. The angle at which the inner wall surface of the frame body 4 is inclined with respect to the XY plane is, for example, an angle of about 55 degrees to 70 degrees.

[0033] <<Sealing member 5>> The sealing member 5 is positioned in a state of being filled in a region excluding a portion along the -Z direction end of the inner space of the frame body 4 surrounded by the frame body 4. Thereby, the sealing member 5 can seal the light-emitting element 3, for example. The sealing member 5 has translucency, for example. Thereby, the sealing member 5 can transmit the light emitted from the light-emitting element 3, for example. As the material of the sealing member 5, a resin having translucency and insulation properties such as silicone resin, acrylic resin, or epoxy resin is applied, for example. The refractive index of the sealing member 5 is set to about 1.4 to 1.6, for example.

[0034] <<Wavelength conversion member 6>> The wavelength conversion member 6 is positioned in a region along the -Z direction end of the inner space of the frame body 4 surrounded by the frame body 4, for example. Here, for example, the wavelength conversion member 6 is positioned along the surface facing the -Z direction of the sealing member 5. The wavelength conversion member 6 is positioned so as to fit into the inner space of the frame body 4, for example. The wavelength conversion member 6 can convert the wavelength of the light emitted by the light-emitting element 3, for example. The wavelength conversion member 6 has a phosphor 7, for example. More specifically, for example, the wavelength conversion member 6 has a form in which the phosphor 7 is contained in a resin (also referred to as an insulating resin) or glass having translucency and insulation properties. As the material of the insulating resin, an insulating resin having translucency such as fluororesin, silicone resin, acrylic resin, or epoxy resin is applied, for example. Here, for example, a large number of phosphors 7 are positioned in a state of being substantially uniformly dispersed in the wavelength conversion member 6. When the light emitted from the light-emitting element 3 enters the wavelength conversion member 6, the phosphor 7 can be excited by this light and emit light, for example. Here, for example, by appropriately setting the phosphor applied to the phosphor 7, the spectrum of the light emitted from the light source 1 can be changed.

[0035] <1-3-4. Translucent substrate> The light-transmissive substrate 13 is positioned, for example, in a state of closing an opening facing the -Z direction of the housing 11. As the material of the light-transmissive substrate 13, a material through which the light emitted from the light source 1 can pass is applied. As the material of the light-transmissive substrate 13, for example, an acrylic resin or glass is applied. As the light-transmissive substrate 13, for example, a plate-like body having a rectangular front surface and back surface is applied. The length along the longitudinal direction (+X direction) of the light-transmissive substrate 13 is, for example, about 98 mm to 1998 mm. The light-transmissive substrate 13 is inserted into a pair of groove portions in the pair of holding portions 21b from an opening located at an end portion in the +X direction or -X direction in the longitudinal direction (+X direction) of the main body portion 21, and is slid along the +X direction, so that the light-transmissive substrate 13 is held by the pair of holding portions 21b in a state of being spaced apart in the -Z direction at positions separated from a plurality of light sources 1. And in the lighting device 10, the lid portion 22 is in a state of closing the openings located at the end portions in the +X direction and -X direction in the longitudinal direction (+X direction) of the main body portion 21, respectively.

[0036] <1-4. Lighting Conditions in Hydroponics> In the hydroponics described above, for example, by appropriately changing the lighting device 10 that irradiates light on vegetables, the lighting conditions when growing vegetables can be changed.

[0037] <1-4-1. Irradiation of the First Light> In the first embodiment, for example, in the third step S3 in the hydroponics of vegetables, during at least a part of the second period P2, light (also referred to as the first light) having a maximum value of light intensity (also referred to as the first maximum value) in the wavelength range of visible light of 500 nm or less, specifically 420 nm to 490 nm, is irradiated to grow the vegetables. Thereby, for example, the content rate of glutamine and the sugar content in the vegetables can be increased. Therefore, for example, the taste of the vegetables after harvesting can be improved. Note that the light intensity (W / m 2(W / nm) is the irradiance of light per unit area and per unit wavelength. Also, for example, regarding the magnitude relationship of the light intensity in the spectrum of light, it is appropriately explained using the relative value of the light intensity (also referred to as relative light intensity) when the maximum value of the light intensity is used as a reference value (for example, 1).

[0038] Here, for example, when growing vegetables by irradiating the first light during at least a part of the second period P2, it is considered that the content rate of glutamine and the sugar content in the harvested vegetables increase by the following mechanism.

[0039] When the vegetable seedlings 32b and the target vegetable 32c are irradiated with the first light during the second period P2, stress is applied to the vegetables, and reactive oxygen species are generated in the cells of the vegetables. In contrast, the vegetables activate, for example, the citric acid cycle to produce a large amount of antioxidants such as citric acid in the vegetables in order to protect their tissues from reactive oxygen species. Here, for example, α-ketoglutaric acid (2-oxoglutaric acid) and glutamic acid are produced in increased amounts. At this time, for example, in the vegetables, the reactions in the reaction cycle (also called the GS / GOGAT cycle) catalyzed by glutamine synthetase (GS) and glutamate synthase (GOGAT) are promoted. In this GS / GOGAT cycle, for example, ammonium absorbed from the roots of plants binds to glutamic acid through the catalysis of glutamine synthetase (GS) to produce glutamine. The glutamine produced in this reaction produces two molecules of glutamic acid by reacting with 2-oxoglutaric acid through the catalysis of glutamate synthase (GOGAT). Of the two molecules of glutamic acid produced here, one molecule of glutamic acid is used in the reaction of binding to ammonium absorbed from the roots of plants through the catalysis of glutamine synthetase (GS). The remaining one molecule of glutamic acid is used for the synthesis of other amino acids. If the reactions in such a GS / GOGAT cycle are promoted, for example, glutamine as a precursor of glutamic acid for producing glutamic acid increases. The ammonium used in the GS / GOGAT cycle is supplied, for example, from ammonia nitrogen and nitrate nitrogen contained in the nutrient solution. Nitrate nitrogen becomes ammonia nitrogen by reduction in the roots and leaves, for example, and thus becomes the source of ammonium. Glutamine synthetase (GS) is an enzyme contained in the chloroplasts of vegetables, for example. Glutamate synthase (GOGAT) is an enzyme contained in vegetables, for example.

[0040] Also, for example, vegetables produce antioxidants such as ascorbic acid and polyphenols to protect their tissues from reactive oxygen species. These ascorbic acid and polyphenols are synthesized using sugars such as glucose and galactose. Therefore, in vegetables, for example, antioxidants accumulate to an appropriate amount necessary for protecting their tissues, and sugars as precursors of antioxidants increase.

[0041] Here, if a blue phosphor that emits fluorescence of about 420 nm to 490 nm, for example, is applied to the phosphor 7 contained in the wavelength conversion member 6 of the light source 1, the first light can be irradiated onto the vegetables. As such a blue phosphor, for example, (Sr,Ca,Ba) 10 (PO4)6Cl2:Eu can be adopted. In this case, the light source 1 can emit light having a spectrum as shown by the thick solid line in FIG. 10. The first light may contain, for example, a component of red light. However, for example, the lower the ratio of the red light component in the first light, the more the energy consumption in the light source 1 can be reduced. Also, the photosynthetic photon flux density of the first light irradiated onto the vegetables is, for example, 80 micromoles per square meter (80 μmol / m 2 ) or more. The photosynthetic photon flux density of the first light irradiated onto the vegetables is, for example, 100 μmol / m 2 to 250 μmol / m 2 may be about that.

[0042] Here, for example, during the period of hydroponic cultivation of vegetables, by appropriately setting a part of the period (also referred to as the first light irradiation period) in which the vegetables are grown by irradiating the first light in the third step S3, the glutamine content and the sugar content in the vegetables can be moderately increased. For example, a setting that includes the latter stage (the second B period) P2b of the second period P2 during the first light irradiation period can be considered. Also, for example, a setting where the length of the first light irradiation period is set to be 1 / 4 to 1 / 2 of the total period (also referred to as the entire period) obtained by summing the first period P1, the second period P2, and the third period P3 can be considered. More specifically, for example, a setting where the first light irradiation period is the second B period P2b can be considered. In this way, by appropriately setting the first light irradiation period, for example, the growth of the vegetables and the increase in the glutamine content and the sugar content in the vegetables can be realized in a well-balanced manner. As a result, for example, vegetables with high taste can be efficiently produced. Also, here, for example, when the photon flux density (light amount) of the first light irradiated on the target vegetable 32c in the second B period P2b of the third step is increased, the glutamine content in the harvested vegetables can increase.

[0043] <1-4-2. Irradiation with the Second Light> In the first embodiment, for example, during the second step S2 to the fourth step S4 in the hydroponic cultivation of vegetables, irradiation with light (also referred to as the second light) having a maximum value of light intensity (also referred to as the second maximum value) in the wavelength range of visible light exceeding 500 nm can be performed on the vegetables during a period different from the first light irradiation period. In this case, for example, excessive generation of antioxidants in the vegetables can be reduced, bitterness due to the presence of excessive antioxidants in the harvested vegetables can be reduced, and the sugar content in the harvested vegetables can be increased. Therefore, for example, the taste of the vegetables can be improved.

[0044] Here, for example, when growing vegetables by irradiating them with a second light during a period different from the first light irradiation period, it is considered that the excessive increase in antioxidants is reduced and the sugar content increases in the harvested vegetables by the following mechanism. The following mechanism is described on the premise of a photosynthesis curve showing the average value of the photosynthesis curves of 61 types of plants shown in Fig. 11 and presented by McCree (1972) and Inada (1976).

[0045] For example, after irradiating with the first light, by irradiating with a second light that can promote photosynthesis in vegetables more than the first light, the stress applied to the vegetables is reduced. As a result, for example, the overproduction of active oxygen and the excessive generation of antioxidants in the vegetables are reduced. Also, for example, by irradiating with the second light, normal photosynthesis is promoted more than the generation of active oxygen in the vegetables. Therefore, for example, the production of amino acids necessary for the growth of vegetables is promoted by the reduction of organic acids. Also, for example, the activation of the citric acid cycle by irradiating with the first light is stopped, and the production of sugar is promoted by the reduction reaction using the organic acids produced in the citric acid cycle as a raw material.

[0046] Here, for the second light, for example, light containing many components of light in the red wavelength range is applied. Specifically, as the second light, for example, having a maximum value of light intensity (also referred to as maximum light intensity) in the wavelength range of 590 nm to 650 nm, and the value of light intensity at the wavelength of 700 nm (also referred to as the first value) is 20% or more of the maximum light intensity and the value of light intensity at the wavelength of 800 nm (also referred to as the second value) is 10% or less of the maximum light intensity. In this case, for example, by irradiating the second light that can promote photosynthesis in vegetables more than the first light, normal photosynthesis can be promoted more than the generation of reactive oxygen species in vegetables. Also, for example, the second light widely contains components of light with wavelengths that greatly contribute to the promotion of photosynthesis, and in the second light, the ratio of components of light with wavelengths that contribute little to the promotion of photosynthesis is low. Thereby, for example, it is possible to promote the growth of vegetables and reduce the energy consumption required for light irradiation. As a result, for example, vegetables with high taste can be efficiently produced.

[0047] Also, here, regarding the spectrum of the second light, let the wavelength (also referred to as the first wavelength) showing the maximum peak (maximum light intensity) be λ1 [nm]. Regarding the spectrum of the second light, the wavelength closest to the first wavelength λ1 (also referred to as the second wavelength) that has a light intensity of 50 percent (%) of the light intensity at the first wavelength λ1 on the shorter wavelength side than the first wavelength λ1 is λ2 [nm]. Regarding the spectrum of the second light, the wavelength closest to the first wavelength λ1 (also referred to as the third wavelength) that has a light intensity of 50% of the light intensity at the first wavelength λ1 on the longer wavelength side than the first wavelength λ1 is λ3 [nm]. In this case, as the spectrum of the second light, for example, having a maximum light intensity in the wavelength range of 610 nm to 630 nm and satisfying the requirements of formula (1) and formula (2), a spectrum can be adopted.

[0048] λ1 - 70 ≤ λ2 ≤ λ1 - 30 ···(1) λ1 + 30 ≤ λ3 ≤ λ1 + 70 ···(2)

[0049] Here, for example, if the first wavelength λ1 is within the range of 615 nm to 625 nm, in the second light, the component of light in the wavelength range of 750 nm or more, which contributes little to the promotion of photosynthesis, can be reduced. Also, in the second light, for example, in the light from a red phosphor, the ratio of the photon flux in the wavelength range of 610 nm to 630 nm to the photon flux in the wavelength range of 540 nm to 700 nm may be 15% to 25%. As a result, in the second light emitted from the light source 1, light of a specific wavelength is not excessively included in the wavelength range of red light from 540 nm to 700 nm, which contributes highly to the promotion of photosynthesis, and the proportion of near-infrared light, which contributes little to the promotion of photosynthesis and can cause a decrease in the photosynthesis rate, is low. Also, here, for example, if the absolute value of the difference between the first wavelength λ1 and the third wavelength λ3 is larger than the absolute value of the difference between the first wavelength λ1 and the second wavelength λ2, in the second light, the proportion of the component of light near 670 nm, which is the peak wavelength in the wavelength range of red light in the photosynthesis action curve shown in FIG. 11, increases.

[0050] Here, the second light may include, for example, light components in the wavelength range from blue to purple. For example, as the second light, light having a peak (also referred to as peak light intensity) with a light intensity smaller than the maximum light intensity in the wavelength range of visible light of 500 nm or less may be used. Thereby, for example, even during the period when the second light is irradiated, the glutamine content and the sugar content in the vegetables can be improved. For example, according to the photosynthesis action curve shown in FIG. 11, light in the wavelength range of blue light from 420 nm to 490 nm also contributes to photosynthesis. Therefore, the spectrum of the second light may have, for example, a peak of the light component emitted from a blue phosphor in the wavelength range of 420 nm to 490 nm. Here, for example, the wavelength (also referred to as the fourth wavelength) indicating the peak of the light intensity in the wavelength range of 420 nm to 490 nm in the spectrum of the second light is defined as λ4 [nm], and the light intensity (relative light intensity) at the first wavelength λ1 is set to 1. In this case, for example, as the spectrum of the second light, the light intensity (relative light intensity) at the fourth wavelength λ4 is 0.3 to 0.5, and the ratio of the light quantum flux in the wavelength range of 420 nm to 490 nm of the light from the blue phosphor to the light quantum flux in the wavelength range of 540 nm to 700 nm of the light from the red phosphor is 10% to 20%. If such a spectrum is adopted, the second light has a good balance of red light and blue light necessary for photosynthesis.

[0051] Furthermore, the second light may include, for example, a component of light in the green wavelength range. Here, for example, according to the photosynthesis action spectrum shown in FIG. 11, light in the wavelength range of green light from 490 nm to 540 nm also contributes to photosynthesis to a certain extent. Therefore, the spectrum of the second light may appropriately include a component of light emitted from a green phosphor in the wavelength range of 490 nm to 540 nm. Specifically, for example, when the light intensity (relative light intensity) at the first wavelength λ1 is set to 1, a spectrum in which the average value of the light intensity (relative light intensity) in the wavelength range of 490 nm to 540 nm is 0.1 or more or 0.3 or more is adopted as the spectrum of the second light. Also, in the spectrum of the second light, for example, the ratio of the photon flux in the wavelength range of light from 490 nm to 540 nm from the green phosphor to the photon flux in the wavelength range of light from 540 nm to 700 nm from the red phosphor may be 5% to 15%. Furthermore, in the spectrum of the second light, for example, the ratio of the photon flux in the wavelength range of light from 490 nm to 540 nm from the green phosphor to the photon flux in the wavelength range of light from 420 nm to 490 nm from the blue phosphor may be 45% to 65%. In this case, the second light has a good balance of red light, blue light, and green light necessary for photosynthesis. Here, the photosynthetic tissue of the leaf is differentiated, for example, into the palisade tissue on the front side of the leaf and the spongy tissue on the back side of the leaf. Red light and blue light are absorbed by chloroplasts in the palisade tissue on the front side of the leaf and contribute to photosynthesis. On the other hand, although green light is hardly absorbed by chloroplasts, for example, the green light that passes through the palisade tissue on the front side of the leaf and reaches the spongy tissue on the back side of the leaf is absorbed by chloroplasts during repeated scattering and the like in the spongy tissue and contributes to photosynthesis. Therefore, for example, if the second light appropriately includes green light, photosynthesis can be promoted.

[0052] Incidentally, since the light emitted from the light source 1 also includes the excitation light in the near-ultraviolet region emitted by the light-emitting element 3, the spectrum of the second light may have a peak, for example, in the wavelength range of 380 nm to 420 nm. Here, for example, the wavelength (also referred to as the fifth wavelength) indicating the peak of the light intensity in the wavelength range of 380 nm to 420 nm in the spectrum of the second light is defined as λ5 [nm], and the light intensity (relative light intensity) at the first wavelength λ1 is set to 1. In this case, for example, in the spectrum of the second light, the light intensity (relative light intensity) at the fifth wavelength λ5 is from 0.2 to 0.4, and the ratio of the photon flux in the wavelength range of 380 nm to 420 nm to the photon flux in the wavelength range of 540 nm to 700 nm of the light from the red phosphor may be from 1% to 10%.

[0053] Regarding the second light emitted from the light source 1, for example, a mode is conceivable in which the color temperature is in the range of 1900 K to 2100 K, the average color rendering index (Ra) is in the range of 70 to 75, and the CIE chromaticity coordinate xy values satisfy the relationship of 0.4 ≦ x ≦ 0.5 and 0.3 ≦ y ≦ 0.4.

[0054] Here, for the phosphor 7 contained in the wavelength conversion member 6 of the light source 1, for example, (Sr,Ca,Ba) 10 (PO4)6Cl2:Eu blue phosphor, (Sr,Ba,Mg)2SiO4:Eu 2+ green phosphor, and (Sr,Ca)AlSiN3:Eu red phosphor are applied at a mixing ratio of 3:1:46, thereby realizing the irradiation of the second light that satisfies the above requirements. In this case, the light source 1 can emit light having a spectrum as shown by the thick solid line in FIG. 12.

[0055] The spectrum shown in FIG. 12 has the following characteristics. A first wavelength λ1 showing the maximum light intensity in the wavelength range of light from the red phosphor is about 616 nm, a second wavelength λ2 is about 578 nm, a third wavelength λ3 is about 677 nm, and the full width at half maximum with respect to the maximum light intensity is about 100 nm. The absolute value of the difference between the first wavelength λ1 and the third wavelength λ3, which is about 61 nm, is larger than the absolute value of the difference between the first wavelength λ1 and the second wavelength λ2, which is about 38 nm. The ratio of the photon flux in the wavelength range of 610 nm to 630 nm to the photon flux in the wavelength range of 540 nm to 700 nm of the light from the red phosphor is about 20%. Also, a fourth wavelength λ4 showing a peak in the wavelength range of light from the blue phosphor is about 453 nm, and when the light intensity (relative light intensity) at the first wavelength λ1 is 1, the light intensity (relative light intensity) at the fourth wavelength λ4 is about 0.41. The ratio of the photon flux in the wavelength range of 420 nm to 490 nm of the light from the blue phosphor to the photon flux in the wavelength range of 540 nm to 700 nm of the light from the red phosphor is about 15%. Also, when the light intensity (relative light intensity) at the first wavelength λ1 is 1, the average value of the light intensity (relative light intensity) in the wavelength range of 490 nm to 540 nm of the light from the green phosphor is about 0.21. The ratio of the photon flux in the wavelength range of 490 nm to 540 nm of the light from the green phosphor to the photon flux in the wavelength range of 540 nm to 700 nm of the light from the red phosphor is about 8.5%, and the ratio of the photon flux in the wavelength range of 490 nm to 540 nm of the light from the green phosphor to the photon flux in the wavelength range of 420 nm to 490 nm of the light from the blue phosphor is about 56%. Further, a fifth wavelength λ5 is about 406 nm, and when the light intensity (relative light intensity) at the first wavelength λ1 is 1, the light intensity (relative light intensity) at the fifth wavelength λ5 is about 0.36.

[0056] Also, the photon flux density of the second light irradiated on the vegetables is, for example, 80 micromoles per square meter (80 μmol / m 2 ) or more. The photon flux density of the second light irradiated on the vegetables may be, for example, on the order of 100 μmol / m 2 to 250 μmol / m 2 .

[0057] <1-5. Conditions of nutrient solution in hydroponics> In the hydroponics described above, for example, by appropriately changing the nutrient solution stored in the cultivation containers 30a and 30b, the nutrients supplied to the vegetables when growing the vegetables can be changed.

[0058] <1-5-1. Use of the first nutrient solution> In the first embodiment, for example, in the third step S3 in the hydroponics of vegetables, during the first light irradiation period in which the vegetables are grown by irradiating the first light, the vegetables may be grown using the first nutrient solution. The first nutrient solution is, for example, a culture solution in which the nitrogen (N) content per liter is from 0.2 mg to 0.47 mg and the calcium oxide (CaO) content per liter is from 0.33 mg to 0.83 mg. Thereby, for example, the sugar content in the vegetables can be increased and the nitrate concentration in the vegetables at the time of harvesting can be reduced.

[0059] Here, the respective contents of nitrogen (N), phosphorus pentoxide (P2O5), potassium oxide (K2O), magnesium oxide (MgO), calcium oxide (CaO) and iron (Fe) per liter in the first nutrient solution are set, for example, within the ranges shown in FIG. 13. Specifically, the nitrogen (N) content per liter in the first nutrient solution is set, for example, from 0.2 mg to 0.47 mg. The phosphorus pentoxide (P2O5) content per liter in the first nutrient solution is set, for example, from 0.13 mg to 0.33 mg. The potassium oxide (K2O) content per liter in the first nutrient solution is set, for example, from 0.4 mg to 1 mg. The magnesium oxide (MgO) content per liter in the first nutrient solution is set, for example, from 0.12 mg to 0.27 mg. The calcium oxide (CaO) content per liter in the first nutrient solution is set, for example, from 0.33 mg to 0.83 mg. The iron (Fe) content per liter in the first nutrient solution is set, for example, from 0.003 mg to 0.01 mg.

[0060] Incidentally, in general hydroponics, for example, in the third step S3, during the second B period P2b, it is conceivable to grow vegetables using the first reference nutrient solution, and during the second A period P2a, to grow vegetables using the second reference nutrient solution. The first reference nutrient solution and the second reference nutrient solution are general-purpose culture solutions widely used for fruit vegetables, leaf vegetables, and flowers. The content of nitrogen (N), phosphorus pentoxide (P2O5), potassium oxide (K2O), magnesium oxide (MgO), calcium oxide (CaO), and iron (Fe) per liter in the first reference nutrient solution and the second reference nutrient solution is set to the values shown in FIG. 13, for example. Specifically, the content of nitrogen (N) per liter in the first reference nutrient solution is set to about 1.3 mg, for example. The content of phosphorus pentoxide (P2O5) per liter in the first reference nutrient solution is set to about 0.6 mg, for example. The content of potassium oxide (K2O) per liter in the first reference nutrient solution is set to about 2.03 mg, for example. The content of magnesium oxide (MgO) per liter in the first reference nutrient solution is set to about 1.15 mg, for example. The content of calcium oxide (CaO) per liter in the first reference nutrient solution is set to about 0.0075 mg, for example. The content of iron (Fe) per liter in the first reference nutrient solution is set to about 0.0135 mg, for example. Also, the content of nitrogen (N) per liter in the second reference nutrient solution is set to about 0.52 mg, for example. The content of phosphorus pentoxide (P2O5) per liter in the second reference nutrient solution is set to about 0.24 mg, for example. The content of potassium oxide (K2O) per liter in the second reference nutrient solution is set to about 0.81 mg, for example. The content of magnesium oxide (MgO) per liter in the second reference nutrient solution is set to about 0.46 mg, for example. The content of calcium oxide (CaO) per liter in the second reference nutrient solution is set to about 0.003 mg, for example. The content of iron (Fe) per liter in the second reference nutrient solution is set to about 0.0054 mg, for example.

[0061] Here, for example, when growing vegetables using a first nutrient solution with a lower nitrogen content and a higher calcium oxide content than the first reference nutrient solution and the second reference nutrient solution during the first light irradiation period, it is considered that the sugar content increases and the nitrate concentration decreases in the harvested vegetables by the following mechanism.

[0062] When growing vegetables using the first nutrient solution during the first light irradiation period, the nitrate nitrogen in the nutrient solution decreases due to the decrease in the nitrogen content in the nutrient solution. As a result, for example, the concentration of nitrate contained in the vegetables at the time of harvest decreases. Also, for example, since the supply amount of nitrogen that becomes the element of amino acids is small, the synthesis of amino acids by the synthesis of nitrogen and carbon (C) is moderately reduced. On the other hand, for example, in response to the irradiation of the first light, the vegetables generate antioxidant substances such as ascorbic acid and polyphenols to protect their tissues from active oxygen. These ascorbic acid and polyphenols are synthesized using sugars such as glucose and galactose, for example. Therefore, for example, in vegetables, antioxidant substances accumulate to an appropriate amount required for protecting their tissues, and furthermore, the sugar as a precursor of antioxidant substances increases. Also, for example, due to the increase in the calcium oxide concentration in the nutrient solution, the generation of antioxidant substances by strong light adaptation is promoted, so the sugar as a precursor of antioxidant substances increases.

[0063] <1-5-2. Use of the Second Nutrient Solution> In the first embodiment, for example, in the second step S2 and the third step S3 in the hydroponic cultivation of vegetables, the vegetables may be grown using the second nutrient solution in a period before the first light irradiation period in which the vegetables are grown by irradiating the first light. The second nutrient solution is, for example, a culture solution having a nitrogen content of 0.06 mg to 0.14 mg per liter and a calcium oxide content of 0.1 mg to 0.25 mg per liter. Thereby, for example, the concentration of nitrate in the vegetables at the time of harvest can be decreased, and the growth of the vegetables can be promoted by promoting photosynthesis.

[0064] Here, the content of each of nitrogen (N), phosphorus pentoxide (P2O5), potassium oxide (K2O), magnesium oxide (MgO), calcium oxide (CaO), and iron (Fe) per liter in the second nutrient solution is set within the range shown in, for example, FIG. 13. Specifically, the content of nitrogen (N) per liter in the second nutrient solution is set to, for example, 0.06 mg to 0.14 mg. The content of phosphorus pentoxide (P2O5) per liter in the second nutrient solution is set to, for example, 0.04 mg to 0.1 mg. The content of potassium oxide (K2O) per liter in the second nutrient solution is set to, for example, 0.12 mg to 0.3 mg. The content of magnesium oxide (MgO) per liter in the second nutrient solution is set to, for example, 0.04 mg to 0.08 mg. The content of calcium oxide (CaO) per liter in the second nutrient solution is set to, for example, 0.1 mg to 0.25 mg. The content of iron (Fe) per liter in the second nutrient solution is set to, for example, 0.001 mg to 0.003 mg.

[0065] Incidentally, in general hydroponics, for example, in the second step S2, vegetables are grown using the second reference nutrient solution described above, and in the third step S3, during the second B period P2b, vegetables are grown using the first reference nutrient solution, and during the second A period P2a, it is conceivable to grow vegetables using the second reference nutrient solution.

[0066] Here, for example, if vegetables are grown using a second nutrient solution that has a lower nitrogen content and a higher calcium oxide content than the first reference nutrient solution and the second reference nutrient solution during a period before the first light irradiation period in the second step S2 and the third step S3, it is considered that the concentration of nitrate in the harvested vegetables decreases and the growth of the vegetables is promoted by accelerating photosynthesis through the following mechanism.

[0067] When growing vegetables using the second nutrient solution during a period prior to the first light irradiation period among the second step S2 and the third step S3, the nitrate nitrogen in the nutrient solution decreases due to a decrease in the nitrogen content in the nutrient solution. As a result, for example, the concentration of nitrate contained in the vegetables at the time of harvest decreases. Also, for example, photosynthesis in plants is promoted due to an increase in the concentration of calcium oxide in the nutrient solution.

[0068] <1-5-3. Use of the Third Nutrient Solution> In the first embodiment, for example, in the third period P3 of the fourth step S4 in the hydroponic cultivation of vegetables, vegetables may be grown using the third nutrient solution. The third nutrient solution is, for example, a nutrient solution that contains nitrogen in the form of ammonium nitrogen and has a nitrogen content of 0.21 mg to 0.42 mg per liter. Thereby, for example, while reducing the concentration of nitrate in the vegetables at the time of harvest, the taste of the vegetables can be improved.

[0069] Here, as an example, a mode in which the third nutrient solution contains nitrogen (N) in the form of ammonium sulfate ((NH4)2SO4) as ammonium nitrogen is conceivable. And the nitrogen (N) content per liter in the third nutrient solution is set, for example, within the range shown in FIG. 13.

[0070] By the way, in general hydroponic cultivation, for example, in the fourth step S4, it is conceivable to grow vegetables using the second reference nutrient solution described above.

[0071] Here, for example, when growing vegetables using the third nutrient solution that has a lower nitrogen content than the second reference nutrient solution and contains nitrogen in the form of ammonium nitrogen in the fourth step S4, it is considered that the concentration of nitrate in the harvested vegetables decreases and the taste of the vegetables improves by the following mechanism.

[0072] In the fourth step S4, when growing vegetables using the third nutrient solution, for example, due to the decrease in nitrate nitrogen in the nutrient solution, the concentration of nitrate contained in the harvested vegetables decreases. Also, for example, by supplying ammonium nitrogen while irradiating with the second light, excessive production of antioxidants is reduced, and the synthesis of amino acids is moderately promoted, adding umami to the taste and improving the taste of the vegetables.

[0073] <1-5-4. Use of the Fourth Nutrient Solution> In the first embodiment, for example, in the third period P3 of the fourth step S4 in the hydroponic cultivation of vegetables, vegetables may be grown using the fourth nutrient solution instead of the third nutrient solution. The fourth nutrient solution is, for example, a nutrient solution having a nitrogen content of 0.01 mg or less per liter, a magnesium oxide content of 0.12 mg to 0.24 mg per liter, and a calcium oxide content of 0.54 mg to 0.8 mg per liter. Thereby, for example, while reducing the concentration of nitrate in the harvested vegetables, the taste of the vegetables can be improved, and the growth of the vegetables can be promoted by promoting photosynthesis.

[0074] Here, the content of each of nitrogen (N), phosphorus pentoxide (P2O5), potassium oxide (K2O), magnesium oxide (MgO), calcium oxide (CaO), and iron (Fe) per liter in the fourth nutrient solution is set within the range shown in, for example, FIG. 13. Specifically, the content of nitrogen (N) per liter in the fourth nutrient solution is set to, for example, 0.01 mg or less. The content of phosphorus pentoxide (P2O5) per liter in the fourth nutrient solution is set to, for example, from 0.2 mg to 0.4 mg. The content of potassium oxide (K2O) per liter in the fourth nutrient solution is set to, for example, from 0.72 mg to 1.2 mg. The content of magnesium oxide (MgO) per liter in the fourth nutrient solution is set to, for example, from 0.12 mg to 0.24 mg. The content of calcium oxide (CaO) per liter in the fourth nutrient solution is set to, for example, from 0.54 mg to 0.8 mg. The content of iron (Fe) per liter in the fourth nutrient solution is set to, for example, from 0.007 mg to 0.024 mg.

[0075] Here, for example, in the fourth step S4, when growing vegetables using a fourth nutrient solution that has a significantly lower nitrogen content, a nearly equal magnesium oxide content, and a significantly higher calcium oxide content compared to the second reference nutrient solution, it is considered that the nitrate concentration in the harvested vegetables decreases, the taste of the vegetables improves, and the growth of the vegetables is promoted by enhancing photosynthesis through the following mechanism.

[0076] In the fourth step S4, when growing vegetables using the fourth nutrient solution, for example, due to a significant decrease in the nitrogen concentration in the nutrient solution, the nitrate nitrogen in the nutrient solution decreases, and the concentration of nitrates contained in the harvested vegetables decreases. Also, for example, due to a significant decrease in the nitrogen concentration in the nutrient solution, among the metabolisms by photosynthesis, since the supply amounts of nitrogen such as ammonia nitrogen and nitrate nitrogen, which are the sources of nitrogen for amino acids, are small, the synthesis of amino acids by the synthesis of nitrogen and carbon (C) etc. is reduced. As a result, for example, in the metabolism by photosynthesis, the synthesis of organic acids as precursors of sugars becomes more active than the synthesis of amino acids, and the production of sugars by the reduction action using organic acids as raw materials is promoted. Consequently, for example, sugars increase preferentially over amino acids in the metabolism of photosynthesis. Also, for example, by increasing the concentration of calcium oxide in the nutrient solution, photosynthesis in plants is promoted, and the growth of vegetables is promoted. Also, for example, by appropriately maintaining the concentration of magnesium oxide in the nutrient solution, magnesium, which is a constituent element of chlorophyll, is appropriately supplied, and the reduction of carbon absorbed using carbon dioxide in the air as a supply source is maintained and promoted. Thereby, for example, the production of sugars is promoted.

[0077] Also, for example, if the fourth nutrient solution is used instead of the third nutrient solution in the fourth step, since the fourth nutrient solution contains various nutrients other than nitrogen components compared to the third nutrient solution, the taste of the vegetables can become a richer flavor. Therefore, for example, when a rich flavor is required as the taste of the vegetables, the fourth nutrient solution is used in the fourth step, and when a fresh and light taste is required as the taste of the vegetables, the third nutrient solution is used in the fourth step. The third nutrient solution and the fourth nutrient solution may be properly selected according to the purpose.

[0078] <1-6. Specific Example> In hydroponics, lettuce grown by irradiating with the second light in the first period (germination period) P1, the first half (second A period) P2a of the second period (main growth period) P2, and the third period (immediately before harvesting period) P3, and lettuce grown by irradiating with the first light in the second half (second B period) P2b of the second period P2 were obtained as vegetables of the first specific example. Also, lettuce grown by irradiating with the second light in all periods of the first period P1, the second period P2, and the third period P3 was obtained as vegetables of the first reference example. Here, except for the lighting conditions, the vegetables of the first specific example and the vegetables of the first reference example were obtained under the same conditions. Specifically, the above-mentioned second nutrient solution was used in the first period P1 and the second A period P2a. The above-mentioned first nutrient solution was used in the second B period P2b. The above-mentioned third nutrient solution was used in the third period P3. Also, based on the conditions for obtaining the vegetables of the first specific example, lettuce grown under the condition that the nutrient solution used in the third period P3 was changed from the above-mentioned third nutrient solution to the above-mentioned fourth nutrient solution was obtained as vegetables of the second specific example. Also, lettuce extracted from commercially available open-field mixed salad was obtained as vegetables of the second reference example. Further, commercially available open-field head lettuce was obtained as vegetables of the third reference example.

[0079] Then, the glutamine content was measured for the vegetables of the first specific example, the vegetables of the first reference example, the vegetables of the second reference example, and the vegetables of the third reference example. For the measurement of the glutamine content, a liquid chromatograph mass spectrometer (LC-MS) was used. More specifically, a liquid chromatograph (LC-20AC) manufactured by Shimadzu Corporation was used, and a mass spectrometer (compact) manufactured by BRUKER was used. In the liquid chromatograph, UHPLC PEEK Colum InterSustain Amide 3μm 2.1×50mm was used as the column. In gradient elution, the ratio of liquid B in the eluent obtained by mixing liquid A, which is an aqueous solution of 0.1% acetic acid, and liquid B, which is acetonitrile containing 0.1% acetic acid, was set to 99% one minute after the start of measurement, 80% two minutes after the start of measurement, and 50% from 10 minutes to 15 minutes after the start of measurement. The flow rate of the eluent was set to 0.4 milliliters per minute (0.4 mL / min). The temperature of the column was set to 40 degrees Celsius (40°C). Also, in the mass spectrometer, the ionization method for various components separated by the liquid chromatograph was set to the electrospray ionization (ESI) method. The measurement time was set from 0.5 minutes to 15 minutes.

[0080] Here, the glutamine content in the vegetables of the first reference example was 27 ppm (parts per million). The glutamine content in the vegetables of the second reference example was 38 ppm. The glutamine content in the vegetables of the third reference example was 61 ppm. In contrast, the glutamine content in the vegetables of the first specific example was 220 ppm. In other words, lettuce with a glutamine content of 220 ppm was obtained. From these measurement results, for example, it was inferred that when the vegetables were grown by irradiating the first light during at least a part of the second period P2 in the third step S3 of hydroponic cultivation of vegetables, the glutamine content in the vegetables increased.

[0081] Also, the Brix value was measured for the vegetables of the first specific example, the vegetables of the second specific example, and the vegetables of the second reference example. The Brix value is a physical quantity used as the sugar content and was measured using a refractive sugar meter.

[0082] Here, the Brix value of the vegetables in the second reference example was 0.9. In contrast, the Brix value of the vegetables in the first specific example was 3 to 5.2. In other words, lettuce with a Brix value of 3 to 5.2 was obtained. From these measurement results, for example, it was inferred that when growing vegetables by irradiating the first light during at least a part of the second period P2 in the third step S3 of hydroponic cultivation of vegetables, the Brix value of the vegetables increases. Also, the Brix value of the vegetables in the second specific example was 5 to 6.4. In other words, lettuce with a Brix value of 5 to 6.4 was obtained. From this measurement result, for example, it was inferred that when growing vegetables using the fourth nutrient solution instead of the third nutrient solution during the third period P3 in the fourth step S4 of hydroponic cultivation of vegetables, the Brix value of the vegetables is more likely to further improve.

[0083] Also, from another perspective, for example, it was confirmed that by growing lettuce by irradiating the first light during at least a part of the second period P2 in the third step S3 of hydroponic cultivation of vegetables, lettuce with a Brix value of 3 or more can be obtained. Also, for example, it was confirmed that by growing lettuce by irradiating the first light during at least a part of the second period P2 in the third step S3 of hydroponic cultivation of vegetables, lettuce with a glutamine content of 220 ppm or more can be obtained. Therefore, for example, it was found that the taste of the vegetables is improved.

[0084] Also, the nitrate concentration was measured for the vegetables of the first specific example, the second specific example, and the second reference example. For the measurement of the nitrate concentration, an ion electrode method was adopted in which the squeezed juice of a sample of a predetermined amount (0.3 milliliters (mL)) or more was dropped and the nitrate concentration was measured by measuring the concentration of nitrate ions. A compact nitrate ion meter (LAQUAtwin <no3-11c no3-11s no3-11>) was used.

[0085] Here, the nitrate concentration in the vegetables of the second reference example was 1860 ppm. In contrast, the nitrate concentration in the vegetables of the first specific example was 760 ppm to 1300 ppm. From these measurement results, for example, by hydroponically cultivating vegetables using the first nutrient solution and the second nutrient solution, which have a lower nitrogen (N) content per liter than the first reference nutrient solution and the second reference nutrient solution commonly used in hydroponics of general vegetables, it was confirmed that the nitrate concentration in the vegetables was reduced. Also, from another perspective, for example, by growing lettuce through hydroponics using the first nutrient solution and the second nutrient solution, it was confirmed that lettuce with a nitrate concentration of 1300 ppm or less could be obtained. Therefore, for example, it was found that healthy vegetables could be obtained. Also, the nitrate concentration in the vegetables of the second specific example was 180 ppm to 1100 ppm. From this measurement result, for example, in the third period P3 of the fourth step S4, by hydroponically cultivating vegetables using a fourth nutrient solution with an even lower nitrogen (N) content per liter than the third nutrient solution, it was confirmed that the nitrate concentration in the vegetables was more likely to be reduced. Also, from another perspective, for example, by growing lettuce through hydroponics using the fourth nutrient solution, it was confirmed that lettuce with a nitrate concentration of 1100 ppm or less could be obtained.

[0086] <1-7. Summary of the First Embodiment> In the method for producing vegetables by hydroponics according to the first embodiment, for example, during the hydroponic cultivation period of the vegetables, in the third step S3, during at least a part of the second period P2, the vegetables are grown by irradiating them with the first light having the maximum value (the first maximum value) of the light intensity in the wavelength range of visible light of 500 nm or less. Thereby, for example, the glutamine content rate and the sugar content in the vegetables can be increased. Therefore, for example, the taste of the vegetables can be improved.

[0087] <2. Other Embodiments> The present disclosure is not limited to the above-described first embodiment, and various changes and improvements can be made without departing from the gist of the present disclosure.

Explanation of Reference Numerals

[0088] 1 Light source 3 Light-emitting element 6 Wavelength conversion member 7 Phosphor 10 Lighting device 30a, 30b Container 31a Seedbed 31b Culture medium 32a Seed 32b Seedling 32c Vegetable to be cultivated 33 Power source 34 Support P1 First period P2 Second period P2a Second A period P2b Second B period P3 Third period S1 First step S2 Second step S3 Third step S4 Fourth step S5 Fifth step

Claims

1. A first step of sowing, A second step of causing cotyledons to emerge from seeds in a first period, A third step of growing vegetables in a second period following the first period, A fourth step of further growing vegetables in a third period following the second period, A fifth step of harvesting vegetables, and having, In the latter stage of the second period, irradiating with a first light having a first maximum value of light intensity in a wavelength range of 420 nm to 490 nm and a maximum value of light intensity in a wavelength range of 500 nm to 600 nm being smaller than the first maximum value, and irradiating with a second light having a second maximum value of light intensity in a wavelength range of 590 nm to 650 nm, having a peak light intensity smaller than the second maximum value in a wavelength range of visible light of 500 nm or less, and an average value of light intensity in a wavelength range of 490 nm to 540 nm being smaller than the peak light intensity, to grow vegetables, a method for producing vegetables.

2. The method for producing vegetables according to claim 1, In the third step, making the length of the latter stage of the second period be from 1 / 4 to 1 / 2 of the total length of the first period, the second period, and the third period combined, a method for producing vegetables.

3. The method for producing vegetables according to claim 1 or claim 2, As the second light, using light having a maximum light intensity which is the maximum value of relative light intensity in a wavelength range of 590 nm to 650 nm, and a first value of relative light intensity at a wavelength of 700 nm being 20% or more of the maximum light intensity and a second value of relative light intensity at a wavelength of 800 nm being 10% or less of the maximum light intensity, a method for producing vegetables.

4. The method for producing vegetables according to any one of claims 1 to 3, The vegetables include leafy vegetables, a method for producing vegetables.

5. The method for producing vegetables according to any one of claims 1 to 4, In the first period, causing cotyledons to emerge from each of a plurality of seeds arranged at intervals to obtain seedlings of a plurality of vegetables, In the early stage of the second period, growing seedlings of a plurality of vegetables, At the timing when the early stage of the second period ends, expanding the interval between adjacent seedlings of a plurality of vegetables, The latter stage of the second period is a period of growing a plurality of vegetables from the seedlings of a plurality of vegetables after the interval has been expanded, and is from 10 days to 16 days, a method for producing vegetables.

6. The method for producing vegetables according to any one of claims 1 to 5, wherein the first half of the second period is a period for growing vegetable seedlings, and is 7 to 14 days, the method for producing vegetables.

7. The method for producing vegetables according to any one of claims 1 to 6, wherein the third period is 1 to 7 days, the method for producing vegetables.

8. The method for producing vegetables according to any one of claims 1 to 7, wherein a plurality of lighting devices that emit light having different spectra are used between the first half of the second period and the second half of the second period, the method for producing vegetables.

9. The method for producing vegetables according to any one of claims 1 to 8, wherein in the second half of the second period, without using sunlight, light emitted from a plurality of lighting devices for 12 to 16 hours per day is irradiated onto a plurality of vegetable seedlings arranged at intervals, the method for producing vegetables.

10. The method for producing vegetables according to any one of claims 1 to 9, wherein the second light includes light in a wavelength range of 500 nm to 590 nm, the method for producing vegetables.

11. The method for producing vegetables according to any one of claims 1 to 10, wherein in the second half of the second period, vegetables are grown using a first nutrient solution in which the nitrogen content per liter is 0.2 mg to 0.47 mg and the calcium oxide content per liter is 0.33 mg to 0.83 mg, the method for producing vegetables.

12. The method for producing vegetables according to any one of claims 1 to 11, wherein in the third period, vegetables are grown using a third nutrient solution that contains nitrogen in the form of ammonia nitrogen and has a nitrogen content per liter of 0.21 mg to 0.42 mg, the method for producing vegetables.

13. The method for producing vegetables according to any one of claims 1 to 11, wherein in the third period, vegetables are grown using a fourth nutrient solution in which the nitrogen content per liter is 0.01 mg or less, the magnesium oxide content per liter is 0.12 mg to 0.24 mg, and the calcium oxide content per liter is 0.54 mg to 0.8 mg, the method for producing vegetables.

14. The method for producing vegetables according to any one of claims 1 to 12, The method for producing vegetables, wherein the vegetables harvested in the fifth step include lettuce having a glutamine content of 220 ppm or more.

15. A method for producing vegetables according to any one of Claims 1 to 14, wherein the vegetables harvested in the fifth step include lettuce having a Brix value of 3 or more.

16. A method for producing vegetables according to any one of Claims 1 to 15, wherein the vegetables harvested in the fifth step include lettuce having a nitrate concentration of 1300 ppm or less.

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