Hydroponic cultivation method

Abstract

To provide a hydroponic method capable of shortening the cultivation period.SOLUTION: A hydroponic method includes: a low liquid temperature maintenance period where liquid temperature is held at 20°C-26°C until plant seeds start root formation, in order to enhance the root development; and a high liquid temperature maintenance period where liquid temperature is held at 29°C-31°C after the seed rooting.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hydroponic cultivation method. [Background technology]

[0002] In a plant factory, hydroponic cultivation equipment is placed inside the factory and light, heat, and air environments are controlled, allowing for planned production of vegetables and other plants. In hydroponic cultivation methods for vegetables and other plants, in addition to controlling light, heat, and air environments, it is also known to manage water temperature and the like (see Patent Documents 1 and 2).

[0003] Paragraphs 0035 to 0037 of Patent Document 1 state that in the "seed sowing mode" and "rooting mode," the water temperature is kept at 20°C throughout the day, and in the "harvesting mode," the water temperature is controlled at 20°C and approximately 15°C during the day and night, respectively. Here, the "seed sowing mode" is a control mode that controls the state from sowing to germination. Note that the period in this mode includes root formation after sowing. Furthermore, the "rooting mode" is a control mode that controls the state from germination until the roots grow to a predetermined length. The "harvesting mode" is a control mode that controls the state from root growth until harvest.

[0004] Paragraph 0071 of Patent Document 2 states that "The liquid temperature does not need to be constant throughout the cultivation period, but may fluctuate within a range of 20 to 30°C, preferably 23 to 27°C.... It may also be controlled so that it fluctuates at intervals during the cultivation period." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-6862 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-60441 Summary of the Invention [Problem to be solved by the invention]

[0006] The water temperature control disclosed in Patent Document 1 has the problem that in the "Hatsuga mode" the water temperature is kept at 20°C all day, and in the "Ikusei mode" the water temperature is kept at 20°C and 15°C during the day and at night, respectively, and therefore it cannot be expected to speed up the growth rate after hatching.

[0007] Patent Document 2 describes conventional general temperature control. The conventional temperature control related to the liquid temperature does not disclose liquid temperature control for shortening the cultivation period from sowing to harvesting.

[0008] In plant factories, the longer the cultivation period from sowing to harvest, the higher the production costs, so there is a demand for shortening the cultivation period in order to reduce production costs. An object of the present invention is to solve the above problems and provide a hydroponic cultivation method that shortens the cultivation period. [Means for solving the problem]

[0009] In order to solve the above problems, the hydroponic cultivation method of the present invention includes a low liquid temperature holding period in which the liquid temperature is maintained at 20°C to 26°C until the plant seeds root, thereby promoting rooting, and a high liquid temperature holding period in which the liquid temperature after the seeds root is maintained at 29°C to 31°C. In this specification, liquid temperature includes the temperature of water or the temperature of a culture solution diluted with water.

[0010] The liquid temperature during the low liquid temperature holding period may be a water temperature, and the liquid temperature may be held at 20°C to 26°C by flowing temperature-adjusted water during the low liquid temperature holding period. The high liquid temperature retention period may include a first period before planting and a second period from planting to harvesting.

[0011] Furthermore, during the high liquid temperature holding period, the liquid temperature may be held at 29°C to 31°C by flowing temperature-adjusted water. The plant may also be a leafy vegetable.

[0012] The plant may also be lettuce, Japanese mustard spinach, mizuna, or bok choy. [Effects of the Invention]

[0013] According to the present invention, there is an effect that the cultivation period can be shortened. [Brief explanation of the drawings]

[0014] [Figure 1] 1(a) is a table showing the rooting rate and germination rate on days 1 to 11 in Comparative Examples 1 and 2, and FIG. 1(b) is a table showing the rooting rate and germination rate on days 1 to 11 in Examples 1 and 2. FIG. [Figure 2] 1 is a table showing rooting rates and germination rates on days 1 to 11 in Comparative Examples 3 and 4. [Figure 3] 1 is a table showing the rooting rate and germination rate on days 1 to 5 in Example 3. [Figure 4] 1 is a table showing rooting rates and germination rates on days 1 to 5 in Examples 4 to 6. [Figure 5] 1(a) is a table showing the rooting rate and germination rate on the 1st to 3rd day in Examples 7 and 8, and FIG. 1(b) is a table showing the rooting rate and germination rate on the 1st to 3rd day in Comparative Examples 5 and 6. FIG. [Figure 6] 1 is a table showing the average weight, maximum weight, and average number of leaves of Comparative Example 7, Comparative Example 8, and Example 9. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Embodiment) DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described. The hydroponic cultivation method of the present embodiment is preferably carried out in a plant factory, particularly a closed-type plant factory. The closed-type plant factory is a factory having a closed space that is not exposed to sunlight or outside air, and has, for example, a clean room.

[0016] (About the hydroponic cultivation method) The hydroponic cultivation apparatus used in the hydroponic cultivation method may be either an NFT (Nutrient Film Technique) system or a DFT (Deep Flow Technique) system.

[0017] The DFT method involves filling a cultivation bed with nutrient solution or water about 5 cm deep with foam culture panels holding plant seeds, and then floating the plants on the bed. This method is preferred because it allows for a large volume of nutrient solution or water and stable cultivation. The nutrient solution or water is supplied intermittently, and any overflow is collected and resupplied to the cultivation bed.

[0018] The NFT method is a method in which nutrient solution or water is constantly flowing through a sloping cultivation bed, and is also collected and circulated. The NFT method has the advantage of using less nutrient solution or water than the DFT method. Another advantage is that the amount of nutrient solution or water used is small, making it easier to control the temperature. In addition, because the roots are not submerged, they are able to absorb oxygen from the air.

[0019] Both DFT and NFT hydroponic cultivation devices preferably include a temperature controller that includes a heater or other heating means for circulating the collected culture solution or water, and a temperature sensor for detecting the temperature of the culture solution or water after heating. The temperature controller controls the temperature of the water or the culture solution diluted with water to a preset temperature during the cultivation period described below. Note that the liquid temperature may be maintained by a method other than flowing temperature-adjusted water.

[0020] (Culture solution) The culture solution is not particularly limited as long as it contains components suitable for plant cultivation. The culture solution usually contains a plurality of elements selected from nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, boron, copper, zinc, molybdenum, and chlorine. The culture solution is supplied when the germination of the plant seeds is confirmed in order to grow the plants after germination.

[0021] (light source) The light source used for photosynthesis by plants is, for example, an artificial light source such as an LED (light-emitting diode), fluorescent lamp, incandescent lamp, sodium lamp, mercury lamp, metal halide lamp, plasma lamp, or electrodeless lamp. The color of the emitted light is not particularly limited, and white light or a combination of light sources with red and blue wavelengths may be used.

[0022] The lighting time is continuous lighting within a predetermined time period. For example, the lighting may be continuous from 6:00 to 22:00, and then turned off from 22:00 to 6:00 the next day during the cultivation period. The lighting time is an example and is not limiting.

[0023] When irradiating plants with a light source, the photosynthetic photon flux density is 150 μmol m -2 s -1 It is preferable that the upper limit of the photosynthetically active photon flux density is not particularly limited. Here, the photosynthetically active photon flux density means the number of photons in the wavelength range of 400 nm to 700 nm that are effective for photosynthesis among the photons that pass through a unit area per unit time.

[0024] (liquid temperature during cultivation period) The cultivation period can be divided into a low liquid temperature maintenance period and a high liquid temperature maintenance period. The low liquid temperature maintenance period is a period during which the water temperature (liquid temperature) is maintained at 20°C to 26°C in order to supply water to the cultivation bed. This period is the period until the sown seeds take root, and is a period to promote rooting. This temperature is maintained by controlling the temperature controller.

[0025] The high liquid temperature retention period is a period during which the liquid temperature is maintained at 29°C to 31°C. This liquid temperature is preferably 31°C, but may be within the aforementioned temperature range. This temperature is maintained by controlling the temperature controller. The high liquid temperature retention period may also include a first period during which germination of the plants is promoted after rooting and the plants are grown until planting, and a second period during which the plants are grown from planting until harvest.

[0026] The first period is a period during which the temperature of the water or the temperature of the culture solution diluted with water (liquid temperature) is maintained at 29°C to 31°C in order to supply water to the cultivation bed. The second period is a period during which the temperature of the culture solution diluted with water (liquid temperature) is maintained at 29°C to 31°C.

[0027] (room temperature) The room temperature is preferably a temperature that does not adversely affect the liquid temperature, for example, room temperature, which is set to 20° C. in this embodiment.

[0028] (About plants) The seeds of the plant of the present invention are preferably leafy vegetables, such as lettuce, Japanese mustard spinach, mizuna, bok choy, spinach, lettuce, arugula, beet, chrysanthemum, and Chinese cabbage. [Example]

[0029] Examples of the present invention will be described in detail below, but the present invention is not limited to the following examples. <1. Example 1, Example 2, Comparative Examples 1 to 4> (Cultivation conditions for Examples 1 and 2) As the plant in Example 1, sunny lettuce (Red Fire (trade name): Takii Seed Co., Ltd.) was used, and as the plant in Example 2, komatsuna (Takii Seed Co., Ltd.) was used.

[0030] The number of plants cultivated was 11, and the cultivation period was 11 days before planting. The room temperature was set at 20°C in a temperature-controlled clean room. The hydroponic cultivation method was the DFT method, in which plant seeds were set on a culture medium panel made of urethane sponge or the like, and the water temperature (liquid temperature) in the cultivation bed was maintained at 20°C. Note that the surface of the culture medium panel was in contact with air, so the temperature was 1°C lower than the water temperature. The period during which the water temperature was maintained at 20°C was the low liquid temperature maintenance period.

[0031] In both Examples 1 and 2, when the seeds rooted, the water temperature was maintained at 31°C by controlling a heater pump (300W) with a temperature controller, and the water in the cultivation bed was circulated to provide running water. During the low liquid temperature maintenance period, the surface of the culture medium panel was in contact with air and therefore 1°C lower than the water temperature. The period during which the water temperature was maintained at 31°C was the high liquid temperature maintenance period.

[0032] The timing for raising the water temperature from 20°C to 31°C was determined when 80% or more of the seeds had rooted, based on the germination rate published by the seed company. During the high liquid temperature period, the surface of the culture medium panel was exposed to air, making it 1°C lower than the water temperature. In Figure 1(b), the timing for raising the water temperature from 20°C to 31°C was on the "second day" in Examples 1 and 2.

[0033] The LED light is made of JAPAN Magnet (150μmol / m -2 s -1 The lighting time was from 06:00 to 22:00, and the lighting time was from 22:00 to 06:00. The CO2 environment was approximately 1500 ppm, and the plants were grown using only water without any nutrient solution during the cultivation period.

[0034] (Cultivation conditions for Comparative Examples 1 and 2) As the plant of Comparative Example 1, sunny lettuce (Red Fire (trade name): Takii Seed Co., Ltd.) was used, and as the plant of Comparative Example 2, komatsuna (Takii Seed Co., Ltd.) was used.

[0035] The number of each plant was increased to 11, and the cultivation period was increased to 11 days. The room temperature was set at 20°C in a temperature-controlled clean room. The hydroponic cultivation method was the DFT method, in which plant seeds were set on a culture medium panel made of urethane sponge or the like, and the water temperature (liquid temperature) in the cultivation bed was maintained at 20°C. Note that the surface of the culture medium panel was in contact with air, so the temperature was 1°C lower than the water temperature (average culture medium temperature: 19°C).

[0036] The LED light is made of JAPAN Magnet (150μmol / m -2 s -1 The lighting time was from 06:00 to 22:00, and the lighting time was from 22:00 to 06:00. The CO2 environment was approximately 1500 ppm, and the plants were grown using only water, without any nutrient solution, during the cultivation period.

[0037] (Cultivation conditions for Comparative Examples 3 and 4) In Comparative Examples 3 and 4, the hydroponic cultivation method was the DFT method, in which plant seeds were set on a culture medium panel made of urethane sponge or the like, and the water temperature (liquid temperature) in the cultivation bed was maintained at 31°C by controlling a heater pump (300W) with a temperature controller. At the same time, the water in the cultivation bed was circulated to provide running water.

[0038] The surface of the culture medium panel was in contact with air, and therefore the temperature was 1° C. lower than the water temperature. Other cultivation conditions were the same as those in Comparative Examples 1 and 2. (Germination rate: Comparison of Examples 1 and 2 with Comparative Examples 1 to 4) FIG. 1(a) is a table showing the rooting rate and germination rate from the first day to the eleventh day after sowing in Comparative Examples 1 and 2.

[0039] FIG. 1(b) is a table showing the rooting rate and germination rate from the first day to the eleventh day after sowing in Examples 1 and 2. FIG. 2 is a table showing the rooting rate and germination rate from the 1st day to the 11th day after sowing in Comparative Examples 3 and 4.

[0040] As shown in Figures 1(a) and 1(b), the sunny lettuce seeds of Comparative Example 1 and Example 1 had a germination rate of 100% on the "7th day," and the timing of root formation and germination was also almost simultaneous. In the Komatsuna seeds of Comparative Example 4 shown in Figure 2, some seeds did not germinate. Furthermore, in Comparative Examples 3 and 4 shown in Figure 2, there was variation in the timing of germination.

[0041] It has been known that temperatures above 25°C reduce the germination rate and induce seed dormancy. Therefore, in Comparative Examples 3 and 4, some seeds did not root after the fourth day.

[0042] (Growth speed after rooting: Comparison of Examples 1 and 2 with Comparative Examples 1 to 4) The water temperature of 20°C in Comparative Examples 1 and 2 in Fig. 1(a) is the temperature that has been conventionally recommended as the water temperature from sowing to germination.

[0043] On the other hand, in Examples 1 and 2, the cultivation conditions were the same as those of Comparative Examples 1 and 2 until rooting, but when the germination rate was examined on the "fourth day" after the "second day" when the water temperature was raised to 31°C, it was confirmed that the growth speed was clearly faster than in Comparative Examples 1 and 2. In other words, it can be seen that the growth speed was promoted during the high liquid temperature retention period in Examples 1 and 2.

[0044] In addition, in Examples 1 and 2, a heater pump was used to generate a water current during the high-temperature maintenance period in order to maintain a constant water temperature in the cultivation bed. This is thought to move the dissolved oxygen in the water in the cultivation bed, further promoting growth. While publicly known literature has shown that high water temperatures can cause root rot due to a lack of dissolved oxygen, it was confirmed that no root rot occurred in this example.

[0045] <2. Example 3> (Cultivation conditions of Example 3) Sunny lettuce (Red Fire (trade name): Takii Seed Co., Ltd.) was used as the plant in Example 3. The number of plants cultivated was 11, and the cultivation period was 6 days before planting.

[0046] The room temperature was set to 20°C in a temperature-controlled clean room. The hydroponic cultivation method was the DFT method, where plant seeds were set on a culture medium panel made of urethane sponge, and the water temperature (liquid temperature) in the cultivation bed was maintained at 26°C. During the low liquid temperature maintenance period, the surface of the culture medium panel was in contact with air, so the temperature was 1°C lower than the water temperature (average culture temperature of 25°C). The period during which the water temperature was maintained at 26°C was the low liquid temperature maintenance period.

[0047] In Example 3, when the seeds rooted, the water temperature was maintained at 31°C by controlling a heater pump (300W) with a temperature controller, and the water in the cultivation bed was circulated to provide running water. During the high liquid temperature maintenance period, the surface of the culture medium panel was in contact with air, and therefore the temperature was 1°C lower than the water temperature (average culture medium temperature 30°C). The period during which the water temperature was maintained at 31°C was the high liquid temperature maintenance period.

[0048] On the first day in Figure 3, the seeds had rooted at over 80% of the germination rate published by the seed company, so the water temperature was raised from 26°C to 31°C. -2 s -1 The lighting time was from 06:00 to 22:00, and the lighting time was from 22:00 to 06:00. The CO2 environment was approximately 1500 ppm, and the plants were grown using only water without any nutrient solution during the cultivation period.

[0049] (Growth speed after rooting: Comparison of Example 3 and Example 1) FIG. 3 is a table showing the rooting rate and germination rate from the first day to the fifth day after sowing in Example 3.

[0050] In sunny lettuce Example 3, the rooting rate was 100% on "Day 1." In sunny lettuce Example 1, the rooting rate was 0% on "Day 1," so it was confirmed that Example 3 had faster rooting. Furthermore, when comparing Example 1 and Example 3 for the germination rate on "Day 4" of the high liquid temperature retention period, Example 3 had a germination rate of 90.9% on "Day 4" while Example 1 had a germination rate of 81.8%, indicating that Example 3 had a faster growth speed.

[0051] This confirmed that the growth rate after rooting was faster in Example 3, where the water temperature was 26°C, than in Example 1, where the water temperature during the low liquid temperature retention period was 20°C. This means that the overall cultivation period can be expected to be shortened.

[0052] <3. Examples 4 to 6> (Cultivation conditions for Examples 4 to 6) As plants used in Examples 4, 5 and 6, komatsuna, mizuna and bok choy (all from Takii Seed Co., Ltd.) were used.

[0053] The number of plants grown was 11, and the cultivation period was 10 days before planting. The room temperature was set at 20°C in a temperature-controlled clean room. The hydroponic cultivation method was the DFT method, where plant seeds were set on a culture medium panel made of urethane sponge, and the water temperature (liquid temperature) in the cultivation bed was maintained at 26°C. Note that the surface of the culture medium panel was in contact with air, so the temperature was 1°C lower than the water temperature (average culture medium temperature: 25°C). The period during which the water temperature was maintained at 26°C was the low liquid temperature maintenance period.

[0054] In all of Examples 4 to 6, when the seeds rooted, the water temperature was maintained at 31°C by controlling a heater pump (300W) with a temperature controller, and the water in the cultivation bed was circulated to provide running water. During the high liquid temperature maintenance period, the surface of the culture medium panel was in contact with air, and therefore the temperature was 1°C lower than the water temperature (average culture medium temperature: 30°C). The period during which the water temperature was maintained at 31°C was the high liquid temperature maintenance period.

[0055] The timing for raising the water temperature from 26°C to 31°C was determined when 80% or more of the seeds had rooted, based on the germination rate published by the seed company. In Figure 4, in Examples 4 and 5, the temperature is raised from 26°C to 31°C on "day 1". In Example 6, the temperature is raised from 26°C to 31°C on "day 2".

[0056] The LED light is made of JAPAN Magnet (150μmol / m -2 s -1 The lighting time was from 06:00 to 22:00, and the lighting time was from 22:00 to 06:00. The CO2 environment was approximately 1500 ppm, and the plants were grown using only water without any nutrient solution during the cultivation period.

[0057] (Rooting rate and growth speed after rooting: Examples 4 to 6) FIG. 4 is a table showing the rooting rate and germination rate from the first day to the fifth day after sowing in Examples 4 to 6.

[0058] The rooting rate of Komatsuna in Example 4 in Figure 4 was 100% on the "2nd day", whereas that of Example 2 in Figure 1(b) was 100% on the "7th day". Furthermore, the germination rate of Example 4 was "100%" on the "4th day", whereas that of Example 2 was "100%" on the "7th day". From this, it can be seen that the rooting rate and growth speed after rooting are faster when the water temperature during the low liquid temperature retention period is set to 26°C than in Example 2.

[0059] Generally, the optimum temperature for germination is considered to be the lower of the two ranges between 15°C and 25°C. However, as can be seen from "Day 2" and "Day 3" in Examples 4 to 6, germination can be accelerated by promoting germination at around 26°C.

[0060] This suggests that when the water temperature is 26°C or higher, root respiration and photosynthesis become more active, resulting in faster growth. This effect can be expected across a wide variety of leafy vegetables. This can also be expected to shorten the cultivation period. In addition, it was confirmed that root rot did not occur in this example.

[0061] 4. Example 7, Example 8, Comparative Example 5, and Comparative Example 6 Examples 7, 8, and Comparative Examples 5 and 6 are for comparing water temperatures from when seeds take root until they germinate. Examples 7, 8, 5, and 6 show examples of optimal water temperatures for aligning the timing of rooting of sown seeds.

[0062] (Cultivation conditions for Examples 7 and 8) As the plant in Example 7, sunny lettuce (Red Fire (trade name): Takii Seed Co., Ltd.) was used, and as the plant in Example 8, leaf lettuce (Takii Seed Co., Ltd.) was used.

[0063] The number of each plant was set to 100, and the cultivation period was set to 4 days. The room temperature was set to 20°C in a temperature-controlled clean room. The hydroponic cultivation method was the DFT method, in which plant seeds were set on a culture medium panel made of urethane sponge, and the water temperature (liquid temperature) in the cultivation bed was maintained at 26°C by controlling a heater pump (300W) with a temperature controller. The water in the cultivation bed was circulated to create a flowing stream. Note that the surface of the culture medium panel was in contact with air, so the temperature was 1°C lower than the water temperature (average culture medium temperature: 25°C). The period during which the water temperature was maintained at 26°C was the low liquid temperature maintenance period.

[0064] The LED light is made of JAPAN Magnet (150μmol / m -2 s -1 The lighting time was from 06:00 to 22:00, and the lighting time was from 22:00 to 06:00. The CO2 environment was approximately 1500 ppm, and the plants were grown using only water without any nutrient solution during the cultivation period.

[0065] (Cultivation conditions for Comparative Examples 5 and 6) Sunny lettuce (Red Fire (trade name): Takii Seed Co., Ltd.) was used as the plant for Comparative Example 5, and leaf lettuce (Takii Seed Co., Ltd.) was used as the plant for Comparative Example 6. 100 plants of each type were cultivated, and the cultivation period was 4 days. The room temperature was set to 20°C in a temperature-controllable clean room.

[0066] The hydroponic cultivation method was the same as in Examples 7 and 8, except that the water temperature was maintained at 31°C. Note that the surface of the culture medium panel was in contact with air, so the temperature was 1°C lower than the water temperature (average culture medium temperature: 30°C).

[0067] (Rooting rate and germination rate: Example 7, Example 8, Comparative Example 5, Comparative Example 6) FIG. 5(a) is a table showing the rooting rate and germination rate from the first day to the third day after sowing in Examples 7 and 8.

[0068] FIG. 5(b) is a table showing the rooting rate and germination rate from the first day to the third day after sowing in Comparative Examples 5 and 6. Comparing the rooting rate of sunny lettuce in Example 7 and Comparative Example 5, the rooting rate on the "third day" was 91% in Example 7, while it was 15% in Comparative Example 5, which was extremely poor. Therefore, it can be seen that the water temperature of 26°C in Example 7 is more preferable for aligning the timing of rooting.

[0069] Comparing leaf lettuce in Example 8 and Comparative Example 6, Example 8 had a rooting rate of 98% on the first day and 100% on the second day. In contrast, Comparative Example 6 had a rooting rate of 79% on the first day, 98% on the second day, and 99% on the third day, showing a gradual increase in rooting rate. However, it can be seen that the water temperature of 26°C in Example 8 is more preferable for aligning the timing of rooting.

[0070] If the timing of root germination of multiple seeds can be synchronized, the germination and growth speed of the multiple seeds will also be accelerated as mentioned above, and it is expected that the overall cultivation period will be shortened.

[0071] 5. Comparative Example 7, Comparative Example 8, and Example 9 Example 9 and Comparative Example 7 show the results of a comparison of yields when cultivated over the same cultivation period. Also, Example 9 and Comparative Example 8 show the results of shortening the cultivation period when the yield is kept at the same level.

[0072] (Cultivation conditions common to Comparative Example 7, Comparative Example 8, and Example 9) As the plant used in Comparative Example 7, Comparative Example 8 and Example 9, leaf lettuce (Green Wave (trade name): Takii Seed Co., Ltd.) was used.

[0073] The number of plants cultivated for each type was 24 at the time of sowing. The number of plants cultivated from planting to harvest was 15. Planting was carried out 10 days after sowing. The planting intervals were 170 mm or more. In a temperature-controlled clean room, air was blown to maintain the room temperature at 20°C, and the temperature was maintained at that level.

[0074] The hydroponic cultivation method was the DFT method, where plant seeds were set on culture medium panels made of urethane sponge or the like, and water or culture solution was circulated in the cultivation bed. That is, water was circulated from sowing until less than 80% of the seeds had true leaves, and once 80% or more of the seeds had true leaves, the following culture solution diluted with water was circulated.

[0075] (Culture fluid components) Calcium nitrate (43%), potassium nitrate (12.6%), magnesium sulfate (20.3%), potassium dihydrogen phosphate (13%), others (compound components including iron, copper, manganese, etc., 11.1%) The liquid temperatures of the circulated water or culture solution in Comparative Example 7, Comparative Example 8 and Example 9 will be described later.

[0076] The LED light is made of JAPAN Magnet (275 μmol / L) -2 s -1 The lighting time was from 06:00 to 22:00, and the lighting time was from 22:00 to 06:00. The CO2 environment was approximately 1500 ppm.

[0077] (Cultivation conditions for Comparative Example 7, Comparative Example 8, and Example 9: liquid temperature and number of days of cultivation) In Comparative Example 7, Comparative Example 8 and Example 9, the seeds were sown on the same day. In Comparative Example 7, the period from sowing to harvesting was 35 days, and the liquid temperature was maintained at 20°C. In Comparative Example 8, the period from sowing to harvesting was (35+α) days, and the liquid temperature was maintained at 20°C. The harvesting date in Comparative Example 8 was the day when the number of leaves reached the same level as that of the plants harvested in Example 9, which will be described later. α is the difference between the harvesting dates in Example 9 and Comparative Example 8.

[0078] In Example 9, the water temperature (liquid temperature) was maintained at 26°C from sowing to rooting, and the temperature of the water or the culture solution diluted with water (liquid temperature) was maintained at 31°C from rooting to harvest. The liquid temperature was controlled by controlling a heater pump (300W) with a temperature controller. Note that because the surface portion of the culture medium panel is exposed to air, when the water temperature is 26°C, the average culture temperature is 25°C, 1°C lower, and when the water temperature is 31°C, the average culture temperature is 30°C, 1°C lower. The period when the water temperature is maintained at 26°C is the low liquid temperature maintenance period. The period when the water temperature is maintained at 31°C is the high liquid temperature maintenance period.

[0079] Here, in Example 9, the period during which the liquid temperature is maintained at 26°C is the low liquid temperature maintenance period. Also, in Example 9, the period during which the liquid temperature is maintained at 31°C is the high liquid temperature maintenance period. The high liquid temperature maintenance period includes a first period during which germination after rooting is promoted and the plant is planted, and a second period during which the plant is grown from planting to harvest.

[0080] (Comparison between Example 9 and Comparative Example 7) As shown in Figure 6, the average weight of the five plants in Example 9 on the 35th day after sowing was 246.36 g, with a maximum weight of 303.68 g. On the other hand, the average weight of the five plants in Comparative Example 7 on the 35th day after sowing was 165.97 g, with a maximum weight of 220.82 g. The average number of leaves was 25, the same number for Example 9 and Comparative Example 7.

[0081] As a result of comparing the two, it is found that Example 9 has a larger harvest yield than Comparative Example 7 in terms of both average weight and maximum weight. (Comparison between Example 9 and Comparative Example 8) As shown in Figure 6, the average weight and maximum weight of the five plants in Comparative Example 8 were obtained when the plants were harvested with 28 leaves, which was the same as the average number of leaves, 25, of the plants harvested in Example 9. In Comparative Example 8, the plants were harvested on day α = 4, after 35 days. In Comparative Example 8, the number of leaves was slightly greater than in Example 9, but the leaves were small and some of the leaves were not firm.

[0082] The average weight of Comparative Example 8 was 245.91 g, and the maximum weight was 297.14 g. Therefore, in Comparative Example 8, in order to obtain plants with average weight and maximum weight comparable to those of Example 9, it is necessary to extend the cultivation period by about four days compared to Example 9. As a result, Comparative Example 8 requires four days' worth of running costs. Conversely, in Example 9, four days' worth of running costs can be reduced.

[0083] This has the following advantages. The cultivation period until harvest is 39 days using the room temperature cultivation method of Comparative Example 8, and 35 days using the cultivation method of Example 9. This means that in the case of cultivation in Example 9, one cultivation cycle can be extended by approximately 7 months compared to the room temperature cultivation. As a result, this contributes greatly to the annual yield (profit). Furthermore, as the annual yield (profit) increases, the book value of the equipment will be depreciated more quickly. Generally, plant factories have high initial costs, and there are concerns that it takes time for them to become profitable. However, if the harvest cycle can be shortened, it will also be advantageous for capital investment.

[0084] Furthermore, the longer the cultivation period, the greater the risks. For example, a power outage could cut off the water supply, or the cultivated plants could become ill (such as root rot) and infect other plants. For these reasons, shortening the cultivation period is extremely important when operating a plant factory.

Claims

1. a low liquid temperature retention period in which the liquid temperature is maintained at 20°C to 26°C until the plant seeds root, thereby promoting rooting; A hydroponic cultivation method including a high liquid temperature holding period in which the liquid temperature after the seeds have rooted is kept at 29°C to 31°C.

2. 2. The hydroponic cultivation method according to claim 1, wherein the liquid temperature during the low liquid temperature retention period is a water temperature, and the liquid temperature is maintained at 20°C to 26°C by flowing temperature-adjusted water during the low liquid temperature retention period.

3. 3. The hydroponic cultivation method according to claim 2, wherein the high liquid temperature holding period includes a first period before planting and a second period from planting to harvesting.

4. 3. The hydroponic cultivation method according to claim 2, wherein the high liquid temperature holding period is maintained at 29°C to 31°C by flowing temperature-adjusted water.

5. 4. The hydroponic cultivation method according to claim 1, wherein the plant is a leafy vegetable.

6. 6. The hydroponic cultivation method according to claim 5, wherein the plant is a leafy vegetable, lettuce.

7. 6. The hydroponic cultivation method according to claim 5, wherein the plant is a leafy vegetable, Komatsuna.

8. The hydroponic cultivation method according to claim 5, wherein the plant is mizuna, a leafy vegetable.

9. 6. The hydroponic cultivation method according to claim 5, wherein the plant is a leafy vegetable, bok choy.

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