JP2024139009A - How to grow spinach - Google Patents

Abstract

[Problem] To provide a method for cultivating spinach that produces a large yield per cultivation area and is rich in nutrients. [Solution] This method involves irradiating light to spinach seedlings held in a culture medium, and cultivating the seedlings hydroponically with the roots of the seedlings submerged in a nutrient solution, in which the density of the spinach seedlings is 120 to 300 (saplings/m2), and the distance between the bottom of the culture medium and the surface of the nutrient solution is 0.5 to 2.5 cm. [Selected Figure] Figure 3

Description

The present invention relates to a method for growing spinach using hydroponic cultivation.

Conventionally, leafy vegetables such as spinach have been grown by hydroponic cultivation. Various proposals have been made for hydroponic cultivation of leafy vegetables such as spinach.
For example, Patent Document 1 describes a hydroponic cultivation method for leafy vegetables such as spinach, in which nutrient water is supplied to the most upstream of a leafy vegetable cultivation container having a longitudinal gradient and is circulated by flowing out from the most downstream of the cultivation container. In Patent Document 1, the cultivation container has a plurality of planting holes on its top surface and has parallel uneven grooves in the longitudinal direction on its bottom surface, and leafy vegetables such as spinach are inserted into the planting holes and contained in the cultivation container, and the roots of the leafy vegetables are cultivated by contacting the nutrient water with them.

International Publication No. 2010/073901

In spinach cultivation, there is a demand for a large yield per cultivation area, and further, there is a demand for the harvested spinach to have a large amount of nutrients.
However, the hydroponic cultivation method for leafy vegetables such as spinach described in Patent Document 1 aims to allow for easy cultivation at home or the like, and does not take into consideration increasing the yield per cultivation area or the nutrients of the harvested spinach.
An object of the present invention is to provide a method for cultivating spinach which has a large yield per cultivation area and is rich in nutrients.

In order to achieve the above-mentioned object, invention [1] is a method for cultivating spinach, in which light is irradiated onto spinach seedlings held in a culture medium, and the seedlings are cultivated hydroponically with the roots of the seedlings immersed in a nutrient solution, in which the plant density of the spinach seedlings is 120 to 300 (plants/ ^m2 ), and the distance between the bottom of the culture medium and the surface of the nutrient solution is 0.5 to 2.5 cm.
Invention [2] is the method for cultivating spinach according to Invention [1], wherein the electrical conductivity of the nutrient solution is 0.8 to 2.7 dS/m.
Invention [3] is a method for cultivating spinach according to Invention [1] or [2], in which the light is white light.
Invention [4] is a method for cultivating spinach according to any one of Inventions [1] to [3], which has a cultivation cycle including a light period and a dark period that is darker than the light period.
Invention [5] is the method for cultivating spinach according to Invention [4], wherein the temperature during the dark period is lower than that during the light period.
Invention [6] is a method for cultivating spinach according to Invention [4] or [5], in which the cultivation cycle has a dark period of 40 to 60% when the sum of the light period and the dark period is 100%.
Invention [7] is a method for cultivating spinach according to any one of Inventions [4] to [6], wherein the temperatures during the light period and the dark period are 25° C. or lower.
Invention [8] is a method for cultivating spinach according to any one of Inventions [1] to [7], in which 1 to 5 spinach seedlings are maintained in one medium.

The present invention provides a method for cultivating spinach that produces a high yield per cultivation area and is rich in nutrients.

FIG. 2 is a schematic plan view showing an example of a cultivation container used in the spinach cultivation method according to the embodiment of the present invention. FIG. 2 is a schematic side view showing an example of a cultivation container used in the spinach cultivation method according to the embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of a cultivation container used in the spinach cultivation method according to the embodiment of the present invention.

Hereinafter, the spinach cultivation method of the present invention will be described in detail based on the preferred embodiment shown in the accompanying drawings.
Note that the embodiments described below and the contents shown in the drawings are merely illustrative for explaining the present invention, and the present invention is not limited to the drawings shown below.
In the following description, the term "to" indicating a range of values includes the values written on both sides. For example, if ε is a value _εα to a value _εβ , the range of ε includes the values _εα and _εβ , and expressed in mathematical notation, _εα ≦ε≦ _εβ .
In addition, unless otherwise specified, various numerical values include an error range generally accepted in the relevant technical field.

(spinach)
Spinach is a vegetable in which the edible green parts are called the true leaves.
Examples of spinach include Aldebaran, Ifrit, Cassini, Green Up, Chrone, Sun Angel, Scoop, Stout, Sauskai, Checkmate, Triton, Newton, Nordic, Hydro, Haydn, Bahamut, Bishop, Fukubay, Perseus, and Luke, all of which are trade names. Of these, Hydro, Chrone, Sun Angel, Green Up, and Newton are preferred.

(Spinach seedlings)
The spinach seedlings refer to young plants of spinach that are grown for the purpose of being transplanted, i.e., planted in a permanent location, in the future.
The spinach seedlings to be planted are not particularly limited, but are preferably seedlings with one or more and eight or less true leaves, more preferably seedlings with one or more and four or less true leaves, even more preferably seedlings with one or more and three or less true leaves, and particularly preferably seedlings with one or more and two or less true leaves.
The term "spinach seedlings" also includes those just before harvest. Spinach seedlings include those from the sowing (sowing) stage to harvesting, without being transplanted, i.e., planted, in the future. Furthermore, the sowing (sowing) density, i.e., the plant density of spinach seedlings, is 120 to 300 plants/ ^m2 .
Plant density is the number of plants per square ^meter . The plant density of spinach seedlings represents the density at which spinach seedlings are arranged. The average plant spacing is expressed as (1/plant density) ^0.5 .

The method for cultivating plants will be described below.
First, the cultivation container used in the plant cultivation method will be described.
<Example of a cultivation container>
FIG. 1 is a schematic plan view showing an example of a cultivation container used in a spinach cultivation method according to an embodiment of the present invention, and FIG. 2 is a schematic side view showing an example of a cultivation container used in a spinach cultivation method according to an embodiment of the present invention.
Spinach is grown, for example, by a hydroponic method using a cultivation container 10 shown in Fig. 1. For example, the shape of a surface 11 of the cultivation container 10 (a surface 12d of a cultivation plate 12 described later) is rectangular. The cultivation container 10 is also called a panel.
A plurality of spinach seedlings P are arranged on a surface 11 of a cultivation container 10 shown in Fig. 1 with a space between adjacent spinach seedlings P. Although some parts are omitted in Fig. 1, for example, a total of 120 spinach seedlings P are arranged on a surface 12d of a cultivation plate 12 described later.
The spinach seedlings P are arranged at equal intervals in the orthogonal X and Y directions, and are arranged so as to be located at the vertices of a rectangle when the surface 11 (panel surface) of the cultivation container 10 is partitioned into a rectangular grid. In Fig. 1, the interval Dx in the X direction and the interval Dy in the Y direction for the spinach seedlings P are different. When the intervals Dx and Dy are different, the average interval of these intervals is set as the interval between the spinach seedlings P.
The spacing between spinach seedlings P refers to the distance between the main axes of adjacent spinach seedlings P at ground level.

The spacing Dx and Dy between the spinach seedlings P are determined appropriately according to the density of the seedlings P. Since the density of the seedlings P is 120 to 300 (saplings/m ² ), it is preferable that the spacing Dx (saplings) and spacing Dy (saplings) between the spinach seedlings P be less than 15 cm. If the spacing between the spinach seedlings P is too narrow, it becomes difficult to harvest and the harvesting workability is deteriorated, so it is preferable that the lower limit of the spacing between the spinach seedlings is 3 cm.
The arrangement pattern of the spinach seedlings P is not limited to the rectangle shown in Fig. 1 above, and may be a polygonal shape such as a triangle, a square other than a rectangle, a pentagon, or a hexagon. Note that the spacing between the spinach seedlings P may vary depending on the direction even in the case of a polygon other than a square. Even in this case, the average spacing between the spinach seedlings P in different directions is defined as the spacing between the spinach seedlings P. As described above, the average spacing between plants is expressed as (1/plant density) ^0.5 .

When the plant density of spinach seedlings P is 120 to 300 (plants/m ² ), the yield per cultivation area is high and the nutrients are rich.
If the density of spinach seedlings P is less than 120 seedlings/ ^m2 , the yield per cultivation area will be low.
If the density of spinach seedlings P exceeds 300 plants/ ^m2 , the weight of each plant will be small and adjacent plants will be close to each other, making harvesting difficult and reducing harvesting workability.

2, a light source 20 emitting, for example, white light is disposed above the surface 11 of the cultivation container 10 (surface 12d of the cultivation plate 12). In the cultivation process, light from the light source is irradiated onto the spinach seedlings P. In the cultivation process, the light intensity of the light source 20 is adjusted so that a predetermined photon flux density (μmol/( ^m2s )) of the light is achieved for the spinach seedlings.
In the cultivation process, the white light irradiated to the spinach seedlings P is not particularly limited, and may be natural light such as sunlight, or artificial light. For example, the photosynthetic photon flux density of sunlight is 1000 μmol/( ^m2s ) or more, while that of artificial light is about 100 to 500 μmol/( ^m2s ).
The light source 20 may be, for example, an inorganic or organic LED (Light Emitting Diode), a semiconductor light emitting element such as a laser, a discharge tube such as a fluorescent lamp, a mercury lamp, a rare gas lamp, or an electrodeless lamp, a filament light emitter such as an incandescent lamp, or a device that emits white light using energy transition such as synchrotron radiation or fluorescence. The light source 20 may be configured to have a mechanism for changing the irradiation range. When a white LED other than sunlight is used as the light source, the white light is artificial light.

Here, Fig. 3 is a schematic cross-sectional side view showing an example of a cultivation container used in the plant cultivation method according to the embodiment of the present invention. Fig. 3 is a cross-sectional view showing a part of the cultivation container 10 shown in Figs. 1 and 2.
As shown in Fig. 3, the cultivation container 10 has a cultivation plate 12 and a liquid tank 14 in which nutrient solution L (liquid fertilizer) is stored. The liquid tank 14 is a container having a bottom 15. The nutrient solution L contains nutrients necessary for the growth of spinach seedlings P to be cultivated. The spinach seedlings P are placed in and held in the cultivation container 10 with the roots Pr of the spinach seedlings P immersed in the nutrient solution L in the liquid tank 14 of the cultivation container 10, and are hydroponically cultivated.
The state where the roots Pr of the spinach seedlings P are immersed in the nutrient solution L means that at least a part of the roots Pr is in the nutrient solution L. It is preferable that the roots Pr are not entirely immersed in the nutrient solution L, and that there is a gap between the lower surface 13b of the medium 13 and the liquid surface Ls of the nutrient solution L.

The cultivation plate 12 supports a plurality of spinach seedlings P. The cultivation plate 12 is, for example, a lid for the liquid tank 14, and can be freely removed from the liquid tank 14. In the case of this configuration, at the time of harvesting, the cultivation plate 12 is removed from the liquid tank 14, and spinach can be harvested from the cultivation plate 12 in a state where it is removed from the liquid tank 14.
When the cultivation plate 12 and the liquid tank 14 are integrated, spinach is harvested in the state of the cultivation container 10.
The cultivation plate 12 has a plurality of holding parts 12a for holding the culture medium 13 for the spinach seedlings P, and a through hole 12c provided in the bottom 12b of each holding part 12a. The holding parts 12a have an opening 12e on the surface 12d side of the cultivation plate 12. For example, the holding parts 12a are cup-shaped, and the culture medium 13 is inserted and held through the opening 12e of the holding parts 12a. For example, the outline shape of the opening 12e is circular when the cultivation plate 12 is viewed from the surface 12d.

In the spinach seedlings P, the distance δ between the lower surface 13b of the medium 13 and the liquid surface Ls of the nutrient solution L is 0.5 to 2.5 cm. The above-mentioned distance δ is preferably 0.5 to 1 cm.
When the distance δ is 0.5 to 2.5 cm, the yield per cultivation area is large and the nutrients are also increased.
If the distance δ is less than 0.5 cm, the roots Pr of the spinach seedlings P will be too immersed in the nutrient solution L, causing the roots Pr to become unhealthy, resulting in a lower yield per cultivation area and less nutrients.
If the distance δ exceeds 2.5 cm, the roots Pr of the spinach seedlings P may not be sufficiently immersed in the nutrient solution L, and the roots Pr may wither.
The distance δ between the lower surface 13b of the culture medium 13 and the liquid level Ls of the nutrient solution L is measured with a ruler, calipers, or the like by partially removing a part of the cultivation container 10 with the nutrient solution L filled therein so as not to spill the nutrient solution L and exposing the lower surface 13b of the culture medium 13 and the liquid level Ls of the nutrient solution L.
The distance δ between the lower surface 13b of the culture medium 13 and the liquid level Ls of the nutrient solution L can be adjusted by at least one of the position of the lower surface 13b of the culture medium 13 relative to the liquid level Ls and the amount of the nutrient solution L.

[How to grow spinach]
The method for cultivating spinach is described below.
The method for cultivating spinach involves irradiating light to spinach seedlings held in a medium, and cultivating the spinach seedlings hydroponically with the roots of the spinach seedlings immersed in a nutrient solution.
In the spinach cultivation method, the density of spinach seedlings is 120 to 300 (saplings/ ^m2 ) and the distance between the bottom of the medium and the surface of the nutrient solution is 0.5 to 2.5 cm. This allows for a high yield per cultivation area and the production of spinach rich in nutrients.

The nutrient solution L is prepared by adding and dissolving various nutrients in a solvent such as water, and adjusting the concentration of each component according to the type of plant to be grown. Examples of components in the nutrient solution L include nitrogen (specifically, ammonia nitrogen or nitrate nitrogen), phosphoric acid (P ₂ O ₅ ), potassium (K ₂ O), lime (CaO), magnesia (MgO), manganese (MnO), boron (B ₂ O ₃ ), iron (Fe), copper (Cu), zinc (Zn), and molybdenum (Mo).

As shown in Fig. 3, the spinach seedlings P are grown in the cultivation container 10 with the roots Pr of the spinach seedlings P immersed in the nutrient solution L in the cultivation container 10 and with the leaf and stem portions of the spinach seedlings P protruding outside the cultivation container 10. In the following, the period during which the spinach seedlings P are grown in the cultivation container 10 with the roots Pr of the spinach seedlings P immersed in the nutrient solution L in the cultivation container 10 is referred to as the growth period of the spinach seedlings P.
During the growing period of the spinach seedlings P, the cultivation container 10 in which the spinach seedlings P are placed may be rotated or swung by a drive device (not shown). This causes a flow in the nutrient solution L in the cultivation container 10 and stirs the nutrient solution L, which can suppress a decrease in the concentration of the nutrient solution L around the roots Pr in the cultivation container 10. This allows the spinach seedlings P to properly absorb the nutrients in the nutrient solution L from the roots Pr, allowing the spinach seedlings P to grow well.
In the cultivation of spinach, it is preferable to control the concentration of the nutrient solution L to be constant. The control of the concentration of the nutrient solution L will be described later.

As described above, the cultivation container 10 is composed of the cultivation plate 12 and the liquid tank 14, and the inside of the cultivation container 10 is surrounded by these walls to form a closed space. A predetermined amount of nutrient solution L is stored in this closed space, and strictly speaking, the nutrient solution L is retained in the cultivation container 10. Here, the nutrient solution L being retained in the cultivation container 10 means that the nutrient solution L is retained in the cultivation container 10 without being circulated. Note that the amount of nutrient solution L in the cultivation container 10 that is absorbed by the spinach seedlings P and the amount that naturally evaporates from the cultivation container 10 are allowed.
As described above, since the space in the cultivation container 10 in which the nutrient solution L is stored is a closed space, the growth of algae caused by irradiation of the nutrient solution L with light can be effectively suppressed.

As shown in FIG. 3, the cultivation plate 12 is provided with a holding portion 12a, and the opening 12e of the holding portion 12a has, for example, a circular outline shape when viewed from the surface 12d side of the cultivation plate 12. The culture medium 13 is stored in the holding portion 12a through the opening 12e, and the spinach seedlings P are held in the holding portion 12a together with the culture medium 13. The spinach seedlings P are stably held in the holding portion 12a by the culture medium 13.

The shape of the cultivation container 10 is not limited to the shape shown in Fig. 1. The size of the cultivation container 10 is also not particularly limited, but it is preferable that the cultivation container 10 is a size that can be carried by a person for harvesting, for example.
The material of the cultivation container 10 is not particularly limited, but in order to suppress the growth of algae caused by the irradiation of light onto the nutrient solution L, it is preferable to grow spinach seedlings P using a cultivation container 10 (cultivation plate 12 and liquid tank 14) made of a material with a visible light transmittance of 10% or less.
The material of the cultivation container 10 (cultivation plate 12 and liquid tank 14) is preferably plastic, such as polyethylene (PE), polypropylene (PP), polystyrene (PS), acrylonitrile-styrene resin (AS), acrylonitrile-butadiene-styrene resin (ABS), polyvinyl chloride (PVC), methacrylic resin (PMMA), and polyethylene terephthalate (PET).
The transmittance can be measured by a known measurement method, for example, a measurement method using a spectrophotometer equipped with an integrating sphere. Specifically, the material to be measured is placed in the opening of an integrating sphere, measurement light is incident on the integrating sphere from the opening, and the transmittance can be measured by detecting the light that travels straight or is scattered within the sphere.

The surface color of the cultivation container 10 (cultivation plate 12) is not particularly limited, but a color with a relatively high light reflectivity, such as white, is preferable for the purpose of reflecting light in the cultivation container 10 and effectively irradiating the leaves and stems of the spinach seedlings P. Furthermore, if lowering the transmittance is a priority, the surface color of the cultivation container 10 is preferably black, blue, red, green, yellow, etc., and the surface of the cultivation container 10 is preferably treated to absorb light using dyes or pigments.

The cultivation plate 12 of the cultivation container 10 is provided with a holding portion 12a, and the roots Pr (see Figure 3) of the spinach seedlings P enter the interior of the cultivation container 10 through the opening of the holding portion 12a and pass through the through-holes 12c and are immersed in the nutrient solution L inside the cultivation container 10.

More specifically, the spinach seedlings P are held by the culture medium 13. The culture medium 13 corresponds to a holding member and holds the spinach seedlings P. The culture medium 13 is accommodated in a cup-shaped holding portion 12a. A through hole 12c is provided in the bottom 12b of the holding portion 12a, and a lower surface 13b of the culture medium 13 is exposed through the through hole 12c. The roots Pr of the spinach seedlings P protrude and extend from the exposed lower surface 13b of the culture medium 13 as shown in FIG. 3. The roots Pr of the spinach seedlings P protruding from the lower surface 13b of the culture medium 13 are immersed in the nutrient solution L in the cultivation container 10. The spinach seedlings P are cultivated with the roots Pr of the spinach seedlings P immersed in the nutrient solution L.
On the other hand, the base of the stem of the spinach seedling P (the part close to the root) is buried in the medium 13, and the leaves PL of the spinach seedling P are developed above the upper surface of the medium 13. The leaf part of the spinach seedling P that is above the upper surface of the medium 13 protrudes outside the cultivation plate 12 through the opening of the holding part 12a. In this state, the spinach seedling P is held in the medium 13.

The culture medium 13 is preferably made of a material softer than the holding portion 12a so that the culture medium 13 can be easily inserted into the opening 12e of the holding portion 12a. In this case, the culture medium 13 is made of, for example, urethane, rock wool, sponge, or the like.
As described above, the opening 12e of the holding portion 12a has, for example, a circular outline shape when the cultivation plate 12 is viewed from the surface 12d. The culture medium 13 has, for example, a rectangular outline shape when the cultivation plate 12 is viewed from the surface 12d. When the culture medium 13 is placed in the opening 12e of the holding portion 12a, a gap (not shown) is formed between the opening 12e and the culture medium 13. Air can enter between the lower surface 13b of the culture medium 13 and the liquid surface Ls of the nutrient solution L through this gap.

As shown in FIG. 1, a plurality of spinach seedlings P are arranged at intervals in the cultivation container 10.
As shown in FIG. 3, in the cultivation container 10, one holding part 12a (culture medium 13) is used to cultivate one spinach seedling P. Here, "individual" is a unit representing the number of individuals (plants) of spinach seedlings P, and one individual corresponds to one spinach seedling P. The number of spinach seedlings P cultivated using one holding part 12a (culture medium 13) may be one individual or two or more individuals, but 1 to 5 individuals are preferable. Even if there are two or more spinach seedlings P in one holding part 12a (culture medium 13), they are treated as one plant in the present invention. That is, in the present invention, one holding part 12a (culture medium 13) is considered as one plant regardless of the number of spinach seedlings P.

In a method for cultivating spinach, for example, a cultivation cycle is provided that includes a light period and a dark period that is darker than the light period.
In this specification, the term "light period" refers to a continuous period during which a plant is placed under light intensity conditions that allow photosynthesis. Examples of light intensity conditions that allow photosynthesis include light intensity (photosynthetic photon flux density) in the range of about 100 to 1500 μmol/(m ² s).
The term "dark period" refers to a period equivalent to night under natural conditions, and in this specification means a period other than the light period. Specifically, the "dark period" is usually defined as a continuous period during which a plant is placed under conditions with a light intensity of 0 μmol/(m ² s), but for example, when cultivating in a greenhouse, the "dark period" can be exemplified as a continuous period during which a plant is placed under conditions with a light intensity of 5 μmol/(m ² s) or less, taking into account the influence of the moon, etc.

The term "cultivation cycle" refers to a repeating unit consisting of one successive light period and one successive dark period, and the repeating unit described above is repeated.
In addition, the total of one continuous light period and one continuous dark period is 24 hours unless otherwise specified in this specification. In this case, the repeating unit is 24 hours. 24 hours corresponds to one day.
In the cultivation cycle, when the sum of the light period and the dark period is taken as 100%, the dark period is preferably 40 to 60%, and more preferably 45 to 55%. That is, in a 24-hour period, the dark period is preferably 9.6 to 14.4 hours, and more preferably 10.8 to 13.2 hours.
As described above, if the ratio of the dark period is 40 to 60%, flower buds are unlikely to form and the number of cultivation days is shortened.

In addition, the temperature during the light and dark periods is preferably 25°C or less, and more preferably 24°C or less. If the temperature during the light and dark periods is 25°C or less, disease is less likely to occur and cultivation efficiency is increased.

It is preferable to set the temperature during the period when light is not irradiated (light period) lower than the temperature during the period when light is not irradiated (dark period). This increases nutrients in the harvested spinach, such as vitamin C as an antioxidant. In this way, spinach with high nutritional value can be obtained.
It is believed that by lowering the temperature during the dark period compared to the temperature during the light period when light is irradiated, stress is imposed during the dark period, which increases the amount of vitamin C.
Furthermore, as described above, the stress reduces the absorption of fertilizer (nutrient solution). This inhibits the increase in the nitrate ion content in the harvested spinach. Nitrate ions (nitrogen components) cause a "bitter" or "astringent" taste. If the nitrate ion content is high, the "bitter" or "astringent" taste is more likely to be felt. On the other hand, if the increase in the nitrate ion content is inhibited, the "bitter" or "astringent" taste is reduced.

The above-mentioned dark period being lower in temperature than the light period means that the temperature difference between the light period and the dark period is 2° C. or more. The temperature difference between the light period and the dark period is more preferably 3° C. or more, even more preferably 4° C. or more, and most preferably 5° C. or more from the viewpoint of increasing nutrients. The upper limit of the temperature difference between the light period and the dark period is not particularly limited, but is, for example, 18° C.
The temperature during the dark period is preferably 25° C. or lower, and more preferably 24° C. or lower. If the temperature during the dark period is 25° C. or lower, the spinach is stressed during the dark period, and thus the nutrients in the harvested spinach, such as vitamin C, increase. In this manner, spinach rich in nutrients can be obtained.
The temperature during the dark period and the temperature during the light period are the indoor temperature if the plant is grown indoors, and the outdoor temperature if the plant is grown outdoors. Both can be measured with a thermometer.
One method for making the temperature lower during the dark period than during the light period is, for example, to lower the temperature setting of the air conditioning in the cultivation room.

The shape of the cultivation container 10 is not limited to the shape shown in Fig. 3. The size of the cultivation container 10 is not particularly limited, but is preferably a size that can be transported. The structure of the cultivation container 10 is not particularly limited, and although the cultivation plate 12 is separable from the liquid tank 14, the cultivation plate 12 may be separable from the other parts, or may be integrated with the other parts. The shape and number of plants of the opening 12e are also not particularly limited as long as the plant density is 120 to 300 plants/ ^m2 .

<Cultivation conditions, etc.>
In the hydroponic cultivation method, the temperature of the nutrient solution supplied to the cultivation container 10 is preferably 10° C. to 30° C., more preferably 18° C. to 28° C., and even more preferably 20° C. to 23° C. If the solution temperature is within the above range, it is possible to prevent nutrient absorption by the roots of the plants from being impaired, which would cause a significant deterioration in growth.
The nutrient solution is generally controlled by controlling its concentration based on its electric conductivity (EC), which is used as a guide for the nutrient solution concentration. If the nutrient solution has an excessively high electric conductivity (EC), this can cause morphological abnormalities due to excess nutrients, or reduced growth due to osmotic stress in the root zone. The electric conductivity (EC) of the nutrient solution is preferably 0.8 dS/m to 2.7 dS/m, and more preferably 1.0 dS/m to 2.4 dS/m. In addition, in terms of promoting the growth of spinach, it is preferable to cultivate the nutrient solution at a pH of 5 to 7.
As a method for controlling the electrical conductivity of the nutrient solution, for example, the electrical conductivity (EC) of the nutrient solution was measured, and if the measured value was 0.1 below the target value for electrical conductivity (EC), a more concentrated nutrient solution (liquid fertilizer) was added until the target value was reached, and if the measured value was 0.1 above the target value for electrical conductivity (EC), water was added until the target value was reached.

When hydroponic cultivation is carried out indoors, such as in a vinyl greenhouse, the indoor temperature is the temperature at which general hydroponic cultivation of plants is carried out, and is preferably 10°C or higher and 30°C or lower, more preferably 15°C or higher and 25°C or lower, and even more preferably 20°C or higher and 23°C or lower.
The indoor relative humidity is the relative humidity used in typical hydroponic cultivation of plants, and is preferably 40% to 90%, more preferably 50% to 80%, and even more preferably 65% to 75%.

When the plant community is not densely planted, it is preferable to adjust the relative humidity within the plant community to 65% or more and 75% or less, as described above. On the other hand, as the plants grow, they become densely planted, and the relative humidity within the plant community becomes very high. Therefore, the relative humidity within the plant community is preferably maintained at 50% or more and 95% or less, more preferably 60% or more and 80% or less, and even more preferably 65% or more and 75% or less.

In order to promote plant growth, it is also suitable to increase the carbon dioxide concentration. From the viewpoint of economic efficiency and favorable effects on growth, the carbon dioxide concentration is preferably 400 ppm by volume or more and 1600 ppm by volume or less. More preferably, it is 600 ppm by volume or more and 1400 ppm by volume or less, and even more preferably, it is 700 ppm by volume or more and 1300 ppm by volume or less. If it is too low, it may cause a decrease in growth due to nutrient deficiency.

The present invention is basically configured as described above. The spinach cultivation method of the present invention has been described in detail above, but the present invention is not limited to the above-mentioned embodiment, and various improvements and modifications may be made without departing from the spirit of the present invention.

The features of the present invention are explained in more detail below with reference to examples. The materials, reagents, weights and ratios of items, and operations shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following examples.

The spinach cultivation method of the present invention will be described in more detail below.
Spinach seedlings grown under the following conditions were irradiated with light and cultivated hydroponically.
Spinach seeds were sown in a commercially available urethane sponge for hydroponic cultivation, one seed per hole, and after one day of dark treatment, the seedlings were grown for 15 days from sowing under white fluorescent lamps with a light intensity of 140 μmol/( ^m2s ) and 16 hours of sunlight per day. Water was used as the nutrient solution from the third day after sowing, and from the seventh day after sowing, irrigation was performed with nutrient solution prepared from Otsuka A prescription (nutrient solution for leafy vegetables, OAT Agrio Co., Ltd.) with an electrical conductivity (EC) of 1.2 dS/m and pH of 6.0.

[Example 1]
The spinach seedlings grown for 15 days from sowing were planted in a cultivation container (panel) and cultivated for 31 days after sowing (16 days after planting). In Example 1, one spinach seedling is grown in one medium.
The outer shape of the cultivation plate is rectangular, and the size of the cultivation plate is 1200 mm (length) × 600 mm (width). That is, the size of the cultivation plate is such that the length Ly in the Y direction shown in FIG. 1 is 1200 mm, and the length Lx in the X direction is 600 mm.
In Example 1, the distance δ (see FIG. 3) between the bottom surface of the medium and the surface of the nutrient solution was set to 1.0 cm.
Cultivation was performed indoors, with the light temperature at 23°C, the dark temperature at 16°C, the relative humidity at 70%, and the carbon dioxide concentration at 1000 ppm by volume. The nutrient solution was controlled by a nutrient solution circulator, with the nutrient solution's electrical conductivity (EC) at 1.2 dS/m, pH at 6.0, and temperature at 22°C. The density of the spinach seedlings ^was 97 seedlings/m2, and a total of 70 seedlings were planted.

After planting, light irradiation was carried out under the following conditions.
As a light source, a PGL-NE-200NWB manufactured by Ryoden Corporation was used as a white light source (artificial light).
The photon flux density of the light was set to 250 μmol/(m ² s) and was measured using a photon meter LI-250A manufactured by LI-COR.
The cultivation cycle was 24 hours, with a light period of 12 hours and a dark period of 12 hours.

In Example 1, spinach that had reached harvest size 16 days after planting was harvested, and the total weight of spinach per panel was measured. In addition, the total weight of spinach per panel was divided by the number of spinach plants in one panel to determine the weight of spinach per plant (per medium).

[Example 2]
Example 2 was the same as Example 1, except that the density of spinach seedlings was 149 seedlings/ ^m2 , and a total of 107 seedlings were planted.
[Example 3]
Example 3 was the same as Example 1, except that the density of spinach seedlings was 167 seedlings/ ^m2 , resulting in a total of 120 seedlings being planted.
[Example 4]
Example 4 was the same as Example 1, except that the density of spinach seedlings was 206 seedlings/ ^m2 , resulting in a total of 148 seedlings being planted.
[Example 5]
Example 5 was the same as Example 1, except that the density of spinach seedlings was 222 seedlings/ ^m2 , resulting in a total of 160 seedlings being planted.

[Example 6]
Example 6 was the same as Example 1, except that the density of spinach seedlings was 278 seedlings/ ^m2 , and a total of 200 seedlings were planted.
[Example 7]
Example 7 was the same as Example 4, except that the electrical conductivity (EC) of the nutrient solution was 0.7 dS/m.
[Example 8]
Example 8 was the same as Example 4, except that the electrical conductivity (EC) of the nutrient solution was 2.2 dS/m.
[Example 9]
Example 9 was the same as Example 4, except that the electrical conductivity (EC) of the nutrient solution was 3.0 dS/m.

[Example 10]
Example 10 was the same as Example 4, except that the above-mentioned distance δ was set to 0 cm.
[Example 11]
Example 11 was the same as Example 4, except that, compared to Example 4, the above-mentioned distance δ was set to 2 cm.
[Example 12]
Example 12 was the same as Example 4, except that, compared to Example 4, the above-mentioned distance δ was set to 3 cm.
[Example 13]
Example 13 was the same as Example 4, except that the temperature during the light period was 26°C.
[Example 14]
Example 14 was the same as Example 4, except that the temperature during the light period was 20°C.
[Example 15]
Example 15 was the same as Example 4, except that the temperature during the dark period was 23°C.

[Example 16]
Example 16 was the same as Example 4, except that the duration of the dark period was 9 hours, and the proportion of the dark period was 38%, as compared with Example 4.
[Example 17]
Example 17 was the same as Example 4, except that the duration of the light period was 9 hours.
[Example 18]
Example 18 was the same as Example 4, except that, unlike Example 4, two seeds were sown per hole in the above-mentioned urethane sponge (culture medium) for hydroponic cultivation, and two spinach seedlings were planted per culture medium.
[Example 19]
Example 19 was the same as Example 4, except that, unlike Example 4, three seeds were sown per hole in the above-mentioned urethane sponge (culture medium) for hydroponic cultivation, and three spinach seedlings were placed on one medium.
[Example 20]
Example 20 was the same as Example 4, except that four seeds were sown per hole in the above-mentioned urethane sponge (culture medium) for hydroponic cultivation, and four spinach seedlings were placed on one medium.
[Example 21]
Example 21 was the same as Example 4, except that five seeds were sown in one hole in the above-mentioned urethane sponge (culture medium) for hydroponic cultivation, and five spinach seedlings were placed in one medium.
[Example 22]
Example 22 was the same as Example 1, except that the density of spinach seedlings was 320 seedlings/ ^m2 , resulting in a total of 230 seedlings being planted.

For Examples 1 to 22, the state of the spinach roots was visually observed at the time of harvest. The observation results were evaluated according to the following root evaluation criteria. The results are shown in Table 1 below.
Root evaluation criteria: A: Roots are white. B: Roots are light brown. C: Roots are brown. D: Roots are dead.

The weight of one harvested spinach plant and the weight per cultivation area were measured for each of Examples 1 to 22. The results are shown in Table 1 below.
The weight of each harvested spinach plant was measured using a scale.
The weight per cultivation area was calculated by first measuring the total weight of the cultivation plate, and then subtracting the weight of the cultivation plate and the weight of the medium, which had been measured in advance, from the total weight of the cultivation plate to obtain the total weight of the spinach. This total weight of the spinach was converted to the cultivation area (1 ^m2 ) to obtain the weight per cultivation area.
The results of the measurements of the weight per cultivation area were evaluated according to the following evaluation criteria for weight per cultivation area. The results are shown in Table 1 below.
Evaluation criteria for weight per cultivation area A: 6000 g/m2 ^{or more} (6 kg/m2 ^or more)
B: 5000 g/m2 or ^more and less ^than 6000 g/m2 (5 kg/m2 or ^more and less than 6 kg/ ^m2 )
C: Less than 5000 g / m ² (less than 5 kg / m ² )

The vitamin C content of the harvested spinach was determined for Examples 1 to 22. The vitamin C content of the harvested spinach was measured using an RQ Flex (Merck Ltd.). The results are shown in Table 1 below.

Among Examples 1 to 22 shown in Table 1, Examples 2 to 9, 11, and 13 to 21, in which the plant density was 120 to 300 (plants/ ^m2 ) and the distance δ between the bottom of the culture medium and the nutrient solution level was 0.5 to 2.5 cm, had a higher yield per cultivation area, a higher vitamin C content, and more nutrients than Examples 1, 10, and 12.
In Example 1, the plant density was less than 120 (plants/m ² ), and the yield per cultivation area was low.
In Example 22, the plant density exceeded 300 (plants/m ² ), the weight per plant was small, and the yield was low. In addition, the color of the roots was brown, and the condition of the roots was poor.
In Example 10, the distance δ was less than 0.5 cm, resulting in a low yield per cultivation area and low nutrient content (vitamin C content).
In Example 12, the distance δ exceeded 2.5 cm, and the roots of the spinach seedlings withered because they were not sufficiently immersed in the nutrient solution L. As a result, the yield per cultivation area was low. In addition, in Example 12, the condition of the roots was poor, so the vitamin C content was not measured.

Comparing Example 4 with Examples 7 to 9, Example 4, in which the electrical conductivity (EC) of the nutrient solution was within the preferred range, had a large yield per cultivation area and also had a large amount of nutrients (vitamin C content).
Comparing Example 4 with Examples 13 and 14, the nutrients (vitamin C content) were greater when the temperature during the light period was lower.
Comparing Example 4 and Example 15, the vitamin C content is higher when the temperature during the dark period is lower.
Comparing Example 4 with Examples 16 and 17, the crop yield per cultivation area was greater when the dark period was shorter.
Comparing Example 4 with Examples 18 to 21, the spinach seedlings with a larger number of individuals had a larger weight per plant and a larger harvest.

10 Cultivation container 11 Surface 12 Cultivation plate 12a Holder 12b Bottom 12c Through hole 12d Surface 12e Opening 13 Medium 13b Bottom surface 14 Liquid tank 15 Bottom Dx, Dy Interval L Nutrient solution Ls Liquid level Lx, Ly Length P Seedling PL Leaf Pr Root

Claims (8)

A method for cultivating spinach, comprising irradiating light to spinach seedlings held in a medium, and cultivating the seedlings by a hydroponic method with the roots of the seedlings immersed in a nutrient solution,
The density of the spinach seedlings is 120 to 300 (saplings/m ² );
The method for cultivating spinach, wherein the distance between the bottom surface of the culture medium and the surface of the nutrient solution is 0.5 to 2.5 cm. The method for cultivating spinach according to claim 1, wherein the electrical conductivity of the nutrient solution is 0.8 to 2.7 dS/m. The method for cultivating spinach according to claim 1, wherein the light is white light. The spinach cultivation method according to claim 1, which has a cultivation cycle that includes a light period and a dark period that is darker than the light period. The method for cultivating spinach according to claim 4, wherein the dark period has a lower temperature than the light period. The method for cultivating spinach according to claim 4, wherein the cultivation cycle has a dark period ratio of 40 to 60% when the sum of the light period and the dark period is 100%. The method for cultivating spinach according to any one of claims 4 to 6, wherein the temperature during the light period and the dark period is 25°C or lower. The method for cultivating spinach according to any one of claims 1 to 5, wherein 1 to 5 spinach seedlings are maintained in one medium.

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