JPH1166A - Plant culturing method and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water culture method and apparatus having a structure to promote the growth of root by sufficiently immersing the plant to the base of the root in a culture liquid and capable of sufficiently supplying oxygen necessary for the growth of root. SOLUTION: The root of a plant is immersed in a culture liquid containing a fertilizer component and the plant is grown under an artificial light source while continuously blowing air having high carbon dioxide gas concentration forcedly into the culture liquid with a pump 3 during the cultivation period of the plant. The apparatus for the above process has a structure to constantly and sufficiently immerse the root of the plant to the base part of the root into the culture liquid. The air having high carbon dioxide gas concentration is produced by generating bubbles at a part immediately below the culture plant or thereabout and the carbon dioxide gas concentration of the air is >=500 ppm, preferably 1,000-5,000 ppm. A fluorescent lamp 16 is used as the artificial light source and whole inner face of the plant growing chamber is lined with a reflection layer to grow the plant with the minimum light quantity. A plant growing bed 10 having sufficient light-shielding property is used for supporting the plant during the culture to prevent the irradiation of the culture liquid with the light of the artificial light source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plant cultivation method and apparatus for hydroponically cultivating vegetables, flowers, grasses and the like using an artificial light source. Further, the present invention provides a plant cultivation method capable of growing a plant very effectively without causing spoilage by forcibly blowing air having a high carbon dioxide concentration into a culture solution inside a cultivation tank by a pump. And improvement of a cultivation apparatus, which is devised so that roots can be sufficiently grown.

[0002]

2. Description of the Related Art There are many known hydroponic cultivation methods and apparatuses for growing plants without using natural soil and sunlight. For example, JP-A-62-55028 to JP-A-6-55028
2-55029 and Japanese Unexamined Patent Publication No.
JP-A-3-240731, JP-B-6-61190, JP-A-7-50929, JP-A-7-5094
The configuration described in Japanese Patent Laid-Open Publication No. HEI 1 (1999) is known.

[0003] The above-mentioned conventional invention uses a fluorescent lamp as a light source for hydroponic cultivation, and further moves the position of the fluorescent lamp as the plant grows so that the distance between the upper end of the plant and the fluorescent lamp is within a predetermined range. It is intended to be kept within. If necessary, the atmosphere in the cultivation room is maintained at a carbon dioxide gas concentration of 500 ppm or more, preferably 1,000 to 5,000 ppm (JP-A-63-240731, JP-B-6-61190). Gazette.).

[0004] Conventional cultivation equipment was thought to require "sufficient oxygen for root development". Therefore, as shown in FIG. Was usually provided with an air layer A of 1 to 3 cm.
However, this structure is unfavorable for the growth of plant roots, since there is a part of the root of the plant that is exposed to the air, and the root hardly develops in the air. Sufficient root development is important for plant cultivation because it makes the plant robust and greatly affects the growth of plant leaves.

[0005] Nevertheless, it has heretofore been thought that if the roots of a plant are immersed to the root, the supply of oxygen to the roots becomes insufficient, causing root rot. In addition, since the conventional structure requires a slight distance between the hydroponic solution and the growing table to provide the air layer, the structure of the growing table on the side of the cultivation layer or the like does not have sufficient light-shielding properties against artificial light sources. There is a drawback that light leaks into the culture solution to generate algae harmful to plant cultivation.

[0006]

SUMMARY OF THE INVENTION The present invention promotes root growth without causing root rot even when the plant is sufficiently immersed in a culture solution, and also provides sufficient oxygen supply for root development. It is an object of the present invention to provide a hydroponic cultivation method and apparatus having a structure that can be performed easily and the generation of microorganisms is suppressed. Another object of the present invention is to prevent the generation of harmful algae by adopting a structure having good light-shielding properties for roots because the root can be immersed in a culture solution.

[0007]

Means for Solving the Problems To solve the above problems, the present invention immerses plant roots in a culture solution containing a fertilizer component, and continuously increases the concentration of carbon dioxide gas in the culture solution during plant cultivation. In a plant cultivation method using an artificial light source for growing plants while forcibly blowing high air with a pump, a configuration is employed in which the roots of the plants are always sufficiently immersed in the culture solution up to the roots. Then, bubbles are generated from immediately below the cultivated plant by forcibly blowing air into the culture solution.

The air has a carbon dioxide concentration of 500 ppm or more, preferably 1,000 to 5,000 ppm, and a fluorescent lamp is used as the artificial light source. Growing plants. further,
In a plant cultivation device using an artificial light source that grows plants while forcibly blowing air into the culture solution by a pump continuously during the cultivation period of the plant, immersing the roots of the plant in a culture solution containing a fertilizer component, The plant cultivation plate supporting the plant during cultivation has a structure having sufficient light-shielding properties, and the plant cultivation apparatus is configured such that the light of the artificial light source does not reach the culture solution.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In hydroponic cultivation, particularly in hydroponic cultivation of root crops, the occurrence of heat damage (chip burn) is a problem. Chip burn is a phenomenon in which artificial lighting is too strong and leaves shrink as the leaves shrink, and if the chip burn occurs partially even if the whole does not wither, the commercial value of the root vegetables cultivated In hydroponics, it is important to take great care not to cause chip burn even at the tip of the leaf.

[0010] Hydroponic cultivation using an artificial light source that generates a large amount of heat, such as a high-pressure sodium lamp or a metal halide lamp, usually fails because the occurrence of the heat damage cannot be solved. Tip ・
Burn is considered to cause the heat of the artificial light source to accumulate on the surface of the leaves, and the accumulated heat is not sufficiently dissipated, causing the surface of the leaves to hurt. This is the phenomenon. Therefore, in order to prevent the accumulation of heat, the efficiency of contribution of the light of the artificial light source to plant growth is increased as much as possible to reduce the generation of heat (particularly radiant heat) by the artificial light source and to reduce the heat from the leaf surface. If the heat is sufficiently dissipated, chip burn can be prevented.

Conventionally, in order to prevent this thermal damage, a method of blowing cold air to the center of a plant or an intermittent irradiation time to give time to stop irradiation (so-called night) has been performed. However, the former has a drawback that the growth of the plant is slowed because the application of wind to the plant with the increase in power consumption inhibits the growth of the plant, and in the latter case, the photosynthesis is not performed during the time when the irradiation is stopped.

For this reason, the inventor of the present invention has previously devised a method for covering as much as possible the upper, lower, left and right surfaces of the inside of a growing room for cultivation with a reflective layer of aluminum foil or the like so as to increase the contribution of the artificial light source to photosynthesis. (For example, Japanese Patent Application Laid-Open No. 7-50941). As the artificial light source, a fluorescent lamp having a small calorific value and a three-wavelength fluorescent lamp whose spectral distribution is considered to be most suitable for the growth of plants as a result of experiments are used.

[0013] Increasing the contribution rate of the artificial light source used by utilizing multiple reflections to the above-mentioned photosynthesis maximizes the light amount (the number of light sources) of the artificial light source to be used relatively, thereby reducing power consumption. This has the effect of reducing heat generation from the artificial light source as much as possible. At the same time, if the amount of light is small, the influence of the radiant heat of the artificial light source is small, so that even if the light source is provided close to the plant, there is an effect that no thermal damage occurs. Providing the light source directly above the plant can also reduce the space in the cultivation tank.

[0014] On the other hand, it is considered that when a plant has sufficient root development, water is well absorbed from the root together with nutrients, and the amount of evaporation from leaves increases. If there is a lot of evaporation from the leaf surface, the temperature of the leaf surface will be reduced by the heat of evaporation, so that thermal damage can be avoided. Conventionally, it is considered that oxygen needs to be supplied to the root portion for root growth. In hydroponic cultivation, a configuration in which the upper portion of the plant root is exposed to the air layer A as shown in FIG. Was common. However, it is clear that most of the roots should be submerged in water for root development. In this case, supply of oxygen to the root and prevention of root rot become problems.

The inventor has previously developed a technique for forcibly sending air having a high carbon dioxide concentration into a culture solution by a pump to prevent the culture solution from spoiling (Japanese Patent Publication No. 6-61190). When this method is used, oxygen is always supplied to the culture solution together with carbon dioxide gas, so that oxygen is sufficiently supplied to the roots even if the root portion is immersed in the culture solution. In other words, even the air having a high carbon dioxide concentration contains sufficient oxygen necessary for root growth, so that oxygen is sufficiently supplied to the roots.

Based on this viewpoint, the present invention provides a hydroponic cultivation method in which air having a high carbon dioxide concentration is constantly and forcibly fed into a culture solution by a pump. Soaked in water to sufficiently promote root development. Sufficient root development allows the leaf to grow sufficiently, and the durable leaf has a high rate of water evaporation from its surface, and the heat of evaporation promotes the dissipation of heat from the leaf surface. This prevents the chip burn phenomenon, which leads to a good circulation, which leads to better plant growth.

In addition to the above-mentioned oxygen supply, the roots are activated because foamy air always permeates into the roots from directly below the roots. Further, the acidification of the hydroponic solution due to the high carbon dioxide gas concentration and the stirring action of the foamy air suppress the generation of microorganisms and the like in the liquid. Together with the supply, the root of the plant does not rot even though the root is constantly immersed in water. Conversely, as described above, immersing the roots completely in the hydroponic solution promotes the growth of the roots to an extent never before possible, thereby improving the growth of the plant, absorbing water from the roots, and removing the roots from the leaves. Is improved, heat dissipation is promoted, and chip burn is suppressed. This further eases the problem of dissipating heat from the leaf surface, which has traditionally been a challenge, and thus allows the fluorescent light to be brought closer to the plant (effective use of light). Combined with the use of multiple reflections, the power consumption, which accounts for more than half of the cost of artificial light cultivation, has been significantly reduced.

Further, if a structure is adopted in which the roots are completely immersed in the culture medium up to the roots, the space between the growing table and the root portion becomes unnecessary, so that the light-shielding structure near the growing table becomes sufficient and the culture medium becomes There is a secondary effect that light can be prevented from entering inside. In hydroponic cultivation, when light is irradiated on the culture solution, unnecessary algae are generated, and nutrients are taken out, and withered alga becomes an impurity and rots, thereby hindering the growth of plants. In addition, the fact that the light hits the root itself also hinders the growth of the root.

Furthermore, the environment in which the cultivation room is located (usually in a building or a concrete factory) is preferably at 15 to 19 ° C. for plant growth, and is therefore air-conditioned to that temperature. The cultivation room has a closed structure in which the inner surface is entirely covered with a reflector, and the temperature is higher than outside air because the artificial light source is installed inside. Separately, as suggested by the same applicant, in order to prevent the temperature inside the cultivation chamber from rising as much as possible, there is a slight gap between the upper and lower sides of the reflector on both sides of the cultivation tank and both sides of the cultivation tank floor and the ceiling reflector. It is. The heated air in the cultivation room is naturally discharged to the outside from the gap, thereby preventing a temperature rise in the cultivation room.

Further, in the apparatus of the present invention, air containing carbon dioxide gas is generated from the culture solution, and an airflow is generated from the bottom toward the back of the leaf, thereby air-cooling the surface of the leaf. effective. In fact, the temperature of the leaf surface is considered to be 1-2 ° C. lower than the temperature of the cultivation room.

Hereinafter, the present invention will be described in detail with reference to embodiments of the drawings. 1 is an overall configuration diagram showing an embodiment of a plant cultivation apparatus used in the present invention, FIG. 2 is an external view of a cultivation tank including a circulation path of a culture solution, and FIG. 3 is a partial detailed view of a conventional example of the above configuration. It is. FIG. 4 is a partially detailed view of the above-described configuration in the case of the present invention, and FIG. 5 is a cross-sectional view of the cultivation tank when FIG. 4 is viewed from the vertical direction. FIG. 6 is a perspective view of a growing table used in the cultivation tank device of the present invention. 1 and 2, reference numeral 1 denotes a rectangular box-shaped cultivation tank made of vinyl chloride. The cultivation tank may be a gutter-shaped cultivation tank having a semicircular cross section. The cultivation tanks are horizontally installed in a two-tiered manner at intervals by a support 2 ′ in the building 2. In FIG. 1, only two stages are shown for simplicity. However, in a plant factory of an actual mass production system, the number of stages that can be set from the floor to the ceiling in the room is set, and therefore, usually 6 to 8 stages. Become. 3 is
It is a circulation pump that supplies a culture solution to the top cultivation tank 1.

The circulation of the hydroponic solution of the conventional example shown in FIG. 3 is as follows. The culture solution supplied by the circulation pump naturally falls into the lower cultivation tank 1 by the siphon 4 and circulates in the cultivation tank through the process of returning to the upper cultivation tank by the pump 3 again. The water level of the culture solution in the cultivation tank 1 is kept constant by the siphon 4. The circulation pump 3 is automatically operated continuously or at regular time intervals (for example, 15 minutes). When the culture solution is sent to the upper cultivation tank by the pump, the water level of the upper stage rises to the upper limit water level H of the siphon in FIG. 3 and the circulation pump 3 stops. Thereafter, spontaneous discharge of the culture solution occurs in the lower cultivation tank at the lower limit water level L,
When the water level in the upper cultivation tank reaches the lower control limit water level L of the siphon, the discharge stops. The water level is adjusted so that the root of the root is submerged in the culture solution even at the lower limit water level. There is also a method in which the above culture solution is entirely exchanged for one or two days without using a siphon. The whole exchange method is preferable for root growth because the culture solution does not always move.

An example of the supply of the hydroponic solution according to the present invention is as follows. As shown in FIG. 4, in the culture solution continuously supplied to the uppermost stage by the circulation pump, as shown in FIG. It circulates in the cultivation tank through the process of returning to the upper cultivation tank. As shown in FIGS. 4 and 5, the depth of the culture solution in each stage of the cultivation tank 1 according to the present invention is maintained at a water level at which the bottom of the cultivation table 10 is immersed, and the water level is controlled by the water level adjustment pipe 51. Be kept constant.

In the cultivation tank 1, as shown in FIG.
A support piece 8 for supporting the breeding table 10 so as to be movable is provided. The support piece 8 is slightly raised so that the support piece does not sink in the culture solution even when the culture solution reaches a water level at which the culture solution is immersed in the bottom surface of the growth table. Is provided at the position. Therefore, as shown in FIG. 6, the growth table 10 has an elongated shape and has a structure in which a central portion in the longitudinal direction is slightly concave. In the cultivation tub, a gap is provided so that the breeding table 10 is supported on the support pieces 8 at both ends as shown in FIG. 2 or at the upper end of the cultivation tub as shown in FIG. Are arranged without leaving an empty space. The breeding table 10 is made of a metal or resin member having a reflective member 13 such as stainless steel or aluminum on the upper surface, and has a hole 12 into which the seedling 11 is inserted. For example, in the case of lettuce, three holes 12 are provided on the breeding table, and the upper part of the root, which is in a state where two or three true leaves protrude from Futaba, is wrapped with urethane or the like (55 in FIG. 5). Insert into the hole. As described above, usually, they are grown in three rows.

The above-mentioned reflecting member reflects the light of the artificial light source, effectively utilizes a small amount of light to minimize power consumption, and minimizes the generation of heat of the artificial light source to prevent chip burn. As shown in FIG. 3, a light entrance preventing plate 14 is provided at a lower end of the breeding table 10. The light entry prevention plate 14 prevents the roots of the seedlings from being exposed to light and causing a growth disorder, and preventing the light from entering the culture solution and generating algae in the culture solution.

At the top of each of the cultivation tanks 1, 1, two white fluorescent lamps 16 are suspended and supported by a chain-like suspending tool 17 which is inclined. Experiments have shown that the three-wavelength fluorescent lamp 16 is more suitable for growing plants. As the seedlings grow, the breeding table is moved to the left in the drawing, and even if the plants grow larger, the upper end of the plants and the fluorescent light 16
Is kept substantially constant.
In this way, the illuminance on the plants is kept constant. When the interval is set to 1 to 10 cm, it is possible to prevent the chip temperature from rising due to the heat of the fluorescent lamp 16 and to achieve extremely rapid growth without uneven illuminance. The breeding table 10 is moved to the left at approximately 5 day intervals from the rightmost seedling to the leftmost growing leaf in FIG. The temperature inside the building 2 is about 17
Kept at ° C. For this purpose, an air conditioner 19 is provided (FIG. 1). Reference numeral 20 denotes a compressor, 21 denotes a condenser, 22 denotes an air cooling fan, 23 denotes a cool air passage, 24 denotes an evaporator, and 25 denotes a blower fan.

In the cultivation tank 1, air having a high carbon dioxide concentration is continuously pumped into the culture solution during the plant cultivation period.
6. While forcibly blowing, send in the form of bubbles. Reference numeral 30 in FIG. 3 denotes an airstone used in the conventional example. In the present invention, as shown in FIG. 4 and FIG.
Is buried, and the air having a high carbon dioxide concentration is blown out from a small hole provided in the air tube 34 to form air bubbles. The outlet of the air supply tube 34 is located directly below the root of the plant from the point of supply of oxygen to the root of the plant, from the point of supply of carbon dioxide to the surface of the leaf, and from the viewpoint of the air cooling effect to the surface of the leaf. It is effective to be provided in the vicinity.

A carbon dioxide gas generated by a carbon dioxide gas generator may be supplied to each air blowing tube 34 by a pump. The air in the factory may be supplied as it is by setting the environment as the concentration of the carbon dioxide gas. As the carbon dioxide generator, for example, a catalytic oxidation type combustion device that burns benzene, butane, or other fuels using platinum as an oxidation combustion catalyst can be used. The device can always burn fuel in a constant state, and carbon dioxide gas is continuously and stably generated according to the burning state. If a combustion device for generating carbon dioxide is installed in one corner of the factory, the amount of carbon dioxide consumed by the plant and the amount of carbon dioxide generated by the above-mentioned combustion device are almost the same, depending on the size of the plant. It has been confirmed that the concentration of carbon dioxide in the sample is almost constant.

Carbon dioxide gas is indispensable for photosynthesis of plants.
pm (preferably between 1,500 and 2,000 ppm). If the concentration of carbon dioxide in the air blown into the culture solution in the cultivation tank 10 is less than 500 ppm, the effect of preventing the decay of the culture solution can hardly be expected, and if the concentration is more than 5,000 ppm, the concentration of carbon dioxide is too high and the pH value becomes low. Since the inorganic fertilizer component contained in the liquid may be precipitated, about 1,000 to 5,000 ppm is preferable. When air having a high carbon dioxide concentration is continuously blown into the culture solution, a nozzle or other structure may be employed without using a porous tube.

In the structure of the present invention, the carbon dioxide gas is supplied in the form of bubbles from directly below the plant, so that the carbon dioxide gas absorption efficiency is superior to the conventional method of separately filling the cultivation chamber with the carbon dioxide gas. At the same time, by continuously blowing air having a high carbon dioxide concentration into the culture solution during the cultivation period of the plant to generate bubbles while forcibly blowing the air,
Oxygen contained in the bubbles also provides sufficient oxygen supply to the roots, and the carbon dioxide gas makes the culture solution weakly acidic, and in combination with the stirring action of the bubbles, prevents decay of microorganisms and fine organic matter in the culture solution. Has the effect of being done.

Furthermore, since the bubbles rise from behind the leaves of the plant, they have the effect of cooling the surface of the leaves, and also have the effect of preventing thermal damage (chip burn) due to temperature rise by artificial light sources on the leaves.

Cultivation experiments were performed using the above cultivation apparatus and lettuce and salad vegetables as plants. Three to four true leaves were used as seedlings, and two seedlings were separated by 30 cm on a breeding stand and inserted into each hole 2 and supported.
The distance D between the upper end of the plant 11 and the fluorescent lamp 16 is set to 1 to 10 cm. As the plant grows, the plant growing board is moved in the horizontal direction (arrow) once every five days, and the distance is set to 3 cm. Nurtured for a week. Further, the circulation pump 3 for the culture solution was operated continuously, and the water level in each stage was kept substantially constant so that it was immersed to the root of the plant. The culture solution uses a commercially available hydroponic fertilizer, the temperature in the building 2 is 17 ° C, the carbon dioxide concentration is 1,000 ppm or more, and the illuminance is
More than 6,000 looks. As a result, each sheet was weighed at 250 g per salad and harvested once every five days, and the quality was good.

The plants to be cultivated are not limited to lettuce and salad vegetables, but may be other root vegetables, ornamental plants, tomatoes and herbs, or even rice.

[0034]

When the above cultivation apparatus is used and plants are cultivated using lettuce and salad vegetables, roots are more active than conventional hydroponic cultivation, leaf growth is sufficiently performed, and chip burn occurs. Without it, it was possible to harvest pesticide-free and delicious lettuce. Moreover, by covering the inner surface of the cultivation tank with a reflective layer on the entire surface and maximizing the use of multiple reflections, the cultivation tank can be grown with an extremely small amount of light that cannot be considered by conventional hydroponic cultivation, such as two fluorescent lamps of 60 watts. Even if the distance between the fluorescent lamps is very close to 1 to 10 cm and the amount of light to the leaf surface is increased, it does not cause thermal damage (chip burn) due to artificial light sources (fluorescent lamps) and is used for alley cultivation We could grow softer leafy vegetables.

In addition, since multiple reflections in the cultivation room and close-up irradiation to plants are made possible, by maximizing the amount of light from the artificial light source, power consumption, which accounts for more than half of the cost of hydroponics, can be reduced by the conventional method. Compared to less than half. Due to this cost reduction, the price competitiveness with the conventional open-field material was able to be obtained, and the vegetables that were softer and more delicious than the open-air material without pesticides could be grown. In addition, unlike the open-air products, they can be harvested year-round regardless of the season or environment, so that fresh vegetables can be obtained every day, for example, in a cold and almost sunless environment such as winter in Northern Europe or in the middle of a summer desert. It is a very good method as a plant factory.

[Brief description of the drawings]

FIG. 1 shows an overall view of a cultivation tank device used in the present invention.

FIG. 2 is a partial structural view of a cultivation tank device used in the present invention.

FIG. 3 is a partial detailed view of the cultivation tank device in the case of the conventional example of the present invention.

FIG. 4 is a partial detailed view of a cultivation tank device used in the present invention.

FIG. 5 is a cross-sectional view of a cultivation tank device used in the present invention.

FIG. 6 is a perspective view of a growing table used in the cultivation tank device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cultivation tank 2 Building 3 Pump 4 Siphon 5 Pipe 8 Supporting piece 10 Growing stand 11 Seedling 12 Hole 13 Reflecting member 14 Light entry prevention plate 15 Urethane etc. 16 Fluorescent lamp 19 Air conditioner 26 Air pump 28 Carbon dioxide gas cylinder 34 Air supply tube 51 Water level adjustment Pipe 52 Liquid level 53 Bubbles 54 Hydroponic liquid

Claims (6)

[Claims] 1. A plant cultivation method using an artificial light source for immersing roots of a plant in a culture solution containing a fertilizer component and continuously growing the plant while blowing air into the culture solution during the plant cultivation period, A plant cultivation method, wherein a plant root is always sufficiently immersed in the culture solution up to the root. 2. The plant cultivation method according to claim 1, wherein air bubbles are generated from immediately below the cultivated plant by forcibly blowing air into the culture solution. 3. The air has a carbon dioxide concentration of 500 ppm or more,
The plant cultivation method according to claim 1 or 2, wherein the concentration is preferably 1,000 to 5,000 ppm. 4. The plant according to claim 1, wherein a fluorescent lamp is used as the artificial light source, and all inner surfaces in the plant growing room are covered with a reflective layer to grow the plant with a minimum amount of light. 2. The method for cultivating a plant according to claim 1. 5. The method according to claim 1, wherein the plant is a root vegetable. 6. An artificial light source for growing a plant while immersing the root of the plant in a culture solution containing a fertilizer component up to the root and continuously blowing air into the culture solution continuously during the cultivation of the plant. In the plant cultivation apparatus, the plant cultivation plate supporting the plant has a sufficiently light-shielding structure during the cultivation, so that light of the artificial light source does not reach the culture solution.