JP2001299116A - Method for hydroponic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent environmental pollution by stably carrying out hydroponics of plants in a high yield and circulating and using a hydroponic drain used for the cultivation without disposing of the drain to the outside of a facility. SOLUTION: This method for hydroponics is capable of demineralizing raw water with a demineralizer 10, feeding the resultant treated water to a mixing tank 1, adding a fertilizer component thereto, preparing a nutritious liquid, feeding the nutritious liquid to a cultivation bed 5, passing the excessive drain of the nutritious liquid from the cultivation bed 5 through a drainage tank 15, removing microbes with a microbial removing device 14 and returning the resultant drain to the mixing tank 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cultivating plants such as vegetables and flowers by supplying a nutrient solution to a cultivation bed. The present invention relates to a nutrient solution cultivation method.

[0002]

2. Description of the Related Art A method of arranging a cultivation floor (cultivation bed) in a greenhouse and supplying a nutrient solution to plants such as vegetables and flowers planted on the cultivation floor for efficient cultivation, that is, a nutrient solution cultivation method is known. Widespread. The nutrient solution used for cultivation is groundwater,
It is adjusted by adding fertilizer components to raw water such as tap water and rainwater, and supplied to the cultivation floor by a pump. FIG. 5 is a process flow diagram of a conventional nutriculture method. The fertilizer component supplied from the fertilizer supply device 2 is added to the raw water in the mixing tank 1 to adjust the nutrient solution. The fertilizer component concentration in the nutrient solution is measured by the conductivity meter 3, and the fertilizer supply device 2 is controlled so that the concentration becomes a predetermined concentration. The adjusted nutrient solution is transferred to a cultivation floor (so-called rock wool slab) 5 on which rock wool or the like is laid by a pump 4, and the plant 6
Sprayed on. The surplus nutrient solution on the cultivation bed 5 is discarded outside as nutrient solution drainage, but this nutrient solution drainage usually accounts for about 10 to 30% of the supply amount.

[0003] Since the nutrient solution wastewater contains substances that cause lakes and marshes such as nitrogen and phosphorus, it is not preferable to dispose of the wastewater in large quantities. Therefore, a method of circulating and repeatedly using nutrient solution drainage without discarding it outside has been proposed.
However, according to the experiments of the present inventors, when the nutrient solution drainage is circulated to the cultivation floor, the concentration of the component that is not absorbed by the plant gradually increases, which accumulates on the cultivation floor and adversely affects the plant. I understood. FIG. 6 shows the process flow diagram of FIG. 5, when the nutrient solution prepared in the mixing tank was circulated for about 4 months in the rock wool slab as the cultivation floor, and the result of measuring the ratio transition of each component contained in the cultivation floor was measured. It is. The initial nutrient solution was adjusted together with a predetermined fertilizer component so as to be within the range of the average salt concentration of groundwater in Japan, that is, the sodium ion (Na ⁺ ) was about 80 mg / l. As is clear from this figure, sodium ion (Na ⁺ )
Chloride ion (Cl ^-) ratio of gradually increased, the proportion of fertilizer components becomes smaller reversed.

[0004]

As described above, it has been found that the method of circulating and using the nutrient solution waste without discarding it outside the plant is not preferable for growing plants because the salt content in the nutrient solution increases. As another problem, there is a possibility that bacteria and the like gradually increase in the nutrient solution, and the disease may spread to plants.
Then, this invention makes it a subject to solve such a problem in nutrient solution circulation, and aims at providing the new nutrient solution cultivation method for that.

[0005]

Means for Solving the Problems According to the first aspect of the present invention, there is provided a method for cultivating a plant by supplying a nutrient solution to a cultivation bed. Then, the raw water is desalinated by a desalter, and a fertilizer component is added to the obtained treated water to adjust a nutrient solution, the nutrient solution is supplied to a cultivation floor, and the nutrient solution drainage discharged from the cultivation floor is sterilized. It is characterized in that the nutrient solution is circulated and used on the cultivation bed by removing bacteria in the device and returning it to the nutrient solution. According to the above method, since the nutrient solution is adjusted by desalinating the raw water with the desalination device, even if the nutrient solution is circulated over the cultivation bed for a long time, the salt does not accumulate and does not adversely affect the plants. In addition, since the nutrient solution wastewater is sterilized by the sterilizer and returned to the nutrient solution, there is little possibility that the cultivation bed will be contaminated with bacteria even if the nutrient solution is circulated through the cultivation bed for a long time.

According to a second aspect of the present invention, there is provided the nutrient solution cultivation method according to the first aspect, wherein a reverse osmosis membrane is used as a desalination apparatus to remove fine particles, bacteria, etc. contained in the raw water together with the desalination of the raw water. It is characterized by removing impurities.
By doing so, the cultivation bed can be maintained in a more bacterially suppressed state, and the adjustment of the fertilizer component can be controlled more precisely. The invention according to claim 3 is
In the nutrient solution cultivation method according to claim 1 or 2, a hollow fiber membrane is used as a sterilization apparatus. The use of such a disinfecting apparatus facilitates maintenance and management, lowers operating costs, and more reliably performs disinfecting operations.

According to a fourth aspect of the present invention, in the method for cultivating nutrient solution according to any one of the first to third aspects, the pH value in the nutrient solution is adjusted to a range suitable for plant growth. It is assumed that. Adjusting the pH value of the nutrient solution in this way can lead to plant growth stages, seasonal factors, etc.
Even when the absorption ratio of the ion component by the plant changes, it is possible to prevent the pH value of the cultivation bed from suddenly changing and adversely affecting the plant. According to a fifth aspect of the invention, in the nutrient solution cultivation method according to any one of the first to fourth aspects, ozone is contained in the nutrient solution at night when plant growth is inactive, and The inside of the piping through which the nutrient solution flows can be sterilized. When the pipes are sterilized with ozone in this manner, the formation and growth of a biofilm on the inner wall of the pipes can be effectively suppressed.
In addition, during the night when plant growth is inactive, the flow rate of the nutrient solution circulating through the cultivation bed may be extremely small, and no adjustment of the nutrient solution is performed, so that the ozone sterilization operation can be effectively performed during that time.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic process flow diagram for implementing the nutrient solution cultivation method of the present invention. Each symbol in FIG. 1 is as follows. That is, 1 is a mixing tank,
2 is a fertilizer supply device, 3 is a conductivity meter, 4 is a pump, 5 is a cultivation bed, 6 is a plant, 10 is a desalination device, 11 is a treated water tank, 12 is a water quality control device, 13 is an ozone sterilization device, 14
Denotes a sterilizer, 15 denotes a drainage tank, and a to q denote pipes.
The desalination apparatus 10 desalinates, for example, raw water having an electric conductivity of about 400 μS / cm to a level of about 4 μS / cm in electric conductivity. The illustrated apparatus uses a reverse osmosis membrane. A pressurizing pump 16 for pressurizing raw water and a plurality of reverse osmosis membrane modules 17 connected in parallel to the outlet side thereof
Having.

The reverse osmosis membrane module 17 contains a large number of reverse osmosis membranes in a container. Raw water supplied to the primary side of the membrane by being pressurized by a pressure pump 16 is supplied to the secondary side of the membrane by reverse osmosis. Then, impurities such as fine particles, bacteria, colloidal substances and the like are separated and removed together with the salt, and the treated water is discharged to the treated water tank 11 through the pipe b. On the other hand, the remaining raw water on the primary side that has not been permeated by the reverse osmosis membrane is discharged to the outside through the pipe c together with impurities. As such a reverse osmosis membrane module 17, for example, a SUL-G10 type module commercially available from Toray Industries, Inc. can be used. When it is sufficient to remove only the salt from the raw water, a desalination apparatus 10 using an ion exchange resin can be used.

[0010] The water quality adjusting device 12 is provided for the purpose of increasing the pH buffering capacity of the nutrient solution.
8. a diaphragm pump 19 and a solution tank 2 containing a pH-adjusted solution such as carbonated water or potassium hydrogen carbonate
It has 0. Each time the flow rate of the treated water in the pipe d from the treated water tank 11 to the mixing tank 3 reaches the set flow integrated value, a pulse is output from the flow integrator 18 and the pulse activates the diaphragm pump 19 to intermittently operate. The pH adjustment solution is poured into the treated water. When using a potassium bicarbonate solution as the pH adjusting solution,
The potassium component becomes part of the potash fertilizer in the nutrient solution.

The ozone sterilizer 13 is provided for ozone sterilization of a nutrient solution, and has an ozone generator 21 for generating ozone from oxygen in the air by a high voltage and a cascade pump 22. The inlet side of the cascade pump 22 is connected to the treated water tank 11 via a pipe o, and the outlet side of the cascade pump 22 is connected to an electric ball valve 23 for pipe switching provided on the outlet side of the pump 4 via a pipe f. You. Further, an ozone gas pipe from the ozone generator 21 is connected to the inlet side of the cascade pump 22. When the cascade pump 22 is operated, ozone gas is sucked together with the treated water, and the ozone-containing treated water is supplied to the cultivation bed 5 downstream of the electric ball valve 23 via the pipe f. The suction ratio of ozone gas to the treated water is, for example, about 10% by volume, and the ratio can be adjusted by an adjusting valve (not shown) provided in the ozone gas pipe.

The fertilizer supply device 2 has a plurality of fertilizer supply pumps 24 such as a diaphragm pump and a plurality of fertilizer solution tanks 25 connected thereto, and an electric conductivity meter 3 for measuring the electric conductivity in the mixing tank 1. A controller (not shown) controls each of the fertilizer supply pumps 24 so that the measured value from the above becomes a preset value. The concentrated fertilizer solution discharged from each fertilizer supply pump 24 is supplied to the mixing tank 1 via a pipe g.
Where it is diluted by stirring and mixing with a stirrer (not shown). As such a fertilizer supply device 2, for example, a device commercially available as “Rakuraku fertilizer management machine” from Shinwa Hydroponics Co., Ltd. can be used.

The disinfecting device 14 is provided for disinfecting the nutrient solution drainage.
6, 27, 28, 32, 31, electric ball valves 29, 30, a pump 34, a filter 35 for closing pipes during sterilization, a plurality of hollow fiber membrane modules 36 for sterilization, and a reverse of the hollow fiber membrane module 36. It has a hollow fiber membrane module 37 for cleaning and a cylinder type cleaning liquid supply section 38 for supplying a cleaning liquid to the hollow fiber membrane module 37. A of the electric ball valve 39
The port is connected to the mixing tank 1 via a pipe i,
The B port is connected to the drainage tank 15 via a pipe j. The C port of the electric ball valve 39 is connected to the A port of the electric ball valve 26 via a pipe h. The electric ball valve 31 is connected to the mixing tank 1 via a pipe k.
The A port of the electric ball valve 27 and the B port of 30 are connected to the drainage tank 15 via a pipe l. Further, the B port of the electric ball valve 26 is connected to the treated water tank 11 via a pipe m, and the C port is connected to a pump 34. The drive of each electric ball valve in FIG. 1 is controlled by a control device such as a computer device or a sequencer (not shown).

Next, a method for cultivating a plant in nutrient solution will be described with reference to the process flow chart of FIG. First, raw water from the pipe a is pressurized by a pressurizing pump 16 to a pressure required for reverse osmosis, and supplied to the membrane primary side of a reverse osmosis membrane module 17. Therefore, raw water that has been treated to a pure water level by removing impurities such as fine particles, bacteria, and colloidal substances together with salts by reverse osmosis is discharged from the pipe b to the treated water tank 11 as treated water. The treated water stored in the treated water tank 11 is supplied to the mixing tank 1 from the pipe d, where it is mixed with a predetermined fertilizer component. The pH adjusting solution is intermittently injected from the water quality adjusting device 12 into the pipe d. The pH of the nutrient solution is adjusted to a predetermined range. For example, when a solution of potassium carbonate is used as the pH adjustment solution, the concentration is adjusted so that the concentration of the treatment water supplied to the mixing tank 1 is in the range of about 30 to 50 mg / l. If the concentration is 30 mg / l or less, the pH buffer capacity of the nutrient solution tends to be insufficient, and if it exceeds 50 mg / l, the pH value becomes too high and the leaves of the plant are liable to yellow.

The amount ratio of the fertilizer component is controlled by the fertilizer supply device 2 in response to a conductivity measurement signal from the conductivity meter 3. In the daytime when plant growth is active, the pump 4 is continuously operated, and the nutrient solution in the mixing tank 1 is supplied to the cultivation bed 5 via the pipe e, the pump 4 and the electric ball valve 23, and is sprayed on the plant from a plurality of nozzles. Is done. Excess nutrient solution that is not absorbed by the plant on the cultivation bed 5 is discharged as a nutrient solution into a drainage tank 15 and temporarily stored. Will be returned. That is, the drainage tank 15
Is provided with a level detector (not shown), and when the liquid level rises to a predetermined liquid level, the detection signal causes the electric ball valve 39 to be driven by a controller (not shown), so that the B port and the C port communicate with each other. As a result, the nutrient solution drainage flows into the removing bacteria device 14 through the pipes j and h, and the hollow fiber membrane module 36 through the electric ball valve 26 and the pump 34.
To the primary side. Then, bacteria are separated from the nutrient solution drainage, and the purified nutrient solution returns to the mixing tank 1 via the pipe k from the secondary side of the membrane.

When the liquid level of the drain tank 15 drops below a certain level by the above operation, the electric ball valve 39 is driven by the detection signal of the liquid level, and the port A and the port C are communicated. Then, the discharge of the nutrient solution drainage from the drainage tank 15 is stopped, and the sterilization operation of the nutrient solution in the mixing tank 1 is started.
That is, the nutrient solution in the mixing tank 1 flows into the removing bacteria device 14 via the pipes i and h, and is supplied from the electric ball valve 26 to the primary side of the hollow fiber membrane module 36 via the pump 34, where bacteria are separated. The cleaned and cleaned nutrient solution returns to the mixing tank 1 from the secondary side of the membrane via the pipe k. In this state, when the liquid level of the nutrient solution drainage of the drainage tank 15 rises above a certain level again, the electric ball valve 3 is detected by the detection signal of the liquid level.
9 is driven, the B port and the C port communicate with each other, the operation of removing the nutrient solution from the mixing tank 1 is stopped, and the operation returns to the operation of removing the sterilization solution from the drainage tank 15. In this way, when the sterilizing operation of the nutrient solution in the mixing tank 1 is performed between the sterilizing operations of the nutrient solution drainage in the drainage tank 15, the operation rate of the removing bacteria device 14 is improved, The effect of suppressing bacterial growth is also improved.

The sterilizer 14 may be operated continuously for 24 hours throughout the day and night. When the sterilizing hollow fiber membrane module 36 is used for a long time, the membrane gradually becomes clogged, and its separation ability is reduced. So at any interval,
For example, at an interval of once / 3 hours, the hollow fiber membrane module 36 is backwashed to recover its separation ability. To backwash the hollow fiber membrane module 36, the electric ball valve 2
6 is driven to operate the pump 34 in a state where the B port and the C port communicate with each other. Then, the treated water in the treated water tank 11 is piped m-electric ball valve 26-pump 34-filter 35-electric ball valve 29-hollow fiber membrane module 37 for backwashing-pipe n-electric ball valve 31-electric ball valve 32
Is supplied to the membrane secondary side of the hollow fiber membrane module 36 through As a result, the hollow fiber membrane module 36 is back-washed, and the contaminated treated water is removed from the electric ball valve 28 -the electric ball valve 2.
It is collected in the drain tank 15 via 7-pipe p-pipe l. The treated water washed by the backwashing hollow fiber membrane module 37 is supplied to the hollow fiber membrane module 36, but a part of the water is also supplied to the upper side of the piston in the cylinder type cleaning liquid supply section 38, and the piston is moved to the lowest position. Press down to the bottom.

On the other hand, the hollow fiber membrane module 37 for back washing
When used repeatedly, the clogging gradually decreases and the processing capacity is reduced. Similarly, the back washing is performed to recover the processing capacity. To backwash the hollow fiber membrane module 37 for backwash,
The pump 34 is operated in a state where the electric ball valve 26 is driven to connect the A port and the C port, and the electric ball valve 29 is further driven to connect the A port and the B port. The cylinder type cleaning liquid supply unit 38 is communicated. Then, the cleaning water of the cleaning liquid supply section 38 is supplied to the lower side of the piston of the cleaning liquid supply section 38, whereby the piston is driven upward, and the clean treated water stored on the upper side of the piston as described above is removed from the hollow fiber membrane module. It is supplied to the secondary side of 37 and backwashing is performed. The contaminated treated water is collected in the drainage tank 15 via the electric ball valve 30 and the pipe l. As described above, since all the back washing liquid is collected and reused, there is no need to discard the nutrient solution outside.

The absorption ratio of the ionic component by the plant changes depending on the growing stage of the plant and seasonal factors. Such a change in the absorption ratio disrupts the pH of the nutrient solution and the balance of the fertilizer components, and adversely affects plants. Therefore, it is preferable to adjust the pH of the nutrient solution and the concentration of the fertilizer component so as to adapt to such a change in the absorption ratio of the ionic component. Changes in the ionic component absorption ratio due to different growth stages and seasonal factors depending on the type of plant to be cultivated,
It can be known in advance by experiments. Therefore, based on the data obtained by the experiment, p
The amount of H adjustment and the amount of fertilizer component supplied by the fertilizer supply device 2 can be controlled. This control can be program-controlled by a control device (not shown).

During nighttime when plant growth is inactive, the pump 4 is stopped to suppress energy consumption. Then, bacteria enter the pipe q from each solution supply hole of the pipe q, so-called reverse contamination occurs. That is, a thin layer of fertilizer components and other biological impurities, that is, a biofilm is often formed on the inner wall of the pipe. Therefore, as a countermeasure, the ozone sterilization apparatus 13 is utilized by using the stop period of the pump 4.
Is preferably operated two or three times at night to ozone-sterilize the interior of piping such as piping and tanks. Then, a liquid containing ozone is caused to flow through a pipe or a tank to remove the biofilm.

To operate the ozone sterilizer 13, the ozone generator 21 and the cascade pump 22 are operated.
The electric ball valve 23 is driven to communicate the pipe f with the cultivation floor 5. By the operation of the ozone sterilizer 13, the treatment liquid containing ozone flows into the cultivation bed 5 from the pipes f and q. The flow rate can be controlled, for example, by a regulating valve (not shown) provided on the outlet side of the cascade pump 22. However, a very small flow rate is sufficient compared with the nutrient solution flow rate during the day when the pump 4 is operating. Also, its ozone content is kept to a minimum necessary so as not to damage plants. For that purpose, ozone is mixed into the clean treated water guided from the treated water tank 11 via the pipe o. If the water containing the ozone contains organic matter such as microorganisms, it consumes ozone,
Excessive ozone must be incorporated, as it can damage plants. The treatment liquid containing ozone supplied to the cultivation bed 5 flows into the cultivation bed 5, where the ozone is completely consumed.

[0022]

EXAMPLES Next, the method for hydroponics according to the present invention will be described more specifically with reference to examples. Hydroponic cultivation of medium tomatoes was performed according to the process flow of FIG. (Cultivation conditions) Cultivar: Middle cat tomato seedling of Kane seedling Seeding date: July 1, Planting date: August 1 (cultivation floor) The following three areas (cultivation area of each area: 11.
(4 tsubo), and 64 medium ball tomato seedlings were planted in each area. In addition, a dummy area is provided between each area,
Eliminates differences in lighting conditions between locations. Example plot (area where the method of the present invention is implemented) Comparative example plot (area in which nutrient solution is circulated and cultivated without desalting and sterilization operations) Control plot (discharge the nutrient solution drainage to the outside as in the conventional method) Cultivated area)

(Management of fertilizer for nutrient solution) Based on the composition of the base fertilizer shown in Table 1, top fertilizer as shown in Table 2 was adjusted for each growing stage.

[0024]

[Table 1]

[0025]

[Table 2]

(Results) FIG. 2 shows the change in pH and electric conductivity of the nutrient solution circulated in the embodiment (measured in the mixing tank 1).
FIG. 3 shows the change in the composition ratio of the fertilizer component of the nutrient solution circulated in the example section (measured in the mixing tank 1). The incidence of root rot and wilt was almost 100 in the comparative plot.
%, Whereas that of the control plot was 3%, which was almost the same as 2% of the control plot where the nutrient solution was discarded outside and cultivated. Further, FIG. 4 (a) shows the change in the fruit yield of tomatoes in the example section, and FIG. 4 (b) shows the change in the fruit yield of tomatoes in the control section. % Increased. From these results, according to the cultivation method by the nutrient solution circulation method of the present invention, no damage due to salt damage was observed, and there was no sudden change in pH of the nutrient solution, an increase in electric conductivity, and no bias in the fertilizer components, and it was stable. Can be cultivated. In addition, the morbidity is extremely low as in the case where the nutrient solution drainage is discarded outside and cultivated, and the fruit yield increases.

[0027]

As described above, according to the nutrient solution cultivation method of the present invention, the nutrient solution is adjusted by desalinating the raw water with the desalting device.
Even if the nutrient solution is circulated through the cultivation bed for a long time, the salt does not accumulate and does not adversely affect the plants. In addition, since the nutrient solution wastewater is sterilized by the sterilizer and returned to the nutrient solution, there is little possibility that the cultivation bed will be contaminated with bacteria even if the nutrient solution is circulated through the cultivation bed for a long time. In the above-mentioned hydroponic cultivation method, a reverse osmosis membrane is used as a desalination apparatus, and impurities such as fine particles and bacteria contained in raw water can be removed together with desalination of raw water.
By doing so, the cultivation bed can be more stably maintained in a state where the bacteria are suppressed, and the adjustment of the fertilizer component can be more precisely controlled. In any of the above-mentioned nutrient solution cultivation methods, a hollow fiber membrane can be used as a sterilization apparatus. The use of such a disinfecting apparatus facilitates maintenance and management, lowers operating costs, and more reliably performs disinfecting operations.

In any of the above-mentioned nutrient solution cultivation methods, the pH value in the nutrient solution can be adjusted to a range suitable for plant growth. When the pH value in the nutrient solution is adjusted in this way, even when the absorption ratio of the ionic component of the plant changes due to the stage of plant growth or seasonal factors, the pH of the cultivation bed can be reduced.
It is possible to prevent the H value from suddenly changing and adversely affecting the plant. In any of the above-mentioned nutrient solution cultivation methods, the nutrient solution piping can be sterilized with ozone at night when plant growth is inactive. When the nutrient solution piping is sterilized with ozone in this manner, the formation and growth of a biofilm on the inner wall of the piping can be effectively suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic process flow diagram for implementing a nutriculture method of the present invention.

FIG. 2 is a graph showing changes in pH and electric conductivity of a nutrient solution circulated and used in an example section.

FIG. 3 is a view showing a change in a composition ratio of a fertilizer component of a nutrient solution circulated in an example section.

FIG. 4 is a graph showing changes in fruit yield of tomatoes in an example section and a control section.

FIG. 5 is a process flow diagram of a conventional nutriculture method.

FIG. 6 is a view showing the results of measuring the change in the ratio of each component contained in the cultivation bed when the nutrient solution prepared in the mixing tank was circulated through the cultivation bed in FIG. 5 for about 4 months.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mixing tank 2 fertilizer supply device 3 conductivity meter 4 pump 5 cultivation floor 6 plant 10 desalination device 11 treated water tank 12 water quality adjustment device 13 ozone sterilization device 14 sterilization device 15 drainage tank 16 pressure pump 17 reverse osmosis membrane Module 18 Flow rate integrator 19 Diaphragm pump 20 Solution tank 21 Ozone generator 22 Cascade pump 23 Electric ball valve 24 Fertilizer supply pump 25 Fertilizer solution tank 26-33 Electric ball valve 34 Pump 35 Filter 36 Hollow fiber membrane module 37 Hollow fiber membrane module 38 Cleaning liquid supply unit 39 Electric ball valve a to q Piping

Continued on the front page (72) Inventor Yoichi Kobayashi F-term (reference) 2B314 MA18 MA45 MA48 ND07 PA03 PA05 PA06 PA13 PA17 PB08 PB64

Claims (5)

[Claims] In a nutrient solution cultivation method for cultivating a plant by supplying a nutrient solution to a cultivation bed 5, raw water is desalted by a desalter 10 and a fertilizer component is added to the treated water obtained. Is adjusted, the nutrient solution is supplied to the cultivation bed 5, and the nutrient solution drainage discharged from the cultivation bed 5 is sterilized by the sterilization device 14 and returned to the nutrient solution. A method for cultivating nutrient solution, wherein the method is used in a circulating manner. 2. The desalination apparatus according to claim 1, wherein the desalination apparatus uses a reverse osmosis membrane, and removes impurities such as fine particles and bacteria contained in the raw water together with desalination of the raw water by the reverse osmosis membrane. Liquid cultivation method. 3. The method for cultivating nutrient solution according to claim 1, wherein the sterilization apparatus 14 uses a hollow fiber membrane. 4. The method for cultivating nutrient solution according to claim 1, wherein the pH value in the nutrient solution is adjusted to a range suitable for plant growth. 5. At night, when plant growth is inactive,
The method for cultivating a nutrient solution according to any one of claims 1 to 4, wherein ozone is contained in pipes through which the nutrient solution flows.