JP2908550B2 - Hydroponic cultivation equipment - Google Patents

Description

Description: Object of the Invention (Industrial application field) The present invention relates to a hydroponic cultivation apparatus for plants, and more particularly to a hydroponic cultivation apparatus that manages the state of components of a nutrient solution.

(Prior art) Hydroponic cultivation in which plants are grown using a nutrient solution (culture solution) has been attracting attention as one cultivation method of facility horticulture because it is easy to control the cultivation environment, and has been implemented. . In addition to controlling the rhizosphere environment of the plant with nutrient solution, it also controls the above-ground environment such as solar radiation, and integrates with actual plant growth information and control software according to the growth stage. Research and development of plant factories, etc., which use computers to optimize the cultivation environment, are being promoted from various fields.

The method of nutrient solution management in this nutrient solution cultivation greatly differs depending on the cultivation method. For example, in a hydroponic system that uses a large amount of nutrient solution, or in a cultivation method that circulates a nutrient solution such as NFT (Nutrient Film Technique), a sensor that detects the concentration of nutrient solution in a cultivation bed or a nutrient solution adjusting tank is used. By arranging the (nutrient solution component sensor), the actual nutrient solution state in the rhizosphere can be indirectly measured, and the nutrient solution can be managed based on the information.

On the other hand, in a cultivation method using a solid medium, the nutrient solution is generally supplied in a flowing manner in many cases, and in this case, it is difficult to secure a sufficient leaking liquid for sensor measurement. what if,
Even if a leaked liquid can be secured, the concentration of the nutrient solution in the solid medium can be accurately determined in real time, such as when there is a large error between the component concentration of the liquid and the actual concentration in the rhizosphere or there is a large time lag. Measurement is difficult. In addition, there is a similar problem in the case of solid culture cultivation in which a nutrient solution is circulated. Therefore, in order to directly measure the nutrient solution in the rhizosphere, it is necessary to arrange the nutrient solution component sensor in the solid medium. However, current electrode type sensors are relatively large and have high electrode resistance, so when placed in a solid medium, the output becomes extremely unstable due to the contact state between the nutrient solution held in the medium and the detection unit. There was an easy problem. In addition, even if the size is reduced and the shape is easily brought into contact with the nutrient solution, there is a problem that the electrode resistance is further increased and the instability of the output is increased. Therefore, in practice, a method of extracting a nutrient solution from a solid medium using a syringe and applying the solution to an analyzer has to be adopted. However, in order to accurately and optimally control the growth of a plant, it is essential to measure the concentration of the nutrient solution component in the solid medium in real time and feed it back as control information of the nutrient solution to be supplied.

In addition, current hydroponic cultivation equipment only uses conductivity (EC) sensors and pH sensors as nutrient solution component sensors. To adjust the nutrient solution concentration, a high-concentration nutrient solution and a mixture of acid and alkali are used. A control liquid is used. That is, when the conductivity of the nutrient solution decreases due to the absorption of nutrients by the plant, the concentration is adjusted by adding a high-concentration stock solution containing each component at a fixed ratio, and when the pH changes, an acid or alkali solution is added. To adjust the pH. However, various components contained in the actual nutrient solution have different degrees of concentration change due to a difference in the absorption rate by the plant. Therefore, the above-mentioned nutrient solution adjustment method cannot correct the bias of the concentration of the specific component,
All of the nutrient solution had to be replaced in a certain period. In particular, in the case of nutrient solution cultivation using a solid medium, it was extremely difficult to grasp the actual nutrient solution state due to drastic changes in concentration and composition due to evapotranspiration and the chemical influence of the solid medium material. Therefore, countermeasures have been taken by washing the solid medium by immersing the solid medium in fresh water and then periodically supplying a new nutrient solution adjusted to optimal conditions. However, in this method, it is difficult to quickly and accurately manage the nutrient solution components in the solid medium, and the labor and cost of the operation are also serious problems.

As described above, in the nutrient solution cultivation using the solid medium, in order to realize the nutrient solution management that enables the optimal growth of the plant, the concentration of each nutrient solution component in the solid medium is directly measured in real time and supplied. It is necessary to feed back as control information of the nutrient solution to manage the nutrient solution, and it is also effective from the viewpoint of economy.

(Problems to be Solved by the Invention) As described above, in the current solid medium type nutrient solution cultivation apparatus, there is no method for accurately detecting the nutrient solution component concentration in the solid medium in real time, and the rapid nutrient solution concentration There was a problem that management was difficult.

The present invention provides a nutrient solution cultivation apparatus including a nutrient solution component sensor that accurately detects a nutrient solution component concentration in a solid medium in real time, and a nutrient solution management system that enables optimal growth of a plant. Aim.

[Constitution of the Invention] (Means for Solving the Problems) The present invention provides a solid medium for growing plants, a nutrient solution adjusting means for supplying a nutrient solution to the solid medium, and a nutrient solution in the solid medium. A hydroponic cultivation apparatus using a nutrient solution component sensor for detecting the concentration of a component, wherein a FET type sensor is used as the nutrient solution component sensor.
As a preferred embodiment of the present invention, there is provided a nutrient solution cultivation device in which a second nutrient solution component sensor is disposed in the nutrient solution adjusting means. Further, the nutrient solution component sensor disposed in the solid medium is a FET type sensor in which a plurality of sensors corresponding to components in the nutrient solution are integrally formed on the same substrate.

(Function) The nutrient solution cultivation apparatus according to the present invention includes, as one component of the medium environment control unit, a nutrient solution component sensor arranged in a solid medium and a nutrient solution component sensor arranged in a nutrient solution adjusting tank. The nutrient solution component sensor placed in the solid medium is based on the FET sensor and measures the nutrient solution concentration in the solid medium directly in real time and feeds it back as concentration control information of the nutrient solution to be supplied. Thereby, quick and accurate nutrient solution management can be realized.

When the nutrient solution component sensor is placed in a solid medium for measurement, the most problem is to obtain a stable output based on the contact between the nutrient solution and the detection unit. That is, in the nutrient cultivation using the solid medium, from the viewpoint of promoting oxygen supply to the roots,
The solid medium is not in a state containing a large amount of nutrient solution, but is actually kept in a semi-dry state. Therefore, in order to efficiently contact with a small amount of nutrient solution held in the solid medium and obtain a stable output, the detection area of the nutrient solution component sensor must necessarily be small, corresponding to various components. It is desirable that the sensor has a structure that can be integrated with the sensor. The nutrient solution sensor using the FET sensor according to the present invention is very effective as a sensor satisfying the above conditions.

On the other hand, in general, there is a considerable distance between the nutrient solution adjusting tank and the solid medium, and the adjusted nutrient solution is supplied to each solid medium using a long tube. Also, in order to create a uniform dispersion state in the solid medium, the nutrient solution is slowly supplied from the microtube at an extremely low pressure. Therefore, when trying to adjust the nutrient solution using only the nutrient solution component sensor arranged in the solid medium, the nutrient solution adjusted based on the sensor information has reached a predetermined concentration again by the sensor in the solid medium. There is a problem that it takes a long time to confirm. Therefore, the nutrient solution cultivation apparatus according to the present invention arranges the same sensor as the nutrient solution component sensor arranged in the solid medium or another kind of nutrient solution component sensor targeting the same kind of ion in the nutrient solution adjusting tank. As a result, the adjustment state of the nutrient solution to be supplied can be measured and managed quickly, and more accurate and accurate control of the nutrient solution component in the solid medium can be performed.

(Example) An example of the present invention will be described below.

FIG. 1 is a configuration diagram of a culture medium environment control unit in one embodiment of the hydroponic cultivation device according to the present invention, and FIG. 2 is an overall configuration diagram of the hydroponic cultivation device. In this embodiment, a solid medium type nutrient cultivation apparatus is constituted by a house 19, a cultivation bed 20, a medium environment control unit 21, a ground environment control unit 22, and a general control unit 18, as shown in FIG. Have a good relationship. The internal configuration and function of each component will be briefly described.

First, the house 19 is a building structure for the purpose of maintaining the cultivation environment and preventing the invasion of pathogens. A translucent covering material such as vinyl chloride is used for sunlight, and a heat insulating wall is used for artificial light. It is configured using materials.

The cultivation bed 20 is composed of a solid medium, a bed for supporting the medium, a coating material for suppressing evaporation of nutrient solution, a liquid supply microtube, and the like.

The ground environment control unit 22 is provided with sensors for the ground environment such as temperature, humidity, CO ₂ concentration, solar radiation (illuminance), wind speed, etc., and air conditioners, windows, curtains, humidifying / dehumidifying air, CO ₂ cylinders, artificial light Control the ground environment using lamps, ventilation fans, etc.

The overall control unit 18 outputs an output signal to each environmental control unit based on the stored database and the environmental information from the sensors of each environmental control unit so as to adjust the environmental conditions so that the plant grows optimally.

Finally, the medium environment control unit 21 will be described with reference to FIG. The medium environment control unit is roughly divided into a medium environment measurement unit and a medium environment control unit. First, the culture medium environment measuring unit includes a nutrient solution component sensor 1, a temperature sensor 3, and a moisture sensor 5 arranged in the solid medium 17, and a nutrient solution component sensor 2, a temperature sensor 4, and It is constituted by a water level sensor 6. The nutrient solution component sensors 1 and 2 include N which is a main component of the nutrient solution.
_{^{O 3 -, NH 4 +,}} HPO 4 2- or _{^{H 2 PO 4 -, K +}} , Ca 2+, Mg 2+, S
O ₄ ^2- , trace components Fe ²⁺ or Fe ³⁺ , BO ₃ ^3- or B ₄ O ₇ ^2- , Zn ²⁺ , Mn ²⁺ , Cu ²⁺ , Cl ⁻ , MoO ₄ ^2- , etc. And a sensor for detecting pH, dissolved oxygen, and conductivity. On the other hand, the culture medium environment control section comprises a nutrient solution adjusting tank 7, a chemical solution tank 8 (a nutrient solution undiluted solution tank and a pH adjusting solution tank) and its valve 9 and flow meter 10,
It is composed of a pump 11 for drawing in tap water, a pump 12 and a flow meter 13 for supplying the adjusted nutrient solution to the cultivation bed, a heat pump 14 for adjusting the solution temperature, a stirrer 15, and a pipe 16 for transporting each solution. . The feature of the present invention resides in that a nutrient solution component sensor arranged in the solid medium 17 and the nutrient solution adjusting tank 7 is provided as one configuration of the medium environment control unit, and further arranged in the solid medium. The most characteristic feature is that the nutrient solution sensor 1 is manufactured based on an FET sensor. The nutrient solution component sensor (hereinafter abbreviated as FET-type nutrient solution sensor) 1 manufactured on the basis of such an FET type sensor is a small-sized, high-input impedance element, and is therefore a nutrient solution held in a solid medium. Even when the amount of the liquid is small, the detection unit effectively contacts the nutrient solution, and a stable output signal can be obtained. Actually, the present inventor has confirmed through experiments that the FET-type nutrient solution sensor 1 shows an accurate and stable output within the water retention rate change range (90 to 10% by weight) of the solid medium during plant cultivation. The real-time information of the concentration of the nutrient solution in the solid medium by the FET-type nutrient solution sensor 1 is
By feeding back to the culture medium environment control unit via the overall control unit 18, it is possible to accurately control the concentration of the nutrient solution, and to realize optimal growth of the plant. Further, by using the nutrient solution component sensor 2 arranged in the nutrient solution adjusting tank, the adjustment state of the nutrient solution to be supplied can be accurately controlled, and the nutrient solution component concentration in the solid medium can be quickly measured. Can be optimized.

FIGS. 3 (a), (b), (c) and (d) are plan views of an embodiment of a FET type nutrient solution component sensor arranged in a solid medium after mounting, and AA 'and BB thereof. ′, CC ′. This embodiment is an FET-type ion sensor 23 manufactured using a wafer having a SIS silicon-insulator-silicon) structure, and a potassium ion sensitive film 30 is formed in a gate region serving as a detection unit. That is, as shown in FIG. 3 (c), a source region 28 and a drain region 29 are provided in an island-like silicon layer 27 formed on a silicon substrate 24 via an SiO ₂ film 25, and a gate insulating film is formed. SiO ₂ film
25 and a SiN _x film 26 are formed, and a potassium ion sensitive film 30 is further formed on the gate insulating film to constitute an FET type potassium ion sensor. In this embodiment, the potassium ion sensitive membrane 30 contains 1% of the sensitive substance valinomycin,
It contains 39% of polyvinyl chloride as a binder, 60% of dioctyl adipate as a plasticizer, and 0.1% of potassium tetraphenylborate. The sensitive membrane material dissolved in tetrahydrofuran is used as a FET-type ion sensor 2
It is obtained by applying to the gate area of No. 3 and air-drying in a low humidity state for 3 days. As shown in FIGS. 3B and 3D, the source electrode 31 and the drain electrode 32 of the FET type ion sensor 23 are connected to the electrode 36 of the flexible printed circuit board 35 through the lead-tin solder 33. ing. further,
In order to protect this electrode connection from the outside, it is sealed with a resin.

Further, the FET type nutrient solution component sensor corresponding to the main component or the trace component of the nutrient solution described above is provided with a potassium ion sensitive film 30 provided in the gate region of the FET type ion sensor 23 shown in FIG. It can be realized by replacing with a sensitive film corresponding to the component.

FIG. 4 is a configuration diagram when the FET-type nutrient solution component sensor as shown in FIG. 3 is arranged in a solid medium. As shown in FIG. 4, the location of the FET-type nutrient solution sensor 1 is located inside a cube (upper solid medium: for raising seedlings) 37, inside a slab (lower solid medium: for planting) 38, and a cube 37. It is roughly divided into three places, between the slabs 38. The location of this arrangement is determined by the state of the nutrient solution that is desired to be known.However, in the case of normal nutrient solution management, the cube 38 is placed in accordance with the growth condition of the plant, that is, the development status of the root. A standard method is to move the inside, the middle between the cube 38 and the slab 39, and the inside of the slab 39. In addition, when it is arranged inside the cube 37 or the slab 38, it is effective to insert the FET-type nutrient solution sensor 1 after making a cut in advance with a cutting tool or the like. Medium-
There is an effect that a cut surface that enables good contact between the sensitive parts is obtained.

On the other hand, the FET type nutrient solution component sensor 1 requires a reference electrode 39 for fixing the potential of the nutrient solution. In FIG. 4, the FET
A reference electrode in a location different from the location of the type nutrient solution sensor 1
39 shows a case in which the FET type nutrient solution component sensor 1 is operated with 39 disposed. In the experiment by the inventor, it was confirmed that a stable output was obtained using the reference electrode 39 in any of the FET-type nutrient solution component sensors 1 in any of the locations shown in FIG. At this time, the stability of the output is increased by the pressure of pressing the liquid junction of the reference electrode 39 against the solid medium 38, and the effect of reducing the initial drift of the output by dropping a few milliliters of the solution around the liquid junction is obtained. Obtained.

FIG. 5 is a configuration diagram when the FET type nutrient solution component sensors arranged on a plurality of cubes on the same slab are operated by one reference electrode. As shown in FIG. 4, a plurality of FET-type nutrient solution component sensors 1 arranged on the same solid medium can be operated by one reference electrode, as shown in FIG. It is also possible to operate each FET-type nutrient solution sensor 1 arranged on a plurality of cubes 37 on the same slab 38 with one reference electrode 39 arranged on the slab 38. In fact, the inventors have confirmed by experiments that the output is constant and a stable signal can be obtained when the distance between the FET-type nutrient solution sensor and the reference electrode is within a range of 90 cm.

As shown in FIGS. 4 and 5, it has been described that the reference electrode functions even if it is arranged at a place different from the place where the FET type nutrient solution component sensor is arranged. It is also possible to use it integrated with the nutrient solution component sensor.

FIGS. 6 (a) and 6 (b) are a plan view and a sectional view taken along the line AA 'of a FET type nutrient solution sensor of another embodiment. In this embodiment, four silicon layers 27 having the FET structure shown in FIG.
They are integrally formed on the same silicon substrate 24. The silicon layer 27 of each FET structure has a good electrical insulation and separation by the SiN _X film and the SiO ₂ film. In the gate region of each silicon layer 27, a pH-sensitive film 40, a nitrate ion-sensitive film 41, a potassium ion-sensitive film 30, and an ion-insensitive reference film 42 are formed, and a pH sensor, a nitrate ion sensor, a potassium ion sensor, A reference FET is configured. By differentially operating the nutrient solution component sensor and the reference FET with respect to the inert metal electrode 43 provided on the same silicon substrate 24, the pH, nitrate ion concentration, and potassium ion concentration in the nutrient solution can be adjusted. It can be detected and does not particularly require a reference electrode. A nutrient solution sensor in which a plurality of sensors corresponding to nutrient solutions are formed on the same substrate as described above is very effective when the nutrient solution contained in the solid medium is small. Further, the type and number of the FET-type nutrient solution components provided on the same substrate are determined according to the nutrient solution to be managed, and are not limited to this embodiment.

FIGS. 7 (a) and 7 (b) show a probe according to still another embodiment.
It is the top view and sectional drawing of the mounting structure of FET type nutrient solution component sensor. Here, the FET sensor chip 44 is the potassium sensor shown in FIG. 3, or the integrated sensor shown in FIG. this
The FET type sensor chip 44 has a metal reinforcing plate 47
Is bonded to a glass-epoxy wiring board 45 attached thereto, and is connected to the electrodes 34 of the wiring board 45 by gold wires 46. Further, the metal reinforcing plate 47 has a tip processed into a pointed shape. In addition, the structure is such that all parts except the detection unit are sealed with the resin 36. Such a probe-like nutrient solution sensor having a sharp tip is used for repeated insertion and withdrawal from a solid medium, for example, when measuring several locations of a solid medium with one nutrient solution sensor. It is valid. That is, the FET type sensor chip 44 is protected from the impact at the time of insertion,
The shape is such that a state of the culture medium that creates stable contact between the detection unit and the nutrient solution can be obtained.

On the other hand, the nutrient solution sensor 2 arranged in the nutrient solution adjusting tank shown in FIG.
It is not always necessary to manufacture the sensor based on the FET sensor. That is, the sensor may be exactly the same as the FET-type nutrient solution component sensor 1 disposed in the solid medium, or may be an electrode-type sensor for detecting similar ions. Further, as a nutrient solution adjusting means, a system may be used in which a pipe from each stock solution is connected to the main pipe in a flow-through manner and injected.

[Effects of the Invention] As described above, according to the present invention, a nutrient solution component sensor disposed in a solid medium and a nutrient solution component sensor disposed in a nutrient solution adjusting tank are provided as one component of the medium environment control unit. In particular, a nutrient solution cultivation apparatus characterized in that the nutrient solution component sensor arranged in the solid medium is manufactured based on the FET type sensor, and the concentration of the nutrient solution component in the solid medium is directly measured in real time. It is possible to measure and feed back as concentration control information of the nutrient solution to be supplied, so that quick and accurate nutrient solution management can be realized.

[Brief description of the drawings]

1 and 2 are diagrams showing the configuration of a nutrient solution cultivation apparatus according to one embodiment of the present invention, FIG. 3 is a plan view and a cross-sectional view of a FET type nutrient solution component sensor for potassium ions, and FIG. Fig. 5 is a configuration diagram when a type nutrient solution component sensor and a reference electrode are arranged in a solid medium. Fig. 5 is a configuration diagram when a plurality of FET type nutrient solution component sensors and reference electrodes are arranged in a cube on the same slab. FIG. 6 is a plan view and a cross-sectional view taken along the line AA 'of an FET type nutrient solution component sensor in which sensors corresponding to a plurality of nutrient components are integrated. FIG. It is a top view and a sectional view. 1. Nutrient solution sensor for solid medium 2. Nutrient component sensor for nutrient solution adjustment tank 3. Water sensor 4. Water level sensor 5. 6, Temperature sensor 7. Nutrient solution adjustment Tank, 17: Solid medium, 18: General control unit, 19: House, 20: Cultivation bed, 21: Medium environment control unit, 22: Ground environment control unit, 23: FET type ion sensor, 24 ... Silicon substrate, 3
0: Potassium ion sensitive film, 33: Lead-tin solder, 35
…… Flexible printed circuit board, 36 …… Resin, 37…
… Cube, 38 …… Slab, 39 …… Reference electrode, 40 …… pH
Sensitive membrane, 41 ... Nitrate ion sensitive membrane, 42 ... Reference membrane, 43 ...
... Inert electrode, 44 ... FET sensor chip, 45 ... Glass / epoxy wiring board, 46 ... Gold wire, 47 ... Metal reinforced plate.

Claims (4)

(57) [Claims] 1. A solid medium for growing a plant, a nutrient solution adjusting means for supplying a nutrient solution to the solid medium, and a nutrient solution sensor for detecting a component concentration of the nutrient solution in the solid medium. In the nutrient solution cultivation device, an FET type sensor is used as the nutrient solution component sensor, and the FET type sensor has a sharp tip that can be inserted into the solid medium. 2. The nutrient solution cultivation apparatus according to claim 1, wherein a second nutrient solution component sensor is arranged in said nutrient solution adjusting means. 3. The nutrient solution component sensor disposed in the solid medium is a FET sensor in which a plurality of sensors corresponding to components in the nutrient solution are integrally formed on the same substrate. The hydroponic cultivation device according to 1. 4. The FET-type sensor includes a reinforcing plate having a sharp tip, a FET-type sensor chip having a detecting portion, and a resin sealing portions other than the detecting portion. The hydroponic cultivation device according to claim 1.