JP2021093994A - Plant growing method and plant growing system - Google Patents

Abstract

To provide a plant growing method capable of easily stabilizing concentration of each nutrient solution component contained in a nutrient solution.SOLUTION: A plant growing method comprises: a discharge step (step 1) in which a part of a nutrient solution having a volume of R is discharged from a nutrient solution system filled with the nutrient solution having a volume of R so that a discharge amount of the nutrient solution per predetermined period becomes M; and an inflow step (step 3) in which a nutrient solution having potassium ion concentration of a, which is mass of potassium ions per unit volume, is poured into the nutrient solution system as a new nutrient solution so that the inflow of the new nutrient solution per the predetermined period is equal to the discharge amount M. The number of plants cultivated in the nutrient solution system is Q strains, the target value of potassium ion concentration is b (b<a), and, when the minimum absorption amount of the potassium ion absorbed in the predetermined period in each of the plants of the Q strains is A, the discharge amount M satisfies ((A×Q)/(a-b))<M<R.SELECTED DRAWING: Figure 6

Description

The present disclosure relates to a plant growing method for hydroponically cultivating plants such as leafy vegetables, for example.

Conventionally, a plant cultivation apparatus for hydroponically cultivating a plant by circulating a nutrient solution has been proposed (see Patent Document 1). In such a plant cultivation device, the cultivation tanks installed at each stage of the cultivation shelf are filled with nutrient solution, and the nutrient solution in the cultivation shelf is circulated by a pump.

Japanese Unexamined Patent Publication No. 2004-73003

However, the plant cultivation apparatus of Patent Document 1 has a problem that it is difficult to stabilize the concentration of each nutrient solution component contained in the nutrient solution.

Therefore, the present disclosure provides a plant growing method and the like capable of easily stabilizing the concentration of each nutrient solution component contained in the nutrient solution.

In the plant growing method according to one aspect of the present disclosure, a nutrient solution system filled with a nutrient solution having a volume R, which is used for hydroponically cultivating at least one kind of leafy vegetables, is used for feeding for a predetermined period. The discharge step of discharging a part of the nutrient solution having the volume R so that the discharge amount of the liquid is M, and the inflow amount of the new nutrient solution per predetermined period are equal to the discharge amount M. Including an inflow step of pouring a nutrient solution having a potassium ion concentration of a, which is the mass of potassium ions per unit volume, into the nutrient solution system as the new nutrient solution, the number of plants cultivated in the nutrient solution system is Q strain. (Q is an integer of 1 or more), the target value of the potassium ion concentration is b (b <a), and potassium absorbed by each of the plants of the Q strain during the seedling raising period per predetermined period. When the minimum absorption amount of the absorption amount which is the mass of the ion is A, the emission amount M satisfies ((A × Q) / (ab)) <M <R.

It should be noted that these comprehensive or specific embodiments may be realized in a recording medium such as a system, method, integrated circuit, computer program or computer readable CD-ROM, system, method, integrated circuit, computer program. And any combination of recording media may be realized. Further, the recording medium may be a non-temporary recording medium.

The plant growing method of the present disclosure can easily stabilize the concentration of each nutrient solution component contained in the nutrient solution.

FIG. 1 is a diagram showing an example of the configuration of a plant growing system according to the embodiment. FIG. 2 is a diagram showing changes in EC and pH of the nutrient solution and changes in the concentration of the nutrient solution component when the nutrient solution is not replaced. FIG. 3 is a diagram showing the amount of change in the concentration of each nutrient solution component when the nutrient solution is not replaced. FIG. 4 is a diagram for explaining replacement of the nutrient solution by the nutrient solution discharge valve and the nutrient solution inflow portion in the embodiment. FIG. 5 is a diagram showing the simulation results of the transition of the potassium ion concentration and the transition of the calcium ion concentration in the plant growing system in the embodiment. FIG. 6 is a flowchart showing the processing operation of the plant growing system according to the embodiment.

(Knowledge on which this disclosure was based)
The present inventor has found that the following problems arise with respect to the above-mentioned Patent Document 1 described in the column of "background technology".

Most of the lettuce on the market these days is produced by open-field cultivation. In such open-field cultivation, it is difficult to grow lettuce as planned if the weather is unseasonable or guerrilla rainstorms occur. As a result, the distribution volume of lettuce decreases, and the price of lettuce tends to rise. In the ready-to-eat industry that handles lettuce, when the distribution volume of lettuce is small, it is necessary to procure lettuce through a production area relay or overseas import, and a stable supply of the lettuce is desired. Therefore, the number of plant factories capable of stable cultivation and shipping all year round has begun to increase, and lettuce made by plant factories has begun to be distributed little by little.

In lettuce cultivation in a plant factory, unlike sunlight in open field cultivation, a fluorescent lamp or LED (light emitting diode) is used as a light source. Furthermore, in lettuce cultivation in a plant factory, unlike soil in open-field cultivation, nutrient-containing water (that is, nutrient solution) is used as a medium. For example, in the plant cultivation apparatus of Patent Document 1, the nutrient solution is supplied to the cultivation shelf for cultivating the plant by a pump, and the nutrient solution flowing out from the cultivation shelf is again supplied to the cultivation shelf by the pump. That is, the nutrient solution is circulated. In addition, air conditioning and carbon dioxide are also used in lettuce cultivation in plant factories.

As described above, lettuce cultivation in a plant factory tends to require a higher cost than open-field cultivation. Therefore, it has been attempted to reduce the cost of lettuce production by shortening the lettuce cultivation period and reducing the amount of nutrient solution.

However, if the cultivation period is shortened and the amount of nutrient solution is reduced, lettuce can be cultivated properly in the early stage of cultivation (that is, the first crop), but in the second crop, the yield of lettuce is reduced and the physiological disorder (physiological disorder). For example, chip burn) tends to occur conspicuously. In addition, the quality of lettuce becomes worse after the third work.

Therefore, as a result of investigating the factors of the decrease in yield and the physiological disorder, the inventors showed that each nutrient solution component contained in the nutrient solution, such as potassium or calcium, changed significantly compared to the start of lettuce cultivation. I found that. That is, it was found that each nutrient solution component contained in the nutrient solution includes a nutrient solution component whose concentration increases with the passage of time and a nutrient solution component whose concentration decreases with the passage of time.

Therefore, it is necessary to stabilize the concentration of the nutrient solution component in order to suppress the decrease in yield and the occurrence of physiological disorders. However, the work of stabilizing the concentration imposes a heavy burden, and even if the work can be stabilized in the first work, it is necessary to perform the work again in the second work.

For example, if all the nutrient solutions filled in the cultivation shelves are replaced with new nutrient solutions, the concentration of the nutrient solution components can be adjusted to an appropriate concentration. Then, if all such nutrient solutions are replaced periodically and repeatedly, the concentration of the nutrient solution components can be stabilized to some extent.

However, when all the old nutrient solution filled in the cultivation shelf is thrown away and new nutrient solution is stored in the cultivation shelf, the larger the cultivation shelf, the larger the amount of the old nutrient solution and the new nutrient solution. Therefore, it takes a long time and a heavy work load to replace those nutrient solutions. Furthermore, in winter, it takes longer for the temperature of the large amount of new nutrient solution to reach room temperature. Therefore, such a method of replacing all the old nutrient solutions with new nutrient solutions requires a large work load and lengthens the rest period during which the plant cultivation is interrupted or suspended. As a result, the utilization rate of the plant factory decreases.

In order to solve such a problem, the plant growing method according to one aspect of the present disclosure is filled with a nutrient solution having a volume R, which is used for hydroponically cultivating at least one kind of leafy vegetables. The discharge step of discharging a part of the nutrient solution of the volume R and the inflow amount of the new nutrient solution per predetermined period so that the discharge amount of the nutrient solution per predetermined period is M from the nutrient solution system. The nutrient solution system includes an inflow step of pouring a nutrient solution having a potassium ion concentration of a, which is the mass of potassium ions per unit volume, into the nutrient solution system as the new nutrient solution so as to be equal to the discharge amount M. The number of plants cultivated in the plant is Q strain (Q is an integer of 1 or more), the target value of the potassium ion concentration is b (b <a), and the seedling raising period is determined by each of the plants of the Q strain. When the minimum absorbed amount of the absorbed amount, which is the mass of potassium ions absorbed per predetermined period, is A, the discharged amount M is ((A × Q) / (ab)) < Satisfy M <R. For example, when the predetermined period is one day, the absorption amount A may be larger than 1 mg and less than 5 mg.

As a result, a part of the nutrient solution in the nutrient solution system is replaced with a new nutrient solution so that the discharge amount and the inflow amount per predetermined period are equal to each other, and the replacement is performed every predetermined period. That is, without replacing the nutrient solution in the nutrient solution system at once, the nutrient solution having the discharge amount M, which is a part of the nutrient solution having the volume R in the nutrient solution system, is replaced with the new nutrient solution at any time. .. Therefore, it is possible to easily suppress the change in the concentration of each nutrient solution component contained in the nutrient solution in the nutrient solution system. Furthermore, since not all the nutrient solutions in the nutrient solution system are replaced with new nutrient solutions, that is, because the discharge amount M <R is satisfied, it is possible to suppress the occurrence or prolongation of the rest period. It is possible to suppress a decrease in the operating rate of the plant factory.

Further, in the plant growing method according to one aspect of the present disclosure, the emission amount M satisfies ((A × Q) / (ab)) <M. Therefore, the amount of potassium ion supplemented per predetermined period, that is, M × (ab), is the minimum amount of potassium ion consumed by the plant of the Q strain per predetermined period, that is, (A × Q). ) More than. Therefore, by replacing the nutrient solution described above, the replenishment amount and the absorption amount can be easily brought close to the same state, and the potassium ion concentration can be stabilized. That is, the potassium ion concentration can be kept constant at the target value b. Furthermore, when the potassium ion concentration is most likely to change among the concentrations of each nutrient solution component contained in the nutrient solution, the concentration of not only potassium ion but also all other nutrient solution components becomes constant by the above-mentioned replacement. Can be kept.

Therefore, the concentration of each nutrient solution component contained in the nutrient solution can be easily stabilized.

Further, when the maximum absorption amount of the absorption amount which is the mass of potassium ions absorbed in the predetermined period by each of the plants of the Q strain is B, the emission amount M is further increased. M <((B × Q) / (ab)) <R may be satisfied. For example, when the predetermined period is one day, the absorption amount B may be larger than 8 mg and less than 20 mg.

As a result, the amount of potassium ions replenished per predetermined period, that is, M × (ab), is the maximum amount of potassium ions absorbed by the plant of the Q strain per predetermined period, that is, (B ×). Less than Q). Therefore, excessive replenishment of potassium ions can be avoided.

Further, in the plant growing method, the hydrogen ion index of the nutrient solution filled in the nutrient solution system and the electric conductivity of the nutrient solution are set to constant values during the cultivation period of the plant of the Q strain, respectively. A nutrient solution adjusting treatment may be performed to keep the temperature at.

As a result, changes in the hydrogen ion index (that is, pH) and the electric conductivity (that is, EC) are suppressed, so that the nutrient solution can be kept in a better state.

Further, in the inflow step, the new nutrient solution containing calcium ions having a concentration lower than the potassium ion concentration a is poured into the nutrient solution system, whereby the Q strain plant is cultivated into the nutrient solution system during the cultivation period. The potassium ion concentration of the filled nutrient solution may be kept higher than the calcium ion concentration.

As a result, the potassium ion concentration does not fall below the calcium ion concentration, so that the occurrence of physiological disorders in each of the plants of the Q strain can be suppressed.

Further, during the cultivation period of the plant of the Q strain, the potassium ion concentration of the nutrient solution filled in the nutrient solution system may be kept higher than 150 ppm depending on the setting of the target value b.

This makes it possible to suppress the occurrence of physiological disorders in each of the plants of the Q strain.

Further, the plant growing method further includes a circulation step in which a pump circulates the nutrient solution filled in the nutrient solution system, and the nutrient solution system includes a nutrient solution tank for storing the nutrient solution and circulation by the pump. It has at least one cultivation tank in which a part of the nutrient solution supplied from the nutrient solution tank is stored and the plant of the Q strain is arranged, and in the discharge step, the pump from the nutrient solution tank. A part of the nutrient solution flowing toward the at least one cultivation tank may be discharged through the above.

For example, when a part of the nutrient solution directed from at least one cultivation tank to the nutrient solution tank is discharged, a part of the nutrient solution is discharged because the nutrient solution contains a relatively large amount of garbage. The discharge port is easily clogged with the dust, and it is difficult to stabilize the discharge of a part of the nutrient solution. Furthermore, since the concentration of the nutrient solution component contained in the nutrient solution changes depending on the number of plants arranged in the cultivation tank, the concentration in the nutrient solution system becomes unstable due to the discharge of a part of the nutrient solution. It is easy to become. On the other hand, in the plant growing method according to one aspect of the present disclosure, a part of the nutrient solution flowing from the nutrient solution tank toward at least one cultivation tank via a pump is discharged. Therefore, since the nutrient solution contains relatively little dust, clogging of the discharge port described above can be suppressed, and the concentration in the nutrient solution system can be stabilized. Further, since a part of the nutrient solution pushed out toward at least one cultivation tank by the pressure of the pump is discharged, the discharge of a part of the nutrient solution can be stabilized.

Further, the plant growing method further includes a circulation step in which a pump circulates the nutrient solution filled in the nutrient solution system, and the nutrient solution system includes a nutrient solution tank for storing the nutrient solution and circulation by the pump. It has at least one cultivation tank in which a part of the nutrient solution supplied from the nutrient solution tank is stored and the plant of the Q strain is arranged, and in the circulation step, it is further circulated by the pump. A part of the nutrient solution flowing from the pump toward the at least one cultivation tank may be returned to the nutrient solution tank.

As a result, a part of the nutrient solution pushed out by the pressure of the pump is directly poured into the nutrient solution tank without passing through the cultivation tank, so that the nutrient solution in the nutrient solution tank can be agitated. As a result, the nutrient solution in the nutrient solution tank and the new nutrient solution are stirred, and the quality of the nutrient solution in the nutrient solution tank can be made uniform.

Hereinafter, embodiments will be specifically described with reference to the drawings.

It should be noted that all of the embodiments described below show comprehensive or specific examples. Numerical values, shapes, materials, components, arrangement positions and connection forms of components, steps, order of steps, etc. shown in the following embodiments are examples, and are not intended to limit the present disclosure. Further, among the components in the following embodiments, the components not described in the independent claims indicating the highest level concept are described as arbitrary components. Further, each figure is a schematic view and is not necessarily exactly illustrated. Further, in each figure, the same components are designated by the same reference numerals.

(Embodiment)
FIG. 1 is a diagram showing an example of the configuration of the plant growing system 100 according to the present embodiment.

The plant growing system 100 in the present embodiment is a system for hydroponically cultivating at least one kind of leafy vegetables, respectively, and includes a cultivation device 109, a light source control unit 102, a nutrient solution management unit 120, and piping. It includes 105a and 105b. Such a plant growing system 100 is used, for example, for hydroponic cultivation of a plurality of strains of lettuce. In the following example, plant 1 of the Q strain (Q is an integer of 2 or more), which is lettuce, is cultivated by the plant growing system 100. In addition, Q may be an integer of 1 or more. That is, the plant growing system 100 may cultivate one plant 1.

In the present embodiment, the vertical direction is referred to as the Z-axis direction, and the two directions orthogonal to each other in the horizontal direction are referred to as the X-axis direction and the Y-axis direction. For example, the X-axis direction is the width direction of the cultivation device 109, and the Y-axis direction is the depth direction of the cultivation device 109. Further, the upward direction in the vertical direction is simply referred to as an upper or upper side, and the downward direction in the vertical direction is simply referred to as a lower or lower side.

The cultivation device 109 has a configuration in which the first cultivation shelf 108a, the second cultivation shelf 108b, and the third cultivation shelf 108c are stacked in the Z-axis direction. Such a cultivation device 109 is arranged in the building of the plant cultivation factory. In the present embodiment, the cultivation device 109 is provided with three cultivation shelves, but the number of the cultivation shelves is not limited to three, and may be one or two. It may be one or more. Further, in the cultivation device 109, not only three cultivation shelves are stacked, but also a plurality of cultivation shelves may be arranged in the horizontal direction. That is, a plurality of rows of three stacked cultivation shelves may be arranged in the horizontal direction. Further, the periphery of such a cultivation device 109 may be air-conditioned by an air conditioner or the like in the room in which the cultivation device 109 is installed.

Each of the first cultivation shelf 108a, the second cultivation shelf 108b, and the third cultivation shelf 108c has substantially the same configuration. Specifically, these cultivation shelves include a cultivation tank 110, a cultivation plate 101, a ceiling plate 104, and a plurality of light sources 10.

A plurality of plants 1 are arranged in the cultivation tank 110. Then, the cultivation tank 110 stores the nutrient solution 2 used for cultivating the plurality of plants 1. Such a cultivation tank 110 is a rectangular container having an opening at the upper end, and is configured as, for example, a resin molded product. Further, the width of the cultivation tank 110 in the X-axis direction in the present embodiment is longer than the depth in the Y-axis direction. Further, in the present embodiment, the plant 1 of the Q strain is arranged in the three cultivation tanks 110. The number of cultivation tanks 110 may be one. That is, the plant growing system 100 in the present embodiment has at least one cultivation tank 110 in which the plant 1 of the Q strain is arranged.

The cultivation plate 101 is attached to the opening of the cultivation tank 110. Then, the cultivation plate 101 covers the opening of the cultivation tank 110 and holds the plant 1 in a state where the roots of the plant 1 are immersed in the nutrient solution 2. Such a cultivation plate 101 is configured as, for example, a resin molded product. Specifically, the cultivation plate 101 is a long member long in the X-axis direction, and holds a plurality of plants 1 arranged along the longitudinal direction (that is, the X-axis direction) of the cultivation plate 101. That is, a plurality of plants 1 are arranged in the cultivation tank 110 using the cultivation plate 101.

The ceiling plate 104 is arranged so as to face the cultivation plate 101 with the cultivation plate 101 sandwiched between the ceiling plate 104 and the bottom surface of the cultivation tank 110. Further, the ceiling plate 104 is arranged apart from the openings of the cultivation plate 101 and the cultivation tank 110.

Each of the plurality of light sources 10 is composed of an LED (light emitting diode) or the like, and is arranged on the lower surface side of the ceiling plate 104. Such a light source 10 lights up according to the electric power supplied from the light source control unit 102, and irradiates a plurality of plants 1 held on the cultivation plate 101 with light. The light may be red light or blue light. Further, the plurality of light sources 10 may irradiate the plant 1 with light of a plurality of different colors.

The light source control unit 102 lights the light sources 10 by supplying electric power to the light sources 10 attached to the cultivation device 109. For example, the light source control unit 102 periodically switches between turning on and off each light source 10. That is, the light source control unit 102 switches the brightness of the first cultivation shelf 108a, the second cultivation shelf 108b, and the third cultivation shelf 108c by turning on or off each of the plurality of light sources 10 at the same time. The period in which the plurality of light sources 10 are lit is the light period, and the period in which the plurality of light sources 10 are extinguished is the dark period. Such a light period and a dark period are repeated alternately.

The nutrient solution management unit 120 keeps the nutrient solution 2 stored in the cultivation tanks 110 of the first cultivation shelf 108a, the second cultivation shelf 108b, and the third cultivation shelf 108c in an appropriate state via the pipes 105a and 105b. While circulating. The nutrient solution 2 contains, for example, potassium ion, calcium ion, nitrate ion, magnesium ion, phosphate ion and the like as nutrient solution components.

Such a nutrient solution management unit 120 includes a nutrient solution inflow unit 121, a nutrient solution tank 122, a nutrient solution adjusting unit 123, a pump 124, a nutrient solution discharge valve 125, and a nutrient solution return flow path 127. ..

The nutrient solution tank 122 stores the nutrient solution 2. Here, in the present embodiment, the nutrient solution tank 122, the pipes 105a and 105b, the cultivation tanks 110 of the first cultivation shelf 108a, the second cultivation shelf 108b, and the third cultivation shelf 108c, and the nutrient solution return flow. The nutrient solution system 20 is composed of the road 127 and the road 127. This nutrient solution system 20 is used for hydroponically cultivating at least one kind of leafy vegetables. In the example shown in FIG. 1, the nutrient solution system 20 is used for hydroponically cultivating the plant 1 of the Q strain, which is lettuce, respectively. Further, the nutrient solution system 20 is filled with the nutrient solution 2 having a volume R.

The pump 124 circulates the nutrient solution 2 filled in the nutrient solution system 20. That is, the pump 124 sends the nutrient solution 2 stored in the nutrient solution tank 122 to the cultivation tanks 110 of the first cultivation shelf 108a, the second cultivation shelf 108b, and the third cultivation shelf 108c via the pipe 105a. .. Then, those cultivation tanks 110 store a part of the nutrient solution 2 supplied from the nutrient solution tank 122 by circulation by the pump 124. On the other hand, the nutrient solution 2 already stored in those cultivation tanks 110 is flushed to the nutrient solution tank 122 via the pipe 105b. As a result, the nutrient solution 2 filled in the nutrient solution system 20 circulates. As described above, the plant nutrient solution method in the present embodiment includes a circulation step.

The nutrient solution adjusting unit 123 sets the pH (that is, hydrogen ion index) of the nutrient solution 2 filled in the nutrient solution system 20 and the EC (that is, electrical conductivity) of the nutrient solution 2 to the plant 1 of the Q strain, respectively. Perform nutrient solution adjustment treatment to keep the value constant during the cultivation period of. For example, the nutrient solution adjusting unit 123 measures the pH of the nutrient solution 2 in the nutrient solution tank 122 in order to keep the pH constant, and puts a pH adjusting agent according to the measurement result into the nutrient solution 2. In addition, EC is used as a guideline for fertilizer concentration. That is, in order to keep the EC constant, the nutrient solution adjusting unit 123 measures the EC of the nutrient solution 2 in the nutrient solution tank 122, and puts fertilizer or water according to the measurement result into the nutrient solution 2. As a result, changes in pH and EC are suppressed, so that the nutrient solution 2 can be kept in a better state.

The nutrient solution discharge valve 125 is configured as a nutrient solution discharge unit that discharges a part of the nutrient solution 2 having a volume R from the nutrient solution system 20. That is, the plant nutrient solution method in the present embodiment includes a discharge step. Further, in the present embodiment, the nutrient solution discharge valve 125 is directed from the nutrient solution tank 122 to the cultivation tanks 110 of the first cultivation shelf 108a, the second cultivation shelf 108b, and the third cultivation shelf 108c via the pump 124. A part of the nutrient solution 2 that flows is discharged. Specifically, the nutrient solution discharge valve 125 is attached to a tributary pipe branching from a pipe 105a connecting the pump 124 and the three cultivation tanks 110.

For example, when a part of the nutrient solution 2 from the cultivation tank 110 to the nutrient solution tank 122 is discharged, since the nutrient solution contains a relatively large amount of dust, a part of the nutrient solution 2 is discharged. The dust is easily clogged in the discharge port, and it is difficult to stabilize the discharge of a part of the nutrient solution 2. Further, since the concentration of the nutrient solution component contained in the nutrient solution 2 changes depending on the number of plants 1 arranged in the cultivation tank 110 and the like, a part of the nutrient solution 2 is discharged into the nutrient solution system 20. Concentration tends to be unstable. However, in the present embodiment, a part of the nutrient solution 2 flowing from the nutrient solution tank 122 toward the cultivation tank 110 via the pump 124 is discharged. Therefore, since the nutrient solution 2 contains relatively little dust, it is possible to suppress the above-mentioned clogging of the discharge port and further stabilize the concentration in the nutrient solution system 20. Further, since a part of the nutrient solution 2 pushed out toward the cultivation tank 110 by the pressure of the pump 124 is discharged, the discharge of a part of the nutrient solution 2 can be stabilized.

The nutrient solution inflow unit 121 flows the nutrient solution 2 into the nutrient solution system 20. That is, the plant growing method in the present embodiment includes an inflow step. The nutrient solution 2 flowing in by the nutrient solution inflow section 121 is a new nutrient solution 2 that has not been used for cultivation. Hereinafter, the new nutrient solution 2 is also referred to as a new nutrient solution.

The nutrient solution return flow path 127 branches from the pipe 105a, which is a flow path of the nutrient solution 2 flowing from the pump 124 to the cultivation tank 110 by circulation by the pump 124, and a part of the nutrient solution 2 is partially supplied to the nutrient solution tank 122. It is a pipe to return to. That is, the nutrient solution return flow path 127 connects the nutrient solution 2 so that the nutrient solution 2 flows from the pipe 105a to the nutrient solution tank 122. As a result, a part of the nutrient solution 2 pushed out by the pressure of the pump 124 is directly poured into the nutrient solution tank 122 without passing through the cultivation tank 110, so that the nutrient solution 2 in the nutrient solution tank 122 can be agitated. it can. As a result, the nutrient solution 2 in the nutrient solution tank 122, the new nutrient solution flowing in from the nutrient solution inflow section 121, and the pH adjuster, fertilizer, or water charged by the nutrient solution adjusting section 123 are stirred. Thereby, the quality of the nutrient solution 2 in the nutrient solution tank 122 can be made uniform.

In the plant growing system 100 according to the present embodiment, the nutrient solution discharge valve 125 has a volume R of the nutrient solution so that the discharge amount of the nutrient solution 2 per predetermined period is M from the nutrient solution system 20. Discharge a part of 2. Further, the nutrient solution inflow unit 121 pours the new nutrient solution into the nutrient solution system 20 so that the inflow amount of the new nutrient solution per predetermined period becomes equal to the discharge amount M. This new nutrient solution is a nutrient solution 2 having a potassium ion concentration of a, which is the mass of potassium ions per unit volume. For example, the predetermined period is one day, and the potassium ion concentration a is 320 ppm. In addition, ppm is treated as [mg / L]. Further, for example, the volume amount R is 4500 L, and the discharge amount M and the inflow amount are 500 L, respectively.

In the present embodiment, the amounts such as the discharge amount, the inflow amount, the absorption amount, the mass, and the replenishment amount described later are the amounts per predetermined period, and the predetermined period used for these amounts is one day. Is. However, each amount per predetermined period does not have to be each amount per day as long as it is each amount per same period, and even if it is each amount per hour, for example, each amount per week. It may be each amount.

A part of the nutrient solution 2 in the nutrient solution system 20 is newly added so that the discharge amount per predetermined period and the inflow amount become equal due to the discharge by the nutrient solution discharge valve 125 and the inflow by the nutrient solution inflow unit 121. It is replaced with a nutrient solution, and the replacement is performed at predetermined intervals. That is, without replacing the nutrient solution in the nutrient solution system 20 at once, the nutrient solution having the discharge amount M, which is a part of the nutrient solution 2 having the volume R in the nutrient solution system 20, becomes the new nutrient solution. It can be replaced at any time. In other words, the nutrient solution 2 filled in the nutrient solution system 20 is gradually replaced with a new nutrient solution. Therefore, it is possible to easily suppress the change in the concentration of each nutrient solution component contained in the nutrient solution 2 in the nutrient solution system 20. Further, since not all the nutrient solutions 2 in the nutrient solution system 20 are replaced with new nutrient solutions, that is, because the discharge amount M <R is satisfied, it is possible to suppress the occurrence or prolongation of the rest period. It is possible to suppress the decrease in the operating rate of the plant factory.

FIG. 2 shows changes in EC and pH of nutrient solution 2 and changes in concentration of nutrient solution components when the nutrient solution 2 is not replaced by the nutrient solution discharge valve 125 and the nutrient solution inflow section 121. It is a figure which shows. Specifically, FIG. 2A is a graph showing the transition of EC of the nutrient solution 2 in the nutrient solution tank 122, and FIG. 2B is a graph showing the transition of the nutrient solution in the nutrient solution tank 122. It is a graph which shows the transition of pH of 2. Further, FIG. 2C is a graph showing changes in the potassium ion concentration and the calcium ion concentration of the nutrient solution 2 in the nutrient solution tank 122. It should be noted that these transitions are transitions during the cultivation period of plant 1.

The nutrient solution adjusting unit 123 performs a nutrient solution adjusting process for keeping the EC and pH of the nutrient solution 2 constant as described above. Therefore, as shown in FIGS. 2 (a) and 2 (b), EC and pH are kept substantially constant.

However, when the nutrient solution 2 is not replaced by the nutrient solution discharge valve 125 and the nutrient solution inflow section 121, the potassium ion concentration is increased as the number of cultivation days elapses, as shown in FIG. 2 (c). It decreases, and conversely, the calcium ion concentration increases with the passage of cultivation days. In addition to potassium ions and calcium ions, there are other ions (that is, nutrient solution components) whose concentration increases or decreases with the lapse of cultivation days.

Therefore, even if the EC and pH are kept constant, the balance of the concentrations of the nutrient solution components contained in the nutrient solution 2 is lost with the lapse of cultivation days. The reason why the concentration of the nutrient solution component increases is that the amount of the nutrient solution component absorbed by the cultivated plant is smaller than the amount of the nutrient solution component contained in the fertilizer input by the nutrient solution adjusting unit 123. Because. In addition, the cause of the decrease in the concentration of the nutrient solution component is the amount of the nutrient solution component absorbed by the cultivated plant with respect to the amount of the nutrient solution component contained in the fertilizer input by the nutrient solution adjusting unit 123. Because there are many.

FIG. 3 is a diagram showing the amount of change in the concentration of each nutrient solution component when the nutrient solution 2 is not replaced by the nutrient solution discharge valve 125 and the nutrient solution inflow portion 121.

When the nutrient solution 2 is not replaced, as shown in FIG. 3, the concentration of some nutrient solution components contained in the nutrient solution 2 decreases, and the concentration of some other nutrient solution components becomes substantially constant. It is preserved and the concentration of some other nutrient solution components increases. Hydroponic components whose concentration decreases include potassium ions and nitrate ions. Further, the nutrient solution component whose concentration increases includes magnesium ion, phosphate ion, sulfate ion, calcium ion and the like. For example, when the number of cultivation days is 28 days, the nutrient solution component whose concentration decreases most during that period is potassium ion, and the potassium ion concentration decreases by 260 ppm. On the other hand, the nutrient solution component whose concentration increases most during the 28 days is calcium ion, and the calcium ion concentration increases by 120 ppm.

Such a change in the concentration of each nutrient solution component, that is, an imbalance in the concentration causes a decrease in the yield of the plant 1 or a physiological disorder.

Therefore, in the plant growing system 100 of the present embodiment, the nutrient solution 2 is replaced by the nutrient solution discharge valve 125 and the nutrient solution inflow section 121. That is, the nutrient solution 2 filled in the nutrient solution system 20 is gradually replaced with a new nutrient solution.

FIG. 4 is a diagram for explaining the replacement of the nutrient solution 2 by the nutrient solution discharge valve 125 and the nutrient solution inflow portion 121 in the present embodiment.

As described above, the pump 124 circulates the nutrient solution 2 having a volume R filled in the nutrient solution system 20. At this time, the nutrient solution discharge valve 125 discharges a part of the nutrient solution 2 having a circulating volume R. For example, the nutrient solution discharge valve 125 nourishes the nutrient solution 2 so that the discharge amount M = 500 [L / day] is satisfied, that is, the discharge amount M of the nutrient solution 2 per day becomes 500 L. It is discharged to the outside of the liquid system 20. Further, the nutrient solution inflow unit 121 pours a new nutrient solution 2, that is, a new nutrient solution into the nutrient solution system 20 so as to supplement the discharged nutrient solution 2. Specifically, the nutrient solution inflow unit 121 supplies the new nutrient solution to the nutrient solution system so that the inflow amount becomes equal to the discharge amount M, that is, the inflow amount of the new nutrient solution per day becomes 500 L. Pour into 20.

Here, the nutrient solution 2 having a volume R filled in the nutrient solution system 20 is circulated in the nutrient solution system 20. That is, the nutrient solution 2 is a nutrient solution that has been poured into the cultivation tanks 110 of the first cultivation shelf 108a, the second cultivation shelf 108b, and the third cultivation shelf 108c and used for a while. Therefore, even if the potassium ion concentration of the nutrient solution 2 having a volume R filled in the nutrient solution system 20 is 320 ppm, which is the initial value at the start of cultivation of the plant 1, for example, after the cultivation is started, It has been reduced to 200 ppm. As described above, a part of the nutrient solution 2 used for cultivating the plant 1, that is, the nutrient solution 2 having a potassium ion concentration of 200 ppm is discharged so as to satisfy the discharge amount M = 500 [L / day].

On the other hand, the new nutrient solution flows into the nutrient solution system 20 at an inflow amount of 500 L per day. The potassium ion concentration a of this new nutrient solution is, for example, 320 ppm, which is equal to the above-mentioned initial value, and is higher than the potassium ion concentration (that is, 200 ppm) of the nutrient solution 2 in the nutrient solution system 20. Therefore, the potassium ion concentration of the nutrient solution 2 in the nutrient solution system 20 can be increased to more than 200 ppm by the discharge of the nutrient solution 2 and the inflow of the new nutrient solution. That is, it is possible to suppress a decrease in the potassium ion concentration of the nutrient solution 2 in the nutrient solution system 20.

In addition, an increase in potassium ion concentration can be suppressed. That is, the calcium ion concentration of the nutrient solution 2 having a volume R filled in the nutrient solution system 20 increases after the cultivation is started even if it is set to the initial value at the start of cultivation of the plant 1. There is. As described above, a part of the nutrient solution 2 used for cultivating the plant 1, that is, the nutrient solution 2 having an increased potassium ion concentration is discharged so as to satisfy the discharge amount M = 500 [L / day].

On the other hand, the new nutrient solution flows into the nutrient solution system 20 at an inflow amount of 500 L per day. The calcium ion concentration of this new nutrient solution is the above-mentioned initial value and is lower than the calcium ion concentration of the nutrient solution 2 in the nutrient solution system 20. Therefore, it is possible to suppress an increase in the calcium ion concentration of the nutrient solution 2 in the nutrient solution system 20 due to the discharge of the nutrient solution 2 and the inflow of the new nutrient solution.

Here, the nutrient solution 2 having a volume R filled in the nutrient solution system 20 is used for cultivating the plant 1 of the Q strain. Plant 1 of these Q strains absorbs each nutrient solution component from the nutrient solution 2. For example, the plant 1 of the Q strain absorbs one nutrient solution component from the nutrient solution 2 by the absorption amount G per day.

Further, in the present embodiment, a part of the nutrient solution 2 is discharged by the nutrient solution discharge valve 125, and the new nutrient solution is flowed into the nutrient solution inflow section 121 by the same amount as the discharge amount M of the nutrient solution 2. Therefore, the difference amount of the nutrient solution component obtained by subtracting the mass of the nutrient solution component contained in the discharged nutrient solution 2 from the mass of one nutrient solution component contained in the new nutrient solution is the replenishment amount. It is added to the nutrient solution system 20 as H.

When the absorption amount G> the replenishment amount H, the concentration of the nutrient solution component contained in the nutrient solution 2 in the nutrient solution system 20 decreases. However, due to the decrease in the concentration, on the contrary, the replenishment amount H increases in the above-mentioned discharge and inflow performed thereafter.

When the absorption amount G <replenishment amount H, the concentration of the nutrient solution component contained in the nutrient solution 2 in the nutrient solution system 20 increases. However, as the concentration increases, on the contrary, the replenishment amount H decreases in the above-mentioned discharge and inflow performed thereafter.

Therefore, the change in the concentration of each nutrient solution component contained in the nutrient solution 2 in the nutrient solution system 20 can be suppressed by the discharge of the nutrient solution 2 and the inflow of the new nutrient solution in the present embodiment. Further, in order to keep the concentration of each nutrient solution component constant, the absorption amount G and the replenishment amount H may be made equal. For that purpose, it is necessary to appropriately set the discharge amount M of the nutrient solution 2, that is, the inflow amount of the new nutrient solution. As a result, it is possible to suppress the change in the concentration of each nutrient solution component and further converge the concentration to the target value.

Therefore, in the present embodiment, attention is paid to the potassium ion concentration having the largest change amount among the nutrient solution components, and the nutrient solution discharge valve 125 has ((A × Q) / (ab)) <M <R. The nutrient solution 2 is discharged by a discharge amount M per predetermined period so as to satisfy the above. Here, Q is the number of plants 1 cultivated in the nutrient solution system 20, and b (b <a) is the target value of the potassium ion concentration. Further, A is the minimum amount of absorption among the amount of potassium ions absorbed per predetermined period during the seedling raising period by each of the plants 1 of the Q strain.

As described above, a is the potassium ion concentration of the new nutrient solution, and R is the volume amount of the nutrient solution 2 in the nutrient solution system 20. Further, for example, the unit of potassium ion concentration is ppm or [mg / L], the unit of emission amount M and volume amount R is L, and the unit of absorption amount A is mg.

As a result, it is possible to suppress a decrease in the concentration of potassium ions and converge the concentration to the target value b.

More specifically, the amount of potassium ions absorbed by plant 1 varies depending on the type and growth stage of plant 1. For example, the daily absorption of potassium ions in one lettuce strain is 1.56 to 9.38 [mg / day]. 1.56 [mg / day] is the minimum absorption amount during the seedling raising period, and 9.38 [mg / day] is the maximum absorption amount during the raising period. The lettuce cultivation period is, for example, 35 days from sowing to harvesting, and the cultivation period is divided into a sowing period, a seedling raising period, and a growing period. The sowing period is, for example, 7 days after sowing, the seedling raising period is, for example, 14 days after the sowing period, and the raising period is, for example, 14 days after the seedling raising period. Further, as a unit of the amount of absorption per day, [ppm · L / day] may be used instead of [mg / day]. Therefore, when each of the plants 1 of the Q strain is lettuce, the above-mentioned absorption amount G of potassium ion is (1.56 to 9.38) × Q [ppm · L / day], and the absorption amount A. Is 1.56 [ppm · L / day].

Further, in the example shown in FIG. 4, the above-mentioned potassium ion replenishment amount H is 500 [L / day] × (320 ppm-200 ppm) = 60,000 [ppm · L / day]. Here, if the replenishment amount H and the above-mentioned absorption amount G are equal, the potassium ion concentration can be maintained at 200 ppm.

Therefore, in the present embodiment, the emission amount M satisfies ((A × Q) / (ab)) <M, in other words, in the cultivation after the seedling raising stage, (A × Q) <replenishment amount H. By satisfying = M × (ab), the replenishment amount H can be easily brought close to a state equal to the absorption amount G. As a result, the potassium ion concentration can be maintained at the target value b (for example, 200 ppm). That is, the potassium ion concentration can be converged to the target value b = 200 ppm, and the decrease to less than the target value b can be suppressed. Further, in the present embodiment, since M <R is satisfied, the potassium ion concentration can be easily stabilized without replacing all of the nutrient solution 2 in the nutrient solution system 20 with a new nutrient solution.

Further, in the present embodiment, when the maximum absorption amount of the absorption amount, which is the mass of potassium ions absorbed by each of the plants 1 of the Q strain per predetermined period during the growing period, is B, the emission amount M. Further may satisfy M <((B × Q) / (ab)) <R. When each of the plants 1 of the Q strain is lettuce, the above-mentioned absorption amount G of potassium ion is (1.56 to 9.38) × Q [ppm · L / day], and the absorption amount B is It is 9.38 [ppm · L / day].

As a result, M × (ab) <(B × Q) is satisfied in the cultivation up to the growing season, and M × (ab) corresponds to the replenishment amount H, so that excessive replenishment of potassium ions is avoided. be able to.

Here, in the present embodiment, paying attention to the potassium ion concentration as described above, the emission amount M is ((A × Q) / (ab)) <M <((B × Q) / (a). −B)) The condition of <R is satisfied. The reason is that, as shown in FIG. 3, the amount of change in the potassium ion concentration tends to be larger than the amount of change in the concentration of other nutrient solution components contained in the nutrient solution 2. Therefore, in the present embodiment, if the discharge amount M satisfies the conditions shown by each of the above-mentioned inequalities, the concentration of the other nutrient solution component whose concentration changes less than that of the potassium ion can be kept constant. That is, the change in the concentration of each nutrient solution component other than the potassium ion contained in the nutrient solution 2 in the nutrient solution system 20 can be suppressed and converged to a constant value.

FIG. 5 is a diagram showing the simulation results of the transition of the potassium ion concentration and the transition of the calcium ion concentration in the plant growing system 100 in the present embodiment.

As shown in FIG. 5A, the potassium ion concentration is an initial value of 320 ppm at the start of cultivation, but decreases to 200 ppm after the start of cultivation. However, in the present embodiment, since the nutrient solution 2 is replaced as described above, the potassium ion concentration can be converged to 200 ppm without lowering it below 200 ppm. That is, conventionally, the potassium ion concentration is reduced to, for example, 80 ppm, but in the present embodiment, such a decrease is suppressed, and the potassium-in concentration is reduced to, for example, 200 ppm, which is an appropriate concentration for cultivation of plant 1 of the Q strain. Can be stabilized.

Similarly, as shown in FIG. 5B, the calcium ion concentration is an initial value of 130 ppm at the start of cultivation, but increases to 200 ppm after the start of cultivation. However, in the present embodiment, since a part of the nutrient solution 2 is discharged and the new nutrient solution is inflowed as described above, the calcium ion concentration is converged to 200 ppm without increasing it from 200 ppm. Can be made to. That is, conventionally, the calcium ion concentration increases to, for example, 250 ppm, but in the present embodiment, such an increase is suppressed, and the calcium ion concentration reaches, for example, 200 ppm, which is an appropriate concentration for cultivating the plant 1 of the Q strain. Can be stabilized.

Such stabilization of the concentration of the nutrient solution component contained in the nutrient solution 2 is realized not only with the potassium ion concentration and the calcium ion concentration but also with other nutrient solution components.

Here, in the present embodiment, the nutrient solution inflow section 121 flows a new nutrient solution containing calcium ions having a concentration lower than the potassium ion concentration a into the nutrient solution system 20. In the above example, the potassium ion concentration a contained in the new nutrient solution is 320 ppm, and the calcium ion concentration contained in the new nutrient solution is 130 ppm, but the calcium ion concentration may be lower than 130 ppm. As a result, in the present embodiment, the potassium ion concentration of the nutrient solution 2 filled in the nutrient solution system 20 is kept higher than the calcium ion concentration during the cultivation period of the plant 1 of the Q strain. As a result, since the potassium ion concentration does not fall below the calcium ion concentration, it is possible to suppress the occurrence of physiological disorders in each of the plants 1 of the Q strain.

Further, in the present embodiment, during the cultivation period of the plant 1 of the Q strain, the potassium ion concentration of the nutrient solution 2 filled in the nutrient solution system 20 becomes larger than 150 ppm depending on the setting of the target value b. Be kept. This makes it possible to suppress the occurrence of physiological disorders in each of the plants 1 of the Q strain. Further, in the present embodiment, the calcium ion concentration of the nutrient solution 2 filled in the nutrient solution system 20 may be maintained at less than 200 ppm or less than 150 ppm during the cultivation period of the plant 1 of the Q strain.

FIG. 6 is a flowchart showing the processing operation of the plant growing system 100 in the present embodiment.

For example, each of the nutrient solution discharge valve 125 and the nutrient solution inflow section 121 of the plant growing system 100 in the present embodiment is provided with an electronic control circuit, and opens and closes the valve provided by itself while performing information processing. You may. In this case, the nutrient solution discharge valve 125 first determines whether or not the current time is the start timing of the predetermined period described above (step S1). For example, the predetermined period is one day. In this case, the nutrient solution discharge valve 125 determines whether or not the current time is the start timing, for example, 6:00 am. Then, when the nutrient solution discharge valve 125 determines that the current time is not the start timing (No in step S1), the process from step S1 is repeatedly executed.

On the other hand, when the nutrient solution discharge valve 125 determines that the current time is the start timing (Yes in step S1), the nutrient solution discharge valve 125 discharges a part of the nutrient solution 2 in the nutrient solution system 20 by opening the valve (step). S2). At this time, the nutrient solution discharge valve 125 discharges a part of the nutrient solution 2 so that the discharge amount of the nutrient solution 2 per a predetermined period becomes M. Further, the emission amount M satisfies the condition of ((A × Q) / (ab)) <M <((B × Q) / (ab)) <R.

Further, the nutrient solution inflow unit 121 flows the new nutrient solution into the nutrient solution system 20 by opening the valve provided therein (step S3). At this time, the nutrient solution inflow unit 121 pours in the new nutrient solution so that the inflow amount per predetermined period becomes equal to the above-mentioned discharge amount M.

Then, the nutrient solution discharge valve 125 and the nutrient solution inflow section 121 determine whether or not the termination condition for terminating the cultivation of the plant 1 is satisfied (step S4). For example, the termination condition may be a condition that the power switch of the plant growing system 100 is turned off, or a condition that a predetermined cultivation period has elapsed. Then, when the nutrient solution discharge valve 125 and the nutrient solution inflow section 121 determine that the end condition is satisfied (Yes in step S4), the replacement of the nutrient solution 2 is completed. On the other hand, when it is determined that the end condition of the nutrient solution discharge valve 125 and the nutrient solution inflow unit 121 is not satisfied (No in step S4), the process from step S1 is repeatedly executed.

Here, the discharge of the nutrient solution 2 in step S2 may be performed in a time shorter than the predetermined period of step S1. That is, the predetermined period may include a stop period in which the nutrient solution 2 is not discharged. Similarly, the inflow of the new nutrient solution in step S3 may be performed in a shorter time than the predetermined period in step S1. That is, the predetermined period may include a suspension period in which the inflow of new nutrient solution is not performed.

On the contrary, the discharge of the nutrient solution 2 in step S2 and the inflow of the new nutrient solution in step S3 do not have to include a stop period within a predetermined period. That is, the nutrient solution discharge valve 125 and the nutrient solution inflow section 121 may continuously open the respective valves during a predetermined period to discharge the nutrient solution 2 and flow in the new nutrient solution at a constant flow velocity. In this case, the determination process in step S1 can be omitted. Therefore, each of the nutrient solution discharge valve 125 and the nutrient solution inflow section 121 does not have an electronic control circuit that performs the determination process of step S1, and according to the opening degree of the valve set by the user of the plant growing system 100. The nutrient solution 2 may be discharged and the new nutrient solution may be inflowed. Further, when there is no rest period as described above, the concentration of each nutrient solution component contained in the nutrient solution 2 in the nutrient solution system 20 can be more appropriately stabilized as compared with the case where there is a rest period.

As described above, in the plant growing system 100 of the present embodiment, a part of the nutrient solution in the nutrient solution system is replaced with a new nutrient solution so that the discharge amount and the inflow amount per predetermined period are equal, and the replacement is performed. It is done every predetermined period. Therefore, it is possible to easily suppress the change in the concentration of each nutrient solution component contained in the nutrient solution in the nutrient solution system. Furthermore, since not all the nutrient solutions in the nutrient solution system are replaced with new nutrient solutions, that is, because the discharge amount M <R is satisfied, it is possible to suppress the occurrence or prolongation of the rest period. It is possible to suppress a decrease in the operating rate of the plant factory. Further, in the plant growing system 100 of the present embodiment, the emission amount M satisfies ((A × Q) / (ab)) <M. Therefore, the replenishment amount H of potassium ions replenished per predetermined period, that is, M × (ab) is the minimum absorption amount of potassium ions consumed by the plant of the Q strain per predetermined period, that is, (A ×). More than Q). Therefore, by replacing the nutrient solution described above, the replenishment amount H and the absorption amount G can be easily brought close to the same state, and the potassium ion concentration can be stabilized. That is, the potassium ion concentration can be kept constant at the target value b. Furthermore, when the potassium ion concentration is most likely to change among the concentrations of each nutrient solution component contained in the nutrient solution, the concentration of not only potassium ion but also all other nutrient solution components becomes constant by the above-mentioned replacement. Can be kept. Further, in the present embodiment, the emission amount M satisfies M <((B × Q) / (ab)) <R. As a result, the replenishment amount H of potassium ions replenished per predetermined period, that is, M × (ab), is the maximum absorption amount of potassium ions consumed by the plant of the Q strain per predetermined period, that is, (B). Less than × Q). Therefore, excessive replenishment of potassium ions can be avoided.

Further, in the above example, each of the plants 1 of the Q strain is lettuce. However, the plant cultivated by the plant growing system 100 in the present embodiment may be a plant other than lettuce as long as it is a leafy vegetable. Therefore, when each of the plants 1 of the Q strain is lettuce, the above-mentioned absorption amount A is 1.56 [ppm · L / day], but since it may be another plant, the absorption amount A Is a value that satisfies 1 [ppm · L / day] <A <5 [ppm · L / day]. That is, when the above-mentioned predetermined period is one day, the absorption amount A may be larger than 1 mg and less than 5 mg. Similarly, when each of the plants 1 of the Q strain is lettuce, the above-mentioned absorption amount B is 9.38 [ppm · L / day], but since it may be another plant, the absorption amount B may be a value satisfying 8 [ppm · L / day] <B <20 [ppm · L / day]. That is, when the above-mentioned predetermined period is one day, the absorption amount B may be larger than 8 mg and less than 20 mg.

(Modification example)
The plant growing system and the plant growing method according to one or more embodiments have been described above based on the embodiments, but the present disclosure is not limited to the embodiments. As long as it does not deviate from the purpose of the present disclosure, various modifications that can be conceived by those skilled in the art may be included in the scope of the present disclosure.

For example, in the above embodiment, the plant growing system 100 cultivates the plant 1 of the Q strain, which is lettuce, respectively. That is, the plants 1 of the Q strain cultivated by the plant growing system 100 are of the same type. However, the plant 1 of the Q strain cultivated by the plant growing system 100 does not have to be the same, and the plant growing system 100 may cultivate a plurality of types of plants. In other words, the plant 1 of the Q strain may contain a plurality of types of plants 1 that are different from each other. Even in this case, the absorption amount A is the minimum absorption amount of the absorption amounts of the plurality of types of plants 1 in each seedling raising period. The amount of absorption per plant 1 in the seedling raising period may be the minimum absorbed amount in the seedling raising period. Similarly, the absorption amount B is the maximum absorption amount of the absorption amounts of the plurality of types of plants 1 in each growing period. The amount of absorption per plant 1 in the growing period may be the maximum amount absorbed in the growing period.

Further, in the above embodiment, as shown in FIG. 5, the potassium ion concentration and the calcium ion concentration slightly change from the initial values in the first crop, but in the second and subsequent crops, after the middle of the first crop. Since their concentrations are kept constant, the change can be further suppressed.

Further, in the above embodiment, the plant growing system 100 includes the nutrient solution adjusting unit 123, but the nutrient solution adjusting unit 123 may not be provided.

Further, in the above embodiment, the volume amount of the nutrient solution 2 per strain may be 1 L or less. That is, the volume amount of the nutrient solution 2 calculated by the volume amount R / Q strain may be 1 L or less. Thereby, the volume amount R can be reduced and the amount of the nutrient solution 2 used can be saved. Further, the smaller the volume R of the nutrient solution 2, the more easily the concentration of each nutrient solution component contained in the nutrient solution 2 changes. However, in the plant growing system 100 of the present embodiment, the change is suppressed and those changes are suppressed. The concentration can be kept constant.

Further, in the plant growing system 100 in the above embodiment, lettuce is mentioned as an example of plant 1, but plant 1 may be a leafy vegetable plant other than lettuce. In leafy vegetable plants, the potassium ion concentration changes significantly, so that even leafy vegetable plants other than lettuce can obtain the same effects as those in the above-described embodiment.

Further, in the plant growing system 100 in the above embodiment, filters and the like may be installed in the pipes 105a and 105b and the like. In this case, the nutrient solution 2 circulated in the nutrient solution system 20 can be purified by the filter.

In the above embodiment, each component such as the light source control unit 102, the nutrient solution inflow unit 121, the nutrient solution discharge valve 125, and the nutrient solution adjusting unit 123 may include an electronic control circuit. The electronic control circuit may be composed of dedicated hardware or may execute a software program suitable for each component. In the electronic control circuit, a program execution unit such as a CPU or a processor may read and execute a software program recorded on a recording medium such as a hard disk or a semiconductor memory. For example, the nutrient solution inflow unit 121 and the nutrient solution discharge valve 125 execute each step included in the flowchart of FIG. 6 by reading and executing a software program.

In the present disclosure, the numerical range may be described as m to n (m and m are integers different from each other), but the numerical range in m to n includes m and n. Further, the numerical range may be not only m to n but also an arbitrary range included in the m to n.

The present disclosure can easily stabilize the concentration of each nutrient solution component contained in the nutrient solution, and can be used for a system or an apparatus for cultivating a plant such as lettuce.

1 Plant 2 nutrient solution 10 light source 20 nutrient solution system 100 plant growth system 101 cultivation plate 102 light source control unit 104 ceiling plate 105a, 105b piping 108a, 108b, 108c cultivation shelf 109 cultivation device 120 nutrient solution management unit 121 nutrient solution inflow unit 122 Nutrient solution tank 123 Nutrient solution adjustment unit 124 Pump 125 Nutrient solution discharge valve

Claims (12)

From the nutrient solution system filled with the nutrient solution of volume R, which is used for hydroponically cultivating at least one kind of leafy vegetables, the amount of nutrient solution discharged per predetermined period is M. A discharge process that discharges a part of the nutrient solution of volume R,
The nutrient solution system using the nutrient solution having a potassium ion concentration of a, which is the mass of potassium ions per unit volume, as the new nutrient solution so that the inflow amount of the new nutrient solution per predetermined period becomes equal to the discharge amount M. Including the inflow process of pouring into
The number of plants cultivated in the nutrient solution system is Q strain (Q is an integer of 1 or more).
The target value of the potassium ion concentration is b (b <a),
When the minimum absorption amount of the absorption amount which is the mass of potassium ions absorbed per predetermined period during the seedling raising period by each of the plants of the Q strain is A.
The emission amount M satisfies ((A × Q) / (ab)) <M <R.
How to grow plants. When the predetermined period is one day, the absorption amount A is larger than 1 mg and less than 5 mg.
The plant growing method according to claim 1. When the maximum absorption amount of the absorption amount which is the mass of potassium ions absorbed in the predetermined period by each of the plants of the Q strain during the growing period is B.
The emission amount M further satisfies M <((B × Q) / (ab)) <R.
The plant growing method according to claim 1 or 2. When the predetermined period is one day, the absorption amount B is larger than 8 mg and less than 20 mg.
The plant growing method according to claim 3. The above-mentioned plant growing method further
Each of the hydrogen ion index of the nutrient solution filled in the nutrient solution system and the electrical conductivity of the nutrient solution is subjected to a nutrient solution adjustment treatment to maintain a constant value during the cultivation period of the plant of the Q strain. ,
The plant growing method according to any one of claims 1 to 4. In the inflow step, the new nutrient solution containing calcium ions having a concentration lower than the potassium ion concentration a is poured into the nutrient solution system.
During the cultivation period of the plant of the Q strain, the potassium ion concentration of the nutrient solution filled in the nutrient solution system is kept higher than the calcium ion concentration.
The plant growing method according to any one of claims 1 to 5. During the cultivation period of the plant of the Q strain, the potassium ion concentration of the nutrient solution filled in the nutrient solution system is kept higher than 150 ppm depending on the setting of the target value b.
The plant growing method according to any one of claims 1 to 5. The above-mentioned plant growing method further
Including a circulation step in which a pump circulates the nutrient solution filled in the nutrient solution system.
The nutrient solution system
A nutrient solution tank for storing nutrient solution and
It has at least one cultivation tank in which a part of the nutrient solution supplied from the nutrient solution tank by circulation by the pump is stored and the plant of the Q strain is arranged.
In the discharge process,
A part of the nutrient solution flowing from the nutrient solution tank toward the at least one cultivation tank via the pump is discharged.
The plant growing method according to any one of claims 1 to 7. The above-mentioned plant growing method further
Including a circulation step in which a pump circulates the nutrient solution filled in the nutrient solution system.
The nutrient solution system
A nutrient solution tank for storing nutrient solution and
It has at least one cultivation tank in which a part of the nutrient solution supplied from the nutrient solution tank by circulation by the pump is stored and the plant of the Q strain is arranged.
In the circulation step, further
A part of the nutrient solution flowing from the pump toward the at least one cultivation tank by circulation by the pump is returned to the nutrient solution tank.
The plant growing method according to any one of claims 1 to 7. A nutrient solution system filled with a nutrient solution having a volume R, which is used for hydroponically cultivating at least one kind of leafy vegetables, respectively.
A nutrient solution discharge unit that discharges a part of the nutrient solution having a volume R from the nutrient solution system so that the amount of the nutrient solution discharged per predetermined period is M.
The nutrient solution system using the nutrient solution having a potassium ion concentration of a, which is the mass of potassium ions per unit volume, as the new nutrient solution so that the inflow amount of the new nutrient solution per predetermined period becomes equal to the discharge amount M. Equipped with a nutrient solution inflow part to pour into
The number of plants cultivated in the nutrient solution system is Q strain (Q is an integer of 1 or more).
The target value of the potassium ion concentration is b (b <a),
When the minimum absorption amount of the absorption amount which is the mass of potassium ions absorbed per predetermined period during the seedling raising period by each of the plants of the Q strain is A.
The emission amount M satisfies ((A × Q) / (ab)) <M <R.
Plant growing system. The plant growing system further
A pump for circulating the nutrient solution filled in the nutrient solution system is provided.
The nutrient solution system
A nutrient solution tank for storing nutrient solution and
It has at least one cultivation tank in which a part of the nutrient solution supplied from the nutrient solution tank by circulation by the pump is stored and the plant of the Q strain is arranged.
The nutrient solution discharge unit
A part of the nutrient solution flowing from the nutrient solution tank toward the at least one cultivation tank via the pump is discharged.
The plant growing system according to claim 10. The plant growing system further
A pump for circulating the nutrient solution filled in the nutrient solution system is provided.
The nutrient solution system
A nutrient solution tank for storing nutrient solution and
At least one cultivation tank in which a part of the nutrient solution supplied from the nutrient solution tank by circulation by the pump is stored and the plant of the Q strain is arranged.
It has a nutrient solution return flow path that branches from the nutrient solution flow path that flows from the pump toward the at least one cultivation tank by circulation by the pump and returns a part of the nutrient solution to the nutrient solution tank.
The plant growing system according to claim 10.

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