Drainage management device, irrigation management system, and drainage management method in hydroponics

Abstract

The purpose of the present invention is to easily manage drainage in hydroponics.　A drainage temperature sensor 12 capable of measuring the temperature of drainage is provided in a discharge path of the drainage, and when the drainage temperature sensor 12 detects a temperature change of a prescribed amount or more, the sensor indicates that the drainage has reached the discharge path. If the temperature change can be measured by the drainage temperature sensor 12, the presence or absence of drainage can be determined, making it easy to know when drainage has occurred throughout the day. A drainage temperature sensor capable of being brought into contact with the drainage is only required to be installed in the discharge path, the structure is extremely simple, and the attaching work is extremely easy.

Description

Drainage management device, irrigation management system, and drainage management method for hydroponics

[0001] The present invention relates to a technique for managing drainage and irrigation in hydroponic cultivation.

[0002] Patent Document 1 discloses an irrigation device for supplying nutrient solution in hydroponics. This device memorizes optimal irrigation times and intervals for each plant type, allowing the user to select the type of plant being cultivated and automatically irrigate the plant appropriately. In addition to the plant type, the device also includes a correction mechanism for further optimizing the irrigation interval. The correction mechanism corrects the irrigation interval using various data obtained from the following: soil compaction, soil specific gravity, soil particle size, soil water retention using the amount of water detected by a water sensor installed in the drainage outlet, water penetration time from the time of water supply to the time when moisture is detected by a water sensor installed directly below the drainage hole of the flowerpot, ambient temperature using a temperature sensor installed around the plant, ambient humidity using a humidity sensor installed around the plant, wind volume around the plant, and solar radiation around the plant.

[0003] Patent Document 2 discloses a technique for detecting the temperature of a water supply path and the temperature of the soil, and controlling the amount of irrigation water based on the relationship between the temperature of the water supply path and the temperature of the soil.

[0004] Patent Document 3 discloses an apparatus in which each hydroponic culture medium placed on a cultivation bench is irrigated using the same number of irrigation tubes branching off from a liquid supply pipe, and a medium weight measuring device is installed between some of the hydroponic culture medium and the cultivation bench, measuring the medium weight together with time information, and thereby graphing and monitoring changes in the cumulative amount of liquid supply due to irrigation conditions over time.

[0005] Non-patent document 1 discloses an apparatus that stores waste liquid in a waste liquid tank, stops supplying the liquid when the amount of waste liquid reaches a predetermined level, drains the waste liquid from the waste liquid tank until the water level returns to a predetermined level, and then repeats the process of supplying the liquid again according to the settings.

[0006] Japanese Patent Laid-Open No. 6-70653 Japanese Patent Laid-Open No. 2024-135 Japanese Patent Laid-Open No. 2018-14902

[0007] Toyotane Corporation, website, product information, description of the supply and drainage measuring device "Haieki Toban" (product name) URL: https: / / www.toyotane.co.jp / products / 001903.html Inochio Holdings Corporation, website, product corresponding to Patent Document 3: description of Slab Sight (registered trademark) URL: https: / / inochio.co.jp / products / cultivation-systems / slabsight Priva, Priva Groscale manual URL: https: / / www.manualslib.com / manual / 1742601 / Priva-Compass.html?page=103#manual

[0008] The technologies disclosed in Patent Documents 1 and 2 use various sensors to monitor soil conditions, the temperature and humidity around the plants, the temperature of the water supply path, and the ground temperature in order to optimize the amount of water supply (irrigation) and the intervals between water supply (irrigation). However, since it is necessary to know various conditions from water supply to drainage, the use of dedicated equipment is required. Furthermore, when managing multiple greenhouses, installing multiple such devices is very costly.

[0009] On the other hand, the device disclosed in Non-Patent Document 1 uses a method for simplifying irrigation management by measuring the amount of water supply and drainage and calculating the daily drainage rate as the ratio between the two. A desirable drainage rate indicates that the moisture content in the medium is appropriate and irrigation management is being carried out well. The desirable drainage rate is, for example, in the range of 8 to 40%, depending on the type of plant, type of medium, and season, with a value of around 30% being considered preferable for tomatoes, for example. This method can be implemented at relatively low cost because it only requires measuring the amount of water supply and drainage.

[0010] However, there are cases where drainage is low during the day and high in the morning and evening. This is because there is sufficient sunlight during the day and plants have a high water demand. On the other hand, since sufficient air needs to be supplied to the medium at night, water supply in the evening needs to be reduced. However, in the case of the device in Non-Patent Document 1, the drainage rate is calculated once a day. Therefore, even if the daily drainage rate is a guideline value, for example, around 30%, it may not be possible to control the rate appropriately to match the changes in the plant's water demand over the course of a day.

[0011] In contrast, Patent Document 3 installs a culture medium weight measuring device and measures culture medium weight along with time information, enabling chronological management of irrigation conditions throughout the day. However, the culture medium weight measuring device of Patent Document 3 is installed on a cultivation bench supporting multiple nutrient culture media to monitor weight changes in the multiple nutrient culture media in order to more accurately determine irrigation conditions. Therefore, as shown in Non-Patent Document 2, which describes a product corresponding to Patent Document 3, the culture medium weight measuring device must be capable of measuring an object of a size equivalent to that of a cultivation bench supporting multiple nutrient culture media, and must be installed to firmly support the cultivation bench and not easily removable. Therefore, the culture medium weight measuring devices of Patent Document 3 and Non-Patent Document 2 are complicated to install, and once installed, relocation requires even more complicated removal and re-installation, resulting in increased labor costs. Note that the device disclosed in Non-Patent Document 3 also measures culture medium weight like the device disclosed in Non-Patent Document 2, but the installation process is extensive and suffers from the same problems as Non-Patent Document 2.

[0012] The present invention has been made in consideration of the above, and aims to provide a technology that does not require large-scale installation work, is easy to attach and detach, is compact, can easily accommodate the relocation of culture media, and can reliably manage drainage.

[0013] In order to solve the above problems, the present invention provides a drainage management device for hydroponics, which has a drainage temperature sensor that is provided in a drainage path for drainage drained from a culture medium in which a plant to be cultivated is planted, and is capable of measuring the temperature of the drainage, and a drainage determination unit that receives measurement data from the drainage temperature sensor and determines the timing at which a temperature change of a predetermined level or more is detected as the drainage timing at which the drainage occurred.

[0014] It is preferable that the device has a culture medium support frame that supports the culture medium, the culture medium support frame is provided with the discharge path, a retention section in the discharge path where the drained liquid temporarily stays, and a temperature-sensing part of the drained liquid temperature sensor is provided so as to be able to contact the drained liquid in the retention section.It is also preferable that the discharge path is configured with a drain pipe, the drained liquid temperature sensor is provided so that its temperature-sensing part is located within the drain pipe, and a guide member is provided in the drain pipe upstream of the position where the temperature-sensing part is provided to guide the drained liquid so that it comes into contact with the temperature-sensing part.It is also preferable that a heating member is provided to heat the drained liquid temperature sensor.

[0015] The present invention also provides an irrigation management system for hydroponics, comprising: the drainage solution management device; a solution supply unit that supplies nutrient solution to a plant to be cultivated; a solution supply temperature sensor capable of measuring the solution supply temperature of the nutrient solution; and a solution supply determination unit that receives measurement data from the solution supply temperature sensor and determines the timing at which a temperature change of a predetermined value or more is detected as the solution supply timing. It is preferable that a heating member be provided to heat the solution supply temperature sensor. It is also preferable that the solution supply temperature sensor be configured such that a temperature sensing unit is provided near the outlet of the solution supply unit and measures the temperature of the nutrient solution discharged from the outlet as the solution supply temperature. It is also preferable that the temperature sensing unit of the solution supply temperature sensor be located in a solution supply pipe that constitutes the solution supply unit and measures the temperature of the nutrient solution passing through the solution supply pipe as the solution supply temperature.

[0016] The present invention also provides a method for managing drainage in hydroponics, which manages the presence or absence of drainage by determining the timing of the occurrence of drainage when a drainage temperature sensor, which is provided in a drainage path of drainage from a culture medium in which a plant to be cultivated is planted and capable of measuring the temperature of the drainage, indicates a temperature change of a predetermined value or more. In this case, it is preferable to preheat the drainage temperature sensor and measure the temperature of the drainage.

[0017] According to the present invention, a wastewater temperature sensor capable of measuring the temperature of the wastewater is provided in the wastewater discharge path, and when the wastewater temperature sensor detects a temperature change of a predetermined value or more, it indicates that the wastewater has reached the discharge path. In other words, it indicates that the culture medium has spread throughout the culture medium and the moisture content of the culture medium has reached a full water level. If the temperature change can be measured using the wastewater temperature sensor, it is possible to determine whether or not wastewater is being discharged, making it easy to know when wastewater has occurred in a day. In this invention, it is sufficient to provide a wastewater temperature sensor in the discharge path that can come into contact with the wastewater, which makes the structure extremely simple and the installation process extremely easy. Since the installation process simply involves fixing the sensor in a predetermined position in the discharge path, it is also easy to remove and to easily accommodate relocation of the culture medium.

[0018] FIG. 1(a) is a diagram showing the schematic configuration of a drainage fluid management device according to one embodiment of the present invention, and FIG. 1(b) is an enlarged view of a portion where a drainage fluid temperature sensor is disposed. FIG. 2 is a diagram for explaining the flow direction of drainage fluid. FIG. 3(a) is a diagram showing the schematic configuration of an irrigation management system including the drainage fluid management device, and FIG. 3(b) is an enlarged view of a portion where a supply fluid temperature sensor is disposed. FIG. 4 is a diagram showing the irrigation management system and a culture medium supported by a culture medium support frame. FIG. 5 is a diagram showing the overall configuration of the irrigation management system with a culture medium set on the culture medium support frame. FIG. 6 is a diagram showing measurement results of Experimental Example 1. FIG. 7 is a diagram showing measurement results of Experimental Example 2. FIG. 8 is a diagram showing an example of measurement results of Experimental Example 3. FIG. 9 is a diagram showing another example of measurement results of Experimental Example 3. FIG. 10 is a diagram showing the schematic configuration of an irrigation management system according to another embodiment of the present invention. FIG. 11(a) is an enlarged view of the area where the supply temperature sensor is located, FIG. 11(b) is a perspective view showing the configuration of the drainage restriction member, and FIG. 11(c) is a diagram illustrating the locations of the drainage restriction member and the drainage temperature sensor. FIG. 12 is a side view of the irrigation control system shown in FIG. 10. FIG. 13 shows the measurement results of Experiment 4, in which neither the supply temperature sensor nor the drainage temperature sensor was heated. FIG. 14 shows the measurement results of Experiment 4, in which both the supply temperature sensor and the drainage temperature sensor were heated. FIG. 15 is a side view of an irrigation control system according to another embodiment of the present invention. FIG. 16 is a diagram illustrating an embodiment in which a supply temperature passage is formed in a sensor support frame for arranging the supply temperature sensor. FIG. 17 is a perspective view illustrating an irrigation control system according to yet another embodiment of the present invention. FIG. 18 is a perspective view illustrating the supply temperature section employed in the embodiment of FIG. 17. 19(a) is a perspective view showing the discharge regulating member employed in the embodiment of FIG. 17, FIG. 19(b) is a diagram showing a cross section of the discharge regulating member in a state where a discharge temperature sensor is disposed on the discharge regulating member, and FIG. 19(c) is a perspective view showing the appearance of the discharge regulating member and the discharge temperature sensor attached to a drainage pipe.

[0019] The present invention will be described in more detail below based on the embodiments shown in the drawings. Fig. 1 is a diagram showing a schematic configuration of a wastewater management device 1 according to one embodiment of the present invention. The wastewater management device 1 has a culture medium support frame 11, a wastewater temperature sensor 12, and a wastewater determination unit 13.

[0020] The culture medium support frame 11 is formed in a roughly rectangular box shape with a predetermined width and length, and has a bottom surface 11a and side surfaces 11b, 11b along the longitudinal direction. A synthetic resin flat plate 11c is placed on the bottom surface 11a, and the culture medium 2 is placed on this flat plate 11c (see Figures 4 and 5). The flat plate 11c has the function of suppressing temperature rise of the culture medium 2. The culture medium 2 is composed of, for example, a planting medium 2a and a seedling raising medium 2b. In this case, the plants to be cultivated are raised in the seedling raising medium 2b and then placed on the planting medium 2a for growth. The culture medium 2 can be composed of rock wool, peat moss, coconut shells, etc. However, the form and material of the culture medium 2 are not limited to these.

[0021] The culture medium support frame 11 is positioned at a slight incline along the longitudinal direction, and as shown in FIG. 2, the drainage liquid flows to the lower side. A retention section 11d is provided at the lower longitudinal end, where the drainage liquid temporarily accumulates. A drainage hole 11e is provided in the retention section 11d (see FIG. 2), and a partition plate 11f is positioned at an angle to direct the drainage liquid toward the retention section 11d and the drainage hole 11e. The drainage liquid from the culture medium 2 flows toward the lower side of the longitudinal direction on the flat plate 11c surrounded by the side sections 11b, 11b, and is restricted by the partition plate 11f toward the retention section 11d and the drainage hole 11e. Therefore, the inside surrounded by the bottom section 11a, side sections 11b, 11b, etc. of the culture medium support frame 11 serves as a drainage path for the drainage liquid.

[0022] The wastewater temperature sensor 12, which may be a glass thermometer, metal thermometer, thermocouple, thermistor, or the like, is disposed via a sensor support frame 12c at any location in the wastewater discharge path, preferably in the retention section 11d, so that the temperature-sensing section 12a is located via the sensor support frame 12c. At the beginning of the day, before new wastewater passes through the discharge path, the temperature-sensing section 12a is not in contact with the new wastewater, and therefore detects a temperature approximately equal to the room temperature (house temperature) in the greenhouse in which the wastewater management device 1 is installed. However, once water supply begins and new wastewater comes into contact with the temperature-sensing section 12a, the detected temperature changes. The temperature change associated with contact with the wastewater is usually manifested as a decrease in the detected temperature because the wastewater temperature is lower than the greenhouse temperature. However, depending on the season, the wastewater temperature may be higher than the greenhouse temperature, resulting in an increase in detection sensitivity.

[0023] The drainage determination unit 13 receives the measurement data from the drainage temperature sensor 12 and determines the timing at which a temperature drop or rise (temperature change) of a predetermined level or more is detected as the timing at which drainage occurred. The drainage determination unit 13 is composed of a control panel including an electric circuit that can receive the measurement data and output the timing at which drainage occurred, or is composed of a computer (personal computer, portable information terminal, etc.) or the like on which a computer program is installed that receives the measurement data from the drainage temperature sensor 12, compares it with previously received data to determine whether a temperature change of a predetermined level or more has occurred, and if a temperature change of a predetermined level or more has occurred, outputs the timing at which drainage occurred.

[0024] According to this embodiment, after the culture medium is supplied and distributed throughout the culture medium 2, the culture medium is discharged as wastewater from the culture medium 2. The wastewater flows through the drainage path of the culture medium support frame 11. When the wastewater reaches the retention section 11d and comes into contact with the temperature-sensing section 12a of the wastewater temperature sensor 12, the temperature indicated by the wastewater temperature sensor 12, which is sent to the wastewater determination section 13, becomes a temperature that is lower or higher than the temperature close to the greenhouse air temperature up to that point. If the wastewater determination section 13 determines that the lowered or higher temperature is equal to or higher than a predetermined threshold, it outputs an indication that wastewater has occurred. According to this embodiment, whether wastewater has occurred can be detected solely by temperature changes. Therefore, the timing of wastewater occurrence during a day can be determined using an extremely inexpensive device.

[0025] Furthermore, since the occurrence of drainage can be detected by detecting temperature changes, even without the device configuration of the drainage management device 1 of this embodiment, by placing the temperature-sensing element 12a of the drainage temperature sensor 12 in the drainage path, such as the retention section 11d, and visually checking the temperature change, an operator can determine the timing of drainage. Confirming that drainage has occurred indicates that sufficient water has been supplied to the medium 2, preventing water shortages even during the daytime when plants have high water demands. If the drainage temperature sensor 12 detects a temperature change greater than a predetermined value during the evening or other times when water supply is unnecessary, this indicates that unnecessary water supply has occurred, and in such cases, the water supply operation should be promptly stopped. As a result, appropriate irrigation management, including water supply operations, can be performed simply by managing the temperature of the drainage water.

[0026] In this embodiment, the occurrence of drainage is determined when the drainage temperature sensor 12 detects a temperature change of a predetermined value or more. However, if the temperature of the drainage is not significantly different from the greenhouse air temperature, which is the temperature detected by the drainage temperature sensor 12 before contacting the drainage, it is difficult to detect a temperature change of a predetermined value or more. Therefore, it is preferable to preheat the drainage temperature sensor 12 to a temperature above the predetermined value. More preferably, it is preheated to a temperature above the highest of the drainage temperature, the supply liquid temperature, and the greenhouse air temperature. In this way, when the drainage comes into contact with the temperature-sensing portion 12a of the drainage temperature sensor 12, a significant temperature drop is observed, allowing the occurrence of drainage to be accurately detected even under conditions of high daytime greenhouse air temperatures.

[0027] 1(a) and 1(b), in order to heat the wastewater temperature sensor 12 to a predetermined temperature or higher, a heating member 14 connected to a heating power source is preferably provided adjacent to the temperature-sensing portion 12a of the wastewater temperature sensor 12. The heating member 14 may be any member capable of raising the temperature of the wastewater temperature sensor 12, and may be, for example, a heater that utilizes resistance heating. Preferably, the heating member 14 is pre-unitized using a sensor support frame 12c so as to be positioned at a predetermined distance from the temperature-sensing portion 12a of the wastewater temperature sensor 12, and the temperature of the heating member 14, which decreases upon contact with the wastewater, is quickly raised to the predetermined temperature.

[0028] As shown in FIGS. 3 to 5 , the drainage liquid management device 1 is combined with a liquid supply unit 21, a liquid supply temperature sensor 22, and a liquid supply determination unit 23 to form an irrigation management system 100. The liquid supply unit 21 may supply liquid to the culture medium in which the target plant is planted. It includes a liquid supply tube 21a made of synthetic resin, rubber, metal, or the like, connected to a liquid supply source (not shown). The liquid supply method is not limited and may include various known methods, such as drip or sprinkler methods. The liquid supply temperature sensor 22 measures the temperature of the culture liquid supplied from the liquid supply unit 21. As shown in FIGS. 3( a) and 3(b), the liquid supply temperature sensor 22 is supported by a sensor support frame 22c. The sensor support frame 22c is generally box-shaped, has a sensor placement hole 22d, and has downwardly protruding legs 22e. The sensor support frame 22c also includes a cylindrical tube tip support 22f that supports the vicinity of the outlet 21b located at the tip of the liquid supply tube 21a that constitutes the liquid supply unit 21. The tube tip support portion 22f is provided adjacent to the sensor placement hole 22d, and when the vicinity of the discharge port 21b is inserted into the tube tip support portion 22f, the culture fluid discharged from the discharge port 21b can come into contact with the temperature sensing portion 22a of the liquid supply temperature sensor 22 arranged in the sensor placement hole 22d.

[0029] The sensor support frame 22c is placed, for example, with its legs 22e inserted into the seedling growing medium 2b. This allows the temperature of the culture solution to be measured by supplying the culture solution to the seedling growing medium 2b from the solution supply unit 21. As with the drainage solution temperature sensor 12, the solution supply temperature sensor 22 can be a thermocouple, a thermistor, or the like.

[0030] The liquid supply determination unit 23 receives measurement data from the liquid supply temperature sensor 22 and determines the timing at which a temperature change of a predetermined value or more is detected as the liquid supply timing. Similar to the liquid discharge temperature sensor 12, the liquid supply temperature sensor 22 detects a temperature change of a predetermined value or more as a temperature decrease or increase depending on the season, etc. Similarly to the liquid discharge determination unit 13, the liquid supply determination unit 23 can be configured from a control panel including an electrical circuit capable of receiving measurement data from the liquid supply temperature sensor 22 and determining whether a temperature change of a predetermined value or more is detected in the measurement data, or a computer on which a computer program executing such a function is installed. The liquid supply determination unit 23 and the liquid discharge determination unit 13 may be separate or may be configured on the same control panel or computer as shown in FIG. 5 . While FIG. 5 schematically illustrates a "Profinder (registered trademark)" 50 manufactured by Seiwa Co., Ltd., which is a device for measuring greenhouse environmental factors such as temperature, humidity, solar radiation, and carbon dioxide, the liquid supply determination unit 23 and the liquid discharge determination unit 13 can be incorporated into the Profinder 50.

[0031] In the irrigation management system 100 of this embodiment, when the culture solution (supply solution) supplied from the outlet 21b of the supply solution unit 21 comes into contact with the temperature-sensing element 22a of the supply solution temperature sensor 22, the temperature detected by the supply solution temperature sensor 22, which had previously indicated a temperature close to the greenhouse air temperature, changes. The supply solution determination unit 23 uses this information to detect the timing of supply solution. The supplied culture solution spreads throughout the culture medium, is discharged from the culture medium 2, and reaches the retention portion 11d of the culture medium support frame 11 as wastewater. The drainage solution temperature sensor 12, whose temperature-sensing element 12a is located in the retention portion 11d, changes its detected temperature upon contact with the wastewater. This allows for confirmation that drainage has occurred a predetermined time after supply, i.e., that the culture solution has permeated the culture medium 2. Therefore, the irrigation management system 100 can detect situations in which wastewater is not detected despite supplying the culture solution, or the time interval between when the culture solution was supplied and when wastewater was detected. As a result, it is possible to know the status of water supply and drainage over the course of a day, allowing for detailed irrigation management.

[0032] 3(a) and 3(b), a heating member 24 connected to a heating power source via a sensor support frame 22c is preferably provided near the temperature-sensing portion 22a of the supply liquid temperature sensor 22, similar to the waste liquid temperature sensor 12. More preferably, the temperature is heated to or above the highest temperature among the waste liquid temperature, the supply liquid temperature, and the air temperature inside the greenhouse. As a result, when the waste liquid comes into contact with the temperature-sensing portion 22a of the supply liquid temperature sensor 22, a significant drop in temperature will occur, similar to the waste liquid temperature sensor 12.

[0033] (Experimental Example 1) As shown in Figure 5, a liquid supply unit 21 (drip tube) was placed in the seedling raising medium 2b of the medium 2, and the temperature sensing unit 22a of the liquid supply temperature sensor 22 was positioned near the outlet of the liquid supply unit 21 to measure the liquid supply temperature. The liquid supply conditions were as follows. The cultivated plants were tomatoes.

[0034] a) Between 1 hour 30 minutes and 5 hours 30 minutes after sunrise: solar radiation 60 J / cm ２ b) Between 5 hours 30 minutes and 9 hours after sunrise: Solar radiation 100 J / cm ２ c) Between 9 hours after sunrise and 1 hour 45 minutes before sunset: Solar radiation 110 J / cm ２ (However, regardless of the cumulative amount of solar radiation, the minimum waiting time for liquid supply is 23 minutes.)

[0035] In addition, a drainage temperature sensor 12 was provided so that its temperature-sensing part 12a could come into contact with the drainage passing through the retention part 11d of the drainage support frame 10. In this experimental example, neither the supply liquid temperature sensor 22 nor the drainage temperature sensor 12 was provided with a heating member 24, 14. The results are shown in Figure 6.

[0036] FIG. 6 shows the measurement data of the wastewater temperature sensor 12 and the measurement data of the supply water temperature sensor 22. As shown in this figure, the wastewater temperature and supply water temperature show a daily trend of changes that follow the changes in the air temperature inside the greenhouse.

[0037] However, when comparing the temperature before and after the water supply, the temperature of the water supply remained almost constant after each water supply (the first, second, third, and fourth water supply), showing a different change from the greenhouse air temperature, which continued to rise during the supply period. The temperature of the drained water did not change after the first water supply. The temperature dropped after the third water supply, and then dropped again with each subsequent water supply. This indicates that no drainage occurred after the first water supply, drainage occurred after the third water supply, and drainage occurred after each subsequent water supply. Ideally, irrigation management should be such that no drainage occurs after the first water supply, some drainage occurs after the second, and sufficient drainage occurs after the third. The measurement data in Figure 4 show that drainage occurred after the third water supply, confirming that irrigation management was near-ideal. It is also recommended to irrigate plants so that drainage occurs during periods when instantaneous solar radiation is around 500 W. In the greenhouse where Experimental Example 1 was carried out, the instantaneous solar radiation was 500 W at 7:50 AM on July 2, 2024, and it was also detected that drainage occurred before that time.

[0038] Thus, according to Experimental Example 1, by detecting changes in the drainage temperature, it is possible to easily grasp changes throughout the day as to whether or not appropriate irrigation management is being performed. Based on the results of this experiment, the drainage determination unit 13 sets a threshold value for the level of decrease in drainage temperature. By detecting measurement data from the drainage temperature sensor 12, it is possible to automatically determine whether drainage has occurred and output a corresponding output. Similarly, the supply determination unit 23 sets a threshold value for the level of decrease in supply temperature, allowing it to automatically determine the timing of supplying water from measurement data from the supply temperature sensor 22. By detecting the timing of supplying water and the timing of draining water, the supply determination unit 23 and the drainage determination unit 13 can determine, based on temperature changes alone, which number of supply cycles during the day that caused drainage, making it easy to determine whether or not irrigation management is being performed appropriately.

[0039] 6, which shows the measurement data of Experimental Example 1, the amount of change in the liquid supply temperature is small between 8:00 and 11:00 and between 12:00 and 18:00. Similarly, the amount of change in the liquid drainage temperature is small between 12:00 and 18:00. If the amount of change is small in both the liquid drainage determining unit 13 and the liquid supply determining unit 23, it becomes difficult to determine the timing of both liquid drainage and liquid supply.

[0040] Therefore, in Experimental Example 2, an experiment was conducted using a configuration in which resistance heaters were provided as heating members 14, 24 near the temperature-sensing portions 12a, 22a of the wastewater temperature sensor 12 and the supply liquid temperature sensor 22. The heating members 14, 24 were used to adjust the temperatures of the wastewater temperature sensor 12 and the supply liquid temperature sensor 22 so that they were always about 20 to 40°C, preferably about 25 to 35°C, higher than the air temperature inside the greenhouse, and irrigation was then carried out. Note that Experimental Example 2 was conducted on the same day as Experimental Example 1, but in a different cultivation bed (the culture medium support frame 11 supporting the culture medium 2 was considered as one cultivation bed).

[0041] FIG. 7 shows the measurement data of the wastewater temperature sensor 12 and the supply water temperature sensor 22 in Experimental Example 2, along with the greenhouse air temperature. From FIG. 7 , it is clear that the supply water temperature dropped significantly at times 5:57, 6:40, 7:10, 7:35, etc., indicating that water supply was performed at these times. The first drop in the wastewater temperature occurred after 7:15, indicating that water was drained immediately after the third supply. Thereafter, water was drained every time water was supplied. Even after 8:00, when the data in Experimental Example 1 showed only small changes, significant temperature changes occurred in both the supply water temperature and the wastewater temperature. Therefore, Experimental Example 2 makes it possible to clearly determine that water was drained, even during periods when the greenhouse air temperature was rising.

[0042] Furthermore, since the amount of temperature change is large, it is easy to set a threshold value for the temperature change level when either drainage or supply of liquid occurs, improving the accuracy of the determination of the timing of drainage and supply of liquid by the drainage determination unit 13 and the supply determination unit 23.

[0043] (Experimental Example 3) As in Experimental Example 2, an irrigation experiment was conducted using the irrigation control system 100 equipped with heating elements 14, 24 attached to the drainage temperature sensor 12 and the supply temperature sensor 22. Liquid supply was performed not only on the culture medium supported by the culture medium support frame 11 of Experimental Example 3, but also on multiple other culture mediums simultaneously. A weight sensor, Priva Groscale, was also attached to two of the other culture mediums to sequentially measure the weight of the culture medium and determine the weight change per culture medium, which served as a comparative example. The irrigation control system 100 is designed to output a liquid supply signal when liquid supply is performed. The results are shown in Figures 8 and 9.

[0044] Figure 8 shows the measurement results for July 6, 2024. First, the timing of the liquid supply signal and the temperature drop detected by the liquid supply temperature sensor 22 are nearly synchronized, demonstrating that the liquid supply timing detected by the liquid supply temperature sensor 22 of this embodiment is accurate. The liquid discharge temperature sensor 12 detects a drop in the drainage temperature only after detecting that the third liquid supply has been performed. After that, a drop in the drainage temperature is detected with each subsequent liquid supply, indicating that the culture medium 2 is constantly being filled with culture medium during the day.

[0045] Weight detection using the Priva Groscale weight sensor shows an increase in weight up to the third liquid supply, but remains almost constant thereafter until the liquid supply is stopped. Therefore, it can be seen that liquid was drained after the third liquid supply, and then drained with each subsequent liquid supply. The detection of liquid drainage by the weight sensor and the detection of liquid drainage using the liquid drainage temperature sensor 12 of this embodiment coincide, demonstrating that the method of this embodiment for detecting temperature changes in the liquid drainage is effective in detecting the timing of liquid drainage. On the other hand, after the initial liquid drainage, the weight sensor indicates a nearly constant detection value, indicating that liquid drainage is occurring with each liquid supply. However, because the detection value remains constant or fluctuates only slightly, it can be difficult to reliably determine whether liquid drainage is occurring with each liquid supply. In contrast, according to this embodiment, particularly by configuring the liquid drainage temperature sensor 12 to be heated by the heating member 14, a significant temperature change is obtained during liquid drainage, allowing for reliable detection of whether liquid drainage is occurring with each liquid supply.

[0046] Figure 9 shows the measurement results from July 8, 2024. The results are similar to those in Figure 8, but the weight sensor indicates that the weight remains constant after the fourth liquid supply, allowing for the determination that liquid was drained on the fourth supply. However, the measurement data from the drainage temperature sensor 12 indicates that the first liquid was drained after the third liquid supply. This is because the amount of liquid drained after the third liquid supply was small. While the weight sensor has difficulty detecting a change in weight if the amount of drainage is below a predetermined level, the drainage temperature sensor 12 detects even smaller amounts of drainage because a temperature change occurs when the drainage liquid comes into contact with the temperature-sensing portion 12a. This demonstrates that the drainage timing detection accuracy is high despite the simple configuration.

[0047] Next, an irrigation management system 100 according to another embodiment of the present invention will be described with reference to FIGS. 10 to 12 . Depending on factors such as the type of plant to be cultivated, the cultivation method, and the scale of cultivation, a long cultivation bed (culture medium support frame 11 supporting culture medium 2) is used, for example, 5 to several tens of meters. In such a case, an irrigation tube 211 having a length approximately equal to the length of the cultivation bed is laid on the culture medium 2, and one end of the tube 211 is connected via a pipe joint 210 a to a liquid supply pipe 210 made of metal or hard plastic and connected to a liquid supply source (such as a nutrient solution tank (not shown)). In this embodiment, the liquid supply unit 21 includes the liquid supply pipe 210 and the irrigation tube 211. However, in this case, providing a liquid supply temperature sensor 22 for each outlet opening at predetermined intervals on the irrigation tube 211 would increase costs. Therefore, in this embodiment, the liquid supply temperature sensor 22 is attached to the liquid supply pipe 210, thereby simplifying the overall configuration. In this embodiment, the culture medium support frame 11 is installed at a predetermined height using leg members 11h, and the liquid supply pipe 210 is piped so as to rise upward so as to reach the height of the irrigation tube 211, which is located at a predetermined height from the liquid supply source.

[0048] 10 and 11(a), in this embodiment, the supply fluid temperature sensor 22 is fixed via a sensor support frame 22c to a pipe joint 210a, which is part of the supply fluid pipe 210. Specifically, a through hole is formed in the pipe joint 210a so that the temperature sensing part 22a can be inserted, and the temperature sensing part 22a is positioned inside the pipe joint 210a through this through hole. In this state, the sensor support frame 22c is fixed to the outer surface of the pipe joint 210a. The temperature sensing part 22a is inserted to a position where it can come into contact with the culture medium passing through the inside of the pipe joint 210a.

[0049] Regarding drainage, a drain hole 11e through which drainage from the culture medium 2 passes is provided at one longitudinal end of the culture medium support frame 11, which is provided at a predetermined height to support the culture medium 2, and a drain pipe 11g made of metal or hard plastic is connected to this drain hole 11e so as to extend downward of the culture medium support frame 11 (see FIGS. 10 and 12). In this embodiment, the drainage path extends from the inner region of the support frame 11 through which drainage discharged from the culture medium 2 passes to the drain hole 11e and the drain pipe 11g. When the cultivation bed composed of the culture medium 2 and the culture medium support frame 11 is several tens of meters long as described above, the cultivation bed is arranged with a predetermined inclination so that drainage collects in the drain hole 11e formed at one longitudinal end.

[0050] 11(c), the drainage temperature sensor 12 is disposed by inserting the temperature sensing portion 11a a predetermined distance into the drainage pipe 11g through a through-hole formed in the middle of the drainage pipe 11g. However, if the drainage pipe 11g is disposed vertically, the drainage passing through the drainage pipe 11g does not flow unevenly in any one area of ​​the inner circumference. Therefore, in this embodiment, a drainage restricting member 110 is provided in the drainage pipe 11g to restrict the flow of the drainage liquid.

[0051] As shown in FIGS. 11(b) and 11(c), the discharge liquid control member 110 includes a receptacle portion 111 having an annular bottom surface 111a, an outer cylindrical portion 111b extending from the outer periphery of the annular bottom surface 111a, and an inner cylindrical portion 111c extending from the inner periphery of the annular bottom surface 111a. A support rod 112 extends from the upper opening of the inner cylindrical portion 111c, and a baffle plate 113 is supported on the upper end of this support rod 112. The diameter of the baffle plate 113 shown in the figures is approximately the same as that of the inner cylindrical portion 111c, but any suitable size can be used as long as it is equal to or greater than the diameter of the inner cylindrical portion 111c and less than the diameter of the outer cylindrical portion 111b. A drain port 111d is also provided in one location on the annular bottom surface 111a.

[0052] The drainage temperature sensor 12 is inserted through a through hole formed in the peripheral wall of the drainage pipe 11g so that the temperature-sensing part 12a is positioned directly below the drain outlet 111d, and the sensor support frame 12c is fixed to the outer peripheral surface of the drainage pipe 11g.

[0053] The drainage liquid flowing through the drainage pipe 11g from the drainage hole 11e of the culture medium support frame 11 is restricted by the baffle plate 113 within the drainage pipe 11g and accumulates between the outer cylindrical portion 111b and the inner cylindrical portion 111c of the receiver portion 111. As a result, the drainage liquid falls through the drain outlet 111d toward the temperature-sensing portion 12a of the drainage liquid temperature sensor 12, allowing the temperature of the drainage liquid to be measured. When the amount of drainage liquid accumulated between the outer cylindrical portion 111b and the inner cylindrical portion 111c exceeds the height of the inner cylindrical portion 111c, the overflowing drainage liquid flows downstream of the drainage liquid restricting member 110 via the inside of the inner cylindrical portion 111c.

[0054] According to this embodiment, even if the cultivation bed is long and the length of the irrigation tube 211 is accordingly long, the supply liquid temperature is measured in the supply liquid pipe 210 that supplies the culture liquid to the tube 211, and the drainage liquid temperature is measured in the drainage pipe 11g through which the drainage liquid passes. This configuration allows the equipment required to measure the supply liquid temperature and the drainage liquid temperature (supply liquid temperature sensor 22, drainage liquid temperature sensor 12, etc.) to be minimized, which contributes to simplifying the equipment and reducing costs.

[0055] (Experimental Example 4) As shown in Figures 10 to 12, a supply liquid temperature sensor 22 was installed at the pipe joint 210a of the supply liquid pipe 210, and a drain liquid temperature sensor 12 was installed at the drain liquid pipe 11g, and the supply liquid temperature and drain liquid temperature were measured. The results are shown in Figure 13. The supply liquid temperature changed in synchronization with the supply liquid signal, and the timing of supplying liquid was detected by the change in supply liquid temperature. The drain liquid temperature sensor 12 also showed a decrease in the drain liquid temperature due to contact with the drain liquid, but the amount of change was small.

[0056] On the other hand, Figure 14 shows data obtained when both the liquid supply temperature sensor 22 and the liquid discharge temperature sensor 12 are heated by approximately 20 degrees Celsius above the greenhouse air temperature. As shown in Figure 14, a significant temperature drop is detected each time liquid is supplied, and also a significant temperature drop is detected each time liquid is discharged, slightly delayed from the time of supply. The timing of the temperature drop is synchronized with the timing of the liquid supply signal, and in this embodiment, by detecting the temperature drop, it is possible to accurately detect the occurrence of liquid supply and liquid discharge.

[0057] As mentioned above, this embodiment is effective when the cultivation bed is long, such as several tens of meters or more. However, even in a short cultivation bed of about 1 to 4 meters as shown in FIGS. 3 to 5, by providing the same liquid supply pipe 210 and liquid drainage pipe 11g as in this embodiment, the temperature of the culture solution passing through them and the temperature of the drainage liquid can be measured, and the liquid supply timing and liquid drainage timing can be detected.

[0058] Furthermore, as shown in FIG. 15 , even when multiple short cultivation beds, each approximately 1 to 4 m long, are installed in a row in the longitudinal direction, a liquid supply unit 21 having a similar configuration to that shown in FIG. 10 may be employed, in which an irrigation tube 211 is laid across each cultivation bed and one end of the tube 211 is connected to a single liquid supply pipe 210. In this case, too, only one liquid supply temperature sensor 22 is required for each liquid supply pipe 210. Meanwhile, a liquid drainage pipe 11g is provided for each cultivation bed. Therefore, it is preferable to provide a liquid drainage temperature sensor 22 for each drainage pipe 11g, as shown in FIG. 15 . This configuration minimizes the equipment required for measuring the liquid supply temperature, while enabling the liquid drainage temperature sensor 22 to detect a temperature drop for each cultivation bed, thereby enabling detailed management of each cultivation bed.

[0059] However, in order to simplify the configuration and reduce costs, it is also possible to provide a drainage temperature sensor 22 only in the drainage pipe 11g of one cultivation bed, and determine whether or not drainage is occurring based on the temperature change.

[0060] In the above embodiment, the drainage temperature sensor 12 and the supply temperature sensor 22 are heated to measure temperature changes more clearly, but as mentioned above, the temperature changes detected by the drainage temperature sensor 12 and the supply temperature sensor 22 may be detected as a temperature rise depending on the season, etc. In that case, instead of the heating members 14, 24 that preheat the drainage temperature sensor 12 and the supply temperature sensor 22, a known cooling member (not shown) may be provided to precool them to a predetermined temperature, thereby enabling a configuration in which temperature rise changes can be detected more clearly.

[0061] In the above embodiment, the legs 22e of the sensor support frame 22c are inserted into the seedling growing medium 2b. However, as shown in FIG. 16, a configuration is also possible in which a liquid supply passage 22g is provided in the sensor support frame 22c, and the temperature-sensing portion 22a of the liquid supply temperature sensor 22 faces the liquid supply passage 22g. In this case, the liquid supply tube 21a is divided, and one of the divided liquid supply tubes 21a1 is connected to the inlet side of the liquid supply passage 22g, and the other divided liquid supply tube 21a2 is connected to the outlet side of the liquid supply passage 22g. The end of the other liquid supply tube 21a2 is then placed on the seedling growing medium 2b or the medium 2. This configuration eliminates limitations on the mounting location of the sensor support frame 22c with the liquid supply passage 22g and the liquid supply temperature sensor 22, for example, by attaching them to the medium support frame 11, which is convenient.

[0062] FIG. 17 shows an overview of yet another embodiment of the present invention, and FIGS. 18 and 19(a)-(c) show the configuration of its essential parts. This embodiment is similar to the embodiment shown in FIGS. 10-12 and 15 in that the liquid supply unit 21 has a liquid supply pipe 210 made of metal or hard plastic. However, as shown in FIGS. 17 and 18, the mechanism for measuring the temperature of the culture medium passing through the liquid supply pipe 210 is separate from the liquid supply pipe 210. That is, a branch pipe 210b is provided at an arbitrary position of the liquid supply pipe 210, for example, at a connector 210a. The branch pipe 210b can be made of a flexible tube or the like, and a liquid supply temperature sensor 22 supported by a sensor support frame 22c is disposed at the outlet located at the end of the branch pipe 210b.

[0063] When the liquid supply starts, a portion of the liquid supply flows into the branch pipe 210b, and the temperature detected by the liquid supply temperature sensor 22 becomes the liquid supply temperature of the culture medium passing through the liquid supply pipe 210. Since the branch pipe 210b is provided and the liquid supply temperature sensor 22 is provided in the branch pipe 210b, there are fewer restrictions on the location of the liquid supply temperature sensor 22 compared to the embodiments shown in Figures 10 to 12 and 15.

[0064] 10 to 12 and 15, a configuration is adopted in which a discharged liquid regulating member 110 having a baffle plate 113 and a receptacle portion 111 is provided in the drainage pipe 11g as a mechanism for measuring the temperature of the discharged liquid in the drainage pipe 11g, and the temperature-sensing portion 12a of the discharged liquid temperature sensor 12 is positioned below the drain outlet 111d of the receptacle portion 111. For this reason, the discharged liquid temperature sensor 12 must be positioned approximately perpendicular to the drainage pipe 11g, and the temperature-sensing portion 12a must be positioned inside the drainage pipe 11g so that it comes into contact with the discharged liquid flowing down from the drain outlet 111d of the receptacle portion 111, making adjustment of the mounting position cumbersome.

[0065] In contrast, in this embodiment, a discharge liquid control member 1100 shown in FIGS. 17 and 19(a) to 19(c) is used instead of the above-described discharge liquid control member 110. The discharge liquid control member 1100 of this embodiment is disposed midway along the discharge pipe 11g and includes a large-diameter tray portion 1110 that protrudes outward and has a diameter larger than that of the discharge pipe 11g. A baffle plate 1113 is provided near the center of the large-diameter tray portion 1110, and an inner cylindrical portion 1111c is provided below the baffle plate 1113. A partition wall portion 1111e is provided between the inner cylindrical portion 1111c and the outer cylindrical portion 1111d of the large-diameter tray portion 1110. A notch portion 1111f is formed in the partition wall portion 1111e, and a drain port 1111g is provided between the notch portion 111f and the outer cylindrical portion 1111d. The baffle plate 1113 is disposed so as to be positioned inside the drain pipe 11g, and the area from the partition wall portion 1111e to the outer circumferential cylinder portion 1111d is disposed so as to protrude outward from the drain pipe 11g.

[0066] The drainage liquid flowing through the drain pipe 11g hits the baffle plate 1113 and flows outward, but when a certain amount flows, it passes over the upper end of the inner cylindrical portion 1111c and enters the inner cylindrical portion 1111e, continuing to flow through the drain pipe 11g. Meanwhile, some of the liquid flows through the cutout portion 1111f toward the outer cylindrical portion 1111d, and in the meantime, it flows into the drain outlet 1111g and flows downward through the drain pipe 11g.

[0067] When the wastewater flows from the notch 1111f into the drain outlet 1111g, the wastewater moves in a substantially horizontal direction, so the temperature-sensing part 12a of the wastewater temperature sensor 12 is positioned so that it comes into contact with the wastewater flowing between the notch 1111f and the drain outlet 1111g. In this case, the wastewater temperature sensor 12 can be positioned in a substantially vertical position outside the drain pipe 11g, so the wastewater temperature sensor 12 supported in a substantially vertical position on the sensor support frame 12c shown in Figure 1 can be used as is. Since the wastewater temperature sensor 12 is positioned so that the temperature-sensing part 12a comes into contact with the wastewater flowing outside the drain pipe 11g, the installation of the wastewater temperature sensor 12 is easier than in the embodiments of Figures 10 to 12 and 15.

[0068] REFERENCE SIGNS LIST 1 Drainage management device 11 Culture medium support frame 11d Retention section 12 Drainage temperature sensor 12a Temperature sensing section (of drainage temperature sensor) 13 Drainage determination section 14 Heating member (for drainage temperature sensor) 21 Liquid supply section 22 Liquid supply temperature sensor 22a Temperature sensing section (of liquid supply temperature sensor) 23 Liquid supply determination section 24 Heating member (for liquid supply temperature sensor) 100 Irrigation management system

Claims

1. A drainage management device for hydroponics, comprising: a drainage temperature sensor that is provided in a drainage path for drainage liquid discharged from a culture medium in which a plant to be cultivated is planted, and that is capable of measuring the temperature of the drainage liquid; and a drainage determination unit that receives measurement data from the drainage temperature sensor and determines the timing at which a temperature change of a predetermined level or more is detected as the drainage timing at which the drainage liquid occurred.

2. A drainage management device for hydroponics according to claim 1, comprising a medium support frame for supporting the medium, the medium support frame being provided with the discharge path, a retention section being provided in the discharge path where the drainage liquid temporarily stays, and a temperature-sensing section of the drainage liquid temperature sensor being provided so as to be able to come into contact with the drainage liquid in the retention section.

3. A drainage management device for hydroponics according to claim 1, wherein the discharge path is configured with a drainage pipe, the drainage temperature sensor is provided so that a temperature-sensing part is located within the drainage pipe, and a guide member is provided within the drainage pipe upstream of the position where the temperature-sensing part is provided, for guiding the drainage so that it comes into contact with the temperature-sensing part.

4. A drainage management device for hydroponics according to claim 1, further comprising a heating member for heating said drainage temperature sensor.

5. An irrigation management system for hydroponics, comprising: a drainage management device according to any one of claims 1 to 4; a liquid supply unit that supplies nutrient solution to a plant to be cultivated; a liquid supply temperature sensor that can measure the temperature of the nutrient solution being supplied; and a liquid supply determination unit that receives measurement data from the liquid supply temperature sensor and determines the timing at which a temperature change of a predetermined level or more is detected as the timing at which the liquid was supplied.

6. An irrigation management system for hydroponics according to claim 5, further comprising a heating member for heating said temperature sensor for supplying said liquid.

7. An irrigation management system as described in claim 5, wherein the temperature sensor for the liquid supply has a temperature sensing part provided near the outlet of the liquid supply part, and measures the temperature of the culture liquid discharged from the outlet as the liquid supply temperature.

8. An irrigation management system as described in claim 5, wherein the temperature sensor for the liquid supply is located in a liquid supply pipe constituting the liquid supply section, and measures the temperature of the culture liquid passing through the liquid supply pipe as the liquid supply temperature.

9. A method for managing drainage in hydroponics, in which a drainage temperature sensor is provided in a drainage path for drainage from a culture medium in which a plant to be cultivated is planted, capable of measuring the temperature of the drainage, and when the sensor indicates a temperature change of a predetermined level or more, the timing at which the drainage occurred is used to manage the presence or absence of drainage.

10. A method for managing drainage in hydroponics according to claim 9, wherein the drainage temperature sensor is preheated to measure the temperature of the drainage.