Soil nutrient detection method, soil nutrient detection device, and soil nutrient sensor

Abstract

To realize a method for detecting a soil nutrient easily and accurately.SOLUTION: The method for detecting a soil nutrient includes: an EC acquisition step of acquiring a liquid EC value, which is the EC value of liquid (14) in a container (11) having a porous cup (12); a pressure acquisition step of acquiring the pressure in the container (11); and a correction step of performing a first correction to correct the liquid EC value to a larger value as the difference between the air pressure and the above pressure is larger and acquiring a corrected EC value to be an index of the state of the soil nutrient buried in the container (11).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for detecting soil nutrients, a device for detecting soil nutrients, and a soil nutrient sensor. [Background technology]

[0002] The concentration of nutrients, such as fertilizers, in soil significantly affects plant growth. Since proper management of soil nutrient status leads to increased plant yields, there is a demand for a method for detecting soil nutrients that can accurately grasp the status of soil nutrients.

[0003] Conventionally, methods that use the electrical conductivity (EC) of liquid contained in soil have been proposed as methods for detecting the state of soil nutrients. For example, Patent Document 1 discloses a method for determining salt accumulation by using a soil EC sensor equipped with an electrode held together with water in a porous cup, and comparing the EC before and after injecting a reference culture solution near the soil EC sensor.

[0004] Furthermore, Patent Document 2 discloses a method for correcting electrical conductivity measurements using the output of a temperature sensor that can measure the temperature at the location where electrical conductivity is measured, since electrical conductivity changes depending on temperature. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-191654 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-25185 Summary of the Invention [Problem to be solved by the invention]

[0006] The method described in Patent Document 1 requires the injection of a reference culture medium and the measurement and comparison of EC values ​​before and after the injection. Therefore, it takes a lot of time and effort to obtain results. Furthermore, EC measurements (EC values) vary depending on factors such as the temperature at the time of measurement, but Patent Document 1 does not disclose how to correct the EC values, leaving accuracy at risk.

[0007] In this regard, the method described in Patent Document 2 corrects the electrical conductivity using the output of a temperature sensor. However, this method is used to measure the electrical conductivity of liquids that reach extremely high temperatures, such as boiler water in a steam boiler. Furthermore, Patent Document 2 does not disclose any correction of electrical conductivity due to factors other than temperature.

[0008] An object of one aspect of the present invention is to provide a simple and highly accurate method for detecting soil nutrients. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, a soil nutrient detection method according to one embodiment of the present invention includes an EC acquisition process for acquiring a liquid EC value, which is the EC value of a liquid in a container equipped with a porous cup; a pressure acquisition process for acquiring the pressure in the container; and a correction process for performing a first correction to correct the liquid EC value to a larger value the greater the difference between atmospheric pressure and the pressure, thereby acquiring a corrected EC value that is an indicator of the nutrient status of the soil in which the container is buried.

[0010] With this configuration, the liquid in the container reaches equilibrium with the liquid in the soil due to the movement and diffusion of the liquid caused by osmotic pressure through the porous cup. Therefore, the EC value of the soil can be obtained by obtaining the liquid EC value of the liquid in the container.

[0011] The pressure inside the container acquired in the pressure acquisition process is an index showing how much the soil is absorbing the liquid inside the container through the porous cup, i.e., an index showing the dryness of the soil. The liquid EC value acquired in the EC acquisition process is affected by the dryness of the soil.

[0012] Therefore, by correcting the liquid EC value obtained in the EC acquisition process using the pressure obtained in the pressure acquisition process, the corrected EC value takes into account the dryness state of the soil, and can be used as an accurate indicator of soil nutrients.

[0013] In one embodiment of the soil nutrient detection method of the present invention, the EC acquisition process may further include a steady-state determination process in which the liquid EC value is acquired over time and a determination is made as to whether a steady state in which the amount of change per unit time of the liquid EC value is less than a predetermined value has elapsed for a predetermined period of time or more.

[0014] This configuration makes it possible to determine whether the change in the acquired liquid EC value is a steady state and whether the steady state continues stably, thereby accurately determining whether the acquired liquid EC value is a stable value acquired during a period with little change or an unstable value acquired during any other period.

[0015] A soil nutrient detection method according to one embodiment of the present invention further includes a temperature acquisition process for acquiring the temperature of the liquid, and in the correction process, in addition to the first correction, a second correction may be performed to correct the liquid EC value to a smaller value as the temperature is higher, thereby obtaining the corrected EC value.

[0016] According to the above configuration, the liquid EC value can be corrected based on the temperature of the liquid. The liquid EC value acquired in the EC acquisition step is affected not only by the dryness state of the soil but also by the temperature of the liquid at the time of acquisition.

[0017] Therefore, by correcting the liquid EC value obtained in the EC acquisition process using the temperature of the liquid obtained in the temperature acquisition process, the corrected EC value after correction takes into account the temperature at the time the liquid EC value was obtained, and can therefore be used as a more accurate indicator of soil nutrients.

[0018] In order to solve the above-mentioned problems, a soil nutrient detection device according to one embodiment of the present invention comprises an EC acquisition unit that acquires a liquid EC value, which is the EC value of a liquid in a container equipped with a porous cup; a pressure acquisition unit that acquires the pressure inside the container; and a correction unit that performs a first correction to correct the liquid EC value to a larger value the greater the difference between atmospheric pressure and the pressure, thereby acquiring a corrected EC value that is an indicator of the nutrient status of the soil in which the container is buried.

[0019] In order to solve the above problem, a soil nutrient sensor according to one embodiment of the present invention comprises a container having a porous cup capable of containing a liquid, an EC detection unit that detects the liquid EC value, which is the EC value of the liquid, and a pressure detection unit that detects the pressure inside the container. [Effects of the Invention]

[0020] According to one aspect of the present invention, a simple and highly accurate method for detecting soil nutrients can be realized. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a diagram illustrating a configuration of a main part of a detection system according to an embodiment. [Figure 2] FIG. 1 is a block diagram showing a functional block configuration of a detection system according to an embodiment. [Figure 3] FIG. 1 is a diagram showing the relationship between the dryness state of soil, the dilution ratio of liquid fertilizer contained in the soil, and the electrical conductivity of soil water. [Figure 4] FIG. 10 is a diagram showing the relationship between the temperature of liquid fertilizer, the set EC of liquid fertilizer, and the electrical conductivity of liquid fertilizer. [Figure 5] FIG. 1 is a flow diagram illustrating an example of a detection method according to an embodiment. [Figure 6] FIG. 1 is a diagram showing the relationship between the internal pressure and the liquid EC value of a soil nutrient sensor according to one embodiment. [Figure 7] FIG. 3 is a diagram showing the relationship between the liquid EC value of the soil nutrient sensor and the liquid temperature. [Figure 8]FIG. 10 is a graph showing the change in liquid EC value over time and the amount of change per 10 minutes when the temperature and type of liquid fertilizer in which the soil nutrient sensor is immersed are changed. [Figure 9] FIG. 10 is a graph showing the change in internal pressure and liquid EC value over time when the internal pressure of the soil nutrient sensor is changed. [Figure 10] FIG. 10 is a graph showing the change in internal pressure over time and the amount of change per minute when the dryness state of the soil in which the soil nutrient sensor is embedded is changed. DETAILED DESCRIPTION OF THE INVENTION

[0022] An embodiment of the present invention will be described below. Note that the following description is intended to provide a better understanding of the gist of the invention and does not limit the present invention unless otherwise specified. Furthermore, in this specification, "A to B" means A or more and B or less unless otherwise specified.

[0023] 1 and 2, a soil nutrient detection system 1 according to one embodiment of the present invention includes a soil nutrient sensor 10 and a detection device 20. The detection system 1 is a system that detects the state of soil nutrients by correcting the electrical conductivity (hereinafter referred to as the "EC value") of the water contained in the soil (hereinafter referred to as the "soil water content") acquired by the soil nutrient sensor 10 based on the dryness and temperature of the soil.

[0024] [Soil nutrient sensor] As shown in FIG. 1, the soil nutrient sensor 10 includes a container 11, an EC detection unit 15, a pressure detection unit 16, and a temperature detection unit 17.

[0025] The container 11 is a cylindrical member having a porous cup 12 at one end and a plug 13 at the other end. The container 11 is configured to be able to contain a liquid 14, and when the soil nutrient sensor 10 is in use, the container 11 contains the liquid 14. It is preferable that the container 11 contains at least an amount of liquid 14 sufficient to fill the container 11.

[0026] The shape of the container 11 is preferably cylindrical so that the porous cup 12 can be easily inserted into the soil, but is not limited to this. The stopper 13 maintains the airtightness of the container 11 and may be, for example, a rubber stopper or a silicone stopper, but is not limited to these. The material of the tubular body portion of the container 11 other than the porous cup 12 is preferably, but is not limited to, a synthetic resin from the viewpoint of weight and durability. The tubular body portion of the container 11 may be made of a transparent material from the viewpoint of facilitating confirmation of the remaining amount of the liquid 14 contained therein, but is not limited to this.

[0027] The porous cup 12 is a water-permeable member. The soil nutrient sensor 10 is used by being buried in the soil. "Buried in the soil" means, for example, that at least a portion of the container 11, including the porous cup 12, is inserted into the soil. The liquid 14 in the container 11 reaches a concentration equilibrium with the soil moisture due to the movement and diffusion of the liquid caused by osmotic pressure via the porous cup 12. In this equilibrium state, the liquid EC value of the liquid 14 in the container 11 indicates the EC value of the soil moisture, so the soil nutrient sensor 10 can obtain the EC value of the soil moisture by obtaining the liquid EC value.

[0028] The material of the porous cup 12 may be, for example, a porous sintered material, but is not limited to this.

[0029] Liquid 14 may be water or a liquid fertilizer using water as a solvent. Examples of water include, but are not limited to, pure water, tap water, environmental water, distilled water, and ion-exchanged water. If the EC value of the soil moisture can be estimated, liquid 14 is preferably a liquid fertilizer having an EC value similar to that of the soil moisture, from the viewpoint of quickly achieving equilibrium in the liquid EC value of liquid 14.

[0030] EC detector 15 is a component that detects the EC value of the liquid. For example, EC detector 15 may be, but is not limited to, a pair of electrodes that are immersed in liquid 14 and pass a current between two electrodes to measure the EC value of the liquid. EC detector 15 may also be, for example, a transformer that detects electromagnetically induced current.

[0031] The pressure detection unit 16 is a component that detects the pressure inside the container 11 (hereinafter referred to as "internal pressure"). The container 11 is sealed by a plug 13. Therefore, the more liquid 14 seeps out of the porous cup 12 of the container 11, the lower the internal pressure becomes compared to atmospheric pressure. The drier the soil in which the soil nutrient sensor 10 is embedded, the more easily the liquid 14 seeps out of the porous cup 12 into the soil due to osmotic pressure, causing the internal pressure to decrease, i.e., become negative pressure. In other words, the internal pressure is an indicator of the dryness of the soil in which the soil nutrient sensor 10 is embedded.

[0032] The pressure detection unit 16 is not particularly limited as long as it can detect internal pressure. For example, the pressure detection unit 16 is preferably a component that measures internal pressure as a gauge pressure based on atmospheric pressure. The pressure detection unit 16 may also output an index that indicates soil moisture suction pressure, which can be calculated based on the detected pressure. Examples of indexes that indicate soil moisture suction pressure include the pF value, soil water potential, and soil moisture suction. In this way, each index that indicates soil moisture suction pressure calculated based on the detection value of the pressure detection unit 16 is also an example of "internal pressure."

[0033] The temperature detection unit 17 is a component that detects the temperature of the liquid 14 (hereinafter referred to as "liquid temperature"). The temperature detection unit 17 is not particularly limited as long as it can detect the temperature of the liquid 14. Note that the soil nutrient sensor 10 does not necessarily have to be equipped with a temperature detection unit 17.

[0034] In the detection system 1 of this embodiment, the liquid EC value, internal pressure, and liquid temperature detected by the soil nutrient sensor 10 may be acquired by a detection device 20, which will be described later. The configuration of the detection device 20 will be described below.

[0035] [Outline of the soil nutrient detection device] (corrected for soil dryness) The soil nutrient detection device 20 corrects the liquid EC value detected by the EC detection unit 15 of the soil nutrient sensor 10 using the internal pressure detected by the pressure detection unit 16.

[0036] In conventional methods for detecting soil nutrients based on the EC value of soil moisture, it is assumed that the state of soil nutrients remains constant, but it is known that the EC value of soil moisture can fluctuate. After extensive research, the inventors have found that the EC value of soil moisture is significantly affected by the dryness state of the soil.

[0037] Figure 3 shows the results of an investigation into the effect of soil dryness on the EC value of soil moisture. Here, several dilutions of liquid fertilizer, Nutrient Solution No. 2 (OAT Agrio Co., Ltd.), were set, and the solution was irrigated via irrigation tubes in each treatment area. A conventional moisture sensor (WD-3-WET-5Y, A·R·P Co., Ltd.) capable of measuring the EC value of soil moisture was buried either directly below the irrigation tube or 15 cm below the irrigation tube for each treatment area, creating either wet or dry conditions.

[0038] For each treatment, the EC value of the soil moisture under both wet and dry conditions was detected by the output voltage (V) of the moisture sensor. The output voltage correlates with the EC value of the soil moisture, and therefore indirectly indicates the EC value of the soil moisture.

[0039] As shown in Figure 3, no consistent trend was observed between the dilution ratio of the liquid fertilizer and the output voltage. In addition, the output voltage was significantly affected by the dryness of the soil. In other words, the EC value of soil moisture obtained when the EC sensor is directly buried in the soil is significantly affected by the dryness of the soil, and it was shown that an accurate EC value of soil moisture cannot be detected.

[0040] (Temperature compensation) Furthermore, it is preferable that the detection device 20 further corrects the liquid EC value using the liquid temperature detected by the temperature detection unit 17. This is because, as shown in Patent Document 2, the EC value is affected by the temperature at the time of measurement.

[0041] Figure 4 shows the results of an investigation into the effect of temperature during measurement on EC values. For nutrient solution No. 2 grown in soil, four dilution ratios were set based on the EC value (dS / m) at 25°C (set EC). These test solutions were adjusted to six different temperatures in an incubator, and the following measurements were carried out. The output voltage (V) of the detector was measured using a tension meter (pressure sensor part: DP101-ZA, Panasonic Corporation) equipped with a container with a porous cup and a built-in electrical conductivity sensor (analog TDS sensor, Gravity).

[0042] As shown in Figure 4, the output voltage was significantly affected by temperature for all test solutions with different EC settings. Specifically, for all test solutions with different dilution ratios, the higher the temperature, the higher the output voltage. This demonstrates that the EC value is significantly affected by the temperature at the time of measurement, even within the normal temperature range.

[0043] As described above, by correcting the detected liquid EC value based on the soil dryness and temperature, the state of soil nutrients can be accurately determined. This facilitates management such as applying the appropriate amount of fertilizer at the appropriate time. By contributing to increasing plant yields, one embodiment of the present invention can contribute to achieving the Sustainable Development Goals (SDGs), such as Goal 2 "Zero Hunger" and Goal 15 "Life on Land."

[0044] [Detection device] 1 and 2, the detection device 20 is configured to be able to transmit and receive data to and from the soil nutrient sensor 10. The soil nutrient sensor 10 and the detection device 20 may be connected by wire and / or wirelessly. If connected wirelessly, both the soil nutrient sensor 10 and the detection device 20 may be equipped with a wireless communication device (not shown).

[0045] The detection device 20 includes a control device 21, a storage device 30, an input device 31, and a display device 32. The storage device 30 is a component that stores various data related to the detection device 20, such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive). The input device 31 is a component that accepts input to the detection device 20, such as a keyboard or a mouse. The display device 32 is a component that has a display screen, such as a liquid crystal display or an organic EL display. The input device 31 and the display device 32 may be configured as touch panels that combine the functions of each other. A user of the detection system 1 may, for example, input setting values, etc. to be used in the first correction, etc., which will be described later, using the input device 31.

[0046] The control device 21 is a component that controls all the parts of the detection device 20. The control device 21 may be a processor such as a CPU (Central Processing Unit). There may be multiple control devices 21, and in this case, the multiple control devices 21 may share or cooperate to realize the functions of each part.

[0047] The control device 21 includes a data acquisition unit 22, a calculation unit 26, and a data output unit 29. The data acquisition unit 22 acquires various data detected by the soil nutrient sensor 10. The data acquisition unit 22 includes an EC acquisition unit 23, a pressure acquisition unit 24, and a temperature acquisition unit 25.

[0048] The EC acquisition unit 23 acquires the liquid EC value detected by the EC detection unit 15. The pressure acquisition unit 24 acquires the internal pressure detected by the pressure detection unit 16. The temperature acquisition unit 25 acquires the liquid temperature detected by the temperature detection unit 17. It is preferable that the EC acquisition unit 23, the pressure acquisition unit 24, and the temperature acquisition unit 25 acquire various data over time.

[0049] The calculation unit 26 performs calculation processing using the various data acquired by the data acquisition unit 22. The calculation unit 26 includes a correction unit 27 and a steady-state determination unit .

[0050] (First Amendment) The correction unit 27 performs a first correction to correct the liquid EC value acquired by the EC acquisition unit 23 using the internal pressure acquired by the pressure acquisition unit 24, thereby acquiring a corrected EC value. Specifically, the correction unit 27 performs a first correction to correct the liquid EC value to a larger value as the difference between atmospheric pressure and internal pressure (hereinafter referred to as "pressure difference") increases, thereby acquiring a corrected EC value. The corrected EC value is a value that reflects the EC value of soil moisture, taking into account fluctuations in EC value due to the dryness state of the soil, and serves as an indicator of the nutrient state of the soil in which the soil nutrient sensor 10 is buried.

[0051] A specific example of the first correction performed by the correction unit 27 is as follows: First, a predetermined pressure reference value, which is a reference value for the pressure difference, is set. Then, if the pressure difference is greater than the pressure reference value, the liquid EC value is corrected by addition.

[0052] The "pressure reference value" may be, for example, the pressure difference value when the soil is in an average dry state. With this configuration, the correction unit 27 can obtain a corrected EC value that reflects the soil dryness state without excessively correcting the acquired liquid EC value. Since the "average soil dryness state" is likely to vary depending on the soil in which the soil nutrient sensor 10 is embedded, the pressure reference value may be set appropriately for the soil. For example, such a pressure reference value is preferably equal to or greater than the pressure corresponding to the field water requirement and equal to or less than the pressure corresponding to the capillary disconnection point, and more preferably equal to or less than the pressure corresponding to the initial wilting point. The pressure corresponding to the field water requirement may be 1.5 to 2.0 pF. The pressure corresponding to the capillary disconnection point may be 2.7 pF. The pressure corresponding to the initial wilting point may be 3.8 pF (Reference: Soil Diagnosis Methods and Applications, Fujiwara Shunrokuro et al., 1996, Agricultural Culture Association). Furthermore, the pressure reference value is not limited to the above, and may be, for example, 0 (a condition in which the atmospheric pressure and the internal pressure are the same), or may be set to any value by the user of the detection system 1.

[0053] The correction value for the liquid EC value in the first correction is not particularly limited, but may be corrected, for example, according to the following formula (1): Corrected EC value after first correction (dS / m) = Liquid EC value (dS / m) + (Pressure difference (KPa) - Pressure reference value (KPa)) × First correction coefficient (1) Here, the first correction coefficient is preferably a value not less than 0.00001 and not more than 0.001, and more preferably a value not less than 0.00005 and not more than 0.0005.

[0054] If the internal pressure acquired by the pressure acquisition unit 24 is an index indicating soil water suction pressure, a calculation method for a correction value for the liquid EC value may be set appropriately depending on the index. Furthermore, the correction unit 27 may calculate the pressure difference (KPa) from the acquired index indicating soil water suction pressure, and then acquire the corrected EC value using the above formula (1) or the like.

[0055] (Second Amendment) In addition to the first correction, it is preferable that the correction unit 27 performs a second correction, which corrects the liquid EC value to a smaller value as the liquid temperature acquired by the temperature acquisition unit 25 increases. The corrected EC value after the second correction reflects the EC value of the soil moisture and takes into account the liquid temperature at the time of detecting the liquid EC value, and is therefore preferable as an indicator of the nutrient status of the soil in which the container 11 is buried.

[0056] The following is a specific example of the second correction performed by correction unit 27. First, a reference temperature, which is a reference value for the liquid temperature, is set. Then, if the liquid temperature is higher than the reference temperature, the liquid EC value is corrected by subtracting it, and if the liquid temperature is lower than the reference temperature, the liquid EC value is corrected by adding it.

[0057] The "reference temperature" is preferably 25°C. With this configuration, the correction unit 27 can obtain a corrected EC value that takes into account the effects of the liquid temperature as well as the dryness state of the soil, without making excessive corrections to the obtained liquid EC value. Since the "average soil temperature" is likely to differ depending on the soil in which the soil nutrient sensor 10 is buried, the reference temperature may be set appropriately depending on the soil. Furthermore, the reference temperature is not limited to the above, and may be set to any value by the user of the detection system 1, for example.

[0058] In the second correction, the correction value for the corrected EC value after the first correction based on the liquid temperature is not particularly limited, but may be corrected, for example, according to the following formula (2): Corrected EC value after second correction (dS / m) = Corrected EC value after first correction (dS / m) - (liquid temperature (℃) - reference temperature (℃)) × second correction coefficient (2) Here, the second correction coefficient is preferably a value not less than 0.01 and not more than 0.03, and more preferably a value not less than 0.0125 and not more than 0.02.

[0059] In the above example, the correction unit 27 is configured to perform the first correction and then the second correction, but this is not limiting. When performing the second correction, the correction unit 27 may perform the second correction on the liquid EC value, and then further perform the first correction.

[0060] (Steady state determination) When the EC acquisition unit 23 acquires the liquid EC value over time, it is preferable that the steady-state determination unit 28 determine whether a steady state in which the change in the liquid EC value per unit time is less than a predetermined value has elapsed for a predetermined period of time or more.

[0061] As mentioned above, the liquid EC value is affected by internal pressure and liquid temperature. Therefore, immediately after irrigation and a change in the soil dryness state, and / or immediately after a change in soil temperature due to a change in sunlight, etc., the internal pressure and / or liquid temperature fluctuate, and the liquid EC value also fluctuates accordingly. To accurately grasp the nutrient status of the soil, it is preferable to use the liquid EC value detected during a steady-state period when the amount of change in the liquid EC value per unit time is small.

[0062] The "steady state" of a liquid EC value refers to a period during which the change in the liquid EC value per unit time is equal to or less than a predetermined value. While the unit time is not particularly limited, in order to obtain a liquid EC value in a stable state with less change, it may be 1 minute or more, preferably 5 minutes or more, and more preferably 10 minutes or more. Furthermore, from the viewpoint of not spending too much time determining whether or not the liquid is in a steady state, the unit time may be 1 hour or less, preferably 30 minutes or less, and more preferably 15 minutes or less.

[0063] The steady-state determination unit 28 may determine the amount of change in the liquid EC value by, for example, determining whether the difference between the liquid EC value at the current time and the liquid EC value at a time point unit time prior to the current time is equal to or less than a predetermined value. The steady-state determination unit 28 may obtain the liquid EC value at a time point unit time prior to the current time from, for example, the storage device 30.

[0064] The "predetermined value" that is the threshold for the amount of change in the liquid EC value may be set appropriately according to the unit time. For example, the steady-state determination unit 28 may set the predetermined value to 0.002 dS / m·min -1 It may be less than 0.001dS / m·min -1That is, when the unit time is 10 minutes, the predetermined value may be 0.02 dS / m or less, and is preferably 0.01 dS / m or less.

[0065] Furthermore, immediately after steady-state determination unit 28 determines that the liquid EC value is in a steady state, there is a possibility that the fluctuations in the liquid EC value have not yet stabilized. If the steady state continues for a predetermined period of time or longer after the liquid EC value is determined to be in a steady state, it is more likely that the fluctuations in the liquid EC value are stable. Therefore, it is preferable that steady-state determination unit 28 not only determines whether the liquid EC value is in a steady state, but also determines whether the current steady state has continued for a predetermined period of time or longer.

[0066] The predetermined time for steady-state determination is not particularly limited. The predetermined time is preferably longer than the unit time for steady-state determination, and may be, for example, at least twice, at least three times, or at least five times the unit time. Furthermore, the steady-state determination unit 28 may set the predetermined time to be the same as the period from the end of the previous steady state to the start of the current steady state. The steady-state determination unit 28 may use, as the predetermined time, a value input by the user of the detection system 1 via the input device 31, or may use an initial setting value previously stored in the storage device 30.

[0067] The steady-state determination unit 28 may generate tag information in a form corresponding to the liquid EC value and / or the corrected EC value, which indicates the result of the steady-state determination as to whether or not the steady state has continued for a predetermined time or more. The form of the tag information is not particularly limited, as long as it indicates that the steady-state determination is "yes" or "no."

[0068] For example, steady-state determination unit 28 may generate data in a format that combines the liquid EC value and / or the corrected EC value with tag information. Alternatively, steady-state determination unit 28 may generate tag information in a format independent of the liquid EC value and / or the corrected EC value. The correspondence between the liquid EC value and / or the corrected EC value and the corresponding tag information may be determined by, for example, the detection date and time of the liquid EC value, or by a data ID or the like.

[0069] Furthermore, the internal pressure, which affects the liquid EC value, fluctuates immediately after the soil dryness state changes. Therefore, the steady-state determination unit 28 may further determine whether the internal pressure is in a steady state. This determination may be made based on whether the amount of change in the internal pressure per unit time is equal to or less than a predetermined value, similar to the determination of whether the liquid EC value is in a steady state.

[0070] The unit time for determining the steady state of the internal pressure is not particularly limited, but may be shorter than the unit time for determining the steady state of the liquid EC value. Such a unit time may be, for example, 30 seconds or more, preferably 1 minute or more, and more preferably 5 minutes or more. The unit time may be 30 minutes or less, preferably 15 minutes or less, and more preferably 10 minutes or less.

[0071] The steady-state determination unit 28 may determine the amount of change in the internal pressure by, for example, determining whether the difference between the internal pressure at the current time and the internal pressure at a time point unit time prior to the current time is equal to or less than a predetermined value. The steady-state determination unit 28 may obtain the internal pressure at a time point unit time prior to the current time from, for example, the storage device 30.

[0072] The "predetermined value" that is the threshold for the amount of change in the internal pressure may be set appropriately according to the unit time. For example, the steady-state determination unit 28 may set the predetermined value to 1.0 KPa·min -1 It may be less than 0.6KPa·min -1That is, when the unit time is 5 minutes, the predetermined value may be 5.0 KPa or less, and is preferably 3.0 KPa or less.

[0073] For example, the steady-state determination unit 28 may determine whether the steady state of the liquid EC value has continued for a predetermined period of time only if it determines that both the liquid EC value and the internal pressure are in a steady state. With this configuration, if the steady-state determination unit 28 determines that the liquid EC value is in a steady state, the liquid EC value can be considered to be a stable value obtained during a period of very little change. Therefore, users of the detection system 1 can accurately grasp the state of soil nutrients using highly reliable liquid EC values.

[0074] The data output unit 29 outputs various data from the control device 21. The data output unit 29 may output and store various data, such as data acquired from the soil nutrient sensor 10 and data acquired by the calculation unit 26, to the storage device 30. The data output unit 29 may also output the various data as images to the display device 32 for display.

[0075] The detection device 20 may include, as a minimum configuration, the EC acquisition unit 23, the pressure acquisition unit 24, and the correction unit 27.

[0076] [Method for detecting soil nutrients] The soil nutrient detection method according to this embodiment (hereinafter referred to as "this detection method") will be described using Figure 5. This detection method corrects the liquid EC value detected by the soil nutrient sensor 10 based on the internal pressure. In this detection method, it is preferable to further correct the liquid EC value based on the liquid temperature.

[0077] 5, the EC acquisition unit 23 first acquires the liquid EC value currently detected by the EC detection unit 15 (S1, EC acquisition step). The pressure acquisition unit 24 acquires the internal pressure detected by the pressure detection unit 16 (pressure acquisition step), and the temperature acquisition unit 25 acquires the liquid temperature detected by the temperature detection unit 17 (temperature acquisition step). The "current time" may be the time when the soil nutrient sensor 10 most recently detected the liquid EC value, etc.

[0078] When the soil nutrient sensor 10 detects liquid EC values ​​over time, the EC acquisition unit 23 preferably acquires past liquid EC values ​​detected by the EC detection unit 15 from the storage device 30 (S2). Similarly, the pressure acquisition unit 24 preferably acquires past internal pressures, and the temperature acquisition unit 25 preferably acquires past liquid temperatures. The term "past liquid EC values" here refers to liquid EC values ​​detected at least from the present time back to a time (reference time) that is the unit time used by the steady-state determination unit 28 to determine whether the soil is in a steady state. Note that, in this specification, when the term "liquid EC value" is used without specifying "past," it refers to the liquid EC value at the present time. The same applies to "past internal pressures" and "past liquid temperatures." When S2 is executed, the EC acquisition unit 23 may execute either S1 or S2 first.

[0079] Next, the correction unit 27 obtains a corrected EC value by correcting the liquid EC value based on the internal pressure (S3, correction step). The specific method of this correction has been explained above in the section "First Correction," and will not be described here.

[0080] Furthermore, when the temperature acquisition unit 25 has acquired the liquid temperature, the correction unit 27 preferably acquires a corrected EC value by further correcting the corrected EC value after the first correction based on the liquid temperature (S4). The specific method of this correction has been explained above in the section "Second Correction," and therefore will not be described here. When S4 is executed, the correction unit 27 may execute either S3 or S4 first.

[0081] Next, it is preferable that steady-state determination unit 28 executes the steady-state determination steps shown in S5 to S10 of Fig. 5. Steady-state determination unit 28 determines whether or not past detection data such as the liquid EC value has been acquired in S2 (S5). If it determines that past detection data has not been acquired (no in S5), steady-state determination unit 28 determines that steady-state determination cannot be performed, and adds tag information indicating that the steady-state determination is "false" to the acquired liquid EC value and corrected EC value (S9).

[0082] If the steady-state determination unit 28 determines in S5 that the steady-state determination cannot be performed, the tagging in S9 may not be performed, and the series of processes shown in FIG. 5 may be ended.

[0083] On the other hand, if past detection data was acquired in S2 (yes in S5), the steady-state determination unit 28 determines whether the amount of change in the liquid EC value per unit time from the reference time point to the present time is equal to or less than a predetermined value (S6). If it determines that the amount of change is not equal to or less than the predetermined value (no in S6), the steady-state determination unit 28 assigns tag information indicating that the steady-state determination is "no" to the acquired liquid EC value and corrected EC value (S9).

[0084] If it is determined that the amount of change in the liquid EC value is equal to or less than a predetermined value (yes in S6), the steady-state determination unit 28 may determine whether the amount of change in the internal pressure per unit time from the reference time point to the current time point is equal to or less than a predetermined value (S7).If it is determined that the amount of change is not equal to or less than the predetermined value (no in S7), the steady-state determination unit 28 assigns tag information indicating that the steady-state determination is "no" to the acquired liquid EC value and corrected EC value (S9).

[0085] When it is determined that the amount of change in the internal pressure is equal to or less than the predetermined value (yes in S7), the steady-state determining unit 28 determines that both the liquid EC value and the internal pressure are in a steady state.

[0086] Next, steady-state determination unit 28 determines whether the steady state of the current liquid EC value has continued for a predetermined time from its start point (S8). If it determines that the steady state has not continued for the predetermined time (no in S8), steady-state determination unit 28 assigns tag information indicating that the steady-state determination is "no" to the acquired liquid EC value and corrected EC value (S9). If it determines that the steady state has continued for the predetermined time (yes in S8), steady-state determination unit 28 assigns tag information indicating that the steady-state determination is "yes" to the acquired liquid EC value and corrected EC value (S10).

[0087] The execution order of S5 to S8 is not limited to the above, and may be any order. Furthermore, the data output unit 29 may output the corrected EC value of S9 or S10 to the display device 32 for display. At this time, the data output unit 29 may also output the tag information added to the corrected EC value in S9 or S10 to the display device 32 for display. Furthermore, the control device 21 may return to the process of S1 after executing S9 or S10. That is, the control device 21 may repeatedly execute the present detection method shown in FIG. 5 in a loop. When repeatedly executing the present detection method, the control device 21 may repeatedly execute the present detection method at predetermined intervals, such as every minute.

[0088] This steady-state determination process allows the user of the detection system 1 to accurately determine whether the liquid EC value at each point in time is a stable value obtained during a period of little change, or an unstable value obtained during any other period. Therefore, the user can accurately grasp the state of soil nutrients by, for example, referring to only the corrected EC values ​​obtained by the detection device 20 that have tag information attached to them indicating that the steady-state determination is "yes."

[0089] Furthermore, the detection system 1 according to this embodiment can provide highly reliable information about the state of soil nutrients. This reduces the need to station personnel near the target soil, making it easier to monitor, for example, the state of soil nutrients, including remote monitoring. Furthermore, by acquiring liquid EC values ​​over time using the detection system 1 according to this embodiment, the exact state of soil nutrients can be detected in real time, enabling accurate optimization and control of the nutrient state in the soil.

[0090] [Software implementation example] The functions of the detection device 20 (hereinafter referred to as the "device") can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block of the device (particularly each part included in the control device 21).

[0091] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program to realize each function described in each of the above embodiments.

[0092] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0093] In addition, some or all of the functions of each control block can be realized by a logic circuit. For example, an integrated circuit in which a logic circuit that functions as each control block is formed is also included in the scope of the present invention. In addition, the functions of each control block can be realized by, for example, a quantum computer.

[0094] Furthermore, each process described in each of the above embodiments may be executed by AI (Artificial Intelligence). In this case, the AI ​​may run on the control device or on another device (for example, an edge computer or a cloud server). [Example]

[0095] Example 1: Relationship between liquid EC value and internal pressure The influence of internal pressure on the EC value of a liquid was investigated. For the investigation, the Example 1 sensor was used, which is a tension meter (pressure sensor part: DP101-ZA, Panasonic Corporation) equipped with a cylindrical container with a porous cup and a built-in electrical conductivity sensor (analog TDS sensor, Gravity Inc.). The container was sealed as tightly as possible. In addition, in the Example 1 sensor used in this investigation, the container was equipped with a syringe-type suction device, and the internal pressure could be adjusted using the suction device.

[0096] Liquid fertilizer (Nutrient Solution No. 2) was poured into the container. The liquid fertilizer was diluted to three conditions: 0.5 dS / m, 1.0 dS / m, and 2.0 dS / m EC values ​​at 25°C (set EC). The liquid temperature was set to 25°C, and the internal pressure (gauge pressure) was set to -70 KPa. The liquid EC and internal pressure were then recorded over time until the internal pressure returned to atmospheric pressure. It is believed that there were tiny gaps in the container, such as at the insertion point of the electrical conductivity sensor, and that air entered the container through these gaps, causing the internal pressure to gradually return to atmospheric pressure.

[0097] Figure 6 shows the results of three repeated trials under each condition. As shown in Figure 6, even when the set EC of the liquid fertilizer was the same, the greater the difference between the internal pressure of the container and atmospheric pressure, the lower the liquid EC value was detected. This was the same regardless of the set EC used in the experiment.

[0098] Figure 6 shows the plots of the detected values ​​over time under each condition, as well as the corresponding approximate line and approximate formula (y = ax + b). In this approximate formula, y represents the liquid EC value (dS / m) and x represents the internal pressure (KPa). Furthermore, a corresponds to the first correction coefficient mentioned above, which is 0.00008≦a≦0.0004. Furthermore, b is a value that varies depending on the set EC of the liquid (liquid fertilizer) in the container.

[0099] It has been shown that extremely accurate correction based on the above-mentioned experimental results is possible when the first correction coefficient is set to 0.00008 or more and 0.0004 or less. On the other hand, for example, if a larger correction to the liquid EC value is desired, the first correction coefficient may be set to a value greater than 0.0004. Conversely, if a smaller correction to the liquid EC value is desired, the first correction coefficient may be set to a value less than 0.00008.

[0100] Example 2: Relationship between liquid EC value, liquid temperature, and type of fertilizer The influence of the liquid temperature and the type of fertilizer on the liquid EC value was examined. For the examination, the sensor of Example 2, which has the same configuration as the sensor of Example 1 except that it does not have a suction device, was used.

[0101] The portion of the sensor in Example 2 containing the porous cup was immersed in approximately 2 L of liquid fertilizer (external solution). The temperature of the external solution was adjusted to four conditions: 10°C, 20°C, 25°C, and 30°C using an incubator (FMU-1331, NK Systems Co., Ltd.). Five external solutions were used: nutrient solution No. 2 (three-element compound fertilizer), ammonium sulfate solution (ammonium sulfate), phosphate fertilizer solution (P), potassium chloride solution (KCl), and sodium chloride solution (NaCl). Each external solution was diluted to an EC value of 1.0 dS / m at 25°C. Distilled water was poured into the container of the sensor in Example 2 at the start of the experiment.

[0102] Figure 7 shows the plots of the detected values ​​over time under each condition, as well as the corresponding approximate line and approximate formula (y = cx + d). In this approximate formula, y represents the liquid EC value (dS / m) and x represents the liquid temperature (°C). c corresponds to the second correction coefficient mentioned above, and is in the range of 0.0138 ≤ c ≤ 0.019. d is a value that varies depending on the type of external liquid. These results indicate that the appropriate range of the second correction coefficient does not change significantly even if the type of external liquid is different.

[0103] Note that if the second correction coefficient is set to 0.0138 or more and 0.019 or less, extremely accurate correction based on the above-mentioned experimental results is possible. On the other hand, for example, if a larger correction to the liquid EC value is desired, the second correction coefficient may be set to a value greater than 0.019. Conversely, if a smaller correction to the liquid EC value is desired, the second correction coefficient may be set to a value less than 0.0138.

[0104] Example 3: Change in liquid EC value at steady state The liquid temperature was changed to study the change in the liquid EC value over time and the amount of change per unit time. The study used the sensor from Example 2 described above. The temperature of the liquid fertilizer (external liquid) in which the sensor from Example 2 was immersed was changed using an incubator. Three types of external liquid were used: nutrient solution No. 2, ammonium sulfate solution (ammonium sulfate), and sodium chloride solution (NaCl), and they were diluted so that the EC value at 25°C was 1.0 dS / m.

[0105] While acquiring the liquid EC value over time, the temperature of the external liquid in the incubator was changed and the type of external liquid was also changed. Example 2 Distilled water was poured into the sensor container at the start of the experiment.

[0106] The upper graph in Figure 8 shows the results of recording the liquid EC values ​​over time, and the lower graph shows the results of calculating the change in the liquid EC value over the past 10 minutes at each detection point. The type and temperature of the external liquid are shown above the graph in Figure 8. The horizontal axis of the graph also shows the "hour:minute" at the detection point. This is the same as Figure 10.

[0107] As shown in Figure 8, immediately after changing the temperature or type of external liquid, the amount of change in the liquid EC value temporarily increased. Furthermore, when the change in the liquid EC value over time was small and could be considered steady, the amount of change in the liquid EC value over 10 minutes was 0.01 dS / m or less.

[0108] From the above, it was shown that if the change in the liquid EC value per unit time is 0.01 dS / m or less, when the unit time is 10 minutes, the liquid EC value can be said to be in a steady state. However, for example, during periods of large temperature changes, the change in the liquid EC value for determining the steady state may be set to a value greater than 0.01 dS / m per 10 minutes.

[0109] Example 4: Change in liquid EC value due to change in internal pressure The internal pressure was changed to study the change in the liquid EC value over time. The Example 2 sensor was used for the study. Nutrient solution No. 2 diluted to an EC value of 1.0 dS / m at 25°C was poured into the container of the Example 2 sensor. The internal pressure was set to -30 KPa by covering the porous cup with a dry cloth, and the Example 2 sensor was then immersed in the liquid fertilizer (external liquid) under each condition, and the change in the liquid EC value and internal pressure over time was recorded. The EC values ​​of the external liquid at 25°C (external EC) were set to three conditions: 0.5 dS / m, 1.0 dS / m, and 2.0 dS / m.

[0110] Figure 9 shows the changes in the liquid EC value and internal pressure over time. The horizontal axis of Figure 9 represents "0 minutes," which is the time when the sensor of Example 2 was immersed in the external solution. As shown in Figure 9, the liquid EC value changes with changes in internal pressure, and converges and reaches a steady state with a delay after the change in internal pressure has converged. It is thought that the liquid fertilizer in the container then changes gradually due to osmotic pressure until it reaches equilibrium with the external solution.

[0111] These results suggest that the time it takes for the change in liquid EC value due to a change in internal pressure to reach a steady state is 300 to 420 seconds after the internal pressure reaches a steady state. In other words, since the steady / unsteady state of liquid EC value is affected by changes in the soil drying state, it is necessary to take changes in the drying state into account when determining the steady state of liquid EC value.

[0112] Example 5: Change in internal pressure in a steady state The changes in internal pressure over time and the amount of change per unit time in response to changes in the soil's dryness state were examined. The study was carried out using the sensor of Example 2 in an incubator set at 30°C, with distilled water poured into the container of the sensor of Example 2. The part of the sensor of Example 2 containing the porous cup was buried in a No. 7 pot filled with soil made from a 1:1 (v / v) mixture of decomposed granite and bark compost. While recording the internal pressure over time, the pot was irrigated three times with 200-300cc of distilled water per irrigation using a beaker.

[0113] The upper graph in Figure 10 shows the results of recording the internal pressure over time, and the lower graph shows the calculated change in internal pressure over the past minute at each detection point. The arrowheads in the upper graph in Figure 10 indicate the time when irrigation was performed. As shown in Figure 10, the change in internal pressure temporarily increased immediately after irrigation. Furthermore, the change in internal pressure over time was small and could be considered steady, with the change in internal pressure over one minute being 0.6 KPa or less.

[0114] From the above, it was shown that, when the unit time is 1 minute, if the change in internal pressure per unit time is 0.6 KPa or less, the internal pressure can be said to be in a steady state. Note that, for example, if the irrigation frequency is low and the amount of irrigation per session is large, and the change in internal pressure due to irrigation is considered to be large, the change in internal pressure for determining a steady state may be set to a value greater than 0.6 KPa per minute. Also, if the amount of irrigation per session is small and the change in internal pressure due to irrigation is considered to be small, the change in internal pressure for determining a steady state may be set to a value sufficiently smaller than 0.6 KPa per minute.

[0115] [Additional Notes] The present invention is not limited to the above-described embodiments / examples, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments / examples are also included in the technical scope of the present invention. [Explanation of symbols]

[0116] 1. Detection System 10 Soil nutrient sensor 11 Container 12 Porous Cup 14 liquid 15 EC detection unit 16 Pressure detection unit 17 Temperature detection unit 20 Detection device 23 EC Acquisition Department 24 Pressure acquisition unit 27 Correction section

Claims

1. an EC acquisition step of acquiring a liquid EC value, which is the EC value of the liquid in a container equipped with a porous cup; a pressure acquiring step of acquiring a pressure inside the container; A soil nutrient detection method characterized by comprising a correction process in which a first correction is performed to correct the liquid EC value to a larger value the greater the difference between atmospheric pressure and the pressure, thereby obtaining a corrected EC value that is an indicator of the nutrient status of the soil in which the container is buried.

2. In the EC acquisition step, the liquid EC value is acquired over time, The detection method according to claim 1, further comprising a steady-state determination step of determining whether a steady state in which the amount of change in the liquid EC value per unit time is equal to or less than a predetermined value has elapsed for a predetermined period of time or more.

3. a temperature acquisition step of acquiring a temperature of the liquid; 3. The detection method according to claim 1, wherein in the correction step, in addition to the first correction, a second correction is performed to correct the liquid EC value to a smaller value as the temperature is higher, thereby obtaining the corrected EC value.

4. an EC acquisition unit that acquires a liquid EC value that is an EC value of a liquid in a container equipped with a porous cup; a pressure acquisition unit that acquires the pressure inside the container; A soil nutrient detection device characterized by having a correction unit that performs a first correction to correct the liquid EC value to a larger value the greater the difference between atmospheric pressure and the pressure, and obtains a corrected EC value that is an indicator of the nutrient status of the soil in which the container is buried.

5. a container having a porous cup and capable of containing a liquid; an EC detection unit that detects a liquid EC value that is the EC value of the liquid; A soil nutrient sensor comprising: a pressure detection unit that detects the pressure inside the container.

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