JP4208764B2 - Automatic irrigation method and automatic irrigation apparatus therefor - Google Patents

Description

  The invention of this application relates to an automatic irrigation method and an automatic irrigation apparatus therefor. More specifically, the invention of this application relates to a method for automatically irrigating by detecting a moisture state of a plant by a moisture sensor and an irrigation apparatus therefor.

  In recent years, industrial activities have become active, and as a result of the large amount of greenhouse gas emissions, global warming, where the temperature rises, has been taken up as an environmental issue. As one of the greening support technologies to prevent global warming, Automatic irrigation technology is drawing attention.

  Water is indispensable for plants to grow by photosynthesis. If the soil in which the plant grows has adequate moisture, there is no problem, but if the moisture is insufficient, it will become drought, and the plant will die if the degree of moisture progresses. In order to prevent this, it is necessary to perform moderate irrigation depending on the dryness of the soil. In general, the timing of irrigation is determined by human observation and judgment of recent weather conditions, soil dry-burning conditions, plant activity on the ground, leaf wilting conditions, and the like. If the timing of irrigation to the plant is significantly delayed, no matter how much water is given, it will die without being revived. For this reason, conventionally, an apparatus and a method for automatically irrigating a plant without requiring manual labor or electric power have been proposed. For example, it consists of a water reservoir that can hold flower pots and an automatic irrigation device that is housed in the water reservoir or connected by a water pipe and installed outside the water reservoir. The automatic irrigation device is directly connected to the water supply source. There has been proposed a plant cultivation apparatus that includes a nozzle to which a water supply pipe is connected and a float, and the water outlet of the nozzle is blocked by the buoyancy of the float when the water level of the water reservoir reaches a predetermined height (for example, , See Patent Document 1). As an automatic irrigation method, a plant for measuring water consumption is cultivated under substantially the same conditions as the irrigation target plant, and the water consumption measuring plant naturally absorbs water from the tank. A method has been proposed in which water is supplied to the aquarium according to the decrease in the amount of water in the aquarium, and the irrigated plant is also irrigated with the amount of water corresponding to the amount of the replenished water (for example, , See Patent Document 2).

  However, according to the plant cultivation apparatus and the automatic irrigation method described above, since water is supplied by detecting a change in the water level of the water storage container or tank, it is effective where water for irrigation can always be prepared abundantly. In dry areas such as deserts, where water resources are scarce, it is difficult to supply water frequently, and the water stored in tanks must be saved as much as possible, and if water is not supplied to plants, it will wither. It is desired to irrigate immediately before the extreme state.

  The water deficiency state of the plant does not come suddenly. If the period without precipitation continues for a long time, the amount of water in the soil gradually decreases, and eventually it becomes an extreme state for the plant. In order to reach this extreme state, there is always a shortage of moisture in the soil. Therefore, a method of irrigating by quantitatively detecting soil moisture with a soil moisture meter or the like can be considered. However, it is difficult to determine whether the detected value is really a limit for plants. For example, it is not known whether the ground location measured by a soil moisture meter is a good representation of the amount of moisture around the roots of the plant. In particular, in dry areas such as deserts, there is a considerable difference between soil moisture near the surface and soil moisture at a depth where the main part of plant roots is present. Although the measurement depth should be appropriate, there is a problem that the depth of the main part of the plant root varies depending on the target plant, and the depth cannot be determined uniformly.

Until now, the method of knowing the extreme state of a plant during drought has been to measure the water potential of the leaf, which is one of the parameters representing the moisture state of the plant, and to measure the extreme value of the water potential inherent to that plant. Are known. A pressure chamber method or a cyclometer method is generally used as the measurement method. However, each measurement method requires excision of a petiole or a part of a leaf, which is partially but destructive, and takes time and labor for measurement. In addition, the limit value of water potential varies depending on the type of plant, so it was necessary to know each of the applicable plants.
Japanese Patent Laid-Open No. 10-113081 JP 10-000040 A

  Therefore, the invention of this application is based on the background as described above, and is effective even in a dry land such as a desert where water resources are scarce. It is an object of the present invention to provide an automatic irrigation method and an automatic irrigation device therefor that can automatically determine the timing of irrigation without intervention and perform irrigation.

In order to solve the above-mentioned problem, this application first detects the moisture state by measuring the electrical impedance of the plant tissue of the plant rooted in the earth or the electrical capacitance of the plant part. An automatic irrigation method characterized by irrigating in response.
Secondly, an automatic irrigation method is provided, wherein the ground impedance between the ground and the root of the plant is measured to detect the water state, and watering is performed according to the water state.

The invention of this application, the third, a device for irrigation to plants rooted in earth and a watering unit and the measurement unit and the irrigation control unit, the measuring unit, the electrical impedance of plant tissue the have one or more plant tissues moisture sensor for measuring, or one or more plant moisture sensor for measuring the electrical capacitance of the site of the plant, irrigation control unit, electrical impedance measured by the measuring unit, from the electrical capacitance Provided is an automatic irrigation apparatus characterized in that a water state of a plant is detected, watering to the plant is controlled according to the water state, and watering is performed in a watering unit.
Fourth, the measurement unit further includes one or more moisture sensors that measure the ground impedance between the ground and the root of the plant, and the irrigation control unit is configured to control the plant according to the moisture state detected from the ground impedance. There is provided an automatic irrigation apparatus characterized in that irrigation is controlled and irrigation is performed in an irrigation unit.

  According to the invention of this application, it is effective even in a dry land such as a desert where water resources are scarce. It is possible to automatically determine the timing of irrigation and perform irrigation.

  The invention of this application has the characteristics as described above, and the embodiments of the invention will be described in more detail below.

  The invention of this application detects the moisture state by measuring at least one of the electrical impedance of the plant tissue of the plant rooted in the ground, the ground impedance between the ground and the root of the plant, and the electrical capacitance of the plant part, The present invention relates to a method of irrigation according to the moisture state and an automatic irrigation apparatus for the method.

  FIG. 1 is a diagram schematically showing an embodiment of the automatic irrigation apparatus of the invention of this application. The electrical impedance of the plant tissue of the plant rooted in the ground is measured by the measurement unit, and the irrigation control unit (9 ) Is an automatic irrigation device that detects the moisture state of the plant and automatically irrigates the irrigation unit (11) according to the moisture state. In FIG. 1, a tree (1) is illustrated as an example of a plant, but plants such as plants and vegetables may be used in addition to trees.

  The water state of a plant can be known from the water potential, but it can be substituted for the water potential by measuring the electrical impedance of the plant tissue related to this even if it is not directly measured. That is, the invention of this application regards the electrical impedance of the plant tissue related to the water potential as a moisture sensor signal from the plant, thereby determining the timing of automatic irrigation.

  The simplest equivalent circuit of the electrical impedance of plant tissue is shown by a parallel circuit of a resistor R and a capacitor C. The resistance R is a resistance where a current flowing mainly through an extracellular tissue is involved. The capacity C is an amount formed by a membrane that controls the inner and outer boundaries of the cell. Evidence that the cell is alive is the presence of this membrane capacity. If the activity of the cells is high, the membrane functions well and inevitably has a large capacity. If activity decreases, membrane function decreases and capacity decreases. If the cell dies, there is no longer a boundary between the inside and the outside of the cell, so the capacity disappears and the impedance of the plant tissue is only resistance. In addition, the resistance becomes a very high value because the moisture becomes less and the electrical conductivity becomes worse if the entire tissue is dried.

  FIG. 2 shows a measurement circuit for measuring the electrical impedance of the plant tissue. Attach four electrodes as shown in the figure to the plant tissue part (6) where you want to measure the electrical impedance of plant stems, trunks, branches, etc., and connect the first electrode for energization (2) and the second electrode for energization (5). An AC current I is passed between them by an AC power source (7), and a voltage V generated between the first electrode for voltage measurement (3) and the second electrode for voltage measurement (4) is measured. Furthermore, if the phase θ of the voltage V with respect to the alternating current I is measured, the electrical impedance Z of the plant tissue between the first electrode for voltage measurement (3) and the second electrode for voltage measurement (4) is Z = lVl / It is expressed as lIl (cos θ + j · sin θ). The method for measuring the electrical impedance in this way is called the four-electrode method (or the four-terminal method or the four-probe method), and this method uses the electrode for measurement and the plant tissue part (6). This is a generally used method because the electrical impedance of the plant tissue part (6) can be measured without being affected by the impedance generated at the contact interface and the measurement lead wire, and based on this principle. The impedance measuring instrument is available as an LCR meter or an impedance meter. When the living body is the measurement target, the measurement lead wire and the living body are coupled by the electrode, but the living body has moisture, and the moisture is an electrolyte, so it is chemically stable to use it with the electrode attached for a long time. Metal materials are considered. As such a metal material, for example, platinum or inexpensive stainless steel is preferably used. As for the shape of the electrode, it is inserted into the plant tissue to an appropriate depth, so that the needle, the stem, and the branches are thin for needles, and the thick one is nail-shaped according to the thickness. The electrode is appropriately selected.

  Since the resistance R and the capacitance C shown in the parallel equivalent circuit are obtained from the impedance measurement described above, how these values change with respect to the change in the moisture content of the plant tissue is shown by an in vitro experiment. The measurement object was Eucalyptus camaldulenis, a woody plant often used for afforestation, and seedlings grown in pots using vermiculite as a medium from seeds collected in dry land in Western Australia were used. A green stem portion (diameter: about 3 mm) which is not made into a xylem from a plurality of seedlings was excised about 15 cm in length, and 3 cm in the central portion was taken as a measurement site. The graphs showing the relationship between the relative moisture content of the cut branches obtained from the measurement results, the electric capacity, and the resistance are shown in FIGS. 3 and 4, respectively. Here, the relative water content is the ratio of the water content to the water content in the saturated state. Of the four samples shown in the figure, except for those with leaves, only the stems with the leaves dropped are samples.

  From FIG. 3, the electric capacity in the kneaded state (relative water content 1 (kg / kg)) was approximately equal to about 500 pF for all samples. When the relative water content decreased from 0.6 (kg / kg), the electric capacity began to decrease gradually, and when the relative water content became 0.4 (kg / kg) or less, the electric capacity decreased rapidly. Although there are individual differences in the method of decreasing the electric capacity, the capacity of all the samples became zero when the relative water content was around 0.2 (kg / kg).

  On the other hand, as shown in FIG. 4, with respect to the resistance, when the relative moisture content is in the range of 0.4 (kg / kg) or more, the increase in resistance accompanying the decrease in the relative moisture content is moderate, and all the samples tend to be almost equal. Indicated. When the relative moisture content decreased below 0.4 (kg / kg), the resistance began to increase rapidly, and reached 1 MΩ or more in the vicinity of the relative moisture content of 0.2 (kg / kg). From these relationships, when the relative water content falls below 0.4 (kg / kg), the activity of the plant changes dramatically, and when the relative water content is about 0.2 (kg / kg), the activity is completely lost. It is thought that it will die. Based on the relationship between the relative water content and water potential measured with the petiole samples of other individuals, the relative water content of 0.4 (kg / kg) and 0.2 (kg / kg) is the water potential of -5 MPa and -9 MPa, respectively. It was estimated that In addition, even when leaves were attached, it was confirmed that the relationship between relative moisture content, resistance, and capacitance was almost the same as that without leaves. In this way, by associating the electrical capacity or resistance of the plant tissue with the relative water content or water potential, it becomes possible to infer the moisture state of the plant from the impedance measurement.

  As described above, in FIG. 1, a plant tissue moisture sensor (8) having four electrodes, which is a measurement unit for measuring the electrical impedance of plant tissue, is placed at an arbitrary position on the tree (1), for example, at the lower part, upper part of the trunk, Attached to a branch, the electrical impedance of the plant tissue is measured. In many plants, the decrease in water content during drought begins at a distance away from the root. Therefore, the plant tissue moisture sensor (8) is attached to several points of the tree (1), and the electrical impedance of the plant tissue is set. By measuring the amount of water in the entire tree (8), the timing of irrigation can be reliably determined.

  The irrigation control unit (9) is composed of, for example, an SW unit (91), a detection unit (92), and an irrigation determination unit (93), and leads from the plurality of plant tissue moisture sensors (8) are SW units ( 91), and the electrical impedance of the plant tissue is detected from each plant tissue moisture sensor (8) by the detection unit (92). In the irrigation determination unit (93), the water injection valve (10) is set to open and close according to the value of the electrical impedance from the relationship between the electrical impedance and the relative moisture content of the plant. For this reason, the timing of irrigation is judged from the detection result of the electrical impedance of the plant tissue, and when the relative moisture content of the plant is low, the water injection valve (10) is opened, and the water storage tank ( 111) is led to an irrigation tube (112) and drip irrigated or sprinkled at the root of the tree (1).

  FIG. 5 is a diagram schematically showing an embodiment of another automatic irrigation apparatus of the invention of this application. According to FIG. 5, in addition to the plant tissue moisture sensor (8) for measuring the electrical impedance of the plant tissue of the plant, the moisture sensor (12) for measuring the ground impedance between the ground and the plant root is a measuring unit. It is attached as.

  In general, the ground impedance Z of a ground metal object is represented by Z = ρ · f (shape, dimension). Here, ρ is the earth resistivity representing the electrical properties of the earth, and the magnitude of ρ depends on the moisture content of the soil. f is a function determined by the shape and size of the ground metal object. Regarding the plant ground impedance, the root tissue impedance further enters the function f, but the product of ρ and f does not change. That is, when the ground impedance of the root of the plant is measured, information on dryness and wetness of the ground can be obtained together with the tissue impedance of the root. From this, since the ground impedance of the root of the plant can be captured as the sensor signal of the plant itself, the disadvantage of the method of measuring soil moisture using the soil moisture meter as described above can be solved.

  The method for measuring the ground impedance of a plant root has been proposed by the present inventors as a method for measuring the ground resistance of a plant root (see Japanese Patent Application Laid-Open Nos. 11-332377 and 2003-245015). According to these methods, the four-electrode method is applied in order to eliminate the influence of electrode resistance as in the case of measuring the electrical impedance of plant tissue.

  Here, as shown in FIG. 5, a moisture sensor (12) including four electrodes of the first auxiliary electrode C, the first electrode T, the second electrode E, and the second auxiliary electrode P is used. An alternating current was passed between the first auxiliary electrode C driven into the ground and the first electrode T or the second electrode E attached to the tree (1), and attached to the other second auxiliary electrode P and the tree (1). The voltage between the second electrode E or the first electrode T is measured. The ground position of the first auxiliary electrode C is usually separated from the tree (1) by 10 m or more so as to satisfy the ground impedance measurement method, and the second auxiliary electrode P is intermediate between the tree (1) and the first auxiliary electrode C. And Since the same detection unit (92) as that for measuring the electrical impedance of the plant tissue can be used to measure the ground impedance of the plant root from the moisture sensor (12), the SW unit (91) as shown in FIG. A switching part may be added to.

  Thus, the irrigation timing can be determined with high accuracy by combining the ground impedance of the root in the underground part of the plant and the electrical impedance of the plant tissue in the ground part. Furthermore, the accuracy can be further improved by combining the wet and dry information on the soil where the plant grows. Of course, the irrigation timing can be determined with high accuracy by measuring only the ground impedance of the root in the underground part of the plant.

  Further, a plant moisture sensor (13) capable of mainly observing a change in capacitance based on the principle of a capacitor may be used as a sensor for knowing the moisture state of a plant and a sensor that performs non-invasively without inserting an electrode. According to this sensor, it can be used as an auxiliary means for the main part of the invention of this application or as a sensor for knowing a simple moisture state. The capacitance of the parallel plate type capacitor is represented by ε · (S / d). Here, ε is the dielectric constant of a substance (plant stem, trunk, leaf, etc.) filled between the electrode plates of the capacitor, S is the area of the electrode plate, and d is the distance between the electrode plates. Since the dielectric constant of water is nearly 80 times greater than that of air, the change in the amount of moisture between the capacitor electrode plates can be known from the change in the capacitance of the capacitor. The parallel plate type is effective for detecting a change in the moisture content of the leaves. Even if the type of the capacitor is not a parallel plate type, it can be applied to a cylindrical stem / stem / branch (14) as shown in FIG. An insulating sheet (16) is inserted between the two electrode plates (15) and the object stems, trunks, and branches (14). In the same manner, even when the object is a leaf, the insulating sheet (16) is inserted between the electrode plate and the leaf. In principle, the connection of the lead wire to the measuring device is based on the four-electrode method. Actually, as shown in FIG. 6, the first lead for energization (17) and the first lead for voltage measurement ( Connect 18). In the other electrode plate, the second lead for voltage measurement (19) and the second lead for energization (20) are connected. The four lead wires of the first lead for energization (17), the first lead for voltage measurement (18), the second lead for voltage measurement (19), and the second lead for energization (20) are shown in FIG. The first electrode (2) for voltage measurement, the first electrode for voltage measurement (3), the second electrode for conduction (4), and the second electrode for voltage measurement (5) correspond to each. By doing so, the influence of the resistance and inductance of the lead wire from the measuring instrument to the capacitor can be eliminated by the principle of the four-electrode method, and only the electric capacity can be measured. Since plant tissue also has resistance components, these can be treated as dielectric loss of capacitors. By attaching the plant moisture sensor (13) to each part of the plant and measuring the electrical capacity of the plant, the moisture content of the whole plant can be grasped and the timing of irrigation can be assured. In addition, by using the plant tissue moisture sensor (8) and the moisture sensor (12) in combination, the irrigation timing can be determined with higher accuracy.

  FIG. 7 is a diagram schematically showing still another embodiment of the invention of this application. According to FIG. 7, drip irrigation or watering equipment is applied to a target plantation or existing forest using existing technology. The water tank (111) is used as the water resource that is the irrigation unit (11), and water can be supplied to the water storage tank (111) by a general method performed in a general area. For example, various modes such as pumping up water from a well by storing rainwater or a windmill, or using this in a place where there is a water supply line can be considered. The irrigation timing is determined by attaching the plant tissue moisture sensor (8), moisture sensor (12), and plant moisture sensor (13), and the irrigation controller (9) uses the electrical impedance of the plant tissue, the ground impedance of the root, Measure the electrical capacity of the trunk, branches and leaves, analyze the detailed information on the moisture content of the tree (1) itself, and open the irrigation valve (10) just before the limit that would lead to death if water is deficient any more. To implement. A comprehensive judgment is made based on information obtained from one tree (1) or a plurality of trees (1) as necessary. Once set, this device is automated and unattended except for maintenance, so it is suitable for implementation in places away from people's residential areas such as deserts and semi-arid areas. In addition, although the Example to a tree (1) was shown in FIG. 7, if a tree (1) is replaced with agricultural products etc., it can apply also to these fences.

  Furthermore, in recent years, in-house (house) cultivation of crops has become increasingly popular in recent years, and rather than the problem of drought, the cultivation method according to the properties of all crops and the water control method for such cultivation have been studied at the practical stage. It is becoming necessary. For example, in tomato cultivation, in order to produce tomatoes having a high sugar content, cultivation is carried out with rather less water supplied. That is, a method of producing tomatoes having a high sugar content by appropriately applying water stress has been performed. However, the current situation is that the determination of an appropriate amount of water does not directly obtain information directly from the plant itself but relies on empirical determination. If the automatic irrigation method of the present invention is applied, comprehensively based on the measured values of the electrical impedance of the plant tissue, the ground impedance between the ground and the root of the plant, the electrical capacity of the plant parts such as stems and leaves. Judging, it is possible to accurately control an appropriate amount of water.

  The above is an example, but the agricultural applicability is considered as follows. There is an inseparable relationship between plants (crop) and water in all crops. Cultivation method and its management method (growth / flowering / fruit adjustment, flower bud formation / differentiation, coloring, enlargement, etc.), soil / cultivation environment control (light wavelength, temperature, humidity control, etc.), harvest target maturity It is necessary to establish biological moisture control methods for grasping, processing and quality control methods (storage, texture, ingredients, taste, freshness maintenance, etc.). In addition to further increasing the added value of future crops through development, there is a large part contributing to safe food production. Specific target crops that can be considered are all useful plants such as flowers, flowering trees, vegetables, fruit trees, grasses, and cereals.

It is the figure which showed typically one Embodiment of the automatic watering apparatus of invention of this application. It is a measurement circuit for measuring the electrical impedance of plant tissue. It is the graph which showed the relationship of the electrical capacity with respect to the relative water content of a trunk. It is the graph which showed the relationship of the resistance with respect to the relative water content of a trunk. It is the figure which showed typically one Embodiment of another automatic irrigation apparatus of invention of this application. It is a figure for demonstrating the plant moisture sensor of invention of this application. It is the figure which showed typically another one Embodiment of invention of this application.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tree 2 1st electrode for electricity supply 3 1st electrode for voltage measurement 4 2nd electrode for voltage measurement 5 2nd electrode for electricity supply 6 Plant tissue part 7 AC power supply 8 Plant tissue moisture sensor 9 Irrigation control part 91 SW part 92 Detection part 93 Irrigation judgment unit 10 Irrigation valve 11 Irrigation unit 111 Water storage tank 112 Irrigation tube 12 Moisture sensor 13 Plant moisture sensor 14 Stem / stem / branch 15 Electrode plate 16 Insulating sheet 17 First lead for energization 18 First lead for voltage measurement 19 Voltage Second lead for measurement 20 Second lead for energization

Claims (4)

An automatic irrigation method characterized by detecting a water state by measuring an electrical impedance of a plant tissue of a plant rooted in the ground or an electric capacity of a plant part, and irrigating according to the water state. The automatic irrigation method according to claim 1, further comprising the step of measuring a ground impedance between the ground and the root of the plant to detect a water state and irrigating according to the water state. An apparatus for irrigating a plant rooted in the earth, comprising a measurement unit, a irrigation control unit, and a irrigation unit, wherein the measurement unit measures one or more plant tissue moisture sensors for measuring the electrical impedance of the plant tissue, or a plant The irrigation control unit detects the moisture state of the plant from the electrical impedance and the electrical capacitance measured by the measurement unit, and according to the moisture state. An automatic irrigation apparatus characterized in that irrigation to a plant is controlled and irrigation is performed in an irrigation unit. The measurement unit further includes one or more moisture sensors that measure the ground impedance between the ground and the plant root, and the irrigation control unit controls irrigation to the plant according to the moisture state detected from the ground impedance. 4. The automatic irrigation apparatus according to claim 3, wherein the irrigation unit performs irrigation.