Root zone sensor and measurement system

Abstract

This rhizosphere sensor 1 is provided with a plate 10 that is provided with a guide 11 disposed in the extending direction DR of a root R of a plant P, and a sensing unit 20 that is disposed in the extending direction DR along the surface of the plate 10. The sensing unit 20 is provided with, in the farther order from the plate 10, a first electrode layer 21 formed from an electroconductive material, an insulating material layer 22 formed from an insulating material, and a second electrode layer 23 formed from an electroconductive material. Each of the first electrode layer 21 and the insulating material layer 22 has a slit of which the length direction is the same as the extending direction DR.

Description

Technical Field

[0001] The present disclosure relates to rhizosphere sensors and measurement systems.

Background Art

[0002] Plants secrete trace amounts of substances such as organic acids or amino acids from their roots. Useful substances contained in the soil around the roots are changed by chemical reactions with the secretions. It is known that plants take in the changed substances and utilize them for growth. The range affected by the secretions of plant roots is called the rhizosphere.

[0003] As soil analysis in horticulture, electrical conductivity (EC) measurement is used (Patent Document 1). In EC measurement, soil acidity and the amount of fertilizer salts are measured. The soil can be used to measure the current between two electrodes in the same way as in an aqueous solution by water supply such as rainfall. Electrical conductivity is measured by an EC meter and is widely used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Secretions from plant roots are trace amounts and local. It is difficult to analyze the amount and chemical composition of secretions from plant roots.

[0006] For example, by inserting the electrode plates of the EC meter described in Patent Document 1 into the soil, it becomes possible to measure the concentration of electrolytes in the soil. However, the diffusion range of secretions from plant roots is limited. Simply inserting the electrode plates into the soil only measures the average electrical conductivity of the area where plant roots spread. The method described in Patent Document 1 cannot measure the characteristics in the rhizosphere with sufficient accuracy.

[0007] This disclosure is made in view of the above circumstances, and the purpose of this disclosure is to provide a technology that can measure characteristics in the rhizosphere. [Means for solving the problem]

[0008] A rhizosphere sensor according to one aspect of the present disclosure comprises a plate having a guide disposed in the direction of extension of a plant root, and a sensing unit disposed along the surface of the plate in the direction of extension. The sensing unit has, in order from furthest from the plate, a first electrode layer formed of a conductor, an insulating layer formed of an insulator, and a second electrode layer formed of a conductor. The first electrode layer and the insulating layer have slits whose longitudinal direction is the direction of extension.

[0009] A measurement system according to one aspect of the present disclosure comprises the root zone sensor and a measuring device for measuring the electrical characteristics between the first electrode layer and the second electrode layer. [Effects of the Invention]

[0010] This disclosure provides a technology that enables the analysis of secretions from plant roots. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a diagram illustrating a root zone sensor according to an embodiment of the present disclosure. [Figure 2] Figure 2 is a top view of the root zone sensor. [Figure 3] Figure 3 illustrates the usage status of the root zone sensor. [Figure 4] Figure 4 is a diagram illustrating the sensing unit and measurement system. [Figure 5] Figure 5 shows a top view and a side view of the first electrode layer of the sensing unit. [Figure 6] Figure 6 illustrates a root zone sensor equipped with a marker. [Modes for carrying out the invention]

[0012] Embodiments of this disclosure will be described below with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals and their descriptions are omitted.

[0013] The root zone sensor 1 according to an embodiment of the present disclosure will be described with reference to Figures 1 to 3. In this disclosure, the directions perpendicular to the ground are referred to as the X direction and the Y direction. The direction perpendicular to the ground is referred to as the Y direction.

[0014] The root zone sensor 1 comprises a plate 10 and a sensing unit 20. The plate 10 has a roughly fan-shaped form with a large upper side and a small lower side. The sensing unit 20 is provided in the direction of the lower side of the plate 10. As shown in Figure 1, the root zone sensor 1 is buried in the ground with the sensing unit 20 positioned downwards and the plate 10 positioned at an angle.

[0015] The plate 10 guides the roots that are in contact with the plate 10 to the sensing unit 20. The plate 10 may be formed in a planar shape. Alternatively, the plate 10 may be formed in a curved shape such that, in the state shown in Figure 1, the left and right sides curve towards the front. The plate 10 is made of an insulator such as biodegradable plastic.

[0016] The sensing unit 20 clamps the root, which has been guided by the plate 10, with electrodes. This makes it possible to measure the electrical properties of secretions near the root R.

[0017] As shown in FIG. 2, the rhizosphere sensor 1 is buried in the ground so that the plate 10 is located directly below the plant P. The plant P is preferably planted at a position directly above the vicinity of the left and right centers of the upper side of the plate 10.

[0018] The root R of the plant P is known to grow vertically downward. Also, it is known that the root R of a plant has the property of growing along an obstacle when there is an obstacle at the tip where the root R extends. As shown in FIG. 3, by being buried so that the plate 10 is located directly below the plant P, the root R of the plant P extends in the vertical direction and when it hits the plate 10, it extends obliquely downward along the plate 10, specifically, in the direction of the sensing unit 20. Therefore, in the present disclosure, the extending direction DR of the root R is the direction from the plate 10 toward the sensing unit 20 as indicated by the arrow in the DR direction of FIG. 1, and is an obliquely downward direction. The extending direction DR is determined by the angle of the plate 10 buried in the ground.

[0019] The plate 10 may include a guide 11 for guiding the root R to the sensing unit 20. The guide 11 is disposed in the extending direction DR of the root R of the plant P. The guide 11 of the plate 10 guides the root R of the plant in the extending direction DR.

[0020] The guide 11 has a convex shape or a concave shape with the extending direction DR of the root R as the longitudinal direction with respect to the surface of the plate 10. When the guide 11 is convex, the root R extends along the convex portion. When the guide 11 is concave, the root R enters and extends into the recessed portion of the concave portion.

[0021] In the embodiment of the present disclosure, the plate 10 has four guides 11a, 11b, 11c, and 11d as shown in FIG. 1. Note that the number of guides 11 shown in FIG. 1 is an example and is not limited thereto. The plate 10 may have five or more guides 11 or may have three or fewer guides 11.

[0022] Guides 11a and 11b are provided approximately parallel to each other near the center of the plate 10 in the left-right direction. This allows for efficient guidance of the roots R extending vertically from the plant P to the sensing unit 20.

[0023] Guides 11c and 11d are provided near the upper left and right ends of the sensing unit 20. Guides 11c and 11d are provided so as to narrow in width from the top to the bottom of the plate 10. This allows roots R located near the left and right ends of the plate 10 to be guided to the sensing unit 20 by guides 11c or 11d without extending outwards from the plate 10.

[0024] The four guides 11a, 11b, 11c, and 11d shown in Figure 1 are described in terms of how each is formed by a single protrusion or recess in the extension direction DR, but are not limited to this. For example, guide 11a may be formed by multiple intermittent protrusions or recesses instead of a single protrusion or recess. Guide 11 may be formed in any way as long as it can guide the root R to the sensing section 20.

[0025] The sensing unit 20 is positioned along the surface of the plate 10 in the direction DR of root extension R. The sensing unit 20 is positioned below the plate 10. As shown in Figure 4, the sensing unit 20 has, in order from furthest from the plate 10, specifically from top to bottom, a first electrode layer 21 made of a conductor, an insulating layer 22 made of an insulator, and a second electrode layer 23 made of a conductor. The insulating layer 22 is made of an insulator such as biodegradable plastic.

[0026] The first electrode layer 21, the insulating layer 22, and the second electrode layer 23 forming the sensing section 20 have the same shape. The first electrode layer 21, the insulating layer 22, and the second electrode layer 23 of the sensing section 20 each have a thickness of approximately 1 mm or less. The portion of the plate 10 that overlaps the sensing section 20 has the same shape as the sensing section 20. The first electrode layer 21, the insulating layer 22, and the second electrode layer 23 are arranged on the plate 10 so as to overlap closely without gaps by a manufacturing method such as crimping or print coating.

[0027] As shown in Figure 4, the first electrode layer 21 and the insulating layer 22 have slits in which the stretching direction DR is the longitudinal direction. In other words, the first electrode layer 21 and the insulating layer 22 have slits that swing longitudinally substantially parallel to the guide 11. The slits are provided so as to penetrate the first electrode layer and the insulating layer 22. The slits in the first electrode layer 21 and the insulating layer 22 guide the roots guided from the guide 11 in the stretching direction. In this disclosure, the case in which the slits are provided radially is described, but they may also be provided parallel to each other.

[0028] Roots R penetrate the slits provided in the first electrode layer 21 and the insulating layer 22, causing dense root hairs to grow and fill the slits. This makes it easier for roots to grow densely between the first electrode layer 21 and the second electrode layer 23.

[0029] In the example shown in Figure 4, the case where the second electrode layer 23 does not have a slit is described, but it is not limited to this. The second electrode layer 23 may have a slit, similar to the first electrode layer 21 and the insulating layer 22. If the second electrode layer 23 does not have a slit, the root R extends along the second electrode layer 23, between the slits of the first electrode layer 21 and the insulating layer 22. If the second electrode layer 23 has a slit, the root R extends along the plate 10 that abuts the second electrode layer 23, between the slits of the first electrode layer 21, the insulating layer 22, and the second electrode layer 23.

[0030] As shown in Figure 4, the measurement system 5 of this disclosure comprises a root zone sensor 1 having a plate 10 and a sensing unit 20, and a measuring device 2. The measuring device 2 connects terminals to the first electrode layer 21 and the second electrode layer 23, respectively. The measuring device 2 measures the electrical characteristics between the first electrode layer 21 and the second electrode layer 23. Since an insulating layer 22 is provided between the first electrode layer 21 and the second electrode layer 23, the measuring device 2 can measure the electrical characteristics of the electrolyte generated between the first electrode layer 21 and the second electrode layer 23. For example, when the electrolyte becomes an electrolyte solution due to moisture in the soil, the measuring device 2 can more easily measure the electrical characteristics.

[0031] If measuring device 2 is an ammeter, the electrical characteristic is the current of the electrolyte. If measuring device 2 is an impedance meter, the electrical characteristic is the resistance of the electrolyte. Measuring device 2 can measure the change in the electrical characteristics of the electrolyte associated with the growth of root R by intermittently or continuously measuring the electrical characteristics. Measuring device 2 can be installed within the limits permitted by its specifications, for example, by being buried underground or installed on the surface.

[0032] As shown in Figure 4, both the plate 10 and the sensing section 20 have recesses of the same shape at their ends in the extension direction. More specifically, the ends of the plate 10 and the sensing section 20 have the same shape of recesses near their lowest points. The depth of the recess in the plate 10 is formed to be greater than the depth of the recess in the sensing section 20.

[0033] The recessed portion is hollow and has a roughly hemispherical recessed shape. The recessed portion is tray-like in shape, with the edges higher than the center. In the example shown in Figure 4, the lowest ends of the plate 10 and the sensing portion 20 each have a recessed shape. Since the plate 10 and the first electrode layer 21, insulating layer 22, and second electrode layer 23 constituting the sensing portion 20 each have recessed shapes of the same shape, the plate 10 and the sensing portion 20 can be stacked in close contact.

[0034] As shown in Figure 5, the first electrode layer 21 of the sensing unit 20 is formed at an angle that allows the root R extending vertically with respect to the upper edge surface of the hemispherical recess 21b to easily penetrate into the slit of the slit 21a. The slit 21a is formed to have an inclination (elevation angle) of, for example, about 30 to 60 degrees with respect to the upper surface of the hemispherical recess 21b. The insulating layer 22 and the second electrode layer 23 also have the same shape as the first electrode layer 21. However, the second electrode layer 23 does not necessarily have a slit.

[0035] The slits in the first electrode layer 21 and the slits in the insulating layer 22 are provided to the vicinity of the lowest point B of the recess. In the example shown in Figure 5, the slits in the first electrode layer 21 terminate before reaching the lowest point B of the recess 21b and do not reach B. Similarly, the slits in the insulating layer 22 terminate before reaching the lowest point of the recess and do not reach B. The recess 21b accommodates the roots R of the plant P guided by the guide 11 of the plate 10, the slits in the first electrode layer 21, and the slits in the insulating layer 22. The measuring device 2 can measure a longer range of the roots R extending within the slits.

[0036] In the examples shown in Figures 4 and 5, the slits in the first electrode layer 21 and the insulator layer 22 are described as being provided linearly to the vicinity of the lowest point B of the recess 21b, but the invention is not limited to this. For example, the slits may be provided so as to pass through the lowest point B, without hindering the extension of the root R, and may also be provided in a spiral shape inside the recess 21b. Furthermore, although the case in which the recess 21b is a hemispherical shape with an open top has been described, the invention is not limited to this. The recess 21b may also be a hollow cylindrical shape with an open bottom at the top, or a hollow inverted cone shape with an open bottom. This allows the measuring device 2 to measure a longer range of the root R extending within the slit.

[0037] After the rhizosphere sensor 1 is buried underground, a plant P is planted. Markers 30 may be provided on the plate 10 to serve as a guide for the planting location of the plant P. In the example shown in Figure 6, the rhizosphere sensor 1 is provided with markers 30a and 30b at the left and right ends of the upper edge of the plate 10. The markers 30 have a convex shape that is upward relative to the upper edge of the plate 10. The markers 30 can be exposed above ground when the rhizosphere sensor 1 is buried underground. By planting the plant P between markers 30a and 30b, the roots of the plant P can be guided to the sensing unit 20, near the left and right center of the upper edge of the plate 10.

[0038] In the rhizosphere sensor 1 according to the embodiment of this disclosure, the roots R that come into contact with the plate 10 are made to crawl along the plate 10 and guided to the sensing unit 20 by the guide 11, and the roots R extend into the slits of the sensing unit 20. As a result, the roots R penetrate into the gaps of the slits and generate densely packed hair roots that fill the slits.

[0039] The sensing unit 20 has a shape in which two metal layers are sandwiched between insulating layers. The measuring device 2 measures the electrical properties between the two metal layers. The measuring device 2 can measure the electrical properties of electrolytes such as chemical substances secreted from roots R densely packed in the slit with high sensitivity.

[0040] This disclosure is not limited to the embodiments described above, and numerous modifications are possible within the scope of its essence. [Explanation of symbols]

[0041] 1. Root zone sensor 2. Measuring device 5. Measurement System 10 plates 11 Guide 20 Sensing Unit 21 First electrode layer 21a Slit section 21b Recess 22 Insulator layer 23 Second electrode layer 30 markers DR extension direction P plant R root

Claims

1. A plate having a guide positioned in the direction of extension of plant roots, The plate is provided with a sensing unit arranged along the surface of the plate in the extension direction, The sensing unit is, In order from furthest from the plate, it has a first electrode layer formed of a conductor, an insulating layer formed of an insulator, and a second electrode layer formed of a conductor. The first electrode layer and the insulating layer have slits whose stretching direction is the longitudinal direction. Root zone sensor.

2. The guide on the plate guides the plant roots in the direction of extension. The slits in the first electrode layer and the insulating layer guide the roots, which have been guided from the guide, in the direction of extension. The root zone sensor according to claim 1.

3. The plate and the sensing portion each have recesses of the same shape at their ends in the extension direction. The root zone sensor according to claim 1.

4. Each of the slits in the first electrode layer and the insulator layer extends to near the lowest point of the recess. The root zone sensor according to claim 3.

5. The plate and the insulating layer are formed from biodegradable plastic. The root zone sensor according to claim 1.

6. The upper edge of the plate further has markers on the left and right ends that can be exposed above ground when the root zone sensor is buried underground. The root zone sensor according to claim 1.

7. A root zone sensor according to any one of claims 1 to 6, Measuring device for measuring the electrical characteristics between the first electrode layer and the second electrode layer. A measurement system equipped with the following features.

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