JP4243014B2 - Plant growth measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plant growth degree measuring apparatus, and more particularly to an apparatus for optically measuring a plant growth degree by measuring reflected sunlight from a plant.
[0002]
[Prior art]
Conventionally, farmers have applied fertilizer according to the growth of crops. At that time, it is important to determine the time and amount of fertilization. Conventionally, (1) plant height, (2) number of stems, (3) SPAD value indicating leaf color (hereinafter referred to as “leaf color ( SPAD value)”) And (4) the degree of plant growth is determined based on dry matter weight, etc., and the fertilization time and amount are determined according to the degree of growth.
[0003]
(1) Plant height refers to the length from the root of the plant to the tip of the leaf. A person enters the field, prepares an appropriate leaf by hand, and the difference between the root of the plant and the tip of the leaf. The length up to is measured. In addition, the above (2) stem number is the number of stems per strain. This is also the case where a person enters a field, selects an appropriate strain, and counts the number of stems while dividing by hand. In the above (3) measurement of leaf color (SPAD value), the leaf is usually sandwiched with a handy type leaf color meter, and the SPAD value is measured from the light transmittance, or the leaf color plate (color sample) is contrasted visually. It is judged by. In the above (4) dry weight measurement, an appropriate amount of plants is collected and dried, and the dry weight is determined by measuring the weight.
[0004]
However, each of the above measurement items has its own problems. (1) Plant height, (2) number of stems, and (3) leaf color (SPAD value) are all complicated by people entering the field. Work is required and requires a lot of labor. Moreover, since it is possible to measure only for each strain or for each leaf, it is difficult to obtain a representative value, and an enormous number of samplings are required to grasp the degree of growth in one field. However, in reality, only about a dozen strains are sampled, and it cannot be said that the growth degree can be accurately grasped. In addition, (4) dry matter weight measurement may require one week or more to dry, and there is a problem in that it cannot be promptly handled.
[0005]
On the other hand, attempts have been made to optically measure the growth of plants for the purpose of reducing the labor of measurement work and shortening the measurement time. For example, in Japanese Patent Laid-Open Nos. 62-282243 and 62-282244, reflected sunlight from a plant community growing in a predetermined area is received, and the chlorophyll concentration as a whole plant community is measured from the received light intensity. Has proposed a growth degree measuring device that measures the degree of growth and determines the degree of growth based on this. This growth measuring device is not a measurement for each strain as in the past, it is not necessary to apply physical differences or understand more, and the measurement result can be obtained instantly. Time is shortened. Furthermore, since the plant community can be sampled by a single measurement, it is advantageous in terms of measurement accuracy. In addition, this measuring apparatus is configured to measure directly incident sunlight at the same time and correct the received light intensity ratio with reflected sunlight to perform more accurate measurement.
[0006]
[Problems to be solved by the invention]
As described above, research toward the realization of so-called “precision agriculture” in which the degree of fertilization and the amount of fertilization are determined by measuring the degree of growth and scientifically and systematically harvesting has been promoted in recent years. The premise is to grasp the degree of growth of crops more accurately and instantaneously, but the above-mentioned measurement of chlorophyll concentration alone is insufficient, and a new index is required. For example, if the relationship between the plant height, the number of stems, and the dry matter weight can be obtained at the same time as in the conventional case, more various analyzes are possible, and a more accurate growth plan can be made.
[0007]
The present invention has been made in view of such a situation, and provides a plant growth degree measuring apparatus capable of grasping the degree of growth more accurately than in the past while maintaining the reduction of measurement labor and measurement time. For the purpose.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is an apparatus for optically measuring the degree of growth of a plant, and the first surface facing the plant is made incident with sunlight reflected by the plant to perform spectroscopy. While providing the 1st light-receiving part which measures the reflection intensity of the light of 2 or more types of specific wavelengths , sunlight is directly incident on the surface on the opposite side to the said 1st surface, and is the same as the said 1st light-receiving part A substrate provided with a second light receiving unit that splits the light into wavelengths and measures the received light intensity as reference light; and the second light receiving unit detects the reflection intensity of the specific wavelength detected by the first light receiving unit. was corrected based on the received light intensity of the detected reference light, based on the corrected reflection intensities, S PAD value of the measurement plant, plant height, dry weight (plant height × tillers) values, (plant height × S PAD value) value and plant characterized by comprising an arithmetic unit for obtaining at least one of (plant height × number of stems × S PAD value) value raw To provide a degree measurement device.
[0009]
The present invention is a method for optically measuring the degree of growth of a plant. Reflectance, leaf color (SPAD value) of the measured plant, plant height, dry weight, (plant height x number of stems), {plant height x leaf color (SPAD value) } And {plant height × number of stems × leaf color (SPAD value)}, and was founded based on this finding. Hereinafter, the present invention will be described in detail.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic perspective view showing an embodiment of a growth degree measuring apparatus according to the present invention, and FIG. 2 is an enlarged sectional view of a light receiving portion shown in FIG.
[0011]
As illustrated, the growth measuring apparatus 1 includes a light receiving unit 10, a support unit 20 for supporting the light receiving unit 10, and a calculation unit (not shown) connected to the light receiving unit 10.
[0012]
For example, the support portion 20 has four legs 21 projecting obliquely outward from the four corners of the light receiving portion 10, and connecting rods 22 a extending horizontally at the tips of the legs 21 and further at intermediate positions as necessary. 22b is connected. The length of the legs 21, the protrusion angle thereof, and the distance between the tips of the legs 21 depend on the general plant height, planting interval, etc. of the plant to be measured (for example, “paddy rice”; hereinafter described based on this paddy rice). When measuring the degree of growth of paddy rice, the height from the upper end of the paddy rice to the light receiving unit 10 is about 50 cm, and the distance between the tips of the legs 21 is about 60 cm. be able to. Further, the leg 21 and the connecting rods 22a and 22b can be made variable and extendable. And this support part 20 is installed in the measurement part of a paddy field so that a paddy rice may be covered from upper direction in the case of a measurement. At this time, the measurement area can be confirmed by the support portion 20. In addition, a handle (not shown) adapted to an appropriate position of the leg 21 may be attached to the support portion 20 so as to be convenient for installation and transportation.
[0013]
The light receiving unit 10 is configured by fixing a first light receiving unit 12 facing the paddy rice and a second light receiving unit 13 facing the sun to the substrate 11. Further, the first light receiving unit 12 is configured by a plurality of light receiving elements 12a, 12b,... According to the number of measurement wavelengths, and the second light receiving unit 13 is also configured by the same number of light receiving elements 13a, 13b. Further, the light receiving elements 12a, 12b,... Constituting the first light receiving part 12 and the light receiving elements 13a, 13b,. Configured. Here, a configuration is shown in which the measurement wavelength is a maximum of four wavelengths. Correspondingly, the light receiving element 12a of the first light receiving unit 12 and the light receiving element 13a of the second light receiving unit 13 correspond to the first measurement wavelength. The light receiving element 12b of the first light receiving unit 12 and the light receiving element 13b of the second light receiving unit 13 form a pair for the second measurement wavelength, and the first light receiving unit 12 for the third measurement wavelength. The light receiving element 12c and the light receiving element 13c of the second light receiving unit 13 form a pair, and the light receiving element 12d of the first light receiving unit 12 and the light receiving element 13d of the second light receiving unit 13 form a pair for the fourth measurement wavelength. It is comprised so that it may make. These four pairs of light receiving elements are arranged one by one at the four corners of the substantially square substrate 11.
[0014]
Each light receiving element may be a known element, for example, a Si photodiode. In addition, a spectral filter (not shown) is attached to the light receiving surface of each light receiving element in order to split incident light into the measurement wavelength. The measurement wavelength can be selected as follows.
[0015]
That is, FIG. 3 shows a wavelength-reflectance characteristic diagram of a plant (paddy rice). A peak with the maximum reflectance appears near the wavelength 550 nm (green), and a peak with the minimum reflectance appears near the wavelength 670 nm (red). It can be seen that the reflectance is constant in the range from 850 nm (near infrared) to 1000 nm (near infrared). Therefore, in the present invention, it is preferable to select two or more of these four wavelengths, which are characterized by changes in reflectance, as measurement wavelengths. In particular, as shown in the examples described later, a combination including 550 nm is preferable, and it is most preferable to select all four wavelengths.
[0016]
In addition, for example, since the incident angle of sunlight differs depending on the daytime, sunset, or season, it is possible to place the white diffuser plate 30 above the second light receiving unit 13 to stabilize the incident sunlight. preferable. Furthermore, in order to prevent unnecessary light from entering from other than the measurement location, it is preferable to set the viewing angle of each light receiving element constituting the first light receiving unit 12 and the second light receiving unit 13 to about 60 °.
[0017]
The growth degree measuring apparatus 1 is configured as described above, and in the measurement, the support portion 20 is installed from above the paddy rice at a measurement point of the paddy rice so as to cover the paddy rice. Thereby, the 1st light-receiving part 12 faces the paddy rice side, and the 2nd light-receiving part 13 faces the sun (sky), and is installed in a measurement location.
[0018]
The measurement is performed by measuring the incident intensity of sunlight that is directly incident on the second light receiving unit 13 in the growth degree measuring apparatus 1 described above. At this time, the sunlight is intensities I ₁ (λ ₁ = 550 nm), I ₂ (λ ₂ = 670 nm), I ₃ (λ ₃ =) in accordance with each selected measurement wavelength (here, the above four wavelengths are assumed). 850 nm) and I ₄ (λ ₄ = 1000 nm), and the second light receiving unit 13 receives the light transmitted through the respective spectral filters by the light receiving elements 13a to 13d, and the received light intensity. A ₁ , A ₂ , A ₃ , A ₄ are output to a calculation unit (not shown).
[0019]
On the other hand, the reflection intensity of sunlight reflected by paddy rice is measured by the first light receiving unit 12. Here, when the reflectance of rice for the wavelength component of the lambda ₁ and R _1, the intensity of the wavelength components lambda ₁ in the reflective sunlight R ₁ × I _1, and the sequence, the intensity of the reflected sunlight for each wavelength component Are R ₂ × I ₂ , R ₃ × I ₃ and R ₄ × I ₄ . In the first light receiving unit 12, the light receiving elements 12 a to 12 d receive the light transmitted through the respective spectral filters and output the received light intensity B ₁ , B ₂ , B ₃ , B ₄ to the arithmetic unit.
[0020]
The calculation unit corrects the light reception signal from the first light receiving unit 12 based on the light reception signal from the second light receiving unit 13 and corrects the reflectance for each measurement wavelength. That is, the received light intensity B ₁ , B ₂ , B ₃ , B ₄ by the first light receiving unit 12 is changed to the received light intensity A ₁ , A ₂ , A ₃ , A ₄ by the second light receiving unit 13 at each wavelength. The value is multiplied by the reflectance. Accordingly, the reflectance of each measurement wavelength is obtained by dividing the light reception intensity by the first light receiving unit 12 by the light reception intensity by the second light receiving unit 13. In the equation, for each measurement wavelength,
R ₁ (λ ₁ = 550 nm) = B ₁ / A ₁
R ₂ (λ ₂ = 670 nm) = B ₂ / A ₂
R ₃ (λ ₃ = 850 nm) = B ₃ / A ₃
R ₄ (λ ₄ = 1000 nm) = B ₄ / A ₄
It is.
[0021]
Actually, since there is a characteristic difference for each light receiving element, it is desirable to measure a dark value (background) and further correct by a white calibration coefficient Ws. In other words, it can be represented by the following formula. B _{10 to} B ₄₀ and A _{10 to} A ₄₀ are dark values of the corresponding light receiving elements.
R ₁ (λ ₁ = 550 nm) = Ws · (B ₁ −B ₁₀ ) / (A ₁ −A ₁₀ )
R ₂ (λ ₂ = 670 nm) = Ws · (B ₂ −B ₂₀ ) / (A ₂ −A ₂₀ )
R ₃ (λ ₃ = 850 nm) = Ws · (B ₃ -B ₃₀ ) / (A ₃ -A ₃₀ )
R ₄ (λ ₄ = 1000 nm) = Ws · (B ₄ -B ₄₀ ) / (A ₄ -A ₄₀ )
[0022]
Based on the above corrected reflectance, paddy rice (1) leaf color (SPAD value), (2) plant height, (3) dry weight, (4) plant height x number of stems, (5) plant height x leaf color (SPAD) Value), (6) any one of plant height × number of stems × leaf color (SPAD value) is obtained. These values are all indexes that have been conventionally used as indicators of the degree of growth of paddy rice. For example, FIG. 4 is a graph showing the correlation between the reflectance at a measurement wavelength of 1000 nm and the value of “plant height × number of stems × SPAD value” obtained by actually measuring each value manually. A high correlation is observed. In addition, almost the same correlation is obtained for other measurement wavelengths, and the correlation increases as the types of measurement wavelengths increase. Therefore, by measuring the reflectance according to the above, (6) plant height × number of stems × leaf color (SPAD value) is obtained, and the growth situation can be estimated based on this.
[0023]
In addition, as shown in the examples described later, other indexes are (1) leaf color (SPAD value), (2) plant height, (3) dry weight, (4) plant height x number of stems, (5) plant height. X The leaf color (SPAD value) is also highly correlated with the reflectance. Therefore, the fact that these indexes that have been conventionally employed can be obtained with high accuracy simply by measuring the reflectance greatly contributes to the reduction of the measurement work. In addition, the measurement result can be obtained instantly and the measurement time can be shortened.
[0024]
Moreover, in the growth measuring apparatus of this invention, it can also map by adding measurement position information to the growth data based on said reflectance. Furthermore, measurement time, climate data (weather, temperature, etc.) may be added. These information is accumulated as annual data and reflected in the growth plan.
[0025]
In the growth degree measuring apparatus described above, the first light receiving unit 12 and the second light receiving unit 13 include a plurality of light receiving elements (photodiodes) according to the type of measurement wavelength. A spectrometer capable of continuously measuring light in the above-described wavelength range of 550 nm to 1000 nm may be disposed in each of the 12 and the second light receiving unit 13. Then, by using the entire obtained spectrum pattern or selecting the measurement wavelength so that the correlation is higher and performing the same calculation as described above, the growth degree can be estimated more precisely.
[0026]
【Example】
Hereinafter, the present invention will be further described with reference to examples.
[0027]
(Example 1)
The growth measuring apparatus shown in FIG. 1 was installed in a paddy field, and 550 nm (G), 670 nm (R), and 1000 nm (IR2) were selected as measurement wavelengths, and the reflectivity of paddy fields was measured by changing the combination of measurement wavelengths. . Note that a Si photodiode “S1336-5BQ” manufactured by Hamamatsu Photonics Co., Ltd. was used as the light receiving element, an opal diffuser plate was used as the white diffuser plate, and the measuring range was about 60 cm (about 8 strains) per side. In addition, the plant height, the number of stems and the leaf color (SPAD value) of the rice grown at the same measurement location were measured by hand as in the conventional method, and the product of these was used as the actual measurement value.
[0028]
For each type of measurement wavelength, the correlation between the value (predicted value) of “plant height × number of stems × SPAD value” obtained from the reflectance and the measured value is shown in FIG. 5 (1000 nm), FIG. 6 (550 nm, 1000 nm, two wavelengths ), FIG. 7 (three wavelengths of 550 nm, 670 nm, and 1000 nm), it can be seen that the correlation increases as the types of measurement wavelengths increase. From this, in the present invention, it was confirmed that it is preferable to set two or more wavelengths, in particular, two or more wavelengths including 550 nm as measurement wavelengths.
[0029]
(Example 2)
550 nm (G) and 1000 nm (IR2) were selected as measurement wavelengths, and the reflectance of paddy fields was measured in the same manner as in Example 1. Then, the correlation between the SPAD value (predicted value) obtained from the reflectance and the SPAD value (actually measured value) obtained by actual measurement in Example 1 was obtained. As shown in FIG. 8, a high correlation was observed between the two.
[0030]
(Example 3)
The reflectance of the paddy field was measured in the same manner as in Example 1 by selecting 550 nm (G), 670 nm (R), and 850 nm (IR1) as measurement wavelengths. Then, the correlation between the plant height (predicted value) obtained from the reflectance and the plant height (actually measured value) obtained by actual measurement in Example 1 was obtained. As shown in FIG. 9, a high correlation was recognized between the two.
[0031]
(Example 4)
The reflectance of the paddy field was measured in the same manner as in Example 1 by selecting 550 nm (G), 670 nm (R), and 1000 nm (IR2) as the measurement wavelengths. Then, a correlation between “plant height × number of stems” (predicted value) obtained from the reflectance and “plant height × number of stems” (actual value) obtained by actual measurement in Example 1 was obtained. As shown in FIG. 10, a high correlation was recognized between the two.
[0032]
(Example 5)
The reflectance of the paddy field was measured in the same manner as in Example 1 by selecting 550 nm (G), 670 nm (R), 850 nm (IR1), and 1000 nm (IR2) as the measurement wavelengths. Then, a correlation between “plant height × SPAD value” (predicted value) obtained from the reflectance and “plant height × SPAD value” (actual value) obtained by actual measurement in Example 1 was obtained. As shown in FIG. 11, a high correlation was observed between the two.
[0033]
(Example 6)
The reflectance of the paddy field was measured in the same manner as in Example 1 by selecting 550 nm (G), 670 nm (R), 850 nm (IR1), and 1000 nm (IR2) as the measurement wavelengths.
In addition, paddy rice grown at the same measurement location was collected manually, and its dry weight was measured to obtain an actual measurement value. Then, the correlation between the “dry weight” (predicted value) obtained from the reflectance and the actually measured value was obtained. As shown in FIG. 12, a high correlation was recognized between the two.
[0034]
【The invention's effect】
As described above, according to the present invention, (1) leaf color (SPAD value), (2) plant height, (3) dry matter weight, (4), which has been conventionally employed based on reflectance. ▼ Plant height x number of stems, ▲ 5 ▼ Plant height x leaf color (SPAD value), ▲ 6 ▼ Plant height x number of stems x leaf color (SPAD value) can be obtained, reducing measurement work and measuring time While maintaining the shortening, it becomes possible to grasp the degree of growth more accurately than before.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing an embodiment of a growth degree measuring apparatus according to the present invention.
FIG. 2 is an enlarged cross-sectional view of the light receiving unit shown in FIG.
FIG. 3 is a wavelength-reflectance characteristic diagram of a plant (paddy rice).
FIG. 4 is a graph showing the correlation between the reflectance at a measurement wavelength of 1000 nm and an actual measurement value of “plant height × number of stems × SPAD value”.
FIG. 5 is a graph showing the correlation between the predicted value of “plant height × number of stems × SPAD value” obtained from the reflectance when the measurement wavelength is a single wavelength (550 nm) and the actual measurement value in Example 1. is there.
FIG. 6 is a graph showing the correlation between the predicted value of “plant height × number of stems × SPAD value” obtained from the reflectance when the measurement wavelength is two wavelengths (550 nm and 1000 nm) and the actual measurement value in Example 1. It is.
7 shows the correlation between the predicted value of “plant height × number of stems × SPAD value” obtained from the reflectance when the measurement wavelength is 3 wavelengths (550 nm, 670 nm, 1000 nm) and the actual measurement value in Example 1. FIG. It is a graph to show.
8 is a graph showing the correlation between the predicted value of the SPAD value and the actual measurement value obtained in Example 2. FIG.
9 is a graph showing the correlation between the predicted value of plant height and the actual measurement value obtained in Example 3. FIG.
10 is a graph showing the correlation between the predicted value of “plant height × the number of stems” and the actual measurement value obtained in Example 4. FIG.
11 is a graph showing a correlation between a predicted value of “plant height × SPAD value” and an actual measurement value obtained in Example 5. FIG.
12 is a graph showing a correlation between a predicted value of “dry matter amount” and an actual measurement value obtained in Example 6. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Growth degree measuring apparatus 10 Light-receiving part 11 Board | substrate 12 1st light-receiving part 13 2nd light-receiving part 20 Support part 21 Leg 30 White diffuser plate

Claims (4)

An apparatus for optically measuring the degree of growth of a plant,
The first surface facing the plant is provided with a first light-receiving unit that makes sunlight reflected by the plant incident on the first surface and measures the reflection intensity of light of two or more specific wavelengths , and the first surface. A substrate provided with a second light receiving portion that directly enters sunlight on the surface opposite to the first light and separates the light into light having the same wavelength as that of the first light receiving portion and measures the received light intensity as reference light; ,
The reflection intensity of the specific wavelength detected by the first light receiving unit is corrected based on the received light intensity of the reference light detected by the second light receiving unit, and based on the corrected reflection intensity, the S PAD value of the measurement plant An arithmetic unit for obtaining at least one of plant height, dry weight, (plant height x number of stems) value , ( plant height x number of S PAD values) and ( plant height x number of stems x S PAD value) ;
A plant growth degree measuring apparatus comprising: The plant growth degree measuring apparatus according to claim 1, further comprising legs for placing the substrate at a measurement location at a predetermined distance from the ground . Furthermore, according to claim 1 or 2 Growth measurement device plant wherein Rukoto comprising a means for mapping the degree of growth on the basis of the measurement location. Each of the 1st light-receiving part and the 2nd light-receiving part is comprised with the spectrometer which can carry out photometry of the wavelength range containing 2 or more types of specific wavelengths continuously, Any one of Claims 1-3 characterized by the above-mentioned. The growth degree measuring apparatus according to claim 1.

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