Nutrient salt deficiency sensing system

Abstract

To provide a nutrient deficiency sensing system capable of detecting nutrient salt deficiency of seaweed in the ocean.SOLUTION: A nutrient salt deficiency sensing system 1 according to the present invention includes: an imaging unit 12 that captures an image of seaweed 10; a color information extraction unit 32 that extracts color information of a plurality of different locations from the captured image; a nutrient salt deficiency index calculation unit 38 that calculates a nutrient salt deficiency index 40 based on values of the plurality of pieces of the color information; and a display unit 42 that displays the nutrient salt deficiency index 40 on a screen. Preferably, the color information extraction unit 32 extracts at least color information of a growth point of the seaweed 10. Preferably, the nutrient salt deficiency index calculation unit 38 calculates, as the nutrient salt deficiency index 40, a difference between values of the extracted color information of the plurality of different locations. Preferably, the seaweed 10 is a large brown alga.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a nutrient deficiency sensing system. [Background technology]

[0002] To mitigate climate change, advances are being made in Direct Air Capture (DAC) technology, which uses marine algae to fix atmospheric carbon dioxide. While this DAC technology can increase the amount of carbon dioxide fixed by growing algae, algae have difficulty growing in nutrient-poor oceans. While fertilizing nutrient-poor oceans with nutrients such as nitrogen, phosphorus, and iron can sometimes promote algae growth, an oversupply of nutrients can lead to red tides, so it is necessary to control the supply of nutrients in appropriate amounts at appropriate times. The following prior art has been proposed in relation to this control:

[0003] The technology described in Patent Document 1 is a method for preventing discoloration of laver algae in laver farms using L * a * b * The color is determined by a color system to determine which of the nutrients (nitrogen, phosphorus, and iron) is causing the discoloration. Based on the results of this determination, the technology described in Patent Document 1 then applies fertilizer containing the nutrients that cause the discoloration to the nori farm, thereby preventing or reversing the discoloration of the nori algae.

[0004] The technology described in Patent Document 2 involves immersing humic substances or fish waste and steel slag in water to elute nitrogen, phosphorus, and iron components into the water, and removing suspended solids contained in the eluate by settling or filtration. The technology described in Patent Document 2 then supplies the eluate after removal to a culture tank containing seawater, and grows bunch-shaped or sticky seaweed in the culture tank. Patent Document 2 also describes the use of an autoanalyzer as a method for controlling nitrogen and phosphorus concentrations. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5505374 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-107061 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, after visually checking the discoloration of the laver body, * a * b * Although the document describes color determination using a color system, it does not describe how to photograph images of the Nori algae. Potential solutions include traveling offshore by boat to visually inspect the Nori algae, or photographing the Nori algae with a surface or underwater camera. However, in this case, ambient light varies depending on the season, weather, time of day, and whether or not there is a sunset or sunrise. Furthermore, the light absorption characteristics of the water vary depending on the quality of the seawater, making it difficult to grasp subtle changes in the color tone of the algae. Therefore, the technology described in Patent Document 1 was difficult to use to detect nutrient deficiencies in seaweed in the ocean.

[0007] The technology disclosed in Patent Document 2 directly measures the concentration of nutrients such as nitrogen and phosphorus. However, the concentration of nutrients required by seaweed for growth varies depending on the photosynthetic conditions. Specifically, because the required concentration varies depending on conditions such as water temperature and sunlight, simply measuring the nutrient concentration in seawater using an autoanalyzer cannot determine whether the seaweed has sufficient or insufficient nutrients. For example, even if the nutrient concentration is below a certain value, if there is insufficient light due to cloudy weather and the photosynthetic reaction does not proceed, the amount of nutrients required is small and it cannot be said that there is a nutrient deficiency. Furthermore, since the photosynthetic reaction does not proceed at night when there is no sunlight, there is no nutrient deficiency. Thus, the technology described in Patent Document 2 also had difficulty detecting nutrient deficiencies in seaweed in the ocean.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a nutrient deficiency sensing system that can detect nutrient deficiency in seaweed in the ocean. [Means for solving the problem]

[0009] The nutrient deficiency sensing system of the present invention, which solves the above-mentioned problems, comprises an imaging unit that captures images of seaweed, a color information extraction unit that extracts color information of multiple different locations from the captured image, a nutrient deficiency index calculation unit that calculates a nutrient deficiency index based on the multiple color information values, and a display unit that displays the nutrient deficiency index on a screen. [Effects of the Invention]

[0010] According to the present invention, a nutrient deficiency sensing system can be provided that can detect nutrient deficiency in seaweed in the ocean. Other objects, configurations, and advantages will become apparent from the following description of the embodiments. Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a system flow diagram of a nutrient salt deficiency sensing system 1 according to a first embodiment of the present invention. [Figure 2] 1 is an explanatory diagram of the seaweed 10 near the base A and near the tip B. [Figure 3] FIG. 10 is an explanatory diagram showing an example of a screen display in which a nutrient salt deficiency index 40 is displayed as a trend graph. [Figure 4] FIG. 10 is a system flow diagram of a nutrient salt deficiency sensing system 2 according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a system flow diagram of a nutrient salt deficiency sensing system 3 according to a third embodiment of the present invention. [Figure 6A] 10 is an explanatory diagram for selecting candidates for color information extraction locations from seaweed 10. FIG. [Figure 6B]10 is an explanatory diagram for selecting candidates for color information extraction locations from seaweed 10. FIG. [Figure 6C] 10 is an explanatory diagram for selecting candidates for color information extraction locations from seaweed 10. FIG. [Figure 6D] 10 is an explanatory diagram for selecting candidates for color information extraction locations from seaweed 10. FIG. [Figure 7] FIG. 10 is a system flow diagram of a nutrient salt deficiency sensing system 4 according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] A nutrient deficiency sensing system according to one embodiment of the present invention will be described below with reference to the accompanying drawings. Note that common components in the following description and drawings may be designated by the same reference numerals and redundant description may be omitted. Furthermore, the present invention is not limited to the following embodiments. Furthermore, the descriptions in this specification are merely typical examples and do not limit the scope of the claims or application examples in any sense.

[0013] [First embodiment] FIG. 1 is a system flow diagram of a nutrient salt deficiency sensing system 1 (hereinafter sometimes simply referred to as "the system 1") according to a first embodiment of the present invention. As shown in FIG. 1, the system 1 includes an imaging unit 12, a color information extraction unit 32, a nutrient salt deficiency index calculation unit , and a display unit . The photographing unit 12 photographs an image of the seaweed 10. The color information extraction unit 32 extracts color information 34 from a plurality of different locations in the photographed image. The nutrient salt deficiency index calculation unit 38 calculates a nutrient salt deficiency index 40 based on the values ​​of the plurality of color information 34. The display unit 42 displays the nutrient salt deficiency index 40 on a screen. A specific example of the operation of the present system 1 will be described below.

[0014] 1, image information 14 relating to an image of seaweed 10 photographed by a photographing unit 12 is provided to a color information extraction unit 32. This photographing unit 12 may be provided in the sea or in the air. The color information 34 of the plurality of different locations extracted from the image information 14 by the color information extraction unit 32 is provided to a nutrient salt deficiency index calculation unit 38. The nutrient salt deficiency index 40 calculated by the nutrient salt deficiency index calculation unit 38 is displayed on a display unit 42.

[0015] The color information extraction unit 32 extracts color information 34 of multiple different locations from the image information 14. The multiple different locations preferably include growing points and non-growing points of the seaweed 10. Large brown algae such as kelp, wakame, and celadon experience a phenomenon called discoloration when seawater is deficient in nutrients, with the color of the growing points becoming light yellow rather than brown. It is known that discoloration is less pronounced in locations other than growing points than in growing points. Therefore, using color information 34 of multiple different locations, including growing points and non-growing points, can be used as an indicator of nutrient deficiency (nutrient deficiency indicator 40). In the case of wakame, the growing point is located at the base leaf near the root of the wakame, and there is no growing point at the tip or leaf. Therefore, it is preferable to use color information 34 near the base as color information 34 of the growing points and color information 34 near the tip as color information 34 of the locations other than the growing points. For this reason, it is preferable that the seaweed 10 to be photographed in this embodiment is large brown algae such as kelp, wakame, and Ecklonia cava. In this way, the seaweed 10 includes both growth points and non-growth points, making it easy and reliable to calculate the nutrient deficiency index 40. It is also preferable that the color information extraction unit 32 extracts color information 34 of at least the growth points of the seaweed 10. As described above, the growth points of the seaweed 10 lose color when there is a nutrient deficiency, making it easier to determine whether there is a nutrient deficiency.

[0016] An example of a calculation method in the nutrient deficiency index calculation unit 38 for calculating the nutrient deficiency index 40 using color information 34 from a plurality of different locations will be described below. FIG. 2 is an explanatory diagram of a base A and a tip B of seaweed 10. FIG. 2 shows an image of seaweed 10 with its base fixed to a rock 44. The color information of the base A and the tip B is calculated as L. * a * b *If the lightness values ​​in the (L-star-A-star-B-star) color space are LA and LB, respectively, the nutrient deficiency index 40 can be expressed as the following formula (1). Nutrient deficiency index 40 = LB - LA Equation (1)

[0017] LA and LB can be multiplied by a coefficient that takes into account the season, weather, date and time, and whether or not there is a sunset or sunrise. For example, if an image of seaweed 10 is taken during the day when there is a lot of light, LA and LB can be multiplied by a coefficient of 0.8, and if an image of seaweed 10 is taken during a sunset or sunrise with low light or on a cloudy day, LA and LB can be multiplied by a coefficient of 1.2. In this way, data can be obtained that is less affected by the season, weather, date and time, and whether or not there is a sunset or sunrise, etc., allowing for a more accurate understanding of the nutrient deficiency of seaweed 10 in the ocean. The coefficients can be set as desired.

[0018] Although formula (1) is the simplest method for calculating the nutrient salt deficiency index 40, this embodiment is not limited to this calculation method. In addition to formula (1), the nutrient salt deficiency index 40 can also be calculated from the RGB color system as follows.

[0019] Generally, captured video and images are expressed in the RGB color system. For example, the color information 34 of seaweed 10 photographed under light source condition X1 is (R, G, B), and C1: (39, 39, 39), C2: (62, 48, 37), and C3: (78, 59, 58) indicate that the color has not faded and that there is sufficient nutritional salts. On the other hand, (R, G, B) C4: (179, 107, 26) and C5: (167, 100, 47) indicate that the color has faded and that there is insufficient nutritional salts. The threshold (R, G, B) is C6: (128, 74, 64).

[0020] When these colors are photographed under different lighting conditions X2, the results are D1: (51, 51, 51), D2: (134, 83, 72), D3: (205, 139, 109), D4: (255, 237, 23), D5: (255, 218, 87), and D6: (230, 144, 76).

[0021] The threshold value C6: (128, 74, 64) changes to D6: (230, 144, 76) when the light source is different, and these RGB values ​​are not suitable as a nutrient deficiency index 40. Therefore, these RGB color system values ​​are converted into L * a * b * Convert to color space. * a * b * When converted into a color space, the color information 34 is obtained as lightness: L, hue: a, and saturation: b.

[0022] Of these, the lightness L calculated from the RGB values ​​of seaweed 10 photographed under light source condition X1 is LC1:16, LC2:21, LC3:27, LC4:52, LC5:49, and LC6:38, corresponding to C1 to C6 mentioned above. On the other hand, the lightness L calculated from the RGB values ​​of seaweed 10 photographed under light source condition X2 is LD1:21, LD2:41, LD3:64, LD4:93, LD5:88, and LD6:67, corresponding to D1 to D6 mentioned above. The threshold value of LC6:38 changes to LD6:67 when the light source is different, and the value of luminosity L alone is not suitable as a nutrient deficiency indicator40.

[0023] On the other hand, in seaweed 10, which has lost its color due to a lack of nutrients, the color of the area near the base A photographed under light source condition X1 is C3: (78, 59, 58), while the color of the area near the tip B is C4: (179, 107, 26). The difference in brightness L between these two areas is LC4-LC3 = 52-27 = 25. In the case of seaweed 10 photographed under light source condition X2, the color of the area near the base A is D3:(205,139,109), and the color of the area near the tip B is D4:(255,237,23). The difference in brightness L between these two areas is LD4-LD3=93-64=29.

[0024] In this way, even when the light source state changes from X1 to X2, the present system 1 (nutrient deficiency index 40) can evaluate the nutrient deficiency of seaweed 10 in the ocean by calculating the difference between the brightness LA near the base A of seaweed 10 and the brightness LB near the tip B using equation (1), for example, by considering a value between 25 and 29 as a threshold value. In other words, the color information 34 and its value are initially L * a * b * If the lightness of the color space is used, that value can be used. However, even if the RGB color system is used, the value can be used as the L * a * b * Converting into a color space and using the resulting lightness can be suitably applied to this embodiment.

[0025] The nutrient salt deficiency index 40 calculated by equation (1) is displayed on the screen of the display unit 42. This may be a display of the numerical value itself, or may be displayed as a time-series trend graph. Figure 3 is an explanatory diagram showing an example of a screen displaying the nutrient salt deficiency index 40 as a trend graph. As shown in Figure 3, the trend graph shows hatching (or lines) around the above-mentioned 25 to 29, and if this is exceeded, it can be immediately determined that there is a nutrient deficiency. For example, in the example of Figure 3, it can be seen that there was no nutrient deficiency two days ago or one day ago, but that a nutrient deficiency is approaching today.

[0026] As described above, the present system 1, which uses color information 34 from multiple different locations on the seaweed 10, can identify nutrient deficiencies in the seaweed 10 in the ocean. In the event of a nutrient deficiency, measures such as appropriately spraying seaweed fertilizer on the seaweed 10 can be taken at an early stage. As a result, the growth of the seaweed 10 is promoted, and more atmospheric carbon dioxide can be fixed by the seaweed 10 in the ocean. Furthermore, the growth and color of the seaweed 10 can be restored, preventing a decline in the commercial value of the seaweed 10.

[0027] Furthermore, by adopting the above-described configuration, the present system 1 can sense the nutrient deficiency of seaweed 10 in the ocean based on the color information 34, even under ambient light conditions that vary depending on the season, weather, and time of day. Therefore, for example, it is possible to control the supply of nutrients based on the sensing results. The present system 1 does not require color samples to compensate for the effects of different ambient light conditions, so there is no need for the effort and cost of maintenance, such as reducing dirt on the surface of the color sample.

[0028] Second Embodiment Figure 4 is a system flow diagram of a nutrient deficiency sensing system 2 (hereinafter, sometimes simply referred to as "this system 2") according to a second embodiment of the present invention. This system 2 differs from the system flow diagram shown in Figure 1 in that it includes a wireless transmitter 20 and a wireless receiver 24. The wireless transmitter 20 is connected to the imaging unit 12. The wireless transmitter 20 is configured so that at least the antenna for wireless transmission is positioned above the sea.

[0029] This system 2 is intended for use when the photographing unit 12 is installed in a sea area. When the photographing unit 12 is located in a sea area, it is not practical to send photographed information to land via a cable. Therefore, image information 22 relating to the image of seaweed 10 photographed by the photographing unit 12 is wirelessly transmitted from the wireless transmitting unit 20 to the wireless receiving unit 24, and the image information 22 received by the wireless receiving unit 24 is provided to the color information extracting unit 32 as image information 26.

[0030] The sea is not always calm. Compared to sending out a boat in rough seas to check for nutrient deficiencies in the sea, the second embodiment uses wireless communication to capture images of the seaweed 10 in the sea (image information 22, 26) on land, making it possible to safely determine whether the seaweed 10 is lacking in nutrients. Depending on the frequency of wireless transmission, this second embodiment makes it possible to obtain image information 22, 26 related to the images of the seaweed 10 in real time, allowing for earlier detection of nutrient deficiencies in the seaweed 10 in the sea. Furthermore, in the event of a nutrient deficiency, appropriate measures such as spraying seaweed fertilizer on the seaweed 10 can be taken at an earlier stage. As a result, the growth and color of the seaweed 10 can be restored.

[0031] When adopting this second embodiment, the photographing unit 12 will be installed in the sea, as described above. If the photographing unit 12 is installed on the sea surface and looks down into the ocean, salt can solidify on the lens surface, adversely affecting image quality. Therefore, it is desirable to provide a water washing mechanism that wets the lens surface to prevent salt from adhering. Alternatively, it is desirable to cover the lens surface of the photographing unit 12 with a transparent, ultra-water-repellent material that prevents seawater from adhering even when splashed onto the surface. On the other hand, a configuration in which the imaging unit 12 is installed underwater is desirable because it eliminates the adverse effects of light reflection on the sea surface, but it has the adverse effect of causing marine organisms to adhere to the lens surface, which reduces image quality. Therefore, in this configuration, it is desirable to provide a wiper mechanism that wipes the lens surface and an ultraviolet irradiation device that irradiates the lens surface with ultraviolet rays.

[0032] Third Embodiment 5 is a system flow diagram of a nutrient deficiency sensing system 3 (hereinafter, simply referred to as "this system 3") according to a third embodiment of the present invention. This system 3 differs from the system flow diagram shown in FIG. 4 in that it includes an image processing unit 28.

[0033] The image processing unit 28 performs image recognition of the growth points and other locations of the seaweed 10 from the obtained image. Seaweed 10 typically grows over time and drifts in the ocean due to waves and currents. When the photographing unit 12 is installed in the ocean, its orientation and position also typically change in the ocean due to waves and currents. Due to these many variable factors, it is difficult to determine the coordinates of the growth points and other locations of the seaweed 10 as fixed positions in the photographed image. Therefore, in the third embodiment, the growth points and other locations of the seaweed 10 are determined by image processing.

[0034] There are various methods for image processing (image recognition) in the image processing unit 28. The method described below is one example of the image processing method in the image processing unit 28, and the invention is not limited to this. In images captured by the image capture unit 12, whose orientation and position change in the sea due to waves and currents, for example, underwater ropes and rocks may appear. Objects to which the seaweed 10 is attached, such as underwater ropes and rocks, can be extracted because they exhibit little change over time, are highly linear, and are a different color from the seaweed 10 and the seawater.

[0035] First, images that appear differently over time are aligned using the extracted underwater rope and rocks as a reference. When the aligned images are added together, the base of the seaweed 10 is fixed to the underwater rope or rock, so it is reflected in the same pixel position for a long time. On the other hand, the tip of the seaweed 10 is located far from the underwater rope or rock, and is fluttering in the sea due to waves and currents, so it is reflected in the same pixel position for a short time.

[0036] 6A to 6D are explanatory diagrams relating to the selection of candidate locations from which color information is extracted from the seaweed 10. As shown in Fig. 6A and Fig. 6B, the vicinity of the base and the vicinity of the tip of the seaweed 10 can be distinguished based on the time information of the first time and the second time and the images taken at each time. Figure 6C is a composite image of the seaweed 10 captured in Figures 6A and 6B. As shown in Figure 6C, the underwater rope 46 to which the seaweed 10 is attached appears at the same pixel position as time passes between the first and second times. The area near the base of the seaweed 10 fluctuates between the first and second times, but the range is narrow. On the other hand, the area near the tip of the seaweed 10 fluctuates greatly between the first and second times, and the range is wide. As mentioned above, the growth point of the seaweed 10 is near the base, and the rest of the seaweed 10 is near the tip. Therefore, as shown in Figure 6D, the image processing unit 28 can determine the position with no fluctuation as the underwater rope 46 and determine its coordinates. Furthermore, the image processing unit 28 can determine the area with little fluctuation and a narrow range close to the coordinates of the underwater rope 46 as the area near the base A of the seaweed 10 (i.e., the location of the growth point of the seaweed 10) and determine its coordinates. Furthermore, the image processing unit 28 can determine that a wide range with large variations away from the coordinates of the underwater rope 46 and the coordinates of the vicinity A of the base of the seaweed 10 is the vicinity B of the tip of the seaweed 10 (i.e., a location other than the growth point of the seaweed 10) and determine its coordinates. By performing image processing (image recognition) using this procedure, the image processing unit 28 can provide the color information extraction unit 32 with an image 30 ( FIG. 5 ) of the growth point and other locations of the seaweed 10. In this way, images of the seaweed 10 in the ocean, particularly images 30 of the growth point and other locations of the seaweed 10, can be reliably obtained, making it easier to detect a nutrient deficiency in the seaweed 10 in the ocean.

[0037] [Fourth embodiment] FIG. 7 is a system flow diagram of a nutrient deficiency sensing system 4 (hereinafter, sometimes simply referred to as "the system 4") according to a fourth embodiment of the present invention. This system 4 differs from the system flow diagrams shown in FIGS. 1, 4, and 5 in that it includes a light quantity measuring unit 16. The light quantity measuring unit 16 is provided adjacent to the photographing unit 12. The light quantity measuring unit 16 measures the value of the light quantity around the photographing unit 12.

[0038] In this system 4, the light intensity value (light intensity information 18) is provided to the wireless transmitter 20 from the light intensity measurement unit 16, and the light intensity value (light intensity information 36) is provided from the wireless receiver 24 to the nutrient deficiency index calculation unit 38. The nutrient deficiency index calculation unit 38 then calculates a nutrient deficiency index 40 based on the multiple color information 34 values ​​and the light intensity value.

[0039] As described in the first embodiment, when the light source condition changes from X1 to X2, the RGB color system values ​​of the captured video or image change significantly. The present system 4 performs a process to correct for this difference in light source condition in advance based on the light intensity information 18, 36 measured by the light intensity measurement unit 16. This allows the present system 4 to improve the accuracy of calculating the nutrient deficiency index 40 performed by the nutrient deficiency index calculation unit 38. Therefore, the present system 4 can improve the accuracy of determining whether seaweed 10 is deficient in nutrients in the ocean. The process to correct for the difference in light source condition may, for example, be multiplying the brightness by a coefficient (e.g., 0.8 or 1.2) that takes into account the season, weather, date and time, the presence or absence of a sunset or sunrise, etc., as described above. As described above, this coefficient can be set arbitrarily.

[0040] Although the nutrient deficiency sensing systems 1 to 4 according to the present invention have been described in detail above using embodiments, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to systems that include all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0041] 1-4 Nutrient deficiency sensing system 10 seaweed 12 Photography Department 14 Image information 16 Light intensity measurement unit 18 Light intensity information 20 Radio transmitter 22 Image information 24 Radio receiver 26 Image Information 28 Image processing section 30 Images of seaweed growth points and areas other than growth points 32 Color information extraction section 34 Color Information 36 Light intensity information 38 Nutrient Deficiency Index Calculation Section 40 Nutrient Deficiency Index 42 Display section

Claims

1. a photographing unit that photographs images of seaweed; a color information extraction unit that extracts color information of a plurality of different locations from the captured image; a nutrient salt deficiency index calculation unit that calculates a nutrient salt deficiency index based on the plurality of color information values; a display unit that displays the nutrient salt deficiency index on a screen; A nutrient deficiency sensing system comprising:

2. The nutrient deficiency sensing system according to claim 1, The color information extraction unit extracts color information of at least the growth points of the seaweed. A nutrient deficiency sensing system characterized by:

3. The nutrient deficiency sensing system according to claim 1, The nutrient salt deficiency index calculation unit calculates a difference between values ​​of the color information of the extracted different portions as the nutrient salt deficiency index. A nutrient deficiency sensing system characterized by:

4. The nutrient deficiency sensing system according to claim 1, The seaweed is a large brown alga. A nutrient deficiency sensing system characterized by:

5. The nutrient deficiency sensing system according to claim 1, The photographing unit is installed in the ocean, a wireless transmission unit that transmits the image captured by the photographing unit to land; A nutrient deficiency sensing system characterized by:

6. The nutrient deficiency sensing system according to claim 1, An image processing unit is provided that performs image recognition of the growing points of the seaweed and areas other than the growing points from the image. A nutrient deficiency sensing system characterized by:

7. The nutrient deficiency sensing system according to claim 1, The display unit displays the nutrient salt deficiency index as a time-series trend graph. A nutrient deficiency sensing system characterized by:

8. The nutrient salt deficiency sensing system according to any one of claims 1 to 7, a light amount measuring unit that measures the amount of light around the photographing unit, The nutrient salt deficiency index calculation unit calculates the nutrient salt deficiency index based on a plurality of values ​​of the color information and the value of the light amount. A nutrient deficiency sensing system characterized by:

9. The nutrient deficiency sensing system according to claim 1, The value of the color information is L ＊ a ＊ b ＊ This is the brightness value when expressed in color space. A nutrient deficiency sensing system characterized by:

Images