1:45 PM - 3:15 PM
[O11-P83] The Soil Investigation Using Digital Analysis of Images – Create a Reproducible Method of Analysis of the Soil Profile Color Information -
Keywords:Munsell color swatches, RGB, light conditions, Sagano High School Woods for Field Studies
1. Introduction
The soil is at the center of the plant ecosystem, and its understanding is based on the survey of the soil profile. The items of the soil profile survey are soil layer thickness, soil color, mottling, soil texture, soil structure, density, cement, and root. The soil color is affected by the components contained in the soil. For example, in the case of organic matter, the soil color becomes dark. In contrast, in the case of lime-rich soil, the color becomes white. We can know the environment and the degree of weathering of the land.
“STANDARD SOIL COLOR CHARTS (Koyama, Takehara, 2019)” is used to decide the soil color, but there is a disadvantage that results can be different depending on each individual (Kawamura, Uda, 2008).
There is another method using the “Soil Color Meter SPAD-503 (KONICA MINOLTA, INC.)”. This meter takes a reading by pressing its measurement window against a sample surface and pushing the measurement button (Nishiyama, Kimura, Isono, Inoue, 2011).
In this study, I developed a reproducible method for soil color survey by using an iPad (iPadOS 17.5 and 18.4) and image analysis software.
2. Method
In the Munsell system, color is expressed by hue, value, and chroma.
The research site is Sagano High School’s Forest (hereinafter “School Forest”) and Sagano High School’s Geoscience Laboratory Room (hereinafter “Laboratory Room”). I made a soil profile and took a photo at the School Forest (hereinafter “under the sun”). The day of the survey was sunny. At the same time, I did a soil color survey using the STANDARD SOIL COLOR CHART (hereinafter “standard soil color chart”).
In addition, I took a photo of the School Forest’s soil (layer A, B, and C) under the fluorescent light in the Laboratory Room (hereinafter “under the fluorescent”).
I extracted RGB from the obtained image data using the free iOS app “Iroshirabe.” I represented the hue as the angle on the color wheel. I calculated the value as 100 × (Max RGB / 255), and the chroma as (Max RGB − Min RGB) / Max RGB.
3. Results and Discussion
The same hue was not observed between the “standard soil color chart” and “under the sun”, and also not between the “standard soil color chart” and “under the fluorescent”.
However, the same hue was observed between “under the sun” and “under the fluorescent”. It is assumed that the hue shown as the angle of the RGB color wheel is different from the hue shown by the Munsell color wheel.
Because the value changed with each change in chroma, it was not possible to compare “standard soil color chart” with “under the sun”, and also not with “under the fluorescent”.
The same values were not obtained for “under the sun” and “under the fluorescent”. This was because no standard was set for the brightness of the light source.
4. Conclusion
I couldn’t get a result that shows we can do soil color surveys using digital images.
However, I could determine the hue. It was suggested that adjusting the brightness of the light source could make it possible to do a soil color survey by analyzing digital images.
5. ReferencesKawamura, A. & Uda, T. (2008). Calibration Curve of the Portable Soil Color Meter (MINOLTA SPAD-503) to the Standard Soil Color Chart – A study of the red paleo soil developed on the Nagaminehara terrace in Niigata Prefecture. Proceedings of the Japan Society of Engineering Geology, 149–150.
Nishiyama, K., Kimura, T., Isono, Y., & Inoue, Y. (2011). Color Measurements of Rocks and Soils Using Colorimeters. Journal of the Japan Society of Engineering Geology, 52(2), 62–71.Ando, K., Oda, S., Hioki, M., Yamamoto, T., & Otake, T. (2022). Estimation of Soil Carbon Content Based on Image Analysis of Soil Captured with a Smartphone in a Vegetable Field. Research Bulletin of the Aichi-Ken Agricultural Research Center, 54, 43–48.
The soil is at the center of the plant ecosystem, and its understanding is based on the survey of the soil profile. The items of the soil profile survey are soil layer thickness, soil color, mottling, soil texture, soil structure, density, cement, and root. The soil color is affected by the components contained in the soil. For example, in the case of organic matter, the soil color becomes dark. In contrast, in the case of lime-rich soil, the color becomes white. We can know the environment and the degree of weathering of the land.
“STANDARD SOIL COLOR CHARTS (Koyama, Takehara, 2019)” is used to decide the soil color, but there is a disadvantage that results can be different depending on each individual (Kawamura, Uda, 2008).
There is another method using the “Soil Color Meter SPAD-503 (KONICA MINOLTA, INC.)”. This meter takes a reading by pressing its measurement window against a sample surface and pushing the measurement button (Nishiyama, Kimura, Isono, Inoue, 2011).
In this study, I developed a reproducible method for soil color survey by using an iPad (iPadOS 17.5 and 18.4) and image analysis software.
2. Method
In the Munsell system, color is expressed by hue, value, and chroma.
The research site is Sagano High School’s Forest (hereinafter “School Forest”) and Sagano High School’s Geoscience Laboratory Room (hereinafter “Laboratory Room”). I made a soil profile and took a photo at the School Forest (hereinafter “under the sun”). The day of the survey was sunny. At the same time, I did a soil color survey using the STANDARD SOIL COLOR CHART (hereinafter “standard soil color chart”).
In addition, I took a photo of the School Forest’s soil (layer A, B, and C) under the fluorescent light in the Laboratory Room (hereinafter “under the fluorescent”).
I extracted RGB from the obtained image data using the free iOS app “Iroshirabe.” I represented the hue as the angle on the color wheel. I calculated the value as 100 × (Max RGB / 255), and the chroma as (Max RGB − Min RGB) / Max RGB.
3. Results and Discussion
The same hue was not observed between the “standard soil color chart” and “under the sun”, and also not between the “standard soil color chart” and “under the fluorescent”.
However, the same hue was observed between “under the sun” and “under the fluorescent”. It is assumed that the hue shown as the angle of the RGB color wheel is different from the hue shown by the Munsell color wheel.
Because the value changed with each change in chroma, it was not possible to compare “standard soil color chart” with “under the sun”, and also not with “under the fluorescent”.
The same values were not obtained for “under the sun” and “under the fluorescent”. This was because no standard was set for the brightness of the light source.
4. Conclusion
I couldn’t get a result that shows we can do soil color surveys using digital images.
However, I could determine the hue. It was suggested that adjusting the brightness of the light source could make it possible to do a soil color survey by analyzing digital images.
5. ReferencesKawamura, A. & Uda, T. (2008). Calibration Curve of the Portable Soil Color Meter (MINOLTA SPAD-503) to the Standard Soil Color Chart – A study of the red paleo soil developed on the Nagaminehara terrace in Niigata Prefecture. Proceedings of the Japan Society of Engineering Geology, 149–150.
Nishiyama, K., Kimura, T., Isono, Y., & Inoue, Y. (2011). Color Measurements of Rocks and Soils Using Colorimeters. Journal of the Japan Society of Engineering Geology, 52(2), 62–71.Ando, K., Oda, S., Hioki, M., Yamamoto, T., & Otake, T. (2022). Estimation of Soil Carbon Content Based on Image Analysis of Soil Captured with a Smartphone in a Vegetable Field. Research Bulletin of the Aichi-Ken Agricultural Research Center, 54, 43–48.