การประเมินปริมาณคาร์บอนอินทรีย์ในดินจากค่าความสว่างด้วยเซนเซอร์วัดสีแบบประหยัด

Sarawut Somnam; Miki Kanna

doi:10.57260/stc.2026.1239

Authors

Sarawut Somnam Department of Chemistry, Faculty of Science and Technology, Chiang Mai Rajabhat University
Miki Kanna Department of Chemistry, Faculty of Science and Technology, Chiang Mai Rajabhat University

DOI:

https://doi.org/10.57260/stc.2026.1239

Keywords:

Organic carbon, Color sensor, Microcontroller, Soil sample

Abstract

This study aimed to investigate the relationship between soil color values and percent organic carbon (%OC) content using a low-cost TCS34725 color sensor integrated with ESP32 microcontroller. A total of 50 soil samples were collected and analyzed for color in the RGB system, which was subsequently converted to the CIELAB color space. %OC content was determined using the Walkley-Black method, and soil pH was also measured to support the analysis. The soil samples exhibited an average pH of 6.6 (range 5.42-7.75), corresponding to slightly acidic to neutral conditions, and %OC contents ranging from 0.059 to 1.091 %OC. The results revealed that the lightness (L*) in the CIELAB system showed a statistically significant negative correlation with %OC (p-value = 1.25 × 10^-7). A linear regression model, %OC = 0.868 – 0.0148L*, was developed to estimate %OC content, yielding R² and RMSE values of 0.4445 and 0.1796, respectively. These findings indicate that the color sensor can serve as a rapid and cost-effective preliminary tool for estimating %OC. However, other CIELAB color parameters (a*, b*) and the R×G×B product did not exhibit statistically significant correlations with %OC. Analysis of the relationship between pH and both color values and %OC showed no significant statistical correlation, suggesting that pH is not a primary factor affecting soil color in this study.

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References

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