Comparison of Different Color Space Model's Performance for Estimation of Nitrate and Phosphate in Soil and Water Using A Smartphone-Integrated Imaging Device

This study introduces a novel smartphone-assisted imaging device for efficient control of agricultural inputs and environmental pollution monitoring by quantifying phosphate (PO₄^3-) and nitrate (NO₃^–) concentrations in soil and water samples. Utilizing the smartphone's digital camera, the cost-effective and portable device employs standard colorimetric procedures with chromotropic acid and ascorbic acid for NO₃^– and PO₄^3- detection, respectively. The integrated back camera connects to a handheld system housing ocular sources and optical components, enabling on-the-go measurements. Leveraging the Value (V) component of the HSV color space model, the device estimates NO₃^– and PO₄^3- concentrations, producing results comparable to laboratory spectrophotometers. Additionally, this study explored RGB, CMYK, and CIELAB color space models, validating the device's effectiveness with 30 soil and 15 water samples. In summary, this user-friendly device offers a reliable, cost-effective solution for measuring NO₃^– and PO₄^3- levels in soil and water, presenting results comparable to traditional spectrophotometers without the need for laboratory apparatus.

Index Terms— soil, water, nitrate, phosphate, smartphone, imaging device, HSV, RGB, CMYK, CIELAB