Environmental factors in image-based soil analysis: Interaction effects of moisture, texture, and illumination

• Image features stabilize after 500 lx; 100–300 lx shows sharp changes. • 24-hour post field capacity gives optimal SOM imaging stability. • Warm light yields more consistent soil images than natural light. • Brightness is highly sensitive; chromaticity stays more stable. • Study guides optimal conditions for reliable SOM image analysis. Image-based characterization of Soil Organic Matter (SOM) has been significantly influenced by varying ambient environmental conditions, moisture levels and texture, with the interplay between these factors remaining largely understudied. This study provides critical insights into the combined effects of moisture levels, texture and lighting conditions on image feature consistency and identifies the optimal parameters for capturing soil sample images for SOM characterization. Soil samples from the Ap horizons of four Canadian provinces were imaged under six different illumination levels, with moisture levels ranging from field capacity to Oven-dry state. The results reveal that lighting intensity and moisture levels significantly impact image stability. Feature values exhibited a sharp rise between 100 and 300 lx and stabilized after 500 lx, followed by minor fluctuations, particularly under natural lighting. Early time points following the field capacity state of the soil (4–12 h) consistently showed minimal variability in image features, highlighting their reliability for consistent soil imaging. While chromaticity components in the La*b* and Lu*v* color spaces demonstrated resilience, brightness was more sensitive to environmental changes. The color difference analysis (ΔE) identified the 24th hour after field capacity as the optimal moisture level, providing stable and accurate measurements compared to the light-independent Nix Pro camera. Warm lighting (2700–3000 Kelvin) conditions consistently outperformed natural light (5000–6500 Kelvin), offering higher stability and reduced variability. Among the tested conditions, the 24th hour excelled in calibration, while the 8th and 12th hours demonstrated strong performance during validation. This study establishes a framework to optimize soil imaging and enhance SOM characterization.