Semiquantitative color profiling of soils over a land degradation gradient in Sakaerat, Thailand

Abstract

In this study, we attempted multivariate color profiling of soils over a land degradation gradient represented by dry evergreen forest (original vegetation), dry deciduous forest (moderately disturbed by fire), and bare ground (severely degraded) in Sakaerat, Thailand. The soils were sampled in a dry-to-wet seasonal transition. Values of the red-green-blue (RGB), cyan-magenta-yellow-key black (CMYK), L*a*b*, and hue-intensity-saturation (HIS) color models were determined using the digital software Adobe Photoshop. Land degradation produced significant variations (p<0.05) in R, C, Y, L*, a*, b*, S, and I values (p<0.05). The seasonal transition produced significant variations (p<0.05) in R, G, B, C, M, K, L*, b*, and I values. In discriminating the soils, the color models did not differ in discriminatory power, while discriminatory power was affected by seasonal changes. Most color variation patterns had nonlinear relationships with the intensity of the land degradation gradient, due to effects of fire that darkened the deciduous forest soil, masking the nature of the soil as the intermediate between the evergreen forest and the bare ground soils. Taking these findings into account, the utilization of color profiling of soils in land conservation and rehabilitation is discussed.

Soil color analysis for statistically estimating total carbon, total nitrogen and active iron contents in Japanese agricultural soils

“…Digital cameras and spectrometers have also been used for measurement of soil color (Viscarra Rossel et al 2006, 2008Doi et al 2010). A soil color reader (SPAD-503, Konica Minolta Optics, Inc.) introduced for soil analysis in 1996 is one of the tristimulus reflectance colorimeters.…”

Discriminating crop and other canopies by overlapping binary image layers

“…5 RGB, CMYK, and L à a à bà color models are unique. 6 In each grayscale layer, (intensity) values of the color component for the pixels in the rhombus frame were reported. In the grayscale layer, the pixels with (intensity) values between mean AE1× or 3× standard deviation (SD) were identified to obtain a binary image layer.…”

Measuring Soil Colour to Estimate Soil Organic Carbon Using a Large-Scale Citizen Science-Based Approach

“…Instead, the rapid development of modern technologies and instrumental methods, such as UV VIS spectrophotometry, allow a more precise and quantitative approach to colour quality control [16,19,37]. They overcome some of the limitations of the Munsell method by removing the human 'judgement' from the analysis and using standard values, such as observer viewing angle and fixed lighting conditions to control the conditions of the measurement [8,9,16,23,[38][39][40]. For this reason, quantitative measures of colour (e.g., spectrophotometers) have seen apparent exponential growth worldwide and there are new applications of colour data in different fields [16,37].…”

“…However, despite the consensus that quantitative assessments of colour increase precision and that they are available, they have not been widely adopted by soil scientists for a variety of reasons, including costs, speed, lack of portability, familiarity with the Munsell method, and small-scale heterogeneity [33]. Consequently, field colour assessment using Munsell soil colour charts are likely to prevail as the standard practice, particularly in the Global South [9,16,20,23,35,38,39].…”