Visual Assessment of Low Chroma Soil Colors.

Color is one of the most obvious properties of soils and is utilized in many soil evaluation strategies.  Color data are usually documented using Munsell notation of hue, value and chroma, with the latter two parameters normally documented to the nearest whole unit.  Soil colors with chroma less than or equal to 2 are particularly important in soil classification and in soil interpretation, especially with regard to the identification of Field Indicators of hydric soils.  During a field study of dunal soils on late Holocene barrier island landscapes, the investigators sought to improve the quality of color data by noting color value and chroma to the nearest half unit, by interpolating between chips in the Munsell book. To evaluate whether interpolating color to half units of value and chroma was justifiable, a study was initiated using 20 homogenized and randomized soil samples collected from dune profiles in the study area. Moist color values were generally 6 or less and moist chromas were 3 or less while hue mostly ranged between 10YR and 5Y.  Four experienced soil morphologists estimated moist and dry colors to the nearest half unit of value and chroma, using the same reference color book and under fixed lighting conditions.  A digital colorimeter was used to measure color of the soil samples to the nearest 0.1 unit of hue, value and chroma.  The accuracy with which these individuals were able to make soil color determinations will be reported and implications for soil morphology, classification and interpretations will be discussed.