Reliability of Soil Color Standards.

For over seventy years, soil scientists have been describing soil colors using the Munsell notation, and standardized color charts have been used at least since the publication of the 1951 Soil Survey Manual. Currently, there are both federal and state regulations affecting land use (particularly in the area of wetland identification and delineation) that utilize Munsell soil color in the decision making process. Over the last couple of decades, modern technologies (such as digital colorimeters) have permitted precise measurement of soil colors – typically to the nearest tenth unit of hue, value and chroma. In an attempt to evaluate the accuracy of standard reference color books, the colors of individual color chips (from the same color book) were measured independently by investigators at five research laboratories using seven different instruments.  Comparisons were also made using pristine quality books of various printings over the last 35 years.  Although measurements of most of the color chips were near to the nominal values, there were notable exceptions.  We will report on the causes of discrepancies and on the implications for using the standard charts in making soil color determinations.