Soil color

The solid portion of soil is composed of inorganic sand, silt, clay, and organic matter (OM), which interact to produce the large soil features1 (i.e., peds, profiles, pedons, and landscapes). These features, not considering rock, are discussed in this chapter. In Chapter 3, components smaller than rock, which soil scientists define as those inorganic particles smaller than 2.00 mm in 

1 Many soils contain gravel, stones, and rock. However, these components, because of their low reactivity, will not be considered in this book. 

Introduction to Soil Chemistry Analysis and Instrumentation, Second Edition. Alfred R. Conklin, Jr. 

Oi 0-5 cm undecomposed organic material, mainly bark, twigs, and needles Oe 5-10 cm partially decomposed organic material like that of the horizon above 

A 10-15 cm dark gray (10YR 4/1) very stony loam, strong granular structure 

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Organic matter The presence of earthworms, plant residues, roots, and darker soil color... 

Fertility High crop yield, dense growth of Chromolaena odorata, no lmperata cylindrica and no Saccharum spontaneum in the field, high organic matter, dark soil color... 

As a soil develops, OM decomposes to produce humus, which is black. Additionally, release of iron from minerals by weathering yields various reds and yellows. Both mechanisms yield soil coloring agents. Under oxidizing conditions, where soil is not saturated with water, the iron will be oxidized and thus in the ferric state [Fe(III)]. When the iron and OM are deposited on the surfaces of sand, silt, clay, and peds, they develop a coat that gives them a surface color. However, soil color is not only a surface characteristic but extends through the soil matrix. Under oxidizing conditions, soil has a reddish color. The chroma of this color depends to some extent on the amount of and the particular iron oxide present. 

While color is often discussed as being closely related to iron and its oxidation state, it is also related to all other soil components. When soil color indicates oxidizing conditions, all multiple oxidative state capable cations are... 

What common soil characteristics are indicated by soil color Explain how a soil s color is described. 

Munsell Soil Color Charts. Baltimore, MD Kollmorgen Corporation 1975. 

Bigham JM, Ciolkosz EJ (eds.). Soil Color. Madison, WI Soil Science Society of America 1993. 

The topography of an area must also be taken into account when gridding it for nonpoint sampling [4,5], The tops of slopes will have more erosion of contaminates and soil. Thus, they will generally be lower in contaminant concentration. Lower areas, particularly where water ponds or accumulates, will have higher concentrations of contaminants. Soil color is a valuable characteristic to observe and record in these situations. The tops of slopes will be lighter and typically redder in color, while lower areas will have darker soil colors. 

In particular, soil color should be determined on dry and moist samples using Munsell Soil Color Charts (1994). Soil color is usually the first property recorded in a morphological description of soils (and may be the only feature of significance to a layperson) and provides an indicator of redox status because soil color relates to soil aeration and organic matter content (Fitzpatrick, McKenzie, and Maschmedt 1999). Soil color has been found to be extremely useful in forensic soil identification by Sugita and Marumo (1996). 

The content and type of iron oxide affects soil chemistry. Several workers (e.g., Scheinost and Schwertmann 1995) have shown that phosphate adsorption maxima increase from red (hematitic) to yellow (goethite-rich) soils. Consequently, because yellow soils in some regions are closely correlated to soil P sorption, soil color has been used to predict the likely need for phosphate applications. 

Munsell Soil Color Charts (1994). Munsell Color. New Windsor, NY Macbeth Division of Kollinorgen Instruments Corporation. 

We have used two techniques in an attempt to compare the "color" of the various adsorbents. First, they have been compared with Munsell soil color charts (17). Second, their diffuse reflectance spectra have been measured (vs. white filter paper as reference). These results are summarized in Tables III and IV, respectively. 

Munsell Soil Color Charts Kollmorgen Corp. Baltimore, 1975. 

Schwertmann, U., 1993, Relations between iron oxides, soil color, and soil formation. Soil Sci Soc Am, Spec Publ no. 31 51-59. 

Fernandez R. N. and Schulze D. G. (1987) Calculation of soil color from reflectance spectra. Soil Sci. Soc. Amer. J. 51 1277-1282. 

Post D. E, Levine S. J., Bryant R. B., Mays M. D., Batchily A. K., Escadafal R., and Huete A. R. (1993) Correlations between field and laboratory measurements of soil color. In Soil Color. In Bigham I M. and Ciolkosz E. (Eds.), Soil Science Society of America, Spec. Publ. No 31 35-49. 

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