Inhaltsangabe
Excerpt from The Color of Soils
The color of soils has long occupied the attention of both geologists and agriculturists and has considerable importance theoretically and practically. Theoretically the color is of importance as a guide to the origin and processes involved in the formation of the soil and as an indication of the relative age of any particular soil. It is of practical importance because it determines to a greater or less extent the absorption of the sun's energy, and is often a guide to the drainage conditions, to the crop adaptations, and to the cultural methods best suited to the soil. It is the object of this bulletin to publish the results of an investiga tion-into the causes of certain colors in soils, and particularly the causes of differences in color between the popularly named red and' yellow soils in connection with the agricultural significance of Such differences. In, addition to this, certain of the chemical and physical properties of iron compounds and their solutions will be considered It must be recognized that soil colors are not pure colors, but at best are Shades and tints. Thus the material by which soils ordinarily considered red are colored is ferric ox1de, which itself is never a pure red, for it varies from dark brown to yellowish, and when in the soil it is further tinted and Shaded by other materials. When applied to soils the color descriptions used in this bulletin mean the tints and shades which for the sake of Simplicity are termed red, yellow, brown black, or Simple combinations of these.
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