The most used unit of soil classification is called the “soil series." Series are determined by studying the horizon characteristics. Such characteristics as number of horizons, color, thickness, texture, erosion phase, slope, organic content, and depth to hardpan are used to differentiate among series. Series are the smallest unit that soils are subdivided into except for the soil type and phase. Soil type subdivides the series on the basis of surface texture, while phases are determined by slope, erosion, or salt content. All soils given the same soil series name would possess the same characteristics across the landscape. Examples of soil series are Holdrege, Nora, Sharpsburg and Valentine. (See Table 1.4 at the end of this lesson) Soil series names are often taken from a nearby town or area where the soil was first described. A soil series, type and phase name might be, for example: Sharpsburg silty clay loam, 5 to 9 percent slope, eroded.
The soil series relates a soil to a specific group of other characteristics that are described by the soil’s complete name. This would be comparable to a person’s given name. Nan’s given name was Nancy Marie Wilson Johnson. Similarly, a Valentine soil’s given name is Valentine loamy fine sand, rolling, mixed, mesic, Typic Ustipsamment.