Soil Taxonomy

Soil names are derived from Latin and English. The most general classification of soils is the soil order. There are 10 soil orders (Table 1.1). All soils around the world can be grouped very generally into these 10 categories. The next level of defining characteristics is the suborder. This scheme follows through to great group, subgroup, family and series. Soil series is the most specific classification for soils. Soil type and phase are not considered part of the formal taxonomy, but are routinely used to more definitively separate very fine variations in characteristics within a soil series.

We will not consider soil taxonomy in any great detail. This knowledge, however, can help us to better understand the differences among soils and their potential, to better manage them to our benefit, and to ensure that soil quality is sustained for future generations.

Our example for understanding soil taxonomy will be the official state soil of Nebraska — the Holdrege soil. It’s formal name is Holdrege silt loam, fine-silty, mixed, mesic, Typic Argiustoll.

Holdrege’s name can be grammatically dissected so that we can unlock a vast reservoir of knowledge. The name contains the most general category of classification on the right and gets progressively more specific as the name develops to the left. Each portion of the name — oll, ust, argi, typic — and so forth, helps to describe this specific soil (Table 1.2). Based on its taxonomy, we can briefly describe the Holdrege soil: a silty grassland soil with some clay, derived from several clay minerals, a thick dark organic-rich surface soil and an accumulation of clay in the subsoil that developed under a relatively cool dry climate with limited rainfall occurring during the spring and summer.

Table 1.1. Classification scheme for soils (Soil Survey Staff, 1975)

Table 1.2. Taxonomy of Holdrege silt loam soil Holdrege silt loam, fine-silty, mixed, mesic, Typic Argiustoll