Spodic Horizon - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 254

loamy, and loamy-skeletal). The two dominant mineral classes are mixed (48 %) and
isotic (27 %). Seventy-eight percent of the soils with a spodic horizon had a cryic
or frigid soil-temperature regime.
22.4 Distribution of Soils with a Spodic Horizon
The total area of soils with a spodic horizon is in excess of 318,000 km 2 (Fig. 22.2 ).
The states with the largest numbers of soil series and areas include MI, AK, WA,
WI, and FL, which account for 65 % of all of the soils in the USA containing a
spodic horizon.
22.5 Factors Influencing the Development of the Spodic
Horizon
The spodic horizon generally occurs in environments with abundant precipitation
and cool temperatures as in the Pacific Northwest, the upper Great Lakes region,
and northern New England and NY (Table 22.3 ). However, soils containing a
Fig. 22.2 Distribution of soils with a spodic horizon (Map from NRCS)