Ochric Epipedon - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 58

Table 7.2 Approximate
classification of soil series
with an ochric epipedon

Order No. of soil series

Alfisols 3,354

Aridisols 2,565

Entisols 2,473

Inceptisols 2,382

Oxisols 64

Ultisols 1,216

Total 12,054

Fig. 7.2 Distribution of soils with an ochric epipedon in the USA (Map prepared by Paul Reich)

of the Aridisols, 96 % of the Entisols, 80 % of the Inceptisols, 95 % of the Oxisols,
and 91 % of the Ultisols. Figure 7.2 is basically a map of these seven soil orders.

7.5 Factors Influencing the Development of the Ochric
Epipedon

In semiarid regions, the ochric epipedon forms in the drier portions of the landscape
and the mollic wetter (Table 7.3 ). Based on a regression model, Bravo et al. ( 2007 )
reported ochric epipedons in Aridisols of Argentina where the mean annual