Duripan Horizon and Durinodes - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 138

Table 14.3 (continued)

No.
series

%of
total

Area
(km 2 )

%of
total Order Suborder Great group Subgroup

Xerolls Durixerolls Abruptic

Argiduridic

3

Argidic 7

Argiduridic 44

Cambidic 5

Haplic 10

Haplic
Haploxerollic

1

Haploduridic 13

Haploxerollic 4

Paleargidic 3

Palexerollic 7

Typic 26

Vertic 3

Vitrandic 9

Vitritorrandic 26

184

22.2 12,443 11.7

Vertisols Aquerts Duraquerts Xeric 5

Xererts Durixererts Aquic 2

Aridic 1

Chromic 3

Haplic 2

13 1.6 718 0.7

Total 787 95 106,645 100

Total USA 20,000 9,147,537

% USA 3.9 1.2

30,000 ha), Durids
are most common (74 soil series), followed by the Argids (45), Xerolls (11), and
Xeralfs (7) (data not shown). Although these soils account for only 17 % of the total
soil series, they comprise 67 % of the total area of duric soils. Thirty-three percent
of the common soil series are defined solely on the basis of durinodes, and 67 %
contain a duripan with or without durinodes. All of the duric soils have an aridic or
xeric soil-moisture regime (Fig. 14.2 ). Although the common soil series range from
frigid to hyperthermic, soil series with a mesic soil-temperature regime account for
75 % of the total. The common soil series tend to exist in the medium to fine
particle-size classes, with 70 % occurring in fine-loamy, coarse-loamy, loamy,
loamy-skeletal classes. Ninety-five percent of the common soil series have a
smectitic or mixed (with superactive cation-exchange activity) mineralogy class.
About 57 % of the common soil series are in the shallow soil class or have a lithic
contact within 50 cm of the surface.

Of the 137 most abundant soil series (i.e., each comprises

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