Soils of Saipan — M cCracken 
275 
TABLE 2. 
Some Constants of Representative Saipan Soils 
(after Kawamura et al.) 
SOIL TYPE 
SAMPLE 
DEPTHS 
CARBON 
HUMUS 
NITROGEN 
c/n 
CATION 
EXCHANGE 
CAPACITY 
Inches 
Per cent 
{Cxl 724) 
Per cent 
Ratio 
m.e./lOO g. 
"Red-colored limestone soli” 
= Saipan clay 
0- 6 
5.95 
10.26 
0.52 
11.4 
7.2 
6-45 
7.2 
"Yellow-colored limestone 
soil” = Chacha clay 
0- 8 
2.48 
4.28 
0.24 
- 10.3 
6.6 
8-22 
"Brown-colored limestone 
soil” = Dandan clay loam. . 
0-10 
3.98 
6.86 
0.34 
11.7 
10-33 
9.0 
"Red andesitic soil” 
= Dago clay 
0-12 
2.9 
5.0 
0.23 
12.6 
12-50 
12.1 
"Red tuffaceous soil” 
“ Akina clay 
0- 8 
0.28 
8-24 
35.2 
These determinations were completed for a limited number of horizons of a few profiles. Though not sufficiently complete 
for basis of conclusions, they are presented here because they do show trends in soil development processes. Carbon was deter- 
mined by the wet oxidation method and nitrogen by the Kjeldahl method. Due to some questions concerning translation, method 
of determining cation exchange is uncertain. 
or extremely high sesquioxide concentrations. 
They were observed to crack in drier seasons 
and swell during wet periods. However, they 
do possess some red color, contain low 
amounts of soluble constituents, and have 
developed under a climate of year-round 
weathering with moderately high rainfall. 
Deep Soils over Volcanic Rocks 
Akina clay has a reddish-brown, granular 
clay surface averaging about 6 inches in thick- 
ness and is acid in reaction {pH 6.0). The 
subsoil is of yellowish-red, firm plastic clay to 
a depth of about 18 inches. Within an approx- 
imate depth range of 18 to 30 inches below 
the surface, the subsoil is of yellowish-red and 
red hues, often displaying light-gray spots 
and flecks which appear to be relict colors of 
highly weathered minerals of the parent ma- 
terial. Below this horizon is a variegated red, 
yellowish-red, and light-gray clay, strongly 
acid (^H 5.0 to 5.5), with relict textures of 
the weathered parent material and feldspar 
''ghosts” (outlines of weathered feldspar crys- 
tals) commonly preserved (profile diagram. 
Fig. 1). Depth to unaltered, moderately basic 
volcanic rocks ranges from 15 to 25 feet or 
more. The chemical data shown in the tables 
for soil samples believed to correlate with this 
soil series are somewhat out of line with sam- 
ples from other soils of the island. More than 
40 per cent silica, a cation exchange capacity 
of 35 milliequivalents per 100 grams of dry 
soil, and a derived silica-sesquioxide ratio of 
greater than two is reported for the subsoil 
in samples believed to correlate with the Aki- 
na soil. These data are indicative of a less 
strongly weathered soil. The Akina subsoil 
was observed to be firm and plastic and ex- 
hibits cracking and swelling at extremes of 
moisture, not indicating extreme sesquioxide 
concentration or silica depletion. 
Dago clay has a dark reddish-brown, gran- 
ular clay surface, slightly acid in reaction. The 
subsoil is a dark-red firm acid (^H 6.0) clay 
(to an average depth of 30 inches) . Below this 
horizon a yellowish-red and dusky red, firm, 
plastic, acid {pH 5.5) clay extends to a depth 
