Laterite Soils in Hawaii — SHERMAN 
309 
weathering will be the iron oxide "laterite 
crust” as the surface soil and a layer of bauxite 
as the subsoil. 
The soil associations which occur in the Ha- 
waiian Islands appear to fit into several phases 
of Mohr’s hypothesis of tropical soil weather- 
ing. The distribution of rainfall in the Hawai- 
ian Islands fits all five of Mohr’s groups. Later i- 
zation is occurring in soils which have devel- 
oped in areas which are predominantly dry, 
those which have alternating wet and dry 
seasons of variable duration, and under pre- 
dominantly wet and continuously wet conditions. 
Also there is good evidence that examples of all 
five stages of soil weathering described by Mohr 
do exist in the Hawaiian Islands. The recent 
discovery of a soil horizon resembling the 
"laterite crust” supports this contention (Fuji- 
moto et al, 1949). 
RELATIONSHIP OF SOIL GROUPS TO 
RAINFALL DISTRIBUTION IN THE 
HAWAIIAN ISLANDS 
The Hawaiian soils which are developed by 
the soil-forming process, laterization, occur un- 
der a wide range of rainfall. Casual observations 
would suggest that each of the latosol groups 
occurs under rather definite regions of rainfall 
distribution. Further inspection of the actual 
rainfall for each month at different locations on 
the island of Oahu revealed a similar rainfall 
distribution for soils belonging to each latosol 
group. The data given in Table 1 were ob- 
tained by classifying the rainfall distribution of 
the regions where each soil group is developed 
according to the wet and dry months proposed 
by Mohr (1944). The data show that the soils 
belonging to the low humic latosol and the 
ferruginous humic latosol have a definite dry 
season. The lack of a clear-cut difference be- 
tween the rainfall distribution would suggest 
that the ferruginous humic latosol may develop 
from the low humic latosol with age. The 
humic and hydrol humic latosol have developed 
under continuous wet conditions. The data in- 
clude the number of very wet months, or the 
months receiving more than 8 inches of rainfall. 
This information is given to show the very wet 
condition under which the hydrol humic latosols 
are developed. The chemical analysis of soils 
has revealed a marked difference in the com- 
position of soils developed in the regions hav- 
ing a definite dry season and of the soils de- 
veloped under continuous wet conditions. The 
TABLE 1 
The Relationship between the Rainfall Distribution and Soil Groups Developed on the 
Island of Oahu* 
GREAT SOIL GROUP 
SOIL 
FAMILY 
NO. OF 
DRY 
MONTHSf 
NO. OF 
INTER- 
MEDIATE 
RAINFALL 
months! 
NO. OF 
WET 
months! 
NO. OF 
VERY WET 
months! 
Low humic latosol 
Molokai 
8 
4 
0 
0 
Low humic latosol 
Lahaina 
6 
6 
0 
0 
Low humic latosol 
Wahiawa 
5 
4 
0 
0 
Low humic latosol 
Kahana 
2 
7 
3 
0 
Low humic latosol 
Kohala 
1 
4 
8 
0 
Ferruginous humic latosol 
Mahana 
9 
2 
1 
0 
Ferruginous humic latosol 
Naiwa 
5 
3 
4 
0 
Humic latosol 
Kaneohe 
1 
5 
6 
0 
Humic latosol 
Honolua 
0 
4 
8 
0 
Hydrol humic latosol 
Koolau 
0 
0 
8 
4 
Hydrol humic latosol 
Koolau 
0 
0 
3 
9 
* Mohr’s definition of dry and wet months was based on mean monthly rainfall. The data given in this table are based 
on monthly median rainfall as presented by Halstead and Leopold (1948). 
t Dry months, less than 2% inches of rainfall; intermediate rainfall months, 2y 8 -4 inches; wet months, 4-8 inches; very 
wet months, more than 8 inches. 
