PHYSICAL PROPERTIES OF HAWAII SOILS 5 
is considerable variation in the efficiency of the bacterial action 
bringing about decomposition. Burgess {10, p. -1! ) states that " other 
conditions being equal, bacterial efficiency decreases as the altitude 
increases," especially in so far as the ammonifiers are concerned. 
Table 1 gives a comparison of the chemical composition of average 
mainland and Hawaii soils, and the specific gravities of the chief 
constituents of these soils. 
Table 1. — Comparison of the chemical composition of average mainland and 
Hawaii soils, and the specific gravities of their chief constituents 
Constituent 
Mainland 
soils ' 
Hawaii 
soils i 
« ! Constituent 
Mainland 
soils 1 
Hawaii Specific 
soils 2 gravity 
I Per cent 3 
SiOi 75.64 
Per cent ' 
25. 78 
34.91 
16.99 
.24 
2.65 MgO 
Per cent 3 
0.72 
1.67 
.73 
3.00-5 
Per cent 3 
0. 14 3 60 
AI2O3 -. 11.00 
3.75-4.00 K 2 
.31 2. 30 
Fe203 4.14 
5.12-5.24 Na*0 
. 44 2. 27 
CaO 
.75 
3. 20-3. 40 Organic matter 
4.00-12 1.20-1.70 
1 Robinson, W. O., Steinkoenig, L. A., and Fry, W. H. (32, p. 7). 
» McGeorge, W. T. (24, p. 6). 
» Averages. 
It is realized that these figures are averages of wide variations and 
are at best only indicative. However, an attempt was made to make 
the figures as representative as possible by the inclusion of data 
typical of large areas. It is noticed that the silica content in Ha- 
waii soils is only about one-third that of mainland soils. Iron 
and alumina in Hawaii soils comprise fully one-half of all the 
constituents and amount to more than three times the proportions 
found in the mainland soils. The basic elements in Hawaii soils 
amount to one-half to one-sixth those of the mainland soils. Cer- 
tain of the rarer elements such as manganese and titanium are pres- 
ent sometimes in larger quantities in Hawaii soils. Manganese is 
found in certain areas, 4 to 9 per cent, and titanium is present to the 
extent of 2 to 4 per cent. Kelley and his coworkers (&/, p. 7) report 
an instance in which the soil contains as high as 35 per cent titanium 
dioxide (Ti0 2 ). The amount of organic matter in Hawaii soils 
is about two to three times as high as in mainland soils. 
In view of these facts the soils of the Hawaiian Islands should 
be expected to exhibit physical characteristics different from those 
of soils of the mainland of the United States. 
DESCRIPTION OF SOILS USED IN THE INVESTIGATION 
In order to obtain the necessary material for the investigation 
herein reported, trips were made to various parts of the islands 
where typical and unusual soil types exist. The larger number of 
samples were obtained from localities widely differing in climate, 
elevation, and the like. The description and physical character- 
istics of these soils are given in tabulated form in the Appendix 
(p. 43). Selection of soil samples was based on the chemical and 
physical differences of the various soils, including soil reaction, per- 
centage of organic matter, mechanical analysis, water-holding ca- 
pacity, hygroscopic moisture, and color, and on geographical loca- 
tion, origin, and climatic condition. Of the 82 samples obtained, 
7 came from Oahu, 25 from Maui, 10 from Kauai, and 40 from Ha- 
