PHYSICAL PROPERTIES OF HAWAII SOILS 11 
Soil No. 69 is a clay from the Lahaina district, Maui, near Olowalu. 
This clay is apparently alluvial in origin and is very sticky and 
plastic, and of very low organic content. It was taken at sea level 
where there is underground seepage of sea water. The colloid com- 
plex is saturated with sodium. In addition, the soil contains a con- 
siderable amount of calcium, in the form of carbonate, from disinte- 
grating coral beds underlying the clay. On this account the nature 
of the soil changes at about 12 inches in depth from clay to sandy 
clay. It is alkaline in reaction and is high in calcium. 
Soil No. 76 is a clay from field 17, section 2, Makee Sugar Co., 
Kealia, Kauai. This highly calcareous clayey topsoil was taken 
at a depth of 4 inches at approximately sea level. Surrounded by 
fertile cane land giving good yields, this area presents an anomalous 
condition causing stunted vegetation. The soil is alkaline in reaction 
due to the calcium carbonate in the layer below. 
Soil No. 77 is a clay and the subsoil of soil No. 76, taken at a depth 
of 24 inches. It is very much lower in organic matter than soil No. 
76, and contains large amounts of calcium carbonate. In both soils 
Nos. 76 and 77 the percentages of colloids are rather low, showing 
that in all probability the anomalous condition is due to unfavorable 
soil reaction and excessive sodium and calcium content. 
CERTAIN PHYSICAL PROPERTIES OF HAWAII SOILS 
TEXTURE 
The various weathering agencies which enter into soil formation 
in different combinations and to varying degrees affect the final 
decomposition product considerably. The texture of the product 
depends chiefly on the nature of the weathering agencies and the 
length of time they have been at work — that is, the age of the 
weathered product. When weathering is chiefly of a physical 
nature, the resulting soil is usually coarser in texture than when 
disintegration is caused by chemical changes, such as occur in 
humid climates. Moreover, the resulting soil is usually more evenly 
divided in the different fractions when weathering is chiefly physi- 
cal. The difference in solubility is also a factor when textural dif- 
ferences are considered. Quartz, on account of its low solubility, 
persists longer in the coarser fractions, whereas minerals of a less 
resistant nature, such as feldspars, hornblende, and augite, con- 
centrate gradually in the finer fractions. It is not surprising, there- 
fore, to learn, in the case of Hawaii soils, the parent material of 
which consists largely of the last three minerals mentioned, that the 
finer separates, such as the fine silts and clay, are present in larger 
amounts than in most of the mainland soils. 
The soils of Hawaii are on the whole heavier than those of the 
mainland of the United States, inasmuch as they contain larger 
percentages of the fine fractions, especially clay. Most soils belong 
to the clay and clay-loam types, these designations being in accord- 
ance with the United States Department of Agriculture Bureau of 
Chemistry and Soils classification on the basis of mechanical analy- 
sis. The Appendix gives the mechanical analyses of 78 Hawaii 
soils, as determined by means of the rapid hydrometer method of 
Bouyoucos (5, 6). 
