12 
greatly increases the ammonia content and is a means of making 
available a considerable portion of the nitrogen, but it should be 
remembered that in so doing considerable loss of nitrogen takes place 
through the destructive effect of the heat. 
PECULIAR SOILS. 
One of the peculiarities of Hawaiian soils is the unusually high con- 
tent of some of the rarer elements, notably manganese and titanium, 
which are supposed not to be necessary for plant growth. The man- 
ganiferous soils, with relatively unimportant exceptions, are located 
only on Oahu between the Koolau and Waianae Mountains, but it 
is not possible to give an accurate estimate of the extent of this type 
or to trace its location in detail. In general, it may be said to occur 
most abundantly toward the lower levels between the mountain 
ranges, in pockets or level stretches that receive the drainage and wash 
from higher levels. This type of soil occurs most abundantly in the 
Waipio, Wahiawa, and Halemanu districts, but may also be found 
in portions of Waialua, Waimea, and in the upper part of the Oahu 
Sugar Co.'s land. There are also small areas of highly manganiferous 
soil near Haiku on Maui, Homestead on Kauai, and in the Palawai 
Basin of Lanai. 
Sometimes the manganese areas are small, while in other places as 
much as 20 or more acres may occur in one body. The percentage of 
manganese varies greatly. A few tenths of 1 per cent occur in nearly 
all Hawaiian soils. The manganiferous soils, however, often contain 
more than 5 per cent, expressed as manganese oxid (Mn 3 4 ). These 
soils are characterized by a dark color, sometimes almost black, due 
to the presence of manganese dioxid, and have a silty texture in con- 
trast to the heavy clay character of the surrounding soils. Generally 
concretions composed of manganese dioxid can be found mixed with 
the soil and more abundantly in the subsoil. The manganese is 
nearly always more abundant in the soil than in the subsoil. In 
some places where the surface soil contains more than 4 per cent the 
subsoil contains less than 1 per cent., A high manganese content is 
quite injurious to pineapples, causing the leaves to become yellow 
and lowering the quality of the fruit. Some other crops are also 
injuriously affected, but sugar cane, sisal, cabbage, turnips, and some 
other crops seem to be unaffected. 
As in the case of the manganiferous soils, it is not possible to locate 
definitely all of the highly titaniferous areas. All Hawaiian soils 
contain comparatively high percentages of titanium. The soils of 
the Kunia section, however, are unusually high in titanium, containing 
in some instances as much as 35 per cent titanium dioxid (Ti0 2 ), but 
the titanium is relatively insoluble, and consequently the usual agri- 
cultural analysis fails to show the total amount present. 
