fertilizers for rice have been conducted by the station. The subject 
has been approached from a number of standpoints, both practical 
and scientific, and it is believed the results are of sufficient interest 
and value to warrant publication at this time. 
ORIGIN OF RICE SOILS. 
The rice soils of Hawaii are located at or near sea level along the 
coast and are not extensive in area, amounting to about 10,000 acres, 
and during recent years the tendency has been to plant other crops 
on some of the lands hitherto devoted to rice because of low yields, 
labor difficulties, etc. The extent of the industry, therefore, is on the 
decline. The soils have their primary origin in basaltic lavas, just 
as is the case with all the soils of the islands, but in addition they 
frequently contain varying amounts of coral lime (CaC0 3 ), which 
has become thoroughly mixed with the lava residues. Whether or 
not the coral is visible on the surface, in practically all cases the rice 
lands are underlain at various depths with deep beds of coral lime- 
stone. Notwithstanding the fact that the lavas are typical basalts, the 
chemical and physical properties vary enormously; moreover, the 
rates of disintegration and the composition of the residuum differ 
greatly from place to place. Therefore the soils coining from lavas 
of essentially the same type may be very different in composition 
and properties. The .low lands in and around Honolulu, for instance, 
having been derived from the disintegration of volcanic cinder, 
typical black sands, are widely different from the rice lands on the 
leeward side of Oahu, both in chemical and physical properties. This 
is especially noticeable in the relative percentages of lime and 
magnesia. 
In most instances the rice soils are strictly alluvial, although on 
account of the close proximity of the mountains there has been but a 
limited transportation of the soil materials. The soils in places 
contain a high percentage of organic matter. 
In certain localities, as, for instance, the Hanalei Valley, on Kauai, 
the soils contain high percentages of clay and are of a close texture. 
The rice lands around Honolulu, on the other hand, contain quantities 
of sand and gravel unusual for Hawaiian soils, and as a consequence 
are open and porous. Samples of soil from all the important rice sec- 
tions have been examined. 
MECHANICAL COMPOSITION. 
In view of its bearing on irrigation, etc., the mechanical composi- 
tion as shown by physical analysis has been determined and is re- 
corded in the following on page 5. 
