THE EFFECT OF FERTILIZERS ON THE PHYSICAL 
PROPERTIES OF HAWAIIAN SOILS. 
INTRODUCTION. 
It has been the custom in Hawaii since agriculture was first placed 
upon a commercial basis to stimulate crops with heavy applications 
of mineral fertiUzers. This procedure has been maintained in spite 
of the fact that a majority of the soils are naturally well supphed with 
plant food, in some instances abnormally so. 
Hawaiian soils are of such a nature that the maintenance of the best 
possible physical state is imperative. They are derived from the 
disintegration of basaltic lava, have since been impregnated with 
coral limestone in many of the lowlands and with large amounts of 
organic matter in the uplands, where the rainfall is high and the 
vegetation profuse. Being derived from highly basic rocks, the result- 
ing soils are highly basic in composition. The silica content varies 
from 15 to 50 per cent, while the basic constituents, iron and alumi- 
num, compose the major part of the remainder. The tendency of 
these metals to form hydrates or sihcates, their influence upon the 
mechanical structure, drainage, cUmatic conditions, temperature, 
aeration, and above all the effect upon the moisture supply, are mat- 
ters which demand the careful consideration of agriculturists in these 
islands. 
Soil moisture is a prime factor in successful plant growth. It not 
only influences the physical condition but also acts as a vehicle for 
the transmission of plant food from the soil to the plant. Since all 
mineral and many organic substances are more or less soluble in 
water and since all dissolved material is known to affect the physical 
properties of the solvent, it may be concluded that the properties of 
soil moisture and also the physical condition of the soil are partially 
dependent upon the composition of the soil solution. 
These physical properties include capillarity, percolation, floccula- 
tion, cohesion, apparent specific gravity, vapor pressure, and hygro- 
scopic moisture. Although the laboratory determinations of these 
properties of a soil and of the effect of salts thereon have little 
direct practical value, since the soil in such cases is not in a natural 
state, and other conditions are abnormal, they may be useful for 
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