8 
studying the relationship of different soil types and the effect of 
fertilizers upon the physical factors influencing plant growth. 
From previous work in this laboratory and the experiences of prac- 
tical farmers, physical factors appear to play a large part in the 
fertility of Hawaiian soils. The effects of heat and volatile antisep- 
tics, the action of lime, the high absorptive power for fertilizers, the 
difficulties in drainage, high cost of tillage, and the pecuUar biological 
effects that ensue, seem to be very largely explainable on a physical 
basis and to be referable in part to coUoids. 
In view of the above facts, this station has devoted considerable 
time to investigations upon the physical properties of soils and the 
function of fertilizers, other than as a source of plant food, with 
special reference to the movement of soil moisture. It is quite gen- 
erally conceded that no simple explanation of the influence of fertili- 
zers upon the soil or the plant is possible. 
SOIL TYPES. 
As in previous investigations upon soils in this laboratory, those of 
widely differing chemical and physical characteristics were chosen. 
The following tables show the physical composition and properties 
of these types. In Table I wiU be found the mechanical composition 
as determined by sedimentation according to Hall.^ 
Table I. — Mechanical analyses of the soils. 
Soil No. 
Moisture. 
Volatile 
matter. 
Fine 
gravel. 
Coarse 
sand. 
Fine 
sand. 
Silt. 
Fine silt. 
Clay. 
428 
Per cent. 
13.80 
12.45 
10.41 
3.58 
7.98 
12.26 
7.60 
Per cent. 
25.65 
28.83 
17.64 
13.90 
17.81 
20.44 
13.96 
Per cent. 
11.89 
1.70 
3.40 
Per cent. 
28.26 
7.52 
5.29 
Per cent. 
13.63 
14.29 
29.66 
5.76 
31.26 
31.48 
8.07 
Per cent. 
4.64 
11.75 
10.30 
10.34 
13.39 
19.10 
9.35 
Per cent. 
1.53 
17.49 
15.75 
37.97 
17.79 
11.93 
24.90 
Per cent. 
0.60 
448 
5.97 
516 
7.55 
530 
0.49 
.81 
1.50 
.36 1 1.15 
27.96 
542 
10.96 
573 . 
3.29 
574 
34.87 
Of the above soil No. 428 is a dark-colored, highly organic, sandy 
soil from Glenwood, Olaa, Hawaii. 
Soil No. 448 is a yellow silty sand from Hilo, Hawaii. 
Soil No. 516 is a sample of manganiferous soil from the Wahiawa 
district, Oahu. It has a chocolate-bro^vn color, silty texture, and 
maintains an excellent mechanical condition. 
Soils Nos. 530 and 574 are samples of red-clay soils, the former of 
a light and the latter of a dark red color. 
Soil No. 542 is a titaniferous soil of grayish red color and silty 
texture. Its physical condition is very similar to that of soil No. 516. 
Soil No. 573 is a ''dust" soil from the island of Hawaii. It is a 
dark-colored, highly organic silt, and very productive. 
1 The Soil. London, 1908, 2. ed., p. 51. 
