Physical analyses of rice soils. 
District. 
Fine 
gravel, 
2 1 nun. 
Coarse 
saint. 
1 0.2 
nun. 
Fine sand 
0.2 0.04 
mm. 
Silt. 
0.04-0.01 
nun. 
Fine silt . 
0.01-0.002 
nun. 
Clay, 
0.002 mm. 
Or less. 
Organic 
matter 
and 
combined 
water 
Waikiki: 
Soil 298 
Ptr c< n(. 
20.91 
18.61 
1.15 
1.02 
. 82 
.35 
.33 
.13 
.06 
.05 
.22 
.15 
.46 
.41 
.22 
1'ti cent. 
18.75 
18.30 
1.61 
1.28 
1.63 
.69 
.86 
.22 
.31 
.19 
.11 
3.09 
3.59 
.83 
. 64 
Per cent. 
22.04 
22. 74 
18.34 
20. 63 
15.33 
18.78 
18.60 
18.13 
16.75 
16.03 
15.29 
25.94 
34.44 
21.49 
11.29 
Pi r a nt. 
8.69 
8.10 
16.28 
17. sS 
15.77 
13.57 
15.97 
20.42 
19.27 
30.79 
28.94 
20.97 
19.30 
27.45 
15.27 
12. 11 
13. 18 
23.88 
22.11 
21.73 
22.92 
21.97 
22.37 
23. 42 
14.64 
20.67 
15.96 
10.96 
7.61 
20.07 
Per cait. 
7.23 
9.52 
25.39 
24.06 
31.61 
25.70 
23. 97 
19.19 
22.98 
20.16 
21.73 
19.84 
14.29 
6.38 
6.19 
Per'cerU. 
s.71 
Subsoil 293 
10.77 
Fort Shatter: 
Soil 332. 
14.37 
Subsoil 333 
14.t).'. 
Soil 334 
15.23 
Kailua: 
Soil 337 
18.72 
Subsoil 338. ... 
19.54 
Soil 339 
21.17 
Subsoil 340 
19.41 
Kaneoho: 
Soil 343 
15.44 
Subsoil 344 
13.20 
Waiaholo: 
Soil 345 
15.04 
Subsoil 34f> 
15.31 
Kalaunui: 
Soil 347 
36.14 
Subsoil 34S 
49.24 
The above data show that the rice soils of Oahu. with the ex- 
ception of those from the Waikiki and Kalaunui districts, are very 
similar in mechanical composition, and are made up of approxi- 
mately equal quantities of fine sand, silt, fine silt, and clay. The 
Waikiki soils, on the other hand, contain relatively small amounts 
of clay, with correspondingly larger amounts of the coarser grained 
particles. None of tHe soils except from this district contains any 
material coarser than fine gravel, while that from Waikiki contains 
several per cent of stones, etc. This point is of importance because 
of its bearing on tillage and drainage: The soils from Kalaunui, 
on the other hand, are very highly organic, and in places this land is 
peaty to a considerable degree. The organic matter of this soil, how- 
ever, retards the passage of water through it, with the result tr^at the 
amounts of water used in its irrigation are practically normal for 
the islands. 
In the main these soils are to be classified as clay loams with a 
rather high organic content. The irrigation of all these soils requires 
relatively large amounts of water on account of their porous nature. 
In considering the mechanical composition cf Hawaiian soils it 
should be especially borne in mind that the terms clay, fine silt, etc., 
have reference only to the size of the particles, and that these art- 
made up of different chemical substances from those that go to 
make up clay in most continental soils. Furthermore, the prop- 
erties of so-called clay in Hawaiian -oils differ from the properties 
of other flay-. It i- not composed primarily of kaolin, but is made 
up of ferric and aluminum hydrates, together with double silicates 
of iron and aluminum and perhaps some aluminum silicate. In 
