60 
BULLETIN 150, U. S. DEPARTMENT OF AGRICULTURE. 
Table XII. — Comparison of the composition of ivet kelp with other inanurial 
products. 
Material. 
Mois- 
ture. 
Nitro- 
gen. 
Potash. 
Phos- 
phoric 
acid. 
Horse manure: 1 
Solid fresh excrement 
Per cent. 
Per cent. 
0.44 
1.55 
.50 
.72 
.27 
.86 
.30 
Per cent. 
0.35 
1.50 
.60 
.45 
.31 
.55 
2.50 
Per cent. 
0.17 
Stable manure 1 
73.27 
75.30 
78.81 
.30 
Green alfalfa l 
.15 
Cowpeas 1 
.98 
Street sweepings, Washington, I). C. 2 
.55 
Wet kelp 
85.00 
.10 
1 From Soils, by S. W. Fletcher. 
2 From Analyses, by J. G. Smith, Bureau of Soils. 
The high content in water of the green kelp and its resulting low 
content in valuable constituents restricts its use to regions within 
easy reach of the points where it is harvested. For that reason any 
scheme for the large-scale utilization of kelp as a fertilizer must be 
based on some method of concentrating its valuable constituents. 
Since all of these are either neutral or beneficial from a fertilizer 
point of view, it is necessary only to concentrate them by the re- 
moval of the water, or in other words by drying. After an investi- 
gation of several years and a careful consideration of the nature of 
the raw materials involved, the value of the products obtainable and 
the costs of obtaining them, together with the demands of the fer- 
tilizer trade and the economic conditions existing on the Pacific 
coast, it appears that kelp, in the beginning at least, most advan- 
tageously can be prepared for the fertilizer trade merely by drying 
and grinding. 
The product obtainable, as shown by small-scale operations, is a 
coarse gray powder of such specific gravity that a cubic foot weighs 
51 pounds. "While it does not absorb moisture readily from the 
air, when wetted it swells and may become sticky and gelatinous. 
In composition it would approximate closely the values obtained 
from the foregoing Tables X and XL The drying would not be 
quantitative ; that is, a certain proportion of water would be allowed 
to remain, probably 7 to 10 per cent. Assuming the larger figure, 
the other values would be reduced proportionately, namely, 10 per 
cent. The pulverized kelp, then, would contain 15.8 per cent potash 
and 1.6 per cent nitrogen. On the retail market of the Pacific Coast 
States, the prices of $1 per unit of potash and $3.30 per unit of 
ammonia are obtainable. On this basis the value of the kelp per ton 
is arrived at, as follows: 
15.75 per cent K 2 at $1 $15. 75 ( 
2.18 per cent NH 3 at $3.30 7.19 
Total value per ton 22.94 
