60 



BULLETIN 150, U. S. DEPARTMENT OF AGRICULTURE. 



Table XII. — Comparison of the composition of wet 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 



Fresh urine 









73.27 

 75.30 



78.81 



.30 





.15 



Cowpeas 1 



.98 



Street sweepings, Washington, E>. C. 2 



.55 



Wet kelp • . 



85.00 



.10 







i 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 XI. The drying would not be 

 quantitative ; that is, a certain proportion of water w T ould 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 



