UTILIZATION OF THE FISH WASTE OF THE PACIFIC OCEAN. 61 
In the wholesale market of the East, the prices obtainable are 
$0.65 per unit of potash and $2.85 per unit of ammonia, on the basis 
of which the value of the kelp would be : 
15.75 per cent KjO at $0.65 $10.24 
2.18 per cent NH 3 at $2.85 6.21 
Total value per ton 16.45 
' From the analyses of the dry kelp it is seen that it is distinctly a 
potassic fertilizer, and would enter the trade as a potash carrier. 
Since the present practice is to use the mixed or " complete " ferti- 
lizers, the kelp, if produced on a large scale, would find its market 
as a potash carrier to be mixed with phosphates and ammoniates to 
form the " complete " fertilizer. For this purpose, it would enter 
into competition with other potash carriers, including the German 
potash salts. These are, principally, kainite, a double salt of po- 
tassium and magnesium. MgS0 4 KC13H 2 0, and "manure salts," a 
mixture of potassium, sodium, calcium, and magnesium salts. 
Kainite, when pure, has a theoretical content of 18.9 per cent potash, 
but in the impure condition in which it is found on the market 
carries about 12.5 per cent potash. It sells for about $8.25 per ton. 
"Manure salts" vary widely in their potash content, but generally 
are of low grade and carry about 12 to 18 per cent potash. At pres- 
ent kainite, as such, is disappearing from the market, being classi- 
fied with " manure salts." 
A comparison of the efficiency as a fertilizer of the potash in 
kelp and that in potassium salts, of the general type used in mixed 
fertilizers, has been made in the laboratories of this bureau by Skin- 
ner and Jackson. 1 The two were applied to growing plants in 
equivalent amounts. The results showed that the kelp as a potassic 
fertilizer was quite as effective as the potash salts. 
Since sodium chloride is found as a constituent of kelp, it has 
been suggested that its use on alkaline soils might prove objection- 
able. In reply to this it should be said that the amount of salt actu- 
ally added to the soil in the kelp is extremely small, and in such 
amounts it has been shown to exhibit fertilizing properties. Fur- 
ther, sodium chloride makes up but a small proportion of alkali, 
that being either sulphate of calcium or magnesium or carbonate of 
soda. If such an objection were valid, it would apply much more to 
the materials now in use as potash carriers, the "manure salts," 
which have been seen to contain soluble salts of both calcium and 
magnesium. In the case of the potash salts, the constituents other 
than potash have no value on a fertilizer basis and therefore are 
merely so much inert material on which transportation must be 
paid. The deleterious action of these in some soils would be un- 
1 Circ. 76, Bureau of Soils, U. S. Dept. of Agr. 
