POTASH FROM KELP. 37 
so that the drift kelp may be caught by the uncut plants and picked 
up later, unless a strong current happens to submerge the attached 
plants, in which case, of course, all loose material would be carried 
away. The disavantages in this method are that, in the long run, 
time is lost because cutting swaths and patches here and there soon 
leaves a bed spotted, and there is then no good cutting anywhere; 
that when the current is strong, or the harvester careless, more kelp 
is lost, because it is set adrift on both sides of the swath; and that, 
if the heavier clumps are cut over several times—as is likely to be 
the case in a month’s harvest—all the first new fronds are topped, 
and the renewal of the bed thereby delayed; furthermore, that with 
the thinner portions left uncut, the full yield of a bed is not ob- 
tained, and, besides these uncut portions may become breeding places 
for black rot. 
ate PERIODS OF HARVESTING. 
_ In some of the kelp beds harvesting was carried on continuously 
for a period of from 4 to 12 months, or even longer, whereas other 
beds were cut periodically, with 2 months or more allowed for re- 
generation after each cutting. The former method was employed 
where there appeared to be an ample supply of kelp near at hand,. 
and in some cases, where harvesting operations could be carried on 
only in summer, as at San Nicolas Island, or where a distant bed 
was used to make up for shortages. Such a system of harvesting 
has the advantage of clearing out any diseased plants, also of keep- 
ing the bed open to sunlight and circulation, but sooner or later 
the plants begin to weaken as a result of such severe pruning, and 
periodic cutting seems to be the better method. Periodic cutting 
controls black rot if the kelp is thoroughly cleaned off each time, 
and it tends to regulate growth and thereby to make the product 
uniform. Three or four months seems to be the proper time to 
allow for growth after cutting, as a large proportion of the fronds 
reach maturity in that time. If longer rest periods are allowed, 
deterioration begins, the older fronds sloughing or becoming covered 
with small plant and animal forms and the lability to loss from 
storms or disease being increased. 
In order for the supply of kelp to be continuous, the beds must 
be cut im rotation. Each section should be of no larger size than can 
be completely cut in a month, and it is still better if cutting does 
_ not continug for more than two weeks in a given section. Consider- 
able latitude must be allowed, however, because strong currents may 
hold down the kelp and delay cutting, storms may interfere with the 
cutting of distant beds, or the occurrence of black rot may make it 
necessary to hasten cutting. Since kelp grows most in winter and 
least in summer, harvesting should be carried on as extensively in 
the winter as the weather permits, and practically discontinued in 
midsummer and early autumn. Such a system would accord well 
with the annual fluctuations in the California labor market. 
YIELDS. 
The tables compiled from the reports on yields by the California 
State Fish and Game Commission (1916 to 1920 inclusive) show the 
comparative effects of continuous and periodic harvesting. In these 
