SIZE OF POTATO SETS. 
37 
The successful determination of the most profitable size of set to 
use and whether it should be planted whole or cut primarily involves 
a careful study of the proper spacing to give to each size of set in 
order to obtain the maximum yield. 
Departmental studies covering several years show rather conflicting 
results, so far as the yield of primes, or marketable potatoes, is concerned. 
The data clearly show that seasonal conditions have a very definite 
influence upon yield, particularly with respect to the size of the 
tubers. Abundance of moisture and plant food throughout the grow- 
ing season insures a maximum crop from whole and large-sized cut 
sets; whereas lack of these two prerequisites favors medium-sized 
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v a 3 *z 3 e 
Fig. 12.— Irish Cobbler stem-frequency correlations from quartered 
sets grown at Presque Isle, Ale., 1915 to 1918, inclusive. 
cut sets, because fewer tubers are produced, and in consequence they 
have a better chance to reach marketable size. 
There is a definite relation between the size of the set used and the 
number of stems and tubers produced to the set. 
A study of stem-frequency correlation shows that as the weight 
of whole seed increases from 2 to 6 ounces the stem frequency shifts 
from three stems in the case of 2-ounce sets to seven stems in the case 
of 6-ounce sets. Halved seed shifts from two stems to four stems. 
Quartered sets on the other hand, whether from 3, 4, 5, or 6 ounce 
tubers, show that the greatest stem frequency falls in the 2-stem 
column in the Presque Isle, Me., data. In the Virginia data whole 
sets shift from 3 to 5 stems, halved sets from 2 to 3 stems, and quar- 
tered sets from 1 to 2 stems. 
