26 
Colorado Experiment Station 
tubers of the Pearl variety appeared to be a little smoother and 
freer from knots on the early irrigated plats than on the others. 
No difference was found in the quality of tubers produced on the ! 
different plats of the Rural New Yorker. It is characteristic of this 
variety, however, to produce smooth tubers under practically all 
conditions. 
While the evidence thus far obtained is wholly in favor of the 
early beginning of irrigation further experiments under a wide 
range of climatic conditions and with a greater number of varieties 
are necessary before the question can be definitely settled. 
SIZE OF SEED 
These experiments, which were started in 1915 for the purpose 
of determining the most economical size of seed to use, are part of 
the general project of the United States Department of Agriculture 
for the study of this problem. In addition to the work along this 
line in Colorado similar experiments have been conducted at Jerome, 
Idaho; Presque Isle, Maine, and Norfolk, Virginia. 
EXPERIMENTS AT GREELEY, COLORADO 
The sizes of seed used for these experiments included 1-, 2-, 3-, 
4-, 5-, and 6-ounce seed pieces. Since the work was carried on with 
both whole and cut tubers the studies also include comparisons be- 
tween these two kinds of seed. The separation of the seed tubers 
into different sizes was performed by first roughly grading them 
with a sorter, using screens of different sizes. The final division 
was then made by weight, placing each tuber on a spring balance 
graduated in grams, allowing a variation of 5 grams on either side 
of the exact ounce equivalent, except that in the case of 8- and 
12-ounce tubers a variation of 10 grams in either direction was 
allowed. Where cut seed was used the tubers which were halved 
were cut lengthwise, while the quartered tubers were first cut length- 
wise then at right angles' to the long axis, the four pieces being of 
approximately the same weight. In 1915, 1916 and 1917 the plant- 
ing was done by hand. In 1918 a planter was used. The distance 
between hills was 14 inches in 1915 and 1918, and 16 inches in 
1916 and 1917. The rows, in all cases, were 36 inches apart. 
The separation of the tubers into the two grades, marketable 
and culls, was based on weight in 1915, 1916 and 1917, those weigh- 
ing three ounces or more (over 85 grams) being classed as market- 
able while those which weighed less than three ounces were con- 
