26 
Colorado Experiment vStation. 
\ 
between two and three degrees cooler in the warmest part of the 
da.y. On extremely hot days the saving at the high point was some¬ 
times as much as 7°. The deeper rooting would be a factor also in 
favor of deep cultivation, as the deeper the roots the less their tem¬ 
perature at the top heat of the day. With heavy soils, the poorer 
aeration of the roots at several inches below the surface would be 
an adverse factor, but potatoes should not be planted on such soils 
in regions of high soil temperatures. 
The temperature of irrigation water is an important factor, 
afso, because water holds from seven to eight times as much heat 
as good potato soils, so that the temperature of such a soil is pro¬ 
foundly influenced by the temperature of the irrigation water. 
Water coming a long way in small ditches is considerably warmed. 
A return to the planting of trees on ditch banks would have some 
excellent results. To mention an extreme case of warm irrigation 
water, we found near the lower end of one of the ditches out of the 
Poudre^ one afternoon in July, 1912, a potato field being irrigated 
with water which was reaching the lower end of the field at 108°. 
At Glenwood Springs, in the same month, we found the Grand river 
at about 52°, and the Roaring Fork water going into' the potato 
rows from the snows of Mount Sopris at 54°. 
V. HISTORY OF POTATO-GROWING DISTRICTS. 
As our fathers have cleared new forests, moved west tO' new 
prairie lands, or brought into cultivation by their labor and engi¬ 
neering skill the new and wonderfully fertile irrigated districts of 
the West, they and we have had for almost three hundred years 
new lands on which to grow potatoes. Virgin soils produce well 
nourished, well rounded tubers from healthy plants. As virgin 
soils are no longer available, we shall be obliged to consider with 
care the soil requirements for the health of potatoies. As time goes 
on, our loose, sandy soils, sometimes held in little respect, will b^ 
better fertilized and more appreciated because of their healthfulness 
for potatoes. 
At the Colorado station, no question came more often to the 
potato specialist than: “Why cannot wc grow potatoes? We did 
here in the early days, but we cannot now.” Only recently an Iowa 
man who had bought land near Denver sent the same question to 
Iowa State College. This question came very often from the 
vicinity of Rocky Ford, from Canon City, from Pueblo, from Rye. 
from the Fountain Valley below Colorado Springs, from Golden and 
Denver, Fongmont, Stove Prairie and Virginia Dale. The 
