26 BULLETIN 1340, IT. S. DEPARTMENT OP AGRICULTURE 
the last half of this time a large quantity of water. The third and 
last crop of the season matured in less than 30 days and required 
somewhat less water than the second crop. The results shown are 
the mean of four experiments. The quantity of water evaporated 
from a water surface during the growing of the three crops, the wind 
velocity, and the temperature are also shown. 
POTATOES 
An essential feature in the production of large yields of market- 
able potatoes is to maintain as constant a soil moisture content as 
conditions will permit. A medium amount of soil moisture is to be 
preferred to either a high or low one. If the soil is too dry at the 
time of planting, it should first be irrigated in order to furnish the 
plants with sufficient moisture until the vines are 4 to 6 inches high. 
From this stage until the potatoes are nearly mature the ideal pro- 
cedure would be to apply a small quantity of water each week. The 
nearest approach to this which is practical in the Great Basin is to 
apply about four light irrigations. If the soil is moist at the time 
of planting, the first of these may be given when the vines are 4 to 
6 inches high, the second when tubers begin to form, the third when 
the vines are in bloom, and the fourth prior to ripening. 
In experimenting with the irrigation of potatoes at the Nevada 
Agricultural Experiment Station during the years 1914 to 1917, 
inclusive, the plan adopted was to apply water when the vines 
showed a tendency to wilt. The depth of water applied at each 
watering was 3 inches for one series of plots, 6 inches for another, 
and 9 inches for the third series. For the 4-year period, the highest 
yields were obtained with 3-inch applications given when the. vines 
started to wilt. 
As a result of years of experimentation with potatoes at the 
Utah Agricultural Experiment Station, the highest yields have been 
obtained by 1-inch applications weekly for a period of 13 weeks. 
Since such light applications are seldom practical under field condi- 
tions, this station has adopted, with good results, the practice of 
applying fairly frequent light irrigations extending from the time 
the vines are 4 inches high until the plants are nearly ripe. Other 
phases of this subject brought out by the Utah experiments are that 
the yields of potatoes are decreased by too much water and by irri- 
gating after planting and before the plants are above ground, that 
if only one irrigation can be applied during the period of growth, 
it should be at the time of full bloom, and that if the soil is allowed 
to dry out to such an extent as to check growth, knobby or gnarled 
tubers may result from a subsequent watering. 
SUGAR BEETS 
It was formerly quite generally held that water should be with- 
held from sugar beets as long as possible during their first stage of 
growth in order to produce long roots. Observations and the results 
of experimentation during the past decade have shown that this 
practice is not profitable. Depriving young beets of water may 
induce deep rooting but this slight advantage is apt to be counter- 
balanced tenfold by the injury done to the plants in thus checking 
