14 
BULLETIN 1340, IT. S. DEPARTMENT OF AGRICULTURE 
land in farms is confined to less than 3,000,000 acres, of which 
2,313,165 acres were irrigated in 1919. It is from this relatively 
small area of irrigated land that the bulk of the soil products are 
derived. The large profits resulting from irrigation in the Basin 
as compared with those from nonirrigated land would seem to 
justify the expenditures which 
have been made in providing water 
supplies for agricultural purposes. 
A large number of experiments 
have been made to determine the 
relationship between the amount 
of water applied to soil and the 
yield of crops. In all cases condi- 
tions were more or less under con- 
trol, effected by growing crops 
under test in plots or in tanks. 
In order to determine the actual 
water requirements of various 
crops during their period of 
growth, the Division of Agricul- 
tural Engineering has for jqhts 
used metal containers known as 
tanks, in which the crops are 
grown and irrigated with varying 
amounts of water. These tanks 
are made of galvanized steel and 
vary in diameter from 18 to 30 
inches and in depth from 4 to 6 
feet. To facilitate weighing at 
short intervals and for the better 
control of temperatures, each tank 
is enclosed within a larger tank of 
similar design and the annular 
space is filled with water. In 
many cases the inner tank has a 
false bottom composed of brass 
gauze over No. 10 gauge plate and 
an outside tap through which 
water percolating through the soil 
column of the inner tank may be 
withdrawn and measured. The 
general design of the tanks is 
shown in Figure 5. 
In 1901 a series of plot experi- 
ments was made on the Utah Agri- 
cultural Experiment Station Farm 
at Logan to determine, among 
other things, the effect of water on 
the yield of crops. The sandy soil, which varied in depth from less 
than 18 inches to 59 inches, was underlaid with gravel to a depth of 
several hundred feet. On account of the porous character of the 
shallow soil and the coarse, gravelly subsoil, more than the average 
quantities of water were used in order to compensate for deep per- 
Fig. 5. — Double soil tank, showing 
shell with eyelets for hoisting and col- 
lar resting on edge of outer shell. Por- 
tion of tank shown as torn away to 
disclose screen resting on perforated 
plate, space for capture of deep percola- 
tion water and Cock for withdrawal of 
this water 
