32 BULLETIN 1340, TJ. S. DEPAKTMENT OF AGRICULTURE 
Closely related to this subject is the proper quantity of water to 
apply at each irrigation. This in turn leads to a consideration of 
how much water soils can retain for the use of plant roots. To 
spread more water over a field than is needed is as bad a practice as 
filling bathtubs to overflowing, yet the former is done on hundreds 
of farms every day of the irrigation season throughout the Great 
Basin. One of the results of this wasteful practice is the annual 
expenditure of large sums of money for the drainage of over- 
irrigated lands. Frank Adams found 9 that the average quantity of 
water retained in the lighter and more permeable soils of the Sacra- 
mento Valley, Calif., was 0.92 acre-inch per acre for each foot in 
depth of soil, or the equivalent of 5 to 6 acre-inches per acre for 6 
feet of soil, Avhereas the clay soils, because of their great impervi- 
ousness, absorbed an average of only 0.37 acre-inch per acre for each 
foot in depth, this being at the rate of only about 21,4 acre-inches for 
6 acre-feet. He found, however, that in the surface foot the light 
soils retained an average of 1.04 acre-inches per acre-foot of soil as 
compared with 1.71 acre-inches per acre-foot held by the clay soils, 
this being in accordance with the well-known fact that clay soils, 
when thoroughly wetted, will hold much more soil water than soils 
of coarser or " lighter " texture. 
Israelsen and West™ state: "It is doubtful if an acre of typical 
upland soil 4 feet deep (in Utah) would retain more than 3 acre- 
inches of irrigation water ". They further state that an average of 
nearly 3,000 tests, made by \Vidtsoe and McLaughlin showed that the 
upper 8 feet of loam soil of the Greenville farm near Logan, Utah, 
retained a little more than 1 inch of water for each foot of soil, 24 
hours after irrigation. The general conclusion reached by Israelsen 
and West is that soils have the capacity to absorb from one-half to 
iy 2 inches of water per foot of soil, the actual capacity for a given 
soil depending on its texture and structure. Sandy and gravelly 
soils retain the smaller quantities and clay loam soils the larger 
quantities. 
In cooperative investigations conducted in Idaho by the Bureau of 
Public Eoads and the State Land Board of Idaho, Bark 11 found 
that alfalfa grown in metal containers filled with porous soil 
utilized only about 13 inches of the 80 inches applied in seven irri- 
gations ; the balance, amounting to more than 83 per cent of the 
volume applied, percolated through the 6 feet of soil and was with- 
drawn from the bottom of the container. 
In addition to those briefly discussed in the preceding paragraphs, 
there are many mors conditions which influence the water require- 
ments of crops, but only two of these, viz., the kind of crops grown 
and ths fertility of the soil will be referred to here. 
THE KIND OF CROPS 
It is a well-established fact that crops differ Avidely in their water 
requirements. The quantity of water required to produce a ton 
of air-dried alfalfa may suffice for the production of 2y 2 tons of 
9 Investigations of the Economical Duty of Water for Alfalfa in Sacramento Valley, 
California. Bnl. No. 3, State of California. Department of Engineering. 
10 Israelsen, O. W.. and West, F. !>., Water-Holding Capacity of Irrigated Soils, Utah 
Agr. Exp. Sta. Bui. No. 183. 
11 Bark, Don H., Experiments on the Economical Use of Irrigation Water in Idaho, 
Bui. No. 339, U. S. Dept. of Agr. 
