Mar. i, 1924 
Movement of Water in Irrigated Soils 
627 
that may be stored.in that zone of the soil by irrigation. It is often 
observed that certain irrigated lands do not take water readily and that 
after the surface of the soil has been saturated for several hours or even 
for two or three days the water has not penetrated downward into the 
subsoil. This condition is sometimes thought to be due to the existence 
of a hardpan or plowsole and that deeper penetration of water could be 
brought about by deeper plowing or subsoiling. It is possible, of course, 
to break up a dry soil with a plow, and immediately after this has been 
done irrigation water will flow downward and fill the spaces between the 
clods. But very often it* is found that by the time of the next irrigation, 
the soil is nearly as compact and impermeable as it was before it was 
plowed. 
While there are many places in irrigated land where a subsurface 
hardpan occurs and prevents the downward movement of irrigation water, 
it is also true that some irrigated soils are naturally slow to take water, 
and this condition is quite independent of any sharply defined imper¬ 
meable layer. 
It is desirable to understand the facts in these cases, for the remedies 
are different in the different circumstances. If the penetration of water 
is retarded or prevented by a well-defined hardpan, such as is sometimes 
formed by limestone known as caliche, this condition may be remedied 
by shattering the hard layer by deep plowing or by blasting. On the 
other hand, if the difficulty is due to what is sometimes termed a “colloi¬ 
dal” or “puddled” condition of the soil, deep plowing or blasting is 
practically useless. The remedy lies in the direction of improving the 
physical condition of the soil. One who has not had actual experience 
with irrigation in districts where so-called “hard soils'’ or “slick spots” 
occur does not appreciate how resistant to water such soils are. One 
thinks of a dry soil as thirsting for water, but on these slick spots the 
water may stand for days and soak down only a few inches. 
THE RATE OF WATER PENETRATION 
It is possible, though somewhat difficult, to measure the rate at which 
irrigation water penetrates the soil under field conditions. This may be 
done by taking a series of soil samples from time to time after the irriga¬ 
tion water is applied. Such investigations have shown that in very 
permeable sandy soils the water may get down as far as 6 feet in 12 hours. 
Ordinarily the rate of penetration is much slower. Even in soils that are 
regarded as readily permeable it may take two or three days for the 
irrigation water to penetrate to the depth of 6 feet. 
The contrast in the rate at which water may penetrate the dry soil may 
be illustrated by a very simple experiment. If dry pulverized soil is put 
into a glass tube and water poured on at the upper end, the rate at which 
the water soaks downward may be observed. The moist soil is much 
darker colored than the dry soil, so that the advancing line of the pene¬ 
trating water may be plainly seen and its position may be recorded from 
time to time by marks on the tube. 
The experiment here described illustrates a method of comparing the 
rate of the penetration of water in two soils, one of which takes water 
readily while the other takes water slowly. Both soils were taken from 
the Newlands reclamation project near Fallon, Nev. Both would be 
classed as sandy loam. When dry and pulverized they resemble each 
