Mar. i, 1924 
Movement of Water in Irrigated Soils 
665 
LEACHING SALINE SOILS IN THE FIELD 
In the ordinary practice of irrigation the aim is to apply the water 
uniformly to the surface of the land. To this end various methods of 
distribution are resorted to, such as furrows, checks, borders, basins, and 
contour ditches. In preparing the land for irrigation a good deal of 
labor is devoted to leveling the surface, so that a uniform distribution of 
the water may be accomplished. The implication is that if the water is 
applied uniformly to the surface it will soak into the ground with equal 
uniformity in each check 
or along each furrow. 
As a matter of fact, this 
does not happen. The 
soil as it occurs in the. 
field is anything but uni¬ 
form in texture and in 
permeability. These 
differences are often 
very great at points only 
a few feet apart. When 
this is so it is not to be 
expected that water ap¬ 
plied uniformly to the 
surface of the land will 
penetrate the soil to the 
same depth in all parts 
of the field. 
An example of the 
differences that may be 
encountered in the pene¬ 
tration of water applied 
to a well-leveled check 
is shown in Table IV and 
illustrated in figure 2. 
This example is taken 
from the Newlands 
Experiment Farm in 
Nevada. The observa¬ 
tions were made at two 
points in the same check 
only 15 feet apart. At 
one of these points the 
water did not penetrate 
beyond the first foot, 
while at .the other it 
reached the third foot 
and may have passedon into the fourth. Similar instances of differences 
of penetration may be observed in any irrigated field. 
Such differences in the character and permeability of the soil con¬ 
stitute one of the most serious problems in irrigation, both as regards the 
watering of crops and the prevention or remedy of the accumulation in the 
soil of injurious quantities of soluble material. 
If it were possible to bring about a uniform penetration of irrigation 
water in the field there would be no such thing as the accumulation of 
Fig. 6.—Turbidity of solution from the same soil (Nq. 369) before 
and after leaching. In each case the tube contains 5 gm. of soil 
in 50 cc. of water. The tube at the right contains untreated soil 
which carried 3 per cent of salt. The tube at the left contains a 
sample of the same soil after leaching. The removal of the salt 
by leaching has caused a marked and persistent turbidity. 
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