The Pioche record. [volume] (Pioche, Nev.) 1908-1925, 1911-11-04
ESCAPE OF MOISTURE
Conditions of the Evaporation OF
Water From Soil.
Under Ordinary Conditions 1t is I'm
possible to Remove All Liquid Mat
ter, for Small Quantity Is
Strongly Attracted.

Evaporation does not alone occur
from the surface of free water. All
wet or moist substances lose by evap-
grafton most of the water that they
hold, providing the conditions OF tenn
perature and relative humidity are ia
GRAFTON is continually removing wa
ter. Yet, under ordinary conditions.
1t is impossible to remove all the
water, for small quantity is attract
ed SO strongly by the soil particles
that only a temperature above the
boiling point of water will drive It
out This part of the soil is the
Microscopic moisture.
Moreover 1t must be kept in mind
that evaporation does not occur as
surface, unless all the soil pores are
so completely filled with water that
the soil surface is practically water
surface. The reason for this reduced
evaporation from wet soil Is almost
seli-evident. There is comparative
ly strong attraction between the soil
and water, which enables the moist
ure to cling as a thin capillary film
around the soil particles, against the
force of gravity. Ordinarily only cap
Hilary water is found in well-tilled
soil, and the force causing evapora-
lion must be strong enough to over
some this attraction besides chang
ng the water into vapor.
The less water there is in the SOIL
the thinner the water film, and the
more firmly is the water held Hence,
the rate of evaporation decreases
with the decrease of soil moisture
This law is confirmed by actual field
tests. For instance, in an average
of 274 trials made at the Utah sta
ton. 1t was found that three soils,
otherwise alike, that contained respec-
lively, 2263 per cent, 1714 per cent,
and 1915 per cent. of water lost in
two weeks to a depth of eight feet,
respectively, 21.0, Ill, and 100 pounds
of water per square foot Similar
experiments conducted elsewhere also
furnish proof of the correctness of
this principle. From this point of
view the dry farmer does not want
his soils to be unnecessarily moist.
The dry farmer can reduce the per
cent of water in the soil without di-
minishing the total amount of water
by so treating the soil that the water
will distribute itself to considerable
depths. This brings into prominence
again the practice of fall blowing,
deep blowing, sub-soiling, and the
choice of deep soils for dry farming.
Very much for the same reasons,
evaporation goes on more slowly from
water in which salt or other sub
stances have been dissolved The at
traction between the water and the
dissolved salt seems to be strong
enough to resist partially the force
causing evaporation. Soil water al
ways contains some of the soil ingre-
dents in solution, and consequently
under the given conditions, evapora.
ticn occurs more slowly from soil
water Now, the more fertile the
soil Is, that is, the more soluble
plant food it contains, the more ma
terial will be dissolved in the soil
water, and as result the more slow
/ ly Will evaporation take place. Fol
lowing. cultivation, thorough blowing
and manuring, which increase the
store of soluble plant food, all tend
TO diminish evaporation. While these
conditions may have little value in
the eyes of the farmer who is under
an abundant rainfall they are OF
great Importance to the dry farmer
1t is only by utilizing every posi-
bility of conserving water and fer.
dlity that dry farming may be made a
perfectly safe practice.