The Keota news., 1912-02-16
Conditions of the Evaporation of
Water From Soil.
Under Ordinary Conditions II 10 I'm
possible to Remove All Liquid Mat
ter, for Small Quantity 10
Strongly Attracted.


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
vornble Thus. from a wet soil. evap-
oration is continually removing wa
ter. Yet, under ordinary conditions,
1t is impossible to remove all the
water, for a small quantity Is attract
ed so strongly by the soil particles
that only a temperature above the
boiling point OF water will drive 1t
out This part OF the soil Is the
hygroscopic moisture.
Moreover. II must be kept In mind
that evaporation does not occur as
rapidly from wet soil as from a water
surface unless all the soil pores are
so completely fllled with water that
the soil surface Is practically water
surface The reason for this reduced
evaporation from wet soil Is almost
sel1-evident. There is a 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 welltilled
sniI. and the force causing evapora-
ton must be strong enough to over
come this attraction besides chang
ing the water into vapor.
The less water there Is in the soil.
the thinner the water aim. and the
more firmly is the water held. Hence.
the rate OF evaporation decreases
with the decrease Of soil moisture.
This law 10 confirmed by actual field
tests. For instance. In an average
Of 274 trials made at the Utah sta
tion. 1t was found that three soils.
otherwise alike. that contained respec-
lively. 22.63 per cent. 17.14 per cent.
and 1878 per cent. Of water lost in
two weeks to depth Of eight feet.
respectively 210. III. 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 d.
minishing the total amount OF water
by 80 treating the soil that the water
will distribute itself to considerable
depths. This brings into prominence
again the practice Of fall plowing.
deep plowing. sub-soiling. and tho
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-
dients in solution, and consequently
under the given conditions. evapora-
tion occurs more slowly from soil
water. Now, the more fertile the
soil Is. that is, the more soluble
plant food 1t contains. the more ma
terial will be dissolved in the soil
water. and az result the more SLOW
ly will evaporation take place Fol-
lowing. cultivation. thorough plowing
and manuring. which increase the
store Of soluble plant food, all tend
to diminish evaporation. While these
conditions may have little value in
tho 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 possi-