The Oakley herald. [volume] (Oakley, Idaho) 1908-1961, 1911-12-15

Conditions Of the Evaporation Of
Water From Soil.
Under Ordinary Conditions II Is I'm
possible to Remove All Liquid Mat
ter, for Small Quantity 10
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
vorable. Thus, from a wet soil, evap-
GRAFTON is continually removing wa
ter. Yet, under ordinary conditions,
II 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
Microscopic moisture.
Moreover, It, must be kept In mind
that evaporation does not occur as
rapidly from wet soil as from water
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
self evident. There is a comparative
ly strong attraction between the soil
ard water which enables the moist
ure to cling as a thin capillary film
al ound 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
come 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 it was found that three soils
otherwise alike, that contained respec'
lively, 2263 per cent, 17.14 per cent.
and 1915 per cent. of water lost in
two weeks to a 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 o.
this principle. From this point O
view the dry farmer does not wan
his soils to be unnecessarily moist
The dry farmer can reduce the pc
cent. of water in the soil without di
J minishing the total amount of waite
t by so treating the soil that the waite
will distribute itself to considerable
depths. This brings into prominence
J again the practice of fall blowing
4 deep blowing, sub-soiling, and thu
choice of deep soils for dry farming.
Very much for the same reasons
evaporation goes on more slowly fron
|, water in which salt or other sui
stances have been dissolved. The al
traction between the water and tn
i dissolved salt seems to be stron
[ enough to resist partially the fore
causing evaporation. Soil water a
ways contains some Of the soil ingrt
l. dents In solution, and consequent
under the given conditions, evapori
J ton occurs more slowly from so
o water. Now, the more fertile tn
e soil is. that is, the more solubl
I plant food 1t contains, the more m;
u terial will be dissolved in the so
= water and as result the more SLOW
d ly will evaporation take place. Fo
/: lowing, cultivation, thorough plowir
and manuring, which increase II
store of soluble plant food, all ter
Il to diminish evaporation. While thes
conditions may have little value
= the eyes Of the farmer who is und,
IL an abundant rainfall, they are
le great Importance to the dry farme
- 1t is only by utilizing every posi-
- bility of conserving water and fe
tility that dry farming may be made
= perfectly safe practice.