The silver messenger. (Challis, Idaho) 1890-1912, 1911-12-26
ESCAPE OF MOISTURE
f,onditjons Of the Evaporation OF
Water From Soil.
Under Ordinary Conditions II Is I'M
,ossibI. 10 Remove All Liquid Mat
ter. for Small Quantity Is
Strongly Attracted.

Evanoration does not alone occur
from the surface of free water an
wet or moist substances lose by evap,
grafton most of the water that 'ne'
hold. providing the conditions Oh 'eln
rorature and relative humidity are Ia
vorable. Thus, from a wet SOIL eVap'
oratjon is continually removing wa
for Yet. under ordinary condltlois'
It is impossible to remove al Tic
water. for a small quantity is attract
ed SO strongly by the SOIL paruciee
that only a temperature above the
boiling point of water Will drive IL
out This part of the soil is the
Microscopic moisture. -,
Moreover. it must be kept in nina
that evaporation does not occur as
RAPIDLY from wet soil as from water
surface. unless all the soil pores are
so completely filed with water that
the soil surface is practically water
surface. The reason for this reduced
evaporation from wet soil Is almost
selt-evident. There Is a comparative
ly strong attraction between the soil
and water. which enables the moist
ure to cling as a thin capillary MIN
around the soil particles, against the
force of gravity. Ordinarily only cap
Hilary water is found in welltllled
soil, and the force causing evapora
ton 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 telC
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 II
two weeks to a depth of eight feet
respectively, 21.0, III, and 100 pounds
Of water per square foot. Simila
experiments conducted elsewhere als'
furnish proof of the correctness 0
this principle. From this point 0
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 d
minishing the total amount of waite
by so treating the soil that the waite
will distribute itself to considerabl
depths. This brings into prominenc
again the practice Of fall blowing
deep blowing, sub-soiling, and thu
choice Of deep soils for dry farming.
Very much for the same reasons
evaporation goes on more slowly fror
water In which salt or other sui
stances have been dissolved The a
traction between the water and tn
dissolved salt seems to be stron
enough to resist partially the fore
causing evaporation. Soil water a
ways contains some of the soil mgr,
dents In solution, and consequent
under the given conditions, evapor
ticn occurs more slowly from so
water. Now, the more fertile tn
soil is. that is, the more solrbl
plant food 1t contains, the more M
terial will be dissolved in the so
water, and as result the more slov
~ Will evaporation take place. Fc
lowing. cultivation, thorough plowir
and manuring, which increase II
store of soluble plant food, all ter
TO diminish evaporation. While tbes
, conditions may have little value
the eyes of the farmer who is und,
an abundant rainfall, they are
great Importance to the dry farme
~ is only by utilizing every DOS,
oillty OF conserving water and fe
) Unity that dry farming may be made
perfectly safe practice.