Deseret evening news. [volume] (Great Salt Lake City [Utah]) 1867-1920, 1907-12-10

called hvrroscopic moisture This form
10 OF no use to plants. 10 exists az a
very thin film around each soil grain.
II Is part Of the capillary water, but is
90 closely held by the soil grain that
plants cannot make use of g. The at
traction which the soil grain has for IL
IS greater than the attraction which the
plant root has. hence IL remains with
the soil grain. In "a sandy soil. plants
have the power Co use oll the capillary
water down 90 within about per cent,
which remains 1s hygroscopic water. I'm
clay soils. plants cannot use the water
~ less than n per cent of moisture oX-
lists boo The SOIL This N per cent ls the
Microscopic water that still remains lu
the soil after 30 has become afr
dry To show that ordinary dry soil
does contain water we may heat
test tube half filled with very dry soil
or dust We shall see the moisture COM
dense on the cold glass IN the upper
part OF the tube. This is microscopic
moisture driven from the air-dry soil
grains
a soil that is fine grained viii re-
tain moro water than course grained
one. This is because more surface is
exposed Co hold the moisture iu a fine
imam 1u coarse soil. when
water enters the soil. DO first forms a
hlm around each soil grain when these
Minis have reached "a definite thickness
the surplus water remains as free wa
ten is subject TO the action of gravity.
and hence may run on H. now. tho
fine clay soil has 1000 grains OF soil 20
TIE coarse sands ono grain, we can
readily see how the thousand films OF
water iu the clay win contain more
water than the one nlm Boz the sand
FILM MOISTURE EXPERIMENT.
An soils are composed OF grains. but
the size OF the grains varies between
VIDE limits. Here IS a tube filled with
coarse shot. and another filled with shot
or "a much liner size. We now shall see
pl how much water each tube viii con-
tam among the shot and CD how much
water VIII be retained as films by the
coarse ana the fine shot respectively
When we pour of the water from each
tube. We pour I'm the water from "a
beakcr graduated or marked showing
I'm cubic ccntimeters how much h holds
az an depths. First we pour into the
luDy containing the finer shot
INC me shot holds "a IS cubic cent?
meters of water TO ON TO the top OF the
shoL The tube containing the large
shot holds 80 cubic centmeters. That
is tune nlled with a given weight
OF me shot holds 2.5 cubic centimeters
more water than a tube containing the
same weight Of coarse shot.
NOW pour out the water from the
coarse shot tube. We get back %
cubic centimeters Of water that Is. the
large shot retains 4 cubic coutimeters
as MIN moisture around the separate
shots.
Pour the water from the fine shot
tube Now we get back only "a cubic
centimeters. that is, the fine shot tube
retains 1913 cubic ceutimctcrs Of water.
This shows iu simple way that the
finer shot In this instance retain about
re times as much film moisture as the
larger size retains. The inner the par
ucles OF the one and the coarser the
particles OF the other, tho greater the
difference viii be I'm amount OF water
retained. as film moisture. So IL IS
with soils
A fine soil say Of clay. viii hold more
capillary and Microscopic water than
VIII a coarse or sandy soil. This is
because the number Of the soil partl-
cles I'm the iine soil is so much greater
than In the coarse. Each grain Is
coated with It's own film OF moisture.
The difference In the amount Of water
held BY the grains Of each soil will
vary as the surface exposed 10 the
water varies.
A marble just one inch IN diameter
VIII just slip inside "A cubic OF the
same size. and will hold a film Of water
5.lilb square inches in area. IL will
take 1000 marbles each one-tenth Of an
inch In diameter 20 an up the same
cubic inch OF space But the ag-
gregate surface arc OF those marbles
is 81 .4l6 inches. II the diameter OF
the spheres Is reduced 90 one-hundredth
Of an inch, enough of them to nm "a
space of one cubic inch, will have n
surface Of 3l4.l6 square inches. and
there viii be 1000 600 OF them. But ID
the diameters is only one-thousaudth
Of an inch, It viii require 10000 600
OF them to I'M cubic inch. and their
aggregate surface win be 3lA so square
inches.
In the case OF very fine soil, I'm which
the measured diameters Of the soil
grains have been found 20 be .O0l Of am
inch In diameter, a cubic foot will have
"a surface capacity Of 81 700 square feet.
Some soils five feet deep iu ordinary
field conditions hold from 70 TO 70 inches
of water.