The Harrison times., 1915-11-20
Origin ana Function Of Soil.

rock particles. called inorganic mat
ter, and finely divided decaying vege-
table matter. 1t occurs in two layers
which are known as soil and sub-soil
The soil or surface layer contains
more decaying animal and vegetable
matter, and for that reason is darker
and coarser in texture.
In the course OF time the finer parti
cles have washed down into the sub
soil and have caused the layer to be.
come tighter and heavier. The sur.
face soil furnishes the physical sup
port for plants and the major portion
of their plant food supply. The sub
soil provides storage place for mois-
| ture and furnishes some food for those
plants which are able to send their
roots into it.
Soils have their origin from rocks.
Geology tells US that the surface Of
the earth was once a molten mass
which solidifed to form rock. Gradual
ly the rock was broken to pieces by
various chemical ard physical agen-
cies. With alternate heating and cool
ing the resultant expansion and con-
traction caused assures to develop.
Water getting into assures and freez.
Ing caused further division. Water
running over rocks ground them down.
Wind carried the covering from rocks
and exposed them anew The gases Of
the atmosphere produced chemical
changes which led to the breaking
down of rock.
After rocks were broken down to
form soil, the development of plant
growth led to the introduction of or.
ganic matter. The leaves of plants
fell to the soil and became a part Of
1t. Upon the death Of the plant the
roots and stem of the plant became
part Of the soil. The decay of plants
enriched the soil by Fastening the
chemical processes as well as by re-
turning plant food which could be
used over again. AS the forests de.
veloped and year after year the
leaves, twigs and dead trunks were
returned to)the soil, the surface layer
became darker and looser and more
porous than that underneath.
Geological Classification.
All soil does not now occupy it's
original position This fact gives rise
to two general classes, first the seden.
tary or those soils which have not
been moved far from their point OF
origin, and second the transported
soils which have been formed by &C.
emulation through the effects Of
wind, ice, water, or gravity The re.
sidual forms the most important class
Of sedentary soils in Arkansas. This
is the main type in the western ana
northwestern parts Of the state. The
residual soils having been formed
practically ip their present position
are old soils, without strata, and pre-.
senting a Heterogeneous mass of ma.
terial They have been subjected TO
teaching for long periods and large
part Of the soluble materials have
been washed out.
All our river bottoms are made up
Of alluval or water transported soils
A large portion Of southern and south.
eastern Arkansas is made up Of ma.
rine soil, or what is commonly known
as coastal plains land. The sediments
which are continually being carried
away by rivers are sooner or later de-
posted in the sea.
Soil Particles.
Soil particles vary in size from
coarse gravel to the very finest par
tlces of clay Between these are
coarse, fine and very fine sand parti
cles and what is known as silt. One
can easily recognize the coarse and
fine grained soils by rubbing very
small amount between the fingers
The finer a soil is the more silt and
clay 1t contains, the more sticky It Is
when wet. When soil contains n
moderate amount OF each of the sew
eral grades of sand, silt and clay It
usually works easily and is called a
loan. When it contains more sand II
IS called sandy loan, or more clay,
clay loan. IL 1t contains a large
amount of clay it is called clay soil.
The condition Of the soil affecting
the ease with which II may be worked
is called tilth. by good tilth' Is
meant friabeness. BY poor tilth" Is