The Hocking sentinel. [volume] (Logan, Ohio) 1871-1906, 1895-08-29
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STRUCTURE AND PHYSICAL
PROPERTIES OF SOILS
-. AND THEIR REUA-
7t. TiONTO CROPS.

Kit, TON TO CROPS.
Abstract of TWO Lectures Delivered by
|, Prof. Milton Whitney, Chief of Divis-
ion of Agricultural Soils, U. S. De-
n partment of Agriculture, at tho
Ohio State University, Co
r lumbus, Ohio.
Soil investigations naturally come
under two heads: l. The soil eonsid-
cred as store of food for plants. 2.
The soil as maintaining certain phy-
sical conditions of moisture and heat
necessary for plant life.
The first part of the subject has
scen elaborately worked out in the
xast fifty years by agricultural chem
tsts, but many o: their results are un-
.ertain and even conflicting because
she second part of the subject-the re-
iation of soils to moisture-has not
Geen adequately recognized. The rec
ord of the yield of crops per acre kept
by many individuals. experiment sta
Sions, and by state boards of ngricul-
ture, show that even with the same
soil and with the same methods of cul-
4ivation the yield varies greatly from
year to year owing to the difference in
the climatic conditions. especially ow-
ing to the variations in the amount and
distribution of the rainfall. This SUBJ
ject OF the amount of moisture avail
nble to plants has, therefore, a very
important bearing upon the develop
ment and yield of crops, SO important
o bearing in fact that the yield of an
entire statemay be twice as much one
season as another.
While climatic conditions determine
the general distribution of plants
make it Improbable, for example, to
crow cotton or bananas in a northern
latitude-the texture of soils and the
relation of different teXturcd soils to
moisture frequently determines the
local distribution of plants and ex-
plains why some soils are adapted to
wheat or to certain grades of TOBACCO.
or to certain truck interests, and why
other soils are not SO well adapted to
these crops
Agricultural plants will not grow
on bare rocks. 1t is necessary in the
first place for the rocks to
be disintesrated or ground up and
for the soils resulting from the disin-
fregration of the rocks to be finely di
vided. ~ to give sufficient area for
plant roots to feed on, (2) to offer re-
sistance to the descent of the rainfall
so that the soils shall maintain suffi-
cient moisture for plants during the
dry weather period between the sue
cessive falls of rain.
The earth has three epvelopes-ap
envelope of air. an envelope of soil and
an envelope of water. The envelope of
nir offers but little resistance to the
descent of rain, as the rain encounters
but little FRICTION in falling SO that it
may pour down in gentle showers or in
torrential storms. The envelope of
soil, being denscr. offers more resist
ance to the descent of the rain, and the
rain, although it continues to fall
through the soil until it reaches finally
the level of the ocean, moves very
slowly by reason of the friction it en-
counters in the minute spaces between
the grains through which it has to
move, and so it falls very slowly
through the envelope of soil. On ac-
count of this resistance to the descent
of the rainfall and the slow rate at
which it moves through the air, water
is held back and maintained for plants
during dry weather between showers.
The amount of the resistance, and
therefore the relative amount of mois-
ture. maintained by different soils de-
pends upon the amount Of space in the
soils for the water to enter; upon the
nrmbee of grains of sand, silt and clay
for this will determine how much
the space is divided up; upon how these
grains are arranged, for this will have
an influence upon the resistance or the
friction the soil offers to the descent of
the rainfall; upon 7the amount of or
ganic matter in the soil, and upon the
cepth of the soil;
Soils contain. as a rule, about fifty
percent by volume of empty space-that
is. in ona cubic foot of soil there will
be one half cubic foot of space into
which water or air can enter. In a
sandy soil this space will not be
divided up SO much as in clay soil, the
sand having fewer grains, tie spaces
between the grains are larger SO there
is less friction and the water moves
downward more quickly. These sandy
soils will MT, therefore, maintain so
much moisture for the plants. The
particles of clay soils, on the other
hand, are SO exceedingly minute and
there are such a vast number of them
in the soil that the spaces between
them are exceedingly small and offer
great resistance to the descent of the
rain so that the water moves very
slowly and 4 large amount is main
tanned for the plants. A strong clay
soil will usually cQntain three or four
times as much water as a sandy soil,
and this has very important effect
upon the development, texture and
yield of crops per acre.
Advantage is taken in this fact in
practical agriculture. In greenhouse
where ali the conditions are under con-
troll florist may hasten or retard the
Eipening of his plants and he may have
them mature at any season of the year
by proper control OF the moisture and
temperature, especially by controlling
The amount of water he gives the
plants. Some plants naturally require
very muci; more water than others.
If he wants to force them to an early
maturity ne keeps the soil moderately
dry; if he wants them 20 make large
leaf growth he keeps the soil more
ploist. ~ nature it is true we can not
control these conditions, we must take
the amount of rain which falls. bat our
different soils being SO different in
texture and differing so much in their
relation to moisture maintain quite as
different conditions of moisture rs sup
piled ip practice under artificial condi- :
lions of greenhouse culture. Light =
sandy soils being moderately dry force /
pants to an early maturity, and these /,
boils are used a. present fca the very
profitable truck farming which
.las developed into SUCH an i'm
portant industry in recent years.
tcch soils are not alapted to
s..e.- or Grass. rot necessarily pc