The Hocking sentinel. [volume] (Logan, Ohio) 1871-1906, 1895-05-02
81 RUCTURE AND PHYSICAL
PROPERTIES OF SOILS
| AND THEIR RELA-
h-- TONIC CROPS,

h-- TONI TO CROPS.
Absfract of Two Lectures Delivered BY
Frof. Milton Whitney, Chief of Divis-
Ion OF Agricultural Soils, U. S. De-
partment OF Agriculture, at tho
Ohio State University, CO.
lumbus, Ohio.
Sol investigations naturally come
under two heads: l. The soil consid.
cred as store of food for plants. g.
Ihe soil as maintaining certain ply.
Steal conditions of moisture and heat
necessary for plant life.
The first part of the subject has
scen elaborately worked cut in the
sast Rfty years by agricultural chem
ssts, hrt many o. their results are I'M
and even conflicting because
she second part OF the subject-the re-
lation OF soils to moisture-has not
Seep adequately recognized The rec
ord of the yield of crops per acre kept
by many individuals, experiment Sta
sions, and by state boards of agricul-
ture, show that even with the same
Soil and with the same methods of cul-
tvation the yield varies greatly from
year to year owing to the difference in
ing to the varias .ons in the amount and
distribution of the rainfall. This sub
feet of the amount of moisture avail
.able to plants has, therefore. a very
important bearing upon the develop
ment and yield of crops, so important
a bearing in fact that the yield of an
entire statemay be twice as much one
season as another. $50 -
. While climatic conditions determine
, the general distribution of plants
make it Improbable, for example, to
grow cottono or bananas In northern
:latitude-the texture of soils and the
relation of different textured soils to
moisture frequently determines the
local distribution of plants and ex.
plains why some soils are ada pied 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 disfntegrated or ground up and
for the soils resulting from the disin-
fregration of the rocks to be finely ,ai-
NAoCos w W give area IOr
plant roots to feed on. (2) to offer n 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. -'s'
The earth has three envelopes-an
envelope of air, an envelope of soil and
an envelope of water. The envelope of |
air 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 |
torrentia1 storms. The envelope of |
soil, Being >denser, offers more resist |
nnce 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-
connt 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
humber 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 the amount of or
ganic matter in the soil, and upon the
Gepth of the SOIL
Soils contain. as a rule, about fifty
percent by volume of empty space-that
is, in one cubic foot of soil there will
be one half cubic foot of space into
which water or air can enter. In
sandy soil this space will not be
divided up SO much as in a clay soil, the
sand having fewer grains, the spaces
between the grains are larger so there
is less friction and the water moves
downward more quickly. These sandy
soils will not, 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 vast number of them
in the soil that the spaces between
them are exceedingly small and offer a
great resistance to the descent of the
rain SO that the water moves very
slowly and large amount is main
tained for the plants. A strong clay
soil will usually contain three or four
times as much water as a sandy soil,
and this has a very important effect
upon the Development, texture and
yield ofcrops per acre.
: Advantage is taken in this fact in
practical agriculture. In a greenhouse
where all the conditions are under con-
troll florist may hasten or retard the
ripening 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 much more water than others.
If he wants to force them to an early
maturity he keeps the soil moderately .
dry; if he wants them to make large
leaf growth he keeps the soil more I
moist In nature it is true we can not
control these conditions, we must take I
the amount of rain which falls, but our !
different soils being SO different in S
texture and differing SO much in their
relation to moisture maintain quite as
different conditions of moisture as sup .
piled in practice under artificial condi-
tons of greenhouse culture. Light ,
sandy soils being moderately dry force I
plants to an early maturity, and these :
soils are used at present for the very
profitable truck farming which
has developed into such an inn
portant industry in recent years.
Such soils are not adapted to Y
rleat or grass, not necessarily be- !
cause they are deficient in any par A
ticular food required for these crops,
but because the dry conditions force /
the plants to an early maturity and the 4
yield per acre is exceedingly small.
Clay soils, on the other hand, are
adapted to wheat and grass because
they maintain uniformly moist condi-
tons and the plants have slow and
prolonged growing period before it is