Shenandoah herald. [volume] (Woodstock, Va.) 1865-1974, 1880-05-05
The Behavior of PhOsphates
in the soil.
PROFESSOR G. c. CALDWELL.

table physiology that no food can
enter the plant except in the liquid
or the gaseous form; that there are
no orifces in the roots or leaves by
which particles of solid matter can
be admitted within the cells and en-
ter the laboratory where the mystic
rious and wonderful work is carried
on of converting dead mineral mat
ter into living vegetable substance.
In an ordinary arabic soil there is
comparatively little plant food that
is soluble into water, while there
may be hundreds or even thousands
of pounds to the acre of insoluble
compounds of nitrogen, potash and
phosphoric acid. Moreover, when
soluble compounds of these impor-
tant substances are added to the
soil they are usually in a short time
almost completely converted into
difficulty soluble compounds, with
the single exception of nitrogen in
the form OF nitrates.
This interesting property of soils
in virtue OF which they seize hold
of, and retain in the uppermost lay
ers, the constituents of orr manures,
is evidently, from one point of view,
useful property,in that these sub
stances are thus protected from be-
ing leached out and entirely lost for
present use. through porous subsoils
or drains hence no notable guam
tity Of ammonia, potash or phos-
phoric acid is ordinarily found in
the drainage water even Of well ma
nured land, But from an other
point Of view it might naturally APP
pear to be a worse than useless
property, since it opposes our efforts
to increase the supply of soluble
plant food for our crops; but the
wide spread and constantly increas-
ing use OF soluble phosphates and
soluble compounds Of nitrogen and
potash, shows that there is profit,
nevertheless, in putting soluble
plant food into the soil. How shall
we dispose Of such all apparent con-
;radiction, and reconcile known facts
concerning the behavior Of soils
and the structure Of plants with our
results in manuring crops?
1t was Liebig whe performed the
first experiments leading to the con-
clusion now so generally adopted
by vegetable Psychologists, that
plants have, to certain extent, the
power OF making their own solution.
The feeding rootlets of the plant are
in closet contact with the particles
of the soil in which they grow, as
may be seen on carefully pulling up
a young plant from dry soil; the
youngest rootlets, and the root hairs
will be found to be sheathed with a
coating Of particles Of soil which
cannot be shaken off, and not even
pulled off without in some cases
taking with them portions Of the
rootlets. These rootIets and hairs
are saturated with say, a liquid that
has a greater solvent power than
pure water or than saltwater, and
as result Of their close contact
with particles Of difficult soluble
phosphates Of lime Or iron, or diff
cult soluble compounds of ammo
MIA or potash, these substances may
be taken into solution, and under
such conditions that they cannot
but enter the plant right then and
there.
But, it may be said, if soluble
phosphate is converted INTO insolu-
bic phosphate in the soil, why take
so much trouble to much trouble to
make insoluble phosphate soluble
before applying it ? Why not use
tho nov dercd rock phosphate or
bone dust directly, instead of first
Treating it with acid? Because in
1.-THE former case we have particle
of the phosphates is taken into So
Hutton by the first rain that thorogh-
Ily the upper laysrs to considerable
extent before conversion INTO lnsol-
uble compounds, and is spread over
the surface OF such great number
of particles Of the soil that the root
lets are constantly meeting with ii
as they press onward in their
Igrowth. That the effect Of a given
quantity OF phosphOric acid as sol,
uble or supcrphosphate, applied to
a soil, for instance, that is suitable
for wheat, is in most cases very
much greater that of the same guam
tity IN powdered rock phosphate
however finely it may be ground
| mas been fully demonstrated BY
both experience and experiment, anC
it is easy to see the reason why il
the above explanation.
The bahayior Of phosphates il
the soil has received a careful study
recently at the hands of Albert anC
Vollbrecht at one of the German
Experiment Stations, and som,
useful conclusions can be drawn
from the interesting results tina
obtain. 1t may be necessary t.
{ state, first, that there are three phos
pilates of lime, one soluble in water
another, the so-called reverted phos
/ plate, difficult soluble in water
, but soluble in water containing am
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