The Dawson news. (Dawson, Ga.) 1889-current, 1903-03-04
LETTER FROM The
STATE CHEMIST
A Treatise on Agricultural
Chemistry.
THE VALUE OF PHosPHoRlo ACID

Most lmportant-ln Same Class with
Nitrogen and Potash-Interesting to
Farmers.
continuing the letters of the State
Chemist to Georgia Farmers).
In letter No. A. bulletin No. 3S, l
alluded to the Importance of phospho-
rio acid as a constituent of plant food.
It is in the same class with nitrogen
and potash, they being the elements
found only in small quantity in most
cultivated soils, all the other elements
necessary to plant life being usually
present in profusion. Phosphoric
acid, then, must be added to the soil
If we expect large yields. The vari-
Gus sources of phosphoric acid, then,
are of interest.
Bones were the first and earliest
form in which phosphoric acid was
applied to the. soil. Bones are com
bination of organic and inorganic
matter. The organic matter in bone
consists mainly of fat and glutin-
GUS matter; the inorganic matter is
chiefly phosphate of lime. This dual
composition of bone can be demon
strated very graphically by taking
the leg bone of an animal and soak
ing it for quite while in weak mu-
ratio acid. The acid will dissolve
away the phosphate of lime, which
gives rightly and stiffness to the
bone, and leave behind the glutinous,
flexible animal matter of the bone,
which will still retain the shape of
the original bone. You can now take
this soft organic matter and tie it
into knot, without breaking it. This
soft animal matter of the bone is rich
in nitrogen, so that bone fertilizer
is double manure, both phosphate
and nitrogenous Bones vary a good
deal in composition, according to the
nature and age of the animal; there
is not so much phosphate in the bones
OF young animal as those of an old
one. Even in the same animal the
hard thigh bones of an OK, for in
stance, will contain more phosphate
OF lime than softer bones from other
parts of the animal. Bones to be of
Fe@AOC oA4OOAu VI NOul sc OC SlOuuU, anu
the finer the grinding the better. A
coarsely crushed or ground raw bone,
which has not been treated to remove
any of its original fatty matter. will
decay with comparative slowness in
the soil, and consequently but little
effect might be perceived from its
application the first season.
A
average % per cent. phosphoric acid
and per cent. of nitrogen. Such
bone is quite difficult to grind fine,
and on its fineness depends in large
measure its value as a fertilizer. But
by boiling and steaming, much Of the
fat is removed, which has no value as
a manure; some of the nitrogen is
also removed in the form of glue and
gelatine by the boiling and steaming
process. This treatment however en-
ables the bone to be ground much
finer than the raw bone and where the
process has been carried out very
thoroughly, as in the manufacture of
glue, the resulting ground bone may
contain as high as 80 per cent g.
phosphoric acid, but the nitrogen in
this case will be reduced to less than
2 per cent. Actual experiments have
shown that all the phosphoric acid
from a finely ground steamed bone
may become available in one to two
seasons in the soil, while that from
coarse ground raw bone would not be-
come fully available In three or four
seasons. ti..~.., /! + ts.~..t.t
The Mineral or Rock Phosphates
If bones were the only source of
phosphoric acid, modern agriculture
would be in distressing condition,
since bones could supply only a very
small part of the demand. The prices
of fertilizers would be very much
higher than they now are; the cotton
crop of the South and the grain crops
of the world would be very much
smaller, and the population of the
earth very much less than it now is
So true is it that life itself as counted
by generations rises and falls in great
er or smaller volume, in unison with
the available supply of plant food in
the soil. A very large proportion of
the dense population and increased
wealth of the Old World is doubtless
due to the discovery of the mineral
phosphates. Deposits of these in
greater or less quantity have been
known for a long time in the Old
World, but l shall. mention only those
fields In this country which are of
great commercial Importance today.
The first of these in point of discov.
cry and development were the South
Carolina phosphate beds. These beds
are in the neighborhood Of Charleston.
S. C. The rock is found both in the
land and in the rivers in that vicin-
ity. This phosphate is found usually
in the form of Jumps or nodules, va.
Tying from the size Of a pebble to
quite large masses. The deposits
vary from one or two feet to twelve
or more in thickness. This rock con.
ta{ns no heterogeneous organic matter