The Dawson news. (Dawson, Ga.) 1889-current, 1905-10-25
STUDY IN PLANT-FOOD
State Chemist Writes Interest
ingly on this Subject.
TALK ON PHosPHoRlc ACID


Learn What Plant Food the Soil
Needs-Where Phospates Are Found.
In letter No. 4, bulletin No. 50, l
alluded to the importance OF phosphor-
ic acid as a constituent of plant-food
II ia 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 II we
expect large yield. The various
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 CON-
bination of organic and inorganic mat
ter. The organic matter in bone
consists mainly of fat and glutinous
matter; the inorganic matter is chief
ly phosphate of lime. This dual com
position of a bone can be demonstrate
ed very graphically by taking the leg
bone of an animal and soaking it for
C1ite while in weak muriatic acid.
This acid will dissolve away the phos-
phate of lime, which gives rightly
and stiffness to the bone, and leave
behind the glutinous flexible animal
natter of the bone, which will still
retain the shape of the original bone.
You can now take this soft organic
breaking it. This soft animal matter
of the bone is rich in nitrogen, so that
a bone fertilizer is double manure,
both phosphate and heterogeneous.
Bones vary a good deal in compost
ton, according to the nature and age
of the animal; there is not so much
animal as in those of an old one.
Even in the same animal, the hard
thign bones Of an OK, for instance,
will contain more phosphate of lime
than softer bones from other parts
of the animal. Bones to be of value
should, of course, be ground, and 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 comparatively slowness in
the soil, and consequently but little
effect. might be perceived from its ap,
plication the first season.
A good raw bone will contain on an
average twenty-five per cent. phos,
phoric acid. and four per cent of nj
trogen. Sucn bone is quite diff
cult to grind fine, and on its fineness
depends in large measure its value as
a fertilizer. But by boiling and steam
ing 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 boil
ing and steaming process. This treat.
ment however, enables the bone to be
ground mucn finer than the raw bone,
and where tne process has been carried
out very thoroughly, as in the manu-.
facture Of glue, the resulting ground
bone may contain as high as 80 per
cen. of phosphOrlc acid, but the nitro
gen in this case will be reduced to
less than two per cent. Actual ex-
periments have SHOWN that all the
phosphoric acid from finely ground
steamed bone may become available
in one or two seasons in the soil,
while that from a coarse ground raw
bone would not become fully available
in three or four seasons.
The Mineral or Rock Phospates.
If bones were the only resource OF
phosphoric acid, modern agriculture
would be in distressing condition,
since bones could supply only very
small part of the demand The prices
Of fertilizers would be very much high.
er than they now are; the cotton crop
of the south and the grain crops of
the world would be very much small,
er. and the population of the earth very
much less than it now is. SO true is
It that life itself as counted by gener-
atoms rises and falls in greater 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 phos-
pilates. Deposits Of these in greater
or less quantity have been known for
, To,,.r +iD7o in f0a old yVorl5 hut T.