Atlanta semi-weekly journal. (Atlanta, Ga.) 1898-1920, 1919-10-10

creased supply of phosphoric acid.
There is a wide difference, however,
in the content of phOsphoric acid in
the different soils The Greenville,
Triton, Ruston and Anlite types con.
tain considerably more than the
other upland soils. The need of
available phosphoric acid has been
generally recognized in the use of
fertilizers relatively high in this
element, but the practice does not
generally take into account the diff
ferent soil types on which the fer
tilizer is to be used. The available
ity of the phosphoric acid is largely
dependent upon the content of or
ganic matter and the general ply
steal condition of the soil, so that
even high content of this element
may be of little value when the land
is allowed to get in q rundown con-
dition from continued clean cultiva-
ton.
Phosphoric Acid Needed
In fertilizers used directly under
crops to meet immediate needs,
phosphoric acid should be applied in
the form of acid phosphate or other
available form. However, in a
scheme of permanent agriculture
where soil building is an object,
rock phosphate affords the cheapest
source of phosphorus. Phosphoric
acid can be bought in this form for
about 1 IL cents per pound, where
as, it costs several times as much
in the form of acid phosphate. How
ever, the soil must be well stocke.,
with humus in order to get good re
suits from rock phosphate; for il
is only in the presence of decaying
organic matter that this material
will give up it's phosphorus. In con-
nectlon with green manures, or with
heavy applications of farm manure.
rock phosphate should give good
results. 1t should be applied broad
cast at the rate of 1000 to 1000
pounds per acre about every five
years. This should be supplemented
with small amounts of acid phos-
plate, if needed, but the amounts of
the expensive form required will be
greatly reduced and a net saving
made. 1t is we'll to remember. how
ever, that rock phosphate, of what
ever brandon cource cannot take the
place of acid phosphate as a source
of available phosphoric acid in mixed
fertilizers or for any other purpose
where an Immediately available ma
terial is desired.
cial function in the fruiting of
plants, and hastens maturity. Poor
fruitage and late maturity in crops
are indications of the need of phos-
phorus.
Many OF the better defined soils
of Southwest, Georgia are extremely
low in potash, the content of this
constituent being considerably be-
low the average for the same soil
types in other sections Of the state.
While the potash content is several
times that Of either nitrogen or
phosphor1c acid, only a fraction Of 4
per cent of the total potash in the
SOIL Dill become available for the
use of crops under best conditions.
and where the soils are poor in or
ganic matter, the chemical changes
that potash minerals must undergo
to become available are further re-
tarded. Tor these reasons potash
becomes limiting factor in crop
production, especially where several
crops have been grown with little or
no potash applied in the fertilizer.
With the restoration of normal
prices, fertilizers carrying a liberia.
amount of potash should be used.
Potash aids in the formation of
the starch and woody material of
plants, giving sturdiness of stalk
and we'll developed branches. 1t is
an especially important fertiIize..
constituent for. all fruit and truck
crops. 1t accumulates chiefly in the
leaves and stems of plants and IS
largely returned to the soil where
plant residues are not removed
Weak, spindling plants, with rusting
leaves indicate need Of potash.
In the table giving the analyses
of the various soils, figures are Civ
en- showing the amount of calcium
oxide (lime) they contain 1t has
been explained that this lime is not
really present as calcium oxide, but
in complex compounds known as
silicates, (which are insoluble and
unavailable, 1t often happens that
analysis will show considerable total
calcium oxide, when in reality the
sell is in ned of lime The active
form of lime in the soil is limestone
or. calcium carbonate, and it is high
ly desirable that the soil should con-
tain it IN this form. Limestone
however, is more soluble in the soil
water than the other minerals. and
it has, there ore, all been leached
out of many Of our soils, or changed
chemically into a refractory COM
pound, thus leaving the soil aci ii
or sour. This is an undesirable con-
dition, and may be corrected by the
application of lime. The amounts of
limestone required to correct the