Atlanta semi-weekly journal. (Atlanta, Ga.) 1898-1920, 1916-02-04
ROCK PHOSPHATE

Great interest is being manifest this
year I'm the use of rock phosphate in
place of acid phosphate on account of
the increased price of the latter. The
use of rock phosphate must be consid-
cred from the standpoint OF general
policy OF soil-building rather than for
immediate returns. Farmers who use
rock phosphate should be in a position
TO make investments and wait on re-
turns, though there may be exceptions
to this rule.
a good many reports of the benefits
. ured from rock phosphate are some
Wat misleading in that they represent
the cumulative effect of general policy
OF sOil-building in practice through a
series of years If rock phosphate is
used with the understanding that, with
its continued use, the effects will be
cumulative, and it is a part of the gen.
eral policy of soil building, its use will
be a good thing; but to use 1t on the
average Georgia soil, with expectations
Of immediate returns, will probably be
disappointing in most cases.
A plentiful supply of organic matter
is essential for the successful use of
rock phosphate: and on most of the
soils of Georgia it will take some time
TO accumulate a sufficient amount of
organic matter for the successful use
of rock phosphate. It will also take
some time TO get the rock phosphate
thoroughly distributed through the soil
so that it will be in contact with the
decaying organic matter.
The best use of rock phosphate is
probably in connection with stable
manure, especially where the rock phos-
plate is distributed in the stalls each
day and the manure allowed to accumu-
late some time before il is put on the
fields.
Experiments with rock phosphate
have been carried on for the last three
years i'm connection with the field tests
with fertilizers i'm different parts of the
state. Rock phosphate was used on
the cotton crop at the rate of 5000
pounds per acre, and it was only applied
once in the course of the rotation Corn
followed the cotton crop, and oats the
corn, and cowpeas followed the oats. No
attempt was made to secure the re-
turns from cowpeas. On each acre a
green crop was plOwed down during the
course of the rotation; and, in most
cases, two crops, cOwpeas, and a cover
crop. between the cotton and the corn.
At present work is in progress at some
p points in the state, but IT has not
been possible to. secure as much as
three years results from but ten of
them.
The returns from the use of rock
phosphate in South Georgia have been
somewhat more marked than in North
Georgia This might be expected for
two reasons: First, the phosphorus con-
tent Of the soils of South Georgia is as
a rule, lower than those of North Geor-
gia; second, returns from sandy soils
are usually obtained quicker than from
the heavier soils prevalent in the north
ern part of the state. Results on COT
ton and corn have been obtained from
five points in North Georgia and FIVE
points in South Georgia for three years,
while results from the oats have been
obtained only for two years. Returns
from corn and oats in North Georgia
have been practically nothing, and an
increase of only 10 1-2 pounds of seed
cotton on an average has been obtained;
while in South Georgia an increase of
% 1-2 pounds of seed cotton per acre
was obtained. Only an increase Of
about two bushels of oats and a little
less than 1-2 bushels of corn.
1t will be seen from the foregoing
that the use OF 5000 pounds of rock
phosphate per acre has not been a prof
liable investment so far as one course
OF the rotation is concerned. Probably
in the second and third course of the
more favorite. This will depend
somewhat on the amount of organic
matter that can be turned under in
green crops, which i'm turn will depend
somewhat on the season during which