Atlanta semi-weekly journal. (Atlanta, Ga.) 1898-1920, 1916-03-07
AGRICULTURAL
'gSa9SSGduCatiOn
~ And SUCCESSFUL EARRING
SZlG ~ AHDREwH coULE
Lime as Influencing the Potash Supply

ing of Iocked-up plant food and thus
make possible the largest returns from
lime.
Ground limestone should be used at
the rate of one and one-half to three
tons per acre. depending upon conditions
such as acidity Of the soil and crops
grown.
Since potash salts have become prac-
tically unobtainable, some of the lime
stone manufacturers have advocated
mixing ground limestone with acid phos-
phate and ammonia goods, claiming
that such a mixture would in a meas
u-e, answer the purposes of a COM
plete fertilizer. These claims are based
on the theory that the few hundred
pounds of ground limestone per ton of
fertilizer will set free sufficient pot
ash in the soil to practically take the
place of potash in the fertilizer.
An ordinary 1922 fertilizer carries
about 500 pounds or sulphate of lime
as a by-product of the acid phosphate
This sulphate of lime is probably fully
as effective in liberating potash by di-
rect action on the potash bearing min
erals of the soils as the ground lime
stone.
Suppose a farmer makes a fertilizer
by mixing 1000 pounds Of 16 per cent
acid phosphate. 700 pounds cotton seed
meal, and 500 pounds Of limestone. This
mixture will analyze about $50 per cent
Pc O5 1.54 per cent nitrogen. and or
per cent K2 o. Now suppose this ferti-
lizer is used at the rate of 400 pounds
per acre. This will mean that the
farmer is putting on lime at the rate
of so pounds per acre. OF course, this
small amount of lime can have no ap-
preciable effect on the physical condi-
tion of the soil nor on the unavailable
potash contained therein.
Leading agricultural chemists agree
that il would not be advisable to mix
limestone. quick-lime Tor slaked lime
with acid phosphate because of its in
furious effect on the soluble acid phos-
phate. The soluble form of phosphoric
acid is the mono-calcium phosphate, or
acid phosphate When lime is mixed
with this material it causes this mono
calcium phosphate to revert TO the di-
calcium phosphate, which is less solu-
BILE and therefore less desirable. 1t is
true that when the soluble mono-calcium
phosphate is put in the ground 1t is
soon reverted to the insOluble di-cal-
cium form. But it is first dissolved
by the soil water and distributed well
throughout the soil water and distribut-
ed we'll through the soil before be-
coming reverted. Being thus widely ais
tributed throughout the soil i'm a thin
film around the particles of soil, it is
in condition TO be readily taken up by
the roots of growing plants. If on the
other hand the phOsphoric acid is re-
verted before applying, il will not go
I'm solution readily. and consequently
cannot become distributed throughout
the soil. and so be in position TO be
readily taken up by plants. This is
especially true where the SOIL Is not
well stocked with humus, as IS the case
with most southern soils.
In order to test the effect of limestone
on the water soluble phosphoric acid,
the department of chemistry at the col
lege of agriculture conducted the fol-
lowing experiment: \ fertilizer was made
containing 500 pounds of ground lime
stone per ton. and the amount OF water
soluble phosphoric acid was determined
after different periods of standing. The
following results were obtained:
AT time of mixing, 9.01 per cent water
soluble phosphorus acid; after two weeks,
7.37 per cent water soluble phosphoric
acid: after four weeks, esq per cent wa
ter soluble phospnoric acid: after eight
weeks, 3.S5 per cent soluble phosphoric
acid: after six weeks, 1.21 per cent water
soluble phosphoric acid.
A mixture containing 500 pounds of
ground limestone showed by analysis