The farmer and mechanic. [volume] (Raleigh, N.C.) 1877-1885, 1878-03-21

no knowledge as TO their extent. In
none of these phosphate rocks 10 We
have pure phosphate of lime; but all
that has been found in this country i,
fortunately, excellent in quality.
Besides these large a~ccumulatiOns OF
phosphoric acid in combination with
lime, containing literally ineXhausti-
bic quantities of it. we find the acid.
and probably also in combination with
lime, in minute proportions IN a great
MANY other kinds of rock, such as
granite, gneiss, porphyry, sandstone.
states. sOapStOne. etc: since there \
so much phosphate in the rocks. and
since it is so widely diffu5ed. hardly
any one of the ommon rocks being
destitute Of it. it might be expected
that we should always find phosphates
in the soil, as the soil 5 in most cases.
if not in all. derived from the rock.
But the quantity Of phosphate in our
arabic soil is never large on the con
trary it is always very small. In the
case of eighteen analyses by GrOuven,
twelve soils contained not owe five
parts of phosphorIc acid in 10000
parts of the soil, three of the remain
ing six containing less than ten. while
one contained as much a. ~thirty-four
parts Of the phosphoric acid in 10000
of soil. Bretschneider determined the
phosphoric acid in thirty seven soils,
with the following results, the guam
Titles given being in all cases the num-
Der of parts of acid in 10000 parts OF
soil: two soils contained four TO five
of the acid, twenty contained five to
ten. eleven contained ten to twenty,
and four contained from twenty to
twentv-six of the acid: some eXcep-
tiOnally rich soils have been found 10
contain from fifty to one hundred and
fifty parts Of phosphoric acid II TO-
600 of soil: but the ordinary limits
will be found to be two IN 10000 as
the lowest. and twenty III 10000 as the
highest. and it will be safe to say that
the average proportion Is about ten of
acid to 10000 OF soil. \ quantity rep
resented By two to twenty ten-thou-
sands is but a small proportion but
when we come to consider how much
this means in the soil of a whole acre,
it does not { that plants needing
phosphates in their food will be 50
nearly starved as might, at first
thought, seem to be the case. The
mass of soil represented by the area of
an acre taken to the depth of one foot
would weigh about three hundred and
fifty times ten thousand, or $500, 600
pounds: therefore to estimate approx
imately the quantity uf phOSphOric
acid i'm an acre of soil within easy
reach of vegetation We have only to
multiply the quantities that | have
given for 10000 parts by three hun
dred and fifty: two III 10000 means
seven hundred pounds to the acre,
while twenty in 10000 means eve
thousand pounds to the acre: and the
average of ten parts in 10000 means
the apparently abundant quantity of
three thousand five hundred pounds to
the acre.
In regard TO the proportion of phos-
phoric acid IN the crops that we ordi-
narily cultivate, no plant or part of a
plant is SO rich III phosphoric acid as
the seeds of wheat and rye, where we
find in the ash an average OF fOrty-slX
per cent: next to these comes Indian
corn, containing about forty-one per
cent. of phospiloric acid IN It's ash,
then barley, with thirty-four per cent,
oats with twenty-five per cent, pota-
toes with twenty, the sugar beet with
fifteen, turnips thirteen, mangOlds
and clover eight per cent, and tino-
thy with about seven per cent. But
the proportion of phosphoric acid in
the ash of these plants possesses less
interest for us than the actual quantity
of the acid required by an average
o How mucl does ii fair crop of
wheat. barley or Indian corr carry
away from our soils in straw and grain,
or a crop of clover or timothy hay. or
of potatoes, mangolds or turnipS?
And how much is exported from the
farm in the crops ordinarily sold: The
answer to this last question Will tell us
how much should be brought back to
the farm, in the shape either of pur-
chased fodder, or else of purchased
to make good the draft upon
the soil and to prevent it from losing
in fertility.
Average crop Pounds of