The Dawson news. (Dawson, Ga.) 1889-current, 1902-06-11

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which gave you in my last letter. we
find that besides the organic SUBJ
stance about which We have just been
talking, there are also the inorganic
or mineral substances, such as we
found in the ashes of the plant we first
analysed.
The Various Elements Found In the
Soil.
J The most abundant substance of all
these mineral or ash elements in the
soil we find to be silica, or as you are
/ quainted with it, sand. You will re.
member there was in this particular
rich soil 71.55 pounds of silica out of
every 100 pounds, and yet the wheat
plant grown on this soil only contained
two and three-quarters pounds of sill
ca out of every 100 pounds, and even
this was not absolutely essential to
the health and growth of the plant.
Although we find alumina in the soil,
we find none in the plant Alumnia
is one of the principal elements of a
clay soil. Iron, magnesia and SULPHUR
1c acid found in the soil are likewise
found in the ash of the plant. Only
small quantities of these however are
required by the plant and they are al
ways abundant in soils. Soda is like
wise found in both soil and plant, but
is not essential to the plant. Phosphor-
ic acid, potash and lime are found in
| only small quantities in most soils,
but exist In considerable quantity in
the ash of the plants, and each one
of them is absolutely necessary to
| the life, growth and development of
the plant. For this reason, the other
elements being usually abundant, a
soil is said to be rich or poor accord
ing to its contents of potash, phosphor-
ic acid, lime and nitrogen.
Potash and pbosphoric acid are
usually contained in soils in small
quantity, varying from about one-tenth
of a pound in hundred pounds of
the soil to one pound in one hundred
pounds. Although that amount looks
small; let us figure it by the acre.
Weight of the Soil Per Acre.
An average soil, when dry, if taken
to the depth of nine inches, will
weigh three to three and one-half mil
lion pounds to the acre. Therefore a
soil containing one-tenth of one per
cent of phosphoric acid, would really
contain three thousand to thirty-five
hundred pounds of phosphoric acid per
acre, or as much as could be obtained
by the application of ten to twelve tons
OF high-grade acid phosphate per acre.
You would at once then say that soil
containing one-tenth per cent of pot
ash or phosphoric acid ought to be
rich soil and should not require any
fertilizers, but there you would be
wrong, because it matters not so much
what is the total amount of potash
or phosphoric acid in an acre of soil
as it does to know in what condition
that phosphoric acid or potash exists.
Availability of the PIant-Food in the
Soil.
The question arises, is it soluble,
is it available? 1t is in such condition
that the soil water can take it up and
convey it to the roots and root hairs
of the plant, ready for absorption by
them into the characterization? That
is why we find it necessary to put
acid phosphate and kainit and other
fertilizers on lands which are being
constantly cropped; it is because the
constant cropping has exhausted or
drawn out of the soil the soluble phos-
phoric acid and potash available to
the plant, and we must either put on
a fertilizer containing them in solu-
BILE form, or we must let the soil rest
a while, that is "lie fallow," in order
that fresh supply of plant food may
be made available by the slow action
of the soil water, the action of car
bonic acid, and the other organic acids
resulting from the decay of vegetable
and animal matters in the soil. If
you cannot afford to either put on fer
tilizer or to let your land "lie fallow,
then your next resource is to rotate
your crop; that is, to plant on the soil
which has begun to fail you some
other crop of different nature, which
may not require so much Of certain
element of plant food as the previous
crop did. For instance, follow cotton
with peas or clover.
What Determines the crop-Producing
Power Of the Soil.
In considering the capacity of soil
to produce crops we must remem-
Der one thing, and that is that the es-
sential element which exists in the
smallest amount settles the QUESTION of
tn crop producing powr of soil. That
is to say, if soil is vry rich in avail
able phosphoric acid. nitrogen, lime,
magnesia, and the other essential ash
elements, and yet be poor in available
potash, that soil cannot produce heavy
crops without the application OF an
available potash fertilizer. If that soil
has only available potash enough in