Lincoln County leader. [volume] (Toledo, Lincoln County, Or.) 1893-1987, 1911-08-18
SOIL CHEMISTRY.

that all substances are made up of GER
tain simple forms of matter, such as
iron, aluminium and carbon, which are
called elements. In most substances
these elements are combined in a more
or less complex form. Although some
eighty of these elementary forms of
matter have been discovered, only
about dozen of these are found in
any quantity in plants. Carbon, hy-
drogen, oxygen and nitrogen make up
about ninety-fve per cent of the total
weight of all plants, i. e., their Or
ganic portion, and are derived either
directly or indirectly from air and wa
ter, the nitrogen being assimilated by
the plant after fixation in the soil.
The remaining five per cent of the
plant consists of mineral matter or
ash, the portion left when the plant is
burned, and is composed mainly of the
elements of iron, aluminium, calcium,
magnesium, phosphorus, potassium,
sodium, silicon, chlorine and sulfur.
These are all taken up by the plant
directly from the soil. Much investi-
cation and experience has proven that
only four of these elements are likely
to be deficient in soil, namely, nitro
gen, potassium generally expressed
as "potash") phosphorus, usually ex-
pressed as "phosphoric acid") and cal
cium, (or "lime," as it is generally
expressed.) These are often termed
the e critical" soil elements, and are
the actual basis of all direct fertiliz-
ers.
1t is singular to note that only very
small quantities of these plant foods
which are so essential to plant growth
are soluble even in strong acids. Rich
soils contain approximately O.20 per
cent of total nitrogen. Analysis of
the acid soluble mineral substance
will show about 0.10 to obs per cent
of phosphorus (phosphoric acid), 0.30
per cent of potassium, (potash), and
0.50 per cent of calcium Qime). The
figures show plainly that proper and
scientific methods of farming must be
practiced for the maintenance of the
fertility of even our richest soils.
The most important of these critical
soil elements is nitrogen. 1t is COM
bined with other elements in the soil
humus (decaying animal and vegetable
matter). In the free state nitrogen
is gas and in this form constitutes
three-fourths of the air. The total
nitrogen supply in the air over each
acre of the earth's surface, if avail
able to plants, would meet the needs
of hundred-bushel crop of corn every
year for half million years. Never
theless nitrogen in available form is
worth 1S to 20 cents pound in the
fertilizer markets. The organic mat
ter in the soil is the nitrogen store
house from which plants derive their
supply. Constant removal by crops,
oxidation of organic matter in clean
cultivation as well as waste through
teaching, all assist in depriving the
soil of this essential element. Exper-
ience has shown that under exhaustive
systems of farming the soil nitrogen
supply is easiest impaired. To add
available nitrogen to the soil in the
form of commercial fertilizers costs
from 1S to 20 cents a pound, which
make it too expensive for use on
general farming scale. Experiments
have shown, however, that leguminous
crops, such as clover, vetch, and al
falfa, have power to obtain free nj
trogen from the air through the inter-
vention of certain microscopic organ
isms which live in tubercles upon the
roots of these plants. Such crops add
nitrogen to the soil, and hence rota-
tion with leguminous crop is an in
expensive and efficient means of sup
plying this element to the soil and one
that is applicable to general farming.
The mineral plant foods, potassium,
phosphorus and lime, exist in the soil
in variuos forms: potassium often in
combination with quartz in the min
eral feldspar; phosphorus in combina-
tion with iron, aluminium and lime as
phosphates; and lime often in the
form of silicate and carbonate Qime-
stone) These compounds are by
chemical processes, which are encour-
aged by tillage, converted into soluble
or available forms which can be as
simulated by plants. The plant can
only obtain these mineral elements
from the soil and when the supply be-
comes deficient they must be furnished
through the addition of appropriate
fertilizers.
The fact that ordinary wood ashes
are so rich in potash as to be valuable
as fertilizer indicates that certain
plants withdraw large amounts of this
element from the soil. Six tons of
well cured alfalfa hay contain $50