The progressive farmer. [volume] (Winston, N.C.) 1886-1904, 1900-10-02
AZ > culture.
SOMETHING OF THE PHILOSOPHY OF
SOIL MANAGEMENT AND PLANT
GROWTH.

The ash of plants is made up of
mineral matter derived from the soil,
chiefly lime, silica, potash, phos-
phorus and very small quantities of
other minerals. That part of the
plant which is driven off by heat
when it is dried is water, that part
which disappears in the form of gas
and smoke when the dried plant is
burned, is called its organic matter.
Nearly all of the organic matter of
plants consists of carbon, hydrogen,
oxygen and nitrogen. Water is
composed of oxygen and hydrogen,
and air also contains large quantities
of oxygen, carbon and nitrogen.
Hence it is known that plants obtain
their oxygen. hydrogen and most of
their carbon from the air and water
and this is 95 pounds of every 100
pounds in weight.
But although fOur-ffths of the air
is composed of nitrogen, only one
family of plants is known to be
capable of using the nitrogen of the
air. Botanists call this family of
plants the leguminOse, or legumes.
They all bear seed pods of some kind.
They include the clovers, vetches,
peas, beans and several kinds of
weeds and some trees. All other
plants must derive their nitrogen
solely from the soil.
It has recently been discovered
that the legumes are enabled to take
nitrogen from the air by means of
bacteria that operate upon their
roots. 1t is true that as falling rain
descends through the air it absOrbs
some atmospheric nitrogen, which it
carries to the soil in a form ready
for the use of plants, but the guam
tity is small-trom to pounds per
acre in a year.
Much nitrogen exists in most soils
in the form of rOtted and rOtting
vegetable matter, called humus.
This quantity varies from 1000 to
three feet in depth of the soil.
But before plants can take up and
use this organic nitrogen already in
the soil or that which may be sup
piled in the form of manures and
commercial fertilizers, it must be
broken down and converted into am
monia and then into nitric acid by
the agency of these soil bacteria.
We thus find that in all cases plants
are dependent upon soil bacteria for
their necessary supplies of nitrogen.
Let us see how it is with their neces-
sary mineral food to form ash.
Originally the earth's crust was
composed of rocks. Ages of exposure
to wind, rain, sun, air and frost
caused the surfaces of rocks to disin-
tegrate and crumble into dust and
upon this layer of dust some plants
grew and animals appeared, and the
decay of the. dead plants and animals
added organic matter and thus the
soil was formed.
Now, one of the most potent agen-
cies in converting rock into soil is
the carbOnic acid gas generated by
soil bacteria.
The rocks being the basis of soils,
the character of soil depends largely
upon the kind of rock from which it
was derived. The most fertile soils
are derived from granite and lime
stone Sandstone soils are inferior.
In the surface soil of cultivated
fields there are from 10000 to 1,5OO,
900 bacteria in each gram Of the soil
about half thimblefuD. The street
dust of Naples was found to contain
from 10000, 900 to 1000, 10000 bac-
terra per gram.
Ithas also been found that the num-
Ier of germs in desert and forest
soils is much smaller than in Guilt
waited soils and fewer in sandy soils
than in clay soils. In cultivated
soils the more active and frequent
the cultivation the more bacteria.
Soils rich in humus are also rich in
bacteria The number of soil bac-
terra is much greater in summer
than in winter. There are more
bacteria in the soil of hoed crops,
Ike potatoes, than in the soil of grain
crops like wheat. We thus find that
IN truth cultivation may take the
place Of manure. But we must re-
member that cultivation only enables