The Southern farm gazette. (Starkville, Miss.) 1895-1909, 1902-12-01
Organic Matter in Soils.

dtlClkIOh W SOtl3 uSNSAS
able discussion to humus and its
formation. The soil is largely
composed of clay lime, (sand) and
humus, and according to Mr..
Freer-Thonger, of England, who
has devoted much of his time to
the Investigation of soils, al! vege-
table matter which grows and
dies on the soil is transformed
into humus. Formerly it was
supposed that humus alone fur
nished food for plants, hence the
fertility of a soil was estimated
according to its content in linus
or organic matter. There was
some truth in the belief, for in
organic matter undergoing de-
comp position there exists nitro
yelou, matters which are grad
uallv converted into ammonia and
nitric acid. Carbonic acid gas is
also a product of decomposition,
which acts powerfully in render
ing soluble the mineral elements
of the soil. Humus soils have
the property of retainingthe solu-
BILE mineral salts, which are so
easily washed away into the sub
soil. Soils containing much HUI
mus are easily worked, and, ow-
ing to their dark color, are easily
warmed by the sun. Such soils
give good returns when dressed
with phosphate, although on clay
soils less potash may be required
than on light, sandy land. The
application of lime favors n!trifi-
cation of the ingenious organic
matter. 1t is claimed that humus
soils are rich in nitrogen, poor in
phosphoric acid, with variable
quantities of potash. Sandy
soils are poor in all the plant
foods. Clay soils are rich in pot.
ash, poor is phosphoric acid, but
vary in nitrogen. These claims,
however, depend greatly upon
the characteristics of soils, their
treatment and the kinds of crops
that have been grown thereon.
Humus is formed under many
conditions. Leaves, roots, straw,
manure and green substances
that have been turned under all
assist in the work. The value
of humus does not depend exclu-
sively upon its content of plant
food, but mostly in the influence
it exerts on the soil in relation TO
it's physical condition, and it's acid
IN rendering the plant food of the
soil available for the sustenance
and growth of plants. The up
per portion Of the soil usually
contains more humus than the
deeper portion, which marks or
constitutes the difference be-
tween soil and subsoil. Humus
is the great reservoir which re-
tains the soil moisture and nitro
gen. Il absorbs moisture like a
sponge, and prevents escape of
moisture that would otherwise be
lost. But while it stores up nj
trogen and other plant food, it
slowly and constantly gives out
carbonic acid gas as a result of
decay of vegetable matter. This
acid acts on stones, soils and all
insoluble materials, setting free
the potash and phosphates con-
tanned, thus providing plant foods
for crops. Besides carbonic acid
evolved from humus, other vege-
table acids are formed, which
combine with lime, potash and
other substances to form hui
mates. ALI of these processes
are constantly occurring, the
plant foods of the soil becoming
available even when the farmer
does not assist III the work, for it
is we'll known that one of the
most direct and effective methods
of adding to the humus of the
soil is by blowing dnder of green
crops, which collect carbon from
the atmosphere; and if clover,
peas, beans or other leguminous
crops are used, a large amount
of nitrogen is also added to the
soil. The use of green crops is
almost in order TO nrO.