The enquirer southerner., 1874-11-20
THE
How Land Becomes Exhausted.

Lie toou ot piaHtS CouSISIS, Ill du>
dition to water. of two kinds of
matter-namely, ten or twelve sub
stances (called fixed constituents
derived solely from the soil !; and
OF four bodies derived by our culti- |
waited crops partly from the air and
partly from the soil, and which fly
away into the air under action of
heat, and are, in consequence, CALI |
ed volatile. Many wild plants have
the power of growing on hard rock,
destitute Of any volatile matter; but
cultivated plants, such as the cab
bage, require for their full growth
soil containing such matter. We
increase the quantity of volatile
matter in the soil by laying it down
to grass, and by the application of
farm-yard manure, of peat, and
other vegetable substances. The
quantity of this matter in the soil
| varies very much. Rich gardens
| contain a great deal of it, and it
| may be said that, with certain ex-
| ceptions, the amount required for
| the growth Of crops should increase
with their luxuranee and delicacy.
| Of farm crops, the cabbage and the
grasses require it in the largest
quantity. The cabbage should
therefore be grown in rich ground.
Of the grass family of plants, there
is none which luxuriates in soil rich
in combustible matter, or matter
! that can be burned away, so much
is Italian rye. grass, of which more
Sill be said further on, and of which
enormous crops are obtained, by
,kilful management, on reclaimed
ocg and moor. The fixed constitu-
.nts of plants, also called the ash
md mineral constituents, are inva"
iably obtained from the soil. A
oil deficient in any one, or in more
than one, of them, is barren. They
xist in very different proportions
n the different families of crops.
The composition of the same sort
r. variety of crop is pretty constant.
| We see, then, that a given weight
f the same crop must take out of
he ground certain quantity of fix,
| d or ash constituents. If the
;rop, or part of it, be sold off the
arm, it is evident the total quanti-
| y Of the ash constituents in the soil
must be lessened. If the quantity
| # these constituents sold off we're
eturned to the soil in manure, it
would not suffer any deterioration ;
'ut if crop after crop be sold with~
,ut any manure. it is evident the
,upply of ash constituents will be-
;ome less and less, and the yield
nay be so far reduced that the crop
would not pay. This actually oc.
cured in some of the slave States
# America, where the land was 50
reduced in condition by crops of to-
'acco following each other year af-
er year, that it had for q time to
De left untitled, and abandoned to
state of nature.
Before we can apply the knowl>
,dge of the foregoing facts to Irish
'gricu.ture, it is necessary to ex"
.olain that only very small part
rarely more than the one-hundred:h
oart-of the soil is, at any one time,
a state to afford food to our crops,
the bulk of the constituents being
ocked up in the structure of the soil
in an unavailable condition-that
s, in such state that the plants
cannot use it. The stones in the
soil may contain the same substance
IS the soil itself, yet we know that
crops can feed on the soil, but not
IN the stones. In the course of
time, and under the influence of air
md moisture, the constituents of the
stones become gradually liberated,
and thus made fit for plants. The
process is slow, but it is continuous.
The stones in our buildings crumble,
md so the stone and particles of the
soil are gradually worn down, and
heir constituents converted into
| plant food. An interesting illustra-
ion of this principle is afforded in
the observation that the removal of
stones from poor land, when they
appear to be in excess, often does
harm. The farmer, in ignorance of
better explanation, says the remo>
val of the stones makes the land
cold; the true explanation is to be
found chiefly in the circumstance
that the stones, by the wearing
down of their surface, afford a cer>
tain amount of food to the crop.
live apply the principles which
we have SO far explained to the oc~
cupiers of land in remote or badly
farmed districts, we shall see that
soil, having for ages been made to
bear corn crops without manure, has
been reduced to poor state. Dali
ry produce, young stock, and the
potato have also taken out of the
and good deal of its most valuable
ash constituents. The potato con-
tains large amount of potash, and
this substance, though abundant in
argillaceous clay, is contained in
very small quantity in the lighs
lands in the hands of many of our
small farmers. Recent research
tends to show that the potato dis,
sease is mitigated by the application
, of a manure containing potash.
Of all the component parts of our
soils, phosphate of lime is most liza,
hla m hacomo dafcient IT. EXISTS