DIFFERENT KINDS OF SOIL
“Four substances, mingled in very variable proportions, enter into the
composition of fertile soil, or arable land, namely: sand or silica,
clay, limestone, and humus, or vegetable mold. Each one of these
ingredients separately would make but very poor soil, quite unsuited
for agriculture; but united, mixed together, they fulfill the
conditions necessary to fertility. Arable land generally contains all
four, with the predominance sometimes of one, sometimes of another. The
soil takes the name of its most abundant constituent. Thus have arisen
the names, silicious soil, argillaceous soil, calcareous soil, and
humous soil, to designate the fertile lands dominated respectively by
sand, clay, limestone, and humus. Compound terms are also used. For
example, when it is said of a certain soil that it is
argillo-calcareous, it is meant that clay and limestone are its chief
constituents.
“Sand consists of particles, more or less minute, of very hard rock,
sometimes opaque, sometimes as transparent as glass, and always easily
recognizable by its property of emitting sparks when struck with steel.
Flint and white pebbles belong to this kind of rock, which is called
silex, silica, or quartz. These three expressions mean about the same.
Sandy soils have little consistency, are easily permeated by water, and
freely absorb the sun’s heat, which makes them very subject to drought.
“The name of granite is given to a rock composed chiefly of silica and
which forms whole mountains, as in central France and in Brittany. The
soil formed by the gradual disintegration of this rock is sometimes
called granite soil. It is not very good for agriculture. Chestnut
trees prosper in it, as well as certain wild plants characteristic of
this kind of land. The principal ones are the various species of
heather and the purple digitalis. Heather, with its dainty little pink
blossoms, carpets in richest abundance the poorest of sandy soils. The
purple digitalis is a large-leaved plant whose flowers, red on the
outside, striped with purple and white inside, are arranged in a long
and magnificent distaff reaching almost to the height of a man. The
flowers are in the shape of long tun-bellied bells or, rather,
glove-fingers; hence the plant is sometimes called foxglove, sometimes
lady’s fingers.
“The soil composed of substances thrown up by volcanoes is also sandy,
and is called volcanic soil. It is generally black and sometimes very
fertile.
“Sandy-clay soil is found in the valleys of great rivers. It is the
most fruitful and the easiest to cultivate. Such are the soils of the
Rhone valley, the valley of the Loire, and that of the Seine. It is
still more fertile if it is flooded by the stream at high water. Then
the river deposits a rich slime composed of clay and organic matter
washed down by the current.
“The soil of heathy or shrubby land is composed of fine sand and of
humus from the decayed leaves of heather and other plants. It is only
used for flower gardens, and furnishes an example of what might be
called sand-and-humus soil.
“Clay is a soil which, when moistened with water and thoroughly
kneaded, becomes a soft and tenacious dough, suitable for molding into
any desired shape. When perfectly pure it is white, and is known as
kaolin, a rare substance of which porcelain is made. Plastic clays are
those that are unctuous to the touch, forming with water a yielding
mass that hardens with firing. They are used in making pottery.
Smectite, or fuller’s earth, is a clay of very different character, not
pliable when moistened, but very absorbent of grease and hence used by
fullers for cleansing cloth of the oil left on it in weaving. Ochres
are clays colored either red or yellow by iron-rust. They are used in
coarse painting. Red chalk belongs to this class of clays. Marl is a
mixture in variable proportions of clay and limestone. According to
which constituent predominates, it is called argillaceous or
calcareous. Subjected to the action of air and moisture, marl becomes
flaky and crumbles to dust. Marl is used in agriculture to improve the
soil.
“A clay soil is quite the opposite of a sandy soil: water makes it
swell and converts it into a sticky paste which clings tenaciously to
farming implements. Once wet, it is cold, that is to say it dries very
slowly. A spade can only divide it into dense clods slow to crumble in
the air and not fit for receiving seed. The farmer must be careful to
drain off the water and break up the ground by working it before and
during frosts. It is improved by mixing with it sand, coal-ashes, and
lime. Wheat flourishes better in a clayey soil than in any other kind.
“Clayey soils are recognized by their vegetation. The wild plants
peculiar to this kind of soil are colt’s-foot and danewort. Colt’s-foot
is also called horse-foot from the shape of its leaves, the outline of
which reminds one of a horse’s hoof. The leaves are white underneath.
The flowers are yellow like little marigolds, and they appear at the
beginning of spring before the leaves. Danewort is a kind of herbaceous
elder of about half the height of a man. Its small white flowers are
succeeded by berries full of a violet-red juice.”