MANURING THE SOIL AND MAKING HOTBEDS.
Most persons imagine that manure is all that is wanted to make a garden
fruitful; and thus, if the fruit-trees do not bear, and the flowers
and vegetables do not thrive, manure is considered the universal
panacea. Now, the fact is, that so far from this being the case, most
small gardens have been manured a great deal too much; and in many,
the surface soil, instead of consisting of rich friable mould, only
presents a soft black shining substance, which is the humic acid from
the manure saturated with stagnant water. No appearance is more common
in the gardens of street-houses than this, from these gardens being
originally ill drained, and yet continually watered; and from their
possessors loading them with manure, in the hope of rendering them
fertile.
As it is known to chemists that it is only the humic acid, and carbonic
acid gas, contained in manure, which make that substance nourishing
to plants; and as these acids must be dissolved in water before the
roots can take them up, it may seem strange that any solution of them
in water, however strong it may be, should be injurious to vegetation.
The fact is, however, that it is the great quantity of food contained
in the water that renders it unwholesome. When the roots of a plant
and their little sponge-like terminations, are examined in a powerful
microscope, it will be clearly seen that no thick substance can pass
through them. Thus water loaded with gross coarse matter, as it is when
saturated with humic acid, must be more than the poor spongioles can
swallow; and yet, as they are truly sponge-like, their nature prompts
them, whenever they find moisture, to attempt to take it up, without
having the power of discriminating between what is good for them, and
what will be injurious. The spongioles thus imbibe the saturated
liquid; and, loaded with this improper food, the fibrous roots, like an
overgorged snake, become distended, the fine epidermis that covers them
is torn asunder, their power of capillary attraction is gone, and they
can neither force the food they have taken up, into the main roots, nor
reject the excrementitious matter sent down to them from the leaves,
after the elaboration of the sap. In this state of things, from the
usual circulation of the fluids being impeded, it is not surprising
that the plant should droop, that its leaves should turn yellow, that
its flowers should not expand, that its fruit should shrivel and drop
off prematurely, and that in the end it should die; as, in fact, it may
be said to expire of apoplexy, brought on by indigestion.
All soil, to be in a fit state for growing plants, should be
sufficiently loose and dry to allow of water passing through it
intermixed with air; as water, when in this state is never more than
slightly impregnated with the nutritious juices of the manure through
which it has passed. The spongioles are thus not supplied with more
food at a time than they can properly take up and digest, and a healthy
circulation of the fluids is kept up through the whole plant. But,
what, it may be asked, is to be done with a garden, the soil of which
has become black and slimy like half-rotten peat? The quickest remedy
is covering it with lime, as that combines readily with the humic acid,
and reduces it to a state of comparative dryness: or, if the sub-soil
be good, the ground may be trenched, and the surface-soil buried two
spits deep; in either case it will be necessary thoroughly to drain the
garden to prevent a recurrence of the evil.
_All the different kinds of soil_ found on level ground, consist of two
parts, which are called the surface-soil and the sub-soil; and as the
sub-soil always consists of one of the three primitive earths, so do
these earths always enter, more or less, into the composition of every
kind of surface-soil. The primitive earths are--silex, (which includes
sand and gravel,) clay, and lime, which includes also chalk; and most
sub-soils consist of a solid bed or rock of one or other of these
materials, probably in nearly the same state as it was left by the
deluge. The surface-soils, on the contrary, are of comparatively recent
date; and they have been slowly formed by the gradual crumbling of
the sub-soil, and its inter-mixture with decayed animal and vegetable
matter, and with other soils which may have been accidentally washed
down upon, or purposely brought to it. In fields, and uncultivated
places, the surface-soil is almost as hard, and as coarse in its
texture, as the sub-soil on which it rests; but in gardens which have
been long in cultivation, the surface-soil becomes so thoroughly
pulverized by frequent diggings, and so mixed with the manure and
decayed vegetables which have been added to it from time to time, that
it is changed into the soft, light, fine, powdery substance, called
garden-mould. If the sub-soil be naturally porous or well drained, this
mould, however rich it may be made by the addition of decayed vegetable
matter or animal manure, will always continue friable; and as long as
it does so, it will be fit for the growth of plants: but if no vent be
allowed for the escape of the water, and it be continually enriched
with manure, it will be changed in time into the black slimy substance
that has been already described.
Surface-soil is called peat-earth when it is composed of decayed
vegetable matter, without any mixture of animal manure; and, as this
excess of vegetable matter could neither be produced nor decayed,
without abundance of stagnant moisture, this kind of earth is almost
always found on a clayey sub-soil, which prevents the water which
falls upon it from escaping. Peat-earth has a spongy, elastic feeling
when trodden upon, arising from the quantity of water that it holds,
and it can only be rendered fit for cultivation by draining. In its
elastic state it is what is called in Scotland a moss, and in England
a peat-bog. Should the water, instead of being afforded a vent by
drainage, be suffered to accumulate for many years, till it completely
saturates the peat, the soil becomes what is called a morass, or
quagmire; and it can no longer be trodden on, as it will engulf any
substance resting upon it. A still further accumulation of water will,
in the course of years, cause the bog to burst its bounds, and overflow
the surrounding country; as the Solway-moss did many years ago, and as
bogs in Ireland have done frequently. An excess of vegetable matter on
a silicious sub-soil, differs from the common black-peat in retaining
less water; and in being mixed with a portion of the primitive earth,
which, from its loose texture, becomes easily detached from the
sub-soil. Peat in this state is called heath mould.
The most productive soils are those in which several ingredients are
combined in proper proportions; and if any one of the primitive earths
preponderates, the soil becomes comparatively unfertile. Thus the best
soil for gardening purposes is generally allowed to be a calcareous
loam on a chalky sub-soil; and this sort of soil is composed of nearly
equal parts of lime, sand, and clay, enriched depositions of decayed
animal and vegetable matter. The next best soil is a sandy loam,
composed of clay and sand, enriched by decayed animal and vegetable
substances, and resting on a sandy or gravelly sub-soil. The worst
soils are peat and sand. A poor sandy soil is necessarily a nearly
barren one; because it will not retain either water, or the nutritious
juices from manure, long enough to afford nourishment to the plants
grown upon it; and it is obvious that a soil of this kind can only be
rendered fertile by mixing it with clay; which would change it into a
sandy loam.
A stiff clay is unfertile from its attracting moisture and retaining it
round the roots of the plants till they become swollen and unhealthy.
It also retards the decomposition of manure, and obstructs the
progress of the roots, which waste their strength in the efforts they
make to penetrate, or twine round, its adhesive clods. Soils of this
description are improved by a mixture of sand, gravel, road grit, or
any substance which tends to separate the particles of the clay, and to
render it light and friable.
Chalky soils succeed better unmixed, than any of the other kinds; but
chalk being a carbonate of lime, can hardly be called a primitive soil.
The chalk, however, from its whiteness is colder than any other soil;
as it does not absorb, but reflects back the rays of the sun. Rain
also penetrates into it very slowly, and not to any great depth. Chalk
mixed with sand forms a kind of calcareous loam admirably adapted for
growing vegetables; and chalky soils are peculiarly susceptible of
improvement from manure.
_Manures._--The kinds of manure generally used in gardens are horse or
cow dung, and decayed vegetable matters; the manure in both cases being
suffered to lie in a heap to rot before it is spread on the ground,
in order that its component parts may be decomposed by fermentation,
and thus brought into a fit state to afford food to the plants.
Old hot-beds or mushroom beds are thus well adapted for manuring a
garden; and when fresh stable-dung is employed for that purpose, it is
generally thrown into a heap, and turned over several times till the
fermentation has abated, before it is dug into the ground. As, however,
a great quantity of carbonic acid gas is evolved and escapes during
the process of fermentation, and as it seems a great pity that so much
of the nutritious properties of the manure should be lost, it is now
customary to cover the dunghill with earth, into which the gases will
rise during the process of fermentation, and in which they will deposit
the greater part of their nutritious properties. A quantity of earth
should also be laid round the dunghill to imbibe the liquid that runs
from it, and this earth, part of which must be removed and fresh added
every time the dunghill is turned over, will be found very nearly as
valuable for manuring the beds of a garden, as the manure itself.
_The modes of applying manure_ differ according to the difference of
the soils. For sandy loams, thoroughly rotten dung, either from an
old hotbed, or from a dunghill sufficiently decayed to be cut easily
with the spade, or the earth that has covered a dunghill during the
process of fermentation, should be laid on the surface of the soil,
and dug in. In very poor sandy soils rotten manure, or earth from a
dunghill, should be laid on the surface of the soil, and not dug in:
being covered, if hot dry weather be expected, with leaves, straw, or
the branches of trees cut off in pruning; or occasionally sprinkled
with water. Soils of this description, and loose sands, are frequently
improved in the South of France and Italy, by sowing them with seeds
of the common white lupine, and then, when the plants have come up and
grown about a foot high, ploughing or digging them into the soil. The
green succulent stems of the lupines, when thus buried in the soil,
supply it with moisture during the process of their decay; and thus
nourishment is afforded to the corn, which is immediately afterwards
sown upon the soil for a crop. Clayey soils should have unfermented
manure mixed with undecayed straw laid in the bottom of the furrows
made in digging; that the process of fermentation, and the remains of
the straw may operate in keeping the particles of the soil open, or, in
other words, in preventing their too close adhesion. Lime (though when
burnt it becomes violently caustic, and will destroy and waste all the
manure applied with it), as carbonate of lime, or chalk (in which state
only it can properly be called a soil), retains the manure applied
to it longer than any other soil. Rotten manure may thus be dug into
chalk, with the certainty that it will be preserved from farther decay
for a very long time, and that every shower will work a small portion
of its fertilizing juices out of it, and carry them into the soil,
where they will be thus presented to the plants in the best possible
state for affording wholesome food.
Peat soils may be improved by the addition of quick-lime as a manure,
which will absorb the superabundant moisture which they contain; or
they may be mixed with sand, gravel, or clay to give them firmness
and tenacity, and then with a small quantity of animal manure. Sandy
peat or heath mould is very useful in gardens for growing heaths,
rhododendrons, kalmias, or any plants with fine hair-like roots; and
from the quantity of vegetable matter that it contains naturally,
it does not require any manure, more than what is furnished by the
decaying leaves of the plants grown in it.
Nearly the same rules apply to decaying leaves and other substances
used as manure, as to stable-dung. They may be buried in an undecayed
state in clayey soil, when it is the object to separate the adhesive
particles of the clay by the process of fermentation; but their
component parts should be separated by fermentation before they are
applied as a manure to growing plants. Vegetable mould (that is, leaves
thoroughly decayed and mixed with a little rich loam) is admirably
adapted for manuring the finer kinds of flowers, and plants in pots.
There are many other kinds of manure used in gardens occasionally;
such as the dung of pigs, rabbits and poultry, grass mown from lawns,
parings of leather, horn shavings, bones, the sweeping of streets, the
emptying of privies, cess-pools, and sewers, the clipping of hedges
and pruning of trees, weeds, the refuse of vegetables, pea halm, &c.
All these should be fermented, and applied, in the same manner as the
common kinds of manure.
_The following is a summary of the general rules to be observed
in manuring and improving soils_:--Never to use animal manure and
quick-lime together, as the one will destroy the other. To use lime
as a manure only in very sandy or peaty soils, or in soils abounding
with sulphate of iron. To remember that rotten manure is considered to
give solidity; and that unfermented manure, buried in trenching, has a
tendency to lighten the soil. To dilute liquid manure from a dunghill
with water, before applying it to growing plants; as otherwise, from
the quantity of ammonia that it contains it will be apt to burn them.
To cover and surround dunghills with earth during the process of
fermentation, to absorb the nutritious gases, that would otherwise
escape. To remember that the manure of cows and all animals that chew
the cud, is cold and suited to a light soil; and that the manure of
horses, pigs, and poultry is hot and suited to a firm soil: also that
all manure, when well rotten, becomes cold in its nature, and should be
treated accordingly. To remember that all mixed soils are more fertile
than soils consisting only of one of the three primitive earths, viz.
lime, sand, or clay; and never to forget that too much manure is quite
as injurious to plants as too little.
_Formation of hotbeds._--Though nearly all the kinds of manure which
have been enumerated may be used occasionally for hotbeds, the only
materials in common use in gardens, are stable manure, dead leaves, and
tan. The first of these, which is by far the most general, consists
partly of horse-dung, and partly of what gardeners call long litter,
that is, straw moistened and discoloured, but not decayed. The manure
is generally in this state, when it is purchased, or taken from the
stable, for the purpose of making a hot-bed.
The necessary quantity of manure is procured at the rate of one cart
load, or from twelve to fifteen large wheel-barrowfuls to every light,
as the gardeners call the sashes of the frames, each light being about
three feet wide; and this manure is laid in a heap to ferment. The heap
should then be covered with earth to receive the gases evolved during
fermentation, and earth laid round it to absorb the liquid manure that
may drain from it. In about a week the earth may be removed, and the
manure turned over with a dung-fork, and well shaken together; this
operation being repeated two or three or more times, at intervals of
two or three days, till the whole mass is become of one colour, and the
straws are sufficiently decomposed to be torn to pieces with the fork.
The size of the hotbed must depend principally on the size of the
frame which is to cover it; observing that the bed must be from six
inches to a foot wider than the frame every way. The manure must then
be spread in layers, each layer being beaten down with the back of the
fork, till the bed is about three feet and a half high. The surface of
the ground on which the hotbed is built, is generally raised about six
inches above the general surface of the garden; and it is advisable to
lay some earth round the bottom of the bed, nearly a foot wide, that it
may receive the juices of the manure that will drain from the bed. As
soon as the bed is made, the frame is put on and the sashes kept quite
close, till a steam appears upon the glass, when the bed is considered
in a fit state to be covered three or four inches deep with mould;
observing, if the bed has settled unequally, to level the surface of
the manure before covering it with earth. The seeds to be raised may
either be sown in this earth, or in pots to be plunged in it.
_The proper average heat_ for a hotbed intended to raise flower
seeds, or to grow cucumbers, is 60°: but melons require a heat of 65°
to grow in, and 75° to ripen their fruit. This heat should be taken
in a morning, and does not include that of the sun in the middle of
the day. When the heat of the bed becomes so great as to be in danger
of injuring the plants, the obvious remedy is to give air by raising
the glasses; and if this be not sufficient, the general heat of the
bed must be lowered by making excavations in the dung from the sides,
so as to reach nearly to the middle of the bed, and filling up these
excavations with cold dung which has already undergone fermentation,
or with leaves, turf, or any other similar material which will receive
heat, but not increase it. When the heat of the bed falls down to
48° or lower, it should be raised, by applying on the outside fresh
coatings of dung, grass, or leaves, which are called linings.
When hotbeds are made of spent tanner’s bark or decayed leaves, a kind
of box or pit must be formed of bricks or boards, or even of layers of
turf, or clay, and the tan or leaves filled in so as to make a bed.
Where neatness is an object, this kind of bed is preferable to any
other; but a common hotbed of stable manure may be made to look neat by
thatching the outside with straw, or covering it with bast mats, pegged
down to keep them close to the bed.