ON CLOVER SICKNESS.
In considering the important question involved in the term “Clover
sickness,” we would first direct attention to the fact that crop clover
is a derivative plant which has been so _forced_ that it is many times
larger and more juicy and succulent than the wild plant from which it
sprung. This _derived_ nature (the propensity, as it were, for
fattening) can only be maintained by a continuance from one generation
to another of those luxuries to which the cultivated family has been
accustomed; hence, then, if seed be brought from a richer soil to a
poorer, or from a warmer to a colder climate, we may expect that its
plants grown amid barley and drawn up during the summer would have but a
poor constitution to withstand the rigours of winter; but can we in such
a case say that the _land_ is clover-sick, that is, sick of growing
clover?
Of course the seed here supposed will grow better in one place than in
another, as, for example, we have traced some American seed of
broad-leaved clover grown by itself in a deep rich soil in the Vale of
Gloucester, where the climate is so much milder as to be a fortnight
before the elevated land of the Cotteswold Hills and producing an
abundant crop; while the same forming part of a mixture of “seeds” with
rye-grass and plantain on the hills, the two latter have taken
possession of the soil, and the clover made no progress at all; whilst
other seed, under precisely the same circumstances, has done remarkably
well.
That there is much reason for these conclusions will be found in the
fact that the more seed we import from warmer climates the more
difficult is it found to make the land produce a plant; still
importation is rapidly on the increase, because warmer climates can
produce seed more certainly and in greater quantity than we can at home.
The difficulty of growing from foreign seed increases in proportion to
the thinness of the soil and the backwardness of the climate, so that
the elevated districts on the stony Cotteswolds just adverted to
present, perhaps, more of the so-called clover-sick land than any other
of like extent.
The seed of clover, then, has become more and more pampered—more the
offspring of large crops from deep alluvial soils under the tropical
summer heat of the south of France and the United States, where it is
grown as a self-crop and not fed merely on what the corn could not carry
away; and so while this enervation, or, if preferred, this civilization,
of plant has gone on, we expect its seed all at once to withstand the
shock of a lower temperature with constant climatal changes and cutting
winds; and if it does not succeed, we say that the land is clover-sick,
when, in truth, it is the seed that sickens under these new and trying
conditions. As well may we say that the Northern States sicken of the
negro, because he there dies out so rapidly, or that the warm south
sickens of humanity, because those who are unacclimated sicken and die
there.
Another circumstance which has contributed to an increased difficulty
in growing clover on thin soils will be found in the farmer discarding
as antiquated the practice of paring and burning, which was formerly the
usual preparation for the turnip crop. In a paper on “Paring and
Burning,” in the 18th volume of the _Journal of the Royal Agricultural
Society_, Professor Voelcker remarks:—
The ashes produced by paring and burning are especially useful to
turnips, and also to other green crops, because they contain a
large proportion of phosphates and potash—constituents which, it is
well known, favour in a high degree the luxuriant growth of
root-crops.
Further, the learned professor closes a most able paper with the
following conclusions:—
Paring and burning, instead of being an antiquated operation, is a
practice the advantages of which are fully confirmed and explained
by modern chemical science.
Paring and burning, to judge from our own experience, had the effect of
converting some of the hard limestone brash into lime, in which case it
broke up by the influences of air and rain, and so restored the lime and
alumina which mostly exist together in limestone, the former of which is
quickly lost in thin soils,—so much so, indeed, that not unfrequently
the whole depth of soil, even upon a limestone, will often be curiously
devoid of lime, which is a necessary ingredient in the constitution of a
clover crop.
Again, we should conclude that the operation under discussion, from its
decomposing that dark vegetable matter called _humus_, which is always
found in large quantities on some of the soils which are called
“_dead_,” from their inability to produce crops, and which often cause
astonishment that such black, nice-looking earth should be unproductive.
Now this soil, though it would favour the growth of some species of
peat-loving plants, as Ling, Heath, &c., is not suitable for clover, as
the wild plant is curiously absent from peaty positions.
Professor Voelcker remarks that “the excess of undecomposed organic
matters in soils is decidedly injurious to vegetation. Roots, stems, and
other vegetable matters remain buried in the ground for years without
undergoing decomposition, and if we attentively study the subjoined
analysis of soil in the neighbourhood of Cirencester, well adapted for
burning, we shall see how the _lime_, _alumina_, and _organic matter_
might be beneficially affected by the process:—
ANALYSIS OF SOIL ADAPTED FOR BURNING, BY PROFESSOR VOELCKER.
Moisture ·93
Organic matter 10·67
Oxides of iron and alumina 13·40
Carbonate of lime with a little sulphate of lime 23·90
Carbonate of magnesia 1·10
Phosphoric acid trace
Potash ·38
Soda ·13
Insoluble silicious matter 49·66
------
100·17”
The ashes, however, are obtained by burning a thin slice pared from the
surface of the land, so that they are derived from surface-soil and
vegetable matter, the latter often yielding a sufficient amount of
phosphoric acid with which to procure a crop, and, what is all important
for us to consider is, that this phosphorus, the alkalies, and lime, are
rendered by the burning in a state just fitted for the growth of the
plants that are to be grown upon them; whereas, before the process,
these ingredients were in a measure locked up, so that plants could not
grow for the want of sustenance; not that it was not in the soil, but
that it was insoluble. If, then, clover or any other plant had not
succeeded, it would have been called “clover-sick.”
The following analysis of vegetable ashes from a field in the
neighbourhood of Cirencester will well repay attentive consideration, as
illustrating these points:—
ANALYSIS OF ASHES FROM PARING AND BURNING, BY PROFESSOR VOELCKER.
Moisture and organic matter 9·12
Oxides of iron and alumina 14·56
Carbonate of lime 17·17
Sulphate of lime 1·73
Magnesia ·40
Chloride of sodium ·08
Chloride of potassium ·32
Potash 1·44
Phosphoric acid 1·84
Equal to bone earth (3·98)
Soluble silica (soluble in potash) 8·70
Insoluble silicious matter 44·64
------
100·00
Now, that land so burnt and containing such ingredients would, after the
process, refuse to grow clovers we cannot at all believe; but we do know
that some of the land of a like composition will not grow even a crop of
turnips until prepared as described; and though the taking a subsequent
barley crop off before the clover would not tend to the improvement of
the latter, it will be too often because the barley has taken all the
available manurial matter, so that there is little left for the clover
to feed upon. In such cases we have seen the clover saved by top
dressing. Paring and burning had also a salutary effect upon the clover
crop in the destruction which it wrought to various insect pests, and
more especially the wire-worm, which now makes such increasing inroads
upon our crops of wheat and barley, and so afterwards in the clover; so
that bare patches, often of great extent, will be the consequence in
every crop in the rotation. Now, these bare patches in the clover crop
are often appealed to as evidence of clover-sickness, whilst we do not
at the same time say that land is wheat-sick or barley-sick.
Insects, indeed, are yearly becoming more destructive, not only on
account of the difference in the mode of farming, but greatly from the
determined destruction of birds. The food of birds is in general very
mixed, but at one season of the year, when they are breeding, they are
most industrious destroyers of insects; but it is just at this time that
they are kept from the crops, exactly when insects are working the most
mischief: hence, then, as the exigencies of a small growing family
become more and more pressing, birds are driven to feed their young upon
seeds, fruits, buds, and other vegetable matters, as unsuitable to build
up the constitution of the young bird as bread diet for an infant.
Let, however, our grand birds of prey be encouraged, instead of being
shot by the keeper as vermin, or knocked over by the prowling
bird-stuffer, in order to be perched up in a box for sale to some
Cockney, who would fain be considered as fond of sport because his
“den,” perchance, contains a stuffed owl, hawk, magpie, or some other
_specimen_.
On a recent visit to Dorsetshire, on our own farm, we saw a man employed
to “keep the birds” from a field where several labourers were engaged
barley sowing; and it is quite true that, unless he had been there, the
rooks would have as industriously followed the drill as they do the
plough; but, as we thought, scarcely to pick up barley in the breeding
season, when there was metal more attractive in the recently-hatched
_Elater obscurus_, parent of the wireworm, which were thicker than we
ever saw them before, and, doubtless, the disturbance of the soil
brought these and two or three generations of wireworms to the surface.
Now, we do not hesitate to give as our opinion that this birdkeeper
would have done more good to the barley and the succeeding clover crop
by picking up a hundred or two of these beetles and destroying them than
by blazing away at rooks for a twelvemonth, and this certainly might
have been done in an hour or two.
Still, that some soils do get incapable of growing a clover crop is
pretty certain; and it may, we think, be equally settled that this does
not entirely depend upon their having been exhausted of the ingredients
which analysis demonstrates clover to contain, for we certainly have
seen clover succeed after the burning of so-called clover-sick land; and
though there is reason to think that this result was partially due to
the setting free of a fresh supply of manurial ingredients, we are still
convinced that the burning out of humus or peaty vegetable matter and
the destruction of insects had their share in the induced change.
Still, however much we may suppose that the failure of the clover crop
is influenced by the alteration of its constitution as the result of
cultivation, the presence of choking weeds, or by the presence of
prejudicial ingredients, especially in thin soils, there can be no doubt
that the principal cause of the difficulty will be found in the fact
that the corn crop with which the clover is grown exhausts the soil, in
the most unsparing manner, of the very chemical ingredients which the
clover requires.
Thus, if sheep are folded on a crop of turnips, the whole of this crop
is converted into a manure at once available for the grain crop, by
which it is quickly appropriated and then taken away. Here, then, we may
suppose at starting that the clover is half starved; and, with a
constitution drawn up in the effort of the plants to obtain a glance of
sunshine, and weakened for the want of nourishment, it is expected to
bear our inclement winters.
This argument will be made all the clearer if we place side by side the
result of the analyses of barley and clovers, and especially if we
consider what a quantity of mineral matter is taken in a short time, and
by a crop ripening its straw and seed.
Now, if we look at these figures we shall see how much of the mineral
matter required for the clover has been previously abstracted by the
barley, and if at the same time we reflect that this robbery may, and
too often does, co-exist with the other causes which we have instanced
as tending to clover-sickness, we should no more call land sick of
clover because it will not bear this crop under our exhaustive system of
cultivation than we should call a barren sand wheat-sick for refusing to
grow corn.
ANALYSES OF BARLEY AND CLOVER.
+----------------------+-----------------++-----------------+
| | PLAYFAIR || WAY. |
| +--------+--------++--------+--------+
| | Barley | Barley || Red | White |
| | Grain. | Straw. || Clover.| Clover.|
+----------------------+--------+--------++--------+--------+
|Silica | 28·97 | 46·30 || 3·34 | 3·68 |
|Phosphoric acid | 35·68 | 3·22 || 6·35 | 11·53 |
|Sulphuric acid | 1·22 | 2·61 || 4·18 | 7·21 |
|Carbonic acid | | || 16·93 | 18·03 |
|Lime | 3·06 | 7·59 || 35·39 | 26·41 |
|Magnesia | 8·04 | 3·55 || 11·22 | 8·15 |
| |and loss|and loss|| | |
|Peroxide of iron | 1·94?| 4·35?|| 0·97 | 1·96 |
|Potash | 15·61 | 22·17 || 14·85 | 14·33 |
|Soda | 5·03 | 0·84 || 1·40 | 3·72 |
|Chloride of sodium | 0·45 | 9·37 || 2·36 | 4·94 |
|Chloride of potassium | | || 2·96 | |
| | ------ | ------ || ----- | ----- |
| | 100·00 | 100·00 || 99·95 | 99·96 |
+----------------------+--------+--------++--------+--------+
We cannot better conclude this chapter than by quoting the following
from Baron Liebig’s _Letters on Modern Agriculture_, so ably translated
by Professor Blyth:—
The simplest peasant has sense enough to see, and all
agriculturists agree with him, that clover, turnips, hay, &c.,
cannot be sold off from a farm without most materially damaging the
cultivation of the corn. Every one willingly admits that the sale
and exportation of clover, turnips, &c., exercise a detrimental
influence on the growing of corn. “Above all, let us take care to
have plenty of fodder; the corn crop will then take care of
itself.” But that the _exportation of corn_ may possibly exercise
an injurious influence on the cultivation of clover or turnips;
that it is, above all, indispensable to restore to the soil the
mineral constituents of the corn, to enable the clover or turnip
crop to “take care of itself;” in other words, that in order to
grow clover, turnip, &c., we must manure the land—this is a notion
utterly incomprehensible, nay absolutely impossible, for most
agriculturists. For, is not the clover grown for the sake of
manure? What advantage, then, would there be if it were necessary
to manure again to produce the clover? _This clover the farmer
expects to grow for nothing._
The mutual relations existing in the order of nature between the
two classes of plants are, however, as clear as daylight. The
mineral constituents of the clover, turnips, &c., and of the corn,
form the conditions for the production of the clover, turnips, &c.,
and of the corn, and they are in their elements quite identical.
The clovers, &c., require for their growth a certain amount of
phosphoric acid, potash, lime, magnesia,—so does the corn. The
mineral constituents contained in the clover are the same as those
in the corn, _plus_ a certain excess of potash, lime, and sulphuric
acid. The clover draws these constituents from the soil; the cereal
plant receives them,—we may so represent it from the clover. In
selling his clover, therefore, the farmer removes from his land the
conditions for the production of corn. If, on the other hand, he
sells his corn, there will be no clover crop in the following year;
_for in his corn he has sold some of the most essential conditions
for the production of a clover crop_.—pp. 183-5.
This discussion, then, upon the so-called clover-sickness leads us to
adopt the following propositions:—
First. That the larger induced plant of our cultivated clovers has not,
as a rule, that perennial constitution of the smaller wild species.
Second. Even its induced habit is much deteriorated by transportation
under adverse climatal circumstances.
Third. The seed itself is often full of weeds, which, by gaining the
mastery, kill out the young clover plant.
Fourth. This effect is enhanced by growing clover with barley, in which,
if not smothered, it must become weakened.
Fifth. We ought not to expect to grow clover where we have taken away
the necessary substances for its growth in the corn crop.