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The Cambridge Manuals of Science and
Literature
THE FERTILITY OF THE SOIL
CAMBRIDGE UNIVERSITY PRESS
C. F. CLAY, Manager
LONDON : FETTER LANE, E.C.4
LONDON : H. K. LEWIS AND CO., Ltd.,
136 Gower Street, W.C. 1
LONDON : WILLIAM WESLEY AND SON,
28 Essex Street, Strand, W.C. 2
NEW YORK : THE MACMILLAN CO.
BOMBAY
CALCUTTA . MACMILLAN AND CO. , Ltd.
MADRAS
TORONTO. : THE MACMILLAN CO. OF
CANADA, Ltd.
TOKYO : M ARUZEN-KABUSHIKI-KAISHA
ALL RIGHTS RESERVED
THE FERTILITY OF
THE SOIL
BY
EDWARD J. RUSSELL
D.SC. (LOND.)
Director of the Rothamsted
Ex^)evitnent Station ". '
Cambridge :
at the University Press
1921
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k
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^Rl
First Edition IQ13
Reprinted 1921
Mil LiJ^fi^y ^Ric, uept;,
ff^it^ the exception of the coat of arms at
the footy the design on the title page is a
reproduction of one used by the earliest known
Cambridge printer y John Siberch, i 5 2 1
PREFACE
fTlHE following pages contain the substance of
-*- talks, lectures and other discourses delivered
before all sorts and conditions of men and women
and in all kinds of meeting places. Sometimes
the listeners were labourers and allotment holders
gathered by the schoolmaster at the close of the
day in the biggest room of the village inn, or in the
adult school on Sunday morning ; sometimes they
were the more polite but not more interested culti-
vators of suburban gardens ; others were farmers
assembled in the market town on market day ; others
again were professed and serious students of agri-
cultural science. But all had this in common: that
they were really keenly interested in the soil they
were cultivating, and wanted to know something
more about it. It is for such readers that this little
book is intended.
E. J. R.
Harpendeit,
July 1913.
SOSS'P'S
CONTENTS
CHAP. PAGE
I. The natural history op the soil ... 1
II. How plant food is made in the soil . . 12
III. What is soil fertility and how may it be
ATTAINED ? 27
IV. Soil fertility and systems of husbandry . 43
V. The raising of the fertility limit ... 64
Vi. The chequered career op the clays . . 86
VII. The rise op the sands 101
VIII. The moor— what shall it become? . . .119
IX. Conclusion 124
Bibliography 126
Index .127
LIST OF ILLUSTRATIONS
FIG.
1. Crops gi'own on partially sterilised soils
2« and 2&. Experiments with Rock Phosphate,
Illinois (Dr Cyril Hopkins) ....
3. The Wilderness, Rothamsted (Dr H. B.
Hutchinson)
4. Reclaimed Feniand (Mr E. R. Dixon) .
5. Taking levels for di*aining in Puritan times .
6. Chalking in Hertfordshire (Dr H. B. Hutchinson)
7. Ridged land on the clay (Mr H. Cranfield) .
8. Coxheath, near Maidstone ....
9. Pot Culture house at Rothamsted , , .
to face
p. 26
M
47
1»
65
yy
72
«
76
»
82
»
90
)}
110
M
126
CHAPTER I
THE NATURAL HISTORY OF THE SOIL
To those who have nevel^ thought about the matter
the study of the soil may st?em very tnviiil;vit has
neither the glory of the celestial nor the glamour of
the unfamiliar ; it is associated with such unintel-
lectual and mundane concerns as food production,
and has no place in our ordinary conception of a
refined and liberal education.
But the soil has not always been looked upon as
commonplace. In the mythology of Greece it held
a very dignified position, the Goddess Gaea being the
mother of mankind and the bounteous provider of
food. Right through into much later times tliis idea
of the kindly Mother Earth can be traced, and even
to-day the reflective gardener takes more than a
utilitarian interest in his soil. And the light of
Science more than justifies this interest, for it has
shown that the soil is far more wonderful than any
human mind had ever pictured it.
In trying to trace out the history of a lump of
soil we must go back to those remote times when the
R. 1
2 THE FERTILITY OF THE SOIL [CH.
earth was first cool enough to allow a solid crust to
form. When the water began to fall some of it
soaked into the chinks and crannies of this crust, and
by its expansion and contraction with change of
temperature caused fragments to split off from the
main rock. Other agencies were also effecting the
same end, and in course of time a great quantity of
this dismtograted vc>ck matter was formed. The
particles did not remain where they were, but were
carried l>y wind or water into the valleys and streams
and many found their way to the bottom ot the sea.
Here they mingled with the residues of plants and
animals, and the whole mass became consolidated.
Later on, when earth movements changed the course
of the waters and the old sea became dry land, this
consolidated material appeared as new rock and went
again through the processes of disintegration and
erosion. For a long period the surface of England
north of the Thames, and of Canada and the northern
part of the United States, was covered with ice which
pounded up and carried away many of the particles,
depositing them again when it melted. When the
particles were lying on the dry land they were subject
to the constant washing of the rain, the oxidising
effect of the atmosphere, and the shattering effect
of changing temperature, processes collectively known
as weathering. Ever since the particles first split off
from the original rock they have been exposed to
I] NATURAL HISTORY OF THE SOIL 3
these continuous disintegi'ating processes. But the
action of these processes is exceedingly slow, or the
particles would have disappeared entirely, or have
become reduced to an impalpable dust. The fact
that they survived proves them to be very resistant
and indicates that they are not likely to undergo any
appreciable change during the short period of time
that interests the agriculturalist. Over longer periods
of time, however, the different particles show different
degrees of resistance, the most resistant being the
grains of quartz and the least resistant the more
complex combinations of silica and oxides of iron,
aluminium, potassium and other metals. The latter
have therefore suffered more than the quartz and
have been reduced to much finer dimensions. Thus
if a soil is separated out by mechanical analysis into
portions, the particles of which fall within certain
definite limits of size, it will be found that the
coarsest particles of all — the stones and gravel —
represent complex rock material, the coarse particles
of the fine earth (the so-called coarse sand, fine sand
and silt) are practically pure silica, while the finest
particles (the clay and to a less extent the fine silt)
contain not only silica, but oxides of iron, aluminium
and of other metals as well. Further, the top 8 inches
of soil that has been exposed to weathering processes
for very long periods of time contains practically as
much coarse material (silica) as the subsoil which has
1—2
4 THE FERTILITY OF THE SOIL [CH.
been shielded from these actions, but it contains
markedly less of the finest material.
These particles constitute the chief portion of the
soil and may be regarded as the framework round
which the soil is built. They show, however, certain
differences which are of fundamental importance to
the subject. The sands and fine silt, being formed of
the silica, are chemically inert and practically un-
alterable under natural conditions except that they
may very slowly be reduced in size by weathering
processes. The finer material, on the other hand, is
chemically active and may not only undergo chemical
changes, but may enter into reaction with various
substances ; it is not a single definite compound like
the silica, however, and cannot be represented by any
chemical formula. It possesses other properties that
mark it off very sharply from the coarse material.
It absorbs a considerable amount of water, swelling
up very much during the process ; conversely when
it dries it shrinks a good deal. In its wet state it is
very sticky, when dry it is very hard. It undergoes
a remarkable change after treatment with traces of
acids or of salts, notably calcium carbonate, and
becomes less sticky and more easily crumbled. All
these properties are readily observed in a clay field
where much of this fine material is present : the
persistent wetness of the soil, its stickiness, the large
gaping cracks that form during its contraction on
I] NATURAL HISTORY OF THE SOIL 5
drying and the hard clots that result, its marked
alteration after treatment with lime, are aU mani-
festations of the special properties of the fine material.
These properties are characteristic of the jelly-like
condition, technically known as the colloidal state,
into which many substances can be brought.
These properties are not shown by the coarse
material ; a sandy soil (in which the coarse particles
predominate and the fine particles do not form more
than 5 — 10 7o of the whole) has no great power of
absorbing water and therefore readily dries, it is not
sticky, does not shrink on drying or form hard clods,
and undergoes no obvious physical change after
treatment with lime.
It must not be supposed that any hard and fast
line can be drawn between the coarse sand material
and the fine clay. One shades ofi* imperceptibly into
the other, and so gradual is the transition that the
special name silt is used to designate the intervening
materiaL The lines separating sand from silt on the
one hand and silt from clay on the other are purely
conventional and are agreed upon by soil chemists
in each country, but unfortunately no two countries
accept quite the same definitions. In Great Britain
clay is defined as any material the particles of which
are less than '002 mm. in diameter (y^Vcio i°-) ^^^
silt as any material the particles of which are above
this but below '04 mm. in diameter (q-^-^ in.) : in the
6 THE FERTIIJTY OF THE SOIL [cH.
United States, however, the limits are '005 mm.
(s^Vt) in.) and '05 mm. (^^^ in.) respectively.
A second group of soil constituents includes those
derived from the organisms deposited along with the
mineral particles while they lay under water. Of
these the most important is calcium carbonate, the
substance of which chalk and limestone are composed,
and into which lime rapidly changes when added to
the soil. As we shall see later on it plays an extremely
important part in the soil, and profoundly influences
the fertility and the vegetation relationships. It
difiers from the substances already described in that
it dissolves somewhat in the soil water, and notable
quantities are washed out, amounting at Rothamsted
to about 800 lbs. per acre per annum.
Calcium phosphate also belongs to this group,
although some is derived fi'om rock. It commonly
occurs only to a small extent, but it is an indis-
pensable food for plants and therefore essential to
fertility.
These two gi'oups of inorganic substances — the
silica and complex silicates derived from the rocks,
and the calcium carbonate and phosphate derived
in part from organisms that once have lived — do not
form the complete soil. A third constituent is present,
the so-called organic matter, derived from previous
generations of plants. It is a familiar observation
that no ordinary soil remains long without a covering
I] NATURAL HISTORY OF THE SOIL 7
of some sort of vegetation. As this dies its residues
mingle with the mineral particles, being carried in by
earthworms and various insects. The effect of this
addition is very great. In the first place it profoundly
influences the amount of plant food in the soil. The
first vegetation that sprang up must obviously have
got its food — its calcium and potassium salts, phos-
phates, etc. — from the mineral particles, but new
sources of food appear for the plants that come after.
The first crop slowly decayed under influences we
shall deal with later on, and in decaying it set free
those substances that its roots had taken as food and
returned them again to the soil. Hence subsequent
plants have food from two sources : the potassium
salts, etc. dissolved by the soil water from the soil
particles ; and in addition a supply of the same
substances drawn by previous generations from the
soil during their lifetime, but afterwards set free on
the decay of the dead tissues. The plant food, in
fact, keeps circulating between the soil and the plant,
and the organic matter constitutes the medium by
which the circulation is completed.
The second effect of the organic matter is even
more important. During its lifetime the plant has
been making a good deal of the substance of its
leaves and stems from the gases of the air and the
rain water, and the materials thus formed contain
stored up energy derived from the sunlight. When
8 THE FERTILITY OF THE SOIL [CH.
they mingle with the soil and begin to decay the
energy is liberated in the form of heat, and by the
time they are completely decayed they have given
out just as much heat as if they had been burned in
a bonfire. The original heap of mineral matter
contained no easily available store of energy ; the
mixture of mineral matter and plant residues on the
other hand does. The consequence of this addition
is very profound : life is now possible in the soil, and
there springs up a vast population of living creatures
all drawing on this accumulated store of energy,
flourishing so long as it holds out, and dying off when
it is exhausted.
In our climate, and in humid climates generally,
the decay of the plant residues is not complete, at
any rate during the course of a few seasons, and some
of the products accumulate as dark brown or black
substances conveniently kno^vn by one name, humus.
These substances have certain physical properties
which they impart to the soil ; they are sticky,
they absorb and retain water, they swell when wet
and shrink when dry. In other words they are
colloids. Thus the third effect of organic matter on
the soil is to increase the amount of colloidal material,
but some of this is of entirely different character
from that already present. By far the most significant
of these effects, however, is the bringing in of stores
of energy because this constitutes the vital distinction
I] NATURAL HISTORY OF THE SOIL 9
between a heap of mineral matter and a soil. There
is no soil without life, and no life is possible without
stored up energy. We are only beginning to know
what this soil life is, but already some hundreds of
different kinds of creature have been found. Some
few are large enough to be seen. Of these the most
important are the earthworms, which burrow in the
soil and effect a fine natural cultivation, letting in air
and drawing in leaves, stems, and other vegetable
debris from the surface to mingle with the mass of
soil below. Most of the soil organisms are micro-
scopic in size ; some lead an active life, others are
in the inert resting stage and are called spores or
cysts. The very incomplete census taken so far
shows that the numbers of micro-organisms living
in a single salt-spoon full of soil must be reckoned
in millions.
Some of these organisms — certain bacteria — play
a controlling part in soil fertility because they bring
about the decay of the plant residues and consequent
liberation of plant food. Out of the old dead plants,
in fact, they make food for new ones. Thus the new
generation of plants is dependent on them, just as
they in turn are dependent on the past generations
of plants. As more and more knowledge is gained
the circle of soil life widens out and other varieties
of organisms are seen to come in, interacting one on
the other, not all making plant food, but all dependent
10 THE FERTILITY OF THE SOIL [CH.
in the last instance on the energy stored up in the
organic matter, in other words, on sunshine that was
caught years ago by plants long since dead.
Tliere is reason to suppose that the four gi'eat
constituents of the soil — the inert fragments of sand,
the reactive clay, the calcium carbonate and the
organic matter — are not merely lying alongside of one
another in the soil. The evidence indicates that the
colloidal constituents form a jelly-like coating over
the inert particles, and this jelly contains much of
the food of plants and of bacteria ; it may be likened
to the nutrient jelly of the bacteriologist.
The soil mass is not solid throughout but is full
of pores like a sponge. In a compact arable soil not
more than 60 — 70 Vo of the volume is soil material,
the remaining 30 or 40 % being empty space ; in
a pasture soil the proportion of empty space is even
greater. This pore space is at times completely filled
with water, but more usually air is also present : at
Rothamsted often to the extent of 10 % of the volume,
leaving 25 Yo filled with water. The water is not
pure but contains in solution carbonic acid, nitrates,
carbonates and other salts of calcium, magnesium,
etc. ; it is held in the soil partly by surface attractions
and partly by the colloids.
We may thus think of the soil as a porous mass
made up of a hard framework plastered over with
a jelly containing chemically active substances, plant
I] NATURAL HISTORY OF THE SOIL 11
foods, and unstable organic compounds rich in stores
of easily liberated energy, while the pores contain air
and a considerable amount of water.
Into the pores of this mass we have no means of
penetrating : no microscope has been devised that
enables us to look into it and see what is going on.
We have indirect but incontrovertible evidence, how-
ever, that it is full of life and that the soil is inhabited
by myriads of organisms of very varied kind, some of
which, like eel-worms, are easily visible with a small
microscope, while others, like bacteria, require a high
power to reveal their presence. They bring about
decay, and thus clear away the residues of previous
plants leaving the soil clear for a new race. They do
even more : they make the old plant material into
new plant food. There are signs of conflicting and
competing groups of organisms, but all at any rate
have this in common : that they are dependent abso-
lutely and entirely on the organic matter of the soil.
In its main outlines this conception of the soil
is probably correct, and every month adds to our
knowledge of the details. But the picture is still
far from complete and it does not enable us to
explain all the facts about the soil that have been
gleaned by good farmers and gardeners. Each im-
portant discovery that is made opens out a wider
field for exploration, and we may be certain that we
never shall know all about the soil.
12 THE FERTILITY OF THE SOIL [cH.
We shall find the study of the soil very unsatisfying
and uninspiring if we become too much absorbed in
its utilitarian aspects and forget to stop and reflect
on the infinite wonder of its honeycombed structure
and its dark recesses, inhabited by a teeming popu-
lation so near to us and yet so hopelessly beyond our
ken that we can only form the dimmest picture of
what the inhabitants are like and how they live.
CHAPTER II
HOW PLANT FOOD IS MADE IN THE SOIL
By far the greater part of the food of the plant
comes from the atmosphere : oxygen, carbon dioxide
and water between them furnish most of the material
out of which the plant is built. But it was discovered
long ago that something is taken from the soil, and
that this part, although small, is absolutely indis-
pensable to the growth of the plant. The food thus
furnished by the soil is really composed of a number
of substances, the most important of which are nitrates,
phosphates and other salts of potassium, calcium,
magnesium, sodium, etc. It is convenient to divide
these into two groups, the nitrogenous group, such
II] THE SOIL AND PLANT FOOD 13
as the nitrates, and the mineral group, inchiding
the phosphates, etc. of potassium and other metals.
There is good ground for the distinction. The nitrates
are derived almost exclusively from organic matter,
but the mineral food, on the other hand, comes
partly from the rock material of the soil. Further,
the nitrates are easily soluble in water, and, there-
fore, readily washed away ; they are, besides, liable
to other sources of loss, while the mineral food only
suffers slight losses. Lastly — and this aspect cannot
be overlooked in a technical subject like ours —
nitrates and other nitrogenous foods are by far the
most expensive when any purchasing has to be done.
In trying to find out how plant food is made in
the soil, investigators have confined themselves almost
exclusively to the nitrogenous portion. This re-
striction was forced on the earlier workers by the
circumstance that our soils stand much in need of
nitrogenous manure: very much of the Rothamsted
work has been and still is devoted to the study of
the nitrogen problem, and a large part of our present
knowledge is built up on the foundations laid by
Lawes, Gilbert and Warington. We also must be
content to accept the restriction, and pass over any
changes which the mineral food may undergo, for
the very good reason that we know so little about
them.
It was early discovered that the plant residues
14 THE FERTILITY OF THE SOIL [ch.
or farm-yard manure (which is essentially the same
thing) added to the soil are not the actual food of
plants, but only the raw materials out of which food
is made. The true food is the nitrate to which the
organic matter gives rise, and our first business is with
this.
O^ing to the losses which the nitrate sufiers there
is rarely any great stock of it in the soil, frequently
not enough for the current season's growth. For-
tunately the process of nitrate production, commonly
called nitrification, goes on fairly readily so that fresh
supplies are forthcoming whenever the conditions are
suitable. The process has turned out to be very
wonderful. It was formerly supposed to be entirely
chemical, but a remarkable piece of work by Schloes-
ing and Miintz in 1877 showed that it was brought
about by bacteria. In studying the purification of
sewage by land filters they caused a stream of sewage
to trickle slowly down a column of sand and lime-
stone, the experiment being continued for some weeks.
For the first 20 days the ammonia in the sewage
remained unaltered, then it began to change into
nitrate, and finally the issuing liquid contained no
ammonia but only nitrate. Why, asked the authors,
was there this delay of 20 days before nitrifica-
tion began ? If the process were a purely chemical
oxidation it should begin at once. If, however, it
were bacterial, they could readily explain the delay,
II] THE SOIL AND PLANT FOOD 15
because the organisms would have to grow. To test
this hypothesis they added a little chloroform vapour
and found that nitrification was stopped entirely : it
could, however, be started again by adding a little
turbid extract of fresh soil after the chloroform was
removed. They concluded, therefore, that nitrifica-
tion was the work of "organised ferments." More
rigid proof was afforded by Waring-ton and later on
by Winogradsky.
More recent experiments render it highly impro-
bable that any chemical or physical process going on
in the soil gives rise to nitrates, and we may take it
that their production is entirely bacterial. Warington
showed that the process takes place in two stages ;
the ammonia is first converted into nitrites by one
organism, and the nitrite is then changed to nitrates
by another organism. Nobody has yet succeeded in
finding any third stage between ammonia and nitrites
although one might be expected on chemical grounds.
There is practically no waste of ammonia during the
process, and the conversion is almost if not entirely
complete, but its mechanism is not at all understood
and it cannot be reproduced artificially.
The organisms which alone can bring it about are
utterly unlike any others and completely baffled the
earlier investigators. Bacteriologists usually grow
their organisms on gelatine or some similar medium.
But this plan invariably failed to bring out the
16 THE FERTILITY OF THE SOIL [CH.
nitrifying bacteria, and it was not till Winogradsky in
1891 hit on the brilliant idea of using a jelly of silica,
that they were grown and studied. Both organisms
are extremely small — they are, in fact, the smallest
known in the soil. Unlike the others they do not
require organic matter as food, they make their own
supply from carbonates or, like plants, from carbon
dioxide. But unlike plants they do not want sun-
light for this purpose, indeed sunlight kills them.
Where, then, do they get their energy from ? Wino-
gradsky adduced very strong evidence, which has
never been disproved, that the energy comes from
oxidation of ammonia : he found a definite relation-
ship between the amount of ammonia oxidised and
the amount of carbon assimilated. It appears that
ammonia is the only compound they can utilise.
Many other substances have been tried, but without
results, and we can take it as proved, as well as any
negative proposition can be proved, that ammonia is
the only substance from which nitrates are made,
and that all the nitrate we find in the soil has pre-
viously been ammonia. This conclusion is very im-
portant and leads us to look for ammonia in the soil.
But in no arable soil yet examined has more than
a trace been discovered at any time of the year. We
must, therefore, conclude that the rate at which
ammonia is oxidised to nitrite is greater than the
rate at which it is formed. But nitrites are never
II] THE SOIL AND PLANT FOOD 17
found in normal soils. It therefore follows that the
rate at which nitrites are oxidised is greater than
the rate at which they are formed.
We have, then, three reactions going on :
Nitrogenous plant residues change to ammonia,
Ammonia changes to nitrite.
Nitrite changes to nitrate.
Of these the last is the quickest, the second is slower
and the first is slowest. The first change, therefore,
limits the rate at which nitrates are produced : if we
could speed up this change we should hasten the
others.
Further, the quickest change (the third) is most
susceptible to external influences. Tlie organisms
are very sensitive, they are more easily kiUed than
the rest and they stop working more readily. Am-
monia producers, on the other hand, are very re-
sistant and will tolerate somewhat rough treatment.
All three compounds, ammonia, nitrites and nitrates
can be used as plant food, but in normal conditions
the plant does not get the chance of using anything
but nitrates, the other two being only transitory
products.
Four important facts have thus been established
with regard to nitrification :
(1) Ammonia is changed to nitrite and this is
then changed into nitrate in the soil, the conversion
being almost completa
R. 2
18 THE FERTILITY OF THE SOIL [CH.
(2) Nitrates are formigd from ammonia alone,
and not from any other substance so far as is known.
(3) Nitrate production is the quickest of all
the chain of processes.
(4) The quickest acting organisms seem to be
the most sensitive.
We now turn to the formation of ammonia. This
has not proved so attractive a subject for investiga-
tion and we do not yet know much about it. Unlike
nitrification it is not a specific property of any one
organism, but is effected by many different kinds : it
is not even confined to bacteria, but goes on in a
vacuum or in presence of antiseptics. But it will not
go on after the soil has been heated to 150°, whence
we may conclude that one of those accelerating agents
technically known as enzymes is also at work. It is
difficult to say precisely how much of the decom-
position is due to enzymes free in the soil and how
much to micro-organisms, but it seems certain that
the latter are by far the most potent agents. No one
has yet gone further back in the chain to discover
the compound antecedent to ammonia. The initial
compound is the nitrogenous part of the plant re-
sidues or of the substances added as manures, and
is generally of a protein nature : enzymes, earth-
worms, fungi and bacteria may all take part in its
decomposition ; we may suppose that its conversion
II] THE SOIL AND PLANT FOOD 19
into ammonia will go on in substantially the same
way in the soil as it would elsewhere : but there is no
definite evidence in proof.
The nitrogen compounds of the soil, however, are
not entirely changed into nitrates: a second action
takes place that is not in the least degree understood.
When protein and other nitrogenous plant compounds
are decomposed by micro-organisms in presence of
air there frequently appears to be a large amount of
gaseous nitrogen given off, especially when much
organic matter is present. This change has been
very little studied and indeed is commonly confused
with another that appears to be wholly distinct —
the so-called denitrification, a reduction of nitrates
brought about by certain bacteria in presence of
organic matter, but in ahse^ice of air. Whatever
its nature it leads to gi-eat losses in rich or heavily
manured soils, and is responsible for much of the
exhaustion of virgin soils that is now going on at an
appalling rate. One of the most pressing problems
before the agricultural chemist is to study these two
sets of reactions, and in particular to find out
whether this wasteful process cannot be suppressed,
so that a larger part of the nitrogen compounds
shall change into the useful nitrates. In modern
farming nitrogenous manures are by far the most
expensive, and profits are cut so low that all sources
of loss are to be avoided as far as possible. Both
2—2
20 THE FERTILITY OF THE SOIL [ch.
these actions, the formation of nitrates as well as the
loss of nitrogen, tend to use up the nitrogen com-
pounds of the soil, because the nitrates not taken
by the plant are speedily washed away and lost in
the rivers and the sea. As the original stock was
probably never high, it is clear that there must be
some reverse process by which the soil gains nitrogen,
or the supply would long since have given out This
has long been realised by men of science, and a
careful and systematic search begun 30 years ago was
ultimately rewarded by the discovery of two ways in
which such a gain takes place.
The old-established cultivator of the land has a
great stock of information about the ways of plants ;
some of it is disconnected and fragmentary, but it
has to be sorted over and examined experimentally
by the man of science. One of the old bits of know-
ledge handed down from time immemorial, and
already traditional when Virgil wrote his Georgics,
was that beans, vetches, and lupins improve the land
for the next crop. Sow your golden corn, says Virgil,
on land where grew the bean, the slender vetch
or the fragile stalks of the bitter lupin \ When
Lawes and Gilbert began their experiments in 1843
one of the early problems was to discover the reason
for this improvement, and they were able to trace it
to the fact that a soil was richer in nitrogen after the
1 Georgics, Book i, lines 73 et seq.
II] THE SOIL AND PLANT FOOD 21
growth of clover than before. Somehow or other
the amount of nitrogenous food in the soil had in-
creased. But no one could give any satisfactory
explanation icliy the nitrogen should increase, and it
was not until 1886 that the solution was found. The
story is so interesting that it must be told again,
although it has often been told before.
Hellriegel and Wilfarth, two distinguished in-
vestigators at the Experiment Station at Dahme, in
Prussia, were studying the eflfect of nitrates on plant
growth and found that the amount of growth of
cereals like barley, oats, etc., increased as the nitrate
supply increased and was, in fact, directly propor-
tional to the amount of nitrate. In the case of lupins
and allied plants, however, no sort of proportionaHty
could be traced, the plants sometimes did as well
or better without nitrate as with it, but sometimes
failed altogether. Further, chemical analysis showed
that the quantity of nitrogen present in the cereal
crops was just about the same as that supplied,
while the quantity present in those peas which made
any growth was much greater. It followed, there-
fore, that these peas had got some of their nitrogen
from the air. But why had not all the peas done so ?
Hellriegel and Wilfarth argued that the success of
the process must depend on something that only
came into the experiment by chance. At that time
men had bacteria very much in their minds because
22 THE FERTILITY OF THE SOIL [CH.
of certain wonderful discoveries that had recently
been made. Hellriegel and Wilfarth, therefore, very
naturally asked if bacteria could be the active agents
here, particularly as they knew that the little swell-
ings on the roots of the pea — the so-called nodules —
contained bacteria, and also that some bacteria could
take in gaseous nitrogen and use it To test the
matter peas were sown in sterilised sand (i.e. sand
baked so as to kill all living organisms), containing
mineral food, but no nitrogenous food; these made
little or no growth and developed no nodules in the
roots. Other peas were also sown in similar sand,
but they received a water extract of ordinary arable
soil ; these made excellent growth and had a marked
development of root nodules. If, however, the ex-
tract was first boiled it had no effect in increasing
growth.
These experiments afforded satisfactory evidence
that the pea could form an association with certain
bacteria which should be self-supporting so far as
nitrogen was concerned in that it could draw on the
immense stores of free nitrogen in the air. The
proof was made more rigorous by other and later
workers, and the proposition is now one of the most
definitely established in modern science.
Thus peas, vetches, lupins, and, we can add, beans,
clover, lucerne, sainfoin, in short all the tribe of the
leguminosae, take in stores of nitrogen from the
iij THE SOIL AND PLANT FOOD 23
atmosphere through their association with the bac-
teria of the root nodules. When their roots, leaves
or stems perish and mingle with the soil these newly-
furnished nitrogen compounds are added to the
general stock already there.
A few years later another set of bacteria was
found able to take in and use the free nitrogen of
the air, differing from the preceding in that they
work on their own account and do not form associa-
tions with plants. The earliest to be discovered was
Clostridium, but interest has centred largely round a
later find, Azotobacter, because it works in presence
of air and not, as happens with certain other organ-
isms, in its absence.
The more one studies these nitrogen-fixing or-
ganisms the more remarkable do they appear. The
absorption of gaseous oxygen by living organisms and
the changes it brings about can be paralleled more
or less closely by artificial processes in the laboratory.
But the absorption of gaseous nitrogen by these
particular organisms cannot be imitated in the
laboratory and is without parallel in our experience.
A source of energy is needed, and a considerable
number of substances are known to serve, including
sugar, starch, cellulose, or residues of plants. As the
organisms are very widely distributed they may be
expected to operate wherever supplies of easily de-
composable organic matter are present in the soil,
24 THE FERTILITY OF THE SOIL [CH.
e.g. wherever vegetation is allowed to die back. It
has been found by actual measurement at Rothamsted
that nitrogen does accumulate in soil left to run wild
and to cover itself with the varied assortment of
plants cropping up in these conditions. How much
of this is due to Azotobacter is not certain, because
leguminous plants occur among the herbage and fix
an unknown quantity of nitrogen.
The organisms that we have been considering
represent the constructive agencies in the nitrogen
cycle in the soil, bringing in new supplies from the
air and so making good the losses already discussed.
It is necessary to remember — this point will con-
stantly recur in future chapters — that these con-
structive processes only manifest themselves in soils
covered with permanent vegetation such as grass-
land, woodland, etc. One exception only is known,
viz. where a leguminous crop is growing, when the
amount of nitrogen fixed may be considerable. With
this exception one general rule holds : losses of
nitrogen preponderate on soil that is cultivated, and
gains of nitrogen preponderate on soils covered with
permanent vegetation. In either case the action
does not go on indefinitely: the losses become less
and less as the soil becomes poorer, till finally they
are so small that it is difficult to detect them, and
the gains also become less and less as the soil be-
comes richer, till finally they also cease or are
n]
THE SOIL AND PLANT FOOD
25
balanced by losses. Thus limits are finally reached,
and no soil becomes absolutely destitute of nitrogen
or very rich in it; few, if any, of our British soils
(leaving out sand dunes and peat bogs, which are not
true soils) contain less than 0'05 per cent, or more
than 1*0 per cent, of nitrogen.
We may summarise the changes of the nitrogen
compounds of the soil in diagram form thus:
Nitrogen
The conversion of the complex nitrogen compounds
into nitrates is the process whereby plant food is
made, and the fixation of gaseous nitrogen is the
means whereby the stock of nitrogen compounds is
maintained. Both these are obviously indispensable
to plant growth and to the fertility of the soil. The
other change, the evolution of gaseous nitrogen from
complex nitrogenous compounds, appears on our
present knowledge to be sheer waste and to serve
26 THE FERTILITY OF THE SOIL [ch.
no useful purpose whatsoever. AVhether or not
further knowledge will show that it is really an
essential part of the scheme we cannot say ; our en-
deavour now is to reduce it as much as possible.
More recent investigations made at Rothamsted
and elsewhere have brought out the striking fact that
conditions which are injurious to active life in the
soil often bring about increases in the numbers
of bacteria and in productiveness, while conditions
favourable to active life often lead to decreases in
bacterial numbers and in productiveness.
This apparent paradox was solved by showing that
two groups of organisms occur in the soil : the useful
makers of plant food, and another set detrimental to
them but, fortunately, more easily killed and slower
in multiplying. When adverse conditions appear the
detrimental forms suffer more than the useful forms :
thus long severe frost, hot dry summer, heat, treat-
ment with mild poisons that can subsequently be
removed, all put them out of action temporarily, if
not permanently, and so lead to greater bacterial
activity and greater productiveness. The detrimental
forms are provisionally identified with the protozoa
in the soil, of which numbers have now been found.
Untreated
Partially
Partially
soil
sterilised
sterilised
by toluol
by heat
^i >i :•.
rartially sterilised
by toluol
Untreated
soil
Partially sterilisei
by carbon
disulpbide
Fig. 1. Crops grown on untreated and on partially sterilised soil
iiij FERTILITY FACTORS 27
CHAPTER III
WHAT IS SOIL FERTILITY AND HOW MAY IT
BE ATTAINED?
The relation between the soil and the plant is
not entirely simple, and in consequence no rigid
definition of soil fertility can be given. Any par-
ticular soil would probably prove very fertile for one
at least of all the thousands of plants in existence,
but if it were useless for ordinary agricultural and
horticultural purposes it would generally be called
barren. A fertile soil may be described as one in
which the conditions are favourable for the growth of
plants useful to man.
Six requirements are necessary for the plant :
water, air, temperature, food, root room, and absence
of harmful factors. We must now briefly discuss
these in their relation to the soil.
Water supply. The soil receives water from the
rain and from the subsoil, but it also loses water
by evaporation and drainage. The actual amount
present in the soil at any time therefore depends
on several factors as it obviously represents the
balance of gains over losses. The amount of rain-
fall is important, but its distribution is even more
28 THE FERTILITY OF THE SOIL [ch.
so, in determining the amount reaching the soil
(heavy rains being liable to run off the surface while
lighter rains soak in), and the temperature and
wind are great factors in determining how much
stays there. February is one of the driest months
so far as actual rainfall goes, but no one who lives in
the country need be reminded how persistently wet
the gi'ound generally is then. August, on the other
hand, is one of the wettest months, but the soil is
usually dry. Equally important factors are the nature
of the surface soil, which determines how much of
the rain percolates ; the position of the soil in respect
of the surrounding land — whether high or low lying —
and the nature of the subsoil, which regulate the flow
of the underground water.
A defective water supply may therefore be either
the fault of the soil or its misfortune. Too much
clay or peaty organic matter may render the soil
impervious to rain and so cause it to lie waterlogged,
while too much coarse sand or chalk may keep it so
open that water rapidly drains away or evaporates ;
in all these cases the soil is to blame. On the other
hand, the very best soils may remain stagnant marshes
if they occupy low-lying ground on which water
drains from the hills without finding an outlet; or
they may suffer badly from drought if they are
spread out thinly on beds of gravel or of rock. The
stagnant marsh may be drained and the soil soon
Ill] WATER SUPPLY 29
reveals its true nature ; the rock, if thin enough, may
be broken or removed; but the thinly spread soil
on a gravel bed is beyond our present powers of
treatment.
When the cultivator has any reason to doubt the
eflBciency of the water supply to his plants he must
first ascertain whether the fault is in the soil or its
surroundings. The bad effects of too much clay may
be modified by liming, chalking, or drainage; exces-
sive sand may be counteracted by additions of clay
or silt or by ploughing in organic manures and green
crops. In all cases the water supply is improved by
extending the range over which the roots may grow,
for the larger the volume of soil on which the plant
draws the less will be the amount of water required
from each portion. And so if any obstacle exists to
the development of the roots it must be removed;
the soil must be dug or ploughed more deeply and,
in a garden, manure must be added to the lower spit ;
any pan or thin rock layer must be broken up and
removed ; and stagnant soil water must be prevented
from rising too high by tapping the springs or by
laying deep drains \ A good deal can be done by
skilful cultivation to check evaporation and thus
reduce the loss of water. A fine layer of soil on the
surface effectually shields the rest of the soil from
the sun's heat and keeps the moisture safe from loss.
1 See p. 78.
30 THE FERTILITY OF THE SOIL [ch.
The constant use of the hoe in the garden reduces
considerably the need for watering, and many a good
gardener will declare that "the hoe is the best water-
ing can." In dry regions the disk-cultivators are
brought out as soon as possible after a shower so
as to break up any crust that may have formed on
the arable land and restore the protective coating of
fine soil.
Air supply. The harm that results from a water-
logged soil is not due to the excess of water but to
the exclusion of air. The plant roots and the food-
making bacteria alike need air, and air must there-
fore be allowed access to all parts of the soil. Once
the excess of water goes the air comes in: such
devices as liming a clay soil, lajdng drains, and break-
ing a pan, therefore have the effect of improving not
only the water supply but the air supply as well.
Temperature. The heat relationships of a soil are
also intimately bound up with the water content. Its
mean temperature is of course directly dependent on
its location, and does not differ gi^eatly from that of
the atmosphere. The top half inch of soil is hotter
than the air in direct sunshine and colder by night :
a little below the surface the fluctuation is no greater
than in the air, while six inches below it is much less.
Heat only travels slowly through dry soil and does
not affect the subsoil till some time after it has
reached the surface. But it travels more quickly
Ill] TEMPERATURE 31
through moist soil ; there is less lag in transmission
and hence less accumulation of heat in the top layers.
Dry soils are therefore hotter at the surface in sunny
weather, but moist soils are the more uniform in
temperature. April showers do much to warm the
subsoil by setting up heat communication with the
surface and enabling the warmth of the sunshine to
travel down ; on the other hand, winter rains cool the
subsoil by letting out the heat stored up there.
Another important factor is the difference in specific
heats: water requires five times as much heat to
raise its temperature through 1° as does dry soil, so
that a given quantity of sunshine is less able to raise
the temperature of a wet than of a dry soil.
Besides these factors concerned in the warming
of the soil there is another that has the effect of
cooling it. Heat is required for the evaporation of
water, and in consequence the soil is cooled when any
of its moisture dries off.
Several devices may be adopted in warming the
soil. The heat received may be concentrated on
certain parts of the soil by laying it up in ridges
running E. and W. and therefore facing S. The
amount retained (for some is always reflected back
into space and lost) is increased by dressing with
a layer of black material, soot being the most con-
venient. Tlie effectiveness of the heat received is
increased by draining away any excess of water.
32 THE FERTILITY OF THE SOIL [CH.
Finally the losses may be reduced by checking evapo-
ration, and this can be done by sheltering from the
wind with windbreaks or hedges and by maintaining
the fine tilth at the surface. Horticulturists some-
times adopt all these, agriculturalists sometimes only
one or two.
Food supply. The supply of plant food in the
soil depends in the first instance on its mineral
composition. The great mass of inert material that
constitutes the framework of the soil and subsoil
affords but little food. The food constituents are to
be sought among the more soluble and reactive
substances, and, in some way that is not sufficiently
understood, their availability is increased when calcium
carbonate is present. A second factor, the accumu-
lation of plant residues, began to come into play
soon after the soil was formed and has in some
cases assumed so much importance that it now con-
trols the situation. And, as plant residues are not
themselves plant food, but have to be converted by
micro-organisms into simpler substances, we can add
as a third factor the activity of the food-making
organisms.
It is a simple matter to increase the supply of
plant food by adding fertilisers to the soil. The
amount of nitrogen may be increased by adding
nitrate of soda, sulphate of ammonia, organic sub-
stances such as farmyard manure, guanos, certain
Ill] FOOD SUPPLY 33
manufacturers' waste products, etc. or by gi'owing
leguminous crops. Since the loss of nitrogen is con-
siderable recourse must often be had to one of
these methods, and grave doubts have at times been
expressed as to how long the world's supply of
nitrogen compounds would last. Of late years, how-
ever, it has been found practicable to make nitrogen
compounds from the inexhaustible stock of nitrogen
in the air; the world's supply of nitrogen manures
can therefore be increased whenever necessary, and
the dreaded nitrogen famine has been relegated to
the time when the energy supply shall give out.
Phosphates are supplied in the form of bones,
guanos, basic slag and rock phosphate. Most soils
contain insufficient to satisfy the large crops pro-
duced by the modern farmer; frequent additions
are therefore necessary, especially under conditions
of high farming. The losses are not as serious as
those of nitrogen. There is practically no washing
out; the agricultural chemist can still detect the
phosphates added to the lands round the cities of
ancient Egypt. Nevertheless there is a steady and
continuous loss in the crops which has to be made
good. There is no way of adding a single ounce to
the world's stock of phosphorus compounds, and this
is being drawn upon even now to the extent of some
millions of tons each year, while the demand increases
steadily as time goes on. If some day the supply
R. 3
34 THE FERTILITY OF THE SOIL [CH.
gives out, and at present it seems inevitable that it
must, mankind will be faced with perhaps the most
serious of all catastrophes, a phosphorus famine.
But there is no immediate cause for alarm, as on
the lowest computation the visible supply will last
for many years. Further, the phosphates lost from
the farm are not destroyed but find their way to the
sewage, and thence to the sea. We must therefore
look to the ocean for the means of replacing the land
deposits of phosphates, and already a fair amount is
drawn from this source in guano, fish meal, etc.
The supplies of potassium compounds already
existing in the soil are in general sufiicient for
ordinary purposes, but additional supplies become
necessary as the character of the farming improves
and larger crops are grown. Some special soils,
such as peats, chalks, and thin sands, need potassium
fertilisers in order to yield even small crops, and
much labour has been lost through ignorance of this
fact. The deposits of potassium salts are extensive
and in Germany's keeping; no needless waste is
therefore to be apprehended. In the last instance
the ocean can be made to give up some of its
enormous stock.
The nature of the plant residues and the ease
with which they are decomposed by bacteria depend
on climatic factors — the temperature, water supply,
etc. — and also on the amount of calcium carbonate
Ill] ROOT RANGE 35
present. These various relationships have already
been discussed at some length: we need now only
point out that a water supply suitable for ordinary
plant growth seems also to be very suitable for
bacterial activity. The rule seems to apply also to
other soil conditions, and we may make the general
statement that a soil suited to the growth of plants
is also suited to the activity of bacteria and there-
fore to the production of plant food. The similarity
becomes even more close after the soil has been
partially sterilised so as to destroy detrimental
organisms.
A further connection between the food supply and
the water supply lies in the fact that the food has
first to be dissolved in the soil water before it can
enter the plant. Roots have no power of taking in
solid matter ; they can only imbibe solutions ; further,
they cannot use strong solutions, but may even be
injured thereby as in some of the alkali lands; and
they do not make very good growth in too weak
solutions.
Even this is not all. The amount of plant food
per unit volume of the soil is not the only factor
determining the amount of food the plant can get;
the extent of the root range is equally important just
as it was in the case of water.
Root range. And this leads to the question of
root room. No plant does well unless it has ample
3—2
36 THE FERTILITY OF THE SOIL [cH.
space for the fall development of its roots. It suffers
from the restriction of its supply of water and of
food, and apparently from other causes as well ; recent
experiments seem to indicate that new factors may
come into play when one set of roots runs up against
others because there is not space for both. In
Mr Pickering's experiments at Woburn growing grass
had a very detrimental effect on the fruit trees
planted in it, and there is also evidence that weeds
may have a directly harmful action on sown crops.
Absence of injurious factors. However good its
food and water supply, a soil may remain infertile if
injurious substances happen to be present. Little
attention has been paid to these in England, but they
have been much studied in the United States where,
indeed, they have given rise to considerable contro-
versy. It seems beyond dispute that substances
harmful to plants do occur in wet soils poor in
calcium carbonate. Nothing is known about these
substances (in English soils, at any rate) but some
years ago the fashion arose of calling them acids
without any sufficiently rigid proof It is distinctly
unwise to prejudice future investigations by assign-
ing a name already used for a definite group of
substances to another that is yet unstudied, and we
shall therefore adopt the nomenclature of the prac-
tical men and speak of such soils as "sour." Whatever
the cause of "sourness" (and the name commits us
Ill] INJURIOUS FACTORS 37
to no hypothesis), it can be remedied by drainage,
lime, and good cultivation.
Cases are recorded of infertility arising from
excess of iron or of manganese in the soil, but no
satisfactory evidence is afforded in proof. Drainage,
lime and good cultivation are here also found to be
beneficial.
"Sickness" of soil has in the past been attributed
to the presence of a toxin, but more recent work
indicates that it is biological in nature and remedied
by partial sterilisation.
The alkali soils of dry regions owe their sterility
to excess of soluble salts; they may be treated by
drainage (which is a first essential), irrigation, and
addition of gypsum where much sodium and potas-
sium carbonates are present. Much interesting work
remains to be done in elucidating the causes of
infertility of certain special soils.
Looking back over these various fertility factors
we see that they are not a mere tangle of unrelated
things, but are very closely connected one with the
other. The water supply, air supply, and temperature
are to a large extent mutually interdependent, and
changes in any of them are reflected in the food
supply. We can simplify matters by selecting three
as the leading factors in normal cases: the water
supply, food supply, and stock of calcium carbonate ;
when these are satisfactory it will usually be found
38 THE FERTILITY OF THE SOIL [CH.
that the other three conditions are also favourable
to plant growth.
Soil Types.
In order to increase the soil fertility it is necessary
first to seek out the factor limiting plant growth and
then to remove it. As the different soil types have
certain characteristic limiting factors we can now
advantageously turn to them for a time.
Sandy soils consist chiefly of inert silica with only
about 6 per cent, or even less of clay, and are con-
stitutionally poor in those mineral compounds that
give rise to plant food. Any stock that might
originally have been present is constantly being
reduced by solution in the rain water that drains
through. They are therefore poor in plant food.
But on the other hand, if they are fi^ee from such
obstructions as layers of rock, hardpan, or stagnant
water, they allow of very copious and deep develop-
ment of plant roots. The actual volume of soil upon
which the plant may draw for food and water is con-
siderable, and in consequence sandy soils yield better
crops than might at first be supposed. Generally
also the crops ripen well and give early produce of
good quality. Only small amounts of calcium car-
bonate appear to be necessary to prevent sourness.
The deficiency in food is readily made good
by frequent small additions of manure. The water
Ill] THE LOAMS 39
supply tends to be erratic because of the great ease
with which rain water soaks into the depths of the
soils, but it can be made more regular by additions
of organic manures or of clay. The defects of a sandy
soil are mainly negative, i.e. they can be remedied
by adding something, whilst its advantages are very
real; it induces good root development, early yield
and high quality. There is, perhaps, a wider range
of possibilities for a sandy soil than for any other ;
it may be a desolate heath, or it may, under proper
management, blossom out as a fruit and vegetable
garden, giving each year two or three crops of good
produce. But the cost of the process may be more
than the result is worth.
Soils that contain more of the fine clay material
and proportionally less sand are called loams. It is
impossible to define loams exactly: the cultivator
recognises them by the fact that they are definitely
coherent and not loose like sand, yet not over-sticky ;
and further that they allow free root development.
But there are no sharp lines of demarcation ; many
soils at one end of the scale would be called light
loams by some practical men and sands by others,
while at the other end soils called heavy loams by
some would be regarded as clays by others. In
between these limits there remains a great body of
soils which most cultivators would agree to call
loams, and these on analysis are found to contain
40 THE FERTILITY OF THE SOIL [CH.
6 to 15 per cent, of clay, 40 to 60 per cent of the
silts and 20 to 50 per cent, of coarse and fine sand.
Loams contain more plant food than sands and in
general have a better water supply ; they therefore
yield heavier crops. But the crops are often not as
early as those grown on sands.
The next group, the clays, cannot be sharply
marked ofi* from the loams but can only be described
generally as sticky soils, persistently wet in winter
and spring, and drying to hard clods in dry weather.
They contain more actual clay^ and less sand than
the loams, but none appears to contain more than
50 per cent, of clay, very few contain as much as
40 per cent., and most "clays" contain only about
25 per cent, or less. In consequence of their sticki-
ness clays do not allow very free root development.
The root range being thus restricted, plants do not
draw on anything like the same volume of soil for
food and water as in the case of loams and sands.
Hence the clays are less fertile than these soils in
spite of the fact that they often actually contain
more food and water. Of course if the plant is in
1 Unfortunately soil chemists use the word "clay" in two distinct
senses: (1) the soil or mineral as a whole, (2) the fine material less
than -002 mm. in diameter (-005 mm. in the United States). In past
years another meaning was given which does not appear to have been
very definite ; this survives in the statement handed solemnly down
through eighty years of text books that a clay soil contains "75 to
95 per cent, of clay." Ceramic chemists adopt a different definition.
m] THE SOIL AND THE PLANT 41
the ground a long time it can develop a big root
system and then it will grow well : trees, grass and
the longer-lived deep rooting arable crops, particu-
larly wheat and beans, do very well. Each of these
types of soil has its advantages: sands are easily
workable and present great possibilities in the way
of cropping : loams give good heavy crops of almost
any of the ordinary farm and market garden plants :
clays are very well suited to grass, wheat, and beans,
three crops of considerable importance to the farmer.
A really strict comparison is not possible because the
types are so different, but in the main we must give
the palm for fertility to the loams. The districts
in our own country famous for their fertility are
commonly loams; they are often alluvial deposits
bordering the sea, as in the Chichester district, or
lying in broad valleys, as in the vale of Evesham;
they are assured of an ample water supply by
their position, and favourably situated in regard to
climate.
But we must never forget that every soil will bear
gome plants well although they may not happen to be
saleable at the time. Gervase Markham's list drawn
up in 1620 needs but little change to-day. "Ground
which, though it bear not any extraordinary abund-
ance of grass, yet will load itself with strong and lusty
weeds, as Hemlocks, Docks, Mallows, Nettles, Ketlock
and such like, is undoubtedly a most rich and fruitful
42 THE FERTILITY OF THE SOIL [cH.
ground for any grain whatsoever. And also, that
ground which beareth Reeds, Rushes, Clover, Daisies
and suchlike, is ever fruitful in Grass and Herbage....
When you see the ground covered with Heath, Ling,
Broom, Bracken, Gorse or such like, they be most
apparent signs of infinite great barrenness.... And of
these infertile places, you shall understand, that it is
the clay ground, which for the most part brings forth
the Moss, the Broom, the Gorse, and such like; the
sand, which bringeth forth Brakes, Ling, Heath, and
the mixt earth, which utters Whinnes, Bryars, and a
world of such like unnatural and bastardly issues."
It was largely owing to the circumstance that
mankind was unwilling to pay for "Whinnes, Bryars,
and a world of such like unnatural and bastardly
issues" that the "mixt earth" was called infertile.
Tastes alter — who would now accept Markham's de-
scription of heather as "only a vile filthy black brown
weed"? — and a plant despised by one generation may
be prized by the next. Perhaps the most permanent
piece of advice one can give to the cultivator of a
piece of poor land is to find out what plants it will
grow well, decide which will be most profitable, then
ascertain what is preventing the soil from growing
these better, and, finally, if possible, remove the
hindrance, whatever it may be. The gap between
the ideal and the actual conditions for the crop may
be narrowed from both ends: the plant may be
IV] FERTILITY AND HUSBANDRY 43
altered somewhat by the breeder, and the soil con-
ditions may be changed in some of the ways to be
described later on. Nothing but disappointment,
however, is likely to follow attempts at growing
plants or crops unsuited to the soil conditions.
CHAPTER IV
SOIL FERTILITY AND SYSTEMS OF HUSBANDRY
We have seen that there is a close relationship
between the composition of the soil and the vegeta-
tion growing on it; an even closer connection can
be traced between the fertility and the system of
husbandry.
Virgin land covered with its native vegetation
appears to alter very little and very slowly in
composition. Plants spring up, assimilate the soil
nitrates, phosphates, potassium salts, etc., and make
considerable quantities of nitrogenous and other
organic compounds : then they die and all this
material is added to the soil. Nitrogen-fixing bac-
teria also add to the stores of nitrogen compounds.
But, on the other hand there are losses: some of
the added substances are dissipated as gas by the
decomposition-bacteria, others are washed away in
44 THE FERTILITY OF THE SOIL [CH.
the drainage water. These losses are small in poor
soils, but they become greater in rich soils, and they
set a limit beyond which accumulation of material
cannot go. Thus a virgin soil does not become
indefinitely rich in nitrogenous and other organic
compounds, but reaches an equilibrium level where
the annual gains are offset by the annual losses so
that no net change results. Tliis equilibrium level
depends on the composition of the soil, its position,
the climate, etc., and it undergoes a change if any of
these factors alter. But for practical purposes it may
be regarded as fairly stationary.
When, however, the virgin land is broken up by
the plough and brought into cultivation the native
vegetation and the crop are alike removed, and there-
fore the sources of gain are considerably reduced.
The losses, on the other hand, are much intensified.
Rain water more readily penetrates, carrying dissolved
substances with it: biochemical decompositions also
proceed. In consequence the soil becomes poorer.
But the impoverishment does not go on indefinitely :
the rate of loss diminishes as the soil becomes poorer,
and finally it is reduced to the same level as the rate
of gain of nitrogenous organic matter. A new and
lower equilibrium level is now reached about which
the composition of the soil remains fairly constant;
this is determined by the same factors as the first,
i.e. the composition of the soil, climate, etc.
IV] FERTILITY LIMITS 45
Thus each soil may vary in composition and
therefore in fertility between two limits: a higher
limit if it is kept permanently covered with vegetation
such as grass, and a lower limit if it is kept permanently
under the plough. These limits are set by the nature
of the soil and the climate, but the cultivator can
attain any level he likes between them simply by
changing his mode of husbandry. The lower equili-
brium level is spoken of as the inherent fertility of
the soil because it represents the part of the fertility
due to the soil and its surroundings, whilst the level
actually reached in any particular case is called its
condition or " heart," the land being in " good heart "
or " bad heart," according as the cultivator has pushed
the actual level up or not : this part of the fertility is
due to the cultivator's efforts.
The difference between the higher and lower fer-
tility level is not wholly a question of percentages of
nitrogen, carbon, etc. At its highest level the soil
possesses a good physical texture owing to the floc-
culation of the clay and the arrangement of the
particles: it can readily be got into the fine tilth
needed for a seed bed But when it has run down
the texture becomes very unsatisfactory. Much
calcium carbonate is also lost during the process:
and when this constituent falls too low the soil
becomes "sour" and unsuited to certain crops.
The simplest system of husbandry is that of
46 THE FERTILITY OF THE SOIL [ch.
continuous wheat cultivation, practised under modern
conditions in new countries. When the virgin land
is first broken up its fertility level is high ; so long as
it remains under cultivation this level can no longer
be maintained, but rapidly runs down. During the
degradation process considerable quantities of plant
food become available and a succession of crops can
be raised without any application of manure. In fact
there is commonly more plant food than the crop
needs and addition of manure gives no crop increase.
Hence arises the idea that the land needs no manure,
and the pioneer, fully occupied with the pressing needs
of the moment, not only supplies none, but does not
even put back into the soil any part of what he takes
away. The grain is sold and the straw is either burnt
or dumped into gullies. After a time the unstable
period is over and the new equilibrium level is
reached at which the soil will stop if the old hus-
bandry continues. In this final state the soil is often
not fertile enough to allow of the profitable raising
of crops; it is now starving for want of those very
nutrients that were so prodigally dissipated in the
first days of its cultivation, and the cultivator starves
with it or moves on.
"0 man, that from thy fair and shining youth
Age might but take the things youth needed not."
Such is the history of many of the derelict farms in
parts of the United States and such must inevitably
Fig. 2 a. Crop grown ^Yithout phosphates on a worn out
soil in Illinois
Fig. 2 b. Showing what phosphalf s will do on worn out
soils in Illinois
IV] THE LOWER LIMIT 47
be the history of many farms elsewhere so long as
continuous wheat culture is adopted. It is futile to
speak of land as inexhaustible: fertility is no more
inexhaustible than any other form of capital. The
pitiful thing is that so much of the loss is sheer
waste: about one third of the plant food goes into
the crop, the rest is lost beyond hope of recall as
gas into the atmosphere or as saline matter in the
drainage water and the streams. It is not the crop
that exhausts the land but the continuous cultivation.
Fortunately recovery is by no means impossible,
though it may be prolonged. It is only necessary to
leave the soil covered mth vegetation for a period of
years when it wiU once more regain much of the
nitrogenous organic matter it has lost. But it does
not wholly recover. The phosphates and potassium
salts removed in the crops, and the calcium carbonate
leached out, are not regained ; for want of them the
growth of recuperative vegetation may suffer.
The problem has been investigated with charac-
teristic energy in the United States, and a remedial
scheme has been evolved by Dr Cyril Hopkins,
Director Thorne and others, based on experience
in the older countries and on careful experiments
in the new. The central feature is that continuous
tillage must stop, and for one third to one half of its
time the land must lie untilled and covered with
vegetation, i.e. in the course of six years not more
48 THE FERTILITY OF THE SOIL [CH.
than three or four gram crops should be taken;
during the remaining time the land grows grass or
leguminous crops, so that it may gain organic matter.
It is not unremunerative during this period; on the
contrary, these crops are distinctly valuable. Much
the best for the purpose are clover, either alone or
mixed with timothy, and lucerne ; these collect gase-
ous nitrogen as well as carbon dioxide to form
nitrogenous organic matter in the soil. It is an
indispensable part of the method that limestone
should previously be added to the soil, or the clover
or lucerne may fail. When the soil has been thus far
improved the supply of phosphates present may be
insufficient for the crop that can be produced, and
this limiting factor has therefore to be removed by
the addition of rock phosphates. The crop now
increases till it is limited by some new factor. It
may happen that the supply of potassium salts in
the soil constitutes this new limiting factor, in which
case addition of potassic fertilisers becomes desirable.
The fertility may then rise higher than it was at first
in the virgin soil.
The whole process, it will be observed, consists in
the successive removal of the limiting factors.
The exhaustion of the virgin lands constitutes the
simplest case because everything is removed from the
soil and nothing is put back. It could only arise under
conditions of cheap transport facilities between the
IV] A MEDIEVAL FARM 49
virgin land and the cities where the gi-ain is to be
consumed. Thus it is essentially a modern pheno-
menon ; it never arose in so acute a form in England
because such facilities did not exist till a complex
system of agriculture was already established. Wheat
has always been grown in this country and records
exist of very early exports. Zosimus relates {Hist
Nova, lib. 3, ch. 5) that Julian brought wheat from
Britain to feed the inhabitants of some of the Rhine
cities whose stores had been destroyed and their
harvest ruined by insurgent tribes. But we have
no knowledge what the agricultural methods were.
When the first definite records of English agriculture
appear a system was already in use that kept the soil
fertility at a sufficient level for the needs of the time.
In medieval England the arable land occurred
partly in the lord's demesne and partly in the com-
mon cultivated field \ The latter was divided into
fields, generally three in number, which were again
divided into strips so distributed among the tenants
that each should have his share of good and bad land.
The pasture consisted of the common grazing land,
certain outlying lands, and the cultivated common
field after the harvest was off"; in addition there were
certain fields and water meadows not held in common.
The live stock thus had a relatively wide area of
ground over which to gather their food; and their
1 Often called "infield" in the North.
50 THE FERTILITY OF THE SOIL [CH.
manure, mingled with any bracken, straw, rushes,
etc., gathered for litter, went to fertilise the arable
land. The distribution was not very uniform, as the
lord often had special claims, but all the arable land
did receive some dung.
The manure having been put on, a crop of wheat
or rye or both was taken. After harvest the in-
dividual cultivators no longer had any special rights
in their strips and the whole field became common ;
the fences were removed and the cattle allowed to
enter and graze the weeds and grasses. The ground
was somewhat enriched by folding on it sheep that
had grazed during part of the day on the common.
This period lasted from Lammas Day^ (August Ist)
till Candlemas (Feb. 2nd). The land was next sown
with barley, oats, or other spring or " Lent " corn, and
after harvest (Lammastide) again grazed until the
following Candlemas. It was then ploughed up and
left fallow throughout the summer ; finally it was
dunged and sown with wheat. Occasionally, however,
barley was taken first and wheat after :
"First rie, and then barlie, the champion saies,
or wheat before barlie be champion waies;
But drink before bread come with Middlesex men,
then lay on more compas, and fallow agen^."
1 Lammas Day (Aug. Ist) may seem early to a modern farmer for
the individual rights to cease and the whole field to become common,
but it must be remembered that the Julian Calendar was then in
force so that the date is really later than it looks.
2 Tusser, Five Hundred Pointes of good Husbandrie, Octobers
IV] A MEDIEVAL FARM 51
Whatever the order, the rotation consisted of two
corn crops and a fallow ; each year one of the fields
was fallow, the second wheat or rye, and the third
Lent corn.
The dung made by the animals contained elements
of fertility derived from the pasture land. The addi-
tion of this dung to the arable land thus involved a
transfer of fertility from the wide areas of the pasture
land to the smaller areas of arable land. The process
maintained the fertility of the arable land, but it must
in time have impoverished the pasture ; but the im-
poverishment of the pasture went on only very slowly
for two very interesting reasons. In England the
supply of nitrogen compounds in the soil is most
frequently the factor limiting the wheat and other
grain crops ; so long as the nitrogen supply is kept
up a certain level of crop production can be main-
tained. In pasture land a considerable amount of
nitrogen fixation is continually going on through
bacterial activity. Hence the element that played
the most serious part in fertility under the conditions
of low yields then obtaining was being brought in as
quickly as necessary from the atmosphere.
The next substance to give out and cause the
collapse of the system would have been calcium
husbandrie, 1573: drink corne = barley ; bread come = wheat ; compas
= farmyard manure (compost); champion = the unenclosed common
field or its farmer.
4—2
52 THE FERTILITY OF THE SOIL [CH.
carbonate. There was a real danger of this, but it
was met by chalking and marling which from time
immemorial had been part of the agricultural practice
of these islands (see p. 80). In consequence soil
exhaustion could only set in through exhaustion of
the phosphates and potassium salts, and this was a
very slow process which, moreover, was still further
delayed by the practice of fertilising with wood
ashes, which supplied potassium salts derived from
the forest, and less frequently with salt (sodium salts
economising the consumption of potassium salts by
the plant). Thus the only weak point in the system
was the exhaustion of phosphate from the soil, but as
the yield of wheat was probably often under 10 bushels
per acre, which would only take out some 5 lbs. of
phosphoric acid (P2O5), and as the total population
was only small and sparsely scattered, the system was
for ail practical purposes permanent. But the yield
was very poor.
The next step up involved some very drastic
changes. Gradually the common arable fields and
pastures began to be enclosed and each man's holding
came into one piece. The process was slow and is
hardly complete even yet; the old strip farming of
common fields may still be seen in the Isle of Axholme,
Lincolnshire, while survivals of it may be detected in
many villages. For example, several arable common
IV] ENCLOSURES AND EXHAUSTION 53
fields can be traced around Harpenden; Manland,
Westfield and Pickford Commons are divided by
balks into strips as in medieval times. During the
fifteenth and sixteenth centuries the enclosure was
accompanied by the wholesale conversion of arable
into grassland induced by the high price of wool, and
both processes were much resented by the peasantry,
who pulled down the new hedges in many places, and
in Norfolk broke out into open rebellion under Kett
in 1549. Shrewd writers of the period saw, however,
that only on enclosed land could a higher level of
productiveness be attained, and history has shown
that only on such land were improved methods
adopted.
Under the new conditions each man could grow
what he liked (unless the landlord forbade him), and
he was no longer tied down to follow ancient custom.
There was a greater incentive to industry, more
manure could be obtained and grea^ter care could be
taken with the cultivations and to keep down weeds.
In consequence larger crops were now obtained ; the
yield of wheat has been estimated for certain districts
at about 20 bushels, barley at 30, oats and pulse at
40 bushels per acre at this period. There can be little
doubt that at this pace exhaustion would have been
hastened, and the more so as chalking, marling and
other permanent improvements were falling into dis-
use through the insecurity of the tenant's position.
54 THE FERTILITY OF THE SOIL [CH.
A further improvement was soon to take place in
soil fertility. A great advantage of the enclosure
over the common fields was that crops could now
be grown in autumn and winter ; obviously this
course was impossible when the village cattle strayed
at will over the land from Lammastide to Candlemas.
Consequently about the middle of the seventeenth
century turnips, clovers, and cultivated grasses came
in from Holland — the source of many of our great
improvements — and slowly took their place in our
agricultural system. Before these new crops could
be cultivated a great improvement was needed in
methods of tillage. The old implements were very
crude: heavy wooden ploughs turned up the earth
in great clods that could not be broken up by the
inefficient harrows ; so that after the seed had been
broadcasted the clods had to be broken in pieces
by large wooden hammers. "It is a greate labour
and payne to the oxen, to goo to harowe; for they
were better to goo to the plowe two dayes, thanne to
harowe one daye. It is an old saying, 'The oxe is
neuer wo, tyll he to the harowe goo.'... And if the
barleye gounde wyll not break with Harrows, but
be clotty, it wolde be braken with malles, and not
streyght downe : for than they brake the corne in-to
the earthe," wrote Fitzherbert in 1543. Two hundred
years later Tull declaims against farmers who, " when
they have thrown in their seed, go over it twenty
IV] JETHRO TULL AND CULTIVATION 55
times with the harrows, until the horses have trodden
it almost as hard as a highway." The young plants
thus had considerable difficulty in getting through,
and later on in the season they were terribly ham-
pered by the excessive gi'owth of weeds which could
never be got rid of by the old methods.
These defects were only slowly remedied, but the
man who probably did more than anyone else in this
direction was Jethro Tull. Travelling in the South of
France and in Italy in the early years of the eighteenth
century, he observed how carefully the vineyards were
cultivated. On his return home he adopted similar
methods on his farm at Shalbourne, on the borders of
Berkshire and Wiltshire, adapting and inventing the
necessary implements. Some farmers, indeed, had
already begun to get a fine tilth : he tells us of
"Great quantities of very light land (in Gloucester-
shire) which when kept in the sat erit^ husbandry were
let for half a crown an acre, but being now brought
into the pulverising method, are let for ten shillings
an acre. But there is a misfortune in many parishes,
that the custom does not permit any one to pulverise
his light lands by tillage, until an enclosure be made
of them."
Tull insisted on three points: (1) that the soil
must be thoroughly pulverised before the seed is
sown, (2) cultivation must continue after the seed is
^ Tail's name for the old style.
56 THE FERTILITY OF THE SOIL [CH.
sown and as long as is practicable, (3) the seed must
therefore be sown in straight lines and not scattered
broadcast. The seed drill and horse hoe that he made
to carry these principles into practice have been the
forerunners of a long line of useful implements, and
they alone made possible the cultivation of turnips,
clovers and other of the new crops that began to
come in.
These new crops completely changed the agricul-
ture of the country. They fell best into the rotation
worked out by Lord Townshend in the middle of the
eighteenth century : clover in place of the old fallow,
then wheat, then turnips, and lastly barley. Three
great advantages followed. The clovers and other
leguminous plants, sainfoin, lucerne, etc., led to a
great increase in the stock of soil nitrogen. The
substitution of a growing crop for the fallow con-
siderably reduced the wastage of plant food through
leaching. The clover hay and turnijjs provided food
for the live stock throughout the winter, so that it
was no longer necessary to slaughter them in late
autumn and salt them down to be eaten ^; the hus-
bandman was able to keep them alive and in good
condition all the year round. The animals consumed
^ **At Hallowtide, slaughter time entereth in,
and then doth the husbandman's feasting begin."
Tusser, 1673.
IV] WHAT THE NEW CROPS DID 57
a great deal of food, but this did not necessitate a
great net loss to the soil. For the carbon, hydrogen
and oxygen (the elements most largely retained in
the body tissues) came from the inexhaustible supplies
in the atmosphere, while of the other constituents,
retained to a less extent and largely passed off into
the manure, the nitrogen was mainly drawn from the
atmosphere through the agency of the clover, and
only the phosphorus, potassium, calcium, etc., came
exclusively from the soil. This manure when put
on to the land actually enriched it in nitrogenous
organic matter, and went far to replace the mineral
substances withdrawn by the previous year's crops.
So far as nitrogen was concerned, the system was
permanent: crop production went on at a higher
level than was ever before possible, and this new
level was determined in principle by the amount of
nitrogen fixed by the quadrennial clover crop, and in
practice by the amount that was returned to the soil
in the manure.
But there still remained the loss of phosphorus,
which was intensified as the cities grew and imported
more and more dairy produce, meat, bread, etc., from
the country. At the end of the eighteenth century, in
spite of all the improvements, an ordinary yield of
wheat was probably only about 23 bushels, little
more than good farmers had been accustomed to
get for 250 years past. The improvements had been
58 THE FERTILITY OF THE SOIL [CH.
by no means universally adopted, and in many dis-
tricts medieval agriculture was still the rule. It is
impossible to determine how far the low yield was
due to this circumstance. But in many cases the
small supply of phosphates in the soil was now the
limiting factor, preventing the crop from rising.
Then gradually bones came into use as manure and
produced such remarkable results that from the early
years of the nineteenth century considerable quantities
were imported from Europe. It would, perhaps, be
unkind to enquire too particularly where they came
from : Liebig roundly declared that " England is
robbing all other countries of their fertility. Already
in her eagerness for bones she has turned up the
battlefields of Leipsic, and Waterloo, and of the
Crimea: already from the catacombs of Sicily she
has carried away the skeletons of many successive
generations.... Like a vampire she hangs upon the
neck of Europe, nay, of the whole world, and sucks
the heart blood from nations without a thought of
justice towards them, without a shadow of lasting
advantage to herself"
But even finely ground bones sometimes acted
only slowly and sometimes failed to act at all. This
was the case at Rothamsted: during the years 1836 —
1838 Lawes had used bone dust on turnips without
avail, although it was effective elsewhere. He there-
fore prepared the soluble calcium phosphate, then
IV] PHOSPHATIC MANURES 59
known as superphosphate, by treating the bone with
sulphuric or other acids. This proved remarkably
effective on turnips; and he took out a patent in
1842 and commenced the manufacture on a large
scale. But as the source of the calcium phosphate
was immaterial, he used mineral phosphates and
guanos instead of bones.
Another source of phosphatic manures was opened
up in 1879 when Thomas and Gilchrist introduced
their process for removing the phosphorus from iron
during its conversion into steel. At first the agri-
cultural value of the basic slag thus produced was not
recognised, but it was slowly revealed by the experi-
ments of Wrightson and Munroe in 1885, and of other
agriculturalists.
Phosphatic guanos, brought fi'om the Pacific
Islands, fish guano worked up fi'om refuse fish, and
meat guano from imported meat, contribute in a
lesser degree to the farmers' supply.
As a result of having these large supplies of
phosphates from various parts of the world, farmers
now very generally add phosphates to their land, and
thus remove the limiting factor which had in many
cases kept down the crops. Concurrently with the
increased use of phosphates there has been a marked
increase in soil fertility, the yields of turnips in
particular have gone up very much, and there have
been very great improvements in the pastures. More
60 THE FERTILITY OF THE SOIL [CH.
cattle can therefore be kept and more manure can be
made for the arable land.
It often happens, especially on the lighter soils,
that the crop supplied with phosphates is now limited
by the deficiency of potassium salts. This deficiency
has long been partially met by dressings of wood
ashes, salt, etc., but a better method was needed.
Fortunately large supplies of potassium salts were
discovered at Stassfurt in Germany and were put on
the market in 1861. Since then they have been ex-
tensively used, although curiously enough no similar
deposits have been found elsewhere.
The modern farmer is no longer dependent on
leguminous plants for his supplies of nitrogen.
Nitrate of soda is imported from Chili, sulphate of
ammonia is manufactured from coal at home, and a
large number of grains and seeds are imported from
over the seas to feed tlie cattle and thus increase the
supply of farmyard manure.
Modern agricultural systems are far too complex
to reduce to any simple rigid order ; but their general
bearing on the fertility of the soil may be briefly
summed up:
1. The supply of plant nutrients is kept up by
the addition of appropriate artificial manures. It is
impossible to determine a priori either by chemical
analysis or otherwise exactly Avhat mixture of manures
will be best ; nothing but direct trials suffice. But a
IV] MODERN METHODS 61
number of trials are being made, and in some cases
on a defmite systematic plan, to ascertain broadly the
needs of the commoner crops on important types of
soil. Chalk or lime is also applied, though, it must
be said, not always as often as necessary.
2. Every effort is made to keep up the supply of
nitrogenous organic matter in the soil. It is not yet
possible, and perhaps never will be, to maintain the
same level as in land permanently covered with grass
or other vegetation. But leguminous crops are grown ;
the " seeds " (i.e. mixture of grass and clover) are left
for two or three years, in which time a dense root
mass forms; and in many instances a crop (such as
mustard, tares, etc.) is sown with the deliberate in-
tention of being ploughed into the ground.
3. Enormous quantities of cattle food are im-
ported from newer countries and from less highly
developed regions. Only a small part — not more
than five or ten per cent. — of their nitrogen, phos-
phorus and potassium is retained by the animal : the
rest passes into the manure and goes to fertilise the
land. There are, however, very considerable losses
in making manure, and as much as one half of the
fertilising constituents may fail to reach the soil.
Greater economy is effected by feeding the animals
on the arable land, thus obviating the necessity for
making farmyard manure.
4. Crops are therefore grown suitable for animals
62 THE FERTILITY OF THE SOIL [ch.
to eat in the field (sheep are the most convenient for
the purpose). These crops include swedes, rape,
kohl-rabi, thousand-headed kale, mustard and the
aftermath of clovers and cultivated grasses \ The
purchased food is su]3plied in troughs and the animals
are confined by hurdles to a particular area till the
crop and sufficient additional food are consumed.
Then they are moved on, till finally they have
covered the whole field.
5. Considerable tracts of land are laid down to
permanent pasture. Judicious management of graz-
ing, combined with dressings of basic slag, lime and
potassium salts if necessary, lead to the formation of
a dense turf of grass and clover. The land thus gains
considerable supplies of nitrogenous organic matter
and its fertility rises to the upper equilibrium level.
These areas of well-managed grass land constitute,
perhaps, the most fertile soils we have, and their
fertility is more permanent, and maintained at lower
cost, than that of any other soils.
Thus the modern English farmer keeps up the
fertility of his soil by importing phosphates from the
United States, Tunis, Algeria, Belgium and France;
nitrates from Chili ; potassium salts from Germany.
He also imports grain — maize, wheat, barley, oil
seeds, etc. — rich in valuable fertilising materials from
the United States, Russia, Roumania, Argentina,
1 Often called '♦ rotation grasses."
IV] MODERN WASTE 63
British East Indies, Canada and other parts of the
Empire. Thus a prodigious transfer of soil fertility
is taking place from these countries to our own. The
process at present is enormously wasteful. We have
seen that terrible losses of fertility may arise under
conditions of pioneer farming ; even the remnant
saved in the crop suffers further loss in many a badly
arranged British farmyard and exposed manure heap.
Lastly, the crops raised on the British farm are
largely sent off to the cities from whence only little
manure ever returns, the great proportion of the
fertilising constituents getting into the sewage and
being destroyed at considerable expense.
It is obvious that such wasteful methods cannot
go on indefinitely. Investigations into the losses and
gains are now going on at Rothamsted and elsewhere.
With fuller knowledge there is little doubt that some
of the waste can be reduced, while the action of the
recuperative agencies in the soil can be accelerated.
It is impossible to overestimate the importance of
evolving a permanent system of maintaining soil
fertility, but such a system must rest on a solid
foundation of scientific fact.
64 THE FERTILITY OF THE SOIL [ch.
CHAPTER V
THE RAISING OF THE FERTILITY LIMIT
We have seen in the previous chapters that the
fertility of a given soil may lie anywhere between
two limits : the higher limit being attained when the
land is allowed to remain with an undisturbed vegeta-
tion of grass and clovers, and the lower when the
land is perpetually under the plough, producing
nothing but cereal crops and receiving no manure to
counterbalance the various losses. We have further
seen how, by a judicious system of husbandry, it is
possible to maintain arable land somewhere near the
higher fertility limit by arranging for recuperative
periods in grass and clover, and systematically adding
manurial substances to replace whatever may be lost.
The higher limit beyond which the fertility of the
soil as it stands cannot be pushed, is set by the nature
of the soil, its position in respect to water supply,
climate, etc. But it is often possible to change these,
and when this is done the fertility is no longer tied
down to the old limit but rises to a new one set by
the new conditions. This process is of course funda-
mentally different fi'om the case we have just dealt
with, and is in practice so much more costly that the
V] RAISING OF THE FERTILITY LIMIT 65
distinction is recognised both by custom and by law :
the maintenance of fertility between the natural
limits is regarded as the tenant's business, while the
extension of the upper limit is considered to be the
landlord's duty.
Over the greater part of England such an exten-
sion of the fertility limit has taken place. Often
indeed the extension was necessary before the adop-
tion of expensive modern methods of farming could
be justified. The process has generally involved some
conflict with natural conditions, and the new order of
things stands only so long as constant care is exercised.
In most cases the original condition is resumed if the
intervention of man ceases for a time ; a plot of land
at Rothamsted that has been left to itself since 1882
is now a dense thicket and bids fair to become an
impenetrable wood before long. But the expenditure
necessary to maintain the new limit is much less than
that required to reach it, so that in this sense the
improvement is entitled to be called permanent.
Some of the land of England has always been
open gi'ass-covered Down land, and this was inhabited
even in prehistoric times. Much of the land, however,
was covered with forest which had to be cleared away
before fields could be made but which would, as the
Rothamsted experiment shows, soon spring up again
if the suppressing hand of man were removed. It is
difficult for us now to realise the magnitude of the
R. 5
66 THE FERTILITY OF THE SOIL [CH.
task which medieval man set himself in clearing the
forest with his imperfect tools and the enormous
amount of labour that must have been required.
Even with modern appliances — explosives and well-
constructed jacks — the task is considerable, and the
traveller round the shores of Lake Erie can still find
many fields from which the timber has been removed,
but the stumps still left, because the labour of
removing them is so great that no adequate return
could be obtained.
Clearance was still going on in England even as
late as the middle of last century and an interesting
account of one is preserved in the Journal of the
Royal Agricultural Society for 1863. About ten
miles west of Woodstock lies the forest of Wychwood,
that formerly occupied considerably more land than
it does now. In 1853 an Act was passed permitting
disafibrestation, and in October 1856 the work was
begun. The account deals only with the portion
allotted to the Crown, an area of nearly 3000 acres
lying in the triangle between Fulbrook, Field Assarts,
and Shorthampton. Of this nearly 2000 acres were
"unreclaimed forest land, dense, dark, and gloomy:
its silence seldom disturbed, except by the axe of the
woodman, tlie gun of the gamekeeper, or the stealthy
tread of the deer stealer."
Ten miles of road were first made, and these, with
their boundary walls, cost £6985. Then it was
V] RAISING OF THE FERTILITY LIMIT 67
necessary to get rid of the deer. "The Commis-
sioners' order had gone forth against the deer 'let
not one remain.' Some few were caught alive in nets,
and taken away to stock distant parks, but by far the
greater number had to be killed, and to effect this
purpose the keepers were fully employed ; to assist
in the slaughter, guns and gunners came from the
surrounding neighbourhood. . . . As a complete clearance
was to be made, bucks, does, and fawns, in season
and out of season, shared the same fate, and the taste
of venison was known in cottage as well as hall."
Next the trees were cut down. "Hundreds and
hundreds of men and boys were engaged, some cutting
the light wood and laying it in drift, some tying the
firewood into faggots, some preparing the larger
pieces for posts and fencing and others busy felling
the timber trees, or stripping off the bark." Some of
the smaller trees were pulled down by a windlass
worked by two horses. The total cost of this was
£7742, but sales of timber, bark, etc. realised £21,823,
and as £2450 worth was left untouched the gain on
this part of the operation was £16,531. Next came
the laborious process of digging out the roots known
by the old Saxon name "grubbing"; this was accom-
plished by hand labour at a cost of £6233 for an
area of 1903 acres. " Some of the roots were carried
away to serve as fuel for the cottages near ; but
great quantities were burned on the land, rough
5—2
68 THE FERTILITY OF THE SOIL [CH.
firewood in the district having become so abundant,
that it was not considered worth the expense of
cartage." The ground being now clear, seven farms
were measured out and whitethorn quicks planted
along the boundaries ; houses and buildings were
put up at a cost of £14,337. Allowing for all sales,
the net outlay apart from the ten miles of road Avas
£10,452 and the total farm land obtained was 2843
acres ; this was let at £5104 per annum, a gain of
£3291 on the revenue derived from the forest. But
the land was by no means ready for cultivation. The
tenants, as they came into possession on 31 years leases,
found " anything but a smooth, inviting appearance :
wide ditches, and long, irregular high banks that
had formed the boundaries of the different coppices ;
deep pits and hollows, where stones had been dug
for the use of bygone generations: small straggling
briars that had escaped the notice of the woodgrub-
bers ; roots of trees and underwood, left a few inches
below the surface by oversight or intentional neglect
on the part of dishonest workmen ; large patches of
rough brown fern-stems, that had afforded covert to
the fawns; all these and many other impediments
stood in the way... it was with the greatest difficulty
that four strong horses drawing a large iron plough
could break up half an acre a day; and many and
long were the blacksmith's bills for repairs. Some of
the tenants tried digging, at a cost of £3 per
V] RAISING OF THE FERTILITY LIMIT 69
acre; some used stocking-hoes, and grubbed the
gi'ound 5 inches deep, carefully picking out the large
stones that were beneath the surface ; this plan cost
50/- per acre. On Potter's Hill farm, breast plough-
ing and burning was adopted ; and this course
appeared to answer better than any of the others."
The banks were either thrown do^vn by spade labour
to fill up the hollows, or gradually ploughed down.
Vast quantities of wood ashes were available for
manure and were spread as required on the fields.
Oats and turnips were grown during the first year,
much of the cultivation being done by hand; the
yield of the former was well up to the average of the
district and of the latter well above it (probably
because this crop had received superphosphate) and
for the five years over which the record extends the
tenant was satisfied with the returns. The landlord
(the Crown) was also well satisfied ^ The recorder
further lays stress on the great moral gain to the
district — a point strongly emphasized by all advocates
of enclosure. "Formerly, when deer and game
abounded on the coverts, deer-stealers and poachers,
idlers, and thieves, were numerous around; conflicts
between them and the keepers were frequent; im-
prisonment and transportation caused many families
to lose their paternal head, and where matters did
1 I understand that over the whole fif t^' years the returns have not
been so satisfactory.
70 THE FERTILITY OF THE SOIL [ch.
not reach this point, perhaps the abiding influences
were still worse, a stolen buck could readily be
disposed of; the amount paid for such plunder
frequently amounted to £2 or £3, but as ill-gotten
booty is seldom well spent, the beer-shops too often
absorbed the greater part of the proceeds. Tliere
was squandered in dissipation, what had been dis-
honestly obtained, a deserted home, a neglected wife,
and children left to their own devices, fill up the
background of this sad picture."
In this particular instance clearing only was
carried out, but in many other cases further opera-
tions have been performed. Chief among these is
drainage, which has been resorted to in all parts of
England owing to the circumstance that the wetness
of many soils more than anything else set the fertility
limits and often in fact rendered them absolutely
sterile. The old method in this country consisted in
throwing the land into high ridges with deep furrows
between, such as can still be traced in almost any clay
district. Considerable waste of land was thus entailed :
the furrows were often so wet that they lay bare of
crop, whilst only the higher parts of the land were
productive. No advance seems to have been possible
in the common arable lands, as nothing could be done
without the consent of all the owners ; but on the
enclosed fields better methods could be adopted.
A special drainage problem had, from time
V] RAISING OF THE FERTILITY LIMIT 71
immemorial, been solved successfully in various parts
of England. Much of Romney Marsh in the South of
Kent was reclaimed from the sea before or during
Roman times, while the adjoining Walland and Denge
Marshes were brought in and drained by successive
Archbishops of Canterbury beginning about 774.
The great monasteries in the Fens had also reclaimed
parts of the surrounding land. In 1626 a great
scheme was set into operation for draining the Fens
and embanking its rivers, the work being executed
by a celebrated Dutchman, Cornelius Vermuyden.
As this is essentially an engineering problem we
cannot go into the details of the methods adopted;
nor does space allow any account of the romantic
story of the project, its interruption by storm, by the
exhaustion of the resources of the Adventurers, by
the Civil War, and finally by the fenmen themselves,
who had no taste for farming and no wish to see
wheat and cattle take the place of fish and waterfowl.
"Behold the great design, which they do now determine,
Will make our bodies pine, a prey to crows and vermin ;
For they do mean all fens to drain and waters overmaster
All will be dry and we must die, 'cause Essex calves want
pasture "
went the old fenman's song.
The scheme as it works to-day consists of two
great parts: (1) the water from the high lands is
intercepted and discharged into the river so that it
n THE FERTILITY OF THE SOIL [cH.
shall not reach the low-lying lands, (2) the water
inside the low-lying area is drained into ditches and
pumped into the river. To effect the first purpose a
catch- water drain is cut at a point just above flood
level and arranged to discharge by gravity into the
nearest river. The second purpose is achieved by
making open drains inside the catch-water and bring-
ing them to the most convenient point for discharge.
The water collected in these is below the level of the
river and will not naturally flow in, but has to be
lifted there. This is done by large scoop wheels,
which are simply under-shot water-wheels driven the
reverse way. In olden times power was furnished by
windmills, and now-a-days by the less picturesque
beam engine. Oil engines and centrifugal pumps are
often used in new work.
The reclamation of Whittlesea Mere near Peter-
borough (Holme Station) affords an interesting in-
stance of this type of problem. The Mere itself
covered 1000 acres, and around it lay another 2000
acres of wet land or shoals. In 1844 an Act was
obtained to improve the drainage of the Middle
Level; a new cut 11 miles long was commenced to
discharge the waters some six miles further down the
Ouse than before, and so effect a lowering of the
water table by six feet. Simultaneously connection
was made with the Mere. In the summer of 1851
the new cut was sufliciently advanced to carry oft' the
Fig. 4. Reclaimed fenland, Lincolnshire
I tf •> «> ■
v] RAISING OF THE FERTILITY LIMIT 73
waters, the last bank was cut through and the Mere
began to empty itself. There was a total fall of only-
two feet from the bottom of the lake and accordingly
the stream was never rapid after the first twenty-four
hours and was still flowing sluggishly even after
three weeks. Fortunately a favourable wind pre-
vailed and assisted materially the movement of the
water. "Long before the last pools of water had
disappeared from off the bed of the Mere," wrote
Mr Wells, from whose description in the Journal of
the Royal Agricultural Society for 1860 this account
is taken, "large crowds of people from all the sur-
rounding neighbourhood had assembled. Some from
a desire to be present at the last moment of a
venerable friend whose fortunes were now reduced to
the lowest ebb: others perhaps with whom the love
of stewed eels preponderated over sentiment, from
the prospect of a ready and abundant gratification of
their taste.... Nine out of ten came provided with
sacks and baskets to carry off" their share of the vast
number of fish, which, wherever the eye turned, were
floundering in the ever-decreasing water. Some
more ambitious speculators brought their carts, and
gathering the fish by the ton weight, despatched
them for sale to Birmingham and Manchester."
A pumping engine was now installed to carry the
water table sufficiently below the surface for crop
production. During the summer of 1852 the great
74 THE FERTILITY OF THE SOIL [CH.
expanse of mud was surveyed, farm boundaries
marked out, and arrangements made for letting some
of the prospective farms, when on November 12th
the bank broke and the whole Mere was flooded
again to a depth of 2 J feet. But the bank was
mended and the engine set to work; in little more
than three weeks the mud surface was once more
exposed. Then a main dyke was cut through the
area, and a number of smaller lateral dykes; this
work was very arduous and the mud frequently fell
in. But it was finished at last and the pump re-
moved the water as fast as it collected. " The effect
of this network of drains was quickly visible. The
bed of the Mere was soon covered with innumerable
cracks and fissures, deep and wide, so as to make it a
matter of no small difficulty to walk along the
surface, while in the surrounding bog the principal
effect was the speedy consolidation of its crust....
" It was no easy matter to reduce the Mere-land
into a state to receive such seed as should be first
sown ; the adhesive condition of the surface making
it impossible to use horses even when shod with
boards, if indeed the wide fissures did not render it
dangerous to try the experiment. The whole area
therefore had to be prepared by hand — over the
largest part light harrows were first drawn by hand —
the seed was then sown, and the harrows used a second
and sometimes a third time, at a cost of about 5/- or
V] RAISING OF THE FERTILITY LIMIT 75
6/- per acre. Other parts were dug or forked at an
average cost of from 25/- to 30/- per acre. Of such a
depth were the cracks, that even this process with all
the subsequent operations attending the first crop,
by no means got rid of these obstinate scars, which
continued until the cultivation of three or four years
at length obliterated them."
Coleseed and Italian rye grass were the first crops
taken, and after that wheat and oats could be grown
owing to the richness of the soil and its large content
of calcium carbonate. Excellent yields of these
cereals, of mangolds, potatoes and carrots were
raised.
There remained the more difficult business of
rendering fit for cultivation the tract of peat land
surrounding part of the old Mere. This was done by
covering the peat to a depth of 4 to 6 inches with
the marl dug out of the dykes; the operation cost
£15 to £19 per acre but proved remunerative as the
land readily let at 30s. per acre.
Thus a vast unhealthy waste of marsh and mere
was transformed into healthy agricultural land and
made to produce food valued then at over £12,000
per annum. To this day it remains a fertile tract.
One interesting change has, however, set in. As the
water drained away so the soil shrunk, and it has
fallen in level to a remarkable extent. Oak posts
driven into the underlying gault till their tops were
76 THE FERTILITY OF THE SOIL [ch.
flush with the mud in 1851 are now more than ten
feet above the surface.
Many of the magnificent alluvial meadows of the
country have been made in the same way from rushy
wastes. The well-known Brooks at Lewes give an
example : originally only a bog of bullrushes, let for
a trifling sum to chair bottom makers, they have for
the past 80 years been fertile pastures carrying sheep
and bullocks, yielding heavy crops of hay and contri-
buting much to the wealth of the district
These large schemes were early imitated by a few
progressive agriculturists troubled with marshy or
boggy fields. Walter Blith, a Yorkshire Puritan and
"lover of Ingenuity," as he styled himself on the title-
page of his English Improver (1649), had indeed
already published methods that the farmer could
adopt. He begins by pointing out that the causes of
soil infertility "are usually two, 1 in Man himself, 2 in
the Laud itself. In Man himself it was occasionally,
who by his sin procured a curse upon the Land, even
Barrennesse." Of the defects in the land, one of the
worst can be removed by " Drayning, or taking away
Superfluous and Venomous Water, which lyeth in
the Earth, and much occasioneth Boggiuess, Miriness,
Rushes, Flags, and other filth, and is indeed the
chief cause of Barrenness in any land of this nature."
He goes on to set out the essential condition that the
drains must fall gradually but consistently from the
Fig. 5, Taking levels for draining in Puritan times
(From Walter Blith, The English Improver Improved or the Survey
of Husbandry Surveyed, 1652)
V] RAISING OF THE FERTILITY LIMIT 77^
highest land to the lowest where the outfall must be, a
condition which, even in the middle of the nineteenth
century, was not always acted upon. "Be sure thy
Drains be such, and so deep, as thou hast a descent
in the end thereof to take away all thy water from
thy Drayn to the very bottom, or else it is to no use
at all, for suppose thou make thy Drain as high as an
house, and canst not take thy wa,ter from it, thy work
is lost ; for look how low soever is thy lowest level in
thy Drain, thou mayst drain thy water so low, and
not one haire's breadth lower will it drain thy gi^ound
than thou hast a fall or descent to take it cleanly
from thy Drain ; therefore be especially carefuU here-
in, and then if thou canst get a low descent from
thence, carry thy Drain upon thy Levell untill thou
art assuredly got under that moysture, miriness, or
water, that either offends thy Bog, or covers thy
Land; and goe one Spades graft deeper... to the
bottom where the spewing spring lyeth thou must
goe."
The drains must be laid out straight with as few
"Angles, Crookes, and Turnings" as possible, and
proper levels taken ; the various tools and appliances
needed are described and pictured in detail. Good
green faggots of willow, alder, elm or thorn or else
"great Pibble stones or Flint stones" are to be put
into the trenches, on top of this some turf facing
downvrards, and then the whole filled in.
78 THE FERTILITY OF THE SOIL [ch.
But it was nearly two hundred years before the
plan was adopted on any wide scale by farmers or
landowners. In 1823 James Smith, of Deanston,
Perthshire, drained a marshy piece of ground in this
manner and converted it into a garden. The interest
of farmers in the experiment was aroused and main-
tained: in 1831 he set out the results of this and
other trials in his Remarks on Thorough drainage
and Deep ploughing. He recommended stone drains
(like Blith's) 2 to 2^ ft. deep to be made in the furrows,
or, on flat land, 10 to 15 ft. apart in heavy soils but at
wider intervals in lighter soils. Josiah Parkes, the
drainer of Chat Moss, took a different view which he
defended in his papers in the Journal of the Royal
Agricultural Society (1846, etc.) and in his book
Philosophy and Art of Land Drainage (1848). He
maintains that drains should be deep — not less than
4 to 6 feet but they could be placed at wider intervals.
The stones were soon displaced by John Reade's pipes
of 1843, which in 1845 were turned out by the
thousand in Thomas Scragg's machine. Throughout
the 'forties and succeeding years drainage became a
very popular improvement ; public loans were raised,
companies were started, and individuals expended
their resources in developing great schemes. But
the question of the depth of the drains was not
settled; considerable controversy went on between
the advocates of Smith's and of Parke's methods;
V] RAISING OF THE FERTILITY LIMIT 79
and it was not till thousands of acres had been
wrongly drained and thousands of pounds wasted,
that the germ of truth underljing both sides was
discovered. For both sides were partially right;
deep drains are needed to carry off subterranean
water and shallow drains to remove surface water.
Modern practice tends to revert to Smith's method ;
the drains are now commonly put 2J to 3| feet deep
and 15 to 30 feet apart. In one other point a change
has been made ; the pipes are now often 3 inches in
diameter instead of one or two inches as formerly.
Where the drainage was carried out effectively
a most striking improvement resulted. The ground
lost its wet sticky character. It could be ploughed
earlier in the year, so that the seed could be sown
early, and the crops safely left growing later. As the
excess of water was removed air took its place ; better
root growth now became possible and considerable
increases in crop were obtained. Great improvement
also set in on the grass land ; the reeds and rushes
disappeared and the grasses and clovers flourished.
But the change is not entirely permanent ; the drains
gradually become blocked up with silt, with a deposit
formed of oxide of iron together with organic matter,
and with roots of trees or plants ; and considerable
areas of land in the country now require redraining.
We have seen that the most generally fertile
80 THE FERTILITY OF THE SOIL [CH.
soils are the loams, which consist of sand, silt and
clay together with calcium carbonate. Soils lacking
any of these constituents are usually less productive,
but the fertility limits are raised directly the lacking
constituent is supplied.
Thus a sandy waste may be made productive after
addition of clay: and a dense clay soil may be
ameliorated by adding calcium carbonate, and to a
less extent by adding sand. These processes are
simple enough in principle but require considerable
human labour in practice, so that now-a-days they are
relatively costly. They are among the earliest im-
provements in our agriculture, being known and
practised by the Britons according to Pliny ^. His
account of the process afibrds an interesting glimpse
of the agriculture of those far-off days. " The peoples
of Britain and Gaul have discovered another method
for nourishing the land. There is something they
call marl (marga). It contains a more condensed
richness, a sort of fatness of the land.... There were
formerly two kinds only, but several have lately been
put to use by clever men: the white, the red, the
columbina, argillaceous, tui^-like, and sandy are all
used now. Marl is two-fold in nature : hard or fatty ;
these can be distinguished by the touch. In like
manner it has a two-fold use ; some kinds are used
for crops (fruges) only, others for herbage (pabulum)
1 Book 17, 6.
V] RAISING OF THE FERTILITY LIMIT 81
only. The tufa-like variety is good for crops. The
white kind found in streams is extremely rich ; it is
hard to the touch ; if too much is put on it burns the
soil. The red kind is called acaumimarga, it contains
hard lumps of petrified sandy fragments. This is
broken on the ^eld itself and in the first years the
stubble is only cut with difiiculty on account of the
stones. It is put on very sparsely, only half as much
being used as of the other kinds. They think it is
mixed with salt. Either of these kinds put on the
land will last for 50 years.
"Of the fatty marls the chief are the white
varieties. There are several of these: the sharpest
is the one above mentioned. Another is the silvery
chalk. It is sought for deep in the ground, wells
being frequently sunk 100 ft. deep with the mouth
narrow and the shaft widening out as in mines. This
is the kind most used in Britain. It lasts for 80 years
and there is no instance of anyone who has put it on
twice in his life time. A third white marl is called
glisomarga, it is a fullers chalk mixed with rich soil
more productive for herbage than for crops, so that
after the harvest and before the next sowing there
springs up a rank growth to be cut. When it is
applied to crops it produces no other vegetation. It
lasts for 30 years ; if put on too thickly it strangles
the soil. The columbina marl is called eglecopala by
the Gauls, it is equally fertile. It is turned up in
B. 6
82 THE FERTILITY OF THE SOIL [CH.
lumps like stones and shatters into little fragments
under sun and frost. They use the sandy kind if no
other is available, and in any case on marshy soil.
The Ubii are the only people I know of who make
land fertile by digging up the soil to a depth of about
3 feet and then throwing on top a foot's thickness.
That kind does not last more than 10 years."
To this day the "silvery chalk" is dug out in
Hertfordshire just as Pliny describes : a well is sunk
and widened out to a chamber as the chalk is reached:
the chalk is hauled up and spread on the gi'ound.
The well is partly filled in and leaves one of those
dells so characteristic of the fields of the county.
The method that Pliny ascribes to the Ubii has
been very much used. Light barren sands are often
underlain by heavier loam or clay which when brought
to the surface give rise to a fertile soil. Instances
will be given in Chap. VII.
It is not always necessary that the material should
be carried by human labour; the forces of Nature
can sometimes be utilised. Perhaps the best illustra-
tion is furnished by warping, a process introduced
during the early eighteenth century into North Lin-
colnshire and South East Yorkshire and practised
under the name of Colmatage in Tuscany, Romagna,
and the neighbourhood of Naples.
The Ouse, the Trent and other rivers connected
with the Humber are tidal, and as the flood travels
V\
V] RAISING OF THE FERTILITY LIMIT 83
up stream it is seen to be loaded with mud scoured
off from the banks and shores lower down. Much of
the land lies below high-water level and consists of
barren sand or peat. It is therefore divided up into
areas of suitable size (200 acres or more is not un-
common) which are surrounded by banks and then
connected with the river by means of wide channels
fitted with sluice gates. When the flood is high the
sluice gates are opened and the water runs over the
area and is left to stand for 3 or 4 hours. There it
deposits its mud: it is then allowed to run off and
the mud is left to dry as much as possible before the
next tide is due. The process is repeated daily at
both tides so long as the tides are high enough ; the
inlets are periodically shifted and the incoming flood
is skilfully managed to ensure that the deposit is
spread fairly uniformly. In course of three years the
deposit is some 2 or 3 feet in depth. The new land is
now left undisturbed to dry for a time and to get
some of its salt washed out; it is so^vn with white
clover and left for some time to consolidate ; then it
can be drained and levelled and used for ordinary
agricultural crops. Potatoes, wheat, roots, clover and
rye-grass are commonly grown ; they are often arranged
in a three-year rotation, first potatoes (well manured
with superphosphate and nitrate of soda, but no
potash, as this is unnecessary), then wheat and finally
roots, the clover mixture or oats. The land is very
6—2
84 THE FERTILITY OF THE SOIL [CH.
fertile, yielding 10 to 14 tons of potatoes, 7 to 9 quarters
of wheat and still larger crops of oats ; it lets readily
at £2 per acre per annum and is considered to be
worth £40 to £50 per acre, whilst the average cost of
warping is only some £20. The improvement is
permanent, although sometimes the shrinkage of the
land becomes so great after a few years that re-
warping is desirable to bring it up to its old level.
The process is obviously only possible where the
land lies below the level of ordinary high tides. One
large district, Thorne Moors, is in the main rather
too high and an interesting modification is here
adopted. The Moors are mainly peat, and peat is an
article of distinct commercial value; it is therefore
dug out, dried, and broken in a disintegrator; the
coarser part is made up into bales and sold in the
cities as peat moss litter, while the finer material
is sent abroad to be soaked with molasses and
then used as cattle food. Some also is distilled
for the sake of its products. An area of about 200
acres is thus excavated to a sufficient depth — some
5 ft. or more — and the warping is then begun.
The defects of a clay soil cannot so easily be
remedied as they arise from an excess of clay and
fine silt rather than a deficiency of anything. Under
special conditions reclamation has been effected by
digging in great quantities of coarser material: a
V] RAISING OF THE FERTILITY LIMIT 85
considerable tract of land is being treated with city
refuse at Murieston, Midcalder, by the Edinburgh
Distress Committee and a marked improvement in
productiveness has resulted.
Thus the land that we cultivate to-day is far
removed from virgin land; it has been cleared, en-
closed, levelled, often embanked, drained, chalked
and marled by successive generations of cultivators.
No small part of the difficulty of dealing with eco-
nomic land problems arises from the great amount of
capital that has been expended in the past in effecting
the necessary improvements. In many cases the rent
now received for agi'icultural land affords no adequate
return for the outlay incurred even during the past
sixty years. On the other hand it is arguable that
improvements in land are a condition of national
existence and therefore lie outside the scope of
investments made for profit. We cannot now go
into a discussion of these social and economic prob-
lems. The important conclusion is that our land
owes much of its fertility to the labours of those who
have gone before us. The improvements they effected
are not wholly permanent but have to be maintained
and renewed by each generation ; any neglect of this
duty may result in marked deterioration of the land
and may necessitate considerable expenditure of time
and money to bring back the fertility to the level at
which it had formerly stood.
86 THE FERTILITY OF THE SOIL [oh.
CHAPTER VI
THE CHEQUERED CAREER OF THE CLAYS
A CLAY soil needs no description. Everyone is
familiar with the grey, green or dirty red coloured
soil, sticky and slippery after rain, on which in
winter time pools of water lie for days or weeks
together. In the summer it dries to hard intract-
able clods, shrinking so much during the process
that great gaping cracks appear, making the fields
unsightly and in extreme cases even somewhat
dangerous.
But although its general properties are very
characteristic and easily recognisable no one has
succeeded in drawing up any rigid definition of what
is and what is not a clay soil. No sharp line of
demarcation exists in IN^ature, and the clays shade
off by imperceptible gradations into the wholly
different class of soils known as the loams.
Agriculturally the clays are diflicult to plough
because of their stickiness, and for the same reason
they make rather dangerous habitats for seedlings.
It is no uncommon experience to have to sow a
secoi^.d time because the first lot of seeds have be-
come asphyxiated Even Avhen the young plants
VI] CHEQUERED CAREER OF THE CLAYS 87
have struggled through, their troubles are not at an
end, for with the first spell of hot dry weather the
soil dries to a solid crust that is little, if any, better
for them than the wet sticky mass produced by heavy
rain.
The great difference in agricultural value between
clays and loams is sharply revealed by a study of the
face of the country.
Loams, as we have already seen, are very generally
fertile and are practically all under cultivation. In
a loamy district almost every available piece of land
has at one time or another been taken up, and little,
if any, waste land is left. Space is economised as
much as possible ; there are few, if any, village greens
or commons, and even the very lanes and roads
are narrow and often worn deep by the heavy traffic
of bygone days when road-making was still a
lost art.
The hedges are straightened out and well kept,
ditches are filled in unless actually wanted, and the
whole country has a well-cared-for appearance. But
in a heavy clay district there was less temptation to
take in the land so completely. Indeed, some of the
worst of the land probably never was taken in at all,
but remains covered with forest apparently pretty
much in its primeval state. Biean Forest near Can-
terbury, King's Wood running along the North Dotvtis,
many acres of wood in the Weald of Kent, all occupy
88 THE FERTILITY OF THE SOIL [CH.
land that has never been coveted by agriculturists,
and so has always remained untouched. Even
where the land has been taken up the process was
very incomplete: village greens and commons have
been left, the roads are wide, much wider, in fact,
than need be now-a-days, so that only a part is made
up and the rest is left as untidy picturesque wastes
of bramble and briar, inhabited occasionally by a
few roving gipsies or tramps, but of no practical
value to anyone else. The fields are often small
and the straggling hedges and ditches occupy a dis-
proportionally large area of the land. The hedges
are badly kept and the bushes have been allowed to
develope into trees, so that looking over a clay region
such as the Weald of Kent one gets the impression
of a heavily wooded country. The farming is reduced
to its simplest, grass only is grown because that
involves least trouble and expense, and the land
is worked with the lowest possible expenditure of
money and labour.
Such heavy unremunerative soils can be found in
places on the clays of the Coal Measures, the Oxford
Clay, the Weald and elsewhere. They merge in-
sensibly into lighter and more tractable soils, which
in turn shade ofi* into the fertile loams. But no
limits can be set anyw^here. At one end of the series
we have valuable fertile loams, at the other end clay
wastes; and somewhere in between come a number
VI] CHEQUERED CAREER OF THE CLAYS 89
of soils which pay to cultivate when prices are high,
but are unprofitable when prices fall; they then
bring disaster on the holders and soon go out of
cultivation. These soils occupy in the aggregate a
pretty considerable area of the country, and their
history is extraordinarily interesting, because it so
accurately reflects the chequered life of the agri-
cultural community.
Many of these borderland soils first came into
cultivation during the Napoleonic wars when prices
of wheat rose to the highest level ever reached. In
the years of depression between 1813 and 1836 they
went out of cultivation and were commonly allowed
to cover themselves with weeds and grasses, and afford
miserable grazing for unfortunate live stock. After
they were drained in the early 'forties they became
once more productive, and during the prosperous years
of the 'fifties and 'sixties they were in great demand.
Then when the bad times came, culminating in the
disastrous season of 1879, the clay lands again fell
out of cultivation. With a return of prosperity they >^'
were once again cultivated, and now-a-days we find. ;
them converted into good pasture for dairy cattle or
fatting stock and into arable land growing wheat,
mangolds, cabbage and, where possible, potatoes. It
needs but little foresight to see that in the next
wave of depression some of them may again go out
of cultivation.
90 THE FERTILITY OF THE SOIL [CH.
All this time, however, the loams have remained
in cultivation in spite of all vicissitudes of prices and
of seasons.
The story that we have briefly sketched out must
now be studied with a little more detail.
The ancient method of dealing with clays was to
lay them up in high backed ridges so that the rain
could run off into the furrows. There it often lay for
long periods. On these high backed lands cross-
ploughing was impossible ; cultivation was not deep ;
the surface being v/orked only to the depth of two or
three inches and the subsoil was never touched. Only
the ridge carried a crop of any size : the furrows were
too wet in winter and too hard in summer to allow of
plant growth.
Chalking and marling were commonly adopted in
good times or whenever circumstances were pro-
pitious to permanent improvements, but they were
neglected in bad times in spite of the advice of all
agricultural writers. " Howsoeuer this Weald," writes
Gervase Markham in 1625^ of the clay plain forming
the Weald of Kent, " be of itselfe vnfruitful and of
a barren nature, yet so it hath pleased the prouidence
of the Almighty to temper the same, that by the
benefit of Margie or Marie (as it is commonly called)
it may be made not onely equall in fertility with the
other grounds of the Shire, as well for Corne as
* The Inrichment of the Weald of Kent, 1625.
a
o
mm
VI] CHEQUERED CAREER OF THE CLAYS 91
Grasse, but also superioiir to the more and greater
part of the same." The antiquity of this process was
demonstrated " by the innumerable Marie pits digged
and spent so many yeeres past, that trees of 200 or
300 years old doe now grow upon them."
Paring and burning was also a common method of
amelioration. The top two or three inches of soil
were pared off, collected into heaps and burned. (The
agricultural labourer has a wonderful facility for
setting fire to the most unpromising material.) The
process was so managed that the clay was not baked
into brick, but sufiiciently heated to disintegrate it
and partially decompose the organic matter. Then
the heated material was spread over the land and
was found to be very productive. In some of the
eastern counties Blith's draining method was early
applied ; thus Vancover in his Report on the Agri-
culture of Essex in 1795 refers to much of the stiff
clay as being "hollow drained" and dressed with
chalk, after which it continues to give good crops for
20 years or more. Wheat and beans have always
been the most suitable crops for clay farming, and
a common Essex rotation was : fallow, wheat, beans,
wheat, or, where greater diversity was required,
fallow, oats or barley, clover and rye-grass, wheat,
beans. But the implements were cumbrous ; in bad
weather it might prove impossible to get the crops in,
so that a season would sometimes be missed. So
92 THE FERTILITY OF THE SOIL [CH.
long, however, as wheat remained high in price
occasional losses of this kind were not serious to the
farmer. But the labourer suffered, for he found him-
self practically out of work all the winter, excepting
when the ground happened to be frozen sufficiently
hard to enable the dung carts to travel, or when
hedging and ditching had to be done.
Next came a period of depression from 1813 to
1836 when much of the clay land became derelict.
A new era of prosperity opened with the reign of
Queen Victoria and gradually the land was taken
into cultivation. A delightful account has been pre-
served^ of the reclamation during this period of a
cold, wet, clay farm. " Every incoming tenant took it
at about half the previous rent ; dabbled about for
a year or two like a duck, and retired — *lame.' It
was but a simple equation — a very simple one — to
say when the rent would come to zero." The water
did not drain away, "it would stand, day after day,
and week after week, and month after month, shining
along the serpentine furrows, as if it never, never,
never would go again. And the only wonder was
when or how, or by what bold amphibious being the
ridges had ever been raised, which it intersected,
like a sample series of Dutch canals and embank-
ments."
1 Talpa^ or The Chronicles of a Clay Farm, by C. Wren Hoskyns,
1852.
VI] CHEQUERED CAREER OF THE CLAYS 93
A careful survey by the owner showed the ap-
parently level area really had a fall of nine feet, so
that systematic drainage was quite possible. This
was clearly the first step to be taken. Calculations
were made to show the amount of fall that must be
obtained in each field, and the men were set to work
to open up the trenches, so that the levels might be
taken previous to laying in the pipes. With so small
a fall it was necessary that the work should be
accurately done.
But the whole idea was new to the labourers.
They had never seen telescopes and levels and they
were convinced that the farm was level and un-
drainable. "The morning after my head-drainer
had commenced operations I found him hard at
work cutting a drain about eighteen inches deep,
laying in the tiles one hy one, and filling the earth in
over them as he went!..! began something in this
way — ' Why, my good friend, what on earth are you
about ? Didn't I tell you to lay the drain open from
bottom to top, and that not a tile was to be put in
till I had seen it and tried the levels? '...Every inch
of depth was of value at the mouth of so long a
drain. * Three feet deep at the outlet' was the
modest extent of my demand ; and there I stood
watching the tiles thrown in p61e-mele to a depth of
eighteen inches, which I was given to understand
was * about two feet ' with as cool an indifierence to
94 THE FERTILITY OF THE SOIL [cH.
the other foot, as if Two and Three had been recently
determined by the common assent of mankind to
mean the same thing.
" * But I must have it three feet deep.'
" ' Oh, it's no use : it'll never drain so dip as that
through this here clay.'
" * But I tell you it must be. There can be no fall
without it.'
" * Well, I've been a-draining this forty year and
I ought to know summut about it.'
"At that instant my eyes began to open to the
true meaning of those 'practical difficulties' which
the uninitiated laugh at, because they have never
encountered them ; and the man of science despises,
who has said to steam, water and machinery 'do this,'
and they do it, but has never known what it is to
try and guide out of the old track, a mind that has
run in the same rut ' this forty year and more '."
By a skilful appeal to the old man's vanity the
matter was rectified and the drains properly laid.
Then came the next improvement — throwing down
the high ridges in which the land had formerly been
laid, and flattening out the field, so that the imple-
ments could work more easily. This met with even
more serious opposition, and a long struggle ensued
with the collective experience of the district. " My own
working bailifi^ headed the attack Avithin the camp ;
while a neighbouring clergyman led on the foe from
VI] CHEQUERED CAREER OF THE CLAYS 95
without, evidently viewing the heresy in a serious
light, and myself as a fit subject for an auto da f4.
The conclusion of our last skirmish was too good to
be lost to posterity. I entered it verbatim in my
farm memoranda.
" 'But tell me in earnest Don't you mean to ridge
up that field again ? *
"'No.'
" * What, you mean to lay it Flat ? '
"'Yes.'
" ' In the name of Goodness, Why ? '
" ' Because the name of Goodness — made it so.*
" If I had suddenly assumed some demoniacal form,
and then, leaving a train of smoke and brimstone,
vanished, with a clap of thunder, from before the eyes
of my catechist, I do not think his face would have
assumed a greater expression of resourceless and
complete astonishment ^"
Next, the material thrown out from the drains
was put on the surface of the land — an operation
that was regarded as the crowning act of folly and
brought up the wise men from far and near to look
and scofi*.
Lime was now put on.
1 The "worthy clergyman's astonishment was not wholly unreason-
able because in levelling the ridges a considerable amount of very
unkindly subsoil must have been exposed, which would only slowly
weather down into a decent soil.
96 THE FERTILITY OF THE SOIL [cH.
Then the small fields had to be made into bigger
ones : hedges were grubbed up and the banks were
thrown down, much to the disgust of the local fox
hunters and rabbit shooters.
Turnips were then sown — they had never pre-
viously been grown on the farm — and they were ferti-
lised with guano which was then just coming into the
country. This evoked much comment from the local
wits, but the crop was magnificent, being far the
best in the countryside. "It was stared at and
stared at again, as a sort of conjuror's trick which
^You couldn't do again.' 'Wise men shook their
heads and held their tongues at it. Nobody would
have been at all surprised if, on going to the field
some fine morning, he had found it altogether
vanished, like faery money, as quickly as it came :
and as the roots swelled and swelled into confirmed
substance and reality through September and October,
the silence about it became perfectly portentous....
Where did the crop come from ? How did it grow ?. . .
Surely it must at any rate be but a fraud upon the
land after all ; and the next crop would show the
different results of real manure and a mere stimulant.
This was the point to which ojnnion at last settled
down. * We'll wait and see ' was the final determina-
tion expressed."
The big crop of turnips enabled sheep and cattle
to be kept, and their manure helped to enrich the
VI] CHEQUERED CAREER OF THE CLAYS 97
land and to keep the fertility up to the new level
to which the drainage and liming had brought it.
But the introduction of live stock had far-reaching
economic effects also : it afforded employment for
the labourers during the winter, and it had a steady-
ing influence on the farm receipts. For when the
price of wheat was low that of meat was high, and
vice versa, a relationship that crystallised into the
saying, " Up corn, down horn."
In this way many clay farms were made fruitful ;
lime and chalk once more came into use, and the
introduction of artificial manures and of concen-
trated feeding stuffs for the animals contributed
largely to the increase in crop production that was
taking place.
But the tide of prosperity began to turn, and in
the late 'seventies a run of bad times set in, ruining
many farmers and throwing out of cultivation much
of the land that had been reclaimed. It lay for
years neglected and covered with grass and weeds ;
its only use was to afford a little poor grazing for
live stock. It was certainly gaining fertility and
increasing its stores of nitrogenous organic matter,
but it afforded little sustenance to the farmer.
Essex, which had in the 'sixties been extremely pros-
perous, looked like becoming derelict : other clay
counties fared no better. Many of the farmers who
survived met the crisis by laying down their land to
R. 7
98 THE FERTILITY OF THE SOIL [ch.
gi'ass, dismissing their labourers and reducing their
working expenses to a minimum. Great was the
distress all round. Tales of those days are still told
in the villages, and are indeed often the only in-
formation possessed by the well-meaning agricultural
reformers who dwell in the cities.
Part of the agricultural depression was due to the
opening up of the western states of Canada, and part
of the recovery was, in return, effected by the labour-
saving machinery invented and made out there.
Under the older system in vogue in 1890 the cost
of harvesting wheat came to 27s. to 305. per acre
on a certain large corn farm : with the new bindera
the cost was reduced from 1897 onwards to 16s. to
18s. per acre on the same farm. Further, new
methods began to come in. Essex was invaded by
good Scotch farmers who were untrammelled with
any views as to the necessity for growing wheat and
beans, and turned instead to dairy produce and
potatoes. For miles round London and other large
cities dairying has saved the situation and once more
brought into use land that had gone derelict. Else-
Avhere (e.g. in parts of Leicestershire) cattle are
bought and fattened, while costs of production are
cut down by the introduction of labour-saving devices
and by skilful management. The introduction of the
mangold into British agriculture has been a great
boon to the clay farmer ; this crop is much more
VI] CHEQUERED CAREER OF THE CLAYS 99
reliable than swedes on clay land and, together with
cabbage, which also does well, affords valuable suc-
culent food to the animals, while on the lighter fields
of the farm swedes can also be grown. Much food
has to be purchased — brewers' grains and cotton cake
being special favourites — and this contributes to the
fertility of the land. Large quantities of manure
are also imported, for mangolds respond perhaps
more than any other crop to liberal treatment, and
are found to yield most profit when well manured.
Thus the fertility of the arable land is being pushed
well up. But the mainstay of clay farming is the
grass land. Grass is the cheapest and easiest crop
to raise and is steadily gaining ground at the expense
of the arable crops. Temporary pastures figure
very prominently, particularly in northern systems
of agriculture. Magnificent permanent pastures are
found on some of the better clays of Leicestershire,
and on the low-lying alluvial flats round the estuaries
of some of the rivers and elsewhere; some of these
with very little trouble will carry and fatten live
stock. Over large areas, however, the grassland is
poor, but it is now receiving considerable attention.
Although for years it often carried nothing more
than a poor, thin growth of weeds and grass it really
did not need any very great outlay to be considerably
improved. A dressing of 10 cwt. of basic slag per
acre has often a wonderful effect in increasing the
7—2
100 THE FERTILITY OF THE SOIL [ch.
growth of clover and producing a more nutritious
herbage.
Trouble still arises from the presence of epizootic
diseases in animals grazing on clay land, but this will
no doubt be overcome as fuller knowledge is gained
of the fauna of the soil. Often, however, the drainage
is faulty. Over much of the Midland clay area the
drains were laid in the middle of the last century
at a depth of 4 ft.; this is now kno^vn to have
been too far down. Here the trouble arises from the
slowness with which the rain water gets away. The
drains should, therefore, only be placed about 2^ feet
deep. In many cases also the grassland needs plough-
ing up and resowing with a suitable mixture. Finally,
many clay farms need a good dressing of lime or
chalk over the whole land, arable and grass alike.
Once the grassland is improved it commonly gets
well treated ; manure is put on if it is cut for hay, and
concentrated food is supplied to the animals put out
to graze on it. The grassland is consequently main-
taining or increasing its fertility. At the present
time, therefore, clays within reach of cities have dis-
tinct possibilities. Those further off, however, are
frequently in a poor state and are more famous for
the fox-hunting they afford than for their agriculture.
Sometimes summer milk is produced to be sold to
the cheese makers, but this trade is at a standstill in
winter ; sometimes also young store stock are raised
VII] THE RISE OF THE SANDS 101
to be sold off to the better farms. For it is a general
rule that the raising ot young store stock is most
suitable to the man who farms poor unimproved land
without much capital, while diiilying and fattening
are most suitable to the man who is going in for high
farming.
The clays have probably never been managed on
sounder lines than they are at present, but the lesson
of history is absolutely clear ; these soils are very apt
to suffer in bad seasons and to ruin their occupiers
in times of depression. A good margin must therefore
be allowed for contingencies. Especially ought small
holders and beginners to remember that the profit
these soils can be shown to yield over a run of good
seasons changes with disastrous suddenness to serious
loss as soon as bad times come.
CHAPTER Vn
THE RISE OP THE SANDS
Starting once more from the fertile loams, a
succession of soils can be traced, getting lighter and
lighter and finally ending in the coarse material of
heaths and sand-dunes. Thus we can begin with
clay wastes, work through the fertile loams, pass on
102 THE FERTILITY OF THE SOIL [CH.
to cultivated sands and finally end in sand wastes,
and find all the way gvadual transitions with never
a break to mark off the different classes of soils.
A typiciil sandy soil is. ^ust as characteristic as a
typical clay, but it equally denes rigid definition.
In many respects sand is the opposite of clay in
general properties. Sandy soils have little power of
holding water and therefore dry very readily ; they do
not long remain wet even after heavy rainfall. They
are not sticky. The rock from which they are formed
is generally somewhat hard, and so it has often hap-
pened that they have suffered less erosion than the
clays, and have not, like the clays, been hollowed out
into broad valleys. The ease with which water per-
colates through sand has led to the washing out of
much of the soluble material, so that little is left
except hard insoluble mineral grains which furnish
but scanty food for plants.
Agriculturally the sands are a very mixed group.
Their small power of retaining water is a serious
disadvantage, partly because they become liable to
drought, and partly also because of the ease with
which manurial substances are washed away and
lost. A good many of these soils happen to lie in
relatively low situations and to receive underground
water from the land above; these are often suffi-
ciently supplied with water for all crop purposes.
Others lie rather too high to enable the underground
VII] THE RISE OF THE SANDS 103
water to be utilised. Thus the value of a sand
depends very much on its situation. A soil that
is fairly uniform may be fertile in one place where
water is available, but infertile in another not far
off, where the water is out of reach. Where cultiva-
tion is possible it is very easy : the land can be
worked almost directly after rain, seeds can (and in
fact must) be sown early in the year, and crops ripen
quickly and easily.
The sands that most resemble the loams — the so-
called sandy loams — have usually been in cultivation
as far back as any record goes. The lighter sands
have only slowly been taken up, and the process is
not yet complete, considerable areas being still left
as waste.
The stretch of country surrounding Fakenham and
Wells in Norfolk is classical ground for the student
of agricultural history. It was to Raynham, near
Fakenham, that Charles, second Viscount Townshend,
retired in 1730, after his political life was over, and
began those farming experiments that were destined
profoundly to influence our methods of husbandry.
At the outset the land was a barren sandy waste.
His first step was to apply marl which considerably
increased its productiveness. This, however, was no
new discovery ; marl was well known in Norfolk,
although it had long fallen into disuse. Lord
Townshend's great advance was the clearness with
104 THE FERTILITY OF THE SOIL [CH.
which he recognised the conditions that make for
fertility in sandy soils. Owing to their small reten-
tive power they have to receive frequent dressings
of manure, and this course is only possible where a
considerable number of animals are kept. Means
therefore had to be designed for combining animal
husbandry with crop growing — two branches of farm-
ing which in the past had often been found mutually
antagonistic. Lord Townshend's method was to grow
turnips on the large scale, and then allow the animals
to eat the crop in situ, so that their manure might
fertilise the land for the next crop and their treading
might consolidate it and so improve it as a seed bed.
After turnips a crop of barley was taken and after
this a crop of grass and clover, part of which could
be cut as hay to supply food for the animals during
winter, and the remainder eaten in the field by the
animals in order to fertilise the ground for the wheat
crop. Then turnips were taken again. The clover
increased the stock of soil nitrogen and insured the
permanency of the system so far as nitrogen is con-
cerned. The plan was thoroughly sound and entirely
successful; a manuring crop was taken, and then a
cereal crop, then a second manuring crop and then
another cereal crop. Both animals and crops
flourished. So good is the plan that it survives to
this day under the name of the Norfolk rotation,
and many progressive farmers still use it with but
VII] THE RISE OF THE SANDS 105
the small modification that they often grow two corn
crops in succession after the turnips.
But it commonly happens in the history of agri-
culture that improvements are adopted only very
slowly, and Townshend's improvements were no
exception to the rule. Certain difficulties also arose
which Townshend did not overcome. Turnips were
found to be liable to attacks of a minute beetle,
Phyllotreta nemorum, commonly known as the Fly,
which in dry weather sometimes almost destroyed
the crop and left the animals without any food for
the winter. Red clover (the ordinary variety grown)
will not always grow every fourth year, but sometimes
fails after the second or third course for some reason
which is still obscure. Thus under the combined
attacks of Turnip Fly and of Clover Sickness the
farmer might find himself with a number of animals
on his hands and no food for them, an awkward
predicament from which he rarely extricated himself
without considerable financial loss.
Fortunately another public-spirited landowner in
the same district came forward and continued the
experiments. Thomas William Coke, afterwards
Earl of Leicester, inherited in 1776 his uncle's estate
at Holkham, about twelve miles north of the scene of
Lord Townshend's labours. The country was poor
in the extreme. "All you will see," said old Lady
Townshend to young Mrs Coke as she was going for
106 THE FERTILITY OF THE SOIL [ch.
the first time to her new home, " will be one blade of
grass and two rabbits fighting for that." Coke's bio-
grapher and great-granddaughter, Mrs Sterling, thus
describes it\ "When Coke came into the property
the whole district round Holkham was little better
than a rabbit warren, varied by long tracts of shingle
and drifting sand, on which vegetation, other than
weeds, was impossible.. . .Indeed throughout the county
of Norfolk the agriculture was of the poorest descrip-
tion. Between Holkham and Lynn not a single ear
of wheat was to be seen, and it was believed that not
one would grow. All the wheat consumed in the
county was imported from abroad. And, meanwhile,
everything that ignorance could do was done to
impoverish further an already miserable soil. The
course of cropping where the land would produce
anything was three white crops in succession, and
then broadcast turnips. No manure was ever pur-
chased. The sheep were a wretched breed, and,
owing to the absence of fodder, no milch cows were
kept on any of the farms." Coke does not seem to
have begun experimental farming out of any abstract
desire for knowledge ; he was led to it by the obstinacy
of an old-time farmer named Brett. The lease under
which this man held his farm had fallen in and was
under discussion for renewal; the original rent had
been eighteen pence per acre ; this was subsequently
1 Coke of Norfolk and his friends. London, 1908.
VII] THE RISE OF THE SANDS 107
raised to three and sixpence, and Coke now wanted
five shillings. " Mr Brett jeered at the suggestion,"
continues Mrs Sterling, "and pointed out that the
land was not worth the eighteen pence an acre
originally paid for it. This was suflScient for a man
of Coke's temperament, he immediately decided to
farm the land himself."
No adequate history of Coke's agi-icultural work
has been written^, but fi-om 1778, when the little
incident just mentioned took place, down almost to
the time of his death in 1842, he continued to make
advances in the management of sandy land and dis-
seminated his results at the great annual gatherings,
the " sheep shearings," which for 43 years he held at
Holkham. Realising the beneficial effects of grass
and clover on the land, he left these crops growing
for two, three, or even four years, thus adding to the
nitrogenous organic matter of the soil, besides getting
supplies of hay for the animals. Marl was applied
in the first year at the rate of 80 to 100 loads per
acre and left to wash into the land as long as the
grasses stood there. When the land was ploughed
up wheat was sown. Usually the amount of farmyard
manure was insufficient for this crop, at any rate in
the early days of the improvements, and manure had
to be purchased. Rape cake (an old fertiliser in
* Some account ia given in Dr Eigby's Holkham, its Agri'
culture^ etc., 1816. 3rd edition, enlarged, 1819.
108 THE FERTILITY OF THE SOIL [ch.
Norfolk, brought in from Ireland and from the English
mills) was therefore applied with excellent results:
it cost £5 per ton and was used at the rate of 5 or
6 cwts. per acre : later on, however, the price rose
considerably. After wheat, turnips were grown, and
then barley followed by grasses as before. Thus the
rotation was that of Lord Townshend except that
the grasses were left growing for several years, and
peas appear sometimes to have been sown after the
grass was ploughed up and before the wheat crop
was taken. Alongside of this improvement in cul-
tivation he elFected great improvements in the live
stock of the district. He compelled his tenants to
adopt a proper rotation and induced them to pur-
chase good animals. So successful were his eflPorts
that as early as 1784 Young states that "Mr Coke
resides in the midst of the best husbandry in Norfolk,
where the fields of every tenant are cultivated like
gardens." There was a great surplus of produce,
wheat and live stock were sold and the whole district
became very prosperous.
Tlie difiiculties inherent in the Norfolk rotation —
turnip fly and clover sickness — now engaged his
attention. Although he did not suimount either
difficulty (no one has done so even yet) he got over
them by increasing his range of crops so that he
should not be wholly dependent on turnips and
clover. Instead of having the whole of the land
VII] THE RISE OF THE SANDS 109
in four crops he devoted some of it to other fodder
plants. Sainfoin in particular proved valuable; it
yielded considerable quantities of nutritious hay for
winter, and, being a leguminous plant, it greatly en-
riched the soil in nitrogenous organic matter. Tares
also were sown; some in October or November, some
in April and May, to alFord more green food to the
animals.
Later on he grew mangolds, cocksfoot, potatoes,
and he made experiments with other fodder crops.
He purchased oil cakes for his animals, and thus
not only fattened them more rapidly but also in-
creased the amount of fertilising material in the
manure. In this way he imported fertility fi^om other
districts to his own, a process which has now become
a regular part of British husbandry. Thus sheep and
cattle were the central feature of the farm as in Lord
Townshend's system, but Coke increased the margin
of safety by having certain areas of other fodder
crops not liable to the same ills as clover and turnips,
so that if one set of troubles intervened he would
still have a reserve of food for his animals.
Little has been added to our knowledge of the best
methods of farming sandy soils, and in all essentials
our best present day methods are practically the same
as these. The reclamation of the sands was now
within the power of any landowner and was soon
taken in hand in many districts. The Duke of
110 THE FERTILITY OF THE SOIL [CH.
Bedford reclaimed much of the sand at Woburn^
and before long the old parish turbary was waving
with corn. An example of a later reclamation is
afforded by Delamere Forest, Cheshire. The marl
pits having been formed and opened, a tramway was
laid from the pits to the land. Dressings of marl
were given varying from 100 to 180 cubic yards per
acre at a cost of £7 to £10 ; in consequence the land
which before marling was not worth 5s. per acre
afterwards let at £1. 10s. per acre I The light sand
of the Pays de Waes, lying between Antwerp and
Ostend and traversed by the Waesland railway, has
also been reclaimed by the application of clay or
marl.
Sometimes, however, the barrenness of a sandy
soil is due to a layer of rock or a "pan" lying near
the surface and interfering so seriously with the move-
ments of the soil water that proper plant growth can-
not take place. In such cases the only possibility is
to break up the rock and pick it out, a laborious
enough process even now when steam implements are
available, and still more so in the early days. An
example is furnished by Coxheath, an area of some
900 acres near Maidstone. This used to be waste
land, but in 1814 an Enclosure Act was obtained.
The gi'ound was then trenched and the layer of rock
broken and removed. Over part of the land no
^ Journal of the Royal Agricultural Society ^ 1864, p, 369.
n3
O
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VII] THE RISE OF THE SANDS 111
further treatment seems to have been necessary, and
good crops were at once obtained after a reasonable
outlay on manure; so permanent was the improve-
ment that the land still lets for £2 per acre per
annum. Other of the land, however, was very poor
and required heavy manuring before it became
productive. Most of the land thus reclaimed was
divided among the lords of the manors and others
possessing rights of common, of cutting turf, etc.,
while part of the remainder was sold to defray the
expense of reclamation ; the stone that was taken
out lay stacked along the roads in enormous quan-
tities, and people thought it never could be used,
but subsequently it was all required for making up
the Weald roads. The reclamation went on between
1814 and 1818, but was not completed: only recently
has the whole of the land been taken in, the last
surviving piece of waste having proved a considerable
nuisance because of the gipsies that encamped there.
The system of managing sandy soils introduced by
Townshend and Coke is, as we have seen, a combina-
tion of crops and live stock : nitrogenous compounds
are added to the soil by clover or other leguminous
crops, and by purchased oilcake: lime, potassium
salts, phosphates are also added : the crops so grown
are (with the exception of grain) fed to animals to
make manure for more crops. Crops and live stock
112 THE FERTILITY OF THE SOIL [CH.
are thus mutually interdependent, and any break-
down on the part of either causes the collapse of
the system.
Another method of dealing with sandy soils has,
however, long been practised. The ease with which
they are cultivated and the earliness at which their
crops ripen marked them out long ago as eminently
suitable for market garden produce. The light loams
of East Kent have grown fruit since Tudor times.
Vegetables and fruit were long ago grown on the
light soils round London, and the practice was ex-
tending by the end of the eighteenth century even
in places as remote as Suffolk; stable manure was
barged from London to Manningtree and sold at lOs.
for a five-horse load at the quay, while carrots were
grown on the sandy soils and sent back to London.
This system has now developed very extensively,
and now-a-days considerable areas of sand produce
potatoes, vegetables or fi'uit to be sent off to the
cities, and are fertilised with stable manure and
other refuse brought back from the cities.
A third system is in use. The introduction of
artificial manures has enabled the sand farmer to
be wholly independent either of live stock or of city
manures for keeping up the fertility of his soil. The
classical instance of tliis type of management is
afforded by the Lupitz estate at Altmark, Saxony.
VII] THE RISE OF THE SANDS 113
When Herr Schultz came into possession in 1855
the land was largely a barren heath, yielding crops
only at considerable expense. He soon observed,
however, that lupins grew well provided the rainfall
was sufficient (the average fall was 27 inches), and
also found that they enriched the soil in nitrogenous
organic matter and fertilised the next crop. His
method as finally worked out was essentially as
follows : leguminous crops were gi'own and fertilised
with mineral manures — lime, phosphates and potas-
sium salts — in order to induce considerable plant
development and therefore considerable nitrogen
fixation. Some of the crops were cut for hay, but
in the main they were ploughed in, thus adding to
the soil the nitrogenous organic matter of the stems
and leaves as well as of the roots. Crops thus
ploughed in are called green manure. An acre of
green crop was found to furnish roughly as much
nitrogen as 10 to 15 tons of farmyard manure, and
this, taken in conjunction with the nutrients added
in the artificial fertilisers, sufficed to yield large crops
of grain and potatoes. Thus, without purchasing
nitrogenous manures (which are very costly), and
without keeping much live stock, Schultz was able
by periodical green manuring enormously to increase
the productiveness of his land. This extremely valu-
able method has been much adopted in Germany.
Where high priced crops are grown it may prove
B. 8
114 THE FERTILITY OF THE SOIL [ch.
more profitable to purchase nitrogenous manure
instead of making it through the agency of legu-
minous crops. Dr C. S. Edwards adopted this course
in his recent successful reclamation of a considerable
area of derelict sand at Tangham, Capel St Andrew,
Sufiblk. The heather and bracken having been
eradicated, 20 to 25 loads per acre of " crag " (finely
divided shells, silts, etc., rich in calcium carbonate
and occurring in deposits just below the surface)
were put on at a cost of about £1 to £2 according
to the distance from the pit, and then the land was
broken up. It was usually necessary to do this with
the steam cultivator because the large number of
rabbit holes made the ground dangerous for horses.
After about four to eight cultivations the land was
sufficiently level, the rabbit holes filled and the weeds
killed : this cost up to £2 per acre. A second cragging
is now advantageous. The crops grown are wheat,
oats, potatoes, blue peas (sold dried for human con-
sumption) and carrots; for the working horses and
the pigs a patch of lucerne is grown. As everything
is sold ofi* and no stock is kept (except pigs to
consume waste potatoes, etc.), it is unnecessary to
adhere to any rigid rotation, and the farmer can
grow whatever promises to yield most profit. The
artificial manures used are : for carrots and potatoes,
1 cwt. of muriate of potash and 1| cwt. of bone meal
applied in April, IJ cwt. each of nitrate of soda or
VII] THE RISE OF THE SANDS 115
lime and sulphate of ammonia applied in two dressings
later on ; for wheat or oats, 1 cwt. nitrate of soda or
lime or sulphate of ammonia, J cwt. sulphate of
potash and f cwt. of bone meal; for peas, ^ cwt.
sulphate of potash and f cwt. bone meal. Such little
dung as is got goes on the lucerne or on the wheat.
Careful cultivation is necessary to preserve a fine
mulch, whereby the soil retains its moisture, and also
to keep down weeds which are apt to be a con-
siderable nuisance: even the freshly-broken ground
covered itself with spear gi'ass (couch), makebeg
(spurry) and sorrel, while later on iron weed (poly-
gonum), pansy, cranesbill and others came in.
The great advantage of the system is that it can
be worked with but little capital and at a minimum
of risk. It is therefore well adapted for small holdings,
for which purpose, indeed, it was devised. The returns
have been very satisfactory : the sales have averaged
£6 to £7 per acre, while a rent of 15s. per acre was
found to pay 5 per cent on the cost of reclamation,
5 per cent, on a sinking fund, and also the rates and
the rental imposed by the superior landlord.
The occupier of a sandy soil has therefore several
possibilities open to him. If he can command capital
he can go in for live stock and work on the Townshend-
Coke system. If he prefers cultivation he can go in
for intensive market gardening. If he has little or
116 THE FERTILITY OF THE SOIL [CH.
no capital he can work on Dr Edward's lines and
gi'ow the more highly priced of the ordinary crops
by the use of suitable artificial manures.
An instance may be given of the modern develop-
ment of the Townshend-Coke treatment of light sandy
soils. The farm is on a light sand in Surrey, and is
so dry in summer that satisfactory grass cannot be
grown ; no sheep are therefore kept during the warm
months of the year. Sheep are bought in from Sussex
and the West Country in September and are fattened
on the land during the winter; they are sold as
fast as they are ready and are all cleared out by the
end of May. Considerable amounts of green crops
are grown for them, including trifolium, green rye,
rape, kale, turnips, swedes, and a mixture of clover
and rye-grass, whilst large quantities of oil-cake and
purchased grains are also supplied. The land thus
becomes well fertilised, and is now sown with spring
oats, which are often succeeded by a crop of malting
barley. Then a mixture of rye-grass and clover is
sown to afibrd hay in June and green food in
September. The land is then ploughed up for winter
wheat, and a dressing of London stable manure is
given so as to ensure a satisfactory crop of sti*aw
which is sometimes a very saleable commodity. Re-
course is had to artificial manures and periodically to
lime in order to maintain fertility at a high level.
Instances of the market garden method occur on
VII] THE RISE OF THE SANDS 117
almost any sandy soil within access of a large city,
especially where one man happens to have prospered
and so given the locality a reputation. No general
rules can be given about the management : the
successful grower generally keeps his land continu-
ously cropped and carefully watches the markets so
as to grow those things likely to yield most projfit.
The following is an actual example. The grower is
near to London and has access to a riverside wharf;
he buys as manure City refuse, cleanings from
cattle steamers, unsold lots of stable manure, con-
demned fish, and any odds and ends of manurial
value. He also takes for a consideration some of
the local sewage. His ground is never idle: early
potatoes, onions, sprouting broccoli, peas and other
crops succeed each other without delay, odd comers
are filled up with early carrots, radishes, etc, all the
crops are carefully nursed so as to be ready for market
while prices are still high, i.e. before other people
have their produce ready. Much fruit is grown, pigs
are kept in the orchards to do the cultivation and
devour unsaleable crops. Considerable advantage is
taken of labour-saving devices. The grower's success
does not stop at production, but extends also to the
business side. Market garden produce is sold to
salesmen in the large markets who in turn have to
keep contracts with large customers. This grower,
being eminently successftd and dependable even in
118 THE FERTILITY OF THE SOIL [CH.
bad seasons, is therefore a useful stand-by for these
people, and receives respectful consideration at their
hands.
Considerable areas of sand, however, still lie waste
in the agricultural sense. But they are not neces-
sarily unproductive from other points of view. Some
of the most delightful scenery in our country is to be
found on the sands; even the most ardent reformer
would hardly wish to root up the New Forest, the
Bournemouth pine woods, the Wareham and Dor-
chester heaths, and substitute fields of turnips and
sheep. Elsewhere, also, golf links have proved
extremely remunerative. Considerable tracts of sand
are given up to game. And there lies one of the
difficulties of the situation. For game sometimes
plays a very large part in the economy of the
countryside, and may dominate pretty completely
the movements both of man and of beast. There
are parts of East Suffolk where the cottagers' cats
have to live chained up like yard dogs in order to
be safe from the gamekeepers' guns, while extensive
damage is often done to the crops by birds, hares and
rabbits. And so it happens that the man who under-
takes to reclaim derelict sand and bring it into culti-
vation has not only to overcome the natural difficulties
of the problem, but also to come to terms with the
game preservers.
Lastly, the sand dunes are now beginning to
VIII] MOORLAND AND FARMING 119
attract attention. It has long been the practice to
plant these up with conifers or other suitable trees,
but in New Zealand dune pastures are produced
instead. Marram grass {Ammophila arundinacea)
is first grown to fix the sand, and then the tree
lupins (Lupinus arbor eus)] finally pasture grasses
are sown, especially such as, under the prevailing
conditions, make considerable root and so add to
the stores of soil organic matter.
CHAPTER VIII
THE MOOR — WHAT SHALL IT BECOME?
We have already dealt with the reclamation of
the fens, we must now turn to the wholly distinct
case of the moors. Speaking generally the moorland
tracts of the country lie in high regions of considerable
rainfall : the fens, on the other hand, are low lying
and have a much smaller rainfall. When the fens are
drained they become at once fit for cultivation and
yield considerable quantities of potatoes, wheat and
other crops. But the high moors do not : their soil
is fundamentally difierent ; their rainfall is too high
for satisfactory crop production ; and owing to their
120 THE FERTILITY OF THE SOIL [CH.
great altitude the winters are so severe that any
kind of farming is attended with risk and difficulty.
Low-lying moor and peat districts may escape
these climatic disadvantages and then their reclama-
tion becomes simply a matter of soil treatment.
Chat Moss in Lancashire affords an instance : it was
first drained to remove excess of water and then
heavily treated with town refuse from Manchester
which enabled it to yield crops. An arrangement of
this sort is mutually advantageous to city and country
so that the expense can be distributed. But else-
where the carriage of bulky extraneous matter
becomes too costly to be borne entirely by the
reclaimed land, and more concentrated ameliorating
agents become necessary.
The problem has attracted considerable attention
in Germany and Sweden and is under investigation
at the special experiment stations at Bremen and
Jonkoping. Enough has been done to show that
treatment with artificial manures leads to profitable
crop production, especially of rye, oats and potatoes,
on drained land. These crops do not stand in great
want of lime, and need only a few hundredweights
per acre of potassic, phosphatic and nitrogenous
fertilisers. But when it is desired to diversify the
agriculture, liming becomes necessary and may prove
costly. In some districts Hiltner has successfully
solved the problem of growing leguminous crops,
VIII] RECLAMATION OF THE MOOR 121
and has thus opened up the possibility of raising
potatoes and cereals more cheaply than before.
An interesting piece of reclamation went on under
Nilsson's direction in Gothland, Sweden. More than
30,000 hectares of the island consisted of barren
swamps, and yet the soil was rich both in lime and
in nitrogen. Nilsson showed that the limiting factor
was lack of phosphorus. The ground was therefore
drained and treated with phosphatic manure ; it then
yielded excellent crops of corn, rape and sugar beet.
Instead of depending wholly on foreign supplies of
phosphates, investigation was made by Wiborgh of
the iron ore occurring in Northern Sweden and known
to contain calcium phosphate : a method of extraction
was devised and quantities of this Wiborgh phos-
phate were produced at Lulia. Subsequently a
cheaper process was worked out by Palmaer.
In the Isle of Ely phosphates are also found to be
the limiting factor and dressings of superphosphate
result in marked crop production ; elsewhere, however,
potassium compounds constitute the limiting factor.
A well-known example is furnished by the Momence
experimental field set out by Dr Cyril Hopkins in
Illinois, where potassic fertilisers yield good crops but
other fertilisers prove useless. Dr Hopkins^ tells
a pathetic story of a settler who spent years of un-
availing labour on some of this black soil and did not
1 The Story of the Soilf Boston, 1912.
122 THE FERTILITY OF THE SOIL [CH.
find out till too late the one thing needful. The man
had brought his wife and children to see the heavy
crop on plots treated with potassic fertiliser alongside
of the miserable one on the untreated land. "As he
stood looking, first at the corn on the treated and un-
treated land, and then at his wife and large family of
children, he broke down and cried like a child. Later
he explained to the superintendent who was showing
him the experiments, that he had put the best of his
life into that kind of land. *The land looked rich,'
said he — ^ as rich as any land I ever saw. I bought
it and drained it and built my home on a sandy knoll.
The first crops were fairly good, and we hoped for
better crops ; but instead they grew worse and worse.
We raised what we could on a small patch of sandy
land, and kept trying to find out what we could grow
on this black bogus land. Sometimes I helped the
neighbours and got a little money, but my wife and
I and my older children have wasted twenty years
on this land. Poverty, poverty always. How was
I to know that this single substance which you call
potassium was all we needed to make this land pro-
ductive and valuable ? '"
The peats can be made productive if the climatic
conditions are favourable. The agricultural utilisation
of moorland depends mainly on this consideration.
Obviously nothing but actual experiment would de-
termine what could be accomplished, but at the
VIII] MOORLAND AND GAME 123
present moment there seems little likelihood of any
serious attempt being made in this comitry. For
game has taken possession of the moorland, as of
other land of low agricultural value, and having once
got possession it is not easily displaced. A system of
farming is in vogue that does not clash with game ;
sheep are allowed to graze on the moorland, while
the lower fields are kept in grass to furnish a little
hay when needed The land thus yields two rents :
the shooting tenant on a Lancashire moor may pay
38. 6cL per acre, while the agricultural tenant pays
2s., a total of 5s. Qd. Any agTicultural development
that involved displacement of the game would have
to yield a sufficiently increased rent over the whole
moor or the owner would lose financially, and it is
difficult to see on our present knowledge what agi'i-
cultural system could do this^. Only a properly
conducted experiment could decide the matter.
1 An instance is given by Mr Pell in the Journal of the Royal
Agricultural Society for 1887, where £24. 7s. 6d. was spent per acre
in reclaiming a moor, and the increased rental only amounted to
Bs. 2d. per acre.
124 THE FERTILITY OF THE SOIL [CH.
CHAPTER IX
CONCLUSION
We can now sum up the general conclusions to
which the previous chapters lead.
The problem of making a soil fertile consists in
finding out first what conditions the plant requires
for its proper development, and then altering the soil
as far as possible to make it meet these requirements.
If the discrepancy between the actual and the ideal
is too great the plant may be altered by the breeder
in such a way that its new requirements shall be
nearer the actual possibilities of the case.
It is always most economical to select crops
naturally adapted to the climatic and soil conditions,
so that the gap to be bridged shall be small. Our
problem is to alter the soil : in the first instance it is
necessary to ascertain what the actual soil conditions
are, and then to find which constitutes the limiting
factor and to change that one. Probably another will
now be found to set the limit : this must in turn be
changed and so on until the limit is set by the
incapacity of the plant to make further growth, and
not by any soil factor. The responsibility of the soil
investigator is now at an end, and the problem becomes
one for the plant breeder.
IX] CONCLUSION 125
The soil conditions fall mainly into four groups.
(1) The physical constitution of the soil determines
the movement of water, of air, and of the plant roots.
(2) The chemical composition shows the amount of
food materials present, and whether there are any
detrimental substances in the soil. (3) The micro-
organisms of the soil are very mixed, some of them
work up certain of the food materials into forms
suitable to the plant and are therefore eminently
useful, others are detrimental in various ways.
(4) Extrinsic factors such as climate, situation of
the soil, nature of the subsoil, etc., play an important
part. Any of these groups may determine the fertility
of a particular soil. To a certain extent, however, all
of them are under control. The physical constitution
is altered and made more favourable to plant growth
by adequate cultivation, by addition of organic matter
(e.g. farmyard manure) and if necessary of lime, chalk,
marl, or clay. The chemical composition may be
entirely altered so far as food constituents are con-
cerned by adding appropriate fertilisers. Control of
the micro-organisms of the soil is as yet in its infancy
although a beginning has been made. The extrinsic
factors are naturally less easy to change, but the
subsoil may be altered by breaking any pan or rock
layer, and drainage may be effected by suitable means.
Soils do not fall into sharply defined classes but
form a perfect gi'adation from intractable clays
126 THE FERTILITY OF THE SOIL [CH. ix
through the loams to light blowing sands. The loams
are very fertile : the extremes of clay and of sand are
infertile. But there is no sharp end-point : a number
of soils near the limit may be productive under one
system of management and not under another, and
may be in cultivation during times of prosperity and
derelict when prices fall.
In applying these general principles to any par-
ticular case a considerable amount of balancing of
probabilities is necessary. Means taken to alter the
physical condition of the soil may react on the micro-
organisms, the chemical composition, etc., and vice
versa. Above all, as the soil is cultivated for profit,
economic considerations come in at every turn. Thus
fertility problems are usually more complex than they
appear at first sight, and require to be studied in the
laboratory, the pot culture house and the field before
they can be regarded as solved.
BIBLIOGRAPHY
Hall, A. D. The Soil. (MuiTay, 1911.)
The Book of the Rothamsted Experiments. (MiiiTay, 1905.)
Hopkins, Cyril G. Soil Fertility and Permanent Agriculture.
(Boston, 1910.)
Prothero, Rowland E. English Farming past and present.
(Longmans, 1912.)
Russell, E. J. Soil Conditions and Plant GrowtlL (Longmans,
1912.)
o
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INDEX
Air supply 30
Ammonia, production of in soil
16, 18
Bacteria in soil 9
Blith and drainage 76
Calcium carbonate 6
Chalking 82, 90
Clay 4
Clay soils 40, 86
Clay soils, reclamation of 92
Clover 56
Coke's system 107
Colmatage 82
Conservation of moisture in soil
29
Derelict land 46, 97
Drainage 29, 76
Edward's system 114
Enclosures 52
Energy stored in soil 8
Exhaustion of virgin soils 46
Fens, reclamation of 71
Fertility limits 44
Food, supply of for plants 32
Game and the farmer 118, 123
Grassland 99
Hellriegel and WUfarth 21
Hopkins, Dr Cyril 47
Humus 8
Lawes and Gilbert 13, 58
Leguminous plants and nitrogen
fixation 20, 57
Liebig 58
Live stock and fertility 104
Loams 39
Market gardening 112
Marling 52, 80, 90
Medieval farming 49
Moorland, reclamation of 120
Nilsson 121
Nitrates in soil 13
Nitrification 14
Nitrogen cycle 25
Nitrogen, evolution from soil 19
Nitrogen fixation 20 et seq.
Pan, removal of 110
Partial sterilisation 26
Phosphates and fertility 33, 58
128
THE FERTILITY OF THE SOIL
Plants, effect on soil 7
Plants, suitability to soil con-
ditions 41
Potassium salts and fertility 34,
121
Protozoa in soil 26
Root range 35
notation of crops
61, 91, 104
Sand dunes 119
Sandy soils 38, 101
Scbloesing and Miintz 14
Schultz-Lupitz system 112
Sheep and fertility 109
Soil sickness 37
Sourness 36
Structure of soil 10
Temperature of soil 30
Townshend's system 103
Tull's system 55
Turnips and what they did
56
Waesland 110
Warington 13, 15
Warping 82
Waste of fertility 63
Waste land 88
Water supply 27
Weathering 2
Whittlesea mere, reclamation of
72
Winogradsky 16
Wychwood, reclamation of 66
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