Plant products and chemical fertilizers

OUSTRIAL CHEMISTRY
Edited by S.RIDEAL

- Prant Propucts

& CHEMICAL | FERTILISERS
S HOARE EF COLLIN S

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INDUSTRIAL CHEMISTRY

BEING A SERIES OF VOLUMES GIVING A
COMPREHENSIVE SURVEY OF

THE CHEMICAL INDUSTRIES

EpIrep By SAMUEL RIDEAL, D.Sc. Lonp., F.I.C.

FELLOW OF UNIVERSITY COLLEGE, LONDON

ASSISTED BY

JAMES A. AUDLEY, B.Sc. J. Re PARTINGTON, D.Sc. (Vict.)

W. BACON, B.Sc., F.LC. ARTHUR E. PRATT, B.Sc.

M. BARROWCLIFF, F.I.C. ERIC K, RIDEAL, Pu.D., M.A., F.LC.
H. GARNER BENNETT, M.Sc. W. H. SIMMONS, B.Sc.

F. H, CARR, F.LC. R. W. SINDALL, F.C.S.

S. HOARE COLLINS, M.Sc., F.1.C. SAMUEL SMILES, D.Sc.

H. H. GRAY, B.Sc. D. A. SUTHERLAND, F.C.S.

H. C. GREENWOOD, D.Sc. HUGH S. TAYLOR, D.Sc.

C. M. WHITTAKER, B.Sc.

De

First Edition . . April, 1918
Reprinted , . « January, 1919

PLANT PRODUCTS AND
CHEMICAL FERTILIZERS

ad
413868

BY

S. HOARE COLLINS, M.Sc., F.I.C.

.
,
;
LECTURER AND ADVISER IN AGRICULTURAL CHEMISTRY, ARMSTRONG
COLLEGE, NEWCASTLE-ON-TYNE (UNIVERSITY OF DURHAM) ;
FORMERLY ASSISTANT AGRICULTURAL CHEMIST TO THE
) GOVERNMENT OF INDIA; AUTHOR OF ‘‘ HAND-
t BOOK OF AGRICULTURAL CHEMISTRY
FOR INDIAN STUDENTS”’
:

i) LONDON
BAILLIERE TINDALL AND COX
8, HENRIETTA STREET, COVENT GARDEN
1919
ht Ve edit rights reserved

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PRINTED IN GREAT BRITAIN

7

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GENERAL PREFACE

THE rapid development of Applied Chemistry in recent years
has brought about a revolution in all branches of technology.
This growth has been accelerated during the war, and the
British Empire has now an opportunity of increasing its
industrial output by the application of this knowledge to the
taw materials available in the different parts of the world.
The subject in this series of handbooks will be treated from
the chemical rather than the engineering standpoint. The
industrial aspect will also be more prominent than that of
the laboratory. Each volume will be complete in itself, and
will give a general survey of the industry, showing how
chemical principles have been applied and have affected
manufacture. The influence of new inventions on the
development of the industry will be shown, as also the
effect of industrial requirements in stimulating invention.
Historical notes will be a feature in dealing with the
different branches of the subject, but they will be kept
within moderate limits. Present tendencies and possible
future developments will have attention, and some space
will be devoted to a comparison of industrial methods and
progress in the chief producing countries. ‘There will be a
general bibliography, and also a select bibliography to follow
each section. Statistical information will only be introduced
in so far as it serves to illustrate the line of argument.

Each book will be divided into sections instead of
chapters, and the sections will deal with separate branches
of the subject in the manner of a special article or mono-
graph. An attempt will, in fact, be made to get away from

Vv

vi GENERAL PREFACE

the orthodox textbook manner, not only to make the treat-
ment original, but also to appeal to the very large class of
readers already possessing good textbooks, of which there
are quite sufficient. ‘The books should also be found useful
by men of affairs having no special technical knowledge, but
who may require from time to time to refer to technical
matters in a book of moderate compass, with references to
the large standard works for fuller details on special points
if required.

To the advanced student the books should be especially
valuable. His mind is often crammed with the hard facts
and details of his subject which crowd out the power of
realizing the industry as a whole. These books are intended
to remedy such a state of affairs. While recapitulating the
essential basic facts, they will aim at presenting the reality
of the living industry. It has long been a drawback of our
technical education that the college graduate, on commencing
his industrial career, is positively handicapped by his
academic knowledge because of his lack of information on
current industrial conditions. A book giving a compre-
hensive survey of the industry can be of very material
assistance to the student as an adjunct to his ordinary text-
' books, and this is one of the chief objects of the present
series. ‘Those actually engaged in the industry who have
specialized in rather narrow limits will probably find these
books more readable than the larger textbooks when they
wish to refresh their memories in regard to branches of the
subject with which they are not immediately concerned.

The volume will also serve as a guide to the standard
literature of the subject, and prove of value to the con-
sultant, so that, having obtained a comprehensive view of
the whole industry, he can go at once to the proper
authorities for more elaborate information on special points,
and thus save a couple of days spent in hunting through the
libraries of scientific societies.

As far as this country is concerned, it is believed that
the general scheme of this series of handbooks is unique,
and it is confidently hoped that it will supply mental

GENERAL PREFACE vii

munitions for the coming industrial war. I have been
fortunate in securing writers for the different volumes who
ate specially connected with the several departments of
Industrial Chemistry, and trust that the whole series will
contribute to the further development of applied chemistry
throughout the Empire.

SAMUEL RIDEAL.

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PREFACE

THE raw materials of Agriculture are often the waste
products of the other industries, and the produce of Agri-
culture again forms the raw material for other industries.
The following pages attempt to pick up the story of those
industrial waste products which are useful as fertilizers,
and carry it on through the soil and crops, until new
products are available for industrial uses. Among the
many plant products which are obtained from the soil, food
takes a high position as an industrial raw product, since
neither men nor horses could work without it. No particular
effort is made to give encyclopzedic completeness of informa-
tion, but the aim has been to give a fair conspectus of a
large subject, with an appended bibliography for those
who are able to pursue their studies further. Details of
analytical chemistry are not considered in this volume
unless the standard text-books named in the Bibliography
appear incomplete or unsuitable. The volume covers the
cycle from factory to fertilizer, from fertilizer to field, and .
from field to factory once more.

I have to thank Mr. A. S. Blatchford, M.Sc., for valuable
help in revising proof-sheets.

S. HOARE COLLINS.
February, 1918.

CONTENTS

PAGE
CONTENTS . ‘ ‘ ‘ ; 5 R ‘ Py ‘ i.)
INTRODUCTION

Brief view of authorities. 3 6 M ‘ I

The Sun as a source of energy. The vegetable lial as an ‘habeuetied
agent to convert Solar energy into Chemical energy. The soil as a
medium for vegetable growth. The chief factors determining
vegetable growth . ° . : ° ‘ . : ° 2

Need for fertilizers. Virgin soils. Barren soils, Exhausted soils,

Losses and gains in Nature. Losses and gains in practice . . 3
The balance of life f ‘ ‘ é ‘ ‘ ; ; vee
References . ‘ ° , 3 ‘ ; . : ; ° 9
PART I.—FERTILIZERS.
SECTION 1.—NITROGEN GROUP OF
FERTILIZERS.
General properties . 4 : ° ; ; : ‘ > s 1 0
(a) Sulphate of Ammonia. Origin. Useful and impracticable mixtures.
Application to the land. Physical and chemical properties. Time to |
apply. Secondary effects on the soil. Effects on crops. Crops most
suited for sulphate of ammonia } . RGN e ‘ “Wee ae
(4) Ammonium Chloride, Nitrate, and Carbonate . ‘ , 17
(c) Nitrate of Soda, Origin. Mixtures. Application to the land. Physical
and chemical properties, Time to apply. Methods of application.
Ultimate effect on the soil. Effect on the crop grown. Crops most
suited to nitrate of soda . : , ‘ . ° 4); 88
(2) Nitrate of Lime. History. Crops best suited. " Difficulties of applica-
tion. Suitable mixtures ‘ . ° ° . . . » 20

(e) Nitrate of Potash. History. Indian and Egyptian methods of manu-
facture. Local agricultural uses. Nitre earths. Nitre wells. Manu-
facturing wastes . ° é . : . ‘ : : s a

(f) Calcium Cyanamide, Nitrolim. Storage. Properties, Difficulties of
application to soil. Times to apply. Crops most suited. Secondary
effects on the soil . ‘ . : ‘ : : : : ece

xi

xii CONTENTS

PAGE
(g) Organic Nitrogen Manures, Fish meal. Composition. Types of soil
and crop most suited. Objections and difficulties. Dried blood. Hoofs ,
and horns. Refuse oil cakes. Industrial waste materials . , +. 32
References . ° . : ° . , . ° ° ° Cuan |

SECTION 2.—THE PHOSPHORUS GROUP OF

FERTILIZERS.
General properties. Chemical condition, The different phosphorus com-
pounds used as fertilizers : . ° ; : ° a 2s

(2) Basie Slag. History and heveissenent Composition. Citric solubility.
Fineness. Application to the soil. Soils most suited. Crops giving
good returns. Factors needed to ensure success. Secondary and
ultimate effects on the physical condition of the soil, Lasting effect . 27

(4) Mineral Phosphates. Occurrence and distribution. Direct use on the
land. Secondary effects, Water solubility. Citric solubility. Solu-
bility in other reagents. Reversion ° ° j ° ‘ Kia 3O

(c) Fertilizers containing both Nitrogen and Phosphorus. Bones, Bone meal.
Bone flour. Dissolved bones. Guano. Mixtures to imitate guano or
dissolved bones. General considerations on time to apply mixed
nitrogen and phosphorus fertilizers. Their relative yalue and suitability
on different soils and to different crops. . ° : oles - 32

References , . : ; : ° ‘ : : . : - 36

SECTION 3.—POTASSIUM GROUP OF MANURES

German potash manures, Geological origin. Kainit. Muriate and sulphate.
Nitre. Wood ashes. Blast furnace dust. General reactions of potash
manures in the soil , ‘ : , . ; PAA eee /

References . ‘ ‘ °

SECTION 4.—MIXED FERTILIZERS.

(2) Containing nitrogen, phosphorus, and potassium. (Artificial mixtures). 40
(4) Farm-yard manure. Its constituents ; cow, pig, sheep, and horse dung.
Urine of farm animals. Litter used in making manure. Physical
properties of litter ° ‘ : . 42
(c) Nitrogen, phosphorus, and potassium, Panaus fri food to dans stave
Relationship between type of food and type of beast and sort of manure
produced. Quantities made under varying conditions } F Ma
(dz) Storage of manure. Denitrification. Drainage. Preservation. Effect
of farm-yard manure on the soil. Valuation of farm-yard manure.

Its lasting effects . : : . : ‘ : : . - 50
(e) Human excreta. Sewage. Sewage farms. Sewage sludge : - 54
(7) Poultry dung. Composts. Vegetable mould. Beech mast. Peat.

Humogen. Seaweed . ; ; ; : ; ‘ A - 56

References . ; ;. . ° ° ° . . . . 58

CONTENTS xiti

PART II.—SOILS.
; SECTION 1.—SOILS AND THEIR PROPERTIES.

PAGE

| (a) Different kinds of soils and their physical properties . , 60
: (4) Relation of soil to water. Methods of modifying the water caatity of

soils : e . ° . 67

| (c) The chemical beckien tien of the different prenas of pery P 70
(2) Useful and useless elements. Balance of fertilizers. Available ue

. total plant food in soils . 72
(e) Relation of soil to air. Biological oii diston ‘in wil. "Fixation of

nitrogen ‘ : ° . : ; : +

(/) The relation of ay to fertitines $ é pe

(g) *‘ The law of diminishing returns ” from both its scientific and Ssraction!

aspects : : ‘ ‘ , . F ‘ ‘ : - 83
References . ‘ : ; ‘ : PR py 5 ° ; 0 |

SECTION 2.—SPECIAL SOIL IMPROVERS.

(2) Lime. Various forms of lime. Industrial waste lime. Gypsum and its

special uses. Reasons why plastering has gone out of fashion . 86
(4) Electricity . A : 89
(c) The partial sterilisation be soils. Application of heat: Gestion. Gas

lime. Naphthalene. Soil injuries. Effect of bad drainage. Injuries

due to unskilful cultivation . ‘ . “ ° : . » 90
References . . . ‘ ‘ ° . ° ° $ ‘ . g2

SECTION 3.—SOIL RECLAMATION.

(2) Barren lands. Causes of barrenness . . : : : - 93
(2) Dry lands. Their treatment and improvement . . ‘. ; - 94
(c) Wetlands. Their treatment and improvement . ‘ : 3) OS
(¢) Peat. Its reclamation and improvement . . : - oF
References . ‘ , :

. . . . . . . . 100

PART III.—CROPS.
SECTION 1.—PHOTOSYNTHESIS.

The conversion of Solar energy into materials which in their turn develop
Animalenergy. The materials in the crops produced by solar energy.
Their relationship to the fertilizers used. The economy in solar

energy obtained by the proper use of fertilizers . : : . + Tol
References . . . * . * . , . . . Ifo

xiv CONTENTS

SECTION 2.—THE CARBOHYDRATES PRODUCED
IN CROPS.

(a) Sugar. Its production in tropical and temperate climates. The manu- ut
facture and purification of sugar. Sugar-cane, sugar beet, dates,
mangels, turnips . : . - Ill

(4) Starch. Its production and coanintabdieded: hin. Wheat, odie: rice,
potatoes, sago, tapioca . . e. 417

(c) Cellulose. Fibres, etc. The chief haite: "Their sitaiiaaitien Be uses,
Cotton, linen, jute, hemp, timber, paper . b é ; ; + 124

(2) Gums and mucilage ‘ 7 S . , ; ; oa

References . : ; : : . ‘ ‘ . > 6 Pe & 3

SECTION 3.—-THE OIL-BEARING PLANTS.

(a) Linseed. Its growth and use for oil and cattle food. Poisonous com-
pounds sometimes developed . : , ° . AN & 1°

(4) Cotton. Its growth and use for oil and cattle fond. Different kinds
of products according to climate and methods of manufacture . hae 2 |

(c) Soya bean. Growth and methods of pressing for oil and cattle food . 138
(Zz) Palm-nuts and coconuts. Their growth and use for oil, butter substi-

tutes, and cattle foods . . . . : , ‘ » « 139
(¢) Earth-nuts. Rape, safflower, sesame, niger, mowha . Ae ene v
(7) The essential oils . i" ° ; ° ; : {ie - 145
References . , : . ‘ : ‘ : . : . - 145

SECTION 4.—THE NITROGEN COMPOUNDS

IN PLANTS.
(a) Cereal proteins ‘ , ‘ ‘ : : . ; - <i: 47
(4) Legumen proteins . ‘ y . ' F : ‘ ‘ anf
(c) Root crop proteins ; , , , ‘ ; ‘ : + X51
(Zz) Oil seed proteins . 7 ‘ 4 ; 5 ‘ q : - 5!
(e) The alkaloids x « . j , F : A A e 1§2
References . ° : ° : < , é ° : : Pia | |,

SECTION 5.—MISCELLANEOUS PLANT

PRODUCTS.
(a) Tea and cocoa : ‘ ‘ : > : ° , ; a BS
(4) Coffee . x R ; ‘ ‘ ‘ . ; : A - 160
(c) Tannin . puna ; ‘ ’ ; . ; ‘ z oi SOR

(dz) Rubber : . ; : . ° ° . A : - 163
(e) Indigo . ' ; ‘ ‘ : . ‘ ‘ ‘ . | £65
(/) Fruit. 4 : : ’ : é : ‘ : ; - 166
References . $ ‘ ; : , v e ‘ J ; - 168

CONTENTS xv

SECTION 6.—PRODUCE VARIABILITY.

The specific effects of the different fertilizers on the different crops and parts
of the same crop. Accelerated and delayed Adie Assisted root
development . ° ° : 169
Substances and conditions which prevent crops tevin obtsining the nutriment
provided by the fertilizers given. : ; : ‘ “ - 4176
References . ° ° ° : . ‘ ; ; : ; ME Sy |

PART IV.—THE PRODUCTION OF MEAT.
SECTION 1.—MANURING FOR MEAT.

The effect of fertilizers on the pastures and then on the beasts grazing. In-
fluence of the fertilizers used on the amount of meat produced. The
animal as a machine for converting the low-grade food into high-grade
food. The metabolic changes taking ae in the animal body.
Tryptophane and the purine bases . ° : - 4178

References . ‘ . : ; ; : ‘ . ; - 182

SECTION 2.—THE FOODS FED TO BEASTS.

(a) Water in foods, The water supply. Amounts necessary. Effects of
excess . . ‘ : ‘ . ° . 183
(6) The fat in Gods. Origin ‘a fat. Composition of fat . : : . 184
(c) The proteins. Theamides . . : . ° - 185
(d) The carbo-hydrates : sugar, starch, pectin, hihtiaba ett. ‘ : - 186
(e) The fibrous materials: cellulose, lignin, etc. . 187
(/) Digestion. Methods by which digestion has been menenved | in fattening
beasts . : , . ° ' : , ; ; ‘ . 188
References . ; ‘ : ° : : ‘ : - ; - 190

SECTION 3—CALORIFIC VALUE OF FOODS.

The animal as a heat engine. Loss of energy due to urea. Bacteria,
chewing, alimentation, etc. Different systems of valuing foods. Their
respective merits under different conditions. The relative values of
different classes of stock as a means of converting cattle food into human
food . ° e b ; ‘ : ‘ ° : P - Igor

References . ‘ : , ‘ , P ‘ ; ; : - 198

SECTION 4.—DAIRY PRODUCTS.

As high-grade products obtained from low- re products : . - 199
References . ‘ ° ; ° . : : : . 202

xvi CONTENTS

SECTION 5.—FUTURE DEVELOPMENTS.

PAGE
(2) Increase of field fertility by sound management . ; ° , wh BO
(4) Development of agriculture at home and abroad x - 205
(c) Financial aspect of agriculture , ‘ ° : ‘ ‘ . 210
(2) Labour difficulties . : : ‘ ; ° ° ‘ . 4, 214
(e) Education : . : ‘ . ’ : : , - 219
(7) Economic production of meat in Winter . . ; ‘ ; s 223
References . : : ° ‘ : ; : ° ‘ ‘ wae
GENERAL BIBLIOGRAPHY ; , , ‘ P 4 ie |

INDEX . e bad e e ° ° . . . . . 225

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PLANT PRODUCTS

INTRODUCTION

THE study of the products.of plant life that are useful
to man formed one of the first deliberate actions of early
intelligence. Ancient records of China, India, and Egypt
alike show that the study of the products of plants attracted
early attention.

The Latin authors, Virgil, Columella, and others who
wrote on Agricultural subjects, are well known in the schools,
and about two hundred years ago, Jethro Tull, the inventor
of the first seed drill, wrote on nitre, water, and fire
and earth, as the origins of plant products. Humphrey
Davy, one hundred years ago, published his Lectures on
Agricultural Chemistry, and up to thirty years ago many
of the Professors of Chemistry in the Universities, as a
means of bringing home the truths of their science to the
members of their audience, drew more illustrations from
rural life than from the urban industries.

Turning now to those who specialized in Agricultural
Science in England in recent years, we find such well-known
names as Lawes and Gilbert, who gave Rothamsted a world-
wide reputation, and Augustus Voelcker, whose work in the
Royal Agricultural Society laid the foundations of many of
the modern inquiries into Agricultural Science. Numerous
investigators have followed in the footsteps of these pioneers,
and the following pages will be found full of references to
their valuable work in building up an exact science of
chemistry applied to economic problems of the agriculture of
to-day.

The sun is the source of power. ‘The effective utilization

D. I

2 PLANT PRODUCTS

of solar energy in the production of plant material lies
at the basis of all Agricultural Science and Practice. The
vegetable leaf in the plant is the prime mover which starts
along chain of chemical change, which begins with the energy
derived from the sun and the crude materials brought
chiefly by the winds, and is supplemented by operations
and materials more under human control.

For nearly all plant products we require—

(1) The radiation from the sun.

(2) A supply of water.

(3) A supply of air.

(4) A supply of fertilizers.

(5) Correct conditions of heat, chemical reaction, and
bacterial development.

In areas which are both tropical and continental the
sun’s heat may be excessive for plant development, whilst
in polar regions the supply of solar heat is deficient ; but the
major part of the earth’s surface receives ae heat for
ample plant life.

In certain districts the amount of water may be excessive
and in other districts the reverse may be the case, but recent
study shows that these difficulties can be minimized if not
overcome. The supply of air to the leaf is usually sufficient,
but the supply of air to the roots of a plant very frequently
needs careful management to obtain the best result.

Some soils are fairly well supplied by nature with
appropriate fertilizers, but since the requirements of man
are very diverse, it is a virtual impossibility for a soil to beso
“fertile ’’ that it needs no manure to produce the intensive
and varied crops which modern conditions may demand.

Economic conditions may, however, prevent the produc-
tion of a maximum crop under intensive cultivation. It does
not always pay to produce maximum crops, and hence some
lands are said to be so fertile as not to need fertilizers. The
present war is teaching us that too much reliance may be
put upon the economic aspect of food production ; that
the interests of the nation are not identical with those of
the producer.

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INTRODUCTION 3

No soil is perfect ; no soil quite hopeless ; much can be
done to improve the bad, and much can be left undone to
injure the good. Those soils which have grown grass or
timber for many years have a great accumulated fertility
and need but little, if any, fertilizer, though it is not
infrequently the case that such “ virgin” soils are not as
rich as reported. In Canada, for example, the prairie soils
grow as good crops of wheat as do the highly farmed fields
of England, but elsewhere most of the soils treated as if they
were fertile virgin soils produce relatively low wheat yields.

Soils that appear naturally barren are often deficient
in water supply, although excess of water is also a cause of
sterility. A class of soil very common in old farmed districts
is the exhausted soil. Wheat can be grown for many years
in sticcession on the same land with a minimum amount of
manure, but the yield per acre gradually falls. Other crops
reach a state of exhaustion at a much greater rate, although
it has been found in many cases that the returns can be
maintained by appropriate treatment and by application of
the right fertilizers.

From the point of view of the Industrial Chemist, the
fertilizers are by-products of industry which proceed to agri-
culture only to reappear in new forms of plant products,
to again form part in some industrial enterprise. It is there-
fore convenient in this volume of the series to begin with a
discussion of the fertilizers. These form a group of bodies
whose values and classifications depend on the uses to which
they are put rather than upon their origins.

For the purpose of studying the fertilizers it is necessary

to consider more than one system of classification.

A useful general system will be to regard the fertilizer

' as a means of supplying a particular chemical element as
follows :—

1. The nitrogen group.
2. ‘The phosphorus group.
3. The potassium group.

There will be many fertilizers that fall into more than
one such group.

4 PLANT PRODUCTS

There will also be the need to consider a classification
which is mainly physical as follows :—

I. Cementive or binding.

2. Opening or aerating.

And lastly we may have to consider fertilizers from a dy-
namic, rather than a static point of view, as in the following :—

I. Lasting.

2. Readily available to the plant.

3. Soluble in water and easily diffusible.

4. Stimulating and only suitable for top dressings.

5. Reactive, t.e. those that induce chemical or biological
activity in the soil.

The purely chemical classification, depending as it does
upon the most important chemical element present, is com-
paratively simple and devoid of ambiguity. In practice it is
not quite so simple as it looks. Later we shall have to discuss
cases where the use of a manure dependent for its value on
one element produces ultimate effects which are best
measured in terms of another element. Also in many cases
the fertilizers are compound sens contain more than one
element of value.

The physical classification demands a knowledge of the
soil to which the fertilizer is applied. But. the ultimate
physical effects resulting from the applications of the
fertilizers are of a very varied kind, some even tending to
destroy completely the proper physical condition of the soil
unless some remedial measures are employed.

The power of a fertilizer to act quickly or slowly is a very
important property. Insome cases a rapid effect is desirable.
For example, when a fertilizer is used as a top-dressing it
must always be soluble, otherwise the action would be too
slow. ‘The case of applying such a fertilizer as dung to the
surface of a permanent pasture might be considered a case
of top-dressing, but this term is usually applied to the use of
a soluble manure on a hay or corn crop when in fairly full
growth, under which circumstance quick action is necessary.
When a fertilizer is applied in the winter or period of little
growth, a much less degree of solubility will suffice and it

eS ee eo

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INTRODUCTION 5

is often undesirable to use a fertilizer that readily dissolves
in water. Very soluble manures may actually wash out of
the soil before the plant can obtain its proper share of the
nourishment.

In considering the actions of fertilizers on the plant and
on the soil it is always important to remember that in no
sense is such a series of actions a static matter. The plant
itself is undergoing rapid chemical change and the soil is
full of life. When a fertilizer is applied to the soil, chemical
change begins at once and may go on foralong time. ‘These
chemical changes induce changes in the development and
rates of growth of organisms in the soil from the common
earth-worm down to bacteria. ‘The equilibrium of the soil
is upset and will only be re-established after an interval
of time. In some cases this interval of time is short, but in
others may last several years. In addition to the above,
there are many secondary points of practical importance.
A manure to be successful must be well distributed. A little
consideration will at once show that the distribution of
fertilizers is a dificult problem. ‘There is no more important
point in presenting any commodity to the consumer than
placing it on the market in a uniform condition. The same
point is just as true of the products of the field as of the
factory. The soil is not by any means uniform by nature,
and all efforts must be made to correct the irregularities
and not intensify them by irregular applications of fertilizers.
Soluble fertilizers have the great advantage that the rain
distributes them automatically. Unfortunately the distri-
bution by this means is only very slight in a horizontal
direction although in a vertical direction it is much more
complete. If we imagine a dressing of a hundredweight or
so applied to an acre and that all the grains of the fertilizer
are about one-tenth of an inch in diameter, then there would
be about one such grain for each square inch. So that even
if we had a perfect distributing machine, the distribution
of such a fertilizer would leave much to be desired, since the
root hairs of the plant are very small and numerous, and if
many of them fail to get their share of plant food there is sure

6 PLANT PRODUCTS

to be a weakness in the complete plant. Very much finer
division is in practice found to be necessary. Some years
ago the author demonstrated on a small scale that the usual
standard sieve for basic slag was about right. (See p. 25.)
When a slag was sieved and only those parts which refused
to pass a sieve with thirty meshes to the linear inch were
used as a dressing on grass land, no visible benefit resulted.
When the sieve was finer and contained sixty meshes to the
linear inch, the part that refused to pass produced a slight
effect. When the sieve contained one hundred meshes to
the linear inch, the part that refused, produced about half
the effect of a complete slag. When the part that passed
the sieve with one hundred meshes to the linear inch was
applied to the grass land the effect was good; and when still
finer sieves were used, no further improvement could be
observed. In short, so far as basic slag on grass land is
concerned, it may be taken as certain that fertilizers of the
order of fineness, represented by just passing a sieve of the
standard dimensions, are at their maximum efficiency.
As already stated above fertilizers do not travel laterally
in the soil, and in consequence even the soluble manures
require some degree of fine grinding, but not to the same
extent as in the case of the insoluble fertilizers.

When the fertilizer is applied, whether by hand in broad
casting, or whether by a drill or other machine, it is desirable
that the fertilizer should be not merely finely divided, but
should also be in a dry condition. If the fertilizer is apt
to form lumps, all the energy expended on fine grinding is
wasted. Materials quite insoluble in water are not likely
to give trouble in this respect, but those that dissolve may
pick up moisture from damp air, and the surface of the grains
become coated with a strong solution, only to dry up later
in an atmosphere less moist, and thus cause the manure to
become caked. It is a well-known fact that dusty mercury
globules do not coalesce, and, similarly, it is a common
household recipe to add a minute amount of rice flour to
salt, so that it does not cake in damp weather. ‘The sticky
grains become coated with a fine dust, and are no longer

INTRODUCTION 7

able to cohere. Many forms of organic matter have a great
capacity for absorbing water. This can be explained by
reference to some familiar instances. Ground linseed cake
will absorb about sixteen times its weight in water, peat
moss litter about ten times its weight of water, and gelatine
about twenty times its weight of water, whilst the material
known as agar, or dried seaweed, is capable of retaining
up to two hundred times its weight of water. The effect
of any manures of this class upon the water supply of the
soil is very pronounced. It will readily be seen that a
material which provides water for lasting out a droughty
period will confer a great advantage, and an equal advantage
will result from a material which will prevent surface washing
of the soil, by absorbing water during excessive rainfall.
It is quite impossible to find out, except by experiment on
the soil itself, what the value of any particular organic
manure may be as regards the water-holding capacity. On
very light soils the value will be due to retention of water,

and cohesion of the sandy particles. On heavy soils the

value will be due to the prevention of surface washing, by
absorption of excessive rain, opening up the soil to air,
and making the soil lighter for spade or plough to work.

An important point in the consideration of the use of
fertilizers is the depth of penetration of the manures.
Nitrates will penetrate to practically any depth. Ammonia
compounds are entirely precipitated on the surface, and do
not usually go more than two or three inches deep. Amides,
such as urea and asparagine, penetrate perhaps to about —
ten or twelve inches. Soluble albuminoids penetrate to a
depth midway between ammonia and amides. ‘The insoluble
albuminoids filter out on the surface. Phosphates are precipi-
tated near the surface and rarely reach a depth of eight
inches. Super-phosphate will be found for the most part
at a depth of about four or five inches. Basic slag does not
readily penetrate more than about one inch. Potash pene-
trates a little further than ammonia. ‘This, of course,
applies only to the immediate action. Secondary actions
of all these materials will alter their position.

8 PLANT PRODUCTS

Much of the disfayour into which so-called chemical
manures fell in the early efforts to use them was due to
injudicious and ignorant use. Probably no one would to-day
make the same mistakes, but to a lower degree similar
mistakes are still made. Very large areas of land in many
countries are urgently in need of dressings of lime, because
all kinds of fertilizers have been used in the past, with only
a partial recognition of the important fact that most ferti-
lizers remove lime from the soil. In the early days of inten-
sive farming lime was used generously and often excessively.
No doubt the disastrous effects of excessive use of lime
made farmers rush to the opposite extreme, and use far too
little lime. To-day we have to make up for past neglect.
Even on soils which stand over chalk or other calcareous
geological formations, lime is not infrequently advantageous.

All life depends on a delicate balance of chemical reactions,
and although living things have a considerable power of
resistance, if one is merely considering them from the
point of view of the struggle for existence, yet when one is
considering the growth of plants from the point of view of
obtaining a paying crop, one cannot permit them to struggle,
one must supply them, with the balance which they require.
Unfortunately, this problem of the balance of the ingredients
needed by the plants has received too little attention. -
The way in which the balance of a soil may be upset is shown
in the following graph, which is taken from a paper by the
author, read to the Society of Chemical Industry, May 31,
1915. This graph shows, with regard to the two constituents
selected for illustration, that when the fertilizing dressing
of magnesia or manganese increased, an increase in crop
occurred at first, but after moderate percentages of the
fertilizing ingredients had been used, a decrease in crop
occurred. There are any number of illustrations of the
same law, in other subjects dealing with the life of plants
or animals.

All the more recent books to be found in the bibliography,
have some reference to the principle that the balance of
the ingredients is an important proposition.

INTRODUCTION 9

The plant products thus obtained are rarely fit for
immediate use and have to undergo fuither manipulations.
Sometimes crops are fed to cows which give milk which

GRAPH.

Correlation between the Hay Crop and MgO% = x or Mn0% =o
Below Mean %. Above Mean %.

+t

MN

Above Mean.

Hay Crop. Cwt. per Acre
~ °
x
{e
Q
Pate °
x x
~
° ~~
eee

=
s x*
2 =f °
, ol
x
o
“15
“10 -O5 G +0°5 +1 %Mn0 1S
%MgO

is turned into cheese, or other products. There is therefore
hardly any ultimate limit to the subject of plant products,
and sooner or later they all appear in some other volume
of this series.

REFERENCES TO INTRODUCTION

Daubeny, ‘“‘ Roman Husbandry ” (Oxford) (from Columella and Virgil).

Davy, ‘‘ Agricultural Chemistry ’’ (Griffin) (1802-12).

Liebig, ‘‘ Chemie fir Agricultur u. Physiologie ’’ (Vieweg) (about 1840).

Boussingault, ‘‘Agronomie, Chimie Agricole et Physiologie’’ (Mallet-
Bachelier) (about 1850).

Collins and Hall, ‘‘ The Inter-relationships between the Constituents
of Basic Slag,”’ Journ. Soc. Chem. Ind., May, 1915, p. 526.

Part I—THE FERTILIZERS

Snotron I.—NITROGEN GROUP OF
FERTILIZERS

THE nitrogen fertilizers have certain properties in common.
Most fertilizers in this group contain the element nitrogen
in a fairly available form and do not contain any large amount
of either phosphorus or potassium. ‘They all tend to stimulate
the active growth of the plant especially as regards the green
parts thereof. A general tendency of this group is to delay
ripening, a result not always beneficial. If applied too freely
they may cause corn to “lodge,” that is to grow too big
and heavy for the stem to properly support the ears. In the
case of plants bearing fruit the result of too liberal dressings
of nitrogenous fertilizers may result in too large development
of leaf or woody stem with a resultant loss of fruit. Used
with discretion this group of fertilizers provides one of the
most valuable means of obtaining large increases in the
crops produced.

That there is a considerable degree of interchangeability
between the members of this group may be seen in Table r.

TABLE I.—NITROGEN STIMULANTS,
Results of field experiments on grain. Crop per acre.

Average of thirteen
Order experiments,
Manure, of
merit,

= Straw
Grain. | and chaff,

Ibs. ewts,
1. No manure .. — | 2196 27%
2. Super-phosphate and potash 6 | 2260 29
3. No. 2 and nitrate of soda. wy 5 | 2595 354
4. No. 2 and sulphate of ammonia .. 2 | 2668 37
5. No. 2 and calcium cyanamide (early application) 4 | 2680 35
6. No. 2 and nitrate of lime . I | 2816 383
7. No. 2 and calcium cyanamide (late application) 3 | 2607 354

ee a a:

NITROGEN GROUP OF FERTILIZERS II

It will be seen that the effect of the nitrogenous fertilizers
is in all cases a very marked one, that some give better results
than others, but the different forms of nitrogenous manures
will not always fall in this order, although for cereal crops
it may be expected that something like this order will be
maintained.

The general subject of the nitrogen fertilizers cannot be
discussed without some reference to the possible alternate
scheme of producing the nitrogen needed on the farm by
indirect means, although this subject can be better discussed
in Part IV.

By the use of phosphatic manures it is possible to develop
the growth of leguminous plants which indirectly extract
nitrogen from the air. The nitrogen so extracted will not
all be sold off as crop, some will remain in the soil as the roots
of the leguminous plant. When the leguminous plants are
fed to stock, most of the nitrogen will find its way into the
manure heap and, provided that care be taken, thence to
the soil. Such accumulations will be slow acting and can
never entirely replace the quick-acting nitrogenous ferti-
lizers ; nevertheless great economy of nitrogenous fertilizers
is possible by these means.

At the present time war has drawn attention to many
methods for the fixation of atmospheric nitrogen. When the
war is over and the demand for explosives slackens, the
synthetic nitrogen compounds will be more extensively
used for agricultural purposes. |

Sulphate of Ammonia.—Sulphate of ammonia is a
product of gas works and coke ovens. The amount obtained
in practice is by no means what could be obtained under
theoretical conditions; for example, the ordinary gas
retort gives little more than twenty pounds of sulphate
of ammonia per ton of coal carbonized, whereas theoretically,
one hundred and fifty pounds of sulphate of ammonia per
ton. of coal carbonized might be obtained. ‘There are,
therefore, great possibilities of an increase in the amount
of sulphate of ammonia available for agricultural purposes.
Sulphate of ammonia has for many years past been obtainable

12 PLANT PRODUCTS

at prices varying from about f9 to {20 per ton at British
ports. Roughly speaking £14 per ton is considered a general
average of English prices.
The demand for sulphate of ammonia for agricultural pur-
poses is almost certain to increase, as the need for it is better
recognized. ‘That the value of, say, {14 per ton is, from the
user’s point of view, not an unreasonable one, may be judged
from Table 2, which is based on recent field experiments and
shows the average increase in the various crops with the value
of such increase that may be expected from the use of I cwt.
of sulphate of ammonia per acre, costing about seventeen
shillings. The crops have been valued at low prices.

TABLE 2.

Increase due to 1 cwt. sulphate of ammonia costing 17s.

ey Syme Ea Be
Wheat -- 4 bush. at 55s. per qr. 504 lbs. «I 7 6 ei ea Se
Wheat Straw.. 5 cwt. at 40s. per ton «0 TO i 7
Barley . 6 bush. at 50s. per qr. 448 Ibs. E19 : Bae ies
Barley Straw.. 6cwt. at 30s. per ton 000s) ) ae
Oats .. . 7 bush. at 30s. per qr. 336 Ibs. r EON, Bary NE
Oat Straw .. 7 cwts. at 40s. per ton oe XO 3
Rye Grass Hay 10 cwts. at 100s. per ton 2 10 Oo
Meadow Hay.. 8 cwts. at 90s. per ton I 16 0
Mangolds .. 32 cwts. at 12s. 6d. per ton A Oe
Potatoes -- 20 cwts. at 60s. per ton 3 oO O

Consideration of the foregoing figures shows that there
is ample justification for the liberal use of reliable manures.

For practical purposes sulphate of ammonia may either
be applied by itself or in mixtures. Probably most of the
sulphate of ammonia actually used is applied in mixtures,
either made by the farmer himself or purchased ready made
from the manufacturer.

Certain of these mixtures are very practicable and useful,
others are not desirable, and others must be avoided at all
costs.

One of the commonest and most useful mixtures is com-
pounded from sulphate of ammonia and super-phosphate,
This mixture has the following special advantages :—both
manures are moderately quick in action; neither are
instantly available for plant life.

NITROGEN GROUP OF FERTILIZERS 13

In both cases changes have to take place in the soil
before the constituents of the fertilizer are suitable for
absorption by the plant ; indeed, in both cases a water culture
of either super-phosphate or sulphate of ammonia, or both
together, would be absolutely injurious to the plant, and the
plant would probably refuse to grow altogether. After,
however, these materials have acted upon the soil they are
rendered suitable to the plant’s needs.

When sulphate of ammonia acts upon the soil a complete
chemical change takes place. ‘This change can be easily
demonstrated so far as the broad effects are concerned by
the following simple experiment :—A couple of glass tubes,
about 2? or 3 inches in diameter, and about a foot in length,
are partially closed at one end with cork and cotton-wool,
and a depth of 6 or 8 inches of soil placed in the tubes.
Into one tube is poured some distilled watensqs to perceive
the effect of plain water upon the soil ;xanto thé¢ther tube
is poured a solution of sulphate of agpmonialim vw Qter. If
a quantity of sulphate of ammonia Weihingvab@ut one-
tenth of a gramme be used for one of thegeraghgs it would
correspond to an application of 2 cwt. sulphate of ammonia
per acre, a quantity comparable to practice.

A litre of water poured on to the quantity of soil men-
tioned above would correspond to a rainfall of about ten
inches.

If the drainage from the two tubes be now collected, the
addition of a small quantity of ‘‘ Nessler’s,’”’ solution will
give a coloration due to the ammonia, and it will be at once
observed that whilst the original manure employed shows
a large amount of ammonia present, the drainage from the
manured soil only shows a fraction of that amount. The
distilled water itself will be found to have washed a little
ammonia out of the soil, unless the soil chosen was a
particularly poor one. We perceive at once from such an

experiment that the ammonia has in some way been removed

from aqueous solution, or in other words, the ammonia
has been fixed by the soil. ‘These fixations of fertilizer
ingredients are always partial reactions which follow the

14 PLANT PRODUCTS

chief chemical laws of mass action, so that the soil water
will always take away some ammonia from the soil.

After the ammonia has become fixed in the soil it still has
to undergo further changes. These changes are, however,
not purely chemical ones, but are dependent upon bacterial
action, and are not so easily demonstrated on the lecture
table or inthe laboratory. ‘They require an elaborate experi-
ment on the field itself. Such elaborate field experiments
have been carried out at Rothamsted.

To return to our experiment with two tubes, another
point that can be easily investigated by such an experiment
is to examine the fate of the sulphuric acid part of the sulphate
of ammonia.

By the use of barium chloride we can see at once that plain
water removes a noticeable amount of sulphuric acid froni
the soil, and that the drainage from the manured soil
practically amounts to the sum of the other two quantities,
namely, that which sulphate of ammonia contains and that
which water washes out of the unmanured soil. Another
very important result that can be seen from this experiment
is the effect of the sulphate of ammonia on the amount of
lime in the soil. The sulphuric acid part of the sulphate
of ammonia combines with the lime in the soil and the two
- go out together as calcium sulphate. A test with ammonium
oxalate on the drainage from the two tubes will show at
once that the lime lost to the soil by drainage is very much
greater when sulphate of ammonia is applied than when the
soil is unmanured. In common agricultural language,
sulphate of ammonia exhausts the soil of its lime. The
demonstration of this point on a large scale in the field has
been very admirably shown in the researches of the Royal
Agricultural Society in their experimental farm at Woburn.
In certain plots of barley continuous application of sulphate
of ammonia results in turning a light but good soil into a mere
desert, which grows nothing at all, except an occasional
weed. When, however, soil, which has been rendered
infertile by deliberate over-manuring is subsequently treated
to a dressing of lime, the fertility is recovered, and crops

a a

pe ee

_ —_— ae ee -

NITROGEN GROUP OF FERTILIZERS 15

grow once again. ‘The success of application of sulphate
of ammonia is, therefore, intimately connected with the
amount of lime which is either naturally present in the soil,
or has been added to the soil.

_ Without the lime, sulphate of ammonia will not undergo
those changes which are necessary. ‘The amount of sulphate
of ammonia which can be applied to the soil may be put down
roughly as one or two hundredweight per acre.

For the purpose of enabling a wheat crop to get over the
dangerous period either at the beginning or the end of the
winter a top dressing of sulphate of ammonia is most useful.
For such purposes as top dressings only about half a cwt.
of sulphate of ammonia need be used at one time, as it is
not difficult to give a second dressing of 4 cwt. later on should
it be found necessary. The farmer will judge for himself
from the look of the crop whether such an application is
desirable or not. Should the plant appear yellow and sickly
it is a safe thing to give a top dressing. Another great use
of top dressings of sulphate of ammonia is to enable a growing
crop or slow crop to get through a droughty period when half
grown. As explained in Part III., Section I., an application
of fertilizer may be equivalent to an application of water,
and of the manures which can be used in this way sulphate
of ammonia takes a very important position. Such small
dressings as are here referred to undoubtedly present some
difficulty in their even distribution; but the sulphate of
ammonia can be mixed with a small quantity of dry earth
or ashes, but not with lime or any substance containing
lime.

Use of sulphate of ammonia demands some knowledge
of the general physical and chemical properties of the sub-
stance. Commercial sulphate of ammonia is a very finely
crystallized substance, having a slight tendency to stick
together, owing to the presence of two or three per cent. of
water, and a few tenths of a per cent. of free sulphuric acid.
It does not, however, exhibit any great tendency to cake,
but may need to be broken by a spade before use. It is very
easily soluble in water,and the common article will just redden

16 PLANT PRODUCTS

a piece of blue litmus paper. When heated it gives up the
small amount of water which it contains, and then proceeds
to undergo a regular and complete decomposition. At first
sulphate of ammonia decomposes into ammonia and
ammonium hydrogen sulphate, then splits off some sulphur
tri-oxide, which reacts as an oxidizing agent, giving off
free nitrogen and sulphur dioxide. The sulphur dioxide,
together with the water, and some of the free ammonia,
then again combine and produce ammonium hydrogen
sulphite. These reactions can easily be perceived when
ammonium sulphate is slowly heated in a test-tube. ‘The
water coming off will at first condense in the colder and upper
part of the test-tube; further heating results in giving off
a smell of ammonia, and in the formation of a sublimate in
the colder part of the test-tube. If, after cooling, one. or
two drops of hot water be added to the contents of the test-
tube, a smell of sulphur dioxide is at once perceived, because
the ammonium hydrogen sulphite is not a very stable
body, but dissociates with hot water. ‘The ultimate result
of heating sulphate of ammonia is that the water, ammonia,
and sulphuric acid are driven off, and nothing left behind
but some mineral impurity which is mostly a trace of soil
or iron oxide.

When sulphate of ammonia comes into contact with an
alkali or strong base, the sulphuric acid combines with the
alkali or base, and the ammonia is set free and diffuses into
the atmosphere. It is for these reasons, that sulphate of
ammonia should never be mixed with lime, wood ashes,
or basic slag. However, very few soils are so calcareous
that the clay and humus do not greatly preponderate over
the lime, so that the ammonia is more readily fixed by the
clay and the humus than it is driven off by the lime materials.
Sulphate of ammonia will take three weeks of very good
weather to nitrify all the ammonia added to the soil.
Nitrification, though very slow in the winter, produces some
nitrate which is lost by drainage, though such loss is not
sufficient to condemn the winter application of sulphate
of ammonia. On general grounds sulphate of ammonia

Rn eee eee

ee eS

NITROGEN GROUP OF FERTILIZERS 17

must be regarded as a manure to be applied shortly before
it is needed. It is not so quick in its action as nitrate of
soda or nitrate of lime, but is a great deal quicker than the
organic nitrogen manures. Its stimulating effects on the
plant are seen in the large development of the leaf. It is
therefore especially valuable for the production of green
stuff, and is deservedly very popular among market gardeners
and all intensive cultivators. For the purpose of fruit
growing it is not such a suitable manure, since some fruits
do not develop well if the plant is too vigorous and rank
in its growth. Such prolific fruits as gooseberries must be
excepted from this general statement (see p. 166).

Sulphate of ammonia, in a very crude form, occurs in
soot (see pp. 66 and 92).

Ammonium Chloride.—Of the other compounds of
ammonia which have been used as fertilizers ammonium
chloride is probably the most important. Ammonium
chloride, sal ammoniac, or muriate of ammonia, has always

_ been used in the Rothamsted experiments, doubtless because

at the date when these experiments were started it was by
no means a foregone conclusion which particular ammonia
salt would prove most practicable. When ammonium
chloride is used as a manure many of the soil reactions
closely resemble those of the sulphate. The ammonia is
fixed in the soil, the chlorine carries away calcium (lime),
so that the ultimate result in the soil is the same. ‘The
actions of sulphates and chlorides on plant life are nearly
but not quite identical, though these points can better be
discussed under the heads of the crops concerned (see
Part III.). At the present time there does not seem any
likelihood that ammonium chloride will be a practicable
fertilizer.

Ammonium Nitrate.—Ammonium nitrate is a very
deliquescent substance, and is for that reason not very
suitable as a fertilizer. Its very high percentage of nitrogen,
however, might make it valuable where transport facilities
were very poor. Though, at present this does not seem
a very practicable manure, it would certainly have the

D. 2

18 PLANT PRODUCTS

advantage that there is nothing in it of an objectionable
character.

Ammonium Carbonate.—Ammonium carbonate itself
is too volatile, but ammonium hydrogen carbonate is a
light, dry powdery substance, which only slightly smells
of ammonia. At present no serious attempt has been made
to produce ammonium bi-carbonate for use as a fertilizer,
but since the gas works have already prepared directly a
strong liquid ammonia there does not seem any reason why
they should not manufacture ammonium hydrogen carbonate,
as, of course, it is obvious that they produce carbonic acid
in quantities many thousands of times more than is needed
for this purpose. At present, however, this also is not a
practicable fertilizer.

Nitrate of Soda.—Nitrate of soda chiefly occurs as
a deposit in Chili, is mined, extracted with water, and re-
crystallized. ‘The composition is fairly constant, containing
rarely less than 93 per cent. pure nitrate of soda, or more than
97 per cent. pure. Of a large number of samples examined,
over one half had between 96 and 97 per cent. pure nitrate
of soda. As it is obtained exclusively from foreign sources
it is imported by ship, and as a rule the shipments are of
a definite known composition. Nitrate of soda does not
lend itself very particularly well to mixtures. It can be
mixed with basic slag, but such a mixture is not particularly
useful, because nitrate of soda is very quick acting, and basic
slag is very slow. It cannot be mixed at all satisfactorily
with super-phosphates, since this mixture becomes somewhat
heated and produces free nitric acid, which then distils
out of the mass and condenses on the outer surface and thus
rots the bags or sacks which may have been used for transport.
The chief method of application of nitrate of soda to the soil
is for a top dressing, as it need not undergo any chemical
change in the soil before absorption by the plant. It is
applied as a top dressing in the same way as sulphate of
ammonia, and is among the quickest of all fertilizers.
Nitrate of soda as sent to the farmer is not infrequently in
large lumps, and requires to be broken up. Owing to its

NITROGEN GROUP OF FERTILIZERS 19

extreme solubility in water, it must be kept dry, and owing
to its deliquescent properties it must be kept away even from
moist air. If it becomes very damp it is likely to cake
together and to need breaking up again before application.
When applied to the soil a slight chemical change takes
place. To a limited extent the soda in nitrate of soda and
the lime in the soil change places with one another.
Continuous application of nitrate of soda will therefore
remove lime from the soil by drainage. Nitrate of soda
does not, however, remove quite so much lime as sulphate
of ammonia. Whilst sulphate of ammonia contains the
relatively unimportant ingredient sulphuric acid, nitrate
of soda contains the equally unimportant ingredient soda.
The former, of course, produces an acid reaction, and the
latter produces an alkaline reaction. Whilst the sulphate
of lime produced from sulphate of ammonia readily drains
away from the soil, in the case of the soda the loss by drainage
is lesstapid. ‘The soda acts chiefly upon the clay and humus

of the soil, and forms a colloidal solution, which results in

the transfer of the fine clay particles from the surface to
the sub-soil, reducing the fertility of the surface soil, whilst
the sub-soil becomes choked with material more or less
impervious to water. From the above causes both sulphate
of ammonia and nitrate of soda, when used in large excess,
as in the Woburn experiments, produce almost equally
bad results. The cure for these objectionable effects from
nitrate of soda lies in the use of lime or sulphate of lime.
The former can be supplied in basic slag, and the latter in
super-phosphates. ‘The chief effect of the use of nitrate
of soda upon the crop grown is to stimulate the production
of green stuff. Hence it is of particular value for such
crops as gooseberries, cabbages, and turnips. Like sulphate
of ammonia, it may also be used as a top dressing for
application either to wheat ortohay. Both of these manures,
sulphate of ammonia and nitrate of soda, are much used in
intensive forms of tropical agriculture, on such crops as
tobacco and coffee. The impurities in nitrate of soda
include potassium iodide, potassium iodate, and potassium

20 PLANT PRODUCTS

perchlorate. It frequently happens that there is quite
enough iodine to produce asmell of that element, and traces
of perchlorate are also common. Cases have been recorded
where these impurities have reached sufficient amounts to
produce prejudicial effects on the crops grown, but the event
is too rare to be of any practical importance. ‘The effects
of rare elements like iodine can be studied in the Royal
Agricultural Society’s Reports.

Nitrate of Lime.—In 1898 Sir William Crookes read
his Presidential address to the British Association at Bristol,
calling attention to the possible diminution in the world’s
supply of wheat, and urged the necessity of the manufacture
of nitrates directly from the air. It is taking a long time
to reach the condition of affairs he described, though the
world’s shortage of wheat is certainly already appearing. The
supply of nitrate of soda has not shown the decrease antici-
pated ; on the other hand, sulphate of ammonia has proved
to be more plentiful, but, nevertheless, some nitrate made
from the air is now a practical fertilizer and after the war
is over may come into more general use. The chief difficulty
in using nitrate of lime is due to its deliquescent properties ;
nitrate of soda is bad enough in this respect, but nitrate
of lime is worse. Nitrate of lime has to be kept in casks,
which are by no means convenient to carry to the field.
When nitrate of lime is broadcast by hand it is extremely
unpleasant to the workers, since small dust particles
settle upon the workers’ faces, and by dissolving in traces
of sweat, produce a stinging strong solution. Nitrate of
lime can be used in much the same way as nitrate of soda.
It is very quick acting, should only be used as a top dressing,
is instantly available, and is easily washed out of the soil.
When nitrate of lime is mixed with a small proportion of
sulphate of ammonia, a very fine dry breadcrumb-like
powder is obtained, which is very convenient to handle.
Nitrate of lime cannot be mixed with super-phosphate
(see p. 35), and admixture with basic slag would be of little
value. One of its great advantages lies in the fact that it
has no useless ingredients ; the whole of the lime and the

ee

NITROGEN GROUP OF FERTILIZERS 21

nitrate can be easily absorbed by the plant, and nothing
is left behind in the soil, either good or evil. It therefore
is especially suited to conditions of drought or bad drainage
where undesirable salts accumulate and cannot be removed.
Like nitrate of soda, it is quite unsuitable for winter
application.

Nitrate of Potash.—Nitrate of potash, or potassium
nitrate, is one of the earliest artificial manures. In the
vicinity of old village sites nitre earths are of comparatively
frequent occurrence, especially in India and Egypt. In
India the collection and working of these is an old-established
industry. ‘The nitre earths, which have accumulated as
the result of the decomposition of organic nitrogenous waste,
ate put into small pits with false bottoms and extracted
with a minimum possible quantity of water. The solution
obtained is then crystallized, and crude nitrate of potash
obtained. Both the original nitre earths and the waste
from this crude manufacture are used regularly for ordinary
manuring of crops. In some localities also, considerable
accumulations of nitrate of potash occur in the well waters,
and some of the districts in India which grow tobacco crops
are situated in areas where there are many nitre wells.

The manufacture of pure nitrate of potash from the
above crude materials has been brought to such a state of
perfection that the waste contains very little potash or
nitric acid.

Nitrate of potash is, of course, a very valuable manure,
as it contains two elements of value to the plant. When
added to the soil the potash combines with the clay and humus
and becomes fixed, and the nitric acid combines with the lime
in the soil (see also Potassium Manures, p. 37).

Calcium Cyanamide. —The manufacture consists, firstly
in producing calcium carbide, which is made in an electric
furnace from lime and coke. ‘The calcium carbide is then
heated, and nitrogen passed through it, when calcium
cyanamide and graphite are produced. ‘The material put
upon the market contains about 50 to 55 per cent. calcium
cyanamide, 25 to 30 per cent. lime 11 to 12 per cent. graphite,

22 PLANT PRODUCTS

and 2 to 3 per cent. silica. The amount of nitrogen varies
from 17 to 20 per cent. Calcium cyanamide, when kept in
store, slowly absorbs water from the air, so that it increases
in weight. In consequence of this fact the percentage of
nitrogen decreases at the rate of I per cent. in two or three
months, but the owner does not thereby lose anything.
At the same time a small amount of decomposition does take
place, and traces of ammonia are given out into the air.
Calcium cyanamide in itself is no use to the plant, and when
acted upon by the water in the soil it will produce the poison
di-cyanamide, which will slowly decompose into ammonia,
and then nitrify. It is only suitable for application some
time before sowing. It is a slow-acting manure, and is quite
unsuited to top dressing. It can be mixed with basic slag,
_ but not with super-phosphate or with sulphate of ammonia.
The amount of lime present is generally beneficial, and the
graphite is absolutely harmless. At first calcium cyanamide
will act as a poison; it will therefore have the value which
will be alluded to again under the head of the “ Partial
Sterilization of Soils ’’ (see p. go).

The Organic Nitrogen Fertilizers.—Fish refuse, fish
meal, or fish guano, is one of the most important in this
group.

Refuse fish is often used locally by farmers, but the
manufacture of fish meal and fish guano are definite industries
in connection with fisheries. ‘The best qualities are used only
for feeding purposes, but the other qualities are applied to
the soil. A very large proportion of the fish guano in Great
Britain comes from herrings. ‘The heads, tails, and guts
that are discarded in salting the herrings are dried, and
then the fat extracted by petroleum spirit. The resulting
material when used for fish guano contains about 9 to 12 per
cent. nitrogen, 3 to 5 per cent. of phosphoric acid, and about
I per cent. of potash. ‘The amount of oil should not exceed
I to 2 per cent. In other parts of the world other systems
ate often in use. Insome parts of America the fish is boiled,
the fat skimmed off, and the resulting mass dried and used
asamanure. In India much refuse fish is dried on the beach,

NITROGEN GROUP OF FERTILIZERS 23

and then sold as a fertilizer. Whilst fish guano is of very
varied composition, the product of any one factory is often
quite constant. ‘The average of a large number of samples
obtained from North Shields has been :—nitrogen 8:0 per
cent. +0*2, phosphoric acid=5'9 per cent. +0°8, potash=1'1
per cent.+0°3. ‘The nitrogen is so much higher in amount
and fertilizing value than the other ingredients that this
fertilizer may be looked upon as belonging to the organic
nitrogen group. Like all the members of this group, fish
guano is much slower in its action than sulphate of ammonia

or nitrate of soda. Its decomposition in the soil depends

upon living things, from bacteria upwards. Moisture,
warmth, and lime in the soil greatly facilitate its action.
In addition to its purely. chemical value the physical properties
must be considered (see p. 68).

An objection to fish meal, not uncommon to the whole
of this group, is that it is sometimes too attractive to birds,
or even four-footed beasts. Crows have been known to
pull it out of the soil almost as fast as the farmer had put
it in, and in India it has sometimes induced the wild pig
to root it out and trample the field. For cold situations,
or for late application, or for top dressing this manure is
inferior to sulphate of ammonia or nitrate of soda.

Dried Blood.—Dried blood is generally only the clot,
and not the entire blood, as the boiling down of big quantities
of blood is a difficult problem. Fresh blood, when obtain-
able, can of course be used also. Blood decomposes in the
soil with great rapidity. Dried blood, as a rule, contains -
from 9 to 12 per cent. nitrogen.

Hoofs and Horns.—These are the product of the
slaughter-house, and are much used by the manufacturers
of artificial manures. ‘They contain from 12 to 16 per cent.
of nitrogen. ‘he raw horn swells very slowly in the soil,
and acts slowly, but if horn be steamed it swells up quickly
in moist soil, and produces a moderately quick-acting fertilizer.
This material must, in any case, be very finely ground.

Wool Waste, Shoddy, Feather Waste, Feather Dust,
and Silk Waste, are all waste products of a fibrous and

24 PLANT PRODUCTS

bulky character. They are much appreciated by the Kentish
hopfarmers, and are particularly adapted for dry, gravel,
and chalk soils. ‘They do not, however, decompose at all
readily in the soil, and their beneficial action is probably
quite as much physical as chemical.

Damaged Cakes.—There are some cakes obtained by
pressing oil seeds which are not suited for cattle feeding.
To animals castor cake is distinctly poisonous and rape cake
is very bitter and distasteful. Further, some meals normally
of value for cattle feeding have become accidentally damaged
by fire, water, or mould. All of these materials come in
usefully as fertilizers for the soil. Part of their value de-
pends upon secondary effects, independent of the percentage
of nitrogen, which will vary from 4 to 7 per cent. Some of
the least edible, such as castor and rape, may very possibly
injure wireworms or other pests. Linseed meal (see p. 136) is
stated to be eaten by wireworms, and then by swelling
inside them cause them to die. .These materials decompose
fairly quickly in the soil. Mowha cake contains saponin
(see p. 145), and is used to remove earthworms from golf
greens.

Meat Meal and Refuse from Meat Extract Works.
— These contain usually about 5 to 8 per cent. nitrogen, and
10 to 15 per cent. phosphoric acid. ‘Their action in the soil
is very similar to fish and blood. ‘The members of this group
of fertilizers stand midway in their action between ‘“‘ Chemical
Manures ’’ and farmyard manure.

REFERENCES TO SECTION I

Russell, ‘‘ Artificial Fertilisers, Their Present Use and Future Pros-
pects,” J. Soc. Chem. Ind., 1917, p. 250.

Hendrick, ‘‘ Field Trials with Nitrogenous Manuring,” J. Soc. Chem.
Ind., 1911, 523.

Special Leaflet No. 57. Board of Agriculture.

Voelcker, J. Roy. Agric. Soc. Eng., 1904, 306; 1916, 244.
is Russell, ‘‘ Manuring for Higher Crop Production,” p. 7 (Camb. Univ.

ress),

Hobsbaum and Grigioni, ‘“ Production of Nitrate of Soda in Chile,”
J. Soc. Chem. Ind., 1917, Pp. 52.

Kilburn Scott, ‘‘ Production of Nitrates from Air, with special reference
to a New Electric Furnace,” J. Soc. Chem. Ind., 1915, p. 113. ‘‘ The
Manufacture of Nitrate of Ammonia,” Chem. News, 1917, P. 175;

Lamb, *‘The Utilization of Condemned Army Boots,” J. Soc. Chem.
Ind., 1917, p. 986.

Srction Il.—THE PHOSPHORUS GROUP
OF FERTILIZERS

THE phosphorus group of fertilizers consists chiefly of
the following compounds :—Mono-calcium phosphate,
CaH,P,03.H,O, which is easily soluble in water, very
deliquescent, and strongly acid; di-calcium phosphate,
CagH,P,0,.4H,O, which is slightly soluble in water, and
is practically neutral to litmus paper; tri-calcium phos-
phate, Ca,P.Og, a rather indefinite compound, much less
soluble in water, but attacked to some extent by carbonic
acid ; tetra-calcium phosphate, Ca,P,0), which has been
found in basic slag; apatite, Ca;(PO,)3F, which is very
insoluble in water ; and some complex compounds, which are
both phosphate and silicate, occurring in basic slag. As,
with one exception, these materials are not very soluble in
water, it is necessary that most of the phosphatic fertilizers
should be very finely ground. In the case of basic slag the
commonly recognized standard of fineness is the ability to
pass a sieve containing 100 wires to the linear inch, or 10,000
meshes per square inch. ‘This sieve is often used for other
fertilizers as well. Small experiments conducted at Cockle
Park, the Northumberland County Council experimental
farm, showed that this degree of fineness was about correct.
Those portions of phosphatic manures which only passed
sieves much coarser than the above had little influence
on the development of clover, whilst phosphatic manures,
which were so finely ground that they could pass a sieve with
200 wires to the inch, showed no appreciable advantage over
the standard. Special distributors have been constructed

to assist in spreading these manures over the land in an even

26 PLANT PRODUCTS

manner. Broadcasting these very fine powders is trouble-
some in windy weather. Whether these phosphatic manures
happen to be soluble in water or not, they very quickly
become insoluble in the soil. The soluble compounds attack
the lime and ferric hydrate in the soil and form compounds
insoluble in water. ‘There is, therefore, no appreciable loss
to phosphatic fertilizers through drainage. At Rothamsted,
all the phosphates added during the preceding fifty-five
years is accounted for in Table 3 :—

TABLE 3.

Phosphorus Balance Sheet, Hall and Amos. -

Broadbalk plots, Hoosfield plots.
P,O, Ib. per acre.
5. 7 2. 40
Supplied in manure .. gt hy: 3960 3810 3390 3390
Removed incrop.. sie te 790 1370 1200 1240
Balance expected in soil .. NON EE? iy. 2440 ‘2190 2150
» found in soil Ke ae 3000 2470 2315 2000

It will be noticed that the very large amount expected to
be left in the soil, estimating the difference between what was
supplied and what was found in the crop, was almost exactly
equal to the amount actually found inthe soil. In two cases
a little too much, and in two cases just too little, quite as
close an agreement as one could possibly expect. ‘These
tesults, however, refer to a soil which, whilst very typical,
is poorer than some agricultural soils. From soils that are
very tich in phosphates, such as some garden soils, drainage
does temove appreciable quantities of phosphate. The
phosphates in the soil, whether natural or added by fertilizets,
ate attacked by the carbonic acid in the soil, and thereby
rendered slightly soluble. The root hairs of a plant are
probably permeable to such a solution of phosphates in
water containing carbonic acid. When such solutions have
entered the root, the acid in the root will take up the phos-
phate itself, and leave the carbonic acid free. ‘The carbonic

THE PHOSPHORUS GROUP OF FERTILIZERS 27

acid then diffuses out again into the soil, and dissolves
more phosphate. Carbonic acid, therefore, acts as a carrier,
and though the organic acids in the root are said not to
pass out into the soil, they nevertheless have an important
relationship to the solution of phosphates in the soil. The
rate at which carbonic acid can be regenerated will depend
upon the amount of acid in the root. Phosphates are
especially valuable for stimulating root development, and
it is probably for this reason that they are so important
for the development of turnip seed in its early stages.
Phosphates usually tend to accelerate the process of ripening.
Phosphates are also very important in assisting nitrogen
fixation in the soil, either directly by bacteria in the soil or
indirectly by encouraging the growth of leguminous plants.

Basic Slag.—Basic slag is a by-product of the steel
industries. ‘The phosphorus contained in the ores, fuel, and
lime accumulates in the pig iron, and is then transferred
to the basic slag. ‘The basic slag, therefore, represents
a phosphorus concentrate, and may contain phosphorus
equivalent up to 40 per cent. of tri-calcium phosphate. In
addition to the phosphoric acid, basic slag also contains
a total amount of lime, equivalent to about 40 per cent.,
with a few per cents. of magnesia and manganese, 6 to 10
per cent. of iron, traces of vanadium and sulphur.

The lime is very largely in some state of combination,
and the amount of lime that can be extracted by such a
reagent as a solution of cane sugar is very small. Lime is .
needed by soils, as is explained in Part II., Section II., for
several different purposes, (1) neutralizing the acid of most
manures (see p. 87), (2) assisting nitrification (see p. 86),
(3) checking disease (see p. 73). For these miscellaneous
purposes it has been found that calcium oxide, calcium
hydrate, and calcium carbonate are approximately equivalent,
calcium for calcium. ‘The more basic calcium silicates are
easily attacked by very feeble acids, and in this case calcium
silicate is almost as good as other forms of lime. Looked at

_from the point of view of the farmer, to whom the application

of lime to the soil is a well-known process, an equivalent to

28 PLANT PRODUCTS

a dressing of lime may be provided by any of the forms of
lime mentioned above. ‘To endeavour to represent in some
way the value of basic slag for replacing lime a conventional
calculation is adopted. Asa means of obtaining information
of degrees of solubility, citric acid is commonly taken as
a convenient standard, but there is no real theoretical reason
why citric acid should be preferred to any other acid, though
it is certainly convenient, and has amply justified itself in
practice. Inthe case of basic slag it has become a recognized
standard to extract the slag by shaking for half an hour
with 2 per cent. citric acid solution, and to consider that the
portion dissolved has a special value tothe plant. ‘If we take
the lime that has been dissolved by citric acid, and deduct
from that the lime equivalent of the phosphoric acid also
dissolved, we shall obtain the lime soluble in citric acid,
over and above what may be regarded as neutralized by the
phosphoric acid. ‘This figure is generally known as the
available lime in the slag, and may fairly represent the relative
ability of the slag to replace the ordinary operation of liming
the soil. It is, of course, purely conventional. There is
a good deal of evidence to show that the citric-acid soluble
phosphate in a slag has a distinct value in pot experiments,
and in all cases where the crop has only a short period of
growth. ‘There is also plenty of evidence to show that in
the case of pasture such solubility is of little advantage.
Citric solubility must, therefore, be regarded as a test
of distinct value, in its proper place, but its importance can
easily be exaggerated. ‘The degree of fineness to which
basic slag has been ground is also a very important point.
The basic slag must be distributed much more completely
than is necessary for a manure soluble in water, and this
can only be achieved if the material is very finely divided
(see p. 6). Basic slag must be put on early to get a full
value. Probably the maximum result is obtainable about
two years after application, but with slags of high citric
solubility the maximum may be reached earlier. Soils
containing much humus or peaty material are especially
benefited by slag. ‘To what extent this benefit is attributable

pe

: sa

7 eg SS es

ee

THE PHOSPHORUS GROUP OF FERTILIZERS 29

to other constituents than the phosphorus is not really known.
With a slow-acting fertilizer of this nature, which is a power-
ful root stimulant, a very considerable portion of the observed
benefits may be quite secondary in their origin. The extra-
ordinary change in the physical condition of a soil to which
basic slag has been regularly applied must be seen before
it can be believed, much less realized and appreciated. At
Cockle Park, where this manure has been applied for many
years on pasture, the final improvement of the soil has not
yet been reached. Between 1897 and 1916 the result on
the physical condition of the soil is shown by comparing a
plot that has had no manure with a plot which has basic slag
at intervals of about once in four years. ‘The plot that has
received no basic slag showed, on careful examination, in
1916, no appreciable true soil at all. There was practically
sub-soil up to the surface. On the other hand, the plot which
had received frequent applications of basic slag now has
ten or twelve inches depth of a good loam, and is apparently
still increasing in depth, at probably a rate of about half
an inch per annum. Such a profound change from a clay
to a fibrous loam would of course explain any result, and it
is, therefore, quite impossible to attempt to distinguish
between the direct results of the addition of so much
phosphorus and the indirect results which have benefited
the plant by roundabout processes, which have certainly all
originated in the application of the slag. As lime, by itself,
has, on other plots, achieved but little result, one can only.
conclude that the phosphorus is the ultimate origin of the
observed fertility. Basic slag must be regarded as one of the
more lasting manures, but it appears to become exhausted
in time, and, generally speaking, an application once in
four years will be necessary. ‘The soils most suited are
undoubtedly heavy clays and soils of a peaty character,
whilst a sandy soil does not show such satisfactory results,
unless it is manured at the same time with one of the
potassium group of fertilizers (see p. 40). Basic slag has
even been used with great success on very poor pastures
on chalk, and seems to be one of the most generally useful

30 PLANT PRODUCTS

of all the fertilizers. ‘There are a considerable number of
slags of low phosphorus content, and it is one of the most
important problems before us to utilize these materials.
In addition to basic slag there are acid slags produced in the
steel industry which do not contain phosphorus. When
they possess any value for applying to the soil it is probably
due either to their lime content, or to the mere mechanical
action of coarse material.

Mineral Phosphates. —Deposits of mineral phosphates
are to be found in many parts of the world; indeed, on
looking at the parts of the world where they have been
found one cannot resist the conviction that they have been
found just where they have been most looked for, and that
probably more extensive search will discover a great many
new deposits. ‘The historical ‘‘ Cambridge Coprolites’”’ have
long since been worked out, and it is chiefly to foreign
sources that we now look. Of these the Florida phosphates
may be regarded as of the highest quality, containing about
75 to 80 per cent. of tri-calcium phosphate. North Africa
and the Pacific Islands provide us with some materials of
slightly lower grade, whilst Australasia possesses some valuable
deposits. These materials, if finely ground, can be applied
directly to the land. ‘They are, however, much less soluble
‘than basic slag, and for direct application to the land it
certainly seems a little contradictory for England to export
basic slag and to import mineral phosphates. Where
mineral phosphates have been systematically applied to
pasture, in comparison with basic slag, some quite good
results have been obtained. Satisfactory results have also
been found when mineral phosphates have been used with
the turnip crop. Nearly all the mineral phosphates actually
mined are used for the manufacture of super-phosphate.
The manufacture of this is described in other volumes of this
series, and need only here be briefly alluded to.

The mineral phosphate, having been finely ground, is
treated with sulphuric acid, and is run into a “ den,”
where the reaction is completed. As the resulting material
is apt to be sticky, it is sometimes, after breaking up, dusted

THE PHOSPHORUS GROUP OF FERTILIZERS 31

over with dry, finely powdered mineral phosphate, which
prevents the sticky grains from cohering. At some works
the super-phosphate is dried and heated. In any case,
it is extremely important to produce a fine, dry powder,
which neither sticks to the hand in broadcasting, nor clogs
the drill in machine application. Super-phosphate should
always be kept in a dry situation, otherwise the skill and
labour of the manufacturer will be wasted (see p. 6).

_ Super-phosphate, when stored, is apt to undergo a process
known as reversion, by which some of the soluble phosphate
once again becomes insoluble. The modern improvements
in manufacture have reduced the risk of depreciation in
value due to reversion during storage. Directly the super-
phosphate is applied to the land, reversion on a big scale
takes place. If the soil is tolerably well supplied with lime,
the mono-calcium phosphate will become converted into
di- or tri-calcium phosphate. When, however, the soil does
not contain very much lime, but is rich in iron, much of
the soluble phosphate will become ferric phosphate. The
former course of events is very much preferable.

For the purpose of examining super-phosphate it is
common to take a portion that is soluble in water for the
estimation of phosphoric acid. In the United States of
America it is also common to determine the amount that
dissolves in ammonium citrate. The difference of the two
standards is not, in modern products, a great one. The
phosphate applied as super-phosphate will not penetrate any .
depth in an ordinary soil beyond about six or eight inches.
Super-phosphate is of especial value as a quick-acting
phosphatic manure, and can be used even as a top dressing.
As many soils are deficient in phosphates, super-phosphate
is often one of the fertilizers which produce the most striking
and obvious results.

A particular type of fertilizer which has proved useful
is called basic super-phosphate. ‘This consists of a mixture
of super-phosphate and lime. By these means the super-
phosphate is turned into phosphate insoluble in water, but
very easily soluble in the very weakest of acids. (See Hughes,

32 PLANT PRODUCTS

Bibliography.) It has the advantage over super-phosphate
that it is not acid in character, and, therefore, does not
encourage the development of “‘ Finger and Toe”’ disease in
turnips. Its extreme solubility in very feeble acids makes
it practically as available to the plant as super-phosphate.
It is also very dry and fine, and easily distributed. A some-
what similar material called precipitated bone phosphate
is obtained as a by-product of the glue and gelatine manu-
facture. (See Bennett.) When bones are treated with cold
dilute hydrochloric acid, the framework of the bone is left
in gelatine and the calcium phosphate dissolved by the acid.
The acid liquids, together with the washings, ‘are then
precipitated with just enough lime to recover all the phos-
phoric acid, giving a precipitate about half di-calcium
phosphate and half tri-calcium phosphate. ‘The two last-
named fertilizers are favourites with those who grow turnips
on a large scale.

Bone Black and Bone Ash.—In sugar refineries con-
siderable quantities of bone black were used. After a time
it is beyond the power of the users to regenerate the bone
black for their purpose, and this is then sold as a fertilizer.
Bone ash, made either by burning bones or by burning the
refuse from the sugar refineries alluded to above, or obtained
direct from South America, is used for fertilizing purposes.
The difference between used-up bone black and bone ash
is, from a fertilizer point of view, of no particular importance,
since a few per cents. more or less of carbon will not influence
the results. Bone ash is fairly readily available in the soil,
and in this respect resembles basic slag. It is, of course,
a purely phosphatic manure, and may contain anything
up to 85 per cent. of tri-calcium phosphate. It is quite
suitable for any of the purposes of precipitated phosphate
or basic super-phosphate, but cannot be used as a top
dressing like super-phosphate. Bone ash, when finely ground,
is almost entirely soluble in weak citric acid.

Fertilizers containing both Nitrogen and Phosphorus.
—The different requirements of crops and soils preclude
the possibility of any fixed ratio between nitrogen and

Sore

x= ine ae s a 1 Saree, it ae = =

THE PHOSPHORUS GROUP OF FERTILIZERS 33

phosphorus in fertilizers, but for most arable purposes both
will be required. Probably fertilizers containing two ingre-
dients are often sources of loss, since one of the ingredients is
likely to be in excess. ‘This loss can only be avoided if very
careful study is made of the conditions, and the ratio of nitro-
gen to phosphorus adjusted to suit the special requirements.

Bones.—Bones became very popular as soon as the early
ideas of phosphatic manure became at all widespread. ‘The
bones of animals invariably contain some grease. The amount
of grease varies with the bone, but on the general average a
raw bone or rag bone contains about 12 per cent. water, 28 per
cent. nitrogenous organic matter, 10 per cent. fat, 44 per cent.
tri-calcium phosphate, and 5 per cent. calcium carbonate.
There are also traces of magnesia and fluorine. Large bones
of such a composition are very slow in decomposing in the
soil, and may be regarded as having no practical value.
If they are finely ground their value is greatly increased, but
the fat content acts as a preservative and diminishes the
value. Fortunately, the fat can be made a better use of.
Under the best systems the rag bones are extracted with
petroleum spirit, and the grease obtained is a valuable
product. The extraction of the fat renders the bones
porous, easy to grind, and available after application to
the soil. ‘The high-class bone meal obtained in this way
will often have over 5 per cent. of nitrogen, and about 40
per cent. to 45 per cent. of tri-calcium phosphate. In some
works, however, the fat is removed by a process of steaming
and boiling, which removes a good deal of gelatine as well
as fat. The remaining bones from this process are very
porous, grind very easily, and are far more readily available
to plants. According to the degree of treatment the bones
have received, the composition will vary from 3 per cent.
nitrogen and 50 per cent. tri-calcium phosphate to I per
cent. nitrogen and 60 per cent. tri-calcium phosphate. The
term ‘“‘bone meal’”’ is commonly wnderstood to mean
materials containing 4 or 5 per cent. nitrogen, which have
been obtained by some petroleum extraction ; whilst the term
“bone flour ’’ is commonly understood to mean the materials

D. 3

34 PLANT PRODUCTS

containing from 1 to 3 per cent. of nitrogen, obtained by some
boiling or steaming process. When finely divided, these
bone fertilizers are readily available in the soil, and may be
considered as more or less equivalent to basic slag, but of
course the nitrogen is in addition. The small amount of
calcium carbonate present in the bones is also useful to the
soil. Like all other manures containing organic matter bones
will provide some food for bacteria or other forms of soil life.

Bones are also treated with sulphuric acid in the same
way as mineral phosphates are treated for the production
of super-phosphates. The product is generally known as
dissolved bones or vitriolated bones, For the manufacture
of this article rather stronger acid is necessary, and it is
not practicable to get the whole of the phosphate into
solution. ‘The general run of dissolved bones contain about
3 per cent. of nitrogen, 15 per cent. of phosphates which have
been rendered soluble, and 15 per cent. of phosphates which
have not been acted on by the acid at all. By these means
the nitrogenous matter is dissolved as well as the phosphatic
material, so that the resulting dissolved bones must be looked
upon as a mixture of four fertilizing ingredients, namely,
soluble phosphates, insoluble phosphates, soluble nitrogen,
and insoluble nitrogen. The advantage of having two
degrees of solubility is very marked : the insoluble phosphates
will, on application to the soil, remain on the surface, and
the soluble will penetrate to a depth of a few inches. In-
soluble nitrogen may be left on the surface, but the soluble
nitrogen in this case will penetrate probably to a foot in
the soil, since those portions which are in the form of amino-
acids will not be at all readily fixed by the soil, but will
penetrate to a greater depth than ammonia salts could
(see pp. 7 and 13). As such materials will be very mixed
the nitrogen will be distributed over a considerable range
and depth of soil, and will therefore suit a variety of crops
in very varied stages of growth.

A very frequent type of bone manure is composed of
supet-phosphate, bone flour, and sulphate of ammonia.
Here again there is the advantage of two kinds of phosphorus

THE PHOSPHORUS GROUP OF FERTILIZERS 35

and two kinds of nitrogen. For the early growth of practically
all crops a rich surface is necessary. When, however, the
plants have grown it is desirable that the fertilizing ingredients
should be deeper in the soil, to prevent an excessive develop-
ment of surface root, with the subsequent susceptibility
to drought.

Guano.—This old-established and favourite type of
- manure is produced on rocky situations with little rainfall,
from the accumulations left by sea-birds during the nesting
season. Where the rainfall is very scanty the amount of
nitrogen in the guano may be as high as II percent. Where
the rainfall is considerable the nitrogen may be removed by
washing till it falls to 1 per cent. In guano produced under
dry conditions the phosphoric acid is partially soluble in
water ; but in that produced in wet situations the constituents
are all insoluble. A small quantity of potash is often
present, say i per cent. The varieties of guano may be
divided into those whose value is chiefly due to the nitrogen
and those whose value is chiefly due to the phosphorus.
The phosphatic kinds will barely differ in their properties
from bone flour. ‘Those of the nitrogenous kind will be of
a more complex character, containing both nitrogen and
phosphorus in various degrees of solubility. Some of the
less valuable guanos are treated with sulphuric acid to render
them more soluble.

A great variety of artificial mixtures are put upon the
market to supply both nitrogen and phosphorus. As a
rule the basis of these is super-phosphate, to which has been
added some bone, any of the nitrogenous organic manures
described above, and not infrequently a miscellaneous
collection of materials of lower value. Some materials, in
themselves almost worthless, can be so treated as to bring
them into use for this group. For example, leather in itself
is of little manurial value, but it can be treated with sulphuric
acid and thereby dissolved. ‘The acid is not lost in the
process, but is still capable of dissolving mineral phosphates.
Such a mixture will contain the leather in a digested form,
as well as soluble and insoluble phosphate.

36 PLANT PRODUCTS

Such mixtures as are here being described are very rarely
suitable for top dressing. They are best, therefore, applied
in the drill either with or without farmyard manure.
Containing a variety of ingredients, they are in many respects
safer, since even if the user possesses the knowledge to apply
crude fertilizers, he still is at the mercy of the weather,
and it is not possible to predict exactly which of the crude
fertilizers would be the best to apply. A mixture which
contains a variety is much more likely to apply at least
something that is necessary (see Introduction).

REFERENCES TO SECTION II

Collins and Hall, ‘‘ The Inter-relationships between the Constituents
of Basic Slag,’”’ Journ. Soc. Chem. Ind., 1915, p. 526.

Robertson, “* The Influence of Fluorspar on the Solubility of Basic
Slag in Citric Acid,” Journ. Soc. Chem. Ind., 1916, p. 216.

Bernard Dyer, “‘ Available Mineral Plant Food,” Journ. Chem. Soe.,
1894, p. II5.

Hughes, Journ. Soc. Chem. Ind., 1901, p. 325.

Robertson, ‘‘ Notes on the N ature of the Pigg ae contained in
Mineral Phosphates, * Journ. Agric. Science, 8, p. 17

Robertson, ‘‘ Solubility of Mineral Phosphates in Citric Acid,” Journ.

Soc. Chem. Ind., 1916, p. 217.

Bennett, ‘‘ Animal Proteids.”

Jones, ‘‘The Wagner Test as a Measure of the Availability of the
Phosphate in Basic Slag,” Journ. Board Agric., 1914-15, p. 201.

Davis, ‘‘The Phosphate Depletion of Soils of Bihar,” Agric. Journ.
Ind., 1917, p. 181.

Jatindra Nath Sen, “The Influence of the Presence of Calcium
Carbonate on the Determination of Available Phosphoric Acid in Soils by

Dyer’s Method,” Agric. Journ. Ind., 1917, p. 258.

Sreotion II].—THE POTASSIUM GROUP OF
FERTILIZERS

For some years past the German potash manures have com-
pletely eclipsed other sources of potash, and it is only since
the war that non-German sources have once again come into
prominence. ‘There is little doubt that the German potash
manures originated in the same way as most salt deposits,
that is to say, sea water has been naturally evaporated,
producing sodium chloride, then complex salts of magnesium
and potassium sulphates or chlorides, together with a deposit
of calcium sulphates. The material put upon the market
as kainit has, for a long time, had little connection with the
mineral properly so named, but has simply been a blend
graded to 124 per cent. pure potash (K,O), the remainder of
the material being chiefly sodium chloride, with some mag-
nesium sulphate. The composition of the German kainit
manure has been very constant, the average over many years
past having been 12°50+0°38 per cent. K,O for any single
sample. Other important potash manures of German origin
have been the sulphate and the muriate (chloride). The
better qualities of these have been about go per cent. purity,
but lower grades have also been on the market. ‘They have
always been sold under guarantee.

A very old type of potash manure is wood ash. The
ashes of full-grown timber do not contain much potash, but
the ashes of small twigs are fairly rich. The table on
p. 38 will roughly show the amount of potash in many
types of wood ashes,

The ashes of coal contain hardly any potash, but certain
particular wind-blown coal ashes in industrial concerns
contain appreciable quantities of potash. ‘The dust deposited

38 PLANT PRODUCTS

TABLE 4.—Woop ASHEs.

K,0 | Cao |S P,O,s|sCSi0,
per cent, per cent, percent. | per cent.
Beech trunk .. ae oie 16 56 6
Beech branch a Bip 14 48 12 I
Birch .. mle we 12 58 8 4
Oak .. ne + oe Io 72 6 2
Larch , Ss bs 15 26 4 4
Scotch pine .. “y as 12 | 50 8 15

If in the Table 4 the figures represent pounds, it would take 4} tons
of beechwood or 8} tons Scotch pine to be burnt for their production.

in flues of blast-furnaces and boilers often contains a con-
centration of certain ingredients which may raise the potash
in the dust to 5 or 10 per cent. ‘The vast majority of these
materials are, however, very disappointing, and rarély
tepay transport, although by evaporation of an aqueous
extract a concentrate. may be obtained. A tseful waste
product is obtained in the case hardening of steel, during
which small parts of machinery are heated, then plunged
into mixtures some of which contain potassium ferro-
cyanide. Although this material when used for case
hardening lasts a long time, when worn out it is still rich
in potassium, and may even contain 20 per cent. potash.
The cyanides present would be prejudicial to plant life if
applied after the plant had started growth, and would also
tend to check germination. Similarly, even wood ashes,
being strongly alkaline, should be allowed some time to work
into the soil before the seeds are sown.

The reactions of potassium sulphate with the soil are
very similar to those of ammonium sulphate. The potash
combines with clay and humus, and the sulphuric acid com-
bines with lime, and then washes out of the soil. Potassium
chloride reacts similarly, the chlorine taking lime and washing
out of the soil. When crude materials, like kainit, are applied
to the soil the sodium chloride washes out, leaving the potash
and most of the magnesia behind. ‘These manures tend to
exhaust the soil of lime. Wood ashes, however, do not take
away lime out of the soil, but tend to make it alkaline and

2 tee ee

_—

—s ————————__———— <=

ear ess — x = =

~~ ee
ESA oe

ao

a —

ag — I
—

0.

o>

PP Rans

THE POTASSIUM GROUP OF FERTILIZERS 39

‘deflocculated, and, therefore, to interfere with bacteria

or plant life. Such refuse materials as contain cyanides
will require a fairly lengthy period to enable the poisonous
cyanogen compounds to be rendered harmless and converted
into useful nitrates. It may be taken as a general rule that
potash manures should be applied early. Potash is not
fixed in the soil with quite the same completeness as phos-
phate, but in a parallel calculation to that given in the
section dealing with phosphatic manures it has been found
at Rothamsted that something like about three-quarters of
the potash can be accounted for, the remainder having
presumably bcen lost in the drainage during fifty odd years.
The need for potash manures is not as great as for phosphates
ot nitrogen. Clay soils contain a sufficient amount of potash
for most crops. It is only on the light and sandy soils that
potash manure is absolutely essential. he really most
important member of the group of potassium fertilizers is,
however, farmyard manure. ‘The recent effort to utilize
blast furnace dust promises a valuable addition to home

potash production.

REFERENCES TO SECTION III

Cresswell, ‘‘ Possible Sources of Potash,”’ Journ. Soc. Chem. Ind., April,

£915, p. 387.
Russell, “‘ How can Crops be Grown without Potash?” Journ. Board

of Agric., 1915-16, p. 393.
Voelcker, ‘‘ Absorption of Potash by Soils of known Composition,”

Journ. Roy. Agric. Soc., 25, 11.
Schreiner, ‘‘ The Absorption of Potassium by Soils,’”’ Journ. Phys. Chem.,

1906, p. 361.
Cranfield, ‘‘ A New Source of Potash,’’ Journ. Board of Agric., 1917-18,

p. 526.

Section IV.—MIXED FERTILIZERS

As a general rule both crops and soils will demand a
mixture of the crude fertilizers, and there are many occa-
sions on which it is convenient to be able to purchase
ready-made mixtures of these crude materials. The chief
difficulty that occurs in the application of crude fertilizers
is in their even distribution over the land. It is, there-
fore, advantageous to obtain a material which is not too
concentrated in any one ingredient. Hence there is a
distinct advantage in obtaining several materials ready
mixed. As, however, the requirements of soils and crops
are very varied, and climatic conditions will modify the
needs of any particular crop or soil, it becomes practically
impossible to design a mixture for any large group of districts,
soils, or crops. Certain general principles are quite well
established, (1) nitrogen for cereals, phosphorus for roots,
potassium for pulses, and (2) phosphorus for heavy soils,
and potassium for light soils. But it is quite impossible to
adhere rigorously to any such system, because in practice
a succession of crops are grown, and what is left over from
one crop is used up by the next. Nevertheless, there is
a distinct demand for specific mixtures. A very popular
mixture is potassic super-phosphate blended so as to contain
about 20 per cent. soluble phosphate, and about 3 per cent.
potash. Such a mixture can be made in a dry form, handier
for distribution than either of its ingredients alone. Mixtures
of super-phosphate, sulphate of ammonia, and potash salts
are often made and sold under specific names, such as “‘ Corn
Manure,’ “‘Grass Manure,” or ‘Turnip Manure.” ‘Too
much attention should not be given tothe name. Estimates
should only be based on the guaranteed analysis. Provided

ee

——"

mee

MIXED FERTILIZERS 41

the guaranteed analysis and the price correspond, and

‘granted that the material is in a good, convenient condition

for sowing, and that the mixture really represents what the
crop on that particular soil and under that particular climate
wants, then this mixture may be used with satisfaction.
For the purpose of checking the prices of these materials,
a unit of 22°4 pounds is commonly adopted. For Great
Britain these unit prices are published in the Journal of
the Board of Agriculture, which will give the values from
time to time. For example, in the number for April, 1917,
one may see that in London the unit price of nitrogen in the
form of sulphate of ammonia was 15s. 44d., but that nitrogen
in other forms was more expensive, and that at all the other
places named inthe table the same wastrue. ‘Thus with any
mixture in which nitrogen is probably derived from sulphate
of ammonia it would be not unreasonable to take this figure.
The value of a unit of soluble phosphate in super-phosphate
varies according to place from 3s. 14d., to 4s. 84d., and for
rough purposes one may call it 4s. At the time potash is
not quoted, but before the war potash was valued at 3s. or
4s.a unit. A calculation can be made as follows :—

TABLE 5.—MANURE.

Bi Bay nk

Nitrogen, 5 per cent., at 15s. ay fac omy Se he
Soluble phosphate, 20 per cent., at 1s. att APU ie) abtk Ta
Potash, 3 per cent., at Ios, ° ws I 10 0
Mixing, bagging, etc, 0 15 0
Total value Peet |: ane. Ve

If less than 5 tons, add 5 percent. .. US wee
If payment delayed till harvest, add 5 per cent, o 10 6

Prices will vary from time to time, but are published
monthly in the Journal of the Board of Agriculture.

It is not difficult to make one’s own estimate of unit
prices for one’s own special conditions. Sulphate of ammonia
contains so nearly 20 per cent. of nitrogen that the unit price
of nitrogen in sulphate of ammonia is almost exactly the
same in shillings as the price is in pounds per ton, that is,
when sulphate of ammonia costs about £16 per ton the unit

42 PLANT PRODUCTS

ptice of nitrogen is 16s. If super-phosphate, with 30 per
cent. of soluble phosphate, cost about £6 per ton, each one
per cent. will cost 4s. It will be noted, in comparing the
tables of the Journal of the Board of Agriculture, that
sometimes special forms are very expensive; for example,
in dissolved bones soluble phosphate is much more expensive
than in super-phosphate. ‘The nitrogen in dissolved bones
is assessed at a high rate, as it is also in the case of nitrate
of soda, but all these conditions are quite temporary, and
a few months later on the relative prices may be different.

In practice, the farmer should endeavour to discover
for himself, by experiments, what particular mixture suits
his soil and system of farming.

Farmyard Manure.—This very ancient and well-
known commodity owes its value partly to its chemical,
partly to its physical, and partly to its biological effects.
The elementary constituents are carbon, hydrogen, oxygen,
and nitrogen, which constitute the non-metallic part;
_ potassium, phosphorus, calcium, which constitute the metallic
part, both parts being of value; with some small amounts
of aluminium, iron, and silicon, which may be considered as
having no value. These materials are combined together
as humus, organic fibre, and salts. Water is present to the
extent of from 60 per cent. to 80 per cent. Farmyard manure
is by no means a dead thing. It is full of bacterial life,
which has a strong influence on its value. Considering, first
of all, the forms in which these elements of value occur, we
find that the nitrogen is very rarely indeed in the oxidized
condition of a nitrate. Very old heaps of farmyard manure,
say two years old, certainly do contain small quantities of
nitrate, but this age is not usual in farm practice. An
important fraction of the nitrogen is present in the form
of ammonia, which chiefly occurs as the result of the
decomposition of urea CO(NH,),. Urea is fermented by
a special micro-coccus, so that in a day or so the urea has
becoine completely converted into ammonium carbonate. The
ultimate result of this change is represented by the equation
CO(NH,),+2H,:0=(NH,);CO;. The ammonia so produced

Se gy ae ——

Ft ROS

ar

ee a

eR OO ae er

MIXED FERTILIZERS 43

will very likely react with some of the sulphates present,
so that in the manure heap the ammonia will be partly as
ammonium sulphate. In addition to this, as the organic
matter is decomposed by bacterial action, a portion of it will
form those vague compounds which we call humic acid,
which will enter into combination with the ammonia and
produce the soluble, dark-brown coloured substance,
ammonium humate. Some nitrogen is also present in the
amide form. Urea itself is an amide, but is not the only
one present. Many other amides are produced by the
action of bacteria upon proteins. Amino-acids and peptones
are also present. A fair proportion of the soluble nitrogen
which exists in the manure heap results from the bacterial
digestion of the proteins. Many of the bacteria in the manure
heap belong to the class that liquefy gelatine. The liquefac-
tion of gelatine is only a special, easily observed case of the
peptonization of proteins, and a part of the proteins which
have not been digested by the beasts goes into the peptone
form inthe manure heap. Of the albuminoids in the dung,
some ate soluble, but most are not merely insoluble in
water, but very resistant to all chemical change ; indeed part
of the proteins that are passed by the beasts is the residuum
of dead bacteria, which needs protracted decomposition.

The potassium in the manure heap will occur as potassium
sulphate and potassium humate. Most of the potassium is
soluble, and therefore very easily lost, unless care be taken
for its preservation.

The phosphorus in the mantre heap is very largely in
the form of phosphates, but some part is organic. Although
the manure heap is alkaline, and contains lime and ferric
hydrate which would normally precipitate all the phosphates,
yet in the presence of so much soluble organic matter, iron
and calcium are not able to precipitate phosphoric acid in
alkaline solution, so that, as a rule, at least one-half of the
phosphorus is soluble.

The calcium present is not in sufficient quantities to
appreciably affect the total value of the manure, but it has
some action upon bacterial life. It will occur mostly in

44 PLANT PRODUCTS

combination with humic acid, with which the calcium forms
an insoluble compound, but some soluble substance, like
calcium sulphate, will often be found in the manure heap.

The organic materials occur chiefly either as fibres or
as gummy matter. ‘The fibrous material is very important
in enabling the manure heap to retain its liquid constituents,
and in maintaining the open structure necessary for admission
of air in limited amounts. The gummy material provides
the humic acid and other colloids, which will fix or absorb
the substances of manurial value. The water present plays
a large part in the decomposition of the manure heap and
is chiefly absorbed by the litter. ‘The bacteria present are
mostly such common forms as coli communis or subtilis,
the former derived from the beasts and the latter from the
fodder.

The study of the proximate constituents is quite as
important as that of the ultimate constituents. ‘These
consist of three parts, the dung, the urine, and the litter.
The dung owes its chief value to nitrogen and phosphorus.
In old animals it is richer than in young animals, because the
young animals utilize food better. In the case of the grain-
fed horse it is rich and decomposes rapidly; but in the case
of the grass-fed horse it is poorer, and slower in action.
Sheep produce the richest and the cow produces the poorest.
A fat bullock will produce better dung than a cow, and the
manure will decompose much quicker.

The urine which decomposes very rapidly owes its chief
value to nitrogen and potassium. With root-fed beasts it
is weak, and with grain-fed beasts it is concentrated. Much
of the nitrogen occurs as urea, and ferments to ammonium
carbonate within two or three days. If the food is very
coarse—that is, contains much straw or inferior hay—as much
as one-third of the nitrogen appears in the form of hippuric
acid (benzamido acetic acid, CgH;.CO.NH.CH2.CO.OH). It
will be noticed at once that nitrogen for nitrogen, hippuric
acid contains very much more carbon than urea, CO(NHg)s,
and its excretion involves loss of food and loss of energy.
When foods contain a big proportion of pentosans the amount

Se eee. =
—
me "

—

a

fi,
see ae

i i

2

et

pA eat

acc i a ree I

a oe ee

-

MIXED FERTILIZERS 45

of hippuric acid secreted is much greater. Of the other
constituents of the urine the potassium occurs as sulphate
and chloride, whilst sodium occurs as sodium chloride.
The litter is a very important part of the manure heap.
Unless there is a generous supply of litter the beasts will
be uncomfortable and the valuable portion of the manure
will be lost by drainage. Most of the potassium and half
of the nitrogen occur in soluble form, which are only retained
by the absorptive capacity of the litter. The litter itself
may contain some nitrogen, phosphorus, and potassium,
but its chief value depends upon the water-absorbing
capacity. One part of leaves will absorb about two parts,
by weight, of water; straw will hold three parts ; sawdust
four parts; tan refuse five parts; rough peat six parts;
and picked peat-moss litter about ten parts. Some very
exceptional peat-moss litter may even hold eleven or twelve
times its weight of water without drainage. It is not practic-
able under ordinary conditions to get such good results
as these, because the trampling of the beasts will compress
the litter, and squeeze something out, but the relative values
of the materials will be roughly as stated. In practice much
will depend upon the relative cost of these different forms
of litter, but where practicable the more absorptive kinds
should be preferred, because it will save so much labour in
handling bulky useless material. However a good deal of
the value of the manure depends upon its physical effect in the
soil, its provision of food for soil organisms, and its production
of carbon dioxide in the soil. It is not possible to lay down
any very strict rules on this subject. Straw will certainly
provide better food for soil organisms than most of the
other ingredients named. Sawdust appears to encourage
harmful organisms if large quantities of manure are used,
if it is badly distributed in the soil, and if the soil is wet
and compact. Admission of air to the soil is also an important
point in the value of farmyard manure, and for such a purpose
peat-moss litter will serve much better than any other member
of the series. It must also not be forgotten that the straw
might be used partly for feeding, as it would then not be

46 PLANT PRODUCTS

necessary to use so much straw for bedding. A very common
and useful solution of these difficulties is to use both, to
put peat moss litter at the bottom and clean straw at the
top. It makes a very comfortable bed for the beasts, and
the liquor is well absorbed by the peat moss underneath.
The relative absorptive value of most of these materials is
increased by fine chopping, and unpromising materials
may be much improved by being passed through a chaff
cutter. The relative absorptive power of different litters
can be so easily determined that it would be wise for users
to test them themselves. All that is necessary is some
sort of scales and measuring vessel. A very convenient
method is to weigh 5 grammes of the material, add 100 cubic
centimetres of water, and allow to soak for a few hours.
The remaining mixture is then poured on to a funnel, which
has placed in it a small filter disc or even a common marble.
The portion of liquor drained through is measured in the
cylinder, and the difference from what was originally taken
gives the portion absorbed. With peat-moss litter it will
be found that 5 grammes will absorb about 50 cubic centi-
metres, or an absorptive capacity of 10 per unit. .

The Manufacture of Farmyard Manure.—As regards
the quantities produced, a cow will give about 45 pounds
of dung every day, containing about 8 pounds of dry matter
and 37 pounds of water. In the average of all animals the
organic matter in the dung represents 43 per cent. of the
organic matter eaten, and the nitrogen yielded is 20 to 40
per cent. of that eaten. This wide range of nitrogen is due
to the great variation in the proportions of nitrogenous
matter in the food. ‘The phosphorus in the dung equals
95 per cent. of that eaten, and the potassium about 16 per
cent. of that eaten.

Urine.—The cow gives about 50 pounds a day, with
4 pounds of dry matter, but the amount is very subject to
variation, according to the type of feeding. The organic
matter equals about 3 percent.of that eaten, the nitrogen from
60 to 80 per cent. of that eaten, the phosphorus about 3 per
cent. of that eaten, and the potassium from 80 to 85 per cent.

MIXED FERTILIZERS 47°

of that eaten. A striking point is the great difference
between the mode of excretion of potassium and phosphorus
—the potassium is almost entirely in the liquid portion,
and the phosphorus almost entirely in the solid portion.

Taking the whole excreta together, the organic matter
corresponds to 46 per cent. of that eaten, the nitrogen from
70 to 95 per cent. of that eaten, and the potassium and
phosphorus from 95 to 98 per cent. of that eaten. It will
be noticed, therefore, that very little phosphorus and
potassium are actually removed and sold off the farm in
theformof meat. ‘The loss of nitrogen by sale from the farm
is slightly greater, but under conditions of feeding livestock
very little of the manurial ingredients are sent away, and the
stock in hand of fertilizing elements is always very large.
The possible loss by drainage of the nitrogen can be made up
on the farm itself by other methods, as shown in Part II.,
but the loss of potassium salts by drainage constitutes a
serious diminution in fertility of the soil. It can only be
replaced by purchases of potassium compounds. In India,
and other countries where cattle feeding is not carried out
systematically, but where bullocks are used for draft purposes
and not fattened for beef, little attention is paid to conserving
the manures from the animals. Very often the cattle dung
is not used as manure at all, but is used as fuel, mixed with
straw, or as a material for plastering walls, etc. Where it
is used as a manure it contains no litter or urine.

TABLE 6.—MANURE IN INDIA.

Caftle.dune- | Capt dune: | catte urine.
Water oe ee ne ‘0 75'0 73°5 93°0
Organic matter .. vs - 14°5 IL"o 3°5
Nitrogen .. .¢ oe ue 0°27 0°35 0°56
Phosphoric acid .. es as o'18 O'l4 0°02
Potash... oe ee ee 0°30 o'18 I'r3
Lime ae eo hee me <2 0°28 0°25 O'12

Passage from Food to Dung.—The history of the
nitrogen that is consumed by the live-stock on the farm is
shown in the following table :—

48 PLANT PRODUCTS

TABLE 7.—NITROGEN HISToRY OF FEEDING.

Excreta %,
As carcase
or milk
%- Solid. Liquid, Total.

Horse at rest ‘ee et 43 57 roo
Horse at work bi ay — 29 71 100
Fattening ox a 4 23 73 96
Fattening pig ‘6 ap 15 21 64 85
Fattening sheep .. yt 4 17 79 96
Milking cows we rH 25 18 57 75
Calf on milk ae, sig 69 5 26 31
Average ofall .. kn 17 22 61 83
Average of working horse,

ox and sheep .. be 3 23 74 97

From which it will be seen that the effect of working a horse
is to increase the proportion of nitrogen that is excreted in
the liquid. The cow gives a higher proportion of nitrogen
as saleable products, and, in consequence, leaves less for
the manure heap. A calf fed on milk uses up. most of the
nitrogen for its growth, and leaves but a small fraction for
manure. ‘The average stock on a farm will vary according
to the system of management, but in no case will the pro-
portion of nitrogen sold be anything but small. The bulk
of the nitrogen that is eaten in the food goes back into the
manure, mostly in the soluble form and liable to loss by
drainage. ‘The farm is, therefore, compelled to carry a very
big working capital in the form of nitrogen, from which the
annual return is comparatively small.

A parallel table can be worked out for the potassium history.

TABLE 8.—PoTAssiumM HISTORY OF FEEDING.

Excreta %.
As carcase
or milk
%- Solid, Liquid. Total.
Horse —_— I 86 100
Fattening ox I 16 83 99
Fattening sheep I 6 93 99
Fattening pig mr 2 14 84 98
Milking cow ss oe te) 16 74 go

Se at ae =

MIXED FERTILIZERS 49

It will be seen in this table that, excepting in the one
case of cows giving milk, the proportion returned as saleable
is very smallindeed. Very nearly the whole of the potassium
in the food is returned to the manure heap in a liquid form,
easily lost by drainage. ‘The conservation of this potassium
is a very important problem, since where there are clay fields
the amount of potassium in the soil is naturally large, but
where the soil is sandy the potassium is needed as a fertilizer.

The phosphorus history of the food eaten is given in
Table 9, from which it will be seen that the major part of
the phosphorus eaten is returned to the manure heap in
the solid form, and is, therefore, not easily lost.

TABLE 9.—PHOSPHORUS HIsToRY OF FEEDING.

Excreta %,.
As carcase
or milk
%- Solid. Liquid. Total.
Horse dis ae és — 99 I roo
Ox rs ve a. 14 85 I 86
Pig ae ‘es os 16 68 16 84
Sheep es PY oe 14 83 3 86
Cow ee ee oe 23 76 I 77

Considering the very big increase in crop often produced
by phosphatic manures, and considering the very small
risk of loss, every possible step should be taken to increase
the use of phosphatic fertilizers. Nothing like the amount
that ought to be used is applied in common practice.

Great variation will occur in the composition of the
manure, according to the particular system employed.
Table 10 shows the comparison between feeding on very wet
food and on very dry food.

These conditions represent extremes, but there is much
room for variation between these limits. When very watery
food is fed, the amount of liquid manure is much increased,
and carries with it a bigger quantity of dry material. In
both the foods actually selected the amount of potassium
is high, and, therefore, there is ample to spare for all purposes.

D. 4

50 PLANT PRODUCTS

TABLE 10.—POUNDS TO OR FROM ONE Cow IN ONE DAY.

Food. | Manure, | Food, é Manure,
Total,

cs Liquid. | Solid, | Liquid, Gis) Reaves Solid, | Liquid.
—_-—

Total -. | 154 — | 42 88 | 26 66 | 48 | 14

Water .. | 135 —— 35 84 | 4 66 38 12

Dry matter | 19 oe 7 4 | 22 oat, WO 2
N ae 030 | — O'14 | OIL || O60) — O16 | O21

P.O; re O14, — o'1o O'Or || O15 | — 008 | —

K,O i O72 |) — 0°06 | 0°53 | 0749 | — OIL | 0°24

Of the nitrogen, much better utilization is made in the
more digestible and watery mangels than in the dry and less
digestible hay. Since there is six times as much liquid in
the excreta from mangels there would have to be used six
times as much litter to obtain.the same degree of conser-
vation.

Storage of Farmyard Manure.—tThe storage of the
manure heap is a matter of considerable practical import-
ance. Soon after production fermentation begins. The
first fermentation results in converting urea into ammo-
nium carbonate. During this process some ammonia may
be lost by fermentation and evaporation. A good supply
of litter acts as an absorbant for ammonia, and the loss by
volatilizing ammonia is probably very small under ordinary
farm conditions, although in town stables, where there are
many highly fed horses, the loss of ammonia may be so
sufficiently marked as to be a nuisance. General decom-
position produced by the actions of various bacteria soon
starts in the manure heap. In broad outline, the anzrobic
bacteria attack the fibre and proteins, which they hydrolyze
with the production of gummy or colloidal substances,
peptones, and amino-acids. ‘The aerobes have little chance
of working in afresh manure heap ; they are mostly confined
to the surface, where they are able to carry on their oxidizing
powers. The rate of action will depend upon the tempera-
ture, much liquid excludes air, lowers the temperature, and
therefore the rate of decomposition. Much carbohydrate

MIXED FERTILIZERS 51

increases the speed of oxidation, raises the temperature,
increases the general rate of decomposition, and sometimes
assists in nitrogen fixation. All the fertilizing elements,
that is, nitrogen, phosphorus, and potassium, increase the
tate of decomposition, because they facilitate the multi-
plication of the bacteria. As the bacterial food is used up
the rate of decomposition slackens.

Decomposition in the manure heap may proceed in
undesirable directions. When nitrogen is made to change
into compounds unsuited to the growth of crops the word
“ denitrification ’’ is commonly applied to this state of
affairs. ‘“‘ Denitrification ’’ is often applied in two different
senses. Firstly the sense of the actual evolution of nitrogen ;
this may occur chemically by the interaction of nitrous acid
upon ammonia, or by bacterial evolution of nitrogen from
proteins. The latter is probably only a special case of the
former, since the action of nitrous acid upon amino-acids
is directly comparable to its action upon ammonia, and such
changes are probably brought about by bacterial agencies.
Once nitrogen is given off from the manure heap as elementary
nitrogen it becomes mixed with the nitrogen of the atmosphere
and may be regarded from a practical point of view as finally
lost. ‘The above is the reversal of the process of nitrogen
fixation. The other meaning of “‘ denitrification’ is the
reversal of the process of nitrification. In the process of
nitrification the protein is broken down to simpler organic
nitrogen bodies, then to ammonia, then to nitrites, and lastly
to nitrates. When this process is reversed the proportion
of nitrates diminishes. ‘The reversion of nitrogen can be
imitated in the laboratory by heating sugar, a nitrate, and
potash in a tube, when organic nitrogen compounds are
formed. In the manure heap these changes are chiefly
controlled by the bacteria. Attempts to prevent the loss
of ammonia from the manure heap by the addition of sub-
stances of an acid nature have done little good, although for
town stables a sprinkling of gypsum is useful for sanitary
purposes.

The main object of storage should be to promote

52 PLANT PRODUCTS

fermentation, and to prevent loss by drainage. ‘The loss by
drainage may be very pronounced, even under carefully
controlled conditions. In aseries of experiments conducted
at Cockle Park I found the results which are condensed in
Table 11. The sampling of farmyard manure presents great
difficulties, hence the error of experiment is very large, but
in the last column of the table I have expressed the average,
with the probable error of the series.

TABLE I1,—STORAGE OF FARMYARD MANURE IN CEMENT Pits,
COCKLE PARK.

LossES AND GAINS DURING S1x MontTHS’ STORAGE.

1899. 1g00, 1gOl. 1902. Mean.
Per cent, | Per cent. | Per cent. | Per cent. Per cent.
Organic matter 7 —22 —20 —I3 — I —14+ 3
Mineral matter is — I +22 — 2 + 5 + 6+ 4
Total nitrogen —23 —29 — 9 + 2 —I5+ 6
Total phosphoric acid +16 —25 +39 —I2 + 5411
Total potash .. ; —I2 —30 —34 —16 —23+ 5

It will be seen that when manure is kept in the circum-
stances stated, the organic matter and total nitrogen that
are lost amount to about 15 per cent., within a reasonable
margin of error, that the loss of potash is even greater, but
that the phosphoric acid gives no evidence of any loss. ‘The
potash could, under those circumstances, only have been
lost by drainage ; the nitrogen might have been lost either
by drainage or as elementary nitrogen. About a half of
the nitrogen would have been insoluble in water, and of the
remaining half some at least would have been in the colloidal
form, difficult of diffusion. One would, therefore, expect
that if 23 per cent. of potash can pass away by drainage,
the nitrogen loss by drainage should be less than half that
figure. Little error in these experiments would occur from
nitrogen fixation, since the dung was made by bullocks.
There may be, therefore, a slight loss of nitrogen into the
atmosphere, but it is very clear that the most pressing
reform is to prevent loss by drainage. In places where there
is a pit, to collect the drainage, the drainage is pumped up

MIXED FERTILIZERS 53

by a pump of the disc and chain type, and allowed to
flow over the dry upper surface of the manure heap. By
persistently pumping the drainage, it evaporates and becomes
concentrated, and the proportion of liquor in the pit becomes
diminished. Where the manure is stored on the field the
most practicable method is to remove the surface of the
ground, to break up the subsoil, to put the manure on top,

_ to use the earth that has been dug out as a cover for the

manure heap, and, when ready, to spread all the manure and
all the broken subsoil on the field. By such means the
loss by drainage can be reduced to a small figure. The
general analysis of farmyard manure, kept under reasonable
but not ideal conditions, is shown in Table 12, which gives
the probable composition of any sample taken at random,
calculated from several analyses.

TABLE I12.—FARMYARD MANURE,

Probable sample,
Moisture ae ae Ha 75°3 to 80'9
Organic matter ee av 14°2 to 18°8
Mineral matter oe ae 0°43 to 5°9
Nitrogen non-albuminoid ue o'15 to 0'27
Nitrogen total .. Ki cis 0°54 to 0°72
Potash .. vr a ie 0°52 to 0°68
Phosphoric acid ee oe 0°26 to 0°34

In attempting to assess the money value of any such
manure by the same standard as is adopted for chemical ferti-
lizers one will see that the phosphorus is of little consequence,
and in any normal circumstance the price would chiefly
depend upon the nitrogen; but from a practical point of
view the value of the manure will depend rather upon its
physical properties in the soil, upon its percentage of potash,
and upon its encouragement of the life of soil organisms.

It will be quite impracticable to have every fertilizer
employed on the farm a quick-acting one. Some of the
ingredients of any fertilizer must be of slow action to provide
for the future. Farmyard manure should, therefore, be
considered not in opposition to chemical fertilizers, but in

54 PLANT PRODUCTS

partnership with them. ‘The chemical fertilizers will supply
the quick-acting and stimulating part, and the farmyard
manure wil supply the more lasting and soil-improving
part. With the present lack of potash manuring, farmyard
manure forms the chief source of that element in farming.
The Utilization of Sewage.—The primitive system
of every man to his own land soon breaks down with
large populations. Simple closets are very unsatisfactory,
since flies communicate disease, and even smells are lowering
to health. ‘Ihe earth closet is a great improvement if enough
dry earth can be obtained. ‘The resulting material, if removed
to the garden, provides a useful fertilizer, but for towns the
weight of the soil is an insuperable objection. Under the
systems where the sewage is allowed to accumulate in cess-
pools great nuisance arises. A better system consists in
removing all household refuse in carts at night. This
mixture, known as “ night soil,’’ or ““ Scavenger,” is carried
to outlying farms, and either put direct upon the soil or
put into trenches which have been previously dug. Farmers
contract with municipalities to supply themselves and
neighbours. Under these systems a rotation is adopted on
the farm to suit periods of excessive manure, followed by
periods of no manure at all. The details of such management
on the farm will depend largely upon the local requirements,
but the system has been found to work passably well when
on a comparatively small scale. A more elaborate and
industrialized system is that generally known by the French
name of ‘‘ Poudrette,’’ where the night soil is taken to a
factory and is there mixed with a suitable proportion of
ashes and soil, allowed to ferment over one or two years,
and then sold to the neighbouring cultivators. Such
Poudrette contains about 20 per cent. of water, 10 to 15 per
cent. of organic matter, $ to 1 per cent. of nitrogen, and $
to I per cent. of phosphoric acid. Such a factory must be
situated well away from the town. In very industrial
districts the night soil collected may be taken to a factory
and dried, and the grease extracted by petroleum spirit,
the resulting material being supplied to the farmers in the

MIXED FERTILIZERS 55

neighbourhood as a dry powder. As the phosphoric acid
content is low, mineral phosphates are sometimes admixed.

For countries with a plentiful seaboard the water-carriage
system supplies a simple solution of the sanitary difficulties,
since everything may be flushed into the sea, but such a
system provides no solution of the agricultural side of the
problem. ‘The introduction of the sewage farm makes an
attempt to get over this difficulty, and utilize the manure for
food production. The conditions necessary for success are,
however, exceptional. Where there happens to exist a
suitable area of light soil, situated below the level of the
town supplying the sewage, with facilities for providing
a pipe with convenient gradients, the system may be a very
great success. When only clay land is available the amount
of land necessary becomes unreasonably large, and if too much
sewage is put upon the land it is ruined for years. Consider-
able skill is therefore necessary in management. In some
cases the sewage farms originally succeeded by an accident,
because the condition of affairs caused an approximation
to bacterial ‘systems of purification. One of the great
difficulties of a sewage farm lies in the fact that it has to
take sewage according to the rate at which it is being produced
in the town, and not to suit the requirements of the farm.
If it were possible to entirely separate the rain-water of the
streets from the pure sewage, much of this difficulty would
be overcome, but it is very difficult to satisfactorily arrange
a farm on the system of always having to take manure,
whether it suits the crops or not. A not infrequent adjunct
to a successful sewage farm is a pig-breeding establishment,
as the pigs can eat up the large quantities of roots, etc.,
grown on a sewage farm, which fastidious people do not
fancy. ‘The hay crop is also a very important part of a
sewage farm, since large crops of succulent, if coarse, hay
can be obtained.

The Sludge Precipitation System.—To prevent the
nuisance of crude sewage the idea arose of precipitating at
least some of the material as a sediment or sludge, and a large
variety of patent mixtures have been used for this purpose.

56 PLANT PRODUCTS

Unfortunately the really valuable and important fertilizing
ingredients remain in solution, whilst the sludge is of
inferior composition. A very large tank space is necessary,
and the materials obtained are of small value.

The Septic Tank Method.—lInstead of trying to
divert the normal course of events, a system of facilitating
the natural decomposition of sewage has been introduced
with very considerable success. In the decomposition of
sewage there are roughly two stages. ‘The first is due to the
decomposition by anzrobic bacteria, much in the same way
as in the fermentation of farmyard manure, described above.
During this process the insoluble matter goes into solution,
even cellulose becoming very largely decomposed during this
stage. Subsequently, the action of srobic bacteria will
oxidize the materials in solution, and convert them into
inoffensive materials. In practice it has often been found
unnecessary to adopt any elaborate plant to separate the ©
two stages, since a preliminary depositing tank of small
dimensions, to remove gravel and grits, followed by larger
tanks, for the bacterial digestion suffices. Coke beds with
sprinklers form a favourite modern oxidizing part of the
system. The resulting liquors contain practically everything
of value, and can either be run on to a farm, or be run into
a river without harm. ‘The sludge from the septic tanks
is usually quite inoffensive, but its composition is very
variable, and the dry matter may contain anything from $
to 2 per cent. of nitrogen. Not infrequently these sludges
are mixed with some phosphatic fertilizer to render them
more generally useful. Popular conceptions are apt to
exaggerate the fertilizing importance of town sewage. ‘The
average produce of one man in one year is about 11 lbs.
nitrogen, 24 lbs. phosphoric acid, and 2} lbs.potash. The sum
of all the population is, no doubt, large, but the problem of
this utilization presents very great difficulties, excepting on
a small scale.

Miscellaneous Organic Mixed Fertilizers. —The drop-
pings of poultry form a very well-known and much-prized
manure for intensive purposes. Birds do not secrete waste

|
eos Stee POS

Po — —

Sm a tg em a Ee - —
a ee — -_ ——_-

ISAM

MIXED FERTILIZERS 57

nitrogen in the form of urea, but in the form of uricacid. The
nitrogen is, therefore, not very soluble in water, although it
decomposes in the soil fairly rapidly. ‘The material varies
considerably, but about 1 per cent. nitrogen, I per cent.
potash, and 2 per cent. phosphoric acid will represent a rough
average.

Seaweed is a useful fertilizer, available on sea-coast
districts, where outlying rocks are covered with weed.
During certain stormy seasons of the year a large amount of
seaweed is thrown up on the coast. Where this becomes a
nuisance local authorities are sometimes prepared to carry
the seaweed some distance inland by traction engine,
but ordinarily the farmer’s own carts will have to tackle
the business. Seaweed contains about 80 per cent. water,
4 per cent. nitrogen, I per cent. potash, and } per cent.
phosphoric acid. One of the best uses for seaweed is
admixture with the ordinary farmyard manure heap. If
a heap be composed of alternate layers, six inches of sea-
weed and six inches of farmyard manure, the amount of
manure at the farmer’s disposal is doubled, and the general
average composition not very seriously affected. Sea-
weed can also be used as a convenient mulch for protecting
young plants against either drought or frost.

Animportant series of mixed organic manures are included
in the group known as composts. ‘These are conveniently
made by mixing lime with all kinds of waste organic material.
Blood, to which has been added about 2 per cent. quicklime,
sets into a solid cake, which dries in the air, and breaks down
to a powder. Lime mixed with hedge clippings, weeds,
etc., will gradually work down into a convenient material
for subsequent use. Attempts to ferment resistant articles,
like bones, with either the drainings from the manure heap
or fresh urine, are not very satisfactory, because nearly half
of the nitrogen is lost during fermentation.

Vegetable or leaf mould is very valuable to gardeners,
being more like rich soil than farmyard manure. In forestry
work much importance is attached to beech mast, as it
greatly improves the soil and facilitates subsequent growth,

58 PLANT PRODUCTS

while carpets of pine needles form a useful mulch on the
surface, but decay only very slowly.

Peat is also a material which can be used for fertilizing
purposes on light sandy soils, or on heavy clays. It improves
the water supply and aeration of the soil. Much attention
has been directed to the attempt to ferment peat into some-
thing more immediately active. ‘This very old idea has been
revived recently, in the effort to give a carefully directed
bacterial fermentation in place of a more haphazard decom-
position. Very valuable reports on humogen have been given
by Voelcker and Russell (see Bibliography). Whenever such
materials as peat, having a very high capacity for absorbing
water, are added in large quantities to a soil, they are perfectly
certain to produce a beneficial result, but the expense and
labour involved will often detract from their value.

Conclusion.—The very varied by-products of the in-
dustries which are capable of being used as fertilizers have
been discussed above in moderate detail. . Consultation with
the various books referred to in the Bibliography will give
many further details. Unintelligent use of fertilizers can
easily do more harm than good, and a knowledge of the proper
fertilizers requires not merely a knowledge of the fertilizers
themselves, but also of the types of soil to which they are to
be applied, the crops proposed to be grown, and the conditions
under which the cultivation of these crops is undertaken.

REFERENCES TO SECTION IV

Collins, “‘ The Valuation of Manures,”’ The Journ. of the Land Agents
Society, Sept.,.1908, p. 452.

Richards, ‘‘ The Fixation of Nitrogen in Feces,” Journ. Agric. Science,
8, p. 299.

Russell and Golding, “ Investigations on ‘ Sickness’ in Soil,’”’ Journ.
Agric. Science, 5, 27.

Fowler and Clifford, “Notes on the Composition of Sundry Residual
Products from Sewage,”’ Journ. Soc. Chem. Ind., 1914, p. 815.

Rideal, ‘‘ Sewage and the Bacterial Purification of Sewage,” p. 330.
(The Sanitary Publishing Co.)

Dibdin, “‘ The Purification of Sewage and Water,” p. 108. (The
Sanitary Publishing Co.)

Rideal, “ Disinfection and Disinfectants,” p. 238. (Griffin.)

Weiss, “‘ Directions for Preparing Manure from Peat,’’ Journ. Board of
Agric., 1916-17, p. 481.

Russell, ‘‘ Report on Humogen,” Journ. Board of Agric., 1917-18, p. 11.

MIXED FERTILIZERS 59

Bottomley, “ Bacterised Peat; the Problem in Relation to Plant
Nutrition,” yay Soc. Chem. Ind., 1916, p. 871.

Hendrick, ‘“‘ The Value of Seaweeds as eet Materials for Chemical
Industry,” Journ. Soc. Chem. Ind., 1916,

ay The Cultivation of Seaweed in Irela s Journ. Board of Agric.,
I9QI5-16, p. 462.

Hendrick, ‘“‘ The Composition and Use of Certain Seaweeds,” Journ.
Board of Agric., 1915-16, p. 1095.

Voelcker, Journ. Roy. Agric. Soc., 1916, p. 246.

Aikman, ‘‘ Farmyard Manure,” (Blac kwood.)

Part II.—THE SOIL

Section I1.—SOILS AND THEIR PROPERTIES

THE soil has two important and entirely distinct functions
for assisting the growth of plants. (a) To supply a support
and room for growth, and (b) to-act as a storehouse for
plant foods. The first of these functions is almost entirely
of a physical character, the second is both physical and
chemical, and very largely on the border-line between those
two sciences.

Inspection of Soils. —Some general observations can
be made on the spot by examining the soil in the field.
Whilst the analysis of soils is a complicated business, which
is not treated in this book, but left to the text-books specially
devoted to such a very highly technical subject, yet the
preparation of a soil sample which is required for analysis
is a very important subject, and can very rarely be carried
out by the actual analyst. For examining the suitability
of a soil for specific crops and fertilizers, a very good plan is
to dig a few holes in the field and inspect the soil. Once
a hole has been dug in the ground it is easy to obtain a smooth
vertically cut surface, which can be observed without
disturbing the soil. It will generally be observed that at
some depth the nature of the soil changes, often fairly
abruptly. ‘This change is brought about partly by the action
of ploughs opening the soil to a particular depth, or by the
natural limitations imposed upon the vegetation of the
surface.

When a hole has been dug in a field, and a good vertical
surface been obtained, it must then be decided how the slice
is to be cut, and divided as regards depth. Where time

a i

SOILS AND THEIR PROPERTIES 61

permits, it will be advisable to separate the soil into a series
of layers, the first three inches, the next three inches, a
third three inches, and possibly a few further depths as well.
A very large number of samples of soil have been taken to
a depth of nine inches, and it is, therefore, desirable, for
comparative purposes, that the amount of plant food to a
depth of nine inches should be known, but it is often advisable
to have further information. The great variation of compo-
sition which occurs in soils from depth to depth must always
be borne in mind, since unless soils be sampled to a definite
depth, no sort of constant results can be obtained. There
are, however, many occasions when a soil is not nine inches
deep, and one is, therefore, compelled to coritent oneself
with less depth. Not infrequently within easy range of a
spade from the surface one may come across rock more
or less broken down by weathering. Many attempts have
been made to obtain some mechanical appliance to obtain
samples of soil with less labour than that involved in first
of all digging a hole and then obtaining a vertical slice.
Within the narrow limitations of particular types of soil
such efforts are perfectly satisfactory, but a universal
method for all soils has yet to be discovered, excepting the
more laborious method here described. All instruments of
the type of a boring tool become unworkable in a soil con-
taining many stones, whilst in humus soils they introduce the
serious difficulty of inaccurate measurement, owing to the
compression of the soil which they produce. They further .
have the great disadvantage that the operator cannot see
the nature of the soil he is sampling, and an observation
on the spot of the actual appearance of the undisturbed
soil will often teach quite as much as the subsequent analysis.

The size of the particles of soil is a matter of great
practical importance. This subject has been investigated
very fully, and much ot the literature on the subject is given
under such names as physical or mechanical analysis. ‘The
manner in which the particles are packed together is also
a point of great importance. The actual size of the particles
is not easily altered, but the manner in which particles are

62 PLANT PRODUCTS

packed is subject to considerable control. If we assume,
for the sake of argument, that all the particles in the soil
are spherical, and that they are packed together with loose
packing, then the air space will amount to 47 per cent. of
the total. With close packing they will give 26 per cent. In
practice, however, such purely theoretical considerations have
little relationship to what actually occurs. The particles are
not spherical, and, at any rate in a temporary manner, they
put themselves into a condition known as “‘ crumb ”’ structure,
in which the particles have built themselves up into irregular
groups, with fairly large openings between groups of particles,
so that in fertile soils the vacant space filled with either
air or water amounts to about 50 to 70 per cent. Where
there is much fibrous, half-decayed root, the openings of
the structure, and consequently the air and water space,
may be further increased. In the operation of tillage the
earth is broken apart and allowed to fall back gently, so
that the structure is much more open. Rolling will compact
the soil and decrease the air and water content. For the
growth and development of any root system space in the
soil is necessary, and the provision of this necessary space
is largely dependent upon tillage operations. The movement
of the water in the soil is much altered by variations in
the open space in the soil.

A very important study in the physical properties of
soils consists in the consideration of the properties of colloidal
material that the soil contains. A rough distinction between
the colloids in the soil and the solid grains may be made
by stirring the soil up with water, allowing the grains to
settle for twenty-four hours, and pouring the muddy liquid
off. Some portions of the soil will practically never settle
in water, but may be made to do so by precipitating with
suitable agents. The addition of sodium carbonate will
increase the proportion of a soil that will not settle in water.
The addition of calcium sulphate will precipitate nearly
all the soil colloids. Any strong solution—sodium chloride
and sodium sulphate—will also precipitate the colloids ;
super-phosphate, lime, basic slag, and farmyard manure all

SOILS AND THEIR PROPERTIES 63

tend to reduce the colloidal condition of the soil. A certain
amount of colloid is certainly valuable in light soils. At
Woburn it has been observed that nitrate of soda removes
colloids from the surface soils, and deposits them again
deeper down, so that the surface soil loses its adhesive
properties, and becomes too dry and sandy. On heavy soils
too much colloidal matter makes the clay almost unworkable.
It should be noted that fertilizers, in addition to their purely
chemical value, have a powerful influence upon the colloidal
character of the soil. It is doubtless perfectly possible that
in a few special places this influence of the fertilizers on the
colloids may help to overwhelm the influence of the chemical
elements, but in most situations it will be found that the
considerations given to the fertilizers in Part I. will be a
fairly correct method of assessing the increment of plant
production. Nevertheless, the secondary influence of the
fertilizers upon the physical properties of the soil must never
be overlooked, since it may produce some profound changes.

Personal observation shows that, on clay lands, basic
slag produces an abundance of deep fibrous root, sulphate
of ammonia a shallow black humus, and muriate of potash
a black humus a few inches deep, with a sticky subsoil.
On light soils, nitrate of soda gives a surface sand with hard
pan subsoil.

Much depends upon the ability for growth of the surface
vegetation, and this is illustrated in a striking manner in
experiments on pasture land. At Cockle Park, in North-
umberland, basic slag has been continuously applied to grass
land, with the result that the soil has been steadily deepened,
so that the active part of the soil on the surface has invaded
the inactive subsoil underneath (see p. 29). No person to-
day, who did not know the history, and was shown slices
of the two soils, would imagine that they ever could have
been the same. ‘This marked change in the soil has been
brought.about by the increased root development of the
natural vegetation, which has been encouraged to grow by
the application of an appropriate fertilizer, in this case basic
slag. It must not be imagined, however, that for any and

64 PLANT PRODUCTS

every soil exactly that treatment would be the ideal one,
but investigation on the soil itself will probably show what
is most required. Similar results have been obtained on
light soils by combined potash and phosphate fertilizers,
whilst on some soils wild white clover seed harrowed in has
produced the desired effect.

Owing to the colloids in a soil, it is difficult to filter a
soil extract through paper. A soil will, however, always
filter itself clear, since any sized particle will always find some
particles a little coarser than itself, the interstices between
which will always be smaller than itself. By fitting up a
funnel with a filter disc and cloth, to which is adapted a
long fall tube for suction purposes, and pouring the soil,
mixed with water, into the funnel, the first cloudy runnings
can be returned to the funnel and then a clear solution will
be obtained. Hence the finest colloids do not penetrate
very deeply into a soil.

Specific Gravity.— The true specific gravity of a soil—
that is, the specific gravity of the particles of which the soil
is composed—is not in itself a matter of much practical
importance, though referred to in nearly all text-books.
The crude gravity—that is, the weight of a given volume of
soil, including air spaces—is, however, a distinctly useful
figure. Commonly this measure is expressed in-pounds per
cubic foot. A sand will weigh 110 pounds per cubic foot
when dry, a good arable soil from 80 to 90 pounds, a heavy
clay 75 pounds. A soil containing very much decomposed
organic matter will weigh about 70 pounds, whilst a peaty
soil containing much fibrous organic matter will only weigh
from 30 to 50 pounds per cubic foot. ‘The soil on Tree Field,
at Cockle Park, in its unimproved condition, weighs between
84 and 87 pounds per cubic foot, and, though a clay, contains
a few stones and a little organic matter. The apparent
heaviness of all the soils of the Cockle Park type is due
rather to utter lack of balance than to the strict physical
properties of the fundamental ingredients, a fact which is
borne out by the above figures, which would classify this
type of soil as having a much higher value than it has in its

\

SOILS AND THEIR PROPERTIES 65

natural condition. Calculated to the weight of soil per
acre, taken to a depth of eight inches, one acre would weigh
a thousand tons; or to two decimetres, a million kilograms.
Sources of Heat to the Soil.—Although under con-
ditions of market gardening and the use or the warm
frame the amount of heat produced by chemical action
may be appreciable, in large-scale agriculture the only
important source of heat is from the sun. ‘The chief fluctua-
tions of heat arise in (1) the photosphere of sun (“sun
spots’), which produces indifferent harvests about once
every ten or twelve years and fortnightly alternations of high
and low temperatures ; (2) the resistance of the atmosphere
to the passage of solar radiant energy, a resistance which
is greatly increased by clouds, moisture and fog; (3) the
angle of incidence of the sun’s rays upon the surface of
the earth, which angle will vary with the season, the latitude,
and.the slope of the soil. Within the limits of the tropics,
that is, 23° north and south of the equator, at some period
of the year the sun’s tays are vertical, and, according to
the proximity of the equator, the sun even passes away
still further from the vertical. In the temperate zones the
sun is never absolutely vertical, but owing to the increase
in the length of days during the summer, the total amount
of solar radiation received within the twenty-four hours
exceeds that received in the tropics. The highest tempera-
tures ate recorded in latitudes of 30° or thereabouts: at
latitudes over 60°, solar radiation does not reach the opti-
mum for plant production. Slopes having a southerly aspect
in the northern hemisphere, or a northerly aspect in the
southern hemisphere, are advantageous, since a definite
quantity of solar radiation has then a smaller area to
distribute itself over. In the northern hemisphere what the
southern slope of a hill gains the northern slope loses.
Altitude is:an important consideration in the growth of
plants. In high altitudes the sun’s rays fall upon the ground
througha shorter, less dense,and clearer columnofatmosphere.
On the other hand, considerable lowering of temperature
is ptoduced on high altitudes by ascensional currents of
D. 5

66 PLANT PRODUCTS

air. When air rises from the plains to the hills it expands,
and in expanding loses heat. The wind, therefore, rising
from the plains to the hills, cools the tops of the hills.

In cold climates the removal of superfluous water by
drainage is of great value in maintaining the temperature of
the soil. Hoeing and harrowing also assist in this direction,
and the use of any kind of mulch effects the same purpose.
In hot climates irrigation not merely supplies water, but also
lowers the temperature. Very shallow ploughing, harrowing,
and hoeing make the surface a relatively bad conductor of
heat, and, therefoie, prevent the penetration of solar heat.

Colour of Soils.—Dark-coloured soils absorb and radiate
more heat than light-coloured soils. In hot climates some
of the black soils show very striking variations between the
temperatures at 2 p.m. and 4a.m., as is well known to those
whocamp out on them. In damper climates the black soils
are oiten visited by mist and fog. On the general average
the black soils will have a higher temperature than light
soils, since at night they will protect themselves from cooling
by a local blanket of fog. Dark soils will accumulate more
dew than the light soils, and are generally regarded with
favour. ‘The origin of the dark colour may be somewhat
varied. It is most frequently due to organic matter, either
produced by natural accumulations or by deliberate addition
of organic manures. In gardens, in the vicinity of towns,
black colour is often due partly to soot and cinders. The
real source of the colour of the Indian black cotton soils has
been much disputed. A red colour is generally due to ferric
hydrate, a blue colour to iron in a lower stage of oxidation.

Conduction of Heat.—Air is a bad conductor, and,
although silica is not a particularly good one, it is relatively
better than air. Compact soils conduct heat best, and will
vary in temperature most. Superficial tillage is, therefore,
advantageous. Observations under experimental conditions
at Cockle Park for very many years prove that cultivated
soils show less variation in temperature than untilled land.
The best conductors of all are moist gravels, which type of
soil produces the earliest crops.. Deep down in the subsoil

SOILS AND THEIR PROPERTIES 67

the temperature is practically constant. At Greenwich
Observatory at a depth of 25°6 feet the seasons are reversed,
with a difference of 3° between summer and winter.

A very great deal of attention has been paid to what has
been called mechanical or physical analysis of soils. Ina
district where one is dealing with geological strata which
have never been seriously interfered with for many years
past there is little doubt that these methods have considerable
value, but where much farmyard manure and lime have been
applied inthe past, and thesurface of the soil has been modified
by road sweepings, then little value can be attached to any
of these methods. The books in the bibliography should
be consulted on this highly technical subject. The fertility
of a soil is dependent upon an almost innumerable number
of factors, and which one happens to be of most importance
at the moment will depend upon an almost innumerable
number of circumstances. For example, many square
miles of the Punjab had for thousands of years borne few
crops, but the introduction of irrigation has converted these
areas into very fertile soils, growing large crops of wheat of
first-class quality. Here the determining factor happens
to be water, but the physical and chemical properties of the
soil are the same. ‘he problem is an engineering one.
There are large areas of very poor pasture in the British
Isles, such as occur in Northumberland in the north, and
Sussex in the south. The,application of basic slag has
revolutionized the whole character of such soils. Here the
determining factor appears to be phosphorus, and possibly
lime as well. In this latter case chemical analysis would have
been of great value for information, but no single test, or
group of tests, can possibly solve the problem of the fertility
of a soil. All any such methods can do is to point out useful
lines of investigation. It must then be left to the cultivator
to experiment upon the land, and find out for himself what
treatment is most satisfactory. The great value of both
physical and chemical analysis lies in suggesting possible
systems of improvement.

Capillarity. —As is well known, water will wet the surface

68 PLANT PRODUCTS

of many materials. The grains of the soil are wetted by
the soil water. The soil water adheres as a thin film to the
grains, and when the grains are close enough together, the
films unite, so that water can pass from the surface of one
grain to the surface of the next, until equilibrium is reached.
As a consequence of this fact, water will move through the
soil by means of the films adhering to the surface of the soil
grains. This action is often called capillary attraction,
because it is more conveniently measured in tubes, but the
problem is one of surfaces, and not tubes. When rain falls
on the soil the water sinks downwards, partly because of
the action of gravity, and partly because capillary equilibrium
has been upset. When evaporation takes place from the
surface, so that the films of moisture adhering to the soil
grains become thin, then equilibrium is again established
by water moving up from those grains which are more
completely wetted. ‘The rate of movement will be dependent
not merely upon the motive power supplied by the difference
of degrees of wetness in one part of the soil. and another,
and the motive power of gravity, but also upon the resistance
due to the varying viscosity of the soil water, and the
magnitude of the interstices between the soil grains.

It is a common observation that drains will run for a
long time after tain has fallen. The resistance to the
passage of water is large in proportion to the small motive
forces, therefore velocity is low. As gravity is all the time
acting upon any such water in the soil, the height to which
water will rise by capillary action reaches a practical, if
not an absolute, limit. It is for this reason that a mulch
on the surface of the ground is so often valuable in conserving
water. The water must rise through the soil quicker than
evaporation can take place, otherwise the growing plant gets
a very poor share of the water. The mulch allows water to
reach a fair degree of concentration at the point where the
plant roots are working. The height to which water will rise
by capillary action in heavy soils composed of small
particles is greater than in light soils composed of coarse
particles, but soils of a coarse character will oppose much

Se ee

SOILS AND THEIR PROPERTIES 69

less resistance to the passage of water, and, therefore, facili-
tate rapidity of movement. The most suitable condition is
cne intermediate, where neither the resistance to passage nor
the lack of capillary attraction are too pronounced. Where
soils have been recently broken up by tillage there will
always be a space in the soil which is too large to permit of
capillary attraction. ‘The water will, therefore, be obliged
to take circuitous routes when it rises, but the open spaces
permit the penetration of the roots, which are thereby enabled
to go down after the water. Deep tillage, whilst facilitating
deep rooting, checks the upward movement of the water
supply to the surface. Where rainfall is scanty, deep tillage
is not satisfactory, because the seeds that are sown do not
easily get enough water for their early stages of growth.
Very shallow tillage dries up an inch or so of the surface,
but protects the subsoil from loss by evaporation. In some
special cases it is possible to obtain a combination of these
different effects. When turnips are sown on land which has
been put up into riggs and subsequently rolled, the roller
only compresses the tops of the riggs, the furrows being
untouched. With a ‘“‘ Cambridge”’ roller the pressure is
mostly on the top of the riggs. Capillarity is, therefore,
increased about the region where the seed is sown, but a
mulch of loose earth remains in the furrows, and hinders
the development of the weeds.

A point to be noted is that evaporation of water from a
thoroughly wet soil is greater than that from an equal area
of water itself, because the surface of a pond is practically
smooth, whilst the surface of a soil is very irregular. As,
however, a soil is by no means always thoroughly wetted,
but is often dry, the total evaporation in a year from a soil
is less than that of an equal area of water surface. At
Rothamsted, 14 inches per annum represents the evaporation
from the soil, and 18 inches per annum from a water surface.
In many parts of the British Isles evaporation is greater than
at Rothamsted, and in hot, dry countries the amount is
still greater. At Alice Springs, in South Australia, evapora-
tion amounts to 103 inches per annum, and at Bombay it

70 PLANT PRODUCTS

is 83 inches. Any green stuff growing on the surface of
soil will increase the evaporation, hence weeds rob the soil
of water. Loose stones on the surface decrease the rate of
evaporation. In some parts of India stones that have been
collected from the surface are carefully put back again as a
mulch, but such a method is only possible in small types of
cultivation. When water evaporates the soil shrinks in
volume, owing to the removal of the water films, which
separate the particles. In sandy soils this shrinkage is
very slight ; with humus soils the shrinkage is very large
indeed. Clay soils shrink to an intermédiate extent, but do
not shrink in a regular manner, and generally develop cracks.
These cracks tend to break the roots of plants, and, therefore,
do harm at the time. The surface soil collects in the cracks
and a slow inversion of the soil takes place. In other types
of soil cracks rarely develop. Whenever water evaporates
from a soil, loss of heat results, owing to the latent heat of
steam, hence wet soils are also cold soils. When the surface
is loosened by slight tillage, the water is kept in the soil.

At Cockle Park the moisture content on one occasion was
Il‘oI per cent. of water where tilled, and 8°84 per cent. of water
where untilled, and on another occasion 13’0I per cent. where
tilled, and 9°53 per cent. where untilled. In very hot, dry
climates the capacity of dry soil to take moisture from damp
air has some distinct value. Dry soil is distinctly hygro-
scopic. During the night, soils will radiate heat, but should
they condense moisture on their surface the latent heat of
the water vapour will check the drop intemperature. During
the day the deposited water will evaporate once more, but
this time the latent heat will check a rise in temperature.

Chemistry of Soils.—When any soil is heated, at
first water is driven off, then complex gases are produced,
and a certain amount of black charcoal left behind. The
charcoal slowly burns off and leaves an ash, which is generally
dark red in colour. During the first of these stages the
amount of water that will be given off will depend upon the
atmospheric conditions prevailing when the sample of soil
was taken. When soils have been wetted by rain and allowed

SOILS AND THEIR PROPERTIES 71

to drain for a considerable time, the amount of water
remaining will vary according to the physical properties of
the soil, as discussed above. In the case of sands and very
light soils, from 5 to 10 per cent. of water will be the amount
commonly reached; whilst in the case of clays and heavy
soils, from 30 to 50 per cent. will be held. When the conditions
are very varied as regards rainfall, drainage, etc., the amount
of water found will correspondingly vary (see p. 95).

The ordinary figures of analysis are generally reckoned
on a soil which has been dried at 100° Centigrade. In some
cases reference is made to air-dried soils containing something
between 2 and 5 per cent. of water. In other cases 120°
Centigrade is taken as the temperature for determining water.
To obtain a soil in complete solution only very drastic methods
will suffice. By ignition at a red heat the whole organic
matter is driven off, and by the subsequent action of hydro-
fluoric acid the silica is volatilized, and the remaining
substances go into solution. It is very rare indeed that
the information obtainable by solution in hydrofluoric acid
has any agricultural value, as neither the plant nor the soil
bacteria nor atmospherical agents can possibly compare
with hydrofluoric acid. The strongest acid commonly
employed in the laboratory is strong hydrochloric acid.
For many purposes the information obtainable from ex-
traction by very weak solvents is of much greater value
than information obtainable by more drastic chemical
agents. Experience and convenience show that a solution
of I per cent. citric acid, as recommended by Dr. Bernard
Dyer, is one of the best of the weak solvents. It is usual
in laboratories to shake a mixture of the soil with 1 per cent.
citric acid by hand at intervals for three to six days, or to
agitate in a mechanical shaker for about twelve hours.
Of the ingredients usually discovered by chemical exami-
nation we have, among the mineral portions, the following
materials :—

Iron.—This element occurs chiefly as ferric hydrate,
and partly as ferric silicates, but, under exceptional circum-
stances, as ferrous compounds and pyrites. All fertile

72 PLANT PRODUCTS

soils contain their iron in the ferric condition, lower conditions
of oxidation are prejudicial to plant life.

Aluminium.—This element occurs in combination
with silica. Substances like felspars are not infrequently
present in soils. Those felspars which contain potassium
are fairly resistant to weathering, but those containing much
sodium are more readily weathered down. Clay soils contain
a larger proportion of aluminium compounds than are found
in sands. The aluminium probably plays but a small part
in the chemical changes of the soil, excepting so far as it is
one of the constituents of complex silicates.

Manganese.— Manganese is present in most soils to
a very small extent, but occasionally the amount rises
as high as Ir per cent. It is possibly an element of some
importance, as it is found invariably in beech trees, and is
a very common constituent of grass and root crops, but
the amounts present are small. The red colour of the red
beech leaf and red hair is believed to be due to manganese
compounds.

Titanium is always present in soil to the extent of
a per cent. or so, but is commonly left mixed with silica in
analytical returns. It is not known to have any value.

Calcium.—This element is one of the most important
in the soil. The most useful form is calcium carbonate,
which by slow solution in water containing carbon dioxide
becomes calcium bi-carbonate, an important agent in the
process of nitrification, and in the flocculation of clays.
Calcium sulphate is often present in small amounts. The
oxidation of sulphur compounds in the soil will result in
the production of calcium sulphate with the aid of some
source of lime. Complex compounds of calcium with
siliceous substances, and complex calcium compounds with
organic materials, are of only slightly less importance than
calcium carbonate. These compounds are respectively
alluded to by the vague general terms of calcium silicates
and calcium humates. It must not be supposed that the
constitution of cither of these bodies is known. These
names are only general terms expressing groups of compounds

SOILS AND THEIR PROPERTIES 73

having certain common properties. When such substances
as sulphate of ammonia come into contact with “ calcium
silicate or humate,” the sulphuric acid part of the sulphate
of ammonia combines with the calcium, whilst the ammonia
enters into combination with the silicic or humic residue.
Such actions are not so beneficial to the soil as the actions
of the same fertilizer on calcium carbonate. It is only where
plant production is carried out to a low degree that calcium
silicate and humate can be considered as a substitute for
calcium carbonate. Intensive plant production necessitates
the presence of calcium carbonate. Water containing
carbon dioxide can also react with these “ calcium silicates
or humates,’”’ producing calcium bi-carbonate. ‘The presence
of calcium carbonate can be detected by the degree of
effervescence which is produced on the addition of hydro-
chloric acid. A little experience will enable one to judge
fairly well of this point, but sodium carbonate and magnesium
carbonate will give the same effervescence. For most
purposes a knowledge of the carbonate present is of more use
than a knowledge of the actual amount of calcium (see p. 75).
Calcium carbonate checks ‘finger and toe’’ in turnips.
Magnesium.—Magnesium in the soil will generally
occur as magnesium carbonate, magnesium bi-carbonate,
complex magnesium silicates, magnesium humates, and,
very rarely, traces of magnesium sulphate or chloride.
Magnesium is certainly a necessity of plant life, and is
stored in the cereal seeds to an appreciable extent. Soils
very deficient in magnesia show beneficial results from the
application of magnesium carbonate, but soils containing
much magnesia usually show bad results from the addition
of magnesium carbonate. A theory has been suggested that
the ratio of magnesia to lime is important in plant life.
A soil in County Durham, for example, which has failed
both for agriculture and forestry shows CaO:MgO::1:9'2.
There is some evidence in support of this view, but it is so
much disguised by other factors that at present the subject
must be left open to doubt. ‘There is no question that soils
containing much magnesia are generally benefited by an

‘

74 PLANT PRODUCTS

application of lime, but that is also true of soils which contain
but little magnesia. ‘There is also plenty of evidence that
the general balance of fertilizing ingredients in a soil is an
important point, and whether the lime-magnesia ratio has
any specially great importance beyond other ratios, say
lime to iron, is a point which has not yet been satisfactorily
settled (see p. 8).

Potassium.—Potassium occurs chiefly in the soil as
felspars, hornblende, and other minerals. A fair proportion
of potassium in the soil also occurs in combination with
organic matter, which is commonly known as potassium
humate. A certain quantity of soluble silicates containing
potassium occurs in soil water. The proportion of potash
extracted by weak acids is very small indeed, sometimes only
a fiftieth part of the total potash in a soil is capable of being
dissolved by a I per cent. solution of citric acid.

Sodium. —Sodium occurs chiefly in silicates of a complex
type, which are not so stable as the corresponding potassium
compounds. The action of weathering these silicates
results in the production of sodium bi-carbonate, which,
reacting upon the fine clay particles, produces a sticky and
impervious mass. In some parts of the world, such as India
and the United States of America, salt incrustations on soils
are common, ruining many miles of otherwise good soil.
Where there is little organic matter the incrustation is
white, where there is much the colour is often black. ‘The
terms, reh, usar, white alkali, black alkali, are the common
names for this type of soil. Lack of drainage is one of the
chief causes of the serious accumulation of sodium salts in
a soil. The addition of calcium sulphate in any form will
result in flocculating the clay, and, therefore, in improving
the drainage. The mere operation of cultivation will also
assist in improving the drainage and thereby prevent the
accumulation of soda. Sodium has no particular value to
the soil, and is, therefore, often omitted from analyses.

Phosphoric Acid.—The only compounds of phos-
phoric acid that are found in the soil are derived from
ortho-phosphoric acid. Phosphoric acid is, of course, a

ee ee

SOILS AND THEIR PROPERTIES 75

most important ingredient in soils. Probably phosphorus
and nitrogen are the two most commonly lacking soil
ingredients. Ferric hydrate in the soil is capable of combining
with phosphoric acid and forming insoluble phosphates,
which undoubtedly react to a limited extent with calcium
salts, so that in the soil phosphorus will occur as phosphates
of all the bases, and will also be found in the organic matter.
Water containing carbonic acid is a better solvent of the
complex phosphates than water itself, and the amount that
will enter into solution will depend partly upon the
concentration of carbonic acid in the water of the soil, which
will in turn depend on the percentage of carbon dioxide in
the soil atmosphere. Large amounts of iron in the soil
hinder the solution of the phosphoric acid by carbonic acid.

Sulphuric Acid.—Sulphuric acid in the form of
calcium sulphate is common in all soils, and is probably the
chief source of the sulphur that is necessary for the formation
of plant proteins. It is being incessantly regenerated in
the soil itself by the oxidation of organic sulphur compounds
acting upon lime, also present in the soil. In the vicinity
of large towns the sulphur thrown into the atmosphere by
the combustion of coal comes down with the rain, washes
into the soil, combines with lime, and produces calcium
sulphate. Where the amount of lime is insufficient, the soil
becomes acid, and less fertile. Whenever super-phosphate
or sulphate of ammonia are used, considerable quantities
of sulphuric acid are added to the soil, so that modern
conditions of agriculture near big industrial districts do not
usually require the addition of sulphate to the soil, but
agricultural districts far removed from industrial scenes may
show a deficiency of this element.

Carbonic Acid.—Carbonic acid occurs in the soil
both in the free and combined condition. When carbon
dioxide in the air dissolves in water a certain amount of
the true carbonic acid exists in solution, and acting upon
any base preset, produces bi-carbonate. When such soil is
dried, and removed to the laboratory, an ordinary carbonate
is formed. The amount of calcium carbonate in the soil

76 PLANT PRODUCTS

is one of the most important points, since the effective use
of most manures will be largely determined by its presence
in sufficient amount. More than 1 per cent. of calcium
carbonate is probably unnecessary, and less than I per cent.
is probably only suitable to parsimonious systems of farming.

Nitric Acid.—The nitrates in the soil are very

evanescent. The plant gradually sucks them up and is

quite prepared to store them in the stem if it has the good
luck to find more than a scanty supply. The bacteria in
the soil will readily steal the oxygen of the nitrates if there
is much undecomposed organic matter present. On the
other hand, nitrates are being incessantly produced by the
beneficial action of bacteria in the soil. The amount of
nitrate in a soil is rather an evidence of the vigour of life in
the soil than of anything else. Nitrates are washed out of
the soil with great ease and rapidity.

The Organic Matter in the Soil.—The ordinary process
of drying a soil in a water oven and then igniting gives a
figure which represents both the organic matter and water
of combination together. ‘The latter figure is, of course,
not constant, and depends upon the amount of hydrated
silicates present. The figure for organic matter in a soil
will, therefore, be nearer the mark in a sandy soil than it
is in a clay soil. Much labour has been devoted to studying
the organic matter in the soil, but it is such a very difficult
problem that it is almost impossible to give any wide view
of the subject. The mere estimation of the carbon will not
give one much insight, whilst the efforts to extract so-called
humic acid only touch the fringe of the question. Some idea
of the amount of decomposed organic matter can certainly
be obtained by a modification of Grandeau’s method, that
is, by first acidifying the soil, washing out all calcium
compounds, extracting with dilute ammonia, and comparing
the colours obtained. An estimation of nitrogen is certainly
valuable, and helps to give one some idea of the amount of
organic matter present. The ratio of carbon to nitrogen
was investigated by Lawes and Gilbert at Rothamsted,
who found that carbon was oxidized away from the soil

eS

SOILS AND THEIR PROPERTIES 77

faster than nitrogen. ‘Those authors showed that in farm-
yard manure the ratio C to N equals 25 to 1. In the top
nine inches of old pasture the ratio was 13 to I, but in the
subsoil 6to1r. Some of the American workers on the subject
have detected smalltraces of a variety of syntheticcompounds,
but it is very difficult to decide whether these are important
or not. We have so many illustrations in living things of
the extraordinary potency of small traces that it does not
do to ignore little things, but until something more definite
is known it is not practicable in a conspectus of this character
to do much more than refer to the authors in the bibliography.

Available Plant Food.—A very distinct advance was
made in soil analysis when Dr. Bernard Dyer introduced
his method of attacking soils by I per cent. citric acid
solution (see Bibliography). Dyer showed that for the
less exhausting crops oor per cent. of phosphoric acid
or potash, soluble in I per cent. citric acid, represented
the margin between fertility and need of manure. The
method has also been found to apply to tropical soils. It
has been pointed out that the method of Dyer is purely
empirical and that if carried out under totally different
conditions different results will be obtained, but the strength
of Dyer’s position lay in the fact that he correlated his method
with actual experiments at Rothamsted, and that his
conclusions have, in the main, been thoroughly well sub-
stantiated in most places where they have been tried. The
objections raised against his method are only general
objections to any single test ; so far as a single test is capable
of use at all, there are few single tests applicable to soils of
such general utility as the phosphoric acid and potash
soluble in 1 per cent. of citric acid. The relationship of
the soil to the soil water, to the plant, or to a I per cent.
solution of citric acid, are all cases of mass action. ‘The state-
ment that repeated extractions with citric acid continue
to dissolve more and more phosphoric acid from the soil
is not a criticism of Dyer’s method at all, but an explana-
tion of the reason of its success. It is just because citric
acid and carbonic acid and the plant in relation to the soil

78

PLANT PRODUCTS

are all cases of reversible reaction, that the extraction with
weak solvents is some kind of analogue to the life of the plant.
The complete analysis of soils is given in many text-books,
but only one or two illustrations can be found room for here.
Whatever part of the world soils come from, there is some

kind of resemblance.

The following table, taken from a

book by the author, gives the composition of a few Indian
soils, to which have been appended one or two analyses from

Northumberland.
TABLE 13.
‘Indo-Gangetic alluvium. Madras. is Ta
Sand. | Loam. | Clay. pe i Sand. Bic | Loam. Heavy, Light.
Sand and Insoluble
Silicates .-|89°92 |82°91 175.69 |57°52 |92°25 |84°44 |72°96 | 76°21 83°20
Iron (Fe,O3) -.| 2°70 | 5°00 | 6°80 | 3°23 | 2°45 | 5°30 | 870 | — | 2°77
Alumina (Al,O3) | 3°65 | 5°30 | 8°00 | 3°39 | 1°75 | 5°71 | 9°70 | — | 3°51
Manganese (MnO)| — | 013 | 0°13 | — | 0°04 | 0°08 | O15 | — | —
Lime (CaO) ..| O'4E | T°00 | I°60 [14°54 | O13 | 0°53 | 1°50 | 0°69) 0°25
Magnesia (MgO) ..| 0°55 | 1°40 | 1°50 | 1°86 | 0°33 | 0°54 | O'10 | 0°65| —
Potash (K,O) 0°49 | 0°52 0°44 | 0°06 | O16 | 0°27 | 0°50) O°31
0°64
Soda (Na,O) -+| 0°09 | 0°20 o'oz | 0°06 | 0°15 | 0175 | — | —
Phosphoric Acid
(P,O;) .. .-| 0708 | o'r3 | O09 | 0°18 | 0°05 | O'0Q | O'LO | 0°07! 0°07
Sulpburic Acid
(S05). .-| 0°05 | o702 | — | o108 | — oa —_|ij—-i-
Carbonic Acid
(CO,) .. .-| 0°32 | O'7I | 0°55 |I1°42 | OTIIT | 0°24 | 0°07 | O'OT| O'O!
Combined water
and organic
matter .. 1°74 | 2°70 | 5°00 | 7°32 | 2°77 | 2°76 | 5°70 | 9°31) 8°40
Nitrogen N ..| 0°054| 0°070} 0°052| 0°180) 0°015| O°016| 0°055| 0°20) O'16
Available P,O; ..| o’o10| 07015) o’oro| — | 0°022| O'012} O°016) 0°05, O'15
Me K,0O O'OIO} O'015| O'OIO} — _- — — | O15} 0°05
Stones over3mm.| — —— — — — aa — | 2°0
Coarse Sand 3-0°5
1 ON a --| — — — — — — — | I°O |24°0
Medium Sand 0°5—
0°25 mm. | — oa - -- o — — | 2°0 |/35°0
Fine Sand 0°25-o'r
mm. ss | — — —- -— — — — | 4°0 |II‘o

To interpret any soil analysis the most important points
to consider are the following. Sand and insoluble silicates
often give a clue to the physical condition of the soil.
Luxmore showed the correlation between insoluble silicates

SOILS AND THEIR PROPERTIES 79

and mechanical analysis. Soils containing large percentages
of sand and insoluble silicates are of a light, sandy character,
those containing low amounts are of a heavy clay character,
unless, when we must always reconsider the results of physical
analyses, the soil also contains much lime or organic matter.
Soils containing much iron are hungry for phosphoric acid,
though when supplied with phosphoric acid they usually
become very fertile soils. The aluminium is an indication
of the amount of clay present. Manganese has little general
interest, although there is distinct evidence that small
quantities of manganese are useful (see p. 9). The lime
is a most important ingredient, and when the lime falls to
low figures fertility is at a low ebb. Magnesia in small
quantities is probably beneficial, in large quantities it appears
to be harmful. ‘The ratio of lime to magnesia is sometimes
considered important. Where the magnesia exceeds the
lime there is considerable evidence that the magnesia is
harmful. ‘The potash extractable by hydrochloric acid is
a figure of no practical value. ‘The phosphoric acid dissolved
by hydrochloric acid should not fall below or per cent.
Sulphuric acid may be ignored except in districts where there
is no coal smoke and little artificial manure used. The
carbonic acid evolved in the cold by dilute acids is valuable
as an indication of the amount of calcium carbonate in the
soil. It will be noticed in the figures given that the organic
matter and water of combination in Northumberland are
very high in proportion to those in the Indian soils quoted.
This is quite typical of the difference between cold and hot
climates. ‘The nitrogen is usually very low in well-cultivated
soils in hot countries and high in forest or pasture in cold
climates. ‘The figures for nitrogen can only be taken in
conjunction with other evidence. ‘The available phosphoric
acid and potash soluble in 1 per cent. citric acid form some of
the most useful figures in the table. Much, of course, will
depend upon the kind of crop grown, but for crops of no
great exhaustive character, 0’or per cent. will make a good
dividing line between fertility and need of manure. In
considering the chemistry of soils one should consider rather

80 PLANT PRODUCTS

the balance of the ingredients than their absolute amounts
(see p. 8). Exactly what balance is necessary for any set of
circumstances is only approximately known, and the actual
cultivator will need to experiment for himself on his own
soil.

Nitrification in Soils.—‘The air in the soil differs from
ordinary air in that it contains less oxygen and more carbonic
acid, owing to the oxidation of organic matter in the soil by
the action of the air. As two volumes of oxygen produce two
volumes of carbon dioxide, this change does not effect the per-
centage of nitrogen. Some small quantities of nitrogen may
be taken out of the air by nitrogen fixing bacteria, and some
small quantities of nitrogen may be added by denitrification.
The atmosphere in the soil and the ordinary atmosphere above
the surface diffuse into one another. The rate at which
this diffusion will take place is lessened by compression,
but is fairly independent of the fineness or coarseness of
the particles of the soil. The effect of rolling the soil will
be to first compress the soil, prevent diffusion taking place,
and, therefore, increase the percentage of carbon dioxide.
When the percentage of carbon dioxide in the soil-air
increases, the amount of carbon dioxide dissolved in the soil
water will also increase, since the amount dissolved depends
upon the partial pressure of the carbon dioxide.

As the amount of carbonic acid dissolved in water increases,
so the solvent action of the soil water increases at the same
time. Rolling, however, by checking the diffusion of fresh
air into the soil, lowers the percentage ot oxygen and dis-
courages oxidizing bacteria. The ultimate effect of rolling
the soil is, therefore, to increase the supply of phosphorus
and potassium to the plant, and decrease the supply of
nitrogen. Opening up the soil by harrowing produces the
opposite effects. ‘These effects are, however, very temporary,
since secondary results, due to bacterial life, quickly come
into play. In addition to the soil atmosphere considerable
quantities of gas are occluded on the surface of the soil
particles. Ferric hydrate is particularly powerful in this
respect. Peat, and all other forms of organic matter, are

SOILS AND THEIR PROPERTIES 81

also good substances for occluding gas. Gases occluded on
the surface are more active than ordinary gases, but little
work has been done to follow up exactly what effect this has
upon soil life. The action of occluded gas is probably
generally overwhelmed by bacterial actions, to which much
more attention has been paid. Russell and Hutchinson have
shown that, in addition to the bacteria in the soil, there
are considerable numbers of bacterial enemies, which reduce
the numbers of the bacteria. Whether the idea that soil
amoebee and paramecia play the part of microscopic
beasts of prey is a true or only a fancy picture has never
been determined, but the ultimate results have been the
subject of careful investigation. Certain organisms living
in the soil are able to fix nitrogen, provided they can obtain
organic matter in some way, and provided they can obtain
a proper supply of phosphates and potash (see p. 29).

At Cockle Park, in Northumberland, the amount of
nitrogen in the soil has been steadily increased by the
application of phosphatic manures. ‘The plot which received
no manure has steadily decreased in its nitrogen content from
0°197 per cent. nitrogen in 1899 to 0°174 per cent. in 1916,
whilst the plot that was treated with basic slag reached
0°227 per cent. nitrogen in 1908 and 0°244 per cent. in 1916.
All these figures refer to the top six inches of soil, and have
for the most part been done in duplicate or triplicate, show-
ing probable errors varying from nothing to 0°008 per cent.
Other plots with other treatments have shown somewhat
similar results. That this fixation of nitrogen is bv no
means purely superficial is also shown in these Cockle Park
experiments by taking the soil to each three inches depth.
In 1916 the unmanured plot gave at each three inches step
the following figures: 0°217, 0°I3I, 0°I00, 0°070, and the
corresponding figures for the manured plot were, 0°304, o°184,
0°137, 0100. It will be noted that the improvement is very
marked in the top three inches, slightly less marked in the
next three inches, while in the depths from six to nine inches,
and from nine to twelve inches, there is still a steady increase.
The gain in nitrogen is clearly still proceeding at all layers

D. 6

82 PLANT PRODUCTS

in the soil, and is still going down deeper and deeper. The
fixation of nitrogen in soil is usually dependent upon the
presence of leguminous crops. At Cockle Park the leguminous
crop concerned is undoubtedly wild white clover, but
in different parts of the world other leguminous crops would
play the same part. Nitrogen that has been fixed in the
soil, or obtained in the soil by any other means, is converted
by other soil bacteria into nitrites and nitrates. It is the
latter that form the nitrogen food of the plant. Much can
be done in practice to improve the rate at which nitrifica-
tion proceeds. In calcareous soils the nitrification proceeds
at a much greater rate than in soils deficient in lime. Clays
can be made to nitrify much faster if they are opened up
so that they admit air. The chief requirements for the
oxidation of nitrogenous matter in the soil are air, warmth,
moisture, and lime. Tillage and bulky manures will supply
more air to the soil, and control the water supply as well.
Iime may need to be added directly to the soil, When
the soil is closely packed, saturated with water, and air
excluded, denitrification may occur (p. 51). The fixation
of nitrogen in the soil by soil bacteria is facilitated by
a good supply of suitable organic matter, such as the straw
in farmyard manure, phosphatic manure, a good supply
of potash, and satisfactory conditions for the growth of the
bacteria.

Soils and Fertilizers. —The relationship between the soil
and the fertilizer used is an important point that must be con-
sidered. ‘To some extent this has already been discussed in
Part I. Generally speaking, lime is a necessity for the sound
working of any of the fertilizers, with the exception of basic slag
and calcium cyanamide, which both contain a certain amount
of lime. Soils that are very deficient in one of the ingredients
will respond specially to that particular ingredient at first,
but it not infrequently occurs that as soon as one has
satisfied the main need of the soil, a second order of necessity
makes its appearance. ‘There are many soils whose chief
demand is phosphate, and very little good can be done to
such soils until phosphates have been supplied. Afterwards

es mm

SS ee

SOILS AND THEIR PROPERTIES 83

potash and nitrogen may have their turn in producing
satistactory crops. In other words, we go back again to the
old proposition that the soil requires a certain balance of
ingredients, and, however lacking the soil may have been
once upon a time, in one ingredient, if you persist in supplying
this ingredient there may come a time when the chief necessity
of the soil is something else altogether. Much harm has
been done in the past by the “rule of thumb” man in this
respect. Inthe relatively early days of agriculture, manuring
with animal refuse was practised to a large extent. At
first this process was good, but it very speedily became over-
done ; then the fashion for applying lime set in. At first
this was very necessary, because it had been neglected in
the past, but that, too, soon became overdone. Then a
fashion for the artificial manures, generally phosphatic
ones, set in which have often been exhaustive of lime in
the soil. To-day the needs of agriculture in populous
countries are often more connected with the mismanagement
of the past than with any other one factor. In taking up
land, therefore, the past agricultural history is always a
matter of great importance. The analysis of the soil will
assist in checking the history of past good or bad manage-
ment.

‘‘The Law of Diminishing Returns ’’ is now a recog-
nized principle. When a manure is applied in increasing
quantities it does not produce a corresponding increase of each
additional amount of manure. ‘The table on p. 84, gives the
standard illustration from Rothamsted, in which it will be
noted that a steady increase in the amounts of ammonia

‘compounds soon becomes unprofitable.

Whether a particular increase of crop obtained from a
particular quantity of manure is, or is not, profitable, depends
upon the prices of both. Whilst in the above table 89
bushels of wheat per acre may be a profitable return for
200 pounds of ammonium salts, yet if the ammonia became
cheap and the wheat dear, the 4°5 bushels of wheat as
returned from 200 pounds of ammonium salts might also be
very profitable. In other words, intensive cultivation which

84 PLANT PRODUCTS

TABLE 14.—CROP YIELDS WITH INCREASING NITROGEN SUPPLY,

ROTHAMSTED.
Wheat grain, Wheat straw,
Bushels per acre, Cwt, per acre,
Increase per Increase per
200 lbs, am- 200 Ibs, am-
monium salts, monium salts.
Mineral manure alone per acre .. 14°5 — I2°I —
Mineral manure -+-200 lbs. ammo-
nium salts per acre .. 1 23'2 8°7 21°4 9°3
Mineral manure-+-400 Ibs. ammo-
nium salts per acre .. ae 32°1 8°9 32°9 II’5
Mineral manure-+600 lbs. ammo-
nium salts peracre .. ‘is 36°6 4°5 41'I 82

is profitable when prices of produce are high becomes
unprofitable when prices are low. Doubtless if every user of
artificial fertilizers were to start using artificial fertilizers
in double quantities because the rise in agricultural produce
justifies such a procedure, then the prices of the agricultural
fertilizers would rise so high as to put a stop to their economic
use. Exactly where the dividing line between what is
practicable and what is not must be determined in every
case by the cultivator of the soil himself.

REFERENCES TO SECTION I

Leake, ‘‘ Some Preliminary Notes on the Physical Properties of the
Soils of the Ganges Valley, more especially in their Relation to Soil Moisture,”
Journ. Agric. Science, i., p. 454.

, sia’ “The Evaporation of Water from the Soil,’’ Journ. Agric. Science,
vi., p. 456.

Luxmore, ‘‘ The Soils of Dorset,’’ pp. 7, 11.

Russell, ‘“‘ Soil Conditions,’”’ pp. 75, 87. (I.ongmans.)

Hilgard, ‘‘ Soils,’’ pp. 83, 107. (Macmillan.)

Hall, ‘‘ The Soil,”” pp. 48, 154. (Murray.)

Fream, “‘ Soils and their Properties.” (Bell.)

Warrington, “‘ Physical Properties of Soils.”” (Clarendon Press.)

Tempany, ‘“‘ The Shrinkage of Soils,” Journ. Agric. Science, viii.,

p. 312.

Balls, ‘‘ The Movements of Soil Water in an Egyptian Cotton Field,”
Journ. Agric. Science, v., p. 469.

Alway, “‘ Studies of Soil Moisture in the ‘ Great Plains ’ Region,” Journ.
Agric. Science, ii., p. 333.

Leather, ‘‘ Memoirs of the Department of Agriculture in India,’ Feb.,
1908, p. 79; July, 1907, p. 49; April, 1906, p. 3; and Feb., 1900, p. 125.
(The Imperial Department of Agriculture in India.)

Poe ee ee

i

SOILS AND THEIR PROPERTIES 85

Leather, “ The Agricultural Ledger,’’ 1898, No. 2, p. 22. ‘“‘ The Water
of the Soil,”’ p. 10. (Government Printing Office, India.)

Hall and Miller, “‘ The Effect of Plant Growth and of Manures upon
the Retention of Bases by the Soil,”” Proc. Royal Soc., B, vol. 77, 1905, p. 39.

Hall, Brenchley, and Underwood, ‘“‘ The Soil Solution and the Mineral
Constituents of the Soil,” Journ. Agric. Science, vi., p. 278.

Collins, ‘‘ Scheibler’s Apparatus for the Determination of Carbonic
Acid in Carbonates,”’ Journ. Soc. Chem. Ind., 1906, p. 518.

Collins, ‘‘ Agricultural Chemistry for Indian Students,” p. 44. (Govern-

_ ment Printing Office, Calcutta.)

Russell and Appleyard, ‘‘ The Atmosphere of the Soil ; its Composition
and the Causes of Variation,” Journ. Agric. Science, vii., 1.

Schreiner, Journ Phys. Chem., 1906, p. 258.

Dyer, ‘“‘ A Chemical Study of the Phosphoric Acid and Potash Contents

of the Wheat Soils of Broadbalk Field, Rothamsted,” Proc. Roy. Soc., 1907,

wi ET

Miller, “‘ The Amount and Composition of the Drainage through Un-
manured and Uncropped Land, Barnfield, Rothamsted,” Journ. Agric.
Science, i., p. 377-

Russell, ‘‘ Washing-out of Nitrate from Arable Soil during Past (1915~16)
Winter,” Journ. Board of Agriculture, 1916-17, p. 22.

Lawes and Gilbert, ‘* The Rothamsted Experiments.”

Gilchrist, ‘‘ Guide to Experiments,” 1917. (Ward, Newcastle.)

Hall and Amos, ‘‘The Determination of Available Plant . Food,”
Journ. Chem. Soc., 1906, T. 205.

Szction IJ.—SPECIAL SOIL IMPROVERS

Lime.—The exact dividing line between what constitutes a
fertilizer and what constitutes a soil improver is rather diffi-
cult to determine, but whilst farmyard manure is commonly
considered a fertilizer, since it contains nitrogen and potash,
yet lime is usually looked upon from a different point of view.
The lime is applied to the soil for the purpose of modifying
the soil. The standard article is quicklime, produced by
burning limestone. ‘This is sometimes applied in big lumps,
called shell lime, but it is much better reduced to powder,
either by actual grinding, or by slacking with water, when
it crumbles down. A high quality burnt lime will contain
from go to 95 per cent. of lime, and this type of lime should
always be used for agricultural purposes. A low quality
lime, such as the following :—

TABLE 15.
Lime és “s fy “s se -. 45 per cent.
Magnesia .. sik ai ce sy! fees 5
Carbonic Acid Right ae ry My Sant hae ie
Water pat Seat nibs ik se ie 2 Wi
Silica iy a ar ave uA SOI “s
Oxides of Iron and Aluminium .. nk ee

is of no use for agricultural purposes. Lime is sometimes
employed to increase the ratio of lime to magnesia, for which
purpose the lime in Table 15 is very nearly useless. Lime,
like other materials, should be distributed as evenly as
possible, although this may not be quite so critical a point
as it is in other fertilizers. One of the purposes for which
lime is necessary in a soil is to assist nitrification. Calcium
bi-carbonate in solution will rise and fall in the soil, according
to the dry or wet weather, though it will not diffuse laterally.

SPECIAL SOIL IMPROVERS 87

Nitrification will, therefore, proceed either above or below
a lump of lime material, but it is much better to get a small
dressing well distributed than to depend upon haphazard
heavy dressing. The lime, as soon as it is applied to the
soil, combines with water and forms calcium hydrate, and then
absorbs carbonic acid, forming calcium carbonate. Lime
also enters into combination, at any rate in a temporary
manner, with the organic matter and clay. The addition
of lime to a soil increases the amount of available potash
and available nitrogen. It does not increase the amount
of available phosphorus, excepting in the case of soils
containing much organic matter, where a considerable
fraction of the total amount of phosphorus in the soil is
in some form of organic combination. Lime, when turned
into calcium bi-carbonate, coagulates clay, and opens up
nearly all types of soil. It is, therefore, particularly suitable
for the heavier types of land. As it tends to dry out clay
soils, lime should be applied fairly early, otherwise the soil
may be too dry for satisfactory germination of the seeds.
Lime is especially necessary with high farming. Super-
phosphates, sulphate of ammonia, nitrate of soda,kainit, farm-
yard manure and organic nitrogen manures all demand lime
in the soil. There are a great many forms of industrial waste
lime which can be used, the relative values of which depend
upon the amount of calcium contained. When limestone is
burned it loses about 40 per cent. of its weight, and the subse-
quent cost of carriage isthat much less. It may be cheaper
to burn coal in the lime kiln, and thus to reduce the weight,
than to burn coal in a steam engine for the purpose of carrying
useless carbonic acid. ‘These varied forms of calcium car-
bonate can only be considered it they are relatively cheap.
Very considerable quantities of waste lime are produced in
the “Teblanc’”’ soda process. Calcium sulphide obtained as
a by-product is treated with carbon dioxide in water with
the evolution of hydrogen sulphide, then used for manufacture
of sulphur. ‘The waste calcium carbonate is run into heaps
and allowed to dry spontaneously. ‘This material, often
called “Chance”? mud, or lime mud, has proved a perfect

88 PLANT PRODUCTS

substitute for lime, but it does not contain more than about
40 per cent. pure lime and has to compete with lime of go
to 95 per cent. purity in the case of burnt lime. It is not
possible to convey it by rail any considerable distance, as
the railway freight soon swallows up any advantage of low
price. In spite of the fact that the ‘‘ Chance” mud is a
fine precipitate, it runs together in lumps in the soil and is as
difficult to distribute as shell lime. Lumps of ‘‘ Chance ”
mud can be found in a soil many years after application.
Another residue of a similar type is produced from magnesian
limestone by the extraction of the magnesia for industrial
purposes. The waste is very similar to ‘‘ Chance’”’ mud,
as the amount of magnesia not extracted is very small.
Where chalk is obtainable, treating soils with chalk is a well-
known process. Even when the soils lie on the top of the
chalk, the surface sometimes contains but little lime. Chalk
pits are dug in the fields, and the chalk then distributed on
the surface. Building mortar can also be employed as a
source of lime. ‘The residue of acetylene gas-plants provides
a very pure source of calcium hydrate. In a very crude
form one may find lime from skin dressers and many small
industries.

The effect of gas lime depends on sulphur and cyanogen far
more than upon the amount of lime contained. Fresh gas
lime contains considerable quantities of calcium sulphide,
which oxidizes on keeping to calcium sulphite. Up to that
stage oxidation is rapid, but the further oxidation of calcium
sulphite to sulphate in a heap of gas lime is slow, although
once it has been distributed in the soil the action is moder-
ately rapid. In addition there are sulpho-cyanides, ferro-
cyanides, and sometimes cyanides themselves. ‘These are all
poisonous bodies, and hence the action of gas lime depends on
partial sterilization (p. 90). Gas lime contains about 30 or 40
per cent. of calcium carbonate, and when the other substances
have had time to decompose, this material produces its
effects. A most important lime compound with very different
properties is gypsum (hydrated calcium sulphate.) This
has no practical resemblance to burnt lime, and its action

:

SPECIAL SOIL IMPROVERS 89

on the soil is totally dissimilar. The great advantages
of gypsum lie (1) in the fact that it is a sulphur compound,
and sulphur is necessary for the formation of proteins ;
(2) that it decomposes sodium carbonate in the soil, and
coagulates colloidal clay better than any other substance.
When clay has been puddled by excessive application of
nitrate of soda, and injudicious working in wet weather,

- calcium sulphate is an admirable cure. At one time plastering

soils was a well-known process, much recommended for the
growth of clovers. It has gone out of fashion in the British
Isles, but the use of gypsum is still important in many parts

_ of the world, and the experience of the British Isles must not

be taken to apply everywhere. The reason why gypsum
has gone out of fashion to such a large extent is that calcium
sulphate is applied to the soil with other materials. Super-
phosphates contain more than half their weight of calcium
sulphate. Soils, therefore, that have been liberally treated
with super-phosphate are likely to be overcharged with
calcium sulphate. Sulphate of ammonia applied in one
year of a rotation, and lime applied in another, will produce
calcium sulphate in the soil. Owing to the powerful action
of gypsum it is still much believed in by some horticulturists,
whose duties are often to break up very unsatisfactory land
and grow crops with as little delay as possible. Hills
composed of little but gypsum occur in some parts of the
world, and as it is mined very easily, such local deposits
of gypsum should always be carefully considered by those
cultivating land at no great distance.

In the vicinity of large towns sulphur in the form of
sulphuricacid is brought down by the rain with the subsequent
formation of gypsum in the soil. On the whole gypsum
reacts with the soil as an acid whilst lime reacts as an
alkali.

The Use of Electricity in Plant Stimulation. —This
subject has attracted much attention for many years past.
It is such an obvious idea that the original suggesters are
probably many in number, but one of the foremost workers
in the first days of any substantial results was Professor

go PLANT PRODUCTS

Lemstr6m. He succeeded by using electricity at a high
tension conveyed by wires over a field. He employed an
ordinary town current to drive a small electric motor,
driving in its turn a small influence static electric machine.
Subsequently the work was taken up by Professor Priestley
at Bristol and Leeds. The method now adopted is to use
a transformer with a rectifier to give positive electricity
at a high tension. ‘The details have by no means yet been
worked out. But the latest ideas suggest that wires are
best distributed overhead at about five feet in height, and
that the wires should be made as thin as possible. Under
these conditions a very marked increase in crops has been
obtained. The actual cost of the electric energy is quite
small, but the initial expense of the machinery is considerable,
and at present requires skilled attention. Until details
have been worked out on the large experimental scale, it
will be difficult to make a commercial success of this method.
Many points remain yet to be discovered, such as the relation-
ship of light and varying humidity of the air, the strength
of the discharge, and the relationship between electrification
and the manure used. All these points require to be investi-
gated thoroughly. ‘The great advance, however, which has
been made since Lemstr6m’s days by Priestley, Jorgensen,
and Blackwood promises future progress.

The Partial Sterilization of Soils.—It is a very old,
well-known fact that the application of heat, and all kinds of
poisonous substances to soils, may increase the ultimate crop
obtained, even though some injury may occur at the moment.
From the elementary cottage idea of putting a flower-pot into
the oven for a short time, up to the laboratory researches of
Dr. Russell, the subject of application of heat to a soil has

been freely discussed. In nature this process occurs in hot —

climates where solar radiation may raise the surface tempera-
ture of the soil up to 60° Cent. (140° Fahr.). Under these
conditions many pests in the soil are destroyed, so that the
ultimate growth of the crop is improved. In greenhouses
steam is not infrequently employed for the purpose of heating
the soil on a moderately large scale. In a similar way all

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SPECIAL SOIL IMPROVERS gti

germicides of a mild character, such as naphthalene, and even
copper sulphate, and zinc sulphate, have been used with
ultimately satisfactory results. Recent researches have
shown that this treatment involves the destruction of all
kinds of harmful organisms, from wireworms or millipedes,
down to microscopic forms like the amcebe, paramecia,
etc., the larger of which directly injure the plant, and the
smaller of which destroy the useful nitrifying bacteria.
The destruction of pests soon produces an improvement
in the crop, whilst the destruction of the enemies of the
nitrifying bacteria results in an increased production of
nitrate, with a subsequent increased production of plant
growth. Heat also produces chemical and physical changes
in the soil. The apparent results of heating the soil with
steam are very similar to those of the action of frost—the
soil becomes lighter, easier to work, easier for the plant to
establish its roots, richer in soluble mineral matter, and the
organic matter is more easily converted into ammonia and
nitrates by the organisms in the soil. The application
of heat is certainly the most efficient of these methods, but
is not very easy to conduct on a large scale. Direct baking
is probably one of the best methods, but steam heating
is also very satisfactory. The application of germicides is
so much easier to carry out that it has attracted a great
deal of attention. Gas lime, the waste product from purifi-
cation of coal gas, contains sulpho-cyanides, ferro-cyanides,
and other poisonous substances. Occasionally, when the
gas lime has been applied to pasture, the iron in the green
grass is turned to Prussian blue, owing to the action of the
cyanogen compounds in the gas lime. The sulphides and
sulphites in the gas lime no doubt also play their part in
acting upon all forms of soil pests. After the sulphides and
sulphites and cyanogen compounds have been oxidized,
the residue acts as a fertilizer. Calcium carbide has also
been used. Naphthalene is another favourite soil fumigant.
Crude naphthalene is a fairly cheap article, and not difficult
to distribute. It is mixed with coke dust, gas lime, or ashes,
for the production of many patent mixtures, which usually

92 PLANT PRODUCTS

contain about 30 to 50 per cent. of crude naphthalene. These
mixtures are rather drier, and more convenient to handle.

Soot may be considered to have a value partly dependent
on tar and other poisonous materials.

There is considerable reason for supposing that many of
these poisonous substances do some slight injury to the crop,
but if the destruction of wireworms, etc., is on a sufficiently
large scale, the subsequent benefit will more than compensate
for the temporary injury. It is desirable that all these
substances should be applied to the soil at a considerable
interval of time before sowing seeds. If that is not practic-
able some slight good may perhaps be done by applying such
germicides between the drills, so as to keep as far away from
the plant as possible, but this latter practice must be
considered as open to some objections. Injudicious use of
soil fumigants has done much harm.

REFERENCES TO SECTION II

Russell, “‘ Chalking: A Useful Improvement for Clays overlying the
Chalk,”’ Journ. Board of Agriculture, 1916-17, p. 625.

Hutchinson and Maclennan, “‘ Studies on the Lime Requirements of
Certain Soils,” Journ. Agric. Science, vii., p. 75.

Collins, ‘‘ Scheibler’s Apparatus for the Determination of Carbonic
Acid in Carbonates,” Journ, Soc. Chem. Ind., 1906, p. 518.

Roscoe and Schorlemmer, vol. ii., p. 290.

Lemstrém, ‘‘ Electricity in Agriculture and Horticulture.”

Jorgensen and Priestley, ‘‘ The Distribution of the Overhead Electrical
Discharge employed in Recent Agricultural Experiments,” Journ. Agric.
Science, vi., p. 337.

Blackman and Jorgensen, ‘‘ The Overhead Electric Discharge and Crop
Production,” Journ. Board of Agriculture, 1917-18, p. 45.

Russell and Petherbridge, “Investigations on ‘Sickness’ in Soil,”’
Journ. Agric. Science, October, 1913. Russell, ‘‘ Partial Sterilization of
Soil for Glasshouse Work,” Journ. Board of Agriculture, 1911-12, p. 809;
I9I2—13, p. 809; I9I4-I5, p. 97.

Russell and Hutchinson, “ The Effect of Partial Sterilization of Soil on
the Production of Plant Food,”’ Journ. Agric. Science, October, 1909.

Buddin, “ Partial Sterilization of Soil by Volatile and Non-Volatile
Antiseptics,” Journ. Agric. Science, vi., p. 417.

Russell, “‘ Soil Conditions,” p. 114. (Longmans, Green.)

Wentworth, ‘‘ Effect of Electricity on Sheep Raising,” Journ. Board
of Agriculture, 1911-12, p. 519.

Brenchley, ‘“‘ Inorganic Plant Poisons.’’ (Camb. Univ. Press.)

Hanley, ‘‘Lime and the Liming of Soils,’ Journ. Soc. Chem. Ind.,
1918, p. 185 T.

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Srotion IIT.—SOIL RECLAMATION AND
IMPROVEMENT

Barrenness.—Very large numbers of soils are not
producing anything approaching to their maximum crop,
although one cannot definitely classify them as being under
the well-recognized types of land difficult of cultivation.
These lands are only partially barren, from improper treat-
ment due frequently to economic causes.

The supply of plant food in the soil is sometimes the
chief cause for the difference between productive and
unproductive land. Table 16 shows the amount of plant
food in productive and unproductive types of soil.

TABLE 16.—COMPOSITION OF SOILS.

Parts per Two Million or Pounds per Acre to a Depth of Seven Inches.

Very productive soils, Non-productive soils,
Elements of plant food,
Holland Scotland German Maryland
alluvium, wheat soil, barrens, barrens,
Phosphorus $i y' 4,100 3,780 trace 180
Potassium et sm 17,040 5,880 none 2000
Calcium .. ve .» | 58,460 17,560 1380 580

A very common cause of unproductiveness in a soil is the
lack of proper plant food. There are many other causes,
but there are few of them quite so common as the question
of the supply of proper mineral plant food in the soil. That
the supply of plant food in the soil is a very fundamental
question is illustrated in Table 17, which shows the relative
supply and demand of the most important elements of plant
food, and it will be noted on purely fundamental grounds

94 PLANT PRODUCTS

that the total amount of phosphate in the crust of the earth
is not super-abundant for the purpose of wheat production.

TABLE 17.—RELATIVE SUPPLY AND DEMAND OF ELEMENTS IN
EARTH AND PLANTS.

Pounds in 2 million :
Essential plant-food elements, of re ecatak tr Abtclocyg atekeat seeae mately
=r acre to 7” depth, and straw. indicated,
Phosphorus we ty eat 2,200 13 170
Potassium "ye ets 49,200 30 1,600
Calcium .. un “fe 68,800 9 55,000
Nitrogen inair .. als 70 million lbs, 70 I,000,000
Over one acre,

There are many districts in the world which we know have
been cultivated for at least a few thousand years, but the
amount of phosphorus in the earth’s crust, as shown in this
table, would only justify us in the conclusion that we could
grow bumper crops for 170 years. A commonly occurring
deficiency of phosphorus is, therefore, to be anticipated.
The other causes besides the lack of plant food are excess
or deficiency of moisture, indifferent physical condition,
absence of beneficial or presence of harmful soil organisms, or
the presence of some substances injurious to plant life. In
sandy soils the lack of colloids is so detrimental that almost
complete sterility may occur. The ordinary sand on the
sea-shore, for example, is very barren, owing to the action
of the sea water having washed out all colloidal material.
A few struggling plants may manage to make themselves
at home, and gradually add a certain amount of humus to
the soil, after which the general growth of plants may
begin.

Dry Lands.—Land that is too dry and has too little
natural water is one that requires some system of irrigation
to be thoroughly satisfactory. Irrigation generally has to be
obtained by some reservoir system of water supply. Where
large rivers are obtainable, as in the northern parts of India,
and in the case of the Nile Valley, dams can be placed across
the rivers. On dry lands shallow tillage is essential, For

SOIL RECLAMATION AND IMPROVEMENT 95

this purpose the most suitable source in dry climates is a
river which can be relied upon to run in dry weather. Such
ate, however, scarce, and are chiefly to be found in rivers
that travel from long distances, or originate in snow moun-
tains. The rivers originating in the Himalayas are specially
suitable for this purpose, since the melting of the snows in
the summer gives ample supplies of water. ‘The Nile, rising
a great distance away, gives a flow of water at the right time.
The erection of dams or barrages across the river will hold
the water up, and divert it into proper channels, which then
communicate with distributing channels of smaller size.
The supply of water by these means depends upon the
organization of distribution. In Madras, and many parts
of India, very old-established tanks occur, which have been
originally produced by the utilization of some natural
depression by building a dam across the original outlet. The
rainfall is collected from a small area, but the natives collect
considerable quantities of water in the rainy season, and
utilize it in the dry season. When the water from such
tanks has been let out, the wet, muddy bottom is used for
cultivation of rice. From such large, open tanks the loss
of water by evaporation is very considerable. The expense
of instituting such a system would be very heavy, but nearly
all these somewhat primitive arrangements have been
produced by degrees, mostly utilizing labour which would
otherwise have been wasted. ‘The water is applied to such
dry lands by running the water along channels, the distance
between which will depend upon the type of crop grown.
There is a great tendency on the part of the users to take
more than is necessary. Deep ploughing only lets the
water of the subsoil evaporate. Mulches should be used as
much as possible. Many soluble manures, especially phos-
phates, economize water. Nitrogenous manures, such as
sulphate of ammonia, if applied when the plant is suffering
from drought, may often increase the crop.

Wet Lands.—Wet lands require, as a rule, drainage.
Drains should be set not too deep, and should lead without
any very sharp angles into the main drain. By such a

96 PLANT PRODUCTS

system of drainage not merely is the water removed, but
also air is let into the soil. In certain particular cases, as,
for example, some of the fens, the soil may be alternately
wet and dry. In these fen districts it is not uncommon
that the level of the rivers and canals exceeds that of the
fields. In this particular case a ditch is dug between the
field and the river. ‘The level of this is below the level
of the field, and considerably below the level of the river.
Into this main ditch branch channels run to carry the surplus
water, which is pumped into the river at a higher level.
When dry weather intervenes, it is only necessary to reverse
the action of the pumps, and let the water run back into the
ditch from the river, and thence into communicating channels.
Very large quantities of rank grass may be obtained by such
a method. Many of the grasses which normally have a
very bad name owe their lack of nutriment to a big develop-
ment of fibrous stalk. Under conditions of perpetual
moisture these grasses never mature, and are, therefore,
always moderately succulent.

One of the results of bad drainage in a ey is a tendency
to accumulate poisonous materials. When the clay con-
stituents of a soil contain large amounts of soda, the soda
is removed from the clay by the action of water containing
carbonic acid, producing sodium carbonate, which defloccu-
lates the soil. One of the cures for this is drainage which
removes the soda salts. The application of gypsum to such
a soil converts the sodium carbonate into sodium sulphate
which washes away with rain, and leaves calcium carbonate
behind. The former is relatively harmless and drains
away in time, the latter is beneficial. Sodium sulphate
does not hinder the germination of seeds as much as sodium
chloride or sodium carbonate. ‘This type of land is known
in America as the black alkali land, whilst in India it is
known as reh or usar. As on many poor soils, persistent
efforts at cultivation result in improvement. Where the
land has been steadily cultivated, maintained in an open
condition, and ample plant food given, the soil remains
fertile. Soils in the vicinity of rivers may need reclamation.

ee ee ee

i we a ee

ee

- eS See

i tity
ee ee

as Pe
SS ST Ee

“ ee

SOIL RECLAMATION AND IMPROVEMENT 97

Peat.—Peat is a very infertile type of soil, but by treat-
ment with lime and basic slag, very fine results may be
obtained. Where a soil merely has a thin layer of partly
peat-like turf, mechanical breaking up of the surface will
often effect a remarkable improvement. Heavy dressings
of gas lime have also proved beneficial for such purposes,
but where the peat is fairly deep, continuous work is necessary
to reclaim it. Peat lands are often very wet, and require
some system of drainage. Experience in Ireland has
shown that these soils are not so hopeless as they were once

3 thought to be. Dressings of potash manures are also very

commonly required for this type of land. In some cases
the process of paring and burning may be employed on peat
lands. ‘This is very drastic, and wasteful, but is sometimes
the most easily managed. The rab cultivation of the
Western Ghats belongs to this type. On many of the fen
districts the application of marl, that is, chalky clay, has been
found to be very beneficial, since it supplies lime in quantity,
and potashinsmallamounts. On peat lands liberal manuring
with common manures is almost always essential, since the
peat contains little of any value to the plant. It has,
however, always an ample capacity for absorbing water,
and its physical properties are, therefore, not excessively
bad. Occasionally peat may be found already mixed with
lime. On such soils super-phosphate will generally give a
better result than basic slag. Whenever lime is applied to
soil for the purpose of reclaiming it, it is desirable that the
lime should contain only a moderate portion of magnesia,
since when the percentage of magnesia exceeds the percentage
of lime, magnesia is harmful.

Reclamation.—There are considerable areas of land
which are only producing very poor pasture, which can
comparatively easily be made to produce far better feeding
for stock. ‘These areas occur in all parts of the world, but
in well-populated districts there is little excuse for their
existence. ‘There are very large areas of land which have
merely been neglected, and which are occupied by poor
pasture. The boulder clay of the northern part of England,

D. 7

98 PLANT PRODUCTS

as well as other lands in other parts, can be immensely
improved by dressings of basic slag, at the average rate of
one or two hundredweight of slag per acre. per annum.
Such treatment encourages the growth of clover, and in
the course of a few years completely alters the physical
and chemical properties of the soil. Many uplands, where
there is much heather and moor, can also, by a dressing
of slag, and possibly lime, effect a steady improvement on
the value of the land by enclosure and stocking with cattle.
Even some soils on chalk have been reclaimed in a wonderful
way by these means. Poverty Bottom, the property of
Professor Somerville, is a case where neglected land on chalk
has been immensely improved by the use of basic slag. Some
of the lighter soils which are growing very indifferent
pasture may be made to do much better by the application
of potash, but, as a rule, the lighter land should not be down
to grass, but should be ploughed, unless there is some specific
difficulty, coming under the heading of the wet lands alluded
to above. The reclamation of this type of.land ultimately
involves considerable amount of capital. The amount of
money necessary to spend in a substantial dressing of basic
slag, probably assisted by lime, is one which the farmer is
often afraid of, but by spreading it out over several years
the amount of money expended is not so severely felt.
The difference between a barren field and a fertile field is
very often more a matter of history than geology. Persistent
efforts to cultivate a piece of land and make it fertile are
rarely altogether unfruitful. Whether the result justifies
the expenditure of labour is, of course, a different matter,
since it is impossible to equate these two by the same method
in different epochs.. The labour that would otherwise have
been wasted is not capable of being put down by any system
of accountancy. ‘The gradual improvement of the land by
this type of utilization of spare moments is one of the most
important results of giving ownership of land to the actual
occupier. The man who hopes to get results many years
hence from his spare moments is only the man who thinks
he is likely to be on the spot for a long time. To attempt

a a. = a

a ae ee ee

ea ES

a

ee

SOIL RECLAMATION AND IMPROVEMENT 99

to reclaim many types of land on an industrial system is
very often unpromising, as the capital necessary to be sunk
is too large in proportion to the returns. ‘The whole question
of reclaiming land is of little value without considering some
system of experiment. ‘The mere fact that a piece of land
is not doing well suggests the idea that probably somebody
has failed to do better, and that the case is, therefore, not
a simple one; but it need not necessarily be very compli-
cated, and a simple type of experiment will not infrequently
solve the riddle as to its failure. A soil is so variable that if
any knowledge is required within a reasonable time, it is
necessary to conduct all experiments in duplicate. It is
not necessary that the piece of land under experiment
should be very large. The most important consideration
is that the person responsible for the experiment should have
a sound knowledge of the process of conducting experiments,
and a clear idea of the errors of practical experiment under
practical conditions. The chief type of such experiment
would be to lay out plots, of which there were two or three
plots containing no manure and no improving treatment
at all, two or three with phosphates, two or three with potash,
two or three with nitrogen, and two or three with lime.
Previous experience of that type of land would avoid many
unnecessary experiments, since at least some things might
be assumed fairly well beforehand, but soils differ so much,
and the causes of fertility and infertility are so many, that it
does not do to assume too much fromatext-book. Roughly
speaking, the errors of experiment on a growing crop ona piece
of land will be about 10 per cent. of the yield. For the purpose
of the reclamation of barren land this is not at all a serious
error, since unless the land is going-to double its capacity
it is hardly likely to pay any very heavy returns for big
initial expense. ‘The difficulties are, therefore, not as great
as they are on an experimental farm. As the reclamation
of land is generally a matter of a fairly big scale, it would
be especially foolish to neglect a few preliminary experiments
before proceeding to effect some system of reclamation.

It is, of course, highly desirable that the materials used for

LOO PLANT PRODUCTS

the experiments should have a fairly accurately known
composition, as otherwise much ot the labour will be thrown
away. A useful type of experiment would be, one plot
of lime, a second plot basic slag, a third plot with sulphate
of ammonia, a fourth plot with potash manure, and a fifth
plot with no manure at all. These might be all cross-
dressed with other manures, or even with the same manures
applied over again. If the same manures are applied over
again in the cross-dressing as in the first dressing, one will
get, of course, a double dressing in one case, and a compound
dressing in another, but each case will have to depend upon
its own merits. The term “reclamation of land ’’ is some-
times restricted to warping. ‘The process of warping consists
in flooding and silting up swamps. Where hill streams or
tidal estuaries exist, the low-lying land can be flooded from
time to time, and a large quantity of silt deposited. Such
silt is very fertile. No general principles can be dictated
on this subject, it is a question of management.

REFERENCES TO SECTION III

Leather, ‘‘ Memoirs of the Department of Agriculture in India,” June,
nor: “ The Pot-Culture House,” p. 43. (Thacker, Spink and Co., Calcutta.)
Hilgard, ‘‘ Soils,” pp. 399 and 422. (Macmillan.)
McConnell, “‘ Agricultural Note Book,” p. 81. (Crosby Lockwood.)
Gorham, ‘‘ Reclaiming the Waste,” pp. 118, 142. (Country Life.)
Stokes, ‘‘Some Cases of Infertility in Peaty Soils,” Journ. Board
Agriculture, 1913-14, p. 672.
‘‘The Reclamation of Waste Land,” Journ. Board Agriculture, 1914-15,
681.
Howard, ‘‘ The Irrigation of Alluvial Soils,’ Agric. Journ. Ind., 1917,
185.
. Carey and Oliver, ‘‘ Tidal Lands.” (Biackie.)

Part IIl.—THE CROPS

Srotion I.—PHOTO-SYNTHESIS

THE natural absorption of solar energy by plants is a process
called photo-synthesis, to account for which there are many
theories, none of which can be considered as proven. Some
outstanding features, however, remain without any question.
The sun’s rays falling upon green leaves are absorbed with
the utilization of energy for the production of plant materials,
The proportion of energy used in this way is small, as is
shown in the following table :—

TABLE 18,—PERCENTAGE OF TOTAL SOLAR ENERGY
FALLING ON A LEAF.

Energy used in assimilation .. At -. 0°66 per cent.
Energy used in evaporation of water .. -» 48°39 te
Energy transmitted Wi aba 4p), era Mi
Energy radiated, convected, etc, i +» 19°55 re,

This table shows that the amount of energy actually utilized
for assimilation of carbon dioxide and its conversion into
organic plant matter is comparatively small, and that a
very great deal of the energy is used merely in evaporating
water (see p. 110). Carbon dioxide is absorbed by the leaf
with very great readiness, in spite of the small proportion
or carbon dioxide in the atmosphere. It is often assumed
that one of the first products is formaldehyde. ‘That form-
aldehyde can polymerize to sugars is undoubtedly well
proved. The mechanism by which formaldehyde can be
produced in the plant is more difficult to discover. Oxygen
appears to be evolved practically simultaneously with the
absorption of carbon dioxide, and therefore very elaborate
chemical changes seem improbable. ‘The energy that will

102 PLANT PRODUCTS

be freed by the combustion of dry plant materials equals
the amount of solar energy necessary for their production,
and the animal energy obtained by consuming plant
products will also be the same amount less some forms of
waste (discussed in Part IV.). Although the actual mechanism
by means of which carbon dioxide is converted into complex
organic bodies is only very little known, the substances
themselves have been the subject of much elaborate inquiry.
The following table gives, in brief form, the chief classes
of substances which are produced in plants by these means.

TABLE 19. Feedi ]
Water— Volatile, such as acetic acid songs dit
| Vegetable Non-volatile. Lactic, citric, tar- Practically
acids taric, oxalic acids. se Dani
Pentosans (gums)asaraban Doubtful.
Cc and xylan.
5 | Pentoses (sugars) as arabi- Do.
nose and xylose.
Ratio, Furfuroids, lignin, etc. None.
oui ken Hexosans (amylans) as cel-
er ia y lulose and starch.
8 ibee CC,’ wg ( Hexoses (glucoses) as | Heat-pro-
3 oe be dextrose, levulose. ducers.
q %) Poly-saccharoses as
= n cane sugar, etc.
True fats and oils. Heat pro-
Fats and ducers.
oils Wax. No value.
Resins and essential oils. Do.
( Proteins. Flesh-
\ Nitrogenous formers.
bodies Amides and Amines. Small heat-
ing values.
Phosphates of lime, potash, and Bone - form-
other bases. ing.
Sulphates of lime, potash, and None,
Mineral matter -.\ other bases.

Silicates of lime, potash, and None.
other bases.
Chlorides of sodium, etc. Digestive.

In some cases they are very well-known organic substances,
in others they are substances only described in the advanced
text-books.

THE VEGETABLE ACIDS.
Formic Acid, H.COOH, occurs in small quantities in

stings of nettles, in butter exposed to sunlight, in the contents
of the stomach, and in many fermented materials. Formic

PHOTO-SYNTHESIS 103

acid is a strong volatile acid, of pungent smell, and very
irritating in contact with scratches on the skin.

Acetic Acid, CH;.COOH, occurs in many plants,
is a common product of fermentation, and is produced in
the distillation of wood (see p. 129), from which latter
source most of the acid of commerce is obtained. It can
be produced from coniferous sawdust, saturated with sodium
_ hydroxide, and subjected to steam and air at 120° Cent.
It is a mono-basic acid, volatile, has a fairly strong smell,
and forms well-recognized salts, mostly soluble in water.
The purer acid is used for pickles and other food purposes.
Calcium acetate is used for the manufacture of acetone, and
for mordanting cotton goods.

Lactic Acid, or hydroxy propionic acid, CH3.CH(OH).-
COOH, is a common product of fermentation, and is also
found in muscular tissue. It can be manufactured from
glucose, chalk, and sour milk. It is not volatile, but on
concentration the solution forms a lactone by loss of water.
This ability to split off water makes it a valuable hydrolytic
agent. In free and uncontrolled fermentation the develop-
ment of lactic acid proceeds best in the presence of much
nitrogenous material. The salts of lactic acid crystallize
poorly. .

Oxalic Acid, (COOH),.2H,O.—The oxidation of almost
any organic substance will produce some oxalic acid. It
is almost universally found in plants, but beet leaves,
rhubarb leaves, and sorrel contain especially large quantities.
Oxalic acid is manufactured from coniferous sawdust,
saturated with sodium hydroxide, subjected to steam, and
a large proportion of air, at 300° Cent. The sodium
oxalate so formed is treated with sulphuric acid. It is a
di-basic acid, non-volatile, forms good crystalline salts
with the alkalies, whilst its calcium salt is marked by its
special insolubility, a property which enables plants to
deposit insoluble calcium oxalate in their tissues as a means
of getting rid of excessive quantities of this acid. Calcium
oxalate is insoluble in any of the acids commonly found in
plants. Oxalic acid is poisonous to both plants and animals.

104 PLANT PRODUCTS

It is very easily oxidized in the laboratory, and becomes
oxidized in the soil by bacterial action. In the presence of
an excess of alkaline oxalates the heavy metals, like iron
and copper, produce double salts with the alkalies, which
are soluble.

The homologues of oxalic acid are also important. A
member of the series, malonic acid, HOOC.CH,COOH, has
no great interest for present purposes, but succinic acid is
present in many plants, and is produced during fermentation,
whilst its oxidized products are met with in still larger
amounts.

Malic Acid, or Hydroxy Succinic Acid, HOOC.CHg.-
- CH(OH).COOH, occurs in apples, gooseberries, cider, and
many other fruit materials.

Tartaric Acid, Dihydroxy Succinic Acid, HOOC.-
CH(OH).CH(OH).COOH, is found in considerable quantities
in grapes and wine. ‘The deposits in wine casks, known as
argol, is one of the chief sources of tartaric acid. Argol,
purified by crystallization, is known as tartar, or cream of
tartar. The purified argol is treated with calcium carbonate
and calcium sulphate to obtain a precipitate of calcium
tartrate, which is subsequently decomposed by sulphuric
acid. ‘The recovered calcium sulphate supplies all that is
necessary for the former part of the process. Tartaric
acid is non-volatile ; crystallizes well ; is easily decomposed
by heat, giving off a smell of burnt sugar; forms soluble
salts with the alkalies; insoluble salts with the alkaline
earths ; complex ions with iron and copper; and produces
a potassium hydrogen tartrate which is insoluble in water,
though soluble with decomposition in either acids or alkalies.
Tartaric acid is used medicinally, for summer drinks, for
photography, for silvering mirrors, for bleaching, and for
dyeing.

Citric Acid, HOOC.CH»,.C(OH)(COOH).CH,.COOH+
H,O, is a very common plant acid. Lemons can produce
as much as five or six per cent., and Dyer found that most
plant roots contained acids, largely citric acid, up to about
I per cent. Lemon juice is boiled with calcium carbonate

PHOTO-SYNTHESIS 105

till nearly, but not quite, neutral, and the calcium citrate
formed acidified with sulphuric acid. Citric acid forms an
insoluble calcium salt, which does not easily form without
boiling. ‘The deposition of calcium citrate by boiling milk
in a saucepan is a well-known phenomenon, which produces
a crust on the bottom of the saucepan, rather difficult to
remove.

THE CARBOHYDRATES.

Fibre. — The members of the carbohydrate group,
which are pentosans, C;H,O,, that is five carbon gums,
are very common in all the fibrous parts of plants.
Straw may contain up to 20 per cent. of this material,
which is consequently often known under the name of
straw gum. The amount of pentosan present in most
plant products is roughly in proportion to the amount of
fibre. No satisfactory use has been made of straw gum as
yet, since its adhesive properties are too feeble. Ifthe amount
of wheat grown in Great Britain is to be doubled, the straw
will also be doubled. It is hence important to discover new
uses for straw, and this subject seems worthy of further
inquiry. When heated with dilute acids the pentosans are
first converted into pentoses, and then condense into
furfuraldehyde, a volatile liquid which can be distilled with
steam and forms many coloured compounds, some of which
are dyestuffs. Straw is the best raw material for the
production of furfuraldehyde. The pentoses themselves
are not common materials in plant life. The pectins, gums,
and such substances, frequently yield substances of both
the C,; and Cg groups, and are, therefore, compound bodies
containing these two groups (see p. 131). The cellulose
group is a very common material to find in plants, most of
the stiffening parts of plants being due to this substance,
which, in its pure form, approaches CgHj 0, in composition.
Cotton-wool and filter paper (see p. 128) may be taken
as practically pure specimens of cellulose. Cellulose is
insoluble in all common reagents, but is soluble in solutions
of copper hydroxide in ammonia, as well as in zinc chloride

106 PLANT PRODUCTS

or sulphuric acid. Solutions of cellulose in cuprammonium
hydroxide are used in making Willesden paper and canvas ;
solutions in zine chloride are used for electric carbon fila-
ments ; and solutions in sulphuric acid are used for parch-
ment paper. Many of the fibrous parts of plants are not
pure, but contain furfuroids, lignin, etc.

Starch, (C,H,,O;), or probably slightly more hydrated,
is a very common form of storing reserves of plant foods in
seeds, stems, bulbs, and other parts of a plant where they
are not required at the time, but at some later stage of the
plant growth. Starch is commonly recognized by its
microscopic form and reaction with iodine. A microscope
with Nicol prisms is of great use in observing starch grains.
Dry heat above 150° Cent. converts starch into dextrin.
In the presence of water, starch grains burst when heated.
Starch is soluble in hot water, forming a colloidal solution.
Potato starch gelatinizes at 65°, but oat starch needs 95°
Cent. On the addition of a drop of copper sulphate to a
solution of starch, followed by a large excess of sodium
hydroxide, a blue precipitate is produced, which is not
altered on boiling. The action of ferments, such as diastase,
turns starch into soluble products, dextrin, malto-dextrin,
maltose, etc. Further treatment with dilute acid will
convert these products into glucose (dextrose). Diastase
is a typical enzyme, and has the power of converting 1000
times its own weight of starch into soluble materials.

Dextrin, a body very similar to starch, is generally
present in plants to a small extent, and can be obtained by
heating statch either by itself or in presence of water or
with traces of nitric acid. It differs from starch in giving
a red colour with iodine. Dextrin is used in place of gum,
especially in hot climates, as it is less hygroscopic than gum
atabic. For small articles, like postage stamps, dextrin
is superior to gum arabic, but for large articles its adhesive
power is too small.

The Mono-Saccharoses, or Hexoses, CgHj.O,5.—
Glucose (dextrose, grape sugar) occurs in all the sweet-tasting
plants, crystallizes with some difficulty, often with one molecule

ee eee

PHOTO-SYNTHESIS 107

of water of crystallization. It is soluble in water, or alcohol,
ferments readily, rotates the plane of polarized light to the
right, and reduces Fehling’s solution, or alkaline solutions
containing copper and tartaric acid. Its properties are
those of an aldo-hexose. Glucose is manufactured by boiling
starch with dilute sulphuric acid, removing the acid with
lime, and concentrating the liquor.

Fructose (levulose, fruit sugar) is also found in plants,
and differs from dextrose, since it is a keto-hexose. Honey
consists of a mixture of glucose and fructose. In cold weather
the glucose separates out as crystals, leaving the fructose
as a liquid. Crystallization of fructose presents many
difficulties, but the material can now be produced com-
mercially in the solid form. Fructose reduces Fehling’s
solution, and rotates the plane of polarized light to the
left.

Galactose, a sugar closely tesembling dextrose, is not
generally found in plants, although it is a common result
of the hydrolysis of many of the gums, where it occurs
in combination with one of the pentoses. It is also a
constituent of raffinose. Many forms of yeast do not ferment
galactose.

The Di-Saccharoses, C).H29O;;.—Maltose, the con-
densed product of two molecules of glucose, is contained
in malt, and is produced from starch during the germination
of barley grains. It is a product of the hydrolysis of starch,
intermediate between dextrin and glucose. Maltose reduces
Fehling’s solutions both before and after hydrolysis, but is
only fermented after hydrolysis.

Lactose (milk sugar) is the product of condensation
of galactose and glucose. It occurs in cows’ milk to the
extent of between four or five per cent., and in human milk
up to eight per cent., but has not been found in plants.
It is made from whey, a cheese by-product, by crystalli-
zation, and is used largely in medicine.

Cane Sugar (sucrose) is the best known of the sugars,
and is contained in sugar cane, sugar beet, and many other
sources. Of the sugars we have dealt with above, this is the

108 PLANT PRODUCTS

only one which does not reduce Fehling’s solution (see
p. 107). |

The Tri-Saccharose (raffinose) is the condensed product
of the three mono-saccharoses glucose, fructose, and galactose,
and occurs in sugar beet. Its admixture with sucrose is
neither easy to detect nor resolve. It does not reduce
Fehling’s solution, and has the high rotary power [a],—=+104°.

The Tetra-Saccharose (stachyose) is the chief carbo-
hydrate in the Japanese artichoke. It hydrolizes to glucose,
fructose, and two molecules of galactose. It does not reduce
Fehling’s solution.

THE FATS AND OILS.

These are all compounds which have glycerine as a
base, and one or more of the fatty acids for the acid
part of the ester. Oils are obtained from seeds either by
pressure or by “ Rendering.’’ The latter process consists
in boiling the seeds with water, when the husks and fibre
sink and the oil rises to the surface. With modern
methods, extraction by solvents like petrol is employed.
The acids universally found are stearic (CjgHs,O0.), oleic
(CygH34O.), and palmitic (CjgH3.0.2). Other special acids
in smaller amount are specific to particular plant products.
All the fats, on treatment with alkali, are hydrolized with the
production of soap and glycerine. Glycerine is miscible with
water, and is non-volatile, although it can be distilled in a
vacuum. ‘The fatty acids, when unsaturated, absorb iodine
from solution, and the iodine absorption is closely connected
with the drying properties of the oil. Sulphur chloride acts
on fats rapidly. Both sulphur and chlorine are taken into
the molecule. These compounds are used as rubber substi-
tutes (see p. 165). Free sulphur also acts upon the unsatu-
rated oils at temperatures above 120° Cent.

Some other materials, which are extracted by ether in
the ordinary analysis, do not belong to the true fats and oils.
These are waxes, which are often compounds of the higher
alcohols, and higher acids. Whilst the fats and oils have a
very high feeding value, the waxes have no value as food.

Ne ee

a eee a

= _—

FL RO ee

PHOTO-SYNTHESIS 109

Essential oils are the volatile constituents found in plants.
Turpentine oil is one of the most important.

THE NITROGENOUS BODIES.

The nitrates are absorbed by plants, and are subse-
quently converted into organic nitrogen compounds. In
cases of drought, plants can store nitrates in their stems.
All the ordinary nitrates are soluble in water. Ammonia
salts are only found in traces in plants. Plants, indeed,
cannot endure any considerable quantities of ammonia, free
or combined (see p. 14).

Ammonia salts in organic materials can be distilled out
with precipitated chalk.

Amides, Amines, etc.—Miscellaneous non-albuminoid
nitrogenous bodies in plants are often called amides. A por-
tion of these are true amides, but some are not. Asparagine,
for example, is both an amide and an amino acid, which on
distillation with moderately strong alkali will yield half
its nitrogen as ammonia. Alkaloids, nitrogenous glucosides
and amines, are also present.

The Albuminoids, or the Proteins, are the complex
bodies of which the amino acids are the basis. ‘They can be
precipitated by copper hydrate, lead acetate, uranium acetate,
or other precipitants, the non-albuminoid nitrogenous matter
remaining in solution. For a rough division the nitrogen
insoluble in lead acetate solution may be considered protein
nitrogen. The ammonia distilled by potash, but not distilled
by calcium carbonate, can be considered as amide nitrogen.
The nitrogen distilled by calcium carbonate can be considered
as ammonia compounds, and the nitrates precipitated by
nitron can be taken as the nitrate nitrogen. It will not
infrequently be found in roots and leaves that the sum of
these fractions of nitrogen will not add up to the total
nitrogen, but in the case of grains, seeds, hay and straw, the
above division will not give any appreciable surplus or
deficiency. Roughly speaking, one may say that mature
plants do not contain any large quantities of nitrogen outside

IIo PLANT PRODUCTS

the groups alluded to, but immature plants will often have
some nitrogen in unknown combinations.

For the production of proteins in the plants it is necessary
to supply nitrogen, phosphorus, and sulphur. The other
plant products which do not contain those elements, are
indirectly dependent upon the proteins, and the production
of full quantities of starch or sugar cannot be obtained without
adequate supplies of fertilizing ingredients containing those
elements.

The waste of solar energy alluded to in Table 18 shows
that much of the energy of the sun is expended in evaporating
water. Experiments, both on the small and on the large
scale, show that the proper utilization of fertilizers results
in economy in use of water (see p. 101). Phosphates
and nitrates appear to be particularly valuable in this respect.
The use of top dressings of nitrate of soda or sulphate of
ammonia during the droughty periods on corn and hay
crops is a very well-known practice, whilst the use of
phosphatic manures, either directly or indirectly, during
the stimulus of root development also produces an economy
of water. ‘The question of the water supply to the plant is,
therefore, very closely bound up with the supply of proper
fertilizing ingredients, and much can be done in dry regions
or during dry periods to economize the water supply by a
liberal use of phosphatic and nitrogenous fertilizers.

REFERENCES TO SECTION I

Haas and Hill, ‘‘ Chemistry of Plant Products,” p. 143. (Longmans.)

Fenton, Journ. Chem, Soc., 1907, T. p. 687.

Borday, Proc. Roy. Soc., 1874, p. 171.

Warner, Proc. Roy. Soc., 1914, B. 87, p. 378.

Dyer, Journ. Chem. Soc., 1894, T. 115.

Cross and Beavan, ‘‘ Cellulose.’’ (Longmans & Co.)

Forster, ‘‘ Bacterial and Enzyme Chemistry.” (Arnold.)

Armstrong, ‘‘ The Simple Carbohydrates ; Monograph on Bio-chemistry.”
(Longmans. )

Rideal, ‘“‘ Practical Organic Chemistry.’’ (Lewis.)

Barnes, ‘‘The After Ripening of Cane,’ Agric. Journ. Ind., 1917,

. 200.

Bayliss, ‘‘The Nature of Enzyme Action.” (Longmans.)

Jorgensen and Stiles, ‘‘Carbon Assimilation.’’ (Wesley.)

—— ee ee be -

nn

Szorion II.—THE CARBOHYDRATES
PRODUCED IN CROPS

(a) Sugar.—Of the various sugars given in Section I., the
di-sacchacrose named sucrose, or cane sugar, is by far
the most important. Cane sugar is present in many plants,
and is extracted from many different sources. Of these,
the sugar cane is the best known, and oldest worked. Sugar
cane is grown chiefly in warm climates, such as the Southern
United States, the West Indies, Queensland, the Philippines,
and India. ‘The sugar cane grows best in a good, deep soil,
generally of a dark colour. It is propagated from sets
in a manner somewhat resembling potato planting ; that is,
sets containing two or three buds are planted a few inches
below the surface, in a well-manured soil. In some places
entire canes are planted, but this tends to produce an
irregular crop. Irrigation equal to 50 inches of rain is always
necessary, unless the rainfall is exceptionally heavy. ‘The
crop lasts about twelve months, and there is some difficulty
in determining when it is ripe. Where irrigated water is
difficult to obtain, mulches are not infrequently used on the
surface. In Mauritius the cane is often planted in pits.
Very frequently the crop is grown for two or three years in
succession, since after the first crop has been cut the old
stem tillers freely, and produces what is called a ratoon crop,
which is, however, never equal to the first year’s growth.
Asin all tall crops, ‘‘ lodging ’’ is a serious cause of loss.
The side leaves have to be removed during the process of
cultivation. Some system of rotation is nearly always
necessary, so that the cane is not cultivated on the same
land more than once in five or six years. The cane is subject
to all kinds of pests. An interesting method for protection

112 PLANT PRODUCTS

against pests adopted in India is to put castor cake and salt
into the water, when the poisonous compounds of the castor
dissolve in the salt water, and destroy many pests. When
the crop is ripe, which takes about twelve months from

TABLE 20.—INDIAN SUGAR.
Composition of Sugar Canes.

Thin cane Thick cane
per cent. per cent
Fibre ‘s Np i ee .. ve 15 84
Juice, not expressed by Bullock Mill (Water) .. 35 164
9 29 9 2 ry) » (Sugar) .. 5 3
Juice expressed (Water) .. Ro ae fy 39 61
si al (Sugar) .. aie ne sb 6 II

’ TABLE 21.—SUGAR CANE, INDIAN, 200-300 ACRE PRODUCTION, ~
Cost of Cultivation in Rupees per Statute Acre.

First year, Second year, Third year,

Cane, t ratoon, d ratoon,

Seed (sets) .. sis ae oi 50 Se peiaelaaibpi
Irrigating .. ae is “s 60 50 40
Manuring .. Wh os “6 180 Too —
Other labour ae i i 55 45 40
Boiling, Marketing, etc. .. a 140 125 go
485 320 170
Value of Brown Sugar .. “yi 560 450 — eb
Profit os os as He 75 130 30

planting, the cane is usually cut with some kind of sickle, and
removed to the mills. When cane is cultivated in primitive
fashion, as is the case in India, the mills containing three
rollers are semi-portable and are worked by four bullocks.
Two of the rollers are about half an inch apart, and the
third roller is only one-eighth of an inch from the centre
roller. By passing the cane through the wide gap first, and
then through the narrow gap, a double squeeze is given,
and about 80 per cent. of the juice extracted. In the West
Indies, the United States of America, and Queensland, with
more efficient machinery, and by moistening the pressed

A LOE TL

THE CARBOHYDRATES PRODUCED IN CROPS 113

cane with a little water, as much as 90 per cent. of the juice
can be extracted. Excepting under the most primitive
conditions, lime is always used for removing many of the
impurities in the juice. In the field methods of manufacture,
adopted in India, the lime is added until the natural colour
of the sugar cane juice, which acts as an indicator, shows
that neutrality has been reached. ‘The liquid is then boiled
down, and very carefully skimmed. In more elaborate
and carefully industrialized systems a slight excess of lime
is used, then filtered, the excessive lime removed, by carbonic
acid, and again filtered. Some of the proteins are precipi-
tated on boiling inany case. In primitive systems the whole
material purified by skimming is boiled down until it becomes
very thick, when it is poured into moulds. ‘The moulds
often consist of holes in the ground, lined with cloth, so
that some portion of the molasses drains away. In such
a case a brown sugar is obtained. Where it is desirable to
get a very white sugar the boiling-down process takes place
ina vacuum pan. Sugar is converted into caramel, a brown
colouring matter, by the action of heat, but by reducing
the pressure, and therefore the boiling point, the heat is
lowered to less than the temperature at which sugar begins
to catamelize. Further improvement can be adopted by
separating the molasses from the sugar by a centrifugal
machine. A small centrifugal machine, worked by hand,
can be obtained for field use. In India, brown sugar is
preferred to white sugar, and hence little effort is made to
carry the purification to any extent. The supply of fuel
is always an important point inthe manufacture. ‘The waste
cane, if dried, makes a useful fuel, and the dried side leaves,
unless required for fodder, can also be used as fuel. In
India the upper leaves are used to feed the bullocks. For
the satisfactory cultivation of sugar cane nitrogenous
fertilizers are essential, and in experimental work conducted
in India quantities of from two to five hundred pounds per
acre of nitrogen have been used, although the larger quantity
seems unnecessary. Other manures, such as phosphatic and
potassic ones, are sometimes necessary, but not to anything
D. 8

114 PLANT PRODUCTS

like the extent that nitrogenous ones are. It appears to
be necessary that the nitrogen should always be in much
larger proportion than the other fertilizing ingredients.
Indeed, where this has not been the case, individual observers
have not infrequently reported that phosphates have done
harm, but that is only a particular case of the importance
of preserving a proper balance of fertilizers, which has so
often been alluded to. In experimental results obtained
under good conditions in India quantities amounting to
nearly five tons of crude sugar per acre have been obtained.
At the larger industrialized concerns in the United States
about 10 or 12 per cent. of the weight of cane is obtained
as sugar. In vegetarian countries sugar replaces the meat
of meat-consuming countries, and the amount produced on
the small scale is in excess of anything recorded in ordinary
Government statistics. Considerable quantities of softer
canes are never made into sugar at all, but are eaten as
they are.

Sugar Beet.—In temperate climates the sugar cane
does not ripen satisfactorily, and sugar is therefore prepared
mostly from the sugar beet. Sugar beet is a crop which
closely resembles the mangel wurzel in its properties. An
enormous amount has been written upon this subject, and
there is no particular reason why the sugar beet should not
be cultivated in many parts of the British Isles. Sugar beet
can certainly be grown in the north of England, as well as
in the south, but if grown will replace some of the other
crops. Whether that will be a profitable arrangement only
the future can tell. The manufacture of sugar from sugar
beet follows a somewhat different course to that of the sugar
cane. The system adopted is called the diffusion process.
In the process the sugar beet is cut into slices, extracted with
water (at 85°—-g0° Cent.), and the weak solution obtained used
to make a stronger solution by extracting more beet. The
concentration of the sugar liquors rises until it becomes
approximate to the strength of the juice in the beet them-
selves, that is to say, it rises to nearly 18 per cent. of sugar.
This process has the great advantage that the cell-wall of

THE CARBOHYDRATES PRODUCED IN CROPS 115

the beet itself is used as the filter and purifier. The
albuminoids and the gums do not diffuse through the cell-
wall as readily as the sugar, and therefore the sugar solution
obtained is in a much purer condition than that obtained
from the sugar cane. The other substances present in raw
cane sugar are pleasant to the taste, and probably most
people prefer the flavour of brown sugar to white when it is
made from cane. It is rather the appearance of white cane
sugar that gives it a high value. The impurities in sugar
beet include substances which are bitter to the tongue
and musty smelling to the nose, and the purification does
not entirely remove these impurities, though they are too
small in amount to estimate. The general process of
purification is much the same as in the case of cane. Where
the resulting beet slices extracted can be used as cattle
food it may easily be more profitable not to attempt to remove
the last trace of sugar, but to leave a little in for the cattle
food. ‘The cultivation of sugar beet accommodates itself
well to the ordinary types of mixed agriculture adopted in
temperate climates, especially where the production of milk
and meat form an essential part of agriculture. ‘This is
an undoubted advantage which the sugar beet possesses over
the sugar cane, inasmuch as the sugar cane gives no useful
by-product and does not lend itself so well to the working
of the general agricultural plan.

About eleven tons of clean beet per acre represent
the European average production, with about 16 per cent. of
sugar obtainable from them, or, say, roughly two tons of
sugar per acre. This is much below the best production
of cane sugar, but it is very difficult to get average figures of
the production of cane sugar, since there are such large
amounts grown in a very primitive manner. Experience
is, however, showing that no nation can afford to be entirely
dependent upon outside sources, and at least some fraction
of the necessary sugar may have to be grown in Great
Britain, even if it is not economically profitable. The other
parts of the British Empire are more nearly self-supporting
as regards sugar.

116 PLANT PRODUCTS

The Date Palm is also one of the minor sources of
sugar. Most species of the palm can be used for the
production of sugar; many of them are used for the
production of sugar for fermentive processes. When it is
desired to manufacture sugar the palm is cut, and the sugar
juice runs into a pot. The pots are collected, and the juice
quickly boiled down before fermentation takes place. With
the aid of a hand centrifugal machine very pure sugar can
be obtained in a simple manner. The quantity made is,
however, small, and can never compete commercially with
the other sources of sugar.

Sugar Refining.—Most of the sugar industry in the
British Isles in the past has rather turned on the purifica-
tion of crude sugars produced elsewhere. Many reasons
have been given for the collapse of the sugar purification
industry in the British Isles. If reference be made to an
old work by Higgins, dated 1797 (see Bibliography), the
following will be found: “It is now well-known that an
artist with a very little education will soon learn all that
is useful to him in mechanics and chemistry.’’ If such
opinions were generally held, the collapse of the industry
is readily understood.

Turnips, etc.—A very large amount of sugar is
produced and consumed in the form of swedes, turnips,
and mangolds. ‘These crops form the essential part of a
rotation, and permit the cleaning of the land. Good seed
beds and liberal manuring are essential, and the land is usually
worked into ridges. Super-phosphate, sulphate of ammonia,
and potash salts are all used as well as farmyard manure.
For mangolds, salt is needed as well. The seed is generally
used somewhat generously, the young plants being “ singled,”’
that is to say, all those that are not needed are hoed out.
In the United Kingdom, about twenty-four million tons of
turnips and swedes are grown. The swede crop in the
northern counties contains about 6 per cent. of sugar, on the
average a little more. The average for the whole country
is probably slightly less, and the white turnips will be
distinctly lower, but it is probably not seriously wrong if

yy

THE CARBOHYDRATES PRODUCED IN CROPS 117

we say that there is about 5 per cent. of sugar in those twenty-
four millions of tons; that is to say, there is well over a
million tons of sugar grown in the British Isles and eaten
chiefly by cattle in the form of turnips and swedes. In
addition to that, there are about ten millions of tons of
mangolds grown, which, on the average, will have a rather
higher percentage of sugar. Taking all together, there
cannot be much less than one and a half millions of tons of
sugar produced in the British Isles and consumed in this
way, or, roughly, one-tenth of the world’s production of
cane and beet sugar. In the case of the mangold, much of
the sugar is cane sugar, in the case of turnips and swedes much
of it is glucose. The crops of swedes, turnips, and mangolds
all present some points of similarity, requiring good manuring
and a fairly deep soil. All of these sources of sugar could
be used for fermentive purposes for the production of alcohol
if the necessity arose. During the war, an increased fraction ~
has been used directly as human food. Some fraction might
be used for the manufacture of jam. No doubt a mixture
of swede turnip pulp and fruit boiled down would not be
a first-class jam, but it would be better than letting the fruit
waste. Unfortunately, turnips do not ripen till after most
of the fruit is over, but some of the later fruits might be
used. Sugar beet will keep well, and could be held over the
winter, when it might be used for the preservation of early
summer truits. Sugar beet can be dried easily, and ground
in the mill to powder, when a crude sugar results. As
war measures, such schemes are worth a trial.

(6) Starch.—Starch is chiefly produced in cereal crops,
although it is a common ingredient of many forms of plant
life. Excepting in some of the oil seeds, it may be found in
any of the finished forms of plant life, and is one of the food
reserves of the plant. ‘The methods of preparing starch are
almost independent of its origin. The systems chiefly
employed are—

(1) The fermentation process, in which the material,
after being ground up with water, is allowed to ferment.
The fermentation results in the solution of the albuminous

t18 PLANT PRODUCTS

part, and the liquor is then run off, leaving the starch as a
deposit. After washing once or twice, the starch is left.
This method is rather wasteful, as it is not easy to get more
than 30 per cent. of any of the grains in the form of
starch.

(2) Alternative methods consist in macerating the raw
material with water, and passing through a fine sieve,
containing about two hundred meshes to the linear inch.
The glutinous parts remain on the sieve, while the fine
grains pass through in the water. ‘The muddy starch liquor
is then allowed to settle, and the liquor is poured off, and
the starch dried. Combinations of these processes are
not infrequently used, in which a certain amount of
fermentation is permitted, and some kind of sieving method
is employed. In more modern systems it is not uncommon
to employ sodium hydrate and sulphurous acid as convenient
means of dissolving the proteins and obtaining a purer
starch. Starch must either be dried without any heat,
or a very low degree of heat must be maintained, otherwise
the starch becomes gelatinized. Potato starch gelatinizes
readily, but rice starch with difficulty. The large starch grains
gelatinize most readily. Air-dried starch will usually contain
about 20 per cent. of water, and that dried with a moderate
degree of heat contains only Io per cent. The starch consists
of very small grains, which are recognized under the
microscope by their characteristic form and size. Potato
starch grains are large and rice starch grains small.

Wheat. — Wheat constitutes one of the most important
of the cereals which contain a high percentage of starch.
Wheat is grown in almost all parts of the world, best on a
fairly heavy soil, and in a climate which is neither very
damp norvery dry. Arid regions can, however, with the aid
of irrigation, produce very fine wheat crops. ‘The intro-
duction of irrigation into the Punjab, in India, has resulted
in converting some almost useless land into very excellent
wheat country and the growth of wheat in Egypt is
dependent on irrigation. Wheat is, of all the crops, the one
which can be cultivated for the longest period of time on

ie Mtge 7

THE CARBOHYDRATES PRODUCED IN CROPS 119

the same land without change, but the best yields are obtained
on virgin lands, or under systems of mixed farming with
rotation. The yields per acre in the British Isles, and in
Canada, are generally about 30 bushels, but the yield in
some other parts of the world does not amount to more
than about one-quarter of that figure (see p. 206). The
use of nitrogenous manures for wheat is important. The
desirability of top dressing with such a manure as sulphate
of ammonia has been alluded to in Part I., Section I.
As a rule, wheat is not used for the industrial manufacture
of starch, because wheat commands too high a price.
Maize. — Three-quarters of the world’s supply of
maize is grown in North America, but the advantages of
maize are gradually becoming more and more recognized
in the warmer parts of the globe. It is better suited to
higher temperatures than wheat, and though much benefited
by a sufficient rainfall, is capable of developing in drier
situations than wheat. ‘The actual amount of maize
yielded is, howeve1, not dissimilar to that of wheat, and
in mediumly warm districts the two cereals compete with
one another. In cooler climates maize does not ripen
satisfactorily, though the crop is often used as green fodder.
The growth of maize is very rapid, four months being not
infrequently sufficient. As a rule, it is best grown under
some system of rotation, needs fairly deep and thorough
cultivation, and is improved by fair dressings of farm-
yard manure, lime, phosphates, potash, and sulphate of
ammonia. On the large scale it is often planted in heaps
three or four feet apart, so as to allow of cultivation in
between. The plant grows from about five to twelve feet
high. Much of the crop is fed to stock, a large fraction
husked in the field and sold for manufacturing purposes.
Maize is admirably suited for the manufacture of starch,
and in the United States of America forms the chief source
of all forms of that article. The composition of maize is
very constant at about 70 per cent. carbohydrates, mostly
starch, and about 4 to 5 per cent. oil. Maize germ meal, the
germ after extracting the oil, is used as cattle food. Gluten

120 PLANT PRODUCTS

feed meal, the residue from starch factories, is used for
cattle food, and is rich in albuminoids.

Rice.—Rice is a cereal particularly suited to wet situa-
tions: It is grown chiefly in Bengal and Burmah, but is also
sown in Japan and China. The number of varieties of rice
seems almost unending. In India there are several different
groups of varieties which belong to the seasons. ‘The winter
rice is generally sown in May or June, the autumn rice is
usually sown in August, the summer rice in January or
February. The growth of the crop is extremely varied,
according to the type of cultivation, some of the very rapid
varieties being able to grow in about two months, and some
of the very slow ones taking the best part of a year. On
the average, however, two crops are obtained in the year.
The best type of soil is a sandy one, lying upon clay, where
the irrigating water can be flooded, held up by the subsoil,
and yet leave the surface soil sufficiently open for the
growth of the plant. With very wet varieties the depth of
water may be so great on the fields that the werkers actually
use boats to transport them over the field; but in the hill
regions, where the slopes are often terraced, only an inch or
so of water is used for irrigating purposes. Rice is best
sown in a seed bed and transplanted. Not infrequently
the ploughing operations are carried out under water, so
that the bullocks have to wade through to do their work.
On those lands that permit of such treatment, where the
growth of the rice is excessive, the young rice is grazed by
cattle, in a similar way to wheat being grazed by sheep in
temperate climates. There are no less than about seventy
millions of acres of rice in India. The rice, as separated by
threshing, contains a large amount of husks, and in this
form is commonly called paddy, the term rice being retained
for the finished product after husking. ‘The term “ paddy”
is frequently employed with reference to the whole system of
cultivation, and the terms ‘‘paddy fields’”’ and ‘‘ paddy bird ”
are more commonly in use in the east than the term “rice,”
which chiefly refers to the finished article ready for the table.
In the countries where rice is grown, the terms ‘‘ paddy ” and

Se a ee
=

THE CARBOHYDRATES PRODUCED IN CROPS tat

“‘rice”’ are used in the same way as sheep and mutton are
used in England. ‘The rice kernel is enclosed in a very hard

_ husk, which requires considerable amount of work over its

separation. On a small scale rice is pounded by hand as the

_ recognized work of the women of India. On the large scale in

Burmese mills rice is decorticated by machinery. ‘The husks
so removed are quite worthless, but the resulting grain is

_ very frequently polished still further to produce white rice.

The resulting white rice is much less nutritious than the
streaked brown rice, which contains the bran adhering to
it. White polished rice kernels are very nearly pure starch,
whilst rice bran contains most of the oil and albuminoids
of the grain. The following table represents the varying
composition of the different parts of the rice plant :—

TABLE 22.
| Rice
Grain, Bran, Husk, Straw,
Moisture... i Als 6 fees 10°3 8'0 70
Oil ve “6 a 1°3 12'0 3°5 2°1
Albuminoids — : ie 4°9 II°3 4°3 1'°8
Other nitrogenous matter os 2°4 1’o -o'8 o'9
Carbo-hydrates, Pentosans, etc. .. trace 3°2 10°! 18'5
” Hexosans, etc. .. 79°5 44°6 24°2 26'8
Woody fibre 5 a si a 1s 8°6 25'9 27°3
Mineral matter ty" al) Dt) 9'0 23'2 15°6
| 100°0 100'0 100°0 100°0
Total nitrogen me Ae GH ie 2 1°90 0°69 0°43
Total phosphoric acid A 060 0°63 o'2I
Total an ee a) Ko hy NOR 0°37 o'51 0°69
Total lime la Ape wi Rls NO O15 0°35 0°35
Insoluble silicates .. eg ae | 0°28 2°00 20°00 12°80
}

Rice may, when merely ground into a powder, serve the
purpose of starch, or the starch may be prepared from rice
by the usual methods (see p. 117). Both maize and rice
lend themselves to the possibility of producing starch by
the dry method of grinding and blowing by currents of air,
but starch is chiefly made by one of the wet methods,

122 PLANT PRODUCTS

Potatoes.—The potato, although well known and
popular to-day, is a very recent introduction into general
use. It is cultivated entirely from the tuber itself, and
not from the seed of the plant. The true seed of the plant
produced from the flowers does not yield usable potatoes
for two or three years, after which time new varieties of
potatoes are obtained and have often fetched extravagant
prices. ‘The old varieties, in process of time, tend to die out.
From the strictly botanical point of view, it must be remem-
bered that all the potatoes of one kind in the world are really
one single plant. They have all come from one single true
seed, and, like all living things, the individual, in process of
time, dies, and there appears, therefore, to be a limit to the
life of any particular so-called variety of potato, since each
variety is only an individual. The potato loves much
manure, especially farmyard manure, but also gives good
results from the use of sulphate of ammonia and super-
phosphate and sulphate of potash. Good cultivation is
also essential for big crops. It is a crop which is particularly
suited to small types of cultivation. It appears to grow in
most types of soil, though it likes a fairly open kind, but
plenty of spade work and manure will go a long way to
remedy any excessive heaviness a particular soil may possess,
and sprouting the potatoes before planting will reduce risk
from early frosts. Five to eight tons per acre of potatoes
represent about ordinary farm experience. Six to eleven
tons per acre are recorded as market garden results. The
potato contains about 75 per cent. of water, 20 per cent. of
carbohydrates, and 18 per cent. of starch, but higher figures
for solids can be obtained, especially where the manuring
has not been so generous. In the uncooked state potatoes
often prove slightly irritating when eaten, but when cooked
this difficulty is removed. Potatoes can be dried by
machinery for the production of potato flour. They can
also, after pulping or rasping, be used for the manufacture
of starch. Potato starch, after fermentation, is used for
the production of alcohol.

In comparing the relative values of maize and potatoes

THE CARBOHYDRATES PRODUCED IN CROPS 123

for the production of starch much will, of course, depend
upon the particular circumstances, but a ton of maize per
acre will be a fairly good crop, and will barely produce half
a ton of starch. This might be compared with about seven
tons of potatoes per acre, producing rather over a ton of
starch. ‘The cultivation of potatoes, to yield good crops, is,
however, expensive, in comparison with most of the cereals.
Potatoes, if kept cool, can be stored quite satisfactorily.
The large amount of water they contain is an objection for
transport purposes in comparison with the cereals,

Sago.—The sago palm grows in tropical countries, best
on boggy soils, which are rich in humus. The palms are
cut down when the trunks have attained a height of about
twenty feet, the sap is allowed to drain, and the trunks,
sawn into lengths, split open, and the pith removed. . The
__ pith consists of starch, mixed with fibrous materials, which
is then pounded in mortars, agitated with water, and the
starch separated as usual. ‘The sago flour so obtainedyisye
imported into this country, and is used for the manu :
of glucose, and in the textile industries. The gramul a
sago which is made for the purpose of food is pte ro
from sago flour by mixing it with water into a veryGstifARia
paste, and gelatinizing by heat. ‘‘ Granulated sago”’
however, sometimes made from starches of other origin
than sago.

Cassava and Tapioca.—The tuberous roots of the
shrub-like plants called sweet cassava and bitter cassava
are cultivated in the tropics for edible purposes. Cassava
flour only contains 2 per cent. albuminoids. Owing to the
low demands of cassava for mineral matter, the crop is very
well suited for poor, sandy soils, but it requires a good supply
of air and water. ‘The cultivation is as that of potatoes
and similar manuring gives increased crops. ‘The yield is
about 5 tons per acre, producing 1 ton of starch and a little
cane sugar. ‘Tapioca is made from cassava starch by stirring
the damp starch on hot iron plates. Cassava root contains
a cyanogenetic glucoside, which develops prussic acid in
the same manner as linseed (see p. 137). As in the case

124 PLANT PRODUCTS

of linseed the crops grown at high temperatures yield most
ptussic acid.

Barley, though a starchy cereal, is not used directly
for the production of starch. ‘The best is used for beer, the
second for bread, and the worst for cattle. It is converted
into malt by steeping the grain at a temperature of from
50° to 55° Fahr., spread in well-ventilated spaces, and
stirred well to permit germination and oxidation to take
place. It is then dried at 100° to 107° Fahr. The higher the
temperature, the lower is the diastase activity. It is then
thrown on to screens, for the removal of the malt coombes
or culms, which latter are used for feeding cattle.

(c) Cellulose.—Cellulose forms the important chemical
compound which constitutes the structural part of nearly
all vegetable matter. ‘There are a great many varieties of
cellulose, and the term must be taken as denoting a group,
and not an individual. Cellulose is much more resistant
to chemical reagents than the other carbohydrates, and
is isolated from vegetable raw material by hydrolysis with
acids and alkalies, or by the more drastic action of chlorine,
bromine, or sulphur dioxide.

All cellulose materials condense a fair amount of moisture
on their surface. In the green plant cellulose occurs in a
fairly hydrated condition, but by long drying or immersion
in alcohol dehydration takes place, so that the amount of cel-
lulose obtained from a material by any method of hydrolysis
depends upon the degree of hydration to which the cellulose
has been subjected. This has an important bearing upon
the subject of the feeding of materials containing much
cellulose, since grass that is grazed by cattle in a wet condition,
and has never become dry, is more digestible than the same
grass after it has been dried in the process of making hay.
It is well known in practical farming that hay which has been
made in exceptionally dry weather is not equal in feeding
value to that made in weather which does not permit of
such rapid and complete drying. Cellulose enters into a
feeble composition with alkalies when treated with sodium
hydrate, and produces alkali cellulose, hence many forms of

THE CARBOHYDRATES PRODUCED IN CROPS 125

cellulose persistently retain ash, some of which has probably
been in forms of partial combination. All forms of cellulose
on destructive distillation yield charcoal and a distillate
containing acetic acid and tar. As a rule, pure cellulose
yields from 30 to 40 per cent. of charcoal, and only I to
2 per cent. of acetic acid. The effect of distilling crude
cellulose, such as timber waste, is, however, very different.
Cotton.—Cotton grows chiefly in tropical and sub-
tropical regions, and requires a fair degree of moisture
and a moderately heavy soil. It grows as a small shrub,
and is planted at sufficient distances to allow hoeing and
picking by hand. In India two crops are sometimes obtained
' ina year, but, as a rule, fallow or millets (Juari, bajra) or
_ pulses (gram) alternate. In the United States a three-course
rotation is adopted, with a resulting increase in the yield
of fibre. The plant yields a seed, to which the cotton
fibres adhere. Some varieties have only long fibres, which
- are easily detached. Other varieties have, in addition,
small short fluff, which refuses to come off by any simple
| process. Cotton fibre is a hollow, flattened, and twisted
tube in the better varieties (Sea Island), from about 1} to
24 inches long ; in the Egyptian kind the fibres are generally
from 14 to 2} inches long, and in the Indian the fibres are
usually not more than about one inch in length, but in Indian
cotton considerable amounts of short fluff remain adhering
_ to the seed. Those varieties which produce a naked seed,
that is,a seed from which the long fibres are easily removed,
- leaving the seed naked, are commonly called black seed.
_ Indian varieties, owing to the adhering fluff, are called white
seed. After the cotton fibre has been removed, the cotton
seed still has a considerable value, and is used as an oil
_ seed (see p. 137). Cotton flowers are used for dyes. ‘The
cotton is bound with iron bands into bales, either circular
or rectangular. On arrival at the mills, the bales are broken
up and cleaned. The cotton fibre is then carded, passed
through a drawing machine, and finally made into thread.
It is then commonly woven into some kind of fabric for
the production of cotton cloth. Cotton is “ mercerized,”’

126 PLANT PRODUCTS

by treatment with caustic soda, when it becomes stronger
and more glossy.

Linen.—The flax plant, like cotton, has a double
utility. The flax plant, or linseed, grows in temperate
climates, and can be used either for the production of fibre
for flax, or linseed for food and oil, but not usually with
much satisfaction for both. The crop is rarely grown more
often than once in six or eight years, and does not need a soil
in a very high condition. Linseed is sown on the flat in
well-ploughed land. Potash fertilizers are good, but phos-
phates only encourage weeds. The plants are preferably
pulled by hand, when the plant is only two-thirds of its
full height, that is, pulled about twenty inches high. The
seeds are then either beaten or ripped off, and the straw or
flax is retted, or rotted, by immersion in soft water. In
some cases the flax stems are merely spread out on the grass,
and allowed to decay with dew and rain falling upon them.
This is a process which takes from two to four weeks. Under
the system of pool-retting, the straw is immersed for about
ten days in standing water. In some cases it is preferable
to rett in running water in a stream. Combinations of the
different methods are sometimes used. The fermented
material is then run through a process of breaking and
scutching, combed out, and finally spun like wool or cotton.
Irish linen has the highest reputation, which is said to be
due to the slow bleaching which takes place from exposure
to the wet, pure air from the Atlantic.

Jute.—Jute is a native plant of Bengal. It requires
moisture, and a fairly high temperature. It is sown in
March to May, and cut in four months’ time, when it is six
feet high. The rough foliage having been removed, the
stems are removed in a similar way to the manufacture
of linen, then beaten, and combed out. The crude jute is
packed into bales and then exported for use in sacking and
other rough purposes. Jute, as a material for cloth, has
tended to die out in India, and has been replaced by cotton
materials. The lower patts of the stem often make an
inferior type of jute, and are, therefore, commonly cut off

THE CARBOHYDRATES PRODUCED IN CROPS 127

and used for rougher material. The crude material, on
arriving in this country, has to undergo a certain amount
of treatment through sub-divisions by a process of combing.
Jute fibre is a very crude type of cellulose, or, more strictly,
ligno-cellulose, and usually contains about 10 per cent. water
and 30 per cent. matter soluble in acids and alkalies.

Hemp.—Hemp is used chiefly for the production of
rope, and is a very crude form of cellulose. Many different
plants are used for the production of hemp, but the chief
hemp-producing plant, Cannabis sativa, grows about nine
feet high, and is treated like flax.

Timber.—A very crude and imperfect form of cellulose
constitutes the main structure of all kinds of timber. The
growth of timber trees constitutes the whole science of
forestry, a very large subject indeed. The hard woods,
like oak and beech, grow slowly, whilst some of the coniferous
trees, such as Japanese larch, grow to a usable size in twenty-
five or thirty years. Timber is only economic on very inferior
land or remote situations. Trees are generally felled in the
middle of the summer or winter, to avoid felling them at
the time when the sap is moving. After felling, the logs
are sawn up into planks.

About 1660 a great move was made in planting timber,
and in 1776 Dr. A. Hunter was able to tell the Royal
Society ‘‘there is reason to believe that many of the ships
which, in the last war, gave laws to the whole world, were
constructed from oaks planted at that time’”’ (i.e. 1660
and thereabouts). To-day it is our Army rather than our
Navy that is so dependent on home-grown timber, but we
cannot congratulate ourselves on the wisdom of our fathers
as Dr. Hunter did in 1776. The resuscitation of home-grown
timber production has happened before, and it must happen
again.

Seasoning timber is necessary to prevent warping after
use. Some form of preservative of timber for building
purposes is often needed. Of these, creosote stands in the
front rank, and a preparation called Burnett’s Fluid, or
strong zinc chloride solution (about 50 per cent.), is also used.

128 PLANT PRODUCTS

It is necessary to make the preservative enter well into the
pores of the wood. If the wood is at all wet, ordinary
creosote fails to penetrate, but a solution of zine chloride
will work under these circumstances. Both treatments are
sometimes used, giving a blue-purplish colour to the wood.
By adding to ordinary creosote I or 2 per cent. of wood tar,
and an equal bulk of water, and adding enough sodium
hydrate to make about } per cent. of sodium hydrate in the
total mixture, an emulsion can be produced which will
penetrate well into any timber, even when other methods
are unsatisfactory. ‘These mixtures of soda, water, creosote,
and wood tar can be applied cold, with a brush, to common
larch and pine, giving a pleasing brown colour to fences and
outhouses. Creosote can also be induced to enter into well-
seasoned wood by heating the creosote, or by the use of
pressure. ‘Timber can be kiln dried when time presses.

Paper.—Many of the above types of cellulose can be
used for the manufacture of paper. In former days, the
materials employed for the manufacture of paper were
linen, cotton rags, flax and hemp. Now, however, wood
pulp, bamboo, straw, many rushes, grass, peat, beetroot
refuse, potato stalks, have all found an entry into the paper-
making industry. The potato stalks of town allotments
could be collected economically. Large quantities of wild
grass, such as Soudan sudd, are at present unused, owing to
transport difficulties.

Mechanical pulp is produced by tearing wood to pulp.
Sulphite pulp is produced by treating wood with sulphur
dioxide and water. The solution often used is one containing
about 10 per cent. of sulphur dioxide, employed at a pressure
of about five atmospheres at 100° Cent. Disintegration
takes about twelve hours, more or less, according to the
nature of the wood.

The miscellaneous materials which can be put to the
making of paper have first of all to be disinfected, then cut
into small pieces, and run through special cutting machines.
To remove greasy matters, the materials are boiled with
a solution of caustic soda and caustic lime. Linen rags will

THE CARBOHYDRATES PRODUCED IN CROPS 129

often lose from one-third to one-fifth of their weight through
the process of boiling, whilst inferior materials will lose much
more, After being boiled, the material is washed, and broken
up, so as to disintegrate all the fibres. When the materials
used for paper-making require bleaching, chlorine gas,
bleaching powder or electrolyzed magnesium chloride is
used. The first named is the least satisfactory, and the last
the best. The paper pulp is then separated from the water
by some kind of sieve. Under old-fashioned systems this
was often done by hand, but it is now mostly done by
continuous machines, which separate the paper pulp from
the liquors, often with the aid of a certain amount of suction,
produced by a pump. The paper is rolled by rollers, some-
times with the aid of steam heat.

Destructive Distillation of Cellulose.—All forms
of cellulose, when destructively distilled, produce char-
coal, tar, acetic acid, water, gas, and a few other special
products. The crude forms of cellulose commonly used for
this process introduce many other substances in small
amounts. ‘The form of cellulose most commonly used for
this distillation is some form of wood which is no longer
useful for other purposes. In felling timber the amount
of wood useless for any of the purposes to which timber is
commonly put will generally exceed in weight that of the
useful material. Probably each 1000 acres of wood produce
forty tons per annum of woody material of no value for
ordinary purposes, much of which can be destructively
distilled and converted into useful products. ‘The distillation
of these materials can be divided into two separate systems,
that in which the wood is brought to the still, and that in
| which the still is taken to the wood. Where it is possible
_ to convey the wood to the still, the still can be constructed
of fairly large dimensions. The best of these systems
needs a large retort, eight or ten feet in diameter, and fifty

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or one hundred feet long. Two or more of these are set
in a big setting, and heated with flue gases from furnaces.
_ The temperature in the flues should be between 400° and
- 500° Cent., and the escaping products of combustion will

* ;

130 PLANT PRODUCTS

be 200° and 250° Cent., so that considerable loss of heat
occurs unless some means of utilization is devised. ‘The
wood is placed in trucks and run into the retorts. If the
wood is fairly dry, 25 per cent. of charcoal will be left behind.
The charcoal is preferably rapidly transported in trucks to
a cooling chamber, which is often externally cooled by sprays
of water. When cold, the charcoal is placed in store. The
products of distillation are passed through a fractionating
arrangement, which causes the condensation of the heavier
tars, and then through an ordinary form of condenser,
. where other substances condense. The gas passing away
contains considerable quantities of carbon monoxide, which
is burnt in the fire and assists in maintaining the temperature.
The tar which is separated in the tar separator is boiled to
drive off the water which it still contains. The portion of
the distillate from which the tar has been removed, commonly
called pyro-ligneous acid, is then distilled, to remove the
acetone and methyl alcohol, which are subsequently
fractionated into pure products, with a still of somewhat
similar type to that used in all industrial concerns for
fractionation of volatile substances. The remaining acid is
then treated with lime, at the rate of about four pounds per
ten gallons liquor, when a heavy black sludge is thrown out,
consisting of any excess lime and compounds of the lime with
higher acids of the acetic series and polymerized forms of
aldehydes. After settling for some days, the clear liquid is
removed, boiled down, and, when nearly dry, run over heated
rollers to obtain the acetate of lime ina fine, dry state. Many
attempts have been made to produce a continuous apparatus,
but such are only suited to small wood. Small vertical retorts
also deal very efficiently with small wood. A very excellent
article on this subject is found in Thorpe’s ‘‘ Dictionary of
Applied Chemistry,’’ under the title of “Wood.” Where
the wood is scattered over large areas, it is necessary to
bring the still to the wood, rather than the reverse. For
this purpose a portable plant has been designed by the author
(see Bibliography). A portable machine of the type
described will consume nearly all the waste wood of about

THE CARBOHYDRATES PRODUCED IN CROPS 131

3000 acres ordinary timber. It would also serve the purpose
of any moderate-sized works dealing with about 150 to 600
tons of waste wood per annum, according to whether the
machine was worked continuously or not. With small
plants it is quite impractical to attempt to conserve the
acetone and methyl alcohol. For the purpose of obtaining
charcoal, however, small forms are more economical. The
old-fashioned method of burning charcoal in heaps (see
Bibliography) produces a charcoal with a high percentage of
ash, which for many industrial purposes is extremely objec-
tionable. Distillation in retorts produces a purer charcoal,
but for the purpose of obtaining a charcoal with little ash
larger pieces of wood only should be carbonized. For the
preparation of high-class charcoal for industrial purposes a
small plant is, therefore, more manageable, as it can be used
to produce charcoal of any particular kind. For annealing
or case-hardening steel a charcoal powder containing a high
percentage of volatile matter is preferred. Where this
is the case, the temperature of distillation must be kept
below that stated above. Where a dense charcoal is required,
long protracted heating is necessary. For average conditions
the period of distillation will occupy three or four hours for
each foot in the diameter of the retort. With small laboratory
size retorts distillation can take place in under half an hour,
but in large retorts running up to eight feet in diameter two
days will be found necessary. Bigger retorts than this are
not practicable. Small pieces of wood distil distinctly more
quickly than large pieces. When coniferous wood is distilled,
a valuable product is turpentine. A ton of hard wood on
distillation gives about eighteen gallons of water with little
acid in the first fraction, which is hardly worth saving,
and thirty gallons of strong pyro-ligneous acid in the second
fraction. The economy in treatment by this fractionation
compensates for some of the disadvantages of an intermittent
machine.

Charcoal from coconut shells has a high absorptive
power for gases or vapours.

(4) Gum and Mucilage.—The name “ gum ” is a general

132 PLANT PRODUCTS

term for a large group of plant products, which are exuded
by wounds and are transparent. Gum arabic, obtained from
the various species of acacia, is one of the best of these. The
gum is obtained by artificial incision of the trees, soon after
the end of the rainy season and is collected at intervals
of every few days, so long as the weather permits. Trees
of about eight to twelve years of age are usually the most
productive. East Indian gum arabic, though shipped from
Bombay, is very often not produced in India, but has been
collected in other parts and transported to Bombay for
shipment. Australian, or wattle-gum, is a product of
several specis of acacia, called by the local name of wattle.
Gum is much more soluble in hot than in cold water, forming
a thick liquid, and is precipitated by alcohol or lead acetate.
Although the gums are commonly included in the carbo-
hydrate group, their constituents are by no means pure
carbohydrate. The chief constituent of gum arabic is
arabin, which, on hydrolysis, yields arabinose, galactose, and
an acid of high molecular weight, CogH 3.099, arabic acid.

Agar.—Agar gum, the dried jelly of seaweed, is chiefly
obtained from China and Japan, but is very plentiful where
there is plenty of seaweed. The special gum contained is
known as gelose, which is soluble in water, weak alcohol, and
alkalies. Even a solution of } per cent. of agar is faitly
solid in ordinary temperatures. Seaweed, when boiled with
water, forms the nucleus of many articles of food used in
Cornwall and in Japan. It is, however, not easily digested,
but is useful, admixed with milk, in preventing the formation
of a hard curd in the stomach.

Mucilage. —Many seeds of plants, for example linseed,
when macerated with water, produce a thick adhesive
mucilage which can be used in place of gum.

REFERENCES TO SECTION II, A (Sucar)

Collins, ‘‘ Value of the Turnip as a Vegetable and Stock Food,” Journ.
Board of Agriculture, 1916-17, p. 66.

Collins, “‘ Variation in the Chemical Composition of the Swede,” Journ.
Agric. Science, i., p. 89.

LHE CARBOHYDRATES PRODUCED IN CROPS 133

Collins, ‘‘ The Relative Amounts of Dry Matter in Several Varieties
of Swedish Turnips,” Proc. Univ. Durham Phil. Soc., vol. iii., p. 303.
(Andrew Reid, Newcastle-on-Tyne.) ;

Hendrick, ‘‘ The Composition of Turnips and Swedes,” Trans. Highland
and Agricultural Soc., Scotland, 1906.

Collins, ‘‘ Sugar in Swedes,”’ Journ. Soc. Chem. Ind., 1901, p. 536; 1902,
p. 1513.

Wood and Berry, “‘ A Rapid Method of Estimating Sugar,’’ Proceedings
of the Cambridge Philosophical Society, vol. xii., part ii., p. 112.

Denbigh, “‘ Beet Sugar as a British Industry,’”’ p. 21. (The National
Sugar Beet Association, Ltd.)

Leather, ‘‘ Memoirs of the Department of Agriculture in India,’’ Oct.,
1913, p. 113. (Thacker and Co.)

Home Counties, ‘‘ Sugar Beet,”’ p. 5. (Horace Cox.)

Leather and Mollison, “* The Agricultural Ledger,” 1898, No. 8, p. 2.
(Government Central Press, Bombay.)

Aubert, ‘‘The Manufacture of Palm Sugar,” Agric. Journ. Ind., tg1t,
Pp. 369.

Martineau, “‘ Sugar,” p. 41. (Pitman.)

Higgins, ‘‘ Observations and Advices for the Improvement of the
Manufacture of Muscado Sugarand Rum,” p.9. (Aikman.)

Mackenzie, “‘ The Sugars and their Simple Derivatives,” p.12. (Garney.)

Collins and Hall, ‘‘ The Composition of Sugar Beets Grown in the
Northern Counties,’ Journ. Soc. Chem. Ind., 1913, p. 929.

“‘ Discussion on Production and Refining of Sugar within the Empire,”
Journ. Soc, Chem. Ind., 1915, p. 316.

Potvliet, ‘‘ The Beet Sugar Industry in Canada,”’ Journ. Soc. Chem. Ind.,
1916, p. 443.

Orwin and Orr, ‘‘ The Cultivation of Sugar Beet in the West of Ireland,”
Journ. Board of Agriculture, 1915-16, p. 210; do. in Norfolk and Suffolk,
1914-15, p. 969.

Leather, “‘ Manuring Sugar Cane,” Agric. Journ. India, 1906, p. 13.

Barber, ‘‘ Sugar Cane Cultivation in Godavari,” Agric. Journ. India,
1907, Pp. 33-

Chadwin, ‘‘ The Cantley Beet Sugar Factory,” Journ. Board Agriculture,
1913-14, p. 569.

Dowling, ‘‘ The Production of Beet Sugar in a Continental Factory,”
Journ. Board Agriculture, 1911-12, p. 1005.

REFERENCES TO SECTION II, B (Srarcn)

dite) and Hill, ‘‘ The Chemistry of Plant Products,” p.93. (Longmans
an -

Radhakamal Mukerjee, ‘‘ The Foundations of Indian Economics.”
(Longmans and Co.)

Archbold, ‘‘ The Manufacture of Maize Starch,” Journ. Soc. Chem. Ind.,
1902, p. 4.

Dyer and Shrivell, “‘ The Manuring of Market-Garden Crops,” p. 92.
(Vinton.)

Wallace, “‘ Indian Agriculture,”’ p. 203. (Oliver and Boyd.)

Wiley, ‘‘ The Manufacture of Starch from Potatoes and Cassava.”’
(Government Printing Office, Washington.)

Howard, “‘ Wheat in India.”” (Thacker.)

Church, “‘ The Food Grains of India.”” (Chapman.)

Gilbert, ‘‘The Potato.” (Macmillan.)

REFERENCES TO SECTION II, C (CELLULOSE)

Hall and Russell, ‘‘ Agriculture and Soils of Kent, Surrey and Sussex,”’
p. 50. (Board of Agriculture and Fisheries.)

134 PLANT PRODUCTS

Watt, “ The Art of Paper-Making.” (Crosby Lockwood and Son.)

“Flax Growing,” Journ. Board Agriculture, 1914-15, p. 1007.

Tom, “‘ Department of Agriculture and Technical Instructions, Ireland,”’
TQOI4, P. 515.

Nystron, “‘ Textiles,” pp. 38 and 112. (Appleton.)

Benson and Davis, ‘“‘ Free Carbon of Wood-Tar Pitches,” Analyst,
June, 1917, p. 212.

Wallace, ‘‘ Indian Agriculture,” pp. 203, 247. (Oliver and Boyd.)

Roberts, ‘‘ Bark Stripping,’ Journ. Land Agents’ Soc., July, 1908, Pp. 314.

Collins, ‘‘A Portable Plant for the Distillation of Wood,’ Journ.
Soc. Chem. Ind., 1917, p. 68.

Collins and Hall, ‘‘ The Use of Coal Tar Creosote and Naphthalene for
Preserving Wooden Fences,” Journ. Soc. Chem. Ind., 1914, p. 466.

“The Manufacture of Charcoal,” Journ. Board Agriculture, 1914-15, Pp.
1033.
Rowley, “‘ The Commercial Utilization of the ‘ Grass Tree ’ (Xanthorrhea)
and ‘ Zamia ’ (Macrozamia) in Western Australia,” Journ. Soc. Chem. Ind.,
Ig16, p. 290.

Briggs, “‘ Some Causes of Damage in the Bleaching of Linen and Cotton
Textiles,” Journ. Soc. Chem. Ind., 1916, p. 78.

Briggs, ‘‘ The Paper Mill Chemist in War Time,’’ Journ. Soc. Chem. Ind.,
1916, p. 798.

Cross, ‘‘ Cellulose and Chemical Industry,’’ Journ. Soc. Chem. Ind.,
LQI7, p. 531.

Klason, Heidstam and Norlin, ‘‘ Dry Distillation of Cellulose,” Journ.
Chem. Soc., 1908, A. 1, p. 717.

Klason, Heidstam and Norlin, ‘‘ Investigations on the Charring of Wood,”'
Journ. Chem. Soc., 1908, A. 1, p. 955.

Boulton, ‘‘ Antiseptic Treatment of Timber,’ Journ. Soc. Chem. Ind.,
1884, p. 622.

Fletcher, ‘‘ Improvement of Cotton,” Agric. Journ. India, 1906, p- 351.

Stebbing, “‘ British Forestry.’’ (Murray.)

“Some Douglas Fir Plantations,” Journ. Board Agriculture, 1913-14,
p. 1087.

Coventry, “‘ Rhea Experiments in India,” Agric. Journ. India, 1907, p. 1.

Smith, “‘ Jute Experiments in Bengal,” Agric. Journ. I ndia, 1907, p. 140.

Elimore and Okey, ‘‘ Osier and Willow Cultivation,’ Journ. Board of
Agriculture, 1911-12, pp. 12, 207, 557, 906.

Somerville, ‘‘ Increasing the Durability of Timber,” Journ. Board of
Agriculture, 1911-12, p. 283.

REFERENCES TO SECTION II, D (Gum)

O'Sullivan, ‘‘ Gum Tragacanth,”’ Journ. Chem. Soc., 1901, T. 1164.

Schryver and Haynes, ‘‘Pectic Substances of Plants,’’ Biochem.
Journ., 1916, p. 539.

Imperial Institute Report, ‘‘ Gums and Resins.”

Section IIJ.—THE FORMATION OF OILS
IN PLANTS

Linseed.—Linseed has already been described under the
subject of linen (p. 126), but it is also used for the
production of an oil seed. Where the plant is grown in
cold, damp climates, the situation favours the production
of fibre, but where it is grown in drier and warmer districts
the situation favours the production of seed. It can be
grown in many countries, but the chief sources of linseed
are Russia, India, and the Argentine. Linseed contains
about 35 per cent. of oil, which is expressed both on the large
and on the small scale. When linseed is imported into Great
Britain it is generally first of all cleaned from its miscellaneous
impurities, often amounting to 10 per cent., and the purified
linseed run through rollers to crush it without actually
expressing oil. It is then passed through a “ kettle,’’ where
it is subjected either to direct steam heat, or to the heat
from steam passing through a coil, or both. Linseed grown
in India is very dry, and requires the moisture content
to be increased, which is conveniently done by blowing steam -
into it. Linseed obtained from the Baltic ports is some-
times rather too damp for the process, and the steam is,
therefore, passed through a coil, so as to both heat and slightly
dry the linseed. ‘The linseed is then placed between felts
which are, in turn, placed between corrugated iron sheets,
which are built up into a pile of twenty or thirty in a hydraulic
ptess. The name ‘hydraulic press” is here somewhat of a
misnomer, because in practice the liquor used in the pumps
is not water, but the oil which is being produced at the time.
If water were used, any leak in the press would damage the
oil, but when the oil itself is used this is not possible. As

136 PLANT PRODUCTS

soon as the pressure is applied the oil begins to run out, and
is collected in a well. On long standing, small quantities
of mucilage are formed in the oil. For the best qualities
of oil the crude oil is filtered. Linseed can be extracted
with petroleum spirit, but it is very rarely treated in this
way, because linseed cake rich in oil has a high value as
cattle food.

Dark linseed oil is commonly refined by treatment with
sulphuric acid. The refined oil is also subjected to sun
bleaching in some cases. L[jinseed oil, in addition to the
ordinary fatty acids, contains linoleic and linolenic acids.
Linseed oil has a high iodine value, and is a drying oil
occupying the first rank. Boiled oil is obtained by heating
linseed oil to a temperature of about 150° Cent., with the
addition of driers, which often contain manganese and lead.
Linseed oil is also vulcanized by sulphur chloride to form a
rubber substitute (see p. 165).

The remaining linseed cake as it comes out of the press
is still somewhat warm, and is sometimes dipped in water,
to give the cakes a bloom. It is then sold for cattle food.
Under ordinary farm conditions, where the chief part of the
home-grown food consists of hay, straw, turnips, and tail
corn, the purchase of a food containing some oil is highly
desirable, and linseed is one of the most popular of these
materials. Linseed cakes generally contain about II per cent.
of oil, rather less in those of American manufacture, rather
more in those of Russian origin, about 32 per cent. of
albuminoids, rather more in cakes of American origin, and
rather less in cakes of Indian origin, and do not contain
more than about 7 per cent. of fibre. Linseed cake is reckoned
as one of the safest of cattle foods, and is a favourite for
rearing calves on. Linseed contains a cyano-genetic
glucoside called linimarin, which, by the action of the proper
enzyme, contained in the linseed, will develop prussic acid,
acetone, and glucose under certain conditions. If ground
linseed cake be placed in water at temperatures between
20° and 60° Cent., the action of the enzyme on the linimarin
will begin. ‘The rate at which the prussic acid is evolved

THE FORMATION OF OILS IN PLANTS 137

depends upon a variety of circumstances, which are not very
likely to occur under ordinary conditions of feeding, but which
may be found when the feeding is conducted on careless
lines. It happens that linseed grown in hot climates contains
mote poison than linseed grown in Great Britain, but since
it is also drier, the manufacturer uses steam before pressing
it, thus undesignedly counteracting the poison. ‘The extent
to which this takes place varies according to the details
of manufacture in the works concerned. ‘There is extremely
little risk of adult animals in good health being poisoned.
So long as the seed is fed whole, or only simply crushed,
there is little risk of poison being formed, but if linseed cake
in the form of fine meal is partly mixed with warm water,
it remains in the form of small balls. Calves, if fed with
such badly made linseed mash, do not properly chew the
balls, but swallow them whole, so that they break up in the
stomach and liberate the prussic acid. Where linseed, or
linseed meal, is actually boiled with water, the enzyme is
completely destroyed. Once the enzyme has been checked
by the action of acid or alkali it is not able to recover its
old vigour. A degree of acidity equal to ,,59 normal
hydrochloric acid is sufficient to check the activity of the
enzyme. Where care is taken in the preparation of the
meal no poisoning cases arise. Linseed, like most of
the oil seeds, contains no starch.

Cotton. —The growth of the cotton plant has been already
described, and its use for the manufacture of fibre (p. 125).
After the cotton fibre has been removed from the seeds, the
latter form a valuable part of the crop. Like linseed, cotton
seed is rich in oil, containing about 30 per cent., although
some varieties, especially those of Indian origin, are all
lower in their oil content. Oil obtained from fresh seed
is paler in colour than that from old seed, but the latter is
clarified by washing with caustic soda and cooling till
stearin separates out. Cotton-seed oil is not a drying oil,
like linseed, and is used for lubricating purposes, and for
replacing olive oil, butter, and other edible fats.

Owing to the large amount of husk enclosing the cotton

138 PLANT PRODUCTS

seeds, the fibre amounts to 18 per cent. ‘Two systems of
pressing the cakes have arisen. (1) Where the seed is
pressed whole, the husk remains in the cake, and whilst
it provides a good channel for the escape of the oil, it acts
as an absorbent, and prevents some of the oil flowing out.
(2) Where the husk is removed, a lower pressure suffices,
but it is not possible to leave the cake with as low a percentage
of oil. There are, consequently, many types of cotton cake
put upon the market. The Indian cotton cakes derived from
seed grown in India and pressed in England usually contain
about 4} per cent. of oil, 19 per cent. of albuminoids, and 21
per cent. of fibre, and are often dirty and sandy. ‘The short
fluff remaining on the seed hinders cleaning previous to
pressing. Most Egyptian cotton cakes contain about 5 per
cent. of oil, 23 per cent. of albuminoids, and 19 per cent.
of fibre, and have a somewhat higher feeding value than
Indian cakes. Decorticated cotton cakes are produced
in America by removing the husks of the seed previous to
pressute. These usually contain 11 per cent.-of oil, 40 per
cent. of albuminoids, and 8 per cent. of fibre, but great
variations occur. Where these cakes are extracted by
petroleum spirit the percentage of oil is reduced, and where
the decortication is indifferently performed the fibre may
rise to 15 percent. At one time there was a habit of treating
Indian cotton cakes with small quantities of borax, for the
purpose of preventing fermentation and subsequent dis-
coloration. ‘The fashion, however, appears to be dying out.

The Soy Bean.—The soy bean is grown very largely
in Japan and Manchuria, as well as in other parts of the world.
Many crops of soya-bean seeds only contain 16 per cent. of
oil. The oil is pressed in the same way as the other oil seeds
named above, and the resulting cake contains about 6 per
cent. of oil, 42 per cent. of albuminoids, and 5 per cent.
of fibre. Soya-bean oil belongs to the drying class of oils,
but it is not equal to linseed in this respect. The cake
remaining is a particularly palatable one, and much appreci-
ated by all cattle. The bean itself is frequently used for
human food in the East, and experiments are being made to

ne

THE FORMATION OF OILS IN PLANTS 139

grow soy beans in Australia, South Africa, the United States,
Italy, Spain, South America, and even in the British Isles.
In the crude preparation of the oil in Manchuria the beans
are soaked in water over-night, crushed, and boiled with
water, so that the oil cells are broken. ‘The oil is then
expressed in a very primitive press. In spite of the primitive
character of this method of preparation, as much as 13 per
cent. of oil is said to be expressed, at the expenditure of
much labour and time, whilst modern machinery rarely

succeeds in extracting more than 12 per cent.

Palm Nuts and Coconuts.—The coconut palm is a
tree growing to a considerable height, chiefly inhabiting
the sea-coasts of the tropical regions. It is propagated from
the nuts in nurseries and planted out. About 7 tons of
coconuts can be obtained per acre of plantation. The
coconut is dehusked and dried, and the resulting material,
known as copra, is expressed for its oil. The palm kernels
contain nearly 50 per cent. of oil. The oil so obtained from
the palm nuts or the coconuts, on cooling, throw out much
solid material, which can be used for the manufacture of
margarine or soap. ‘The remaining cakes are of the following
composition. ‘The coconut cakes vary from about 7 to
12 per cent. of oil, from 19 to 22 per cent. of albuminoids,
and 10 to 13 per cent. of fibre, whilst the palm nut cakes
vary from about 7 to 10 per cent. of oil, from about 17 to
21 per cent. of albuminoids, and 11 to 16 per cent. of fibre.
The palm kernels are not infrequently extracted with
petroleum spirit, in which case the oil in the residue, which
is often sold as palm kernel meal, is as low as I to 3 per cent.
of oil. Whilst coconut and palm nut cakes and oils have a

considerable degree of resemblance, there are some points

which differentiate them, both in their history and in the
character of their products. ‘The coconut has been known
since the earliest times as a food material in India, and the
South Sea Islands. When unripe they are often used as
drinking coconuts—that is, they are removed from the trees
in the green condition, the top sliced off, and the “ milk,”
which looks more like ginger beer, drunk from the shell.

140 PLANT PRODUCTS

For the preparation of oil the primitive system consisted in
removing the husk, cutting up the kernel into small pieces,
exposing in piles to the heat of the sun, so that the oil ran
off and was collected. Another method was that of pulping
the kernels and placing them in a kind of sieve exposed to
the sun, when the oil ran off and was collected. Sometimes
artificial heat was used. In India the dried kernels were
ground in the primitive oil press, or were thrown into
boiling water and the oil skimmed off. The residues were often
used locally for cattle food. The dried husk, known as
copra, is liable to ferment, due to the presence of water, and
many of the difficulties of manufacture and the prejudice
against the materials resulted from this cause. Modern
systems eliminate much of this difficulty, by first removing
the fibrous matter (coir) and then striking the nut on a
sharp spike. ‘The husk is removed by hand and the nut split,
drained and put in the sun to dry. Sun-dried copra gives
better quality oil than that which has been dried in kilns, -
but improvements in the kiln system of drying are likely
to remove this difficulty. ‘The coconut shells are used for
firing the kilns (see p. 131). In the modern system of
pressure, two pressings are carried out, the temperatures
adopted being higher than those used for linseed as described
above. About 65 per cent. of oil can be obtained from the
best qualities of copra. Owing to the fermentive changes
alluded toabove it is not infrequent for considerable quantities
of free fatty acid to be present in the oil, but the great care
taken in modern manufacture tends to reduce this degree
of acidity. Owing to its high melting point, coconut
oil is not infrequently met with in the solid or semi-solid
condition. Although coconut oil requires a high strength
of alkali and high temperature for saponification, yet
with alkali of the right strength soap is formed at ordinary
temperatures. Soap made from coconut oil is soluble in
weak salt solutions and is used for washing in sea-water.
Although this confers an advantage in certain uses of the
soap, it compels the manufacturer to employ more salt
to throw soap out of solution in the boiling vat.

THE FORMATION OF OILS IN PLANTS 141

The oil palm tree, which gives the palm kernel oil, more
frequently grows inland in open country and bush land, in
contradistinction to the coconut, which grows chiefly on
the sea border. Neither trees are commonly met with at any
considerable altitude. The rough method by which the
palm nuts are collected causes much injury to the kernels
and results in subsequent hydrolysis of the oil. The outer
layer of the fruit is removed for making palm oil, and the
nuts are shelled. In the rough preparation the kernels
are often fermented before pressing, which also causes the
same difficulty alluded to above in coconut oil. The rough
purification of this crude oil is often carried out by boiling
up with water. Palm oils not infrequently have as high
as one half of their total amount of fatty acids in the free
condition, accompanied, of course, by the corresponding
amount of free glycerine. In recent years the palm kernels
have been brought into Great Britain and have been pressed
in home machinery of modern type. The result has been
that much superior oils have been obtained, with far less
free fatty acids, and the resulting oil cakes have also been
superior. The oil is mostly used for soap, candles, and
margarine. Whilst many of the early makes of both cakes
were distinctly rancid, yet the modern cakes are relatively
free from this objection. Nevertheless, cattle do not take
kindly to either of these cakes at first. It is usually less
difficult to persuade cattle to eat coconut cake than palm-
nut cake. When coconut cake has been only slightly
pressed it is very apt to absorb moisture so readily as to break
itself up and burst the sacks in which it has been placed.
As much as 10 per cent. of water may easily be absorbed by
such cake when standing in ordinary barns on the farmstead.
As, however, this difficulty has become recognized, and as the
oil is very valuable, manufacturers are now usually taking
greater care to press the cakes more completely, and they
are thereby producing a bigger yield of oil and at the same
time a cake which, though it may look less satisfactory
on analysis, is more practically useful, because it does not
absorb water nor turn rancid on storage. Palm kernel

142 PLANT PRODUCTS

cake has a very dry and unsatisfactory flavour. Unless
it be mixed with some damp food the cattle will merely
blow it away with their noses, and never eat it at all, but if
it be moistened, or mixed with turnips, the cattle, after a
little experience, can be induced to eat it. The difficulty
under this head is only what has been observed on many
occasions before, cattle do not take readily to new-fashioned
food, and it takes a good deal of patience and persuasion
to induce them to eat something they have never tasted
before. In time, of course, these difficulties are overcome.
Earth Nuts.—The earth nut, or ground nut, is a tropical
annual leguminous crop which has the peculiarity that the
fruits bury themselves in the earth. It will grow in sandy
soils, is very valuable as a course in tropical rotations, and
lends itself well in conjunction with cotton on irrigated light
land. In some cases the ripe fruits are actually dug out of
the earth, or in others the crop is taken before the fruits
have had time to enter. Earth nuts are largely grown in
Madras, and shipped from Pondicherry to Marseilles. The
best qualities come from Rufisque, in Senegal. Sometimes
the pods are removed from the beans, and sometimes the
materials are pressed whole. The actual bean contains
about 40 to 45 per cent. of oil, and 28 per cent. of albuminoids.
Earth nuts are not infrequently fractionally expressed, the
best quality oil, cold drawn, being expressed at the ordinary
temperature, and one or two other fractions made at
increasing temperatures afterwards. The best qualities
of oil, that is, those that are cold drawn, are used in the
manufacture of salad oil, and the second qualities for the
preservation of sardines, and the manufacture of margarine.
The lowest quality, that expressed at the highest temperature,
is used for soap-making. A characteristic fatty acid of
earth nuts is arachidic acid. Earth-nut oil is a non-drying
oil. Earth-nut oil is largely used to replace olive oil in all
its uses. When the husks are removed, the resulting cake
contains 7 tog per cent, of oil, and 45 to 48 per cent. of albu-
minoids, and 5 to 7 per cent, of fibre. When the husks
have not been removed, the fibre may vary from about

THE FORMATION OF OILS IN PLANTS 143

18 to 30 per cent., with a corresponding reduction in the
other constituents. ‘The resulting cake is highly esteemed
as a cattle food, being of a very palatable nature.

Rape Seed (Colza, Sarson).—Rape seed is grown in
European countries and also very largely in India. The
bulk of the East Indian seed is imported from Calcutta,
Madras, and Bombay, the large-growing districts being in
Guzerat and Ferozepore. Rape seed contains about 33
to 43 per cent. of oil, 22 to 27 per cent. albuminoids, and 4
per cent. fibre, the French seed being the richest in oil.
It is crushed between rollers in the same way as the other
oilseeds. ‘The crude oil is dark coloured, and generally needs
to be refined by treating at the ordinary temperature with
about I per cent. strong sulphuric acid. The cold-drawn
oil is used in India as an edible oil. ‘The oil is also used for
lubricating purposes, and for the manufacture of soap.
The cakes obtained after pressing the oil are of somewhat
doubtful utility for feeding cattle. Rapeseed often contains
materials which develop a mustard oil after hydrolysis
by an enzyme. The amount of proper enzyme in rape is
commonly deficient, but the admixture of mustard seed
provides the necessary enzyme for developing the mustard
oil. ‘The problem is, therefore, parallel to the development
of prussic acid in linseed. When the cakes are perfectly
pure, and free from mustard seed, and have not become
acted upon by heat and moisture, the material may be
fed with safety, but there is always the risk that either
insufficient cleaning in manufacture, or improper systems
of feeding the cattle, may give rise to the development of
mustard oil, which is pungent and irritating to the animals,
and has been reported to have actually caused death.

Safflower Seed.—‘This plant has been grown in India
to a large extent, originally for the preparation of saffron
dye, but the seeds are also pressed for their oil. They are
rich in oil, containing 30 to 35 per cént., but, owing to the
very thick, springy husk, great difficulty occurs in expressing
the oil, but the oil is prepared in India on a small scale for
local purposes, being largely used for human consumption.

144 PLANT PRODUCTS

On the small scale, it is not infrequent to mix the safflower
seed with other seeds before pressing. Safflower oil has good
drying properties, but not equal to linseed. It, nevertheless,
can replace linseed for such purposes as preserving ropes,
etc., from the action of water and air. It is used in India
also largely for decorative purposes, the “ wax cloth’ being
largely made by drawing artistic designs with the aid of this
oil, and then dusting on mica, or other glistening materials.
The saffron dye is made from the yellow florets, which are
plucked and dried.

Sesame, Gingelly, Til Seed (Sesamum Indicum).—
This is an annual plant grown throughout the tropics and
sub-tropics. Sesame seeds are rich in oil, containing from
45 to 57 per cent. of oil and usually have to be pressed more
than once. The bulk of the business has previously been
carried out at Marseilles, where a cold-pressed oil is obtained
first, and then further oils obtained by the addition of water
and the raising of the temperature, by which means another
I0 per cent. can be obtained. The best quality oil, cold
pressed, is a good, colourless and odourless oil, but that
obtained from the later pressings is of inferior quality.
Sesame oil is a slow-drying oil, and is liable to become rancid
with considerable rapidity. It can, however, be used as a
substitute for olive oil, and is used in the manufacture of
margarine, the lower qualities being used for soap-making
and for rather inferior lubricating oils. ‘The cake contains
about 30 to 40 per cent. of albuminoids and only 6 per cent.
fibre.

Niger Seed is a plant originally coming from Abyssinia,
but is now also cultivated in India. The seeds contain
about 40 per cent. of oil, Ig per cent. albuminoids, and 14
per cent. fibre, whilst the cake contains 30 to 35 per cent.
albuminoids and 18 per cent. fibre.

Mowha or Mowra Seed (Bassia Seed).—The two
species of bassia which provide the mowha seed are grown
in India and Ceylon, one species grown in the northern or
extra-peninsular portion, and the other in the southern or
peninsular portion. Mowha fat is soft and yellow, like

THE FORMATION OF OILS IN PLANTS 145

butter, and can be used for edible purposes. It is removed
from the mowha kernels in the same way as most forms of
oil. The cake left after crushing the oil contains much
saponin, a poisonous glucoside. The cake has been fed to
cattle without actually killing them, but the feeding results
have been very unsatisfactory. Efforts have been made to
extract the saponin by a commercial method, but, up to the
present, no particular success has resulted. Mowha cake,
as well as the true soap nut, has been used for exterminating
worms from lawns, and for several other horticultural
purposes. As the mowha cake has some manurial value,
and is relatively rather rich in potash, after the saponin has
done its work of destroying insect life, it serves as a manure,
the nitrogen amounting to 2} per cent. and the potash to
1} per cent.

Hemp Seed Oil.—Hemp has been referred to for its
fibre (see p. 127), but the seed can also be pressed for its
oil. When fresh drawn, the oil is of a pale colour, but soon
becomes darker on keeping. It is used for illuminating
purposes, for soap, and also in varnishes.

The Essential Oils.—The greater number of these oils
are used as scents, requiring a special trade, but of the
common materials under this class, oil of turpentine is
the most important. Many species of pine trees serve as
sources for this material. Under the best systems, after
carefully removing the bark, vertical incisions are made in
the tree. Sticky resinous matter oozes out, and is received
by a cup, which is placed immediately under the slits. ‘These
slits are gradually extended in an upward direction, and the
cups follow them. When the crude exudation of the trees
is distilled with water, oil of turpentine distils over, and the
remaining material is known as colophony or rosin.

REFERENCES TO SECTION III

Sern “Notes on Some Fatty Oils,” Journ. Soc. Chem. Ind., 1916,
p. 1089.

Imperial Institute Monograph, ‘‘ Oil Seeds and Feeding Cakes.”
(Murray.)

Leathes, “‘ The Fats. Monograph on Bio-chemistry.” (Longmans.)
D. Io

146 PLANT PRODUCTS

Collins, ‘‘The Rate of Evolution of Hydrocyanic Acid from Linseed
under Digestive Conditions,’’ Proc. Univ. Durham Phil. Soc., 1912, iv.
p. 99; Journ. Chem. Soc., 1912, A. ii. 586.

Collins, ‘‘ The Feeding of Linseed to Calves,”’ Journ. Board of Agriculture,
IQI5-16, p. 120.

‘Linseed as a Farm Crop,” Journ. Board of Agriculture, 1915-16,
p- 1069.

Morrell, ‘‘ Polymerized Drying Oils,” Journ. Soc. Chem. Ind., 1915,
p. 105.

Hyland and Lloyd, “‘ The Oxidation of Fatty Acids,” Journ. Soc. Chem.
Ind., 1915, p. 62.

Maidment, ‘‘ The Home Dairy,” pp. 13 and 94. (Simpkin, Marshall.)

Collins and Blair, ‘‘ The Liberation of Hydrocyanic Acid from Linseed,”
Analyst, 1914, p. 70.

Fowler, ‘‘ Bacterial and Enzyme Chemistry,” p. 160. (Arnold.)

Voelcker, ‘‘ The Characters of Pure and Mixed Linseed Cakes.” (Clowes.)
Journ. Roy. Agric. Soc.

Vakil, ‘‘ Cotton Seed Products,” Journ. Soc. Chem. Ind., 1917, p. 685.

Crowther, ‘‘ Palm Kernel Cake,’”’ Journ. Board of Agriculiwre, 1916-17,
P. 734-

Crowther, ‘‘ Palm Kernel Cake and Meal as Food for Pigs,” Journ.
Board of Agriculture, 1916-17, p. 850.

Browning and Symons, “‘ Cocoanut Toddy in Ceylon,” Journ. Soc.
Chem. Ind., 1916, p. 1138.

‘‘Ground Nut Cake,” Journ. Board of Agriculture, 1915-16, p. 308.

Collins, ‘‘ Agricultural Chemistry,” p. 14. (Government Printing
Office, Calcutta.)

Roure Bertrand Fils, Bulletins. (Grasse, France.)

Copeland, ‘‘ The Coconut.’’ (Macmillan.) .

Dunstan and Henry, ‘‘ Cyanogenesis in Plants,’ Proc. Roy. Soc., 1903,
p. 285.

Auld, ‘‘The Hydrolysis of Amygdalin,” Journ. Chem. Soc., 1908,
T. 1251. :

Bulletin Imperial Institute, ‘‘Palm Kernels,” 1914, p. 459.

“The Cultivation of Soy Beans in Britain,” Journ. Board of Agri-
culture, 1912-1913, p. 33.

“The Growing of Linseed for Feeding Purposes,” Journ. Board of
Agriculture, 1913-14, P. 377.

Eyre and Fisher, ‘‘Some Considerations affecting the Growing of
Linseed as a Farm Crop in England,”’ Journ. Agric. Science, vii., p. 120.

Mitchell, ‘‘ Edible Oils and Fats,” p. 24. (Longmans.)

Parry, ‘‘Gums and Resins.”’ (Pitman.)

ae

Section [V.—THE NITROGEN COMPOUNDS
IN PLANTS

As the study of the animal proteins already forms the
chief subject matter of one of the other books of this series
(Bennett), it will only be necessary to indicate in this section
some of the differences occurring between the vegetable
proteins and the animal proteins, and to give details of
nitrogenous bodies other than proteins.

The Cereal Proteins.—In the eighteenth century a
considerable amount of work was done in examining the
protein matter in wheat. In 1747 Beccari examined wheat
flour, and concluded that wheat gluten resembled animal
matter. ‘The process chiefly used in that day was destructive
distillation. Kessel Myer, in 1759, determined the action
of various sulphates upon wheat gluten, and in 1773 Rouelle
showed that the wheat gluten was also present in various
other plants. Parmentier showed that wheat gluten was
insoluble in mineral acids, but soluble in vinegar, and that
there was some relationship between the colour of flour and
its gluten content. In the nineteenth century the solubility .
of wheat gluten in alcohol was also considered, and the
elementary position of the proteins began to be accurately
studied. Destructive distillation at this period seems to have
been the method of the investigators.

The chief protein in wheat grain is now called glutenin,
and the next most important gliadin, ‘These are contained
in slightly greater quantities in spring wheat than in winter
wheat, but this variation is very likely due to the longer
period during which winter wheat grows. Reserve seed
proteins are usually more stable towards reagents than the
proteins which form part of the living substances of the

148 PLANT PRODUCTS

plant, and the composition of the reserve proteins appears
to vary more than does the composition of the proteins that
‘take part in the active life of the plant. Extraction with
somewhat diluted alcohol has been employed to remove some
of the proteins of cereal seeds, although in other seeds such
_extraction with alcohol yields but little protein. Extraction
with alcohol can be made at any temperature up to its boiling
point, if the alcohol is sufficiently concentrated to inhibit
hydrolysis. By evaporating such a solution in fairly strong
alcohol, the alcohol evaporates first, the percentage of water
increases, and the proteins become insoluble. On the other
hand, from fairly concentrated solutions protein may also
be separated by adding absolute alcohol, since in absolute
alcohol proteins are insoluble. ‘The addition of ether
assists in this precipitation of protein. Roughly speaking,
solutions containing less than 50 per cent. of alcohol,
ot more than 93 per cent. of alcohol, do not dissolve cereal
proteins. Other alcohols than ethyl alcohol can be used for
solutions. Zein, from maize, can be dissolved in boiling
acetic acid without any apparent change, and is also particu-

larly resistant to the action of alkalies, even 2 per cent..

of potassium hydrate at 40° Cent. during 24 hours giving
little evidence of alteration. Zein also shows a unique
behaviour towards alcohol, because, when dissolved in strong
alcohol, the solution becomes gelatinated. In such circum-
stances, however, the original nature of the protein appears
to be permanently altered. The globulins differ in a marked
degree from the animal proteins, for most of them are very
incompletely coagulated by heating the solution, even to
boiling point. The vegetable proteins have a fairly marked
specific rotary power towards polarized light. Gliadin,
from wheat, rye, and barley, has a high rotary power,
corresponding to about — 100°; but zein, from maize, has
a telatively low specific rotary power of about — 30°.
The hydrolysis by acids of the vegetable proteins are of
much the same general character as those from the animal
proteins. The vegetable proteins are generally more difficult
to completely hydrolize than the animal proteins, and a

St

THE NITROGEN COMPOUNDS IN PLANTS 149

much longer hydrolysis is generally found necessary. The
amino acids which have been obtained from the vegetable
proteins are the same as those yielded by the animal proteins
with the exception of di-amino-trioxy-dodecanic acid. In
general, the plant proteins yield more glutaminic acid and
ammonia than do the animal proteins. The proteins soluble
in alcohol yield the basic amino acids in a very small pro-
portion, and yield no lysine. The vegetable proteins always
contain more nitrogen than the animal proteins. The split-
ting products of the cereal proteins are marked by the high
proportion of non-basic nitrogen, the low proportion of
basic nitrogen, the high proportion of ammoniacal nitrogen,
and the small amount of lysine. Glutenin and gliadin,
both wheat products, are characterized by the high yield
of ammonia in comparison with the glutaminic and aspartic
acids present. These proteins must, therefore, contain some
nitrogen not occurring in the usual type of amino-acid amide
like asparagine. A marked division between the cereal
proteins and those of animal origin lies in the fact that the
former are completely free from phosphorus. Of course,
imperfectly purified specimens will contain some phosphorus
adhering to them. A very important correlation is brought
out when the character of the proteinsin the seeds is compared
with the ordinary botanical relationship of the natural
orders concerned. ‘The proteins contained in the seeds of
the cereals contain a relatively large proportion of those
protamins which yield no lysine, much proline, glutaminic —
acid, and ammonia, with a little arginine and histidine.
Hordein, in barley, is characterized by its low percentage of
oxygen and large heat of combustion.

The chief properties and behaviour of the cereal proteins
are much alike, and present marked differences from the
proteins from other groups of seeds. It is thus found that
similar proteins are found only in seeds which are botanically
closely related. ‘The embryo in its early periods of growth
is fed on special food, but when the plant has reached the
stage of finding food from its surroundings, the chemical
processes have already become established on fixed lines.

150 PLANT PRODUCTS

Wheat grown on irrigated land contains less nitrogen
than that grown on non-itrigated land, but this may quite
possibly be only part of the general principle that vigorous
growth results in the production of carbohydrates.

Crude gluten from wheat amounts to 8 to 15 per cent. of
the wheat flour, No. 1 Manitoba wheat flour containing over
13 per cent. and English flours under 10 per cent.

Crude gluten dried at a low temperature is used to make
biscuits for diabetes patients.

Leguminous Proteins.—Many of the leguminous seeds,
such as peas, beans, and lentils, contain relatively much
protein soluble in water, which, after the addition of acetic
and carbonic acids, is largely precipitated, but is soluble
again in concentrated saline solutions, and is generally
considered as a globulin. It was formerly supposed that
many proteins were strong acids in all but name, and formed
salts with bases, on which grounds many of the proteins
were desctibed in older literature as caseins. The legumin
from peas atid beans was long regarded as a protein of strong
acid character. Recent studies have, however, shown that
the solubility caused by the addition of large quantities
of alkali is not due to this. Jegumin in the free state is
soluble with water, but when combined with acids forms
salts which are insoluble, and the idea that legumin is a strong
acid in a free state, but forming salts, is no longer a tenable
hypothesis. Many of the leguminous seeds, when freshly
ground, yield water extract, from which the protein separates
by the development of acid. The separation can quickly
be effected by adding a small quantity of any common acid.
Legumin, previously dissolved in dilute sodium hydrate,
is not precipitated by adding enough acid to combine with
all the alkali that has been added, but very little more acid
forms an insoluble salt of legumin. Still further addition
of acid, however, suffices to redissolve the precipitate.
The leguminous proteins are ustially particularly rich in
nitrogen, and yield on hydrolysis a large proportion of
arginine.

Vicilin, from peas, is characterized by the small amount

a

THE NITROGEN COMPOUNDS IN PLANTS 151

of ammonia in proportion to the amount of glutaminic
and aspartic acids, and must, therefore, contain those
amino acids in a form different from that of the amide.
This protein has also been found to contain very little sulphur.
The proteins from leguminous seeds resemble one another
in many respects, but differ from those of the cereals. The
proteins of the pea, horse bean, lentil, and vetch all yield
preparations of legumin which are apparently identical.
Other members of the leguminous seties yield proteins which
are very similar to those yielding legumin, and though not
identical, are much nearer to legumin than any of the
proteins found in the cereals. The legumin of soy bean is
used in Japan to make a vegetable cheese. The soy beans
are treated as in the manufacture of starch (see p. 117),
but the non-starch residue is kept, boiled, strained, and
precipitated with brine. The cheese resembles a half milk
cheese.

The Proteins in Root Crops.—Early investigators
examined the proteins of the potato, but no great amount
of work has been done in this group. ‘The hydrolysis of
the protein of the swede turnip produces substances which
differ from those yielded by the legumins chiefly in the
following points :—The percentage of arginine resembles
that yielded by the ceieals, and is distinctly less than that
from the leguminous crops. The percentage of histidine
is rather high. ‘The percentage of lysine is faitly high, and
cotresponds to that from the legumes. ‘The low content of -
glutaminic acid in the soluble protein of swedes will counter-
balance the high content of that amino acid in the proteins
of cereals when these two are fed together, as is common in
ordinary farm practice. Both cystine and tryptophane are
also present in the swede protein.

The Proteins of the Oil Seeds.—’The globulin in
castor bean can be freed by dialysis from all but minute traces
of the toxic substances contained in the beans, a fact which
forms one of the best pieces of evidence that these materials
can be obtained in at least some degree of purity. Edestin,
the chief protein of hemp seed, is entirely insoluble in water,

152 PLANT PRODUCTS

but is very readily soluble in small traces of acid, in the
absence of other salts. From such a solution the edestin is
readily precipitated by sodium chloride. Edestin, in fact,
has proved to be a fairly strong base, and the combined acid
in its salts can be titrated by potash and phenol-phthalein.
The maximum acid binding power of edestin is very
high indeed. The solubility of edestin in salt solutions is
approximately the same, but the iodides and bromides dis-
solve edestin more readily than the chlorides. Acetates
behave in a somewhat remarkable manner, for the acetates
of the alkalies have no solvent action on edestin, while the
acetates of heavy metals dissolve it freely. The acetates
of lead, copper, and silver, which are commonly supposed
to be protein precipitants, are as good solvents for edestin
as is pure acetic acid, provided other salts be absent. The
metallic ion of the acetate unites in organic combination
with the protein. Corylin, from hazel nuts, is characterized
by containing the very high amount of 19 per cent. of nitrogen,
of which nearly one-third is basic nitrogen. ‘The proteins
in this group are, on the whole, characterized by high
percentages of nitrogen, with moderate amounts of ammonia,
and very high amounts of basic nitrogen, with large quantities
of arginine and moderate amounts of histidine. The castor
bean contains toxic substances, which appear to be of
protein character, although this is not accepted by all
workers, but preparations have been made of ricin, of which
sooo part of a milligram per kilogram weight was a fatal
dose when subcutaneously injected into rabbits, and such
rich preparations contain a high percentage of albumen.
The Alkaloids.—Opium is the dried milky juice (latex)
of the unripe capsules of the poppy. The opium poppy is
cultivated in India and China from seed, which is sown from
November to March, and the crops are ready from May to
July. A few days after the petals have fallen the capsules
are cut round the middle with a knife, and on the following
morning the juice has flowed out, hardened, and is ready for
collection. After further drying on poppy leaves, the dark
masses are made up intolumps. Opium is used medicinally,

aN

THE NITROGEN COMPOUNDS IN PLANTS 153

and also is smoked, chiefly by the Chinese. Opium contains
many alkaloids—morphine about 9 per cent., narcotine about
5 per cent., and other alkaloids about 1 per cent. Morphine
exists in opium in the form of two soluble salts, so that
extraction with water removes all this alkaloid. Gregory’s
method for the manufacture of morphia consists in extracting
the drug with water at about 40° Cent., mixing the liquor
with excess of calcium carbonate, and evaporating to a small
volume. Calcium chloride is added to a slight excess, the
liquid diluted, and a precipitate, consisting of resin and
calcium meconate, filtered off. On concentrating the liquid
the hydrochloride of morphine crystallizes out. This
is dissolved in water, the solution decolorized with charcoal,
and decomposed by ammonia, which precipitates the morphia
neatly pure. Further purification is effected by ether and
benzene.

Cinchona (Peruvian Bark).—The tree which yields this
bark is a native of Peru, and the value of the bark for curing
intermittent fevers was known to the American natives
before the conquest of Peru, but they concealed its value
for a long time. In 1638, however, the Countess Cinchon
obtained the use of this for the cure of fever, and subsequently
brought quantities of ground bark to Europe, where it was
known by the name of the “‘ Powder of the Countess.”
Subsequently it became known to the Jesuits, and was
usually called “‘ Jesuit’s Bark.”’ Three kinds of bark are
commonly known, the pale bark, the yellow bark, and the ©
red bark. ‘The cinchona trees are now cultivated in many
parts of the world, considerable quantities being grown and
manufactured in India under Government supervision.
The use of plain bark is no longer very large in medical
practice, being replaced by the purer drugs. The total
alkaloids of Peruvian bark are first extracted with water,
and dissolved for the most part. The cincho-tannates may
be dissolved by a dilute acid, or they may be decomposed
by mixing the bark with lime and water. Extraction
with dilute hydrochloric acid is not usually employed now.
On the large scale, finely powdered bark is mixed with lime,

154 PLANT PRODUCTS

atid made into a paste with water. The mixtute is thoroughly
dtied, powdered, and extracted with chloroform, ether, etc.
The alkaloids are removed from the solvent by agitating
it with dilute acid, and then precipitated by ammonia.
The alkaloids thus obtained are chiefly composed of quinine,
hydroquinine, cinchonine, cinchonidine, and a little quinidine.
Crude alkaloids of this nature are not infrequently employed
as medicine, especially in India, where they may be sold
under such titles as cinchona febrifuge, sometimes misnamed
by the natives as cinquinine. A nearly complete separation
of the quinine may be effected by taking advantage of the
small solubility of quinine in cold water. Quinine is a
fairly strong base, giving two sets of salts, mono-acid and
di-acid.

Nicotine. —Nicotine is prepared chiefly from the tobacco
leaf, mid-ribs, and waste tobacco, and from the liquors which
ate by-products of tobacco intended for chewing purposes.
These materials are extracted with water, and the liquor
concentrated. After the addition, steam distillation gives a
liquor containing a crude form of nicotine. ‘This is acidified
with oxalic acid, and evaporated to a small bulk, subsequently
decomposed by potash, and the nicotine floats on the surface,
and is separated mechanically. Waste tobacco and crude
forms of nicotine are largely used as insecticides, especially
for horticultural work.

Tobacco.—Tobacco can be grown in the British Isles
where the cool moist temperature on the west coast makes the
tobacco plant fairly independent of variations of soil moisture,
which is such an important point in all tobacco-growing
districts, and perhaps accounts for the fact that on the west
coast of the British Isles small degrees of frost are not found
to be fatal, whilst on the European continent a frost is con-
sidered a fatal difficulty. Any good soils can be made
suitable by tillage for the production of tobacco, but the
plant flourishes best in a fairly open soil, which is well
supplied with organic tnatter.

Tobacco is especially sensitive to the amount of lime in
the soil. Continental practice considers that the amount

THE NITROGEN COMPOUNDS IN PLANTS 155

of lime in the soil should not be less than } per cent., and not
more than 2 per cent.

The manures used contain a high percentage of potash,
but no large amount of phosphates. ‘The fields on which
tobacco is planted out must be well sheltered from wind.
Tobacco may be substituted for potatoes or other crops in
the rotation or can be grown several years successively.
On the continent phosphates are not usually applied direct
to the tobacco, the previous crop in the rotation having
already received heavy dressings of phosphates in advance.
Chlorides are considered bad for the development of the plant.
Compound manures containing about 5 per cent. nitrogen,
17 per cent. soluble phosphate, and 7 per cent. potash are
considered very suitable for this crop, which corresponds
roughly to about one part of sulphate of potash, two parts
of sulphate of ammonia, and four parts of super-phosphate.
Kainit should not be used since it contains too much chlorine.
The plant is usually grown on low, flat drills, very frequently
being planted out in the furrow, and subsequently earthed
up. The seed is generally sown about the middle of March
or April in hot beds. The suckers and lateral growth should
be broken off, and the plant allowed to bear ten leaves.
The better qualities are not harvested all at once, but plucked
leaf by leaf. They are then dried, and taken to curing
barns, in which ventilation is an important point. ‘The first
process consists in wilting the leaves, when they lose moisture,
and become limp, but the drying should not take place too ©
fast. The second process is that of yellowing the leaf.
This subsequently turns to brown, and the leaf becomes
fairly well dried. ‘Then drying must proceed fairly rapidly,
in order to prevent mould setting in. About one half of
a ton of dry tobacco per acre represents the ordinary
yield.

In tropical climates a rich, sandy loam is preferred,
containing considerable quantities of potash and lime.
In India a great many of the most suitable districts contain
well waters with nitrates in solution, which are used for
irrigating purposes. ‘The land is usually thoroughly ploughed

156 PLANT PRODUCTS

and thrown up into riggs and furrows. The seeds are sown
in nurseries in a shady situation, and in very hot districts
it is necessary to protect the seedlings from excessive heat
at this stage. Some form of partial sterilization of the soil
is often adopted by burning the soil, along with weeds,
brushwood or other waste. ‘The seedlings are generally
transplanted into furrows, where they may possibly be
irrigated, and the position of rigg and furrow subsequently
reversed in the process of earthing up. Growth has usually
proceeded fairly far in thirty or forty days, when side shoots
and small buds are cut off. In the fields twigs and sticks
are arranged somewhat like a towel-horse, and the leaves
arranged on these for drying purposes. In some cases the
leaves are fixed to strings, very much like a washerwoman
might hang out stockings to dry. Rapid drying produces
a pale leaf, but slow drying produces a dark-coloured leaf.
The process of maturing does not consist in merely losing
water, but the action of oxidizing enzymes is an important _
part of the process. The starch and sugar almost entirely
disappear, and the albuminoids and the tannin decrease,
with an increase in the amounts of amides. ‘These changes
are all explained by ordinary oxidizing decomposition.

Caffeine or Theine.—This is the alkaloid of tea and coffee
(see Section V., pp. 158, 160). Coffee beans contain about I
per cent., and tea leaves from about I to 5 per cent.; 34
per cent. is considered an ordinary amount of caffeine
in tea leaves. Tea is heated for about an hour with three
or four times its weight of boiling water, and after filtration
is mixed with a quantity of lime equal to that of the tea
originally taken. ‘The mixture is subsequently dried on the
water-bath, extracted with boiling chloroform, and the
solution subsequently recrystallized by alcohol. ‘Theobro-
mine, the alkaloid in cocoa, is closely related to caffeine.

Strychnine is the chief alkaloid in Nux Vomica. The
finely powdered seeds are treated with lime and water, and
the mixture extracted with chloroform, benzene, or amyl
alcohol.

THE NITROGEN COMPOUNDS IN PLANTS 157

REFERENCES TO SECTION IV

Shutt, “Influence of Environment on the Composition of Wheat,”
Journ. Soc. Chem. Ind., 1909, p. 336.

Osborne, ‘‘ The Vegetable Proteins.”” (Longmans.)

ye? “ The Chemical Constitution of the Proteins,” p. 76. (Long-
mans.

Wood and Hardy, Proc. Roy. Soc., 1909, B. 81, 38.

Hardy, Brit. Assoc. Report, 1909, p. 784.

Gwilym Williams, ‘‘ Hydrolysis of the Soluble Protein of Swede
Turnips,” Journ. Agric. Science, viii., p. 182.

Thomas Thomson, ‘‘ Chemistry of Vegetables,” p. 799. (Bailliére.)

Wallace, “‘ Indian Agriculture,’ p. 235. (Oliver and Boyd.)
” rg hn “Dictionary of Applied Chemistry,” v. 627. (Longmans,

reen.

Garrad, ‘‘ Tobacco Growing for Insecticidal Purposes,”’ Journ. Board
of Agriculture, 1911-12, p. 378.

“Cultivation of Tobacco for the Preparation of Fruit and Hop
Washes,” Journ. Board of Agriculture, 1912-13, p. 985.

Whatnough, ‘‘ The Cultivation and Collection of Medicinal Plants in
England,” Journ. Board of Agriculture, 1914-15, p. 492.

SEoTION V.—MISCELLANEOUS PLANT
PRODUCTS

Tea.—Tea was first introduced into Europe by the Dutch
East India Company. At first it was mostly of Chinese
production, but of recent years India has taken the major
part of the trade. Tea thrives best in the hilly tracts, and
is not usually grown in any low-lying districts, or at any
pronounced altitude. It is raised from seed, and the bushes
in the tea plantation are kept about four or five feet apart,
so as to permit ample room for the workers to get in between
for hoeing operations. The aim of the planter is to obtain
a constant succession of leaf-bearing shoots, but the plant
requires a period of rest. At the time of the “flush,” or
period of most active vegetation, the youngest leaves of each
shoot are alone used in the manufacture. The bushes
must on no account be allowed to produce flowers or fruit.
The rainfall in tea-growing districts is invariably high, about
eighty inches per annum representing a fairly satisfactory
figure; long droughts are very disadvantageous. ‘The soil
must be well drained, but situations on the sides of hills
are not considered very satisfactory. Light, sandy, loose,
deep loams are the best type of soil, clays and shallow soils
being quite unsuited. Nitrogenous manures are extremely
valuable, and moderate amounts of vegetable manure
desirable, but excessive vegetable matter leads to inferior
grades. In Japan fish manure is used. Lime is generally
considered to be very harmful except in small amounts,
though in Assam lime is regarded more favourably. In
Dehra Dun gypsum is used. There seems some reason to
believe that tea needs an abnormal value of the ratio MgO:
CaO in the soil, and requires the magnesia to be in marked

TEA 159

excess. The amount of phosphoric acid and potash appears
to have an important influence on the flavour. The seed
is sown in nurseries, and the plants are ready for transplanting
about May. Under old systems of planting the bushes were
arranged almost entirely on the square, but it is becoming
more popular now to plant them on the triangular system.
By this arrangement a greater number of plants can be put
on an acre with the same distance from bush to bush,
Incessant hoeing is one of the most important parts of the
cultivation. Farmyard manure is not obtainable and bullock
dung is scarce and needed for food production, but some
form of green manure is often used to take its place.
Unpalatable oil cakes are also freely used, but there is great
difficulty in obtaining sufficient suitable supplies of organic
nitrogen materials, and sulphate of ammonia is used to make
up for this deficiency. The tea bush will often last out from
forty to sixty years, depending upon the amount of pruning.
Frequent light prunings are practised and heavy prunings
at intervals of every few years. The pluckings are made
by pressure, and not by pulling, and the number of leaves
taken off at a time will determine the quality of the tea ;
the better qualities having about three leaves, and the lower
qualities about five leaves. ‘The period of plucking is most
active during July, August, and September, when the result
of the rains produces its maximum moisture in the soil. The
tea leaves are transferred as quickly as possible to a withering
house, where they are spread out intrays. This place must:
be kept as cool as possible, and with the greatest possible
amount of ventilation, to allow rapid evaporation of water.
When the leaf has become sufficiently flaccid it is carried to
a rolling machine, which imitates rolling between the palms
of the hands as in the original primitive Chinese system.
This operation breaks up the cells of the leaf, and allows the
different parts of the plant juice to come into contact with
one another, so that much of the chemical change which
takes place is due to the enzymes which occur in the tea
itself, and as little as possible due to bacterial decomposition.
The tea is then transferred to the sirocco, or drying machine,

160 PLANT PRODUCTS

which usually consists of a long boiler-shaped vessel, heated
by flues, with trays which are transferred from one end
to the other to allow drying to take place in a steady manner.
Once the tea has been thoroughly dried it is necessary that
it should on no account come into contact with moist air.
It is sieved into different grades as quickly as possible, and
packed into lead-lined boxes. Many qualities of tea are
very sensitive to damp atmosphere, so that some qualities
which are known in the immediate vicinities of the tea-
producing districts are quite unknown overseas, as, in spite
of all efforts to obtain an air-tight tea chest, these teas
deteriorate on the sea passage. Anything approaching to
free admission of sea air is immediately fatal to most teas.
No matter what varieties of tea are taken on board a ship in
loosely closed vessels, within a day or two of leaving port
they all seem to have sunk to the same low level of flavour.
The greatest possible care is taken at the tea-packing stations
to discover even pinpricks in the lead casings. Many of
the very finest qualities of tea manufacture in China and
Japan are still made by the old hand-rolling process, but
modern Indian methods are becoming very common.
Steaming is often an important part of the hand process,
and probably prevents bacterial decomposition. The leaves
produced in small cottage holdings are often put upon
plates of copper and held over the fire. Insome dry districts.
the leaves are dried by tossing them in the sun.

Cocoa contains theobromine, an alkaloid similar to that
in tea, associated with a large percentage of fat.

Coffee.—Coffee is most generally raised from seed sown
in nurseries, but for economy is sometimes sown directly
on the ground. A few seeds are usually sown together,
the weaker ones being removed. ‘The land should be well
drained, and is usually situated at moderate elevations of
two thousand to five thousand feet above the sea-level,
where the rainfall is between fifty and one hundred inches,
and the temperature 55° to 85° Fahr. Shade is a most
important point in considering coffee plantations. At
least temporary shade must be provided for the seedlings.

]

COFFEE 161

Small bushes are often only five feet apart, but under the
tree system as much as fifteen feet is sometimes allowed.
Catch crops are not infrequently grown along with the
bushes. Steep hillsides are more frequently used for
coffee plantations than tea plantations, but where they are
used terracing is necessary. In coffee districts, the hedges
may be coffee bushes, but such do not yield the best crop.
Weeding is not considered an important point, at least not
so important as in tea plantations. The coffee plantation
usually comes into bearing about the third year and lasts
for about forty years. ‘The fruits are usually hand picked,
and are frequently called cherries, whilst the seeds contained
are alluded to as berries. The coffee fruit consists of an
external pulp, a loose tissue called “ parchment” and the
silver skin, inside of which is the coffee berry. The fruits, on
removal to the factory, are usually thrown into water, when
the ripe cherries sink to the bottom. ‘The ripe cherries are
then removed to a pulping machine, which tears off the outer
succulent part. This part is mixed up with water, and is,
under the best management, carefully preserved and used
as manure. After the pulp is removed, the seeds are dried.
The “parchment” which surrounds the seed is usually
left on, and the seeds with their ‘‘ parchment” dried in
the sun on large concrete floors resembling tennis courts.
The machines specially designed for removing the “ parch-
ment ’’ are usually situated near some large town, or sea-
port, since the weight of the “‘ parchment ”’ is small, and the
berries carry better in their natural coat. ‘The produce of
one acre of land is about seven cwt. of prepared coffee,
containing about Io or 12 per cent. of moisture. Compared
to this the total weight of the wet berry, at plucking, will be
about 1400 pounds, with about 270 pounds of “ parchment,”’
and yielding 1280 pounds of wet pulp. These will contain
about 15 pounds of nitrogen in the form of the berry, about
2 pounds of nitrogen in the form of “ parchment,’’ and about
3 pounds of nitrogen in the form of pulp. ‘There will be
about 3 pounds of phosphoric acid in the coffee berry,
only fractions of a pound in the skin of “ parchment,”
D. II

162 PLANT PRODUCTS

and about 1 pound in the flesh of pulp. ‘There will be 16
pounds of potash in the berry, about 4 pounds in the “ parch-
ment,’ and about 12 pounds in the pulp. The return of
the pulp does not make up for the losses, and considering
the general nature of the soils on which these crops are
grown, it seems highly probable that potash manure should
receive more consideration. ‘The soils on which the coffee
is grown are usually fairly well supplied with phosphates.
It is quite well known in common practice that nitrate of
potash is an excellent manure, but owing to its expense
the amount used is less than what is desirable. There is
good scope here for the use of increased quantities of sulphate
of ammonia. The cultivation both in Biazil and Madras
are similar in this respect, that a red soil is much preferred.
In Brazil steep slopes are not employed to the same extent
that they are in Madras. In some kinds of treatment
the ‘‘ parchment ”’ is fermented, and removed on the station,
but in others both ‘‘ parchment ”’ and silver skin are treated
alike, and the coffee berry is sold with both the silver skin
and the “ parchment ”’ adhering to it.

Tannin.—The subject of tanning leather is treated very
fully in another volume of this series (Bennett), but a brief
abstract can be given here from a different point of view.
The word ‘tannin’ expresses a large number of materials,
which have all the common property that they are used
for manufacturing leather. ‘The chief sources are the bark
of oak and many other trees, together with myrobalans.
Catechu tannin is a decomposed product of Catechin,
ot Khair, the extract obtained by boiling the wood of acacia
catechu (mimosa catechu). As a rule more vigorous trees
yield more tannin, but the character of the soil appears to
be of very greatimportance. There are very large quantities
of oak bark grown in the British Isles which are not made
mutch use of owing to the cost of collection. This subject must
be‘treated as a part of the whole question of forestry of
the British Isles. Reafforestation and the management of
woods can only be successfully carried out if all possible
sources of revenue are considered. The practical management

TANNIN 163

of the collection of bark in the British Isles will be closely
connected with the utilization of waste wood in forest
problems. If it can be made profitable to bark the trees,
and dispose of the bark for tannin, the waste wood can be
distilled for the production of a much better quality charcoal,
and in practice, therefore, the two subjects are closely
connected. Calcareous soils probably produce more tannin
than others, and since, in the British Isles, it is only the
poorest land that can be left down to timber, this condition
does not often prevail. The proportion of tannin appears
to be greatest in bark removed about Aprilor May. Charac-
teristics of the tannins are that they reduce Fehling solution,
are precipitated by basic lead acetate, give a blue-black
colour with ferric chloride, and are precipitated with many
bases. Phlobaphenes are the decomposed products of
the tannins proper, and are nearly always contained in
extracts of bark. ‘They are red-coloured substances, and
though almost insoluble in water, they dissolve in solutions
of tannins. Whilst a great many of the common tannins
contain the glucose grouping, such is by no means invariably
the case. Gall nuts are very rich in gallo-tannic acid, and
may contain as much as 50 per cent. Ordinary tannin,
or gallo-tannic acid, is probably a compound containing
five molecules of di-gallic acid, with one molecule of glucose.
Catechin, whilst not properly tannin itself, is easily converted
into catechu tannin, a change which takes place readily
on heating to 120°, or slowly by merely boiling with
water. The common extracts from the acacia or mimosa
are usually mixtures of catechin and catechu tannin. ‘The
catechin itself is used medicinally in India, or as a chewing
material. ‘Tannin is abundant in the leaves, in all active
growing parts and in diseased parts, like galls. Any irritation
to the protoplasm appears to increase the amount of tannin.
Tannin is very common in all unripe fruits, but disappears
as the fruit becomes ripe.

Rubber. — Rubber, or India rubber, is the material which
exudes as the result of an injury to many particular trees.
Rubber is generally derived by a process of coagulation from

164 PLANT PRODUCTS

such trees, creeper, shrubs, etc. The laticiferous system,
which is distinct from the sap-bearing cell system, generally
lies between the outer bark and cambium. By cutting
through the bark into the latex cells the latex is obtained.
This operation is referred to as tapping. In wild rubber
V-shaped cuts are generally made, but in plantation rubber
the trees are tapped by one central channel. The latex is
collected in a cup which is fastened to the tree below the
channel. In wild rubber the sticky latex is smoked over a
fire from very smoky materials, which produce much
creosote, tarry matter, acetic acid, etc. Only small quantities
are treated at a time, and gradually a substantial piece
of rubber, thirty or forty pounds weight, is produced.
Plantation latex is generally coagulated by the addition
of a small quantity of acetic acid, the smoking process being
carried out later whilst drying. Recently some efforts have
been made to produce on the estates themselves a crude
pyro-ligneous acid obtained by the distillation of waste wood
in a small form of retort (see p. 131), as apparently the
single application of crude pyro-ligneous acid is better than
successive applications of acetic acid and smoke. The
plantation rubber, being produced under at least some
partial scientific treatment, is much superior to the wild
rubber. The crude material often includes much resin
and other vegetable matter. The impure varieties require
to be cleaned in a special machine. Rubber, when stretched,
does not return to its original condition, but remains stretched
for some time. It does not, however, alter in volume.
Rubber appears to be as incompressible as water. The fact
that rubber does not return to its original length when
stretched is commonly alluded to as hysteresis. The
freshly cut surfaces of rubber readily adhere to one another.
As rubber is, strictly speaking, an organic gel, it absorbs
water freely, and may increase to an extent of twenty-five
per cent. in its weight, and fifteen per cent. in its volume.
Many organic liquors, like petroleum, coal tar, etc., are
absorbed by rubber, and some of these make good typical
colloidal solutions.

RUBBER 165

Vulcanization.—Heat and sulphur produce a profound
change in the character of rubber, known as the process of
Vulcanization. The ordinary slightly vulcanized rubber
corresponds to a formula of about (Cj9Hj¢)j9Se, but the
fully vulcanized rubber, called ebonite, corresponds to about
CioHig52. Mixing is an jmportant part of the preparation
of any rubbers for commercial purposes, absolutely pure
rubber having little utility. Fillers added for some purposes
are such materials as pyrites. For increasing mechanical
strength zinc oxide, lime, and a few other substances are
employed. Asphalte is often used to increase the resistance
to water. Pigments of various types are employed to alter
the colour. “Oil substitutes’ are made by the action of
sulphur chloride on oils (see p. 136). Vegetable oils are used
for producing low-grade goods. Reclaimed or waste rubber
is also much used for admixture. Rubber tubing is generally
made either by pressing together the edges of sheet, or by
squirting through a die. Canvas and other fabrics built
up with rubber constitute an important part of the rubber
industry, for all purposes where special strength is re-
quired.

Indigo.—Indigo is grown in Bengal, but is also grown
very largely in other parts of India, either for local production
of dyestuff, or as a green crop for increasing the amount
of organic matter in the soil. It grows very freely, and does
not appear to need very much manure, but the problem
of the relationship of manure to indigo production has not ©
been by any means completely settled as yet. The plant
is cut before flowering, and tied up into bundles. It is
carried as quickly as possible to the factories. If it is allowed
to ferment, the amount of dye ultimately obtained is reduced.
The bundles are filled into a-large vat, pressed down by
bamboos. ‘The whole is covered with water, steeped for about
ten hours, the yellow-coloured liquor thrown off, and beaten
either by hand-working bamboos, or by a kind of paddle
wheel, It is then carried to a boiler, where the liquor is
heated. The indigo is filtered off, and the mass dried.
Sometimes a further fermentation is allowed to take place

166 PLANT PRODUCTS

in the cake. An acre of land produces about 60 bundles
of indigo plants, each about five feet in girth, which yield
about ten pounds of indigo cake. Different parts of the
plant yield different quantities of indigo, the upper parts
of the plant being most prolific. About one-half per cent.
of crude indigo is obtained, representing about } per cent. of
real indigotin. The actual manufacture usually commences
about the middle of June, which is a compromise, as the
greatest percentage of indigotin does not correspond with the
greatest yield of crop. New varieties are also being intro-
duced, which are said to be able to yield as much as
twenty-five pounds of crude indigo per acre. ‘The processes
of dyeing are described by Knecht (see p. 168).

Fruit Products.—Fruit farming is practised on a very
large scale in America, where considerable areas of special
land are covered with only one or two species. In Europe
genetally more variety is displayed. In Great Britain
fruit growing is chiefly of the market garden type, although
on the continent of Euiope considerable quantities of fruit are
grown on communistic lines in the villages and small towns.

The manuring of fruit trees cannot be placed on the
same basis as the fertilizing of other crops. Newly planted
trees should on no account receive large applications of
concentrated chemical manure, and the manuring of
established trees must be considered individually. The great
point of variation in the requirements of fruit trees is that
of the supply of nitrogen; on the other hand, phosphates
are always needed. Many trees are inclined to run to wood,
whilst others become stunted from bearing too heavy crops.
Old or unhealthy trees receive much benefit from nitrogenous
fertilizers. Grazing by poultry, etc., in the orchard is also
useful. Apple trees are especially benefited by phosphates ;
a dressing of basic slag in the autumn, followed by a small
dressing of super-phosphate in the spring is a very excellent
method of procedure. Kainit makes a very good source
of potash for trees that are growing on light soils, whilst
many growers apply nitrate of soda, before the flowering
time. ‘The preservation of fruit may be conducted either

FRUIT 167

by a process of bottling, in which the fruit is placed in bottles
along with water with or without sugar, and sterilized by
heating with steam, or by making intojam. In the bottling
method, so long as bacteria can be prevented from obtaining
access to the fruit it will keep indefinitely.

Jam and similar preserves are the result of preserving
fruit, even though it subsequently comes into contact with
air, and, therefore, bacteria. The object aimed at in producing
such a type of preserve is to obtain a solution of such strength
that even the hardiest bacterial spores undergo plasmolysis.
For this purpose it is not the percentage composition of the
solution that is the determining point, but the molecular
concentration, and 26 per cent. of glucose will be equivalent
to 50 per cent. of cane sugar in producing a definite molecular
concentration. During the process of boiling jam, much of
the cane sugar is hydrolyzed, and the molecular concentration
of the liquid is therefore almost doubled. In Japan salt
is used for the preservation of fruit, and the French dried-
fruit industry is animportantone. Fruit can be dried in the
sun, or by artificial heat. ‘The gas industry is now supplying
suitable fruit-drying ovens heated by gas. Crystallized
fruit is produced by soaking the fruit in a saturated solution
of cane sugar. Many of these processes, however, depend
upon secret details, which often involve a limited amount of
fermentation to bring out special flavours. In spite of the
acid flavour of many fruits, a fair proportion of sugar is
always present as shown in Table 23. Anapple, for example, —
contains more sugar than a red beetroot.

TABLE 23.—SUGAR IN FRUITS.

Apple .. os os ee i -» 12 percent,
Apricot .. oe es ve 08 oo 52 *
one ad ss Age ¥ ja: Se as
ckberry es is ee as a fe
Grape .. os ae e's ee .. 8 to 26 per cent,
Orange ve ve ee ne -» 6 percent.
Peach .,. ‘i ve er die ES a
Pear a% aa nie ar a eee %
Plum... Le a ee wk nee |. Mm
Raspberry Bey ed
Strawberry 6 mh

168 PLANT PRODUCTS

Injuries from Chemical Fumes.—Near industrial
towns it not infrequently happens that fumes of sulphuric
and hydrochloric acids do much harm to fruittrees. Currant
bushes appear to be very susceptible to such fumes, but
rhubarb is nearly as much injured and beans and potatoes
in market gardens are also sometimes damaged. Whilst the
removal of the acid vapours is to be desired from every
point of view yet for prompt protection something can be
done by sprays. At the author’s suggestion experiments
are being tried with a spray made from one pound of pre-
cipitated chalk in ten gallons of water (=I per cent.) applied
with the ordinary knapsack potato sprayer to the upper
surface of the leaves of such plants as show signs of black
spots. So far the experiments are very promising.

REFERENCES TO SECTION V

Mann, ‘‘The Renovation of Deteriorated Tea,’”’ Agric. Journ. India,
1906, p. 84.

Coombs, Alcock and Sterling, ‘‘ Comparative Tests with Mangrove and
Wattle Barks,” Journ. Soc. Chem. Ind., 1917, p. 188.

Stevens, ‘‘ The Function of Litharge in the Vulcanization Process,”
Journ, Soc. Chem. Ind., 1915, p. 524.

Davies, “‘ Hysteresis Tests for Rubber,” Journ. Soc. Chem. Ind., 1914,
Pp. 992.

Stevens, ‘‘ The Vulcanization of Rubber Agents other than Sulphur,”
Journ. Soc. Chem. Ind., 1917, pp. 107, 872.

Eaton and Grantham, ‘ Vulcanization Experiments on Plantation
Para Rubber,”’ Journ. Soc. ‘Chem. Ind., 1915; p. 989; 1916, pp. 715, 1046.

Eaton and Day, “ Estimation of Free and Combined Sulphur in
Vulcanized Rubber, and the Rate of Combination of Sulphur with Plan-
tation Para Rubber, ”* Journ. Soc. Chem. Ind., 1917, p. 16.

Whitby, ‘“‘ A Comparison of the Brazilian and Plantation Methods of
preparing Para Rubber,’’ Journ. Soc. Chem. Ind., 1916, p. 493.

Luff, ‘Some Aspects of the Synthesis of Caout-chouc,’’ Journ. Soc.
Chem. Ind., 1916, p. 983.

Porritt, ‘‘ Some Notes on the Raw Materials used by the Rubber
Manufacturer,” Journ. Sac. Chem. Ind., 1916, p. 989.

Mann, ‘‘ Assam Rubber,’’ Agric. Journ. India, 1906, p. 390.

Fowler, ‘‘ Bacterial and Enzyme Chemistry,” p. 245. (Arnold.)

Basu, ‘‘ Orange Cultivation,”’ Agric. Journ. India, 1906, p. 62; Wright,
‘* Hevea Braziliensis.’’ (Maclaren.)

Joshi, ‘‘ Orange Cultivation,’ Agric. Journ. India, 1907, p. 62.

Knecht, Rawson and Leewenthal, ‘‘A Manual of Dyeing.”

Money, ‘‘ Tea Cultivation.’”’ (Whittingham.)

Crowther and Ruston, ‘Effect upon Vegetation of Atmospheric
Impurities,’ Journ. Agric. Science, iv., P. 25.

Szotion VI.—FERTILIZERS IN RELATION
TO PLANT PRODUCTS

DIFFERENT crops require different fertilizers for their develop-
ment, but it must not be imagined that the fertilizers
required for a particular crop are specific types of mixtures.
Some general conceptions of the relationship between the
fertilizers and the crops are possible, however. Proper
manures for any particular crop always depend upon a
very large number of circumstances, many of which may be
peculiar to the district, and even to the particular field.
Mixtures sold as “ turnip manure,’ “ potato manure,’’ etc.,
can only give a kind of general average, and it is the business
of the farmer to understand his own land, and not leave
the management of it in the hands of somebody who has
never seen it. No proper idea of the manure required
for the crop can be obtained without a knowledge of the
system of rotation adopted, and although this may also
be worked down into general averages, again it is not a
subject of which the farmer can leave the details to a general
average of the country, but he must adopt his manure to
his own particular requirements. Moreover, some land may
be naturally in a high condition, whilst other land may
be in a very low condition. One farmer may be justified
in building up the fertility of the soil to a much higher
condition, whilst another would not be justified in making
any such effort. At the present time, when prices are going
upwards, and while the relationship of labour to the farm
is being completely altered in the British Isles, ideas which
were formerly sound have become quite impracticable. The
question of the markets, the supply of labour, and the rent
of the land will always be in need of careful consideration.

170 PLANT PRODUCTS

Contrasting the state of affairs in the British Isles, where
there is a fairly conservative system in vogue, with that
prevailing in the more recently developed parts of the
United States, where the farmer is largely living upon
capital originally stored in the soil, and also with that
prevailing among some of the aboriginal tribes of India,
who merely burn a patch of waste land and move on, and
taking into account the relatively new lands of Australia,
we may see that the system of farming will have much
effect upon the suitability of fertilizers. The Western
American farmer may often go on growing maize and wheat
and burning the straw, and putting hardly any manure upon
the land. For a time such a process may be suitable, but it
cannot represent a permanent condition of agriculture. The
type of pioneer farmer on the Western parts of America
only represents a particular period in the opening up of the
country. The American pioneer has turned out the redskin,
only to be in his turn replaced by a farmer who works a
mixed farm. ‘The aboriginal Indian has originally replaced
the wild animals of the forests, and he himself has been
turned out by the more progressive Hindu, who to-day is
being blamed for his relatively unprogressive character, and
the Australian squatter, with his sheep, has turned out the
aboriginal, who only hunted the kangaroo, and the squatter
is feeling aggrieved because he is being replaced by the so-
called “free selector.’’ Agriculture will need to progress
in all countries, and what is suitable for one step in the
process is not at all suitable for another step. Further, as
agriculture passes through the stage of mixed farming, it
goes further, and produces the intensive farmer, who
endeavours to produce the maximum amount of food from
his land, and we now have to consider the question of the
industrialization of agriculture, so as to induce still further
improvement in the manufacture of plant products from
the soil. Although it is quite impossible to set down any
rigid relationship between fertilizers and plant products,
it is, nevertheless, quite feasible to adopt some general
principles.

FERTILIZERS AND PLANT PRODUCTS 171

The Carbohydrate Producing Crops.—Wheat is
one of the most important plants grown in all countries of
advanced agriculture, as part of a system of rotation of
four or more years. Wheat is particularly suited to ploughed-
up land which has borne grass or clover, or mixtures of the
two. In such cases little fertilizer is necessary, a top
dressing of sulphate of ammonia, to the extent of half a
hundredweight per acre in the winter and spring, being
generally considered sufficient. When many white crops
are grown with a degree of frequency beyond that of once
in four years, some phosphatic manures will generally be
found necessary, and on the lighter soils some potash.
Oats also require comparatively little manure when grown
afterahaycrop. Barley, when required for malting purposes,
should have comparatively little nitrogenous manure,
though when required for feeding purposes more may be
supplied. Phosphates are particularly desirable for purposes
of producing sound ripening, as alluded to below. Potatoes
are grown on stich a great variety of soils that it is difficult
to lay down any particular rules, excepting that farmyard
manure is generally desirable, although in some districts
no farmyard manure is employed, potatoes being grown
after about two years clover. A good deal of the advantage
of using farmyard manure for potatoes is purely physical,
as the potato does not develop good root system unless the
soil is very open, and even actually hollow. Sulphate of
ammonia is generally preferable to nitrate of soda and
super-phosphate is often better than basic slag. Lime is
also generally considered unsuited for potatoes. Excessive
nitrogenous manure causes the potatoes to produce less
starch, and more nitrogenous and fibrous tissue. In garden
cultivation of potatoes working the land so as to produce
a somewhat hollow structure is useful, as it induces the
roots to go down after water, and leaves the soil loose for the
development of the tubers. Sugar-producing crops are often
more exhaustive. Swedes and mangolds require much
nitrogenous as well as phosphatic manure. A standard
dressing is used fot mangolds at Cockle Park, containing

172 PLANT PRODUCTS

eighty pounds of nitrogen, forty pounds phosphoric acid,
one hundred and fifty pounds potash, and two hundred
pounds common salt, a relatively somewhat expensive
mixture. The root crops in general, when grown with a
large amount of nitrates, especially nitrate of soda, decrease
in food value, the plants being of a rather watery, poor
feeding quality. Potash, which is so essential for the
mangold crop, can be economized to a partial extent by the
use of sodium salts. A particularly useful waste industrial
product is a mixture of calcium sulphate and sodium chloride,
obtained from some salt works. Where sodium chloride
is desirable for cultivation, as it is in the case of mangolds,
the sodium has the tendency to render the clay sticky, but
an admixture of calcium sulphate overcomes this difficulty,
as it prevents the formation of colloidal compounds.

The Leguminous Crops obtain much of their nitrogen
from the atmosphere, and therefore do not require nitro-
genous manure, excepting very small quantities to get over
their early stages, when they are particularly subject to
the attack of all kinds of pests. Small quantities of nitro-
genous manure enable them to get out of the reach of many
of their enemies at a period when their capacity for obtaining
nitrogen from the air is very small indeed. They are
particularly dependent upon lime, potash, and phosphoric
acid. ‘The importance of clover in the hay crop as part of
the rotation has been recognized from the earliest times,
the procedure being known to the Romans, This system
is also adopted in tropical countries, like India, where a
leguminous crop is grown either mixed with one of the millets,
or as a separate part of the rotation. ‘The increase in the
nitrogen content of the soil, by the growth of clover, has
been already alluded to (see p. 81). Among the different kinds
of clover, the wild white clover has been found particularly
suitable for development in the pastures. Where, however,
the conditions of the soil are of a rather moist character,
probably the wild red clover is equally suitable. ‘There is
a great difference between growing mixed crops of herbage
and. growing a single crop in the ordinary way. Where

FERTILIZERS AND PLANT PRODUCTS 173

there are many species all struggling with one another, hardy
varieties are essential, hence the wild forms of the clover
plant are particularly suited for development in a pasture,
Seed which has been sown on well-tilled land for many
generations has no necessity to struggle with other species,
is weakened in the process, and is no longer able to fight for
itself. There is a great difference between land which is
laid up for hay and land which is down to permanent
pasture. The species which will establish themselves in
the two kinds of soil are not the same, and, therefore, it is
not desirable that land should be sometimes cut for hay and
sometimes grazed, since no permanent equilibrium would
result. In the Tree Field experiment at Cockle Park the
use of basic slag has completely altered the physical properties
of the soil, the deep roots of the clover having altered the
physical texture of the soil down to about twelve inches in
depth. Somewhat similar to the action of wild white
clover in the British Isles is the action of the celebrated
dub grass of India, a grass which possesses a creeping stem,
which opens up the soil in a more efficient way than many
other forms of grass. Where land is cut for hay for any period
of time, one-sided manures become impractical. Well-
balanced manuring is far more important for this purpose
than for crops which are grown in a rotation. Generally
speaking, it is the heavy land which should be down to grass,
and such lands will not usually require much potash. ‘The
lighter lands should properly be ploughed, and not be
permanently down to grass at all. Grass should only be
part of the ordinary rotation on such lands, where it should
be ‘‘seeds hay’”’ for one or more years. Where land is down
permanently to hay, very generous manuring is necessary.
At Cockle Park, on Palace Leas Field, which has been cut
for hay for over twenty years, slag has been found very
profitable, but is not yielding such big crops as more mixed
systems of manuring. For obtaining large crops of hay,
farmyard manure is almost essential, although very fair crops
have been obtained by phosphatic manures, supplemented

_ by potassic manures. ‘The relative feeding values of the

174 PLANT PRODUCTS

hay so obtained show much variation. The amount
of albuminoids in the hays so produced are much greater
where phosphatic manures are applied, the best results being
obtained with both phosphatic and potassic manures.
Generally speaking, the hays of the higher feeding values

have been those obtained by both slag and potash, even

though, on the whole, the soil is towards the heavy side.
Land, however, which is down to pasture, will only require
much smaller dressings, and occasional quantities of lime
and basic slag, giving about an average of three hundred-
weight of lime and one hundredweight of basic slag for
each year. This is for permanent pasture, which, by rights,
would only be on the heavier lands. A large amount of
weeds, especially buttercup and wild geranium, are indications
of excessive richness, produced by cake feeding, which has.
never been supported by proper supplies of phosphatic
manures. For pasture lands, nitrogenous manures are
generally unsatisfactory, as sufficient nitrogen is supplied
by the droppings of the cattle.

Sugar Cane. —Sugar cane, like most of the sugar-
producing crops, requires considerable quantities of nitro-
genous fertilizers. Owing to its long period of growth,
these should be of the slow-acting type. For the ratoon crops
there is some difference of opinion as to whether the residues
of the manuring of the previous crop can be economically
replaced by more active forms of nitrogen. On the lighter
soils potash is also very necessary. ‘The chemical activities
of the soil are greater in hot than in cold climates. The
decay of organic matter takes place with great rapidity in
hot climates, and even after ploughing-in green crops for
many years the accumulation of organic matter will not
‘ reach the amount of a single green-manuring in colder
climates. As carbon dioxide is produced in the soil at a
greater rate than in cold climates, the general amount of
carbonic acid dissolved in the soil water will be greater,
in spite of the warm weather. Hence weathering of soil

will take place more rapidly in tropical aang than in
cold climates.

FERTILIZERS AND PLANT PRODUCTS 175

Cotton having a somewhat shorter period of growth,
and producing a seed rich in mineral matter, needs the
application of larger quantities of fertilizers. Phosphates
and organic nitrogen manures are very valuable for this
type of crop, and sulphate of ammonia can be also used
profitably here.

Tea being a perennial crop has rather more resemblance
to hay than many of the other types of crop. Whilst a
certain amount of nitrogenous manure is desirable, excessive
amounts tend to produce an inferior quality of leaf. Some
of those who experimented in the use of sulphate of ammonia
obtained rather unsatisfactory results at first. The reason
for this was that excessive quantities were supplied in an
unsuitable manner. Where an ample supply of organic
manures can be obtained, sulphate of ammonia is not
so necessary, but in many situations small and cautious
applications of sulphate of ammonia will probably be found
useful (see Bald, p. 177).

Coffee is a somewhat exhaustive crop, and requites
a fair amount of nitrogen, phosphates, and potash.

Succulent Crops.—The general effect of nitrogenous
manuring is to delay the ripening of the plant, and to produce
a large quantity of green material. Nitrogenous manures
tend to produce large quantities of succulent matter, but
do not tend to produce flowers, fruit, and seed.

These manures are, therefore, especially valuable for
such crops as lettuces, cabbages, mangolds, tea, etc. The .
phosphatic manures are generally characterized by the
production of deep roots, and it is for this reason that
the shallow-rooted crops need considerable quantities of
phosphates, because they have no deep root system to go
after plant food, and require something to strengthen this
system. Potash manure tends rather to the production
of seeds and flowers, but does not help root development to
any very large extent, but it has no delaying action, in the
same way as the nitrogen. Development of deep roots will
also depend upon the position of the water supply. Deep
water will encourage deep rooting, and surface water will

176 PLANT PRODUCTS

encourage surface roots. The influence of the different
manures upon the composition of pasture is very marked
indeed. In the experiments at Tree Field, Cockle Park,
the addition of phosphatic manures not merely increased the
amount of grazing, but also increased the feeding value of
the grass that was cut from this pasture. The phosphoric
acid was more than doubled in amount, the potash increased
about 80 per cent., and the nitrogen increased about the
same figure, although no nitrogen or potash was applied.
The addition of lime produced comparatively little effect,
either in the quality or quantity of the herbage, since this
was not the material which was most urgently needed. ‘This
large increase in the percentage composition of nitrogen and
potash as well as phosphoric acid has been brought about by
the application of a phosphatic manure. As explained
before, in the case of the hay crop more general manurial
treatment is desirable, and the results are, therefore, not
so striking, but the use of a manure like sulphate of ammonia
does not increase the albuminoids in the hay to any appreci-
able extent. In the case of the swede turnip crop, manures
containing little phosphates produce, on the whole, swedes
which contain less sugar than those manures which are
deficient in potash and nitrogen.

Food and Growth.—When very wet periods intervene
there is a liability to considerable loss of nitrogen in the
form of nitrates, and under these circumstances only a
portion of the nitrogen supplied will go into the crop.
Plants having, therefore, a short period of growth are much
more likely to miss a large fraction of the fertilizing materials
than those very slow growing crops that only reach maturity
after many months of growth. In tropical climates, where the
growth of the plant and the chemical changes in the soil are
both very rapid, the manure has a greater fertilizing efficiency
than in cold climates. Where soils are excessively cold, or
excessively hot, full utilization of the fertilizers is impossible.
Water and manure must be considered together. ‘To some
extent, a large supply of moisture, either from the sky or
by means of irrigation, will make up for a deficiency in the

FERTILIZERS AND PLANT PRODUCTS 177

supply of fertilizer supplied. In wet climates, like Ireland,
unsatisfactory soils and insufficient manure may produce
partially successful results, which could not possibly be
imitated in a drier and colder climate. Accumulations of
either acidity or alkalinity are harmful. Acidity is more
frequently produced by excessive quantities of organic
matter than by any accumulation of mineral acid, although
the use of sulphate of ammonia in large excess may pro-
duce the latter result. Alkalinity is produced by the appli-
cation of lime or by the residues of soda left from excessive
applications of nitrate of soda or by natural decomposition
of soda felspar in the soil. The removal of acidity is
generally obtained by the use of lime, while the removal of
alkalinity can be accomplished by the use of super-phos-
phates and gypsum. In the former case the neutralization
of the acid is due to the calcium bi-carbonate formed from
lime, carbon dioxide, and water. In the latter case sodium
carbonate, sodium humate, or soluble sodium silicate is
decomposed by calcium sulphate with the formation of
neutral sodium sulphate and other harmless substances.
Cultivation is one of the best means by which most is made of
the fertilizing ingredients in the soil, or supplied in the form
of fertilizers. Without efficient cultivation, full utilization
of the fertilizers will always be impossible.

REFERENCE TO SECTION VI

“Compound Manures,”’ Journ. Board of Agriculture, 1915-16, p. 675.

Clouston, ‘ Artificial Fertilizers for Cotton,” Agric. Journ. India, 1908,
p. 246.

Bald, ‘‘Experiments in Manuring on a Tea Estate,” Agric. Journ.
India, 1913, p. 157; 1914, p. 182

Part [V.—THE PRODUCTION OF MEAT

Section I.—MANURING FOR MEAT

To make the most of all plant products is to make the most
efficient use of agriculture. Experience in all lines of business
has shown that there are certain methods common to all com-
mercial concerns, and the plan to industrialize agriculture can
only mean the adoption in agriculture of the lessons learnt
in promoting efficiency in other businesses. Industrialization
of agriculture is, however, no new thing ; it has been done
before. The large Collieries in County Durham (see p. 209),
for example, employ managers and sub-managers for large
estates, and many colonial concerns are also worked in the
same way. Much land in the British Isles is unsuited to
corn, and hence the industrial improvement of agriculture
will largely turn on the improvement and development
of manuring for meat and the production of cheese. One
strong point in favour of industrialization is that the manager
of a large concern can buy and sell on better terms than
the manager of a small concern. The chief difficulty of
the farm lies in the immense difference between what the
consumer pays and what the farmer gets. Sometimes the
farmer does not receive one-third of what the consumer
pays, and the management of an industrialized farm can
check this source of loss (see p. 209).

Manuring for Meat.—The change from pioneer types
of agriculture to general conditions of mixed farming needs
stock feeding as an essential part, since such conditions of
general farming combine two entirely distinct objects,
namely, stock and crop production. The amount of meat
that can be produced from an area in pasture is less than that

ee

TT ROLE ae ie a al te My,

eee ac . =

MANURING FOR MEAT 179

produced from an equal area of mixed farming, whilst that
area, if entirely cultivated, would not be so productive,
unless the farmyard manure could be replaced. The
greatest efficiency, therefore, can be produced by combining
crop and stock production. ‘The first efforts to measure
meat production in terms of fertilizers were those initiated
in Tree Field, Cockle Park, by Dr. William Somerville,
continued by Professor Middleton and Professor Gilchrist,
and repeated in other places with similar results. ‘The
general effect of the use of basic slag on the heavy types of
clay land have been to very markedly increase the amount
of meat produced, as measured by means of the sheep
grazing. After allowing for the cost of manure the profits
ate several times larger than the rental. By employing
larger plots, grazed by mixed cattle and sheep, better results
have been obtained. ‘The most economical system has proved
to be the application of ten hundredweight of basic slag,
_ followed by five hundredweight every three years. Where
the animal is set grazing it may be regarded as a machine
for converting low-grade into high-grade food, that is, food
of low value to human beings is converted into food suitable
for human consumption.

In this process of conversion of crude materials into
atticles valuable for human purposes, considerable changes
have to take place in the animal body. Grazing beasts may
generally be said to be composed of about 9 per cent. bone,
40 per cent. muscle, 24 per cent. fat, and 27 per cent. blood,
intestines, and other offal. Of this, the muscular part,
together with the fat, forms the chief eatable material.
The actual amount of human food is roughly about one-half
of the total beast. At birth, young animals contain large
quantities of water, about 80 to 85 per cent., but in a very
fat beast the amount of water will only be about 40 per cent.
If the various parts of the beast are corrected for the amount
of water contained, there will be about 6 per cent. of dry
material in the bones of an average farm animal, in the
muscle 13 per cent., in the fat 20 per cent., leaving about
7 per cent. dry matter in the offal, the whole body containing

180 PLANT PRODUCTS

about 46 per cent. of dry material, the rest being water.
The fat of the animal body, like most of the other compounds
of this group, is a glycerine ester, and the fatty acids are
stearic, palmitic, and oleic. The fat of the animal body as
separated by the butcher consists of the chemical fat,
enclosed in membranes. In a fat beast the amount of
membrane in the fat is comparatively small, but in a lean
beast it might amount to one-quarter of the weight of the
fat. Carbohydrates are only present to a very small
extent. Small quantities of dextrose are always present
in the blood, to the amount of about o'r to o-2 per cent.,
any excess of carbohydrate being stored in the liver. The
proteins have been fully described (see Bennett, Bibliography).
During the life of the animal, the chief metabolic changes
consist in the hydrolysis of the proteins, fats, and sugars,
followed subsequently by their oxidation. The major part
of the proteins in the animal body exist in the form of the
organs, and are semi-permanent. ‘The remaining portion
is temporary, and undergoes rapid chemical changes. It
is this portion which supplies the vital energy necessary
tothe beast. The chief effect of setting an animal to perform
work is to increase the rate of chemical breakdown of the
fats and carbohydrates. It is only overworking which
will produce any large breakdown of the animal proteins.
Stimulants, excitement, and the consumption of salt increase
the amount of protein decomposed in the animal body.
The heat that is lost by the animal is chiefly lost by radiation
and conduction from the surface and by evaporation from
lungs and skin. The evaporation from the lungs depends
upon the amount of breathing, and, therefore, upon the
amount of exercise.

When the proteins are broken down in the animal body,
during the process of digestion, they are resolved into the
corresponding amino acids. The number of these amino
acids that are necessary is comparatively very limited.
Most of the amino acids into which the proteins are broken
down in digestion are aliphatic, some mono-carboxylic,
and some di-carboxylic. Some of them are mono-amino

MANURING FOR MEAT 181

acids and some di-amino. Some of them are straight, and
some of them are branched. An important cyclic compound
is indole, which the animal body does not seem capable of
synthesizing. A common hydrolytic product of the break-
down of some proteins is tryptophane, which contains the
indole ring. ‘The proper utilization of the proteins absorbed
from the food appears to depend upon minute traces of
substances which are known as food hormones. Little is
known about the exact character of these bodies, although
some are compounds of pyridine. When tryptophane is
broken up in the animal body, it is probably excreted as
skatole, which is of a purgative character. One of the
results of feeding excessive quantities of protein material
is usually to produce a loosening effect. This is probably,
at least in part, due to the excretion of superfluous quantities
of bodies like skatole. Frequent mistakes in feeding cattle
have been made by the use of excessive quantities of nitro-
genous food, but it is not always practical to get, on
economic lines, the exact mixture one requires. Maize which
contains no tryptophane is known to be somewhat binding
and heating in its effects. The simple amino acids, like
aspartic and glutaminic acids, are produced by the hydrolysis
of proteins in such large amount that relatively they are
not urgently needed. Even the benzene nucleus seems to be
fairly easily obtainable either synthetically or analytically.
The substances constituting the nucleus of most cells
contains some of the purine bases, which give rise to uric
acid in man, but to allantoin in beasts. ‘There does not,
therefore, seem to be the same risk of over supply of purine
bases to animals that there is to man. In estimating the
feeding value of foodstuffs, it is not uncommon to differentiate
between the true albuminoids and the amides, that is to
say, between nitrogen precipitated by lead acetate and
ammonia volatile with caustic alkali and steam, or some such
similar division. Such bodies as asparagine will only yield
half their nitrogen by distillation with caustic alkali and
steam. Such a division, at the best, does not really answer
the question we wish to ask. What we really want to know

182 PLANT PRODUCTS

is the relative proportion of important ring compounds,
like indole, benzene, or purine. The reason why the so-
called amides have little value is that the compounds
which yield ammonia on hydrolysis are plentiful in the
products of hydrolysis of the protein in most cattle foods.
Compounds like aspartic and glutaminic acids will probably
supply twenty times as much nitrogen as substances of
the tryptophane type, hence the indole groupings are
comparatively scarce, and, therefore, valuable, whilst the
simple amino acids, like aspartic acid, are plentiful, and,
therefore, not very valuable. All these substances are
probably utilized by the animal, but those that ate scarce
in amount are the ones whose supply we have to consider.
Under special conditions even ammonium acetate has proved
useful for increasing the protein laid on by beasts. Never-
theless, no very practical system has yet been discovered
to obtain a clear idea of the value of the different proteins
in the foods.

The metabolic changes of the fats result in hydrolysis,
oxidation, and production of sugars. The sugars themselves
break down with the production of carbonic acid. The
proteins are chiefly concerned in the building up and repairing
of the structural part of the animal body, the fats and the
sugars being chiefly concerned with the production of
energy. :

REFERENCES TO SECTION I

Wood and Yule, ‘‘ Statistics of British Feeding Trials, and the Starch
Equivalent Theory,” Journ. Agric. Science, vi., p. 233.

Wood and Hill, ‘“‘ Skin Temperature and Fattening Capacity i in Oxen,”
Journ. Agric. Science, vi., p. 252.

Hall,’ Agriculture after the War,” p. 39. (Murray.)

Armsby, “‘ The Principles of Animal Nutrition.”

Bennett, ‘‘ Animal Proteids.”’ (Bailliére, Tindall and Cox.)

Luck, ‘‘ The Elements of the Science of Nutrition.” (Philadelphia.)

Section II.—THE FOODS FED TO BEASTS

Water in Foods.—All foods fed to stock contain a
certain amount of water in their composition. Soft turnips
contain as much as 92 per cent. of water, mangolds about
86 per cent. of water, and concentrated foodstuffs, like
the oil cakes and grains, contain about 12 per cent. of water.
When foods contain large quantities of water, little extra
water is needed for drinking purposes, but when consider-
able quantities of dry food are fed, water must be used in
addition. ‘The consideration of the water supply for stock
closely resembles the study of the water supply for human
consumption, but a considerably lower standard may be
adopted. Drainage from fields may be utilized for this
purpose, but care should be taken that the water is not muddy
or fouled by any trampling by the cattle themselves. A
short lead of underground pipes, conveying the water from
this source to a properly constructed cattle trough, will
tesult in the supply of a considerably purer water. The
mere process of running through pipes tends to purify the
water, as it comes into contact with fresh air in the course
of its fall. A small underground reservoir is also convenient
to remove earthy matters in suspension. Where large
quantities of vegetable growths occur in the drinking supply,
unsatisfactory results may be observed. Each pound of
dry food used needs seven pounds of water for pigs, four or
six pounds for cows, or oxen, and two or three pounds for
horses. Well-fed animals with a good coat usually develop
excessive heat, and, therefore, do not suffer from drinking
cold water. Pigs, however, being smaller animals, and being
ill protected by hair, not infrequently show some good
results from heating the water supply. When water, in

184 PLANT PRODUCTS

combination with food, is supplied in excess, an unnecessary
strain is placed upon the kidneys of the animals concerned.
Increased metabolism therefore takes place, and the water
actually passed has to be heated to the body temperature.
Waste of energy, and therefore food, is the result of supply-
ing unnecessary amounts of water. It is, of course, not
practical to cut the water supply down below the figure which
is necessary for the health and comfort of the beasts. They
themselves will be the first to make objection should they
be kept thirsty.

The Fat in Foods.—The foods fed to beasts generally
contain fat in small quantities. The common analytical
figures, which represent the total amount of material
extracted from the food by the use of ether, include other
substances than true oils and fats. Anything in the nature
of wax or resin will also be extracted by ether. In the case
of the oil seeds, the proportion of waxes and resins is relatively
small, but in such food materials as hay, the proportion
of ether extract which is not true fat is very considerable,
and may amount to one-half. In such cases, however, the
total percentage of oil is too small to make much difference,
whether it is considered or not in calculating rations. The
true fats are glycerine esters of some of the fatty acids (see
p. 108). When fed to stock, the fat undergoes hydrolysis
in the process of digestion with the production of the
corresponding fatty acids and glycerine, which are absorbed
and built up into the fatty tissues of the animal body.
Considerable portions of the breaking-down products of
the fats will be oxidized, for the purpose of producing heat,
in consequence of which the properties of the fat laid on
by the animal are more dependent upon the animal con-
suming the food than on the properties of the fat in the food
consumed: For rough purposes, the food value of fats is
about 24 times the value of the same weight of carbo-
hydrates.

The Nitrogenous Matter in Food. —The proteins in the
foods are similar to those described in Part III., p. 147.
So far as regards the more concentrated foods, the ‘total

Ieee

aa al

ee Se eT

THE FOODS FED TO BEASTS 185

nitrogen multiplied by 6}is a good enough approximation, but
in some of the less concentrated foods, like hay and turnips,
it has been found in practice that some further information
is desirable. For this reason the nitrogenous matter is
commonly divided into the two groups of the “ true albumi-
noids’’ and the ‘‘ amides” (see p. 147). The particular
amino acids required by the beasts will vary according to
the needs of the animal, which will depend partly upon the
species, partly upon the age, and partly upon the condition
of health. Foods may not infrequently contain a few special
nitrogenous matters, such as some of the nitrogenous gluco-
sides. Some of these, of which amygdalin and linimarin
may be taken as types, evolve prussic acid under certain con-
ditions (see p.137). Potatoes contain another special nitro-
genous glucoside called solanin. Potato eyes may contain
large quantities, even up to 5 per cent., but the haulms do
not usually contain more than about 0°03 percent. This
substance is slightly poisonous, but the amount present is
usually too small to produce any serious effect. Special
foods may sometimes contain nitrates, especially crops grown
under droughty conditions. Probably the nitrates them-
selves are not very harmful, but they usually accompany other
forms of nitrogen, neither protein nor amide, and injurious
results have been observed under these conditions. Man-
golds, for example, are not satisfactory to feed immediately
after pulling, but after an interval of storage they become
riper, the nitrates, among other changes, being converted
into organic nitrogen bodies, and the irritating compounds
being built up into proteins. In India, juari and other
fodders when cut unripe in droughts act in a similar
manner. In sound food the nitrogen in the forms of true
albuminoids and amides (see p. 181) usually adds up to the
total nitrogen, but in unripe root crops and leaves there
are often other forms of nitrogen than these. A portion
of the other forms will often be nitrates, but there are other
nitrogenous compounds whose constitution is little under-
stood. For a large number of purposes no effort is made to
do more than determine the total nitrogen in the foodstufis.

186 PLANT PRODUCTS

It is only in the case of the root crops and hay that any
serious error would be introduced by neglecting to measure
the amides separately.

The Carbohydrates.—Sugar is much appreciated by
stock, as it gives a considerable flavour to the food, and is
often valuable to the farmer by inducing stock to eat other-
wise not very palatable articles. ‘The sugars found in cattle
foods are cane sugar and glucose. Whilst these materials
are much appreciated by stock, experimental evidence
shows that their body-building power is lower than that
of the starches, but as such experimental results can only
be obtained by feeding sugar in large quantities, it is
probable that they do not reflect the conditions of ordinary
farm practice. Sugar, being instantly soluble in water,
will enter the blood stream, and pass through the liver at
a great rate. Very small quantities of sugar will not throw
any strain upon the liver. It is, therefore, to be expected
that the food value of sugar will depend largely upon the
amounts fed, and that, whilst it may have a high value when
the quantity is small, it may have a low value when the
quantity is large. In practice, owing to the expense, large
quantities of sugar are probably not fed. In the case of
stock consuming large quantities of swedes, the total amount
of sugar fed is very considerable. Swedes contain more than
one-half of their total solid material in the form of sugar,
and if these constitute half of the dry matter fed, it would
mean that 25 per cent. of the ration wassugar. Experience
shows that this is not economical, the inefficiency of heavy
root feeding being generally attributed to the water being
in excess, but it may partly be due to the sugar also being
in excess. Sugar which is consumed by beasts in the form
of swede turnips would not be digested at the same rate
as sugar in the form of treacle, and, therefore, the strain
upon the liver would not be so marked. Possibly this in
the explanation why feeding sugar in the form of roots
appears to be more satisfactory than feeding it in the more
concentrated form.

Starch.—In the case of feeding animals there does not

ee

a at

—e =

=

c+

Pt ee ee

THE FOODS FED TO BEASTS 187

seem to be any advantage in boiling starch, the digestibilities
appearing about the same in boiled and unboiled starches.
The starch is converted during the process of digestion into
glucose, and this passes through the liver, where it may be
temporarily deposited as glycogen. Starch is particularly
liable to bacterial decomposition in the intestines, probably
due to the fact that its digestion is somewhat slow. Starch
may, therefore, very easily suffer considerable loss.

Pectins, Mucilage, etc.—This group of carbohydrates
for the most part resembles starch, but sometimes contains
a proportion of pentosans. ‘The general feeding value of the
carbohydrates is the same as that of starch. Under digestive
conditions these change into glucose, though some pentose is
also formed.

The Fibrous Materials in Foods.—‘The portion
of the food material which is not soluble in ether, dilute
sulphuric acid, and dilute potash is considered the indigestible
fibre. This material is composed largely of cellulose,
together with lignin, and other materials. The ordinary
analytical processes rather resemble an attempt to give a
rough imitation of digestion than any effort to obtain a
definite chemical subdivision. ‘The common method of
analysis will give very valuable figures representing the
indigestible material, and is quite a fair approximation of
the actual digestive process of the animal. Up to a certain
point the ruminants require fibre in their food, as their
digestive processes are adjusted to foods of this type, and
if fibrous materials are withheld, the digestion is interfered
with. Within limitations, therefore, fibre possesses a real
value, but it is not common to consider this fact, because
the fibrous foodstuffs are relatively cheap, and, therefore,
the tendency is to feed rather more fibre than is absolutely
necessary, but this consideration would not apply to a
town cowkeeper, who has to purchase everything in the way
of food, as it does to a farmer who grows his own hay. In
small quantities, therefore, one must regard fibre as being
useful. In large quantities it is not merely useless but
highly objectionable.

188 PLANT PRODUCTS

Digestion.—Attempts have been made to measure the
ultimate results of the digestive processes in animals. In
such experiments all the food consumed by the animal is
analysed, and, in addition, all the solid excreta are analysed
inthesame way. ‘Ihe difference between the two is supposed
to represent the material which has been digested. ‘There
are several errors, nevertheless, in this assumption. In the
process of digestion, portions of the food are first absorbed,
converted into intestinal mucus, etc., and are excreted.
The ultimate gain to the animal is quite correctly represented
by the difference between the two analyses named above,
but a more serious error is introduced by bacterial activity.
The bacteria are, allthe time digestion is going on, struggling
to get ashare of the food. Such bacteria as oxidize the food
materials will produce just the same amount of heat ,as
the oxidation would give under other circumstances. If
the animal requires this heat there would be no loss. If the
animal does not require the heat, as might be the case in
hot weather, then the heat produced is not merely useless,
but a nuisance. ‘The bacteria, however, that flourish in
the intestinal tracts, are for the most part of a different type,
and much of their energy is devoted to the decomposition
of carbohydrates with the production of marsh gas and
carbon dioxide. As much as 700 litres of marsh gas from
one beast in one day has been observed, which is equivalent
to a waste of four pounds of carbohydrate. ‘These carbo-
hydrates, of course, disappear, and are considered as digested,
although they have produced little heat, and no good of
any kind to the animal. Such fermentive changes depend
upon slow digestion, the quicker the animal can digest the
food the smaller is the share available for the bacteria.
As the result of such experiments, tables of digestibilities
have been constructed (see Kellner). Such tables will
allow one to calculate the probable amount of food actually
digested by the beasts from any particular food supplied.
The ordinary analysis can be carried out according to the
text-books (see Bibliography), and then the digestive
coefficients used to convert these figures into digestibilities.

THE FOODS FED TO BEASTS 189

Such a calculation assumes that the figures apply to the
particular case in question. ‘The full table given in Kellner’s
work supplies a considerable amount of information which
permits one to apply these values with a fair degree of
certainty. ‘There is, however, always the difference between
the actual conditions prevailing and those under which the
tables were deduced. A study of the tables in Kellner’s
work shows that in some cases very wide variations in the
results were obtained. ‘The variations compensate for one
another to some slight extent. Probably the great variations
that may be observed in the digestible fibre are really
attributable to the fact that some of the materials which
are possibly called “‘ fibre ’”’ in the solid excreta of the beasts
are really bacterial residues. ‘The fluctuations observable
in the column “total matter digested ’’ are more valuable
in assessing the probable error inthese experiments. Astudy
of the tables will convince one that the use of these tables
will give a figure for the digestible ingredient per cent. which
is true to two or three units, but cannot be considered as
being any closer than that. In some instances it is quite
obvious that Kellner himself recognized that the figures of a
few experiments are not very reliable. It will be noted, on
referring to p. 388, that Kellner gives digestible coefficients
for “palm nut cake’ and “ palm nut meal, extracted,”
which differ from one another to a degree which is difficult
to credit ; but when he makes use of these figures for compiling
the table on p. 377, he uses for calculating the digestible .
nutrients in those two substances, not the figures he has
himself quoted, but the average of the two cases. ‘That is to
say, in calculating the digestibility of palm nut cake, he
does not use his own figures but an average obtained from
palm nut cake and palm nut meal. This procedure is quite
legitimate, of course, but shows that Kellner did not himself
attribute to his own work that degree of precision which is
sometimes assumed by those who use his tables. Such
apparent discrepancies in the table of digestibility of decorti-
cated cotton seed meal, where the digestibility coefficient
of the fibre varies from 0 to 100, though appearing very big,

190 PLANT PRODUCTS

are not of great importance, because the percentage of crude
fibre in this meal is very small. The fluctuations in the
digestibility of the crude fibre in undecorticated cotton cake,
which vary from 2 to 24 per cent., although superficially
not so serious, are in practice of more importance, since
the percentage of fibre in this food is about 20 per cent.
In spite, however, of these apparently large discrepancies,
experience has shown that feeding standards which are
based ultimately on these experiments are practically
sound. |

During digestion, the lining of the stomach itself is
protected by a supply of anti-pepsin, which is produced
for this purpose. If an animal were to die suddenly during
the process of digestion, the supply of this anti-pepsin would
fail along with the rest of the circulation, and the lining of
the stomach would be partly digested by the digestive
juices. Some portion of the materials which are considered
as not having been digested are really bacterial remains,
which, of course, have been produced from the food by the
life of bacteria, and have done no good to the animal.

REFERENCES TO SECTION II

Wanklyn, “‘ Water Analysis.” (Kegan Paul.)

Evans, ‘‘ Driage,’’ Agric. Journ. India, 1917, p. 234. —

Leathes, ‘‘ The Fats. Monograph on Biochemistry.’”’ (Longmans,)

Collins, ‘‘ The Feeding of Linseed to Calves,” Journ. Board of Agricul-
tuve, 1915-16, p. 120. i

Bainbridge, Collins, and Menzies, ‘‘ Experiments on the Kidneys of the
Frog,” Proc. Roy. Soc., B., vol. 86, 1013.

Plimmer, ‘‘ The Chemical Constitution of the Proteins. Monograph of
Biochemistry. (Longmans.)

Armstrong, “‘ The Simple Carbohydrates.’’ (Longmans.)

A. Rendall Short, ‘“* The New Physiology,” p. 84. (Simpkin.)

Kellner, “‘ The Scientific Feeding of Animals,” p. 379. (Duckworth.)

Warington, ‘‘ Chemistry of the Farm,’ p. 144. (Vinton.)

Srotion III.—CALORIFIC VALUE OF FOODS

The Animal as a Heat Engine. —Just as an engine may
be regarded as a means of converting the fuel supplied into
work done, so a food fed to a horse may be also regarded in the
same light, and the food fed to a milk-producing or fattening
beast may be also regarded from the energy point of view.
Energy is usually represented in terms of calories. The
calorie adopted in theoretical considerations is the amount of
heat necessary to raise the temperature of one gramme of
water one degree Centigrade. In practical, big-scale work it
is preferable to employ a unit 1000 times that size, and to
define this large Calorie as the amount of heat required to
raise the temperature of 1 kilogramme of water 1° Cent. On
such a scale, the complete combustion of earth nut oil
would give 8°8 Calories, wheat gluten 5°8 Calories, starch
4'r Calories, and urea 2°5 Calories. In the animal body the
final products of the decomposition of the foods differ from
those obtained in the steel bomb used for determining heat
equivalents, owing to the fact that the nitrogen is not given
off as elementary nitrogen, but is given off in the form of .
urea. As the amount of nitrogen in urea is nearly three
times as great as that in the ordinary albuminoid or protein,
one part of protein may be assumed to produce one-third
of a part of urea, giving a loss of 2.5~+3 Calories, and,
therefore, the 5°8 Calories from wheat gluten would only
produce about 5 Calories in the animal body, because the
fractional part would represent the loss due to producing
urea instead of nitrogen. No such deduction, of course,
has to be made for the carbohydrates or oils. The calories
evolved in the consumption of a food, therefore, needs
two deductions to be made from them. Firstly the

192 PLANT PRODUCTS

deduction for indigestible material (see p. 188), and
secondly, the deduction due to the urea produced in
place of nitrogen. Further, during the process of diges-
tion, bacterial fermentation produces considerable loss, and
further there is a loss of energy in production, due to
such operations as chewing tough fibres, intestinal move-
ment, circulation of the blood, the action of the lungs,
etc. It is, however, possible to prepare a balance-sheet of
income and expenditure in terms of calories. The following
represents the result of a particular experiment on a well-
fed ox :—

TABLE 24.
Income, Expenditure,

Calories, Calories,
Food oi ong $5 $2,929 Feeces nn “ye aa (35,016
Urine "he b's <“s 1,686
Marsh gas on tr Be

Maintenance (other experi-
ments) .. se APTA by fhe
Flesh ae “ oa 246
Fat... vs “9 -- 8,069
Energy for fattening bs gem
52,929

As regards the internal work in the animal, if the heat
produced is really required there will be no loss due to the
food itself; but if the heat produced by this work is not
necessary, then such energy will have to be considered in
the above table under the head of the extra energy for fatten-
ing processes. The conditions are much the same as those
prevailing in a steam engine. A locomotive “standing in
steam ’’ is roughly reckoned to consume half as much coal
as if it were really working, and similarly, the animal takes
a good deal of food for mere maintenance, as is exhibited in
the table given above. If an animal is fed with more food
than is necessary for mere maintenance, a portion of the food
will be used for the production of flesh and fat, but the putting
on of this flesh and fat will involve a certain consumption

CALORIFIC VALUE OF FOODS 193

of food, just in the same way as a steam engine will require
a certain amount of coal to keep up the steam pressure,
though doing no work, and any work required from it would
necessitate a further allowance of coal, a portion only of
which would be accounted for inthe work done. The amount
of energy required for the utilization of food materials depends
upon the way in which the food materials are presented

tothe animal. Pure foods and sugars can be digested with

the least exertion, but when these substances occur in food
among hay or straw, then the animal will have to do much
chewing, and other work, before the fats, carbohydrates,
and proteins are acted on by the enzymes in the digestive
tracts. Moreover, a far larger quantity of enzyme will have
to be produced, because a great many enzymes are condensed
on the surface of the fibrous matter in the alimentary tract,
and most rates of decomposition depending upon enzymes are
considerably retarded by the presence of cellulose in the
digestive tracts ; bulky food will also need a greater amount
of fluid, which has to be produced by the animal, at some
expenditure of energy. Under very extreme circumstances,
energy expended in the effort to digest food may exceed
the energy obtained from the digested part of the food.
Ruminants swallow much of their food with only partial
mastication but regurgitate it, “‘chew the cud,” and
again swallow. ‘The finely comminated material is filtered
out by the third stomach and the insufficiently chewed fibres
again regurgitated. In this way a ruminant can make much
more effective use of fibrous food than a non-ruminant
herbivorous animal. A horse is quite incapable of living upon
straw alone, although an ox may just manage to keep itself
alive. If, however, part of the work of digestion be done
beforehand, much better results can be obtained. Kellner
found that straw pulp, as used for papermaking, was far more
digestible than straw itself. Of the straw pulp as much as
88 per cent. could be digested by an ox, and, after allowing
for the work of digestion, the straw pulp was worth rather
more than one-half its weight of starch as a food material.
As, however, in the process of turning straw into paper pulp,
D. 13

194 PLANT PRODUCTS

about one-half the weight is removed, the ultimate advantage
of such treatment is not very marked, although it does
undoubtedly show that if the ox is assisted in his digestive
process, a larger amount of energy will be left for him to
make some good use of. In a similar way, merely chaffing
straw or hay reduces the work necessary to be done by the
beasts, and, therefore, a higher feeding value can be obtained.
When animals are merely maintained in store condition
the amount of food necessary to keep them is small, and may
be of a coarse quality, since the energy expended in chewing
is useful for maintaining the temperature. If, however,
animals are called upon for a big output of energy, they must
be fed on foods which do not involve so much internal
expenditure. A horse that is doing nothing can live upon
hay and grass, but the harder the work given, the greater
must be the proportion of concentratedfoods. If the external
work is to be increased, the internal work must be decreased.
The same remark applies to cattle and sheep. ‘The relation-
ship between the amount of calories necessary for maintenance
and the live weight is not constant, but depends upon the
size of the beast. Roughly speaking, the loss of heat from
an animal body is proportionate to the surface, though the
amount of hair and fur will effect this considerably. ‘The
theory, however, that the amount of heat is proportionate to
the surface is surprisingly close to what is obtained in practice,
although it is very easy to push the theory too far. If
the ‘“‘surfacelaw’’ is considered, it will be seen that the
weight of a beast will vary as the cube of the length, whilst
the surface will vary as the square of the length. Hence, a
small increment in the weight of the beast corresponds with
two-thirds of that small increment in the food.!

But as a beast grows older its digestion diminishes, and
more food has to be fed to counteract the decrease in
digested nutriments, hence the common rule of reckoning

1 Since wl, foros erltos wi
. af _ -}

where w=weight, /=length, f=food, s=surface.

CALORIFIC VALUE OF FOODS 195

the food as proportionate to the live weight is not so very
far out in practice. ‘The surface law is more useful in com-
paring dissimilar animals at the same period of growth than
of similar animals at different periods of growth. The surface
law enables one to equate the rations of a guinea pig and a
galloway, both three-quarters grown, but does not enable one
to equate the rations of a calf and a Christmas fat beast.

An ox weighing 1200 lbs. needs 12,000 Calories per
diem for its maintenance, whilst a sheep weighing about 100
lbs. requires 2000 Calories. Directly any work or fattening
is needed, the amount of food must be increased. A horse
weighing 1125 lbs. required for maintenance 12,600 Calories,
but when doing fairly heavy work, required more than
double that quantity for its output of energy.

Many different systems have arisen to use the purely
theoretical considerations given above, and apply them to
the practical rule-of-thumb methods of feeding commonly
adopted. These systems have followed the needs of the
day. At the time when purchased cattle foods came into
common use there was much more corn grown than at present.
Much of this corn was grown on poor land, insufficiently
manured, with a correspondingly big proportion of tail corn,
or with entire crops unsuited for the production of bread.
The beasts, therefore, received plenty of carbohydrates
in corn and straw whilst the albuminoids were supplied by
good hay, but the oil was very deficient. Hence the “ oil
theory’ of the day. Later, as wheat was grown less and ©
less, and as the land fell back to grass of little fattening
value, the general feeding of the cows became low in albumi-
noids, but the increasing use of oil cakes removed the oil
shortage, and the “oil theory” dropped out, and the
“ albuminoid theory’’ came in. Of recent years we have
had a dearth of carbohydrates, and the weak link in the
chain has occurred at that point. But carbohydrates are
too indefinite, being only a ‘difference figure,’’ hence the
present use of the ‘‘ starch equivalent ’’ theory.

Practical if rough ratios were studied in early research in
Agriculture. Iawes and Gilbert, at Rothamsted, deduced

196 PLANT PRODUCTS

the general principles that to obtain one pound live
weight increase in the weight of oxen, thirteen pounds
of dry food material were necessary, whilst about nine
pounds of dry food sufficed in the case of sheep, and
five pounds in the case of pigs, the foods fed being of
a mixed kind common to the diet used in most parts of
England. The rate of increase of an animal is, however,
much greater in proportion to its food in the early
stages of its growth. Some of the early experiments of
Lawes and Gilbert on pigs are convenient evidence on this
point. In the first month they found that four pounds of
food produced an increase of one pound, and in the second
month it took five pounds, and in the last month of fattening
it took as much as six and a quarter pounds to produce this

increase. ‘There is here no resemblance between the’

objects in fattening and the objects in obtaining work,
since a young horse is not capable of putting forth much
energy in return for its food, being occupied chiefly in growing.
One method of attempting the assessment of foods is to
merely take the dry matter, which is an advance on the
crude methods commonly adopted. The next advance on
that is to deduct the fibre or indigestible matter. A further
advance is to utilize the complicated tables given by Kellner,
and a further method is to deduce Kellner’s starch equivalent
or Hanson’s milk unit. Another system consists of having
standard rations, tabulated for all kinds of stock, giving so
much digestible oil and carbohydrates. The latter method
has the objection that it requires rather complicated sets
of tables, but- is perhaps the most comprehensible to the
ordinary practical feeder, who finds starch equivalents rather
a little beyond him. At the present time the knowledge of
feeding is not sufficiently advanced to reduce the question
of feeding to a scientific basis, and probably all these systems
will remain in vogue. The difference between individual
animals is always very great, and individuality must be
allowed for, and hence great precision on the theoretical
side is not of first-rate importance. In many instances, a
study of Kellner’s tables will show what big variations occur,

Fy ne
a

ay

—s

| ae ee A es

Be he

~

a

PDs =

CALORIFIC VALUE OF FOODS 197

even under carefully controlled experimental conditions.
Where a large portion of the food consists of hay, large
variations in digestion must be expected. Kellner found,
for example, in meadow hay, that the digestibility varied
from 46 to 79 per cent. ‘The digestibility varies roughly
with the fibre, and the relative food values can be obtained
by the formula, 24 x oil per cent. + albuminoids per cent.
+ carbohydrates per cent. — 4 fibre per cent. Kellner’s
tables, however, are the best available method.

The most efficient animals for converting cattle food into
human food are undoubtedly those producing milk. The
daily ration for a fattening beast is very similar to that for
a cow giving about two gallons of milk a day. Ina weeka
fattening beast would give perhaps about 11 Ibs. of beef, as
against 140 lbs. of milk from a cow. As the food value of
the beef is about double that of the milk, weight for weight,
the advantage of milk is seen to be enormous. Even if the
milk is converted into cheese, about 14 Ibs. of cheese would
be obtained, and again, cheese is more than double the feeding
value of beef, weight for weight, so that under any circum-
stances the cow is far more efficient than the bullock for
converting cattle food into human food. Of course, the
amount of labour involved with dairy stock is greater than
that of fattening stock. ‘The next most efficient animal to
the cow is probably the pig, and sheep are generally rather
better than the ox for the utilization of food material,
though mixed grazing is best. On the general average,
the sheep get lower quality food, and give a better return.
If, however, cattle were slaughtered early, for the production
of much more veal and less beef, economy would be effected
in this way ; but, on the other hand, the earlier slaughtered
animals will need to be fed with an average higher quality
food, and an average greater expenditure of labour. Poultry
are not economical converters of low-grade food into human
food. It is only if they are fed to a large extent on such
things as clover meal and fish meal that they can be considered
as producing human food economically. ‘Tables 25 and 26
give the data necessary to convert calories into human

198 PLANT PRODUCTS

feeding equivalents. ‘The figuresin Table 25 refer to a man
at ease, in temperate climates. A man at perfect rest,
lying in bed, would only need about 2000 Calories a day ;
with eight hours’ hard work, 3250 Calories (Table 26) ; with
very hard work, not actually detrimental to health, 3830
Calories.

TABLE 25.—HumMAN Heat Account. AT EASE.

Calories
per diem.
Radiation (ordinary clothing) ae aS 1536
Evaporation of water from skin and lungs a 611
Heating respired air vie 80
Heating food and water to body temperature te 53
Working of heart, etc. ea oy 150
Total ve ne “9 oe 4 2430

TABLE 26.—DaiLty HUMAN RATIONS FoR EIGHT Hours’
Harp Work. :

Total, Digestible,
, gm. gm. Calories,
Protein .. Wie sm Too 92 377
Fats ay ss SC 100 95 883
Carbohydrates .. nd 500 485 1988
3248

One hundred head of population, consisting of mixed
men, women, and children, may be considered as equal to
seventy-seven men. One “‘ person”’ needs a million Calories
per annum.

REFERENCES TO SECTION III

Maidment, “ The Home Dairy,” pp. 15, 23. (Simpkin, Marshall.)

Wright, ‘‘ The Composition yea ri utritive Value of Mutton and Lamb,”
Journ. Soc. Chem. Ind., s9te p28

“* Comparative Values of Goalie Stuffs,” Journ. Board of Agriculture,
1915-16, p. 53.

James Long, “‘ Food and Fitness.” (Chapman and Hall.)

Crowther, ‘‘ The Feeding of Farm Stock,” Journ. Board of Agriculture,

1912-13, p. 107,

Srotion IV.—DAIRY PRODUCTS

MILK is composed of about 87 per cent. water, about
3°8 per cent. of fat, and 9g’o per cent. of other solids. The
fat resembles ordinary animal fat, excepting that it con-
tains rather higher proportions of butyrin and other fats
containing the lower fatty acids. The chief nitrogenous
material is casein, or caseinogen, which is characterized
by being precipitated in acid solutions. Milk also con-
tains a small quantity of albumen, which is precipitable
by heat. Milk sugar is the only form of sugar present
in milk, and on hydrolysis or digestion gives glucose
and galactose. The mineral matter is fairly constant at
0°75 per cent. of which calcium phosphate, sodium chloride,
and potassium chloride constitute the major part. Milk
is produced directly by the breaking-down process of the
tissues in the glands, and is not dependent upon the composi-
tion of the food supplied, but is maintained in molecular
equilibrium with the blood. Consequently, the molecular
concentration of the soluble portions is fairly constant,
but a deficiency of milk sugar may be replaced by an increase
in the amount of soluble salts. The freezing-point of milk
is in consequence regular. ‘There is a constant relationship
between the specific gravity and the materials of which the
milk is composed. This has been brought out by many
authors (see Bibliography), and may be very simply ex-
pressed by the formula that the non-fatty solids = } of the
gravity + } of the fat + 0°14, the fat being represented as
percentages, and the gravity being the final figures of the
specific gravity, after removing the 1:0 which is constant in
all milks. The composition of the milk will vary according
to many causes :—

200 PLANT: PRODUCTS

(x) ‘The period of lactation. Immediately after calving,
the milk is commonly called colostrum, when the composition
is very abnormal. ‘The total amount of nitrogenous material,
albumen, and casein may be as high as 23 per cent., most of
which is albumen, the casein being comparatively small in
amount. Even the second milking on the first day shows
a distinct drop in the percentage of albumen and casein,
and during the first day the majority of the figures that have
been obtained by the author show over ro per cent. of these
two substances. The third day after calving brings the
figures down to about 6 per cent. of albumen and casein.
By about the seventh day the percentage of albumen and
casein has fallen to 4 per cent. as against 34 per cent. in
ordinary milk. During the same period the milk sugar
undergoes a very marked increase. On the first day the
amount is only about I per cent., steadily rising until about
the fifth day, when it reaches the normal figures between
4 and 5 percent. The ashis also usually high after calving.
From the second to the seventh week the greatest quantity
of milk is produced, the quantity decreasing and the quality
improving after that. During the last two or three weeks
before going dry the milk is usually of very uncertain
composition, but as the amount is very small, little trouble
results.

(2) In the spring, milk is usually at its poorest, and in
November at its richest. Owing to the disturbance in the
times of milking which occurs on Sunday, it is not infrequently
found that the Monday morning’s milk is rather poor. ‘The
difference between the morning and evening milk follows a
fairly regular rule, depending upon times of milking. The
following formula represents the change in composition,
which was obtained on an average of a very large number of

experiments, EH — M = - — 6'2, where E stands for the even-

ing fat per cent. and M for the morning fat per cent., and
the e stands for the interval between the evening and morn-
ing periods of milking, calculated in hours. ‘The portions
of milk first drawn may contain only 1 per cent. fat, whilst

SS

eee

=.
et ee

i Le,

DAIRY PRODUCTS 201

the last portions drawn may contain as much as 10 per cent.
fat.

(3) Some breeds, such as Jerseys, Guernseys, and Kerries,
give richer milk than other breeds, such as Shorthorns and
Ayrshires. Individual cows vary a great deal. Some short-
horn cows, fed and housed under the same conditions, will
give 24 per cent. of butter fat and 8 per cent. of non-fatty
solids, whilst others of their companions will give 5 per cent.
of butter fat and 10 per cent. of non-fatty solids.

(4) When cows have been fed indifferently, they cannot
be expected to give good quality milk, and under these
circumstances improvements in the system of feeding will
result in a great improvement in the quality of the milk,
but there is a limit which is soon reached as regards feeding.
Overfeeding does as much harm as underfeeding. With
skilful management the maximum of quality and quantity
can be obtained, and beyond this no one can go.

(5) When milk stands, the cream rises to the surface,
especially in hot weather. In some experiments by the
author, in hot weather the butter fat in the top portion of
a can increased from 3 to 7 per cent. in a quarter of an hour,
whilst the bottom portions decreased to 2 per cent. In
cold weather, however, a variation of only I per cent. was
observed in the same interval of time.

For the production of milk from plant products in the
form of cattle food, it is only on the very best pastures
that satisfactory results can be obtained without the use -
of some of the artificial foods, and during the winter-time
artificial foods are always essential. Much can certainly
be done to improve both pastures and hayfields, and,
therefore, reduce the consumption of higher-class foods.
Swedes, mangolds, or yellow turnips are fed to cows in large
amounts. Grass and hay are, of course, of no direct value
for human feeding, and mangolds, etc., are not worth much
as human food. ‘The cow can be regarded as a machine for
the conversion of low-grade food into high-grade food, for
which purpose it is more efficient than the fattening beast.
Where the situation of a farm is unsuitable for the delivery of

202 PLANT PRODUCTS

milk, milk can be converted into butter and cheese. ‘The
production of cream or butter fits in well with the rearing
of calves, which constitutes an essential part of the milk-
production problem. It is distinctly advantageous that
the calf-producing districts should be well away from the
large towns, and that the milk-producing districts should
be within comparatively easy reach of the large towns.
The production of butter in itself is not a very economical
use to put milk to, but, taken in conjunction with calf
rearing, it is useful enough as a side issue. ‘The production
of cheese stands on a higher plane as regards human food
production, since, for each pound of butter, at least three
pounds of cheese may be obtained, but if the milk is turned
into cheese, there will be less food available for rearing
calves.

REFERENCES TO SECTION IV

** Clotted Cream,” Journ. Board of Agriculture, 1915-16, p. 105.

Pegler, ‘‘ The Goat'as a Source of Milk,” Journ. Board of Agriculture,
I915-16, p. 642.

Mohan, “‘ ‘The Manufacture of Condensed Milk, Milk Powders, Casein,
etc,,”’ Journ. Soc. Chem. Ind., 1915, p. 109.

Aikman, “ Milk, its Nature and Composition.” (Black.)

Richmond, Hi Dairy Chemistry.” (Griffin. )

Warington, *“ Chemistry of the Farm,” p. 223. (Vinton.)

Maidment, “ The Home Dairy,” p. 34. (Simpkin, Marshall.)

Collins, “‘ The Composition of Milk in the North of England,” Journ.
Soc. Chem. Ind., 1904, p. 3.

Collins, “‘ The Natural Occurrence of Boric Acid in Milk,” Univ. Dur.
Phil. Soc.

Collins, *‘ Investigations on Milk,” Supplement Journ. Board of Agricul-
ture, Nov. IgIT, p. 48.

Leather, Analyst, 1914, p. 432.

1 Inquiry into i Methods of sampling Milk,’’ Journ. Board of Agri-
culture, L91I-12, p. 3

Collins, « Difference in the Amount of Fat in Morning and Evening
Milk owing to Uneven Intervals of Milking,” Proc. Univ. Dur. Phil. Soc.,
Vol. IV. pt. 1; Journ. Board of Agriculture, 1911-12, p. 334.

St. John, ‘‘ The Milking Machine in India,” Agric. Journ. Ind., 1917,
p. 291.

Fleischmann, ‘‘ The Book of the Dairy.” (Blackie.)

ae a ee ee

Szotion V.—FUTURE DEVELOPMENT

Increase of Field Fertility by Good Management. —
A very important system by which management can increase
the amount of plant products is by developing the amount
of grass and hay upon the heavier type of land with the aid
of basic slag. When a field is under grass, and is used for
grazing, the plant food contained in the grass grown is
returned to the soil by the cattle grazing upon it, with only
very small losses. When, however, the grass is cut for hay,
and the hay fed to beasts, the manure will, for the most part,
be given to the lighter lands. Hence, by means of the
development of the heavy lands on a farm by basic slag,
the lighter lands are indirectly benefited. On the very poor,
heavy boulder clay at Cockle Park, in Northumberland,
phosphatic manure has produced not merely double the
quantity of hay, but in quality the hay is twice as good as it
was before. In practice considerable losses occur in storing
manure, but there is no reason why they should be
proportionately greater with basic slag than without basic
slag. If, by these means, the amount of plant food added
to the lighter lands can be practically quadrupled by the
proper management of the heavier lands, then a portion of
the medium lands can be ploughed up and added to the
arable lands of the farm. Moreover, it has been shown
time after time that the replacement of grass by arable lands
does not necessitate the lessening of the quantity of stock,
but quite the contrary. Mr. A. D. Hall reckons that one
acre of wheat will produce four quarters grain and 1} tons
straw. This food material, fed to cattle, will produce 256
Ibs. of meat, or 360 gallons of milk. ‘The same land, under
grass, will produce 14 tons of hay, giving 120 lbs. of meat,

204 PLANT PRODUCTS

or 168 gallons of milk. Both of these estimates are on the
modest side. There is plenty of land which, in the past,
has been under bad management and considered of very
indifferent quality, which to-day, after several years of
good management, has been brought up to the standard of
producing 5 quarters of grain, or 2 tons of hay. Mr. A. D.
Hall also shows that, on the average, the arable land of the
ordinary farm is producing three times as much cattle food
as the permanent grass.

Mr. T. H. Middleton considers that on grazing land
the live weight increase per acre varies from 320 lbs. on
exceptional pasture, down to as little as 50 Ibs. on very poor
grass. That is, good land: bad land::6:1. At Cockle
Park, the plot grazed by sheep, where no improvement of
any sort has been carried out, produces only 22 lbs. live
weight increase per acre per annum (1906-15) in the form
of mutton, although by stocking the land with cattle and
sheep, the general experience at Cockle Park has been that
the mixture of stock produces almost double the amount
of meat that stocking with sheep alone will do. By treat-
ment with basic slag, this same land has been raised to the
production of 130 lbs. of live weight increase per acre per
annum, with sheep only, or 194 lbs. live-weight increase
per acre per annum (1906-15) with mixed cattle and sheep.
That is, good management: bad management::9:1. It
is, therefore, often found that the very same land may
show greater variations than those of Mr. Middleton’s
Minimum and Maximum, according to management. ‘There
is not any reason whatever for supposing that the improve-
ment obtained at Cockle Park might not have been made both
quicker and larger if considerations of financial caution had
not been necessary. Nor is there any reason for supposing
that Cockle Park is exceptional.

In many districts the prevailing weather introduces
many risks in corn-growing, but these districts’ will often
grow large quantities of green food, which can produce
greater amounts of milk or beef. ‘There are very large
areas, in almost all parts of the country, where there is

atin se at ee. »« ~—< —
ed. a ee ee eee

FUTURE DEVELOPMENTS 205

hardly any corn grown at all, but where the whole farming
industry turns upon the production of milk, butter, cream,
and calves. One may travel many miles in some of the
fertile valleys of the Upper Tyne, and hardly ever see any
arable land at all. No doubt some of the land is too far
removed from the rail and road, but there is still a large
area of land which could be used for the growth of, at any
tate, oats and potatoes.

Greater care is needed in the storage of farmyard manure.
Much loss occurs by drainage, and it is only by persistent
care that this loss can be reduced (see p. 52). <A greater
amount of artificial manures could also often be satisfactorily
employed. Even where artificial manures have been em-
ployed to a fairly large extent, it will often be found that
increasing quantities will still pay. It is very rare indeed
that the amounts of manuring in practice are sufficiently
large to reach the stage when the “Law of Diminishing
Returns’ comes into force. There is probably hardly any
enterprise that has been so little exploited in this country
as the land, consequently it is to be expected that it will
yield the best returns for labour and capital.

Economic Production of Meat in Winter.—
Medium cows and bullocks may be taken to breathe out
about 8 cubic feet of carbon dioxide in an hour, and it is
usually considered a good allowance to give 600 cubic feet
of air space and 30 square inches ventilation to each cow.
Assuming a velocity of air current equal to a wind of one
mile per hour through the opening, then the air in motion
at the disposal of the cow during one hour is about twice
the air at rest in the byre. Probably rather less than this
allowance is generally given, and we may assume on a
general basis that a cow has to heat up and moisten 1100
cubic feet of air. If there were no loss of heat by conduction
through the walls and roof, the 1100 cubic feet of air passing
per hour through the ventilators, rising in temperature
from 50° F. (10° C.) to 68° F. (20° C.) and evaporating the
water necessary to saturate it, there would be needed
239 calories per hour, ‘The. actual heat produced by the

206 PLANT PRODUCTS

cow is 1460 calories per hour. It is clear therefore that a
very large fraction of the heat produced by a cow in a byre
is lost by conduction of heat by the walls and roof of the
byre. The byres, if better constructed, might keep the cows
warm, permit of greater ventilation, and yet save food.
It seems highly probable that the waste of food alluded to
in Government pronouncements is often due to faulty
buildings compelling the practical farmer to use more food
than is strictly necessary, as judged by careful trials con-
ducted in buildings which are more suited to the purpose
than many of those that the farmer has to make the best
he can of.

If we compare the type of buildings used by cattle in
Great Britain with those in use in Norway, it is very obvious
that the Norwegian farmer has found out by practice the
necessity of saving cattle food by using warm buildings. The
Norwegian cattle byre is built of wood, with double walls
and an interior lining of hay. Such a structure provides
better ventilation but less draughts and less loss of heat
by conduction of heat through the walls, and permits winter
feeding of cattle in a land where cattle food is very scarce.

It would be quite impossible to alter the cattle sheds
during war time, but much might be done in small ways by
the individual farmer if he could be helped by the local
advisers in agricultural subjects. With the increase in the
production of wheat, barley, and oats there will be an
increase in the production of straw. A good use might be
made of straw mats placed over ventilators, doors, roofs, etc.,
or any exposed parts of the buildings. Straw mats would
oppose but little hindrance to ventilation. As shown
above a very large fraction, say five-sixths, of the heat
produced by the cow is lost through the walls, etc., of the
building. It would take but little improvement to save
some of this and produce more meat and milk with a saving
of food.

- Development of Agriculture at Home and Abroad.
—Only one-fifth part of the quantity of wheat and wheat
flour necessary for human consumption is produced in

FUTURE DEVELOPMENT 207

the British Isles. The great problem that is being dis-
cussed at present is how to increase the amount of wheat
without decreasing the supply of meat; but by comnvert-
ing grass land into arable land, the amount of meat
produced need not be decreased. Which farms will pay
best to produce grain and which to produce meat will
depend upon the situation, and there is little doubt that
one of the chief difficulties in inducing changes in the
general farming of the country lies in the fact that what
is true for the country as a whole is not necessarily true for
the individual farmer, and that, whilst it could be shown
readily enough in statistics that ploughing up grass land will
not decrease the meat, but will increase the bread, yet from
the point of view of the farmer, there will often be a need for
him to alter his system on lines which do not correspond
with those of the average of the country. If, however,
more wheat is grown in the British Isles, less wheat must
certainly be imported. No doubt there would be a tendency
to restrict those imports from foreign countries, as far as
possible, but it is difficult to see how this decrease could be
prevented from affecting India and the Colonies. It is,
therefore, essential that each section of the British Empire
should be made more self-contained.

In the statement that only one-fifth of the wheat and
wheat flour are produced at home, reference, of course, is
made to pre-war conditions. Probably to any such estimates
at least 20 per cent. could be added by milling the wheat,
so as to avoid losing the outer nutritious part of the wheat
grain, and another 10 per cent. could be added by the use
of barley, without in any way causing inconvenience, but,
on the contrary, producing a better loaf than ever. The
attempts to introduce other grains have, however, in practice
not proved very successful. The chief part of this difficulty
lies in the fact that the starch grains of the different cereals
have different temperatures of gelatinization, and, there-
fore, the time needed for cooking also differs. ‘This difficulty
is likely to be still further increased if potato flour is used
in addition, since the gelatinizing temperature of potato

208 PLANT PRODUCTS

flour and that of rice flour differ by as much as 40° on the
Fahrenheit scale, and it is, therefore, a practical impossibility
to cook any mixture of potato flour and rice flour. Home
efforts at making bread by first boiling the rice, oats, etc.,
independently, and then mixing with wheat flour, are satis-
factory enough, because in this case each part of the flour
can be given its own proper cooking (see p. 118). In any
case, one may say that the 20 per cent. of home-produced
wheat and wheat flour can be made up to 25 per cent.
without any inconvenience or any injury. Roughly speaking,
the wheat crops in 1872 were about double what they are at
present. If, therefore, we could go back to that condition
of affairs, the 25 per cent. could be turned into 50 per cent.,
that is, the British Isles could be half self-supporting in
the matter of wheat. We are already more than half self-
supporting in the matter of meat, and the proposed changes
in the system of agriculture should not affect these figures.

In addition to these considerations, one must remember
that there are other cereals besides wheat which can be
consumed. ‘The amount of barley produced in the British
Isles is not much behind the amount of wheat, and the
amount of oats is very much larger. If more motor ploughing
comes into force, the amount of oats necessary to maintain
the plough horses on the farm would be reduced, and a
larger quantity of oats rendered available for human con-
sumption, but unless motor ploughing comes into general
use the increase of horses for ploughing will result in the
increase of oats consumed by plough horses. Potatoes
are particularly suited for small systems of cultivation, and
much help could be given by town allotments, thus relieving
the farmer of a portion of his work, in growing potatoes.

Experiment has shown that, with the use of more liberal
dressings of artificial manures, the fertility of the land can
be well maintained, even though white crops are grown
far more frequently.

Under the present condition of high prices and urgency,
it would certainly be wise to employ safe manures, like
basic slag, with a more lavish hand, since the conditions

—

FUTURE DEVELOPMENTS 209

to-day are totally dissimilar to those prevailing when any
agricultural experiment was instituted. In Great Britain
the land has been limited in amount, and there have been
very good markets, but for many years past agriculture has
been severely handicapped by lack of capital and lack
of labour (see p. 215).

The industrial farm is a subject of much discussion to-day.
By having very large farms on the industrialized scheme
the number of skilled managers would be reduced, and since
highly skilled men are scarce, there would be more avail-
able. In addition, such farms would be able to attract
capital and labour better than a small farm. Labour of
all kinds, whether of the highest or the lowest, is always
attracted to a big concern. ‘There is a better security,
and there is less interference with liberty. Abroad, this work
has been carried out for a long time on quite a large scale.
There are many very large estates in India and the Colonies
which have been managed as industrial concerns, and of
recent years special industries, like rubber, etc., have been
added to the list. Many of these concerns are so highly
industrialized that a portion of their capital is dealt in on
the stock exchanges, but for the most part such concerns
have been in situations where labour was plentiful, a state
of affairs entirely distinct from that prevailing in the British
Isles. Nevertheless, even in Great Britain, one may find
many instances of highly industrializedfarms. For example,
some colliery companies in the northern counties manage
their agricultural affairs like the rest of their business.
Managers, with a scientific training, are appointed, with
several assistant managers placed under them, and the men
selected have, in most cases, been given an agricultural
education. Unfortunately, as is inevitable, the industrialized
farm does not advertise itself, and does not tell the public
all about how it manages its own affairs, and it would be
necessary to obtain information from the companies before
any other industrialized farm could copy the methods of
those farms which have been working on this scale for
many years past. In a few cases, the managers of these

D. 14

210 PLANT PRODUCTS

industrialized farms are permitted to take one or two pupils.
Common sense would suggest that other industrialized farms
should secure the services of such men. Nevertheless, if
industrialized farms are to be pushed at a great pace, the
number of men who are qualified to take a managership
will hardly be sufficient to goround. Fortunately, however,
we are in a much better position to-day to develop this farm
than we were twenty years ago.

There is a great contrast between the state of affairs of
agriculture in the British Isles and in Germany, Holland, and
Belgium during the last twenty or thirty years. It is only
in Great Britain that land has been going out of cultiva-
tion. On the other hand, one may find even in Great
Britain, that some farmers have put small amounts of land
into cultivation. ‘There are to be found, all over the country,
what Mr. A. D. Hall very aptly calls the “ little farms bitten
out of the waste,’ for one finds them in Northumberland
quite as frequently as in the south country places he mentions,
and precisely as he describes it for the south, so it is true
for the north, that this work has been carried out in a slow
and unscientific manner. Very little attempt has been made
to find out what the moors require. For the most part,
they have been surrounded by walls, and stocked with cattle.
Sometimes the scheme happened to succeed, and sometimes
success was very small indeed. No serious attempt appears
to have been made to discover whether the infertility was
due to the absence of lime, or phosphoric acid, or potash, or
whether it was due to bad drainage. Of recent years a
few farmers have used basic slag on such moor enclosures,
_ but their experience has been little copied by their neighbours,
and the process of bringing in new land has been carried out
in a very haphazard manner. In considering the question
of taking up new land to-day, the high prices of labour
undoubtedly is a serious difficulty. Not merely is the labour
expensive, but the provision of new buildings seems almost
prohibitive. On the other hand, the increase in agricultural
machinery offers some compensation. Not merely does it
reduce the actual cost, but it speeds up the work, and

eee

FINANCIAL ASPECTS 211

places the farmer in a position of less dependence upon the
weather.

For an emergency, a country with a considerable quantity
of arable land is much safer than a country containing much
grass land. It takes, roughly, from 8 to 10 lbs. of absolute
food of vegetable origin to produce 1 lb. of absolute food in
the form of meat, though some part of that vegetable food,
such as grass, is of no value for human consumption. ‘The
advantage in an emergency of having plenty of tillage is very
marked, and if it had to be paid for in normal times the
expense must be looked upon as an insurance against mis-
fortune. ‘To develop agriculture at home it is necessary to
have more capital, labour, and machines. Farmyard manure
must be better stored, more land should be cultivated,
market gardens and allotments in the vicinity of towns must
be increased. As far as possible, milk should be consumed
in preference to butter, but where milk cannot be transported,
owing to carriage difficulties, more attention should be paid
to the production of cheese.

Increased facilities for cold storage of summer milk,
summer beef, and summer mutton would enable a larger
fraction of cattle food to be derived from grass.

The Financial Aspects of Agriculture.—The supply
of better credit and capital to agriculture needs the earnest
attention of the Government. If the Government supply
a better security as regards prices, an improvement in credit
will follow automatically. ‘The mere fixing of a price here
and there is no solution of the difficulty. Directly one
attempts to regulate prices, one must be prepared to go in
for the whole business thoroughly and systematically. ‘The
attempt to fix a maximum price for wheat, and no maximum
price for meat, has the inevitable result that the farmer
directs his attention more to meat than to wheat, which is
directly opposite to what is wanted. A complete scheme
is required before action is taken. Of course, mistakes are
bound to be made at the beginning, but unnecessary changes
should be avoided. It is a rather striking fact that, in spite
of the great rise in the price of wheat, so little increase of

212 PLANT PRODUCTS

cultivation should, as yet, have happened, but it must not
be forgotten that the conduct of the business of agriculture
is essentially different from the conduct of a retail shop.
The shopkeeper may buy in a stock of goods one day, and
sell most of them within a few days’ time, and he can
practically close his books as far as that transaction is
concerned in a very short space of time. In agriculture,
however, no business affair of any particular importance
will happen in less than twelve months, and a farmer is
compelled to think more in terms of four yearly rotations
than in shorter periods of time. As is known, there is far
too little capital, and far too little labour for the land.
In 1872, when the amount of land under cultivation was
roughly double what it is to-day, the average price of cereals
was about 40s. a bushel. In 1916 it was just under 50s. -a
bushel, and in the first half of 1917 it was about 65s. a bushel,
yet it is taking a large expenditure of energy to induce the

farmer to increase his arable land. It is, therefore, certain’

that price alone has very small power indeed in causing a
change. Whether time and price together might not have
effected a change has not yet been proved, but, considering
that prices have risen steadily for many years before the
wat, it looks as though price and time together were not
sufficiently powerful to make a change in the condition of
agriculture, and that some other considerations will have
to be taken into account. Nevertheless, the money side
of the question is very important, and must be considered.
There is the position of the landlord to consider. What money
he has made out of the land has chiefly been by sales, and
not by cultivation, and he has found all his amusement out
of sport, and very little out of the cultivating side of country
life. From his point of view, therefore, crop production
does not appear very important, and has been neglected.
The farmer has to make a living out of farming; he will
not change from grass to tillage unless he sees his way to
make more money out of it. Mr. A. D. Hall gives figures
which suggest that grazing can produce returns to cover
interest, sinking fund, profit, management, etc., of about 27

er a ee

FINANCIAL ASPECTS 213

per cent. on the capital sunk, as against 17 per cent. for
arable land. That is, of course, under past prices, but
obviously if prices for meat, milk, corn, and labour all go
up proportionately, it does not alter the relative position
of the twosystems of farming. It is not so much the absolute
price of wheat that is so important, as the ratio of the price
of wheat to the price of meat that will determine the relative
proportions of arable to grass land, and that is why the rise
in price has produced so little effect. Once the State begins
to interfere in the question of prices, it is almost driven into
considering what kind of partial ownership of the land will
have to be adopted by the State. By means of the Excess
Profits Tax it is obvious that the State can assume a large
share in any industry. At present the State is taxing excess
profits at the rate of 80 per cent., that is to say, the State
occupies the same position towards the industries of the
country as the holders of founders’ shares in an ordinary
industrial concern do. ‘There are many concerns where there
are a small number of such founders, who in bad times
receive no dividends but in good times obtain a quite
disproportionate share of the profits. Under a type of
taxation such as we have at present, the State is undoubtedly
part owner of all the industries that are under excess profits
taxation. Ifthe Government were to put all concerns which
deal in human food on the same basis, the State would
become a partner in the whole of these businesses, including
land, and this is a point which has to be carefully considered, -
The present position of affairs in the British Isles is not
altogether dissimilar to the state of affairs in India, when the
chaos and disorganization, resulting from the complete break-
up of central authority, induced the British East India
Company, and later the Crown, to adopt the attitude that
the land belonged to the State, and that the State must
assess what rent should be paid. When prices rise, and the
supply of labour fails, and both are partly controlled by
the State, then the difference between State ownership and
such a condition of affairs is not, after all, a big one,
and it would be wise to consider the attitude of the State

214 PLANT PRODUCTS

towards a part ownership, which is already effective if
unacknowledged.

The relationship between the price of grain and the wages
of labour must always determine the amount of labour
available upon the farm. The discussion of a possible
sliding scale between prices and wages presents many
difficulties, but sliding scales have been adopted in other
industries which, in spite of their crudity, have been success-
ful. The sliding scale which affects the price of gas and the
dividends of shareholders has played a very useful part,
though it would be difficult to conceive a more hopelessly
crude basis than that on which it was founded.

The amount of capital per acre in England is about £7,
whereas in former days it was much higher, {10 per acre
being regarded as a kind of minimum. Other parts of
Western Europe have needed capital of £20 per acre. Capital,
in agriculture, stands in a rather different position to what it
does in many other industries, because in agriculture currency
also occupies a different position. In primitive farming,
currency is practically negligible. Currency to-day stands
also in a peculiar position, but Great Britain has been far less
affected than other countries in this respect. The currency of
this country is supposed to rest on a gold basis, and nominally
the treasury note is payable in gold at the Bank of England.
In Germany, the gold currency is practically suspended.
The German Government paper bond for ten kilogrammes
of potatoes is honoured at the proper place for dealing
with those articles, but the German Government paper
bond for a weight of gold corresponding to twenty marks is
not honoured at the place commonly dealing in gold. It
would be, therefore, more correct to say that Germany has a
potato currency than that she has a gold currency.

Money plays no practical part in the business of Indian
agriculture. It is, therefore, perfectly possible to conduct
agriculture without currency, but it would be incorrect
to say that an Indian village had no capital, because it has
houses, implements, etc., but such capital is very immobile.
Not very many years ago the farmer in Great Britain had

|

THE LABOUR QUESTION 215

large stocks of bacon and other commodities ; to-day he
depends much more upon the local shops. ‘The capital in
commodities has decreased quite as strikingly as the capital
acknowledged by the bank.

It is always well to look to the future, and we ourselves
may be placed in straits like Germany. Should that be so,
it will be worth considering whether we should not, as a
nation, adopt a logical position and start an institution
which would amount to a wheat bank, with wheat bonds
and wheat deposits, paid for both in regard to capital and
interest interms of wheat. Perhaps some of the difficulties of
supplying agriculture with the necessary capital could be
overcome if we more frankly recognized that in the past
agricultural capital has not altogether depended upon the
acknowledged currency, but has depended very largely upon
the currency of commodities and custom. To the old-
fashioned British farmer capital means fat stock and a full
stackyard, whilst currency means bacon and potatoes;
and to the Indian villager currency is dastoor and capital
a bullock. By returning to some of our old ideas we might
teduce the strain resulting from the lack of that capital
which has come to be defined in terms suited only to the
city bank.

The Labour Question.—Many of the difficulties of agri-
culture during the last fifty years have arisen from the fact
that the old industries which used to exist in the country
have migrated to the towns. The agricultural population of a.
hundred years ago was not purely dependent upon agriculture,
but was partly dependent ‘upon rural industries, and it is
not quite correct to say that when the rural population
removed to the towns they were leaving their old employ-
ments. In part, they merely followed their old employments.
To foster rural industries is part of the business of agricultural
development, and the full utilization of all woods and forests
is a natural part of rural economy. Whilst it is true that
arable land may produce twice as much food as grass land,
it would take nearly ten times as much labour to obtain
such a result. And where is this labour tocome from? The

216 PLANT PRODUCTS

effective labour of one man, however, shows the greatest
conceivable variations. It is very difficult to represent this
in any very definite terms, but Government statistics enable
us to make some rough calculations, from which I should
conclude that one British agricultural worker by his labours
feeds about eight persons, one German agricultural worker
feeds about four persons, and one Indian agricultural worker
can feed no more than two, on the same scale of diet. How-
ever much doubt may be thrown upon the validity of any
such crude calculations, the order of merit in the three
cases is not likely to be seriously affected. The British
agricultural worker has been far the most efficient. ‘There
ate several reasons why such great differences are easily
explainable. The ‘“‘Law of Diminishing Returns’”’ applies
with quite as much force to labour as it does to fertilizers:
Indeed, this is almost a self-evident proposition. A piece of
land growing nothing but weeds, with its first increment of
labour, will add hardly anything for human consumption,
but, as more and more labour is expended -upon it, its
fertility rises, till, after a certain point, its limit is reached,
and further labour does no good. It, therefore, is inevitable
that there must be some point, in the application of labour
to the soil, when a maximum of efficiency of labour is
reached, after which the more work put upon the land the
less is the return per unit of labour.

Further increase of arable land means taking up land
which is less suited for the purpose and putting upon the
land labour which is also, on the average, less suitable.
It is, therefore, urgently necessary to consider how the
efficiency of labour is to be increased, in order that we may
counteract the inevitable tendency to produce less per head
of labour employed.

As regards the quantity of labour, there is a considerable
tisk that England may lose her open-air population after
the war, just exactly when she wants it most. The future
may show that we are less prepared for peace than we were
for war. Bothold and new sources of labour must be directed
to the land. There are a large number of men who were

THE LABOUR QUESTION 217

previously employed merely as routine clerks and shop
assistants, who have now become accustomed to an outdoor
life. ‘They will be very unwilling to go back to indoor life,
and it is now the time to consider whether their wishes
and the country’s needs might not be united. Much of this
routine work is now being done by women who will at the
end of the war be more efficient than the returned soldiers.
The returned soldier will have learnt the use of spade and
pick and be more suited to agriculture or forestry. ‘Those
men who are of exceptionally high mental ability, but belong
to a somewhat low physical category, will all be needed
for the professions, skilled trades, and directorships. In
agriculture there is room for both those who have a higher
degree of mental ability, and those who are chiefly physically
strong. One thing is clear, we shall not need any compulsion ;
we shall only need encouragement and proper facilities.
Among the sources under Government control there are
nearly a quarter of a million of Poor Law children, many of
whom might be trained specially for the land.

As regards the efficiency of labour it should be noted
that no little part of farm labour has been carried out by
the “‘ sweated labour ”’ of the family of the small or medium-
sized farmer. There are many farmers, especially at the
present time, every member of whose family is working
sixteen hours a day. Such a state of affairs is not in the
interests of the nation. At least one of the causes which
have driven men from the land has been the excessive hours -
of labour. Of course, one hour of labour in the factory is
not the same as one hour of labour on the field. ‘The factory
is more unhealthy, and, therefore, more exhausting. Never-
theless, however great the amelioration may be, the hours
of labour on the land are not infrequently excessive, and
probably do not conduce to efficiency.

As regards the economy of labour one of the great
difficulties on a farm is the heavy work, due to bad roads,
not merely on the horses but also on the men. ‘These
difficulties, however, are most strongly marked on farms
which are largely under grass, and if the grassland is ploughed,

218 PLANT PRODUCTS

the construction of roads must also be undertaken. Both
the quantity and quality of labour are intimately concerned
with the supply of proper accommodation. ‘The lack of
cottages is undoubtedly very serious in England, but it is
not so serious in Ireland, where there are very large numbers
of cottages, uninhabitable at present but possible to repair.

Undoubtedly the climate of Ireland is not that of a corn-
growing country, but the use of basic slag and lime would
produce more milk, butter, cheese, and calves, and thus
relieve the English farmer of part of this work. As regards
machinery, very great progress has already taken place
in machines for reaping grain and mowing hay, and it does
not seem likely that further progress can be of a very striking
character. Milking machines have now reached a thoroughly
practical condition, and economize labour in a very striking
manner. They are not suitable for very small holders,
although satisfactorily used on farms which have only
twenty cows. The motor tractor and plough are not so
advanced, but if men could be trained to understand both
the machinery and the land, the efficiency of these machines
could be enormously improved. ‘These machines have,
however, undoubtedly come to stay, and every effort should
be made to overcome the difficulties in connection with
them.

If we have to increase both quantity and quality of
labour, we must provide a proper step to enable the labourer
torise inthe world. Undoubtedly one of the great attractions
of town life lies in the fact that a man has a much better
chance of advancement. Whatever the merits or demerits
of smallholdings may be, they provide a very valuable step
between farm labourers and farmers, and even if small-
holdings were not in themselves very efficient food producers,
it would still be worth while pushing them, to encourage
labour.

The only cure for the unsatisfactory conditions of buying
and selling among smallholders seems to be some system
of co-operation. It is difficult to see how any system of co-
operation among smallholders can be superior to that which

a

a) —

EDUCATION 219

still exists in an Indian village, the inhabitants of which
are more at the mercy of the money-lender and grain dealer
than we would wish our smallholders to be. Nevertheless,
the enormous strides which have been made in modern
co-operation in India, and elsewhere, lead one to hope that
much may be achieved in this direction. In considering
the labour of the country, we must also consider the town
labourer. At present, of our total consumption of wheat,
only 19 per cent. is home grown, as against 75 per cent. of
oats. Yet we each eat twice as much wheat as oats. Ina
similar way, we produce practically all the potatoes we eat,
as against only 19 per cent. of the wheat we eat, yet our
consumption per head of wheat is greater than that of

potatoes. Are the town workers willing to change their

diet so as to make the consumption more nearly fit the
production? We ought to consume more home-grown
food and less foreign-grown food. ‘The town workers may
have to learn to eat less wheat but more barley, oats, and
potatoes. Undoubtedly the chief reason why our consump-
tion of wheat is so high is because wheat lends itself to the
production of bread, which can be purchased ready cooked,
whilst barley, oats, and potatoes all need some treatment at
home before they can be rendered fit for consumption.
Germany has, to some extent, solved the problem, by
producing large quantities of dried potato flour. As it
happens, dried potato flour is more suitedfor mixing with
wheat than either barley or oats for the production of bread,
because potato starch gelatinizes at a temperature below
that of wheat starch, whilst barley and oats require higher
temperatures for cooking.

Labour must, however, be considered in relationship to
other factors determining plant production. ‘The trouble in
Great Britain is that the supply of land has been in excess
of the land we were willing to cultivate, and that the labour
that the farmer could afford to pay for has been insufficient
for that cultivation. ‘The ratio of labour to land must be
increased to obtain an increased plant production, and,
since the land in the\British Isles is almost a fixed quantity,

220 PLANT PRODUCTS

labour must therefore be increased, and to increase the
efficiency of labour the ratio of machinery to men must be
increased, and also the ratio of manure to land must be
increased in order to economize labour. Where much hand
work can be put into the soil, very large crops can be raised,
without the expenditure of much manure. Extra labour will,
indeed, cure many of the troubles which the land suffers from,
although it may sometimes be more economical to employ the
soil fertilizers described in the earlier parts of this volume.
To increase the efficiency of labour, one must also consider
the question of management. One of the difficulties in the
way of industrialized farms is that the ratio of managers
to men must decrease, since the employment of many
managers would ruin the balance sheet. It will probably
be found that there is a limit to the industrialization of
agriculture, because, if you decrease the ratio of management
to labour, the labour will gradually become more and more
inefficient. Moreover, we require to increase the yield per
acre as much as anything else. It is the last quarter of
grain that takes the greatest amount of management, labour
and manure to obtain. High farming is only possible with
high prices, and unless the town labourer is prepared to
pay these high prices, and thus support his companion on
the farm, increased plant production becomes impossible.
If prices are increased, wages must also be increased. If
the farmer pays out much larger amounts of money for wages,
he, like any other business man, must make larger profits to
pay for the risks and interest on the capital that he handles,
and, indeed, this is truer of the farmer than it is of many
other business men, because the interval between the time
when he has to pay out and the time when he begins to
receive is, on the average, not less than six months.
Education.—Education concerns all classes on the
land. The landowner himself must be prepared to study
agriculture seriously, and to send his sons to receive an
agricultural education. At present the landowner is content
to send his son to the University for a purely classical
style of education, whereas he should prefer his son to

eS as =

EDUCATION 221

be educated in agricultural technology. He is the trustee
on behalf of the nation for the proper management of the
land under his control, and his sons will have ultimately
to take his place, and, meanwhile, must act as his deputy.
The exact type of education that is best suited to the land-
owner or his son has yet to be evolved, but it cannot possibly
be evolved without the landowner’s active participation.
If the landowner’s sons came to the University in sufficient
numbers, the type of education given would adjust itself
to suit their needs. Further, the bailiffs appointed by the
landowners to manage some part of their estate should be
better paid and better educated men, who would be in a
position toset anexampletothetenantfarmers Agriculture
possesses the great disadvantage of being situated away
from the centres where much of the education is given, but,
as it is in the interests of the country that agriculture should
be advanced, it is necessary that money and energy should
be expended upon rural schools, even if the expenditure
appears out of proportion to the number of those attending.

It is difficult to form any very general opinion as to how
much of the energy expended on agricultural education
has so far produced direct results. Like all other teachers,
those engaged in teaching agriculture cannot possibly keep
in touch with the after-history of all their pupils. It is,
however, possible to compile a list of those that one does
keep in contact with, and assume that those one loses touch
with exhibit the same ratio as those one knows. The -
Armstrong College Agricultural Students’ Association was
originally founded for the purpose of keeping in touch with
old students, and the latest published proceedings of that
Association show that, of the 164 members who have kept
in contact with the Association, there are 70 known to be
farming, there are 9 known to have received an agricultural
education and known not to be farming, there are 19 who
were not educated in agricultural subjects, but who are now
taking some part in assisting agriculture. ‘The term ‘‘farm-
ing’ as given in the above, includes those who are managing
farms on somebody else’s account as well as those who are

222 PLANT PRODUCTS

actually farming with their own capital. So far, therefore,
as such figures go, the energy of the teacher which has been
lost is counterbalanced by the energy which goes into
agriculture.

One Bachelor of Science is farming on his own account,
another is managing on behalf of a big company, and as far
as one can see, the education, even of the most scientific
type, has produced most admirable practical results, whether
expressed in terms of so much food material, or of so much
cash profit.

I do not know that there can be any more complete proof
that the labours of those who are engaged in teaching
agricultural subjects in Armstrong College has been fully
utilized for the cultivation of land and plant production.
Whether the agricultural education in any other district
has been equally satisfactory can only be decided by those
who are intimately connected with that district, but Govern-
ment statistics show that there is no reason for supposing
that these results are exceptional. Agriculture has certainly
used the advancements of science quite as readily as any
other industry in the country, which is but faint praise.

REFERENCES TO SECTION V

Middleton, ‘‘ The Farmer and Self-Improvement,” Journ. Board of

Agriculture, 1916-17, p. 760.

Hall, ‘‘ Agriculture after the War,” pp. 31, 32. (Murray.)
Middleton, “‘ Systems of Farming and the Production of Food,” Journ.

Board of Agriculture, 1915-16, p. 520. .

Baden-Powell, ‘‘ Land Systems of British India,” p. 282. (Clarendon

Press.)

“The Food Supply of the United Kingdom,” Journ. Soc. Chem. Ind.,

1917, p. 279.

Drage, ‘‘ The Imperial Organization of Trade,” p. 285. (Smith.)

Hobson, ‘‘ Gold Prices and Wages,’’ p. 129. (Methuen.)

Simpson, “‘ Co-operative Credit,” Agric. Journ. India, 1906, p. 131.

Gourlay, ‘‘ Co-operative Credit in Bengal,” Agric. Journ. India, 1906,
Eaty:

F Matthai, “‘ Village Government in British India,’ p.17. (Fisher Unwin.)
Green, “‘ The Rural Industries of England,’ p. 146. (Marlborough.)
Report of the Board of Agriculture, Cd. 6151, 1912, p. 31.

Smetham, ‘‘Present Conditions in Relation to Food Supplies.”

(Toulmin, Fishergate, Preston.)

Wood, ‘‘ The National Food Supply in Peace and War.”’ (Cambridge

University Press.)

Noyes, ‘‘ Financial Chapters of the War,” pp. 34, 44. (Macmillan.)
Cunningham, ‘‘ The Progress of Capitalism in England,” p. 40. (Cam-
bridge University Press.)

wl

ee OO Oe

PO ee ee,

GENERAL BIBLIOGRAPHY 223

Turnor, ‘‘ The Land and the Empire.’’ (Murray.)

‘Occupations of Agricultural Students after leaving College,’’ Journ.
Board of Agriculture, 1911-12, p. 848,

“ Agricultural Credit and -operation,” Journ. Board of Agriculture,
1912-1913, P. 43-

ra Improvement of Poor Hill Pasture,” Journ. Board of Agriculture,

12-1
7 Wibberley, “Continuous Cropping,” Journ. Board of Agriculture,
1914-1915, p. 817.

Clouston, “Rural Education in its Relation to Agricultural Develop-
ment,” Agric. Journ. India, 1917, p. 216.

Allen, ‘‘ The Housing of the Agricultural Labourer,”’ Journ. Roy. Agric.
Soc. Eng., 1914, p- 20.

GENERAL BIBLIOGRAPHY

[The sectional references, which form part of the Bibliography, are
given at the end of each section, and may be readily traced by consulting
the Contents Table, pp. xi.-xvi. 7

(1) ENCYCLOPAEDIZ AND JOURNALS

Encyclopedia Britannica.

Wiley, ‘‘ The Principles of Agricultural Analysis.’’ (Chemical Publish-
ing Co.) .

Thorpe, “ Dictionary of Applied Chemistry.’”’ (Longmans.)

Newsham, ‘‘ The Horticultural Note-Book.”’ (Crosby Lockwood.)

aii McConnell, “‘ The Agricultural Note-Book. (Crosby Lock-
wood.)

Wright, ‘‘ A Modern Encyclopedia of Agriculture.” (Gresham Pub-
lishing Co.)

The Journal of the Board of Agriculture. (The Board of Agriculture
and Fisheries.)

The Agricultural Journal of India. (Thacker, London; Thacker,
Spink, Calcutta.)

The Journal of Agricultural Science. (Cambridge University Press.)

The Journals of the Royal Agricultural Society, the Chemical Society,
and the Society of Chemical Industry.

(2) AGRICULTURE

Somerville, ‘‘ Agriculture.”” (Williams & Norgate. )

Shaw, “‘ Market and Kitchen Gardening.’’ (Crosby Lockwood.)

Hall, “« An Account of the Rothamsted Experiments.”’ (Murray.)

Middleton, “The Recent Development of German Agriculture.”
[Ca. 8305.] |

Fream, ‘‘ Elements of Agriculture.’”’ (Murray.)

James Macdonald, “‘ Stephen’s Book of the Farm,’’ (William Bryce.)

Vanna “Improvement of Indian Agriculture.’”’ (Eyre and Spottis-
wood.)

Mukerji, “‘Handbook of Indian Agriculture.’’ (Thacker, Spink,
Calcutta. )

Geerligs, ‘‘ The World’s Cane Sugar Industry.” (Rodger, Manchester.)

Vorhees, ‘‘ Fertilizers.’”’ (Macmillan.)

224 GENERAL BIBLIOGRAPHY

(3) CHEMISTRY

Addyman, “ Agricultural Analysis: A Manual of Quantitative Analysis.”
(William Bryce.)

Snyder, ‘ Chemistry of Plant and Animal Life.’’ (Macmillan.)

Fritsch, ‘‘ The Manufacture of Chemical Manures.”” (Scott Greenwood.)

Cousins, ‘‘ The Chemistry of the Garden.”’” (Macmillan.)

Warington, ‘‘ Chemistry of the Farm.” (Vinton.)

Hopkins, “‘ Soil Fertility and Permanent Agriculture.’’ (Ginn.)

Hilgard, “ Soils.’”” (Macmillan.)

Collins, ‘‘ Agricultural Chemistry for Indian Students.”’ (Government
of India Central Printing Office, Calcutta.)

Hall, “‘ The Feeding of Crops and Stock.” (Murray.)

Hall, ‘‘ The Soil.” (Murray.)

Johnson, ‘‘ How Crops Grow.”” (Orange Judd Company.)

Russell, ‘‘ Soil Conditions and Growth.”’ (Longmans.)

Hall, ‘‘ Fertilizers and Manures.”’ (Murray.)

Cameron and Aikman, ‘‘ Johnston’s Elements of Agricultural Chemistry.”’
(Blackwood.)

Johnson, ‘‘ How Crops Feed.”” (Orange Judd Company.),

Bernard Dyer, ‘‘ Fertilizers and Feeding Stuffs.’’ (Crosby Lockwood.)

Chamberlain, ‘‘ Organic Agricultural Chemistry.’”? (Macmillan.) ‘

Tibbles, ‘‘ Foods.”’ (Bailliére, Tindall & Cox.)

Ingle, ‘‘ Manual of Agricultural Chemistry.’”’ (Scott, Greenwood.)

Storer, “‘ Agriculture in Some of its Relations with Chemistry.”
(Sampson Low.)

Haas and Hill, ‘‘ An Introduction to the Chemistry of Plant Products.”
(Longmans & Co.)

Fowler, ‘‘ Bacteriological and Enzyme Chemistry.”’ (Arnold.)

Roscoe and Schorlemmer, ‘‘ Treatise on Chemistry.”” (Macmillan.)

Bennett, ‘‘ Animal Proteids.”’ (Bailli¢re, Tindall & Cox.)

(4) ECONOMICS

Theodore Morrison, ‘‘ The Economic Transition in India.” (Murray.)

Radhakamal Mukerjee, “‘ The Foundation of Indian Economics.”
(Longmans & Co.) R

Leather, “ The Agricultural Ledger, 1898,” No. 2. (Government
Printing Office, Calcutta.) :

~Money’s Fiscal Dictionary. (Methuen.)

Fisher, ‘‘ The Purchasing Power of Money.’ (Macmillan.)

Dunlop, ‘‘ The Farm Labourer.”’ (Unwin.)

Se A eR

INDEX
(Chief References are in heavy type.)

ABYSSINIA, 144 Ammonium hydrogen sulphite, 16

Acacia, 132, 162

Acetate of lime, 125, 130
Acetates, 152

Acetic acid, 103, 125, 129, 164
Acetone, 103, 130, 136
Acetylene, 88

Acid vapours, 168
Addyman, 223

Aeration, 4

Aerobes, 50

Africa, 30

Agar, 7, 132

Aikman, 202

Air, 2, 7, 20, 82, 205
Albumen, 109, 147, 200
Albuminoids, 109, 174, 181
Albuminoid theory, 195
Alcock, 168

Alcohol, 117, 122
Aldehydes, 130
Aldo-hexose, 107

Alice springs, 69

Alkali, black, 74

Alkali cellulose, 124
Alkali, white, 74
Alkaloids, 109, 152, 156
Allantoin, 181
Allotments, 208, 211
Altitude, 65

_ Aluminium, 72

Alway, 84

America, 22, 77, 136, 138

Amide, 43, 109, 181

Amines, 109

Amino-acid, 34, 43, 51, 109, 149,
180 ?

Ammonia, 13, 22, 109

Ammonia, sulphate of, 11, 89, 175

Ammonium acetate, 182

Ammonium bi-carbonate, 18

Ammonium citrate, 3l

Ammonium chloride, 17

Ammonium humate, 43

Ammonium hydrogen carbonate, 18

Ammonium hydrogen sulphate, 16

D.

Ammonium nitrate, 17
Ameoebe, 81, 91

Amos, 26

Amygdalin, 185

Anzrobe, 50

Analysis, soil, 67, 78
Annealing, 38, 131
Anti-pepsin, 190

Apatite, 25

Apple, 104, 166, 167
Appleyard, 85

Apricot, 167

Arabic, gum, 106, 132
Arabin, 132

Arabinose, 132

Arable land, 211

Arachidic acid, 142
Archbold, 133

Argentine, 135

Arginine, 149, 151, 152
Argol, 104

Armsby, 182

Armstrong, 110, 190
Armstrong College, 221
Artichoke, 108
Ascensional currents, 65
Asparagine, 7, 109, 149, 181
Aspartic acid, 149, 151, 181, 182
Aspect, 65

Asphalte, 165

Assam, 158

Assimilation, 101, 188, 192
Atlantic, 126

Aubert, 133

Auld, 146

Australia, 30, 69, 132, 139, 170
Available lime, 28
Available nitrogen, 34, 81
Available phosphorus, 28, 87
Available plant food, 4, 77
Available potash, 87
Ayrshire cow, 201

BACHELOR of Science, 222
Bacteria, 23, 27, 42, 50, 81

)

226

Baden-Powell, 222

Bailiffs, 221

Bainbridge, 190

Bajra, 125

Balance of ingredients, 8, 64, 83

Bald, 177

Bales, 125, 126

Balls, 84

Baltic linseed, 135

Bamboo, 128

Banana, 167

Bank, 214, 215

Barber, 133

Bark, 162

Barley, 12, 107, 124, 148, 171, 219

Barley straw, 12

Barnes, 110

Barrages, 95

Barrenness, 93

Basic nitrogen from proteins, 149,
152

Basic slag, 6, 16, 19, 20, 22, 27, 63, 67,
97, 171, 174, 179, 203, 207, 216

Basic superphosphate, 31

Bassia, 144

Basu, 168

Bayliss, 110

Beans, 150, 168

Beaven, 110

Beccari, 147

Bedding, 46

Beech, 127

Beech leaf, 72

Beech mast, 57

Beef, 197, 204

Beer, 124

Berries, 161, 167

Berry, 133

Beet, 103, 114, 128

Beet sugar, 107, 108, 114

Bengal, 120, 126, 165

Bennett, 32, 147, 162, 182, 224

Benson, 134

Benzamido acetic acid, 44

Benzene, 181

Bitter cassava, 123

Black alkali, 74, 98

Blackberry, 167

Blackman, 92

Back cotton seed, 125

Black soils, 66, 74, 96

Blackwood, 90

Blair, 146

Blast furnace dust, 38, 39

Blood, 23, 57, 179

Boiled oil, 136

Boiler flue dust, 38

Bombay, 69, 132, 143

Bone, 32, 33

| Calves, 48, 136, 137, 218
| Calving, 200

INDEX

Bone, dissolved, 34

Bone phosphate, 32

Bone, vitriolated, 34

Borax, 138

Borday, 110

Bottomley, 59

Boulder clay, 29, 78, 97, 203
Boulton, 134

Brazil, 162

Bread, 118, 124, 147, 208, 219
Brenchley, 85, 92

Briggs, 134

British agricultural workers, 216 ;
British East India Company, 213
British Isles, 139

Broad-casting, 6, 20, 26, 31
Broadbalk, Rothamsted, 26
Bromides, 152

Bromine, 124

Browning, 146

Brown sugar, 113

Buildings, 206, 210

Bullock Mill, 112

Bullocks, 48, 178, 192, 197

Burma, 120

Burnett’s fluid, 127 |
Burning soil, 97 |
Burnt lime, 86 .
Butter, 102, 137, 201, 211 |
Buttercup, 174
Butyrin, 199
Byres, 206

CABBAGES, 19, 175

Caffeine, 156

Calcareous soil, 16, 72, 82, 163

Calcium acetate, 103, 130

Calcium bi-carbonate, 73, 86

Calcium carbide, 21, 88, 91

Calcium carbonate, 27, 73, 85, 86,
168

Calcium citrate, 105

Calcium cyanamide, 21

Calcium hydrate, 27, 88

Calcium oxalate, 103

Calcium oxide, 27, 72, 86

Calcium silicate, 27

Calcium sulphate, 19, 51, 74, 89,
104, 172, 177

Calcium sulphide, 87

Calcium sulphite, 91

Calcutta, 143

Calf rearing, 137, 202, 218

Calories, 191, 195, 198

Cambium, 164
Cambridge coprolites, 30
Cameron, 224

INDEX 227

Canada, 119

Candles, 141

Cane sugar, 102, 107, 111, 174

Cannabis sativa, 127

Canvas, 106

Capillary action, 67

Capital, 210, 212, 222, 224

Caramel, 113

Carbide, calcium, 21, 88, 91

Carbohydrates, 102, 105, 111, 195

Carbon dioxide, 26, 73, 75, 85, 101,
205

Carbon monoxide, 130

Carbonic acid, 26, 73, 75, 85, 87, 101

Carding, 125

Carey, 100

Case-hardening, 38, 131

Casein, 150, 199, 200

Caseinogen, 150, 199, 200

Casks, 20

Cassava, 123

Castor bean, 151

Castor cake, 24, 112

Catch crops, 161, 223

Catechin, 162

Catechu, 162

Cattle, 136, 142, 206

Cellulose, 105, 124, 187, 193

Centrifugal machine, 113, 116

Cereal proteins, 147

Cereals, 11, 40, 117, 118, 120, 124

Cesspools, 54

Ceylon, 144

Chadwin, 133

Chalk, 8, 24, 73, 85, 86, 88,98, 103, 168

Chamberlain, 224

Chance mud, 87

Charcoal, 125, 129

Cheese, 107, 197, 202, 211, 218

Chemical fumes, 168

Chemistry, soil, 70

Chewing, 192, 193

Children, 198

Chili, 18

China, 120, 132, 152, 158, 160

Chlorides, 17, 108, 152, 168

Chlorine, 108, 124

Church, 133

Cider, 104

Cinchona, 153

Cinchonin, 154

Citric acid, 28, 71, 77, 104

Classification of fertilizers, 3

Clay, 16, 19, 21, 40, 55, 64, 70, 82,
96, 97, 203

Clerks, 217

Clifford, 58

Close packing, 62

Clot, Blood, 23

Clouds, 65

Clouston, 177, 223

Clover meal, 107

Clovers, 25, 82, 98, 171, 172

Coagulation, clay, 87

Coal, 11, 75

Cockle Park, 25, 29, 63, 66, 70, 81,
171, 173, 179, 203, 204

Coconuts, 131, 139

Coffee, 19, 156, 160, 175

Coir, 140

Coke, 21

Coke ovens, ll

Collins, 9

Colloidal clay, 89

Colloids, 19, 44, 62, 64, 94, 106, 164,
172

Colonies, 207, 209

Colophony, 145

Colostrum, 200

Colour of soils, 66

Colza, 143

Compact soils, 66

Composts, 57

Compound manures, 32, 40, 155

Conduction of heat, 66

Conifers, 127, 131

Cooking starch, 207

Coombes, malt, 124

Coombs, 168

Copeland, 146

Copper, 104, 152

Copper hydrate, 109

Copper sulphate, 91

Copra, 140

Corn manure, 40

Cornwall, 132

Corylin, 152

Cotton, 105, 125, 137, 175

Cotton rags, 128

Cotton-wool, 105

Countess Cinchon, 153

Cousins, 224

Coventry, 134

Cows, 48, 188, 197, 201, 205

Cracks in soil, 70

Cranfield, 39

Cream, 201

Credit, 210

Creosote, 127, 128, 164

Crookes, 20

Cross, 110, 134,

Crowther, 146, 168, 198 .

Crumb structure, 62

Crystallized fruit, 167

Cud, 193

Culms, 124

Cuprammonium hydroxide, 105

Cunningham, 222

228 INDEX

Curd, 132, 199

Currant, 168

Currency, 214

Custom, 215

Cyanamide, calcium, 10, 21
Cyanides, 38, 88, 123, 136
Cyanogenetic glucoside, 123, 136
Cystine, 151

Dairy, 197, 199

Dams, 95

Dark soils, 66

Dastoor, 215

Date palm, 116

Davies, 168

Davis, 134

Davy, Humphrey, 1, 9

Day, 168

Decorticated rice, 12]

Decorticated cotton cake, 138

Deep rooting, 175

Deep tillage, 69

Deflocculation of clay, 87

Dehra Dun, 158

Delay of ripening, 10

Deliquescence of fertilizers, 17, 19,
20

Den, 30

Denbigh, 133

Denitrification, 51, 82

Depth of penetration of manures,

Destructive distillation, 125,129,147

Development of Jeaf, 17

Dextrin, 106

Dextrose, 106, 180

Diabetes, 150

Diastase, 106, 124

Dibdin, 58

Di-calcium phosphate, 25, 31, 32

Di-cyanamide, 22

Diffusion process, 114

Di-gallic acid, 163

Digestion, 188, 194

Dihydroxy succinic acid, 104

Diminishing returns, 83, 205, 216

Di-saccharose, 107, 111

Disease, 27, 73

Dissolved bones, 34

Distillation, destructive, 125, 129,
147

Distribution of fertilizers, 5, 7, 25

Distributors, manure, 25

Dowling, 133

Drage, 222

Drainage, 16, 17, 19, 21, 45, 47, 52,
68, 95, 183, 205

Draughts, 206

Dried fruit, 167

Driers for oil, 108, 136, 143

Drill, 6, 21

Drinking coconuts, 139

Drought, 7, 15, 21, 35, 95, 109, 110
Drying oil, 108, 136, 138, 143, 146
Dry lands, 94

Dub grass, 173

Dung, 46, 192, 205

Dunlop, 224

Dunstan, 146

Durham, 73, 178

Dyer, 36, 77, 85, 104, 110, 133, 224
Dyes, 125, 165

EARTH closet, 54

Earth nut, 142, 191

Earths, nitre, 21

Earthworms, 5, 24

East Indian rape, 143

Eaton, 168

Ebonite, 165

Economy of water, 95, 101, 110
Edestin, 151

Education, 220

Efficiency of labour, 216

Egypt, 21, 118, 125, 138
Electric carbon filament, 106
Electricity, 89, 92 _
Elementary nitrogen, 51, 82, 191
Ellmore, 134

Embryo, 149

Emulsion, 128

Enclosure, moor, 98, 210
Enzyme, 106, 136, 137, 159, 193
Errors of experiment, 99
Essential oils, 109, 145

Ester, 108

Evans, 190

Evaporation, 69, 95, 161, 180, 198
Evolution of nitrogen, 51, 82
Excreta, 47, 54, 188, 192
Exhausted soil, 3, 14, 86, 93
Eyre, 146

FABRIC, 125

Feces, 47, 54, 188, 192

Farmyard manure, 42, 52, 122, 173,
179

Fashions in farming, 83, 89

Fat stock, 188, 215

Fats, 22, 33, 102, 108, 135, 179, 184,
192

Fattening, 192, 196

Fatty acids, 102, 108, 141

Faulty buildings, 206, 210

Feather waste, 23

Febrifuge, 154

Feed meal, gluten, 120

Fehling’s solution, 107, 108

ee

INDEX 229

Felling timber, 127

Fens, 96, 97

Fenton, 110

Fermentation, 50, 103, 117, 124,
192

Ferozepore, 143

Ferric hydrate, 26, 66, 71, 75

Ferro cyanide, 88

Fertility, 2, 3, 67, 93, 169

Fertilizers, 2, 10, 73, 86, 169

Furfuraldehyde, 105

Furfuroids, 106

Fibres, 106, 125, 126

Filter paper, 105

Financial aspect, 211

Fine grinding, 6, 25, 41

Finger and toe, 32, 73

Fish, 22, 24, 158, 197

Fisher, 146, 224, 197

Fixation of atmospheric nitrogen,
11, 51, 81, 82, 176, 203

Fixation of fertilizer, 13

Flax. 126, 128, 135

Flesh, 185, 192, 199

Fletcher, 134

Flocculation, clay, 19, 74, 89, 96

Florida phosphate, 30

Flour, 118, 122, 147, 207, 219

Flour, potato, 122, 219

Fluff, cotton, 125

Fluorine, 25, 33

Flush of tea, 158

Fog, 65

Foreign-grown food, 219

Forestry, 127, 215

Formaldehyde, 101

Formic acid, 102

Forster, 110

Fowler, 58, 146, 168, 224

Fream, 84, 223

Free selector, 170

Fritsch, 224

Frost, 91

Fructose, 107, 108

Fruit, 10, 163, 166, 175

Fruit sugar, 107

Fungicides, 91

GALACTOSE, 107, 108, 132, 199
Gall nuts, 163

Gallo-tannic acid, 163
Gardens, 17, 54, 66, 122, 208, 211
Garden soils, 26, 54, 66
Garrad, 157

Gas, wood, 129

Gas lime, 88, 91, 97

Gas works, 11, 18

Gases occluded by soils, 81
Geerligs, 223

Gel, 7, 44, 164

Gelatine, 7, 32, 33

Gelatinization, starch, 106, 118, 207,
219

Gelose, 132

Geranium, wild, 174

Germany, 37, 93, 214, 215

Germicides, 91

Germination of seeds, 38, 96

Gilbert, 1, 76, 85, 195

Gilchrist, 85, 179

Gingelly, 144

Gliadin, 147, 149

Globulin, 150

Glucose, 103, 106, 108, 123, 163,
167, 186, 199

Glucoside, 145, 185

Glucosides, cyanogenetic, 123, 136

Glucosides, nitrogenous, 109, 185

Glue, 32

Glutaminic acid, 149, 151, 181

Gluten, 147

Gluten feed meal, 119, 120

Glutenin, 147, 149

Glycerine, 108, 141, 180, 184

Glycogen, 187

Goat, 202

Gold currency, 214

Golding, 58

Golf-green worms, 24

Gooseberries, 17, 19, 104

Gorham, 100

Gourlay, 222

Gram (pea), 125

Grandeau, 76

Grantham, 168

Grape sugar, 106

Grapes, 104, 167

Graphite, 21

Grass, 124, 128, 173, 201, 203

Grass land, 29, 30, 63, 81, 179,
211 .

Grass manure, 25, 40, 176

Gravel soil, 24, 66, 94, 160

Gravity, specific, 64, 199

Grazing, 120, 179

Green, 222

Green crop, 19, 119, 168, 175

Greenhouses, 65, 90

Greenwich, 67

Gregory, 153

Grigioni, 24

Guano, 22, 35

Guernsey, cow, 201

Gum, 106, 131, 132

Guzerat, 143

Gwilym Williams, 157

Gypsum, 19, 51, 74, 88, 96, 104,
172, 177

230 INDEX

Haas, 110, 133, 224

Hall, 9, 36, 84, 85, 133, 182, 203,
210, 212, 222, 223

Hanley, 92

Hanson, 196

Hard pan, 19, 63

Hard woods, 127

Hard work rations, 198

Hardy, 157

Harrowing, 66

Haulms, 185

Hay, 9, 12, 19, 124, 136, 171, 173, 201

Haynes, 134

Hazel nuts, 152

Heat, soii, 65, 90

Heather, 98

Heavy soils, 16, 19, 21, 40, 55, 64,
70, 82, 96, 97, 203

Hedge clippings, 57

Heidstam, 134

Hemp, 127, 128, 145, 151

Hendrick, 24, 59, 133

Henry, 146

Herring waste, 22

Hexoses, 106

Higgins, 116, 133

High farming, 220

High prices, 220

Hilgard, 84, 100, 224

Hill, 110, 133, 182, 224

Himalayan rivers, 95

Hindu cultivation, 170

Hippuric acid, 44

Histidine, 149, 152

Hobsbaum, 24

Hobson, 222

Hoeing, 66, 116

Holland soil, 93

Hollow soil, 171

Home-grown food, 219

Honey, 107

Hoofs, 23

Hoosfield, Rothamsted, 26

Hop farmers, 24

Hopkins, 224

Hordein, 149

Hormones, 181

Horns, 23

Horse feeding, 48, 50, 188, 193

Howard, 100, 133

Hughes, 36

Human heat, 198

Human rations, 198

Humic acid, 43, 76

Humogen, 58

Humphry Davy, 1, 9

Humus, 16, 19, 21, 28, 42, 63, 70,
76, 97

Hutchinson, 81, 92

Hydraulic press, 125, 135
Hydrochloric acid, 32, 71, 168
Hydrofluoric acid, 71
Hydrolysis, 124, 137, 143
Hydroxy propionic acid, 103
Hydroxy succinic acid, 104
Hyland, 146

Hysteresis, 164

Inp1A, 21, 47, 70, 94, 110, 111, 120,
125, 126, 132, 135, 138, 143, 152,
158, 165, 173, 207, 209, 213

Indian village, 214, 219

Indiarubber, 163

Indigo, 165

Indigotin, 166

Indo-Gangetic alluvium, 78

Indole, 181

Industria] farm, 178, 209, 210

Infertile soil, 14, 97

Ingle, 224

Insecticides, 154

Insoluble albuminoids, 7, 43, 147

Insoluble nitrogen, 34

Insoluble phosphates, 30, 34

Intestinal mucus, 188

Intestines, 179, 184, 188, 193

Iodine, 20, 106, 108, 152

Iodine value of oils, 136

Ireland, 97, 126, 177, 218

Irish linen, 126

Iron, 27, 66, 71, 74

Irrigation, 66, 67, 94, 111, 118, 150

Island, Sea, 125

Italy, 139

Jam, 117, 167

Japan, 120, 132, pete 151,158, 160,167
Japanese larch, 127
Jatindra Nath Sen, 36
Jersey cow, 201
Jesuit’s bark, 153
Jethro Tull, 1
Johnson, 224

Jones, 36

Jorgensen, 90, 92, 110
Joshi, 168

Juari, 125, 185

Jute, 126

KAInitT, 37

Kangaroo, 170

Keen, 84

Kellner, 189, 196, 193, 196
Kent hops, 24

Kernels, rice, 121

Kerry cow, 201

Kessel Myer, 147
Keto-hexose, 107

ES ee ee a

INDEX

Kettle, Linseed, 135
Khair, 162

Kidneys, 184

Klason, 134

Knapsack sprayer, 168
Knecht, 168

LABour, 209, 210, 212, 215

Lack of balance in soil, 8, 64, 83

Lactation, 200

Lactic acid, 103

Lactones, 103

Lactose, 107, 199

Levulose, 107

Lamb, 24

Landowners, 220

Latex, 164

Laticiferous system, 164

Lawes, 1, 76, 85, 195

Lawns, 145

Lead, 136, 152

Lead acetate, 109, 152

Lead-lined tea chests, 160

Leaf mould, 57

Leake, 84

Leather (tanned), 35, 162

Leather, J. W., 85, 100, 133, 202, 224

Leathes, 145, 190

Leaves as litter, 45

Leblanc, 87

Leguminous crops, 11, 27, 82, 150,
172

Leguminous proteins, 150

Lemons, 104

Lemstrém, 90, 92

Lentils, 150

Lettuces, 175

Light soils, 40, 55

Lignin, 106, 127, 129, 187

Lime, 8, 14, 16, 19, 21. 23, 27, 28,
72, 82, 86, 97, 113, 153, 165, 177,
218

Lime, gas, 88

Lime-magnesia ratio, 9, 74

Lime, nitrate of, 20

Limestone, 86

Linen, 126, 128, 135

Linimarin, 123, 136, 185

Linoleic acid, 136

Linseed, 24, 123, 126, 135, 143

Linseed cake, 7, 136, 183

Linseed mash, 137

Litter, 44, 50

Little farms, 209

Live weight increase, 204

Lloyd, 146

Loaf, 118, 124, 147, 207, 219

Loam, 29, 78

Lodging of crops, 10, 111

23t

Loewenthal, 168

Logs, 127

Long, 198

Loose packing in soil, 62
Lubricating oil, 144

Luff, 168

Luxmore, 78, 84

Lying in bed, calories, 198
Lysine, 149, 151

MACDONALD, JAMES, 223

Machinery, 210, 218

Mackenzie, 133

Maclennan, 92

Madras, 78, 95, 142, 143, 162

Magnesia, 8, 27, 33, 73, 86, 97, 158

Maidment, 146, 198, 202

Maintenance, 192, 198

Maize, 119, 122, 148, 181

Maize germ meal, 119

Malic acid, 104

Malonic acid, 104

Malt, 106, 124, 171

Malto-dextrin, 106

Maltose, 106, 107

Managers, farm, 209

Manchuria, 138

Manganese, 8, 27, 72, 135

Mangel wurzel, 12, 114, 116, 17],
175, 185, 201

Manitoba flour, 150

Mann, 168

‘Manure heap, 43, 48

Margarine, 141, 142, 144

Market garden, 17, 66, 122, 166,
168, 211

Marl, 97

Marseilles oil extraction, 142, 144

Marsh gas, 188, 192

Martineau, 133

Maryland soil, 93

Matthai, 222

Mauritius sugar, 111

Meadow hay, 12, 19, 124, 136, 173,
193, 201, 222

Meal, gluten feed, 120

Meal, maize germ, 119

Meat, waste, 24, 178, 206, 211, 213

Mechanical pulp, 128

Mechanical analysis of soil, 67

Menzies, 190

Mercerized cotton, 125

Meshes of sieves, 6, 25, 118

Methyl alcohol, 130

Mica, 144

Micro-coccus, 42

Middleton, 179, 204, 222, 223

Milk, 103, 105, 107, 197, 199, 206,
211, 213

232

Milking machines, 218
Milk sugar, 107, 199
Miller, 85

Millets, 125
Millipedes, 91
Mimosa, 163

Mineral phosphate, 30
Mitchell, 146

Mixed farming, 178
Mixed fertilizer, 40
Mixed stock, 204
Mohan, 202

Moist air, 19, 205
Moisture, 19, 23, 65, 82
Molasses, 113

Money. (author), 168, 224
Money (cash), 212, 220
Moneylenders, 219
Mono-calcium phosphate, 25, 31
Mono-saccharose, 106
Moors, 98, 210
Mordanting, 103
Morphine, 153

Morrel, 146

Morrison, 224

Motor ploughing, 208, 218
Mowha, 24, 144
Mowra, 144

Mucilage, 131, 136, 187
Mukerjee, 133, 224
Mulch, 66, 68, 95, 111
Muriate of ammonia, 17
Muscle, 179

Mustard oil, 143

Myer, Kessel, 147
Myrobalan, 162

NAKED cotton seed, 125

Naphthalene, 91

Narcotine, 153

New land, 210

Newsham, 223

Nicol prisms, 106

Nicotine, 154

Niger seed, 144

Night soil, 54

Nile, 94, 95

Nitrate, ammonium, 17

Nitrate of lime, 17, 20

Nitrate of potash, 21

Nitrate of soda, 17, 18, 20, 21, 23,
63, 87, 110, 171

Nitrate, soil, 51, 76, 80, 82, 109

Nitre earth, 21

Nitre well, 21

Nitric acid, 18, 21, 76

Nitrification, 16, 22, 27, 51, 80, 82, 87

Nitrifying bacteria, 23, 91

Nitrite, 51, 82

INDEX

Nitrogen, 10, 21, 22, 23, 47

Nitrogen, available, 13, 23, 87

Nitrogen, elementary, 51, 52

Nitrogen fixation, 51, 81, 82

Nitrogen in feeding, 48

Nitrogen in soil, 81

Nitrogen in unripe fodder, 110

Nitrogenous glucosides, 109, 123.
126, 136, 185

Nitrogenous organic manures, 22, 35

Nitrous acid, 51, 82

Non-albuminoid nitrogen, 109

Norlin, 134

North American maize, 119

Northerly aspect, 65

Northern counties, 208

Northumberland, 67, 78, 203,209,210 |

Norway, 206

Noyes, 222 |

Nux vomica, 156 )

Nystron, 134 |

Oak, 127, 162 ‘|

Oats, 12, 106, 171, 205, 219
Occluded gas, 81

Offal, 22, 179

Oil, 22, 108, 135, 184, 191
Oils, drying, 108, 136, 138, 143
Oil seeds, 108, 117, 125, 135, 145
Oil substitutes, 136, 165

Oil theory of feeding, 195
Okey, 134

Old village sites, 21

Oleic acid, 108, 180

Olive oil, 137, 142, 144
Oliver, 100

Opium, 152

Orange, 167

Organic matter in soil, 76
Organic nitrogen, 17, 22, 109
Orr, 133

Orwin, 133

Osborne, 157

O’Sullivan, 134
Over-feeding of cows, 201

Ox feeding, 48, 178, 192, 197
Oxalic acid, 103

Oxidation, 50, 51, 156

Pacific Island phosphate, 30
Packing in soils, 62

Paddy, 120

Palace leas hay, 173

Palm kernels, 139

Palmitic acid, 108, 180
Palm nuts, 139, 189

Palm sago, 123

Pan, hard, 19, 63

Paper, 105, 128

a

os

_—

INDEX 233

Paramecia, 81, 91

Parchment, 106, 161

Paring soils, 97

Parmentier, 147

Parry, 146

Partial sterilization, 90

Pasture, 29, 30, 81, 173, 204, 210

Peach, 167

Pear, 167

Peas, 150

Peat, 7, 45, 58, 97, 128

Peat moss litter, 45

Pectins, 105, 187

Pegler, 202

Penetration, 5, 7, 31, 34

Pentosans, 44, 105, 187

Pentoses, 105, 187

Peptones, 43, 50, 188

Perchlorate, potassium, 20

Peru, 35, 153

Pests, soil, 90

Petherbridge, 92

Petroleum spirit, 22, 33, 108, 136

Philippines, 111

Phlobaphenes, 163

Phosphate, 7, 22, 25, 74, 77, 94,
171, 174

Phosphorus in animal, 49

Phosphorus in fertilizers, 25, 27

Phosphorus in soil, 26, 87, 94

Photosphere of sun, 65

Photo-synthesis, 101

Physical analysis of soil, 61, 67

Physical condition of soil, 29, 86

Pickles, 103

Pig, 23, 48, 55, 183, 196, 197

Pig iron, 27

Pine needles, 58

Pine trees, 127, 145

Pith, sago, 123

Plant food, 10, 93, 169

Plimmer, 157, 190

Ploughing, 60, 66, 208, 218

Plum, 167

Polar regions, 2

Pondicherry, 142

Pool retting, 126

Poppy, 152

Porritt, 168

Postage stamp gum, 106

Potash, 7, 22, 37, 74, 97, 126, 171, 174

Potash, available, 36, 77, 87

Potash manure, 37, 162

Potassic super-phosphate, 40

Potassium ferro-cyanide, 38

Potassium in feeding, 48

_ Potassium hydrogen tartrate, 104

Potassium iodate, 19
Potassium nitrate, 21

Potassium perchlorate, 19

Potato, 12, 122, 151, 168, 171, 185,
205

Potato eyes, 185

Potato flour, 122, 207, 219

Potato stalks, 128, 185

Potato starch, 106, 122, 207

Potvliet, 133

Poudrette, 54

Poultry, 22, 56, 197

Poverty bottom, 98

Prairie soils, 3, 86

Precipitated chalk spray, 168

Preservatives for timber, 127

Preservation of fruit, 167

Priestley, 90, 92

Primrose McConnell, 100, 223

Protein, 22, 109, 147, 185, 191

Prussian blue, 91

Prussic acid, 123, 136, 137, 143, 185

Pulp, 128, 161

Pulses, 40, 150

Punjab, 67, 118

Pupils, Agricultural, 210, 221

Purgative, 181

Purine, 181

Pyridine, 181

Pyrites, 71, 75, 165

Pyro-ligneous acid, 125, 130, 164

QUEENSLAND, 111, 112
Quicklime, 86
Quinidine, 154
Quinine, 154

RAB cultivation, 97

Radiation, 2, 65, 101, 198

Raffinose, 107, 108

Rag-bone, 33

Rank grass, 96

Rape, 24, =o

Raspberry, 16

Ratlo Ct N in soil, 77

Ratio of labour to land, 219

Ratio of lime to magnesia, 9, 73, 86

Ratio of manure to land, 3, 40, 169,
220

Ratoon crops, 111, 174

Rawson, 168

Re-afforestation, 127, 162, 215

Reclamation, 92, 97, 100

Red beech, 72

Red hair, 72

Red soil, 66, 162

Ren, 74, 96

Rendering oil, 108

Resin, 145

Retort charcoal, 129

Retting, 126

234 INDEX

Reversion of plant food, 31, 51
Rhubarb, 103, 168

Rice, 95, 120, 121, 208

Ricin, 152

Richards, 58

Richmond, 202

Rideal, 58, 110

Ripening, 10, 17, 27, 175

Road sweepings, 67

Roberts, 134

Robertson, 36

Roller, use of, 62, 69, 80

Root crops, 114, 116, 122, 151, 169
Roots, 5, 26, 40, 62

Ropes, 127, 143

Roscoe, 92, 224

Rosin, 145

Rotation, of crops, 119, 212
Rotation of light, 108, 148
Rothamsted, 1, 17, 69, 76, 83, 195
Rotting, 50, 126

Rouelle, 147

Rowley, 134

Rubber, 108, 136, 163, 209
Rufisque, 142

Ruminants, 187, 193

Rural industries, 215

Rural schools, 221

Rushes, 128

Russell, 24, 58, 81, 84, 92 133, 224

’ . Russian linseed, 135, 136

Ruston, 168
Rye grass, 12

SACKING, 18, 126
Safflower, 143

Saffron, 143, 144

Sago, 123

Salad oil, 142

Sal ammoniac, 17

Salt, common, 37, 116, 172, 180
Sand, 39, 64, 71, 78, 94, 161
Saponification, 108, 140
Saponin, 24, 145
Sardines, 142

Sarson, 143

Sawdust, 45, 103, 127, 129
Scavenger, 54

Scents, 145

Schorlemmer, 92, 224
Schreiner, 85

Schryver, 134

Scientific training, 209
Scotland, soil, 93

Scott, 24

Scutching, 126

Sea-bird guano, 35

Sea Island cotton, 125

Sea water, 37, 94, 140

Seaweed, 57, 132

Seeds, 38, 96, 108, 175

Seeds, hay, 173

Senegal, 142

Septic tank, 56

Sesame, 144

Sewage, 54 |

Sewage farm, 55

Shallow tillage, 69, 94

Sheep, 48, 178, 196, 197, 204

Shell lime, 86

Shoddy, 23

Short, 190

Shortage of wheat, 20, 206

Shorthorn cows, 201

Shrinkage of soils, 70

Shrivell, 133

Shutt, 157

Sieve, 6, 25, 118

Silk waste, 23

Silt, 100

Silver, acetate, 152

Silvering mirrors, 104

Silver skin, 161

Simpson, 222

Singling turnips, 116

Sirocco, 159

Size of soil particles, 61, 67, 78

Skatole, 181

Slag, 6, 8, 16, 20, 27, 63, 67, 97, 171,
174, 179, 203, 208, 218

Slaughter house waste, 23

Slopes, terraced, 120, 158, 161

Sludge, 55

Smetham, 222

Smith, 134

Snyder, 224

Soap, 108, 140, 141, 142, 143, 144,
145

Soap nut, 24, 145

Sodium, 19, 74, 96

Sodium carbonate, 96

Sodium chloride, 37, 116, 172, 180

Sodium sulphate, 96

Soil, 7, 60, 161

Soil improvement, 86

Soil nitrogen, 81

Soil pests, 90

Soil water, 68

Solanin, 122, 185

Solar energy, 2, 65, 90, 101

Solubility of fertilizers, 4, 10, 27, 34,
41, 169

Soluble albuminoids, 7, 22, 147

Soluble nitrogen, 10, 34, 41

Soluble phosphate, 25, 34, 41

Somerville, 98, 134, 179, 228

Soot, 17, 66, 92

Sorrel, 103

a

en

INDEX

Souchida, 145

Soudan sudd, 128

South African soya, 139

South America, 32, 139

Southerly aspect, 65

South Sea Island coconut, 139

Sowing seeds, 38, 92, 96

Soy bean, 138, 151

Spain, 139

Specific gravity, 64, 199

Specific rotary power, 108, 148

Sprayer, potato, 168

Spring wheat, 147

Squatter, Australian, 170

Standard sieve, 6, 25

Starch, 102, 106, 117, 119, 121, 122,
123, 124, 137, 186, 191, 207

Starch equivalent, 195

Starch gelatinization, 106, 118, 207,
219

Steam sterilization of soil, 90

Stearic acid, 108, 180, 184

Stebbing, 134

Steel bomb calorimeter, 191

Steel, by-products, 27

Sterilization, 22, 90, 156

Sterling, 168

Stevens, 168

Stiles, 110 .

Stimulating manures, 4, 11, 18, 20,
31, 63, 169

Stinging nettles, 102

St. John, 202

Stock, live, 178

Stokes, 100

Stomach, 102, 188, 190, 193

Stones, 61, 78

Storage of manure, 50

Store beasts, 194

Storer, 224

Straw, 12, 45,105, 126, 128, 136, 206

Strawberry, 167

Straw gum, 105

Straw pulp, 128, 193

Structure of soil, 61, 171

Struggle for existence among plants,
8

Stachyose, 108

Strychnine, 156

Sub-soil, 19, 29, 60

Succulent crops, 17, 19, 175

Sucrose, 27, 107, 111, 167, 186

Sudd, Soudan, 128

Sugar, 27, 102, 111, 117, 167, 186

Sugar beet, 107, 108, 114

Sugar cane, 107, 111, 114, 174

Sugar refineries, 32, 116

Sulphate of ammonia, 11, 40, 89,
110, 119, 159, 162, 171, 175

235

Sulphate of lime, 19, 51, 74, 75, 88,
96, 104, 172, 177

Sulphide, calcium, 87

Sulphite, calcium, 91

Sulphite pulp, 128

Sulpho-cyanide, 88

Sulphur, 27, 75, 88, 89, 108, 165

Sulphur chloride, 108, 136

Sulphur dioxide, 16, 124, 128

Sulphur trioxide, 16

Sulphuric acid, 15, 75, 105, 136, 168

Sun, 1, 65, 101

Super-phosphate, 7, 12, 18, 19, 20,
22, 30, 35, 97, 171, 177

Supply and demand of plant food,
94

Supply of meat, 178, 207

Surface law of feeding, 194

Surface root, 35, 176

Surface washing, soil, 7, 19

Sussex pasture, 67

Sweated labour, 217

Swedes, 116, 151, 171, 176, 186,
201

Sweet cassava, 123

Symons, 146

Synthetic nitrogen compounds, 11,
20, 21

TANKS, Irrigation, 95

Tannin, 162

Tan refuse, 45

Tapioca, 123

Tapping trees, 145, 164

Tar, 125, 127, 128, 129

Tartar, 104

Tartaric acid, 104

Tea, 156, 158, 161, 175

Teaching, agricultural, 221

Tempany, 84

Temperate climates, 65

Terracing slopes, 120, 158, 161

Tetra-calcium phosphate, 25

Tetra-saccharose, 108

Textiles, 123, 125

Theine, 156, 158, 160

Thomson, 157

Thorpe, 157, 223

Thread, 125

Tibbles, 224

Tillage, 62, 69, 94, 211

Til seed, 144

Timber, 125, 127, 129, 168, 215

Titanium, 72

Tobacco, 19, 21, 154

Tom, 134

Top dressing, 4, 15, 18, 19, 20, 22,
33, 31, 110, 119

Town stables, 50

236

Tree Field, Cockle Park, 64, 81,
173, 179

Trees, 123, 125, 127, 129, 139, 153,
163, 215

Tri-calcium phosphate, 25, 31, 32

Tri-saccharose, 108

Tropical agriculture, 19, 54, 65, 95,
111, 116, 119, 120, 123, 125, 139,
153, 158

Tryptophane, 151, 181

Tull, Jethro, 1

Turnips, 19, 27, 30, 32, 69, 116,
136, 183, 201

Turnip manure, 40, 116, 169

Turnor, 221

Turpentine, 109, 131, 145

UNDERWOOD, 85

United States, 111, 112, 119, 139,
170

Unit price, 41

Universities and agriculture, 220

Unsaturated oils, 108

Upper Tyne, 205

Uranium acetate, 109

Urea, 7, 42, 50, 191

Uric acid, 57, 181

Urine, 44, 47, 57, 192

Unripe fruits, 163

Usar, 74, 96

VACUUM pan, 113

Vakil, 146

Vanadium, 27

Varnishes, 145

Vegetable cheese, 151
Vegetarian countries, 114
Ventilation of cow byres, 221
Vetch, 151

Vicilin, 150

Vinegar, 103, 125, 129, 147
Virgin soils, 3, 60

Vitriolated bones, 34
Voelcker, 1, 24, 58, 59, 146, 223
Vorhees, 223

Vulcanization, 136, 165

WAGES, agricultural, 214, 220
Wallace, 133, 157

Wanklyn, 190

Warington, 84, 190, 202, 224
Warner, 110

Warping, 100

Waste animal matter, 23
Waste lime, 87

INDEX

Waste wood, 125, 129, 163

Water, 2, 49, 95, 183

Water in soil, 7, 62, 82, 110

Water, sewer, 55

Watt, 134

Wattle gum, 132

Wax, 108

Wax cloth, 144

Weathering of soil, 61

Weiss, 58

Well water, 21

Wentworth, 92

Western Ghats, cultivation, 97

West Indies, sugar, 111, 112

Wet lands, 95

Whatnough, 157

Wheat, 3, 12, 19, 20, 67, 105, 118,
147, 150, 171, 191, 195

Wheat straw, 12, 105, 206

Whey, 107

Whitby, 168

White alkali, 74

White clover, wild, 82, 172

White cotton seed, 125

White crops, 118, 171

White rice, 121

White sugar, 113

Wibberley, 223

Wild geranium, 174

Wild white clover, 82, 172

Wiley, 133, 223

Willesden paper, 106

Williams, Gwilym, 157

_ Winter application of fertilizers,

16, 21, 23

Winter wheat, 147

Wine, 104

Wireworms, 91, 92

Woburn, 19, 63

Wood (author), 133, 157, 182, 222

Wood (timber), 103, 125, 127, 128,
129, 163, 215

Wood ash, 16, 37, 38

Wood tar, 128

Wool waste, 23

Worms, 5, 24, 145

Wright, 198, 223

Wurzel, mangel, 50, 114, 116

YELLOw plants, 15
Yule, 182

ZEIN, 148

Zinc chloride, 105, 106, 127, 128
Zinc oxide, 165

Zinc sulphate, 91

Bailliéve, Tindall & Cox, 8, Henrietta Street, Covent Garden, W.C. 2.

INDUSTRIAL CHEMISTRY

Being a Series of Volumes giving a Comprehensive Survey of

THE CHEMICAL INDUSTRIES.

Edited by SAMUEL RIDEAL, D.Sc. (Lond.), F.LC., Fellow of
University College, London.

NOW READY
Plant Products and Chemical Fertilisers S. H. Coruins, M.Sc., F.I.C.
Pp. xvi + 236. Price 7/6 net.

The Alkali Industry . . . J. R. Partincron, D.Sc. (Vict.)
Pp. xvi + 304, with 63 figs. Price 7/6 net.

Industrial Electrometallurgy E.K. Ripa, M.A. (Cantab.),Ph.D., F.LC.
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The Application of the Coal Tar Dyestuffs | C. M. Wurrraxer, B.Sc.
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IN THE PRESS
Coal Tar Dyes and ya

mediates .... . E. DE Barry Barnett, B.Sc., A,I.C.
Animal Proteids . . . . H. G. Bennett, M.Sc. (Leeds).
The Carbohydrates. . . . S. RgAt, D.Sc. (Lond.), F.LC., and

Associates.
IN PREPARATION
The Industrial Gases . . . H.C. Greenwoop, D.Sc. (Manchester).
Fats, Waxes, & Essential Oils W.H. Simmons, B.Sc. (Lond.), F.LC.
| Silica and the Silicates . . J. A. AupLEy, B.Sc. (Lond.), F.I.C.

The Rare Earths and Metals E. K. Rmeat, M.A. (Cantab.), Ph.D., F.LC.
The Iron Industry . . . . A. E. Pratt, B.Sc. (Lond.), Assoc. R.S.M.°
The Steel Industry. . . . A. E. Prart, B.Sc. (Lond.), Assoc. R.S.M.
Gas-Works Products . . . H. H. Gray, B.Sc.
Organic Medicinal Chemicals a Pngehbamma F.1.C., and F. H. Carr,
The Petroleum Industry . . D. A. SurHERLAND, F.L.C.
Wood and Cellulose . . . R. W. Srnpatt, F.C.S,, and W. Bacon,

B.Sc., F.1.C., F.C.S.

Rubber, Resins, Paints and
Varnishes. ... . . R. S. Morrett, M.A., Ph.D.; A. E.

WAELE, and the Editor,

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